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Sample records for high beta frequency

  1. High-. beta. theory of low-frequency magnetic pulsations

    SciTech Connect

    Migliuolo, S.

    1983-03-01

    The theory of low-frequency (compared to ion cyclotron) arbitrary-..beta.. modes is developed for the following system: a two-component (hot and cold) inhomogeneous plasma, and a straight inhomogeneous magnetic field. This system is taken to model the magnetosphere, near the geomagnetic equator. The stability properties of three modes are presented in detail: the drift-compressional mode (driven by pressure gradients) the firehose mode (driven by T/sub parallel/>T/sub perpendicular/), and the drift mirror mode (driven by T/sub perpendicular/>T/sub parallel/). Comparisons to earlier models and to one observed event are also presented.

  2. Total beta-globin gene deletion has high frequency in Filipinos

    SciTech Connect

    Patrick, N.; Miyakawa, F.; Hunt, J.A.

    1994-09-01

    The distribution of {beta}-thalassemia [{beta}{sup Th}] mutations is unique to each ethnic group. Most mutations affect one or a few bases; large deletions have been rare. Among families screened in Hawaii, [{beta}{sup Th}] heterozygotes were diagnosed by microcytosis, absence of abnormal hemoglobins on isoelectric focusing, and raised Hb A{sub 2} by chromatography. Gene frequency for {beta}{sup Th} was 0.02 in Filipinos. In Filipinos, polymerase chain reaction [PCR] with denaturing gradient gel electrophoresis for {beta}{sup Th} mutations detected a mutation in only 6 of 42 {beta}{sup Th} heterozygotes; an IVS2-666 C/T polymorphism showed non-heterozygosity in 37 and heterozygosity in only 5 of these {beta}{sup Th} heterozygotes. One {beta}{sup Th}/{beta}{sup Th} major patient and his mother had no mutation detected by allele-specific oligomer hybridization; PCR failed to amplify any DNA from his {beta}-globin gene. After a total {beta}-globin gene deletion [{beta}{sup Del}] was found in a Filipino family in Ontario, specific PCR amplification for {beta}{sup Del} detected this in 43 of 53 {beta}{sup Th} Filipino samples tested; the above {beta}{sup Th}/{beta}{sup Th} patient was a ({beta}{sup Del}/{beta}{sup Del}) homozygote. The {beta}{sup Del} may account for over 60% of all {beta}{sup Th} alleles in Filipinos; this is the highest proportion of a deletion {beta}{sup Th} mutation reported from any population. Most but not all {beta}{sup Del} heterozygotes had high Hb F [5.13 {plus_minus} 3.94 mean {plus_minus} 1 s.d.] compared to the codon 41/42 four base deletion common in Chinese [2.30 {plus_minus} 0.86], or to {beta}{sup Th} heterozygotes with normal {alpha}-globin genes [2.23 {plus_minus} 0.80].

  3. Beta-coupled high-frequency activity and beta-locked neuronal spiking in the subthalamic nucleus of Parkinson's disease.

    PubMed

    Yang, Andrew I; Vanegas, Nora; Lungu, Codrin; Zaghloul, Kareem A

    2014-09-17

    Beta frequency (13-30 Hz) oscillatory activity in the subthalamic nucleus (STN) of Parkinson's disease (PD) has been shown to influence the temporal dynamics of high-frequency oscillations (HFOs; 200-500 Hz) and single neurons, potentially compromising the functional flexibility of the motor circuit. We examined these interactions by simultaneously recording both local field potential and single-unit activity from the basal ganglia of 15 patients with PD during deep brain stimulation (DBS) surgery of the bilateral STN. Phase-amplitude coupling (PAC) in the STN was specific to beta phase and HFO amplitude, and this coupling was strongest at the dorsal STN border. We found higher beta-HFO PAC near DBS lead contacts that were clinically effective compared with the remaining non-effective contacts, indicating that PAC may be predictive of response to STN DBS. Neuronal spiking was locked to the phase of 8-30 Hz oscillations, and the spatial topography of spike-phase locking (SPL) was similar to that of PAC. Comparisons of PAC and SPL showed a lack of spatiotemporal correlations. Beta-coupled HFOs and field-locked neurons had different preferred phase angles and did not co-occur within the same cycle of the modulating oscillation. Our findings provide additional support that beta-HFO PAC may be central to the pathophysiology of PD and suggest that field-locked neurons alone are not sufficient for the emergence of beta-coupled HFOs. PMID:25232117

  4. Magnetic fields, plasma densities, and plasma beta parameters estimated from high-frequency zebra fine structures

    NASA Astrophysics Data System (ADS)

    Karlický, M.; Jiricka, K.

    2002-10-01

    Using the recent model of the radio zebra fine structures (Ledenev et al. 2001) the magnetic fields, plasma densities, and plasma beta parameters are estimated from high-frequency zebra fine structures. It was found that in the flare radio source of high-frequency (1-2 GHz) zebras the densities and magnetic fields vary in the intervals of (1-4)×1010 cm-3 and 40-230 G, respectively. Assuming then the flare temperature as about of 107K, the plasma beta parameters in the zebra radio sources are in the 0.05-0.81 interval. Thus the plasma pressure effects in such radio sources, especially in those with many zebra lines, are not negligible.

  5. Low-frequency waves in a high-beta collisionless plasma Polarization, compressibility and helicity

    NASA Technical Reports Server (NTRS)

    Gary, S. P.

    1986-01-01

    This paper considers the linear theory of waves near and below the ion cyclotron frequency in an isothermal electron-ion Vlasov plasma which is isotropic, homogeneous and magnetized. Numerical solutions of the full dispersion equation for the magnetosonic/whistler and Alfven/ion cyclotron modes at beta(i) = 1.0 are presented, and the polarizations, compressibilities, helicities, ion Alfven ratios and ion cross-helicities are exhibited and compared. At sufficiently large beta(i) and theta, the angle of propagation with respect to the magnetic field, the real part of the polarization of the Alfven/ion cyclotron wave changes sign, so that, for such parameters, this mode is no longer left-hand polarized. The Alfven/ion cyclotron mode becomes more compressive as the wavenumber increases, whereas the magnetosonic/whistler becomes more compressive with increasing theta.

  6. Finite beta effects on low- and high-frequency magnetosonic waves in a two-ion-species plasma

    SciTech Connect

    Toida, Mieko; Aota, Yukio

    2013-08-15

    A magnetosonic wave propagating perpendicular to a magnetic field in a two-ion-species plasma has two branches, high-frequency and low-frequency modes. The finite beta effects on these modes are analyzed theoretically on the basis of the three-fluid model with finite ion and electron pressures. First, it is shown that the Korteweg-de Vries (KdV) equation for the low-frequency mode is valid for amplitudes ε<ε{sub max}, where the upper limit of the amplitude ε{sub max} is given as a function of β (β is the ratio of the kinetic and magnetic energy densities), the density ratio, and the cyclotron frequency ratio of two ion species. Next, the linear dispersion relation and KdV equation for the high-frequency mode are derived, including β as a factor. In addition, the theory for heavy ion acceleration by the high-frequency mode pulse and the pulse damping due to this energy transfer in a finite beta plasma are presented.

  7. Excitation of high frequency pressure driven modes by non-axisymmetric equilibrium at high {beta}{sub pol} in PBX-M

    SciTech Connect

    Sesnic, S.; Kaita, R.; Kaye, S.; Okabayashi, M.; Takahashi, H.; Bell, R.E.; Bernabei, S.; Chance, M.S.; Hatcher, R.E.; Jardin, S.C.; Kessel, C.E.; Kugel, H.W.; LeBlanc, B.; Manickam, J.; Ono, M.; Paul, S.F.; Sauthoff, N.R.; Holland, A.; Asakura, N.; Duperrex, P.A.; Fonck, R.J.; Gammel, G.M.; Greene, G.J.; Jiang, T.W.; Levinton, F.M.; Powell, E.T.; Roberts, D.W.; Qin, Y.

    1993-06-01

    High-frequency pressure-driven modes have been observed in high-poloidal-{beta} discharges in the Princeton Beta Experiment-Modification (PBX-M). These modes are excited in a non-axisymmetric equilibrium characterized by a large, low frequency m{sub 1}=1/n{sub 1}=1 island, and they are capable of expelling fast ions. The modes reside on or very close to the q=1 surface, and have mode numbers with either m{sub h}=n{sub h} or (less probably) m{sub h}/n{sub h}=m{sub h}/(m{sub h}-1), with m{sub h} varying between 3 and 10. Occasionally, these modes are, simultaneously localized in the vicinity of the m{sub 1}=2/n{sub 1}=1 island. The high frequency modes near the q=1 surface also exhibit a ballooning character, being significantly stronger on the large major radius side of the plasma. When a large m{sub 1}=1/n{sub 1}=1 island is present the mode is poloidally localized in the immediate vicinity of the x-point of the island. The modes, which occur exclusively in high-{beta} discharges, appear to be driven by the plasma pressure or pressure gradient. They can thus be a manifestation of either a toroidicity-induced shear Alfven eigenmode (TAE) at q=(2m{sub h}+ 1)/2n{sub h}, a kinetic ballooning mode (KBM), or some other type of pressure-driven mode. Theory predicts that the TAE mode is a gap mode, but the high frequency modes in PBX-M are found exclusively on or in the immediate neighborhood of magnetic surfaces with low rational numbers.

  8. High frequency capacitance-voltage characteristics of thermally grown SiO2 films on beta-SiC

    NASA Technical Reports Server (NTRS)

    Tang, S. M.; Berry, W. B.; Kwor, R.; Zeller, M. V.; Matus, L. G.

    1990-01-01

    Silicon dioxide films grown under dry and wet oxidation environment on beta-SiC films have been studied. The beta-SiC films had been heteroepitaxially grown on both on-axis and 2-deg off-axis (001) Si substrates. Capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor structures were measured in a frequency range of 10 kHz to 1 MHz. From these measurements, the interface trap density and the effective fixed oxide charge density were observed to be generally lower for off-axis samples.

  9. High Beta Tokamaks

    SciTech Connect

    Cowley, S.

    1998-11-14

    Perhaps the ideal tokamak would have high {beta} ({beta} {approx}> 1) and classical confinement. Such a tokamak has not been found, and we do not know if one does exist. We have searched for such a possibility, so far without success. In 1990, we obtained analytic equilibrium solutions for large aspect ratio tokamaks at {beta} {approx} {Omicron}(1) [1]. These solutions and the extension at high {beta} poloidal to finite aspect ratio [2] provided a basis for the study of high {beta} tokamaks. We have shown that these configurations can be stable to short scale MHD modes [3], and that they have reduced neoclassical transport [4]. Microinstabilities (such as the {del}T{sub i} mode) seem to be stabilized at high {beta} [5] - this is due to the large local shear [3] and the magnetic well. We have some concerns about modes associated with the compressional branch which may appear at high {beta}. Bill Dorland and Mike Kotschenreuther have studied this issue and our concerns may be unfounded. It is certainly tantalizing, especially given the lowered neoclassical transport values, that these configurations could have no microinstabilities and, one could assume, no anomalous transport. Unfortunately, while this work is encouraging, the key question for high {beta} tokamaks is the stability to large scale kink modes. The MHD {beta} limit (Troyon limit) for kink modes at large aspect ratio is problematically low. There is ample evidence from computations that the limit exists. However, it is not known if stable equilibria exist at much higher {beta}--none have been found. We have explored this question in the asymptotic high {beta} poloidal limit. Unfortunately, we are unable to find stable equilibrium and also unable to show that they don't exist. The results of these calculations will be published when a more definitive answer is found.

  10. High beta multipoles

    SciTech Connect

    Prager, S C

    1982-05-01

    Multipoles are being employed as devices to study fusion issues and plasma phenomena at high values of beta (plasma pressure/magnetic pressure) in a controlled manner. Due to their large volume, low magnetic field (low synchrotron radiation) region, they are also under consideration as potential steady state advanced fuel (low neutron yield) reactors. Present experiments are investigating neoclassical (bootstrap and Pfirsch-Schlueter) currents and plasma stability at extremely high beta.

  11. High frequency of beta-propeller protein-associated neurodegeneration (BPAN) among patients with intellectual disability and young-onset parkinsonism.

    PubMed

    Nishioka, Kenya; Oyama, Genko; Yoshino, Hiroyo; Li, Yuanzhe; Matsushima, Takashi; Takeuchi, Chisen; Mochizuki, Yoko; Mori-Yoshimura, Madoka; Murata, Miho; Yamasita, Chikara; Nakamura, Norimichi; Konishi, Yohei; Ohi, Kazuki; Ichikawa, Keiji; Terada, Tatsuhiro; Obi, Tomokazu; Funayama, Manabu; Saiki, Shinji; Hattori, Nobutaka

    2015-05-01

    Neurodegeneration with brain iron accumulation (NBIA) is a genetically heterogeneous disorder, characterized by the accumulation of iron in regions such as the basal ganglia. We enrolled 28 patients with childhood intellectual disability and young-onset parkinsonism (≤40 years at onset) and 4 patients with infantile neuroaxonal dystrophy. All had been clinically diagnosed, and the prevalence of genetic mutations linked to NBIA (PANK2 [exons 1-7], PLA2G6 [exons 2-17], C19orf12 [exons 1-3], WDR45 [exons 2-11], COASY [exons 1-9], FA2H [exons 1-7], and RAB39B [exons 1, 2]) was evaluated. We detected 7 female patients (25.0%, 7 of 28) with de novo heterozygote WDR45 mutations, which are known to be pathogenic for beta-propeller protein-associated neurodegeneration. All 7 patients had common clinical features. Pathogenic mutations in other NBIA genes were not found. We also screened 98 patients with early-onset parkinsonism without intellectual disability and 110 normal controls of Japanese origin for WDR45 mutations. None had WDR45 mutations. Our data suggest a high frequency of beta-propeller protein-associated neurodegeneration mutations in the Japanese population. PMID:25744623

  12. DC and high-frequency conductivity of the organic metals {beta}"-(BEDT-TFF){sub 2}SF{sub 5}RSO{sub 3} (R=CH{sub 2}CF{sub 2} and CHF).

    SciTech Connect

    Glied, M.; Yasin, S.; Kaiser, S.; Drichko, N.; Dressel, M.; Schlueter, J. A.; Materials Science Division; Univ. Stuttgart

    2009-01-01

    The temperature dependences of the electric-transport properties of the two-dimensional organic conductors {beta}''-(BEDT-TTF)2SF5CH2CF2SO3, {beta}''-(d8-BEDT-TTF)2SF5CH2CF2SO3, and {beta}''-(d8-BEDT-TTF)2SF5CH2CF2SO3 are measured by dc methods in and perpendicular to the highly conducting plane. Microwave measurements are performed at 24 and 33.5 GHz to probe the high-frequency behavior from room temperature down to 2 K. Superconductivity is observed in {beta}''-(BEDT-TTF)2SF5CH2CF2SO3 and its deuterated analogue. Although all the compounds remain metallic down to low-temperatures, they are close to a charge-order transition. This leads to deviations from a simple Drude behavior of the optical conductivity which become obvious already in the microwave range. In {beta}''-(BEDT-TTF)2SF5CH2CF2SO3, for instance, charge fluctuations cause an increase in microwave resistivity for T<20 K which is not detected in dc measurements. {beta}''-(BEDT-TTF)2SF5CHFSO3 exhibits a simple metallic behavior at all frequencies. In the dc transport, however, we observe indications of localization in the perpendicular direction.

  13. High beta plasmas in the PBX tokamak

    SciTech Connect

    Bol, K.; Buchenauer, D.; Chance, M.; Couture, P.; Fishman, H.; Fonck, R.; Gammel, G.; Grek, B.; Ida, K.; Itami, K.

    1986-04-01

    Bean-shaped configurations favorable for high ..beta.. discharges have been investigated in the Princeton Beta Experiment (PBX) tokamak. Strongly indented bean-shaped plasmas have been successfully formed, and beta values of over 5% have been obtained with 5 MW of injected neutral beam power. These high beta discharges still lie in the first stability regime for ballooning modes, and MHD stability analysis implicates the external kink as responsible for the present ..beta.. limit.

  14. Linkage disequilibrium between the beta frequency of the human EEG and a GABAA receptor gene locus

    PubMed Central

    Porjesz, Bernice; Almasy, Laura; Edenberg, Howard J.; Wang, Kongming; Chorlian, David B.; Foroud, Tatiana; Goate, Alison; Rice, John P.; O'Connor, Sean J.; Rohrbaugh, John; Kuperman, Samuel; Bauer, Lance O.; Crowe, Raymond R.; Schuckit, Marc A.; Hesselbrock, Victor; Conneally, P. Michael; Tischfield, Jay A.; Li, Ting-Kai; Reich, Theodore; Begleiter, Henri

    2002-01-01

    Human brain oscillations represent important features of information processing and are highly heritable. A common feature of beta oscillations (13–28 Hz) is the critical involvement of networks of inhibitory interneurons as pacemakers, gated by γ-aminobutyric acid type A (GABAA) action. Advances in molecular and statistical genetics permit examination of quantitative traits such as the beta frequency of the human electroencephalogram in conjunction with DNA markers. We report a significant linkage and linkage disequilibrium between beta frequency and a set of GABAA receptor genes. Uncovering the genes influencing brain oscillations provides a better understanding of the neural function involved in information processing. PMID:11891318

  15. Neoclassical transport in high [beta] tokamaks

    SciTech Connect

    Cowley, S.C.

    1992-12-01

    Neoclassical, transport in high [beta] large aspect ratio tokamaks is calculated. The variational method introduced by Rosenbluth, et al., is used to calculate the full Onsager matrix in the banana regime. These results are part of a continuing study of the high [beta] large aspect ratio equilibria introduced in Cowley, et al. All the neoclassical coefficients are reduced from their nominal low [beta] values by a factor ([var epsilon]/q[sup 2][beta])[sup [1/2

  16. Beta Frequency Synchronization in Basal Ganglia Output during Rest and Walk in a Hemiparkinsonian Rat

    PubMed Central

    Avila, Irene; Parr-Brownlie, Louise C.; Brazhnik, Elena; Castañeda, Edward; Bergstrom, Debra A.; Walters, J. R.

