Causes and consequences of asymmetric lateral plume flow during South Atlantic rifting.

Volcanic rifted margins are typically associated with a thick magmatic layer of seaward dipping reflectors and anomalous regional uplift. This is conventionally interpreted as due to melting of an arriving mantle plume head at the onset of rifting. However, seaward dipping reflectors and uplift are sometimes asymmetrically distributed with respect to the subsequent plume track. Here we investigate if these asymmetries are induced by preexisting lateral variations in the thickness of continental lithosphere and/or lithospheric stretching rates, variations that promote lateral sublithospheric flow of plume material below only one arm of the extending rift. Using three-dimensional numerical experiments, we find that South Atlantic rifting is predicted to develop a strong southward asymmetry in its distribution of seaward dipping reflectors and associated anomalous relief with respect to the Tristan Plume that "drove" this volcanic rifted margin, and that the region where plume material drains into the rift should experience long-lived uplift during rifting-both as observed. We conclude that a mantle plume is still needed to source the anomalously hot sublithospheric material that generates a volcanic rifted margin, but lateral along-rift flow from this plume, not a broad starting plume head, is what controls when and where a volcanic rifted margin will form.

Behavioral strategies for periodontal health.

The impact of lifestyle factors has been increasingly studied and discussed in oral healthcare. Positive lifestyle factors are important in maintaining oral health or controlling disease, but they are not easy to adopt over the long term. Along with public health initiatives within communities and groups, there is a role for behavior change interventions delivered in dental practice settings to improve the periodontal health of individuals. Behavior management is now seen as a part of both prevention and therapy of periodontal diseases. This article summarizes the evidence on behavioral strategies for periodontal health to inform and assist oral healthcare professionals in implementing behavior change in their practice. In addition, strategies for education and training in communication and behavior change techniques are considered.

Insecticidal properties and chemical composition of Piper aduncum L., Lippia sidoides Cham. and Schinus terebinthifolius Raddi essential oils against Plutella xylostella L.

In the laboratory, were evaluated the effects (residual contact and feeding deterrence) of the essential oils from the leaves of Piper aduncum, Lippia sidoides and Schinus terebinthifolius, as well as eleven selected constituents and binary blends of oils in different proportions against 3rd instar larvae of Plutella xylostella (L.). The Piper oil demonstrated the greatest toxicity (LC50 = 0.31 µL/mL) and feeding deterrence (DC50 = 1.08 µL/mL) between oils tested. Dillapiole (LC50 = 1.01 µL/mL; DC50 = 1.10 µL/mL) and carvacrol (LC50 = 6.03 µL/mL; DC50 = 0.075 µL/mL) demonstrated the greatest toxicity and feeding deterrence between constituents tested, respectively. Based on the fractional effects indices for the blends, a synergistic interaction was found for the blend of the Lippia and Schinus oils at a proportion of 75 and 25%, respectively. The present findings indicate that this blend could be used in the control of P. xylostella, as the literature reports populations resistant to the active ingredient in the positive control, Premio®. Further studies are needed for the development of a new botanical insecticide based on the active ingredients in oils from L. sidoides and S. terebinthifolius to improve efficiency, stability and the cost-benefit in the control of P. xylostella.

Acaricidal activity of binary blends of essential oils and selected constituents against Tetranychus urticae in laboratory/greenhouse experiments and the impact on Neoseiulus californicus.

