Normal Range of Human Left Ventricular Volumes and Mass Using Steady State Free Precession MRI in the Radial Long Axis Orientation

Background: The radial long-axis orientation for the measurement of left ventricular (LV) volume and mass has been shown to have advantages over the short-axis orientation. Previous work has highlighted the need for technique specific normal ranges. The purpose of this study was therefore to establish normal ranges of LV volume and mass for the radial long-axis orientation. Materials and methods: Forty normal subjects (20 males, average age 32.3, age range 19–58; 20 females, average age 37.4, age range 21–54) were examined utilising a steady state free precession (SSFP) pulse sequence. Two observers analysed the images independently using in-house validated software. Results: The normal ranges for LV end-diastolic volume measurements after adjustment to body surface area (BSA) were 62–120 ml for males and 58–103 ml for females. LV mass indexed to BSA ranged from 50–86 g for males and 36–72 g for females. The normal range for ejection fraction was 49–73 % for males and 54–73 % for females. Conclusion: A gender specific normal range using SSFP in the radial long-axis orientation was established.     

How price responsive is industrial demand for electricity in the United States?

We use five parametric specifications and monthly data for the lower 48 states in 2001–2019 to document that industrial demand for electricity in the United States (US) is price inelastic, with statistically significant (p-values ≤ 0.05) estimates of ? 0.029 to ? 0.130 for the static own-price elasticity, ? 0.021 to ? 0.133 for the short-run own-price elasticity, and ? 0.043 to ? 0.214 for the long-run own-price elasticity. Absent significant price escalation (e.g., 10% per year), the US industrial customer class’s price-induced conservation of electricity is likely modest, justifying the continued use of energy efficiency standards and demand side management programs to achieve deep decarbonization.     

Reliable k⋅p band structure calculation for nanostructures using finite elements

The k⋅p envelope function method is a popular tool for the study of electronic properties of III–V nanostructures. The equations are usually transferred to real-space and solved using standard numerical techniques. The powerful and flexible finite element method was seldom employed due to problems with spurious solutions. The method would be favorable for the calculation of electronic properties of large strained nanostructures as it allows a flexible representation of complex geometries. In this paper, we show our consistent implementation of the k⋅p envelope equations for nanostructures of any dimensionality. By including Burt-Foreman operator ordering and ensuring the ellipticity of the equations, we are able to calculate reliable and spurious solution free subband structures for the standard k⋅p 4×4, 6×6 and 8×8 models for zinc-blende and wurtzite crystals. We further show how to consistently include strain effects up to second order by means of the Pikus-Bir transformation. Finally, we analyze the performance of our implementation using benchmark examples.     

Lead Free Piezoelectric Materials

Lead oxide based ferroelectrics, represented by lead zirconate titanate (Pb(Zr, Ti)O₃) or PZT) are the most widely used materials for piezoelectric actuators, sensors and transducers due to their excellent piezoelectric properties. Considering lead toxicity, there is interest in developing piezoelectric materials that are biocompatible and environmentally friendlier. The low density of non-lead based materials can also be an advantage in transducers for underwater and medical imaging due to expected lower acoustical impedance. Another impetus for seeking alternative to lead based compositions is the need for piezoelectric materials for operation at high temperatures. Several classes of materials are now being reconsidered as potentially attractive alternatives to PZT for special applications. The potassium niobate family, KNbO₃, exhibits low dielectric constants, large thickness coupling coefficient along certain non-polar directions, and low density, all of which have advantages for high frequency transducer applications. Several compositions belonging to bismuth titanate family, Bi₄Ti₃O₁₂, such as SrTi₄Bi₄O₁₅, are promising candidates for high temperature applications. Lead free materials alone (eg. (Na_0.5Bi_0.5)TiO₃) or in solution with PT (BiScO₃ – PbTiO₃) are also potentially interesting as they combine high piezoelectric activity and, in some cases, relatively high T_c. For these families of piezoelectric materials, the processing and piezoelectric response under different conditions of pressure, frequency, and temperature are presently much less understood than for the classical lead containing systems. In this presentation we review and discuss piezoelectric properties of selected lead free compositions (principally for members of the potassium niobate family and bismuth titanate layered compounds) in relation to structural and microstructural features as well as extrinsic contributions (domain walls displacement, conductivity) to their electromechanical properties. It is shown that it is possible to obtain remarkably stable piezoelectric response in some compositions, while others exhibit strong dependence of piezoelectric properties on driving field and frequency. Origins of these different behaviours are discussed.     

