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The term Harmonic Nanoparticles (HNPs) designates a family of metal oxide nanocrystals. Possessing appealing optical properties aside from classical luminescence. In fact, becauseof the lack of inversion symmetry in their crystal structure, these materials display high nonlinear optical response. In particular, the lowest nonlinear term of their nonlinear susceptibility, χ(2), is non vanishing differently from the case of isotropic materials. For this reason, they are primarily employed in imaging applicationsbased on second harmonic generation. We have recently shown that third and even fourth harmonic generation are also very efficient for some of these materials, hence the name.The distinctive features of HNPs as opposed to luminescent ones include their fully coherent emission, the absence of bleaching/blinking, and spectralflexibility(spanning from the ultraviolet to the infrared). This last assetis particularly appealing for bio-imaging applications, as HNPs allows imaging beyond the “classical” tissue transparency window (NIR I: 650-950 nm), in the newly investigated NIR II (1100-1350 nm) and NIR III (1600-1870 nm) windows. Working in these spectral regions enables sensibly deeper imaging penetration because of reduced scattering at longer wavelengths.After introducing the nonlinear optical properties of HNPs we will discuss their in vivo use for tracking labelled cells by simultaneous second and third harmonic acquisition, demonstrating highly specific retrieval of cancer metastases in lungs and stem cells in muscle tissue at > 1 mm depth.

Triggering rain on demand is an old dream of mankind with a huge potential socio economical benefit. To date efforts have mainly focused on cloud seeding using silver salt particles. We demonstrate that self guided ionized filaments generated by ultrashort laser pulses are also able to induce water cloud condensation in the free sub saturated atmosphere. Potential contributing mechanisms include photo oxidative chemistry and electrostatic effects. As well as revealing the potential for influencing or triggering water precipitation laser induced water condensation provides a new tool for the remote sensing of nucleation processes in clouds.

We experimentally measured the supercontinuum generation using 3 J 30 fs laser pulses and measured white light generation at the level of 1 J. Such high energy is allowed by a strong contribution to the continuum by the photon bath as compared to the self guided filaments. This contribution due to the recently observed congestion of the filament number density in the beam profile at very high intensity also results in a wider broadening for positively chirped pulses rather than for negatively chirped ones similar to broadening in hollow core fibers.

We have experimentally measured that laser filaments in air generate up to 10(14) 3x10(12) and 3x10(13) molecules of O 3 NO and NO2 respectively. The corresponding local concentrations in the filament active volume are 10(16) 3x10(14) and 3x10(15) cm( 3) and allows efficient oxidative chemistry of nitrogen resulting in concentrations of HNO3 in the parts per million range. The latter forming binary clusters with water our results provide a plausible pathway for the efficient nucleation recently observed in laser filaments. (C) 2010 American Institute of Physics. [doi:10.1063/1.3462937]

We numerically investigate the pulse compression mechanism in the infrared spectral range based on the successive action of nonlinear pulse propagation in a hollow core fiber followed by linear propagation through bulk material. We found an excellent agreement of simulated pulse properties with experimental results at 1.8 mu m in the two optical cycle regime close to the Fourier limit. In particular the spectral phase asymmetry attributable to self steepening combined with self phase modulation is a necessary prerequisite for subsequent compensation by the phase introduced by glass material in the anomalous dispersion regime. The excellent agreement of the model enabled simulating pressure and wavelength tunability of sub two cycles in the range from 1.5 to 4 mu m with this cost efficient and robust approach.

Six healthy men were investigated to determine the osmotic efficiency of hypertonic monosaccharide solutes on the release of plasma arginine vasopressin (AVP). Twenty percent hypertonic glucose infused at 0.187 mmol/kg body weight/min. over 15 min. increases plasma osmolality but not AVP. In contrast, 20% hypertonic fructose administered identically obtains an increase in both. An initial 71% rise in AVP concentration (p less than 0.01) occurred 10 min. post-infusion accompanied by a peak in plasma osmolality and we did not expect AVP to rise by 336% (p less than 0.01) 45 minutes after infusion as plasma osmolality was returning to baseline values. The first increase in plasma AVP reflects an osmotic efficiency probably resulting from the fact that fructose does not cross the membrane of osmoreceptor cells. The mechanism of the second and unexpected increase is discussed, especially the influence of plasma insulin released as a result of fructose infusion.