The aim of this study was to test the effectiveness of essential oils form Piper aduncum, Melaleuca leucadendra and Schinus terebinthifolius and their blends by fumigation and residual contact on Tetranychus urticae and its natural enemy, Neoseiulus californicus. Bioassays were performed in a greenhouse with the best blend of the oils and compared to the individual oils and Vertimec® (positive control). The main constituents identified by GC-MS were dillapiole, (E)-nerolidol and limonene in the oils from P. aduncum (76.5%), M. leucadendra (87.3%) and S. terebinthifolius (unripe/ripe fruits, 42.5/34.1%). The P. aduncum and M. leucadendra oils were the most toxic to the pest. Among the blends, the greatest toxicity to T. urticae occurred by residual contact with the M. leucadendra + S. terebinthifolius ripe fruit blend (50/50). The evaluation of the effects on N. californicus showed the compatibility of the oils and blends with the predator mite for use in the integrated management of T. urticae. ß-Caryophyllene was the most toxic, independent of the method used. Based on toxicities of 11 oil constituents, the structure-activity relationship of these compounds is also discussed. This study showed that the acaricidal effect of the Piper, Melaleuca and Schinus oils can easily be increased by the binary combination of these oils. The binary blend between the oils of the Melaleuca leaves and ripe Schinus fruit in the greenhouse was effective at controlling the mite after 72 h, exhibiting the same level of toxicity as that found for the positive control (Vertimec 18 EC).

Self-regulation in oral hygiene behaviours in adults with gingivitis: The mediating role of coping planning and action control.

AIM: This study investigates the joint role of volitional predictors of oral hygiene behaviours of flossing and brushing in adults with gingivitis, framed by the Health Action Process Approach model (HAPA). MATERIALS AND METHODS: In a longitudinal online survey, 201 participants aged 18-75, of which 56.7% were women, completed assessments at baseline(T1), 2 weeks(T2) and 4 months(T3). Oral hygiene behaviours(OH) (brushing and flossing) and social cognitive determinants of behaviour in the HAPA: action and maintenance self-efficacy(ASE & MSE), intention(INT), coping planning(CP) and action control(AC) were evaluated. Structural equation modelling was used to test a series of three nested models. In Model 1, action self-efficacy would determine MSE and INT, and INT would determine OH; in Model 2, INT would determine both CP and AC and the two OH behaviours; and in Model 3, CP and AC would be sequential mediators between INT and OH. RESULTS: Model 3, predicting a mediating process from intention to behaviour via coping planning and action control, showed the best fit according to the fit indices and explained more of the variance in dental hygiene. The mediating role of coping planning and action control between intention and oral hygiene behaviours was thus confirmed. Importantly, coping planning did not mediate between intention and oral hygiene behaviours, which means that oral hygiene intention influences action control through coping planning, and both sequentially mediate this influence on behaviour. CONCLUSIONS: For individuals who are not yet following the recommendations for specific oral hygiene behaviours, coping planning and action control represent psychological mechanisms by which intentions are put into practice.

AGK-BRAF is associated with distant metastasis and younger age in pediatric papillary thyroid carcinoma.

BACKGROUND: The incidence of thyroid carcinoma has increased in most populations, including pediatric patients. The increase is almost exclusively due to an increase in the incidence of papillary thyroid carcinoma (PTC). Genetic alterations leading to mitogen-activated protein kinase (MAPK) pathway activation are highly prevalent in PTC, with BRAF V600E mutation being the most common event in adult PTC. Although a lower prevalence of BRAF V600E had been reported among pediatric patients, a higher prevalence of BRAF fusion has been identified in both radiation-exposed and sporadic pediatric PTC. However, little is known about the prognostic implications of BRAF fusions in pediatric PTC. PROCEDURE: In this study, we investigated the prevalence of BRAF alterations (AGK-BRAF fusion and BRAF V600E mutation) in a large set of predominantly sporadic pediatric PTC cases and correlate with clinicopathological features. Somatic AGK-BRAF fusion was investigated by RT-PCR and confirmed by FISH break-apart. The BRAF V600E mutation was screened using Sanger sequencing. RESULTS: AGK-BRAF fusion, found in 19% of pediatric PTC patients, was associated with distant metastasis and younger age. Conversely, the BRAF V600E, found in 15% of pediatric PTC patients, was correlated with older age and larger tumor size. CONCLUSION: Collectively, our results advance knowledge concerning genetic bases of pediatric thyroid carcinoma, with potential implications for diagnosis, prognosis, and therapeutic approaches.

An eight-month randomized controlled trial on the use of intra-oral cameras and text messages for gingivitis control among adults.

