The Sensitivity of Adolescent Hearing Screens Significantly Improves by Adding High Frequencies.

PubMed

Sekhar, Deepa L; Zalewski, Thomas R; Beiler, Jessica S; Czarnecki, Beth; Barr, Ashley L; King, Tonya S; Paul, Ian M

2016-09-01

One in 6 US adolescents has high-frequency hearing loss, often related to hazardous noise. Yet, the American Academy of Pediatrics (AAP) hearing screen (500, 1,000, 2,000, 4,000 Hertz) primarily includes low frequencies (<3,000 Hertz). Study objectives were to determine (1) sensitivity and specificity of the AAP hearing screen for adolescent hearing loss and (2) if adding high frequencies increases sensitivity, while repeat screening of initial referrals reduces false positive results (maintaining acceptable specificity). Eleventh graders (n = 134) participated in hearing screening (2013-2014) including "gold-standard" sound-treated booth testing to calculate sensitivity and specificity. Of the 43 referrals, 27 (63%) had high-frequency hearing loss. AAP screen sensitivity and specificity were 58.1% (95% confidence interval 42.1%-73.0%) and 91.2% (95% confidence interval 83.4-96.1), respectively. Adding high frequencies (6,000, 8,000 Hertz) significantly increased sensitivity to 79.1% (64.0%-90.0%; p = .003). Specificity with repeat screening was 81.3% (71.8%-88.7%; p = .003). Adolescent hearing screen sensitivity improves with high frequencies. Repeat testing maintains acceptable specificity. Copyright © 2016 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

75 FR 74668 - Airworthiness Directives; The Boeing Company Model 777-200, -200LR, -300, and -300ER Series...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-01

... investigative actions include a surface high- frequency eddy current inspection for cracking of the inner.... The related investigative actions include a surface high-frequency eddy current inspection for... total flight hours and 5,335 total flight cycles. Analysis by the manufacturer revealed that the broken...

The Sensitivity of Adolescent School-Based Hearing Screens Is Significantly Improved by Adding High Frequencies

ERIC Educational Resources Information Center

Sekhar, Deepa L.; Zalewski, Thomas R.; Beiler, Jessica S.; Czarnecki, Beth; Barr, Ashley L.; King, Tonya S.; Paul, Ian M.

2016-01-01

High frequency hearing loss (HFHL), often related to hazardous noise, affects one in six U.S. adolescents. Yet, only 20 states include school-based hearing screens for adolescents. Only six states test multiple high frequencies. Study objectives were to (1) compare the sensitivity of state school-based hearing screens for adolescents to gold…

Power components for the Space Station 20-kHz power distribution system

NASA Technical Reports Server (NTRS)

Renz, David D.

1988-01-01

Since 1984, NASA Lewis Research Center was developing high power, high frequency space power components as part of The Space Station Advanced Development program. The purpose of the Advanced Development program was to accelerate existing component programs to ensure their availability for use on the Space Station. These components include a rotary power transfer device, remote power controllers, remote bus isolators, high power semiconductor, a high power semiconductor package, high frequency-high power cable, high frequency-high power connectors, and high frequency-high power transformers. All the components were developed to the prototype level and will be installed in the Lewis Research Center Space Station power system test bed.

Power components for the space station 20-kHz power distribution system

NASA Technical Reports Server (NTRS)

Renz, David D.

1988-01-01

Since 1984, NASA Lewis Research Center was developing high power, high frequency space power components as part of The Space Station Advanced Development program. The purpose of The Advanced Development program was to accelerate existing component programs to ensure their availability for use on the Space Station. These components include a rotary power transfer device, remote power controllers, remote bus isolators, high power semiconductor, a high power semiconductor package, high frequency-high power cable, high frequency-high power connectors, and high frequency-high power transformers. All the components were developed to the prototype level and will be installed in the Lewis Research Center Space Station power system test bed.

Comparison of electroacupuncture frequency-related effects on heart rate variability in healthy volunteers: a randomized clinical trial.

PubMed

Lee, Jong-Ho; Kim, Kyu-Hyeong; Hong, Jin-Woo; Lee, Won-Chul; Koo, Sungtae

2011-06-01

This study aimed to compare the effects of high frequency electroacupuncture (EA) and low-frequency EA on the autonomic nervous system by using a heart rate variability measuring device in normal individuals. Fourteen participants were recruited and each participated in the high-frequency and low-frequency sessions (crossover design). The order of sessions was randomized and the interval between the two sessions was over 2 weeks. Participants received needle insertion with 120-Hz stimulation during the high-frequency session (high-frequency EA group), and with 2-Hz stimulation during the low-frequency session (low-frequency EA group). Acupuncture needles were directly inserted perpendicularly to LI 4 and LI 11 acupoints followed by delivery of electric pulses to these points for 15 minutes. Heart rate variability was measured 5 minutes before and after EA stimulation by a heart rate variability measuring system. We found a significant increase in the standard deviation of the normal-to-normal interval in the high-frequency EA group, with no change in the low-frequency EA group. Both the high-frequency and low-frequency EA groups showed no significant differences in other parameters including high-frequency power, low-frequency power, and the ratio of low-frequency power to high-frequency power. Based on these findings, we concluded that high-frequency EA stimulation is more effective than low-frequency EA stimulation in increasing autonomic nervous activity and there is no difference between the two EA frequencies in enhancing sympathovagal balance. Copyright © 2011 Korean Pharmacopuncture Institute. Published by .. All rights reserved.

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.

High Frequency Acoustic Reflection and Transmission in Ocean Sediments

DTIC Science & Technology

2006-09-30

06-1-0766 http://www.arlut.utexas.edu LONG-TERM GOALS Development of a physical model of high-frequency acoustic interaction with the...shallow water. OBJECTIVES 1) A comparative study of acoustic sediment interaction models including visco-elastic, Biot, BICSQS, and grain...experimental measurements of the bistatic return, for the purpose of defining the best physical model of high-frequency acoustic interaction with the ocean

78 FR 73457 - Airworthiness Directives; the Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-06

... frequency eddy current inspections for cracking of the tension tie at BS 760 or 780, as applicable, and do... ties, including doing an open-hole high frequency eddy current inspection for cracks, as applicable...) and paragraph (i) of this AD, but not as AMOCs for the high frequency eddy current inspections...

High frequency ultrasound: a new frontier for ultrasound.

PubMed

Shung, K; Cannata, Jonathan; Qifa Zhou, Member; Lee, Jungwoo

2009-01-01

High frequency ultrasonic imaging is considered by many to be the next frontier in ultrasonic imaging because higher frequencies yield much improved spatial resolution by sacrificing the depth of penetration. It has many clinical applications including visualizing blood vessel wall, anterior segments of the eye and skin. Another application is small animal imaging. Ultrasound is especially attractive in imaging the heart of a small animal like mouse which has a size in the mm range and a heart beat rate faster than 600 BPM. A majority of current commercial high frequency scanners often termed "ultrasonic backscatter microscope or UBM" acquire images by scanning single element transducers at frequencies between 50 to 80 MHz with a frame rate lower than 40 frames/s, making them less suitable for this application. High frequency linear arrays and linear array based ultrasonic imaging systems at frequencies higher than 30 MHz are being developed. The engineering of such arrays and development of high frequency imaging systems has been proven to be highly challenging. High frequency ultrasound may find other significant biomedical applications. The development of acoustic tweezers for manipulating microparticles is such an example.

THE CRAB PULSAR AT CENTIMETER WAVELENGTHS. II. SINGLE PULSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hankins, T. H.; Eilek, J. A.; Jones, G., E-mail: thankins@aoc.nrao.edu

2016-12-10

We have carried out new, high-frequency, high-time-resolution observations of the Crab pulsar. Combining these with our previous data, we characterize bright single pulses associated with the Main Pulse, both the Low-Frequency and High-Frequency Interpulses, and the two  High-Frequency Components. Our data include observations at frequencies ranging from 1 to 43 GHz with time resolutions down to a fraction of a nanosecond. We find that at least two types of emission physics are operating in this pulsar. Both Main Pulses and Low-Frequency Interpulses, up to ∼10 GHz, are characterized by nanoshot emission—overlapping clumps of narrowband nanoshots, each with its own polarization signature.more » High-Frequency Interpulses, between 5 and 30 GHz, are characterized by spectral band emission—linearly polarized emission containing ∼30 proportionately spaced spectral bands. We cannot say whether the longer-duration High-Frequency Components pulses are due to a scattering process, or if they come from yet another type of emission physics.« less

An inkjet vision measurement technique for high-frequency jetting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Kye-Si, E-mail: kskwon@sch.ac.kr; Jang, Min-Hyuck; Park, Ha Yeong

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 ofmore » 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.« less

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.

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.

A Wide Band Absorbing Material Design Using Band-Pass Frequency Selective Surface

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Xu, Qiang; Liu, Ting; Zheng, Dianliang; Zhou, Li

2018-03-01

Based on the high frequency advantage characteristics of the Fe based absorbing coating, a method for designing the structure of broadband absorbing structure by using frequency selective surface (FSS) is proposed. According to the transmission and reflection characteristic of the different size FSS structure, the frequency variation characteristic was simulated. Secondly, the genetic algorithm was used to optimize the high frequency broadband absorbing materials, including the single and double magnetic layer material. Finally, the absorbing characteristics in iron layer were analyzed as the band pass FSS structure was embedded, the results showed that the band-pass FSS had the influence on widening the absorbing frequency. As the FSS was set as the bottom layer, it was effective to achieve the good absorbing property in low frequency and the high frequency absorbing performance was not weakened, because the band-pass FSS led the low frequency absorption and the high frequency shielding effect. The results of this paper are of guiding significance for designing and manufacturing the broadband absorbing materials.

Design and calibration of a high-frequency oscillatory ventilator.

PubMed

Simon, B A; Mitzner, W

1991-02-01

High-frequency ventilation (HFV) is a modality of mechanical ventilation which presents difficult technical demands to the clinical or laboratory investigator. The essential features of an ideal HFV system are described, including wide frequency range, control of tidal volume and mean airway pressure, minimal dead space, and high effective internal impedance. The design and performance of a high-frequency oscillatory ventilation system is described which approaches these requirements. The ventilator utilizes a linear motor regulated by a closed loop controller and driving a novel frictionless double-diaphragm piston pump. Finally, the ventilator performance is tested using the impedance model of Venegas [1].

Ferroresonant flux coupled battery charger

NASA Technical Reports Server (NTRS)

McLyman, Colonel W. T. (Inventor)

1987-01-01

A battery charger for incorporation into an electric-powered vehicle is disclosed. The charger includes a ferroresonant voltage-regulating circuit for providing an output voltage proportional to the frequency of an input AC voltage. A high frequency converter converts a DC voltage supplied, for example, from a rectifier connected to a standard AC outlet, to a controlled frequency AC voltage which is supplied to the input of the ferroresonant circuit. The ferroresonant circuit includes an output, a saturable core transformer connected across the output, and a first linear inductor and a capacitor connected in series across the saturable core transformer and tuned to resonate at the third harmonic of the AC voltage from the high frequency converter. The ferroresonant circuit further includes a second linear inductor connected between the input of the ferroresonant circuit and the saturable core transformer. The output voltage from the ferroresonant circuit is rectified and applied across a pair of output terminals adapted to be connected to the battery to be charged. A feedback circuit compares the voltage across the output terminals with a reference voltage and controls the frequency of the AC voltage produced by the high frequency converter to maintain the voltage across the output terminals at a predetermined value. The second linear inductor provides a highly reactive load in the event of a fault across the output terminals to render the charger short-circuit proof.

Allele frequency distribution of 1691G >A F5 (which confers Factor V Leiden) across Europe, including Slavic populations.

PubMed

Clark, Jeremy S C; Adler, Grażyna; Salkic, Nermin N; Ciechanowicz, Andrzej

2013-11-01

The allele 1691A F5, conferring Factor V Leiden, is a common risk factor in venous thromboembolism. The frequency distribution for this allele in Western Europe has been well documented; but here data from Central, Eastern and South-Eastern Europe has been included. In order to assess the significance of the collated data, a chi-squared test was applied, and Tukey tests and z-tests with Bonferroni correction were compared. A distribution with a North-Southeast band of high frequency of the 1691A F5 allele was discovered with a pocket including some Southern Slavic populations with low frequency. European countries/regions can be arbitrarily delimited into low (group 1, <2.8 %, mean 1.9 % 1691A F5 allele) or high (group 2, ≥2.8 %, mean 4.0 %) frequency groups, with many significant differences between groups, but only one intra-group difference (the Tukey test is suggested to be superior to the z-tests). In Europe a North-Southeast band of 1691A F5 high frequency has been found, clarified by inclusion of data from Central, Eastern and South-Eastern Europe, which surrounds a pocket of low frequency in the Balkans which could possibly be explained by Slavic migration. There seem to be no indications of variation in environmental selection due to geographical location.

A Reassessment of Frequency and Vocabulary Size in L2 Vocabulary Teaching

ERIC Educational Resources Information Center

Schmitt, Norbert; Schmitt, Diane

2014-01-01

The high-frequency vocabulary of English has traditionally been thought to consist of the 2,000 most frequent word families, and low-frequency vocabulary as that beyond the 10,000 frequency level. This paper argues that these boundaries should be reassessed on pedagogic grounds. Based on a number of perspectives (including frequency and…

Rectenna for high-voltage applications

NASA Technical Reports Server (NTRS)

Epp, Larry W. (Inventor); Khan, Abdur R. (Inventor)

2002-01-01

An energy transfer system is disclosed. The system includes patch elements, shielding layers, and energy rectifying circuits. The patch elements receive and couple radio frequency energy. The shielding layer includes at least one opening that allows radio frequency energy to pass through. The openings are formed and positioned to receive the radio frequency energy and to minimize any re-radiating back toward the source of energy. The energy rectifying circuit includes a circuit for rectifying the radio frequency energy into dc energy. A plurality of energy rectifying circuits is arranged in an array to provide a sum of dc energy generated by the energy rectifying circuit.

Power enhanced frequency conversion system

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

2001-01-01

A frequency conversion system includes at least one source providing a first near-IR wavelength output including a gain medium for providing high power amplification, such as double clad fiber amplifier, a double clad fiber laser or a semiconductor tapered amplifier to enhance the power output level of the near-IR wavelength output. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Ra-man/Brillouin amplifier or oscillator between the high power source and the NFM device.

Electrically protected resonant exchange qubits in triple quantum dots.

PubMed

Taylor, J M; Srinivasa, V; Medford, J

2013-08-02

We present a modulated microwave approach for quantum computing with qubits comprising three spins in a triple quantum dot. This approach includes single- and two-qubit gates that are protected against low-frequency electrical noise, due to an operating point with a narrowband response to high frequency electric fields. Furthermore, existing double quantum dot advances, including robust preparation and measurement via spin-to-charge conversion, are immediately applicable to the new qubit. Finally, the electric dipole terms implicit in the high frequency coupling enable strong coupling with superconducting microwave resonators, leading to more robust two-qubit gates.

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.

Device and method for imaging of non-linear and linear properties of formations surrounding a borehole

DOEpatents

Johnson, Paul A; Tencate, James A; Le Bas, Pierre-Yves; Guyer, Robert; Vu, Cung Khac; Skelt, Christopher

2013-10-08

In some aspects of the disclosure, a method and an apparatus is disclosed for investigating material surrounding the borehole. The method includes generating within a borehole an intermittent low frequency vibration that propagates as a tube wave longitudinally to the borehole and induces a nonlinear response in one or more features in the material that are substantially perpendicular to a longitudinal axis of the borehole; generating within the borehole a sequence of high frequency pulses directed such that they travel longitudinally to the borehole within the surrounding material; and receiving, at one or more receivers positionable in the borehole, a signal that includes components from the low frequency vibration and the sequence of high frequency pulses during intermittent generation of the low frequency vibration, to investigate the material surrounding the borehole.

77 FR 68050 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-15

... repetitive [high frequency eddy current] inspections [for cracks] of certain crossbeams including those... actions have already been done. (g) Repetitive High Frequency Eddy Current Inspections (1) For airplanes... AD, whichever occurs first. FedEx stated that the current repetitive inspection interval is ten times...

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.

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.

Extrinsic and Intrinsic Frequency Dispersion of High-k Materials in Capacitance-Voltage Measurements

PubMed Central

Tao, J.; Zhao, C.Z.; Zhao, C.; Taechakumput, P.; Werner, M.; Taylor, S.; Chalker, P. R.

2012-01-01

In capacitance-voltage (C-V) measurements, frequency dispersion in high-k dielectrics is often observed. The frequency dependence of the dielectric constant (k-value), that is the intrinsic frequency dispersion, could not be assessed before suppressing the effects of extrinsic frequency dispersion, such as the effects of the lossy interfacial layer (between the high-k thin film and silicon substrate) and the parasitic effects. The effect of the lossy interfacial layer on frequency dispersion was investigated and modeled based on a dual frequency technique. The significance of parasitic effects (including series resistance and the back metal contact of the metal-oxide-semiconductor (MOS) capacitor) on frequency dispersion was also studied. The effect of surface roughness on frequency dispersion is also discussed. After taking extrinsic frequency dispersion into account, the relaxation behavior can be modeled using the Curie-von Schweidler (CS) law, the Kohlrausch-Williams-Watts (KWW) relationship and the Havriliak-Negami (HN) relationship. Dielectric relaxation mechanisms are also discussed. PMID:28817021

A model for studying the energetics of sustained high frequency firing

PubMed Central

Morris, Catherine E.

2018-01-01

Regulating membrane potential and synaptic function contributes significantly to the energetic costs of brain signaling, but the relative costs of action potentials (APs) and synaptic transmission during high-frequency firing are unknown. The continuous high-frequency (200-600Hz) electric organ discharge (EOD) of Eigenmannia, a weakly electric fish, underlies its electrosensing and communication. EODs reflect APs fired by the muscle-derived electrocytes of the electric organ (EO). Cholinergic synapses at the excitable posterior membranes of the elongated electrocytes control AP frequency. Based on whole-fish O2 consumption, ATP demand per EOD-linked AP increases exponentially with AP frequency. Continual EOD-AP generation implies first, that ion homeostatic processes reliably counteract any dissipation of posterior membrane ENa and EK and second that high frequency synaptic activation is reliably supported. Both of these processes require energy. To facilitate an exploration of the expected energy demands of each, we modify a previous excitability model and include synaptic currents able to drive APs at frequencies as high as 600 Hz. Synaptic stimuli are modeled as pulsatile cation conductance changes, with or without a small (sustained) background conductance. Over the full species range of EOD frequencies (200–600 Hz) we calculate frequency-dependent “Na+-entry budgets” for an electrocyte AP as a surrogate for required 3Na+/2K+-ATPase activity. We find that the cost per AP of maintaining constant-amplitude APs increases nonlinearly with frequency, whereas the cost per AP for synaptic input current is essentially constant. This predicts that Na+ channel density should correlate positively with EOD frequency, whereas AChR density should be the same across fish. Importantly, calculated costs (inferred from Na+-entry through Nav and ACh channels) for electrocyte APs as frequencies rise are much less than expected from published whole-fish EOD-linked O2 consumption. For APs at increasingly high frequencies, we suggest that EOD-related costs external to electrocytes (including packaging of synaptic transmitter) substantially exceed the direct cost of electrocyte ion homeostasis. PMID:29708986

Evaluation of a multi-Kw, high frequency transformer for space applications

NASA Astrophysics Data System (ADS)

Roth, Mary Ellen

1994-08-01

Various NASA studies have shown that high power (multi-kW and higher) electrical systems for various aerospace applications favor high frequency distribution systems, due to the improved safety and weight factors associated with those systems. Other favorable characteristics include low EMI, minimal wiring and ease of system parameter sensing and control of a single phase system. In aerospace power systems, as in terrestrial AC distribution systems, transformers are needed to provide voltage changes, isolation and the resetting of ground. Under NASA contract NAS3-21948 a multi-kW high frequency transformer was designed, fabricated and tested by Thermal Technology Lab, Inc. of Buffalo, New York. 'The goals of this program included the determination of the relationships between transformer weight, efficiency and operating frequency; low internal temperatures and reduced specific weight; and the validation of these new design concepts through experimentation and the fabrication and testing of transformers and their insulation systems.' The transformer was delivered to NASA-Lewis, where an evaluation program was conducted in Lewis' High Power High Frequency Component Test Facility. The transformer was tested in both atmosphere and under vacuum conditions. This paper will discuss the design of the transformer, the evaluation program and test results, the failures experienced and conclusions.

Evaluation of a Multi-kw, High Frequency Transformer for Space Applications

NASA Technical Reports Server (NTRS)

Roth, Mary Ellen

1994-01-01

Various NASA studies have shown that high power (multi-kW and higher) electrical systems for various aerospace applications favor high frequency distribution systems, due to the improved safety and weight factors associated with those systems. Other favorable characteristics include low EMI, minimal wiring and ease of system parameter sensing and control of a single phase system. In aerospace power systems, as in terrestrial AC distribution systems, transformers are needed to provide voltage changes, isolation and the resetting of ground. Under NASA contract NAS3-21948 a multi-kW high frequency transformer was designed, fabricated and tested by Thermal Technology Lab, Inc. of Buffalo, New York. 'The goals of this program included the determination of the relationships between transformer weight, efficiency and operating frequency; low internal temperatures and reduced specific weight; and the validation of these new design concepts through experimentation and the fabrication and testing of transformers and their insulation systems.' The transformer was delivered to NASA-Lewis, where an evaluation program was conducted in Lewis' High Power High Frequency Component Test Facility. The transformer was tested in both atmosphere and under vacuum conditions. This paper will discuss the design of the transformer, the evaluation program and test results, the failures experienced and conclusions.

Audiometric notch and extended high-frequency hearing threshold shift in relation to total leisure noise exposure: An exploratory analysis.

PubMed

Wei, Wenjia; Heinze, Stefanie; Gerstner, Doris G; Walser, Sandra M; Twardella, Dorothee; Reiter, Christina; Weilnhammer, Veronika; Perez-Alvarez, Carmelo; Steffens, Thomas; Herr, Caroline E W

2017-01-01

Studies investigating leisure noise effect on extended high frequency hearing are insufficient and they have inconsistent results. The aim of this study was to investigate if extended high-frequency hearing threshold shift is related to audiometric notch, and if total leisure noise exposure is associated with extended high-frequency hearing threshold shift. A questionnaire of the Ohrkan cohort study was used to collect information on demographics and leisure time activities. Conventional and extended high-frequency audiometry was performed. We did logistic regression between extended high-frequency hearing threshold shift and audiometric notch as well as between total leisure noise exposure and extended high-frequency hearing threshold shift. Potential confounders (sex, school type, and firecrackers) were included. Data from 278 participants (aged 18-23 years, 53.2% female) were analyzed. Associations between hearing threshold shift at 10, 11.2, 12.5, and 14 kHz with audiometric notch were observed with a higher prevalence of threshold shift at the four frequencies, compared to the notch. However, we found no associations between total leisure noise exposure and hearing threshold shift at any extended high frequency. This exploratory analysis suggests that while extended high-frequency hearing threshold shifts are not related to total leisure noise exposure, they are strongly associated with audiometric notch. This leads us to further explore the hypothesis that extended high-frequency threshold shift might be indicative of the appearance of audiometric notch at a later time point, which can be investigated in the future follow-ups of the Ohrkan cohort.

Design, Fabrication and Characterization of A Bi-Frequency Co-Linear Array

PubMed Central

Wang, Zhuochen; Li, Sibo; Czernuszewicz, Tomasz J; Gallippi, Caterina M.; Liu, Ruibin; Geng, Xuecang

2016-01-01

Ultrasound imaging with high resolution and large penetration depth has been increasingly adopted in medical diagnosis, surgery guidance, and treatment assessment. Conventional ultrasound works at a particular frequency, with a −6 dB fractional bandwidth of ~70 %, limiting the imaging resolution or depth of field. In this paper, a bi-frequency co-linear array with resonant frequencies of 8 MHz and 20 MHz was investigated to meet the requirements of resolution and penetration depth for a broad range of ultrasound imaging applications. Specifically, a 32-element bi-frequency co-linear array was designed and fabricated, followed by element characterization and real-time sectorial scan (S-scan) phantom imaging using a Verasonics system. The bi-frequency co-linear array was tested in four different modes by switching between low and high frequencies on transmit and receive. The four modes included the following: (1) transmit low, receive low, (2) transmit low, receive high, (3) transmit high, receive low, (4) transmit high, receive high. After testing, the axial and lateral resolutions of all modes were calculated and compared. The results of this study suggest that bi-frequency co-linear arrays are potential aids for wideband fundamental imaging and harmonic/sub-harmonic imaging. PMID:26661069

Evaluation of factors associated with severe and frequent back pain in high school athletes.

PubMed

Noll, Matias; Silveira, Erika Aparecida; Avelar, Ivan Silveira de

2017-01-01

Several studies have shown that half of all young athletes experience back pain (BP). However, high intensity and frequency of BP may be harmful, and the factors associated with BP severity have not been investigated in detail. Here, we investigated the factors associated with a high intensity and high frequency of BP in high school athletes. We included 251 athletes (173 boys and 78 girls [14-20 years old]) in this cross-sectional study. The dependent variables were a high frequency and high intensity of BP, and the independent variables were demographic, socioeconomic, psychosocial, hereditary, anthropometric, behavioural, and postural factors and the level of exercise. The effect measure is presented as prevalence ratio (PR) with 95% confidence interval (CI). Of 251 athletes, 104 reported BP; thus, only these athletes were included in the present analysis. Results of multivariable analysis showed an association between high BP intensity and time spent using a computer (PR: 1.15, CI: 1.01-1.33), posture while writing (PR: 1.41, CI: 1.27-1.58), and posture while using a computer (PR: 1.39, CI: 1.26-1.54). Multivariable analysis also revealed an association of high BP frequency with studying in bed (PR: 1.19, CI: 1.01-1.40) and the method of carrying a backpack (PR: 1.19, CI: 1.01-1.40). In conclusion, we found that behavioural and postural factors are associated with a high intensity and frequency of BP. To the best of our knowledge, this study is the first to compare different intensities and frequencies of BP, and our results may help physicians and coaches to better understand BP in high school athletes.

Evaluation of factors associated with severe and frequent back pain in high school athletes

PubMed Central

Noll, Matias; Silveira, Erika Aparecida; de Avelar, Ivan Silveira

2017-01-01

Several studies have shown that half of all young athletes experience back pain (BP). However, high intensity and frequency of BP may be harmful, and the factors associated with BP severity have not been investigated in detail. Here, we investigated the factors associated with a high intensity and high frequency of BP in high school athletes. We included 251 athletes (173 boys and 78 girls [14–20 years old]) in this cross-sectional study. The dependent variables were a high frequency and high intensity of BP, and the independent variables were demographic, socioeconomic, psychosocial, hereditary, anthropometric, behavioural, and postural factors and the level of exercise. The effect measure is presented as prevalence ratio (PR) with 95% confidence interval (CI). Of 251 athletes, 104 reported BP; thus, only these athletes were included in the present analysis. Results of multivariable analysis showed an association between high BP intensity and time spent using a computer (PR: 1.15, CI: 1.01–1.33), posture while writing (PR: 1.41, CI: 1.27–1.58), and posture while using a computer (PR: 1.39, CI: 1.26–1.54). Multivariable analysis also revealed an association of high BP frequency with studying in bed (PR: 1.19, CI: 1.01–1.40) and the method of carrying a backpack (PR: 1.19, CI: 1.01–1.40). In conclusion, we found that behavioural and postural factors are associated with a high intensity and frequency of BP. To the best of our knowledge, this study is the first to compare different intensities and frequencies of BP, and our results may help physicians and coaches to better understand BP in high school athletes. PMID:28222141

Pump Frequency Noise Coupling into a Microcavity by Thermo-optic Locking

DTIC Science & Technology

2014-06-05

high coherence, Brillouin microcavity laser on silicon ,” Opt. Express 20, 20170–20180 (2012). 19. J. Li, H. Lee, and K. J. Vahala, “Microwave...measurements in a range of subjects including cavity optomechanics, microresonator-based frequency combs and microcavity Brillouin lasers ...SECURITY CLASSIFICATION OF: As thermo-optic locking is widely used to establish a stable frequency detuning between an external laser and a high Q

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.

The spectrum of the geoid from altimeter data

NASA Technical Reports Server (NTRS)

Wagner, C. A.

1977-01-01

A variety of sources of detailed information has been analyzed to arrive at a geoid power spectrum from global altimeter data. Using the equivalent of only two revolutions of data (mostly from GEOS-3) from all the major oceans, the high frequency geoid power (rms) is estimated (most simply) to be 80.7 n to the minus 1.47th power meters, where n is in cycles/global revolutions. This law is valid for all frequencies above 19 cycles but includes sea state. The (simple) law has more power than predicted by Kaula's rule for the geopotential. However, the data shows significantly less power for frequencies below 100 cycles. A closer approximation to the altimetry accumulates 2.18m (rss) for all frequencies higher than 19 cycles/rev. (including sea state), somewhat less power than predicted by the rule. The data permits up to 1.25 (rms) non-gravitational departures from the high frequency marine geoid.

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.

A validation of LTRAN2 with high frequency extensions by comparisons with experimental measurements of unsteady transonic flows

NASA Technical Reports Server (NTRS)

Hessenius, K. A.; Goorjian, P. M.

1981-01-01

A high frequency extension of the unsteady, transonic code LTRAN2 was created and is evaluated by comparisons with experimental results. The experimental test case is a NACA 64A010 airfoil in pitching motion at a Mach number of 0.8 over a range of reduced frequencies. Comparisons indicate that the modified code is an improvement of the original LTRAN2 and provides closer agreement with experimental lift and moment coefficients. A discussion of the code modifications, which involve the addition of high frequency terms of the boundary conditions of the numerical algorithm, is included.

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 ...

Cryogenic Pound Circuits for Cryogenic Sapphire Oscillators

NASA Technical Reports Server (NTRS)

Dick, G. John; Wang, Rabi

2006-01-01

Two modern cryogenic variants of the Pound circuit have been devised to increase the frequency stability of microwave oscillators that include cryogenic sapphire-filled cavity resonators. The original Pound circuit is a microwave frequency discriminator that provides feedback to stabilize a voltage-controlled microwave oscillator with respect to an associated cavity resonator. In the present cryogenic Pound circuits, the active microwave devices are implemented by use of state-of-the-art commercially available tunnel diodes that exhibit low flicker noise (required for high frequency stability) and function well at low temperatures and at frequencies up to several tens of gigahertz. While tunnel diodes are inherently operable as amplitude detectors and amplitude modulators, they cannot, by themselves, induce significant phase modulation. Therefore, each of the present cryogenic Pound circuits includes passive circuitry that transforms the AM into the required PM. Each circuit also contains an AM detector that is used to sample the microwave signal at the input terminal of the high-Q resonator for the purpose of verifying the desired AM null at this point. Finally, each circuit contains a Pound signal detector that puts out a signal, at the modulation frequency, having an amplitude proportional to the frequency error in the input signal. High frequency stability is obtained by processing this output signal into feedback to a voltage-controlled oscillator to continuously correct the frequency error in the input signal.

Audiometric Notch and Extended High-Frequency Hearing Threshold Shift in Relation to Total Leisure Noise Exposure: An Exploratory Analysis

PubMed Central

Wei, Wenjia; Heinze, Stefanie; Gerstner, Doris G.; Walser, Sandra M.; Twardella, Dorothee; Reiter, Christina; Weilnhammer, Veronika; Perez-Alvarez, Carmelo; Steffens, Thomas; Herr, Caroline E.W.

2017-01-01

Background: Studies investigating leisure noise effect on extended high frequency hearing are insufficient and they have inconsistent results. The aim of this study was to investigate if extended high-frequency hearing threshold shift is related to audiometric notch, and if total leisure noise exposure is associated with extended high-frequency hearing threshold shift. Materials and Methods: A questionnaire of the Ohrkan cohort study was used to collect information on demographics and leisure time activities. Conventional and extended high-frequency audiometry was performed. We did logistic regression between extended high-frequency hearing threshold shift and audiometric notch as well as between total leisure noise exposure and extended high-frequency hearing threshold shift. Potential confounders (sex, school type, and firecrackers) were included. Results: Data from 278 participants (aged 18–23 years, 53.2% female) were analyzed. Associations between hearing threshold shift at 10, 11.2, 12.5, and 14 kHz with audiometric notch were observed with a higher prevalence of threshold shift at the four frequencies, compared to the notch. However, we found no associations between total leisure noise exposure and hearing threshold shift at any extended high frequency. Conclusion: This exploratory analysis suggests that while extended high-frequency hearing threshold shifts are not related to total leisure noise exposure, they are strongly associated with audiometric notch. This leads us to further explore the hypothesis that extended high-frequency threshold shift might be indicative of the appearance of audiometric notch at a later time point, which can be investigated in the future follow-ups of the Ohrkan cohort. PMID:29319010

Morpheme-based Reading and Spelling in Italian Children with Developmental Dyslexia and Dysorthography.

PubMed

Angelelli, Paola; Marinelli, Chiara Valeria; De Salvatore, Marinella; Burani, Cristina

2017-11-01

Italian sixth graders, with and without dyslexia, read pseudowords and low-frequency words that include high-frequency morphemes better than stimuli not including any morpheme. The present study assessed whether morphemes affect (1) younger children, with and without dyslexia; (2) spelling as well as reading; and (3) words with low-frequency morphemes. Two groups of third graders (16 children with dyslexia and dysorthography and 16 age-matched typically developing children) read aloud and spelt to dictation pseudowords and words. Pseudowords included (1) root + suffix in not existing combinations (e.g. lampadista, formed by lampad-, 'lamp', and -ista, '-ist') and (2) orthographic sequences not corresponding to any Italian root or suffix (e.g. livonosto). Words had low frequency and included: (1) root + suffix, both of high frequency (e.g. bestiale, 'beastly'); (2) root + suffix, both of low frequency (e.g. asprigno, 'rather sour'); and (3) simple words (e.g. insulso, 'vapid'). Children with dyslexia and dysorthography were less accurate than typically developing children. Root + suffix pseudowords were read and spelt more accurately than non-morphological pseudowords by both groups. Morphologically complex (root + suffix) words were read and spelt better than simple words. However, task interacted with morphology: reading was not facilitated by low-frequency morphemes. We conclude that children acquiring a transparent orthography exploit morpheme-based reading and spelling to face difficulties in processing long unfamiliar stimuli. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Utilization of high-frequency Rayleigh waves in near-surface geophysics

USGS Publications Warehouse

Xia, J.; Miller, R.D.; Park, C.B.; Ivanov, J.; Tian, G.; Chen, C.

2004-01-01

Shear-wave velocities can be derived from inverting the dispersive phase velocity of the surface. The multichannel analysis of surface waves (MASW) is one technique for inverting high-frequency Rayleigh waves. The process includes acquisition of high-frequency broad-band Rayleigh waves, efficient and accurate algorithms designed to extract Rayleigh-wave dispersion curves from Rayleigh waves, and stable and efficient inversion algorithms to obtain near-surface S-wave velocity profiles. MASW estimates S-wave velocity from multichannel vertical compoent data and consists of data acquisition, dispersion-curve picking, and inversion.

Rate and timing cues associated with the cochlear amplifier: level discrimination based on monaural cross-frequency coincidence detection.

PubMed

Heinz, M G; Colburn, H S; Carney, L H

2001-10-01

The perceptual significance of the cochlear amplifier was evaluated by predicting level-discrimination performance based on stochastic auditory-nerve (AN) activity. Performance was calculated for three models of processing: the optimal all-information processor (based on discharge times), the optimal rate-place processor (based on discharge counts), and a monaural coincidence-based processor that uses a non-optimal combination of rate and temporal information. An analytical AN model included compressive magnitude and level-dependent-phase responses associated with the cochlear amplifier, and high-, medium-, and low-spontaneous-rate (SR) fibers with characteristic frequencies (CFs) spanning the AN population. The relative contributions of nonlinear magnitude and nonlinear phase responses to level encoding were compared by using four versions of the model, which included and excluded the nonlinear gain and phase responses in all possible combinations. Nonlinear basilar-membrane (BM) phase responses are robustly encoded in near-CF AN fibers at low frequencies. Strongly compressive BM responses at high frequencies near CF interact with the high thresholds of low-SR AN fibers to produce large dynamic ranges. Coincidence performance based on a narrow range of AN CFs was robust across a wide dynamic range at both low and high frequencies, and matched human performance levels. Coincidence performance based on all CFs demonstrated the "near-miss" to Weber's law at low frequencies and the high-frequency "mid-level bump." Monaural coincidence detection is a physiologically realistic mechanism that is extremely general in that it can utilize AN information (average-rate, synchrony, and nonlinear-phase cues) from all SR groups.

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.

Analysis of propellant feedline dynamics

NASA Technical Reports Server (NTRS)

Astleford, W. J.; Holster, J. L.; Gerlach, C. R.

1972-01-01

An analytical model and computer program were developed for studying the disturbances of liquid propellants in engine feedline systems. It was found that the predominant effect of turbulence is to increase the spatial attenuation at low frequencies; at high frequencies the laminar and turbulent frequencies coincide. Recommendations for future work are included.

High-frequency self-aligned graphene transistors with transferred gate stacks.

PubMed

Cheng, Rui; Bai, Jingwei; Liao, Lei; Zhou, Hailong; Chen, Yu; Liu, Lixin; Lin, Yung-Chen; Jiang, Shan; Huang, Yu; Duan, Xiangfeng

2012-07-17

Graphene has attracted enormous attention for radio-frequency transistor applications because of its exceptional high carrier mobility, high carrier saturation velocity, and large critical current density. Herein we report a new approach for the scalable fabrication of high-performance graphene transistors with transferred gate stacks. Specifically, arrays of gate stacks are first patterned on a sacrificial substrate, and then transferred onto arbitrary substrates with graphene on top. A self-aligned process, enabled by the unique structure of the transferred gate stacks, is then used to position precisely the source and drain electrodes with minimized access resistance or parasitic capacitance. This process has therefore enabled scalable fabrication of self-aligned graphene transistors with unprecedented performance including a record-high cutoff frequency up to 427 GHz. Our study defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra-high-frequency circuits.

A Phase-Only technique 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 ...

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.

High power RF solid state power amplifier system

NASA Technical Reports Server (NTRS)

Sims, III, William Herbert (Inventor); Chavers, Donald Gregory (Inventor); Richeson, James J. (Inventor)

2011-01-01

A high power, high frequency, solid state power amplifier system includes a plurality of input multiple port splitters for receiving a high-frequency input and for dividing the input into a plurality of outputs and a plurality of solid state amplifier units. Each amplifier unit includes a plurality of amplifiers, and each amplifier is individually connected to one of the outputs of multiport splitters and produces a corresponding amplified output. A plurality of multiport combiners combine the amplified outputs of the amplifiers of each of the amplifier units to a combined output. Automatic level control protection circuitry protects the amplifiers and maintains a substantial constant amplifier power output.

Comparative Assessment of Tactics to Improve Primary Frequency Response Without Curtailing Solar Output in High Photovoltaic Interconnection Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Jin; Zhang, Yingchen; You, Shutang

Power grid primary frequency response will be significantly impaired by Photovoltaic (PV) penetration increase because of the decrease in inertia and governor response. PV inertia and governor emulation requires reserving PV output and leads to solar energy waste. This paper exploits current grid resources and explores energy storage for primary frequency response under high PV penetration at the interconnection level. Based on the actual models of the U.S. Eastern Interconnection grid and the Texas grid, effects of multiple factors associated with primary frequency response, including the governor ratio, governor deadband, droop rate, fast load response. are assessed under high PVmore » penetration scenarios. In addition, performance of batteries and supercapacitors using different control strategies is studied in the two interconnections. The paper quantifies the potential of various resources to improve interconnection-level primary frequency response under high PV penetration without curtailing solar output.« less

Device and method for imaging of non-linear and linear properties of formations surrounding a borehole

DOEpatents

Johnson, Paul A; Tencate, James A; Le Bas, Pierre-Yves; Guyer, Robert; Vu, Cung Khac; Skelt, Christopher

2013-11-05

In some aspects of the disclosure, a method and an apparatus is disclosed for investigating material surrounding the borehole. The method includes generating a first low frequency acoustic wave within the borehole, wherein the first low frequency acoustic wave induces a linear and a nonlinear response in one or more features in the material that are substantially perpendicular to a radius of the borehole; directing a first sequence of high frequency pulses in a direction perpendicularly with respect to the longitudinal axis of the borehole into the material contemporaneously with the first acoustic wave; and receiving one or more second high frequency pulses at one or more receivers positionable in the borehole produced by an interaction between the first sequence of high frequency pulses and the one or more features undergoing linear and nonlinear elastic distortion due to the first low frequency acoustic wave to investigate the material surrounding the borehole.

Graphene-hexagonal boron nitride resonant tunneling diodes as high-frequency oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaskell, J.; Fromhold, T. M.; Greenaway, M. T.

We assess the potential of two-terminal graphene-hexagonal boron nitride-graphene resonant tunneling diodes as high-frequency oscillators, using self-consistent quantum transport and electrostatic simulations to determine the time-dependent response of the diodes in a resonant circuit. We quantify how the frequency and power of the current oscillations depend on the diode and circuit parameters including the doping of the graphene electrodes, device geometry, alignment of the graphene lattices, and the circuit impedances. Our results indicate that current oscillations with frequencies of up to several hundred GHz should be achievable.

Apparatus and method for microwave processing of materials

DOEpatents

Johnson, A.C.; Lauf, R.J.; Bible, D.W.; Markunas, R.J.

1996-05-28

Disclosed is a variable frequency microwave heating apparatus designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity for testing or other selected applications. The variable frequency heating apparatus is used in the method of the present invention to monitor the resonant processing frequency within the furnace cavity depending upon the material, including the state thereof, from which the workpiece is fabricated. The variable frequency microwave heating apparatus includes a microwave signal generator and a high-power microwave amplifier or a microwave voltage-controlled oscillator. A power supply is provided for operation of the high-power microwave oscillator or microwave amplifier. A directional coupler is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load. 10 figs.

Inner ear involvement in Behçet's disease.

PubMed

Süslü, Ahmet Emre; Polat, Mualla; Köybaşi, Serap; Biçer, Yusuf Ozgür; Funda, Yasemin Ongun; Parlak, Ali Haydar

2010-06-01

To assess cochlear involvement and hearing loss in patients with Behçet's disease (BD). Forty-two patients with BD and 24 sex and age matched healthy subjects were included in the study. pure-tone audiometry including high frequencies (250-16000Hz) and DPOAE were performed to all participants. Results of the audiological evaluation were compared and correlation between the audiologic status and clinical manifestations of the BD were investigated. Bilateral sensorineural hearing loss was detected in 27 (64.3%) patients. Hearing thresholds were found to be higher in patients with BD at all of the frequencies except at 500Hz when compared to control group (p<0.05). The difference in the hearing levels tend to increase in high frequencies. Compared with control group, distortion products and SNR of the BD patients were lower in all of the tested frequencies (p<0.05) which indicates weaker outer hair cell motility. There was no correlation between the clinical manifestations and the audiological parameters. Even having hearing levels within normal limits in speech frequencies, increased hearing thresholds in high frequencies and decreased signal-noise ratios (SNR) in distortion product otoacoustic emission (DPOAE) indicate a cochlear involvement in patients with BD. Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.

Predation by killer whales (Orcinus orca) and the evolution of whistle loss and narrow-band high frequency clicks in odontocetes.

PubMed

Morisaka, T; Connor, R C

2007-07-01

A disparate selection of toothed whales (Odontoceti) share striking features of their acoustic repertoires including the absence of whistles and high frequency but weak (low peak-to-peak source level) clicks that have a relatively long duration and a narrow bandwidth. The non-whistling, high frequency click species include members of the family Phocoenidae, members of one genus of delphinids, Cephalorhynchus, the pygmy sperm whale, Kogia breviceps, and apparently the sole member of the family Pontoporiidae. Our review supports the 'acoustic crypsis' hypothesis that killer whale predation risk was the primary selective factor favouring an echolocation and communication system in cephalorhynchids, phocoenids and possibly Pontoporiidae and Kogiidae restricted to sounds that killer whales hear poorly or not at all (< 2 and > 100 kHz).

Digital pressure transducer for use at high temperatures

DOEpatents

Karplus, Henry H. B.

1981-01-01

A digital pressure sensor for measuring fluid pressures at relatively high temperatures includes an electrically conducting fiber coupled to the fluid by a force disc that causes tension in the fiber to be a function of fluid pressure. The tension causes changes in the mechanical resonant frequency of the fiber, which is caused to vibrate in a magnetic field to produce an electrical signal from a positive-feedback amplifier at the resonant frequency. A count of this frequency provides a measure of the fluid pressure.

Digital pressure transducer for use at high temperatures

DOEpatents

Karplus, H.H.B.

A digital pressure sensor for measuring fluid pressures at relatively high temperatures includes an electrically conducting fiber coupled to the fluid by a force disc that causes tension in the fiber to be a function of fluid pressure. The tension causes changes in the mechanical resonant frequency of the fiber, which is caused to vibrate in a magnetic field to produce an electrical signal from a positive-feedback amplifier at the resonant frequency. A count of this frequency provides a measure of the fluid pressure.

Effect of Vibration Training on Anaerobic Power and Quardroceps Surface EMG in Long Jumpers

ERIC Educational Resources Information Center

Liu, Bin; Luo, Jiong

2015-01-01

Objective: To explore the anaerobic power and surface EMG (sEMG) of quardrocep muscle in lower extremities after single vibration training intervention. Methods: 8 excellent male long jumpers voluntarily participated in this study. Four intervention modes were devised, including high frequency high amplitude (HFHA,30Hz,6mm), low frequency low…

A study of the high-frequency hearing thresholds of dentistry professionals

PubMed Central

Lopes, Andréa Cintra; de Melo, Ana Dolores Passarelli; Santos, Cibele Carmelo

2012-01-01

Summary Introduction: In the dentistry practice, dentists are exposed to harmful effects caused by several factors, such as the noise produced by their work instruments. In 1959, the American Dental Association recommended periodical hearing assessments and the use of ear protectors. Aquiring more information regarding dentists', dental nurses', and prosthodontists' hearing abilities is necessary to propose prevention measures and early treatment strategies. Objective: To investigate the auditory thresholds of dentists, dental nurses, and prosthodontists. Method: In this clinical and experimental study, 44 dentists (Group I; GI), 36 dental nurses (Group II; GII), and 28 prosthodontists (Group III; GIII) were included, , with a total of 108 professionals. The procedures that were performed included a specific interview, ear canal inspection, conventional and high-frequency threshold audiometry, a speech reception threshold test, and an acoustic impedance test. Results: In the 3 groups that were tested, the comparison between the mean hearing thresholds provided evidence of worsened hearing ability relative to the increase in frequency. For the tritonal mean at 500 to 2,000 Hz and 3,000 to 6,000 Hz, GIII presented the worst thresholds. For the mean of the high frequencies (9,000 and 16,000 Hz), GII presented the worst thresholds. Conclusion: The conventional hearing threshold evaluation did not demonstrate alterations in the 3 groups that were tested; however, the complementary tests such as high-frequency audiometry provided greater efficacy in the early detection of hearing problems, since this population's hearing loss impaired hearing ability at frequencies that are not tested by the conventional tests. Therefore, we emphasize the need of utilizing high-frequency threshold audiometry in the hearing assessment routine in combination with other audiological tests. PMID:25991940

Selective Impairment in Frequency Discrimination in a Mouse Model of Tinnitus

PubMed Central

Mwilambwe-Tshilobo, Laetitia; Davis, Andrew J. O.; Aizenberg, Mark; Geffen, Maria N.

2015-01-01

Tinnitus is an auditory disorder, which affects millions of Americans, including active duty service members and veterans. It is manifested by a phantom sound that is commonly restricted to a specific frequency range. Because tinnitus is associated with hearing deficits, understanding how tinnitus affects hearing perception is important for guiding therapies to improve the quality of life in this vast group of patients. In a rodent model of tinnitus, prolonged exposure to a tone leads to a selective decrease in gap detection in specific frequency bands. However, whether and how hearing acuity is affected for sounds within and outside those frequency bands is not well understood. We induced tinnitus in mice by prolonged exposure to a loud mid-range tone, and behaviorally assayed whether mice exhibited a change in frequency discrimination acuity for tones embedded within the mid-frequency range and high-frequency range at 1, 4, and 8 weeks post-exposure. A subset of tone-exposed mice exhibited tinnitus-like symptoms, as demonstrated by selective deficits in gap detection, which were restricted to the high frequency range. These mice exhibited impaired frequency discrimination both for tones in the mid-frequency range and high-frequency range. The remaining tone exposed mice, which did not demonstrate behavioral evidence of tinnitus, showed temporary deficits in frequency discrimination for tones in the mid-frequency range, while control mice remained unimpaired. Our findings reveal that the high frequency-specific deficits in gap detection, indicative of tinnitus, are associated with impairments in frequency discrimination at the frequency of the presumed tinnitus. PMID:26352864

Challenges and regulatory considerations in the acoustic measurement of high-frequency (>20 MHz) ultrasound.

PubMed

Nagle, Samuel M; Sundar, Guru; Schafer, Mark E; Harris, Gerald R; Vaezy, Shahram; Gessert, James M; Howard, Samuel M; Moore, Mary K; Eaton, Richard M

2013-11-01

This article examines the challenges associated with making acoustic output measurements at high ultrasound frequencies (>20 MHz) in the context of regulatory considerations contained in the US Food and Drug Administration industry guidance document for diagnostic ultrasound devices. Error sources in the acoustic measurement, including hydrophone calibration and spatial averaging, nonlinear distortion, and mechanical alignment, are evaluated, and the limitations of currently available acoustic measurement instruments are discussed. An uncertainty analysis of acoustic intensity and power measurements is presented, and an example uncertainty calculation is done on a hypothetical 30-MHz high-frequency ultrasound system. This analysis concludes that the estimated measurement uncertainty of the acoustic intensity is +73%/-86%, and the uncertainty in the mechanical index is +37%/-43%. These values exceed the respective levels in the Food and Drug Administration guidance document of 30% and 15%, respectively, which are more representative of the measurement uncertainty associated with characterizing lower-frequency ultrasound systems. Recommendations made for minimizing the measurement uncertainty include implementing a mechanical positioning system that has sufficient repeatability and precision, reconstructing the time-pressure waveform via deconvolution using the hydrophone frequency response, and correcting for hydrophone spatial averaging.

High-resolution monitoring of nutrients in groundwater and surface waters: process understanding, quantification of loads and concentrations, and management applications

NASA Astrophysics Data System (ADS)

van Geer, Frans C.; Kronvang, Brian; Broers, Hans Peter

2016-09-01

Four sessions on "Monitoring Strategies: temporal trends in groundwater and surface water quality and quantity" at the EGU conferences in 2012, 2013, 2014, and 2015 and a special issue of HESS form the background for this overview of the current state of high-resolution monitoring of nutrients. The overview includes a summary of technologies applied in high-frequency monitoring of nutrients in the special issue. Moreover, we present a new assessment of the objectives behind high-frequency monitoring as classified into three main groups: (i) improved understanding of the underlying hydrological, chemical, and biological processes (PU); (ii) quantification of true nutrient concentrations and loads (Q); and (iii) operational management, including evaluation of the effects of mitigation measures (M). The contributions in the special issue focus on the implementation of high-frequency monitoring within the broader context of policy making and management of water in Europe for support of EU directives such as the Water Framework Directive, the Groundwater Directive, and the Nitrates Directive. The overview presented enabled us to highlight the typical objectives encountered in the application of high-frequency monitoring and to reflect on future developments and research needs in this growing field of expertise.

Wiring design for the control of electromagnetic interference (EMI)

NASA Technical Reports Server (NTRS)

Kopasakis, George

1995-01-01

Wiring design is only one important aspect of EMI control. Other important areas for EMI are: circuit design, filtering, grounding, bonding, shielding, lighting, electrostatic discharge (ESD), transient suppression, and electromagnetic pulse (EMP). Topics covered include: wire magnetic field emissions at low frequencies; wire radiated magnetic field emissions at frequencies; wire design guidelines for EMI control; wire design guidelines for EMI control; high frequency emissions from cables; and pulse frequency spectra.

Frequency-Shift Hearing Aid

NASA Technical Reports Server (NTRS)

Weinstein, Leonard M.

1994-01-01

Proposed hearing aid maps spectrum of speech into band of lower frequencies at which ear remains sensitive. By redirecting normal speech frequencies into frequency band from 100 to 1,500 Hz, hearing aid allows people to understand normal conversation, including telephone calls. Principle operation of hearing aid adapted to other uses such as, clearing up noisy telephone or radio communication. In addition, loud-speakers more easily understood in presence of high background noise.

Microresonator Frequency Comb Optical Clock

DTIC Science & Technology

2014-07-22

lithic construction with small size and power consumption. Microcomb development has included frequency control of their spectra [8–11...frequency f eo and amplified to a maximum of 140 mW. The first-order sideband powers are approximately 3 dB lower than the pump, and the piece of highly...resonator offers sufficient peak power for our experiments and is stable and repeatable even for different settings of pump frequency and power

High-frequency profile in adolescents and its relationship with the use of personal stereo devices.

PubMed

Silvestre, Renata Almeida Araújo; Ribas, Ângela; Hammerschmidt, Rogério; de Lacerda, Adriana Bender Moreira

2016-01-01

To analyze and correlate the audiometric findings of high frequencies (9-16 kHz) in adolescents with their hearing habits and attitudes, in order to prevent noise-induced hearing loss. This was a descriptive cross-sectional study, which included 125 adolescents in a sample of normal-hearing students, at a state school. The subjects performed high-frequency audiometry testing and answered a self-administered questionnaire addressing information on sound habits concerning the use of personal stereo devices. The sample was divided according to the exposure characteristics (time, duration, intensity, etc.) and the results were compared with the observed thresholds, through the difference in proportions test, chi-squared, Student's t-test, and ANOVA, all at a significance level of 0.05. Average high-frequency thresholds were registered below 15 dB HL and no significant correlation was found between high frequency audiometric findings and the degree of exposure. The prevalence of harmful sound habits due to the use of personal stereo devices is high in the adolescent population, but there was no correlation between exposure to high sound pressure levels through personal stereos and the high-frequency thresholds in this population. Copyright © 2016 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

Frequency-dependent local field factors in dielectric liquids by a polarizable force field and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof

2015-12-01

A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities.

Method for high resolution magnetic resonance analysis using magic angle technique

DOEpatents

Wind, Robert A.; Hu, Jian Zhi

2003-11-25

A method of performing a magnetic resonance analysis of a biological object that includes placing the biological object in a main magnetic field and in a radio frequency field, the main magnetic field having a static field direction; rotating the biological object at a rotational frequency of less than about 100 Hz around an axis positioned at an angle of about 54.degree.44' relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. According to another embodiment, the radio frequency is pulsed to provide a sequence capable of producing a spectrum that is substantially free of spinning sideband peaks.

Piezoelectric Vibrational and Acoustic Alert for a Personal Communication Device

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor); Hellbaum, Richard F. (Inventor); Daugherty, Robert H. (Inventor); Scholz, Raymond C. (Inventor); Little, Bruce D. (Inventor); Fox, Robert L. (Inventor); Denhardt, Gerald A. (Inventor); Jang, SeGon (Inventor); Balein, Rizza (Inventor)

2001-01-01

An alert apparatus for a personal communication device includes a mechanically prestressed piezoelectric wafer positioned within the personal communication device and an alternating voltage input line coupled at two points of the wafer where polarity is recognized. The alert apparatus also includes a variable frequency device coupled to the alternating voltage input line, operative to switch the alternating voltage on the alternating voltage input line at least between an alternating voltage having a first frequency and an alternating voltage having a second frequency. The first frequency is preferably sufficiently high so as to cause the wafer to vibrate at a resulting frequency that produces a sound perceptible by a human ear, and the second frequency is preferably sufficiently low so as to cause the wafer to vibrate at a resulting frequency that produces a vibration readily felt by a holder of the personal communication device.

Adolescent Alcohol-Drinking Frequency and Problem-Gambling Severity: Adolescent Perceptions Regarding Problem-Gambling Prevention and Parental/Adult Behaviors and Attitudes

PubMed Central

Rahman, Ardeshir S.; Balodis, Iris M.; Pilver, Corey E.; Leeman, Robert F.; Hoff, Rani A.; Steinberg, Marvin A.; Rugle, Loreen; Krishnan-Sarin, Suchitra; Potenza, Marc N.

2014-01-01

Background To examine in adolescents how alcohol-drinking frequency relates to gambling-related attitudes and behaviors and their perceptions of both problem-gambling prevention strategies and adult (including parental) behaviors/attitudes. Methods A survey assessing alcohol, gambling and health and functioning measures in 1609 high-school students. Students were stratified into low-frequency/non-drinking and high-frequency drinking groups, and into low-risk and at-risk/problematic gambling groups. Results High-frequency drinking was associated with at-risk/problematic gambling (χ2(1, N=1842)=49.22, p<.0001). High-frequency-drinking versus low-frequency/non-drinking adolescents exhibited more permissive attitudes towards gambling (e.g., less likely to report multiple problem-gambling prevention efforts to be important). At-risk problematic gamblers exhibited more severe drinking patterns and greater likelihood of acknowledging parental approval of drinking (χ2(1, N=1842)=31.58, p<.0001). Problem-gambling severity was more strongly related to gambling with adults among high-frequency-drinking adolescents (odds ratio [OR]=3.17, 95% confidence interval [95%CI]=[1.97, 5.09]) versus low-frequency/non-drinking (OR=1.86, 95%CI=[0.61, 2.68]) adolescents (Interaction OR=1.78, 95%CI=[1.05, 3.02]). Conclusions Inter-relationships between problematic drinking and gambling in youth may relate to more permissive attitudes across these domains. Stronger links between at-risk/problem gambling and gambling with adults in the high-frequency-drinking group raises the possibility that interventions targeting adults may help mitigate youth gambling and drinking. PMID:25147928

Systematic study of high-frequency ultrasonic transducer design for laser-scanning photoacoustic ophthalmoscopy

PubMed Central

Ma, Teng; Zhang, Xiangyang; Chiu, Chi Tat; Chen, Ruimin; Kirk Shung, K.; Zhou, Qifa; Jiao, Shuliang

2014-01-01

Abstract. Photoacoustic ophthalmoscopy (PAOM) is a high-resolution in vivo imaging modality that is capable of providing specific optical absorption information for the retina. A high-frequency ultrasonic transducer is one of the key components in PAOM, which is in contact with the eyelid through coupling gel during imaging. The ultrasonic transducer plays a crucial role in determining the image quality affected by parameters such as spatial resolution, signal-to-noise ratio, and field of view. In this paper, we present the results of a systematic study on a high-frequency ultrasonic transducer design for PAOM. The design includes piezoelectric material selection, frequency selection, and the fabrication process. Transducers of various designs were successfully applied for capturing images of biological samples in vivo. The performances of these designs are compared and evaluated. PMID:24441942

Systematic study of high-frequency ultrasonic transducer design for laser-scanning photoacoustic ophthalmoscopy.

PubMed

Ma, Teng; Zhang, Xiangyang; Chiu, Chi Tat; Chen, Ruimin; Kirk Shung, K; Zhou, Qifa; Jiao, Shuliang

2014-01-01

Photoacoustic ophthalmoscopy (PAOM) is a high-resolution in vivo imaging modality that is capable of providing specific optical absorption information for the retina. A high-frequency ultrasonic transducer is one of the key components in PAOM, which is in contact with the eyelid through coupling gel during imaging. The ultrasonic transducer plays a crucial role in determining the image quality affected by parameters such as spatial resolution, signal-to-noise ratio, and field of view. In this paper, we present the results of a systematic study on a high-frequency ultrasonic transducer design for PAOM. The design includes piezoelectric material selection, frequency selection, and the fabrication process. Transducers of various designs were successfully applied for capturing images of biological samples in vivo. The performances of these designs are compared and evaluated.

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.

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

High-frequency self-aligned graphene transistors with transferred gate stacks

PubMed Central

Cheng, Rui; Bai, Jingwei; Liao, Lei; Zhou, Hailong; Chen, Yu; Liu, Lixin; Lin, Yung-Chen; Jiang, Shan; Huang, Yu; Duan, Xiangfeng

2012-01-01

Graphene has attracted enormous attention for radio-frequency transistor applications because of its exceptional high carrier mobility, high carrier saturation velocity, and large critical current density. Herein we report a new approach for the scalable fabrication of high-performance graphene transistors with transferred gate stacks. Specifically, arrays of gate stacks are first patterned on a sacrificial substrate, and then transferred onto arbitrary substrates with graphene on top. A self-aligned process, enabled by the unique structure of the transferred gate stacks, is then used to position precisely the source and drain electrodes with minimized access resistance or parasitic capacitance. This process has therefore enabled scalable fabrication of self-aligned graphene transistors with unprecedented performance including a record-high cutoff frequency up to 427 GHz. Our study defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra–high-frequency circuits. PMID:22753503

Gigatron microwave amplifier

DOEpatents

McIntyre, P.M.

1993-07-13

An electron tube for achieving high power at high frequency with high efficiency is described, including an input coupler, a ribbon-shaped electron beam and a traveling wave output coupler. The input coupler is a lumped constant resonant circuit that modulates a field emitter array cathode at microwave frequency. A bunched ribbon electron beam is emitted from the cathode in periodic bursts at the desired frequency. The beam has a ribbon configuration to eliminate limitations inherent in round beam devices. The traveling wave coupler efficiently extracts energy from the electron beam, and includes a waveguide with a slot there through for receiving the electron beam. The ribbon beam is tilted at an angle with respect to the traveling wave coupler so that the electron beam couples in-phase with the traveling wave in the waveguide. The traveling wave coupler thus extracts energy from the electron beam over the entire width of the beam.

Gigatron microwave amplifier

DOEpatents

McIntyre, Peter M.

1993-01-01

An electron tube for achieving high power at high frequency with high efficiency, including an input coupler, a ribbon-shaped electron beam and a traveling wave output coupler. The input coupler is a lumped constant resonant circuit that modulates a field emitter array cathode at microwave frequency. A bunched ribbon electron beam is emitted from the cathode in periodic bursts at the desired frequency. The beam has a ribbon configuration to eliminate limitations inherent in round beam devices. The traveling wave coupler efficiently extracts energy from the electron beam, and includes a waveguide with a slot therethrough for receiving the electron beam. The ribbon beam is tilted at an angle with respect to the traveling wave coupler so that the electron beam couples in-phase with the traveling wave in the waveguide. The traveling wave coupler thus extracts energy from the electron beam over the entire width of the beam.

Effects of the intensity of masking noise on ear canal recorded low-frequency cochlear microphonic waveforms in normal hearing subjects.

PubMed

Zhang, Ming

2014-07-01

Compared to auditory brainstem responses (ABRs), cochlear microphonics (CMs) may be more appropriate to serve as a supplement to the test of otoacoustic emissions (OAEs). Researchers have shown that low-frequency CMs from the apical cochlea are measurable at the tympanic membrane using high-pass masking noise. Our objective is to study the effect of such noise at different intensities on low-frequency CMs recorded at the ear canal, which is not completely known. Six components were involved in this CM measurement including an ear canal electrode (1), a relatively long and low-frequency toneburst (2), and high-pass masking noise at different intensities (3). The rest components include statistical analysis based on multiple human subjects (4), curve modeling based on amplitudes of CM waveforms (CMWs) and noise intensity (5), and a technique based on electrocochleography (ECochG or ECoG) (6). Results show that low-frequency CMWs appeared clearly. The CMW amplitude decreased with an increase in noise level. It decreased first slowly, then faster, and finally slowly again. In conclusion, when masked with high-pass noise, the low-frequency CMs are measurable at the human ear canal. Such noise reduces the low-frequency CM amplitude. The reduction is noise-intensity dependent but not completely linear. The reduction may be caused by the excited basal cochlea which the low-frequency has to travel and pass through. Although not completely clear, six mechanisms related to such reduction are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Post-Flight Analysis of GPSR Performance During Orion Exploration Flight Test 1

NASA Technical Reports Server (NTRS)

Barker, Lee; Mamich, Harvey; McGregor, John

2016-01-01

On 5 December 2014, the first test flight of the Orion Multi-Purpose Crew Vehicle executed a unique and challenging flight profile including an elevated re-entry velocity and steeper flight path angle to envelope lunar re-entry conditions. A new navigation system including a single frequency (L1) GPS receiver was evaluated for use as part of the redundant navigation system required for human space flight. The single frequency receiver was challenged by a highly dynamic flight environment including flight above low Earth orbit, as well as single frequency operation with ionospheric delay present. This paper presents a brief description of the GPS navigation system, an independent analysis of flight telemetry data, and evaluation of the GPSR performance, including evaluation of the ionospheric model employed to supplement the single frequency receiver. Lessons learned and potential improvements will be discussed.

