A hierarchical model for the analysis of spatial rainfall extremes

In this article, we propose a spatial model for analyzing extreme rainfall values over the Triveneto region (Italy). We assess the existence of a long-term trend in the extremes. To integrate data coming from the different stations, we propose a hierarchical model. At the first level, for each monitoring station we model data by making use of a generalized extreme value distribution; at the second level, we combine results from the first stage by exploiting recent advances in modeling nonstationary spatial random fields.     

Development of new fungicides against Magnaporthe grisea: synthesis and biological activity of pyrazolo[3,4-d][1,3]thiazine,pyrazolo[1,5-c][1,3,5]thiadiazine,and pyrazolo[3,4-d]pyrimidine derivatives

Some pyrazolo[3,4-d]pyrimidin-4(5H)-thione, pyrazolo[3,4-d][1,3]thiazin-4-one/thione, and pyrazolo[1,5-c][1,3,5]thiadiazine-4-one/thione derivatives were synthesized and screened for antifungal activity against the causal agent of rice blast disease, Magnaporthe grisea. In all cases a remarkable inhibition of fungal growth was found in the range from 10 to 200 microg x mL(-1). Several compounds were able to control mycelium growth at a rate of 10 microg x mL(-1), a concentration at which the reference compound tricyclazole was completely ineffective. At least in the case of the most active substance, at the same dose the growth of seedlings or cultured cells of rice was substantially unaffected. Results allowed definition of structural requirements either to maintain or to enhance mycotoxic activity.     

Phytochemical changes induced by different nitrogen supply forms and radiation levels in two leafy Brassica species

The effect of three different nitrogen (N) supply forms differing in their ammonium-to-nitrate (NH(4):NO(3)) ratio (100% NH(4), 50% NH(4) + 50% NO(3), 100% NO(3)) under three different levels of daily photosynthetic active radiation (PAR) (low, 5.0; medium, 6.8; high, 9.0 mol m(-2) day(-1)) on a range of desirable health-promoting phytochemicals in Brassica rapa subsp. nipposinica var. chinoleifera and Brassica juncea was determined. The 100% NH(4) supply under medium PAR levels led to the highest concentration of glucosinolates based on a low nitrogen/sulfur ratio as well as high levels of carotenoids in the leaves of both Brassica species. However, the 100% NH(4) supply under low and medium PAR levels resulted in low concentrations of flavonoids based on high N concentration in the leaves. Thus, the data provided here have strong implications for crop management strategies aimed at optimizing both the concentration and composition of a range of phytochemicals.     

Use of electrochemical biosensor and gas chromatography for determination of dichlorvos in wheat

Two methods for the determination of dichlorvos in durum wheat by electrochemical assay and gas chromatography, respectively, have been developed. Dichlorvos, an organophosphorus anticholinesterase pesticide, was extracted from wheat with hexane, and the filtered extract was directly analyzed by gas chromatography with nitrogen-phosphorus flame detection (NPD). Recoveries of dichlorvos from milled wheat spiked at 0.25-1.5 microg/g ranged from 96.5 to 100.9%, and the limit of detection was 0.02 microg/g. The electrochemical assay was based on the detection of choline, the acetylcholinesterase product, via a choline oxidase biosensor. An aliquot of the filtered hexane extract was partitioned with phosphate buffer solution, and the organic layer was evaporated prior to electrochemical analysis. A limit of detection of 0.05 microg/g of dichlorvos was obtained with mean recoveries of 97-103% at spiking levels of 0.25-1.5 microg/g. A good correlation (r = 0.9919) was found between the results obtained with the electrochemical and those obtained with the gas chromatographic methods. The electrochemical method was peer-validated in two laboratories that analyzed 10 blind samples (5 duplicates), including a blank and 4 spiked samples with dichlorvos at levels of 0.25, 0.60, 1.00, and 1.50 microg/g. Within-laboratory repeatability (RSDr) and between-laboratory reproducibility (RSDR) ranged from 5.5 to 7.8% and from 9.9 to 17.6%, respectively.     

