bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis and Design of Novel Absorption Power Cycle Plants
Authors: Novotny Vaclav , Kolovratnik Michal , Vitvarova Monika , Jakobsen Jana P.
Published: November 2016

Absorption Power Cycles (APCs) provide an interesting field within power cycles. The multicomponent mixture with variable temperature across boiling is employed as a working fluid. This has a potential for decreasing exergy loss associated with heat transfer during phase change processes (boiling and condensation). Absorption process has also an effect of lowering exhaust pressure of a turbine. The APCs hold a potential for heat recovery applications at very low temperatures, where constant temperature of boiling and condensation largely limits performance and economic effectiveness of Organic Rankine cycles (ORCs). Theoretical calculations show superiority of APC over extensive range of considered ORC working fluid. The advantage of APC further increases when air cooled condenser needs to be used instead of wet cooling tower. With the same boundary conditions for all cycles the APC provides higher utilization efficiency and power output at source temperatures below approximately 120 °C, for temperatures as low as 60 °C the net power output can be surpassed even more than three times.

The proposed APC employs aqueous solution of salts considered generally for absorption cooling (Lithium Bromide, Lithium Chloride, Calcium Chloride) as a working fluid. Unlike ammonia used in mixture with water in Kalina APC or often ORC working fluids, used salts are non-toxic, environmentally friendly and pure water in expander simplifies its design. After summary of theoretical research from thermodynamics point of view are discussed principles, aspects and issues for design of single components of the cycle. Results of sizing are presented on two examples with 100 °C heat source. First one is 20 kWe unit using hot air as a heat source and air cooled condenser, second one is 500 kWe unit with heat source being pressurized water and using wet cooling tower heat rejection. Results show possibility of building relatively efficient system for even small power output with turbine isentropic efficiency nearly 80 % for the 20 kWe unit, but relatively large heat exchangers.
Improvement in Spiral Heliostat Field Layout Thermo-Economic Performance by Field Zoning Implementation
Authors: Saghafifar Mohammad , Gadalla Mohamed
Published: November 2016

Arguably, the most complicated and problematic mathematical formulation for solar collectors belongs to the heliostat field collectors. Consequently, extensive researches are carried out in order to develop several codes capable of providing heliostat field analysis and optimization. Noting that most of the aforementioned heliostat field codes are developed based on the radial-staggered field layout which is arguably the most popular and widely implemented heliostat field configuration in the literature. Nevertheless, a ground-breaking heliostat field layout based on the spiral patterns of phyllotaxis discs is recently proposed. It was argued that the transition between the areas with high and low heliostat field density is not continuous in radial-staggered configuration. In a study by the authors, the spiral and radial-staggered field layouts thermo-economic analyses are compared and the results points to the superiority of the radial-staggered layout. Nevertheless, it is believed that utilizing two design variables might be only sufficient for small number of mirrors. Therefore, more design variables must be implemented to fully control different areas of the field for larger capacity heliostat fields. In this paper, spiral field zoning is proposed and its impact on the spiral heliostat field layout performance is assessed. By dividing the heliostat field into multiple zones, each zone is designed with a set of design variables (two design variables: a and b). Consequently, the impacts heliostat field zoning might have on the field thermo-economic performance are investigated.
Selective Emitters Design and Optimization for Energy Harvesting Using Rectennas
Authors: Zeyghami Mehdi , Myers Philip D. , Goswami D. Yogi , Stefanakos Elias
Published: November 2016

Recently, rectennas have drawn attention as an attractive option to harvest radiative thermal energy from the sun and terrestrial thermal sources. In order to achieve the potential high energy conversion efficiencies by this technology, matching conditions between the incident electromagnetic wavelength and the rectenna characteristic length must be satisfied. Therefore, a selective emitter is a key element in high efficiency rectennas. Photonic structures were designed for selective emission using the transfer matrix method and genetic algorithm optimization. Two types of emitters were developed using aluminum as the supporting substrate. This paper presents narrowband selective emitters with a peak emissivity at 9.45 μm made of alternating layers of Al2O3 and SiO2 on a substrate, and broadband selective emitters made of alternating layers of Al2O3 and SiC on a substrate with a high emissivity band between 9.5 μm and 10.5 μm.
Effect of Power Characteristics on Solar Panels: Hands-On Projects for Clean Energy Systems Class
Authors: Dikici Birce , Jalandoni Javier
Published: November 2016

In this paper, experiments that can be introduced to Clean Energy Systems classes are described. The experiments investigate the effect of power characteristics (temperature, shade and tilt angle) on solar panel electricity production. Solar cell efficiency is the ratio of the electrical output of a solar cell to the incident energy in the form of sunlight. The energy conversion efficiency of a solar cell is the percentage of the solar energy to which the cell is exposed that is converted into electrical energy. Extreme temperatures can cause a decrease in solar panel’s power output and airstream can dissipate the heat and bring the solar panel to its normal operating condition. Solar panel efficiency is undesirably affected by heat and improved with introducing cooler medium.

