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1.
A new sample business survey for agriculture, the REA survey, and a project of integration with the FADN network (RICA in
Italy) have significantly changed the production of statistical information nowadays available with reference to the agricultural
sector. On the basis of this relevant information, new economic analyses are being developed on farms’ performance, agricultural
households’ income and the Common Agricultural Policy (CAP). In this paper the authors estimate the relationship between the
levels of variables of interest and their sampling errors using models in order to improve the accessibility of the information
on estimates accuracy to the final users (agricultural analysts, policy makers).
The paper is the result of a joint research of the three authors. Sections 1–3 and 6 by Pizzoli, Sects. 4 and 5 by Rondinelli,
Sect. 7 by Filiberti, conclusions joint to the three authors. 相似文献
2.
Summary The results of local meteorology, solar radiation and ground-level ozone measurements taken in Antarctica during the second
Italian expedition (December 86–February 87) at Terra Nova Bay are presented. During the summer months the site of the Italian
base camp is characterized by a thin strip of deglaciated ground, along which the temperature measurements close to the ground
and up to 6 m high show a strongly superdiabatic profile. This irregular trend of the temperature in the surface layer is
mainly due to the notable incoming amounts of radiation and to the extreme transparency of the atmosphere. This is also shown
by the low values of the ratio between total radiation and diffuse radiation. The ground is thus subjected to intense heating,
especially in the warmer hours of the day, while the surface layer of the atmosphere will be characterized by strong upward
heat fluxes and by turbulent convective movements. Vertical-temperature-profile measurements show an almost forced persistence
in the superdiabatic trend, which tends towards isothermic values only as a resultof rapid variations in the direction and
intensity of the wind, connected to the downward flux of cold air masses, shown also by the simultaneous increases in ground-level
ozone concentrations which would support the presence of dry-deposition processes in the lower layer. However, the complex
local orography and the horizontal discontinuity (sea, deglaciated coast, snow-covered surfaces) do not permit a correct application
of profile flux relations, normally used in studies on groundlevel dry-deposition.
Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome. 相似文献
3.
Here we prove that every compact differential manifold has a smooth algebraic model defined over Q. In dimension 2 we find an algebraic model (may be singular) defined over Q and birational over Q to the projective plane. 相似文献
4.
Giancarlo Marconi Sandra Monti Francesco Manoli Alessandra DegliEsposti Andrea Guerrini 《Helvetica chimica acta》2004,87(9):2368-2377
The circular dichroism (CD) spectra of the powerful antimalarian active principle artemisinin (ART; 1 ) from Artemisia annua, and of epiartemisinin (EPI, 2), its C(7) epimer, were studied in solution in the presence and absence of β‐cyclodextrin (β‐cd). A significant inversion of sign in the region of the second electronic transition was detected. The rotational strengths were successfully calculated within the time‐dependent density functional theory (DFT), which enabled us to establish a correlation between the molecular recognition and the biological acitivities of the two isomers. 相似文献
5.
Onida B Borello L Busco C Ugliengo P Goto Y Inagaki S Garrone E 《The journal of physical chemistry. B》2005,109(24):11961-11966
Joint IR and computational results allow a detailed characterization of the surface properties of a mesoporous benzene-silica hybrid material with crystal-like wall structure. After outgassing at 450 degrees C, hydroxyl species mainly consist of noninteracting silanols, with both O-H and Si-O stretching modes at lower frequencies than those of SiOH in silica. Interaction with several probe molecules, followed both by experiment and calculus, shows that the aryl group in the coordination sphere of Si imparts a lesser acidity with respect to the isolated silanol in silica. In contrast, adsorption isotherms indicate that the interaction with acetone is stronger with benzene-silica than with silica: this is interpreted in terms of secondary interactions taking place between the slightly acidic CH in acetone and the electronic cloud in benzene-like rings. This suggests that both the inorganic component and the organic one play a role in dictating the surface behavior. 相似文献
6.
Cobalt and chromium release in patients undergone a metal-on-metal total hip replacement (THR) is a matter recently discussed and whose we do not have enough information about it yet. In literature there is little data and not completely indicative, in the biological fluids and organs the amounts of released metals are different. This is also due to the fact that cobalt and chromium blood levels can change depending on physical and working activity, individual feeding and metabolism. The results obtained confirm the presence of an increase of cobalt inthe blood of patients after total hip replacement, while the chromium levels are almost alike: average values in patients operated are 4.1 +/- 1.5 microg/L for cobalt (0.3 +/- 0.1 microg/L in the control group) and 4.5 +/- 2.9 microg/L for chromium (4.7 +/- 2.4 microg/L in the control group). In spite of the cobalt values stand below the concentration generally considered dangerous, the difference between the two examined groups points out that a risk exists for the health of these patients. These results must be confirmed by further studies, providing better information and more reliable and biocompatible materials. 相似文献
7.
