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Sample records for implanted detection structures

  1. Detection of degradation in polyester implants by analysing mode shapes of structure vibration.

    PubMed

    Samami, Hassan; Pan, Jingzhe

    2016-09-01

    This paper presents a numerical study on using vibration analysis to detect degradation in degrading polyesters. A numerical model of a degrading plate sample is considered. The plate is assumed to degrade following the typical behaviour of amorphous copolymers of polylactide and polyglycolide. Due to the well-known autocatalytic effect in the degradation of these polyesters, the inner core of the plate degrades faster than outer surface region, forming layers of materials with varying Young׳s modulus. Firstly the change in molecular weight and corresponding change in Young׳s modulus at different times are calculated using the mathematical models developed in our previous work. Secondly the first four mode shapes of transverse vibration of the plate are calculated using the finite element method. Finally the curvature of the mode shapes are calculated and related to the spatial distribution of the polymer degradation. It is shown that the curvature of the mode shapes can be used to detect the onset and distribution of polymer degradation. The level of measurement accuracy required in an experiment is presented to guide practical applications of the method. At the end of this paper a demonstration case of coronary stent is presented showing how the method can be used to detect degradation in an implant of sophisticated structure.

  2. In Vivo Ultrasonic Detection of Polyurea Crosslinked Silica Aerogel Implants

    PubMed Central

    Sabri, Firouzeh; Sebelik, Merry E.; Meacham, Ryan; Boughter, John D.; Challis, Mitchell J.; Leventis, Nicholas

    2013-01-01

    Background Polyurea crosslinked silica aerogels are highly porous, lightweight, and mechanically strong materials with great potential for in vivo applications. Recent in vivo and in vitro studies have demonstrated the biocompatibility of this type of aerogel. The highly porous nature of aerogels allows for exceptional thermal, electric, and acoustic insulating capabilities that can be taken advantage of for non-invasive external imaging techniques. Sound-based detection of implants is a low cost, non-invasive, portable, and rapid technique that is routinely used and readily available in major clinics and hospitals. Methodology In this study the first in vivo ultrasound response of polyurea crosslinked silica aerogel implants was investigated by means of a GE Medical Systems LogiQe diagnostic ultrasound machine with a linear array probe. Aerogel samples were inserted subcutaneously and sub-muscularly in a) fresh animal model and b) cadaveric human model for analysis. For comparison, samples of polydimethylsiloxane (PDMS) were also imaged under similar conditions as the aerogel samples. Conclusion/significance Polyurea crosslinked silica aerogel (X-Si aerogel) implants were easily identified when inserted in either of the regions in both fresh animal model and cadaveric model. The implant dimensions inferred from the images matched the actual size of the implants and no apparent damage was sustained by the X-Si aerogel implants as a result of the ultrasonic imaging process. The aerogel implants demonstrated hyperechoic behavior and significant posterior shadowing. Results obtained were compared with images acquired from the PDMS implants inserted at the same location. PMID:23799093

  3. Structural and Optical Behaviour of Ar+ Implanted Polycarbonate

    NASA Astrophysics Data System (ADS)

    Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Deshpande, S. K.; Nair, K. G. M.

    2011-07-01

    Effects of 130 keV Ar+ ion implantation on the structural and optical properties of polycarbonate specimens have been studied using Raman, UV-Visible spectroscopy and glancing angle X-ray diffraction techniques. Formation of disordered carbonaceous network in the implanted layers has been observed using Raman and UV-Visible spectroscopy. A sharp decline in band gap values (4.1 eV to 0.63 eV) with increase in implantation dose has been observed. This decrease in optical band gap has been correlated with the formation of disordered structures in the implanted layers of polycarbonate.

  4. Detection and removal of pathogenic biofilms on medical implant surfaces.

    PubMed

    Dunlop, Patrick; Oliver, Louise; Byrne, Tony; McAdams, Eric

    2005-01-01

    Advances in sensor technology have had a significant impact in medical research and practice in the last decade. However, within the hospital environment problems still exist where the application of sensing technology could provide the solution. The presence of antibiotic resistant bacteria within hospitals and the risk of serious infection that they pose is a cause for concern. This paper describes a research project that has recently started at the University of Ulster investigating the potential of "Sense and Destroy" tactics to reduce the spread of medical device related infections. It is proposed that Electrical Impedance Spectroscopy (EIS) probes implanted within a catheter may be used to detect subclinical biofilm formation. Furthermore, if the presence of a biofilm is detected, activation of a photocatalytic coating on the catheter wall may be used to inactivate the responsible microorganisms.

  5. Investigation of NMR limits of detection for implantable microcoils.

    PubMed

    Baxan, N; Rengle, A; Pasquet, G; Châteaux, J-F; Briguet, A; Morin, P; Fakri-Bouchet, L

    2007-01-01

    Although NMR has the ability to investigate biological systems non-destructively, its low sensitivity primarily has hampered their investigation compared to other analytical techniques. Therefore, optimi zing radio frequency (RF) coils to improve sensitivity do offer benefits in MR spectroscopy (MRS). Sensitivity may be improved for mass- and volume-limited samples if the size of the detection RF coils matches the sample size. In this paper, the mass- and concentration-limit of detection (LOD(m), LOD(c)) for an implantable microcoil will be estimated by MRS measurements and then compared with their analytical values. For a sample containing a solution of several cerebral metabolites, for the Choline case, the LODm is 5.7 . 10(-9)mol and LODc of 3.8 mM. These preliminary results enable to open largely the biomedical applications based on cerebral metabolism investigation on small animal experiments.

  6. Spectrotemporal Modulation Detection and Speech Perception by Cochlear Implant Users.

    PubMed

    Won, Jong Ho; Moon, Il Joon; Jin, Sunhwa; Park, Heesung; Woo, Jihwan; Cho, Yang-Sun; Chung, Won-Ho; Hong, Sung Hwa

    2015-01-01

    Spectrotemporal modulation (STM) detection performance was examined for cochlear implant (CI) users. The test involved discriminating between an unmodulated steady noise and a modulated stimulus. The modulated stimulus presents frequency modulation patterns that change in frequency over time. In order to examine STM detection performance for different modulation conditions, two different temporal modulation rates (5 and 10 Hz) and three different spectral modulation densities (0.5, 1.0, and 2.0 cycles/octave) were employed, producing a total 6 different STM stimulus conditions. In order to explore how electric hearing constrains STM sensitivity for CI users differently from acoustic hearing, normal-hearing (NH) and hearing-impaired (HI) listeners were also tested on the same tasks. STM detection performance was best in NH subjects, followed by HI subjects. On average, CI subjects showed poorest performance, but some CI subjects showed high levels of STM detection performance that was comparable to acoustic hearing. Significant correlations were found between STM detection performance and speech identification performance in quiet and in noise. In order to understand the relative contribution of spectral and temporal modulation cues to speech perception abilities for CI users, spectral and temporal modulation detection was performed separately and related to STM detection and speech perception performance. The results suggest that that slow spectral modulation rather than slow temporal modulation may be important for determining speech perception capabilities for CI users. Lastly, test-retest reliability for STM detection was good with no learning. The present study demonstrates that STM detection may be a useful tool to evaluate the ability of CI sound processing strategies to deliver clinically pertinent acoustic modulation information.

  7. Spectrotemporal Modulation Detection and Speech Perception by Cochlear Implant Users

    PubMed Central

    Won, Jong Ho; Moon, Il Joon; Jin, Sunhwa; Park, Heesung; Woo, Jihwan; Cho, Yang-Sun; Chung, Won-Ho; Hong, Sung Hwa

    2015-01-01

    Spectrotemporal modulation (STM) detection performance was examined for cochlear implant (CI) users. The test involved discriminating between an unmodulated steady noise and a modulated stimulus. The modulated stimulus presents frequency modulation patterns that change in frequency over time. In order to examine STM detection performance for different modulation conditions, two different temporal modulation rates (5 and 10 Hz) and three different spectral modulation densities (0.5, 1.0, and 2.0 cycles/octave) were employed, producing a total 6 different STM stimulus conditions. In order to explore how electric hearing constrains STM sensitivity for CI users differently from acoustic hearing, normal-hearing (NH) and hearing-impaired (HI) listeners were also tested on the same tasks. STM detection performance was best in NH subjects, followed by HI subjects. On average, CI subjects showed poorest performance, but some CI subjects showed high levels of STM detection performance that was comparable to acoustic hearing. Significant correlations were found between STM detection performance and speech identification performance in quiet and in noise. In order to understand the relative contribution of spectral and temporal modulation cues to speech perception abilities for CI users, spectral and temporal modulation detection was performed separately and related to STM detection and speech perception performance. The results suggest that that slow spectral modulation rather than slow temporal modulation may be important for determining speech perception capabilities for CI users. Lastly, test–retest reliability for STM detection was good with no learning. The present study demonstrates that STM detection may be a useful tool to evaluate the ability of CI sound processing strategies to deliver clinically pertinent acoustic modulation information. PMID:26485715

  8. Suburothelial Bladder Contraction Detection with Implanted Pressure Sensor

    PubMed Central

    Fletter, Paul C.; Ferry, Elizabeth K.; Zhu, Hui; Gustafson, Kenneth J.; Damaser, Margot S.

    2017-01-01

    Aims Managing bladder pressure in patients with neurogenic bladders is needed to improve rehabilitation options, avoid upper tract damage, incontinence, and their associated co-morbidities and mortality. Current methods of determining bladder contractions are not amenable to chronic or ambulatory settings. In this study we evaluated detection of bladder contractions using a novel piezoelectric catheter-free pressure sensor placed in a suburothelial bladder location in animals. Methods Wired prototypes of the pressure monitor were implanted into 2 nonsurvival (feline and canine) and one 13-day survival (canine) animal. Vesical pressures were obtained from the device in both suburothelial and intraluminal locations and simultaneously from a pressure sensing catheter in the bladder. Intravesical pressure was monitored in the survival animal over 10 days from the suburothelial location and necropsy was performed to assess migration and erosion. Results In the nonsurvival animals, the average correlation between device and reference catheter data was high during both electrically stimulated bladder contractions and manual compressions (r = 0.93±0.03, r = 0.89±0.03). Measured pressures correlated strongly (r = 0.98±0.02) when the device was placed in the bladder lumen. The survival animal initially recorded physiologic data, but later this deteriorated. However, endstage intraluminal device recordings correlated (r = 0.85±0.13) with the pressure catheter. Significant erosion of the implant through the detrusor was found. Conclusions This study confirms correlation between suburothelial pressure readings and intravesical bladder pressures. Due to device erosion during ambulatory studies, a wireless implant is recommended for clinical rehabilitation applications. PMID:28060842

  9. A New Ion Implant Monitor Electrical Test Structure.

    DTIC Science & Technology

    1986-01-01

    In this paper, a new Ion Implant Monitor test structure and measurement method is reported. A direct measurement of the sheet resistance of the...probe measurements. Voltage measurements are directly converted to sheet resistance , thus measurements may be performed rapidly.

  10. Method for fabricating MNOS structures utilizing hydrogen ion implantation

    NASA Astrophysics Data System (ADS)

    Saks, N. S.

    1984-05-01

    An improved method for reducing the density of electronic trapping states and fixed insulator charge in the thin oxide layer of an MNOS structure is discussed. The method includes the steps of implanting hydrogen ions in field region of the oxide layer and annealing the MNOS structure at 400 deg C to cause the ions to diffuse laterally into the gate region of the oxide layer.

  11. Implantation-induced structural and surface modification of silica

    NASA Astrophysics Data System (ADS)

    Johnson, C. M.; Thompson, T. D.; Ridgway, M. C.; Gurarie, V.

    1998-05-01

    Ion irradiation of silica causes compaction of the substrate over the extent of the ion range and the resulting increase in refractive index has applications to optical waveguide fabrication. Several analytical techniques have been utilized to characterize implantation-induced structural and surface modifications of silica with the aim of yielding further insight into this technologically relevant process. Substrates of both fused silica and plasma-enhanced chemical vapor deposited silica-on-Si were implanted with C, Si or Ge ions at an energy of 5 MeV and a temperature of -196°C over a range of ion fluences. Compaction of the substrate was characterized as a function of ion dose with both standard profilometry and extended X-ray absorption fine structure (EXAFS). With the former, the extent of compaction was dependent on the silica density with a saturation of the compaction for all substrates at an ion fluence of ˜10 15/cm 2. With EXAFS, complementary information on implantation-induced effects at the atomic scale were determined to differentiate the influences of bond length and bond angle changes in the compaction process. No changes in nearest-neighbour bond length were observed following compaction. The condition of the substrate surface during ion implantation was recorded by in situ photography. Cracking of the surface, as a means of stress relief, was observed and thereafter, the evolution of the cracked surface was quantitatively characterized as a function of ion fluence.

  12. Label-free detection of antigens using implantable SERS nanosensors

    NASA Astrophysics Data System (ADS)

    Li, Honggang; Baum, Caitlin E.; Cullum, Brian M.

    2005-11-01

    Monitoring the presence, production and transport of proteins inside individual living cells can provide vital information about cellular signaling pathways and the overall biological response of an organism. For example, cellular response to external stimuli, such as biological warfare (BW) agents, can be monitored by measuring interleukin-II (IL-2) expression inside T-cells as well as other chemical species associated with T-cell activation. By monitoring such species, pre-symptomatic detection of exposure to BW agents can be achieved, leading to significantly increased post-exposure survival rates. To accomplish such monitoring, we have developed and optimized implantable nanosphere-based nanosensors for the intracellular analysis of specific proteins in a label-free fashion. These sensors consist of 300-520 nm diameter silica spheres that have been coated with silver and antibodies to allow for trace protein detection via surface enhanced Raman spectroscopy (SERS). They have been optimized for SERS response by evaluating the size of the nanospheres best suited to 632.8 nm laser excitation, as well as the various nanosensor fabrication steps (i.e., silver deposition process, antibody binding, etc.). During usage, the presence of the specific protein of interest is monitored by either directly measuring SERS signals associated with the protein and/or changes in the SERS spectrum of the antibodies resulting from conformational changes after antigen binding. In this work, human insulin was used as a model compound for initial studies into the sensitivity of these optimized nanosensors.

  13. Microbial Profiles and Detection Techniques in Peri-Implant Diseases: a Systematic Review

    PubMed Central

    Padial-Molina, Miguel; López-Martínez, Jesús; O’Valle, Francisco

    2016-01-01

    ABSTRACT Objectives To describe the microbial profiles of peri-implant diseases and the main detection methods. Material and Methods A literature search was performed in MEDLINE via PubMed database to identify studies on microbial composition of peri-implant surfaces in humans published in the last 5 years. Studies had to have clear implant status definition for health, peri-implant mucositis and/or peri-implantitis and specifically study microbial composition of the peri-implant sulcus. Results A total of 194 studies were screened and 47 included. Peri-implant sites are reported to be different microbial ecosystems compared to periodontal sites. However, differences between periodontal and peri-implant health and disease are not consistent across all studies, possibly due to the bias introduced by the microbial detection technique. New methods non species-oriented are being used to find ‘unexpected’ microbiota not previously described in these scenarios. Conclusions Microbial profile of peri-implant diseases usually includes classic periodontopathogens. However, correlation between studies is difficult, particularly because of the use of different detection methods. New metagenomic techniques should be promoted for future studies to avoid detection bias. PMID:27833735

  14. Defect engineering in the MOSLED structure by ion implantation

    NASA Astrophysics Data System (ADS)

    Prucnal, S.; Wójtowicz, A.; Pyszniak, K.; Drozdziel, A.; Zuk, J.; Turek, M.; Rebohle, L.; Skorupa, W.

    2009-05-01

    When amorphous SiO2 films are bombarded with energetic ions, various types of defects are created as a consequence of ion-solid interaction (peroxy radicals POR, oxygen deficient centres (ODC), non-bridging oxygen hole centres (NBOHC), E‧ centres, etc.). The intensity of the electroluminescence (EL) from oxygen deficiency centres at 2.7 eV, non-bridging oxygen hole centres at 1.9 eV and defect centres with emission at 2.07 eV can be easily modified by the ion implantation of the different elements (H, N, O) into the completely processed MOSLED structure. Nitrogen implanted into the SiO2:Gd layer reduces the concentration of the ODC and NBOHC while the doping of the oxygen increases the EL intensity observed from POR defect and NBOHC. Moreover, after oxygen or hydrogen implantation into the SiO2:Ge structure fourfold or fifth fold increase of the germanium related EL intensity was observed.

  15. Magnetic and structural properties of manganese ion implanted silicon

    NASA Astrophysics Data System (ADS)

    Awo-Affouda, Chaffra A.

    2007-12-01

    This thesis focuses on semiconductor based spin electronics. The integration of ferromagnetic regions into semiconductor "spintronic" devices to produce spin polarized current is a dynamic research area. One avenue is to make conventional semiconductors ferromagnetic by doping with a transition metal impurity such as Mn. For this, we first investigated the magnetic properties of Mn-implanted Si. We were able to measure above room temperature ferromagnetic hysteresis loops. The high Curie temperature obtained (>400 K), indicated that the synthesis of a technologically useful Si-based magnetic semiconductor is possible. We then focused on studying the structure of the implanted samples in order to establish a correlation between the magnetic and structural properties. The structural investigation involved secondary ion mass spectrometry, Rutherford backscattering, and transmission electron microscopy (TEM) as the main characterization techniques. The combination of the structural and magnetic studies allowed us to isolate an "active" region from which the ferromagnetism originates. We then found that the magnetic properties of the samples are strongly dependant on the interaction of the Mn atoms with the residual implant damage. The evolution of the Mn concentration profiles was also found to be closely related to the distribution of the Si lattice defects. We also observed the formation of Mn rich secondary phases at high enough annealing temperatures >800°C. However, we argued that theses crystallites cannot account for all the observed magnetic properties due to the low Curie temperature of these compounds in bulk form. We concluded that achieving a room temperature Si-based DMS has great potential but careful synthesis of this material system is needed to prevent secondary phase formation.

  16. Structural and electrical properties of In-implanted Ge

    SciTech Connect

    Feng, R. Kremer, F.; Mirzaei, S.; Medling, S. A.; Ridgway, M. C.; Sprouster, D. J.; Decoster, S.; Glover, C. J.; Russo, S. P.

    2015-10-28

    We report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of ≤ 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations ≥0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated with the substitutional In fraction.

  17. Structural and electrical properties of In-implanted Ge

    DOE PAGES

    Feng, R.; Kremer, F.; Sprouster, D. J.; ...

    2015-10-22

    Here, we report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of ≤ 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations ≥0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated withmore » the substitutional In fraction.« less

  18. Structural and electrical properties of In-implanted Ge

    SciTech Connect

    Feng, R.; Kremer, F.; Sprouster, D. J.; Mirzaei, S.; Decoster, S.; Glover, C. J.; Medling, S. A.; Russo, S. P.; Ridgway, M. C.

    2015-10-22

    Here, we report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of ≤ 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations ≥0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated with the substitutional In fraction.

  19. Influence of the chemical nature of implanted ions on the structure of a silicon layer damaged by implantation

    SciTech Connect

    Shcherbachev, K. D. Voronova, M. I.; Bublik, V. T.; Mordkovich, V. N. Pazhin, D. M.; Zinenko, V. I.; Agafonov, Yu. A.

    2013-12-15

    The influence of the implantation of silicon single crystals by fluorine, nitrogen, oxygen, and neon ions on the distribution of strain and the static Debye-Waller factor in the crystal lattice over the implanted-layer depth has been investigated by high-resolution X-ray diffraction. The density depth distribution in the surface layer of native oxide has been measured by X-ray reflectometry. Room-temperature implantation conditions have ensured the equality of the suggested ranges of ions of different masses and the energies transferred by them to the target. It is convincingly shown that the change in the structural parameters of the radiation-damaged silicon layer and the native oxide layer depend on the chemical activity of the implanted ions.

  20. Self-powered instrumented knee implant for early detection of postoperative complications.

    PubMed

    Almouahed, Shaban; Gouriou, Manuel; Hamitouche, Chafiaa; Stindel, Eric; Roux, Christian

    2010-01-01

    In-vivo measurement of tibiofemoral forces transmitted through Total Knee Replacement (TKR) during normal walking allows the early detection of postoperative complications such as the tibiofemoral misalignment and soft-tissue imbalance. In addition, the in-vivo data can help to improve the design of TKR in order to reduce polyethylene wear and consequently to increase the lifespan of knee implant. A self-powered custom-designed tibial implant instrumented with four piezoceramics has been developed in order to detect the aforementioned complications by measuring the relative change in pressure center (COP) position for different levels of eccentric compressive loading. Moreover, the energy harvested by the piezoceramics can be used to power a transmission system located at the stem of knee implant to wirelessly transmit the in-vivo data outside the implant for further processing and display.

  1. A hardware-algorithm co-design approach to optimize seizure detection algorithms for implantable applications.

    PubMed

    Raghunathan, Shriram; Gupta, Sumeet K; Markandeya, Himanshu S; Roy, Kaushik; Irazoqui, Pedro P

    2010-10-30

    Implantable neural prostheses that deliver focal electrical stimulation upon demand are rapidly emerging as an alternate therapy for roughly a third of the epileptic patient population that is medically refractory. Seizure detection algorithms enable feedback mechanisms to provide focally and temporally specific intervention. Real-time feasibility and computational complexity often limit most reported detection algorithms to implementations using computers for bedside monitoring or external devices communicating with the implanted electrodes. A comparison of algorithms based on detection efficacy does not present a complete picture of the feasibility of the algorithm with limited computational power, as is the case with most battery-powered applications. We present a two-dimensional design optimization approach that takes into account both detection efficacy and hardware cost in evaluating algorithms for their feasibility in an implantable application. Detection features are first compared for their ability to detect electrographic seizures from micro-electrode data recorded from kainate-treated rats. Circuit models are then used to estimate the dynamic and leakage power consumption of the compared features. A score is assigned based on detection efficacy and the hardware cost for each of the features, then plotted on a two-dimensional design space. An optimal combination of compared features is used to construct an algorithm that provides maximal detection efficacy per unit hardware cost. The methods presented in this paper would facilitate the development of a common platform to benchmark seizure detection algorithms for comparison and feasibility analysis in the next generation of implantable neuroprosthetic devices to treat epilepsy.

  2. The relationship between structures and in vitro properties of a polyanhydride implant containing gentamicin sulfate.

    PubMed

    Deng, J S; Li, L; Tian, Y; Meisters, M; Chang, H C; Stephens, D; Chen, S; Robinson, D

    2001-11-01

    Laboratory scale injection-molding equipment was utilized to fabricate an implant consisting of poly(FAD:SA 1:1) and 20% (w/w) gentamicin sulfate. Characterizations were performed to determine the molecular weight and glass transition temperature of poly(FAD:SA 1:1). A study was carried out to investigate the relationships between the in vitro performance, morphology, and micro-structures of the molded implants. It was found that implants produced with different structures exhibited different physical integrities in water, i.e., cracking or non-cracking. For the non-cracking implants, a skin-core structure formed by an oriented skin layer was observed under a polarized light microscope. The same morphology was not seen in the cracking implants. The crystal orientation in the skin layer of the non-cracking implants was further identified using a wide-angle x-ray diffraction method (WAXD). No crystal orientation could be found in the cracking implants by WAXD. Furthermore, studies were carried out to evaluate the in vitro drug release for implants showing different degrees of integrity in water. The in vitro drug release of the cracking implants was markedly faster than that of the non-cracking implants due to the pronounced initial drug-burst effect as a result of crack formation in the implants.

  3. Carbon nanotubes implanted manganese-based MOFs for simultaneous detection of biomolecules in body fluids.

    PubMed

    Wang, Min-Qiang; Ye, Cui; Bao, Shu-Juan; Zhang, Yan; Yu, Ya-Nan; Xu, Mao-wen

    2016-02-21

    Metal-organic frameworks (MOFs) have recently attracted much interest in electrochemical fields due to their controlled porosity, large internal surface area, and countless structural topologies. However, the direct application of single component MOFs is limited since they also exhibit poor electronic conductivity, low mechanical stability, and inferior electrocatalytic ability. To overcome these problems, we implanted multi-walled carbon nanotubes (MWCNTs) into manganese-based metal-organic frameworks (Mn-BDC) using a one-step solvothermal method and found that the introduction of MWCNTs can initiate the splitting of bulky Mn-BDC into thin layers. This splitting is highly significant in that it enhances the electronic conductivity and electrocatalytic ability of Mn-BDC. The constructed Mn-BDC@MWCNT composites were utilized as an electrode modifying material in the fabrication of an electrochemical sensor and then were used successfully for the determination of biomolecules in human body fluid. The sensor displayed successful detection performance with wide linear detection ranges (0.1-1150, 0.01-500, and 0.02-1100 μM for AA, DA and UA, respectively) and low limits of detection (0.01, 0.002, and 0.005 μM for AA, DA and UA, respectively); thus, this preliminary study presents an electrochemical biosensor constructed with a novel electrode modifying material that exhibits superior potential for the practical detection of AA, DA and UA in urine samples.

  4. Seizure detection methods using a cascade architecture for real-time implantable devices.

    PubMed

    Kim, Taehoon; Artan, N Sertac; Selesnick, Ivan W; Chao, H Jonathan

    2013-01-01

    Implantable high-accuracy, and low-power seizure detection is a challenge. In this paper, we propose a cascade architecture to combine different seizure detection algorithms to optimize power and accuracy of the overall seizure detection system. The proposed architecture consists of a cascade of two seizure detection stages. In the first-stage detector, a lightweight (low-power) algorithm is used to detect seizure candidates with the understanding that there will be a high number of false positives. In the second-stage detector-and only for the seizure candidates detected in the first detector-a high-accuracy algorithm is used to eliminate the false positives. We show that the proposed cascade architecture can reduce power consumption of seizure detection by 80% with high accuracy, offering a suitable option for real-time implantable seizure detectors.

  5. Detection and manipulation of sychronization processes during depth electrode implantation

    NASA Astrophysics Data System (ADS)

    Schiek, Michael; Zimmermann, Egon; Freund, Hans-Joachim; Sturm, Volker; Tass, Peter

    2002-03-01

    Population of phase oscillators can effectively be desynchronized with composite stimulation techniques using stochastic phase resetting principles [1]. This approach is used to design the first model-based demand controlled deep brain stimulation techniques for the therapy of neurological diseases like Parkinson's disease. We report on first tests of these novel techniques performed in patients during electrode implantation. [1] P.A. Tass: Europhys.Lett. 53(2001) 15-21; 55(2001) 171-177; Biol. Cybern. 85(2001) 343-354

  6. The generation, detection and measurement of laser-induced carbon plasma ions and their implantation effects on brass substrate

    NASA Astrophysics Data System (ADS)

    Ahmad, Shahbaz; Bashir, Shazia; Shahid Rafique, M.; Yousaf, Daniel; Ahmad, Riaz

    2016-05-01

    The generation, detection and measurement of laser-induced carbon plasma ions and their implantation effects on brass substrate have been investigated. Thomson parabola technique was employed to measure the energy and flux of carbon ions. The magnetic field of strength 80 mT was applied on the graphite plasma plume to provide an appropriate trajectory to the generated ions. The energy of carbon ions is 678 KeV for laser fluence of 5.1 J/cm2 which was kept constant for all exposures. The flux of ions varies from 32 × 1011 to 72 × 1014 ions/cm2 for varying numbers of laser pulses from 3000 to 12,000. In order to explore the ion irradiation effects on brass, four brass substrates were irradiated by carbon ions of different flux. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) are used to analyze the surface morphology and crystallographic structure of ion-implanted brass, respectively. SEM analysis reveals the formation and growth of nano-/micro-sized cavities, pores and pits for the various ion flux for varying numbers of laser pulses from 3000 to 12,000. By increasing ion flux by increasing the number of pulses up to 9000 shots, the dendritic structures initiate to grow along with cavities and pores. At the maximum ion flux for 12,000 shots, the unequiaxed dendritic structures become distinct and the distance between the dendrites is decreased, whereas cavities, pores and pits are completely finished. The XRD analysis reveals that a new phase of ZnC (0012) is formed in the brass substrate after ion implantation. Universal tensile testing machine and Vickers microhardness tester are used to explore the yield stress, ultimate tensile strength and microhardness of ion-implanted brass substrate. The mechanical properties monotonically increase by increasing the ion flux. Variations in mechanical properties are correlated with surface and structural modifications of brass.

  7. Charge transport and storage in ion implanted metal-oxide-semiconductor structures

    NASA Astrophysics Data System (ADS)

    Augulis, L.; Pranevičius, L.; Vosylius, J.

    A physical model that predicts charge accumulation in MOS structures with implanted SiO 2 is investigated theoretically and experimentally. It is shown that, to achieve memory effects, MOS structures have to include a SiO 2 layer with different conduction mechanism along its thickness. The sign of the flat-band voltage shift depends on the localization of traps in oxide created by ion implantation. The time characteristics of charge accumulation and discharging of implanted SiO 2 by the pulses of applied voltage are similar to those observed in MNOS structures.

  8. Electrochemical detection of arsenic(III) using iridium-implanted boron-doped diamond electrodes.

    PubMed

    Ivandini, Tribidasari A; Sato, Rika; Makide, Yoshihiro; Fujishima, Akira; Einaga, Yasuaki

    2006-09-15

    Iridium-modified, boron-doped diamond electrodes fabricated by an ion implantation method have been developed for electrochemical detection of arsenite (As(III)). Ir+ ions were implanted with an energy of 800 keV and a dose of 10(15) ion cm(-2). An annealing treatment at 850 degrees C for 45 min in H2 plasma (80 Torr) was required to rearrange metastable diamond produced by an implantation process. Characterization was investigated by SEM, AFM, Raman, and X-ray photoelectron spectroscopy. Cyclic voltammetry and flow injection analysis with amperometric detection were used to study the electrochemical reaction. The electrodes exhibited high catalytic activity toward As(III) oxidation with the detection limit (S/N = 3), sensitivity, and linearity of 20 nM (1.5 ppb), 93 nA microM(-1) cm(-2), and 0.999, respectively. The precision for 10 replicate determinations of 50 microM As(III) was 4.56% relative standard deviation. The advantageous properties of the electrodes were its inherent stability with a very low background current. The electrode was applicable for analysis of spiked arsenic in tap water containing a significant amount of various ion elements. The results indicate that the metal-implanted method could be promising for controlling the electrochemical properties of diamond electrodes.

  9. Structure and mechanical properties of polycrystalline alumina implanted with Ti + and Cr +

    NASA Astrophysics Data System (ADS)

    Halitim, F.; Ikhlef, N.; Mesghouni, T.; Kherrat, R.; Fantozzi, G.

    1997-01-01

    In ion implantation, the interaction between the ions and target atoms result in modifications to the crystallographic structure of the implanted substrate. The chemical nature of the implanted ion can in certain cases, if thermal treatments after implantation are done, produce a chemical composite of two oxides types. The crystallographic modifications can produce an enhancement of the surface mechanical properties. Polycrystalline alumina was implanted with Ti or Cr ions at 110 keV and heat treated at a series of temperatures. We have examined the resulting implanted layers by the following analysis techniques: Secondary Ion Mass Spectroscopy (SIMS), to obtain the as-implanted profiles, Scanning Electron Microscopy (SEM), for investigation the chemical composite formation on the surface, and finally grazing incidence X-ray diffraction (GXRD), for determination of the crystallographic nature of the precipitates. By the Vickers indentation method, using different loads we determined the hardness and the fracture toughness of the implanted layer. The residual surface compressive stresses produced by these implantations, were measured by the Lawn and Fuller [1] technique.

  10. Detection and classification of multiple finger movements using a chronically implanted Utah Electrode Array.

    PubMed

    Egan, Joshua; Baker, Justin; House, Paul; Greger, Bradley

    2011-01-01

    The ability to detect and classify individual and combined finger movements from neural data is rapidly advancing. The work that has been done has demonstrated the feasibility of decoding finger movements from acutely recorded neurons. There is a need for a recording model that meets the chronic requirements of a neuroprosthetic application and to address this need we have developed an algorithm that can detect and classify individual and combined finger movements using neuronal data acquired from a chronically implanted Utah Electrode Array (UEA). The algorithm utilized the firing rates of individual neurons and performed with an average sensitivity and an average specificity that were both greater than 92% across all movement types. These results lend further support that a chronically implanted UEA is suitable for acquiring and decoding neuronal data and also demonstrate a decoding method that can detect and classify finger movements without any a priori knowledge of the data, task, or behavior.

  11. Interference detection in implantable defibrillators induced by therapeutic radiation therapy

    PubMed Central

    Uiterwaal, G.J.; Springorum, B.G.F.; Scheepers, E.; de Ruiter, G.S.; Hurkmans, C.W.

    2006-01-01

    Background Electromagnetic fields and ionising radiation during radiotherapy can influence the functioning of ICDs. Guidelines for radiotherapy treatment were published in 1994, but only based on experience with pacemakers. Data on the influence of radiotherapy on ICDs is limited. Objectives We determined the risk to ICDs of interference detection induced by radiotherapy. Methods In our study we irradiated 11 ICDs. The irradiation was performed with a 6 megavolt photon beam. In each individual device test, a total of 20 Gray was delivered in a fractionated fashion. During each irradiation the output stimulation rate was monitored and electrogram storage was activated. In case of interference the test was repeated with the ICD outside and the lead(s) inside and outside the irradiation field. Results With the ICD inside the irradiation field, interference detection was observed in all ICDs. This caused pacing inhibition or rapid ventricular pacing. Ventricular tachycardia (VT) or ventricular fibrillation (VF) detection occurred, which would have caused tachycardia-terminating therapy. If the ICD was placed outside the irradiation field, no interference was observed. Conclusion Interference by ionising radiation on the ICDs is demonstrated both on bradycardia and tachycardia therapy. This can have consequences for patients. Recommendations for radiotherapy are presented in this article. ImagesFigure 1Figure 5 PMID:25696559

  12. Shallow nitrogen ion implantation: Evolution of chemical state and defect structure in titanium

    NASA Astrophysics Data System (ADS)

    Manojkumar, P. A.; Chirayath, V. A.; Balamurugan, A. K.; Krishna, Nanda Gopala; Ilango, S.; Kamruddin, M.; Amarendra, G.; Tyagi, A. K.; Raj, Baldev

    2016-09-01

    Evolution of chemical states and defect structure in titanium during low energy nitrogen ion implantation by Plasma Immersion Ion Implantation (PIII) process is studied. The underlying process of chemical state evolution is investigated using secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The implantation induced defect structure evolution as a function of dose is elucidated using variable energy positron annihilation Doppler broadening spectroscopy (PAS) and the results were corroborated with chemical state. Formation of 3 layers of defect state was modeled to fit PAS results.

  13. Towards a bimodal proximity sensor for in situ neurovascular bundle detection during dental implant surgery

    PubMed Central

    Weber, Jessie R.; Baribeau, François; Grenier, Paul; Émond, Frédéric; Dubois, Sylvain; Duchesne, François; Girard, Marc; Pope, Timothy; Gallant, Pascal; Mermut, Ozzy; Moghadam, Hassan Ghaderi

    2013-01-01

    Proof of concept results are presented towards an in situ bimodal proximity sensor for neurovascular bundle detection during dental implant surgery using combined near infrared absorption (NIR) and optical coherence tomography (OCT) techniques. These modalities are shown to have different sensitivity to the proximity of optical contrast from neurovascular bundles. NIR AC and DC signals from the pulsing of an artery enable qualitative ranging of the bundle in the millimeter range, with best sensitivity around 0.5-3mm distance in a custom phantom setup. OCT provides structural mapping of the neurovascular bundle at sub-millimeter distances in an ex vivo human jaw bone. Combining the two techniques suggests a novel ranging system for the surgeon that could be implemented in a “smart drill.” The proximity to the neurovascular bundle can be tracked in real time in the range of a few millimeters with NIR signals, after which higher resolution imaging OCT to provide finer ranging in the sub-millimeter distances. PMID:24466473

  14. Integrated contour detection and pose estimation for fluoroscopic analysis of knee implants.

    PubMed

    Prins, A H; Kaptein, B L; Stoel, B C; Nelissen, R G H H; Reiber, J H C; Valstar, E R

    2011-08-01

    With fluoroscopic analysis of knee implant kinematics the implant contour must be detected in each image frame, followed by estimation of the implant pose. With a large number of possibly low-quality images, the contour detection is a time-consuming bottleneck. The present paper proposes an automated contour detection method, which is integrated in the pose estimation. In a phantom experiment the automated method was compared with a standard method, which uses manual selection of correct contour parts. Both methods demonstrated comparable precision, with a minor difference in the Y-position (0.08 mm versus 0.06 mm). The precision of each method was so small (below 0.2 mm and 0.3 degrees) that both are sufficiently accurate for clinical research purposes. The efficiency of both methods was assessed on six clinical datasets. With the automated method the observer spent 1.5 min per image, significantly less than 3.9 min with the standard method. A Bland-Altman analysis between the methods demonstrated no discernible trends in the relative femoral poses. The threefold increase in efficiency demonstrates that a pose estimation approach with integrated contour detection is more intuitive than a standard method. It eliminates most of the manual work in fluoroscopic analysis, with sufficient precision for clinical research purposes.

  15. A micro-structured ion-implanted magnonic crystal

    SciTech Connect

    Obry, Bjoern; Pirro, Philipp; Chumak, Andrii V.; Ciubotaru, Florin; Serga, Alexander A.; Hillebrands, Burkard; Braecher, Thomas; Osten, Julia; Fassbender, Juergen

    2013-05-20

    We investigate spin-wave propagation in a microstructured magnonic-crystal waveguide fabricated by localized ion implantation. The irradiation caused a periodic variation in the saturation magnetization along the waveguide. As a consequence, the spin-wave transmission spectrum exhibits a set of frequency bands, where spin-wave propagation is suppressed. A weak modification of the saturation magnetization by 7% is sufficient to decrease the spin-wave transmission in the band gaps by a factor of 10. These results evidence the applicability of localized ion implantation for the fabrication of efficient micron- and nano-sized magnonic crystals for magnon spintronic applications.

  16. Structural transformations in austenitic stainless steel induced by deuterium implantation: irradiation at 100 K

    NASA Astrophysics Data System (ADS)

    Morozov, Oleksandr; Zhurba, Volodymyr; Neklyudov, Ivan; Mats, Oleksandr; Rud, Aleksandr; Chernyak, Nikolay; Progolaieva, Viktoria

    2015-03-01

    Deuterium thermal desorption spectra were investigated on the samples of austenitic stainless steel 18Cr10NiTi preimplanted at 100 K with deuterium ions in the dose range from 3 × 1015 to 5 × 1018 D/cm2. The kinetics of structural transformation development in the implantation steel layer was traced from deuterium thermodesorption spectra as a function of implanted deuterium concentration. At saturation of austenitic stainless steel 18Cr10NiTi with deuterium by means of ion implantation, structural-phase changes take place, depending on the dose of implanted deuterium. The maximum attainable concentration of deuterium in steel is C = 1 (at.D/at.met. = 1/1). The increase in the implanted dose of deuterium is accompanied by the increase in the retained deuterium content, and as soon as the deuterium concentration attains C ≈ 0.5 the process of shear martensitic structural transformation in steel takes place. It includes the formation of bands, body-centered cubic (bcc) crystal structure, and the ferromagnetic phase. Upon reaching the deuterium concentration C > 0.5, the presence of these molecules causes shear martensitic structural transformations in the steel, which include the formation of characteristic bands, bcc crystal structure, and the ferromagnetic phase. At C ≥ 0.5, two hydride phases are formed in the steel, the decay temperatures of which are 240 and 275 K. The hydride phases are formed in the bcc structure resulting from the martensitic structural transformation in steel.

  17. The local structure and ferromagnetism in Fe-implanted SrTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Lobacheva, O.; Chavarha, M.; Yiu, Y. M.; Sham, T. K.; Goncharova, L. V.

    2014-07-01

    We report a connection between the local structure of low-level Fe impurities and vacancies as the cause of ferromagnetic behavior observed in strontium titanate single crystals (STO), which were implanted with Fe and Si ions at different doses then annealed in oxygen. The effects of Fe doping and post-implantation annealing of STO were studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy and Superconducting Quantum Interference Device magnetometry. XANES spectra for Fe and Ti K- and L-edge reveal the changes in the local environment of Fe and Ti following the implantation and annealing steps. The annealing in oxygen atmosphere partially healed implantation damages and changed the oxidation state of the implanted iron from metallic Fe0 to Fe2+/Fe3+ oxide. The STO single crystals were weak ferromagnets prior to implantation. The maximum saturation moment was obtained after our highest implantation dose of 2 × 1016 Fe atom/cm2, which could be correlated with the metallic Fe0 phases in addition to the presence of O/Ti vacancies. After recrystallization annealing, the ferromagnetic response disappears. Iron oxide phases with Fe2+ and Fe3+ corresponding to this regime were identified and confirmed by calculations using Real Space Multiple Scattering program (FEFF9).

  18. The local structure and ferromagnetism in Fe-implanted SrTiO₃ single crystals

    SciTech Connect

    Lobacheva, O. Chavarha, M.; Yiu, Y. M.; Sham, T. K.; Goncharova, L. V.

    2014-07-07

    We report a connection between the local structure of low-level Fe impurities and vacancies as the cause of ferromagnetic behavior observed in strontium titanate single crystals (STO), which were implanted with Fe and Si ions at different doses then annealed in oxygen. The effects of Fe doping and post-implantation annealing of STO were studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy and Superconducting Quantum Interference Device magnetometry. XANES spectra for Fe and Ti K- and L-edge reveal the changes in the local environment of Fe and Ti following the implantation and annealing steps. The annealing in oxygen atmosphere partially healed implantation damages and changed the oxidation state of the implanted iron from metallic Fe⁰ to Fe²⁺/Fe³⁺ oxide. The STO single crystals were weak ferromagnets prior to implantation. The maximum saturation moment was obtained after our highest implantation dose of 2×10¹⁶ Fe atom/cm², which could be correlated with the metallic Fe⁰ phases in addition to the presence of O/Ti vacancies. After recrystallization annealing, the ferromagnetic response disappears. Iron oxide phases with Fe²⁺ and Fe³⁺ corresponding to this regime were identified and confirmed by calculations using Real Space Multiple Scattering program (FEFF9).

  19. Analysis of ion-implanted surface and interface structures by computer-simulated backscattering spectra

    NASA Astrophysics Data System (ADS)

    Kido, Y.; Kakeno, M.; Yamada, K.; Kawamoto, J.; Ohsawa, H.

    1985-10-01

    Computer codes for synthesizing random and channeling backscattering spectra have been elaborated to characterize the surface and interface structures formed or modified by ion implantation. Both effects of isotopes and energy fluctuation are taken into account in the spectrum simulation. This backscattering measurement combined with the simulation method is applied to characterization of the N(+)-implanted Al films and to quantitative analysis of chemical reaction and interdiffusion induced by ion-beam mixing. An ion-beam-induced damage profile and its epitaxial recovery of crystallinity are analyzed by the simulation of channeling spectra from ion-implanted Al2O3 substrates.

  20. Formation of SIMOX-SOI structure by high-temperature oxygen implantation

    NASA Astrophysics Data System (ADS)

    Hoshino, Yasushi; Kamikawa, Tomohiro; Nakata, Jyoji

    2015-12-01

    We have performed oxygen ion implantation in silicon at very high substrate-temperatures (⩽1000 °C) for the purpose of forming silicon-on-insulator (SOI) structure. We have expected that the high-temperature implantation can effectively avoids ion-beam-induced damages in the SOI layer and simultaneously stabilizes the buried oxide (BOX) and SOI-Si layer. Such a high-temperature implantation makes it possible to reduce the post-implantation annealing temperature. In the present study, oxygen ions with 180 keV are incident on Si(0 0 1) substrates at various temperatures from room temperature (RT) up to 1000 °C. The ion-fluencies are in order of 1017-1018 ions/cm2. Samples have been analyzed by atomic force microscope, Rutherford backscattering, and micro-Raman spectroscopy. It is found in the AFM analysis that the surface roughness of the samples implanted at 500 °C or below are significantly small with mean roughness of less than 1 nm, and gradually increased for the 800 °C-implanted sample. On the other hand, a lot of dents are observed for the 1000 °C-implanted sample. RBS analysis has revealed that stoichiometric SOI-Si and BOX-SiO2 layers are formed by oxygen implantation at the substrate temperatures of RT, 500, and 800 °C. However, SiO2-BOX layer has been desorbed during the implantation. Raman spectra shows that the ion-beam-induced damages are fairly suppressed by such a high-temperatures implantation.

  1. Implantable neural spike detection using lifting-based stationary wavelet transform.

    PubMed

    Yang, Yuning; Mason, Andrew J

    2011-01-01

    Spike detection from high data rate neural recordings is desired to ease the bandwidth bottleneck of bio-telemetry. An appropriate spike detection method should be able to detect spikes under low signal-to-noise ratio (SNR) while meeting the power and area constraints of implantation. This paper introduces a spike detection system utilizing lifting-based stationary wavelet transform (SWT) that decomposes neural signals into 2 levels using 'symmlet2' wavelet basis. This approach enables accurate spike detection down to an SNR of only 2. The lifting-based SWT architecture permits a hardware implementation consuming only 6.6 μW power and 0.07 mm(2) area for 32 channels with 3.2 MHz master clock.

  2. Tribological properties and surface structures of ion implanted 9Cr18Mo stainless steels

    NASA Astrophysics Data System (ADS)

    Fengbin, Liu; Guohao, Fu; Yan, Cui; Qiguo, Sun; Min, Qu; Yi, Sun

    2013-07-01

    The polished quenched-and-tempered 9Cr18Mo steels were implanted with N ions and Ti ions respectively at a fluence of 2 × 1017 ions/cm2. The mechanical properties of the samples were investigated by using nanoindenter and tribometer. The results showed that the ion implantations would improve the nanohardness and tribological property, especially N ion implantation. The surface analysis of the implanted samples was carried out by using XRD, XPS and AES. It indicated that the surface exhibits graded layers after ion implantation. For N ion implantation, the surface about 20 nm thickness is mainly composed of supersaturated interstitial N solid solution, oxynitrides, CrxCy phase and metal nitrides. In the subsurface region, the metal nitrides dominate and the other phases disappear. For Ti ion implantation, the surface of about 20 nm thickness is mainly composed of titanium oxides and carbon amorphous phase, the interstitial solid solution of Ti in Fe is abundant in the subsurface region. The surface components and structures have significant contributions to the improved mechanical properties.

  3. Brief ultrasonication improves detection of biofilm-formative bacteria around a metal implant.

    PubMed

    Kobayashi, Naomi; Bauer, Thomas W; Tuohy, Marion J; Fujishiro, Takaaki; Procop, Gary W

    2007-04-01

    Biofilms are complex microenvironments produced by microorganisms on surfaces. Ultrasonication disrupts biofilms and may make the microorganism or its DNA available for detection. We determined whether ultrasonication could affect our ability to detect bacteria adherent to a metal substrate. A biofilm-formative Staphylococcus aureus strain was used for an in vitro implant infection model (biofilm-formative condition). We used quantitative culture and real time-polymerase chain reaction to determine the influence of different durations of ultrasound on bacterial adherence and viability. Sonication for 1 minute increased the yield of bacteria. Sonication longer than 5 minutes led to fewer bacterial colonies by conventional culture but not by polymerase chain reaction. This suggests short periods of sonication help release bacteria from the metal substrate by disrupting the biofilm, but longer periods of sonication lyse bacteria prohibiting their detection in microbiologic cultures. A relatively short duration of sonication may be desirable for maximizing detection of biofilm-formative bacteria around implants by culture or polymerase chain reaction.

  4. Oxygen Implant Isolation of n-GaN Field-Effect Transistor Structures

    SciTech Connect

    Dang, G.; Cao, X.A.; Ren, F.; Pearton, S.J.; Han, J.; Baca, A.G.; Shul, R.J.

    1999-07-20

    Multiple-energy (30-325 keV) O{sup +} implantation into GaN field-effect transistor structures (n {approximately} 10{sup 18} cm{sup {minus}3}, 3000 {angstrom} thick) can produce as-implanted sheet resistances of 4 x 10{sup 12} {Omega}/{open_square}, provided care is taken to ensure compensation of the region up to the projected range of the lowest energy implant. The sheet resistance remains above 10{sup 7} {Omega}/{open_square} to annealing temperatures of {approximately} 650 C and displays an activation energy of 0.29 eV. No diffusion of the implanted oxygen was observed for anneals up to 800 C.

  5. Structural disorder in hard amorphous carbon films implanted with nitrogen ions

    SciTech Connect

    Freire, F.L. Jr.; Franceschini, D.F.; Achete, C.A.; Brusa, R.S.; Mariotto, G.; Karwasz, G.P.; Canteri, R.

    1996-12-31

    Hard amorphous hydrogenated carbon films deposited by self-bias glow discharge were implanted at room temperature with 70 keV-nitrogen ions at fluences between 2.0 and 9.0 {times} 10{sup 16} N/cm{sup 2}. The implanted samples were analyzed by Raman spectroscopy, SIMS and positron annihilation spectroscopy (Doppler broadening technique with the determination of the parameter S). For samples implanted with 2.0 {times} 10{sup 16} N/cm{sup 2} the S parameter follows the vacancies depth profile predicted by Monte Carlo simulation. For higher fluences the authors observed a reduction in the measured value of S. This result is discussed in terms of both hydrogen loss and structural modifications (increase of disorder at local scale and of the number of graphitic domains) induced in the carbon film by ion implantation.

  6. Structural Transformations in Austenitic Stainless Steel Induced by Deuterium Implantation: Irradiation at 295 K

    NASA Astrophysics Data System (ADS)

    Morozov, Oleksandr; Zhurba, Volodymir; Neklyudov, Ivan; Mats, Oleksandr; Progolaieva, Viktoria; Boshko, Valerian

    2016-02-01

    Deuterium thermal desorption spectra were investigated on the samples of austenitic steel 18Cr10NiTi pre-implanted at 295 K with deuterium ions in the dose range from 8 × 1014 to 2.7 × 1018 D/cm2. The kinetics of structural transformation development in the steel layer was traced from deuterium thermodesorption spectra as a function of deuterium concentration. Three characteristic regions with different low rates of deuterium amount desorption as the implantation dose increases were revealed: I—the linear region of low implantation doses (up to 1 × 1017 D/cm2); II—the nonlinear region of medium implantation doses (1 × 1017 to 8 × 1017 D/cm2); III—the linear region of high implantation doses (8 × 1017 to 2.7 × 1018 D/cm2). During the process of deuterium ion irradiation, the coefficient of deuterium retention in steel varies in discrete steps. Each of the discrete regions of deuterium retention coefficient variation corresponds to different implanted-matter states formed during deuterium ion implantation. The low-dose region is characterized by formation of deuterium-vacancy complexes and solid-solution phase state of deuterium in the steel. The total concentration of the accumulated deuterium in this region varies between 2.5 and 3 at.%. The medium-dose region is characterized by the radiation-induced action on the steel in the presence of deuterium with the resulting formation of the energy-stable nanosized crystalline structure of steel, having a developed network of intercrystalline boundaries. The basis for this developed network of intercrystalline boundaries is provided by the amorphous state, which manifests itself in the thermodesorption spectra as a widely temperature-scale extended region of deuterium desorption (structure formation with a varying activation energy). The total concentration of the accumulated deuterium in the region of medium implantation doses makes 7 to 8 at.%. The resulting structure shows stability against the action of

  7. Structural Transformations in Austenitic Stainless Steel Induced by Deuterium Implantation: Irradiation at 295 K.

    PubMed

    Morozov, Oleksandr; Zhurba, Volodymir; Neklyudov, Ivan; Mats, Oleksandr; Progolaieva, Viktoria; Boshko, Valerian

    2016-12-01

    Deuterium thermal desorption spectra were investigated on the samples of austenitic steel 18Cr10NiTi pre-implanted at 295 K with deuterium ions in the dose range from 8 × 10(14) to 2.7 × 10(18) D/cm(2). The kinetics of structural transformation development in the steel layer was traced from deuterium thermodesorption spectra as a function of deuterium concentration. Three characteristic regions with different low rates of deuterium amount desorption as the implantation dose increases were revealed: I-the linear region of low implantation doses (up to 1 × 10(17) D/cm(2)); II-the nonlinear region of medium implantation doses (1 × 10(17) to 8 × 10(17) D/cm(2)); III-the linear region of high implantation doses (8 × 10(17) to 2.7 × 10(18) D/cm(2)). During the process of deuterium ion irradiation, the coefficient of deuterium retention in steel varies in discrete steps. Each of the discrete regions of deuterium retention coefficient variation corresponds to different implanted-matter states formed during deuterium ion implantation. The low-dose region is characterized by formation of deuterium-vacancy complexes and solid-solution phase state of deuterium in the steel. The total concentration of the accumulated deuterium in this region varies between 2.5 and 3 at.%. The medium-dose region is characterized by the radiation-induced action on the steel in the presence of deuterium with the resulting formation of the energy-stable nanosized crystalline structure of steel, having a developed network of intercrystalline boundaries. The basis for this developed network of intercrystalline boundaries is provided by the amorphous state, which manifests itself in the thermodesorption spectra as a widely temperature-scale extended region of deuterium desorption (structure formation with a varying activation energy). The total concentration of the accumulated deuterium in the region of medium implantation doses makes 7 to 8 at.%. The

  8. Offline Impedance Measurements for Detection and Mitigation of Dangerous Implant Interactions: An RF Safety Prescreen

    PubMed Central

    Ellenor, Christopher W; Stang, Pascal P; Etezadi-Amoli, Maryam; Pauly, John M; Scott, Greig C

    2015-01-01

    Purpose The concept of a “radiofrequency safety prescreen” is investigated, wherein dangerous interactions between radiofrequency fields used in MRI, and conductive implants in patients are detected through impedance changes in the radiofrequency coil. Theory The behavior of coupled oscillators is reviewed, and the resulting, observable impedance changes are discussed. Methods A birdcage coil is loaded with a static head phantom and a wire phantom with a wire close to its resonant length, the shape, position, and orientation of which can be changed. Interactions are probed with a current sensor and network analyzer. Results Impedance spectra show dramatic, unmistakable splitting in cases of strong coupling, and strong correlation is observed between induced current and scattering parameters. Conclusions The feasibility of a new, low-power prescreening technique has been demonstrated in a simple phantom experiment, which can unambiguously detect resonant interactions between an implanted wire and an imaging coil. A new technique has also been presented which can detect parallel transmit null modes for the wire. Magn Reson Med 73:1328–1339, 2015. © 2014 Wiley Periodicals, Inc. PMID:24623586

  9. Anomalous diffusion of isoelectronic antimony implant induced defects in GaAs-AlGaAs multiquantum well structures

    NASA Astrophysics Data System (ADS)

    Rao, E. V. K.; Krauz, Ph.; Thibierge, H.; Azoulay, R.; Vieu, C.

    1994-03-01

    We present here evidence on the deep diffusion of isoelectronic Sb implant induced defects in thick GaAs-AlGaAs multiquantum well structures (MQW) to depths as far as ˜30 times the implant projected range (Rp). This observation has been confirmed by performing low temperature photoluminescence depth scanning measurements and cross-sectional transmission electron microscopy (XTEM) analysis on room temperature Sb implanted thick MQW samples. An explanation based on the isoelectronic nature of Sb and its substitution on As site (SbAs) has been proposed to understand the anomalous diffusion of defects during implant and their contribution to Al/Ga disordering during post-implant annealing.

  10. Plasma immersion ion implantation for surface treatment of complex branched structures

    NASA Astrophysics Data System (ADS)

    Kashin, Oleg A.; Lotkov, Alexander I.; Borisov, Dmitry P.; Slabodchikov, Vladimir A.; Kuznetsov, Vladimir M.; Kudryashov, Andrey N.; Krukovsky, Konstantin V.

    2016-11-01

    The paper presents experimental results demonstrating the capabilities of plasma immersion ion implantation of silicon (Si) for surface treatment of complex branched structures such are self-expanding intravascular nickel-titanium (NiTi) stents. Using NiTi stents of diameter 4 and 8 mm, it is shown that plasma immersion ion implantation can provide rather homogeneous doping of their outer and inner surfaces with Si atoms. Also presented are research data on the processes that determine the thickness, composition, and structure of surface layers subjected to this type of treatment.

  11. Structural characterization of dual ion implantation in silicon

    NASA Astrophysics Data System (ADS)

    Nunes, B.; Franco, N.; Botelho do Rego, A. M.; Alves, E.; Colaço, R.

    2015-12-01

    <1 0 0> Si wafers were dual implanted at room temperature with Fe + C and Ti + C with fluences of 2 × 1017 cm-2. The samples were annealed in vacuum at 800 °C and 1000 °C respectively, and characterized in scanning electron microscope (FEG-SEM), grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS). The scanning electron microscopy characterization showed that both annealings generated precipitates, with sizes within the range of 10-100 nm at 800 °C and 1-10 μm for the 1000 °C annealing. The GIXRD measurements revealed the presence of different silicides phases. For the Fe + C implantation β-FeSi2 was observed at 800 °C while at 1000 °C α-FeSi2 and SiC were found. The Ti + C sample at 800 °C showed simultaneously the presence of four different phases, both metastable C49 and stable C54 silicide TiSi2, poly-Si and SiC. At higher temperatures the metastable C49-TiSi2 silicide phase was no longer observed, all the others remaining. The XPS analysis confirmed the existence of the SiC at 1000 °C temperature, and showed that the initial carbon clusters get richer in Si with the increase of temperature to form SiC. It was also possible to see that among all present species, C was the one that oxidized the most with increasing temperature.

  12. Structural Changes in Polymer Films by Fast Ion Implantation

    NASA Astrophysics Data System (ADS)

    Parada, M. A.; Minamisawa, R. A.; Muntele, C.; Muntele, I.; De Almeida, A.; Ila, D.

    2006-11-01

    In applications from food wrapping to solar sails, polymers films can be subjected to intense charged panicle bombardment and implantation. ETFE (ethylenetetrafluoroethylene) with high impact resistance is used for pumps, valves, tie wraps, and electrical components. PFA (tetrafluoroethylene-per-fluoromethoxyethylene) and FEP (tetrafluoroethylene-hexa-fluoropropylene) are sufficiently biocompatible to be used as transcutaneous implants since they resist damage from the ionizing space radiation, they can be used in aerospace engineering applications. PVDC (polyvinyllidene-chloride) is used for food packaging, and combined with others plastics, improves the oxygen barrier responsible for the food preservation. Fluoropolymers are also known for their radiation dosimetry applications, dependent on the type and energy of the radiation, as well as of the beam intensity. In this work ETFE, PFA, FEP and PVDC were irradiated with ions of keV and MeV energies at several fluences and were analyzed through techniques as RGA, OAP, FTIR, ATR and Raman spectrophotometry. CF3 is the main specie emitted from PFA and FEP when irradiated with MeV protons. H and HF are released from ETFE due to the broken C-F and C-H bonds when the polymer is irradiated with keV Nitrogen ions and protons. At high fluence, especially for keV Si and N, damage due to carbonization is observed with the formation of hydroperoxide and polymer dehydroflorination. The main broken bonds in PVDC are C-O and C-Cl, with the release of Cl and the formation of double carbon bonds. The ion fluence that causes damage, which could compromise fluoropolymer film applications, has been determined.

  13. Influence of Si ion implantation on structure and morphology of g-C3N4

    NASA Astrophysics Data System (ADS)

    Varalakshmi, B.; Sreenivasulu, K. V.; Asokan, K.; Srikanth, V. V. S. S.

    2016-07-01

    Effect of Si ion implantation on structural and morphological features of graphite-like carbon nitride (g-C3N4) was investigated. g-C3N4 was prepared by using a simple atmospheric thermal decomposition process. The g-C3N4 pellets were irradiated with a Si ion beam of energy 200 keV with different fluencies. Structural, morphological and elemental, and phase analysis of the implanted samples in comparison with the pristine samples was carried out by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) techniques, respectively. The observations revealed that Si ion implantation results in a negligible change in the crystallite size and alteration of the network-like to the sheet-like morphology of g-C3N4 and Si ions in the g-C3N4 network.

  14. Structural transformations in austenitic stainless steel induced by deuterium implantation: irradiation at 100 K.

    PubMed

    Morozov, Oleksandr; Zhurba, Volodymyr; Neklyudov, Ivan; Mats, Oleksandr; Rud, Aleksandr; Chernyak, Nikolay; Progolaieva, Viktoria

    2015-01-01

    Deuterium thermal desorption spectra were investigated on the samples of austenitic stainless steel 18Cr10NiTi preimplanted at 100 K with deuterium ions in the dose range from 3 × 10(15) to 5 × 10(18) D/cm(2). The kinetics of structural transformation development in the implantation steel layer was traced from deuterium thermodesorption spectra as a function of implanted deuterium concentration. At saturation of austenitic stainless steel 18Cr10NiTi with deuterium by means of ion implantation, structural-phase changes take place, depending on the dose of implanted deuterium. The maximum attainable concentration of deuterium in steel is C = 1 (at.D/at.met. = 1/1). The increase in the implanted dose of deuterium is accompanied by the increase in the retained deuterium content, and as soon as the deuterium concentration attains C ≈ 0.5 the process of shear martensitic structural transformation in steel takes place. It includes the formation of bands, body-centered cubic (bcc) crystal structure, and the ferromagnetic phase. Upon reaching the deuterium concentration C > 0.5, the presence of these molecules causes shear martensitic structural transformations in the steel, which include the formation of characteristic bands, bcc crystal structure, and the ferromagnetic phase. At C ≥ 0.5, two hydride phases are formed in the steel, the decay temperatures of which are 240 and 275 K. The hydride phases are formed in the bcc structure resulting from the martensitic structural transformation in steel.

  15. Applications of Fault Detection in Vibrating Structures

    NASA Technical Reports Server (NTRS)

    Eure, Kenneth W.; Hogge, Edward; Quach, Cuong C.; Vazquez, Sixto L.; Russell, Andrew; Hill, Boyd L.

    2012-01-01

    Structural fault detection and identification remains an area of active research. Solutions to fault detection and identification may be based on subtle changes in the time series history of vibration signals originating from various sensor locations throughout the structure. The purpose of this paper is to document the application of vibration based fault detection methods applied to several structures. Overall, this paper demonstrates the utility of vibration based methods for fault detection in a controlled laboratory setting and limitations of applying the same methods to a similar structure during flight on an experimental subscale aircraft.

  16. Bone bonding strength of diamond-structured porous titanium-alloy implants manufactured using the electron beam-melting technique.

    PubMed

    Hara, Daisuke; Nakashima, Yasuharu; Sato, Taishi; Hirata, Masanobu; Kanazawa, Masayuki; Kohno, Yusuke; Yoshimoto, Kensei; Yoshihara, Yusuke; Nakamura, Akihiro; Nakao, Yumiko; Iwamoto, Yukihide

    2016-02-01

    The present study examined the bone bonding strength of diamond-structured porous titanium-alloy (Porous-Ti-alloy) manufactured using the electron beam-melting technique in comparison with fiber mesh-coated or rough-surfaced implants. Cylindrical implants with four different pore sizes (500, 640, 800, and 1000μm) of Porous-Ti-alloy, titanium fiber mesh (FM), and surfaces roughened by titanium arc spray (Ti-spray) were implanted into the distal femur of rabbits. Bone bonding strength and histological bone ingrowth were evaluated at 4 and 12weeks after implantation. The bone bonding strength of Porous-Ti-alloy implants (640μm pore size) increased over time from 541.4N at 4weeks to 704.6N at 12weeks and was comparable to that of FM and Ti-spray implants at both weeks. No breakage of the porous structure after mechanical testing was found with Porous-Ti-alloy implants. Histological bone ingrowth that increased with implantation time occurred along the inner structure of Porous-Ti-alloy implants. There was no difference in bone ingrowth in Porous-Ti-alloy implants with pore sizes among 500, 640, and 800μm; however, less bone ingrowth was observed with the 1000μm pore size. These results indicated Porous-Ti-alloy implants with pore size under 800μm provided biologically active and mechanically stable surface for implant fixation to bone, and had potential advantages for weight bearing orthopedic implants such as acetabular cups.

  17. Implantable self-reset CMOS image sensor and its application to hemodynamic response detection in living mouse brain

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Takahiro; Takehara, Hiroaki; Sunaga, Yoshinori; Haruta, Makito; Motoyama, Mayumi; Ohta, Yasumi; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Ohta, Jun

    2016-04-01

    A self-reset pixel of 15 × 15 µm2 with high signal-to-noise ratio (effective peak SNR ≃64 dB) for an implantable image sensor has been developed for intrinsic signal detection arising from hemodynamic responses in a living mouse brain. For detecting local conversion between oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) in brain tissues, an implantable imaging device was fabricated with our newly designed self-reset image sensor and orange light-emitting diodes (LEDs; λ = 605 nm). We demonstrated imaging of hemodynamic responses in the sensory cortical area accompanied by forelimb stimulation of a living mouse. The implantable imaging device for intrinsic signal detection is expected to be a powerful tool to measure brain activities in living animals used in behavioral analysis.

  18. Tachycardia detection in modern implantable cardioverter-defibrillators.

    PubMed

    Brüggemann, Thomas; Dahlke, Daniel; Chebbo, Amin; Neumann, Ilka

    2016-09-01

    Implantable cardioverter-defibrillators (ICD) have to reliably sense, detect, and treat malignant ventricular tachyarrhythmias. Inappropriate treatment of non life-threatening tachyarrhythmias should be avoided. This article outlines the functionality of ICDs developed and manufactured by BIOTRONIK. Proper sensing is achieved by an automatic sensitivity control which can be individually tailored to solve special under- and oversensing situations. The programming of detection zones for ventricular fibrillation (VF), ventricular tachycardia (VT), and zones to monitor other tachyarrhythmias is outlined. Dedicated single-chamber detection algorithms based on average heart rate, cycle length variability, sudden rate onset, and changes in QRS morphology as used in ICDs by BIOTRONIK are described in detail. Preconditions and confirmation algorithms for therapy deliveries as antitachycardia pacing (ATP) and high energy shocks are explained. Finally, a detailed description of the dual-chamber detection algorithm SMART is given. It comprises additional detection criteria as stability of atrial intervals, 1:1 conduction, atrial-ventricular (AV) multiplicity, AV trend, and AV regularity to differentiate between ventricular and supraventricular tachyarrhythmias.

  19. Synergistic effects of surface chemistry and topologic structure from modified microarc oxidation coatings on Ti implants for improving osseointegration.

    PubMed

    Zhou, Rui; Wei, Daqing; Cao, Jianyun; Feng, Wei; Cheng, Su; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

    2015-04-29

    Microarc oxidation (MAO) coating containing Ca, P, Si, and Na elements on a titanium (Ti) implant has been steam-hydrothermally treated and further mediated by post-heat treatment to overcome the compromised bone-implant integration. The bone regeneration, bone-implant contact, and biomechanical push-out force of the modified Ti implants are discussed thoroughly in this work. The best in vivo performances for the steam-hydrothermally treated one is attributed to the synergistic effects of surface chemistry and topologic structure. Through post-heat treatment, we can decouple the effects of surface chemistry and the nanoscale topologic structure easily. Attributed to the excellent in vivo performance of the surface-modified Ti implant, the steam-hydrothermal treatment could be a promising strategy to improve the osseointegration of the MAO coating covered Ti implant.

  20. Compositional and Structural Study of Gd Implanted ZnO Films

    SciTech Connect

    Murmu, Peter P.; Kennedy, John V.; Markwitz, Andreas; Ruck, Ben J.

    2009-07-23

    We report a compositional and structural study of ZnO films implanted with 30 keV Gd ions. The depth profile of the implanted ions, measured by Rutherford backscattering spectrometry, matches predictions of DYNAMIC-TRIM calculations. However, after annealing at temperatures above 550 deg. C the Gd ions are observed to migrate towards the bulk, and at the same time atomic force microscope images of the film surfaces show significant roughening. Raman spectroscopy shows that the annealed films have a reduced number of crystalline defects. The overall results are useful for developing an implantation-annealing regime to produce well characterized samples to investigate magnetism in the ZnO:Gd system.

  1. Compositional and Structural Study of Gd Implanted ZnO Films

    NASA Astrophysics Data System (ADS)

    Murmu, Peter P.; Kennedy, John V.; Markwitz, Andreas; Ruck, Ben J.

    2009-07-01

    We report a compositional and structural study of ZnO films implanted with 30 keV Gd ions. The depth profile of the implanted ions, measured by Rutherford backscattering spectrometry, matches predictions of DYNAMIC-TRIM calculations. However, after annealing at temperatures above 550° C the Gd ions are observed to migrate towards the bulk, and at the same time atomic force microscope images of the film surfaces show significant roughening. Raman spectroscopy shows that the annealed films have a reduced number of crystalline defects. The overall results are useful for developing an implantation-annealing regime to produce well characterized samples to investigate magnetism in the ZnO:Gd system.

  2. Structural and photoluminescence properties of Gd implanted ZnO single crystals

    NASA Astrophysics Data System (ADS)

    Murmu, P. P.; Mendelsberg, R. J.; Kennedy, J.; Carder, D. A.; Ruck, B. J.; Markwitz, A.; Reeves, R. J.; Malar, P.; Osipowicz, T.

    2011-08-01

    We present the structural and photoluminescence properties of 30 keV gadolinium implanted and subsequently annealed zinc oxide (ZnO) single crystals. Rutherford backscattering and channeling results reveal a low surface region defect density which was reduced further upon annealing. For low implantation fluence, around 85% of the Gd atoms are estimated to be in sites aligned with the ZnO lattice, while for higher fluences the Gd is largely disordered and likely forms precipitates. The Raman spectra of the implanted samples show defect-induced modes, which match the one-phonon density of states for the most heavily implanted samples. Annealing eliminates these features implying the removal of Gd-associated lattice disorder. Low temperature photoluminescence spectra revealed a red-shift in the defect emission, from green to orange/yellow, indicating the suppression of a deep level, which is thought to be due to oxygen vacancies. It is suggested that the orange/yellow emission is unmasked when the green emission is quenched by the presence of the implanted Gd atoms.