Dynamic interleaved 1H/31P STEAM MRS at 3 Tesla using a pneumatic force-controlled plantar flexion exercise rig

Objective: To develop a measurement method for interleaved acquisition of ¹H and ³¹ STEAM localised spectra of exercising human calf muscle. Materials and Methods: A non-magnetic exercise rig with a pneumatic piston and sensors for force and pedal angle was constructed to enable plantar flexion measured in the 3 T MR scanner, which holds the dual tuned (¹H ,³¹P) surface coil used for signal transmission and reception. Results: ³¹ spectra acquired in interleaved mode benefit from higher Signal to noice ratio (factor of 1.34 ±0.06 for PCr) compared to standard acquisition due to the Nuclear Overhauser effect and substantial PCr/P_i changes during exercise can be observed in ³¹P spectra. ¹H spectral quality is equal to that in single mode experiments and allows Cr2 changes to be monitored. Conclusion: The feasibility of dynamic interleaved localised ¹H and ³¹P spectroscopy during plantar flexion exercise has been demonstrated using a custom-built pneumatic system for muscle activation. This opens the possibility of studying the dynamics of metabolism with multi nuclear MRS in a single run.     

Measurement and analysis of field-induced crystallographic texture using curved position-sensitive diffraction detectors

This paper outlines measurement and analysis methodologies created for determining the structural responses of electroceramics to an electric field. A sample stage is developed to apply electric fields to ceramic materials at elevated temperatures during neutron diffraction experiments. The tested voltages and temperatures range from ?20 kV to +20 kV and room temperature to 200 °C, respectively. The use of the sample environment for measuring the response of ferroelectric ceramics to an electrical stimulus is demonstrated on the instrument Wombat, a monochromatic neutron diffractometer employing a curved positive sensitive detector. Methodologies are proposed to account for the geometrical effects when vector fields are applied to textured materials with angularly dispersive detector geometries. Representative results are presented for the ferroelectric (Bi_1/2Na_1/2)TiO₃-6%BaTiO₃ (BNT-6BT) which show both phase transformation and ferroelectric domain texturing under the application of an electric field. This experimental and analysis approach is well suited for time-resolved measurements such as stroboscopic and in situ studies on a variety of electro-active materials.     

Post mortem brain temperature and its influence on quantitative MRI of the brain

Objective

MRI temperature sensitivity presents a major issue in in situ post mortem MRI (PMMRI), as the tissue temperatures differ from living persons due to passive cooling of the deceased. This study aims at computing brain temperature effects on the MRI parameters to correct for temperature in PMMRI, laying the foundation for future projects on post mortem validation of in vivo MRI techniques.

Materials and methods

Brain MRI parameters were assessed in vivo and in situ post mortem using a 3 T MRI scanner. Post mortem brain temperature was measured in situ transethmoidally. The temperature effect was computed by fitting a linear model to the MRI parameters and the corresponding brain temperature.

Results

Linear positive temperature correlations were observed for T₁, T₂* and mean diffusivity in all tissue types. A significant negative correlation was observed for T₂ in white matter. Fractional anisotropy revealed significant correlations in all gray matter regions except for the thalamus.

Discussion

The linear models will allow to correct for temperature in post mortem MRI. Comparing in vivo to post mortem conditions, the mean diffusivity, in contrast to T₁ and T₂, revealed additional effects besides temperature, such as cessation of perfusion and active diffusion.

     

Effects of post-treatments on the electrochemical properties of solid-state reacted Li4Ti5O12—high energy milling and annealing

This study is designed and performed to verify whether nano-sized Li₄Ti₅O₁₂ particles can be acquired by simple high energy milling from the economic solid-state reacted coarse powder for high power lithium ion battery applications. For this, Li₄Ti₅O₁₂ is synthesized by heat treatment at 800 and 850°C for 3?h using Li₂CO₃ and TiO₂, followed by high energy milling. Even though a comparable particle size to that of expensive wet chemical methods, or even a smaller particle size of 25?nm, can be acquired by 5?h of milling, the electrochemical properties of the particles are found to be deteriorated due to the decrease in Li₄Ti₅O₁₂ crystallinity associated with the milling. On the other hand, a subsequent annealing at 750°C for the milled powder is shown to recover both the capacity and rate capability of the anode electrode owing to the increased crystallinity, indicating the importance of particle crystallinity besides a fine particle size for the enhanced electrochemical properties for high power applications.     