Benincori T Brenna E Sannicolò F Trimarco L Antognazza P Cesarotti E Demartin F Pilati T 《The Journal of organic chemistry》1996,61(18):6244-6251
The synthesis and application of three examples of a new class of chiral (C(2)) atropisomeric diphosphines characterized by two interconnected five-membered heteroaromatic rings, with hindered rotation around the interanular bond, are described. Optically pure (+)- and (-)-2,2'-bis(diphenylphosphino)-4,4',6,6'-tetramethyl-3,3'-bibenzo[b]thiophene (tetraMe-bitianp) (1a) and the parent unsubstituted system (+)- and (-)-bitianp (1b) were synthesized. They were found to be optically stable at 100 degrees C and were successfully employed as ligands in the Ru(II)-catalyzed hydrogenation of alpha- and beta-oxo esters to the corresponding alpha- and beta-hydroxy esters and in the hydrogenation of olefinic substrates. The optical and chemical yields were comparable with those reported for the same Ru(II)-binap-catalyzed reactions carried out under the same experimental conditions. The 2,2'-bis(diphenylphosphino)-3,3'-bibenzo[b]furan (1c), the oxygenated analogue of bitianp, was found to be configurationally unstable at room temperature. Complete structural X-ray elucidation of the Pd complexes of 1a-c is reported. The advantages of these biheteroaromatic ligands over the classical biaryl systems are discussed. 相似文献
8.
Edoardo Ballico 《Annals of Global Analysis and Geometry》1996,14(3):257-261
Here we show that many numerical computations and bounds on the degrees of the algebraic leaves for singular meromorphic foliations on 2 may be extended to large classes of foliations and complex projective surfaces.The author was partially supported by MURST and GNSAGA of CNR (Italy) 相似文献
9.
Maria Concetta Bruzzoniti Edoardo Mentasti Corrado Sarzanini Peter Hajs 《Journal of chromatography. A》1997,770(1-2):13-22
The retention behavior of biologically relevant monovalent (formic, acetic, propionic, lactic and pyruvic) and divalent (oxalic, malonic, succinic, fumaric, maleic and tartaric acids) car☐ylic acids together with inorganic analytes (chloride and sulphate) has been studied. The separation was performed on a latex-based strong anion-exchange resin using carbonate buffer systems in suppressed IC. The retention behaviour of analytes was investigated at different pH values and [HCO3−]+[CO32−] concentrations. A theoretical model, involving ion-exchange equilibria of sample and eluent anions, was derived and applied to the chromatographic data obtained. Chromatographic ion exchange selectivity values were determined and retention data were calculated for the anions using different carbonate eluent conditions. The average of errors between the predicted and the measured retention volumes of the analytes studied does not exceed 4.0%. The study effectively characteristics the behaviour of different analytes under elution conditions of practical importance. 相似文献
10.
Fiorilli S Onida B Bonelli B Garrone E 《The journal of physical chemistry. B》2005,109(35):16725-16729
Two samples of SBA-15 mesoporous silica with a different content of carboxylic groups (-COOH) were prepared by a co-condensation route, using 4-(triethoxysilil)butyronitrile as the organosilane agent, then treating the samples with sulfuric acid, which removes the template and simultaneously hydrolyses the -CN to -COOH groups, as shown by IR spectroscopy. Both incorporation of organosilane agents and subsequent acid treatment do not affect the ordered SBA-15 structure. The proton-donor ability of carboxylic groups, as well their accessibility to reactants, has been studied in the IR by dosing ammonia, which forms reversibly COO- groups and NH4+ ions. The related equilibrium constants have been determined by elaboration of IR data. Outgassing the samples at progressively increasing temperatures destabilizes to an increasing extent the ammonium/carboxylate ion pair, because of the decrease in surface polarity brought about by dehydration: this decreases the related equilibrium constants. The amount of carboxylic groups undergoing reaction appears instead to be constant with dehydration, and to coincide with the whole population of COOH groups. Titration with alkali solutions yielded surface concentrations for the two samples of ca. 1.0 and 0.45 COOH/nm2. Proportionality between the surface concentrations and the intensities of the C=O IR band is observed: this suggests that COOH groups are noninteracting with each other and allows the computation of the related extinction molar coefficient. 相似文献