  3. Monopolar Detection Thresholds Predict Spatial Selectivity of Neural Excitation in Cochlear Implants: Implications for Speech Recognition

    PubMed Central

    2016-01-01

    The objectives of the study were to (1) investigate the potential of using monopolar psychophysical detection thresholds for estimating spatial selectivity of neural excitation with cochlear implants and to (2) examine the effect of site removal on speech recognition based on the threshold measure. Detection thresholds were measured in Cochlear Nucleus® device users using monopolar stimulation for pulse trains that were of (a) low rate and long duration, (b) high rate and short duration, and (c) high rate and long duration. Spatial selectivity of neural excitation was estimated by a forward-masking paradigm, where the probe threshold elevation in the presence of a forward masker was measured as a function of masker-probe separation. The strength of the correlation between the monopolar thresholds and the slopes of the masking patterns systematically reduced as neural response of the threshold stimulus involved interpulse interactions (refractoriness and sub-threshold adaptation), and spike-rate adaptation. Detection threshold for the low-rate stimulus most strongly correlated with the spread of forward masking patterns and the correlation reduced for long and high rate pulse trains. The low-rate thresholds were then measured for all electrodes across the array for each subject. Subsequently, speech recognition was tested with experimental maps that deactivated five stimulation sites with the highest thresholds and five randomly chosen ones. Performance with deactivating the high-threshold sites was better than performance with the subjects’ clinical map used every day with all electrodes active, in both quiet and background noise. Performance with random deactivation was on average poorer than that with the clinical map but the difference was not significant. These results suggested that the monopolar low-rate thresholds are related to the spatial neural excitation patterns in cochlear implant users and can be used to select sites for more optimal speech

  4. Evaluation of Cochlear Implant Candidates using a Non-linguistic Spectrotemporal Modulation Detection Test

    PubMed Central

    Choi, Ji Eun; Hong, Sung Hwa; Won, Jong Ho; Park, Hee-Sung; Cho, Young Sang; Chung, Won-Ho; Cho, Yang-Sun; Moon, Il Joon

    2016-01-01

    Adults who score 50% correct or less in open-set sentence recognition test under the best aided listening condition may be considered as candidates for cochlear implant (CI). However, the requirement for ‘the best aided listening condition’ needs significant time and clinical resources to ensure such condition. As speech signals are composed of dynamic spectral and temporal modulations, psychoacoustic sensitivity to the combinations of spectral and temporal modulation cues may be a strong predictor for aided speech recognition. In this study, we tested 27 adults with moderately severe to profound hearing loss to explore the possibility that a non-linguistic unaided spectrotemporal modulation (STM) detection test might be a viable option as a surrogate measure to evaluate CI candidacy. Our results showed that STM detection thresholds were significantly correlated with aided sentence recognition scores for the 27 hearing impaired listeners. The receiver operator characteristic (ROC) curve analysis demonstrated that the CI candidacy evaluation by both unaided STM detection test and the traditional best-aided sentence recognition test was fairly consistent. More specifically, our results demonstrated that the STM detection test using a low spectral and temporal modulation rate might provide an efficient process for CI candidacy evaluation. PMID:27731425

  5. The Structure of Sapphire Implanted with Carbon at Room Temperature and 1000 deg. C

    SciTech Connect

    Alves, E.; Marques, C.; Safran, G.; McHargue, Carl J.

    2009-03-10

    Carbon was implanted into sapphire at various temperatures as part of a study of the different defect structures produced by a series of light ions. Implantations were made with 150 keV ions to fluences of 1x10{sup 16} and 1x10{sup 17} ions/cm{sup 2} at room temperature (RT) and 1000 deg. C. The defect structures were characterized using Rutherford backscattering-channeling (RBS-C) and transmission electron microscopy (TEM). The RBS-C spectra indicated low residual disorder for RT implantation at 1x10{sup 16} C{sup +}/cm{sup 2}. The de-channeling approached the random value at 1x10{sup 17} C{sup +}/cm{sup 2} and the TEM examination revealed a buried amorphous layer containing embedded sapphire nanocrystals. Damaged layers containing planar defects generally aligned parallel to the surface surrounded this layer. The RBS-C spectra for the sample implanted at 1000 deg. C with 1x10{sup 17} C{sup +}/cm{sup 2} suggested a highly damaged but crystalline surface that was confirmed by TEM micrographs.

  6. Direct observation of enhanced emission sites in nitrogen implanted hybrid structured ultrananocrystalline diamond films

    SciTech Connect

    Panda, Kalpataru; Sundaravel, B.; Panigrahi, B. K.; Chen, Huang-Chin; Lin, I.-Nan

    2013-02-07

    A hybrid-structured ultrananocrystalline diamond (h-UNCD) film, synthesized on Si-substrates by a two-step microwave plasma enhanced chemical vapour deposition (MPECVD) process, contains duplex structure with large diamond aggregates evenly dispersed in a matrix of ultra-small grains ({approx}5 nm). The two-step plasma synthesized h-UNCD films exhibit superior electron field emission (EFE) properties than the one-step MPECVD deposited UNCD films. Nitrogen-ion implantation/post-annealing processes further improve the EFE properties of these films. Current imaging tunnelling spectroscopy in scanning tunnelling spectroscopy mode directly shows increased density of emission sites in N implanted/post-annealed h-UNCD films than as-prepared one. X-ray photoelectron spectroscopy measurements show increased sp{sup 2} phase content and C-N bonding fraction in N ion implanted/post-annealed films. Transmission electron microscopic analysis reveals that the N implantation/post-annealing processes induce the formation of defects in the diamond grains, which decreases the band gap and increases the density of states within the band gap of diamond. Moreover, the formation of nanographitic phase surrounding the small diamond grains enhanced the conductivity at the diamond grain boundaries. Both of the phenomena enhance the EFE properties.

  7. Detection of underground structures and tunnels

    SciTech Connect

    Mack, J.M.; Moses, R.W.; Kelly, R.E.; Flynn, E.R.; Kraus, R.H.; Cogbill, A.H.; Stolarczyk, L.G.

    1996-09-01

    This is the final report of a one year, Laboratory Directed Research and Development project at Los Alamos National Laboratory. There is a continuing need in the United States defense and drug interdiction for effective over, convert, and standoff means of detecting underground tunnels, structures, and objects. This project sought to begin an assessment of electromagnetic and gravitational gradient detection approaches to the detection of underground structures and tunnels.

  8. Temporal Fine Structure and Applications to Cochlear Implants

    ERIC Educational Resources Information Center

    Li, Xing

    2013-01-01

    Complex broadband sounds are decomposed by the auditory filters into a series of relatively narrowband signals, each of which conveys information about the sound by time-varying features. The slow changes in the overall amplitude constitute envelope, while the more rapid events, such as zero crossings, constitute temporal fine structure (TFS).…

  9. Probability of detection of internal voids in structural ceramics using microfocus radiography

    NASA Technical Reports Server (NTRS)

    Baaklini, G. Y.; Roth, D. J.

    1985-01-01

    The reliability of microfocus x-radiography for detecting subsurface voids in structural ceramic test specimens was statistically evaluated. The microfocus system was operated in the projection mode using low X-ray photon energies (20 keV) and a 10 micro m focal spot. The statistics were developed for implanted subsurface voids in green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously-obtained statistics for implanted surface voids in similar specimens. Problems associated with void implantation are discussed. Statistical results are given as probability-of-detection curves at a 95 percent confidence level for voids ranging in size from 20 to 528 micro m in diameter.

  10. LADAR for structural damage detection

    NASA Astrophysics Data System (ADS)

    Moosa, Adil G.; Fu, Gongkang

    1999-12-01

    LADAR here stands for laser radar, using laser reflectivity for measurement. This paper presents a new technique using LADAR for structure evaluation. It is experimentally investigated in the laboratory. With cooperation of the US Federal Highway Administration, a recently developed LADAR system was used to measure structural deformation. The data were then treated for reducing noise and used to derive multiple features for diagnosis. The results indicate a promising direction of nondestructive evaluation using LADAR.

  11. Impact of implantation geometry and fluence on structural properties of AlxGa1-xN implanted with thulium

    NASA Astrophysics Data System (ADS)

    Fialho, M.; Magalhães, S.; Chauvat, M. P.; Ruterana, P.; Lorenz, K.; Alves, E.

    2016-10-01

    AlxGa1-xN (x = 0.15 and 0.77) films, grown by halide vapor phase epitaxy, were implanted with 300 keV Tm ions. Implantation damage accumulation is investigated with Rutherford backscattering spectrometry/channeling (RBS/C), transmission electron microscopy (TEM), and high resolution X-ray diffraction (XRD). Distinct damage behavior for samples with different AlN contents was found. Surface nanocrystallization occurs for samples with x = 0.15, similar to implantation effects observed in GaN. Samples with x = 0.77 approach the behavior of AlN. In particular, surface nanocrystallization is suppressed and the depth range of the stacking fault network, typical for implanted III-nitrides, is decreased. The crystalline quality of the sample with x = 0.15 was investigated to compare random and channeled implantation, showing less concentration of damage but with a higher range for channeled implantation. Surprisingly, the strain field caused by the implantation reaches much deeper into the sample than the defect profiles measured by RBS/C and TEM. This is attributed to the fact that XRD is much more sensitive to low defect densities caused by ions which are channeled to deep regions of the sample.

  12. Acoustic temporal modulation detection and speech perception in cochlear implant listeners.

    PubMed

    Won, Jong Ho; Drennan, Ward R; Nie, Kaibao; Jameyson, Elyse M; Rubinstein, Jay T

    2011-07-01

    The goals of the present study were to measure acoustic temporal modulation transfer functions (TMTFs) in cochlear implant listeners and examine the relationship between modulation detection and speech recognition abilities. The effects of automatic gain control, presentation level and number of channels on modulation detection thresholds (MDTs) were examined using the listeners' clinical sound processor. The general form of the TMTF was low-pass, consistent with previous studies. The operation of automatic gain control had no effect on MDTs when the stimuli were presented at 65 dBA. MDTs were not dependent on the presentation levels (ranging from 50 to 75 dBA) nor on the number of channels. Significant correlations were found between MDTs and speech recognition scores. The rates of decay of the TMTFs were predictive of speech recognition abilities. Spectral-ripple discrimination was evaluated to examine the relationship between temporal and spectral envelope sensitivities. No correlations were found between the two measures, and 56% of the variance in speech recognition was predicted jointly by the two tasks. The present study suggests that temporal modulation detection measured with the sound processor can serve as a useful measure of the ability of clinical sound processing strategies to deliver clinically pertinent temporal information.

  13. Preservation of Rhythmic Clocking in Cochlear Implant Users: A Study of Isochronous Versus Anisochronous Beat Detection

    PubMed Central

    Kim, Irene; Yang, Eunice; Donnelly, Patrick J.; Limb, Charles J.

    2010-01-01

    The capacity for internal rhythmic clocking involves a relationship between perceived auditory input and subsequent cognitive processing by which isochronous auditory stimuli induce a temporal beat expectancy in a listener. Although rhythm perception has previously been examined in cochlear implant (CI) users through various tasks based primarily on rhythm pattern identification, such tasks may not have been sufficiently nuanced to detect defects in internal rhythmic clocking, which requires temporal integration on a scale of milliseconds. The present study investigated the preservation of such rhythmic clocking in CI participants through a task requiring detection of isochronicity in the final beat of a four-beat series presented at different tempos. Our results show that CI users performed comparably to normal hearing (NH) participants in all isochronous rhythm detection tasks but that professionally trained musicians (MUS) significantly outperformed both NH and CI participants. These results suggest that CI users have intact rhythm perception even on a temporally demanding task that requires tight preservation of timing differences between a series of auditory events. Also, these results suggest that musical training might improve rhythmic clocking in CI users beyond normal hearing levels, which may be useful in light of the deficits in spectral processing commonly observed in CI users. PMID:21109551

  14. Erbium ion implantation into diamond - measurement and modelling of the crystal structure.

    PubMed

    Cajzl, Jakub; Nekvindová, Pavla; Macková, Anna; Malinský, Petr; Sedmidubský, David; Hušák, Michal; Remeš, Zdeněk; Varga, Marián; Kromka, Alexander; Böttger, Roman; Oswald, Jiří

    2017-02-22

    Diamond is proposed as an extraordinary material usable in interdisciplinary fields, especially in optics and photonics. In this contribution we focus on the doping of diamond with erbium as an optically active centre. In the theoretical part of the study based on DFT simulations we have developed two Er-doped diamond structural models with 0 to 4 carbon vacancies in the vicinity of the Er atom and performed geometry optimizations by the calculation of cohesive energies and defect formation energies. The theoretical results showed an excellent agreement between the calculated and experimental cohesive energies for the parent diamond. The highest values of cohesive energies and the lowest values of defect formation energies were obtained for models with erbium in the substitutional carbon position with 1 or 3 vacancies in the vicinity of the erbium atom. From the geometry optimization the structural model with 1 vacancy had an octahedral symmetry whereas the model with 3 vacancies had a coordination of 10 forming a trigonal structure with a hexagonal ring. In the experimental part, erbium doped diamond crystal samples were prepared by ion implantation of Er(+) ions using ion implantation fluences ranging from 1 × 10(14) ions per cm(2) to 5 × 10(15) ions per cm(2). The experimental results revealed a high degree of diamond structural damage after the ion implantation process reaching up to 69% of disordered atoms in the samples. The prepared Er-doped diamond samples annealed at the temperatures of 400, 600 and 800 °C in a vacuum revealed clear luminescence, where the 〈110〉 cut sample has approximately 6-7 times higher luminescence intensity than the 〈001〉 cut sample with the same ion implantation fluence. The reported results are the first demonstration of the Er luminescence in the single crystal diamond structure for the near-infrared spectral region.

  15. Autonomous assembly of epithelial structures by subrenal implantation of dissociated embryonic inner-ear cells.

    PubMed

    Wang, Li; Zhang, Kaiqing; Zhu, Helen He; Gao, Wei-Qiang

    2015-05-27

    Microenvironment and cell-cell interactions play an important role during embryogenesis and are required for the stemness and differentiation of stem cells. The inner-ear sensory epithelium, containing hair cells and supporting cells, is derived from the stem cells within the otic vesicle at early embryonic stages. However, whether or not such microenvironment or cell-cell interactions within the embryonic otic tissue have the capacity to regulate the proliferation and differentiation of stem cells and to autonomously reassemble the cells into epithelial structures is unknown. Here, we report that on enzymatic digestion and dissociation to harvest all the single cells from 13.5-day-old rat embryonic (E13.5) inner-ear tissue as well as on implantation of these cells under renal capsules; the dissociated cells are able to reassemble themselves to form epithelial structures as early as 7 days after implantation. By 25 days after implantation, more mature epithelial structures are formed. Immunostaining with cell-type-specific markers reveals that hair cells and supporting cells are not only formed, but are also well aligned with the hair cells located in the apical layer surrounded by the supporting cells. These findings suggest that microenvironment and cell-cell interactions within the embryonic inner-ear tissue have the autonomous signals to induce the formation of sensory epithelial structures. This method may also provide a useful system to study the potential of stem cells to differentiate into hair cells in vivo.

  16. Electrically detected magnetic resonance of ion-implantation damage centers in silicon large-scale integrated circuits

    NASA Astrophysics Data System (ADS)

    Umeda, T.; Mochizuki, Y.; Okonogi, K.; Hamada, K.

    2003-12-01

    We used electrically detected magnetic resonance to study the microscopic structure of ion-implantation-induced point defects that remained in large-scale Si integrated circuits (Si LSIs). Two types of defects were detected in the source/drain (n+-type) region of 0.25-μm-gate-length n-channel metal oxide semiconductor field-effect-transistors on LSIs: (i) a spin-1 Si dangling-bond (DB) pair in divacancy-oxygen complexes (DB-DB distance, R≈0.6 nm); and (ii) a series of larger Si vacancies involving distant Si DBs (R⩾1.4 nm). These vacancy-type defects were much more thermally stable in Si LSIs than those in bulk Si crystals. We suggested two physical mechanisms for this enhanced stability: internal mechanical stress and oxygen incorporation in the active regions of LSIs. After examining the relationship between the defects and current-voltage characteristics, we concluded that these defects are distributed in the near-surface n+-type region close to the gate and that they are the source of the gate-induced drain leakage currents.

  17. Structural and magnetic studies of Co and Fe implanted BaTiO 3 crystals

    NASA Astrophysics Data System (ADS)

    Khalitov, N. I.; Khaibullin, R. I.; Valeev, V. F.; Dulov, E. N.; Ivoilov, N. G.; Tagirov, L. R.; Kazan, S.; Şale, A. G.; Mikailzade, F. A.

    2012-02-01

    Singly-charged Co or Fe ions with energy 40 keV were implanted into single-domain ferroelectric plates of barium titanate (BaTiO 3) with high fluences in the range of (0.5-1.5) × 10 17 ion/cm 2 to create new magnetoelectric materials. Scanning electron microscopy (SEM) and conversion electron Mössbauer spectroscopy (CEMS) studies have shown that high-fluence implantation with 3d-ions results in formation of cobalt or iron nanoparticles in the near-surface irradiated region of perovskite-type crystal. With increasing the fluence, the both Co- and Fe-implanted BaTiO 3 samples reveal at first superparamagnetic, and then ferromagnetic properties at room temperature. Analysis of magnetic hysteresis loops measured in the in-plane and out-of-plane geometries have shown that ferromagnetic BaTiO 3:Co(Fe) nanocomposite layers display the "easy plane" magnetic anisotropy similar to that found for thin granular magnetic films. Together with our previous observation of the magnetoelectric effect in these samples, our structural and magnetic investigations show that the ion implantation is suitable to synthesize the desired magnetoelectric nanocomposite materials.

  18. Laser annealing of Al implanted silicon carbide: Structural and optical characterization

    NASA Astrophysics Data System (ADS)

    Boutopoulos, C.; Terzis, P.; Zergioti, I.; Kontos, A. G.; Zekentes, K.; Giannakopoulos, K.; Raptis, Y. S.

    2007-07-01

    Pulsed-laser-based methods have been applied for post-implant annealing of p-type Al-doped 4H-SiC wafers in order to restore the crystal structure and to electrically activate the doping species. The annealing was performed with the third harmonic (355 nm) of a Nd:YAG laser at 4 ns pulse duration. The epilayers were characterized by micro-Raman spectroscopy under surface and cross-sectional backscattering. Changes in the phonon mode-intensity were related to the laser annealing induced recrystallization of the implanted material. The results were compared with changes in the infrared reflectivity across the Reststrahlen band. Transmission electron microscopy analysis showed the formation of columnar polycrystalline structure after the laser annealing process.

  19. EXAFS study of the structural properties of In and In + C implanted Ge

    NASA Astrophysics Data System (ADS)

    Feng, R.; Kremer, F.; Sprouster, D. J.; Mirzaei, S.; Decoster, S.; Glover, C. J.; Medling, S. A.; Russo, S. P.; Ridgway, M. C.

    2016-05-01

    The structural configurations of In implanted Ge have been studied via x-ray absorption spectroscopy with and without the codoping of C. In the case of In singly implanted Ge, while the In atoms occupy an substitutional site in Ge (InGe4) at low In concentration (≤ 2 at. %), they precipitate into a metallic phase (In metal) and form complexes composed of one vacancy and three Ge atoms (InVGe3) at concentration ≥ 0.6 at. %. This behaviour can be suppressed by the addition of C leading to In-C pairing to form InCGe3 complexes. This cluster enables In atoms to recover a four-fold coordinated structure and has the potential to improve the electrical activation of In atoms in Ge.

  20. A new microtomographic technique for non-invasive evaluation of the bone structure around implants.

    PubMed

    Sennerby, L; Wennerberg, A; Pasop, F

    2001-02-01

    A new X-ray microtomographic technique for non-invasive assessment of the structure of bone surrounding implants was tested. Three titanium microimplants retrieved directly (n = 2) or 6 months (n = 1) after insertion in 3 patients were used as test samples. Two samples were used dry and one was embedded in plastic resin prior to microtomography. The technique provided high-resolution consecutive cross-sectional X-ray images of the specimens with a slice-to-slice distance of 4.4 to 11.0 microns. The pictures could be imported into an image analysing software with which semiautomatic quantitative measurement of the bone area and three-dimensional images of the specimens could be made. It is suggested that the technique may be used for non-invasive assessment of the bone structure around implants. Further studies are needed to evaluate the accuracy of the technique, for instance by comparing tomographic sections with histologic ones.

  1. Investigation of the structural properties of ferromagnetic Mn-implanted Si

    NASA Astrophysics Data System (ADS)

    Bolduc, M.; Awo-Affouda, C.; Stollenwerk, A.; Huang, M. B.; Ramos, F.; LaBella, V. P.

    2006-01-01

    The structural properties of Si crystals that were made ferromagnetic through Mn-ion implantation are studied. 300-keV Mn+ ions were implanted at 350 °C at doses of 1-10 × 1015 cm-2 reaching peak concentrations of 0.1-0.8 at.%. Ferromagnetic hysteresis loops were obtained using a SQUID magnetometer at temperature of 300 K, yielding a saturation magnetization of 0.2 emu/g after annealing at 800 °C for 5 min. The Curie temperature for all samples was found to be greater than 400 K. After annealing, a pronounced redistribution of Mn is observed in the depth profiles as measured through SIMS profiling. The quality of the resulting crystal structure has been investigated by RBS in the channeling mode.

  2. Shaping scaffold structures in rapid manufacturing implants: a modeling approach toward mechano-biologically optimized configurations for large bone defect.

    PubMed

    Razi, Hajar; Checa, Sara; Schaser, Klaus-Dieter; Duda, Georg N

    2012-10-01

    Large segmental bone defects remain a clinical challenge. Titanium lattice-structured implants in combination with laser sintering technology promises to be an alternative to bone grafting in the treatment of critical sized bone defects. Laser sintering allows the rapid manufacturing of patient specific 3D-structured scaffolds with highly interconnected macroporous networks and tunable mechanical properties. Unknown remains to what degree the mechanical properties of these implants could be tuned, without leading to mechanical failure but still providing adequate mechanical stimuli for tissue ingrowth. The aim of this study was to evaluate various implant designs for their mechanical potential towards (a) optimized safety against stress failure and (b) optimal intrastructural straining for bone ingrowth. Finite element analyses of several lattice-structured configurations were performed. Results illustrated a strong influence of the configuration on the load carrying capacity of the constructs. The likelihood of mechanical failure was predicted to be highly dependent on structure configuration with little influence of implant porosity. Increasing porosity did not result in an increase in the implant intrastructural straining in all configurations; however, the lattice configuration was the determinant factor for implant load transfer capacity. This study provides a framework for the design of effective implants with open pore structures to ensure mechanical stability as well as promote mechanical stimulation and encourage in vivo osseointegration.

  3. Osteoinduction of porous Ti implants with a channel structure fabricated by selective laser melting.

    PubMed

    Fukuda, A; Takemoto, M; Saito, T; Fujibayashi, S; Neo, M; Pattanayak, Deepak K; Matsushita, T; Sasaki, K; Nishida, N; Kokubo, T; Nakamura, T

    2011-05-01

    Many studies have shown that certain biomaterials with specific porous structures can induce bone formation in non-osseous sites without the need for osteoinductive biomolecules, however, the mechanisms responsible for this phenomenon (intrinsic osteoinduction of biomaterials) remain unclear. In particular, to our knowledge the type of pore structure suitable for osteoinduction has not been reported in detail. In the present study we investigated the effects of interconnective pore size on osteoinductivity and the bone formation processes during osteoinduction. Selective laser melting was employed to fabricate porous Ti implants (diameter 3.3mm, length 15 mm) with a channel structure comprising four longitudinal square channels, representing pores, of different diagonal widths, 500, 600, 900, and 1200 μm (termed p500, p600, p900, and p1200, respectively). These were then subjected to chemical and heat treatments to induce bioactivity. Significant osteoinduction was observed in p500 and p600, with the highest observed osteoinduction occurring at 5mm from the end of the implants. A distance of 5mm probably provides a favorable balance between blood circulation and fluid movement. Thus, the simple architecture of the implants allowed effective investigation of the influence of the interconnective pore size on osteoinduction, as well as the relationship between bone quantity and its location for different pore sizes.

  4. Three-Dimensional High-Frequency Ultrasonography for Early Detection and Characterization of Embryo Implantation Site Development in the Mouse

    PubMed Central

    Peavey, Mary C.; Reynolds, Corey L.; Szwarc, Maria M.; Gibbons, William E.; Valdes, Cecilia T.

    2017-01-01

    Ultrasonography is a powerful tool to non-invasively monitor in real time the development of the human fetus in utero. Although genetically engineered mice have served as valuable in vivo models to study both embryo implantation and pregnancy progression, such studies usually require sacrifice of parous mice for subsequent phenotypic analysis. To address this issue, we used three-dimensional (3-D) reconstruction in silico of high-frequency ultrasound (HFUS) imaging data for early detection and characterization of murine embryo implantation sites and their development in utero. With HFUS imaging followed by 3-D reconstruction, we were able to precisely quantify embryo implantation site number and embryonic developmental progression in pregnant C57BL6J/129S mice from as early as 5.5 days post coitus (d.p.c.) through to 9.5 d.p.c. using a VisualSonics Vevo 2100 (MS550S) transducer. In addition to measurements of implantation site number, location, volume and spacing, embryo viability via cardiac activity monitoring was also achieved. A total of 12 dams were imaged with HFUS with approximately 100 embryos examined per embryonic day. For the post-implantation period (5.5 to 8.5 d.p.c.), 3-D reconstruction of the gravid uterus in mesh or solid overlay format enabled visual representation in silico of implantation site location, number, spacing distances, and site volume within each uterine horn. Therefore, this short technical report describes the feasibility of using 3-D HFUS imaging for early detection and analysis of post-implantation events in the pregnant mouse with the ability to longitudinally monitor the development of these early pregnancy events in a non-invasive manner. As genetically engineered mice continue to be used to characterize female reproductive phenotypes, we believe this reliable and non-invasive method to detect, quantify, and characterize early implantation events will prove to be an invaluable investigative tool for the study of female

  5. Damage detection in a framed building structure

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Pines, Darryll J.

    1999-05-01

    Interest in infrastructure health monitoring and damage detection has received a considerable amount of attention over the past two decades. Previous approaches to non- destructive evaluation of structures to assess their integrity typically involved some form of human interaction. Recent advances in smart materials and structures technology has resulted in a renewed interest in developing advanced self-diagnostic capability for assessing the state of a structure without any human interaction. The goal is to reduce human interaction while at the same time monitor the integrity of a structure. With this goal in mind, many researchers have made significant strides in developing damage detection methods for civil structures based on traditional modal analysis techniques. These techniques are of the well suited for structures which can be modeled by discrete lumped-parameter elements where the presence of damage leads to some low frequency change in the global behavior of the system. On the other hand small defects such as cracks are obscured by modal approaches since such phenomena are high frequency effects not easily discovered by examining changes in modal mass, stiffness or damping parameters. This is because at high frequency modal structural models are subject to uncertainty. This uncertainty can be reduced by increasing the spatial order of discrete model, however, this increases the computational effort of modal-based damage detection schemes. On the other hand, wave propagation models of structures have higher spatial order model fidelity. Thus, they are better suited for detecting and global wave propagation models to detect damage in a discrete model of a farmed building structure, consisting of discrete structural elements. Simulated damage in the form of mass or stiffness loss is used to determine the effect on the resonant and incident wave response of the structure. Examination of the incident transfer function response of the structure reveals the

  6. Predictors of Arrhythmic Events Detected by Implantable Loop Recorders in Renal Transplant Candidates

    PubMed Central

    Silva, Rodrigo Tavares; Martinelli Filho, Martino; Peixoto, Giselle de Lima; de Lima, José Jayme Galvão; de Siqueira, Sérgio Freitas; Costa, Roberto; Gowdak, Luís Henrique Wolff; de Paula, Flávio Jota; Kalil Filho, Roberto; Ramires, José Antônio Franchini

    2015-01-01

    Background The recording of arrhythmic events (AE) in renal transplant candidates (RTCs) undergoing dialysis is limited by conventional electrocardiography. However, continuous cardiac rhythm monitoring seems to be more appropriate due to automatic detection of arrhythmia, but this method has not been used. Objective We aimed to investigate the incidence and predictors of AE in RTCs using an implantable loop recorder (ILR). Methods A prospective observational study conducted from June 2009 to January 2011 included 100 consecutive ambulatory RTCs who underwent ILR and were followed-up for at least 1 year. Multivariate logistic regression was applied to define predictors of AE. Results During a mean follow-up of 424 ± 127 days, AE could be detected in 98% of patients, and 92% had more than one type of arrhythmia, with most considered potentially not serious. Sustained atrial tachycardia and atrial fibrillation occurred in 7% and 13% of patients, respectively, and bradyarrhythmia and non-sustained or sustained ventricular tachycardia (VT) occurred in 25% and 57%, respectively. There were 18 deaths, of which 7 were sudden cardiac events: 3 bradyarrhythmias, 1 ventricular fibrillation, 1 myocardial infarction, and 2 undetermined. The presence of a long QTc (odds ratio [OR] = 7.28; 95% confidence interval [CI], 2.01–26.35; p = 0.002), and the duration of the PR interval (OR = 1.05; 95% CI, 1.02–1.08; p < 0.001) were independently associated with bradyarrhythmias. Left ventricular dilatation (LVD) was independently associated with non-sustained VT (OR = 2.83; 95% CI, 1.01–7.96; p = 0.041). Conclusions In medium-term follow-up of RTCs, ILR helped detect a high incidence of AE, most of which did not have clinical relevance. The PR interval and presence of long QTc were predictive of bradyarrhythmias, whereas LVD was predictive of non-sustained VT. PMID:26351983

  7. The structural, chemical, and electrical properties of He-implantation-induced nanocavities in silicon

    SciTech Connect

    Seager, C.H.; Myers, S.M.; Follstaedt, D.M.; Stein, H.J.; Wampler, W.R.

    1993-11-01

    Si implanted with He to doses of about 2 {times} 10{sup 16}cm{sup {minus}2} and greater and annealed at high temperatures develops a layer of internal nanocavities near the end of the He range. Above an annealing temperature of 700 C, all the implanted He escapes from these implanted samples, and the resultant internal cavity surfaces can be shown to possess a high density of chemically reactive Si dangling orbitals. These structures, in addition to possessing a variety of interesting electronic properties, have recently been shown to hold great promise as getters for removing undesirable impurities from the silicon matrix. Here the authors describe some of the structural features of these nanocavities and studies which have been used to accurately determine the binding energy of H and Cu to Si atoms at the cavity walls. Recently, they have also demonstrated that these nanocavities capture large densities of majority carriers in n- and p-type silicon. These electrical measurements have demonstrated that the nanocavity electronic states possess both acceptor and donor levels in the Si forbidden gap. The approximate location of these levels has been determined by a variety of different types of capacitance transient spectroscopy.

  8. Critical issues in the formation of quantum computer test structures by ion implantation

    SciTech Connect

    Schenkel, T.; Lo, C. C.; Weis, C. D.; Schuh, A.; Persaud, A.; Bokor, J.

    2009-04-06

    The formation of quantum computer test structures in silicon by ion implantation enables the characterization of spin readout mechanisms with ensembles of dopant atoms and the development of single atom devices. We briefly review recent results in the characterization of spin dependent transport and single ion doping and then discuss the diffusion and segregation behaviour of phosphorus, antimony and bismuth ions from low fluence, low energy implantations as characterized through depth profiling by secondary ion mass spectrometry (SIMS). Both phosphorus and bismuth are found to segregate to the SiO2/Si interface during activation anneals, while antimony diffusion is found to be minimal. An effect of the ion charge state on the range of antimony ions, 121Sb25+, in SiO2/Si is also discussed.

  9. High Structural Stability of Textile Implants Prevents Pore Collapse and Preserves Effective Porosity at Strain

    PubMed Central

    Klinge, Uwe; Otto, Jens; Mühl, Thomas

    2015-01-01

    Reinforcement of tissues by use of textiles is encouraged by the reduced rate of recurrent tissue dehiscence but for the price of an inflammatory and fibrotic tissue reaction to the implant. The latter mainly is affected by the size of the pores, whereas only sufficiently large pores are effective in preventing a complete scar entrapment. Comparing two different sling implants (TVT and SIS), which are used for the treatment of urinary incontinence, we can demonstrate that the measurement of the effective porosity reveals considerable differences in the textile construction. Furthermore the changes of porosity after application of a tensile load can indicate a structural instability, favouring pore collapse at stress and questioning the use for purposes that are not “tension-free.” PMID:25973427

  10. Extended contrast detection on fluoroscopy and angiography for image-guided trans-catheter aortic valve implantations (TAVI)

    NASA Astrophysics Data System (ADS)

    Liu, Yinxiao; Liao, Rui; Lv, Xudong

    2012-02-01

    Navigation and deployment of the prosthetic valve during trans-catheter aortic valve implantation (TAVI) can be greatly facilitated with 3-D models showing detailed anatomical structures. Fast and robust automatic contrast detection at the aortic root on X-ray images is indispensable for automatically triggering a 2-D/3-D registration to align the 3-D model. Previously, we have proposed an automatic method for contrast detection at the aortic root on fluoroscopic and angiographic sequences [4]. In this paper, we extend that algorithm in several ways, making it more robust to handle more general and difficult cases. Specifically, the histogram likelihood ratio test is multiplied with the histogram portion computation to handle faint contrast cases. Histogram mapping corrects sudden changes in the global brightness, thus avoiding potential false positives. Respiration and heart beating check further reduces the false positive rate. In addition, a probe mask is introduced to enhance the contrast feature curve when the dark ultrasound probe partially occludes the aortic root. Lastly, a semi-global registration method for aligning the aorta shape model is implemented to improve the robustness of the algorithm with respect to the selection of region of interest (ROI) containing the aorta. The extended algorithm was evaluated on 100 sequences, and improved the detection accuracy from 94% to 100%, compared to the original method. Also, the robustness of the extended algorithm was tested with 20 different shifts of the ROI, and the error rate was as low as 0.2%, in comparison to 6.6% for the original method.

  11. Structural Damage Detection Using Virtual Passive Controllers

    NASA Technical Reports Server (NTRS)

    Lew, Jiann-Shiun; Juang, Jer-Nan

    2001-01-01

    This paper presents novel approaches for structural damage detection which uses the virtual passive controllers attached to structures, where passive controllers are energy dissipative devices and thus guarantee the closed-loop stability. The use of the identified parameters of various closed-loop systems can solve the problem that reliable identified parameters, such as natural frequencies of the open-loop system may not provide enough information for damage detection. Only a small number of sensors are required for the proposed approaches. The identified natural frequencies, which are generally much less sensitive to noise and more reliable than the identified natural frequencies, are used for damage detection. Two damage detection techniques are presented. One technique is based on the structures with direct output feedback controllers while the other technique uses the second-order dynamic feedback controllers. A least-squares technique, which is based on the sensitivity of natural frequencies to damage variables, is used for accurately identifying the damage variables.

  12. Directional structures detection using steerable pyramid

    NASA Astrophysics Data System (ADS)

    Denis, Florence; Baskurt, Atilla M.

    2003-04-01

    The object of the work described in this paper concerns directional structures detection for particular aspects of inspection, such as scratches and marbling defect detection in leather images. Because of the very specific geometry of these structures, we intend to apply a multiscale and orientation-shiftable method. Scratches and marbling have various shapes and sizes. Multiscale approaches using oriented filters have proved to be efficient to detect such curvilinear patterns. We first use the information given by the increase of gray levels in the image to locate suspicious regions. The detection is then based on steerable filters, which can be steered to any orientation fixed by the user, and are synthesized using a limited number of basic filters. These filters are used in a recursive multi-scale transform: the steerable pyramid. Then, the curvilinear structures are extracted from the directional images at different scales.

  13. Effects of nickel ions implantation and subsequent thermal annealing on structural and magnetic properties of titanium dioxide

    NASA Astrophysics Data System (ADS)

    Vakhitov, I. R.; Lyadov, N. M.; Valeev, V. F.; Nuzhdin, V. I.; Tagirov, L. R.; Khaibullin, R. I.

    2014-12-01

    Wide bandgap semiconducting rutile (TiO2) doped with 3d-elements is a promising material for spintronic applications. In our work a composite material of TiO2:Ni has been formed by using implantation of Ni+ ions into single-crystalline (100)- and (001)- plates of TiO2. Sub-micron magnetic layers of TiO2 containing nickel dopant have been obtained at high implantation fluence of 1×1017 ion/cm2. A part of the implanted samples was then annealed in vacuum at different temperatures Tann = 450-1200 K for 30 min. The influence of the implantation fluence, crystalline orientation, as well as subsequent annealing on the structural and magnetic properties of the nickel-implanted TiO2 have been investigated by using X-ray photoelectron spectroscopy, scanning electron microscopy and coil magnetometry techniques.

  14. Detection of changes in DNA methylation induced by low-energy ion implantation in Arabidopsis thaliana.

    PubMed

    Yu, Haichan; Zhao, Jin; Xu, Jing; Li, Xiaoqu; Zhang, Fengshou; Wang, Yugang; Carr, Christopher; Zhang, Jun; Zhang, Genfa

    2011-05-01

    This study evaluated changes in DNA methylation in Arabidopsis thaliana plants grown from seeds implanted with low-energy N(+) and Ar(+) ions. Methylation-sensitive amplified polymorphism (MSAP) testing revealed altered DNA methylation patterns after ion implantation at doses of 1 × 10(14) to 1 × 10(16) ions/cm(2). Comparison of the MSAP electrophoretic profiles revealed nine types of polymorphisms in ion-implanted seedlings relative to control seedlings, among which four represented methylation events, three represented demethylation events, and the methylation status of two was uncertain. The diversity of plant DNA methylation was increased by low-energy ion implantation. At the same time, total genomic DNA methylation levels at CCGG sites were unchanged by ion implantation. Moreover, a comparison of polymorphisms seen in N(+) ion-implanted, Ar(+) ion-implanted, and control DNA demonstrated that the species of incident ion influenced the resulting DNA methylation pattern. Sequencing of eight isolated fragments that showed different changing patterns in implanted plants allowed their mapping onto variable regions on one or more of the five Arabidopsis chromosomes; these segments included protein-coding genes, transposon and repeat DNA sequence. A further sodium bisulfite sequencing of three fragments also displayed alterations in methylation among either different types or doses of incident ions. Possible causes for the changes in methylation are discussed.

  15. Impact of nucleation of carbonaceous clusters on structural, electrical and optical properties of Cr+-implanted PMMA

    NASA Astrophysics Data System (ADS)

    Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Naab, Fabian; Toader, Ovidiu; Mahmood, Arshad; Aziz, Uzma

    2016-09-01

    Specimens of polymethylmethacrylate (PMMA) have been implanted with 400 keV Cr+ ions at different ion fluences ranging from 5 × 1013 to 5 × 1015 ions/cm2. The possible chemical reactions involved in the nucleation of conjugated carbonaceous clusters in implanted PMMA are discussed. Furthermore, impact of formation of carbonaceous clusters on structural, optical, electrical and morphological properties of implanted PMMA has been examined. The structural modifications in implanted PMMA are observed by Raman spectroscopy. The variation in optical band gap and Urbach energy is measured using UV-visible spectroscopic analysis. The effects of Cr+ ion implantation on electrical and morphological properties are investigated by four-probe apparatus and atomic force microscopy, respectively. The Raman spectroscopic analysis confirmed the formation of carbonaceous clusters with the transformation of implanted layer of PMMA into amorphous carbon. Simultaneously, the optical band gap of implanted PMMA has reduced from 3.13 to 0.85 eV. The increase in Urbach energy favors the decline in band gap together with the structural modification in implanted PMMA. As a result of Cr+ ion implantation, the electrical conductivity of PMMA has improved from 2.14 ± 0.06 × 10-10 S/cm (pristine) to 7.20 ± 0.36 × 10-6 S/cm. The AFM images revealed a decrease in surface roughness with an increment in ion fluence up to 5 × 1014 ions/cm2. The modification in the electrical, optical and structural properties makes the PMMA a promising candidate for its future utilization, as a semiconducting and optically active material, in various fields like plastic electronics and optoelectronic devices.

  16. Three Dimensional Finite Element Analysis to Detect Stress Distribution in Spiral Implants and Surrounding Bone

    PubMed Central

    Danza, Matteo; Palmieri, Annalisa; Farinella, Francesca; Brunelli, Giorgio; Carinci, Francesco; Girardi, Ambra; Spinelli, Giuseppe

    2009-01-01

    Background: The aim of research was to study spiral family implant by finite element analysis (FEA) inserted in different bone qualities connected with abutments of different angulations. Methods: The biomechanical behaviour of 4.2 × 13 mm dental implants, connecting screw, straight and 15° and 25° angulated abutments subjected to static loads, in contact with high and poor bone qualities was evaluated by FEA. Results: The lowest stress value was found in the system composed by implants and straight abut-ments loaded with a vertical force, while the highest stress value was found in implants with 15° angulated abutment loaded with an angulated force. In addition, we found the lower the bone quality, the higher the distribution of the stress within the bone. Conclusion: Spiral family implants can be used successfully in low bone quality but applying a straight force is recommended. PMID:21528032

  17. Detecting Structural Failures Via Acoustic Impulse Responses

    NASA Technical Reports Server (NTRS)

    Bayard, David S.; Joshi, Sanjay S.

    1995-01-01

    Advanced method of acoustic pulse reflectivity testing developed for use in determining sizes and locations of failures within structures. Used to detect breaks in electrical transmission lines, detect faults in optical fibers, and determine mechanical properties of materials. In method, structure vibrationally excited with acoustic pulse (a "ping") at one location and acoustic response measured at same or different location. Measured acoustic response digitized, then processed by finite-impulse-response (FIR) filtering algorithm unique to method and based on acoustic-wave-propagation and -reflection properties of structure. Offers several advantages: does not require training, does not require prior knowledge of mathematical model of acoustic response of structure, enables detection and localization of multiple failures, and yields data on extent of damage at each location.

  18. A Structural Equation Modeling Approach to Examining Factors Influencing Outcomes with Cochlear Implant in Mandarin-Speaking Children

    PubMed Central

    Chen, Yuan; Wong, Lena L. N.; Zhu, Shufeng; Xi, Xin

    2015-01-01

    Objective To examine the direct and indirect effects of demographical factors on speech perception and vocabulary outcomes of Mandarin-speaking children with cochlear implants (CIs). Methods 115 participants implanted before the age of 5 and who had used CI before 1 to 3 years were evaluated using a battery of speech perception and vocabulary tests. Structural equation modeling was used to test the hypotheses proposed. Results Early implantation significantly contributed to speech perception outcomes while having undergone a hearing aid trial (HAT) before implantation, maternal educational level (MEL), and having undergone universal newborn hearing screening (UNHS) before implantation had indirect effects on speech perception outcomes via their effects on age at implantation. In addition, both age at implantation and MEL had direct and indirect effects on vocabulary skills, while UNHS and HAT had indirect effects on vocabulary outcomes via their effects on age at implantation. Conclusion A number of factors had indirect and direct effects on speech perception and vocabulary outcomes in Mandarin-speaking children with CIs and these factors were not necessarily identical to those reported among their English-speaking counterparts. PMID:26348360

  19. Optimization of an acoustic telemetry array for detecting transmitter-implanted fish

    USGS Publications Warehouse

    Clements, S.; Jepsen, D.; Karnowski, M.; Schreck, C.B.

    2005-01-01

    The development of miniature acoustic transmitters and economical, robust automated receivers has enabled researchers to study the movement patterns and survival of teleosts in estuarine and ocean environments, including many species and age-classes that were previously considered too small for implantation. During 2001-2003, we optimized a receiver mooring system to minimize gear and data loss in areas where current action or wave action and acoustic noise are high. In addition, we conducted extensive tests to determine (1) the performance of a transmitter and receiver (Vemco, Ltd.) that are widely used, particularly in North America and Europe and (2) the optimal placement of receivers for recording the passage of fish past a point in a linear-flow environment. Our results suggest that in most locations the mooring system performs well with little loss of data; however, boat traffic remains a concern due to entanglement with the mooring system. We also found that the reception efficiency of the receivers depends largely on the method and location of deployment. In many cases, we observed a range of 0-100% reception efficiency (the percentage of known transmissions that are detected while the receiver is within range of the transmitter) when using a conventional method of mooring. The efficiency was improved by removal of the mounting bar and obstructions from the mooring line. ?? Copyright by the American Fisheries Society 2005.

  20. Porous Tantalum Structures for Bone Implants: Fabrication, Mechanical and In vitro Biological Properties

    PubMed Central

    Balla, Vamsi Krishna; Bodhak, Subhadip; Bose, Susmita; Bandyopadhyay, Amit

    2010-01-01

    Relatively high cost of manufacturing and inability to produce modular all tantalum implants has limited its widespread acceptance, in spite of its excellent in vitro and in vivo biocompatibility. In this article, we report how to process Ta to create net shape porous structures with varying porosity using Laser Engineered Net Shaping (LENS™) for the first time. Porous Ta samples with relative densities between 45 to 73% have been successfully fabricated and characterized for their mechanical properties. In vitro cell materials interactions, using human osteoblast cell line hFOB, have been accessed on these porous Ta structures and compared with porous Ti control samples. The results show that the Young’s modulus of porous Ta can be tailored between 1.5 to 20 GPa by changing the pore volume fraction between 27 and 55%. In vitro biocompatibility in terms of MTT assay and immunochemistry study showed excellent cellular adherence, growth and differentitation with abundant extracellular matrix formation on porous Ta structures compared to porous Ti control. These results indicate that porous Ta structures can promote enhanced/early biological fixation. The enhanced in vitro cell-materials interactions on porous Ta surface are attributed to chemistry and its high wettability and surface energy relative to porous Ti. Our results show that these laser processed porous Ta structures can find numerous applications, particularly among older patients, for metallic implants because of their excellent bioactivity. PMID:20132912

  1. Perception of Interaural Phase Differences With Envelope and Fine Structure Coding Strategies in Bilateral Cochlear Implant Users

    PubMed Central

    Arndt, Susan; Aschendorff, Antje; Laszig, Roland; Wesarg, Thomas

    2016-01-01

    The ability to detect a target signal masked by noise is improved in normal-hearing listeners when interaural phase differences (IPDs) between the ear signals exist either in the masker or in the signal. To improve binaural hearing in bilaterally implanted cochlear implant (BiCI) users, a coding strategy providing the best possible access to IPD is highly desirable. In this study, we compared two coding strategies in BiCI users provided with CI systems from MED-EL (Innsbruck, Austria). The CI systems were bilaterally programmed either with the fine structure processing strategy FS4 or with the constant rate strategy high definition continuous interleaved sampling (HDCIS). Familiarization periods between 6 and 12 weeks were considered. The effect of IPD was measured in two types of experiments: (a) IPD detection thresholds with tonal signals addressing mainly one apical interaural electrode pair and (b) with speech in noise in terms of binaural speech intelligibility level differences (BILD) addressing multiple electrodes bilaterally. The results in (a) showed improved IPD detection thresholds with FS4 compared with HDCIS in four out of the seven BiCI users. In contrast, 12 BiCI users in (b) showed similar BILD with FS4 (0.6 ± 1.9 dB) and HDCIS (0.5 ± 2.0 dB). However, no correlation between results in (a) and (b) both obtained with FS4 was found. In conclusion, the degree of IPD sensitivity determined on an apical interaural electrode pair was not an indicator for BILD based on bilateral multielectrode stimulation. PMID:27659487

  2. Silicate antibodies in women with silicone breast implants: development of an assay for detection of humoral immunity.

    PubMed Central

    Shen, G Q; Ojo-Amaize, E A; Agopian, M S; Peter, J B

    1996-01-01

    Silicon, in the form of sodium silicate (Na2SiO3), adsorbed onto bovine serum albumin (BSA)-precoated plates served as the solid-phase antigen in an enzyme immunoassay to detect silicate-reactive antibodies in the plasma of 40 symptomatic women with silicone breast implants, 91 asymptomatic women with silicone breast implants, 50 healthy control women, and 52 women with rheumatic diseases and without silicone breast implants, Silicate-reactive antibodies of immunoglobulin G (IgG) or IgM isotypes were detected in the plasma of 30% (12 of 40) of the symptomatic women with silicone breast implants; 9% (8 of 91) of the asymptomatic women with silicone breast implants; 5% (1 of 20) of the women without implants who had systemic lupus erythematosus; and 0% (0 of 32) of the women without implants who had either Sjögren syndrome, scleroderma, or rheumatoid arthritis. Only 2% (1 of 50) of the sera from the healthy control women contained silicate-reactive antibodies. Preincubation of sera with silicate and eight other metal compounds (including SiO2) demonstrated that the IgG and IgM antibodies bound specifically to silicate, because preincubation with Na2SiO3 inhibited more than 90% of the activity, whereas CrO3, Li2SO4, MgSO4, NiSO4, HgCl2, ZrOCl2, BeSO4, and SiO2 failed to inhibit the IgG or IgM antibody binding to the silicate-BSA plates. Furthermore, the F(ab')2 portion and not the Fc portion of the silicate-reactive IgG was reactive with BSA-bound silicate in the enzyme immunoassay. The assay for silicate-reactive antibodies was quantified by assigning arbitrary units to a standard curve composed of serial twofold dilutions of high-positive (ten times higher than the cutoff) silicate antibody sera. This novel assay is a useful method for detecting and quantifying humoral immune response to silicate. PMID:8991630

  3. Growth of surface structures correlated with structural and mechanical modifications of brass by laser-induced Si plasma ions implantation

    NASA Astrophysics Data System (ADS)

    Ahmad, Shahbaz; Bashir, Shazia; Rafique, M. Shahid; Yousaf, Daniel

    2017-04-01

    Laser-produced Si plasma is employed as an ion source for implantation on the brass substrate for its surface, structural, and mechanical modifications. Thomson parabola technique is employed for the measurement of energy and flux of Si ions using CR-39. In response to stepwise increase in number of laser pulses from 3000 to 12000, four brass substrates were implanted by laser-induced Si plasma ions of energy 290 keV at different fluxes ranging from 45 × 1012 to 75 × 1015 ions/cm2. SEM analysis reveals the formation of nano/micro-sized irregular shaped cavities and pores for the various ion fluxes for varying numbers of laser pulses from 3000 to 9000. At the maximum ion flux for 12,000 pulses, distinct and organized grains with hexagonal and irregular shaped morphology are revealed. X-ray diffractometer (XRD) analysis exhibits that a new phase of CuSi (311) is identified which confirms the implantation of Si ions in brass substrate. A significant decrease in mechanical properties of implanted brass, such as Yield Stress (YS), Ultimate Tensile Strength (UTS), and hardness, with increasing laser pulses from 3000 to 6000 is observed. However, with increasing laser pulses from 9000 to a maximum value of 12,000, an increase in mechanical properties like hardness, YS, and UTS is observed. The generation as well as annihilation of defects, recrystallization, and intermixing of Si precipitates with brass matrix is considered to be responsible for variations in surface, structural, and mechanical modifications of brass.

  4. Morphological detection method with girdle structure

    NASA Astrophysics Data System (ADS)

    Chen, Yong; Yan, Gao-shi; Huo, Yu

    2013-09-01

    A flat structure element is usually used in the traditional morphological detection. In this processing method, the infrared target is regarded as a single point without considering the imaging characteristics of infrared dim and small target. There is a gray transition zone between target and background. It is unreasonable that the transition region processed as background in the traditional morphological method. So, the infrared dim target detection results are not ideal by using the traditional morphological processing method. Aimed at this problem, the imaging characteristic of infrared dim and small target is analyzed. The Spatial distribution of infrared target gray scale is calculated. The result shows it is a tip package structure. The top peak is the target. Based on theoretical research on the morphological detection, the girdle structure elements are designed. This structure is composed of two circles. The target neighborhood zones are protected in this structure. They do not participate in the morphological calculation. The sixteen external zones are only participated in the calculation. The morphology of infrared target detection method is established based on this neighborhood zoned structure. The designed girdle structure is used in the opening operation and the traditional flat structure is used in the closing operation. The traditional Top-Hat algorithm is improved according to the girdle structure morphology method. And used the real infrared target image, the improved algorithm is simulated. The processed result shows that the girdle structure morphology method is effective in the background noise restraining. In order to evaluate the image processed result quantitatively, the signal noise ratio and signal noise ratio gain factor are used. Accordingly to the calculated result, the improved algorithm compared with the traditional morphological methods, inhibition of complex background with better.

  5. Detection of lesions in mammographic structure

    NASA Astrophysics Data System (ADS)

    Burgess, Arthur E.; Jacobson, Francine L.; Judy, Philip F.

    1999-05-01

    This paper is a report on very surprising results from recent work on detection of real lesions in digitized mammograms. The experiments were done using a novel experimental procedure with hybrid images. The lesions (signals) were real tumor masses extracted from breast tissue specimen radiographs. In the detection experiments, the tumors were added to digitized normal mammographic backgrounds. The results of this new work have been both novel and very surprising. Contrast thresholds increased with increasing lesion size for lesions larger than approximately 1 mm in diameter. Earlier work with white noise, radiographic image noise, computed tomography (CT) noise and some types of patient structure have accustomed us to a particular relationship between lesion size and contrast for constant detectability. All previous contrast/detail (CD) diagrams have been similar, the contrast threshold decreases as lesion size increases and flattens at large lesion sizes. The CD diagram for lesion detection in mammographic structure is completely different. It will be shown that this is a consequence of the power-law dependence of the projected breast tissue structure spectral density on spatial frequency. Mammographic tissue structure power spectra have the form P(f) equals B/f(beta ), with an average exponent of approximately 3 (range from 2 to 4), and are approximately isotropic (small angular dependence). Results for two-alternative forced-choice (2AFC) signal detection experiments using 4 tumor lesions and one mathematically generated signal will be presented. These results are for an unbiased selection of mammographic backgrounds. It is possible that an additional understanding of the effects of breast structure on lesion detectability can be obtained by investigating detectability in various classes of mammographic backgrounds. This will be the subject of future research.

  6. Detecting Curvilinear Features Using Structure Tensors.

    PubMed

    Vicas, Cristian; Nedevschi, Sergiu

    2015-11-01

    Few published articles on curvilinear structures exist compared with works on detecting lines or corners with high accuracy. In medical ultrasound imaging, the structures that need to be detected appear as a collection of microstructures correlated along a path. In this paper, we investigated techniques that extract meaningful low-level information for curvilinear structures, using techniques based on structure tensor. We proposed a novel structure tensor enhancement inspired by bilateral filtering. We compared the proposed approach with five state-of-the-art curvilinear structure detectors. We tested the algorithms against simulated images with known ground truth and real images from three different domains (medical ultrasound, scanning electron microscope, and astronomy). For the real images, we employed experts to delineate the ground truth for each domain. Techniques borrowed from machine learning robustly assessed the performance of the methods (area under curve and cross validation). As a practical application, we used the proposed method to label a set of 5000 ultrasound images. We conclude that the proposed tensor-based approach outperforms the state-of-the-art methods in providing magnitude and orientation information for curvilinear structures. The evaluation methodology ensures that the employed feature-detection method will yield reproducible performance on new, unseen images. We published all the implemented methods as open-source software.

  7. Reliability of scanning laser acoustic microscopy for detecting internal voids in structural ceramics

    NASA Technical Reports Server (NTRS)

    Roth, D. J.; Baaklini, G. Y.

    1986-01-01

    The reliability of 100 MHz scanning laser acoustic microscopy (SLAM) for detecting internal voids in sintered specimens of silicon nitride and silicon carbide was evaluated. The specimens contained artificially implanted voids and were positioned at depths ranging up to 2 mm below the specimen surface. Detection probability of 0.90 at a 0.95 confidence level was determined as a function of material, void diameter, and void depth. The statistical results presented for void detectability indicate some of the strengths and limitations of SLAM as a nondestructive evaluation technique for structural ceramics.

  8. Processing and mechanical behavior of lamellar structured degradable magnesium-hydroxyapatite implants.

    PubMed

    Ratna Sunil, B; Ganapathy, C; Sampath Kumar, T S; Chakkingal, Uday

    2014-12-01

    Multilayered (laminated) composites exhibit tunable mechanical behavior compared to bulk materials due to the presence of more interfaces and therefore magnesium based composites are gaining wide popularity as biodegradable materials targeted for temporary implant applications. The objective of the present work is to fabricate magnesium based lamellar metal matrix composites (MMCs) for degradable implant applications. Nano-hydroxyapatite (HA) powder was selected as the secondary phase and lamellar structured magnesium-nano-hydroxyapatite (Mg-HA) composites of 8, 10 and 15wt% HA were fabricated by ball milling and spark plasma sintering. It was found that HA particles were coated on the Mg flakes after 20h of ball milling carried out using tungsten carbide (WC) as the milling media. Spark plasma sintering of the milled powders resulted in the formation of lamellar structure of Mg with the presence of HA and magnesium oxide (MgO) at the inter-lamellar sites of the composites. Phase analysis of the milled powder by an X-ray diffraction (XRD) method confirms the presence of HA and MgO along with Mg after sintering. Corrosion behavior of the composites investigated by potentiodynamic polarization tests shows a reduction in the inter-lamellar corrosion with increase in HA content and the best corrosion resistance is found for the Mg-10% HA composite. This composite also exhibits maximum Vickers hardness. Young׳s modulus and fracture toughness measured by nano-indentation method were higher for the Mg-8% HA composite. The results thus suggest that lamellar structured Mg composites with 8% and 10% HA show promise for temporary degradable orthopedic implant applications because of their improved corrosion resistance and superior mechanical properties.

  9. The “accumulation effect” of positrons in the stack of foils, detected by measurements of the positron implantation profile

    SciTech Connect

    Dryzek, Jerzy; Siemek, Krzysztof

    2013-12-14

    The profiles of positrons implanted from the radioactive source {sup 22}Na into a stack of foils and plates are the subject of our experimental and theoretical studies. The measurements were performed using the depth scanning of positron implantation profile method, and the theoretical calculations using the phenomenological multi-scattering model (MSM). Several stacks consisting of silver, gold and aluminum foils, and titanium and germanium plates were investigated. We notice that the MSM describes well the experimental profiles; however when the stack consisting of silver and gold foils, the backscattering and linear absorption coefficients differ significantly from those reported in the literature. We suggest the energy dependency of the backscattering coefficient for silver and gold. In the stacks which comprise titanium and germanium plates, there were observed the features, which indicate the presence of the “accumulation effect” in the experimental implantation profile. This effect was previously detected in implantation profiles in Monte Carlo simulations using the GEANT4 tool kit, and it consists in higher localization of positrons close the interface. We suppose that this effect can be essential for positron annihilation in any heterogeneous materials.

  10. Optimal wireless receiver structure for omnidirectional inductive power transmission to biomedical implants.

    PubMed

    Gougheri, Hesam Sadeghi; Kiani, Mehdi

    2016-08-01

    In order to achieve omnidirectional inductive power transmission to biomedical implants, the use of several orthogonal coils in the receiver side (Rx) has been proposed in the past. In this paper, the optimal Rx structure for connecting three orthogonal Rx coils and the power management is found to achieve the maximum power delivered to the load (PDL) in the presence of any Rx coil tilting. Unlike previous works, in which a separate power management has been used for each coil to deliver power to the load, different resonant Rx structures for connecting three Rx coils to a single power management are studied. In simulations, connecting three Rx coils with the diameters of 3 mm, 3.3 mm, and 3.6 mm in series and resonating them with a single capacitor at the operation frequency of 100 MHz led to the maximum PDL for large loads when the implant was tilted for 45o. This optimal Rx structure achieves higher PDL in worst-case scenarios as well as reduces the number of power managements to only one.

  11. Development of oral and extra-oral endosseous craniofacial implants by using a mesh structure for connective tissue attachment.

    PubMed

    Mita, Atsushi; Yagihara, Atsushi; Wang, Wei; Takakuda, Kazuo

    2014-03-19

    Connective tissue attachment to a mesh structure incorporated on the surface of oral implants and extra-oral endosseous craniofacial implants (EOECI) was investigated. Two types of implants were prepared: TI and TI-Mesh. TI was composed of an upper and a lower component, both comprised of a titanium cylinder, which could be connected using a titanium screw. The composition of the TIMesh was similar, but the lower cylinder had a lateral groove that was covered with a titanium mesh. In animal experiments performed using rat calvaria, the lower component was first implanted and was left submerged for 3 weeks, then the upper component was mounted percutaneously. After an additional 2 weeks, each implant and the surrounding tissues were harvested and evaluated. Histological observations revealed collagen fibers originating from surrounding hypodermal tissues anchored to the mesh structures of the TI-Mesh whereas no such collagen fibers were observed around TI. Significantly greater values of the attachment strength, the thickness of the dermal tissue, the thickness of hypodermal tissue, and the attachment lengths were observed in TI-Mesh than those of TI. Thus connective tissue attachment with collagen fibers anchored to the mesh was achieved by incorporating mesh structures into the percutaneously placed implants.

  12. Evaluation of suction detection during different pumping states in an implantable rotary blood pump.

    PubMed

    Ng, Siew-Cheok; Lim, Einly; Mason, David G; Avolio, Alberto P; Lovell, Nigel H

    2013-08-01

    In recent times, the problem of noninvasive suction detection for implantable rotary blood pumps has attracted substantial research interest. Here, we compare the performance of various suction indices for different types of suction and non-suction events based on pump speed irregularity. A total of 171 different indices that consist of previously proposed as well as newly introduced suction indices are tested using regularized logistic regression. These indices can be classified as amplitude based (derived from the mean, maximum, and minimum values of a cycle), duration based (derived from the duration of a cycle), gradient based (derived from the first order as well as higher order differences) and frequency based (derived from the power spectral density). The non-suction event data consists of ventricular ejection with or without arrhythmia and intermittent and continuous non-opening of the aortic valve. The suction event data consists of partial ventricular collapse that occurs intermittently as well as continuously with or without arrhythmia. In addition, we also attempted to minimize the usage of multiple indices by applying the sequential forward floating selection method to find which combination of indices gives the best performance. In general, the amplitude-based and gradient-based indices performed quite well while the duration-based and frequency-based indices performed poorly. By having only two indices ([i] the maximum gradient change in positive slope; and [ii] the standard deviation of the maximum value in a cycle), we were able to achieve a sensitivity of 98.9% and a specificity of 99.7%.

  13. Short Implants: New Horizon in Implant Dentistry.

    PubMed

    Jain, Neha; Gulati, Manisha; Garg, Meenu; Pathak, Chetan

    2016-09-01

    The choice of implant length is an essential factor in deciding the survival rates of these implants and the overall success of the prosthesis. Placing an implant in the posterior part of the maxilla and mandible has always been very critical due to poor bone quality and quantity. Long implants can be placed in association with complex surgical procedures such as sinus lift and bone augmentation. These techniques are associated with higher cost, increased treatment time and greater morbidity. Hence, there is need for a less invasive treatment option in areas of poor bone quantity and quality. Data related to survival rates of short implants, their design and prosthetic considerations has been compiled and structured in this manuscript with emphasis on the indications, advantages of short implants and critical biomechanical factors to be taken into consideration when choosing to place them. Studies have shown that comparable success rates can be achieved with short implants as those with long implants by decreasing the lateral forces to the prosthesis, eliminating cantilevers, increasing implant surface area and improving implant to abutment connection. Short implants can be considered as an effective treatment alternative in resorbed ridges. Short implants can be considered as a viable treatment option in atrophic ridge cases in order to avoid complex surgical procedures required to place long implants. With improvement in the implant surface geometry and surface texture, there is an increase in the bone implant contact area which provides a good primary stability during osseo-integration.

  14. Short Implants: New Horizon in Implant Dentistry

    PubMed Central

    Gulati, Manisha; Garg, Meenu; Pathak, Chetan

    2016-01-01

    The choice of implant length is an essential factor in deciding the survival rates of these implants and the overall success of the prosthesis. Placing an implant in the posterior part of the maxilla and mandible has always been very critical due to poor bone quality and quantity. Long implants can be placed in association with complex surgical procedures such as sinus lift and bone augmentation. These techniques are associated with higher cost, increased treatment time and greater morbidity. Hence, there is need for a less invasive treatment option in areas of poor bone quantity and quality. Data related to survival rates of short implants, their design and prosthetic considerations has been compiled and structured in this manuscript with emphasis on the indications, advantages of short implants and critical biomechanical factors to be taken into consideration when choosing to place them. Studies have shown that comparable success rates can be achieved with short implants as those with long implants by decreasing the lateral forces to the prosthesis, eliminating cantilevers, increasing implant surface area and improving implant to abutment connection. Short implants can be considered as an effective treatment alternative in resorbed ridges. Short implants can be considered as a viable treatment option in atrophic ridge cases in order to avoid complex surgical procedures required to place long implants. With improvement in the implant surface geometry and surface texture, there is an increase in the bone implant contact area which provides a good primary stability during osseo-integration. PMID:27790598

  15. Detecting structure of haplotypes and local ancestry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We present a two-layer hidden Markov model to detect the structure of haplotypes for unrelated individuals. This allows us to model two scales of linkage disequilibrium (one within a group of haplotypes and one between groups), thereby taking advantage of rich haplotype information to infer local an...

  16. In vitro and in vivo studies of surface-structured implants for bone formation

    PubMed Central

    Xia, Lu; Feng, Bo; Wang, Peizhi; Ding, Siyang; Liu, Zhiyuan; Zhou, Jie; Yu, Rong

    2012-01-01

    Background and methods Micronanoscale topologies play an important role in implant osteointegration and determine the success of an implant. We investigated the effect of three different implant surface topologies on osteoblast response and bone regeneration. In this study, implants with nanotubes and micropores were used, and implants with flat surfaces were used as the control group. Results Our in vitro studies showed that the nanostructured topologies improved the proliferation, differentiation, and development of the osteoblastic phenotype. Histological analysis further revealed that the nanotopology increased cell aggregation at the implant-tissue interfaces and enhanced bone-forming ability. Pushout testing indicated that the nanostructured topology greatly increased the bone-implant interfacial strength within 4 weeks of implantation. Conclusion Nanotopography may improve regeneration of bone tissue and shows promise for dental implant applications. PMID:23028216

  17. Wrong detection of ventricular fibrillation in an implantable cardioverter defibrillator caused by the movement near the MRI scanner bore.

    PubMed

    Mattei, Eugenio; Censi, Federica; Triventi, Michele; Mancini, Matteo; Napolitano, Antonio; Genovese, Elisabetta; Cannata, Vittorio; Falsaperla, Rosaria; Calcagnini, Giovanni

    2015-01-01

    The static magnetic field generated by MRI systems is highly non-homogenous and rapidly decreases when moving away from the bore of the scanner. Consequently, the movement around the MRI scanner is equivalent to an exposure to a time-varying magnetic field at very low frequency (few Hz). For patients with an implanted cardiac stimulators, such as an implantable cardioverter/defibrillator (ICD), the movements inside the MRI environment may thus induce voltages on the loop formed by the leads of the device, with the potential to affect the behavior of the stimulator. In particular, the ICD's detection algorithms may be affected by the induced voltage and may cause inappropriate sensing, arrhythmia detections, and eventually inappropriate ICD therapy.We performed in-vitro measurements on a saline-filled humanshaped phantom (male, 170 cm height), equipped with an MRconditional ICD able to transmit in real-time the detected cardiac activity (electrograms). A biventricular implant was reproduced and the ICD was programmed in standard operating conditions, but with the shock delivery disabled. The electrograms recorded in the atrial, left and right ventricle channels were monitored during rotational movements along the vertical axis, in close proximity of the bore. The phantom was also equipped with an accelerometer and a magnetic field probe to measure the angular velocity and the magnetic field variation during the experiment. Pacing inhibition, inappropriate detection of tachyarrhythmias and of ventricular fibrillation were observed. Pacing inhibition began at an angular velocity of about 7 rad/s, (dB/dt of about 2 T/s). Inappropriate detection of ventricular fibrillation occurred at about 8 rad/s (dB/dt of about 3 T/s). These findings highlight the need for a specific risk assessment of workers with MR-conditional ICDs, which takes into account also effects that are generally not considered relevant for patients, such as the movement around the scanner bore.

  18. Mechanisms of formation of nonlinear optical light guide structures in metal cluster composites produced by ion beam implantation

    SciTech Connect

    Sarkisov, S.S.; Williams, E.K.; Curley, M.; Smith, C.C.; Ila, D.; Venkateswarlu, P.; Poker, D.B.; Hensley, D.K.

    1997-11-01

    Ion implantation has been shown to produce a high density of metal colloids in glasses and crystalline materials. The high-precipitate volume fraction and small size of metal nanoclusters formed leads to values for the third-order susceptibility much greater than those for metal doped solids. This has stimulated interest in use of ion implantation to make nonlinear optical materials. On the other side, LiNbO{sub 3} has proved to be a good material for optical waveguides produced by MeV ion implantation. Light confinement in these waveguides is produced by refractive index step difference between the implanted region and the bulk material. Implantation of LiNbO{sub 3} with MeV metal ions can therefore result into nonlinear optical waveguide structures with great potential in a variety of device applications. The authors describe linear and nonlinear optical properties of a waveguide structure in LiNbO{sub 3}-based composite material produced by silver ion implantation in connection with mechanisms of its formation.

  19. The structure and tribological properties of gradient layers prepared by plasma-based ion implantation on 2024 Al alloy

    NASA Astrophysics Data System (ADS)

    Liao, J. X.; Xia, L. F.; Sun, M. R.; Liu, W. M.; Xu, T.; Xue, Q. J.

