Invasion velocity

Earlier studies (ref. 440-442) with ordinary air microbubbles (without any synthetic surfactant coating) have already shown that echocardiographic contrast produced by microbubbles is useful in the qualitative analysis of blood flow and valvular regurgitation. In addition, quantitative studies (ref. 440) have shown a correlation between individual contrast trajectories on M-mode echocardiography and invasive velocity measurements in human beings. Meltzer et al. (ref. 441) have shown that velocities derived from the slopes of contrast trajectories seen on M-mode echocardiography correlate with simultaneous velocities obtained by Doppler techniques. (This correlation is expected because both measures represent the same projection of the microbubble velocity vector, that is, in the direction of the sound beam.) More detailed studies (ref. 442) confirmed that microbubble velocity obtained from either Doppler echocardiography or M-mode contrast trajectory slope analysis correlates well with actual (Doppler-measured) red blood cell velocity. Thus, these early studies have shown that microbubbles travel with intracardiac velocities similar to those of red blood cells. 

An order-of-magnitude estimate of the critical stirring rate can be obtained from the balance between the typical flow velocity and the speed of the propagating fronts. The assumption behind this is that the flow produces a topological transition by generating a quasi-one-dimensional filamental structure. This naturally leads to the break down of coexistence, due to the different invasion velocities of the fronts separating the patches of different strains. 

To calculate T, note that when the adult age is reached, individuals leave the paternal territory and fly to new places. The value of this time has been estimated from observations to fall between 1.5 and 2 years [196] we choose 1.75 yr as a typical value. In fact, values of T between 1.5 and 2 yr do not change the results we derive below. From Fig. 7.13 (main figure) and (7.44) we obtain D = (10.1 2.4) x 10 km /yr. From (7.43) one finds that both RD and RT models yield an invasion velocity of 28 4 km/yr with a relative difference (urd — Urt) /wrt of 1.8 0.4. The observed velocity is 28 1 km/yr and can be estimated from experimental... 

These results can be discussed in light of those obtained in [413], where the invasion velocities for C. acanthoides and C. nutans were also studied. In that work, the authors obtained some predictions for the front velocities by using nonparametric [78] and mechanistic estimates of the dispersal kernel. Their work was specially... 

This technique is invasive however, the particle can be designed to be neutrally buoyant so that it well represents the flow of the phase of interest. An array of detectors is positioned around the reactor vessel. Calibration must be performed by positioning the particle in the vessel at a number of known locations and recording each of the detector counts. During actual measurements, the y-ray emissions from the particle are monitored over many hours as it moves freely in the system maintained at steady state. Least-squares regression methods can be applied to evaluate the temporal position of the particle and thus velocity field [13, 14]. This technique offers modest spatial resolutions of 2-5 mm and sampling frequencies up to 25 Hz. 

In summary, we have commented briefly on the microscopic applications of NMR velocity imaging in complex polymer flows in complex geometries, where these applications have been termed Rheo-NMR [23]. As some of these complex geometries can be easily established in small scales, NMR velocimetry and visc-ometry at microscopic resolution can provide an effective means to image the entire Eulerian velocity field experimentally and to measure extensional properties in elastic liquids non-invasively. 

A non-invasive infrared (IK) method has been developed for the measurement of temperatures of small moving fuel droplets in combustion chambers. 7111 The IR system is composed of two coupled off-axis parabolic mirrors and a MCT LWIR detector. The system was used to measure the temperature variations in a chain of monosized droplets generated with equal spacing and diameter (200 pm), moving at a velocity of >5 m/s and evaporating in ambient air. The system was also evaluated for droplet temperature measurements in flames under combustion conditions. 

In contractile experiments the time from the stimulation of the nerve to the CMAP recorded in muscle provides an estimate of NCV. The length of the nerve from the stimulating electrode to the muscle can simply be measured and divided by the time. However, the time recorded in this way includes the delay for synaptic transmission, which may be increased in models with synaptic defects. If this is a concern or if the only parameter desired is NCV, then the measurement can be obtained non-invasively with a relatively simple setup (e.g., (3)). Using the sciatic nerve, NCV can be calculated by measuring the latency of compound motor action potentials recorded in the muscle of a rear paw. Action potentials are produced by subcutaneous stimulation at two separate sites proximal stimulation at the sciatic notch and distally at the ankle. NCV is then calculated by using the two latencies and conduction distance. Decreases in nerve conduction velocity most often reflect defects in myelination, but may also be the result of changes in internodal distance, decreased axon diameters, or altered excitability. 

Notably, the 5 0 of soil water affects more than just the isotopic composition of respired CO2. It also affects the isotopic composition of ambient CO2, which makes contact with soil water by diffusing into and out of the soil. Depending upon its residence time in the soil, the diffusing ambient CO2 can partially or fully equihbrate with the soil water. This diffusion-equilibration-retro-diffusion process is termed the invasion effect (Tans, 1998) and was demonstrated experimentally by Miller et al. (1999). The impact of this effect on atmospheric 5 0 is defined in Equation (43) as Fi(5a — SJ/Ca. This non-biological invasion flux, Fi, is a function of the CO2 concentration near the soil surface, c and the speed with which CO2 in the air above the soil diffuses into the soil and equilibrates with soil water, v (the piston velocity with values for typical soil of —0.012 cm s and effective penetration of invading CO2 of —3 cm) ... 

This probe measured the densification and increase in size of the granules (changes in momentum of granules moving with constant velocity because of a mass change of the granules). The method did not gain popularity because of its invasive nature. 

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