    2012-01-01

    Synchronized oscillatory neuronal activity in the beta frequency range has been observed in the basal ganglia of Parkinson’s disease patients and hypothesized to be antikinetic. The unilaterally lesioned rat model of Parkinson’s disease allows examination of this hypothesis by direct comparison of beta activity in basal ganglia output in non-lesioned and dopamine cell lesioned hemispheres during motor activity. Bilateral substantia nigra pars reticulata (SNpr) recordings of units and local field potentials (LFP) were obtained with EMG activity from the scapularis muscle in control and unilaterally nigrostriatal lesioned rats trained to walk on a rotary treadmill. After left hemispheric lesion, rats had difficulty walking contraversive on the treadmill but could walk in the ipsiversive direction. During inattentive rest, SNpr LFP power in the 12–25 Hz range (low beta) was significantly greater in the dopamine-depleted hemisphere than in non-lesioned and control hemispheres. During walking, low beta power was reduced in all hemispheres, while 25–40 Hz (high beta) activity was selectively increased in the lesioned hemisphere. High beta power increases were reduced by L-DOPA administration. SNpr spiking was significantly more synchronized with SNpr low beta LFP oscillations during rest and high beta LFP oscillations during walking in the dopamine-depleted hemispheres compared with non-lesioned hemispheres. Data show that dopamine loss is associated with opposing changes in low and high beta range SNpr activity during rest and walk and suggest that increased synchronization of high beta activity in SNpr output from the lesioned hemisphere during walking may contribute to gait impairment in the hemiparkinsonian rat. PMID:19948166

  17. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique. PMID:25636803

  18. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

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

  19. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

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

  20. Hypnotic induction is followed by state-like changes in the organization of EEG functional connectivity in the theta and beta frequency bands in high-hypnotically susceptible individuals

    PubMed Central

    Jamieson, Graham A.; Burgess, Adrian P.

    2014-01-01

    Altered state theories of hypnosis posit that a qualitatively distinct state of mental processing, which emerges in those with high hypnotic susceptibility following a hypnotic induction, enables the generation of anomalous experiences in response to specific hypnotic suggestions. If so then such a state should be observable as a discrete pattern of changes to functional connectivity (shared information) between brain regions following a hypnotic induction in high but not low hypnotically susceptible participants. Twenty-eight channel EEG was recorded from 12 high susceptible (highs) and 11 low susceptible (lows) participants with their eyes closed prior to and following a standard hypnotic induction. The EEG was used to provide a measure of functional connectivity using both coherence (COH) and the imaginary component of coherence (iCOH), which is insensitive to the effects of volume conduction. COH and iCOH were calculated between all electrode pairs for the frequency bands: delta (0.1–3.9 Hz), theta (4–7.9 Hz) alpha (8–12.9 Hz), beta1 (13–19.9 Hz), beta2 (20–29.9 Hz) and gamma (30–45 Hz). The results showed that there was an increase in theta iCOH from the pre-hypnosis to hypnosis condition in highs but not lows with a large proportion of significant links being focused on a central-parietal hub. There was also a decrease in beta1 iCOH from the pre-hypnosis to hypnosis condition with a focus on a fronto-central and an occipital hub that was greater in high compared to low susceptibles. There were no significant differences for COH or for spectral band amplitude in any frequency band. The results are interpreted as indicating that the hypnotic induction elicited a qualitative change in the organization of specific control systems within the brain for high as compared to low susceptible participants. This change in the functional organization of neural networks is a plausible indicator of the much theorized “hypnotic-state.” PMID:25104928

  1. High frequency electromagnetic tomography

    SciTech Connect

    Daily, W.; Ramirez, A.; Ueng, T.; Latorre, R.

    1989-09-01

    An experiment was conducted in G Tunnel at the Nevada Test Site to evaluate high frequency electromagnetic tomography as a candidate for in situ monitoring of hydrology in the near field of a heater placed in densely welded tuff. Tomographs of 200 MHz electromagnetic permittivity were made for several planes between boreholes. Data were taken before the heater was turned on, during heating and during cooldown of the rockmass. This data is interpreted to yield maps of changes in water content of the rockmass as a function of time. This interpretation is based on laboratory measurement of electromagnetic permittivity as a function of water content for densely welded tuff. 8 refs., 6 figs.

  2. High-frequency ventilation.

    PubMed

    Crawford, M R

    1986-08-01

    Over the last six years high-frequency ventilation has been extensively evaluated both in the clinical and laboratory settings. It is now no longer the great mystery it once was, and it is now no longer believed (as many had hoped), that it will solve all the problems associated with mechanical pulmonary ventilation. Although the technique is safe and appears to cause no harm even in the long term, it has not yet been shown to offer any major advantages over conventional mechanical ventilation. PMID:3530042

  3. Increased frequency of CD4{sup -}8{sup -}T cells bearing T-cell receptor {alpha}{beta} chains in peripheral blood of atomic bomb survivors exposed to high doses

    SciTech Connect

    Yoichiro Kusunoki; Seishi Kyoizumi; Yuko Hirai; Shoichiro Fujita; Mitoshi Akiyama

    1994-07-01

    A rare T-cell subpopulation, CD4{sup -z}8{sup -}{alpha}{beta} cells, may be differentiated through a pathway (or pathways) different from the pathway(s) of conventional CD4+ or CD8+ cells. In the present study, the frequencies of CD4{sup -}8{sup -} T cells in peripheral-blood {alpha}{beta} T cells in 409 atomic bomb survivors were determined to investigate late effects of radiation on the composition of human T-cell subpopulations. The frequency of CD4{sup -}8{sup -}{alpha}{beta} T-cell decreased significantly with the subject`s age and was higher in females than males. A significant increase in the frequency was found in the survivors exposed to more than 1.5Gy, suggesting that the previous radiation exposure altered differentiation and development of T cells. 25 refs., 4 figs., 3 tabs.

  4. High-frequency ECG

    NASA Technical Reports Server (NTRS)

    Tragardh, Elin; Schlegel, Todd T.

    2006-01-01

    The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal. With high-resolution technology, it is possible to record and analyze these higher frequencies. The highest amplitudes of the high-frequency components are found within the QRS complex. In past years, the term "high frequency", "high fidelity", and "wideband electrocardiography" have been used by several investigators to refer to the process of recording ECGs with an extended bandwidth of up to 1000 Hz. Several investigators have tried to analyze HF-QRS with the hope that additional features seen in the QRS complex would provide information enhancing the diagnostic value of the ECG. The development of computerized ECG-recording devices that made it possible to record ECG signals with high resolution in both time and amplitude, as well as better possibilities to store and process the signals digitally, offered new methods for analysis. Different techniques to extract the HF-QRS have been described. Several bandwidths and filter types have been applied for the extraction as well as different signal-averaging techniques for noise reduction. There is no standard method for acquiring and quantifying HF-QRS. The physiological mechanisms underlying HF-QRS are still not fully understood. One theory is that HF-QRS are related to the conduction velocity and the fragmentation of the depolarization wave in the myocardium. In a three-dimensional model of the ventricles with a fractal conduction system it was shown that high numbers of splitting branches are associated with HF-QRS. In this experiment, it was also shown that the changes seen in HF-QRS in patients with myocardial ischemia might be due to the slowing of the conduction velocity in the region of ischemia. This mechanism has been tested by Watanabe et al by infusing sodium channel blockers into the left anterior descending artery in dogs. In their study, 60 unipolar ECGs were recorded from the entire

  5. Study of high-beta ballooning modes

    SciTech Connect

    Price, H.D.; Benjamin, N.M.P.; Kang, B.K.; Lichtenberg, A.J.; Lieberman, M.A.

    1985-01-01

    Ballooning instabilities are studied in the Berkeley multiple mirror experiment. Counterstreaming theta pinch and Marshall gun source hydrogen plasmas are used to achieve a high beta ( ..beta..>25%), where ..beta.. is the ratio of plasma to magnetic pressure at temperatures T/sub e/ = T/sub i/roughly-equal15 eV. Four magnetic field configurations are investigated, each at varying mirror ratios, to explore a range of drive and connection length parameters. In two of these the magnetic field is pulsed from a stable to a locally unstable configuration for initiation of ballooning activity. The other two (static) configurations are a weakly unstable local field region, and the standard linked quadrupole multiple-mirror configuration. Depending on the configuration, critical ..beta..'s are found for the onset of ballooning that vary from 5% for the most unstable configuration to greater than 25% for the standard multiple-mirror configuration. The m = 1 azimuthal mode is predominant, with some admixture of m = 2. The experimental results are compared with predictions from a magnetohydrodynamic theory. In the model the pressure is taken to be isotropic and constant along the axis, except in the diverging field regions at the device ends where the pressure falls to maintain beta constant, consistent with experimental observations. The theoretical results generally predict somewhat higher critical betas for the m = 1 mode than those observed. Estimates of the effect of finite Larmor radii, nearby conducting walls, axially nonuniform pressure profiles and resistivity, are also given.

  6. High-Frequency Gated Oscillator

    NASA Technical Reports Server (NTRS)

    Berard, C. A.

    1982-01-01

    New gated oscillator generates bursts of high-frequency sine waves, square waves, and triangular waves in response to control signals. Each burst starts at zero phase, with tight tolerances on signal amplitude and frequency. Frequencies in megahertz range are made possible by using high-speed comparators and high-speed flip-flop as fast-response threshold detector.

  7. Neoclassical transport in high {beta} tokamaks

    SciTech Connect

    Cowley, S.C.

    1992-12-01

    Neoclassical, transport in high {beta} large aspect ratio tokamaks is calculated. The variational method introduced by Rosenbluth, et al., is used to calculate the full Onsager matrix in the banana regime. These results are part of a continuing study of the high {beta} large aspect ratio equilibria introduced in Cowley, et al. All the neoclassical coefficients are reduced from their nominal low {beta} values by a factor ({var_epsilon}/q{sup 2}{beta}){sup {1/2}} II. This factor is the ratio of plasma volume in the boundary layer to the volume in the core. The fraction of trapped particles on a given flux surface (f{sub t}) is also reduced by this factor so that {approximately} {sub ({var_epsilon}}/q{sup 2}{beta}){sup {1/2}}. Special attention is given to the current equation, since this is thought to be relevant at low 3 and therefore may also be relevant at high {beta}. The bootstrap current term is found to exceed the actual current by a factor of the square root of the aspect ratio.

  8. High beta and confinement studies of TFTR

    SciTech Connect

    Navratil, G.A.; Bhattacharjee, A.; Iacono, R.; Mauel, M.E.; Sabbagh, S.A. ); Kesner, J. )

    1993-01-01

    The project discussed in this report are: Enhanced High Poloidal Beta Operation in TFTR with Deuterium Pellet Injection; Approaching High Q by Utilizing High [beta][sub p] Operation in TFTR; Advanced Tokamak Regime Experiment, and Second Regime Studies at large Major Radius High [beta][sub p] Plasmas. Analysis of the data taken during these experiments as well as continuing analysis of earlier data led to a number important results described in publications in the past year including two invited presentations at the 1992 American Physical Society Division of Plasma Physics Meeting in Seattle an oral presentation at the 1992 IAEA Meeting in Wuertzburg, Germany, and a Physical Review Letter. These results included extending the high 11/2 regime to 1.2 MA current and neutron production rates to more than 3 [times] 10[sup 16] sec[sup [minus

  9. Observations of high-beta toroidal plasmas

    NASA Astrophysics Data System (ADS)

    Halle, J. H.; Kellman, A. G.; Post, R. S.; Prager, S. C.; Strait, E. J.; Zarnstorff, M. C.

    1981-05-01

    A range of MHD stable high-beta plasmas is attained both in the kinetic regime with beta equal to 33% (nine times the fluid ballooning limit) and near the single-fluid regime with beta equal to 8% (twice the theoretical limit). It is found that MHD theory is inadequate and that kinetic effects are apparently more powerful than is generally assumed. It is pointed out that since a reactor (with trapped particles, large-gyroradii ions from neutral beams) may be no more fluid-like than the octupole experiments, their designs should perhaps not necessarily be constrained by the MHD ballooning instability beta limit. Diamagnetic current measurements are found to agree roughly with single-fluid results in the fluid-like case but to depart sharply in the kinetic regime.

  10. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing; Zettl, Alexander K.

    2012-02-21

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

  11. Numerical models for high beta magnetohydrodynamic flow

    SciTech Connect

    Brackbill, J.U.

    1987-01-01

    The fundamentals of numerical magnetohydrodynamics for highly conducting, high-beta plasmas are outlined. The discussions emphasize the physical properties of the flow, and how elementary concepts in numerical analysis can be applied to the construction of finite difference approximations that capture these features. The linear and nonlinear stability of explicit and implicit differencing in time is examined, the origin and effect of numerical diffusion in the calculation of convective transport is described, and a technique for maintaining solenoidality in the magnetic field is developed. Many of the points are illustrated by numerical examples. The techniques described are applicable to the time-dependent, high-beta flows normally encountered in magnetically confined plasmas, plasma switches, and space and astrophysical plasmas. 40 refs.

  12. Beta Peak Frequencies at Rest Correlate with Endogenous GABA+/Cr Concentrations in Sensorimotor Cortex Areas

    PubMed Central

    Baumgarten, Thomas J.; Oeltzschner, Georg; Hoogenboom, Nienke; Wittsack, Hans-Jörg; Schnitzler, Alfons; Lange, Joachim

    2016-01-01

    Neuronal oscillatory activity in the beta band (15–30 Hz) is a prominent signal within the human sensorimotor cortex. Computational modeling and pharmacological modulation studies suggest an influence of GABAergic interneurons on the generation of beta band oscillations. Accordingly, studies in humans have demonstrated a correlation between GABA concentrations and power of beta band oscillations. It remains unclear, however, if GABA concentrations also influence beta peak frequencies and whether this influence is present in the sensorimotor cortex at rest and without pharmacological modulation. In the present study, we investigated the relation between endogenous GABA concentration (measured by magnetic resonance spectroscopy) and beta oscillations (measured by magnetoencephalography) at rest in humans. GABA concentrations and beta band oscillations were measured for left and right sensorimotor and occipital cortex areas. A significant positive linear correlation between GABA concentration and beta peak frequency was found for the left sensorimotor cortex, whereas no significant correlations were found for the right sensorimotor and the occipital cortex. The results show a novel connection between endogenous GABA concentration and beta peak frequency at rest. This finding supports previous results that demonstrated a connection between oscillatory beta activity and pharmacologically modulated GABA concentration in the sensorimotor cortex. Furthermore, the results demonstrate that for a predominantly right-handed sample, the correlation between beta band oscillations and endogenous GABA concentrations is evident only in the left sensorimotor cortex. PMID:27258089

  13. High Temperature Stability of Potassium Beta Alumina

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Kisor, A.; Ryan, M. A.

    1996-01-01

    None. From Objectives section: Evaluate the stability of potassium beta alumina under potassium AMTEC operating conditions. Evaluate the stability regime in which potassium beta alumina can be fabricated.

  14. Project 8: Determining neutrino mass from tritium beta decay using a frequency-based method

    SciTech Connect

    Doe, Peter J.; Kofron, Jared N.; MCBride, Lisa; Robertson, R. G. H.; Rosenberg, Leslie; Rybka, Gray; Doelman, S.; Rogers, Alan E.; Formaggio, Joseph; Furse, Daniel; Oblath, Noah S.; LaRoque, Benjamin; Leber, Michelle; Monreal, Ben; Bahr, Matthew; Asner, David M.; Jones, Anthony M.; Fernandes, Justin L.; VanDevender, Brent A.; Patterson, Ryan B.; Bradley, Rich; Thummler, Thomas

    2013-10-04

    A general description is given of Project 8, a new approach to measuring the neutrino mass scale via the beta decay of tritium. In Project 8, the energy of electrons emitted in beta decay is determined from the frequency of cyclotron radiation emitted as the electrons spiral in a uniform magnetic field

  15. The high sensitivity double beta spectrometer TGV

    NASA Astrophysics Data System (ADS)

    Briancon, Ch.; Brudanin, V. B.; Egorov, V. G.; Janout, Z.; Koníček, J.; Kovalík, A.; Kovalenko, V. E.; Kubašta, J.; Pospíšil, S.; Revenko, A. V.; Rukhadze, N. I.; Salamatin, A. V.; Sandukovsky, V. G.; Štekl, I.; Timkin, V. V.; Tsupko-Sitnikov, V. V.; Vorobel, V.; Vylov, Ts.

    1996-02-01

    A high sensitivity double beta spectrometer TGV (Telescope Germanium Vertical) has been developed. It is based on 16 HPGe detectors of volume 1200 × 6 mm 3 each in the same cryostat. The TGV spectrometer was proposed for the study of ultrarare nuclear processes (e.g. 2νββ, 0νββ, 2νEC/EC). Details of the TGV spectrometer construction are described, the principles of background suppression, the results of Monte Carlo simulations and the results of test background measurements (in Dubna and Modane underground laboratory) are provided.

  16. Mobile high frequency vibrator system

    SciTech Connect

    Fair, D.W.; Buller, P.L.

    1985-01-08

    A carrier mounted seismic vibrator system that is primarily adapted for generation of high force, high frequency seismic energy into an earth medium. The apparatus includes first and second vibrators as supported by first and second lift systems disposed in tandem juxtaposition generally centrally in said vehicle, and the lift systems are designed to maintain equal hold-down force on the vibrator coupling baseplates without exceeding the weight of the carrier vehicle. The juxtaposed vibrators are then energized in synchronized relationship to propagate increased amounts of higher frequency seismic energy into an earth medium.

  17. Bound-state beta decay of highly ionized atoms

    SciTech Connect

    Takahashi, K.; Boyd, R.N.; Mathews, G.J.; Yokoi, K.