A highly parallelized framework for computationally intensive MR data analysis

Object

The goal of this study was to develop a comprehensive magnetic resonance (MR) data analysis framework for handling very large datasets with user-friendly tools for parallelization and to provide an example implementation.

Materials and methods

Commonly used software packages (AFNI, FSL, SPM) were connected via a framework based on the free software environment R, with the possibility of using Nvidia CUDA GPU processing integrated for high-speed linear algebra operations in R. Three hundred single-subject datasets from the 1,000 Functional Connectomes project were used to demonstrate the capabilities of the framework.

Results

A framework for easy implementation of processing pipelines was developed and an R package for the example implementation of Fully Exploratory Network ICA was compiled. Test runs on data from 300 subjects demonstrated the computational advantages of a processing pipeline developed using the framework compared to non-parallelized processing, reducing computation time by a factor of 15.

Conclusion

The feasibility of computationally intensive exploratory analyses allows broader access to the tools for discovery science.     

Relaxation for online frequency estimator of bias‐affected damped sinusoidal signals based on Dynamic Regressor Extension and Mixing

This paper considers the problem of continuous‐time online frequency estimation for a biased damped sinusoidal signal. The previous result for a sinusoidal signal with time‐varying amplitude requires a persistency of excitation condition for regressor, which is not satisfied in the considered case. To relax this condition, we propose to use Dynamic Regressor Extension and Mixing method on the first step to replace nth‐order regression with n first‐order regression models. On the second step, two simple relaxation methods are proposed to establish necessary excitation for the first‐order gradient‐based estimator. The efficiency of the proposed approach is demonstrated through the set of numerical simulations for the exponentially damped sinusoidal signal.     

Multistage multiphase switched‐capacitor DC–DC converter with variable‐phase and PWM control

A closed‐loop multistage multiphase switched‐capacitor converter (n‐stage p‐phase MPSC) is proposed with a variable‐phase control (VPC) and a pulse‐width‐modulation (PWM) technique for low‐power step‐up conversion and high‐efficiency regulation. In this n‐stage MPSC, n voltage doublers are connected in series for boosting the voltage gain up to 2ⁿ at most. Here, VPC is suggested to realize a variable multiphase operation by changing the phase number p and topological path for the more suitable level of voltage gain so as to improve the power efficiency, especially for the lower output voltage Besides, PWM is adopted not only to enhance output regulation for different desired outputs, but also to reinforce output robustness to source/loading variation. Further, some theoretical analyses and designs include: n‐stage p‐phase MPSC model, steady‐state analysis, conversion ratio, power efficiency, output ripple, stability, capacitance selection, and control design. Finally, the closed‐loop MPSC is simulated, and the hardware is implemented and tested. All the results are illustrated to show the efficacy of the proposed scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

Learning for non-stationary Dirichlet processes

The Dirichlet process prior (DPP) is used to model an unknown probability distribution, F. This eliminates the need for parametric model assumptions, providing robustness in problems where there is significant model uncertainty. Two important parametric techniques for learning are extended to this non-parametric context for the first time. These are (i) sequential stopping, which proposes an optimal stopping time for on-line learning of F using i.i.d. sampling; and (ii) stabilized forgetting, which updates the DPP in response to changes in F, but without the need for a formal transition model. In each case, a practical and highly tractable algorithm is revealed, and simulation studies are reported. Copyright © 2007 John Wiley & Sons, Ltd.     

Central suboptimal H∞ filter design for nonlinear polynomial systems

This paper presents the central finite‐dimensional H_∞ filter for nonlinear polynomial systems, which is suboptimal for a given threshold γ with respect to a modified Bolza–Meyer quadratic criterion including the attenuation control term with the opposite sign. In contrast to the previously obtained results, the paper reduces the original H_∞ filtering problem to the corresponding optimal H₂ filtering problem, using the technique proposed in (IEEE Trans. Automat. Control 1989; 34 :831–847). The paper presents the central suboptimal H_∞ filter for the general case of nonlinear polynomial systems based on the optimal H₂ filter given in (Int. J. Robust Nonlinear Control 2006; 16 :287–298). The central suboptimal H_∞ filter is also derived in a closed finite‐dimensional form for third (and less) degree polynomial system states. Numerical simulations are conducted to verify performance of the designed central suboptimal filter for nonlinear polynomial systems against the central suboptimal H_∞ filter available for the corresponding linearized system. Copyright © 2008 John Wiley & Sons, Ltd.     

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.