OBJECTIVE: To investigate the effects of using an intra-oral camera (IOC) during a dental hygiene consultation and mobile text messages (TM) between appointments on clinical, behavioural and psychological parameters of patients with gingivitis. MATERIALS AND METHODS: Patients were randomly assigned into four conditions: IOC, TM, IOC + TM and control, and examined at three assessment points over eight months (N = 142). Bleeding on marginal probing (BOMP), dental hygiene (brushing and flossing) and social cognitive determinants of behaviour change (outcome expectancies, action and volitional self-efficacy, intention, planning and action control) were evaluated in an examiner-blind controlled study. Mixed-effects modelling was employed to examine changes in study outcomes. Mediations by the psychological determinants were inspected for the effect on treatment groups in clinical parameters and behaviour. RESULTS: Compared to the control group, all treatment conditions improved dental hygiene and revealed a significant decrease in BOMP from baseline to 4 months, maintained at 8 months; this was clinically relevant in the IOC + TM group, where individuals had more positive outcome expectancies as well as higher levels of action self-efficacy and intention from baseline to four months, maintained at eight months. Volitional self-efficacy was reinforced in all treatments. The psychological determinants did not prove to be the mechanisms responsible for these effects. CONCLUSIONS: A multiple-strategy benefit from using the IOC in consultation and TM between appointments improves clinical, behavioural and psychological parameters of periodontal health four months after treatment, maintained at eight months' follow-up. Insights are provided for the efficacy of the images and text messages for oral hygiene changes.

Macroemulsion-based dispersive magnetic solid phase extraction for preconcentration and determination of copper(II) in gasoline.

A new method referred to as microemulsion-based Dispersive Magnetic Solid-Phase Extraction (MDM-SPE) is presented for use in the extraction and preconcentration of metal ions from complex organic matrices. MDM-SPE combines the features of magnetic nanoparticles (MNPs) and microemulsions. It was successfully applied to the extraction of copper(II) from gasoline prior to its determination by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS). The material for use in MDM-SPE was obtained by first functionalizing MNPs of the type Fe3O4@Al2O3 with sodium dodecyl sulfate and the chelator 1-(2-pyridylazo)-2-naphthol (PAN) dispersed in 1-propanol. The resulting functionalized magnetic MNPs were dispersed in a microemulsion prepared from gasoline, buffer, and 1-propanol. After waiting for 5 s (during which the formation of the copper complex on the MNPs is complete), the MNPs are magnetically separated. The complex was then eluted with 2 mol L-1 HNO3, and the eluate submitted to GF-AAS. Various parameters were optimized. Copper(II) can be quantified by this method over a linear range that extends from 2.0 to 10.0 µg·L-1. Other figures of merit include (a) a 37 ng·L-1 detection limit, (b) a repeatability of 1.1%, (c) a reproducibility of 2.1%, and (d) an enrichment factor of nine. The high surface-to-volume ratio of the microemulsion containing the dispersed magnetic sorbent warrants an efficient contact for reaction between copper(II) and the complexing agent, and this results in fast (about 40 s) extraction and pre-concentration of copper(II). MDM-SPE is accurate, precise and efficient. Microemulsions do not break down, and phase separation, heating, laborious, and time-consuming sample preparation, and incorporation of impurities into the graphite furnace (which can generate inaccuracies in GF-AAS analysis) are not needed. Graphical abstract Schematic of a new method for Microemulsion-based Dispersive Magnetic Solid-Phase Extraction (MDMSPE) using functionalized magnetic nanoparticles (FMNPs). It was applied to the preconcentration of copper(II) in gasoline.

Clostridioides difficile infection in dogs with chronic-recurring diarrhea responsive to dietary changes.

Five dogs with chronic-recurring diarrhea were positive for Clostridioides difficile infection (CDI), but were unresponsive to treatment with metronidazole. One of these animals was subjected to a colonoscopy, which revealed eosinophilic infiltration of the colon. All five animals completely recovered after dietary changes. The present work suggests that CDI might occur in dogs with other intestinal alterations. In addition, this report suggests that dysbiosis should be considered in animals that have chronic-recurring diarrhea and test positive for C. difficile.