    1987-10-01

    Nuclear ..beta.. decays of highly ionized atoms under laboratory conditions are studied. Theoretical predictions of ..beta..-decay rates are given for a few cases in which bound-state ..beta.. decay produces particularly interesting effects. A possible storage-ring experiment is proposed for measuring bound-state ..beta..-decay rates, which will be most easily applied to the decay of /sup 3/H/sup +/. .AE

  18. High frequency integrated MOS filters

    NASA Technical Reports Server (NTRS)

    Peterson, C.

    1990-01-01

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

  19. Interaction of high-energy trapped particles with ballooning modes in a tokamak with a high-. beta. plasma

    SciTech Connect

    Mikhailovskii, A. B.; Novakovaskii, S. V.; Smolyakov, A. I.

    1988-12-01

    A theory is derived for the interaction of high-energy trapped particleswith ballooning modes in a tokamak with a high-..beta.. plasma. A dispersionrelation is derived to describe the ballooning modes in the presence ofsuch particles; the effects of the high plasma ..beta.. are taken into account.The stability boundary for ballooning modes with zero and finite frequenciesis studied. The effects of finite bananas on the stability of ballooningmodes with zero frequencies are determined.

  20. Resistive MHD studies of high-beta Tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Lynch, V. E.; Hicks, H. R.; Holmes, J. A.; Carreras, B. A.; Garcia, L.

    1982-02-01

    The magnetohydrodynamic (MHD) activity in high beta Tokamaks such as ISX-B was calculated. These initial value calculations are built on earlier low beta techniques, but the beta effects create several new numerical issues. In addition to time stepping modules, the system of computer codes includes equilibrium solvers (used to provide an initial condition) and output modules, such as a magnetic field line follower and an X-ray diagnostic code. The transition from current driven modes a low beta to predominantly pressure driven modes at high beta is described. The nonlinear studies yield X-ray emissivity plots which are compared with experiment.

  1. Bioavailability of beta-carotene (betaC) from purple carrots is the same as typical orange carrots while high-betaC carrots increase betaC stores in Mongolian gerbils (Meriones unguiculatus)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vitamin A (VA) deficiency is a worldwide public health problem. Biofortifying existing sources of beta-carotene (betaC) and increasing dietary betaC could help combat the issue. Two studies were performed to investigate the relative betaC bioavailability of a betaC supplement to purple, high-betaC o...

  2. Gyrokinetic turbulence simulations at high plasma beta

    SciTech Connect

    Pueschel, M. J.; Kammerer, M.; Jenko, F.

    2008-10-15

    Electromagnetic gyrokinetic turbulence simulations employing Cyclone Base Case parameters are presented for {beta} values up to and beyond the kinetic ballooning threshold. The {beta} scaling of the turbulent transport is found to be linked to a complex interplay of linear and nonlinear effects. Linear investigation of the kinetic ballooning mode is performed in detail, while nonlinearly, it is found to dominate the turbulence only in a fairly narrow range of {beta} values just below the respective ideal limit. The magnetic transport scales like {beta}{sup 2} and is well described by a Rechester-Rosenbluth-type ansatz.

  3. High frequency power distribution system

    NASA Technical Reports Server (NTRS)

    Patel, Mikund R.

    1986-01-01

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

  4. Alfven cascade modes at high {beta} in the National Spherical Torus Experiment

    SciTech Connect

    Crocker, N. A.; Kubota, S.; Fredrickson, E. D.; Gorelenkov, N. N.; Kramer, G. J.; Darrow, D. S.; Menard, J. E.; LeBlanc, B. P.; Bell, R. E.; Heidbrink, W. W.; Levinton, F. M.; Yuh, H.

    2008-10-15

    Alfven cascade (AC) modes are observed in the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] reversed shear plasmas over a wide range (up to {approx}25% on axis, or {approx}11% at minimum q) of {beta} (ratio of kinetic pressure to magnetic pressure). At low {beta}, the AC mode spectrum shows characteristics similar to conventional tokamaks. At higher {beta}, distinct {beta} and {nabla}{beta} effects are observed in the spectrum, including a significant reduction in the relative size of the frequency sweep and a toroidal mode number dependence in the minimum mode frequency. AC mode structure is obtained using reflectometry. Fast-ion loss associated with AC mode activity is observed. AC mode polarization at the plasma edge is consistent with expectation. Magnetohydrodynamic (MHD) spectroscopy is shown to be usable to determine q{sub min} at both low {beta} and high {beta}. Observed AC mode structure and frequency are found to be consistent with calculations for the same plasma conditions and geometry using the linear, ideal MHD hybrid kinetic code NOVA-K[C. Z. Cheng, Phys. Rep. 211, 1 (1992)].

  5. 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.

  6. Frequency shifts of high frequency p-modes

    NASA Technical Reports Server (NTRS)

    Jain, Rekha

    1995-01-01

    Frequency shifts of high frequency p-modes during the solar cycle are calculated for a non-magnetic polytrope convection zone model. An isothermal chromospheric atmosphere threaded by a uniform horizontal magnetic field is correlated to this model. The relevant observations of such frequency changes are discussed. The calculated simultaneous changes in the field strength and chromospheric temperature result in the frequency shifts that are similar to those of the observations.

  7. High-frequency Broadband Modulations of Electroencephalographic Spectra

    PubMed Central

    Onton, Julie; Makeig, Scott

    2009-01-01

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

  8. Observation of a fast beta collapse during high poloidal-beta discharges in JT-60

    SciTech Connect

    Ishida, S.; Koide, Y.; Ozeki, T.; Kikuchi, M.; Tsuji, S.; Shirai, H.; Naito, O.; Azumi, M. )

    1992-03-09

    A nondisruptive {beta}-limiting phenomenon in a large tokamak under a large bootstrap current fraction, up to {similar to}80% of the plasma current, is described; {beta}=(plasma pressure)/(magnetic pressure). During long-pulse neutral-beam-heated discharges in the JT-60 tokamak, it occurs at {beta}{sub {ital p}}{similar to}3, leading to a limit of the normalized {beta} lower than the Troyon limit. The MHD feature is characterized by a large-amplitude partial relaxation with a fast growth time. A hollow current profile evolution in the high-{beta}{sub {ital p}} regime plays an essential role in the MHD stability, analysis of which shows that the ideal {ital n}=1 kink-ballooning modes can be unstable just before the collapse.

  9. A beta2-frequency (20–30 Hz) oscillation in nonsynaptic networks of somatosensory cortex

    PubMed Central

    Roopun, Anita K.; Middleton, Steven J.; Cunningham, Mark O.; LeBeau, Fiona E. N.; Bibbig, Andrea; Whittington, Miles A.; Traub, Roger D.

    2006-01-01

    Beta2 frequency (20–30 Hz) oscillations appear over somatosensory and motor cortices in vivo during motor preparation and can be coherent with muscle electrical activity. We describe a beta2 frequency oscillation occurring in vitro in networks of layer V pyramidal cells, the cells of origin of the corticospinal tract. This beta2 oscillation depends on gap junctional coupling, but it survives a cut through layer 4 and, hence, does not depend on apical dendritic electrogenesis. It also survives a blockade of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors or a blockade of GABAA receptors that is sufficient to suppress gamma (30–70 Hz) oscillations in superficial cortical layers. The oscillation period is determined by the M type of K+ current. PMID:17030821

  10. High Frequency Stable Oscillate boiling

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  11. High frequency dynamic nuclear polarization.

    PubMed

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

    2013-09-17

    During the three decades 1980-2010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical, and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited by the low sensitivity of the experiments, due in large part to the necessity of observing spectra of low-γ nuclei such as the I = 1/2 species (13)C or (15)N. The difficulty is still greater when quadrupolar nuclei, such as (17)O or (27)Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime, roughly 150-660 GHz, and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades, scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low

  12. High Frequency Dynamic Nuclear Polarization

    PubMed Central

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

    2013-01-01

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

  13. Beta-globin gene cluster haplotype frequencies in Khalkhs and Buryats of Mongolia.

    PubMed

    Shimizu, Koji; Tokimasa, Kozue; Takeuchi, Yukiko; Gereksaikhan, Tudevdagva; Tanabe, Yuichi; Omoto, Keiichi; Imanishi, Tadashi; Harihara, Shinji; Hao, Luping; Jing, Feng

    2006-12-01

    Beta-globin gene cluster haplotype frequencies of 169 Khalkhs and 145 Buryats were estimated, and their characteristics were compared with those of Evenkis, Oroqens, Koreans, Japanese, and three Colombian Amerindian groups. The present study suggests that Colombian Amerindians diverged first from Asian populations and then Buryats diverged from other Asian populations. PMID:17564253

  14. High-Frequency Inductor Materials

    NASA Astrophysics Data System (ADS)

    Varga, L. K.

    2014-01-01

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

  15. Beta and gamma frequency-range abnormalities in parkinsonian patients under cognitive sensorimotor task.

    PubMed

    Dushanova, Juliana; Philipova, Dolja; Nikolova, Gloria

    2010-06-15

    Parkinson's disease (PD) is a neurodegenerative disorder caused by a disruption of dopaminergic neurotransmission in the basal ganglia. Some of PD clinical symptoms are suggested to stem directly from the excessive synchrony between the basal ganglia and cortical circuits. Our present investigation explores the functional relationships between event-related desynchronization/synchronization (ERD/ERS) of beta and gamma band activity for idiopathic non-demented Parkinson's patients (PP) and control subjects (CS) during auditory discrimination tasks between two tone types (LT: 800 Hz, HT: 1000 Hz) within two post-stimulus intervals of 0-250 and 250-600 ms. Beta1 (13-20 Hz) ERD was found for both groups within both intervals more expressed in CS except for frontal beta1 synchronization in CS during the second interval. Beta2 (20-32 Hz) ERD was revealed in CS after both tones during both post-stimulus intervals. Beta2 ERS was only observed in PP. The most prominent beta2 ERS followed HT during the second interval. Gamma frequency (32-50 Hz) ERD was found in both groups except for fronto-parietal ERS for PP during the first interval after LT. During the second interval, either tone, we found prominent ERS for PP and ERD for CS everywhere except for a frontal ERS after HT. Deviations of the beta and gamma ERD/ERS for the PP compared with CS during the sensorimotor and cognitive processing are a clear evidence for disturbances in the temporal and regional integration of these frequency components and the relationships between cortical and the basal ganglia circuits in parkinsonism. PMID:20392453

  16. Pressurized high frequency thermoacoustic engines

    NASA Astrophysics Data System (ADS)

    Webb, Nicholas D.

    Acoustic heat engines show much promise for converting waste heat to electricity. Since most applications require high power levels, high frequency thermoacoustic engines can reach such performance by operating with a pressurized working gas. Results on a 3 kHz prime mover, consisting of a quarter-wave resonator and a random stack material between two heat exchangers, show that the acoustic power from such a device is raised substantially as the working gas is pressurized. At pressures up to approximately 10 bar, the increase in acoustic power is approximately linear to the increase in pressure, and thus is an effective way to increase the power output of thermoacoustic engines. Since the heat input was not changed during the experiments, the increases in acoustic power translate directly to increases in engine efficiency which is calculated as the output acoustic power divided by the input heat power. In most experiments run in this study, the engine efficiency increased by a factor of at least 4 as the pressure was increased from 2 bar up to about 10 bar. Further increases in pressure lead to acoustic power saturation and eventual attenuation. This is most likely due to a combination of several factors including the shrinking thermal penetration depth, and the fact that the losses increase faster with pressure in a random stack material than in traditional parallel plates. Pressurization also leads to a lower DeltaT for onset of oscillations in the range of 10 bar of mean pressure, potentially opening up even more heat sources that can power a thermoacoustic engine. Results from another 3 kHz engine, one that was pressurized itself as opposed to being placed in a pressurized chamber, are also presented. The configuration of this engine solves the problem of how to simultaneously pressurize the engine and inject heat into the hot heat exchanger. It was also noted that the geometry of the resonator cavity in the quarter wavelength pressurized engine plays an

  17. 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.

  18. Special Aspects in Designing High - Frequency Betatron

    NASA Astrophysics Data System (ADS)

    Filimonov, A. A.; Kasyanov, S. V.; Kasyanov, V. A.

    2016-01-01

    The article is devoted to designing the high - frequency betatron. In high - frequency betatron most important problem is overheating of the elements of the body radiator unit. In an article some directions of solving this problem are shown.

  19. 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.

  20. Resistive MHD studies of high-. beta. -tokamak plasmas

    SciTech Connect

    Lynch, V.E.; Carreras, B.A.; Hicks, H.R.; Holmes, J.A.; Garcia, L.

    1981-01-01

    Numerical calculations have been performed to study the MHD activity in high-..beta.. tokamaks such as ISX-B. These initial value calculations built on earlier low ..beta.. techniques, but the ..beta.. effects create several new numerical issues. These issues are discussed and resolved. In addition to time-stepping modules, our system of computer codes includes equilibrium solvers (used to provide an initial condition) and output modules, such as a magnetic field line follower and an X-ray diagnostic code. The transition from current driven modes at low ..beta.. to predominantly pressure driven modes at high ..beta.. is described. The nonlinear studies yield X-ray emissivity plots which are compared with experiment.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  2. High-beta discharges in the DIII-D tokamak

    SciTech Connect

    Ferron, J.R.; Chu, M.S.; Helton, F.J.; Howl, W.; Kellman, A.G.; Lao, L.L.; Lazarus, E.A.; Lee, J.K.; Osborne, T.H.; Strait, E.J.; Taylor, T.S.; Turnbull, A.D. )

    1990-06-01

    Low-{ital q} ({ital q}{sub 95}{lt}3) double-null divertor discharges with values of the volume-average toroidal beta as high as 9.3% have been operated in the DIII-D tokamak (Fusion Technol. {bold 8}, 441 (1985)). In discharges with {ital q}{sub 95}{approx}5, values of {beta}{sub {ital T}}/({ital I}/{ital aB}) as high as 5 have been obtained. These discharges are shown to be at or below the stability limit to the value of beta for infinite-{ital n}, ideal ballooning modes. The discharges are significantly below the beta limit for ideal,low toroidal mode number kink modes. The kink mode beta limit is shown to be strongly dependent on the radial profiles of plasma pressure and current. The theoretical beta limit in DIII-D is shown to be in the range {beta}{sub {ital T}}/({ital I}/{ital aB})=4 --5 depending on the value of {ital I}/{ital aB}, and this is consistent with the experiment. High-beta discharges have been operated with ion temperature up to 17 keV. Steady-state, high-beta, low-{ital q} operation is demonstrated by a discharge with {ital I}/{ital aB}=2.6, {ital q}{sub 95}=2.7, in which {beta}{sub {ital T}}{gt}7% is maintained for 1.5 sec.

  3. High frequency-heated air turbojet

    NASA Technical Reports Server (NTRS)

    Miron, J. H. D.

    1986-01-01

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

  4. 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. PMID:12071247

  5. Stability of high. beta. large aspect ratio tokamaks

    SciTech Connect

    Cowley, S.C.

    1991-10-01

    High {beta}({beta}{much gt} {epsilon}/q{sup 2}) large aspect ratio ({epsilon} {much gt} 1) tokamak equilibria are shown to be always stable to ideal M.H.D. modes that are localized about a flux surface. Both the ballooning and interchange modes are shown to be stable. This work uses the analytic high {beta} large aspect ratio tokamak equilibria developed by Cowley et.al., which are valid for arbitrary pressure and safety factor profiles. The stability results make no assumption about these profiles or the shape of the boundary. 14 refs., 4 figs.

  6. High Frequency Electronic Packaging Technology

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  7. High. beta. studies in the Wisconsin Toroidal Octupole

    SciTech Connect

    Halle, J. H.; Kellman, A.; Post, R. S.; Prager, S. C.; Strait, E. J.; Zarnstorff, M. C.

    1980-09-01

    A wide range of MHD stable high ..beta.. plasmas is produced in the Wisconsin Levitated Octupole. At or near the single fluid regime we obtain, in the bad curvature region, ..beta.. = nk(T/sub e/ + T/sub i/)8..pi../B/sup 2/ approx. = 8%, twice the theoretical single fluid ballooning instability limit of 4%. We also obtain stable plasmas at ..beta.. approx. = 35%, 9 times the theoretical limit, in a regime in which both finite ion gyroradius and gyroviscosity effects are important.

  8. High frequency gyrokinetic particle simulation

    SciTech Connect

    Kolesnikov, R. A.; Lee, W. W.; Qin, H.; Startsev, E.

    2007-07-15

    The gyrokinetic approach for arbitrary frequency dynamics in magnetized plasmas is explored, using the gyrocenter-gauge kinetic theory. Contrary to low-frequency gyrokinetics, which views each particle as a rigid charged ring, arbitrary frequency response of a particle is described by a quickly changing Kruskal ring. This approach allows the separation of gyrocenter and gyrophase responses and thus allows for, in many situations, larger time steps for the gyrocenter push than for the gyrophase push. The gyrophase response which determines the shape of Kruskal rings can be described by a Fourier series in gyrophase for some problems, thus allowing control over the cyclotron harmonics at which the plasma responds. A computational algorithm for particle-in-cell simulation based on this concept has been developed. An example of the ion Bernstein wave is used to illustrate its numerical properties, and comparison with a direct Lorentz-force approach is presented.

  9. Transponder System for High-Frequency Ranging

    NASA Technical Reports Server (NTRS)

    Lichtenberg, C. L.; Shores, P. W.; Kobayashi, H. S.

    1986-01-01

    Transponder system uses phase difference between transmitted and reflected high-frequency radio waves to measure distance to target. To suppress spurious measurements of reflections from objects near target at transmitted frequency and its harmonics, transponder at target generates return signal at half transmitted frequency. System useful in such applications as surveying, docking of ships, and short-range navigation.

