1,721,158 research outputs found
Reaction centre accessibility. I. Calculation of reaction centre congestion and influence of structure flexibility
No full textThe fate of a reaction depends on many factors like the electronic reactivity of the ground state molecules, conformation/configuration needs and solvent influence. It is often impossible to predict with any certainty the result, in terms of yield and products, of the interaction between two reactants. Thus the role of reaction centre accessibility is definitely determining but is itself difficult to determine. Nevertheless, within the framework of reaction product prediction it is essential to search for an acceptable solution of predictive modelling. A new approach to both the calculation of steric congestion near reaction centres and its regulation is presented as a first step towards the prediction of centre accessibility. The approach is based on a two dimensional representation of molecules and on the calculation of the steric congestion of each branch, calculated by means of intersecting circles that indicate the extent of the reactivity space and the congestion space
Lo Stato, la violenza, il democidio : realtà e conseguenze della concentrazione moderna del potere nell'analisi scientifica di Rudoph J. Rummel
No full textPlastic detection in the sediments of Lambro River (North Italy): a preliminary study
No full textL'inquinamento da plastica rappresenta un problema globale emergente e le
acque dolci contribuiscono in modo massiccio alla contaminazione da plastica a livello
oceanico. Per questo motivo, l'obiettivo del presente studio preliminare è stata la valuta-
zione della presenza di plastiche nei sedimenti del fiume Lambro, un affluente del fiume
Po che attraversa una delle principali aree industrializzate del Nord Italia. I sedimenti
sono stati raccolti utilizzando una benna Van Veen e le plastiche sono state separate da
questa matrice complessa attraverso un'estrazione densimetrica. In particolare, abbiamo
confrontato l'efficienza di estrazione di due soluzioni ipersaline di cloruro di sodio (NaCl;
densità di 1,2 g/cm 3
) e cloruro di zinco (ZnCl 2; densità di 1,6 g/cm 3
). I risultati ottenuti
hanno evidenziato la presenza di plastiche nei sedimenti del Lambro e una differenza
statisticamente significativa (p < 0,05) nella capacità di estrazione delle soluzioni consi-
derate, con 8,3 ± 10,4 plastiche/Kg di sedimenti wet weight (w.w.), estratti dalla soluzione
di NaCl, e 53,3 ± 16,1 plastiche/Kg sedimenti w.w. estratti con ZnCl 2. Questo studio pre-
liminare rappresenta la prima evidenza di plastiche nei sedimenti del fiume Lambro e
mette in risalto l'importanza di utilizzare soluzioni ad alta densità, come ZnCl 2, nel pro-
tocollo di estrazione della plastica. Altri studi sono necessari per confermare questa evi-
denza e per caratterizzare a fondo questo tipo di inquinamento in una matrice, come i
sedimenti, ancora poco indagata.Plastic pollution represents an emerging global problem, and freshwaters mas-
sively contribute to the ocean plastic contamination. For this reason, the aim of this pre-
liminary study was the evaluation of the plastic presence in the sediments of Lambro
River, a tributary of the Po River, which crosses one of the main industrialized areas of
North Italy. Sediments were collected using a Van Veen grab and plastics were separated
from this complex matrix through a density extraction. In particular, we compared the
extraction efficiency of two hypersaline solutions of sodium chloride (NaCl; density of
1.2 g/cm 3) and zinc chloride (ZnCl 2; density of 1.6 g/cm 3
). Obtained results highlighted
the presence of plastics in the Lambro sediments, as well as a significant difference (p <
0.05) in the extraction performance of selected solutions, with 8.3 ± 10.4 number of plas-
tics/Kg sediments wet weight (w.w.), extracted by NaCl solution, and 53.3 ± 16.1 number
of plastics/Kg sediments w.w. extracted by ZnCl 2 solution. This preliminary study repre-
sents the first evidence of plastics in the Lambro River sediments and highlights the im-
portance to use high-density solutions, as ZnCl 2, in the plastic extraction protocol. Other
studies are needed to deeply characterize this type of pollution in a matrix, as sediments,
still poorly investigated
PHARMACEUTICALS AND ILLICIT DRUGS AS NEW ENVIRONMENTAL CONTAMINANTS: ECOTOXICOLOGICAL EFFECTS AND NEW DEPURATION METHODOLOGIES
Full text linkPharmaceuticals and personal care products (PPCPs) and illicit drugs are now widely considered emerging aquatic contaminants because of their high usage worldwide and their consequent presence in surface water with concentrations ranging from ng/L to μg/L. In fact, once hired, these substances are eliminated by urine and faeces in their unaltered form or as metabolites and poured in sewage system. However, the traditional wastewater treatment plants (WWTPs) are not able to
eliminate these compounds from wastewaters, consequently spilled placed in the aquatic environment.
Thus, this research project suggests a natural process based on the natural bivalve filtration as a complementary method to traditional wastewater treatment, seeking thereby to remove the abovementioned contaminants from the aqueous matrix. In detail, we chose the invasive freshwater mussel Dreissena polymorpha to study this possible alternative depuration method. For this purpose, we built a pilot-plant within the Milano-Nosedo WWTP in which twenty removal Plexiglas® panels were placed. Moreover, we placed about 40,000 D. polymorpha specimens on these substrates appointed to the wastewater filtration. During the experiment we tested the abatement of 13 pharmaceutical compounds (atenolol, carbamazepine, ciprofloxacin, clarithromycin, dehydro-erythromycin, diclofenac, furosemide, ibuprofen, hydrochlorothiazide,
ketoprofen, naproxen, paracetamol and ofloxacin), 4 illicit drugs (cocaine, benzoylecgonine, methamphetamine and methadone) and 7 heavy metals (Al, Cr, Cu, Fe, Mn, Ni and Pb) after D. polymorpha exposition.
