Background: Lymph flow depends on both the rate of lymph production by tissues and the extent of passive and active pumping. Here we aim to characterize the passive mechanical properties of a lymphangion in both midlymphangion and valve segments to assess regional differences along a lymphangion, as well as evaluating its structural composition. Methods and Results: Mesenteric lymphatic vessels were isolated and cannulated in a microchamber for pressure-diameter (P-D) testing. Vessels were inflated from 0 to 20 cmH 2 O at a rate of 4 cmH 2 O/min, and vessel diameter was continuously tracked, using an inverted microscope, video camera, and custom LabVIEW program, at both mid-lymphangion and valve segments. Isolated lymphatic vessels were also pressure-fixed at 2 and 7 cmH 2 O and imaged using a nonlinear optical microscope (NLOM) to obtain collagen and elastin structural information. We observed a highly nonlinear P-D response at low pressures (3-5 cmH 2 O), which was modeled using a three-parameter constitutive equation. No significant difference in the passive P-D response was observed between mid-lymphangion and valve regions. NLOM imaging revealed an inner elastin layer and outer collagen layer at all locations. Lymphatic valve leaflets were predominantly elastin with thick axially oriented collagen bands at the insertion points. Conclusions: We observed a highly nonlinear P-D response at low pressures (3-5 cmH 2 O) and developed the first constitutive equation to describe the passive P-D response for a lymphangion. The passive P-D response did not vary among regions, in agreement with the composition of elastin and collagen in the lymphatic wall.
A total of 180 Ss served in 1 of 2 paired-associate learning transfer studies in which the 1st task allowed Ss to integrate the stimulus and/ or the response terras, form either backward or forward associations, or some combination of these factors which were appropriate for the subsequent transfer task. The experiments were designed to test the 2-phase conception of paired-associate learning as applied to transfer phenomena. This conception gave a good approximation of the 1st list and subsequent transfer task performance, and it was concluded that this notion can be fruitfully extended to the area of transfer.
Virginia opossums were gillen 600 trials In a T-maze on a 70-10 .fpatiol probablUty problem. The opossums maximized the perc'entage of their responses to the 70'}l, altematil1e. choosing it on more than 90% of the trials at asymptote. TIle learning CUI'W! of OpO.tfUms did not differ from the learning curI1e of a control group of rut.1. It was concluded that In the Bitterman /bh-mt dichotomy, the opo.uum if classified as a rul on this problem.
To investigate the effects of degree of original list leaming (DOL) and intralist response similarity (IRS) on transfer phenomena, 260 Ss were assigned to learn, by the study-test trialprocedure, oneoffive transfer paradigms. The main transfer results were: (a) paradigm C-B > C-A = A-Br > Br-A; and (b) an IRS by DOL interaction.
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