  10. High frequency oscillations in the intact brain

    PubMed Central

    Buzsáki, György; da Silva, Fernando Lopes

    2016-01-01

    High frequency oscillations (HFOs) constitute a novel trend in neurophysiology that is fascinating neuroscientists in general, and epileptologists in particular. But what are HFOs? What is the frequency range of HFOs? Are there different types of HFOs, physiological and pathological? How are HFOs generated? Can HFOs represent temporal codes for cognitive processes? These questions are pressing and this symposium volume attempts to give constructive answers. As a prelude to this exciting discussion, we summarize the physiological high frequency patterns in the intact brain, concentrating mainly on hippocampal patterns, where the mechanisms of high frequency oscillations are perhaps best understood. PMID:22449727

  11. High-frequency oscillations and the neurobiology of schizophrenia

    PubMed Central

    Uhlhaas, Peter J.; Singer, Wolf

    2013-01-01

    Neural oscillations at low- and high-frequency ranges are a fundamental feature of large-scale networks. Recent evidence has indicated that schizophrenia is associated with abnormal amplitude and synchrony of oscillatory activity, in particular, at high (beta/gamma) frequencies. These abnormalities are observed during task-related and spontaneous neuronal activity which may be important for understanding the pathophysiology of the syndrome. In this paper, we shall review the current evidence for impaired beta/gamma-band oscillations and their involvement in cognitive functions and certain symptoms of the disorder. In the first part, we will provide an update on neural oscillations during normal brain functions and discuss underlying mechanisms. This will be followed by a review of studies that have examined high-frequency oscillatory activity in schizophrenia and discuss evidence that relates abnormalities of oscillatory activity to disturbed excitatory/inhibitory (E/I) balance. Finally, we shall identify critical issues for future research in this area. PMID:24174902

  12. Lightweight, high-frequency transformers

    NASA Technical Reports Server (NTRS)

    Schwarze, G. E.

    1983-01-01

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

  13. Beta-frequency EEG activity increased during transcranial direct current stimulation.

    PubMed

    Song, Myeongseop; Shin, Yungjae; Yun, Kyongsik

    2014-12-17

    Transcranial direct current stimulation (tDCS) is a technique for noninvasively stimulating specific cortical regions of the brain with small (<2 mA) and constant direct current on the scalp. tDCS has been widely applied, not only for medical treatment, but also for cognitive and somatosensory function enhancement, motor learning improvement, and social behavioral change. However, the mechanism that underlies the effect of tDCS is unclear. In this study, we performed simultaneous electroencephalogram (EEG) monitoring during tDCS to understand the dynamic electrophysiological changes throughout the stimulation. A total of 10 healthy individuals participated in this experiment. We recorded EEGs with direct current stimulation, as well as during a 5-min resting state before and after the stimulation. All participants kept their eyes closed during the experiment. Anode and cathode patches of tDCS were placed on the left and the right dorsolateral prefrontal cortex, respectively. In addition, an EEG electrode was placed on the medial prefrontal cortex. The beta-frequency power increased promptly after starting the stimulation. The significant beta-power increase was maintained during the stimulation. Other frequency bands did not show any significant changes. The results indicate that tDCS of the left dorsolateral prefrontal cortex changed the brain to a ready state for efficient cognitive functioning by increasing the beta-frequency power. This is the first attempt to simultaneously stimulate the cortex and record the EEG and then systematically analyze the prestimulation, during-stimulation, and poststimulation EEG data. PMID:25383460

  14. HIGH CURRENT RADIO FREQUENCY ION SOURCE

    DOEpatents

    Abdelaziz, M.E.

    1963-04-01

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

  15. MHD activity and energy loss during beta saturation and collapse at high beta poloidal in PBX

    SciTech Connect

    Kugel, H.W.; Sesnic, S.; Bol, K.; Chance, M.; Fishman, H.; Fonck, R.; Gammel, G.; Kaita, R.; Kaye, S.; LeBlanc, B.

    1987-10-01

    High-..beta.. experiments, in medium to high-q tokamak plasmas, exhibit a temporal ..beta.. saturation and collapse. This behavior has been attributed to ballooning, ideal kink, or tearing modes. In PBX, a unique diagnostic capability allowed studies of the relation between MHD and energy loss for neutral-beam-heated (<6 MW), mildly indented (10 to 15%), nearly steady I/sub p/ discharges that approached the Troyon-Gruber limit. Under these conditions, correlations between MHD activity and energy losses have shown that the latter can be almost fully accounted for by various long wavelength MHD instabilities and that there is no need to invoke high-n ballooning modes in PBX. 6 refs., 4 figs.

  16. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

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

  17. Measurement of helicon wave coupling for current drive and anticipated role for high beta KSTAR plasmas

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Kim, H. J.; Joung, M.; Jeong, J. H.; Kim, J. H.; Bae, Y. S.; Kwak, J. G.; Wi, H. H.; Kim, H.-S.

    2015-11-01

    Helicon wave current drive has been suggested for efficient off-axis current drive in high electron beta tokamak plasmas. Fast wave drives centrally peaking current in the frequency range up to several ion cyclotron harmonics in the present tokamaks, such as KSTAR. Increasing fast wave frequency up to LH resonance frequency at the plasma edge, the spiral propagation of wave at the outer region of plasma lengthens the wave path to the plasma center. Also, optical thickness increases with frequency. It is expected that these effects produce efficient off-axis power deposition depending on the electron beta and magnetic field pitch. A low power TWA for helicon wave was installed and tested in KSTAR tokamak which is aiming for the steady-state high beta plasma requiring off-axis current drive. The power coupling properties of TWA at various plasma conditions will be presented. In addition to the coupling efficiency, issues such as load sensitivity and unwanted slow wave coupling will be addressed. Also, the simulation of plasma performance with the combination of helicon wave current drive and other conventional heating and current drive power in KSTAR will be discussed. This work was supported by the Korean Ministry of Science, ICT and Future Planning and by R&D Program through the National Fusion Research Institute of Korea (NFRI) funded by the Government funds.

  18. Brain oscillatory activity during motor preparation: effect of directional uncertainty on beta, but not alpha, frequency band

    PubMed Central

    Tzagarakis, Charidimos; West, Sarah; Pellizzer, Giuseppe

    2015-01-01

    In time-constraint activities, such as sports, it is advantageous to be prepared to act even before knowing precisely what action will be needed. Here, we studied the relation between neural oscillations during motor preparation and amount of uncertainty about the direction of the upcoming target. Ten right-handed volunteers participated in a cued center-out task. A brief visual cue identified the region of space in which the target would appear. Three cue sizes were used to vary the amount of information about the direction of the upcoming target. The target appeared at a random location within the region indicated by the cue, and the participants moved a joystick-controlled cursor toward it. Time-frequency analyses showed phasic increases of power in low (delta/theta: <7 Hz) and high (gamma: >30 Hz) frequency-bands in relation to the onset of visual stimuli and of the motor response. More importantly in regard to motor preparation, there was a tonic reduction of power in the alpha (8–12 Hz) and beta (14–30 Hz) bands during the period between cue presentation and target onset. During motor preparation, the main source of change of power of the alpha band was localized over the contralateral sensorimotor region and both parietal cortices, whereas for the beta-band the main source was the contralateral sensorimotor region. During cue presentation, the reduction of power of the alpha-band in the occipital lobe showed a brief differentiation of condition: the wider the visual cue, the more the power of the alpha-band decreased. However, during motor preparation, only the power of the beta-band was dependent on directional uncertainty: the less the directional uncertainty, the more the power of the beta-band decreased. In conclusion, the results indicate that the power in the alpha-band is associated briefly with cue size, but is otherwise an undifferentiated indication of neural activation, whereas the power of the beta-band reflects the level of motor preparation

  19. 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.

  20. Ultra-High-Frequency Capacitive Displacement Sensor

    NASA Technical Reports Server (NTRS)

    Vanzandt, Thomas R.; Kenny, Thomas W.; Kaiser, William J.

    1994-01-01

    Improved class of compact, high-resolution capacitive displacement sensors operates at excitation frequency of 915 MHz and measures about 7.5 by 4 by 2 centimeters. Contains commercially available 915-MHz oscillator and transmission-line resonator. Resonator contains stripline inductor in addition to variable capacitor. Ultrahigh excitation frequency offers advantages of resolution and frequency response. Not deleteriously affected by mechanical overdriving, or contact between electrodes.

  1. [IMPACT OF INDIVIDUAL PERSONALITY FEATURES ON ABILITY TO VOLUNTARY REGULATION OF EXPRESSION EEG ALPHA AND BETA FREQUENCIES].

    PubMed

    Aslanyan, E V; Kiroy, V N; Stoletniy, A S; Lazurenko, D M; Bahtin, O M; Minyaeva, N R; Kiroy, R I

    2015-05-01

    The ability to voluntary control severity of alpha- and beta-2 frequency bands in the parietal and frontal cortical areas was investigated at 17 volunteers using biofeedback. The impact of different personality traits on the effectiveness of control was evaluated. According to the data, it was easier task to decrease expression beta-2 frequency in the frontal cortex than to decline the power of alpha frequency in the parietal cortex. The effectiveness of voluntary control of brain activity is influenced by personality features as extraversion, psychoticism, neuroticism, mobility and steadiness of nerve processes, level of person anxiety. PMID:26263685

  2. Internal Kink Mode Dynamics in High-beta NSTX Plasmas

    SciTech Connect

    J.E. Menard; R.E. Bell; E.D. Fredrickson; D.A. Gates; S.M. Kaye; B.P. LeBlanc; S.S. Medley; W. Park; S.A. Sabbagh; A. Sontag; D. Stutman; K. Tritz; W. Zhu; the NSTX Research Team

    2004-12-22

    Saturated internal kink modes have been observed in many of the highest toroidal {beta} discharges of the National Spherical Torus Experiment (NSTX). These modes often cause rotation flattening in the plasma core, can degrade energy confinement, and in some cases contribute to the complete loss of plasma angular momentum and stored energy. Characteristics of the modes are measured using soft X-ray, kinetic profile, and magnetic diagnostics. Toroidal flows approaching Alfvenic speeds, island pressure peaking, and enhanced viscous and diamagnetic effects associated with high-{beta} may contribute to mode nonlinear stabilization. These saturation mechanisms are investigated for NSTX parameters and compared to experimental data.

  3. High frequency pressure oscillator for microcryocoolers.

    PubMed

    Vanapalli, S; ter Brake, H J M; Jansen, H V; Zhao, Y; Holland, H J; Burger, J F; Elwenspoek, M C

    2008-04-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80 K, delivering a cooling power of 10 mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5 MPa and compression volume of about 22.6 mm(3) when operating the actuator with a peak-to-peak sinusoidal voltage of 100 V at a frequency of 1 kHz. The electrical power input was 2.73 W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers. PMID:18447548

  4. Turbulence in unsteady flow at high frequencies

    NASA Technical Reports Server (NTRS)

    Kuhn, Gary D.

    1990-01-01

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

  5. Real-time, high frequency QRS electrocardiograph

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  6. Overview of the Advanced High Frequency Branch

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    2015-01-01

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

  7. High beta plasma operation in a toroidal plasma producing device

    DOEpatents

    Clarke, John F.

    1978-01-01

    A high beta plasma is produced in a plasma producing device of toroidal configuration by ohmic heating and auxiliary heating. The plasma pressure is continuously monitored and used in a control system to program the current in the poloidal field windings. Throughout the heating process, magnetic flux is conserved inside the plasma and the distortion of the flux surfaces drives a current in the plasma. As a consequence, the total current increases and the poloidal field windings are driven with an equal and opposing increasing current. The spatial distribution of the current in the poloidal field windings is determined by the plasma pressure. Plasma equilibrium is maintained thereby, and high temperature, high beta operation results.

  8. Extremely high frequency RF effects on electronics.

    SciTech Connect

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

    2012-01-01

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

  9. 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.

  10. High power, high frequency, vacuum flange

    DOEpatents

    Felker, B.; McDaniel, M.R.

    1993-03-23

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

  11. High power, high frequency, vacuum flange

    DOEpatents

    Felker, Brian; McDaniel, Michael R.

    1993-01-01

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

  12. High beta and second stability region transport and stability analysis

    SciTech Connect

    Hughes, M.H.; Phillps, M.W.; Todd, A.M.M.; Krishnaswami, J.; Hartley, R.

    1992-09-01

    This report describes ideal and resistive studies of high-beta plasmas and of the second stability region. Emphasis is focused on supershot'' plasmas in TFIR where MHD instabilities are frequently observed and which spoil their confinement properties. Substantial results are described from the analysis of these high beta poloidal plasmas. During these studies, initial pressure and safety factor profiles were obtained from the TRANSP code, which is used extensively to analyze experimental data. Resistive MBD stability studies of supershot equilibria show that finite pressure stabilization of tearing modes is very strong in these high {beta}p plasmas. This has prompted a detailed re-examination of linear tearing mode theory in which we participated in collaboration with Columbia University and General Atomics. This finite pressure effect is shown to be highly sensitive to small scale details of the pressure profile. Even when an ad hoc method of removing this stabilizing mechanism is implemented, however, it is shown that there is only superficial agreement between resistive MBD stability computation and the experimental data. While the mode structures observed experimentally can be found computationally, there is no convincing correlation with the experimental observations when the computed results are compared with a large set of supershot data. We also describe both the ideal and resistive stability properties of TFIR equilibria near the transition to the second region. It is shown that the highest {beta} plasmas, although stable to infinite-n ideal ballooning modes, can be unstable to the so called infernal'' modes associated with small shear. The sensitivity of these results to the assumed pressure and current density profiles is discussed. Finally, we describe results from two collaborative studies with PPPL. The first involves exploratory studies of the role of the 1/1 mode in tokamaks and, secondly, a study of sawtooth stabilization using ICRF.

  13. High frequency electromagnetic response of the moon

    NASA Technical Reports Server (NTRS)

    Schubert, G.; Schwartz, K.

    1971-01-01

    It is shown that the contribution of higher harmonics to the lunar transfer functions for the tangential components of the surface magnetic field is significant at frequencies greater than 0.01 Hz. The inclusion of the higher harmonics shows that there are two distinct transfer functions corresponding to the components of the tangential surface magnetic field perpendicular and parallel to the direction of the wave vector of the external disturbance forcing the lunar induction. The dependences of these transfer functions on frequency and location are determined. The effects of the higher harmonics can: (1) account for a hitherto unexplained feature in the Apollo 12-Explorer 35 transfer functions, namely the rolloff at high frequencies; and (2) offer a possible explanation for the frequency dependence of the difference between the transfer functions for the two orthogonal components of the surface magnetic field. The harmonic response of a simple current layer model of the moon is derived.

  14. GABA-mediated changes in inter-hemispheric beta frequency activity in early-stage Parkinson's disease.

    PubMed

    Hall, S D; Prokic, E J; McAllister, C J; Ronnqvist, K C; Williams, A C; Yamawaki, N; Witton, C; Woodhall, G L; Stanford, I M

    2014-09-28

    In Parkinson's disease (PD), elevated beta (15-35Hz) power in subcortical motor networks is widely believed to promote aspects of PD symptomatology, moreover, a reduction in beta power and coherence accompanies symptomatic improvement following effective treatment with l-DOPA. Previous studies have reported symptomatic improvements that correlate with changes in cortical network activity following GABAA receptor modulation. In this study we have used whole-head magnetoencephalography to characterize neuronal network activity, at rest and during visually cued finger abductions, in unilaterally symptomatic PD and age-matched control participants. Recordings were then repeated following administration of sub-sedative doses of the hypnotic drug zolpidem (0.05mg/kg), which binds to the benzodiazepine site of the GABAA receptor. A beamforming based 'virtual electrode' approach was used to reconstruct oscillatory power in the primary motor cortex (M1), contralateral and ipsilateral to symptom presentation in PD patients or dominant hand in control participants. In PD patients, contralateral M1 showed significantly greater beta power than ipsilateral M1. Following zolpidem administration contralateral beta power was significantly reduced while ipsilateral beta power was significantly increased resulting in a hemispheric power ratio that approached parity. Furthermore, there was highly significant correlation between hemispheric beta power ratio and Unified Parkinson's Disease Rating Scale (UPDRS). The changes in contralateral and ipsilateral beta power were reflected in pre-movement beta desynchronization and the late post-movement beta rebound. However, the absolute level of movement-related beta desynchronization was not altered. These results show that low-dose zolpidem not only reduces contralateral beta but also increases ipsilateral beta, while rebalancing the dynamic range of M1 network oscillations between the two hemispheres. These changes appear to underlie the

  15. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  16. 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.

  17. 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.

  18. Measuring pion beta decay with high-energy pion beams

    SciTech Connect

    McFarlane, W.K. Temple Univ., Philadelphia, PA ); Hoffman, C.M. )

    1993-01-01

    Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay [pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon] is predicted by the Standard Model (SM) to be R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.3999[plus minus]0.0005 s[sup [minus]1]. The best experimental number, obtained using in-flight decays, is R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.394 [plus minus] 0.015 s[sup [minus]1]. A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required.

  19. Measuring pion beta decay with high-energy pion beams

    SciTech Connect

    McFarlane, W.K. |; Hoffman, C.M.

    1993-02-01

    Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay {pi}{sup +} {yields} {pi}{sup 0}e{sup +}v{epsilon} is predicted by the Standard Model (SM) to be R({pi}{sup +} {yields} {pi}{sup 0}e{sup +}v{epsilon}) = 0.3999{plus_minus}0.0005 s{sup {minus}1}. The best experimental number, obtained using in-flight decays, is R({pi}{sup +} {yields} {pi}{sup 0}e{sup +}v{epsilon}) = 0.394 {plus_minus} 0.015 s{sup {minus}1}. A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required.

  20. Modular low aspect ratio-high beta torsatron

    DOEpatents

    Sheffield, George V.; Furth, Harold P.

