Current Prototype Research Articles

Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs

Photon counting arrays (PCAs), defined as pixelated imagers which measure the absorbed energy of x-ray photons individually and record this information digitally, are of increasing clinical interest. A number of PCA prototypes with a 1 mm pixel-to-pixel pitch have recently been fabricated with polycrystalline silicon (poly-Si)—a thin-film technology capable of creating monolithic imagers of a size commensurate with human anatomy. In this study, analog and digital simulation frameworks were developed to provide insight into the influence of individual poly-Si transistors on pixel circuit performance—information that is not readily available through empirical means. The simulation frameworks were used to characterize the circuit designs employed in the prototypes. The analog framework, which determines the noise produced by individual transistors, was used to estimate energy resolution, as well as to identify which transistors contribute the most noise. The digital framework, which analyzes how well circuits function in the presence of significant variations in transistor properties, was used to estimate how fast a circuit can produce an output (referred to as output count rate). In addition, an algorithm was developed and used to estimate the minimum pixel pitch that could be achieved for the pixel circuits of the current prototypes. The simulation frameworks predict that the analog component of the PCA prototypes could have energy resolution as low as 8.9% full width at half maximum (FWHM) at 70 keV; and the digital components should work well even in the presence of significant thin-film transistor (TFT) variations, with the fastest component having output count rates as high as 3 MHz. Finally, based on conceivable improvements in the underlying fabrication process, the algorithm predicts that the 1 mm pitch of the current PCA prototypes could be reduced significantly, potentially to between ~240 and 290 μm.

A novel two-degree-of-freedom MEMS electromagnetic vibration energy harvester

In this paper, a vibration-based MEMS electromagnetic energy harvester (EM-EH) device with two-degree-of-freedom (2DOF) configuration has been presented, modeled and characterized. The proposed 2DOF system comprises a primary subsystem for power generation, and an accessory subsystem for frequency tuning. A lumped parametric 2DOF model is built and examined in respect of energy harvesting capabilities. By controlling the mass ratio and frequency ratio, the first two resonances of primary mass can be tuned close to each other while maintaining comparable magnitudes. The 2DOF configuration is expected to be more adaptive and efficient than the conventional 1DOF structure, which could only operate near its sole resonance. The 2DOF EM-EH chip is fabricated on silicon-on-insulator (SOI) wafer through double-sided deep reactive-ion etching (DRIE). Induction coil is only patterned on the primary mass for energy conversion. With current prototype at an acceleration of 0.12 g, two resonances of 326 and 391 Hz with output voltages of 3.6 and 6.5 mV are obtained respectively, providing good validation for the modeling results. This paper offers new insights of implementing a multimodal MEMS EM-EH device.

Feasibility and usability of a wearable orthotic for stroke survivors with hand impairment

Purpose: The concept of a vibrating wristband, to improve dextrous hand function of stroke survivors, was recently proposed with clinical results and is referred to as ‘TheraBracelet’ in this paper. The purpose of this study was to demonstrate feasibility of a portable, wearable TheraBracelet, and to apply usability evaluation techniques to assess potential demands of TheraBracelet and to identify critical improvement needs of the prototype. Method: A prototype was developed with a vibrating element housed in an elastic wristband and connected to a wearable electronics box via a cable. Expectation for TheraBracelet and evaluation of the prototype were obtained from 10 chronic stroke survivors using surveys before and after using the prototype and House of Quality analysis. Results: The survey for expectation showed stroke survivors’ willingness to try out TheraBracelet at a low cost. The survey evaluating the prototype showed that the current prototype was overall satisfactory with a mean rating of 3.7 out of 5. The House of Quality analysis revealed that the priority improvement needs for the prototype are to improve clinical knowledge on long-term effectiveness, reduce cost, ease donning/doffing and waterproof.Conclusions: This study presents a potential for a low-cost wearable hand orthotic likable by stroke survivors.Implications for RehabilitationFeasibility for a portable wearable wristband-type hand orthotic was demonstrated.The survey showed stroke survivors are willing to try such an orthotic at low cost.The current prototype was rated overall satisfactory by stroke survivors.This study provides a potential for a low-cost wearable hand orthotic likable by stroke survivors.

