A comparison of the ECMWF forecast model with observations over the annual cycle at SHEBA

A central objective of the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment was to provide a comprehensive observational test for single-column models of the atmosphere-sea ice-ocean system over the Arctic Ocean. For single-column modeling, one must specify the time-varying tendencies due to horizontal and vertical advection of air through the column. Due to the difficulty of directly measuring these tendencies, it was decided for SHEBA to obtain them from short-range forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) global forecast model, into which SHEBA rawinsonde and surface synoptic observations were routinely assimilated. The quality of these forecasts directly affects the reliability of the derived advective tendencies. In addition, the ECMWF-forecast thermodynamic and cloud fields, and radiative and turbulent fluxes present an illuminating comparison of the SHEBA observations with a state-of-the-art global numerical model. The authors compare SHEBA soundings, cloud and boundary layer observations with the ECMWF model output throughout the SHEBA year. They find that above the boundary layer, the model was faithful to the SHEBA rawinsonde observations and maintained a proper long-term balance between advective and nonadvective tendencies of heat and moisture. This lends credence to use of the ECMWF-predicted advective tendencies for single-column modeling studies. The model-derived cloud properties and precipitation (which were not assimilated from observations) are compared with cloud radar, lidar, microwave radiometer, surface turbulent and radiative measurements, and basic surface meteorology. The model s slab sea-ice model led to large surface temperature errors and insufficient synoptic variability of temperature. The overall height distribution of cloud was fairly well simulated (though somewhat overestimated) in all seasons, as was precipitation. However, the model clouds typically had a much higher ratio of cloud ice to cloud water than suggested by lidar depolarization measurements, and a smaller optical depth, leading to monthly biases of up to 50 W m^(-2) in the monthly surface downwelling longwave and shortwave radiation. Further biases in net radiation were due to the inaccurate model assumption of constant surface albedo. Observed turbulent sensible and latent heat fluxes tended to be small throughout SHEBA. During high-wind periods during the winter, the ECMWF model predicted sustained downward heat fluxes of up to 60 W m^(-2), much higher than observed. A detailed comparison suggests that this error was due to both inadequate resolution of the 31-level model and a deficient parameterization of sea-ice thermodynamics

Aziridination of alkenes promoted by iron or ruthenium complexes

Molecules containing an aziridine functional group are a versatile class of organic synthons due to the presence of a strained three member, which can be easily involved in ring-opening reactions and the aziridine functionality often show interesting pharmaceutical and/or biological behaviours. For these reasons, the scientific community is constantly interested in developing efficient procedures to introduce an aziridine moiety into organic skeletons and the one-pot reaction of an alkene double bond with a nitrene [NR] source is a powerful synthetic strategy.Herein we describe the catalytic activity of iron or ruthenium complexes in promoting the reaction stated above by stressing the potential and limits of each synthetic protocol

Expression of genes associated with anthocyanin synthesis in red-purplish, pink, pinkish-green and green grape berries from mutated 'Sangiovese' biotypes: A case study

Using normal red-purplish grape bunches and pink, pink-green and green berry colour-mutated biotypes of cv. Sangiovese (V. vinifera L.), we investigated their anthocyanin metabolism via biochemical and molecular assays. The number and composition of the different types of anthocyanins were analysed by spectrophotometry and chromatography. The expression of six structural genes of the biosynthetic pathway (chalcone synthase [CHS], chalcone isomerase [CHI], flavanon-3-hydroxylase [F3H], dihydroflavonol 4-reductase [DFR], leucoanthocyanidin dioxygenase [LDOX] and UDP-glucose 3-O-flavonoid:glucosyltransferase [UFGT]) was determined over the four weeks subsequent to veraison via Northen blot and Real Time PCR.The grapes from the non-mutated biotype showed a prevailing accumulation of monoglycoside anthocyanin fractions, with only traces of acetyl and p-coumaroyl derivatives. The berries of the mutated biotypes showed a gradual berry pigment loss associated with a reduction in total anthocyanin content, although anthocyanin composition was the same of the non-mutant biotype. Indeed, the Northern blot assay data, as confirmed by the quantitative Real Time PCR tests, showed a differential expression in the berries of the non mutated and mutated biotypes for the UFGT gene, proving normal in the red-purplish, lower in the biotypes with pink and pink-green berries and wholly lacking in the green one. Thus, the UFGT gene in berry skin of colour-mutated 'Sangiovese' biotypes is controlled independently of the other structural genes encoding enzymes in the anthocyanin biosynthetic pathway and its capacity of expression is a critical factor in the synthesis and storage of these compounds.