Broadband unidirectional ultrasound propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinha, Dipen N.; Pantea, Cristian

A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystalmore » provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.« less

Application of Excitation from Multiple Locations on a Simplified High-Lift System

NASA Technical Reports Server (NTRS)

Melton, LaTunia Pack; Yao, Chung-Sheng; Seifert, Avi

2004-01-01

A series of active flow control experiments were recently conducted on a simplified high-lift system. The purpose of the experiments was to explore the prospects of eliminating all but simply hinged leading and trailing edge flaps, while controlling separation on the supercritical airfoil using multiple periodic excitation slots. Excitation was provided by three. independently controlled, self-contained, piezoelectric actuators. Low frequency excitation was generated through amplitude modulation of the high frequency carrier wave, the actuators' resonant frequencies. It was demonstrated, for the first time, that pulsed modulated signal from two neighboring slots interact favorably to increase lift. Phase sensitivity at the low frequency was measured, even though the excitation was synthesized from the high-frequency carrier wave. The measurements were performed at low Reynolds numbers and included mean and unsteady surface pressures, surface hot-films, wake pressures and particle image velocimetry. A modest (6%) increase in maximum lift (compared to the optimal baseline) was obtained due t o the activation of two of the three actuators.

Frequency of Testing for Dyslipidemia: An Evidence-Based Analysis

PubMed Central

2014-01-01

Background Dyslipidemias include high levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides and low levels of high-density lipoprotein (HDL) cholesterol. Dyslipidemia is a risk factor for cardiovascular disease, which is a major contributor to mortality in Canada. Approximately 23% of the 2009/11 Canadian Health Measures Survey (CHMS) participants had a high level of LDL cholesterol, with prevalence increasing with age, and approximately 15% had a total cholesterol to HDL ratio above the threshold. Objectives To evaluate the frequency of lipid testing in adults not diagnosed with dyslipidemia and in adults on treatment for dyslipidemia. Research Methods A systematic review of the literature set out to identify randomized controlled trials (RCTs), systematic reviews, health technology assessments (HTAs), and observational studies published between January 1, 2000, and November 29, 2012, that evaluated the frequency of testing for dyslipidemia in the 2 populations. Results Two observational studies assessed the frequency of lipid testing, 1 in individuals not on lipid-lowering medications and 1 in treated individuals. Both studies were based on previously collected data intended for a different objective and, therefore, no conclusions could be reached about the frequency of testing at intervals other than the ones used in the original studies. Given this limitation and generalizability issues, the quality of evidence was considered very low. No evidence for the frequency of lipid testing was identified in the 2 HTAs included. Canadian and international guidelines recommend testing for dyslipidemia in individuals at an increased risk for cardiovascular disease. The frequency of testing recommended is based on expert consensus. Conclusions Conclusions on the frequency of lipid testing could not be made based on the 2 observational studies. Current guidelines recommend lipid testing in adults with increased cardiovascular risk, with the frequency of testing based on individual cardiovascular risk. PMID:26316920

High Precision Laser Range Sensor

NASA Technical Reports Server (NTRS)

Dubovitsky, Serge (Inventor); Lay, Oliver P. (Inventor)

2003-01-01

The present invention is an improved distance measuring interferometer that includes high speed phase modulators and additional phase meters to generate and analyze multiple heterodyne signal pairs with distinct frequencies. Modulation sidebands with large frequency separation are generated by the high speed electro-optic phase modulators, requiring only a single frequency stable laser source and eliminating the need for a fist laser to be tuned or stabilized relative to a second laser. The combination of signals produced by the modulated sidebands is separated and processed to give the target distance. The resulting metrology apparatus enables a sensor with submicron accuracy or better over a multi- kilometer ambiguity range.

Alcohol marketing in televised international football: frequency analysis.

PubMed

Adams, Jean; Coleman, James; White, Martin

2014-05-20

Alcohol marketing includes sponsorship of individuals, organisations and sporting events. Football (soccer) is one of the most popular spectator sports worldwide. No previous studies have quantified the frequency of alcohol marketing in a high profile international football tournament. The aims were to determine: the frequency and nature of visual references to alcohol in a representative sample of EURO2012 matches broadcast in the UK; and if frequency or nature varied between matches broadcast on public service and commercial channels, or between matches that did and did not feature England. Eight matches selected by stratified random sampling were recorded. All visual references to alcohol were identified using a tool with high inter-rater reliability. 1846 visual references to alcohol were identified over 1487 minutes of broadcast--an average of 1.24 references per minute. The mean number of references per minute was higher in matches that did vs did not feature England (p = 0.004), but did not differ between matches broadcast on public service vs commercial channels (p = 0.92). The frequency of visual references to alcohol was universally high and higher in matches featuring the only UK home team--England--suggesting that there may be targeting of particularly highly viewed matches. References were embedded in broadcasts, and not particular to commercial channels including paid-for advertising. New UK codes-of-conduct on alcohol marketing at sporting events will not reduce the level of marketing reported here.

Optical air-coupled NDT system with ultra-broad frequency bandwidth (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fischer, Balthasar; Rohringer, Wolfgang; Heine, Thomas

2017-05-01

We present a novel, optical ultrasound airborne acoustic testing setup exhibiting a frequency bandwidth of 1MHz in air. The sound waves are detected by a miniaturized Fabry-Pérot interferometer (2mm cavity) whilst the sender consists of a thermoacoustic emitter or a short laser pulse We discuss characterization measurements and C-scans of a selected set of samples, including Carbon fiber reinforced polymer (CFRP). The high detector sensitivity allows for an increased penetration depth. The high frequency and the small transducer dimensions lead to a compelling image resolution.

Multi-sensor image fusion algorithm based on multi-objective particle swarm optimization algorithm

NASA Astrophysics Data System (ADS)

Xie, Xia-zhu; Xu, Ya-wei

2017-11-01

On the basis of DT-CWT (Dual-Tree Complex Wavelet Transform - DT-CWT) theory, an approach based on MOPSO (Multi-objective Particle Swarm Optimization Algorithm) was proposed to objectively choose the fused weights of low frequency sub-bands. High and low frequency sub-bands were produced by DT-CWT. Absolute value of coefficients was adopted as fusion rule to fuse high frequency sub-bands. Fusion weights in low frequency sub-bands were used as particles in MOPSO. Spatial Frequency and Average Gradient were adopted as two kinds of fitness functions in MOPSO. The experimental result shows that the proposed approach performances better than Average Fusion and fusion methods based on local variance and local energy respectively in brightness, clarity and quantitative evaluation which includes Entropy, Spatial Frequency, Average Gradient and QAB/F.

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.

Variable frequency microwave heating apparatus

DOEpatents

Bible, Don W.; Lauf, Robert J.; Johnson, Arvid C.; Thigpen, Larry T.

1999-01-01

A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity (34) for testing or other selected applications. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a high-power microwave oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

Apparatus and method for microwave processing of materials

DOEpatents

Johnson, Arvid C.; Lauf, Robert J.; Bible, Don W.; Markunas, Robert J.

1996-01-01

A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34) for testing or other selected applications. The variable frequency heating apparatus (10) is used in the method of the present invention to monitor the resonant processing frequency within the furnace cavity (34) depending upon the material, including the state thereof, from which the workpiece (36) is fabricated. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a microwave voltage-controlled oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

Visual information processing of faces in body dysmorphic disorder.

PubMed

Feusner, Jamie D; Townsend, Jennifer; Bystritsky, Alexander; Bookheimer, Susan

2007-12-01

Body dysmorphic disorder (BDD) is a severe psychiatric condition in which individuals are preoccupied with perceived appearance defects. Clinical observation suggests that patients with BDD focus on details of their appearance at the expense of configural elements. This study examines abnormalities in visual information processing in BDD that may underlie clinical symptoms. To determine whether patients with BDD have abnormal patterns of brain activation when visually processing others' faces with high, low, or normal spatial frequency information. Case-control study. University hospital. Twelve right-handed, medication-free subjects with BDD and 13 control subjects matched by age, sex, and educational achievement. Intervention Functional magnetic resonance imaging while performing matching tasks of face stimuli. Stimuli were neutral-expression photographs of others' faces that were unaltered, altered to include only high spatial frequency visual information, or altered to include only low spatial frequency visual information. Blood oxygen level-dependent functional magnetic resonance imaging signal changes in the BDD and control groups during tasks with each stimulus type. Subjects with BDD showed greater left hemisphere activity relative to controls, particularly in lateral prefrontal cortex and lateral temporal lobe regions for all face tasks (and dorsal anterior cingulate activity for the low spatial frequency task). Controls recruited left-sided prefrontal and dorsal anterior cingulate activity only for the high spatial frequency task. Subjects with BDD demonstrate fundamental differences from controls in visually processing others' faces. The predominance of left-sided activity for low spatial frequency and normal faces suggests detail encoding and analysis rather than holistic processing, a pattern evident in controls only for high spatial frequency faces. These abnormalities may be associated with apparent perceptual distortions in patients with BDD. The fact that these findings occurred while subjects viewed others' faces suggests differences in visual processing beyond distortions of their own appearance.

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.

Calcium Input Frequency, Duration and Amplitude Differentially Modulate the Relative Activation of Calcineurin and CaMKII

PubMed Central

Li, Lu; Stefan, Melanie I.; Le Novère, Nicolas

2012-01-01

NMDA receptor dependent long-term potentiation (LTP) and long-term depression (LTD) are two prominent forms of synaptic plasticity, both of which are triggered by post-synaptic calcium elevation. To understand how calcium selectively stimulates two opposing processes, we developed a detailed computational model and performed simulations with different calcium input frequencies, amplitudes, and durations. We show that with a total amount of calcium ions kept constant, high frequencies of calcium pulses stimulate calmodulin more efficiently. Calcium input activates both calcineurin and Ca2+/calmodulin-dependent protein kinase II (CaMKII) at all frequencies, but increased frequencies shift the relative activation from calcineurin to CaMKII. Irrespective of amplitude and duration of the inputs, the total amount of calcium ions injected adjusts the sensitivity of the system to calcium input frequencies. At a given frequency, the quantity of CaMKII activated is proportional to the total amount of calcium. Thus, an input of a small amount of calcium at high frequencies can induce the same activation of CaMKII as a larger amount, at lower frequencies. Finally, the extent of activation of CaMKII signals with high calcium frequency is further controlled by other factors, including the availability of calmodulin, and by the potency of phosphatase inhibitors. PMID:22962589

High Frequency Acoustic Reflection and Transmission in Ocean Sediments

DTIC Science & Technology

2003-09-30

Development of a physical model of high-frequency acoustic interaction with the ocean floor, including penetration through and reflection from smooth and...experiments and additional laboratory measurements in the ARL:UT sand tank, an improved model of sediment acoustics will be developed that is...distinct areas of concentration: development of a broadband the oretical model to describe the acoustic interaction with the ocean floor in littoral

MMIC Replacement for Gunn Diode Oscillators

NASA Technical Reports Server (NTRS)

Crowe, Thomas W.; Porterfield, David

2011-01-01

An all-solid-state replacement for high-frequency Gunn diode oscillators (GDOs) has been proposed for use in NASA s millimeter- and submillimeter-wave sensing instruments. Highly developed microwave oscillators are used to achieve a low-noise and highly stable reference signal in the 10-40-GHz band. Compact amplifiers and high-power frequency multipliers extend the signal to the 100-500-GHz band with minimal added phase noise and output power sufficient for NASA missions. This technology can achieve improved output power and frequency agility, while maintaining phase noise and stability comparable to other GDOs. Additional developments of the technology include: a frequency quadrupler to 145 GHz with 18 percent efficiency and 15 percent fixed tuned bandwidth; frequency doublers featuring 124, 240, and 480 GHz; an integrated 874-GHz subharmonic mixer with a mixer noise temperature of 3,000 K DSB (double sideband) and mixer conversion loss of 11.8 dB DSB; a high-efficiency frequency tripler design with peak output power of 23 mW and 14 mW, and efficiency of 16 and 13 percent, respectively; millimeter-wave integrated circuit (MMIC) power amplifiers to the 30-40 GHz band with high DC power efficiency; and an 874-GHz radiometer suitable for airborne observation with state-of-the-art sensitivity at room temperature and less than 5 W of total power consumption.

Extended high frequency audiometry can diagnose sub-clinic involvement in a seemingly normal hearing systemic lupus erythematosus population.

PubMed

Lasso de la Vega, Mar; Villarreal, Ithzel María; López Moya, Julio; García-Berrocal, José Ramón

2017-02-01

Sensorineural hearing loss must be considered within the clinical picture of systemic lupus erythematosus. The results confirm the usefulness of extended high-frequency audiometry in the audiologic testing of these patients, enabling the possibility of modifying or applying a preventive treatment for a possible hearing loss. Hearing involvement is usually under-diagnosed with routine auditory examination. This study proposes the use of extended high-frequency audiometry to achieve a correct detection of a possible asymptomatic hypoacusis in early stages of the disease. The aim of this study is to analyze the hearing levels in extended high-frequencies in these patients and to correlate the hearing loss with the severity of the disease and the immunological parameters. A descriptive cross-sectional study was performed. Fifty-five patients with systemic lupus erythematosus were included in the study. The control group consisted of 71 patients paired by age and sex with the study population. Both a pure tone audiometry and an extended high-frequency audiometry (8-18 KHz) were performed. In total, 70% were diagnosed with sensorineural hearing loss with extended high-frequency audiometry, overcoming the results obtained with pure tone audiometry (30.9%). Statistically significant correlations were found within the patients regarding sensorineural hearing loss related with age, disease activity and cryoglobulinemia.

Frequency of CDH1 germline mutations in gastric carcinoma coming from high- and low-risk areas: metanalysis and systematic review of the literature

PubMed Central

2012-01-01

Background The frequency of E-cadherin germline mutations in countries with different incidence rates for gastric carcinoma has not been well established. The goal of this study was to assess the worldwide frequency of CDH1 germline mutations in gastric cancers coming from low- and high-risk areas. Methods English articles using MEDLINE access (from 1998 to 2011). Search terms included CDH1, E-cadherin, germline mutation, gastric cancer, hereditary, familial and diffuse histotype. The study included all E-cadherin germline mutations identified in gastric cancer patients; somatic mutations and germline mutations reported in other tumors were excluded. The method of this study was scheduled in accordance with the "PRISMA statement for reporting systematic reviews and meta-analyses". Countries were classified as low- or middle/high risk-areas for gastric carcinoma incidence. Statistical analysis was performed to correlate the CDH1 mutation frequency with gastric cancer incidence areas. Results A total of 122 E-cadherin germline mutations have been identified; the majority (87.5%) occurred in gastric cancers coming from low-risk areas. In high-risk areas, we identified 16 mutations in which missense mutations were predominant. (68.8%). We verified a significant association between the mutation frequency and the gastric cancer risk area (p < 0.001: overall identified mutations in low- vs. middle/high-risk areas). Conclusions E-cadherin genetic screenings performed in low-risk areas for gastric cancer identified a higher frequency of CDH1 germline mutations. This data could open new approaches in the gastric cancer prevention test; before proposing a proband candidate for the CDH1 genetic screening, geographic variability, alongside the family history should be considered. PMID:22225527

Holographic radar imaging privacy techniques utilizing dual-frequency implementation

NASA Astrophysics Data System (ADS)

McMakin, Douglas L.; Hall, Thomas E.; Sheen, David M.

2008-04-01

Over the last 15 years, the Pacific Northwest National Laboratory has performed significant research and development activities to enhance the state of the art of holographic radar imaging systems to be used at security checkpoints for screening people for concealed threats hidden under their garments. These enhancement activities included improvements to privacy techniques to remove human features and providing automatic detection of body-worn concealed threats. The enhanced privacy and detection methods used both physical and software imaging techniques. The physical imaging techniques included polarization-diversity illumination and reception, dual-frequency implementation, and high-frequency imaging at 60 GHz. Software imaging techniques to enhance the privacy of the person under surveillance included extracting concealed threat artifacts from the imagery to automatically detect the threat. This paper will focus on physical privacy techniques using dual-frequency implementation.

Holographic Radar Imaging Privacy Techniques Utilizing Dual-Frequency Implementation

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMakin, Douglas L.; Hall, Thomas E.; Sheen, David M.

2008-04-18

Over the last 15 years, the Pacific Northwest National Laboratory has performed significant research and development activities to enhance the state of the art of holographic radar imaging systems to be used at security checkpoints for screening people for concealed threats hidden under their garments. These enhancement activities included improvements to privacy techniques to remove human features and providing automatic detection of body-worn concealed threats. The enhanced privacy and detection methods used both physical and software imaging techniques. The physical imaging techniques included polarization-diversity illumination and reception, dual-frequency implementation, and high-frequency imaging at 60 GHz. Software imaging techniques to enhancemore » the privacy of the person under surveillance included extracting concealed threat artifacts from the imagery to automatically detect the threat. This paper will focus on physical privacy techniques using dual-frequency implementation.« less

Low-frequency noise reduction of lightweight airframe structures

NASA Technical Reports Server (NTRS)

Getline, G. L.

1976-01-01

The results of an experimental study to determine the noise attenuation characteristics of aircraft type fuselage structural panels were presented. Of particular interest was noise attenuation at low frequencies, below the fundamental resonances of the panels. All panels were flightweight structures for transport type aircraft in the 34,050 to 45,400 kg (75,000 to 100,000 pounds) gross weight range. Test data include the results of vibration and acoustic transmission loss tests on seven types of isotropic and orthotropically stiffened, flat and curved panels. The results show that stiffness controlled acoustically integrated structures can provide very high noise reductions at low frequencies without significantly affecting their high frequency noise reduction capabilities.

Volume conductor model of transcutaneous electrical stimulation with kilohertz signals

PubMed Central

Medina, Leonel E.; Grill, Warren M.

2014-01-01

Objective Incorporating high-frequency components in transcutaneous electrical stimulation (TES) waveforms may make it possible to stimulate deeper nerve fibers since the impedance of tissue declines with increasing frequency. However, the mechanisms of high-frequency TES remain largely unexplored. We investigated the properties of TES with frequencies beyond those typically used in neural stimulation. Approach We implemented a multilayer volume conductor model including dispersion and capacitive effects, coupled to a cable model of a nerve fiber. We simulated voltage- and current-controlled transcutaneous stimulation, and quantified the effects of frequency on the distribution of potentials and fiber excitation. We also quantified the effects of a novel transdermal amplitude modulated signal (TAMS) consisting of a non-zero offset sinusoidal carrier modulated by a square-pulse train. Main results The model revealed that high-frequency signals generated larger potentials at depth than did low frequencies, but this did not translate into lower stimulation thresholds. Both TAMS and conventional rectangular pulses activated more superficial fibers in addition to the deeper, target fibers, and at no frequency did we observe an inversion of the strength-distance relationship. Current regulated stimulation was more strongly influenced by fiber depth, whereas voltage regulated stimulation was more strongly influenced by skin thickness. Finally, our model reproduced the threshold-frequency relationship of experimentally measured motor thresholds. Significance The model may be used for prediction of motor thresholds in TES, and contributes to the understanding of high-frequency TES. PMID:25380254

Volume conductor model of transcutaneous electrical stimulation with kilohertz signals

NASA Astrophysics Data System (ADS)

Medina, Leonel E.; Grill, Warren M.

2014-12-01

Objective. Incorporating high-frequency components in transcutaneous electrical stimulation (TES) waveforms may make it possible to stimulate deeper nerve fibers since the impedance of tissue declines with increasing frequency. However, the mechanisms of high-frequency TES remain largely unexplored. We investigated the properties of TES with frequencies beyond those typically used in neural stimulation. Approach. We implemented a multilayer volume conductor model including dispersion and capacitive effects, coupled to a cable model of a nerve fiber. We simulated voltage- and current-controlled transcutaneous stimulation, and quantified the effects of frequency on the distribution of potentials and fiber excitation. We also quantified the effects of a novel transdermal amplitude modulated signal (TAMS) consisting of a non-zero offset sinusoidal carrier modulated by a square-pulse train. Main results. The model revealed that high-frequency signals generated larger potentials at depth than did low frequencies, but this did not translate into lower stimulation thresholds. Both TAMS and conventional rectangular pulses activated more superficial fibers in addition to the deeper, target fibers, and at no frequency did we observe an inversion of the strength-distance relationship. Current regulated stimulation was more strongly influenced by fiber depth, whereas voltage regulated stimulation was more strongly influenced by skin thickness. Finally, our model reproduced the threshold-frequency relationship of experimentally measured motor thresholds. Significance. The model may be used for prediction of motor thresholds in TES, and contributes to the understanding of high-frequency TES.

Space Operations

DTIC Science & Technology

2013-05-29

support, products, and services, as required. US Tenth Fleet is the SSE for fleet satellite (FLTSAT) and ultrahigh frequency follow-on ( UFO ). b...direct support of Navy and joint forces. These systems include FLTSAT, UFO , MUOS, and varied payloads (Interim Polar and GBS). 10. Air Force Component...33-50 GHz S S-band, 2-4 GHz SHF super high frequency UFO ultrahigh frequency (UHF) follow-on WGS Wideband Global Satellite Communications System X

On the temporal and spatial characteristics of tornado days in the United States

NASA Astrophysics Data System (ADS)

Moore, Todd W.

2017-02-01

More tornadoes are produced per year in the United States than in any other country, and these tornadoes have produced tremendous losses of life and property. Understanding how tornado activity will respond to climate change is important if we wish to prepare for future changes. Trends in various tornado and tornado day characteristics, including their annual frequencies, their temporal variability, and their spatial distributions, have been reported in the past few years. This study contributes to this body of literature by further analyzing the temporal and spatial characteristics of tornado days in the United States. The analyses performed in this study support previously reported findings in addition to providing new perspectives, including that the temporal trends are observed only in low-frequency and high-frequency tornado days and that the eastward shift in tornado activity is produced, in part, by the increasing number of high-frequency tornado days, which tend to occur to the east of the traditionally depicted tornado alley in the Great Plains.

Analysis of high-frequency oscillations in mutually-coupled nano-lasers.

PubMed

Han, Hong; Shore, K Alan

2018-04-16

The dynamics of mutually coupled nano-lasers has been analyzed using rate equations which include the Purcell cavity-enhanced spontaneous emission factor F and the spontaneous emission coupling factor β. It is shown that in the mutually-coupled system, small-amplitude oscillations with frequencies of order 100 GHz are generated and are maintained with remarkable stability. The appearance of such high-frequency oscillations is associated with the effective reduction of the carrier lifetime for larger values of the Purcell factor, F, and spontaneous coupling factor, β. In mutually-coupled nano-lasers the oscillation frequency changes linearly with the frequency detuning between the lasers. For non-identical bias currents, the oscillation frequency of mutually-coupled nano-lasers also increases with bias current. The stability of the oscillations which appear in mutually coupled nano-lasers offers opportunities for their practical applications and notably in photonic integrated circuits.

Investigating the Quality of Service of Current and Future Tactical Information Exchanges - Net Warrior

DTIC Science & Technology

2010-05-01

as Link-11, Link-16 and VMF. It also includes future systems such as Link-22 (using the typical HF & UHF frequency bands) and technologies that...triangulate and find the precise geolocation of the enemy target. If the target happens to relocate, TTNT is able to update the target with high accuracy...22 operates in either the HF or UHF frequency bands. In each of these frequency bands the system can operate on a single frequency or a pseudo-random

High Torque-to-Inertia Servo System for Stabilizing Sensor Systems. Candidate Systems Include Missile Guidance, Surveillance, and Tracking

DTIC Science & Technology

1980-04-01

specifications ... 3-10 25. Typical isolation curve ... 3-12 26. Servo amp/motor/load frequency response (inner gimbal) ... 4-3 27. Slave loop ( open loop...slave loop ( open loop) frequency response (inner gimbal) . . . 4-4 30. Slave loop (closed loop) frequency response (inner gimbal) ... 4-5 3 . Slave...loop inner gimbal time response ... 4-5 32. Servo amp/motor/load frequency response (outer gimbal) ... 4-6 33. Slave loop ( open loop) uncompensated

Chip-Scale Architectures for Precise Optical Frequency Synthesis

NASA Astrophysics Data System (ADS)

Yang, Jinghui

Scientists and engineers have investigated various types of stable and accurate optical synthesizers, where mode-locked laser based optical frequency comb synthesizers have been widely investigated. These frequency combs bridge the frequencies from optical domain to microwave domain with orders of magnitude difference, providing a metrological tool for various platforms. The demand for highly robust, scalable, compact and cost-effective femtosecond-laser synthesizers, however, are of great importance for applications in air- or space-borne platforms, where low cost and rugged packaging are particularly required. This has been afforded in the past several years due to breakthroughs in chip-scale nanofabrication, bringing advances in optical frequency combs down to semiconductor chips. These platforms, with significantly enhanced light-matter interaction, provide a fertile sandbox for research rich in nonlinear dynamics, and offer a reliable route towards low-phase noise photonic oscillators, broadband optical frequency synthesizers, miniaturized optical clockwork, and coherent terabit communications. The dissertation explores various types of optical frequency comb synthesizers based on nonlinear microresonators. Firstly, the fundamental mechanism of mode-locking in a high-quality factor microresonator is examined, supported by ultrafast optical characterizations, analytical closed-form solutions and numerical modeling. In the evolution of these frequency microcombs, the key nonlinear dynamical effect governing the comb state coherence is rigorously analyzed. Secondly, a prototype of chip-scale optical frequency synthesizer is demonstrated, with the laser frequency comb stabilized down to instrument-limited 50-mHz RF frequency inaccuracies and 10-16 fractional frequency inaccuracies, near the fundamental limits. Thirdly, a globally stable Turing pattern is achieved and characterized in these nonlinear resonators with high-efficiency conversion, subsequently generating coherent high-power terahertz radiation via plasmonic photomixers. Finally, a new universal modality of frequency combs is discussed, including satellite states, dynamical tunability, and high efficiency conversion towards direct chip-scale optical frequency synthesis at the precision metrology frontiers.

Exploring the limits of frequency lowering

PubMed Central

Souza, Pamela E.; Arehart, Kathryn H.; Kates, James M.; Croghan, Naomi B.H.; Gehani, Namita

2013-01-01

Objective This study examined how frequency lowering affected sentence intelligibility and quality, for adults with postlingually acquired, mild-to-moderate hearing loss. Method Listeners included adults aged 60–92 years with sloping sensorineural loss and a control group of similarly-aged adults with normal hearing. Sentences were presented in quiet and babble at a range of signal-to-noise ratios. Intelligibility and quality were measured with varying amounts of frequency lowering, implemented using a form of frequency compression. Results Moderate amounts of compression, particularly with high cutoff frequencies, had minimal effects on intelligibility. Listeners with the greatest high-frequency hearing loss showed the greatest benefit. Sentence intelligibility decreased with more compression. Listeners were more affected by a given set of parameters in noise. In quiet, any amount of compression resulted in lower speech quality for most listeners, with the greatest degradation for listeners with better high-frequency hearing. Quality ratings were lower with background noise, and in noise the effect of changing compression parameters was small. Conclusions The benefits of frequency lowering in adults were affected by the compression parameters as well as individual hearing thresholds. Data are consistent with the idea that frequency lowering can be viewed in terms of an improved audibility vs increased distortion tradeoff. PMID:23785188

Optimum conditions for producing Cs2 molecular condensates by stimulated Raman adiabatic passage

NASA Astrophysics Data System (ADS)

Feng, Zhifang; Li, Weidong; Wang, Lirong; Xiao, Liantuan; Jia, Suotang

2009-10-01

The optimum conditions for producing Cs2 molecular condensates from Cs atomic condensates with high transfer efficiency by stimulated Raman adiabatic passage are presented. Under the extended “two-photon” resonance condition, including the two-photon process, the mean-field correction, and the tunneling coupling between two upper excited molecular levels, a high and stable conversion efficiency is realized. The high conversion efficiency could be achieved by following two methods under experimentally less demanding conditions (relatively small effective Rabi frequency for pump laser pulse). One is adjusting the detuning difference between two laser pulses for same effective Rabi frequencies with up to 87.2% transfer efficiency. Another one is adjusting the effective Rabi frequency, the detuning of dump laser for given effective Rabi frequency, and the detuning of pump laser with up to 80.7% transfer efficiency.

Broadband linear high-voltage amplifier for radio frequency ion traps.

PubMed

Kuhlicke, Alexander; Palis, Klaus; Benson, Oliver

2014-11-01

We developed a linear high-voltage amplifier for small capacitive loads consisting of a high-voltage power supply and a transistor amplifier. With this cost-effective circuit including only standard parts sinusoidal signals with a few volts can be amplified to 1.7 kVpp over a usable frequency range at large-signal response spanning four orders of magnitude from 20 Hz to 100 kHz under a load of 10 pF. For smaller output voltages the maximum frequency shifts up to megahertz. We test different capacitive loads to probe the influence on the performance. The presented amplifier is sustained short-circuit proof on the output side, which is a significant advantage over other amplifier concepts. The amplifier can be used to drive radio frequency ion traps for single charged nano- and microparticles, which will be presented in brief.

High Frequency Acoustic Reflection and Transmission in Ocean Sediments

DTIC Science & Technology

2005-09-30

the magnitude and phase of the reflection coefficient from a smooth water/sand interface with elastic and poroelastic models ”, J. Acoust . Soc. Am...physical model of high-frequency acoustic interaction with the ocean floor, including penetration through and reflection from smooth and rough water...and additional laboratory measurements in the ARL:UT sand tank, an improved model of sediment acoustics will be developed that is consistent with

Multimachine data–based prediction of high-frequency sensor signal noise for resistive wall mode control in ITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yueqiang; Sabbagh, S. A.; Chapman, I. T.

The high-frequency noise measured by magnetic sensors, at levels above the typical frequency of resistive wall modes, is analyzed across a range of present tokamak devices including DIII-D, JET, MAST, ASDEX Upgrade, JT-60U, and NSTX. A high-pass filter enables identification of the noise component with Gaussian-like statistics that shares certain common characteristics in all devices considered. A conservative prediction is made for ITER plasma operation of the high-frequency noise component of the sensor signals, to be used for resistive wall mode feedback stabilization, based on the multimachine database. The predicted root-mean-square n = 1 (n is the toroidal mode number)more » noise level is 10 4 to 10 5 G/s for the voltage signal, and 0.1 to 1 G for the perturbed magnetic field signal. The lower cutoff frequency of the Gaussian pickup noise scales linearly with the sampling frequency, with a scaling coefficient of about 0.1. As a result, these basic noise characteristics should be useful for the modeling-based design of the feedback control system for the resistive wall mode in ITER.« less

Multimachine data–based prediction of high-frequency sensor signal noise for resistive wall mode control in ITER

DOE PAGES

Liu, Yueqiang; Sabbagh, S. A.; Chapman, I. T.; ...

2017-03-27

The high-frequency noise measured by magnetic sensors, at levels above the typical frequency of resistive wall modes, is analyzed across a range of present tokamak devices including DIII-D, JET, MAST, ASDEX Upgrade, JT-60U, and NSTX. A high-pass filter enables identification of the noise component with Gaussian-like statistics that shares certain common characteristics in all devices considered. A conservative prediction is made for ITER plasma operation of the high-frequency noise component of the sensor signals, to be used for resistive wall mode feedback stabilization, based on the multimachine database. The predicted root-mean-square n = 1 (n is the toroidal mode number)more » noise level is 10 4 to 10 5 G/s for the voltage signal, and 0.1 to 1 G for the perturbed magnetic field signal. The lower cutoff frequency of the Gaussian pickup noise scales linearly with the sampling frequency, with a scaling coefficient of about 0.1. As a result, these basic noise characteristics should be useful for the modeling-based design of the feedback control system for the resistive wall mode in ITER.« less

Frequency Response Assessment and Enhancement of the U.S. Power Grids towards Extra-High Photovoltaic Generation Penetrations – an Industry Perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yong; You, Shutang; Tan, Jin

Nonsynchronous generations such as photovoltaics (PVs) are expected to undermine bulk power systems (BPSs)' frequency response at high penetration levels. Though the underlying mechanism has been relatively well understood, the accurate assessment and effective enhancement of the U.S. interconnections, frequency response under extra-high PV penetration conditions remains an issue. In this paper, the industry-provided full-detail interconnection models were further validated by synchrophasor frequency measurements and realistically-projected PV geographic distribution information were used to develop extra-high PV penetration scenarios and dynamic models for the three main U.S. interconnections, including Eastern Interconnection (EI), Western Electricity Coordinating Council (WECC), and Electric Reliability Councilmore » of Texas (ERCOT). Up to 65% instantaneous PV and 15% wind penetration were simulated and the frequency response change trend of each U.S. interconnection due to the increasing PV penetration level were examined. Most importantly, the practical solutions to address the declining frequency response were discussed. This paper will provide valuable guidance for policy makers, utility operators and academic researchers not only in the U.S. but also other countries in the world.« less

Frequency Response Assessment and Enhancement of the U.S. Power Grids towards Extra-High Photovoltaic Generation Penetrations – an Industry Perspective

DOE PAGES

Liu, Yong; You, Shutang; Tan, Jin; ...

2018-01-30

Nonsynchronous generations such as photovoltaics (PVs) are expected to undermine bulk power systems (BPSs)' frequency response at high penetration levels. Though the underlying mechanism has been relatively well understood, the accurate assessment and effective enhancement of the U.S. interconnections, frequency response under extra-high PV penetration conditions remains an issue. In this paper, the industry-provided full-detail interconnection models were further validated by synchrophasor frequency measurements and realistically-projected PV geographic distribution information were used to develop extra-high PV penetration scenarios and dynamic models for the three main U.S. interconnections, including Eastern Interconnection (EI), Western Electricity Coordinating Council (WECC), and Electric Reliability Councilmore » of Texas (ERCOT). Up to 65% instantaneous PV and 15% wind penetration were simulated and the frequency response change trend of each U.S. interconnection due to the increasing PV penetration level were examined. Most importantly, the practical solutions to address the declining frequency response were discussed. This paper will provide valuable guidance for policy makers, utility operators and academic researchers not only in the U.S. but also other countries in the world.« less

78 FR 46536 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-01

... eddy current inspection of the fastener holes for defects and repair if necessary. We are proposing... also includes doing a high frequency eddy current inspection of the fastener holes for defects and... frequency eddy current inspection of the fastener holes for defects and all applicable repairs, in...

Physical and Psychological Effects of Head Treatment in the Supine Position Using Specialized Ayurveda-Based Techniques

PubMed Central

Iwawaki, Yoko; Uebaba, Kazuo; Yamamoto, Yoko; Takishita, Yukie; Harada, Kiyomi; Shibata, Akemi; Narumoto, Jin; Fukui, Kenji

2016-01-01

Abstract Objective: To clarify the physical and psychological effects of head massage performed in the supine position using Ayurveda-based techniques (head treatment). Design: Twenty-four healthy female students were included in the study. Using a crossover study design, the same participants were enrolled in both the head treatment intervention group and control group. There was an interval of 1 week or more between measurements. Outcome measures: The physiologic indices measured included blood pressure and heart rate fluctuations (high frequency and low frequency/high frequency). The psychological markers measured included liveliness, depression, and boredom using the visual analogue scale method. State anxiety was measured using the State-Trait Anxiety Inventory method. Results: The parasympathetic nerve activity increased immediately after head treatment. Upon completion of head treatment, the parasympathetic nerve predominance tended to gradually ease. Head treatment boosted freshness and relieved anxiety. Conclusions: The results suggest that head treatment has a relaxing and refreshing effect and may be used to provide comfort. PMID:27163344

Alcohol marketing in televised international football: frequency analysis

PubMed Central

2014-01-01

Background Alcohol marketing includes sponsorship of individuals, organisations and sporting events. Football (soccer) is one of the most popular spectator sports worldwide. No previous studies have quantified the frequency of alcohol marketing in a high profile international football tournament. The aims were to determine: the frequency and nature of visual references to alcohol in a representative sample of EURO2012 matches broadcast in the UK; and if frequency or nature varied between matches broadcast on public service and commercial channels, or between matches that did and did not feature England. Methods Eight matches selected by stratified random sampling were recorded. All visual references to alcohol were identified using a tool with high inter-rater reliability. Results 1846 visual references to alcohol were identified over 1487 minutes of broadcast - an average of 1.24 references per minute. The mean number of references per minute was higher in matches that did vs did not feature England (p = 0.004), but did not differ between matches broadcast on public service vs commercial channels (p = 0.92). Conclusions The frequency of visual references to alcohol was universally high and higher in matches featuring the only UK home team - England - suggesting that there may be targeting of particularly highly viewed matches. References were embedded in broadcasts, and not particular to commercial channels including paid-for advertising. New UK codes-of-conduct on alcohol marketing at sporting events will not reduce the level of marketing reported here. PMID:24885718

Cerebral Palsy

MedlinePlus

... movement disorder. Neuroimaging methods include: Cranial ultrasound uses high-frequency sound waves to produce pictures of the brains of young babies. It is used for high-risk premature infants because it is the least ...

Advanced RF and microwave functions based on an integrated optical frequency comb source.

PubMed

Xu, Xingyuan; Wu, Jiayang; Nguyen, Thach G; Shoeiby, Mehrdad; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

2018-02-05

We demonstrate advanced transversal radio frequency (RF) and microwave functions based on a Kerr optical comb source generated by an integrated micro-ring resonator. We achieve extremely high performance for an optical true time delay aimed at tunable phased array antenna applications, as well as reconfigurable microwave photonic filters. Our results agree well with theory. We show that our true time delay would yield a phased array antenna with features that include high angular resolution and a wide range of beam steering angles, while the microwave photonic filters feature high Q factors, wideband tunability, and highly reconfigurable filtering shapes. These results show that our approach is a competitive solution to implementing reconfigurable, high performance and potentially low cost RF and microwave signal processing functions for applications including radar and communication systems.

Wedding ring shaped excitation coil

DOEpatents

MacLennan, Donald A.; Tsai, Peter

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/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.

High Frequency Adaptive Instability Suppression Controls in a Liquid-Fueled Combustor

NASA Technical Reports Server (NTRS)

Kopasakis, George

2003-01-01

This effort extends into high frequency (>500 Hz), an earlier developed adaptive control algorithm for the suppression of thermo-acoustic instabilities in a liquidfueled combustor. The earlier work covered the development of a controls algorithm for the suppression of a low frequency (280 Hz) combustion instability based on simulations, with no hardware testing involved. The work described here includes changes to the simulation and controller design necessary to control the high frequency instability, augmentations to the control algorithm to improve its performance, and finally hardware testing and results with an experimental combustor rig developed for the high frequency case. The Adaptive Sliding Phasor Averaged Control (ASPAC) algorithm modulates the fuel flow in the combustor with a control phase that continuously slides back and forth within the phase region that reduces the amplitude of the instability. The results demonstrate the power of the method - that it can identify and suppress the instability even when the instability amplitude is buried in the noise of the combustor pressure. The successful testing of the ASPAC approach helped complete an important NASA milestone to demonstrate advanced technologies for low-emission combustors.

Transparent megahertz circuits from solution-processed composite thin films.

PubMed

Liu, Xingqiang; Wan, Da; Wu, Yun; Xiao, Xiangheng; Guo, Shishang; Jiang, Changzhong; Li, Jinchai; Chen, Tangsheng; Duan, Xiangfeng; Fan, Zhiyong; Liao, Lei

2016-04-21

Solution-processed amorphous oxide semiconductors have attracted considerable interest in large-area transparent electronics. However, due to its relative low carrier mobility (∼10 cm(2) V(-1) s(-1)), the demonstrated circuit performance has been limited to 800 kHz or less. Herein, we report solution-processed high-speed thin-film transistors (TFTs) and integrated circuits with an operation frequency beyond the megahertz region on 4 inch glass. The TFTs can be fabricated from an amorphous indium gallium zinc oxide/single-walled carbon nanotube (a-IGZO/SWNT) composite thin film with high yield and high carrier mobility of >70 cm(2) V(-1) s(-1). On-chip microwave measurements demonstrate that these TFTs can deliver an unprecedented operation frequency in solution-processed semiconductors, including an extrinsic cut-off frequency (f(T) = 102 MHz) and a maximum oscillation frequency (f(max) = 122 MHz). Ring oscillators further demonstrated an oscillation frequency of 4.13 MHz, for the first time, realizing megahertz circuit operation from solution-processed semiconductors. Our studies represent an important step toward high-speed solution-processed thin film electronics.

Peak high-frequency HRV and peak alpha frequency higher in PTSD.

PubMed

Wahbeh, Helané; Oken, Barry S

2013-03-01

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.

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

The Polar Plasma Wave Instrument

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Persoon, A. M.; Randall, R. F.; Odem, D. L.; Remington, S. L.; Averkamp, T. F.; Debower, M. M.; Hospodarsky, G. B.; Huff, R. L.; Kirchner, D. L.

1995-01-01

The Plasma Wave Instrument on the Polar spacecraft is designed to provide measurements of plasma waves in the Earth's polar regions over the frequency range from 0.1 Hz to 800 kHz. Three orthogonal electric dipole antennas are used to detect electric fields, two in the spin plane and one aligned along the spacecraft spin axis. A magnetic loop antenna and a triaxial magnetic search coil antenna are used to detect magnetic fields. Signals from these antennas are processed by five receiver systems: a wideband receiver, a high-frequency waveform receiver, a low-frequency waveform receiver, two multichannel analyzers; and a pair of sweep frequency receivers. Compared to previous plasma wave instruments, the Polar plasma wave instrument has several new capabilities. These include (1) an expanded frequency range to improve coverage of both low- and high-frequency wave phenomena, (2) the ability to simultaneously capture signals from six orthogonal electric and magnetic field sensors, and (3) a digital wideband receiver with up to 8-bit resolution and sample rates as high as 249k samples s(exp -1).

[Effect of coherent extremely high-frequency and low-intensity electromagnetic radiation on the activity of membrane systems in Escherichia coli].

PubMed

Tadevosian, A; Trchunian, A

2009-01-01

It has been shown that the exposure of wild-type Escherichia coli K12 bacteria grown in anaerobic conditions upon fermentation of glucose to coherent extremely high-frequency (51.8 and 53 GHz) electromagnetic radiation (EMR) or millimeter waves (wavelength 5.8 to 6.7 mm) of low intensity (flux capacity 0.06 mW/cm2) caused a marked decrease in energy-dependent and N,N'-dicyclohexylcarbodiimide- or azide-sensitive proton and potassium ions transport fluxes through the membrane, including proton fluxes via proton F0F1-ATPase and through the potassium uptake Trk system, correspondingly. K+ uptake was less for the E. coli mutant Trk 1110. The rate of molecular hydrogen production by formate hydrogen lyase 2 is strongly inhibited. The results indicate that the bacterial effect of coherent extremely high-frequency EMR includes changes in the activity of membrane transport and enzymatic systems in which the F0F1-ATPase plays a key role.

Interplay between morphology and frequency in lexical access: The case of the base frequency effect

PubMed Central

Vannest, Jennifer; Newport, Elissa L.; Newman, Aaron J.; Bavelier, Daphne

2011-01-01

A major issue in lexical processing concerns storage and access of lexical items. Here we make use of the base frequency effect to examine this. Specifically, reaction time to morphologically complex words (words made up of base and suffix, e.g., agree+able) typically reflects frequency of the base element (i.e., total frequency of all words in which agree appears) rather than surface word frequency (i.e., frequency of agreeable itself). We term these complex words decomposable. However, a class of words termed whole-word do not show such sensitivity to base frequency (e.g., serenity). Using an event-related MRI design, we exploited the fact that processing low-frequency words increases BOLD activity relative to high frequency ones, and examined effects of base frequency on brain activity for decomposable and whole-word items. Morphologically complex words, half high and half low base frequency, were compared to matched high and low frequency simple monomorphemic words using a lexical decision task. Morphologically complex words increased activation in left inferior frontal and left superior temporal cortices versus simple words. The only area to mirror the behavioral distinction between decomposable and whole-word types was the thalamus. Surprisingly, most frequency-sensitive areas failed to show base frequency effects. This variety of responses to frequency and word type across brain areas supports an integrative view of multiple variables during lexical access, rather than a dichotomy between memory-based access and on-line computation. Lexical access appears best captured as interplay of several neural processes with different sensitivities to various linguistic factors including frequency and morphological complexity. PMID:21167136

Global Observations of Magnetospheric High-m Poloidal Waves During the 22 June 2015 Magnetic Storm

NASA Technical Reports Server (NTRS)

Le, G.; Chi, P. J.; Strangeway, R. J.; Russell, C. T.; Slavin, J. A.; Takahashi, K.; Singer, H. J.; Anderson, B. J.; Bromund, K.; Fischer, D.;

Global observations of magnetospheric high-m poloidal waves during the 22 June 2015 magnetic storm.

PubMed

Le, G; Chi, P J; Strangeway, R J; Russell, C T; Slavin, J A; Takahashi, K; Singer, H J; Anderson, B J; Bromund, K; Fischer, D; Kepko, E L; Magnes, W; Nakamura, R; Plaschke, F; Torbert, R B

2017-04-28

We report global observations of high- m poloidal waves during the recovery phase of the 22 June 2015 magnetic storm from a constellation of widely spaced satellites of five missions including Magnetospheric Multiscale (MMS), Van Allen Probes, Time History of Events and Macroscale Interactions during Substorm (THEMIS), Cluster, and Geostationary Operational Environmental Satellites (GOES). The combined observations demonstrate the global spatial extent of storm time poloidal waves. MMS observations confirm high azimuthal wave numbers ( m  ~ 100). Mode identification indicates the waves are associated with the second harmonic of field line resonances. The wave frequencies exhibit a decreasing trend as L increases, distinguishing them from the single-frequency global poloidal modes normally observed during quiet times. Detailed examination of the instantaneous frequency reveals discrete spatial structures with step-like frequency changes along L . Each discrete L shell has a steady wave frequency and spans about 1  R E , suggesting that there exist a discrete number of drift-bounce resonance regions across L shells during storm times.

Stop Saying That It Is Wrong! Psychophysiological, Cognitive, and Metacognitive Markers of Children’s Sensitivity to Punishment

PubMed Central

Gonzalez-Gadea, Maria Luz; Scheres, Anouk; Tobon, Carlos Andres; Damm, Juliane; Baez, Sandra; Huepe, David; Marino, Julian; Marder, Sandra; Manes, Facundo; Abrevaya, Sofia; Ibanez, Agustin

2015-01-01

Neurodevelopmental evidence suggests that children’s main decision-making strategy is to avoid options likely to induce punishment. However, the cognitive and affective factors contributing to children’s avoidance to high punishment frequency remain unknown. The present study explored psychophysiological, cognitive, and metacognitive processes associated with sensitivity to punishment frequency. We evaluated 54 participants (between 8 and 15 years old) with a modified Iowa Gambling Task for children (IGT-C) which included options with varying long-term profit and punishment frequencies. Skin conductance responses (SCRs) were recorded during this task. Additionally, we assessed IGT-C metacognitive knowledge, fluid intelligence, and executive functions. Participants exhibited behavioral avoidance and high anticipatory SCRs to options with high frequency of punishment. Moreover, age, IGT-C metacognitive knowledge, and inhibitory control were associated with individual differences in sensitivity to punishment frequency. Our results suggest that children’s preference for infrequently punished decisions is partially explained by psychophysiological signals as well as task complexity and development of cognitive control. PMID:26218584

Stop Saying That It Is Wrong! Psychophysiological, Cognitive, and Metacognitive Markers of Children's Sensitivity to Punishment.

PubMed

Gonzalez-Gadea, Maria Luz; Scheres, Anouk; Tobon, Carlos Andres; Damm, Juliane; Baez, Sandra; Huepe, David; Marino, Julian; Marder, Sandra; Manes, Facundo; Abrevaya, Sofia; Ibanez, Agustin

2015-01-01

Neurodevelopmental evidence suggests that children's main decision-making strategy is to avoid options likely to induce punishment. However, the cognitive and affective factors contributing to children's avoidance to high punishment frequency remain unknown. The present study explored psychophysiological, cognitive, and metacognitive processes associated with sensitivity to punishment frequency. We evaluated 54 participants (between 8 and 15 years old) with a modified Iowa Gambling Task for children (IGT-C) which included options with varying long-term profit and punishment frequencies. Skin conductance responses (SCRs) were recorded during this task. Additionally, we assessed IGT-C metacognitive knowledge, fluid intelligence, and executive functions. Participants exhibited behavioral avoidance and high anticipatory SCRs to options with high frequency of punishment. Moreover, age, IGT-C metacognitive knowledge, and inhibitory control were associated with individual differences in sensitivity to punishment frequency. Our results suggest that children's preference for infrequently punished decisions is partially explained by psychophysiological signals as well as task complexity and development of cognitive control.

Clonal evolution revealed by whole genome sequencing in a case of primary myelofibrosis transformed to secondary acute myeloid leukemia.

PubMed

Engle, E K; Fisher, D A C; Miller, C A; McLellan, M D; Fulton, R S; Moore, D M; Wilson, R K; Ley, T J; Oh, S T

2015-04-01

Clonal architecture in myeloproliferative neoplasms (MPNs) is poorly understood. Here we report genomic analyses of a patient with primary myelofibrosis (PMF) transformed to secondary acute myeloid leukemia (sAML). Whole genome sequencing (WGS) was performed on PMF and sAML diagnosis samples, with skin included as a germline surrogate. Deep sequencing validation was performed on the WGS samples and an additional sample obtained during sAML remission/relapsed PMF. Clustering analysis of 649 validated somatic single-nucleotide variants revealed four distinct clonal groups, each including putative driver mutations. The first group (including JAK2 and U2AF1), representing the founding clone, included mutations with high frequency at all three disease stages. The second clonal group (including MYB) was present only in PMF, suggesting the presence of a clone that was dispensable for transformation. The third group (including ASXL1) contained mutations with low frequency in PMF and high frequency in subsequent samples, indicating evolution of the dominant clone with disease progression. The fourth clonal group (including IDH1 and RUNX1) was acquired at sAML transformation and was predominantly absent at sAML remission/relapsed PMF. Taken together, these findings illustrate the complex clonal dynamics associated with disease evolution in MPNs and sAML.

Respiratory muscle activity and patient–ventilator asynchrony during different settings of noninvasive ventilation in stable hypercapnic COPD: does high inspiratory pressure lead to respiratory muscle unloading?

PubMed Central

Duiverman, Marieke L; Huberts, Anouk S; van Eykern, Leo A; Bladder, Gerrie; Wijkstra, Peter J

2017-01-01

Introduction High-intensity noninvasive ventilation (NIV) has been shown to improve outcomes in stable chronic obstructive pulmonary disease patients. However, there is insufficient knowledge about whether with this more controlled ventilatory mode optimal respiratory muscle unloading is provided without an increase in patient–ventilator asynchrony (PVA). Patients and methods Ten chronic obstructive pulmonary disease patients on home mechanical ventilation were included. Four different ventilatory settings were investigated in each patient in random order, each for 15 min, varying the inspiratory positive airway pressure and backup breathing frequency. With surface electromyography (EMG), activities of the intercostal muscles, diaphragm, and scalene muscles were determined. Furthermore, pressure tracings were derived simultaneously in order to assess PVA. Results Compared to spontaneous breathing, the most pronounced decrease in EMG activity was achieved with the high-pressure settings. Adding a high breathing frequency did reduce EMG activity per breath, while the decrease in EMG activity over 1 min was comparable with the high-pressure, low-frequency setting. With high backup breathing frequencies less breaths were pressure supported (25% vs 97%). PVAs occurred more frequently with the low-frequency settings (P=0.017). Conclusion High-intensity NIV might provide optimal unloading of respiratory muscles, without undue increases in PVA. PMID:28138234

Respiratory muscle activity and patient-ventilator asynchrony during different settings of noninvasive ventilation in stable hypercapnic COPD: does high inspiratory pressure lead to respiratory muscle unloading?

PubMed

Duiverman, Marieke L; Huberts, Anouk S; van Eykern, Leo A; Bladder, Gerrie; Wijkstra, Peter J

2017-01-01

High-intensity noninvasive ventilation (NIV) has been shown to improve outcomes in stable chronic obstructive pulmonary disease patients. However, there is insufficient knowledge about whether with this more controlled ventilatory mode optimal respiratory muscle unloading is provided without an increase in patient-ventilator asynchrony (PVA). Ten chronic obstructive pulmonary disease patients on home mechanical ventilation were included. Four different ventilatory settings were investigated in each patient in random order, each for 15 min, varying the inspiratory positive airway pressure and backup breathing frequency. With surface electromyography (EMG), activities of the intercostal muscles, diaphragm, and scalene muscles were determined. Furthermore, pressure tracings were derived simultaneously in order to assess PVA. Compared to spontaneous breathing, the most pronounced decrease in EMG activity was achieved with the high-pressure settings. Adding a high breathing frequency did reduce EMG activity per breath, while the decrease in EMG activity over 1 min was comparable with the high-pressure, low-frequency setting. With high backup breathing frequencies less breaths were pressure supported (25% vs 97%). PVAs occurred more frequently with the low-frequency settings ( P =0.017). High-intensity NIV might provide optimal unloading of respiratory muscles, without undue increases in PVA.

High-power ultrafast Yb:fiber laser frequency combs using commercially available components and basic fiber tools

NASA Astrophysics Data System (ADS)

Li, Xinlong; Reber, Melanie A. R.; Corder, Christopher; Chen, Yuning; Zhao, Peng; Allison, Thomas K.

2016-09-01

We present a detailed description of the design, construction, and performance of high-power ultrafast Yb:fiber laser frequency combs in operation in our laboratory. We discuss two such laser systems: an 87 MHz, 9 W, 85 fs laser operating at 1060 nm and an 87 MHz, 80 W, 155 fs laser operating at 1035 nm. Both are constructed using low-cost, commercially available components, and can be assembled using only basic tools for cleaving and splicing single-mode fibers. We describe practical methods for achieving and characterizing low-noise single-pulse operation and long-term stability from Yb:fiber oscillators based on nonlinear polarization evolution. Stabilization of the combs using a variety of transducers, including a new method for tuning the carrier-envelope offset frequency, is discussed. High average power is achieved through chirped-pulse amplification in simple fiber amplifiers based on double-clad photonic crystal fibers. We describe the use of these combs in several applications, including ultrasensitive femtosecond time-resolved spectroscopy and cavity-enhanced high-order harmonic generation.

Navy Applications of High-Frequency Acoustics

NASA Astrophysics Data System (ADS)

Cox, Henry

2004-11-01

Although the emphasis in underwater acoustics for the last few decades has been in low-frequency acoustics, motivated by long range detection of submarines, there has been a continuing use of high-frequency acoustics in traditional specialized applications such as bottom mapping, mine hunting, torpedo homing and under ice navigation. The attractive characteristics of high-frequency sonar, high spatial resolution, wide bandwidth, small size and relatively low cost must be balanced against the severe range limitation imposed by attenuation that increases approximately as frequency-squared. Many commercial applications of acoustics are ideally served by high-frequency active systems. The small size and low cost, coupled with the revolution in small powerful signal processing hardware has led to the consideration of more sophisticated systems. Driven by commercial applications, there are currently available several commercial-off-the-shelf products including acoustic modems for underwater communication, multi-beam fathometers, side scan sonars for bottom mapping, and even synthetic aperture side scan sonar. Much of the work in high frequency sonar today continues to be focused on specialized applications in which the application is emphasized over the underlying acoustics. Today's vision for the Navy of the future involves Autonomous Undersea Vehicles (AUVs) and off-board ASW sensors. High-frequency acoustics will play a central role in the fulfillment of this vision as a means of communication and as a sensor. The acoustic communication problems for moving AUVs and deep sensors are discussed. Explicit relationships are derived between the communication theoretic description of channel parameters in terms of time and Doppler spreads and ocean acoustic parameters, group velocities, phase velocities and horizontal wavenumbers. Finally the application of synthetic aperture sonar to the mine hunting problems is described.

Coherent Doppler Lidar for Measuring Altitude, Ground Velocity, and Air Velocity of Aircraft and Spaceborne Vehicles

NASA Technical Reports Server (NTRS)

Amzajerdian, Farzin (Inventor); Pierrottet, Diego F. (Inventor)

2015-01-01

A Doppler lidar sensor system includes a laser generator that produces a highly pure single frequency laser beam, and a frequency modulator that modulates the laser beam with a highly linear frequency waveform. A first portion of the frequency modulated laser beam is amplified, and parts thereof are transmitted through at least three separate transmit/receive lenses. A second portion of the laser beam is used as a local oscillator beam for optical heterodyne detection. Radiation from the parts of the laser beam transmitted via the transmit/receive lenses is received by the respective transmit/receive lenses that transmitted the respective part of the laser beam. The received reflected radiation is compared with the local oscillator beam to calculate the frequency difference there between to determine various navigational data.

Interferometry theory for the block 2 processor

NASA Technical Reports Server (NTRS)

Thomas, J. B.

1987-01-01

Presented is the interferometry theory for the Block 2 processor, including a high-level functional description and a discussion of data structure. The analysis covers the major processing steps: cross-correlation, fringe counter-rotation, transformation to the frequency domain, phase calibration, bandwidth synthesis, and extraction of the observables of amplitude, phase, phase rate, and delay. Also included are analyses for fractional bitshift correction, station clock error, ionosphere correction, and effective frequencies for the observables.

Method and apparatus for radio frequency ceramic sintering

DOEpatents

Hoffman, Daniel J.; Kimrey, Jr., Harold D.

1993-01-01

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

Method and apparatus for radio frequency ceramic sintering

DOEpatents

Hoffman, D.J.; Kimrey, H.D. Jr.

1993-11-30

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents. 6 figures.

Dynamic Scattering Mode LCDs

NASA Astrophysics Data System (ADS)

Bahadur, Birendra

The following sections are included: * INTRODUCTION * CELL DESIGNING * EXPERIMENTAL OBSERVATIONS IN NEMATICS RELATED WITH DYNAMIC SCATTERING * Experimental Observations at D.C. Field and Electrode Effects * Experimental Observation at Low Frequency A.C. Fields * Homogeneously Aligned Nematic Regime * Williams Domains * Dynamic Scattering * Experimental Observation at High Frequency A.C. Field * Other Experimental Observations * THEORETICAL INTERPRETATIONS * Felici Model * Carr-Helfrich Model * D.C. Excitation * Dubois-Violette, de Gennes and Parodi Model * Low Freqency or Conductive Regime * High Frequency or Dielectric Regime * DYNAMIC SCATTERING IN SMECRIC A PHASE * ELECTRO-OPTICAL CHARACTERISTICS AND LIMITATIONS * Contrast Ratio vs. Voltage, Viewing Angle, Cell Gap, Wavelength and Temperature * Display Current vs. Voltage, Cell Gap and Temperature * Switching Time * Effect of Alignment * Effect of Conductivity, Temperature and Frequency * Addressing of DSM LCDs * Limitations of DSM LCDs * ACKNOWLEDGEMENTS * REFERENCES

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

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.

Climate Change: A New Metric to Measure Changes in the Frequency of Extreme Temperatures using Record Data

NASA Technical Reports Server (NTRS)

Munasinghe, L.; Jun, T.; Rind, D. H.

2012-01-01

Consensus on global warming is the result of multiple and varying lines of evidence, and one key ramification is the increase in frequency of extreme climate events including record high temperatures. Here we develop a metric- called "record equivalent draws" (RED)-based on record high (low) temperature observations, and show that changes in RED approximate changes in the likelihood of extreme high (low) temperatures. Since we also show that this metric is independent of the specifics of the underlying temperature distributions, RED estimates can be aggregated across different climates to provide a genuinely global assessment of climate change. Using data on monthly average temperatures across the global landmass we find that the frequency of extreme high temperatures increased 10-fold between the first three decades of the last century (1900-1929) and the most recent decade (1999-2008). A more disaggregated analysis shows that the increase in frequency of extreme high temperatures is greater in the tropics than in higher latitudes, a pattern that is not indicated by changes in mean temperature. Our RED estimates also suggest concurrent increases in the frequency of both extreme high and extreme low temperatures during 2002-2008, a period when we observe a plateauing of global mean temperature. Using daily extreme temperature observations, we find that the frequency of extreme high temperatures is greater in the daily minimum temperature time-series compared to the daily maximum temperature time-series. There is no such observable difference in the frequency of extreme low temperatures between the daily minimum and daily maximum.

GaN transistors on Si for switching and high-frequency applications

NASA Astrophysics Data System (ADS)

Ueda, Tetsuzo; Ishida, Masahiro; Tanaka, Tsuyoshi; Ueda, Daisuke

2014-10-01

In this paper, recent advances of GaN transistors on Si for switching and high-frequency applications are reviewed. Novel epitaxial structures including superlattice interlayers grown by metal organic chemical vapor deposition (MOCVD) relieve the strain and eliminate the cracks in the GaN over large-diameter Si substrates up to 8 in. As a new device structure for high-power switching application, Gate Injection Transistors (GITs) with a p-AlGaN gate over an AlGaN/GaN heterostructure successfully achieve normally-off operations maintaining high drain currents and low on-state resistances. Note that the GITs on Si are free from current collapse up to 600 V, by which the drain current would be markedly reduced after the application of high drain voltages. Highly efficient operations of an inverter and DC-DC converters are presented as promising applications of GITs for power switching. The high efficiencies in an inverter, a resonant LLC converter, and a point-of-load (POL) converter demonstrate the superior potential of the GaN transistors on Si. As for high-frequency transistors, AlGaN/GaN heterojuction field-effect transistors (HFETs) on Si designed specifically for microwave and millimeter-wave frequencies demonstrate a sufficiently high output power at these frequencies. Output powers of 203 W at 2.5 GHz and 10.7 W at 26.5 GHz are achieved by the fabricated GaN transistors. These devices for switching and high-frequency applications are very promising as future energy-efficient electronics because of their inherent low fabrication cost and superior device performance.

Characterization of Early Partial Seizure Onset: Frequency, Complexity and Entropy

PubMed Central

Jouny, Christophe C.; Bergey, Gregory K.

2011-01-01

Objective A clear classification of partial seizures onset features is not yet established. Complexity and entropy have been very widely used to describe dynamical systems, but a systematic evaluation of these measures to characterize partial seizures has never been performed. Methods Eighteen different measures including power in frequency bands up to 300Hz, Gabor atom density (GAD), Higuchi fractal dimension (HFD), Lempel-Ziv complexity, Shannon entropy, sample entropy, and permutation entropy, were selected to test sensitivity to partial seizure onset. Intracranial recordings from forty-five patients with mesial temporal, neocortical temporal and neocortical extratemporal seizure foci were included (331 partial seizures). Results GAD, Lempel-Ziv complexity, HFD, high frequency activity, and sample entropy were the most reliable measures to assess early seizure onset. Conclusions Increases in complexity and occurrence of high-frequency components appear to be commonly associated with early stages of partial seizure evolution from all regions. The type of measure (frequency-based, complexity or entropy) does not predict the efficiency of the method to detect seizure onset. Significance Differences between measures such as GAD and HFD highlight the multimodal nature of partial seizure onsets. Improved methods for early seizure detection may be achieved from a better understanding of these underlying dynamics. PMID:21872526

Effect of laser pulse shaping parameters on the fidelity of quantum logic gates.

PubMed

Zaari, Ryan R; Brown, Alex

2012-09-14

The effect of varying parameters specific to laser pulse shaping instruments on resulting fidelities for the ACNOT(1), NOT(2), and Hadamard(2) quantum logic gates are studied for the diatomic molecule (12)C(16)O. These parameters include varying the frequency resolution, adjusting the number of frequency components and also varying the amplitude and phase at each frequency component. A time domain analytic form of the original discretized frequency domain laser pulse function is derived, providing a useful means to infer the resulting pulse shape through variations to the aforementioned parameters. We show that amplitude variation at each frequency component is a crucial requirement for optimal laser pulse shaping, whereas phase variation provides minimal contribution. We also show that high fidelity laser pulses are dependent upon the frequency resolution and increasing the number of frequency components provides only a small incremental improvement to quantum gate fidelity. Analysis through use of the pulse area theorem confirms the resulting population dynamics for one or two frequency high fidelity laser pulses and implies similar dynamics for more complex laser pulse shapes. The ability to produce high fidelity laser pulses that provide both population control and global phase alignment is attributed greatly to the natural evolution phase alignment of the qubits involved within the quantum logic gate operation.

