Predictability and Non-Gaussian Characteristics of the North Atlantic Oscillation

AbstractThe North Atlantic Oscillation (NAO) is the dominant mode of climate variability over the North Atlantic basin and has a significant impact on seasonal climate and surface weather conditions. It is the result of complex and nonlinear interactions between many spatiotemporal scales. Here, the authors study the statistical properties of two time series of the daily NAO index. Previous NAO modeling attempts only considered Gaussian noise, which can be inconsistent with the system complexity. Here, it is found that an autoregressive model with non-Gaussian noise provides a better fit to the time series. This result holds also when considering time series for the four seasons separately. The usefulness of the proposed model is evaluated by means of an investigation of its forecast skill

Effect of Thiourea on Yield and Quality of Potato (Solanum tuberosum L.)

A field experiment was carried out to study the effect of five concentrations (0, 250, 500, 750 and 1000 mM) of thiourea application on mother tubers on yield and quality attributes of harvested potato, variety Spunta in the region of Chott-Mariem in Tunisia. Treated tubers (Ш = 50 mm) were planted in field after breaking dormancy at a spacing of 80 cm x 30 cm according to completely randomized design (CRD) in three replications. Quality attributes of potato tubers especially fresh matter and dry matter of plant, total reducing sugars in leaves, tuber yield, number and diameter of tubers per plant and number of sprouts per tuber was measured. Soluble proteins and starch content in potato tubers were also quantified.In general we noted that application of thiourea showed significant influence on yield and on quality of tubers comparing to control. Maximum tuber yield per plant, maximum number of tubers per plant and maximum starch content was recorded with 250 mM of thiourea. Moreover, highest dry matter of potato plant was found also at this concentration. While increasing dose of thiourea thereafter it showed slight significant improvement and do not affect significantly the diameter of tubers comparing to control

Response of sesame seedlings to different concentrations of humic acids or calcium nitrate at germination and early growth

This study was conducted in order to evaluate the response of sesame seeds (Sesamum indicum L.) to organic or mineral fertilization. The effects of two fertilizers, which were calcium nitrate and humic acids were studied separately at germination and early seedlings growth. Different concentrations of humic acids (HA0: 0, HA1: 500, HA2: 1000 and HA3: 2000 mg L–1) or calcium nitrate (CaN0: 0, CaN1: 50, CaN2: 100 and CaN3: 200 mg L–1) were applied distinctly to the growth media. The experimental design was accomplished in a completely randomized block design with three replications. Germination measurements, seedlings length, fresh seedling weight, total chlorophylls and carotenoids, total soluble proteins and sugars were determined. Results showed that humic acids applied at 1000 mg L-1 or calcium nitrate applied at 100 mg L-1 reduced the mean germination time (3.5 and 3.61 days) and had the highest germination index (GI) and the highest coefficient of velocity (CV). The longest seedling was obtained at the concentrations HA2 and CaN2 (+22%). Total chlorophyll and carotenoids were significantly higher in seedlings receiving the HA2 and CaN2 and these treatments increased total soluble proteins content by 32%. Higher concentrations of humic acids or calcium nitrate HA3 and CaN3 delayed germination and enhanced proline and total soluble sugars, respectively, by 42% and 46%, compared to control. These preliminary results indicated that the use of fertilizers should be optimized and they can be transformed at high level to an abiotic stress menacing plant productivity. On the other hand, suitable concentrations of fertilizers can be used in the future as a remedy to improve growth under abiotic stress

Impeller optimization in crossflow hydraulic turbines

Crossflow turbines represent a valuable choice for energy recovery in aqueducts, due to their constructive simplicity and good efficiency under variable head jump conditions. Several experimental and numerical studies concerning the optimal design of crossflow hydraulic turbines have already been proposed, but all of them assume that structural safety is fully compatible with the sought after geometry. We show first, with reference to a specific study case, that the geometry of the most efficient impeller would lead shortly, using blades with a traditional circular profile made with standard material, to their mechanical failure. A methodology for fully coupled fluid dynamic and mechanical optimization of the blade cross-section is then proposed. The methodology assumes a linear variation of the curvature of the blade external surface, along with an iterative use of two-dimensional (2D) computational fluid dynamic (CFD) and 3D structural finite element method (FEM) simulations. The proposed methodology was applied to the design of a power recovery system (PRS) turbine already installed in an operating water transport network and was finally validated with a fully 3D CFD simulation coupled with a 3D FEM structural analysis of the entire impeller

