Determination of pulmonary microvascular reflection coefficient in sheep by venous occlusion

We devised a technique that permitted elevation of pulmonary pressures in unanesthetized sheep by occluding their pulmonary veins. Using this technique, we raised pulmonary capillary pressure from a baseline of 13.2 +/- 2.2 to 35.3 +/- 5.1 mmHg. This increased lung lymph flow (from 8.8 +/- 2.7 to 53.1 +/- 13.9 ml/h). We estimated the pulmonary microvascular oncotic reflection coefficient and found it to be 0.82 +/- 0.05 (SD). The filtration coefficient was 0.019 +/- 0.005 ml.mmHg-1.min-1. During the period of increased pressure, the animals had stable arterial pressures and cardiac outputs. None of the animals developed blood coagulation problems. These data illustrate the usefulness of pulmonary venous occlusion to elevate pulmonary microvascular pressure to obtain plasma-to-lymph protein concentration ratios independent of flow, allowing for the calculation of the oncotic reflection coefficient.     

Dynamical and Static Spin Susceptibilities of Doped Gapped Graphene Nanoribbon Due to Local Electronic Interaction

We present the behaviors of both dynamical and static spin susceptibilities of doped gapped armchair graphene nanoribbon using the Green’s function approach in the context of Hubbard model Hamiltonian. Specially, the effects of spin polarization and gap parameter on the spin excitation modes of armchair graphene nanoribbon are investigated via calculating correlation function of spin density operators. Our results show the increase of electron concentration leads to disappear low frequency spin excitation mode for gapless case. We also show that low frequency excitation mode for both gapped and gapless nanoribbon disappears under spin full polarization condition. Finally, the electron density dependence of static charge structure factor of armchair graphene nanoribbon is studied. The effects of both gap parameter and magnetic ordering on the static structure factor are discussed in details.