Ozone contamination in aircraft cabins - Results from GASP data and analyses

NASA Technical Reports Server (NTRS)

Holdeman, J. D.; Nastrom, G. D.

1981-01-01

The paper reviews results from the NASA Global Atmospheric Sampling Program (GASP) pertaining to the problem of ozone contamination in commercial aircraft cabins. Specifically, analyses of GASP data have (1) confirmed the high ozone levels in aircraft cabins and documented the ratio of ozone inside and outside the cabins of two B747 airliners, including the effects of air conditioning modifications on that ratio; (2) defined ambient ozone climatology at commercial aircraft cruise altitudes, including tabulation of encounter frequency data; and (3) outlined procedures for estimating the frequency of flights encountering high cabin ozone levels using climatological ambient ozone data and verified these procedures against cabin measurements.

Ozone contamination in aircraft cabins: Results from GASP data and analyses

NASA Technical Reports Server (NTRS)

Holdeman, J. D.; Nastrom, G. D.

1981-01-01

The global atmospheric sampling program pertaining to the problem of ozone contamination in commercial airplane cabins is described. Specifically, analyses of GASP data have: confirmed the occurrence of high ozone levels in aircraft cabins and documented the ratio of ozone inside and outside the cabins of two B747 airliners, including the effects of air conditioning modifications on that ratio; defined ambient ozone climatology at commercial airplane cruise altitudes, including tabulation of encounter frequency data which were not available before GASP; and outlined procedures for estimating the frequency of flights encountering high cabin ozone levels using climatological ambient ozone data, and verified these procedures against cabin measurements.

Swept-frequency feedback interferometry using terahertz frequency QCLs: a method for imaging and materials analysis.

PubMed

Rakić, Aleksandar D; Taimre, Thomas; Bertling, Karl; Lim, Yah Leng; Dean, Paul; Indjin, Dragan; Ikonić, Zoran; Harrison, Paul; Valavanis, Alexander; Khanna, Suraj P; Lachab, Mohammad; Wilson, Stephen J; Linfield, Edmund H; Davies, A Giles

2013-09-23

The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of high-power radiation with a narrow intrinsic linewidth. As such, THz QCLs are extremely promising sources for applications including high-resolution spectroscopy, heterodyne detection, and coherent imaging. We exploit the remarkable phase-stability of THz QCLs to create a coherent swept-frequency delayed self-homodyning method for both imaging and materials analysis, using laser feedback interferometry. Using our scheme we obtain amplitude-like and phase-like images with minimal signal processing. We determine the physical relationship between the operating parameters of the laser under feedback and the complex refractive index of the target and demonstrate that this coherent detection method enables extraction of complex refractive indices with high accuracy. This establishes an ultimately compact and easy-to-implement THz imaging and materials analysis system, in which the local oscillator, mixer, and detector are all combined into a single laser.

High power pumped MID-IR wavelength devices using nonlinear frequency mixing (NFM)

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

2001-01-01

Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

High power pumped mid-IR wavelength systems using nonlinear frequency mixing (NFM) devices

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

1999-01-01

Laser diode pumped mid-IR wavelength systems include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

Plastic straw: future of high-speed signaling

NASA Astrophysics Data System (ADS)

Song, Ha Il; Jin, Huxian; Bae, Hyeon-Min

2015-11-01

The ever-increasing demand for bandwidth triggered by mobile and video Internet traffic requires advanced interconnect solutions satisfying functional and economic constraints. A new interconnect called E-TUBE is proposed as a cost-and-power-effective all-electrical-domain wideband waveguide solution for high-speed high-volume short-reach communication links. The E-TUBE achieves an unprecedented level of performance in terms of bandwidth-per-carrier frequency, power, and density without requiring a precision manufacturing process unlike conventional optical/waveguide solutions. The E-TUBE exhibits a frequency-independent loss-profile of 4 dB/m and has nearly 20-GHz bandwidth over the V band. A single-sideband signal transmission enabled by the inherent frequency response of the E-TUBE renders two-times data throughput without any physical overhead compared to conventional radio frequency communication technologies. This new interconnect scheme would be attractive to parties interested in high throughput links, including but not limited to, 100/400 Gbps chip-to-chip communications.

The experience of high-frequency gambling behavior of older adult females in the United Kingdom: An interpretative phenomenological analysis.

PubMed

Pattinson, Julie; Parke, Adrian

2017-01-01

The prevalence of older adult female gambling participation and gambling disorder is increasing in the UK, and there is a paucity of published research available to understand possible risk factors for frequent gambling in this demographic. The aim of the current study was to identify and explore motivations and patterns of gambling behavior in high-frequency older adult female gamblers in the UK, from the perspective of the individual and in the context of their experience of aging. Ten UK older adult female high-frequency gamblers were recruited via stratified purposive sampling, with a mean age of 70.4 years. Data was collected via semistructured interviews and analyzed using interpretative phenomenological analysis. Three core themes representative of the experience of this phenomenon emerged from the transcripts, including: Filling voids, emotional escape, and overspending. The present study has provided a contextualized understanding of motivating factors and several age-related vulnerabilities that may account for high gambling frequency in this population.

The potential of high-frequency profiling to assess vertical and seasonal patterns of phytoplankton dynamics in lakes: An extension of the Plankton Ecology Group (PEG) model

USGS Publications Warehouse

Brentrup, Jennifer A.; Williamson, Craig E.; Colom-Montero, William; Eckert, Werner; de Eyto, Elvira; Grossart, Hans-Peter; Huot, Yannick; Isles, Peter D. F.; Knoll, Lesley B.; Leach, Taylor H.; McBride, Christopher G.; Pierson, Don; Pomati, Francesco; Read, Jordan S.; Rose, Kevin C.; Samal, Nihar R.; Staehr, Peter A.; Winslow, Luke A.

2016-01-01

The use of high-frequency sensors on profiling buoys to investigate physical, chemical, and biological processes in lakes is increasing rapidly. Profiling buoys with automated winches and sensors that collect high-frequency chlorophyll fluorescence (ChlF) profiles in 11 lakes in the Global Lake Ecological Observatory Network (GLEON) allowed the study of the vertical and temporal distribution of ChlF, including the formation of subsurface chlorophyll maxima (SSCM). The effectiveness of 3 methods for sampling phytoplankton distributions in lakes, including (1) manual profiles, (2) single-depth buoys, and (3) profiling buoys were assessed. High-frequency ChlF surface data and profiles were compared to predictions from the Plankton Ecology Group (PEG) model. The depth-integrated ChlF dynamics measured by the profiling buoy data revealed a greater complexity that neither conventional sampling nor the generalized PEG model captured. Conventional sampling techniques would have missed SSCM in 7 of 11 study lakes. Although surface-only ChlF data underestimated average water column ChlF, at times by nearly 2-fold in 4 of the lakes, overall there was a remarkable similarity between surface and mean water column data. Contrary to the PEG model’s proposed negligible role for physical control of phytoplankton during the growing season, thermal structure and light availability were closely associated with ChlF seasonal depth distribution. Thus, an extension of the PEG model is proposed, with a new conceptual framework that explicitly includes physical metrics to better predict SSCM formation in lakes and highlight when profiling buoys are especially informative.

Low-frequency 1/f noise in graphene devices

NASA Astrophysics Data System (ADS)

Balandin, Alexander A.

2013-08-01

Low-frequency noise with a spectral density that depends inversely on frequency has been observed in a wide variety of systems including current fluctuations in resistors, intensity fluctuations in music and signals in human cognition. In electronics, the phenomenon, which is known as 1/f noise, flicker noise or excess noise, hampers the operation of numerous devices and circuits, and can be a significant impediment to the development of practical applications from new materials. Graphene offers unique opportunities for studying 1/f noise because of its two-dimensional structure and widely tunable two-dimensional carrier concentration. The creation of practical graphene-based devices will also depend on our ability to understand and control the low-frequency noise in this material system. Here, the characteristic features of 1/f noise in graphene and few-layer graphene are reviewed, and the implications of such noise for the development of graphene-based electronics including high-frequency devices and sensors are examined.

Low-frequency 1/f noise in graphene devices.

PubMed

Balandin, Alexander A

2013-08-01

Low-frequency noise with a spectral density that depends inversely on frequency has been observed in a wide variety of systems including current fluctuations in resistors, intensity fluctuations in music and signals in human cognition. In electronics, the phenomenon, which is known as 1/f noise, flicker noise or excess noise, hampers the operation of numerous devices and circuits, and can be a significant impediment to the development of practical applications from new materials. Graphene offers unique opportunities for studying 1/f noise because of its two-dimensional structure and widely tunable two-dimensional carrier concentration. The creation of practical graphene-based devices will also depend on our ability to understand and control the low-frequency noise in this material system. Here, the characteristic features of 1/f noise in graphene and few-layer graphene are reviewed, and the implications of such noise for the development of graphene-based electronics including high-frequency devices and sensors are examined.

Electromagnetic interference modeling and suppression techniques in variable-frequency drive systems

NASA Astrophysics Data System (ADS)

Yang, Le; Wang, Shuo; Feng, Jianghua

2017-11-01

Electromagnetic interference (EMI) causes electromechanical damage to the motors and degrades the reliability of variable-frequency drive (VFD) systems. Unlike fundamental frequency components in motor drive systems, high-frequency EMI noise, coupled with the parasitic parameters of the trough system, are difficult to analyze and reduce. In this article, EMI modeling techniques for different function units in a VFD system, including induction motors, motor bearings, and rectifierinverters, are reviewed and evaluated in terms of applied frequency range, model parameterization, and model accuracy. The EMI models for the motors are categorized based on modeling techniques and model topologies. Motor bearing and shaft models are also reviewed, and techniques that are used to eliminate bearing current are evaluated. Modeling techniques for conventional rectifierinverter systems are also summarized. EMI noise suppression techniques, including passive filter, Wheatstone bridge balance, active filter, and optimized modulation, are reviewed and compared based on the VFD system models.

Method and system for efficient video compression with low-complexity encoder

NASA Technical Reports Server (NTRS)

Chen, Jun (Inventor); He, Dake (Inventor); Sheinin, Vadim (Inventor); Jagmohan, Ashish (Inventor); Lu, Ligang (Inventor)

2012-01-01

Disclosed are a method and system for video compression, wherein the video encoder has low computational complexity and high compression efficiency. The disclosed system comprises a video encoder and a video decoder, wherein the method for encoding includes the steps of converting a source frame into a space-frequency representation; estimating conditional statistics of at least one vector of space-frequency coefficients; estimating encoding rates based on the said conditional statistics; and applying Slepian-Wolf codes with the said computed encoding rates. The preferred method for decoding includes the steps of; generating a side-information vector of frequency coefficients based on previously decoded source data, encoder statistics, and previous reconstructions of the source frequency vector; and performing Slepian-Wolf decoding of at least one source frequency vector based on the generated side-information, the Slepian-Wolf code bits and the encoder statistics.

Factors associated with poor sleep during menopause: results from the Midlife Women's Health Study.

PubMed

Smith, Rebecca L; Flaws, Jodi A; Mahoney, Megan M

2018-05-01

Poor sleep is one of the most common problems reported during menopause, and is known to vary throughout the menopause transition. The objective of this study was to describe the dynamics of poor sleep among participants of the Midlife Women's Health Study and to identify risk factors associated with poor sleep during the menopausal transition. Annual responses to surveys that included questions about the frequency of sleep disturbances and insomnia were analyzed to determine the likelihood of persistent poor sleep throughout the menopausal transition and the correlation of responses to the different sleep-related questions, including frequency of restless sleep during the first year of the study. Responses to questions about a large number of potential risk factors were used to identify risk factors for poor sleep. Poor sleep in premenopause was not predictive of poor sleep in perimenopause, and poor sleep in perimenopause was not predictive of poor sleep in postmenopause. Frequencies of each of the measures of poor sleep were highly correlated. For all sleep outcomes, high frequency of depression was related to a high frequency of poor sleep. Vasomotor symptoms were also significantly related with a higher frequency of all poor sleep outcomes. A history of smoking was also associated with higher frequencies of insomnia and sleep disturbances. The risk factors identified for poor sleep, depression and vasomotor symptoms, were consistently associated with poor sleep throughout the menopausal transition. The likelihood of these risk factors changed from premenopause, through perimenopause, and into postmenopause, however, which could explain changes in sleep difficulties across the menopausal transition. Treatment of these risk factors should be considered when addressing sleep difficulties in menopausal women. Copyright © 2018 Elsevier B.V. All rights reserved.

Heart rate variability measured early in patients with evolving acute coronary syndrome and 1-year outcomes of rehospitalization and mortality.

PubMed

Harris, Patricia R E; Stein, Phyllis K; Fung, Gordon L; Drew, Barbara J

2014-01-01

This study sought to examine the prognostic value of heart rate variability (HRV) measurement initiated immediately after emergency department presentation for patients with acute coronary syndrome (ACS). Altered HRV has been associated with adverse outcomes in heart disease, but the value of HRV measured during the earliest phases of ACS related to risk of 1-year rehospitalization and death has not been established. Twenty-four-hour Holter recordings of 279 patients with ACS were initiated within 45 minutes of emergency department arrival; recordings with ≥18 hours of sinus rhythm were selected for HRV analysis (number [N] =193). Time domain, frequency domain, and nonlinear HRV were examined. Survival analysis was performed. During the 1-year follow-up, 94 patients were event-free, 82 were readmitted, and 17 died. HRV was altered in relation to outcomes. Predictors of rehospitalization included increased normalized high frequency power, decreased normalized low frequency power, and decreased low/high frequency ratio. Normalized high frequency >42 ms(2) predicted rehospitalization while controlling for clinical variables (hazard ratio [HR] =2.3; 95% confidence interval [CI] =1.4-3.8, P=0.001). Variables significantly associated with death included natural logs of total power and ultra low frequency power. A model with ultra low frequency power <8 ms(2) (HR =3.8; 95% CI =1.5-10.1; P=0.007) and troponin >0.3 ng/mL (HR =4.0; 95% CI =1.3-12.1; P=0.016) revealed that each contributed independently in predicting mortality. Nonlinear HRV variables were significant predictors of both outcomes. HRV measured close to the ACS onset may assist in risk stratification. HRV cut-points may provide additional, incremental prognostic information to established assessment guidelines, and may be worthy of additional study.

High-frequency ultrasonic methods for determining corrosion layer thickness of hollow metallic components.

PubMed

Liu, Hongwei; Zhang, Lei; Liu, Hong Fei; Chen, Shuting; Wang, Shihua; Wong, Zheng Zheng; Yao, Kui

2018-05-16

Corrosion in internal cavity is one of the most common problems occurs in many hollow metallic components, such as pipes containing corrosive fluids and high temperature turbines in aircraft. It is highly demanded to non-destructively detect the corrosion inside hollow components and determine the corrosion extent from the external side. In this work, we present two high-frequency ultrasonic non-destructive testing (NDT) technologies, including piezoelectric pulse-echo and laser-ultrasonic methods, for detecting corrosion of Ni superalloy from the opposite side. The determination of corrosion layer thickness below ∼100 µm has been demonstrated by both methods, in comparison with X-CT and SEM. With electron microscopic examination, it is found that with multilayer corrosion structure formed over a prolonged corrosion time, the ultrasonic NDT methods can only reliably reveal outer corrosion layer thickness because of the resulting acoustic contrast among the multiple layers due to their respective different mechanical parameters. A time-frequency signal analysis algorithm is employed to effectively enhance the high frequency ultrasonic signal contrast for the piezoelectric pulse-echo method. Finally, a blind test on a Ni superalloy turbine blade with internal corrosion is conducted with the high frequency piezoelectric pulser-receiver method. Copyright © 2018 Elsevier B.V. All rights reserved.

Higher-order vibrational mode frequency tuning utilizing fishbone-shaped microelectromechanical systems resonator

NASA Astrophysics Data System (ADS)

Suzuki, Naoya; Tanigawa, Hiroshi; Suzuki, Kenichiro

2013-04-01

Resonators based on microelectromechanical systems (MEMS) have received considerable attention for their applications for wireless equipment. The requirements for this application include small size, high frequency, wide bandwidth and high portability. However, few MEMS resonators with wide-frequency tuning have been reported. A fishbone-shaped resonator has a resonant frequency with a maximum response that can be changed according to the location and number of several exciting electrodes. Therefore, it can be expected to provide wide-frequency tuning. The resonator has three types of electrostatic forces that can be generated to deform a main beam. We evaluate the vibrational modes caused by each exciting electrodes by comparing simulated results with measured ones. We then successfully demonstrate the frequency tuning of the first to fifth resonant modes by using the algorithm we propose here. The resulting frequency tuning covers 178 to 1746 kHz. In addition, we investigate the suppression of the anchor loss to enhance the Q-factor. An experiment shows that tapered-shaped anchors provide a higher Q-factor than rectangular-shaped anchors. The Q-factor of the resonators supported by suspension beams is also discussed. Because the suspension beams cause complicated vibrational modes for higher frequencies, the enhancement of the Q-factor for high vibrational modes cannot be obtained here. At present, the tapered-anchor resonators are thought to be most suitable for frequency tuning applications.

Invited article: Dielectric material characterization techniques and designs of high-Q resonators for applications from micro to millimeter-waves frequencies applicable at room and cryogenic temperatures.

PubMed

Le Floch, Jean-Michel; Fan, Y; Humbert, Georges; Shan, Qingxiao; Férachou, Denis; Bara-Maillet, Romain; Aubourg, Michel; Hartnett, John G; Madrangeas, Valerie; Cros, Dominique; Blondy, Jean-Marc; Krupka, Jerzy; Tobar, Michael E

2014-03-01

Dielectric resonators are key elements in many applications in micro to millimeter wave circuits, including ultra-narrow band filters and frequency-determining components for precision frequency synthesis. Distributed-layered and bulk low-loss crystalline and polycrystalline dielectric structures have become very important for building these devices. Proper design requires careful electromagnetic characterization of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique for microwave applications, which has now become the standard for characterizing low-loss structures. This paper will give some of the most common characterization techniques used in the micro to millimeter wave regime at room and cryogenic temperatures for designing high-Q dielectric loaded cavities.

Timing and frequency considerations in the worldwide testing of a spread spectrum communication system

NASA Technical Reports Server (NTRS)

Woodring, D. G.; Nichols, S. A.; Swanson, R.

1979-01-01

During 1978 and 1979, an Air Force C-135 test aircraft was flown to various locations in the North and South Atlantic and Pacific Oceans for satellite communications experiments. A part of the equipment tested on the aircraft was the SEACOM spread spectrum modem. The SEACOM modem operated at X band frequency from the aircraft via the DSCS II satellite to a ground station. For data to be phased successfully, it was necessary to maintain independent time and frequency accuracy over relatively long periods of time (up to two weeks) on the aircraft and at the ground station. To achieve this goal, two Efratom atomic frequency standards were used. The performance of these frequency standards as used in the spread spectrum modem is discussed, including the effects of high relative velocity, synchronization and the effects of the frequency standards on data performance is discussed. The aircraft environment, which includes extremes of temperature, as well as long periods of shutdown followed by rapid warmup requirements, is also discussed.

Age may contribute to the increased frequency of axonal Guillain-Barré syndrome.

PubMed

Hawkes, Maximiliano A; Wilken, Miguel; Vázquez, Gabriel; Farez, Mauricio F

2017-12-01

The frequency of axonal Guillain-Barré syndrome (GBS) varies among countries. Previous studies supporting the high frequency of axonal GBS in South America have been carried out with pediatric populations. We seek to determine the frequency of axonal GBS in both children and adults in South America. This is a retrospective cohort analysis of patients who were diagnosed with GBS between January 2006 and December 2013 in a neurological center in Buenos Aires, Argentina. Adults and children with a diagnosis of GBS were included and classified by applying Ho and colleagues' criteria 1 for axonal GBS. The study included 105 patients with GBS. Among 58 adults, only 5 individuals were classified as axonal GBS compared with 16 of 47 children. The frequency of axonal GBS was significantly higher in children than in adults (34% vs. 8.6%, P = 0.0001). As shown in a cohort of South American patients, age may impact the frequency of axonal GBS. Muscle Nerve 56: 1311-1313, 2017. © 2017 Wiley Periodicals, Inc.

Eliminating the zero spectrum in Fourier transform profilometry using empirical mode decomposition.

PubMed

Li, Sikun; Su, Xianyu; Chen, Wenjing; Xiang, Liqun

2009-05-01

Empirical mode decomposition is introduced into Fourier transform profilometry to extract the zero spectrum included in the deformed fringe pattern without the need for capturing two fringe patterns with pi phase difference. The fringe pattern is subsequently demodulated using a standard Fourier transform profilometry algorithm. With this method, the deformed fringe pattern is adaptively decomposed into a finite number of intrinsic mode functions that vary from high frequency to low frequency by means of an algorithm referred to as a sifting process. Then the zero spectrum is separated from the high-frequency components effectively. Experiments validate the feasibility of this method.

Extended high-frequency thresholds in college students: effects of music player use and other recreational noise.

PubMed

Le Prell, Colleen G; Spankovich, Christopher; Lobariñas, Edward; Griffiths, Scott K

2013-09-01

Human hearing is sensitive to sounds from as low as 20 Hz to as high as 20,000 Hz in normal ears. However, clinical tests of human hearing rarely include extended high-frequency (EHF) threshold assessments, at frequencies extending beyond 8000 Hz. EHF thresholds have been suggested for use monitoring the earliest effects of noise on the inner ear, although the clinical usefulness of EHF threshold testing is not well established for this purpose. The primary objective of this study was to determine if EHF thresholds in healthy, young adult college students vary as a function of recreational noise exposure. A retrospective analysis of a laboratory database was conducted; all participants with both EHF threshold testing and noise history data were included. The potential for "preclinical" EHF deficits was assessed based on the measured thresholds, with the noise surveys used to estimate recreational noise exposure. EHF thresholds measured during participation in other ongoing studies were available from 87 participants (34 male and 53 female); all participants had hearing within normal clinical limits (≤25 HL) at conventional frequencies (0.25-8 kHz). EHF thresholds closely matched standard reference thresholds [ANSI S3.6 (1996) Annex C]. There were statistically reliable threshold differences in participants who used music players, with 3-6 dB worse thresholds at the highest test frequencies (10-16 kHz) in participants who reported long-term use of music player devices (>5 yr), or higher listening levels during music player use. It should be possible to detect small changes in high-frequency hearing for patients or participants who undergo repeated testing at periodic intervals. However, the increased population-level variability in thresholds at the highest frequencies will make it difficult to identify the presence of small but potentially important deficits in otherwise normal-hearing individuals who do not have previously established baseline data. American Academy of Audiology.

Evaluation of cross-connected waveguides as transfer standards of transmission at high millimetre-wave frequencies

NASA Astrophysics Data System (ADS)

Ridler, Nick; Clarke, Roland; Huang, Hui; Zinal, Sherko

2016-08-01

At the present time, transfer and verification standards of transmission coefficient (or, equivalently, transmission loss) are not readily available at high millimetre-wave frequencies (i.e. at frequencies ranging typically from 100 GHz to 300 GHz). In recent years, cross-connected waveguide devices have been proposed to provide calculable standards of transmission loss at these frequencies. This paper investigates the viability of these cross-connected waveguides as transfer standards of transmission for inter-laboratory measurement comparison exercises. This relates to their potential use in activities such as international key comparison exercises and measurement audit programmes. A trial inter-laboratory comparison involving four laboratories using two cross-connected waveguides in the WR-05 waveguide size (covering frequencies from 140 GHz to 220 GHz) is described and includes an analysis of the measurement results obtained during the comparison exercise.

Frequency response of portable PEF meters.

PubMed

Hankinson, J L; Das, M K

1995-08-01

Peak expiratory flow (PEF) is a dynamic parameter and therefore requires a measuring device with a high-frequency response. This study evaluated the frequency-response characteristics of eight commercially available PEF meters, using simulated forced-expiratory maneuvers with a computer-controlled mechanical pump. Three different PEF levels were used (200, 400, and 600 L/min) at six levels of harmonic-frequency content similar to those observed in human subjects. For waveforms with higher frequency content (at the high end or above the physiologic range), the Assess, Vitalograph, Pocket Peak, and Spir-O-Flow PEF meters all overread PEF (greater than 15% difference from target values) at all three PEF levels. These results suggest that the frequency response of PEF meters is an important consideration in the selection of such meters and should be included in device requirements. The current practice of using various levels of American Thoracic Society (ATS) waveform 24 with its low-frequency content may not adequately evaluate the frequency characteristics of PEF meters. An upper range (5% of the fundamental frequency) of 12 Hz, within the range observed in normal subjects, appears to be more practical than an upper limit of 20 Hz.

Radio frequency (RF) microwave components and subsystems using loaded ridge waveguide

DOEpatents

Kang, Yoon W.

2013-08-20

A waveguide having a non-conductive material with a high permeability (.mu., .mu..sub.r for relative permeability) and/or a high permittivity (.di-elect cons., .di-elect cons..sub.r for relative permittivity) positioned within a housing. When compared to a hollow waveguide, the waveguide of this invention, reduces waveguide dimensions by .varies..mu. ##EQU00001## The waveguide of this invention further includes ridges which further reduce the size and increases the usable frequency bandwidth.

Apollo experience report: Very high frequency ranging system

NASA Technical Reports Server (NTRS)

Panter, W. C.; Shores, P. W.

1972-01-01

The history of the Apollo very-high-frequency ranging system development program is presented from the program-planning stage through the final-test and flight-evaluation stages. Block diagrams of the equipment are presented, and a description of the theory of operation is outlined. A sample of the distribution of errors measured in the aircraft-flight test program is included. The report is concluded with guidelines or recommendations for the management of development programs having the same general constraints.

Design of a fiber-optic transmitter for microwave analog transmission with high phase stability

NASA Technical Reports Server (NTRS)

Logan, R. T., Jr.; Lutes, G. F.; Primas, L. E.; Maleki, L.

1990-01-01

The principal considerations in the design of fiber-optic transmitters for highly phase-stable radio frequency and microwave analog transmission are discussed. Criteria for a fiber-optic transmitter design with improved amplitude and phase-noise performance are developed through consideration of factors affecting the phase noise, including low-frequency laser-bias supply noise, the magnitude and proximity of external reflections into the laser, and temperature excursions of the laser-transmitter package.

Frequency-independent approach to calculate physical optics radiations with the quadratic concave phase variations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yu Mao, E-mail: yumaowu@fudan.edu.cn; Teng, Si Jia, E-mail: sjteng12@fudan.edu.cn

In this work, we develop the numerical steepest descent path (NSDP) method to calculate the physical optics (PO) radiations with the quadratic concave phase variations. With the surface integral equation method, the physical optics (PO) scattered fields are formulated and further reduced to the surface integrals. The high frequency physical critical points contributions, including the stationary phase points, the boundary resonance points and the vertex points are comprehensively studied via the proposed NSDP method. The key contributions of this work are twofold. One is that together with the PO integrals taking the quadratic parabolic and hyperbolic phase terms, this workmore » makes the NSDP theory be complete for treating the PO integrals with quadratic phase variations. Another is that, in order to illustrate the transition effect of the high frequency physical critical points, in this work, we consider and further extend the NSDP method to calculate the PO integrals with the coalescence of the high frequency critical points. Numerical results for the highly oscillatory PO integral with the coalescence of the critical points are given to verify the efficiency of the proposed NSDP method. The NSDP method could achieve the frequency independent computational workload and error controllable accuracy in all the numerical experiments, especially for the case of the coalescence of the high frequency critical points.« less

Opto-electronic device for frequency standard generation and terahertz-range optical demodulation based on quantum interference

DOEpatents

Georgiades, Nikos P.; Polzik, Eugene S.; Kimble, H. Jeff

1999-02-02

An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100's THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 .mu.m to 1.66 .mu.m for fiber optics can be accomplished with a nearly continuous frequency coverage.

A dual frequency microstrip antenna for Ka band

NASA Technical Reports Server (NTRS)

Lee, R. Q.; Baddour, M. F.

1985-01-01

For fixed satellite communication systems at Ka band with downlink at 17.7 to 20.2 GHz and uplink at 27.5 to 30.0 GHz, the focused optics and the unfocused optics configurations with monolithic phased array feeds have often been used to provide multiple fixed and multiple scanning spot beam coverages. It appears that a dual frequency microstrip antenna capable of transmitting and receiving simultaneously is highly desirable as an array feed element. This paper describes some early efforts on the development and experimental testing of a dual frequency annular microstrip antenna. The antenna has potential application for use in conjunction with a monolithic microwave integrated circuit device as an active radiating element in a phased array of phased array feeds. The antenna is designed to resonate at TM sub 12 and TM sub 13 modes and tuned with a circumferential microstrip ring to vary the frequency ratio. Radiation characteristics at both the high and low frequencies are examined. Experimental results including radiating patterns and swept frequency measurements are presented.

Demonstration of Space Optical Transmitter Development for Multiple High Frequency Bands

NASA Technical Reports Server (NTRS)

Nguyen, Hung; Simons, Rainee; Wintucky, Edwin; Freeman, Jon

2013-01-01

As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

The Effect of Adaptive Nonlinear Frequency Compression on Phoneme Perception.

PubMed

Glista, Danielle; Hawkins, Marianne; Bohnert, Andrea; Rehmann, Julia; Wolfe, Jace; Scollie, Susan

2017-12-12

This study implemented a fitting method, developed for use with frequency lowering hearing aids, across multiple testing sites, participants, and hearing aid conditions to evaluate speech perception with a novel type of frequency lowering. A total of 8 participants, including children and young adults, participated in real-world hearing aid trials. A blinded crossover design, including posttrial withdrawal testing, was used to assess aided phoneme perception. The hearing aid conditions included adaptive nonlinear frequency compression (NFC), static NFC, and conventional processing. Enabling either adaptive NFC or static NFC improved group-level detection and recognition results for some high-frequency phonemes, when compared with conventional processing. Mean results for the distinction component of the Phoneme Perception Test (Schmitt, Winkler, Boretzki, & Holube, 2016) were similar to those obtained with conventional processing. Findings suggest that both types of NFC tested in this study provided a similar amount of speech perception benefit, when compared with group-level performance with conventional hearing aid technology. Individual-level results are presented with discussion around patterns of results that differ from the group average.

Sensitivity and resolution in frequency comb spectroscopy of buffer gas cooled polyatomic molecules

NASA Astrophysics Data System (ADS)

Changala, P. Bryan; Spaun, Ben; Patterson, David; Doyle, John M.; Ye, Jun

2016-12-01

We discuss the use of cavity-enhanced direct frequency comb spectroscopy in the mid-infrared region with buffer gas cooling of polyatomic molecules for high-precision rovibrational absorption spectroscopy. A frequency comb coupled to an optical enhancement cavity allows us to collect high-resolution, broad-bandwidth infrared spectra of translationally and rotationally cold (10-20 K) gas-phase molecules with high absorption sensitivity and fast acquisition times. The design and performance of the combined apparatus are discussed in detail. Recorded rovibrational spectra in the CH stretching region of several organic molecules, including vinyl bromide (CH_2CHBr), adamantane (C_{10}H_{16}), and diamantane (C_{14}H_{20}) demonstrate the resolution and sensitivity of this technique, as well as the intrinsic challenges faced in extending the frontier of high-resolution spectroscopy to large complex molecules.

High power water load for microwave and millimeter-wave radio frequency sources

DOEpatents

Ives, R. Lawrence; Mizuhara, Yosuke M.; Schumacher, Richard V.; Pendleton, Rand P.

1999-01-01

A high power water load for microwave and millimeter wave radio frequency sources has a front wall including an input port for the application of RF power, a cylindrical dissipation cavity lined with a dissipating material having a thickness which varies with depth, and a rear wall including a rotating reflector for the reflection of wave energy inside the cylindrical cavity. The dissipation cavity includes a water jacket for removal of heat generated by the absorptive material coating the dissipation cavity, and this absorptive material has a thickness which is greater near the front wall than near the rear wall. Waves entering the cavity reflect from the rotating reflector, impinging and reflecting multiple times on the absorptive coating of the dissipation cavity, dissipating equal amounts of power on each internal reflection.

Low speed phaselock speed control system. [for brushless dc motor

NASA Technical Reports Server (NTRS)

Fulcher, R. W.; Sudey, J. (Inventor)

1975-01-01

A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry.

I. S. Shklovsky and Low-Frequency Radio Astronomy

NASA Astrophysics Data System (ADS)

Konovalenko, A. A.

2017-03-01

Purpose: Proving of the high astrophysical significance of the low-frequency radio astronomy (decameter and adjacent hectometer and meter wavelengths), demonstration of the priority results of the Ukrainian low-frequency radio astronomy as well as significant contribution of I. S. Shklovsky to its development. Design/methodology/approach: The requirements to characteristics of high efficiency radio telescopes UTR-2, URAN, GURT and to sensitive and interference immune observational methods at low frequencies are formulated by using the theoretical analysis and astrophysical predictions including those I. S. Shklovsky’s. Findings: New generation radio telescopes UTR-2, URAN, GURT are created and modernized. New observational methods at low frequencies are introduced. Large-scale investigations of the Solar system, Galaxy and Methagalaxy are carried out. They have allowed to detect new objects and phenomena for the continuum, monochromatic, pulse and sporadic cosmic radio emission. The role of I. S. Shklovsky in the development of many low-frequency radio astronomy directions is noted, too. Conclusions: The unique possibilities of the low-frequency radio astronomy which gives new information about the Universe, inaccessible with the other astrophysical methods, are shown. The progress of the low-frequency radio astronomy opens the impressive possibilities for the future. It includes modernization of the largest radio telescopes UTR-2, URAN, NDA and creation of new instruments GURT, NenuFAR, LOFAR, LWA, MWA, SKA as well as making multi-antenna and ground-space experiments. The contribution of outstanding astrophysicist of the XX century I. S. Shklovsky to this part of actual astronomical science is evident, claiming for attention and will never be forgotten.

Low-frequency high-definition power Doppler in visualizing and defining fetal pulmonary venous connections.

PubMed

Liu, Lin; He, Yihua; Li, Zhian; Gu, Xiaoyan; Zhang, Ye; Zhang, Lianzhong

2014-07-01

The use of low-frequency high-definition power Doppler in assessing and defining pulmonary venous connections was investigated. Study A included 260 fetuses at gestational ages ranging from 18 to 36 weeks. Pulmonary veins were assessed by performing two-dimensional B-mode imaging, color Doppler flow imaging (CDFI), and low-frequency high-definition power Doppler. A score of 1 was assigned if one pulmonary vein was visualized, 2 if two pulmonary veins were visualized, 3 if three pulmonary veins were visualized, and 4 if four pulmonary veins were visualized. The detection rate between Exam-1 and Exam-2 (intra-observer variability) and between Exam-1 and Exam-3 (inter-observer variability) was compared. In study B, five cases with abnormal pulmonary venous connection were diagnosed and compared to their anatomical examination. In study A, there was a significant difference between CDFI and low-frequency high-definition power Doppler for the four pulmonary veins observed (P < 0.05). The detection rate of each pulmonary vein when employing low-frequency high-definition power Doppler was higher than that when employing two-dimensional B-mode imaging or CDFI. There was no significant difference between the intra- and inter-observer variabilities using low-frequency high-definition power Doppler display of pulmonary veins (P > 0.05). The coefficient correlation between Exam-1 and Exam-2 was 0.844, and the coefficient correlation between Exam-1 and Exam-3 was 0.821. In study B, one case of total anomalous pulmonary venous return and four cases of partial anomalous pulmonary venous return were diagnosed by low-frequency high-definition power Doppler and confirmed by autopsy. The assessment of pulmonary venous connections by low-frequency high-definition power Doppler is advantageous. Pulmonary venous anatomy can and should be monitored during fetal heart examination.

Spatial resolution dependence on spectral frequency in human speech cortex electrocorticography.

PubMed

Muller, Leah; Hamilton, Liberty S; Edwards, Erik; Bouchard, Kristofer E; Chang, Edward F

2016-10-01

Electrocorticography (ECoG) has become an important tool in human neuroscience and has tremendous potential for emerging applications in neural interface technology. Electrode array design parameters are outstanding issues for both research and clinical applications, and these parameters depend critically on the nature of the neural signals to be recorded. Here, we investigate the functional spatial resolution of neural signals recorded at the human cortical surface. We empirically derive spatial spread functions to quantify the shared neural activity for each frequency band of the electrocorticogram. Five subjects with high-density (4 mm center-to-center spacing) ECoG grid implants participated in speech perception and production tasks while neural activity was recorded from the speech cortex, including superior temporal gyrus, precentral gyrus, and postcentral gyrus. The cortical surface field potential was decomposed into traditional EEG frequency bands. Signal similarity between electrode pairs for each frequency band was quantified using a Pearson correlation coefficient. The correlation of neural activity between electrode pairs was inversely related to the distance between the electrodes; this relationship was used to quantify spatial falloff functions for cortical subdomains. As expected, lower frequencies remained correlated over larger distances than higher frequencies. However, both the envelope and phase of gamma and high gamma frequencies (30-150 Hz) are largely uncorrelated (<90%) at 4 mm, the smallest spacing of the high-density arrays. Thus, ECoG arrays smaller than 4 mm have significant promise for increasing signal resolution at high frequencies, whereas less additional gain is achieved for lower frequencies. Our findings quantitatively demonstrate the dependence of ECoG spatial resolution on the neural frequency of interest. We demonstrate that this relationship is consistent across patients and across cortical areas during activity.

Spatial resolution dependence on spectral frequency in human speech cortex electrocorticography

NASA Astrophysics Data System (ADS)

Muller, Leah; Hamilton, Liberty S.; Edwards, Erik; Bouchard, Kristofer E.; Chang, Edward F.

2016-10-01

Objective. Electrocorticography (ECoG) has become an important tool in human neuroscience and has tremendous potential for emerging applications in neural interface technology. Electrode array design parameters are outstanding issues for both research and clinical applications, and these parameters depend critically on the nature of the neural signals to be recorded. Here, we investigate the functional spatial resolution of neural signals recorded at the human cortical surface. We empirically derive spatial spread functions to quantify the shared neural activity for each frequency band of the electrocorticogram. Approach. Five subjects with high-density (4 mm center-to-center spacing) ECoG grid implants participated in speech perception and production tasks while neural activity was recorded from the speech cortex, including superior temporal gyrus, precentral gyrus, and postcentral gyrus. The cortical surface field potential was decomposed into traditional EEG frequency bands. Signal similarity between electrode pairs for each frequency band was quantified using a Pearson correlation coefficient. Main results. The correlation of neural activity between electrode pairs was inversely related to the distance between the electrodes; this relationship was used to quantify spatial falloff functions for cortical subdomains. As expected, lower frequencies remained correlated over larger distances than higher frequencies. However, both the envelope and phase of gamma and high gamma frequencies (30-150 Hz) are largely uncorrelated (<90%) at 4 mm, the smallest spacing of the high-density arrays. Thus, ECoG arrays smaller than 4 mm have significant promise for increasing signal resolution at high frequencies, whereas less additional gain is achieved for lower frequencies. Significance. Our findings quantitatively demonstrate the dependence of ECoG spatial resolution on the neural frequency of interest. We demonstrate that this relationship is consistent across patients and across cortical areas during activity.

An Investigation of the Dynamic Response of a Seismically Stable Platform

DTIC Science & Technology

1982-08-01

PAD. The controls on the -9system are of two types. A low frequency tilt control, with a 10 arc second sensitivity, 2-axis tiltmeter as sensor ...Inertial Sensors Structural Analysis Holloman AFB, NiM. Support to this effort includes structural analyses toward active servo frequency band. This report...controlled to maintain a null position of a sensitive height sensor . The 6-degree-of- freedom high frequency controls are based on seismometers as sensors

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.

Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms

PubMed Central

Zhang, S. Y.; Wu, J. T.; Zhang, Y. L.; Leng, J. X.; Yang, W. P.; Zhang, Z. G.; Zhao, J. Y.

2015-01-01

Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios. PMID:26459877

Refinements to the Graves and Pitarka (2010) Broadband Ground Motion Simulation Method

USGS Publications Warehouse

Graves, Robert; Arben Pitarka,

2015-01-01

This brief article describes refinements to the Graves and Pitarka (2010) broadband ground motion simulation methodology (GP2010 hereafter) that have been implemented in version 14.3 of the SCEC Broadband Platform (BBP). The updated version of our method on the current SCEC BBP is referred to as GP14.3. Our simulation technique is a hybrid approach that combines low-­‐frequency and high-­‐frequency motions computed with different methods into a single broadband response. The separate low-­‐ and high-­‐frequency components have traditionally been called “deterministic” and “stochastic”, respectively; however, this nomenclature is an oversimplification. In reality, the low-­‐frequency approach includes many stochastic elements, and likewise, the high-­‐frequency approach includes many deterministic elements (e.g., Pulido and Kubo, 2004; Hartzell et al., 2005; Liu et al., 2006; Frankel, 2009; Graves and Pitarka, 2010; Mai et al., 2010). While the traditional terminology will likely remain in use by the broader modeling community, in this paper we will refer to these using the generic terminology “low-­‐frequency” and “high-­‐ frequency” approaches. Furthermore, one of the primary goals in refining our methodology is to provide a smoother and more consistent transition between the low-­‐ and high-­‐ frequency calculations, with the ultimate objective being the development of a single unified modeling approach that can be applied over a broad frequency band. GP2010 was validated by modeling recorded strong motions from four California earthquakes. While the method performed well overall, several issues were identified including the tendency to over-­‐predict the level of longer period (2-­‐5 sec) motions and the effects of rupture directivity. The refinements incorporated in GP14.3 are aimed at addressing these issues with application to the simulation of earthquakes in Western US (WUS). These refinements include the addition of a deep weak zone (details in following section) to the rupture characterization and allowing perturbations in the correlation of rise time and rupture speed with the specified slip distribution. Additionally, we have extended the parameterization of GP14.3 so that it is also applicable for simulating Eastern North America (ENA) earthquakes. This work has been guided by the comprehensive set of validation studies described in Goulet and Abrahamson (2014) and Dreger et al. (2014). The GP14.3 method shows improved performance relative to GP2010, and we direct the interested reader to Dreger et al. (2014) for a detailed assessment of the current methodology. In this paper, we concentrate on describing the modifications in more detail, and also discussing additional refinements that are currently being developed.

Low-Magnitude, High-Frequency Vibration Fails to Accelerate Ligament Healing but Stimulates Collagen Synthesis in the Achilles Tendon.

PubMed

Thompson, William R; Keller, Benjamin V; Davis, Matthew L; Dahners, Laurence E; Weinhold, Paul S

2015-05-01

Low-magnitude, high-frequency vibration accelerates fracture and wound healing and prevents disuse atrophy in musculoskeletal tissues. To investigate the role of low-magnitude, high-frequency vibration as a treatment to accelerate healing of an acute ligament injury and to examine gene expression in the intact Achilles tendon of the injured limb after low-magnitude, high-frequency vibration. Controlled laboratory study. Complete surgical transection of the medial collateral ligament (MCL) was performed in 32 Sprague-Dawley rats, divided into control and low-magnitude, high-frequency vibration groups. Low-magnitude, high-frequency vibration started on postoperative day 2, and rats received vibration for 30 minutes a day for 12 days. All rats were sacrificed 2 weeks after the operation, and their intact and injured MCLs were biomechanically tested or used for histological analysis. Intact Achilles tendons from the injured limb were evaluated for differences in gene expression. Mechanical testing revealed no differences in the ultimate tensile load or the structural stiffness between the control and vibration groups for either the injured or intact MCL. Vibration exposure increased gene expression of collagen 1 alpha (3-fold), interleukin 6 (7-fold), cyclooxygenase 2 (5-fold), and bone morphogenetic protein 12 (4-fold) in the intact Achilles tendon when compared with control tendons ( P < .05). While no differences were observed in the mechanical or histological properties of the fully transected MCL after low-magnitude, high-frequency vibration treatment, significant enhancements in gene expression were observed in the intact Achilles tendon. These included collagen, several inflammatory cytokines, and growth factors critical for tendons. As low-magnitude, high-frequency vibration had no negative effects on ligament healing, vibration therapy may be a useful tool to accelerate healing of other tissues (bone) in multitrauma injuries without inhibiting ligament healing. Additionally, the enhanced gene expression in response to low-magnitude, high-frequency vibration in the intact Achilles tendon suggests the need to further study its potential to accelerate tendon healing in partial injury or repair models.

Frequencies and Characteristics of Global Oceanic Precipitation from Shipboard Present-Weather Reports

NASA Technical Reports Server (NTRS)

Petty, Grant W.

1995-01-01

Ship reports of present weather obtained from the Comprehensive Ocean-Atmosphere Data Set are analyzed for the period 1958-91 in order to elucidate regional and seasonal variations in the climatological frequency, phase, intensity, and character of oceanic precipitation. Specific findings of note include the following: 1) The frequency of thunderstorm reports, relative to all precipitation reports, is a strong function of location, with thunderstorm activity being favored within 1000-3000 km of major tropical and subtropical land masses, while being quite rare at other locations, even within the intertropical convergence zone. 2) The latitudinal frequency of precipitation over the southern oceans increases steadily toward the Antarctic continent and shows relatively little seasonal variation. The frequency of convective activity, however, shows considerable seasonal variability, with sharp winter maxima occurring near 38 deg. latitude in both hemispheres. 3) Drizzle is the preferred form of precipitation in a number of regions, most of which coincide with known regions of persistent marine stratus and stratocumulus in the subtropical highs. Less well documented is the high relative frequency of drizzle in the vicinity of the equatorial sea surface temperature front in the eastern Pacific. 4) Regional differences in the temporal scale of precipitation events (e.g., transient showers versus steady precipitation) are clearly depicted by way of the ratio of the frequency of precipitation at the observation time to the frequency of all precipitation reports, including precipitation during the previous hour. The results of this study suggest that many current satellite rainfall estimation techniques may substantially underestimate the fractional coverage or frequency of precipitation poleward of 50 deg. latitude and in the subtropical dry zones. They also draw attention to the need to carefully account for regional differences in the physical and spatial properties of rainfall when developing calibration relationships for satellite algorithms.

Small Scale Motions Observed by Aircraft in the Tropical Tropopause Layer - Convective and Non-Convective Environments

NASA Technical Reports Server (NTRS)

Pfister, Leonhard; Bui, T. P.; Dean-Day, J.

2016-01-01

Indirect evidence indicates a role for vertical mixing in the Tropical Tropopause Layer (TTL). In particular, detailed model studies suggest that such vertical mixing may be required to explain the value of the water vapor minimum in the TTL. There have been previous observations during the STEP Tropical aircraft campaign (1987) of bursts of high frequency activity associated with convectively generated gravity waves in the tropical western Pacific. Higher frequency, higher quality measurements from NASA high altitude aircraft (ER-2, WB-57, and Global Hawk) have been made available in the last 20 years. These include measurements of vertical velocity and other meteorological parameters. Most recently, during the ATTREX Global Hawk aircraft mission (Airborne Tropical TRopopause EXperiment), there have been extensive measurements at all altitudes of the TTL in both convective (winter western Pacific) and less convective (winter eastern Pacific) regions. This presentation represents an initial analysis of high frequency small scale (a few km max) meteorological measurements from the ATTREX dataset. We obtain some basic information about the distribution and character of high frequency activity in vertical velocity in the TTL. In particular, we focus on relating the high frequency activity to nearby tropical convection and to vertical shears associated with gravity and inertia-gravity waves.

Relaxation phenomena in AOT-water-decane critical and dense microemulsions

NASA Astrophysics Data System (ADS)

Letamendia, L.; Pru-Lestret, E.; Panizza, P.; Rouch, J.; Sciortino, F.; Tartaglia, P.; Hashimoto, C.; Ushiki, H.; Risso, D.

2001-11-01

We report on extensive measurements of the low and high frequencies sound velocity and sound absorption in AOT-water-decane microemulsions deduced from ultrasonic and, for the first time as far as the absorption is concerned, from Brillouin scattering experiments. New experimental results on dielectric relaxation are also reported. Our results, which include data taken for critical as well as dense microemulsions, show new interesting relaxation phenomena. The relaxation frequencies deduced from very high frequency acoustical measurements are in good agreement with new high frequency dielectric relaxation measurements. We show that along the critical isochore, sound dispersion, relaxation frequency, and static dielectric permittivity can be accurately fitted to power laws. The absolute values of the new exponents we derived from experimental data are nearly equal, and they are very close to β=0.33 characterising the shape of the coexistence curve. The exponent characterising the infinite frequency permittivity is very close to 0.04 relevant to the diverging shear viscosity. For dense microemulsions, two well defined relaxation domains have been identified and the temperature variations of the sound absorption and the zero frequency dielectric permittivity bear striking similarities. We also show that the relaxation frequency of the slow relaxation process is almost independent of temperature and volume fraction and so cannot be attributed to percolation phenomena, whereas it can more likely be attributed to an intrinsic relaxation process probably connected to membrane fluctuations.

Modelling of high-frequency structure-borne sound transmission on FEM grids using the Discrete Flow Mapping technique

NASA Astrophysics Data System (ADS)

Hartmann, Timo; Tanner, Gregor; Xie, Gang; Chappell, David; Bajars, Janis

2016-09-01

Dynamical Energy Analysis (DEA) combined with the Discrete Flow Mapping technique (DFM) has recently been introduced as a mesh-based high frequency method modelling structure borne sound for complex built-up structures. This has proven to enhance vibro-acoustic simulations considerably by making it possible to work directly on existing finite element meshes circumventing time-consuming and costly re-modelling strategies. In addition, DFM provides detailed spatial information about the vibrational energy distribution within a complex structure in the mid-to-high frequency range. We will present here progress in the development of the DEA method towards handling complex FEM-meshes including Rigid Body Elements. In addition, structure borne transmission paths due to spot welds are considered. We will present applications for a car floor structure.

Advanced Global Atmospheric Gases Experiment (AGAGE)

NASA Technical Reports Server (NTRS)

Prinn, Ronald G.

2001-01-01

AGAGE comprises continuous high frequency in-situ gas chromatographic FID/ECD measurements of two biogenic/anthropogenic gases (CH4, N2O) and five anthropogenic gases (CFCl3, CF2Cl2, CH3CCl3, CF2ClCFCl2, CCl4) which are carried out at five globally distributed sites (Ireland, California, Barbados, Samoa, Tasmania). Also, high frequency in-situ gas-chromatographic mass spectrometric measurements of about 30 species including chlorofluorocarbon replacements and many natural halocarbons are made at two sites (Ireland, Tasmania), and will soon begin at the other three sites. Finally, high frequency in-situ gas chromatographic HgO-RD measurements of CO and H2 are performed at two sites (Ireland, Tasmania). The goal is quantitative determination of the sources, sinks, and circulation of these environmentally important gases.

Experimental observation of multi-scale interactions among kink /tearing modes and high-frequency fluctuations in the HL-2A core NBI plasmas

NASA Astrophysics Data System (ADS)

Chen, W.; Jiang, M.; Xu, Y.; Shi, P. W.; Yu, L. M.; Ding, X. T.; Shi, Z. B.; Ji, X. Q.; Yu, D. L.; Li, Y. G.; Yang, Z. C.; Zhong, W. L.; Qiu, Z. Y.; Li, J. Q.; Dong, J. Q.; Yang, Q. W.; Liu, Yi.; Yan, L. W.; Xu, M.; Duan, X. R.

2017-11-01

Multi-scale interactions have been observed recently in the HL-2A core NBI plasmas, including the synchronous coupling between m/n=1/1 kink mode and m/n=2/1 tearing mode, nonlinear couplings of TAE/BAE and m/n=2/1 TM near q=2 surface, AITG/KBM/BAE and m/n=1/1 kink mode near q=1 surface, and between m/n=1/1 kink mode and high-frequency turbulence. Experimental results suggest that several couplings can exist simultaneously, Alfvenic fluctuations have an important contribution to the high-frequency turbulence spectra, and the couplings reveal the electromagnetic character. Multi-scale interactions via the nonlinear modulation process maybe enhance plasma transport and trigger sawtooth-crash onset.

Facilitation of epileptic activity during sleep is mediated by high amplitude slow waves

PubMed Central

von Ellenrieder, Nicolás; Ferrari-Marinho, Taissa; Avoli, Massimo; Dubeau, François; Gotman, Jean

2015-01-01

Epileptic discharges in focal epilepsy are frequently activated during non-rapid eye movement sleep. Sleep slow waves are present during this stage and have been shown to include a deactivated (‘down’, hyperpolarized) and an activated state (‘up’, depolarized). The ‘up’ state enhances physiological rhythms, and we hypothesize that sleep slow waves and particularly the ‘up’ state are the specific components of non-rapid eye movement sleep that mediate the activation of epileptic activity. We investigated eight patients with pharmaco-resistant focal epilepsies who underwent combined scalp-intracerebral electroencephalography for diagnostic evaluation. We analysed 259 frontal electroencephalographic channels, and manually marked 442 epileptic spikes and 8487 high frequency oscillations during high amplitude widespread slow waves, and during matched control segments with low amplitude widespread slow waves, non-widespread slow waves or no slow waves selected during the same sleep stages (total duration of slow wave and control segments: 49 min each). During the slow waves, spikes and high frequency oscillations were more frequent than during control segments (79% of spikes during slow waves and 65% of high frequency oscillations, both P ∼ 0). The spike and high frequency oscillation density also increased for higher amplitude slow waves. We compared the density of spikes and high frequency oscillations between the ‘up’ and ‘down’ states. Spike and high frequency oscillation density was highest during the transition from the ‘up’ to the ‘down’ state. Interestingly, high frequency oscillations in channels with normal activity expressed a different peak at the transition from the ‘down’ to the ‘up’ state. These results show that the apparent activation of epileptic discharges by non-rapid eye movement sleep is not a state-dependent phenomenon but is predominantly associated with specific events, the high amplitude widespread slow waves that are frequent, but not continuous, during this state of sleep. Both epileptic spikes and high frequency oscillations do not predominate, like physiological activity, during the ‘up’ state but during the transition from the ‘up’ to the ‘down’ state of the slow wave, a period of high synchronization. Epileptic discharges appear therefore more associated with synchronization than with excitability. Furthermore, high frequency oscillations in channels devoid of epileptic activity peak differently during the slow wave cycle from those in channels with epileptic activity. This property may allow differentiating physiological from pathological high frequency oscillations, a problem that is unresolved until now. PMID:25792528

Radiometer Testbed Development for SWOT

NASA Technical Reports Server (NTRS)

Kangaslahti, Pekka; Brown, Shannon; Gaier, Todd; Dawson, Douglas; Harding, Dennis; Fu, Lee-Lueng; Esteban-Fernandez, Daniel

2010-01-01

Conventional altimeters include nadir looking colocated 18-37 GHz microwave radiometer to measure wet tropospheric path delay. These have reduced accuracy in coastal zone (within 50 km from land) and do not provide wet path delay over land. The addition of high frequency channels to Jason-class radiometer will improve retrievals in coastal regions and enable retrievals over land. High-frequency window channels, 90, 130 and 166 GHz are optimum for improving performance in coastal region and channels on 183 GHz water vapor line are ideal for over-land retrievals.

When ottoman is easier than chair: an inverse frequency effect in jargon aphasia.

PubMed

Marshall, J; Pring, T; Chiat, S; Robson, J

2001-02-01

This paper presents evidence of an inverse frequency effect in jargon aphasia. The subject (JP) showed a pre-disposition for low frequency word production on a range of tasks, including picture naming, sentence completion and naming in categories. Her real word errors were also striking, in that these tended to be lower in frequency than the target. Reading data suggested that the inverse frequency effect was present only when production was semantically mediated. It was therefore hypothesised that the effect was at least partly due to the semantic characteristics of low frequency items. Some support for this was obtained from a comprehension task showing that JP's understanding of low frequency terms, which she often produced as errors, was superior to her understanding of high frequency terms. Possible explanations for these findings are considered.

Improving timing sensitivity in the microhertz frequency regime: limits from PSR J1713+0747 on gravitational waves produced by supermassive black hole binaries

NASA Astrophysics Data System (ADS)

Perera, B. B. P.; Stappers, B. W.; Babak, S.; Keith, M. J.; Antoniadis, J.; Bassa, C. G.; Caballero, R. N.; Champion, D. J.; Cognard, I.; Desvignes, G.; Graikou, E.; Guillemot, L.; Janssen, G. H.; Karuppusamy, R.; Kramer, M.; Lazarus, P.; Lentati, L.; Liu, K.; Lyne, A. G.; McKee, J. W.; Osłowski, S.; Perrodin, D.; Sanidas, S. A.; Sesana, A.; Shaifullah, G.; Theureau, G.; Verbiest, J. P. W.; Taylor, S. R.

2018-07-01

We search for continuous gravitational waves (CGWs) produced by individual supermassive black hole binaries in circular orbits using high-cadence timing observations of PSR J1713+0747. We observe this millisecond pulsar using the telescopes in the European Pulsar Timing Array with an average cadence of approximately 1.6 d over the period between 2011 April and 2015 July, including an approximately daily average between 2013 February and 2014 April. The high-cadence observations are used to improve the pulsar timing sensitivity across the gravitational wave frequency range of 0.008-5μHz. We use two algorithms in the analysis, including a spectral fitting method and a Bayesian approach. For an independent comparison, we also use a previously published Bayesian algorithm. We find that the Bayesian approaches provide optimal results and the timing observations of the pulsar place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to be ≲3.5 × 10-13 at a reference frequency of 1 μHz. We also find a 95 per cent upper limit on the sky-averaged strain amplitude of low-frequency CGWs to be ≲1.4 × 10-14 at a reference frequency of 20 nHz.

Improving timing sensitivity in the microhertz frequency regime: limits from PSR J1713+0747 on gravitational waves produced by super-massive black-hole binaries

NASA Astrophysics Data System (ADS)

Perera, B. B. P.; Stappers, B. W.; Babak, S.; Keith, M. J.; Antoniadis, J.; Bassa, C. G.; Caballero, R. N.; Champion, D. J.; Cognard, I.; Desvignes, G.; Graikou, E.; Guillemot, L.; Janssen, G. H.; Karuppusamy, R.; Kramer, M.; Lazarus, P.; Lentati, L.; Liu, K.; Lyne, A. G.; McKee, J. W.; Osłowski, S.; Perrodin, D.; Sanidas, S. A.; Sesana, A.; Shaifullah, G.; Theureau, G.; Verbiest, J. P. W.; Taylor, S. R.

2018-05-01

We search for continuous gravitational waves (CGWs) produced by individual super-massive black-hole binaries (SMBHBs) in circular orbits using high-cadence timing observations of PSR J1713+0747. We observe this millisecond pulsar using the telescopes in the European Pulsar Timing Array (EPTA) with an average cadence of approximately 1.6 days over the period between April 2011 and July 2015, including an approximately daily average between February 2013 and April 2014. The high-cadence observations are used to improve the pulsar timing sensitivity across the GW frequency range of 0.008 - 5 μHz. We use two algorithms in the analysis, including a spectral fitting method and a Bayesian approach. For an independent comparison, we also use a previously published Bayesian algorithm. We find that the Bayesian approaches provide optimal results and the timing observations of the pulsar place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to be ≲ 3.5 × 10-13 at a reference frequency of 1 μHz. We also find a 95 per cent upper limit on the sky-averaged strain amplitude of low-frequency CGWs to be ≲ 1.4 × 10-14 at a reference frequency of 20 nHz.

Method for high resolution magnetic resonance analysis using magic angle technique

DOEpatents

Wind, Robert A.; Hu, Jian Zhi

2003-12-30

A method of performing a magnetic resonance analysis of a biological object that includes placing the object in a main magnetic field (that has a static field direction) and in a radio frequency field; rotating the object at a frequency of less than about 100 Hz around an axis positioned at an angle of about 54.degree.44' relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a phase-corrected magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. The object may be reoriented about the magic angle axis between three predetermined positions that are related to each other by 120.degree.. The main magnetic field may be rotated mechanically or electronically. Methods for magnetic resonance imaging of the object are also described.

Method for high resolution magnetic resonance analysis using magic angle technique

DOEpatents

Wind, Robert A.; Hu, Jian Zhi

2004-12-28

A method of performing a magnetic resonance analysis of a biological object that includes placing the object in a main magnetic field (that has a static field direction) and in a radio frequency field; rotating the object at a frequency of less than about 100 Hz around an axis positioned at an angle of about 54.degree.44' relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a phase-corrected magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. The object may be reoriented about the magic angle axis between three predetermined positions that are related to each other by 120.degree.. The main magnetic field may be rotated mechanically or electronically. Methods for magnetic resonance imaging of the object are also described.

75 FR 28667 - Market Structure Roundtable

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-21

... views of investors, issuers, exchanges, alternative trading systems, financial services firms, high... roundtable will focus on market structure performance, including the events of May 6, metrics for evaluating market structure performance, high frequency trading, and undisplayed liquidity. The roundtable...

Admissible Diffusion Wavelets and Their Applications in Space-Frequency Processing.

PubMed

Hou, Tingbo; Qin, Hong

2013-01-01

As signal processing tools, diffusion wavelets and biorthogonal diffusion wavelets have been propelled by recent research in mathematics. They employ diffusion as a smoothing and scaling process to empower multiscale analysis. However, their applications in graphics and visualization are overshadowed by nonadmissible wavelets and their expensive computation. In this paper, our motivation is to broaden the application scope to space-frequency processing of shape geometry and scalar fields. We propose the admissible diffusion wavelets (ADW) on meshed surfaces and point clouds. The ADW are constructed in a bottom-up manner that starts from a local operator in a high frequency, and dilates by its dyadic powers to low frequencies. By relieving the orthogonality and enforcing normalization, the wavelets are locally supported and admissible, hence facilitating data analysis and geometry processing. We define the novel rapid reconstruction, which recovers the signal from multiple bands of high frequencies and a low-frequency base in full resolution. It enables operations localized in both space and frequency by manipulating wavelet coefficients through space-frequency filters. This paper aims to build a common theoretic foundation for a host of applications, including saliency visualization, multiscale feature extraction, spectral geometry processing, etc.

The Effects of Perceived Racial/Ethnic Discrimination on Substance Use among Youths Living in the Cherokee Nation

ERIC Educational Resources Information Center

Garrett, Brady A.; Livingston, Bethany J.; Livingston, Melvin D.; Komro, Kelli A.

2017-01-01

We examined frequency and intensity of racial/ethnic discrimination and the longitudinal relationship to substance use. The sample included (N = 1,421) American Indian, American Indian and White, and White adolescents. A high frequency of perceived racial discrimination was associated with an increased risk for heavy alcohol use, prescription drug…

High Power HF Excitation of Low Frequency Stimulated Electrostatic Waves in the Ionospheric Plasma over HAARP

NASA Astrophysics Data System (ADS)

Bernhardt, Paul; Selcher, Craig A.

High Power electromagnetic (EM) waves transmitted from the HAARP facility in Alaska can excite low frequency electrostatic waves by several processes including (1) direct magnetized stimulated Brillouin scatter (MSBS) and (2) parametric decay of high frequency electrostatic waves into electron and ion Bernstein waves. Either an ion acoustic (IA) wave with a frequency less than the ion cyclotron frequency (fCI) or an electrostatic ion cyclotron (EIC) wave just above fCI can be produced by MSBS. The coupled equations describing the MSBS instabil-ity show that the production of both IA and EIC waves is strongly influenced by the wave propagation direction relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions (SEE) using the HAARP transmitter in Alaska have confirmed the theoretical predictions that only IA waves are excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The electron temperature in the heated plasma is obtained from the IA spectrum offsets from the pump frequency. The ion composition can be determined from the measured EIC frequency. Near the second harmonic of the electron cyclotron frequency, the EM pump wave is converted into an electron Bernstein (EB) wave that decays into another EB wave and an ion Bernstein (IB) wave. Strong cyclotron resonance with the EB wave leads to acceleration of the electrons. Ground based SEE observations are related to the theory of low-frequency electrostatic wave generation.