Row orientation effects on whole-canopy gas exchange of potted and field-grown grapevines

The effects of canopy orientation (North-South vs. East-West) on total canopy assimilation (TCA) and transpiration (TCE) were evaluated on potted grapevines mounted on wheeled platforms for full swivel relation. Eight vines were assembled in pairs to form four canopy walls 2 m long, 1.1 m tall and 0.25-0.30 m wide. TCA and TCE readings were also taken in the field on four NS-oriented, hedgerow cordon-trained grapevines. Diurnal trends of TCA recorded on potted vines showed little variability when related to row orientation. The TCE pattern for EW followed essentially that of light intensity, whereas a NS orientation induced a marked decrease in TCE at midday before recovering in mid-afternoon. As a result, water use efficiency (WUE) in NS rows was higher during the midday hours. Total canopy water loss in NS was linearly correlated with estimates of intercepted light, suggesting that water use was a function of both, light intensity and canopy geometry (i.e. more light lost to the ground at noon, hence less transpiration). The results for the NS-oriented field-grown canopies differed to some extent from those of the pot experiments. TCA showed a more marked afternoon decline and TCE flattened at noon, though with no apparent decrease. WUE efficiency was lowest at the highest evaporative demand. The daily water loss of field vines could not be predicted by total light interception estimates only, indicating a more complex regulation of canopy transpiration than recorded on potted plants

Gas-exchange response of grapevine leaves under fluctuating light

Gas exchange responses to lightflecks of different frequency and duration were studied in mature grapevine leaves. Light-response curves under intermittent light showed lower carbon exchange rate (CER) than continuous light at non-saturating PFD levels (10-500 µ molm-2 s-1). White-dark and white-green alternating light of equal bright and shade periods at 0.33-5.33 Hz systematically resulted in improved light utilization as compared to high continuous light. Transpiration (T) was slightly more limited than the CER under intermittent light, resulting in higher water use efficiency. No differences in carboxylation efficiency were found by comparing the high continuous light treatment to white-dark lightflecks at 0.33 and 2.67 Hz. Our results show that, under short-term alternating light, CER of the grapevine leaf fully responds to the mean PFD level resulting from light oscillations

Synthesis of cyclic carbonates by ruthenium(VI) bis -imido porphyrin/TBACl-catalyzed reaction of epoxide with CO2

The catalytic activity of the ruthenium(VI) bis-imido porphyrin complex/TBACl binary system in promoting the CO2 cycloaddition to epoxides forming cyclic carbonates is here reported. The system was very efficient in catalyzing the conversion of differently substituted epoxides under mild experimental conditions (100 °C and 0.6 MPa of CO2). Even if the sole TBACl resulted active under the optimized experimental conditions, the addition of ruthenium species was fundamental to maximizing the reaction productivity both in terms of epoxide conversions and cyclic carbonate selectivities. A preliminary mechanistic study indicated a positive role of ruthenium imido nitrogen atom in activating carbon dioxide

Porphyrin-based homogeneous catalysts for the CO 2 cycloaddition to epoxides and aziridines