    2004-02-01

    Using plasma-based ion implantation, two types of gradient layers have been prepared on 2024 Al alloy. One is prepared by N-implantation then C-deposition, the other adds an interlayer composed of a Ti layer and a Ti-N layer between N-implantation and C-deposition. C-deposition is carried out at various implanting voltages or C2H2/H2 ratios. The composition depth profiles of these layers were characterized by x-ray photoelectron spectroscopy. The structure, morphologies and microstructure of the C layers were studied using Raman spectroscopy, atomic force microscope and transmission electron microscope, respectively. The surface hardness was measured with a Knoop tester and a mechanical property microprobe. The dry ball-on-disc wear tests were performed in ambient air. The gradient layer without interlayer is composed of an N-implanted layer rich in AlN and a diamond-like carbon (DLC) layer (film), and the two layers are connected with a C-Al transition layer containing Al4C3. The Ti layer rich in agr -Ti and the N-implanted layer are connected by a Ti-Al transition layer containing TiAl3, while the Ti-N layer rich in TiN and the DLC film are connected by a C-Ti transition layer containing TiC, TiCN, etc. Thus, the gradient layer with interlayers has optimized the gradient structure. DLC films are compact and amorphous, contain high sp3/sp2 ratios and depend on the implanting voltage and the C2H2/H2 ratio. Similarly, these gradient layers exhibit significant improvement in morphologies, surface hardness and tribological properties; the interlayer, the implanting voltage and the C2H2/H2 ratio all have prominent effects on these properties.

  20. Feasibility of Structural and Functional MRI Acquisition with Unpowered Implants in Argus II Retinal Prosthesis Patients: A Case Study

    PubMed Central

    Cunningham, Samantha I.; Shi, Yonggang; Weiland, James D.; Falabella, Paulo; Olmos de Koo, Lisa C.; Zacks, David N.; Tjan, Bosco S.

    2015-01-01

    Purpose Magnetic resonance imaging (MRI) can measure the effects of vision loss and recovery on brain function and structure. In this case study, we sought to determine the feasibility of acquiring anatomical and functional MRI data in recipients of the Argus II epiretinal prosthesis system. Methods Following successful implantation with the Argus II device, two retinitis pigmentosa (RP) patients completed MRI scans with their implant unpowered to measure primary visual cortex (V1) functional responses to a tactile task, whole-brain morphometry, V1 cortical thickness, and diffusion properties of the optic tract and optic radiation. Measurements in the subjects with the Argus II implant were compared to measurements obtained previously from RP patients and sighted individuals. Results The presence of the Argus II implant resulted in artifacts that were localized around the patient's implanted eye and did not extend into cortical regions or white matter tracts associated with the visual system. Structural data on V1 cortical thickness and the retinofugal tract obtained from the two Argus II subjects fell within the ranges of sighted and RP groups. When compared to the RP and sighted subjects, Argus II patients' tactile-evoked cross-modal functional MRI (fMRI) blood oxygen level-dependent (BOLD) responses in V1 also fell within the range of either sighted or RP groups, apparently depending on time since implantation. Conclusions This study demonstrates that successful acquisition and quantification of structural and functional MR images are feasible in the presence of the inactive implant and provides preliminary information on functional changes in the brain that may follow sight restoration treatments. Transitional Relevance Successful MRI and fMRI acquisition in Argus II recipients demonstrates feasibility of using MRI to study the effect of retinal prosthesis use on brain structure and function. PMID:26693097

  1. Implantable polymer/metal thin film structures for the localized treatment of cancer by Joule heating

    NASA Astrophysics Data System (ADS)

    Kan-Dapaah, Kwabena; Rahbar, Nima; Theriault, Christian; Soboyejo, Wole

    2015-04-01

    This paper presents an implantable polymer/metal alloy thin film structure for localized post-operative treatment of breast cancer. A combination of experiments and models is used to study the temperature changes due to Joule heating by patterned metallic thin films embedded in poly-dimethylsiloxane. The heat conduction within the device and the surrounding normal/cancerous breast tissue is modeled with three-dimensional finite element method (FEM). The FEM simulations are used to explore the potential effects of device geometry and Joule heating on the temperature distribution and lesion (thermal dose). The FEM model is validated using a gel model that mimics biological media. The predictions are also compared to prior results from in vitro studies and relevant in vivo studies in the literature. The implications of the results are discussed for the potential application of polymer/metal thin film structures in hyperthermic treatment of cancer.

  2. Electrical and structural characterization of Fe implanted GaInP

    NASA Astrophysics Data System (ADS)

    Fraboni, B.; Cesca, T.; Gasparotto, A.; Mattei, G.; Boscherini, F.; Impellizzeri, G.; Priolo, F.; Jakomin, R.; Longo, M.; Tarricone, L.

    2007-12-01

    We have investigated the structural and electrical properties of GaInP/GaAs epilayers that we have implanted with Fe atoms (190 keV) to produce a shallow high resistivity layer. SIMS, PIXE-channeling and EXAFS were used to provide a structural characterization. Current-voltage analyses as a function of temperature indicate the activation of an efficient and stable electrical compensation process, that we have ascribed to the interplay between a deep donor and a deep acceptor, located at EC-0.50 eV and EV+0.74 eV, respectively. We have focused our attention on the latter deep level, attributed to the Fe 2+/3+ related acceptor trap, that we have directly identified and characterized by spectral photocurrent analyses and by capacitance transient spectroscopy carried out under below band gap illumination that stimulated the direct emission/trapping of carriers from the deep trap.

  3. Nanopore sequencing detects structural variants in cancer.

    PubMed

    Norris, Alexis L; Workman, Rachael E; Fan, Yunfan; Eshleman, James R; Timp, Winston

    2016-01-01

    Despite advances in sequencing, structural variants (SVs) remain difficult to reliably detect due to the short read length (<300 bp) of 2nd generation sequencing. Not only do the reads (or paired-end reads) need to straddle a breakpoint, but repetitive elements often lead to ambiguities in the alignment of short reads. We propose to use the long-reads (up to 20 kb) possible with 3rd generation sequencing, specifically nanopore sequencing on the MinION. Nanopore sequencing relies on a similar concept to a Coulter counter, reading the DNA sequence from the change in electrical current resulting from a DNA strand being forced through a nanometer-sized pore embedded in a membrane. Though nanopore sequencing currently has a relatively high mismatch rate that precludes base substitution and small frameshift mutation detection, its accuracy is sufficient for SV detection because of its long reads. In fact, long reads in some cases may improve SV detection efficiency. We have tested nanopore sequencing to detect a series of well-characterized SVs, including large deletions, inversions, and translocations that inactivate the CDKN2A/p16 and SMAD4/DPC4 tumor suppressor genes in pancreatic cancer. Using PCR amplicon mixes, we have demonstrated that nanopore sequencing can detect large deletions, translocations and inversions at dilutions as low as 1:100, with as few as 500 reads per sample. Given the speed, small footprint, and low capital cost, nanopore sequencing could become the ideal tool for the low-level detection of cancer-associated SVs needed for molecular relapse, early detection, or therapeutic monitoring.

  4. Nano-structured silicide formation by focused ion beam implantation and integration of silver metallization with thin film silicide layers

    NASA Astrophysics Data System (ADS)

    Mitan, Martin M.

    Nano-structured silicide formation was mediated through ion implantation. Silicide structures with dimensions of 170 nm were produced on (100) silicon substrates by ion implantation of 200 KeV As++ through a thin cobalt film on SiO2/Si structure. A selective reaction barrier at the Si/Co interface comprising of a thin (˜2 nm) oxide (SiO 2) prevents unwanted reactions. Ion-beam mixing was instrumental in the fracturing of the oxide layer, thereby allowing the migration of metal atoms across the SiO2/Co boundary for the silicidation reaction to proceed during subsequent rapid thermal anneal (RTA) treatments. A threshold dose of 3 x 1015 cm-2 was required for process initiation. Four-terminal resistance test structures were formed for electrical measurements. Resistivity values obtained ranged from 12 to 23 muO-cm, improving with increased ion dose. Application of this method can facilitate a wide variety of silicide structures. Part two of this study focused on the reliability study of silver metalization with silicides. Silicide thin films of CoSi2 and NiSi were prepared by solid phase reactions utilizing the bi-layer technique. Silver thin films were then deposited on the silicides to evaluate the thermal stability of the films during vacuum annealing. Rutherford backscattering spectrometry of annealed films revealed Ag film changes to occur at 700°C. No changes in the silicide thin films could be detected. Scanning electron microscopy of annealed films shows grain coarsening of the Ag film with increasing anneal temperature. At 650°C, voids begin to appear in the film. Increasing anneal temperature up to 700°C agglomerates the film. X-ray diffraction glancing angle scans revealed no phase changes in annealed films. The as-deposited case and 700°C both show the same reflection peaks being present. Secondary ion mass spectroscopy depth profiling revealed trace amounts of Ag at the silicide/silicon interface following a heat treatment. This occurrence appears to

  5. Leak detection using structure-borne noise

    NASA Technical Reports Server (NTRS)

    Holland, Stephen D. (Inventor); Chimenti, Dale E. (Inventor); Roberts, Ronald A. (Inventor)

    2010-01-01

    A method for detection and location of air leaks in a pressure vessel, such as a spacecraft, includes sensing structure-borne ultrasound waveforms associated with turbulence caused by a leak from a plurality of sensors and cross correlating the waveforms to determine existence and location of the leak. Different configurations of sensors and corresponding methods can be used. An apparatus for performing the methods is also provided.

  6. Doping of Graphene by Low-Energy Ion Beam Implantation: Structural, Electronic, and Transport Properties.

    PubMed

    Willke, Philip; Amani, Julian A; Sinterhauf, Anna; Thakur, Sangeeta; Kotzott, Thomas; Druga, Thomas; Weikert, Steffen; Maiti, Kalobaran; Hofsäss, Hans; Wenderoth, Martin

    2015-08-12

    We investigate the structural, electronic, and transport properties of substitutional defects in SiC-graphene by means of scanning tunneling microscopy and magnetotransport experiments. Using ion incorporation via ultralow energy ion implantation, the influence of different ion species (boron, nitrogen, and carbon) can directly be compared. While boron and nitrogen atoms lead to an effective doping of the graphene sheet and can reduce or raise the position of the Fermi level, respectively, (12)C(+) carbon ions are used to study possible defect creation by the bombardment. For low-temperature transport, the implantation leads to an increase in resistance and a decrease in mobility in contrast to undoped samples. For undoped samples, we observe in high magnetic fields a positive magnetoresistance that changes to negative for the doped samples, especially for (11)B(+)- and (12)C(+)-ions. We conclude that the conductivity of the graphene sheet is lowered by impurity atoms and especially by lattice defects, because they result in weak localization effects at low temperatures.

  7. Electrical and structural properties of In-implanted Si1–xGex alloys

    DOE PAGES

    Feng, Ruixing; Kremer, F.; Sprouster, D. J.; ...

    2016-01-14

    Here, we report on the effects of dopant concentration and substrate stoichiometry on the electrical and structural properties of In-implanted Si1–xGex alloys. Correlating the fraction of electrically active In atoms from Hall Effect measurements with the In atomic environment determined by X-ray absorption spectroscopy, we observed the transition from electrically active, substitutional In at low In concentration to electrically inactive metallic In at high In concentration. The In solid-solubility limit has been quantified and was dependent on the Si1–xGex alloy stoichiometry; the solid-solubility limit increased as the Ge fraction increased. This result was consistent with density functional theory calculations ofmore » two In atoms in a Si1–xGex supercell that demonstrated that In–In pairing was energetically favorable for x ≲ 0.7 and energetically unfavorable for x ≳ 0.7. Transmission electron microscopy imaging further complemented the results described earlier with the In concentration and Si1–xGex alloy stoichiometry dependencies readily visible. We have demonstrated that low resistivity values can be achieved with In implantation in Si1–xGex alloys, and this combination of dopant and substrate represents an effective doping protocol.« less

  8. High Mobility SiGe/Si Transistor Structures on Sapphire Substrates Using Ion Implantation

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Mueller, C. H.; Croke, E. T.

    2003-01-01

    High mobility n-type SiGe/Si transistor structures have been fabricated on sapphire substrates by ion implanting phosphorus ions into strained 100 Angstrom thick silicon channels for the first time. The strained Si channels were sandwiched between Si(sub 0.7)Ge(sub 0.3) layers, which, in turn, were deposited on Si(sub 0.7)Ge(sub 0.3) virtual substrates and graded SiGe buffer layers. After the molecular beam epitaxy (MBE) film growth process was completed, ion thick silicon channels implantation and post-annealing were used to introduce donors. The phosphorous ions were preferentially located in the Si channel at a peak concentration of approximately 1x10(exp 18)/cu cm. Room temperature electron mobilities exceeding 750 sq cm/V-sec at carrier densities of 1x10(exp 12)/sq cm were measured. Electron concentration appears to be the key factor that determines mobility, with the highest mobility observed for electron densities in the 1 - 2x10(exp 12)/sq cm range.

  9. The photoluminescence response to structural changes of Yb implanted ZnO crystals subjected to non-equilibrium processing

    NASA Astrophysics Data System (ADS)

    Ratajczak, R.; Prucnal, S.; Guziewicz, E.; Mieszczynski, C.; Snigurenko, D.; Stachowicz, M.; Skorupa, W.; Turos, A.

    2017-02-01

    In this paper, we present the detailed study of optical and structural properties of Yb implanted single ZnO crystals. Hydrothermally grown wurtzite (0001) ZnO crystals were implanted with 150 keV Yb ions to fluencies of 5 × 1014 and 1 × 1015 at/cm2. After ion implantation, two different types of annealing were performed: rapid thermal annealing (RTA) and millisecond range flash lamp annealing (FLA). Crystalline quality, damage recovery, and Yb lattice site location were evaluated by the Channeling Rutherford Backscattering Spectrometry (RBS/c). It is shown that independent of the used annealing technique, defects formed in ZnO during ion implantation can be removed. Upon RTA performed at the temperature higher than 800 °C, strong out-diffusion of implanted Yb atoms and precipitation on the surface takes place. Consequently, the degradation of the photoluminescence (PL) efficiency is observed. The diffusion of implanted Yb during millisecond range FLA does not occur for such experimental conditions. Moreover, FLA treatment for 20 ms leads to the formation of single crystalline ZnO layer with Yb incorporated in the substitutional lattice sites. According to RBS/c and PL data, Yb atoms substituted in the Zn sublattice are predominantly in the 2+ oxidation state. The most intensive PL has been observed after annealing at 800 °C for 20 min which is accompanied with the reduction of Yb substitutional fraction and formation of octahedron Yb-oxygen clusters within ZnO.

  10. Quantum structures for multiband photon detection

    NASA Astrophysics Data System (ADS)

    Perera, A. G. U.

    2006-06-01

    The work describes multiband photon detectors based on semiconductor micro-and nano-structures. The devices considered include quantum dot, homojunction, and heterojunction structures. In the quantum dot structures, transitions are from one state to another, while free carrier absorption and internal photoemission play the dominant role in homo or heterojunction detectors. Quantum dots-in-a-well (DWELL) detectors can tailor the response wavelength by varying the size of the well. A tunnelling quantum dot infrared photodetector (T-QDIP) could operate at room temperature by blocking the dark current except in the case of resonance. Photoexcited carriers are selectively collected from InGaAs quantum dots by resonant tunnelling, while the dark current is blocked by AlGaAs/InGaAs tunnelling barriers placed in the structure. A two-colour infrared detector with photoresponse peaks at ˜6 and ˜17 μm at room temperature will be discussed. A homojunction or heterojunction interfacial workfunction internal photoemission (HIWIP or HEIWIP) infrared detector, formed by a doped emitter layer, and an intrinsic layer acting as the barrier followed by another highly doped contact layer, can detect near infrared (NIR) photons due to interband transitions and mid/far infrared (MIR/FIR) radiation due to intraband transitions. The threshold wavelength of the interband response depends on the band gap of the barrier material, and the MIR/FIR response due to intraband transitions can be tailored by adjusting the band offset between the emitter and the barrier. GaAs/AlGaAs will provide NIR and MIR/FIR dual band response, and with GaN/AlGaN structures the detection capability can be extended into the ultraviolet region. These detectors are useful in numerous applications such as environmental monitoring, medical diagnosis, battlefield-imaging, space astronomy applications, mine detection, and remote-sensing.

  11. Quantum structures for multiband photon detection

    NASA Astrophysics Data System (ADS)

    Perera, A. G. U.

    2005-09-01

    The work describes multiband photon detectors based on semiconductor micro- and nano-structures. The devices considered include quantum dot, homojunction, and heterojunction structures. In the quantum dot structures, transitions are from one state to another, while free carrier absorption and internal photoemission play the dominant role in homo or heterojunction detectors. Quantum Dots-in-a-Well (DWELL) detectors can tailor the response wavelength by varying the size of the well. A tunneling Quantum Dot Infrared Photodetector (T-QDIP) could operate at room temperature by blocking the dark current except in the case of resonance. Photoexcited carriers are selectively collected from InGaAs quantum dots by resonant tunneling, while the dark current is blocked by AlGaAs/InGaAs tunneling barriers placed in the structure. A two-color infrared detector with photoresponse peaks at ~6 and ~17 μm at room temperature will be discussed. A Homojunction or HEterojunction Interfacial Workfunction Internal Photoemission (HIWIP or HEIWIP) infrared detector, formed by a doped emitter layer, and an intrinsic layer acting as the barrier followed by another highly doped contact layer, can detect near infrared (NIR) photons due to interband transitions and mid/far infrared (MIR/FIR) radiation due to intraband transitions. The threshold wavelength of the interband response depends on the band gap of the barrier material, and the MIR/FIR response due to intraband transitions can be tailored by adjusting the band offset between the emitter and the barrier. GaAs/AlGaAs will provide NIR and MIR/FIR dual band response, and with GaN/AlGaN structures the detection capability can be extended into the ultraviolet region. These detectors are useful in numerous applications such as environmental monitoring, medical diagnosis, battlefield-imaging, space astronomy applications, mine detection, and remote-sensing.

  12. Thermal migration of deuterium implanted in graphite: Influence of free surface proximity and structure

    NASA Astrophysics Data System (ADS)

    Le Guillou, M.; Moncoffre, N.; Toulhoat, N.; Pipon, Y.; Ammar, M. R.; Rouzaud, J. N.; Deldicque, D.

    2016-03-01

    This paper is a contribution to the study of the behavior of activation products produced in irradiated nuclear graphite, graphite being the moderator of the first French generation of CO2 cooled nuclear fission reactors. This paper is focused on the thermal release of Tritium, a major contributor to the initial activity, taking into account the role of the free surfaces (open pores and graphite surface). Two kinds of graphite were compared. On one hand, Highly Oriented Pyrolitic Graphite (HOPG), a model well graphitized graphite, and on the other hand, SLA2, a porous less graphitized nuclear graphite. Deuterium ion implantation at three different energies 70, 200 and 390 keV allows simulating the presence of Tritium at three different depths, corresponding respectively to projected ranges Rp of 0.75, 1.7 and 3.2 μm. The D isotopic tracing is performed thanks to the D(3He,p)4He nuclear reaction. The graphite structure is studied by Raman microspectrometry. Thermal annealing is performed in the temperature range 200-1200 °C up to 300 h annealing time. As observed in a previous study, the results show that the D release occurs according to three kinetic regimes: a rapid permeation through open pores, a transient regime corresponding to detrapping and diffusion of D located at low energy sites correlated to the edges of crystallites and finally a saturation regime attributed to detrapping of interstitial D located at high energy sites inside the crystallites. Below 600 °C, D release is negligible whatever the implantation depth and the graphite type. The present paper clearly puts forward that above 600 °C, the D release decreases at deeper implantation depths and strongly depends on the graphite structure. In HOPG where high energy sites are more abundant, the D release is less dependent on the surface proximity compared to SLA2. In SLA2, in which the low energy sites prevail, the D release curves are clearly shifted towards lower temperatures when D is located

  13. An ontology-based annotation of cardiac implantable electronic devices to detect therapy changes in a national registry.

    PubMed

    Rosier, Arnaud; Mabo, Philippe; Chauvin, Michel; Burgun, Anita

    2015-05-01

    The patient population benefitting from cardiac implantable electronic devices (CIEDs) is increasing. This study introduces a device annotation method that supports the consistent description of the functional attributes of cardiac devices and evaluates how this method can detect device changes from a CIED registry. We designed the Cardiac Device Ontology, an ontology of CIEDs and device functions. We annotated 146 cardiac devices with this ontology and used it to detect therapy changes with respect to atrioventricular pacing, cardiac resynchronization therapy, and defibrillation capability in a French national registry of patients with implants (STIDEFIX). We then analyzed a set of 6905 device replacements from the STIDEFIX registry. Ontology-based identification of therapy changes (upgraded, downgraded, or similar) was accurate (6905 cases) and performed better than straightforward analysis of the registry codes (F-measure 1.00 versus 0.75 to 0.97). This study demonstrates the feasibility and effectiveness of ontology-based functional annotation of devices in the cardiac domain. Such annotation allowed a better description and in-depth analysis of STIDEFIX. This method was useful for the automatic detection of therapy changes and may be reused for analyzing data from other device registries.

  14. Intelligent-based Structural Damage Detection Model

    SciTech Connect

    Lee, Eric Wai Ming; Yu, K.F.

    2010-05-21

    This paper presents the application of a novel Artificial Neural Network (ANN) model for the diagnosis of structural damage. The ANN model, denoted as the GRNNFA, is a hybrid model combining the General Regression Neural Network Model (GRNN) and the Fuzzy ART (FA) model. It not only retains the important features of the GRNN and FA models (i.e. fast and stable network training and incremental growth of network structure) but also facilitates the removal of the noise embedded in the training samples. Structural damage alters the stiffness distribution of the structure and so as to change the natural frequencies and mode shapes of the system. The measured modal parameter changes due to a particular damage are treated as patterns for that damage. The proposed GRNNFA model was trained to learn those patterns in order to detect the possible damage location of the structure. Simulated data is employed to verify and illustrate the procedures of the proposed ANN-based damage diagnosis methodology. The results of this study have demonstrated the feasibility of applying the GRNNFA model to structural damage diagnosis even when the training samples were noise contaminated.

  15. Feasibility of fully automated detection of fiducial markers implanted into the prostate using electronic portal imaging: A comparison of methods

    SciTech Connect

    Harris, Emma J. . E-mail: eharris@icr.ac.uk; McNair, Helen A.; Evans, Phillip M.

    2006-11-15

    Purpose: To investigate the feasibility of fully automated detection of fiducial markers implanted into the prostate using portal images acquired with an electronic portal imaging device. Methods and Materials: We have made a direct comparison of 4 different methods (2 template matching-based methods, a method incorporating attenuation and constellation analyses and a cross correlation method) that have been published in the literature for the automatic detection of fiducial markers. The cross-correlation technique requires a-priory information from the portal images, therefore the technique is not fully automated for the first treatment fraction. Images of 7 patients implanted with gold fiducial markers (8 mm in length and 1 mm in diameter) were acquired before treatment (set-up images) and during treatment (movie images) using 1MU and 15MU per image respectively. Images included: 75 anterior (AP) and 69 lateral (LAT) set-up images and 51 AP and 83 LAT movie images. Using the different methods described in the literature, marker positions were automatically identified. Results: The method based upon cross correlation techniques gave the highest percentage detection success rate of 99% (AP) and 83% (LAT) set-up (1MU) images. The methods gave detection success rates of less than 91% (AP) and 42% (LAT) set-up images. The amount of a-priory information used and how it affects the way the techniques are implemented, is discussed. Conclusions: Fully automated marker detection in set-up images for the first treatment fraction is unachievable using these methods and that using cross-correlation is the best technique for automatic detection on subsequent radiotherapy treatment fractions.

  16. Impaired perception of temporal fine structure and musical timbre in cochlear implant users.

    PubMed

    Heng, Joseph; Cantarero, Gabriela; Elhilali, Mounya; Limb, Charles J

    2011-10-01

    Cochlear implant (CI) users demonstrate severe limitations in perceiving musical timbre, a psychoacoustic feature of sound responsible for 'tone color' and one's ability to identify a musical instrument. The reasons for this limitation remain poorly understood. In this study, we sought to examine the relative contributions of temporal envelope and fine structure for timbre judgments, in light of the fact that speech processing strategies employed by CI systems typically employ envelope extraction algorithms. We synthesized "instrumental chimeras" that systematically combined variable amounts of envelope and fine structure in 25% increments from two different source instruments with either sustained or percussive envelopes. CI users and normal hearing (NH) subjects were presented with 150 chimeras and asked to determine which instrument the chimera more closely resembled in a single-interval two-alternative forced choice task. By combining instruments with similar and dissimilar envelopes, we controlled the valence of envelope for timbre identification and compensated for envelope reconstruction from fine structure information. Our results show that NH subjects utilize envelope and fine structure interchangeably, whereas CI subjects demonstrate overwhelming reliance on temporal envelope. When chimeras were created from dissimilar envelope instrument pairs, NH subjects utilized a combination of envelope (p = 0.008) and fine structure information (p = 0.009) to make timbre judgments. In contrast, CI users utilized envelope information almost exclusively to make timbre judgments (p < 0.001) and ignored fine structure information (p = 0.908). Interestingly, when the value of envelope as a cue was reduced, both NH subjects and CI users utilized fine structure information to make timbre judgments (p < 0.001), although the effect was quite weak in CI users. Our findings confirm that impairments in fine structure processing underlie poor perception of musical timbre in CI

  17. Assessing the role of spectral and intensity cues in spectral ripple detection and discrimination in cochlear-implant users.

    PubMed

    Anderson, Elizabeth S; Oxenham, Andrew J; Nelson, Peggy B; Nelson, David A

    2012-12-01

    Measures of spectral ripple resolution have become widely used psychophysical tools for assessing spectral resolution in cochlear-implant (CI) listeners. The objective of this study was to compare spectral ripple discrimination and detection in the same group of CI listeners. Ripple detection thresholds were measured over a range of ripple frequencies and were compared to spectral ripple discrimination thresholds previously obtained from the same CI listeners. The data showed that performance on the two measures was correlated, but that individual subjects' thresholds (at a constant spectral modulation depth) for the two tasks were not equivalent. In addition, spectral ripple detection was often found to be possible at higher rates than expected based on the available spectral cues, making it likely that temporal-envelope cues played a role at higher ripple rates. Finally, spectral ripple detection thresholds were compared to previously obtained speech-perception measures. Results confirmed earlier reports of a robust relationship between detection of widely spaced ripples and measures of speech recognition. In contrast, intensity difference limens for broadband noise did not correlate with spectral ripple detection measures, suggesting a dissociation between the ability to detect small changes in intensity across frequency and across time.

  18. Optimization of a low noise detection circuit for probing the structure of damage cascades with IBIC

    SciTech Connect

    Auden, Elizabeth C.; Doyle, Barney L.; Bielejec, Edward; Vizkelethy, Gyorgy; Wampler, William R.

    2015-06-18

    Optimal detector / pre-amplifier combinations have been identified for the use of light ion IBIC (ion beam induced charge) to probe the physical structure of electrically active defects in damage cascades caused by heavy ion implantation. The ideal detector must have a sufficiently thin dead layer that incident ions will produce the majority of damage cascades in the depletion region of the detector rather than the dead layer. Detector and circuit noise must be low enough to detect the implantation of a single heavy ion as well as the decrease in the light ion IBIC signal caused by Shockley-Read-Hall recombination when the beam scans regions of the detector damaged by the heavy ion. The IBIC signals from three detectors irradiated with 750 keV He⁺ ions are measured with commercial and bespoke charge sensitive pre-amplifiers to identify the combination with the lowest noise.

  19. Optimization of a low noise detection circuit for probing the structure of damage cascades with IBIC

    DOE PAGES

    Auden, Elizabeth C.; Doyle, Barney L.; Bielejec, Edward; ...

    2015-06-18

    Optimal detector / pre-amplifier combinations have been identified for the use of light ion IBIC (ion beam induced charge) to probe the physical structure of electrically active defects in damage cascades caused by heavy ion implantation. The ideal detector must have a sufficiently thin dead layer that incident ions will produce the majority of damage cascades in the depletion region of the detector rather than the dead layer. Detector and circuit noise must be low enough to detect the implantation of a single heavy ion as well as the decrease in the light ion IBIC signal caused by Shockley-Read-Hall recombinationmore » when the beam scans regions of the detector damaged by the heavy ion. The IBIC signals from three detectors irradiated with 750 keV He⁺ ions are measured with commercial and bespoke charge sensitive pre-amplifiers to identify the combination with the lowest noise.« less

  20. Changes in local surface structure and Sr depletion in Fe-implanted SrTiO3 (001)

    NASA Astrophysics Data System (ADS)

    Lobacheva, O.; Yiu, Y. M.; Chen, N.; Sham, T. K.; Goncharova, L. V.

    2017-01-01

    Local surface structure of single crystal strontium titanate SrTiO3 (001) samples implanted with Fe in the range of concentrations between 2 × 1014 to 2 × 1016 Fe/cm2 at 30 keV has been investigated. In order to facilitate Fe substitution (doping), implanted samples were annealed in oxygen at 350 °C. Sr depletion was observed from the near-surface layers impacted by the ion-implantation process, as revealed by Rutherford Backscattering Spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray Absorption Near Edge Spectroscopy (XANES), and Atomic Force Microscopy (AFM). Hydrocarbon contaminations on the surface may contribute to the mechanisms of Sr depletion, which have important implications for Sr(Ti1-xFex)O3-δ materials in gas sensing applications.

  1. Structural and electrical properties of oxygen complexes in Cz and FZ silicon crystals implanted with carbon ions

    NASA Astrophysics Data System (ADS)

    Romanyuk, Boris; Melnik, Victor; Popov, Valentin; Babich, Vilik; Kladko, Vasyl; Gudymenko, Olexandr; Ilchenko, Volodimir; Vasyliev, Iegor; Goriachko, Andrii

    2014-12-01

    We present a comparative study of thermal donor (TD) center formation mechanisms as a result of carbon ion implantation into float zone (FZ-Si) and Czochralski (Cz-Si) silicon crystals. The kinetics of the TD center formation and transformation of their structure during annealing have been investigated. Also, the TD center formation takes place after additional oxygen implantation into FZ/Cz-Si, and an important role of recoil oxygen atoms (from the screen oxide) has been demonstrated for the FZ-Si case. Their concentration in the Si surface layer depends on the implantation dose and the screen oxide thickness, reaching up to values 1018 to 1019 cm-3, which is comparable with the oxygen concentration in Cz-Si. These oxygen atoms can lead to additional thermal donor centers generation, especially in the FZ-Si.

  2. Structural and Optical Properties Studies Of Ar{sup 2+} Ion Implanted Mn Deposited GaAs

    SciTech Connect

    Tripthi, S.; Dubey, R. L.; Dubey, S. K.; Yadav, A. D.

    2010-12-01

    Mn thin film deposited GaAs samples were implanted with 250 keV Ar{sup +2} ions for various fluences 5x10{sup 15}, 1x10{sup 16} and 5x10{sup 16} ions cm{sup -2}. Optical and structural properties of the samples have been investigated by using ultraviolet spectroscopy and X-ray diffraction techniques. Optical absorbance of the implanted samples was found to decrease with increase in argon ion fluence. XRD spectra of the samples implanted for ion fluences 5x10{sup 15} and 1x10{sup 16} showed the formation of (GaMn)As at 2{theta} value of 65.34 deg. The XRD spectrum of sample 1x10{sup 16} cm{sup -2} annealed at 450 deg. C showed the formation of magnetic phases.

  3. Structural-phase changes in Al6061-T6 alloy during high-dose N-2(+) implantation

    NASA Astrophysics Data System (ADS)

    Soukieh, M.

    2004-02-01

    N 2 + nitrogen ions with an energy of 50 keV were implanted into Al6061-T6 alloy with high dose (10(16) - 2 x 10(17) ions/cm(2)) at room temperature in order to form thin aluminium nitride (AlN) layers. The structural-phase changes in implanted Al 6061-T6 alloy were investigated using Rutherford back-scattering and transmission electron microscopic techniques. The results indicate that nitrogen implantation led to the formation of nitride phases (AlN, Al7N C-3(3)) which improved the surface hardness by 80% and increased the electrical resistance up to 1800% at maximum dose (2 x 10(17) ions/cm(2)).

  4. Shot detection combining Bayesian and structural information

    NASA Astrophysics Data System (ADS)

    Han, Seung H.; Kweon, In-So

    2000-12-01

    There are a number of shots in a video, each of which has boundary types, such as cut, fade, dissolve and wipe. Many previous approaches can find the cut boundary without difficulty. However, most of them often produce false alarms for the videos with large motions of camera and objects. We propose a shot boundary detection method combining Bayesian and structural information. In the Bayesian approach, a probability distribution function models each transition type, e.g., normal, abrupt, gradual transition, and also models shot length. But inseparability between those distributions causes unwanted results and degrades the precision. In this paper, we demonstrate that the shape of the filtered frame difference, called the structural information, provides an important cue to distinguish fade and dissolve effects form cut effects and gradual changes caused by motion of camera and objects. The proposed method has been tested for a few golf video segments and shown good performances in detecting fade and dissolve effects as well as cut.

  5. Structural outlier detection for automatic landmark extraction

    NASA Astrophysics Data System (ADS)

    Mattes, Julian; Demongeot, Jacques

    2001-07-01

    The aim of this paper is to introduce a structural dissimilarity measure which allows to detect outliers in automatically extracted landmark pairs in two images. In previous work, to extract landmarks automatically, candidate points have been defined using invariance criteria coming from differential geometry such as maximum curvature; or they are statistical entities such as gravity centers of confiners, where the confiners are defined as the connected components of the level sets. After a first estimation of the semi-rigid transformation (representing translation, rotation, and scaling) relating the candidate point sets, outliers are detected applying the euclidian distance between corresponding points. However, this approach does not allow to distinguish between real deformations and outliers coming from noise or additional features in one of the images. In this paper, we define a structural dissimilarity measure which we use to decide if two associated candidate points come from two corresponding confiners. We select landmarks pairs with a dissimilarity value smaller than a given threshold and we calculate the affine transformation relating best all selected landmark pairs. We evaluated our technique on successive slices of a MRI image of the human brain and show that we obtain a significantly sharper error diminution using the new dissimilarity measure instead of the euclidian distance for outlier rejection.

  6. Structural, optical, and magnetic properties of highly-resistive Sm-implanted GaN thin films

    SciTech Connect

    Lo, Fang-Yuh Huang, Cheng-De; Chou, Kai-Chieh; Guo, Jhong-Yu; Liu, Hsiang-Lin; Chia, Chi-Ta; Ney, Verena; Ney, Andreas; Shvarkov, Stepan; Reuter, Dirk; Wieck, Andreas D.; Pezzagna, Sébastien; Chern, Ming-Yau; Massies, Jean

    2014-07-28

    Samarium ions of 200 keV in energy were implanted into highly-resistive molecular-beam-epitaxy grown GaN thin films with a focused-ion-beam implanter at room temperature. The implantation doses range from 1 × 10{sup 14} to 1 × 10{sup 16 }cm{sup −2}. Structural properties studied by x-ray diffraction and Raman-scattering spectroscopy revealed Sm incorporation into GaN matrix without secondary phase. The optical measurements showed that the band gap and optical constants changed very slightly by the implantation. Photoluminescence measurements showed emission spectra similar to p-type GaN for all samples. Magnetic investigations with a superconducting quantum interference device identified magnetic ordering for Sm dose of and above 1 × 10{sup 15 }cm{sup −2} before thermal annealing, while ferromagnetism was only observed after thermal annealing from the sample with highest Sm dose. The long-range magnetic ordering can be attributed to interaction of Sm ions through the implantation-induced Ga vacancy.

  7. Structural and Magnetic Properties of Fe and Au Ion-Implanted Al2O3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Kinoshita, Ryosuke; Sakamoto, Isao; Hayashi, Nobuyuki; Nomura, Kiyoshi; Honda, Shigeo; Ishida, Tomoya; Iio, Satoshi; Tashiro, Hiroyuki; Toriyama, Tamotsu

    2011-01-01

    Au ion implantation in Fe ion-implanted Al2O3 (Fe/Al2O3) has been performed in order to tailor the structural, magnetic and optical properties of Fe granules in Al2O3 matrix. After Au ion implantation, Rutherford backscattering (RBS) measurements indicate the decrease and the redistribution of retained Fe atoms with the inclusion of Au atoms, and the patterns of X-ray diffraction (XRD) show the formation of Au granules in the Fe/Al2O3. Besides, the magnetization curves of the Fe/Al2O3 after Au ion implantation show still the superparamagnetic characteristics and the decrease of saturation magnetization, and the optical absorption measurements indicate the formation of Au granules in the Fe/Al2O3 in accordance with the XRD result. In addition, we investigated a behavior of Fe granules in Al2O3 matrix by conversion electron Mössbauer spectroscopy (CEMS), which indicates the decrease of superparamagnetic state as a function of Au ion dose. As a result, it is suggested that Au ion implantation has potentialities to tailor the physical properties of Fe granules in Al2O3 matrix.

  8. Osseointegration of zirconia implants: an SEM observation of the bone-implant interface

    PubMed Central

    Depprich, Rita; Zipprich, Holger; Ommerborn, Michelle; Mahn, Eduardo; Lammers, Lydia; Handschel, Jörg; Naujoks, Christian; Wiesmann, Hans-Peter; Kübler, Norbert R; Meyer, Ulrich

    2008-01-01

    Background The successful use of zirconia ceramics in orthopedic surgery led to a demand for dental zirconium-based implant systems. Because of its excellent biomechanical characteristics, biocompatibility, and bright tooth-like color, zirconia (zirconium dioxide, ZrO2) has the potential to become a substitute for titanium as dental implant material. The present study aimed at investigating the osseointegration of zirconia implants with modified ablative surface at an ultrastructural level. Methods A total of 24 zirconia implants with modified ablative surfaces and 24 titanium implants all of similar shape and surface structure were inserted into the tibia of 12 Göttinger minipigs. Block biopsies were harvested 1 week, 4 weeks or 12 weeks (four animals each) after surgery. Scanning electron microscopy (SEM) analysis was performed at the bone implant interface. Results Remarkable bone attachment was already seen after 1 week which increased further to intimate bone contact after 4 weeks, observed on both zirconia and titanium implant surfaces. After 12 weeks, osseointegration without interposition of an interfacial layer was detected. At the ultrastructural level, there was no obvious difference between the osseointegration of zirconia implants with modified ablative surfaces and titanium implants with a similar surface topography. Conclusion The results of this study indicate similar osseointegration of zirconia and titanium implants at the ultrastructural level. PMID:18990214

  9. Impact detection on airborne multilayered structures

    NASA Astrophysics Data System (ADS)

    Noharet, Bertrand; Chazelas, Jean; Bonniau, Philippe; Lecuellet, Jerome; Turpin, Marc J.

    1995-04-01

    This paper reviews the progress of an ongoing research program at Thomson-CSF and Bertin & Cie which addresses an optical fiber system dedicated to the assessment of impact induced damages on airborne multilayered structures. The method is based on the use of embedded high birefringence optical fiber sensors and distributed white light interfero-polarimetry. The first part is devoted to the transduction process efficiency within optical fibers depending on the applied force intensity, direction versus the fiber eigen axes and the interaction length. To understand the behavior of these optical fibers and calibrate the detection system, experiments have been conducted on elliptical core fibers, `bow-tie' fibers and side-hole fibers and showed a wide range of available sensitivities. The second step is related to the inclusion of optical fibers in a sandwich structure representative of an airborne dome, and composed of foam between glass/epoxy composite skins. Different designs of grooves in the foam and tube sheathings have been investigated to support and protect the optical fiber. Impacts have been performed on the structure in the 1 to 10 Joules energy range. Experimental impact location and energy measurements have been achieved for a variety of stress fields.

  10. Laser beam melting 3D printing of Ti6Al4V based porous structured dental implants: fabrication, biocompatibility analysis and photoelastic study.

    PubMed

    Yang, Fei; Chen, Chen; Zhou, QianRong; Gong, YiMing; Li, RuiXue; Li, ChiChi; Klämpfl, Florian; Freund, Sebastian; Wu, XingWen; Sun, Yang; Li, Xiang; Schmidt, Michael; Ma, Duan; Yu, YouCheng

    2017-03-28

    Fabricating Ti alloy based dental implants with defined porous scaffold structure is a promising strategy for improving the osteoinduction of implants. In this study, we use Laser Beam Melting (LBM) 3D printing technique to fabricate porous Ti6Al4V dental implant prototypes with three controlled pore sizes (200, 350 and 500 μm). The mechanical stress distribution in the surrounding bone tissue is characterized by photoelastography and associated finite element simulation. For in-vitro studies, experiments on implants' biocompatibility and osteogenic capability are conducted to evaluate the cellular response correlated to the porous structure. As the preliminary results, porous structured implants show a lower stress-shielding to the surrounding bone at the implant neck and a more densed distribution at the bottom site compared to the reference implant. From the cell proliferation tests and the immunofluorescence images, 350 and 500 μm pore sized implants demonstrate a better biocompatibility in terms of cell growth, migration and adhesion. Osteogenic genes expression of the 350 μm group is significantly increased alone with the ALP activity test. All these suggest that a pore size of 350 μm provides an optimal provides an optimal potential for improving the mechanical shielding to the surrounding bones and osteoinduction of the implant itself.

  11. Cochlear implant speech intelligibility outcomes with structured and unstructured binary mask errors.

    PubMed

    Kressner, Abigail A; Westermann, Adam; Buchholz, Jörg M; Rozell, Christopher J

    2016-02-01

    It has been shown that intelligibility can be improved for cochlear implant (CI) recipients with the ideal binary mask (IBM). In realistic scenarios where prior information is unavailable, however, the IBM must be estimated, and these estimations will inevitably contain errors. Although the effects of both unstructured and structured binary mask errors have been investigated with normal-hearing (NH) listeners, they have not been investigated with CI recipients. This study assesses these effects with CI recipients using masks that have been generated systematically with a statistical model. The results demonstrate that clustering of mask errors substantially decreases the tolerance of errors, that incorrectly removing target-dominated regions can be as detrimental to intelligibility as incorrectly adding interferer-dominated regions, and that the individual tolerances of the different types of errors can change when both are present. These trends follow those of NH listeners. However, analysis with a mixed effects model suggests that CI recipients tend to be less tolerant than NH listeners to mask errors in most conditions, at least with respect to the testing methods in each of the studies. This study clearly demonstrates that structure influences the tolerance of errors and therefore should be considered when analyzing binary-masking algorithms.

  12. Fabrication, pore structure and compressive behavior of anisotropic porous titanium for human trabecular bone implant applications.

    PubMed

    Li, Fuping; Li, Jinshan; Xu, Guangsheng; Liu, Gejun; Kou, Hongchao; Zhou, Lian

    2015-06-01

    Porous titanium with average pore size of 100-650 μm and porosity of 30-70% was fabricated by diffusion bonding of titanium meshes. Pore structure was characterized by Micro-CT scan and SEM. Compressive behavior of porous titanium in the out-of-plane direction was studied. The effect of porosity and pore size on the compressive properties was also discussed based on the deformation mode. The results reveal that the fabrication process can control the porosity precisely. The average pore size of porous titanium can be tailored by adjusting the pore size of titanium meshes. The fabricated porous titanium possesses an anisotropic structure with square pores in the in-plane direction and elongated pores in the out-of-plane direction. The compressive Young's modulus and yield stress are in the range of 1-7.5 GPa and 10-110 MPa, respectively. The dominant compressive deformation mode is buckling of mesh wires, but some uncoordinated buckling is present in porous titanium with lower porosity. Relationship between compressive properties and porosity conforms well to the Gibson-Ashby model. The effect of pore size on compressive properties is fundamentally ascribed to the aspect ratio of titanium meshes. Porous titanium with 60-70% porosity has potential for trabecular bone implant applications.

  13. Implantable multiprogrammable microstimulator dedicated to bladder control.

    PubMed

    Arabi, K; Sawan, M

    1996-01-01

    An implantable multiprogrammable microstimulator that is intended to restore normal bladder functions (retention and incontinence) to spinal cord injured patients is presented. The implantable microstimulator circuitry is externally controlled and is powered by a single encoded radio frequency carrier and has four bipolar (eight monopolar) independently controlled channels. It offers a higher degree of reprogrammability and flexibility and can be used in any neuromuscular applications. The implant system is adaptable to the patient's needs and to future developments in stimulation algorithms, without changing the implant. Features of the microstimulator include its capabilities to generate a wide range of waveforms and to combine up to four different programmable frequencies in each wave train. By using a forward error detection and correction communication protocol, the reliability of the implant is increased. The chip has been designed for structural testability by means of a scan-based test approach and uses circuit techniques to reduce power consumption and ensure long-term stability.

  14. Experimental and theoretical investigations of electronic and atomic structure of Si-nanocrystals formed in sapphire by ion implantation

    NASA Astrophysics Data System (ADS)

    Wainstein, D.; Kovalev, A.; Tetelbaum, D.; Mikhailov, A.; Bulutay, C.; Aydinli, A.

    2008-03-01

    The semiconductor nanocomposites based on Si nanocrystals in dielectric matrices attract a great amount of attention due to their ability for luminescence in visible and near-IR part of the electromagnetic spectrum. Si nanocrystals in sapphire matrix were formed by Si+ ion implantation with doses from 5×1016 to 3×1017 cm-2 at an accelerating voltage 100 kV and post-implantation annealing at 500 - 1100 °C for 2 hours. Depth distribution of lattice defects, impurities and Si nanocrystals, the peculiarities of interband electronic transitions were investigated by XPS and HREELS. The molecular orbitals and local electronic structure of the Al2O3 matrix with Si nanocrystals was calculated using an atomistic pseudopotential technique. The electronic structure of Si nanocrystals as determined from HREELS measurements is in good agreement with the theoretically calculated electronic structure for Si nanocrystals.

  15. The Effect of Thermal Annealing on Structural-phase Changes in the Ni-Ti Alloy Implanted with Krypton Ions

    NASA Astrophysics Data System (ADS)

    Poltavtseva, V. P.; Kislitsin, S. B.; Ghyngazov, S. A.

    2016-06-01

    The influence of thermal annealing within the temperature range 100-300°C on the structural-phase state of a Ni-Ti alloy with shape memory effect (SME) implanted with 84Kr ions at the energies E = 280 keV and 1.75 MeV/nucl and the fluences within 5·1012-1·1020 ion/m2 is investigated. For the samples modified by 84Kr ions at E = 1.75 MeV/nucl up to the fluences 1·1020 and 5·1012 ion/m2, the formation of a martensitic NiTi phase with the B19 ' structure, responsible for the SME, is revealed at the annealing temperatures 100 and 300°C, respectively, in the near-surface region corresponding to the outrange area. This is accompanied by the formation of nanosized NiTi particles in the R-phase. As the implantation fluence increases, the probability of their formation decreases. It is shown that annealing of the implanted structures can increase the strength of the Ni-Ti alloy. The degree of hardening is determined by the value of annealing temperature, and an increase in strength is primarily due to ordering of the radiation-induced defect structures (phases). A correlation between the onset temperature of a forward martensitic transition and the structural-phase state of the thermally annealed Ni-Ti alloy is established.

  16. Lagrangian based methods for coherent structure detection

    SciTech Connect

    Allshouse, Michael R.; Peacock, Thomas

    2015-09-15

    There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows.

  17. Case report and brief review of literature on sonographic detection of accidentally implanted wooden foreign body causing persistent sinus

    PubMed Central

    2012-01-01

    Despite advances in imaging techniques, the detection of vegetative foreign bodies in soft tissues remains a difficult and sometimes even a challenging task. Clinical evaluation of such patient may present several months or even years after the initial injury and clinician may fail to elicit an antecedent skin puncture. X-ray examination will miss radiolucent foreign bodies. A 15-year-old boy presented with a draining non-healing sinus at the lateral aspect of his right thigh for 9 months. Musculoskeletal ultrasonography was ordered after ruling out chronic osteomyelitis to detect possible lesions around the thigh. High-frequency linear ultrasonic probe readily detected an elongated foreign body within the vastus lateralis muscle. A long piece of wood was confirmed at surgery. Non-healing sinus with normal finding in radiograph following old trauma should raise the suspicion of implanted radiolucent foreign body/bodies. The role of diagnostic ultrasound as a valuable screening tool for the detection of foreign body is briefly reviewed. PMID:22871025

  18. Detecting slab structure beneath the Mediterranean

    NASA Astrophysics Data System (ADS)

    Miller, Meghan S.; Sun, Daoyuan; Piana Agostinetti, Nicola

    2013-04-01

    The presence of subducted slabs in the Mediterranean has been well documented with seismic tomography, however, these images, which are produced by smoothed, damped inversions, underestimate the sharpness of the structures. The position and extent of the slabs and the presence possible tears or gaps in the subducted lithosphere are still debated, yet the shape and location these structures are important for kinematic reconstructions and evolution of the entire subduction zone system. Extensive distribution of broadband seismic instrumentation in the Mediterranean (Italian National Seismic Network in Italy and the NSF-PICASSO project in Spain and Morocco) has allowed us to use alternative methodologies to detect the position of the slabs and slab tears beneath the Central and Western Mediterranean. Using S receiver functions we are able to identify S-to-p conversions from the bottom of the subducted slab and a lack of these signals where there are gaps or tears in the slab. We also analyze broadband waveforms for changes in P wave coda from deep (> 300 km depth) local earthquakes. The waveform records for stations in southern Italy and around the Betic-Rif show large amplitude, high frequency (f > 5 Hz) late arrivals with long coda after relatively low-frequency onset. High frequency arrivals are the strongest from events whose raypaths travel within the slab to the stations where they are recorded allowing for mapping of where the subducted material is located within the upper mantle. These two methods, along with inferring the slab position from fast P-wave velocity perturbations in tomography and intermediate depth seismicity, provide additional geophysical evidence to aid in interpretation of the complex, segmented slab structure beneath the Mediterranean.

  19. Visible and near-infrared planar waveguide structure of polycrystalline zinc sulfide from C ions implantation.

    PubMed

    Liu, Tao; Liu, Peng; Zhang, Lian; Zhou, Yu-Fan; Yu, Xiao-Fei; Zhao, Jin-Hua; Wang, Xue-Lin

    2013-02-25

    We report the fabrication of a planar waveguide in polycrystalline zinc sulfide by 6.0 MeV C ions implantation with a fluence of 5 × 10¹⁴ ion/cm² at room temperature. The near-field light intensity profiles in the visible and near-infrared bands are measured by the end-face coupling method with different laser sources. Investigation of the Raman spectra demonstrates that the microstructure of the polycrystalline zinc sulfide has no significant change after C ion implantation. The absorption spectra show that the implantation processes have no influence on the visible and infrared bands.

  20. Simulation of fracture of the bone implant with the porous structure

    NASA Astrophysics Data System (ADS)

    Korobenkov, M. V.; Kulkov, S. N.

    2016-08-01

    Different approaches to bone defects reconstruction with the use of ceramic materials have been developed recently. Ceramics are identical with bone matrix, provide biomedical compatibility with bone tissue and possess high strength. But with an overall high strength ceramic implants destruct in dynamic mode. The paper presents a study of the effect of the porosity gradient on the destruction of the bone implants under dynamic loading. It is shown that the fracture behavior of the bone implants is changed with increasing levels of the gradient of porosity.

  1. Dual-carrier processing to convey temporal fine structure cues: Implications for cochlear implants

    PubMed Central

    Apoux, Frédéric; Youngdahl, Carla L.; Yoho, Sarah E.; Healy, Eric W.

    2015-01-01

    Speech intelligibility in noise can be degraded by using vocoder processing to alter the temporal fine structure (TFS). Here it is argued that this degradation is not attributable to the loss of speech information potentially present in the TFS. Instead it is proposed that the degradation results from the loss of sound-source segregation information when two or more carriers (i.e., TFS) are substituted with only one as a consequence of vocoder processing. To demonstrate this segregation role, vocoder processing involving two carriers, one for the target and one for the background, was implemented. Because this approach does not preserve the speech TFS, it may be assumed that any improvement in intelligibility can only be a consequence of the preserved carrier duality and associated segregation cues. Three experiments were conducted using this “dual-carrier” approach. All experiments showed substantial sentence intelligibility in noise improvements compared to traditional single-carrier conditions. In several conditions, the improvement was so substantial that intelligibility approximated that for unprocessed speech in noise. A foreseeable and potentially promising implication for the dual-carrier approach involves implementation into cochlear implant speech processors, where it may provide the TFS cues necessary to segregate speech from noise. PMID:26428784

  2. Magnesium behavior and structural defects in Mg+ ion implanted silicon carbide

    NASA Astrophysics Data System (ADS)

    Jiang, Weilin; Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-03-01

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the <1 0 0> axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C-SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C-SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4 × 10-19 m2/s.

  3. Sensitivity of bilateral cochlear implant users to fine-structure and envelope interaural time differences.

    PubMed

    Noel, Victor A; Eddington, Donald K

    2013-04-01

    Bilateral cochlear implant users have poor sensitivity to interaural time differences (ITDs) of high-rate pulse trains, which precludes use of these stimuli to convey fine-structure ITD cues. However, previous reports of single-neuron recordings in cats demonstrated good ITD sensitivity to 1000 pulses-per-second (pps) pulses when the pulses were sinusoidally amplitude modulated. The ability of modulation to restore ITD sensitivity to high-rate pulses in humans was tested by measuring ITD thresholds for three conditions: ITD encoded in the modulated carrier pulses alone, in the envelope alone, and in the whole waveform. Five of six subjects were not sensitive to ITD in the 1000-pps carrier, even with modulation. One subject's 1000-pps carrier ITD sensitivity did significantly improve due to modulation. Sensitivity to ITD encoded in the envelope was also measured as a function of modulation frequency, including at frequencies from 4 to 16 Hz where much of the speech envelope's energy and information resides. Sensitivity was best at the modulation frequency of 100 Hz and degraded rapidly outside of a narrow range. These results provide little evidence to support encoding ITD in the carrier of current bilateral processors, and suggest envelope ITD sensitivity is poor for an important segment of the speech modulation spectrum.

  4. Sensitivity of bilateral cochlear implant users to fine-structure and envelope interaural time differencesa

    PubMed Central

    Noel, Victor A.; Eddington, Donald K.

    2013-01-01

    Bilateral cochlear implant users have poor sensitivity to interaural time differences (ITDs) of high-rate pulse trains, which precludes use of these stimuli to convey fine-structure ITD cues. However, previous reports of single-neuron recordings in cats demonstrated good ITD sensitivity to 1000 pulses-per-second (pps) pulses when the pulses were sinusoidally amplitude modulated. The ability of modulation to restore ITD sensitivity to high-rate pulses in humans was tested by measuring ITD thresholds for three conditions: ITD encoded in the modulated carrier pulses alone, in the envelope alone, and in the whole waveform. Five of six subjects were not sensitive to ITD in the 1000-pps carrier, even with modulation. One subject's 1000-pps carrier ITD sensitivity did significantly improve due to modulation. Sensitivity to ITD encoded in the envelope was also measured as a function of modulation frequency, including at frequencies from 4 to 16 Hz where much of the speech envelope's energy and information resides. Sensitivity was best at the modulation frequency of 100 Hz and degraded rapidly outside of a narrow range. These results provide little evidence to support encoding ITD in the carrier of current bilateral processors, and suggest envelope ITD sensitivity is poor for an important segment of the speech modulation spectrum. PMID:23556598

  5. Airport and superficial femoral artery obstruction due to a wandering coronary stent: the possibility of airport detection of modern implant metals.

    PubMed

    Teijink, J A W; van Herwaarden, J A; van den Berg, J C; Overtoom, T C; Moll, F L

    2004-06-01

    In the treatment of coronary artery disease, peripheral loss of a coronary stent is an unusual complication. We present the case of a patient who suggested that his right leg claudication was caused by a slipped coronary stent 2 years previously. The patient was convinced about this unusual finding based on an airport security check. Examination proved him to be right. However, the ability to detect an object using eddy currents is dependent on the object's permeability and its conductivity. Ferrous (iron) content is not the critical factor. Modern implant materials and processing techniques result in implants that are difficult to magnetize i.e. their permeability is very low. In addition their conductivity is very low. This enables modern implants to escape detection at airports. For this reason the event at the airport, as described by our patient, is considered coincidental.

  6. Laser beam melting 3D printing of Ti6Al4V based porous structured dental implants: fabrication, biocompatibility analysis and photoelastic study

    PubMed Central

    Yang, Fei; Chen, Chen; Zhou, QianRong; Gong, YiMing; Li, RuiXue; Li, ChiChi; Klämpfl, Florian; Freund, Sebastian; Wu, XingWen; Sun, Yang; Li, Xiang; Schmidt, Michael; Ma, Duan; Yu, YouCheng

    2017-01-01

    Fabricating Ti alloy based dental implants with defined porous scaffold structure is a promising strategy for improving the osteoinduction of implants. In this study, we use Laser Beam Melting (LBM) 3D printing technique to fabricate porous Ti6Al4V dental implant prototypes with three controlled pore sizes (200, 350 and 500 μm). The mechanical stress distribution in the surrounding bone tissue is characterized by photoelastography and associated finite element simulation. For in-vitro studies, experiments on implants’ biocompatibility and osteogenic capability are conducted to evaluate the cellular response correlated to the porous structure. As the preliminary results, porous structured implants show a lower stress-shielding to the surrounding bone at the implant neck and a more densed distribution at the bottom site compared to the reference implant. From the cell proliferation tests and the immunofluorescence images, 350 and 500 μm pore sized implants demonstrate a better biocompatibility in terms of cell growth, migration and adhesion. Osteogenic genes expression of the 350 μm group is significantly increased alone with the ALP activity test. All these suggest that a pore size of 350 μm provides an optimal provides an optimal potential for improving the mechanical shielding to the surrounding bones and osteoinduction of the implant itself. PMID:28350007

  7. Chemical and structural analysis of the bone-implant interface by TOF-SIMS, SEM, FIB and TEM: Experimental study in animal

    NASA Astrophysics Data System (ADS)

    Palmquist, Anders; Emanuelsson, Lena; Sjövall, Peter

    2012-06-01

    Although bone-anchored implants are widely used in reconstructive medicine, the mechanism of osseointegration is still not fully understood. Novel analytical tools are needed to further understand this process, where both the chemical and structural aspects of the bone-implant interface are important. The aim of this study was to evaluate the advantages of combining time-of-flight secondary ion mass spectroscopy (TOF-SIMS) with optical (LM), scanning (SEM) and transmission electron microscopy (TEM) techniques for studying the bone-implant interface of bone-anchored implants. Laser-modified titanium implants with surrounded bone retrieved after 8 weeks healing in rabbit were dehydrated and resin embedded. Three types of sample preparation were studied to evaluate the information gained by combining TOF-SIMS, SEM, FIB and TEM. The results show that imaging TOF-SIMS can provide detailed chemical information, which in combination with structural information from microscopy methods provide a more complete characterization of anatomical structures at the bone-implant interface. By investigating various sample preparation techniques, it is shown that grinded cross section samples can be used for chemical imaging using TOF-SIMS, if careful consideration of potential preparation artifacts is taken into account. TOF-SIMS analysis of FIB-prepared bone/implant cross section samples show distinct areas corresponding to bone tissue and implant with a sharp interface, although without chemical information about the organic components.

  8. Animal Models for Evaluation of Bone Implants and Devices: Comparative Bone Structure and Common Model Uses.

    PubMed

    Wancket, L M

    2015-09-01

    Bone implants and devices are a rapidly growing field within biomedical research, and implants have the potential to significantly improve human and animal health. Animal models play a key role in initial product development and are important components of nonclinical data included in applications for regulatory approval. Pathologists are increasingly being asked to evaluate these models at the initial developmental and nonclinical biocompatibility testing stages, and it is important to understand the relative merits and deficiencies of various species when evaluating a new material or device. This article summarizes characteristics of the most commonly used species in studies of bone implant materials, including detailed information about the relevance of a particular model to human bone physiology and pathology. Species reviewed include mice, rats, rabbits, guinea pigs, dogs, sheep, goats, and nonhuman primates. Ultimately, a comprehensive understanding of the benefits and limitations of different model species will aid in rigorously evaluating a novel bone implant material or device.

  9. Structural phase states in nickel-titanium surface layers doped with silicon by plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Kashin, Oleg A.; Lotkov, Aleksandr I.; Kudryashov, Andrey N.; Krukovsky, Konstantin V.; Ostapenko, Marina G.; Neiman, Alexey A.; Borisov, Dmitry P.

    2015-10-01

    The paper reports on a study of NiTi-based alloys used for manufacturing self-expanding intravascular stents to elucidate how the technological modes of plasma immersion ion implantation with silicon influence the chemical and phase composition of their surface layers. It is shown that two types of surface structure can be obtained depending on the mode of plasma immersion implantation: quasi-amorphous Si coating and Si-doped surface layer. The Si-doped surface layer contains new phases: a phase structured as the main B2 phase of NiTi but with a lower lattice parameter, R phase, and phase of highly dispersed SiO2 precipitates.

  10. Stress influenced trapping processes in Si based multi-quantum well structures and heavy ions implanted Si

    SciTech Connect

    Ciurea, Magdalena Lidia Lazanu, Sorina

    2014-10-06

    Multi-quantum well structures and Si wafers implanted with heavy iodine and bismuth ions are studied in order to evaluate the influence of stress on the parameters of trapping centers. The experimental method of thermostimullatedcurrents without applied bias is used, and the trapping centers are filled by illumination. By modeling the discharge curves, we found in multilayered structures the parameters of both 'normal' traps and 'stress-induced' ones, the last having a Gaussian-shaped temperature dependence of the cross section. The stress field due to the presence of stopped heavy ions implanted into Si was modeled by a permanent electric field. The increase of the strain from the neighborhood of I ions to the neighborhood of Bi ions produces the broadening of some energy levels and also a temperature dependence of the cross sections for all levels.

  11. Hydrogen interstitial in H-ion implanted ZnO bulk single crystals: Evaluation by elastic recoil detection analysis and electron paramagnetic resonance

    NASA Astrophysics Data System (ADS)

    Kaida, T.; Kamioka, K.; Nishimura, T.; Kuriyama, K.; Kushida, K.; Kinomura, A.

    2015-12-01

    The origins of low resistivity in H ion-implanted ZnO bulk single crystals are evaluated by elastic recoil detection analysis (ERDA), electron paramagnetic resonance (EPR), and Van der Pauw methods. The H-ion implantation (peak concentration: 5.0 × 1015 cm-2) into ZnO is performed using a 500 keV implanter. The maximum of the concentration of the implanted H estimated by a TRIM simulation is at 3600 nm in depth. The resistivity decreases from ∼103 Ω cm for un implanted ZnO to 6.5 Ω cm for as-implanted, 2.3 × 10-1 Ω cm for 200 °C annealed, and 3.2 × 10-1 Ω cm for 400 °C annealed samples. The ERDA measurements can evaluate the concentration of hydrogens which move to the vicinity of the surface (surface to 300 nm or 100 nm) because of the diffusion by the annealing at 200 °C and 400 °C. The hydrogen concentration near the surface estimated using the 2.0 MeV helium beam is ∼3.8 × 1013 cm-2 for annealed samples. From EPR measurements, the oxygen vacancy of +charge state (Vo+) is observed in as-implanted samples. The Vo+ related signal (g = 1.96) observed under no illumination disappears after successive illumination with a red LED and appears again with a blue light illumination. The activation energy of as-implanted, 200 °C annealed, and 400 °C annealed samples estimated from the temperature dependence of carrier concentration lies between 29 meV and 23 meV, suggesting the existence of H interstitial as a shallow donor level.

  12. Hydrogen ion-implantation induced low resistive layer in KNbO3 bulk single crystal: Evaluation by elastic recoil detection analysis

    NASA Astrophysics Data System (ADS)

    Shinkawa, A.; Shibasaki, Y.; Nishimura, T.; Tanuma, C.; Kuriyama, K.

    2016-03-01

    Origins of low resistivity in H-ion implanted KNbO3 bulk single crystals are studied by elastic recoil detection analysis (ERDA) and Van der Pauw methods. The H-ion implantation (peak ion fluence: 5.0 × 1015 cm-2) into KNbO3 is performed using a 500 keV implanter. The sheet resistance decreases from ∼108 Ω/□ for an un-implanted KNbO3 sample to 2.33 × 105 Ω/□ for as-implanted, 2.29 × 105 Ω/□ for 100 °C annealed, and 4.25 × 105 Ω/□ for 150 °C annealed samples, respectively. The ERDA experiment using the 1.5 MeV-4He+ beam can evaluate hydrogen from the surface to around 60 nm. The hydrogen concentration near the surface estimated using the 1.5 MeV helium beam is 5.1 × 1014 cm-2 for un-implanted KNbO3 sample, 5.6 × 1014 cm-2 for as-implanted, 3.4 × 1014 cm-2 for 150 °C annealed samples, respectively, indicating that a part of hydrogen is diffused out by annealing. The low resistive layer induced in H-ion implanted KNbO3 suggests the existence of a shallow energy level related to the complex defect consisting of hydrogen interstitial and the proton induced defect such as oxygen vacancy.

  13. Investigating the structure and biocompatibility of niobium and titanium oxides as coatings for orthopedic metallic implants.

    PubMed

    Pradhan, D; Wren, A W; Misture, S T; Mellott, N P

    2016-01-01

    Applying sol gel based coatings to orthopedic metallic implant materials can significantly improve their properties and lifespan in vivo. For this work, niobium (Nb2O5) and titanium (TiO2) oxides were prepared via solution processing in order to determine the effect of atomic arrangement (amorphous/crystalline) on bioactivity. Thermal evaluation on the synthesized materials identified an endotherm for Nb2O5 at 75 °C with 40% weight loss below 400 °C, and minimal weight loss between 400 and 850 °C. Regarding TiO2 an endotherm was present at 92 °C with 25% weight loss below 400 °C, and 4% between 400 and 850 °C. Phase evolution was determined using High Temperature X-ray Diffraction (HT-XRD) where amorphous-Nb2O5 (450 °C), hexagonal-Nb2O5 (525 °C), orthorhombic-Nb2O5 (650 °C), amorphous-TiO2 (275 °C) and tetragonal TiO2 (500 °C) structures were produced. Simulated body fluid (SBF) testing was conducted over 1, 7 and 30 days and resulted in positive chemical and morphological changes for crystalline Nb2O5 (525 °C) and TiO2 (500 °C) after 30 days of incubation. Rod-like CaP deposits were observed on the surfaces using Scanning Electron Microscopy (FE-SEM) and Grazing Incidence-X-ray Diffraction (GI-XRD) shows that the deposits were X-ray amorphous. Cell viability was higher with the TiO2 (122%) samples when compared to the growing cell population while Nb2O5 samples exhibited a range of viability (64-105%), partially dependent on materials atomic structure.

  14. Structural, mechanical and optical properties of nitrogen-implanted titanium at different pulse frequency

    NASA Astrophysics Data System (ADS)

    Raaif, Mohamed; Mohamed, Sodky H.; Abd El-Rahman, Ahmed M.; Kolitsch, Andreas

    2013-04-01

    Plasma-immersion ion implantation (PIII) is a potent method to obtain hard and wear-resistant surface on Ti by nitrogen implantation. This presentation is one part of a sequence of experiments to optimize the microstructure and physical properties of TiN through adapting the plasma-processing parameters. In this work, nitrogen ions were implanted into samples of pure Ti at different nitrogen pulse frequency without using any external source of heating. The nitrogen-implanted surfaces were characterized by X-ray diffraction (XRD), Auger electron spectroscopy (AES), optical microscope, nano-indentation technique, ball-on-disk type tribometer, surface profilemeter, Tafel polarization technique for corrosion performance and ellipsometry. The outcomes show that, nitrogen PIII is an effectual method for nitriding titanium and nitrogen pulse frequency affected the microstructure and physical properties of the treated Ti. X-ray diffraction depicted the formation of α-Ti (N) and the cubic TiN after implanting titanium by nitrogen and the thickness of the nitrided layer increased as the nitrogen pulse frequency increased. The wear and corrosion resistance of the nitrogen-implanted titanium are improved and the friction coefficient decreased from nearly 0.8 for the un-implanted titanium to 0.3 for the implanted titanium, this ascribed to the formation of the titanium nitrided phases. Ellipsometric measurements were carried out on the PIII titanium samples at different nitrogen pulse frequency. The ellipsometric measurements show that, the thickness of the nitrided layer and surface roughness increased while the refractive index decreased with increasing nitrogen pulse frequency.

  15. STN area detection using K-NN classifiers for MER recordings in Parkinson patients during neurostimulator implant surgery

    NASA Astrophysics Data System (ADS)

    Schiaffino, L.; Rosado Muñoz, A.; Guerrero Martínez, J.; Francés Villora, J.; Gutiérrez, A.; Martínez Torres, I.; Kohan, y. D. R.

    2016-04-01

    Deep Brain Stimulation (DBS) applies electric pulses into the subthalamic nucleus (STN) improving tremor and other symptoms associated to Parkinson’s disease. Accurate STN detection for proper location and implant of the stimulating electrodes is a complex task and surgeons are not always certain about final location. Signals from the STN acquired during DBS surgery are obtained with microelectrodes, having specific characteristics differing from other brain areas. Using supervised learning, a trained model based on previous microelectrode recordings (MER) can be obtained, being able to successfully classify the STN area for new MER signals. The K Nearest Neighbours (K-NN) algorithm has been successfully applied to STN detection. However, the use of the fuzzy form of the K-NN algorithm (KNN-F) has not been reported. This work compares the STN detection algorithm of K-NN and KNN-F. Real MER recordings from eight patients where previously classified by neurophysiologists, defining 15 features. Sensitivity and specificity for the classifiers are obtained, Wilcoxon signed rank non-parametric test is used as statistical hypothesis validation. We conclude that the performance of KNN-F classifier is higher than K-NN with p<0.01 in STN specificity.