Stellar interferometers and hypertelescopes: new insights on an angular spatial frequency approach to their non-invariant imaging

NASA Astrophysics Data System (ADS)

Dettwiller, L.; Lépine, T.

2017-12-01

A general and pure wave theory of image formation for all types of stellar interferometers, including hypertelescopes, is developed in the frame of Fresnel's paraxial approximations of diffraction. For a hypertelescope, we show that the severe lack of translation invariance leads to multiple and strong spatial frequency heterodyning, which codes the very high frequencies detected by the hypertelescope into medium spatial frequencies and introduces a moiré-type ambiguity for extended objects. This explains mathematically the disappointing appearance of poor resolution observed in some image simulations for hypertelescopes.

Opto-electronic device for frequency standard generation and terahertz-range optical demodulation based on quantum interference

DOEpatents

Georgiades, N.P.; Polzik, E.S.; Kimble, H.J.

1999-02-02

An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies are disclosed. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100`s THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 {micro}m to 1.66 {micro}m for fiber optics can be accomplished with a nearly continuous frequency coverage. 7 figs.

Recent developments in novel freezing and thawing technologies applied to foods.

PubMed

Wu, Xiao-Fei; Zhang, Min; Adhikari, Benu; Sun, Jincai

2017-11-22

This article reviews the recent developments in novel freezing and thawing technologies applied to foods. These novel technologies improve the quality of frozen and thawed foods and are energy efficient. The novel technologies applied to freezing include pulsed electric field pre-treatment, ultra-low temperature, ultra-rapid freezing, ultra-high pressure and ultrasound. The novel technologies applied to thawing include ultra-high pressure, ultrasound, high voltage electrostatic field (HVEF), and radio frequency. Ultra-low temperature and ultra-rapid freezing promote the formation and uniform distribution of small ice crystals throughout frozen foods. Ultra-high pressure and ultrasound assisted freezing are non-thermal methods and shorten the freezing time and improve product quality. Ultra-high pressure and HVEF thawing generate high heat transfer rates and accelerate the thawing process. Ultrasound and radio frequency thawing can facilitate thawing process by volumetrically generating heat within frozen foods. It is anticipated that these novel technologies will be increasingly used in food industries in the future.

Influence of excitation frequency on the metastable atoms and electron energy distribution function in a capacitively coupled argon discharge

NASA Astrophysics Data System (ADS)

Sharma, S.; Sirse, N.; Turner, M. M.; Ellingboe, A. R.

2018-06-01

One-dimensional particle-in-cell simulation is used to simulate the capacitively coupled argon plasma for a range of excitation frequency from 13.56 MHz to 100 MHz. The argon chemistry set can, selectively, include two metastable levels enabling multi-step ionization and metastable pooling. The results show that the plasma density decreases when metastable atoms are included with higher discrepancy at a higher excitation frequency. The contribution of multistep ionization to the overall density increases with the excitation frequency. The electron temperature increases with the inclusion of metastable atoms and decreases with the excitation frequency. At a lower excitation frequency, the density of Ar** (3p5 4p, 13.1 eV) is higher than that of Ar* (3p5 4s, 11.6 eV), whereas at higher excitation frequencies, the Ar* (3p5 4s, 11.6 eV) is the dominant metastable atom. The metastable and electron temperature profile evolve from a parabolic profile at a lower excitation frequency to a saddle type profile at a higher excitation frequency. With metastable, the electron energy distribution function (EEDF) changes its shape from Druyvesteyn type, at a low excitation frequency, to bi-Maxwellian, at a high frequency plasma excitation; however, a three-temperature EEDF is observed without metastable atoms.

High frequency longitudinal profiling reveals hydrologic controls on solute sourcing, transport and processing in a karst river

NASA Astrophysics Data System (ADS)

Hensley, R. T.; Cohen, M. J.; Spangler, M.; Gooseff, M. N.

2017-12-01

The lower Santa Fe River is a large, karst river of north Florida, fed by numerous artesian springs and also containing multiple sink-rise systems. We performed repeated longitudinal profiles collecting very high frequency measurements of multiple stream parameters including temperature, dissolved oxygen, carbon dioxide, pH, dissolved organic matter, nitrate, ammonium, phosphate and turbidity. This high frequency dataset provided a spatially explicit understanding of solute sources and coupled biogeochemical processing rates along the 25 km study reach. We noted marked changes in river profiles as the river transitioned from low to high flow during the onset of the wet season. The role of lateral inflow from springs as the primary solute source was greatly reduced under high flow conditions. Effects of sink-rise systems, which under low flow conditions allow the majority of flow to bypass several kilometer long sections of the main channel, virtually disappeared under high flow conditions. Impeded light transmittance at high flow reduced primary production and by extension assimilatory nutrient uptake. This study demonstrates how high frequency longitudinal profiling can be used to observe how hydrologic conditions can alter groundwater-surface water interactions and modulate the sourcing, transport and biogeochemical processing of stream solutes.

Heart Rate Variability Indexes in Dementia: A Systematic Review with a Quantitative Analysis.

PubMed

da Silva, Vanessa Pereira; Ramalho Oliveira, Bruno Ribeiro; Tavares Mello, Roger Gomes; Moraes, Helena; Deslandes, Andrea Camaz; Laks, Jerson

2018-01-01

Decreased heart rate variability (HRV) indexes indicate low vagal activity and may be associated with development of dementia. The neurodegenerative process is associated with the cardiovascular autonomic control. The aim of this systematic review was to investigate the effect size (ES) magnitude of the HRV indexes in the evaluation of autonomic dysfunction in older persons with dementia. PubMed (Medline), Web of Science, Scopus, Scielo, Lilacs, and APA Psycnet were consulted. Complete original articles published in English or Portuguese, investigating the association between autonomic dysfunction and dementia, using the HRV indexes were included. The search identified 97 potentially relevant articles. After screening the full text, eight articles were included in the qualitative analysis and six were included in the quantitative analysis. Almost all indexes showed a negative ES for all types of dementia and mild cognitive impairment. The most common frequency band of the power spectrum density function was the high frequency, which was reported by six studies. The meta-analysis of high frequency power in Alzheimer's disease group showed high heterogeneity and inconsistent results. The negative effect size suggests an autonomic dysfunction in all types of dementia as well as mild cognitive impairment. However, further analysis is necessary to support these results. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Overview of the High Performance Antiproton Trap (HiPAT) Experiment

NASA Technical Reports Server (NTRS)

Martin, James; Chakrabarti, Suman; Pearson, Boise; Sims, W. Herbert; Lewis, Raymond; Fant, Wallace; Rodgers, Stephen (Technical Monitor)

2002-01-01

A general overview of the High Performance Antiproton Trap (HiPAT) Experiment is presented. The topics include: 1) Why Antimatter? 2) HiPAT Applicability; 3) Approach-Goals; 4) HiPAT General Layout; 5) Sizing For Containment; 6) Laboratory Operations; 7) Vacuum System Cleaning; 8) Ion Production Via Electron Gun; 9) Particle Capture Via Ion Sources; 10) Ion Beam Steering/Focusing; 11) Ideal Ion Stacking Sequence; 12) Setup For Dynamic Capture; 13) Dynamic Capture of H(+) Ions; 14) Dynamic Capture; 15) Radio Frequency Particle Detection; 16) Radio Frequency Antenna Modeling; and 17) R.F. Stabilization-Low Frequencies. A short presentation of propulsion applications of Antimatter is also given. This paper is in viewgraph form.

Reduction in menopause-related symptoms associated with use of a noninvasive neurotechnology for autocalibration of neural oscillations.

PubMed

Tegeler, Charles H; Tegeler, Catherine L; Cook, Jared F; Lee, Sung W; Pajewski, Nicholas M

2015-06-01

Increased amplitudes in high-frequency brain electrical activity are reported with menopausal hot flashes. We report outcomes associated with the use of High-resolution, relational, resonance-based, electroencephalic mirroring--a noninvasive neurotechnology for autocalibration of neural oscillations--by women with perimenopausal and postmenopausal hot flashes. Twelve women with hot flashes (median age, 56 y; range, 46-69 y) underwent a median of 13 (range, 8-23) intervention sessions for a median of 9.5 days (range, 4-32). This intervention uses algorithmic analysis of brain electrical activity and near real-time translation of brain frequencies into variable tones for acoustic stimulation. Hot flash frequency and severity were recorded by daily diary. Primary outcomes included hot flash severity score, sleep, and depressive symptoms. High-frequency amplitudes (23-36 Hz) from bilateral temporal scalp recordings were measured at baseline and during serial sessions. Self-reported symptom inventories for sleep and depressive symptoms were collected. The median change in hot flash severity score was -0.97 (range, -3.00 to 1.00; P = 0.015). Sleep and depression scores decreased by -8.5 points (range, -20 to -1; P = 0.022) and -5.5 points (range, -32 to 8; P = 0.015), respectively. The median sum of amplitudes for the right and left temporal high-frequency brain electrical activity was 8.44 μV (range, 6.27-16.66) at baseline and decreased by a median of -2.96 μV (range, -11.05 to -0.65; P = 0.0005) by the final session. Hot flash frequency and severity, symptoms of insomnia and depression, and temporal high-frequency brain electrical activity decrease after High-resolution, relational, resonance-based, electroencephalic mirroring. Larger controlled trials with longer follow-up are warranted.

A novel photonic oscillator

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1995-01-01

We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

A high-throughput flow cytometry-on-a-CMOS platform for single-cell dielectric spectroscopy at microwave frequencies.

PubMed

Chien, Jun-Chau; Ameri, Ali; Yeh, Erh-Chia; Killilea, Alison N; Anwar, Mekhail; Niknejad, Ali M

2018-06-06

This work presents a microfluidics-integrated label-free flow cytometry-on-a-CMOS platform for the characterization of the cytoplasm dielectric properties at microwave frequencies. Compared with MHz impedance cytometers, operating at GHz frequencies offers direct intracellular permittivity probing due to electric fields penetrating through the cellular membrane. To overcome the detection challenges at high frequencies, the spectrometer employs on-chip oscillator-based sensors, which embeds simultaneous frequency generation, electrode excitation, and signal detection capabilities. By employing an injection-locking phase-detection technique, the spectrometer offers state-of-the-art sensitivity, achieving a less than 1 aFrms capacitance detection limit (or 5 ppm in frequency-shift) at a 100 kHz noise filtering bandwidth, enabling high throughput (>1k cells per s), with a measured cellular SNR of more than 28 dB. With CMOS/microfluidics co-design, we distribute four sensing channels at 6.5, 11, 17.5, and 30 GHz in an arrayed format whereas the frequencies are selected to center around the water relaxation frequency at 18 GHz. An issue in the integration of CMOS and microfluidics due to size mismatch is also addressed through introducing a cost-efficient epoxy-molding technique. With 3-D hydrodynamic focusing microfluidics, we perform characterization on four different cell lines including two breast cell lines (MCF-10A and MDA-MB-231) and two leukocyte cell lines (K-562 and THP-1). After normalizing the higher frequency signals to the 6.5 GHz ones, the size-independent dielectric opacity shows a differentiable distribution at 17.5 GHz between normal (0.905 ± 0.160, mean ± std.) and highly metastatic (1.033 ± 0.107) breast cells with p ≪ 0.001.

A self-mixing based ring-type fiber-optic acoustic sensor

NASA Astrophysics Data System (ADS)

Wang, Lutang; Wu, Chunxu; Fang, Nian

2014-07-01

A novel, simple fiber-optic acoustic sensor consisting of a self-mixing effect based laser source and a ring-type interferometer is presented. With weak external optical feedbacks, the acoustic wave signals can be detected by measuring the changes of oscillating frequency of the laser diode, induced by the disturbances of sensing fiber, with the ring-type interferometer. The operation principles of the sensor system are explored in-depth and the experimental researches are carried out. The acoustic wave signals produced by various actions, such as by pencil broken, mental pin free falling and PZT are detected for evaluating the sensing performances of the experimental system. The investigation items include the sensitivity as well as frequency responses of the sensor system. An experiment for the detection of corona discharges is carried out, which occur in a high-voltage environment between two parallel copper electrodes, under different humidity levels. The satisfied experimental results are obtained. These experimental results well prove that our proposed sensing system has very high sensitivity and excellent high frequency responses characteristics in the detections of weak, high-frequency acoustic wave signals.

Generation of mechanical oscillation applicable to vibratory rate gyroscopes

NASA Technical Reports Server (NTRS)

Lemkin, Mark A. (Inventor); Juneau, Thor N. (Inventor); Clark, William A. (Inventor); Roessig, Allen W. (Inventor)

2001-01-01

To achieve a drive-axis oscillation with improved frequency and amplitude stability, additional feedback loops are used to adjust force-feedback loop parameters. An amplitude-control loop measures oscillation amplitude, compares this value to the desired level, and adjusts damping of the mechanical sense-element to grow or shrink oscillation amplitude as appropriate. A frequency-tuning loop measures the oscillation frequency, compares this value with a highly stable reference, and adjusts the gain in the force-feedback loop to keep the drive-axis oscillation frequency at the reference value. The combined topology simultaneously controls both amplitude and frequency. Advantages of the combined topology include improved stability, fast oscillation start-up, low power consumption, and excellent shock rejection.

[The substantiation of the use of high-frequency intrapulmonary ventilation in the patients presenting with chronic obstructive pulmonary disease at the spa and health resort stage of rehabilitation].

PubMed

Zaripova, T N; Zhilyakova, L V; Bulanova, Z P

The importance of the development of the new methods for the rehabilitation of the patients presenting with chronic obstructive pulmonary disease under conditions of the spa and health resort-based treatment arises from the high prevalence and the progressive character of this disease, poor quality of the patients' life, great economic losses due to the reduction of the working capacity of the patients, and the high cost of COPD treatment. The objective of the present study was to substantiate the advisability of inclusion of high-frequency intrapulmonary ventilation in the program of the therapeutic and rehabilitative treatment of the patients with COPD based at a spa and health resort facility. The analysis of the results of examination and rehabilitative treatment included 49 patients treated at the «Belokurikha» health resort (14 women and 35 men presenting with stage 1 and 2 COPD). The patients were divided into two groups. The main one included 23 patients while the group of comparison consisted of 26 patients. Those of the main group were given the treatment that included the mineral water baths, inhalations, exercise therapy for the training of skeletal muscles, manual massage, high-frequency intrapulmonary ventilation, intake of extract maral root (Rhaponticum carthamoides) and the «Yantar antiox» (amber antiox) preparation. The patients of the comparison group received the same rehabilitative treatment but without high-frequency intrapulmonary ventilation. The effectiveness of the rehabilitative measures was comprehensively estimated from the dynamics of the clinical data, indices of the inflammatory activity, the results of spirography and 6 minute walking test. It has been shown that the introduction of high-frequency intrapulmonary ventilation into the spa and health resort-based rehabilitative program facilitates the elimination of clinical manifestation of the disease, promotes recovery of the external respiration function due to sputum recruiting and stimulation of mucociliary clearance that in turn decreases the activity of the inflammatory processes. Simultaneously, the thoracic mobility and physical efficiency of the patients increased. The overall result of the treatment was the enhanced quality of rehabilitation of the patients suffering COPD within 14-16 days of their stay at the health resort with excellent tolerability of the proposed therapeutic modality.

Miniature L-Band Radar Transceiver

NASA Technical Reports Server (NTRS)

McWatters, Dalia; Price, Douglas; Edelstein, Wendy

2007-01-01

A miniature L-band transceiver that operates at a carrier frequency of 1.25 GHz has been developed as part of a generic radar electronics module (REM) that would constitute one unit in an array of many identical units in a very-large-aperture phased-array antenna. NASA and the Department of Defense are considering the deployment of such antennas in outer space; the underlying principles of operation, and some of those of design, also are applicable on Earth. The large dimensions of the antennas make it advantageous to distribute radio-frequency electronic circuitry into elements of the arrays. The design of the REM is intended to implement the distribution. The design also reflects a requirement to minimize the size and weight of the circuitry in order to minimize the weight of any such antenna. Other requirements include making the transceiver robust and radiation-hard and minimizing power demand. Figure 1 depicts the functional blocks of the REM, including the L-band transceiver. The key functions of the REM include signal generation, frequency translation, amplification, detection, handling of data, and radar control and timing. An arbitrary-waveform generator that includes logic circuitry and a digital-to-analog converter (DAC) generates a linear-frequency-modulation chirp waveform. A frequency synthesizer produces local-oscillator signals used for frequency conversion and clock signals for the arbitrary-waveform generator, for a digitizer [that is, an analog-to-digital converter (ADC)], and for a control and timing unit. Digital functions include command, timing, telemetry, filtering, and high-rate framing and serialization of data for a high-speed scientific-data interface. The aforementioned digital implementation of filtering is a key feature of the REM architecture. Digital filters, in contradistinction to analog ones, provide consistent and temperature-independent performance, which is particularly important when REMs are distributed throughout a large array. Digital filtering also enables selection among multiple filter parameters as required for different radar operating modes. After digital filtering, data are decimated appropriately in order to minimize the data rate out of an antenna panel. The L-band transceiver (see Figure 2) includes a radio-frequency (RF)-to-baseband down-converter chain and an intermediate- frequency (IF)-to-RF up-converter chain. Transmit/receive (T/R) switches enable the use of a single feed to the antenna for both transmission and reception. The T/R switches also afford a built-in test capability by enabling injection of a calibration signal into the receiver chain. In order of decreasing priority, components of the transceiver were selected according to requirements of radiation hardness, then compactness, then low power. All of the RF components are radiation-hard. The noise figure (NF) was optimized to the extent that (1) a low-noise amplifier (LNA) (characterized by NF < 2 dB) was selected but (2) the receiver front-end T/R switches were selected for a high degree of isolation and acceptably low loss, regardless of the requirement to minimize noise.

Pressure and Thrust Measurements of a High-Frequency Pulsed Detonation Tube

NASA Technical Reports Server (NTRS)

Nguyen, N.; Cutler, A. D.

2008-01-01

This paper describes measurements of a small-scale, high-frequency pulsed detonation tube. The device utilized a mixture of H2 fuel and air, which was injected into the device at frequencies of up to 1200 Hz. Pulsed detonations were demonstrated in an 8-inch long combustion volume, at about 600 Hz, for the quarter wave mode of resonance. The primary objective of this experiment was to measure the generated thrust. A mean value of thrust was measured up to 6.0 lb, corresponding to H2 flow based specific impulse of 2970 s. This value is comparable to measurements in H2-fueled pulsed detonation engines (PDEs). The injection and detonation frequency for this new experimental case was much higher than typical PDEs, where frequencies are usually less than 100 Hz. The compact size of the device and high frequency of detonation yields a thrust-per-unit-volume of approximately 2.0 pounds per cubic inch, and compares favorably with other experiments, which typically have thrust-per-unit-volume of order 0.01 pound per cubic inch. This much higher volumetric efficiency results in a potentially much more practical device than the typical PDE, for a wide range of potential applications, including high-speed boundary layer separation control, for example in hypersonic engine inlets, and propulsion for small aircraft and missiles.

267 Spanish Exomes Reveal Population-Specific Differences in Disease-Related Genetic Variation

PubMed Central

Dopazo, Joaquín; Amadoz, Alicia; Bleda, Marta; Garcia-Alonso, Luz; Alemán, Alejandro; García-García, Francisco; Rodriguez, Juan A.; Daub, Josephine T.; Muntané, Gerard; Rueda, Antonio; Vela-Boza, Alicia; López-Domingo, Francisco J.; Florido, Javier P.; Arce, Pablo; Ruiz-Ferrer, Macarena; Méndez-Vidal, Cristina; Arnold, Todd E.; Spleiss, Olivia; Alvarez-Tejado, Miguel; Navarro, Arcadi; Bhattacharya, Shomi S.; Borrego, Salud; Santoyo-López, Javier; Antiñolo, Guillermo

2016-01-01

Recent results from large-scale genomic projects suggest that allele frequencies, which are highly relevant for medical purposes, differ considerably across different populations. The need for a detailed catalog of local variability motivated the whole-exome sequencing of 267 unrelated individuals, representative of the healthy Spanish population. Like in other studies, a considerable number of rare variants were found (almost one-third of the described variants). There were also relevant differences in allelic frequencies in polymorphic variants, including ∼10,000 polymorphisms private to the Spanish population. The allelic frequencies of variants conferring susceptibility to complex diseases (including cancer, schizophrenia, Alzheimer disease, type 2 diabetes, and other pathologies) were overall similar to those of other populations. However, the trend is the opposite for variants linked to Mendelian and rare diseases (including several retinal degenerative dystrophies and cardiomyopathies) that show marked frequency differences between populations. Interestingly, a correspondence between differences in allelic frequencies and disease prevalence was found, highlighting the relevance of frequency differences in disease risk. These differences are also observed in variants that disrupt known drug binding sites, suggesting an important role for local variability in population-specific drug resistances or adverse effects. We have made the Spanish population variant server web page that contains population frequency information for the complete list of 170,888 variant positions we found publicly available (http://spv.babelomics.org/), We show that it if fundamental to determine population-specific variant frequencies to distinguish real disease associations from population-specific polymorphisms. PMID:26764160

Relationships between frequency of family meals, BMI and nutritional aspects of the home food environment among New Zealand adolescents.

PubMed

Utter, Jennifer; Scragg, Robert; Schaaf, David; Mhurchu, Cliona Ni

2008-10-23

Previous research has documented the positive effects of family meals on the dietary quality of adolescents. The objective of the current study is to examine associations between frequency of family meals and body mass index (BMI), other aspects of the home food environment, and related nutrition behaviors. Data were collected during baseline measurements of the Pacific Obesity Prevention In Communities study. In total, 3245 ethnically diverse students completed a questionnaire about their nutrition behaviors and were weighed and measured for height. In total, 42% of adolescents ate a family meal on all of the previous five school nights. Frequency of family meals was modestly associated with BMI in bivariate analysis (p = 0.045), but lost significance when demographic characteristics were included in the model. Frequency of family meals was associated with many positive aspects of home food environment and positive nutrition behaviors, including parental support for healthy eating, limits on television use, having fruit available at home, consuming five fruits and vegetables a day, eating breakfast, and bringing lunch from home. Surprisingly, no relationships were observed between frequency of family meals and accessibility and consumption of many high fat/high sugar foods. Our findings suggest that the positive effect of family meals may reflect an overall positive home food environment. Families who have meals together have more healthful foods available at home and support their child in eating healthfully. There were no relationships between family meals and high fat/high sugar foods; this suggest that while families may prioritize eating together, messages about limiting the availability and consumption of these snack foods are not getting through.

A Novel Intracranial Pressure Readout Circuit for Passive Wireless LC Sensor.

PubMed

Wang, Fa; Zhang, Xuan; Shokoueinejad, Mehdi; Iskandar, Bermans J; Medow, Joshua E; Webster, John G

2017-10-01

We present a wide frequency range, low cost, wireless intracranial pressure monitoring system, which includes an implantable passive sensor and an external reader. The passive sensor consists of two spiral coils and transduces the pressure change to a resonant frequency shift. The external portable reader reads out the sensor's resonant frequency over a wide frequency range (35 MHz-2.7 GHz). We propose a novel circuit topology, which tracks the system's impedance and phase change at a high frequency with low-cost components. This circuit is very simple and reliable. A prototype has been developed, and measurement results demonstrate that the device achieves a suitable measurement distance (>2 cm), sufficient sample frequency (>6 Hz), fine resolution, and good measurement accuracy for medical practice. Responsivity of this prototype is 0.92 MHz/mmHg and resolution is 0.028 mmHg. COMSOL specific absorption rate simulation proves that this system is safe. Considerations to improve the device performance have been discussed, which include the size of antenna, the power radiation, the Analog-to-digital converter (ADC) choice, and the signal processing algorithm.

Direct current ballast circuit for metal halide lamp

NASA Technical Reports Server (NTRS)

Lutus, P. (Inventor)

1981-01-01

A direct current ballast circuit for a two electrode metal halide lamp is described. Said direct current ballast circuit includes a low voltage DC input and a high frequency power amplifier and power transformer for developing a high voltage output. The output voltage is rectified by diodes and filtered by inductor and capacitor to provide a regulated DC output through commutating diodes to one terminal of the lamp at the output terminal. A feedback path from the output of the filter capacitor through the bias resistor to power the high frequency circuit which includes the power amplifier and the power transformer for sustaining circuit operations during low voltage transients on the input DC supply is described. A current sensor connected to the output of the lamp through terminal for stabilizing lamp current following breakdown of the lamp is described.

Highly Accurate Quartic Force Fields, Vibrational Frequencies, and Spectroscopic Constants for Cyclic and Linear C3H3(+)

NASA Technical Reports Server (NTRS)

Huang, Xinchuan; Taylor, Peter R.; Lee, Timothy J.

2011-01-01

High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C H + molecular cation, referred to as c-C H + and I-C H +. Specifically the 33 3333 singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants using both vibrational 2nd-order perturbation theory and variational methods to solve the nuclear Schroedinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C H +, 33 obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C H + 33 and I-C H + are the most reliable available for the free gas-phase species and it is hoped that 33 these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations.

Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at the HAARP Facility

NASA Astrophysics Data System (ADS)

Scales, Wayne; Bernhardt, Paul; McCarrick, Michael; Briczinski, Stanley; Mahmoudian, Alireza; Fu, Haiyang; Ranade Bordikar, Maitrayee; Samimi, Alireza

There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. There is also important parametric behavior on both classes of NSEE depending on the pump wave parameters including the field strength, antenna beam angle, and electron gyro-harmonic number. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Bernstein Scatter SIBS observations will be discussed as well as their relationship to each other. Possible theoretical formulation in terms of parametric decay instabilities will be provided. Computer simulation model results will be presented to provide insight into associated higher order nonlinear effects including particle acceleration and wave-wave processes. Both theory and model results will be put into the context of the experimental observations. Finally, possible applications of NSEE will be pointed out including triggering diagnostics for artificial ionization layer formation, proton precipitation event diagnostics, and electron temperature measurements in the heated volume.

Effects of Navigated Repetitive Transcranial Magnetic Stimulation After Stroke.

PubMed

Chervyakov, Alexander V; Poydasheva, Alexandra G; Lyukmanov, Roman H; Suponeva, Natalia A; Chernikova, Ludmila A; Piradov, Michael A; Ustinova, Ksenia I

2018-03-01

The purpose of this study was to test the effects of navigated repetitive transcranial magnetic stimulation, delivered in different modes, on motor impairments and functional limitations after stroke. The study sample included 42 patients (58.5 ± 10.7 years; 26 males) who experienced a single unilateral stroke (1-12 months previously) in the area of the middle cerebral artery. Patients completed a course of conventional rehabilitation, together with 10 sessions of navigated repetitive transcranial magnetic stimulation or sham stimulation. Stimulation was scheduled five times a week over two consecutive weeks in an inpatient clinical setting. Patients were randomly assigned to one of four groups and received sham stimulation (n = 10), low-frequency (1-Hz) stimulation of the nonaffected hemisphere (n = 11), high-frequency (10-Hz) stimulation of the affected hemisphere (n = 13), or sequential combination of low- and high-frequency stimulations (n = 8). Participants were evaluated before and after stimulation with clinical tests, including the arm and hand section of the Fugl-Meyer Assessment Scale, modified Ashworth Scale of Muscle Spasticity, and Barthel Index of Activities of Daily Living. Participants in the three groups receiving navigated repetitive transcranial magnetic stimulation showed improvements in arm and hand functions on the Fugl-Meyer Stroke Assessment Scale. Ashworth Scale of Muscle Spasticity and Barthel Index scores were significantly reduced in groups receiving low- or high-frequency stimulation alone. Including navigated repetitive transcranial magnetic stimulation in a conventional rehabilitation program positively influenced motor and functional recovery in study participants, demonstrating the clinical potential of the method. The results of this study will be used for designing a large-scale clinical trial.

High energy efficient solid state laser sources

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1988-01-01

Recent progress in the development of highly efficient coherent optical sources is reviewed. This work focusses on nonlinear frequency conversion of the highly coherent output of the Non-Planar Ring Laser Oscillators developed earlier in the program, and includes high efficiency second harmonic generation and the operation of optical parametric oscillators for wavelength diversity and tunability.

The matrix exponential in transient structural analysis

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

1987-01-01

The primary usefulness of the presented theory is in the ability to represent the effects of high frequency linear response with accuracy, without requiring very small time steps in the analysis of dynamic response. The matrix exponential contains a series approximation to the dynamic model. However, unlike the usual analysis procedure which truncates the high frequency response, the approximation in the exponential matrix solution is in the time domain. By truncating the series solution to the matrix exponential short, the solution is made inaccurate after a certain time. Yet, up to that time the solution is extremely accurate, including all high frequency effects. By taking finite time increments, the exponential matrix solution can compute the response very accurately. Use of the exponential matrix in structural dynamics is demonstrated by simulating the free vibration response of multi degree of freedom models of cantilever beams.

High-speed three-dimensional shape measurement for dynamic scenes using bi-frequency tripolar pulse-width-modulation fringe projection

NASA Astrophysics Data System (ADS)

Zuo, Chao; Chen, Qian; Gu, Guohua; Feng, Shijie; Feng, Fangxiaoyu; Li, Rubin; Shen, Guochen

2013-08-01

This paper introduces a high-speed three-dimensional (3-D) shape measurement technique for dynamic scenes by using bi-frequency tripolar pulse-width-modulation (TPWM) fringe projection. Two wrapped phase maps with different wavelengths can be obtained simultaneously by our bi-frequency phase-shifting algorithm. Then the two phase maps are unwrapped using a simple look-up-table based number-theoretical approach. To guarantee the robustness of phase unwrapping as well as the high sinusoidality of projected patterns, TPWM technique is employed to generate ideal fringe patterns with slight defocus. We detailed our technique, including its principle, pattern design, and system setup. Several experiments on dynamic scenes were performed, verifying that our method can achieve a speed of 1250 frames per second for fast, dense, and accurate 3-D measurements.

Development of a compact optical absolute frequency reference for space with 10^-15 instability.

PubMed

Schuldt, Thilo; Döringshoff, Klaus; Kovalchuk, Evgeny V; Keetman, Anja; Pahl, Julia; Peters, Achim; Braxmaier, Claus

2017-02-01

We report on a compact and ruggedized setup for laser frequency stabilization employing Doppler-free spectroscopy of molecular iodine near 532 nm. Using a 30 cm long iodine cell in a triple-pass configuration in combination with noise-canceling detection and residual amplitude modulation control, a frequency instability of 6×10^-15 at 1 s integration time and a Flicker noise floor below 3×10^-15 for integration times between 100 and 1000 s was found. A specific assembly-integration technology was applied for the realization of the spectroscopy setup, ensuring high beam pointing stability and high thermal and mechanical rigidity. The setup was developed with respect to future applications in space, including high-sensitivity interspacecraft interferometry, tests of fundamental physics, and navigation and ranging.

Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.

PubMed

Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P

2012-01-01

Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (<100 nW) of the radiation emitted from the quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.

Calculating rhythmicity of infant breathing using wavelets

NASA Astrophysics Data System (ADS)

Macey, Katherine E.; Page, Wyatt H.; Harper, Ronald M.; Macey, Paul M.; Ford, Rodney P. K.

2000-12-01

Breathing signals are one set of physiological data that may provide information regarding the mechanisms that cause SIDS. Isolated breathing pauses have been implicated in fatal events. Other features of interest include slow amplitude modulation of the breathing signal, a phenomenon whose origin is unclear, and periodic breathing. The latter describes a repetitive series of apnea, and may be considered an extreme manifestation of amplitude modulation with successive cessations of breathing. Rhythmicity is defined to assess the impact of amplitude modulation on breathing signals and describes the extent to which frequency components remain constant for the duration of the signal. The wavelet transform was used to identify sections of constant frequency components within signals. Rhythmicity can be evaluated for all the frequency components in a signal, for individual frequencies. The rhythmicity of eight breathing epochs from sleeping infants at high and low risk for SIDS was calculated. Initial results show breathing from infants at high risk for SIDS exhibits greater rhythmicity of modulating frequencies than breathing from low risk infants.

Plasma Physics Challenges of MM-to-THz and High Power Microwave Generation

NASA Astrophysics Data System (ADS)

Booske, John

2007-11-01

Homeland security and military defense technology considerations have stimulated intense interest in mobile, high power sources of millimeter-wave to terahertz regime electromagnetic radiation, from 0.1 to 10 THz. While sources at the low frequency end, i.e., the gyrotron, have been deployed or are being tested for diverse applications such as WARLOC radar and active denial systems, the challenges for higher frequency sources have yet to be completely met for applications including noninvasive sensing of concealed weapons and dangerous agents, high-data-rate communications, and high resolution spectroscopy and atmospheric sensing. The compact size requirements for many of these high frequency sources requires miniscule, micro-fabricated slow wave circuits with high rf ohmic losses. This necessitates electron beams with not only very small transverse dimensions but also very high current density for adequate gain. Thus, the emerging family of mm-to-THz e-beam-driven vacuum electronics devices share many of the same plasma physics challenges that currently confront ``classic'' high power microwave (HPM) generators [1] including bright electron sources, intense beam transport, energetic electron interaction with surfaces and rf air breakdown at output windows. Multidimensional theoretical and computational models are especially important for understanding and addressing these challenges. The contemporary plasma physics issues, recent achievements, as well as the opportunities and outlook on THz and HPM will be addressed. [1] R.J. Barker, J.H. Booske, N.C. Luhmann, and G.S. Nusinovich, Modern Microwave and Millimeter-Wave Power Electronics (IEEE/Wiley, 2005).

Ultrasonic techniques for measuring physical properties of fluids in harsh environments

NASA Astrophysics Data System (ADS)

Pantea, Cristian

Ultrasonic-based measurement techniques, either in the time domain or in the frequency domain, include a wide range of experimental methods for investigating physical properties of materials. This discussion is specifically focused on ultrasonic methods and instrumentation development for the determination of liquid properties at conditions typically found in subsurface environments (in the U.S., more than 80% of total energy needs are provided by subsurface energy sources). Such sensors require materials that can withstand harsh conditions of high pressure, high temperature and corrosiveness. These include the piezoelectric material, electrically conductive adhesives, sensor housings/enclosures, and the signal carrying cables, to name a few. A complete sensor package was developed for operation at high temperatures and pressures characteristic to geothermal/oil-industry reservoirs. This package is designed to provide real-time, simultaneous measurements of multiple physical parameters, such as temperature, pressure, salinity and sound speed. The basic principle for this sensor's operation is an ultrasonic frequency domain technique, combined with transducer resonance tracking. This multipurpose acoustic sensor can be used at depths of several thousand meters, temperatures up to 250 °C, and in a very corrosive environment. In the context of high precision measurement of sound speed, the determination of acoustic nonlinearity of liquids will also be discussed, using two different approaches: (i) the thermodynamic method, in which precise and accurate frequency domain sound speed measurements are performed at high pressure and high temperature, and (ii) a modified finite amplitude method, requiring time domain measurements of the second harmonic at room temperature. Efforts toward the development of an acoustic source of collimated low-frequency (10-150 kHz) beam, with applications in imaging, will also be presented.

Effect of Cigarette Smoking and Passive Smoking on Hearing Impairment: Data from a Population–Based Study

PubMed Central

Chang, Jiwon; Ryou, Namhyung; Jun, Hyung Jin; Hwang, Soon Young; Song, Jae-Jun; Chae, Sung Won

2016-01-01

Objectives In the present study, we aimed to determine the effect of both active and passive smoking on the prevalence of the hearing impairment and the hearing thresholds in different age groups through the analysis of data collected from the Korea National Health and Nutrition Examination Survey (KNHANES). Study Design Cross-sectional epidemiological study. Methods The KNHANES is an ongoing population study that started in 1998. We included a total of 12,935 participants aged ≥19 years in the KNHANES, from 2010 to 2012, in the present study. Pure-tone audiometric (PTA) testing was conducted and the frequencies tested were 0.5, 1, 2, 3, 4, and 6 kHz. Smoking status was categorized into three groups; current smoking group, passive smoking group and non-smoking group. Results In the current smoking group, the prevalence of speech-frequency bilateral hearing impairment was increased in ages of 40−69, and the rate of high frequency bilateral hearing impairment was elevated in ages of 30−79. When we investigated the impact of smoking on hearing thresholds, we found that the current smoking group had significantly increased hearing thresholds compared to the passive smoking group and non-smoking groups, across all ages in both speech-relevant and high frequencies. The passive smoking group did not have an elevated prevalence of either speech-frequency bilateral hearing impairment or high frequency bilateral hearing impairment, except in ages of 40s. However, the passive smoking group had higher hearing thresholds than the non-smoking group in the 30s and 40s age groups. Conclusion Current smoking was associated with hearing impairment in both speech-relevant frequency and high frequency across all ages. However, except in the ages of 40s, passive smoking was not related to hearing impairment in either speech-relevant or high frequencies. PMID:26756932

The role of superconductivity in the Space Program: An assessment of present capabilities and future potential

NASA Technical Reports Server (NTRS)

Sullivan, D. B. (Editor)

1978-01-01

Technical subject areas discussed include: (1) high field magnets; (2) magnetometers; (3) digital electronics; (4) high frequency detectors; (5) instruments related to gravitational studies; and (6) ultra high Q cavities. Applications of superconductivity which are of potential interest to NASA were identified.

Very Low Frequency Breakdown Properties of Electrical Insulation Materials at Cryogenic Temperatures

NASA Astrophysics Data System (ADS)

Sauers, I.; Tuncer, E.; Polizos, G.; James, D. R.; Ellis, A. R.; Pace, M. O.

2010-04-01

For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex™ (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0.1 Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.

Processing of frequency-modulated sounds in the lateral auditory belt cortex of the rhesus monkey.

PubMed

Tian, Biao; Rauschecker, Josef P

2004-11-01

Single neurons were recorded from the lateral belt areas, anterolateral (AL), mediolateral (ML), and caudolateral (CL), of nonprimary auditory cortex in 4 adult rhesus monkeys under gas anesthesia, while the neurons were stimulated with frequency-modulated (FM) sweeps. Responses to FM sweeps, measured as the firing rate of the neurons, were invariably greater than those to tone bursts. In our stimuli, frequency changed linearly from low to high frequencies (FM direction "up") or high to low frequencies ("down") at varying speeds (FM rates). Neurons were highly selective to the rate and direction of the FM sweep. Significant differences were found between the 3 lateral belt areas with regard to their FM rate preferences: whereas neurons in ML responded to the whole range of FM rates, AL neurons responded better to slower FM rates in the range of naturally occurring communication sounds. CL neurons generally responded best to fast FM rates at a speed of several hundred Hz/ms, which have the broadest frequency spectrum. These selectivities are consistent with a role of AL in the decoding of communication sounds and of CL in the localization of sounds, which works best with broader bandwidths. Together, the results support the hypothesis of parallel streams for the processing of different aspects of sounds, including auditory objects and auditory space.

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.

High frequency switched-mode stimulation can evoke post synaptic responses in cerebellar principal neurons

PubMed Central

van Dongen, Marijn N.; Hoebeek, Freek E.; Koekkoek, S. K. E.; De Zeeuw, Chris I.; Serdijn, Wouter A.

2015-01-01

This paper investigates the efficacy of high frequency switched-mode neural stimulation. Instead of using a constant stimulation amplitude, the stimulus is switched on and off repeatedly with a high frequency (up to 100 kHz) duty cycled signal. By means of tissue modeling that includes the dynamic properties of both the tissue material as well as the axon membrane, it is first shown that switched-mode stimulation depolarizes the cell membrane in a similar way as classical constant amplitude stimulation. These findings are subsequently verified using in vitro experiments in which the response of a Purkinje cell is measured due to a stimulation signal in the molecular layer of the cerebellum of a mouse. For this purpose a stimulator circuit is developed that is able to produce a monophasic high frequency switched-mode stimulation signal. The results confirm the modeling by showing that switched-mode stimulation is able to induce similar responses in the Purkinje cell as classical stimulation using a constant current source. This conclusion opens up possibilities for novel stimulation designs that can improve the performance of the stimulator circuitry. Care has to be taken to avoid losses in the system due to the higher operating frequency. PMID:25798105

Frequency-agile THz-wave generation and detection system using nonlinear frequency conversion at room temperature.

PubMed

Guo, Ruixiang; Ikar'i, Tomofumi; Zhang, Jun; Minamide, Hiroaki; Ito, Hiromasa

2010-08-02

A surface-emitting THz parametric oscillator is set up to generate a narrow-linewidth, nanosecond pulsed THz-wave radiation. The THz-wave radiation is coherently detected using the frequency up-conversion in MgO: LiNbO(3) crystal. Fast frequency tuning and automatic achromatic THz-wave detection are achieved through a special optical design, including a variable-angle mirror and 1:1 telescope devices in the pump and THz-wave beams. We demonstrate a frequency-agile THz-wave parametric generation and THz-wave coherent detection system. This system can be used as a frequency-domain THz-wave spectrometer operated at room-temperature, and there are a high possible to develop into a real-time two-dimensional THz spectral imaging system.

Comb-based radiofrequency photonic filters with rapid tunability and high selectivity

NASA Astrophysics Data System (ADS)

Supradeepa, V. R.; Long, Christopher M.; Wu, Rui; Ferdous, Fahmida; Hamidi, Ehsan; Leaird, Daniel E.; Weiner, Andrew M.

2012-03-01

Photonic technologies have received considerable attention regarding the enhancement of radiofrequency electrical systems, including high-frequency analogue signal transmission, control of phased arrays, analog-to-digital conversion and signal processing. Although the potential of radiofrequency photonics for the implementation of tunable electrical filters over broad radiofrequency bandwidths has been much discussed, the realization of programmable filters with highly selective filter lineshapes and rapid reconfigurability has faced significant challenges. A new approach for radiofrequency photonic filters based on frequency combs offers a potential route to simultaneous high stopband attenuation, fast tunability and bandwidth reconfiguration. In one configuration, tuning of the radiofrequency passband frequency is demonstrated with unprecedented (~40 ns) speed by controlling the optical delay between combs. In a second, fixed filter configuration, cascaded four-wave mixing simultaneously broadens and smoothes the comb spectra, resulting in Gaussian radiofrequency filter lineshapes exhibiting an extremely high (>60 dB) main lobe to sidelobe suppression ratio and (>70 dB) stopband attenuation.

Electromagnetic properties of polycrystalline diamond from 35 K to room temperature and microwave to terahertz frequencies

NASA Astrophysics Data System (ADS)

Floch, Jean-Michel Le; Bara, Romain; Hartnett, John G.; Tobar, Michael E.; Mouneyrac, David; Passerieux, Damien; Cros, Dominique; Krupka, Jerzy; Goy, Philippe; Caroopen, Sylvain

2011-05-01

Dielectric resonators are key components for many microwave and millimeter wave applications, including high-Q filters and frequency-determining elements for precision frequency synthesis. These often depend on the quality of the dielectric material. The commonly used material for building the best cryogenic microwave oscillators is sapphire. However, sapphire is becoming a limiting factor for higher frequency designs. It is, then, important to find new candidates that can fulfill the requirements for millimeter wave low noise oscillators at room and cryogenic temperatures. These clocks are used as a reference in many fields, such as modern telecommunication systems, radio astronomy (very-long-baseline interferometry), and precision measurements at the quantum limit. High resolution measurements were taken of the temperature-dependence of the electromagnetic properties of a polycrystalline diamond disk at temperatures between 35 and 330 K at microwave to submillimeter wave frequencies. The cryogenic measurements were made using a TE01δ dielectric mode resonator placed inside a vacuum chamber connected to a single-stage pulse-tube cryocooler. The high frequency characterization was performed at room temperature using a combination of a quasi-optical two-lens transmission setup, a Fabry-Perot cavity, and a whispering gallery mode resonator excited with waveguides. Our CVD diamond sample exhibits a decreasing loss tangent with increasing frequencies. We compare the results with well known crystals. This comparison makes it clear that polycrystalline diamond could be an important material for generating stable frequencies at millimeter waves.

Variable frequency iteration MPPT for resonant power converters

DOEpatents

Zhang, Qian; Bataresh, Issa; Chen, Lin

2015-06-30

A method of maximum power point tracking (MPPT) uses an MPPT algorithm to determine a switching frequency for a resonant power converter, including initializing by setting an initial boundary frequency range that is divided into initial frequency sub-ranges bounded by initial frequencies including an initial center frequency and first and second initial bounding frequencies. A first iteration includes measuring initial powers at the initial frequencies to determine a maximum power initial frequency that is used to set a first reduced frequency search range centered or bounded by the maximum power initial frequency including at least a first additional bounding frequency. A second iteration includes calculating first and second center frequencies by averaging adjacent frequent values in the first reduced frequency search range and measuring second power values at the first and second center frequencies. The switching frequency is determined from measured power values including the second power values.

Serotonin transporter gene polymorphism in eating disorders: Data from a new biobank and META-analysis of previous studies.

PubMed

Solmi, M; Gallicchio, D; Collantoni, E; Correll, C U; Clementi, M; Pinato, C; Forzan, M; Cassina, M; Fontana, F; Giannunzio, V; Piva, I; Siani, R; Salvo, P; Santonastaso, P; Tenconi, E; Veronese, N; Favaro, A

2016-06-01

Objectives Growing interest focuses on the association between 5-HTTLPR polymorphism and eating disorders (ED), but published findings have been conflicting. Methods The Italian BIO.VE.D.A. biobank provided 976 samples (735 ED patients and 241 controls) for genotyping. We conducted a literature search of studies published up to 1 April 2015, including studies reporting on 5HTTLPR genotype and allele frequencies in obesity and/or ED. We ran a meta-analysis, including data from BIO.VE.D.A. - comparing low and high-functioning genotype and allele frequencies in ED vs. Results Data from 21 studies, plus BIO.VE.D.A., were extracted providing information from 3,736 patients and 2,707 controls. Neither low- nor high-functioning genotype frequencies in ED patients, with both bi- and tri-allelic models, differed from controls. Furthermore, neither low- nor high-functioning allele frequencies in ED or in BN, in both bi- and triallelic models, differed from control groups. After sensitivity analysis, results were the same in AN vs. Results remained unaltered when investigating recessive and dominant models. Conclusions 5HTTLPR does not seem to be associated with ED in general, or with AN or BN in particular. Future studies in ED should explore the role of ethnicity and psychiatric comorbidity as a possible source of bias.

Science highlights from high-sensitivity pulsar observations with the MWA

NASA Astrophysics Data System (ADS)

McSweeney, Samuel; Bhat, Ramesh; Tremblay, Steven; Ord, Stephen

2016-01-01

Pulsars are exquisite probes of the turbulent interstellar medium (ISM), capable of resolving structures down to tens of thousands of kilometres. Understanding the ISM is important for many areas of astrophysics, such as galactic dynamics, the chemical evolution of the galaxy, and the identification of timing noise in the search for gravitational waves using pulsar timing arrays. Low frequency observations of pulsars are key, because the strength of propagation effects scales strongly with frequency.We present the Murchison Widefield Array (MWA) as a key science tool for making high quality observations of pulsars at low frequencies (~80-300 MHz). Recently commissioned software for making tied-array beams and the MWA's high time resolution voltage capture system (VCS) allow an order of magnitude increase in sensitivity, vital for pulsar and other time-domain science. A pipeline has now been developed for observing the scintillation patterns of important pulsars at low frequencies, including a new computational technique for measuring the curvature of parabolic arcs in noisy secondary spectra. A program of MWA observations is being undertaken to sample a large number of millisecond pulsars. We present recent highlights including PSR J0437-4715, which yielded a new measurement of scattering screen distance of ~120 pc from Earth, consistent with a Parkes observation at ~730 MHz, and matching the predicted perimeter of the Local Bubble.

Prediction of broadband ground-motion time histories: Hybrid low/high-frequency method with correlated random source parameters

USGS Publications Warehouse

Liu, P.; Archuleta, R.J.; Hartzell, S.H.

2006-01-01

We present a new method for calculating broadband time histories of ground motion based on a hybrid low-frequency/high-frequency approach with correlated source parameters. Using a finite-difference method we calculate low- frequency synthetics (< ∼1 Hz) in a 3D velocity structure. We also compute broadband synthetics in a 1D velocity model using a frequency-wavenumber method. The low frequencies from the 3D calculation are combined with the high frequencies from the 1D calculation by using matched filtering at a crossover frequency of 1 Hz. The source description, common to both the 1D and 3D synthetics, is based on correlated random distributions for the slip amplitude, rupture velocity, and rise time on the fault. This source description allows for the specification of source parameters independent of any a priori inversion results. In our broadband modeling we include correlation between slip amplitude, rupture velocity, and rise time, as suggested by dynamic fault modeling. The method of using correlated random source parameters is flexible and can be easily modified to adjust to our changing understanding of earthquake ruptures. A realistic attenuation model is common to both the 3D and 1D calculations that form the low- and high-frequency components of the broadband synthetics. The value of Q is a function of the local shear-wave velocity. To produce more accurate high-frequency amplitudes and durations, the 1D synthetics are corrected with a randomized, frequency-dependent radiation pattern. The 1D synthetics are further corrected for local site and nonlinear soil effects by using a 1D nonlinear propagation code and generic velocity structure appropriate for the site’s National Earthquake Hazards Reduction Program (NEHRP) site classification. The entire procedure is validated by comparison with the 1994 Northridge, California, strong ground motion data set. The bias and error found here for response spectral acceleration are similar to the best results that have been published by others for the Northridge rupture.

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.

The impact of gravity waves and cloud nucleation threshold on stratospheric water and tropical tropospheric cloud fraction

NASA Astrophysics Data System (ADS)

Schoeberl, Mark; Dessler, Andrew; Ye, Hao; Wang, Tao; Avery, Melody; Jensen, Eric

2016-08-01

Using the Modern Era Retrospective-Analysis for Research and Applications (MERRA) and MERRA-2 reanalysis winds, temperatures, and anvil cloud ice, we explore the impact of varying the cloud nucleation threshold relative humidity (RH) and high-frequency gravity waves on stratospheric water vapor (H2O) and upper tropical tropopause cloud fraction (TCF). Our model results are compared to 2008/2009 winter TCF derived from Cloud-Aerosol Lidar with Orthogonal Polarization and H2O observations from the Microwave Limb Sounder (MLS). The RH threshold affects both model H2O and TCF, while high-frequency gravity waves mostly impact TCF. Adjusting the nucleation RH and the amplitude of high-frequency gravity waves allows us to tune the model to observations. Reasonable observational agreement is obtained with a nucleation threshold between 130% and 150% RH consistent with airborne observations. For the MERRA reanalysis, we lower the tropopause temperature by 0.5 K roughly consistent with GPS radio occultation measurements and include ~0.1 K high-frequency gravity wave temperature oscillations in order to match TCF and H2O observations. For MERRA-2 we do not need to adjust the tropopause temperature nor add gravity waves, because there are sufficient high-frequency temperature oscillations already present in the MERRA-2 reanalysis to reproduce the observed TCF.

Improved extraction of avocado oil by application of sono-physical processes.

PubMed

Martínez-Padilla, Laura Patricia; Franke, Lisa; Xu, Xin-Qing; Juliano, Pablo

2018-01-01

Ultrasound treatment is known to increase the oil extractability in olive and palm oil processes. This work examined the effect of ultrasound conditioning of avocado puree on oil extractability and quality, at low (18+40kHz) and high (2MHz) frequencies, at litre-scale. Other ultrasound parameters evaluated included high frequency effect (0.4, 0.6, and 2MHz; 5min; 90kJ/kg) and sonication time (2.5-10min at 2MHz), without malaxation. Finally, a megasonic post-malaxation intervention was assessed at selected malaxation times (15, 30, and 60min). Both low and high frequency ultrasound treatments of the non-malaxed avocado puree improved extractability by 15-24% additional oil recovery, with the highest extractability achieved after 2MHz treatments, depending on the fruit maturity and oil content. There was no preferential improvement on oil extractability observed across high frequencies, even though extractability increased with sonication time. Ultrasound treatment also showed a positive effect after puree malaxation. Oils obtained from sonicated purees showed peroxide and free fatty acid values below the industrial specification levels and an increase in total phenolic compounds after 2MHz treatment. High frequency ultrasound conditioning of avocado puree can enhance oil separation and potentially decrease the malaxation time in industrial processes without impacting on oil quality. Copyright © 2017 Elsevier B.V. All rights reserved.

The evolution of social learning rules: payoff-biased and frequency-dependent biased transmission.

PubMed

Kendal, Jeremy; Giraldeau, Luc-Alain; Laland, Kevin

2009-09-21

Humans and other animals do not use social learning indiscriminately, rather, natural selection has favoured the evolution of social learning rules that make selective use of social learning to acquire relevant information in a changing environment. We present a gene-culture coevolutionary analysis of a small selection of such rules (unbiased social learning, payoff-biased social learning and frequency-dependent biased social learning, including conformism and anti-conformism) in a population of asocial learners where the environment is subject to a constant probability of change to a novel state. We define conditions under which each rule evolves to a genetically polymorphic equilibrium. We find that payoff-biased social learning may evolve under high levels of environmental variation if the fitness benefit associated with the acquired behaviour is either high or low but not of intermediate value. In contrast, both conformist and anti-conformist biases can become fixed when environment variation is low, whereupon the mean fitness in the population is higher than for a population of asocial learners. Our examination of the population dynamics reveals stable limit cycles under conformist and anti-conformist biases and some highly complex dynamics including chaos. Anti-conformists can out-compete conformists when conditions favour a low equilibrium frequency of the learned behaviour. We conclude that evolution, punctuated by the repeated successful invasion of different social learning rules, should continuously favour a reduction in the equilibrium frequency of asocial learning, and propose that, among competing social learning rules, the dominant rule will be the one that can persist with the lowest frequency of asocial learning.

Effects of Music Therapy on the Cardiovascular and Autonomic Nervous System in Stress-Induced University Students: A Randomized Controlled Trial.

PubMed

Lee, Kyoung Soon; Jeong, Hyeon Cheol; Yim, Jong Eun; Jeon, Mi Yang

2016-01-01

Stress is caused when a particular relationship between the individual and the environment emerges. Specifically, stress occurs when an individual's abilities are challenged or when one's well-being is threatened by excessive environmental demands. The aim of this study was to measure the effects of music therapy on stress in university students. Randomized controlled trial. Sixty-four students were randomly assigned to the experimental group (n = 33) or the control group (n = 31). Music therapy. Initial measurement included cardiovascular indicators (blood pressure and pulse), autonomic nervous activity (standard deviation of the normal-to-normal intervals [SDNN], normalized low frequency, normalized high frequency, low/high frequency), and subjective stress. After the first measurement, participants in both groups were exposed to a series of stressful tasks, and then a second measurement was conducted. The experimental group then listened to music for 20 minutes and the control group rested for 20 minutes. A third and final measurement was then taken. There were no significant differences between the two groups in the first or second measurement. However, after music therapy, the experimental group and the control group showed significant differences in all variables, including systolic blood pressure (p = .026), diastolic blood pressure (p = .037), pulse (p < .001), SDNN (p = .003), normalized low frequency (p < .001), normalized high frequency (p = .010), and subjective stress (p = .026). Classical music tends to relax the body and may stimulate the parasympathetic nervous system. These results suggest music therapy as an intervention for stress reduction.

The influence of seizure frequency on anterograde and remote memory in mesial temporal lobe epilepsy.

PubMed

Voltzenlogel, Virginie; Vignal, Jean-Pierre; Hirsch, Edouard; Manning, Liliann

2014-10-01

Seizure frequency, although considered as an important factor in memory impairment in mesial temporal epilepsy (mTLE), is mostly confounded with other clinical variables, making it unclear to what extent recurrent seizures actually interfere with memory. The present study focuses on the influence of seizure frequency, studied as a main variable, on anterograde and remote memory. Seventy-one patients with unilateral mTLE were divided into two subgroups, as a function of their seizure frequency (monthly versus weekly seizures). Other seizure-related variables were controlled, namely, lateralisation and type of lesion, age at onset, years of ongoing seizures, etiologic factors, and number of AED. A comprehensive neuropsychological examination, including anterograde memory (verbal and non verbal recognition memory and free recall) tasks together with a large range of tests exploring different domains of remote memory, was carried out. Despite similar results on IQ, executive functions and attention, the low seizure-frequency group performed significantly better than the high seizure-frequency group on anterograde memory tests. Loss of autobiographical episodes and public-events memory, concomitant with spared personal semantic knowledge, was observed in both patient groups compared with healthy subjects. A worsening effect of high seizure frequency was recorded for autobiographical incidents and news-events memory, but unexpectedly, not for memory for famous people. The study of seizure frequency as the main variable leads us to suggest that high seizure frequency, itself, potentiates the effects of mesial temporal lobe damage on episodic memory deficits. Copyright © 2014 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

A compact planar multi-broad band monopole antenna for mobile devices

NASA Astrophysics Data System (ADS)

Zhong, Xiaoqing; Yao, Bin; Zheng, Qinhong; Yang, Jikong; Cao, Xiangqi

2015-10-01

A Multiple-frequency broadband planar monopole antenna is proposed in this Paper. The antenna is stimulated and numerically optimized by HFSS13.0 (High Frequency Structure Simulator). The size of it is 39mm×22mm×1.7mm. The antenna resonates at many frequencies. The parameter S11<=-6dB means the proposed antenna matches well with its feed-line and covers many useful operation frequency bands, including 2G(DCS1800 and PCS1900), 3G(UMTS), 4G(LTE2300 and LTE2500), ISM, WLAN. It is quiet appropriate for the present ultra-thin smart phones

Epistatic selection of a sequence 5{prime} of the gene responsible for cystic fibrosis may account for the high frequency of this disease in the Caucasian population

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macek, M. Jr.; Nash, E.; Cutting, G.R.

1994-09-01

Cystic fibrosis (CF) is one of the more common lethal autosomal recessive disorders in Caucasian populations. Numerous hypotheses including genetic drift, founder effect, sex ratio, segregation distortions and various forms of heterozygote advantage have been proposed to explain the relatively high frequency of CF alleles. The observation of high linkage disequilibrium between markers at the 5{prime} end of CFTR and mutations that cause CF raised the possibility of epistatic selection. CF-linked marker allele frequencies were determined in 417 elderly individuals from a stable Czech population that survived high levels of infant and childhood mortality in the pre-antibiotic era. These datamore » were compared with allele frequencies of 646 contemporary newborns and 345 young adults drawn from the same population who had significantly lower mortality rates in the antibiotic era. Allele frequencies of markers CS7/Hhal and KM19/Pstl from the D7S23 locus are significantly different (p<0.05) between elderly female and male subjects in this population. Furthermore, there is a significant difference in the allele frequencies of marker CS7/Hhal when newborn females and elderly women are compared (p<0.05). Taken together, these data suggest that the allele status at the CS7 region influenced female survival in the period of high infant and childhood mortality in the pre-antibiotic era. Under this selective pressure, CFTR mutations that occurred on the {open_quotes}favorable{close_quotes} background would marginally increase in frequency in each successive generation and more ancient mutations residing on this background would become the most frequent in the general population.« less

Frequency conversion system

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor)

2001-01-01

Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

220 microJ Monolithic Single-Frequency Q-switched Fiber Laser at 2 micrometers by Using Highly Tm-doped Germanate Fibers

DTIC Science & Technology

2011-09-15

actively Q-switching all-fiber lasers include mag- netostriction modulation of fiber Bragg gratings ( FBGs ), stretching of FBGs with piezoelectric...report an all- fiber single-frequency actively Q-switched laser operat- ing at ∼1920 nm by using a piezo to press the fiber in the FBG cavity based on...fusion-spliced between two FBGs as shown in Fig. 1. One FBG has a high reflectivity (HR) grating imprinted on a non-PM silica fiber. The other FBG

Supersonic Pulsed Injection

NASA Technical Reports Server (NTRS)

Cutler, A. D.; Harding, G. C.; Diskin, G. S.

2001-01-01

An injector has been developed to provide high-speed high-frequency (order 10 kHz) pulsed a supersonic crossflow. The injector nozzle is formed between the fixed internal surface of the nozzle and a freely rotating three- or four-sided wheel embedded within the device. Flow-induced rotation of the wheel causes the nozzle throat to open and close at a frequency proportional to the speed of sound of the injected gas. Measurements of frequency and mass flow rate as a function of supply pressure are discussed for various injector designs. Preliminary results are presented for wall-normal injection of helium into a Mach-2 ducted airflow. The data include schlieren images in the injectant plume in a plane normal to the flow, downstream of injection.

The information content of high-frequency seismograms and the near-surface geologic structure of "hard rock" recording sites

USGS Publications Warehouse

Cranswick, E.

1988-01-01

Due to hardware developments in the last decade, the high-frequency end of the frequency band of seismic waves analyzed for source mechanisms has been extended into the audio-frequency range (>20 Hz). In principle, the short wavelengths corresponding to these frequencies can provide information about the details of seismic sources, but in fact, much of the "signal" is the site response of the nearsurface. Several examples of waveform data recorded at "hard rock" sites, which are generally assumed to have a "flat" transfer function, are presented to demonstrate the severe signal distortions, including fmax, produced by near-surface structures. Analysis of the geology of a number of sites indicates that the overall attenuation of high-frequency (>1 Hz) seismic waves is controlled by the whole-path-Q between source and receiver but the presence of distinct fmax site resonance peaks is controlled by the nature of the surface layer and the underlying near-surface structure. Models of vertical decoupling of the surface and nearsurface and horizontal decoupling of adjacent sites on hard rock outcrops are proposed and their behaviour is compared to the observations of hard rock site response. The upper bound to the frequency band of the seismic waves that contain significant source information which can be deconvolved from a site response or an array response is discussed in terms of fmax and the correlation of waveform distortion with the outcrop-scale geologic structure of hard rock sites. It is concluded that although the velocity structures of hard rock sites, unlike those of alluvium sites, allow some audio-frequency seismic energy to propagate to the surface, the resulting signals are a highly distorted, limited subset of the source spectra. ?? 1988 Birkha??user Verlag.

High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak

DOE PAGES

Truong, D. D.; Austin, M. E.

2014-11-01

The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. Heterodyning divides this frequency range into three 2-18 GHz intermediate frequency (IF) bands. The frequency spacing of the radiometer’s channels results in a spatial resolution of ~1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels’ IF bands andmore » consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. We achieved a higher spatial resolution through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters’ center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a “zoomed-in” analysis of a ~2-4 cm radial region. These high resolution channels will be most useful in the low-field side edge region where modest Te values (1-2 keV) result in a minimum of relativistic broadening. Some expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, is presented.« less

Development and implementation of a visual card-sorting technique for assessing food and activity preferences and patterns in African American girls.

PubMed

Sherwood, Nancy E; Story, Mary; Neumark-Sztainer, Dianne; Adkins, Sarah; Davis, Marsha

2003-11-01

Card-sorting tasks for assessing food and activity preferences and patterns among African American girls were developed. Associations among food preference and intake frequency, activity preference and frequency, and body mass index were examined. Participants completed newly developed card-sorting tasks assessing food and activity preferences and patterns. Height and weight were measured. Ninety-six 8- to 10-year-old African American girls from schools and community centers in Minneapolis-St. Paul. Preference and frequency data for 64 foods/beverages and 34 activities. Frequencies for food and activity preference and frequency categories were computed. Pearson correlations among food and activity preference, frequency, and body mass index were computed. High-sugar (eg, fruit drinks, soda) and/or high-fat (eg, ice cream, cookies) foods were among the most popular and frequently consumed. Ninety-six percent of girls liked fruit drinks, with 35% consuming them "almost every day." Less-structured activities such as biking, games, jump rope, and dance were most popular. Biking was preferred by 85% of girls, with 48% biking "almost every day." Food preference and frequency categories were moderately correlated (r=0.30 to 0.58), as were activity preference and frequency (r=0.37 to 0.49). The card-sorting tasks are useful tools for assessing food and activity preferences and patterns in girls. Obesity prevention programs for African American girls should include preferred activities such as dance, jump rope, and active play. Programs may also benefit from a focus on replacing high fat/high sugar snacks and sweetened beverages with low-fat, lower-calorie snacks and beverages (eg, fruit, vegetables, water).

