Preparation of thin SnO2 layers by inorganic sol-gel process

SnO₂ sols were prepared in the following way: (1) precipitation of metastannic acid with aqueous ammonia from aqueous solutions of SnCl₄, (2) washing the precipitates with NH₄NO₃ solution and water, (3) peptization of precipitates in water, sometimes with an addition of HNO₃, at elevated temperature using mechanical stirring. In those sols, sometimes diluted with water or ethanol, substrates (glass or silica derived wafers) were dipped and withdrawn at various rates. Gel coatings were converted into crystalline SnO₂ by thermal treatment at 600°C. Coatings with thickness between 300–2000 Å were prepared.     

LIGHT CONTROL OF ELONGATION OF FILAMENT IN SUNFLOWER (Helianthus annuus L.)

Abstract— In sunflower ( Helianthus annuus L.) it has been found that continuous white-light during the flowering stage causes loss of protandry so that filaments do not elongate. Experiments have been carried out to test the nature of the pigment involved in the photoinhibition of elongation. The results suggest that the elongation of the filament is controlled by the phytochrome system and that a low photoequilibrium is required to obtain the response. Our results do not show light control of style elongation.     

Small-perturbation theory of steady plane relativistic flows

Summary Small-perturbation theory for relativistic irrotational steady flows past profiles is developed. Subsonic or supersonic approximation, as well as transonic, is determined. Similarity rules, in both cases, are established.

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Sommario Viene sviluppata la teoria delle piccole perturbazioni per le correnti relativistiche irrotazionali stazionarie che lambiscono profili sottili. Vengono esaminate le approssimazioni valide nel caso subsonico o supersonico, e nel caso transonico. Vengono stabilite le regole di similitudine che sussistono per le correnti subsoniche o supersoniche, e la regola che vige in condizioni transoniche.

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This work was done in the sphere of activity of the C.N.R. groups for mathematical research.     

The Use of UV Radiation to Control the Architecture of Salvia splendens Plants. I. Effects on Plant Growth, Water Relations and Gas Exchange

In experiments with Salvia splendens plants grown in the greenhouse we evaluated the possible use of irradiation with unfiltered UV (UVA + UVB + UVC) lamps for the control of plant growth. The effect of UV Irradiation on the growth of S. splendens plants in the grcenhouse was closely dependent on the growing season and the level of available photosynthetically active radiation. In summer UV treatments were ineffective, but in the low light conditions of winter UV irradiation inhibited the growth via both photomorphogenic and photosynthetic effects. The reduction of stomatal conductance and expansion growth, which in turn depressed photosynthesis and dry matter accumulation, were not a consequence of an impairment of plant water status but appeared to be a direct UV effect on stomata and cell wall rheological propertles. Our findings suggest that the use of unfiltered UV irradiation could become an effective tool for the regulation of growth in greenhouse crops, particularly during the poor light conditions of the winter season.     

Approaching the theoretical limit in periodic local MP2 calculations with atomic-orbital basis sets: the case of LiH

The atomic orbital basis set limit is approached in periodic correlated calculations for solid LiH. The valence correlation energy is evaluated at the level of the local periodic second order M?ller-Plesset perturbation theory (MP2), using basis sets of progressively increasing size, and also employing "bond"-centered basis functions in addition to the standard atom-centered ones. Extended basis sets, which contain linear dependencies, are processed only at the MP2 stage via a dual basis set scheme. The local approximation (domain) error has been consistently eliminated by expanding the orbital excitation domains. As a final result, it is demonstrated that the complete basis set limit can be reached for both HF and local MP2 periodic calculations, and a general scheme is outlined for the definition of high-quality atomic-orbital basis sets for solids.     

Hodograph relativistic equations of plane flows

Summary Various forms of hodograph equations for relativistic irrotational steady plane flows are worked out. The transformation from the hodograph to the physical plane is studied. Elementary solutions of these equations are found. An approximate hodograph equation for relativistic transonic flows is determined.

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Sommario Si ricavano, in diverse forme, le equazioni odografiche per le correnti relativistiche irrotazionali stazionarie piane. Si esamina il passaggio dal piano odografico al piano fisico. Si trovano alcune soluzioni elementari delle dette equazioni. Si determina un'equazione odografica approssimata per le correnti transoniche relativistiche.

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This work was done in the sphere of activity of the C.N.R. groups for mathematical research.