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Sample records for high positive frequency

  1. Phone positioning influence in high-frequency audiometry.

    PubMed

    Crepaldi de Almeida, Elizabeth Oliveira; Nishimori, Aparecida Yumi

    2006-01-01

    Research considers high frequency tonal audiometry as a tool for the early diagnosis of auditory alterations derived from etiological agents. to investigate possible differences in high frequency audiometry of individuals with normal hearing, based on the person who places the earphone. clinical and experimental study with 55 undergraduate students from a country side branch of the São Paulo State University, with normal hearing, underwent two tests each; for the first, the evaluator positioned the earphone on the participant; for the second one, the participant did it by him/herself. An AC40 audiometer calibrated to emit pure tone was used in the frequencies of 10, 12.5, and 16 kHz. The kappa(k) coefficient statistical analysis was used to verify the agreement between the two ways of earphone positioning of earphone, bearing a [FORMULA: SEE TEXT]0.70 kappa value as a criterion. Results attained for both ears were below this criterion, with k average of 0.50. results indicate a risk of compromising the exam reliability when the patient him/herself adjusts phone to his/her own ear. when performing audiometric assessment, this variable must be considered in order to attain reliable results.

  2. Frequencies of inaudible high-frequency sounds differentially affect brain activity: positive and negative hypersonic effects.

    PubMed

    Fukushima, Ariko; Yagi, Reiko; Kawai, Norie; Honda, Manabu; Nishina, Emi; Oohashi, Tsutomu

    2014-01-01

    The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs) above the human audible range (max. 20 kHz) activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz) of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz) to observe changes in the alpha2 frequency component (10-13 Hz) of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG), which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC). When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect), while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect). These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC.

  3. Frequencies of Inaudible High-Frequency Sounds Differentially Affect Brain Activity: Positive and Negative Hypersonic Effects

    PubMed Central

    Fukushima, Ariko; Yagi, Reiko; Kawai, Norie; Honda, Manabu; Nishina, Emi; Oohashi, Tsutomu

    2014-01-01

    The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs) above the human audible range (max. 20 kHz) activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect. In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz) of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz) to observe changes in the alpha2 frequency component (10–13 Hz) of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG), which we previously reported as an index of the hypersonic effect. Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC). When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect), while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect). These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC. PMID:24788141

  4. Carbon dioxide elimination and gas displacement vary with piston position during high-frequency oscillatory ventilation.

    PubMed

    Hamel, Donna S; Katz, Andrew L; Craig, Damian M; Davies, John D; Cheifetz, Ira M

    2005-03-01

    Alterations in gas displacement in pediatric patients ventilated with the SensorMedics 3100A high-frequency oscillator are most commonly manipulated by adjusting the amplitude, frequency, and percent inspiratory time. The piston-position-and-displacement indicator is commonly centered and subsequently not adjusted. That practice may limit the clinician's ability to optimize carbon dioxide elimination. We hypothesized that varying the piston position would alter gas displacement and carbon dioxide elimination. We conducted an observational study in a tertiary pediatric intensive care unit and a correlated bench study. In the clinical study, 24 patients were ventilated with a SensorMedics 3100A high-frequency oscillator. Transcutaneously measured carbon dioxide ((tCO(2))) values were documented with the piston-position-and-displacement indicator in left, center, and right positions. In the bench study the oscillator was set and maintained at: mean airway pressure 15 cm H(2)O, inspiratory time 33% of respiratory-cycle time, bias flow 20 L/min. A pneumotachometer attached to a respiratory mechanics monitor was placed between the ventilator circuit and a test lung. Data were collected with the piston-position-and-displacement indicator at the left, center, and right positions with frequencies of 4-14 Hz and amplitudes of 25-55 cm H(2)O. Data were collected over a 3-minute time period for each combination of frequency, amplitude, and piston-position-and-displacement-indicator position. We compared the data with repeated-measures analysis of variance. Pairwise comparisons were performed with a 2-tailed Student's test with Bonferroni correction. Among the 24 patients (tCO(2)) was significantly associated with the position of the piston (p < 0.007). In the bench study, gas displacement was higher when the piston-position-and-displacement indicator was positioned to the left (than when at the center position) 91.7% of the time (p < 0.0001). When the piston-position

  5. Low Frequency Error Analysis and Calibration for High-Resolution Optical Satellite's Uncontrolled Geometric Positioning

    NASA Astrophysics Data System (ADS)

    Wang, Mi; Fang, Chengcheng; Yang, Bo; Cheng, Yufeng

    2016-06-01

    The low frequency error is a key factor which has affected uncontrolled geometry processing accuracy of the high-resolution optical image. To guarantee the geometric quality of imagery, this paper presents an on-orbit calibration method for the low frequency error based on geometric calibration field. Firstly, we introduce the overall flow of low frequency error on-orbit analysis and calibration, which includes optical axis angle variation detection of star sensor, relative calibration among star sensors, multi-star sensor information fusion, low frequency error model construction and verification. Secondly, we use optical axis angle change detection method to analyze the law of low frequency error variation. Thirdly, we respectively use the method of relative calibration and information fusion among star sensors to realize the datum unity and high precision attitude output. Finally, we realize the low frequency error model construction and optimal estimation of model parameters based on DEM/DOM of geometric calibration field. To evaluate the performance of the proposed calibration method, a certain type satellite's real data is used. Test results demonstrate that the calibration model in this paper can well describe the law of the low frequency error variation. The uncontrolled geometric positioning accuracy of the high-resolution optical image in the WGS-84 Coordinate Systems is obviously improved after the step-wise calibration.

  6. Effects of Position and Operator on High-frequency Ultrasound Scan Quality

    PubMed Central

    Burk, Ruth S.; Parker, Angela; Sievers, Lisa; Rooney, Melissa B.; Pepperl, Anathea; Schubert, Christine M.; Grap, Mary Jo

    2015-01-01

    Objectives High-frequency ultrasound may evaluate those at risk for pressure ulcers. Images may be obtained by clinicians with limited training. The prone position is recommended for obtaining sacral scans but may not be feasible in the critically ill. This study investigated image quality using multiple operators and a variety of patient positions. Research Methodology Sacral scans were performed in three randomized positions in 50 volunteers by three different investigators using a 20 MHz ultrasound system. General linear models and ANOVA random effects models were used to examine the effects of operator and position on image quality rating, and measures of dermal thickness, and dermal density. Results The best scan for each position and operator was used for analysis (N=447 images). Image rating varied by operator (p=0.0004), although mean ratings were 3.5 or above for all operators. Dermal thickness was less for the prone position than in 90° or 60° side-lying positions (p=0.0137, p=0.0003). Dermal density was lower for the prone position than for the 90° or 60° positions (p<0.0001 for both). Conclusions These data show that overall scan quality was acceptable in all positions with all operators. However, differences were found between side-lying positions and the prone for dermal thickness and dermal density measures. PMID:25636253

  7. Effect of high-frequency positive-pressure ventilation on halothane ablation of hypoxic pulmonary vasoconstriction.

    PubMed

    Hall, S M; Chapleau, M; Cairo, J; Levitzky, M G

    1985-08-01

    High-frequency positive-pressure ventilation (HFPPV) was compared to intermittent positive-pressure ventilation (IPPV) during unilateral atelectasis with and without halothane anesthesia. Dogs with electromagnetic flow probes chronically implanted on their main (Qt) and left (Ql) pulmonary arteries were ventilated via Carlen's dual-lumen endotracheal tubes. In eight closed-chest dogs, about 43% of the cardiac output perfused the left lung during bilateral ventilation by either a Harvard animal respirator (IPPV) or a Health-dyne model 300 high-frequency ventilator (HFPPV). Unilateral atelectasis decreased blood flow (Ql/Qt) to that lung. Ql/Qt was 19 +/- 1% with HFPPV during left-lung atelectasis and right-lung ventilation, compared to 32 +/- 1% with unilateral IPPV. This suggests that HFPPV permits stronger hypoxic pulmonary vasoconstriction. Addition of 1% halothane increased blood flow to the atelectatic left lung during unilateral ventilation with IPPV but not with HFPPV. This suggests that halothane decreases the effects of hypoxic pulmonary vasoconstriction during conventional ventilation but not during HFPPV.

  8. Inferring Behavioral States of Grazing Livestock from High-Frequency Position Data Alone

    PubMed Central

    Homburger, Hermel; Schneider, Manuel K.; Hilfiker, Sandra; Lüscher, Andreas

    2014-01-01

    Studies of animal behavior are crucial to understanding animal-ecosystem interactions, but require substantial efforts in visual observation or sensor measurement. We investigated how classifying behavioral states of grazing livestock using global positioning data alone depends on the classification approach, the preselection of training data, and the number and type of movement metrics. Positions of grazing cows were collected at intervals of 20 seconds in six upland areas in Switzerland along with visual observations of animal behavior for comparison. A total of 87 linear and cumulative distance metrics and 15 turning angle metrics across multiple time steps were used to classify position data into the behavioral states of walking, grazing, and resting. Five random forest classification models, a linear discriminant analysis, a support vector machine, and a state-space model were evaluated. The most accurate classification of the observed behavioral states in an independent validation dataset was 83%, obtained using random forest with all available movement metrics. However, the state-specific accuracy was highly unequal (walking: 36%, grazing: 95%, resting: 58%). Random undersampling led to a prediction accuracy of 77%, with more balanced state-specific accuracies (walking: 68%, grazing: 82%, resting: 68%). The other evaluated machine-learning approaches had lower classification accuracies. The state-space model, based on distance to the preceding position and turning angle, produced a relatively low accuracy of 64%, slightly lower than a random forest model with the same predictor variables. Given the successful classification of behavioral states, our study promotes the more frequent use of global positioning data alone for animal behavior studies under the condition that data is collected at high frequency and complemented by context-specific behavioral observations. Machine-learning algorithms, notably random forest, were found very useful for classification

  9. High frequency of neurosyphilis in HIV-positive patients diagnosed with early syphilis.

    PubMed

    Firlag-Burkacka, E; Swiecki, P; Cielniak, I; Siwak, E; Gizinska, J; Bakowska, E; Kubicka, J; Pulik, P; Kowalski, J; Podlasin, R; Horban, A

    2016-05-01

    Syphilis is an infection frequently seen with HIV, and European guidelines on the management of syphilis suggest that HIV-infected patients may have an increased risk of early neurological involvement, sometimes asymptomatic. Recent study shows a relationship between neurosyphilis and cerebrospinal fluid (CSF) HIV viral load (VL), which in turn may be associated with subsequent neurocognitive decline. The aim of the study was estimation of the frequency of neurosyphilis among HIV-positive patients with early syphilis. The study included all patients diagnosed with early syphilis who had lumbar puncture performed in the years 2008-2012. Analysis included CSF parameters (serology, mononuclear cells, protein, glucose, chloride and lactate levels), CD4 count, serum VL and highly active antiretroviral therapy (HAART). Diagnosis of neurosyphilis was confirmed by CSF serology [positive fluorescent treponemal antibody and/or Venereal Disease Research Laboratory (VDRL) test(s)] and increased number of mononuclear cells. Statistical analysis included χ(2) tests with an accepted significance level of P < 0.05. Lumbar puncture was performed in 72 patients, all men, with median age 33 (interquartile range 11) years. Neurosyphilis was confirmed in 65 (90.28%) of the patients. No statistically significant association between CSF parameters and CD4 count was found. However, statistically significant associations were found only between pleocytosis and serum VL > 1000 HIV-1 RNA copies/mL (P = 0.0451), as well as HAART treatment (P = 0.0328). The proportion of confirmed neurosyphilis cases, also in patients with low serum VDRL titres, was very high. Considering the high proportion of patients who objected to having LP performed in the absence of neurological symptoms and the risk associated with this procedure, it may be preferable to use treatments with good CNS penetration in all HIV-positive patients with early syphilis. © 2015 British HIV Association.

  10. High mass positive ions and molecules in capacitively-coupled radio-frequency CF4 plasmas

    NASA Astrophysics Data System (ADS)

    Schwarzenbach, W.; Cunge, G.; Booth, J. P.

    1999-06-01

    The positive ions and neutral radicals arriving at the earthed walls of a capacitively-coupled radio-frequency pure CF4 plasma were analyzed using a quadrupole mass spectrometer adapted for high masses. Experiments were performed at 50 and 200 mTorr, in an empty reactor and with Si and SiO2-coated Si substrates on the powered electrode. High mass ions and neutrals were detected, up to 500 and 300 amu, respectively. The abundance of high-mass species was greatest in the presence of silicon wafers and at higher pressure. The observed ion masses can be separated into distinct series, originating from different initial bases to which successive CF2 units have been added. We, therefore, propose that these high-mass species are the result of a gas phase polymerization process consisting of CF2 addition reactions, in agreement with a model proposed recently by our group. The influence of a silicon substrate derives primarily from the strong decrease that it induces in the concentration of F atoms, which otherwise limit the concentration of CF2 and of chain initiating species.

  11. High-frequency variations in Earth rotation from Global Positioning System data

    NASA Astrophysics Data System (ADS)

    Rothacher, M.; Beutler, G.; Weber, R.; Hefty, J.

    2001-01-01

    Using the data of the global, dense Global Positioning System (GPS) network established by the International GPS Service a continuous, uninterrupted series of subdaily Earth rotation parameters (ERPs) with a time resolution of 2 hours has been generated at the Center for Orbit Determination in Europe. The series starts in January 1995 and has a length of more than 3 years. Starting from the 2-hour ERP values of this, to our knowledge, unique time series, the high-frequency variations in Universal Time (UT1) and polar motion (PM) due to ocean tides are studied and a set of sine and cosine coefficients is estimated for all the major tidal terms at nearly diurnal and semidiurnal frequencies. The GPS series is not very homogeneous (various processing changes during the 3 years) and still short compared to the length of very long baseline interferometry (VLBI) and satellite laser ranging (SLR) data sets. However, the results derived from this series are already of the same quality as the results from VLBI and SLR. A comparison of the tidal coefficients stemming from all three space-geodetic techniques shows an agreement on the 1 μs level for UT1 and 10 microarc seconds (μas) for PM, respectively. The RMS difference between the ocean tide amplitudes estimated from GPS data and from TOPEX/Poseidon altimeter data amounts to 0.7-0.9 μs in UT1 and 9-13 μas in PM. The residual spectrum that remains after the removal of all tidal terms has a noise level of ˜5-10 μas in PM and 0.5-1 μs in UT1 and contains nontidal signals (up to 55 μas in PM and 3 μs in UT1) that might be due to the impact of the satellite orbit modeling (12-hour revolution period of the satellites) or, alternatively, due to atmospheric or oceanic normal modes.

  12. Short-Term Effects of High-Frequency Chest Compression and Positive Expiratory Pressure in Patients With Cystic Fibrosis

    PubMed Central

    Fainardi, Valentina; Longo, Francesco; Faverzani, Silvia; Tripodi, Maria Candida; Chetta, Alfredo; Pisi, Giovanna

    2011-01-01

    Background Cystic fibrosis patients require daily airway clearance therapies. The primary objective of this study was to compare the short-term efficacy of high-frequency chest compression and positive expiratory pressure mask on expectorated sputum, pulmonary function, and oxygen saturation in patients with CF hospitalized for an acute pulmonary exacerbation. Methods A controlled randomized cross-over trial with 24 hours between treatments was used. Thirty-four CF patients (26 ± 6.5 years) were included in the study. Before and 30 minutes after each treatment were recorded: pulmonary function testing, oxygen saturation, and perceived dyspnea. Preference for the two devices was assessed. Results No statistically significant difference between high-frequency chest compression and positive expiratory pressure mask was found in sputum production and in lung function testing. A reduction in SpO2 was found after positive expiratory pressure mask (98 ± 1.0% versus 97 ± 1.2%; P < 0.001). Both treatments induced a statistically significant increase in Borg scale for dyspnea without differences between them. Patients reported greater satisfaction with positive expiratory pressure mask than with high-frequency chest compression (P < 0.001). Conclusion High-frequency chest compression and positive expiratory pressure mask have comparable short-term effects on expectorated sputum and lung function. Although positive expiratory pressure mask was associated with a lower SpO2, it was better tolerated than high-frequency chest compression. Keywords Airway clearance therapies; High-frequency chest compression; Sputum; Cystic fibrosis PMID:22393338

  13. Coexistence under positive frequency dependence.

    PubMed Central

    Molofsky, J.; Bever, J. D.; Antonovics, J.

    2001-01-01

    Negative frequency dependence resulting from interspecific interactions is considered a driving force in allowing the coexistence of competitors. While interactions between species and genotypes can also result in positive frequency dependence, positive frequency dependence has usually been credited with hastening the extinction of rare types and is not thought to contribute to coexistence. In the present paper, we develop a stochastic cellular automata model that allows us to vary the scale of frequency dependence and the scale of dispersal. The results of this model indicate that positive frequency dependence will allow the coexistence of two species at a greater rate than would be expected from chance. This coexistence arises from the generation of banding patterns that will be stable over long time-periods. As a result, we found that positive frequency-dependent interactions over local spatial scales promote coexistence over neutral interactions. This result was robust to variation in boundary conditions within the simulation and to variation in levels of disturbance. Under all conditions, coexistence is enhanced as the strength of positive frequency-dependent interactions is increased. PMID:11217898

  14. The Effect of Ionospheric Variability on the Accuracy of High Frequency Position Location

    DTIC Science & Technology

    1981-08-01

    are superpositions of several frequency components . Figure 2 shows the constant plasma frequency contours (that is, variation of reflection heights) as...basic space and time decorrelation parameters have been listed above. If the concept of the single-station locator is retained, then the inherent...Entered) CONTENTS LIST OF FIGURES ........................................................... 4 LIST OF TABLES

  15. High frequency strand slippage mutations in CTCF in MSI-positive endometrial cancers.

    PubMed

    Zighelboim, Israel; Mutch, David G; Knapp, Amy; Ding, Li; Xie, Mingchao; Cohn, David E; Goodfellow, Paul J

    2014-01-01

    Tumors with defective mismatch repair acquire large numbers of strand slippage mutations including frameshifts in coding sequence repeats. We identified a mutational hotspot, p.T204fs, in the insulator-binding protein (CTCF) in MSI-positive endometrial cancers. Although CTCF was described as a significantly mutated gene by the endometrial cancer TCGA, the A₇ track variants leading to T204 frameshifts were not reported. Reanalysis of TCGA data using Pindel revealed frequent T204fs mutations, confirming CTCF is an MSI target gene and revealed the same frameshifts in tumors with intact mismatch repair. We show that T204fs transcripts are subject to nonsense-mediated decay and as such, T204fs mutations are unlikely to act as dominant negatives. The spectrum and pattern of mutations observed is consistent with CTCF acting as a haploinsufficient tumor suppressor.

  16. High frequency jet ventilation and intermittent positive pressure ventilation. Effect of cerebral blood flow in patients after open heart surgery

    SciTech Connect

    Pittet, J.F.; Forster, A.; Suter, P.M. )

    1990-02-01

    Attenuation of ventilator-synchronous pressure fluctuations of intracranial pressure has been demonstrated during high frequency ventilation in animal and human studies, but the consequences of this effect on cerebral blood flow have not been investigated in man. We compared the effects of high frequency jet ventilation and intermittent positive pressure ventilation on CBF in 24 patients investigated three hours after completion of open-heart surgery. The patients were investigated during three consecutive periods with standard sedation (morphine, pancuronium): a. IPPV; b. HFJV; c. IPPV. Partial pressure of arterial CO{sub 2} (PaCO{sub 2}: 4.5-5.5 kPa) and rectal temperature (35.5 to 37.5{degree}C) were maintained constant during the study. The CBF was measured by intravenous {sup 133}Xe washout technique. The following variables were derived from the cerebral clearance of {sup 133}Xe: the rapid compartment flow, the initial slope index, ie, a combination of the rapid and the slow compartment flows, and the ratio of fast compartment flow over total CBF (FF). Compared to IPPV, HFJV applied to result in the same mean airway pressure did not produce any change in pulmonary gas exchange, mean systemic arterial pressure, and cardiac index. Similarly, CBF was not significantly altered by HFJV. However, important variations of CBF values were observed in three patients, although the classic main determinants of CBF (PaCO{sub 2}, cerebral perfusion pressure, Paw, temperature) remained unchanged. Our results suggest that in patients with normal systemic hemodynamics, the effects of HFJV and IPPV on CBF are comparable at identical levels of mean airway pressure.

  17. High positive frequency of antibodies to metallothionein and heat shock protein 70 in sera of patients with metal allergy

    PubMed Central

    JIN, G-B; NAKAYAMA, H; SHMYHLO, M; INOUE, S; KONDO, M; IKEZAWA, Z; OUCHI, Y; CYONG, J-C

    2003-01-01

    Two principal types of stress protein, heat shock proteins (hsps) and metallothionein (MT), are induced in cells responding to a variety of stresses. They play an important role in protecting cells from these stresses. However, many reports indicate that antibodies to hsps are present in human serum and are associated with several autoimmunity diseases. Metals, which are commonly allergenic to humans, induce both MT and hsp70 (one of the hsps family). Until now, there has been no report of any antibody to MT in human serum. In the present study, serum samples from healthy controls (Group I), and patients suffering from atopic dermatitis without (Group II) or with (Group III) metal allergy, were measured for antibodies to MT and hsp70, using an enzyme-linked immunosorbent assay (ELISA). Metal allergy was confirmed by patch testing. We first found that antibody to MT exists in human serum. We also found a high positive frequency of antibody to MT (51·3%) and to hsp70 (43·6%) in the sera of Group III, compared to those of Group I (3·8% and 5·1%) or Group II (6·4% and 5·1%). Furthermore, there was a strong positive correlation between antibody to MT and antibody to hsp70 in Group III (P = 0·0013), but not in Group I and Group II. Our results indicate that antibody to MT exists in human serum, as do antibodies to hsps, and suggest that elevated levels of MT and hsp70 antibodies are associated with metal allergy in atopic patients. PMID:12562388

  18. A high frequency of MDSCs in sepsis patients, with the granulocytic subtype dominating in gram-positive cases.

    PubMed

    Janols, Helena; Bergenfelz, Caroline; Allaoui, Roni; Larsson, Anna-Maria; Rydén, Lisa; Björnsson, Sven; Janciauskiene, Sabina; Wullt, Marlene; Bredberg, Anders; Leandersson, Karin

    2014-11-01

    The causative microorganisms dictate the type of MDSC generated in sepsis patients, and a large proportion of PMN-MDSCs in gram-positive sepsis includes immunosuppressive myeloid blasts. MDSCs constitute a heterogeneous population of immature myeloid cells that potently suppress immune responses. They were identified originally in cancer patients and have since been reported to occur also in chronic inflammation, autoimmunity, and even bacterial infections. Human MDSCs are commonly divided into Mo-MDSCs and granulocytic (PMN-MDSCs) subtypes. To what extent the bona fide cancer MDSCs are representative of the proposed MDSCs found in other diseases is not well known. PMN-MDSCs have been found previously to be enriched among LDGs in density gradient-centrifuged blood. In this study, we analyzed potential MDSCs in sepsis patients with different causative microorganisms, using total peripheral blood compared with density gradient-centrifuged blood. We found a high frequency of typical CD14(+)HLA-DR(low) Mo-MDSCs in all sepsis patients, whereas the typical PMN-MDSCs, as well as a prominent CD14(low) PMN-MDSC-like population, appeared preferentially in gram-positive cases. The CD14(low) PMN-MDSC variant was demonstrated to suppress T cell proliferation in vitro via a ROS-dependent mechanism, to display an increased IL-10:TNF-α ratio, and to present with signs of immaturity: blast morphology and low cytokine levels. We conclude that a spectrum of cells with MDSC features is enriched in sepsis and that the microbial origin of sepsis contributes to the substantial interindividual patient variation in the MDSC pattern.

  19. Assessment of the accuracy of PPP for very-high-frequency dynamic, satellite positioning and earthquake modeling

    NASA Astrophysics Data System (ADS)

    Moschas, F.; Avallone, A.; Moschonas, N.; Saltogianni, V.; Stiros, S.

    2012-04-01

    With the advent of various GPS/GNSS Point Positioning techniques, it became possible to model the dynamic displacement history of specific points during large and rather moderate earthquakes using satellite positioning, 1Hz and occasionally 10Hz sampling data. While there is evidence that the obtained data are precise, experience from monitoring of engineering structures like bridges, indicates that GPS/GNSS records are contaminated by coloured (mostly background noise) noise even in the cases of differential-type analysis of the satellite signals. This made the necessary the assessment of the results of different PPP processing using supervised learning techniques. Our work was based on a modification of an experiment first made to assess the potential of GPS to measure oscillations of civil engineering structures. A 10Hz GNSS antenna-receiver unit was mounted on the top of a vertical rod, fixed on the ground and forced to controlled oscillations. Oscillations were also recorded by a robotic theodolite and an accelerometer, and the whole experiment was video-recorded. A second 10Hz GNSS antenna-receiver unit was left on stable ground, in a nearby position. The rod was forced to semi-static motion (bending) and then was left to oscillate freely until still, and the whole movement was recorded by all sensors. GNSS data were analyzed both in kinematic mode and in PPP mode, using the GIPSY-OASIS II (http://gipsy-oasis.jpl.nasa.gov) (only GPS) and the PPP CRCS facility (GPS + GLONAS). Recorded PPP and differential kinematic processing coordinates (apparent displacements) were found to follow the real motion, but to be contaminated by a long-period noise. On the contrary, the short-period component of the apparent PPP displacements, obtained using high-pass filtering, were very much consistent with the real motion, with sub-mm mean deviation, though occasionally contaminated by clipping. The assessment of the very-high frequency GPS noise will provide useful information

  20. Low frequency of positive skin tests in asthmatic patients infected with Schistosoma mansoni exposed to high levels of mite allergens.

    PubMed

    Medeiros, Manoel; Almeida, Maria C; Figueiredo, Joanemile P; Atta, Ajax M; Mendes, Carlos M C; Araújo, Maria I; Taketomi, Ernesto A; Terra, Silvia A; Silva, Deise A O; Carvalho, Edgar M

    2004-04-01

    Helminthic infections and allergic diseases are highly prevalent in many parts of the world. Although skin reactivity to indoor allergens is decreased in subjects from helminthic endemic areas, the degree of exposure to mite allergens has not yet been investigated in these areas. This study evaluated the association between exposure to dust mites and skin reactivity to mite allergens in subjects with a history of wheezing in the last 12 months selected from a rural endemic area for schistosomiasis (group I, n = 21), and two non-Schistosoma mansoni endemic locale, a rural area (group II, n = 21) and a urban slum area (group III, n = 21). All subjects were evaluated by skin prick tests with mite allergens, and for total and specific immunoglobulin E (IgE) against dust mites, antibodies for S. mansoni, and for intestinal parasites. Dust samples from each subjects' home were quantified for mite allergen and species of the mite identification. Except for S. mansoni infection which was more prevalent in group I than in groups II and III (p < 0.0001), the prevalence of intestinal parasites, and total and specific IgE levels were similar for all groups. Despite the levels of mite allergens and specifically to Der p 1 detected in dust samples of subjects home from all three areas, the frequency of positive skin reactivity to mite antigens was significantly lower (19.0%) in subjects from group I relative to group II (76.2%) and group III (57.1%; p < 0.001). This result suggests that S. mansoni infection could modulate the immediate hypersensitivity skin response to mite allergens in highly exposed subjects.

  1. High-frequency ECG

    NASA Technical Reports Server (NTRS)

    Tragardh, Elin; Schlegel, Todd T.

    2006-01-01

    ventricular surface and were signal-averaged and filtered in the 30-250 Hz frequency range. The results showed that the decrease noted in the HF-QRS correlated linearly with the local conduction delay. The results suggest that HF-QRS is a potent indicator of disturbed local conduction. An alternative theory is that HF-QRS reflect the shape of the original electrocardiographic signal. Bennhagen et al showed that root mean square (RMS) voltage values of the depolarization signal correlate poorly with the signal amplitude but highly with the first and second derivatives, i.e. the velocity and the acceleration of the signal. It has also been suggested that the autonomic nervous system affects HF-QRS. For example, sitting up causes significant changes in HF-QRS in some leads compared to the supine position [Douglas et al., 2006]. Unpublished results indicate that familial dysautonomic patients (both vagal and sympathetic degeneration) have very little Reduced Amplitude Zones (RAZ) formation . Athletic individuals, especially elite athletes, who have vagally-mediated changes on the conventional ECG (i.e. early repolarization, bradycardia) have increased RAZ formation. Further electrophysiological studies are needed, however, to better understand the underlying mechanisms of HF-QRS. Several investigators have studied HF-QRS in different cardiac conditions, including acute myocardial ischemia and myocardial infarction (MI). However, in order for clinicians to confidently use HF-QRS as an adjunct to standard ECG, more knowledge about the characteristics of HF-QRS is needed.

  2. Positional stability and radial dynamics of sonoluminescent bubbles under bi-harmonic driving: Effect of the high-frequency component and its relative phase.

    PubMed

    Rosselló, J M; Dellavale, D; Bonetto, F J

    2016-07-01

    The use of bi-frequency driving in sonoluminescence has proved to be an effective way to avoid the spatial instability (pseudo-orbits) developed by bubbles in systems with high viscous liquids like sulfuric or phosphoric acids. In this work, we present extensive experimental and numerical evidence in order to assess the effect of the high frequency component (PAc(HF)) of a bi-harmonic acoustic pressure field on the dynamic of sonoluminescent bubbles in an aqueous solution of sulfuric acid. The present study is mainly focused on the role of the harmonic frequency (Nf0) and the relative phase between the two frequency components (φb) of the acoustic field on the spatial, positional and diffusive stability of the bubbles. The results presented in this work were analyzed by means of three different approaches. First, we discussed some qualitative considerations about the changes observed in the radial dynamics, and the stability of similar bubbles under distinct bi-harmonic drivings. Later, we have investigated, through a series of numerical simulations, how the use of high frequency harmonic components of different order N, affects the positional stability of the SL bubbles. Furthermore, the influence of φb in their radius temporal evolution is systematically explored for harmonics ranging from the second to the fifteenth harmonic (N=2-15). Finally, a multivariate analysis based on the covariance method is performed to study the dependences among the parameters characterizing the SL bubble. Both experimental and numerical results indicate that the impact of PAc(HF) on the positional instability and the radial dynamics turns to be progressively negligible as the order of the high frequency harmonic component grows (i.e. N ≫ 1), however its effectiveness on the reduction of the spatial instability remains unaltered or even improved.

  3. High frequency of false-positive signals in a real-time PCR-based "Plus/Minus" assay.

    PubMed

    Nowrouzian, Forough L; Adlerberth, Ingegerd; Wold, Agnes E

    2009-01-01

    Molecular biological methods using real-time polymerase chain reaction (RT-PCR) for detection of bacterial and viral genes in different environments have been developed into assays from different commercial sources. Applied Biosystems include and support two applications with their TaqMan instrument: the "Plus/Minus" and the "Allelic Discrimination" assays. These approaches are RT-PCR based, use short primers and fluorescent-labeled TaqMan probes and include three processes: a pre-read run, a PCR-amplification run, and a post-read run. In the "Plus/Minus" assay, samples and controls (distilled water) are loaded into the instrument, which calculates a positive or a negative outcome based on differences in signals between samples and the controls. When testing the "Plus/Minus" assay for detection of usp genes encoding a uropathogenic specific protein in Escherichia coli, an inordinately high proportion of false-positive signals was observed. This was shown to be due to a serious methodological deficiency. Our observations indicate that an adequate no-template control closely matching the target samples in all aspects, including amount of DNA, is required to establish a correct threshold in the pre-read run that forms the basis for further calculations in the post-read run of the "Plus/Minus" assay.

  4. Experimentally constrained CA1 fast-firing parvalbumin-positive interneuron network models exhibit sharp transitions into coherent high frequency rhythms

    PubMed Central

    Ferguson, Katie A.; Huh, Carey Y. L.; Amilhon, Bénédicte; Williams, Sylvain; Skinner, Frances K.

    2013-01-01

    The coupling of high frequency oscillations (HFOs; >100 Hz) and theta oscillations (3–12 Hz) in the CA1 region of rats increases during REM sleep, indicating that it may play a role in memory processing. However, it is unclear whether the CA1 region itself is capable of providing major contributions to the generation of HFOs, or if they are strictly driven through input projections. Parvalbumin-positive (PV+) interneurons may play an essential role in these oscillations due to their extensive connections with neighboring pyramidal cells, and their characteristic fast-spiking. Thus, we created mathematical network models to investigate the conditions under which networks of CA1 fast-spiking PV+ interneurons are capable of producing high frequency population rhythms. We used whole-cell patch clamp recordings of fast-spiking, PV+ cells in the CA1 region of an intact hippocampal preparation in vitro to derive cellular properties, from which we constrained an Izhikevich-type model. Novel, biologically constrained network models were constructed with these individual cell models, and we investigated networks across a range of experimentally determined excitatory inputs and inhibitory synaptic strengths. For each network, we determined network frequency and coherence. Network simulations produce coherent firing at high frequencies (>90 Hz) for parameter ranges in which PV-PV inhibitory synaptic conductances are necessarily small and external excitatory inputs are relatively large. Interestingly, our networks produce sharp transitions between random and coherent firing, and this sharpness is lost when connectivity is increased beyond biological estimates. Our work suggests that CA1 networks may be designed with mechanisms for quickly gating in and out of high frequency coherent population rhythms, which may be essential in the generation of nested theta/high frequency rhythms. PMID:24155715

  5. High Frequency EPR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gatteschi, D.

    EPR has traditionally been used in order to obtain structural information on transition metal compounds, with exciting frequencies in the range 9-35 GHz.The recent availability of high magnetic field has prompted the use of higher frequencies. In this contribution the advantages of using High-Field-High-Frequency EPR (HF EPR) experiments are reviewed. After a brief introduction aiming to recall the fundamentals of EPR spectroscopy, a short description of the experimental apparatus needed to perform HF EPR measurements is provided. The remaining sections report selected examples showing how much information can be obtained by HF EPR spectra. They range from individual ions with integer spin to molecular clusters. Particular attention is devoted to the so called Single Molecule Magnets, SMM, i.e. to molecular clusters which show slow relaxation of the magnetization at low temperature. This effect is due to Ising type magnetic anisotropy which has been efficiently monitored through HF EPR s pectroscopy.

  6. ALMA High Frequency Techniques

    NASA Astrophysics Data System (ADS)

    Meyer, J. D.; Mason, B.; Impellizzeri, V.; Kameno, S.; Fomalont, E.; Chibueze, J.; Takahashi, S.; Remijan, A.; Wilson, C.; ALMA Science Team

    2015-12-01

    The purpose of the ALMA High Frequency Campaign is to improve the quality and efficiency of science observing in Bands 8, 9, and 10 (385-950 GHz), the highest frequencies available to the ALMA project. To this end, we outline observing modes which we have demonstrated to improve high frequency calibration for the 12m array and the ACA, and we present the calibration of the total power antennas at these frequencies. Band-to-band (B2B) transfer and bandwidth switching (BWSW), techniques which improve the speed and accuracy of calibration at the highest frequencies, are most necessary in Bands 8, 9, and 10 due to the rarity of strong calibrators. These techniques successfully enable increased signal-to-noise on the calibrator sources (and better calibration solutions) by measuring the calibrators at lower frequencies (B2B) or in wider bandwidths (BWSW) compared to the science target. We have also demonstrated the stability of the bandpass shape to better than 2.4% for 1 hour, hidden behind random noise, in Band 9. Finally, total power observing using the dual sideband receivers in Bands 9 and 10 requires the separation of the two sidebands; this procedure has been demonstrated in Band 9 and is undergoing further testing in Band 10.

  7. Positive Selection of Deleterious Alleles through Interaction with a Sex-Ratio Suppressor Gene in African Buffalo: A Plausible New Mechanism for a High Frequency Anomaly

    PubMed Central

    van Hooft, Pim; Greyling, Ben J.; Getz, Wayne M.; van Helden, Paul D.; Zwaan, Bas J.; Bastos, Armanda D. S.

    2014-01-01

    Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations), we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has important

  8. Positive selection of deleterious alleles through interaction with a sex-ratio suppressor gene in African Buffalo: a plausible new mechanism for a high frequency anomaly.

    PubMed

    van Hooft, Pim; Greyling, Ben J; Getz, Wayne M; van Helden, Paul D; Zwaan, Bas J; Bastos, Armanda D S

    2014-01-01

    Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations), we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has important

  9. High Frequency of CD8 Positive Lymphocyte Infiltration Correlates with Lack of Lymph Node Involvement in Early Rectal Cancer

    PubMed Central

    Däster, Silvio; Eppenberger-Castori, Serenella; Hirt, Christian; Zlobec, Inti; Delko, Tarik; Nebiker, Christian A.; Soysal, Savas D.; Amicarella, Francesca; Iezzi, Giandomenica; Sconocchia, Giuseppe; Heberer, Michael; Lugli, Alessandro; Spagnoli, Giulio C.; Kettelhack, Christoph; Terracciano, Luigi; Oertli, Daniel; von Holzen, Urs; Tornillo, Luigi; Droeser, Raoul A.

    2014-01-01

    Aims. A trend towards local excision of early rectal cancers has prompted us to investigate if immunoprofiling might help in predicting lymph node involvement in this subgroup. Methods. A tissue microarray of 126 biopsies of early rectal cancer (T1 and T2) was stained for several immunomarkers of the innate and the adaptive immune response. Patients' survival and nodal status were analyzed and correlated with infiltration of the different immune cells. Results. Of all tested markers, only CD8 (P = 0.005) and TIA-1 (P = 0.05) were significantly more frequently detectable in early rectal cancer biopsies of node negative as compared to node positive patients. Although these two immunomarkers did not display prognostic effect “per se,” CD8+ and, marginally, TIA-1 T cell infiltration could predict nodal involvement in univariate logistic regression analysis (OR 0.994; 95% CI 0.992–0.996; P = 0.009 and OR 0.988; 95% CI 0.984–0.994; P = 0.05, resp.). An algorithm significantly predicting the nodal status in early rectal cancer based on CD8 together with vascular invasion and tumor border configuration could be calculated (P < 0.00001). Conclusion. Our data indicate that in early rectal cancers absence of CD8+ T-cell infiltration helps in predicting patients' nodal involvement. PMID:25609852

  10. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique.

  11. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  12. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  13. High frequency of mutations in exon 10 of the porphobilinogen deaminase gene in patients with a CRIM-positive subtype of acute intermittent porphyria

    SciTech Connect

    Gu, X.F.; Rooij, F. de; Voortman, G.; Velde, K.T.; Nordmann, Y.; Grandchamp, B.

    1992-09-01

    Acute intermittent porphyria (AIP) is an autosomal dominant disease characterized by a partial deficiency of porphobilinogen (PBG) deaminase. Different subtypes of the disease have been defined, and more than 10 different mutations have been described. The authors focused their study on exon 10, since they previously found that three different mutations were located in this exon and that two of them seemed to be relatively common. They used denaturing gradient gel electrophoresis (DGGE) after in vitro amplification to detect all possible mutations in exon 10 in 41 unrelated AIP patients. In about one-fourth of these patients they could distinguish three abnormal migration patterns, indicating the presence of various mutations. Additional sequencing demonstrated the presence of three different single-base substitutions. Two of these mutations had already been described. A third one consisted of a C-to-T transition located at position 499 of the PBG deaminase mRNA and resulted in an Arg-to-Trp substitution. All three mutations were found in patients with crossreacting immunological material (CRIM)-positive forms of AlP. The high frequency of these mutations make DGGE analysis of exon 10 a useful approach allowing the direct detection of the DNA abnormality in most of the families with the CRIM-positive subtype of AlP. 23 refs., 3 figs., 1 tab.

  14. Age related vascular endothelial function following lifelong sedentariness: positive impact of cardiovascular conditioning without further improvement following low frequency high intensity interval training.

    PubMed

    Grace, Fergal M; Herbert, Peter; Ratcliffe, John W; New, Karl J; Baker, Julien S; Sculthorpe, Nicholas F

    2015-01-01

    Aging is associated with diffuse impairments in vascular endothelial function and traditional aerobic exercise is known to ameliorate these changes. High intensity interval training (HIIT) is effective at improving vascular function in aging men with existing disease, but its effectiveness remains to be demonstrated in otherwise healthy sedentary aging. However, the frequency of commonly used HIIT protocols may be poorly tolerated in older cohorts. Therefore, the present study investigated the effectiveness of lower frequency HIIT (LfHIIT) on vascular function in a cohort of lifelong sedentary (SED; n = 22, age 62.7 ± 5.2 years) men compared with a positive control group of lifelong exercisers (LEX; n = 17, age 61.1 ± 5.4 years). The study consisted of three assessment phases; enrolment to the study (Phase A), following 6 weeks of conditioning exercise in SED (Phase B) and following 6 weeks of low frequency HIIT in both SED and LEX (LfHIIT; Phase C). Conditioning exercise improved FMD in SED (3.4 ± 1.5% to 4.9 ± 1.1%; P < 0.01) such that the difference between groups on enrolment (3.4 ± 1.5% vs. 5.3 ± 1.4%; P < 0.01) was abrogated. This was maintained but not further improved following LfHIIT in SED whilst FMD remained unaffected by LfHIIT in LEX. In conclusion, LfHIIT is effective at maintaining improvements in vascular function achieved during conditioning exercise in SED. LfHIIT is a well-tolerated and effective exercise mode for reducing cardiovascular risk and maintaining but does not improve vascular function beyond that achieved by conditioning exercise in aging men, irrespective of fitness level.

  15. Age related vascular endothelial function following lifelong sedentariness: positive impact of cardiovascular conditioning without further improvement following low frequency high intensity interval training

    PubMed Central

    Grace, Fergal M.; Herbert, Peter; Ratcliffe, John W.; New, Karl J.; Baker, Julien S.; Sculthorpe, Nicholas F.

    2015-01-01

    Abstract Aging is associated with diffuse impairments in vascular endothelial function and traditional aerobic exercise is known to ameliorate these changes. High intensity interval training (HIIT) is effective at improving vascular function in aging men with existing disease, but its effectiveness remains to be demonstrated in otherwise healthy sedentary aging. However, the frequency of commonly used HIIT protocols may be poorly tolerated in older cohorts. Therefore, the present study investigated the effectiveness of lower frequency HIIT (LfHIIT) on vascular function in a cohort of lifelong sedentary (SED; n =22, age 62.7 ± 5.2 years) men compared with a positive control group of lifelong exercisers (LEX; n = 17, age 61.1 ± 5.4 years). The study consisted of three assessment phases; enrolment to the study (Phase A), following 6 weeks of conditioning exercise in SED (Phase B) and following 6 weeks of low frequency HIIT in both SED and LEX (LfHIIT; Phase C). Conditioning exercise improved FMD in SED (3.4 ± 1.5% to 4.9 ± 1.1%; P <0.01) such that the difference between groups on enrolment (3.4 ± 1.5% vs. 5.3 ± 1.4%; P <0.01) was abrogated. This was maintained but not further improved following LfHIIT in SED whilst FMD remained unaffected by LfHIIT in LEX. In conclusion, LfHIIT is effective at maintaining improvements in vascular function achieved during conditioning exercise in SED. LfHIIT is a well‐tolerated and effective exercise mode for reducing cardiovascular risk and maintaining but does not improve vascular function beyond that achieved by conditioning exercise in aging men, irrespective of fitness level. PMID:25626864

  16. High Resolution Frequency Swept Imaging.

    DTIC Science & Technology

    1980-02-14

    image resolution comparable to an ordinary photographic camera. In addition to inconvenient size, the cost of filling such a large aperture with... cost of implementing a LFTDR. Because of the large difference between the high frequency imaging frequencies and the low frequency reference frequency... cost . In addition since the measured reference phase must be multiplied by a factor a equal to the ratio of the imaging to the reference frequency

  17. High-frequency broadband transformers

    NASA Astrophysics Data System (ADS)

    London, S. E.; Tomashevich, S. V.

    1981-05-01

    A systematic review of the theory and design principles of high-frequency broadband transformers is presented. It is shown that the transformers of highest performance are those whose coils consist of strips of double-wire and multiwire transmission lines. Such devices are characterized by a wide operating frequency range, and make possible operation at microwave frequencies at high levels of transmitted power.

  18. Long-term multicentre randomised controlled study of high frequency chest wall oscillation versus positive expiratory pressure mask in cystic fibrosis.

    PubMed

    McIlwaine, Maggie Patricia; Alarie, Nancy; Davidson, George F; Lands, Larry C; Ratjen, Felix; Milner, Ruth; Owen, Blythe; Agnew, Jennifer L

    2013-08-01

    Positive expiratory pressure (PEP) is the most commonly used method of airway clearance (AC) in Canada for patients with cystic fibrosis (CF) whereas, in some countries, high frequency chest wall oscillation (HFCWO) is the preferred form of AC. There have been no long-term studies comparing the efficacy of HFCWO and PEP in the CF population. To determine the long-term efficacy of HFCWO compared with PEP mask therapy in the treatment of CF as measured by the number of pulmonary exacerbations (PEs). A randomised controlled study was performed in 12 CF centres in Canada. After a 2-month washout period, subjects were randomised to perform either HFCWO or PEP mask therapy for 1 year. 107 subjects were enrolled in the study; 51 were randomised to PEP and 56 to HFCWO. There were 19 dropouts within the study period, of which 16 occurred prior to or at the time of randomisation. There were significant differences between the groups in the mean number of PEs (1.14 for PEP vs 2.0 for HFCWO) and time to first PE (220 days for PEP vs 115 days for HFCWO, p=0.02). There was no significant difference in lung function, health-related quality of life scores or patient satisfaction scores between the two groups. PEP mask therapy required a shorter treatment time. The results of this study favour PEP and do not support the use of HFCWO as the primary form of AC in patients with CF. NCT00817180.

  19. High frequency pulsed electromigration

    NASA Astrophysics Data System (ADS)

    Malone, David Wayne

    Electromigration life tests were performed on copper-alloyed aluminum test structures that were representative of modern CMOS metallization schemes, complete with Ti/TiN cladding layers and a tungsten-plug contact at the cathode. A total of 18 electrical stress treatments were applied. One was a DC current of 15 mA. The other 17 were pulsed currents, varied according to duty cycle and frequency. The pulse amplitude was 15 mA (˜2.7 × 10sp6 A/cmsp2) for all treatments. Duty cycles ranged from 33.3% to 80%, and frequencies fell into three rough ranges-100 KHz, 1 MHz, and 100 MHz. The ambient test temperature was 200sp°C in all experiments. Six to 9 samples were subjected to each treatment. Experimental data were gathered in the form of test stripe resistance versus time, R(t). For purposes of lifetime analysis, "failure" was defined by the criterion R(t)/R(0) = 1.10, and the median time to failure, tsb{50}, was used as the primary basis of comparison between test groups. It was found that the dependence of tsb{50} on pulse duty cycle conformed rather well to the so-called "average current density model" for duty cycles of 50% and higher. Lifetimes were less enhanced for a duty cycle of 33.3%, but they were still considerably longer than an "on-time" model would predict. No specific dependence of tsb{50} on pulse frequency was revealed by the data, that is, reasonably good predictions of tsb{50} could be made by recognizing the dominant influence of duty cycle. These findings confirm that IC miniaturization can be more aggressively pursued than an on-time prediction would allow. It is significant that this was found to be true for frequencies on the order of 100 MHz, where many present day digital applications operate. Post-test optical micrographs were obtained for each test subject in order to determine the location of electromigration damage. The pulse duty cycle was found to influence the location. Most damage occurred at the cathode contact, regardless of

  20. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing [Houston, TX; Zettl, Alexander K [Kensington, TX

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  1. Comparison of high-frequency chest wall oscillation and oscillating positive expiratory pressure in the home management of cystic fibrosis: a pilot study.

    PubMed

    Oermann, C M; Sockrider, M M; Giles, D; Sontag, M K; Accurso, F J; Castile, R G

    2001-11-01

    Enhanced airway clearance is thought to result in better-maintained pulmonary function in cystic fibrosis (CF). Postural drainage, percussion, and vibration (PDPV) have been the primary airway clearance technique (ACT) employed in CF for over 40 years. Two new airway clearance modalities are high-frequency chest wall oscillation (HFCWO) and oscillating positive expiratory pressure (OPEP). This pilot study was undertaken to evaluate the efficacy of these techniques during home use, assess patient satisfaction with them as compared to PDPV, and assess the feasibility of performing a definitive comparative trial. The prospective, randomized, multicenter crossover trial was conducted at three urban academic CF Care Centers. Twenty-nine CF patients, 9-39 years of age, participated. Subjects performed 4 weeks each of HFCWO and OPEP following 2-week lead-in/washout periods. Spirometry, lung volumes, National Institutes of Health and Petty Scores, and a satisfaction survey were performed at baseline and after each treatment period. An ACT preference survey was completed at the conclusion of the study. Twenty-four subjects completed both therapies. There were no statistically significant differences between therapies for spirometry, lung volumes, or clinical scores. No significant safety issues arose during the study period. Compliance between therapies was similar. Significant differences among therapies existed in patient satisfaction. Given a choice of therapy, 50% of subjects chose HFCWO, 37% OPEP, and 13% PDPV. This study suggests that HFCWO and OPEP are safe and as effective as patients' routine therapies when used for airway clearance in a home setting. Patient satisfaction and preference differ among ACTs and should be considered when prescribing home therapy. A definitive, multi-center, comparative study evaluating long-term efficacy of these techniques is feasible.

  2. Binaural beats at high frequencies.

    PubMed

    McFadden, D; Pasanen, E G

    1975-10-24

    Binaural beats have long been believed to be audible only at low frequencies, but an interaction reminiscent of a binaural beat can sometimes be heard when different two-tone complexes of high frequency are presented to the two ears. The primary requirement is that the frequency separation in the complex at one ear be slightly different from that in the other--that is, that there be a small interaural difference in the envelope periodicities. This finding is in accord with other recent demonstrations that the auditory system is not deaf to interaural time differences at high frequencies.

  3. Intensity and frequency: dimensions underlying positive and negative affect.

    PubMed

    Diener, E; Larsen, R J; Levine, S; Emmons, R A

    1985-05-01

    Research on emotions and several happiness scales suggest that positive and negative affect are strongly inversely correlated. However, work on subjective well-being indicates that over time, positive and negative affect are independent across persons. In order to reconcile this inconsistency, two dimensions are proposed for personal affective structure: the frequency of positive versus negative affect and the intensity of affect. Subjects in three studies completed daily and momentary reports on their moods. In support of the intensity dimension, the correlations between positive and negative intensity were strong and positive in all three studies. The intensities of specific emotions across persons were also highly correlated. Across the three studies the frequency and intensity of affect varied independently. Although average levels of positive and negative affect showed low correlations, this relation became strongly inverse when intensity was partialed out. Thus the intensity dimension helps explain the relative independence of positive and negative affect. In addition, emotional intensity is offered as a new personality dimension that manifests interesting characteristics.

  4. High power, high frequency component test facility

    NASA Technical Reports Server (NTRS)

    Roth, Mary Ellen; Krawczonek, Walter

    1990-01-01

    The NASA Lewis Research Center has available a high frequency, high power laboratory facility for testing various components of aerospace and/or terrestrial power systems. This facility is described here. All of its capabilities and potential applications are detailed.

  5. Screening for latent tuberculosis in Norwegian health care workers: high frequency of discordant tuberculin skin test positive and interferon-gamma release assay negative results.

    PubMed

    Gran, Gerd; Aßmus, Jörg; Dyrhol-Riise, Anne Ma

    2013-04-17

    Tuberculosis (TB) presents globally a significant health problem and health care workers (HCW) are at increased risk of contracting TB infection. There is no diagnostic gold standard for latent TB infection (LTBI), but both blood based interferon-gamma release assays (IGRA) and the tuberculin skin test (TST) are used. According to the national guidelines, HCW who have been exposed for TB should be screened and offered preventive anti-TB chemotherapy, but the role of IGRA in HCW screening is still unclear. A total of 387 HCW working in clinical and laboratory departments in three major hospitals in the Western region of Norway with possible exposure to TB were included in a cross-sectional study. The HCW were asked for risk factors for TB and tested with TST and the QuantiFERON®TB Gold In-Tube test (QFT). A logistic regression model analyzed the associations between risk factors for TB and positive QFT or TST. A total of 13 (3.4%) demonstrated a persistent positive QFT, whereas 214 (55.3%) had a positive TST (≥ 6 mm) and 53 (13.7%) a TST ≥ 15 mm. Only ten (4.7%) of the HCW with a positive TST were QFT positive. Origin from a TB-endemic country was the only risk factor associated with a positive QFT (OR 14.13, 95% CI 1.37 - 145.38, p=0.026), whereas there was no significant association between risk factors for TB and TST ≥ 15 mm. The five HCW with an initial positive QFT that retested negative all had low interferon-gamma (IFN-γ) responses below 0.70 IU/ml when first tested. We demonstrate a low prevalence of LTBI in HCW working in hospitals with TB patients in our region. The "IGRA-only" seems like a desirable screening strategy despite its limitations in serial testing, due to the high numbers of discordant TST positive/IGRA negative results in HCW, probably caused by BCG vaccination or boosting due to repetitive TST testing. Thus, guidelines for TB screening in HCW should be updated in order to secure accurate diagnosis of LTBI and offer proper

  6. Screening for latent tuberculosis in Norwegian health care workers: high frequency of discordant tuberculin skin test positive and interferon-gamma release assay negative results

    PubMed Central

    2013-01-01

    Background Tuberculosis (TB) presents globally a significant health problem and health care workers (HCW) are at increased risk of contracting TB infection. There is no diagnostic gold standard for latent TB infection (LTBI), but both blood based interferon-gamma release assays (IGRA) and the tuberculin skin test (TST) are used. According to the national guidelines, HCW who have been exposed for TB should be screened and offered preventive anti-TB chemotherapy, but the role of IGRA in HCW screening is still unclear. Methods A total of 387 HCW working in clinical and laboratory departments in three major hospitals in the Western region of Norway with possible exposure to TB were included in a cross-sectional study. The HCW were asked for risk factors for TB and tested with TST and the QuantiFERON®TB Gold In-Tube test (QFT). A logistic regression model analyzed the associations between risk factors for TB and positive QFT or TST. Results A total of 13 (3.4%) demonstrated a persistent positive QFT, whereas 214 (55.3%) had a positive TST (≥ 6 mm) and 53 (13.7%) a TST ≥ 15 mm. Only ten (4.7%) of the HCW with a positive TST were QFT positive. Origin from a TB-endemic country was the only risk factor associated with a positive QFT (OR 14.13, 95% CI 1.37 - 145.38, p = 0.026), whereas there was no significant association between risk factors for TB and TST ≥ 15 mm. The five HCW with an initial positive QFT that retested negative all had low interferon-gamma (IFN-γ) responses below 0.70 IU/ml when first tested. Conclusions We demonstrate a low prevalence of LTBI in HCW working in hospitals with TB patients in our region. The “IGRA-only” seems like a desirable screening strategy despite its limitations in serial testing, due to the high numbers of discordant TST positive/IGRA negative results in HCW, probably caused by BCG vaccination or boosting due to repetitive TST testing. Thus, guidelines for TB screening in HCW should be updated in order to

  7. [Principals of high frequency surgery].

    PubMed

    Bergler, W F; Hörmann, K; Hammerschmitt, N; Huber, K

    2004-10-01

    Electrosurgical instruments are routinely and daily applied at a variety of indications in Otorhinolaryngology. They can be used for cutting, coagulation and devitalisation. All have in common that the high frequency energy is transported into the tissue via an instrument and by this causes a thermal change. Depending on the duration and characteristic of the electricity a vaporisation of the tissue is effected through coagulation, devitalisation and carbonisation. The knowledge of the effects on the tissue by the choice of the different instrument parameters and application systems is essential for an ingenious therapeutically indication. In principal the following application methods for electrosurgery by modulation of the high frequency parameters are distinguished: the monopolar and the bipolar coagulation and devitalisation and the monopolar and the bipolar cutting. This article deals with the physical basis, the effects in the tissue as well as the single application methods of the high frequency surgery.

  8. High-Frequency Channel Characterization

    DTIC Science & Technology

    2005-09-30

    High-Frequency Channel Characterization Michael B. Porter, Paul Hursky, Martin Siderius Heat , Light, and Sound Research, Inc. 12730 High...Physical Sciences (Bruce Abraham) • Arizona State University (Tolga Duman, Subhadeep Roy) • Heat , Light, and Sound Research, Inc.(M. Porter, A. Abawi, P...NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Heat , Light, and Sound Research, Inc,12730 High

  9. High frequency integrated MOS filters

    NASA Technical Reports Server (NTRS)

    Peterson, C.

    1990-01-01

    Several techniques exist for implementing integrated MOS filters. These techniques fit into the general categories of sampled and tuned continuous-time filters. Advantages and limitations of each approach are discussed. This paper focuses primarily on the high frequency capabilities of MOS integrated filters.

  10. Quantum position verification in bounded-attack-frequency model

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Liu, Bin; Wen, QiaoYan

    2016-11-01

    In 2011, Buhrman et al. proved that it is impossible to design an unconditionally secure quantum position verification (QPV) protocol if the adversaries are allowed to previously share unlimited entanglements. Afterwards, people started to design secure QPV protocols in practical settings, e.g. the bounded-storage model, where the adversaries' pre-shared entangled resources are supposed to be limited. Here we focus on another practical factor that it is very difficult for the adversaries to perform attack operations with unlimitedly high frequency. Concretely, we present a new kind of QPV protocols, called non-simultaneous QPV. And we prove the security of a specific non-simultaneous QPV protocol with the assumption that the frequency of the adversaries' attack operations is bounded, but no assumptions on their pre-shared entanglements or quantum storage. Actually, in our nonsimultaneous protocol, the information whether there comes a signal at present time is also a piece of command. It renders the adversaries "blind", that is, they have to execute attack operations with unlimitedly high frequency no matter whether a signal arrives, which implies the non-simultaneous QPV is also secure in the bounded-storage model.

  11. Low occurrence of HBsAg but high frequency of transient occult HBV infection in vaccinated and HBIG-administered infants born to HBsAg positive mothers.