As well as heat, solar panel loses its power when a part of it is shaded by trees or surrounding buildings. Before solar panel systems are designed for homes, usually a detailed shading analysis of the roof is conducted to reveal its patterns of shade and sunlight throughout the year.

By the same manner, how solar panels react to the direct and indirect rays from the sun in order to produce electricity is examined through experiments. Voltage, current and power flowing into a resistor are measured when the angle of the solar panel relative to the light source is changed. The tilt angles to the electrical measurements are linked to the differences in electrical generation.

Students can perform experimental procedures explained here and gain the conceptual understanding of the Solar Energy better. The investigations require student explanation of the question, method, display of data with the critical response from peers.
Performance of Concentrated Photovoltaic Cells Using Various Microchannel Heat Sink Designs
Authors: Radwan Ali , Ahmed Mahmoud , Ookawara Shinichi
Published: November 2016

The photovoltaic output power is directly proportional to the solar radiation and inversely with the cell temperature. The higher the photovoltaic temperature is, the lower the electrical efficiency is with possible damage to the cell. To improve the electrical efficiency and to avoid the possible damage, a concentrating PV system associated with an effective cooling technique is of great importance. In the present study, a new cooling technique for concentrated photovoltaic (CPV) systems was introduced using various designs of micro-channel heat sinks. The suggested configurations included parallel flow, counter flow single and double layer micro-channels, and single layer flat micro-channel integrated with CPV system. A comprehensive three-dimensional thermo-fluid model for photovoltaic layers integrated with microchannel heat sink was developed. The model was simulated numerically to estimate the solar cell temperature. The numerical results were validated with the available experimental and numerical results. In the meantime, the effects of different operational parameters were investigated such as solar concentration ratio and cooling mass flow rate. Performance analysis of CPV using different microchannel configurations was implemented to determine the average and local solar cell temperature, pumping power, and temperature uniformity. Results indicated that the use of microchannel heat sink was a very effective cooling technique which highly attained temperature uniformity, viz., eliminated the hot spots formation with a significant reduction in the average temperature of CPV. The single layer parallel flow achieved the minimum solar cell temperature while the counter flow attained the most uniform temperature distribution compared with other configurations. Furthermore, the double layer parallel flow microchannel attained the minimum pumping power for a given cooling mass flow rate.
Techno-Economic Comparative Study on Hydrogen and Electricity Cogeneration Systems With CO2 Capture
Authors: Zohrabian Angineh , Mansouri Majoumerd Mohammad , Soltanieh Mohammad , Arild Øystein
Published: November 2016

In order to achieve the international climate goals and to keep the global temperature increase below 2 °C, carbon capture and storage in large point sources of CO2 emissions has received considerable attention. In recent years, mitigation of CO2 emissions from the power sector has been studied extensively whereas other industrial point source emitters such as hydrogen industry have also great potential for CO2 abatement.

This study aims to draw an updated comparison between different hydrogen and power cogeneration systems using natural gas and coal as feedstock. The goal is to show the relative advantage of cogeneration systems with respect to CO2 emission reduction costs. Accordingly, the Reference Case is selected as a large-scale H2 production system with CO2 venting using natural gas based on steam methane reforming. In this work, H2 and electricity cogeneration with CO2 capture based on auto-thermal reforming of natural gas has been simulated using ASPEN Plus™, while the cost and performance indicators for the plant based on steam methane reforming of natural gas and the coal-based plants have been adopted from the literature. Using a consistent approach, different plants are compared techno-economically. A sensitivity analysis has also been performed with variation in the most important input parameters including natural gas price (2–8 $/GJ), coal price (1–4 $/GJ), electricity price (30–90 $/MWh) and capacity factors (85–50%) and the results are presented here.

The results demonstrate that the total efficiency of the system is slightly higher in natural gas-based systems than in coal-based systems. The results also indicate that although H2 production cost increases with power cogeneration and CO2 capture, cogeneration is a promising and attractive alternative for clean power generation. The highest sensitivity of the results has been observed for the fuel price.
Assessing the Policy Interaction Effect of Renewable Portfolio Standards (RPS) and Clean Power Plan (CCP) Emissions Goals for States in the U.S. Northeast
Authors: Chandramowli Shankar N. , Felder Frank A. , Shan Xiaojun G.
Published: November 2016