    1984-02-07

    A fusion reactor device in which the toroidal magnetic field and at least a portion of the poloidal magnetic field are provided by a single set of modular coils. The coils are arranged on the surface of a low aspect ratio toroid in planes having the cylindrical coordinate relationship .phi.=.phi..sub.i +kz where k is a constant equal to each coil's pitch and .phi..sub.i is the toroidal angle at which the i'th coil intersects the z=o plane. The device may be described as a modular, high beta torsation whose screw symmetry is pointed along the systems major (z) axis. The toroid defined by the modular coils preferably has a racetrack minor cross section. When vertical field coils and preferably a toroidal plasma current are provided for magnetic field surface closure within the toroid, a vacuum magnetic field of racetrack shaped minor cross section with improved stability and beta valves is obtained.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    PubMed

    2002-09-01

    High-frequency oscillatory ventilation (HFOV) may be considered as an alternative in the management of severe neonatal respiratory failure requiring mechanical ventilation. In patients with diffuse pulmonary disease, HFOV can applied as a rescue therapy with a high lung volume strategy to obtain adequate alveolar recruitment. We review the mechanisms of gas exchange, as well as the indications, monitoring and special features of the use HVOF in the neonatal period. PMID:12199947

  5. Ionospheric modifications in high frequency heating experiments

    SciTech Connect

    Kuo, Spencer P.

    2015-01-15

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

  6. High levels of circulating beta-amyloid peptide do not cause cerebral beta-amyloidosis in transgenic mice.

    PubMed Central

    Fukuchi, K.; Ho, L.; Younkin, S. G.; Kunkel, D. D.; Ogburn, C. E.; LeBoeuf, R. C.; Furlong, C. E.; Deeb, S. S.; Nochlin, D.; Wegiel, J.; Wisniewski, H. M.; Martin, G. M.

    1996-01-01

    We have established transgenic mice that constitutively overproduce the signal sequence and the 99-amino-acid carboxyl-terminal region of the human beta-amyloid precursor protein. The transgenic mice strongly expressed the transgene in multiple tissues under the control of a cytomegalovirus enhancer/chick beta-actin promoter. There were exceptionally high levels of beta-amyloid peptides in the plasma (approximately 17 times or more compared with the human plasma level). Although some transgenic mice from one founder line developed amyloidosis in the intestine, no neuropathology was found in transgenic mice up to age 29 months. Given the absence of cerebral beta-amyloidosis despite extremely high levels of circulating beta-amyloid peptides in the transgenic mice, the results suggest that local cerebral metabolism of beta-amyloid precursor protein may play a predominant role in cerebral beta-amyloidosis in transgenic mice. Such transgenic mice may be useful for the investigation of the etiology of the disease and for the establishment of therapeutic strategies. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:8686746

  7. The LASI high-frequency ellipticity system

    SciTech Connect

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

    1995-12-31

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

  8. The LASI high-frequency ellipticity system

    SciTech Connect

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

    1995-10-01

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

  9. High Frequency Laser-Based Ultrasound

    SciTech Connect

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

    2005-09-12

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

  10. High-frequency resonant-tunneling oscillators

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  11. High Frequency Plasma Generators for Ion Thrusters

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  12. Noise temperature in graphene at high frequencies

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  13. Frequency of Sensory Neural Hearing Loss in Major Beta-Thalassemias in Southern Iran

    PubMed Central

    Faramarzi, Abolhassan; Karimi, Mehran; Heydari, Seyed-Taghi; Shishegar, Mahmoud; Kaviani, Masoud

    2010-01-01

    Objective The thalassemias are among the most common genetic disorders worldwide, occurring more frequently in the Mediterranean region. The aim of this study was to determined frequency of sensory-neural hearing loss in major ß- thalassemias transfusion dependent patients in south of Iran. Methods A cross sectional study on 308 cases of major beta-thalassemia patients referring to Thalassemia Center of Shiraz University of Medical Sciences between 2006–2007 years. The diagnosis of ß- thalassemia major was based on clinical history, complete blood count and hemoglobine electrophoresis. Clinical data such as serum ferritin level, deferoxamine (DFO) dose, mean daily doses of DFO (mg/kg) and audiometric variables was recorded. Findings Out of 308 cases, 283 (96.5%) had normal hearing and 10 (3.5%) sensorineural hearing loss. There was no statically significant difference between two groups regarding mean age, weight, age at the first blood transfusion, age at the first DFO infusion. Conclusion We found the lowest incidence of sensorineural hearing loss in a large population of patients suffered from major thalassemia who received DFO. We show that DFO is not ototoxic at a low dose. When considering all related literature, as a whole there has been much critical misrepresentation about DFO ototoxicity. PMID:23056722

  14. 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.

  15. High-frequency neural oscillations and visual processing deficits in schizophrenia

    PubMed Central

    Tan, Heng-Ru May; Lana, Luiz; Uhlhaas, Peter J.

    2013-01-01

    Visual information is fundamental to how we understand our environment, make predictions, and interact with others. Recent research has underscored the importance of visuo-perceptual dysfunctions for cognitive deficits and pathophysiological processes in schizophrenia. In the current paper, we review evidence for the relevance of high frequency (beta/gamma) oscillations towards visuo-perceptual dysfunctions in schizophrenia. In the first part of the paper, we examine the relationship between beta/gamma band oscillations and visual processing during normal brain functioning. We then summarize EEG/MEG-studies which demonstrate reduced amplitude and synchrony of high-frequency activity during visual stimulation in schizophrenia. In the final part of the paper, we identify neurobiological correlates as well as offer perspectives for future research to stimulate further inquiry into the role of high-frequency oscillations in visual processing impairments in the disorder. PMID:24130535

  16. BBO sapphire compound for high-power frequency conversion

    NASA Astrophysics Data System (ADS)

    Rothhardt, Carolin; Rothhardt, Jan; Klenke, Arno; Peschel, Thomas; Eberhardt, Ramona; Limpert, Jens; Tünnermann, Andreas

    2015-02-01

    Lasers used for diverse applications from industry to fundamental science tend to increasing output powers. Some applications require frequency conversion via nonlinear optical crystals, which suffer from the formation of temperature gradients at high power operation which causes thermal lensing or destruction of the crystal due to tensile stresses. To avoid these unwanted effects we joined a beta barium borate (BBO) crystal with sapphire disks serving as effective heat spreaders due to their high thermal conductivity (thermal conductivity κ = 42 W/Km). Therefore, smooth and flat crystal surfaces were joined by plasma-activated bonding. The joining relies on covalent bonds, which are formed via a condensation reaction of the surfaces which are first connected by Van der Waals forces. The cleaned surfaces are activated by plasma and brought into contact, pressed together and heat treated at a temperature of about 100°C. Special attention has been paid to the cleaning of the surfaces. Therefor the surfaces have been evaluated before and after treatment by means of atomic force microscopy. A stable connection has been formed successfully, which has been tested in a proof of principle experiment and demonstrated efficient second harmonic generation at up to 253 W of input power. Compared to a bare single BBO crystal it could be shown that the temperature within the crystal compound is significantly reduced. Such hybrid structures pave the way for frequency conversion at kilowatts of average power for future high power lasers.

  17. High-frequency fishbones at JET: theoretical interpretation of experimental observations

    NASA Astrophysics Data System (ADS)

    Zonca, F.; Chen, L.; Botrugno, A.; Buratti, P.; Cardinali, A.; Cesario, R.; Ridolfini, V. Pericoli; JET-EFDA contributors

    2009-08-01

    The existence of fishbone fluctuations at frequencies comparable to those of geodesic acoustic modes (GAM) and beta induced Alfvén eigenmodes (BAE) has been demonstrated theoretically in a recent work (Zonca et al 2007 Nucl. Fusion 47 1588). Here, we show that observation of fishbones at unexpectedly high frequencies in JET (Nabais et al 2005 Phys. Plasmas 12 102509) is well interpreted as experimental evidence of high (GAM/BAE range) frequency fishbones and discuss the insights concerning both supra-thermal particles as well as thermal plasma properties that can be obtained from experimental observations.

  18. Performance of annular high frequency thermoacoustic engines

    NASA Astrophysics Data System (ADS)

    Rodriguez, Ivan A.

    This thesis presents studies of the behavior of miniature annular thermoacoustic prime movers and the imaging of the complex sound fields using PIV inside the small acoustic wave guides when driven by a temperature gradient. Thermoacoustic engines operating in the standing wave mode are limited in their acoustic efficiency by a high degree of irreversibility that is inherent in how they work. Better performance can be achieved by using traveling waves in the thermoacoustic devices. This has led to the development of an annular high frequency thermoacoustic prime mover consisting of a regenerator, which is a random stack in-between a hot and cold heat exchanger, inside an annular waveguide. Miniature devices were developed and studied with operating frequencies in the range of 2-4 kHz. This corresponds to an average ring circumference of 11 cm for the 3 kHz device, the resonator bore being 6 mm. A similar device of 11 mm bore, length of 18 cm was also investigated; its resonant frequency was 2 kHz. Sound intensities as high as 166.8 dB were generated with limited heat input. Sound power was extracted from the annular structure by an impedance-matching side arm. The nature of the acoustic wave generated by heat was investigated using a high speed PIV instrument. Although the acoustic device appears symmetric, its performance is characterized by a broken symmetry and by perturbations that exist in its structure. Effects of these are observed in the PIV imaging; images show axial and radial components. Moreover, PIV studies show effects of streaming and instabilities which affect the devices' acoustic efficiency. The acoustic efficiency is high, being of 40% of Carnot. This type of device shows much promise as a high efficiency energy converter; it can be reduced in size for microcircuit applications.

  19. Inverter design for high frequency power distribution

    NASA Technical Reports Server (NTRS)

    King, R. J.

    1985-01-01

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

  20. High temperature plasma in beta Lyrae, observed from Copernicus

    NASA Technical Reports Server (NTRS)

    Kondo, Y.; Hack, M.; Hutchings, J. B.; Mccluskey, G. E., Jr.; Plavec, M.; Polidan, R. S.

    1975-01-01

    High-resolution UV spectrophotometry of the complex close binary system beta Lyrae was performed with a telescope spectrometer on board Copernicus. Observations were made at phases 0.0, 0.25, 0.5, and 0.75 with resolutions of 0.2 A (far-UV) and 0.4 A (mid-UV). The far-UV spectrum is completely dominated by emission lines indicating the existence of a high-temperature plasma in this binary. The spectrum of this object is unlike that of any other object observed from Copernicus. It is believed that this high-temperature plasma results from dynamic mass transfer taking place in the binary. The current results are compared with OAO-2 observations and other observational results. The possibility that the secondary component is a collapsed object is also discussed; the Copernicus observations are consistent with the hypothesis that the spectroscopically invisible secondary component is a black hole.

  1. High frequency stimulation can block axonal conduction.

    PubMed

    Jensen, Alicia L; Durand, Dominique M

    2009-11-01

    High frequency stimulation (HFS) is used to control abnormal neuronal activity associated with movement, seizure, and psychiatric disorders. Yet, the mechanisms of its therapeutic action are not known. Although experimental results have shown that HFS suppresses somatic activity, other data has suggested that HFS could generate excitation of axons. Moreover it is unclear what effect the stimulation has on tissue surrounding the stimulation electrode. Electrophysiological and computational modeling literature suggests that HFS can drive axons at the stimulus frequency. Therefore, we tested the hypothesis that unlike cell bodies, axons are driven by pulse train HFS. This hypothesis was tested in fibers of the hippocampus both in-vivo and in-vitro. Our results indicate that although electrical stimulation could activate and drive axons at low frequencies (0.5-25 Hz), as the stimulus frequency increased, electrical stimulation failed to continuously excite axonal activity. Fiber tracts were unable to follow extracellular pulse trains above 50 Hz in-vitro and above 125 Hz in-vivo. The number of cycles required for failure was frequency dependent but independent of stimulus amplitude. A novel in-vitro preparation was developed, in which, the alveus was isolated from the remainder of the hippocampus slice. The isolated fiber tract was unable to follow pulse trains above 75 Hz. Reversible conduction block occurred at much higher stimulus amplitudes, with pulse train HFS (>150 Hz) preventing propagation through the site of stimulation. This study shows that pulse train HFS affects axonal activity by: (1) disrupting HFS evoked excitation leading to partial conduction block of activity through the site of HFS; and (2) generating complete conduction block of secondary evoked activity, as HFS amplitude is increased. These results are relevant for the interpretation of the effects of HFS for the control of abnormal neural activity such as epilepsy and Parkinson's disease. PMID

  2. High-frequency plasma-heating apparatus

    DOEpatents

    Brambilla, Marco; Lallia, Pascal

    1978-01-01

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

  3. High power and high SFDR frequency conversion using sum frequency generation in KTP waveguides.

    PubMed

    Barbour, Russell J; Brewer, Tyler; Barber, Zeb W

    2016-08-01

    We characterize the intermodulation distortion of high power and efficient frequency conversion of modulated optical signals based on sum frequency generation (SFG) in a periodically poled potassium titanyl phosphate (KTP) waveguide. Unwanted frequency two-tone spurs are generated near the converted signal via a three-step cascaded three-wave mixing process. Computer simulations describing the process are presented along with the experimental measurements. High-conversion efficiencies and large spur-free dynamic range of the converted optical signal are demonstrated. PMID:27472638

  4. A high frequency electromagnetic impedance imaging system

    SciTech Connect

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

    2003-01-15

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

  5. Production of high intensity Beta beams at the ISOLDE facility

    NASA Astrophysics Data System (ADS)

    Hodák, Rastislav; Stora, Thierry; Mendonça, Tania M.

    2011-12-01

    We discuss a design study devoted to a construction of the Beta beams facility at CERN, a next generation European facility aiming for a production of pure and collimated ultra-relativistic beam of electron (anti)neutrinos with help of accelerated β-decaying radioactive ions circulating in a storage decay ring. This high intense source of (anti)neutrinos directed towards a remote underground neutrino detector will allow to measure neutrino oscillations with high accuracy offering a unique chance for establishing a value of the β13 mixing angle and CP violating phase. Recently, a significant progress have been achieved on the conceptual design of high power targets required for a production and an extraction of two baseline isotopes, 6He and 18Ne, at the unexampled rate of several 1013 ions/s. There is a possibility to produce these isotopes using the so-called Isotope Separation On Line (ISOL) method at the ISOLDE facility (CERN). The 6He production is realized by taking advantage of the 9Be(n,α)6He reaction and with help of spallation neutrons and porous BeO target material. The production of 18Ne through the 19F(p,2n)18Ne reaction at required intensities is even more challenging. Currently, a molten salt (NaF) loop target is proposed for a production of high rate of 18Ne required for the Beta beams project. The progress on the design study associated with new data and plans for future is briefly presented.

  6. Aerodynamics of high frequency flapping wings

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  7. High frequency plasma generator for ion thrusters

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  8. High-frequency graphene voltage amplifier.

    PubMed

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

    2011-09-14

    While graphene transistors have proven capable of delivering gigahertz-range cutoff frequencies, applying the devices to RF circuits has been largely hindered by the lack of current saturation in the zero band gap graphene. Herein, the first high-frequency voltage amplifier is demonstrated using large-area chemical vapor deposition grown graphene. The graphene field-effect transistor (GFET) has a 6-finger gate design with gate length of 500 nm. The graphene common-source amplifier exhibits ∼5 dB low frequency gain with the 3 dB bandwidth greater than 6 GHz. This first AC voltage gain demonstration of a GFET is attributed to the clear current saturation in the device, which is enabled by an ultrathin gate dielectric (4 nm HfO(2)) of the embedded gate structures. The device also shows extrinsic transconductance of 1.2 mS/μm at 1 V drain bias, the highest for graphene FETs using large-scale graphene reported to date. PMID:21805988

  9. High Frequency Self-pulsing Microplasmas

    NASA Astrophysics Data System (ADS)

    Lassalle, John; Pollard, William; Staack, David

    2014-10-01

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

  10. High frequency ultrasonic mitigation of microbial corrosion

    NASA Astrophysics Data System (ADS)

    Almahamedh, Hussain H.; Meegan, G. Douglas; Mishra, Brajendra; Olson, David L.; Spear, John R.

    2012-05-01

    Microbiologically Influenced Corrosion (MIC) is a major problem in oil industry facilities, and considerable effort has been spent to mitigate this costly issue. More environmentally benign methods are under consideration as alternatives to biocides, among which are ultrasonic techniques. In this study, a high frequency ultrasonic technique (HFUT) was used as a mitigation method for MIC. The killing percentages of the HFUT were higher than 99.8 percent and their corrosivity on steel was reduced by more than 50 percent. The practice and result will be discussed.

  11. Inviscid fluid in high frequency excitation field

    NASA Technical Reports Server (NTRS)

    Zak, M.

    1984-01-01

    The influence of high frequency excitations (HFE) on a fluid is investigated. The response to these excitations is decomposed in two parts: 'slow' motion, which practically remains unchanged during the vanishingly small period tau, and 'fast' motion whose value during this period is negligible in terms of displacements, but is essential in terms of the kinetic energy. After such a decomposition the 'slow' and 'fast' motions become nonlinearly coupled by the corresponding governing equations. This coupling leads to an 'effective' potential energy which imparts some 'elastic' properties to the fluid and stabilizes laminar flows.

  12. High frequency homogenization for structural mechanics

    NASA Astrophysics Data System (ADS)

    Nolde, E.; Craster, R. V.; Kaplunov, J.

    2011-03-01

    We consider a net created from elastic strings as a model structure to investigate the propagation of waves through semi-discrete media. We are particularly interested in the development of continuum models, valid at high frequencies, when the wavelength and each cell of the net are of similar order. Net structures are chosen as these form a general two-dimensional example, encapsulating the essential physics involved in the two-dimensional excitation of a lattice structure whilst retaining the simplicity of dealing with elastic strings. Homogenization techniques are developed here for wavelengths commensurate with the cellular scale. Unlike previous theories, these techniques are not limited to low frequency or static regimes, and lead to effective continuum equations valid on a macroscale with the details of the cellular structure encapsulated only through integrated quantities. The asymptotic procedure is based upon a two-scale approach and the physical observation that there are frequencies that give standing waves, periodic with the period or double-period of the cell. A specific example of a net created by a lattice of elastic strings is constructed, the theory is general and not reliant upon the net being infinite, none the less the infinite net is a useful special case for which Bloch theory can be applied. This special case is explored in detail allowing for verification of the theory, and highlights the importance of degenerate cases; the specific example of a square net is treated in detail. An additional illustration of the versatility of the method is the response to point forcing which provides a stringent test of the homogenized equations; an exact Green's function for the net is deduced and compared to the asymptotics.