Rivaroxaban Used in the Treatment Patients With Gynecologic Cancer and Venous Thromboembolism: The Experience of Instituto Nacional de Câncer-Rio de Janeiro, Brazil.

INTRODUCTION: Venous thromboembolism (VTE) is a major complication of malignant diseases and is a frequent cause of death in patients with cancer. Managing anticoagulation in these patients is challenging because of the high risk of recurrent VTE and bleeding events. Rivaroxaban is an oral anticoagulant that provides rapid onset of anticoagulation. OBJECTIVE: The aim of this study was to describe the complications of rivaroxaban and potentially associated factors in patients with gynecologic cancer and VTE. METHODS: This was an observational study in women with gynecological cancer who developed VTE and were treated with 15 and 20 mg rivaroxaban at Instituto Nacional de Câncer from July 2014 to July 2015. RESULTS: Forty-one patients were treated with rivaroxaban. Most patients were younger than 60 years and presented cervical cancer; 58.5% of women did not have complications, thus remaining at a dose of 20 mg/d. Because of complications, 12.2% had the dose reduced to 15 mg/d, 12.2% had the drug suspended, 7.3% had progressive worsening of the disease with suspension of anticoagulation, and 9.8% progressed to death because of progression of the disease. CONCLUSIONS: Rivaroxaban has been documented as a low-cost, easily controlled option compared with standard therapy. Most participants in this study had no complications. However, it was not possible to assess associations with statistical significance. Further analytical studies with larger samples are required to evaluate the safety and efficacy of this treatment in patients with gynecologic cancer.

Second-order capillary electrophoresis diode array detector data modeled with the Tucker3 algorithm: A novel strategy for Argentinean white wine discrimination respect to grape variety.

Data obtained by capillary electrophoresis with diode array detection (CE-DAD) were modeled with the purpose to discriminate Argentinean white wines samples produced from three grape varieties (Torrontés, Chardonnay, and Sauvignon blanc). Thirty-eight samples of commercial white wine from four wine-producing provinces of Argentina (Mendoza, San Juan, Salta, and Rio Negro) were analyzed. CE-DAD matrices with dimensions of 421 elution times (from 1.17 to 7.39 minutes) × 71 wavelengths (from 227 to 367 nm) were joined in a three way data array and decomposed by Tucker3 method under non-negativity constraint, employing 18, 18 and six factors in the modes 1, 2 and 3, respectively. Using the scores of Tucker model, it was possible to discriminate samples of Argentinean white wine by linear discriminant analysis and Kernel linear discriminant analysis. Core element analysis of the Tucker3 model allows identifying the loading profiles in spectral mode related to Argentinean white wine samples.

Species tree phylogeny and biogeography of the Neotropical genus Pradosia (Sapotaceae, Chrysophylloideae).

Recent phylogenetic studies in Sapotaceae have demonstrated that many genera need to be redefined to better correspond to natural groups. The Neotropical genus Pradosia is believed to be monophyletic and includes 26 recognized species. Here we reconstruct the generic phylogeny by a species-tree approach using (∗)BEAST, 21 recognized species (36 accessions), sequence data from three nuclear markers (ITS, ETS, and RPB2), a relaxed lognormal clock model, and a fossil calibration. We explore the evolution of five selected morphological characters, reconstruct the evolution of habitat (white-sand vs. clayish soils) preference, as well as space and time by using a recently developed continuous diffusion model in biogeography. We find Pradosia to be monophyletic in its current circumscription and to have originated in the Amazon basin at ∼47.5Ma. Selected morphological characters are useful to readily distinguish three clades. Preferences to white-sand and/or clay are somewhat important for the majority of species, but speciation has not been powered by habitat shifts. Pradosia brevipes is a relative young species (∼1.3Ma) that has evolved a unique geoxylic life strategy within Pradosia and is restricted to savannahs. Molecular dating and phylogenetic pattern indicate that Pradosia reached the Brazilian Atlantic coast at least three times: at 34.4Ma (P. longipedicellata), at 11.7Ma (P. kuhlmannii), and at 3.9Ma (weakly supported node within the red-flowered clade).