    PubMed

    Zhou, Shan; Li, Tingting; Allain, Jean-Pierre; Zhou, Bin; Zhang, Yuming; Zhong, Mei; Fu, Yongshui; Li, Chengyao

    2017-05-23

    The status of chronic and occult HBV infection (OBI) in neonatal hepatitis B vaccine and immunoglobulin (HBIG) vaccinated infants born to HBsAg+ mothers was investigated at a major hospital in China. Seventy-seven and 15 blood samples were collected in first or second follow-up detection from the vaccinated babies aged 3-36 months born to 43 HBsAg+ or plus 25 HBeAg+ mothers. HBV infection was analyzed between the paired baby and mother by serology and DNA analysis. Among 77 children born to 68 HBsAg+ mothers, 3.9% (3/77) were HBsAg+, and 36.4% (28/77) were HBV DNA+/HBsAg- (OBIs) by a single PCR, respectively. Thirteen of 28 HBV DNA+/HBsAg- samples were conformed by two PCRs or S sequence, which accounted for 16.9% (13/77) of children. Three HBsAg+ and six OBIs were genotyped in consistent with their mother's HBV strains. Of 77 babies' blood samples, anti-HBs reactivity varied slightly according to age groups, while passively transmitted anti-HBc reactivity declined from 100% high reactivity at age 3-5 months to mostly negative at age ≥12 months. Babies with apparent OBI had higher levels of anti-HBc and lower levels of anti-HBs than those without OBI but all eight OBI babies with second follow-up samples became HBV DNA negative beyond 1 year of age. The vaccinated infants born to HBsAg+ mothers presented the low rate of HBsAg occurrence as vaccination failure and high frequency of viral persistence in the form of transient OBIs since no evidence of active HBV infection occurred beyond 1 year of age. © 2017 Wiley Periodicals, Inc.

  12. High frequency of DQB1*05 and absolute absence of DRB1*13 in muscle-specific tyrosine kinase positive myasthenia gravis.

    PubMed

    Nikolic, A V; Andric, Z P; Simonovic, R B; Rakocevic Stojanovic, V M; Basta, I Z; Bojic, S D; Lavrnic, D V

    2015-01-01

    Myasthenia gravis (MG) is an autoimmune disease but certain genetic factors predispose its development. Since susceptibility to different forms of MG is linked to a number of allelic variants, the aim of this study was to explore the human leukocyte antigen (HLA) profile of our patients with muscle-specific tyrosine kinase (MuSK) MG. Human leukocyte antigen (HLA) typing was performed in our cohort of 31 MuSK MG patients available for the study. The allele groups of DRB1* and DQB1* loci were typed with sequence-specific oligonucleotide probes and high resolution typing for DQB1* was performed using sequence-specific primers. HLA frequencies were compared with unrelated healthy bone marrow donors. Significant association of MuSK MG with alleles DRB1*14 [odds ratio (OR) 3.8], DRB1*16 (OR 3.3) (P < 0.01) and DQB1*05 (OR 2.2) (P < 0.05) was found. In our patients the most frequent DQB1* allele was DQB1*05:02. An absolute absence of DRB1*13 in our cohort of MuSK MG patients was also found, whilst this allele was present in 25% (495/1992) of control subjects (OR 0) (P < 0.01). The HLA DRB1*16-DQB1*05 (OR 2.9) haplotype was found to be associated with MuSK MG (P < 0.05). The strong association of MuSK MG with DQB1*05 alleles observed in patient series from other countries was confirmed. The novel finding in our cohort of MuSK MG patients was the absolute absence of DRB1*13 allele, which might have a protective role in the development of MuSK MG, at least in our population. © 2014 EAN.

  13. High frequency power distribution system

    NASA Technical Reports Server (NTRS)

    Patel, Mikund R.

    1986-01-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  14. High frequency power distribution system

    NASA Astrophysics Data System (ADS)

    Patel, Mikund R.

    1986-04-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  15. High-current, high-frequency capacitors

    NASA Astrophysics Data System (ADS)

    Renz, D. D.

    1983-06-01

    The NASA Lewis high-current, high-frequency capacitor development program was conducted under a contract with Maxwell Laboratories, Inc., San Diego, California. The program was started to develop power components for space power systems. One of the components lacking was a high-power, high-frequency capacitor. Some of the technology developed in this program may be directly usable in an all-electric airplane. The materials used in the capacitor included the following: the film is polypropylene, the impregnant is monoisopropyl biphenyl, the conductive epoxy is Emerson and Cuming Stycast 2850 KT, the foil is aluminum, the case is stainless steel (304), and the electrode is a modified copper-ceramic.

  16. High-current, high-frequency capacitors

    NASA Technical Reports Server (NTRS)

    Renz, D. D.

    1983-01-01

    The NASA Lewis high-current, high-frequency capacitor development program was conducted under a contract with Maxwell Laboratories, Inc., San Diego, California. The program was started to develop power components for space power systems. One of the components lacking was a high-power, high-frequency capacitor. Some of the technology developed in this program may be directly usable in an all-electric airplane. The materials used in the capacitor included the following: the film is polypropylene, the impregnant is monoisopropyl biphenyl, the conductive epoxy is Emerson and Cuming Stycast 2850 KT, the foil is aluminum, the case is stainless steel (304), and the electrode is a modified copper-ceramic.

  17. Relationship between tongue positions and formant frequencies in female speakers.

    PubMed

    Lee, Jimin; Shaiman, Susan; Weismer, Gary

    2016-01-01

    This study examined the relationship (1) between acoustic vowel space and the corresponding tongue kinematic vowel space and (2) between formant frequencies (F1 and F2) and tongue x-y coordinates for the same time sampling point. Thirteen healthy female adults participated in this study. Electromagnetic articulography and synchronized acoustic recordings were utilized to obtain vowel acoustic and tongue kinematic data across ten speech tasks. Intra-speaker analyses showed that for 10 of the 13 speakers the acoustic vowel space was moderately to highly correlated with tongue kinematic vowel space; much weaker correlations were obtained for inter-speaker analyses. Correlations of individual formants with tongue positions showed that F1 varied strongly with tongue position variations in the y dimension, whereas F2 was correlated in equal magnitude with variations in the x and y positions. For within-speaker analyses, the size of the acoustic vowel space is likely to provide a reasonable inference of size of the tongue working space for most speakers; unfortunately there is no a priori, obvious way to identify the speakers for whom the covariation is not significant. A second conclusion is that F1 variations reflect tongue height, but F2 is a much more complex reflection of tongue variation in both dimensions.

  18. High Frequency Guided Wave Virtual Array SAFT

    NASA Astrophysics Data System (ADS)

    Roberts, R.; Pardini, A.; Diaz, A.

    2003-03-01

    The principles of the synthetic aperture focusing technique (SAFT) are generalized for application to high frequency plate wave signals. It is shown that a flaw signal received in long-range plate wave propagation can be analyzed as if the signals were measured by an infinite array of transducers in an unbounded medium. It is shown that SAFT-based flaw sizing can be performed with as few as three or less actual measurement positions.

  19. High Frequency Stable Oscillate boiling

    NASA Astrophysics Data System (ADS)

    Li, Fenfang; Gonzalez-Avila, Silvestre Roberto; Ohl, Claus Dieter

    2015-11-01

    We present an unexpected regime of resonant bubble oscillations on a thin metal film submerged in water, which is continuously heated with a focused CW laser. The oscillatory bubble dynamics reveals a remarkably stable frequency of several 100 kHz and is resolved from the side using video recordings at 1 million frames per second. The emitted sound is measured simultaneously and shows higher harmonics. Once the laser is switched on the water in contact with the metal layer is superheated and an explosively expanding cavitation bubble is generated. However, after the collapse a microbubble is nucleated from the bubble remains which displays long lasting oscillations. Generally, pinch-off from of the upper part of the microbubble is observed generating a continuous stream of small gas bubbles rising upwards. The cavitation expansion, collapse, and the jetting of gas bubbles are detected by the hydrophone and are correlated to the high speed video. We find the bubble oscillation frequency is dependent on the bubble size and surface tension. A preliminary model based on Marangoni flow and heat transfer can explain the high flow velocities observed, yet the origin of bubble oscillation is currently not well understood.

  20. High Frequency Dynamic Nuclear Polarization

    PubMed Central

    Ni, Qing Zhe; Daviso, Eugenio; Can, Thach V.; Markhasin, Evgeny; Jawla, Sudheer K.; Swager, Timothy M.; Temkin, Richard J.; Herzfeld, Judith; Griffin, Robert G.

    2013-01-01

    Conspectus During the three decades 1980–2010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited by the low sensitivity of the experiments, due in large part to the necessity of observing spectra of low-γ nuclei such as the I = ½ species 13C or 15N. The difficulty is still greater when quadrupolar nuclei, like 17O or 27Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime — roughly 150–660 GHz — and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low

  1. High-Frequency Inductor Materials

    NASA Astrophysics Data System (ADS)

    Varga, L. K.

    2014-01-01

    The Finemet-type nanocrystalline alloy represents an advanced soft-magnetic metal-metal-type nanocomposite with an eddy-current-determined high- frequency limit. A survey of different heat treatments under tensile stress is presented to tailor the hysteresis loop by induced transversal anisotropy. The flattened loop having reduced effective permeability enhances the eddy- current limit in the MHz region; For example, continuous stress annealing in a tubular furnace of 1 m length at 650°C, pulling the ribbon with a velocity of 4 m/min under a tensile stress of 200 MPa, results in a wound core having a permeability of 120 and a frequency limit of 10 MHz. Careful annealing preserves the static coercivity below 10 A/m. The power loss at 0.1 T and 100 kHz is only 82 mW/cm3, which is an order of magnitude lower then the values obtained for Sendust™ cores in similar conditions.

  2. Amplifying High Frequency Acoustic Signals

    SciTech Connect

    Kunz, C

    2004-02-05

    In search of the hypothetical Higgs boson, a prototype electron accelerator structure has been developed for use in the Next Linear Collider (NLC), SLAC's proposed version of the machine necessary to create the predicted particle. The Next Linear Test Accelerator (NLCTA), designed to provide O.5GeV-lTeV center-of-mass collision energy, generates electromagnetic breakdowns inside its copper structure while the beam is running. The sparks vaporize the surface of the copper, and will eventually ruin the accelerator. They also create high-frequency (hf) acoustic signals (100 kHz-1 MHz). Acoustic sensors have been placed on the structure, however current knowledge regarding sound propagation in copper limits spark location to within one centimeter. A system was needed that simulates the sparks so further study of acoustic propagation can be pursued; the goal is locate them to within one millimeter. Various tests were done in order to identify an appropriate hf signal source, and to identify appropriate acoustic sensors to use. A high-voltage spark generator and the same sensors used on the actual structure proved most useful for the system. Two high-pass filters were also fabricated in order to measure signals that might be created above 2MHz. The 11-gain filter was used on the acoustic simulation system that was developed, and the 100-gain filter will be used on the NLCTA.

  3. High Frequency Linacs for Hadrontherapy

    NASA Astrophysics Data System (ADS)

    Amaldi, Ugo; Braccini, Saverio; Puggioni, Paolo

    The use of radiofrequency linacs for hadrontherapy was proposed about 20 years ago, but only recently has it been understood that the high repetition rate together with the possibility of very rapid energy variations offers an optimal solution to the present challenge of hadrontherapy: "paint" a moving tumor target in three dimensions with a pencil beam. Moreover, the fact that the energy, and thus the particle range, can be electronically adjusted implies that no absorber-based energy selection system is needed, which, in the case of cyclotron-based centers, is the cause of material activation. On the other side, a linac consumes less power than a synchrotron. The first part of this article describes the main advantages of high frequency linacs in hadrontherapy, the early design studies, and the construction and test of the first high-gradient prototype which accelerated protons. The second part illustrates some technical issues relevant to the design of copper standing wave accelerators, the present developments, and two designs of linac-based proton and carbon ion facilities. Superconductive linacs are not discussed, since nanoampere currents are sufficient for therapy. In the last two sections, a comparison with circular accelerators and an overview of future projects are presented.

  4. Variation of Static-PPP Positioning Accuracy Using GPS-Single Frequency Observations (Aswan, Egypt)

    NASA Astrophysics Data System (ADS)

    Farah, Ashraf

    2017-06-01

    Precise Point Positioning (PPP) is a technique used for position computation with a high accuracy using only one GNSS receiver. It depends on highly accurate satellite position and clock data rather than broadcast ephemeries. PPP precision varies based on positioning technique (static or kinematic), observations type (single or dual frequency) and the duration of collected observations. PPP-(dual frequency receivers) offers comparable accuracy to differential GPS. PPP-single frequency receivers has many applications such as infrastructure, hydrography and precision agriculture. PPP using low cost GPS single-frequency receivers is an area of great interest for millions of users in developing countries such as Egypt. This research presents a study for the variability of single frequency static GPS-PPP precision based on different observation durations.

  5. Optical zooming interferometer for subnanometer positioning using an optical frequency comb

    SciTech Connect

    Kajima, Mariko; Minoshima, Kaoru

    2010-10-20

    A high-precision positioning stage based on an optical zooming interferometer is proposed. Two external-cavity diode lasers, stabilized to a femtosecond optical frequency comb, are used as optical sources. The zooming principle is demonstrated, and the positioning resolution of 0.2 nm is achieved. The positioning accuracy was partly evaluated.

  6. High to very high frequency metal/anomaly detector

    NASA Astrophysics Data System (ADS)

    Heinz, Daniel C.; Brennan, Michael L.; Steer, Michael B.; Melber, Adam W.; Cua, John T.

    2014-05-01

    Typical metal detectors work at very low to low frequencies. In this paper, a metal/anomaly detector design that operates in the high to very high frequency range is presented. This design uses a high-Q tuned loop antenna for metal/anomaly detection. By measuring the return loss or voltage standing wave ratio a frequency notch can be detected. Tuning to the optimal location of the notch can be accomplished by monitoring the phase response. This phase monitoring technique can be used to ground balance the detector. As a metal object is moved along the longitudinal axis of the loop antenna a substantial shift in the frequency of the notch is detected. For metal targets, the frequency shift is positive, and for ferrite and other targets, the frequency shift is negative. This frequency shift is created by the proximity of the target causing a change in the impedance of the antenna. Experiments with a prototype antenna show long-range detection with low power requirements. The detector requires only one loop with one winding which is used for both transmit and receive. This allows for a metal/anomaly detector with a very simple design. The design is lightweight and, depending on loop size, significantly increases detection depth performance. In the full paper, modeling and further experimental results will be presented. Performance results for various types of soil and for different types of targets are presented.

  7. High frequency, high power capacitor development

    NASA Technical Reports Server (NTRS)

    White, C. W.; Hoffman, P. S.

    1983-01-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  8. High frequency, high power capacitor development

    NASA Astrophysics Data System (ADS)

    White, C. W.; Hoffman, P. S.

    1983-03-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  9. A novel multiregion hybridization assay reveals high frequency of dual inter-subtype infections among HIV-positive individuals in Cameroon, West Central Africa.

    PubMed

    Vidal, Nicole; Diop, Halimatou; Montavon, Céline; Butel, Christelle; Bosch, Stéphanie; Ngole, Eitel Mpoudi; Touré-Kane, Coumba; Mboup, Souleymane; Delaporte, Eric; Peeters, Martine

    2013-03-01

    In West and West Central Africa, multiple subtypes, circulating recombinant forms (CRF), and high proportions of unique recombinant forms (URF) are documented. The predominance of recombinants strongly suggests that dual infections occur frequently. In the present study, we adapted the multi-region hybridization assay (MHA), previously developed to identify dual infections in geographic regions where few HIV-1 variants circulate, to identify HIV-1 variants and dual infections. We designed clade-specific probes in three genomic regions (gag p17, vpu, nef) to detect eight different variants that are common in this part of Africa (A, B/D, C, F, G, CRF02_AG, CRF06_cpx, CRF22_01A1). The assay was validated with 163 samples representing the corresponding HIV-1 variants. Depending on the genomic regions, the global sensitivity of the assay ranged from 86% to 94%, and the global specificity was between 85% and 96%. The assay was then applied on 156 antiretroviral treatment-naive patients from Cameroon. The MHA assay identified 79%, 85% and 90% of the strains in nef, gag and vpu regions, respectively. The subtype/CRF distribution and the proportion of inter-region recombinants obtained by the new MHA assay were in accordance with known subtype/CRF distribution in Cameroon. Moreover, the MHA assay identified 35 (22.4%) patients as dually infected, from which 20 were reactive in more than one region and/or with concordant multigenomic recombination pattern. Despite the high genetic diversity, we successfully developed an hybridization assay allowing identification of eight common HIV-1 variants circulating in West and West Central Africa. We documented high rates of dual infection in a low-risk population group, illustrating that the global evolution of HIV diversity is driven by dual infections. This assay could become a useful screening tool for the global surveillance and monitoring of inter-subtype/CRF dual infections in West and West Central Africa. Copyright © 2012

  10. High-frequency nanophotonic devices

    NASA Astrophysics Data System (ADS)

    Bimberg, D.; Fiol, G.; Meuer, C.; Laemmlin, M.; Kuntz, M.

    2007-02-01

    Recent results on GaAs-based high-speed mode-locked quantum dot (QD) lasers and optical amplifiers with an operation wavelength centered at 1290 nm are reviewed and their complex dependence on device and operating parameters is discussed on the basis of experimental data obtained with integrated fiber-based QD device modules. Hybrid and passive mode-locking of QD lasers with repetition frequencies between 5 and 80 GHz, sub-ps pulse widths, ultra-low timing jitter down to 190 fs, high output peak power beyond 1 W and suppression of Q-switching are reported, showing the large potential of this class of devices for O-band optical fiber applications. Results on cw and dynamical characterization of quantum dot semiconductor optical amplifiers are presented. QD amplifiers exhibit a close-to-ideal noise figure of 4 dB and demonstrate multi-wavelength amplification of three CWDM wavelengths simultaneously. Modelling of QD polarization dependence shows that it should be possible to achieve polarization insensitive SOAs using vertically coupled QD stacks. Amplification of ultra-fast 80 GHz optical combs and bit-error-free data signal amplification at 40 Gb/s with QD SOAs show the potential for their application in future 100 Gb Ethernet networks.

  11. Atomic frequency standards for ultra-high-frequency stability

    NASA Technical Reports Server (NTRS)

    Maleki, L.; Prestage, J. D.; Dick, G. J.

    1987-01-01

    The general features of the Hg-199(+) trapped-ion frequency standard are outlined and compared to other atomic frequency standards, especially the hydrogen maser. The points discussed are those which make the trapped Hg-199(+) standard attractive: high line Q, reduced sensitivity to external magnetic fields, and simplicity of state selection, among others.

  12. High frequency-heated air turbojet

    NASA Technical Reports Server (NTRS)

    Miron, J. H. D.

    1986-01-01

    A description is given of a method to heat air coming from a turbojet compressor to a temperature necessary to produce required expansion without requiring fuel. This is done by high frequency heating, which heats the walls corresponding to the combustion chamber in existing jets, by mounting high frequency coils in them. The current transformer and high frequency generator to be used are discussed.

  13. High Frequency Chandler Wobble Excitation

    NASA Astrophysics Data System (ADS)

    Seitz, F.; Stuck, J.; Thomas, M.

    2003-04-01

    and OMCT forcing fields give no hint for increased excitation power in the Chandler band. Thus it is assumed, that continuous high frequency excitation due to stochastic weather phenomena is responsible for the perpetuation of the Chandler wobble.

  14. High frequency testing of rubber mounts.

    PubMed

    Vahdati, Nader; Saunders, L Ken Lauderbaugh

    2002-04-01

    Rubber and fluid-filled rubber engine mounts are commonly used in automotive and aerospace applications to provide reduced cabin noise and vibration, and/or motion accommodations. In certain applications, the rubber mount may operate at frequencies as high as 5000 Hz. Therefore, dynamic stiffness of the mount needs to be known in this frequency range. Commercial high frequency test machines are practically nonexistent, and the best high frequency test machine on the market is only capable of frequencies as high as 1000 Hz. In this paper, a high frequency test machine is described that allows test engineers to study the high frequency performance of rubber mounts at frequencies up to 5000 Hz.

  15. High Frequency Electronic Packaging Technology

    NASA Technical Reports Server (NTRS)

    Herman, M.; Lowry, L.; Lee, K.; Kolawa, E.; Tulintseff, A.; Shalkhauser, K.; Whitaker, J.; Piket-May, M.

    1994-01-01

    Commercial and government communication, radar, and information systems face the challenge of cost and mass reduction via the application of advanced packaging technology. A majority of both government and industry support has been focused on low frequency digital electronics.

  16. High Frequency Electronic Packaging Technology

    NASA Technical Reports Server (NTRS)

    Herman, M.; Lowry, L.; Lee, K.; Kolawa, E.; Tulintseff, A.; Shalkhauser, K.; Whitaker, J.; Piket-May, M.

    1994-01-01

    Commercial and government communication, radar, and information systems face the challenge of cost and mass reduction via the application of advanced packaging technology. A majority of both government and industry support has been focused on low frequency digital electronics.

  17. High frequency and poor prognosis of late childhood BCR-ABL-positive and MLL-AF4-positive ALL define the need for advanced molecular diagnostics and improved therapeutic strategies in pediatric B-ALL in Pakistan.

    PubMed

    Iqbal, Zafar; Akhtar, Tanveer; Awan, Tashfin; Aleem, Aamer; Sabir, Noreen; Rasool, Mahmood; Absar, Muhammad; Akram, Afia M; Shammas, Masood A; Shah, Ijaz H; Khalid, Muhammad; Taj, Abid S; Jameel, Abid; Alanazi, Abdullah; Gill, Ammara T; Hashmi, Jamil Amjad; Hussain, Akhtar; Sabar, Muhammad Farooq; Khalid, Ahmad M; Qazi, Mehmood Hussain; Karim, Sajjad; Siddiqi, Muhammad Hassan; Mahmood, Aamir; Iqbal, Mudassar; Saeed, Anjum; Irfan, Muhammad Imran

    2015-10-01

    Fusion oncogenes (FOs) resulting from chromosomal abnormalities have an important role in leukemogenesis in pediatric B cell acute lymphoblastic leukemia (ALL). The most common FOs are BCR-ABL, MLL-AF4, ETV6-RUNX1, and TCF3-PBX1, all of which have important prognostic and drug selection implications. Moreover, frequencies of FOs have ethnic variations. We studied Pakistani frequencies of FOs, clinical pattern, and outcome in pediatric B-ALL. FOs were studied in 188 patients at diagnosis using reverse transcriptase-polymerase chain reaction (RT-PCR) and interphase fluorescent in situ hybridization (FISH). Data were analyzed using SPSS version 17 (SPSS Inc., Chicago, IL, USA). FOs were detected in 87.2 % of patients. Mean overall survival was 70.9 weeks, 3-year survival was 31.9 %, and 3-year relapse-free survival was 18.1 %. Four patients died of drug toxicities. ETV6-RUNX1 (19.14 %) had better survival (110.9 weeks; p = 0.03); TCF3-PBX1 (2.1 %) was associated with inferior outcome and higher central nervous system (CNS) relapse risk; MLL-AF4 (18.1 %) was more common in the 8- to 15-year age group (24/34; p = 0.001) and was associated with organomegaly, low platelet count, and poor survival; and BCR-ABL (47.9 %) was associated with older age (7-15 years, 52/90), lower remission rates, shorter survival (43.73 ± 4.24 weeks) and higher white blood cell count. Overall, MLL-AF4 and BCR-ABL were detected in 66 % of B-ALL, presented in later childhood, and were associated with poor prognosis and inferior survival. This study reports the highest ethnic frequency of BCR-ABL FO in pediatric ALL, and is consistent with previous reports from our region. Poor prognosis BCR-ABL and MLL-AF4 was detected in two-thirds of pediatric B-ALL and is likely to be the reason for the already reported poor survival of childhood ALL in South-East Asia. Furthermore, MLL-AF4, usually most common in infants, presented in later childhood in most of the ALL patients, which was

  18. 75 FR 81284 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Draft...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-27

    ... SECURITY Coast Guard Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology... of High Frequency (HF) and Ultra High Frequency (UHF) Sound Navigation and Ranging (SONAR) Technology... less than a week; however, for environmental disasters such as the Deepwater Horizon oil spill,...

  19. Single-track absolute position encoding method based on spatial frequency of stripes

    NASA Astrophysics Data System (ADS)

    Xiang, Xiansong; Lu, Yancong; Wei, Chunlong; Zhou, Changhe

    2014-11-01

    A new method of single-track absolute position encoding based on spatial frequency of stripes is proposed. Instead of using pseudorandom-sequence arranged stripes as in conventional situations, this kind of encoding method stores the location information in the frequency space of the stripes, which means the spatial frequency of stripes varies with position and indicates position. This encoding method has a strong fault-tolerant capability with single-stripe detecting errors. The method can be applied to absolute linear encoders, absolute photoelectric angle encoders or two-dimensional absolute linear encoders. The measuring apparatus includes a CCD image sensor and a microscope system, and the method of decoding this frequency code is based on FFT algorithm. This method should be highly interesting for practical applications as an absolute position encoding method.

  20. The impact of the microphone position on the frequency analysis of snoring sounds.

    PubMed

    Herzog, Michael; Kühnel, Thomas; Bremert, Thomas; Herzog, Beatrice; Hosemann, Werner; Kaftan, Holger

    2009-08-01

    Frequency analysis of snoring sounds has been reported as a diagnostic tool to differentiate between different sources of snoring. Several studies have been published presenting diverging results of the frequency analyses of snoring sounds. Depending on the position of the used microphones, the results of the frequency analysis of snoring sounds vary. The present study investigated the influence of different microphone positions on the outcome of the frequency analysis of snoring sounds. Nocturnal snoring was recorded simultaneously at six positions (air-coupled: 30 cm middle, 100 cm middle, 30 cm lateral to both sides of the patients' head; body contact: neck and parasternal) in five patients. The used microphones had a flat frequency response and a similar frequency range (10/40 Hz-18 kHz). Frequency analysis was performed by fast Fourier transformation and frequency bands as well as peak intensities (Peaks 1-5) were detected. Air-coupled microphones presented a wider frequency range (60 Hz-10 kHz) compared to contact microphones. The contact microphone at cervical position presented a cut off at frequencies above 300 Hz, whereas the contact microphone at parasternal position revealed a cut off above 100 Hz. On an exemplary base, the study demonstrates that frequencies above 1,000 Hz do appear in complex snoring patterns, and it is emphasised that high frequencies are imported for the interpretation of snoring sounds with respect to the identification of the source of snoring. Contact microphones might be used in screening devices, but for a natural analysis of snoring sounds the use of air-coupled microphones is indispensable.

  1. Landau damping with high frequency impedance

    SciTech Connect

    Blaskiewicz,M.

    2009-05-04

    Coupled bunch longitudinal stability in the presence of high frequency impedances is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the new 56 MHz RF system.

  2. High Frequency Radar Astronomy With HAARP

    DTIC Science & Technology

    2003-01-01

    a period of several years, the High frequency Active Auroral Research Program ( HAARP ) transmitting array near Gakona, Alaska , has increased in total...High Frequency Radar Astronomy With HAARP Paul Rodriguez Naval Research Laboratory Information Technology Division Washington, DC 20375, USA Edward...high frequency (HF) radar facility used for research purposes. The basic science objective of HAARP is to study nonlinear effects associated with

  3. Appearance-based exercise motivation moderates the relationship between exercise frequency and positive body image.

    PubMed

    Homan, Kristin J; Tylka, Tracy L

    2014-03-01

    Individuals with a positive body image appreciate their bodies, hold an internal perspective of their bodies, and are satisfied with the functionality of their bodies. Research shows that positive body image is more complex than the absence of body dissatisfaction. Although exercise reduces women's body dissatisfaction, very little research has explored how, or even whether, exercise is associated with positive body image. Therefore, we examined whether exercise frequency was positively related to three aspects of positive body image (body appreciation, internal body orientation, and functional body satisfaction) among 321 college women. Appearance-based exercise motivation (the extent exercise is pursued to influence weight or shape) was hypothesized to moderate these associations. Hierarchical moderated regression analyses showed that exercise frequency was related to higher positive body image, but high levels of appearance-based exercise motivation weakened these relationships. Thus, messages promoting exercise need to de-emphasize weight loss and appearance for positive body image.

  4. Lightweight, high-frequency transformers

    NASA Technical Reports Server (NTRS)

    Schwarze, G. E.

    1983-01-01

    The 25-kVA space transformer was developed under contract by Thermal Technology Laboratory, Buffalo, N. Y. The NASA Lewis transformer technology program attempted to develop the baseline technology. For the 25-kVA transformer the input voltage was chosen as 200 V, the output voltage as 1500 V, the input voltage waveform as square wave, the duty cycle as continuous, the frequency range (within certain constraints) as 10 to 40 kHz, the operating temperatures as 85 deg. and 130 C, the baseplate temperature as 50 C, the equivalent leakage inductance as less than 10 micro-h, the operating environment as space, and the life expectancy as 10 years. Such a transformer can also be used for aircraft, ship and terrestrial applications.

  5. High Resolution Frequency Swept Imaging.

    DTIC Science & Technology

    1983-09-30

    elements can be em- ployed to cut cost. However a systematic study of ordered and random aperture thinning [1], [21 Indicates rapid deterioration in...yield 3-D image information. Impulse illumination is desirable incertain instances of rapid target motion but may be more difficlt to implement than...various slices are seen in depth * at different VFT planes that are determined by the positions of the axially incremented point source. Repeated rapid

  6. Propagation of high frequencies in Scandinavia

    SciTech Connect

    Bame, D.

    1989-04-01

    To determine if seismic signals at frequencies up to 50 Hz are useful for detecting events and discriminating between earthquakes and explosions, approximately 180 events from the three-component high-frequency seismic element (HFSE) installed at the center of the Norwegian Regional Seismic Array (NRSA) have been analyzed. The attenuation of high-frequency signals in Scandinavia varies with distance, azimuth, magnitude, and source effects. Most of the events were detected with HFSE, although detections were better on the NRSA where signal processing techniques were used. Based on a preliminary analysis, high-frequency data do not appear to be a useful discriminant in Scandinavia. 21 refs., 29 figs., 3 tabs.

  7. HIGH CURRENT RADIO FREQUENCY ION SOURCE

    DOEpatents

    Abdelaziz, M.E.

    1963-04-01

    This patent relates to a high current radio frequency ion source. A cylindrical plasma container has a coil disposed around the exterior surface thereof along the longitudinal axis. Means are provided for the injection of an unionized gas into the container and for applying a radio frequency signal to the coil whereby a radio frequency field is generated within the container parallel to the longitudinal axis thereof to ionize the injected gas. Cathode and anode means are provided for extracting transverse to the radio frequency field from an area midway between the ends of the container along the longitudinal axis thereof the ions created by said radio frequency field. (AEC)

  8. Lightning protection devices for high frequencies equipments

    SciTech Connect

    Pierre, J.

    1983-01-01

    Contents: Mechanism of a Lightning Stroke from Antenna to Ground; Principles of Protection Devices for Feeders; Electrical Characteristics of H.F. Protection Devices; Calculation of H.F. Protection Devices; Catalogue Devices for High Frequency Protection; Some Measurement Results for Tees; Measurement Results for Decoupling Line Devices; Installation of High Frequency Devices.

  9. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

    For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

  10. 78 FR 70567 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-26

    ...] Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final Programmatic... Programmatic Environmental Assessment (PEA) for the Nationwide Use of High Frequency (HF) and Ultra High..., for environmental disasters such as the Deepwater Horizon oil spill, SONAR equipment could be used...

  11. A high frequency silicon pressure sensor

    NASA Technical Reports Server (NTRS)

    Kahng, S. K.; Gross, C.

    1980-01-01

    Theoretical and design considerations as well as fabrication and experimental work involved in the development of high-frequency silicon pressure sensors with an ultra-small diaphragm are discussed. A sensor is presented with a rectangular diaphragm of 0.0127 cm x 0.0254 cm x 1.06 micron; the sensor has a natural frequency of 625 kHz and a sensitivity of 0.82 mv/v-psi. High-frequency results from shock tube testing and low-frequency (less than 50 kHz) comparison with microphones are given.

  12. High dynamic global positioning system receiver

    NASA Technical Reports Server (NTRS)

    Hurd, W. J. (Inventor)

    1986-01-01

    A Global Positioning System (GPS) receiver having a number of channels, receives an aggregate of pseudorange code time division modulated signals. The aggregate is converted to baseband and then to digital form for separate processing in the separate channels. A fast fourier transform processor computes the signal energy as a function of Doppler frequency for each correlation lag, and a range and frequency estimator computes estimates of pseudorange, and frequency. Raw estimates from all channels are used to estimate receiver position, velocity, clock offset and clock rate offset in a conventional navigation and control unit, and based on the unit that computes smoothed estimates for the next measurement interval.

  13. Apparatus for measuring high frequency currents

    NASA Technical Reports Server (NTRS)

    Hagmann, Mark J. (Inventor); Sutton, John F. (Inventor)

    2003-01-01

    An apparatus for measuring high frequency currents includes a non-ferrous core current probe that is coupled to a wide-band transimpedance amplifier. The current probe has a secondary winding with a winding resistance that is substantially smaller than the reactance of the winding. The sensitivity of the current probe is substantially flat over a wide band of frequencies. The apparatus is particularly useful for measuring exposure of humans to radio frequency currents.

  14. Alternatives to percussion and postural drainage. A review of mucus clearance therapies: percussion and postural drainage, autogenic drainage, positive expiratory pressure, flutter valve, intrapulmonary percussive ventilation, and high-frequency chest compression with the ThAIRapy Vest.

    PubMed

    Langenderfer, B

    1998-01-01

    The purpose of this article is to review published studies on the efficacy of old and new mucus clearance techniques and to develop recommendations for different groups of patients. Mucus clearance is a problem in cystic fibrosis, bronchiectasis, and many other pulmonary conditions. Percussion and postural drainage (P & PD) was the traditional method of facilitating mucus clearance, but the many hazards and contraindications along with the onerous nature and resultant poor patient compliance of this procedure have led to the development of alternative therapies. Research studies with cystic fibrosis patients support the efficacy of P & PD in patients who can tolerate it. However, equivalent sputum production can be accomplished with autogenic drainage, positive expiratory pressure, and Flutter valve therapy without the assistance of another caregiver, as long as the patient has the motivation, breath control, and neuromuscular function to perform these modalities. The Intrapulmonary Percussive Ventilation device and high-frequency chest compression with the ThAIRapy vest involve more elaborate and expensive equipment, yet these devices provide mucus clearance assistance to patients who lack the ability to perform the simpler techniques. Both mechanized modalities promote independence and self-care in the patient, and the effectiveness of both has been supported by the limited research published to date. Which alternative to recommend depends on the ability, motivation, preference, needs, and resources of each patient.

  15. High-frequency conductivity of photoionized plasma

    SciTech Connect

    Anakhov, M. V.; Uryupin, S. A.

    2016-08-15

    The tensor of the high-frequency conductivity of a plasma created via tunnel ionization of atoms in the field of linearly or circularly polarized radiation is derived. It is shown that the real part of the conductivity tensor is highly anisotropic. In the case of a toroidal velocity distribution of photoelectrons, the possibility of amplification of a weak high-frequency field polarized at a sufficiently large angle to the anisotropy axis of the initial nonequilibrium distribution is revealed.

  16. Prestin and high frequency hearing in mammals

    PubMed Central

    Zhang, Shuyi; Liu, Yang

    2011-01-01

    Recent evidence indicates that the evolution of ultrasonic hearing in echolocating bats and cetaceans has involved adaptive amino acid replacements in the cochlear gene prestin. A substantial number of these changes have occurred in parallel in both groups, suggesting that particular amino acid residues might confer greater auditory sensitivity to high frequencies. Here we review some of these findings, and consider whether similar signatures of prestin protein sequence evolution also occur in mammals that possess high frequency hearing for passive localization and conversely, whether this gene has undergone less change in mammals that lack high frequency hearing. PMID:21655450

  17. Turbulence in unsteady flow at high frequencies

    NASA Technical Reports Server (NTRS)

    Kuhn, Gary D.

    1990-01-01

    Turbulent flows subjected to oscillations of the mean flow were simulated using a large-eddy simulation computer code for flow in a channel. The objective of the simulations was to provide better understanding of the effects of time-dependent disturbances on the turbulence of a boundary layer and of the underlying physical phenomena regarding the basic interaction between the turbulence and external disturbances. The results confirmed that turbulence is sensitive to certain ranges of frequencies of disturbances. However, no direct connection was found between the frequency of imposed disturbances and the characteristic 'burst' frequency of turbulence. New insight into the nature of turbulence at high frequencies was found. Viscous phenomena near solid walls were found to be the dominant influence for high-frequency perturbations.

  18. Turbulence in unsteady flow at high frequencies

    NASA Technical Reports Server (NTRS)

    Kuhn, Gary D.

    1990-01-01

    Turbulent flows subjected to oscillations of the mean flow were simulated using a large-eddy simulation computer code for flow in a channel. The objective of the simulations was to provide better understanding of the effects of time-dependent disturbances on the turbulence of a boundary layer and of the underlying physical phenomena regarding the basic interaction between the turbulence and external disturbances. The results confirmed that turbulence is sensitive to certain ranges of frequencies of disturbances. However, no direct connection was found between the frequency of imposed disturbances and the characteristic 'burst' frequency of turbulence. New insight into the nature of turbulence at high frequencies was found. Viscous phenomena near solid walls were found to be the dominant influence for high-frequency perturbations.

  19. High-Frequency and Very-high-Frequency (HF&VHF) above-groundelectromagnetic impedance measurements

    SciTech Connect

    Frangos, William; Becker, Alex; Lee, K.H.

    2002-09-20

    We have field-tested an apparatus for measuring the electromagnetic impedance above the ground at a plurality of frequencies in the 0.3 - 30 MHz range. This window in the frequency spectrum, which lies between frequencies used for GPR and those used for conventional loop-loop EM soundings, has not been used because of difficulties in fielding equipment for making absolute and accurate measurements. Model and physical parameter studies however confirm that data in this frequency band can be used to construct high-resolution maps of electrical conductivity and permittivity of near-surface material. Our equipment was assembled using commercial electric and magnetic antennas. The magnetic loop source is excited by a conventional signal generator - power amplifier assembly. Signal detection is accomplished using RF lock-in amplifiers. All system elements are appropriately isolated by optic - fiber links. We estimate a measurement accuracy of about {+-} 10% for an 8-m separation between source and detector. Field tests were done at the University of California Richmond Field Station where the near surface electrical structure is well known. The experimental data at this site are mainly a function of electrical conductivity. In this context, we have obtained good agreement with the known local variations in resistivity both with depth and with position along a 35-m traverse. Additional tests in more resistive regimes where dielectric permittivity is not negligible yield spectral data compatible with the less well known near-surface electrical properties.

  20. Overview of the Advanced High Frequency Branch

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    2015-01-01

    This presentation provides an overview of the competencies, selected areas of research and technology development activities, and current external collaborative efforts of the NASA Glenn Research Center's Advanced High Frequency Branch.

  1. An introduction to high frequency radioteletype systems

    NASA Astrophysics Data System (ADS)

    Pinnau, Roger R.

    1989-10-01

    A basic introductory guide is provided to modern High Frequency (HF) data communications systems. Described are modern commercial radioteletype systems, data communication protocols, and various secrets of the trade.

  2. Neural coding of high-frequency tones

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1976-01-01

    Available evidence was presented indicating that neural discharges in the auditory nerve display characteristic periodicities in response to any tonal stimulus including high-frequency stimuli, and that this periodicity corresponds to the subjective pitch.

  3. Real-time, high frequency QRS electrocardiograph

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

    2006-01-01

    Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as RAZs. RAZs are displayed as go, no-go signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

  4. High frequency conductivity in carbon nanotubes

    SciTech Connect

    Abukari, S. S. Mensah, S. Y.; Twum, A.; Mensah, N. G.; Adu, K. A.; Rabiu, M.

    2012-12-15

    We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ω{sub B} for metallic zigzag CNs and ω < ω{sub B} for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.

  5. Accuracy of High Frequency Maximum Usable Frequencies (MUF) Prediction.

    DTIC Science & Technology

    1981-09-15

    shown in Figure 35 to be rat er constant at about 20 percent for MINIMUF-3.5. Whereas for HFMUFES 4 it is above 30 per- 57 CL - a / C 4L 4’ w I Z. LL U...Predictin2 the Performance of High-Frequency Skywave Telecomunication Systems (the use of the HFMJFES 4 Program), by GW Haydon, M Leftin , and R Rosich...in Ionospheric Maping by Numerical Methods, by WB Jones, RP Graham, and M Leftin , 12 May 1966. (Also Environmental Science Services Administration

  6. Extremely high frequency RF effects on electronics.

    SciTech Connect

    Loubriel, Guillermo Manuel; Vigliano, David; Coleman, Phillip Dale; Williams, Jeffery Thomas; Wouters, Gregg A.; Bacon, Larry Donald; Mar, Alan

    2012-01-01

    The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of effects as frequency increases into the millimeter-wave regime. Our purpose was to answer the questions, 'What are the tradeoffs between coupling, transmission losses, and device responses as frequency increases?', and, 'How high in frequency do effects on electronic systems continue to occur?' Using full wave electromagnetics codes and a transmission-line/circuit code, we investigated how extremely high-frequency RF propagates on wires and printed circuit board traces. We investigated both field-to-wire coupling and direct illumination of printed circuit boards to determine the significant mechanisms for inducing currents at device terminals. We measured coupling to wires and attenuation along wires for comparison to the simulations, looking at plane-wave coupling as it launches modes onto single and multiconductor structures. We simulated the response of discrete and integrated circuit semiconductor devices to those high-frequency currents and voltages, using SGFramework, the open-source General-purpose Semiconductor Simulator (gss), and Sandia's Charon semiconductor device physics codes. This report documents our findings.

  7. High power, high frequency, vacuum flange

    DOEpatents

    Felker, Brian; McDaniel, Michael R.

    1993-01-01

    An improved waveguide flange is disclosed for high power operation that helps prevent arcs from being initiated at the junctions between waveguide sections. The flanges at the end of the waveguide sections have counterbores surrounding the waveguide tubes. When the sections are bolted together the counterbores form a groove that holds a fully annealed copper gasket. Each counterbore has a beveled step that is specially configured to insure the gasket forms a metal-to-metal vacuum seal without gaps or sharp edges. The resultant inner surface of the waveguide is smooth across the junctions between waveguide sections, and arcing is prevented.

  8. High frequency dynamic pressure calibration technique

    NASA Technical Reports Server (NTRS)

    Davis, P. A.; Zasimowich, R. F.

    1985-01-01

    A high frequency dynamic calibration technique for pressure transducers has been developed using a siren pressure generator (SPG). The SPG is an inlet-area-modulated device generating oscillating waveforms with dynamic pressure amplitudes up to 58.6 kPa (8.5 psi) in a frequency range of 1 to 10 kHz. A description of the generator, its operating characteristics and instrumentation used for pressure amplitude and frequency measurements is given. Waveform oscillographs and spectral analysis of the pressure transducers' output signals are presented.

  9. High frequency dynamic pressure calibration technique

    NASA Astrophysics Data System (ADS)

    Davis, P. A.; Zasimowich, R. F.

    A high frequency dynamic calibration technique for pressure transducers has been developed using a siren pressure generator (SPG). The SPG is an inlet-area-modulated device generating oscillating waveforms with dynamic pressure amplitudes up to 58.6 kPa (8.5 psi) in a frequency range of 1 to 10 kHz. A description of the generator, its operating characteristics and instrumentation used for pressure amplitude and frequency measurements is given. Waveform oscillographs and spectral analysis of the pressure transducers' output signals are presented.

  10. High power radio frequency attenuation device

    DOEpatents

    Kerns, Quentin A.; Miller, Harold W.

    1984-01-01

    A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

  11. High-Frequency Observations of Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.; Marchenko-Jorstad, S. G.; Mattox, J. R.; Wehrle, A. E.; Aller, M. F.

    2000-01-01

    We report on the results of high-frequency VLBA observations of 42 gamma-ray bright blazars monitored at 22 and 43 GHz between 1993.9 and 1997.6. In 1997 the observations included polarization-sensitive imaging. The cores of gamma-ray blazars are only weakly polarized, with EVPAs (electric-vector position angles) usually within 40 deg of the local direction of the jet. The EVPAs of the jet components are usually within 20 deg of the local jet direction. The apparent speeds of the gamma-ray bright blazars are considerably faster than in the general population of bright compact radio sources. Two X-ray flares (observed with RXTE) of the quasar PKS 1510-089 appear to be related to radio flares, but with the radio leading the X-ray variations by about 2 weeks. This can be explained either by synchrotron self-Compton emission in a component whose variations are limited by light travel time or by the Mirror Compton model.

  12. High-Frequency Observations of Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.; Marchenko-Jorstad, S. G.; Mattox, J. R.; Wehrle, A. E.; Aller, M. F.

    2000-01-01

    We report on the results of high-frequency VLBA observations of 42 gamma ray bright blazars monitored at 22 and 43 GHz between 1993.9 and 1997-6. In 1997 the observations included polarization-sensitive imaging. The cores of gamma ray blazars are only weakly polarized, with EVPAs (electric-vector position angles) usually within 40 degrees of the local direction of the jet. The EVPAs of the jet components are usually within 20 degrees of the local jet direction. The apparent speeds of the gamma ray bright blazars are considerably faster than in the general population of bright compact radio sources. Two X-ray flares (observed with RXTE) of the quasar PKS 1510-089 appear to be related to radio flares, but with the radio leading the X-ray variations by about 2 weeks. This can be explained either by synchrotron self-Compton emission in a component whose variations are limited by light travel time or by the Mirror Compton model.

  13. High-Frequency Observations of Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.; Marchenko-Jorstad, S. G.; Mattox, J. R.; Wehrle, A. E.; Aller, M. F.

    2000-01-01

    We report on the results of high-frequency VLBA observations of 42 gamma ray bright blazars monitored at 22 and 43 GHz between 1993.9 and 1997-6. In 1997 the observations included polarization-sensitive imaging. The cores of gamma ray blazars are only weakly polarized, with EVPAs (electric-vector position angles) usually within 40 degrees of the local direction of the jet. The EVPAs of the jet components are usually within 20 degrees of the local jet direction. The apparent speeds of the gamma ray bright blazars are considerably faster than in the general population of bright compact radio sources. Two X-ray flares (observed with RXTE) of the quasar PKS 1510-089 appear to be related to radio flares, but with the radio leading the X-ray variations by about 2 weeks. This can be explained either by synchrotron self-Compton emission in a component whose variations are limited by light travel time or by the Mirror Compton model.

  14. [High-frequency ventilation. I. Distribution of alveolar pressure amplitudes during high frequency oscillation in the lung model].

    PubMed

    Theissen, J; Lunkenheimer, P P; Niederer, P; Bush, E; Frieling, G; Lawin, P

    1987-09-01

    The pattern of intrapulmonary pressure distribution was studied during high-frequency ventilation in order to explain the inconsistent results reported in the literature. Methods. Pressure and flow velocity (hot-wire anemometry) were measured in different lung compartments: 1. In transalveolar chambers sealed to the perforated pleural surfaces of dried pig lungs; 2. In emphysema-simulating airbags sealed to the isolated bronchial trees of dried pig lungs; and 3. In transalveolar chambers sealed to the perforated pleural surfaces of freshly excised pig lungs. Results. 1. The pressure amplitudes change from one area to another and depending on the exciting frequency. 2. High-frequency oscillation is associated with an increase in pressure amplitude when the exciting frequency rises, whereas with conventional high-frequency jet ventilation the pressure amplitude is more likely to decrease with frequency. 3. During high-frequency jet ventilation the local pressure amplitude changes with the position of the tube in the trachea rather than with the exciting frequency. 4. When the volume of the measuring chamber is doubled the resulting pressure amplitude falls to half the control value. 5. The pressure amplitude and mean pressure measured in the transalveolar chamber vary more or less independently from the peak flow velocity. High-frequency ventilation is thus seen to be a frequency-dependant, inhomogeneous mode of ventilation that can essentially be homogenized by systematically changing the exciting frequency. The frequency-dependant response to different lung areas to excitation is likely to result from an intrabronchially-localized aerodynamic effect rather than the mechanical properties of the lung parenchyma.

  15. High frequency ultrasonic scattering by biological tissues

    NASA Astrophysics Data System (ADS)

    Shung, K. Kirk; Maruvada, Subha

    2002-05-01

    High frequency (HF) diagnostic ultrasonic imaging devices at frequencies higher than 20 MHz have found applications in ophthalmology, dermatology, and vascular surgery. To be able to interpret these images and to further the development of these devices, a better understanding of ultrasonic scattering in biological tissues such as blood, liver, myocardium in the high frequency range is crucial. This work has previously been hampered by the lack of suitable transducers. With the availability of HF transducers going to 90 MHz, HF attenuation and backscatter experiments have been made on porcine red blood cell (RBC) suspensions, for which much data on attenuation and backscatter can be found in the literature in the lower frequency range for frequencies, from 30 to 90 MHz and on bovine tissues for frequencies from 10 to 30 MHz using a modified substitution method that allow the utilization of focused transducers. These results will be reviewed in this talk along with relevant theoretical models that could be applied to interpreting them. The relevance of the parameter that has been frequently used in the biomedical ultrasound literature to describe backscattering, the backscattering coefficient, will be critically examined.

  16. Degradation of PAHs by high frequency ultrasound.

    PubMed

    Manariotis, Ioannis D; Karapanagioti, Hrissi K; Chrysikopoulos, Constantinos V

    2011-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are persistent organic compounds, which have been reported in the literature to efficiently degrade at low (e.g. 20 kHz) and moderate (e.g. 506 kHz) ultrasound frequencies. The present study focuses on degradation of naphthalene, phenanthrene, and pyrene by ultrasound at three different relatively high frequencies (i.e. 582, 862, and 1142 kHz). The experimental results indicate that for all three frequencies and power inputs ≥ 133 W phenanthrene degrades to concentrations lower than our experimental detection limit (<1 μg/L). Phenanthrene degrades significantly faster at 582 kHz than at 862 and 1142 kHz. For all three frequencies, the degradation rates per unit mass are similar for naphthalene and phenanthrene and lower for pyrene. Furthermore, naphthalene degradation requires less energy than phenanthrene, which requires less energy than pyrene under the same conditions. No hexane-extractable metabolites were identified in the solutions.

  17. High-frequency micromechanical columnar resonators

    PubMed Central

    Kehrbusch, Jenny; Ilin, Elena A; Bozek, Peter; Radzio, Bernhard; Oesterschulze, Egbert

    2009-01-01

    High-frequency silicon columnar microresonators are fabricated using a simple but effective technological scheme. An optimized fabrication scheme was invented to obtain mechanically protected microcolumns with lateral dimensions controlled on a scale of at least 1 μm. In this paper, we investigate the influence of the environmental conditions on the mechanical resonator properties. At ambient conditions, we observed a frequency stability δf/f of less than 10−6 during 5 h of operation at almost constant temperature. However, varying the temperature shifts the frequency by approximately −173 Hz °C− 1. In accordance with a viscous damping model of the ambient gas, we perceived that the quality factor of the first flexural mode decreased with the inverse of the square root of pressure. However, in the low-pressure regime, a linear dependence was observed. We also investigated the influence of the type of the immersing gas on the resonant frequency. PMID:27877296

  18. RF Breakdown in High Frequency Accelerators

    SciTech Connect

    Doebert, S

    2004-05-27

    RF breakdown in high-frequency accelerators appears to limit the maximum achievable gradient as well as the reliability of such devices. Experimental results from high power tests, obtained mostly in the framework of the NLC/GLC project at 11 GHz and from the CLIC study at 30 GHz, will be used to illustrate the important issues. The dependence of the breakdown phenomena on rf pulse length, operating frequency and fabrication material will be described. Since reliability is extremely important for large scale accelerators such as a linear collider, the measurements of breakdown rate as a function of the operating gradient will be highlighted.

  19. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

    Thompson, Robert J.; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute

    2003-01-01

    This viewgraph presentation reports on the development of a high power 780 nm laser suitable for space applications of laser cooling. A possible solution is to use frequency doubling of high power 1560 nm telecom lasers. The presentation shows a diagram of the frequency conversion, and a graph of the second harmonic generation in one crystal, and the use of the cascading crystals. Graphs show the second harmonic power as a function of distance between crystals, second harmonic power vs. pump power, tunability of laser systems.

  20. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

    Thompson, Robert J.; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute

    2003-01-01

    This viewgraph presentation reports on the development of a high power 780 nm laser suitable for space applications of laser cooling. A possible solution is to use frequency doubling of high power 1560 nm telecom lasers. The presentation shows a diagram of the frequency conversion, and a graph of the second harmonic generation in one crystal, and the use of the cascading crystals. Graphs show the second harmonic power as a function of distance between crystals, second harmonic power vs. pump power, tunability of laser systems.

  1. Metrology For High-Frequency Nanoelectronics

    SciTech Connect

    Wallis, T. Mitch; Imtiaz, Atif; Nembach, Hans T.; Rice, Paul; Kabos, Pavel

    2007-09-26

    Two metrological tools for high-frequency measurements of nanoscale systems are described: (i) two/N-port analysis of nanoscale devices as well as (ii) near-field scanning microwave microscopy (NSMM) for materials characterization. Calibrated two/N-port measurements were made on multiwalled carbon nanotubes (MWNT) welded to a coplanar waveguide. Significant changes in the extracted high-frequency electrical response of the welded MWNT were measured when the contacts to the MWNT were modified. Additionally, NSMM was used to characterize films of nanotube soot deposited on copper and sapphire substrates. The material properties of the films showed a strong dependence on the substrate material.

  2. High frequency inductive lamp and power oscillator

    DOEpatents

    MacLennan, Donald A.; Dymond, Jr., Lauren E.; Gitsevich, Aleksandr; Grimm, William G.; Kipling, Kent; Kirkpatrick, Douglas A.; Ola, Samuel A.; Simpson, James E.; Trimble, William C.; Tsai, Peter; Turner, Brian P.

    2001-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and I or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to adjust the driving frequency of the oscillator.

  3. High frequency inductive lamp and power oscillator

    DOEpatents

    MacLennan, Donald A.; Turner, Brian P.; Dolan, James T.; Kirkpatrick, Douglas A.; Leng, Yongzhang

    2000-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.

  4. Positive Reinforcement at Pocomoke High School.

    ERIC Educational Resources Information Center

    Van Sciver, James H.

    1983-01-01

    Describes the efforts of a Maryland high school to strengthen its position in the community by means of public service radio messages, a "positive family contact" system that emphasizes positive reinforcement of student achievements, and a weekly newspaper column that acknowledges the contributions of "students, staff members and…

  5. Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions

    SciTech Connect

    Parui, Subir E-mail: l.hueso@nanogune.eu; Ribeiro, Mário; Atxabal, Ainhoa; Llopis, Roger; Bedoya-Pinto, Amilcar; Sun, Xiangnan; Casanova, Fèlix; Hueso, Luis E. E-mail: l.hueso@nanogune.eu

    2016-08-01

    The relevance for modern computation of non-volatile high-frequency memories makes ac-transport measurements of magnetic tunnel junctions (MTJs) crucial for exploring this regime. Here, we demonstrate a frequency-mediated effect in which the tunnel magnetoimpedance reverses its sign in a classical Co/Al{sub 2}O{sub 3}/NiFe MTJ, whereas we only observe a gradual decrease in the tunnel magnetophase. Such effects are explained by the capacitive coupling of a parallel resistor and capacitor in the equivalent circuit model of the MTJ. Furthermore, we report a positive tunnel magnetocapacitance effect, suggesting the presence of a spin-capacitance at the two ferromagnet/tunnel-barrier interfaces. Our results are important for understanding spin transport phenomena at the high frequency regime in which the spin-polarized charge accumulation due to spin-dependent penetration depth at the two interfaces plays a crucial role.

  6. Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Parui, Subir; Ribeiro, Mário; Atxabal, Ainhoa; Bedoya-Pinto, Amilcar; Sun, Xiangnan; Llopis, Roger; Casanova, Fèlix; Hueso, Luis E.

    2016-08-01

    The relevance for modern computation of non-volatile high-frequency memories makes ac-transport measurements of magnetic tunnel junctions (MTJs) crucial for exploring this regime. Here, we demonstrate a frequency-mediated effect in which the tunnel magnetoimpedance reverses its sign in a classical Co/Al2O3/NiFe MTJ, whereas we only observe a gradual decrease in the tunnel magnetophase. Such effects are explained by the capacitive coupling of a parallel resistor and capacitor in the equivalent circuit model of the MTJ. Furthermore, we report a positive tunnel magnetocapacitance effect, suggesting the presence of a spin-capacitance at the two ferromagnet/tunnel-barrier interfaces. Our results are important for understanding spin transport phenomena at the high frequency regime in which the spin-polarized charge accumulation due to spin-dependent penetration depth at the two interfaces plays a crucial role.

  7. High resolution low frequency ultrasonic tomography.

    PubMed

    Lasaygues, P; Lefebvre, J P; Mensah, S

    1997-10-01

    Ultrasonic reflection tomography results from a linearization of the inverse acoustic scattering problem, named the inverse Born approximation. The goal of ultrasonic reflection tomography is to obtain reflectivity images from backscattered measurements. This is a Fourier synthesis problem and the first step is to correctly cover the frequency space of the object. For this inverse problem, we use the classical algorithm of tomographic reconstruction by summation of filtered backprojections. In practice, only a limited number of views are available with our mechanical rig, typically 180, and the frequency bandwidth of the pulses is very limited, typically one octave. The resolving power of the system is them limited by the bandwidth of the pulse. Low and high frequencies can be restored by use of a deconvolution algorithm that enhances resolution. We used a deconvolution technique based on the Papoulis method. The advantage of this technique is conservation of the overall frequency information content of the signals. The enhancement procedure was tested by imaging a square aluminium rod with a cross-section less than the wavelength. In this application, the central frequency of the transducer was 250 kHz so that the central wavelength was 6 mm whereas the cross-section of the rod was 4 mm. Although the Born approximation was not theoretically valid in this case (high contrast), a good reconstruction was obtained.

  8. Real-Time Single Frequency Precise Point Positioning Using SBAS Corrections

    PubMed Central

    Li, Liang; Jia, Chun; Zhao, Lin; Cheng, Jianhua; Liu, Jianxu; Ding, Jicheng

    2016-01-01

    Real-time single frequency precise point positioning (PPP) is a promising technique for high-precision navigation with sub-meter or even centimeter-level accuracy because of its convenience and low cost. The navigation performance of single frequency PPP heavily depends on the real-time availability and quality of correction products for satellite orbits and satellite clocks. Satellite-based augmentation system (SBAS) provides the correction products in real-time, but they are intended to be used for wide area differential positioning at 1 meter level precision. By imposing the constraints for ionosphere error, we have developed a real-time single frequency PPP method by sufficiently utilizing SBAS correction products. The proposed PPP method are tested with static and kinematic data, respectively. The static experimental results show that the position accuracy of the proposed PPP method can reach decimeter level, and achieve an improvement of at least 30% when compared with the traditional SBAS method. The positioning convergence of the proposed PPP method can be achieved in 636 epochs at most in static mode. In the kinematic experiment, the position accuracy of the proposed PPP method can be improved by at least 20 cm relative to the SBAS method. Furthermore, it has revealed that the proposed PPP method can achieve decimeter level convergence within 500 s in the kinematic mode. PMID:27517930

  9. High spectral purity Kerr frequency comb radio frequency photonic oscillator

    PubMed Central

    Liang, W.; Eliyahu, D.; Ilchenko, V. S.; Savchenkov, A. A.; Matsko, A. B.; Seidel, D.; Maleki, L.

