Benchtop nuclear magnetic resonance (NMR) pulsed field gradient (PFG) and relaxation measurements were used to monitor the clathrate hydrate shell growth occurring in water droplets dispersed in a continuous cyclopentane phase. These techniques allowed the growth of hydrate inside the opaque exterior shell to be monitored and, hence, information about the evolution of the shell's morphology to be deduced. NMR relaxation measurements were primarily used to monitor the hydrate shell growth kinetics, while PFG NMR diffusion experiments were used to determine the nominal droplet size distribution (DSD) of the unconverted water inside the shell core. A comparison of mean droplet sizes obtained directly via PFG NMR and independently deduced from relaxation measurements showed that the assumption of the shell model-a perfect spherical core of unconverted water-for these hydrate droplet systems is correct, but only after approximately 24 h of shell growth. Initially, hydrate growth is faster and heat-transfer-limited, leading to porous shells with surface areas larger than that of spheres with equivalent volumes. Subsequently, the hydrate growth rate becomes mass-transfer-limited, and the shells become thicker, spherical, and less porous.
Insertion of a hooked stylet into the region of a mammographic abnormality is a simple method of localization prior to biopsy. The hook on the stylet does not permit movement of the localization device away from the lesion during the interval between placement and surgical excision. A xeroradiograph of the biopsy specimen determines whether the suspected region was obtained surgically.
Extraperitoneal, perivesical pelvic effusions may be hemorrhagic or uriniferous, the latter resulting from extraperitoneal rupture of the bladder or disruption of the posterior urethra. The effusions may be recognized on anteroposterior radiographs of the pelvis by (a) displacement of the bladder (small effusion); (b) obliteration of the normal soft-tissue anatomy within the pelvis (moderate effusion); and (c) upward displacement of the pelvic ileal loops and extension of the effusion into the flank stripes (large effusion). Perivesical effusions most frequently accompany anterior pelvic arch injuries, i.e., double vertical and Malgaigne fractures and fractures involving, or separation of, the pubic symphysis.
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