Doppler reduction

A remarkable feature of these spectra is the resolution of individual rotational lines in such large molecules. [Note that the expanded specttum in, for example. Figure 9.47(a) covers only 5000 MFIz (0.17 cm )]. This is due partly to the very low rotational temperature (3.0 K for aniline and 2.2 K for aniline Ar), partly to the reduction of the Doppler broadening and partly to the very high resolution of the ring dye laser used. 

Markus HS, Droste DW, Kaps M, Larrue V, Lees KR, Siebler M, Ringelstein EB. Dual antiplatelet therapy with clopidogrel and aspirin in s3miptomatic carotid stenosis evaluated using doppler embolic signal detection the Clopidogrel and Aspirin for Reduction of Emboli in Symptomatic Carotid Stenosis (CARESS) trial. Circulation 2005 lll(17) 2233-2240. 

The zeta potential of the formulations was determined by Doppler velocimetry and PCS on a Zetasizer 4 (Malvern Instruments, U.K.), without further dilution. The zeta potential of LC-AmB under these conditions was —44 mV, slightly lower than that measured for the same lipid composition without AmB, —55 mV, but remaining consistent with colloidal stability. This reduction in the absolute value of the zeta potential could be due to the presence of AmB at the surface, because free AmB dispersed in water under the same conditions had a less negative zeta potential about —27 mV. 

Helioseismic waves are detected by measuring the Doppler shift of lines in the solar spectrum due to vertical motion of the Sun s surface along the line of sight. With appropriate data-reduction techniques, the frequencies for global oscillations can be determined to an accuracy of 5 ppm. This extreme accuracy requires long-term, continuous observations that are best done by spacecraft such as the joint ESA/NASA SOHO spacecraft, which observes the Sun from the Lagrangian point where the Earth gravity balances that of the Sun. 

Even in a molecule the size of benzene the resolution achieved in this way is sufficient to investigate the dynamic behavior of individual rotational states. For this it is necessary to eliminate the Doppler broadening of the rovibronic transitions. Two methods have been applied (i) the elimination of Doppler broadening in a Doppler-free two-photon-transition and (ii) the reduction of Doppler broadening in a molecular beam. Measurements of the dynamic behavior have been performed in the frequency [3] and time domain [4]. We will briefly summarize the results from high-resolution measurements and discuss the conclusions on the intramolecular decay mechanism. Then it will be discussed how the intramolecular dynamics is influenced by the attachment of an Ar or Kr atom to the benzene molecule, leading to a weakly bound van der Waals complex. 

FIGURE 37.4 SLS irritation and moisturizer treatment, (a) No significant differences in skin color (a-values) were detectable with the Chromameter. (b) The same sites as in (a) scanned with the laser Doppler imager showed marked reduction of erythema. Volar forearms were treated with a water-in-oil emulsion twice daily for four weeks. Statistical significance was determined using the paired r-test ( p >. 05, p <. 01). 

Richter and Doppler (1997) Nickel and copper on supports Phase evolution, amorphous co-phases + + Reductive activation, various reactions... 

A rise in the resistance index of the kidneys and a reduction in renal perfusion as shown by Doppler duplex sonography make possible an early diagnosis before renal dysfunction is clinically evident. (47) Coloured sonography has proved of great value in determining renal haemodynamics (which is in posture position deteriorates). 

The effects of tafluprost on IOP and retinal blood flow (RBF) were studied in adult cats [41]. A single drop of tafluprost was placed in one eye and IOP, vessel diameter, blood velocity, and RBF were measured simultaneously by laser Doppler velocimetry. Measurements carried out at 30 and 60min after dosing showed 16.1% and 21.0% IOP reduction, respectively, as well as 1% and 2.4% reduction in mean vessel diameter, respectively. The mean blood velocity increases were 17.4% and 13.7%, respectively, and the mean RBF increases were 20.7% and 18.8%, respectively, 30 and 60min after dosing. 

The exact determination of such a small splitting requires molecular beam techniques. The molecules are cooled in a supersonic expansion which leads to a population distribution among the rotational states corresponding to a Boltzmann distribution with 10-12 K. This leads to a considerable reduction of populated states and thereby to a simplification of the spectrum. In a supersonic expansion we find a considerable decrease in the line width due to the decrease in translational motion, especially when the laser is perpendicular to the expansion direction. The corresponding reduction in Doppler width allows an improved frequency resolution, which will later be shown to be crucial for the success of the experiment. 

A reduction of the Doppler width by a factor ItP is attainable. As an example, the barium resonance at 535 nm would, with an ion source temperature of 2000K and an acceleration of 60keV, have a residual Doppler width of about 1 MHz, compared with the natural linewidth of 19 MHz. In practice the experimental linewidths are 10-50 MHz depending on the natural linewidth, ion source, acceleration voltage stability and beam optics. 

The practice of cooling discharge tubes in liquid air allowed some reduction in the Doppler width, but this technique was not always fully exploited since it was common to use high current densities in order to obtain a bright atomic spectrum. A considerable advance wras made after the discovery of deuterium in 1932, since the Doppler width of these lines compared with those of the light isotope is smaller by the factor (see Fig. 3). 

Of a number of studies of this line since the war, the best resolution was obtained by Series [122]. Reduction of therf Doppler width was again achieved by liquid hydrogen cooling of a discharge as gentle as possible. Spectroscopic analysis was by means of multiple Fabry-Perot interferometers, which allow an extension of spectral range without sacrifice of resolving power. 

---