On the period function of Newtonian systems

We study the existence of centers of planar autonomous system of the form $$(S) \quad \dot x=y,\qquad \dot y = -h(x) - g(x)y - f(x)y^2.$$ We are interested in the period function $T$ around a center 0. A sufficient condition for the isochronicity of (S) at 0 is given. Such a condition is also necessary when $f,g,h$ are analytic functions. In that case a characterization of isochronous centers of system (S) is given. Some applications will be derived. In particular, new families of isochronous centers will be describedComment: 16 page

Subharmonic solutions for nonautonomous sublinear first order Hamiltonian systems

In this paper, the existence of subharmonic solutions for a class of non-autonomous first-order Hamiltonian systems is investigated. We also study the minimality of periods for such solutions. Our results which extend and improve many previous results will be illustrated by specific examples. Our main tools are the minimax methods in critical point theory and the least action principle. {\bf Key words.} Hamiltonian systems. Critical point theory. Least action principle. Subharmonic solutions.Comment: 17 page

Behavior of new entries and developed tomato hybrids carrying Ty-2 gene

Tomato yellow leaf curl disease (TYLCD) is a serious problem hampering tomato production worldwide. In the Mediterranean Basin, disease incidence and severity are higher in the dry season increasing whitefly (Bemisia tabaci) populations. Effectiveness of resistance to Tomato yellow leaf curl virus (TYLCV) depends on both tomato host resistance and TYLCV complex species. So far, six different Ty tomato resistance genes have been identified. Two main TYLCV complex species, Tomato yellow leaf curl virus-Israel (TYLCV-Is) and Tomato yellow leaf curl Sardinia virus (TYLCSV), have been identified in Tunisia. The present work aimed to evaluate entries heterozygous for Ty-2 gene to help predict hybrid performance. Two tomato entries homozygous for the Ty-2 TYLCV resistance gene, one tomato hybrid homozygous for Ty-2 and two heterozygous hybrids were included, besides two susceptible tomato entries. Resistance response to TYLCD was recorded based on disease incidence and severity levels. Data analysis was performed according to presence/absence of Ty-2 gene and taking into account homozygosity and heterozygosity of Ty-2. Generalized linear model analysis was applied to check significance of individual factors' effects (i.e. effect of tomato entries or tomato groups of entries based on presence or absence of homozygous/heterozygous Ty-2 gene, block unit within the field trial and the year of the trial) on the dependent variables (disease incidence and severity). Further multi-comparison tests gave evidence on significant effect of Ty-2 homozygous gene tomato entries on TYLCD incidence and severity levels. The results were discussed with special focus on the relevance use of heterozygous hybrid tomato varieties

Metabolism of triflumuron in the human liver: Contribution of cytochrome P450 isoforms and esterases.

Abstract Triflumuron (TFM) is a benzoylurea insecticide commonly used in Tunisian agriculture and around the world to control crop pests and flies as a promising alternative to conventional insecticides for its arthropod specificity and low toxicity. From the evidence available in animal models, it can be expected that the metabolism of TFM is catalyzed by cytochrome P450 (CYP) and esterases. However, no data are available on human metabolism of TFM with regards to phase I metabolism and CYP isoform specificity. Hence, this manuscript describes experimental investigations to underpin in vitro phase I TFM metabolism in human samples for the first time. TFM biotransformation by recombinant human CYPs was characterized, then human liver microsomes (HLM) and chemical specific inhibitors have been used to identify the relative contribution of CYPs and esterases. Our results showed that all CYP isoforms were able to metabolize TFM with different affinity and efficiency. The relative contribution based both on the kinetic parameters and the CYP hepatic content was 3A4 > >2C9 > 2C8 > 2A6 > 1A2 > 2B6 > 2D6 > 2C19 > 2C18 > 1A1 at low TFM concentration, whilst at high TFM concentration it was 1A2 > >2C9 = 3A4 = 2A6 > 2C19 > 2B6 = 2C8 > 2D6 > 1A1 > 2C18. Experiments with HLMs confirmed the involvement of the most relevant CYPs in the presence of specific chemical inhibitors with a catalytic efficiency (Cliapp) lower by an order of magnitude compared with recombinant enzymes. Esterases were also relevant to the overall TFM kinetics and metabolism, with catalytic efficiency higher than that of CYPs. It is foreseen that such isoform-specific information in humans will further support in silico models for the refinement of the human risk assessment of single pesticides or mixtures

