Measurement of vertebral bone marrow proton density fat fraction in children using quantitative water–fat MRI

Objectives

To investigate the feasibility of employing a 3D time-interleaved multi-echo gradient-echo (TIMGRE) sequence to measure the proton density fat fraction (PDFF) in the vertebral bone marrow (VBM) of children and to examine cross-sectional changes with age and intra-individual variations from the lumbar to the cervical region in the first two decades of life.

Materials and methods

Quantitative water–fat imaging of the spine was performed in 93 patients (49 girls; 44 boys; age median 4.5 years; range 0.1–17.6 years). For data acquisition, a six-echo 3D TIMGRE sequence was used with phase correction and complex-based water–fat separation. Additionally, single-voxel MR spectroscopy (MRS) was performed in the L4 vertebrae of 37 patients. VBM was manually segmented in the midsagittal slice of each vertebra. Univariable and multivariable linear regression models were calculated between averaged lumbar, thoracic and cervical bone marrow PDFF and age with adjustments for sex, height, weight, and body mass index percentile.

Results

Measured VBM PDFF correlated strongly between imaging and MRS (R ² = 0.92, slope = 0.94, intercept = ?0.72%). Lumbar, thoracic and cervical VBM PDFF correlated significantly (all p < 0.001) with the natural logarithm of age. Differences between female and male patients were not significant (p > 0.05).

Conclusion

VBM development in children showed a sex-independent cross-sectional increase of PDFF correlating with the natural logarithm of age and an intra-individual decrease of PDFF from the lumbar to the cervical region in all age groups. The present results demonstrate the feasibility of using a 3D TIMGRE sequence for PDFF assessment in VBM of children.

     

Analysing a power transformer’s internal response to system transients using a hybrid modelling methodology

This article presents a novel approach to analysing a power transformer’s internal response to system transients. In this approach a hybrid modelling methodology is adopted which leverages the distinct advantages offered by both Black and Grey Box modelling techniques. The Black Box model of the transformer is used within the EMTP system study environment in order to take advantage of its mathematical flexibility and modelling accuracy. Transients derived from network switching operations within the study can then be used for injection tests within the Grey Box modelling environment. The Grey Box model, which is based upon the physical structure of the transformer, will facilitate analysis of the transformer’s internal voltage response to the external stimulus. A fundamental difference between the approach described in this paper and more traditional approaches is that it does not require prior knowledge of the internal geometry of the transformer. All of the modelling parameters are derived from external tests, nameplate details and an intrinsic understanding of common transformer design principles. This can be a distinct advantage since in most cases a transformer’s design specifications are not readily available outside of the laboratory due to the manufacturer’s intellectual property restrictions. A study of a gas insulated substation within a hydroelectric power plant in Brazil is used to demonstrate the proposed technique.     

Dynamic MR imaging of a minipig’s knee using a high-density multi-channel receive array and a movement device

Object

To construct an optimised, high-density receive array and a movement device to achieve dynamic imaging of the knee in orthopedic large animal models (e.g., minipigs) at 1.5 T.

Materials and methods

A 13-channel RF receive array was constructed, and the crucial choice of the array element size (based on considerations like region of interest, geometry of the minipig’s knee, achievable signal-to-noise ratio, applicability of parallel imaging, etc.) was determined using the Q factors of loops with different sizes. A special movement device was constructed to guide and produce a reproducible motion of the minipig’s knee during acquisition.

Results

The constructed array was electrically characterised and the reproducibility of the cyclic motion was validated. Snapshots of dynamic in vivo images taken at a temporal resolution (308 ms) are presented. Some of the fine internal structures within the minipig’s knee, like cruciate ligaments, are traced in the snapshots.

Conclusion

This study is a step towards making dynamic imaging which can give additional information about joint injuries when static MRI is not able to give sufficient information, a routine clinical application. There, the combination of a high-density receive array and a movement device will be highly helpful in the diagnosis and therapy monitoring of knee injuries in the future.     

Morphologic and functional changes in the unilateral 6-hydroxydopamine lesion rat model for Parkinson’s disease discerned with μSPECT and quantitative MRI

Object

In the present study, we aimed to evaluate the impact of neurodegeneration of the nigrostriatal tract in a rodent model of Parkinson’s disease on the different MR contrasts (T₂, T₁, CBF and CBV) measured in the striatum.