Contribution of the phenolic fraction to the antioxidant activity and oxidative stability of olive oil

Antioxidant activity of the phenolic fraction of extra virgin olive oil (EVOO) was measured by means of a chemical and an electrochemical method. Both methods were tested in predicting the oxidative spoilage and stability to oxidation of 22 EVOO samples and resulted correlated with peroxide values and oxidative stability measured by Rancimat. The main phenolic compounds of EVOOs were detected by HRGC. To study the contribution of single polyphenols (PPs) to antioxidant activity of phenolic fraction and oxidative stability of EVOOs, multivariate statistical analyses were applied on HRGC data. An isomer of oleuropein aglycon was shown to affect significantly antioxidant activity of phenolic fraction but not oil stability to oxidation. No individual compounds was identified as the main cause of the overall antioxidant activity, and the total polyphenol determination by the Folin reagent was better correlated to antioxidant activity and oxidative stability than each tested PP or PPs groups such as o-diphenols.     

Comparison among differential pulse voltammetry, amperometric biosensor, and HPLC/DAD analysis for polyphenol determination

Polyphenols are widespread in vegetables and fruits. They can play an important role in human diet and health, and they influence the sensorial properties of many foods, and act as natural antioxidants. This study was conducted using HPLC/DAD, tyrosinase biosensor, and differential pulse voltammetry (DPV) analyses to detect polyphenolic compounds in natural complex matrices. The analyses were applied to a series of both standards and natural extracts derived from grape, olives, and green tea. The pure compounds include phenolic acids, flavones, flavonols, catechins, tannins, and oleuropein. HPLC/DAD, DPV, and the biosensor approach were used as independent analytical techniques. Bare graphite screen-printed electrodes were employed in DPV and in the biosensor analysis. The most accurate data were obtained by HPLC/DAD analysis, while the DPV approach using screen-printed electrodes could represent a quick screening method for the determination of polyphenols in natural extracts. Use of the biosensor for the analysis of complex matrices needs further study in order to improve its performance.     

Latent Process Modelling of Threshold Exceedances in Hourly Rainfall Series

Two features are often observed in analyses of both daily and hourly rainfall series. One is the tendency for the strength of temporal dependence to decrease when looking at the series above increasing thresholds. The other is the empirical evidence for rainfall extremes to approach independence at high enough levels. To account for these features, Bortot and Gaetan (Scand J Stat 41:606–621, 2014) focus on rainfall exceedances above a fixed high threshold and model their dynamics through a hierarchical approach that allows for changes in the temporal dependence properties when moving further into the right tail. It is found that this modelling procedure performs generally well in analyses of daily rainfalls, but has some inherent theoretical limitations that affect its goodness of fit in the context of hourly data. In order to overcome this drawback, we develop here a modification of the Bortot and Gaetan model derived from a copula-type technique. Application of both model versions to rainfall series recorded in Camborne, England, shows that they provide similar results when studying daily data, but in the analysis of hourly data the modified version is superior.     

Evaluation of the antioxidant capacity of individual phenolic compounds in virgin olive oil

Virgin olive oil has a high resistance to oxidative deterioration due to its tryacylglycerol composition low in polyunsaturated fatty acids and due to the presence of a group of phenolic antioxidants composed mainly of polyphenols and tocopherols. We isolated several phenolic compounds of extra virgin olive oil (phenyl-ethyl alcohols, lignans, and secoiridoids) by semipreparative high-performance liquid chromatography (HPLC) and identified them using ultraviolet, atmospheric pressure chemical ionization, and electrospray ionization MS detection. The purity of these extracts was confirmed by analytical HPLC using two different gradients. Finally, the antioxidant capacity of the isolated compounds was evaluated by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl radical, by accelerated oxidation in a lipid model system (OSI, oxidative stability instrument), and by an electrochemical method.