Investigation of heat transfer in the petal detector structure

This paper describes the CFD numerical simulation of heat transfer in the petal complex structure. Petal consists of core structure and detectors designed to improve the detection capabilities of the ATLAS detector and take advantage of operating at the High Luminosity LHC (HL-LHC). New generation silicon detectors in the petal require more efficient cooling of the front-end electronics and the silicon sensors themselves. To minimize reverse annealing of the silicon sensors the operating temperatures need to be reduced. In this case the evaporative CO2 cooling medium is used as it is ideal for this purpose. This work describes the flow simulation setup and results for the current prototype and heat transfer behavior for different operating states.

A Measurement Experimentation Platform at the Internet's Edge

Poor visibility into the network hampers progress in a number of important research areas, from network troubleshooting to Internet topology and performance mapping. This persistent, well-known problem has served as motivation for numerous proposals to build or extend existing Internet measurement platforms by recruiting larger, more diverse vantage points. Capturing the edge of the network, however, remains an elusive goal. We argue that at its root the problem is one of incentives. Today's measurement platforms build on the assumption that the goals of experimenters and those hosting the platform are the same. As much of the Internet growth occurs in residential broadband networks, this assumption no longer holds. We present a measurement experimentation platform that reaches the network edge by explicitly aligning the objectives of the experimenters with those of the users hosting the platform. Dasu—our current prototype—is designed to support both network measurement experimentation and broadband characterization. Dasu has been publicly available since July 2010 and has been installed by over 100 $\,$ 000 users with a heterogeneous set of connections spreading across 2431 autonomous systems (ASs) and 166 countries. We discuss some of the challenges we faced building and using a platform for the Internet's edge, describe its design and implementation, and illustrate the unique perspective its current deployment brings to Internet measurement.

A Data Stream-Based, Integrative Approach to Reliable and Easily Manageable Real Time Environmental Monitoring

Real time environmental monitoring (hereafter, RTEM) is crucial for observing and studying dynamic, rare, or abrupt phenomena in the environment. Conventional RTEM systems are developed in a domain-specific way and not based on a well-defined distributed system model. Therefore, it is challenging to develop such RTEM systems, to extend them to support new requirements, and to integrate them with other application systems. In this paper, we raise challenging issues in RTEM, propose a generic distributed system model for RTEM to address those issues, and present the Galilee middleware system for RTEM based on the model. The distributed system model is based on the concept of data streams. It is intended to simplify and to conceptualize the design of RTEM systems. Therefore, the simple data stream-based distributed system model facilitates the development of general RTEM middleware system. The Galilee middleware system for RTEM is based on the distributed system model and designed to support various RTEM applications in a reliable and easily manageable way. In this paper, we also demonstrate and evaluate the current prototype implementation of the Galilee system with those datasets obtained from the previous sensor-based water quality monitoring project for Lake Soyang from 2011 to 2012.

Light-Activated Nuclear Translocation of Adeno-Associated Virus Nanoparticles Using Phytochrome B for Enhanced, Tunable, and Spatially Programmable Gene Delivery.

Gene delivery vectors that are activated by external stimuli may allow improved control over the location and the degree of gene expression in target populations of cells. Light is an attractive stimulus because it does not cross-react with cellular signaling networks, has negligible toxicity, is noninvasive, and can be applied in space and time with unparalleled precision. We used the previously engineered red (R)/far-red (FR) light-switchable protein phytochrome B (PhyB) and its R light dependent interaction partner phytochrome interacting factor 6 (PIF6) from Arabidopsis thaliana to engineer an adeno-associated virus (AAV) platform whose gene delivery efficiency is controlled by light. Upon exposure to R light, AAV engineered to display PIF6 motifs on the capsid bind to PhyB tagged with a nuclear localization sequence (NLS), resulting in significantly increased translocation of viruses into the host cell nucleus and overall gene delivery efficiency. By modulating the ratio of R to FR light, the gene delivery efficiency can be tuned to as little as 35% or over 600% of the unengineered AAV. We also demonstrate spatial control of gene delivery using projected patterns of codelivered R and FR light. Overall, our successful use of light-switchable proteins in virus capsid engineering extends these important optogenetic tools into the adjacent realm of nucleic acid delivery and enables enhanced, tunable, and spatially controllable regulation of viral gene delivery. Our current light-triggered viral gene delivery prototype may be broadly useful for genetic manipulation of cells ex vivo or in vivo in transgenic model organisms, with the ultimate prospect of achieving dose- and site-specific gene expression profiles for either therapeutic (e.g., regenerative medicine) or fundamental discovery research efforts.