Material and methods

Animals were injected with 6-hydroxydopamine (6OHDA) in the substantia nigra resulting in massive loss of nigrostriatal neurons and hence dopamine depletion in the ipsilateral striatum. Using 7T MRI imaging, we have quantified T₂, T₁, CBF and CBV in the striata of 6OHDA and control rats. To validate the lesion size, behavioral testing, dopamine transporter μSPECT and tyrosine hydroxylase staining were performed.

Results

No significant differences were demonstrated in the absolute MRI values between 6OHDA animals and controls; however, 6OHDA animals showed significant striatal asymmetry for all MRI parameters in contrast to controls.

Conclusions

These PD-related asymmetry ratios might be the result of counteracting changes in both intact and affected striatum and allowed us to diagnose PD lesions. As lateralization is known to occur also in PD patients and might be expected in transgenic PD models as well, we propose that MR-derived asymmetry ratios in the striatum might be a useful tool for in vivo phenotyping of animal models of PD.     

Electricity tariffs in a high-penetration renewable system: Insights from Australia’s National Electricity Market

This paper considers the various supply-chain segments in the Australian NEM where significant adoption of renewable technologies has occurred. In the long-term, customers may be best served by 'fixed' or 'cap' style pricing contracts that allow unlimited energy consumption within a 'fixed' capacity band. This would be underpinned by economically regulated transmission and distribution 'demand' tariffs and a liquid market for innovative derivative products alongside an efficient wholesale energy dispatch engine.     

Determining a set of suspicious electricity customers using statistical ACL Tukey’s control charts method

Estimation a set of suspicious electricity customers is the first stage for detecting fraud of electricity. This paper deals with this stage. Based on historical data about monthly measurements of electricity, customers’ time series are formed and then analysis of these series is performed using Tukey’s control charts as one of the statistical method. The asymmetric control limit (ACL) Tukey’s control charts are chosen due to a rather expressed asymmetry and dominantly presented right distribution of time series data. As usual, the choice of upper (UCL) and lower (LCL) control limits is not based on allowed number of observations outside of the control limits. The choice of these limits is based on the balance of total energy, registered energy and energy losses. The essence of this approach is the simultaneous observation all customers’ time series of the controlled set with the same control limits and the same percentage of total and normalized energy losses in the observed distribution network. The criterion for finding the number of suspicious customers and their addresses is allowed error between the number of registered customers with one or more data (observations) outside the control limits for given losses and the number of suspicious customers’ indicators based on certain balance of energy and the estimated total percentage of losses in distribution network.     

Including electricity imports in California’s cap-and-trade program: A case study of a border carbon adjustment in practice

This article examines the inclusion of electricity imports in California’s cap-and-trade program. Having struggled to prevent the circumvention of the compliance obligation for imported electricity, policymakers weakened the policy’s environmental effectiveness during implementation. Drawing on empirical data, this case study finds that political opposition from utilities led to this policy outcome. The reason behind this opposition lay in concerns about regulatory uncertainty and the policy’s effectiveness in achieving emissions reductions.     

Revisiting Bonbright’s principles of public utility rates in a DER world

Professor James Bonbright’s Principles of Public Utility Rates, first published in 1961, was built around a model of vertically integrated electricity monopolies and approached ratemaking largely as an exercise in balancing the interests of capital attraction with those of ratepayers, all within a ‘public interest’ framework. This article seeds a new conversation about changes to the venerable Bonbright principles and introduces new principles of public utility rates for an era of electric utility transformation.     

Can FERC’s Standard Market Design Work in Large RTOs?

The two major FERC initiatives right now are Standard Market Design—which includes locational marginal pricing—and consolidation of regional transmission organizations. But SMD in combination with large RTOs can cause serious new inefficiencies unless corrective actions are taken.     

Emerging shadows in national solar policy? Nevada’s net metering transition in context

Nevada’s recent overhaul of its net energy metering policy, which instituted a new net billing program in its place, underscores two key insights. First, decisions about whether net metering should continue separate from the design of a given program. From an institutional perspective, legislatures are best equipped to answer the first question; PUCs have comparative expertise on the second. Further, as net metering policies are likely to become more diverse across states over time, it is critical to maximize policy stability by using—rather than abdicating—grandfathering for existing customers.     

