ABSTRACT
A flow of independent particles, traveling across a biased heterostructure, is shown to produce an essentially constant probability current density in the gate. Based on this observation, a phenomenological boundary condition was proposed for evaluating the eigenfunctions of the Hamiltonian and for the computing the gate probability current density in a three-layer metal-oxide-semiconductor (MOS) heterostructure. Sharp antiresonances are obtained in the probability current, which are interpreted as quasi-bound states in the heterostructure. Results show that the antiresonant states should contribute the least to the gate current as the particles are strongly localized behind the interfacial barrier. The main contribution to the gate current of the MOS structure should come from the states between the antiresonances which are always supplied with particles from the bulk.
ABSTRACT
A theoretical framework for the electron field emission from carbon nanotubes (CNTs) is discussed. Using the tunneling theory, the influence of the detailed electron energy dispersion is proven to be of little importance for the electron field emission. By means of numerical computations in a simplified model, the influence of the environment on the local field on a CNT is discussed for an aligned CNT film. In a simple triangular model for the potential energy barrier at the tube end, a tunneling probability was obtained. A statistical model was developed for the structural and functional parameters of aligned CNT films. Practical CNT films of excellent alignment, obtained directly on a tungsten wire by plasma-enhanced chemical vapor deposition, were analyzed by this statistical model. Their distribution in the enhancement factors was thus deduced. An indirect method to get the average electrical parameters of the film using only a limited amount of experimental data was thus established.
ABSTRACT
The plasma volume (PV) was determined in 109 patients with chronic arterial hypertension (AH) by 131I-labeled serumalbumin, expressing the results in ml/cm body height. An attempt was made to establish a statistical correlation between PV and diastolic pressure (DP). In essential AH three types of PV were found: normal, hypovolemic and hypervolemic; in hypertensive patients with stenosis of the renal aorta and in those with pheochromocytoma PV was slightly diminished; in hyperaldosteronism it was increased. In AH due to renal parenchymatous lesions the mean PV values were normal, a positive correlation being found between PV and DP (r + 0.929 and p = 0.05) in contrast to the other types of AH, where r was non significant or negative (stenosis of the renal artery, pheochromocytoma, malignant AH).