Concept Design for a 1-Lead Wearable/Implantable ECG Front-End: Power Management.

Power supply quality and stability are critical for wearable and implantable biomedical applications. For this reason we have designed a reconfigurable switched-capacitor DC-DC converter that, aside from having an extremely small footprint (with an active on-chip area of only 0.04 mm), uses a novel output voltage control method based upon a combination of adaptive gain and discrete frequency scaling control schemes. This novel DC-DC converter achieves a measured output voltage range of 1.0 to 2.2 V with power delivery up to 7.5 mW with 75% efficiency. In this paper, we present the use of this converter as a power supply for a concept design of a wearable (15 mm × 15 mm) 1-lead ECG front-end sensor device that simultaneously harvests power and communicates with external receivers when exposed to a suitable RF field. Due to voltage range limitations of the fabrication process of the current prototype chip, we focus our analysis solely on the power supply of the ECG front-end whose design is also detailed in this paper. Measurement results show not just that the power supplied is regulated, clean and does not infringe upon the ECG bandwidth, but that there is negligible difference between signals acquired using standard linear power-supplies and when the power is regulated by our power management chip.

Estimation of extravascular lung water using the transpulmonary ultrasound dilution (TPUD) method: a validation study in neonatal lambs.

Increased extravascular lung water (EVLW) may contribute to respiratory failure in neonates. Accurate measurement of EVLW in these patients is limited due to the lack of bedside methods. The aim of this pilot study was to investigate the reliability of the transpulmonary ultrasound dilution (TPUD) technique as a possible method for estimating EVLW in a neonatal animal model. Pulmonary edema was induced in 11 lambs by repeated surfactant lavages. In between the lavages, EVLW indexed by bodyweight was estimated by TPUD (EVLWItpud) and transpulmonary dye dilution (EVLWItpdd) (n = 22). Final EVLWItpud measurements were also compared with EVLWI estimations by gold standard post mortem gravimetry (EVLWIgrav) (n = 6). EVLWI was also measured in two additional lambs without pulmonary edema. Bland–Altman plots showed a mean bias between EVLWItpud and EVLWItpdd of −3.4 mL/kg (LOA ± 25.8 mL/kg) and between EVLWItpud and EVLWIgrav of 1.7 mL/kg (LOA ± 8.3 mL/kg). The percentage errors were 109 and 43 % respectively. The correlation between changes in EVLW measured by TPUD and TPDD was r2 = 0.22. Agreement between EVLWI measurements by TPUD and TPDD was low. Trending ability to detect changes between these two methods in EVLWI was questionable. The accuracy of EVLWItpud was good compared to the gold standard gravimetric method but the TPUD lacked precision in its current prototype. Based on these limited data, we believe that TPUD has potential for future use to estimate EVLW after adaptation of the algorithm. Larger studies are needed to support our findings.

Abstract 13504: RV Cardiac Output Calculated From an Implantable Hemodynamic Device: A Correlative Approach Using CMR in PAH Patients