A change in the air? The role of offshore wind in Australia’s transition to a 100 % renewable grid

Rapid decarbonisation of electricity production is required if Australia is to meet its obligations under the Paris Agreement. Critical to achieving this at low cost while maintaining system reliability is the selection of an appropriate mix of generation technologies to service electrical demand. Australia has seen extensive deployment of renewable energy technologies such as onshore wind and solar but has not yet seen the adoption of offshore wind technology. However, there is currently significant interest in developing this resource, with ongoing debate occurring about future technology costs and the potential of onshore renewables to meet electrical demand.This article presents the results of an investigation into the techno-economic impact of exogenously fixing offshore wind capacity on a future least-cost Australian National Electricity Market with 100 % renewable generation. An existing open-source cost optimisation model, National Electricity Market Optimiser, was used for the study.It was found that increasing the capacity of offshore wind in the generation mix leads to displacement of both onshore wind and solar generators. This is due to the greater magnitude and consistency of the offshore wind resource relative to onshore. Increasing offshore wind capacity therefore tends to reduce the total system generation capacity, as well as the amount of unused surplus generation. Using lowest published projections for future capital costs, inclusion of offshore wind was found to reduce total system costs. Using an average of future cost projections, total system costs were found to increase. However, adding up to 15 GW of offshore wind capacity to a 100 % renewable system would only impact total system costs by 5 %. Given the other potential advantages of offshore wind, namely closer siting to load centres, reduced need for onshore land resources, and the potential to transition existing fossil fuel workers, our results suggest that offshore wind may be a suitable candidate for inclusion in Australia’s transition to a low carbon electricity system, under a range of future cost scenarios.     

3D gradient system for two B 0 field directions in earth’s field MRI

Object

A new gradient system for earth’s field magnetic resonance imaging (EFMRI) is presented that can be rotated relatively to the earth’s field direction while maintaining the ability to encode images. Orthogonal components of the gradient field are exploited to reduce the number of gradient coils.

Materials and methods

Two favorable orientations of the gradient system relative to the earth’s magnetic field (parallel and perpendicular) are discussed. We introduce the theory for the magnetic fields of the new gradient system and illustrate the design of the coil geometries which were worked out with the help of simulations and a numerical optimization algorithm. Field mapping measurements and imaging experiments in the two different orientations of the gradient system were carried out.

Results

Orthogonal components of the gradient field take over the role of the additionally needed gradient fields when the gradient system is rotated relative to the earth’s magnetic field. The results from the field mapping and imaging experiments verify the presented theory and show the functionality of the new gradient system.

Conclusion

The presented system demonstrates that gradient coils can be used for image encoding in multiple directions. This fact can be exploited to realize an EFMRI setup for parallel and perpendicular prepolarization with a single set of gradient coils.     

A household’s power load response to a change in the electricity pricing scheme: An expanded microeconomic-physical approach

Energy economists are interested in how changes in electricity prices prompt a response in end-user electricity demand. If historical prices are low or seldom change, it becomes difficult to estimate price elasticities statistically, especially in the short-run. Thus, a framework that merges the physical equations that govern how electricity is consumed, and a utility-maximizing household the responds to varying expenditures on electricity, is used.We have parameterized the physical component to a house in Saudi Arabia. Three electricity pricing schemes are analyzed: progressive tariffs, time-of-use prices, and real-time prices. We show that for a household with a low preference for electricity, slight price increases do warrant adjustment in indoor temperature in the hot summer months and lower consumer electronics use. Since we adopt a dwelling in Saudi Arabia, the response measure that is most exercised is the thermostat set-point adjustment. A subdued response is found for households that have adopted higher energy efficiency, or have high preference for electricity.     

Challenging the system: The role of community choice aggregation in California’s transition to a renewable energy future

There has been a rapid adoption of Community Choice Aggregation (CCA) programs in California. CCAs allow communities to choose their electricity supply through a locally-controlled public agency, disrupting the electric power sector as part of an energy transition. An analysis of how stakeholders in Sonoma and San Diego counties have pursued the implementation of CCAs is conducted through interviews. The findings demonstrate how macro-level pressures created opportunities for niche policies to be developed and challenge the utility-centered electricity model.     

