1,354,361 research outputs found
Development of a multiresidue method for analyzing herbicide and fungicide residues in bovine milk based on solid-phase extraction and liquid chromatography-tandem mass spectrometry
No full textThis report describes a liquid chromatography (LC)-tandem mass spectrometry (MS) multiresidue method for determining traces of 30 base/neutral/acid herbicides and fungicides in bovine whole milk. Four milliliters of milk was spiked with the analytes and two surrogate analytes (SAs) and then diluted with 35 mL of a water/methanol solution (50:50, v/v). This mixture was passed through a 0.5-g Carbograph 4 (TM) cartridge. After washings, analytes were re-extracted by back-flushing the cartridge with 1.5 mL of methanol followed by 6 mL of methylene chloride/methanol (80:20, v/v), 50 mmol/L formic acid. After partial solvent removal down to about 0.1, 0.15 mL of I mmol/L formic acid aqueous solution and an internal standard (IS) were added. After filtration, 50 mu L of the final extract was then introduced into the LC analytical column. During the chromatographic run, the MS system was operated in both positive and negative ion modes. MS data acquisition was performed in the multi-reaction monitoring mode, selecting two precursor ion > product ion transitions for each target compound, except for pentachlorophenol. On analyzing six milk samples from different sources, absolute recovery of the analytes and the two SAs ranged between 78% and 104% with RSDs not larger than 13%. The accuracy of the method at three different spike levels was assessed by adding the two SAs to analyte-containing milk samples and varied between 82% and 120% with RSDs not larger than 11%. Limits of quantification were estimated to range between 0.008 and 1.4 mu g/L. Compared to the Carbograph 4 cartridge, one filled with a N-vinylpyrrolidone-m-divinylbenzene co-polymer (Oasis HLB (TM)) sorbent was much less efficient in recovering several of the acidic herbicides considered and, in addition, its relative final extract produced a severe negative matrix effect that drastically weakened ion signal intensities of several non acidic analytes
Steady-state mathematical models of battery storage plants with line-commutated converters
No full textFailure rates reduction in SmartGrid MV underground distribution cables: Influence of temperature
No full textTemperature plays an important role on the failure rate of electrical cables and their joints as well as of any electrical components. In fact, Arrhenius's Law (1889) states that temperature accelerates any chemical reaction and, hence, it is evident that aging, or a fast degradation, of any insulating materials increases with temperature. For this reason the maximum operational temperature which can be accepted for the insulation of the extruded underground cables must be limited controlling the transmitted current by proper relays (integrated in the switchgear). Anyway, the temperature of the insulation of underground cables is function of both ambient temperature and thermal resistivity of the ground, which have to be carefully evaluated, case by case, at the time of the original installation. Anyway, during the hottest months of the year both these parameters (ambient temperature and thermal resistivity of the ground) present their highest values and in consequence it is possible that the cable insulation may reach higher temperatures of those admitted, with faster degradation of the insulating materials and, hence, an increase of failure rate. For this reason the thermal current capacity of the cables installed in the distribution networks of modern Smart Grid can be optimized having on-line information on both ambient temperatures and load currents. Also a more accurate control of the same parameters may lead at a reduction of the number of failure registered on these distribution cables. This paper reports a preliminary study which classifies failures of medium voltage underground cables and their joints in function of the estimated or measured ambient temperatures and other parameters. Also some remarks on the relation exiting among failures of cables, ambient and cable temperatures and thermal resistivity of the ground are reported
Development of a multiresidue method for analyzing herbicide and fungicide residues in bovine milk based on solid-phase extraction and liquid chromatography tandem mass spectrometry
No full textThis report describes a liquid chromatography (LC)-tandem mass spectrometry (MS) multiresidue method for determining traces of 30 base/neutral/acid herbicides and fungicides in bovine whole milk. Four milliliters of milk was spiked with the analytes and two surrogate analytes (SAs) and then diluted with 35 mL of a water/methanol solution (50:50, v/v). This mixture was passed through a 0.5-g Carbograph 4 cartridge. After washings, analytes were re-extracted by back-flushing the cartridge with 1.5 mL of methanol followed by 6 mL of methylene chloride/methanol (80:20, v/v), 50 mmol/L formic acid. After partial solvent removal down to about 0.1, 0.15 mL of 1 mmol/L formic acid aqueous solution and an internal standard (IS) were added. After filtration, 50 microL of the final extract was then introduced into the LC analytical column. During the chromatographic