Simultaneous parametric generation and up-conversion of entangled optical images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saygin, M. Yu., E-mail: mihasyu@gmail.com; Chirkin, A. S., E-mail: aschirkin@rambler.r

A quantum theory of parametric amplification and frequency conversion of an optical image in coupled nonlinear optical processes that include one parametric amplification process at high-frequency pumping and two up-conversion processes in the same pump field is developed. The field momentum operator that takes into account the diffraction and group velocities of the waves is used to derive the quantum equations related to the spatial dynamics of the images during the interaction. An optical scheme for the amplification and conversion of a close image is considered. The mean photon number density and signal-to-noise ratio are calculated in the fixed-pump-field approximationmore » for images at various frequencies. It has been established that the signal-to-noise ratio decreases with increasing interaction length in the amplified image and increases in the images at the generated frequencies, tending to asymptotic values for all interacting waves. The variance of the difference of the numbers of photons is calculated for various pairs of frequencies. The quantum entanglement of the optical images formed in a high-frequency pump field is shown to be converted to higher frequencies during the generation of sum frequencies. Thus, two pairs of entangled optical images are produced in the process considered.« less

Power Electronic Transformer based Three-Phase PWM AC Drives

NASA Astrophysics Data System (ADS)

Basu, Kaushik

A Transformer is used to provide galvanic isolation and to connect systems at different voltage levels. It is one of the largest and most expensive component in most of the high voltage and high power systems. Its size is inversely proportional to the operating frequency. The central idea behind a power electronic transformer (PET) also known as solid state transformer is to reduce the size of the transformer by increasing the frequency. Power electronic converters are used to change the frequency of operation. Steady reduction in the cost of the semiconductor switches and the advent of advanced magnetic materials with very low loss density and high saturation flux density implies economic viability and feasibility of a design with high power density. Application of PET is in generation of power from renewable energy sources, especially wind and solar. Other important application include grid tied inverters, UPS e.t.c. In this thesis non-resonant, single stage, bi-directional PET is considered. The main objective of this converter is to generate adjustable speed and magnitude pulse width modulated (PWM) ac waveforms from an ac or dc grid with a high frequency ac link. The windings of a high frequency transformer contains leakage inductance. Any switching transition of the power electronic converter connecting the inductive load and the transformer requires commutation of leakage energy. Commutation by passive means results in power loss, decrease in the frequency of operation, distortion in the output voltage waveform, reduction in reliability and power density. In this work a source based partially loss-less commutation of leakage energy has been proposed. This technique also results in partial soft-switching. A series of converters with novel PWM strategies have been proposed to minimize the frequency of leakage inductance commutation. These PETs achieve most of the important features of modern PWM ac drives including 1) Input power factor correction, 2) Common-mode voltage suppression at the load end, 3) High quality output voltage waveform (comparable to conventional space vector PWM modulated two level inverter) and 4) Minimization of output voltage loss, common-mode voltage switching and distortion of the load current waveform due to leakage inductance commutation. All of the proposed topologies along with the proposed control schemes have been analyzed and simulated in MATLABSimulink. A hardware prototype has been fabricated and tested. The simulation and experimental results verify the operation and advantages of the proposed topologies and their control.

Exploring the parahippocampal cortex response to high and low spatial frequency spaces.

PubMed

Zeidman, Peter; Mullally, Sinéad L; Schwarzkopf, Dietrich Samuel; Maguire, Eleanor A

2012-05-30

The posterior parahippocampal cortex (PHC) supports a range of cognitive functions, in particular scene processing. However, it has recently been suggested that PHC engagement during functional MRI simply reflects the representation of three-dimensional local space. If so, PHC should respond to space in the absence of scenes, geometric layout, objects or contextual associations. It has also been reported that PHC activation may be influenced by low-level visual properties of stimuli such as spatial frequency. Here, we tested whether PHC was responsive to the mere sense of space in highly simplified stimuli, and whether this was affected by their spatial frequency distribution. Participants were scanned using functional MRI while viewing depictions of simple three-dimensional space, and matched control stimuli that did not depict a space. Half the stimuli were low-pass filtered to ascertain the impact of spatial frequency. We observed a significant interaction between space and spatial frequency in bilateral PHC. Specifically, stimuli depicting space (more than nonspatial stimuli) engaged the right PHC when they featured high spatial frequencies. In contrast, the interaction in the left PHC did not show a preferential response to space. We conclude that a simple depiction of three-dimensional space that is devoid of objects, scene layouts or contextual associations is sufficient to robustly engage the right PHC, at least when high spatial frequencies are present. We suggest that coding for the presence of space may be a core function of PHC, and could explain its engagement in a range of tasks, including scene processing, where space is always present.

Low-frequency Carbon Radio Recombination Lines. I. Calculations of Departure Coefficients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salgado, F.; Morabito, L. K.; Oonk, J. B. R.

In the first paper of this series, we study the level population problem of recombining carbon ions. We focus our study on high quantum numbers, anticipating observations of carbon radio recombination lines to be carried out by the Low Frequency Array. We solve the level population equation including angular momentum levels with updated collision rates up to high principal quantum numbers. We derive departure coefficients by solving the level population equation in the hydrogenic approximation and including low-temperature dielectronic capture effects. Our results in the hydrogenic approximation agree well with those of previous works. When comparing our results including dielectronicmore » capture, we find differences that we ascribe to updates in the atomic physics (e.g., collision rates) and to the approximate solution method of the statistical equilibrium equations adopted in previous studies. A comparison with observations is discussed in an accompanying article, as radiative transfer effects need to be considered.« less

High power, high frequency helix TWT's

NASA Astrophysics Data System (ADS)

Sloley, H. J.; Willard, J.; Paatz, S. R.; Keat, M. J.

The design and performance characteristics of a 34-GHz pulse tube capable of 75 W peak power output at 30 percent duty cycle and a broadband CW tube are presented. Particular attention is given to the engineering problems encountered during the development of the tubes, including the suppression of backward wave oscillation, the design of electron guns for small-diameter high-current beams, and the thermal capability of small helix structures. The discussion also covers the effects of various design parameters and choice of engineering materials on the ultimate practical limit of power and gain at the operating frequencies. Measurements are presented for advanced experimental tubes.

High Bypass Ratio Jet Noise Reduction and Installation Effects Including Shielding Effectiveness

NASA Technical Reports Server (NTRS)

Thomas, Russell H.; Czech, Michael J.; Doty, Michael J.

2013-01-01

An experimental investigation was performed to study the propulsion airframe aeroacoustic installation effects of a separate flow jet nozzle with a Hybrid Wing Body aircraft configuration where the engine is installed above the wing. Prior understanding of the jet noise shielding effectiveness was extended to a bypass ratio ten application as a function of nozzle configuration, chevron type, axial spacing, and installation effects from additional airframe components. Chevron types included fan chevrons that are uniform circumferentially around the fan nozzle and T-fan type chevrons that are asymmetrical circumferentially. In isolated testing without a pylon, uniform chevrons compared to T-fan chevrons showed slightly more low frequency reduction offset by more high frequency increase. Phased array localization shows that at this bypass ratio chevrons still move peak jet noise source locations upstream but not to nearly the extent, as a function of frequency, as for lower bypass ratio jets. For baseline nozzles without chevrons, the basic pylon effect has been greatly reduced compared to that seen for lower bypass ratio jets. Compared to Tfan chevrons without a pylon, the combination with a standard pylon results in more high frequency noise increase and an overall higher noise level. Shielded by an airframe surface 2.17 fan diameters from nozzle to airframe trailing edge, the T-fan chevron nozzle can produce reductions in jet noise of as much as 8 dB at high frequencies and upstream angles. Noise reduction from shielding decreases with decreasing frequency and with increasing angle from the jet inlet. Beyond an angle of 130 degrees there is almost no noise reduction from shielding. Increasing chevron immersion more than what is already an aggressive design is not advantageous for noise reduction. The addition of airframe control surfaces, including vertical stabilizers and elevon deflection, showed only a small overall impact. Based on the test results, the best overall nozzle configuration design was selected for application to the N2A Hybrid Wing Body concept that will be the subject of the NASA Langley 14 by 22 Foot Subsonic Tunnel high fidelity aeroacoustic characterization experiment. The best overall nozzle selected includes T-fan type chevrons, uniform chevrons on the core nozzle, and no additional pylon of the type that created a strong acoustic effect at lower bypass ratios. The T-fan chevrons are oriented azimuthally away from the ground observer locations. This best overall nozzle compared to the baseline nozzle was assessed, at equal thrust, to produce sufficient installed noise reduction of the jet noise component to enable the N2A HWB to meet NASA s noise goal of 42 dB cumulative below Stage 4.

Aeroacoustics of large wind turbines

NASA Technical Reports Server (NTRS)

Hubbard, Harvey H.; Shepherd, Kevin P.

1991-01-01

This paper reviews published information on aerodynamically generated noise from large horizontal axis wind turbines operated for electric power generation. Methods are presented for predicting both the discrete frequency rotational noise components and the broadband noise components, and results are compared with measurements. Refraction effects that result in the formation of high-frequency shadow zones in the upwind direction and channeling effects for the low frequencies in the downwind direction are illustrated. Special topics such as distributed source effects in prediction and the role of building dynamics in perception are also included.

High energy efficient solid state laser sources

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1989-01-01

Recent progress in the development of highly efficient coherent optical sources was reviewed. This work has focused on nonlinear frequency conversion of the highly coherent output of the non-planar ring laser oscillators developed earlier in the program, and includes high efficiency second harmonic generation and the operation of optical parametric oscillators for wavelength diversity and tunability.

Using magnetic resonance elastography to assess the dynamic mechanical properties of cartilage

NASA Astrophysics Data System (ADS)

Lopez, Orlando; Amrami, Kimberly; Rossman, Phillip; Ehman, Richard L.

2004-04-01

This work explored the feasibility of using Magnetic Resonance Elastography (MRE) technology to enable in vitro quantification of dynamic mechanical behavior of cartilage through its thickness. A customized system for MRE of cartilage was designed to include components for adequate generation and detection of high frequency mechanical shear waves within small and stiff materials. The system included components for mechanical excitation, motion encoding, and imaging of small samples. Limitations in sensitivity to motion encoding of high frequency propagating mechanical waves using a whole body coil (i.e. Gmax = 2.2 G/cm) required the design of a local gradient coil system to achieve a gain in gradient strength of at least 5 times. The performance of the new system was tested using various cartilage-mimicking phantom materials. MRE of a stiff 5% agar gelatin phantom demonstrated gains in sensitivity to motion encoding of high frequency mechanical waves in cartilage like materials. MRE of fetal bovine cartilage samples yielded a distribution of shear stiffness within the thickness of the cartilage similar to values found in the literature, hence, suggesting the feasibility of using MRE to non-invasively and directly assess the dynamic mechanical properties of cartilage.

High frequency modulation circuits based on photoconductive wide bandgap switches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sampayan, Stephen

Methods, systems, and devices for high voltage and/or high frequency modulation. In one aspect, an optoelectronic modulation system includes an array of two or more photoconductive switch units each including a wide bandgap photoconductive material coupled between a first electrode and a second electrode, a light source optically coupled to the WBGP material of each photoconductive switch unit via a light path, in which the light path splits into multiple light paths to optically interface with each WBGP material, such that a time delay of emitted light exists along each subsequent split light path, and in which the WBGP materialmore » conducts an electrical signal when a light signal is transmitted to the WBGP material, and an output to transmit the electrical signal conducted by each photoconductive switch unit. The time delay of the photons emitted through the light path is substantially equivalent to the time delay of the electrical signal.« less

The effect of changing disk parameters on whirling frequency of high speed rotor system

NASA Astrophysics Data System (ADS)

Wahab, A. M. Abdul; Rasid, Z. A.; Abu, A.; Rudin, N. F. Mohd Noor; Yakub, F.

2017-12-01

The requirement for efficiency improvement of machines has caused machine rotor to be designed to rotate at high speeds. It is known that whirling natural frequency of a shaft changes with the change of shaft speed and the design needs to avoid points of resonance where the whirling frequency equals the shaft speed. At high speeds, a shaft may have to carry a huge torque along and this torsional effect has been neglected in past shaft analyses. Whirling behaviour of high speed rotating shaft is investigated in this study with consideration of the torsional effect of the shaft. The shaft system under study consists of a shaft, discs and two bearings, and the focus is on the effect of the disc parameters. A finite element formulation is developed based on Nelson’s 5 degrees of freedom (DOF) per node element that includes the torsional degree of freedom. Bolotin’s method is applied to the derived Mathieu-Hill type of equation to get quadratic eigenvalues problem that gives the forward and backward frequencies of the shaft. Campbell’s diagrams are drawn in studying the effect of discs on the whirling behaviour of the shaft. It is found that the addition of disks on the shaft decreases the whirling frequency of the shaft and the frequency is lower for mass located at the centre of the shaft compared to the one located near to the end. The effect of torsional motion is found to be significant where the difference between critical speed of 4DOF and 5DOF models can be as high as 15%.

Poor adherence to treatment associated with a high recurrence in a bipolar disorder outpatient sample.

PubMed

Gutiérrez-Rojas, Luis; Jurado, Dolores; Martínez-Ortega, José María; Gurpegui, Manuel

2010-12-01

We analyzed the association of previous course-of-illness and other variables of clinical interest with a high frequency of both depressive or (hypo)manic episodes controlling for the effect of socio-demographic characteristics. A total of 108 outpatients with a DSM-IV diagnosis of bipolar disorder (BD) were recruited. A retrospective and naturalistic study was conducted to examine the number of affective episodes and their relationship with socio-demographic, clinical and course-of-illness variables, including adherence to medication, type of medication used and the use of addictive substances. The episode frequency was estimated as the number of "major instances" of depression, hypomania and mania during the illness. To classify the patients into two groups (higher and lower-episode frequency), we used the statistical criterion of median split. Results were analyzed with logistic regression models to control for the effects of potential confounders. A high episode frequency (nine or more episodes) was associated with age (36-55years), delay in diagnosis, poor adherence to medication and current use of antipsychotic medication. In addition, a high frequency of manic episodes (four or more) was associated with female sex, age (>36years) and a manic onset of the illness, whereas a high frequency of depressive episodes (five or more) was associated with delay in diagnosis and poor adherence to medication. Cross-sectional study design. Avoiding delay in diagnosis and enhancing treatment adherence might be important targets for reducing recurrences in BD. Copyright © 2010 Elsevier B.V. All rights reserved.

267 Spanish Exomes Reveal Population-Specific Differences in Disease-Related Genetic Variation.

PubMed

Dopazo, Joaquín; Amadoz, Alicia; Bleda, Marta; Garcia-Alonso, Luz; Alemán, Alejandro; García-García, Francisco; Rodriguez, Juan A; Daub, Josephine T; Muntané, Gerard; Rueda, Antonio; Vela-Boza, Alicia; López-Domingo, Francisco J; Florido, Javier P; Arce, Pablo; Ruiz-Ferrer, Macarena; Méndez-Vidal, Cristina; Arnold, Todd E; Spleiss, Olivia; Alvarez-Tejado, Miguel; Navarro, Arcadi; Bhattacharya, Shomi S; Borrego, Salud; Santoyo-López, Javier; Antiñolo, Guillermo

2016-05-01

Recent results from large-scale genomic projects suggest that allele frequencies, which are highly relevant for medical purposes, differ considerably across different populations. The need for a detailed catalog of local variability motivated the whole-exome sequencing of 267 unrelated individuals, representative of the healthy Spanish population. Like in other studies, a considerable number of rare variants were found (almost one-third of the described variants). There were also relevant differences in allelic frequencies in polymorphic variants, including ∼10,000 polymorphisms private to the Spanish population. The allelic frequencies of variants conferring susceptibility to complex diseases (including cancer, schizophrenia, Alzheimer disease, type 2 diabetes, and other pathologies) were overall similar to those of other populations. However, the trend is the opposite for variants linked to Mendelian and rare diseases (including several retinal degenerative dystrophies and cardiomyopathies) that show marked frequency differences between populations. Interestingly, a correspondence between differences in allelic frequencies and disease prevalence was found, highlighting the relevance of frequency differences in disease risk. These differences are also observed in variants that disrupt known drug binding sites, suggesting an important role for local variability in population-specific drug resistances or adverse effects. We have made the Spanish population variant server web page that contains population frequency information for the complete list of 170,888 variant positions we found publicly available (http://spv.babelomics.org/), We show that it if fundamental to determine population-specific variant frequencies to distinguish real disease associations from population-specific polymorphisms. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Overview on the standardization in the field of electromagnetic compatibility

NASA Astrophysics Data System (ADS)

Goldberg, Georges

1989-04-01

Standardization in the domain of electromagnetic compatibility (EMC) is discussed, with specific reference to the standards of the International Electrotechnical Commission, the Comite International Special des Perturbations Radioelectriques, and the Comite Europeen de Normalisation Electrotechnique. EMC fields considered include radiocommunications, telecommunications, biological effects, and data transmission. Standards are presented for such electromagnetic disturbances as low-frequency, high-frequency, conduction, and radiation phenomena.

Artifacts Of Spectral Analysis Of Instrument Readings

NASA Technical Reports Server (NTRS)

Wise, James H.

1995-01-01

Report presents experimental and theoretical study of some of artifacts introduced by processing outputs of two nominally identical low-frequency-reading instruments; high-sensitivity servo-accelerometers mounted together and operating, in conjunction with signal-conditioning circuits, as seismometers. Processing involved analog-to-digital conversion with anti-aliasing filtering, followed by digital processing including frequency weighting and computation of different measures of power spectral density (PSD).

Cross-Language Distributions of High Frequency and Phonetically Similar Cognates

PubMed Central

Schepens, Job; Dijkstra, Ton; Grootjen, Franc; van Heuven, Walter J. B.

2013-01-01

The coinciding form and meaning similarity of cognates, e.g. ‘flamme’ (French), ‘Flamme’ (German), ‘vlam’ (Dutch), meaning ‘flame’ in English, facilitates learning of additional languages. The cross-language frequency and similarity distributions of cognates vary according to evolutionary change and language contact. We compare frequency and orthographic (O), phonetic (P), and semantic similarity of cognates, automatically identified in semi-complete lexicons of six widely spoken languages. Comparisons of P and O similarity reveal inconsistent mappings in language pairs with deep orthographies. The frequency distributions show that cognate frequency is reduced in less closely related language pairs as compared to more closely related languages (e.g., French-English vs. German-English). These frequency and similarity patterns may support a better understanding of cognate processing in natural and experimental settings. The automatically identified cognates are available in the supplementary materials, including the frequency and similarity measurements. PMID:23675449

Microwave Frequency Multiplier

NASA Astrophysics Data System (ADS)

Velazco, J. E.

2017-02-01

High-power microwave radiation is used in the Deep Space Network (DSN) and Goldstone Solar System Radar (GSSR) for uplink communications with spacecraft and for monitoring asteroids and space debris, respectively. Intense X-band (7.1 to 8.6 GHz) microwave signals are produced for these applications via klystron and traveling-wave microwave vacuum tubes. In order to achieve higher data rate communications with spacecraft, the DSN is planning to gradually furnish several of its deep space stations with uplink systems that employ Ka-band (34-GHz) radiation. Also, the next generation of planetary radar, such as Ka-Band Objects Observation and Monitoring (KaBOOM), is considering frequencies in the Ka-band range (34 to 36 GHz) in order to achieve higher target resolution. Current commercial Ka-band sources are limited to power levels that range from hundreds of watts up to a kilowatt and, at the high-power end, tend to suffer from poor reliability. In either case, there is a clear need for stable Ka-band sources that can produce kilowatts of power with high reliability. In this article, we present a new concept for high-power, high-frequency generation (including Ka-band) that we refer to as the microwave frequency multiplier (MFM). The MFM is a two-cavity vacuum tube concept where low-frequency (2 to 8 GHz) power is fed into the input cavity to modulate and accelerate an electron beam. In the second cavity, the modulated electron beam excites and amplifies high-power microwaves at a frequency that is a multiple integer of the input cavity's frequency. Frequency multiplication factors in the 4 to 10 range are being considered for the current application, although higher multiplication factors are feasible. This novel beam-wave interaction allows the MFM to produce high-power, high-frequency radiation with high efficiency. A key feature of the MFM is that it uses significantly larger cavities than its klystron counterparts, thus greatly reducing power density and arcing concerns. We present a theoretical analysis for the beam-wave interactions in the MFM's input and output cavities. We show the conditions required for successful frequency multiplication inside the output cavity. Computer simulations using the plasma physics code MAGIC show that 100 kW of Ka-band (32-GHz) output power can be produced using an 80-kW X-band (8-GHz) signal at the MFM's input. The associated MFM efficiency - from beam power to Ka-band power - is 83 percent. Thus, the overall klystron-MFM efficiency is 42 percent - assuming that a klystron with an efficiency of 50 percent delivers the input signal.

Noninvasive Diagnosis of Coronary Artery Disease Using 12-Lead High-Frequency Electrocardiograms

NASA Technical Reports Server (NTRS)

Schlegel, Todd T.; Arenare, Brian

2006-01-01

A noninvasive, sensitive method of diagnosing certain pathological conditions of the human heart involves computational processing of digitized electrocardiographic (ECG) signals acquired from a patient at all 12 conventional ECG electrode positions. In the processing, attention is focused on low-amplitude, high-frequency components of those portions of the ECG signals known in the art as QRS complexes. The unique contribution of this method lies in the utilization of signal features and combinations of signal features from various combinations of electrode positions, not reported previously, that have been found to be helpful in diagnosing coronary artery disease and such related pathological conditions as myocardial ischemia, myocardial infarction, and congestive heart failure. The electronic hardware and software used to acquire the QRS complexes and perform some preliminary analyses of their high-frequency components were summarized in Real-Time, High-Frequency QRS Electrocardiograph (MSC- 23154), NASA Tech Briefs, Vol. 27, No. 7 (July 2003), pp. 26-28. To recapitulate, signals from standard electrocardiograph electrodes are preamplified, then digitized at a sampling rate of 1,000 Hz, then analyzed by the software that detects R waves and QRS complexes and analyzes them from several perspectives. The software includes provisions for averaging signals over multiple beats and for special-purpose nonrecursive digital filters with specific low- and high-frequency cutoffs. These filters, applied to the averaged signal, effect a band-pass operation in the frequency range from 150 to 250 Hz. The output of the bandpass filter is the desired high-frequency QRS signal. Further processing is then performed in real time to obtain the beat-to-beat root mean square (RMS) voltage amplitude of the filtered signal, certain variations of the RMS voltage, and such standard measures as the heart rate and R-R interval at any given time. A key signal feature analyzed in the present method is the presence versus the absence of reduced-amplitude zones (RAZs). In terms that must be simplified for the sake of brevity, an RAZ comprises several cycles of a high-frequency QRS signal during which the amplitude of the high-frequency oscillation in a portion of the signal is abnormally low (see figure). A given signal sample exhibiting an interval of reduced amplitude may or may not be classified as an RAZ, depending on quantitative criteria regarding peaks and troughs within the reduced-amplitude portion of the high-frequency QRS signal. This analysis is performed in all 12 leads in real time.

Effects of Osteopathic Manipulative Therapy on Pain and Mood Disorders in Patients With High-Frequency Migraine.

PubMed

D'Ippolito, Mariagrazia; Tramontano, Marco; Buzzi, Maria Gabriella

2017-06-01

The substantial functional impairment associated with migraine has both physical and emotional ramifications. Mood disorders are often comorbid in patients with migraine and are known to adversely affect migraine activity. To explore the effects of osteopathic manipulative therapy (OMTh; manipulative care provided by foreign-trained osteopaths) on pain and mood disorders in patients with high-frequency migraine. Retrospective review of the medical records of patients with high-frequency migraine who were treated with OMTh at the Headache Istituto di Ricovero e Cura a Carattere Scientifico Fondazione Santa Lucia from 2011 to 2015. Clinical assessments were made using the Headache Disability Inventory (HDI), the Headache Impact Test (HIT-6), the Hamilton Depression Rating Scale (HDRS), and the State-Trait Anxiety Inventory (STAI) forms X-1 and X-2. Medical records of 11 patients (6 women; mean age, 47.5 [7.8] years) with a diagnosis of high-frequency migraine who participated in an OMTh program met the inclusion criteria and were included in the study. When the questionnaire scores obtained at the first visit (T0) and after 4 OMTh sessions (T1) were compared, significant improvement in scores were observed on STAI X-2 (T0: 43.18 [2.47]; T1: 39.45 [2.52]; P<.05), HIT-6 (T0: 63 [2.20]; T1: 56.27 [2.24]; P<.05), and HDI (T0: 58.72 [6.75]; T1: 45.09 [7.01]; P<.05). This preliminary study revealed that patients with high-frequency migraine and comorbid mood disorders showed significant improvement after four 45-minute OMTh sessions. Further investigation into the effects of OMTh on pain and mood disorders in patients with high-frequency migraine is needed.

Exploring the Last Electromagnetic Frontier with the Long Wavelength Array (LWA)

NASA Astrophysics Data System (ADS)

Kassim, Namir E.; Cohen, A. S.; Crane, P. C.; Gross, C. A.; Hicks, B. C.; Lane, W. M.; Lazio, J.; Polisensky, E. J.; Ray, P. S.; Weiler, K. W.; Clarke, T. E.; Schmitt, H. R.; Hartman, J. M.; Helmboldt, J. F.; Craig, J.; Gerstle, W.; Pihlstrom, Y.; Rickard, L. J.; Taylor, G. B.; Ellingson, S. W.; D'Addario, L. R.; Navarro, R.

2009-05-01

Several decades ago, instruments like the Very Large Array (VLA) first opened the GHz frequency sky to high dynamic range imaging. Today, a path-finding VLA 74 MHz system is providing the first sub-arcminute resolution view of the radio universe below 100 MHz, a technical innovation inspiring an emerging suite of large (> 100 km), much more powerful long-wavelength instruments including the Long Wavelength Array (LWA). Similar in philosophy to the VLA and also located in New Mexico, the LWA will be a versatile, user-oriented electronic array designed to open the 20--80 MHz frequency range to detailed exploration for the first time. The LWA's mJy sensitivity and near-arcsecond resolution will surpass, by 2--3 orders of magnitude, the imaging power of previous interferometers in its frequency range. LWA scientific frontiers include: (1) the high-z universe, including distant radio galaxies and clusters - tools for understanding the earliest black holes and the cosmological evolution of Dark Matter and Dark Energy, respectively; (2) acceleration, propagation, and turbulence in the ISM, including the space-distribution and spectrum of Galactic cosmic rays and supernova remnants; (3) planetary, solar, and space science, including space-weather prediction and extra-solar planet searches; and (4) the radio transient universe including GRBs, ultra-high energy cosmic rays, and new sources of unknown origin. Because the LWA will explore one of the most poorly investigated spectral regions the potential for new discoveries is high, and there is a strong synergy with exciting new X-ray and Gamma-ray measurements. The LWA will also provide an unparalleled measure of small-scale ionospheric structure, a pre-requisite for accurate calibration and imaging. This presentation focuses on LWA science, while a companion paper reviews the technical design subjected to Preliminary Design Review in March 2009. Basic research in radio astronomy at the Naval Research Laboratory is supported by 6.1 base funding.

Global Precipitation Measurement Program and the Development of Dual-Frequency Precipitation Radar

NASA Technical Reports Server (NTRS)

Iguchi, Toshio; Oki, Riko; Smith, Eric A.; Furuhama, Yoji

2002-01-01

The Global Precipitation Measurement (GPM) program is a mission to measure precipitation from space, and is a similar but much expanded mission of the Tropical Rainfall Measuring Mission. Its scope is not limited to scientific research, but includes practical and operational applications such as weather forecasting and water resource management. To meet the requirements of operational use, the GPM uses multiple low-orbiting satellites to increase the sampling frequency and to create three-hourly global rain maps that will be delivered to the world in quasi-real time. A dual-frequency radar (DPR) will be installed on the primary satellite that plays an important role in the whole mission. The DPR will realize measurement of precipitation with high sensitivity, high precision and high resolutions. This paper describes an outline of the GPM program, its issues and the roles and development of the DPR.

High-power microwave amplifier based on overcritical relativistic electron beam without external magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurkin, S. A., E-mail: KurkinSA@gmail.com; Koronovskii, A. A.; Saratov State Technical University, Politechnicheskaja 77, Saratov 410028

2015-04-13

The high-power scheme for the amplification of powerful microwave signals based on the overcritical electron beam with a virtual cathode (virtual cathode amplifier) has been proposed and investigated numerically. General output characteristics of the virtual cathode amplifier including the dependencies of the power gain on the input signal frequency and amplitude have been obtained and analyzed. The possibility of the geometrical working frequency tuning over the range about 8%–10% has been shown. The obtained results demonstrate that the proposed virtual cathode amplifier scheme may be considered as the perspective high-power microwave amplifier with gain up to 18 dB, and with themore » following important advantages: the absence of external magnetic field, the simplicity of construction, the possibility of geometrical frequency tuning, and the amplification of relatively powerful microwave signals.« less

Suppressing unsteady flow in arterio-venous fistulae

NASA Astrophysics Data System (ADS)

Grechy, L.; Iori, F.; Corbett, R. W.; Shurey, S.; Gedroyc, W.; Duncan, N.; Caro, C. G.; Vincent, P. E.

2017-10-01

Arterio-Venous Fistulae (AVF) are regarded as the "gold standard" method of vascular access for patients with end-stage renal disease who require haemodialysis. However, a large proportion of AVF do not mature, and hence fail, as a result of various pathologies such as Intimal Hyperplasia (IH). Unphysiological flow patterns, including high-frequency flow unsteadiness, associated with the unnatural and often complex geometries of AVF are believed to be implicated in the development of IH. In the present study, we employ a Mesh Adaptive Direct Search optimisation framework, computational fluid dynamics simulations, and a new cost function to design a novel non-planar AVF configuration that can suppress high-frequency unsteady flow. A prototype device for holding an AVF in the optimal configuration is then fabricated, and proof-of-concept is demonstrated in a porcine model. Results constitute the first use of numerical optimisation to design a device for suppressing potentially pathological high-frequency flow unsteadiness in AVF.

Automated calculation of surface energy fluxes with high-frequency lake buoy data

USGS Publications Warehouse

Woolway, R. Iestyn; Jones, Ian D; Hamilton, David P.; Maberly, Stephen C; Muroaka, Kohji; Read, Jordan S.; Smyth, Robyn L; Winslow, Luke A.

2015-01-01

Lake Heat Flux Analyzer is a program used for calculating the surface energy fluxes in lakes according to established literature methodologies. The program was developed in MATLAB for the rapid analysis of high-frequency data from instrumented lake buoys in support of the emerging field of aquatic sensor network science. To calculate the surface energy fluxes, the program requires a number of input variables, such as air and water temperature, relative humidity, wind speed, and short-wave radiation. Available outputs for Lake Heat Flux Analyzer include the surface fluxes of momentum, sensible heat and latent heat and their corresponding transfer coefficients, incoming and outgoing long-wave radiation. Lake Heat Flux Analyzer is open source and can be used to process data from multiple lakes rapidly. It provides a means of calculating the surface fluxes using a consistent method, thereby facilitating global comparisons of high-frequency data from lake buoys.

Study on the high-frequency laser measurement of slot surface difference

NASA Astrophysics Data System (ADS)

Bing, Jia; Lv, Qiongying; Cao, Guohua

2017-10-01

In view of the measurement of the slot surface difference in the large-scale mechanical assembly process, Based on high frequency laser scanning technology and laser detection imaging principle, This paragraph designs a double galvanometer pulse laser scanning system. Laser probe scanning system architecture consists of three parts: laser ranging part, mechanical scanning part, data acquisition and processing part. The part of laser range uses high-frequency laser range finder to measure the distance information of the target shape and get a lot of point cloud data. Mechanical scanning part includes high-speed rotary table, high-speed transit and related structure design, in order to realize the whole system should be carried out in accordance with the design of scanning path on the target three-dimensional laser scanning. Data processing part mainly by FPGA hardware with LAbVIEW software to design a core, to process the point cloud data collected by the laser range finder at the high-speed and fitting calculation of point cloud data, to establish a three-dimensional model of the target, so laser scanning imaging is realized.

High Frequency High Spectral Resolution Focal Plane Arrays for AtLAST

NASA Astrophysics Data System (ADS)

Baryshev, Andrey

2018-01-01

Large collecting area single dish telescope such as ATLAST will be especially effective for medium (R 1000) and high (R 50000) spectral resolution observations. Large focal plane array is a natural solution to increase mapping speed. For medium resolution direct detectors with filter banks (KIDs) and or heterodyne technology can be employed. We will analyze performance limits of comparable KID and SIS focal plane array taking into account quantum limit and high background condition of terrestrial observing site. For large heterodyne focal plane arrays, a high current density AlN junctions open possibility of large instantaneous bandwidth >40%. This and possible multi frequency band FPSs presents a practical challenge for spatial sampling and scanning strategies. We will discuss phase array feeds as a possible solution, including a modular back-end system, which can be shared between KID and SIS based FPA. Finally we will discuss achievable sensitivities and pixel co unts for a high frequency (>500 GHz) FPAs and address main technical challenges: LO distribution, wire counts, bias line multiplexing, and monolithic vs. discrete mixer component integration.

Mutational influences of low-dose and high let ionizing radiation in drosophila melanogaster

NASA Astrophysics Data System (ADS)

Lei, Huang; Fanjun, Kong; Sun, Yeqing

For cosmic environment consists of a varying kinds of radiation particles including high Z and energy ions which was charactered with low-dose and high RBE, it is important to determine the possible biofuctions of high LET radiation on human beings. To analyse the possible effectes of mutational influences of low-dose and high-LET ionizing radiation, wild fruit flies drosophila melanogaster were irradiated by 12C6+ ions in two LET levels (63.3 and 30 keV/µum) with different low doses from 2mGy to 2000mGy (2, 20, 200, 2000mGy) in HIRFL (Heavy ion radiation facility laboratory, lanzhou, China).In the same LET value group, the average polymorphic frequency was elevated along with adding doses of irradation, the frequency in 2000 mGy dose samples was significantly higher than other samples (p<0.01).These results suggest that genomic DNA sequence could be effected by low-dose and high-LET ionizing radiation, the irradiation dose is an important element in genomic mutation frequency origination.

Changes in the frequency of family meals from 1999 to 2010 in the homes of adolescents: trends by sociodemographic characteristics.

PubMed

Neumark-Sztainer, Dianne; Wall, Melanie; Fulkerson, Jayne A; Larson, Nicole

2013-02-01

To examine secular trends from 1999 to 2010 in family meal frequency in a population-based sample of adolescents across sociodemographic characteristics. A repeated cross-sectional design was used. Participants were from middle schools and high schools in the Minneapolis/St. Paul area and included 3,072 adolescents (mean age = 14.6 ± 1.8 years) in 1999 and 2,793 adolescents (mean age = 14.4 ± 2.0 years) in 2010 from diverse ethnic/racial and socioeconomic backgrounds. Trends in family meal frequency were examined using inverse probability weighting to control for changes in sociodemographic characteristics over time. Family meal frequency remained fairly constant from 1999 to 2010 in the overall sample, but decreases were found in population subgroups including girls, middle school students (grade: 6-8), Asians, and youth from low socioeconomic backgrounds. Among youth from the lowest socioeconomic backgrounds, the mean number of family meals in the past week decreased from 4.0 in 1999 to 3.6 in 2010 (p = .003). Furthermore, the percentage of youth from low socioeconomic backgrounds eating five or more meals in the past week decreased from 46.9% in 1999 to 38.8% in 2010 (p < .001). In contrast, family meal frequency tended to increase over time among youth from higher socioeconomic backgrounds. The widening gap in family meal frequency between youth from low and high socioeconomic backgrounds is concerning, particularly given the greater risk for poor health outcomes among low-income youth. Given findings from other studies suggesting multiple benefits of family meals, interventions to increase family meal frequency are needed that target adolescents and their families from the most vulnerable segments of the population. Copyright © 2013 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

Changes in the frequency of family meals from 1999-2010 in the homes of adolescents: Trends by sociodemographic characteristics

PubMed Central

Neumark-Sztainer, Dianne; Wall, Melanie; Fulkerson, Jayne A.; Larson, Nicole

2012-01-01

Objective To examine secular trends from 1999 to 2010 in family meal frequency in a population-based sample of adolescents across sociodemographic characteristics. Methods A repeated cross-sectional design was used. Participants were from Minneapolis/St. Paul middle schools and high schools and included 3,072 adolescents in 1999 (mean age=14.6±1.8) and 2,793 adolescents in 2010 (mean age=14.4±2.0) from diverse ethnic/racial and socioeconomic backgrounds. Trends in family meal frequency were examined using inverse probability weighting to control for changes in sociodemographic characteristics over time. Results Family meal frequency remained fairly constant from 1999 to 2010 in the overall sample, but decreases were found in population subgroups including girls, middle school students (grade 6-8), Asians, and youth from low socioeconomic backgrounds. Among youth from the lowest socioeconomic backgrounds, the mean number of family meals in the past week decreased from 4.0 in 1999 to 3.6 in 2010 (p=.003). Furthermore, the percentage of youth from low socioeconomic backgrounds eating five or more meals in the past week decreased from 46.9% in 1999 to 38.8% in 2010 (p<.001). In contrast, family meal frequency tended to increase over time among youth from higher socioeconomic backgrounds. Conclusions The widening gap in family meal frequency between youth from low and high socioeconomic backgrounds is concerning, particularly given the greater risk for poor health outcomes among low-income youth. Given findings from other studies suggesting multiple benefits of family meals, interventions to increase family meal frequency are needed that target adolescents and their families from the most vulnerable segments of the population. PMID:23332485

Reduced Nucleus Pulposus Glycosaminoglycan Content Alters Intervertebral Disc Dynamic Viscoelastic Mechanics

PubMed Central

Boxberger, John I.; Orlansky, Amy S.; Sen, Sounok; Elliott, Dawn M.

2009-01-01

The intervertebral disc functions over a range of dynamic loading regimes including axial loads applied across a spectrum of frequencies at varying compressive loads. Biochemical changes occurring in early degeneration, including reduced nucleus pulposus glycosaminoglycan content, may alter disc mechanical behavior and thus may contribute to the progression of degeneration. The objective of this study was to determine disc dynamic viscoelastic properties under several equilibrium loads and loading frequencies, and further, to determine how reduced nucleus glycosaminglycan content alters dynamic mechanics. We hypothesized (1) that dynamic stiffness would be elevated with increasing equilibrium load and increasing frequency, (2) that the disc would behave more elastically at higher frequencies, and finally, (3) that dynamic stiffness would be reduced at low equilibrium loads under all frequencies due to nucleus glycosaminoglycan loss. We mechanically tested control and chondroitinase-ABC injected rat lumbar motion segments at several equilibrium loads using oscillatory loading at frequencies ranging from 0.05 to 5 Hz. The rat lumbar disc behaved non-linearly with higher dynamic stiffness at elevated compressive loads irrespective of frequency. Phase angle was not affected by equilibrium load, although it decreased as frequency was increased. Reduced glycosaminoglycan decreased dynamic stiffness at low loads but not at high equilibrium loads and led to increased phase angle at all loads and frequencies. The findings of this study demonstrate the effect of equilibrium load and loading frequencies on dynamic disc mechanics and indicate possible mechanical mechanisms through which disc degeneration can progress. PMID:19539936

Power system frequency estimation based on an orthogonal decomposition method

NASA Astrophysics Data System (ADS)

Lee, Chih-Hung; Tsai, Men-Shen

2018-06-01

In recent years, several frequency estimation techniques have been proposed by which to estimate the frequency variations in power systems. In order to properly identify power quality issues under asynchronously-sampled signals that are contaminated with noise, flicker, and harmonic and inter-harmonic components, a good frequency estimator that is able to estimate the frequency as well as the rate of frequency changes precisely is needed. However, accurately estimating the fundamental frequency becomes a very difficult task without a priori information about the sampling frequency. In this paper, a better frequency evaluation scheme for power systems is proposed. This method employs a reconstruction technique in combination with orthogonal filters, which may maintain the required frequency characteristics of the orthogonal filters and improve the overall efficiency of power system monitoring through two-stage sliding discrete Fourier transforms. The results showed that this method can accurately estimate the power system frequency under different conditions, including asynchronously sampled signals contaminated by noise, flicker, and harmonic and inter-harmonic components. The proposed approach also provides high computational efficiency.

A new high-frequency Agrobacterium-mediated transformation technique for Sesamum indicum L. using de-embryonated cotyledon as explant.

PubMed

Chowdhury, Supriyo; Basu, Arpita; Kundu, Surekha

2014-09-01

In spite of the economic importance of sesame (Sesamum indicum L.) and the recent availability of its genome sequence, a high-frequency transformation protocol is still not available. The only two existing Agrobacterium-mediated transformation protocols that are available have poor transformation efficiencies of less than 2%. In the present study, we report a high-frequency, simple, and reproducible transformation protocol for sesame. Transformation was done using de-embryonated cotyledons via somatic embryogenic stages. All the critical parameters of transformation, like incubation period of explants in pre-regeneration medium prior to infection by Agrobacterium tumefaciens, cocultivation period, concentrations of acetosyringone in cocultivation medium, kanamycin concentration, and concentration of plant hormones, including 6-benzylaminopurine, have been optimized. This protocol is superior to the two existing protocols in its high regeneration and transformation efficiencies. The transformed sesame lines have been tested by PCR, RT-PCR for neomycin phosphotransferase II gene expression, and β-glucuronidase (GUS) assay. The regeneration frequency and transformation efficiency are 57.33 and 42.66%, respectively. T0 and T1 generation transgenic plants were analyzed, and several T1 plants homozygous for the transgenes were obtained.

To eat or not to eat pork, how frequently and how varied? Insights from the quantitative Q-PorkChains consumer survey in four European countries.

PubMed

Verbeke, Wim; Pérez-Cueto, Federico J A; Grunert, Klaus G

2011-08-01

This study uses pork consumption frequency and variety to identify and profile European pork consumer segments. Data (n=1931) were collected in January 2008 in Belgium, Denmark, Germany and Poland. "Non-pork eaters" are profiled as predominantly younger (<35 years) females, with a high likelihood of living single and being underweight (BMI<18.5 kg/m²). Three segments of pork eaters were identified. The "Low variety, Low frequency" segment (17.4%) has a similar profile as the non-pork eaters, though it is a largely non-Polish and non-German segment. The "High variety, High frequency" segment (18.6%) consists mainly of rural, lower educated and overweight or obese (BMI>30 kg/m²) males. The segment "High variety, Medium frequency" (50.1%) includes families and other non-single households, with a profile that matches the overall sample. Their pork consumption is balanced over a wide range of pork cuts and pork meat products. Each segment entails specific challenges for the industry and the public health sector. Copyright © 2011 Elsevier Ltd. All rights reserved.

Nanolaminated Permalloy Core for High-Flux, High-Frequency Ultracompact Power Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J; Kim, M; Galle, P

2013-09-01

Metallic magnetic materials have desirable magnetic properties, including high permeability, and high saturation flux density, when compared with their ferrite counterparts. However, eddy-current losses preclude their use in many switching converter applications, due to the challenge of simultaneously achieving sufficiently thin laminations such that eddy currents are suppressed (e.g., 500 nm-1 mu m for megahertz frequencies), while simultaneously achieving overall core thicknesses such that substantial power can be handled. A CMOS-compatible fabrication process based on robot-assisted sequential electrodeposition followed by selective chemical etching has been developed for the realization of a core of substantial overall thickness (tens to hundreds ofmore » micrometers) comprised of multiple, stacked permalloy (Ni80Fe20) nanolaminations. Tests of toroidal inductors with nanolaminated cores showed negligible eddy-current loss relative to total core loss even at a peak flux density of 0.5 T in the megahertz frequency range. To illustrate the use of these cores, a buck power converter topology is implemented with switching frequencies of 1-2 MHz. Power conversion efficiency greater than 85% with peak operating flux density of 0.3-0.5 T in the core and converter output power level exceeding 5 W was achieved.« less

The effects of passive leg press training on jumping performance, speed, and muscle power.

PubMed

Liu, Chiang; Chen, Chuan-Shou; Ho, Wei-Hua; Füle, Róbert János; Chung, Pao-Hung; Shiang, Tzyy-Yuang

2013-06-01

Passive leg press (PLP) training was developed based on the concepts of the stretch-shortening cycle (SSC) and the benefits of high muscle contraction velocity. Passive leg press training enables lower limb muscle groups to apply a maximum downward force against a platform moved up and down at high frequency by an electric motor. Thus, these muscle groups accomplished both concentric and eccentric isokinetic contractions in a passive, rapid, and repetitive manner. This study investigates the effects of 10 weeks of PLP training at high and low movement frequencies have on jumping performance, speed, and muscle power. The authors selected 30 college students who had not performed systematic resistance training in the previous 6 months, including traditional resistance training at a squat frequency of 0.5 Hz, PLP training at a low frequency of 0.5 Hz, and PLP training at a high frequency of 2.5 Hz, and randomly divided them into 3 groups (n = 10). The participants' vertical jump, drop jump, 30-m sprint performance, explosive force, and SSC efficiency were tested under the same experimental procedures at pre- and post-training. Results reveal that high-frequency PLP training significantly increased participants' vertical jump, drop jump, 30-m sprint performance, instantaneous force, peak power, and SSC efficiency (p < 0.05). Additionally, their change rate abilities were substantially superior to those of the traditional resistance training (p < 0.05). The low-frequency PLP training significantly increased participants' vertical jump, 30-m sprint performance, instantaneous force, and peak power (p < 0.05). However, traditional resistance training only increased participants' 30-m sprint performance and peak power (p < 0.05). The findings suggest that jump performance, speed, and muscle power significantly improved after 10 weeks of PLP training at high movement frequency. A PLP training machine powered by an electrical motor enables muscles of the lower extremities to contract faster compared with voluntary contraction. Therefore, muscle training with high contraction velocity is one of the main methods of increasing muscle power. Passive leg press training is a unique method for enhancing jump performance, speed, and muscle power.

Multiscale Thermo-Mechanical Design and Analysis of High Frequency and High Power Vacuum Electron Devices

NASA Astrophysics Data System (ADS)

Gamzina, Diana

Diana Gamzina March 2016 Mechanical and Aerospace Engineering Multiscale Thermo-Mechanical Design and Analysis of High Frequency and High Power Vacuum Electron Devices Abstract A methodology for performing thermo-mechanical design and analysis of high frequency and high average power vacuum electron devices is presented. This methodology results in a "first-pass" engineering design directly ready for manufacturing. The methodology includes establishment of thermal and mechanical boundary conditions, evaluation of convective film heat transfer coefficients, identification of material options, evaluation of temperature and stress field distributions, assessment of microscale effects on the stress state of the material, and fatigue analysis. The feature size of vacuum electron devices operating in the high frequency regime of 100 GHz to 1 THz is comparable to the microstructure of the materials employed for their fabrication. As a result, the thermo-mechanical performance of a device is affected by the local material microstructure. Such multiscale effects on the stress state are considered in the range of scales from about 10 microns up to a few millimeters. The design and analysis methodology is demonstrated on three separate microwave devices: a 95 GHz 10 kW cw sheet beam klystron, a 263 GHz 50 W long pulse wide-bandwidth sheet beam travelling wave tube, and a 346 GHz 1 W cw backward wave oscillator.

New equivalent-electrical circuit model and a practical measurement method for human body impedance.

PubMed

Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako

2015-01-01

Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance.

Objective evaluation of the knocking sound of a diesel engine considering the temporal and frequency masking effect simultaneously

NASA Astrophysics Data System (ADS)

Yun, Dong-Un; Lee, Sang-Kwon

2017-06-01

In this paper, we present a novel method for an objective evaluation of knocking noise emitted by diesel engines based on the temporal and frequency masking theory. The knocking sound of a diesel engine is a vibro-acoustic sound correlated with the high-frequency resonances of the engine structure and a periodic impulsive sound with amplitude modulation. Its period is related to the engine speed and includes specific frequency bands related to the resonances of the engine structure. A knocking sound with the characteristics of a high-frequency impulsive wave can be masked by low-frequency sounds correlated with the harmonics of the firing frequency and broadband noise. The degree of modulation of the knocking sound signal was used for such objective evaluations in previous studies, without considering the masking effect. However, the frequency masking effect must be considered for the objective evaluation of the knocking sound. In addition to the frequency masking effect, the temporal masking effect occurs because the period of the knocking sound changes according to the engine speed. Therefore, an evaluation method considering the temporal and frequency masking effect is required to analyze the knocking sound objectively. In this study, an objective evaluation method considering the masking effect was developed based on the masking theory of sound and signal processing techniques. The method was applied successfully for the objective evaluation of the knocking sound of a diesel engine.

Investigating Efficient Tar Management from Biomass and Waste to Energy Gasification Processes

DTIC Science & Technology

2015-04-01

Non-thermal plasma systems, including low-pressure glow, radio frequency and corona discharges , offer high chemical selectivity and relatively...Chemosphere 2007;68(10):1821-9; Van Durme, Jim, et. al; Abatement and degredation pathways of toluene of indoor air by positive corona discharge . xi... discharges including high temperature plasma torchesviii, microwaveix, coronax and as related to this study, gliding arc nonthermal plasmaxi and catalystsxii

Advanced Seismic While Drilling System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert Radtke; John Fontenot; David Glowka

A breakthrough has been discovered for controlling seismic sources to generate selectable low frequencies. Conventional seismic sources, including sparkers, rotary mechanical, hydraulic, air guns, and explosives, by their very nature produce high-frequencies. This is counter to the need for long signal transmission through rock. The patent pending SeismicPULSER{trademark} methodology has been developed for controlling otherwise high-frequency seismic sources to generate selectable low-frequency peak spectra applicable to many seismic applications. Specifically, we have demonstrated the application of a low-frequency sparker source which can be incorporated into a drill bit for Drill Bit Seismic While Drilling (SWD). To create the methodology ofmore » a controllable low-frequency sparker seismic source, it was necessary to learn how to maximize sparker efficiencies to couple to, and transmit through, rock with the study of sparker designs and mechanisms for (a) coupling the sparker-generated gas bubble expansion and contraction to the rock, (b) the effects of fluid properties and dynamics, (c) linear and non-linear acoustics, and (d) imparted force directionality. After extensive seismic modeling, the design of high-efficiency sparkers, laboratory high frequency sparker testing, and field tests were performed at the University of Texas Devine seismic test site. The conclusion of the field test was that extremely high power levels would be required to have the range required for deep, 15,000+ ft, high-temperature, high-pressure (HTHP) wells. Thereafter, more modeling and laboratory testing led to the discovery of a method to control a sparker that could generate low frequencies required for deep wells. The low frequency sparker was successfully tested at the Department of Energy Rocky Mountain Oilfield Test Center (DOE RMOTC) field test site in Casper, Wyoming. An 8-in diameter by 26-ft long SeismicPULSER{trademark} drill string tool was designed and manufactured by TII. An APS Turbine Alternator powered the SeismicPULSER{trademark} to produce two Hz frequency peak signals repeated every 20 seconds. Since the ION Geophysical, Inc. (ION) seismic survey surface recording system was designed to detect a minimum downhole signal of three Hz, successful performance was confirmed with a 5.3 Hz recording with the pumps running. The two Hz signal generated by the sparker was modulated with the 3.3 Hz signal produced by the mud pumps to create an intense 5.3 Hz peak frequency signal. The low frequency sparker source is ultimately capable of generating selectable peak frequencies of 1 to 40 Hz with high-frequency spectra content to 10 kHz. The lower frequencies and, perhaps, low-frequency sweeps, are needed to achieve sufficient range and resolution for realtime imaging in deep (15,000 ft+), high-temperature (150 C) wells for (a) geosteering, (b) accurate seismic hole depth, (c) accurate pore pressure determinations ahead of the bit, (d) near wellbore diagnostics with a downhole receiver and wired drill pipe, and (e) reservoir model verification. Furthermore, the pressure of the sparker bubble will disintegrate rock resulting in an increased overall rates of penetration. Other applications for the SeismicPULSER{trademark} technology are to deploy a low-frequency source for greater range on a wireline for Reverse Vertical Seismic Profiling (RVSP) and Cross-Well Tomography. Commercialization of the technology is being undertaken by first contacting stakeholders to define the value proposition for rig site services utilizing SeismicPULSER{trademark} technologies. Stakeholders include national oil companies, independent oil companies, independents, service companies, and commercial investors. Service companies will introduce a new Drill Bit SWD service for deep HTHP wells. Collaboration will be encouraged between stakeholders in the form of joint industry projects to develop prototype tools and initial field trials. No barriers have been identified for developing, utilizing, and exploiting the low-frequency SeismicPULSER{trademark} source in a variety of applications. Risks will be minimized since Drill Bit SWD will not interfere with the drilling operation, and can be performed in a relatively quiet environment when the pumps are turned off. The new source must be integrated with other Measurement While Drilling (MWD) tools. To date, each of the oil companies and service companies contacted have shown interest in participating in the commercialization of the low-frequency SeismicPULSER{trademark} source. A technical paper has been accepted for presentation at the 2009 Offshore Technology Conference (OTC) in a Society of Exploration Geologists/American Association of Petroleum Geophysicists (SEG/AAPG) technical session.« less

Nuclear quadrupole resonance studies project. [spectrometer design and spectrum analysis

NASA Technical Reports Server (NTRS)

Murty, A. N.

1978-01-01

The participation of undergraduates in nuclear quadrupole resonance research at Grambling University was made possible by NASA grants. Expanded laboratory capabilities include (1) facilities for high and low temperature generation and measurement; (2) facilities for radio frequency generation and measurement with the modern spectrum analyzers, precision frequency counters and standard signal generators; (3) vacuum and glass blowing facilities; and (4) miscellaneous electronic and machine shop facilities. Experiments carried out over a five year period are described and their results analyzed. Theoretical studies on solid state crystalline electrostatic fields, field gradients, and antishielding factors are included.

High frequency oscillations evoked by peripheral magnetic stimulation.

PubMed

Biller, S; Simon, L; Fiedler, P; Strohmeier, D; Haueisen, J

2011-01-01

The analysis of somatosensory evoked potentials (SEP) and / or fields (SEF) is a well-established and important tool for investigating the functioning of the peripheral and central human nervous system. A standard technique to evoke SEPs / SEFs is the stimulation of the median nerve by using a bipolar electrical stimulus. We aim at an alternative stimulation technique enabling stimulation of deep nerve structures while reducing patient stress and error susceptibility. In the current study, we apply a commercial transcranial magnetic stimulation system for peripheral magnetic stimulation of the median nerve. We compare the results of simultaneously recorded EEG signals to prove applicability of our technique to evoke SEPs including low frequency components (LFC) as well as high frequency oscillations (HFO). Therefore, we compare amplitude, latency and time-frequency characteristics of the SEP of 14 healthy volunteers after electric and magnetic stimulation. Both low frequency components and high frequency oscillations were detected. The HFOs were superimposed onto the primary cortical response N20. Statistical analysis revealed significantly lower amplitudes and increased latencies for LFC and HFO components after magnetic stimulation. The differences indicate the inability of magnetic stimulation to elicit supramaximal responses. A psycho-perceptual evaluation showed that magnetic stimulation was less unpleasant for 12 out of the 14 volunteers. In conclusion, we showed that LFC and HFO components related to median nerve stimulation can be evoked by peripheral magnetic stimulation.

Utterance Detection by Intraoral Acceleration Sensor

NASA Astrophysics Data System (ADS)

Saiki, Tsunemasa; Takizawa, Yukako; Hashizume, Tsutomu; Higuchi, Kohei; Fujita, Takayuki; Maenaka, Kazusuke

In order to establish monitoring systems for home health in elderly people including the prevention of mental illness, we investigated the acceleration of teeth in utterance on the assumption that an acceleration sensor can be implanted into an artificial denture in the near future. In the experiment, an acceleration sensor was fixed in front of the central incisors on the lower jaw by using a denture adhesive, and female and male subjects spoke five Japanese vowels. We then measured the teeth accelerations in three (front-to-back, right-to-left and top-to-bottom) axes and conducted frequency analyses. The result showed that high power spectral densities of the teeth accelerations were observed at a low frequency range of 2-10Hz (both the female and the male) and at a high frequency range of 200-300Hz (the female) or 100-150 Hz (the male). The low and high frequency components indicate movements of the lower jaw and voice sounds by bone conduction, respectively. Especially in the top-to-bottom axis of the central incisor, the frequency component appeared to be significant. Therefore, we found that utterance can be efficiently detected using the acceleration in this axis. We also found that three conditions of normal speech, lip synchronizing and humming can be recognized by using frequency analysis of the acceleration in the top-to-bottom axis of the central incisor.

Low-cost FM oscillator for capacitance type of blade tip clearance measurement system

NASA Technical Reports Server (NTRS)

Barranger, John P.

1987-01-01

The frequency-modulated (FM) oscillator described is part of a blade tip clearance measurement system that meets the needs of a wide class of fans, compressors, and turbines. As a result of advancements in the technology of ultra-high-frequency operational amplifiers, the FM oscillator requires only a single low-cost integrated circuit. Its carrier frequency is 42.8 MHz when it is used with an integrated probe and connecting cable assembly consisting of a 0.81 cm diameter engine-mounted capacitance probe and a 61 cm long hermetically sealed coaxial cable. A complete circuit analysis is given, including amplifier negative resistance characteristics. An error analysis of environmentally induced effects is also derived, and an error-correcting technique is proposed. The oscillator can be calibrated in the static mode and has a negative peak frequency deviation of 400 kHz for a rotor blade thickness of 1.2 mm. High-temperature performance tests of the probe and 13 cm of the adjacent cable show good accuracy up to 600 C, the maximum permissible seal temperature. The major source of error is the residual FM oscillator noise, which produces a clearance error of + or - 10 microns at a clearance of 0.5 mm. The oscillator electronics accommodates the high rotor speeds associated with small engines, the signals from which may have frequency components as high as 1 MHz.

X-Ray Variability Characteristics of the Seyfert 1 Galaxy NGC 3783

NASA Astrophysics Data System (ADS)

Markowitz, A.

2005-12-01

We have characterized the energy-dependent X-ray variability properties of the Seyfert 1 galaxy NGC 3783 using archival XMM-Newton and Rossi X-Ray Timing Explorer data. The high-frequency fluctuation power spectral density function (PSD) slope is consistent with flattening toward higher energies. Light-curve cross-correlation functions yield no significant lags, but peak coefficients generally decrease as energy separation of the bands increases on both short and long timescales. We have measured the coherence between various X-ray bands over the temporal frequency range of 6×10-8-1×10-4 Hz; this range includes the temporal frequency of the low-frequency PSD break tentatively detected by Markowitz et al. and includes the lowest temporal frequency over which coherence has been measured in any active galactic nucleus to date. Coherence is generally near unity at these temporal frequencies, although it decreases slightly as energy separation of the bands increases. Temporal frequency-dependent phase lags are detected on short timescales; phase lags are consistent with increasing as energy separation increases or as temporal frequency decreases. All of these results are similar to those obtained previously for several Seyfert galaxies and stellar mass black hole systems. Qualitatively, these results are consistent with the variability models of Kotov et al. and Lyubarskii, wherein the X-ray variability is due to inwardly propagating variations in the local mass accretion rate.

Terahertz lens made out of natural stone.

PubMed

Han, Daehoon; Lee, Kanghee; Lim, Jongseok; Hong, Sei Sun; Kim, Young Kie; Ahn, Jaewook

2013-12-20

Terahertz (THz) time-domain spectroscopy probes the optical properties of naturally occurring solid aggregates of minerals, or stones, in the THz frequency range. Refractive index and extinction coefficient measurement reveals that most natural stones, including mudstone, sandstone, granite, tuff, gneiss, diorite, slate, marble, and dolomite, are fairly transparent for THz frequency waves. Dolomite in particular exhibits a nearly uniform refractive index of 2.7 over the broad frequency range from 0.1 to 1 THz. The high index of refraction allows flexibility in lens designing with a shorter accessible focal length or a thinner lens with a given focal length. Good agreement between the experiment and calculation for the THz beam profile confirms that dolomite has high homogeneity as a lens material, suggesting the possibility of using natural stones for THz optical elements.

Stroboscopic versus nonstroboscopic dynamics in the Floquet realization of the Harper-Hofstadter Hamiltonian

NASA Astrophysics Data System (ADS)

Bukov, Marin; Polkovnikov, Anatoli

2014-10-01

We study the stroboscopic and nonstroboscopic dynamics in the Floquet realization of the Harper-Hofstadter Hamiltonian. We show that the former produces the evolution expected in the high-frequency limit only for observables, which commute with the operator to which the driving protocol couples. On the contrary, nonstroboscopic dynamics is capable of capturing the evolution governed by the Floquet Hamiltonian of any observable associated with the effective high-frequency model. We provide exact numerical simulations for the dynamics of the number operator following a quantum cyclotron orbit on a 2×2 plaquette, as well as the chiral current operator flowing along the legs of a 2×20 ladder. The exact evolution is compared with its stroboscopic and nonstroboscopic counterparts, including finite-frequency corrections.

Risks and injuries in laser and high-frequency applications

NASA Astrophysics Data System (ADS)

Giering, K.; Philipp, Carsten M.; Berlien, Hans-Peter

1995-01-01

An analysis of injuries and risks using high frequency (HF) and lasers in medicine based on a literature search with MEDLINE was performed. The cases reported in the literature were classified according to the following criteria: (1) Avoidable in an optimal operational procedure. These kind of injuries are caused by a chain of unfortunate incidents. They are in principle avoidable by the 'right action at the right time' which presupposes an appropriate training of the operating team, selection of the optimal parameters for procedure and consideration of all safety instructions. (2) Avoidable, caused by malfunction of the equipment and/or accessories. The injuries classified into this group are avoidable if all safety regulations were fulfilled. This includes a pre-operational check-up and the use of medical lasers and high frequency devices only which meet the international safety standards. (3) Avoidable, caused by misuse/mistake. Injuries of this group were caused by an inappropriate selection of the procedure, wrong medical indication or mistakes during application. (4) Unavoidable, fateful. These injuries can be caused by risks inherent to the type of energy used, malfunction of the equipment and/or accessories though a pre-operational check-up was done. Some risks and complications are common to high frequency and laser application. But whereas these risks can be excluded easily in laser surgery there is often a great expenditure necessary or they are not avoidable if high frequency if used. No unavoidable risks due to laser energy occur.

Planck 2015 results: VII. High Frequency Instrument data processing: Time-ordered information and beams

DOE PAGES

Adam, R.; Ade, P. A. R.; Aghanim, N.; ...

2016-09-20

The Planck High Frequency Instrument (HFI) has observed the full sky at six frequencies (100, 143, 217, 353, 545, and 857 GHz) in intensity and at four frequencies in linear polarization (100, 143, 217, and 353 GHz). In order to obtain sky maps, the time-ordered information (TOI) containing the detector and pointing samples must be processed and the angular response must be assessed. The full mission TOI is included in the Planck 2015 release. This study describes the HFI TOI and beam processing for the 2015 release. HFI calibration and map making are described in a companion paper. The mainmore » pipeline has been modified since the last release (2013 nominal mission in intensity only), by including a correction for the nonlinearity of the warm readout and by improving the model of the bolometer time response. The beam processing is an essential tool that derives the angular response used in all the Planck science papers and we report an improvement in the effective beam window function uncertainty of more than a factor of 10 relative to the2013 release. Noise correlations introduced by pipeline filtering function are assessed using dedicated simulations. Finally, angular cross-power spectra using data sets that are decorrelated in time are immune to the main systematic effects.« less

Planck 2015 results. VII. High Frequency Instrument data processing: Time-ordered information and beams

NASA Astrophysics Data System (ADS)

Planck Collaboration; Adam, R.; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bertincourt, B.; Bielewicz, P.; Bock, J. J.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Le Jeune, M.; Leahy, J. P.; Lellouch, E.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Moreno, R.; Morgante, G.; Mortlock, D.; Moss, A.; Mottet, S.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sandri, M.; Santos, D.; Sauvé, A.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vibert, L.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Watson, R.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-09-01

The Planck High Frequency Instrument (HFI) has observed the full sky at six frequencies (100, 143, 217, 353, 545, and 857 GHz) in intensity and at four frequencies in linear polarization (100, 143, 217, and 353 GHz). In order to obtain sky maps, the time-ordered information (TOI) containing the detector and pointing samples must be processed and the angular response must be assessed. The full mission TOI is included in the Planck 2015 release. This paper describes the HFI TOI and beam processing for the 2015 release. HFI calibration and map making are described in a companion paper. The main pipeline has been modified since the last release (2013 nominal mission in intensity only), by including a correction for the nonlinearity of the warm readout and by improving the model of the bolometer time response. The beam processing is an essential tool that derives the angular response used in all the Planck science papers and we report an improvement in the effective beam window function uncertainty of more than a factor of 10 relative to the2013 release. Noise correlations introduced by pipeline filtering function are assessed using dedicated simulations. Angular cross-power spectra using data sets that are decorrelated in time are immune to the main systematic effects.