Introduction: The CardioMEMS™ HF System (CMHFS)(St. Jude) is used for wireless monitoring of pulmonary artery (PA) pressure. Pulmonary flow is difficult to model due to prominent reflected waves and McDonald et al have shown that the temporal differential of the initial positive pressure pulse effectively provides the flow driving force for cardiac output (CO), with mean pressure indicating resistance. However, the response of this model to stress conditions in vivo is unknown. Hypothesis: We hypothesize that the temporal differentiation of pressure model of CO applied to the CMHRS data at baseline and during stress provides an accurate calculation of noninvasive CO in PAH. Methods: 10 pts with PAH were implanted with the CMHFS to measure PA pressure, HR, and CO longitudinally. Cardiovascular Magnetic Resonance (CMR) was performed at baseline, and after 1) inhalation of nitric oxide (20 ppm), 2) dobutamine (20 μcg/kg/min), and 3) volumetric challenge (500ml NaCl). Flow through the MPA was measured using phase velocity mapping. The mean pressure and area of the temporal differential of the initial positive pressure pulse from the CMHFS device were measured (Fig 1A) to calculate CO. In each case the calibrating constant to relate to CMR CO was calculated at baseline and then applied during stress. Results: The pressure derived CO correlated with CMR CO via a linear relationship for 32 comparison measures according to the following equation: Pressure CO = 1.1 CMR CO + 0.8Bland-Altman analysis has an offset bias of 0.2, a four standard deviation range of ±3.1 l/m and a correlation of 0.9. (Fig 1B). Conclusions: The temporal differential of the initial positive pressure pulse forms the effective driving force for pulmonary blood supply. This formulation overcomes the difficulties in identifying reflected waves and is highly responsive to stress conditions and may advance current prototypes. This approach may provide additional value once validated for implantable PA manometers.

Evaluation of a Horizontal Air Flow In-Bin Grain Drying System

<abstract> <b><sc>Abstract. </sc></b>Drying is the major post-harvest operation carried out to reduce the moisture content of harvested grains to increase storage period and reduce storage losses. A prototype horizontal airflow in-bin drying system was developed and evaluated for drying wheat. The results proved that the moisture front moved radially from the center to the sidewall of the bin throughout the grain bulk and there were no significant differences (p<0.05) in drying at the bottom, middle, and top layers of the grain bulk when the airflow control valve was set at 2 m (equal to radius of the bin) from the top surface of the grain bulk. When the airflow control valve was set at 4 m (diameter of the bin), there were significant differences among the drying patterns at the three different heights. The results of the air pressure measurements showed that the air pressure distribution was equal around the radius of the bin. These results indicated that the current prototype dried the grain evenly from bottom to top of the grain bulk and can be used effectively at commercial level to dry grain in hopper bottom bins (tested) as well as in flat-bottom bins.

Novel optical current sensor for metering and protection in high power applications

ABSTRACTA clamp-on optical current sensor prototype for metering and protection applications in high power systems was developed and characterized. The system is based on the Faraday effect in a low birefringence, high Verdet constant, 8 cm long SF57 Schott glass prism. It was incorporated in a nylon casing suitable for clamp-on applications in the power line. The sensor operation was tested at 630 nm, 830 nm, and 1550 nm to access its applicability in remote interrogation via fiber links. Optimal operation at 830 nm is reported with a linear response up to 65.28kA, with 0.1 or 0.2 accuracy class considering a nominal currents of 1.2 and 0.3 kA (root mean square), respectively. Twelve calibrations procedures performed over six days showed an estimated maximum error of 11 m A. Preliminary measurements were made from 40 to 400 Hz. The sensor was exposed to transient signals less than 10 µs that demonstrated its use in protection applications.

Structural and properties of heavy metal oxide Faraday glass for optical current transducer

The influences of PbO, Bi2O3 and GeO2 contents on mechanical, thermal, magneto-optical and structural properties of PbO–Bi2O3–GeO2–B2O3 glass system were investigated. A magneto-optical current transducer MOCT prototype with sensitivity of 7.56nW/A was constructed based on selected glass with good properties.

Low-Profile Jamming Technology for Medical Rehabilitation

Integrating novel feedback mechanisms into wearable devices could support medical rehabilitation applications and enhance existing interaction methods. One such feedback mechanism is layer jamming, which can be used to alter material stiffness in real time under computer control. Jamming can be integrated into smart garments, allowing clothing to adapt to environmental conditions or support a particular user task. For example, a person with a knee injury that requires restricted movement for their treatment would normally wear a knee brace. Layer jamming-enabled smart pants can be integrated as part of the treatment to restrict both speed and angular movement of the affected joint during recovery. This article explores the use of smart materials that combine low-profile jamming with clothing items for computer-controlled material stiffness. The authors present a current prototype system that employs jamming technology for this variable stiffness function and discuss future applications.