Modélisation du rendement grain du pois chiche (Cicer arietinum L.) du type « kabuli » sous les conditions édapho-climatiques du semi-aride supérieur Tunisien

Un essai est conduit, in situ, en pots, sous des conditions édapho-climatiques contrôlées du semi aride supérieur Tunisien. Le matériel végétal est composé de huit génotypes de pois chiche du type « kabuli ». Quatre doses d’irrigation ont été administrées, notamment, 100%, 75%, 50% et 25% de la réserve facilement utilisable (RFU). Les résultats indiquent que seuls le poids des gousses/m2 et le nombre de graines/m2 ont des effets directs significatifs sur le rendement en graines. Le nombre de graines/m2, la biomasse aérienne, la dose d’irrigation et le poids de 100 graines ont présenté les effets indirects positifs les plus élevés; alors que les dates de floraison précoce, de floraison et de maturité précoce et le poids des gousses/m2 ont présenté les effets indirects négatifs les plus élevés. La régression linéaire multiple « pas à pas » a permis de réduire le nombre de covariables qui expliquent le rendement en graines. L’analyse séquentielle de piste, fondée sur le classement des covariables en premier et second ordre sur la base de leurs effets directs les plus élevés et de leurs colinéarités minimales, a montré que le poids des gousses/m2 et le nombre de graines/m2 ont des effets directs hautement significatifs et que l’indice de récolte et la biomasse aérienne ont les effets indirects les plus élevés sur le rendement en graines

PHYSIOLOGICAL MECHANISMS FOR POTATO DORMANCY RELEASE AND SPROUTING: A REVIEW

Potato ( Solanum tuberosum \ua0L.) tubers undergo a period of dormancy, during which visible bud growth is inhibited. The length of the dormancy is determined by environmental, physiological and hormonal control mechanisms. Dormancy is the final stage of tuber life, which serves to preserve tubers as organs of vegetative reproduction under unfavourable growth conditions. Since the duration of potato tuber dormancy and sprouting time bear significant economic importance, this review considers the regulation of dormancy and sprouting of potato by phytohormones and reactive oxygen species. Two phytohormones, ABA and ethylene suppress tuber sprouting; however, the exact role of ethylene remains to be elucidated. Cytokinins and gibberellins are required for bud breaking and sprout growth, respectively. The auxin seems to play a role in vascular development. Thus, tuber dormancy and sprouting can be controlled in potato by manipulation of Reactive Oxygen Species (ROS), especially H2O2\ua0metabolism via the inhibition of catalase (CAT) activity.The possible mechanisms by which CAT inhibitors or H2O2\ua0overcome dormancy and promote sprouting in the potato tuber are discussed.La pomme de terre ( Solanum tuberosum \ua0L.) conna\ueet une p\ue9riode de dormance durant laquelle la germination des bourgeons visibles est inhib\ue9e. La dur\ue9e de dormance est d\ue9termin\ue9e par des m\ue9canismes de contr\uf4le environnemental, physiologique and hormonal. La dormance est le stade final de la vie des tubercules servant \ue0 pr\ue9server les tubercules comme organes de reproduction v\ue9g\ue9tative sous condition de germination d\ue9favorables. Etant donn\ue9 que la dur\ue9e de la dormance des tubercules de la pomme de terre et le temps de rejet rev\ueatent une importance \ue9conomique significative, cette revue consid\ue8re la r\ue9gulation de la dormance et le rejet de la pomme de terre par des hormones et d\u2019esp\ue8ces r\ue9actives d\u2019oxyg\ue8ne (ROS). Deux phytohormones\ua0; ABA et \ue9thyl\ue8ne emp\ueachent le rejet des tubercules\ua0; par ailleurs, le r\uf4le extractif de l\u2019\ue9thyl\ue8ne reste \ue0 \ue9lucider. Les cytokinines and les gibb\ue9rellines sont n\ue9cessaires dans l\u2019\ue9limination des bourgeons et la croissance des rejets, respectivement. L\u2019auxine semble jouer un r\uf4le dans le d\ue9veloppement vasculaire. Ainsi, la dormance et les rejets des tubercules peuvent \ueatre contr\uf4l\ue9s par manipulation d\u2019esp\ue8ces r\ue9actives d\u2019oxyg\ue8ne (ROS), sp\ue9cialement le m\ue9tabolisme du H2O2\ua0\ue0 travers l\u2019inhibition de l\u2019activit\ue9 de la catalase (CAT). Les m\ue9canismes possibles par lesquels les inhibiteurs du CAT ou H2O2\ua0 surmontent la dormance et facilitent le rejet de la pomme de terre sont discut\ue9s

