Moment properties of estimators for an exponential regression with type 1 censoring

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Degradation on wood by insects and the effects on furniture production

In the tropics, biodegradation of wood progresses rapidly due to the biologically favourable temperatures and humidity conditions all year round. The population growth rate of insects is high and they reproduce throughout the year. To understand the degradation caused by insects on wood and how it can affect furniture production, the nature of the particular insect attack and the characteristic forms of damage must be understood. In this paper, the characteristic habits of major insect pests, particularly ambrosia beetles, powderpost beetles and termites are described. The diagnostic signs of infestation and how the different forms of damage affect furniture production are discussed. Precautionary as well as remedial measures are also described

Improved estimators for the shape parameter in gamma regression

A regression model is considered in which the response variables have gamma distributions with a common shape parameter. A review is given of existing estimators for the shape parameter. Bias expressions for the maximum likelihood estimates of the regression coe f f i c i ent s and the shape parameter are developed. A new estima t o r f o r t h e shape parameter based on bias correction for the maximum likelihood estimator is shown to have markedly better variance and mean square error properties in small to moderate sized samples. Approximations to the low order moments of the Pearson statistic are derived for gamma regression models with general link functions. These are used for the case of a logarithmic link to develop new estimators for the shape parameter which have better moment properties than the estimators based on the Pearson statistic which have been used previously. Finally, the small sample variance and mean square error efficiencies of the estimators relative to the maximum likelihood estimator are evaluated by simulation for the case of a single explanatory variable and a logarithmic link, for a range of sample sizes less than or equal to 100

Mechanisms of modulation of brain microvascular endothelial cells function by thrombin.

Brain microvascular endothelial cells are a critical component of the blood-brain barrier. They form a tight monolayer which is essential for maintaining the brain homeostasis. Blood-derived proteases such as thrombin may enter the brain during pathological conditions like trauma, stroke, and inflammation and further disrupts the permeability of the blood-brain barrier, via incompletely characterized mechanisms. We examined the underlying mechanisms evoked by thrombin in rat brain microvascular endothelial cells (RBMVEC). Our results indicate that thrombin, acting on protease-activated receptor 1 (PAR1) increases cytosolic C

World distribution of Minthea rugicollis (Coleoptera : Lyctidae)

The distribution of Minthea rugicollis worldwide is presented based on a compilation of literature records of population establishments and also from the world collection of M. rugicollis at the Natural History Museum, London. The distribution map derived indicates the limits of distribution for M. rugicollis to be 40° north and south of the Equator, with maximum distribution within 20° north and south. The present compiled records of occurrence of established populations as well as reports on repeated accidental introductions strongly suggest M. rugicollis is not capable of establishing populations under outdoor temperate conditions

HUNTING PHENOMENON STUDY OF RAILWAY CONVENTIONAL TRUCK ON TANGENT TRACKS DUE TO CHANGE IN RAIL WHEEL GEOMETRY

A mathematical dynamic model of railway conventional truck is presented with 12 degrees of freedom equations of motion. The presented dynamic system consists of conventional truck attached with two single wheelsets in which equipped with lateral, longitudinal and vertical linear stiffness and damping primary and secondary suspensions. This investigated model governs lateral displacement, vertical displacement, roll yaw angles of each of wheelset and the lateral displacement, vertical displacement, roll and yaw angle of conventional truck. Kalker's linear theory has been adopted to evaluate the creep forces which are introduced on rail wheels due to rail wheel contact. The railway truck mathematical equations of motion are solved using fourth order Rung-Kutta method which requires that differential equations to be transformed into a set of first order differential equations. The transformed state space equations are simulated with computer aided simulation to represent the dynamic behavior and time solution of dynamics of conventional truck moving on tangent tracks. Influences of the geometric parameters of the rail wheel such as wheel conicity and nominal rolling radius on the dynamic stability of the system are investigated. It is concluded that the geometric parameters of the rail wheel have different effects on the hunting instability and on the change of the critical hunting velocity of the system. In addition critical hunting velocity of rail trucks is proportional inversely with the square roots of wheel conicity but high critical hunting velocity obtained by increasing the nominal rolling radius of the rail wheel