Unfolded partial least squares/residual bilinearization combined with the Successive Projections Algorithm for interval selection: enhanced excitation-emission fluorescence data modeling in the presence of the inner filter effect.

The use of the successive projections algorithm (SPA) for elimination of uninformative variables in interval selection, and unfold partial least squares regression (U-PLS) modeling of excitation-emission matrices (EEM), when under the inner filter effect (IFE) is reported for first time. Post-calibration residual bilinearization (RBL) was employed against events of unknown components in the test samples. The inner filter effect can originate changes in both the shape and intensity of analyte spectra, leading to trilinearity losses in both modes, and thus invalidating most multiway calibration methods. The algorithm presented in this paper was named iSPA-U-PLS/RBL. Both simulated and experimental data sets were used to compare the prediction capability during: (1) simulated EEM; and (2) quantitation of phenylephrine (PHE) in the presence of paracetamol (PAR) (or acetaminophen) in water samples. Test sets containing unexpected components were built in both systems [a single interference was taken into account in the simulated data set, while water samples were added with varying amounts of ibuprofen (IBU), and acetyl salicylic acid (ASA)]. The prediction results and figures of merit obtained with the new algorithm were compared with those obtained with U-PLS/RBL (without intervals selection), and with the well-known parallel factors analysis (PARAFAC). In all cases, U-PLS/RBL displayed better EEM handling capability in the presence of the inner filter effect compared with PARAFAC. In addition, iSPA-U-PLS/RBL improved the results obtained with the full U-PLS/RBL model, in this case demonstrating the potential of variable selection.

One-step microwave-assisted synthesis of fluorescent carbon quantum dots for determination of ascorbic acid and riboflavin in vitamin supplements.

The synthesis of carbon quantum dots (CQDs) using chemical precursors with different organic groups is a strategy to improve optical properties and expand applications in several fields of research such as Analytical Chemistry. Ascorbic acid and riboflavin are widely used in human food supplementation, making quality monitoring of these vitamin supplements relevant and necessary. In this work, disodium ethylenediaminetetraacetic, sodium thiosulfate and urea were applied to obtain CQDs through a single-step microwave-assisted synthesis. The CQDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, infrared spectroscopy, zeta potential measurements, ultraviolet-visible spectroscopy and photoluminescence spectroscopy. The synthesized nanoparticles exhibited satisfactory and stable optical properties with luminescence at 430 nm, water solubility, and fluorescence quantum yield of 8.9 %. They were applied in the quantification of ascorbic acid and riboflavin in vitamin supplements. The fluorescence mechanisms observed were dynamic quenching for the CQDs/Cr(VI) sensor, followed by a return of fluorescence in the presence of ascorbic acid, and static quenching and inner filter effect in the interaction with riboflavin. Factorial designs 23 and 24 were used to optimize the analytical parameters. The CQDs/Cr(VI) sensor used in the determination of ascorbic acid, employing an on-off-on strategy, resulted in a linear range of 0.5 to 50 µg mL-1 and a limit of detection of 0.15 µg mL-1. The ratiometric fluorescence used in the determination of riboflavin resulted in a linear range of 0.1 to 7 µg mL-1 and a limit of detection of 0.09 µg mL-1. The analytical results for ascorbic acid were compared to the reference method of the Brazilian pharmacopeia, showing accuracy and precision according to the Brazilian Health Regulation Agency. Therefore, the synthesized CQDs were used to determine ascorbic acid and riboflavin in vitamin supplements, and the application of this nanomaterial can be expanded to different analytes and matrices, using simple and low-cost analysis techniques.

Long-term monitoring of the fish community in the Minho Estuary (NW Iberian Peninsula).

