Mean Loss Rate Research Articles

A New Linear Model for Stability Prediction

AbstractBased upon Okusa's observation (Chem. Pharm. Bull. 1975) that the slopes of a linear plot of logo log fraction of active substance degraded vs log time for first order decay kinetics and a linear plot of log of drug remaining vs log time for a zero order decay kinetics are both unity, an algorithm has been developed to resolve both the energy of activation (E) and the rate constant (Ko or Lo) at the desired shelf-life temperature (To) by analysis of the y-intercepts of parallel slopes at more than one elevated temperature (T).Preliminary estimates of both E and either Ko or Lo are then substituted into a series of mathematical expressions based upon well known Arrhenius relationship:k = A ·exp -E/1.987) (1/T-l/To) where A = Ko or LoUsing converging and interative techniques to treat elevated temperature data, the resulting mean loss rate (eithri Ko or Lo at the designated shelf-life temperature plus a residual error term thus obtained, is used to distinguish statistically between zero and first or...

New concepts of destructive periodontal disease.

The most common forms of destructive periodontal disease have been thought to slowly and continuously progress until treatment or tooth loss. Recently, data have become available which are inconsistent with this "continuous disease" hypothesis. Data from longitudinal monitoring of periodontal attachment levels and alveolar bone in humans and in animals suggest that periodontal disease progresses by recurrent acute episodes. In addition, rates of attachment loss have been measured in individual sites which are faster than those consistent with the continuous disease hypothesis or slower than those expected from estimates of prior loss rates. To account for these observations, a model of destructive periodontal disease is described in which bursts of activity occur for short periods of time in individual sites. These bursts appear to occur randomly at periodontal sites throughout the mouth. Some sites demonstrate a brief active burst of destructive periodontal disease (which could take a few days to a few months) before going into a period of remission. Other sites appear to be free of destructive periodontal disease throughout the individual's life. The sites which demonstrate destructive periodontal activity may show no further activity or could be subject to one or more bursts of activity at later time periods. Comparison of monitored loss rates for a year with mean loss rates prior to monitoring suggested that there may be relatively short periods in an individual's life in which many sites undergo periodontal destruction followed by periods of extended remission. An extension of the random disease model is also suggested in which bursts of destructive periodontal disease activity occur with higher frequency during certain periods of an individual's life.

The distant interplanetary wake of Venus: Plasma observations from Pioneer Venus

In June 1979 the Pioneer Venus orbiter made its first series of passes through the distant solar wind wake of Venus at distances of 8–12 Rv behind the planet. During this period the plasma analyzer aboard the spacecraft detected disturbed magnetosheath plasma that intermittently disappeared and reappeared, suggesting a tattered, filamentary cavity trailing behind the planet. The magnetosheath dropouts almost always occurred inside the region of ‘magnetotail’ observed by Russell et al. Sporadic bursts of energetic ions (E/q ≳ 4 kV) are detected inside and, occasionally, outside the magnetotail; all such bursts are consistent with identification of the ion as O+ of planetary origin moving at the local magnetosheath flow speed. The morphology of the plasma dropouts and of the O+ bursts is analyzed in detail. The cavity appears to contract at times of high solar wind dynamic pressure. The intensity of the O+ component is highly variable, and appears not to be strongly correlated with solar wind dynamic pressure. The most intense bursts correspond to a flux ≲107 ions cm−2 s−1. This maximum flux, if steady and filling a cylinder 1 Rv in radius would correspond to a mass loss rate of ≲1025 ions s−1; the intermittency and variability of the flux suggest that the true mean loss rate is very much lower. The kinetic temperature of the O+ component is estimated as 105–106 K in order of magnitude.

An Air-Flow System for Measuring Total Transpiration and Cuticular Permeability in Arthropods: Studies on the Centipede Scolopendra Polymorpha

An air-flow system (transpiration monitor) for measuring small and sporadic losses of water from intact arthropods and across isolated integument or artificial membranes is described and tested on the desert centipede Scolopendra polymorpha. Mean water loss rates (WLR) at 40 C (2.03 mg cm⁻² h⁻¹) were approximately three times those at 30 C (0.64 mg cm⁻² h⁻¹). The first hour's water loss at both temperatures featured numerous small bursts of moisture associated with oral discharges; peaks corresponding to these bursts decreased in amplitude and frequency during the second hour. Water loss increased in normal (unsealed), alive (mouth and anus sealed), and dead (mouth and anus sealed) centipedes as temperatures were gradually raised from 30 to 42 C; the lowest WLR over the entire temperature range was observed in alive-sealed centipedes. The permeability of a piece of untreated cuticle between 25 and 42 C was greater than its permeability after coating the same piece with 10 μg cm⁻² of the hydrocarbon, n-eicosane (C20). Comparison of the water relations of S. polymorpha with other arthropods as well as the potential and limitations of the transpiration monitor are discussed.

Estimation of the mean loss rate of precipitation and its characteristics

Estimation of the mean loss rate of precipitation and its characteristics

Circulation of Na, Cl, and Br in the tropical marine atmosphere

Concentrations of Na, Cl, Br, and I in aerosols and Cl, Br, and I in inorganic gases were measured in the marine atmosphere off the west African coast (∼0°N, ∼0°W) in June 1977 and used to estimate their mean lifetimes and rates of production. Mean concentrations (in micrograms per cubic meter) during an 8‐day, stable, rain‐free period of the voyage follows: for paniculate Na 4.0, Cl 5.3, Br 0.017, and 1 0.004; for inorganic gas Cl 1.0, Br 0.012, and 1 0.013. The results of a steady state analysis suggest a ∼3‐day mean residence time for the marine aerosol during the period of our observations, a ∼667 μg m−2 d−1 loss rate of Cl (probably as HCl) from the marine aerosol, and a subsequent ‐day mean residence time in the marine atmosphere. A similar analysis for gaseous inorganic Br gave a μg m−2 d−1 mean loss rate from the marine aerosol and a ∼7‐day mean residence time. Computed dry deposition coefficients were (in centimeters per second) ∼0.4 for the marine aerosol, ∼0.77 for gaseous inorganic Cl, and ∼0.24 for gaseous inorganic Br.