Planck 2015 results: VII. High Frequency Instrument data processing: Time-ordered information and beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adam, R.; Ade, P. A. R.; Aghanim, N.

The Planck High Frequency Instrument (HFI) has observed the full sky at six frequencies (100, 143, 217, 353, 545, and 857 GHz) in intensity and at four frequencies in linear polarization (100, 143, 217, and 353 GHz). In order to obtain sky maps, the time-ordered information (TOI) containing the detector and pointing samples must be processed and the angular response must be assessed. The full mission TOI is included in the Planck 2015 release. This study describes the HFI TOI and beam processing for the 2015 release. HFI calibration and map making are described in a companion paper. The mainmore » pipeline has been modified since the last release (2013 nominal mission in intensity only), by including a correction for the nonlinearity of the warm readout and by improving the model of the bolometer time response. The beam processing is an essential tool that derives the angular response used in all the Planck science papers and we report an improvement in the effective beam window function uncertainty of more than a factor of 10 relative to the2013 release. Noise correlations introduced by pipeline filtering function are assessed using dedicated simulations. Finally, angular cross-power spectra using data sets that are decorrelated in time are immune to the main systematic effects.« less

Numerical investigation of the inertial cavitation threshold under multi-frequency ultrasound.

PubMed

Suo, Dingjie; Govind, Bala; Zhang, Shengqi; Jing, Yun

2018-03-01

Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), enhancement of efficiency has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. One key experimental observation is that multi-frequency ultrasound can help lower the inertial cavitation threshold, thereby improving the power efficiency. However, this has not been well corroborated by the theory. In this paper, a numerical investigation on the inertial cavitation threshold of microbubbles (MBs) under multi-frequency ultrasound irradiation is conducted. The relationships between the cavitation threshold and MB size at various frequencies and in different media are investigated. The results of single-, dual and triple frequency sonication show reduced inertial cavitation thresholds by introducing additional frequencies which is consistent with previous experimental work. In addition, no significant difference is observed between dual frequency sonication with various frequency differences. This study, not only reaffirms the benefit of using multi-frequency ultrasound for various applications, but also provides a possible route for optimizing ultrasound excitations for initiating inertial cavitation. Copyright © 2017 Elsevier B.V. All rights reserved.

[Multi-channel in vivo recording techniques: signal processing of action potentials and local field potentials].

PubMed

Xu, Jia-Min; Wang, Ce-Qun; Lin, Long-Nian

2014-06-25

Multi-channel in vivo recording techniques are used to record ensemble neuronal activity and local field potentials (LFP) simultaneously. One of the key points for the technique is how to process these two sets of recorded neural signals properly so that data accuracy can be assured. We intend to introduce data processing approaches for action potentials and LFP based on the original data collected through multi-channel recording system. Action potential signals are high-frequency signals, hence high sampling rate of 40 kHz is normally chosen for recording. Based on waveforms of extracellularly recorded action potentials, tetrode technology combining principal component analysis can be used to discriminate neuronal spiking signals from differently spatially distributed neurons, in order to obtain accurate single neuron spiking activity. LFPs are low-frequency signals (lower than 300 Hz), hence the sampling rate of 1 kHz is used for LFPs. Digital filtering is required for LFP analysis to isolate different frequency oscillations including theta oscillation (4-12 Hz), which is dominant in active exploration and rapid-eye-movement (REM) sleep, gamma oscillation (30-80 Hz), which is accompanied by theta oscillation during cognitive processing, and high frequency ripple oscillation (100-250 Hz) in awake immobility and slow wave sleep (SWS) state in rodent hippocampus. For the obtained signals, common data post-processing methods include inter-spike interval analysis, spike auto-correlation analysis, spike cross-correlation analysis, power spectral density analysis, and spectrogram analysis.

[Burnout syndrome in teachers from two universities in Popayán, Colombia].

PubMed

Correa-Correa, Zamanda; Muñoz-Zambrano, Isabel; Chaparro, Andrés F

2010-08-01

Evaluating professional exhaustion or burnout syndrome: background, syndrome and consequences amongst half-time and full-time staff working in two private universities in the city of Popayán during 2008. The study population included 44 male and female participants aged 20 to 40 who were evaluated by using a brief burnout questionnaire (BBQ). This questionnaire had been validated for Latin-American and for teachers. It was not exclusively focused on the structure of the syndrome itself but rather included background elements and consequences. The study was quantitative and cross-sectional, having a deductive hypothetical methodological focus. Descriptive statistics and the Chi-square test were used for data analysis, accepting p<0.05 statistical significance. The analysis was univariate and bivariate. The results indicated low burnout syndrome frequency in the study population. However, 9.1 % high depersonalization frequency was found (i.e. teachers had developed negative attitudes and were insensitive to those receiving their services) and 15.9 % and 9.1 % frequencies for high physical and social consequences, respectively. Bivariate analysis revealed significant association of several factors. The results indicated low burnout syndrome frequency in this population. However, factors which were highly associated with physical and social consequences were: being male, aged 20 to 40, having a marital relationship with a habitual partner, working full-time, working at home and spending more than 75 % of the working day interacting with the beneficiaries of the services being provided.

Mechanisms of Left-Right Coordination in Mammalian Locomotor Pattern Generation Circuits: A Mathematical Modeling View

PubMed Central

Talpalar, Adolfo E.; Rybak, Ilya A.

2015-01-01

The locomotor gait in limbed animals is defined by the left-right leg coordination and locomotor speed. Coordination between left and right neural activities in the spinal cord controlling left and right legs is provided by commissural interneurons (CINs). Several CIN types have been genetically identified, including the excitatory V3 and excitatory and inhibitory V0 types. Recent studies demonstrated that genetic elimination of all V0 CINs caused switching from a normal left-right alternating activity to a left-right synchronized “hopping” pattern. Furthermore, ablation of only the inhibitory V0 CINs (V0D subtype) resulted in a lack of left-right alternation at low locomotor frequencies and retaining this alternation at high frequencies, whereas selective ablation of the excitatory V0 neurons (V0V subtype) maintained the left–right alternation at low frequencies and switched to a hopping pattern at high frequencies. To analyze these findings, we developed a simplified mathematical model of neural circuits consisting of four pacemaker neurons representing left and right, flexor and extensor rhythm-generating centers interacting via commissural pathways representing V3, V0D, and V0V CINs. The locomotor frequency was controlled by a parameter defining the excitation of neurons and commissural pathways mimicking the effects of N-methyl-D-aspartate on locomotor frequency in isolated rodent spinal cord preparations. The model demonstrated a typical left-right alternating pattern under control conditions, switching to a hopping activity at any frequency after removing both V0 connections, a synchronized pattern at low frequencies with alternation at high frequencies after removing only V0D connections, and an alternating pattern at low frequencies with hopping at high frequencies after removing only V0V connections. We used bifurcation theory and fast-slow decomposition methods to analyze network behavior in the above regimes and transitions between them. The model reproduced, and suggested explanation for, a series of experimental phenomena and generated predictions available for experimental testing. PMID:25970489

Frequency mode excitations in two-dimensional Hindmarsh-Rose neural networks

NASA Astrophysics Data System (ADS)

Tabi, Conrad Bertrand; Etémé, Armand Sylvin; Mohamadou, Alidou

2017-05-01

In this work, we explicitly show the existence of two frequency regimes in a two-dimensional Hindmarsh-Rose neural network. Each of the regimes, through the semi-discrete approximation, is shown to be described by a two-dimensional complex Ginzburg-Landau equation. The modulational instability phenomenon for the two regimes is studied, with consideration given to the coupling intensities among neighboring neurons. Analytical solutions are also investigated, along with their propagation in the two frequency regimes. These waves, depending on the coupling strength, are identified as breathers, impulses and trains of soliton-like structures. Although the waves in two regimes appear in some common regions of parameters, some phase differences are noticed and the global dynamics of the system is highly influenced by the values of the coupling terms. For some values of such parameters, the high-frequency regime displays modulated trains of waves, while the low-frequency dynamics keeps the original asymmetric character of action potentials. We argue that in a wide range of pathological situations, strong interactions among neurons can be responsible for some pathological states, including schizophrenia and epilepsy.

Planck intermediate results: XXXI. Microwave survey of Galactic supernova remnants

DOE PAGES

Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; ...

2016-02-09

The all-sky Planck survey in 9 frequency bands was used in this paper to search for emission from all 274 known Galactic supernova remnants. Of these, 16 were detected in at least two Planck frequencies. The radio-through-microwave spectral energy distributions were compiled to determine the mechanism for microwave emission. In only one case, IC 443, is there high-frequency emission clearly from dust associated with the supernova remnant. In all cases, the low-frequency emission is from synchrotron radiation. As predicted for a population of relativistic particles with energy distribution that extends continuously to high energies, a single power law is evidentmore » for many sources, including the Crab and PKS 1209-51/52. A decrease in flux density relative to the extrapolation of radio emission is evident in several sources. Their spectral energy distributions can be approximated as broken power laws, S ν ∝ ν -α, with the spectral index, α, increasing by 0.5–1 above a break frequency in the range 10–60 GHz. Finally, the break could be due to synchrotron losses.« less

Frequency of EEG arousals from nocturnal sleep in normal subjects.

PubMed

Mathur, R; Douglas, N J

1995-06-01

Brief arousals are clinically important and increasingly scored during polysomnography. However, the frequency of arousals during routine polysomnography in the normal population is unknown. We performed overnight polysomnography in the 55 of 59 control subjects from a family practice list who were approached and agreed to undergo polysomnography. Awakenings were scored according to the criteria of Rechtschaffen and Kales and briefer arousals according to three different criteria, including the American Sleep Disorders Association (ASDA) definition. There was a mean of 4 [95% confidence interval (CI), 1-15) Rechtschaffen and Kales awakenings per hour, whereas the ASDA definition gave 21 (95% CI, 7-56) per hour slept. Arousal frequencies increased significantly (p < 0.001) with age in our subjects, who ranged from the late teens to early 70s. The high upper limit of the frequency of brief arousals was not altered by exclusion of patients who snored or had witnessed apneas or daytime sleepiness. It is important that those scoring arousals on routine polysomnography recognize that high arousal frequencies occur in the normal population on 1-night polysomnography.

Analysis of the unusual wavelength dependence of the first hyperpolarizability of porphyrin derivatives

NASA Astrophysics Data System (ADS)

De Mey, K.; Clays, K.; Therien, Michael J.; Beratan, David N.; Asselberghs, Inge

2010-08-01

Successfully predicting the frequency dispersion of electronic hyperpolarizabilities is an unresolved challenge in materials science and electronic structure theory. It has been shown1 that the generalized Thomas-Kuhn sum rules combined with linear absorption data and measured hyperpolarizabilities at one or two frequencies, may be used to predict the entire frequency-dependent electronic hyperpolarizability spectrum. This treatment includes two- and threelevel contributions that arise from the lowest two or three excited state manifolds, enabling us to describe the unusual observed frequency dispersion of the dynamic hyperpolarizability in high oscillator strength M-PZn chromophores, where (porphinato)zinc(II) (PZn) and metal(II)polypyridyl (M) units are connected via an ethyne unit that aligns the high oscillator strength transition dipoles of these components in a head-to-tail arrangement. Importantly, this approach provides a quantitative scheme to use linear optical absorption spectra and very few individual hyperpolarizability values to predict the entire frequency-dependent nonlinear optical response. In addition we provide here experimental dynamic hyperpolarizability values determined by hyper-Rayleigh scattering that underscore the validity of our approach.

21 CFR 884.4150 - Bipolar endoscopic coagulator-cutter and accessories.

Code of Federal Regulations, 2014 CFR

2014-04-01

... high frequency electrical current through tissue between two electrical contacts of a probe. This generic type of device may include the following accessories: an electrical generator, probes, and...

21 CFR 884.4150 - Bipolar endoscopic coagulator-cutter and accessories.

Code of Federal Regulations, 2012 CFR

2012-04-01

... high frequency electrical current through tissue between two electrical contacts of a probe. This generic type of device may include the following accessories: an electrical generator, probes, and...

21 CFR 884.4150 - Bipolar endoscopic coagulator-cutter and accessories.

Code of Federal Regulations, 2011 CFR

2011-04-01

... high frequency electrical current through tissue between two electrical contacts of a probe. This generic type of device may include the following accessories: an electrical generator, probes, and...

21 CFR 884.4150 - Bipolar endoscopic coagulator-cutter and accessories.

Code of Federal Regulations, 2013 CFR

2013-04-01

... high frequency electrical current through tissue between two electrical contacts of a probe. This generic type of device may include the following accessories: an electrical generator, probes, and...

Preliminary study of the interactions caused by crossing shock waves and a turbulent boundary layer

NASA Technical Reports Server (NTRS)

Ketchum, A. C.; Bogdonoff, S. M.; Fernando, E. M.; Batcho, P. F.

1989-01-01

The subject research, the first phase of an extended study of the interaction of crossing shock waves with a turbulent boundary layer, has revealed the complexity of the resulting flow. Detailed surface visualization and mean wall static pressure distributions show little resemblance to the inviscid flow approximation, and the exploratory high frequency measurements show that the flow downstream of the theoretical inviscid shock crossing position has a significant unsteady characteristic. Further developments of the (unsteady) high frequency measurements are required to fully characterize the unsteadiness and the requirements to include this component in flowfield modeling.

Raman spectroscopy and lattice dynamics of MgSiO3-perovskite at high pressure

NASA Astrophysics Data System (ADS)

Hemley, R. J.; Cohen, R. E.; Yeganeh-Haeri, A.; Mao, H. K.; Weidner, D. J.; Ito, E.

Vibrational Raman spectra have been obtained for 50 to 100 μm single crystals of MgSiO3 perovskite in situ at high pressure. Seven bands were tracked as a function of pressure to 26 GPa using a diamond-anvil high-pressure cell with rare-gas pressure-transmitting media. The frequency shifts with pressure are positive, and no soft modes were observed, in agreement with the present and previous lattice dynamics calculations. Zero-pressure frequency shifts (dυi/dP)0 vary between 1.7 and 4.2 cm-1/GPa, which contrasts with the uniform shift of 2.6 cm-1/GPa for modes measured in high-pressure mid-infrared spectra. The mode-Grüneisen parameters γi, determined from the present data span the range 1.6-1.9, and are generally higher than those reported in the infrared study. The Raman data are interpreted using the lattice dynamics calculated from the potential-induced breathing (PIB) model, a Gordon-Kim approach that includes the effects of charge relaxation on the dynamics. Good agreement with the experimentally determined frequencies is obtained, particularly in the lower frequency range, in comparison with previous rigid-ion results. The high thermal expansivity for MgSiO3-perovskite is shown to be due to the comparatively high values for γi associated with the lower frequency modes. Thermal weighting of the individual γi is required for an accurate calculation of the thermal Grüneisen parameter γTH and thermal expansivity.

[High frequency of dyslipidemia in VIH-infected patients in aa peruvian public hospital].

PubMed

Rondan, Paola L; Flores-Flores, Oscar; Doria, Nicole A; Valencia-Mesias, Gustavo; Chávez-Pérez, Víctor; Soria, Jaime

2017-01-01

The objective of the study was to determine the frequency and characteristics of dyslipidemia in patients with HIV in highly active antiretroviral therapy (HAART) in a Peruvian public hospital. A cross-sectional study was carried out in patients with complete lipid profile after receiving at least six months of HAART. Dyslipidemia was defined according to the criteria of the NCEP-ATP III. We reviewed 2 975 clinical histories, and included 538 (18.1%) in the analysis. The frequency of dyslipidemia was 74.7%. HAART regimens which include protease inhibitors (PI) (odds ratio [OR]: 1.22; confidence interval at 95% [CI 95%]: 1.11-1.33) and to be older than 40 years (OR: 1.17; CI 95%: 1.05-1.28) were associated with dyslipidemia, adjusted by viral load, CD4 lymphocyte level and gender. In conclusion, dyslipidemia was very common in our sample and was mainly associated with the use of PI. It is necessary to promote the dyslipidemia control as part of the comprehensive care of the patient with HIV.

BRITE-Constellation reveals evidence for pulsations in the enigmatic binary η Carinae

NASA Astrophysics Data System (ADS)

Richardson, Noel D.; Pablo, Herbert; Sterken, Christiaan; Pigulski, Andrzej; Koenigsberger, Gloria; Moffat, Anthony F. J.; Madura, Thomas I.; Hamaguchi, Kenji; Corcoran, Michael F.; Damineli, Augusto; Gull, Theodore R.; Hillier, D. John; Weigelt, Gerd; Handler, Gerald; Popowicz, Adam; Wade, Gregg A.; Weiss, Werner W.; Zwintz, Konstanze

2018-04-01

η Car is a massive, eccentric binary with a rich observational history. We obtained the first high-cadence, high-precision light curves with the BRITE-Constellation nanosatellites over 6 months in 2016 and 6 months in 2017. The light curve is contaminated by several sources including the Homunculus nebula and neighbouring stars, including the eclipsing binary CPD -59°2628. However, we found two coherent oscillations in the light curve. These may represent pulsations that are not yet understood but we postulate that they are related to tidally excited oscillations of η Car's primary star, and would be similar to those detected in lower mass eccentric binaries. In particular, one frequency was previously detected by van Genderen et al. and Sterken et al. through the time period of 1974-1995 through timing measurements of photometric maxima. Thus, this frequency seems to have been detected for nearly four decades, indicating that it has been stable in frequency over this time span. These pulsations could help provide the first direct constraints on the fundamental parameters of the primary star if confirmed and refined with future observations.

Characterization of Axial Inducer Cavitation Instabilities via High Speed Video Recordings

NASA Technical Reports Server (NTRS)

Arellano, Patrick; Peneda, Marinelle; Ferguson, Thomas; Zoladz, Thomas

2011-01-01

Sub-scale water tests were undertaken to assess the viability of utilizing high resolution, high frame-rate digital video recordings of a liquid rocket engine turbopump axial inducer to characterize cavitation instabilities. These high speed video (HSV) images of various cavitation phenomena, including higher order cavitation, rotating cavitation, alternating blade cavitation, and asymmetric cavitation, as well as non-cavitating flows for comparison, were recorded from various orientations through an acrylic tunnel using one and two cameras at digital recording rates ranging from 6,000 to 15,700 frames per second. The physical characteristics of these cavitation forms, including the mechanisms that define the cavitation frequency, were identified. Additionally, these images showed how the cavitation forms changed and transitioned from one type (tip vortex) to another (sheet cavitation) as the inducer boundary conditions (inlet pressures) were changed. Image processing techniques were developed which tracked the formation and collapse of cavitating fluid in a specified target area, both in the temporal and frequency domains, in order to characterize the cavitation instability frequency. The accuracy of the analysis techniques was found to be very dependent on target size for higher order cavitation, but much less so for the other phenomena. Tunnel-mounted piezoelectric, dynamic pressure transducers were present throughout these tests and were used as references in correlating the results obtained by image processing. Results showed good agreement between image processing and dynamic pressure spectral data. The test set-up, test program, and test results including H-Q and suction performance, dynamic environment and cavitation characterization, and image processing techniques and results will be discussed.

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.

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.

High frequency and large deposition of acid fog on high elevation forest.

PubMed

Igawa, Manabu; Matsumura, Ko; Okochi, Hiroshi

2002-01-01

We have collected and analyzed fogwater on the mountainside of Mt. Oyama (1252 m) in the Tanzawa Mountains of Japan and observed the fog event frequency from the base of the mountain with a video camera. The fog event frequency increased with elevation and was observed to be present 46% of the year at the summit. The water deposition via throughfall increased with elevation because of the increase in fogwater interception and was about twice that via rain at the summit, where the air pollutant deposition via throughfall was several times that via rainwater. The dry deposition and the deposition via fogwater were dominant factors in the total ion deposition at high elevation sites. In a fog event, nitric acid, the major acid component on the mountain, is formed during the transport of the air mass from the base of the mountain along the mountainside, where gases including nitric acid deposit and are scavenged by fogwater. Therefore, high acidity caused by nitric acid and relatively low ion strength are observed in the fogwater at high elevation sites.

An analysis of the relationships between subthreshold electrical properties and excitability in skeletal muscle

PubMed Central

L.-H. Huang, Christopher; Fraser, James A.

2011-01-01

Skeletal muscle activation requires action potential (AP) initiation followed by its sarcolemmal propagation and tubular excitation to trigger Ca2+ release and contraction. Recent studies demonstrate that ion channels underlying the resting membrane conductance (GM) of fast-twitch mammalian muscle fibers are highly regulated during muscle activity. Thus, onset of activity reduces GM, whereas prolonged activity can markedly elevate GM. Although these observations implicate GM regulation in control of muscle excitability, classical theoretical studies in un-myelinated axons predict little influence of GM on membrane excitability. However, surface membrane morphologies differ markedly between un-myelinated axons and muscle fibers, predominantly because of the tubular (t)-system of muscle fibers. This study develops a linear circuit model of mammalian muscle fiber and uses this to assess the role of subthreshold electrical properties, including GM changes during muscle activity, for AP initiation, AP propagation, and t-system excitation. Experimental observations of frequency-dependent length constant and membrane-phase properties in fast-twitch rat fibers could only be replicated by models that included t-system luminal resistances. Having quantified these resistances, the resulting models showed enhanced conduction velocity of passive current flow also implicating elevated AP propagation velocity. Furthermore, the resistances filter passive currents such that higher frequency current components would determine sarcolemma AP conduction velocity, whereas lower frequency components excite t-system APs. Because GM modulation affects only the low-frequency membrane impedance, the GM changes in active muscle would predominantly affect neuromuscular transmission and low-frequency t-system excitation while exerting little influence on the high-frequency process of sarcolemmal AP propagation. This physiological role of GM regulation was increased by high Cl− permeability, as in muscle endplate regions, and by increased extracellular [K+], as observed in working muscle. Thus, reduced GM at the onset of exercise would enhance t-system excitation and neuromuscular transmission, whereas elevated GM after sustained activity would inhibit these processes and thereby accentuate muscle fatigue. PMID:21670208

Opto-electronic microwave oscillator

NASA Astrophysics Data System (ADS)

Yao, X. Steve; Maleki, Lute

1996-12-01

Photonic applications are important in RF communication systems to enhance many functions including remote transfer of antenna signals, carrier frequency up or down conversion, antenna beam steering, and signal filtering. Many of these functions require reference frequency oscillators. However, traditional microwave oscillators cannot meet all the requirements of photonic communication systems that need high frequency and low phase noise signal generation. Because photonic systems involve signals in both optical and electrical domains, an ideal signal source should be able to provide electrical and optical signals. In addition, it should be possible to synchronize or control the signal source by both electrical and optical means. We present such a source1-2 that converts continuous light energy into stable and spectrally pure microwave signals. This Opto-Electronic Oscillator, OEO, consists of a pump laser and a feedback circuit including an intensity modulator, an optical fiber delay line, a photodetector, an amplifier, and a filter, as shown in Figure 1a. Its oscillation frequency, limited only by the speed of the modulator, can be up to 75 GHz.

Frequency stabilization in injection controlled pulsed CO2 lasers

NASA Technical Reports Server (NTRS)

Menzies, Robert T.; Ancellet, Gerard M.

1987-01-01

Longitudinal mode selection by injection has been demonstrated as a viable technique for tailoring a TEA-CO2 laser with pulse energies of a Joule or greater to fit the requirements of a coherent lidar transmitter. Once reliable generation of single-longitudinal-mode (SLM) pulses is obtained, one can study the intrapulse frequency variation and attempt to determine the sources of frequency sweeping, or chirp. These sources include the effect of the decaying plasma, the thermal gradient due to the energy dissipation associated with the laser mechanism itself, and the pressure shift of the center frequency of the laser transition. The use of the positive-branch unstable resonator as an efficient means of coupling a discharge with transverse spatial dimensions of the order of centimeters to an optical cavity mode introduces another concern: namely, what can be done to emphasize transverse mode discrimination in an unstable resonator cavity while maintaining high coupling efficiency. These issues are briefly discussed in the paper, and representative experimental examples are included.

Tissue classification using depth-dependent ultrasound time series analysis: in-vitro animal study

NASA Astrophysics Data System (ADS)

Imani, Farhad; Daoud, Mohammad; Moradi, Mehdi; Abolmaesumi, Purang; Mousavi, Parvin

2011-03-01

Time series analysis of ultrasound radio-frequency (RF) signals has been shown to be an effective tissue classification method. Previous studies of this method for tissue differentiation at high and clinical-frequencies have been reported. In this paper, analysis of RF time series is extended to improve tissue classification at the clinical frequencies by including novel features extracted from the time series spectrum. The primary feature examined is the Mean Central Frequency (MCF) computed for regions of interest (ROIs) in the tissue extending along the axial axis of the transducer. In addition, the intercept and slope of a line fitted to the MCF-values of the RF time series as a function of depth have been included. To evaluate the accuracy of the new features, an in vitro animal study is performed using three tissue types: bovine muscle, bovine liver, and chicken breast, where perfect two-way classification is achieved. The results show statistically significant improvements over the classification accuracies with previously reported features.

Sources and Propagation of High Frequency Waves in the Solar Photosphere and Chromosphere

NASA Astrophysics Data System (ADS)

Lawrence, John K.; Cadavid, A. C.

2009-05-01

We study the spatial distribution of oscillatory power in two sequences of high-cadence, high-resolution images taken by the Solar Optical Telescope on board Hinode. The sequences consist of simultaneous, co-registered G-Band (GB) and Ca II H-Line (HL) images with pixel scale 80 km and fields of view 40 x 40 Mm and 80 x 40 Mm. The first sequence has cadence 21 s over 3 hours on 2007 April 14; the other has cadence 24 s over 2 hours on 2007 March 30. Both sequences include network and internetwork at heliocentric angle 35 degrees. Time averaging of Morlet wavelet transforms gives smoothed Fourier spectra for each spatial location in the GB and HL data. We averaged over four different frequency bands to highlight different physical regimes: "evolutionary” timescales (f < 1.2 mHz); evanescent frequencies just below the acoustic cutoff ( 2.6 mHz < f < 4.2 mHz); high frequencies just above the cutoff (5.5 mHz

Parametric Flutter Analysis of the TCA Configuration and Recommendation for FFM Design and Scaling

NASA Technical Reports Server (NTRS)

Baker, Myles; Lenkey, Peter

1997-01-01

The current HSR Aeroelasticity plan to design, build, and test a full span, free flying transonic flutter model in the TDT has many technical obstacles that must be overcome for a successful program. One technical obstacle is the determination of a suitable configuration and point in the sky to use in setting the scaling point for the ASE models program. Determining this configuration and point in the sky requires balancing several conflicting requirements, including model buildability, tunnel test safety, and the ability of the model to represent the flutter mechanisms of interest. As will be discussed in detail in subsequent sections, the current TCA design exhibits several flutter mechanisms of interest. It has been decided that the ASE models program will focus on the low frequency symmetric flutter mechanism, and will make no attempt to investigate high frequency flutter mechanisms. There are several reasons for this choice. First, it is believed that the high frequency flutter mechanisms are similar in nature to classical wing bending/torsion flutter, and therefore there is more confidence that this mechanism can be predicted using current techniques. The low frequency mode, on the other hand, is a highly coupled mechanism involving wing, body, tail, and engine motion which may be very difficult to predict. Second, the high frequency flutter modes result in very small weight penalties (several hundred pounds), while suppression of the low frequency mechanism inside the flight envelope causes thousands of pounds to be added to the structure. In order to successfully test the low frequency flutter mode of interest, a suitable starting configuration and point in the sky must be identified. The configuration and point in the sky must result in a wind tunnel model that (1) represents the low-frequency wing/body/engine/empennage flutter mechanisms that are unique to HSCT configurations, (2) flutters at an acceptably low frequency in the tunnel, (3) flutters at an acceptably low dynamic pressure in the tunnel, (4) allows sufficient weight for model buildability without inordinately high cost, and (5) has significant separation between the target flutter mechanism and other, potentially catastrophic, flutter mechanisms.

Optical image and laser slope meter intercomparisons of high-frequency waves

NASA Technical Reports Server (NTRS)

Lubard, S. C.; Krimmel, J. E.; Thebaud, L. R.; Evans, D. D.; Shemdin, O. H.

1980-01-01

Spectral analyses of optical images of the ocean surface, obtained by a digital video system, are presented and compared with wave data measured simultaneously by the JPL Waverider-mounted laser slope meter. The image analyses, which incorporate several new ideas, provide two-dimensional wave number spectra of slope, covering wavelengths from 10 cm to 10 m. These slope spectra are converted to wave height spectra by a new technique which includes the effects of sky radiance gradients. Space-time spectra are also presented for waves whose frequencies are less than 2 Hz. The JPL slope frequency spectra are compared with image wave number spectra which have been converted to frequency spectra by use of the gravity wave dispersion relation. Results of comparisons between the frequency spectra obtained from the two different measurements show reasonable agreement for frequencies less than 3 Hz.

Image enhancement by non-linear extrapolation in frequency space

NASA Technical Reports Server (NTRS)

Anderson, Charles H. (Inventor); Greenspan, Hayit K. (Inventor)

1998-01-01

An input image is enhanced to include spatial frequency components having frequencies higher than those in an input image. To this end, an edge map is generated from the input image using a high band pass filtering technique. An enhancing map is subsequently generated from the edge map, with the enhanced map having spatial frequencies exceeding an initial maximum spatial frequency of the input image. The enhanced map is generated by applying a non-linear operator to the edge map in a manner which preserves the phase transitions of the edges of the input image. The enhanced map is added to the input image to achieve a resulting image having spatial frequencies greater than those in the input image. Simplicity of computations and ease of implementation allow for image sharpening after enlargement and for real-time applications such as videophones, advanced definition television, zooming, and restoration of old motion pictures.

ciliaFA: a research tool for automated, high-throughput measurement of ciliary beat frequency using freely available software

PubMed Central

2012-01-01

Background Analysis of ciliary function for assessment of patients suspected of primary ciliary dyskinesia (PCD) and for research studies of respiratory and ependymal cilia requires assessment of both ciliary beat pattern and beat frequency. While direct measurement of beat frequency from high-speed video recordings is the most accurate and reproducible technique it is extremely time consuming. The aim of this study was to develop a freely available automated method of ciliary beat frequency analysis from digital video (AVI) files that runs on open-source software (ImageJ) coupled to Microsoft Excel, and to validate this by comparison to the direct measuring high-speed video recordings of respiratory and ependymal cilia. These models allowed comparison to cilia beating between 3 and 52 Hz. Methods Digital video files of motile ciliated ependymal (frequency range 34 to 52 Hz) and respiratory epithelial cells (frequency 3 to 18 Hz) were captured using a high-speed digital video recorder. To cover the range above between 18 and 37 Hz the frequency of ependymal cilia were slowed by the addition of the pneumococcal toxin pneumolysin. Measurements made directly by timing a given number of individual ciliary beat cycles were compared with those obtained using the automated ciliaFA system. Results The overall mean difference (± SD) between the ciliaFA and direct measurement high-speed digital imaging methods was −0.05 ± 1.25 Hz, the correlation coefficient was shown to be 0.991 and the Bland-Altman limits of agreement were from −1.99 to 1.49 Hz for respiratory and from −2.55 to 3.25 Hz for ependymal cilia. Conclusions A plugin for ImageJ was developed that extracts pixel intensities and performs fast Fourier transformation (FFT) using Microsoft Excel. The ciliaFA software allowed automated, high throughput measurement of respiratory and ependymal ciliary beat frequency (range 3 to 52 Hz) and avoids operator error due to selection bias. We have included free access to the ciliaFA plugin and installation instructions in Additional file 1 accompanying this manuscript that other researchers may use. PMID:23351276

Major features of immunesenescence, including reduced thymic output, are ameliorated by high levels of physical activity in adulthood.

PubMed

Duggal, Niharika Arora; Pollock, Ross D; Lazarus, Norman R; Harridge, Stephen; Lord, Janet M

2018-04-01

It is widely accepted that aging is accompanied by remodelling of the immune system including thymic atrophy and increased frequency of senescent T cells, leading to immune compromise. However, physical activity, which influences immunity but declines dramatically with age, is not considered in this literature. We assessed immune profiles in 125 adults (55-79 years) who had maintained a high level of physical activity (cycling) for much of their adult lives, 75 age-matched older adults and 55 young adults not involved in regular exercise. The frequency of naïve T cells and recent thymic emigrants (RTE) were both higher in cyclists compared with inactive elders, and RTE frequency in cyclists was no different to young adults. Compared with their less active counterparts, the cyclists had significantly higher serum levels of the thymoprotective cytokine IL-7 and lower IL-6, which promotes thymic atrophy. Cyclists also showed additional evidence of reduced immunesenescence, namely lower Th17 polarization and higher B regulatory cell frequency than inactive elders. Physical activity did not protect against all aspects of immunesenescence: CD28 -ve CD57 +ve senescent CD8 T-cell frequency did not differ between cyclists and inactive elders. We conclude that many features of immunesenescence may be driven by reduced physical activity with age. © 2018 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

29 CFR 1910.134 - Respiratory protection.

Code of Federal Regulations, 2012 CFR

2012-07-01

... impact and penetration. High efficiency particulate air (HEPA) filter means a filter that is at least 99... as a high efficiency particulate air (HEPA) filter, or an air-purifying respirator equipped with a... frequency of respirator use (including use for rescue and escape); (C) The expected physical work effort; (D...

29 CFR 1910.134 - Respiratory protection.

Code of Federal Regulations, 2014 CFR

2014-07-01

... impact and penetration. High efficiency particulate air (HEPA) filter means a filter that is at least 99... as a high efficiency particulate air (HEPA) filter, or an air-purifying respirator equipped with a... frequency of respirator use (including use for rescue and escape); (C) The expected physical work effort; (D...

29 CFR 1910.134 - Respiratory protection.

Code of Federal Regulations, 2013 CFR

2013-07-01

... impact and penetration. High efficiency particulate air (HEPA) filter means a filter that is at least 99... as a high efficiency particulate air (HEPA) filter, or an air-purifying respirator equipped with a... frequency of respirator use (including use for rescue and escape); (C) The expected physical work effort; (D...

Op-amp gyrator simulates high Q inductor

NASA Technical Reports Server (NTRS)

Sutherland, W. C.

1977-01-01

Gyrator circuit consisting of dual operational amplifier and four resistors inverts impedance of capacitor to simulate inductor. Synthetic inductor has high Q factor, good stability, wide bandwidth, and easily determined value of inductance that is independent of frequency. It readily lends itself to integrated-circuit applications, including filter networks.

Non-destructive evaluation techniques, high temperature ceramic component parts for gas turbines

NASA Technical Reports Server (NTRS)

Reiter, H.; Hirsekorn, S.; Lottermoser, J.; Goebbels, K.

1984-01-01

This report concerns studies conducted on various tests undertaken on material without destroying the material. Tests included: microradiographic techniques, vibration analysis, high-frequency ultrasonic tests with the addition of evaluation of defects and structure through analysis of ultrasonic scattering data, microwave tests and analysis of sound emission.

A Joint Method of Envelope Inversion Combined with Hybrid-domain Full Waveform Inversion

NASA Astrophysics Data System (ADS)

CUI, C.; Hou, W.

2017-12-01

Full waveform inversion (FWI) aims to construct high-precision subsurface models by fully using the information in seismic records, including amplitude, travel time, phase and so on. However, high non-linearity and the absence of low frequency information in seismic data lead to the well-known cycle skipping problem and make inversion easily fall into local minima. In addition, those 3D inversion methods that are based on acoustic approximation ignore the elastic effects in real seismic field, and make inversion harder. As a result, the accuracy of final inversion results highly relies on the quality of initial model. In order to improve stability and quality of inversion results, multi-scale inversion that reconstructs subsurface model from low to high frequency are applied. But, the absence of very low frequencies (< 3Hz) in field data is still bottleneck in the FWI. By extracting ultra low-frequency data from field data, envelope inversion is able to recover low wavenumber model with a demodulation operator (envelope operator), though the low frequency data does not really exist in field data. To improve the efficiency and viability of the inversion, in this study, we proposed a joint method of envelope inversion combined with hybrid-domain FWI. First, we developed 3D elastic envelope inversion, and the misfit function and the corresponding gradient operator were derived. Then we performed hybrid-domain FWI with envelope inversion result as initial model which provides low wavenumber component of model. Here, forward modeling is implemented in the time domain and inversion in the frequency domain. To accelerate the inversion, we adopt CPU/GPU heterogeneous computing techniques. There were two levels of parallelism. In the first level, the inversion tasks are decomposed and assigned to each computation node by shot number. In the second level, GPU multithreaded programming is used for the computation tasks in each node, including forward modeling, envelope extraction, DFT (discrete Fourier transform) calculation and gradients calculation. Numerical tests demonstrated that the combined envelope inversion + hybrid-domain FWI could obtain much faithful and accurate result than conventional hybrid-domain FWI. The CPU/GPU heterogeneous parallel computation could improve the performance speed.

Deep whole-genome sequencing of 90 Han Chinese genomes.

PubMed

Lan, Tianming; Lin, Haoxiang; Zhu, Wenjuan; Laurent, Tellier Christian Asker Melchior; Yang, Mengcheng; Liu, Xin; Wang, Jun; Wang, Jian; Yang, Huanming; Xu, Xun; Guo, Xiaosen

2017-09-01

Next-generation sequencing provides a high-resolution insight into human genetic information. However, the focus of previous studies has primarily been on low-coverage data due to the high cost of sequencing. Although the 1000 Genomes Project and the Haplotype Reference Consortium have both provided powerful reference panels for imputation, low-frequency and novel variants remain difficult to discover and call with accuracy on the basis of low-coverage data. Deep sequencing provides an optimal solution for the problem of these low-frequency and novel variants. Although whole-exome sequencing is also a viable choice for exome regions, it cannot account for noncoding regions, sometimes resulting in the absence of important, causal variants. For Han Chinese populations, the majority of variants have been discovered based upon low-coverage data from the 1000 Genomes Project. However, high-coverage, whole-genome sequencing data are limited for any population, and a large amount of low-frequency, population-specific variants remain uncharacterized. We have performed whole-genome sequencing at a high depth (∼×80) of 90 unrelated individuals of Chinese ancestry, collected from the 1000 Genomes Project samples, including 45 Northern Han Chinese and 45 Southern Han Chinese samples. Eighty-three of these 90 have been sequenced by the 1000 Genomes Project. We have identified 12 568 804 single nucleotide polymorphisms, 2 074 210 short InDels, and 26 142 structural variations from these 90 samples. Compared to the Han Chinese data from the 1000 Genomes Project, we have found 7 000 629 novel variants with low frequency (defined as minor allele frequency < 5%), including 5 813 503 single nucleotide polymorphisms, 1 169 199 InDels, and 17 927 structural variants. Using deep sequencing data, we have built a greatly expanded spectrum of genetic variation for the Han Chinese genome. Compared to the 1000 Genomes Project, these Han Chinese deep sequencing data enhance the characterization of a large number of low-frequency, novel variants. This will be a valuable resource for promoting Chinese genetics research and medical development. Additionally, it will provide a valuable supplement to the 1000 Genomes Project, as well as to other human genome projects. © The Authors 2017. Published by Oxford University Press.

A methodology for spectral wave model evaluation

NASA Astrophysics Data System (ADS)

Siqueira, S. A.; Edwards, K. L.; Rogers, W. E.

2017-12-01

Model evaluation is accomplished by comparing bulk parameters (e.g., significant wave height, energy period, and mean square slope (MSS)) calculated from the model energy spectra with those calculated from buoy energy spectra. Quality control of the observed data and choice of the frequency range from which the bulk parameters are calculated are critical steps in ensuring the validity of the model-data comparison. The compared frequency range of each observation and the analogous model output must be identical, and the optimal frequency range depends in part on the reliability of the observed spectra. National Data Buoy Center 3-m discus buoy spectra are unreliable above 0.3 Hz due to a non-optimal buoy response function correction. As such, the upper end of the spectrum should not be included when comparing a model to these data. Bioufouling of Waverider buoys must be detected, as it can harm the hydrodynamic response of the buoy at high frequencies, thereby rendering the upper part of the spectrum unsuitable for comparison. An important consideration is that the intentional exclusion of high frequency energy from a validation due to data quality concerns (above) can have major implications for validation exercises, especially for parameters such as the third and fourth moments of the spectrum (related to Stokes drift and MSS, respectively); final conclusions can be strongly altered. We demonstrate this by comparing outcomes with and without the exclusion, in a case where a Waverider buoy is believed to be free of biofouling. Determination of the appropriate frequency range is not limited to the observed spectra. Model evaluation involves considering whether all relevant frequencies are included. Guidance to make this decision is based on analysis of observed spectra. Two model frequency lower limits were considered. Energy in the observed spectrum below the model lower limit was calculated for each. For locations where long swell is a component of the wave climate, omitting the energy in the frequency band between the two lower limits tested can lead to an incomplete characterization of model performance. This methodology was developed to aid in selecting a comparison frequency range that does not needlessly increase computational expense and does not exclude energy to the detriment of model performance analysis.

Transfer and dissipation of energy during wave group propagation on a gentle beach slope

NASA Astrophysics Data System (ADS)

Padilla, Enrique M.; Alsina, José M.

2017-08-01

The propagation of bichromatic wave groups over a constant 1:100 beach slope and the influence of the group modulation is presented. The modulation is controlled by varying the group frequency, fg, which is shown to remarkably affect the energy transfer to high and low frequency components. The growth of the high frequency (hf) wave skewness increases when fg decreases. This is explained by nonlinear coupling between the primary frequencies, which results in a larger growth of hf components as fg decreases, causing the hf waves to break earlier. Due to high spatial resolution, wave tracking has provided an accurate measurement of the varying breakpoint. These breaking locations are very well described (R2>0.91) by the wave-height to effective-depth ratio (γ). However, for any given Iribarren number, this γ is shown to increase with fg. Therefore, a modified Iribarren number is proposed to include the grouping structure, leading to a considerable improvement in reproducing the measured γ-values. Within the surf zone, the behavior of the Incident Long Wave also depends on the group modulation. For low fg conditions, the lf wave decays only slightly by transferring energy back to the hf wave components. However, for high fg wave conditions, strong dissipation of low frequency (lf) components occurs close to the shoreline associated with lf wave breaking. This mechanism is explained by the growth of the lf wave height, induced partly by the self-self interaction of fg, and partly by the nonlinear coupling between the primary frequencies and fg.

Success of capture of toads improved by manipulating acoustic characteristics of lures.

PubMed

Muller, Benjamin J; Schwarzkopf, Lin

2017-11-01

Management of invasive vertebrates is a crucial component of conservation. Trapping reproductive adults is often effective for control, and modification of traps may greatly increase their attractiveness to such individuals. Cane toads (Rhinella marina) are invasive, and males use advertisement vocalisations to attract reproductive females. In amphibians, including toads, specific structural parameters of calls (e.g. dominant frequency and pulse rate) may be attractive to females. Some cane toad traps use an artificial advertisement vocalisation to attract toads. We determined whether variation of the call's parameters (volume, dominant frequency and pulse rate) could increase the capture rate of gravid females. Overall, traps equipped with loud calls (80 dB at 1 m) caught significantly more toads, and proportionally more gravid females, than traps with quiet calls (60 dB at 1 m), and traps with low dominant frequency calls caught more gravid females than traps with median frequency calls. Traps with high pulse rate calls attracted more females than traps with low pulse rate calls. Approximately 91% of the females trapped using a low frequency and high pulse rate combination call were gravid, whereas in traps using a call with population median parameters only approximately 75% of captured females were gravid. Calls that indicated large-bodied males (low frequency) with high energy reserves (high pulse rate) are often attractive to female anurans and were effective lures for female toads in our study. The design of future trapping regimes should account for behavioural preferences of the target sex. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Energy-Based Tetrahedron Sensor for High-Temperature, High-Pressure Environments

NASA Technical Reports Server (NTRS)

Gee, Kent L.; Sommerfeldt, Scott D.; Blotter, Jonathan D.

2012-01-01

An acoustic energy-based probe has been developed that incorporates multiple acoustic sensing elements in order to obtain the acoustic pressure and three-dimensional acoustic particle velocity. With these quantities, the user can obtain various energy-based quantities, including acoustic energy density, acoustic intensity, and acoustic impedance. In this specific development, the probe has been designed to operate in an environment characterized by high temperatures and high pressures as is found in the close vicinity of rocket plumes. Given these capabilities, the probe is designed to be used to investigate the acoustic conditions within the plume of a rocket engine or jet engine to facilitate greater understanding of the noise generation mechanisms in those plumes. The probe features sensors mounted inside a solid sphere. The associated electronics for the probe are contained within the sphere and the associated handle for the probe. More importantly, the design of the probe has desirable properties that reduce the bias errors associated with determining the acoustic pressure and velocity using finite sum and difference techniques. The diameter of the probe dictates the lower and upper operating frequencies for the probe, where accurate measurements can be acquired. The current probe design implements a sphere diameter of 1 in. (2.5 cm), which limits the upper operating frequency to about 4.5 kHz. The sensors are operational up to much higher frequencies, and could be used to acquire pressure data at higher frequencies, but the energy-based measurements are limited to that upper frequency. Larger or smaller spherical probes could be designed to go to lower or higher frequency range

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.

Self-consistent modeling of terahertz waveguide and cavity with frequency-dependent conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Y. J.; Chu, K. R., E-mail: krchu@yahoo.com.tw; Thumm, M.

The surface resistance of metals, and hence the Ohmic dissipation per unit area, scales with the square root of the frequency of an incident electromagnetic wave. As is well recognized, this can lead to excessive wall losses at terahertz (THz) frequencies. On the other hand, high-frequency oscillatory motion of conduction electrons tends to mitigate the collisional damping. As a result, the classical theory predicts that metals behave more like a transparent medium at frequencies above the ultraviolet. Such a behavior difference is inherent in the AC conductivity, a frequency-dependent complex quantity commonly used to treat electromagnetics of metals at opticalmore » frequencies. The THz region falls in the gap between microwave and optical frequencies. However, metals are still commonly modeled by the DC conductivity in currently active vacuum electronics research aimed at the development of high-power THz sources (notably the gyrotron), although a small reduction of the DC conductivity due to surface roughness is sometimes included. In this study, we present a self-consistent modeling of the gyrotron interaction structures (a metallic waveguide or cavity) with the AC conductivity. The resulting waveguide attenuation constants and cavity quality factors are compared with those of the DC-conductivity model. The reduction in Ohmic losses under the AC-conductivity model is shown to be increasingly significant as the frequency reaches deeper into the THz region. Such effects are of considerable importance to THz gyrotrons for which the minimization of Ohmic losses constitutes a major design consideration.« less

Efficacy of Current Practices for Pain Assessment in Premature Ventilated Infants in the NICU Exposed to a High Number of Pain-Associated Procedures.

PubMed

Rohan, Annie J

2015-01-01

To study infant factors, characteristics of pain scores, and analgesic practices associated with patient-days in the NICU with a high frequency of pain-associated procedures (defined as >10 pain-associated procedures in the day). This is a secondary analysis of data from a cross-sectional study that used medical record audits of premature, ventilated infants. The primary two-institution study yielded data for 196 patient-days. Data included 804 pain scores and 836 pain-associated procedures. A high frequency of pain-associated procedures occurred in 8% of days at Site A and in 25% of days at Site B. Prevalence of days with high frequency of pain-associated procedures differed by institution, and was higher at the institution where infants were more mature at birth and had fewer surgical procedures. High frequency of pain-associated procedures was related to endotracheal intubation at both institutions. There were no elevated pain scores and no documented analgesic administrations on days with over 20 pain-associated procedures. High exposure to pain-associated procedures during a 24-hour period for a premature, ventilated infant is rarely associated with elevated pain scores or analgesic administration. Prevalence of days with high-procedural exposure at an institution appears to be closely related to use of invasive ventilation and to individual institutional practices. Examination and discussion of the daily frequency of pain-associated procedures for premature, ventilated infants (especially for those receiving invasive ventilation) may be helpful in developing approaches for attenuating the cumulative pain experience for these babies. Resources that are expended on regular pain reassessment documentation processes in the NICU may need to be reconsidered in light of the very low yield for clinical alterations in care in this setting.

Numerical Investigation of the Microscopic Heat Current Inside a Nanofluid System Based on Molecular Dynamics Simulation and Wavelet Analysis.

PubMed

Jia, Tao; Gao, Di

2018-04-03

Molecular dynamics simulation is employed to investigate the microscopic heat current inside an argon-copper nanofluid. Wavelet analysis of the microscopic heat current inside the nanofluid system is conducted. The signal of the microscopic heat current is decomposed into two parts: one is the approximation part; the other is the detail part. The approximation part is associated with the low-frequency part of the signal, and the detail part is associated with the high-frequency part of the signal. Both the probability distributions of the high-frequency and the low-frequency parts of the signals demonstrate Gaussian-like characteristics. The curves fit to data of the probability distribution of the microscopic heat current are established, and the parameters including the mean value and the standard deviation in the mathematical formulas of the curves show dramatic changes for the cases before and after adding copper nanoparticles into the argon base fluid.

Robustness of continuous-time adaptive control algorithms in the presence of unmodeled dynamics

NASA Technical Reports Server (NTRS)

Rohrs, C. E.; Valavani, L.; Athans, M.; Stein, G.

1985-01-01

This paper examines the robustness properties of existing adaptive control algorithms to unmodeled plant high-frequency dynamics and unmeasurable output disturbances. It is demonstrated that there exist two infinite-gain operators in the nonlinear dynamic system which determines the time-evolution of output and parameter errors. The pragmatic implications of the existence of such infinite-gain operators is that: (1) sinusoidal reference inputs at specific frequencies and/or (2) sinusoidal output disturbances at any frequency (including dc), can cause the loop gain to increase without bound, thereby exciting the unmodeled high-frequency dynamics, and yielding an unstable control system. Hence, it is concluded that existing adaptive control algorithms as they are presented in the literature referenced in this paper, cannot be used with confidence in practical designs where the plant contains unmodeled dynamics because instability is likely to result. Further understanding is required to ascertain how the currently implemented adaptive systems differ from the theoretical systems studied here and how further theoretical development can improve the robustness of adaptive controllers.

A Stewart isolator with high-static-low-dynamic stiffness struts based on negative stiffness magnetic springs

NASA Astrophysics Data System (ADS)

Zheng, Yisheng; Li, Qingpin; Yan, Bo; Luo, Yajun; Zhang, Xinong

2018-05-01

In order to improve the isolation performance of passive Stewart platforms, the negative stiffness magnetic spring (NSMS) is employed to construct high static low dynamic stiffness (HSLDS) struts. With the NSMS, the resonance frequencies of the platform can be reduced effectively without deteriorating its load bearing capacity. The model of the Stewart isolation platform with HSLDS struts is presented and the stiffness characteristic of its struts is studied firstly. Then the nonlinear dynamic model of the platform including both geometry nonlinearity and stiffness nonlinearity is established; and its simplified dynamic model is derived under the condition of small vibration. The effect of nonlinearity on the isolation performance is also evaluated. Finally, a prototype is built and the isolation performance is tested. Both simulated and experimental results demonstrate that, by using the NSMS, the resonance frequencies of the Stewart isolator are reduced and the isolation performance in all six directions is improved: the isolation frequency band is increased and extended to a lower-frequency level.

[Polymorphism of DYS287 on Y chromosome in 28 ethnic populations of China].

PubMed

Chen, Yang; Chu, Jia-you; Yu, Jian-kun; Yu, Liang; Sun, Hao; Lin, Ke-qin; Tao, Yu-fen; Shi, Lei; Huang, Xiao-qin; Shi, Tie-liu; Fu, Song-bin

2006-04-01

To investigate the polymorphism of DYS287 among 28 ethnic populations in 9 provinces of China. YAP element was detected by Touchdown PCR amplification and 2% agarose gel electrophoresis. YAP+ frequencies in these ethnic populations were as follows: Zang 36.7%, Tu 23.8%, Yi 18.4%, Pumi 11.3%, Tajik 7.4%, Bai 6.7%, Jino 5.1%, Shandong Han 4%, Mulao 2.7%, and Maonan 1.3%. The rest ethnic populations in our study, including Gansu Han, Yunnan Han, Zhuangzu, Daizu, Lizu, Nuzu, Lisu, Naxi, Lahu, Dulong, Hani, Shezu, Weiwuer, Sala, Kerkizi, Dongxiang, Vazu, and Korea didn't carry YAP + element. Zangzu, Tuzu, Yizu, Pumi, Jino, and Baizu, which belong to Sino-Tibetan language family, carry a high YAP + frequency. Sala, Tuzu, and Tajik, regarded as Central Asia by origin in history and linguistics, also have a high YAP + frequency. Mulao and Maonan, which origin from "Baiyue" ancient ethnic groups, also have a considerable YAP + frequency.

Sensors, Cyberinfrastructure, and Examination of Hydrologic and Hydrochemical Response in the Little Bear River Observatory Test Bed

NASA Astrophysics Data System (ADS)

Horsburgh, J. S.; Stevens, D. K.; Tarboton, D. G.; Mesner, N. O.; Spackman Jones, A.

2008-12-01

The Little Bear River environmental observatory test bed is one of 11 test bed projects that are focused on developing techniques and technologies for environmental observatories ranging from innovative application of environmental sensors to publishing observations data in common formats that can be accessed by investigators nationwide. Specific objectives of the Little Bear test bed include the estimation of water quality constituent fluxes from surrogate data, relation of fluxes to watershed attributes and management practices, examination of high frequency hydrologic and hydrochemical responses, and development of cyberinfrastructure that supports these analyses and publication of the data. We have installed high frequency water quality and discharge monitoring instrumentation at seven locations in the Little Bear, along with two continuous weather stations. Cyberinfrastructure that has been implemented includes the sensors, a telemetry system that transmits data from the field to a central location, a central observations database, software that automates the ingestion of these data into the database so they are available in near real time, and software tools for screening and quality control of the raw data. We have implemented a CUAHSI Hydrologic Information System (HIS) Server that includes an instance of the Observations Data Model (ODM) relational database that stores the data, web services that provide programmatic data access over the Internet using WaterML, the Data Access System for Hydrology (DASH) that provides an Internet map based interface for data access, and the Time Series Analyst that provides Internet-based plotting and summary functionality. The high frequency data have illustrated the dynamic nature of hydrologic and hydrochemical response in the Little Bear as well as the importance of sampling frequency on estimation of constituent fluxes. Annual estimates of total phosphorus and total suspended solids loads vary over orders of magnitude as sample frequency decreases from half hourly to monthly, implying that high frequency data are necessary for quantifying fluxes of these constituents. Daily fluctuations in dissolved oxygen and dissolved oxygen saturation deficit have illustrated the importance of land use, pollutant loading, and flow regime on photosynthesis, respiration, and reaeration rates at each of the monitoring sites. Conductivity results have provided insights into contributions from differing hydrologic pathways that include baseflow, surface runoff, agricultural return flows, and reservoir releases, and together with the hydrochemical data have informed our conceptual model of the structure and function of the Little Bear River watershed. This presentation will cover both the development and implementation of cyberinfrastructure within the Little Bear River test bed as well as the results of our scientific analyses using the data that we have collected.

Improving Planck calibration by including frequency-dependent relativistic corrections

NASA Astrophysics Data System (ADS)

Quartin, Miguel; Notari, Alessio

2015-09-01

The Planck satellite detectors are calibrated in the 2015 release using the "orbital dipole", which is the time-dependent dipole generated by the Doppler effect due to the motion of the satellite around the Sun. Such an effect has also relativistic time-dependent corrections of relative magnitude 10-3, due to coupling with the "solar dipole" (the motion of the Sun compared to the CMB rest frame), which are included in the data calibration by the Planck collaboration. We point out that such corrections are subject to a frequency-dependent multiplicative factor. This factor differs from unity especially at the highest frequencies, relevant for the HFI instrument. Since currently Planck calibration errors are dominated by systematics, to the point that polarization data is currently unreliable at large scales, such a correction can in principle be highly relevant for future data releases.

Evaluation of overhead support inspection program.

DOT National Transportation Integrated Search

2015-01-01

This study evaluated the adequacy and frequency of the current structural support inspection program for overhead : sign supports (including bridge mounted), mast arm signal supports and high mast light supports. While ODOT provides : statewide guida...

Spinal Cord Stimulation for Treating Chronic Pain: Reviewing Preclinical and Clinical Data on Paresthesia-Free High-Frequency Therapy.

PubMed

Chakravarthy, Krishnan; Richter, Hira; Christo, Paul J; Williams, Kayode; Guan, Yun

2018-01-01

Traditional spinal cord stimulation (SCS) requires that paresthesia overlaps chronic painful areas. However, the new paradigm high-frequency SCS (HF-SCS) does not rely on paresthesia. A review of preclinical and clinical studies regarding the use of paresthesia-free HF-SCS for various chronic pain states. We reviewed available literatures on HF-SCS, including Nevro's paresthesia-free ultra high-frequency 10 kHz therapy (HF10-SCS). Data sources included relevant literature identified through searches of PubMed, MEDLINE/OVID, and SCOPUS, and manual searches of the bibliographies of known primary and review articles. The primary goal is to describe the present developing conceptions of preclinical mechanisms of HF-SCS and to review clinical efficacy on paresthesia-free HF10-SCS for various chronic pain states. HF10-SCS offers a novel pain reduction tool without paresthesia for failed back surgery syndrome and chronic axial back pain. Preclinical findings indicate that potential mechanisms of action for paresthesia-free HF-SCS differ from those of traditional SCS. To fully understand and utilize paresthesia-free HF-SCS, mechanistic study and translational research will be very important, with increasing collaboration between basic science and clinical communities to design better trials and optimize the therapy based on mechanistic findings from effective preclinical models and approaches. Future research in these vital areas may include preclinical and clinical components conducted in parallel to optimize the potential of this technology. © 2017 International Neuromodulation Society.

Ionospheric effects to antenna impedance

NASA Technical Reports Server (NTRS)

Bethke, K. H.

1986-01-01

The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

Development of an Autonomous, Compact, Broadband Acoustic Backscattering System for Remote Characterization of Zooplankton Variability (PART II)

DTIC Science & Technology

2010-09-30

proposal include: 1) complete the development of second-generation sonar boards, 2) complete the integration of new transducers with the second... sonar board and transducer. APPROACH Over the last 40 years, there has been significant research effort directed towards the use of high...narrowband frequency, and some AUVs carry single-frequency sidescan sonars (and this technology has been adapted for gliders), the lack of suitable

Travel Mode Detection with Varying Smartphone Data Collection Frequencies

PubMed Central

Shafique, Muhammad Awais; Hato, Eiji

2016-01-01

Smartphones are becoming increasingly popular day-by-day. Modern smartphones are more than just calling devices. They incorporate a number of high-end sensors that provide many new dimensions to smartphone experience. The use of smartphones, however, can be extended from the usual telecommunication field to applications in other specialized fields including transportation. Sensors embedded in the smartphones like GPS, accelerometer and gyroscope can collect data passively, which in turn can be processed to infer the travel mode of the smartphone user. This will solve most of the shortcomings associated with conventional travel survey methods including biased response, no response, erroneous time recording, etc. The current study uses the sensors’ data collected by smartphones to extract nine features for classification. Variables including data frequency, moving window size and proportion of data to be used for training, are dealt with to achieve better results. Random forest is used to classify the smartphone data among six modes. An overall accuracy of 99.96% is achieved, with no mode less than 99.8% for data collected at 10 Hz frequency. The accuracy is observed to decrease with decrease in data frequency, but at the same time the computation time also decreases. PMID:27213380

Piezohydraulic Pump Development

NASA Technical Reports Server (NTRS)

Lynch, Christopher S.

2005-01-01

Reciprocating piston piezohydraulic pumps were developed originally under the Smart Wing Phase II program (Lynch) and later under the CHAP program (CSA, Kinetic Ceramics). These pumps focused on 10 cm scale stack actuators operating below resonance and, more recently, at resonance. A survey of commercially available linear actuators indicates that obtaining power density and specific power greater than electromagnetic linear actuators requires driving the stacks at frequencies greater than 1 KHz at high fields. In the case of 10 cm scale actuators the power supply signal conditioning becomes large and heavy and the soft PZT stack actuators generate a lot of heat due to internal losses. Reciprocation frequencies can be increased and material losses significantly decreased through use of millimeter scale single crystal stack actuators. We are presently targeting the design of pumps that utilize stacks at the 1-10 mm length scale and run at reciprocating frequencies of 20kHz or greater. This offers significant advantages over current approaches including eliminating audible noise and significantly increasing the power density and specific power of the system (including electronics). The pump currently under development will comprise an LC resonant drive of a resonant crystal and head mass operating against a resonant fluid column. Each of these resonant systems are high Q and together should produce a single high Q second order system.

First results from the energetic particle instrument on the OEDIPUS-C sounding rocket

NASA Astrophysics Data System (ADS)

Gough, M. P.; Hardy, D. A.; James, H. G.

The Canadian / US OEDIPUS-C rocket was flown from the Poker Flat Rocket Range November 6th 1995 as a mother-son sounding rocket. It was designed to study auroral ionospheric plasma physics using active wave sounding and prove tether technology. The payload separated into two sections reaching a separation of 1200m along the Earth's magnetic field. One section included a frequency stepped HF transmitter and the other included a synchronised HF receiver. Both sections included Energetic Particle Instruments, EPI, stepped in energy synchronously with the transmitter steps. On-board EPI particle processing in both payloads provided direct measurements of electron heating, wave-particle interactions via particle correlators, and a high resolution measurement of wave induced particle heating via transmitter synchronised fast sampling. Strong electron heating was observed at times when the HF transmitter frequency was equal to a harmonic of the electron gyrofrequency, f_ce, or equal to the upper hybrid frequency, f_uh.

Geotail MCA plasma wave data analysis

NASA Astrophysics Data System (ADS)

Anderson, Roger R.

NASA Grant NAG 5-2346 supports the data analysis effort at The University of Iowa for the GEOTAIL Multi-Channel Analyzer (MCA) which is a part of the GEOTAIL Plasma Wave Instrument (PWI). At the beginning of this reporting period we had just begun to receive our GEOTAIL Sirius data on CD-ROMs. Much programming effort went into adapting and refining the data analysis programs to include the CD-ROM inputs. Programs were also developed to display the high-frequency-resolution PWI Sweep Frequency Analyzer (SFA) data and to include in all the various plot products the electron cyclotron frequency derived from the magnitude of the magnetic field extracted from the GEOTAIL Magnetic Field (MGF) data included in the GEOTAIL Sirius data. We also developed programs to use the MGF data residing in the Institute of Space and Astronautical Science (ISAS) GEOTAIL Scientific Data Base (SDB). Our programmers also developed programs and provided technical support for the GEOTAIL data analysis efforts of Co-lnvestigator William W. L. Taylor at Nichols Research Corporation (NRC). At the end of this report we have included brief summaries of the NRC effort and the progress being made.

Geotail MCA plasma wave data analysis

NASA Technical Reports Server (NTRS)

Anderson, Roger R.

1994-01-01

NASA Grant NAG 5-2346 supports the data analysis effort at The University of Iowa for the GEOTAIL Multi-Channel Analyzer (MCA) which is a part of the GEOTAIL Plasma Wave Instrument (PWI). At the beginning of this reporting period we had just begun to receive our GEOTAIL Sirius data on CD-ROMs. Much programming effort went into adapting and refining the data analysis programs to include the CD-ROM inputs. Programs were also developed to display the high-frequency-resolution PWI Sweep Frequency Analyzer (SFA) data and to include in all the various plot products the electron cyclotron frequency derived from the magnitude of the magnetic field extracted from the GEOTAIL Magnetic Field (MGF) data included in the GEOTAIL Sirius data. We also developed programs to use the MGF data residing in the Institute of Space and Astronautical Science (ISAS) GEOTAIL Scientific Data Base (SDB). Our programmers also developed programs and provided technical support for the GEOTAIL data analysis efforts of Co-lnvestigator William W. L. Taylor at Nichols Research Corporation (NRC). At the end of this report we have included brief summaries of the NRC effort and the progress being made.

