Ex vivo gadoxetate relaxivities in rat liver tissue and blood at five magnetic field strengths from 1.41 to 7 T

Quantitative mapping of gadoxetate uptake and excretion rates in liver cells has shown potential to significantly improve the management of chronic liver disease and liver cancer. Unfortunately, technical and clinical validation of the technique is currently hampered by the lack of data on gadoxetate relaxivity. The aim of this study was to fill this gap by measuring gadoxetate relaxivity in liver tissue, which approximates hepatocytes, in blood, urine and bile at magnetic field strengths of 1.41, 1.5, 3, 4.7 and 7 T. Measurements were performed ex vivo in 44 female Mrp2 knockout rats and 30 female wild‐type rats who had received an intravenous bolus of either 10, 25 or 40 μmol/kg gadoxetate. T1 was measured at 37 ± 3°C on NMR instruments (1.41 and 3 T), small‐animal MRI (4.7 and 7 T) and clinical MRI (1.5 and 3 T). Gadolinium concentration was measured with optical emission spectrometry or mass spectrometry. The impact on measurements of gadoxetate rate constants was determined by generalizing pharmacokinetic models to tissues with different relaxivities. Relaxivity values (L mmol−1 s−1) showed the expected dependency on tissue/biofluid type and field strength, ranging from 15.0 ± 0.9 (1.41) to 6.0 ± 0.3 (7) T in liver tissue, from 7.5 ± 0.2 (1.41) to 6.2 ± 0.3 (7) T in blood, from 5.6 ± 0.1 (1.41) to 4.5 ± 0.1 (7) T in urine and from 5.6 ± 0.4 (1.41) to 4.3 ± 0.6 (7) T in bile. Failing to correct for the relaxivity difference between liver tissue and blood overestimates intracellular uptake rates by a factor of 2.0 at 1.41 T, 1.8 at 1.5 T, 1.5 at 3 T and 1.2 at 4.7 T. The relaxivity values derived in this study can be used retrospectively and prospectively to remove a well‐known bias in gadoxetate rate constants. This will promote the clinical translation of MR‐based liver function assessment by enabling direct validation against reference methods and a more effective translation between in vitro findings, animal models and patient studies

Coherent States Measurement Entropy

Coherent states (CS) quantum entropy can be split into two components. The dynamical entropy is linked with the dynamical properties of a quantum system. The measurement entropy, which tends to zero in the semiclassical limit, describes the unpredictability induced by the process of a quantum approximate measurement. We study the CS--measurement entropy for spin coherent states defined on the sphere discussing different methods dealing with the time limit $n \to \infty$. In particular we propose an effective technique of computing the entropy by iterated function systems. The dependence of CS--measurement entropy on the character of the partition of the phase space is analysed.Comment: revtex, 22 pages, 14 figures available upon request (e-mail: [email protected]). Submitted to J.Phys.

Benchmark Frames for Structural Analysis

The data provided here were created as part of an extensive study conducted by the contributors. As described in detail in the article titled "Efficient geometric nonlinear elastic analysis for design of steel structures: Benchmark studies" (Journal of Constructional Steel Research, 186, doi: 10.1016/j.jcsr.2021.106870), a set of twenty-two planar benchmark frames was compiled in order to validate a proposed finite element-based approximate method of second-order elastic analysis. The frames offer a broad range of two-dimensional geometries and stability sensitivities, with critical buckling load ratios ranging from 1.2 - 7.9. These benchmark frames are useful for studying structural design and analysis methods. The data and supplementary information include: 1. Frame descriptions (PDF file): geometry, member sizes, and loading details for each of the 22 benchmark frames 2. Finite element models (MASTAN2 files) of benchmark frames: both perfect and imperfect geometries (with global sway) 3. Finite element model data (Excel file) for each frame – both perfect and imperfect geometries; This includes node coordinates and element conductivity etc. useful for creating frame models with any FEA program. 4. Simulation results: (a) Joint displacements and member design moments for each benchmark frame as determined by 3 different analyses; (b) Critical buckling load ratio of each frame. MASTAN2 software can be downloaded for free at http://mastan2.com/.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Comparison of steady-state and transient thermo-mechanical responses of unprotected aluminum columns at elevated temperatures

In modern construction, aluminum is often used as a structural material due to its relatively high strength-to-weight ratio, resistance to corrosion, and architecturally pleasing finish. For instance, aluminum has been an important component for the development of skyscrapers atriums and exterior facades, as aluminum structures can weigh up to sixty percent less than similar steel structures with comparable strength. However, the thermo-mechanical behavior of aluminum makes design against building fires challenging, mainly because aluminum has a low melting point, and experimental data and analysis-based models for fire design are limited. Generally, steady-state and transient tests are used to determine material properties at high temperatures. In a steady-state test, a tensile specimen is heated up to a target temperature, and then subjected to axial load under constant temperature. Alternatively, a transient tensile test is completed by applying static axial load to the specimen, and then gradually heating the material to realistically simulate fire conditions. Results from steady-state tests are easier to obtain and, therefore, more commonly used in computational models. This project investigates the accuracy of numerical results obtained through “transient” models that adopt steady-state mechanical properties to study the effects of fire on aluminum structures. Thin-walled columns were analyzed using nonlinear finite element models with mechanical properties from steady-state and transient tests. Results from Abaqus collapse analyses are used to compare the load-carrying capacities and critical temperatures of slender and non-slender hollow members. Parametric studies were completed to characterize the impact of member slenderness and geometric imperfections on the stability of hollow aluminum columns at elevated temperatures

Three-Dimensional Benchmark Problems for Design by Advanced Analysis: Impact of Twist

Design codes for steel structures continue to provide additional opportunities for the use of more advanced methods of nonlinear analysis. As the complexity of the analysis increases, it becomes more important for the designer to validate the capabilities of their analysis software and, just as importantly, their ability to properly utilize it. Many benchmark problems can be found in the literature; however, few include three-dimensional behavior and fewer include I-shaped sections, which are torsionally flexible and where warping restraint can be significant. This paper introduces a new set of benchmark problems that contribute to a much needed database of examples in which the accurate modeling of three-dimensional or spatial behavior is essential. A secondary goal of the paper is to illustrate new steel design provisions and the type of comparisons that were part of their development