With the proposed Clean Power Plan for regulating carbon emissions from the power sector in the U.S, policymakers are likely to use a cost optimization framework to plan for future scenarios and implementation strategies. The modeling framework introduced in this paper would help such policymakers to make the appropriate investment decisions for the power sector. This paper applies an analytical model and an optimization model to investigate the implications of coimplementing an emission cap and a Renewable Portfolio Standards (RPS) policy for the U.S. Northeast. A simplified analytical model is specified and the first order optimality conditions are derived. The results from the analytical model are verified by running simulations using LP-CEM, a linear programming-based supply cost optimization model. The LP-CEM simulation results are analyzed under the recently proposed Clean Power Plan emissions cap rules and RPS scenarios for the U.S. Northeast region. The marginal abatement cost estimates, derived from a limited set of LP-CEM runs, are analyzed and compared to the theoretical results. For encouraging renewables generation, an RPS instrument is cost-effective at higher policy targets, while an emissions cap instrument is cost-effective at lower policy targets. For CO2 emissions reduction, an emissions cap instrument is found be cost-effective for all policy targets. There is a trade-off between emissions levels and supply costs when the two instruments are co-implemented.
Performance and Applicability of the New Material Heat Exchanger to Substitute for Titanium
Authors: Kim Hyeon-Ju , Lee Ho-Saeng , Jung Young-Kwon , Oh Wee-Yeong
Published: November 2016

Heat exchanger takes important role in economic feasibility for Ocean Thermal Energy Conversion (OTEC) or Sea Water Air Conditioning (SWAC) systems. As the portion of heat exchanger made of titanium (Ti) with anti-corrosion function against seawater is more than 20∼30% of total initial cost, the economical feasibility can be enhanced by replacing titanium with cheaper corrosion-resistant materials or treatment methods. This study carry out to examine the corrosion-resistant property of Electrodeposited Oxy-Nitriding Steel (EONS) plate, it turns out life time of the EONS plate is more than 13.9 years. Also, the heat transfer performance for condensation and evaporation of the EONS plate heat exchanger were found to be 11.3% and 7% higher than those of Ti plate heat exchanger. If the life time of the EONS plate of 13.9 years compared to the Ti plate which could be assumed about 30 years, then practical application is possible whether its production cost is found to be less than 46.5% of Ti plate. Lower cost of mass-producing EONS plate by 45% than existing Ti plate seems to enable the substitution in OTEC and SWAC.
A Particle/sCO2 Heat Exchanger Testbed and Reference Cycle Cost Analysis
Authors: Carlson Matt D. , Ho Clifford K.
Published: November 2016

The high-temperature particle – supercritical carbon dioxide (sCO2) Brayton power system is a promising option for concentrating solar power (CSP) plants to achieve SunShot metrics for high-temperature operation, efficiency, and cost. This system includes a falling particle receiver to collect solar thermal radiation, a dry-cooled sCO2 Brayton power block to produce electricity, and a particle to sCO2 heat exchanger to couple the previous two. While both falling particle receivers and sCO2 Brayton cycles have been demonstrated previously, a high temperature, high pressure particle/sCO2 heat exchanger has never before been demonstrated. Industry experience with similar heat exchangers is limited to lower pressures, lower temperatures, or alternative fluids such as steam. Sandia is partnering with three experienced heat exchanger manufacturers to develop and down-select several designs for the unit that achieves both high performance and low specific cost to retire risks associated with a solar thermal particle/sCO2 power system. This paper describes plans for the construction of a particle sCO2 heat exchanger testbed at Sandia operating above 700 °C and 20 MPa, with the ability to couple directly with a previously-developed falling particle receiver for on-sun testing at the National Solar Thermal Test Facility (NSTTF).
Experimental Testing of s-CO2 Regenerator for Use as a Replacement to High Cost Printed Circuit Recuperators for Use in s-CO2 Recompression Brayton Cycle
Authors: Hinze Jacob F. , Nellis Gregory F. , Anderson Mark H.
Published: November 2016

Supercritical Carbon Dioxide (sCO2) power cycles have the potential to deliver high efficiency at low cost. However, in order for s-CO2 cycle to reach high efficiency, highly effective recuperators are needed. These recuperative heat exchangers must transfer heat at a rate that is substantially larger than the heat transfer to the cycle itself and can therefore represent up to 24% of the total power block cost in a recompression Brayton cycle [1]. Lower cost regenerators are proposed as a cost saving alternative to high cost printed circuit recuperators. A regenerator is a heat exchanger that alternately has hot and cold fluid passing through it. During the first half of its cycle the hot gas is passed over a storage media bed (stainless steel balls, screens, or similar fill material) where thermal energy is stored. During the next half of the cycle, cold fluid is passed through in the opposite direction, extracting the thermal energy from the bed. By operating a cycle with two (or more) regenerators, where one is always in a hot to cold (HTC) blow and the other in a cold to hot blow (CTH), a quasi-steady state can be achieved in the cycle to allow continuous operation. A model of the regenerator was created and used in place of a recuperator in a model of a 10MW power plant. The thermal effectiveness of the regenerator cycle was slightly lower than the recuperator cycle, however the regenerator cycle had a saving of about 9.3 percent in the Levelized Cost of Energy (LCoE). A scale model of the regenerator is under construction which will verify the performance of the regenerator model.
Track and Tilt Collection for Central Receiver CSP
Authors: Angel Roger , Hyatt Justin
Published: November 2016

Here we describe a new type of point-focus solar collector for CSP called “track and tilt”. It bridges the gap between dish and heliostat arrays collectors, having the high optical efficiency of a dish but with larger aperture (> 1000 m2) focused to a tower mounted receiver in fixed gravity orientation. It is well matched to the next generation of high efficiency cavity receivers transferring heat to a storage medium at temperatures exceeding 700C.