    2015-01-01

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than −60 dBc Hz−1 at 10 Hz, −90 dBc Hz−1 at 100 Hz and −170 dBc Hz−1 at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10−10 at 1–100 s integration time—orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption. PMID:26260955

  10. High spectral purity Kerr frequency comb radio frequency photonic oscillator.

    PubMed

    Liang, W; Eliyahu, D; Ilchenko, V S; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L

    2015-08-11

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz(-1) at 10 Hz, -90 dBc Hz(-1) at 100 Hz and -170 dBc Hz(-1) at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10(-10) at 1-100 s integration time-orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption.

  11. [High-frequency oscillatory ventilation in neonates].

    PubMed

    2002-09-01

    High-frequency oscillatory ventilation (HFOV) may be considered as an alternative in the management of severe neonatal respiratory failure requiring mechanical ventilation. In patients with diffuse pulmonary disease, HFOV can applied as a rescue therapy with a high lung volume strategy to obtain adequate alveolar recruitment. We review the mechanisms of gas exchange, as well as the indications, monitoring and special features of the use HVOF in the neonatal period.

  12. High efficiency quantum cascade laser frequency comb

    PubMed Central

    Lu, Quanyong; Wu, Donghai; Slivken, Steven; Razeghi, Manijeh

    2017-01-01

    An efficient mid-infrared frequency comb source is of great interest to high speed, high resolution spectroscopy and metrology. Here we demonstrate a mid-IR quantum cascade laser frequency comb with a high power output and narrow beatnote linewidth at room temperature. The active region was designed with a strong-coupling between the injector and the upper lasing level for high internal quantum efficiency and a broadband gain. The group velocity dispersion was engineered for efficient, broadband mode-locking via four wave mixing. The comb device exhibits a narrow intermode beatnote linewidth of 50.5 Hz and a maximum wall-plug efficiency of 6.5% covering a spectral coverage of 110 cm−1 at λ ~ 8 μm. The efficiency is improved by a factor of 6 compared with previous demonstrations. The high power efficiency and narrow beatnote linewidth will greatly expand the applications of quantum cascade laser frequency combs including high-precision remote sensing and spectroscopy. PMID:28262834

  13. High efficiency quantum cascade laser frequency comb

    NASA Astrophysics Data System (ADS)

    Lu, Quanyong; Wu, Donghai; Slivken, Steven; Razeghi, Manijeh

    2017-03-01

    An efficient mid-infrared frequency comb source is of great interest to high speed, high resolution spectroscopy and metrology. Here we demonstrate a mid-IR quantum cascade laser frequency comb with a high power output and narrow beatnote linewidth at room temperature. The active region was designed with a strong-coupling between the injector and the upper lasing level for high internal quantum efficiency and a broadband gain. The group velocity dispersion was engineered for efficient, broadband mode-locking via four wave mixing. The comb device exhibits a narrow intermode beatnote linewidth of 50.5 Hz and a maximum wall-plug efficiency of 6.5% covering a spectral coverage of 110 cm‑1 at λ ~ 8 μm. The efficiency is improved by a factor of 6 compared with previous demonstrations. The high power efficiency and narrow beatnote linewidth will greatly expand the applications of quantum cascade laser frequency combs including high-precision remote sensing and spectroscopy.

  14. High efficiency quantum cascade laser frequency comb.

    PubMed

    Lu, Quanyong; Wu, Donghai; Slivken, Steven; Razeghi, Manijeh

    2017-03-06

    An efficient mid-infrared frequency comb source is of great interest to high speed, high resolution spectroscopy and metrology. Here we demonstrate a mid-IR quantum cascade laser frequency comb with a high power output and narrow beatnote linewidth at room temperature. The active region was designed with a strong-coupling between the injector and the upper lasing level for high internal quantum efficiency and a broadband gain. The group velocity dispersion was engineered for efficient, broadband mode-locking via four wave mixing. The comb device exhibits a narrow intermode beatnote linewidth of 50.5 Hz and a maximum wall-plug efficiency of 6.5% covering a spectral coverage of 110 cm(-1) at λ ~ 8 μm. The efficiency is improved by a factor of 6 compared with previous demonstrations. The high power efficiency and narrow beatnote linewidth will greatly expand the applications of quantum cascade laser frequency combs including high-precision remote sensing and spectroscopy.

  15. High-frequency jet ventilation in a neonatal foal.

    PubMed

    Bain, F T; Brock, K A; Koterba, A M

    1988-04-01

    High-frequency jet ventilation was performed on a premature foal for respiratory difficulty attributable to in utero-acquired pneumonia. The procedure involves delivery of compressed gas through a small-bore cannula at frequencies up to 400 cycles/min. Ventilation settings of drive pressure, frequency, and FIO2 were varied to optimize PaO2 and PaCO2 values. The foal was ventilated with this equipment for 14 hours. Evidence of a favorable response to this method of ventilation was observed in the form of improvement in arterial blood gas values as well as the foal's attitude and degree of respiratory effort. High-frequency jet ventilation appears to be a useful method of ventilation for respiratory disease in neonatal foals; however, there remains no clear-cut advantage over conventional positive-pressure ventilation.

  16. Ionospheric modifications in high frequency heating experiments

    SciTech Connect

    Kuo, Spencer P.

    2015-01-15

    Featured observations in high-frequency (HF) heating experiments conducted at Arecibo, EISCAT, and high frequency active auroral research program are discussed. These phenomena appearing in the F region of the ionosphere include high-frequency heater enhanced plasma lines, airglow enhancement, energetic electron flux, artificial ionization layers, artificial spread-F, ionization enhancement, artificial cusp, wideband absorption, short-scale (meters) density irregularities, and stimulated electromagnetic emissions, which were observed when the O-mode HF heater waves with frequencies below foF2 were applied. The implication and associated physical mechanism of each observation are discussed and explained. It is shown that these phenomena caused by the HF heating are all ascribed directly or indirectly to the excitation of parametric instabilities which instigate anomalous heating. Formulation and analysis of parametric instabilities are presented. The results show that oscillating two stream instability and parametric decay instability can be excited by the O-mode HF heater waves, transmitted from all three heating facilities, in the regions near the HF reflection height and near the upper hybrid resonance layer. The excited Langmuir waves, upper hybrid waves, ion acoustic waves, lower hybrid waves, and field-aligned density irregularities set off subsequent wave-wave and wave-electron interactions, giving rise to the observed phenomena.

  17. Ionospheric modifications in high frequency heating experiments

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer P.

    2015-01-01

    Featured observations in high-frequency (HF) heating experiments conducted at Arecibo, EISCAT, and high frequency active auroral research program are discussed. These phenomena appearing in the F region of the ionosphere include high-frequency heater enhanced plasma lines, airglow enhancement, energetic electron flux, artificial ionization layers, artificial spread-F, ionization enhancement, artificial cusp, wideband absorption, short-scale (meters) density irregularities, and stimulated electromagnetic emissions, which were observed when the O-mode HF heater waves with frequencies below foF2 were applied. The implication and associated physical mechanism of each observation are discussed and explained. It is shown that these phenomena caused by the HF heating are all ascribed directly or indirectly to the excitation of parametric instabilities which instigate anomalous heating. Formulation and analysis of parametric instabilities are presented. The results show that oscillating two stream instability and parametric decay instability can be excited by the O-mode HF heater waves, transmitted from all three heating facilities, in the regions near the HF reflection height and near the upper hybrid resonance layer. The excited Langmuir waves, upper hybrid waves, ion acoustic waves, lower hybrid waves, and field-aligned density irregularities set off subsequent wave-wave and wave-electron interactions, giving rise to the observed phenomena.

  18. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-12-31

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  19. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-10-01

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  20. Frequency dependent polarization analysis of high-frequency seismograms

    NASA Astrophysics Data System (ADS)

    Park, Jeffrey; Vernon, Frank L., III; Lindberg, Craig R.

    1987-11-01

    We present a multitaper algorithm to estimate the polarization of particle motion as a function of frequency from three-component seismic data. This algorithm is based on a singular value decomposition of a matrix of eigenspectra at a given frequency. The right complex eigenvector zˆ corresonding to the largest singular value of the matrix has the same direction as the dominant polarization of seismic motion at that frequency. The elements of the polarization vector zˆ specify the relative amplitudes and phases of motion measured along the recorded components within a chosen frequency band. The width of this frequency band is determined by the time-bandwidth product of the prolate spheroidal tapers used in the analysis. We manipulate the components of zˆ to determine the apparent azimuth and angle of incidence of seismic motion as a function of frequency. The orthogonality of the eigentapers allows one to calculate easily uncertainties in the estimated azimuth and angle of incidence. We apply this algorithm to data from the Anza Seismic Telemetered Array in the frequency band 0 ≤ ƒ ≤ 30 Hz. The polarization is not always a smooth function of frequency and can exhibit sharp jumps, suggesting the existence of scattered modes within the crustal waveguide and/or receiver site resonances.

  1. High-frequency resonant-tunneling oscillators

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Parker, C. D.; Calawa, A. R.; Manfra, M. J.; Chen, C. L.

    1991-01-01

    Advances in high-frequency resonant-tunneling-diode (RTD) oscillators are described. Oscillations up to a frequency of 420 GHz have been achieved in the GaAs/AlAs system. Recent results obtained with In0.53Ga0.47As/AlAs and InAs/AlSb RTDs show a greatly increased power density and indicate the potential for fundamental oscillations up to about 1 THz. These results are consistent with a lumped-element equivalent circuit model of the RTD. The model shows that the maximum oscillation frequency of the GaAs/AlAs RTDs is limited primarily by series resistance, and that the power density is limited by low peak-to-valley current ratio.

  2. High Frequency Laser-Based Ultrasound

    SciTech Connect

    Huber, R; Chinn, D; Balogun, O; Murray, T

    2005-09-12

    To obtain micrometer resolution of materials using acoustics requires frequencies around 1 GHz. Attenuation of such frequencies is high, limiting the thickness of the parts that can be characterized. Although acoustic microscopes can operate up to several GHz in frequency, they are used primarily as a surface characterization tool. The use of a pulsed laser for acoustic generation allows generation directly in the part, eliminating the loss of energy associated with coupling the energy from a piezoelectric transducer to the part of interest. The use of pulsed laser acoustic generation in combination with optical detection is investigated for the non-contact characterization of materials with features that must be characterized to micrometer resolution.

  3. Protection circuitry for high frequency ultrasonic NDE

    NASA Astrophysics Data System (ADS)

    Chaggares, N. Chris; Tang, Raymond K.; Sinclair, A. N., Prof.; Foster, F. S., Prof.; Haraierciwz, Kasia; Starkoski, Brian

    2000-05-01

    Most commercial ultrasonic NDE equipment employs a voltage spike to stimulate a piezoelectric transducer. To protect the signal processing unit from damage from this spike, a voltage limiter or "diode clamp" is included in the pulser-receiver, and limits the voltage reaching the amplifier or oscilloscope. In this project, the deleterious effects of such limiters on the ultrasonic echo in the high frequency (50-100 MHz range) have been quantified: these effects include significant distortion in the frequency content, and oscillations causing a drop in timing resolution by over a factor of 2. To address these problems, a high-voltage high-frequency switch has been designed to replace the voltage limiter; the switch directs the high-voltage spike away from the signal processing/display unit, towards an impedance-matched termination. A prototype circuit has been built, based on two high-voltage MOSFET's acting as a switch for the bi-polar stimulation pulse. The reduction in echo distortion and improvement in time resolution have been successfully modeled with the CAD tool HSPICE, although parasitic capacitance in the current generation of commercial MOSFET's is a continuing concern.

  4. High frequency x-ray generator basics.

    PubMed

    Sobol, Wlad T

    2002-02-01

    The purpose of this paper is to present basic functional principles of high frequency x-ray generators. The emphasis is put on physical concepts that determine the engineering solutions to the problem of efficient generation and control of high voltage power required to drive the x-ray tube. The physics of magnetically coupled circuits is discussed first, as a background for the discussion of engineering issues related to high-frequency power transformer design. Attention is paid to physical processes that influence such factors as size, efficiency, and reliability of a high voltage power transformer. The basic electrical circuit of a high frequency generator is analyzed next, with focus on functional principles. This section investigates the role and function of basic components, such as power supply, inverter, and voltage doubler. Essential electronic circuits of generator control are then examined, including regulation of voltage, current and timing of electrical power delivery to the x-ray tube. Finally, issues related to efficient feedback control, including basic design of the AEC circuitry are reviewed.

  5. High Frequency Plasma Generators for Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Divergilio, W. F.; Goede, H.; Fosnight, V. V.

    1981-01-01

    The results of a one year program to experimentally adapt two new types of high frequency plasma generators to Argon ion thrusters and to analytically study a third high frequency source concept are presented. Conventional 30 cm two grid ion extraction was utilized or proposed for all three sources. The two plasma generating methods selected for experimental study were a radio frequency induction (RFI) source, operating at about 1 MHz, and an electron cyclotron heated (ECH) plasma source operating at about 5 GHz. Both sources utilize multi-linecusp permanent magnet configurations for plasma confinement. The plasma characteristics, plasma loading of the rf antenna, and the rf frequency dependence of source efficiency and antenna circuit efficiency are described for the RFI Multi-cusp source. In a series of tests of this source at Lewis Research Center, minimum discharge losses of 220+/-10 eV/ion were obtained with propellant utilization of .45 at a beam current of 3 amperes. Possible improvement modifications are discussed.

  6. Noise temperature in graphene at high frequencies

    NASA Astrophysics Data System (ADS)

    Rengel, Raúl; Iglesias, José M.; Pascual, Elena; Martín, María J.

    2016-07-01

    A numerical method for obtaining the frequency-dependent noise temperature in monolayer graphene is presented. From the mobility and diffusion coefficient values provided by Monte Carlo simulation, the noise temperature in graphene is studied up to the THz range, considering also the influence of different substrate types. The influence of the applied electric field is investigated: the noise temperature is found to increase with the applied field, dropping down at high frequencies (in the sub-THz range). The results show that the low-frequency value of the noise temperature in graphene on a substrate tends to be reduced as compared to the case of suspended graphene due to the important effect of remote polar phonon interactions, thus indicating a reduced emitted noise power; however, at very high frequencies the influence of the substrate tends to be significantly reduced, and the differences between the suspended and on-substrate cases tend to be minimized. The values obtained are comparable to those observed in GaAs and semiconductor nitrides.

  7. High-frequency Rayleigh-wave method

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

    2009-01-01

    High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  8. Frequency of positive states of mind as a moderator of the effects of stress on psychological functioning and perceived health.

    PubMed

    Bränström, Richard

    2013-01-01

    Emerging evidence indicates that individuals reporting more positive affect are healthier and live longer. The aim of this study was to examine if positive states of mind moderates the effect of perceived stress on psychological functioning and perceived health. A cross-sectional sample, n = 382, responded to questions regarding perceived stress, depression, anxiety, perceived health, and frequency of positive states of mind. Using a series of regression analyses, the results confirmed a moderating role of positive states of mind on the association between perceived stress and psychological outcomes. Among people experiencing a high frequency of positive states of mind, perceived stress seems to have a low correspondence with depression, anxiety, and perceived health. But among those reporting a low frequency of positive states of mind, perceived stress was more strongly related and depression, anxiety, and perceived health suggesting a buffering effect of positive states of mind against the negative influence of stress.

  9. Bootstrap position analysis for forecasting low flow frequency

    USGS Publications Warehouse

    Tasker, Gary D.; Dunne, P.

    1997-01-01

    A method of random resampling of residuals from stochastic models is used to generate a large number of 12-month-long traces of natural monthly runoff to be used in a position analysis model for a water-supply storage and delivery system. Position analysis uses the traces to forecast the likelihood of specified outcomes such as reservoir levels falling below a specified level or streamflows falling below statutory passing flows conditioned on the current reservoir levels and streamflows. The advantages of this resampling scheme, called bootstrap position analysis, are that it does not rely on the unverifiable assumption of normality, fewer parameters need to be estimated directly from the data, and accounting for parameter uncertainty is easily done. For a given set of operating rules and water-use requirements for a system, water managers can use such a model as a decision-making tool to evaluate different operating rules. ?? ASCE,.

  10. High-Frequency Percussive Ventilation Revisited

    DTIC Science & Technology

    2010-01-01

    physiologic and clin- ical outcomes. Pediatric and adult inhalational injury studies have linked HFPV to an improvement in static lung compliance...sedation–analgesic combinations (usually fentanyl with the individual or combined use of midazolam and propofol and/or dexmedetomidine), patient...1998;84:1174–7. 34. Frantz ID III, Close RH. Alveolar pressure swings during high frequency ventilation in rabbits. Pediatr Res 1985;19:162–6. 35. Pillow

  11. Triangle and concave pentagon electrodes for an improved broadband frequency response of stripline beam position monitors

    NASA Astrophysics Data System (ADS)

    Shobuda, Yoshihiro; Chin, Yong Ho; Takata, Koji; Toyama, Takeshi; Nakamura, Keigo

    2016-02-01

    The frequency domain performance of a stripline beam position monitor depends largely on the longitudinal shape of its electrode. Some shapes other than a conventional rectangle have been proposed and tested. To attain a good impedance matching along the electrode, they need to be precisely bent down toward their downstream in proportion to their width. This is a considerable task, and a failure to comply with it will result in a large distortion of the frequency-domain transfer function from the ideal one due to unwanted signal reflections. In this report, we first propose a triangle electrode for easy fabrication and setup: it only requires that a triangularly cut flat electrode will be placed in a chamber while being obliquely inclined toward the downstream port. Theoretical and simulation results show that the simple triangle electrode has a remarkably flatter frequency response than the rectangle one. The frequency response, in particular at high frequencies, can be further improved by attaching an "apron" plate, perpendicular to the upstream edge of the electrode. The overshooting of the frequency response at low frequency can be eliminated by replacing the straight sidelines of the triangle by three-point polylines (with a result that the triangle is transformed to a concave pentagon). The concave pentagon electrode needs to be bent only once at the middle point of the polylines for a good impedance matching and thus its fabrication and setup remain to be easy. Rf measurements for the various electrode shapes have been carried out. We found that the concave pentagon electrode achieves a wide and flat frequency response up to about 4 GHz for the J-PARC Main Ring (MR).

  12. High-resolution frequency measurement method with a wide-frequency range based on a quantized phase step law.

    PubMed

    Du, Baoqiang; Dong, Shaofeng; Wang, Yanfeng; Guo, Shuting; Cao, Lingzhi; Zhou, Wei; Zuo, Yandi; Liu, Dan

    2013-11-01

    A wide-frequency and high-resolution frequency measurement method based on the quantized phase step law is presented in this paper. Utilizing a variation law of the phase differences, the direct different frequency phase processing, and the phase group synchronization phenomenon, combining an A/D converter and the adaptive phase shifting principle, a counter gate is established in the phase coincidences at one-group intervals, which eliminates the ±1 counter error in the traditional frequency measurement method. More importantly, the direct phase comparison, the measurement, and the control between any periodic signals have been realized without frequency normalization in this method. Experimental results show that sub-picosecond resolution can be easily obtained in the frequency measurement, the frequency standard comparison, and the phase-locked control based on the phase quantization processing technique. The method may be widely used in navigation positioning, space techniques, communication, radar, astronomy, atomic frequency standards, and other high-tech fields.

  13. Inverter design for high frequency power distribution

    NASA Technical Reports Server (NTRS)

    King, R. J.

    1985-01-01

    A class of simple resonantly commutated inverters are investigated for use in a high power (100 KW - 1000 KW) high frequency (10 KHz - 20 KHz) AC power distribution system. The Mapham inverter is found to provide a unique combination of large thyristor turn-off angle and good utilization factor, much better than an alternate 'current-fed' inverter. The effects of loading the Mapham inverter entirely with rectifier loads are investigated by simulation and with an experimental 3 KW 20 KHz inverter. This inverter is found to be well suited to a power system with heavy rectifier loading.

  14. ERP correlates of letter identity and letter position are modulated by lexical frequency

    PubMed Central

    Vergara-Martínez, Marta; Perea, Manuel; Gómez, Pablo; Swaab, Tamara Y.

    2013-01-01

    The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created two pseudowords: A transposed-letter (TL: BRIGDE) and a replaced-letter pseudoword (RL: BRITGE). ERPs were recorded while participants read words and pseudowords in two tasks: Semantic categorization (Experiment 1) and lexical decision (Experiment 2). For high-frequency stimuli, similar ERPs were obtained for words and TL-pseudowords, but the N400 component to words was reduced relative to RL-pseudowords, indicating less lexical/semantic activation. In contrast, TL- and RL-pseudowords created from low-frequency stimuli elicited similar ERPs. Behavioral responses in the lexical decision task paralleled this asymmetry. The present findings impose constraints on computational and neural models of visual-word recognition. PMID:23454070

  15. High-frequency plasma-heating apparatus

    DOEpatents

    Brambilla, Marco; Lallia, Pascal

    1978-01-01

    An array of adjacent wave guides feed high-frequency energy into a vacuum chamber in which a toroidal plasma is confined by a magnetic field, the wave guide array being located between two toroidal current windings. Waves are excited in the wave guide at a frequency substantially equal to the lower frequency hybrid wave of the plasma and a substantially equal phase shift is provided from one guide to the next between the waves therein. For plasmas of low peripheral density gradient, the guides are excited in the TE.sub.01 mode and the output electric field is parallel to the direction of the toroidal magnetic field. For exciting waves in plasmas of high peripheral density gradient, the guides are excited in the TM.sub.01 mode and the magnetic field at the wave guide outlets is parallel to the direction of the toroidal magnetic field. The wave excited at the outlet of the wave guide array is a progressive wave propagating in the direction opposite to that of the toroidal current and is, therefore, not absorbed by so-called "runaway" electrons.

  16. Parametric nanomechanical amplification at very high frequency.

    PubMed

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  17. Computer modeling of tactical high frequency antennas

    NASA Astrophysics Data System (ADS)

    Gregory, Bobby G., Jr.

    1992-06-01

    The purpose of this thesis was to compare the performance of three tactical high frequency antennas to be used as possible replacement for the Tactical Data Communications Central (TDCC) antennas. The antennas were modeled using the Numerical Electromagnetics Code, Version 3 (NEC3), and the Eyring Low Profile and Buried Antenna Modeling Program (PAT7) for several different frequencies and ground conditions. The performance was evaluated by comparing gain at the desired takeoff angles, the voltage standing wave ratio of each antenna, and its omni-directional capability. The buried antenna models, the ELPA-302 and horizontal dipole, were most effective when employed over poor ground conditions. The best performance under all conditions tested was demonstrated by the HT-20T. Each of these antennas have tactical advantages and disadvantages and can optimize communications under certain conditions. The selection of the best antenna is situation dependent. An experimental test of these models is recommended to verify the modeling results.

  18. High-frequency ultrasonic wire bonding systems

    PubMed

    Tsujino; Yoshihara; Sano; Ihara

    2000-03-01

    The vibration characteristics of longitudinal-complex transverse vibration systems with multiple resonance frequencies of 350-980 kHz for ultrasonic wire bonding of IC, LSI or electronic devices were studied. The complex vibration systems can be applied for direct welding of semiconductor tips (face-down bonding, flip-chip bonding) and packaging of electronic devices. A longitudinal-complex transverse vibration bonding system consists of a complex transverse vibration rod, two driving longitudinal transducers 7.0 mm in diameter and a transverse vibration welding tip. The vibration distributions along ceramic and stainless-steel welding tips were measured at up to 980 kHz. A high-frequency vibration system with a height of 20.7 mm and a weight of less than 15 g was obtained.

  19. High-power femtosecond Raman frequency shifter.

    PubMed

    Vicario, Carlo; Shalaby, Mostafa; Konyashchenko, Aleksandr; Losev, Leonid; Hauri, Christoph P

    2016-10-15

    We report on the generation of broadband, high-energy femtosecond pulses centered at 1.28 μm by stimulated Raman scattering in a pressurized hydrogen cell. Stimulated Raman scattering is performed by two chirped and delayed pulses originating from a multi-mJ Ti:sapphire amplifier. The Stokes pulse carries record-high energy of 4.4 mJ and is recompressed down to 66 fs by a reflective grating pair. We characterized the short-wavelength mid-infrared source in view of energy stability, beam profile, and conversion efficiency at repetition rates of 100 and 10 Hz. The demonstrated high-energy frequency shifter will benefit intense THz sources based on highly nonlinear organic crystals.

  20. A high frequency electromagnetic impedance imaging system

    SciTech Connect

    Tseng, Hung-Wen; Lee, Ki Ha; Becker, Alex

    2003-01-15

    Non-invasive, high resolution geophysical mapping of the shallow subsurface is necessary for delineation of buried hazardous wastes, detecting unexploded ordinance, verifying and monitoring of containment or moisture contents, and other environmental applications. Electromagnetic (EM) techniques can be used for this purpose since electrical conductivity and dielectric permittivity are representative of the subsurface media. Measurements in the EM frequency band between 1 and 100 MHz are very important for such applications, because the induction number of many targets is small and the ability to determine the subsurface distribution of both electrical properties is required. Earlier workers were successful in developing systems for detecting anomalous areas, but quantitative interpretation of the data was difficult. Accurate measurements are necessary, but difficult to achieve for high-resolution imaging of the subsurface. We are developing a broadband non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using an EM impedance approach similar to the MT exploration technique. Electric and magnetic sensors were tested to ensure that stray EM scattering is minimized and the quality of the data collected with the high-frequency impedance (HFI) system is good enough to allow high-resolution, multi-dimensional imaging of hidden targets. Additional efforts are being made to modify and further develop existing sensors and transmitters to improve the imaging capability and data acquisition efficiency.

  1. Fuzzy and conventional control of high-frequency ventilation.

    PubMed

    Noshiro, M; Matsunami, T; Takakuda, K; Ryumae, S; Kagawa, T; Shimizu, M; Fujino, T

    1994-07-01

    A high-frequency ventilator was developed, consisting of a single-phase induction motor, an unbalanced mass and a mechanical vibration system. Intermittent positive pressure respiration was combined with high-frequency ventilation to measure end-tidal pCO2. Hysteresis was observed between the rotational frequency of the high-frequency ventilator and end-tidal pCO2. A fuzzy proportional plus integral control system, designed on the basis of the static characteristics of the controlled system and a knowledge of respiratory physiology, successfully regulated end-tidal pCO2. The characteristics of gas exchange under high-frequency ventilation was approximated by a first-order linear model. A conventional PI control system, designed on the basis of the approximated model, regulated end-tidal pCO2 with a performance similar to that of the fuzzy PI control system. The design of the fuzzy control system required less knowledge about the controlled system than that of the conventional control system.

  2. Material considerations for high frequency, high power capacitors

    NASA Technical Reports Server (NTRS)

    White, W.; Galperin, I.

    1983-01-01

    Dielectric materials chosen for use in this high frequency, high power capacitor must endure hard vacuum conditions, high currents (up to 125 A rms), and frequencies up to 40 kHz. Temperature requirements for this type of capacitor are that capacitor operation must be efficient up to 125 C. A more stringent requirement for the sold dielectric is that the temperature coefficient of dissipation factor should indicate self stabilization well below 125 C. In addition, the dielectric temperature coefficient of capacitance should be negative.

  3. Material considerations for high frequency, high power capacitors

    NASA Astrophysics Data System (ADS)

    White, W.; Galperin, I.

    1983-10-01

    Dielectric materials chosen for use in this high frequency, high power capacitor must endure hard vacuum conditions, high currents (up to 125 A rms), and frequencies up to 40 kHz. Temperature requirements for this type of capacitor are that capacitor operation must be efficient up to 125 C. A more stringent requirement for the sold dielectric is that the temperature coefficient of dissipation factor should indicate self stabilization well below 125 C. In addition, the dielectric temperature coefficient of capacitance should be negative.

  4. High frequency plasma generator for ion thrusters

    NASA Technical Reports Server (NTRS)

    Goede, H.; Divergilio, W. F.; Fosnight, V. V.; Komatsu, G.

    1984-01-01

    The results of a program to experimentally develop two new types of plasma generators for 30 cm electrostatic argon ion thrusters are presented. The two plasma generating methods selected for this study were by radio frequency induction (RFI), operating at an input power frequency of 1 MHz, and by electron cyclotron heating (ECH) at an operating frequency of 5.0 GHz. Both of these generators utilize multiline cusp permanent magnet configurations for plasma confinement and beam profile optimization. The program goals were to develop a plasma generator possessing the characteristics of high electrical efficiency (low eV/ion) and simplicity of operation while maintaining the reliability and durability of the conventional hollow cathode plasma sources. The RFI plasma generator has achieved minimum discharge losses of 120 eV/ion while the ECH generator has obtained 145 eV/ion, assuming a 90% ion optical transparency of the electrostatic acceleration system. Details of experimental tests with a variety of magnet configurations are presented.

  5. Aerodynamics of high frequency flapping wings

    NASA Astrophysics Data System (ADS)

    Hu, Zheng; Roll, Jesse; Cheng, Bo; Deng, Xinyan

    2010-11-01

    We investigated the aerodynamic performance of high frequency flapping wings using a 2.5 gram robotic insect mechanism developed in our lab. The mechanism flaps up to 65Hz with a pair of man-made wing mounted with 10cm wingtip-to-wingtip span. The mean aerodynamic lift force was measured by a lever platform, and the flow velocity and vorticity were measured using a stereo DPIV system in the frontal, parasagittal, and horizontal planes. Both near field (leading edge vortex) and far field flow (induced flow) were measured with instantaneous and phase-averaged results. Systematic experiments were performed on the man-made wings, cicada and hawk moth wings due to their similar size, frequency and Reynolds number. For insect wings, we used both dry and freshly-cut wings. The aerodynamic force increase with flapping frequency and the man-made wing generates more than 4 grams of lift at 35Hz with 3 volt input. Here we present the experimental results and the major differences in their aerodynamic performances.

  6. High-frequency graphene voltage amplifier.

    PubMed

    Han, Shu-Jen; Jenkins, Keith A; Valdes Garcia, Alberto; Franklin, Aaron D; Bol, Ageeth A; Haensch, Wilfried

    2011-09-14

    While graphene transistors have proven capable of delivering gigahertz-range cutoff frequencies, applying the devices to RF circuits has been largely hindered by the lack of current saturation in the zero band gap graphene. Herein, the first high-frequency voltage amplifier is demonstrated using large-area chemical vapor deposition grown graphene. The graphene field-effect transistor (GFET) has a 6-finger gate design with gate length of 500 nm. The graphene common-source amplifier exhibits ∼5 dB low frequency gain with the 3 dB bandwidth greater than 6 GHz. This first AC voltage gain demonstration of a GFET is attributed to the clear current saturation in the device, which is enabled by an ultrathin gate dielectric (4 nm HfO(2)) of the embedded gate structures. The device also shows extrinsic transconductance of 1.2 mS/μm at 1 V drain bias, the highest for graphene FETs using large-scale graphene reported to date.

  7. High Frequency Self-pulsing Microplasmas

    NASA Astrophysics Data System (ADS)

    Lassalle, John; Pollard, William; Staack, David

    2014-10-01

    Pulsing behavior in high-pressure microplasmas was studied. Microplasmas are of interest because of potential application in plasma switches for robust electronics. These devices require fast switching. Self-pulsing microplasmas were generated in a variable-length spark gap at pressures between 0 and 220 psig in Air, Ar, N2, H2, and He for spark gap lengths from 15 to 1810 μm. Resulting breakdown voltages varied between 90 and 1500 V. Voltage measurements show pulse frequencies as high as 8.9 MHz in argon at 100 psig. These findings demonstrate the potential for fast switching of plasma switches that incorporate high-pressure microplasmas. Work was supported by the National Science Foundation, Grant #1057175, and the Department of Defense, ARO Grant #W911NF1210007.

  8. ERP Correlates of Letter Identity and Letter Position Are Modulated by Lexical Frequency

    ERIC Educational Resources Information Center

    Vergara-Martinez, Marta; Perea, Manuel; Gomez, Pablo; Swaab, Tamara Y.

    2013-01-01

    The encoding of letter position is a key aspect in all recently proposed models of visual-word recognition. We analyzed the impact of lexical frequency on letter position assignment by examining the temporal dynamics of lexical activation induced by pseudowords extracted from words of different frequencies. For each word (e.g., BRIDGE), we created…

  9. Sleep Apnea in Patients with Acromegaly. Frequency, Characterization and Positive Pressure Titration

    PubMed Central

    Hernández-Gordillo, Daniel; Ortega-Gómez, María del Rocío; Galicia-Polo, Lourdes; Castorena-Maldonado, Armando; Vergara-López, Alma; Guillén-González, Miguel Ángel; Torre-Bouscoulet, Luis

    2012-01-01

    Objectives: to describe the frequency of sleep apnea in patients with acromegaly;to identify the proportion of candidates for treatment with positive airway pressure;to report our experience with the positive pressure titration process in acromegaly patients. Methods: A cross-sectional study that included the acromegaly cohort at the Centro Medico Nacional “20 de Noviembre” in Mexico City (n=44). A standard polysomnography (PSG) was carried out for each patient. A second PSG was done for purposes of CPAP titration. Results: A total of 35 patients were studied (80% of the cohort, 20 [57%] women). Polysomnography results showed that 34 subjects (97%, 95%CI 91-100%) had apnea hypopnea indexes (AHI) ≥ 5. No patient had central apnea. We identified 19 subjects with AHI ≥5 and Epworth ≥10, for a frequency of obstructive sleep apnea syndrome of 54% (95%CI 36-71%). A total of 31 patients (88%; 95%CI 77-99%) were deemed to be candidates for positive pressure treatment, but only 8 of them accepted CPAP. They required pressures that ranged from 10 to 18 cmH2O. Conclusions: Our results confirm a high prevalence of sleep apnea in patients with acromegaly, and provide evidence that the majority of those patients are candidates for treatment with positive pressure. Contrary to what has been reported, we identified no patients with central apnea. PMID:22754597

  10. Automated Screening for High-Frequency Hearing Loss

    PubMed Central

    MacKinnon, Robert C.; Jansen, Marije; Moore, David R.

    2014-01-01

    Objective: Hearing loss at high frequencies produces perceptual difficulties and is often an early sign of a more general hearing loss. This study reports the development and validation of two new speech-based hearing screening tests in English that focus on detecting hearing loss at frequencies above 2000 Hz. Design: The Internet-delivered, speech-in noise tests used closed target-word sets of digit triplets or consonant–vowel–consonant (CVC) words presented against a speech-shaped noise masker. The digit triplet test uses the digits 0 to 9 (excluding the disyllabic 7), grouped in quasi-random triplets. The CVC test uses simple words (e.g., “cat”) selected for the high-frequency spectral content of the consonants. During testing, triplets or CVC words were identified in an adaptive procedure to obtain the speech reception threshold (SRT) in noise. For these new, high-frequency (HF) tests, the noise was low-pass filtered to produce greater masking of the low-frequency speech components, increasing the sensitivity of the test for HF hearing loss. Individual test tokens (digits, CVCs) were first homogenized using a group of 10 normal-hearing (NH) listeners by equalizing intelligibility across tokens at several speech-in-noise levels. Both tests were then validated and standardized using groups of 24 NH listeners and 50 listeners with hearing impairment. Performance on the new high frequency digit triplet (HF-triplet) and CVC (HF-CVC) tests was compared with audiometric hearing loss, and with that on the unfiltered, broadband digit triplet test (BB-triplet) test, and the ASL (Adaptive Sentence Lists) speech-in-noise test. Results: The HF-triplet and HF-CVC test results (SRT) both correlated positively and highly with high-frequency audiometric hearing loss and with the ASL test. SRT for both tests as a function of high-frequency hearing loss increased at nearly three times the rate as that of the BB-triplet test. The intraindividual variability (SD) on the

  11. Automated screening for high-frequency hearing loss.

    PubMed

    Vlaming, Marcel S M G; MacKinnon, Robert C; Jansen, Marije; Moore, David R

    2014-01-01

    Hearing loss at high frequencies produces perceptual difficulties and is often an early sign of a more general hearing loss. This study reports the development and validation of two new speech-based hearing screening tests in English that focus on detecting hearing loss at frequencies above 2000 Hz. The Internet-delivered, speech-in noise tests used closed target-word sets of digit triplets or consonant-vowel-consonant (CVC) words presented against a speech-shaped noise masker. The digit triplet test uses the digits 0 to 9 (excluding the disyllabic 7), grouped in quasi-random triplets. The CVC test uses simple words (e.g., "cat") selected for the high-frequency spectral content of the consonants. During testing, triplets or CVC words were identified in an adaptive procedure to obtain the speech reception threshold (SRT) in noise. For these new, high-frequency (HF) tests, the noise was low-pass filtered to produce greater masking of the low-frequency speech components, increasing the sensitivity of the test for HF hearing loss. Individual test tokens (digits, CVCs) were first homogenized using a group of 10 normal-hearing (NH) listeners by equalizing intelligibility across tokens at several speech-in-noise levels. Both tests were then validated and standardized using groups of 24 NH listeners and 50 listeners with hearing impairment. Performance on the new high frequency digit triplet (HF-triplet) and CVC (HF-CVC) tests was compared with audiometric hearing loss, and with that on the unfiltered, broadband digit triplet test (BB-triplet) test, and the ASL (Adaptive Sentence Lists) speech-in-noise test. The HF-triplet and HF-CVC test results (SRT) both correlated positively and highly with high-frequency audiometric hearing loss and with the ASL test. SRT for both tests as a function of high-frequency hearing loss increased at nearly three times the rate as that of the BB-triplet test. The intraindividual variability (SD) on the tests was about 2.1 (HF-triplet) and 1

  12. High-Frequency Fluctuations During Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Jara-Almonte, J.; Ji, H.; Daughton, W. S.; Roytershteyn, V.; Yamada, M.; Yoo, J.; Fox, W. R., II

    2014-12-01

    During collisionless reconnection, the decoupling of the field from the plasma is known to occur only within the localized ion and electron diffusion regions, however predictions from fully kinetic simulations do not agree with experimental observations on the size of the electron diffusion region, implying differing reconnection mechanisms. Previous experiments, along with 2D and 3D simulations, have conclusively shown that this discrepancy cannot be explained by either classical collisions or Lower-Hybrid Drift Instability (Roytershtyn 2010, 2013). Due to computational limitations, however, previous simulations were constrained to have minimal scale separation between the electron skin depth and the Debye length (de/λD ~ 10), much smaller than in experiments (de/λD ~ 300). This lack of scale-separation can drastically modify the electrostatic microphysics within the diffusion layer. Using 3D, fully explicit kinetic simulations with a realistic and unprecedentedly large separation between the Debye length and the electron skin depth, de/λD = 64, we show that high frequency electrostatic waves (ω >> ωLH) can exist within the electron diffusion region. These waves generate small-scale turbulence within the electron diffusion region which acts to broaden the layer. Anomalous resistivity is also generated by the turbulence and significantly modifies the force balance. In addition to simulation results, initial experimental measurements of high frequency fluctuations (electrostatic and electromagnetic, f ≤ 1 GHz) in the Magnetic Reconnection Experiment (MRX) will be presented.

  13. Instantaneous Real-Time Kinematic Decimeter-Level Positioning with BeiDou Triple-Frequency Signals over Medium Baselines

    PubMed Central

    He, Xiyang; Zhang, Xiaohong; Tang, Long; Liu, Wanke

    2015-01-01

    Many applications, such as marine navigation, land vehicles location, etc., require real time precise positioning under medium or long baseline conditions. In this contribution, we develop a model of real-time kinematic decimeter-level positioning with BeiDou Navigation Satellite System (BDS) triple-frequency signals over medium distances. The ambiguities of two extra-wide-lane (EWL) combinations are fixed first, and then a wide lane (WL) combination is reformed based on the two EWL combinations for positioning. Theoretical analysis and empirical analysis is given of the ambiguity fixing rate and the positioning accuracy of the presented method. The results indicate that the ambiguity fixing rate can be up to more than 98% when using BDS medium baseline observations, which is much higher than that of dual-frequency Hatch-Melbourne-Wübbena (HMW) method. As for positioning accuracy, decimeter level accuracy can be achieved with this method, which is comparable to that of carrier-smoothed code differential positioning method. Signal interruption simulation experiment indicates that the proposed method can realize fast high-precision positioning whereas the carrier-smoothed code differential positioning method needs several hundreds of seconds for obtaining high precision results. We can conclude that a relatively high accuracy and high fixing rate can be achieved for triple-frequency WL method with single-epoch observations, displaying significant advantage comparing to traditional carrier-smoothed code differential positioning method. PMID:26703614

  14. Fundamentals of bipolar high-frequency surgery.

    PubMed

    Reidenbach, H D

    1993-04-01

    In endoscopic surgery a very precise surgical dissection technique and an efficient hemostasis are of decisive importance. The bipolar technique may be regarded as a method which satisfies both requirements, especially regarding a high safety standard in application. In this context the biophysical and technical fundamentals of this method, which have been known in principle for a long time, are described with regard to the special demands of a newly developed field of modern surgery. After classification of this method into a general and a quasi-bipolar mode, various technological solutions of specific bipolar probes, in a strict and in a generalized sense, are characterized in terms of indication. Experimental results obtained with different bipolar instruments and probes are given. The application of modern microprocessor-controlled high-frequency surgery equipment and, wherever necessary, the integration of additional ancillary technology into the specialized bipolar instruments may result in most useful and efficient tools of a key technology in endoscopic surgery.

  15. The interaction between body position and vibration frequency on acute response to whole body vibration.

    PubMed

    Di Giminiani, Riccardo; Masedu, Francesco; Tihanyi, Jozsef; Scrimaglio, Renato; Valenti, Marco

    2013-02-01

    The present study was designed to investigate the electromyographic (EMG) response in leg muscles to whole-body vibration while using different body positions and vibration frequencies. Twenty male sport sciences students voluntarily participated in this single-group, repeated-measures study in which EMG data from the vastus lateralis (VL) and the lateral gastrocnemius (LG) were collected over a total of 36 trials for each subject (4 static positions × 9 frequencies). We found that vibration frequency, body position and the muscle stimulated had a significant effect (P-values ranged from 0.001 to 0.031) on the EMG response. Similarly, the muscle × frequency and position × muscle interactions were significant (P < 0.001). Interestingly, the frequency × positions interactions were not significant (P > 0.05). Our results indicate that lower frequencies of vibration (25-35 Hz) result in maximal activation of LG, whereas higher frequencies (45-55 Hz) elicit the highest responses in the VL. In addition, the position P2 (half squat position with the heels raised) is beneficial both for VL and LG, independently of the vibration frequency. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. High frequency alternating current chip nano calorimeter with laser heating

    SciTech Connect

    Shoifet, E.; Schick, C.; Chua, Y. Z.; Huth, H.

    2013-07-15

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (∼1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm{sup 2}). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10{sup −3} Hz and 10{sup 6} Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  17. High frequency alternating current chip nano calorimeter with laser heating.

    PubMed

    Shoifet, E; Chua, Y Z; Huth, H; Schick, C

    2013-07-01

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (~1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm(2)). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10(-3) Hz and 10(6) Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  18. High frequency alternating current chip nano calorimeter with laser heating

    NASA Astrophysics Data System (ADS)

    Shoifet, E.; Chua, Y. Z.; Huth, H.; Schick, C.

    2013-07-01

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (˜1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm2). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10-3 Hz and 106 Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  19. Plasma effects in high frequency radiative transfer

    SciTech Connect

    Alonso, C.T.

    1981-02-08

    This paper is intended as a survey of collective plasma processes which can affect the transfer of high frequency radiation in a hot dense plasma. We are rapidly approaching an era when this subject will become important in the laboratory. For pedagogical reasons we have chosen to examine plasma processes by relating them to a particular reference plasma which will consist of fully ionized carbon at a temperature kT=1 KeV (10/sup 70/K) and an electron density N = 3 x 10/sup 23/cm/sup -3/, (which corresponds to a mass density rho = 1 gm/cm/sup 3/ and an ion density N/sub i/ = 5 x 10/sup 22/ cm/sup -3/). We will consider the transport in such a plasma of photons ranging from 1 eV to 1 KeV in energy. Such photons will probably be frequently used as diagnostic probes of hot dense laboratory plasmas.

  20. Frequency stable high power lasers in space

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.

    1989-01-01

    The concept of a laser heterodyne gravity wave antenna that would operate in solar orbit with a one million kilometer path length is discussed. Laser technology that would be appropriate for operation of this space-based gravity wave detector is also discussed. The rapid progress in diode laser coupled with the energy storage and potentially sub-Hertz linewidths of solid state lasers, and the possibility of efficient frequency conversion by nonlinear optical techniques defines a technology that is appropriate for laser interferometry in space. The present status of diode-laser-pumped, solid state lasers is summarized and future progress is projected in areas of linewidth control, high average power, operating efficiency, and operational lifetimes that are essential for space-based applications.

  1. High frequency oscillators for chaotic radar

    NASA Astrophysics Data System (ADS)

    Beal, A. N.; Blakely, J. N.; Corron, N. J.; Dean, R. N.

    2016-05-01

    This work focuses on implementing a class of exactly solvable chaotic oscillators at speeds that allow real world radar applications. The implementation of a chaotic radar using a solvable system has many advantages due to the generation of aperiodic, random-like waveforms with an analytic representation. These advantages include high range resolution, no range ambiguity, and spread spectrum characteristics. These systems allow for optimal detection of a noise-like signal by the means of a linear matched filter using simple and inexpensive methods. This paper outlines the use of exactly solvable chaos in ranging systems, while addressing electronic design issues related to the frequency dependence of the system's stretching function introduced by the use of negative impedance converters (NICs).

  2. High-Frequency Mechanostimulation of Cell Adhesion.

    PubMed

    Kadem, Laith F; Suana, K Grace; Holz, Michelle; Wang, Wei; Westerhaus, Hannes; Herges, Rainer; Selhuber-Unkel, Christine

    2017-01-02

    Cell adhesion is regulated by molecularly defined protein interactions and by mechanical forces, which can activate a dynamic restructuring of adhesion sites. Previous attempts to explore the response of cell adhesion to forces have been limited to applying mechanical stimuli that involve the cytoskeleton. In contrast, we here apply a new, oscillatory type of stimulus through push-pull azobenzenes. Push-pull azobenzenes perform a high-frequency, molecular oscillation upon irradiation with visible light that has frequently been applied in polymer surface relief grating. We here use these oscillations to address single adhesion receptors. The effect of molecular oscillatory forces on cell adhesion has been analyzed using single-cell force spectroscopy and gene expression studies. Our experiments demonstrate a reinforcement of cell adhesion as well as upregulated expression levels of adhesion-associated genes as a result of the nanoscale "tickling" of integrins. This novel type of mechanical stimulus provides a previously unprecedented molecular control of cellular mechanosensing.

  3. The positive effects of high-frequency right dorsolateral prefrontal cortex repetitive transcranial magnetic stimulation on memory, correlated with increases in brain metabolites detected by proton magnetic resonance spectroscopy in recently detoxified alcohol-dependent patients

    PubMed Central

    Qiao, Jun; Jin, Guixing; Lei, Licun; Wang, Lan; Du, Yaqiang; Wang, Xueyi

    2016-01-01

    Objective To explore the effect of right dorsolateral prefrontal cortex (DLPFC) repetitive transcranial magnetic stimulation (rTMS) on memory, and its correlation with levels of hippocampal brain metabolites detected by proton magnetic resonance spectroscopy (1H-MRS) in recently detoxified alcohol-dependent patients. Materials and methods In this randomized, double-blind sham-controlled trial, alcohol-dependent patients were enrolled and randomized into two groups: the experimental group (rTMS, 10 Hz, on right DLPFC, 20 sessions) and the control group (sham stimulation). Memory function was assessed using Hopkins Verbal Learning Test-Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R) before and after treatment. 1H-MRS was used to detect the levels of N-acetyl aspartic acid (NAA), choline (Cho), and creatine (Cr) in bilateral hippocampi before and after treatment. Results Thirty-eight patients (18 in the experimental group and 20 in the control group) were included in the analyses. The experimental group showed significantly greater changes in HVLT-R, BVMT-R, NAA/Cr, and Cho/Cr after rTMS from baseline than the control group. The percentage change in BVMT-R and HVLT-R correlated with the percentage change in NAA/Cr and Cho/Cr in the right brain. Conclusion High-frequency right DLPFC rTMS was associated with improvement in memory dysfunction, which is correlated with levels of hippocampal brain metabolites detected by 1H-MRS in recently detoxified alcohol-dependent patients. PMID:27695332

  4. Position Distinctiveness, Item Familiarity, and Presentation Frequency Affect Reconstruction of Order in Immediate Episodic Memory

    ERIC Educational Resources Information Center

    Healy, Alice F.; Shea, Kathleen M.; Kole, James A.; Cunningham, Thomas F.

    2008-01-01

    Three experiments examined the effects of position distinctiveness, item familiarity, and frequency of presentation on serial position functions in a task involving reconstructing the order of a subset of 12 names in a list of 20 names. Three different serial position conditions were compared in which the subset of names occurred in Positions…

  5. Modulating action of low frequency oscillations on high frequency instabilities in Hall thrusters

    SciTech Connect

    Liqiu, Wei E-mail: weiliqiu@hit.edu.cn; Liang, Han; Ziyi, Yang; Jing, Li; Yong, Cao; Daren, Yu; Jianhua, Du

    2015-02-07

    It is found that the low frequency oscillations have modulating action on high frequency instabilities in Hall thrusters. The physical mechanism of this modulation is discussed and verified by numerical simulations. Theoretical analyses indicate that the wide-range fluctuations of plasma density and electric field associated with the low frequency oscillations affect the electron drift velocity and anomalous electron transport across the magnetic field. The amplitude and frequency of high frequency oscillations are modulated by low frequency oscillations, which show the periodic variation in the time scale of low frequency oscillations.

  6. Advances in high frequency ultrasound separation of particulates from biomass.

    PubMed

    Juliano, Pablo; Augustin, Mary Ann; Xu, Xin-Qing; Mawson, Raymond; Knoerzer, Kai

    2017-03-01

    In recent years the use of high frequency ultrasound standing waves (megasonics) for droplet or cell separation from biomass has emerged beyond the microfluidics scale into the litre to industrial scale applications. The principle for this separation technology relies on the differential positioning of individual droplets or particles across an ultrasonic standing wave field within the reactor and subsequent biomass material predisposition for separation via rapid droplet agglomeration or coalescence into larger entities. Large scale transducers have been characterised with sonochemiluminescence and hydrophones to enable better reactor designs. High frequency enhanced separation technology has been demonstrated at industrial scale for oil recovery in the palm oil industry and at litre scale to assist olive oil, coconut oil and milk fat separation. Other applications include algal cell dewatering and milk fat globule fractionation. Frequency selection depends on the material properties and structure in the biomass mixture. Higher frequencies (1 and 2MHz) have proven preferable for better separation of materials with smaller sized droplets such as milk fat globules. For palm oil and olive oil, separation has been demonstrated within the 400-600kHz region, which has high radical production, without detectable impact on product quality. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

  7. Low frequency/high sensitivity triaxial monolithic sensor

    NASA Astrophysics Data System (ADS)

    Acernese, F.; Canonico, R.; De Rosa, R.; Giordano, G.; Romano, R.; Barone, F.

    2013-04-01

    This paper describes a new mechanical implementation of a triaxial sensor, configurable as seismometer and/or as accelerometer, consisting of three one-dimensional monolithic FP sensors, suitably geometrically positioned. The triaxial sensor is, therefore, compact, light, scalable, tunable instrument (frequency < 100 mHz with large band (10-7 Hz - 10 Hz), high quality factor (Q < 1500 in air) with good immunity to environmental noises, guaranteed by an integrated laser optical readout. The measured sensitivity curve is in very good agreement with the theoretical ones (10-12m/√Hz) in the band (0.1 ÷ 10Hz). Typical applications are in the field of earthquake engineering, geophysics, civil engineering and in all applications requiring large band-low frequency performances coupled with high sensitivities.

  8. Very low frequency/high sensitivity triaxial monolithic inertial sensor

    NASA Astrophysics Data System (ADS)

    Acernese, F.; De Rosa, R.; Giordano, G.; Romano, R.; Barone, F.

    2014-03-01

    This paper describes a new mechanical implementation of a triaxial sensor, configurable as seismometer and/or as accelerometer, consisting of three one-dimensional monolithic FP sensors, suitably geometrically positioned. The triaxial sensor is, therefore, compact, light, scalable, tunable instrument (frequency < 100mHz), with large band (10-7 Hz - 10Hz), high quality factor (Q > 2500 in air) with good immunity to environmental noises, guaranteed by an integrated laser optical readout. The measured sensitivity curve is in very good agreement with the theoretical ones (10-12m/√Hz) in the band (0.1 ÷ 10Hz). Typical applications are in the field of earthquake engineering, geophysics, civil engineering and in all applications requiring large band-low frequency performances coupled with high sensitivities.

  9. Low frequency/high sensitivity triaxial monolithic inertial sensor

    NASA Astrophysics Data System (ADS)

    Acernese, F.; De Rosa, R.; Giordano, G.; Romano, Rocco; Barone, F.

    2013-10-01

    This paper describes a new mechanical implementation of a triaxial sensor, configurable as seismometer and/or as accelerometer, consisting of three one-dimensional monolithic FP sensors, suitably geometrically positioned. The triaxial sensor is, therefore, compact, light, scalable, tunable instrument (frequency < 100mHz), with large band (10-7 Hz - 10Hz), high quality factor (Q < 2500 in air) with good immunity to environmental noises, guaranteed by an integrated laser optical readout. The measured sensitivity curve is in very good agreement with the theoretical ones (10-12m/pHz) in the band (0.1 ÷ 10Hz). Typical applications are in the field of earthquake engineering, geophysics, civil engineering and in all applications requiring large band-low frequency performances coupled with high sensitivities.

  10. Plant Responses to High Frequency Electromagnetic Fields

    PubMed Central

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre

    2016-01-01

    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  11. Extremely high-frequency therapy in oncology.

    PubMed

    Teppone, Mikhail; Avakyan, Romen

    2010-11-01

    This article represents a review of the literature, mainly from Russian sources, dealing with the therapeutic application of low-intensity electromagnetic radiation in the millimeter band applied to experimental and clinical oncology. At the early stage of these studies, efficacy and safety of millimeter electromagnetic radiation (extremely high frequency [EHF]) was proved for various types of malignant tumors. The majority of the further studies demonstrated the high efficacy and safety of millimeter wave radiation in treating patients suffering from both benign and malignant tumors. Developments led to treatment on skin melanoma, cancer of the ear-nose-throat, bowel and breast cancer, cancer of the uterus, lung, and stomach, solid tumors, as well as lymphoma. The main indications for this therapy are (1) preparation prior to radical treatment; (2) prevention and treatment of side-effects and complications from chemotherapy and radiotherapy; (3) prevention of metastases, relapses, and dissemination of the tumor; (4) treatment of the paraneoplastic syndrome; and (5) palliative therapy of incurable patients. In spite of the fact that not all mechanisms underlying effects of EHF therapy are known as yet, this therapeutic modality has been shown to have great potential in clinical oncology from studies performed in Eastern Europe and Russia.

  12. Thinking positively: The genetics of high intelligence

    PubMed Central

    Shakeshaft, Nicholas G.; Trzaskowski, Maciej; McMillan, Andrew; Krapohl, Eva; Simpson, Michael A.; Reichenberg, Avi; Cederlöf, Martin; Larsson, Henrik; Lichtenstein, Paul; Plomin, Robert

    2015-01-01

    High intelligence (general cognitive ability) is fundamental to the human capital that drives societies in the information age. Understanding the origins of this intellectual capital is important for government policy, for neuroscience, and for genetics. For genetics, a key question is whether the genetic causes of high intelligence are qualitatively or quantitatively different from the normal distribution of intelligence. We report results from a sibling and twin study of high intelligence and its links with the normal distribution. We identified 360,000 sibling pairs and 9000 twin pairs from 3 million 18-year-old males with cognitive assessments administered as part of conscription to military service in Sweden between 1968 and 2010. We found that high intelligence is familial, heritable, and caused by the same genetic and environmental factors responsible for the normal distribution of intelligence. High intelligence is a good candidate for “positive genetics” — going beyond the negative effects of DNA sequence variation on disease and disorders to consider the positive end of the distribution of genetic effects. PMID:25593376

  13. Thinking positively: The genetics of high intelligence.

    PubMed

    Shakeshaft, Nicholas G; Trzaskowski, Maciej; McMillan, Andrew; Krapohl, Eva; Simpson, Michael A; Reichenberg, Avi; Cederlöf, Martin; Larsson, Henrik; Lichtenstein, Paul; Plomin, Robert

    2015-01-01

    High intelligence (general cognitive ability) is fundamental to the human capital that drives societies in the information age. Understanding the origins of this intellectual capital is important for government policy, for neuroscience, and for genetics. For genetics, a key question is whether the genetic causes of high intelligence are qualitatively or quantitatively different from the normal distribution of intelligence. We report results from a sibling and twin study of high intelligence and its links with the normal distribution. We identified 360,000 sibling pairs and 9000 twin pairs from 3 million 18-year-old males with cognitive assessments administered as part of conscription to military service in Sweden between 1968 and 2010. We found that high intelligence is familial, heritable, and caused by the same genetic and environmental factors responsible for the normal distribution of intelligence. High intelligence is a good candidate for "positive genetics" - going beyond the negative effects of DNA sequence variation on disease and disorders to consider the positive end of the distribution of genetic effects.

  14. Radial Photonic Crystal for Detection of Frequency and Position of Radiation Sources

    DTIC Science & Technology

    2012-08-06

    able to perform beam shaping of punctual wave sources, and also to sense position and frequency of external radiators. Owing to the flexibility offered...shaping of punctual wave sources, and also to sense position and frequency of external radiators. Owing to the flexibility offered by the design...setup (see Fig. 3(b)) is a parallel plate waveguide where the RPC is illuminated with punctual sources (within the inner cavity or extern- ally) or

  15. High Frequency Electromagnetic Propagation/Scattering Codes

    DTIC Science & Technology

    2000-09-01

    Journal of Mathematical Analysis and Applications , 77...Frequency Limiting, Journal of Mathematical Analysis and Applications , 77, 469-481 (1980). [12] Y.T. Lo, S.W. Lee, editors, Antenna Handbook, Theory...Widom, Eigenvalue Distribution of Time and Frequency Limiting, Journal of Mathematical Analysis and Applications , 77, 469-481 (1980). [20] D.