In seven healthy male volunteers we investigated changes in plasma atrial natriuretic factor ([ANF]), arginine vasopressin ([AVP]) and plasma volume (PV) during supine immersion. Twenty minutes head-out water immersion in a supine position in a thermo-neutral water bath attenuated the increase in PV induced by 20 min in a supine position in air, but increased the mean plasma [ANF] from 32.0 pg · ml−1, SEM 5.1 to 53.3 pg · m−1, SEM 3.6 and decreased the mean plasma [AVP] from 1.4 pg · ml −1, SEM 0.1 to 0.9 pg · ml−1, SEM 0.04. Simultaneously, diuresis and natriuresis increased markedly. During a 20-min control period in the supine posture without immersion, PV, plasma [ANF] and [AVP] remained unaffected while diuresis and natriuresis did not increase to the same extent. These data suggest that an increase in the central blood volume induced by a weak external hydrostatic pressure during supine immersion triggered the changes in plasma [ANF] and [AVP] and that the increase was probably due to a shift of blood volume from peripheral to central vessels. The changes in plasma [ANF] contributed to the changes in natriuresis.

Supine and upright plasma renin activities (PRA) were measured in 151 normal subjects on free sodium intake. Supine and upright plasma renin activities were then related to the 24-hour urinary sodium or the 2-hour urinary sodium excretion, measured in the morning after overnight fasting. Urinary sodium excretion was expressed as the urinary rate per hour or as the urinary Na/creatinine ratio. Correlations were found between both supine and upright PRA and 2 h urinary sodium excretion expressed as the Na/creatinine ratio. Supine and upright PRA values are expressed in terms of these correlations with confidence intervals.

We studied urinary calcium and oxalate excretion in response to oral fructose load and to oral glucose load each on two different randomized mornings in twelve healthy subjects. Oral fructose load provoked an increase in calciuria and a decrease in oxaluria while oral glucose load induced an increase in both calciuria and oxaluria. These results suggested that in healthy subject, the decrease in oxaluria observed during fructose load reduced the product urinary [calcium] x [oxalate] which was the main factor in the genesis of urinary calcium oxalate stones while glucose load increased the risks of urolithiasis by means of the rise in both calciuria and oxaluria.

The relative influences of the supine posture and of immersion on the renin-aldosterone system (RAS) were studied at rest and during moderate exercise in five healthy men. When supine, resting or immersion to the neck for 20 min in a thermoneutral environment both induced a decrease in plasma renin activity (PRA) when compared with the levels measured after 15 min sitting at rest (resting: -44%, p less than 0.05. Immersion: -45%, p less than 0.05). There was no significant difference in PRA decrease between the two situations. Aldosterone (ALDO) values were lower after supine rest or immersion than those observed after sitting at rest, but the difference was not significant. Two types of exercise at a constant relative work load (40-50% maximal oxygen uptake), namely cycling on an ergocycle in the supine position and free-style swimming, induced increases in PRA and ALDO when compared with the levels measured after 15 min rest when sitting (respectively, PRA = +35%, p less than 0.05, and +45%, p less than 0.05, ALDO = +32%, p less than 0.01 and +35%, p less than 0.05). Increases in PRA and ALDO did not differ between the two exercises. Thus inhibitory effects on RAS of change in external pressure are negligible during water immersion to the neck in the supine position and during swimming at moderate intensity.

The influence of posture on plasma renin and aldosterone changes during exercise performed at a constant relative work load (40%–50% maximal oxygen uptake) was studied in eight healthy men. Each subject carried out two 20-min exercises on an ergocycle at an interval of 8 days; the first exercise was performed in the normal sitting position (upright exercise), the second in a comfortable supine position (supine exercise). In both cases, heart rate and blood pressure were measured as well as plasma renin activity (PRA), aldosterone (ALDO) and osmolality, before and immediately after exercise, and 15 min following the end of exercise. An increase in heart rate, blood pressure, PRA, ALDO and osmolality was noted at the end of each exercise. This increase was greater in the supine exercise than when upright for PRA and ALDO; plasma osmolality and blood pressure showed identical increases for both types of exercise; increase in heart rate was greater when supine than when upright. PRA and ALDO were still elevated 15 min after the upright activity, but had regained their base values in that time after the supine exercise. Our results show that moderate, relatively brief periods of exercise stimulate the production of renin and aldosterone, but the response is less when supine than in the normal upright position.