Imaging of prompt gamma rays emitted during delivery of clinical proton beams with a Compton camera: feasibility studies for range verification

The purpose of this paper is to evaluate the ability of a prototype Compton camera (CC) to measure prompt gamma rays (PG) emitted during delivery of clinical proton pencil beams for prompt gamma imaging (PGI) as a means of providing in vivo verification of the delivered proton radiotherapy beams.A water phantom was irradiated with clinical 114 MeV and 150 MeV proton pencil beams. Up to 500 cGy of dose was delivered per irradiation using clinical beam currents. The prototype CC was placed 15 cm from the beam central axis and PGs from 0.2 MeV up to 6.5 MeV were measured during irradiation. From the measured data (2D) images of the PG emission were reconstructed. (1D) profiles were extracted from the PG images and compared to measured depth dose curves of the delivered proton pencil beams.The CC was able to measure PG emission during delivery of both 114 MeV and 150 MeV proton beams at clinical beam currents. 2D images of the PG emission were reconstructed for single 150 MeV proton pencil beams as well as for a 5 × 5 cm mono-energetic layer of 114 MeV pencil beams. Shifts in the Bragg peak (BP) range were detectable on the 2D images. 1D profiles extracted from the PG images show that the distal falloff of the PG emission profile lined up well with the distal BP falloff. Shifts as small as 3 mm in the beam range could be detected from the 1D PG profiles with an accuracy of 1.5 mm or better. However, with the current CC prototype, a dose of 400 cGy was required to acquire adequate PG signal for 2D PG image reconstruction.It was possible to measure PG interactions with our prototype CC during delivery of proton pencil beams at clinical dose rates. Images of the PG emission could be reconstructed and shifts in the BP range were detectable. Therefore PGI with a CC for in vivo range verification during proton treatment delivery is feasible. However, improvements in the prototype CC detection efficiency and reconstruction algorithms are necessary to make it a clinically viable PGI system.

PhantomNet

The PhantomNet facility allows experimenters to combine mobile networking, cloud computing and software-defined networking in a single environment. It is an end-to-end testbed , meaning that it supports experiments not just with mobile end-user devices but also with a cellular core network that can be configured and extended with new technologies. This article introduces PhantomNet and presents a road map for its future development. The current PhantomNet prototype is available now at no cost to researchers and educational users.

Testing a new automated single ring infiltrometer for Beerkan infiltration experiments

The Beerkan method along with BEST algorithms is an alternative technique to conventional laboratory or field measurements for rapid and low-cost estimation of soil hydraulic properties. The Beerkan method is simple to conduct but requires an operator to repeatedly pour known volumes of water through a ring positioned at the soil surface. A cheap infiltrometer equipped with a data acquisition system was recently designed to automate Beerkan infiltration experiments. In this paper, the current prototype of the automated infiltrometer was tested to validate its applicability to the Beerkan infiltration experiment under several experimental circumstances. In addition, the accuracy of the estimated saturated soil hydraulic conductivity, Ks, and sorptivity, S, was assessed by applying different BEST algorithms to the data obtained with the infiltrometer. At this purpose, both analytically generated and real experimental data were used. The analytical assessment showed that the use of the infiltrometer along with BEST methods could lead to accurate estimates of the considered soil properties in most cases, which validated the design of the infiltrometer and its combination with BEST algorithms. Loamy soils and high initial water contents led to misestimating Ks and S or to failure of BEST algorithms, but advices about the infiltrometer design were developed to alleviate such problems. A comparison between the automated procedure and the original BEST procedure was made at three field sites in Sicily (Italy). Other experiments were carried out in an infiltration basin located in the pumping well field of Crépieux-Charmy (Lyon, France), in order to assess the ability of the automated infiltrometer to check clogging effects on Ks. The experiments showed that the automatic data collection increased measurement speed, allowed a more efficient data handling and analysis, and reduced sensitivity of the calculated hydraulic parameters on the applied BEST algorithm.