run, the MS system was operated in both positive and negative ion modes. MS data acquisition was performed in the multi-reaction monitoring mode, selecting two precursor ion>product ion transitions for each target compound, except for pentachlorophenol. On analyzing six milk samples from different sources, absolute recovery of the analytes and the two SAs ranged between 78% and 104% with RSDs not larger than 13%. The accuracy of the method at three different spike levels was assessed by adding the two SAs to analyte-containing milk samples and varied between 82% and 120% with RSDs not larger than 11%. Limits of quantification were estimated to range between 0.008 and 1.4 microg/L. Compared to the Carbograph 4 cartridge, one filled with a N-vinylpyrrolidone-m-divinylbenzene co-polymer (Oasis HLB) sorbent was much less efficient in recovering several of the acidic herbicides considered and, in addition, its relative final extract produced a severe negative matrix effect that drastically weakened ion signal intensities of several non acidic analytes
Natural esters distribution transformers: A solution for environmental and fire risk prevention
No full textThe electrical transformers insulated and cooled with mineral oils remain, still today, the most widespread and effective solution for converting electrical energy. Mineral oils are used for their excellent dielectric and thermal properties, but have a low flash/fire points and biodegradability and these factors may negatively contribute in cases of fire and toxic release with contamination of soil and surface water and groundwater. For these reasons, innovative insulating fluids, such as natural esters (vegetable oils), have been suggested worldwide. Natural esters, compared to conventional mineral oils, in fact, have some advantages, such as high flash/fire points, lower toxicity, higher biodegradability and possibility of recycling. In addition, natural esters may have very positive heat exchange properties, allowing a more effective cooling of the electrical power transformers. Distribution transformers are often used as pole transformers, which, in case of failures and thefts, may release and spill in the surrounding environment their insulating liquid with possible soil contamination. Other distribution transformers are located in urban area, internally to buildings and, in this case, the flammability of their insulating liquid may create some limitation in compliance with the local fire regulations. This paper presents the first results of the experimental work performed by an Italian Working Group (WG) supported also by Experts of the Italian Firefighters Authority, the Department of Land Protection of the Ministry of Environment (ISPRA) and the Department of Safety of the National Institute for the Accidents at Work Prevention (INAIL). These results have shown as the use of natural esters in transformers may positively reduce the risk of fire and environmental accidents
Thermal behavior of distribution MV underground cables
No full textThe present paper reports an experimental investigation on the thermal behavior of medium voltage underground cables laid in different types of soils and under different conditions of the ambient temperatures. The same paper shows as thermal degradation of the insulating system of the cables and their joints can become more consistent and faster due to the effect of the continuously overheating due to the ambient temperatures and to the thermal resistivity of the soil of higher values. An other source of thermal degradation of the cables and their joints may be indicated in the fault currents affecting the metallic shields in systems operating with a compensated neutral connection to ground. In particular, in these systems the fault current is lasted for a time of some tens of seconds to allow a faster localization of the failure, through the automatic sectioning switches. During this time, currents flow through the metallic shields of the cables, overheating the same shields especially in correspondence of pour connections which may be present inside the joints. In case that the single-fault-to-ground evolves in a double-fault-to-ground the same shield will be interested by much higher current (short-circuit) which will create a deeper degradation of the semiconductive compounds and the insulation located nearby the metallic shields. The paper also presents the results of visual inspections of failed cable joints, due to thermal causes. Based on these considerations, important solutions may be indicated to reduce the failure rate of the MV electrical system allowing improvements in the overall power quality of the entire electrical systems
Pathogenic transformations of shape and function of 'amyloid proteins' (Poster)
No full textThis is the visual CC BY 4.0 interpretation and simplification by @Sparks4PD of the article by Malmberg, M., Malm, T., Gustafsson, O., Sturchio, A., Graff, C., Espay, A.J., Wright, A.P., El Andaloussi, S., Lindén, A., Ezzat, K. (2020) Disentangling the amyloid pathways: A mechanistic approach to etiology, Frontiers in Neuroscience, vol.14, p 256. https://doi.org/10.3389/fnins.2020.00256</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
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