It’s high time to transition away from volumetric distribution rates: Why not a 3-part tariff?

This essay attempts to contribute to the ongoing debate about the design of electricity rates for residential customers. The debate has centered on fixed versus volumetric charges, and then later about introducing demand charges. The interest in demand charges has sprung largely from fundamental flaws in the prevailing rate design for residential electric service, especially as those flaws have magnified under a continuously evolved market and public-policy environment. This essay argues that demand charges are worthy of study by regulators because of their superior features compared with prominent alternatives, namely, volumetric and straight-fixed variable rates. But it can be a long road before they become commonly accepted. This will only happen when the political cost of the prevailing rate structure becomes prohibitively high. In the meantime, regulators should begin the process of moving away from volumetric rates, for the sake of both efficiency and equity.     

A method of using neural fuzzy models to determine the technical state of a diesel locomotive’s electrical equipment

Equipment for carrying out onboard diagnostics is an important component in systems for controlling the state and reliability of rolling stock, in particular, that of diesel locomotives. It makes it possible to monitor a locomotive’s service quality, to detect and predict changes in its technical state without interrupting the carriage process, and to efficiently use the high-cost stationary and local diagnostic means, as well as to correct service time and volume by taking into account the real technical state. Therefore, it is important to develop methods for determining the technical state of locomotive units by using an MCS-T(N,E) (micro-processor control system) locomotive’s diagnostic subsystem of a locomotive and software for processing the measurement data. The main aim of such a method is to monitor the technical state of a locomotive’s equipment and predict changes in it. At the present time, simplified diagnostic models are used to solve such problems. However, to increase the efficiency and reliability of the process of checking complicated objects such as a locomotive, it is necessary to use more complex diagnostic models based on artificial neural networks. A way to use a neural-network method and neural fuzzy diagnostic models for diagnosing the excitation system of traction generators of modern diesel locomotives is presented in this paper. Information collected by the MCS-TP subsystem is used as diagnostic information. It is transferred online to a remote diagnostic server. The method for diagnosing the excitation system of a traction generator is checked by processing the measurement information.     

Assessment of Supply-Voltage Quality in a Ship’s Electric-Power System by Means of Computer Simulation

A ship’s electric-power system (SEPS) provides reliable functioning of ship systems, as well as safety in navigation and the living conditions and work of the crew. SEPSs in large-displacement vessels can have a capacity of more than 100 MW and consist of thousands of interconnected components and subsystems. On ships with a propulsion system (PS), the SEPS powers both the PS, which consumes most of the power generated by a ship power plant, and numerous general consumers of power on the ship. The PS includes frequency converters with dc links; for a ship’s power plant, these converters are a high-power nonlinear load that causes significant voltage distortions in the ship’s network. When designing a vessel, at the stage of selecting the structure and components of the SEPS, electromagnetic compatibility between the PS and general vessel users needs to be provided. According to the requirements specified in the Russian Maritime Register of Shipping, the nonsinusoidal voltage in the ship’s electrical network must not exceed 10%. Computer simulation is the only effective tool for assessing the quality of ship-network voltage at the initial stages of design. In this paper, we present the results of estimating two alternative SEPS designs by means of the MATLAB Simulink package. It is shown that high-power transformers can be removed from the PS without significant deterioration of network-voltage quality, which makes it possible to reduce the cost, weight, and dimensions of electrical equipment.     

Getting it Right: Filling the Gaps in FERC’s Stranded Cost Policies

Major gaps in the wholesale stranded cost policies of the Federal Energy Regulatory Commission (FERC) threaten to introduce inefficiencies during the transition to competition in the form of uneconomic bypass and uneconomic new entry.     

Made in the Keystone State: Pennsylvania’s Approach to Retail Electric Competition

Many states that are considering embracing retail choice will find themselves trying to decide between the Pennsylvania model, which offers all consumers immediate savings, or that offered by California and Massachusetts. Here are some of the mechanics involved in bringing retail choice to Pennsylvania.     

Analyzing the Blackout Report’s Recommendations: Alternatives for a Flexible,Dynamic Grid

The report shows that industry, regulators, and policymakers still take a very physical supply-oriented view of the system. They would be more innovative, and come up with better policies for more robust networks, if they treated the grid as an organic, dynamic system.