  16. A Three-Dimensional Finite Element Study on the Biomechanical Simulation of Various Structured Dental Implants and Their Surrounding Bone Tissues

    PubMed Central

    Zhang, Gong; Yuan, Hai; Chen, Xianshuai; Wang, Weijun; Chen, Jianyu; Liang, Jimin; Zhang, Peng

    2016-01-01

    Background/Purpose. This three-dimensional finite element study observed the stress distribution characteristics of 12 types of dental implants and their surrounding bone tissues with various structured abutments, implant threads, and healing methods under different amounts of concentrated loading. Materials and Methods. A three-dimensional geometrical model of a dental implant and its surrounding bone tissue was created; the model simulated a screw applied with a preload of 200 N or a torque of 0.2 N·m and a prosthetic crown applied with a vertical or an inclined force of 100 N. The Von Mises stress was evaluated on the 12 types of dental implants and their surrounding bone tissues. Results. Under the same loading force, the stress influence on the implant threads was not significant; however, the stress influence on the cancellous bone was obvious. The stress applied to the abutment, cortical bone, and cancellous bone by the inclined force applied to the crown was larger than the stress applied by the vertical force to the crown, and the abutment stress of the nonsubmerged healing implant system was higher than that of the submerged healing implant system. Conclusion. A dental implant system characterised by a straight abutment, rectangle tooth, and nonsubmerged healing may provide minimum value for the implant-bone interface. PMID:26904121

  17. Benefits of preserving stationary and time-varying formant structure in alternative representations of speech: implications for cochlear implants.

    PubMed

    Nittrouer, Susan; Lowenstein, Joanna H; Wucinich, Taylor; Tarr, Eric

    2014-10-01

    Cochlear implants have improved speech recognition for deaf individuals, but further modifications are required before performance will match that of normal-hearing listeners. In this study, the hypotheses were tested that (1) implant processing would benefit from efforts to preserve the structure of the low-frequency formants and (2) time-varying aspects of that structure would be especially beneficial. Using noise-vocoded and sine-wave stimuli with normal-hearing listeners, two experiments examined placing boundaries between static spectral channels to optimize representation of the first two formants and preserving time-varying formant structure. Another hypothesis tested in this study was that children might benefit more than adults from strategies that preserve formant structure, especially time-varying structure. Sixty listeners provided data to each experiment: 20 adults and 20 children at each of 5 and 7 years old. Materials were consonant-vowel-consonant words, four-word syntactically correct, meaningless sentences, and five-word syntactically correct, meaningful sentences. Results showed that listeners of all ages benefited from having channel boundaries placed to optimize information about the first two formants, and benefited even more from having time-varying structure. Children showed greater gains than adults only for time-varying formant structure. Results suggest that efforts would be well spent trying to design processing strategies that preserve formant structure.

  18. Benefits of preserving stationary and time-varying formant structure in alternative representations of speech: Implications for cochlear implants

    PubMed Central

    Nittrouer, Susan; Lowenstein, Joanna H.; Wucinich, Taylor; Tarr, Eric

    2014-01-01

    Cochlear implants have improved speech recognition for deaf individuals, but further modifications are required before performance will match that of normal-hearing listeners. In this study, the hypotheses were tested that (1) implant processing would benefit from efforts to preserve the structure of the low-frequency formants and (2) time-varying aspects of that structure would be especially beneficial. Using noise-vocoded and sine-wave stimuli with normal-hearing listeners, two experiments examined placing boundaries between static spectral channels to optimize representation of the first two formants and preserving time-varying formant structure. Another hypothesis tested in this study was that children might benefit more than adults from strategies that preserve formant structure, especially time-varying structure. Sixty listeners provided data to each experiment: 20 adults and 20 children at each of 5 and 7 years old. Materials were consonant-vowel-consonant words, four-word syntactically correct, meaningless sentences, and five-word syntactically correct, meaningful sentences. Results showed that listeners of all ages benefited from having channel boundaries placed to optimize information about the first two formants, and benefited even more from having time-varying structure. Children showed greater gains than adults only for time-varying formant structure. Results suggest that efforts would be well spent trying to design processing strategies that preserve formant structure. PMID:25324085

  19. A Brief Survey of β-Detected NMR of Implanted 8Li+ in Organic Polymers

    NASA Astrophysics Data System (ADS)

    McGee, F. H.; McKenzie, I.; Buck, T.; Daley, C. R.; Forrest, J. A.; Harada, M.; Kiefl, R. F.; Levy, C. D. P.; Morris, G. D.; Pearson, M. R.; Sugiyama, J.; Wang, D.; MacFarlane, W. A.

    2014-12-01

    Unlike the positive muon, we expect the chemistry of the implanted 8Li+β-NMR probe in organic polymers to be simply that of the monovalent ion, but almost nothing is known about the NMR of isolated Li+ in this context. Here, we present a brief survey of 8Li+β-NMR in a variety of insulating polymers at high magnetic field, including polyimide, PET, polycarbonate, polystyrene and polyethylene oxide. In all cases, we find a large-amplitude, broad Lorentzian resonance near the Larmor frequency, consistent with the expected diamagnetic charge state. We also find remarkably fast spin-lattice relaxation rates 1/T1. There is very little dependence of either linewidth or 1/T1 on the proton density, the main source of nuclear dipolar magnetic fields, leading us to conclude the main contribution to both broadening and spin relaxation at room temperature is quadrupolar in origin. This behaviour is very different from crystalline insulators such as MgO and Al2O3, and suggests that 8Li+β-NMR will be an important probe of polymer dynamics. Additionally, we note dramatically different behaviour of one sample above its glass transition, motivating the construction of a high temperature spectrometer to enable further exploration at elevated temperature.

  20. Detection of atrial arrhythmia for cardiac rhythm management by implantable devices.

    PubMed

    Morris, M M; KenKnight, B H; Lang, D J

    2000-01-01

    Implantable atrial defibrillators (IAD) should provide pacing therapy whenever appropriate (ie, typical atrial flutter) to minimize shock-related patient discomfort. Additionally, IADs should provide diagnostics regarding atrial arrhythmia type and frequency of occurrence to enable improved physician management of atrial arrhythmia. To achieve this, IADs should accurately classify atrial arrhythmia such as atrial fibrillation (AF) and atrial flutter (AFL) This article evaluates the performance of an algorithm, atrial rhythm classification (ARC), designed to classify AF and AFL. The ARC algorithm uses maximum rate, standard deviation, and range of the 12 most recent atrial cycle lengths to plot a point in a three-dimensional space. A decision boundary divides the space into 2 regions--faster/unstable atrial cycle lengths (AF) or slower/stable cycle lengths (AFL). Classifications are made on a sliding window of 12 consecutive cycles until the end of the episode is reached. In this way, continuous episode feedback is provided that can be used to help guide device therapy, measure arrhythmia type and frequency of occurrence. Bipolar (1-cm) electrogram episodes of AF (n = 16) and AFL (n = 7) were acquired from 20 patients and retrospectively analyzed using the ARC algorithm. The sensitivity and specificity in this study was 0.993 and 0.982, respectively. The ARC algorithm would have appropriately guided atrial therapy and minimized discomfort associated with defibrillation shocks in this small patient data set warranting further studies. The ARC algorithm may also be beneficial as a diagnostic tool to assist physician management of atrial arrhythmia.

  1. Comparison of the specificity of implantable dual chamber defibrillator detection algorithms.

    PubMed

    Hintringer, Florian; Deibl, Martina; Berger, Thomas; Pachinger, Otmar; Roithinger, Franz Xaver

    2004-07-01

    The aim of the study was to compare the specificity of dual chamber ICDs detection algorithms for correct classification of supraventricular tachyarrhythmias derived from clinical studies according to their size to detect an impact of sample size on the specificity. Furthermore, the study sought to compare the specificities of detection algorithms calculated from clinical data with the specificity calculated from simulations of tachyarrhythmias. A survey was conducted of all available sources providing data regarding the specificity of five dual chamber ICDs. The specificity was correlated with the number of patients included, number of episodes, and number of supraventricular tachyarrhythmias recorded. The simulation was performed using tachyarrhythmias recorded in the electrophysiology laboratory. The range of the number of patients included into the studies was 78-1,029, the range of the total number of episodes recorded was 362-5,788, and the range of the number of supraventricular tachyarrhythmias used for calculation of the specificity for correct detection of these arrhythmias was 100 (Biotronik) to 1662 (Medtronic). The specificity for correct detection of supraventricular tachyarrhythmias was 90% (Biotronik), 89% (ELA Medical), 89% (Guidant), 68% (Medtronic), and 76% (St. Jude Medical). There was an inverse correlation (r = -0.9, P = 0.037) between the specificity for correct classification of supraventricular tachyarrhythmias and the number of patients. The specificity for correct detection of supraventricular tachyarrhythmias calculated from the simulation after correction for the clinical prevalence of the simulated tachyarrhythmias was 95% (Biotronik), 99% (ELA Medical), 94% (Guidant), 93% (Medtronic), and 92% (St. Jude Medical). In conclusion, the specificity of ICD detection algorithms calculated from clinical studies or registries may depend on the number of patients studied. Therefore, a direct comparison between different detection algorithms

  2. Effect of retention design of artificial teeth and implant-supported titanium CAD-CAM structures on fracture resistance

    PubMed Central

    Ladetzki, Kristin; Mateos-Palacios, Rocío; Pascual-Moscardó, Agustín

    2016-01-01

    Background For implant-supported hybrid prostheses, high mastication forces and reduced acrylic resin thickness over a metal substructure often cause failures arising from tooth or resin fractures. To assay fracture resistance of artificial teeth and resin in implant-supported hybrid prostheses in relation to the titanium structure and retention design supporting teeth. Material and Methods 40 specimens bearing incisors were divided into four groups according to the titanium structure supporting the teeth and the type of load force applied: Group I (Control; n=10): Application of static loading to ten incisors set over a metal structure with internal retention. Group II (Control; n=10): Application of static loading to ten incisors set over a metal structure with external retention. The remaining study specimens (n=20) were subjected to 120,000 masticatory and thermal cycles in a chewing simulator. Afterwards, static loading was applied until the point of fracture using an Instron machine. Group III (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with internal retention. Group IV (Study; n=10): Application of dynamic and static loading to ten incisors set over a metal structure with external retention. Data obtained for the four groups was analyzed and compared, determining the type of fracture (cohesive or adhesive) using a reflected light microscope. Results Statistical analysis confirmed that there were significant differences in fracture resistance between the four groups. External retention was found to have more fracture resistance than the internal retention. Conclusions Hybrid prostheses with titanium substructures and external retention obtained significantly better results than samples with internal retention. Key words:Chewing simulator, thermocycler, fatigue, implant-supported hybrid prosthesis, acrylic teeth, fracture, metal structure design. PMID:27034748

  3. Nanostructured multielement (TiHfZrNbVTa)N coatings before and after implantation of N+ ions (1018 cm-2): Their structure and mechanical properties

    NASA Astrophysics Data System (ADS)

    Pogrebnjak, A. D.; Bondar, O. V.; Borba, S. O.; Abadias, G.; Konarski, P.; Plotnikov, S. V.; Beresnev, V. M.; Kassenova, L. G.; Drodziel, P.

    2016-10-01

    Multielement high entropy alloy (HEA) nitride (TiHfZrNbVTa)N coatings were deposited by vacuum arc and their structural and mechanical stability after implantation of high doses of N+ ions, 1018 cm-2, were investigated. The crystal structure and phase composition were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy, while depth-resolved nanoindentation tests were used to determine the evolution of hardness and elastic modulus along the implantation depth. XRD patterns show that coatings exhibit a main phase with fcc structure, which preferred orientation varies from (1 1 1) to (2 0 0), depending on the deposition conditions. First-principles calculations reveal that the presence of Nb atoms could favor the formation of solid solution with fcc structure in multielement HEA nitride. TEM results showed that amorphous and nanostructured phases were formed in the implanted coating sub-surface layer (∼100 nm depth). Concentration of nitrogen reached 90 at% in the near-surface layer after implantation, and decreased at higher depth. Nanohardness of the as-deposited coatings varied from 27 to 38 GPa depending on the deposition conditions. Ion implantation led to a significant decrease of the nanohardness to 12 GPa in the implanted region, while it reaches 24 GPa at larger depths. However, the H/E ratio is ⩾0.1 in the sub-surface layer due to N+ implantation, which is expected to have beneficial effect on the wear properties.

  4. Percutaneous Implants with Porous Titanium Dermal Barriers: An In Vivo Evaluation of Infection Risk

    PubMed Central

    Isackson, Dorthyann; McGill, Lawrence D.; Bachus, Kent N.

    2010-01-01

    Osseointegrated percutaneous implants are a promising prosthetic alternative for a subset of amputees. However, as with all percutaneous implants, they have an increased risk of infection since they breach the skin barrier. Theoretically, host tissues could attach to the metal implant creating a barrier to infection. When compared with smooth surfaces, it is hypothesized that porous surfaces improve the attachment of the host tissues to the implant, and decrease the infection risk. In this study, 4 titanium implants, manufactured with a percutaneous post and a subcutaneous disk, were placed subcutaneously on the dorsum of eight New Zealand White rabbits. Beginning at four weeks post-op, the implants were inoculated weekly with 108 CFU Staphylococcus aureus until signs of clinical infection presented. While we were unable to detect a difference in the incidence of infection of the porous metal implants, smooth surface (no porous coating) percutaneous and subcutaneous components had a 7-fold increased risk of infection compared to the implants with a porous coating on one or both components. The porous coated implants displayed excellent tissue ingrowth into the porous structures; whereas, the smooth implants were surrounded with a thick, organized fibrotic capsule that was separated from the implant surface. This study suggests that porous coated metal percutaneous implants are at a significantly lower risk of infection when compared to smooth metal implants. The smooth surface percutaneous implants were inadequate in allowing a long-term seal to develop with the soft tissue, thus increasing vulnerability to the migration of infecting microorganisms. PMID:21145778

  5. PROGRESS IN CHARACTERIZATION OF PRECIPITATES AND DEFECT STRUCTURES IN Mg+ ION IMPLANTED CUBIC SILICON CARBIDE

    SciTech Connect

    Jiang, Weilin; Zhang, Jiandong; Zhu, Zihua; Roosendaal, Timothy J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-09-01

    This report describes the progress of our current experimental effort on Mg+ ion implanted 3C-SiC. Following our initial study [ ] that suggests possible formation of Mg2Si and MgC2 precipitates as well as tetrahedral voids in 24Mg+ ion implanted 3C-SiC, we have designed specific experiments to confirm the results and examine the inclusions and defects. Relatively low fluence (5.0×1015 24Mg+/cm2) implantation in 3C-SiC was performed to reduce defect concentrations and isolate individual defect features for characterization. In addition, 25Mg+ isotope was implanted in 3C-SiC to the same previously applied ion fluence (9.6×1016 ions/cm2) for atom probe tomography (APT) study of precipitates. Each set of the samples was annealed at 1573 K for 2, 6 and 12 h, respectively. The depth profiles of the implanted Mg were measured using secondary ion mass spectrometry (SIMS) before and after the annealing steps. The samples are currently being analyzed using transmission electron microscopy (TEM) and APT.

  6. Accurate estimation of entropy in very short physiological time series: the problem of atrial fibrillation detection in implanted ventricular devices.

    PubMed

    Lake, Douglas E; Moorman, J Randall

    2011-01-01

    Entropy estimation is useful but difficult in short time series. For example, automated detection of atrial fibrillation (AF) in very short heart beat interval time series would be useful in patients with cardiac implantable electronic devices that record only from the ventricle. Such devices require efficient algorithms, and the clinical situation demands accuracy. Toward these ends, we optimized the sample entropy measure, which reports the probability that short templates will match with others within the series. We developed general methods for the rational selection of the template length m and the tolerance matching r. The major innovation was to allow r to vary so that sufficient matches are found for confident entropy estimation, with conversion of the final probability to a density by dividing by the matching region volume, 2r(m). The optimized sample entropy estimate and the mean heart beat interval each contributed to accurate detection of AF in as few as 12 heartbeats. The final algorithm, called the coefficient of sample entropy (COSEn), was developed using the canonical MIT-BIH database and validated in a new and much larger set of consecutive Holter monitor recordings from the University of Virginia. In patients over the age of 40 yr old, COSEn has high degrees of accuracy in distinguishing AF from normal sinus rhythm in 12-beat calculations performed hourly. The most common errors are atrial or ventricular ectopy, which increase entropy despite sinus rhythm, and atrial flutter, which can have low or high entropy states depending on dynamics of atrioventricular conduction.

  7. In Situ Characterization of Stimulating Microelectrode Arrays: Study of an Idealized Structure Based on Argus II Retinal implants

    NASA Astrophysics Data System (ADS)

    Kandagor, Vincent; Cela, Carlos J.; Sanders, Charlene A.; Greenbaum, Elias; Lazzi, Gianluca; Zhou, David D.; Castro, Richard; Gaikwad, Sanjay; Little, Jim

    The development of a retinal prosthesis for artificial sight includes a study of the factors affecting the structural and functional stability of chronically implanted microelectrode arrays. Although neuron depolarization and propagation of electrical signals have been studied for nearly a century, the use of multielectrode stimulation as a proposed therapy to treat blindness is a frontier area of modern ophthalmology research. Mapping and characterizing the topographic information contained in the electric field potentials and understanding how this information is transmitted and interpreted in the visual cortex is still very much a work in progress. In order to characterize the electrical field patterns generated by the device, an in vitro prototype that mimics several of the physical and chemical parameters of the in vivo visual implant device was fabricated. We carried out multiple electrical measurements in a model "eye," beginning with a single electrode, followed by a 9-electrode array structure, both idealized components based on the Argus II retinal implants. Correlating the information contained in the topographic features of the electric fields with psychophysical testing in patients may help reduce the time required for patients to convert the electrical patterns into graphic signals.

  8. Imaging of common breast implants and implant-related complications: A pictorial essay.

    PubMed

    Shah, Amisha T; Jankharia, Bijal B

    2016-01-01

    The number of women undergoing breast implant procedures is increasing exponentially. It is, therefore, imperative for a radiologist to be familiar with the normal and abnormal imaging appearances of common breast implants. Diagnostic imaging studies such as mammography, ultrasonography, and magnetic resonance imaging are used to evaluate implant integrity, detect abnormalities of the implant and its surrounding capsule, and detect breast conditions unrelated to implants. Magnetic resonance imaging of silicone breast implants, with its high sensitivity and specificity for detecting implant rupture, is the most reliable modality to asses implant integrity. Whichever imaging modality is used, the overall aim of imaging breast implants is to provide the pertinent information about implant integrity, detect implant failures, and to detect breast conditions unrelated to the implants, such as cancer.

  9. Community structure detection based on the neighbor node degree information

    NASA Astrophysics Data System (ADS)

    Tang, Li-Ying; Li, Sheng-Nan; Lin, Jian-Hong; Guo, Qiang; Liu, Jian-Guo

    2016-11-01

    Community structure detection is of great significance for better understanding the network topology property. By taking into account the neighbor degree information of the topological network as the link weight, we present an improved Nonnegative Matrix Factorization (NMF) method for detecting community structure. The results for empirical networks show that the largest improved ratio of the Normalized Mutual Information value could reach 63.21%. Meanwhile, for synthetic networks, the highest Normalized Mutual Information value could closely reach 1, which suggests that the improved method with the optimal λ can detect the community structure more accurately. This work is helpful for understanding the interplay between the link weight and the community structure detection.

  10. Cochlear Implants.

    ERIC Educational Resources Information Center

    Clark, Catherine; Scott, Larry

    This brochure explains what a cochlear implant is, lists the types of individuals with deafness who may be helped by a cochlear implant, describes the process of evaluating people for cochlear implants, discusses the surgical process for implanting the aid, traces the path of sound through the cochlear implant to the brain, notes the costs of…

  11. Detection of ventricular suction in an implantable rotary blood pump using support vector machines.

    PubMed

    Wang, Yu; Faragallah, George; Divo, Eduardo; Simaan, Marwan A

    2011-01-01

    A new suction detection algorithm for rotary Left Ventricular Assist Devices (LVAD) is presented. The algorithm is based on a Lagrangian Support Vector Machine (LSVM) model. Six suction indices are derived from the LVAD pump flow signal and form the inputs to the LSVM classifier. The LSVM classifier is trained and tested to classify pump flow patterns into three states: No Suction, Approaching Suction, and Suction. The proposed algorithm has been tested using existing in vivo data. When compared to three existing methods, the proposed algorithm produced superior performance in terms of classification accuracy, stability, and learning speed. The ability of the algorithm to detect suction provides a reliable platform in the development of a pump speed controller that has the capability of avoiding suction.

  12. In situ plasma fabrication of ceramic-like structure on polymeric implant with enhanced surface hardness, cytocompatibility and antibacterial capability.

    PubMed

    Liu, Jun; Zhang, Wei; Shi, Haigang; Yang, Kun; Wang, Gexia; Wang, Pingli; Ji, Junhui; Chu, Paul K

    2016-05-01

    Polymeric materials are commonly found in orthopedic implants due to their unique mechanical properties and biocompatibility but the poor surface hardness and bacterial infection hamper many biomedical applications. In this study, a ceramic-like surface structure doped with silver is produced by successive plasma implantation of silicon (Si) and silver (Ag) into the polyamine 66 (PA66) substrate. Not only the surface hardness and elastic modulus are greatly enhanced due to the partial surface carbonization and the ceramic-like structure produced by the reaction between energetic Si and the carbon chain of PA66, but also the antibacterial activity is improved because of the combined effects rendered by Ag and SiC structure. Furthermore, the modified materials which exhibit good cytocompatibility upregulate bone-related genes and proteins expressions of the contacted bone mesenchymal stem cells (BMSCs). For the first time, it explores out that BMSCs osteogenesis on the antibacterial ceramic-like structure is mediated via the iNOS and nNOS signal pathways. The results reveal that in situ plasma fabrication of an antibacterial ceramic-like structure can endow PA66 with excellent surface hardness, cytocompatibility, as well as antibacterial capability.

  13. Effects of thermal annealing on the structural and optical properties of carbon-implanted SiO2.

    PubMed

    Poudel, P R; Paramo, J A; Poudel, P P; Diercks, D R; Strzhemechny, Y M; Rout, B; McDaniel, F D

    2012-03-01

    Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.

  14. On the Structure of Phoneme Categories in Listeners with Cochlear Implants

    ERIC Educational Resources Information Center

    Lane, Harlan; Denny, Margaret; Guenther, Frank H.; Hanson, Helen M.; Marrone, Nicole; Matthies, Melanie L.; Perkell, Joseph S.; Stockmann, Ellen; Tiede, Mark; Vick, Jennell; Zandipour, Majid

    2007-01-01

    Purpose: To describe cochlear implant users' phoneme labeling, discrimination, and prototypes for a vowel and a sibilant contrast, and to assess the effects of 1 year's experience with prosthetic hearing. Method: Based on naturally produced clear examples of "boot," "beet," "said," and "shed" by 1 male and 1 female speaker, continua with 13…

  15. Geometrically structured implants for cranial reconstruction made of biodegradable polyesters and calcium phosphate/calcium carbonate.

    PubMed

    Schiller, Carsten; Rasche, Christian; Wehmöller, Michael; Beckmann, Felix; Eufinger, Harald; Epple, Matthias; Weihe, Stephan

    2004-01-01

    The aim of this study was the development of a processing pathway for manufacturing of biodegradable skull implants with individual geometry. The implants on the basis of polylactide and calcium phosphate/calcium carbonate were prepared by a combination of hot pressing and gas foaming. On the inside, the implant consists of a macroporous and faster degradable material (poly(D,L-lactide)+CaCO3) to allow the ingrowth of bone cells. The pore size is in the range of 200-400 microm. On the outside, the implant consists of a compact and slower biodegradable material (poly(L-lactide) and calcium phosphate) to ensure mechanical stability and protection. To overcome problems like inflammatory reactions caused by acidic degradation products of polylactide, the polyester was combined with basic filling materials (calcium salts). The filler neutralises the lactic acid produced during polymer degradation and increases the bioactivity of the material. The stabilised pH was demonstrated by long-term in vitro pH studies. Over a time period of 250 d in demineralised water, the pH was in the physiological range. The in vitro biocompatibility was shown by cell cultures with human osteoblasts. A good proliferation of the cells was observed over the whole test period of 4 weeks.

  16. Structural damage detection using active members and neural networks

    NASA Astrophysics Data System (ADS)

    Manning, R. A.

    1994-06-01

    The detection of damage in structures is a topic which has considerable interest in many fields. In the past many methods for detecting damage in structures has relied on finite element model refinement methods. This note presents a structural damage methodology in which only active member transfer function data are used in conjunction with an artificial neural network to detect damage in structures. Specifically, the method relies on training a neural network using active member transfer function pole/zero information to classify damaged structure measurements and to predict the degree of damage in the structure. The method differs from many of the past damage detection algorithms in that no attempt is made to update a finite element model or to match measured data with new finite element analyses of the structure in a damaged state.

  17. The Effect of Study Design Biases on the Diagnostic Accuracy of Magnetic Resonance Imaging to Detect Silicone Breast Implant Ruptures: A Meta-Analysis

    PubMed Central

    Song, Jae W.; Kim, Hyungjin Myra; Bellfi, Lillian T.; Chung, Kevin C.

    2010-01-01

    Background All silicone breast implant recipients are recommended by the US Food and Drug Administration to undergo serial screening to detect implant rupture with magnetic resonance imaging (MRI). We performed a systematic review of the literature to assess the quality of diagnostic accuracy studies utilizing MRI or ultrasound to detect silicone breast implant rupture and conducted a meta-analysis to examine the effect of study design biases on the estimation of MRI diagnostic accuracy measures. Method Studies investigating the diagnostic accuracy of MRI and ultrasound in evaluating ruptured silicone breast implants were identified using MEDLINE, EMBASE, ISI Web of Science, and Cochrane library databases. Two reviewers independently screened potential studies for inclusion and extracted data. Study design biases were assessed using the QUADAS tool and the STARDS checklist. Meta-analyses estimated the influence of biases on diagnostic odds ratios. Results Among 1175 identified articles, 21 met the inclusion criteria. Most studies using MRI (n= 10 of 16) and ultrasound (n=10 of 13) examined symptomatic subjects. Meta-analyses revealed that MRI studies evaluating symptomatic subjects had 14-fold higher diagnostic accuracy estimates compared to studies using an asymptomatic sample (RDOR 13.8; 95% CI 1.83–104.6) and 2-fold higher diagnostic accuracy estimates compared to studies using a screening sample (RDOR 1.89; 95% CI 0.05–75.7). Conclusion Many of the published studies utilizing MRI or ultrasound to detect silicone breast implant rupture are flawed with methodological biases. These methodological shortcomings may result in overestimated MRI diagnostic accuracy measures and should be interpreted with caution when applying the data to a screening population. PMID:21364405

  18. Influence of 400 keV carbon ion implantation on structural, optical and electrical properties of PMMA

    NASA Astrophysics Data System (ADS)

    Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Sagheer, Riffat; Naab, Fabian; Toader, Ovidiu; Mahmood, Arshad; Rashid, Rashad; Mahmood, Mazhar

    2015-09-01

    Ion implantation is a useful technique to modify surface properties of polymers without altering their bulk properties. The objective of this work is to explore the 400 keV C+ ion implantation effects on PMMA at different fluences ranging from 5 × 1013 to 5 × 1015 ions/cm2. The surface topographical examination of irradiated samples has been performed using Atomic Force Microscope (AFM). The structural and chemical modifications in implanted PMMA are examined by Raman and Fourier Infrared Spectroscopy (FTIR) respectively. The effects of carbon ion implantation on optical properties of PMMA are investigated by UV-Visible spectroscopy. The modifications in electrical conductivity have been measured using a four point probe technique. AFM images reveal a decrease in surface roughness of PMMA with an increase in ion fluence from 5 × 1014 to 5 × 1015 ions/cm2. The existence of amorphization and sp2-carbon clusterization has been confirmed by Raman and FTIR spectroscopic analysis. The UV-Visible data shows a prominent red shift in absorption edge as a function of ion fluence. This shift displays a continuous reduction in optical band gap (from 3.13 to 0.66 eV) due to formation of carbon clusters. Moreover, size of carbon clusters and photoconductivity are found to increase with increasing ion fluence. The ion-induced carbonaceous clusters are believed to be responsible for an increase in electrical conductivity of PMMA from (2.14 ± 0.06) × 10-10 (Ω-cm)-1 (pristine) to (0.32 ± 0.01) × 10-5 (Ω-cm)-1 (irradiated sample).

  19. Detection of entrapped moisture in honeycomb sandwich structures

    NASA Technical Reports Server (NTRS)

    Hallmark, W. B.

    1967-01-01

    Thermal neutron moisture detection system detects entrapped moisture in intercellular areas of bonded honeycomb sandwich structures. A radium/beryllium fast neutron source bombards a specimen. The emitted thermal neutrons from the target nucleus are detected and counted by a boron trifluoride thermal neutron detector.

  20. Efficacy and Limitations of Tachycardia Detection Interval Guided Reprogramming for Reduction of Inappropriate Shock in Implantable Cardioverter-Defibrillator Patients.

    PubMed

    Fujiishi, Tamami; Niwano, Shinichi; Murakami, Masami; Nakamura, Hironori; Igarashi, Tazuru; Ishizue, Naruya; Oikawa, Jun; Kishihara, Jun; Fukaya, Hidehira; Niwano, Hiroe; Ako, Junya

    2016-05-25

    The avoidance of inappropriate shock therapy is an important clinical issue in implantable cardioverter-defibrillator (ICD) patients. We retrospectively analyzed therapeutic events in ICD patients, and the effect of tachycardia detection interval (TDI) and tachycardia cycle length (TCL) guided reprograming on the reduction of inappropriate ICD therapy. The clinical determinants of after reprogramming were also evaluated.A total of 254 consecutive ICD patients were included in the study, and the incidence of antitachycardia therapy was evaluated during the follow-up period of 27.3 ± 18.7 months. When inappropriate antitachycardia therapy appeared, TDI was reprogrammed not to exceed the detected TCL and the patients continued to be followed-up. Various clinical parameters were compared between patients with and without inappropriate ICD therapy. During the initial follow-up period of 18.6 ± 15.6 months, ICD therapy occurred in 127/254 patients (50%) including inappropriate antitachycardia pacing (ATP) (12.9%) and shock (44.35%). Determinants of initial inappropriate therapy were dilated cardiomyopathy (DCM), history of therapeutic hypothermia, and QRS duration. Of the 61 patients with inappropriate therapy, 24 received TCL guided reprogramming. During the additional observation period of 17.0 ± 16.8 months, inappropriate therapy recurred in 5/24 patients (2 ATP, 3 shocks). The determinant of these inappropriate therapy events after reprogramming was the presence of supraventricular tachycardia.By applying simple TCL and TDI guided reprogramming, inappropriate therapy was reduced by 79%. The determinant of inappropriate therapy after reprogramming was the presence of supraventricular tachycardia.

  1. Etching and structure transformations in uncured epoxy resin under rf-plasma and plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Kondyurin, Alexey; Bilek, Marcela

    2010-05-01

    Uncured epoxy resin was spun onto silicon wafer and treated by plasma and plasma immersion ion implantation (PIII) by argon ions with energy up to 20 keV. Ellipsometry, FTIR spectroscopy and optical microscopy methods were used for analysis. The etching, carbonization, oxidation and crosslinking effects were observed. The curing reactions in modified epoxy resin are observed without a hardening agent. A model of structural transformations in epoxy resin under plasma and ion beam irradiation is proposed and discussed in relation to processes in a space environment.

  2. Morphometric and mechanical evaluation of titanium implant integration: comparison of five surface structures.

    PubMed

    Svehla, M; Morberg, P; Zicat, B; Bruce, W; Sonnabend, D; Walsh, W R

    2000-07-01

    Achieving a stable bone-implant interface is an important factor in the long-term outcome of joint arthroplasty. In this study, we employed an ovine bicortical model to compare the bone-healing response to five different surfaces on titanium alloy implants: grit blasted (GB), grit blasted plus hydroxyapatite (50 microm thick) coating (GBHA), Porocoat(R) (PC), Porocoat(R) with HA (PCHA) and smooth (S). Push-out testing, histology, and backscatter scanning electron microscope (SEM) imaging were employed to assess the healing response at 4, 8, and 12 weeks. Push-out testing revealed PC and PCHA surfaces resulted in significantly greater mechanical fixation over all other implant types at all time points (p <.05). HA coating on the grit-blasted surface significantly improved fixation at 8 and 12 weeks (p <.05). The addition of HA onto the porous coating did not significantly improve fixation in this model. Quantification of ingrowth/ongrowth from SEM images revealed that HA coating of the grit-blasted surfaces resulted in significantly more ongrowth at 4 weeks (p <.05).

  3. Characterization of interfaces of metal/amorphized (by implantation) Si/c-Si structures

    NASA Astrophysics Data System (ADS)

    Golan, A.; Fastow, R.; Eizenberg, M.

    1990-02-01

    The electrical properties of metal/implanted (amorphous) Si contacts were studied, emphasizing the effects of the doping level, of the metal type, and of the heat treatments applied prior to the metal deposition. The implantation was carried out using 60-keV Ar+ ions at a dose of 1016 cm-2, and resulted in the formation of a thin (1000-Å-thick) amorphous layer on top of the crystalline substrate. The doping level of the implanted Si affected the current-voltage (I-V) characteristics of the contacts mainly in the reverse bias (low doping-low currents), while the forward bias characteristics were quite independent of this parameter. The device characteristics were very sensitive to the metal type, Al, Ti-W, or Pt. Thermal treatments applied prior to the metal deposition affected the characteristics by lowering the device resistance in correspondence with the thinning of the amorphous layer as a result of epitaxial regrowth. The I-V characteristics, as well as their dependence on the different process parameters, are explained using a model of charge injection into a thin layer of trap rich amorphous Si bounded by a metal/a-Si interface on one side and by an a-Si/c-Si heterojunction on the other side.

  4. Crack detection in offshore platform structure based on structural intensity approach

    NASA Astrophysics Data System (ADS)

    Tian, Xiaojie; Liu, Guijie; Gao, Zhiming; Chen, Pengfei; Mu, Weilei

    2017-02-01

    Structural intensity approach is introduced to study the crack detection for offshore platform in the paper. The Line Spring Model (LSM) of surface crack is proposed based on plate crack structure, and thus the relationship between the additional angle, displacement and crack relative depth is achieved. Besides, the concept of appended structure-borne sound intensity is introduced. The expression of appended structural intensity for crack damage is derived. By observing the input energy, distribution, transmission and vibration performance of structure intensity, evidence is provided for detection of crack location. Vibration analysis is conducted on the whole platform under multi environment load. Using the structural intensity approach, the crack is detected on the key point easily. Moreover, the K-shape welded pipe point is detected using structural intensity approach, and the crack can be detected accurately. Therefore, development structural intensity approach would be extremely useful to spread out technologies that can be applied for offshore platform crack detection accurately.

  5. Effect of Piezoelectric Implant on the Structural Integrity of Composite Laminates Subjected to Tensile Loads

    NASA Astrophysics Data System (ADS)

    Masmoudi, Sahir; El Mahi, Abderrahim; Turki, Saïd

    2016-07-01

    The embedment of sensors within composite structures gives the opportunity to develop smart materials for health and usage monitoring systems. This study investigates the use of acoustic emission monitoring with embedded piezoelectric sensor during mechanical tests in order to identify the effects of introducing the sensor into the composite materials. The composite specimen with and without embedded sensor were subject to tensile static and fatigue loading. The analysis and observation of AE signals show that the integration of a sensor presents advantage of the detection of the acoustic events and also show the presence of three or four types of damage during tests. The incorporation of piezoelectric sensor has a negligible influence on the mechanical properties of materials.

  6. Effect of Piezoelectric Implant on the Structural Integrity of Composite Laminates Subjected to Tensile Loads

    NASA Astrophysics Data System (ADS)

    Masmoudi, Sahir; El Mahi, Abderrahim; Turki, Saïd

    2017-02-01

    The embedment of sensors within composite structures gives the opportunity to develop smart materials for health and usage monitoring systems. This study investigates the use of acoustic emission monitoring with embedded piezoelectric sensor during mechanical tests in order to identify the effects of introducing the sensor into the composite materials. The composite specimen with and without embedded sensor were subject to tensile static and fatigue loading. The analysis and observation of AE signals show that the integration of a sensor presents advantage of the detection of the acoustic events and also show the presence of three or four types of damage during tests. The incorporation of piezoelectric sensor has a negligible influence on the mechanical properties of materials.

  7. Risks of Breast Implants

    MedlinePlus

    ... has traveled to other parts of the body. Connective Tissue Disease The FDA has not detected any association between silicone gel-filled breast implants and connective tissue disease, breast cancer, or reproductive problems. In order ...

  8. Teeth and implants.

    PubMed

    Palmer, R

    1999-08-28

    An osseointegrated implant restoration may closely resemble a natural tooth. However, the absence of a periodontal ligament and connective tissue attachment via cementum, results in fundamental differences in the adaptation of the implant to occlusal forces, and the structure of the gingival cuff.

  9. Implantable CMOS Biomedical Devices

    PubMed Central

    Ohta, Jun; Tokuda, Takashi; Sasagawa, Kiyotaka; Noda, Toshihiko

    2009-01-01

    The results of recent research on our implantable CMOS biomedical devices are reviewed. Topics include retinal prosthesis devices and deep-brain implantation devices for small animals. Fundamental device structures and characteristics as well as in vivo experiments are presented. PMID:22291554

  10. Damage detection of bridgelike structures using neural networks

    NASA Astrophysics Data System (ADS)

    Valentin-Sivico, Javier; Rao, Vittal S.; Samanthula, Vasudha

    1998-06-01

    It is well known that the static and dynamic structural response of materials can indirectly indicate the health of structural systems. The changes in natural frequencies, mode shapes, and stiffness matrices due to damage are utilized for determination of occurrence, location and extent of damages. In recent years, many researchers have developed global damage detection algorithms using structural modal response. However most of these methods are off-line techniques based on frequency domain data. In this paper we have proposed real- time damage detection methods based on time domain data. In this method damages in the structure can be detected while the structure is kept on its regular use. The algorithm determines reduction in stiffness and/or damping of the structural elements, while assuming that the mass of the structure does not vary due to damage. This algorithm is based on the state space representation of the structure, which is identified from the time domain data. We have also determined a linear transformation matrix for converting the identified model into a state space representation based on physical coordinates of the structural system. The self-organization and learning capabilities of neural networks can be effectively used for structural damage detection purpose. In this paper a hybrid method for the damage detection has been proposed by combining the features of best achievable eigenvector method and neural network classification techniques for detection of location and extent of damage in the structural systems. The feasibility of the proposed method is verified by using simple three-bar truss structure and a cantilever beam test article.

  11. The Effect of Automatic Gain Control Structure and Release Time on Cochlear Implant Speech Intelligibility

    PubMed Central

    Khing, Phyu P.; Swanson, Brett A.; Ambikairajah, Eliathamby

    2013-01-01

    Nucleus cochlear implant systems incorporate a fast-acting front-end automatic gain control (AGC), sometimes called a compression limiter. The objective of the present study was to determine the effect of replacing the front-end compression limiter with a newly proposed envelope profile limiter. A secondary objective was to investigate the effect of AGC speed on cochlear implant speech intelligibility. The envelope profile limiter was located after the filter bank and reduced the gain when the largest of the filter bank envelopes exceeded the compression threshold. The compression threshold was set equal to the saturation level of the loudness growth function (i.e. the envelope level that mapped to the maximum comfortable current level), ensuring that no envelope clipping occurred. To preserve the spectral profile, the same gain was applied to all channels. Experiment 1 compared sentence recognition with the front-end limiter and with the envelope profile limiter, each with two release times (75 and 625 ms). Six implant recipients were tested in quiet and in four-talker babble noise, at a high presentation level of 89 dB SPL. Overall, release time had a larger effect than the AGC type. With both AGC types, speech intelligibility was lower for the 75 ms release time than for the 625 ms release time. With the shorter release time, the envelope profile limiter provided higher group mean scores than the front-end limiter in quiet, but there was no significant difference in noise. Experiment 2 measured sentence recognition in noise as a function of presentation level, from 55 to 89 dB SPL. The envelope profile limiter with 625 ms release time yielded better scores than the front-end limiter with 75 ms release time. A take-home study showed no clear pattern of preferences. It is concluded that the envelope profile limiter is a feasible alternative to a front-end compression limiter. PMID:24312408

  12. Structures in magnetohydrodynamic turbulence: Detection and scaling

    NASA Astrophysics Data System (ADS)

    Uritsky, V. M.; Pouquet, A.; Rosenberg, D.; Mininni, P. D.; Donovan, E. F.

    2010-11-01

    We present a systematic analysis of statistical properties of turbulent current and vorticity structures at a given time using cluster analysis. The data stem from numerical simulations of decaying three-dimensional magnetohydrodynamic turbulence in the absence of an imposed uniform magnetic field; the magnetic Prandtl number is taken equal to unity, and we use a periodic box with grids of up to 15363 points and with Taylor Reynolds numbers up to 1100. The initial conditions are either an X -point configuration embedded in three dimensions, the so-called Orszag-Tang vortex, or an Arn’old-Beltrami-Childress configuration with a fully helical velocity and magnetic field. In each case two snapshots are analyzed, separated by one turn-over time, starting just after the peak of dissipation. We show that the algorithm is able to select a large number of structures (in excess of 8000) for each snapshot and that the statistical properties of these clusters are remarkably similar for the two snapshots as well as for the two flows under study in terms of scaling laws for the cluster characteristics, with the structures in the vorticity and in the current behaving in the same way. We also study the effect of Reynolds number on cluster statistics, and we finally analyze the properties of these clusters in terms of their velocity-magnetic-field correlation. Self-organized criticality features have been identified in the dissipative range of scales. A different scaling arises in the inertial range, which cannot be identified for the moment with a known self-organized criticality class consistent with magnetohydrodynamics. We suggest that this range can be governed by turbulence dynamics as opposed to criticality and propose an interpretation of intermittency in terms of propagation of local instabilities.

  13. Detection and Characterization of R Loop Structures.

    PubMed

    Boque-Sastre, Raquel; Soler, Marta; Guil, Sonia

    2017-01-01

    R loops are special three stranded nucleic acid structures that comprise a nascent RNA hybridized with the DNA template strand, leaving a non-template DNA single-stranded. More specifically, R loops form in vivo as G-rich RNA transcripts invade the DNA duplex and anneal to the template strand to generate an RNA:DNA hybrid, leaving the non-template, G-rich DNA strand in a largely single-stranded conformation (Aguilera and Garcia-Muse, Mol Cell 46:115-124, 2012).DNA-RNA hybrids are a natural occurrence within eukaryotic cells, with levels of these hybrids increasing at sites with high transcriptional activity, such as during transcription initiation, repression, and elongation. RNA-DNA hybrids influence genomic instability, and growing evidence points to an important role for R loops in active gene expression regulation (Ginno et al., Mol Cell 45, 814-825, 2012; Sun et al., Science 340: 619-621, 2013; Bhatia et al., Nature 511, 362-365, 2014). Analysis of the occurrence of such structures is therefore of increasing relevance and herein we describe methods for the in vivo and in vitro identification and characterization of R loops in mammalian systems.R loops (DNA:RNA hybrids and the associated single-stranded DNA) have been traditionally associated with threats to genome integrity, making some regions of the genome more prone to DNA-damaging and mutagenic agents. Initially considered to be rare byproducts of transcription, over the last decade accumulating evidence has pointed to a new view in which R loops form more frequently than previously thought. The R loop field has become an increasingly expanded area of research, placing these structures as a major threat to genome stability but also as potential regulators of gene expression. Special interest has arisen as they have also been linked to a variety of diseases, including neurological disorders and cancer, positioning them as potential therapeutic targets [5].

  14. Enhancing community detection by using local structural information

    NASA Astrophysics Data System (ADS)

    Xiang, Ju; Hu, Ke; Zhang, Yan; Bao, Mei-Hua; Tang, Liang; Tang, Yan-Ni; Gao, Yuan-Yuan; Li, Jian-Ming; Chen, Benyan; Hu, Jing-Bo

    2016-03-01

    Many real-world networks, such as gene networks, protein-protein interaction networks and metabolic networks, exhibit community structures, meaning the existence of groups of densely connected vertices in the networks. Many local similarity measures in the networks are closely related to the concept of the community structures, and may have a positive effect on community detection in the networks. Here, various local similarity measures are used to extract local structural information, which is then applied to community detection in the networks by using the edge-reweighting strategy. The effect of the local similarity measures on community detection is carefully investigated and compared in various networks. The experimental results show that the local similarity measures are crucial for the improvement of community detection methods, while the positive effect of the local similarity measures is closely related to the networks under study and applied community detection methods.

  15. Multi-Dimensional Damage Detection for Surfaces and Structures

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Lewis, Mark; Roberson, Luke; Medelius, Pedro; Gibson, Tracy; Parks, Steen; Snyder, Sarah

    2013-01-01

    Current designs for inflatable or semi-rigidized structures for habitats and space applications use a multiple-layer construction, alternating thin layers with thicker, stronger layers, which produces a layered composite structure that is much better at resisting damage. Even though such composite structures or layered systems are robust, they can still be susceptible to penetration damage. The ability to detect damage to surfaces of inflatable or semi-rigid habitat structures is of great interest to NASA. Damage caused by impacts of foreign objects such as micrometeorites can rupture the shell of these structures, causing loss of critical hardware and/or the life of the crew. While not all impacts will have a catastrophic result, it will be very important to identify and locate areas of the exterior shell that have been damaged by impacts so that repairs (or other provisions) can be made to reduce the probability of shell wall rupture. This disclosure describes a system that will provide real-time data regarding the health of the inflatable shell or rigidized structures, and information related to the location and depth of impact damage. The innovation described here is a method of determining the size, location, and direction of damage in a multilayered structure. In the multi-dimensional damage detection system, layers of two-dimensional thin film detection layers are used to form a layered composite, with non-detection layers separating the detection layers. The non-detection layers may be either thicker or thinner than the detection layers. The thin-film damage detection layers are thin films of materials with a conductive grid or striped pattern. The conductive pattern may be applied by several methods, including printing, plating, sputtering, photolithography, and etching, and can include as many detection layers that are necessary for the structure construction or to afford the detection detail level required. The damage is detected using a detector or

  16. Use of prefabricated titanium abutments and customized anatomic lithium disilicate structures for cement-retained implant restorations in the esthetic zone.

    PubMed

    Lin, Wei-Shao; Harris, Bryan T; Zandinejad, Amirali; Martin, William C; Morton, Dean

    2014-03-01

    This report describes the fabrication of customized abutments consisting of prefabricated 2-piece titanium abutments and customized anatomic lithium disilicate structures for cement-retained implant restorations in the esthetic zone. The heat-pressed lithium disilicate provides esthetic customized anatomic structures and crowns independently of the computer-aided design and computer-aided manufacturing process.

  17. Detection of cystic structures using pulsed ultrasonically induced resonant cavitation

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph (Inventor); Kovach, John S. (Inventor)

    2002-01-01

    Apparatus and method for early detection of cystic structures indicative of ovarian and breast cancers uses ultrasonic wave energy at a unique resonance frequency for inducing cavitation in cystic fluid characteristic of cystic structures in the ovaries associated with ovarian cancer, and in cystic structures in the breast associated with breast cancer. Induced cavitation bubbles in the cystic fluid implode, creating implosion waves which are detected by ultrasonic receiving transducers attached to the abdomen of the patient. Triangulation of the ultrasonic receiving transducers enables the received signals to be processed and analyzed to identify the location and structure of the cyst.

  18. Detection of Cracks in Aluminum Structure Beneath Inconel Repair Bushings

    DTIC Science & Technology

    2008-04-01

    conductivity (i.e. Inconel 718 ) – Primary challenge then becomes detecting the weak eddy current field in the structure beyond the bushing wall...was able to be selected with inspectability as a goal. – Inconel 718 • low permeability (~μ0) • low conductivity (< 2% IACS) • Combined with...Detection of Cracks in Aluminum Structure beneath Inconel Repair Bushings Mr. Kenneth J. LaCivita (USAF) AFRL/RXSA Air Force Research Laboratory

  19. Automatic detection of contrast injection on fluoroscopy and angiography for image guided trans-catheter aortic valve implantations (TAVI)

    NASA Astrophysics Data System (ADS)

    Liao, Rui; You, Wei; Yan, Michelle; John, Matthias

    2011-03-01

    Presentation of detailed anatomical structures via 3-D models helps navigation and deployment of the prosthetic valve in TAVI procedures. Fast and automatic contrast detection in the aortic root on X-ray images facilitates a seamless workflow to utilize the 3-D models by triggering 2-D/3-D registration automatically when motion compensation is needed. In this paper, we propose a novel method for automatic detection of contrast injection in the aortic root on fluoroscopic and angiographic sequences. The proposed method is based on histogram analysis and likelihood ratio test, and is robust to variations in the background, the density and volume of the injected contrast, and the size of the aorta. The performance of the proposed algorithm was evaluated on 26 sequences from 5 patients and 3 clinical sites, with 16 out of 17 contrast injections correctly detected and zero false detections. The proposed method is of general form and can be extended for detection of contrast injection in other organs and/or applications.

  20. Compositional and structural requirements for laminin and basement membranes during mouse embryo implantation and gastrulation.

    PubMed

    Miner, Jeffrey H; Li, Cong; Mudd, Jacqueline L; Go, Gloriosa; Sutherland, Ann E

    2004-05-01

    Laminins are components of all basement membranes and have well demonstrated roles in diverse developmental processes, from the peri-implantation period onwards. Laminin 1 (alpha1beta1gamma1) is a major laminin found at early stages of embryogenesis in both embryonic and extraembryonic basement membranes. The laminin gamma1 chain has been shown by targeted mutation to be required for endodermal differentiation and formation of basement membranes; Lamc1(-/-) embryos die within a day of implantation. We report the generation of mice lacking laminin alpha1 and laminin beta1, the remaining two laminin 1 chains. Mutagenic insertions in both Lama1 and Lamb1 were obtained in a secretory gene trap screen. Lamb1(-/-) embryos are similar to Lamc1(-/-) embryos in that they lack basement membranes and do not survive beyond embryonic day (E) 5.5. However, in Lama1(-/-) embryos, the embryonic basement membrane forms, the embryonic ectoderm cavitates and the parietal endoderm differentiates, apparently because laminin 10 (alpha5beta1gamma1) partially compensates for the absent laminin 1. However, such compensation did not occur for Reichert's membrane, which was absent, and the embryos died by E7. Overexpression of laminin alpha5 from a transgene improved the phenotype of Lama1(-/-) embryos to the point that they initiated gastrulation, but this overexpression did not rescue Reichert's membrane, and trophoblast cells did not form blood sinuses. These data suggest that both the molecular composition and the integrity of basement membranes are crucial for early developmental events.

  1. Finite element analysis of provisional structures of implant-supported complete prostheses.

    PubMed

    Carneiro, Bruno Albuquerque; de Brito, Rui Barbosa; França, Fabiana Mantovani Gomes

    2014-04-01

    The use of provisional resin implant-supported complete dentures is a fast and safe procedure to restore mastication and esthetics of patients soon after surgery and during the adaptation phase to the new denture. This study assessed stress distribution of provisional implant-supported fixed dentures and the all-on-4 concept using self-curing acrylic resin (Tempron) and bis-acrylic resin (Luxatemp) to simulate functional loads through the three-dimensional finite element method. Solidworks software was used to build three-dimensional models using acrylic resin (Tempron, model A) and bis-acrylic resin (Luxatemp, model B) for denture captions. Two loading patterns were applied on each model: (1) right unilateral axial loading of 150 N on the occlusal surfaces of posterior teeth and (2) oblique loading vector of 150 N at 45°. The results showed that higher stress was found on the bone crest below oblique load application with a maximum value of 187.57 MPa on model A and 167.45 MPa on model B. It was concluded that model B improved stress distribution on the denture compared with model A.

  2. FINITE ELEMENT ANALYSIS OF PROVISIONAL STRUCTURES OF IMPLANT-SUPPORTED COMPLETE PROSTHESES.

    PubMed

    Carneiro, Bruno Albuquerque; Brito Jr, Rui Barbosa; França, Fabiana Mantovani Gomes

    2012-03-01

    Abstract The use of provisional resin implant-supported complete dentures is a fast and safe procedure to restore mastication and aesthetics of patients soon after surgery and during the adaptation phase to the new denture. This study assessed stress distribution of provisional implant-supported fixed dentures and the all-on-four concept using self-curing acrylic resin (Tempron) and bis-acrylic resin (Luxatemp) to simulate functional loads through the 3D finite element method. The Solidworks software was used to build 3D models, using acrylic resin (Tempron - A) and bis-acrylic resin (Luxatemp - B) for denture captions. Two loading patterns were applied on each model: 1) right unilateral axial loading of 150 N on the occlusal surfaces of posterior teeth; 2) oblique loading vector of 150 N at 45 degrees. The results showed that higher stress was found on the bone crest below oblique load application with maximum value of 187.57 MPa on model A and 167.45 MPa on model B. It was concluded that model B improved stress distribution on the denture compared to model A.

  3. Optical and structural properties of Si nanocrystals produced by Si hot implantation

    SciTech Connect

    Sias, U. S.; Behar, M.; Boudinov, H.; Moreira, E. C.

    2007-08-15

    It was already demonstrated that Si hot implantation followed by high-temperature annealing induces the formation of Si nanocrystals (Si NCs) which when excited in a linear excitation regime present two photoluminescence (PL) bands (at 780 and 1000 nm). We have undertaken the present work in order to investigate three features: First, to determine the origin of each band. With this aim we have changed the implantation fluence and the high-temperature annealing time. Second, to investigate the influence of the postannealing atmosphere on the PL recovering process after bombarding the Si NCs. Third, we have annealed the as-produced Si NCs in a forming gas (FG) atmosphere in order to observe the PL behavior of each band. The results have shown that the 780 nm PL band has its origin in radiative interfacial states, while the 1000 nm one is due to quantum size effects. From the experiments we have concluded that the PL recovery after the Si NCs irradiation strongly depends on the type of postannealing atmosphere. Finally, it was found that the FG treatment strongly affects the line shape of the PL spectrum.

  4. Detection of five potentially periodontal pathogenic bacteria in peri-implant disease: A comparison of PCR and real-time PCR.

    PubMed

    Schmalz, Gerhard; Tsigaras, Sandra; Rinke, Sven; Kottmann, Tanja; Haak, Rainer; Ziebolz, Dirk

    2016-07-01

    The aim of this study was to compare the microbial analysis methods of polymerase chain reaction (PCR) and real-time PCR (RT-PCR) in terms of detection of five selected potentially periodontal pathogenic bacteria in peri-implant disease. Therefore 45 samples of healthy, mucositis and peri-implantitis (n = 15 each) were assessed according to presence of the following bacteria using PCR (DNA-strip technology) and RT-PCR (fluorescent dye SYBR green-system): Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Treponema denticola (Td), Tanerella forsythia (Tf), and Fusobacterium nucleatum (Fn). There were no significant correlations between the bacterial and disease patterns, so the benefit of using microbiological tests for the diagnosis of peri-implant diseases is questionable. Correlations between the methods were highest for Tf (Kendall's Tau: 0.65, Spearman: 0.78), Fn (0.49, 0.61) and Td (0.49, 0.59). For Aa (0.38, 0.42) and Pg (0.04, 0.04), lower correlation values were detected. Accordingly, conventional semi-quantitative PCR seems to be sufficient for analyzing potentially periodontal pathogenic bacterial species.

  5. Capacitance-based damage detection sensing for aerospace structural composites

    NASA Astrophysics Data System (ADS)

    Bahrami, P.; Yamamoto, N.; Chen, Y.; Manohara, H.

    2014-04-01

    Damage detection technology needs improvement for aerospace engineering application because detection within complex composite structures is difficult yet critical to avoid catastrophic failure. Damage detection is challenging in aerospace structures because not all the damage detection technology can cover the various defect types (delamination, fiber fracture, matrix crack etc.), or conditions (visibility, crack length size, etc.). These defect states are expected to become even more complex with future introduction of novel composites including nano-/microparticle reinforcement. Currently, non-destructive evaluation (NDE) methods with X-ray, ultrasound, or eddy current have good resolutions (< 0.1 mm), but their detection capabilities is limited by defect locations and orientations and require massive inspection devices. System health monitoring (SHM) methods are often paired with NDE technologies to signal out sensed damage, but their data collection and analysis currently requires excessive wiring and complex signal analysis. Here, we present a capacitance sensor-based, structural defect detection technology with improved sensing capability. Thin dielectric polymer layer is integrated as part of the structure; the defect in the structure directly alters the sensing layer's capacitance, allowing full-coverage sensing capability independent of defect size, orientation or location. In this work, capacitance-based sensing capability was experimentally demonstrated with a 2D sensing layer consisting of a dielectric layer sandwiched by electrodes. These sensing layers were applied on substrate surfaces. Surface indentation damage (~1mm diameter) and its location were detected through measured capacitance changes: 1 to 250 % depending on the substrates. The damage detection sensors are light weight, and they can be conformably coated and can be part of the composite structure. Therefore it is suitable for aerospace structures such as cryogenic tanks and rocket

  6. Leveraging disjoint communities for detecting overlapping community structure

    NASA Astrophysics Data System (ADS)

    Chakraborty, Tanmoy

    2015-05-01

    Network communities represent mesoscopic structure for understanding the organization of real-world networks, where nodes often belong to multiple communities and form overlapping community structure in the network. Due to non-triviality in finding the exact boundary of such overlapping communities, this problem has become challenging, and therefore huge effort has been devoted to detect overlapping communities from the network. In this paper, we present PVOC (Permanence based Vertex-replication algorithm for Overlapping Community detection), a two-stage framework to detect overlapping community structure. We build on a novel observation that non-overlapping community structure detected by a standard disjoint community detection algorithm from a network has high resemblance with its actual overlapping community structure, except the overlapping part. Based on this observation, we posit that there is perhaps no need of building yet another overlapping community finding algorithm; but one can efficiently manipulate the output of any existing disjoint community finding algorithm to obtain the required overlapping structure. We propose a new post-processing technique that by combining with any existing disjoint community detection algorithm, can suitably process each vertex using a new vertex-based metric, called permanence, and thereby finds out overlapping candidates with their community memberships. Experimental results on both synthetic and large real-world networks show that PVOC significantly outperforms six state-of-the-art overlapping community detection algorithms in terms of high similarity of the output with the ground-truth structure. Thus our framework not only finds meaningful overlapping communities from the network, but also allows us to put an end to the constant effort of building yet another overlapping community detection algorithm.

  7. Structural and electrical properties of Ge nanocrystals embedded in SiO{sub 2} by ion implantation and annealing

    SciTech Connect

    Duguay, S.; Grob, J.J.; Slaoui, A.; Le Gall, Y.; Amann-Liess, M.

    2005-05-15

    Silicon dioxide (SiO{sub 2}) on Si layers with embedded germanium nanocrystals (Ge-ncs) were fabricated using Ge{sup +} implantation and subsequent annealing. Transmission electron microscopy and Rutherford backscattering spectrometry have been used to study the Ge redistribution in the SiO{sub 2} films as a function of annealing temperature. A monolayer of Ge-ncs near the Si/SiO{sub 2} interface was formed under specific annealing conditions. This layer, with a nc density and mean size measured to be, respectively, 1.1x10{sup 12}/cm{sup 2} and 5 nm, is located at approximately 4 nm from the Si/SiO{sub 2} interface. Capacitance-voltage measurements were performed on metal-oxide-semiconductor structures containing such implanted SiO{sub 2} layers in order to study their electrical properties. The results indicate a strong memory effect at relatively low programming voltages (<5 V) due to the presence of Ge-ncs near the Si/SiO{sub 2} interface.

  8. Electrical and structural properties of In-implanted Si{sub 1−x}Ge{sub x} alloys

    SciTech Connect

    Feng, R. Kremer, F.; Mirzaei, S.; Medling, S. A.; Ridgway, M. C.; Sprouster, D. J.; Decoster, S.; Glover, C. J.; Hansen, J. L.; Nylandsted-Larsen, A.; Russo, S. P.

    2016-01-14

    We report on the effects of dopant concentration and substrate stoichiometry on the electrical and structural properties of In-implanted Si{sub 1−x}Ge{sub x} alloys. Correlating the fraction of electrically active In atoms from Hall Effect measurements with the In atomic environment determined by X-ray absorption spectroscopy, we observed the transition from electrically active, substitutional In at low In concentration to electrically inactive metallic In at high In concentration. The In solid-solubility limit has been quantified and was dependent on the Si{sub 1−x}Ge{sub x} alloy stoichiometry; the solid-solubility limit increased as the Ge fraction increased. This result was consistent with density functional theory calculations of two In atoms in a Si{sub 1−x}Ge{sub x} supercell that demonstrated that In–In pairing was energetically favorable for x ≲ 0.7 and energetically unfavorable for x ≳ 0.7. Transmission electron microscopy imaging further complemented the results described earlier with the In concentration and Si{sub 1−x}Ge{sub x} alloy stoichiometry dependencies readily visible. We have demonstrated that low resistivity values can be achieved with In implantation in Si{sub 1−x}Ge{sub x} alloys, and this combination of dopant and substrate represents an effective doping protocol.

  9. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Artificial Modulation of Ferroelectric Thin Films into Antiferroelectric through H+ Implantation for High-Density Charge Storage

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-Jun; Fei, Jin-Wen; Tang, Ting-Ao; Jiang, An-Quan

    2008-05-01

    Hydrogen ions are implanted into Pb(Zr0.3Ti0.7)O3 thin films at the energy of 40 keV with a flux of 5 × 1014 ions/cm2. Pseudo-antiferroelectric behaviour in the implanted thin films is observed, as confirmed by the measurements of polarization versus electric hysteresis loops and capacitance versus voltage curves. X-ray diffraction patterns show the film structures before and after H+ implantation both to be perovskite of a tetragonal symmetry. These findings indicate that hydrogen ions exist as stable dopants within the films. It is believed that the dopants change domain-switching behaviour via the boundary charge compensation. Meanwhile, time dependence of leakage current density after time longer than 10s indicates the enhancement of the leakage current nearly in one order for the implanted film, but the current at time shorter than 1 s is mostly the same as that of the original film without the ionic implantation. The artificial tailoring of the antiferroelectric behaviour through H+ implantation in ferroelectric thin films is finally proven to be achievable for the device application of high-density charge storage.

  10. Graph spectra and the detectability of community structure in networks.

    PubMed

    Nadakuditi, Raj Rao; Newman, M E J

    2012-05-04

    We study networks that display community structure--groups of nodes within which connections are unusually dense. Using methods from random matrix theory, we calculate the spectra of such networks in the limit of large size, and hence demonstrate the presence of a phase transition in matrix methods for community detection, such as the popular modularity maximization method. The transition separates a regime in which such methods successfully detect the community structure from one in which the structure is present but is not detected. By comparing these results with recent analyses of maximum-likelihood methods, we are able to show that spectral modularity maximization is an optimal detection method in the sense that no other method will succeed in the regime where the modularity method fails.

  11. Detection of karst structures using airborne EM and VLF

    SciTech Connect

    Beard, L.P. Nyquist, J.E.; Carpenter, P.J.

    1994-12-31

    Through the combined use of multi-frequency helicopter electromagnetic and VLF data, it is possible to detect and delineate a wide variety of karst structures and possibly to assess their interconnectedness. Multi-frequency EM Can detect karst features if some element of the structure is conductive. This conductive aspect may derive from thick, moist soils in the depression commonly associated with a doline, from conductive fluids in the cavity, or from conductive sediments in the cavity if these occupy a significant portion of it. Multiple loop configurations may also increase the likelihood of detecting karst features. Preliminary evidence indicates total field VLF measurements may be able to detect interconnected karst pathways, so long as the pathways are water or sediment filled. Neither technique can effectively detect dry, resistive air-filled cavities.

  12. Configurational statistical model for the damaged structure of silicon oxide after ion implantation

    NASA Astrophysics Data System (ADS)

    Garrido, B.; Samitier, J.; Morante, J. R.; Montserrat, J.; Domínguez, C.

    1994-06-01

    A configurational model for silicon oxide damaged after a high-dose ion implantation of a nonreactive species is presented. Based on statistics of silicon-centered tetrahedra, the model takes into account not only the closest environment of a given silicon atom, but also the second neighborhood, so it is specified whether the oxygen attached to one given silicon is bridging two tetrahedra or not. The frequencies and intensities of infrared vibrational bands have been calculated by averaging over the distributions and these results are in agreement with the ones obtained from infrared experimental spectra. Likewise, the chemical shifts obtained from x-ray photoelectron spectroscopy (XPS) analysis are similar to the reported values for the charge-transfer model of SiOx compounds.

  13. Modification of implant material surface properties by means of oxide nano-structured coatings deposition

    NASA Astrophysics Data System (ADS)

    Safonov, Vladimir; Zykova, Anna; Smolik, Jerzy; Rogowska, Renata; Lukyanchenko, Vladimir; Kolesnikov, Dmitrii

    2014-08-01

    The deposition of functional coatings on the metal surface of artificial joints is an effective way of enhancing joint tribological characteristics. It is well-known that nanostructured oxide coatings have specific properties advantageous for future implant applications. In the present study, we measured the high hardness parameters, the adhesion strength and the low friction coefficient of the oxide magnetron sputtered coatings. The corrosion test results show that the oxide coating deposition had improved the corrosion resistance by a factor of ten for both stainless steel and titanium alloy substrates. Moreover, the hydrophilic nature of coated surfaces in comparison with the metal ones was investigated in the tensiometric tests. The surfaces with nanostructured oxide coatings demonstrated improved biocompatibility for in vitro and in vivo tests, attributed to the high dielectric constants and the high values of the surface free energy parameters.

  14. Structural-mechanical and antibacterial properties of a soft elastic polyurethane surface after plasma immersion N2(+) implantation.

    PubMed

    Morozov, Ilya A; Mamaev, Alexander S; Osorgina, Irina V; Lemkina, Larisa M; Korobov, Vladimir P; Belyaev, Anton Yu; Porozova, Svetlana E; Sherban, Marina G

    2016-05-01

    The surface of elastic polyurethane treated by plasma immersion N2(+) ion implantation at different fluences has been investigated. A folded surface structure is observed in all cases. Analysis has been performed to study the structural (roughness, steepness and fraction of folds, fractal characteristics), mechanical (stiffness, adhesion force between the AFM probe and the material) and wetting properties of surfaces. Under uniaxial stretching the cracks orthogonal to the axis of deformation and longitudinal folds are formed on the examined surfaces. After unloading the initial structure of the surface of deformed materials exposed to low fluences becomes smoother and does not recover, i.e. it has plastic properties. By contrast, the structure of the surfaces of materials subjected to high-fluence treatment recovers without visible changes and the cracks are fully closed. The study of Staphylococcus colonies grown on these materials has demonstrated significant reduction (from 3 to 5 times) in the vitality of bacteria on treated surfaces. This result was repeated on samples after 11 months of storage. Such antibacterial properties are primarily related to the structural changes of the surfaces accompanied by the increased hydrophilicity.

  15. Dental Implants.

    PubMed

    Zohrabian, Vahe M; Sonick, Michael; Hwang, Debby; Abrahams, James J

    2015-10-01

    Dental implants restore function to near normal in partially or completely edentulous patients. A root-form implant is the most frequently used type of dental implant today. The basis for dental implants is osseointegration, in which osteoblasts grow and directly integrate with the surface of titanium posts surgically embedded into the jaw. Radiologic assessment is critical in the preoperative evaluation of the dental implant patient, as the exact height, width, and contour of the alveolar ridge must be determined. Moreover, the precise locations of the maxillary sinuses and mandibular canals, as well as their relationships to the site of implant surgery must be ascertained. As such, radiologists must be familiar with implant design and surgical placement, as well as augmentation procedures utilized in those patients with insufficient bone in the maxilla and mandible to support dental implants.

  16. Cochlear Implants

    MedlinePlus

    ... NIDCD A cochlear implant is a small, complex electronic device that can help to provide a sense ... are better able to hear, comprehend sound and music, and speak than their peers who receive implants ...

  17. Cochlear implant

    MedlinePlus

    ... antenna. This part of the implant receives the sound, converts the sound into an electrical signal, and sends it to ... implants allow deaf people to receive and process sounds and speech. However, these devices do not restore ...

  18. Influences of thicknesses and structures of barrier cap layers on As ion profiles and implant damages in HgCdTe epilayers

    NASA Astrophysics Data System (ADS)

    Shi, Changzhi; Lin, Chun; Wei, Yanfeng; Chen, Lu; Ye, Zhenhua

    2016-05-01

    The barrier cap layer (BCL) is considered to be able to absorb partially implant induced damages during ion implantation, thus its structure and property could impact the result of ion implantation. In this paper, for As ion implantation in HgCdTe, the different BCLs were deposited on the CdZnTe-based (LPE) and GaAs-based (MBE) HgCdTe epilayers, respectively. Then, the influences of thicknesses and structures of these BCLs on dopant profiles and implant damages were investigated. The as-grown BCLs include thermally evaporated (TE) ZnS, TE CdTe, electron beam evaporated (EBE) CdTe and in-situ CdTe/ZnTe grown by MBE. The SIMS profiles and TEM characterization indicate: For TE ZnS BCLs, there exists an optimized thickness to obtain the deepest As indiffusion after high temperature annealing, and the end-of-range (EOR) depth is linearly proportional to the thickness ratio of a-MCT layer/damage layer. For TE CdTe BCLs, the barrier layer induced channeling effect (BLICE) occurs to the thin BCL samples, while this effect is suppressed in the thick BCL samples. The phenomenon might be due to that the blocking effect of the layered structure inside each crystal column becomes dominate in the thick BCL samples. Additionally, the EBE CdTe BCL with layered structure can suppress effectively the BLICE effect; in the in-situ CdTe/ZnTe BCL, the short defect layer generated in the CdTe buffer layer and the amorphization of the ZnTe layer during ion implantation also play a significant role in suppressing the BLICE effect.

