1,354,552 research outputs found
Stomatal size and frequency in wild and cultivated almonds
No full textStomatal size and frequency are features commonly related to plant water stress tolerance. In
general, size and number are negatively correlated and may vary greatly among species and genotypes. The
number of stomata per leaf area unit is considered a peculiar characteristic of species and plant varieties. In
order to provide information concerning this topic, a study was carried out on the stomata size and frequency of
15 cultivated almonds (A. communis) and 5 Apulian wild almonds (A. webbii). The varieties of A. communis were
chosen taking into consideration their country of origin (extra Mediterranean/Mediterranean/Apulian), shell
hardness (paper/hard) and kernel taste (sweet/bitter). The only evident difference between the cultivated and wild
almonds concerned the leaf area; stomata frequency and size were independent of other characteristics, such as
origin, country of origin, shell hardness and kernel taste of the twenty varieties/seedlings investigated
Preliminary observations about the performance of 13 varieties according to the super high density oliveculture training system in Apulia (southern Italy)
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Yield, harvesting efficiency and oil chemical quality of cultivars Arbequina and Arbosana harvested by straddle machine in two Apulian growing areas
No full textAbstract
Super-high-density olive culture is characterized by hedgerow trees with planting density ranging from 1200 up to 2000 trees ha-1, in order to allow continuous harvesting by straddle machines. The genotype cultivated is the key factor for both the agronomic and economic sustainability of this new cropping system. ‘Arbequina’ and ‘Arbosana’, together with a few others, are the most-used cultivars up to now. Yield, harvesting efficiency and oil quality are strongly affected by agronomical and environmental factors, among others. We report yields, harvesting efficiencies and chemical characteristics of oils of the cultivars ‘Arbequina’ and ‘Arbosana’ grown in two different pedoclimatic Apulian areas (southern Italy), with the same planting density, tree age, cropping practices and harvesting machine. Each cultivar was harvested at the same ripening stage for both sites. Site 1 was warmer and more arid than site 2. Mean harvesting efficiency was 98%; ‘Arbequina’ had higher harvesting efficiency with respect to ‘Arbosana’, due to different detachment force. The colder site reduced fruit yield and yield efficiencies of both cultivars but increased yield quality, by increasing both unsaturation level of fatty acids and polyphenol content of the extracted oil. The selection of appropriate growing areas was an important tool to define levels of both fruit yield and oil quality for the high-density olive orchards. Moreover, cultivar and harvesting time influenced not only the above-mentioned yield parameters, but also the performance of the straddle harvesters both in terms of harvesting efficiency and canopy damage
Aspetti qualitativi e quantitativi della raccolta meccanica in continuo di un giovane oliveto superintensivo
No full textData on harvesting efficiency, shoot and fruit damage of eight oil olive varieties (Arbequina, Arbosana, Coratina, Don Carlo, Fs-17, I/77, Koroneiki and Urano), trained in Apulia according to super high density system and mechanically harvested by a grape-harvester are reported. The average harvesting efficiency was 95.5%, damaged lateral shoots and branches were 0.3%. I/77, a very early ripening variety, showed the highest values of damaged shoots (1.6%) and fruits (60%). In general, the grape harvester worked very well on the young super high density olive planting. Both genotype and harvesting time played a leading role on the involved parameters
Pulsed laser deposition and characterization of NiTi-based MEMS prototypes
No full textWe report the fabrication and characterization of microelectromechanical systems (MEMS) prototypes based on a microcantilever coated with a NiTi thin film. The NiTi film was deposited by laser ablation and deposition in ultra-high vacuum. The samples were characterized from the mechanical point of view by measuring the resonance frequency of the cantilever as a function of the temperature. Data show a clear phase transition of the NiTi film, with relevant transition temperatures close to those of the bulk, which demonstrates the congruency of the deposition method. We have also developed a technique to control the deflection of the NiTi-coated cantilever by all-optical means, both continuous and pulsed, the latter with typical time scales in the hundreds of mus range