The collector uses silvered glass reflectors mounted on a rotating, rigid structure in the form of a 120 degree conical arc. In operation, this large structure rotates in azimuth on a track around the central receiver tower, keeping the gravity load on the structure constant. The central receiver is rotated about a vertical axis so as to face the reflector arc. The reflectors are concave, all with the same focal length, and are individually tilted to follow solar elevation to focus sunlight onto the tower-mounted receiver.

A detailed optical model made of a collector with 40 m focal length has 1,450 m2 total reflector area, and delivers on average 1.2MW of sunlight to the receiver, (under 1000 W/m2 DNI and allowing for reflector and small geometric losses). The collector forms an only slightly aberrated image of the sun at the receiver, showing a concentration of 2000x averaged over the receiver entrance with spillage < 2%. The overall annual averaged efficiency, defined as (total sunlight energy delivered to the receiver entrance)/(direct normal irradiance × total reflector area) is >80%. This calculation includes 90% reflectivity of the mirrors.

To avoid the high mass and cost of a structure which must withstand 85 mph winds, our unique arc support structure takes the form of four lightly built panels which are lowered to the ground in high wind and for maintenance. Cables from the central tower are used to lower and raise the panels into operating position where they are locked together. The top section of the tower carrying the cable mechanism and the receiver rotate on a bearing in synchronization with the track mounted reflector assembly.

The small scale of the collector unit means that a first prototype of the radical new architecture can be built and tested at relatively modest cost. Higher power systems with multiple collectors and receivers might be built either with individual storage and turbines, such as sCO2, or with heat transfer to a common storage and power generation facility (as in trough systems). Continual improvements of the collector should be affordable, as system iteration costs are low.
Experimental Analysis of Loss Mechanisms in a Gas Spring
Authors: Sapin Paul , Fabris Drazen , White Alexander J. , Taleb Aly , Markides Christos N.
Published: November 2016

Reciprocating-piston compressors and expanders are promising solutions to achieve higher overall efficiencies in various energy storage solutions. This article presents an experimental study of the exergetic losses in a gas spring. Considering a valveless piston-cylinder system allows us to focus on the thermodynamic losses due to thermal-energy exchange processes in reciprocating components. To differentiate this latter loss mechanism from mass leakages or frictional dissipation, three bulk parameters are measured. Pressure and volume are respectively measured with a pressure transducer and a rotary sensor. The gas temperature is estimated by measuring the Time-Of-Flight (TOF) of an ultrasonic pulse signal across the gas chamber. This technique has the advantage of being fast and non-invasive. The measurement of three bulk parameters allows us to calculate the work as well as the heat losses throughout a cycle. The thermodynamic loss is also measured for different rotational speeds. The results are in good agreement with previous experimental studies and can be employed to validate CFD or analytical studies currently under development.
High Performance Reduction/Oxidation Metal Oxides for Thermochemical Energy Storage (PROMOTES)
Authors: Miller James E. , Ambrosini Andrea , Babiniec Sean M. , Coker Eric N. , Ho Clifford K. , Al-Ansary Hany , Jeter Sheldon M. , Loutzenhiser Peter G. , Johnson Nathan G. , Stechel Ellen B.
Published: November 2016

Thermochemical energy storage (TCES) offers the potential for greatly increased storage density relative to sensible-only energy storage. Moreover, heat may be stored indefinitely in the form of chemical bonds via TCES, accessed upon demand, and converted to heat at temperatures significantly higher than current solar thermal electricity production technology and is therefore well-suited to more efficient high-temperature power cycles. The PROMOTES effort seeks to advance both materials and systems for TCES through the development and demonstration of an innovative storage approach for solarized Air-Brayton power cycles and that is based on newly-developed redox-active metal oxides that are mixed ionic-electronic conductors (MIEC). In this paper we summarize the system concept and review our work to date towards developing materials and individual components.
The Utilization of Ground Surroundings for Seasonal Solar Energy Storage
Authors: Weber Bernd , Solís Figueroa Eduardo , Durán García M. Dolores , Martínez Cienfuegos Iván G. , Rincón-Mejía Eduardo A.
Published: November 2016

In European countries seasonal thermal energy storage is an emergent task due to availability of solar energy in summer and thermal energy demand in winter. In this study the performance of an uninsulated buried storage tank is analyzed. Summer temperatures reached 45 °C in the storage tank and 22 °C in the soil, 1 m from the tank shell. Wintertime temperature of the storage tank dropped to 8 °C, near the freezing limit of the heat pump, and soil cooled down to 9 °C. While in wintertime heat transfer from earth to water was the limiting factor, a summertime temperature difference of more than 20 °C allowed enough energy transport to charge the soil storage system. An analytical model showed that more than 50% of the solar energy stored could be recovered by this application.
Achieving Ultra-Low Energy Consumption in Data Center Mechanical Systems Through Indirect Airside Economization
Authors: Comperchio Dan , Behere Sameer
Published: November 2016

