A 2D nanosphere array for atomic spectroscopy

We are interested in the spectroscopic behaviour of a gas confined in a micrometric or even nanometric volume. Such a situation could be encountered by the filling-up of a porous medium, such as a photonic crystal, with an atomic gas. Here, we discuss the first step of this program, with the generation and characterization of a self-organized 2D film of nanospheres of silica. We show that an optical characterization by laser light diffraction permits to extract some information on the array structure and represents an interesting complement to electron microscopy.Comment: accept\'e pour publication \`a Annales de Physique- proceedings of COLOQ1

Utjecaj dodavanja fosfora u hranu na značajke kostiju svinja u rastu

The objectives of this study were to examine the response of growing pigs to a level of phosphorus in excess of current usage and also to examine the effect of reducing phosphorus level in the later growing stages on bone characteristics. After slaughter, third metacarpals were removed from the front right foot of experimental pigs and the bones were weighed. Overall length of each bone and the width of bone shaft at the narrow and wide dimension were measured. Wall thickness, shear force resistance and ash percentage were also measured. Dry weight of bone was significantly affected by treatment (P<0.05). There was a similar trend for both bone ash weight and ash percentage, with those fed a phase phosphorus diet (low phosphorus level in the later growing stages) having significantly lower values than the other treatments (P<0.01). There was a trend for increased stress as dietary phosphorus level increased. We can conclude that pig bone development was significantly affected by dietary phosphorus level. The low-phosphorus diet gave significantly poorer results than the adequate-phosphorus diet; while there were no beneficial effects of supplementing phosphorus at a level higher than 2.4 g/kg. Lowering the phosphorus level to 1.6 g/kg in the late finishing stage seemed to produce a deleterious effect.Istražen je utjecaj prekomjernog dodavanja i smanjivanja količine fosfora na značajke kostiju u kasnijoj fazi rasta svinja. Nakon klanja svinjama je s prednje desne noge uzeta treća metakarpalna kost te je svakoj uzetoj kosti izmjerena masa, dužina i obujam na najužem i najširem dijelu. Također je mjerena debljina kompaktne supstancije, jačina otpornosti i udio pepela. Dodavanje fosfora u hrani znatno je utjecalo na suhu tvar kostiju (P<0,05). Slično je ustanovljeno za sadržaj pepela i njegov udio za vrijeme dodavanja fosfora (niska razina fosfora u kasnijoj fazi rasta) pri čemu su ustanovljene signifikantno niže vrijednosti u odnosu na druge tretmane (P<0,01). Ustanovljena je i povećana sklonost stresu ovisno o povećanju fosfora u obroku. Zaključuje se da je na razvoj kostiju u svinja značajno utjecala količina fosfora u obroku. Niska razina fosfora u obroku dovela je do znatno lošijih rezultata u odnosu na obrok s primjerenom količinom fosfora, iako nije bilo povoljnog učinka kad je fosfor dodan u količini većoj od 2,4 g/kg. Smanjenje količine fosfora na 1,6 g/kg u završnoj fazi rasta imalo je štetan učinak

Detection of slow atoms confined in a Cesium vapor cell by spatially separated pump and probe laser beams

proceedings of 17th International School on Quantum Electronics: Laser Physics and Applications, neesebar, bulgaria Sept 2012 edited by Tanja Dreischuh, Albena DaskalovaInternational audienceThe velocity distribution of atoms in a thermal gas is usually described through a Maxwell-Boltzman distribution of energy, and assumes isotropy. As a consequence, the probability for an atom to leave the surface under an azimuth angle θ should evolve as cos θ, in spite of the fact that there is no microscopic basis to justify such a law. The contribution of atoms moving at a grazing incidence towards or from the surface, i.e. atoms with a small normal velocity, here called "slow" atoms, reveals essential in the development of spectroscopic methods probing a dilute atomic vapor in the vicinity of a surface, enabling a sub-Doppler resolution under a normal incidence irradiation. The probability for such "slow" atoms may be reduced by surface roughness and atom-surface interaction. Here, we describe a method to observe and to count these slow atoms relying on a mechanical discrimination, through spatially separated pump and probe beams. We also report on our experimental progresses toward such a goal

Dicke Coherent Narrowing in Two-Photon and Raman Spectroscopy of Thin Vapour Cells

The principle of coherent Dicke narrowing in a thin vapour cell, in which sub-Doppler spectral lineshapes are observed under a normal irradiation for a l/2 thickness, is generalized to two-photon spectroscopy. Only the sum of the two wave vectors must be normal to the cell, making the two-photon scheme highly versatile. A comparison is provided between the Dicke narrowing with copropagating fields, and the residual Doppler-broadening occurring with counterpropagating geometries. The experimental feasibility is discussed on the basis of a first observation of a two-photon resonance in a 300 nm-thick Cs cell. Extension to the Raman situation is finally considered

Laser spectroscopy with nanometric gas cells : distance dependence of atom-surface interaction and collisions under confinement

The high sensitivity of Laser Spectroscopy has made possible the exploration of atomic resonances in newly designed "nanometric" gas cells, whose local thickness varies from 20nm to more than 1000 nm. Following the initial observation of the optical analogous of the coherent Dicke microwave narrowing, the newest prospects include the exploration of long-range atom surface van der Waals interaction with spatial resolution in an unprecedented range of distances, modification of atom dielectric resonant coupling under the influence of the coupling between the two neighbouring dielectric media, and even the possible modification of interatomic collisions processes under the effect of confinement

Testing the distance-dependence of the van der Waals interaction between an atom and a surface through spectroscopy in a vapor nanocell

This paper presents our current measurements in a vapor nanocell aiming at a test of the distance-dependence of the atom-surface interaction, when simple asymptotic descriptions may turn to be not valid. A state-of-the-art of atom-surface interaction measurements is provided as an introduction, along with the comparison with the theory of the van der Waals (or Casimir-Polder) interaction; it is followed by a presentation of the most salient features of nanocell spectroscop

A Semiotic Interpretation of an Economic-Mathematical Problem in Agriculture

The attempt for a semiotic interpretation of the economic-mathematical problem in Agriculture is motivated by the necessity of finding out an extremely simplified and universal method for working out the great variety of economic-mathematical models for specific objects and concrete tasks. This method is made out by representation of an economic-mathematical model in Agriculture as a sign-system, i.e. as an object of semiotics. U. Eco’s theory for producing of sign-systems is applied. Finally, the semiotic interpretation promotes the in-depth study of the system analysis in the agrarian economics.

Determinants of Consumers’ Demand of Foods in Bulgaria

The results of an empiric analysis of consumers’ behaviour regarding the demand of foods in Bulgaria are presented here. The principles of income distribution in home budgets in respect to food expenditures are established on the basis of a regression- and co-relation analysis. A tree of preferences is outlined which details consumers motivations and describes the cause and effect chain of demand.

Experimental test of the distribution of atomic trajectories at grazing incidence in a micrometric thin vapour cell

poster présenté par D BlochInternational audienc