Feasibility of intravoxel incoherent motion in the assessment of tumor microvasculature and blood–brain barrier integrity: a case-based evaluation of gliomas

Magnetic Resonance Materials in Physics, Biology and Medicine - To evaluate the feasibility of intravoxel incoherent motion (IVIM) in assessing blood–brain barrier (BBB) integrity and...     

Radiofrequency antenna concepts for human cardiac MR at 14.0 T

Objective

To examine the feasibility of human cardiac MR (CMR) at 14.0 T using high-density radiofrequency (RF) dipole transceiver arrays in conjunction with static and dynamic parallel transmission (pTx).

Materials and methods

RF arrays comprised of self-grounded bow-tie (SGBT) antennas, bow-tie (BT) antennas, or fractionated dipole (FD) antennas were used in this simulation study. Static and dynamic pTx were applied to enhance transmission field (B₁⁺) uniformity and efficiency in the heart of the human voxel model. B₁⁺ distribution and maximum specific absorption rate averaged over 10 g tissue (SAR_10g) were examined at 7.0 T and 14.0 T.

Results

At 14.0 T static pTx revealed a minimum B₁⁺_ROI efficiency of 0.91 μT/√kW (SGBT), 0.73 μT/√kW (BT), and 0.56 μT/√kW (FD) and maximum SAR_10g of 4.24 W/kg, 1.45 W/kg, and 2.04 W/kg. Dynamic pTx with 8 kT points indicate a balance between B₁⁺_ROI homogeneity (coefficient of variation < 14%) and efficiency (minimum B₁⁺_ROI > 1.11 µT/√kW) at 14.0 T with a maximum SAR_10g < 5.25 W/kg.

Discussion

MRI of the human heart at 14.0 T is feasible from an electrodynamic and theoretical standpoint, provided that multi-channel high-density antennas are arranged accordingly. These findings provide a technical foundation for further explorations into CMR at 14.0 T.

     

In vitro digestion and characterisation of 2S albumin and digestion‐resistant peptides in pecan

The 2S albumins are one of the major protein families involved in severe food allergic reactions to nuts, seeds and legumes, thus potentially making these proteins clinically relevant for allergic sensitisation and potential diagnostic markers. In this study, we sought to purify native 2S albumin protein from pecan to further characterise this putative allergen. The purified 2S albumin, Car i 1, from pecan was found to be resistant to digestion by pepsin in simulated gastric fluid (SGF) and comparatively stable to proteolysis by trypsin and pancreatin in simulated intestinal fluid (SIF). Digestion of purified Car i 1 in SGF and SIF resulted in formation of different digestion‐resistant peptides that were capable of binding IgE antibodies from allergic individuals. Digestion stability of Car i 1 and formation of digestion‐resistant antigenic peptides may explain why it is a potent sensitising protein in pecan for susceptible individuals. The observation that digestion‐resistant peptides are able to bind IgE implies that pecan can trigger systemic allergic reactions even after digestion in the stomach and small intestine.     

Mimicking Bubble Use in Nature: Propulsion of Janus Particles due to Hydrophobic‐Hydrophilic Interactions

Bubbles are widely used by animals in nature in order to fulfill important functions. They are used by animals in order to walk underwater or to stabilize themselves at the water/air interface. The main aim of this work is to imitate such phenomena, which is the essence of biomimetics. Here, bubbles are used to propel and to control the location of Janus particles in an aqueous medium. The synthesis of Janus SiO₂‐Ag and polystyrene‐Ag (PS‐Ag) particles through embedment in Parafilm is presented. The Janus particles, partially covered with catalytically active Ag nanoparticles, are redispersed in water and placed on a glass substrate. The active Ag sites are used for the splitting of H₂O₂ into water and oxygen. As a result, an oxygen bubble is formed on one side of the particle and promotes its propulsion. Once formed, the bubble‐particle complex is stable and therefore, can be manipulated by tuning hydrophilic‐hydrophobic interactions with the surface. In this way a transition between two‐ and three‐ dimensional motion is possible by changing the hydrophobicity of the substrate. Similar principles are used in nature.     

Influence of operational tolerances on HMA performance

This study focuses on determining the effects of variability on key mix design factors, such as asphalt content, gradation, and density, on the laboratory performance of different HMA samples that were produced in the laboratory. Mixture variables were kept within specified limits as per allowable operational tolerances, and performance was monitored through the evaluation of the results obtained from volumetric properties and laboratory tests, such as flexural fatigue test, Hamburg wheel-tracking test, and overlay tester. A series of statistical analyses were conducted to develop relationships between the key mix design factors and the observed laboratory performances of each type of mixture. From the analysis, the effects of the main variables on the results of the performance tests used in this study were found.Finally, a statistical sensitivity analysis was conducted to reveal the relationship between different tolerance levels and mixture performance. Based on the findings of this sensitivity analysis, recommendations to revise the current TxDOT operational tolerances and performance-based pay adjustment factors for contractual jobs were provided that not only commends high quality and a consistent end product but also promotes superior performing mixtures based on the analysis of laboratory data.     