The implication of ROS production on triflumuron-induced oxidative stress and genotoxicity in human colon carcinoma (HCT-116) cells

The aim of this study is to evaluate the cytotoxic and the genotoxic effects of triflumuron (TFM) on human colon carcinoma cells (HCT-116). Indeed, TFM is used to protect vegetables, fruits, and domestic animals against a large spectrum of parasites causing animal and human disorders. However, studies revealing its toxicity and its mode of action in mammalian systems remain very limited. We monitored our work with the cytotoxicity assay starting with the cell viability test, the ROS generation, the malondialdehyde (MDA) production, the DNA fragmentation, and the measurement of some antioxidant enzymes activities such as catalase, superoxide dismutase, and the glutathione S-transferase. Also, we measured the mitochondrial transmembrane potential. We showed that TFM induced a dose-dependent cell death. This decrease in cell viability was accompanied by a significant reduction in the mitochondrial membrane potential. We also have shown that TFM induced oxidative stress as revealed by the generation of reactive oxygen species, the increase of the MDA levels, and the activation of the antioxidant enzymes. Moreover, our results indicated that TFM induced DNA damage in HCT-116 cells as monitored by the comet assay. We demonstrate, for the first time, the cytotoxic and the genotoxic potentials of TFM on human cultured cells

Modeling Ultrasonically Assisted Convective Drying of Eggplan

[EN] Modeling constitutes a fundamental tool with which to analyze the influence of ultrasound on mass transfer phenomena during drying. In this work, the study of the effect of power ultrasound application on the drying kinetics of eggplant was addressed by using different models based on theoretical (diffusion) or empirical approaches. Drying kinetics of eggplant cylinders (height 20mm and diameter 24 mm) were carried at 40°C and 1 m/s applying different ultrasonic powers: 0, 6, 12, 19, 25, 31, and 37 kW/m 3. The experiments were carried out at least three times at each different ultrasonic power. Shrinkage and sorption isotherms were also addressed in order to attain an optimal description of eggplant drying. Applying ultrasound sped up the drying kinetics. The ultrasonic power was identified as having a significant (p<0.05) influence on both the effective moisture diffusivity and the mass transfer coefficient, which was well explained by linear relationships. The most complex model, which considered both external resistance and shrinkage to be significant phenomena, provided the best agreement with experimental data, giving percentages of explained variance of over 99.9% and mean relative errors of under 1.2% in every case. According to these results, ultrasound technology could have the potential to improve the convective drying of eggplant at an industrial scale. © 2011 Taylor & Francis Group, LLC.García Pérez, JV.; Ozuna López, C.; Ortuño Cases, C.; Carcel Carrión, JA.; Mulet Pons, A. (2011). Modeling Ultrasonically Assisted Convective Drying of Eggplan. Drying Technology. 29(13):1499-1509. doi:10.1080/07373937.2011.576321S149915092913Mujumdar, A. S. (2006). An overview of innovation in industrial drying: current status and R&D needs. Transport in Porous Media, 66(1-2), 3-18. doi:10.1007/s11242-006-9018-yChou, S. K., & Chua, K. J. (2001). New hybrid drying technologies for heat sensitive foodstuffs. Trends in Food Science & Technology, 12(10), 359-369. doi:10.1016/s0924-2244(01)00102-9Lewicki, P. P. (2006). Design of hot air drying for better foods. Trends in Food Science & Technology, 17(4), 153-163. doi:10.1016/j.tifs.2005.10.012Santos, P. H. S., & Silva, M. A. (2009). Kinetics ofL-Ascorbic Acid Degradation in Pineapple Drying under Ethanolic Atmosphere. Drying Technology, 27(9), 947-954. doi:10.1080/07373930902901950Suvarnakuta, P., Devahastin, S., & Mujumdar, A. S. (2005). Drying Kinetics and β-Carotene Degradation in Carrot Undergoing Different Drying Processes. Journal of Food Science, 70(8), s520-s526. doi:10.1111/j.1365-2621.2005.tb11528.xMayor, L., & Sereno, A. M. (2004). Modelling shrinkage during convective drying of food materials: a review. Journal of Food Engineering, 61(3), 373-386. doi:10.1016/s0260-8774(03)00144-4Gallego-Juarez, J. A. (2010). High-power ultrasonic processing: Recent developments and prospective advances. Physics Procedia, 3(1), 35-47. doi:10.1016/j.phpro.2010.01.006De la Fuente-Blanco, S., Riera-Franco de Sarabia, E., Acosta-Aparicio, V. M., Blanco-Blanco, A., & Gallego-Juárez, J. A. (2006). Food drying process by power