Germination and growth in control and primed seeds of pepper as affected by salt stress

Salinity is an important abiotic stress which can affect crop production in the world. One of the simplest methods for improving salinity tolerance of plants is seeds priming. This experiment was conducted to evaluate the effects of seeds priming with three solutions (KCl , NaCl and CaCl2) in germination and later growth of three pepper (Capsicum annuum L.) cultivars: Beldi, Baklouti and Anaheim Chili. Seeds germination was conducted in a completely randomized design under seven salinity levels (0, 2, 4, 6, 8, 10 and 12 g L-1) at room temperature for primed and control seeds. Plants derived from these germinated seeds (control and primed) were transplanted and cultivated in a greenhouse for 4 months and were irrigated permanently with seven salinity levels (0, 2, 4, 6, 8, 10 and 12 g L-1). The results showed that salinity affected all parameters under study like total germination percentage and chlorophyll level (a and b). As well, proline content increased as response to increasing salinity. The plants derived and grown from primed seeds showed a considerable tolerance to salt stress and gave better results. In fact, priming improved the salt resistance of pepper owing to more chlorophyll and proline accumulation. These results suggest that seed priming induced possible physiological adjustments in pepper seeds, especially in the early stages of development, and could be used as a suitable tool for improving germination and growth characteristics under salt stress conditions

Comportement agronomique d'une collection de pois (Pisum sativum L)

Agronomical Behaviour of a Pea Collection (Pisum sativum L.). This experience was achieved under greenhouse conditions. Twelve genotypes of pea were used (Asgrow, Jumbo, Lincoln, Merveille de Kelvedon, Purser, Rajai Torpe, Snajor Kosep, Korai,Wando, Rondo, local genotype, Major Kosep Korai and Surgevil). They were cultivated on peat during 5.5 months (from October to April). Some agronomical parameters were studied: resistance to diseases, (Powdery-mildew, mildew, top yellow virus, anthracnose, browning), fresh matter, number of branches/plant, number of flowers/plant, number of pods/ plant and the yield of grains /plant. Results showed that only the genotype Purser is resistant to all diseases and Surgevil is sensitive only to the Top Yellow virus. The local genotype is sensitive to three frequent diseases (Powdery-mildew, mildew and Anthracnose). With regard to vegetative growth, the highest yield of fresh matter do not contribute towards a high fertility rate. In fact, only the genotypes having a weak yield of fresh matter (Snajor Kosep Korai, Asgrow, Major Kosep Korai, Rajai Torpe and Purser) have the most important rate of fertility (> 30%). Within this group, the most important yield (> 9 g/plant) is a result of high: number of pods/plant (7.5 to 21.6) and of grains/pod (2.8 to 4.92). Finally, genotype Purser should be retained for farmers and programs of genetic amelioration for its resistance to diseases and agronomical performances

Elements Discrimination in the Study of Super-Heavy Elements using an Ionization Chamber

Dedicated ionization chamber was built and installed to measure the energy loss of very heavy nuclei at 2.7 MeV/u produced in fusion reactions in inverse kinematics (beam of 208Pb). After going through the ionization chamber, products of reactions on 12C, 18O targets are implanted in a Si detector. Their identification through their alpha decay chain is ambiguous when their half-life is short. After calibration with Pb and Th nuclei, the ionization chamber signal allowed us to resolve these ambiguities. In the search for rare super-heavy nuclei produced in fusion reactions in inverse or symmetric kinematics, such a chamber will provide direct information on the nuclear charge of each implanted nucleus.Comment: submitted to NIMA, 10 pages+4 figures, Latex, uses elsart.cls and grahpic