High Resolution Human Leukocyte Antigen Class I Allele Frequencies and HIV-1 Infection Associations in Chinese Han and Uyghur Cohorts

PubMed Central

Liu, Yanhou; Zhao, Zhongfang; Li, Tianyi; Liao, Qi; Kushner, Nicholas; Touzjian, Neal Y.; Shao, Yiming; Sun, Yongtao; Strong, Amie J.; Lu, Yichen

2012-01-01

Background Host immunogenetic factors such as HLA class I polymorphism are important to HIV-1 infection risk and AIDS progression. Previous studies using high-resolution HLA class I profile data of Chinese populations appeared insufficient to provide information for HIV-1 vaccine development and clinical trial design. Here we reported HLA class I association with HIV-1 susceptibility in a Chinese Han and a Chinese Uyghur cohort. Methodology/Principal Findings Our cohort included 327 Han and 161 Uyghur ethnic individuals. Each cohort included HIV-1 seropositive and HIV-1 seronegative subjects. Four-digit HLA class I typing was performed by sequencing-based typing and high-resolution PCR-sequence specific primer. We compared the HLA class I allele and inferred haplotype frequencies between HIV-1 seropositive and seronegative groups. A neighbor-joining tree between our cohorts and other populations was constructed based on allele frequencies of HLA-A and HLA-B loci. We identified 58 HLA-A, 75 HLA-B, and 32 HLA-Cw distinct alleles from our cohort and no novel alleles. The frequency of HLA-B*5201 and A*0301 was significantly higher in the Han HIV-1 negative group. The frequency of HLA-B*5101 was significantly higher in the Uyghur HIV-1 negative group. We observed statistically significant increases in expectation-maximization (EM) algorithm predicted haplotype frequencies of HLA-A*0201-B*5101 in the Uyghur HIV-1 negative group, and of Cw*0304-B*4001 in the Han HIV-1 negative group. The B62s supertype frequency was found to be significantly higher in the Han HIV-1 negative group than in the Han HIV-1 positive group. Conclusions At the four-digit level, several HLA class I alleles and haplotypes were associated with lower HIV-1 susceptibility. Homogeneity of HLA class I and Bw4/Bw6 heterozygosity were not associated with HIV-1 susceptibility in our cohort. These observations contribute to the Chinese HLA database and could prove useful in the development of HIV-1 vaccine candidates. PMID:23251376

High Electron Mobility Transistor Structures on Sapphire Substrates Using CMOS Compatible Processing Techniques

NASA Technical Reports Server (NTRS)

Mueller, Carl; Alterovitz, Samuel; Croke, Edward; Ponchak, George

2004-01-01

System-on-a-chip (SOC) processes are under intense development for high-speed, high frequency transceiver circuitry. As frequencies, data rates, and circuit complexity increases, the need for substrates that enable high-speed analog operation, low-power digital circuitry, and excellent isolation between devices becomes increasingly critical. SiGe/Si modulation doped field effect transistors (MODFETs) with high carrier mobilities are currently under development to meet the active RF device needs. However, as the substrate normally used is Si, the low-to-modest substrate resistivity causes large losses in the passive elements required for a complete high frequency circuit. These losses are projected to become increasingly troublesome as device frequencies progress to the Ku-band (12 - 18 GHz) and beyond. Sapphire is an excellent substrate for high frequency SOC designs because it supports excellent both active and passive RF device performance, as well as low-power digital operations. We are developing high electron mobility SiGe/Si transistor structures on r-plane sapphire, using either in-situ grown n-MODFET structures or ion-implanted high electron mobility transistor (HEMT) structures. Advantages of the MODFET structures include high electron mobilities at all temperatures (relative to ion-implanted HEMT structures), with mobility continuously improving to cryogenic temperatures. We have measured electron mobilities over 1,200 and 13,000 sq cm/V-sec at room temperature and 0.25 K, respectively in MODFET structures. The electron carrier densities were 1.6 and 1.33 x 10(exp 12)/sq cm at room and liquid helium temperature, respectively, denoting excellent carrier confinement. Using this technique, we have observed electron mobilities as high as 900 sq cm/V-sec at room temperature at a carrier density of 1.3 x 10(exp 12)/sq cm. The temperature dependence of mobility for both the MODFET and HEMT structures provides insights into the mechanisms that allow for enhanced electron mobility as well as the processes that limit mobility, and will be presented.

Organic solvent exposure and hearing loss in a cohort of aluminium workers.

PubMed

Rabinowitz, P M; Galusha, D; Slade, M D; Dixon-Ernst, C; O'Neill, A; Fiellin, M; Cullen, M R

2008-04-01

Organic solvent exposure has been shown to cause hearing loss in animals and humans. Less is known about the risk of hearing loss due to solvent exposures typically found in US industry. The authors performed a retrospective cohort study to examine the relationship between solvent exposure and hearing loss in US aluminium industry workers. A cohort of 1319 workers aged 35 years or less at inception was followed for 5 years. Linkage of employment, industrial hygiene and audiometric surveillance records allowed for estimation of noise and solvent exposures and hearing loss rates over the study period. Study subjects were classified as "solvent exposed" or not, on the basis of industrial hygiene records linked with individual job histories. High frequency hearing loss was modelled as both a continuous and a dichotomous outcome. Typical solvent exposures involved mixtures of xylene, toluene and/or methyl ethyl ketone (MEK). Recorded solvent exposure levels varied widely both within and between jobs. In a multivariate logistic model, risk factors for high frequency hearing loss included age (OR = 1.06, p = 0.004), hunting or shooting (OR = 1.35, p = 0.049), noisy hobbies (OR = 1.74, p = 0.01), baseline hearing level (OR = 1.04, p<0.001) and solvent exposure (OR = 1.87, p = 0.004). A multivariate linear regression analysis similarly found significant associations between high frequency hearing loss and age (p<0.001), hunting or shooting (p<0.001), noisy hobbies (p = 0.03), solvent exposure (p<0.001) and baseline hearing (p = 0.03). These results suggest that occupational exposure to organic solvent mixtures is a risk factor for high frequency hearing loss, although the data do not allow conclusions about dose-response relationships. Industries with solvent-exposed workers should include such workers in hearing conservation programs.

The Effects of the Menstrual Cycle on Vibratory Characteristics of the Vocal Folds Investigated With High-Speed Digital Imaging.

PubMed

Kunduk, Melda; Vansant, Mathew B; Ikuma, Takeshi; McWhorter, Andrew

2017-03-01

This study investigated the effect of menstrual cycle on vocal fold vibratory characteristics in young women using high-speed digital imaging. This study examined the menstrual phase effect on five objective high-speed imaging parameters and two self-rated perceptual parameters. The effects of oral birth control use were also investigated. Thirteen subjects with no prior voice complaints were included in this study. All data were collected at three different time periods (premenses, postmenses, ovulation) over the course of one menstrual cycle. For five of the 13 subjects, data were collected for two consecutive cycles. Six of 13 subjects were oral birth control users. From high-speed imaging data, five objective parameters were computed: fundamental frequency, fundamental frequency deviation, harmonics-to-noise ratio, harmonic richness factor, and ratio of first and second harmonics. They were supplemented by two self-rated parameters: Reflux Severity Index and perceptual voice quality rating. Analysis included mixed model linear analysis with repeated measures. Results indicated no significant main effects for menstrual phase, between-cycle, or birth control use in the analysis for mean fundamental frequency, fundamental frequency deviation, harmonics-to-noise ratio, harmonic richness factor, first and second harmonics, Reflux Severity Index, and perceptual voice quality rating. Additionally, there were no interaction effects. Hormone fluctuations observed across the menstrual cycle do not appear to have direct effect on vocal fold vibratory characteristics in young women with no voice concerns. Birth control use, on the other hand, may have influence on spectral richness of vocal fold vibration. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Pressure attenuation during high-frequency airway clearance therapy across different size endotracheal tubes: An in vitro study.

PubMed

Smallwood, Craig D; Bullock, Kevin J; Gouldstone, Andrew

2016-08-01

High-frequency airway clearance therapy is a positive pressure secretion clearance modality used in pediatric and adult applications. However, pressure attenuation across different size endotracheal tubes (ETT) has not been adequately described. This study quantifies attenuation in an in vitro model. The MetaNeb® System was used to deliver high-frequency pressure pulses to 3.0, 4.0, 6.0 and 8.0mm ID ETTs connected to a test lung during mechanical ventilation. The experimental setup included a 3D-printed trachea model and imbedded pressure sensors. The pressure attenuation (Patt%) was calculated: Patt%=[(Pproximal-Pdistal)/Pproximal]x100. The effect of pulse frequency on Pdistal and Pproximal was quantified. Patt% was inversely and linearly related to ETT ID and (y=-7.924x+74.36; R(2)=0.9917, P=.0042 for 4.0Hz pulse frequency and y=-7.382+9.445, R(2)=0.9964, P=.0018 for 3.0Hz pulse frequency). Patt% across the 3.0, 4.0, 6.0 and 8.0mm I.D. ETTs was 48.88±10.25%, 40.87±5.22%, 27.97±5.29%, and 9.90±1.9% respectively. Selecting the 4.0Hz frequency mode demonstrated higher Pproximal and Pdistal compared to the 3.0Hz frequency mode (P=.0049 and P=.0065). Observed Pdistal was <30cmH2O for all experiments. In an in vitro model, pressure attenuation was linearly related to the inner diameter of the endotracheal tube; with decreasing attenuation as the ETT size increased. Copyright © 2016 Elsevier Inc. All rights reserved.

Reduction of a grid moiré pattern by integrating a carbon-interspaced high precision x-ray grid with a digital radiographic detector.

PubMed

Yoon, Jai-Woong; Park, Young-Guk; Park, Chun-Joo; Kim, Do-Il; Lee, Jin-Ho; Chung, Nag-Kun; Choe, Bo-Young; Suh, Tae-Suk; Lee, Hyoung-Koo

2007-11-01

The stationary grid commonly used with a digital x-ray detector causes a moiré interference pattern due to the inadequate sampling of the grid shadows by the detector pixels. There are limitations with the previous methods used to remove the moiré such as imperfect electromagnetic interference shielding and the loss of image information. A new method is proposed for removing the moiré pattern by integrating a carbon-interspaced high precision x-ray grid with high grid line uniformity with the detector for frequency matching. The grid was aligned to the detector by translating and rotating the x-ray grid with respect to the detector using microcontrolled alignment mechanism. The gap between the grid and the detector surface was adjusted with micrometer precision to precisely match the projected grid line pitch to the detector pixel pitch. Considering the magnification of the grid shadows on the detector plane, the grids were manufactured such that the grid line frequency was slightly higher than the detector sampling frequency. This study examined the factors that affect the moiré pattern, particularly the line frequency and displacement. The frequency of the moiré pattern was found to be sensitive to the angular displacement of the grid with respect to the detector while the horizontal translation alters the phase but not the moiré frequency. The frequency of the moiré pattern also decreased with decreasing difference in frequency between the grid and the detector, and a moiré-free image was produced after complete matching for a given source to detector distance. The image quality factors including the contrast, signal-to-noise ratio and uniformity in the images with and without the moiré pattern were investigated.

Parametric Effects of Word Frequency in Memory for Mixed Frequency Lists

ERIC Educational Resources Information Center

Lohnas, Lynn J.; Kahana, Michael J.

2013-01-01

The "word frequency paradox" refers to the finding that low frequency words are better recognized than high frequency words yet high frequency words are better recalled than low frequency words. Rather than comparing separate groups of low and high frequency words, we sought to quantify the functional relation between word frequency and…

Modelling of propagation and scintillation of a laser beam through atmospheric turbulence

NASA Astrophysics Data System (ADS)

Shugaev, Fedor V.; Shtemenko, Ludmila S.; Dokukina, Olga I.; Nikolaeva, Oxana A.; Suhareva, Natalia A.; Cherkasov, Dmitri Y.

2017-09-01

The investigation was fulfilled on the basis of the Navier-Stokes equations for viscous heat-conducting gas. The Helmholtz decomposition of the velocity field into a potential part and a solenoidal one was used. We considered initial vorticity to be small. So the results refer only to weak turbulence. The solution has been represented in the form of power series over the initial vorticity, the coefficients being multiple integrals. In such a manner the system of the Navier- Stokes equations was reduced to a parabolic system with constant coefficients at high derivatives. The first terms of the series are the main ones that determine the properties of acoustic radiation at small vorticity. We modelled turbulence with the aid of an ensemble of vortical structures (vortical rings). Two problems have been considered : (i) density oscillations (and therefore the oscillations of the refractive index) in the case of a single vortex ring; (ii) oscillations in the case of an ensemble of vortex rings (ten in number). We considered vortex rings with helicity, too. The calculations were fulfilled for a wide range of vortex sizes (radii from 0.1 mm to several cm). As shown, density oscillations arise. High-frequency oscillations are modulated by a low-frequency signal. The value of the high frequency remains constant during the whole process excluding its final stage. The amplitude of the low-frequency oscillations grows with time as compared to the high-frequency ones. The low frequency lies within the spectrum of atmospheric turbulent fluctuations, if the radius of the vortex ring is equal to several cm. The value of the high frequency oscillations corresponds satisfactorily to experimental data. The results of the calculations may be used for the modelling of the Gaussian beam propagation through turbulence (including beam distortion, scintillation, beam wandering). A method is set forth which describes the propagation of non-paraxial beams. The method admits generalization to the case of inhomogeneous medium.

Effects of processing parameters in the sonic assisted water extraction (SAWE) of 6-gingerol.

PubMed

Syed Jaapar, Syaripah Zaimah; Morad, Noor Azian; Iwai, Yoshio; Nordin, Mariam Firdhaus Mad

2017-09-01

The use of water in subcritical conditions for extraction has several drawbacks. These include the safety features, higher production costs and possible degradation of the bioactive compounds. To overcome these problems, sonic energy and an entrainer were used as external interventions to decrease the polarity of water at milder operating conditions. The effect of low (28kHz) and high (800kHz) frequencies of sonication in the extraction of the main ginger bioactive compound (6-gingerol) were compared. Six parameters were studied: mean particle size (MPS, mm), time of extraction, applied power, sample to solvent ratio (w/v), temperature of extraction, and the percentage of entrainer. The optimum conditions for high frequency SAWE prototype were MPS 0.89-1.77mm, 45min, 40W applied power, 1:30 (w/v), 45°C, and 15% of ethanol as entrainer. Two-way analysis of variance (ANOVA) gave the most significant parameter, which was power with F (1, 45.07), p<2.50×10 -9 . Although the effect of low frequency was stronger than high frequency, at the optimum conditions of the sample to solvent ratio 1:30 (w/v) with 700mL solvent and temperature 45°C, the concentration and recovery of 6-gingerol from high frequency of SAWE prototype was 2.69 times higher than at low frequency of SAWE. It was found that although the effects of high frequency (800kHz) were negligible in other studies, it could extract suitable compounds, such as 6-gingerol, at lower temperature. Therefore, the effects of sonication, which cause an enlargement in the cell wall of the ginger plant matrix, were observed using a Scanning Electron Microscope (SEM). It was found that the applied power of sonication was the most significant parameter compared to the other parameters. Copyright © 2017 Elsevier B.V. All rights reserved.

Spin polarization of {sup 87}Rb atoms with ultranarrow linewidth diode laser: Numerical simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Z. G.; Interdisciplinary Center of Quantum Information, National University of Defense Technology, Changsha, 410073; College of Science, National University of Defense Technology, Changsha, 410073

2016-08-15

In order to polarize {sup 87}Rb vapor effectively with ultranarrow linewidth diode laser, we studied the polarization as a function of some parameters including buffer gas pressure and laser power. Moreover, we also discussed the methods which split or modulate the diode laser frequency so as to pump the two ground hyperfine levels efficiently. We obtained some useful results through numerical simulation. If the buffer gas pressure is so high that the hyperfine structure is unresolved, the polarization is insensitive to laser frequency at peak absorption point so frequency splitting and frequency modulation methods do not show improvement. At lowmore » pressure and laser power large enough, where the hyperfine structure is clearly resolved, frequency splitting and frequency modulation methods can increase polarization effectively. For laser diodes, frequency modulation is easily realized with current modulation, so this method is attractive since it does not add any other components in the pumping laser system.« less

Factors affecting acceptability of an email-based intervention to increase fruit and vegetable consumption.

PubMed

Kothe, Emily J; Mullan, Barbara A

2014-09-30

Fresh Facts is a 30-day email-delivered intervention designed to increase the fruit and vegetable consumption of Australian young adults. This study investigated the extent to which the program was acceptable to members of the target audience and examined the relationships between participant and intervention characteristics, attrition, effectiveness, and acceptability ratings. Young adults were randomised to two levels of message frequency: high-frequency (n = 102), low-frequency (n = 173). Individuals in the high-frequency group received daily emails while individuals in the low-frequency group received an email every 3 days. Individuals in the high-frequency group were more likely to indicate that they received too many emails than individuals in the low-frequency group. No other differences in acceptability were observed. Baseline beliefs about fruit and vegetables were an important predictor of intervention acceptability. In turn, acceptability was associated with a number of indicators of intervention success, including change in fruit and vegetable consumption. The findings highlight the importance of considering the relationship between these intervention and participant factors and acceptability in intervention design and evaluation. Results support the ongoing use of email-based interventions to target fruit and vegetable consumption within young adults. However, the relationships between beliefs about fruit and vegetable consumption and acceptability suggest that this intervention may be differentially effective depending on individual's existing beliefs about fruit and vegetable consumption. As such, there is a pressing need to consider these factors in future research in order to minimize attrition and maximize intervention effectiveness when interventions are implemented outside of a research context.

Advanced ACTPol Low-Frequency Array: Readout and Characterization of Prototype 27 and 39 GHz Transition Edge Sensors

NASA Astrophysics Data System (ADS)

Koopman, B. J.; Cothard, N. F.; Choi, S. K.; Crowley, K. T.; Duff, S. M.; Henderson, S. W.; Ho, S. P.; Hubmayr, J.; Gallardo, P. A.; Nati, F.; Niemack, M. D.; Simon, S. M.; Staggs, S. T.; Stevens, J. R.; Vavagiakis, E. M.; Wollack, E. J.

2018-05-01

Advanced ACTPol (AdvACT) is a third-generation polarization upgrade to the Atacama Cosmology Telescope, designed to observe the cosmic microwave background (CMB). AdvACT expands on the 90 and 150 GHz transition edge sensor (TES) bolometer arrays of the ACT Polarimeter (ACTPol), adding both high-frequency (HF, 150/230 GHz) and low-frequency (LF, 27/39 GHz) multichroic arrays. The addition of the high- and low-frequency detectors allows for the characterization of synchrotron and spinning dust emission at the low frequencies and foreground emission from galactic dust and dusty star-forming galaxies at the high frequencies. The increased spectral coverage of AdvACT will enable a wide range of CMB science, such as improving constraints on dark energy, the sum of the neutrino masses, and the existence of primordial gravitational waves. The LF array will be the final AdvACT array, replacing one of the MF arrays for a single season. Prior to the fabrication of the final LF detector array, we designed and characterized prototype TES bolometers. Detector geometries in these prototypes are varied in order to inform and optimize the bolometer designs for the LF array, which requires significantly lower noise levels and saturation powers (as low as {˜ } 1 pW) than the higher-frequency detectors. Here we present results from tests of the first LF prototype TES detectors for AdvACT, including measurements of the saturation power, critical temperature, thermal conductance, and time constants. We also describe the modifications to the time-division SQUID readout architecture compared to the MF and HF arrays.

Efferent innervation to the auditory basilar papilla of scincid lizards.

PubMed

Wibowo, Erik; Brockhausen, Jennifer; Köppl, Christine

2009-09-01

Hair cells of the inner ear of vertebrates are innervated by afferent neurons that transmit sensory information to the brain as well as efferent neurons that receive feedback from the brainstem. The function of the efferent feedback system is poorly understood and may have changed during evolution when different tetrapod groups acquired sensitivity to airborne sound and extended their hearing ranges to higher frequencies. Lizards show a unique subdivision of their basilar papilla (homologous to the mammalian organ of Corti) into a low-frequency (<1 kHz) and a high-frequency (approximately 1-5 kHz) region. The high-frequency region was reported to have lost its efferent innervation, suggesting it was insignificant or even functionally detrimental at higher frequencies. We re-examined the innervation to the basilar papilla of five species of Australian scincid lizards, by using immunohistochemistry. Anti-choline acetyltransferase (ChAT) was used as an efferent marker. Co-localization with anti-synaptic vesicle protein 2 confirmed the synaptic identity of label. Cholinergic terminals were observed along the whole length of the basilar papilla, including the regions that had previously been described as devoid of efferent innervation. However, there was a clear decrease in terminal density from apical, low-frequency to basal, high-frequency locations. Our findings suggest that efferent innervation is a general feature of the hair cells in the basilar papilla of lizards, irrespective of tonotopic location. This re-enforces the notion that efferent feedback control of hair cells is a fundamental and important property of all vertebrate hearing organs. (c) 2009 Wiley-Liss, Inc.

Exposure safety standards for nonionizing radiation (NIR) from collision-avoidance radar

NASA Astrophysics Data System (ADS)

Palmer-Fortune, Joyce; Brecher, Aviva; Spencer, Paul; Huguenin, Richard; Woods, Ken

1997-02-01

On-vehicle technology for collision avoidance using millimeter wave radar is currently under development and is expected to be in vehicles in coming years. Recently approved radar bands for collision avoidance applications include 47.5 - 47.8 GHz and 76 - 77 GHz. Widespread use of active radiation sources in the public domain would contribute to raised levels of human exposure to high frequency electromagnetic radiation, with potential for adverse health effects. In order to design collision avoidance systems that will pose an acceptably low radiation hazard, it is necessary to determine what levels of electromagnetic radiation at millimeter wave frequencies will be acceptable in the environment. This paper will summarize recent research on NIR (non-ionizing radiation) exposure safety standards for high frequency electromagnetic radiation. We have investigated both governmental and non- governmental professional organizations worldwide.

A bootstrapped, low-noise, and high-gain photodetector for shot noise measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Haijun; Yang, Wenhai; Li, Zhixiu

2014-01-15

We presented a low-noise, high-gain photodetector based on the bootstrap structure and the L-C (inductance and capacitance) combination. Electronic characteristics of the photodetector, including electronic noise, gain and frequency response, and dynamic range, were verified through a single-frequency Nd:YVO{sub 4} laser at 1064 nm with coherent output. The measured shot noise of 50 μW laser was 13 dB above the electronic noise at the analysis frequency of 2 MHz, and 10 dB at 3 MHz. And a maximum clearance of 28 dB at 2 MHz was achieved when 1.52 mW laser was illuminated. In addition, the photodetector showed excellent linearitiesmore » for both DC and AC amplifications in the laser power range between 12.5 μW and 1.52 mW.« less

Note: A calibration method to determine the lumped-circuit parameters of a magnetic probe.

PubMed

Li, Fuming; Chen, Zhipeng; Zhu, Lizhi; Liu, Hai; Wang, Zhijiang; Zhuang, Ge

2016-06-01

This paper describes a novel method to determine the lumped-circuit parameters of a magnetic inductive probe for calibration by using Helmholtz coils with high frequency power supply (frequency range: 10 kHz-400 kHz). The whole calibration circuit system can be separated into two parts: "generator" circuit and "receiver" circuit. By implementing the Fourier transform, two analytical lumped-circuit models, with respect to these separated circuits, are constructed to obtain the transfer function between each other. Herein, the precise lumped-circuit parameters (including the resistance, inductance, and capacitance) of the magnetic probe can be determined by fitting the experimental data to the transfer function. Regarding the fitting results, the finite impedance of magnetic probe can be used to analyze the transmission of a high-frequency signal between magnetic probes, cables, and acquisition system.

Invariants of electromechanical coupling coefficients in piezoceramics.

PubMed

Mezheritsky, Alex V

2003-12-01

The relationships between coefficients of electromechanical coupling (CEMC) of various types of piezoceramic resonator (PR) vibrations are considered. Being constant for a given piezoceramic state, the range of variation of piezoceramics dielectric permittivity from a mechanically "free" condition at relatively low frequencies up to an "overall clamped" condition at high frequencies is determined by a consecutive "clamping", caused by a complex of CEMCs of various particular vibrational modes peculiar to the resonator. As the difference between "free" and "overall clamped" permittivities is always determined by the maximal piezomaterial ki3 coupling coefficient, the difference does not depend on the path that was gone through the low-high frequency range, which includes all the vibrational modes possible for a particular PR. The influence of the piezoelectric and elastic anisotropy of lead-zirconate-titanate (PZT) piezoceramic materials on relative CEMC variations was experimentally investigated.

Single molecule molecular inversion probes for targeted, high-accuracy detection of low-frequency variation.

PubMed

Hiatt, Joseph B; Pritchard, Colin C; Salipante, Stephen J; O'Roak, Brian J; Shendure, Jay

2013-05-01

The detection and quantification of genetic heterogeneity in populations of cells is fundamentally important to diverse fields, ranging from microbial evolution to human cancer genetics. However, despite the cost and throughput advances associated with massively parallel sequencing, it remains challenging to reliably detect mutations that are present at a low relative abundance in a given DNA sample. Here we describe smMIP, an assay that combines single molecule tagging with multiplex targeted capture to enable practical and highly sensitive detection of low-frequency or subclonal variation. To demonstrate the potential of the method, we simultaneously resequenced 33 clinically informative cancer genes in eight cell line and 45 clinical cancer samples. Single molecule tagging facilitated extremely accurate consensus calling, with an estimated per-base error rate of 8.4 × 10(-6) in cell lines and 2.6 × 10(-5) in clinical specimens. False-positive mutations in the single molecule consensus base-calls exhibited patterns predominantly consistent with DNA damage, including 8-oxo-guanine and spontaneous deamination of cytosine. Based on mixing experiments with cell line samples, sensitivity for mutations above 1% frequency was 83% with no false positives. At clinically informative sites, we identified seven low-frequency point mutations (0.2%-4.7%), including BRAF p.V600E (melanoma, 0.2% alternate allele frequency), KRAS p.G12V (lung, 0.6%), JAK2 p.V617F (melanoma, colon, two lung, 0.3%-1.4%), and NRAS p.Q61R (colon, 4.7%). We anticipate that smMIP will be broadly adoptable as a practical and effective method for accurately detecting low-frequency mutations in both research and clinical settings.

Single molecule molecular inversion probes for targeted, high-accuracy detection of low-frequency variation

PubMed Central

Hiatt, Joseph B.; Pritchard, Colin C.; Salipante, Stephen J.; O'Roak, Brian J.; Shendure, Jay

2013-01-01

The detection and quantification of genetic heterogeneity in populations of cells is fundamentally important to diverse fields, ranging from microbial evolution to human cancer genetics. However, despite the cost and throughput advances associated with massively parallel sequencing, it remains challenging to reliably detect mutations that are present at a low relative abundance in a given DNA sample. Here we describe smMIP, an assay that combines single molecule tagging with multiplex targeted capture to enable practical and highly sensitive detection of low-frequency or subclonal variation. To demonstrate the potential of the method, we simultaneously resequenced 33 clinically informative cancer genes in eight cell line and 45 clinical cancer samples. Single molecule tagging facilitated extremely accurate consensus calling, with an estimated per-base error rate of 8.4 × 10−6 in cell lines and 2.6 × 10−5 in clinical specimens. False-positive mutations in the single molecule consensus base-calls exhibited patterns predominantly consistent with DNA damage, including 8-oxo-guanine and spontaneous deamination of cytosine. Based on mixing experiments with cell line samples, sensitivity for mutations above 1% frequency was 83% with no false positives. At clinically informative sites, we identified seven low-frequency point mutations (0.2%–4.7%), including BRAF p.V600E (melanoma, 0.2% alternate allele frequency), KRAS p.G12V (lung, 0.6%), JAK2 p.V617F (melanoma, colon, two lung, 0.3%–1.4%), and NRAS p.Q61R (colon, 4.7%). We anticipate that smMIP will be broadly adoptable as a practical and effective method for accurately detecting low-frequency mutations in both research and clinical settings. PMID:23382536

Repetitive transcranial magnetic stimulation as an alternative therapy for dysphagia after stroke: a systematic review and meta-analysis.

PubMed

Liao, Xiang; Xing, Guoqiang; Guo, Zhiwei; Jin, Yu; Tang, Qing; He, Bin; McClure, Morgan A; Liu, Hua; Chen, Huaping; Mu, Qiwen

2017-03-01

A meta-analysis and systematic review was conducted to investigate the potential effects of repetitive transcranial magnetic stimulation on dysphagia in patients with stroke, including different parameters of frequency and stimulation site. PubMed, Embase, MEDLINE databases and the Cochrane Library, were searched for randomized controlled studies of repetitive transcranial magnetic stimulation treatment of dysphagia published before March 2016. Six clinical randomized controlled studies of a total of 163 stroke patients were included in this meta-analysis. A significant effect size of 1.24 was found for dysphagic outcome (mean effect size, 1.24; 95% confidence interval (CI), 0.67-1.81). A subgroup analysis based on frequency showed that the clinical scores were significantly improved in dysphagic patients with low frequency repetitive transcranial magnetic stimulation treatment ( P < 0.05) as well as high frequency repetitive transcranial magnetic stimulation treatment ( P < 0.05). A stimulation site stratified subgroup analysis implied significant changes in stroke patients with dysphagia for the unaffected hemisphere ( P < 0.05) and the bilateral hemisphere stimulation ( P < 0.05), but not for the affected hemisphere ( P > 0.05). The analysis of the follow-up data shows that patients in the repetitive transcranial magnetic stimulation groups still maintained the therapeutic benefit of repetitive transcranial magnetic stimulation four weeks after the last session of repetitive transcranial magnetic stimulation therapy ( P < 0.05). This meta-analysis indicates that repetitive transcranial magnetic stimulation has a positive effect on dysphagia after stroke. Compared with low-frequency repetitive transcranial magnetic stimulation, high-frequency repetitive transcranial magnetic stimulation may be more beneficial to the patients. This meta-analysis also supports that repetitive transcranial magnetic stimulation on an unaffected - or bilateral - hemisphere has a significant therapeutic effect on dysphagia.

How much is enough? Examining frequency criteria for NSSI disorder in adolescent inpatients.

PubMed

Muehlenkamp, Jennifer J; Brausch, Amy M; Washburn, Jason J

2017-06-01

To empirically evaluate the diagnostic relevance of the proposed Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5 ; APA, 2013) Criterion-A frequency threshold for nonsuicidal self-injury (NSSI) disorder. Archival, de-identified, self-reported clinical assessment data from 746 adolescent psychiatric patients (Mage = 14.97; 88% female; 76% White) were used. The sample was randomly split into 2 unique samples for data analyses. Measures included assessments of NSSI, proposed DSM-5 NSSI-disorder criteria, psychopathology, dysfunction, distress, functional impairment, and suicidality. Discriminant-function analyses run with Sample A identified a significant differentiation of groups based on a frequency of NSSI at 25 or more days in the past year, Λ = .814, χ2(54) = 72.59, p < .05, canonical R2 = .36. This cutoff was replicated in the second sample. All patients were coded into 1 of 3 empirically derived NSSI-frequency cutoff groups: high (>25 days), moderate (5-24 days), and low (1-4 days) and compared. The high-NSSI group scored higher on most NSSI features, including DSM-5 -proposed Criterion-B and -C symptoms, depression, psychotic symptoms, substance abuse, borderline personality-disorder features, suicidal ideation, and suicide plans, than the moderate- and low-NSSI groups, who did not differ from each other on many of the variables. The currently proposed DSM-5 Criterion-A frequency threshold for NSSI disorder lacks validity and clinical utility. The field needs to consider raising the frequency threshold to ensure that a meaningful and valid set of diagnostic criteria are established, and to avoid overpathologizing individuals who infrequently engage in NSSI. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Increased Anatomical Specificity of Neuromodulation via Modulated Focused Ultrasound

PubMed Central

Mehić, Edin; Xu, Julia M.; Caler, Connor J.; Coulson, Nathaniel K.; Moritz, Chet T.; Mourad, Pierre D.

2014-01-01

Transcranial ultrasound can alter brain function transiently and nondestructively, offering a new tool to study brain function now and inform future therapies. Previous research on neuromodulation implemented pulsed low-frequency (250–700 kHz) ultrasound with spatial peak temporal average intensities (ISPTA) of 0.1–10 W/cm2. That work used transducers that either insonified relatively large volumes of mouse brain (several mL) with relatively low-frequency ultrasound and produced bilateral motor responses, or relatively small volumes of brain (on the order of 0.06 mL) with relatively high-frequency ultrasound that produced unilateral motor responses. This study seeks to increase anatomical specificity to neuromodulation with modulated focused ultrasound (mFU). Here, ‘modulated’ means modifying a focused 2-MHz carrier signal dynamically with a 500-kHz signal as in vibro-acoustography, thereby creating a low-frequency but small volume (approximately 0.015 mL) source of neuromodulation. Application of transcranial mFU to lightly anesthetized mice produced various motor movements with high spatial selectivity (on the order of 1 mm) that scaled with the temporal average ultrasound intensity. Alone, mFU and focused ultrasound (FUS) each induced motor activity, including unilateral motions, though anatomical location and type of motion varied. Future work should include larger animal models to determine the relative efficacy of mFU versus FUS. Other studies should determine the biophysical processes through which they act. Also of interest is exploration of the potential research and clinical applications for targeted, transcranial neuromodulation created by modulated focused ultrasound, especially mFU’s ability to produce compact sources of ultrasound at the very low frequencies (10–100s of Hertz) that are commensurate with the natural frequencies of the brain. PMID:24504255

The Fe removal in pyrophyllite by physical method

NASA Astrophysics Data System (ADS)

Cho, Kanghee; Jo, Jiyu; Bak, GeonYeong; Choi, NagChoul; Park*, CheonYoung

2015-04-01

The presence of Fe in ingredient material such as limestone, borax and pyrophyllite can prevent their use mainly in the glass fiber manufacturing industry. The red to yellow pigmentation in pyrophyllite is mainly due to the associated oxides and sulfides of Fe such as hematite, pyrite, etc. The removal of Fe in the pyrophyllite was investigated using high frequency treatment and magnetic separation under various alumina grades in pyrophyllite. The hematite and pyrite were observed in the pyrophyllite from photomicrograph and XRD analysis results. On the decrease of Al2O3 content in pyrophyllite was showed that SiO2, Fe2O3 and TiO2 content were increased by XRF analysis. The high frequency treatment experiment for the pyrophyllite showed that the (1) pyrite phase was transformed hematite and magnetite, (2) mass loss of the sample by volatilization of included sulfur(S) in pyrite. The results of magnetic separation for treated sample by high frequency were identified that Fe removal percent were in the range of 97.6~98.8%. This study demonstrated that physical method (high frequency treatment and magnetic separation) was effective for the removal of Fe in pyrophyllite. This subject is supported by Korea Ministry of Environment(MOE) as "Advanced Technology Program for Environmental Industry".

Early cognitive and language skills are linked to resting frontal gamma power across the first 3 years.

PubMed

Benasich, April A; Gou, Zhenkun; Choudhury, Naseem; Harris, Kenneth D

2008-12-22

High-frequency cortical activity in humans and animals has been linked to a wide variety of higher cognitive processes. This research suggests that specific changes in neuronal synchrony occur during cognitive processing, distinguished by emergence of fast oscillations in the gamma frequency range. To determine whether the development of high-frequency brain oscillations can be related to the development of cognitive abilities, we studied the power spectra of resting EEG in children 16, 24 and 36 months of age. Individual differences in the distribution of frontal gamma power during rest were highly correlated with concurrent language and cognitive skills at all ages. Gamma power was also associated with attention measures; children who were observed as having better inhibitory control and more mature attention shifting abilities had higher gamma power density functions. We included a group of children with a family history of language impairment (FH+) and thus at higher risk for language disorders. FH+ children, as a group, showed consistently lower gamma over frontal regions than the well-matched FH- controls with no such family history (FH-). We suggest that the emergence of high-frequency neural synchrony may be critical for cognitive and linguistic development, and that children at risk for language impairments may lag in this process.

Study on rejection characteristic of current loop to the base disturbance of optical communication system

NASA Astrophysics Data System (ADS)

Mao, Yao; Deng, Chao; Liu, Qiong; Cao, Zheng

2016-10-01

As laser has narrow transmitting beam and small divergence angle, the LOS (Line of Sight) stabilization of optical communication system is a primary precondition of laser communication links. Compound axis control is usually adopted in LOS stabilization of optical communication system, in which coarse tracking and fine tracking are included. Rejection against high frequency disturbance mainly depends on fine tracking LOS stabilization platform. Limited by different factors such as mechanical characteristic of the stabilization platform and bandwidth/noise of the sensor, the control bandwidth of LOS stabilization platform is restricted so that effective rejection of high frequency disturbance cannot be achieved as it mainly depends on the isolation characteristic of the platform itself. It is proposed by this paper that current loop may reject the effect of back-EMF. By adopting the method of electric control, high frequency isolation characteristic of the platform can be improved. The improvement effect is similar to increasing passive vibration reduction devices. Adopting the double closed loop control structure of velocity and current with the combining of the rejection effect of back-EMF caused by current loop is equivalent to reducing back-EMF coefficient, which can enhance the isolation ability of the LOS stabilization platform to high frequency disturbance.

Cannabinoid Receptors Mediate Methamphetamine Induction of High Frequency Gamma Oscillations in the Nucleus Accumbens

PubMed Central

Morra, Joshua T.; Glick, Stanley D.; Cheer, Joseph F.

2012-01-01

Patients suffering from amphetamine---induced psychosis display repetitive behaviors, partially alleviated by antipsychotics, which are reminiscent of rodent stereotypies. Due to recent evidence implicating endocannabinoid involvement in brain disorders, including psychosis, we studied the effects of endocannabinoid signaling on neuronal oscillations of rats exhibiting methamphetamine stereotypy. Neuronal network oscillations were recorded with multiple single electrode arrays aimed at the nucleus accumbens of freely moving rats. During the experiments, animals were dosed intravenously with the CB1 receptor antagonist rimonabant (0.3 mg/kg) or vehicle followed by an ascending dose regimen of methamphetamine (0.01, 0.1, 1, and 3 mg/kg; cumulative dosing). The effects of drug administration on stereotypy and local gamma oscillations were evaluated. Methamphetamine treatment significantly increased high frequency gamma oscillations (~ 80 Hz). Entrainment of a subpopulation of nucleus accumbens neurons to high frequency gamma was associated with stereotypy encoding in putative fast-spiking interneurons, but not in putative medium spiny neurons. The observed ability of methamphetamine to induce both stereotypy and high frequency gamma power was potently disrupted following CB1 receptor blockade. The present data suggest that CB1 receptor-dependent mechanisms are recruited by methamphetamine to modify striatal interneuron oscillations that accompany changes in psychomotor state, further supporting the link between endocannabinoids and schizophrenia spectrum disorders. PMID:22609048

Evaluation of components, subsystems, and networks for high rate, high frequency space communications

NASA Technical Reports Server (NTRS)

Kerczewski, Robert J.; Ivancic, William D.; Zuzek, John E.

1991-01-01

The development of new space communications technologies by NASA has included both commercial applications and space science requirements. NASA's Systems Integration, Test and Evaluation (SITE) Space Communication System Simulator is a hardware based laboratory simulator for evaluating space communications technologies at the component, subsystem, system, and network level, geared toward high frequency, high data rate systems. The SITE facility is well-suited for evaluation of the new technologies required for the Space Exploration Initiative (SEI) and advanced commercial systems. Described here are the technology developments and evaluation requirements for current and planned commercial and space science programs. Also examined are the capabilities of SITE, the past, present and planned future configurations of the SITE facility, and applications of SITE to evaluation of SEI technology.

High frequency optical communications; Proceedings of the Meeting, Cambridge, MA, Sept. 23, 24, 1986

NASA Astrophysics Data System (ADS)

Ramer, O. Glenn; Sierak, Paul

Topics discussed in this volume include systems and applications, detectors, sources, and coherent communications. Papers are presented on RF fiber optic links for avionics applications, fiber optics and optoelectronics for radar and electronic warfare applications, symmetric coplanar electrodes for high-speed Ti:LiNbO3 devices, and surface wave electrooptic modulator. Attention is given to X-band RF fiber-optic links, fiber-optic links for microwave signal transmission, GaAs monolithic receiver and laser driver for GHz transmission rates, and monolithically integrable high-speed photodetectors. Additional papers are on irregular and chaotic behavior of semiconductor lasers under modulation, high-frequency laser package for microwave optical communications, receiver modeling for coherent light wave communications, and polarization sensors and controllers for coherent optical communication systems.

Associations Between Sleep Quality and Migraine Frequency

PubMed Central

Lin, Yu-Kai; Lin, Guan-Yu; Lee, Jiunn-Tay; Lee, Meei-Shyuan; Tsai, Chia-Kuang; Hsu, Yu-Wei; Lin, Yu-Zhen; Tsai, Yi-Chien; Yang, Fu-Chi

2016-01-01

Abstract Migraine has been associated with sleep disturbances. Relationship between sleep quality and migraine frequency is yet to be determined. The present study aimed to investigate sleep disturbances among low-frequency, moderate-frequency, high-frequency, and chronic migraineurs, with and without auras, with well-controlled confounding variables. This cross-sectional controlled study included 357 subjects from an outpatient headache clinic in Taiwan. Standardized questionnaires were utilized to collect demographic, migraine, sleep, depression, anxiety, and restless leg syndrome characteristics in all participants. According to frequency of migraine attacks, patients were divided into 4 groups: with 1 to 4 migraine days per month, 5 to 8 migraine days in a month, 9 to 14 migraine days in a month, and >14 migraine days per month. The Pittsburgh Sleep Quality Index (PSQI) and subgroup items were used to evaluate sleep quality. The association between migraine frequency and sleep quality was investigated using multivariable linear regression and logistic regression. The PSQI total score was highest in patients with high frequent migraine (10.0 ± 3.4) and lowest in controls (7.0 ± 3.4) with a significant trend analysis (P for trend = 0.006). Migraine frequency had an independent effect on the items “Cannot get to sleep within 30 minutes” (P < 0.001), “Wake up in the middle of the night or early morning” (P < 0.001), “Bad dreams” (P = 0.001), “Pain” (P = 0.004), and “Quality of sleep” (P < 0.001). The result showed the effect of migraine frequency in both the aura-present (P for trend = 0.008) and the aura-absent subgroups (P for trend = 0.011). High migraine frequency correlates with poor sleep quality and a higher prevalence of poor sleepers. These associations occur in migraine with aura and without aura. PMID:27124064

77 FR 49412 - Takes of Marine Mammals Incidental to Specified Activities; Navy Research, Development, Test and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-16

...; high-pitched sounds contain high frequencies and low-pitched sounds contain low frequencies. Natural... estimated to occur between approximately 150 Hz and 160 kHz. High-frequency cetaceans (eight species of true... masking by high frequency sound. Human data indicate low-frequency sound can mask high-frequency sounds (i...

Anatomy and physiology of a set of low-frequency vibratory interneurons in a nonhearing ensiferan (Troglophilus neglectus, rhaphidophoridae).

PubMed

Stritih, Natasa

2009-10-20

Vibratory interneurons were investigated in a primitive nonhearing ensiferan (orthopteran) species (Troglophilus neglectus, Rhaphidophoridae), using intracellular recording and staining technique. The study included 26 morphologically and/or physiologically distinct types of neurons from the prothoracic ganglion responding to vibration of the front legs. Most of these neurons are tuned to frequencies below 400 Hz. The morphology, anatomical position in the ganglion, and physiological responses are described in particular for a set of these low-frequency-tuned elements, including one local neuron, two T-shaped fibers, and five descending neurons, for which no putative homologues are known from the hearing Orthoptera. Their lowest thresholds are between about 0.01 and 0.4 m/second(2) at frequencies of 50-400 Hz, and the shortest latencies between 10 and 16 msec, suggesting that they are first- or second-order interneurons. Six interneurons have dendritic arborizations in the neuropile region that contains projections of tibial organ vibratory receptors, but their sensitivity suggests predominating inputs from vibrational sensilla of another origin. Responses of most neurons are composed of frequency-specific excitatory and inhibitory synaptic potentials, most of the latter being received in the high-frequency range. The function of these neurons in predator detection and intraspecific communication is discussed.

Kinetic scale structure of low-frequency waves and fluctuations

NASA Astrophysics Data System (ADS)

Lopez Herrera, R. A.; Figueroa-Vinas, A.; Araneda, J. A.; Yoon, P. H.

2017-12-01

The dissipation of solar wind turbulence at kinetic scales is believed to be important for heating the corona and accelerating the wind. Linear Vlasov kinetic theory is a useful tool in identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, ion-acoustic (or kinetic slow mode), and their possible roles in the dissipation. However, kinetic mode structure near the vicinity of ion cyclotron modes is not clearly understood. The present poster aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. The theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion Bernstein versus quasi modes. The spontaneous emission theory and simulation also confirm the findings of Vlasov theory in that the kinetic Alfvén wave can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave-particle interactions.

High force vibration testing with wide frequency range

DOEpatents

Romero, Edward F.; Jepsen, Richard A.; Gregory, Danny Lynn

2013-04-02

A shaker assembly for vibration testing includes first and second shakers, where the first shaker includes a piezo-electric material for generating vibration. A support structure permits a test object to be supported for vibration of the test object by both shakers. An input permits an external vibration controller to control vibration of the shakers.

Effect of More vs Less Frequent Follow-up Testing on Overall and Colorectal Cancer-Specific Mortality in Patients With Stage II or III Colorectal Cancer: The COLOFOL Randomized Clinical Trial.

PubMed

Wille-Jørgensen, Peer; Syk, Ingvar; Smedh, Kenneth; Laurberg, Søren; Nielsen, Dennis T; Petersen, Sune H; Renehan, Andrew G; Horváth-Puhó, Erzsébet; Påhlman, Lars; Sørensen, Henrik T

2018-05-22

Intensive follow-up of patients after curative surgery for colorectal cancer is common in clinical practice, but evidence of a survival benefit is limited. To examine overall mortality, colorectal cancer-specific mortality, and colorectal cancer-specific recurrence rates among patients with stage II or III colorectal cancer who were randomized after curative surgery to 2 alternative schedules for follow-up testing with computed tomography and carcinoembryonic antigen. Unblinded randomized trial including 2509 patients with stage II or III colorectal cancer treated at 24 centers in Sweden, Denmark, and Uruguay from January 2006 through December 2010 and followed up for 5 years; follow-up ended on December 31, 2015. Patients were randomized either to follow-up testing with computed tomography of the thorax and abdomen and serum carcinoembryonic antigen at 6, 12, 18, 24, and 36 months after surgery (high-frequency group; n = 1253 patients) or at 12 and 36 months after surgery (low-frequency group; n = 1256 patients). The primary outcomes were 5-year overall mortality and colorectal cancer-specific mortality rates. The secondary outcome was the colorectal cancer-specific recurrence rate. Both intention-to-treat and per-protocol analyses were performed. Among 2555 patients who were randomized, 2509 were included in the intention-to-treat analysis (mean age, 63.5 years; 1128 women [45%]) and 2365 (94.3%) completed the trial. The 5-year overall patient mortality rate in the high-frequency group was 13.0% (161/1253) compared with 14.1% (174/1256) in the low-frequency group (risk difference, 1.1% [95% CI, -1.6% to 3.8%]; P = .43). The 5-year colorectal cancer-specific mortality rate in the high-frequency group was 10.6% (128/1248) compared with 11.4% (137/1250) in the low-frequency group (risk difference, 0.8% [95% CI, -1.7% to 3.3%]; P = .52). The colorectal cancer-specific recurrence rate was 21.6% (265/1248) in the high-frequency group compared with 19.4% (238/1250) in the low-frequency group (risk difference, 2.2% [95% CI, -1.0% to 5.4%]; P = .15). Among patients with stage II or III colorectal cancer, follow-up testing with computed tomography and carcinoembryonic antigen more frequently compared with less frequently did not result in a significant rate reduction in 5-year overall mortality or colorectal cancer-specific mortality. clinicaltrials.gov Identifier: NCT00225641.

Analysis of high-frequency energy in long-term average spectra of singing, speech, and voiceless fricatives.

PubMed

Monson, Brian B; Lotto, Andrew J; Story, Brad H

2012-09-01

The human singing and speech spectrum includes energy above 5 kHz. To begin an in-depth exploration of this high-frequency energy (HFE), a database of anechoic high-fidelity recordings of singers and talkers was created and analyzed. Third-octave band analysis from the long-term average spectra showed that production level (soft vs normal vs loud), production mode (singing vs speech), and phoneme (for voiceless fricatives) all significantly affected HFE characteristics. Specifically, increased production level caused an increase in absolute HFE level, but a decrease in relative HFE level. Singing exhibited higher levels of HFE than speech in the soft and normal conditions, but not in the loud condition. Third-octave band levels distinguished phoneme class of voiceless fricatives. Female HFE levels were significantly greater than male levels only above 11 kHz. This information is pertinent to various areas of acoustics, including vocal tract modeling, voice synthesis, augmentative hearing technology (hearing aids and cochlear implants), and training/therapy for singing and speech.

Pressure effects on the dissipative behavior of nanocrystalline diamond microelectromechanical resonators

NASA Astrophysics Data System (ADS)

Santos, J. T.; Holz, T.; Fernandes, A. J. S.; Costa, F. M.; Chu, V.; Conde, J. P.

2015-02-01

Diamond-based microelectromechanical resonators have the potential of enhanced performance due to the chemical inertness of the diamond structural layer and its high Young’s modulus, high wear resistance, low thermal expansion coefficient, and very high thermal conductivity. In this work, the resonance frequency and quality factor of MEMS resonators based on nanocrystalline diamond films are characterized under different air pressures. The dynamic behavior of 50-300 μm long linear bridges and double ended tuning forks, with resonance frequencies between 0.5 and 15 MHz and quality factors as high as 50 000 are described as a function of measurement pressure from high vacuum(~10 mTorr) up to atmospheric conditions. The resonance frequencies and quality factors in vacuum show good agreement with the theoretical models including anchor and thermoelastic dissipation (TED). The Young’s moduli for nanocrystalline diamond films extrapolated from experimental data are between 840-920 GPa. The critical pressure values, at which the quality factor starts decreasing due to dissipation in air, are dependent on the resonator length. Longer structures, with quality factors limited by TED and lower resonance frequencies, have low critical pressures, of the order of 1-10 Torr and go from an intrinsic dissipation, to a molecular dissipation regime and finally to a region of viscous dissipation. Shorter resonators, with higher resonance frequencies and quality factors limited by anchor losses, have higher critical pressures, some higher than atmospheric pressure, and enter directly into the viscous dissipation regime from the intrinsic region.

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.

A novel high-frequency encoding algorithm for image compression

NASA Astrophysics Data System (ADS)

Siddeq, Mohammed M.; Rodrigues, Marcos A.

2017-12-01

In this paper, a new method for image compression is proposed whose quality is demonstrated through accurate 3D reconstruction from 2D images. The method is based on the discrete cosine transform (DCT) together with a high-frequency minimization encoding algorithm at compression stage and a new concurrent binary search algorithm at decompression stage. The proposed compression method consists of five main steps: (1) divide the image into blocks and apply DCT to each block; (2) apply a high-frequency minimization method to the AC-coefficients reducing each block by 2/3 resulting in a minimized array; (3) build a look up table of probability data to enable the recovery of the original high frequencies at decompression stage; (4) apply a delta or differential operator to the list of DC-components; and (5) apply arithmetic encoding to the outputs of steps (2) and (4). At decompression stage, the look up table and the concurrent binary search algorithm are used to reconstruct all high-frequency AC-coefficients while the DC-components are decoded by reversing the arithmetic coding. Finally, the inverse DCT recovers the original image. We tested the technique by compressing and decompressing 2D images including images with structured light patterns for 3D reconstruction. The technique is compared with JPEG and JPEG2000 through 2D and 3D RMSE. Results demonstrate that the proposed compression method is perceptually superior to JPEG with equivalent quality to JPEG2000. Concerning 3D surface reconstruction from images, it is demonstrated that the proposed method is superior to both JPEG and JPEG2000.

Numerical investigation of frequency spectrum in the Hasegawa-Wakatani model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Juhyung; Terry, P. W.

2013-10-15

The wavenumber-frequency spectrum of the two-dimensional Hasegawa-Wakatani model is investigated in the hydrodynamic, intermediate, and adiabatic regimes. A nonlinear frequency and a line width related to energy transfer properties provide a measure of the average frequency and spectral broadening, respectively. In the adiabatic regime, narrow spectra, typical of wave turbulence, are observed with a nonlinear frequency shift in the electron drift direction. In the hydrodynamic regime, broad spectra with almost zero nonlinear frequencies are observed. Nonlinear frequency shifts are shown to be related to nonlinear energy transfer by vorticity advection through the high frequency region of the spectrum. In themore » intermediate regime, the nonlinear frequency shift for density fluctuations is observed to be weaker than that of electrostatic potential fluctuations. The weaker frequency shift of the density fluctuations is due to nonlinear density advection, which favors energy transfer in the low frequency range. Both the nonlinear frequency and the spectral width increase with poloidal wavenumber k{sub y}. In addition, in the adiabatic regime where the nonlinear interactions manifest themselves in the nonlinear frequency shift, the cross-phase between the density and potential fluctuations is observed to match a linear relation, but only if the linear response of the linearly stable eigenmode branch is included. Implications of these numerical observations are discussed.« less

Spike Phase Locking in CA1 Pyramidal Neurons depends on Background Conductance and Firing Rate

PubMed Central

Broiche, Tilman; Malerba, Paola; Dorval, Alan D.; Borisyuk, Alla; Fernandez, Fernando R.; White, John A.

2012-01-01

Oscillatory activity in neuronal networks correlates with different behavioral states throughout the nervous system, and the frequency-response characteristics of individual neurons are believed to be critical for network oscillations. Recent in vivo studies suggest that neurons experience periods of high membrane conductance, and that action potentials are often driven by membrane-potential fluctuations in the living animal. To investigate the frequency-response characteristics of CA1 pyramidal neurons in the presence of high conductance and voltage fluctuations, we performed dynamic-clamp experiments in rat hippocampal brain slices. We drove neurons with noisy stimuli that included a sinusoidal component ranging, in different trials, from 0.1 to 500 Hz. In subsequent data analysis, we determined action potential phase-locking profiles with respect to background conductance, average firing rate, and frequency of the sinusoidal component. We found that background conductance and firing rate qualitatively change the phase-locking profiles of CA1 pyramidal neurons vs. frequency. In particular, higher average spiking rates promoted band-pass profiles, and the high-conductance state promoted phase-locking at frequencies well above what would be predicted from changes in the membrane time constant. Mechanistically, spike-rate adaptation and frequency resonance in the spike-generating mechanism are implicated in shaping the different phase-locking profiles. Our results demonstrate that CA1 pyramidal cells can actively change their synchronization properties in response to global changes in activity associated with different behavioral states. PMID:23055508

High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak.

PubMed

Truong, D D; Austin, M E

2014-11-01

The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. The frequency spacing of the radiometer's channels results in a spatial resolution of ∼1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels' IF bands and consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. Higher spatial resolution is achieved through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters' center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a "zoomed-in" analysis of a ∼2-4 cm radial region. Expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, are presented.

Circuit for monitoring temperature of high-voltage equipment

DOEpatents

Jacobs, Martin E.

1976-01-01

This invention relates to an improved circuit for measuring temperature in a region at high electric potential and generating a read-out of the same in a region at lower potential. The circuit is specially designed to combine high sensitivity, stability, and accuracy. A major portion of the circuit situated in the high-potential region can take the form of an integrated circuit. The preferred form of the circuit includes an input section which is situated in the high-potential region and comprises a temperature-compensated thermocouple circuit for sensing temperature, an oscillator circuit for generating a train of ramp voltages whose rise time varies inversely with the thermocouple output, a comparator and switching circuit for converting the oscillator output to pulses whose frequency is proportional to the thermocouple output, and a light-emitting diode which is energized by these pulses. An optical coupling transmits the light pulses generated by the diode to an output section of the circuit, situated in a region at ground. The output section comprises means for converting the transmitted pulses to electrical pulses of corresponding frequency, means for amplifying the electrical pulses, and means for displaying the frequency of the same. The preferred embodiment of the overall circuit is designed so that the frequency of the output signal in hertz and tenths of hertz is equal to the sensed temperature in degrees and tenths of degrees.

Prevalence and clinical implications of improper filter settings in routine electrocardiography.

PubMed

Kligfield, Paul; Okin, Peter M

2007-03-01

High- and low-filter bandwidth governs the fidelity of electrocardiographic waveforms, including the durations used in established criteria for infarction, the amplitudes used for the diagnosis of ventricular hypertrophy, and the accuracy of the magnitudes of ST-segment elevation and depression. Electrocardiographs allow users to reset high- and low-filter settings for special electrocardiographic applications, but these may be used inappropriately. To examine the prevalence of standard and nonstandard electrocardiographic filtering at 1 general medical community, 256 consecutive outpatient electrocardiograms (ECGs) submitted in advance of ambulatory or same-day admission surgery during a 3-week period were examined. ECGs were considered to meet standards for low-frequency cutoff when equal to 0.05 Hz and to meet standards for high-frequency cutoff when equal to 100 Hz, according to American Heart Association recommendations established in 1975. Only 25% of ECGs (65 of 256) conformed to recommended standards; 75% of ECGs (191 of 254) did not. The most prevalent deviation from standard was reduced high-frequency cutoff, which was present in 96% of tracings with nonstandard bandwidth (most commonly 40 Hz). Increased low-frequency cutoff was present in 62% of ECGs in which it was documented. In conclusion, improper electrocardiographic filtering, with potentially adverse clinical consequences, is highly prevalent at 1 large general medical community and is likely a generalized problem. This problem should be resolvable by targeted educational efforts to reinforce technical standards in electrocardiography.

Keep Your Scanners Peeled: Gaze Behavior as a Measure of Automation Trust During Highly Automated Driving.

PubMed

Hergeth, Sebastian; Lorenz, Lutz; Vilimek, Roman; Krems, Josef F

2016-05-01

The feasibility of measuring drivers' automation trust via gaze behavior during highly automated driving was assessed with eye tracking and validated with self-reported automation trust in a driving simulator study. Earlier research from other domains indicates that drivers' automation trust might be inferred from gaze behavior, such as monitoring frequency. The gaze behavior and self-reported automation trust of 35 participants attending to a visually demanding non-driving-related task (NDRT) during highly automated driving was evaluated. The relationship between dispositional, situational, and learned automation trust with gaze behavior was compared. Overall, there was a consistent relationship between drivers' automation trust and gaze behavior. Participants reporting higher automation trust tended to monitor the automation less frequently. Further analyses revealed that higher automation trust was associated with lower monitoring frequency of the automation during NDRTs, and an increase in trust over the experimental session was connected with a decrease in monitoring frequency. We suggest that (a) the current results indicate a negative relationship between drivers' self-reported automation trust and monitoring frequency, (b) gaze behavior provides a more direct measure of automation trust than other behavioral measures, and (c) with further refinement, drivers' automation trust during highly automated driving might be inferred from gaze behavior. Potential applications of this research include the estimation of drivers' automation trust and reliance during highly automated driving. © 2016, Human Factors and Ergonomics Society.

Circuit Training.

ERIC Educational Resources Information Center

Nelson, Jane B.

1998-01-01

Describes a research-based activity for high school physics students in which they build an LC circuit and find its resonant frequency of oscillation using an oscilloscope. Includes a diagram of the apparatus and an explanation of the procedures. (DDR)

Vibro-acoustography: Recent advances and future promises

NASA Astrophysics Data System (ADS)

Fatemi, Mostafa; Alizad, Azra; Greenleaf, James F.

2005-09-01

Vibro-acoustography is an imaging modality that uses ultrasound as the source of energy to explore objects at two ends of the spectrum. Employing two ultrasound beams at slightly different frequencies, this technique produces a highly localized radiation stress field that vibrates the object at the difference frequency. In response, the object produces a secondary acoustic field. This sound, which contains information about the dynamics of the object at the low difference frequency as well as objects characteristics at the ultrasound range, is used to produce an image of the object. This combination makes vibro-acoustography a unique tool to study biological tissues at low and high frequencies simultaneously. Utility of this method has already been demonstrated for a wide range of applications in vitro. In vivo applications of vibro-acoustography have been demonstrated in a recent study on human breast. It has been shown that this technique can produce high quality in vivo images at ultrasound intensities within the recommended FDA limits. Vibro-acoustography may also be used for imaging solids, such as metallic implants. This paper describes recent achievements in vibro-acoustography as well as possible future role of this technology in medicine. [This abstract includes materials patented by MF and JFG.

A low-frequency MEMS piezoelectric energy harvester with a rectangular hole based on bulk PZT film

NASA Astrophysics Data System (ADS)

Tian, Yingwei; Li, Guimiao; Yi, Zhiran; Liu, Jingquan; Yang, Bin

2018-06-01

This paper presents a high performance piezoelectric energy harvester (PEH) with a rectangular hole to work at low-frequency. This PEH used thinned bulk PZT film on flexible phosphor bronze, and its structure included piezoelectric layer, supporting layer and proof mass to reduce the resonant frequency of the device. Here, thinned bulk PZT thick film was used as piezoelectric layer due to its high piezoelectric coefficient. A Phosphor bronze was deployed as supporting layer because it had better flexibility compared to silicon and could work under high acceleration ambient with good durability. The maximum open-circuit voltage of the PEH was 15.7 V at low resonant frequency of 34.3 Hz when the input vibration acceleration was 1.5 g (g = 9.81 m/s2). Moreover, the maximum output power, the output power density and the actually current at the same acceleration were 216.66 μW, 1713.58 μW/cm3 and 170 μA, respectively, when the optimal matched resistance of 60 kΩ was connected. The fabricated PEH scavenged the vibration energy of the vacuum compression pump and generated the maximum output voltage of 1.19 V.

EFFECTIVE INDICES FOR MONITORING MENTAL WORKLOAD WHILE PERFORMING MULTIPLE TASKS.

PubMed

Hsu, Bin-Wei; Wang, Mao-Jiun J; Chen, Chi-Yuan; Chen, Fang

2015-08-01

This study identified several physiological indices that can accurately monitor mental workload while participants performed multiple tasks with the strategy of maintaining stable performance and maximizing accuracy. Thirty male participants completed three 10-min. simulated multitasks: MATB (Multi-Attribute Task Battery) with three workload levels. Twenty-five commonly used mental workload measures were collected, including heart rate, 12 HRV (heart rate variability), 10 EEG (electroencephalography) indices (α, β, θ, α/θ, θ/β from O1-O2 and F4-C4), and two subjective measures. Analyses of index sensitivity showed that two EEG indices, θ and α/θ (F4-C4), one time-domain HRV-SDNN (standard deviation of inter-beat intervals), and four frequency-domain HRV: VLF (very low frequency), LF (low frequency), %HF (percentage of high frequency), and LF/HF were sensitive to differentiate high workload. EEG α/θ (F4-C4) and LF/HF were most effective for monitoring high mental workload. LF/HF showed the highest correlations with other physiological indices. EEG α/θ (F4-C4) showed strong correlations with subjective measures across different mental workload levels. Operation strategy would affect the sensitivity of EEG α (F4-C4) and HF.

A sophisticated, multi-channel data acquisition and processing system for high frequency noise research

NASA Technical Reports Server (NTRS)

Hall, David G.; Bridges, James

1992-01-01

A sophisticated, multi-channel computerized data acquisition and processing system was developed at the NASA LeRC for use in noise experiments. This technology, which is available for transfer to industry, provides a convenient, cost-effective alternative to analog tape recording for high frequency acoustic measurements. This system provides 32-channel acquisition of microphone signals with an analysis bandwidth up to 100 kHz per channel. Cost was minimized through the use of off-the-shelf components. Requirements to allow for future expansion were met by choosing equipment which adheres to established industry standards for hardware and software. Data processing capabilities include narrow band and 1/3 octave spectral analysis, compensation for microphone frequency response/directivity, and correction of acoustic data to standard day conditions. The system was used successfully in a major wind tunnel test program at NASA LeRC to acquire and analyze jet noise data in support of the High Speed Civil Transport (HSCT) program.