  16. ENGLISH WORDS OF VERY HIGH FREQUENCY.

    ERIC Educational Resources Information Center

    CARD, WILLIAM; MCDAVID, VIRGINIA

    THE BIAS OF THE FREQUENCY OF THE 122 MOST COMMONLY USED ENGLISH WORDS WAS STUDIED. THE METHOD USED TO ASSEMBLE THESE DATA IS DESCRIBED FULLY. THE MOST FREQUENTLY USED WORDS WERE TAKEN FROM A DISSERTATION BY GEORGE K. MONROE, "PHONEMIC TRANSCRIPTION OF GRAPHIC POSTBASE AFFIXES IN ENGLISH," GODFREY DEWEY, "RELATIVE FREQUENCY OF ENGLISH SPEECH…

  17. Clinical Utilisation of High-frequency DPOAEs.

    PubMed

    Poling, Gayla; Lee, Jungmee; Siegel, Jonathan; Dhar, Sumitrajit

    2012-01-01

    The value of assessing auditory function at frequencies above 8kHz to detect age-related changes and ototoxic damage in the cochlea is well established but not commonplace. Physiological changes in the auditory periphery due to age and ototoxicity are initially evident, and most prominent, at frequencies above 8kHz [1]. The most well investigated use of hearing thresholds and otoacoustic emissions above 8kHz is in monitoring auditory function in patients undergoing chemotherapy [2]. Ototoxic changes in hearing thresholds at frequencies between 10-14kHz prior to the manifestation of any changes at lower frequencies have been consistently documented in these patients. Age-related changes in hearing also appear at frequencies above 8kHz prior to any observable changes at regular audiometric frequencies [3]. The value of using hearing thresholds at frequencies above 8kHz to detect noise-induced hearing loss is debated in the literature with some reports of hearing thresholds at frequencies above 8kHz demonstrating more sensitivity to noise-induced damage than others [4].

  18. A High Frequency Model of Cascade Noise

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    1998-01-01

    Closed form asymptotic expressions for computing high frequency noise generated by an annular cascade in an infinite duct containing a uniform flow are presented. There are two new elements in this work. First, the annular duct mode representation does not rely on the often-used Bessel function expansion resulting in simpler expressions for both the radial eigenvalues and eigenfunctions of the duct. In particular, the new representation provides an explicit approximate formula for the radial eigenvalues obviating the need for solutions of the transcendental annular duct eigenvalue equation. Also, the radial eigenfunctions are represented in terms of exponentials eliminating the numerical problems associated with generating the Bessel functions on a computer. The second new element is the construction of an unsteady response model for an annular cascade. The new construction satisfies the boundary conditions on both the cascade and duct walls simultaneously adding a new level of realism to the noise calculations. Preliminary results which demonstrate the effectiveness of the new elements are presented. A discussion of the utility of the asymptotic formulas for calculating cascade discrete tone as well as broadband noise is also included.

  19. Laser for high frequency modulated interferometry

    DOEpatents

    Mansfield, D.K.; Vocaturo, M.; Guttadora, L.J.

    1991-07-23

    A Stark-tuned laser operating in the 119 micron line of CH[sub 3]OH has an output power of several tens of milliwatts at 30 Watts of pump power while exhibiting a doublet splitting of about ten MHz with the application of a Stark field on the order of 500 volts/cm. This output power allows for use of the laser in a multi-channel interferometer, while its high operating frequency permits the interferometer to measure rapid electron density changes in a pellet injected or otherwise fueled plasma such as encountered in magnetic fusion devices. The laser includes a long far-infrared (FIR) pyrex resonator tube disposed within a cylindrical water jacket and incorporating charged electrodes for applying the Stark field to a gas confined therein. With the electrodes located within the resonator tube, the resonator tube walls are cooled by a flowing coolant without electrical breakdown in the coolant liquid during application of the Stark field. Wall cooling allows for substantially increased FIR output powers. Provision is made for introducing a buffer gas into the resonator tube for increasing laser output power and its operating bandwidth. 10 figures.

  20. Laser for high frequency modulated interferometry

    DOEpatents

    Mansfield, Dennis K.; Vocaturo, Michael; Guttadora, Lawrence J.

    1991-01-01

    A Stark-tuned laser operating in the 119 micron line of CH.sub.3 OH has an output power of several tens of milliwatts at 30 Watts of pump power while exhibiting a doublet splitting of about ten MHz with the application of a Stark field on the order of 500 volts/cm. This output power allows for use of the laser in a multi-channel interferometer, while its high operating frequency permits the interferometer to measure rapid electron density changes in a pellet injected or otherwise fueled plasma such as encountered in magnetic fusion devices. The laser includes a long far-infrared (FIR) pyrex resonator tube disposed within a cylindrical water jacket and incorporating charged electrodes for applying the Stark field to a gas confined therein. With the electrodes located within the resonator tube, the resonator tube walls are cooled by a flowing coolant without electrical breakdown in the coolant liquid during application of the Stark field. Wall cooling allows for substantially increased FIR output powers. Provision is made for introducing a buffer gas into the resonator tube for increasing laser output power and its operating bandwidth.

  1. Positioning performance improvements with European multiple-frequency satellite navigation - Galileo

    NASA Astrophysics Data System (ADS)

    Ji, Shengyue

    2008-10-01

    The rapid development of Global Positioning System has demonstrated the advantages of satellite based navigation systems. In near future, there will be a number of Global Navigation Satellite System (GNSS) available, i.e. modernized GPS, Galileo, restored GLONASS, BeiDou and many other regional GNSS augmentation systems. Undoubtedly, the new GNSS systems will significantly improve navigation performance over current GPS, with a better satellite coverage and multiple satellite signal bands. In this dissertation, the positioning performance improvement of new GNSS has been investigated based on both theoretical analysis and numerical study. First of all, the navigation performance of new GNSS systems has been analyzed, particularly for urban applications. The study has demonstrated that Receiver Autonomous Integrity Monitoring (RAIM) performance can be significantly improved with multiple satellite constellations, although the position accuracy improvement is limited. Based on a three-dimensional urban building model in Hong Kong streets, it is found that positioning availability is still very low in high-rising urban areas, even with three GNSS systems. On the other hand, the discontinuity of navigation solutions is significantly reduced with the combined constellations. Therefore, it is possible to use cheap DR systems to bridge the gaps of GNSS positioning, with high accuracy. Secondly, the ambiguity resolution performance has been investigated with Galileo multiple frequency band signals. The ambiguity resolution performance of three different algorithms is compared, including CAR, ILS and improved CAR methods (a new method proposed in this study). For short baselines, with four frequency Galileo data, it is highly possible to achieve reliable single epoch ambiguity resolution, when the carrier phase noise level is reasonably low (i.e. less than 6mm). For long baselines (up to 800 km), the integer ambiguity can be determined within 1 min on average. Ambiguity

  2. Acoustic trapping with a high frequency linear phased array.

    PubMed

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K Kirk

    2012-11-19

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  3. Acoustic trapping with a high frequency linear phased array

    PubMed Central

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K. Kirk

    2012-01-01

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array. PMID:23258939

  4. Fibre Bragg gratings subject to high strain at high frequencies

    NASA Astrophysics Data System (ADS)

    Jackson, D. A.

    2011-05-01

    A simple optical interrogation scheme based on an erbium doped fibre super-fluorescent source and a high Finesse Fabry Perot driven at effective frequencies of 20 kHz over ~ 60nm range is used to recover the output signals from Fibre Bragg Gratings (FBG) that can be deployed in a serial array. The FBG were modulated at frequencies up to 10 kHz and strains up to ~4000μstrain. These signals were recovered in the time domain with a very high bandwidth digital scope using a two dimensional waterfall display consisting of a number of segments where the time between segments is equal to the inverse of the system scanning frequency; essentially the sequential 'x' axis tick markers in a conventional x-y graph format. The amplitude induced changes in the wavelength of the FBG are converted to different times and observed as sequential horizontal scans along the time axis of the waterfall, correspond to the variations in the wavelength of the FBG (y axis). Signals from serial FBG arrays appear at different time slices on the time axis enabling near simultaneous determination of the induced strain of each grating.

  5. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

    Thompson, Rob; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute

    2003-01-01

    This slide presentation reviews the power frequencies for the doubled fiber laser. It includes information on the 780 nm laser, second harmonic generation in one crystal, cascading crystals, the tenability of laser systems, laser cooling, and directions for future work.

  6. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

    Thompson, Rob; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute

    2003-01-01

    This slide presentation reviews the power frequencies for the doubled fiber laser. It includes information on the 780 nm laser, second harmonic generation in one crystal, cascading crystals, the tenability of laser systems, laser cooling, and directions for future work.

  7. Modeling and assessment of triple-frequency BDS precise point positioning

    NASA Astrophysics Data System (ADS)

    Guo, Fei; Zhang, Xiaohong; Wang, Jinling; Ren, Xiaodong

    2016-11-01

    The latest generation of GNSS satellites such as GPS BLOCK-IIF, Galileo and BDS are transmitting signals on three or more frequencies, thus having more choices in practice. At the same time, new challenges arise for integrating the new signals. This paper contributes to the modeling and assessment of triple-frequency PPP with BDS data. First, three triple-frequency PPP models are developed. The observation model and stochastic model are designed and extended to accommodate the third frequency. In particular, new biases such as differential code biases and inter-frequency biases as well as the parameterizations are addressed. Then, the relationships between different PPP models are discussed. To verify the triple-frequency PPP models, PPP tests with real triple-frequency data were performed in both static and kinematic scenarios. Results show that the three triple-frequency PPP models agree well with each other. Additional frequency has a marginal effect on the positioning accuracy in static PPP tests. However, the benefits of third frequency are significant in situations of where there is poor tracking and contaminated observations on frequencies B1 and B2 in kinematic PPP tests.

  8. RF behavior of triple-frequency high power fusion gyrotron

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Singh, Udaybir; Kumar, Anil; Sinha, A. K.

    2014-05-01

    The RF behavior of high power, triple frequency (170-, 127.5-, and 85 GHz) gyrotron for fusion application is presented in this paper. The operating mode selection is discussed in detail for each corresponding frequencies and TE34,10, TE25,8 and TE17,5 modes are selected as the operating mode for 170 GHz, 127.5 GHz and 85 GHz operation of the device, respectively. The interaction cavity geometry and beam parameters are finalized by the cold cavity analysis and beam-wave interaction simulations. Considering the beam parameters and the beam launching positions in cavity (beam radius), the design of Magnetically Tunable MIG (MT-MIG) is also presented. Results of MT-MIG confirm the beam launching with desired beam parameters at the beam radius corresponding to the selected operating modes for all three frequencies. The CVD diamond window is also designed for RF power transmission. The beam-wave interaction simulations confirm more than 1 MW power at all three frequencies (170-, 127.5-, and 85 GHz).

  9. High-frequency instability of the sheath-plasma resonance

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.

    1989-01-01

    Coherent high frequency oscillations near the electron plasma frequency (omega approx. less than omega sub p) are generated by electrodes with positive dc bias immersed in a uniform Maxwellian afterglow plasma. The instability occurs at the sheath-plasma resonance and is driven by a negative RF sheath resistance associated with the electron inertia in the diode-like electron-rich sheath. With increasing dc bias, i.e., electron transit time, the instability exhibits a hard threshold, downward frequency pulling, line broadening and copious harmonics. The fundamental instability is a bounded oscillation due to wave evanescence, but the harmonics are radiated as electromagnetic waves from the electrodes acting like antennas. Wavelength and polarization measurements confirm the emission process. Electromagnetic waves are excited by electrodes of various geometries (planes, cylinders, spheres) which excludes other radiation mechanisms such as orbitrons or beam-plasma instabilities. The line broadening mechanism was identified as a frequency modulation via the electron transit time by dynamic ions. Ion oscillations at the sheath edge give rise to burst-like RF emissions. These laboratory observations of a new instability are important for antennas in space plasmas, generation of coherent beams with diodes, and plasma diagnostics.

  10. High-speed high-resolution heterodyne interferometer using a laser with low beat frequency.

    PubMed

    Diao, Xiaofei; Hu, Pengcheng; Xue, Zi; Kang, Yanhui

    2016-01-01

    A high-speed high-resolution heterodyne interferometer using a laser with low beat frequency is developed. The interferometer has two spatially separated parallel beams with different frequencies. Two interference signals with opposite Doppler shift are optically generated by the interferometric optics. The measurement electronics uses two identical phasemeters for the two opposite interference signals. The two interference signals are selectively used according to the speed of the target, which makes sure that the Doppler shift of the selected signal is always positive, so that the measurable speed is no longer limited by the beat frequency of the laser source. Experimental results show that the measurement resolution is 0.62 nm. The measurable speed can exceed the restriction determined by the beat frequency. Compared with a commercial interferometer, the displacement difference is less than 40 nm in a travel range of 900 mm.

  11. High Frequency QRS ECG Accurately Detects Cardiomyopathy

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds

    2005-01-01

    High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing

  12. High Frequency QRS ECG Accurately Detects Cardiomyopathy

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds

    2005-01-01

    High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing

  13. Ionospheric total-electron-content estimation for single-frequency Global-positioning-system receivers

    SciTech Connect

    Smith, C.A.

    1987-01-01

    The ionosphere delays transmissions from the Global Positioning System (GPS), as well as those from other satellite systems. At the GPS frequencies (L-Band), this delay is directly proportional to the total ionospheric electron content (TEC) along the line-of-sight to the satellite. Classified receivers have access to 2 frequencies to allow them to measure this delay through the difference in the ionospheric effect at the 2 frequencies, but commercial, single-frequency receivers have had no direct method for estimating the ionospheric delay; they have had to rely on a TEC prediction. Two methods are described for single-frequency GPS receivers to estimate the ionospheric TEC directly. These methods take advantage of the dispersive nature of the ionosphere at L-Band frequencies, which causes a phase advance of the carrier that is opposite to the group delay of the GPS code and data.

  14. Attenuation estimation using the peak frequency method with high-resolution time-frequency transforms

    NASA Astrophysics Data System (ADS)

    Tary, J. B.; Van der Baan, M.; Herrera, R. H.

    2016-12-01

    Seismic waves attenuate during their propagation due to Earth anelasticity. Attenuation is usually estimated by frequency domain methods such as the spectral ratio and frequency shift methods. These methods compare large frequency bandwidths of the spectra of two waveforms to compute attenuation. Time-frequency distribution resulting from high-resolution time-frequency transforms are highly localized which prevent their use to compute attenuation with these methods.The peak frequency method only requires the estimation of peak frequencies for a pair of waveforms to estimate attenuation, which is then compatible with high-resolution transforms. We here employ three transforms, namely basis pursuit, synchrosqueezing transform, and complete ensemble empirical mode decomposition (CEEMD). We evaluate their performance regarding attenuation estimation using synthetic examples with different signal-to-noise ratios, and compare their results to those of the spectral ratio and frequency shift methods. In most cases basis pursuit and the synchrosqueezing transform provide accurate results, while CEEMD show a higher sensitivity to the presence of noise.We then apply the three high-resolution transforms and the peak frequency method to two case studies, a seismic reflection profile and a vertical seismic profile (VSP). We employ centroid frequencies instead of peak frequencies because they provide stabler frequency estimates which are then transferred to stabler attenuation estimates. In the case of the seismic reflection profile, the three time-frequency transforms show small increases in centroid frequencies superimposed on a general decreasing trend. This likely corresponds to local tuning effects due to the layering superimposed on the effect of intrinsic attenuation. For the VSP, the three time-frequency transforms show consistent patterns in centroid frequencies and quality factors. These results show the worth of high-resolution transforms for attenuation estimation.

  15. Hearing Risk among Young Personal Listening Device Users: Effects at High-Frequency and Extended High-Frequency Audiogram Thresholds.

    PubMed

    Sulaiman, Ainul Huda; Husain, Ruby; Seluakumaran, Kumar

    2015-08-01

    The usage of personal listening devices (PLDs) is associated with risks of hearing loss. The aim of this study is to evaluate the effects of music exposure from these devices on high-frequency hearing thresholds of PLD users. A total of 282 young adults were questioned regarding their listening habits and symptoms associated with PLD listening. Their audiogram thresholds were determined at high (3-8 kHz) frequencies and extended high frequencies (EHFs, 9-16 kHz). The preferred listening volumes of PLD users were used to compute their overall 8-h equivalent music exposure levels (LAeq8h). Approximately 80% of the subjects were regular PLD users. Of these, 20.1% had LAeq8h of ≥75 dBA, while 4.4% of them had LAeq8h of ≥85 dBA, which carries a high risk of hearing damage. Compared with those exposed to LAeq8h of <75 dBA, subjects who had LAeq8h of ≥75 dBA reported a significantly higher incidence of tinnitus and difficulty in hearing others immediately after using PLDs. PLD users who were exposed to LAeq8h of ≥75 dBA and had been using their devices for ≥4 years also showed significantly higher mean audiogram thresholds compared with non-users at most EHFs tested. In addition, the thresholds of PLD users at EHFs showed a weak but significant positive correlation with their LAeq8h. The present findings suggest that excessive exposure to music among PLD users may lead to initial effects on their hearing at very high frequencies.

  16. An inkjet vision measurement technique for high-frequency jetting

    SciTech Connect

    Kwon, Kye-Si Jang, Min-Hyuck; Park, Ha Yeong; Ko, Hyun-Seok

    2014-06-15

    Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance.

  17. An inkjet vision measurement technique for high-frequency jetting.

    PubMed

    Kwon, Kye-Si; Jang, Min-Hyuck; Park, Ha Yeong; Ko, Hyun-Seok

    2014-06-01

    Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance.

  18. High speed curved position sensitive detector

    DOEpatents

    Hendricks, Robert W.; Wilson, Jack W.

    1989-01-01

    A high speed curved position sensitive porportional counter detector for use in x-ray diffraction, the detection of 5-20 keV photons and the like. The detector employs a planar anode assembly of a plurality of parallel metallic wires. This anode assembly is supported between two cathode planes, with at least one of these cathode planes having a serpentine resistive path in the form of a meander having legs generally perpendicular to the anode wires. This meander is produced by special microelectronic fabrication techniques whereby the meander "wire" fans outwardly at the cathode ends to produce the curved aspect of the detector, and the legs of the meander are small in cross-section and very closely spaced whereby a spatial resolution of about 50 .mu.m can be achieved. All of the other performance characteristics are about as good or better than conventional position sensitive proportional counter type detectors. Count rates of up to 40,000 counts per second with 0.5 .mu.s shaping time constants are achieved.

  19. A Novel Micro- and Nano-Scale Positioning Sensor Based on Radio Frequency Resonant Cavities

    PubMed Central

    Asua, Estibaliz; Etxebarria, Victor; García-Arribas, Alfredo; Feutchwanger, Jorge; Portilla, Joaquín; Lucas, Julio

    2014-01-01

    In many micro- and nano-scale technological applications high sensitivity displacement sensors are needed, especially in ultraprecision metrology and manufacturing. In this work a new way of sensing displacement based on radio frequency resonant cavities is presented and experimentally demonstrated using a first laboratory prototype. The principle of operation of the new transducer is summarized and tested. Furthermore, an electronic interface that can be used together with the displacement transducer is designed and proved. It has been experimentally demonstrated that very high and linear sensitivity characteristic curves, in the range of some kHz/nm; are easily obtainable using this kind of transducer when it is combined with a laboratory network analyzer. In order to replace a network analyzer and provide a more affordable, self-contained, compact solution, an electronic interface has been designed, preserving as much as possible the excellent performance of the transducer, and turning it into a true standalone positioning sensor. The results obtained using the transducer together with a first prototype of the electronic interface built with cheap discrete elements show that positioning accuracies in the micrometer range are obtainable using this cost-effective solution. Better accuracies would also be attainable but using more involved and costly electronics interfaces. PMID:24887041

  20. A novel micro- and nano-scale positioning sensor based on radio frequency resonant cavities.

    PubMed

    Asua, Estibaliz; Etxebarria, Victor; García-Arribas, Alfredo; Feutchwanger, Jorge; Portilla, Joaquín; Lucas, Julio

    2014-05-30

    In many micro- and nano-scale technological applications high sensitivity displacement sensors are needed, especially in ultraprecision metrology and manufacturing. In this work a new way of sensing displacement based on radio frequency resonant cavities is presented and experimentally demonstrated using a first laboratory prototype. The principle of operation of the new transducer is summarized and tested. Furthermore, an electronic interface that can be used together with the displacement transducer is designed and proved. It has been experimentally demonstrated that very high and linear sensitivity characteristic curves, in the range of some kHz/nm; are easily obtainable using this kind of transducer when it is combined with a laboratory network analyzer. In order to replace a network analyzer and provide a more affordable, self-contained, compact solution, an electronic interface has been designed, preserving as much as possible the excellent performance of the transducer, and turning it into a true standalone positioning sensor. The results obtained using the transducer together with a first prototype of the electronic interface built with cheap discrete elements show that positioning accuracies in the micrometer range are obtainable using this cost-effective solution. Better accuracies would also be attainable but using more involved and costly electronics interfaces.

  1. Auto-correlation function and frequency spectrum due to a super-position of uncorrelated exponential pulses

    NASA Astrophysics Data System (ADS)

    Garcia, O. E.; Theodorsen, A.

    2017-03-01

    The auto-correlation function and the frequency power spectral density due to a super-position of uncorrelated exponential pulses are considered. These are shown to be independent of the degree of pulse overlap and thereby the intermittency of the stochastic process. For constant pulse duration and a one-sided exponential pulse shape, the power spectral density has a Lorentzian shape which is flat for low frequencies and a power law at high frequencies. The algebraic tail is demonstrated to result from the discontinuity in the pulse function. For a strongly asymmetric two-sided exponential pulse shape, the frequency spectrum is a broken power law with two scaling regions. In the case of a symmetric pulse shape, the power spectral density is the square of a Lorentzian function. The steep algebraic tail at high frequencies in these cases is demonstrated to follow from the discontinuity in the derivative of the pulse function. A random distribution of pulse durations is shown to result in apparently longer correlation times but has no influence on the asymptotic power law tail of the frequency spectrum. The effect of additional random noise is also discussed, leading to a flat spectrum for high frequencies. The probability density function for the fluctuations is shown to be independent of the distribution of pulse durations. The predictions of this model describe the variety of auto-correlation functions and power spectral densities reported from experimental measurements in the scrape-off layer of magnetically confined plasmas.

  2. The tRNA-Tyr gene family of Saccharomyces cerevisiae: agents of phenotypic variation and position effects on mutation frequency.

    PubMed Central

    Ito-Harashima, Sayoko; Hartzog, Phillip E; Sinha, Himanshu; McCusker, John H

    2002-01-01

    Extensive phenotypic diversity or variation exists in clonal populations of microorganisms and is thought to play a role in adaptation to novel environments. This phenotypic variation or instability, which occurs by multiple mechanisms, may be a form of cellular differentiation and a stochastic means for modulating gene expression. This work dissects a case of phenotypic variation in a clinically derived Saccharomyces cerevisiae strain involving a cox15 ochre mutation, which acts as a reporter. The ochre mutation reverts to sense at a low frequency while tRNA-Tyr ochre suppressors (SUP-o) arise at a very high frequency to produce this phenotypic variation. The SUP-o mutations are highly pleiotropic. In addition, although all SUP-o mutations within the eight-member tRNA-Tyr gene family suppress the ochre mutation reporter, there are considerable phenotypic differences among the different SUP-o mutants. Finally, and of particular interest, there is a strong position effect on mutation frequency within the eight-member tRNA-Tyr gene family, with one locus, SUP6, mutating at a much higher than average frequency and two other loci, SUP2 and SUP8, mutating at much lower than average frequencies. Mechanisms for the position effect on mutation frequency are evaluated. PMID:12196388

  3. High permeability-high frequency stable MnZn ferrites

    NASA Astrophysics Data System (ADS)

    Kalarus, J.; Kogias, G.; Holz, D.; Zaspalis, V. T.

    2012-09-01

    Modern MnZn ferrite applications require high magnetic initial permeability and exceptional frequency stability; the former implies large grains, while the latter high grain boundary resistivity. In this article the optimization of the final firing process is described for achieving both. The optimization is based on the homogeneous dissolution of dopants under oxidative conditions and their subsequent precipitation along grain boundaries. This was accomplished by integrating isothermal plateaus at the upper stadia of the cooling stage of the final firing process. MnZn ferrites of the basic composition [Mn0.47Zn0.47Fe0.062+]Fe23+O4 were synthesized with initial permeability (measured at f=10 kHz, B<0.1 mT, T=25 °C) 12,600 and losses, expressed as tan(δ)/μi, of 3.1×10-6 at 10 kHz and 20.5×10-6 at 100 kHz (B<0.1 mT, T=25 °C), that reflect good frequency stability. These results could be reproduced in pilot production scale.

  4. High vs low frequency neural oscillations in schizophrenia.

    PubMed

    Moran, Lauren V; Hong, L Elliot

    2011-07-01

    There is growing recognition that neural oscillations are important in a wide range of perceptual and cognitive functions. One of the key issues in electrophysiological studies of schizophrenia is whether high or low frequency oscillations, or both, are related to schizophrenia because many brain functions are modulated with frequency specificities. Many recent electrophysiological studies of schizophrenia have focused on high frequency oscillations at gamma band and in general support gamma band dysfunction in schizophrenia. We discuss the concept that gamma oscillation abnormalities in schizophrenia often occur in the background of oscillation abnormalities of lower frequencies. The review discusses the basic neurobiology for the emergence of oscillations of all frequency bands in association with networks of inhibitory interneurons and the convergence and divergence of such mechanisms in generating high vs low frequency oscillations. We then review the literature of oscillatory frequency abnormalities identified in each frequency band in schizophrenia. By describing some of the key functional roles exerted by gamma, low frequencies, and their cross-frequency coupling, we conceptualize that even isolated alterations in gamma or low frequency oscillations may impact the interactions of high and low frequency bands that are involved in key cognitive functions. The review concludes that studying the full spectrum and the interaction of gamma and low frequency oscillations may be critical for deciphering the complex electrophysiological abnormalities observed in schizophrenia patients.

  5. High frequency noise studies at the Hartousov mofette area (CZE)

    NASA Astrophysics Data System (ADS)

    Schmidt, Andreas; Flores-Estrella, Hortencia; Pommerencke, Julia; Umlauft, Josefine

    2014-05-01

    Ambient noise analysis has been used as a reliable tool to investigate sub-surface structures at seismological quiet regions with none or less specific seismic events. Here, we consider the acoustic signals from a single mofette at the Hartoušov area (CZE) as a noise-like high frequency source caused by multiple near surface degassing processes in a restricted location. From this assumption we have used different array geometries for recording at least one hour of continuous noise. We installed triangular arrays with 3 component geophones: the first deployment consisted on two co-centric triangles with side length of 30 and 50 m with the mofette in the center; the second deployment consisted on two triangular arrays, both with side length of 30 m, co-directional to the mofette. Furthermore, we also installed profiles with 24 channels and vertical geophones locating them in different positions with respect to the mofette. In this work, we present preliminary results from the data analysis dependent on the geometry, to show the characteristics of the noise wave-field referring to frequency content and propagation features, such as directionality and surface wave velocity. The spectral analysis shows that the energy is concentrated in a frequency band among 10 and 40 Hz. However, in this interval there is no evidence of any exclusive fundamental frequencies. From this, man-induced influences can be identified as intermittent signal peaks in narrow frequency bands and can be separated to receive the revised mofette wave-field record. The inversion of dispersive surface waves, that were detected by interferometric methods, provides a velocity model down to 12 m with an S-wave velocity between 160 and 180 m/s on the uppermost layer. Furthermore, the interferometric signal properties indicate that it is not possible to characterize the mofette as a punctual source, but rather as a conglomerate of multiple sources with time and location variations.

  6. High-Frequency, High-Temperature Fretting Experiments

    NASA Technical Reports Server (NTRS)

    Matlik, J. F.; Farris, T. N.; Haake, F. K.; Swanson, G. R.; Duke, G. C.

    2005-01-01

    Fretting is a structural damage mechanism observed when two nominally clamped surfaces are subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high-temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact. These contact stresses drive crack nucleation and propagation in fretting and are very sensitive to the geometry of the contacting bodies, the contact loads, materials, temperature, and contact surface tribology (friction). To diagnose the threat that small and relatively undetectable fretting cracks pose to damage tolerance and structural integrity of in-service components, the objective of this work is to develop a well-characterized experimental fretting rig capable of investigating fretting behavior of advanced aerospace alloys subjected to load and temperature conditions representative of such turbomachinery components.

  7. High Frequency Shock During Random Vibration Testing

    DTIC Science & Technology

    2016-05-10

    Testing Level Natural Frequency (Hz) Ch. 17 Q Factor Test 1: White Noise 192.5 47.97 Test 2: -18 dB 192.5 51.11 Test 3: -15 dB 192.5 50.14 Test 4...12 dB 192.5 52.55 Test 5: -9 dB 192.5 44.99 Test 6: -6 dB 190 47.22 Test 7: White Noise 192.5 48.78 • -6dB Random Input • Shock origination...c o u s ti c P re s s u re ( P a ) Pre and Post White Noise Comparison Resonant frequencies and damping are unchanged after the shock event during

  8. High frequency model of stacked film capacitors

    NASA Astrophysics Data System (ADS)

    Talbert, T.; Joubert, C.; Daude, N.; Glaize, C.

    2001-11-01

    Polypropylene metallized capacitors are of general use in power electronics because of their reliability, their self-healing capabilities, and their low price. Though the behavior of metallized coiled capacitors has been discussed, no work has been carried out on stacked and flattened metallized capacitors. The purpose of this article is to suggest an analytical model of resonance frequency, stray inductance and impedance of stacked capacitors. We first solve the equation of propagation of the magnetic potential vector (A) in the dielectric of an homogeneous material. Then, we suggest an original method of resolution, like the one used for resonant cavities, in order to present an analytical solution of the problem. Finally, we give some experimental results proving that the physical knowledge of the parameters of the capacitor (dimension of the component, and material constants), enables us to calculate an analytical model of resonance frequency, stray inductance and impedance of stacked capacitors.

  9. Space position measurement using long-path heterodyne interferometer with optical frequency comb.

    PubMed

    Wang, Xiaonan; Takahashi, Satoru; Takamasu, Kiyoshi; Matsumoto, Hirokazu

    2012-01-30

    A heterodyne interference system was developed for position measurement. A stabilized optical-frequency comb is used as the laser source. The preliminary experiment to measure a distance of 22.478 m shows a drift of 1.6 μm in 20 minutes after the temperature compensation. Comparison and frequency shift experiments have been done for a distance of about 7.493 m. The experimental results show that the drift is mainly caused by environmental condition changes and the vibration of the table and floor also has some effects. It was verified that the absolute distance measurement can be realized by fringe scanning and frequency-shifting methods.

  10. Effects of interelectrode gap on high frequency and very high frequency capacitively coupled plasmas

    SciTech Connect

    Bera, Kallol; Rauf, Shahid; Ramaswamy, Kartik; Collins, Ken

    2009-07-15

    Capacitively coupled plasma (CCP) discharges using high frequency (HF) and very high frequency (VHF) sources are widely used for dielectric etching in the semiconductor industry. A two-dimensional fluid plasma model is used to investigate the effects of interelectrode gap on plasma spatial characteristics of both HF and VHF CCPs. The plasma model includes the full set of Maxwell's equations in their potential formulation. The peak in plasma density is close to the electrode edge at 13.5 MHz for a small interelectrode gap. This is due to electric field enhancement at the electrode edge. As the gap is increased, the plasma produced at the electrode edge diffuses to the chamber center and the plasma becomes more uniform. At 180 MHz, where electromagnetic standing wave effects are strong, the plasma density peaks at the chamber center at large interelectrode gap. As the interelectrode gap is decreased, the electron density increases near the electrode edge due to inductive heating and electrostatic electron heating, which makes the plasma more uniform in the interelectrode region.

  11. Micromachined high Q inductors for high-frequency applications

    NASA Astrophysics Data System (ADS)

    Park, Jae Y.; Allen, Mark G.

    1998-09-01

    To meet requirements in mobile communication and microwave integrated circuits, miniaturization of the inductive components that many of these systems require is of key importance. At present, active circuitry is used which simulates inductor performance and which has high Q-factor and inductance; however, such circuitry has higher power consumption and higher potential for noise injection than passive inductive components. An alternate approach is to fabricate integrated inductors, in which lithographic techniques are used to pattern an inductor directly on a substrate or a chip. However, integrated inductors can suffer from low Q-factor and high parasitic effects due to substrate proximity. To expand the applications of integrated inductors, these characteristics must be improved. High Q integrated spiral inductors are investigated using olymer/metal multilayer processing techniques and surface micromachining techniques. These inductors have spiral geometry with an air core and a large air gap (4Oim height) between the coils and the substrate (to reduce substrate capacitance), and thick, highly conductive electroplated copper conductor lines (to increase the quality factor). Various inductor geometries are investigated by designing and fabricating several inductors with differing core areas and numbers of turns. The fabricated inductors have a Q-factor of 40-75 at 300-700 MHz and an inductance at these frequencies between 30-7OnH.

  12. Ultra high frequency imaging acoustic microscope

    DOEpatents

    Deason, Vance A.; Telschow, Kenneth L.

    2006-05-23

    An imaging system includes: an object wavefront source and an optical microscope objective all positioned to direct an object wavefront onto an area of a vibrating subject surface encompassed by a field of view of the microscope objective, and to direct a modulated object wavefront reflected from the encompassed surface area through a photorefractive material; and a reference wavefront source and at least one phase modulator all positioned to direct a reference wavefront through the phase modulator and to direct a modulated reference wavefront from the phase modulator through the photorefractive material to interfere with the modulated object wavefront. The photorefractive material has a composition and a position such that interference of the modulated object wavefront and modulated reference wavefront occurs within the photorefractive material, providing a full-field, real-time image signal of the encompassed surface area.

  13. High Frequency Acoustic Propagation using Level Set Methods

    DTIC Science & Technology

    2007-01-01

    solution of the high frequency approximation to the wave equation. Traditional solutions to the Eikonal equation in high frequency acoustics are...curvature can be extracted at any point of the front from the level set function (provided the normal and curvature are well-defined at that point ), and... points per wavelength to resolve the wave). Ray tracing is therefore the current standard for high frequency propagation modeling. LSM may provide

  14. High-frequency Probing Diagnostic for Hall Current Plasma Thrusters

    SciTech Connect

    A.A. Litvak; Y. Raitses; N.J. Fisch

    2001-10-25

    High-frequency oscillations (1-100 MHz) in Hall thrusters have apparently eluded significant experimental scrutiny. A diagnostic setup, consisting of a single Langmuir probe, a special shielded probe connector-positioner, and an electronic impedance-matching circuit, was successfully built and calibrated. Through simultaneous high-frequency probing of the Hall thruster plasma at multiple locations, high-frequency plasma waves have been identified and characterized for various thruster operating conditions.

  15. On-clip high frequency reliability and failure test structures

    DOEpatents

    Snyder, E.S.; Campbell, D.V.

    1997-04-29

    Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer. 22 figs.

  16. On-clip high frequency reliability and failure test structures

    DOEpatents

    Snyder, Eric S.; Campbell, David V.

    1997-01-01

    Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer.

  17. High Frequency Acoustic Suppression - Experimental & Computational Overview

    DTIC Science & Technology

    2003-02-01

    mechanisms were the same. One of the drawbacks to the microjet impinging jet experiments was, however, that there was no obvious forcing frequency...Reduced In Impinging Jet Problem With 110 psi (Ref. 31) Application of Supersonic Microjets (Ref. 31). -s3 ~100. i 1 0 r 14’ ~10 100 10’ log top...cavity problem. The first step was to use the same actuator as in the Wiltse & Glezer experiment (Figure 5) and to modify the original free -jet

  18. A high frequency resonance gravity gradiometer

    NASA Astrophysics Data System (ADS)

    Bagaev, S. N.; Bezrukov, L. B.; Kvashnin, N. L.; Krysanov, V. A.; Oreshkin, S. I.; Motylev, A. M.; Popov, S. M.; Rudenko, V. N.; Samoilenko, A. A.; Skvortsov, M. N.; Yudin, I. S.

    2014-06-01

    A new setup OGRAN—the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events—gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS.

  19. A high frequency resonance gravity gradiometer

    SciTech Connect

    Bagaev, S. N.; Kvashnin, N. L.; Skvortsov, M. N.; Bezrukov, L. B.; Krysanov, V. A.; Oreshkin, S. I.; Motylev, A. M.; Popov, S. M.; Samoilenko, A. A.; Yudin, I. S.; Rudenko, V. N.

    2014-06-15

    A new setup OGRAN—the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events—gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS.

  20. A high frequency resonance gravity gradiometer.

    PubMed

    Bagaev, S N; Bezrukov, L B; Kvashnin, N L; Krysanov, V A; Oreshkin, S I; Motylev, A M; Popov, S M; Rudenko, V N; Samoilenko, A A; Skvortsov, M N; Yudin, I S

    2014-06-01

    A new setup OGRAN--the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events--gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS.

  1. Self isolating high frequency saturable reactor

    DOEpatents

    Moore, James A.

    1998-06-23

    The present invention discloses a saturable reactor and a method for decoupling the interwinding capacitance from the frequency limitations of the reactor so that the equivalent electrical circuit of the saturable reactor comprises a variable inductor. The saturable reactor comprises a plurality of physically symmetrical magnetic cores with closed loop magnetic paths and a novel method of wiring a control winding and a RF winding. The present invention additionally discloses a matching network and method for matching the impedances of a RF generator to a load. The matching network comprises a matching transformer and a saturable reactor.

  2. Analysis of High Frequency Seismic Data

    DTIC Science & Technology

    1990-10-01

    2 -4 iv 2.3 Relative noise power ia, narrow frequency bands as a function of time for noise segments at NORESS and KKL...Central Sweden Figure 2. The upper perspective diagram shows the number of events (ill all 5946) as a function of geograp ~hical location out to 1500 kml...al. (1986) obtained 1-18 I~igure i2. Number of events with magnitude ML>2.O and ML>3.Q as a fUnction of geograp ~hical location in relation to NORr.SS

  3. High efficiency, oxidation resistant radio frequency susceptor

    DOEpatents

    Besmann, Theodore M.; Klett, James W.

    2004-10-26

    An article and method of producing an article for converting energy from one form to another having a pitch-derived graphitic foam carbon foam substrate and a single layer coating applied to all exposed surfaces wherein the coating is either silicon carbide or carbides formed from a Group IVA metal. The article is used as fully coated carbon foam susceptors that more effectively absorb radio frequency (RF) band energy and more effectively convert the RF energy into thermal band energy or sensible heat. The essentially non-permeable coatings also serve as corrosion or oxidation resistant barriers.

  4. High-frequency asymptotics of circular dichroism

    NASA Astrophysics Data System (ADS)

    Pospelov, M. E.

    1996-07-01

    Circular dichroism of optically active isotropic media of chiral molecules Im(n+-n-)/Im(n++n-) falls off as ω-2 at frequencies Ry<<ω<>Z2Ry, where Z is a typical nuclear charge of atoms in the chiral group. The contribution of the spin of electron to the circular dichroism appears in the second order in spin-orbit perturbation only. The polarization of photoelectrons in the absorption of unpolarized light is connected with the chirality of molecule and constitutes Z2α3 from the degree of geometrical asymmetry.

  5. Warning signals are under positive frequency-dependent selection in nature.

    PubMed

    Chouteau, Mathieu; Arias, Mónica; Joron, Mathieu

    2016-02-23

    Positive frequency-dependent selection (FDS) is a selection regime where the fitness of a phenotype increases with its frequency, and it is thought to underlie important adaptive strategies resting on signaling and communication. However, whether and how positive FDS truly operates in nature remains unknown, which hampers our understanding of signal diversity. Here, we test for positive FDS operating on the warning color patterns of chemically defended butterflies forming multiple coexisting mimicry assemblages in the Amazon. Using malleable prey models placed in localities showing differences in the relative frequencies of warningly colored prey, we demonstrate that the efficiency of a warning signal increases steadily with its local frequency in the natural community, up to a threshold where protection stabilizes. The shape of this relationship is consistent with the direct effect of the local abundance of each warning signal on the corresponding avoidance knowledge of the local predator community. This relationship, which differs from purifying selection acting on each mimetic pattern, indicates that predator knowledge, integrated over the entire community, is saturated only for the most common warning signals. In contrast, among the well-established warning signals present in local prey assemblages, most are incompletely known to local predators and enjoy incomplete protection. This incomplete predator knowledge should generate strong benefits to life history traits that enhance warning efficiency by increasing the effective frequency of prey visible to predators. Strategies such as gregariousness or niche convergence between comimics may therefore readily evolve through their effects on predator knowledge and warning efficiency.

  6. Warning signals are under positive frequency-dependent selection in nature

    PubMed Central

    Chouteau, Mathieu; Arias, Mónica; Joron, Mathieu

    2016-01-01

    Positive frequency-dependent selection (FDS) is a selection regime where the fitness of a phenotype increases with its frequency, and it is thought to underlie important adaptive strategies resting on signaling and communication. However, whether and how positive FDS truly operates in nature remains unknown, which hampers our understanding of signal diversity. Here, we test for positive FDS operating on the warning color patterns of chemically defended butterflies forming multiple coexisting mimicry assemblages in the Amazon. Using malleable prey models placed in localities showing differences in the relative frequencies of warningly colored prey, we demonstrate that the efficiency of a warning signal increases steadily with its local frequency in the natural community, up to a threshold where protection stabilizes. The shape of this relationship is consistent with the direct effect of the local abundance of each warning signal on the corresponding avoidance knowledge of the local predator community. This relationship, which differs from purifying selection acting on each mimetic pattern, indicates that predator knowledge, integrated over the entire community, is saturated only for the most common warning signals. In contrast, among the well-established warning signals present in local prey assemblages, most are incompletely known to local predators and enjoy incomplete protection. This incomplete predator knowledge should generate strong benefits to life history traits that enhance warning efficiency by increasing the effective frequency of prey visible to predators. Strategies such as gregariousness or niche convergence between comimics may therefore readily evolve through their effects on predator knowledge and warning efficiency. PMID:26858416

  7. Calibration of High Frequency MEMS Microphones

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Humphreys, William M.; Bartram, Scott M.; Zuckewar, Allan J.

    2007-01-01

    Understanding and controlling aircraft noise is one of the major research topics of the NASA Fundamental Aeronautics Program. One of the measurement technologies used to acquire noise data is the microphone directional array (DA). Traditional direction array hardware, consisting of commercially available condenser microphones and preamplifiers can be too expensive and their installation in hard-walled wind tunnel test sections too complicated. An emerging micro-machining technology coupled with the latest cutting edge technologies for smaller and faster systems have opened the way for development of MEMS microphones. The MEMS microphone devices are available in the market but suffer from certain important shortcomings. Based on early experiments with array prototypes, it has been found that both the bandwidth and the sound pressure level dynamic range of the microphones should be increased significantly to improve the performance and flexibility of the overall array. Thus, in collaboration with an outside MEMS design vendor, NASA Langley modified commercially available MEMS microphone as shown in Figure 1 to meet the new requirements. Coupled with the design of the enhanced MEMS microphones was the development of a new calibration method for simultaneously obtaining the sensitivity and phase response of the devices over their entire broadband frequency range. Over the years, several methods have been used for microphone calibration. Some of the common methods of microphone calibration are Coupler (Reciprocity, Substitution, and Simultaneous), Pistonphone, Electrostatic actuator, and Free-field calibration (Reciprocity, Substitution, and Simultaneous). Traditionally, electrostatic actuators (EA) have been used to characterize air-condenser microphones for wideband frequency ranges; however, MEMS microphones are not adaptable to the EA method due to their construction and very small diaphragm size. Hence a substitution-based, free-field method was developed to

  8. High-precision positioning of radar scatterers

    NASA Astrophysics Data System (ADS)

    Dheenathayalan, Prabu; Small, David; Schubert, Adrian; Hanssen, Ramon F.

    2016-05-01

    Remote sensing radar satellites cover wide areas and provide spatially dense measurements, with millions of scatterers. Knowledge of the precise position of each radar scatterer is essential to identify the corresponding object and interpret the estimated deformation. The absolute position accuracy of synthetic aperture radar (SAR) scatterers in a 2D radar coordinate system, after compensating for atmosphere and tidal effects, is in the order of centimeters for TerraSAR-X (TSX) spotlight images. However, the absolute positioning in 3D and its quality description are not well known. Here, we exploit time-series interferometric SAR to enhance the positioning capability in three dimensions. The 3D positioning precision is parameterized by a variance-covariance matrix and visualized as an error ellipsoid centered at the estimated position. The intersection of the error ellipsoid with objects in the field is exploited to link radar scatterers to real-world objects. We demonstrate the estimation of scatterer position and its quality using 20 months of TSX stripmap acquisitions over Delft, the Netherlands. Using trihedral corner reflectors (CR) for validation, the accuracy of absolute positioning in 2D is about 7 cm. In 3D, an absolute accuracy of up to ˜ 66 cm is realized, with a cigar-shaped error ellipsoid having centimeter precision in azimuth and range dimensions, and elongated in cross-range dimension with a precision in the order of meters (the ratio of the ellipsoid axis lengths is 1/3/213, respectively). The CR absolute 3D position, along with the associated error ellipsoid, is found to be accurate and agree with the ground truth position at a 99 % confidence level. For other non-CR coherent scatterers, the error ellipsoid concept is validated using 3D building models. In both cases, the error ellipsoid not only serves as a quality descriptor, but can also help to associate radar scatterers to real-world objects.

  9. Comparison of the Frequency and Effectiveness of Positive and Negative Reinforcement Practices in Schools

    ERIC Educational Resources Information Center

    Dad, Hukam; Ali, Riasat; Janjua, Muhammad Zaigham Qadeer; Shahzad, Saqib; Khan, Muhammad Saeed

    2010-01-01

    The major purpose of the study was to compare the frequency and effectiveness of positive and negative reinforcement practices deployed by teachers in boys' and girls' secondary schools in urban and rural areas. It was hypothesized that there would be no difference in use of reward and punishment by teachers in secondary schools in urban and rural…

  10. High frequency properties of resonant tunneling diode

    NASA Astrophysics Data System (ADS)

    Sheng, H. Y.; Sinkkonen, J.

    The small signal analysis for the resonant tunneling diode (RTD) is carried out by using a semiclassical transport theory. Multiple scattering effects are accounted for in an optical approximation by using a complex mean free path. An analytical expression for the conduction current is given. The results show that the negative differential conductance prevails up to the frequency f0 limited by the quantum well transit time. The imaginary part of the admittance can be presented by a series inductance as has been recently found experimentally. In addition, the equivalent circuit has a capacitor in parallel with the conductance-inductance branch. Above f0 the admittance shows an oscillatory behaviour. The oscillations are associated with the quantum well transit time resonances.

  11. Transformed eddy-PV flux and positive synoptic eddy feedback onto low-frequency flow

    NASA Astrophysics Data System (ADS)

    Ren, Hong-Li; Jin, Fei-Fei; Kug, Jong-Seong; Gao, Li

    2011-06-01

    Interaction between synoptic eddy and low-frequency flow (SELF) has been the subject of many studies. In this study, we further examine the interaction by introducing a transformed eddy-potential-vorticity (TEPV) flux that is obtained from eddy-potential-vorticity flux through a quasi-geostrophic potential-vorticity inversion. The main advantage of using the TEPV flux is that it combines the effects of the eddy-vorticity and heat fluxes into the net acceleration of the low-frequency flow in such a way that the TEPV flux tends to be analogous to the eddy-vorticity fluxes in the barotropic framework. We show that the anomalous TEPV fluxes are preferentially directed to the left-hand side of the low-frequency flow in all vertical levels throughout the troposphere for monthly flow anomalies and for climate modes such as the Arctic Oscillation (AO). Furthermore, this left-hand preference of the TEPV flux direction is a convenient three-dimensional indicator of the positive reinforcement of the low-frequency flow by net eddy-induced acceleration. By projecting the eddy-induced net accelerations onto the low-frequency flow anomalies, we estimate the eddy-induced growth rates for the low frequency flow anomalies. This positive eddy-induced growth rate is larger (smaller) in the lower (upper) troposphere. The stronger positive eddy feedback in the lower troposphere may play an important role in maintaining an equivalent barotropic structure of the low-frequency atmospheric flow by balancing some of the strong damping effect of surface friction.

  12. Transformed Eddy-PV Flux and Positive Synoptic Eddy Feedback onto Low-Frequency Flow

    NASA Astrophysics Data System (ADS)

    Ren, H.; Jin, F.; Kug, J.; Gao, L.

    2010-12-01

    Interaction between synoptic eddy and low-frequency flow (SELF) has been the subject of many studies. In this study, we further examine the interaction by introducing a transformed eddy-potential-vorticity (TEPV) flux that is obtained from eddy-potential-vorticity flux through a quasi-geostrophic potential-vorticity inversion. The main advantage of using the TEPV flux is that it combines the effects of the eddy-vorticity and heat fluxes into the net acceleration of the low-frequency flow in such a way that the TEPV flux tends to be analogous to the eddy-vorticity fluxes in the barotropic framework. We show that the anomalous TEPV fluxes are preferentially directed to the left-hand side of the low-frequency flow in all vertical levels throughout the troposphere for monthly flow anomalies and for climate modes such as the Arctic Oscillation (AO). Furthermore, this left-hand preference of the TEPV flux direction is a convenient three-dimensional indicator of the positive reinforcement of the low-frequency flow by net eddy-induced acceleration. By projecting the eddy-induced net accelerations onto the low-frequency flow anomalies, we estimate the eddy-induced growth rates for the low frequency flow anomalies. This positive eddy-induced growth rate is larger (smaller) in the lower (upper) troposphere. The stronger positive eddy feedback in the lower troposphere may play an important role in maintaining an equivalent barotropic structure of the low-frequency atmospheric flow by balancing some of the strong damping effect of surface friction.

  13. Frequency of head-impact-related outcomes by position in NCAA division I collegiate football players.

    PubMed

    Baugh, Christine M; Kiernan, Patrick T; Kroshus, Emily; Daneshvar, Daniel H; Montenigro, Philip H; McKee, Ann C; Stern, Robert A

    2015-03-01

    Concussions and subconcussive impacts sustained in American football have been associated with short- and long-term neurological impairment, but differences in head impact outcomes across playing positions are not well understood. The American Medical Society for Sports Medicine has identified playing position as a key risk factor for concussion in football and one for which additional research is needed. This study examined variation in head impact outcomes across primary football playing positions in a group of 730 National Collegiate Athletic Association Division I Football Championship Series athletes, using a self-report questionnaire. Although there were no significant differences between position groups in the number of diagnosed concussions during the 2012 football season, there were significant differences between groups in undiagnosed concussions (p=0.008) and "dings" (p<0.001); offensive linemen reported significantly higher numbers than most other positions. Significant differences were found between position groups in the frequencies of several postimpact symptoms, including dizziness (p<0.001), headache (p<0.001), and seeing stars (p<0.001) during the 2012 football season, with offensive linemen reporting significantly more symptoms compared to most other groups. There were also positional differences in frequency of returning to play while symptomatic (p<0.001) and frequency of participating in full-contact practice (p<0.001). Offensive linemen reported having returned to play while experiencing symptoms more frequently and participating in more full-contact practices than other groups. These findings suggest that offensive linemen, a position group that experiences frequent, but low-magnitude, head impacts, develop more postimpact symptoms than other playing positions, but do not report these symptoms as a concussion.

  14. Frequency of Head-Impact–Related Outcomes by Position in NCAA Division I Collegiate Football Players

    PubMed Central

    Kiernan, Patrick T.; Kroshus, Emily; Daneshvar, Daniel H.; Montenigro, Philip H.; McKee, Ann C.; Stern, Robert A.

    2015-01-01

    Abstract Concussions and subconcussive impacts sustained in American football have been associated with short- and long-term neurological impairment, but differences in head impact outcomes across playing positions are not well understood. The American Medical Society for Sports Medicine has identified playing position as a key risk factor for concussion in football and one for which additional research is needed. This study examined variation in head impact outcomes across primary football playing positions in a group of 730 National Collegiate Athletic Association Division I Football Championship Series athletes, using a self-report questionnaire. Although there were no significant differences between position groups in the number of diagnosed concussions during the 2012 football season, there were significant differences between groups in undiagnosed concussions (p=0.008) and “dings” (p<0.001); offensive linemen reported significantly higher numbers than most other positions. Significant differences were found between position groups in the frequencies of several postimpact symptoms, including dizziness (p<0.001), headache (p<0.001), and seeing stars (p<0.001) during the 2012 football season, with offensive linemen reporting significantly more symptoms compared to most other groups. There were also positional differences in frequency of returning to play while symptomatic (p<0.001) and frequency of participating in full-contact practice (p<0.001). Offensive linemen reported having returned to play while experiencing symptoms more frequently and participating in more full-contact practices than other groups. These findings suggest that offensive linemen, a position group that experiences frequent, but low-magnitude, head impacts, develop more postimpact symptoms than other playing positions, but do not report these symptoms as a concussion. PMID:25155288

  15. Self-demodulation of high-frequency ultrasound.

    PubMed

    Vos, Hendrik J; Goertz, David E; de Jong, Nico

    2010-03-01

    High-frequency (>10 MHz) ultrasound is used in, e.g., small animal imaging or intravascular applications. Currently available ultrasound contrast agents (UCAs) have a suboptimal response for high frequencies. This study therefore investigates the nonlinear propagation effects in a high-frequency ultrasound field (25 MHz) and its use for standard UCA and diagnostic frequencies (1-3 MHz). Nonlinear mixing of two high-frequency carrier waves produces a low-frequency wave, known as the self-demodulation or parametric array effect. Hydrophone experiments showed that the self-demodulated field of a focused 25 MHz transducer (850 kPa source pressure) has an amplitude of 45 kPa at 1.5 MHz in water. Such pressure level is sufficient for UCA excitation. Experimental values are confirmed by numerical simulations using the Khokhlov-Zabolotskaya-Kuznetsov equation on a spatially convergent grid.

  16. Digital holographic microscope with low-frequency attenuation filter for position measurement of a nanoparticle.

    PubMed

    Pham, Quang Duc; Kusumi, Yuichi; Hasegawa, Satoshi; Hayasaki, Yoshio

    2012-10-01

    We propose a new method for three-dimensional (3D) position measurement of nanoparticles using an in-line digital holographic microscope. The method improves the signal-to-noise ratio of the amplitude of the interference fringes to achieve higher accuracy in the position measurement by increasing weak scattered light from a nanoparticle relative to the reference light by using a low spatial frequency attenuation filter. We demonstrated the improvements of signal-to-noise ratio of the optical system and contrast of the interference fringes, allowing the 3D positions of nanoparticles to be determined more precisely.

  17. Absolute positioning by multi-wavelength interferometry referenced to the frequency comb of a femtosecond laser.

    PubMed

    Wang, Guochao; Jang, Yoon-Soo; Hyun, Sangwon; Chun, Byung Jae; Kang, Hyun Jay; Yan, Shuhua; Kim, Seung-Woo; Kim, Young-Jin

    2015-04-06

    A multi-wavelength interferometer utilizing the frequency comb of a femtosecond laser as the wavelength ruler is tested for its capability of ultra-precision positioning for machine axis control. The interferometer uses four different wavelengths phase-locked to the frequency comb and then determines the absolute position through a multi-channel scheme of detecting interference phases in parallel so as to enable fast, precise and stable measurements continuously over a few meters of axis-travel. Test results show that the proposed interferometer proves itself as a potential candidate of absolute-type position transducer needed for next-generation ultra-precision machine axis control, demonstrating linear errors of less than 61.9 nm in peak-to-valley over a 1-meter travel with an update rate of 100 Hz when compared to an incremental-type He-Ne laser interferometer.

  18. CLASSIFICATION OF CATTLE ACTIVITY BASED UPON HIGH FREQUENCY SPATIAL POSITIONING

    USDA-ARS?s Scientific Manuscript database

    Animal behaviorists are interested in the spatial pattern of animals on landscapes because of their implications for species survival, resource use, and niche definition, as well as inter- nd intra -specific dominance, facilitation and competition. In the last several years it has become possible t...

  19. High frequency inductive lamp and power oscillator

    DOEpatents

    Kirkpatrick, Douglas A.; Gitsevich, Aleksandr

    2005-09-27

    An oscillator includes an amplifier having an input and an output, a feedback network connected between the input of the amplifier and the output of the amplifier, the feedback network being configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and a tuning circuit connected to the input of the amplifier, wherein the tuning circuit is continuously variable and consists of solid state electrical components with no mechanically adjustable devices including a pair of diodes connected to each other at their respective cathodes with a control voltage connected at the junction of the diodes. Another oscillator includes an amplifier having an input and an output, a feedback network connected between the input of the amplifier and the output of the amplifier, the feedback network being configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and transmission lines connected to the input of the amplifier with an input pad and a perpendicular transmission line extending from the input pad and forming a leg of a resonant "T", and wherein the feedback network is coupled to the leg of the resonant "T".

  20. DNA in nanopores: negative capacitance and delta-relaxation at high frequency.

    PubMed

    Mandal, S K

    2006-05-01

    We measured the high frequency dielectric relaxation behavior of DNA molecules confined in nanopores of polycarbonate membrane. The data revealed the existence of a critical frequency omega(c) approximately GHz at which the ac conductivity showed delta-relaxation. Interestingly, the DNA molecules also exhibited a crossover from positive to negative capacitance corresponding to omega(c). The negative capacitance at the critical frequency suggested a strong inductive behavior of DNA molecules in the high frequency regime. The results are interpreted in terms of the confined geometry of the DNA molecules in the nanopores. The interfacial water H-bonded to DNA played a crucial role in determining the high frequency relaxation of DNA molecules. The results indicated that the DNA in nanopores could be designed for application in high frequency bandpass/notch filters.

  1. Phase velocity limit of high-frequency photon density waves

    NASA Astrophysics Data System (ADS)

    Haskell, Richard C.; Svaasand, Lars O.; Madsen, Sten; Rojas, Fabio E.; Feng, T.-C.; Tromberg, Bruce J.

    1995-05-01

    In frequency-domain photon migration (FDPM), two factors make high modulation frequencies desirable. First, with frequencies as high as a few GHz, the phase lag versus frequency plot has sufficient curvature to yield both the scattering and absorption coefficients of the tissue under examination. Second, because of increased attenuation, high frequency photon density waves probe smaller volumes, an asset in small volume in vivo or in vitro studies. This trend toward higher modulation frequencies has led us to re-examine the derivation of the standard diffusion equation (SDE) from the Boltzman transport equation. We find that a second-order time-derivative term, ordinarily neglected in the derivation, can be significant above 1 GHz for some biological tissue. The revised diffusion equation, including the second-order time-derivative, is often termed the P1 equation. We compare the dispersion relation of the P1 equation with that of the SDE. The P1 phase velocity is slower than that predicted by the SDE; in fact, the SDE phase velocity is unbounded with increasing modulation frequency, while the P1 phase velocity approaches c/sqrt(3) is attained only at modulation frequencies with periods shorter than the mean time between scatterings of a photon, a frequency regime that probes the medium beyond the applicability of diffusion theory. Finally we caution that values for optical properties deduced from FDPM data at high frequencies using the SDE can be in error by 30% or more.

