Towards an integrated neonatal brain and cardiac examination capability at 7 T: electromagnetic field simulations and early phantom experiments using an 8-channel dipole array

Objective

Neonatal brain and cardiac imaging would benefit from the increased signal-to-noise ratio levels at 7 T compared to lower field. Optimal performance might be achieved using purpose designed RF coil arrays. In this study, we introduce an 8-channel dipole array and investigate, using simulations, its RF performances for neonatal applications at 7 T.

Methods

The 8-channel dipole array was designed and evaluated for neonatal brain/cardiac configurations in terms of SAR efficiency (ratio between transmit-field and maximum specific-absorption-rate level) using adjusted dielectric properties for neonate. A birdcage coil operating in circularly polarized mode was simulated for comparison. Validation of the simulation model was performed on phantom for the coil array.

Results

The 8-channel dipole array demonstrated up to 46% higher SAR efficiency levels compared to the birdcage coil in neonatal configurations, as the specific-absorption-rate levels were alleviated. An averaged normalized root-mean-square-error of 6.7% was found between measured and simulated transmit field maps on phantom.

Conclusion

The 8-channel dipole array design integrated for neonatal brain and cardiac MR was successfully demonstrated, in simulation with coverage of the baby and increased SAR efficiency levels compared to the birdcage. We conclude that the 8Tx-dipole array promises safe operating procedures for MR imaging of neonatal brain and heart at 7 T.

     

Dynamic characterization and modification of dynamic properties of a micro scanner

Micro electro mechanical systems (MEMS) are used in many application areas in different disciplines and took their place among the most promising technologies. The performance of such systems is primarily related to their dynamical characteristics. This study presents the dynamic characterization techniques that are used to identify the modal parameters of a MEMS device and the methods that can be implemented to change its dynamic response. An electrostatic scanner is chosen as the case study to demonstrate the developed methodologies. Initially, the micro scanner is characterized using experimental modal analysis techniques to obtain frequency response function, modal damping, resonance frequencies, and mode shapes. Then, velocity and position feedback control loops are implemented to the scanner system to alter the damping and stiffness characteristics. A closed-loop Simulink model of the scanner is developed to verify the experimental measurements. Several curve fitting methods are used in order to have an accurate representation of the scanner system. Using the model, the influence of both position and velocity feedback on the effective damping, resonance frequency and the transient behavior of the scanner is investigated. The stability limits of the scanner under velocity feedback are also studied via numerical simulations. Based on the experimental and simulation results, the methodology developed in this study proves itself to be very efficient to alter the dynamical characteristics of the MEMS structures and it can be easily adapted to other MEMS applications.     

Potential of peanut skin phenolic extract as antioxidative and antibacterial agent in cooked and raw ground beef

This study investigated the potential of peanut skin extract (PSE) as inhibitor of lipid oxidation in cooked and raw ground beef (GB) and as antimicrobial agent in raw GB. Results show that addition of PSE to raw GB before cooking significantly inhibited the formation of peroxides and TBARS in cooked GB during the refrigerated storage. PSE at concentration ≥0.06% was as effective as BHA/BHT at 0.02% in inhibiting lipid oxidation. PSE also inhibited the oxidation of meat pigments thereby preserving the fresh redness of treated meat when used at 0.02–0.10%. Microplate assay showed complete inhibition of test bacteria (Bacillus subtilis, Salmonella typhimurium, Staphylococcus aureus, Streptococcus faecalis and Escherichia coli) in the presence of PSE at 0.4% or higher. However, the antimicrobial effect of PSE in GB was less potent. Hence, PSE can primarily serve the dual purposes of preserving the colour of raw GB and preventing lipid oxidation in cooked products.     

Synthesis,Biochemistry, and Computational Studies of Brominated Thienyl Chalcones: A New Class of Reversible MAO‐B Inhibitors

A series of (2E)‐1‐(5‐bromothiophen‐2‐yl)‐3‐(para‐substituted phenyl)prop‐2‐en‐1‐ones ( TB1 – TB11 ) was synthesized and tested for inhibitory activity toward human monoamine oxidase (hMAO). All compounds were found to be competitive, selective, and reversible toward hMAO‐B except (2E)‐1‐(5‐bromothiophen‐2‐yl)‐3‐(4‐nitrophenyl)prop‐2‐en‐1‐one ( TB7 ) and (2E)‐1‐(5‐bromothiophen‐2‐yl)‐3‐(4‐chlorophenyl)prop‐2‐en‐1‐one ( TB8 ), which were selective inhibitors of hMAO‐A. The most potent compound, (2E)‐1‐(5‐bromothiophen‐2‐yl)‐3‐[4‐(dimethylamino)phenyl]prop‐2‐en‐1‐one ( TB5 ), showed the best inhibitory activity and higher selectivity toward hMAO‐B, with K_i and SI values of 0.11±0.01 μm and 13.18, respectively. PAMPA assays for all compounds were carried out in order to evaluate the capacity of the compounds to cross the blood–brain barrier. Moreover, the most potent MAO‐B inhibitor, TB5 , was found to be nontoxic at 5 and 25 μm , with 95.75 and 84.59 % viability among cells, respectively. Molecular docking simulations were carried out to understand the crucial interactions responsible for selectivity and potency.     