What Are the Primary Limitations in B-Cell Affinity Maturation, and How Much Affinity Maturation Can We Drive with Vaccination?

PubMed Central

2017-01-01

A key goal of HIV-1 vaccine development is the induction of broadly neutralizing antibodies (bnAbs) targeted to the vulnerable regions of the HIV envelope. BnAbs develop overtime in ∼50%of HIV-1-infected individuals. However, to date, no vaccines have induced bnAbs and few or none of these vaccine-elicited HIV-1 antibodies carry the high frequencies of V(D)J mutations characteristic of bnAbs. Do the high frequencies of mutations characteristic of naturally induced bnAbs represent a fundamental barrier to the induction of bnAbs by vaccines? Recent studies suggest that high frequencies of V(D)J mutations can be achieved by serial vaccination strategies. Rather, it appears that, in the absence of HIV-1 infection, physiologic immune tolerance controls, including a germinal center process termed affinity reversion, may limit vaccine-driven bnAb development by clonal elimination or selecting for mutations incompatible with bnAb activity. PMID:28630077

Thin-film piezoelectric-on-silicon resonators for high-frequency reference oscillator applications.

PubMed

Abdolvand, Reza; Lavasani, Hossein M; Ho, Gavin K; Ayazi, Farrokh

2008-12-01

This paper studies the application of lateral bulk acoustic thin-film piezoelectric-on-substrate (TPoS) resonators in high-frequency reference oscillators. Low-motional-impedance TPoS resonators are designed and fabricated in 2 classes--high-order and coupled-array. Devices of each class are used to assemble reference oscillators and the performance characteristics of the oscillators are measured and discussed. Since the motional impedance of these devices is small, the transimpedance amplifier (TIA) in the oscillator loop can be reduced to a single transistor and 3 resistors, a format that is very power-efficient. The lowest reported power consumption is approximately 350 microW for an oscillator operating at approximately 106 MHz. A passive temperature compensation method is also utilized by including the buried oxide layer of the silicon-on-insulator (SOI) substrate in the structural resonant body of the device, and a very small (-2.4 ppm/ degrees C) temperature coefficient of frequency is obtained for an 82-MHz oscillator.

Analysis of the cochlear microphonic to a low-frequency tone embedded in filtered noise

PubMed Central

Chertoff, Mark E.; Earl, Brian R.; Diaz, Francisco J.; Sorensen, Janna L.

2012-01-01

The cochlear microphonic was recorded in response to a 733 Hz tone embedded in noise that was high-pass filtered at 25 different frequencies. The amplitude of the cochlear microphonic increased as the high-pass cutoff frequency of the noise increased. The amplitude growth for a 60 dB SPL tone was steeper and saturated sooner than that of an 80 dB SPL tone. The growth for both signal levels, however, was not entirely cumulative with plateaus occurring at about 4 and 7 mm from the apex. A phenomenological model of the electrical potential in the cochlea that included a hair cell probability function and spiral geometry of the cochlea could account for both the slope of the growth functions and the plateau regions. This suggests that with high-pass-filtered noise, the cochlear microphonic recorded at the round window comes from the electric field generated at the source directed towards the electrode and not down the longitudinal axis of the cochlea. PMID:23145616

Active Control of Separation From the Flap of a Supercritical Airfoil

NASA Technical Reports Server (NTRS)

Melton, LaTunia Pack; Yao, Chung-Sheng; Seifert, Avi

2006-01-01

Zero-mass-flux periodic excitation was applied at several regions on a simplified high-lift system to delay the occurrence of flow separation. The NASA Energy Efficient Transport (EET) supercritical airfoil was equipped with a 15% chord simply hinged leading edge flap and a 25% chord simply hinged trailing edge flap. Detailed flow features were measured in an attempt to identify optimal actuator placement. The measurements included steady and unsteady model and tunnel wall pressures, wake surveys, arrays of surface hot-films, flow visualization, and particle image velocimetry (PIV). The current paper describes the application of active separation control at several locations on the deflected trailing edge flap. High frequency (F(+) approximately equal to 10) and low frequency amplitude modulation (F(+) sub AM approximately equal to 1) of the high frequency excitation were used for control. It was noted that the same performance gains were obtained with amplitude modulation and required only 30% of the momentum input required by pure sine excitation.

Active Control of Separation From the Flap of a Supercritical Airfoil

NASA Technical Reports Server (NTRS)

Melton, La Tunia Pack; Yao, Chung-Sheng; Seifert, Avi

2003-01-01

Active flow control in the form of periodic zero-mass-flux excitation was applied at several regions on the leading edge and trailing edge flaps of a simplified high-lift system t o delay flow separation. The NASA Energy Efficient Transport (EET) supercritical airfoil was equipped with a 15% chord simply hinged leading edge flap and a 25% chord simply hinged trailing edge flap. Detailed flow features were measured in an attempt to identify optimal actuator placement. The measurements included steady and unsteady model and tunnel wall pressures, wake surveys, arrays of surface hot-films, flow visualization, and particle image velocimetry (PIV). The current paper describes the application of active separation control at several locations on the deflected trailing edge flap. High frequency (F(+) approx.= 10) and low frequency amplitude modulation (F(+)AM approx.= 1) of the high frequency excitation were used for control. Preliminary efforts to combine leading and trailing edge flap excitations are also reported.

Hotspots in research on the measurement of medical students' clinical competence from 2012-2016 based on co-word analysis.

PubMed

Chang, Xing; Zhou, Xin; Luo, Linzhi; Yang, Chengjia; Pan, Hui; Zhang, Shuyang

2017-09-12

This study aimed to identify hotspots in research on clinical competence measurements from 2012 to 2016. The authors retrieved literature published between 2012 and 2016 from PubMed using selected medical subject headings (MeSH) terms. They used BibExcel software to generate high-frequency MeSH terms and identified hotspots by co-word analysis and cluster analysis. The authors searched 588 related articles and identified 31 high-frequency MeSH terms. In addition, they obtained 6 groups of high-frequency MeSH terms that reflected the domain hotspots. This study identified 6 hotspots of domain research, including studies on influencing factors and perception evaluation, improving and developing measurement tools, feedback measurement, measurement approaches based on computer simulation, the measurement of specific students in different learning phases, and the measurement of students' communication ability. All of these research topics could provide useful information for educators and researchers to continually conduct in-depth studies.

[A co-word analysis of current research on neonatal jaundice].

PubMed

Bao, Shan; Yang, Xiao-Yan; Tang, Jun; Wu, Jin-Lin; Mu, De-Zhi

2014-08-01

To investigate the research on neonatal jaundice in recent years by co-word analysis and to summarize the hot spots and trend of research in this field in China. The CNKI was searched with "neonate" and "jaundice" as the key words to identify the papers published from January 2009 to July 2013 that were in accordance with strict inclusion and exclusion criteria. To reveal the relationship between different high-frequency key words, Microsoft Office Excel 2013 was used for statistical analysis of key words, and Ucinet 6.0 and Netdraw were used for co-occurrence analysis. A total of 2 054 papers were included, and 44 high-frequency key words were extracted. The current hotspots of research on neonatal jaundice in China were displayed, and the relationship between different high-frequency key words was presented. There has been in-depth research on clinical manifestations and diagnosis of neonatal jaundice in China, but further research is needed to investigate the etiology, mechanism, and treatment of neonatal jaundice.

Mitigating artifacts in back-projection source imaging with implications for frequency-dependent properties of the Tohoku-Oki earthquake

NASA Astrophysics Data System (ADS)

Meng, Lingsen; Ampuero, Jean-Paul; Luo, Yingdi; Wu, Wenbo; Ni, Sidao

2012-12-01

Comparing teleseismic array back-projection source images of the 2011 Tohoku-Oki earthquake with results from static and kinematic finite source inversions has revealed little overlap between the regions of high- and low-frequency slip. Motivated by this interesting observation, back-projection studies extended to intermediate frequencies, down to about 0.1 Hz, have suggested that a progressive transition of rupture properties as a function of frequency is observable. Here, by adapting the concept of array response function to non-stationary signals, we demonstrate that the "swimming artifact", a systematic drift resulting from signal non-stationarity, induces significant bias on beamforming back-projection at low frequencies. We introduce a "reference window strategy" into the multitaper-MUSIC back-projection technique and significantly mitigate the "swimming artifact" at high frequencies (1 s to 4 s). At lower frequencies, this modification yields notable, but significantly smaller, artifacts than time-domain stacking. We perform extensive synthetic tests that include a 3D regional velocity model for Japan. We analyze the recordings of the Tohoku-Oki earthquake at the USArray and at the European array at periods from 1 s to 16 s. The migration of the source location as a function of period, regardless of the back-projection methods, has characteristics that are consistent with the expected effect of the "swimming artifact". In particular, the apparent up-dip migration as a function of frequency obtained with the USArray can be explained by the "swimming artifact". This indicates that the most substantial frequency-dependence of the Tohoku-Oki earthquake source occurs at periods longer than 16 s. Thus, low-frequency back-projection needs to be further tested and validated in order to contribute to the characterization of frequency-dependent rupture properties.

Multiple Logistic Regression Analysis of Cigarette Use among High School Students

ERIC Educational Resources Information Center

Adwere-Boamah, Joseph

2011-01-01

A binary logistic regression analysis was performed to predict high school students' cigarette smoking behavior from selected predictors from 2009 CDC Youth Risk Behavior Surveillance Survey. The specific target student behavior of interest was frequent cigarette use. Five predictor variables included in the model were: a) race, b) frequency of…

A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters

PubMed Central

Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

2015-01-01

We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies. PMID:26552584

A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters.

PubMed

Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

2015-11-10

We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies.

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.

Trirotron: triode rotating beam radio frequency amplifier

DOEpatents

Lebacqz, Jean V.

1980-01-01

High efficiency amplification of radio frequencies to very high power levels including: establishing a cylindrical cloud of electrons; establishing an electrical field surrounding and coaxial with the electron cloud to bias the electrons to remain in the cloud; establishing a rotating electrical field that surrounds and is coaxial with the steady field, the circular path of the rotating field being one wavelength long, whereby the peak of one phase of the rotating field is used to accelerate electrons in a beam through the bias field in synchronism with the peak of the rotating field so that there is a beam of electrons continuously extracted from the cloud and rotating with the peak; establishing a steady electrical field that surrounds and is coaxial with the rotating field for high-energy radial acceleration of the rotating beam of electrons; and resonating the rotating beam of electrons within a space surrounding the second field, the space being selected to have a phase velocity equal to that of the rotating field to thereby produce a high-power output at the frequency of the rotating field.

Electron cyclotron resonance sources: Historical review and future prospects (invited)

NASA Astrophysics Data System (ADS)

Geller, R.

1998-03-01

Low charge state electron cyclotron resonance ion source (ECRIS) work since 1965 and high charge state ECRIS since 1974. These ECR sources are categorized into three main sections: (1) Low charged ion (ECRIS) inside simple magnetic mirror or Bucket configurations. (2) High charged ion ECRIS inside min-B mirror configurations. (3) Short pulsed ECRIS with highly charged ions where the ion confinement is disturbed for a short while, which allows the extraction of intense ion pulses. Future prospects are based on rational scaling of the magnetic confinement including high B modes, by increasing the radio frequency (rf) frequency and ECR magnetic field. In this case, charge exchange has to be minimized and plasma instabilities have to be avoided. However, clever empirical tricks lead also to outstanding not always predicted improvements. Let us cite: optimized rf plasma coupling, electron guns, gas mixing, wall coating, biased electrodes, and more recently multiple ECR frequency heating. ECRIS have not yet achieved their optimal possibilities. Let us wait for the next generation of superconducting ECRIS and the possible use of subcentimeter waves.

Electron cyclotron resonance sources: Historical review and future prospects (invited)

NASA Astrophysics Data System (ADS)

Geller, R.

1998-02-01

Low charge state electron cyclotron resonance ion source (ECRIS) work since 1965 and high charge state ECRIS since 1974. These ECR sources are categorized into three main sections: (1) Low charged ion (ECRIS) inside simple magnetic mirror or Bucket configurations. (2) High charged ion ECRIS inside min-B mirror configurations. (3) Short pulsed ECRIS with highly charged ions where the ion confinement is disturbed for a short while, which allows the extraction of intense ion pulses. Future prospects are based on rational scaling of the magnetic confinement including high B modes, by increasing the radio frequency (rf) frequency and ECR magnetic field. In this case, charge exchange has to be minimized and plasma instabilities have to be avoided. However, clever empirical tricks lead also to outstanding not always predicted improvements. Let us cite: optimized rf plasma coupling, electron guns, gas mixing, wall coating, biased electrodes, and more recently multiple ECR frequency heating. ECRIS have not yet achieved their optimal possibilities. Let us wait for the next generation of superconducting ECRIS and the possible use of subcentimeter waves.

Thermal-distortion analysis of an antenna strongback for geostationary high-frequency microwave applications

NASA Technical Reports Server (NTRS)

Farmer, Jeffrey T.; Wahls, Deborah M.; Wright, Robert L.

1990-01-01

The global change technology initiative calls for a geostationary platform for Earth science monitoring. One of the major science instruments is the high frequency microwave sounder (HFMS) which uses a large diameter, high resolution, high frequency microwave antenna. This antenna's size and required accuracy dictates the need for a segmented reflector. On-orbit disturbances may be a significant factor in its design. A study was performed to examine the effects of the geosynchronous thermal environment on the performance of the strongback structure for a proposed antenna concept for this application. The study included definition of the strongback and a corresponding numerical model to be used in the thermal and structural analyses definition of the thermal environment, determination of structural element temperature throughout potential orbits, estimation of resulting thermal distortions, and assessment of the structure's capability to meet surface accuracy requirements. Analyses show that shadows produced by the antenna reflector surface play a major role in increasing thermal distortions. Through customization of surface coating and element expansion characteristics, the segmented reflector concept can meet the tight surface accuracy requirements.

Recent Advances in Narrowband Stimulated Electromagnetic Emission NSEE Investigations at HAARP and EISCAT

NASA Astrophysics Data System (ADS)

Scales, Wayne

2016-07-01

Investigation of stimulated radiation, commonly known as Stimulated Electromagnetic Emissions (SEE), produced by the interaction of high-power, High Frequency HF radiowaves with the ionospheric plasma has been a vibrant area of research since the early 1980's. Substantial diagnostic information about ionospheric plasma characteristics, dynamics, and turbulence can be obtained from the frequency spectrum of the stimulated radiation. During the past several decades, so-called wideband SEE (WSEE) which exists in a frequency band of ±100 KHz or so of the transmit wave frequency (which is several MHz) has been investigated relatively thoroughly. Upgrades both in transmitter power and diagnostic receiver frequency sensitivity at major ionosphere interaction facilities (i.e. HAARP and EISCAT) have allowed new breakthroughs in the ability to study a plethora of processes associated with the ionospheric plasma during these active experiments. A primary advance is in observations of so-called narrowband SEE (NSEE) which exists roughly within ±1 kHz of the transmit wave frequency. NSEE investigation has opened the door for a potentially powerful tool for aeronomy investigations as well. An overview of several important new results associated with NSEE are discussed in this presentation, including observations, theory, computational modeling, as well as implications to new diagnostics of space plasma physics occurring during ionospheric interaction experiments.

Cochlear partition tuning within the 2nd apical turn of the intact gerbil cochlea

NASA Astrophysics Data System (ADS)

Dong, Wei; Xia, Anping; Puria, Sunil; Applegate, Brian E.; Oghalai, John S.

2018-05-01

Our understanding of cochlear amplification has been mainly informed by observations of the high-frequency basal region. Results from the few existing in vivo studies from the low-frequency apical region have suggested that cochlear amplification may be more broadly tuned and not as nonlinear as in the base. The current study explored micromechanics via sound evoked vibrations of the cochlear partition, including the organ of Corti (OoC), the basilar membrane (BM) and the tectorial membrane (TM), within the 2nd apical turn, corresponding to the 2.5 kHz best frequency region, of the gerbil cochlea using volumetric optical coherence tomography vibrometry (VOCTV), imaged non-invasively through the otic capsule bone in vivo. Sound induced radial displacements below 4 kHz showed similarities and differences to the well-established BM transverse responses at high-frequency basal region. Responses showed broader tuning, but similar gains at the best frequency and similar phase accumulation. The distinct difference found was the presence of compressive nonlinear growth with SPL below the best frequency down to 0.1 kHz observed at the outer hair cell (OHC) and reticular laminar (RL) locations but not in the BM or inner hair cell regions. These relative motions provide further insight on how OHC somatic forces are distributed within the cochlear partition.

Reference-free, high-resolution measurement method of timing jitter spectra of optical frequency combs

PubMed Central

Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon

2017-01-01

Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10−9 fs2/Hz (equivalent to −174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources. PMID:28102352

Eating breakfast and dinner together as a family: Associations with sociodemographic characteristics and implications for diet quality and weight status

PubMed Central

Larson, Nicole; MacLehose, Rich; Fulkerson, Jayne A.; Berge, Jerica M.; Story, Mary; Neumark-Sztainer, Dianne

2013-01-01

Background Research has shown that adolescents who frequently share evening meals with their families experience more positive health outcomes, including diets of higher nutritional quality. However, little is known about families eating together at breakfast. Objectives This study examined sociodemographic differences in family meal frequencies in a population-based adolescent sample. Additionally, this study examined associations of family breakfast meal frequency with dietary quality and weight status. Design Cross-sectional data from EAT 2010 (Eating and Activity in Teens) included anthropometric assessments and classroom-administered surveys completed in 2009-2010. Participants/setting Participants included 2,793 middle and high school students (53.2% girls, mean age=14.4 years) from Minneapolis/St. Paul, MN, public schools. Main outcome measures Usual dietary intake was self-reported on a food frequency questionnaire. Height and weight were measured. Statistical analyses performed Regression models adjusted for sociodemographic characteristics, family dinner frequency, family functioning, and family cohesion were used to examine associations of family breakfast frequency with dietary quality and weight status. Results On average, adolescents reported having family breakfast meals 1.5 times (SD=2.1) and family dinner meals 4.1 times (SD=2.6) in the past week. There were racial/ethnic differences in family breakfast frequency, with the highest frequencies reported by adolescents of Black, Hispanic, Native American, and mixed race/ethnicity. Family breakfast frequency was also positively associated with male sex; younger age; and living in a two-parent household. Family breakfast frequency was associated with several markers of better diet quality (such as higher intake of fruit, whole grains, and fiber) and lower risk for overweight/obesity. For example, adolescents who reported seven family breakfasts in the past week consumed an average of 0.37 additional daily fruit servings compared to adolescents who never had a family breakfast meal. Conclusions Results suggest that eating breakfast together as a family may have benefits for adolescents’ dietary intake and weight status. PMID:24139290

High-Performance Solid-State W-Band Power Amplifiers

NASA Technical Reports Server (NTRS)

Gaier, Todd; Samoska, Lorene; Wells, Mary; Ferber, Robert; Pearson, John; Campbell, April; Peralta, Alejandro; Swift, Gerald; Yocum, Paul; Chung, Yun

2003-01-01

The figure shows one of four solid-state power amplifiers, each capable of generating an output power greater than or equal to 240 mW over one of four overlapping frequency bands from 71 to 106 GHz. (The bands are 71 to 84, 80 to 92, 88 to 99, and 89 to 106 GHz.) The amplifiers are designed for optimum performance at a temperature of 130 K. These amplifiers were developed specifically for incorporation into frequency-multiplier chains in local oscillators in a low-noise, far-infrared receiving instrument to be launched into outer space to make astrophysical observations. The designs of these amplifiers may also be of interest to designers and manufacturers of terrestrial W-band communication and radar systems. Each amplifier includes a set of six high-electron-mobility transistor (HEMT) GaAs monolithic microwave integrated-circuit (MMIC) chips, microstrip cavities, and other components packaged in a housing made from A-40 silicon-aluminum alloy. This alloy was chosen because, for the original intended spacecraft application, it offers an acceptable compromise among the partially competing requirements for high thermal conductivity, low mass, and low thermal expansion. Problems that were solved in designing the amplifiers included designing connectors and packages to fit the available space; designing microstrip signal-power splitters and combiners; matching of impedances across the frequency bands; matching of the electrical characteristics of those chips installed in parallel power-combining arms; control and levelling of output power across the bands; and designing the MMICs, microstrips, and microstrip cavities to suppress tendencies toward oscillation in several modes, both inside and outside the desired frequency bands.

PCR/oligonucleotide probe typing of HLA class II alleles in a Filipino population reveals an unusual distribution of HLA haplotypes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bugawan, T.L.; Chang, J.D.; Erlich, H.A.

1994-02-01

The authors have analyzed the distribution of HLA class II alleles and haplotypes in a Filipino population by PCR amplification of the DRB1, DQB1, and DPB1 second-exon sequences from buccal swabs obtained from 124 family members and 53 unrelated individuals. The amplified DNA was typed by using nonradioactive sequence-specific oligonucleotide probes. Twenty-two different DRB1 alleles, including the novel Filipino *1105, and 46 different DRB1/DQB1 haplotypes, including the unusual DRB1*0405-DQB1*0503, were identified. An unusually high frequency (f = .383) of DPB1*0101, a rare allele in other Asian populations, was also observed. In addition, an unusual distribution of DRB1 alleles and haplotypesmore » was seen in this population, with DR2 (f = .415) and DRB1*1502-DQB1*0502 (f = .233) present at high frequencies. This distribution of DRB1 alleles differs from the typical HLA population distribution, in which the allele frequencies are more evenly balanced. The distribution of HLA class II alleles and haplotypes in this Filipino population is different from that of other Asian and Pacific groups: of those populations studied to date, the Indonesian population is the most similar. DRB1*1502-DQB1*0502 was in strong linkage disequilibrium (D[prime] = .41) with DPB 1*0101 (f = .126, for the extended haplotype), which is consistent with selection for this DR, DQ, DP haplotype being responsible for the high frequency of these three class II alleles in this populations. 30 refs., 2 figs., 6 tabs.« less

Damping control of micromachined lowpass mechanical vibration isolation filters using electrostatic actuation with electronic signal processing

NASA Astrophysics Data System (ADS)

Dean, Robert; Flowers, George; Sanders, Nicole; MacAllister, Ken; Horvath, Roland; Hodel, A. S.; Johnson, Wayne; Kranz, Michael; Whitley, Michael

2005-05-01

Some harsh environments, such as those encountered by aerospace vehicles and various types of industrial machinery, contain high frequency/amplitude mechanical vibrations. Unfortunately, some very useful components are sensitive to these high frequency mechanical vibrations. Examples include MEMS gyroscopes and resonators, oscillators and some micro optics. Exposure of these components to high frequency mechanical vibrations present in the operating environment can result in problems ranging from an increased noise floor to component failure. Passive micromachined silicon lowpass filter structures (spring-mass-damper) have been demonstrated in recent years. However, the performance of these filter structures is typically limited by low damping (especially if operated in near-vacuum environments) and a lack of tunability after fabrication. Active filter topologies, such as piezoelectric, electrostrictive-polymer-film and SMA have also been investigated in recent years. Electrostatic actuators, however, are utilized in many micromachined silicon devices to generate mechanical motion. They offer a number of advantages, including low power, fast response time, compatibility with silicon micromachining, capacitive position measurement and relative simplicity of fabrication. This paper presents an approach for realizing active micromachined mechanical lowpass vibration isolation filters by integrating an electrostatic actuator with the micromachined passive filter structure to realize an active mechanical lowpass filter. Although the electrostatic actuator can be used to adjust the filter resonant frequency, the primary application is for increasing the damping to an acceptable level. The physical size of these active filters is suitable for use in or as packaging for sensitive electronic and MEMS devices, such as MEMS vibratory gyroscope chips.

Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

NASA Astrophysics Data System (ADS)

Cha, Sungsu; Kim, Yujong; Lee, Byung Cheol; Park, Hyung Dal; Lee, Seung Hyun; Buaphad, Pikad

2017-05-01

KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per turn). The developed system is a more compact new resonance frequency control system. In addition, a frequency measuring part is included and it can measure the real-time resonance frequency from the magnetron. We have succeeded in the stable provisioning of RF power by recording the results of a 0.01% frequency deviation in the AFC during an RF test. Accordingly, in this paper, the detailed design, fabrication, and a high power test of the AFC system for the X-band linac are presented.

Pushing the Limits of Broadband and High-Frequency Metamaterial Silicon Antireflection Coatings

NASA Astrophysics Data System (ADS)

Coughlin, K. P.; McMahon, J. J.; Crowley, K. T.; Koopman, B. J.; Miller, K. H.; Simon, S. M.; Wollack, E. J.

2018-05-01

Broadband refractive optics realized from high-index materials provide compelling design solutions for the next generation of observatories for the cosmic microwave background and for sub-millimeter astronomy. In this paper, work is presented which extends the state of the art in silicon lenses with metamaterial antireflection coatings toward larger-bandwidth and higher-frequency operation. Examples presented include octave bandwidth coatings with less than 0.5% reflection, a prototype 4:1 bandwidth coating, and a coating optimized for 1.4 THz. For these coatings, the detailed design, fabrication and testing processes are described as well as the inherent performance trade-offs.

Nullomers and High Order Nullomers in Genomic Sequences

PubMed Central

Vergni, Davide; Santoni, Daniele

2016-01-01

A nullomer is an oligomer that does not occur as a subsequence in a given DNA sequence, i.e. it is an absent word of that sequence. The importance of nullomers in several applications, from drug discovery to forensic practice, is now debated in the literature. Here, we investigated the nature of nullomers, whether their absence in genomes has just a statistical explanation or it is a peculiar feature of genomic sequences. We introduced an extension of the notion of nullomer, namely high order nullomers, which are nullomers whose mutated sequences are still nullomers. We studied different aspects of them: comparison with nullomers of random sequences, CpG distribution and mean helical rise. In agreement with previous results we found that the number of nullomers in the human genome is much larger than expected by chance. Nevertheless antithetical results were found when considering a random DNA sequence preserving dinucleotide frequencies. The analysis of CpG frequencies in nullomers and high order nullomers revealed, as expected, a high CpG content but it also highlighted a strong dependence of CpG frequencies on the dinucleotide position, suggesting that nullomers have their own peculiar structure and are not simply sequences whose CpG frequency is biased. Furthermore, phylogenetic trees were built on eleven species based on both the similarities between the dinucleotide frequencies and the number of nullomers two species share, showing that nullomers are fairly conserved among close species. Finally the study of mean helical rise of nullomers sequences revealed significantly high mean rise values, reinforcing the hypothesis that those sequences have some peculiar structural features. The obtained results show that nullomers are the consequence of the peculiar structure of DNA (also including biased CpG frequency and CpGs islands), so that the hypermutability model, also taking into account CpG islands, seems to be not sufficient to explain nullomer phenomenon. Finally, high order nullomers could emphasize those features that already make simple nullomers useful in several applications. PMID:27906971

A piecewise probabilistic regression model to decode hand movement trajectories from epidural and subdural ECoG signals

NASA Astrophysics Data System (ADS)

Farrokhi, Behraz; Erfanian, Abbas

2018-06-01

Objective. The primary concern of this study is to develop a probabilistic regression method that would improve the decoding of the hand movement trajectories from epidural ECoG as well as from subdural ECoG signals. Approach. The model is characterized by the conditional expectation of the hand position given the ECoG signals. The conditional expectation of the hand position is then modeled by a linear combination of the conditional probability density functions defined for each segment of the movement. Moreover, a spatial linear filter is proposed for reducing the dimension of the feature space. The spatial linear filter is applied to each frequency band of the ECoG signals and extract the features with highest decoding performance. Main results. For evaluating the proposed method, a dataset including 28 ECoG recordings from four adult Japanese macaques is used. The results show that the proposed decoding method outperforms the results with respect to the state of the art methods using this dataset. The relative kinematic information of each frequency band is also investigated using mutual information and decoding performance. The decoding performance shows that the best performance was obtained for high gamma bands from 50 to 200 Hz as well as high frequency ECoG band from 200 to 400 Hz for subdural recordings. However, the decoding performance was decreased for these frequency bands using epidural recordings. The mutual information shows that, on average, the high gamma band from 50 to 200 Hz and high frequency ECoG band from 200 to 400 Hz contain significantly more information than the average of the rest of the frequency bands ≤ft( p<0.001 \\right) for both subdural and epidural recordings. The results of high resolution time-frequency analysis show that ERD/ERS patterns in all frequency bands could reveal the dynamics of the ECoG responses during the movement. The onset and offset of the movement can be clearly identified by the ERD/ERS patterns. Significance. Reliable decoding the kinematic information from the brain signals paves the way for robust control of external devices.

High-Speed, high-power, switching transistor

NASA Technical Reports Server (NTRS)

Carnahan, D.; Ohu, C. K.; Hower, P. L.

1979-01-01

Silicon transistor rate for 200 angstroms at 400 to 600 volts combines switching speed of transistors with ruggedness, power capacity of thyristor. Transistor introduces unique combination of increased power-handling capability, unusally low saturation and switching losses, and submicrosecond switching speeds. Potential applications include high power switching regulators, linear amplifiers, chopper controls for high frequency electrical vehicle drives, VLF transmitters, RF induction heaters, kitchen cooking ranges, and electronic scalpels for medical surgery.

Tone based command system for reception of very weak signals

NASA Technical Reports Server (NTRS)

Bokulic, Robert Steven (Inventor); Jensen, James Robert (Inventor)

2006-01-01

This disclosure presents a communication receiver system for spacecraft that includes an open loop receiver adapted to receive a communication signal. An ultrastable oscillator (USO) and a tone detector are connected to the open loop receiver. The open loop receiver translates the communication signal to an intermediate frequency signal using a highly stable reference frequency from the USO. The tone detector extracts commands from the communication signal by evaluating the difference between tones of the communication signal.

Radiofrequency electromagnetic fields; male infertility and sex ratio of offspring.

PubMed

Baste, Valborg; Riise, Trond; Moen, Bente E

2008-01-01

Concern is growing about exposure to electromagnetic fields and male reproductive health. The authors performed a cross-sectional study among military men employed in the Royal Norwegian Navy, including information about work close to equipment emitting radiofrequency electromagnetic fields, one-year infertility, children and sex of the offspring. Among 10,497 respondents, 22% had worked close to high-frequency aerials to a "high" or "very high" degree. Infertility increased significantly along with increasing self-reported exposure to radiofrequency electromagnetic fields. In a logistic regression, odds ratio (OR) for infertility among those who had worked closer than 10 m from high-frequency aerials to a "very high" degree relative to those who reported no work near high-frequency aerials was 1.86 (95% confidence interval (CI): 1.46-2.37), adjusted for age, smoking habits, alcohol consumption and exposure to organic solvents, welding and lead. Similar adjusted OR for those exposed to a "high", "some" and "low" degree were 1.93 (95% CI: 1.55-2.40), 1.52 (95% CI: 1.25-1.84), and 1.39 (95% CI: 1.15-1.68), respectively. In all age groups there were significant linear trends with higher prevalence of involuntary childlessness with higher self-reported exposure to radiofrequency fields. However, the degree of exposure to radiofrequency radiation and the number of children were not associated. For self-reported exposure both to high-frequency aerials and communication equipment there were significant linear trends with lower ratio of boys to girls at birth when the father reported a higher degree of radiofrequency electromagnetic exposure.

Rare-earth-doped materials with application to optical signal processing, quantum information science, and medical imaging technology

NASA Astrophysics Data System (ADS)

Cone, R. L.; Thiel, C. W.; Sun, Y.; Böttger, Thomas; Macfarlane, R. M.

2012-02-01

Unique spectroscopic properties of isolated rare earth ions in solids offer optical linewidths rivaling those of trapped single atoms and enable a variety of recent applications. We design rare-earth-doped crystals, ceramics, and fibers with persistent or transient "spectral hole" recording properties for applications including high-bandwidth optical signal processing where light and our solids replace the high-bandwidth portion of the electronics; quantum cryptography and information science including the goal of storage and recall of single photons; and medical imaging technology for the 700-900 nm therapeutic window. Ease of optically manipulating rare-earth ions in solids enables capturing complex spectral information in 105 to 108 frequency bins. Combining spatial holography and spectral hole burning provides a capability for processing high-bandwidth RF and optical signals with sub-MHz spectral resolution and bandwidths of tens to hundreds of GHz for applications including range-Doppler radar and high bandwidth RF spectral analysis. Simply stated, one can think of these crystals as holographic recording media capable of distinguishing up to 108 different colors. Ultra-narrow spectral holes also serve as a vibration-insensitive sub-kHz frequency reference for laser frequency stabilization to a part in 1013 over tens of milliseconds. The unusual properties and applications of spectral hole burning of rare earth ions in optical materials are reviewed. Experimental results on the promising Tm3+:LiNbO3 material system are presented and discussed for medical imaging applications. Finally, a new application of these materials as dynamic optical filters for laser noise suppression is discussed along with experimental demonstrations and theoretical modeling of the process.

Land mobile spectrum utilization: San Francisco, California and Chicago, Illinois

NASA Astrophysics Data System (ADS)

Reed, L. D.

1980-08-01

Radio frequency utilization by Federal Communication Commission licenses in the San Francisco and Chicago urbanized areas is described. The license include among others: police and fire departments; hospitals; public utilities; marine; and common carrier users. The extent of frequency utilization is described in terms of four occupancy categorizations (zero, low, substantial and very high). The rationale for these categories and their relationship to measured usage data is given. Summary tables enable direct comparison of the use by various individual, radio services, e.g., police, business, taxicab, etc. Separate analyses are given for utilization by each of the land mobile radio services and for each frequency band.

Production of large resonant plasma volumes in microwave electron cyclotron resonance ion sources

DOEpatents

Alton, Gerald D.

1998-01-01

Microwave injection methods for enhancing the performance of existing electron cyclotron resonance (ECR) ion sources. The methods are based on the use of high-power diverse frequency microwaves, including variable-frequency, multiple-discrete-frequency, and broadband microwaves. The methods effect large resonant "volume" ECR regions in the ion sources. The creation of these large ECR plasma volumes permits coupling of more microwave power into the plasma, resulting in the heating of a much larger electron population to higher energies, the effect of which is to produce higher charge state distributions and much higher intensities within a particular charge state than possible in present ECR ion sources.

High-fiber rye diet increases ileal excretion of energy and macronutrients compared with low-fiber wheat diet independent of meal frequency in ileostomy subjects.

PubMed

Isaksson, Hanna; Landberg, Rikard; Sundberg, Birgitta; Lundin, Eva; Hallmans, Göran; Zhang, Jie-Xian; Tidehag, Per; Erik Bach Knudsen, Knud; Moazzami, Ali A; Aman, Per

2013-01-01

Whole-grain foods and cereal dietary fiber intake is associated with lower body weight. This may partly result from lower energy utilization of high-fiber diets. In the present study, the impact on ileal excretion of energy and macronutrients in response to a rye bread high-fiber diet compared to a refined wheat low-fiber diet was investigated. Furthermore, the effect of meal frequency on apparent absorption of nutrients was studied for the first time. Ten participants that had undergone ileostomy consumed standardized iso-caloric diets, including low-fiber wheat bread (20 g dietary fiber per day) for 2 weeks followed by high-fiber rye bread (52 g dietary fiber per day) for 2 weeks. The diets were consumed in an ordinary (three meals per day) and a nibbling (seven meals per day) meal frequency in a cross-over design. Ileal effluents were collected during 24 h at the third day of each of the four dietary periods and analyzed for gross energy and nutrient contents. The results showed that intake of rye bread high-fiber diet compared to the refined wheat low-fiber diet caused an increase in ileal excretion of energy and macronutrients. The effect was independent of meal frequency. This suggests that a high intake of rye may result in lower availability of macronutrients for small intestinal digestion and absorption. A regular intake of rye may therefore have implications for weight management.

Use of Sine Shaped High-Frequency Rhythmic Visual Stimuli Patterns for SSVEP Response Analysis and Fatigue Rate Evaluation in Normal Subjects

PubMed Central

Keihani, Ahmadreza; Shirzhiyan, Zahra; Farahi, Morteza; Shamsi, Elham; Mahnam, Amin; Makkiabadi, Bahador; Haidari, Mohsen R.; Jafari, Amir H.

2018-01-01

Background: Recent EEG-SSVEP signal based BCI studies have used high frequency square pulse visual stimuli to reduce subjective fatigue. However, the effect of total harmonic distortion (THD) has not been considered. Compared to CRT and LCD monitors, LED screen displays high-frequency wave with better refresh rate. In this study, we present high frequency sine wave simple and rhythmic patterns with low THD rate by LED to analyze SSVEP responses and evaluate subjective fatigue in normal subjects. Materials and Methods: We used patterns of 3-sequence high-frequency sine waves (25, 30, and 35 Hz) to design our visual stimuli. Nine stimuli patterns, 3 simple (repetition of each of above 3 frequencies e.g., P25-25-25) and 6 rhythmic (all of the frequencies in 6 different sequences e.g., P25-30-35) were chosen. A hardware setup with low THD rate (<0.1%) was designed to present these patterns on LED. Twenty two normal subjects (aged 23–30 (25 ± 2.1) yrs) were enrolled. Visual analog scale (VAS) was used for subjective fatigue evaluation after presentation of each stimulus pattern. PSD, CCA, and LASSO methods were employed to analyze SSVEP responses. The data including SSVEP features and fatigue rate for different visual stimuli patterns were statistically evaluated. Results: All 9 visual stimuli patterns elicited SSVEP responses. Overall, obtained accuracy rates were 88.35% for PSD and > 90% for CCA and LASSO (for TWs > 1 s). High frequency rhythmic patterns group with low THD rate showed higher accuracy rate (99.24%) than simple patterns group (98.48%). Repeated measure ANOVA showed significant difference between rhythmic pattern features (P < 0.0005). Overall, there was no significant difference between the VAS of rhythmic [3.85 ± 2.13] compared to the simple patterns group [3.96 ± 2.21], (P = 0.63). Rhythmic group had lower within group VAS variation (min = P25-30-35 [2.90 ± 2.45], max = P35-25-30 [4.81 ± 2.65]) as well as least individual pattern VAS (P25-30-35). Discussion and Conclusion: Overall, rhythmic and simple pattern groups had higher and similar accuracy rates. Rhythmic stimuli patterns showed insignificantly lower fatigue rate than simple patterns. We conclude that both rhythmic and simple visual high frequency sine wave stimuli require further research for human subject SSVEP-BCI studies. PMID:29892219

Use of Sine Shaped High-Frequency Rhythmic Visual Stimuli Patterns for SSVEP Response Analysis and Fatigue Rate Evaluation in Normal Subjects.

PubMed

Keihani, Ahmadreza; Shirzhiyan, Zahra; Farahi, Morteza; Shamsi, Elham; Mahnam, Amin; Makkiabadi, Bahador; Haidari, Mohsen R; Jafari, Amir H

2018-01-01

Background: Recent EEG-SSVEP signal based BCI studies have used high frequency square pulse visual stimuli to reduce subjective fatigue. However, the effect of total harmonic distortion (THD) has not been considered. Compared to CRT and LCD monitors, LED screen displays high-frequency wave with better refresh rate. In this study, we present high frequency sine wave simple and rhythmic patterns with low THD rate by LED to analyze SSVEP responses and evaluate subjective fatigue in normal subjects. Materials and Methods: We used patterns of 3-sequence high-frequency sine waves (25, 30, and 35 Hz) to design our visual stimuli. Nine stimuli patterns, 3 simple (repetition of each of above 3 frequencies e.g., P25-25-25) and 6 rhythmic (all of the frequencies in 6 different sequences e.g., P25-30-35) were chosen. A hardware setup with low THD rate (<0.1%) was designed to present these patterns on LED. Twenty two normal subjects (aged 23-30 (25 ± 2.1) yrs) were enrolled. Visual analog scale (VAS) was used for subjective fatigue evaluation after presentation of each stimulus pattern. PSD, CCA, and LASSO methods were employed to analyze SSVEP responses. The data including SSVEP features and fatigue rate for different visual stimuli patterns were statistically evaluated. Results: All 9 visual stimuli patterns elicited SSVEP responses. Overall, obtained accuracy rates were 88.35% for PSD and > 90% for CCA and LASSO (for TWs > 1 s). High frequency rhythmic patterns group with low THD rate showed higher accuracy rate (99.24%) than simple patterns group (98.48%). Repeated measure ANOVA showed significant difference between rhythmic pattern features ( P < 0.0005). Overall, there was no significant difference between the VAS of rhythmic [3.85 ± 2.13] compared to the simple patterns group [3.96 ± 2.21], ( P = 0.63). Rhythmic group had lower within group VAS variation (min = P25-30-35 [2.90 ± 2.45], max = P35-25-30 [4.81 ± 2.65]) as well as least individual pattern VAS (P25-30-35). Discussion and Conclusion: Overall, rhythmic and simple pattern groups had higher and similar accuracy rates. Rhythmic stimuli patterns showed insignificantly lower fatigue rate than simple patterns. We conclude that both rhythmic and simple visual high frequency sine wave stimuli require further research for human subject SSVEP-BCI studies.

The Design and Operation of Ultra-Sensitive and Tunable Radio-Frequency Interferometers.

PubMed

Cui, Yan; Wang, Pingshan

2014-12-01

Dielectric spectroscopy (DS) is an important technique for scientific and technological investigations in various areas. DS sensitivity and operating frequency ranges are critical for many applications, including lab-on-chip development where sample volumes are small with a wide range of dynamic processes to probe. In this work, we present the design and operation considerations of radio-frequency (RF) interferometers that are based on power-dividers (PDs) and quadrature-hybrids (QHs). Such interferometers are proposed to address the sensitivity and frequency tuning challenges of current DS techniques. Verified algorithms together with mathematical models are presented to quantify material properties from scattering parameters for three common transmission line sensing structures, i.e., coplanar waveguides (CPWs), conductor-backed CPWs, and microstrip lines. A high-sensitivity and stable QH-based interferometer is demonstrated by measuring glucose-water solution at a concentration level that is ten times lower than some recent RF sensors while our sample volume is ~1 nL. Composition analysis of ternary mixture solutions are also demonstrated with a PD-based interferometer. Further work is needed to address issues like system automation, model improvement at high frequencies, and interferometer scaling.

Multi-Species Test of Ion Cyclotron Resonance Heating at High Altitudes

NASA Technical Reports Server (NTRS)

Persoon, A. M.; Peterson, W. K.; Andre, M.; Chang, T.; Gurnett, D. A.; Retterer, J. M.; Crew, G. B.

1997-01-01

Observations of ion distributions and plasma waves obtained by the Dynamics Explorer 1 satellite in the high-altitude, nightside auroral zone are used to study ion energization for three ion species. A number of theoretical models have been proposed to account for the transverse heating of these ion populations. One of these, the ion cyclotron resonance heating (ICRH) mechanism, explains ion conic formation through ion cyclotron resonance with broadband electromagnetic wave turbulence in the vicinity of the characteristic ion cyclotron frequency. The cyclotron resonant heating of the ions by low- frequency electromagnetic waves is an important energy source for the transport of ions from the ionosphere to the magnetosphere. In this paper we test the applicability of the ICRH mechanism to three simultaneously heated and accelerated ion species by modelling the ion conic formation in terms of a resonant wave-particle interaction in which the ions extract energy from the portion of the broadband electromagnetic wave spectrum which includes the ion cyclotron frequency. Using a Monte Carlo technique we evaluate the ion heating produced by the electromagnetic turbulence at low frequencies and find that the wave amplitudes near the ion cyclotron frequencies are sufficient to explain the observed ion energies.

Multi-Species Test of Ion Cyclotron Resonance Heating at High Altitudes

NASA Technical Reports Server (NTRS)

Persoon, A. M.; Peterson, W. K.; Andre, M.; Chang, T.; Gurnett, D. A.; Retterer, J. M.; Crew, G. B.

1997-01-01

Observations of ion distributions and plasma waves obtained by the Dynamics Explorer 1 satellite in the high-altitude, nightside auroral zone are used to study ion energization for three ion species. A number of theoretical models have been proposed to account for the transverse heating of these ion populations. One of these, the ion cyclotron resonance heating (ICRH) mechanism, explains ion conic formation through ion cyclotron resonance with broadband electromagnetic wave turbulence in the vicinity of the characteristic ion cyclotron frequency. The cyclotron resonant heating of the ions by low-frequency electromagnetic waves is an important energy source for the transport of ions from the ionosphere to the magnetosphere. In this paper we test the applicability of the ICRH mechanism to three simultaneously heated and accelerated ion species by modelling the ion conic formation in terms of a resonant wave-particle interaction in which the ions extract energy from the portion of the broadband electromagnetic wave spectrum which includes the ion cyclotron frequency. Using a Monte Carlo technique we evaluate the ion heating produced by the electromagnetic turbulence at low frequencies and find that the wave amplitudes near the ion cyclotron frequencies are sufficient to explain the observed ion energies.

Hail frequency estimation across Europe based on a combination of overshooting top detections and the ERA-INTERIM reanalysis

NASA Astrophysics Data System (ADS)

Punge, H. J.; Bedka, K. M.; Kunz, M.; Reinbold, A.

2017-12-01

This article presents a hail frequency estimation based on the detection of cold overshooting cloud tops (OTs) from the Meteosat Second Generation (MSG) operational weather satellites, in combination with a hail-specific filter derived from the ERA-INTERIM reanalysis. This filter has been designed based on the atmospheric properties in the vicinity of hail reports registered in the European Severe Weather Database (ESWD). These include Convective Available Potential Energy (CAPE), 0-6-km bulk wind shear and freezing level height, evaluated at the nearest time step and interpolated from the reanalysis grid to the location of the hail report. Regions highly exposed to hail events include Northern Italy, followed by South-Eastern Austria and Eastern Spain. Pronounced hail frequency is also found in large parts of Eastern Europe, around the Alps, the Czech Republic, Southern Germany, Southern and Eastern France, and in the Iberic and Apennine mountain ranges.

Frequency stabilization and transverse mode discrimination in injection-seeded unstable resonator TEA CO2 lasers

NASA Technical Reports Server (NTRS)

Ancellet, G. M.; Menzies, R. T.; Brothers, A. M.

1987-01-01

Longitudinal mode selection by injection has been demonstrated as a viable technique for TEA-CO2 lasers with pulse energies of a Joule or greater. Once reliable generation of single-longitudinal-mode (SLM) pulses is obtained, the characteristics and the causes of intrapulse frequency variation can be studied. These include the effect of the decaying plasma, the thermal gradient due to the energy dissipation associated with the laser mechanism itself, and the pressure shift of the center frequency of the laser transition. The use of the positive-branch unstable resonator as an efficient means of coupling a discharge with large spatial dimensions to an optical cavity mode introduces another concern: namely, what can be done to emphasize transverse mode discrimination in an unstable resonator cavity while maintaining high coupling efficiency. These issues are discussed in this paper, and relevant experimental results are included.

An intelligent health monitoring system using radio-frequency identification technology.

PubMed

Lai, Yeong-Lin; Chen, Chin-Ling; Chang, Ching-Hisang; Hsu, Chih-Yu; Lai, Yeong-Kang; Tseng, Kuo-Kun; Chen, Chih-Cheng; Zheng, Chun-Yi

2015-01-01

Long-term care (LTC) for the elderly has become extremely important in recent years. It is necessary for the different physiological monitoring systems to be integrated on the same interface to help oversee and manage the elderly's needs. This paper presents a novel health monitoring system for LTC services using radio-frequency identification (RFID) technology. Dual-band RFID protocols were included in the system, in which the high-frequency (HF) band of 13.56 MHz was used to identify individuals and the microwave band of 2.45 GHz was used to monitor physiological information. Distinct physiological data, including oxyhemoglobin saturation by pulse oximetry (SpO2), blood pressure, blood sugar, electrocardiogram (ECG) readings, body temperature, and respiration rate, were monitored by various biosensors. The intelligent RFID health monitoring system provided the features of the real-time acquisition of biomedical signals and the identification of personal information pertaining to the elderly and patients in nursing homes.

Improving Planck calibration by including frequency-dependent relativistic corrections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quartin, Miguel; Notari, Alessio, E-mail: mquartin@if.ufrj.br, E-mail: notari@ffn.ub.es

2015-09-01

The Planck satellite detectors are calibrated in the 2015 release using the 'orbital dipole', which is the time-dependent dipole generated by the Doppler effect due to the motion of the satellite around the Sun. Such an effect has also relativistic time-dependent corrections of relative magnitude 10{sup −3}, due to coupling with the 'solar dipole' (the motion of the Sun compared to the CMB rest frame), which are included in the data calibration by the Planck collaboration. We point out that such corrections are subject to a frequency-dependent multiplicative factor. This factor differs from unity especially at the highest frequencies, relevantmore » for the HFI instrument. Since currently Planck calibration errors are dominated by systematics, to the point that polarization data is currently unreliable at large scales, such a correction can in principle be highly relevant for future data releases.« less

Clinical and audiologic characteristics of patients with sensorineural tinnitus and its association with psychological aspects: an analytic retrospective study.

PubMed

Al-Swiahb, Jamil Nasser; Hwang, Eul Seung; Kong, Ji Sun; Kim, Woo Jin; Yeo, Sang Won; Park, Shi Nae

2016-12-01

This study was performed to analyze clinical and audiologic characteristics of sensorineural tinnitus and to investigate the associating factors reflecting psychological aspects of stress and depression of the patients. This is a retrospective analytical study conducted in a tinnitus clinic of a tertiary referral center of a university hospital. The medical records of 216 patients suffering from sensorineural tinnitus were thoroughly evaluated to determine correlations between clinical and audiological characteristics, including age, sex, predisposing or etiologic factors, hearing levels up to extended high frequencies, and tinnitus severity. Psychological aspects of stress and depression were also evaluated and analyzed to seek the associations with tinnitus severity. All data were stored in our database bank and were statistically analyzed. Our study subjects showed a slight male predominance. The highest percentage of tinnitus was found in patients of 60-80 years old. Only 32.5 % of tinnitus patients were subjectively aware of their hearing loss, whereas 73 % of subjects had hearing deficits in some frequencies in their audiogram. Hearing impairments were of the low-frequency sensorineural type in 18.2 % of patients and were limited to the high frequencies in 77.9 % of patients. Tinnitus was unilateral in 51 % of patients and had a tonal nature in 45 % of patients. In total, 45.8 % of patients with high-frequency sensorineural hearing loss had high-pitched tinnitus. There were significant correlations between tinnitus severity, loudness and annoyance. Correlations with THI (Tinnitus Handicap Inventory) and Beck depression index scores were also found. Sensorineural tinnitus was related with hearing loss in some frequencies nevertheless of patients' own awareness of hearing loss. Loudness and annoyance of tinnitus seems to be two important factors reflecting psychological problems of patients' stress and depression.

Frequency of common polymorphisms in Caveolin 1 (CAV1 ) gene in adults with high serum triglycerides from Colombian Caribbean Coast

PubMed Central

Ruiz-Diaz, Maria Stephany; Gomez-Camargo, Doris Esther; Gomez-Alegria, Claudio Jaime

2017-01-01

Abstract Background: Caveolin 1 gene (CAV1) has been associated with insulin resistance, metabolic syndrome and hypertension in humans. Also, it has been related to high serum triglycerides in rodents, however there is little evidence of this relation in humans. Aim: To describe frequencies of common variations in CAV1 in adults with high serum triglycerides. Methods: A case-control study was carried out with adults from Colombian Caribbean Coast. A whole blood sample was employed to measure serum concentrations of triglycerides, glucose, total cholesterol and HDLc. Six common Single Nucleotide Polymorphism (SNP) in CAV1 were genotyped (rs926198, rs3779512, rs10270569, rs11773845, rs7804372 and rs1049337). Allelic and genotypic frequencies were determined by direct count and Hardy-Weinberg Equilibrium (HWE) was assessed. Case and control groups were compared with null-hypothesis tests. Results: A total of 220 cases and 220 controls were included. For rs3779512 an excess in homozygotes frequency was found within case group (40.4% (GG), 41.3% (GT) and 18.1% (TT); Fis=0.13, p=0.03). Another homozygotes excess among case group was found in rs7804372 (59.5% (TT), 32.3% (TA) and 8.2% (AA); Fis= 0.12, p= 0.04). In rs1049337, cases also showed an excess in homozygotes frequency (52.7% (CC), 35.0% (CT) and 12.3% (TT); Fis= 0.16, p= 0.01). Finally, for rs1049337 there were differences in genotype distribution between case and control groups (p <0.05). Conclusion: An increased frequency of homozygote genotypes was found in subjects with high serum triglycerides. These findings suggest that minor alleles for SNPs rs3779512, rs7804372 and rs1049337 might be associated to higher risk of hypertriglyceridemia. PMID:29662258

Equivalent circuit parameters of nickel/metal hydride batteries from sparse impedance measurements

NASA Astrophysics Data System (ADS)

Nelatury, Sudarshan Rao; Singh, Pritpal

In a recent communication, a method for extracting the equivalent circuit parameters of a lead acid battery from sparse (only three) impedance spectroscopy observations at three different frequencies was proposed. It was based on an equivalent circuit consisting of a bulk resistance, a reaction resistance and a constant phase element (CPE). Such a circuit is a very appropriate model of a lead-acid cell at high state of charge (SOC). This paper is a sequel to it and presents an application of it in case of nickel/metal hydride (Ni/MH) batteries, which also at high SOC are represented by the same circuit configuration. But when the SOC of a Ni/MH battery under interrogation goes low, The EIS curve has a positive slope at the low frequency end and our technique yields complex values for the otherwise real circuit parameters, suggesting the need for additional elements in the equivalent circuit and a definite relationship between parameter consistency and SOC. To improvise the previous algorithm, in order that it works reasonably well at both high and low SOCs, we propose three more measurements—two at very low frequencies to include the Warburg response and one at a high frequency to model the series inductance, in addition to the three in the mid frequency band—totally six measurements. In most of the today's instrumentation, it is the user who should choose the circuit configuration and the number of frequencies where impedance should be measured and the accompanying software performs data fitting by complex nonlinear least squares. The proposed method has built into it an SOC-based decision-making capability—both to choose the circuit configuration and to estimate the values of the circuit elements.

Evaluation of patients with gastric polyps.

PubMed

Olmez, Sehmus; Sayar, Suleyman; Saritas, Bunyamin; Savas, Ayla Yildiz; Avcioglu, Ufuk; Tenlik, Ilyas; Ozaslan, Ersan; Koseoglu, Hasan Tankut; Altiparmak, Emin

2018-01-01

The incidence of gastric polyps (GPs) greatly differs according to study populations and was found to be 0.33%-6.7% in various studies. The majority of GPs are composed of hyperplastic polyps (HPs), fundic gland polyps (FGPs), and adenomatous polyps (APs). Although APs have a high risk of malignant potential, sporadic FGPs have no malignant potential. Conversely, HPs have a low risk of malignant potential. It is not sufficient to perform a biopsy to identify the polyp type and the presence of dysplasia; thus, some polyps may require multiple biopsies or total excision. This retrospective study included patients with GPs or polypoid lesions found on esophagogastroscopy with polyp or malignant histology on biopsy at Ankara Numune Training and Research Hospital Endoscopy Unit between 2005 and 2011. In a series of 56.300 upper endoscopies, 192 patients (0.34%) were found to have GPs. Among the patients, 51 (26.6%) were men and 151 (73.4%) were women. The average age of the patients was 61.9±13.3 (14-90) years. The frequency of HPs, APs, and FGPs were 88%, 2.6%, and 1.6%, respectively. The size of the polyps was ≤1 cm in 137 (70%) patients. One polyp was determined in 141 (73.4%) patients. The most common localizations of polyps were the antrum and corpus. Endoscopic snare polypectomy was performed in 64 patients. One bleeding episode was observed, which required endoscopic treatment after ESP. In our study, the GP frequency was low (0.34%), whereas the frequency of HP maybe high due to the high frequency of Helicobacter pylori (HPy) infection in our country. The frequency of FGP is probably low due to the high frequency of HPy infection and the short-term use of proton-pump inhibitors.

Generation of uniform large-area very high frequency plasmas by launching two specific standing waves simultaneously

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Hsin-Liang, E-mail: hlchen@iner.gov.tw; Tu, Yen-Cheng; Hsieh, Cheng-Chang

2014-09-14

With the characteristics of higher electron density and lower ion bombardment energy, large-area VHF (very high frequency) plasma enhanced chemical vapor deposition has become an essential manufacturing equipment to improve the production throughput and efficiency of thin film silicon solar cell. However, the combination of high frequency and large electrodes leads to the so-called standing wave effect causing a serious problem for the deposition uniformity of silicon thin film. In order to address this issue, a technique based on the idea of simultaneously launching two standing waves that possess similar amplitudes and are out of phase by 90° in timemore » and space is proposed in this study. A linear plasma reactor with discharge length of 54 cm is tested with two different frequencies including 60 and 80 MHz. The experimental results show that the proposed technique could effectively improve the non-uniformity of VHF plasmas from >±60% when only one standing wave is applied to <±10% once two specific standing waves are launched at the same time. Moreover, in terms of the reactor configuration adopted in this study, in which the standing wave effect along the much shorter dimension can be ignored, the proposed technique is applicable to different frequencies without the need to alter the number and arrangement of power feeding points.« less

Polymorphism of Trp64Arg in beta3-adrenergic receptor gene among Bolivian people in rural areas at high and low altitudes.

PubMed

Karasaki, Yuji; Kashiwazaki, Hiroshi

2004-01-01

To investigate whether population differences in food and/or lifestyle could affect the distribution frequencies of polymorphism in the gene for beta3-adrenergic receptor (beta3-AR), the frequency of Trp64Arg polymorphism was studied among Bolivian people living in rural areas of high (about 4000 m above sea level) and low (about 300 m above sea level) altitudes. Genomic DNA samples of Bolivian subjects (n=508) were amplified by polymerase chain reaction (PCR) for part of the beta3-AR gene. The amplified PCR products were digested with restriction enzyme NciI and analysed by agarose gel electrophoresis. We found no significant difference in the frequency of Arg allele in the beta3-AR gene between 331 native low-altitude Bolivian subjects (18.1%) and 177 native high-altitude Bolivian subjects (17.5%). Body mass index was not associated with Trp64Arg polymorphism among native Bolivian adults. The frequency of this allele in the complete Bolivian population (18%) was lower than that reported in Pima Indians (32%), is comparable to the Japanese (19%) and is higher than several ethnic groups, including Finns (12%) and French (4%). Our data indicate that the altitude-related lifestyle of a population has had little influence on the frequency of Trp64Arg polymorphism and obesity in Bolivian natives.

Anatomical evidence for low frequency sensitivity in an archaeocete whale: comparison of the inner ear of Zygorhiza kochii with that of crown Mysticeti.

PubMed

Ekdale, Eric G; Racicot, Rachel A

2015-01-01

The evolution of hearing in cetaceans is a matter of current interest given that odontocetes (toothed whales) are sensitive to high frequency sounds and mysticetes (baleen whales) are sensitive to low and potentially infrasonic noises. Earlier diverging stem cetaceans (archaeocetes) were hypothesized to have had either low or high frequency sensitivity. Through CT scanning, the morphology of the bony labyrinth of the basilosaurid archaeocete Zygorhiza kochii is described and compared to novel information from the inner ears of mysticetes, which are less known than the inner ears of odontocetes. Further comparisons are made with published information for other cetaceans. The anatomy of the cochlea of Zygorhiza is in line with mysticetes and supports the hypothesis that Zygorhiza was sensitive to low frequency noises. Morphological features that support the low frequency hypothesis and are shared by Zygorhiza and mysticetes include a long cochlear canal with a high number of turns, steeply graded curvature of the cochlear spiral in which the apical turn is coiled tighter than the basal turn, thin walls separating successive turns that overlap in vestibular view, and reduction of the secondary bony lamina. Additional morphology of the vestibular system indicates that Zygorhiza was more sensitive to head rotations than extant mysticetes are, which likely indicates higher agility in the ancestral taxon. © 2014 Anatomical Society.

Anatomical evidence for low frequency sensitivity in an archaeocete whale: comparison of the inner ear of Zygorhiza kochii with that of crown Mysticeti

PubMed Central

Ekdale, Eric G; Racicot, Rachel A

2015-01-01

The evolution of hearing in cetaceans is a matter of current interest given that odontocetes (toothed whales) are sensitive to high frequency sounds and mysticetes (baleen whales) are sensitive to low and potentially infrasonic noises. Earlier diverging stem cetaceans (archaeocetes) were hypothesized to have had either low or high frequency sensitivity. Through CT scanning, the morphology of the bony labyrinth of the basilosaurid archaeocete Zygorhiza kochii is described and compared to novel information from the inner ears of mysticetes, which are less known than the inner ears of odontocetes. Further comparisons are made with published information for other cetaceans. The anatomy of the cochlea of Zygorhiza is in line with mysticetes and supports the hypothesis that Zygorhiza was sensitive to low frequency noises. Morphological features that support the low frequency hypothesis and are shared by Zygorhiza and mysticetes include a long cochlear canal with a high number of turns, steeply graded curvature of the cochlear spiral in which the apical turn is coiled tighter than the basal turn, thin walls separating successive turns that overlap in vestibular view, and reduction of the secondary bony lamina. Additional morphology of the vestibular system indicates that Zygorhiza was more sensitive to head rotations than extant mysticetes are, which likely indicates higher agility in the ancestral taxon. PMID:25400023

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daling, P.M.; Marler, J.E.; Vo, T.V.

This study evaluates the values (benefits) and impacts (costs) associated with potential resolutions to Generic Issue 143, ``Availability of HVAC and Chilled Water Systems.`` The study identifies vulnerabilities related to failures of HVAC, chilled water, and room cooling systems; develops estimates of room heatup rates and safety-related equipment vulnerabilities following losses of HVAC/room cooler systems; develops estimates of the core damage frequencies and public risks associated with failures of these systems; develops three proposed resolution strategies to this generic issue; and performs a value/impact analysis of the proposed resolutions. Existing probabilistic risk assessments for four representative plants, including one plantmore » from each vendor, form the basis for the core damage frequency and public risk calculations. Both internal and external events were considered. It was concluded that all three proposed resolution strategies exceed the $1,000/person-rem cost-effectiveness ratio. Additional evaluations were performed to develop ``generic`` insights on potential design-related and configuration-related vulnerabilities and potential high-frequency ({approximately}1E-04/RY) accident sequences that involve failures of HVAC/room cooling functions. It was concluded that, although high-frequency accident sequences may exist at some plants, these high-frequency sequences are plant-specific in nature or have been resolved through hardware and/or operational changes. The plant-specific Individual Plant Examinations are an effective vehicle for identification and resolution of these plant-specific anomalies and hardware configurations.« less

Frequency and expression of mutacin biosynthesis genes in isolates of Streptococcus mutans with different mutacin-producing phenotypes.

PubMed

Kamiya, Regianne Umeko; Höfling, José Francisco; Gonçalves, Reginaldo Bruno

2008-05-01

The aim of this study was to analyse the frequency and expression of biosynthesis genes in 47 Streptococcus mutans isolates with different mutacin-producing phenotypes. Detection of the frequency and expression of genes encoding mutacin types I, II, III and IV were carried out by PCR and semi-quantitative RT-PCR, respectively, using primers specific for each type of biosynthesis gene. In addition, a further eight genes encoding putative bacteriocins, designated bsm 283, bsm 299, bsm 423, bsm 1889c, bsm 1892c, bsm 1896, bsm 1906c and bsm 1914, were also screened. There was a high phenotypic diversity; some Streptococcus mutans isolates presented broad antimicrobial spectra against other Streptococcus mutans clinical isolates, including bacteria resistant to common antibiotics, as well as Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis and Streptococcus pyogenes. The expression frequency of the bsm gene was higher than that of the previously characterized mutacins (I-IV). There was no positive correlation between the number of indicator strains inhibited (antimicrobial spectra) and the number of biosynthesis genes expressed (Spearman correlation test, r=-0.03, P>0.05). In conclusion, the high diversity of mutacin-producing phenotypes, associated with high frequency of expression of the biosynthesis genes screened, reveals a broad repertoire of genetic determinants encoding antimicrobial peptides that can act in different combinations.