  2. High frequency properties of a CNT-based nanorelay

    NASA Astrophysics Data System (ADS)

    Jonsson, L. M.; Axelsson, S.; Nord, T.; Viefers, S.; Kinaret, J. M.

    2004-11-01

    We have theoretically investigated the high frequency properties of a carbon-nanotube-based three-terminal nanoelectromechanical relay. The intrinsic mechanical frequency of the relay is in the GHz regime, and the electromechanical coupling shows a non-linear resonant behaviour in this frequency range. We discuss how these resonances may be detected and show that the resonance frequencies can be tuned by the bias voltage. Also, we show that the influence of external electromagnetic fields on the relay is negligible at all frequencies.

  3. Effects of high frequency current in welding aluminum alloy 6061

    NASA Technical Reports Server (NTRS)

    Fish, R. E.

    1968-01-01

    Uncontrolled high frequency current causes cracking in the heat-affected zone of aluminum alloy 6061 weldments during tungsten inert gas ac welding. Cracking developed when an improperly adjusted superimposed high frequency current was agitating the semimolten metal in the areas of grain boundary.

  4. Influence of Smoking on Ultra-High-Frequency Auditory Sensitivity.

    PubMed

    Prabhu, Prashanth; Varma, Gowtham; Dutta, Kristi Kaveri; Kumar, Prajwal; Goyal, Swati

    2017-04-01

    In this study, an attempt was made to determine the effect of smoking on ultra-high-frequency auditory sensitivity. The study also attempted to determine the relationship between the nature of smoking and ultra-high-frequency otoacoustic emissions (OAEs) and thresholds. The study sample included 25 smokers and 25 non-smokers. A detailed history regarding their smoking habits was collected. High-frequency audiometric thresholds and amplitudes of high-frequency distortion-product OAEs were analyzed for both ears from all participants. The results showed that the ultra-high-frequency thresholds were elevated and that there was reduction in the amplitudes of ultra-high-frequency OAEs in smokers. There was an increased risk of auditory damage with chronic smoking. The study results highlight the application of ultra-high-frequency OAEs and ultra-high-frequency audiometry for the early detection of auditory impairment. However, similar studies should be conducted on a larger population for better generalization of the results.

  5. Parametric excitation of high-frequency electromagnetic waves by the lower-frequency dipole pumping

    SciTech Connect

    Gamayunov, K.V. ); Khazanov, G.V. ); Krivorutsky, E.N.; Veryaev, A.A. )

    1993-01-01

    The possibility of parametric excitation of high-frequency electromagnetic waves by lower-frequency dipole pumping is studied. It is shown that the obtained general dispersive equation may be reduced to the Mathieu equation, provided the case of the flux instability is neglected. In the framework of the developed approach, the excitation of magnetohydrodynamic waves and whistler oscillations is examined.

  6. Low and High-Frequency Field Potentials of Cortical Networks ...

    EPA Pesticide Factsheets

    Neural networks grown on microelectrode arrays (MEAs) have become an important, high content in vitro assay for assessing neuronal function. MEA experiments typically examine high- frequency (HF) (>200 Hz) spikes, and bursts which can be used to discriminate between different pharmacological agents/chemicals. However, normal brain activity is additionally composed of integrated low-frequency (0.5-100 Hz) field potentials (LFPs) which are filtered out of MEA recordings. The objective of this study was to characterize the relationship between HF and LFP neural network signals, and to assess the relative sensitivity of LFPs to selected neurotoxicants. Rat primary cortical cultures were grown on glass, single-well MEA chips. Spontaneous activity was sampled at 25 kHz and recorded (5 min) (Multi-Channel Systems) from mature networks (14 days in vitro). HF (spike, mean firing rate, MFR) and LF (power spectrum, amplitude) components were extracted from each network and served as its baseline (BL). Next, each chip was treated with either 1) a positive control, bicuculline (BIC, 25μM) or domoic acid (DA, 0.3μM), 2) or a negative control, acetaminophen (ACE, 100μM) or glyphosate (GLY, 100μM), 3) a solvent control (H2O or DMSO:EtOH), or 4) a neurotoxicant, (carbaryl, CAR 5, 30μM ; lindane, LIN 1, 10μM; permethrin, PERM 25, 50μM; triadimefon, TRI 5, 65μM). Post treatment, 5 mins of spontaneous activity was recorded and analyzed. As expected posit

  7. Structural drilling using the high-frequency (sonic) rotary method

    NASA Astrophysics Data System (ADS)

    Šporin, Jurij; Vukelić, Željko

    2017-03-01

    In Slovenia, there is widespread use of structural drilling along with classical core drilling. Recently, however, the need has arisen for a highly effective core drilling method with the aid of which high-quality core might be obtained. In order to achieve this aim, one among several Slovenian companies dealing with geological surveying has decided to implement structural drilling using a high-frequency drilling method. The following article presents the theoretical foundations for such a high-frequency method, as well as the manner of its implementation. In the final part of the article, a practical comparison between the conventional and the high-frequency core drilling methods is also provided.

  8. An investigation into the effect of joint frequency and spatial positioning on pre-splitting

    SciTech Connect

    Tariq, S.M.; Worsey, P.N.

    1995-12-31

    Pre-splitting is now widely used to minimize overbreak and to protect final surface rock excavation profiles in large scale civil construction projects, open pit mining and quarrying. Jointing has been shown to affect the success of pre-splitting and the smoothness and integrity of the resulting rock face. Many facets of jointing have been investigated in detail, including the inclination of joints with respect to the desired pre-split plane, the effects of various filling materials, etc. However, the effects of joint frequency and spatial positioning has been paid little attention. The paper addresses this issue. The results of experimental model testing carried out in concrete blocks are presented. The program consisted of modeling closed joints with varying frequency between two 3/8 inch boreholes, drilled in 12 x 9 x 6 inch concrete blocks charged with 15 grains per foot PETN cord. It was found that by increasing the joint frequency from zero to two between boreholes decreases the maximum successful split-hole spacing. However, with increasing joint frequency the trend is reversed. These results are attributed to the overall rock mass being weakened by the slabs between the discontinuities becoming thinner with increasing discontinuity frequency. It was also revealed that the spatial positioning of discontinuities plays an important role in pre-split formation and integrity.

  9. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, H.D.

    1996-04-30

    A method and apparatus for monitoring an electrical-motor-driven device by injecting a high frequency carrier signal onto the power line current. The method is accomplished by injecting a high frequency carrier signal onto an AC power line current. The AC power line current supplies the electrical-motor-driven device with electrical energy. As a result, electrical and mechanical characteristics of the electrical-motor-driven device modulate the high frequency carrier signal and the AC power line current. The high frequency carrier signal is then monitored, conditioned and demodulated. Finally, the modulated high frequency carrier signal is analyzed to ascertain the operating condition of the electrical-motor-driven device. 6 figs.

  10. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, Howard D.

    1996-01-01

    A method and apparatus for monitoring an electrical-motor-driven device by injecting a high frequency carrier signal onto the power line current. The method is accomplished by injecting a high frequency carrier signal onto an AC power line current. The AC power line current supplies the electrical-motor-driven device with electrical energy. As a result, electrical and mechanical characteristics of the electrical-motor-driven device modulate the high frequency carrier signal and the AC power line current. The high frequency carrier signal is then monitored, conditioned and demodulated. Finally, the modulated high frequency carrier signal is analyzed to ascertain the operating condition of the electrical-motor-driven device.

  11. Nanohertz frequency determination for the gravity probe B high frequency superconducting quantum interference device signal.

    PubMed

    Salomon, M; Conklin, J W; Kozaczuk, J; Berberian, J E; Keiser, G M; Silbergleit, A S; Worden, P; Santiago, D I

    2011-12-01

    In this paper, we present a method to measure the frequency and the frequency change rate of a digital signal. This method consists of three consecutive algorithms: frequency interpolation, phase differencing, and a third algorithm specifically designed and tested by the authors. The succession of these three algorithms allowed a 5 parts in 10(10) resolution in frequency determination. The algorithm developed by the authors can be applied to a sampled scalar signal such that a model linking the harmonics of its main frequency to the underlying physical phenomenon is available. This method was developed in the framework of the gravity probe B (GP-B) mission. It was applied to the high frequency (HF) component of GP-B's superconducting quantum interference device signal, whose main frequency f(z) is close to the spin frequency of the gyroscopes used in the experiment. A 30 nHz resolution in signal frequency and a 0.1 pHz/s resolution in its decay rate were achieved out of a succession of 1.86 s-long stretches of signal sampled at 2200 Hz. This paper describes the underlying theory of the frequency measurement method as well as its application to GP-B's HF science signal.

  12. High temperature pressurized high frequency testing rig and test method

    DOEpatents

    De La Cruz, Jose; Lacey, Paul

    2003-04-15

    An apparatus is described which permits the lubricity of fuel compositions at or near temperatures and pressures experienced by compression ignition fuel injector components during operation in a running engine. The apparatus consists of means to apply a measured force between two surfaces and oscillate them at high frequency while wetted with a sample of the fuel composition heated to an operator selected temperature. Provision is made to permit operation at or near the flash point of the fuel compositions. Additionally a method of using the subject apparatus to simulate ASTM Testing Method D6079 is disclosed, said method involving using the disclosed apparatus to contact the faces of prepared workpieces under a measured load, sealing the workface contact point into the disclosed apparatus while immersing said contact point between said workfaces in a lubricating media to be tested, pressurizing and heating the chamber and thereby the fluid and workfaces therewithin, using the disclosed apparatus to impart a differential linear motion between the workpieces at their contact point until a measurable scar is imparted to at least one workpiece workface, and then evaluating the workface scar.

  13. Real-Time, High-Frequency QRS Electrocardiograph

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; DePalma, Jude L.; Moradi, Saeed

    2003-01-01

    An electronic system that performs real-time analysis of the low-amplitude, high-frequency, ordinarily invisible components of the QRS portion of an electrocardiographic signal in real time has been developed. Whereas the signals readily visible on a conventional electrocardiogram (ECG) have amplitudes of the order of a millivolt and are characterized by frequencies <100 Hz, the ordinarily invisible components have amplitudes in the microvolt range and are characterized by frequencies from about 150 to about 250 Hz. Deviations of these high-frequency components from a normal pattern can be indicative of myocardial ischemia or myocardial infarction

  14. A MEMS-based high frequency x-ray chopper.

    PubMed

    Siria, A; Dhez, O; Schwartz, W; Torricelli, G; Comin, F; Chevrier, J

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  15. Condenser Microphone Protective Grid Correction for High Frequency Measurements

    NASA Technical Reports Server (NTRS)

    Lee, Erik; Bennett, Reginald

    2010-01-01

    Use of a protective grid on small diameter microphones can prolong the lifetime of the unit, but the high frequency effects can complicate data interpretation. Analytical methods have been developed to correct for the grid effect at high frequencies. Specifically, the analysis pertains to quantifying the microphone protective grid response characteristics in the acoustic near field of a rocket plume noise source. A frequency response function computation using two microphones will be explained. Experimental and instrumentation setup details will be provided. The resulting frequency response function for a B&K 4944 condenser microphone protective grid will be presented, along with associated uncertainties

  16. High frequency microbubble-switched oscillations modulated by microfluidic transistors

    NASA Astrophysics Data System (ADS)

    Yang, Fanghao; Dai, Xianming; Li, Chen

    2012-08-01

    Creating high frequency two-phase oscillations (HF-TPOs) remains an important goal in advancing microscale fluidic logic devices, micro-mixers, micro-actuators, and flow controls. However, thermally driven TPO frequency has been hindered by confinements of compressible vapor bubbles and low thermal diffusivity in microfluidic systems. In this study, a mechanism creating high frequency microbubbles growth/collapse cycle has been developed to achieve HF-TPOs. A "microfluidic transistor" was conceptualized and fabricated to passively sustain and modulate HF-TPOs. Three orders of magnitude higher TPO frequency has been achieved compared to TPOs reported in literatures under similar working conditions.

  17. Positive Parenting for High-Risk Families

    ERIC Educational Resources Information Center

    Devall, Esther L.

    2004-01-01

    Teen, single, divorced, foster, abusive, substance affected, and incarcerated parents and their children participated in intensive parenting education classes lasting 9 to 24 weeks. Participants were primarily single (58%), Hispanic (60%), and female (60%). Parents showed significant increases in empathy and knowledge of positive discipline…

  18. Correlation Between the Position of the Hyoid Bone on Lateral Cephalographs and Formant Frequencies.

    PubMed

    Macari, Anthony T; Ziade, Georges; Turfe, Zaahir; Chidiac, Alissar; Alam, Elie; Hamdan, Abdul-Latif

    2016-11-01

    The objective of this study is to examine the F1, F2, F3, and F4 during sustained vowels /ɑ/, /i/, /o/, /u/. Prospective cross-sectional study. Fifty-two consecutive patients aged between 9 years and 38 years were invited to participate in this study. Linear measurements included linear vertical distance from the hyoid bone to the sella turcica (H-S); linear vertical distance from the hyoid bone to the posterior nasal spine (H-PNS); linear measure from the hyoid bone to the most anterior point of the cervical vertebra C3 (H-C3); and linear vertical distance from the hyoid bone to the mandibular plane (H-MP). The results showed a moderate and statistically significant correlation between the average fundamental frequency for the vowel /ɑ/ and H-C3, H-S, and H-PNS and another moderate negative correlation between F3 and F4, and the vertical position of the hyoid bone H-C3 and H-S. For the vowel /i/, there was a moderate negative correlation between F1, F3, and F4 and H-S and also a moderate negative correlation between F3 and F4 and H-C3. For the vowel /o/, there was a moderate negative correlation between F4 and H-S and H-PNS. For the vowel /u/, only F4 correlated significantly with H-S. There is a moderate correlation between the high formants, mostly F4, and the cephalo-caudal position of the hyoid bone. Copyright © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  19. High-frequency filtering of strong-motion records

    USGS Publications Warehouse

    Douglas, J.; Boore, D.M.

    2011-01-01

    The influence of noise in strong-motion records is most problematic at low and high frequencies where the signal to noise ratio is commonly low compared to that in the mid-spectrum. The impact of low-frequency noise (5 Hz) on computed pseudo-absolute response spectral accelerations (PSAs). In contrast to the case of low-frequency noise our analysis shows that filtering to remove high-frequency noise is only necessary in certain situations and that PSAs can often be used up to 100 Hz even if much lower high-cut corner frequencies are required to remove the noise. This apparent contradiction can be explained by the fact that PSAs are often controlled by ground accelerations associated with much lower frequencies than the natural frequency of the oscillator because path and site attenuation (often modelled by Q and κ, respectively) have removed the highest frequencies. We demonstrate that if high-cut filters are to be used, then their corner frequencies should be selected on an individual basis, as has been done in a few recent studies.

  20. Broadband high-frequency waves detected at dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Yang, J.; Cao, J. B.; Fu, H. S.; Wang, T. Y.; Liu, W. L.; Yao, Z. H.

    2017-04-01

    Dipolarization front (DF) is a sharp boundary most probably separating the reconnection jet from the background plasma sheet. So far at this boundary, the observed waves are mainly in low-frequency range (e.g., magnetosonic waves and lower hybrid waves). Few high-frequency waves are observed in this region. In this paper, we report the broadband high-frequency wave emissions at the DF. These waves, having frequencies extending from the electron cyclotron frequency fce, up to the electron plasma frequency fpe, could contribute 10% to the in situ measurement of intermittent energy conversion at the DF layer. Their generation may be attributed to electron beams, which are simultaneously observed at the DF as well.

  1. Polarization Properties of AGN at High Frequencies

    NASA Astrophysics Data System (ADS)

    Jorstad, S. G.

    2009-08-01

    I discuss variability of polarization in the core region of parsec scale radio jets and connections between 7 mm polarization in the VLBI core and polarization at shorter wavelengths from the whole source for a sample of AGN with highly relativistic jets known as blazars. The sources show pronounced diversity in polarization behavior that is not clearly understood. I discuss possible reasons for these differences as well as the role that VSOP-2 can play in exploring the magnetic field in the most compact regions of jets.

  2. Advanced high frequency partial discharge measuring system

    NASA Technical Reports Server (NTRS)

    Karady, George G.

    1994-01-01

    This report explains the Advanced Partial Discharge Measuring System in ASU's High Voltage Laboratory and presents some of the results obtained using the setup. While in operation an insulation is subjected to wide ranging temperature and voltage stresses. Hence, it is necessary to study the effect of temperature on the behavior of partial discharges in an insulation. The setup described in this report can be used to test samples at temperatures ranging from -50 C to 200 C. The aim of conducting the tests described herein is to be able to predict the behavior of an insulation under different operating conditions in addition to being able to predict the possibility of failure.

  3. HF (High-Frequency) Channel Probe.

    DTIC Science & Technology

    1985-05-31

    ionosphere can be calculated from the relation [Basler and Scott, 19731 (~ 2R(R + [’ -Cos (D-)] +h’(5.1) where R is the radius of the earth (6359 km for...emanating from the earth at high latitudes are a convected sunward on the dawn- and dusk-sides of the auroral zones. When they reach the noon sector, the...for refracting HF radio waves back to the earth , the plasma is essentially swept along with the flux tubes delineated by the magnetic field lines. The

  4. Transient high-frequency ultrasonic water atomization

    NASA Astrophysics Data System (ADS)

    Barreras, F.; Amaveda, H.; Lozano, A.

    2002-06-01

    An experimental study was performed to improve the understanding of the characteristics of ultrasonic water atomization when excited with waves in the MHz range. In the present experiments, small volumes of water were atomized, observing the temporal evolution of the process. Typical diameters of the resulting droplets are of the order of a few microns. To visualize them, images were acquired with very high magnification. Appropriate lenses were used to enable high resolution at a distance from the flow. Droplet size distributions were also calculated with a Malvern diffractometer. Droplet exit velocity was measured using particle image velocimetry. It was noticeable that, as the remaining liquid mass deposited over the ultrasonic transducer decreased, the atomization characteristics changed, and a second peak of larger droplets appeared in the size distribution function. This phenomenon is related to the change in the curvature of the liquid surface. Although results are not conclusive, it appears that, under the conditions in this study, some observations about droplet formation are better described by cavitation phenomena rather than by the simplified surface wave theory usually invoked to explain these processes.

  5. Development of Graphene for High Frequency Electronics

    NASA Astrophysics Data System (ADS)

    Robinson, Joshua; Snyder, David; Fanton, Mark; Hollander, Matthew; Labella, Michael; Trumbull, Kathleen; Cavalero, Randall; Weiland, Brian; The Pennsylvania State University Team

    2011-03-01

    The practicality and success of a graphene technology depends on the ability to regularly and controllably synthesize graphene; integrate it with metals and dielectrics; and to develop device designs that take advantage of graphene's unique properties. We demonstrate graphene synthesis on SiC(0001) and Sapphire with 1.5% variation in sheet resistance across 100mm wafers. Hall mobility measurements indicate that direct growth of graphene on sapphire leads to a 2x increase in mobility (2200 cm2 /Vs) compared to silicon sublimation from SiC(0001). Additionally, we have developed high quality ohmic contacts to graphene, which improves the contact resistance by nearly 6000x (5 x 10-8 Ohm-cm2) compared to untreated metal/graphene interfaces. Finally, we discuss integration of ultra-thin high-k dielectrics and their impact on graphene transport. Atomic layer deposited oxide heterostructures (seed not equal to overlayer) have deleterious effects on Hall mobility while homostructures lead to an increase in Hall mobility. Importantly, 5nm thick EBPVD Hf O2 gate dielectrics are successfully demonstrated and show improved Hall mobility, on-off ratio, and transconductance relative to Al 2 O3 gates and heterostructure gates.

  6. High frequency fishbones excited by near perpendicular neutral beam injection

    SciTech Connect

    Zhou Deng

    2006-07-15

    The high frequency fishbone instability observed in experiments with near perpendicular neutral beam injection is interpreted as the ideal internal kink mode destabilized by circulating energetic ions. The mode frequency is close to the transit frequency of circulating ions. The beta value of the circulating ions is required to peak on the magnetic axis and the average value within the q=1 magnetic surface must exceed a critical value for the mode to grow up.

  7. High-frequency energy in singing and speech

    NASA Astrophysics Data System (ADS)

    Monson, Brian Bruce

    While human speech and the human voice generate acoustical energy up to (and beyond) 20 kHz, the energy above approximately 5 kHz has been largely neglected. Evidence is accruing that this high-frequency energy contains perceptual information relevant to speech and voice, including percepts of quality, localization, and intelligibility. The present research was an initial step in the long-range goal of characterizing high-frequency energy in singing voice and speech, with particular regard for its perceptual role and its potential for modification during voice and speech production. In this study, a database of high-fidelity recordings of talkers was created and used for a broad acoustical analysis and general characterization of high-frequency energy, as well as specific characterization of phoneme category, voice and speech intensity level, and mode of production (speech versus singing) by high-frequency energy content. Directionality of radiation of high-frequency energy from the mouth was also examined. The recordings were used for perceptual experiments wherein listeners were asked to discriminate between speech and voice samples that differed only in high-frequency energy content. Listeners were also subjected to gender discrimination tasks, mode-of-production discrimination tasks, and transcription tasks with samples of speech and singing that contained only high-frequency content. The combination of these experiments has revealed that (1) human listeners are able to detect very subtle level changes in high-frequency energy, and (2) human listeners are able to extract significant perceptual information from high-frequency energy.

  8. The ADMX-HF (High Frequency) Experiment

    NASA Astrophysics Data System (ADS)

    Lehnert, K. W.

    2013-04-01

    For many years, the Axion Dark Matter eXperiment (ADMX) has searched for dark-matter axions by their resonant conversion to photons in a high-Q microwave cavity embedded in a strong magnetic field; to date focusing on the ˜1 GHz range, or ma˜ few micro-eV. A second platform, ADMX-HF is now being constructed at Yale University which will focus on technology development and a first look at data in the ˜10 GHz range. Consisting of a 9T superconducting magnet (40 cm long x 14 cm diameter), a dilution refrigerator and a quantum-limited receiver based on Josephson Parametric Amplifiers (JPA) ADMX-HF is projected to achieve sensitivity within the axion model band, despite its smaller volume than ADMX. ADMX-HF is a collaboration of Yale, JILA/Colorado, UC Berkeley and LLNL, and by agreement will create a unified data set with ADMX.

  9. High-frequency multimodal atomic force microscopy

    PubMed Central

    Nievergelt, Adrian P; Adams, Jonathan D; Odermatt, Pascal D

    2014-01-01

    Summary Multifrequency atomic force microscopy imaging has been recently demonstrated as a powerful technique for quickly obtaining information about the mechanical properties of a sample. Combining this development with recent gains in imaging speed through small cantilevers holds the promise of a convenient, high-speed method for obtaining nanoscale topography as well as mechanical properties. Nevertheless, instrument bandwidth limitations on cantilever excitation and readout have restricted the ability of multifrequency techniques to fully benefit from small cantilevers. We present an approach for cantilever excitation and deflection readout with a bandwidth of 20 MHz, enabling multifrequency techniques extended beyond 2 MHz for obtaining materials contrast in liquid and air, as well as soft imaging of delicate biological samples. PMID:25671141

  10. [Experiences in high frequency audiometry and possible applications (author's transl)].

    PubMed

    Dieroff, H G

    1976-09-01

    Observations on the ultrasonic perception of noise-impaired persons gave rise to use the high frequency audiometry described by Fletcher for the early recognition of noise-induced damages. Using commercial equipment we found that the earpiece was not adapted to high frequency conditions. The adaptation problem and ways of modification are described in detail. After having improved the coupling features reproducible hearing curves were obtained. Examinations were carried out on workers, whose noise exposure exceeded the critical intensity by only a few dB. The following 3 categories of impairment were found: 1. Normal hearing between 125 and 8,000 Hz as well as in the high frequency region. 2. Unsignificant noise-induced impairments between 125 and 8,000 Hz; no high frequency hearing. 3. Acoustic hearing; no high frequency hearing. The results are discussed. It is supposed that high frequency hearing losses due to noise and chemical noxious exposure (streptomycin) are valuable in diagnostics and prognostics. Accordingly persons are to be assessed as noise sensitive, when there is no more high frequency hearing before practising noise work.

  11. High-frequency Broadband Modulations of Electroencephalographic Spectra

    PubMed Central

    Onton, Julie; Makeig, Scott

    2009-01-01

    High-frequency cortical potentials in electroencephalographic (EEG) scalp recordings have low amplitudes and may be confounded with scalp muscle activities. EEG data from an eyes-closed emotion imagination task were linearly decomposed using independent component analysis (ICA) into maximally independent component (IC) processes. Joint decomposition of IC log spectrograms into source- and frequency-independent modulator (IM) processes revealed three distinct classes of IMs that separately modulated broadband high-frequency (∼15–200 Hz) power of brain, scalp muscle, and likely ocular motor IC processes. Multi-dimensional scaling revealed significant but spatially complex relationships between mean broadband brain IM effects and the valence of the imagined emotions. Thus, contrary to prevalent assumption, unitary modes of spectral modulation of frequencies encompassing the beta, gamma, and high gamma frequency ranges can be isolated from scalp-recorded EEG data and may be differentially associated with brain sources and cognitive activities. PMID:20076775

  12. Interface Strategy To Achieve Tunable High Frequency Attenuation.

    PubMed

    Lv, Hualiang; Zhang, Haiqian; Ji, Guangbin; Xu, Zhichuan J

    2016-03-01

    Among all polarizations, the interface polarization effect is the most effective, especially at high frequency. The design of various ferrite/iron interfaces can significantly enhance the materials' dielectric loss ability at high frequency. This paper presents a simple method to generate ferrite/iron interfaces to enhance the microwave attenuation at high frequency. The ferrites were coated onto carbonyl iron and could be varied to ZnFe2O4, CoFe2O4, Fe3O4, and NiFe2O4. Due to the ferrite/iron interface inducing a stronger dielectric loss effect, all of these materials achieved broad effective frequency width at a coating layer as thin as 1.5 mm. In particular, an effective frequency width of 6.2 GHz could be gained from the Fe@NiFe2O4 composite.

  13. High performance vapour-cell frequency standards

    NASA Astrophysics Data System (ADS)

    Gharavipour, M.; Affolderbach, C.; Kang, S.; Bandi, T.; Gruet, F.; Pellaton, M.; Mileti, G.

    2016-06-01

    We report our investigations on a compact high-performance rubidium (Rb) vapour-cell clock based on microwave-optical double-resonance (DR). These studies are done in both DR continuous-wave (CW) and Ramsey schemes using the same Physics Package (PP), with the same Rb vapour cell and a magnetron-type cavity with only 45 cm3 external volume. In the CW-DR scheme, we demonstrate a DR signal with a contrast of 26% and a linewidth of 334 Hz; in Ramsey-DR mode Ramsey signals with higher contrast up to 35% and a linewidth of 160 Hz have been demonstrated. Short-term stabilities of 1.4×10-13 τ-1/2 and 2.4×10-13 τ-1/2 are measured for CW-DR and Ramsey-DR schemes, respectively. In the Ramsey-DR operation, thanks to the separation of light and microwave interactions in time, the light-shift effect has been suppressed which allows improving the long-term clock stability as compared to CW-DR operation. Implementations in miniature atomic clocks are considered.

  14. Applications of high-frequency radar

    NASA Astrophysics Data System (ADS)

    Headrick, J. M.; Thomason, J. F.

    1998-07-01

    Efforts to extend radar range by an order of magnitude with use of the ionosphere as a virtual mirror started after the end of World War II. A number of HF radar programs were pursued, with long-range nuclear burst and missile launch detection demonstrated by 1956. Successful east coast radar aircraft detect and track tests extending across the Atlantic were conducted by 1961. The major obstacles to success, the large target-to-clutter ratio and low signal-to-noise ratio, were overcome with matched filter Doppler processing. To search the areas that a 2000 nautical mile (3700 km) radar can reach, very complex and high dynamic range processing is required. The spectacular advances in digital processing technology have made truly wide-area surveillance possible. Use of the surface attached wave over the oceans can enable HF radar to obtain modest extension of range beyond the horizon. The decameter wavelengths used by both skywave and surface wave radars require large physical antenna apertures, but they have unique capabilities for air and surface targets, many of which are of resonant scattering dimensions. Resonant scattering from the ocean permits sea state and direction estimation. Military and commercial applications of HF radar are in their infancy.

  15. The Influence of High-Frequency Envelope Information on Low-Frequency Vowel Identification in Noise.

    PubMed

    Schubotz, Wiebke; Brand, Thomas; Kollmeier, Birger; Ewert, Stephan D

    2016-01-01

    Vowel identification in noise using consonant-vowel-consonant (CVC) logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4-8 kHz). CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz) and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception.

  16. High-frequency threshold measurements using insert earphones.

    PubMed

    Tang, H; Letowski, T

    1992-10-01

    Several recent studies have reported large intersubject variability of high-frequency thresholds measured with circumaural earphones. In the present study, high-frequency thresholds of 10 subjects were measured with circumaural (Sennheiser HD-250) and insert (Etymotic ER-1) earphones at 10, 12, 14, and 16 kHz. Overall results show significantly smaller variability of the threshold data obtained with insert earphones than with circumaural earphones. The above data indicate that insert earphones may be more suitable for high-frequency testing than circumaural earphones.

  17. Factors Affecting the Benefits of High-Frequency Amplification

    ERIC Educational Resources Information Center

    Horwitz, Amy R.; Ahlstrom, Jayne B.; Dubno, Judy R.

    2008-01-01

    Purpose: This study was designed to determine the extent to which high-frequency amplification helped or hindered speech recognition as a function of hearing loss, gain-frequency response, and background noise. Method: Speech recognition was measured monaurally under headphones for nonsense syllables low-pass filtered in one-third-octave steps…

  18. High-frequency hearing in seals and sea lions.

    PubMed

    Cunningham, Kane A; Reichmuth, Colleen

    2016-01-01

    Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Frequency of Sinus Disease in Normal Subjects and Patients with Benign Paroxysmal Positional Vertigo

    PubMed Central

    Cohen, H.S.; Stewart, M.G.; Brissett, A.E.; Olson, K.L.; Takashima, M.; Sangi-Haghpeykar, H.

    2010-01-01

    Background/Aims To determine if patients with benign paroxysmal positional vertigo (BPPV) have a higher frequency of rhinosinusitis than people with normal vestibular function. Methods The subjects were 52 patients with BPPV and 46 normal people. Every subject had a sinus CT scan, a blood draw for IgE and a rhinologic examination by an otolaryngologist. Results The frequency of rhinosinusitis based on physician diagnosis was 49% and based on CT scan findings 59%. This difference approached significance (p = 0.08). The observed frequency of rhinosinusitis was higher than predicted by survey data about the southern US region. The data trended toward higher prevalence of rhinosinusitis (by physician diagnosis) in the BPPV patients versus controls (58 vs. 39%, p = 0.06). Conclusion BPPV patients have a higher frequency of sinus disease compared to people with normal vestibular systems, perhaps due to age differences, but physiologic factors may also be involved. The higher frequency of rhinosinusitis in this geographical area than reported rates based on survey data raises concerns about the usefulness of questionnaire data for estimating population prevalence. PMID:20424495

  20. Radio-frequency (RF) electromagnetic emissions from materials under high-frequency mechanical excitation

    NASA Astrophysics Data System (ADS)

    Sorensen, Christian; Moore, David

    2017-01-01

    Direct contact piezoelectric transducers were used to excite compacted polycrystalline dielectric material samples with high amplitude but short duration ultrasound through a frequency range of 50 kHz to 10 MHz, while near field RF emissions were measured in 12 frequency bands from 18 to 750 GHz using a suite of detectors. Emissions were observed only in three detectors, covering the 40-75 GHz, 110-170 GHz, and 170-260 GHz frequency ranges. Emission amplitudes appear to rise nonlinearly with applied ultrasound amplitude, and the emission amplitudes versus ultrasound frequency are different than the thermal responses of these samples. Data comparing thermal responses and electromagnetic emissions versus ultrasound frequency and amplitude for several sample types (oxidizers and energetic materials) are reported.

  1. Analysis of high frequency geostationary ocean colour data using DINEOF

    NASA Astrophysics Data System (ADS)

    Alvera-Azcárate, Aida; Vanhellemont, Quinten; Ruddick, Kevin; Barth, Alexander; Beckers, Jean-Marie

    2015-06-01

    DINEOF (Data Interpolating Empirical Orthogonal Functions), a technique to reconstruct missing data, is applied to turbidity data obtained through the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat Second Generation 2. The aim of this work is to assess if the tidal variability of the southern North Sea in 2008 can be accurately reproduced in the reconstructed dataset. Such high frequency data have not previously been analysed with DINEOF and present new challenges, like a strong tidal signal and long night-time gaps. An outlier detection approach that exploits the high temporal resolution (15 min) of the SEVIRI dataset is developed. After removal of outliers, the turbidity dataset is reconstructed with DINEOF. In situ Smartbuoy data are used to assess the accuracy of the reconstruction. Then, a series of tidal cycles are examined at various positions over the southern North Sea. These examples demonstrate the capability of DINEOF to reproduce tidal variability in the reconstructed dataset, and show the high temporal and spatial variability of turbidity in the southern North Sea. An analysis of the main harmonic constituents (annual cycle, daily cycle, M2 and S2 tidal components) is performed, to assess the contribution of each of these modes to the total variability of turbidity. The variability not explained by the harmonic fit, due to the natural processes and satellite processing errors as noise, is also assessed.

  2. High-frequency thresholds: circumaural earphone versus insert earphone.

    PubMed

    Valente, M; Valente, M; Goebel, J

    1992-11-01

    Benefits of high-frequency audiometry in monitoring hearing sensitivity of patients administered ototoxic medications are well established. High-frequency thresholds have been reported to be variable, due in part to small differences in the placement of the earphone diaphragm over the opening of the ear canal. Reliability may be improved by using insert earphones (ER-2) when obtaining high-frequency thresholds. The purposes of this study were to determine high-frequency threshold test-retest reliability using Koss HV/1A+ and ER-2 earphones and to determine if significant differences are present between high-frequency thresholds obtained using these two earphones. Results obtained on 40 ears of 20 normal hearing adults revealed that differences between the test and retest thresholds for each earphone were not significant. Intrasubject threshold differences between the test and retest thresholds for each earphone were, for the most part, within +/- 10 dB at all test frequencies. Further, significantly greater intensity was required to measure threshold when using the ER-2 earphone when compared to the Koss HV/1A+ at all test frequencies.

  3. High-frequency subband compressed sensing MRI using quadruplet sampling.

    PubMed

    Sung, Kyunghyun; Hargreaves, Brian A

    2013-11-01

    To present and validate a new method that formalizes a direct link between k-space and wavelet domains to apply separate undersampling and reconstruction for high- and low-spatial-frequency k-space data. High- and low-spatial-frequency regions are defined in k-space based on the separation of wavelet subbands, and the conventional compressed sensing problem is transformed into one of localized k-space estimation. To better exploit wavelet-domain sparsity, compressed sensing can be used for high-spatial-frequency regions, whereas parallel imaging can be used for low-spatial-frequency regions. Fourier undersampling is also customized to better accommodate each reconstruction method: random undersampling for compressed sensing and regular undersampling for parallel imaging. Examples using the proposed method demonstrate successful reconstruction of both low-spatial-frequency content and fine structures in high-resolution three-dimensional breast imaging with a net acceleration of 11-12. The proposed method improves the reconstruction accuracy of high-spatial-frequency signal content and avoids incoherent artifacts in low-spatial-frequency regions. This new formulation also reduces the reconstruction time due to the smaller problem size. Copyright © 2012 Wiley Periodicals, Inc.

  4. High-frequency dynamics of hybrid oxide Josephson heterostructures

    NASA Astrophysics Data System (ADS)

    Komissinskiy, P.; Ovsyannikov, G. A.; Constantinian, K. Y.; Kislinski, Y. V.; Borisenko, I. V.; Soloviev, I. I.; Kornev, V. K.; Goldobin, E.; Winkler, D.

    2008-07-01

    We summarize our results on Josephson heterostructures Nb/Au/YBa2Cu3Ox that combine conventional (S) and oxide high- Tc superconductors with a dominant d -wave symmetry of the superconducting order parameter (D). The heterostructures were fabricated on (001) and (1 1 20) YBa2Cu3Ox films grown by pulsed laser deposition. The structural and surface studies of the (1 1 20) YBa2Cu3Ox thin films reveal nanofaceted surface structure with two facet domain orientations, which are attributed as (001) and (110)-oriented surfaces of YBa2Cu3Ox and result in S/D(001) and S/D(110) nanojunctions formed on the facets. Electrophysical properties of the Nb/Au/YBa2Cu3Ox heterostructures are investigated by the electrical and magnetic measurements at low temperatures and analyzed within the faceting scenario. The superconducting current-phase relation (CPR) of the heterostructures with finite first and second harmonics is derived from the Shapiro steps, which appear in the I-V curves of the heterostructures irradiated at frequencies up to 100 GHz. The experimental positions and amplitudes of the Shapiro steps are explained within the modified resistive Josephson junction model, where the second harmonic of the CPR and capacitance of the Josephson junctions are taken into account. We experimentally observe a crossover from a lumped to a distributed Josephson junction limit for the size of the heterostructures smaller than Josephson penetration depth. The effect is attributed to the variations of the harmonics of the superconducting CPR across the heterojunction, which may give rise to splintered vortices of magnetic flux quantum. Our investigations of parameters and phenomena that are specific for superconductors having d -wave symmetry of the superconducting order parameter may be of importance for applications such as high-frequency detectors and novel elements of a possible quantum computer.

  5. Modelling The Effects of Density Gradients and Fluctuations on the Apparent Sizes and Positions of Low Frequency Solar Radio Sources

    NASA Astrophysics Data System (ADS)

    Alcock, Benjamin Thomas; Kontar, Eduard; Jeffrey, Natasha

    2017-08-01

    Recent high spatial and temporal resolution imaging of <250 MHz solar radio emission has enabled us to observe rapid variations in Type-III solar radio burst characteristics, revealing fast growth of the Type-III source and movement of the source centroid. In this work, we use a Monte-Carlo ray tracing simulation to model the passage of low frequency (5-240 MHz) radio waves through the solar corona from a point source, considering both isotropic and dipole emission. We model the effects of random density fluctuations and an isotropic density gradient on the transport of the rays, varying the strength of the scattering to observe the effects on images of the source from an observer at 1 AU. Absorption of photons is included, and the effects on the reproduced images and flux curves are observed. The apparent source size and centroid position are tracked through the simulation, and we find a general increase in source size with time, and a variation of centroid position in both directions throughout the simulation. We find that the size of the variation is strongly dependant upon frequency, with lower frequency sources appearing to move further on the disk than higher frequency sources. We also observe the strength of the effects at different viewing angles, finding that the greatest variation occurs closer to the solar limb. Further observational work is required to limit the scattering parameters, in order to allow for comparison with current radio images.

  6. Feasibility of High Frequency Acoustic Imaging for Inspection of Containments

    SciTech Connect

    C.N. Corrado; J.E. Bondaryk; V. Godino

    1998-08-01

    The Nuclear Regulatory Commission has a program at the Oak Ridge National Laboratory to provide assistance in their assessment of the effects of potential degradation on the structural integrity and Ieaktightness of metal containment vessels and steel liners of concrete containment in nuclear power plants. One of the program objectives is to identify a technique(s) for inspection of inaccessible portions of the containment pressure boundary. Acoustic imaging has been identified as one of these potential techniques. A numerical feasibility study investigated the use of high-frequency bistatic acoustic imaging techniques for inspection of inaccessible portions of the metallic pressure boundary of nuclear power plant containment. The range-dependent version of the OASES Code developed at the Massachusetts Institute of Technology was utilized to perform a series of numerical simulations. OASES is a well developed and extensively tested code for evaluation of the acoustic field in a system of stratified fluid and/or elastic layers. Using the code, an arbitrary number of fluid or solid elastic layers are interleaved, with the outer layers modeled as halfspaces. High frequency vibrational sources were modeled to simulate elastic waves in the steel. The received field due to an arbitrary source array can be calculated at arbitrary depth and range positions. In this numerical study, waves that reflect and scatter from surface roughness caused by modeled degradations (e.g., corrosion) are detected and used to identify and map the steel degradation. Variables in the numerical study included frequency, flaw size, interrogation distance, and sensor incident angle.Based on these analytical simulations, it is considered unlikely that acoustic imaging technology can be used to investigate embedded steel liners of reinforced concrete containment. The thin steel liner and high signal losses to the concrete make this application difficult. Results for portions of steel containment

  7. Design of a standing-wave multicell radio frequency cavity beam monitor for simultaneous position and emittance measurement

    SciTech Connect

    Kim, Jin-Soo; Miller, Roger; Nantista, Christopher

    2005-07-15

    High precision, nondisruptive emittance measurement through second moment monitoring requires precise beam position at the measurement location. We present the design and analysis of a multicavity standing wave structure for a pulse-to-pulse beam position-emittance measurement system in which the quadrupole and the dipole standing wave modes resonate at harmonics of a presumed beam bunch train frequency. As an application for the Next Linear Collider (NLC) beams, an optimized nine-cavity standing-wave structure is designed for simultaneous high precision beam position and emittance measurement. It operates with the {pi}-phase advance quadrupole mode resonating at the 16th harmonic (11.424 GHz) of the NLC bunch frequency and the 3{pi}/4-phase advance dipole mode at the 12th harmonic (8.568 GHz). The output powers from these modes are estimated for the NLC beams. Measurement resolution is estimated to be on the micron scale for rms beam size and on the nanometer scale for beam position.

  8. High density terahertz frequency comb produced by coherent synchrotron radiation

    PubMed Central

    Tammaro, S.; Pirali, O.; Roy, P.; Lampin, J.-F.; Ducournau, G.; Cuisset, A.; Hindle, F.; Mouret, G.

    2015-01-01

    Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10−10 and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile. PMID:26190043

  9. High density terahertz frequency comb produced by coherent synchrotron radiation.

    PubMed

    Tammaro, S; Pirali, O; Roy, P; Lampin, J-F; Ducournau, G; Cuisset, A; Hindle, F; Mouret, G

    2015-07-20

    Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10(-10) and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile.

  10. High-frequency matrix converter with square wave input

    DOEpatents

    Carr, Joseph Alexander; Balda, Juan Carlos

    2015-03-31

    A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

  11. Synthetic Aperture Sonar Low Frequency vs. High Frequency Automatic Contact Generation

    DTIC Science & Technology

    2010-06-01

    resurveyed the harbor with both sidescan sonar (on REMUS) and SAS (on the SSAM AUV) provided by NAVSEA Costal Systems Command. NOMWC, NAVOCEANO and...Synthetic Aperture Sonar Low Frequency vs. High Frequency Automatic Contact Generation J. R. Dubberley and M. L. Gendron Naval Research...Laboratory Code 7440.1 Building 1005 Stennis Space Center, MS 39529 USA Abstract- Synthetic Aperture Sonar (SAS) bottom mapping sensors are on the

  12. High frequency ultrasound with color Doppler in dermatology*

    PubMed Central

    Barcaui, Elisa de Oliveira; Carvalho, Antonio Carlos Pires; Lopes, Flavia Paiva Proença Lobo; Piñeiro-Maceira, Juan; Barcaui, Carlos Baptista

    2016-01-01

    Ultrasonography is a method of imaging that classically is used in dermatology to study changes in the hypoderma, as nodules and infectious and inflammatory processes. The introduction of high frequency and resolution equipments enabled the observation of superficial structures, allowing differentiation between skin layers and providing details for the analysis of the skin and its appendages. This paper aims to review the basic principles of high frequency ultrasound and its applications in different areas of dermatology. PMID:27438191

  13. Basis of Ionospheric Modification by High-Frequency Waves

    DTIC Science & Technology

    2007-06-01

    for conducting ionospheric heating experiments in Gakona, Alaska, as part of the High Frequency Active Auroral Research Program ( HAARP ) [5], is being...upgraded. The upgraded HAARP HF transmitting system will be a phased-array antenna of 180 elements. Each element is a cross dipole, which radiates a...supported by the High Frequency Active Auroral Research Program ( HAARP ), the Air Force Research Laboratory at Hanscom Air Force Base, MA, and by the Office

  14. High frequency, small signal MH loops of ferromagnetic thin films

    NASA Technical Reports Server (NTRS)

    Grimes, C. A.; Ong, K. G.

    2000-01-01

    A method is presented for transforming the high frequency bias susceptibility measurements of ferromagnetic thin films into the form of a MH loop with, depending upon the measurement geometry, the y-axis zero crossing giving a measure of the coercive force or anisotropy field. The loops provide a measure of the quantitative and qualitative high frequency switching properties of ferromagnetic thin films. c2000 American Institute of Physics.

  15. Frequency measurement of a Sr lattice clock using an SI-second-referenced optical frequency comb linked by a global positioning system (GPS)

    NASA Astrophysics Data System (ADS)

    Hong, Feng-Lei; Takamoto, Masao; Higashi, Ryoichi; Fukuyama, Yasuhiro; Jiang, Jie; Katori, Hidetoshi

    2005-07-01

    We have established a transportable frequency measurement system using an optical frequency comb linked to a commercial Cs atomic clock, which is in turn linked to international atomic time (TAI) through global positioning system (GPS) time. An iodine-stabilized Nd:YAG laser is used as a flywheel in the frequency measurement system. This system is used to measure the absolute frequency of the clock transition of 87Sr in an optical lattice. We obtained a fractional uncertainty of 2×10-14 in the frequency measurement with a total averaging time of ~ 105 s over 9 days.

  16. Frequency measurement of a Sr lattice clock using an SI-second-referenced optical frequency comb linked by a global positioning system (GPS).

    PubMed

    Hong, Feng-Lei; Takamoto, Masao; Higashi, Ryoichi; Fukuyama, Yasuhiro; Jiang, Jie; Katori, Hidetoshi

    2005-07-11

    We have established a transportable frequency measurement system using an optical frequency comb linked to a commercial Cs atomic clock, which is in turn linked to international atomic time (TAI) through global positioning system (GPS) time. An iodine-stabilized Nd:YAG laser is used as a flywheel in the frequency measurement system. This system is used to measure the absolute frequency of the clock transition of (87)Sr in an optical lattice. We obtained a fractional uncertainty of 2x10(-14) in the frequency measurement with a total averaging time of ~ 10(5) s over 9 days.

  17. High and low spatial frequencies in website evaluations.

    PubMed

    Thielsch, Meinald T; Hirschfeld, Gerrit

    2010-08-01

    Which features of websites are important for users' perceptions regarding aesthetics or usability? This study investigates how evaluations of aesthetic appeal and usability depend on high vs. low spatial frequencies. High spatial frequencies convey information on fine details, whereas low spatial frequencies convey information about the global layout. Participants rated aesthetic appeal and usability of 50 website screenshots from different domains. Screenshots were presented unfiltered, low-pass filtered with blurred targets or high-pass filtered with high-pass filtered targets. The main result is that low spatial frequencies can be seen to have a unique contribution in perceived website aesthetics, thus confirming a central prediction from processing fluency theory. There was no connection between low spatial frequencies and usability evaluations, whereas strong correlations were found between ratings of high-pass filtered websites and those of unfiltered websites in aesthetics and usability. This study thus offers a new perspective on the biological basis of users' website perceptions. This research links ergonomics to neurocognitive models of visual processing. This paper investigates how high and low spatial frequencies, which are neurologically processed in different visual pathways, independently contribute to users' perceptions of websites. This is very relevant for theories of website perceptions and for practitioners of web design.

  18. Characterizing Earthquake Rupture Properties Using Peak High-Frequency Offset

    NASA Astrophysics Data System (ADS)

    Wen, L.; Meng, L.

    2014-12-01

    Teleseismic array back-projection (BP) of high frequency (~1Hz) seismic waves has been recently applied to image the aftershock sequence of the Tohoku-Oki earthquake. The BP method proves to be effective in capturing early aftershocks that are difficult to be detected due to the contamination of the mainshock coda wave. Furthermore, since the event detection is based on the identification of the local peaks in time series of the BP power, the resulting event location corresponds to the peak high-frequency energy rather than the hypocenter. In this work, we show that the comparison between the BP-determined catalog and conventional phase-picking catalog provides estimates of the spatial and temporal offset between the hypocenter and the peak high-frequency radiation. We propose to measure this peak high-frequency shift of global earthquakes between M4.0 to M7.0. We average the BP locations calibrated by multiple reference events to minimize the uncertainty due to the variation of 3D path effects. In our initial effort focusing on the foreshock and aftershock sequence of the 2014 Iquique earthquake, we find systematic shifts of the peak high-frequency energy towards the down-dip direction. We find that the amount of the shift is a good indication of rupture length, which scales with the earthquake magnitude. Further investigations of the peak high frequency offset may provide constraints on earthquake source properties such as rupture directivity, rupture duration, rupture speed, and stress drop.

  19. Postural stabilization on a moving platform oscillating at high frequencies.

    PubMed

    Pyykkö, I; Aalto, H; Starck, J; Ishizaki, H

    1993-04-01

    The effect of a fore-aft oscillating platform on postural stability was studied in nine healthy volunteers. The force platform technique was used with automatic analysis that evaluated the position of the center point of force as a function of time. The duration of stimulation lasted 90 s and the perturbation frequencies ranged from 8 to 24 Hz, and were given at constant rms acceleration of 4 m/s2. When compared with a vibration-free baseline stance, horizontal vibration of the platform caused significantly worse postural stability in all subjects. Test frequencies of 8 and 10 Hz produced greater sway velocities than perturbation at frequencies of 14 and 16 Hz. The results indicate that horizontal perturbation of the support surface leads to postural instability that is frequency-dependent.

  20. Microscale capillary wave turbulence excited by high frequency vibration.

    PubMed

    Blamey, Jeremy; Yeo, Leslie Y; Friend, James R

    2013-03-19

    Low frequency (O(10 Hz-10 kHz)) vibration excitation of capillary waves has been extensively studied for nearly two centuries. Such waves appear at the excitation frequency or at rational multiples of the excitation frequency through nonlinear coupling as a result of the finite displacement of the wave, most often at one-half the excitation frequency in so-called Faraday waves and twice this frequency in superharmonic waves. Less understood, however, are the dynamics of capillary waves driven by high-frequency vibration (>O(100 kHz)) and small interface length scales, an arrangement ideal for a broad variety of applications, from nebulizers for pulmonary drug delivery to complex nanoparticle synthesis. In the few studies conducted to date, a marked departure from the predictions of classical Faraday wave theory has been shown, with the appearance of broadband capillary wave generation from 100 Hz to the excitation frequency and beyond, without a clear explanation. We show that weak wave turbulence is the dominant mechanism in the behavior of the system, as evident from wave height frequency spectra that closely follow the Rayleigh-Jeans spectral response η ≈ ω(-17/12) as a consequence of a period-halving, weakly turbulent cascade that appears within a 1 mm water drop whether driven by thickness-mode or surface acoustic Rayleigh wave excitation. However, such a cascade is one-way, from low to high frequencies. The mechanism of exciting the cascade with high-frequency acoustic waves is an acoustic streaming-driven turbulent jet in the fluid bulk, driving the fundamental capillary wave resonance through the well-known coupling between bulk flow and surface waves. Unlike capillary waves, turbulent acoustic streaming can exhibit subharmonic cascades from high to low frequencies; here it appears from the excitation frequency all the way to the fundamental modes of the capillary wave at some four orders of magnitude in frequency less than the excitation frequency

  1. High-frequency sensorineural hearing loss in children.

    PubMed

    Johnson, Kaalan; Tabangin, Meredith; Meinzen-Derr, Jareen; Cohen, Aliza P; Greinwald, John H

    2016-05-01

    Determine the prevalence of high-frequency sensorineural hearing loss (HFSNHL) in our hearing loss population and a diagnostic algorithm for these patients. Retrospective case series. We identified patients diagnosed with sensorineural hearing loss (SNHL) at our pediatric tertiary care institution from 1981 to 2010. Based on audiometric profiles, these patients were subdivided into those with a flat SNHL configuration and those with HFSNHL. Imaging and genetic testing data and data regarding age at diagnosis, laterality, and risk factors were obtained for both groups. Comparisons were then made between the two groups. Of 2,867 patients included in the study, 7.6% had HFSNHL. Age at diagnosis was significantly higher in HFSNHL patients (8.3 years vs. 6.1 years; P < .0001). These patients also had a significantly higher proportion of unilateral versus bilateral loss (49.1% vs. 26.1%; P < .0001); unilateral losses were also less severe. Genetic testing showed no significant difference between groups in the proportion of patients tested or in those who tested positive. Similarly, imaging data revealed no difference in the proportion of patients tested in the two groups; however, overall diagnostic yield was significantly higher in flat SNHL patients (29.5% vs.17.3; P = .02). The positive predictive value of simple genetic testing is similar to that of imaging studies. However, given cost differences between genetic testing and imaging, it is prudent to perform genetic testing as the initial diagnostic test. Determination of whether high-throughput, multigene diagnostic platforms offer an added benefit in the evaluation of children requires further study. 4. Laryngoscope, 126:1236-1240, 2016. © 2015 The American Laryngological, Rhinological and Otological Society, Inc.

  2. Parametric Study of High Frequency Pulse Detonation Tubes

    NASA Technical Reports Server (NTRS)

    Cutler, Anderw D.

    2008-01-01

    This paper describes development of high frequency pulse detonation tubes similar to a small pulse detonation engine (PDE). A high-speed valve injects a charge of a mixture of fuel and air at rates of up to 1000 Hz into a constant area tube closed at one end. The reactants detonate in the tube and the products exit as a pulsed jet. High frequency pressure transducers are used to monitor the pressure fluctuations in the device and thrust is measured with a balance. The effects of injection frequency, fuel and air flow rates, tube length, and injection location are considered. Both H2 and C2H4 fuels are considered. Optimum (maximum specific thrust) fuel-air compositions and resonant frequencies are identified. Results are compared to PDE calculations. Design rules are postulated and applications to aerodynamic flow control and propulsion are discussed.

  3. Switch over to the high frequency rf systems near transition

    SciTech Connect

    Brennan, J.M.; Wei, J.

    1988-01-01

    The purpose of this note is to point out that since bunch narrowing naturally occurs in the acceleration process in the vicinity of transition, it should be possible to switch over to the high frequency system close to transition when the bunch has narrowed enough to fit directly into the high frequency bucket. The advantage of this approach is the simplicity, no extra components or gymnastics are required of the low frequency system. The disadvantage, of course, is for protons which do not go through transition. But on the other hand, there is no shortage of intensity for protons and so it should be possible to keep the phase space area low for protons, and then matching to the high frequency bucket should be easily accomplished by adiabatic compression. 3 refs., 7 figs.

  4. Extended high frequency audiometry in users of personal listening devices.

    PubMed

    Kumar, Poornima; Upadhyay, Prabhakar; Kumar, Ashok; Kumar, Sunil; Singh, Gautam Bir

    Noise exposure leads to high frequency hearing loss. Use of Personal Listening Devices may lead to decline in high frequency hearing sensitivity because of prolonged exposure to these devices at high volume. This study explores the changes in hearing thresholds by Extended High Frequency audiometry in users of personal listening devices. A descriptive, hospital based observational study was performed with total 100 subjects in age group of 15-30years. Subjects were divided in two groups consisting of 30 subjects (Group A) with no history of Personal Listening Devices use and (Group B) having 70 subjects with history of use of Personal Listening Devices. Conventional pure tone audiometry with extended high frequency audiometry was performed in all the subjects. Significant differences in hearing thresholds of Personal Listening Device users were seen at high frequencies (3kHz, 4kHz and 6kHz) and extended high frequencies (9kHz, 10kHz, 11kHz, 13kHz, 14kHz, 15kHz and 16kHz) with p value <0.05. Elevated hearing thresholds were observed in personal listening devices users which were directly proportional to volume and duration of usage. In present study no significant changes were noted in hearing thresholds in PLD users before 5years of PLD use. However, hearing thresholds were significantly increased at 3kHz, 10kHz, 13kHz in PLD users having >5years usage at high volume. Thus, it can be reasonably concluded that extended high frequencies can be used for early detection of NIHL in PLD users. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Cooperative behavior between oscillatory and excitable units: the peculiar role of positive coupling-frequency correlations

    NASA Astrophysics Data System (ADS)

    Sonnenschein, Bernard; Peron, Thomas K. DM.; Rodrigues, Francisco A.; Kurths, Jürgen; Schimansky-Geier, Lutz

    2014-08-01

    We study the collective dynamics of noise-driven excitable elements, so-called active rotators. Crucially here, the natural frequencies and the individual coupling strengths are drawn from some joint probability distribution. Combining a mean-field treatment with a Gaussian approximation allows us to find examples where the infinite-dimensional system is reduced to a few ordinary differential equations. Our focus lies in the cooperative behavior in a population consisting of two parts, where one is composed of excitable elements, while the other one contains only self-oscillatory units. Surprisingly, excitable behavior in the whole system sets in only if the excitable elements have a smaller coupling strength than the self-oscillating units. In this way positive local correlations between natural frequencies and couplings shape the global behavior of mixed populations of excitable and oscillatory elements.

  6. Intercontinental time and frequency transfer using a global positioning system timing receiver

    NASA Technical Reports Server (NTRS)

    Clements, P. A.

    1983-01-01

    The DSN has a requirement to maintain knowledge of the frequency offset between DSN stations with 3 x 10 to the minus 13th power and time offset within 10 microseconds. It is further anticipated that in the 1987-1990 era the requirement for knowledge of time offset between DSN stations will be less than 10 nanoseconds. JPL is using the Global Positioning System (GPS) Space Vehicles, as a development project, to transfer time and frequency over intercontinental distances between stations of the DSN and between the DSN and other agencies. JPL has installed GPS timing receivers at its tracking station near Barstow, California, and at its tracking station near Madrid, Spain. The details of the experiment and the data are reported. There is a discussion of the ultimate capabilities of these techniques for meeting the functional requirements of the DSN.

  7. Time-frequency representation of a highly nonstationary signal via the modified Wigner distribution

    NASA Technical Reports Server (NTRS)

    Zoladz, T. F.; Jones, J. H.; Jong, J.

    1992-01-01

    A new signal analysis technique called the modified Wigner distribution (MWD) is presented. The new signal processing tool has been very successful in determining time frequency representations of highly non-stationary multicomponent signals in both simulations and trials involving actual Space Shuttle Main Engine (SSME) high frequency data. The MWD departs from the classic Wigner distribution (WD) in that it effectively eliminates the cross coupling among positive frequency components in a multiple component signal. This attribute of the MWD, which prevents the generation of 'phantom' spectral peaks, will undoubtedly increase the utility of the WD for real world signal analysis applications which more often than not involve multicomponent signals.