Data center cooling systems have long been burdened by high levels of redundancy requirements, resulting in inefficient system designs to satisfy a risk-adverse operating environment. As attitudes, technologies, and sustainability awareness change within the industry, data centers are beginning to realize higher levels of energy efficiency without sacrificing operational security. By exploiting the increased temperature and humidity tolerances of the information technology equipment (ITE), data center mechanical systems can leverage ambient conditions to operate in economization mode for increased times during the year. Economization provides one of the largest methodologies for data centers to reduce their energy consumption and carbon footprint. As outside air temperatures and conditions become more favorable for cooling the data center, mechanical cooling through vapor-compression cycles is reduced or entirely eliminated. One favorable method for utilizing low outside air temperatures without sacrificing indoor air quality is through deploying rotary heat wheels to transfer heat between the data center return air and outside air without introducing outside air into the white space. A metal corrugated wheel is rotated through two opposing airstreams with varying thermal gradients to provide a net cooling effect at significantly reduced electrical energy over traditional mechanical cooling topologies. To further extend the impacts of economization, data centers are also able to significantly raise operating temperatures beyond what is traditionally found in comfort cooling applications. The increase in the dry bulb temperature provided to the inlet of the information technology equipment, as well as an elevated temperature rise across the equipment significantly reduces the energy use within a data center.
Exergetic and Thermoeconomic Analysis of the “Villa de Reyes” Steam Power Plant Operating on Partial Load
Authors: Duran García María D. , Jiménez García Juan A. , Weber Bernd
Published: November 2016

In this paper a thermoeconomic and exergy analysis of a steam power plant located at Villa de Reyes, México is presented. This study is focused on the analysis on partial load of this plant. According to the steam power plant operation manual this plant is able to operate at 25%, 50%, 75% and 100% of the total load installed, and some design parameters are established for this operation loads. Nevertheless during this study it was observed that this parameters and operation loads conditions are not the most efficient from the energetic and exergetic point of view, and also, the values of the thermal parameters used for these operation loads were not the optimum. In this context the objective of this research was to design a model for the power plant simulation in order to determine the best design parameters and operation loads conditions for this particular facility. First of all the model was validated, with the information of the operation manual of the steam generator. Once the model was validated, it was achieved the thermal, exergetic and thermoeconomic analysis. As a result it was observed that the best operation load conditions are at 100%, 98.4%, 93.3% and 75.6%. Also some optimal values of air-gas relation, extraction pressure and drum pressure were found. It was observed that an energetic efficiency up to 35.5% and exergetic efficiency up to 29% may be achieved. Finally it was achieved the thermoeconomic analysis in order to determine the cost of the energetic and exergetic loses and identify the elements that produce the higher irreversibility.
Fabrication process for 200 nm-pitch polished freestanding ultrahigh aspect ratio gratings
Authors: Bruccoleri Alexander R. , Heilmann Ralf K. , Schattenburg Mark L.
Published: November 2016

A fully integrated fabrication process has been developed to fabricate freestanding, ultrahigh aspect ratio silicon gratings with potassium hydroxide (KOH)-polished sidewalls. The gratings are being developed for wavelength-dispersive, soft x-ray spectroscopy on future space telescopes. For this application, the grating needs to have a large open-area fraction and smooth sidewalls (roughness < 1 nm) to maximize efficiency. The prototype gratings fabricated with the process presented here have been tested on a synchrotron beamline and have demonstrated an absolute diffraction efficiency greater than 30% for 2 nm-wavelength x-rays in blazed orders. This efficiency is greater than twice the efficiency of previously fabricated gratings. The fabrication process utilizes silicon-on-insulator wafers where the grating and a cross support are etched in the device layer, and an additional structural support is etched in the handle layer. The device layer and handle layer are both etched via deep reactive-ion etching using a Bosch process. The buried SiO2 layer stops both etches and is removed at the end of the process to create a freestanding structure. The gratings have a pitch of 200 nm, a depth of 4 μm, and the bars are polished via KOH. The polishing process reduces both the roughness and the grating-bar thickness. The finished gratings span an area of approximately 10 by 30 mm, supported by 1 mm-wide hexagons in the handle layer.
Automated detection of white matter hyperintensities of all sizes in cerebral small vessel disease
Authors: Ghafoorian Mohsen , Karssemeijer Nico , van Uden Inge W. M. , de Leeuw Frank‐Erik , Heskes Tom , Marchiori Elena , Platel Bram
Published: November 2016

Purpose:

White matter hyperintensities (WMH) are seen on FLAIR‐MRI in several neurological disorders, including multiple sclerosis, dementia, Parkinsonism, stroke and cerebral small vessel disease (SVD). WMHs are often used as biomarkers for prognosis or disease progression in these diseases, and additionally longitudinal quantification of WMHs is used to evaluate therapeutic strategies. Human readers show considerable disagreement and inconsistency on detection of small lesions. A multitude of automated detection algorithms for WMHs exists, but since most of the current automated approaches are tuned to optimize segmentation performance according to Jaccard or Dice scores, smaller WMHs often go undetected in these approaches. In this paper, the authors propose a method to accurately detect all WMHs, large as well as small.

