Survey of MRI Usefulness for the Clinical Assessment of Bone Microstructure

Bone microarchitecture has been shown to provide useful information regarding the evaluation of skeleton quality with an added value to areal bone mineral density, which can be used for the diagnosis of several bone diseases. Bone mineral density estimated from dual-energy X-ray absorptiometry (DXA) has shown to be a limited tool to identify patients’ risk stratification and therapy delivery. Magnetic resonance imaging (MRI) has been proposed as another technique to assess bone quality and fracture risk by evaluating the bone structure and microarchitecture. To date, MRI is the only completely non-invasive and non-ionizing imaging modality that can assess both cortical and trabecular bone in vivo. In this review article, we reported a survey regarding the clinically relevant information MRI could provide for the assessment of the inner trabecular morphology of different bone segments. The last section will be devoted to the upcoming MRI applications (MR spectroscopy and chemical shift encoding MRI, solid state MRI and quantitative susceptibility mapping), which could provide additional biomarkers for the assessment of bone microarchitecture.     

Variables related to premature terminations in a university counseling service: A reply to Saltzman's (1984) comment.

The authors respond to comments by C. Saltzman (see record 1984-30126-001) regarding their (see record 1983-11046-001) examination of variables related to premature termination in a university counseling service. Specifically discussed are Saltzman's concerns regarding the meaningfulness of the results, the citation of previous research, the definition of premature termination, and the operational definitions and procedures used. Issues involved in undertaking research using an existing data base and the influence of organizational/administrative factors on counseling process are also considered. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

NMR,optical, and plastic flow experiments in bcc3He —4 He mixture crystals — in pursuit of a vacancy fluid

We describe experiments on the properties of bcc³He —⁴ He solid mixtures on the melting curve between 0.5K and 1.9K. In this paper we focus on effects related to the presence of thermal vacancies. First, we used NMR to image the³He distribution within the solid in equilibrium with the superfluid, as well as its T₁ and t₂. The most surprising result was that above about 1K, vacancy related motion of³He atoms in the solid becomes faster than in the liquid. To check the macroscopic aspects of this motion, we used the vibrating wire technique to look at plastic flow of the bcc solid phase, by moving the wire through the crystal. The temperature dependence of the plastic flow velocity indicates that the vacancy population in the bcc solid behaves like a viscous fluid. The extent to which the vacancy population causes the solid to have liquid like properties is best demonstrated through optical observations of the distillation of³He atoms out of the crystal, which takes place via formation of fluid bubbles within the solid, which then percolate into the liquid, creating a vivid impression of boiling.     

CAD model of effective dielectric constant of microstrip line on M-cut sapphire substrate

Simple and correct formulas in regard to frequency dispersion are derived for the calculation of an isotropic effective dielectric constant for the microstrip line on m-cut sapphire substrate. The formulas were verified by comparison to the results of full-wave analysis based on the equivalent surface impedance approach. The temperature dependence of the dielectric permittivity of sapphire is taken into account.     

Approximate mathematical models in high-speed hydrodynamics

Approximate solutions of some problems in high-speed hydrodynamics are given, the solutions being based upon well-known approaches, such as the principle of independence of cavity expansion (Logvinovich), formulation of the problem of the immersion of a solid contour into liquid (Wagner), various models of cavity closure in its tail, etc. Theoretical studies of the dynamic properties of slender ventilated cavities are performed. The mathematical model of a cavity is obtained in the form of a system of nonlinear time-delay differential equations. The linear theory of cavity stability and oscillations is developed for various cavity types. The mechanism of nonlinear cavity oscillations accounting for gas-bubble detachment is considered, and the results of extensive numerical experimentation are presented. A theoretical model of cavity closure is proposed that develops the well-known Efros approach with a re-entrant jet. An approximate analysis of the model has been performed. A planar problem of the impact and immersion of an expanding cylinder into liquid with a cylindrical free surface of variable radius is solved in Wagner’s formulation.     

Determination of fat in infant formula by robotic automated method

A method has been developed for the determination of fat in infant formula using a commercially available robotic system. The procedure and chemistry at large are the same as the manual method,Official Methods of Analysis 16.064, by the Association of Official Analytical Chemists (AOAC). Both liquid and powder forms of milk-protein-based and soy-protein-based matrices were analyzed in this study. The robotic operations are described in detail. The evaluation of the accuracy is accomplished by comparing the data obtained by the robotic automated method to those obtained by the official manual method. The analysis of variance does not indicate a statistically significant difference (p-value 0.0620, mean difference 0.0056%) between the mean results of the two methods for the milk-protein-based infant formula. The results of other matrices tested by both methods agreed within 1% relative of each other. The precision of the robotic automated method is slightly better than the manual method as shown by the overall relative standard deviation (RSD) of 0.167% vs 0.269%. The ruggedness of the instrument has been satisfactory. The results of this study suggest that the robotic automated method is suitable for this application.