  8. THE RELATION OF FREQUENCY TO THE PHYSIOLOGICAL EFFECTS OF ULTRA-HIGH FREQUENCY CURRENTS

    PubMed Central

    Christie, Ronald V.; Loomis, Alfred L.

    1929-01-01

    1. Biological effects of electromagnetic waves emitted by a vacuum tube oscillator have been studied at frequencis ranging from 8,300,000 to 158,000,000 cycles per second (1.9 to 38 meters wave-length). 2. The effects produced on animals can be fully explained on the basis of the heat generated by high frequency currents which are induced in them. 3. No evidence was obtained to support the theory that certain wave-lengths have a specific action on living cells. 4. At frequencies below 50,000,000 cycles, the effect of these radiations on animals is proportionate to the intensity of the electro-magnetic field. As the frequency is increased beyond this point, the amount of induced current is diminished and the apparent lethality of the radiation is decreased. This can be explained by changes occurring in the dielectric properties of tissues at low wave-lengths. PMID:19869549

  9. Instrumentation for direct, low frequency scanning capacitance microscopy, and analysis of position dependent stray capacitance

    NASA Astrophysics Data System (ADS)

    Lee, David T.; Pelz, J. P.; Bhushan, Bharat

    2002-10-01

    We describe instrumentation for scanning capacitance microscopy (SCM), using an atomic force microscope, that is designed to make calibrated, low frequency measurements of tip-sample capacitance and spreading resistance of thin dielectric films. We also characterize spatial variations in stray capacitance Cstray that must be understood before such measurements can be interpreted. Existing SCM circuits are generally optimized for measuring dC/dV, and not for calibrated low frequency measurements of absolute capacitance. Our circuit uses a commercially available current amplifier and low frequency (˜5 kHz) lock-in detection. This circuit adds an inverted, constant amplitude current to suppress the stray displacement current from the large (˜0.5 pF) stray capacitance Cstray between the sample and the mm-sized cantilever-probe assembly. The capacitance noise spectrum is ˜0.35 aF/√Hz and is flat down to 1 Hz measurement frequency, with an integrated noise <5 aF integrated over a 1-160 Hz bandwidth. We have also used this instrumentation to identify and characterize significant (>1 fF) variations in Cstray that must be understood in order to accurately measure aF-level variations in the nm-scale tip-sample capacitance. We find that Cstray varies with lateral probe position. This is due to tilting of the probe assembly as the piezoelectric scanner tube bends during scanning. We also find that Cstray varies significantly with probe-assembly height. This causes topography related artifacts in capacitance images of rough surfaces. However, we show that stray capacitance artifacts can be mostly eliminated by properly characterizing position and height dependent variations in Cstray and subtracting them from measured capacitance data.

  10. Effect of Radio Frequency Interference (RFI) on the Precision of GPS Relative Positioning

    NASA Astrophysics Data System (ADS)

    Idris, A. N.; Sathyamoorthy, D.; Suldi, A. M.; Hamid, J. R. A.

    2014-02-01

    The successful of GPS observations are dependent on several factors between satellite vehicles and GPS receivers, where low GPS power levels have led to the threat of radio frequency interference (RFI) on the GPS signals. This study was conducted to evaluate the effect of RFI on the precision of positions of single and dual frequency receivers through relative positioning technique by taking into consideration the radius of GPS receiver from interference source, length of baseline and response of rejection. Several tests were conducted in real environment by simulating the interference signal towards GPS receivers in the nominated GPS L1 and L2 bands. Calculations were made to indentify the distance and interference signal power between interference source and GPS receiver in order to investigate the level of effect. To be able to study this effect on the precision of GPS positions, the 3D residual positions and geometric dilution of precision (GDOP) have been used. The findings of this study have demonstrated that a sufficient time for the GPS receiver to respond in particular interference signal power level and the radius from the interference source were made as compared to previous work. It was also indicated that the residual positions and GDOPs were affected proportionally when nearly to interference source but not similar for both days due to GPS coverage and other probable errors. Therefore, a good investigation on RFI towards GPS signals should be conducted in secured environment which can control the various GPS error parameters in order to obtain a reliable result on this effect.

  11. Low-frequency and high-frequency all-fiber modulators based on birefringence modulation.

    PubMed

    Boyain, A R; Martínez-León, L; Cruz, J L; Diez, A; Andrés, M V

    1999-10-20

    In-line optical modulators with low insertion losses and high maximum optical powers are required for Q switching and cavity dumping of fiber lasers as well as for nonlinear optical-fiber experiments. We report the design of polarimetric all-fiber modulators based on optical-fiber birefringence modulation combined with an all-fiber polarizer. Birefringence modulation involves a piezoelectric ceramic tube. This simple technique permits efficient low-frequency and high-frequency harmonic modulation, up to the megahertz range, as well as modulation of pulses shorter than 1 micros.

  12. First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers

    SciTech Connect

    Chou, Aaron S.; Gustafson, Richard; Hogan, Craig; Kamai, Brittany; Kwon, Ohkyung; Lanza, Robert; McCuller, Lee; Meyer, Stephan S.; Richardson, Jonathan; Stoughton, Chris; Tomlin, Raymond; Waldman, Samuel; Weiss, Rainer

    2016-09-01

    Measurements are reported of high frequency cross-spectra of signals from the Fermilab Holometer, a pair of co-located 39 m, high power Michelson interferometers. The instrument obtains differential position sensitivity to cross-correlated signals far exceeding any previous measurement in a broad frequency band extending to the 3.8 MHz inverse light crossing time of the apparatus. A model of universal exotic spatial shear correlations that matches the Planck scale holographic information bound of space-time position states is excluded to 4.6{\\sigma} significance.

  13. Magnetoresistive polyaniline-silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity.

    PubMed

    Gu, Hongbo; Guo, Jiang; Khan, Mojammel Alam; Young, David P; Shen, T D; Wei, Suying; Guo, Zhanhu

    2016-07-20

    The Drude model modified by Debye relaxation time was introduced to determine the plasma frequency (ωp) in the surface initiated polymerization (SIP) synthesized β-silicon carbide (β-SiC)/polyaniline (PANI) metacomposites. The calculated plasma frequency for these metacomposites with different loadings of β-SiC nanoparticles was ranging from 6.11 × 10(4) to 1.53 × 10(5) rad s(-1). The relationship between the negative permittivity and plasma frequency indicates the existence of switching frequency, at which the permittivity was changed from negative to positive. More interestingly, the synthesized non-magnetic metacomposites, observed to follow the 3-dimensional (3-D) Mott variable range hopping (VRH) electrical conduction mechanism, demonstrated high positive magnetoresistance (MR) values of up to 57.48% and high MR sensitivity at low magnetic field regimes.

  14. High Frequency VLBI Studies of Sagittarius A* and NRAO 530

    NASA Astrophysics Data System (ADS)

    Lu, Ru-Sen

    2010-10-01

    Compact radio sources (Kellermann & Pauliny-Toth 1981) are widely accepted to be associated with supermassive black holes at the centers of active galaxies. Very long baseline interferometry (VLBI) observations at short millimeter wavelengths offer the unique advantage to look "deeper" into the central core regions. In this thesis we study two com pact radio sources (Sagittarius A* and NRAO 530) with high frequency VLBI techniques. As a starting point, we give in Chapter 1 a general introduction to observational properties of Active galactic nuclei (AGNs) and a theoretical basis. In Chapter 2, the compact radio source at the center of the Milky Way, Sagittarius A*, is reviewed. In Chapter 3, the technical basis of VLBI is outlined and then the difficulties of VLBI (and therefore the ways to improve) at short millimeter wavelengths are discussed. Due to its proximity, Sagittarius A* has the largest apparent event horizon of any black hole candidate and therefore it provides a unique opportunity for testing the SMBH paradigm. However, direct imaging of the nucleus is only accessible at short millimeter wavelengths due to the scatter broadening. In Chapter 4, we present results of an inter-day VLBI monitoring of Sagittarius A* at wavelengths of 13, 7, and 3 mm during a global observing campaign in 2007. We measure the flux density and source structure and study their variability on daily time scales. In addition to the VLBI monitoring of the Galactic Center, we present in Chapter 5 results of multi-epoch multi-frequency VLBI observations of the blazar nrao 530. NRAO 530 is an optically violent variable (OVV) source and was observed as a VLBI calibrator in our observations of Sagittarius A*. We investigate the spectral properties of jet components, their frequency-dependent position shifts, and variability of flux density and structure on daily time scales. Analysis of archival data over the last ten years allows us to study the detailed jet kinematics. Finally, a

  15. High Frequency Resonant Electromagnetic Generation and Detection of Ultrasonic Waves

    NASA Astrophysics Data System (ADS)

    Kawashima, Katsuhiro; Wright, Oliver; Hyoguchi, Takao

    1994-05-01

    High frequency resonant mode electromagnetic ultrasonic generation and detection in metals is demonstrated at frequencies up to ˜150 MHz with various metal sheet samples. Using a unified theory of the generation and detection process, it is shown how various physical quantities can be measured. The sound velocity or thickness of the sheets can be derived from the resonant frequencies. At resonance the detected amplitude is inversely proportional to the ultrasonic attenuation of the sample, whereas the resonance half-width is proportional to this attenuation. We derive the ultrasonic attenuation coefficient from the half-width, and show how the grain size of the material can be probed. In addition we present results for thin bonded sheets, and show how a measure of the bonding or delamination can be obtained. This high frequency resonant method shows great promise for the non-destructive evaluation of thin sheets and coatings in the sub- 10-µm to 1-mm thickness range.

  16. A high frequency transformer model for the EMTP

    SciTech Connect

    Morched, A.; Marti, L.; Ottevangers, J. )

    1993-07-01

    A model to simulate the high frequency behavior of a power transformer is presented. This model is based on the frequency characteristics of the transformer admittance matrix between its terminals over a given range of frequencies. The transformer admittance characteristics can be obtained from measurements or from detailed internal models based on the physical layout of the transformer. The elements of the nodal admittance matrix are approximated with rational functions consisting of real as well as complex conjugate poles and zeros. These approximations are realized in the form of an RLC network in a format suitable for direct use with EMTP. The high frequency transformer model can be used as a stand-alone linear model or as an add-on module of a more comprehensive model where iron core nonlinearities are represented in detail.

  17. Effects of core position of locally resonant scatterers on low-frequency acoustic absorption in viscoelastic panel

    NASA Astrophysics Data System (ADS)

    Zhong, Jie; Wen, Ji-Hong; Zhao, Hong-Gang; Yin, Jian-Fei; Yang, Hai-Bin

    2015-08-01

    Locally resonant sonic materials, due to their ability to control the propagation of low-frequency elastic waves, have become a promising option for underwater sound absorption materials. In this paper, the finite element method is used to investigate the absorption characteristics of a viscoelastic panel periodically embedded with a type of infinite-long non-coaxially cylindrical locally resonant scatterers (LRSs). The effect of the core position in the coating layer of the LRS on the low-frequency (500 Hz-3000 Hz) sound absorption property is investigated. With increasing the longitudinal core eccentricity e, there occur few changes in the absorptance at the frequencies below 1500 Hz, however, the absorptance above 1500 Hz becomes gradually better and the valid absorption (with absorptance above 0.8) frequency band (VAFB) of the viscoelastic panel becomes accordingly broader. The absorption mechanism is revealed by using the displacement field maps of the viscoelastic panel and the steel slab. The results show two typical resonance modes. One is the overall resonance mode (ORM) caused by steel backing, and the other is the core resonance mode (CRM) caused by LRS. The absorptance of the viscoelastic panel by ORM is induced mainly by the vibration of the steel slab and affected little by core position. On the contrary, with increasing the core eccentricity, the CRM shifts toward high frequency band and decouples with the ORM, leading to two separate absorption peaks and the broadened VAFB of the panel. Project supported by the National Natural Science Foundation of China (Grant No. 51275519).

  18. High-Frequency-Induced Cathodic Breakdown during Plasma Electrolytic Oxidation

    NASA Astrophysics Data System (ADS)

    Nominé, A.; Nominé, A. V.; Braithwaite, N. St. J.; Belmonte, T.; Henrion, G.

    2017-09-01

    The present communication shows the possibility of observing microdischarges under cathodic polarization during plasma electrolytic oxidation at high frequency. Cathodic microdischarges can ignite beyond a threshold frequency found close to 2 kHz. The presence (respectively, absence) of an electrical double layer is put forward to explain how the applied voltage can be screened, which therefore prevents (respectively, promotes) the ignition of a discharge. Interestingly, in the conditions of the present study, the electrical double layer requires between 175 and 260 μ s to form. This situates the expected threshold frequency between 1.92 and 2.86 kHz, which is in good agreement with the value obtained experimentally.

  19. High-power radio-frequency attenuation device

    DOEpatents

    Kerns, Q.A.; Miller, H.W.

    1981-12-30

    A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

  20. Optical wireless communication using positive real-valued orthogonal frequency-division multiplexing and optical beamforming

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Man; Kwon, Ki-Keun

    2017-07-01

    The relatively unsatisfactory performance of optical wireless communication (OWC) with respect to WiFi and millimeter-wave communications has formed a key issue preventing its commercialization. We experimentally demonstrate an OWC technology using a combination of positive real-valued orthogonal frequency-division multiplexing (OFDM) and optical beamforming (OB). Due to the intensity-modulation and direct-detection aspects of OWC systems, a positive real-valued OFDM signal can be suitably utilized to maximize the OWC data rate. Further, the OB technique, which can focus laser light on a desired target, can be utilized to increase the OWC data rate and transmission distance. Our experimental results show that the received optical signal power and electrical signal increase by up to 42 and 25 dB, respectively. Further, the data rate increases by a factor of 200 with OB over the conventional approach.

  1. Planar Position Sensor Based on Mono Sensing Electrode and Hybrid-Frequency Excitation

    PubMed Central

    Yu, Hongxiang; Zhang, Yu; Shen, Mengfeng; Zhang, Hongli; Gao, Zhao; Wang, Dongyun

    2016-01-01

    A new way of measuring planar position for micrometric and sub-micrometric applications is presented with a mono sensing electrode and hybrid-frequency excitation. The sensing theory and operation principle are described and summarized, and a printed circuit board (PCB) sensor prototype is built and tested. It is shown by the experimental results that a very simple structure and geometric relationship are achieved. Meanwhile, displacement sensitivity on an order of 1.50 mV per micron and measurement repeatability better than 0.002 mm are easily fulfilled for a square zone of 256 mm2, making it a valuable alternative measurement device candidate for flexible and low-cost planar position detection. PMID:27187404

  2. Decameter type III bursts with positive and negative frequency drift rates

    NASA Astrophysics Data System (ADS)

    Melnik, V. N.; Brazhenko, A. I.; Konovalenko, A. A.; Briand, C.; Dorovskyy, V. V.; Zarka, P.; Frantzusenko, A. V.; Rucker, H. O.; Rutkevych, B. P.; Panchenko, M.; Zaqarashvili, T.; Shergelashvili, B.

    2013-09-01

    We report about observations of decameter type III bursts whose frequency drift rates vary their signs from negative to positive. Moreover drift rates of some bursts vary the sign some times. Positive drift rates for some bursts are changed from 0.44 MHz/s to 12 MHz/s. At the same time the negative drift rates of these bursts are standard values for decameter type III bursts. A possible interpretation of such phenomenon on the base of plasma mechanism of type III burst generation is discussed. The sense of this interpretation is that group velocity of type III electromagnetic waves generated by fast electrons at some conditions can be smaller than velocity of these electrons.

  3. High frequency fluoroptic thermometry current sensing for weapon susceptibility testing

    SciTech Connect

    Cernosek, R.W.

    1988-01-01

    A high frequency current measurement technique for susceptibility testing is proposed. This technique uses a resistive element to produce a temperature change that is sensed by a fluoroptic thermometer. Laboratory testing has shown that RF currents as small as 1.5 mA are measureable for frequencies up to 10 GHz. Errors bounds in determining the current are 6 dB. 7 refs., 6 figs.

  4. High-Frequency Gravitational Wave Induced Nuclear Fusion

    SciTech Connect

    Fontana, Giorgio; Baker, Robert M. L. Jr.

    2007-01-30

    Nuclear fusion is a process in which nuclei, having a total initial mass, combine to produce a single nucleus, having a final mass less than the total initial mass. Below a given atomic number the process is exothermic; that is, since the final mass is less than the combined initial mass and the mass deficit is converted into energy by the nuclear fusion. On Earth nuclear fusion does not happen spontaneously because electrostatic barriers prevent the phenomenon. To induce controlled, industrial scale, nuclear fusion, only a few methods have been discovered that look promising, but net positive energy production is not yet possible because of low overall efficiency of the systems. In this paper we propose that an intense burst of High Frequency Gravitational Waves (HFGWs) could be focused or beamed to a target mass composed of appropriate fuel or target material to efficiently rearrange the atomic or nuclear structure of the target material with consequent nuclear fusion. Provided that efficient generation of HFGW can be technically achieved, the proposed fusion reactor could become a viable solution for the energy needs of mankind and alternatively a process for beaming energy to produce a source of fusion energy remotely - even inside solid materials.

  5. Engineering Graphene Conductivity for Flexible and High-Frequency Applications.

    PubMed

    Samuels, Alexander J; Carey, J David

    2015-10-14

    Advances in lightweight, flexible, and conformal electronic devices depend on materials that exhibit high electrical conductivity coupled with high mechanical strength. Defect-free graphene is one such material that satisfies both these requirements and which offers a range of attractive and tunable electrical, optoelectronic, and plasmonic characteristics for devices that operate at microwave, terahertz, infrared, or optical frequencies. Essential to the future success of such devices is therefore the ability to control the frequency-dependent conductivity of graphene. Looking to accelerate the development of high-frequency applications of graphene, here we demonstrate how readily accessible and processable organic and organometallic molecules can efficiently dope graphene to carrier densities in excess of 10(13) cm(-2) with conductivities at gigahertz frequencies in excess of 60 mS. In using the molecule 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane (F2-HCNQ), a high charge transfer (CT) of 0.5 electrons per adsorbed molecule is calculated, resulting in p-type doping of graphene. n-Type doping is achieved using cobaltocene and the sulfur-containing molecule tetrathiafulvalene (TTF) with a CT of 0.41 and 0.24 electrons donated per adsorbed molecule, respectively. Efficient CT is associated with the interaction between the π electrons present in the molecule and in graphene. Calculation of the high-frequency conductivity shows dispersion-less behavior of the real component of the conductivity over a wide range of gigahertz frequencies. Potential high-frequency applications in graphene antennas and communications that can exploit these properties and the broader impacts of using molecular doping to modify functional materials that possess a low-energy Dirac cone are also discussed.

  6. Design of matching layers for high-frequency ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Fei, Chunlong; Ma, Jianguo; Chiu, Chi Tat; Williams, Jay A.; Fong, Wayne; Chen, Zeyu; Zhu, BenPeng; Xiong, Rui; Shi, Jing; Hsiai, Tzung K.; Shung, K. Kirk; Zhou, Qifa

    2015-09-01

    Matching the acoustic impedance of high-frequency (≥100 MHz) ultrasound transducers to an aqueous loading medium remains a challenge for fabricating high-frequency transducers. The traditional matching layer design has been problematic to establish high matching performance given requirements on both specific acoustic impedance and precise thickness. Based on both mass-spring scheme and microwave matching network analysis, we interfaced metal-polymer layers for the matching effects. Both methods hold promises for guiding the metal-polymer matching layer design. A 100 MHz LiNbO3 transducer was fabricated to validate the performance of the both matching layer designs. In the pulse-echo experiment, the transducer echo amplitude increased by 84.4% and its -6dB bandwidth increased from 30.2% to 58.3% comparing to the non-matched condition, demonstrating that the matching layer design method is effective for developing high-frequency ultrasonic transducers.

  7. Design of matching layers for high-frequency ultrasonic transducers.

    PubMed

    Fei, Chunlong; Ma, Jianguo; Chiu, Chi Tat; Williams, Jay A; Fong, Wayne; Chen, Zeyu; Zhu, BenPeng; Xiong, Rui; Shi, Jing; Hsiai, Tzung K; Shung, K Kirk; Zhou, Qifa

    2015-09-21

    Matching the acoustic impedance of high-frequency (≥100 MHz) ultrasound transducers to an aqueous loading medium remains a challenge for fabricating high-frequency transducers. The traditional matching layer design has been problematic to establish high matching performance given requirements on both specific acoustic impedance and precise thickness. Based on both mass-spring scheme and microwave matching network analysis, we interfaced metal-polymer layers for the matching effects. Both methods hold promises for guiding the metal-polymer matching layer design. A 100 MHz LiNbO3 transducer was fabricated to validate the performance of the both matching layer designs. In the pulse-echo experiment, the transducer echo amplitude increased by 84.4% and its -6dB bandwidth increased from 30.2% to 58.3% comparing to the non-matched condition, demonstrating that the matching layer design method is effective for developing high-frequency ultrasonic transducers.

  8. Frequency of L-SIL and H-SIL Findings in HPV Positive Women.

    PubMed

    Asotic, Amir; Taric, Suada; Asotic, Jasminka

    2014-04-01

    Cervical carcinoma is one of the leading health issues for women throughout the world. In 90% of the cases cervical carcinoma develops after development of invasive lesions of the uterine cervix or 10-15 years before they are diagnosed using cytological screening-Papanicolau test. Infection with human papilloma virus is considered to be the basic etiological cause of development of CIN and cervical carcinoma. Of this research was to determine frequency and type of abnormal cytological results in HPV positive and HPV negative patients. Research is descriptive analytical, comparative and partly epidemiological, of mostly clinically applicable character. Used data included information on total number of examinations, type of exam, results of cytological and pathohistological diagnostics, HPV findings in cervix smear and HPV type in the period between January 1, 2009 and December 31, 2011. During the period of analysis total number of Pap tests was 6376 (43.33%), in comparison to other exams 7828 (56.67%). For this period total number of L-SIL and H-SIL (PAPA III) was 395 (6.20%), in comparison to other results 5894 (92.44%). After analysis largest subset of HPV positive patients had pathohistological diagnosis of CIN I that is 250 (43.10%) of them, then CIN II with 162 (27.93%) patients, CIN III with 149 (25.69) and 3 (0.52%) patients had CIS while 16 (2.76%) had a clear test result. We can conclude there is a statistically significant margin of frequency between positive HPV results in relation to diagnosis. Highest percentage of L-SIL and H-SIL (PAPA III) test results was in 2010 and was 9.5%, and lowest in 2009 with 4.34%. Largest number of patients, 43.0%, with HPV positive results after cervical smear had pathohistological diagnosis of CIN I.

  9. Frequency of L-SIL and H-SIL Findings in HPV Positive Women

    PubMed Central

    Asotic, Amir; Taric, Suada; Asotic, Jasminka

    2014-01-01

    Introduction: Cervical carcinoma is one of the leading health issues for women throughout the world. In 90% of the cases cervical carcinoma develops after development of invasive lesions of the uterine cervix or 10-15 years before they are diagnosed using cytological screening–Papanicolau test. Infection with human papilloma virus is considered to be the basic etiological cause of development of CIN and cervical carcinoma. Goal: Of this research was to determine frequency and type of abnormal cytological results in HPV positive and HPV negative patients. Material and Methods: Research is descriptive analytical, comparative and partly epidemiological, of mostly clinically applicable character. Used data included information on total number of examinations, type of exam, results of cytological and pathohistological diagnostics, HPV findings in cervix smear and HPV type in the period between January 1, 2009 and December 31, 2011. Results: During the period of analysis total number of Pap tests was 6376 (43.33%), in comparison to other exams 7828 (56.67%). For this period total number of L-SIL and H-SIL (PAPA III) was 395 (6.20%), in comparison to other results 5894 (92.44%). After analysis largest subset of HPV positive patients had pathohistological diagnosis of CIN I that is 250 (43.10%) of them, then CIN II with 162 (27.93%) patients, CIN III with 149 (25.69) and 3 (0.52%) patients had CIS while 16 (2.76%) had a clear test result. We can conclude there is a statistically significant margin of frequency between positive HPV results in relation to diagnosis. Highest percentage of L-SIL and H-SIL (PAPA III) test results was in 2010 and was 9.5%, and lowest in 2009 with 4.34%. Largest number of patients, 43.0%, with HPV positive results after cervical smear had pathohistological diagnosis of CIN I. PMID:24944529

  10. High-frequency generation in two coupled semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Matharu, Satpal; Kusmartsev, Feodor V.; Balanov, Alexander G.

    2013-10-01

    We theoretically show that two semiconductor superlattices arranged on the same substrate and coupled with the same resistive load can be used for a generation of high-frequency periodic and quasiperiodic signals. Each superlattice involved is capable to generate current oscillations associated with drift of domains of high charge concentration. However, the coupling with the common load can eventually lead to synchronization of the current oscillations in the interacting superlattices. We reveal how synchronization depends on detuning between devices and the resistance of the common load, and discuss the effects of coupling and detuning on the high-frequency power output from the system.

  11. Effects of High-Frequency Torsional Impacts on Rock Drilling

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaohua; Tang, Liping; Tong, Hua

    2014-07-01

    High-frequency torsional impact drilling (HFTID) is a new technology which provides stable and efficient drilling. The goal of the present study is to investigate the effects of high-frequency torsional impacts on rock drilling. The impact parameters of the high-frequency torsional impact generator (HFTIG) are obtained by conducting a series of laboratory tests. The results of the tests reveal that the impact time decreases and the impact force increases with increasing impact frequency. The parameters are used as input for simulations of the rock crushing process, and a series of models for investigating the respective performance of HFTID and conventional drilling are developed. In addition, the Drucker-Prager criterion is used to describe the constitutive laws of the rock element, and the equivalent plastic strain criterion is adopted as the damage criterion. The models are run to simulate the dynamic rock crushing processes. The results of the simulations show that increase of the impact frequency results in a significant improvement in the rate of penetration (ROP), and a decrease in the life of the HFTIG. Considering the tool life and ROP, the optimum impact frequency of the HFTIG is 15 Hz. Finally, the performance of the HFTID technique is evaluated.

  12. Carbon nanotube transistor based high-frequency electronics

    NASA Astrophysics Data System (ADS)

    Schroter, Michael

    At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks. Carbon nanotube transistor based high-frequency electronics.

  13. High frequency ocean acoustic tomography observation at coastal estuary areas

    NASA Astrophysics Data System (ADS)

    Zhao, Zongxi; Zhang, Yu; Yang, Wuyi; Chen, Dongsheng

    2012-11-01

    The ocean acoustic tomography (OAT) technique can obtain oceanographic information and has received much interest. High frequency OAT (in a narrow kHz range) can be used for small and confined areas, such as estuaries and bays, with complicated hydrological conditions. In this study, we investigate the application of high-frequency reciprocal transmission OAT to assess the sound speed, temperature, and current field in the Xiamen sea area using computer simulations and sea experiments. Based on the temperature data obtained from remote sensing and the predefined stream function, high frequency OAT is employed to reconstruct the two-dimensional sound speed, temperature, and current fields of a 1.2km×1.2km small-scale region. The correlation coefficient of the computer inversion result and the original data is higher than 0.8. The result shows that increasing the number of acoustic stations decreases the influence of the travel-time errors in high frequency OAT; however, excessively increasing the number of stations could not significantly improve the inversion accuracy. Furthermore, this method has been tested by a sea experiment on monitoring the shallow water temperature of Wuyuan Bay. High frequency OAT might provide an effective method for temperature and current observation at coastal estuary areas.

  14. Frequency of detection of periodontopathic and superinfecting bacteria in HIV-positive patients with periodontitis.

    PubMed

    Botero, Javier Enrique; Arce, Roger Mauricio; Escudero, Mónica; Betancourth, Marisol; Jaramillo, Adriana; Contreras, Adolfo

    2007-01-01

    The aim of this investigation was to establish the frequency of detection of periodontopathic bacteria and Gram-negative enteric rods in HIV-positive (HIV+) patients with periodontitis. Clinical parameters and microbiological samples were obtained from 31 HIV+ periodontitis (H+PG) patients, 32 HIV-negative (HIV-) periodontitis (H-PG) patients and 32 systemically and periodontally healthy (CG) patients. Microbial samples were analyzed using culturing techniques for periodontopathic and superinfecting microorganisms. The ANOVA test was used to assess differences in the clinical parameters, and the Chi square and two-tailed Mann Whitney tests were used to find differences in the composition of the microbiota (p < 0.05). The frequency of detection of periodontopathic bacteria was higher in HIV- periodontitis patients (p < 0.05) compared to HIV+ and healthy subjects. In contrast, HIV+ patients harbor higher levels of superinfecting microorganisms (p < 0.05). Pseudomonas aeruginosa, Enterobacter cloacae and Klebsiella pneumoniae were identified. The frequency of detection and levels of periodontopathic bacteria were higher in the HIV- periodontitis patients compared to HIV+ patients and healthy subjects. In contrast, levels of superinfecting bacteria were found to be elevated in HIV+ periodontitis patients. Special attention should be paid to the presence of periodontopathic and superinfecting bacteria in these patients in order to avoid further periodontal and systemic complications.

  15. Investigation of iron cobalt nanocomposites for high frequency applications

    NASA Astrophysics Data System (ADS)

    Miller, Kelsy J.

    FeCo-based nanocomposite soft magnetic materials were developed in collaboration with Magnetics, Division of Spang and Co., for high frequency and high temperature application. Excellent soft magnetic properties include: low coercivity, high permeability, low energy losses, etc. These and large saturation inductions make these alloys attractive for fundamental studies and industrial applications. In this thesis, nanocrystalline composites will be developed from amorphous precursors for applications in two frequency regimes: 1) High frequency (0.01-30 MHz) such as high temperature power inductors, pulsed power transformers, and radio frequency (rf) magnetic heating; and 2) Ultra high frequency (30 MHz - 30 GHz) for radio frequency materials and electromagnetic interference (EMI) or radio frequency interference (RFI) absorption. New nanocomposites with higher saturation induction and high-temperature stability were developed with reduced glass forming elements such as Zr, Nb, Si and B. The amounts of the magnetic transition metals and early transition metal growth inhibitors were varied to determine trade-offs between higher inductions and fine microstructures and consequently low magnetic losses. Alloys having (Fe1-xCox)80+y+zNb4-y B13-zSi2Cu1 (25 ≤ x ≤ 50 and y = 0-4 and z = 0-3) nominal compositions were cast using planar flow casting (PFC) at Magnetics. Technical magnetic properties: permeability, maximum induction, remanence ratio, coercive field and high frequency magnetic losses as a function of composition and annealing temperature are reported after primary crystallization for 1 hr in a transverse magnetic field (TMF). Of note is the development of inductor cores with maximum inductions in excess of 1.76 T and 1.67 T in cores that exhibit power losses comparable with state of the art commercial soft magnetic alloys. For application in EMI/RFI absorption, FeCo-based alloys have the largest saturation induction and a tunable magnetic anisotropy which may

  16. Increased mitochondrial mutation frequency after an island colonization: positive selection or accumulation of slightly deleterious mutations?

    PubMed

    Hardouin, Emilie A; Tautz, Diethard

    2013-04-23

    Island colonizations are excellent models for studying early processes of evolution. We found in a previous study on mice that had colonized the sub-Antarctic Kerguelen Archipelago about 200 years ago that they were derived from a single founder lineage and that this showed an unexpectedly large number of new mutations in the mitochondrial D-loop. To assess whether positive selection has played a role in the emergence of these variants, we have obtained 16 full mitochondrial genome sequences from these mice. For comparison, we have compiled 57 mitochondrial genome sequences from laboratory inbred lines that became established about 100 years ago, also starting from a single founder lineage. We find that the island mice and the laboratory lines show very similar mutation frequencies and patterns. None of the patterns in the Kerguelen mice provides evidence for positive selection. We conclude that nearly neutral evolutionary processes that assume the presence of slightly deleterious variants can fully explain the patterns. This supports the notion of time-dependency of molecular evolution and provides a new calibration point. Based on the observed mutation frequency, we calculate an average evolutionary rate of 0.23 substitutions per site per Myr for the earliest time frame of divergence, which is about six times higher than the long-term rate of 0.037 substitutions per site per Myr.

  17. Employing GPS L5 Carrier-Frequency in Precise Point Positioning

    NASA Astrophysics Data System (ADS)

    Spits, J.; Santos, M. C.

    2012-12-01

    Justine Spits and Marcelo C. Santos Dept. of Geodesy and Geomatics Engineering, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3 Tel: (1-506) 453-4698, Email: msantos@unb.ca, jspits@unb.ca Precise Point Positioning (PPP) is a GNSS technique which, in most cases nowadays, makes use of Global Positioning System (GPS) dual-frequency signals. The increasing availability of the new GPS L5 signal brings about the question on how much can PPP benefit if it uses L5 in conjunction with the legacy L1 and L2 signals. This poster discusses this issue. It involves the study of the use of L5 in conjunction with the other GPS signals (L1 and L2) with emphasis on the potentialities associated with the various combinations, such as L1-L5, L2-L5 and L1-L2-L5. These combinations will bring benefits in different ways, for example, for ionospheric delay mitigation, ambiguity resolution, convergence time and accuracy. Simulated L5 data will be used to test the PPP algorithms. Performance will be compared against the current dual-frequency PPP methodology. Justine Spits: Ph.D. (Liège, Belgium); Post-Doctoral Fellow, University of New Brunswick Marcelo. C. Santos: Ph.D. (New Brunswick); Professor, University of New Brunswick

  18. Electrojet-independent ionospheric extremely low frequency/very low frequency wave generation by powerful high frequency waves

    SciTech Connect

    Kuo, Spencer; Snyder, Arnold; Chang, Chia-Lie

    2010-08-15

    Results of extremely low frequency/very low frequency (ELF/VLF) wave generation by intensity-modulated high frequency (HF) heaters of 3.2 MHz in Gakona, Alaska, near local solar noon during a geomagnetic quiet time, are presented to support an electrojet-independent ELF/VLF wave generation mechanism. The modulation was set by splitting the HF transmitter array into two subarrays; one was run at cw full power and the other run alternatively at 50% and 100% power modulation by rectangular waves of 2.02, 5, 8, and 13 kHz. The most effective generation was from the X-mode heater with 100% modulation. While the 8 kHz radiation has the largest wave amplitude, the spectral intensity of the radiation increases with the modulation frequency, i.e., 13 kHz line is the strongest. Ionograms recorded significant virtual height spread of the O-mode sounding echoes. The patterns of the spreads and the changes of the second and third hop virtual height traces caused by the O/X-mode heaters are distinctively different, evidencing that it is due to differently polarized density irregularities generated by the filamentation instability of the O/X-mode HF heaters.

  19. Music students: conventional hearing thresholds and at high frequencies.

    PubMed

    Lüders, Débora; Gonçalves, Cláudia Giglio de Oliveira; Lacerda, Adriana Bender de Moreira; Ribas, Ângela; Conto, Juliana de

    2014-01-01

    Research has shown that hearing loss in musicians may cause difficulty in timbre recognition and tuning of instruments. To analyze the hearing thresholds from 250 Hz to 16,000 Hz in a group of music students and compare them to a non-musician group in order to determine whether high-frequency audiometry is a useful tool in the early detection of hearing impairment. Study design was a retrospective observational cohort. Conventional and high-frequency audiometry was performed in 42 music students (Madsen Itera II audiometer and TDH39P headphones for conventional audiometry, and HDA 200 headphones for high-frequency audiometry). Of the 42 students, 38.1% were female students and 61.9% were male students, with a mean age of 26 years. At conventional audiometry, 92.85% had hearing thresholds within normal limits; but even within the normal limits, the worst results were observed in the left ear for all frequencies, except for 4000 Hz; compared to the non-musician group, the worst results occurred at 500 Hz in the left ear, and at 250 Hz, 6000 Hz, 9000 Hz, 10,000 Hz, and 11,200 Hz in both the ears. The periodic evaluation of high-frequency thresholds may be useful in the early detection of hearing loss in musicians. Copyright © 2014 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

  20. Dynamics of high-frequency synchronization during seizures.

    PubMed

    Krishnan, Giri P; Filatov, Gregory; Bazhenov, Maxim

    2013-05-01

    Pathological synchronization of neuronal firing is considered to be an inherent property of epileptic seizures. However, it remains unclear whether the synchrony increases for the high-frequency multiunit activity as well as for the local field potentials (LFPs). We present spatio-temporal analysis of synchronization during epileptiform activity using wide-band (up to 2,000 Hz) spectral analysis of multielectrode array recordings at up to 60 locations throughout the mouse hippocampus in vitro. Our study revealed a prominent structure of LFP profiles during epileptiform discharges, triggered by elevated extracellular potassium, with characteristic distribution of current sinks and sources with respect to anatomical structure. The cross-coherence of high-frequency activity (500-2,000 Hz) across channels was reduced during epileptic bursts compared with baseline activity and showed the opposite trend for lower frequencies. Furthermore, the magnitude of cross-coherence during epileptiform activity was dependent on distance: electrodes closer to the epileptic foci showed increased cross-coherence and electrodes further away showed reduced cross-coherence for high-frequency activity. These experimental observations were re-created and supported in a computational model. Our study suggests that different intrinsic and synaptic processes can mediate paroxysmal synchronization at low, medium, and high frequencies.

  1. High frequency optical pulse generation by frequency doubling using polarization rotation

    NASA Astrophysics Data System (ADS)

    Liu, Yang

    2016-05-01

    In this work, we propose and experimentally characterize a stable 40 GHz optical pulse generation by frequency doubling using polarization rotation in a phase modulator (PM). Only half the electrical driving frequency is required (i.e. 20 GHz); hence the deployment cost can be reduced. Besides, precise control of the bias of the PM is not required. The generated optical pulses have a high center-mode-suppression-ratio (CMSR) of  >  28 dB. The single sideband (SSB) noise spectrum is also measured, and the time-domain waveforms under different CMSRs are also analyzed and discussed.

  2. High-frequency oscillations and the neurobiology of schizophrenia.

    PubMed

    Uhlhaas, Peter J; Singer, Wolf

    2013-09-01

    Neural oscillations at low- and high-frequency ranges are a fundamental feature of large-scale networks. Recent evidence has indicated that schizophrenia is associated with abnormal amplitude and synchrony of oscillatory activity, in particular, at high (beta/gamma) frequencies. These abnormalities are observed during task-related and spontaneous neuronal activity which may be important for understanding the pathophysiology of the syndrome. In this paper, we shall review the current evidence for impaired beta/gamma-band oscillations and their involvement in cognitive functions and certain symptoms of the disorder. In the first part, we will provide an update on neural oscillations during normal brain functions and discuss underlying mechanisms. This will be followed by a review of studies that have examined high-frequency oscillatory activity in schizophrenia and discuss evidence that relates abnormalities of oscillatory activity to disturbed excitatory/inhibitory (E/I) balance. Finally, we shall identify critical issues for future research in this area.

  3. High frequency amplitude detector for GMI magnetic sensors.

    PubMed

    Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul

    2014-12-19

    A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted.

  4. High Frequency Amplitude Detector for GMI Magnetic Sensors

    PubMed Central

    Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul

    2014-01-01

    A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted. PMID:25536003

  5. Frequency and temperature dependence of high damping elastomers

    SciTech Connect

    Kulak, R.F.; Hughes, T.H.

    1993-08-01

    High damping steel-laminated elastomeric seismic isolation bearings are one of the preferred devices for isolating large buildings and structures. In the US, the current reference design for the Advanced Liquid Metal Reactor (ALMR) uses laminated bearings for seismic isolation. These bearings are constructed from alternating layers of high damping rubber and steel plates. They are typically designed for shear strains between 50 and 100% and are expected to sustain two to three times these levels for beyond design basis loading conditions. Elastomeric bearings are currently designed to provide a system frequency between 0.4 and 0.8 Hz and expected to operate between {minus}20 and 40 degrees Centigrade. To assure proper performance of isolation bearings, it is necessary to characterize the elastomer`s response under expected variations of frequency and temperature. The dynamic response of the elastomer must be characterized within the frequency range that spans the bearing acceptance test frequency, which may be as low as 0.005 Hz, and the design frequency. Similarly, the variation in mechanical characteristics of the elastomer must be determined over the design temperature range, which is between {minus}20 and 40 degrees Centigrade. This paper reports on (1) the capabilities of a testing facility at ANL for testing candidate elastomers, (2) the variation with frequency and temperature of the stiffness and damping of one candidate elastomer, and (3) the effect of these variations on bearing acceptance testing criteria and on the choice of bearing design values for stiffness and damping.

  6. Determination of gas-trapping during high frequency oscillatory ventilation.

    PubMed

    Alexander, J; Milner, A D

    1997-03-01

    To determine the effect of frequency and percent inspiratory time on tidal volume and gas-trapping during high-frequency oscillatory ventilation (HFOV). Nine preterm infants with respiratory distress syndrome tested in the first 48 h of life. Tidal volumes and the presence of gas-trapping were measured by respiratory jacket plethysmography at frequencies of 10, 14, and 17.8 Hz and at inspiratory times of 30%, 50% and 70%, using a commercially available high frequency oscillator.74 Mean (SD) tidal volumes were 2.40 (1.06) ml/kg at 10 Hz, 2.52 (1.07) ml/kg at 14 Hz and fell significantly to 1.96 (0.92) at 17.8 Hz (p < 0.05). Tidal volumes at 50% inspiratory time were significantly greater than at 30% inspiratory time [2.81 (1.42) ml/kg and 2.32 (1.18) ml/kg, respectively] but fell to baseline levels at 70% inspiratory time. There was no significant gas-trapping with increases in either frequency or percent inspiratory time. Gas-trapping is not a significant problem during HFOV in premature infants. Changes in tidal volume with increases in frequency and percent inspiratory time are similar to that seen in animal models.

  7. High-Frequency Wave Measurements in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Bjorkqvist, J. V.; Kahma, K. K.; Pettersson, H.; Drennan, W. M.

    2016-02-01

    The high-frequency part of the wave field is essential for the understanding of air-sea exchange related processes and the turbulent energy dissipation of breaking waves. The quantification of the dimensionless spectra will aid wave model development and contribute to a better understanding of the fundamental laws governing the evolution of wind driven waves. However, typical wave observation devices, such as wave buoys, are limited to observing frequencies under e.g. 0.6 Hz. Dedicated experiments with devices suitable for high-frequency measurements are, in comparison, rare.We have made high-frequency wave measurements with capacitive wave staffs from RV Aranda. Air turbulence and wind speed measurements are also available and a full motion correction was applied to all measurements. A frequency rage up to 2-3 Hz is enough to study the tail of the wave spectra even during its early development. The unusually high sampling frequency of 200 Hz guarantees that spurious spectral shapes that could be the joint effect of noise and the anti-aliasing filter can be excluded. Directional measurements were made using four wave staffs located 15 or 50 cm apart in the grid.The mobility of the research vessel has enabled measurements in a wide variety of conditions from the Baltic Proper to the irregular Finnish coastal archipelagos. The aim is to determine the conditions and frequency ranges when the shape of the dimensionless spectra is wind dependent. Especially, it's still not clear whether the use of the wind speed or the friction velocity as the scaling parameter produces better results, or where the transition to the Phillips spectra takes place. The directional measurements can shed light on theories that use the directional spread of the two-dimensional spectrum to explain the shape of the one-dimensional spectrum.

  8. High-frequency oscillations in the Belousov-Zhabotinsky reaction.

    PubMed

    Bánsági, Tamás; Leda, Marcin; Toiya, Masahiro; Zhabotinsky, Anatol M; Epstein, Irving R

    2009-05-14

    Chemical oscillations in the classic Belousov-Zhabotinsky (BZ) system typically have a period of a few minutes, which can be increased significantly by changing the organic substrate. Here we show that by changing the temperature and concentrations, an increase of 3-4 orders of magnitude in the frequency of BZ oscillations can be obtained. At elevated temperatures, in high concentration mixtures, the cerium-catalyzed reaction exhibits sinusoidal oscillations with frequencies of 10 Hz or greater. We report the effect of temperature on the frequency and shape of oscillations in experiments under batch conditions and in a four-variable model. We show that our simple model accurately captures the complex temporal behavior of the system and suggests paths toward even higher frequencies.

  9. Reduced length fibre Bragg gratings for high frequency acoustic sensing

    NASA Astrophysics Data System (ADS)

    Davis, Claire; Robertson, David; Brooks, Chris; Norman, Patrick; Rosalie, Cedric; Rajic, Nik

    2014-12-01

    In-fibre Bragg gratings (FBGs) are now well established for applications in acoustic sensing. The upper frequency response limit of the Bragg grating is determined by its gauge length, which has typically been limited to about 1 mm for commercially available Type 1 gratings. This paper investigates the effect of FBG gauge length on frequency response for sensing of acoustic waves. The investigation shows that the ratio of wavelength to FBG length must be at least 8.8 in order to reliably resolve the strain response without significant gain roll-off. Bragg gratings with a gauge length of 200 µm have been fabricated and their capacity to measure low amplitude high frequency acoustic strain fields in excess of 2 MHz is experimentally demonstrated. The ultimate goal of this work is to enhance the sensitivity of acoustic damage detection techniques by extending the frequency range over which acoustic waves may be reliably measured using FBGs.

  10. High frequency conductivity of hot electrons in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac-dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons' source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  11. Lead extraction experience with high frequency excimer laser.

    PubMed

    Tanawuttiwat, Tanyanan; Gallego, Daniel; Carrillo, Roger G

    2014-09-01

    A higher frequency Excimer laser sheath using an 80-Hz pulse repetitive rate was approved by the Food and Drug Administration in April 2012. We reported our initial clinical experience with a high-frequency Excimer laser sheath and compared it with lower-frequency laser sheaths which have been previously used. In this single center, retrospective cohort study, we evaluated patients who underwent lead extraction from December 2008 to May 2013. Those who underwent lead removal without using a laser sheath or with approaches other than subclavian were excluded. Primary endpoints included total laser time, number of pulses, and complications. Data on clinical characteristics, lead type, indications, and outcomes were prospectively collected and analyzed. A total of 427 patients were included in the study (72.6% male; age 67.9 ± 15.23 years). Lower frequency and higher frequency laser sheaths were used in 315 and 112 patients, respectively. A total of 821 leads were removed with 765 leads (93.2%) extracted using the Excimer laser sheath. Lead age was 5.71 ± 4.96 years. Complete extraction was seen in all patients. A higher-frequency laser sheath was associated with a lower laser time and a lower total number of laser pulses even after adjustments for the number of leads, type of leads, and lead age. In the higher frequency group, mortality rate was 0.9% and minor complication rate was 3.6%. When compared with the lower-frequency laser sheath, the higher-frequency laser sheath requires less laser times and more efficient amount of pulses for lead extraction with comparable success rate. Due to the rarity of major and minor complications, no statistical significance was found between the two groups. ©2014 Wiley Periodicals, Inc.

  12. High-frequency audiometric assessment of a young adult population.

    PubMed

    Green, D M; Kidd, G; Stevens, K N

    1987-02-01

    The hearing thresholds of 37 young adults (18-26 years) were measured at 13 frequencies (8, 9,10,...,20 kHz) using a newly developed high-frequency audiometer. All subjects were screened at 15 dB HL at the low audiometric frequencies, had tympanometry within normal limits, and had no history of significant hearing problems. The audiometer delivers sound from a driver unit to the ear canal through a lossy tube and earpiece providing a source impedance essentially equal to the characteristic impedance of the tube. A small microphone located within the earpiece is used to measure the response of the ear canal when an impulse is applied at the driver unit. From this response, a gain function is calculated relating the equivalent sound-pressure level of the source to the SPL at the medial end of the ear canal. For the subjects tested, this gain function showed a gradual increase from 2 to 12 dB over the frequency range. The standard deviation of the gain function was about 2.5 dB across subjects in the lower frequency region (8-14 kHz) and about 4 dB at the higher frequencies. Cross modes and poor fit of the earpiece to the ear canal prevented accurate calibration for some subjects at the highest frequencies. The average SPL at threshold was 23 dB at 8 kHz, 30 dB at 12 kHz, and 87 dB at 18 kHz. Despite the homogeneous nature of the sample, the younger subjects in the sample had reliably better thresholds than the older subjects. Repeated measurements of threshold over an interval as long as 1 month showed a standard deviation of 2.5 dB at the lower frequencies (8-14 kHz) and 4.5 dB at the higher frequencies.

  13. A comparison of frequency estimation techniques for high-dynamic trajectories

    NASA Technical Reports Server (NTRS)

    Vilnrotter, V. A.; Hinedi, S.; Kumar, R.

    1988-01-01

    A comparison is presented for four different estimation techniques applied to the problem of continuously estimating the parameters of a sinusoidal Global Positioning System (GPS) signal, observed in the presence of additive noise, under extremely high-dynamic conditions. Frequency estimates are emphasized, although phase and/or frequency rate are also estimated by some of the algorithms. These parameters are related to the velocity, position, and acceleration of the maneuvering transmitter. Estimated performance at low carrier-to-noise ratios and high dynamics is investigated for the purpose of determining the useful operating range of an approximate Maximum Likelihood (ML) estimator, an Extended Kalman Filter (EKF), a Cross-Product Automatic Frequency Control (CPAFC) loop, and a digital phase-locked loop (PPL). Numerical simulations are used to evaluate performance while tracking a common trajectory exhibiting high dynamics.

  14. Early deactivation of slower muscle fibres at high movement frequencies.

    PubMed

    Blake, Ollie M; Wakeling, James M

    2014-10-01

    Animals produce rapid movements using fast cyclical muscle contractions. These types of movements are better suited to faster muscle fibres within muscles of mixed fibre types as they can shorten at faster velocities and achieve higher activation-deactivation rates than their slower counterparts. Preferential recruitment of faster muscle fibres has previously been shown during high velocity contractions. Additionally, muscle deactivation takes longer than activation and therefore may pose a limitation to fast cyclical contractions. It has been speculated that slower fibres may be deactivated before faster fibres to accommodate their longer deactivation time. This study aimed to test whether shifts in muscle fibre recruitment occur with derecruitment of slow fibres before faster fibres at high cycle frequencies. Electromyographic (EMG) signals were collected from the medial gastrocnemius at an extreme range of cycle frequencies and workloads. Wavelets were used to resolve the EMG signals into time and frequency space and the primary sources of variability within the EMG frequency spectra were identified through principal component analysis. Early derecruitment of slower fibres was evident at the end of muscle excitation at higher cycle frequencies, as determined by reduced low-frequency EMG content, and additional slower fibre recruitment was present at the highest cycle frequency. The duration of muscle excitation reached a minimum of about 150 ms and did not change for the three highest cycle frequencies, suggesting a duration limit for the medial gastrocnemius. This study provides further evidence of modifications of muscle fibre recruitment strategies to meet the mechanical demands of movement. © 2014. Published by The Company of Biologists Ltd.

  15. Exploring the Positional Identities of High School Science Teachers

    ERIC Educational Resources Information Center

    Blackwell, Edith Lavonne

    2012-01-01

    The identity of the teacher has been determined to influence classroom practices. Positional identity is defined as one's perception of self relative to others. This qualitative research study investigates the positional identity of five high school science teachers of different ethnicities and how their positional identities influence their…

  16. High-Level Visual Object Representations Are Constrained by Position

    PubMed Central

    Kriegeskorte, Nikolaus; Baker, Chris I.

    2010-01-01

    It is widely assumed that high-level visual object representations are position-independent (or invariant). While there is sensitivity to position in high-level object-selective cortex, position and object identity are thought to be encoded independently in the population response such that position information is available across objects and object information is available across positions. Contrary to this view, we show, with both behavior and neuroimaging, that visual object representations are position-dependent (tied to limited portions of the visual field). Behaviorally, we show that the effect of priming an object was greatly reduced with any change in position (within- or between-hemifields), indicating nonoverlapping representations of the same object across different positions. Furthermore, using neuroimaging, we show that object-selective cortex is not only highly sensitive to object position but also the ability to differentiate objects based on its response is greatly reduced across different positions, consistent with the observed behavior and the receptive field properties observed in macaque object-selective neurons. Thus, even at the population level, the object information available in response of object-selective cortex is constrained by position. We conclude that even high-level visual object representations are position-dependent. PMID:20351021

  17. High-level visual object representations are constrained by position.

    PubMed

    Kravitz, Dwight J; Kriegeskorte, Nikolaus; Baker, Chris I

    2010-12-01

    It is widely assumed that high-level visual object representations are position-independent (or invariant). While there is sensitivity to position in high-level object-selective cortex, position and object identity are thought to be encoded independently in the population response such that position information is available across objects and object information is available across positions. Contrary to this view, we show, with both behavior and neuroimaging, that visual object representations are position-dependent (tied to limited portions of the visual field). Behaviorally, we show that the effect of priming an object was greatly reduced with any change in position (within- or between-hemifields), indicating nonoverlapping representations of the same object across different positions. Furthermore, using neuroimaging, we show that object-selective cortex is not only highly sensitive to object position but also the ability to differentiate objects based on its response is greatly reduced across different positions, consistent with the observed behavior and the receptive field properties observed in macaque object-selective neurons. Thus, even at the population level, the object information available in response of object-selective cortex is constrained by position. We conclude that even high-level visual object representations are position-dependent.

  18. Exploring the Positional Identities of High School Science Teachers

    ERIC Educational Resources Information Center

    Blackwell, Edith Lavonne

    2012-01-01

    The identity of the teacher has been determined to influence classroom practices. Positional identity is defined as one's perception of self relative to others. This qualitative research study investigates the positional identity of five high school science teachers of different ethnicities and how their positional identities influence their…

  19. High-frequency nonreciprocal reflection from magnetic films with overlayers

    SciTech Connect

    Wang, Ying; Nie, Yan; Camley, R. E.

    2013-11-14

    We perform a theoretical study of the nonreciprocal reflection of high-frequency microwave radiation from ferromagnetic films with thin overlayers. Reflection from metallic ferromagnetic films is always near unity and shows no nonreciprocity. In contrast, reflection from a structure which has a dielectric overlayer on top of a film composed of insulated ferromagnetic nanoparticles or nanostructures can show significant nonreciprocity in the 75–80 GHz frequency range, a very high value. This can be important for devices such as isolators or circulators.

  20. ZCS High Frequency Inverter for Aluminum Vessel Induction Heating

    NASA Astrophysics Data System (ADS)

    Ogiwara, Hiroyuki; Nakaoka, Mutsuo

    Recent induction cooking apparatus are utilized for induction heating of ferromagnetic materials at 20-50kHz with a high efficiency. They can not, however, be applied for non-magnetic materials such as aluminum vessels. Here, we present a voltage-clamp reverse conducting ZCS high frequency inverter of half bridge type for induction heating of an aluminum vessel. The switching devices utilized for this inverter are SITs and its operating frequency is determined as 200kHz. This paper describes its circuit constitution and the obtained experimental results from a practical point of view.

  1. High frequency SAW devices based on third harmonic generation.

    PubMed

    Le Brizoual, L; Elmazria, O; Sarry, F; El Hakiki, M; Talbi, A; Alnot, P

    2006-12-01

    We demonstrate the third harmonic generation in a ZnO/Si layered structure to obtain high frequency SAW devices. This configuration eliminates the need of high lithography resolution and allows easy integration of such devices and electronics on the same wafer. A theoretical study was carried out for the determination of the phase velocity and the electromechanical coupling coefficient (K(2)) dispersion curves of the surface acoustic waves. These results are also in agreement with those measured on a SAW filter designed for the third harmonic generation and the operating frequency is up to 2468 MHz.

  2. Motor monitoring method and apparatus using high frequency current components

    DOEpatents

    Casada, D.A.

    1996-05-21

    A motor current analysis method and apparatus for monitoring electrical-motor-driven devices are disclosed. The method and apparatus utilize high frequency portions of the motor current spectra to evaluate the condition of the electric motor and the device driven by the electric motor. The motor current signal produced as a result of an electric motor is monitored and the low frequency components of the signal are removed by a high-pass filter. The signal is then analyzed to determine the condition of the electrical motor and the driven device. 16 figs.

  3. Motor monitoring method and apparatus using high frequency current components

    DOEpatents

    Casada, Donald A.

    1996-01-01

    A motor current analysis method and apparatus for monitoring electrical-motor-driven devices. The method and apparatus utilize high frequency portions of the motor current spectra to evaluate the condition of the electric motor and the device driven by the electric motor. The motor current signal produced as a result of an electric motor is monitored and the low frequency components of the signal are removed by a high-pass filter. The signal is then analyzed to determine the condition of the electrical motor and the driven device.

  4. Casimir force between δ -δ' mirrors transparent at high frequencies

    NASA Astrophysics Data System (ADS)

    Braga, Alessandra N.; Silva, Jeferson Danilo L.; Alves, Danilo T.

    2016-12-01

    We investigate, in the context of a real massless scalar field in 1 +1 dimensions, models of partially reflecting mirrors simulated by Dirac δ -δ' point interactions. In the literature, these models do not exhibit full transparency at high frequencies. In order to provide a more realistic feature for these models, we propose a modified δ -δ' point interaction that enables full transparency in the limit of high frequencies. Taking this modified δ -δ' model into account, we investigate the Casimir force, comparing our results with those found in the literature.

  5. High frequency fatigue testing of Udimet 700 at 1400 F

    NASA Technical Reports Server (NTRS)

    Conn, A. F.; Rudy, S. L.

    1972-01-01

    An investigation pertaining to the development of life prediction methods for materials subjected to high temperature creep/fatigue conditions is presented. High frequency (13.4 kHz) fatigue data were measured at 1400 F on specimens of the nickel-based alloy Udimet 700. Tests were conducted on the virgin material, as well as on specimens which had received prior exposures to high temperature, fatigue, and creep.

  6. High-Frequency Normal Mode Propagation in Aluminum Cylinders

    USGS Publications Warehouse

    Lee, Myung W.; Waite, William F.

    2009-01-01

    Acoustic measurements made using compressional-wave (P-wave) and shear-wave (S-wave) transducers in aluminum cylinders reveal waveform features with high amplitudes and with velocities that depend on the feature's dominant frequency. In a given waveform, high-frequency features generally arrive earlier than low-frequency features, typical for normal mode propagation. To analyze these waveforms, the elastic equation is solved in a cylindrical coordinate system for the high-frequency case in which the acoustic wavelength is small compared to the cylinder geometry, and the surrounding medium is air. Dispersive P- and S-wave normal mode propagations are predicted to exist, but owing to complex interference patterns inside a cylinder, the phase and group velocities are not smooth functions of frequency. To assess the normal mode group velocities and relative amplitudes, approximate dispersion relations are derived using Bessel functions. The utility of the normal mode theory and approximations from a theoretical and experimental standpoint are demonstrated by showing how the sequence of P- and S-wave normal mode arrivals can vary between samples of different size, and how fundamental normal modes can be mistaken for the faster, but significantly smaller amplitude, P- and S-body waves from which P- and S-wave speeds are calculated.