A simulation study on proton computed tomography (CT) stopping power accuracy using dual energy CT scans as benchmark

ABSTRACTBackground. Accurate stopping power estimation is crucial for treatment planning in proton therapy, and the uncertainties in stopping power are currently the largest contributor to the employed dose margins. Dual energy x-ray computed tomography (CT) (clinically available) and proton CT (in development) have both been proposed as methods for obtaining patient stopping power maps. The purpose of this work was to assess the accuracy of proton CT using dual energy CT scans of phantoms to establish reference accuracy levels.Material and methods. A CT calibration phantom and an abdomen cross section phantom containing inserts were scanned with dual energy and single energy CT with a state-of-the-art dual energy CT scanner. Proton CT scans were simulated using Monte Carlo methods. The simulations followed the setup used in current prototype proton CT scanners and included realistic modeling of detectors and the corresponding noise characteristics. Stopping power maps were calculated for all three scans, and compared with the ground truth stopping power from the phantoms.Results. Proton CT gave slightly better stopping power estimates than the dual energy CT method, with root mean square errors of 0.2% and 0.5% (for each phantom) compared to 0.5% and 0.9%. Single energy CT root mean square errors were 2.7% and 1.6%. Maximal errors for proton, dual energy and single energy CT were 0.51%, 1.7% and 7.4%, respectively.Conclusion. Better stopping power estimates could significantly reduce the range errors in proton therapy, but requires a large improvement in current methods which may be achievable with proton CT.

Hand planter for maize (Zea mays L.) in the developing world

ABSTRACTThird world maize (Zea mays L.) production is characterized by having extremely low yields, attributed in part to the poor planting methods employed. Maize planting in most third world countries involves placing 2–3 seeds per hill, with hills being roughly 30 cm apart. The variability in seeds per hill and distance between hills result in heterogeneous plant stands that are directly responsible for lower yields. Oklahoma State University (OSU) has developed a durable hand planter with a reciprocating internal drum that delivers single maize seeds per strike and that can also be used for mid-season application of urea fertilizer. The hand planter is 1.4 m in length, 5.8 cm in diameter, and weighs 1.9 kg when empty. The seed hopper has the capacity to hold 1 kg of seed and the tip has a sharp pointed shovel which can deliver seed to a planting depth of 5 cm in no-till and tilled soils. The current prototype has been comprehensively tested and evaluated to deliver at least 80% single seeds (singulation), with 0% misses and work well across varying seed sizes (2652–4344 seeds/kg) and different operators. Using the OSU hand planter, third world maize producers with average yields of 2.0 Mg ha−1 could increase yields by 20%.

Development and Pilot Testing of the Eating4two Mobile Phone App to Monitor Gestational Weight Gain.

BackgroundThe number of pregnant women with a body mass index (BMI) of 30kg/m2 or more is increasing, which has important implications for antenatal care. Various resource-intensive interventions have attempted to assist women in managing their weight gain during pregnancy with limited success. A mobile phone app has been proposed as a convenient and cost-effective alternative to face-to-face interventions.ObjectiveThis paper describes the process of developing and pilot testing the Eating4Two app, which aims to provide women with a simple gestational weight gain (GWG) calculator, general dietary information, and the motivation to achieve a healthy weight gain during pregnancy.MethodsThe project involved the development of app components, including a graphing function that allows the user to record their weight throughout the pregnancy and to receive real-time feedback on weight gain progress and general information on antenatal nutrition. Stakeholder consultation was used to inform development. The app was pilot tested with 10 pregnant women using a mixed method approach via an online survey, 2 focus groups, and 1 individual interview.ResultsThe Eating4Two app took 7 months to develop and evaluate. It involved several disciplines--including nutrition and dietetics, midwifery, public health, and information technology--at the University of Canberra. Participants found the Eating4Two app to be a motivational tool but would have liked scales or other markers on the graph that demonstrated exact weight gain. They also liked the nutrition information; however, many felt it should be formatted in a more user friendly way.ConclusionsThe Eating4Two app was viewed by participants in our study as an innovative support system to help motivate healthy behaviors during pregnancy and as a credible resource for accessing nutrition-focused information. The feedback provided by participants will assist with refining the current prototype for use in a clinical intervention trial.