ultrasound. Ultrasonics, 44, e523-e527. doi:10.1016/j.ultras.2006.05.181García-Pérez, J. V., Cárcel, J. A., Riera, E., & Mulet, A. (2009). Influence of the Applied Acoustic Energy on the Drying of Carrots and Lemon Peel. Drying Technology, 27(2), 281-287. doi:10.1080/07373930802606428García-Pérez, J. V., Cárcel, J. A., Clemente, G., & Mulet, A. (2008). Water sorption isotherms for lemon peel at different temperatures and isosteric heats. LWT - Food Science and Technology, 41(1), 18-25. doi:10.1016/j.lwt.2007.02.010Mulet, A. (1994). Drying modelling and water diffusivity in carrots and potatoes. Journal of Food Engineering, 22(1-4), 329-348. doi:10.1016/0260-8774(94)90038-8Cunha, L. M., Oliveira, F. A. R., & Oliveira, J. C. (1998). Optimal experimental design for estimating the kinetic parameters of processes described by the Weibull probability distribution function. Journal of Food Engineering, 37(2), 175-191. doi:10.1016/s0260-8774(98)00085-5Azzouz, S., Guizani, A., Jomaa, W., & Belghith, A. (2002). Moisture diffusivity and drying kinetic equation of convective drying of grapes. Journal of Food Engineering, 55(4), 323-330. doi:10.1016/s0260-8774(02)00109-7Simal, S., Femenia, A., Garau, M. C., & Rosselló, C. (2005). Use of exponential, Page’s and diffusional models to simulate the drying kinetics of kiwi fruit. Journal of Food Engineering, 66(3), 323-328. doi:10.1016/j.jfoodeng.2004.03.025Maroulis, Z. B., Saravacos, G. D., Panagiotou, N. M., & Krokida, M. K. (2001). MOISTURE DIFFUSIVITY DATA COMPILATION FOR FOODSTUFFS: EFFECT OF MATERIAL MOISTURE CONTENT AND TEMPERATURE. International Journal of Food Properties, 4(2), 225-237. doi:10.1081/jfp-100105189Simal, S., Femenia, A., Garcia-Pascual, P., & Rosselló, C. (2003). Simulation of the drying curves of a meat-based product: effect of the external resistance to mass transfer. Journal of Food Engineering, 58(2), 193-199. doi:10.1016/s0260-8774(02)00369-2Queiroz, M. R., & Nebra, S. A. (2001). Theoretical and experimental analysis of the drying kinetics of bananas. Journal of Food Engineering, 47(2), 127-132. doi:10.1016/s0260-8774(00)00108-4Hassini, L., Azzouz, S., Peczalski, R., & Belghith, A. (2007). Estimation of potato moisture diffusivity from convective drying kinetics with correction for shrinkage. Journal of Food Engineering, 79(1), 47-56. doi:10.1016/j.jfoodeng.2006.01.025Hernández, J. A., Pavón, G., & Garcı́a, M. A. (2000). Analytical solution of mass transfer equation considering shrinkage for modeling food-drying kinetics. Journal of Food Engineering, 45(1), 1-10. doi:10.1016/s0260-8774(00)00033-9Souma, S., Tagawa, A., & Iimoto, M. (2004). Structural Properties for Fruits and Vegetables during Drying. NIPPON SHOKUHIN KAGAKU KOGAKU KAISHI, 51(11), 577-584. doi:10.3136/nskkk.51.577García-Pérez, J. V., Cárcel, J. A., de la Fuente-Blanco, S., & Riera-Franco de Sarabia, E. (2006). Ultrasonic drying of foodstuff in a fluidized bed: Parametric study. Ultrasonics, 44, e539-e543. doi:10.1016/j.ultras.2006.06.059Cárcel, J. A., García-Pérez, J. V., Riera, E., & Mulet, A. (2007). Influence of High-Intensity Ultrasound on Drying Kinetics of Persimmon. Drying Technology, 25(1), 185-193. doi:10.1080/07373930601161070Blasco, M., García-Pérez, J. V., Bon, J., Carreres, J. E., & Mulet, A. (2006). Effect of Blanching and Air Flow Rate on Turmeric Drying. Food Science and Technology International, 12(4), 315-323. doi:10.1177/1082013206067352Garau, M. C., Simal, S., Femenia, A., & Rosselló, C. (2006). Drying of orange skin: drying kinetics modelling and functional properties. Journal of Food Engineering, 75(2), 288-295. doi:10.1016/j.jfoodeng.2005.04.017Wu, L., Orikasa, T., Ogawa, Y., & Tagawa, A. (2007). Vacuum drying characteristics of eggplants. Journal of Food Engineering, 83(3), 422-429. doi:10.1016/j.jfoodeng.2007.03.030Chaves , M. ; Sgroppo , S.C. ; Avanza , J.R. Cinéticas de secado de berenjena (Solanum melongenaL.). Comunicaciones Científicas y Tecnológicas (Universidad Nacional del Nordeste Corrientes Argentina),2003,Resumen E-060 .Akpinar, E. K., & Bicer, Y. (2005). Modelling of the drying of eggplants in thin-layers. International Journal of Food Science and Technology, 40(3), 273-281. doi:10.1111/j.1365-2621.2004.00886.xDe Lima, A. (2002). Simultaneous moisture transport and shrinkage during drying of solids with ellipsoidal configuration. Chemical Engineering Journal, 86(1-2), 85-93. doi:10.1016/s1385-8947(01)00276-5RAHMAN, N., & KUMAR, S. (2007). INFLUENCE OF SAMPLE SIZE AND SHAPE ON TRANSPORT PARAMETERS DURING DRYING OF SHRINKING BODIES. Journal of Food Process Engineering, 30(2), 186-203. doi:10.1111/j.1745-4530.2007.00104.

Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Nutritional composition, chlorophyll and β-carotene contents of fennel seeds

Foeniculum vulgare has an important medicinal and economic role due to the frequent use of different parts of the plant. However, fennel seeds are the most exploited especially in culinary preparations and food industries. In order to highlight the benefits of this spice, physico-chemical composition of 7 fennel cultivars was carried out. Results revealed high contents of sugars, proteins and ash, and low contents of fat and water. The highest sugar content was displayed by the cultivar Cv2 (61±1.87 %) and the lowest one was obtained by cultivar Cv5 (31.41±1.77 %). Statistically significant differences between the 7 fennel cultivars were shown among their respective protein contents. Interestingly, all of the 7 cultivars, except one (Cv3: 7.91±0.07 %), revealed high levels of protein contents. Moreover, assessment of physiological parameters of the 7 cultivars gave evidence of high β-carotene contents. Despite, chlorophyll assessment results gave moderate content levels. Taking into account results from the present work, in addition to our previous published findings, 4 fennel cultivars were selected, essentially, based on their nutritional composition while searching for future potential industrial applications

Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Diversity assessment and selection among a local fennel germplasm

Fennel (Foeniculum vulgare Mill.) is a very popular, aromatic, herbaceous plant that belongs to the Apiaceae family. It is among most important spices and medicinal species over the world. Nevertheless, in Tunisia fennel cultivation doesn't cover the local market needs. Also, fennel seeds are produced by farmers traditionally, and none of the local cultivars is named nor labelled in the market. Efforts have been deployed during the present work aiming to the characterization and valorization of genetic fennel resources. Hence, morphological diversity assessment was carried out among 62 entries of fennel acquired from different origins. Two steps principle component analysis (PCA) were applied. It came out with 7 selected cultivars of fennel representative of the initial diversity as assessed within the 62 collected fennel entries. Interestingly, among these latter, some of them exhibited particular phenotypic features linked to production traits