  7. Neuronal morphology generates high-frequency firing resonance.

    PubMed

    Ostojic, Srdjan; Szapiro, Germán; Schwartz, Eric; Barbour, Boris; Brunel, Nicolas; Hakim, Vincent

    2015-05-06

    The attenuation of neuronal voltage responses to high-frequency current inputs by the membrane capacitance is believed to limit single-cell bandwidth. However, neuronal populations subject to stochastic fluctuations can follow inputs beyond this limit. We investigated this apparent paradox theoretically and experimentally using Purkinje cells in the cerebellum, a motor structure that benefits from rapid information transfer. We analyzed the modulation of firing in response to the somatic injection of sinusoidal currents. Computational modeling suggested that, instead of decreasing with frequency, modulation amplitude can increase up to high frequencies because of cellular morphology. Electrophysiological measurements in adult rat slices confirmed this prediction and displayed a marked resonance at 200 Hz. We elucidated the underlying mechanism, showing that the two-compartment morphology of the Purkinje cell, interacting with a simple spiking mechanism and dendritic fluctuations, is sufficient to create high-frequency signal amplification. This mechanism, which we term morphology-induced resonance, is selective for somatic inputs, which in the Purkinje cell are exclusively inhibitory. The resonance sensitizes Purkinje cells in the frequency range of population oscillations observed in vivo.

  8. Asynchronous BCI control using high-frequency SSVEP.

    PubMed

    Diez, Pablo F; Mut, Vicente A; Avila Perona, Enrique M; Laciar Leber, Eric

    2011-07-14

    Steady-State Visual Evoked Potential (SSVEP) is a visual cortical response evoked by repetitive stimuli with a light source flickering at frequencies above 4 Hz and could be classified into three ranges: low (up to 12 Hz), medium (12-30) and high frequency (> 30 Hz). SSVEP-based Brain-Computer Interfaces (BCI) are principally focused on the low and medium range of frequencies whereas there are only a few projects in the high-frequency range. However, they only evaluate the performance of different methods to extract SSVEP. This research proposed a high-frequency SSVEP-based asynchronous BCI in order to control the navigation of a mobile object on the screen through a scenario and to reach its final destination. This could help impaired people to navigate a robotic wheelchair. There were three different scenarios with different difficulty levels (easy, medium and difficult). The signal processing method is based on Fourier transform and three EEG measurement channels. The research obtained accuracies ranging in classification from 65% to 100% with Information Transfer Rate varying from 9.4 to 45 bits/min. Our proposed method allows all subjects participating in the study to control the mobile object and to reach a final target without prior training.

  9. Frequencies and amplitudes of high-degree solar oscillations

    NASA Astrophysics Data System (ADS)

    Kaufman, James Morris

    Measurements of some of the properties of high-degree solar p- and f-mode oscillations are presented. Using high-resolution velocity images from Big Bear Solar Observatory, we have measured mode frequencies, which provide information about the composition and internal structure of the Sun, and mode velocity amplitudes (corrected for the effects of atmospheric seeing), which tell us about the oscillation excitation and damping mechanisms. We present a new and more accurate table of the Sun's acoustic vibration frequencies, nunl, as a function of radial order n and spherical harmonic degree l. These frequencies are averages over azimuthal order m and approximate the normal mode frequencies of a nonrotating spherically symmetric Sun near solar minimum. The frequencies presented here are for solar p- and f-modes with 180 less than or = l less than or = 1920, 0 less than or = n less than or = 8, and 1.7 mHz less than or = nunl less than or = 5.3 mHz. The uncertainties, sigmanl, in the frequencies areas are as low as 3.1 micro-Hz. The theoretically expected f-mode frequencies are given by omega squared = gkh approx. = gl/R, where g is the gravitational acceleration at the surface, kh is the horizontal component of the wave vector, and R is the radius of the Sun. We find that the observed frequencies are significantly less than expected for l greater than 1000, for which we have no explanation. Observations of high-degree oscillations, which have very small spatial features, suffer from the effects of atmospheric image blurring and image motion (or 'seeing'), thereby reducing the amplitudes of their spatial-frequency components. In an attempt to correct the velocity amplitudes for these effects, we simultaneously measured the atmospheric modulation transfer function (MTF) by looking at the effects of seeing on the solar limb. We are able to correct the velocity amplitudes using the MTF out to l approx. = 1200. We find that the frequency of the peak velocity power (as a

  10. Eating Frequency Is Positively Associated with Overweight and Central Obesity in U.S. Adults.

    PubMed

    Murakami, Kentaro; Livingstone, M Barbara E

    2015-12-01

    Evidence of the association between eating frequency (EF) and adiposity is inconsistent. With the use of data from the NHANES 2003-2012, this cross-sectional study examined the associations between EF, meal frequency (MF), and snack frequency (SF) and overweight/obesity and central obesity. Dietary intake was assessed with the use of two 24-h dietary recalls in 18,696 US adults ≥20 y of age. All eating occasions providing ≥50 kcal of energy were divided into meals or snacks on the basis of contribution to energy intake (≥15% or <15%), self-report, and time (0600-1000, 1200-1500, 1800-2100, or other). Multivariable logistic regression was used to compute ORs and 95% CIs. When analyzed without adjustment for the ratio of energy intake to estimated energy requirement (EI:EER), all measures of EF, MF, and SF showed inverse or null associations. After adjustment for EI:EER, however, EF was positively associated with overweight/obesity (body mass index ≥25 kg/m2) and central obesity (waist circumference ≥102 cm in men and ≥88 cm in women). Compared with the lowest category (≤3 times/d), the OR (95% CI) for overweight/obesity in the highest category (≥5 times/d) was 1.54 (1.23, 1.93) in men (P-trend = 0.003) and 1.45 (1.17, 1.81) in women (P-trend = 0.001). The corresponding value for central obesity was 1.42 (1.15, 1.75) in men (P-trend = 0.002) and 1.29 (1.05, 1.59) in women (P-trend = 0.03). The self-report-based MF and time-based MF were positively associated with overweight/obesity, central obesity, or both, although MF based on energy contribution showed no associations. There were positive associations for all SF measures in men and for the energy-contribution-based SF in women. This cross-sectional study suggests that higher EF, MF, and SF are associated with an increased likelihood of overweight/obesity and central obesity in US adults. Prospective studies are needed to confirm the associations observed in this study. © 2015 American Society for

  11. Note: High precision measurements using high frequency gigahertz signals

    NASA Astrophysics Data System (ADS)

    Jin, Aohan; Fu, Siyuan; Sakurai, Atsunori; Liu, Liang; Edman, Fredrik; Pullerits, Tõnu; Öwall, Viktor; Karki, Khadga Jung

    2014-12-01

    Generalized lock-in amplifiers use digital cavities with Q-factors as high as 5 × 108 to measure signals with very high precision. In this Note, we show that generalized lock-in amplifiers can be used to analyze microwave (giga-hertz) signals with a precision of few tens of hertz. We propose that the physical changes in the medium of propagation can be measured precisely by the ultra-high precision measurement of the signal. We provide evidence to our proposition by verifying the Newton's law of cooling by measuring the effect of change in temperature on the phase and amplitude of the signals propagating through two calibrated cables. The technique could be used to precisely measure different physical properties of the propagation medium, for example, the change in length, resistance, etc. Real time implementation of the technique can open up new methodologies of in situ virtual metrology in material design.

  12. Note: High precision measurements using high frequency gigahertz signals.

    PubMed

    Jin, Aohan; Fu, Siyuan; Sakurai, Atsunori; Liu, Liang; Edman, Fredrik; Pullerits, Tõnu; Öwall, Viktor; Karki, Khadga Jung

    2014-12-01

    Generalized lock-in amplifiers use digital cavities with Q-factors as high as 5 × 10(8) to measure signals with very high precision. In this Note, we show that generalized lock-in amplifiers can be used to analyze microwave (giga-hertz) signals with a precision of few tens of hertz. We propose that the physical changes in the medium of propagation can be measured precisely by the ultra-high precision measurement of the signal. We provide evidence to our proposition by verifying the Newton's law of cooling by measuring the effect of change in temperature on the phase and amplitude of the signals propagating through two calibrated cables. The technique could be used to precisely measure different physical properties of the propagation medium, for example, the change in length, resistance, etc. Real time implementation of the technique can open up new methodologies of in situ virtual metrology in material design.

  13. Estimation of frequency wave spectrum from high frequency radar data using a parametric model

    NASA Astrophysics Data System (ADS)

    Toro, V. G.; Ocampo, F. J.; Flores-Vidal, X.; Durazo, R.; Flament, P. J.

    2011-12-01

    Models that obtain wave information from high frequency radars (HF) use information of the measured second order Doppler spectrum. The estimation is completed through an integral equation as in the case of the Barrick model, or linearly as in the Hasselmann model. For the latter, the linear form uses a parameter (α) obtained using an exclusive set of data (EuroROSE) which suggests a universal expression of such parameter. In this work we developed a methodology and better approach to extract second order information from the Doppler spectra, and a new parameterization for α was obtained by comparing with in situ measured information in the Gulf of Tehuantepec (GT), Mexico. We present frequency spectra and significant wave height obtained for a four-month data set in the GT, during the season of strong (> 10 ms-1) northerly gap winds. We found that signal strength of Doppler spectra showed a clear diurnal cycle. The time average of these spectra allowed us to select the spectra with high SNR value. The second-order information obtained was used in the mathematical model of Hasselmann, and found that α, which is a function of frequency, depends on wind speed (U10). The results suggest a good agreement between the data measured by the ASIS buoy and those obtained by the Hasselmann model. The results showed improvement in the estimation of wave frequency spectrum and pointed at the need to have a theoretical model for α to be used in any data set.

  14. Peak High-Frequency HRV and Peak Alpha Frequency Higher in PTSD

    PubMed Central

    Oken, Barry S.

    2012-01-01

    Posttraumatic stress disorder (PTSD) is difficult to treat and current PTSD treatments are not effective for all people. Despite limited evidence for its efficacy, some clinicians have implemented biofeedback for PTSD treatment. As a first step in constructing an effective biofeedback treatment program, we assessed respiration, electroencephalography (EEG) and heart rate variability (HRV) as potential biofeedback parameters for a future clinical trial. This cross-sectional study included 86 veterans; 59 with and 27 without PTSD. Data were collected on EEG measures, HRV, and respiration rate during an attentive resting state. Measures were analyzed to assess sensitivity to PTSD status and the relationship to PTSD symptoms. Peak alpha frequency was higher in the PTSD group (F(1,84) = 6.14, p = 0.01). Peak high-frequency HRV was lower in the PTSD group (F(2,78) = 26.5, p<0.00005) when adjusting for respiration rate. All other EEG and HRV measures and respiration were not different between groups. Peak high-frequency HRV and peak alpha frequency are sensitive to PTSD status and may be potential biofeedback parameters for future PTSD clinical trials. PMID:23178990

  15. Clustered Desynchronization from High-Frequency Deep Brain Stimulation

    PubMed Central

    Wilson, Dan; Moehlis, Jeff

    2015-01-01

    While high-frequency deep brain stimulation is a well established treatment for Parkinson’s disease, its underlying mechanisms remain elusive. Here, we show that two competing hypotheses, desynchronization and entrainment in a population of model neurons, may not be mutually exclusive. We find that in a noisy group of phase oscillators, high frequency perturbations can separate the population into multiple clusters, each with a nearly identical proportion of the overall population. This phenomenon can be understood by studying maps of the underlying deterministic system and is guaranteed to be observed for small noise strengths. When we apply this framework to populations of Type I and Type II neurons, we observe clustered desynchronization at many pulsing frequencies. PMID:26713619

  16. Self-integrating inductive loop for measuring high frequency pulses

    NASA Astrophysics Data System (ADS)

    Rojas-Moreno, Mónica V.; Robles, Guillermo; Martínez-Tarifa, Juan M.; Sanz-Feito, Javier

    2011-08-01

    High frequency pulses can be measured by means of inductive sensors. The main advantage of these sensors consists of non-contact measurements that isolate and protect measuring equipment. The objective of this paper is to present the implementation of an inductive sensor for measuring rapidly varying currents. It consists of a rectangular loop with a resistor at its terminals. The inductive loop gives the derivative of the current according to Faraday's law and the resistor connected to the loop modifies the sensor's frequency response to obtain an output proportional to the current pulse. The self-integrating inductive sensor was validated with two sensors, a non-inductive resistor and a commercial high frequency current transformer. The results were compared to determine the advantages and drawbacks of the probe as an adequate inductive transducer.

  17. High-frequency microrheology reveals cytoskeleton dynamics in living cells

    NASA Astrophysics Data System (ADS)

    Rigato, Annafrancesca; Miyagi, Atsushi; Scheuring, Simon; Rico, Felix

    2017-08-01

    Living cells are viscoelastic materials, dominated by an elastic response on timescales longer than a millisecond. On shorter timescales, the dynamics of individual cytoskeleton filaments are expected to emerge, but active microrheology measurements on cells accessing this regime are scarce. Here, we develop high-frequency microrheology experiments to probe the viscoelastic response of living cells from 1 Hz to 100 kHz. We report the viscoelasticity of different cell types under cytoskeletal drug treatments. On previously inaccessible short timescales, cells exhibit rich viscoelastic responses that depend on the state of the cytoskeleton. Benign and malignant cancer cells revealed remarkably different scaling laws at high frequencies, providing a unique mechanical fingerprint. Microrheology over a wide dynamic range--up to the frequency characterizing the molecular components--provides a mechanistic understanding of cell mechanics.

  18. A 3-D high accuracy positioning system based on visible light communication with novel positioning algorithm

    NASA Astrophysics Data System (ADS)

    Zheng, Huanhuan; Xu, Zhaowen; Yu, Changyuan; Gurusamy, Mohan

    2017-08-01

    A novel indoor positioning system (IPS) with high positioning precision, based on visible light communication (VLC), is proposed and demonstrated with the dimensions of 100 cm×118.5 cm×128.7 cm. The average positioning distance error is 1.72 cm using the original 2-D positioning algorithm. However, at the corners of the test-bed, the positioning errors are relatively larger than other places. Thus, an error correcting algorithm (ECA) is applied at the corners in order to improve the positioning accuracy. The average positioning errors of four corners decrease from 3.67 cm to 1.55 cm. Then, a 3-D positioning algorithm is developed and the average positioning error of 1.90 cm in space is achieved. Four altitude levels are chosen and on each receiver plane with different heights, four points are picked up to test the positioning error. The average positioning errors in 3-D space are all within 3 cm on these four levels and the performance on each level is similar. A random track is also drawn to show that in 3-D space, the positioning error of random point is within 3 cm.

  19. Determining the frequency, depth and velocity of preferential flow by high frequency soil moisture monitoring

    NASA Astrophysics Data System (ADS)

    Hardie, Marcus; Lisson, Shaun; Doyle, Richard; Cotching, William

    2013-01-01

    Preferential flow in agricultural soils has been demonstrated to result in agrochemical mobilisation to shallow ground water. Land managers and environmental regulators need simple cost effective techniques for identifying soil - land use combinations in which preferential flow occurs. Existing techniques for identifying preferential flow have a range of limitations including; often being destructive, non in situ, small sampling volumes, or are subject to artificial boundary conditions. This study demonstrated that high frequency soil moisture monitoring using a multi-sensory capacitance probe mounted within a vertically rammed access tube, was able to determine the occurrence, depth, and wetting front velocity of preferential flow events following rainfall. Occurrence of preferential flow was not related to either rainfall intensity or rainfall amount, rather preferential flow occurred when antecedent soil moisture content was below 226 mm soil moisture storage (0-70 cm). Results indicate that high temporal frequency soil moisture monitoring may be used to identify soil type - land use combinations in which the presence of preferential flow increases the risk of shallow groundwater contamination by rapid transport of agrochemicals through the soil profile. However use of high frequency based soil moisture monitoring to determine agrochemical mobilisation risk may be limited by, inability to determine the volume of preferential flow, difficulty observing macropore flow at high antecedent soil moisture content, and creation of artificial voids during installation of access tubes in stony soils.

  20. Determining the frequency, depth and velocity of preferential flow by high frequency soil moisture monitoring.

    PubMed

    Hardie, Marcus; Lisson, Shaun; Doyle, Richard; Cotching, William

    2013-01-01

    Preferential flow in agricultural soils has been demonstrated to result in agrochemical mobilisation to shallow ground water. Land managers and environmental regulators need simple cost effective techniques for identifying soil - land use combinations in which preferential flow occurs. Existing techniques for identifying preferential flow have a range of limitations including; often being destructive, non in situ, small sampling volumes, or are subject to artificial boundary conditions. This study demonstrated that high frequency soil moisture monitoring using a multi-sensory capacitance probe mounted within a vertically rammed access tube, was able to determine the occurrence, depth, and wetting front velocity of preferential flow events following rainfall. Occurrence of preferential flow was not related to either rainfall intensity or rainfall amount, rather preferential flow occurred when antecedent soil moisture content was below 226 mm soil moisture storage (0-70 cm). Results indicate that high temporal frequency soil moisture monitoring may be used to identify soil type - land use combinations in which the presence of preferential flow increases the risk of shallow groundwater contamination by rapid transport of agrochemicals through the soil profile. However use of high frequency based soil moisture monitoring to determine agrochemical mobilisation risk may be limited by, inability to determine the volume of preferential flow, difficulty observing macropore flow at high antecedent soil moisture content, and creation of artificial voids during installation of access tubes in stony soils.

  1. Orbital positioning of domestic satellites. [area coverage and radio frequency interference optimization

    NASA Technical Reports Server (NTRS)

    Gubin, S.; Kane, D.

    1973-01-01

    An important factor in establishing domestic or regional communication satellite systems which share a given frequency band is the positioning of the satellites in the arc of the geostationary orbit that is visible to the area to be served. A description is given of the results of orbit spacing studies performed with respect to the eight different space systems proposed to provide U.S. domestic communication services. Some tentative guidelines which may be of general use are proposed. Four sets of computer models were studied, taking into account quasi-homogeneous models, a five-system model, a heterogeneous model with 3-degree spacings, and a heterogeneous model with unequal spacings and with coordination.

  2. High frequency electrical conduction block of the pudendal nerve

    NASA Astrophysics Data System (ADS)

    Bhadra, Narendra; Bhadra, Niloy; Kilgore, Kevin; Gustafson, Kenneth J.

    2006-06-01

    A reversible electrical block of the pudendal nerves may provide a valuable method for restoration of urinary voiding in individuals with bladder-sphincter dyssynergia. This study quantified the stimulus parameters and effectiveness of high frequency (HFAC) sinusoidal waveforms on the pudendal nerves to produce block of the external urethral sphincter (EUS). A proximal electrode on the pudendal nerve after its exit from the sciatic notch was used to apply low frequency stimuli to evoke EUS contractions. HFAC at frequencies from 1 to 30 kHz with amplitudes from 1 to 10 V were applied through a conforming tripolar nerve cuff electrode implanted distally. Sphincter responses were recorded with a catheter mounted micro-transducer. A fast onset and reversible motor block was obtained over this range of frequencies. The HFAC block showed three phases: a high onset response, often a period of repetitive firing and usually a steady state of complete or partial block. A complete EUS block was obtained in all animals. The block thresholds showed a linear relationship with frequency. HFAC pudendal nerve stimulation effectively produced a quickly reversible block of evoked urethral sphincter contractions. The HFAC pudendal block could be a valuable tool in the rehabilitation of bladder-sphincter dyssynergia.

  3. Extremely high-frequency micro-Doppler measurements of humans

    NASA Astrophysics Data System (ADS)

    Hedden, Abigail S.; Silvious, Jerry L.; Dietlein, Charles R.; Green, Jeremy A.; Wikner, David A.

    2014-05-01

    The development of sensors that are capable of penetrating smoke, dust, fog, clouds, and rain is critical for maintaining situational awareness in degraded visual environments and for providing support to the Warfighter. Atmospheric penetration properties, the ability to form high-resolution imagery with modest apertures, and available source power make the extremely high-frequency (EHF) portion of the spectrum promising for the development of radio frequency (RF) sensors capable of penetrating visual obscurants. Comprehensive phenomenology studies including polarization and backscatter properties of relevant targets are lacking at these frequencies. The Army Research Laboratory (ARL) is developing a fully-polarimetric frequency-modulated continuous-wave (FMCW) instrumentation radar to explore polarization and backscatter properties of in-situ rain, scattering from natural and man-made surfaces, and the radar cross section and micro-Doppler signatures of humans at EHF frequencies, specifically, around the 220 GHz atmospheric window. This work presents an overview of the design and construction of the radar system, hardware performance, data acquisition software, and initial results including an analysis of human micro-Doppler signatures.

  4. Osteogenic Effect of High-frequency Acceleration on Alveolar Bone

    PubMed Central

    Alikhani, M.; Khoo, E.; Alyami, B.; Raptis, M.; Salgueiro, J.M.; Oliveira, S.M.; Boskey, A.; Teixeira, C.C.

    2012-01-01

    Mechanical stimulation contributes to the health of alveolar bone, but no therapy using the osteogenic effects of these stimuli to increase alveolar bone formation has been developed. We propose that the application of high-frequency acceleration to teeth in the absence of significant loading is osteogenic. Sprague-Dawley rats were divided among control, sham, and experimental groups. The experimental group underwent localized accelerations at different frequencies for 5 min/day on the occlusal surface of the maxillary right first molar at a very low magnitude of loading (4 µε). Sham rats received a similar load in the absence of acceleration or frequency. The alveolar bone of the maxilla was evaluated by microcomputed tomography (µCT), histology, fluorescence microscopy, scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR imaging), and RT-PCR for osteogenic genes. Results demonstrate that application of high-frequency acceleration significantly increased alveolar bone formation. These effects were not restricted to the area of application, and loading could be replaced by frequency and acceleration. These studies propose a simple mechanical therapy that may play a significant role in alveolar bone formation and maintenance. PMID:22337699

  5. High-frequency Pulse-tube Refrigerator for 4 K

    NASA Astrophysics Data System (ADS)

    Tanaeva, I. A.; Klaasse Bos, C. G.; de Waele, A. T. A. M.

    2006-04-01

    At present pulse-tube refrigerators (PTRs), used for the important temperature region of 4 K, are of the Gifford-McMahon (GM)-type. The main sources of losses in GM-type PTRs are the compressor and the rotary valve. The efficiency of the combination of the compressor and the rotary valve is only about 30%. In addition to that GM-type compressors are heavy and need periodic maintenance. The main goal of this research is to develop a Stirling-type 4-K pulse-tube refrigerator. This implies higher operating frequencies, compared to the usual 1-2 Hz. At higher frequencies a number of properties of a pulse-tube system, such as length-to-diameter ratios of the pulse tubes and the regenerator, volume and configuration of a regenerator material, phase-shift control method, etc., change significantly, and, therefore, require detailed study. The interactions between various parameters of the pulse tube and of the linear compressor are very complicated. Therefore, as a first part of this research, we study the pulse tube at high frequencies, independent of the compressor. We generate high-frequency pressure oscillations, using a GM-type compressor and a special type of rotary valve, which enables us to operate at frequencies up to 20 Hz. Results of this work are described in this contribution.

  6. Disruption of microalgal cells using high-frequency focused ultrasound.

    PubMed

    Wang, Meng; Yuan, Wenqiao; Jiang, Xiaoning; Jing, Yun; Wang, Zhuochen

    2014-02-01

    The objective of this study was to evaluate the effectiveness of high-frequency focused ultrasound (HFFU) in microalgal cell disruption. Two microalgal species including Scenedesmus dimorphus and Nannochloropsis oculata were treated by a 3.2-MHz, 40-W focused ultrasound and a 100-W, low-frequency (20kHz) non-focused ultrasound (LFNFU). The results demonstrated that HFFU was effective in the disruption of microalgal cells, indicated by significantly increased lipid fluorescence density, the decrease of cell sizes, and the increase of chlorophyll a fluorescence density after treatments. Compared with LFNFU, HFFU treatment was more energy efficient. The combination of high and low frequency treatments was found to be even more effective than single frequency treatment at the same processing time, indicating that frequency played a critical role in cell disruption. In both HFFU and LFNFU treatments, the effectiveness of cell disruption was found to be dependent on the cell treated. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Collocations of High Frequency Noun Keywords in Prescribed Science Textbooks

    ERIC Educational Resources Information Center

    Menon, Sujatha; Mukundan, Jayakaran

    2012-01-01

    This paper analyses the discourse of science through the study of collocational patterns of high frequency noun keywords in science textbooks used by upper secondary students in Malaysia. Research has shown that one of the areas of difficulty in science discourse concerns lexis, especially that of collocations. This paper describes a corpus-based…

  8. Practical techniques for enhancing the high-frequency MASW method

    USDA-ARS?s Scientific Manuscript database

    For soil exploration in the vadose zone, a high-frequency multi-channel analysis of surface waves (HF-MASW) method has been developed. In the study, several practical techniques were applied to enhance the overtone image of the HF-MASW method. They included (1) the self-adaptive MASW method using a ...

  9. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications

    PubMed Central

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K. Kirk

    2011-01-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol–gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed. PMID:21720451

  10. Carbon nanotube transistor based high-frequency electronics

    NASA Astrophysics Data System (ADS)

    Schroter, Michael

    At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks.

  11. Measurement of high frequency waves using a wave follower

    NASA Technical Reports Server (NTRS)

    Tang, S.; Shemdin, O. H.

    1983-01-01

    High frequency waves were measured using a laser-optical sensor mounted on a wave follower. Measured down-wind wave slope spectra are shown to be wind speed dependent; the mean square wave-slopes are generally larger than those measured by Cox and Munk (1954) using the sun glitter method.

  12. High-Frequency Oscillations and Seizure Generation in Neocortical Epilepsy

    ERIC Educational Resources Information Center

    Worrell, Greg A.; Parish, Landi; Cranstoun, Stephen D.; Jonas, Rachel; Baltuch, Gordon; Litt, Brian

    2004-01-01

    Neocortical seizures are often poorly localized, explosive and widespread at onset, making them poorly amenable to epilepsy surgery in the absence of associated focal brain lesions. We describe, for the first time in an unselected group of patients with neocortical epilepsy, the finding that high-frequency (60--100 Hz) epileptiform oscillations…

  13. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications.

    PubMed

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K Kirk

    2011-02-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol-gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed.

  14. High-Frequency Axial Fatigue Test Procedures for Spectrum Loading

    DTIC Science & Technology

    2016-07-20

    UNCLASSIFIED UNCLASSIFIED NAVAL AIR WARFARE CENTER AIRCRAFT DIVISION PATUXENT RIVER, MARYLAND TECHNICAL INFORMATION MEMORANDUM...REPORT NO: NAWCADPAX/TIM-2016/49 HIGH-FREQUENCY AXIAL FATIGUE TEST PROCEEDURES FOR SPECTRUM LOADING by David T. Rusk, AIR ...4.3.3.5 Robert E. Taylor, AIR 4.3.4.1 20 July 2016 Approved for public release; distribution unlimited. DEPARTMENT

  15. High temporal frequency measurements of greenhouse gas emissions from soils

    USDA-ARS?s Scientific Manuscript database

    Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the most important anthropogenic greenhouse gases (GHGs). Variation in soil moisture can be very dynamic, and it is one of the dominant factors controlling the net exchange of these three GHGs. Although technologies for high-frequency,...

  16. Surface modification of lignocellulosic fibers using high-frequency ultrasound

    Treesearch

    Jayant B. Gadhe; Ram B. Gupta; Thomas Elder

    2005-01-01

    Enzymatic and chemical oxidation of fiber surfaces has been reported in the literature as a method for producing medium density fiberboards without using synthetic adhesives. This work focuses on modifying the surface properties of wood fibers by the generation of free radicals using high-frequency ultrasound. A sonochemical reactor operating at 610 kHz is used to...

  17. Frequency of Guns in the Households of High School Seniors

    ERIC Educational Resources Information Center

    Coker, Ann L.; Bush, Heather M.; Follingstad, Diane R.; Brancato, Candace J.

    2017-01-01

    Background: In 2013, President Obama lifted the federal ban on gun violence research. The current study provides one of the first reports to estimate household gun ownership as reported by youth. Methods: In this cohort study of 3,006 high school seniors from 24 schools, we examined the frequency of household guns ownership. Results: About 65%…

  18. Phase controlled dc-ac converter with high frequency switching

    NASA Astrophysics Data System (ADS)

    Harada, Koosuke; Sakamoto, Hiroshi; Shoyama, Masahito

    A sinusoidal dc-ac converter is presented in which a pair of switches is placed on each side of the primary and secondary of the isolation transformer. This converter is controlled by the phase difference between the two pairs of switches. The transformer is miniaturized by making the switching frequency high. This converter is especially suitable for small uninterruptible power supply systems.

  19. Frequency of Guns in the Households of High School Seniors

    ERIC Educational Resources Information Center

    Coker, Ann L.; Bush, Heather M.; Follingstad, Diane R.; Brancato, Candace J.

    2017-01-01

    Background: In 2013, President Obama lifted the federal ban on gun violence research. The current study provides one of the first reports to estimate household gun ownership as reported by youth. Methods: In this cohort study of 3,006 high school seniors from 24 schools, we examined the frequency of household guns ownership. Results: About 65%…

  20. High-Frequency Oscillations and Seizure Generation in Neocortical Epilepsy

    ERIC Educational Resources Information Center

    Worrell, Greg A.; Parish, Landi; Cranstoun, Stephen D.; Jonas, Rachel; Baltuch, Gordon; Litt, Brian

    2004-01-01

    Neocortical seizures are often poorly localized, explosive and widespread at onset, making them poorly amenable to epilepsy surgery in the absence of associated focal brain lesions. We describe, for the first time in an unselected group of patients with neocortical epilepsy, the finding that high-frequency (60--100 Hz) epileptiform oscillations…

  1. Studies of high-frequency seismic wave propagation

    NASA Astrophysics Data System (ADS)

    Minster, Jean-Bernard; Berger, Jonathan

    1991-03-01

    This final report results are: (1) a study of the location of regional seismic events using a sparse network, with an application to eastern Kazakhstan; (2) an analysis of high frequency seismic observations collected in eastern Kazakhstan, including in particular calibration chemical explosions; (3) a study of the discrimination of quarry blasts from single explosions, using sonogram analysis of data collected in eastern Kazakhstan; (4) the extension of the discrimination methodology developed in the previous paper to small aperture array data, and application to the automated discrimination between earthquake and quarry blasts at NORESS; (5) the use of a new technique, labelled beam stack imaging, to map shallow crust scatterers near a small aperture array, with applications to NORESS; (6) a study of the polarization characteristics of high-frequency borehole seismograms recorded near Anza, California; and (7) an analysis of attenuation and site effects on high-frequency seismic waves, using high-frequency borehole seismograms recorded in the San Jacinto fault zone, near Anza, California.

  2. Frequency of positive patch test reactions to preservatives: The Australian experience.

    PubMed

    Chow, Elizabeth T; Avolio, Andrea M; Lee, Adriene; Nixon, Rosemary

    2013-02-01

    Preservatives are important causes of allergic contact dermatitis. The frequency of allergy to preservatives in Australia has been unknown to date. Our objectives are to report the frequency of positive preservative patch test reactions in Australia, comparing them to the published international data, as well as exploring the current regulations in place for preservative use in Australia. This was the first retrospective study of patch testing results, aggregated from four patch test clinics in three centres in Melbourne and Sydney. In all, 6845 patients were patch-tested during 1993-2006 and in this period the five most frequent preservative allergens were formaldehyde (4.6%), Euxyl K400 (containing methyldibromo glutaronitrile and phenoxyethanol) (3.3%), quaternium-15 (2.9%), diazolidinyl urea (2.4%), and methylchloroisothiazolinone/methylisothiazolinone (2.3%). These were followed by dimethylol dimethyl DMDM hydantoin (2.1%), chloroacetamide (2.1%) and imidazolidinyl urea (1.9%). The least frequent sensitisers were parabens (1.1%), 2-bromo-2-nitropropane-1, 3-diol (0.9%) and benzyl alcohol (0.4%). Formaldehyde was the most prevalent preservative allergen. Chloroacetamide allergy was more commonly seen in Australia. Parabens, 2-bromo-2-nitropropane-1,3-diol and benzyl alcohol were the least frequent sensitisers. Household products in Australia are not required to list all ingredients preventing sensitised individuals from properly assessing their exposure. © 2012 The Authors Australasian Journal of Dermatology © 2012 The Australasian College of Dermatologists.

  3. Frequency of inducible clindamycin resistance among gram-positive cocci in a tertiary hospital, Tehran, Iran

    PubMed Central

    Saffar, Hiva; Rajabiani, Afsaneh; Abdollahi, Alireza; Habibi, Shirin; Baseri, Zohreh

    2016-01-01

    Background and Objectives: Accurate designation of antimicrobial susceptibility pattern of the infecting microorganisms is an important crucial factor in making appropriate therapeutic decisions. Macrolide, lincosamide and streptogramin B antibiotics are in a family, reserved as an alternative approach in treatment of resistant Gram positive cocci. Amongst them, clindamycin has been considered as the preferred agent due to its excellent pharmacokinetic properties. The inducible resistance to clindamycin in Gram positive staphylococci and streptococci cannot be recognized by routine broth or agar based susceptibility tests and D-zone testing is necessary. This study is conducted to evaluate the frequency of inducible clindamycin resistance in Gram positive cocci. Materials and Methods: Using traditional culture methods, 487 isolates of staphylococcus and β-hemolytic streptococcus were evaluated. If they were resistant to erythromycin and sensitive to clindamycin in primary antibiotic susceptibility testing by Kirby-Bauer method, they were subjected to D-zone testing to detect possible inducible clindamycin resistance. Results: Thirty three out of 172 isolates of Staphylococcus aureus and 50 out of 277 isolates of coagulase-negative staphylococci (CoNS) were subjected for D-zone testing. Among them 13/33 and 28/50 showed inducible clindamycin resistance, respectively. There was no significant difference in inducible clindamycin resistance regarding to methicillin susceptibility pattern. Positive D-test was observed in 17.39 and 13.33% of Group B streptococci and Streptococcus spp., respectively. Conclusion: Considerable number of isolates showed inducible clindamycin resistance in our study which falsely would be reported susceptible if D-zone testing was not performed. Thus, performing D-Zone testing is necessary to avoid misleading results which may cause treatment failure. PMID:28210463

  4. Castration alters protein balance after high-frequency muscle contraction.

    PubMed

    Steiner, Jennifer L; Fukuda, David H; Rossetti, Michael L; Hoffman, Jay R; Gordon, Bradley S

    2017-02-01

    Resistance exercise increases muscle mass by shifting protein balance in favor of protein accretion. Androgens independently alter protein balance, but it is unknown whether androgens alter this measure after resistance exercise. To answer this, male mice were subjected to sham or castration surgery 7-8 wk before undergoing a bout of unilateral, high-frequency, electrically induced muscle contractions in the fasted or refed state. Puromycin was injected 30 min before euthanasia to measure protein synthesis. The tibialis anterior was analyzed 4 h postcontraction. In fasted mice, neither basal nor stimulated rates of protein synthesis were affected by castration despite lower phosphorylation of mechanistic target of rapamycin in complex 1 (mTORC1) substrates [p70S6K1 (Thr389) and 4E-BP1 (Ser65)]. Markers of autophagy (LC3 II/I ratio and p62 protein content) were elevated by castration, and these measures remained elevated above sham values after contractions. Furthermore, in fasted mice, the protein content of Regulated in Development and DNA Damage 1 (REDD1) was correlated with LC3 II/I in noncontracted muscle, whereas phosphorylation of uncoordinated like kinase 1 (ULK1) (Ser757) was correlated with LC3 II/I in the contracted muscle. When mice were refed before contractions, protein synthesis and mTORC1 signaling were not affected by castration in either the noncontracted or contracted muscle. Conversely, markers of autophagy remained elevated in the muscles of refed, castrated mice even after contractions. These data suggest the castration-mediated elevation in baseline autophagy reduces the absolute positive shift in protein balance after muscle contractions in the refed or fasted states.

  5. Lung mucociliary transport during high-frequency ventilation

    SciTech Connect

    McEvoy, R.D.; Davies, N.J.; Hedenstierna, G.; Hartman, M.T.; Spragg, R.G.; Wagner, P.D.

    1982-09-01

    The effects of high-frequency, low-tidal-volume ventilation (HFV) and conventional intermittent positive-pressure ventilation (IPPV) on lung mucociliary transport were compared in 5 anesthetized, intubated mongrel dogs using a radioactive label. An aerosol of (/sup 99m/Tc)sulfur colloid was delivered to the dogs' airways and the subsequent clearance of isotope was followed over 4 h of either HFV or IPPV. After 4 h of IPPV, approximately 8 to 10% of the initial activity had cleared from the lung. By contrast, practically all the isotope remained in the lung after 4 h of HFV. Although the reasons for this were not definitely established in this study, several other observations were made that relate to this question. First, large amounts of mucus were visible in the trachea immediately after each of the 4-h HFV studies, whereas this was so in only one of the IPPV studies. Second, in 5 of 6 studies, a bolus of radioactive label placed on the posterior trachea after 4 h of HFV was noticed to disperse and move rapidly toward distal airways under the influence of HFV. Third, despite these findings of disturbed mucociliary transport during HFV, measurements of tracheal velocity, using a radioactive bolus technique during conventional ventilation, were the same after 4 h of HFV as after 4 h of IPPV (18.4 +/- 2.6 and 15.0 +/- 1.6 mm/min, respectively). We conclude that in the anesthetized dog HFV may alter mucociliary transport. This is unlikely to be the result of major structural damage to the mucosal surface, because tracheal mucous velocity measured after 4 h of HFV was not different from that after IPPV. It may be partly explained, however, by the retrograde flow of mucus that was observed during HFV in 5 of 6 studies.

  6. High-frequency Oscillations in Eyewalls of Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Li, Weibiao; Chen, Shumin

    2017-04-01

    High-frequency oscillations, with periods of about 2 hours, are first identified by applying wavelet analysis to observed minutely wind speeds around the eye and eyewall of tropical cyclones (TCs). Analysis of a model simulation of Typhoon Hagupit (2008) shows that the oscillations also occur in the intensity of TC, vertical motion, convergence activity and air density around the eyewall. Sequences of oscillations in these variables follow a certain order. In a typical cycle, the drop of density in the planetary boundary layer (PBL) is followed by an increase in the inward radial wind; this enhanced frictional convergence causes increase in density, followed by a decrease in the inward radial wind. The increase in convergence in the PBL causes increase of updraft at the top of the PBL, followed by high vertical velocity at high altitude of 8-10 km, then the increase of the maximum wind speed, and vice versa. Key words: tropical cyclone, high-frequency oscillations, eyewall, intensity

  7. Analysis of winding losses in high frequency foil wound inductors

    SciTech Connect

    Kutkut, N.H.; Novotny, D.W.; Divan, D.M.; Yeow, E.

    1995-12-31

    The design of high power and high frequency foil wound inductors is not a straightforward task. At high frequencies, additional losses occur within the foil windings due to the eddy currents induced by skin, proximity, fringing and other ac effects. In addition, the winding structure greatly affects the distribution of losses within the windings. In this paper, the various loss mechanisms of a foil winding are analyzed and quantified. Both analytical and finite element analysis tools are utilized to investigate and understand the different loss mechanisms. The results show a strong correlation between the current and field distributions within the windings where the current is always attracted to the high field regions. By shaping and controlling the field distribution in a given design, the current distribution can be improved which results in an improvement in the winding losses.

  8. High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars

    DOE PAGES

    Giroletti, M.; Massaro, F.; D’Abrusco, R.; ...

    2016-04-01

    Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies. In this paper, we characterize the spectral properties of the blazar population at low radio frequency, compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources. We cross-correlated the 6100 deg2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected bymore » Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by Fermi-LAT. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray blazar candidates. The mean low-frequency (120–180 MHz) blazar spectral index is (αlow) = 0.57 ± 0.02: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at ~GHz frequencies. Low-frequency radio flux density and gamma-ray energy flux display a mildly significant and broadly scattered correlation. Ten unidentified gamma-ray sources have a (probably fortuitous) positional match with low radio frequency sources. Low-frequency radio astronomy provides important information about sources with a flat radio spectrum and high energy. However, the relatively low sensitivity of the present surveys still misses a significant fraction of these objects. Finally, upcoming deeper surveys, such as the GaLactic and Extragalactic All-Sky MWA (GLEAM) survey, will provide further insight into this population.« less

  9. Testing the high turbulence level breakdown of low-frequency gyrokinetics against high-frequency cyclokinetic simulations

    SciTech Connect

    Deng, Zhao; Waltz, R. E.

    2015-05-15

    This paper presents numerical simulations of the nonlinear cyclokinetic equations in the cyclotron harmonic representation [R. E. Waltz and Zhao Deng, Phys. Plasmas 20, 012507 (2013)]. Simulations are done with a local flux-tube geometry and with the parallel motion and variation suppressed using a newly developed rCYCLO code. Cyclokinetic simulations dynamically follow the high-frequency ion gyro-phase motion which is nonlinearly coupled into the low-frequency drift-waves possibly interrupting and suppressing gyro-averaging and increasing the transport over gyrokinetic levels. By comparing the more fundamental cyclokinetic simulations with the corresponding gyrokinetic simulations, the breakdown of gyrokinetics at high turbulence levels is quantitatively tested over a range of relative ion cyclotron frequency 10 < Ω*{sup  }< 100 where Ω*{sup  }= 1/ρ*, and ρ* is the relative ion gyroradius. The gyrokinetic linear mode rates closely match the cyclokinetic low-frequency rates for Ω*{sup  }> 5. Gyrokinetic transport recovers cyclokinetic transport at high relative ion cyclotron frequency (Ω*{sup  }≥ 50) and low turbulence level as required. Cyclokinetic transport is found to be lower than gyrokinetic transport at high turbulence levels and low-Ω* values with stable ion cyclotron (IC) modes. The gyrokinetic approximation is found to break down when the density perturbations exceed 20%. For cyclokinetic simulations with sufficiently unstable IC modes and sufficiently low Ω*{sup  }∼ 10, the high-frequency component of cyclokinetic transport level can exceed the gyrokinetic transport level. However, the low-frequency component of the cyclokinetic transport and turbulence level does not exceed that of gyrokinetics. At higher and more physically relevant Ω*{sup  }≥ 50 values and physically realistic IC driving rates, the low-frequency component of the cyclokinetic transport and turbulence level is still smaller than that of

  10. The high dependency of supine position in obstructive sleep apnea.

    PubMed

    Guven, Selma F; Ciftci, Bulent; Lakadamyali, Huseyin; Ciftci, Tansu U

    2013-02-01

    To define the frequency of supine positional obstructive sleep apnea (OSA) in patients diagnosed with OSA and to describe the demographic associations with positional OSA (PO). A retrospective study was performed in a total of 3813 patients who underwent full-night polysomnography at the Sleep Disorders Center of the Ataturk Chest Diseases, Thoracic Surgery Education and Research Hospital, Ankara, Turkey between June 2007 and June 2010. A total of 3214 patients diagnosed with OSA were included in the study. Positional OSA was defined as a total AHI more than or equal to 5, and supine AHI/non-supine AHI more than or equal to 2. Characteristics of positional OSA and non-positional OSA groups were compared statistically. Patients classified as positional OSA composed 39.9% of all OSA patients. Positional OSA patients were younger with lower body mass index and their OSA was less severe. Positional OSA, which may require different treatment approaches, is not uncommon among OSA patients and should be understood as a different clinical entity.

  11. High-overtone Self-Focusing Acoustic Transducers for High Frequency Ultrasonic Doppler

    PubMed Central

    Zhu, Jie; Lee, Chuangyuan; Kim, Eun Sok; Wu, Dawei; Hu, Changhong; Zhou, Qifa; Shung, K. Kirk.; Wang, Gaofeng; Yu, Hongyu

    2010-01-01

    This work reports the potential use of high-overtone self-focusing acoustic transducers for high frequency ultrasonic Doppler. By using harmonic frequencies of a thick bulk Lead Zirconate Titanate (PZT) transducer with a novel air-reflector Fresnel lens, we obtained strong ultrasound signals at 60 MHz (3rd harmonic) and 100 MHz (5th harmonic). Both experimental and theoretical analysis has demonstrated that the transducers can be applied to Doppler systems with high frequencies up to 100 MHz. PMID:20206371

  12. High frequency columnar silicon microresonators for mass detection

    SciTech Connect

    Kehrbusch, J.; Ilin, E. A.; Hullin, M.; Oesterschulze, E.

    2008-07-14

    A simple but effective technological scheme for the fabrication of high frequency silicon columnar microresonators is presented. With the proposed technique the dimensions of the microresonators are controlled on a scale of at least 1 {mu}m. Characterization of the mechanical properties of silicon columns gave resonant frequencies of the lowest flexural mode of 3-7 MHz with quality factors of up to 2500 in air and {approx}8800 under vacuum condition. Columnar microresonators were operated as mass balance with a sensitivity of 1 Hz/fg. A mass detection limit of 25 fg was deduced from experiments.

  13. Compact high voltage, high peak power, high frequency transformer for converter type modulator applications.

    PubMed

    Reghu, T; Mandloi, V; Shrivastava, Purushottam

    2016-04-01

    The design and development of a compact high voltage, high peak power, high frequency transformer for a converter type modulator of klystron amplifiers is presented. The transformer has been designed to operate at a frequency of 20 kHz and at a flux swing of ±0.6 T. Iron (Fe) based nanocrystalline material has been selected as a core for the construction of the transformer. The transformer employs a specially designed solid Teflon bobbin having 120 kV insulation for winding the high voltage secondary windings. The flux swing of the core has been experimentally found by plotting the hysteresis loop at actual operating conditions. Based on the design, a prototype transformer has been built which is per se a unique combination of high voltage, high frequency, and peak power specifications. The transformer was able to provide 58 kV (pk-pk) at the secondary with a peak power handling capability of 700 kVA. The transformation ratio was 1:17. The performance of the transformer is also presented and discussed.

  14. Compact high voltage, high peak power, high frequency transformer for converter type modulator applications

    NASA Astrophysics Data System (ADS)

    Reghu, T.; Mandloi, V.; Shrivastava, Purushottam

    2016-04-01

    The design and development of a compact high voltage, high peak power, high frequency transformer for a converter type modulator of klystron amplifiers is presented. The transformer has been designed to operate at a frequency of 20 kHz and at a flux swing of ±0.6 T. Iron (Fe) based nanocrystalline material has been selected as a core for the construction of the transformer. The transformer employs a specially designed solid Teflon bobbin having 120 kV insulation for winding the high voltage secondary windings. The flux swing of the core has been experimentally found by plotting the hysteresis loop at actual operating conditions. Based on the design, a prototype transformer has been built which is per se a unique combination of high voltage, high frequency, and peak power specifications. The transformer was able to provide 58 kV (pk-pk) at the secondary with a peak power handling capability of 700 kVA. The transformation ratio was 1:17. The performance of the transformer is also presented and discussed.

  15. Feasibility of using frequency offset on very high frequency air/ground voice channels

    NASA Astrophysics Data System (ADS)

    Badinelli, Martin; Cushman, Arthur; Randazzo, Philip

    1990-03-01

    In some large Federal Aviation Administration (FAA) air traffic control sectors, the controller manually switches between multiple ground transmitters to communicate with aircraft at opposite ends of the sector. This puts an additional burden on the controller. Aeronautical Radio, Inc. (ARINC) uses a frequency offset system which produces five frequencies from one channel assignment. ARINC provides this service to commercial air carriers who use receivers designed to ARINC specifications. These receivers are capable of eliminating the audio heterodyne generated by the offsetting process. The commercial air carriers use this system for airline business. The testing performed at the FAA Technical Center to evaluate this system as a means of controlling the air traffic in large sectors is described. The tests indicate that a frequency offset system cannot be used with general aviation aircraft receivers because many cannot filter out the audio heterodyne. Use of frequency offset may be possible in high altitude sectors where commercial aviation receivers, which meet ARINC specifications, are used if some additional concerns are resolved.

  16. Pressures and Oscillation Frequencies Generated by Bubble-Positive Expiratory Pressure Devices.

    PubMed

    Santos, Mary D; Milross, Maree A; Eisenhuth, John P; Alison, Jennifer A

    2017-04-01

    Positive expiratory pressure (PEP) devices are used to assist with airway clearance. Little is known about the therapist-made or commercially available bubble-PEP devices. The aim of this study was to determine the end-expiratory pressures (cm H2O) and oscillation frequencies (Hz) generated when a range of flows were applied to the therapist-made bubble-PEP devices (Bubble-PEP-3cm and Bubble-PEP-0cm) and commercial bubble-PEP devices (AguaPEP, Hydrapep, and Therabubble). This was a bench-top experimental study using a compressed air source, flow rotameter (flows of 5, 10, 15, 20, and 25 L/min), and pressure transducer. Data were collected using a data acquisition device with PhysioDAQxs software and analyzed with Breathalyser software to determine the pressures and oscillation frequencies generated by 5 bubble-PEP devices. Each flow was constant for a 30-s measurement period, and measurements were repeated in triplicate. The 5 devices were: a therapist-made Bubble-PEP-3cm device (filled with 13 cm of water, tubing resting 3 cm from the base of the container); the therapist-made Bubble-PEP-0cm (filled with 10 cm of water, tubing resting at the base of the container); and the AguaPEP, Hydrapep, and Therabubble devices with water to the 10 cm mark on the containers. Flows of 5-25 L/min produced the following mean ± SD PEP and oscillation frequencies (Hz): the Bubble-PEP-3cm produced PEP of 10.4 ± 0.14 to 10.8 ± 0.24 cm H2O, oscillations between 13 and 17 Hz; the Bubble-PEP-0cm produced PEP of 10.9 ± 0.01 to 12.9 ± 0.08 cm H2O, oscillations between 12 and 14 Hz; the AguaPEP produced PEP from 9.7 ± 0.02 to 11.5 ± 0.02 cm H2O, oscillations between 11 and 17 Hz; the Hydrapep produced PEP of 9.6 ± 0.35 to 10.7 ± 0.39 cm H2O, oscillations between 14 and 17 Hz; and the Therabubble produced PEP from 8.6 ± 0.01 to 12.8 ± 0.03 cm H2O, oscillations between 14 and 17 Hz. Bubble-PEP-3cm maintained the most stable pressure throughout the range of flows tested. All

  17. First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers

    NASA Astrophysics Data System (ADS)

    Chou, Aaron S.; Gustafson, Richard; Hogan, Craig; Kamai, Brittany; Kwon, Ohkyung; Lanza, Robert; McCuller, Lee; Meyer, Stephan S.; Richardson, Jonathan; Stoughton, Chris; Tomlin, Raymond; Waldman, Samuel; Weiss, Rainer; Holometer Collaboration

    2016-09-01

    Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of colocated 39 m long, high power Michelson interferometers with flat broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light-crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2 ×1 08 independent spectral measurements with 381 Hz frequency resolution to obtain 2.1 ×10-20m /√{Hz } sensitivity to stationary signals. For signal bandwidths Δ f >11 kHz , the sensitivity to strain h or shear power spectral density of classical or exotic origin surpasses a milestone PSDδ h

  18. High frequency resolution terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Sangala, Bagvanth Reddy

    2013-12-01

    A new method for the high frequency resolution terahertz time-domain spectroscopy is developed based on the characteristic matrix method. This method is useful for studying planar samples or stack of planar samples. The terahertz radiation was generated by optical rectification in a ZnTe crystal and detected by another ZnTe crystal via electro-optic sampling method. In this new characteristic matrix based method, the spectra of the sample and reference waveforms will be modeled by using characteristic matrices. We applied this new method to measure the optical constants of air. The terahertz transmission through the layered systems air-Teflon-air-Quartz-air and Nitrogen gas-Teflon-Nitrogen gas-Quartz-Nitrogen gas was modeled by the characteristic matrix method. A transmission coefficient is derived from these models which was optimized to fit the experimental transmission coefficient to extract the optical constants of air. The optimization of an error function involving the experimental complex transmission coefficient and the theoretical transmission coefficient was performed using patternsearch algorithm of MATLAB. Since this method takes account of the echo waveforms due to reflections in the layered samples, this method allows analysis of longer time-domain waveforms giving rise to very high frequency resolution in the frequency-domain. We have presented the high frequency resolution terahertz time-domain spectroscopy of air and compared the results with the literature values. We have also fitted the complex susceptibility of air to the Lorentzian and Gaussian functions to extract the linewidths.

  19. Motion analysis using 3D high-resolution frequency analysis.

    PubMed

    Ueda, Takaaki; Fujii, Kenta; Hirobayashi, Shigeki; Yoshizawa, Toshio; Misawa, Tadanobu

    2013-08-01

    The spatiotemporal spectra of a video that contains a moving object form a plane in the 3D frequency domain. This plane, which is described as the theoretical motion plane, reflects the velocity of the moving objects, which is calculated from the slope. However, if the resolution of the frequency analysis method is not high enough to obtain actual spectra from the object signal, the spatiotemporal spectra disperse away from the theoretical motion plane. In this paper, we propose a high-resolution frequency analysis method, described as 3D nonharmonic analysis (NHA), which is only weakly influenced by the analysis window. In addition, we estimate the motion vectors of objects in a video using the plane-clustering method, in conjunction with the least-squares method, for 3D NHA spatiotemporal spectra. We experimentally verify the accuracy of the 3D NHA and its usefulness for a sequence containing complex motions, such as cross-over motion, through comparison with 3D fast Fourier transform. The experimental results show that increasing the frequency resolution contributes to high-accuracy estimation of a motion plane.

  20. High-frequency audiometry: test reliability and procedural considerations.

    PubMed

    Stelmachowicz, P G; Beauchaine, K A; Kalberer, A; Kelly, W J; Jesteadt, W

    1989-02-01

    This study compared the reliability of a recently developed high-frequency audiometer (HFA) [Stevens et al., J. Acoust. Soc. Am. 81, 470-484 (1987)] with a less complicated system that uses supraaural earphones (Koss system). The new approach permits calibration on an individual basis, making it possible to express thresholds at high frequencies in dB SPL. Data obtained from 50 normal-hearing subjects, ranging in age from 10-60 years, were used to evaluate the effects on reliability of threshold variance, earpiece/earphone fitting variance, and the variance associated with the HFA calibration process. Without earpiece/earphone replacement, the reliability of thresholds for the two systems is similar. With replacement, the HFA showed poorer reliability than the Koss system above 11 kHz, largely due to errors in estimating the calibration function. HFA reliability is greater for subjects with valid calibration functions over the entire frequency range. When average correction factors are applied to the Koss data in an effort to convert threshold estimates to dB SPL, individual transfer functions are not represented accurately. Thus the benefit of being able to express thresholds at high frequencies in dB SPL must be weighed against the additional source of variability introduced by the HFA calibration process.

  1. Natural similarity measures between position frequency matrices with an application to clustering.

    PubMed

    Pape, Utz J; Rahmann, Sven; Vingron, Martin

    2008-02-01

    Transcription factors (TFs) play a key role in gene regulation by binding to target sequences. In silico prediction of potential binding of a TF to a binding site is a well-studied problem in computational biology. The binding sites for one TF are represented by a position frequency matrix (PFM). The discovery of new PFMs requires the comparison to known PFMs to avoid redundancies. In general, two PFMs are similar if they occur at overlapping positions under a null model. Still, most existing methods compute similarity according to probabilistic distances of the PFMs. Here we propose a natural similarity measure based on the asymptotic covariance between the number of PFM hits incorporating both strands. Furthermore, we introduce a second measure based on the same idea to cluster a set of the Jaspar PFMs. We show that the asymptotic covariance can be efficiently computed by a two dimensional convolution of the score distributions. The asymptotic covariance approach shows strong correlation with simulated data. It outperforms three alternative methods. The Jaspar clustering yields distinct groups of TFs of the same class. Furthermore, a representative PFM is given for each class. In contrast to most other clustering methods, PFMs with low similarity automatically remain singletons. A website to compute the similarity and to perform clustering, the source code and Supplementary Material are available at http://mosta.molgen.mpg.de.

  2. Regenerator Operation at Very High Frequencies for Microcryocoolers

    NASA Astrophysics Data System (ADS)

    Radebaugh, Ray; O'Gallagher, Agnes

    2006-04-01

    The size of Stirling and Stirling-type pulse tube cryocoolers is dominated by the size of the pressure oscillator. Such cryocoolers typically operate at frequencies up to about 60 Hz for cold-end temperatures above about 60 K. Higher operating frequencies would allow the size and mass of the pressure oscillator to be reduced for a given power input. However, simply increasing the operating frequency leads to large losses in the regenerator. The simple analytical equations derived here show how the right combination of frequency and pressure, along with optimized regenerator geometry, can lead to successful regenerator operation at frequencies up to 1 kHz. Efficient regenerator operation at such high frequencies is possible only with pressures of about 5 to 8 MPa and with very small hydraulic diameters and lengths. Other geometrical parameters must also be optimized for such conditions. The analytical equations are used to provide guidance to the right combination of parameters. We give example numerical calculations with REGEN3.2 in the paper for 60 Hz, 400 Hz, and 1000 Hz operation of optimized screen regenerators and show that the coefficient of performance at 400 Hz and 1000 Hz is about 78 % and 68 %, respectively, of that for 60 Hz when an average pressure of 7 MPa is used with the higher frequency, compared with 2.5 MPa for 60 Hz operation. The 1000 Hz coefficient of performance for parallel tubes is about the same as that of the screen geometry at 60 Hz. The compressor and cold-end swept volumes are reduced by a factor of 47 at 1000 Hz, compared with the 60 Hz case for the same input acoustic power, which can enable the development of microcryocoolers for MEMS applications.

  3. A high-performance Hg(+) trapped ion frequency standard

    NASA Technical Reports Server (NTRS)

    Prestage, J. D.; Tjoelker, R. L.; Dick, G. J.; Maleki, L.

    1992-01-01

    A high-performance frequency standard based on (199)Hg(+) ions confined in a hybrid radio frequency (RF)/dc linear ion trap is demonstrated. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. A 160-mHz-wide atomic resonance line for the 40.5-GHz clock transition is used to steer the output of a 5-mHz crystal oscillator to obtain a stability of 2 x 10(exp -15) for 24,000-second averaging times. Measurements with a 37-mHz line width for the Hg(+) clock transition demonstrate that the inherent stability for this frequency standard is better than 1 x 10(exp -15) at 10,000-second averaging times.

  4. High-frequency electric field measurement using a toroidal antenna

    DOEpatents

    Lee, Ki Ha

    2002-01-01

    A simple and compact method and apparatus for detecting high frequency electric fields, particularly in the frequency range of 1 MHz to 100 MHz, uses a compact toroidal antenna. For typical geophysical applications the sensor will be used to detect electric fields for a wide range of spectrum starting from about 1 MHz, in particular in the frequency range between 1 to 100 MHz, to detect small objects in the upper few meters of the ground. Time-varying magnetic fields associated with time-varying electric fields induce an emf (voltage) in a toroidal coil. The electric field at the center of (and perpendicular to the plane of) the toroid is shown to be linearly related to this induced voltage. By measuring the voltage across a toroidal coil one can easily and accurately determine the electric field.