     

An efficient algorithm for analysis of piecewise-linear resistive circuits: Driving-point and transfer characteristic plots

A new efficient algorithm is presented for finding all driving-point characteristic (DP) and transfer characteristic (TC) plots for a broad class of piecewise-linear (PWL) resistive circuits without the need for initial points for each solution branch. the piecewise-linear circuits to be considered need not be continuous nor need their linear regions be divided by grid-like hyperplanes. the computation of the new algorithm is based on zone-by-zone instead of the conventional region-by-region. Since each zone includes several regions and only one matrix inversion is needed for each zone, a significant reduction of computation can be achieved. Furthermore, the computational complexity for finding all solution branches, i.e. finding the DC operating points over the entire range of input values u, is no more than for finding all DC operating points over a single value u as far as the number of matrices needed to be inverted is concerned.     

The impact of susceptibility gradients on cartesian and spiral EPI for BOLD fMRI

High sensitivity to magnetic susceptibility changes and accurate localization of functional activations are key requisites for pulse sequences used for BOLD fMRI. This paper seeks to develop a framework for analysing the performance of various k-space sampling techniques in this respect, with special emphasis on spiral EPI (spiral) and cartesian EPI (EPI) and their performance under influence of induced field gradients (SFGs) and stochastic noise. A numerical method for calculating synthetic MR images is developed and used to simulate BOLD fMRI experiments using EPI and spirals. The data is then examined for activation using a pixel-wise t test. Nine subjects are scanned with both techniques while performing a motor task. SPM99 is used for analysing the experimental data. The simulated spirals provide generally higher t scores at low SFGs but lose more strength than EPI at higher SFGs, where EPI activation is offset from the true position. In the primary motor area spirals provide significantly higher t scores (P < 0.0002). In-plane variation of EPI is higher in phase-encoding direction than in frequency-encoding direction (P < 0.003). In the low SFG areas spirals provide stronger activation than EPI and less spatial variability. Thus, spirals are recommended for fMRI in motor area and language areas.     

Strong thickness dependence of aurivillius phase formation in SrBi2Ta2O9 thin films

Sr_0.7Bi_2.4Ta₂O₉ (SBT) thin films were studied for the dependence of Aurivillius phase formation kinetics on their film thickness. SBT thin films were fabricated using a sol-gel process and spin coating, and their thickness was varied controlling the number of spin coating. The films were first heated at a low temperature for the complete crystallization of amorphous film to fluorite phase and then further heated at different elevated temperatures for the phase transformation to Aurivillius for 40 min. It was found that the phase transformation kinetics apparently increased with thickness up to ∼390 nm, and then it sharply decreased at higher values. The Aurivillius crystal size decreased and the density of crystals increased with the increase of film thickness up to ∼390 nm, implying increasing number of nuclei due to the reduced energy barrier for nucleation. Above the critical value both the size and density of crystals decreased. It is suggested that up to ∼390 nm the tensile strain energy in the films, which was stored by the shrinkage of thin films during the removal of remaining organic components from sol-gel chemistry, plays a major role for determining the phase transformation kinetics and above the critical value SBT films act as a free bulk material without substrate constraints.     

La2O3–B2O3–TiO2 Glass/BaO–Nd2O3–TiO2 ceramic for high quality factor low temperature co-fired ceramic dielectric

A conventional BaO–Nd₂O₃–TiO₂ ceramic of microwave dielectric material was added to rare-earth derived borate glasses (La₂O₃–B₂O₃–TiO₂) for use as LTCC (low temperature co-fired ceramic) materials. The sintering behavior, phase evaluation, and microwave dielectric properties were investigated. It was found that increasing the sintering temperature from 750 to 850 °C led to increases in shrinkage and microwave dielectric properties (≈15 for ?_r , >10,000 GHz for Q*f₀ and >94 ppm/ °C for τ _f at 7–8 GHz for resonant frequency). The results suggest that a composite with suitable additives for τ _f could feasibly be developed as a material for LTCC applications.     

Über den optimalen Übertrager und Oszillator für Gleichspannungs-Hochspannungsquellen

Übersicht Es werden Berechnungsunterlagen für den bisher nicht gelösten optimalen Eingangsübertrager vom Standpunkt der Spannungsübersetzung aus für die Kaskadengeneratoren entwickelt.

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Contents We are going to determinate the conditions for the maximum voltage efficiency for the input transformer without link, and also for oscillator, of the Cockroft-Walton multiplying circuit.