The direct insertion of carbon dioxide (CO2) into three-membered rings, such as epoxides and aziridines, represents a relevant strategy to obtain cyclic carbonates and oxazolidinones, which are two useful classes of fine chemicals. The synthesis of these compounds can be efficiently catalyzed by a combination of metal porphyrin complexes and various co-catalysts in homogeneous systems. The catalytic efficiency of these systems is discussed herein by taking into account both the characteristics of the metals and the nature of the co-catalysts, either when used as two-component systems or when combined in bifunctional catalysts. Moreover, mechanistic proposals of the CO2 cycloaddition processes are reported to provide a rationale of catalytic cycles in order to pave the way for designing more active and efficient catalytic procedures

Effects of canopy manipulations on whole-vine photosynthesis: Results from pot and field experiments

A two-year study was conducted with potted and field-grown grapevines to examine the effects of canopy restriction and leaf removal on total vine assimilation (TVA). TVA was measured using a flow-through gas exchange system equipped with flexible plastic chambers enclosing the entire canopy. Canopy restriction was applied to potted bush-shaped (BS) and field-grown spur-pruned cordon (SPC) vines on trellises to force the foliage into the smallest canopy volume. Leaf removal was performed on free cordon (FC) and SPC-trained vines at different dates to eliminate internal leaves shaded to varying extent. Canopy restriction reduced TVA more severely in the BS canopies than in the trellised SPC vines. Leaf removal elicited varying responses depending upon canopy shape, initial canopy density and leaf/fruit ratio. The FC vine showed no decrease in TVA after 27 % of its total leaf area had been removed, suggesting the occurrence of active photosynthetic compensation. TVA decreased with defoliation in the SPC vine, although the effect was mostly due to the leaf removal applied earlier in the season. In the FC vine a regression of total leaf area versus TVA showed maximum TVA at 6.0-6.5 m(2) of leaf area per meter of canopy. In SPC vines this relationship indicated a linear increase of TVA with leaf area and the lack of a saturation threshold under our experimental conditions. Sugar accumulation in the grapes of SPC vines correlated closely to the ratios leaf area/fruit and TVA/yield

Molecular characterization of officially registered Sangiovese clones and of other Sangiovese-like biotypes in Tuscany, Corsica and Emilia-Romagna

The present study was designed (1) to identify and determine the origin of the genetic variability via SSR and AFLP within a group of 39 Sangiovese clones officially listed in the National Grapevine Registry, (2) to pinpoint varietal differences and potential family relations among 34 Sangiovese-like biotypes, via the SSR markers. Most biotypes are regarded as Sangiovese but sometimes are known under different names. In both studies the reference standard was the registered Sangiovese clone SG 12T.No polymorphism was found among the officially listed 39 clones analysed at 6 microsatellite loci. This enabled us to confirm their origin from a single mother plant, thereby supporting the view that any morphological or qualitative differences may be the result of propagation-related mutagenic events. A subsequent AFLP analysis of 26 of the 39 clones showed polymorphic bands in three of them (two identical) that may correspond to a mutagenic event. Assays with SSR markers on 34 Sangiovese-like biotypes collected in Tuscany, Corsica and Emilia-Romagna showed that 28 are identical with the reference Sangiovese clone SG 12T, while the remaining 6 (Sangiovese 1, Sangiovese 6, Morellino, Poverina, Sangiovese forte and Brunellone) are genetically different from SG 12T and among one another so that no direct family relations could be established

Preliminary results on the use of a modified point quadrat method for estimating canopy structure of grapevine training systems

The reliability of a modified point quadrat method designed to describe the structure and seasonal canopy dynamics of the training systems simple curtain (SC) and traditional spur-pruned cordon (SPC) was tested in a two-year study. The method relies upon an unbiased sampling procedure as each canopy insertion is first identified within a ground-projected area by a random number generation routine (RND). From each insertion, the height of each contact with either leaves or clusters is then recorded along the vertical axis. Although the method suffered from a somewhat low percentage of effective insertions early in the season, the total leaf area-to-surface area ratio and the leaf layer number calculated for both canopy types are in accordance with those reported by others for high vigour canopies. Canopy dynamics showed an asymmetric growth in the SC starting at bloom. Both trellises resulted in similar canopy density indices and a high correlation was found between total leaf area and total number of leaf contacts