  5. High-frequency measurements of multilayer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Lafferty, R. E.; Maher, J. P.

    1981-06-01

    A resonant coaxial transmission line, short circuited at one end and open circuited at the other, whose fundamental resonant frequency and Q factor are known, is perturbed with a test capacitor connected either in series at the shorted end of the line, or in shunt at the open end. Measuring the Q factor of the system with the delta f technique yields the effective series resistance, capacitance, and the Q factor of the test specimen. This method of measurement has the advantage that there are no adjustable elements to alter circuit conditions in an unprescribed way, the only variable is the frequency which can be measured with an uncertainty of less than 1 ppm, the loss of the line as a function of frequency is quite predictable, and the Q factor of the line can be made sufficiently high to support accurate measurements of low loss capacitors.

  6. Highly flexible distributions to fit multiple frequency financial returns

    NASA Astrophysics Data System (ADS)

    BenSaïda, Ahmed; Slim, Skander

    2016-01-01

    Financial data are usually studied via low flexible distributions, independently of the frequency of the data, due to their simplicity and analytical tractability. In this paper we analyze two highly flexible five-parameter distributions into fitting financial returns, these are the skewed generalized t (SGT) and the generalized hyperbolic (GH). Applications carried on two exchange rates (Euro-Dollar and Dollar-Yen), and two indexes (S&P 500 and Nikkei 225) over four frequencies: weekly, daily, 30-min and 5-min, confirm the superiority of the SGT and GH in approximating the distribution of a given data at a remarkable precision. Moreover, as we move from higher to lower frequency, the distribution's overall shape does indeed change radically, and the estimated parameters refute the tendency to normality, which calls into question the aggregational Gaussianity's stylized fact.

  7. Graphene Quantum Capacitors for High Frequency Tunable Analog Applications.

    PubMed

    Moldovan, Clara F; Vitale, Wolfgang A; Sharma, Pankaj; Tamagnone, Michele; Mosig, Juan R; Ionescu, Adrian M

    2016-08-10

    Graphene quantum capacitors (GQC) are demonstrated to be enablers of radio-frequency (RF) functions through voltage-tuning of their capacitance. We show that GQC complements MEMS and MOSFETs in terms of performance for high frequency analog applications and tunability. We propose a CMOS compatible fabrication process and report the first experimental assessment of their performance at microwaves frequencies (up to 10 GHz), demonstrating experimental GQCs in the pF range with a tuning ratio of 1.34:1 within 1.25 V, and Q-factors up to 12 at 1 GHz. The figures of merit of graphene variable capacitors are studied in detail from 150 to 350 K. Furthermore, we describe a systematic, graphene specific approach to optimize their performance and predict the figures of merit achieved if such a methodology is applied.

  8. Recent Improvements in High-Frequency Eddy Current Conductivity Spectroscopy

    NASA Astrophysics Data System (ADS)

    Abu-Nabah, Bassam A.; Nagy, Peter B.

    2008-02-01

    Due to its frequency-dependent penetration depth, eddy current measurements are capable of mapping near-surface residual stress profiles based on the so-called piezoresistivity effect, i.e., the stress-dependence of electric conductivity. To capture the peak compressive residual stress in moderately shot-peened (Almen 4-8A) nickel-base superalloys, the eddy current inspection frequency has to go as high as 50-80 MHz. Recently, we have reported the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz. Unfortunately, spurious self- and stray-capacitance effects render the complex coil impedance variation with lift-off more nonlinear as the frequency increases, which makes it difficult to achieve accurate apparent eddy current conductivity (AECC) measurements with the standard four-point linear interpolation method beyond 25 MHz. In this paper, we will demonstrate that reducing the coil size reduces its sensitivity to capacitive lift-off variations, which is just the opposite of the better known inductive lift-off effect. Although reducing the coil size also reduces its absolute electric impedance and relative sensitivity to conductivity variations, a smaller coil still yields better overall performance for residual stress assessment. In addition, we will demonstrate the benefits of a semi-quadratic interpolation scheme that, together with the reduced lift-off sensitivity of the smaller probe coil, minimizes and in some cases completely eliminates the sensitivity of AECC measurements to lift-off uncertainties. These modifications allow us to do much more robust measurements up to as high as 80-100 MHz with the required high relative accuracy of +/-0.1%.

  9. Software for Displaying High-Frequency Test Data

    NASA Technical Reports Server (NTRS)

    Elmore, Jason L.

    2003-01-01

    An easy-to-use, intuitive computer program was written to satisfy a need of test operators and data requestors to quickly view and manipulate high-frequency test data recorded at the East and West Test Areas at Marshall Space Flight Center. By enabling rapid analysis, this program makes it possible to reduce times between test runs, thereby potentially reducing the overall cost of test operations. The program can be used to perform quick frequency analysis, using multiple fast- Fourier-transform windowing and amplitude options. The program can generate amplitude-versus-time plots with full zoom capabilities, frequency-component plots at specified time intervals, and waterfall plots (plots of spectral intensity versus frequency at successive small time intervals, showing the changing frequency components over time). There are options for printing of the plots and saving plot data as text files that can be imported into other application programs. The program can perform all of the aforementioned plotting and plot-data-handling functions on a relatively inexpensive computer; other software that performs the same functions requires computers with large amounts of power and memory.

  10. High-speed frequency-domain terahertz coherence tomography.

    PubMed

    Yahng, Ji Sang; Park, Choon-Su; Lee, Hwi Don; Kim, Chang-Seok; Yee, Dae-Su

    2016-01-25

    High-speed frequency-domain terahertz (THz) coherence tomography is demonstrated using frequency sweeping of continuous-wave THz radiation and beam steering. For axial scanning, THz frequency sweeping with a kHz sweep rate and a THz sweep range is executed using THz photomixing with an optical beat source consisting of a wavelength-swept laser and a distributed feedback laser diode. During the frequency sweep, frequency-domain THz interferograms are measured using coherent homodyne detection employing signal averaging for noise reduction and used as axial-scan data via fast Fourier transform. Axial-scan data are acquired while scanning a transverse range of 100 × 100 mm(2) by use of a THz beam scanner with moving neither sample nor THz transmitter/receiver unit. It takes 100 s to acquire axial-scan data for 100 × 100 points with 5 averaged traces at a sweep rate of 1 kHz. THz tomographic images of a glass fiber reinforced polymer sample with artificial internal defects are presented, acquired using the tomography system.

  11. High-performing vapor-cell frequency standards

    NASA Astrophysics Data System (ADS)

    Godone, A.; Levi, F.; Calosso, C. E.; Micalizio, S.

    2015-03-01

    Many nowadays scientific and technological applications need very precise time and frequency reference signals. Very often, only atomic clocks can guarantee the high level of accuracy and stability required by these signals. In the current scenario of atomic frequency standards, vapor-cell clocks are particularly suited to be employed in those activities that demand good frequency stability performances joined to compactness, reliability and low power consumption. Recently, due to better-performing laser sources and to innovative techniques to prepare and detect the atoms, several cell-based prototypes exhibiting unprecedented frequency stability have been developed. We review advances in the field of laser-pumped vapor-cell clocks and we provide an overview of the techniques that allowed to achieve frequency stabilities in the order of 1×10-13 at 1s (short term) and in the range of 10-15 for the medium-long term. These stabilities are two orders of magnitude better than current commercial Rb clocks. We also prospect the possibility of further improving these results.

  12. Toward a High-Frequency Pulsed-Detonation Actuator

    NASA Technical Reports Server (NTRS)

    Cutler, Andrew D.; Drummond, J. Philip

    2006-01-01

    This paper describes the continued development of an actuator, energized by pulsed detonations, that provides a pulsed jet suitable for flow control in high-speed applications. A high-speed valve, capable of delivering a pulsed stream of reactants a mixture of H2 and air at rates of up to 1500 pulses per second, has been constructed. The reactants burn in a resonant tube and the products exit the tube as a pulsed jet. High frequency pressure transducers have been used to monitor the pressure fluctuations in the device at various reactant injection frequencies, including both resonant and off-resonant conditions. Pulsed detonations have been demonstrated in the lambda/4 mode of an 8 inch long tube at approx. 600 Hz. The pulsed jet at the exit of the device has been observed using shadowgraph and an infrared camera.

  13. Toward a High-Frequency Pulsed-Detonation Actuator

    NASA Technical Reports Server (NTRS)

    Cutler, Andrew D.; Drummond, J. Philip

    2006-01-01

    This paper describes the continued development of an actuator, energized by pulsed detonations, that provides a pulsed jet suitable for flow control in high-speed applications. A high-speed valve, capable of delivering a pulsed stream of reactants a mixture of H2 and air at rates of up to 1500 pulses per second, has been constructed. The reactants burn in a resonant tube and the products exit the tube as a pulsed jet. High frequency pressure transducers have been used to monitor the pressure fluctuations in the device at various reactant injection frequencies, including both resonant and off-resonant conditions. Pulsed detonations have been demonstrated in the lambda/4 mode of an 8 inch long tube at approximately 600 Hz. The pulsed jet at the exit of the device has been observed using shadowgraph and an infrared camera.

  14. Classification of high frequency oscillations in epileptic intracerebral EEG.

    PubMed

    Jrad, Nisrine; Kachenoura, Amar; Merlet, Isabelle; Nica, Anca; Benar, Christian G; Wendling, Fabrice

    2015-08-01

    High Frequency Oscillations (HFOs 40-500 Hz), recorded from intracerebral electroencephalography (iEEG) in epileptic patients, are categorized into four distinct sub-bands (Gamma, High-Gamma, Ripples and Fast Ripples). They have recently been used as a reliable biomarker of epileptogenic zones. The objective of this paper is to investigate the possibility of discriminating between the different classes of HFOs which physiological/pathological value is critical for diagnostic but remains to be clarified. The proposed method is based on the definition of a relevant feature vector built from energy ratios (computed using Wavelet Transform-WT) in a-priori-defined frequency bands. It makes use of a multiclass Linear Discriminant Analysis (LDA) and is applied to iEEG signals recorded in patients candidate to epilepsy surgery. Results obtained from bootstrap on training/test datasets indicate high performances in terms of sensitivity and specificity.

  15. High-frequency H-PDLC optical chopper for frequency division multiplexing fluorescence confocal microscope system

    NASA Astrophysics Data System (ADS)

    Jiang, Yanmeng; Zheng, Jihong; Tang, Pingyu; Wang, Tingting; Huang, Aiqin; Zhou, Zengjun; Zhuang, Songlin

    2011-10-01

    The optical chopper array based on Holographic Polymer Dispersed Liquid Crystal (H-PDLC) working at high frequencies, for example 1KHz, 2KHz, and its application in an improved Frequency Division Multiplexed Fluorescence Confocal Microscope (FDMFCM) system are reported in this article. The system is a combination of the confocal microscopy and the frequency division multiplexing technique. Taking advantages of the optical chopper array based on H-PDLC that avoids mechanical movements, the FDMFCM system is able to obtain better Signal-Noise Ratio (SNR), smaller volume, more independent channels and more efficient scanning. What's more, the FDMCFM maintained the high special resolution ability and realized faster temporal resolution than pervious system. Using the proposed device, the FDMFCM system conducts successful parallel detection of rat neural cells. Fluorescence intensity signals from two different points on the specimen, which represent concentration of certain kind of proteins in the sample cells, are achieved. The experimental results show that the proposed H-PDLC optical chopper array has feasibility in FDMFCM system, which owes to its unique characteristics such as fast response, simple fabrication and lower consumption etc. With the development of H-PDLC based devices, there will be prospective in upgrading FDMFCM system's performance in the biomedical area.

  16. Factors controlling high-frequency radiation from extended ruptures

    NASA Astrophysics Data System (ADS)

    Beresnev, Igor A.

    2017-04-01

    Small-scale slip heterogeneity or variations in rupture velocity on the fault plane are often invoked to explain the high-frequency radiation from earthquakes. This view has no theoretical basis, which follows, for example, from the representation integral of elasticity, an exact solution for the radiated wave field. The Fourier transform, applied to the integral, shows that the seismic spectrum is fully controlled by that of the source time function, while the distribution of final slip and rupture acceleration/deceleration only contribute to directivity. This inference is corroborated by the precise numerical computation of the full radiated field from the representation integral. We compare calculated radiation from four finite-fault models: (1) uniform slip function with low slip velocity, (2) slip function spatially modulated by a sinusoidal function, (3) slip function spatially modulated by a sinusoidal function with random roughness added, and (4) uniform slip function with high slip velocity. The addition of "asperities," both regular and irregular, does not cause any systematic increase in the spectral level of high-frequency radiation, except for the creation of maxima due to constructive interference. On the other hand, an increase in the maximum rate of slip on the fault leads to highly amplified high frequencies, in accordance with the prediction on the basis of a simple point-source treatment of the fault. Hence, computations show that the temporal rate of slip, not the spatial heterogeneity on faults, is the predominant factor forming the high-frequency radiation and thus controlling the velocity and acceleration of the resulting ground motions.

  17. Factors controlling high-frequency radiation from extended ruptures

    NASA Astrophysics Data System (ADS)

    Beresnev, Igor A.

    2017-09-01

    Small-scale slip heterogeneity or variations in rupture velocity on the fault plane are often invoked to explain the high-frequency radiation from earthquakes. This view has no theoretical basis, which follows, for example, from the representation integral of elasticity, an exact solution for the radiated wave field. The Fourier transform, applied to the integral, shows that the seismic spectrum is fully controlled by that of the source time function, while the distribution of final slip and rupture acceleration/deceleration only contribute to directivity. This inference is corroborated by the precise numerical computation of the full radiated field from the representation integral. We compare calculated radiation from four finite-fault models: (1) uniform slip function with low slip velocity, (2) slip function spatially modulated by a sinusoidal function, (3) slip function spatially modulated by a sinusoidal function with random roughness added, and (4) uniform slip function with high slip velocity. The addition of "asperities," both regular and irregular, does not cause any systematic increase in the spectral level of high-frequency radiation, except for the creation of maxima due to constructive interference. On the other hand, an increase in the maximum rate of slip on the fault leads to highly amplified high frequencies, in accordance with the prediction on the basis of a simple point-source treatment of the fault. Hence, computations show that the temporal rate of slip, not the spatial heterogeneity on faults, is the predominant factor forming the high-frequency radiation and thus controlling the velocity and acceleration of the resulting ground motions.

  18. High temporal frequency measurements of greenhouse gas emissions from soils

    NASA Astrophysics Data System (ADS)

    Savage, K.; Phillips, R.; Davidson, E.

    2013-11-01

    Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the most important anthropogenic greenhouse gases. Variation in soil moisture can be very dynamic, and it is one of the dominant factors controlling the net exchange of these three greenhouse gases (GHG). Although technologies for high frequency, precise measurements of CO2 have been available for years, methods for measuring soil fluxes of CH4 and N2O at high temporal frequency have been hampered by lack of appropriate technology for in situ real-time measurements. A previously developed automated chamber system for measuring CO2 flux from soils was configured to run in-line with a new quantum cascade laser (QCLAS) instrument that measures N2O and CH4. Here we present data from a forested wetland in Maine and an agricultural field in North Dakota, which provided examples of both net uptake and production for N2O and CH4. The objective was to provide a range of conditions in which to run the new system and to compare results to a traditional manual static chamber method. The high precision and more than ten-times lower minimum detectable flux of the QCLAS system, compared to the manual system, provided confidence in measurements of small N2O uptake in the forested wetland. At the agricultural field, the greatest difference between the automated and manual sampling systems came from the effect of the relatively infrequent manual sampling of the high spatial variation, or "hot spots", in GHG fluxes. "Hot spots" greatly influenced the seasonal estimates, particularly for N2O, over one 74 day alfalfa crop cycle. The high temporal frequency of the automated system clearly characterized the transient response of all three GHG's to precipitation and demonstrated a clear diel pattern related to temperature for GHG's. A combination of high frequency automated, and spatially distributed chambers would be ideal for characterizing "hot spots" and "hot moments" of GHG fluxes.

  19. High temporal frequency measurements of greenhouse gas emissions from soils

    NASA Astrophysics Data System (ADS)

    Savage, K.; Phillips, R.; Davidson, E.

    2014-05-01

    Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the most important anthropogenic greenhouse gases (GHGs). Variation in soil moisture can be very dynamic, and it is one of the dominant factors controlling the net exchange of these three GHGs. Although technologies for high-frequency, precise measurements of CO2 have been available for years, methods for measuring soil fluxes of CH4 and N2O at high temporal frequency have been hampered by lack of appropriate technology for in situ real-time measurements. A previously developed automated chamber system for measuring CO2 flux from soils was configured to run in line with a new quantum cascade laser (QCLAS) instrument that measures N2O and CH4. Here we present data from a forested wetland in Maine and an agricultural field in North Dakota, which provided examples of both net uptake and production for N2O and CH4. The objective was to provide a range of conditions in which to run the new system and to compare results to a traditional manual static-chamber method. The high-precision and more-than-10-times-lower minimum detectable flux of the QCLAS system, compared to the manual system, provided confidence in measurements of small N2O uptake in the forested wetland. At the agricultural field, the greatest difference between the automated and manual sampling systems came from the effect of the relatively infrequent manual sampling of the high spatial variation, or "hot spots", in GHG fluxes. Hot spots greatly influenced the seasonal estimates, particularly for N2O, over one 74-day alfalfa crop cycle. The high temporal frequency of the automated system clearly characterized the transient response of all three GHGs to precipitation and demonstrated a clear diel pattern related to temperature for GHGs. A combination of high-frequency automated and spatially distributed chambers would be ideal for characterizing hot spots and "hot moments" of GHG fluxes.

  20. High-Frequency Excitation of a Plane Wake

    NASA Technical Reports Server (NTRS)

    Cain, Alan B.; Rogers, Michael M.

    2000-01-01

    In the early 1990's, Glezer and his co-workers at Georgia Tech made a startling discovery. They found that forcing at frequencies too high to directly affect the production scales led to a dramatic alteration in the development of a turbulent shear layer. An experimental study of this phenomenon is presented in Wiltse and Glezer. They used piezoelectric actuators located near the jet exit plane to force the shear layers of a square low-speed jet. The actuators were driven at a high frequency in the Kolmogorov inertial subrange, much higher than the frequencies associated with the large-scale motion (where the turbulent energy is produced and located) but much lower than those associated with the Kolmogorov scale (where the turbulent energy is dissipated). Measurements of the shear-layer turbulence showed that direct excitation of small-scale motion by high-frequency forcing led to an increase in the turbulent dissipation of more than an order of magnitude in the initial region of the shear layer! The turbulent dissipation gradually decreased with downstream distance but remained above the corresponding level for the unforced flow at all locations examined. The high-frequency forcing increased the turbulent kinetic energy in the initial region near the actuators, but the kinetic energy decreased quite rapidly with downstream distance, dropping to levels that were a small fraction of the level for the unforced case. Perhaps most importantly from the present standpoint, the high-frequency forcing significantly decreased the energy in the large-scale motion, increasingly so with downstream distance. Wiltse and Glezer interpreted this behavior as an enhanced transfer of energy from the large scales to the small scales. The initial work by Wiltse and Glezer has expanded into other applications. To explore the potential of high-frequency forcing for active acoustic suppression, in 1998 the first author proposed a set of experiments involving an edge tone shear layer and

  1. DC and High-Frequency Characteristics of GaN Schottky Varactors for Frequency Multiplication

    NASA Astrophysics Data System (ADS)

    Jin, Chong; Pavlidis, Dimitris; Considine, Laurence

    The design, fabrication and characterization of GaN based varactor diodes are presented. MOCVD was used for layer growth and the DC characteristic of 4µm diameter diodes showed a turn-on voltage of 0.5V, a breakdown voltage of 21V and a modulation ratio of 1.63. High frequency characterization allowed obtaining the diode equivalent circuit and observed the bias dependence of the series resistance. The diode cutoff frequency was 900GHz. A large-signal model was developed for the diode and the device power performance was evaluated. A power of 7.2dBm with an efficiency of 16.6% was predicted for 47GHz to 94GHz doubling.

  2. High-frequency wave normals in the solar wind

    SciTech Connect

    Herbert, F.; Smith, L.D.; Sonett, C.P.

    1984-05-01

    High-frequency (0.01--0.04 Hz) magnetic fluctuations in 506 ten-minute intervals of contemporaneous Explorer 35 and Apollo 12 measurements made in the solar wind near the morning side of the Earth's bow shock show the presence of a large population of disturbances resembling Alfven waves. Each wavefront normal n is systematically aligned (median deviation = 35/sup 0/) with , the associated ten-minute average of the magnetic field. Because of variability in the direction of from one interval to another, the coupled distribution of n is nearly isotropic in solar ecliptic coordinates, in contrast with the results of other studies of waves at much lower frequency indicating outward propagation from the sun. Presumably the high frequency waves discussed here are stirred into isotropy (in solar ecliptic coordinates) by following the low frequency fluctuations. As these waves maintain their alignement of n with despite the great variation of , a strong physical alignment constraint is inferred.

  3. A high-frequency electrospray driven by gas volume charges

    SciTech Connect

    Lastochkin, Dmitri; Chang, H.-C.

    2005-06-15

    High-frequency (>10 kHz) ac electrospray is shown to eject volatile dielectric liquid drops by an entirely different mechanism from dc sprays. The steady dc Taylor conic tip is absent and continuous spraying of submicron drops is replaced by individual dynamic pinchoff events involving the entire drop. We attribute this spraying mechanism to a normal Maxwell force produced by an undispersed plasma cloud in front of the meniscus that produces a visible glow at the spherical tip. The volume charge within the cloud is formed by electron-induced gas ionization of the evaporated liquid and produces a large normal field that is much higher than the nominal applied field such that drop ejection occurs at a voltage (at high frequencies) that is as much as ten times lower than that for dc sprays. The ejection force is sensitive to the liquid properties (but not its electrolyte composition), the ac frequency and trace amounts of inert gases, which are believed to catalyze the ionization reactions. As electroneutral drops are ejected, due to the large (>100) ratio between individual drop ejection time and the ac frequency, this mechanism can produce large (microns) electroneutral drops at relatively low voltages.

  4. Development and optimization of acoustic bubble structures at high frequencies.

    PubMed

    Lee, Judy; Ashokkumar, Muthupandian; Yasui, Kyuichi; Tuziuti, Toru; Kozuka, Teruyuki; Towata, Atsuya; Iida, Yasuo

    2011-01-01

    At high ultrasound frequencies, active bubble structures are difficult to capture due to the decrease in timescale per acoustic cycle and size of bubbles with increasing frequencies. However the current study demonstrates an association between the spatial distribution of visible bubbles and that of the active bubble structure established in the path of the propagating acoustic wave. By monitoring the occurrence of these visible bubbles, the development of active bubbles can be inferred for high frequencies. A series of still images depicting the formation of visible bubble structures suggest that a strong standing wave field exists at early stages of wave propagation and weakens by the increase in the attenuation of the acoustic wave, caused by the formation of large coalesced bubbles. This attenuation is clearly demonstrated by the occurrence of a force which causes bubbles to be driven toward the liquid surface and limit standing wave fields to near the surface. This force is explained in terms of the acoustic streaming and traveling wave force. It is found that a strong standing wave field is established at 168 kHz. At 448 kHz, large coalesced bubbles can significantly attenuate the acoustic pressure amplitude and weaken the standing wave field. When the frequency is increased to 726 kHz, acoustic streaming becomes significant and is the dominant force behind the disruption of the standing wave structure. The disruption of the standing wave structure can be minimized under certain pulse ON and OFF ratios.

  5. High-frequency BiCMOS transconductance integrators

    NASA Astrophysics Data System (ADS)

    Beards, R. Douglas

    1990-10-01

    The capabilities of a fine-line bipolar complementary metal oxide semiconductor (BiCMOS) process in the design of wideband transconductance integrators for precision monolithic continuous time filtering are explored. The design considerations of such an integrator are examined in detail, with an emphasis on tunability and phase compensation as a means for realizing a precision wideband design. The concept of open-loop transconductance filtering is described and possible circuit topologies are investigated. Detailed small-signal and large-signal analysis of one proposed circuit which has both tunable bandwidth and tunable phase compensation is presented. Application of such an integrator to open-loop transconductance filtering in the 10-50 MHz frequency range is studied. Simulation results show specific performance expectations of the proposed circuit. The tunable compensation circuit was seen to restrict the amplitude of signals which the integrator can pass without severe distortion or even instability occurring. A potential solution to this problem is deemed to be unsuitable for high frequency applications. The general design philosophy of applying low-frequency techniques to realize a high frequency circuit was seen to result in several fundamental problems.

  6. Very High Frequency (Beyond 100 MHz) PZT Kerfless Linear Arrays

    PubMed Central

    Wu, Da-Wei; Zhou, Qifa; Geng, Xuecang; Liu, Chang-Geng; Djuth, Frank; Shung, K. Kirk

    2010-01-01

    This paper presents the design, fabrication, and measurements of very high frequency kerfless linear arrays prepared from PZT film and PZT bulk material. A 12-µm PZT thick film fabricated from PZT-5H powder/solution composite and a piece of 15-µm PZT-5H sheet were used to fabricate 32-element kerfless high-frequency linear arrays with photolithography. The PZT thick film was prepared by spin-coating of PZT sol-gel composite solution. The thin PZT-5H sheet sample was prepared by lapping a PZT-5H ceramic with a precision lapping machine. The measured results of the 2 arrays were compared. The PZT film array had a center frequency of 120 MHz, a bandwidth of 60% with a parylene matching layer, and an insertion loss of 41 dB. The PZT ceramic sheet array was found to have a center frequency of 128 MHz with a poorer bandwidth (40% with a parylene matching layer) but a better sensitivity (28 dB insertion loss). PMID:19942516

  7. Resent developments in high-frequency surface-wave techniques

    NASA Astrophysics Data System (ADS)

    Xia, J.; Pan, Y.; Zeng, C.

    2012-12-01

    High-frequency Rayleigh-wave methods, such as Multi-channel Analysis of Surface Waves (MASW), are getting increasingly attention in the near-surface geophysics and geotechnique community in the last 20 years because of their non-invasive, non-destructive, efficient, and low-cost advantages and their success in environmental and engineering applications. They are viewed by near-surface geophysics community as the one of most promise techniques in the future. However, they face unique problems related to extremely irregular velocity variations in near-surface geology or man-made constructions, for example, highway, foundation, dam, levee, jetty, etc., which are not solvable by techniques or algorithms widely used in earthquake seismology or oil/gas seismic exploration. We present solutions to the problems associated with near-surface materials that possess velocity inverse and high Poisson's ratio. Calculation of dispersion curves by existing algorithms may fail for some special velocity models due to velocity inverse (a high-velocity layer on the top of a low-velocity layer). Two velocity models are most common in near-surface applications. One is a low-velocity half space model and the other a high-velocity topmost layer. The former model results in a complex matrix that no roots can be found in the real number domain, which implies that no phase velocities can be calculated in certain frequency ranges based on current exist algorithms. A solution is to use the real part of the root of the complex number. It is well-known that phase velocities approach about 91% of the shear (S)-wave velocity of the topmost layer when wavelengths are much shorter than the thickness of the topmost layer. The later model, however, results in that phase velocities in a high-frequency range calculated using the current algorithms approach a velocity associated with the S-wave velocity of the second layer NOT the topmost layer. A solution to this problem is to use a two-layer model to

  8. Soft Magnetic Materials in High-Frequency, High-Power Conversion Applications

    SciTech Connect

    Leary, AM; Ohodnicki, PR; McHenry, ME

    2012-07-04

    Advanced soft magnetic materials are needed to match high-power density and switching frequencies made possible by advances in wide band-gap semiconductors. Magnetics capable of operating at higher operating frequencies have the potential to greatly reduce the size of megawatt level power electronics. In this article, we examine the role of soft magnetic materials in high-frequency power applications and we discuss current material's limitations and highlight emerging trends in soft magnetic material design for high-frequency and power applications using the materials paradigm of synthesis -> structure -> property -> performance relationships.

  9. Design of matching layers for high-frequency ultrasonic transducers

    PubMed Central

    Fei, Chunlong; Ma, Jianguo; Chiu, Chi Tat; Williams, Jay A.; Fong, Wayne; Chen, Zeyu; Zhu, BenPeng; Xiong, Rui; Shi, Jing; Hsiai, Tzung K.; Shung, K. Kirk; Zhou, Qifa

    2015-01-01

    Matching the acoustic impedance of high-frequency (≥100 MHz) ultrasound transducers to an aqueous loading medium remains a challenge for fabricating high-frequency transducers. The traditional matching layer design has been problematic to establish high matching performance given requirements on both specific acoustic impedance and precise thickness. Based on both mass-spring scheme and microwave matching network analysis, we interfaced metal-polymer layers for the matching effects. Both methods hold promises for guiding the metal-polymer matching layer design. A 100 MHz LiNbO3 transducer was fabricated to validate the performance of the both matching layer designs. In the pulse-echo experiment, the transducer echo amplitude increased by 84.4% and its −6dB bandwidth increased from 30.2% to 58.3% comparing to the non-matched condition, demonstrating that the matching layer design method is effective for developing high-frequency ultrasonic transducers. PMID:26445518

  10. Nonlinear cavity dumping of a high finesse frequency mixing module

    NASA Astrophysics Data System (ADS)

    Tidemand-Lichtenberg, Peter; Andersen, Martin T.; Johansson, Sandra; Canalias, Carlota; Laurell, Fredrik; Buchhave, Preben; Karamehmedovic, Emir; Pedersen, Christian

    2007-07-01

    We present a novel generic approach for pulsed light generation in the visible spectrum. We demonstrate how the circulating field of a high finesse laser can be efficiently cavity dumped through sum-frequency mixing with externally injected high peak power single pass pulses. Periodically poled KTP is used as the nonlinear medium to minimize the peak power requirement of the injected beam. The experimental setup consists of a high finesse 1342 nm Nd:YVO4 laser cavity and a passively Qswitched Nd:YAG laser. Yellow pulses at 593 nm are generated.

  11. The influence of vibration type, frequency, body position and additional load on the neuromuscular activity during whole body vibration.

    PubMed

    Ritzmann, Ramona; Gollhofer, Albert; Kramer, Andreas

    2013-01-01

    This study aimed to assess the influence of different whole body vibration (WBV) determinants on the electromyographic (EMG) activity during WBV in order to identify those training conditions that cause highest neuromuscular responses and therefore provide optimal training conditions. In a randomized cross-over study, the EMG activity of six leg muscles was analyzed in 18 subjects with respect to the following determinants: (1) vibration type (side-alternating vibration (SV) vs. synchronous vibration (SyV), (2) frequency (5-10-15-20-25-30 Hz), (3) knee flexion angle (10°-30°-60°), (4) stance condition (forefoot vs. normal stance) and (5) load variation (no extra load vs. additional load equal to one-third of the body weight). The results are: (1) neuromuscular activity during SV was enhanced compared to SyV (P < 0.05); (2) a progressive increase in frequency caused a progressive increase in EMG activity (P < 0.05); (3) the EMG activity was highest for the knee extensors when the knee joint was 60° flexed (P < 0.05); (4) for the plantar flexors in the forefoot stance condition (P < 0.05); and (5) additional load caused an increase in neuromuscular activation (P < 0.05). In conclusion, large variations of the EMG activation could be observed across conditions. However, with an appropriate adjustment of specific WBV determinants, high EMG activations and therefore high activation intensities could be achieved in the selected muscles. The combination of high vibration frequencies with additional load on an SV platform led to highest EMG activities. Regarding the body position, a knee flexion of 60° and forefoot stance appear to be beneficial for the knee extensors and the plantar flexors, respectively.

  12. Piezoelectric Shaker Development for High Frequency Calibration of Accelerometers

    SciTech Connect

    Payne, Bev; Harper, Kari K.; Vogl, Gregory W.

    2010-05-28

    Calibration of vibration transducers requires sinusoidal motion over a wide frequency range with low distortion and low cross-axial motion. Piezoelectric shakers are well suited to generate such motion and are suitable for use with laser interferometric methods at frequencies of 3 kHz and above. An advantage of piezoelectric shakers is the higher achievable accelerations and displacement amplitudes as compared to electro-dynamic (ED) shakers. Typical commercial ED calibration shakers produce maximum accelerations from 100 m/s{sup 2} to 500 m/s{sup 2}. Very large ED shakers may produce somewhat higher accelerations but require large amplifiers and expensive cooling systems to dissipate heat. Due to the limitations in maximum accelerations by ED shakers at frequencies above 5 kHz, the amplitudes of the generated sinusoidal displacement are frequently below the resolution of laser interferometers used in primary calibration methods. This limits the usefulness of ED shakers in interferometric based calibrations at higher frequencies.Small piezoelectric shakers provide much higher acceleration and displacement amplitudes for frequencies above 5 kHz, making these shakers very useful for accelerometer calibrations employing laser interferometric measurements, as will be shown in this paper. These piezoelectric shakers have been developed and used at NIST for many years for high frequency calibration of accelerometers. This paper documents the construction and performance of a new version of these shakers developed at NIST for the calibration of accelerometers over the range of 3 kHz to 30 kHz and possibly higher. Examples of typical calibration results are also given.

  13. High-Frequency Resonance in the Gerbil Medial Superior Olive

    PubMed Central

    Mikiel-Hunter, Jason; Kotak, Vibhakar; Rinzel, John

    2016-01-01

    A high-frequency, subthreshold resonance in the guinea pig medial superior olive (MSO) was recently linked to the efficient extraction of spatial cues from the fine structure of acoustic stimuli. We report here that MSO neurons in gerbil also have resonant properties and, based on our whole-cell recordings and computational modeling, that a low-voltage-gated potassium current, IKLT, underlies the resonance. We show that resonance was lost following dynamic clamp replacement of IKLT with a leak conductance and in the model when voltage-gating of IKLT was suppressed. Resonance was characterized using small amplitude sinusoidal stimuli to generate impedance curves as typically done for linear systems analysis. Extending our study into the nonlinear, voltage-dependent regime, we increased stimulus amplitude and found, experimentally and in simulations, that the subthreshold resonant frequency (242Hz for weak stimuli) increased continuously to the resonant frequency for spiking (285Hz). The spike resonance of these phasic-firing (type III excitable) MSO neurons and of the model is of particular interest also because previous studies of resonance typically involved neurons/models (type II excitable, such as the standard Hodgkin-Huxley model) that can fire tonically for steady inputs. To probe more directly how these resonances relate to MSO neurons as slope-detectors, we presented periodic trains of brief, fast-rising excitatory post-synaptic potentials (EPSCs) to the model. While weak subthreshold EPSC trains were essentially low-pass filtered, resonance emerged as EPSC amplitude increased. Interestingly, for spike-evoking EPSC trains, the threshold amplitude at spike resonant frequency (317Hz) was lower than the single ESPC threshold. Our finding of a frequency-dependent threshold for repetitive brief EPSC stimuli and preferred frequency for spiking calls for further consideration of both subthreshold and suprathreshold resonance to fast and precise temporal processing

  14. High-frequency acoustic modes in an ionic liquid.

    PubMed

    Ribeiro, Mauro C C

    2013-09-21

    High-frequency collective dynamics of the ionic liquid 1-hexyl-3-methylimidazolium bromide, [C6C1im]Br, has been investigated by molecular dynamics simulations. Time correlation functions of mass current fluctuations were calculated for several wavevectors and the dispersion curves of excitations, ω(k), for longitudinal and transverse acoustic sound modes were obtained at different temperatures and pressures. Two different thermodynamic states have the same high-frequency sound velocity irrespective of the temperature provided that both have the same density. Partial time correlation functions of mass currents were calculated for the atoms belonging to the polar or the non-polar domains resulting from the heterogeneous structure of [C6C1im]Br. The partial correlation functions indicate that the polar domains are stiffer than the non-polar domains of the simulated ionic liquid.

  15. High-Frequency Power Gain in the Mammalian Cochlea

    NASA Astrophysics Data System (ADS)

    Maoiléidigh, Dáibhid Ó.; Hudspeth, A. J.

    2011-11-01

    Amplification in the mammalian inner ear is thought to result from a nonlinear active process known as the cochlear amplifier. Although there is much evidence that outer hair cells (OHCs) play a central role in the cochlear amplifier, the mechanism of amplification remains uncertain. In non-mammalian ears hair bundles can perform mechanical work and account for the active process in vitro, yet in the mammalian cochlea membrane-based electromotility is required for amplification in vivo. A key issue is how OHCs conduct mechanical power amplification at high frequencies. We present a physical model of a segment of the mammalian cochlea that can amplify the power of external signals. In this representation both electromotility and active hair-bundle motility are required for mechanical power gain at high frequencies. We demonstrate how the endocochlear potential, the OHC resting potential, Ca2+ gradients, and ATP-fueled myosin motors serve as the energy sources underlying mechanical power gain in the cochlear amplifier.

  16. How High Frequency Trading Affects a Market Index

    PubMed Central

    Kenett, Dror Y.; Ben-Jacob, Eshel; Stanley, H. Eugene; gur-Gershgoren, Gitit

    2013-01-01

    The relationship between a market index and its constituent stocks is complicated. While an index is a weighted average of its constituent stocks, when the investigated time scale is one day or longer the index has been found to have a stronger effect on the stocks than vice versa. We explore how this interaction changes in short time scales using high frequency data. Using a correlation-based analysis approach, we find that in short time scales stocks have a stronger influence on the index. These findings have implications for high frequency trading and suggest that the price of an index should be published on shorter time scales, as close as possible to those of the actual transaction time scale. PMID:23817553

  17. Status asthmaticus treated by high-frequency oscillatory ventilation.

    PubMed

    Duval, E L; van Vught, A J

    2000-10-01

    We present a 2.5-year-old girl in severe asthma crisis who clinically deteriorated on conventional mechanical ventilation, but was successfully ventilated with high-frequency oscillatory ventilation (HFOV). Although HFOV is accepted as a technique for managing pediatric respiratory failure, its use in obstructive airway disease is generally thought to be contraindicated because of the risk of dynamic air-trapping. However, we suggest that obstructive airway disease can safely be managed with HFOV, provided certain conditions are met. These include the application of sufficiently high mean airway pressures to open and stent the airways ("an open airway strategy"), lower frequencies to overcome the greater attenuation of the oscillatory waves in the narrowed airways, permissive hypercapnia to enable reducing pressure swings as much as possible, longer expiratory times, and muscle paralysis to avoid spontaneous breathing.

  18. High-frequency oscillation of the airway and chest wall.

    PubMed

    Fink, James B; Mahlmeister, Michael J

    2002-07-01

    High-frequency oscillation (HFO), applied to either the airway or chest wall, has been associated with changes in sputum attributes and clearance. The evolution of evidence, both in vitro and in vivo, supporting the use of HFO is reviewed. Devices that apply HFO to the airway range from the relatively simple mechanical Flutter and Acapella devices to the more complex Percussionaire Intrapercussive Ventilators. and the Hayek Oscillator are designed to provide high-frequency chest wall compression. Operation and use of these devices are described with examples of differentiation of device types by characterization of flows, and airway and esophageal pressures. Although HFO devices span a broad range of costs, they provide a reasonable therapeutic option to support secretion clearance for patients with cystic fibrosis.

  19. Extracting cardiac myofiber orientations from high frequency ultrasound images

    NASA Astrophysics Data System (ADS)

    Qin, Xulei; Cong, Zhibin; Jiang, Rong; Shen, Ming; Wagner, Mary B.; Kirshbom, Paul; Fei, Baowei

    2013-03-01

    Cardiac myofiber plays an important role in stress mechanism during heart beating periods. The orientation of myofibers decides the effects of the stress distribution and the whole heart deformation. It is important to image and quantitatively extract these orientations for understanding the cardiac physiological and pathological mechanism and for diagnosis of chronic diseases. Ultrasound has been wildly used in cardiac diagnosis because of its ability of performing dynamic and noninvasive imaging and because of its low cost. An extraction method is proposed to automatically detect the cardiac myofiber orientations from high frequency ultrasound images. First, heart walls containing myofibers are imaged by B-mode high frequency (<20 MHz) ultrasound imaging. Second, myofiber orientations are extracted from ultrasound images using the proposed method that combines a nonlinear anisotropic diffusion filter, Canny edge detector, Hough transform, and K-means clustering. This method is validated by the results of ultrasound data from phantoms and pig hearts.

  20. Recording and analysis techniques for high-frequency oscillations.

    PubMed

    Worrell, G A; Jerbi, K; Kobayashi, K; Lina, J M; Zelmann, R; Le Van Quyen, M

    2012-09-01

    In recent years, new recording technologies have advanced such that, at high temporal and spatial resolutions, high-frequency oscillations (HFO) can be recorded in human partial epilepsy. However, because of the deluge of multichannel data generated by these experiments, achieving the full potential of parallel neuronal recordings depends on the development of new data mining techniques to extract meaningful information relating to time, frequency and space. Here, we aim to bridge this gap by focusing on up-to-date recording techniques for measurement of HFO and new analysis tools for their quantitative assessment. In particular, we emphasize how these methods can be applied, what property might be inferred from neuronal signals, and potentially productive future directions.

  1. How high frequency trading affects a market index.

    PubMed

    Kenett, Dror Y; Ben-Jacob, Eshel; Stanley, H Eugene; Gur-Gershgoren, Gitit

    2013-01-01

    The relationship between a market index and its constituent stocks is complicated. While an index is a weighted average of its constituent stocks, when the investigated time scale is one day or longer the index has been found to have a stronger effect on the stocks than vice versa. We explore how this interaction changes in short time scales using high frequency data. Using a correlation-based analysis approach, we find that in short time scales stocks have a stronger influence on the index. These findings have implications for high frequency trading and suggest that the price of an index should be published on shorter time scales, as close as possible to those of the actual transaction time scale.

  2. Aftershock Prediction for High-Frequency Financial Markets' Dynamics

    NASA Astrophysics Data System (ADS)

    Baldovin, Fulvio; Camana, Francesco; Caraglio, Michele; Stella, Attilio L.; Zamparo, Marco

    The occurrence of aftershocks following a major financial crash manifests the critical dynamical response of financial markets. Aftershocks put additional stress on markets, with conceivable dramatic consequences. Such a phenomenon has been shown to be common to most financial assets, both at high and low frequency. Its present-day description relies on an empirical characterization proposed by Omori at the end of 1800 for seismic earthquakes. We point out the limited predictive power in this phenomenological approach and present a stochastic model, based on the scaling symmetry of financial assets, which is potentially capable to predict aftershocks occurrence, given the main shock magnitude. Comparisons with S&P high-frequency data confirm this predictive potential.

  3. Recording and analysis techniques for high-frequency oscillations

    PubMed Central

    Worrell, G.A.; Jerbi, K.; Kobayashi, K.; Lina, J.M.; Zelmann, R.; Le Van Quyen, M.

    2013-01-01

    In recent years, new recording technologies have advanced such that, at high temporal and spatial resolutions, high-frequency oscillations (HFO) can be recorded in human partial epilepsy. However, because of the deluge of multichannel data generated by these experiments, achieving the full potential of parallel neuronal recordings depends on the development of new data mining techniques to extract meaningful information relating to time, frequency and space. Here, we aim to bridge this gap by focusing on up-to-date recording techniques for measurement of HFO and new analysis tools for their quantitative assessment. In particular, we emphasize how these methods can be applied, what property might be inferred from neuronal signals, and potentially productive future directions. PMID:22420981

  4. Extracting Cardiac Myofiber Orientations from High Frequency Ultrasound Images.

    PubMed

    Qin, Xulei; Cong, Zhibin; Jiang, Rong; Shen, Ming; Wagner, Mary B; Kishbom, Paul; Fei, Baowei

    2013-03-29

    Cardiac myofiber plays an important role in stress mechanism during heart beating periods. The orientation of myofibers decides the effects of the stress distribution and the whole heart deformation. It is important to image and quantitatively extract these orientations for understanding the cardiac physiological and pathological mechanism and for diagnosis of chronic diseases. Ultrasound has been wildly used in cardiac diagnosis because of its ability of performing dynamic and noninvasive imaging and because of its low cost. An extraction method is proposed to automatically detect the cardiac myofiber orientations from high frequency ultrasound images. First, heart walls containing myofibers are imaged by B-mode high frequency (>20 MHz) ultrasound imaging. Second, myofiber orientations are extracted from ultrasound images using the proposed method that combines a nonlinear anisotropic diffusion filter, Canny edge detector, Hough transform, and K-means clustering. This method is validated by the results of ultrasound data from phantoms and pig hearts.

  5. Robust Optimization Design Algorithm for High-Frequency TWTs

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Chevalier, Christine T.

    2010-01-01

    Traveling-wave tubes (TWTs), such as the Ka-band (26-GHz) model recently developed for the Lunar Reconnaissance Orbiter, are essential as communication amplifiers in spacecraft for virtually all near- and deep-space missions. This innovation is a computational design algorithm that, for the first time, optimizes the efficiency and output power of a TWT while taking into account the effects of dimensional tolerance variations. Because they are primary power consumers and power generation is very expensive in space, much effort has been exerted over the last 30 years to increase the power efficiency of TWTs. However, at frequencies higher than about 60 GHz, efficiencies of TWTs are still quite low. A major reason is that at higher frequencies, dimensional tolerance variations from conventional micromachining techniques become relatively large with respect to the circuit dimensions. When this is the case, conventional design- optimization procedures, which ignore dimensional variations, provide inaccurate designs for which the actual amplifier performance substantially under-performs that of the design. Thus, this new, robust TWT optimization design algorithm was created to take account of and ameliorate the deleterious effects of dimensional variations and to increase efficiency, power, and yield of high-frequency TWTs. This design algorithm can help extend the use of TWTs into the terahertz frequency regime of 300-3000 GHz. Currently, these frequencies are under-utilized because of the lack of efficient amplifiers, thus this regime is known as the "terahertz gap." The development of an efficient terahertz TWT amplifier could enable breakthrough applications in space science molecular spectroscopy, remote sensing, nondestructive testing, high-resolution "through-the-wall" imaging, biomedical imaging, and detection of explosives and toxic biochemical agents.

  6. Microstrip antenna modeling and measurement at high frequencies

    SciTech Connect

    Bevensee, R.M.

    1986-04-30

    This report addresses the task C(i) of the Proposal for Microstrip Antenna Modeling and Measurement at High Frequencies by the writer, July 1985. The task is: Assess the advantages and disadvantages of the three computational approaches outlined in the Proposal, including any difficulties to be resolved and an estimate of the time required to implement each approach. The three approaches are (1) Finite Difference, (2) Sommerfeld-GTD-MOM, and (3) Surface Intergral Equations - MOM. These are discussed in turn.

  7. High-Frequency Propagation in the Ocean Waveguide

    DTIC Science & Technology

    2007-09-30

    High-Frequency Propagation in the Ocean Waveguide Michael B. Porter Heat , Light, and Sound Research, Inc. 3366 N. Torrey Pines Court, Suite 310...La Jolla, CA 92037 phone: (858) 457-0800 email: michael.porter@HLSResearch.com Katherine H. Kim Heat , Light, and Sound Research, Inc. 3366 N...ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Heat , Light

  8. High Frequency Acoustic Reflection and Transmission in Ocean Sediments

    DTIC Science & Technology

    2011-09-01

    scattering in ocean environments with special emphasis on propagation in shallow water waveguides and scattering from ocean sediments. 3 ) Development of...TYPE 3 . DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE High Frequency Acoustic Reflection and Transmission in Ocean Sediments...REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 2 3

  9. Study of switching transients in high frequency converters

    NASA Astrophysics Data System (ADS)

    Zinger, Donald S.; Elbuluk, Malik E.; Lee, Tony

    1993-06-01

    As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented.

  10. Automated composite ellipsoid modelling for high frequency GTD analysis

    NASA Technical Reports Server (NTRS)

    Sze, K. Y.; Rojas, R. G.; Klevenow, F. T.; Scheick, J. T.

    1991-01-01

    The preliminary results of a scheme currently being developed to fit a composite ellipsoid to the fuselage of a helicopter in the vicinity of the antenna location are discussed under the assumption that the antenna is mounted on the fuselage. The parameters of the close-fit composite ellipsoid would then be utilized as inputs into NEWAIR3, a code programmed in FORTRAN 77 for high frequency Geometrical Theory of Diffraction (GTD) Analysis of the radiation of airborne antennas.

  11. Study of switching transients in high frequency converters

    NASA Technical Reports Server (NTRS)

    Zinger, Donald S.; Elbuluk, Malik E.; Lee, Tony

    1993-01-01

    As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented. A current regulated ac/ac PDM converter built using MCT's and IGBT's is

  12. Cholinergic mechanisms of high-frequency stimulation in entopeduncular nucleus

    PubMed Central

    Luo, Feng

    2015-01-01

    Chronic, high-frequency (>100 Hz) electrical stimulation, known as deep brain stimulation (DBS), of the internal segment of the globus pallidus (GPi) is a highly effective therapy for Parkinson's disease (PD) and dystonia. Despite some understanding of how it works acutely in PD models, there remain questions about its mechanisms of action. Several hypotheses have been proposed, such as depolarization blockade, activation of inhibitory synapses, depletion of neurotransmitters, and/or disruption/alteration of network oscillations. In this study we investigated the cellular mechanisms of high-frequency stimulation (HFS) in entopeduncular nucleus (EP; rat equivalent of GPi) neurons using whole cell patch-clamp recordings. We found that HFS applied inside the EP nucleus induced a prolonged afterdepolarization that was dependent on stimulation frequency, pulse duration, and current amplitude. The high frequencies (>100 Hz) and pulse widths (>0.15 ms) used clinically for dystonia DBS could reliably induce these afterdepolarizations, which persisted under blockade of ionotropic glutamate (kynurenic acid, 2 mM), GABAA (picrotoxin, 50 μM), GABAB (CGP 55845, 1 μM), and acetylcholine nicotinic receptors (DHβE, 2 μM). However, this effect was blocked by atropine (2 μM; nonselective muscarinic antagonist) or tetrodotoxin (0.5 μM). Finally, the muscarinic-dependent afterdepolarizations were sensitive to Ca2+-sensitive nonspecific cationic (CAN) channel blockade. Hence, these data suggest that muscarinic receptor activation during HFS can lead to feedforward excitation through the opening of CAN channels. This study for the first time describes a cholinergic mechanism of HFS in EP neurons and provides new insight into the underlying mechanisms of DBS. PMID:26334006

  13. Design of 1 MHz Solid State High Frequency Power Supply

    NASA Astrophysics Data System (ADS)

    Parmar, Darshan; Singh, N. P.; Gajjar, Sandip; Thakar, Aruna; Patel, Amit; Raval, Bhavin; Dhola, Hitesh; Dave, Rasesh; Upadhay, Dishang; Gupta, Vikrant; Goswami, Niranjan; Mehta, Kush; Baruah, Ujjwal

    2017-04-01

    High Frequency Power supply (HFPS) is used for various applications like AM Transmitters, metallurgical applications, Wireless Power Transfer, RF Ion Sources etc. The Ion Source for a Neutral beam Injector at ITER-India uses inductively coupled power source at High Frequency (∼1 MHz). Switching converter based topology used to generate 1 MHz sinusoidal output is expected to have advantages on efficiency and reliability as compared to traditional RF Tetrode tubes based oscillators. In terms of Power Electronics, thermal and power coupling issues are major challenges at such a high frequency. A conceptual design for a 200 kW, 1 MHz power supply and a prototype design for a 600 W source been done. The prototype design is attempted with Class-E amplifier topology where a MOSFET is switched resonantly. The prototype uses two low power modules and a ferrite combiner to add the voltage and power at the output. Subsequently solution with Class-D H-Bridge configuration have been evaluated through simulation where module design is stable as switching device do not participate in resonance, further switching device voltage rating is substantially reduced. The rating of the modules is essentially driven by the maximum power handling capacity of the MOSFETs and ferrites in the combiner circuit. The output passive network including resonance tuned network and impedance matching network caters for soft switching and matches the load impedance to 50ohm respectively. This paper describes the conceptual design of a 200 kW high frequency power supply and experimental results of the prototype 600 W, 1 MHz source.

  14. Correlations and multi-affinity in high frequency financial datasets

    NASA Astrophysics Data System (ADS)

    Baviera, Roberto; Pasquini, Michele; Serva, Maurizio; Vergni, Davide; Vulpiani, Angelo

    2001-11-01

    In this paper we perform a quantitative check of long term correlations and multi-affinity in Deutsche Mark/US Dollar exchange rates using high frequency data. We show that the use of business time, i.e., the ranking of the quotes in the sequences, eliminates most of the seasonality in financial-time series, allowing a precise estimation of some return anomalies.

  15. High frequency scattering by a thin lossless dielectric slab

    NASA Technical Reports Server (NTRS)

    Burnside, W. D.; Burgener, K. W.

    1983-01-01

    A high frequency solution for scattering from a thin dielectric slab is developed, based on a modification of the uniform geometrical theory of diffraction solution for a half-plane, with the intention of developing a model for a windshield of a small private aircraft. Results of the theory are compared with experimental measurements and moment method calculations showing good agreement. Application of the solution is also addressed.

  16. Design and characterization of very high frequency pulse tube prototypes

    NASA Astrophysics Data System (ADS)

    Lopes, Diogo; Duval, Jean-Marc; Charles, Ivan; Butterworth, James; Trollier, Thierry; Tanchon, Julien; Ravex, Alain; Daniel, Christophe

    2012-06-01

    Weight and size are important features of a cryocooler when it comes to space applications. Given their reliability and low level of exported vibrations (due to the absence of moving cold parts), pulse tubes are good candidates for spatial purposes and their miniaturization has been the focus of many studies. We report on the design and performance of a small-scale very high frequency pulse tube prototype, modeled after two previous prototypes which were optimized with a numerical code.

  17. Modeling high-frequency capacitance in SOI MOS capacitors

    NASA Astrophysics Data System (ADS)

    Łukasiak, Lidia; Jasiński, Jakub; Beck, Romuald B.; Ikraiam, Fawzi A.

    2016-12-01

    This paper presents a model of high frequency capacitance of a SOI MOSCAP. The capacitance in strong inversion is described with minority carrier redistribution in the inversion layer taken into account. The efficiency of the computational process is significantly improved. Moreover, it is suitable for the simulation of thin-film SOI structures. It may also be applied to the characterization of non-standard SOI MOSCAPS e.g. with nanocrystalline body.

  18. Nonlinear interactions in planar jet flow with high frequency excitation

    NASA Astrophysics Data System (ADS)

    Kreutzfeldt, Timothy

    An experimental active flow control study was conducted involving excitation of a tabletop planar turbulent jet with a high frequency piezoelectric actuator. The excitation frequencies considered corresponded to the dissipative subrange of turbulent kinetic energy and were orders of magnitude greater than classical shear layer instability modes. Single-wire and dual-wire hot wire probes were used to determine how excitation induces alterations to bulk flow quantities as well as nonlinear interactions. Differences in flow receptivity to high frequency excitation were investigated by varying the development length of the turbulent jet at a Reynolds number of 8,700 and Strouhal number of 21.3. Excitation of developed turbulent flow yielded larger increases in the energy dissipation rate and higher magnitude velocity power spectrum peaks at the forcing frequency than undeveloped turbulent flow. Further tests with excitation of reduced mean velocity flow at a Reynolds number of 6,600 and a Strouhal number of 27.8 demonstrated that high frequency forcing resulted in transfer of energy from large to small scales in the turbulent kinetic energy spectrum. This phenomenon appeared to support past literature that indicated that the mechanics of high frequency forcing are fundamentally different from conventional instability-based forcing. Theoretical arguments are presented to support these experimental observations where it is shown that coupling between the applied forcing and background turbulent fluctuations is enhanced. An eddy viscosity model first proposed under the assumption of instability-based forcing was shown to be an effective approximation for the experimental measurements presented here in which the flow was forced directly at turbulence scales. Dimensional analysis of the coupling between the induced oscillations and the turbulent fluctuations supported experimental findings that receptivity to excitation was increased for forced flow with higher turbulent

  19. Direct frequency comb spectroscopy and high-resolution coherent control

    NASA Astrophysics Data System (ADS)

    Stowe, Matthew C.

    We present the first experiments demonstrating absolute frequency measurements of one- and two-photon transitions using direct frequency comb spectroscopy (DFCS). In particular we phase stabilized the inter-pulse period and optical phases of the pulses emitted from a mode-locked Ti:Sapphire laser, creating a broad-bandwidth optical frequency comb. By referencing the optical comb directly to the cesium microwave frequency standard, we were able to measure absolute transition frequencies over greater than a 50 nm bandwidth, utilizing the phase coherence between wavelengths spanning from 741 nm to 795 nm. As an initial demonstration of DFCS we studied transitions from the 5S to 5P, 5D, and 7S states in Rb. To reduce Doppler broadening the atoms were laser cooled in a magneto-optical trap. We present an overview of several systematic error sources that perturb the natural transition frequencies, magnitudes, and linewidths. These include radiation pressure from the probe beam, AC-Stark shifts, Zeeman shifts, power-broadening, and incoherent optical pumping. After careful study and suppression of these systematic error sources, we measured transition linewidths as narrow as 1.1 MHz FWHM and 10 kHz linecenter uncertainties. Our measurements of the 5S to 7S two-photon transition frequency demonstrated the ability to determine the comb mode order numbers when the initial transition frequency is not known to better than the comb mode frequency spacing. By modifying the spectral phase of the pulses we demonstrated high-resolution coherent control. Our first coherent control experiment utilized a grating based pulse stretcher/compressor to apply a large chirp to the pulses. We measured the two-photon transition rate as a function of linear frequency chirp. The results illustrate the differences between similar classic coherent experiments done with a single femtosecond pulse and ours conducted with multiple pulses. Furthermore, we show that it is possible to reduce the two

  20. Mechanism of high frequency signaling at a depressing ribbon synapse

    PubMed Central

    Grabner, Chad P.; Ratliff, Charles P.; Light, Adam C.; DeVries, Steven H.

    2016-01-01

    SUMMARY Ribbon synapses mediate continuous release in neurons that have graded voltage responses. While mammalian retinas can signal visual flicker at 80-100 Hz, the time constant, τ, for refilling of a depleted vesicle release pool at cone photoreceptor ribbons is 0.7–1.1 s. Due to this prolonged depression, the mechanism for encoding high temporal frequencies is unclear. To determine the mechanism of high frequency signaling, we focused on an Off cone bipolar cell type in the ground squirrel, the cb2, whose transient postsynaptic responses recovered following presynaptic depletion with a τ of ~0.1 s, or 7-10-fold faster than the τ for presynaptic pool refilling. The difference in recovery time course is caused by AMPA receptor saturation, where partial refilling of the presynaptic pool is sufficient for a full postsynaptic response. By limiting the dynamic range of the synapse, receptor saturation counteracts ribbon depression to produce rapid recovery and facilitate high frequency signaling. PMID:27292536