  19. Implant-supported overdenture manufactured using CAD/CAM techniques to achieve horizontal path insertion between the primary and secondary structure: A clinical case report

    PubMed Central

    Agustín-Panadero, Rubén; Peñarrocha-Oltra, David; Gomar-Vercher, Sonia; Ferreiroa, Alberto

    2015-01-01

    This report describes the case of an edentulous patient with an atrophic maxilla and severe class III malocclusion. Prosthetic rehabilitation was performed using CAD/CAM techniques for manufacturing an implant-supported overdenture with horizontal insertion. A vestibulo-lingual insertion overdenture is a precision prosthesis with a fixation system affording a good fit between the primary and secondary structure. Both structures exhibit passive horizontal adjustment. This treatment option requires the same number of implants as implant-supported fixed dentures. The horizontal assembly system prevents the prosthesis from loosening or moving in response to axial and non-axial forces. The technique was used to rehabilitate a patient presenting an atrophic upper maxilla, with the insertion of 8 implants. No complications were reported at follow-up 3, 6 and 12 months after fitting of the prosthesis. This system offers solutions to the clinical and laboratory complications associated with hybrid prostheses, concealing emergence of the chimneys and improving implant-prosthesis hygiene. PMID:26140179

  20. Textured and smooth breast implants: is there a difference in the chemical structure of silicone?: an analysis with fourier transformation infrared and attenuated total reflectance spectroscopy.

    PubMed

    Persichetti, Paolo; Tenna, Stefania; Delfino, Sergio; Abbruzzese, Franca; Trombetta, Marcella; Scuderi, Nicolò

    2009-10-01

    Scientific controversy concerning silicone and its biocompatibility has been ongoing for the last 10 years. This study on textured and smooth silicone breast implant shells using fourier transformation infrared spectroscopy associated with attenuated total reflectance cells aimed to identify eventual chemical modifications of silicone induced by texturization. The surfaces of 8 new implants produced by 2 well-known manufactures have been taken into consideration. A sample 1 cm2 has been harvested from the anterior and posterior sides of textured and smooth shells. Infrared spectra were then recorded, evaluated, and compared with the reference spectrum of pure silicone. Potentially reactive groups, known as silanols, were identified, in all shells, intensity increasing in textured implants (P < 0.05), whereas no silanols were detected in the spectrum of pure silicone. These results suggest that polar groups, present in manipulated silicone might influence capsula formation.

  1. Statistical method for detecting structural change in the growth process.

    PubMed

    Ninomiya, Yoshiyuki; Yoshimoto, Atsushi

    2008-03-01

    Due to competition among individual trees and other exogenous factors that change the growth environment, each tree grows following its own growth trend with some structural changes in growth over time. In the present article, a new method is proposed to detect a structural change in the growth process. We formulate the method as a simple statistical test for signal detection without constructing any specific model for the structural change. To evaluate the p-value of the test, the tube method is developed because the regular distribution theory is insufficient. Using two sets of tree diameter growth data sampled from planted forest stands of Cryptomeria japonica in Japan, we conduct an analysis of identifying the effect of thinning on the growth process as a structural change. Our results demonstrate that the proposed method is useful to identify the structural change caused by thinning. We also provide the properties of the method in terms of the size and power of the test.

  2. Gain analysis of higher-order-mode amplification in a dielectric-implanted multi-beam traveling wave structure

    SciTech Connect

    Gee, Anthony; Shin, Young-Min

    2013-07-15

    A multi-beam traveling wave amplifier designed with an overmoded staggered double grating array was examined by small signal analysis combined with simulation. Eigenmode and S-parameter analyses show that the 2 cm long slow wave structure (SWS) has 1–5 dB insertion loss over the passband (TM{sub 31} mode) with ∼28% cold bandwidth. Analytic gain calculation indicates that in the SWS, TM{sub 31}-mode is amplified with 15–20 dB/beam at 64–84 GHz with three elliptical beams of 10 kV and 150 mA/beam, which was compared with particle-in-cell (PIC) simulations. PIC analysis on the analysis of instability with zero-input driving excitations demonstrated that background noises and non-operating lower order modes are noticeably suppressed by implanting equidistant dielectric absorbers; the overmoded structure only allowed the desired 3rd order mode to propagate in the structure. The designed circuit structure can be widely applied to multi-beam devices for high power RF generation.

  3. Gain analysis of higher-order-mode amplification in a dielectric-implanted multi-beam traveling wave structure

    SciTech Connect

    Gee, Anthony; Shin, Young-Min

    2013-01-01

    A multi-beam traveling wave amplifier designed with an overmoded staggered double grating array was examined by small signal analysis combined with simulation. Eigenmode and S-parameter analyses show that the 2cm long slow wave structure (SWS) has 1-5dB insertion loss over the passband (TM31 mode) with ~28% cold bandwidth. Analytic gain calculation indicates that in the SWS, TM31-mode is amplified with 15–20 dB/beam at 64–84GHz with three elliptical beams of 10kV and 150mA/beam, which was compared with particle-in-cell (PIC) simulations. PIC analysis on the analysis of instability with zero-input driving excitations demonstrated that background noises and non-operating lower order modes are noticeably suppressed by implanting equidistant dielectric absorbers; the overmoded structure only allowed the desired 3rd order mode to propagate in the structure. The designed circuit structure can be widely applied to multi-beam devices for high power RF generation.

  4. Tailoring the structural and optical properties of TiN thin films by Ag ion implantation

    NASA Astrophysics Data System (ADS)

    Popović, M.; Novaković, M.; Rakočević, Z.; Bibić, N.

    2016-12-01

    Titanium nitride (TiN) thin films thickness of ∼260 nm prepared by dc reactive sputtering were irradiated with 200 keV silver (Ag) ions to the fluences ranging from 5 × 1015 ions/cm2 to 20 × 1015 ions/cm2. After implantation TiN layers were annealed 2 h at 700 °C in a vacuum. Ion irradiation-induced microstructural changes were examined by using Rutherford backscattering spectrometry, X-ray diffraction and transmission electron microscopy, while the surface topography was observed using atomic force microscopy. Spectroscopic ellipsometry was employed to get insights on the optical and electronic properties of TiN films with respect to their microstructure. The results showed that the irradiations lead to deformation of the lattice, increasing disorder and formation of new Ag phase. The optical results demonstrate the contribution of surface plasmon resonace (SPR) of Ag particles. SPR position shifted in the range of 354.3-476.9 nm when Ag ion fluence varied from 5 × 1015 ions/cm2 to 20 × 1015 ions/cm2. Shift in peak wavelength shows dependence on Ag particles concentration, suggesting that interaction between Ag particles dominate the surface plasmon resonance effect. Presence of Ag as second metal in the layer leads to overall decrease of optical resistivity of TiN.

  5. Rutherford backscattering and channelling studies of erbium implanted SIMOX **

    SIMOX: separation by implanted oxygen.

    structures

    NASA Astrophysics Data System (ADS)

    Zhang, Jingping; Tang, Y. S.; Hemment, P. L. F.; Sealy, B. J.

    1990-04-01

    The behaviour of 250 keV 166Er + implanted into SIMOX structures has been investigated by Rutherford backscattering and channelling analysis. The implantation doses were 1.5 ×10 14 cm -2 and 1.5 × 10 15 cm -2. Both conventional furnace and rapid therm annealing were carried out in the temperature range 600°C-1100°C. Regrowth of the amorphized silicon and redistribution of the erbium were found to be strongly influenced by the status of the damaged layer. Different regrowth processes of the completely damaged silicon overlayer were suggested respectively for conventional furnace and rapid thermal annealing. It is found that the regrowth rate increases rapidly when the temperature is higher than 900° C in both cases. The redistribution of the erbium atoms was controlled by the regrowth boundary between the damaged and the recrystallized silicon.

  6. Structural and Thermal Characterization of Ti+O Ion Implanted UltraHigh Molecular Weight Polyethylene (UHMWPE)

    SciTech Connect

    Oztarhan, A.; Urkac, E. Sokullu; Kaya, N.; Tihminlioglu, F.; Ila, D.; Chhay, B.; Muntele, C.; Budak, S.; Oks, E.; Nikolaev, A.

    2009-03-10

    In this work, Metal-Gas Hybrid Ion Implantation technique was used as a tool for the surface modification of Ultra High Molecular Weight Polyethylene (UHMWPE). Samples were Ti+O ion implanted by using Metal-Vapour Vacuum Arc (MEVVA) ion implanter to a fluence of 5x10{sup 16} ion/cm{sup 2} for each species and extraction voltage of 30 kV. Untreated and surface treated samples were investigated by Rutherford Back Scattering (RBS) Spectrometry, Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) Spectroscopy, Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Results indicate that Ti+O ion implantation can be applied on UHMWPE surfaces successfully. ATR-FTIR spectra indicate that the C-H concentration on the surface decreased after Ti+O implantation. Thermal characterization with TGA and DSC shows that polymeric decomposition temperature is shifted after ion implantation.

  7. Ti-6Al-4V triply periodic minimal surface structures for bone implants fabricated via selective laser melting.

    PubMed

    Yan, Chunze; Hao, Liang; Hussein, Ahmed; Young, Philippe

    2015-11-01

    Triply periodic minimal surface (TPMS) structures have already been shown to be a versatile source of biomorphic scaffold designs. Therefore, in this work, Ti-6Al-4V Gyroid and Diamond TPMS lattices having an interconnected high porosity of 80-95% and pore sizes in the range of 560-1600 μm and 480-1450 μm respectively were manufactured by selective laser melting (SLM) for bone implants. The manufacturability, microstructure and mechanical properties of the Ti-6Al-4V TPMS lattices were evaluated. Comparison between 3D micro-CT reconstructed models and original CAD models of the Ti-6Al-4V TPMS lattices shows excellent reproduction of the designs. The as-built Ti-6Al-4V struts exhibit the microstructure of columnar grains filled with very fine and orthogonally oriented α' martensitic laths with the width of 100-300 nm and have the microhardness of 4.01 ± 0.34 GPa. After heat treatment at 680°C for 4h, the α' martensite was converted to a mixture of α and β, in which the α phase being the dominant fraction is present as fine laths with the width of 500-800 nm and separated by a small amount of narrow, interphase regions of dark β phase. Also, the microhardness is decreased to 3.71 ± 0.35 GPa due to the coarsening of the microstructure. The 80-95% porosity TPMS lattices exhibit a comparable porosity with trabecular bone, and the modulus is in the range of 0.12-1.25 GPa and thus can be adjusted to the modulus of trabecular bone. At the same range of porosity of 5-10%, the moduli of cortical bone and of the Ti-6Al-4V TPMS lattices are in a similar range. Therefore, the modulus and porosity of Ti-6Al-4V TPMS lattices can be tailored to the levels of human bones and thus reduce or avoid "stress shielding" and increase longevity of implants. Due to the biomorphic designs, and high interconnected porosity and stiffness comparable to human bones, SLM-made Ti-6Al-4V TPMS lattices can be a promising material for load bearing bone implants.

  8. Fabrication and Structural Characterization of Co-implanted Ultra Shallow Junctions for Integration in Piezoresistive Silicon Sensors Compatible with CMOS Processing

    NASA Astrophysics Data System (ADS)

    Ahmed, S.; Mustafa, R.

    2013-12-01

    Fabrication and structural characterization of Indium and Carbon implanted n-type Silicon layers forming ultra-shallow junction for integration in piezoresistive sensors compatible with CMOS processing is studied in detail. The co-implantation technology together with medium range annealing temperature regimes seem to play an important role at atomistic level and provide a process control to engineer the strain and maintain the quality of surface/layer/active device region for further manufacturing process cycle. This is likely to impact the yield and reliability for the fabrication of these devices for diverse applications.

  9. Multilayer perceptron in damage detection of bridge structures

    NASA Astrophysics Data System (ADS)

    Pandey, P. C.; Barai, S. V.

    1995-02-01

    Recent developments in artificial neural networks (ANN) have opened up new possibilities in the domain of structural engineering. For inverse problems like structural identification of large civil engineerlng structures such as bridges and buildings where the in situ measured data are expected to be imprecise and often incomplete, the ANN holds greater promise. The detection of structural damage and identification of damaged element in a large complex structure is a challenging task indeed. This paper presents an application of multilayer perceptron in the damage detection of steel bridge structures. The ssues relating to the design of network and learning paradigm are addressed and network architectures have been developed with reference to trussed bridge structures. The training patterns are generated for multiple damaged zones in a structure and performance of the networks with one and two hidden layers are examined. It has been observed that the performance of the network with two hidden layers was better than that of a single-layer architecture in general. The engineering importance of the whole exercise is demonstrated from the fact that measured input at only a few locations in the structure is needed in the identification process using the ANN.

  10. High holding voltage segmentation stacking silicon-controlled-rectifier structure with field implant as body ties blocking layer

    NASA Astrophysics Data System (ADS)

    Yen, Shiang-Shiou; Cheng, Chun-Hu; Lan, Yu-Pin; Chiu, Yu-Chien; Fan, Chia-Chi; Hsu, Hsiao-Hsuan; Chang, Shao-Chin; Jiang, Zhe-Wei; Hung, Li-Yue; Tsai, Chi-Chung; Chang, Chun-Yen

    2016-04-01

    High electrostatic discharge (ESD) protection robustness and good transient-induced latchup immunity are two important issues for high voltage integrate circuit application. In this study, we report a high-voltage-n-type-field (HVNF) implantation to act as the body ties blocking layer in segmented topology silicon-controlled-rectifier (SCR) structure in 0.11 µm 32 V high voltage process. This body ties blocking layer eliminate the elevated triggered voltage in segmented technique. Using a large resistance as shunt resistor in resistor assisted triggered SCRs stacking structure, the double snapback phenomenon is eliminate. The series SCR could be decoupled a sufficient voltage drop to turned-on when a very low current flow through the shunt resistor. The holding voltage and the failure current of 22 V and 3.4 A are achieved in the best condition of segmented topology SCR stacking structure, respectively. It improves the latchup immunity at high voltage ICs application. On the other hand, the triggered voltage almost keep the same value which is identical to SCR single cell without using segmented topology.

  11. Language Structures Used by Kindergartners with Cochlear Implants: Relationship to Phonological Awareness, Lexical Knowledge and Hearing Loss

    PubMed Central

    Nittrouer, Susan; Sansom, Emily; Low, Keri; Rice, Caitlin; Caldwell-Tarr, Amanda

    2014-01-01

    Objective Listeners use their knowledge of how language is structured to aid speech recognition in everyday communication. When it comes to children with congenital hearing loss severe enough to warrant cochlear implants (CIs), the question arises of whether these children can acquire the language knowledge needed to aid speech recognition, in spite of only having spectrally degraded signals available to them. That question was addressed in the current study. Specifically there were three goals: (1) to compare the language structures used by children with CIs to those of children with normal hearing (NH); (2) to assess the amount of variance in the language measures explained by phonological awareness and lexical knowledge; and (3) to assess the amount of variance in the language measures explained by factors related to the hearing loss itself and subsequent treatment. Design Language samples were obtained and transcribed for 40 children who had just completed kindergarten: 19 with NH and 21 with CIs. Five measures were derived from Systematic Analysis of Language Transcripts (SALT): (1) mean length of utterance in morphemes, (2) number of conjunctions, excluding and, (3) number of personal pronouns, (4) number of bound morphemes, and (5) number of different words. Measures were also collected on phonological awareness and lexical knowledge. Statistics examined group differences, as well as the amount of variance in the language measures explained by phonological awareness, lexical knowledge, and factors related to hearing loss and its treatment for children with CIs. Results Mean scores of children with CIs were roughly one standard deviation below those of children with NH on all language measures, including lexical knowledge, matching outcomes of other studies. Mean scores of children with CIs were closer to two standard deviations below those of children with NH on two out of three measures of phonological awareness (specifically those related to phonemic

  12. Rapid detection and quantification of impact damage in composite structures

    NASA Technical Reports Server (NTRS)

    Smith, Barry T.

    1992-01-01

    It is shown that a multidisciplinary nondestructive evaluation approach for impact damage detection in composite structures can be used to produce a more efficient inspection. The multidisciplinary NDE approach relies on fast large area thermographic inspections along with detailed ultrasonic volumetric imaging. The thermal inspection technique rapidly identifies the impact damage. The ultrasonic volumetric imaging quantifies the impact generated delaminations through the volume of the structure.

  13. Rapid detection and quantification of impact damage in composite structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Farley, Gary; Smith, Barry T.

    1991-01-01

    NDE results from thermographic and volumetric ultrasonic techniques are presented to illustrate the multidisciplinary NDE approach to impact-damage detection in such composite structures as are increasingly prevalent in helicopters. Attention is given to both flat-panel and 'y-stiffened' panel specimens; these were fabricated either with kevlar or carbon fiber through-the-thickness reinforcements. While thermal inspection identifies impact damage, volumetric imaging quantifies the impact-generated delaminations through the volume of the structure.

  14. A damage detection technique for reinforced concrete structures

    NASA Astrophysics Data System (ADS)

    Wu, Ai-Lun; Yang, Jann N.; Loh, Chin-Hsiung

    2012-04-01

    Civil engineering structures, such as reinforced concrete frames, exhibit nonlinear hysteretic behavior when subject to dynamic loads, such as earthquakes. The ability to detect damages in structures after a major earthquake will ensure their reliability and safety. Innovative analysis techniques for damage detection of structures have been extensively studied recently. However, practical and effective damage identification techniques remain to be developed for nonlinear structures, in particular hysteretic reinforced concrete (RC) structures. In this paper, a smooth hysteretic model with stiffness and strength degradations and with the pinching effect is used to represent the dynamic characteristics of reinforced concrete (RC) frames. A system identification method capable of detecting damages in nonlinear structures, referred to as the adaptive quadratic sum-square error with unknown inputs (AQSSE-UI), is used to detect damages in hysteretic RC frames. The performance of the AQSSE-UI technique is demonstrated by the experimental data. A 1/3 scale 2-story RC frame has been tested experimentally on the shake table at NCREE, Taiwan. This 2-story RC frame was subject to different levels of ground excitations back to back. The RC frame is firstly considered as a linear model with rotational springs and the tracking of the degradation of the stiffness parameters is carried out using the AQSSE-UI technique. Then the same RC frame is considered as a nonlinear structure with plastic hinges following a smooth hysteretic model. Experimental results show that the AQSSE-UI technique is quite effective for tracking of : (i) the stiffness degradation of linear structures, and (ii) the non-linear hysteretic parameters with stiffness and strength degradations.

  15. Detection of Wavelike Structures in Saturn's Cassini Division

    NASA Astrophysics Data System (ADS)

    Horn, L. J.; Showalter, M. R.

    1996-09-01

    Several features with wavelike characteristics were detected in the Voyager Radio Science (RSS) earth occultation data of Saturn's Cassini Division. We identified these structures using a non-linear autoregressive power spectral algorithm called Burg. This method is powerful for detecting short sections of quasiperiodic structure. We successfully used this same technique to identify six previously unseen Pan wakes in the Voyager photopolarimeter (PPS) stellar occultation data and the Voyager RSS occultation data (Horn, Showalter and Russell, Icarus, in press). When we apply the Burg technique to the RSS data we find many wavelike structures in the Cassini Division. We see three distinct features that look like moonlet wakes. Two are Cassini Division features detected by Marouf and Tyler (1986, Nature 323, 120) in the Voyager RSS data. Flynn and Cuzzi (1989, Icarus 82, 180) determined that these features were azimuthally symmetric in the Voyager images and were most likely not satellite wakes. The third wavelike structure resembles an outer satellite wake. If it is a wake, it corresponds to a previously undetected moonlet 84 degrees away which resides in a Cassini Division gap located between 118,929 km and 118,966 km. Several other wavelike structures in the Cassini Division are reminiscent of satellite wakes. We plan to pursue these structures further in the future. We will also look at the Voyager PPS data as well although this data set is somewhat noisier in the Cassini Division. This work was performed at JPL under contract with NASA.

  16. Plastic optical fibre sensor for damage detection in offshore structures

    NASA Astrophysics Data System (ADS)

    Kuang, K. S. C.; Koh, C. G.

    2009-12-01

    It is important to ensure the safe and reliable use of massive engineering structures such as offshore platforms, including all aspects of safety and design code compliance. Although routine inspection is an integral part of the safety protocol in operating and maintaining these structures, regular assessment of the effectiveness and efficiency of existing safety evaluation methods is clearly desired in view of emerging technologies for structural health monitoring of engineering structures. The recent advancement in plastic optical fibre (POF) materials and processing render POF sensors an attractive alternative to glass-based optical fibre sensors as they offer much greater being flexibility, high resistance to fracture and hence the ease in their handling and installation. In this paper, some preliminary results demonstrating the use of plastic optical fibre sensors for damage detection and structural health monitoring for offshore and marine-related applications will be summarized. In this study, POF will be used for crack detection in tubular steel specimens in conjunction with a high-resolution photon-counting optical time-domain reflectrometry (v-OTDR). Although the use of OTDR technique is an established method in the telecommunication industry, this study is new in that it is now possible, with the availability of v-OTDR and graded-index perfluorinated POF, to detect and locate the crack position in the host structure to within 10 cm accuracy or better. It will also be shown that this technique could readily be configured to monitor crack growth in steel tubular members.

  17. Plastic optical fibre sensor for damage detection in offshore structures

    NASA Astrophysics Data System (ADS)

    Kuang, K. S. C.; Koh, C. G.

    2010-03-01

    It is important to ensure the safe and reliable use of massive engineering structures such as offshore platforms, including all aspects of safety and design code compliance. Although routine inspection is an integral part of the safety protocol in operating and maintaining these structures, regular assessment of the effectiveness and efficiency of existing safety evaluation methods is clearly desired in view of emerging technologies for structural health monitoring of engineering structures. The recent advancement in plastic optical fibre (POF) materials and processing render POF sensors an attractive alternative to glass-based optical fibre sensors as they offer much greater being flexibility, high resistance to fracture and hence the ease in their handling and installation. In this paper, some preliminary results demonstrating the use of plastic optical fibre sensors for damage detection and structural health monitoring for offshore and marine-related applications will be summarized. In this study, POF will be used for crack detection in tubular steel specimens in conjunction with a high-resolution photon-counting optical time-domain reflectrometry (v-OTDR). Although the use of OTDR technique is an established method in the telecommunication industry, this study is new in that it is now possible, with the availability of v-OTDR and graded-index perfluorinated POF, to detect and locate the crack position in the host structure to within 10 cm accuracy or better. It will also be shown that this technique could readily be configured to monitor crack growth in steel tubular members.

  18. Structural impact detection with vibro-haptic interfaces

    NASA Astrophysics Data System (ADS)

    Jung, Hwee-Kwon; Park, Gyuhae; Todd, Michael D.

    2016-07-01

    This paper presents a new sensing paradigm for structural impact detection using vibro-haptic interfaces. The goal of this study is to allow humans to ‘feel’ structural responses (impact, shape changes, and damage) and eventually determine health conditions of a structure. The target applications for this study are aerospace structures, in particular, airplane wings. Both hardware and software components are developed to realize the vibro-haptic-based impact detection system. First, L-shape piezoelectric sensor arrays are deployed to measure the acoustic emission data generated by impacts on a wing. Unique haptic signals are then generated by processing the measured acoustic emission data. These haptic signals are wirelessly transmitted to human arms, and with vibro-haptic interface, human pilots could identify impact location, intensity and possibility of subsequent damage initiation. With the haptic interface, the experimental results demonstrate that human could correctly identify such events, while reducing false indications on structural conditions by capitalizing on human’s classification capability. Several important aspects of this study, including development of haptic interfaces, design of optimal human training strategies, and extension of the haptic capability into structural impact detection are summarized in this paper.

  19. Superelastic Orthopedic Implant Coatings

    NASA Astrophysics Data System (ADS)

    Fournier, Eric; Devaney, Robert; Palmer, Matthew; Kramer, Joshua; El Khaja, Ragheb; Fonte, Matthew

    2014-07-01

    The demand for hip and knee replacement surgery is substantial and growing. Unfortunately, most joint replacement surgeries will fail within 10-25 years, thereby requiring an arduous, painful, and expensive revision surgery. To address this issue, a novel orthopedic implant coating material ("eXalt") has been developed. eXalt is comprised of super elastic nitinol wire that is knit into a three-dimensional spacer fabric structure. eXalt expands in vivo to conform to the implantation site and is porous to allow for bone ingrowth. The safety and efficacy of eXalt were evaluated through structural analysis, mechanical testing, and a rabbit implantation model. The results demonstrate that eXalt meets or exceeds the performance of current coating technologies with reduced micromotion, improved osseointegration, and stronger implant fixation in vivo.

  20. Detection and location of metallic objects imbedded in nonmetallic structures

    NASA Technical Reports Server (NTRS)

    Brown, R. L.; Neuschaefer, R. W.

    1968-01-01

    Small battery operated eddy current proximity measuring device detects and locates metal objects the size of a dime at distances up to one foot within nonmetallic structures. This device weighs approximately two pounds, occupies approximately 60 cubic inches, and is battery powered.

  1. Detection of structural deterioration and associated airline maintenance problems

    NASA Technical Reports Server (NTRS)

    Henniker, H. D.; Mitchell, R. G.

    1972-01-01

    Airline operations involving the detection of structural deterioration and associated maintenance problems are discussed. The standard approach to the maintenance and inspection of aircraft components and systems is described. The frequency of inspections and the application of preventive maintenance practices are examined. The types of failure which airline transport aircraft encounter and the steps taken to prevent catastrophic failure are reported.

  2. Statistical Inference for Detecting Structures and Anomalies in Networks

    DTIC Science & Technology

    2015-08-27

    community structure in dynamic networks, along with the discovery of a detectability phase transition as a function of the rate of change and the...local in- formation, about the known nodes and their neighbors. But when this fraction crosses a critical threshold, our knowledge becomes global

  3. Structure damage detection based on random forest recursive feature elimination

    NASA Astrophysics Data System (ADS)

    Zhou, Qifeng; Zhou, Hao; Zhou, Qingqing; Yang, Fan; Luo, Linkai

    2014-05-01

    Feature extraction is a key former step in structural damage detection. In this paper, a structural damage detection method based on wavelet packet decomposition (WPD) and random forest recursive feature elimination (RF-RFE) is proposed. In order to gain the most effective feature subset and to improve the identification accuracy a two-stage feature selection method is adopted after WPD. First, the damage features are sorted according to original random forest variable importance analysis. Second, using RF-RFE to eliminate the least important feature and reorder the feature list each time, then get the new feature importance sequence. Finally, k-nearest neighbor (KNN) algorithm, as a benchmark classifier, is used to evaluate the extracted feature subset. A four-storey steel shear building model is chosen as an example in method verification. The experimental results show that using the fewer features got from proposed method can achieve higher identification accuracy and reduce the detection time cost.

  4. Damage detection and health monitoring of operational structures

    SciTech Connect

    James, G.; Mayes, R.; Carne, T.; Reese, G.

    1994-09-01

    Initial damage detection/health monitoring experiments have been performed on three different operational structures: a fracture critical bridge, a composite wind turbine blade, and an aging aircraft. An induced damage test was performed on the Rio Grande/I40 bridge before its demolition. The composite wind turbine test was fatgued to failure with periodic modal testing performed throughout the testing. The front fuselage of a DC-9 aircraft was used as the testbed for an induced damage test. These tests have yielded important insights into techniques for experimental damage detection on real structures. Additionally, the data are currently being used with current damage detection algorithms to further develop the numerical technology. State of the art testing technologies such as, high density modal testing, scanning laser vibrometry and natural excitation testing have also been utilized for these tests.

  5. TEM investigation of the surface layer structure [111]{sub B2} of the single NiTi crystal modified by the Si-ion beam implantation

    SciTech Connect

    Girsova, S. L. Poletika, T. M.; Meisner, S. N. Meisner, L. L.

    2015-10-27

    The study was carried on for the single NiTi crystals subjected to the Si-ion beam implantation. Using the transmission electron microscopy technique (TEM), the surface layer structure [111]{sub B2} was examined for the treated material. The modified near-surface sublayers were found to have different composition. Thus the uppermost sublayer contained mostly oxides; the lower-lying modified sublayer material was in an amorphous state and the thin underlying sublayer had a defect structure.

  6. Method for Real-Time Model Based Structural Anomaly Detection

    NASA Technical Reports Server (NTRS)

    Smith, Timothy A. (Inventor); Urnes, James M., Sr. (Inventor); Reichenbach, Eric Y. (Inventor)

    2015-01-01

    A system and methods for real-time model based vehicle structural anomaly detection are disclosed. A real-time measurement corresponding to a location on a vehicle structure during an operation of the vehicle is received, and the real-time measurement is compared to expected operation data for the location to provide a modeling error signal. A statistical significance of the modeling error signal to provide an error significance is calculated, and a persistence of the error significance is determined. A structural anomaly is indicated, if the persistence exceeds a persistence threshold value.

  7. Detecting Community Structure by Using a Constrained Label Propagation Algorithm

    PubMed Central

    Ratnavelu, Kuru

    2016-01-01

    Community structure is considered one of the most interesting features in complex networks. Many real-world complex systems exhibit community structure, where individuals with similar properties form a community. The identification of communities in a network is important for understanding the structure of said network, in a specific perspective. Thus, community detection in complex networks gained immense interest over the last decade. A lot of community detection methods were proposed, and one of them is the label propagation algorithm (LPA). The simplicity and time efficiency of the LPA make it a popular community detection method. However, the LPA suffers from instability detection due to randomness that is induced in the algorithm. The focus of this paper is to improve the stability and accuracy of the LPA, while retaining its simplicity. Our proposed algorithm will first detect the main communities in a network by using the number of mutual neighbouring nodes. Subsequently, nodes are added into communities by using a constrained LPA. Those constraints are then gradually relaxed until all nodes are assigned into groups. In order to refine the quality of the detected communities, nodes in communities can be switched to another community or removed from their current communities at various stages of the algorithm. We evaluated our algorithm on three types of benchmark networks, namely the Lancichinetti-Fortunato-Radicchi (LFR), Relaxed Caveman (RC) and Girvan-Newman (GN) benchmarks. We also apply the present algorithm to some real-world networks of various sizes. The current results show some promising potential, of the proposed algorithm, in terms of detecting communities accurately. Furthermore, our constrained LPA has a robustness and stability that are significantly better than the simple LPA as it is able to yield deterministic results. PMID:27176470

  8. Effect of alpha lipoic acid co-administration on structural and immunohistochemical changes in subcutaneous tissue of anterior abdominal wall of adult male albino rat in response to polypropylene mesh implantation.

    PubMed

    Mazroa, Shireen A; Asker, Samar A; Asker, Waleed; Abd Ellatif, Mohamed

    2015-06-01

    Polypropylene mesh is commonly used in the treatment of abdominal hernia. Different approaches were addressed to improve their tissue integration and consequently reduce long-term complications. This study aimed to investigate the effect of alpha-lipoic acid (ALA) co-administration on structural and immunohistochemical (IHC) changes in the subcutaneous tissues of the anterior abdominal wall of the adult rat in response to polypropylene mesh implantation. Forty adult male albino rats were divided into: group I (control), group II (receiving ALA), group III (polypropylene mesh implantation) and group IV (mesh implantation + ALA co-administration). After 4 weeks, subcutaneous tissue samples were prepared for light microscopy and IHC study of CD34 as a marker for angiogenesis. In groups I and II rats, positive CD34 expression was demonstrated by IHC reaction, localized to endothelial cells lining small blood vessels. Group III showed an excess inflammatory reaction, deposition of both regular and irregularly arranged collagen fibres around mesh pores and few elastic fibres. CD34-positive was detected not only in cells lining small blood vessels but also in other cells scattered in the connective tissue indicating angiogenesis. In group IV, ALA co-administration resulted in less inflammatory reaction, regular collagen deposition, enhanced elastic fibres synthesis and a significant increase in CD34-positive cells and small blood vessels reflecting improved angiogenesis. ALA co-administration with polypropylene mesh implantation controlled the inflammatory reaction, helped regular collagen deposition, enhanced elastic fibres synthesis and improved angiogenesis in the subcutaneous tissue of anterior abdominal wall of adult albino rats, suggesting a possible role of ALA in optimizing mesh integration in subcutaneous tissue.

  9. Effect of alpha lipoic acid co-administration on structural and immunohistochemical changes in subcutaneous tissue of anterior abdominal wall of adult male albino rat in response to polypropylene mesh implantation

    PubMed Central

    Mazroa, Shireen A; Asker, Samar A; Asker, Waleed; Abd Ellatif, Mohamed

    2015-01-01

    Polypropylene mesh is commonly used in the treatment of abdominal hernia. Different approaches were addressed to improve their tissue integration and consequently reduce long-term complications. This study aimed to investigate the effect of alpha-lipoic acid (ALA) co-administration on structural and immunohistochemical (IHC) changes in the subcutaneous tissues of the anterior abdominal wall of the adult rat in response to polypropylene mesh implantation. Forty adult male albino rats were divided into: group I (control), group II (receiving ALA), group III (polypropylene mesh implantation) and group IV (mesh implantation + ALA co-administration). After 4 weeks, subcutaneous tissue samples were prepared for light microscopy and IHC study of CD34 as a marker for angiogenesis. In groups I and II rats, positive CD34 expression was demonstrated by IHC reaction, localized to endothelial cells lining small blood vessels. Group III showed an excess inflammatory reaction, deposition of both regular and irregularly arranged collagen fibres around mesh pores and few elastic fibres. CD34-positive was detected not only in cells lining small blood vessels but also in other cells scattered in the connective tissue indicating angiogenesis. In group IV, ALA co-administration resulted in less inflammatory reaction, regular collagen deposition, enhanced elastic fibres synthesis and a significant increase in CD34-positive cells and small blood vessels reflecting improved angiogenesis. ALA co-administration with polypropylene mesh implantation controlled the inflammatory reaction, helped regular collagen deposition, enhanced elastic fibres synthesis and improved angiogenesis in the subcutaneous tissue of anterior abdominal wall of adult albino rats, suggesting a possible role of ALA in optimizing mesh integration in subcutaneous tissue. PMID:25891652

  10. Structural and mechanical implications of PMMA implant shape and interface geometry in cranioplasty--A finite element study.

    PubMed

    Ridwan-Pramana, Angela; Marcián, Petr; Borák, Libor; Narra, Nathaniel; Forouzanfar, Tim; Wolff, Jan

    2016-01-01

    This computational study investigates the effect of shape (defect contour curvature) and bone-implant interface (osteotomy angle) on the stress distribution within PMMA skull implants. Using finite element methodology, 15 configurations--combinations of simplified synthetic geometric shapes (circular, square, triangular, irregular) and interface angulations--were simulated under 50N static loads. Furthermore, the implant fixation devices were modelled and analysed in detail. Negative osteotomy configurations demonstrated the largest stresses in the implant (275 MPa), fixation devices (1258 MPa) and bone strains (0.04). The circular implant with zero and positive osteotomy performed well with maximum observed magnitudes of--implant stress (1.2 MPa and 1.2 MPa), fixation device stress (11.2 MPa and 2.2 MPa), bone strain (0.218e-3 and 0.750e-4). The results suggest that the preparation of defect sites is a critical procedure. Of the greatest importance is the angle at which the edges of the defect are sawed. If under an external load, the implant has no support from the interface and the stresses are transferred to the fixation devices. This can endanger their material integrity and lead to unphysiological strains in the adjacent bone, potentially compromising the bone morphology required for anchoring. These factors can ultimately weaken the stability of the entire implant assembly.

  11. Nonlinear damage detection in composite structures using bispectral analysis

    NASA Astrophysics Data System (ADS)

    Ciampa, Francesco; Pickering, Simon; Scarselli, Gennaro; Meo, Michele

    2014-03-01

    Literature offers a quantitative number of diagnostic methods that can continuously provide detailed information of the material defects and damages in aerospace and civil engineering applications. Indeed, low velocity impact damages can considerably degrade the integrity of structural components and, if not detected, they can result in catastrophic failure conditions. This paper presents a nonlinear Structural Health Monitoring (SHM) method, based on ultrasonic guided waves (GW), for the detection of the nonlinear signature in a damaged composite structure. The proposed technique, based on a bispectral analysis of ultrasonic input waveforms, allows for the evaluation of the nonlinear response due to the presence of cracks and delaminations. Indeed, such a methodology was used to characterize the nonlinear behaviour of the structure, by exploiting the frequency mixing of the original waveform acquired from a sparse array of sensors. The robustness of bispectral analysis was experimentally demonstrated on a damaged carbon fibre reinforce plastic (CFRP) composite panel, and the nonlinear source was retrieved with a high level of accuracy. Unlike other linear and nonlinear ultrasonic methods for damage detection, this methodology does not require any baseline with the undamaged structure for the evaluation of the nonlinear source, nor a priori knowledge of the mechanical properties of the specimen. Moreover, bispectral analysis can be considered as a nonlinear elastic wave spectroscopy (NEWS) technique for materials showing either classical or non-classical nonlinear behaviour.

  12. Making the difference: integrating structural variation detection tools.

    PubMed

    Lin, Ke; Smit, Sandra; Bonnema, Guusje; Sanchez-Perez, Gabino; de Ridder, Dick

    2015-09-01

    From prokaryotes to eukaryotes, phenotypic variation, adaptation and speciation has been associated with structural variation between genomes of individuals within the same species. Many computer algorithms detecting such variations (callers) have recently been developed, spurred by the advent of the next-generation sequencing technology. Such callers mainly exploit split-read mapping or paired-end read mapping. However, as different callers are geared towards different types of structural variation, there is still no single caller that can be considered a community standard; instead, increasingly the various callers are combined in integrated pipelines. In this article, we review a wide range of callers, discuss challenges in the integration step and present a survey of pipelines used in population genomics studies. Based on our findings, we provide general recommendations on how to set-up such pipelines. Finally, we present an outlook on future challenges in structural variation detection.

  13. Implantable Microimagers

    PubMed Central

    Ng, David C.; Tokuda, Takashi; Shiosaka, Sadao; Tano, Yasuo; Ohta, Jun

    2008-01-01

    Implantable devices such as cardiac pacemakers, drug-delivery systems, and defibrillators have had a tremendous impact on the quality of live for many disabled people. To date, many devices have been developed for implantation into various parts of the human body. In this paper, we focus on devices implanted in the head. In particular, we describe the technologies necessary to create implantable microimagers. Design, fabrication, and implementation issues are discussed vis-à-vis two examples of implantable microimagers; the retinal prosthesis and in vivo neuro-microimager. Testing of these devices in animals verify the use of the microimagers in the implanted state. We believe that further advancement of these devices will lead to the development of a new method for medical and scientific applications. PMID:27879873

  14. Impression techniques for implant dentistry.

    PubMed

    Chee, W; Jivraj, S

    2006-10-07

    The object of making an impression in implant dentistry is to accurately relate an analogue of the implant or implant abutment to the other structures in the dental arch. This is affected by use of an impression coping which is attached to the implant or implant abutment. This impression coping is incorporated in an impression - much as a metal framework is 'picked up' in a remount impression for fixed prosthodontics. With implant copings the coping is usually attached to the implant or abutment with screws. The impression material used is usually an elastomeric impression material; the two types most widely used and shown to be the most appropriate are polyether and polyvinyl siloxane impression materials.

  15. Engineered porous metals for implants

    NASA Astrophysics Data System (ADS)

    Vamsi Krishna, B.; Xue, Weichang; Bose, Susmita; Bandyopadhyay, Amit

    2008-05-01

    Interest is significant in patient-specific implants with the possibility of guided tissue regeneration, particularly for load-bearing implants. For such implants to succeed, novel design approaches and fabrication technologies that can achieve balanced mechanical and functional performance in the implants are necessary. This article is focused on porous load-bearing implants with tailored micro-as well as macrostructures using laser-engineered net shaping (LENS™), a solid freeform fabrication or rapid prototyping technique that can be used to manufacture patient-specific implants. This review provides an insight into LENS, some properties of porous metals, and the potential applications of this process to fabricate unitized structures which can eliminate longstanding challenges in load-bearing implants to increase their in-vivo lifetime, such as in a total hip prosthesis.

  16. Extended Kalman filter based structural damage detection for MR damper controlled structures

    NASA Astrophysics Data System (ADS)

    Jin, Chenhao; Jang, Shinae; Sun, Xiaorong; Jiang, Zhaoshuo; Christenson, Richard

    2016-04-01

    The Magneto-rheological (MR) dampers have been widely used in many building and bridge structures against earthquake and wind loadings due to its advantages including mechanical simplicity, high dynamic range, low power requirements, large force capacity, and robustness. However, research about structural damage detection methods for MR damper controlled structures is limited. This paper aims to develop a real-time structural damage detection method for MR damper controlled structures. A novel state space model of MR damper controlled structure is first built by combining the structure's equation of motion and MR damper's hyperbolic tangent model. In this way, the state parameters of both the structure and MR damper are added in the state vector of the state space model. Extended Kalman filter is then used to provide prediction for state variables from measurement data. The two techniques are synergistically combined to identify parameters and track the changes of both structure and MR damper in real time. The proposed method is tested using response data of a three-floor MR damper controlled linear building structure under earthquake excitation. The testing results show that the adaptive extended Kalman filter based approach is capable to estimate not only structural parameters such as stiffness and damping of each floor, but also the parameters of MR damper, so that more insights and understanding of the damage can be obtained. The developed method also demonstrates high damage detection accuracy and light computation, as well as the potential to implement in a structural health monitoring system.

  17. Ti-Nb-(Zr,Ta) superelastic alloys for medical implants: Thermomechanical processing, structure, phase transformations and functional properties

    NASA Astrophysics Data System (ADS)

    Dubinskiy, Sergey

    The aim of this project is to develop a new class of orthopaedic implant materials that combine the excellent biocompatibility of pure titanium with the outstanding biomechanical compatibility of Ti-Ni-based shape memory alloys. The most suitable candidates for such a role are Ti-Nb-Zr and Ti-Nb-Ta near-beta shape memory alloys. Since this class of materials was developed quite recently, the influence of thermomechanical treatment on their structure and functional properties has not as yet been the subject of any comprehensive study. Consequently, this project is focused on the interrelations between the composition, the microstructure and the functional properties of superelastic Ti-Nb-Zr and Ti-Nb-Ta alloys for biomedical application. The principal objective is to improve the functional properties of these alloys, more specifically their superelastic properties and fatigue resistance, through optimization of the alloys' composition and thermomechanical processing. It is shown in this thesis that the structure and functional properties of Ti-Nb-based shape memory alloys can be effectively controlled by thermomechanical processing including cold deformation with post-deformation annealing and ageing. It is also shown that the formation of nanosubgrain substructure leads to a significant improvement of superelasticity and fatigue resistance in these alloys. The influence of ageing on the ω-phase precipitation kinetics and, consequently, on the functional properties of Ti-Nb-Zr and Ti-Nb-Ta alloys is also observed. Based on the results obtained, optimized regimes of thermomechanical treatment resulting in a best combination of functional properties are recommended for each alloy, from the orthopaedic implant materials standpoint. An original tensile stage for a low-temperature chamber of an X-ray diffractometer is developed and used in this project. A unique low-temperature (-150...+100°C) comparative in situ X-ray study of the transformations' features and crystal

  18. Endodontic implants

    PubMed Central

    Yadav, Rakesh K.; Tikku, A. P.; Chandra, Anil; Wadhwani, K. K.; Ashutosh kr; Singh, Mayank

    2014-01-01

    Endodontic implants were introduced back in 1960. Endodontic implants enjoyed few successes and many failures. Various reasons for failures include improper case selection, improper use of materials and sealers and poor preparation for implants. Proper case selection had given remarkable long-term success. Two different cases are being presented here, which have been treated successfully with endodontic implants and mineral trioxide aggregate Fillapex (Andreaus, Brazil), an MTA based sealer. We suggest that carefully selected cases can give a higher success rate and this method should be considered as one of the treatment modalities. PMID:25298723

  19. 3D lattice distortions and defect structures in ion-implanted nano-crystals

    DOE PAGES

    Hofmann, Felix; Robinson, Ian K.; Tarleton, Edmund; ...

    2017-04-06

    The ability of Focused Ion Beam (FIB) techniques to cut solid matter at the nano-scale revolutionized the study of material structure across the life-, earth- and material sciences. But a detailed understanding of the damage caused by the ion beam and its effect on material properties remains elusive. We examine this damage in 3D using coherent X-ray diffraction to measure the full lattice strain tensor in FIB-milled gold nano-crystals. We also found that even very low ion doses, previously thought to be negligible, cause substantial lattice distortions. At higher doses, extended self-organized defect structures appear. Combined with detailed numerical calculations,more » these observations allow fundamental insight into the nature of the damage created and the structural instabilities that lead to a surprisingly inhomogeneous morphology.« less

  20. Ultrasonic Techniques for Baseline-Free Damage Detection in Structures

    NASA Astrophysics Data System (ADS)

    Dutta, Debaditya

    This research presents ultrasonic techniques for baseline-free damage detection in structures in the context of structural health monitoring (SHM). Conventional SHM methods compare signals obtained from the pristine condition of a structure (baseline signals) with those from the current state, and relate certain changes in the signal characteristics to damage. While this approach has been successful in the laboratory, there are certain drawbacks of depending on baseline signals in real field applications. Data from the pristine condition are not available for most existing structures. Even if they are available, operational and environmental variations tend to mask the effect of damage on the signal characteristics. Most important, baseline measurements may become meaningless while assessing the condition of a structure after an extreme event such as an earthquake or a hurricane. Such events may destroy the sensors themselves and require installation of new sensors at different locations on the structure. Baseline-free structural damage detection can broaden the scope of SHM in the scenarios described above. A detailed discussion on the philosophy of baseline-free damage detection is provided in Chapter 1. Following this discussion, the research questions are formulated. The organization of this document and the major contributions of this research are also listed in this chapter. Chapter 2 describes a fully automated baseline-free technique for notch and crack detection in plates using a collocated pair of piezoelectric wafer transducers for measuring ultrasonic signals. Signal component corresponding to the damage induced mode-converted Lamb waves is extracted by processing the originally measured ultrasonic signals. The damage index is computed as a function of this mode-converted Lamb wave signal component. An over-determined system of Lamb wave measurements is used to find a least-square estimate of the measurement errors. This error estimate serves as the

  1. Detecting small scale CO2 emission structures using OCO-2

    NASA Astrophysics Data System (ADS)

    Schwandner, Florian M.; Eldering, Annmarie; Verhulst, Kristal R.; Miller, Charles E.; Nguyen, Hai M.; Oda, Tomohiro; O'Dell, Christopher; Rao, Preeti; Kahn, Brian; Crisp, David; Gunson, Michael R.; Sanchez, Robert M.; Ashok, Manasa; Pieri, David; Linick, Justin P.; Yuen, Karen

    2016-04-01

    Localized carbon dioxide (CO2) emission structures cover spatial domains of less than 50 km diameter and include cities and transportation networks, as well as fossil fuel production, upgrading and distribution infra-structure. Anthropogenic sources increasingly upset the natural balance between natural carbon sources and sinks. Mitigation of resulting climate change impacts requires management of emissions, and emissions management requires monitoring, reporting and verification. Space-borne measurements provide a unique opportunity to detect, quantify, and analyze small scale and point source emissions on a global scale. NASA's first satellite dedicated to atmospheric CO2 observation, the July 2014 launched Orbiting Carbon Observatory (OCO-2), now leads the afternoon constellation of satellites (A-Train). Its continuous swath of 2 to 10 km in width and eight footprints across can slice through coincident emission plumes and may provide momentary cross sections. First OCO-2 results demonstrate that we can detect localized source signals in the form of urban total column averaged CO2 enhancements of ~2 ppm against suburban and rural backgrounds. OCO-2's multi-sounding swath observing geometry reveals intra-urban spatial structures reflected in XCO2 data, previously unobserved from space. The transition from single-shot GOSAT soundings detecting urban/rural differences (Kort et al., 2012) to hundreds of soundings per OCO-2 swath opens up the path to future capabilities enabling urban tomography of greenhouse gases. For singular point sources like coal fired power plants, we have developed proxy detections of plumes using bands of imaging spectrometers with sensitivity to SO2 in the thermal infrared (ASTER). This approach provides a means to automate plume detection with subsequent matching and mining of OCO-2 data for enhanced detection efficiency and validation. © California Institute of Technology

  2. Surface flaw detection in structural ceramics by scanning photoacoustic spectroscopy

    NASA Technical Reports Server (NTRS)

    Khandelwal, P. K.; Heitman, P. W.; Wakefield, T. D.; Silversmith, A. J.

    1980-01-01

    Laser-scanned photoacoustic spectroscopy has been used to detect tightly closed surface cracks in three structural ceramic materials: sintered silicon nitride, reaction-bonded silicon nitride, and sintered silicon carbide. It is found that the amplitude of the photoacoustic signal from the flaws is greater for the silicon nitrides than for silicon carbide, which is attributed to the lower thermal diffusivity of silicon nitride as well as differences in the grain size distribution and chemical composition. Signal amplitude, reproducibility, and signal-to-noise ratio are acceptable for effective flaw detection

  3. Fast Detection of Material Deformation through Structural Dissimilarity

    SciTech Connect

    Ushizima, Daniela; Perciano, Talita; Parkinson, Dilworth

    2015-10-29

    Designing materials that are resistant to extreme temperatures and brittleness relies on assessing structural dynamics of samples. Algorithms are critically important to characterize material deformation under stress conditions. Here, we report on our design of coarse-grain parallel algorithms for image quality assessment based on structural information and on crack detection of gigabyte-scale experimental datasets. We show how key steps can be decomposed into distinct processing flows, one based on structural similarity (SSIM) quality measure, and another on spectral content. These algorithms act upon image blocks that fit into memory, and can execute independently. We discuss the scientific relevance of the problem, key developments, and decomposition of complementary tasks into separate executions. We show how to apply SSIM to detect material degradation, and illustrate how this metric can be allied to spectral analysis for structure probing, while using tiled multi-resolution pyramids stored in HDF5 chunked multi-dimensional arrays. Results show that the proposed experimental data representation supports an average compression rate of 10X, and data compression scales linearly with the data size. We also illustrate how to correlate SSIM to crack formation, and how to use our numerical schemes to enable fast detection of deformation from 3D datasets evolving in time.

  4. Nano-crystalline diamond-coated titanium dental implants - a histomorphometric study in adult domestic pigs.

    PubMed

    Metzler, Philipp; von Wilmowsky, Cornelius; Stadlinger, Bernd; Zemann, Wolfgang; Schlegel, Karl Andreas; Rosiwal, Stephan; Rupprecht, Stephan

    2013-09-01

    Promising biomaterial characteristics of diamond-coatings in biomedicine have been described in the literature. However, there is a lack of knowledge about implant osseointegration of this surface modification compared to the currently used sandblasted acid-etched Ti-Al6-V4 implants. The aim of this study was to investigate the osseointegration of microwave plasma-chemical-vapour deposition (MWP-CVD) diamond-coated Ti-Al6-V4 dental implants after healing periods of 2 and 5 months. Twenty-four MWP-CVD diamond-coated and 24 un-coated dental titanium-alloy implants (Ankylos(®)) were placed in the frontal skull of eight adult domestic pigs. To evaluate the effects of the nano-structured surfaces on bone formation, a histomorphometric analysis was performed after 2 and 5 months of implant healing. Histomorphometry analysed the bone-to-implant contact (BIC). No significant difference in BIC for the diamond-coated implants in comparison to reference implants could be observed for both healing periods. Scanning electron microscopy revealed an adequate interface between the bone and the diamond surface. No delamination or particle-dissociation due to shearing forces could be detected. In this study, diamond-coated dental titanium-alloy implants and sandblasted acid-etched implants showed a comparable degree of osseointegration.

  5. Nanotechnology for dental implants.

    PubMed

    Tomsia, Antoni P; Lee, Janice S; Wegst, Ulrike G K; Saiz, Eduardo

    2013-01-01

    With the advent of nanotechnology, an opportunity exists for the engineering of new dental implant materials. Metallic dental implants have been successfully used for decades, but they have shortcomings related to osseointegration and mechanical properties that do not match those of bone. Absent the development of an entirely new class of materials, faster osseointegration of currently available dental implants can be accomplished by various surface modifications. To date, there is no consensus regarding the preferred method(s) of implant surface modification, and further development will be required before the ideal implant surface can be created, let alone become available for clinical use. Current approaches can generally be categorized into three areas: ceramic coatings, surface functionalization, and patterning on the micro- to nanoscale. The distinctions among these are imprecise, as some or all of these approaches can be combined to improve in vivo implant performance. These surface improvements have resulted in durable implants with a high percentage of success and long-term function. Nanotechnology has provided another set of opportunities for the manipulation of implant surfaces in its capacity to mimic the surface topography formed by extracellular matrix components of natural tissue. The possibilities introduced by nanotechnology now permit the tailoring of implant chemistry and structure with an unprecedented degree of control. For the first time, tools are available that can be used to manipulate the physicochemical environment and monitor key cellular events at the molecular level. These new tools and capabilities will result in faster bone formation, reduced healing time, and rapid recovery to function.

  6. Apparatus and method for detecting tampering in flexible structures

    DOEpatents

    Maxey, Lonnie C [Knoxville, TN; Haynes, Howard D [Knoxville, TN

    2011-02-01

    A system for monitoring or detecting tampering in a flexible structure includes taking electrical measurements on a sensing cable coupled to the structure, performing spectral analysis on the measured data, and comparing the spectral characteristics of the event to those of known benign and/or known suspicious events. A threshold or trigger value may used to identify an event of interest and initiate data collection. Alternatively, the system may be triggered at preset intervals, triggered manually, or triggered by a signal from another sensing device such as a motion detector. The system may be used to monitor electrical cables and conduits, hoses and flexible ducts, fences and other perimeter control devices, structural cables, flexible fabrics, and other flexible structures.

  7. Community detection in networks: Structural communities versus ground truth

    NASA Astrophysics Data System (ADS)

    Hric, Darko; Darst, Richard K.; Fortunato, Santo

    2014-12-01

    Algorithms to find communities in networks rely just on structural information and search for cohesive subsets of nodes. On the other hand, most scholars implicitly or explicitly assume that structural communities represent groups of nodes with similar (nontopological) properties or functions. This hypothesis could not be verified, so far, because of the lack of network datasets with information on the classification of the nodes. We show that traditional community detection methods fail to find the metadata groups in many large networks. Our results show that there is a marked separation between structural communities and metadata groups, in line with recent findings. That means that either our current modeling of community structure has to be substantially modified, or that metadata groups may not be recoverable from topology alone.

  8. Laser irradiation, ion implantation, and e-beam writing of integrated optical structures

    NASA Astrophysics Data System (ADS)

    Righini, Giancarlo C.; Banyasz, I.; Berneschi, S.; Brenci, M.; Chiasera, A.; Cremona, M.; Ehrt, D.; Ferrari, M.; Montereali, R. M.; Nunzi Conti, G.; Pelli, S.; Sebastiani, S.; Tosello, C.

    2005-07-01

    Much attention is currently being paid to the materials and processes that allow one to directly write or to imprint waveguiding structures and/or diffractive elements for optical integrated circuits by exposure from a source of photons, electrons or ions. Here a brief overview of the results achieved in our laboratories is presented, concerning the fabrication and characterization of optical guiding structures based on different materials and exposure techniques. These approaches include: electron and ion beam writing of waveguides in (poly)-crystalline lithium fluoride, uv-laser printing of waveguides and gratings in photorefractive glass thin films, and fs-laser writing in tellurite glasses. Properties and perspectives of these approaches are also discussed.

  9. Spatial hearing benefits demonstrated with presentation of acoustic temporal fine structure cues in bilateral cochlear implant listeners.

    PubMed

    Churchill, Tyler H; Kan, Alan; Goupell, Matthew J; Litovsky, Ruth Y

    2014-09-01

    Most contemporary cochlear implant (CI) processing strategies discard acoustic temporal fine structure (TFS) information, and this may contribute to the observed deficits in bilateral CI listeners' ability to localize sounds when compared to normal hearing listeners. Additionally, for best speech envelope representation, most contemporary speech processing strategies use high-rate carriers (≥900 Hz) that exceed the limit for interaural pulse timing to provide useful binaural information. Many bilateral CI listeners are sensitive to interaural time differences (ITDs) in low-rate (<300 Hz) constant-amplitude pulse trains. This study explored the trade-off between superior speech temporal envelope representation with high-rate carriers and binaural pulse timing sensitivity with low-rate carriers. The effects of carrier pulse rate and pulse timing on ITD discrimination, ITD lateralization, and speech recognition in quiet were examined in eight bilateral CI listeners. Stimuli consisted of speech tokens processed at different electrical stimulation rates, and pulse timings that either preserved or did not preserve acoustic TFS cues. Results showed that CI listeners were able to use low-rate pulse timing cues derived from acoustic TFS when presented redundantly on multiple electrodes for ITD discrimination and lateralization of speech stimuli.

  10. Multicycle rapid thermal annealing optimization of Mg-implanted GaN: Evolution of surface, optical, and structural properties

    SciTech Connect

    Greenlee, Jordan D.; Feigelson, Boris N.; Anderson, Travis J.; Hite, Jennifer K.; Mastro, Michael A.; Eddy, Charles R.; Hobart, Karl D.; Kub, Francis J.; Tadjer, Marko J.

    2014-08-14

    The first step of a multi-cycle rapid thermal annealing process was systematically studied. The surface, structure, and optical properties of Mg implanted GaN thin films annealed at temperatures ranging from 900 to 1200 °C were investigated by Raman spectroscopy, photoluminescence, UV-visible spectroscopy, atomic force microscopy, and Nomarski microscopy. The GaN thin films are capped with two layers of in-situ metal organic chemical vapor deposition -grown AlN and annealed in 24 bar of N{sub 2} overpressure to avoid GaN decomposition. The crystal quality of the GaN improves with increasing annealing temperature as confirmed by UV-visible spectroscopy and the full widths at half maximums of the E{sub 2} and A{sub 1} (LO) Raman modes. The crystal quality of films annealed above 1100 °C exceeds the quality of the as-grown films. At 1200 °C, Mg is optically activated, which is determined by photoluminescence measurements. However, at 1200 °C, the GaN begins to decompose as evidenced by pit formation on the surface of the samples. Therefore, it was determined that the optimal temperature for the first step in a multi-cycle rapid thermal anneal process should be conducted at 1150 °C due to crystal quality and surface morphology considerations.

  11. Optical and structural properties of Eu-implanted In{sub x}Al{sub 1-x}N

    SciTech Connect

    Roqan, I. S.; O'Donnell, K. P.; Martin, R. W.; Trager-Cowan, C.; Matias, V.; Vantomme, A.; Lorenz, K.; Alves, E.; Watson, I. M.

    2009-10-15

    Off-axis implantation of 80 keV Eu ions into epitaxial c-plane InAlN/GaN bilayers confines rare-earth (RE) doping largely to the InAlN layer. Rutherford backscattering spectrometry and x-ray diffraction show good correlations between the Eu{sup 3+} emission linewidth and key structural parameters of In{sub x}Al{sub 1-x}N films on GaN in the composition range near lattice matching (xapprox0.17). In contrast to GaN:Eu, selectively excited photoluminescence (PL) and PL excitation spectra reveal the presence of a single dominant optical center in InAlN. Eu{sup 3+} emission from In{sub 0.13}Al{sub 0.87}N:Eu also shows significantly less thermal quenching than GaN:Eu. InAlN films are therefore superior to GaN for RE optical doping.

  12. The Effects of Losartan in Preserving the Structural Integrity of Decellularized Small Diameter Vascular Allograft Conduit Implants In Vivo.

    PubMed

    Lee, Seung Hyun; Lee, Byoung Wook; Kim, Seong Who; Choo, Suk Jung

    2017-01-01

    Decellularization is a proposed method of preparing nonautologous biological arterial vascular scaffolding; however, the fate of the supporting medial elastic fiber, which is important in preserving the vascular structural integrity, is uncertain. The influence of losartan on preserving the medial elastic fiber integrity in decellularized small diameter vascular conduits (SDVC) was investigated. Decellularized infrarenal abdominal aortic allografts were implanted in Sprague-Dawley rats treated either with (study rats, n = 6) or without oral losartan (control rats, n = 6) and graded 8 weeks later according to a remodeling scoring system (1-mild, 2-moderate, 3-severe) which we devised based on the intimal hyperplasia degree, morphologic changes, and elastic fiber fragmentation of the conduits. DAPI immunohistochemistry analysis was performed in 47 (25 decellularization only and 22 losartan treatment) cross-sectional slide specimens. The losartan versus decellularization only SDVC showed a significantly lower medial elastic fragmentation score (1.32 vs. 2.24, P < 0.001), superior medial layer preservation, and relatively more normal appearing intimal cellular morphology. The results suggested rats receiving decellularized SDVCs treated with losartan may yield superior medial layer elastic fiber preservation.

  13. Structural Damage Detection with Piezoelectric Wafer Active Sensors

    NASA Astrophysics Data System (ADS)

    Giurgiutiu, Victor

    2011-07-01

    Piezoelectric wafer active sensors (PWAS) are lightweight and inexpensive enablers for a large class of damage detection and structural health monitoring (SHM) applications. This paper starts with a brief review of PWAS physical principles and basic modelling and continues by considering the various ways in which PWAS can be used for damage detection: (a) embedded guided-wave ultrasonics, i.e., pitch-catch, pulse-echo, phased arrays, thickness mode; (b) high-frequency modal sensing, i.e., the electro-mechanical (E/M) impedance method; (c) passive detection, i.e., acoustic emission and impact detection. An example of crack-like damage detection and localization with PWAS phased arrays on a small metallic plate is given. The modelling of PWAS detection of disbond damage in adhesive joints is achieved with the analytical transfer matrix method (TMM). The analytical methods offer the advantage of fast computation which enables parameter studies and carpet plots. A parametric study of the effect of crack size and PWAS location on disbond detection is presented. The power and energy transduction between PWAS and structure is studied analytically with a wave propagation method. Special attention is given to the mechatronics modeling of the complete transduction cycle from electrical excitation into ultrasonic acoustic waves by the piezoelectric effect, the transfer through the structure, and finally reverse piezoelectric transduction to generate the received electric signal. It is found that the combination of PWAS size and wave frequency/wavelength play an important role in identifying transduction maxima and minima that could be exploited to achieve an optimum power-efficient design. The multi-physics finite element method (MP-FEM), which permits fine discretization of damaged regions and complicated structural geometries, is used to study the generation of guided waves in a plate from an electrically excited transmitter PWAS and the capture of these waves as electric

  14. Detection of electromagnetic radiation using micromechanical multiple quantum wells structures

    DOEpatents

    Datskos, Panagiotis G [Knoxville, TN; Rajic, Slobodan [Knoxville, TN; Datskou, Irene [Knoxville, TN

    2007-07-17

    An apparatus and method for detecting electromagnetic radiation employs a deflectable micromechanical apparatus incorporating multiple quantum wells structures. When photons strike the quantum-well structure, physical stresses are created within the sensor, similar to a "bimetallic effect." The stresses cause the sensor to bend. The extent of deflection of the sensor can be measured through any of a variety of conventional means to provide a measurement of the photons striking the sensor. A large number of such sensors can be arranged in a two-dimensional array to provide imaging capability.

  15. Breast Implants

    MedlinePlus

    ... sale in the United States: saline-filled and silicone gel-filled. Both types have a silicone outer shell. They vary in size, shell thickness, ... implant them. Provide information on saline-filled and silicone gel-filled breast implants, including data supporting a ...

  16. A method for detecting structural deterioration in bridges

    NASA Technical Reports Server (NTRS)

    Cole, H. A., Jr.; Reed, R. E., Jr.

    1974-01-01

    The problem of detecting deterioration in bridge structures is studied with the use of Randomdec analysis. Randomdec signatures, derived from the ambient bridge vibrations in the acoustic range, were obtained for a girder bridge over a period of a year to show the insensitivity of the signatures to environmental changes. A laboratory study was also conducted to show the sensitivity of signatures to fatigue cracks on the order of a centimeter in length in steel beams.

  17. Sensor failure detection using generalized parity relations for flexible structures

    NASA Technical Reports Server (NTRS)

    Mercadal, Mathieu

    1989-01-01

    Analytical redundancy may be preferable to hardware redundancy in failure detection/isolation tasks for such large-scale systems as space structures. Generalized single-sensor parity relations are presently applied to this problem; they are noted to yield a very simple isolation logic, and their generation is found to be extremely rapid, even in the case of extremely complex systems, provided only that the eigenstructure of the system be known. Their implementation is, however, extremely sensitive to modeling errors and noise.

  18. Airframe structural damage detection: a non-linear structural surface intensity based technique.

    PubMed

    Semperlotti, Fabio; Conlon, Stephen C; Barnard, Andrew R

    2011-04-01

    The non-linear structural surface intensity (NSSI) based damage detection technique is extended to airframe applications. The selected test structure is an upper cabin airframe section from a UH-60 Blackhawk helicopter (Sikorsky Aircraft, Stratford, CT). Structural damage is simulated through an impact resonator device, designed to simulate the induced vibration effects typical of non-linear behaving damage. An experimental study is conducted to prove the applicability of NSSI on complex mechanical systems as well as to evaluate the minimum sensor and actuator requirements. The NSSI technique is shown to have high damage detection sensitivity, covering an extended substructure with a single sensing location.

  19. Temporal Structure and Complexity Affect Audio-Visual Correspondence Detection

    PubMed Central

    Denison, Rachel N.; Driver, Jon; Ruff, Christian C.

    2013-01-01

    Synchrony between events in different senses has long been considered the critical temporal cue for multisensory integration. Here, using rapid streams of auditory and visual events, we demonstrate how humans can use temporal structure (rather than mere temporal coincidence) to detect multisensory relatedness. We find psychophysically that participants can detect matching auditory and visual streams via shared temporal structure for crossmodal lags of up to 200 ms. Performance on this task reproduced features of past findings based on explicit timing judgments but did not show any special advantage for perfectly synchronous streams. Importantly, the complexity of temporal patterns influences sensitivity to correspondence. Stochastic, irregular streams – with richer temporal pattern information – led to higher audio-visual matching sensitivity than predictable, rhythmic streams. Our results reveal that temporal structure and its complexity are key determinants for human detection of audio-visual correspondence. The distinctive emphasis of our new paradigms on temporal patterning could be useful for studying special populations with suspected abnormalities in audio-visual temporal perception and multisensory integration. PMID:23346067

  20. Electronic origin and structural instabilities of Ti-based alloys suitable for orthopaedic implants

    NASA Astrophysics Data System (ADS)

    Lekka, Ch. E.; Gutiérrez-Moreno, J. J.; Calin, M.

    2017-03-01

    We present electronic structure calculations results on Ti, Nb and TiNb model systems seeking for the electronic origin of structural instabilities. It came out that the β-Ti instability is associated with the presence of: a) degenerated states, b) few first neighbor bonds (FN) close to Fermi level (EF), c) "critical crossing electron states" along the soft phonon directions, usually with 3deg→3dt2g transitions and d) semi-core 3p that reduce FN. In β-Nb these features are altered, while, importantly, FN homogeneous hybridizations dominate the Brillouin zone. Indeed, the amount of low energy Nb-Nb FN (even next FN) results in various Ti-Nb phases that are also correlated with the phase's coordination number. The stability of β-TiNb upon sp dopant additions and their elastic softening also follows these electronic characteristics. This approach may provide an alternative path towards the design of stable Ti-based biocompatible alloys.

  1. Optical, structural, and chemical properties of CR-39 implanted with 5.2 MeV doubly charged carbon ions

    NASA Astrophysics Data System (ADS)

    Ali, Dilawar; Butt, M. Z.; Ishtiaq, Mohsin; Waqas Khaliq, M.; Bashir, Farooq

    2016-11-01

    Poly-allyl-diglycol-carbonate (CR-39) specimens were irradiated with 5.2 MeV doubly charged carbon ions using Pelletron accelerator. Ion dose was varied from 5 × 1013 to 5 × 1015 ions cm-2. Optical, structural, and chemical properties were investigated by UV-vis spectroscopy, x-ray diffractometer, and FTIR/Raman spectroscopy, respectively. It was found that optical absorption increases with increasing ion dose. Absorption edge shifts from UV region to visible region. The measured opacity values of pristine and ion implanted CR-39 range from 0.0519 to 4.7959 mm-1 following an exponential growth (9141%) with the increase in ion dose. The values of direct and indirect band gap energy decrease exponentially with an increase in ion dose by 59% and 71%, respectively. However, average refractive index in the visible region increases from 1.443 to 2.864 with an increase in ion dose, by 98%. A linear relation between band gap energy and crystallite size was observed. Both the number of carbon atoms in conjugation length and the number of carbon atoms per cluster increase linearly with the increase in ion dose. FTIR spectra showed that on C+2 ions irradiation, the intensity of all bands decreases gradually without appearance of any new band, indicating degradation of polymer after irradiation. Raman spectra revealed that the density of -CH2- group decreases on C+2 ions irradiation. However, the structure of CR-39 is completely destroyed on irradiation with ion dose 1 × 1015 and 5 × 1015 ions cm-2.

  2. Formation of donor centers upon the annealing of silicon light-emitting structures implanted with oxygen ions

    SciTech Connect

    Sobolev, N. A. Danilov, D. V.; Aleksandrov, O. V.; Loshachenko, A. S.; Sakharov, V. I.; Serenkov, I. T.; Shek, E. I.; Trapeznikova, I. N.

    2015-03-15

    It is found that the implantation of silicon with oxygen ions and subsequent annealing at high temperatures are accompanied by the formation of electrically active donor centers and by the p-n conversion of the conductivity of silicon. The concentration and spatial distribution of these centers depend on the annealing temperature. The results are accounted for by the interaction of oxygen atoms with intrinsic point defects formed upon the annealing of implantation damages.

