The impact of muscular dystrophy on limb bone growth and scaling in mice

Muscular loading affects bone growth and the factors determining size and shape. However, it is not known what epigenetic impact muscular dystrophy (dystrophia muscularis) has on limb bone growth or ontogenetic scaling. To assess the effects of two types of muscular dystrophy (genotypes dy/dy and dy2J/dy2J) on limb bone growth, we measured lengths and widths of the right humerus, femur and tibia, and lengths of the ulna and radius from dorsal/ventral radiographs of mice taken over a period of 270 days. Radiographs were taken approximately 3 times a week, and the sampling frequency was gradually reduced to once a month. We plotted measurements from each individual against time and fit a Gompertz equation to the growth of each bone. Parameters of the equation were compared using ANOVA across genotypes and between sexes. Slopes of length versus width were calculated for the limb bones of each individual using linear regression. Slope differences among genotypes and between sexes were tested using ANOVA. Control and dy2J values were significantly longer than those of dy mice in all bones, but there was considerable variation across genotypes for the various width measurements. Sexual dimorphism was found in several measurements, where males were always larger than females. There were few significant differences in limb scaling (lengths vs. widths) among genotypes and almost no scaling differences between sexes despite the size differences. Differences among widths suggest that muscular dystrophy affects different parts of limb bones in different ways. This may be the effect of the type and number of muscular attachments, as well as the usage of the limb. The sexually dimorphic measurements suggest that there are size differences in the skeleton between sexes, regardless of the genotype. Our ontogenetic allometry results indicate that size is affected by the muscular dystrophic condition and by sexual dimorphism, while shape remains largely unchanged.     

Acquisition of lexical translation relations from MRDS

In this paper we present a methodology for extracting information about lexical translation equivalences from the machine readable versions of conventional dictionaries (MRDs), and describe a series of experiments on semi-automatic construction of a linked multilinguallexical knowledge base for English, Dutch, and Spanish. We discuss the advantages and limitations of using MRDs that this has revealed, and some strategies we have developed to cover gaps where no direct translation can be found.     

Toughness variation with test temperature and

A two phase heavy alloy composite based on 95 W-3.5 Ni-1.5 Fe (wt pct) was fabricated from elemental powders by liquid phase sintering. Past reports on the heavy alloys indicate considerable disagreement concerning cooling rate effects on toughness. The present experiments determined the effect of both cooling rate and test temperature on the properties of the 95 W heavy alloy. This alloy undergoes a ductile to brittle transition with decreasing test temperature; the transition temperature is close to room temperature. The cooling rate from post-sintering anneals carried out at temperatures greater than 1000 °C has a large influence on toughness; rapid quenching gives superior toughness. These findings support an impurity segregation explanation for embrittlement in the heavy alloys.     

Enhanced low-temperature sintering of tungsten

The effects of various transition metal additions on the sintering of a well-characterized, fine tungsten powder were analyzed using both isothermal and constant heating rate experiments in the temperature range 900 to 1400‡ C. Approximately four atomic monolayers of palladium on the tungsten powder surface were found to be the optimal enhancer, followed by nickel, cobalt, platinum, and iron. The addition of Cu to the tungsten had no appreciable effect on the sintering kinetics. Sintering enhancement by these transition metals is related to their periodic chart position(i.e., electron structure). An overall non-Arrhenius shrinkage temperature dependence is attributed to grain growth in the activator-treated specimens. The activation energy for tungsten densification was determined to be 430 to 450 kJ/mol, which is in general agreement with a grain boundary diffusion process.     

A Comment on "Probability of Error in PN-Modulated Spread Spectrum Binary Communication Systems"

Examination of the interference power of spread spectrum PN systems gives a result approximately twice as large as that reported by Hopkins and Simpson [1]. The additional factor is due to a correlation between intersymbol interferences at different chip times. A corrected characteristic function for the interference is given here.     

Palladium sintering: Shrinkage kinetics for a sponge powder

Pellets pressed from sponge palladium powder were sintered both isothermally and with constant heating rates using a precision low force dilatometer. Computer analysis of the data is used to determine shrinkage and shrinkage rate behavior during the sintering operation. The data are used in conjunction with metallographic examination to correlate the shrinkage phenomena to the change in grain size and pore morphology. The results show a characteristic shrinkage rate behavior associated with grain growth during sintering which can effectively halt densification.