Calcium carbonate composite hydrogel films: Particle packing and optical properties

Composite hydrogel films are prepared by photocrosslinking of partially polymerized poly(2‐hydroxyethyl methacrylate‐co‐methyl methacrylate) prepolymer solution dispersed with aragonite precipitated calcium carbonate (PCC) particles. The effects of PCC aspect ratio (AR, 4.2–6.6) and volume fraction (?_PCC) are studied with respect to the prepolymer viscosity, the maximum packing fraction (?_m), and optical properties. ?_m obtained from Kreigher–Dougherty fitting is found to decrease with increasing AR of PCC particles, from ?_m = 0.33 (AR = 4.2) to ?_m = 0.21 (AR = 6.6). Scanning electron microscopy images revealed that the particles are uniformly dispersed and randomly orientated in the polymer network when ?_PCC < ?_m. Optically transparent neat hydrogel films become opaque with increasing particle concentration and AR because of random light scattering from the PCC particles. A whiteness up to 80 is obtained from 100 μm thick composite hydrogel film in the wet state with PCC AR = 6.6 and ?_PCC = 0.19 (near ?_m). POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Influence of liquid back mixing on a kinetically controlled reactive distillation process

The state of the art equilibrium model and the rate-based models for reactive distillation (RD) are very well known and have been used since a couple of decades. However, these models are not sufficient to accurately represent a slow reaction process that is kinetically controlled. The shortcoming is due to neglecting the effect of liquid back mixing (LBM) on the whole process. This work presents a review of the available modeling approaches for RD, then discusses the applicability of various models and finally, it applies the findings to an industrially relevant case study—polyester synthesis. The main focus is on extending the dynamic rate-based model to take into account the liquid back mixing. We also show how the axial dispersion can be introduced into the RD model, without adopting the axial dispersion model. The comparison of the results of the rate-based model, with and without axial dispersion, clearly demonstrates that the extended model predicts more accurately the kinetically controlled process as compared to the conventional rate-based model.     

Asymptotic behavior of quantum walks with spatio-temporal coin fluctuations

Quantum walks subject to decoherence generically suffer the loss of their genuine quantum feature, a quadratically faster spreading compared to classical random walks. This intuitive statement has been verified analytically for certain models and is also supported by numerical studies of a variety of examples. In this paper we analyze the long-time behavior of a particular class of decoherent quantum walks, which, to the best of our knowledge, was only studied at the level of numerical simulations before. We consider a local coin operation which is randomly and independently chosen for each time step and each lattice site and prove that, under rather mild conditions, this leads to classical behavior: With the same scaling as needed for a classical diffusion the position distribution converges to a Gaussian, which is independent of the initial state. Our method is based on non-degenerate perturbation theory and yields an explicit expression for the covariance matrix of the asymptotic Gaussian in terms of the randomness parameters.     

Design of a Graphical User Interface for Process Control Based on the Example of a Paper Recycling Plant

The following article is the third of 3 articles that focus on user-centered design and usability in the field of industrial process control. Whereas the first article in this series (Burmester, Komischke, & Wust, this issue) dealt with usability engineering methods in the area of process control, this article explains the practical application of this procedure. To this end, a pilot project for the user-centered design of a user interface for a paper recycling plant is described here by way of example. Here a new layout based on users' mental models was systematically prepared. Extensive usability tests revealed that the design was understood and accepted both by users without any knowledge of the system (pupils at a paper technology college) and those with a knowledge of the system.     

A COMBINATION OF SUPPORT VECTOR MACHINE AND k-NEAREST NEIGHBORS FOR MACHINE FAULT DETECTION

This article presents a combination of support vector machine (SVM) and k-nearest neighbor (k-NN) to monitor rotational machines using vibrational data. The system is used as triage for human analysis and, thus, a very low false negative rate is more important than high accuracy. Data are classified using a standard SVM, but for data within the SVM margin, where misclassifications are more like, a k-NN is used to reduce the false negative rate. Using data from a month of operations of a predictive maintenance company, the system achieved a zero false negative rate and accuracy ranging from 75% to 84% for different machine types such as induction motors, gears, and rolling-element bearings.