Because of the well-known presence of PPCPs and illicit drugs in the environment, the second part of this project was devoted to the assessment of their ecotoxicological effects. We decided to evaluate the potential chronic toxicity of these chemicals on the same model organism used in the bio-filtration process since D. polymorpha is particularly representative of the aquatic ecosystem and, at the same time, sensitive to environmental changes.
The illicit drugs and PPCPs assayed at environmental concentrations in this study were the following: morphine, 3,4-methylenedioxymethamphetamine (MDMA), tonalide and galaxolide. Furthermore, because in the environment such substances form complex mixtures, we also tested the toxicity of an illicit drugs’ mixture composed by cocaine, benzoylecgonine, morphine, MDMA and amphetamine administered at environmental concentrations.
The chronic toxicity of these substances was investigated by a biomarker battery: cytotoxicity was evaluated by the Neutral Red Retention Assay (NRRA) while, we assessed the activity of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) for monitoring the raise of oxidative stress, the phase II detoxifying enzyme glutathione-Stransferase (GST), as well as the levels of lipid peroxidation (LPO) and protein carbonylation content (PCC) in order to highlight eventual oxidative damage. The potential injury at the genetic level induced by PPCPs and illicit drugs was assessed on D. polymorpha haemocytes by Comet Test, Micronucleus Test (MN test), percentage of apoptotic frequencies (DNA Diffusion Assay) and DNA fragmentation (DNA Precipitation Assay). Finally, the filtration rate of D. polymorpha has been tested as a physiological biomarker.
Data obtained on the D. polymorpha removal ability due to the bio-filtration process are very encouraged. The bivalve activity has shown a great capacity in the concentration reduction of various PPCPs, illicit drugs and mainly heavy metals. The ecological importance of these results is high, taking into account the ecotoxicological effects of these substances on the aquatic communities.
The main results for the evaluation of ecotoxicological effects of some emerging environmental contaminants highlighted that morphine and MDMA seem to induce a significant increase of oxidative stress in the bivalve, but not followed to genetic fixed damage; these results were partially confirmed by the exposure to the illicit drugs’ mixture that showed a significant increase in antioxidant enzyme activity and in protein carbonylation content. Finally, the exposure to the musks galaxolide and tonalide caused a significant increase in the DNA fragmentation percentage on bivalve haemocytes.
Therefore, the results obtained during this research project contributed to point out the importance of new wastewater depuration methods allowing the removal of emerging contaminants whose ecotoxicological effects must not be underestimated, as they may ultimately affect the higher biological levels. Moreover, the use of an invasive species such as D. polymorpha in the depuration context may also have interesting implications for the economic sector and initiate an exploitation processes of alien species, that, being difficult to remove, constitute a serious problem for ecosystems.
Despite the good results obtained, further studies are necessary to clarify both the bio-filtration treatment and toxic effects of illicit drugs and PPCPs on aquatic communities
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
Environmental concentrations of 3,4-methylenedioxymethamphetamine (MDMA)-induced cellular stress and modulated antioxidant enzyme activity in the zebra mussel
No full textRecent monitoring studies showed measurable levels of the 3,4-methylenedioxymethamphetamine (MDMA) in aquatic environments. However, no information is currently available on its potential hazard to aquatic non-target organisms. The aim of this study was to investigate the potential sub-lethal effects induced by 14-day exposures to low MDMA concentrations (0.05 and 0.5 mu g/L) to zebra mussel (Dreissena polymorpha) specimens through the application of a biomarker suite. The trypan blue exclusion method and the neutral red retention assay (NRRA) were used to assess MDMA cytotoxicity. The activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST), as well as the lipid peroxidation (LPO) and protein carbonyl content (PCC), were measured as oxidative stress indexes. The single cell gel electrophoresis (SCGE) assay, the DNA diffusion assay, and the micronucleus test (MN test) were applied to investigate DNA damage, while filtration rate was measured as physiological parameter. Despite significant decrease in lysosome membrane stability, hemocyte viability and imbalances in CAT and GST activities pointed out at the end of the exposure to 0.5 mu g/L, no significant variations for the other end points were noticed at both the treatments, suggesting that environmentally relevant MDMA concentrations did not induce deleterious effects to the zebra mussel
Sublethal effects induced by morphine to the freshwater biological model Dreissena polymorpha
Full text linkOpioids are considered as emerging contaminants in aquatic ecosystems, mainly due to their large illicit consume worldwide. Morphine (MOR) is the main opiate and it was commonly found at measurable concentrations in freshwaters. Even though its occurrence is well documented, just limited information is available regarding its hazard to nontarget organisms. The aim of this study was of the evaluation of sublethal effects induced by MOR to the freshwater bivalve Dreissena polymorpha. We exposed mussels to two MOR concentrations (0.05 μg/L and 0.5 μg/L) for 14 days and we investigated the sublethal effects by a suite of biomarkers. The Neutral Red Retention Assay (NRRA) was used as a test of cytotoxicity, while the oxidative stress was evaluated by the activity of antioxidant and detoxifying enzymes, namely catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), and by measuring the levels of lipid peroxidation (LPO) and protein carbonylation (PCC). The genetic damage was assessed by the Single Cell Gel Electrophoresis (SCGE) assay, the DNA diffusion assay and the micronucleus test (MN test). Finally, the filtration rate of D. polymorpha was evaluated in order to investigate possible physiological effects. Both tested concentrations reduced the lysosome membrane stability of bivalves, but only the highest MOR concentration induced significant changes in the activity of antioxidant enzymes (SOD, CAT, and GPx) and increase in lipid peroxidation levels. Slight increase in primary DNA fragmentation was noticed, while no fixed genetic damage and alterations of the filtering rate were found
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