Momentum diffusion for coupled atom-cavity oscillators

It is shown that the momentum diffusion of free-space laser cooling has a natural correspondence in optical cavities when the internal state of the atom is treated as a harmonic oscillator. We derive a general expression for the momentum diffusion which is valid for most configurations of interest: The atom or the cavity or both can be probed by lasers, with or without the presence of traps inducing local atomic frequency shifts. It is shown that, albeit the (possibly strong) coupling between atom and cavity, it is sufficient for deriving the momentum diffusion to consider that the atom couples to a mean cavity field, which gives a first contribution, and that the cavity mode couples to a mean atomic dipole, giving a second contribution. Both contributions have an intuitive form and present a clear symmetry. The total diffusion is the sum of these two contributions plus the diffusion originating from the fluctuations of the forces due to the coupling to the vacuum modes other than the cavity mode (the so called spontaneous emission term). Examples are given that help to evaluate the heating rates induced by an optical cavity for experiments operating at low atomic saturation. We also point out intriguing situations where the atom is heated although it cannot scatter light.Comment: More information adde

Estudo da desidratação osmótica de abóbora utilizando metodologia de superfície de resposta.

Suplemento 1. Edição dos Resumos do 43 Congresso Brasileiro de Olericultura, Recife, jul. 2003

On the suppression of the diffusion and the quantum nature of a cavity mode. Optical bistability; forces and friction in driven cavities

A new analytical method is presented here, offering a physical view of driven cavities where the external field cannot be neglected. We introduce a new dimensionless complex parameter, intrinsically linked to the cooperativity parameter of optical bistability, and analogous to the scaled Rabbi frequency for driven systems where the field is classical. Classes of steady states are iteratively constructed and expressions for the diffusion and friction coefficients at lowest order also derived. They have in most cases the same mathematical form as their free-space analog. The method offers a semiclassical explanation for two recent experiments of one atom trapping in a high Q cavity where the excited state is significantly saturated. Our results refute both claims of atom trapping by a quantized cavity mode, single or not. Finally, it is argued that the parameter newly constructed, as well as the groundwork of this method, are at least companions of the cooperativity parameter and its mother theory. In particular, we lay the stress on the apparently more fundamental role of our structure parameter.Comment: 24 pages, 7 figures. Submitted to J. Phys. B: At. Mol. Opt. Phy

Psychological talent predictors in youth soccer: A systematic review of the prognostic relevance of psychomotor, perceptual-cognitive and personality-related factors

Within the multidimensional nature of soccer talent, recently there has been an increasing interest in psychological characteristics. The aim of this present research was to systematically review the predictive value of psychological talent predictors and provide better comprehension of the researchers’ methodological approaches and the empirical evidence for individual factors (i.e., psychomotor, perceptual-cognitive and personality-related). Results highlighted heterogeneous study designs (e.g., participants, measurement methods, statistical analyses) which may limit the comparability of studies’ findings. Analyzing the number of included studies, psychomotor (n = 10) and personality-related factors (n = 8) received more consideration within the literature than perceptual-cognitive factors (n = 4). In regard to empirical evidence, dribbling (0.47 ≤ d ≤ 1.24), ball control (0.57 ≤ d ≤ 1.28) and decision-making (d = 0.81) demonstrated good predictive values as well as the achievement motives hope for success (0.27 ≤ d ≤ 0.74) and fear of failure (0.21 ≤ d ≤ 0.30). In conclusion, there is growing acceptance of the need for more complex statistical analyses to predict future superior performance based on measures of current talent. New research addresses the necessity for large-scale studies that employ multidisciplinary test batteries to assess youth athletes at different age groups prospectively.</div

Influence of osmotic dehydration and high temperature short time processes on dried sweet potato (Ipomoea batatas Lam.).

The puffing operation is carried out at as intermediate stage in the drying process. When reconstituted, the dehydrated puffed productpresents a more pleasing appearance than the material that has not been puffed. The high temperature and short time process (HTST) was employed to obtain puffed sweet potato slices from both in natura and osmotically pretreated with sucrose and salt solutions samples. Processing time was the most significant variable affecting moisture content, water activity and rehydration. All the empirical models obtained using response surface methodology were considered predictive. The best conditions for the HTST sweet potato slices were obtained using a temperature of 160 C and time of 22 min for samples with no osmotic treatment and a temperature of 150 C and time of 10 min for samples submitted to the osmotic treatment. Scanning electronic microscopy confirmed the formation of pores within the tissue, and surface sealing during the HTST process as the samples puffed up (volume increase). The shortest convective drying time corresponded to the sample treated only by the HTST process. 2007 Elsevier Ltd. All rights reserved

Effect of concentration on the physical properties of cashew juice.

Thermal conductivity, thermal diffusivity, density and viscosity of cashew juice were measured at 30 oC for soluble solids content ranging from 5.5 to 25 oBrix. Thermal conductivity and diffusivity were determined using a linear hest source probe. Both properties were found to decrease with the increase of soluble solids content, while density and viscosity increased. Empirical models were fitted to the experimental data for each property and the accuracy of those models was checked

Estudo reológico de polpa de caju em diferentes concentrações.

Neste estudo foi avaliado o comportamento reológico de polpa de caju em diferentes concentrações (5,5 a 25,0°Brix) na temperatura de 30°C. Os resultados indicaram um aumento da viscosidade com o aumento da concentração. A polpa de caju teve o comportamento de um fluido não Newtoniano com características pseudoplásticas. Palavras-chave: Anacardium occidentale L., reologia, viscosidade

Observation of squeezed light from one atom excited with two photons

Single quantum emitters like atoms are well-known as non-classical light sources which can produce photons one by one at given times, with reduced intensity noise. However, the light field emitted by a single atom can exhibit much richer dynamics. A prominent example is the predicted ability for a single atom to produce quadrature-squeezed light, with sub-shot-noise amplitude or phase fluctuations. It has long been foreseen, though, that such squeezing would be "at least an order of magnitude more difficult" to observe than the emission of single photons. Squeezed beams have been generated using macroscopic and mesoscopic media down to a few tens of atoms, but despite experimental efforts, single-atom squeezing has so far escaped observation. Here we generate squeezed light with a single atom in a high-finesse optical resonator. The strong coupling of the atom to the cavity field induces a genuine quantum mechanical nonlinearity, several orders of magnitude larger than for usual macroscopic media. This produces observable quadrature squeezing with an excitation beam containing on average only two photons per system lifetime. In sharp contrast to the emission of single photons, the squeezed light stems from the quantum coherence of photon pairs emitted from the system. The ability of a single atom to induce strong coherent interactions between propagating photons opens up new perspectives for photonic quantum logic with single emittersComment: Main paper (4 pages, 3 figures) + Supplementary information (5 pages, 2 figures). Revised versio