Collagen fibril diameter in relation to bone site. a quantitative ultrastructural study

The collagen fibril diameter was measured in cortical bone samples from the femoral neck, rear and front tibia of rats using electron microscopy analysis. Statistically significant differences (0.001<p<0.04) in mean fibril diameter values between different bone sites were detected demonstrating a dependence upon bone use.     

Addendum to: “Dissipative and Entropy Solutions to Non-Isotropic Degenerate Parabolic Balance Laws”

This note generalizes the notion of dissipative solutions to non-isotropic degenerate parabolic balance laws introduced in [3]. The new definition allows us to use a larger class of test functions than the one used in [3] to study the equivalence between dissipative and entropy solutions. As a result, it is possible to study general relaxation-type approximations (limits).Arch. Rational Mech. Anal. 170 (2003) 359–370 Digital Object Identifier (DOI) 10.1007/s00205-003-0282-5 Published online September 30, 2003Acknowledgement This work was partially supported by HYKE programme HPRN-CT-2002-00282 (http://www.hyke.org), and PANAGIOTIS E. SOUGANIDIS by the National Science Foundation.     

A limited memory descent Perry conjugate gradient method

In this work, we present a new limited memory conjugate gradient method which is based on the study of Perry’s method. An attractive property of the proposed method is that it corrects the loss of orthogonality that can occur in ill-conditioned optimization problems, which can decelerate the convergence of the method. Moreover, an additional advantage is that the memory is only used to monitor the orthogonality relatively cheaply; and when orthogonality is lost, the memory is used to generate a new orthogonal search direction. Under mild conditions, we establish the global convergence of the proposed method provided that the line search satisfies the Wolfe conditions. Our numerical experiments indicate the efficiency and robustness of the proposed method.     

The use of models in the study of stresses during soil compaction

In the present study, it is described the experimental method for measuring the direction and the magnitude of stresses during mechanical soil compaction. These stresses result in an increase in soil density. The greatest effect during the compaction results from developing a vertical component of stress in the soil. This component of stress can be measured experimentally. This stress is a function of many soil factors and the characteristics of the compaction machine. Considering the particular and, in many aspects, unknown processes of these effects on the compaction, the determination of soil compaction with models becomes very difficult. The system equation in the model is obtained by means of dimensional and numerical analysis using special computer programs.     

Estimating the technical efficiency of health care systems: A cross-country comparison using the directional distance function

Economic activity produces not only desirable outputs but also undesirable outputs. Undesirable outputs are usually omitted from efficiency assessments (i.e., applications of Data Envelopment Analysis) which fail to express the true production process. The directional distance function model has been used for handling asymmetrically both desirable and undesirable outputs in the assessment process. In the present paper, we apply a generalized directional distance function to measure the efficiency of the health systems of 171 countries. We incorporate both desirable and undesirable outputs into the efficiency assessment without transforming the latter type of outputs into inputs or into their inverse form, as is done in most of the extant studies that deal with the measurement of health efficiency. The methodology that we apply introduces a modified definition of the efficiency score which yields results consistent with those obtained from radial DEA models. In addition, our results are independent of the length of the direction vector.