EFFECTIVE DETERMINATION OF POISSON NOISE

We give an effective definition of higher dimensional parameter Poisson noise. The idea comes from the observation of the conditional probablistic behavior of a Poisson process under the condition that it jumps over the unit time interval exactly as many times as n. Also, taking the optimality into account we can give effective determination of a Poisson noise with multi-dimensional parameter, which is in agreement with the formal generalization of a Poisson noise in terms of the characteristic functional.

Ion Diffusion

The microregional transport of ions under an externally applied electric field has been discussed previously. When ions are distributed heterogeneously in soil on a macroscopic scale, because of the presence of concentration gradient (i.e., the difference in chemical potential), ions tend to migrate from a site of high concentration to a site of low concentration. Such a phenomenon is called ion diffusion. The diffusion rate of various ions in a soil is related to the nature of the ions and the interaction among them and is also affected by the chemical processes in the soil, such as adsorption, desorption, and repulsion. For variable charge soils carrying both positive and negative surface charges, the factors that affect ion diffusion are rather complex. In the present chapter, after treatment of basic principles of ion diffusion, the characteristic features of ion diffusion in variable charge soils will be discussed, with the emphasis on diffusion of anions because this is one of the important means for elucidating the characteristics of variable charge soils. In a solution, if the ion concentration in point A is higher than that in point B, under static conditions, the number of ions moving from point A to point B will be larger than that moving in the opposite direction due to the random thermal motion of ions. In order to express the net ion flux J within an unit time interval through an unit area, Fick introduced the first diffusion law: . . . J = –D dC/dX . . . (9-1) where dC/dX is the concentration gradient. The negative sign in the equation denotes that the flux is from high concentration to low concentration; that is, the direction of the flux is opposite to that of the concentration gradient. D is called the diffusion coefficient. It can be seen from the equation that the diffusion coefficient is the flux passing through an unit cross-sectional area within a unit time interval under a unit concentration gradient. D is the most important parameter in ion diffusion. Fick’s first diffusion law is applicable to both homogeneous and heterogeneous medium such as soil.

Correlation among Si, Ge, and B deposition rates in low-pressure CVD with SiH4−GeH4−B2H6-He mixtures

The deposition process at 500 °C with SiH4–GeH4–B2H6–He mixtures, which yields the amorphous Si–Ge–B alloy, was studied. Although in crystalline Si and Ge the maximum B content is limited to the solid solubility, any amount of B can uniformly be contained in amorphous Si–Ge–B. Thus, films with a B content up to 64 at.% have been prepared. The deposition rate of atoms, defined as the number of atoms deposited in a unit time interval, is obtained for each element by analyzing the growth rate together with the composition and the mass density of the film. When the SiH4 and the B2H6 partial pressures are constant, the Si and the B deposition rates are almost independent of the GeH4 partial pressure. In contrast, the Si deposition rate increases remarkably as the B2H6 partial pressure increases, even when the SiH4 partial pressure is maintained constant. A simple model is proposed for explaining the relationship between the Si and the B deposition rates.

Comparison of Surgical and Conservative Management in 208 Patients with Acute Spinal Cord Injury

ABSTRACT:The role of surgery in the management of acute spinal cord or cauda equina injuries remains controversial. The present study analyzed ten admission features and three outcome variables in 208 patients treated in an Acute Spinal Cord Injury Unit, 116 (56%) of whom underwent at least one spinal operation. The surgical and non-surgical groups showed no significant differences in the following seven clinical features: age, sex, distance travelled to the Unit, time interval between trauma and admission, type of accident, severity of injuries to the spinal cord, and severity of associated injuries. However, the two groups showed significant differences in level and type of vertebral column injury, and in the frequency of pre-existing spinal abnormalities. These differences were due to management policies which selected certain injuries for surgical or non-surgical treatment. One-third of the operative procedures were performed primarily for neural decompression, one-third primarily for reduction of bony structures and one-third for fusion. However, 95% of the operative patients had a fusion at the initial operation. Operative treatment was associated with a lower overall mortality rate (6.1%) than non-operative (15.2%), despite a higher frequency of thrombo-embolic complications in the surgical group. Overall, there was no difference between operated and non-operated patients in length of stay or neurological recovery. Surgical management of patients with acute spinal cord injury appears safe in terms of mortality rate and neurological recovery, but it has not been proven to improve the latter.