Methods:

A two‐stage learning approach was used to discriminate WMHs from normal brain tissue. Since small and larger WMHs have quite a different appearance, the authors have trained two probabilistic classifiers: one for the small WMHs (⩽3 mm effective diameter) and one for the larger WMHs (>3 mm in‐plane effective diameter). For each size‐specific classifier, an Adaboost is trained for five iterations, with random forests as the basic classifier. The feature sets consist of 22 features including intensities, location information, blob detectors, and second order derivatives. The outcomes of the two first‐stage classifiers were combined into a single WMH likelihood by a second‐stage classifier. Their method was trained and evaluated on a dataset with MRI scans of 362 SVD patients (312 subjects for training and validation annotated by one and 50 for testing annotated by two trained raters). To analyze performance on the separate test set, the authors performed a free‐response receiving operating characteristic (FROC) analysis, instead of using segmentation based methods that tend to ignore the contribution of small WMHs.

Results:

Experimental results based on FROC analysis demonstrated a close performance of the proposed computer aided detection (CAD) system to human readers. While an independent reader had 0.78 sensitivity with 28 false positives per volume on average, their proposed CAD system reaches a sensitivity of 0.73 with the same number of false positives.

Conclusions:

The authors have developed a CAD system with all its ingredients being optimized for a better detection of WMHs of all size, which shows performance close to an independent reader.
Thermoacoustic imaging of rabbit knee joints
Authors: Chi Zihui , Zhao Yuan , Huang Lin , Zheng Zhu , Jiang Huabei
Published: November 2016

Purpose:

Knee joint is one of the largest and most complex joints of the body. Knee joint diseases are common, and current clinical imaging technologies such as x‐ray computed tomography, magnetic resonance imaging, and ultrasound imaging have limitations in the diagnosis of knee joint diseases. Emerging imaging technologies such as diffuse optical tomography and photoacoustic imaging (PAI) have been applied to the detection of osteoarthritis (OA). However, they are limited to small joints such as the finger and difficult to be used for large joints such as the knee. Thermoacoustic imaging (TAI), also an emerging modality, provides high contrast and deep tissue penetration. Here, the authors apply TAI to the knee joint and demonstrate the potential of TAI for imaging large joints.

Methods:

Adult New Zealand male rabbits (average weight = 2 kg) were chosen for this study. In a TAI experiment, a rabbit was placed in a holder to keep in a genuflex position after being injected with pentobarbital through its ear margin intravenous (30 mg/kg). The holder and the rabbit were then positioned under the horn antenna of the TAI system for signal acquisition and image reconstruction. After the experiment, the imaged knee joint was dissected and photographed. Identical procedures were performed for several rabbits (n = 4). Finally, detailed comparative analyses between TAI images and anatomical pictures of the knee joint were conducted.

Results:

There were high similarities between the reconstructed TAI images and anatomical pictures of the knee joint, in terms of the shape and size of various knee joint tissues. TAI could clearly image ligament, fat pad, and other joint tissues. The differences in appearance of TAI images due to motion effect of the knee joint were also discussed.

Conclusions:

TAI could reveal details of rabbit knee joint in high resolution. As the recovered TAI images represent the dielectric property distributions of joint tissues, TAI may offer a new tool for noninvasive detection of joint diseases such as OA.
Energy deposition clustering as a functional radiation quality descriptor for modeling relative biological effectiveness
Authors: Villegas Fernanda , Bäckström Gloria , Tilly Nina , Ahnesjö Anders
Published: November 2016

Purpose:

To explore the use of the frequency of the energy deposition (ED) clusters of different sizes (cluster order, CO) as a surrogate (instead of, e.g., LET) classification of the physical characteristics of ionizing radiation at a nanometer scale, to construct a framework for the calculation of relative biological effectiveness (RBE) with cell survival as endpoint.

Methods:

The frequency of cluster order fCO is calculated by sorting the ED sites generated with the Monte Carlo track structure code LIonTrack into clusters based on a single parameter called the cluster distance dC being the maximum allowed distance between two neighboring EDs belonging to a cluster. Published cell survival data parameterized with the linear‐quadratic (LQ) model for V79 cells exposed to 15 different radiation qualities (including brachytherapy sources, proton, and carbon ions) were used as input to a fitting procedure, designed to determine a weighting function wCO that describes the capacity of a cluster of a certain CO to damage the cell's sensitive volume. The proposed framework uses both fCO and wCO to construct surrogate based functions for the LQ parameters α and β from which RBE values can be derived.