  3. Structure-Assisted Functional Anchor Implantation in Robust Metal–Organic Frameworks with Ultralarge Pores

    SciTech Connect

    Park, Jihye; Feng, Dawei; Zhou, Hong-Cai

    2015-02-04

    A facile functionalization assisted by the structural attributes of PCN-333 has been studied while maintaining the integrity of the parent MOF including ultralarge pores, chemical robustness, and crystallinity. Herein we thoroughly analyzed ligand exchange phenomena in PCN-333 and demonstrate that the extent of exchange can be tailored by varying the exchange conditions as potential applications may require. Through this method a variety of functional groups are incorporated into PCN-333. To further show the capabilities of this system introduction of a BODIPY fluorophore as a secondary functionality was performed to the functionalized framework via a click reaction. We anticipate the PCN-333 with functional anchor can serve as a stable platform for further chemistry to be explored in future applications.

  4. Structure-Assisted Functional Anchor Implantation in Robust Metal-Organic Frameworks with Ultra large Pores

    SciTech Connect

    Park, J; Feng, DW; Zhou, HC

    2015-02-04

    A facile functionalization assisted by the structural attributes of PCN-333 has been studied while maintaining the integrity of the parent MOF including ultralarge pores, chemical robustness, and crystallinity. Herein we thoroughly analyzed ligand exchange phenomena in PCN-333 and demonstrate that the extent of exchange can be tailored by varying the exchange conditions as potential applications may require. Through this method a variety of functional groups are incorporated into PCN-333. To further show the capabilities of this system introduction of a BODIPY fluorophore as a secondary functionality was performed to the functionalized framework via a click reaction. We anticipate the PCN-333 with functional anchor can serve as a stable platform for further chemistry to be explored in future applications

  5. Photogrammetric detection technique for rotor blades structural characterization

    NASA Astrophysics Data System (ADS)

    Enei, C.; Bernardini, G.; Serafini, J.; Mattioni, L.; Ficuciello, C.; Vezzari, V.

    2015-11-01

    This paper describes an innovative use of photogrammetric detection techniques to experimentally estimate structural/inertial properties of helicopter rotor blades. The identification algorithms for the evaluation of mass and flexural stiffness distributions are an extension of the ones proposed by Larsen, whereas the procedure for torsional properties determination (stiffness and shear center position) is based on the Euler-Prandtl beam theory. These algorithms rely on measurements performed through photogrammetric detection, which requires the collection of digital photos allowing the identification of 3D coordinates of labeled points (markers) on the structure through the correlation of 2D pictures. The displacements are evaluated by comparing the positions of markers in loaded and reference configuration. Being the applied loads known, the structural characteristics can be directly obtained from the measured displacements. The accuracy of the proposed identification algorithms has been firstly verified by comparison with numerical and experimental data, and then applied to the structural characterization of two main rotor blades, designed for ultra-light helicopter applications.

  6. Detection of bondline delaminations in multilayer structures with lossy components

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Winfree, William P.; Smith, B. T.; Heyman, Joseph H.

    1988-01-01

    The detection of bondline delaminations in multilayer structures using ultrasonic reflection techniques is a generic problem in adhesively bonded composite structures such as the Space Shuttles's Solid Rocket Motors (SRM). Standard pulse echo ultrasonic techniques do not perform well for a composite resonator composed of a resonant layer combined with attenuating layers. Excessive ringing in the resonant layer tends to mask internal echoes emanating from the attenuating layers. The SRM is made up of a resonant steel layer backed by layers of adhesive, rubber, liner and fuel, which are ultrasonically attenuating. The structure's response is modeled as a lossy ultrasonic transmission line. The model predicts that the acoustic response of the system is sensitive to delaminations at the interior bondlines in a few narrow frequency bands. These predictions are verified by measurements on a fabricated system. Successful imaging of internal delaminations is sensitive to proper selection of the interrogating frequency. Images of fabricated bondline delaminations are presented based on these studies.

  7. Structural Change Can Be Detected in Advanced-Glaucoma Eyes

    PubMed Central

    Belghith, Akram; Medeiros, Felipe A.; Bowd, Christopher; Liebmann, Jeffrey M.; Girkin, Christopher A.; Weinreb, Robert N.; Zangwill, Linda M.

    2016-01-01

    Purpose To compare spectral-domain optical coherence tomography (SD-OCT) standard structural measures and a new three-dimensional (3D) volume optic nerve head (ONH) change detection method for detecting change over time in severely advanced-glaucoma (open-angle glaucoma [OAG]) patients. Methods Thirty-five eyes of 35 patients with very advanced glaucoma (defined as a visual field mean deviation < −21 dB) and 46 eyes of 30 healthy subjects to estimate aging changes were included. Circumpapillary retinal fiber layer thickness (cpRNFL), minimum rim width (MRW), and macular retinal ganglion cell–inner plexiform layer (GCIPL) thicknesses were measured using the San Diego Automated Layer Segmentation Algorithm (SALSA). Progression was defined as structural loss faster than 95th percentile of healthy eyes. Three-dimensional volume ONH change was estimated using the Bayesian-kernel detection scheme (BKDS), which does not require extensive retinal layer segmentation. Results The number of progressing glaucoma eyes identified was highest for 3D volume BKDS (13, 37%), followed by GCPIL (11, 31%), cpRNFL (4, 11%), and MRW (2, 6%). In advanced-OAG eyes, only the mean rate of GCIPL change reached statistical significance, −0.18 μm/y (P = 0.02); the mean rates of cpRNFL and MRW change were not statistically different from zero. In healthy eyes, the mean rates of cpRNFL, MRW, and GCIPL change were significantly different from zero. (all P < 0.001). Conclusions Ganglion cell–inner plexiform layer and 3D volume BKDS show promise for identifying change in severely advanced glaucoma. These results suggest that structural change can be detected in very advanced disease. Longer follow-up is needed to determine whether changes identified are false positives or true progression. PMID:27454660

  8. 3D lattice distortions and defect structures in ion-implanted nano-crystals

    PubMed Central

    Hofmann, Felix; Tarleton, Edmund; Harder, Ross J.; Phillips, Nicholas W.; Ma, Pui-Wai; Clark, Jesse N.; Robinson, Ian K.; Abbey, Brian; Liu, Wenjun; Beck, Christian E.

    2017-01-01

    Focussed Ion Beam (FIB) milling is a mainstay of nano-scale machining. By manipulating a tightly focussed beam of energetic ions, often gallium (Ga+), FIB can sculpt nanostructures via localised sputtering. This ability to cut solid matter on the nano-scale revolutionised sample preparation across the life, earth and materials sciences. Despite its widespread usage, detailed understanding of the FIB-induced structural damage, intrinsic to the technique, remains elusive. Here we examine the defects caused by FIB in initially pristine objects. Using Bragg Coherent X-ray Diffraction Imaging (BCDI), we are able to spatially-resolve the full lattice strain tensor in FIB-milled gold nano-crystals. We find that every use of FIB causes large lattice distortions. Even very low ion doses, typical of FIB imaging and previously thought negligible, have a dramatic effect. Our results are consistent with a damage microstructure dominated by vacancies, highlighting the importance of free-surfaces in determining which defects are retained. At larger ion fluences, used during FIB-milling, we observe an extended dislocation network that causes stresses far beyond the bulk tensile strength of gold. These observations provide new fundamental insight into the nature of the damage created and the defects that lead to a surprisingly inhomogeneous morphology. PMID:28383028

  9. Biocompatible implant surface treatments.

    PubMed

    Pattanaik, Bikash; Pawar, Sudhir; Pattanaik, Seema

    2012-01-01

    Surface plays a crucial role in biological interactions. Surface treatments have been applied to metallic biomaterials in order to improve their wear properties, corrosion resistance, and biocompatibility. A systematic review was performed on studies investigating the effects of implant surface treatments on biocompatibility. We searched the literature using PubMed, electronic databases from 1990 to 2009. Key words such as implant surface topography, surface roughness, surface treatment, surface characteristics, and surface coatings were used. The search was restricted to English language articles published from 1990 to December 2009. Additionally, a manual search in the major dental implant journals was performed. When considering studies, clinical studies were preferred followed by histological human studies, animal studies, and in vitro studies. A total of 115 articles were selected after elimination: clinical studies, 24; human histomorphometric studies, 11; animal histomorphometric studies, 46; in vitro studies, 34. The following observations were made in this review: · The focus has shifted from surface roughness to surface chemistry and a combination of chemical manipulations on the porous structure. More investigations are done regarding surface coatings. · Bone response to almost all the surface treatments was favorable. · Future trend is focused on the development of osteogenic implant surfaces. Limitation of this study is that we tried to give a broader overview related to implant surface treatments. It does not give any conclusion regarding the best biocompatible implant surface treatment investigated till date. Unfortunately, the eventually selected studies were too heterogeneous for inference of data.

  10. The role of well-defined nanotopography of titanium implants on osseointegration: cellular and molecular events in vivo

    PubMed Central

    Karazisis, Dimitrios; Ballo, Ahmed M; Petronis, Sarunas; Agheli, Hossein; Emanuelsson, Lena; Thomsen, Peter; Omar, Omar

    2016-01-01

    Purpose Mechanisms governing the cellular interactions with well-defined nanotopography are not well described in vivo. This is partly due to the difficulty in isolating a particular effect of nanotopography from other surface properties. This study employed colloidal lithography for nanofabrication on titanium implants in combination with an in vivo sampling procedure and different analytical techniques. The aim was to elucidate the effect of well-defined nanotopography on the molecular, cellular, and structural events of osseointegration. Materials and methods Titanium implants were nanopatterned (Nano) with semispherical protrusions using colloidal lithography. Implants, with and without nanotopography, were implanted in rat tibia and retrieved after 3, 6, and 28 days. Retrieved implants were evaluated using quantitative polymerase chain reaction, histology, immunohistochemistry, and energy dispersive X-ray spectroscopy (EDS). Results Surface characterization showed that the nanotopography was well defined in terms of shape (semispherical), size (79±6 nm), and distribution (31±2 particles/µm2). EDS showed similar levels of titanium, oxygen, and carbon for test and control implants, confirming similar chemistry. The molecular analysis of the retrieved implants revealed that the expression levels of the inflammatory cytokine, TNF-α, and the osteoclastic marker, CatK, were reduced in cells adherent to the Nano implants. This was consistent with the observation of less CD163-positive macrophages in the tissue surrounding the Nano implant. Furthermore, periostin immunostaining was frequently detected around the Nano implant, indicating higher osteogenic activity. This was supported by the EDS analysis of the retrieved implants showing higher content of calcium and phosphate on the Nano implants. Conclusion The results show that Nano implants elicit less periimplant macrophage infiltration and downregulate the early expression of inflammatory (TNF-α) and

  11. Positron annihilation study of P implanted Si

    SciTech Connect

    Asoka-Kumar, P.; Au, H.L.; Lynn, K.G. ); Sferlazzo, P. . SED Division)

    1992-01-01

    High-energy ion implantation (above 200 keV) is now commonly used in a variety of VLSI processes. The high energy required for these implants is often achieved by implanting multiply charged ions, which inevitably brings in the problem of low-energy ion contamination. The low-energy contamination is difficult to diagnose and detect. Positron annihilation spectroscopy is used to examine the defect distributions in these high energy implants with varying degrees of contamination.

  12. Positron annihilation study of P implanted Si

    SciTech Connect

    Asoka-Kumar, P.; Au, H.L.; Lynn, K.G.; Sferlazzo, P.

    1992-12-01

    High-energy ion implantation (above 200 keV) is now commonly used in a variety of VLSI processes. The high energy required for these implants is often achieved by implanting multiply charged ions, which inevitably brings in the problem of low-energy ion contamination. The low-energy contamination is difficult to diagnose and detect. Positron annihilation spectroscopy is used to examine the defect distributions in these high energy implants with varying degrees of contamination.

  13. The challenges and importance of structural variation detection in livestock

    PubMed Central

    Bickhart, Derek M.; Liu, George E.

    2014-01-01

    Recent studies in humans and other model organisms have demonstrated that structural variants (SVs) comprise a substantial proportion of variation among individuals of each species. Many of these variants have been linked to debilitating diseases in humans, thereby cementing the importance of refining methods for their detection. Despite progress in the field, reliable detection of SVs still remains a problem even for human subjects. Many of the underlying problems that make SVs difficult to detect in humans are amplified in livestock species, whose lower quality genome assemblies and incomplete gene annotation can often give rise to false positive SV discoveries. Regardless of the challenges, SV detection is just as important for livestock researchers as it is for human researchers, given that several productive traits and diseases have been linked to copy number variations (CNVs) in cattle, sheep, and pig. Already, there is evidence that many beneficial SVs have been artificially selected in livestock such as a duplication of the agouti signaling protein gene that causes white coat color in sheep. In this review, we will list current SV and CNV discoveries in livestock and discuss the problems that hinder routine discovery and tracking of these polymorphisms. We will also discuss the impacts of selective breeding on CNV and SV frequencies and mention how SV genotyping could be used in the future to improve genetic selection. PMID:24600474

  14. Detection of Critical Camera Configurations for Structure from Motion

    NASA Astrophysics Data System (ADS)

    Michelini, M.; Mayer, H.

    2014-03-01

    This paper deals with the detection of critical, i.e., poor or degenerate camera configurations, with a poor or undefined intersection geometry between views. This is the basis for a calibrated Structure from Motion (SfM) approach employing image triplets for complex, unordered image sets, e.g., obtained by combining terrestrial images and images from small Unmanned Aerial Systems (UAS). Poor intersection geometry results from a small ratio between the baseline length and the depth of the scene. If there is no baseline between views, the intersection geometry becomes undefined. Our approach can detect image pairs without or with a very weak baseline (motion degeneracy). For the detection we have developed various metrics and evaluated them by means of extensive experiments with about 1500 image pairs. The metrics are based on properties of the reconstructed 3D points, such as the roundness of the error ellipsoid. The detection of weak baselines is formulated as a classification problem using the metrics as features. Machine learning techniques are applied to improve the classification. By taking into account the critical camera configurations during the iterative composition of the image set, a complete, metric 3D reconstruction of the whole scene could be achieved also in this case. We sketch our approach for the orientation of unordered image sets and finally demonstrate that the approach is able to produce very accurate and reliable orientations.

  15. Optoelectronic leak detection system for monitoring subsea structures

    NASA Astrophysics Data System (ADS)

    Moodie, D.,; Costello, L.; McStay, D.

    2010-04-01

    Leak detection and monitoring on subsea structures is an area of increasing interest for the detection and monitoring of production and control fluids for the oil and gas industry. Current techniques such as capacitive (dielectric) based measurement or passive acoustic systems have limitations and we report here an optoelectronic solution based upon fluorescence spectroscopy to provide a permanent monitoring solution. We report here a new class of optoelectronic subsea sensor for permanent, real time monitoring of hydrocarbon production systems. The system is capable of detecting small leaks of production or hydraulic fluid (ppm levels) over distances of 4-5 meters in a subsea environment. Ideally systems designed for such applications should be capable of working at depths of up to 3000m unattended for periods of 20+ years. The system uses advanced single emitter LED technology to meet the challenges of lifetime, power consumption, spatial coverage and delivery of a cost effective solution. The system is designed for permanent deployment on Christmas tree (XT), subsea processing systems (SPS) and associated equipment to provide enhanced leak detection capability.

  16. Soft electronic structure modulation of surface (thin-film) and bulk (ceramics) morphologies of TiO2-host by Pb-implantation: XPS-and-DFT characterization

    NASA Astrophysics Data System (ADS)

    Zatsepin, D. A.; Boukhvalov, D. W.; Gavrilov, N. V.; Zatsepin, A. F.; Shur, V. Ya.; Esin, A. A.; Kim, S. S.; Kurmaev, E. Z.

    2017-04-01

    The results of combined experimental and theoretical study of substitutional and clustering effects in the structure of Pb-doped TiO2-hosts (bulk ceramics and thin-film morphologies) are presented. Pb-doping of the bulk and thin-film titanium dioxide was made with the help of pulsed ion-implantation without posterior tempering (Electronic Structure Modulation Mode). The X-ray photoelectron spectroscopy (XPS) qualification of core-levels and valence bands and Density-Functional Theory (DFT) calculations were employed in order to study the yielded electronic structure of Pb-ion modulated TiO2 host-matrices. The combined XPS-and-DFT analysis has agreed definitely with the scenario of the implantation stimulated appearance of PbO-like structures in the bulk morphology of TiO2:Pb, whereas in thin-film morphology the PbO2-like structure becomes dominating, essentially contributing weak O/Pb bonding (PbxOy defect clusters). The crucial role of the oxygen hollow-type vacancies for the process of Pb-impurity "insertion" into the structure of bulk TiO2 was pointed out employing DFT-based theoretical background. Both experiment and theory established clearly the final electronic structure re-arrangement of the bulk and thin-film morphologies of TiO2 because of the Pb-modulated deformation and shift of the initial Valence Base-Band Width about 1 eV up.

  17. A structural framework for anomalous change detection and characterization

    SciTech Connect

    Prasad, Lakshman; Theiler, James P

    2009-01-01

    We present a spatially adaptive scheme for automatically searching a pair of images of a scene for unusual and interesting changes. Our motivation is to bring into play structural aspects of image features alongside the spectral attributes used for anomalous change detection (ACD). We leverage a small but informative subset of pixels, namely edge pixels of the images, as anchor points of a Delaunay triangulation to jointly decompose the images into a set of triangular regions, called trixels, which are spectrally uniform. Such decomposition helps in image regularization by simple-function approximation on a feature-adaptive grid. Applying ACD to this trixel grid instead of pixels offers several advantages. It allows: (1) edge-preserving smoothing of images, (2) speed-up of spatial computations by significantly reducing the representation of the images, and (3) the easy recovery of structure of the detected anomalous changes by associating anomalous trixels with polygonal image features. The latter facility further enables the application of shape-theoretic criteria and algorithms to characterize the changes and recognize them as interesting or not. This incorporation of spatial information has the potential to filter out some spurious changes, such as due to parallax, shadows, and misregistration, by identifying and filtering out those that are structurally similar and spatially pervasive. Our framework supports the joint spatial and spectral analysis of images, potentially enabling the design of more robust ACD algorithms.

  18. Damage Detection in Composite Structures with Wavenumber Array Data Processing

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Leckey, Cara; Yu, Lingyu

    2013-01-01

    Guided ultrasonic waves (GUW) have the potential to be an efficient and cost-effective method for rapid damage detection and quantification of large structures. Attractive features include sensitivity to a variety of damage types and the capability of traveling relatively long distances. They have proven to be an efficient approach for crack detection and localization in isotropic materials. However, techniques must be pushed beyond isotropic materials in order to be valid for composite aircraft components. This paper presents our study on GUW propagation and interaction with delamination damage in composite structures using wavenumber array data processing, together with advanced wave propagation simulations. Parallel elastodynamic finite integration technique (EFIT) is used for the example simulations. Multi-dimensional Fourier transform is used to convert time-space wavefield data into frequency-wavenumber domain. Wave propagation in the wavenumber-frequency domain shows clear distinction among the guided wave modes that are present. This allows for extracting a guided wave mode through filtering and reconstruction techniques. Presence of delamination causes spectral change accordingly. Results from 3D CFRP guided wave simulations with delamination damage in flat-plate specimens are used for wave interaction with structural defect study.

  19. Online anomaly detection in crowd scenes via structure analysis.

    PubMed

    Yuan, Yuan; Fang, Jianwu; Wang, Qi

    2015-03-01

    Abnormal behavior detection in crowd scenes is continuously a challenge in the field of computer vision. For tackling this problem, this paper starts from a novel structure modeling of crowd behavior. We first propose an informative structural context descriptor (SCD) for describing the crowd individual, which originally introduces the potential energy function of particle's interforce in solid-state physics to intuitively conduct vision contextual cueing. For computing the crowd SCD variation effectively, we then design a robust multi-object tracker to associate the targets in different frames, which employs the incremental analytical ability of the 3-D discrete cosine transform (DCT). By online spatial-temporal analyzing the SCD variation of the crowd, the abnormality is finally localized. Our contribution mainly lies on three aspects: 1) the new exploration of abnormal detection from structure modeling where the motion difference between individuals is computed by a novel selective histogram of optical flow that makes the proposed method can deal with more kinds of anomalies; 2) the SCD description that can effectively represent the relationship among the individuals; and 3) the 3-D DCT multi-object tracker that can robustly associate the limited number of (instead of all) targets which makes the tracking analysis in high density crowd situation feasible. Experimental results on several publicly available crowd video datasets verify the effectiveness of the proposed method.

  20. FRF-based structural damage detection of controlled buildings with podium structures: Experimental investigation

    NASA Astrophysics Data System (ADS)

    Xu, Y. L.; Huang, Q.; Zhan, S.; Su, Z. Q.; Liu, H. J.

    2014-06-01

    How to use control devices to enhance system identification and damage detection in relation to a structure that requires both vibration control and structural health monitoring is an interesting yet practical topic. In this study, the possibility of using the added stiffness provided by control devices and frequency response functions (FRFs) to detect damage in a building complex was explored experimentally. Scale models of a 12-storey main building and a 3-storey podium structure were built to represent a building complex. Given that the connection between the main building and the podium structure is most susceptible to damage, damage to the building complex was experimentally simulated by changing the connection stiffness. To simulate the added stiffness provided by a semi-active friction damper, a steel circular ring was designed and used to add the related stiffness to the building complex. By varying the connection stiffness using an eccentric wheel excitation system and by adding or not adding the circular ring, eight cases were investigated and eight sets of FRFs were measured. The experimental results were used to detect damage (changes in connection stiffness) using a recently proposed FRF-based damage detection method. The experimental results showed that the FRF-based damage detection method could satisfactorily locate and quantify damage.

  1. Detecting and representing predictable structure during auditory scene analysis.

    PubMed

    Sohoglu, Ediz; Chait, Maria

    2016-09-07

    We use psychophysics and MEG to test how sensitivity to input statistics facilitates auditory-scene-analysis (ASA). Human subjects listened to 'scenes' comprised of concurrent tone-pip streams (sources). On occasional trials a new source appeared partway. Listeners were more accurate and quicker to detect source appearance in scenes comprised of temporally-regular (REG), rather than random (RAND), sources. MEG in passive listeners and those actively detecting appearance events revealed increased sustained activity in auditory and parietal cortex in REG relative to RAND scenes, emerging ~400 ms of scene-onset. Over and above this, appearance in REG scenes was associated with increased responses relative to RAND scenes. The effect of temporal structure on appearance-evoked responses was delayed when listeners were focused on the scenes relative to when listening passively, consistent with the notion that attention reduces 'surprise'. Overall, the results implicate a mechanism that tracks predictability of multiple concurrent sources to facilitate active and passive ASA.

  2. Information-theoretical noninvasive damage detection in bridge structures.

    PubMed

    Sudu Ambegedara, Amila; Sun, Jie; Janoyan, Kerop; Bollt, Erik

    2016-11-01

    Damage detection of mechanical structures such as bridges is an important research problem in civil engineering. Using spatially distributed sensor time series data collected from a recent experiment on a local bridge in Upper State New York, we study noninvasive damage detection using information-theoretical methods. Several findings are in order. First, the time series data, which represent accelerations measured at the sensors, more closely follow Laplace distribution than normal distribution, allowing us to develop parameter estimators for various information-theoretic measures such as entropy and mutual information. Second, as damage is introduced by the removal of bolts of the first diaphragm connection, the interaction between spatially nearby sensors as measured by mutual information becomes weaker, suggesting that the bridge is "loosened." Finally, using a proposed optimal mutual information interaction procedure to prune away indirect interactions, we found that the primary direction of interaction or influence aligns with the traffic direction on the bridge even after damaging the bridge.

  3. Information-theoretical noninvasive damage detection in bridge structures

    NASA Astrophysics Data System (ADS)

    Sudu Ambegedara, Amila; Sun, Jie; Janoyan, Kerop; Bollt, Erik

    2016-11-01

    Damage detection of mechanical structures such as bridges is an important research problem in civil engineering. Using spatially distributed sensor time series data collected from a recent experiment on a local bridge in Upper State New York, we study noninvasive damage detection using information-theoretical methods. Several findings are in order. First, the time series data, which represent accelerations measured at the sensors, more closely follow Laplace distribution than normal distribution, allowing us to develop parameter estimators for various information-theoretic measures such as entropy and mutual information. Second, as damage is introduced by the removal of bolts of the first diaphragm connection, the interaction between spatially nearby sensors as measured by mutual information becomes weaker, suggesting that the bridge is "loosened." Finally, using a proposed optimal mutual information interaction procedure to prune away indirect interactions, we found that the primary direction of interaction or influence aligns with the traffic direction on the bridge even after damaging the bridge.

  4. Detection of damage in welded structure using experimental modal data

    NASA Astrophysics Data System (ADS)

    Abu Husain, N.; Ouyang, H.

    2011-07-01

    A typical automotive structure could contain thousands of spot weld joints that contribute significantly to the vehicle's structural stiffness and dynamic characteristics. However, some of these joints may be imperfect or even absent during the manufacturing process and they are also highly susceptible to damage due to operational and environmental conditions during the vehicle lifetime. Therefore, early detection and estimation of damage are important so necessary actions can be taken to avoid further problems. Changes in physical parameters due to existence of damage in a structure often leads to alteration of vibration modes; thus demonstrating the dependency between the vibration characteristics and the physical properties of structures. A sensitivity-based model updating method, performed using a combination of MATLAB and NASTRAN, has been selected for the purpose of this work. The updating procedure is regarded as parameter identification which aims to bring the numerical prediction to be as closely as possible to the measured natural frequencies and mode shapes data of the damaged structure in order to identify the damage parameters (characterised by the reductions in the Young's modulus of the weld patches to indicate the loss of material/stiffness at the damage region).

  5. Nano-structure analysis of Fe implanted SnO2 films by 57Fe and 119Sn CEMS

    NASA Astrophysics Data System (ADS)

    Nomura, Kiyoshi; Reuther, Helfried

    2009-06-01

    SnO2 films were implanted with 57Fe at substrate temperatures of room temperature and 300°C. The chemical states of Fe and Sn were characterized by 57Fe CEMS and 119Sn CEMS, respectively. The implanted Fe species exist as Fe(II) and Fe(III) in SnO2 films, which also are reduced into Sn(II)on the implanted surface. The as prepared and post annealed at 500°C samples did not show Kerr effect, but the sample implanted with 1 × 1017 Fe ions/cm2 at 300°C showed Kerr effect although magnetic sextets were not clearly observed in the 57Fe CEM spectra. The Kerr effect disappeared after annealing. It suggests that the number of magnetic defects decreases by absorption of oxygen. Magnetic relaxation appeared in the case of low implantation of 5 × 1016 Fe ions/cm2, which is considered to be due to anti-ferromagnetism or paramagnetic relaxation.

  6. Histrelin Implant

    MedlinePlus

    ... implant (Supprelin LA) is used to treat central precocious puberty (CPP; a condition causing children to enter puberty too soon, resulting in faster than normal bone growth and development of sexual characteristics) in girls ...

  7. Penile Implants

    MedlinePlus

    ... placed inside the penis to allow men with erectile dysfunction (ED) to get an erection. Penile implants are ... complications and follow-up care. For most men, erectile dysfunction can be successfully treated with medications or use ...

  8. Detecting 3D Vegetation Structure with the Galileo Space Probe: Can a Distant Probe Detect Vegetation Structure on Earth?

    PubMed

    Doughty, Christopher E; Wolf, Adam

    2016-01-01

    Sagan et al. (1993) used the Galileo space probe data and first principles to find evidence of life on Earth. Here we ask whether Sagan et al. (1993) could also have detected whether life on Earth had three-dimensional structure, based on the Galileo space probe data. We reanalyse the data from this probe to see if structured vegetation could have been detected in regions with abundant photosynthetic pigments through the anisotropy of reflected shortwave radiation. We compare changing brightness of the Amazon forest (a region where Sagan et al. (1993) noted a red edge in the reflectance spectrum, indicative of photosynthesis) as the planet rotates to a common model of reflectance anisotropy and found measured increase of surface reflectance of 0.019 ± 0.003 versus a 0.007 predicted from only anisotropic effects. We hypothesize the difference was due to minor cloud contamination. However, the Galileo dataset had only a small change in phase angle (sun-satellite position) which reduced the observed anisotropy signal and we demonstrate that theoretically if the probe had a variable phase angle between 0-20°, there would have been a much larger predicted change in surface reflectance of 0.1 and under such a scenario three-dimensional vegetation structure on Earth could possibly have been detected. These results suggest that anisotropic effects may be useful to help determine whether exoplanets have three-dimensional vegetation structure in the future, but that further comparisons between empirical and theoretical results are first necessary.

  9. Detecting 3D Vegetation Structure with the Galileo Space Probe: Can a Distant Probe Detect Vegetation Structure on Earth?

    PubMed Central

    2016-01-01

    Sagan et al. (1993) used the Galileo space probe data and first principles to find evidence of life on Earth. Here we ask whether Sagan et al. (1993) could also have detected whether life on Earth had three-dimensional structure, based on the Galileo space probe data. We reanalyse the data from this probe to see if structured vegetation could have been detected in regions with abundant photosynthetic pigments through the anisotropy of reflected shortwave radiation. We compare changing brightness of the Amazon forest (a region where Sagan et al. (1993) noted a red edge in the reflectance spectrum, indicative of photosynthesis) as the planet rotates to a common model of reflectance anisotropy and found measured increase of surface reflectance of 0.019 ± 0.003 versus a 0.007 predicted from only anisotropic effects. We hypothesize the difference was due to minor cloud contamination. However, the Galileo dataset had only a small change in phase angle (sun-satellite position) which reduced the observed anisotropy signal and we demonstrate that theoretically if the probe had a variable phase angle between 0–20°, there would have been a much larger predicted change in surface reflectance of 0.1 and under such a scenario three-dimensional vegetation structure on Earth could possibly have been detected. These results suggest that anisotropic effects may be useful to help determine whether exoplanets have three-dimensional vegetation structure in the future, but that further comparisons between empirical and theoretical results are first necessary. PMID:27973530

  10. Do Finite-Size Lyapunov Exponents detect coherent structures?

    SciTech Connect

    Karrasch, Daniel; Haller, George

    2013-12-15

    Ridges of the Finite-Size Lyapunov Exponent (FSLE) field have been used as indicators of hyperbolic Lagrangian Coherent Structures (LCSs). A rigorous mathematical link between the FSLE and LCSs, however, has been missing. Here, we prove that an FSLE ridge satisfying certain conditions does signal a nearby ridge of some Finite-Time Lyapunov Exponent (FTLE) field, which in turn indicates a hyperbolic LCS under further conditions. Other FSLE ridges violating our conditions, however, are seen to be false positives for LCSs. We also find further limitations of the FSLE in Lagrangian coherence detection, including ill-posedness, artificial jump-discontinuities, and sensitivity with respect to the computational time step.

  11. Cochlear implants.

    PubMed

    Connell, Sarah S; Balkany, Thomas J

    2006-08-01

    Cochlear implants are cost-effective auditory prostheses that safely provide a high-quality sensation of hearing to adults who are severely or profoundly deaf. In the past 5 years, progress has been made in hardware and software design, candidate selection, surgical techniques, device programming, education and rehabilitation,and, most importantly, outcomes. Cochlear implantation in the elderly is well tolerated and provides marked improvement in auditory performance and psychosocial functioning.

  12. A Coupled Approach for Structural Damage Detection with Incomplete Measurements

    NASA Technical Reports Server (NTRS)

    James, George; Cao, Timothy; Kaouk, Mo; Zimmerman, David

    2013-01-01

    This historical work couples model order reduction, damage detection, dynamic residual/mode shape expansion, and damage extent estimation to overcome the incomplete measurements problem by using an appropriate undamaged structural model. A contribution of this work is the development of a process to estimate the full dynamic residuals using the columns of a spring connectivity matrix obtained by disassembling the structural stiffness matrix. Another contribution is the extension of an eigenvector filtering procedure to produce full-order mode shapes that more closely match the measured active partition of the mode shapes using a set of modified Ritz vectors. The full dynamic residuals and full mode shapes are used as inputs to the minimum rank perturbation theory to provide an estimate of damage location and extent. The issues associated with this process are also discussed as drivers of near-term development activities to understand and improve this approach.

  13. Community structures and role detection in music networks

    NASA Astrophysics Data System (ADS)

    Teitelbaum, T.; Balenzuela, P.; Cano, P.; Buldú, Javier M.

    2008-12-01

    We analyze the existence of community structures in two different social networks using data obtained from similarity and collaborative features between musical artists. Our analysis reveals some characteristic organizational patterns and provides information about the driving forces behind the growth of the networks. In the similarity network, we find a strong correlation between clusters of artists and musical genres. On the other hand, the collaboration network shows two different kinds of communities: rather small structures related to music bands and geographic zones, and much bigger communities built upon collaborative clusters with a high number of participants related through the period the artists were active. Finally, we detect the leading artists inside their corresponding communities and analyze their roles in the network by looking at a few topological properties of the nodes.

  14. Procedure to detect anatomical structures in optical fundus images

    NASA Astrophysics Data System (ADS)

    Gagnon, Langis; Lalonde, Marc; Beaulieu, Mario; Boucher, Marie-Carole

    2001-07-01

    We present an overview of the design and test of an image processing procedure for detecting all important anatomical structures in color fundus images. These structures are the optic disk, the macula and the retinal network. The algorithm proceeds through five main steps: (1) automatic mask generation using pixels value statistics and color threshold, (2) visual image quality assessment using histogram matching and Canny edge distribution modeling, (3) optic disk localization using pyramidal decomposition, Hausdorff-based template matching and confidence assignment, (4) macula localization using pyramidal decomposition and (5) bessel network tracking using recursive dual edge tracking and connectivity recovering. The procedure has been tested on a database of about 40 color fundus images acquired from a digital non-mydriatic fundus camera. The database is composed of images of various types (macula- and optic disk-centered) and of various visual quality (with or without abnormal bright or dark regions, blurred, etc).

  15. Interest area selection for navigation based on structured edge detection

    NASA Astrophysics Data System (ADS)

    Sun, Xiao; Shang, Ke; Li, ShaoJun; Dou, Hao; Tian, JinWen; Ming, Delie

    2015-12-01

    The scene matching based navigation is an important precision navigation technology for unmanned aerial vehicles (UAV). Selection of interest area where reference image is made has an important influence on the precision of matching result besides the performance of match algorithm. In this paper, a method to select interest area based on structured edge detection is proposed. We use a data driven approach that classifies each pixel with a typical structured edge label. We propose a method that combines these labels into a feature measuring suitable to match of a region. Then a SVM classifier is trained to classify the features and get the final result of the selection of interest area. The experimental result shows that the proposed method is valid and effective.

  16. Multienergy gold ion implantation for enhancing the field electron emission characteristics of heterogranular structured diamond films grown on Au-coated Si substrates

    NASA Astrophysics Data System (ADS)

    Sankaran, K. J.; Manoharan, D.; Sundaravel, B.; Lin, I. N.

    2016-09-01

    Multienergy Au-ion implantation enhanced the electrical conductivity of heterogranular structured diamond films grown on Au-coated Si substrates to a high level of 5076.0 (Ω cm)-1 and improved the field electron emission (FEE) characteristics of the films to low turn-on field of 1.6 V/μm, high current density of 5.4 mA/cm2 (@ 2.65 V/μm), and high lifetime stability of 1825 min. The catalytic induction of nanographitic phases in the films due to Au-ion implantation and the formation of diamond-to-Si eutectic interface layer due to Au-coating on Si together encouraged the efficient conducting channels for electron transport, thereby improved the FEE characteristics of the films.

  17. Contraceptive implants.

    PubMed

    McDonald-Mosley, Raegan; Burke, Anne E

    2010-03-01

    Implantable contraception has been extensively used worldwide. Implants are one of the most effective and reversible methods of contraception available. These devices may be particularly appropriate for certain populations of women, including women who cannot use estrogen-containing contraception. Implants are safe for use by women with many chronic medical problems. The newest implant, Implanon (Organon International, Oss, The Netherlands), is the only device currently available in the United States and was approved in 2006. It is registered for 3 years of pregnancy prevention. Contraceptive implants have failure rates similar to tubal ligation, and yet they are readily reversible with a return to fertility within days of removal. Moreover, these contraceptive devices can be safely placed in the immediate postpartum period, ensuring good contraceptive coverage for women who may be at risk for an unintended pregnancy. Irregular bleeding is a common side effect for all progestin-only contraceptive implants. Preinsertion counseling should address possible side effects, and treatment may be offered to women who experience prolonged or frequent bleeding.

  18. Optical integration of laterally modified multiple quantum well structures by implantation enhanced intermixing to realize gain coupled DFB lasers

    NASA Astrophysics Data System (ADS)

    Hofsäß, V.; Kuhn, J.; Kaden, C.; Härle, V.; Bolay, H.; Scholz, F.; Schweizer, H.; Hillmer, H.; Lösch, R.; Schlapp, W.

    1995-12-01

    We report on the realization of gain coupled distributed feedback (GC-DFB) lasers using masked implantation enhanced intermixing (MIEI) in a full planar technology. The process requires only planar epitaxy steps to minimize ion straggling. We present a detailed investigation on the integration processing steps as implantation, subsequent annealing and regrowth with InP (MOCVD). We also discuss critical technology steps. Surface morphology depends very sensitive on implantation and annealing. Nonradiative recombination caused by defects leads to high losses in optical devices. We achieve good results for an AsH 3 stabilized annealing step in a MOCVD equipment, compared to rapid thermal annealing (RTA), which proceeds as the second epitaxial step. Photoluminescence (PL) studies show the excellent interface quality. High homogeneity and small linewidth after the integration process indicate sufficient quality to realize electrical gain coupled DFB-laser devices by IEI.

  19. Effect of calcium-ion implantation on the corrosion resistance and biocompatibility of titanium.

    PubMed

    Krupa, D; Baszkiewicz, J; Kozubowski, J A; Barcz, A; Sobczak, J W; Bilińiski, A; Lewandowska-Szumieł, M D; Rajchel, B

    2001-08-01

    This work presents data on the structure and corrosion resistance of titanium after calcium-ion implantation with a dose of 10(17) Ca+/cm2. The ion energy was 25 keV. Transmission electron microscopy was used to investigate the microstructure of the implanted layer. The chemical composition of the surface layer was examined by XPS and SIMS. The corrosion resistance was examined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C. Biocompatibility tests in vitro were performed in a culture of human derived bone cells (HDBC) in direct contact with the materials tested. Both, the viability of the cells determined by an XTT assay and activity of the cells evaluated by alkaline phosphatase activity measurements in contact with implanted and non-implanted titanium samples were detected. The morphology of the cells spread on the surface of the materials examined was also observed. The results confirmed the biocompatibility of both calcium-ion-implanted and non-implanted titanium under the conditions of the experiment. As shown by TEM results, the surface layer formed during calcium-ion implantation was amorphous. The results of electrochemical examinations indicate that calcium-ion implantation increases the corrosion resistance, but only under stationary conditions; during anodic polarization the calcium-ion-implanted samples undergo pitting corrosion. The breakdown potential is high (2.7-3 V).

  20. Using chaotic forcing to detect damage in a structure

    USGS Publications Warehouse

    Moniz, L.; Nichols, J.; Trickey, S.; Seaver, M.; Pecora, D.; Pecora, L.

    2005-01-01

    In this work we develop a numerical test for Holder continuity and apply it and another test for continuity to the difficult problem of detecting damage in structures. We subject a thin metal plate with incremental damage to the plate changes, its filtering properties, and therefore the phase space trajectories of the response chaotic excitation of various bandwidths. Damage to the plate changes its filtering properties and therefore the phase space of the response. Because the data are multivariate (the plate is instrumented with multiple sensors) we use a singular value decomposition of the set of the output time series to reduce the embedding dimension of the response time series. We use two geometric tests to compare an attractor reconstructed from data from an undamaged structure to that reconstructed from data from a damaged structure. These two tests translate to testing for both generalized and differentiable synchronization between responses. We show loss of synchronization of responses with damage to the structure. ?? 2005 American Institute of Physics.

  1. Surface plasmon resonance for detecting clenbuterol: Influence of monolayer structure

    NASA Astrophysics Data System (ADS)

    Suherman; Morita, Kinichi; Kawaguchi, Toshikazu

    2015-03-01

    Surface plasmon resonance sensor equipped with a fabricated immunosensor chip is used for detecting clenbuterol in this study. Since clenbuterol is a small analyte, indirect competitive inhibition immunoassay is employed. For fabricating the immunosurface, the Au-chip was functionalized by succinimidyl-terminated alkanethiol, and the terminal N-hydroxysuccinimide group of the self-assembled monolayer was either replaced with clenbuterol or blocked with ethanolamine. Scanning tunneling microscope experiments and electrochemical measurements depicted the domain structures of the succinimide group of succinimidyl-terminated propanethiol monolayer. The surface concentration and the orientation of succinimide group was significantly dependent on the concentration of dithiobis(succinimidyl) propionate (DSP) used in fabricating the monolayer. Furthermore, the structure of monolayer significantly influenced both the surface concentration and the orientation of clenbuterol on the sensor surface. Consequently, high coverage and standing-up configuration of clenbuterol showed high affinity for clenbuterol antibody. However, high affinity constant exhibited by the sensor surface was coupled with a low sensitivity. By contrast, lowest concentration of DSP solution (0.1 mM) used in fabricating the immunosurface showed a detection sensitivity of 3 ppt - the highest reported sensitivity for clenbuterol. For regeneration the immunosurface, 0.1 M NaOH was used and the same sensor surface could be reused for performing >100 rapid immunoreaction.

  2. Vibration-based detection of fatigue cracks in structures

    NASA Astrophysics Data System (ADS)

    Razi, P.; Taheri, F.

    2011-04-01

    This paper presents the application of a novel vibration based technique for detecting fatigue cracks in structures. The method utilizes the empirical mode decomposition method (EMD) to establish an effective energy-based damage index. To investigate the feasibility of the method, fatigue cracks of different sizes were introduced in an aluminum beam subjected to a cyclic load under three point bending configuration. The vibration signals corresponding to the healthy and the damaged states of the beam were acquired via piezoceramic sensors. The signals were then processed by the proposed methodology to obtain the damage indices. In addition, for the sake of comparison, the natural frequencies of the healthy and damaged states of the beam were obtained through the Fast Fourier Transform (FFT). The results of this study concluded in two major observations. Firstly, the method was highly successful in not only predicting the presence of the fatigue crack, but also in quantifying its progression. Secondly, the proposed energy-based damage index was proved to be superior over the frequency-based method in terms of sensitivity to the damage detection and quantification. Moreover, this technique could be regarded as an efficient non-destructive tool, since it is simple, cost effective, and does not rely on analytical modelling of the structure.

  3. Structural Damage Detection Using Slopes of Longitudinal Vibration Shapes

    SciTech Connect

    Xu, W.; Zhu, W. D.; Smith, S. A.; Cao, M. S.

    2016-03-18

    While structural damage detection based on flexural vibration shapes, such as mode shapes and steady-state response shapes under harmonic excitation, has been well developed, little attention is paid to that based on longitudinal vibration shapes that also contain damage information. This study originally formulates a slope vibration shape for damage detection in bars using longitudinal vibration shapes. To enhance noise robustness of the method, a slope vibration shape is transformed to a multiscale slope vibration shape in a multiscale domain using wavelet transform, which has explicit physical implication, high damage sensitivity, and noise robustness. These advantages are demonstrated in numerical cases of damaged bars, and results show that multiscale slope vibration shapes can be used for identifying and locating damage in a noisy environment. A three-dimensional (3D) scanning laser vibrometer is used to measure the longitudinal steady-state response shape of an aluminum bar with damage due to reduced cross-sectional dimensions under harmonic excitation, and results show that the method can successfully identify and locate the damage. Slopes of longitudinal vibration shapes are shown to be suitable for damage detection in bars and have potential for applications in noisy environments.

  4. Experimental detection of transverse particle movement with structured light

    PubMed Central

    Rosales-Guzmán, Carmelo; Hermosa, Nathaniel; Belmonte, Aniceto; Torres, Juan P.

    2013-01-01

    One procedure widely used to detect the velocity of a moving object is by using the Doppler effect. This is the perceived change in frequency of a wave caused by the relative motion between the emitter and the detector, or between the detector and a reflecting target. The relative movement, in turn, generates a time-varying phase which translates into the detected frequency shift. The classical longitudinal Doppler effect is sensitive only to the velocity of the target along the line-of-sight between the emitter and the detector (longitudinal velocity), since any transverse velocity generates no frequency shift. This makes the transverse velocity undetectable in the classical scheme. Although there exists a relativistic transverse Doppler effect, it gives values that are too small for the typical velocities involved in most laser remote sensing applications. Here we experimentally demonstrate a novel way to detect transverse velocities. The key concept is the use of structured light beams. These beams are unique in the sense that their phases can be engineered such that each point in its transverse plane has an associated phase value. When a particle moves across the beam, the reflected light will carry information about the particle's movement through the variation of the phase of the light that reaches the detector, producing a frequency shift associated with the movement of the particle in the transverse plane. PMID:24085150

  5. Structural Damage Detection Using Slopes of Longitudinal Vibration Shapes

    DOE PAGES

    Xu, W.; Zhu, W. D.; Smith, S. A.; ...

    2016-03-18

    While structural damage detection based on flexural vibration shapes, such as mode shapes and steady-state response shapes under harmonic excitation, has been well developed, little attention is paid to that based on longitudinal vibration shapes that also contain damage information. This study originally formulates a slope vibration shape for damage detection in bars using longitudinal vibration shapes. To enhance noise robustness of the method, a slope vibration shape is transformed to a multiscale slope vibration shape in a multiscale domain using wavelet transform, which has explicit physical implication, high damage sensitivity, and noise robustness. These advantages are demonstrated in numericalmore » cases of damaged bars, and results show that multiscale slope vibration shapes can be used for identifying and locating damage in a noisy environment. A three-dimensional (3D) scanning laser vibrometer is used to measure the longitudinal steady-state response shape of an aluminum bar with damage due to reduced cross-sectional dimensions under harmonic excitation, and results show that the method can successfully identify and locate the damage. Slopes of longitudinal vibration shapes are shown to be suitable for damage detection in bars and have potential for applications in noisy environments.« less

  6. Using Aerospace Technology To Design Orthopedic Implants

    NASA Technical Reports Server (NTRS)

    Saravanos, D. A.; Mraz, P. J.; Davy, D. T.

    1996-01-01

    Technology originally developed to optimize designs of composite-material aerospace structural components used to develop method for optimizing designs of orthopedic implants. Development effort focused on designing knee implants, long-term goal to develop method for optimizing designs of orthopedic implants in general.

  7. Detection and Monitoring of Microparticles Under Skin by Optical Coherence Tomography as an Approach to Continuous Glucose Sensing Using Implanted Retroreflectors

    PubMed Central

    Wang, Shang; Sherlock, Tim; Salazar, Betsy; Sudheendran, Narendran; Manapuram, Ravi Kiran; Kourentzi, Katerina; Ruchhoeft, Paul; Willson, Richard C.; Larin, Kirill V.

    2015-01-01

    We demonstrate the feasibility of using optical coherence tomography (OCT) to image and detect 2.8 μm diameter microparticles (stationary and moving) on a highly-reflective gold surface both in clear media and under skin in vitro. The OCT intensity signal can clearly report the microparticle count, and the OCT response to the number of microparticles shows a good linearity. The detect ability of the intensity change (2.9% ± 0.5%) caused by an individual microparticle shows the high sensitivity of monitoring multiple particles using OCT. An optical sensing method based on this feasibility study is described for continuously measuring blood sugar levels in the subcutaneous tissue, and a molecular recognition unit is designed using competitive binding to modulate the number of bound microparticles as a function of glucose concentration. With further development, an ultra-small, implantable sensor might provide high specificity and sensitivity for long-term continuous monitoring of blood glucose concentration. PMID:26413034

  8. Corrosion and fatigue of surgical implants

    NASA Technical Reports Server (NTRS)

    Lisagor, W. B.

    1975-01-01

    Implants for the treatment of femoral fractures, mechanisms leading to the failure or degradation of such structures, and current perspectives on surgical implants are discussed. Under the first heading, general usage, materials and procedures, environmental conditions, and laboratory analyses of implants after service are considered. Corrosion, crevice corrosion, stress corrosion cracking, intergranular corrosion, pitting corrosion, fatigue, and corrosion fatigue are the principal degradation mechanisms described. The need for improvement in the reliability of implants is emphasized.

  9. Local pulmonary structure classification for computer-aided nodule detection

    NASA Astrophysics Data System (ADS)

    Bahlmann, Claus; Li, Xianlin; Okada, Kazunori

    2006-03-01

    We propose a new method of classifying the local structure types, such as nodules, vessels, and junctions, in thoracic CT scans. This classification is important in the context of computer aided detection (CAD) of lung nodules. The proposed method can be used as a post-process component of any lung CAD system. In such a scenario, the classification results provide an effective means of removing false positives caused by vessels and junctions thus improving overall performance. As main advantage, the proposed solution transforms the complex problem of classifying various 3D topological structures into much simpler 2D data clustering problem, to which more generic and flexible solutions are available in literature, and which is better suited for visualization. Given a nodule candidate, first, our solution robustly fits an anisotropic Gaussian to the data. The resulting Gaussian center and spread parameters are used to affine-normalize the data domain so as to warp the fitted anisotropic ellipsoid into a fixed-size isotropic sphere. We propose an automatic method to extract a 3D spherical manifold, containing the appropriate bounding surface of the target structure. Scale selection is performed by a data driven entropy minimization approach. The manifold is analyzed for high intensity clusters, corresponding to protruding structures. Techniques involve EMclustering with automatic mode number estimation, directional statistics, and hierarchical clustering with a modified Bhattacharyya distance. The estimated number of high intensity clusters explicitly determines the type of pulmonary structures: nodule (0), attached nodule (1), vessel (2), junction (>3). We show accurate classification results for selected examples in thoracic CT scans. This local procedure is more flexible and efficient than current state of the art and will help to improve the accuracy of general lung CAD systems.

  10. The evolution of structure and defects in the implanted Si surface: Inspecting by reflective second harmonic generation

    NASA Astrophysics Data System (ADS)

    Brahma, Sanjaya; Liu, Chung-Wei; Lo, Kuang-Yao

    2016-12-01

    Detailed information about the recrystallization and formation of defects in the ultra-shallow junction of implanted Si is a key for semiconductor fabrication below 20 nm regime. The surface quality of highly doped Si via annealing treatment would influence the fabrication and yield. Here, we employ nonlinear optics to study the correlated physical phenomena and underlying evolution of restructure of P+ ion implanted Si. Reflective second harmonic generation (RSHG) results reveal the restructure of the implanted Si layer that involves recrystallization, dopant activation and dopant diffusion in correlation with annealing temperature. In the implanted Si layer, defects cause inactivity in electrical properties and generate isotropic dipole contribution to the RSHG pattern. The trend of isotropic dipole contribution is consistent with the sheet resistance measurement that presents more information about the evolution of the restructure. At lower annealing temperatures, the precipitation and the interstitialcy pairs form due to the effect of transient enhanced diffusion, and then the isotropic contribution of the RSHG pattern and sheet resistance sharply increases because of aggregation of the dopants. The isotropic contribution of RSHG is an index of the transformation of the electrical property as well as estimate recrystallization during rapid thermal annealing.

  11. The structure of crystallographic damage in GaN formed during rare earth ion implantation with and without an ultrathin AlN capping layer

    NASA Astrophysics Data System (ADS)

    Gloux, F.; Ruterana, P.; Wojtowicz, T.; Lorenz, K.; Alves, E.

    2006-10-01

    The crystallographic nature of the damage created in GaN implanted by rare earth ions at 300 keV and room temperature has been investigated by transmission electron microscopy versus the fluence, from 7×10 13 to 2×10 16 at/cm 2, using Er, Eu or Tm ions. The density of point defect clusters was seen to increase with the fluence. From about 3×10 15 at/cm 2, a highly disordered 'nanocrystalline layer' (NL) appears on the GaN surface. Its structure exhibits a mixture of voids and misoriented nanocrystallites. Basal stacking faults (BSFs) of I 1, E and I 2 types have been noticed from the lowest fluence, they are I 1 in the majority. Their density increases and saturates when the NL is observed. Many prismatic stacking faults (PSFs) with Drum atomic configuration have been identified. The I 1 BSFs are shown to propagate easily through GaN by folding from basal to prismatic planes thanks to the PSFs. When implanting through a 10 nm AlN cap, the NL threshold goes up to about 3×10 16 at/cm 2. The AlN cap plays a protective role against the dissociation of the GaN up to the highest fluences. The flat surface after implantation and the absence of SFs in the AlN cap indicate its high resistance to the damage formation.

  12. Preimplantation Exposure to Bisphenol A and Triclosan May Lead to Implantation Failure in Humans

    PubMed Central

    Yuan, Mu; Bai, Ming-Zhu; Huang, Xu-Feng; Zhang, Yue; Liu, Jing; Hu, Min-Hao; Zheng, Wei-Qian; Jin, Fan

    2015-01-01

    Endocrine disrupting chemicals (EDCs) are chemicals that have the capacity to interfere with normal endocrine systems. Two EDCs, bisphenol A (BPA) and triclosan (TCS), are mass-produced and widespread. They both have estrogenic properties and similar chemical structures and pharmacokinetic features and have been detected in human fluids and tissues. Clinical evidence has suggested a positive association between BPA exposure and implantation failure in IVF patients. Studies in mouse models have suggested that preimplantation exposure to BPA and TCS can lead to implantation failure. This paper reviews the relationship between preimplantation exposure to BPA and TCS and implantation failure and discusses the remaining problems and possible solutions. PMID:26357649

  13. Choice of a dental implant system.

    PubMed

    Hunt, Peter R; Gartner, Judith L; Norkin, Frederic J

    2005-04-01

    Many dentists are bewildered by the intricacies and complexities of dental implants. They are constantly besieged by product advertisements and can find it difficult to choose which systems to work with. Some dentists are so intimidated by the subject that they choose to avoid getting involved with implants and instead stick to traditional tooth replacement systems. By breaking implants down into 4 main components, the body, collar, connection, and restorative post, it is easier to understand the structure and function of dental implants. Each portion should be designed to achieve certain objectives. Once these structural components are understood, it is easier to compare and contrast differing implant systems.

  14. Laser-structured bacterial nanocellulose hydrogels support ingrowth and differentiation of chondrocytes and show potential as cartilage implants.

    PubMed

    Ahrem, Hannes; Pretzel, David; Endres, Michaela; Conrad, Daniel; Courseau, Julien; Müller, Hartmut; Jaeger, Raimund; Kaps, Christian; Klemm, Dieter O; Kinne, Raimund W

    2014-03-01

    The small size and heterogeneity of the pores in bacterial nanocellulose (BNC) hydrogels limit the ingrowth of cells and their use as tissue-engineered implant materials. The use of placeholders during BNC biosynthesis or post-processing steps such as (touch-free) laser perforation can overcome this limitation. Since three-dimensionally arranged channels may be required for homogeneous and functional seeding, three-dimensional (3-D) laser perforation of never-dried BNC hydrogels was performed. Never-dried BNC hydrogels were produced in different shapes by: (i) the cultivation of Gluconacetobacter xylinus (DSM 14666; synonym Komagataeibacter xylinus) in nutrient medium; (ii) the removal of bacterial residues/media components (0.1M NaOH; 30 min; 100 °C) and repeated washing (deionized water; pH 5.8); (iii) the unidirectional or 3-D laser perforation and cutting (pulsed CO2 Rofin SC × 10 laser; 220 μm channel diameter); and (iv) the final autoclaving (2M NaOH; 121 °C; 20 min) and washing (pyrogen-free water). In comparison to unmodified BNC, unidirectionally perforated--and particularly 3-D-perforated - BNC allowed ingrowth into and movement of vital bovine/human chondrocytes throughout the BNC nanofiber network. Laser perforation caused limited structural modifications (i.e. fiber or globular aggregates), but no chemical modifications, as indicated by Fourier transform infrared spectroscopy, X-ray photoelectron scattering and viability tests. Pre-cultured human chondrocytes seeding the surface/channels of laser-perforated BNC expressed cartilage-specific matrix products, indicating chondrocyte differentiation. 3-D-perforated BNC showed compressive strength comparable to that of unmodified samples. Unidirectionally or 3-D-perforated BNC shows high biocompatibility and provides short diffusion distances for nutrients and extracellular matrix components. Also, the resulting channels support migration into the BNC, matrix production and phenotypic stabilization of

  15. Detection of Coherent Structures in Extreme-Scale Simulations

    SciTech Connect

    Kamath, C; Iverson, J; Kirk, R; Karypis, G

    2012-03-24

    The analysis of coherent structures is a common problem in many scientific domains ranging from astrophysics to combustion, fusion, and materials science. The data from three-dimensional simulations are analyzed to detect the structures, extract statistics on them, and track them over time to gain insights into the phenomenon being modeled. This analysis is typically done off-line, using data that have been written out by the simulations. However, the move towards extreme scale architectures, with multi-core processors and graphical processing units, will affect how such analysis is done as it is unlikely that the systems will support the I/O bandwidth required for off-line analysis. Moving the analysis in-situ is a solution only if we know a priori what analysis will be done, as well as the algorithms used and their parameter settings. Even then, we need to ensure that this will not substantially increase the memory requirements or the data movement as the former will be limited and the latter will be expensive. In the Exa-DM project, a collaboration between Lawrence Livermore National Laboratory and University of Minnesota, we are exploring ways in which we can address the conflicting demands of coherent structure analysis of simulation data and the architecture of modern parallel systems, while enabling scientific discovery at the exascale. In this paper, we describe our work in two areas: the in situ implementation of an existing algorithm for coherent structure analysis and the use of graph-based techniques to efficiently compress the data.

  16. Dark matter direct detection with non-Maxwellian velocity structure

    SciTech Connect

    Kuhlen, Michael; Weiner, Neal; Diemand, Jürg; Moore, Ben; Potter, Doug; Stadel, Joachim; Madau, Piero; Zemp, Marcel E-mail: neal.weiner@nyu.edu E-mail: pmadau@ucolick.org E-mail: dpotter@physik.uzh.ch E-mail: mzemp@umich.edu

    2010-02-01

    The velocity distribution function of dark matter particles is expected to show significant departures from a Maxwell-Boltzmann distribution. This can have profound effects on the predicted dark matter - nucleon scattering rates in direct detection experiments, especially for dark matter models in which the scattering is sensitive to the high velocity tail of the distribution, such as inelastic dark matter (iDM) or light (few GeV) dark matter (LDM), and for experiments that require high energy recoil events, such as many directionally sensitive experiments. Here we determine the velocity distribution functions from two of the highest resolution numerical simulations of Galactic dark matter structure (Via Lactea II and GHALO), and study the effects for these scenarios. For directional detection, we find that the observed departures from Maxwell-Boltzmann increase the contrast of the signal and change the typical direction of incoming DM particles. For iDM, the expected signals at direct detection experiments are changed dramatically: the annual modulation can be enhanced by more than a factor two, and the relative rates of DAMA compared to CDMS can change by an order of magnitude, while those compared to CRESST can change by a factor of two. The spectrum of the signal can also change dramatically, with many features arising due to substructure. For LDM the spectral effects are smaller, but changes do arise that improve the compatibility with existing experiments. We find that the phase of the modulation can depend upon energy, which would help discriminate against background should it be found.

  17. Application of electromagnetic waves in damage detection of concrete structures

    NASA Astrophysics Data System (ADS)

    Feng, Maria Q.; De Flaviis, Franco; Kim, Yoo J.; Diaz, Rodolfo E.

    2000-04-01

    Jacketing technology using fiber reinforced polymer (FRP) composites is being applied for seismic retrofit of reinforced concrete (RC) columns designed and constructed under older specifications. In this study, the authors develop an electromagnetic (EM) imaging technology for detecting voids and debonding between the jacket and the column, which may significantly weaken the structural performance of the column otherwise attainable by jacketing. This technology is based on the reflection analysis of a continuous EM wave sent toward and reflected from layered FRP-adhesive-concrete medium: Poor bonding conditions including voids and debonding will generate air gaps which produce additional reflections of the EM wave. In this study, dielectric properties of various materials involved in the FRP-jacketed RC column were first measured. Second, the measured properties were used for a computer simulation of the proposed EM imaging technology. The simulation demonstrated the difficulty in detecting imperfect bonding conditions by using plane waves, as the scattering contribution from the voids and debonding is very small compared to that from the jacketed column. Third, in order to alleviate this difficulty, a special dielectric lens was designed and fabricated to focus the EM wave on the bonding interface. Furthermore, the time gating technique is used in order to reduce the noise resulting from various uncertainties associated with the jacketed columns. Finally, three concrete columns were constructed and wrapped with glass-FRP jackets with various voids and debonding condition artificially introduced in the bonding interface. Using the proposed EM imaging technology with the lens especially designed and installed, these voids and debonding condition were successfully detected.

  18. Predictive modeling of neuroanatomic structures for brain atrophy detection

    NASA Astrophysics Data System (ADS)

    Hu, Xintao; Guo, Lei; Nie, Jingxin; Li, Kaiming; Liu, Tianming

    2010-03-01

    In this paper, we present an approach of predictive modeling of neuroanatomic structures for the detection of brain atrophy based on cross-sectional MRI image. The underlying premise of applying predictive modeling for atrophy detection is that brain atrophy is defined as significant deviation of part of the anatomy from what the remaining normal anatomy predicts for that part. The steps of predictive modeling are as follows. The central cortical surface under consideration is reconstructed from brain tissue map and Regions of Interests (ROI) on it are predicted from other reliable anatomies. The vertex pair-wise distance between the predicted vertex and the true one within the abnormal region is expected to be larger than that of the vertex in normal brain region. Change of white matter/gray matter ratio within a spherical region is used to identify the direction of vertex displacement. In this way, the severity of brain atrophy can be defined quantitatively by the displacements of those vertices. The proposed predictive modeling method has been evaluated by using both simulated atrophies and MRI images of Alzheimer's disease.

  19. Detecting and representing predictable structure during auditory scene analysis

    PubMed Central

    Sohoglu, Ediz; Chait, Maria

    2016-01-01

    We use psychophysics and MEG to test how sensitivity to input statistics facilitates auditory-scene-analysis (ASA). Human subjects listened to ‘scenes’ comprised of concurrent tone-pip streams (sources). On occasional trials a new source appeared partway. Listeners were more accurate and quicker to detect source appearance in scenes comprised of temporally-regular (REG), rather than random (RAND), sources. MEG in passive listeners and those actively detecting appearance events revealed increased sustained activity in auditory and parietal cortex in REG relative to RAND scenes, emerging ~400 ms of scene-onset. Over and above this, appearance in REG scenes was associated with increased responses relative to RAND scenes. The effect of temporal structure on appearance-evoked responses was delayed when listeners were focused on the scenes relative to when listening passively, consistent with the notion that attention reduces ‘surprise’. Overall, the results implicate a mechanism that tracks predictability of multiple concurrent sources to facilitate active and passive ASA. DOI: http://dx.doi.org/10.7554/eLife.19113.001 PMID:27602577

  20. Acoustic Emission Detection of Impact Damage on Space Shuttle Structures

    NASA Technical Reports Server (NTRS)

    Prosser, William H.; Gorman, Michael R.; Madaras, Eric I.

    2004-01-01

    The loss of the Space Shuttle Columbia as a result of impact damage from foam debris during ascent has led NASA to investigate the feasibility of on-board impact detection technologies. AE sensing has been utilized to monitor a wide variety of impact conditions on Space Shuttle components ranging from insulating foam and ablator materials, and ice at ascent velocities to simulated hypervelocity micrometeoroid and orbital debris impacts. Impact testing has been performed on both reinforced carbon composite leading edge materials as well as Shuttle tile materials on representative aluminum wing structures. Results of these impact tests will be presented with a focus on the acoustic emission sensor responses to these impact conditions. These tests have demonstrated the potential of employing an on-board Shuttle impact detection system. We will describe the present plans for implementation of an initial, very low frequency acoustic impact sensing system using pre-existing flight qualified hardware. The details of an accompanying flight measurement system to assess the Shuttle s acoustic background noise environment as a function of frequency will be described. The background noise assessment is being performed to optimize the frequency range of sensing for a planned future upgrade to the initial impact sensing system.

  1. Structural Plasticity Controlled by Calcium Based Correlation Detection

    PubMed Central

    Helias, Moritz; Rotter, Stefan; Gewaltig, Marc-Oliver; Diesmann, Markus

    2008-01-01

    Hebbian learning in cortical networks during development and adulthood relies on the presence of a mechanism to detect correlation between the presynaptic and the postsynaptic spiking activity. Recently, the calcium concentration in spines was experimentally shown to be a correlation sensitive signal with the necessary properties: it is confined to the spine volume, it depends on the relative timing of pre- and postsynaptic action potentials, and it is independent of the spine's location along the dendrite. NMDA receptors are a candidate mediator for the correlation dependent calcium signal. Here, we present a quantitative model of correlation detection in synapses based on the calcium influx through NMDA receptors under realistic conditions of irregular pre- and postsynaptic spiking activity with pairwise correlation. Our analytical framework captures the interaction of the learning rule and the correlation dynamics of the neurons. We find that a simple thresholding mechanism can act as a sensitive and reliable correlation detector at physiological firing rates. Furthermore, the mechanism is sensitive to correlation among afferent synapses by cooperation and competition. In our model this mechanism controls synapse formation and elimination. We explain how synapse elimination leads to firing rate homeostasis and show that the connectivity structure is shaped by the correlations between neighboring inputs. PMID:19129936

  2. Influence of residual pressure and ion implantation on the structure, elemental composition, and properties of (TiZrAlYNb)N nitrides

    NASA Astrophysics Data System (ADS)

    Pogrebnjak, A. D.; Yakushchenko, I. V.; Sobol', O. V.; Beresnev, V. M.; Kupchishin, A. I.; Bondar, O. V.; Lisovenko, M. A.; Amekura, H.; Kono, K.; Oyoshi, K.; Takeda, Y.

    2015-08-01

    The nitrides of high-entropy alloys, (TiZrAlYNb)N, fabricated by cathodic vacuum arc evaporation are studied with electron microscopy, atomic force microscopy, laser scanning microscopy; energy-dispersive X-ray analysis, X-ray phase analysis, time-of-flight secondary-ion mass spectrometry; and hardness measurements. It is found that the deposition parameters influence the structure, surface morphology, element distribution, and mechanical properties. The structural—phase state of the coatings before and after the ion implantation of heavy negative gold ions Au- are compared.

  3. Singularity detection for structural health monitoring using holder exponents.

    SciTech Connect

    Robertson, A. N.; Farrar, C. R.; Sohn, H.

    2003-01-01

    The majority of structural health monitoring studies reported in the technical literature focus on identifying damage sensitive features that can be extracted from dynamic response data . However, many of these studies assume the structure can be modeled as a linear system before and after damage and use parameters of these models as the damage sensitive features. The study summarized in this paper proposes a damage sensitive feature that takes advantage of the nonlinearities associated with discontinuities introduced into the dynamic response data as a result of certain types of damage. Specifically, the Holder exponent, a measure of the degree to which a signal is differentiable, is the feature that is used to detect the presence of damage and when that damage occurred . A procedure for capturing the time varying nature of the Holder exponent based on wavelet transforms is demonstrated through applications to non-stationary random signals with underlying discontinuities and then to a harmonically excited mechanical system that contains a loose part . Also, a classification procedure is developed to quantify when changes in the Holder exponent are significant . The results presented herein show the Holder exponent to be an effective feature for identifying damage that introduces discontinuities into the measured dynamic response data .

  4. Caustic Structures and Detectability of Circumbinary Planets in Microlensing

    NASA Astrophysics Data System (ADS)

    Luhn, Jacob K.; Penny, Matthew T.; Gaudi, B. Scott

    2016-08-01

    Recent discoveries of circumbinary planets in Kepler data show that there is a viable channel of planet formation around binary main-sequence stars. Motivated by these discoveries, we have investigated the caustic structures and detectability of circumbinary planets in microlensing events. We have produced a suite of animations of caustics as a function of the projected separation and angle of the binary host to efficiently explore caustic structures over the entire circumbinary parameter space. Aided by these animations, we have derived a semi-empirical analytic expression for the location of planetary caustics, which are displaced in circumbinary lenses relative to those of planets with a single host. We have used this expression to show that the dominant source of caustic motion will be due to the planet’s orbital motion and not that of the binary star. Finally, we estimate the fraction of circumbinary microlensing events that are recognizable as such to be significant (5%-50%) for binary projected separations in the range 0.1-0.5 in units of Einstein radii.

  5. Effect of nitrogen ion implantation on corrosion inhibition of nickel coated 316 stainless steel and correlation with nano-structure

    NASA Astrophysics Data System (ADS)

    Grayeli-Korpi, Ali-Reza; Savaloni, Hadi

    2012-10-01

    The influence of implantation of N+ with 20 keV energy and different fluences in the range of 1 × 1017 and 5 × 1018 ions/cm2 in the nickel coated type 316 stainless steel (SS) on the corrosion inhibition of SS in 3.5 wt% NaCl solution is investigated. The highest available N+ fluence showed highest corrosion inhibition. X-ray diffraction (XRD) analysis showed formation of nickel nitride phases that enhanced by increasing the N+ fluence. Surface morphology was studied by atomic force microscope (AFM) and scanning electron microscope (SEM) before and after corrosion test, respectively. AFM results showed that by increasing N+ fluence surface of the sample becomes smoother that may be the result of heat accumulation during implantation causing higher rate of diffusion in the sample.

  6. Detection of diffuse sea floor venting using structured light imaging

    NASA Astrophysics Data System (ADS)

    Inglis, G.; Smart, C.; Roman, C.; Carey, S.

