204 research outputs found
Separazione e dosaggio di zuccheri nei mieli per GC-capillare dopo reazione con metossiammina e silanizzazione
No full textFirst and second sound in cylindrically trapped gases
Get PDFWe investigate the propagation of density and temperature waves in a cylindrically trapped gas with radial harmonic confinement. Starting from two-fluid hydrodynamic theory we derive effective 1D equations for the chemical potential and the temperature which explicitly account for the effects of viscosity and thermal conductivity. Differently from quantum fluids confined by rigid walls, the harmonic confinement allows for the propagation of both first and second sound in the long wavelength limit. We provide quantitative predictions for the two sound velocities of a superfluid Fermi gas at unitarity. For shorter wavelengths we discover a new surprising class of excitations continuously spread over a finite interval of frequencies. This results in a nondissipative damping in the response function which is analytically calculated in the limiting case of a classical ideal gas
Are the differences among samples from agricultural trials analyzed by routine procedures experimental or only analytical?
No full textMany experimental researches in the agricultural field involve chemical analyses. For a correct statistical data processing, it should be important to discriminate between the variability induced by the analytical method and by other sources of variation (experimental treatments and other causes of systematic variability). The object of the present communication is to present a simple and economical method for the evaluation of the analytical variability which does not require to replicate the analysis of each sample. The analytical method used in this study was the plant tissue determination of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), boron (B), copper (Cu), zinc (Zn), and sulfur (S) by plasma emission spectrometry (ICP). The repeatability and the reproducibility of the method for each element was obtained by analysing two times per day a reference sample. The use of these parameters in the statistical processing of the analytical data from experimental trials for a correct result interpretation are discussed
Influence of two grinding methods on the uncertainty of determinations of heavy metals in atomic absorption spectrometry/electrothermal atomisation of plant samples
No full textChemical analyses of trace elements are affected by relatively high analytical errors due to the different steps of the laboratory procedures: samples grinding, mineralisation and instrumental measurements. In the present communication, the influence of the grinding phase on the global uncertainty of Pb, Cd, Ni and Cr determinations in plant samples by the classical method of atomic absorption spectrometry/electrothermal atomisation (AAS-ETA) after dry ashing is quantified. Two grinding machines, a planetary mill with balls and jars of agate versus a stainless steel grinder were compared by analysing leaf samples of cucumber, strawberry, kiwivines, apple trees and grapevines from agricultural experimental plots under controlled conditions. Variance components due to the difference between grinding methods and experimental plots were estimated. Further, the simultaneous effects of the grinding methods on all considered metals have been evaluated by analysis of variance. With the stainless steel grinder, on average, higher levels of the considered heavy metals were obtained (up to 67% of the mean values). On average, the increments were similar for metals contained in steel (Ni and Cr) and those not contained (Pb and Cd). The true causes of these differences need further investigation to determine whether the higher metal detection is due to possible contamination, to a different grinding quality or to other reasons. Finally, the grinding methods did not seem to affect the combined uncertainty of the analyses
Andamento meteorologico e stato nutrizionale dei meleti e vigneti trentini: analisi dei dati del decennio 1987-1996
No full textThirteen years of leaf analysis applied to Italian viticulture, olive and fruit growing
No full textIn 1987 a project to develop an Italian national centre for research on the use of leaf analyses was initiated in order to undertake and interpret leaf analyses on behalf of fruit and grape grower advisory services, and to allow the management of research both for sampling techniques and data collection in the field and in laboratory analyses. Leaves were sampled by technicians of the advisory services from different regions according to the method recommended by our laboratory. All leaf analyses were collected automatically in a data bank which recorded the data reported on the sample label (location, variety, rootstock, vegetative and productive status of the planting) and the nutrient concentrations. More than 12,500 leaf analyses have been gathered in a thirteen year period, from twelve regions from northern, central and southern Italy. Seven tree crop species were mainly included: grapevines, apple trees, peach trees, kiwi vines, olive trees, pear trees and sweet cherry trees. The following main outcomes were developed: local standards for leaf analysis interpretation; certification for low input fertilisation farming; use of leaf analysis in land evaluation and agro-ecological zoning; nutritional aspects of eco-physiological and cultural researches; studies on the relations among mineral nutrition and crop quality; field trials to test fertiliser design and products; and new analytical and diagnostic methods
Investigation of compost-mulch in the vineyards of Trentino: effects on the soil and culture
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A method to assess and manage leaf analysis standards according to genetic and environmental variability
No full textA simple and robust statistical method to process data collected in a Leaf Analysis Data Bank which allows to establish reference standards according to the main environmental, genetic and cultural factors affecting the plant nutritional status is presented. The method also permits to determine quickly and easily new tentative standards and to adjust yearly standards already defined
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