Background: The paper presents an extensive fish sampling dataset spanning a long-term period from 2010 to 2019. The data were collected in Lenta Marina, an upstream area in the Minho Estuary of the NW Iberian Peninsula, which belongs to a LTSER (Long-Term Socio-Ecological Research) platform. To capture fish, fyke nets were utilised as the sampling method and deployed at Lenta Marina. This dataset offers valuable insights into the abundance of each collected taxa recorded over time. New information: The dataset reports a comprehensive compilation of data on the abundance of fish species observed in the area during the sampling period (includes zeroes when a given taxonomic entity was absent in a given sampling event). It provides a detailed record of the abundances of the fish community through time in a frequent sampling regime (on average, sampling was done every 6 days). The dataset shows that the amount of fish from invasive taxa exceeds the count of fish from native taxa in the Minho Estuary.

Electrochemical study of ricin at glassy carbon electrode.

Ricin, Ricinus communis agglutinin 60 - RCA 60, is a deadly phytotoxic protein which inhibits ribosomes (class II), and there is no known effective antidote in living organisms. Ricin is composed of two polypeptide chains, A and B, linked covalently by a single disulfide bond. The analytical methods for the detection of RCA 60 are commonly laborious, expensive, require skilled labor, and involve sophisticated equipment. Aimed at the development of electroanalytical methods for RCA 60 detection, here we studied the electrochemical oxidation of RCA 60 on a glassy carbon (GC) electrode over a wide pH range, using cyclic voltammetry, differential pulse voltammetry (DPV) and square wave voltammetry (SWV). Two quasi-reversible electrochemical RCA 60 oxidation peaks were identified on the GC electrode by SWV. For values of 2.2 ≤ pH ≤ 10.2, DPV studies revealed that the peak potentials, EP1 and EP2, display a linear dependence with pH and the reaction mechanism involves the transfer of 2H⁺/2e⁻ (peak 1) and 1H⁺/1e⁻ (peak 2). The first and second RCA 60 oxidation steps may correspond to the oxidation of cysteine and tyrosine-tryptophan residues, respectively. The oxidation product of the second RCA 60 oxidation step appears at 7.0 ≤ pH ≤ 11.8. For pH ≥ 10.2, both processes are pH independent, resulting in a pKa of ca. 10.2. A third RCA 60 oxidation peak only appears at acidic pH. RCA 60 samples extracted from different castor seed cultivars showed similar electrochemical behavior, enabling the implementation of an analytical voltammetric method.

Tracing the fate of microcystins from irrigation water to food chains: Studies with Fragaria vulgaris and Meriones shawi.

Microcystins (MCs) are cyanobacterial toxins that can negatively impact human and animal health. This study investigated the bioaccumulation, transfer, depuration, and health risks of MCs in strawberry plants (Fragaria vulgaris) and Meriones shawi animals. The plants were irrigated with 1, 5, 10, and 20 µg/L MCs for 60 days (bioaccumulation phase) and then with clean water for 30 days (depuration phase). The harvested plants (roots and leaves) were then prepared in an aliquot form and used as feed for Meriones shawi. Liquid chromatography-mass spectrometry (LC/MS/MS) was used to measure MC concentrations in plant and animal tissues. The bioaccumulation of MCs was found to be highest in the roots, followed by leaves, fruits, liver, stomach, and fecal matter. The bioaccumulation factor (BAF) was highest in perlite (8.48), followed by roots (5.01), leaves (1.55), stomach (0.87), and fecal matter (1.18), indicating that the parts with high bioaccumulation factor had high translocation of MCs. The transfer of MCs to animal organs was low, and the daily toxin intake of adult consumers of strawberry fruit irrigated with 1, 5, 10, and 20 µg/L MC did not exceed the WHO-recommended limit of 0.04 µg MC-LR/Kg of bw/day. However, fruits from plants irrigated with 10 and 20 µg/L may pose a moderate health risk to children (25 Kg bw), and Meriones' consumption of leaves may pose a significant health risk. After the depuration phase, MC concentration in perlite, roots, leaves, and fruits decreased, indicating that depuration reduced the danger of MC transmission and bioaccumulation. The study also found that glutathione reductase and glutathione S-transferase activity were essential in the depuration of MCs in the tested plants. The findings suggest that legislation regulating the quality of irrigation water in terms of MC concentrations is necessary to prevent detrimental consequences to crops and human exposure.