    2011-12-01

    Efficiently identifying and localizing diffuse sea floor venting at hydrothermal and cold seep sites is often difficult. Actively venting fluids are usually identified by a temperature induced optical shimmering seen during direct visual inspections or in video data collected by vehicles working close to the sea floor. Relying on such direct methods complicates establishing spatial relations between areas within a survey covering a broad area. Our recent work with a structured light laser system has shown that venting can also be detected in the image data in an automated fashion. A structured light laser system consists of a camera and sheet laser projected at the sea floor. The camera and laser are fixed to a rigid calibrated mount such that the optical axis of the camera and the laser plane intersect at some distance away from the camera, typically 2 to 5 meters. The position of the laser line, visible on the sea floor in the image, can be extracted using standard computer vision techniques (Fig. 1) and used to determine the height of the bottom along the laser line. By collecting images in a survey pattern at a high frame rate, typically 20 to 30 Hz, a bathymetric map can be produced using the individual profiles. In the presence of venting, temperature anomalies refract the laser sheet such that it does not project a crisp and clear line on the sea floor. The laser will instead appear blurred and visible over a larger section of the image. By processing the images to segment out clear laser lines from refracted lines it is possible to identify areas of venting. Our initial approach uses calculated image moments relative to the peak intensity level detected in each column of the image matrix. In the presence of venting the calculated moments differ from those of the undistorted laser shining on the sea floor. Test results from the Kolumbo submarine volcano near Santorini, Greece demonstrate this approach and show the utility of the method for survey work. Test

  7. Ion implantation in Al{sub x}Ga{sub 1-x}As : damage structures and amorphization mechanisms.

    SciTech Connect

    Lagow, B. W.; Turkot, B. A.; Robertson, I. M.; Coleman, J. J.; Roh, S. D.; Forbes, D. V.; Rehn, L. E.; Baldo, P. M.; Materials Science Division; Univ. of Illinois

    1998-07-01

    We review previous research on ion implantation in Al{sub x}Ga{sub 1-x}As-GaAs heterostructures, and include observations from our current work in order to assess the various mechanisms that have been proposed to account for damage accumulation and amorphization in this system. In considering all of the experimental observations, the most consistent description is one where amorphization occurs by a combination of point-defect buildup and direct impact amorphization mechanisms.

  8. Cochlear Implants

    MedlinePlus

    ... outside of the body, behind the ear. A second part is surgically placed under the skin. An implant does not restore normal hearing. It can help a person understand speech. Children and adults can benefit from them. National Institute on Deafness and Other Communication Disorders

  9. Cryogenic Silicon Detectors with Implanted Contacts for the Detection of Visible Photons Using the Neganov-Trofimov-Luke Effect

    NASA Astrophysics Data System (ADS)

    Defay, X.; Mondragon, E.; Willers, M.; Langenkämper, A.; Lanfranchi, J.-C.; Münster, A.; Zöller, A.; Wawoczny, S.; Steiger, H.; Hitzler, F.; Bruhn, C.; Schönert, S.; Potzel, W.; Chapellier, M.

    2016-07-01

    There is a common need in astroparticle experiments such as direct dark matter detection, double-beta decay without emission of neutrinos [0 ν β β ] and coherent neutrino nucleus scattering experiments for light detectors with a very low energy threshold. By employing the Neganov-Trofimov-Luke Effect, the thermal signal of particle interactions in a semiconductor absorber operated at cryogenic temperatures can be amplified by drifting the photogenerated electrons and holes in an electric field. This technology is not used in current experiments, in particular because of a reduction of the signal amplitude with time which is due to trapping of the charges within the absorber. We present here the first results of a novel type of Neganov-Trofimov-Luke Effect light detector with an electric field configuration designed to improve the charge collection within the semiconductor.

  10. Implant Maintenance: A Clinical Update

    PubMed Central

    Gulati, Minkle; Govila, Vivek; Anand, Vishal; Anand, Bhargavi

    2014-01-01

    Introduction. The differences in the supporting structure of the implant make them more susceptible to inflammation and bone loss when plaque accumulates as compared to the teeth. Therefore, a comprehensive maintenance protocol should be followed to ensure the longevity of the implant. Material and Method. A research to provide scientific evidence supporting the feasibility of various implant care methods was carried out using various online resources to retrieve relevant studies published since 1985. Results. The electronic search yielded 708 titles, out of which a total of 42 articles were considered appropriate and finally included for the preparation of this review article. Discussion. A typical maintenance visit for patients with dental implants should last 1 hour and should be scheduled every 3 months to evaluate any changes in their oral and general history. It is essential to have a proper instrument selection to prevent damage to the implant surface and trauma to the peri-implant tissues. Conclusion. As the number of patients opting for dental implants is increasing, it becomes increasingly essential to know the differences between natural teeth and implant care and accept the challenges of maintaining these restorations. PMID:27437506

  11. Early detection of ovarian cancer: background, rationale, and structure of the Yale Early Detection Program.

    PubMed Central

    Schwartz, P. E.; Chambers, J. T.; Taylor, K. J.; Pellerito, J.; Hammers, L.; Cole, L. A.; Yang-Feng, T. L.; Smith, P.; Mayne, S. T.; Makuch, R.

    1991-01-01

    Ovarian cancer has received national attention as a highly virulent disease. Its lack of early warning symptoms and the failure to develop highly sensitive screening tests have led some physicians to recommend prophylactic oophorectomies to women with relatives who have had ovarian cancer. Others have recommended routine screening of otherwise normal women for CA 125, a circulating tumor marker, and ultrasound examinations. Each of these techniques is associated with substantial false-positive rates that could lead to unnecessary surgery. A review of epidemiologic data suggests that familial ovarian cancer kindreds are rare, but women with first-degree relatives who have had ovarian cancer have a significant risk themselves for developing ovarian cancer. In addition, women with a great number of ovulatory cycles are at an increased risk for the disease. Circulating tumor markers are frequently elevated in women with advanced ovarian cancer, but their value in early detection of ovarian cancer has yet to be established. Advances in endovaginal ultrasound and color Doppler flow technology have significantly improved our ability to assess pelvic organs. This article presents the background, rationale, and structure of the Yale Early Detection Program for ovarian cancer, whose goals are to identify the best techniques for diagnosing ovarian cancer in an early stage, to determine the frequency with which such tests should be employed, to assess false-positive results, and to identify women who might benefit from prophylactic oophorectomies. PMID:1810100

  12. Chemical, corrosion and topographical analysis of stainless steel implants after different implantation periods.

    PubMed

    Chrzanowski, Wojciech; Armitage, David Andrew; Knowles, Jonathan Campbell; Szade, Jacek; Korlacki, Wojciech; Marciniak, Jan

    2008-07-01

    The aim of this work is to examine the corrosion properties, chemical composition, and material-implant interaction after different periods of implantation of plates used to correct funnel chest. The implants are made of 316L stainless steel. Examinations are carried out on three implants: new (nonimplanted) and two implanted for 29 and 35 months. The corrosion study reveals that in the potential range that could occur in the physiological condition the new bar has the lowest current density and the highest corrosion potential. This indicates that the new plate has the highest corrosion resistance and the corrosion resistance could be reduced during implantation by the instruments used during the operation. XPS analysis reveals changes in the surface chemistry. The longer the implantation time the more carbon and oxygen are observed and only trace of elements such as Cr, Mo are detected indicating that surface is covered by an organic layer. On some parts of the implants whitish tissue is observed: the thickness of which increased with the time of implantation. This tissue was identified as an organic layer; mainly attached to the surface on the areas close to where the implant was bent to attain anatomical fit and thus where the implant has higher surface roughness. The study indicates that the chest plates are impaired by the implantation procedure and contact with biological environment. The organic layer on the surface shows that the implant did not stay passive but some reactions at the tissue-implant interface occurred. These reactions should be seen as positive, as it indicates that the implants were accepted by the tissues. Nevertheless, if the implants react, they may continue to release chromium, nickel, and other harmful ions long term as indicated by lower corrosion resistance of the implants following implantation.

  13. Optical detection of structural changes in human carotid atherosclerotic plaque

    NASA Astrophysics Data System (ADS)

    Korol, R. M.; Canham, P. B.; Finlay, H. M.; Hammond, R. R.; Quantz, M.; Ferguson, G. G.; Liu, L. Y.; Lucas, A. R.

    2005-08-01

    spectroscopy is an effective method for evaluating ECM (collagen and elastin) associated with vascular remodeling despite the considerable variability in the plaque structure. Consistent regional differences were detected in the carotid specimens.

  14. Three-dimensional image contribution for evaluation of operative procedural errors in endodontic therapy and dental implants.

    PubMed

    Silva, Julio Almeida; de Alencar, Ana Helena Gonçalves; da Rocha, Sicknan Soares; Lopes, Lawrence Gonzaga; Estrela, Carlos

    2012-01-01

    Acceptable therapeutic protocol in dentistry depends on the outcomes obtained with follow up. Operative procedural errors (OPE) may occur and they represent risk factors able to compromise a tooth or a dental implant. The aim of this study was to detect the OPE in endodontically treated teeth and dental implants, using cone beam computed tomography (CBCT).Eight hundred and sixteen CBCT exams were performed between January 2009 and October 2010, and only those which presented endodontically treated teeth and/or dental implants were selected. The sample was as follows: 195 CBCT exams (n=200 teeth and 200 dental implants), 72 male, 123 female, with mean age of 51 years.In endodontically treated teeth, OPE included underfilling, overfilling, and root perforation; OPEin dental implants were thread exposures, contact with anatomical structures, and contact with adjacent teeth. Kolmogorov-Smirnov test was used for statistical analysis, with significance level set at α=0.05. Underfilling, overfilling, and root perforations were detected in 33.5%, 8% and 4.5% of the teeth, respectively. Dental implants with thread exposures, contact with important anatomical structures and contact with adjacent teeth were seen in 37.5%, 13% and 6.5% of the cases, respectively. OPE were detected in endodontically treated teeth and dental implants, and underfilling and thread exposures were the most frequent occurrences, respectively.

  15. Effect of implant design and bioactive glass coating on biomechanical properties of fiber-reinforced composite implants.

    PubMed

    Ballo, Ahmed M; Akca, Eralp; Ozen, Tuncer; Moritz, Niko; Lassila, Lippo; Vallittu, Pekka; Närhi, Timo

    2014-08-01

    This study aimed to evaluate the influence of implant design and bioactive glass (BAG) coating on the response of bone to fiber-reinforced composite (FRC) implants. Three different FRC implant types were manufactured for the study: non-threaded implants with a BAG coating; threaded implants with a BAG coating; and threaded implants with a grit-blasted surface. Thirty-six implants (six implants for each group per time point) were installed in the tibiae of six pigs. After an implantation period of 4 and 12 wk, the implants were retrieved and prepared for micro-computed tomography (micro-CT), push-out testing, and scanning electron microscopy analysis. Micro-CT demonstrated that the screw-threads and implant structure remained undamaged during the installation. The threaded FRC/BAG implants had the highest bone volume after 12 wk of implantation. The push-out strengths of the threaded FRC/BAG implants after 4 and 12 wk (463°N and 676°N, respectively) were significantly higher than those of the threaded FRC implants (416°N and 549°N, respectively) and the nonthreaded FRC/BAG implants (219°N and 430°N, respectively). Statistically significant correlation was found between bone volume and push-out strength values. This study showed that osseointegrated FRC implants can withstand the static loading up to failure without fracture, and that the addition of BAG significantly improves the push-out strength of FRC implants.

  16. Temporal variation in the deposition of different types of collagen within a porous biomaterial implant.

    PubMed

    White, Jacinta F; Werkmeister, Jerome A; Bisucci, Teresa; Darby, Ian A; Ramshaw, John A M

    2014-10-01

    The deposition of new collagen in association with a medical implant has been studied using expanded polytetrafluoroethylene vascular replacement samples implanted subcutaneously in sheep, for up to 28 days. New type I collagen mRNA synthesis was followed by in situ hybridization, while the accumulation of new collagen types III, V, VI, XII, and XIV was followed by immunohistochemistry. All the collagen detected in the pores of the implant were newly deposited at various times after implantation and were not due to any pre-existing dermal collagen that may have been present around the implant. Collagen deposition was seen initially surrounding the implant and, with time, was seen to infiltrate within its pores. In situ hybridization showed that the majority of infiltrating cells had switched on mRNA that coded for type I collagen production. Histology showed that cellular infiltration increased with time, accompanied by increasing collagen deposition. The deposition of different collagen types happened at different rates. The type V and VI collagens preceded the major interstitial collagens in the newly deposited tissue, although at longer time points, detection of type V collagen appeared to decrease. After disruption of the interstitial collagens with enzyme, the "masked" type V collagen was clearly still visible by immunohistochemistry. Little type XII collagen could be seen within the porous mesh, although it was seen in the surrounding tissues. By contrast, type XIV was seen throughout the porous structure of the implanted mesh, with less being visible outside the material where type XII was more abundant.

  17. Detection Enhancement of Protein Structural Vibrations: Measurements and Calculations

    NASA Astrophysics Data System (ADS)

    Niessen, Katherine; Xu, Mengyang; Snell, Edward; Cody, Vivian; Pace, James; Schmidt, Marius; Markelz, Andrea

    2015-03-01

    Narrow band intramolecular protein vibrations have been successfully measured using crystal anisotropy THz microscopy (CATM), a near-field technique, on protein crystals. To address the question of how these motions are related to protein function we developed a variation of this technique to rapidly measure a variety of protein crystals. The variation anisotropy measurement consists of introducing a wire-grid polarizer in the THz path and rotating the polarizer between measurements, instead of the sample. While the resulting anisotropic spectra confirm reproducibility and protein specific nature of the response the signal is not directly related to the absorption spectra and in fact shows more structure than CATM. This is due to the polarization sensitivity of the electro-optical detection crystal and the changing THz polarization direction and amplitude at the detector. This combination leads to an enhancement of specific resonances and increased sensitivity to rotation of the THz polarization from the sample itself. Preliminary calculations suggest that the technique is sensitive to the birefringence associated with anisotropic absorbance. The results and significance of these measurements on protein and sucrose crystals and the calculated expected response will be discussed.

  18. Structural health monitoring and probability of detection estimation

    NASA Astrophysics Data System (ADS)

    Forsyth, David S.

    2016-02-01

    Structural health monitoring (SHM) methods are often based on nondestructive testing (NDT) sensors and are often proposed as replacements for NDT to lower cost and/or improve reliability. In order to take advantage of SHM for life cycle management, it is necessary to determine the Probability of Detection (POD) of the SHM system just as for traditional NDT to ensure that the required level of safety is maintained. Many different possibilities exist for SHM systems, but one of the attractive features of SHM versus NDT is the ability to take measurements very simply after the SHM system is installed. Using a simple statistical model of POD, some authors have proposed that very high rates of SHM system data sampling can result in high effective POD even in situations where an individual test has low POD. In this paper, we discuss the theoretical basis for determining the effect of repeated inspections, and examine data from SHM experiments against this framework to show how the effective POD from multiple tests can be estimated.

  19. Optimization of control laws for damage detection in smart structures

    NASA Astrophysics Data System (ADS)

    Ray, Laura R.; Marini, Solomon

    2000-06-01

    A prevalent method of damage detection is based on identifying changes in modal characteristics due to damage induced variations in stiffness or mass along a structure. It is known that modal frequencies can be insensitive to damage, and the open-loop sensitivity itself depends on modal properties and damage location. Here, we develop methods of designing control laws that enhance the sensitivity of modal characteristics to damage. Sensitivity enhancing control exploits the relationship between control gains and closed-loop dynamics in order to increase the observability of damage. The design methods are based on optimization of cost functions that involve the dependence of classic measures of sensitivity on design variables, which include placement of sensors and actuators and state feedback control gains. Due to the size of the design space and the unknown nature of the cost surface, genetic algorithms are used to find control laws that maximize sensitivity to specific damage types subject to control effort and stability constraints. Optimized control laws designed for sensitivity enhancement of stiffness damage in a cantilevered beam are demonstrated by numerical simulation.

  20. Changes in the surface of bone and acid-etched and sandblasted implants following implantation and removal

    PubMed Central

    Eroglu, Cennet Neslihan; Ertugrul, Abdullah Seckin; Eskitascioglu, Murat; Eskitascioglu, Gurcan

    2016-01-01

    Objective: The aim of this study was to determine whether there are any changes in the surface of bone or implant structures following the removal of a screwed dental implant. Materials and Methods: For this, six individual samples of acid-etched and sandblasted implants from three different manufacturers’ implant systems were used. They were screwed in a D1 bovine bone, and they were removed after primary stabilization. The bone and implant surfaces are evaluated with scanning electron microscope. Results: Through examination of the surfaces of the bone prior to implantation and of the used and unused implant surfaces, it was found that inhomogeneity in the implant surface can cause microcracking in the bone. Conclusions: This is attributed to the stress induced during the implantation of self-tapping implants and suggests that a tap drill may be required in some instances to protect the implant surface. PMID:27011744

  1. Effect of the Graded-Gap Layer Composition on the Formation of n + -n - -p Structures in Boron-Implanted Heteroepitaxial Cd x Hg1- x Te Layers

    NASA Astrophysics Data System (ADS)

    Talipov, N. Kh.; Voitsekhovskii, А. V.; Grigor'ev, D. V.

    2014-07-01

    Processes of formation of n + -n--p-structures in boron-implanted heteroepitaxial (HEL) CdxHg1-xTe (CMT) layers of p-type grown by molecular beam epitaxy (HEL CMT MBE) with different compositions of the upper graded-gap layer are studied. It is shown that the surface composition (xs) of HEL CMT MBE significantly affects both the electrical parameters of the implanted layer and the spatial distribution of radiation defects of donor type. For HEL CMT MBE with the small surface composition xs = 0.22-0.33, it is found that the layer electron concentration (Ns) is decreased after saturation with accumulation of radiation defects, as the dose of B+ ions is increased in the range of D = 1ṡ1011-3ṡ1015 сm-2. An increase of the surface composition up to xs = 0.49-0.56 results in a significant decrease in Ns and a disappearance of the saturation of concentration in the whole dose range. The value of Ns monotonically increases with the energy (E) of boron ions and composition xs. It is found that for B+-ion energies E = 20-100 keV, the depth of the surface n + -layer increases with increasing energy and exceeds the total projected path of boron ions. However, in the energy range E = 100-150 keV, the depth of n+-layer stops increasing with the increase of the surface composition. The depth (dn) of a lightly doped n--layer monotonically decreases with increasing energy of boron ions in the entire range of E = 20-150 keV. With increasing dose (D) of B+ ions in the interval D = 1ṡ1014-1ṡ1015сm-2, deep n--layers with dn = 4-5 μm are formed only in the HEL CMT MBE with xs = 0.22-0.33. For the samples with xs = 0.49-0.56, the depth changes in the interval dn = 1.5-2.5 μm. At D ≤ 3ṡ1013сm-2, n + -n--p-structure is not formed for all surface compositions, if implantation is performed at room temperature. However, implantation at T = 130°C leads to the formation of a deep n--layer. Planar photodiodes with the n-p-junction area of A = 35×35 μm2 made on the basis of

  2. Influence of different implant materials on the primary stability of orthodontic mini-implants.

    PubMed

    Pan, Chin-Yun; Chou, Szu-Ting; Tseng, Yu-Chuan; Yang, Yi-Hsin; Wu, Chao-Yi; Lan, Ting-Hsun; Liu, Pao-Hsin; Chang, Hong-Po

    2012-12-01

    This study evaluates the influence of different implant materials on the primary stability of orthodontic mini-implants by measuring the resonance frequency. Twenty-five orthodontic mini-implants with a diameter of 2 mm were used. The first group contained stainless steel mini-implants with two different lengths (10 and 12 mm). The second group included titanium alloy mini-implants with two different lengths (10 and 12 mm) and stainless steel mini-implants 10 mm in length. The mini-implants were inserted into artificial bones with a 2-mm-thick cortical layer and 40 or 20 lb/ft(3) trabecular bone density at insertion depths of 2, 4, and 6 mm. The resonance frequency of the mini-implants in the artificial bone was detected with the Implomates(®) device. Data were analyzed by two-way analysis of variance followed by the Tukey honestly significant difference test (α = 0.05). Greater insertion depth resulted in higher resonance frequency, whereas longer mini-implants showed lower resonance frequency values. However, resonance frequency was not influenced by the implant materials titanium alloy or stainless steel. Therefore, the primary stability of a mini-implant is influenced by insertion depth and not by implant material. Insertion depth is extremely important for primary implant stability and is critical for treatment success.

  3. Practicing implant dentistry profitably.

    PubMed

    Stump, G; Adams, M; Alwan, M

    1997-03-01

    The success of dental implants has opened up countless treatment possibilities for restorative dentists to offer to their patients. Just as our clinical paradigms have had to change because of this new technology, so too must our paradigms concerning the way we communicate with our patients change if we are to get them to say "yes" to treatment that we know that they need. Success in clinical treatment using implants requires a systematic approach. A systematic approach to communicating with your patients will allow you to have the same high degree of success with treatment acceptance that is possible with dental implants. The key to the systems we have discussed is Relationship Centered Care. A relationship is fostered and enhanced through a Comprehensive Examination Process, a structured Consultation Process utilizing the influencing process and Financial Arrangements that allow the patient to receive what they want while the office maintains the profitability that it needs. A system for calculating rational fees can be utilized that allows the practice to have control over an area that traditionally was controlled by anecdotal factors. The Pride Institute has developed this material and is presenting it to the profession so that restorative dentists can truly practice implant dentistry profitably.

  4. Hip Implant Modified To Increase Probability Of Retention

    NASA Technical Reports Server (NTRS)

    Canabal, Francisco, III

    1995-01-01

    Modification in design of hip implant proposed to increase likelihood of retention of implant in femur after hip-repair surgery. Decreases likelihood of patient distress and expense associated with repetition of surgery after failed implant procedure. Intended to provide more favorable flow of cement used to bind implant in proximal extreme end of femur, reducing structural flaws causing early failure of implant/femur joint.

  5. Ion-implantation-induced stress in glasses: Variation of damage mode efficiency with changes in glass structure

    NASA Astrophysics Data System (ADS)

    Arnold, G. W.

    1988-05-01

    Ion implantation induces lateral stress in glass due to the volume dilatation in the implanted near-surface region. Cantilever-beam experiments allow these quantities to be measured as a function of fluence. For fused silica the stress data for various incident ions are found to scale with atomic collision energy deposition. In sharp contrast, Pyrex (alkali-borosilicate) glass, (1 - x)(Na, K) 2O· xB 2O 3·3SiO 2 glass, and a sodalime (microscope slide) glass, yield stress values which scale with energy deposition into electronic processes. More significantly, this mode of damage production is dominant for the nuclear waste glasses PNL 76-68 and SRP. The void space in fused silica allows room for displaced Si and/or O. For the complex alkali-containing silicates, the interstitial volume is restricted. In the latter case, the probability increases that permanent defects can be formed by ionization-induced bond-breaking and network relaxation. These data imply that alpha-particle ionization energy deposition may be an important factor in nuclear waste glass radiation damage production, but the magnitude of this contribution has not yet been evaluated.

  6. Anomalous wear-out phenomena of europium-implanted light emitters based on a metal-oxide-semiconductor structure

    NASA Astrophysics Data System (ADS)

    Rebohle, L.; Lehmann, J.; Prucnal, S.; Nazarov, A.; Tyagulskii, I.; Tyagulskii, S.; Kanjilal, A.; Voelskow, M.; Grambole, D.; Skorupa, W.; Helm, M.

    2009-12-01

    The anomalous wear-out phenomena of Eu-implanted metal-oxide-semiconductor devices were investigated. It will be shown that in contrast to other rare earth elements the electroluminescence (EL) intensity of Eu-implanted SiO2 layers can rise under constant current injection before the known EL quenching will start. Under certain circumstances, this rise may amount up to two orders of magnitude. The EL behavior will be correlated with the microstructural and electrical properties of the devices. Transmission electron microscopy and Rutherford backscattering spectroscopy were applied to trace the development of Eu/Eu oxide clusters and the diffusion of Eu to the interfaces of the gate oxide layer. The hydrogen profile within the SiO2-SiON interface region was determined by nuclear reaction analysis. Current-voltage characteristics, EL decay times, and the progression of the voltage and the EL spectrum with increasing charge injection were measured to study charge and trapping phenomena in the oxide layer to reveal details of the EL excitation mechanism. A first qualitative model for the anomalous life time behavior is proposed.

  7. Clinical and economic consequences of non-cardiac incidental findings detected on cardiovascular computed tomography performed prior to transcatheter aortic valve implantation (TAVI).

    PubMed

    Lindsay, Alistair C; Sriharan, Mona; Lazoura, Olga; Sau, Arunashis; Roughton, Michael; Jabbour, Richard J; Di Mario, Carlo; Davies, Simon W; Moat, Neil E; Padley, Simon P G; Rubens, Michael B; Nicol, Edward D

    2015-10-01

    Transcatheter aortic valve implantation (TAVI) is an effective treatment option for patients with severe degenerative aortic valve stenosis who are high risk for conventional surgery. Computed tomography (CT) performed prior to TAVI can detect pathologies that could influence outcomes following the procedure, however the incidence, cost, and clinical impact of incidental findings has not previously been investigated. 279 patients underwent CT; 188 subsequently had TAVI and 91 were declined. Incidental findings were classified as clinically significant (requiring treatment), indeterminate (requiring further assessment), or clinically insignificant. The primary outcome measure was all-cause mortality up to 3 years. Costs incurred by additional investigations resultant to incidental findings were estimated using the UK Department of Health Payment Tariff. Incidental findings were common in both the TAVI and medical therapy cohorts (54.8 vs. 70.3%; P = 0.014). Subsequently, 45 extra investigations were recommended for the TAVI cohort, at an overall average cost of £32.69 per TAVI patient. In a univariate model, survival was significantly associated with the presence of a clinically significant or indeterminate finding (HR 1.61; P = 0.021). However, on multivariate analysis outcomes after TAVI were not influenced by any category of incidental finding. Incidental findings are common on CT scans performed prior to TAVI. However, the total cost involved in investigating these findings is low, and incidental findings do not independently identify patients with poorer outcomes after TAVI. The discovery of an incidental finding on CT should not necessarily influence or delay the decision to perform TAVI.

  8. Material structure of two-/three-dimensional Si–C layers fabricated by hot-C+-ion implantation into Si-on-insulator substrate

    NASA Astrophysics Data System (ADS)

    Mizuno, Tomohisa; Omata, Yuhsuke; Nagamine, Yoshiki; Aoki, Takashi; Sameshima, Toshiyuki

    2017-04-01

    We experimentally studied the material structures of two-/three-dimensional (2D/3D) silicon carbon layers Si1‑ Y C Y with Y ≤ 0.25 and 5 ≤ N L ≤ 162 [N L is the atomic layer number of Si1‑ Y C Y )] on buried oxide (BOX), which were fabricated by hot-C+-ion implantation into a (100) silicon-on-insulator (SOI) substrate before an oxidation process. A 2D Si layer was also fabricated as a reference. The C 1s spectrum obtained by X-ray photoemission spectroscopy shows that the implanted C atoms segregate at the oxide interface. Using a scanning transmission electron microscope and a high-resolution scanning transmission electron microscope to observe cross sections of Si0.75C0.25 layers, 2-nm-thick 3C-SiC layers were found be partially formed in the C segregation layer near the BOX interface. At Y > 0.1 and 5 ≤ N L ≤ 162, we observed very strong photoluminescence (PL) emission in the UV/visible regions from a 3C-SiC area and a Si1‑ Y C Y area in the C segregation layer, whereas a 2D Si emitted weak PL photons only at N L < 10. Thus, the silicon carbon technique is very promising for Si photonics and bandgap engineering in CMOS.

  9. Electrical and structural properties of In-implanted Si1–xGex alloys

    SciTech Connect

    Feng, Ruixing; Kremer, F.; Sprouster, D. J.; Mirzaei, S.; Decoster, S.; Glover, C. J.; Medling, S. A.; Hansen, J. L.; Nylandsted-Larsen, A.; Russo, S. P.; Ridgway, M. C.

    2016-01-14

    Here, we report on the effects of dopant concentration and substrate stoichiometry on the electrical and structural properties of In-implanted Si1–xGex alloys. Correlating the fraction of electrically active In atoms from Hall Effect measurements with the In atomic environment determined by X-ray absorption spectroscopy, we observed the transition from electrically active, substitutional In at low In concentration to electrically inactive metallic In at high In concentration. The In solid-solubility limit has been quantified and was dependent on the Si1–xGex alloy stoichiometry; the solid-solubility limit increased as the Ge fraction increased. This result was consistent with density functional theory calculations of two In atoms in a Si1–xGex supercell that demonstrated that In–In pairing was energetically favorable for x ≲ 0.7 and energetically unfavorable for x ≳ 0.7. Transmission electron microscopy imaging further complemented the results described earlier with the In concentration and Si1–xGex alloy stoichiometry dependencies readily visible. We have demonstrated that low resistivity values can be achieved with In implantation in Si1–xGex alloys, and this combination of dopant and substrate represents an effective doping protocol.

  10. Effect of annealing atmosphere on the structure and luminescence of Sn-implanted SiO{sub 2} layers

    SciTech Connect

    Lopes, J.M.J.; Zawislak, F.C.; Fichtner, P.F.P.; Lovey, F.C.; Condo, A.M.

    2005-01-10

    Sn nanoclusters are synthesized in 180 nm SiO{sub 2} layers after ion implantation and heat treatment. Annealings in N{sub 2} ambient at high temperatures (T{>=}700 deg. C) lead to the formation of Sn nanoclusters of different sizes in metallic and in oxidized phases. High-resolution transmission electron microscopy (TEM) analyses revealed that the formed larger nanoparticles are composed by a Sn metallic core and a SnO{sub x} shell. The corresponding blue-violet photoluminescence (PL) presents low intensity. However, for heat treatments in vacuum, the PL intensity is increased by a factor of 5 and the TEM data show a homogeneous size distribution of Sn nanoclusters. The low intensity of PL for the N{sub 2} annealed samples is associated with Sn oxidation.

  11. Electronic structure of ytterbium-implanted GaN at ambient and high pressure: experimental and crystal field studies.

    PubMed

    Kaminska, A; Ma, C-G; Brik, M G; Kozanecki, A; Boćkowski, M; Alves, E; Suchocki, A

    2012-03-07

    The results of high-pressure low-temperature optical measurements in a diamond-anvil cell of bulk gallium nitride crystals implanted with ytterbium are reported in combination with crystal field calculations of the Yb(3+) energy levels. Crystal field analysis of splitting of the (2)F(7/2) and (2)F(5/2) states has been performed, with the aim of assigning all features of the experimental luminescence spectra. A thorough analysis of the pressure behavior of the Yb(3+) luminescence lines in GaN allowed the determination of the ambient-pressure positions and pressure dependence of the Yb(3+) energy levels in the trigonal crystal field as well as the pressure-induced changes of the spin-orbit coupling coefficient.

  12. Dental Implant Surgery

    MedlinePlus

    Dental implant surgery Overview By Mayo Clinic Staff Dental implant surgery is a procedure that replaces tooth roots with ... look and function much like real ones. Dental implant surgery can offer a welcome alternative to dentures ...

  13. Hip Implant Systems

    MedlinePlus

    ... Devices Products and Medical Procedures Implants and Prosthetics Metal-on-Metal Hip Implants Hip Implants Share Tweet Linkedin Pin ... devices available with different bearing surfaces. These are: Metal-on-Polyethylene: The ball is made of metal ...

  14. Detecting Instances of Shape Classes That Exhibit Variable Structure

    DTIC Science & Technology

    2006-02-17

    Active hand tracking. In: Face and Gesture Recognition . (1998) 573–578 30. Ong, E., Bowden, R.: A boosted classifier tree for hand shape detection. In: Face and Gesture Recognition . (2004) 889–894

  15. Experimental detection of cracks at rivets using structural wave propagation

    NASA Astrophysics Data System (ADS)

    Fromme, Paul; Sayir, Mahir B.

    2001-04-01

    Guided bending waves are used to detect defects in aluminum plates. The scattered field of a notched hole is studied as a model for a crack at a rivet hole in an airplane fuselage. The first anti-symmetric Lamb wave mode is excited using piezoelectric transducers. The scattered field is measured with a heterodyne laser-interferometer. Good agreement between measurements and an analytical model was found. A small notch changes the scattered field and can be detected.

  16. Piezosurgery in implant dentistry

    PubMed Central

    Stübinger, Stefan; Stricker, Andres; Berg, Britt-Isabelle

    2015-01-01

    Piezosurgery, or the use of piezoelectric devices, is being applied increasingly in oral and maxillofacial surgery. The main advantages of this technique are precise and selective cuttings, the avoidance of thermal damage, and the preservation of soft-tissue structures. Through the application of piezoelectric surgery, implant-site preparation, bone grafting, sinus-floor elevation, edentulous ridge splitting or the lateralization of the inferior alveolar nerve are very technically feasible. This clinical overview gives a short summary of the current literature and outlines the advantages and disadvantages of piezoelectric bone surgery in implant dentistry. Overall, piezoelectric surgery is superior to other methods that utilize mechanical instruments. Handling of delicate or compromised hard- and soft-tissue conditions can be performed with less risk for the patient. With respect to current and future innovative surgical concepts, piezoelectric surgery offers a wide range of new possibilities to perform customized and minimally invasive osteotomies. PMID:26635486

  17. Characterization of high energy ion implantation into Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Carroll, M. P.; Stephenson, K.; Findley, K. O.

    2009-06-01

    Ion implantation is a surface modification process that can improve the wear, fatigue, and corrosion resistance for several metals and alloys. Much of the research to date has focused on ion energies less than 1 MeV. With this in mind, Ti-6Al-4V was implanted with Al 2+, Au 3+, and N + ions at energies of 1.5 and 5 MeV and various doses to determine the effects on strengthening of a high energy beam. A post heat treatment on the specimens implanted with Al 2+ samples was conducted to precipitate Ti xAl type intermetallics near the surface. Novel techniques, such as nanoindentation, are available now to determine structure-mechanical property relationships in near-surface regions of the implanted samples. Thus, nanoindentation was performed on pre-implanted, as-implanted, and post heat treated samples to detect differences in elastic modulus and hardness at the sub-micron scale. In addition, sliding wear tests were performed to qualitatively determine the changes in wear performance. The effect of this processing was significant for samples implanted with Al 2+ ions at 1.5 MeV with a dose higher than 1 × 10 16 ions/cm 2 where precipitation hardening likely occurs and with N + ions.

  18. Abridged Technique for Precise Implant Angulation

    PubMed Central

    Perumal, Praveen; Chander, Gopi Naveen; Reddy, Ramesh; Muthukumar, B.

    2015-01-01

    Enormous scientific knowledge with evidence and clinical dexterity impart definitive ground for success in implant dentistry. Nevertheless, the unfeasibility to access the inner bone tissue makes the situation altogether more demanding. Presently the advent of numerous imaging techniques and associated surgical guide templates are documented for evaluation of implant angulation. However, they are not cost effective and consume more time to plan and design the structure. This article describes a simple concise technique for precise implant angulation. PMID:26816997

  19. Damage detection in mechanical structures using extreme value statistic.

    SciTech Connect

    Worden, K.; Allen, D. W.; Sohn, H.; Farrar, C. R.

    2002-01-01

    The first and most important objective of any damage identification algorithms is to ascertain with confidence if damage is present or not. Many methods have been proposed for damage detection based on ideas of novelty detection founded in pattern recognition and multivariate statistics. The philosophy of novelty detection is simple. Features are first extracted from a baseline system to be monitored, and subsequent data are then compared to see if the new features are outliers, which significantly depart from the rest of population. In damage diagnosis problems, the assumption is that outliers are generated from a damaged condition of the monitored system. This damage classification necessitates the establishment of a decision boundary. Choosing this threshold value is often based on the assumption that the parent distribution of data is Gaussian in nature. While the problem of novelty detection focuses attention on the outlier or extreme values of the data i.e. those points in the tails of the distribution, the threshold selection using the normality assumption weighs the central population of data. Therefore, this normality assumption might impose potentially misleading behavior on damage classification, and is likely to lead the damage diagnosis astray. In this paper, extreme value statistics is integrated with the novelty detection to specifically model the tails of the distribution of interest. Finally, the proposed technique is demonstrated on simulated numerical data and time series data measured from an eight degree-of-freedom spring-mass system.

  20. Dosimetry of a thyroid uptake detected in seed migration survey following a patient's iodine-125 prostate implant and in vitro measurements of intentional seed leakages

    SciTech Connect

    Chen Qinsheng; Russell, John L. Jr.; Macklis, Roger R.; Weinhous, Martin S.; Blair, Henry F.

    2006-07-15

    As a quality control procedure, a post-implant seed migration survey has been accomplished on 340 prostate cancer patients since November 2001. Pulmonary seed embolization and intracardiac seed embolization have been detected. A case of thyroid uptake due to leaking iodine-125 (I-125) sources was also seized. In order to determine the dose to the thyroid, a dosimetry method was developed to link in vivo measurements and the cumulated dose to the thyroid. The calculated source leakage half-life in the case was approximately 15 days based on the measurements and the estimated cumulated dose to thyroid was 204 cGy. It is concluded that one seed was leaking. In order to verify the in vivo measurements, intentional in vitro seed leakage tests were performed. A seed was cut open and placed in a sealed glass container filled with a given volume of saline. The I-125 concentration in the saline was subsequently measured over a period of six months. Consistent in vivo and in vitro results were obtained. Recent incidents of seed leaks reported from other centers have drawn practitioners' attention to this problem. In order to make the measurements more useful, the seed leakage tests were expanded to include I-125 seeds from six other vendors. The results show that the leakage half-lives of those seeds varied from nine days to a half-year. Two seed models demonstrated least leakage. Since the measurements lasted for six months, the escape of iodine resulted from oxidation of iodide in the saline was a concern for the measurement accuracy. As a reference, another set of leakage tests were performed by adding sodium thiosulfate salt (Na{sub 2}S{sub 2}O{sub 3}{center_dot}5H{sub 2}O) to the saline. Sodium thiosulfate is a reducing agent that prevents the conversion of iodide to iodate so as to minimize I-125 evaporation. As a result, significantly shortened leakage half-lives were observed in this group. Seed agitation was also performed and no significant deviations of the

  1. Fine Structural Detection of Calcium Ions by Photoconversion

    PubMed Central

    Poletto, V.; Galimberti, V.; Guerra, G.; Rosti, V.; Moccia, F.; Biggiogera, M.

    2016-01-01

    We propose a tool for a rapid high-resolution detection of calcium ions which can be used in parallel with other techniques. We have applied a new approach by photo-oxidation of diaminobenzidine in presence of the emission of an excited fluorochrome specific for calcium detection. This method combines the selectivity of available fluorophores to the high spatial resolution offered by transmission electron microscopy to detect fluorescing molecules even when present in low amounts in membrane-bounded organelles. We show in this paper that Mag-Fura 2 photoconversion via diaminobenzidine oxidation is an efficient way for localizing Ca2+ ions at electron microscopy level, is easily carried out and reproducible, and can be obtained on a good amount of cells, since the exposure in our conditions is not limited to the direct irradiation of the sample via an objective but obtained with a germicide lamp. The end product is sufficiently electron dense to be detected clearly when present in sufficient amount within a membrane boundary. PMID:27734989

  2. Structural, mechanical and hydrophobic properties of fluorine-doped diamond-like carbon films synthesized by plasma immersion ion implantation and deposition (PIII?D)

    NASA Astrophysics Data System (ADS)

    Yao, Zh. Q.; Yang, P.; Huang, N.; Sun, H.; Wang, J.

    2004-05-01

    Fluorine-doped diamond-like carbon (a-C:F) films with different fluorine content were fabricated on Si wafer by plasma immersion ion implantation and deposition (PIII-D). Film composition and structure were characterized by X-ray photoelectron spectroscopy (XPS) and Raman scattering spectroscopy. Surface morphology and roughness were analyzed by atomic force microscopy (AFM). Hardness and scratch resistance were measured by nano-indentation and nano-scratch, respectively. Water contact angles were measured by sessile drop method. With the increase of the CF 4 flux, fluorine content was gradually increased to the film. Raman spectra indicates that these films have a diamond-like structure. The addition of fluorine to diamond-like carbon films had a critical influence on the film properties. The film surface becomes more smoother due to the etching behavior of F +. Hardness was significantly reduced, while the scratch resistance results show that these films have a fairly good adhesion to the substrate. Evident improvements of the hydrophobicity have been made to these films, with contact angles of double-stilled water approaching that of polytetrafluoroethylene (PTFE). Our study suggests that broad application regions of the fluorine-doped amorphous carbon films with diamond-like structure, synthesized by PIII-D, can be extended by combining the non-wetting properties and mechanical properties which are far superior to those of PTFE.

  3. Biomechanics of Corneal Ring Implants

    PubMed Central

    2015-01-01

    Purpose: To evaluate the biomechanics of corneal ring implants by providing a related mathematical theory and biomechanical model for the treatment of myopia and keratoconus. Methods: The spherical dome model considers the inhomogeneity of the tunica of the eye, dimensions of the cornea, lamellar structure of the corneal stroma, and asphericity of the cornea. It is used in this study for calculating a strengthening factor sf for the characterization of different ring-shaped corneal implant designs. The strengthening factor is a measure of the amount of strengthening of the cornea induced by the implant. Results: For ring segments and incomplete rings, sf = 1.0, which indicates that these implants are not able to strengthen the cornea. The intracorneal continuous complete ring (MyoRing) has a strengthening factor of up to sf = 3.2. The MyoRing is, therefore, able to strengthen the cornea significantly. Conclusions: The result of the presented biomechanical analysis of different ring-shaped corneal implant designs can explain the different postoperative clinical results of different implant types in myopia and keratoconus. PMID:26312619

  4. Electronic retinal implant surgery.

    PubMed

    MacLaren, R E

    2017-02-01

    Blindness due to outer retinal degeneration still remains largely untreatable. Photoreceptor loss removes light sensitivity, but the remaining inner retinal layers, the optic nerve, and indeed the physical structure of the eye itself may be unaffected by the degenerative processes. This provides the opportunity to restore some degree of vision with an electronic device in the subretinal space. In this lecture I will provide an overview of our experiences with the first-generation retinal implant Alpha IMS, developed by Retina Implant AG and based on the technology developed by Eberhart Zrenner as part of a multicentre clinical trial (NCT01024803). We are currently in the process of running a second NIHR-funded clinical trial to assess the next-generation device. The positive results from both studies to date indicate that the retinal implant should be included as a potential treatment for patients who are completely blind from retinitis pigmentosa. Evolution of the technology in future may provide further opportunities for earlier intervention or for other diseases.

  5. Effects of implantation of three-dimensional engineered bone tissue with a vascular-like structure on repair of bone defects

    NASA Astrophysics Data System (ADS)

    Nishi, Masanori; Matsumoto, Rena; Dong, Jian; Uemura, Toshimasa

    2012-12-01

    Previously, to create an implantable bone tissue associated with blood vessels, we co-cultured rabbit bone marrow mesenchymal stem cells (MSCs) with MSC-derived endothelial cells (ECs) within a porous polylactic acid-based scaffold utilizing a rotating wall vessel (RWV) bioreactor. Here, this engineered tissue was orthotopically implanted into defects made in femurs of immunodeficient rats, and histological analysis were carried out to examine the repair of the damage and the formation of bone around the implant. The bone defects were better repaired in the implanted group than control group after 3 weeks. The results indicate that the engineered bone could repair bone defects.

  6. A technique for autonomous structural damage detection with smart wireless sensor network

    NASA Astrophysics Data System (ADS)

    Lei, Y.; Mao, Y. K.; Tang, Y. L.; Wang, J. X.

    2010-03-01

    In this paper, a distributed structural damage detection approach is proposed for large size structures under limited input and output measurements. A large size structure is decomposed into small size substructures based on its finite element formulation. Interaction effect between adjacent substructures is considered as 'additional unknown inputs' to each substructure. By sequentially utilizing the extended Kalman estimator for the extended state vector and the least squares estimation for the unmeasured inputs, the approach can not only estimate the 'additional unknown inputs' based on their formulations but also identify structural dynamic parameters, such as the stiffness and damping of each substructure. Local structural damage in the large size structure can be detected by tracking the changes in the identified values of structural dynamic parameters at element level, e.g., the degrading of stiffness parameters. Numerical example of detecting structural local damages in a large-size plane truss bridge illustrates the efficiency of the proposed approach. A new smart wireless sensor network is developed by the authors to combine with the proposed approach for autonomous structural damage detection of large size structures. The distributed structural damage detection approach can be embedded into the smart wireless sensor network based on its two-level cluster-tree topology architecture and the distributed computation capacity of each cluster head.

  7. Detection of Anatomic Structures in Human Retinal Imagery

    SciTech Connect

    Tobin Jr, Kenneth William; Chaum, Edward; Muthusamy Govindasamy, Vijaya Priya; Karnowski, Thomas Paul

    2007-01-01

    The widespread availability of electronic imaging devices throughout the medical community is leading to a growing body of research on image processing and analysis to diagnose retinal disease such as diabetic retinopathy (DR). Productive computer-based screening of large, at-risk populations at low cost requires robust, automated image analysis. In this paper we present results for the automatic detection of the optic nerve and localization of the macula using digital red-free fundus photography. Our method relies on the accurate segmentation of the vasculature of the retina followed by the determination of spatial features describing the density,average thickness, and average orientation of the vasculature in relation to the position of the optic nerve. Localization of the macula follows using knowledge of the optic nerve location to detect the horizontal raphe of the retina using a geometric model of the vasculature. We report 90.4% detection performance for the optic nerve and 92.5% localization performance for the macula for red-free fundus images representing a population of 345 images corresponding to 269 patients with 18 different pathologies associated with DR and other common retinal diseases such as age-related macular degeneration.

  8. Structural Properties of Potexvirus Coat Proteins Detected by Optical Methods.

    PubMed

    Semenyuk, P I; Karpova, O V; Ksenofontov, A L; Kalinina, N O; Dobrov, E N; Makarov, V V

    2016-12-01

    It has been shown by X-ray analysis that cores of coat proteins (CPs) from three potexviruses, flexible helical RNA-containing plant viruses, have similar α-helical structure. However, this similarity cannot explain structural lability of potexvirus virions, which is believed to determine their biological activity. Here, we used circular dichroism (CD) spectroscopy in the far UV region to compare optical properties of CPs from three potexviruses with the same morphology and similar structure. CPs from Alternanthera mosaic virus (AltMV), potato aucuba mosaic virus (PAMV), and potato virus X (PVX) have been studied in a free state and in virions. The CD spectrum of AltMV virions was similar to the previously obtained CD spectrum of papaya mosaic virus (PapMV) virions, but differed significantly from the CD spectrum of PAMV virions. The CD spectrum of PAMV virions resembled in its basic characteristics the CD spectrum of PVX virions characterized by molar ellipticity that is abnormally low for α-helical proteins. Homology modeling of the CP structures in AltMV, PAMV, and PVX virions was based on the known high-resolution structures of CPs from papaya mosaic virus and bamboo mosaic virus and confirmed that the structures of the CP cores in all three viruses were nearly identical. Comparison of amino acid sequences of different potexvirus CPs and prediction of unstructured regions in these proteins revealed a possible correlation between specific features in the virion CD spectra and the presence of disordered N-terminal segments in the CPs.

  9. [Bilateral cochlear implantation].

    PubMed

    Kronenberg, Jona; Migirov, Lela; Taitelbaum-Swead, Rikey; Hildesheimer, Minka

    2010-06-01

    Cochlear implant surgery became the standard of care in hearing rehabilitation of patients with severe to profound sensorineural hearing loss. This procedure may alter the lives of children and adults enabling them to integrate with the hearing population. In the past, implantation was performed only in one ear, despite the fact that binaural hearing is superior to unilateral, especially in noisy conditions. Cochlear implantation may be performed sequentially or simultaneously. The "sensitive period" of time between hearing loss and implantation and between the two implantations, when performed sequentially, significantly influences the results. Shorter time spans between implantations improve the hearing results after implantation. Hearing success after implantation is highly dependent on the rehabilitation process which includes mapping, implant adjustments and hearing training. Bilateral cochlear implantation in children is recommended as the proposed procedure in spite of the additional financial burden.

  10. A new approach for structural health monitoring by applying anomaly detection on strain sensor data

    NASA Astrophysics Data System (ADS)

    Trichias, Konstantinos; Pijpers, Richard; Meeuwissen, Erik

    2014-03-01

    Structural Health Monitoring (SHM) systems help to monitor critical infrastructures (bridges, tunnels, etc.) remotely and provide up-to-date information about their physical condition. In addition, it helps to predict the structure's life and required maintenance in a cost-efficient way. Typically, inspection data gives insight in the structural health. The global structural behavior, and predominantly the structural loading, is generally measured with vibration and strain sensors. Acoustic emission sensors are more and more used for measuring global crack activity near critical locations. In this paper, we present a procedure for local structural health monitoring by applying Anomaly Detection (AD) on strain sensor data for sensors that are applied in expected crack path. Sensor data is analyzed by automatic anomaly detection in order to find crack activity at an early stage. This approach targets the monitoring of critical structural locations, such as welds, near which strain sensors can be applied during construction and/or locations with limited inspection possibilities during structural operation. We investigate several anomaly detection techniques to detect changes in statistical properties, indicating structural degradation. The most effective one is a novel polynomial fitting technique, which tracks slow changes in sensor data. Our approach has been tested on a representative test structure (bridge deck) in a lab environment, under constant and variable amplitude fatigue loading. In both cases, the evolving cracks at the monitored locations were successfully detected, autonomously, by our AD monitoring tool.

  11. Damage Detection of Laminated CFRP Structures using Electric Pulse Wave Transmission

    DTIC Science & Technology

    2010-05-05

    SUPPLEMENTARY NOTES 14. ABSTRACT For laminated CFRP structures, it is quite difficult to detect internal damage such as delamination, matrix cracks, and...unclassified Abstract. Carbon Fiber Reinforced Polymer ( CFRP ) laminates are applied to many aerospace structures. For these laminated CFRP ...Carbon Fiber Reinforced Polymer ( CFRP ) has been increasingly applied to the aerospace primary structures because of its high specific strength and

  12. Viscoelastic properties of a synthetic meniscus implant.

    PubMed

    Shemesh, Maoz; Asher, Roy; Zylberberg, Eyal; Guilak, Farshid; Linder-Ganz, Eran; Elsner, Jonathan J

    2014-01-01

    There are significant potential advantages for restoration of meniscal function using a bio-stable synthetic implant that combines long-term durability with a dependable biomechanical performance resembling that of the natural meniscus. A novel meniscus implant made of a compliant polycarbonate-urethane matrix reinforced with high modulus ultrahigh molecular weight polyethylene fibers was designed as a composite structure that mimics the structural elements of the natural medial meniscus. The overall success of such an implant is linked on its capability to replicate the stress distribution in the knee over the long-term. As this function of the device is directly dependent on its mechanical properties, changes to the material due to exposure to the joint environment and repeated loading could have non-trivial influences on the viscoelastic properties of the implant. Thus, the goal of this study was to measure and characterize the strain-rate response, as well as the viscoelastic properties of the implant as measured by creep, stress relaxation, and hysteresis after simulated use, by subjecting the implant to realistic joint loads up to 2 million cycles in a joint-like setting. The meniscus implant behaved as a non-linear viscoelastic material. The implant underwent minimal plastic deformation after 2 million fatigue loading cycles. Under low compressive loads, the implant was fairly flexible, and able to deform relatively easily (E=120-200 kPa). However as the compressive load applied on the implant was increased, the implant became stiffer (E=3.8-5.2 MPa), to resist deformation. The meniscus implant appears well-matched to the viscoelastic properties of the natural meniscus, and importantly, these properties were found to remain stable and minimally affected by potentially degradative and loading conditions associated with long-term use.

  13. Damage Detection with Streamlined Structural Health Monitoring Data

    PubMed Central

    Li, Jian; Deng, Jun; Xie, Weizhi

    2015-01-01

    The huge amounts of sensor data generated by large scale sensor networks in on-line structural health monitoring (SHM) systems often overwhelms the systems’ capacity for data transmission and analysis. This paper presents a new concept for an integrated SHM system in which a streamlined data flow is used as a unifying thread to integrate the individual components of on-line SHM systems. Such an integrated SHM system has a few desirable functionalities including embedded sensor data compression, interactive sensor data retrieval, and structural knowledge discovery, which aim to enhance the reliability, efficiency, and robustness of on-line SHM systems. Adoption of this new concept will enable the design of an on-line SHM system with more uniform data generation and data handling capacity for its subsystems. To examine this concept in the context of vibration-based SHM systems, real sensor data from an on-line SHM system comprising a scaled steel bridge structure and an on-line data acquisition system with remote data access was used in this study. Vibration test results clearly demonstrated the prominent performance characteristics of the proposed integrated SHM system including rapid data access, interactive data retrieval and knowledge discovery of structural conditions on a global level. PMID:25884788

  14. DETECTING UNSPECIFIED STRUCTURE IN LOW-COUNT IMAGES

    SciTech Connect

    Stein, Nathan M.; Dyk, David A. van; Kashyap, Vinay L.; Siemiginowska, Aneta E-mail: dvandyk@imperial.ac.uk E-mail: asiemiginowska@cfa.harvard.edu

    2015-11-01

    Unexpected structure in images of astronomical sources often presents itself upon visual inspection of the image, but such apparent structure may either correspond to true features in the source or be due to noise in the data. This paper presents a method for testing whether inferred structure in an image with Poisson noise represents a significant departure from a baseline (null) model of the image. To infer image structure, we conduct a Bayesian analysis of a full model that uses a multiscale component to allow flexible departures from the posited null model. As a test statistic, we use a tail probability of the posterior distribution under the full model. This choice of test statistic allows us to estimate a computationally efficient upper bound on a p-value that enables us to draw strong conclusions even when there are limited computational resources that can be devoted to simulations under the null model. We demonstrate the statistical performance of our method on simulated images. Applying our method to an X-ray image of the quasar 0730+257, we find significant evidence against the null model of a single point source and uniform background, lending support to the claim of an X-ray jet.

  15. Detecting and visualizing structural changes in groundwater head time series

    NASA Astrophysics Data System (ADS)

    van Geer, Frans

    2013-04-01

    Since the fifties of the past century the dynamic behavior of the groundwater head has been monitored at many locations throughout the Netherlands and elsewhere. The data base of the Geological Survey of the Netherlands contains over 30,000 groundwater time series. For many water management purposes characteristics of the dynamic behavior are required, such as average, median, percentile etc.. These characteristics are estimated from the time series. In principle, the longer the time series, the more reliable the estimate. However, due to natural as well as man induced changes, the characteristics of a long time series are often changing in time as well. For water management it is important to be able to distinguish extreme values as part of the 'normal' pattern from structural changes in the groundwater regime. Whether or not structural changes are present in the time series can't be decided completely objective. Choices have to be made concerning the length of the period and the statistical parameters. Here a method is proposed to visualize the probability of structural changes in the time series using well known basic statistical tests. The visualization method is based on the mean values and standard deviation in a moving window. Apart from several characteristics that are calculated for each period separately, all pairs of two periods are compared and the difference is statistically tested. The results of these well known tests are combined in a visualization to supply to the user comprehensive information to examine structural changes in time series.

  16. Detection and assessment of damage in 2D structures using measured modal response

    NASA Astrophysics Data System (ADS)

    Banan, Mohammad Reza; Mehdi-pour, Yousef

    2007-10-01

    Motivated by one of the concepts in the field of health monitoring for structural systems, a damage detection procedure is developed. In order to perform the system health monitoring, structural health along with sensor and actuator malfunction must be continuously checked. As a step toward developing a system health-monitoring scheme, this paper investigated structural damage detection, using a constrained eigenstructure assignment. The proposed damage detection method is constructed based on a concept of control theory and subspace rotation for two-dimensional (2D)-structural systems. To demonstrate the capabilities of the developed damage detection algorithm, the behavior of a simulated degraded braced-frame structure is studied. Using Monte Carlo simulation, the performance of the approach is evaluated. It shows that the proposed algorithm is potentially promising for application to real cases.

  17. [Structural analyses of unknown red dyes detected in dried strawberry].

    PubMed

    Shindo, Tetsuya; Sadamasu, Yuki; Suzuki, Keiko; Tanaka, Yasukazu; Togawa, Akiko; Nakajima, Junichi; Nakazato, Mitsuo; Uematsu, Yoko

    2012-01-01

    We examined two unknown red dyes (designated as red dyes "A" and "B") from a dried strawberry package with a label that indicated the presence of food red No. 40 (R40). Red dye "A" was identified as trisodium 3-hydroxy-4-[(2'-methoxy-5'-methyl-4'-sulfonatophenyl)azo]-2,7-naphthalenedisulfonate (CSA-R) by HPLC, UV-VIS spectra and MS spectra. This compound is one of the four reported subsidiary colors of R40. Detailed analyses of red dye "B" by MS and NMR demonstrated that its structure was disodium 3-hydroxy-4-[(2'-methoxy-5'-methyl-4'-sulfonatophenyl)azo]-2-naphthalenesulfonate. Red dye "B" is a structural isomer of R40, that has not been reported previously. Our results suggest that the two minor red dyes were subsidiary colors contained in R40, which had been added to the dried strawberries.

  18. [High performance of an implantable Holter monitor in the detection of concealed paroxysmal atrial fibrillation in patients with cryptogenic stroke and a suspected embolic mechanism].

    PubMed

    Rojo-Martinez, Esther; Sandín-Fuentes, María; Calleja-Sanz, Ana I; Cortijo-García, Elisa; García-Bermejo, Pablo; Ruiz-Piñero, Marina; Rubio-Sanz, Jerónimo; Arenillas-Lara, Juan F

    2013-09-16

    Introduccion. El holter implantable permite detectar fibrilacion auricular paroxistica (FAP) oculta en pacientes con ictus criptogenico, pero se desconoce que algoritmo de seleccion tiene un mayor rendimiento y la duracion optima de monitorizacion. Objetivo. Conocer la frecuencia y el tiempo hasta detectar la FAP mediante un holter implantable Reveal XT ® en pacientes con ictus criptogenico seleccionados por sospecha elevada de embolismo cerebral. Pacientes y metodos. Criterios de seleccion: ausencia de etiologia del ictus tras el estudio completo incluyendo un ecocardiograma transesofagico, monitorizacion ECG y holter de 24 horas, asi como confirmacion de oclusion aguda embolica de la arteria intracraneal por duplex transcraneal o bien alta sospecha de embolismo por caracteristicas de neuroimagen. Tras implantar el holter Reveal XT se formo a los pacientes para que emprendieran transmisiones todos los meses o ante sintomas. Se reviso la informacion online mensualmente y se realizaron visitas clinicas en las unidades de Neurologia y Cardiologia. Resultados. Se incluyeron 101 pacientes con ictus criptogenico y al menos un mes de seguimiento: edad media de 67 años, 54 mujeres (53,5%). Tiempo medio de seguimiento: 281 ± 212 dias. Se detecto FAP oculta en 34 pacientes (33,7%) y falsos positivos en 23 (22,8%). Mediana desde el implante hasta la deteccion de la arritmia: 102 dias (rango: 26-240 dias). En un 70% de los pacientes se registraron multiples episodios de FAP. El 75% de los eventos se detectaron durante los primeros seis meses de monitorizacion. Conclusiones. El algoritmo de seleccion de pacientes con ictus criptogenico segun sospecha de embolismo cerebral se asocio a una elevada frecuencia (33,7%) de FAP oculta con holter implantable. Uno de cada cuatro eventos sucedio tras los primeros seis meses de monitorizacion.

  19. Surface characteristics of TiN/ZrN coated nanotubular structure on the Ti-35Ta-xHf alloy for bio-implant applications

    NASA Astrophysics Data System (ADS)

    Moon, Byung-Hak; Choe, Han-Cheol; Brantley, William A.

    2012-01-01

    In this study, we investigated the surface characteristics of the TiN/ZrN-coated nanotubular structure on Ti-35Ta-xHf ternary alloys for bio-implant applications. These ternary alloys contained from 3 wt.% to 15 wt.% Hf contents and were manufactured in an arc-melting furnace. The Ti-35Ta-xHf alloys were heat treated in Ar atmosphere at 1000 °C for 24 h, followed by water quenching. Formation of the nanotubular structure was achieved by an electrochemical method in 1 M H3PO4 electrolytes containing 0.8 wt.% NaF. The TiN coating and ZrN coating were subsequently prepared by DC-sputtering on the nanotubular surface. Microstructures and nanotubular morphology of the alloys were examined by FE-SEM, EDX and XRD. The microstructure showed a duplex (α‧‧ + β) phase structure. Traces of martensite disappeared with increasing Hf content, and the Ti-35Nb-15Hf alloy had an entirely equiaxed structure of β phase. This research has shown that highly ordered, high aspect ratio, and nanotubular morphology surface oxide layers can be formed on the ternary titanium alloys by anodization. The TiN and ZrN coatings formed on the nanotubular surfaces were uniform and stable. The top of the nanotube layers was uniformly covered with the ZrN film compared to the TiN film when the Ti-35Ta-xHf alloys had high Hf content.

  20. Real-time vibration-based structural damage detection using one-dimensional convolutional neural networks

    NASA Astrophysics Data System (ADS)

    Abdeljaber, Osama; Avci, Onur; Kiranyaz, Serkan; Gabbouj, Moncef; Inman, Daniel J.

    2017-02-01

    Structural health monitoring (SHM) and vibration-based structural damage detection have been a continuous interest for civil, mechanical and aerospace engineers over the decades. Early and meticulous damage detection has always been one of the principal objectives of SHM applications. The performance of a classical damage detection system predominantly depends on the choice of the features and the classifier. While the fixed and hand-crafted features may either be a sub-optimal choice for a particular structure or fail to achieve the same level of performance on another structure, they usually require a large computation power which may hinder their usage for real-time structural damage detection. This paper presents a novel, fast and accurate structural damage detection system using 1D Convolutional Neural Networks (CNNs) that has an inherent adaptive design to fuse both feature extraction and classification blocks into a single and compact learning body. The proposed method performs vibration-based damage detection and localization of the damage in real-time. The advantage of this approach is its ability to extract optimal damage-sensitive features automatically from the raw acceleration signals. Large-scale experiments conducted on a grandstand simulator revealed an outstanding performance and verified the computational efficiency of the proposed real-time damage detection method.

  1. [Current dental implant design and its clinical importance].

    PubMed

    Ye, Lin

    2017-02-01

    The development of clinical implant dentistry was intensively affected by dental implant design improvement and innovation, which brought about new concept, even milestone-like changes of clinical protocol. The current improvements of dental implant design and their clinical importance could be highlighted as followings: 1) The implant apical design influences the implant preliminary stability in immediate implant. The apical 3-5 mm design of implant makes implant stable in immediate implant, because this part would be screwed into alveolar bone through fresh socket, the other part of implant could not be tightly screwed in the socket because of smaller implant diameter. Implant apical form, screw design, self-taping of apical part would be essential for immediate implant. 2) The enough preliminary stability of implant makes immediate prosthesis possible. When osseointegration does not occur, the implant stability comes from a mechanical anchorage, which depends on implant form, screw thread and self-taping design. 3) Implant neck design may have influence for soft tissue recession in esthetic zone. The implant with large shoulder would not be selected for the esthetic area. The platform design may be more favorable in the area. 4) The connection design between implant and abutment is thought a very important structure in implant long-term stability. Moose taper and "tube in tube" were well documented structure design in 20-year clinical practice in Peking University. 5) In last 15 years, the plenty studies showed the platform design of implant had positive influence in implant marginal bone level. Whatever in single implant restoration or multi-implant prosthesis. 6) The digital technology makes clinical work more precise and high-tech. This would be a trend in implant dentistry. New generation of chair-side digital computer-aided design/computer-aided manufacturing makes immediate prosthesis without conventional impression possible. 7) New abutment design have

  2. Detecting the temporal structure of sound sequences in newborn infants.

    PubMed

    Háden, Gábor P; Honing, Henkjan; Török, Miklós; Winkler, István

    2015-04-01

    Most high-level auditory functions require one to detect the onset and offset of sound sequences as well as registering the rate at which sounds are presented within the sound trains. By recording event-related brain potentials to onsets and offsets of tone trains as well as to changes in the presentation rate, we tested whether these fundamental auditory capabilities are functional at birth. Each of these events elicited significant event-related potential components in sleeping healthy neonates. The data thus demonstrate that the newborn brain is sensitive to these acoustic features suggesting that infants are geared towards the temporal aspects of segregating sound sources, speech and music perception already at birth.

  3. Wireless system for explosion detection in underground structures

    NASA Astrophysics Data System (ADS)

    Chikhradze, M.; Bochorishvili, N.; Akhvlediani, I.; Kukhalashvili, D.; Kalichava, I.; Mataradze, E.

    2009-06-01

    Considering the growing threat of terrorist or accidental explosions in underground stations, underground highway and railway sections improvement of system for protecting people from explosions appears urgent. Current automatic protective devices with blast identification module and blast damping absorbers of various designs as their basic elements cannot be considered effective. Analysis revealed that low reliability of blast detection and delayed generation of start signal for the activation of an absorber are the major disadvantages of protective devices. Besides the transmission of trigger signal to an energy absorber through cable communication reduces the reliability of the operation of protective device due to a possible damage of electric wiring under blast or mechanical attack. This paper presents the outcomes of the studies conducted to select accurate criteria for blast identification and to design wireless system of activation of defensive device. The results of testing of blast detection methods (seismic, EMP, optical, on overpressure) showed that the proposed method, which implies constant monitoring of overpressure in terms of its reliability and response speed, best meets the requirements. Proposed wireless system for explosions identification and activation of protective device consists of transmitter and receiver modules. Transmitter module contains sensor and microprocessor equipped with blast identification software. Receiver module produces activation signal for operation of absorber. Tests were performed in the underground experimental base of Mining Institute. The time between the moment of receiving signal by the sensor and activation of absorber - 640 microsecond; distance between transmitter and receiver in direct tunnel - at least 150m; in tunnel with 900 bending - 50m. This research is sponsored by NATO's Public Diplomacy Division in the framework of "Science for Peace".

  4. Structural Damage Detection Using Frequency Domain Error Localization.

    DTIC Science & Technology

    1994-12-01

    113 rn ~l-,I T X ~oy Ul C 114 APPENDIX D. FE MODEL / COMPUTER CODES The following is a brief description of MATLAB routines employed in this thesis...R.R., Structural Dynamics, An Introduction to Computer Methods , pp. 383-387, John Wiley and Sons, Inc., 1981. 8. Guyan , R.J., "Reduction of Stiffness...official policy or position of the Department of Defense or the U.S. Government. 12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

  5. Buried archaeological structures detection using MIVIS hyperspectral airborne data

    NASA Astrophysics Data System (ADS)

    Merola, P.; Allegrini, A.; Guglietta, D.; Sampieri, S.

    2006-08-01

    The identification of buried archaeological structures, using remote sensing technologies (aerophotos or satellite and airborne images) is based on the analysis of surface spectral features changes that overlying underground terrain units, located on the basis of texture variations, humidity and vegetation cover. The study of these anomalies on MIVIS (Multispectral Infrared and Visible Imaging Spectrometer) hyperspectral data is the main goal of a research project that the CNR-IIA has carried on over different archaeological test sites. The major archaeological information were gathered by data analysis in the VIS and NIR spectral region and by use of the apparent thermal inertia image and their different vegetation index.

  6. Clinical Management of Implant Prostheses in Patients with Bruxism

    PubMed Central

    Komiyama, Osamu; Lobbezoo, Frank; De Laat, Antoon; Iida, Takashi; Kitagawa, Tsuyoshi; Murakami, Hiroshi; Kato, Takao; Kawara, Misao

    2012-01-01

    There is general agreement that excessive stress to the bone-implant interface may result in implant overload and failure. Early failure of the implant due to excessive loading occurs shortly after uncovering the implant. Excess load on a final restoration after successful implant integration can result in physical failure of the implant structure. Many clinicians believe that overload of dental implants is a risk factor for vertical peri-implant bone loss and/or may be detrimental for the suprastructure in implant prostheses. It has been documented that occlusal parafunction, such as, bruxism (tooth grinding and clenching) affects the outcome of implant prostheses, but there is no evidence for a causal relation between the failures and overload of dental implants. In spite of this lack of evidence, often metal restorations are preferred instead of porcelain for patients in whom bruxism is presumed on the basis of tooth wear. The purpose of this paper is to discuss the importance of the occlusal scheme used in implant restorations for implant longevity and to suggest a clinical approach and occlusal materials for implant prostheses in order to prevent complications related to bruxism. PMID:22701484

  7. Clinical management of implant prostheses in patients with bruxism.

    PubMed

    Komiyama, Osamu; Lobbezoo, Frank; De Laat, Antoon; Iida, Takashi; Kitagawa, Tsuyoshi; Murakami, Hiroshi; Kato, Takao; Kawara, Misao

    2012-01-01

    There is general agreement that excessive stress to the bone-implant interface may result in implant overload and failure. Early failure of the implant due to excessive loading occurs shortly after uncovering the implant. Excess load on a final restoration after successful implant integration can result in physical failure of the implant structure. Many clinicians believe that overload of dental implants is a risk factor for vertical peri-implant bone loss and/or may be detrimental for the suprastructure in implant prostheses. It has been documented that occlusal parafunction, such as, bruxism (tooth grinding and clenching) affects the outcome of implant prostheses, but there is no evidence for a causal relation between the failures and overload of dental implants. In spite of this lack of evidence, often metal restorations are preferred instead of porcelain for patients in whom bruxism is presumed on the basis of tooth wear. The purpose of this paper is to discuss the importance of the occlusal scheme used in implant restorations for implant longevity and to suggest a clinical approach and occlusal materials for implant prostheses in order to prevent complications related to bruxism.

  8. Detection for flatness of large surface based on structured light

    NASA Astrophysics Data System (ADS)

    He, Wenyan; Cao, Xuedong; Long, Kuang; Peng, Zhang

    2016-09-01

    In order to get flatness of a large plane, this paper set up a measurement system, composed by Line Structured Light, imaging system, CCD, etc. Line Structured Light transmits parallel fringes at a proper angle onto the plane which is measured; the imaging system and CCD locate above the plane to catch the fringes. When the plane is perfect, CCD will catch straight fringes; however, the real plane is not perfect; according to the theory of projection, the fringes caught by CCD will be distorted by convex and concave. Extract the center of line fringes to obtain the distortion of the fringe, according to the functional relationship between the distortion of fringes and the height which is measured, then we will get flatness of the entire surface. Data from experiment approached the analysis of theory. In the simulation, the vertical resolution is 0.0075 mm per pixel when measuring a plane of 400mm×400mm, choosing the size of CCD 4096×4096, at the angle 85°. Helped by sub-pixel, the precision will get the level of submicron. There are two obvious advantages: method of surface sampling can increase the efficiency for auto-repairing of machines; considering the center of fringe is required mainly in this system, as a consequence, there is no serious demand for back light.