Cold atom deposition for nanoscale structuring of surfaces
No full textAtom lithography [1] has attracted a great interest in the scientific community as a technique for the fabrication of nanometer-scale ordered structures with a relatively simple apparatus. The atom lithography approach is similar to conventional optical litography, the light beam and the mechanical mask being replaced by an atomic beam and an immaterial light mask, respectively. Nanostructures are produced by space segregation of the atomic beam, due to its interaction with a quasi-resonant standing wave, that allows to realize ordered structures with interferometric precision and a space resolution well below 100 nm through either direct deposition or resist-assisted processes. The ultimate limits of the technique and the role of the interactions between the deposited atoms and the substrate are under recent debate. In order to better understand the relevant growth processes and the limits of atom lithography in terms of space definition, we have built an apparatus where a continuous beam produced out of a pyramidal-MOT funnel is used. The funnel is followed by a collimation stage, based on 2D optical molasses along the transverse directions. The main advantage of this choice is the lower translational velocity of the atoms composing the beam with respect to conventional effusive sources (10 m/s vs hundreds of m/s typical for thermal beams). This leads to a larger interaction time during the collimating and immaterial mask (focusing) stages, which is expected to give rise to sharper deposited structures thanks to a significant reduction of aberration effects and of the amount of uncollimated/unfocused atoms arriving onto the substrate.
The experimental set-up exploits a pyramidal funnel, made of two prisms and two mirrors arranged in the shape of an inverted pyramid with a small hole (1mm x 2 mm) at its apex, mounted on a stainless-steel holder inside an ultra high vacuum system. The light for manipulating cesium atoms is produced by diode lasers operating around 850 nm, mounted in the external cavity configuration. The quadrupolar magnetic field for the pyramidal-MOT operation is produced by two coils in anti-Helmholtz configuration.
We have characterized the atomic beam leaving the funnel [2], i.e., we have measured its density, divergence, longitudinal velocity and temperature. Induced fluorescence images, acquired using a CCD camera, and absorption measurements show a beam divergence of 25 mrad, a longitudinal velocity in the range 10-15 m/s (depending on the trapping parameters) and a flux up to 4 x 109 atoms/s. The atomic beam diameter (FWHM) is 1 cm measured 30 cm downward the funnel apex.
The collimation stage is based on 2D optical molasses. The collimating laser beam is elliptical in shape (13 mm x 6 mm), with the longer axis along the longitudinal direction, which leads to an interaction time of 1 ms. We have explored both the "lin perp lin" and the σ+σ - polarization configuration. With the "lin perp lin" configuration we found a minimum divergence of 8 mrad at a collimating laser detuning of -9Γ (Γ being the cesium natural linewith, 5.13 MHz), limited by the presence in the collimation region of stray magnetic fields produced by the MOT coils. We were able to reach less than 2 mrad (corresponding to the measurement uncertainty) in beam divergence with the σ+σ - polarization configuration. The collimation stage allows us also to reduce the beam diameter to 4 mm at 30 cm from the funnel apex, with an increase of the atomic beam intensity relevant for our applicative purposes.
The next step of the experiment will be deposition of cesium through a light mask (a one-dimensional laser standing wave) on several kinds of substrates. Currently we are working on the deposition of nanostructured cesium beam on Self Assembled Monolayer (a nonanethiol layer grown on a gold substrate). Our preliminary results demonstrate that the SAM is efficiently impressed by the arrival of the laser-cooled cesium atoms. By the time of the Conference we expect to obtain nanostructures (arrays of parallel planes, spaced by half the laser wavelength) through resist-assisted atom lithography.
The work is supported by EC through RTD-IST "NANOCOLD", and by CNR through Progetto Applicativo "Nanotecnologie".
[1] J.J.McClelland, "Nanofabrication via Atom Optics", in Handbook of Nanostructured Materials and Technology, Academic Press, Cambridge, (1999).
[2] A. Camposeo, A. Piombini, F. Cervelli, F. Tantussi, F. Fuso, and E. Arimondo, Optics Comm. 200 231 (2001
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