  13. High-frequency laser sonar system

    NASA Astrophysics Data System (ADS)

    Cray, Benjamin A.; Sarma, Ashwin; Kirsteins, Ivars P.

    2002-11-01

    A set of measurements recently completed at the Naval Undersea Warfare Center (NUWC) demonstrated that a laser-based sonar system can be used to detect acoustic particle velocity on the surface of a thin acoustically-compliant plate embedded beneath a standard acoustic window. The theoretical acoustic and measured surface particle velocity varied by less than 1 dB (reference m/s) over a wide frequency band (10 kHz to 100 kHz). However, the Polytec Model PSV-100 Scanning Laser Vibrometer System (SLVS) used in the experiments had relatively poor acoustic sensitivity, presumably due to high electronic noise, speckle noise, stand-off distance, and drifting laser focus. The laser's acoustic sensitivity appears to be inversely proportional to the backscatter signal level. The existing SLVS can sample a grid of 512 by 512 points, with each grid point having a spot size of approximately 10 mm (0.0004 in.). Such fine sampling may be used to create essentially a continuous aperture, eliminating acoustic grating lobes at all frequencies of practical sonar interest.

  14. Frequency metrology using highly charged ions

    NASA Astrophysics Data System (ADS)

    Crespo López-Urrutia, J. R.

    2016-06-01

    Due to the scaling laws of relativistic fine structure splitting, many forbidden optical transitions appear within the ground state configurations of highly charged ions (HCI). In some hydrogen-like ions, even the hyperfine splitting of the 1s ground state gives rise to optical transitions. Given the very low polarizability of HCI, such laser-accessible transitions are extremely impervious to external perturbations and systematics that limit optical clock performance and arise from AC and DC Stark effects, such as black-body radiation and light shifts. Moreover, AC and DC Zeeman splitting are symmetric due to the much larger relativistic spin-orbit coupling and corresponding fine-structure splitting. Appropriate choice of states or magnetic sub-states with suitable total angular momentum and magnetic quantum numbers can lead to a cancellation of residual quadrupolar shifts. All these properties are very advantageous for the proposed use of HCI forbidden lines as optical frequency standards. Extremely magnified relativistic, quantum electrodynamic, and nuclear size contributions to the binding energies of the optically active electrons make HCI ideal tools for fundamental research, as in proposed studies of a possible time variation of the fine structure constant. Beyond this, HCI that cannot be photoionized by vacuum-ultraviolet photons could also provide frequency standards for future lasers operating in that range.

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

    NASA Astrophysics Data System (ADS)

    Liqiu, Wei; Liang, Han; Ziyi, Yang; Jing, Li; Yong, Cao; Daren, Yu; Jianhua, Du

    2015-02-01

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

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

    SciTech Connect

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

    2015-02-07

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

  17. Frequency distribution of sickle cell anemia, sickle cell trait and sickle/beta-thalassemia among anemic patients in Saudi Arabia

    PubMed Central

    Elsayid, Mohieldin; Al-Shehri, Mohammed Jahman; Alkulaibi, Yasser Abdullah; Alanazi, Abdullah; Qureshi, Shoeb

    2015-01-01

    Background: Notwithstanding, the growing incidence of sickle cell hemoglobinopathies (SCH) such as sickle cell anemia (SCA) or sickle cell disease, sickle/beta-thalassemia; the exact prevalence remains obscure in Saudi Arabia. Hence, this study is an attempt to determine the frequency of SCA and sickle cell trait (SCT) among all anemic patients with SCH treated at the King Abdul-Aziz Medical City (KAMC), Riyadh, Saudi Arabia. Furthermore, the hemoglobin (Hb) S and other Hb patterns (Hb AS and Hb F) were also estimated in SCA and SCT patients. Materials and Methods: Results of Hb capillary electrophoresis performed on all patients with SCH from January 2011 to December 2013 were evaluated retrospectively. Results: Of a total of 3332 patient data analyzed, 307 were anemic patients (58% males and 42% females) with SCH. The sickling test showed all the patients to be positive. Hb electrophoresis revealed the incidence of 96.7%, 3.3%, and 0% of the patients suffered from SCA, SCT and sickle/beta-thalassemia, respectively. Patients with SCA had a higher level of Hb F and showed no crisis when compared with other SCA patients who had lower or no Hb F levels. Conclusion: SCA is relatively frequent among males (56.4%) than females out of all patients with SCH. The SCA incidence was more common (48.5%) among children, frequency of SCT among adult age group was 1.6%, while sickle/beta-thalassemia was 0%. PMID:26604627

  18. High frequency oscillators for chaotic radar

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  19. Plasma effects in high frequency radiative transfer

    SciTech Connect

    Alonso, C.T.

    1981-02-08

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

  20. Inline high frequency ultrasonic particle sizer

    NASA Astrophysics Data System (ADS)

    Lefebvre, F.; Petit, J.; Nassar, G.; Debreyne, P.; Delaplace, G.; Nongaillard, B.

    2013-07-01

    This paper reports the development of a new method of particle sizing in a liquid. This method uses high frequency focused ultrasounds to detect particles crossing the focal zone of an ultrasonic sensor and to determine their size distribution by processing the reflected echoes. The major advantage of this technique compared to optical sizing methods is its ability to measure the size of particles suspended in an opaque liquid without any dedicated sample preparation. Validations of ultrasonic measurements were achieved on suspensions of polymethyl methacrylate beads in a size range extending from a few micrometer to several hundred micrometer with a temporal resolution of 1 s. The inline detection of aggregate formation was also demonstrated.

  1. Electromagnetic effects on dynamics of high-beta filamentary structures

    SciTech Connect

    Lee, Wonjae; Krasheninnikov, Sergei I.; Umansky, Maxim V.; Angus, J. R.

    2015-01-15

    The impacts of the electromagnetic effects on blob dynamics are considered. Electromagnetic BOUT++ simulations on seeded high-beta blobs demonstrate that inhomogeneity of magnetic curvature or plasma pressure along the filament leads to bending of the blob filaments and the magnetic field lines due to increased propagation time of plasma current (Alfvén time). The bending motion can enhance heat exchange between the plasma facing materials and the inner scrape-off layer (SOL) region. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time. Using linear analysis and BOUT++ simulations, it is found that electromagnetic effects in high temperature and high density plasmas reduce the growth rate of resistive drift wave instability when resistivity drops below a certain value. The blobs temperature decreases in the course of its motion through the SOL and so the blob can switch from the electromagnetic to the electrostatic regime where resistive drift waves become important again.

  2. Electromagnetic effects on dynamics of high-beta filamentary structures

    SciTech Connect

    Lee, Wonjae; Umansky, Maxim V.; Angus, J. R.; Krasheninnikov, Sergei I.

    2015-01-12

    The impacts of the electromagnetic effects on blob dynamics are considered. Electromagnetic BOUT++ simulations on seeded high-beta blobs demonstrate that inhomogeneity of magnetic curvature or plasma pressure along the filament leads to bending of the blob filaments and the magnetic field lines due to increased propagation time of plasma current (Alfvén time). The bending motion can enhance heat exchange between the plasma facing materials and the inner SOL region. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time. Using linear analysis and the BOUT++ simulation, it is found that electromagnetic effects in high temperature and high density plasmas reduce the growth rate of resistive drift wave turbulence when resistivity drops below some certain value. Lastly, in the course of blobs motion in the SOL its temperature is reduced, which leads to enhancement of resistive effects, so the blob can switch from electromagnetic to electrostatic regime, where resistive drift wave turbulence become important.

  3. Electromagnetic effects on dynamics of high-beta filamentary structures

    DOE PAGESBeta

    Lee, Wonjae; Umansky, Maxim V.; Angus, J. R.; Krasheninnikov, Sergei I.

    2015-01-12

    The impacts of the electromagnetic effects on blob dynamics are considered. Electromagnetic BOUT++ simulations on seeded high-beta blobs demonstrate that inhomogeneity of magnetic curvature or plasma pressure along the filament leads to bending of the blob filaments and the magnetic field lines due to increased propagation time of plasma current (Alfvén time). The bending motion can enhance heat exchange between the plasma facing materials and the inner SOL region. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time. Using linear analysis and the BOUT++ simulation,more » it is found that electromagnetic effects in high temperature and high density plasmas reduce the growth rate of resistive drift wave turbulence when resistivity drops below some certain value. Lastly, in the course of blobs motion in the SOL its temperature is reduced, which leads to enhancement of resistive effects, so the blob can switch from electromagnetic to electrostatic regime, where resistive drift wave turbulence become important.« less

  4. Analytic, High-beta Solutions of the Helical Grad-Shafranov Equation

    SciTech Connect

    D.R. Smith; A.H. Reiman

    2004-05-19

    We present analytic, high-beta ({beta} {approx} O(1)), helical equilibrium solutions for a class of helical axis configurations having large helical aspect ratio, with the helix assumed to be tightly wound. The solutions develop a narrow boundary layer of strongly compressed flux, similar to that previously found in high beta tokamak equilibrium solutions. The boundary layer is associated with a strong localized current which prevents the equilibrium from having zero net current.

  5. High Power Third Gyroharmonic Frequency Multiplier

    NASA Astrophysics Data System (ADS)

    Lapointe, M. A.; Ganguly, A. K.; Hirshfield, J. L.; Wang, Changbiao; Yoder, R. B.; Wang, Mei

    1998-11-01

    A high power freqeuncy multplier which uses a cyclotron autoresonance accelerator (CARA)(M.A. LaPointe, R.B. Yoder, Changbiao Wang, A.K. Ganguly and J.L. Hirshfield, Phys. Rev. Lett., 76), 2718 (1996) and a third harmonic, TE_311 cavity is being tested. Primary power at 2.856 GHz is used to accelerate a 20--30 A, 75--96kV electron beam up to 320 kV in a CARA. The prepared beam interacts with the TE_311 cavity tuned to the third harmonic of the drive frequency. Simulations show that conversion efficiencies from beam power to microwave power can be as high as 48% producing up to 4.5 MW of 8.568 GHz power. Experiments to date have shown under certain conditions only third harmonic radiation has been generated with a FWHM of 350 kHz, the Fourier limit for the length of the radiation pulse. High power experiments are underway to measure the efficiency of the device.

  6. High frequency of tumours in Mulibrey nanism.

    PubMed

    Karlberg, Niklas; Karlberg, Susann; Karikoski, Riitta; Mikkola, Sakari; Lipsanen-Nyman, Marita; Jalanko, Hannu

    2009-06-01

    Mulibrey nanism (MUL) is a monogenic disorder with prenatal-onset growth failure, typical clinical characteristics, cardiopathy and tendency for a metabolic syndrome. It is caused by recessive mutations in the TRIM37 gene encoding for the peroxisomal TRIM37 protein with ubiquitin-ligase activity. In this work, the frequency and pathology of malignant and benign tumours were analysed in a national cohort of 89 Finnish MUL patients aged 0.7-76 years. The subjects had a clinical and radiological evaluation, and histological and immunohistocemical analyses on specimens obtained from biopsy, surgery or autopsy, were performed. The results show that the MUL patients have disturbed architecture with ectopic tissues and a high frequency of both benign and malignant tumours detectable in several internal organs. A total of 210 tumorous lesions were detected in 66/89 patients (74%). Fifteen malignancies occurred in 13 patients (15%), seven of them in the kidney (five Wilms' tumours), three in the thyroid gland, two gynaecological cancers, one gastrointestinal carcinoid tumour, one neuropituitary Langerhans cell histiocytosis and one case of acute lymphoblastic leukaemia (ALL). Tumours detected by radiology in the liver and other organs mainly comprised strongly dilated blood vessels (peliosis), vascularized cysts and nodular lesions. The lesions showed strong expression of the endothelial cell markers CD34 and CD31 as well as the myocyte marker alpha-smooth muscle actin (alpha-SMA). Our findings show that MUL is associated with frequent malignant tumours and benign adenomatous and vascular lesions, as well as disturbed organ development. PMID:19334051

  7. Plant Responses to High Frequency Electromagnetic Fields.

    PubMed

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

    2016-01-01

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

  8. Plant Responses to High Frequency Electromagnetic Fields

    PubMed Central

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

    2016-01-01

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

  9. Increased Beta Frequency (15-30 Hz) Oscillatory Responses in Euthymic Bipolar Patients Under Lithium Monotherapy.

    PubMed

    Tan, Devran; Özerdem, Ayşegül; Güntekin, Bahar; Atagün, M Ilhan; Tülay, Elif; Karadağ, Figen; Başar, Erol

    2016-04-01

    The effect of lithium on neurocognition is not still fully explored. Brain oscillatory activity is altered in bipolar disorder. We aimed to assess the oscillatory responses of euthymic bipolar patients and how they are affected by lithium monotherapy. Event-related oscillations in response to visual target stimulus during an oddball paradigm in 16 euthymic drug-free and 13 euthymic lithium-treated bipolar patients were compared with 16 healthy controls. The maximum peak-to-peak amplitudes were measured for each subject's averaged beta (15-30 Hz) responses in the 0- to 300-ms time window over frontal (F3, Fz, F4), central (C3, Cz, C4), temporal (T7, T8), temporo-parietal (TP7, TP8), parietal (P3, Pz, P4), and occipital (O1, Oz, O2) areas. Patients under lithium monotherapy had significantly higher beta responses to visual target stimuli than healthy controls (P=.017) and drug-free patients (P=.015). The increase in beta response was observed at all electrode locations, however, the difference was statistically significant for the left (T7; P=.016) and right (T8; P=.031) temporal beta responses. Increased beta responses in drug-free patients and further significant increase in lithium-treated patients may be indicative of a core pathophysiological process of bipolar disorder and how it is affected by lithium. Whether the finding corresponds to lithium's corrective effect on the underlying pathology or to its neurocognitive side effect remains to be further explored. In either case, the finding is a sign that the oscillatory activity may be useful in tracking medication effect in bipolar disorder. PMID:25465436

  10. MHD analysis of high (. beta. /sub t/) disruptions in PBX (Princeton Beta Experiment)

    SciTech Connect

    Jahns, G.L.; Chance, M.S.; Kaye, S.M.; Manickam, J.; Takahashi, H.; LeBlanc, B.; Morris, A.W.; Reusch, M.; Sesnic, S.

    1987-10-01

    PBX discharges run at the lowest q and highest (..beta../sub t/) always terminated in a hard disruption. The discharges, with (..beta../sub t/) values of up to 5.5% and q-values down to 2.2, were obtained by employing large current ramps and large gas feed rates during neutral beam injection. Previous work has indicated that the achieved (..beta../sub t/)-values were consistent with the limit imposed by the n = 1 ideal external kink with a conducting wall at b/a = 2. In this work, we investigate further the validity of ideal MHD theory in explaining the low-q/sub psi/j disruptions. In particular, the character of the pre-disruption MHD activity in these low-q discharges, specifically the time scales of growth and internal and external mode structures, was compared with those determined from theoretical calculations. The results of these comparisons indicate that non-ideal effects must be considered to obtain detailed agreement between theory and experiment. 13 refs., 6 figs.

  11. Exploration of multi-fold symmetry element-loaded superconducting radio frequency structure for reliable acceleration of low- & medium-beta ion species

    SciTech Connect

    Huang, Shichun; Geng, Rongli

    2015-09-01

    Reliable acceleration of low- to medium-beta proton or heavy ion species is needed for future high-current superconducting radio frequency (SRF) accelerators. Due to the high-Q nature of an SRF resonator, it is sensitive to many factors such as electron loading (from either the accelerated beam or from parasitic field emitted electrons), mechanical vibration, and liquid helium bath pressure fluctuation etc. To increase the stability against those factors, a mechanically strong and stable RF structure is desirable. Guided by this consideration, multi-fold symmetry element-loaded SRF structures (MFSEL), cylindrical tanks with multiple (n>=3) rod-shaped radial elements, are being explored. The top goal of its optimization is to improve mechanical stability. A natural consequence of this structure is a lowered ratio of the peak surface electromagnetic field to the acceleration gradient as compared to the traditional spoke cavity. A disadvantage of this new structure is an increased size for a fixed resonant frequency and optimal beta. This paper describes the optimization of the electro-magnetic (EM) design and preliminary mechanical analysis for such structures.

  12. An analytic solution of high. beta. equilibrium in a large aspect ratio tokamak

    SciTech Connect

    Cowley, S.C.; Kaw, P.K.; Kelly, R.S.; Kulsrud, R.M.

    1991-03-01

    An analytic solution of the high {beta} ({epsilon}{bar {beta}}{sub p} {approximately} {beta}q{sup 2}/{epsilon} {much gt} 1) equilibrium of a large aspect ratio tokamak is presented. Two arbitrary flux functions, the pressure profile p({psi}) and the safety factor profile q({psi}), specify the equilibrium. The solution splits into two asymptotic regions: the core region where {psi} is a function of the major radius alone and a narrow boundary layer region adjoining the conducting wall. The solutions in the two regions are asymptotically matched to each other. For monotonic pressure profiles, the Shafranov shift is equal to the minor radius. For {beta} much bigger than one, the solution contains a region (in place of the magnetic axis) of zero magnetic field and constant pressure. At high {beta} the quantity {beta}{sub I}, which is essentially proportional to the pressure over the total current squared, is largely independent of pressure. We discuss the important ramifications of limited {beta}{sub I} for high {beta} reactors. Generalizations to shaped cross sections and hollow pressure profiles are outlined. We also consider the problem of equilibrium reconstruction in the high {beta} regime. 8 refs., 7 figs.