Getting fat and stressed: Effects of dietary intake of titanium dioxide nanoparticles in the liver of turbot Scophthalmus maximus.

The extensive use of nanomaterials, including titanium dioxide nanoparticles (TiO2 NPs), raises concerns about their persistence in ecosystems. Protecting aquatic ecosystems and ensuring healthy and safe aquaculture products requires the assessment of the potential impacts of NPs on organisms. Here, we study the effects of a sublethal concentration of citrate-coated TiO2 NPs of two different primary sizes over time in flatfish turbot, Scophthalmus maximus (Linnaeus, 1758). Bioaccumulation, histology and gene expression were assessed in the liver to address morphophysiological responses to citrate-coated TiO2 NPs. Our analyses demonstrated a variable abundance of lipid droplets (LDs) in hepatocytes dependent on TiO2 NPs size, an increase in turbot exposed to smaller TiO2 NPs and a depletion with larger TiO2 NPs. The expression patterns of genes related to oxidative and immune responses and lipid metabolism (nrf2, nfκb1, and cpt1a) were dependent on the presence of TiO2 NPs and time of exposure supporting the variance in hepatic LDs distribution over time with the different NPs. The citrate coating is proposed as the likely catalyst for such effects. Thus, our findings highlight the need to scrutinize the risks associated with exposure to NPs with distinct properties, such as primary size, coatings, and crystalline forms, in aquatic organisms.

Microcystin-LR and chemically degraded microcystin-LR electrochemical oxidation.

Microcystins (MCs) are cyclic hepatotoxic heptapeptides produced by certain strains of freshwater cyanobacteria toxic for humans and animals. The electrochemical behaviour of microcystin-LR (MC-LR) at a glassy carbon electrode (GCE) was investigated using cyclic voltammetry (CV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV). The oxidation of MC-LR is a diffusion-controlled irreversible and pH-independent process that occurs with the transfer of only one electron and does not involve the formation of any electroactive oxidation product. Upon incubation in different pH electrolytes, homogeneous degradation of MC-LR in solution was electrochemically detected by the appearance of a new oxidation peak at a lower potential. The electrochemical behaviour of chemically degraded MC-LR is an irreversible, pH-dependent process, and involves the formation of two redox products that undergo reversible oxidation. The formation of degradation products of MC-LR was confirmed by HPLC with UV detection at room temperature. Experiments were also carried out in solutions containing constituent MC-LR amino acids, which enabled the understanding of the MC-LR electron transfer reaction and degradation. An oxidation mechanism for MC-LR is proposed.

Acaricidal activity and repellency of essential oil from Piper aduncum and its components against Tetranychus urticae.

The chemical composition of essential oil of leaves of Piper aduncum L., growing wild in a fragment of the Atlantic Rainforest biome in northeastern Brazil, was determined through gas chromatography-mass spectrometry. The acaricidal activity and repellency of the essential oil and its components [dillapiole (0.28 g/ml), α-humulene (0.016 g/ml), (E)-nerolidol (0.0007 g/ml) and ß-caryophyllene (0.0021 g/ml)] were evaluated in the laboratory against adults of Tetranychus urticae Koch. The mites were more susceptible to the oil in fumigation tests (LC(50) = 0.01 µl/l of air) than in contact test with closed Petri dish (LC(50) = 7.17 µl/ml); mortality was reduced by approximately 50 % in the latter test. The repellent action of the oil and toxicity by fumigation and contact did not differ significantly from the positive control (eugenol). The repellent activity was attributed to the components (E)-nerolidol, α-humulene and ß-caryophyllene, whereas toxicity by fumigation and contact was attributed to ß-caryophyllene. The effect of Piper oil and the role of its components regarding host plant preference with a two-choice leaf disk test are also discussed.