Results:

The results demonstrate that radiation quality independent weights wCO exist for both the α and β parameters. This enables the calculation of α values that correlate to their experimental counterparts within experimental uncertainties (relative residual of 15% for dC = 2.5 nm). The combination of both α and β surrogate based functions, despite the higher relative residuals for β values, yielded an RBE function that correlated to experimentally derived RBE values (relative residual of 16.5% for dC = 2.5 nm) for all radiation qualities included in this work.

Conclusions:

The fCO cluster characterization of ionizing radiation at a nanometer scale can effectively be used to calculate particle and energy dependent α and β values to predict RBE values with potential applications to, e.g., treatment planning systems in radiotherapy.
Respiratory motion compensation for simultaneous PET/MR based on highly undersampled MR data
Authors: Rank Christopher M. , Heußer Thorsten , Wetscherek Andreas , Freitag Martin T. , Sedlaczek Oliver , Schlemmer Heinz–Peter , Kachelrieß Marc
Published: November 2016

Purpose:

Positron emission tomography (PET) of the thorax region is impaired by respiratory patient motion. To account for motion, the authors propose a new method for PET/magnetic resonance (MR) respiratory motion compensation (MoCo), which uses highly undersampled MR data with acquisition times as short as 1 min/bed.

Methods:

The proposed PET/MR MoCo method (4D jMoCo PET) uses radial MR data to estimate the respiratory patient motion employing MR joint motion estimation and image reconstruction with temporal median filtering. Resulting motion vector fields are incorporated into the system matrix of the PET reconstruction. The proposed approach is evaluated for the thorax region utilizing a PET/MR simulation with 1 min MR acquisition time and simultaneous PET/MR measurements of six patients with MR acquisition times of 1 and 5 min and radial undersampling factors of 11.2 and 2.2, respectively. Reconstruction results are compared to 3D PET, 4D gated PET and a standard MoCo method (4D sMoCo PET), which performs iterative image reconstruction and motion estimation sequentially. Quantitative analysis comprises the parameters SUVmean, SUVmax, full width at half‐maximum/lesion volume, contrast and signal‐to‐noise ratio.

Results:

For simulated PET data, our quantitative analysis shows that the proposed 4D jMoCo PET approach with temporal filtering achieves the best quantification accuracy of all tested reconstruction methods with a mean absolute deviation of 2.3% when compared to the ground truth. For measured PET patient data, the mean absolute deviation of 4D jMoCo PET using a 1 min MR acquisition for motion estimation is 2.1% relative to the 5 min MR acquisition. This demonstrates a robust behavior even in case of strong undersampling at MR acquisition times as short as 1 min. In contrast, 4D sMoCo PET shows considerable reduction of quantification accuracy for the 1 min MR acquisition time. Relative to 3D PET, the proposed 4D jMoCo PET approach with temporal filtering yields an average increase of SUVmean, SUVmax, and contrast of 29.9% and 13.8% for simulated and measured PET data, respectively.

Conclusions:

Employing artifact‐robust motion estimation enables PET/MR respiratory MoCo with MR acquisition times as short as 1 min/bed improving PET image quality and quantification accuracy.
Real‐time electromagnetic seed drop detection for permanent implants brachytherapy: Technology overview and performance assessment
Authors: Racine E. , Hautvast G. , Binnekamp D. , Beaulieu L.
Published: November 2016

Purpose:

To describe the principles and report on the performance of a novel real‐time electromagnetic (EM) seed drop detection technology for permanent implants brachytherapy procedures.

Methods:

A novel EM hollow needle prototype was recently developed by Philips. It possesses standard 3D tracking capability as well as a seed drop detection mechanism, both performed from a single custom built EM sensor. The detection mechanism is based on the magnetic permeability changes in the sensor as the seeds pass through. Drop position estimates are generated by the tracking information at the dropping instants. Three validation experiments were carried out in this study. First, the robustness of the detection mechanism was tested in free air with four different seed types. Detection waveforms were measured and commented. The accuracy of the seed drop position estimates was then evaluated using both 2D and 3D experiments. The procedures consisted of dropping seeds in phantoms, recording the drop position estimates, and finally registering the resulting spatial distributions on reference ones obtained by accurate modalities. Seeds were dropped on a specially designed plastic support adapted to brachytherapy template dimensions for 2D experiments, and true seed positions (reference distribution) were obtained by optical detection. In 3D experiments, seeds were dropped in edible gelatin and reference distributions were obtained by localizing the implants from CT scans of the phantoms.

Results:

All four seed types were correctly detected by the needle prototype. In total, 250 seeds were dropped on the plastic support, and 96 were dropped in gelatin phantoms. The detection rate was 100% in both cases. The minimum, maximum, and average drop position errors were, respectively, 0.1(+1.6/ − 0.1), 2.9(+1.4/ − 1.5), and 0.9(+1.4/ − 0.7) mm for 2D, and 0.1(+1.0/ − 0.1), 2.1(+1.1/ − 0.8), and 0.6(+1.2/ − 0.5) mm for 3D experiments.