  13. ENGLISH WORDS OF VERY HIGH FREQUENCY.

    ERIC Educational Resources Information Center

    CARD, WILLIAM; MCDAVID, VIRGINIA

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

  14. Laser for high frequency modulated interferometry

    DOEpatents

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

    1991-07-23

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

  15. Laser for high frequency modulated interferometry

    DOEpatents

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

    1991-01-01

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

  16. A High Frequency Model of Cascade Noise

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    1998-01-01

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

  17. High-Frequency Observations of Blazars

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  18. Disentangling seasonal bacterioplankton population dynamics by high-frequency sampling.

    PubMed

    Lindh, Markus V; Sjöstedt, Johanna; Andersson, Anders F; Baltar, Federico; Hugerth, Luisa W; Lundin, Daniel; Muthusamy, Saraladevi; Legrand, Catherine; Pinhassi, Jarone

    2015-07-01

    Multiyear comparisons of bacterioplankton succession reveal that environmental conditions drive community shifts with repeatable patterns between years. However, corresponding insight into bacterioplankton dynamics at a temporal resolution relevant for detailed examination of variation and characteristics of specific populations within years is essentially lacking. During 1 year, we collected 46 samples in the Baltic Sea for assessing bacterial community composition by 16S rRNA gene pyrosequencing (nearly twice weekly during productive season). Beta-diversity analysis showed distinct clustering of samples, attributable to seemingly synchronous temporal transitions among populations (populations defined by 97% 16S rRNA gene sequence identity). A wide spectrum of bacterioplankton dynamics was evident, where divergent temporal patterns resulted both from pronounced differences in relative abundance and presence/absence of populations. Rates of change in relative abundance calculated for individual populations ranged from 0.23 to 1.79 day(-1) . Populations that were persistently dominant, transiently abundant or generally rare were found in several major bacterial groups, implying evolution has favoured a similar variety of life strategies within these groups. These findings suggest that high temporal resolution sampling allows constraining the timescales and frequencies at which distinct populations transition between being abundant or rare, thus potentially providing clues about physical, chemical or biological forcing on bacterioplankton community structure. PMID:25403576

  19. Effect of dose and frequency of interferon beta-1a administration on clinical and magnetic resonance imaging parameters in relapsing-remitting multiple sclerosis.

    PubMed

    Cocco, Eleonora; Marchi, Piernicola; Floris, Gianluca; Mascia, Maria Giuseppina; Deriu, Marcello; Sirca, Antonella; Mamusa, Elena; Lai, Marina; Mura, Marco; Mallarini, Giorgio; Marrosu, Maria Giovanna

    2006-01-01

    There is still debate over the optimal dosage, frequency and route of administration of interferon (IFN) beta in multiple sclerosis (MS). A prospective, non-randomized, comparative study was performed to evaluate differences in magnetic resonance imaging and clinical outcomes of two IFN beta-1a preparations (30mcg intramuscular [im] once-weekly [qw], AVO; and 22 mcg subcutaneous [sc] three-times-weekly [tiw]; R22). Relapsing-remitting MS patients on one of the two IFN preparations (AVO, n=47; R22, n=48) were assessed at baseline and after 6 months of further treatment. There were no significant differences between the two groups at baseline. Both groups showed significantly reduced relapse rates (F=19.5; p<0.001) from baseline (0.6) to 6-month assessment (0.2; p<0.001). Univariate analysis showed a significant difference in favour of R22 on T2 lesion volume (F=14.4; p<0.001) and T1 black hole lesion load (F=8.5; p=0.004), the latter showing a significant increase in the AVO group (p<0.001). The incidence of patients with new T1 black holes was also higher for AVO than R22 (23.5% vs 8.3%; p=0.025). These results from patients receiving AVO or R22 in normal clinical practice are in line with randomized clinical studies that show the benefits of high-dose, high-frequency administration of IFN beta-1a in MS therapy. PMID:17049133

  20. Reversible tobramycin-induced bilateral high-frequency vestibular toxicity.

    PubMed

    Walsh, R M; Bath, A P; Bance, M L

    2000-01-01

    We report an unusual case of tobramycin-induced bilateral high-frequency vestibular toxicity with subsequent clinical and objective evidence of functional recovery. In those patients with a clinical presentation suggestive of aminoglycoside-induced bilateral vestibular toxicity (ataxia and oscillopsia) and normal low-frequency (ENG-caloric) responses, high-frequency rotation chair testing should be performed to exclude a high-frequency vestibular deficit. PMID:10810261

  1. Other important applications for beta-blockers in high-risk patients.

    PubMed

    Egan, Brent M; Chilton, Robert J

    2003-12-01

    Beta-blockers suppress the adverse effects of chronic activation of the sympathetic nervous system-which plays an important role in the progression of cardiovascular disease- and the drugs are also recommended as primary therapy in other diverse medical conditions that present treatment problems. For many patients with atrial fibrillation, a common condition that poses a high risk of stroke, heart rate control with beta-blockers is increasingly seen as a critical therapeutic component. Similarly, perioperative beta-blocker use provides clinical benefits in patients undergoing noncardiac surgery who are at risk of cardiac events. In migraine therapy, beta-blockers are well established as effective agents for prophylaxis, and beta-blockers may reduce levels of C-reactive protein, a sensitive marker of inflammation in cardiovascular disease. Reviewing the role of beta-blockers in several ancillary conditions should help illuminate various aspects of the complex progression of cardiovascular disease and clarify the drugs' various therapeutic benefits. PMID:19667668

  2. [Beta amyloid in blood and cerebrospinal fluid is associated with high density lipoproteins].

    PubMed

    Kudinova, N V; Kudinov, A R; Berezov, T T

    1996-01-01

    Cerebrovascular and parenchymal amyloid deposits found in brains of Alzheimer's disease, Down's syndrome and normal aging are mainly composed of aggregated amyloid beta protein (A beta), a unique peptide 39 to 44 amino acids long. A similar but soluble A beta (s A beta) has been identified in plasma, cerebrospinal fluid (CSF) and cell supernatants, indicating that it is a normal protein. We report here that s A beta in normal human plasma and CSF is complexed to high density lipoprotein (HDL) 3 and very high density lipoprotein (VHDL). Biotinylated synthetic peptide A beta 1-40 was traced in normal human plasma in in vitro experiments. Both tracer biotin-labeled A beta 1-40 and native s A beta were specifically recovered in HDL3 and VHDL as it was assessed in immunoprecipitation experiments of purified plasma lipoproteins and lipoprotein depleted plasma. This fact prompted us to ascertain whether the interaction of s A beta with HDL does occur in normal human CSF in vivo. For this purpose normals human CSF was fractionated by means of sequential flotation ultracentrifugation. The presence of s A beta in the resulting lipoprotein fractions as well as in the lipoprotein depleted CSF was analysed by immunoblot analysis, electron and immune-electron microscopy and native size exclusion chromatography. Immunoblot analysis with 6E10 monoclonal anti-A beta antibodies revealed s A beta association with all HDL subspecies of CSF, primarily HDL3 and VHDL and immunoelectron microscopy confirmed an association of s A beta with CSF-HDL particles of 16.8 + 3.2 nm. Native size exclusion chromatography followed by immunoblot analysis with antibodies against A beta and different apoliproproteins indicated an association of s A beta with HDL complexes of approximately 200 kDa molecular weight. Soluble A beta association with HDL3 and VHDL may be involved in maintaining the solubility of A beta in biological fluids and points to a possible role of lipoproteins and lipoprotein lipid

  3. A High Power Frequency Doubled Fiber Laser

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  4. Development and application of nonflammable, high-temperature beta fibers

    NASA Technical Reports Server (NTRS)

    Dawn, Frederic S.

    1989-01-01

    Recent advances in fiber technology have contributed to the success of the U.S. space program. The inorganic fiber Beta, developed as a result of efforts begun in the early 1960's and heightened following the January 27, 1967 Apollo fire is unique among inorganic and organic fibers. It has been developed into woven, nonwoven, knitted, braided, coated and printed structures. All of these were used extensively for the Apollo, Skylab, Apollo-Soyuz test project, space shuttle, Spacelab, and satellite programs. In addition to being used successfully in the space program, Beta fibers are being used commercially as firesafe fabrics in homes, hospitals, institutions, public buildings, aircraft, and public transportation, wherever total nonflammability is required. One of the most unique applications of the Beta composite structure is the roofing material for the 80,000-seat Detroit Lion's Silverdome and 5 square miles of the Jeddah International Airport in Saudi Arabia. This fiber has been successfully incorporated into 165 major public construction projects around the globe. The United States alone has used more than 12 million square yards of the material. Beta fiber has been used successfully to date and has a promising future with unlimited potential for both space and commercial application. Efforts are currently underway to improve Beta fiber to meet the requirements of extended service life for the Space Station Freedom, lunar outpost, and Mars exploration missions.

  5. Milestone report: Status report on high {beta}p experiments at high plasma current

    SciTech Connect

    Casper, T.A.; James, R.A.; Rice, B.W.; Stallard, B.W.

    1995-07-01

    This report summarizes LLNL`s involvement in recent high {beta}{sub p} experiments on the DIII-D tokamak at General Atomics. These experiments were done in collaboration with several members of the DIII-D physics staff from GA and from other collaborating institutions and could not have succeeded without this joint effort. In this report, the authors summary a specific, limited set of experiments to extend high {beta}{sub p} operation with enhanced core confinement to higher plasma currents. The interest in these experiments stems from the non-inductive current drive requirement for steady-state advanced tokamak regimes which can most reasonably be met by operation with a high bootstrap current fraction.

  6. High Frequency QRS ECG Accurately Detects Cardiomyopathy

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    SciTech Connect

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

    2014-06-15

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

  8. Near infrared frequency dependence of high-order sideband generation

    SciTech Connect

    Zaks, Benjamin; Banks, Hunter; Sherwin, Mark; Liu, Ren-Bao

    2013-12-04

    The near infrared frequency dependence of high order sideband generation in InGaAs quantum wells is discussed. The NIR frequency dependence of the sidebands indicates that the HSG phenomenon is excitonic in nature.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  10. Causal evidence that intrinsic beta-frequency is relevant for enhanced signal propagation in the motor system as shown through rhythmic TMS

    PubMed Central

    Romei, Vincenzo; Bauer, Markus; Brooks, Joseph L.; Economides, Marcos; Penny, Will; Thut, Gregor; Driver, Jon; Bestmann, Sven

    2016-01-01

    Correlative evidence provides support for the idea that brain oscillations underpin neural computations. Recent work using rhythmic stimulation techniques in humans provide causal evidence but the interactions of these external signals with intrinsic rhythmicity remain unclear. Here, we show that sensorimotor cortex follows externally applied rhythmic TMS (rTMS) stimulation in the beta-band but that the elicited responses are strongest at the intrinsic individual beta peak frequency. While these entrainment effects are of short duration, even subthreshold rTMS pulses propagate through the network and elicit significant cortico-spinal coupling, particularly when stimulated at the individual beta-frequency. Our results show that externally enforced rhythmicity interacts with intrinsic brain rhythms such that the individual peak frequency determines the effect of rTMS. The observed downstream spinal effect at the resonance frequency provides evidence for the causal role of brain rhythms for signal propagation. PMID:26584867

  11. Causal evidence that intrinsic beta-frequency is relevant for enhanced signal propagation in the motor system as shown through rhythmic TMS.

    PubMed

    Romei, Vincenzo; Bauer, Markus; Brooks, Joseph L; Economides, Marcos; Penny, Will; Thut, Gregor; Driver, Jon; Bestmann, Sven

    2016-02-01

    Correlative evidence provides support for the idea that brain oscillations underpin neural computations. Recent work using rhythmic stimulation techniques in humans provide causal evidence but the interactions of these external signals with intrinsic rhythmicity remain unclear. Here, we show that sensorimotor cortex follows externally applied rhythmic TMS (rTMS) stimulation in the beta-band but that the elicited responses are strongest at the intrinsic individual beta peak frequency. While these entrainment effects are of short duration, even subthreshold rTMS pulses propagate through the network and elicit significant cortico-spinal coupling, particularly when stimulated at the individual beta-frequency. Our results show that externally enforced rhythmicity interacts with intrinsic brain rhythms such that the individual peak frequency determines the effect of rTMS. The observed downstream spinal effect at the resonance frequency provides evidence for the causal role of brain rhythms for signal propagation. PMID:26584867

  12. High-performance iodine fiber frequency standard.

    PubMed

    Lurie, Anna; Baynes, Fred N; Anstie, James D; Light, Philip S; Benabid, Fetah; Stace, Thomas M; Luiten, Andre N

    2011-12-15

    We have constructed a compact and robust optical frequency standard based around iodine vapor loaded into the core of a hollow-core photonic crystal fiber (HC-PCF). A 532 nm laser was frequency locked to one hyperfine component of the R(56) 32-0 (127)I(2) transition using modulation transfer spectroscopy. The stabilized laser demonstrated a frequency stability of 2.3×10(-12) at 1 s, almost an order of magnitude better than previously reported for a laser stabilized to a gas-filled HC-PCF. This limit is set by the shot noise in the detection system. We present a discussion of the current limitations to the performance and a route to improve the performance by more than an order of magnitude. PMID:22179880

  13. Alexandrite laser frequency doubling in. beta. -BaB/sub 2/O/sub 4/ crystals

    SciTech Connect

    Chen, D.; Yeh, J.

    1988-10-01

    Efficient and tunable coherent ultraviolet (360--390 nm) generation in ..beta..-BaB/sub 2/O/sub 4/ crystals using type-I phase matching at room temperature is presented. The phase-matching angle is characterized with an alexandrite laser with a wavelength tuning range of 725--785 nm. The crystal angular bandwidth of 0.9 mrad-cm and spectral bandwidth of 1.15 nm-cm are also measured. UV output pulse energy of 105 mJ at 378 nm with 31% energy conversion efficiency is achieved.

  14. High-Frequency, High-Temperature Fretting Experiments

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  15. Electromagnetic inhibition of high frequency thermal bonding machine

    NASA Astrophysics Data System (ADS)

    He, Hong; Zhang, Qing-qing; Li, Hang; Zhang, Da-jian; Hou, Ming-feng; Zhu, Xian-wei

    2011-12-01

    The traditional high frequency thermal bonding machine had serious radiation problems at dominant frequency, two times frequency and three times frequency. Combining with its working principle, the problems of electromagnetic compatibility were studied, three following measures were adopted: 1.At the head part of the high frequency thermal bonding machine, resonant circuit attenuator was designed. The notch groove and reaction field can make the radiation being undermined or absorbed; 2.The electromagnetic radiation shielding was made for the high frequency copper power feeder; 3.Redesigned the high-frequency oscillator circuit to reduce the output of harmonic oscillator. The test results showed that these measures can make the output according with the national standard of electromagnetic compatibility (GB4824-2004-2A), the problems of electromagnetic radiation leakage can be solved, and good social, environmental and economic benefits would be brought.

  16. The High Frequency Stabilization of a Magnetoplasmadynamic Thruster

    NASA Astrophysics Data System (ADS)

    Kirdyashev, K.

    2004-10-01

    Experimental data on the high-frequency stabilization of the MPD thruster and the suppression of low-frequency oscillations in the frequency range from 20 to 100 kHz are presented. Conditions for the stabilizing effect of a high-frequency magnetic field at the frequency of 40 MHz on the plasma jet produced by the thruster are determined, and the efficiency of this action is evaluated. The action of high frequency field on the MPD thruster consists in the contention of two processes - the stabilization of the plasma drift instability by the magnetic component of high frequency field and the energy conversion of natural plasma oscillations excited by the external field to the ion-sound wave energy.

  17. Mechanisms of high-frequency song generation in brachypterous crickets and the role of ghost frequencies.

    PubMed

    Robillard, Tony; Montealegre-Z, Fernando; Desutter-Grandcolas, Laure; Grandcolas, Philippe; Robert, Daniel

    2013-06-01

    Sound production in crickets relies on stridulation, the well-understood rubbing together of a pair of specialised wings. As the file of one wing slides over the scraper of the other, a series of rhythmic impacts causes harmonic oscillations, usually resulting in the radiation of pure tones delivered at low frequencies (2-8 kHz). In the short-winged crickets of the Lebinthini tribe, acoustic communication relies on signals with remarkably high frequencies (>8 kHz) and rich harmonic content. Using several species of the subfamily Eneopterinae, we characterised the morphological and mechanical specialisations supporting the production of high frequencies, and demonstrated that higher harmonics are exploited as dominant frequencies. These specialisations affect the structure of the stridulatory file, the motor control of stridulation and the resonance of the sound radiator. We placed these specialisations in a phylogenetic framework and show that they serve to exploit high-frequency vibrational modes pre-existing in the phylogenetic ancestor. In Eneopterinae, the lower frequency components are harmonically related to the dominant peak, suggesting they are relicts of ancestral carrier frequencies. Yet, such ghost frequencies still occur in the wings' free resonances, highlighting the fundamental mechanical constraints of sound radiation. These results support the hypothesis that such high-frequency songs evolved stepwise, by a form of punctuated evolution that could be related to functional constraints, rather than by only the progressive increase of the ancestral fundamental frequency. PMID:23430987

  18. Processing of superconductive materials and high frequency

    SciTech Connect

    Smith, J.L.

    1987-01-01

    We do not know yet if superconductivity will become useful without refrigeration. Now, the superconductors are so different from copper that it is difficult to imagine replacing copper with such a brittle material. Superconductors conduct dc with no loss, ac with small losses, and microwaves in co-axial lines with almost no loss and with no dispersion from dc to the highest frequencies. They will probably allow us to close the gap between radio frequency and infrared optical transmission. Clearly your industry should know some things about where superconductivity may lead us and must consider whether the greater risk is to develop them or to let others try it. There are no easy answers yet.