  9. Structural damage detection and estimation using a scanning laser vibrometer

    NASA Astrophysics Data System (ADS)

    Pai, Perngjin F.; Lee, Seung-Yoon; Schulz, Mark J.

    2001-07-01

    This paper presents a model-independent boundary effect evaluation (BEE) method for pinpointing crack locations and estimating crack sizes using only operational deflection shapes (ODSs) measured by a scanning laser vibrometer. An ODS consists of central and boundary solutions. Central solutions are periodic functions, and boundary solutions are exponentially decaying functions due to boundary constraints. The BEE method uses a sliding-window curve-fitting technique to extract boundary solutions from an experimental ODS. Because cracks introduce localized small boundaries to a structure, boundary solutions exist around cracks as well as structural boundaries. Since crack-induced boundary solutions show characteristics different from those of actual boundaries, cracks can be easily located. A local strain energy method is derived for estimating crack sizes. In the method, the crack-induced strain energy extracted from an ODS is compared with the one calculated using fracture mechanics to estimate the crack size. To verify the capability and accuracy of this BEE method, experiments are performed on six 22' X 1' X 0.25' 2024-T4 aluminum beams each having a through-the-width Mode I crack at its midpoint. These cracks are slots having a width of 0.039' and depths of 0.0625' (25% of the beam thickness), 0.05' (20%), 0.0375' (15%), 0.025' (10%), 0.0125' (5%), and 0.005' (2%), respectively. Results show that this BEE method is capable of locating and estimating small cracks.

  10. Local concurrent error detection and correction in data structures using virtual backpointers

    NASA Technical Reports Server (NTRS)

    Li, C. C.; Chen, P. P.; Fuchs, W. K.

    1987-01-01

    A new technique, based on virtual backpointers, for local concurrent error detection and correction in linked data structures is presented. Two new data structures, the Virtual Double Linked List, and the B-tree with Virtual Backpointers, are described. For these structures, double errors can be detected in 0(1) time and errors detected during forward moves can be corrected in 0(1) time. The application of a concurrent auditor process to data structure error detection and correction is analyzed, and an implementation is described, to determine the effect on mean time to failure of a multi-user shared database system. The implementation utilizes a Sequent shared memory multiprocessor system operating on a shared databased of Virtual Double Linked Lists.

  11. Structural Damage Detection Using Changes in Natural Frequencies: Theory and Applications

    NASA Astrophysics Data System (ADS)

    He, K.; Zhu, W. D.

    2011-07-01

    A vibration-based method that uses changes in natural frequencies of a structure to detect damage has advantages over conventional nondestructive tests in detecting various types of damage, including loosening of bolted joints, using minimum measurement data. Two major challenges associated with applications of the vibration-based damage detection method to engineering structures are addressed: accurate modeling of structures and the development of a robust inverse algorithm to detect damage, which are defined as the forward and inverse problems, respectively. To resolve the forward problem, new physics-based finite element modeling techniques are developed for fillets in thin-walled beams and for bolted joints, so that complex structures can be accurately modeled with a reasonable model size. To resolve the inverse problem, a logistical function transformation is introduced to convert the constrained optimization problem to an unconstrained one, and a robust iterative algorithm using a trust-region method, called the Levenberg-Marquardt method, is developed to accurately detect the locations and extent of damage. The new methodology can ensure global convergence of the iterative algorithm in solving under-determined system equations and deal with damage detection problems with relatively large modeling error and measurement noise. The vibration-based damage detection method is applied to various structures including lightning masts, a space frame structure and one of its components, and a pipeline. The exact locations and extent of damage can be detected in the numerical simulation where there is no modeling error and measurement noise. The locations and extent of damage can be successfully detected in experimental damage detection.

  12. Evolution of secondary defects in arsenic implanted Si

    NASA Astrophysics Data System (ADS)

    Zhu, He; Wang, Miao; Zhang, Bingpo; Wu, Huizhen; Sun, Yan; Hu, Gujin; Dai, Ning

    2016-04-01

    Behavior of defects in ion-implanted semiconductors is an everlasting topic and becomes even more critical as semiconductor devices continuously shrink and ion implantation technique has been increasingly employed. High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) were employed to investigate the structural evolution of arsenic (As) implanted silicon (Si). Project range (PR) defects and end of range (EOR) dislocations are observed via HRTEM. EDX characterization proves the two types of defects are related to dopant atoms precipitations. The sizes of both PR defects and EOR dislocations enlarge at the expense of small ones with the elevation of annealing temperature. The characterizations of electrochemical capacitance-voltage and EDX conclude that the SiO2/Si interface is playing an indispensable role in the deactivation of dopant atoms during the annealing process. As atoms are detected in the As-implanted Si region near the SiO2/Si interface but not in the silica layer. Nanoparticles composed of Si atoms in the silica layer are observed in the 1150 °C-annealed samples, which proves the migration of oxygen atoms at the SiO2/Si interface.

  13. Techniques for dental implant nanosurface modifications

    PubMed Central

    Bathala, Lakshmana Rao; Sangur, Rajashekar

    2014-01-01

    PURPOSE Dental implant has gained clinical success over last decade with the major drawback related to osseointegration as properties of metal (Titanium) are different from human bone. Currently implant procedures include endosseous type of dental implants with nanoscale surface characteristics. The objective of this review article is to summarize the role of nanotopography on titanium dental implant surfaces in order to improve osseointegration and various techniques that can generate nanoscale topographic features to titanium implants. MATERIALS AND METHODS A systematic electronic search of English language peer reviewed dental literature was performed for articles published between December 1987 to January 2012. Search was conducted in Medline, PubMed and Google scholar supplemented by hand searching of selected journals. 101 articles were assigned to full text analysis. Articles were selected according to inclusion and exclusion criterion. All articles were screened according to inclusion standard. 39 articles were included in the analysis. RESULTS Out of 39 studies, seven studies demonstrated that bone implant contact increases with increase in surface roughness. Five studies showed comparative evaluation of techniques producing microtopography and nanotopography. Eight studies concluded that osteoblasts preferably adhere to nano structure as compared to smooth surface. Six studies illustrated that nanotopography modify implant surface and their properties. Thirteen studies described techniques to produce nano roughness. CONCLUSION Modification of dental osseous implants at nanoscale level produced by various techniques can alter biological responses that may improve osseointegration and dental implant procedures. PMID:25558347

  14. Digital photoelastic analysis applied to implant dentistry

    NASA Astrophysics Data System (ADS)

    Ramesh, K.; Hariprasad, M. P.; Bhuvanewari, S.

    2016-12-01

    Development of improved designs of implant systems in dentistry have necessitated the study of stress fields in the implant regions of the mandible/maxilla for better understanding of the biomechanics involved. Photoelasticity has been used for various studies related to dental implants in view of whole field visualization of maximum shear stress in the form of isochromatic contours. The potential of digital photoelasticity has not been fully exploited in the field of implant dentistry. In this paper, the fringe field in the vicinity of the connected implants (All-On-Four® concept) is analyzed using recent advances in digital photoelasticity. Initially, a novel 3-D photoelastic model making procedure, to closely mimic all the anatomical features of the human mandible is proposed. By choosing appropriate orientation of the model with respect to the light path, the essential region of interest were sought to be analysed while keeping the model under live loading conditions. Need for a sophisticated software module to carefully identify the model domain has been brought out. For data extraction, five-step method is used and isochromatics are evaluated by twelve fringe photoelasticity. In addition to the isochromatic fringe field, whole field isoclinic data is also obtained for the first time in implant dentistry, which could throw important information in improving the structural stability of the implant systems. Analysis is carried out for the implant in the molar as well as the incisor region. In addition, the interaction effects of loaded molar implant on the incisor area are also studied.

  15. Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency Harmonics Interrogation for Structural Damage Detection

    DTIC Science & Technology

    2014-09-17

    Harmonics Interrogation for Structural Damage Detection FA9550-11-1-0072 Kon-Well Wang and Jiong Tang The Regents of the University of Michigan, 3003...Well Wang 734-764-8464 1    Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency Harmonics Interrogation for Structural Damage Detection...limitations. This research explores damage identification via advancing a third type of approach: high-frequency harmonic excitation-based self

  16. Highly Sensitive and Robust Damage Detection of Periodic Structures with Piezoelectric Networking

    DTIC Science & Technology

    2008-05-01

    REPORT TYPE Final 3. DATES COVERED (From - To) December 15. 2006 to May 3 1. 2008 4. TITLE AND SUBTITLE Highly Sensitive and Robust Damage...localization characteristics of such periodic structures to enhance damage detection sensitivity and robustness through piezoelectric circuitry...ANSI Sid Z39 18 Adobe Professional 7.0 Highly Sensitive and Robust Damage Detection of Periodic Structures with Piezoelectric Networking GRANT

  17. A new momenclature for structural aberrations detected by chromosome painting

    SciTech Connect

    Tucker, J.D.; Morgan, W.F.; Awa, A.A.; Bauchinger, M.; Blakey, D.; Cornforth, N.N.; Littlefield, L.G.; Natarajan, A.T.; Shasserre, C.

    1994-12-31

    The advent of chromosome painting has brought the realization that structural aberrations can be far more complex than previously imagined. Different laboratories have devised their own nomenclature systems to deal with this complexity, with the result that the terminology has become inconsistent and confusing. Recently, an international group of cytogeneticists experienced with chromosome painting convened to address this issue. The result is a systematic nomenclature capable of describing chromosome aberrations occurring between painted and unpainted chromosomes, as well as aberrations involving only painted chromosomes. The nomenclature is flexible enough to describe accurately even the most extensively rearranged chromosomes. As a consequence of this flexibility, the scheme upon which the nomenclature is based differs substantially from other systems of aberration classification. We call this system the Protocol for Aberration Identification and Nomenclature Terminology (PAINT).

  18. Structural brain alterations can be detected early in HIV infection

    PubMed Central

    Ochs, Renee; Wu, Ying; Sammet, Christina L.; Shoukry, Alfred; Epstein, Leon G.

    2012-01-01

    Objective: Brain changes occurring early in HIV infection are not well characterized. The Chicago Early HIV Infection Study aimed to evaluate the presence and extent of structural brain alterations using quantitative MRI. Methods: Forty-three HIV and 21 control subjects were enrolled. Mean length of infection was estimated as less than 1 year based on assay results. High-resolution neuroanatomical images were acquired. Automated image analysis was used to derive measurements for total brain, ventricular volume, and for tissue classes (total and cortical gray matter, white matter, and CSF). A separate image analysis algorithm was used to calculate measurements for individual brain regions. Cognitive function was assessed by neuropsychological evaluation. Results: Reductions were quantified in total (p = 0.0547) and cortical (p = 0.0109) gray matter in the HIV group. Analysis of individual brain regions with a separate image analysis algorithm revealed consistent findings of reductions in cerebral cortex (p = 0.042) and expansion of third ventricle (p = 0.046). The early HIV group also demonstrated weaker performance on several neuropsychological tests, with the most pronounced difference in psychomotor speed (p = 0.001). Conclusions: This cross-sectional brain volumetric study indicates structural alterations early in HIV infection. The findings challenge the prevailing assumption that the brain is spared in this period. Revisiting the question of the brain's vulnerability to processes unfolding in the initial virus-host interaction and the early natural history may yield new insights into neurologic injury in HIV infection and inform neuroprotection strategies. PMID:23197750

  19. Automatic detection and measurement of structures in fetal head ultrasound volumes using sequential estimation and Integrated Detection Network (IDN).

    PubMed

    Sofka, Michal; Zhang, Jingdan; Good, Sara; Zhou, S Kevin; Comaniciu, Dorin

    2014-05-01

    Routine ultrasound exam in the second and third trimesters of pregnancy involves manually measuring fetal head and brain structures in 2-D scans. The procedure requires a sonographer to find the standardized visualization planes with a probe and manually place measurement calipers on the structures of interest. The process is tedious, time consuming, and introduces user variability into the measurements. This paper proposes an automatic fetal head and brain (AFHB) system for automatically measuring anatomical structures from 3-D ultrasound volumes. The system searches the 3-D volume in a hierarchy of resolutions and by focusing on regions that are likely to be the measured anatomy. The output is a standardized visualization of the plane with correct orientation and centering as well as the biometric measurement of the anatomy. The system is based on a novel framework for detecting multiple structures in 3-D volumes. Since a joint model is difficult to obtain in most practical situations, the structures are detected in a sequence, one-by-one. The detection relies on Sequential Estimation techniques, frequently applied to visual tracking. The interdependence of structure poses and strong prior information embedded in our domain yields faster and more accurate results than detecting the objects individually. The posterior distribution of the structure pose is approximated at each step by sequential Monte Carlo. The samples are propagated within the sequence across multiple structures and hierarchical levels. The probabilistic model helps solve many challenges present in the ultrasound images of the fetus such as speckle noise, signal drop-out, shadows caused by bones, and appearance variations caused by the differences in the fetus gestational age. This is possible by discriminative learning on an extensive database of scans comprising more than two thousand volumes and more than thirteen thousand annotations. The average difference between ground truth and automatic

  20. Corrosion of machined titanium dental implants under inflammatory conditions.

    PubMed

    Messer, Regina L W; Tackas, Gyula; Mickalonis, John; Brown, Yolanda; Lewis, Jill B; Wataha, John C

    2009-02-01

    The effects of hyperglycemia, altered cell function, or inflammatory mediators on implant corrosion are not well studied; yet, these effects are critical to implant biocompatibility and osseointegration. Because implant placement is burgeoning, patients with medically compromising systemic conditions such as diabetes are increasingly receiving implants, and the role of other inflammatory diseases on implant corrosion also needs investigation. In the current study, the corrosion properties of commercially available, machined titanium implants were studied in blood, cultures of monocytic cells, and solutions containing elevated dextrose concentrations. Implant corrosion was estimated by open circuit potentials, linear polarization resistance, and electrical impedance spectroscopy (EIS) for 26 h. In selected samples, THP1 monocytic cells were activated for 2 h with Lipopolysaccharide prior to implant exposure, and IL-1beta secretion was measured to assess the affect of the implants on monocyte activation. Implants under conditions of inflammatory stress exhibited more negative E(corr) values, suggesting an increased potential for corrosion. Linear polarization measurements detected increased corrosion rates in the presence of elevated dextrose conditions over PBS conditions. EIS measurements suggested that implants underwent surface passivation reactions that may have limited corrosion over the short term of this test. This result was supported by cyclic polarization tests. IL-1beta secretion was not altered under conditions of corrosion or implant exposure. The results suggest that inflammatory stress and hyperglycemia may increase the corrosion of dental endosseous titanium-based implants, but that longer, more aggressive electrochemical conditions may be necessary to fully assess these effects.

  1. Fabricating specialised orthopaedic implants using additive manufacturing

    NASA Astrophysics Data System (ADS)

    Unwin, Paul

    2014-03-01

    It has been hypothesised that AM is ideal for patient specific orthopaedic implants such as those used in bone cancer treatment, that can rapidly build structures such as lattices for bone and tissues to in-grow, that would be impossible using current conventional subtractive manufacturing techniques. The aim of this study was to describe the adoption of AM (direct metal laser sintering and electron beam melting) into the design manufacturing and post-manufacturing processes and the early clinical use. Prior to the clinical use of AM implants, extensive metallurgical and mechanical testing of both laser and electron beam fabrications were undertaken. Concurrently, post-manufacturing processes evaluated included hipping, cleaning and coating treatments. The first clinical application of a titanium alloy mega-implant was undertaken in November 2010. A 3D model of the pelvic wing implant was designed from CT scans. Novel key features included extensive lattice structures at the bone interfaces and integral flanges to fix the implant to the bone. The pelvic device was implanted with the aid of navigation and to date the patient remains active. A further 18 patient specific mega-implants have now been implanted. The early use of this advanced manufacturing route for patient specific implants has been very encouraging enabling the engineer to produce more advanced and anatomical conforming implants. However, there are a new set of design, manufacturing and regulatory challenges that require addressing to permit this technique to be used more widely. This technology is changing the design and manufacturing paradigm for the fabrication of specialised orthopaedic implants.

  2. Osteocyte density in the peri-implant bone of implants retrieved after different time periods (4 weeks to 27 years).

    PubMed

    Piattelli, Adriano; Artese, Luciano; Penitente, Enrico; Iaculli, Flavia; Degidi, Marco; Mangano, Carlo; Shibli, Jamil Awad; Coelho, Paulo G; Perrotti, Vittoria; Iezzi, Giovanna

    2014-02-01

    Bone tissue is characterized by a constant turnover in response to mechanical stimuli, and osteocytes play an essential role in bone mechanical adaptation. However, little to no information has been published regarding osteocyte density as a function of implantation time in vivo. The aim of this retrospective histological study was to evaluate the osteocyte density of the peri-implant bone in implants retrieved because of different reasons in a time period from 4 weeks to 27 years. A total of 18 samples were included in the present study. Specimens were divided into 3 groups depending on the loading history of the implants: loading between 4 weeks and 7 months (group 1); loading between 1 and 5 years (group 2); loading between 14 and 27 years (group 3). All the samples were histologically evaluated and osteocyte density was obtained using the ratio of the number of osteocytes to the bone-area (mm(2) ). The osteocyte density values significantly increased in the Group 2 (1-5 years) compared with Group 1 (4 weeks-7 months), and significantly decreased in the Group 3 (14-27 years) compared to Group 2. No significant differences were detected between Group 1 and Group 3. The decrease in osteocyte density observed in samples that were in vivo for long periods of time under loading is possibly because of the fact that once the bone structure is well aligned and biomechanically competent, a lower number of osteocytes are necessary to keep the tissue homeostasis under loading.

  3. Comparative Analysis of Structural Responses of Rat Subcutaneous Fat on the Implantation of Samples of Polymethyl Methacrylate with Hydrophobic and Hydrophilic Surface.

    PubMed

    Kudasova, E O; Vlasova, L F; Semenov, D E; Lushnikova, E L

    2017-03-31

    Morphological analysis of the subcutaneous fat was performed in rats after subcutaneous implantation of basic dental plastic materials with different hydrophobic and hydrophilic properties. It was shown that subcutaneous implantation of dental plastics with mostly hydrophobic surface and low biocompatibility induced destructive and inflammatory processes of various intensities, sometimes with allergic component; morphological signs of processes persisted for 6 weeks. Modification of basic plastics using glow-discharge plasma and enhancement of their hydrophilicity and biocompatibility significantly reduced the intensity of destructive and inflammatory processes and ensured more rapid (in 2 weeks) repair of the destroyed tissues with the formation of fibrous capsule around the implant.

  4. Study on the neotype zirconia's implant coated nanometer hydroxyapatite ceramics

    NASA Astrophysics Data System (ADS)

    Zhu, J. W.; Yang, D. W.

    2007-07-01

    In recent years, biologic ceramics is a popular material of implants and bioactive surface modification of dental implant became a research emphasis, which aims to improve bioactivity of implants materials and acquire firmer implants-bone interface. The zirconia ceramic has excellent mechanical properties and nanometer HA ceramics is a bioceramic well known for its bioactivity, therefore, nanometer HA ceramics coating on zirconia, allows combining the excellent mechanical properties of zirconia substrates with its bioactivity. This paper shows a new method for implant shape design and bioactive modification of dental implants surface. Zirconia's implant substrate was prepared by sintered method, central and lateral tunnels were drilled in the zirconia hollow porous cylindrical implants by laser processing. The HA powders and needle-like HA crystals were made by a wet precipitation and calcining method. Its surface was coated with nanometer HA ceramics which was used brush HA slurry and vacuum sintering. Mechanical testing results revealed that the attachment strength of nanometer HA ceramics coated zirconia samples is high. SEM and interface observation after inserted experiment indicated that calcium and phosphor content increased and symmetrically around coated implant-bone tissue interface. A significantly higher affinity index was demonstrated in vivo by histomorphometric evaluation in coated versus uncoated implants. SEM analysis demonstrated better bone adhesion to the material in coated implant at any situation. In addition, the hollow porous cylindrical implant coated with nanometer HA ceramics increase the interaction of bone and implant, the new bone induced into the surface of hollow porous cylindrical implant and through the most tunnels filled into central hole. The branch-like structure makes the implant and bone a body, which increased the contact area and decreased elastic ratio. Therefore, the macroscopical and microcosmic nested structure of

  5. Persistent photoconductivity in oxygen-ion implanted KNbO3 bulk single crystal

    NASA Astrophysics Data System (ADS)

    Tsuruoka, R.; Shinkawa, A.; Nishimura, T.; Tanuma, C.; Kuriyama, K.; Kushida, K.

    2016-12-01

    Persistent Photoconductivity (PPC) in oxygen-ion implanted KNbO3 ([001] oriented bulk single crystals; perovskite structure; ferroelectric with a band gap of 3.16 eV) is studied in air at room temperature to prevent the degradation of its crystallinity caused by the phase transition. The residual hydrogens in un-implanted samples are estimated to be 5×1014 cm-2 from elastic recoil detection analysis (ERDA). A multiple-energy implantation of oxygen ions into KNbO3 is performed using energies of 200, 400, and 600 keV (each ion fluence:1.0×1014 cm-2). The sheet resistance varies from >108 Ω/□ for an un-implanted sample to 1.9×107 Ω/□ for as-implanted one, suggesting the formation of donors due to hydrogen interstitials and oxygen vacancies introduced by the ion implantation. The PPC is clearly observed with ultraviolet and blue LEDs illumination rather than green, red, and infrared, suggesting the release of electrons from the metastable conductive state below the conduction band relating to the charge states of the oxygen vacancy.

  6. Capacitive Feedthroughs for Medical Implants

    PubMed Central

    Grob, Sven; Tass, Peter A.; Hauptmann, Christian

    2016-01-01

    Important technological advances in the last decades paved the road to a great success story for electrically stimulating medical implants, including cochlear implants or implants for deep brain stimulation. However, there are still many challenges in reducing side effects and improving functionality and comfort for the patient. Two of the main challenges are the wish for smaller implants on one hand, and the demand for more stimulation channels on the other hand. But these two aims lead to a conflict of interests. This paper presents a novel design for an electrical feedthrough, the so called capacitive feedthrough, which allows both reducing the size, and increasing the number of included channels. Capacitive feedthroughs combine the functionality of a coupling capacitor and an electrical feedthrough within one and the same structure. The paper also discusses the progress and the challenges of the first produced demonstrators. The concept bears a high potential in improving current feedthrough technology, and could be applied on all kinds of electrical medical implants, even if its implementation might be challenging. PMID:27660602

  7. A Novel Structurally Stable Multiepitope Protein for Detection of HCV

    PubMed Central

    Galdino, Alexsandro S.; Santos, José C.; Souza, Marilen Q.; Nóbrega, Yanna K. M.; Xavier, Mary-Ann E.; Felipe, Maria S. S.; Freitas, Sonia M.; Torres, Fernando A. G.

    2016-01-01

    Hepatitis C virus (HCV) has emerged as the major pathogen of liver diseases in recent years leading to worldwide blood-transmitted chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Accurate diagnosis for differentiation of hepatitis C from other viruses is thus of pivotal importance for proper treatment. In this work we developed a recombinant multiepitope protein (rMEHCV) for hepatitis C diagnostic purposes based on conserved and immunodominant epitopes from core, NS3, NS4A, NS4B, and NS5 regions of the virus polyprotein of genotypes 1a, 1b, and 3a, the most prevalent genotypes in South America (especially in Brazil). A synthetic gene was designed to encode eight epitopes in tandem separated by a flexible linker and bearing a his-tag at the C-terminal end. The recombinant protein was produced in Escherichia coli and purified in a single affinity chromatographic step with >95% purity. Purified rMEHCV was used to perform an ELISA which showed that the recombinant protein was recognized by IgG and IgM from human serum samples. The structural data obtained by circular dichroism (CD) spectroscopy showed that rMEHCV is a highly thermal stable protein at neutral and alkaline conditions. Together, these results show that rMEHCV should be considered an alternative antigen for hepatitis C diagnosis. PMID:26942007

  8. [Biomaterials in cochlear implants].

    PubMed

    Stöver, T; Lenarz, T

    2009-05-01

    Cochlear implants (CI) represent the "gold standard" for the treatment of congenitally deaf children and postlingually deafened adults. Thus, cochlear implantation is a success story of new bionic prosthesis development. Owing to routine application of cochlear implants in adults but also in very young children (below the age of one), high demands are placed on the implants. This is especially true for biocompatibility aspects of surface materials of implant parts which are in contact with the human body. In addition, there are various mechanical requirements which certain components of the implants must fulfil, such as flexibility of the electrode array and mechanical resistance of the implant housing. Due to the close contact of the implant to the middle ear mucosa and because the electrode array is positioned in the perilymphatic space via cochleostomy, there is a potential risk of bacterial transferral along the electrode array into the cochlea. Various requirements that have to be fulfilled by cochlear implants, such as biocompatibility, electrode micromechanics, and although a very high level of technical standards has been carried out there is still demand for the improvement of implants as well as of the materials used for manufacturing, ultimately leading to increased implant performance. General considerations of material aspects related to cochlear implants as well as potential future perspectives of implant development will be discussed.

  9. A novel texture descriptor for detection of glandular structures in colon histology images

    NASA Astrophysics Data System (ADS)

    Sirinukunwattana, Korsuk; Snead, David R.; Rajpoot, Nasir M.

    2015-03-01

    The first step prior to most analyses on most histopathology images is the detection of area of interest. In this work, we present a superpixel-based approach for glandular structure detection in colon histology images. An image is first segmented into superpixels with the constraint on the presence of glandular boundaries. Texture and color information is then extracted from each superpixel to calculate the probability of that superpixel belonging to glandular regions, resulting in a glandular probability map. In addition, we present a novel texture descriptor derived from a region covariance matrix of scattering coefficients. Our approach shows encouraging results for the detection of glandular structures in colon tissue samples.

  10. A New Approach to Overcoming Spatial Aliasing in Structural Damage Detection

    NASA Technical Reports Server (NTRS)

    Schulz, Mark J.; Naser, Ahmad S.; Thyagarajan, Sunil K.; Mickens, Travluss; Pai, Frank

    1998-01-01

    Aircraft, reusable launch vehicles,unmanned aircraft, and other advanced structures are being built using lightweight composite materials/metals with design safety factors as low as 1.25. These advanced structures operate in uncertain and severe environments and are susceptible to damage such as delamination, fiber/matrix damage, hydrothermal strain in composite materials, and fatigue and cracking in metals. To ensure human safety and load-bearing integrity these structures must be inspected to detect and locate often invisible damage and faults before they become catastrophic. Conventional methods of non-destructive evaluation sometimes miss significant damage and are time consuming and expensive to perform. In contrast, vibrometry or vibration signature techniques are a global method of structural integrity monitoring that potentially can efficiently detect damage on large structures, including damage that is away from sensor locations, and in the interior of structures. However, a barrier problem in damage detection using vibration measurements is the need to measure the vibration response at a large number of points on the structure. Typically, model reduction or expansion procedures such as Guyan reduction or dynamic expansion are attempted to overcome the problem of insufficient measurements or spatial aliasing. These approaches depend on using information from the healthy model, and thus put error into the reduction used to represent the damaged structure. In this paper, a Frequency Response Function technique is used to detect damage to a fixed-free beam. The technique uses measured frequency response functions from the healthy structure as reference data, and then monitors vibration measurements during the life of the structure to detect damage. In an analytical simulation using a finite-element model of a beam, damage was located using only sparse measurements because the technique uses both rotation and translation measurements from the damaged structure.

  11. Breast Implants: Saline vs. Silicone

    MedlinePlus

    ... to women of any age for breast reconstruction. Silicone breast implants Silicone implants are pre-filled with ... likely be inserted at the same time. Ruptured silicone implant If a silicone breast implant ruptures, you ...

  12. Similarity between community structures of different online social networks and its impact on underlying community detection

    NASA Astrophysics Data System (ADS)

    Fan, W.; Yeung, K. H.

    2015-03-01

    As social networking services are popular, many people may register in more than one online social network. In this paper we study a set of users who have accounts of three online social networks: namely Foursquare, Facebook and Twitter. Community structure of this set of users may be reflected in these three online social networks. Therefore, high correlation between these reflections and the underlying community structure may be observed. In this work, community structures are detected in all three online social networks. Also, we investigate the similarity level of community structures across different networks. It is found that they show strong correlation with each other. The similarity between different networks may be helpful to find a community structure close to the underlying one. To verify this, we propose a method to increase the weights of some connections in networks. With this method, new networks are generated to assist community detection. By doing this, value of modularity can be improved and the new community structure match network's natural structure better. In this paper we also show that the detected community structures of online social networks are correlated with users' locations which are identified on Foursquare. This information may also be useful for underlying community detection.

  13. Effect of Ar+ ion post-irradiation on crystal structure, magnetic behavior and optical band gap of Co-implanted ZnO wafers

    NASA Astrophysics Data System (ADS)

    Xu, N. N.; Li, G. P.; Lin, Q. L.; Liu, H.; Bao, L. M.

    2016-12-01

    Single crystals wurtzite ZnO with (001) orientation were implanted with Co+ ions at room temperature (RT). To tune their magnetic behavior as well as the band gap of the implanted wafers, Ar+ ion post-irradiation (PI) was performed using the calculated energy and ion dose. The formed Co clusters present in the high dose Co-implanted ZnO wafer were observed to be absent after the PI, which is quite different from the low dose doped one. It is found that all the implanted samples showed a giant magnetic moment and a narrowing optical band gap, and that the post-irradiated ones exhibited an even further redshifted absorption edge and ferromagnetic behavior but with saturation magnetization (MS) drastically decreased.

  14. Microbial colonization in orthodontic mini-implants.

    PubMed

    de Freitas, Amanda Osório Ayres; Alviano, Celuta Sales; Alviano, Daniela Sales; Siqueira, José Freitas; Nojima, Lincoln Issamu; Nojima, Matilde da Cunha Gonçalves

    2012-01-01

    Peri-implant inflammation contributes for loss of secondary stability of orthodontic mini-implants. The investigation of microbial colonization in this area would benefit its control, and consequently favor the long-term success of mini-implants. Therefore, the aim of this study was to determine the establishment and the evolution of microbial colonization process in orthodontic mini-implants for 3 months, since the time of their installation. One-hundred and fifty samples collected from 15 mini-implants were investigated from baseline up to 3 months. The biological material was obtained from peri-implant area using paper points. Nonspecific, Streptococcus spp, Lactobacillus casei and Candida spp colonizations were analyzed by cell growth methods. Porphyromonas gingivalis colonization was observed by 16S rDNA-directed polymerase chain reaction. Data from cell growth were submitted to the Wilcoxon sign rank test and results from molecular analysis were presented in a descriptive way. There was no significant difference in the microbial colonization among the examined time intervals, except for Streptococcus spp, between baseline and 24 h, which characterized the initial colonization in this time interval. Lactobacillus casei and Candida spp colonizations were insignificant. No Porphyromonas gingivalis was detected among the analyzed samples. The microbial colonization of mini-implants did not significantly change during the study. However, it should be monitored by orthodontists, since it is an important factor for mini-implants success.

  15. CHAPTER: In-Situ Characterization of Stimulating Microelectrode Arrays: Study of an Idealized Structure Based on Argus II Retinal implantsBOOK TITLE: Implantable Neural Prostheses 2: Techniques and Engineering Approaches, D.M. Zhou and E. Greenbaum, Eds., Springer, NY 2009

    SciTech Connect

    Greenbaum, Elias; Sanders, Charlene A; Kandagor, Vincent

    2010-01-01

    The development of a retinal prosthesis for artificial sight includes a study of the factors affecting the structural and functional stability of chronically implanted microelectrode arrays. Although neuron depolarization and propagation of electrical signals have been studied for nearly a century, the use of multielectrode stimulation as a proposed therapy to treat blindness is a frontier area of modern ophthalmology research. Mapping and characterizing the topographic information contained in the electric field potentials and understanding how this information is transmitted and interpreted in the visual cortex is still very much a work in progress. In order to characterize the electrical field patterns generated by the device, an in vitro prototype that mimics several of the physical and chemical parameters of the in vivo visual implant device was fabricated. We carried out multiple electrical measurements in a model 'eye,' beginning with a single electrode, followed by a 9-electrode array structure, both idealized components based on the Argus II retinal implants. Correlating the information contained in the topographic features of the electric fields with psychophysical testing in patients may help reduce the time required for patients to convert the electrical patterns into graphic signals.

  16. Using Structured Telephone Follow-up Assessments to Improve Suicide-related Adverse Event Detection

    PubMed Central

    Arias, Sarah A.; Zhang, Zi; Hillerns, Carla; Sullivan, Ashley F.; Boudreaux, Edwin D.; Miller, Ivan; Camargo, Carlos A.

    2014-01-01

    Adverse event (AE) detection and reporting practices were compared during the first phase of the Emergency Department Safety Assessment and Follow-up Evaluation (ED-SAFE), a suicide intervention study. Data were collected using a combination of chart reviews and structured telephone follow-up assessments post-enrollment. Beyond chart reviews, structured telephone follow-up assessments identified 45% of the total AEs in our study. Notably, detection of suicide attempts significantly varied by approach with 53 (18%) detected by chart review, 173 (59%) by structured telephone follow-up assessments, and 69 (23%) marked as duplicates. Findings provide support for utilizing multiple methods for more robust AE detection in suicide research. PMID:24588679

  17. Local concurrent error detection and correction in data structures using virtual backpointers

    NASA Technical Reports Server (NTRS)

    Li, Chung-Chi Jim; Chen, Paul Peichuan; Fuchs, W. Kent

    1989-01-01

    A new technique, based on virtual backpointers, for local concurrent error detection and correction in linked data strutures is presented. Two new data structures, the Virtual Double Linked List, and the B-tree with Virtual Backpointers, are described. For these structures, double errors can be detected in 0(1) time and errors detected during forward moves can be corrected in 0(1) time. The application of a concurrent auditor process to data structure error detection and correction is analyzed, and an implementation is described, to determine the effect on mean time to failure of a multi-user shared database system. The implementation utilizes a Sequent shared memory multiprocessor system operating on a shared database of Virtual Double Linked Lists.

  18. More-reliable SOS ion implantations

    NASA Technical Reports Server (NTRS)

    Woo, D. S.

    1980-01-01

    Conducting layer prevents static charges from accumulating during implantation of silicon-on-sapphire MOS structures. Either thick conducting film or thinner film transparent to ions is deposited prior to implantation, and gaps are etched in regions to be doped. Grounding path eliminates charge flow that damages film or cracks sapphire wafer. Prevention of charge buildup by simultaneously exposing structure to opposite charges requires equipment modifications less practical and more expensive than deposition of conducting layer.

  19. Implants for lucky few

    NASA Astrophysics Data System (ADS)

    Brandon, David

    2011-08-01

    In his article "Vision of beauty" (May pp22-27), Richard Taylor points the way to fractal design for retinal implants and makes an enthusiastic case for incorporating such features into the next generation of such implants.

  20. Application of Ultrasonic Phased Array Technology to the Detection of Defect in Composite Stiffened-structures

    NASA Astrophysics Data System (ADS)

    Zhou, Yuan-Qi; Zhan, Li-Hua

    2016-05-01

    Composite stiffened-structure consists of the skin and stringer has been widely used in aircraft fuselage and wings. The main purpose of the article is to detect the composite material reinforced structure accurately and explore the relationship between defect formation and structural elements or curing process. Based on ultrasonic phased array inspection technology, the regularity of defects in the manufacture of composite materials are obtained, the correlation model between actual defects and nondestructive testing are established. The article find that the forming quality of deltoid area in T-stiffened structure is obviously improved by pre-curing, the defects of hat-stiffened structure are affected by the mandrel. The results show that the ultrasonic phased array inspection technology can be an effectively way for the detection of composite stiffened-structures, which become an important means to control the defects of composite and improve the quality of the product.

  1. Evaluation of modal-based damage detection techniques for composite aircraft sandwich structures

    NASA Astrophysics Data System (ADS)

    Oliver, J. A.; Kosmatka, J. B.

    2005-05-01

    Composite sandwich structures are important as structural components in modern lightweight aircraft, but are susceptible to catastrophic failure without obvious forewarning. Internal damage, such as disbonding between skin and core, is detrimental to the structures' strength and integrity and thus must be detected before reaching critical levels. However, highly directional low density cores, such as Nomex honeycomb, make the task of damage detection and health monitoring difficult. One possible method for detecting damage in composite sandwich structures, which seems to have received very little research attention, is analysis of global modal parameters. This study will investigate the viability of modal analysis techniques for detecting skin-core disbonds in carbon fiber-Nomex honeycomb sandwich panels through laboratory testing. A series of carbon fiber prepreg and Nomex honeycomb sandwich panels-representative of structural components used in lightweight composite airframes-were fabricated by means of autoclave co-cure. All panels were of equal dimensions and two were made with predetermined sizes of disbonded areas, created by substituting areas of Teflon release film in place of epoxy film adhesive during the cure. A laser vibrometer was used to capture frequency response functions (FRF) of all panels, and then real and imaginary FRFs at different locations on each plate and operating shapes for each plate were compared. Preliminary results suggest that vibration-based techniques hold promise for damage detection of composite sandwich structures.

  2. Simulations to Improve Structural Defect Detection and Classification in Swiss-Cheese

    NASA Astrophysics Data System (ADS)

    Eskelinen, J.; Haapalainen, J.; Alavuotunki, A.; Hæggström, E.; Alatossava, T.

    2008-02-01

    Ultrasonic 2D simulations to facilitate defect detection and classification for structural quality control of Swiss-cheese are presented. Three economically relevant structure types were modeled with different geometry parameters and the back-scattered ultrasonic field from the structure boundary was simulated to obtain reference data for waveform analysis. Simulated waveform characteristics were evaluated and compared to the experimental ones. Two parameters were introduced to classify different defects by exploiting the frequency spectrum of the signals. Signal waveform and correlation analysis, based on the simulation results, improved defect detection probability.

  3. Thermography Inspection for Early Detection of Composite Damage in Structures During Fatigue Loading

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Burke, Eric R.; Parker, F. Raymond; Seebo, Jeffrey P.; Wright, Christopher W.; Bly, James B.

    2012-01-01

    Advanced composite structures are commonly tested under controlled loading. Understanding the initiation and progression of composite damage under load is critical for validating design concepts and structural analysis tools. Thermal nondestructive evaluation (NDE) is used to detect and characterize damage in composite structures during fatigue loading. A difference image processing algorithm is demonstrated to enhance damage detection and characterization by removing thermal variations not associated with defects. In addition, a one-dimensional multilayered thermal model is used to characterize damage. Lastly, the thermography results are compared to other inspections such as non-immersion ultrasonic inspections and computed tomography X-ray.

  4. Rapid detection of delamination areas in laminated structural elements by means of optically monitored strain solitons

    NASA Astrophysics Data System (ADS)

    Semenova, I. V.; Belashov, A. V.; Dreiden, G. V.; Petrov, N. V.; Samsonov, A. M.

    2015-05-01

    Modern structural elements are often made of laminated polymer materials or composites on the base of polymer matrices. The proper functioning of these elements may be of vital importance especially in automotive and aerospace industries, in gas and oil transportation. The major problem in their performance is a possibility of a sudden and irreversible delamination caused by various factors. We propose and study a NDT approach aimed to detect delamination areas in adhesively bonded layered structural elements made of different materials. The proposed approach is evaluated by use of holographic detection and monitoring of the evolution of bulk strain solitons generated in such structures.

  5. Single-hole borehole radar detection of layered structures orthogonal to the borehole

    NASA Astrophysics Data System (ADS)

    Murray, W.; Williams, C.; Lewis, C.; Josh, M.

    2000-04-01

    A vertical borehole may pass through natural layered structures which are orthogonal or near-orthogonal to the borehole. Such structures, particularly if they are layers with a smooth surface, can be very difficult to detect with a borehole radar which has the required long range and low center frequency for remote structure detection. Methods of supplementing the radar data are discussed and include the use of an additional radar with a much higher center frequency, the use of a dielectric probe and the use of a look-ahead radar.

  6. Nano hydroxyapatite-coated implants improve bone nanomechanical properties.

    PubMed

    Jimbo, R; Coelho, P G; Bryington, M; Baldassarri, M; Tovar, N; Currie, F; Hayashi, M; Janal, M N; Andersson, M; Ono, D; Vandeweghe, S; Wennerberg, A

    2012-12-01

    Nanostructure modification of dental implants has long been sought as a means to improve osseointegration through enhanced biomimicry of host structures. Several methods have been proposed and demonstrated for creating nanotopographic features; here we describe a nanoscale hydroxyapatite (HA)-coated implant surface and hypothesize that it will hasten osseointegration and improve its quality relative to that of non-coated implants. Twenty threaded titanium alloy implants, half prepared with a stable HA nanoparticle surface and half grit-blasted, acid-etched, and heat-treated (HT), were inserted into rabbit femurs. Pre-operatively, the implants were morphologically and topographically characterized. After 3 weeks of healing, the samples were retrieved for histomorphometry. The nanomechanical properties of the surrounding bone were evaluated by nanoindentation. While both implants revealed similar bone-to-implant contact, the nanoindentation demonstrated that the tissue quality was significantly enhanced around the HA-coated implants, validating the postulated hypothesis.

  7. Structure of collagen adsorbed on a model implant surface resolved by polarization modulation infrared reflection-absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Brand, Izabella; Habecker, Florian; Ahlers, Michael; Klüner, Thorsten

    2015-03-01

    The polarization modulation infrared reflection-absorption spectra of collagen adsorbed on a titania surface and quantum chemical calculations are used to describe components of the amide I mode to the protein structure at a sub-molecular level. In this study, imino acid rich and poor fragments, representing the entire collagen molecule, are taken into account. The amide I mode of the collagen triple helix is composed of three absorption bands which involve: (i) (∼1690 cm-1) the Cdbnd O stretching modes at unhydrated groups, (ii) (1655-1673 cm-1) the Cdbnd O stretching at carbonyl groups at imino acids and glycine forming intramolecular hydrogen bonds with H atoms at both NH2 and, unusual for proteins, CH2 groups at glycine at a neighbouring chain and (iii) (∼1640 cm-1) the Cdbnd O stretching at carbonyl groups forming hydrogen bonds between two, often charged, amino acids as well as hydrogen bonds to water along the entire helix. The IR spectrum of films prepared from diluted solutions (c < 50 μg ml-1) corresponds to solution spectra indicating that native collagen molecules interact with water adsorbed on the titania surface. In films prepared from solutions (c ⩾ 50 μg ml-1) collagen multilayers are formed. The amide I mode is blue-shifted by 18 cm-1, indicating that intramolecular hydrogen bonds at imino acid rich fragments are weakened. Simultaneous red-shift of the amide A mode implies that the strength of hydrogen bonds at the imino acid poor fragments increases. Theoretically predicted distortion of the collagen structure upon adsorption on the titania surface is experimentally confirmed.

  8. Structure of collagen adsorbed on a model implant surface resolved by polarization modulation infrared reflection-absorption spectroscopy.

    PubMed

    Brand, Izabella; Habecker, Florian; Ahlers, Michael; Klüner, Thorsten

    2015-03-05

    The polarization modulation infrared reflection-absorption spectra of collagen adsorbed on a titania surface and quantum chemical calculations are used to describe components of the amide I mode to the protein structure at a sub-molecular level. In this study, imino acid rich and poor fragments, representing the entire collagen molecule, are taken into account. The amide I mode of the collagen triple helix is composed of three absorption bands which involve: (i) (∼1690cm(-1)) the CO stretching modes at unhydrated groups, (ii) (1655-1673cm(-1)) the CO stretching at carbonyl groups at imino acids and glycine forming intramolecular hydrogen bonds with H atoms at both NH2 and, unusual for proteins, CH2 groups at glycine at a neighbouring chain and (iii) (∼1640cm(-1)) the CO stretching at carbonyl groups forming hydrogen bonds between two, often charged, amino acids as well as hydrogen bonds to water along the entire helix. The IR spectrum of films prepared from diluted solutions (c<50μgml(-1)) corresponds to solution spectra indicating that native collagen molecules interact with water adsorbed on the titania surface. In films prepared from solutions (c⩾50μgml(-1)) collagen multilayers are formed. The amide I mode is blue-shifted by 18cm(-1), indicating that intramolecular hydrogen bonds at imino acid rich fragments are weakened. Simultaneous red-shift of the amide A mode implies that the strength of hydrogen bonds at the imino acid poor fragments increases. Theoretically predicted distortion of the collagen structure upon adsorption on the titania surface is experimentally confirmed.

  9. Following the course of pre-implantation embryo patterning by non-linear microscopy.

    PubMed

    Kyvelidou, Christiana; Tserevelakis, George J; Filippidis, George; Ranella, Anthi; Kleovoulou, Anastasia; Fotakis, Costas; Athanassakis, Irene

    2011-12-01

    Embryo patterning is subject to intense investigation. So far only large, microscopically obvious structures like polar body, cleavage furrow, pro-nucleus shape can be evaluated in the intact embryo. Using non-linear microscopic techniques, the present work describes new methodologies to evaluate pre-implantation mouse embryo patterning. Third Harmonic Generation (THG) imaging, by detecting mitochondrial/lipid body structures, could provide valuable and complementary information as to the energetic status of pre-implantation embryos, time evolution of different developmental stages, embryo polarization prior to mitotic division and blastomere equivalence. Quantification of THG imaging detected highest signalling in the 2-cell stage embryos, while evaluating a 12-18% difference between blastomeres at the 8-cell stage embryos. Such a methodology provides novel, non-intrusive imaging assays to follow up intracellular structural patterning associated with the energetic status of a developing embryo, which could be successfully used for embryo selection during the in vitro fertilization process.

  10. Dynamic community detection based on network structural perturbation and topological similarity

    NASA Astrophysics Data System (ADS)

    Wang, Peizhuo; Gao, Lin; Ma, Xiaoke

    2017-01-01

    Community detection in dynamic networks has been extensively studied since it sheds light on the structure-function relation of the overall complex systems. Recently, it has been demonstrated that the structural perturbation in static networks is excellent in characterizing the topology. In order to investigate the perturbation structural theory in dynamic networks, we extend the theory by considering the dynamic variation information between networks of consecutive time. Then a novel similarity is proposed by combing structural perturbation and topological features. Finally, we present an evolutionary clustering algorithm to detect dynamic communities under the temporal smoothness framework. Experimental results on both artificial and real dynamic networks demonstrate that the proposed similarity is promising in dynamic community detection since it improves the clustering accuracy compared with state-of-the-art methods, indicating the superiority of the presented similarity measure.

  11. An implantable blood pressure and flow transmitter.

    NASA Technical Reports Server (NTRS)

    Rader, R. D.; Meehan, J. P.; Henriksen, J. K. C.

    1973-01-01

    A miniature totally implantable FM/FM telemetry system has been developed to simultaneously measure blood pressure and blood flow, thus providing an appreciation of the hemodynamics of the circulation to the entire body or to a particular organ. Developed for work with animal subjects, the telemetry system's transmission time is controlled by an RF signal that permits an operating life of several months. Pressure is detected by a miniature intravascular transducer and flow is detected by an extravascular interferometric ultrasonic technique. Both pressure and flow are calibrated prior to implanting. The pressure calibration can be checked after the implanting by cannulation; flow calibration can be verified only at the end of the experiment by determining the voltage output from the implanted sensing system as a function of several measured flow rates. The utility of this device has been established by its use in investigating canine renal circulation during exercise, emotional encounters, administration of drugs, and application of accelerative forces.

  12. Reduced representation of protein structure: implications on efficiency and scope of detection of structural similarity

    PubMed Central

    2010-01-01

    Background Computational comparison of two protein structures is the starting point of many methods that build on existing knowledge, such as structure modeling (including modeling of protein complexes and conformational changes), molecular replacement, or annotation by structural similarity. In a commonly used strategy, significant effort is invested in matching two sets of atoms. In a complementary approach, a global descriptor is assigned to the overall structure, thus losing track of the substructures within. Results Using a small set of geometric features, we define a reduced representation of protein structure, together with an optimizing function for matching two representations, to provide a pre-filtering stage in a database search. We show that, in a straightforward implementation, the representation performs well in terms of resolution in the space of protein structures, and its ability to make new predictions. Conclusions Perhaps unexpectedly, a substantial discriminating power already exists at the level of main features of protein structure, such as directions of secondary structural elements, possibly constrained by their sequential order. This can be used toward efficient comparison of protein (sub)structures, allowing for various degrees of conformational flexibility within the compared pair, which in turn can be used for modeling by homology of protein structure and dynamics. PMID:20338066

  13. Implantable Heart Aid

    NASA Technical Reports Server (NTRS)

    1984-01-01

    CPI's human-implantable automatic implantable defibrillator (AID) is a heart assist system, derived from NASA's space circuitry technology, that can prevent erratic heart action known as arrhythmias. Implanted AID, consisting of microcomputer power source and two electrodes for sensing heart activity, recognizes onset of ventricular fibrillation (VF) and delivers corrective electrical countershock to restore rhythmic heartbeat.

  14. Machine oil inhibits the osseointegration of orthopaedic implants by impairing osteoblast attachment and spreading.

    PubMed

    Bonsignore, Lindsay A; Goldberg, Victor M; Greenfield, Edward M

    2015-07-01

    The most important factor contributing to short-term and long-term success of cementless total joint arthroplasties is osseointegration. Osseointegration leads to a direct structural and functional connection between living bone and the surface of an implant. Surface contaminants may remain on orthopaedic implants after sterilization procedures and impair osseointegration. For example, specific lots of hip replacement Sulzer Inter-OP(TM) acetabular shells that were associated with impaired osseointegration and early failure rates were found to be contaminated with both bacterial debris and machine oil residues. However, the effect of machine oil on implant integration is unknown. Therefore, the goal of this study was to determine if machine oil inhibits the osseointegration of orthopaedic implants. To test this hypothesis in vivo we used our murine model of osseointegration where titanium alloy implants are implanted into a unicortical pilot hole in the mid-diaphysis of the femur. We found that machine oil inhibited bone-to-implant contact and biomechanical pullout measures. Machine oil on titanium alloy discs inhibited early stages of MC3T3-E1 osteogenesis in vitro such as attachment and spreading. Inhibition of osteoblast attachment and spreading occurred in both areas with and without detectable oil. Osteoblast growth was in turn inhibited on discs with machine oil due to both a decrease in proliferation and an increase in cell death. Later stages of osteogenic differentiation and mineralization on titanium alloy discs were also inhibited. Thus, machine oil can inhibit osseointegration through cell autonomous effects on osteoblast cells. These results support routine testing by manufacturers of machine oil residues on orthopaedic implants.

  15. Electronic structure and ferromagnetism of Mn implanted n-type and p-type ZnO

    NASA Astrophysics Data System (ADS)

    Petit, Leon; Schulthess, Thomas; Svane, Axel; Temmerman, Walter; Szotek, Zdzislawa

    2004-03-01

    The prediction of room temperature magnetism in Mn doped ZnO has generated considerable interest in this compound, both from the experimental and theoretical point of views. In order to take into account the strong on-site correlations of the rather localized d-electrons, we use the self-interaction corrected (SIC)-LSD approximation. Within this scheme, the 3d electron manifold is considered to consist of both localized and itinerant states, both of which are treated on an equal footing, by adding a contribution for each d-electron to localize. By varying the relative proportions of localized and delocalized states, the most favourable (groundstate) configuration can be established. Our calculations show that the 3d electrons in Mn doped ZnO prefer to localize. We furthermore have studied the effects on the electronic structure, when Zn_1-xMn_xO is codoped with N atoms (n-type ZnOMn), and Ga and Sn atoms (n-type ZnOMn) respectively.

  16. The effect of bruxism on treatment planning for dental implants.

    PubMed

    Misch, Carl E

    2002-09-01

    Bruxism is a potential risk factor for implant failure. Excessive force is the primary cause of late implant complications. An appreciation of the etiology of crestal bone loss, failure of implants, failure to retain implant restorations, and fracture of components will lead the practitioner to develop a treatment plan that reduces force on implants and their restorations. The forces are considered in terms of magnitude, duration, direction, type, and magnification. Once the dentist has identified the source(s) of additional force on the implant system, the treatment plan is altered to contend with and reduce the negative sequelae on the bone, implant, and final restoration. One viable approach is to increase the implant-bone surface area. Additional implants can be placed to decrease stress on any one implant, and implants in molar regions should have an increased width. Use of more and wider implants decreases the strain on the prosthesis and also dissipates stress to the bone, especially at the crest. The additional implants should be positioned with intent to eliminate cantilevers when possible. Greater surface area implant designs made of titanium alloy and with an external hex design can also prove advantageous. Anterior guidance in mandibular excursions further decreases force and eliminates or reduces lateral posterior force. Metal occlusal surfaces decrease the risk of porcelain fracture and do not require as much abutment reduction, which in turn enhances prosthesis retention. The retention of the final prosthesis or super-structure is also improved with additional implant abutments. Night guards designed with specific features also are a benefit to initially diagnose the influence of occlusal factors for the patient, and as importantly, to reduce the influence of extraneous stress on implants and implant-retained restorations.

  17. Evaluation of Peri-Implant Bone Response in Implants Retrieved for Fracture After More Than 20 Years of Loading: A Case Series.

    PubMed

    Mangano, Carlo; Piattelli, Adriano; Mortellaro, Carmen; Mangano, Francesco; Perrotti, Vittoria; Iezzi, Giovanna

    2015-08-01

    Analysis of human retrieved dental implants is a useful tool in the evaluation of implant success and failure. More human histological data are needed from samples of long-term implant service. The aim of the present case series was a histological and histomorphometrical evaluation of the peri-implant bone responses in implants retrieved for fracture after more than 20 years loading. The archives of the Implant Retrieval Center of the Department of Medical, Oral and Biotechnological Sciences of the University of Chieti-Pescara, Italy were searched. A total of 5 implants, retrieved after a loading period of more than 20 years, were found: 2 had been retrieved after 20 years, 1 after 22 years, 1 after 25 years, and 1 after 27 years. All these implants were histologically processed. Compact, mature bone in close contact with the implant surface was observed in all specimens, with no gaps or connective tissue at the interface. Bone in different maturation stages was found around some implants. Primarily newly formed bone was observed in proximity of the implant surface, while mature compact bone with many remodeling areas and cement lines were detected in areas distant from the implant. Many primary and secondary osteons were present. Bone to implant contact percentage varied from 37.2% to 76%. In conclusion, histology and histomorphometry showed that even after many years of function, all implants presented more than adequate bone to implant contact and they appeared to be very well integrated in the peri-implant bone.

  18. A dynamic social systems model for considering structural factors in HIV prevention and detection.

    PubMed

    Latkin, Carl; Weeks, Margaret R; Glasman, Laura; Galletly, Carol; Albarracin, Dolores

    2010-12-01

    We present a model for HIV-related behaviors that emphasizes the dynamic and social nature of the structural factors that influence HIV prevention and detection. Key structural dimensions of the model include resources, science and technology, formal social control, informal social influences and control, social interconnectedness, and settings. These six dimensions can be conceptualized on macro, meso, and micro levels. Given the inherent complexity of structural factors and their interrelatedness, HIV prevention interventions may focus on different levels and dimensions. We employ a systems perspective to describe the interconnected and dynamic processes of change among social systems and their components. The topics of HIV testing and safer injection facilities (SIFs) are analyzed using this structural framework. Finally, we discuss methodological issues in the development and evaluation of structural interventions for HIV prevention and detection.

  19. A dynamic social systems model for considering structural factors in HIV prevention and detection

    PubMed Central

    Latkin, Carl; Weeks, Margaret; Glasman, Laura; Galletly, Carol; Albarracin, Dolores

    2010-01-01

    We present a model for HIV-related behaviors that emphasizes the dynamic and social nature of the structural factors that influence HIV prevention and detection. Key structural dimensions of the model include resources, science and technology, formal social control, informal social influences and control, social interconnectedness, and settings. These six dimensions can be conceptualized on macro, meso, and micro levels. Given the inherent complexity of structural factors and their interrelatedness, HIV prevention interventions may focus on different levels and dimensions. We employ a systems perspective to describe the interconnected and dynamic processes of change among social systems and their components. The topics of HIV testing and safer injection facilities are analyzed using this structural framework. Finally, we discuss methodological issues in the development and evaluation of structural interventions for HIV prevention and detection. PMID:20838871

  20. In situ and glancing angle X-ray diffraction of the structure change during and after the high temperature oxidation at 1000 ^{circ}C in air of an yttrium-implanted 304 steel

    NASA Astrophysics Data System (ADS)

    Riffard, F.; Buscail, H.; Caudron, E.; Cueff, R.; Rabaste, F.; Issartel, C.

    2002-07-01

    A study has been made of the initial stages of oxidation of yttrium ion implanted 304 steel in an attempt to shed some light on the so-called `reactive element effect' observed on chromia forming alloys. In situ XRD was used in order to observe the initial local structural changes during the high temperature oxidation process, while glancing angle XRD was used to monitor the longer range structural transformations taking place near the surface after cooling of oxidised samples. The treatment by ion implantation promotes the intensive establishment of the chromic layer, which leads to the inhibition of the formation of iron rich oxides, by preventing the diffusion of iron through the more compact and more uniform layer initially formed than it would be in the absence of yttrium. However, the identification of yttried phases could not be established. L'effet bénéfique d'un traitement par implantation ionique d'yttrium sur un acier 304 a été mis en évidence par le suivi d'analyses in situ développées par diffraction des rayons X au cours de son oxydation isotherme à 1000^{circ}C sous air. Malgré l'altération superficielle du substrat, le traitement par implantation ionique favorise l'établissement accéléré de la couche de chromine et inhibe la formation au cours du processus d'oxydation des oxydes contenant du fer, réputés peu protecteurs, car faiblement adhérents. Des analyses conduites après refroidissement des échantillons oxydés par diffraction des rayons X sous incidence rasante révèlent la localisation de la structure spinelle au manganèse à l'interface le plus externe. L'identification de phases yttriées n'a cependant pu être établie.

  1. The structural and bio-corrosion barrier performance of Mg-substituted fluorapatite coating on 316L stainless steel human body implant

    NASA Astrophysics Data System (ADS)

    Sharifnabi, A.; Fathi, M. H.; Eftekhari Yekta, B.; Hossainalipour, M.

    2014-01-01

    In this study, Mg-substituted fluorapatite coatings were deposited on medical grade AISI 316L stainless steel via sol-gel dip coating method. Phase composition, crystallite size and degree of crystallinity of the obtained coatings were evaluated by X-ray diffraction (XRD) analysis. Fourier transform infrared (FTIR) spectroscopy was also used to evaluate functional groups of the obtained coatings. The surface morphology and cross-section of the final coatings were studied using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy was used to determine elemental chemical composition of the obtained coatings. In order to determine and compare the corrosion behavior of uncoated and Mg-substituted fluorapatite coated 316L stainless steel, electrochemical potentiodynamic polarization tests were performed in physiological solutions at 37 ± 1 °C. Moreover, the released metallic ions from uncoated and coated substrates were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES) within 2 months of immersing in Ringer's solution at 36.5 ± 1 °C as an indication of biocompatibility. The results showed that fluoride and magnesium were successfully incorporated into apatite lattice structure and the prepared coatings were nanostructured with crystallinity of about 70%. Obtained coatings were totally crack-free and uniform and led to decrease in corrosion current densities of 316L stainless steel in physiological solutions. In addition, coated sample released much less ions such as Fe, Cr and Ni in physiological media. Therefore, it was concluded that Mg-substituted fluorapatite coatings could improve the corrosion resistance and biocompatibility of 316L stainless steel human body implants.

  2. Hidden corrosion detection in aircraft aluminum structures using laser ultrasonics and wavelet transform signal analysis.

    PubMed

    Silva, M Z; Gouyon, R; Lepoutre, F

    2003-06-01

    Preliminary results of hidden corrosion detection in aircraft aluminum structures using a noncontact laser based ultrasonic technique are presented. A short laser pulse focused to a line spot is used as a broadband source of ultrasonic guided waves in an aluminum 2024 sample cut from an aircraft structure and prepared with artificially corroded circular areas on its back surface. The out of plane surface displacements produced by the propagating ultrasonic waves were detected with a heterodyne Mach-Zehnder interferometer. Time-frequency analysis of the signals using a continuous wavelet transform allowed the identification of the generated Lamb modes by comparison with the calculated dispersion curves. The presence of back surface corrosion was detected by noting the loss of the S(1) mode near its cutoff frequency. This method is applicable to fast scanning inspection techniques and it is particularly suited for early corrosion detection.

  3. Trends in Cochlear Implants

    PubMed Central

    Zeng, Fan-Gang

    2004-01-01

    More than 60,000 people worldwide use cochlear implants as a means to restore functional hearing. Although individual performance variability is still high, an average implant user can talk on the phone in a quiet environment. Cochlear-implant research has also matured as a field, as evidenced by the exponential growth in both the patient population and scientific publication. The present report examines current issues related to audiologic, clinical, engineering, anatomic, and physiologic aspects of cochlear implants, focusing on their psychophysical, speech, music, and cognitive performance. This report also forecasts clinical and research trends related to presurgical evaluation, fitting protocols, signal processing, and postsurgical rehabilitation in cochlear implants. Finally, a future landscape in amplification is presented that requires a unique, yet complementary, contribution from hearing aids, middle ear implants, and cochlear implants to achieve a total solution to the entire spectrum of hearing loss treatment and management. PMID:15247993

  4. Embedded Ultrasonic Structural Radar with Piezoelectric Wafer Active Sensors for Damage Detection in Cylindrical Shell Structures

    DTIC Science & Technology

    2004-04-01

    nuclear steam generator tubing. Alleyne et. al.13 used guided waves to detect cracks and corrosion in chemical plant pipework . A brief review of the...310, 1994 13. Alleyne, D.N., Pavlakovic, B., Lowe, M.J.S., Cawley, P. (2001) "Rapid, Long Range Inspection of Chemical Plant Pipework Using Guided

  5. [Conceptual approach to classification of implant supported prosthesis for edentulous patients].

    PubMed

    Trezubov, V N; Rozov, R A; Azarin, G S

    2017-01-01

    The aim of this study was the creation of a conceptual model of the standard implant prosthetics for edentulous patients using the data of comprehensive examination and implantation prosthetics in 372 patients aged 38 to 80 years (201 women, 171 men) with 582 implant supported prosthesis of various types, supporting on implants «Nobel Replace Select/Groove» and «Nobel Speedy Groove» (3675 implants). Clinical classification of implant-supported prosthesis for edentulous patients included 5 classes: class 1 (1-2 implants) included 6.2% of implant supported prosthesis, class 2 (3-4 implant) - 19.2% of prostheses, class 3 (5-6 implants) - 30.2% of replacement structures; IV (7-10 implants) - 44%, and V - 0,3%. Restoration class was age-dependent.

  6. Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence

    SciTech Connect

    Yerci, S.; Serincan, U.; Dogan, I.; Tokay, S.; Genisel, M.; Aydinli, A.; Turan, R.

    2006-10-01

    Silicon nanocrystals, average sizes ranging between 3 and 7 nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800 deg. C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. While the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix.

  7. Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence

    NASA Astrophysics Data System (ADS)

    Yerci, S.; Serincan, U.; Dogan, I.; Tokay, S.; Genisel, M.; Aydinli, A.; Turan, R.

    2006-10-01

    Silicon nanocrystals, average sizes ranging between 3 and 7nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800°C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. While the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix.

  8. Structure-dependent deuterium release from ion implanted beryllium: Comparison between Be(1 1 2¯ 0) and Be(poly)

    NASA Astrophysics Data System (ADS)

    Oberkofler, M.; Reinelt, M.; Lindig, S.; Linsmeier, Ch.

    2009-02-01

    The temperature-driven release of deuterium implanted as keV ions into metallic beryllium is measured by temperature-programmed desorption (TPD). TPD spectra from single and polycrystalline Be implanted with 1 keV ions are compared. The high-temperature desorption stage (T > 700 K) is attributed to the release of deuterium trapped at several types of energetically different ion-induced defects. A release peak around 850 K is recorded in the single crystal, while in the polycrystal all deuterium desorbs below this temperature. An increase in the maximum release temperature is observed after implantation of the polycrystal with higher ion energies (2 and 3 keV). We propose an interpretation of the experimental results based on two types of traps, with depth distributions adapted to the implantation energy. Preliminary TMAP7 calculations qualitatively reproduce the shifts in the maximum desorption temperature, observed in the polycrystal at different implantation energies. The difference between the single and the polycrystal is explained by a higher density of surviving defects in the single crystal. Diffusion of mobile defects to grain boundaries and subsequent annihilation is proposed as the dominant mechanism for differences in deuterium desorption from Be(1 1 2 bar 0) and Be(poly).

  9. Detection of sudden structural damage using blind source separation and time-frequency approaches

    NASA Astrophysics Data System (ADS)

    Morovati, V.; Kazemi, M. T.

    2016-05-01

    Seismic signal processing is one of the most reliable methods of detecting the structural damage during earthquakes. In this paper, the use of the hybrid method of blind source separation (BSS) and time-frequency analysis (TFA) is explored to detect the changes in the structural response data. The combination of the BSS and TFA is applied to the seismic signals due to the non-stationary nature of them. Firstly, the second-order blind identification technique is used to decompose the response signal of structural vibration into modal coordinate signals which will be mono-components for TFA. Then each mono-component signal is analyzed to extract instantaneous frequency of structure. Numerical simulations and a real-world seismic-excited structure with time-varying frequencies show the accuracy and robustness of the developed algorithm. TFA of extracted sources shows that used method can be successfully applied to structural damage detection. The results also demonstrate that the combined method can be used to identify the time instant of structural damage occurrence more sharply and effectively than by the use of TFA alone.

  10. Reliability of void detection in structural ceramics using scanning laser acoustic microscopy

    NASA Technical Reports Server (NTRS)

    Roth, D. J.; Klima, S. J.; Kiser, J. D.; Baaklini, G. Y.

    1985-01-01

    The reliability of scanning laser acoustic microscopy (SLAM) for detecting surface voids in structural ceramic test specimens was statistically evaluated. Specimens of sintered silicon nitride and sintered silicon carbide, seeded with surface voids, were examined by SLAM at an ultrasonic frequency of 100 MHz in the as fired condition and after surface polishing. It was observed that polishing substantially increased void detectability. Voids as small as 100 micrometers in diameter were detected in polished specimens with 0.90 probability at a 0.95 confidence level. In addition, inspection times were reduced up to a factor of 10 after polishing. The applicability of the SLAM technique for detection of naturally occurring flaws of similar dimensions to the seeded voids is discussed. A FORTRAN program listing is given for calculating and plotting flaw detection statistics.

  11. Self-adaptive asymmetric on-line boosting for detecting anatomical structures

    NASA Astrophysics Data System (ADS)

    Wu, Hong; Tajbakhsh, Nima; Xue, Wenzhe; Liang, Jianming

    2012-03-01

    In this paper, we propose a self-adaptive, asymmetric on-line boosting (SAAOB) method for detecting anatomical structures in CT pulmonary angiography (CTPA). SAAOB is novel in that it exploits a new asymmetric loss criterion with self-adaptability according to the ratio of exposed positive and negative samples and in that it has an advanced rule to update sample's importance weight taking account of both classification result and sample's label. Our presented method is evaluated by detecting three distinct thoracic structures, the carina, the pulmonary trunk and the aortic arch, in both balanced and imbalanced conditions.

  12. Modified timing characteristic of a scintillation detection system with photonic crystal structures.

    PubMed

    Liu, Jinliang; Liu, Bo; Zhu, Zhichao; Chen, Liang; Hu, Jing; Xu, Mengxuan; Cheng, Chuanwei; Ouyang, Xiaoping; Zhang, Zhongbing; Ruan, Jinlu; He, Shiyi; Liu, Linyue; Gu, Mu; Chen, Hong

    2017-03-01

    It is intuitively expected that an enhanced light extraction of a scintillator can be easily achieved by photonic crystal structures. Here, we demonstrate a modified timing characteristic for a detection system induced by enhanced light extraction with photonic crystal structures. Such improvement is due to the enhanced light extraction which can be clearly proven by the independent measurements of the light output and the timing resolution. The present investigation is advantageous to promote the development of a scintillation detection system performance based on the time-of-flight measurement.

  13. High-sensitive nonlinear detection of steroids by resonant double grating waveguide structures-based immunosensors

    NASA Astrophysics Data System (ADS)

    Muriano, Alejandro; Salvador, J.-Pablo; Galve, Roger; Marco, M.-Pilar; Thayil K. N., Anisha; Loza-Alvarez, Pablo; Soria, Silvia

    2011-01-01

    We report the non linear fluorescence real-time detection of methylboldenone, an androgenic anabolic steroid used illegally as growth promoter based on a resonant sensing chip: a double grating waveguide structure. The limit of detection of this synthetic steroid is two orders of magnitude lower than the Minimum Required Performance Limit required by the World Anti-Doping Agency. The immunoreagents have been have been immobilized onto the surface of the resonant sensor after being activated with phosphonohexanoic acid spacers. The developed immunosensor presents great potential as a robust sensing device for fast and early detection of illegal dopants and food contaminants.

  14. A Unified Framework for Salient Structure Detection by Contour-Guided Visual Search.

    PubMed

    Yang, Kai-Fu; Li, Hui; Li, Chao-Yi; Li, Yong-Jie

    2016-08-01

    We define the task of salient structure (SS) detection to unify the saliency-related tasks, such as fixation prediction, salient object detection, and detection of other structures of interest in cluttered environments. To solve such SS detection tasks, a unified framework inspired by the two-pathway-based search strategy of biological vision is propo