Conclusions:

The hollow needle prototype combines both EM tracking and automatic seed drop detection in a compact and convenient form. The EM detection mechanism is robust, and the seed drop position estimates appear sufficiently accurate for potential integration of the technology to current brachytherapy treatment planning systems. In that context, it would serve as a valuable tool for rapid dosimetry validation in real‐time treatment delivery.
Addressing the Problem of Student- Athlete Sleepiness: Feasibility of Implementing an Interactive Sleep Workshop at a Division I School
Authors: Kaier Emily , Zanotti Danielle , Davis Joanne L. , Strunk Kathleen , Cromer Lisa DeMarni
Published: November 2016

Sleep concerns are prevalent among student-athletes and can result in impaired athletic and academic performance. The current study investigated the feasibility and effectiveness of a brief sleep workshop for student-athletes. Athletes (N = 152) completed baseline and follow-up questionnaires (n = 104) after the intervention. Greater than half of the athletes (51%) who attended the workshops and followup reported at least one change in sleep behaviors. Results revealed a significant decrease in sleepiness from baseline to follow-up and an improvement in daytime functioning. Although athletes reported an increase in problematic sleep hygiene behaviors, they recorded significant increases in sleep knowledge from baseline to follow-up, which was maintained at the second follow-up. These longitudinal data provide evidence that a brief psychoeducation sleep workshop for student-athletes is promising for improving sleep knowledge and daily functioning.
Workaholism, Home–Work/Work–Home Interference, and Exhaustion Among Sports Coaches
Authors: Lundkvist Erik , Gustafsson Henrik , Davis Paul , Hassmén Peter
Published: November 2016

The aims of this study were to (a) examine the associations between workaholism and work-related exhaustion and (b) examine associations between work–home/ home–work interference and work-related exhaustion in 261 Swedish coaches. Quantile regression showed that workaholism is only associated with exhaustion for coaches who score high on exhaustion, that negative work–home interference has a stronger association with exhaustion than negative home–work interference, and that the coaches on a mean level scored low on all measured constructs. In addition, coaches in the higher percentiles have a higher risk for burnout. Our results highlight the importance of studying coach exhaustion with respect to aspects that extend beyond the sports life.
Cardiac repair in guinea pigs with human engineered heart tissue from induced pluripotent stem cells
Authors: Weinberger Florian , Breckwoldt Kaja , Pecha Simon , Kelly Allen , Geertz Birgit , Starbatty Jutta , Yorgan Timur , Cheng Kai-Hung , Lessmann Katrin , Stolen Tomas , Scherrer-Crosbie Marielle , Smith Godfrey , Reichenspurner Hermann , Hansen Arne , Eschenhagen Thomas
Published: November 2016

Human engineered heart tissue derived from induced pluripotent stem cells improves cardiac function in guinea pigs.
Fat weighing down the insulin receptor
Authors: Brown J. Mark
Published: November 2016

Threonine phosphorylation of the insulin receptor promotes diabetes.
Transcriptional analysis of promoter mutations in the Klebsiella pneumoniae nifHDKY operon
Authors: Lers A , Bitoun R , Zamir A
Published: November 2016

Previously isolated promoter mutations that allow expression of the Klebsiella pneumoniae nifHDKY operon in the absence of nifA (R. Bitoun, J. Berman, A. Zilberstein, D. Holland, J.B. Cohen, D. Givol, and A. Zamir, Proc. Natl. Acad. Sci. USA, 80:5812-5816, 1983) were further characterized. pRB1 and pRB5, containing, respectively, point and duplication mutations in the nifHDKY regulatory region, were transformed into Escherichia coli and K. pneumoniae hosts with different nifA and ntrA backgrounds. nif transcription start sites were determined by nuclease S1 mapping. The results indicated that nifA-independent expression from both mutants did not require ntrA. Transcription from pBR5 started 3 base pairs (bp) upstream of the start site of nif-regulated transcription and could stem from a canonical promoter sequence generated at the junction between the two copies of the duplicated sequence. In the presence of nifA-ntrA, transcription from pRB5 started predominantly at the site characteristic of the nif-regulated promoter. The site of constitutive transcription initiation in pRB1 was located 33 bp upstream of the point mutation and 40 bp upstream of the start of nifA-ntrA-activated transcription. Low-level transcription from the upstream site was also evident, in the absence of nifA or nifA or both, with the plasmid containing the wild-type nifHDKY regulatory region. However, when nifA and ntrA were present to activate transcription from the major nif promoter, no activity was evident from the upstream site in either pRB1 or the parental plasmid. Thus, the mutation enhanced the activity of a pre-existing constitutive promoter, the activity of which was repressed on nifA-ntrA activation of the major nif promoter.