Investigation of electrochromic properties of poly(3,5-bis(4-methoxyphenyl)dithieno[3,2-b;2′,3′-d]thiophene)

Electropolymerization of 3,5-bis(4-methoxyphenyl)dithieno[3,2-b;2′,3′-d]thiophene BMPhDTT, having strong electron-donating methoxy groups, was performed, utilizing potentiodynamic method. The homopolymer was characterized by cyclic voltammetry (CV), Fourier transform infrared (FTIR) and UV–vis spectroscopy. Spectroelectrochemical and electrochromic properties of the homopolymer film were investigated and a PBMPhDTT/PEDOT device was constructed to understand its characteristics in detail. It was revealed that the potential range of 0.0–2.0 V is suitable for operating the device between yellow and blue colors. It indicated a good open circuit memory and stability.     

Effect of TiO<Subscript>2</Subscript> addition on crystallization and machinability of potassium mica and fluorapatite glass ceramics

In this study, the effect of TiO₂ addition as a nucleating agent on the crystallization and machinability of potassium mica and fluorapatite base glass ceramics were investigated. Glass compositions were prepared and casted at predetermined temperatures. Differential thermal analysis and XRD methods were applied to characterize phase precipitation sequence and identification of phases. Disc and cylindrical shaped samples were prepared to determine microstructural and mechanical properties in terms of microhardness and machinability. FEG-SEM was used to characterize variation of microstructural constituents depending on the amount of nucleating agent. The results indicate that optimum microstructure and machinability can be obtained in machinable glass-ceramic by the addition of 1 wt% TiO₂ for the composition having 3:7 weight ratio of fluorapatite to potassium mica.     

An exploration of social networking site use,multitasking, and academic performance among United States and European university students

Studies have shown that multitasking with technology, specifically using Social Networking Sites (SNSs), decreases both efficiency and productivity in an academic setting. This study investigates multitasking’s impact on the relationship between SNS use and Grade Point Average (GPA) in United States (US; n = 451) and European (n = 406) university students using quantitative and qualitative data analysis. Moderated Multiple Regression analysis results showed that the negative relationship between SNS use and GPA was moderated by multitasking only in the US sample. This may be due to European students being less prone to “disruptive” multitasking. The results provide valuable cautionary information about the impact of multitasking and using SNSs in a learning environment on university students’ GPAs.     

Effect of ZrO2 on phase transformation of Al2O3

This study investigates the effect of ZrO₂ on phase transformation of alumina. Alumina and alumina–zirconia composite powders were produced by the precipitation method from aluminum sulfate and zirconium sulfate precursors. Precipitates obtained at 15 °C were dried at 80 °C for 72 h, and then calcinated at four different temperatures; 1000 °C, 1100 °C, 1200 °C and 1300 °C for 1 h. Powders calcinated at 1300 °C were pressed uniaxially and sintered at 1600 °C for 1 h. XRD and DSC analyses showed that the presence of zirconia retarded the transformation to α-alumina. SEM studies on the powders calcinated at 1300 °C revealed that both alumina and alumina–zirconia particles were 100–300 nm in size and of near spherical shape. Zirconia additions inhibited abnormal grain growth of alumina and provided homogeneous, equaxied grain structure.     

Using a chemical equilibrium model to predict amendments required to precipitate phosphorus as struvite in liquid swine manure

Precipitation of phosphate minerals from liquid swine manure is an established means of reducing the orthophosphate (OP) concentration. This project investigated the usefulness of a chemical equilibrium model, Visual Minteq, for prescribing the amendments needed to maximize struvite precipitation from liquid swine manure and thus reduce the OP phosphorus concentration. The actual concentrations of Mg(2+), Ca(2+), K(+), OP, NH(4)(+), alkalinity and pH from a liquid swine manure system were used as inputs to the model. The model was modified to remove species with extremely low formation rates, because they would not significantly precipitate in the reaction occurring in a short retention-time process such as those envisioned for swine manure struvite-formation reactors. Using the model's output, a series of 19-L reactors were used to verify the results. Verification results demonstrated that Visual Minteq can be used to pre-determine the concentration of amendments required to maximize struvite recovery.     

Microstructure and densification of ZrB2–SiC composites prepared by spark plasma sintering

ZrB₂–SiC composites were prepared by spark plasma sintering (SPS) at temperatures of 1800–2100 °C for 180–300 s under a pressure of 20 MPa and at higher temperatures of above 2100 °C without a holding time under 10 MPa. Densification, microstructure and mechanical properties of ZrB₂–SiC composites were investigated. Fully dense ZrB₂–SiC composites containing 20–60 mass% SiC with a relative density of more than 99% were obtained at 2000 and 2100 °C for 180 s. Below 2120 °C, microstructures consisted of equiaxed ZrB₂ grains with a size of 2–5 μm and α-SiC grains with a size of 2–4 μm. Morphological change from equiaxed to elongated α-SiC grains was observed at higher temperatures. Vickers hardness of ZrB₂–SiC composites increased with increasing sintering temperature and SiC content up to 60 mass%, and ZrB₂–SiC composite containing 60 mass% SiC sintered at 2100 °C for 180 s had the highest value of 26.8 GPa. The highest fracture toughness was observed for ZrB₂–SiC composites containing 50 mass% SiC independent of sintering temperatures.