  19. High-Frequency, Conformable Organic Amplifiers.

    PubMed

    Reuveny, Amir; Lee, Sunghoon; Yokota, Tomoyuki; Fuketa, Hiroshi; Siket, Christian M; Lee, Sungwon; Sekitani, Tsuyoshi; Sakurai, Takayasu; Bauer, Siegfried; Someya, Takao

    2016-05-01

    Large-bandwidth, low-operation-voltage, and uniform organic amplifiers are fabricated on ultrathin foils. By the integration of short-channel OTFTs and AlOx capacitors, organic amplifiers with a bandwidth of 25 kHz are realized, demonstrating the highest gain-bandwidth product (GBWP) reported to date. Owing to material and process advancements, closed-loop architectures operate at frequencies of several kilohertz with an area smaller than 30 mm(2) . PMID:26922899

  20. High-Frequency Radiation and Tritium Channel

    NASA Astrophysics Data System (ADS)

    Afonichev, D. D.

    2005-12-01

    In the process of deformation of titanium alloy samples preliminarily saturated by deuterium (at a temperature T = 710°C) radiation, which is not a neutron flux, was detected. Electromagnetic radiation in the range of radio frequencies was detected in titanium alloy samples in the process of their saturation by deuterium. The probable mechanism of its occurrence may be the retardation of charged particles in the metallic matrix.

  1. Coplanar stripline components for high frequency application

    NASA Technical Reports Server (NTRS)

    Goverdhanam, Kavita; Simons, Rainee N.; Dib, Nihad; Katehi, Linda P. B.

    1996-01-01

    In this paper, coplanar stripline discontinuities such as a slit, a right angle bend and a T-junction are characterized and their performance is parameterized with respect to frequency and geometry. Lumped equivalent circuits are presented for some of them. The element values are obtained from the measured discontinuity scattering (S) parameters. The experimental results are compared with theoretical data obtained using the Finite Difference Time Domain (FD-TD) technique for validation and show very good agreement.

  2. High Precision Noise Measurements at Microwave Frequencies

    SciTech Connect

    Ivanov, Eugene; Tobar, Michael

    2009-04-23

    We describe microwave noise measurement system capable of detecting the phase fluctuations of rms amplitude of 2{center_dot}10{sup -11} rad/{radical}(Hz). Such resolution allows the study of intrinsic fluctuations in various microwave components and materials, as well as precise tests of fundamental physics. Employing this system we discovered a previously unknown phenomenon of down-conversion of pump oscillator phase noise into the low-frequency voltage fluctuations.

  3. Osteocalcin protects pancreatic beta cell function and survival under high glucose conditions

    SciTech Connect

    Kover, Karen; Yan, Yun; Tong, Pei Ying; Watkins, Dara; Li, Xiaoyu; Tasch, James; Hager, Melissa; Clements, Mark; Moore, Wayne V.

    2015-06-19

    Diabetes is characterized by progressive beta cell dysfunction and loss due in part to oxidative stress that occurs from gluco/lipotoxicity. Treatments that directly protect beta cell function and survival in the diabetic milieu are of particular interest. A growing body of evidence suggests that osteocalcin, an abundant non-collagenous protein of bone, supports beta cell function and proliferation. Based on previous gene expression data by microarray, we hypothesized that osteocalcin protects beta cells from glucose-induced oxidative stress. To test our hypothesis we cultured isolated rat islets and INS-1E cells in the presence of normal, high, or high glucose ± osteocalcin for up to 72 h. Oxidative stress and viability/mitochondrial function were measured by H{sub 2}O{sub 2} assay and Alamar Blue assay, respectively. Caspase 3/7 activity was also measured as a marker of apoptosis. A functional test, glucose stimulated insulin release, was conducted and expression of genes/protein was measured by qRT-PCR/western blot/ELISA. Osteocalcin treatment significantly reduced high glucose-induced H{sub 2}O{sub 2} levels while maintaining viability/mitochondrial function. Osteocalcin also significantly improved glucose stimulated insulin secretion and insulin content in rat islets after 48 h of high glucose exposure compared to untreated islets. As expected sustained high glucose down-regulated gene/protein expression of INS1 and BCL2 while increasing TXNIP expression. Interestingly, osteocalcin treatment reversed the effects of high glucose on gene/protein expression. We conclude that osteocalcin can protect beta cells from the negative effects of glucose-induced oxidative stress, in part, by reducing TXNIP expression, thereby preserving beta cell function and survival. - Highlights: • Osteocalcin reduces glucose-induced oxidative stress in beta cells. • Osteocalcin preserves beta cell function and survival under stress conditions. • Osteocalcin reduces glucose

  4. Order-disorder transition in conflicting dynamics leading to rank-frequency generalized beta distributions

    NASA Astrophysics Data System (ADS)

    Alvarez-Martinez, R.; Martinez-Mekler, G.; Cocho, G.

    2011-01-01

    The behavior of rank-ordered distributions of phenomena present in a variety of fields such as biology, sociology, linguistics, finance and geophysics has been a matter of intense research. Often power laws have been encountered; however, their validity tends to hold mainly for an intermediate range of rank values. In a recent publication (Martínez-Mekler et al., 2009 [7]), a generalization of the functional form of the beta distribution has been shown to give excellent fits for many systems of very diverse nature, valid for the whole range of rank values, regardless of whether or not a power law behavior has been previously suggested. Here we give some insight on the significance of the two free parameters which appear as exponents in the functional form, by looking into discrete probabilistic branching processes with conflicting dynamics. We analyze a variety of realizations of these so-called expansion-modification models first introduced by Wentian Li (1989) [10]. We focus our attention on an order-disorder transition we encounter as we vary the modification probability p. We characterize this transition by means of the fitting parameters. Our numerical studies show that one of the fitting exponents is related to the presence of long-range correlations exhibited by power spectrum scale invariance, while the other registers the effect of disordering elements leading to a breakdown of these properties. In the absence of long-range correlations, this parameter is sensitive to the occurrence of unlikely events. We also introduce an approximate calculation scheme that relates this dynamics to multinomial multiplicative processes. A better understanding through these models of the meaning of the generalized beta-fitting exponents may contribute to their potential for identifying and characterizing universality classes.

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

    DOEpatents

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

    1997-04-29

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

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

    DOEpatents

    Snyder, Eric S.; Campbell, David V.

    1997-01-01

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

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

    SciTech Connect

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

    2001-10-25

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

  8. Phoneme categorization relying solely on high-frequency energy.

    PubMed

    Vitela, A Davi; Monson, Brian B; Lotto, Andrew J

    2015-01-01

    Speech perception studies generally focus on the acoustic information present in the frequency regions below 6 kHz. Recent evidence suggests that there is perceptually relevant information in the higher frequencies, including information affecting speech intelligibility. This experiment examined whether listeners are able to accurately identify a subset of vowels and consonants in CV-context when only high-frequency (above 5 kHz) acoustic information is available (through high-pass filtering and masking of lower frequency energy). The findings reveal that listeners are capable of extracting information from these higher frequency regions to accurately identify certain consonants and vowels. PMID:25618101

  9. Phoneme categorization relying solely on high-frequency energy

    PubMed Central

    Vitela, A. Davi; Monson, Brian B.; Lotto, Andrew J.

    2015-01-01

    Speech perception studies generally focus on the acoustic information present in the frequency regions below 6 kHz. Recent evidence suggests that there is perceptually relevant information in the higher frequencies, including information affecting speech intelligibility. This experiment examined whether listeners are able to accurately identify a subset of vowels and consonants in CV-context when only high-frequency (above 5 kHz) acoustic information is available (through high-pass filtering and masking of lower frequency energy). The findings reveal that listeners are capable of extracting information from these higher frequency regions to accurately identify certain consonants and vowels. PMID:25618101

  10. Reduced fluid-kinetic equations for low-frequency dynamics, magnetic reconnection, and electron heating in low-beta plasmas

    SciTech Connect

    Zocco, Alessandro; Schekochihin, Alexander A.

    2011-10-15

    A minimal model for magnetic reconnection and, generally, low-frequency dynamics in low-beta plasmas is proposed. The model combines analytical and computational simplicity with physical realizability: it is a rigorous limit of gyrokinetics for plasma beta of order the electron-ion mass ratio. The model contains collisions and can be used both in the collisional and collisionless reconnection regimes. It includes gyrokinetic ions (not assumed cold) and allows for the topological rearrangement of the magnetic field lines by either resistivity or electron inertia, whichever predominates. The two-fluid dynamics are coupled to electron kinetics--electrons are not assumed isothermal and are described by a reduced drift-kinetic equation. The model, therefore allows for irreversibility and conversion of magnetic energy into electron heat via parallel phase mixing in velocity space. An analysis of the exchanges between various forms of free energy and its conversion into electron heat is provided. It is shown how all relevant linear waves and regimes of the tearing instability (collisionless, semicollisional, and fully resistive) are recovered in various limits of our model. An efficient way to simulate our equations numerically is proposed, via the Hermite representation of the velocity space. It is shown that small scales in velocity space will form, giving rise to a shallow Hermite-space spectrum, whence it is inferred that, for steady-state or sufficiently slow dynamics, the electron heating rate will remain finite in the limit of vanishing collisionality.

  11. A high frequency resonance gravity gradiometer

    SciTech Connect

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

    2014-06-15

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

  12. Self isolating high frequency saturable reactor

    DOEpatents

    Moore, James A.

    1998-06-23

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

  13. High efficiency, oxidation resistant radio frequency susceptor

    DOEpatents

    Besmann, Theodore M.; Klett, James W.

    2004-10-26

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

  14. A high frequency resonance gravity gradiometer.

    PubMed

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

    2014-06-01

    A new setup OGRAN--the large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare events--gravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS. PMID:24985859

  15. Fronto-Parietal Anatomical Connections Influence the Modulation of Conscious Visual Perception by High-Beta Frontal Oscillatory Activity.

    PubMed

    Quentin, Romain; Chanes, Lorena; Vernet, Marine; Valero-Cabré, Antoni

    2015-08-01

    May white matter connectivity influence rhythmic brain activity underlying visual cognition? We here employed diffusion imaging to reconstruct the fronto-parietal white matter pathways in a group of healthy participants who displayed frequency-specific ameliorations of visual sensitivity during the entrainment of high-beta oscillatory activity by rhythmic transcranial magnetic stimulation over their right frontal eye field. Our analyses reveal a strong tract-specific association between the volume of the first branch of the superior longitudinal fasciculus and improvements of conscious visual detection driven by frontal beta oscillation patterns. These data indicate that the architecture of specific white matter pathways has the ability to influence the distributed effects of rhythmic spatio-temporal activity, and suggest a potentially relevant role for long-range connectivity in the synchronization of oscillatory patterns across fronto-parietal networks subtending the modulation of conscious visual perception. PMID:24554730

  16. Plasma Characteristics and High-Beta Operation at Near-Unity Aspect Ratio

    NASA Astrophysics Data System (ADS)

    Thorson, T. A.

    2000-10-01

    Research on PEGASUS presently focuses on exploring the extremely low aspect ratio regime of operation (A<1.2) at low toroidal field with ohmic heating. Plasmas are typically created with A = 1.1-1.4 at Bt <= 0.07 T. Relatively high current ramp rates (typically 15-45 MA/s) and high elongation (between 1.5-4) are associated with these low A plasmas. Magnetic equilibrium reconstructions of plasmas at lower toroidal fields (down to Bt = 0.04 T) indicate high normalized currents (>5), normalized beta (>4), and toroidal beta (>20%). These high beta cases are consistent with temperature estimates from spectroscopy, the high densities (up to 10^20 m-3) observed with interferometry, and estimates from confinement models using scalings that best described START results (ITER98pby1). Present experiments are focusing on determining the minimum q required for stability as a function of shape (elongation, A) and beta. In this regime, ohmic plasmas may also challenge beta limits. Beta limit studies will be expanded to both low and high q plasmas with the advent of the 2 MW HHFW heating system.

  17. Calibration of High Frequency MEMS Microphones

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  18. High-frequency electrostatic waves near earth's bow shock

    NASA Technical Reports Server (NTRS)

    Onsager, T. G.; Holzworth, R. H.; Koons, H. C.; Bauer, O. H.; Gurnett, D. A.

    1989-01-01

    Electrostatic wave measurements from the Active Magnetospheric Particle Tracer Explorer Ion Release Module have been used to investigate the wave modes and their possible generation mechanisms in the earth's bow shock and magnetosheath. It is demonstrated that electrostatic waves are present in the bow shock and magnetosheath with frequencies above the maximum frequency for Doppler-shifted ion acoustic waves, yet below the plasma frequency. Waves in this frequency range are tentatively identified as electron beam mode waves. Data from 45 bow shock crossings are then used to investigate possible correlations between the electrostatic wave properties and the near-shock plasma parameters. The most significant relationships found are anticorrelations with Alfven Mach number and electron beta. Mechanisms which might produce electron beams in the shock and magnetosheath are discussed in terms of the correlation study results. These mechanisms include acceleration by the cross-shock electric field and by lower hybrid frequency waves. A magnetosheath 'time of flight' mechanism, in analogy to the electron foreshock region, is introduced as another possible beam generation mechanism.

  19. High power single-frequency Innoslab amplifier.

    PubMed

    Han, Ke-Zhen; Ning, Jian; Zhang, Bai-Tao; Wang, Yi-Ran; Zhang, Hai-Kun; Nie, Hong-Kun; Sun, Xiao-Li; He, Jing-Liang

    2016-07-10

    A laser diode array (LDA) end-pumped continuous-wave single-frequency Innoslab amplifier has been demonstrated. The Gaussian ray bundle method was used to model the light propagation in the Innoslab amplifier for the first time to the best of our knowledge. With discrete reflectors, the maximum output of 60 W with a linewidth of 44 MHz was achieved under the pump power of 245 W, corresponding to the optical-optical efficiency of 24.5%. The beam quality factor M2 at the output power of 51 W in the horizontal and vertical direction was measured to be 1.4 and 1.3, respectively. The long-term power instability in 2 h was less than 0.25%. PMID:27409308

  20. Aqueous environmental crack propagation in high-strength beta titanium alloys

    SciTech Connect

    Young, L.M.; Young, G.A. Jr.; Scully, J.R.; Gangloff, R.P.

    1995-05-01

    The aqueous environment-assisted cracking (EAC) behavior of two peak-aged beta-titanium was characterized with a fracture mechanics method. Beta-21S is susceptible to EAC under rising load in neutral 3.5 pct NaCi at 25 C and {minus}600 mV{sub SCE}, as indicated by a reduced threshold for subcritical crack growth (K{sub TH}), an average crack growth rate of up to 10 {mu}m s, and intergranular fracture compared to microvoid rupture in air. In contrast, the initiation fracture toughness (K{sub ICi}) of Ti-15-3 in moist air is lower than that of Beta-21S at similar high {sigma}{sub YS} (1,300 MPa) but is not degraded by chloride, and cracking is by transgranular microvoid formation. The intergranular EAC susceptibility of Beta-21S correlates with both {alpha}-colonies precipitated at {beta} grain boundaries and intense slip localization; however, the causal factor is not defined. Data suggest that both features, and EAC, are promoted by prolonged solution treatment at high temperature. In a hydrogen environment embrittlement (HEE) scenario, crack-tip H could be transported by planar slip bands to strongly binding trap sites and stress/strain concentrations at {alpha} colony or {beta} grain boundaries. The EAC in Beta-21S is eliminated by cathodic polarization (to {minus}1,000 mV{sub SCE}), as well as by static loading for times that otherwise produce rising-load EAC.

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

    NASA Technical Reports Server (NTRS)

    Fish, R. E.

    1968-01-01

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

  2. Assessment of the frequency of the transforming growth factor beta-1 sequence polymorphisms in patients with alcohol dependence syndrome.

    PubMed

    Augustyńska, Beata; Araszkiewicz, Aleksander; Woźniak, Marcin; Grzybowski, Tomasz; Skonieczna, Katarzyna; Woźniak, Alina; Żyła, Magdalena

    2015-01-01

    Alcohol abuse is one of the most significant factors in the development of liver fibrosis. The pathomechanism of liver fibrosis is the same regardless of its etiology. Fibrosis is a sign of an imbalance between the synthesis of the extracellular matrix components and their degradation. Among the many cytokines that affect hepatic stellate cell activation it seems that transforming growth factor beta (TGF-β) is the most significant, either as the direct factor stimulating polymerase chain reaction (HSC) proliferation and transformation into myofibroblasts, or as the direct factor causing an increase in the activity of genes responsible for the synthesis of extracellular matrix components. The aim of the study was to reveal possible dependencies and differences between the presence of certain alleles of the TGF-β1 gene and its blood level in the study and control group. Blood samples were obtained from 39 patients, the control group consisted of 21 patients. The results obtained in the course of this study showed no statistically significant differences between the frequencies of particular polymorphisms. In the case of haplotype frequencies, insignificant differences were found for the algorithm Excoffier-Laval-Balding predicted haplotypes while one significant difference between the study and control groups was detected in case of the TC haplotype frequency predicted using the Expectation-Maximization algorithm. However, the difference in frequency of TC haplotype predicted by both algorithms was not significant. Genetic analysis of two single nucleotide polymorphisms (SNPs) in exon I of the TGF-β1 gene did not show significant differences between the occurrence of particular polymorphisms and haplotypes in the populations under study. PMID:25710054

  3. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, H.D.

    1996-04-30

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

  4. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, Howard D.

    1996-01-01

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

  5. Real-Time, High-Frequency QRS Electrocardiograph

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  6. Condenser Microphone Protective Grid Correction for High Frequency Measurements

    NASA Technical Reports Server (NTRS)

    Lee, Erik; Bennett, Reginald

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Yang, Fanghao; Dai, Xianming; Li, Chen

    2012-08-01

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

  8. Microanalyses of beta-cyclodextrin in plasma by high-performance liquid chromatography.

    PubMed

    Koizumi, K; Kubota, Y; Okada, Y; Utamura, T

    1985-05-31

    Procedures for the micro-determination of beta-cyclodextrin (beta-CyD) in plasma were investigated by four methods using high-performance liquid chromatography (HPLC). In methods A and B, underivatized beta-CyD was detected with a refractive index detector and determined by the absolute calibration graph method. An NH2-bonded silica/acetonitrile-water system was used in A and a C18-bonded silica/methanol-water system in B. In method C, the percarbanilate of beta-CyD was separated on a C8-bonded silica column with acetonitrile-water and determined using gamma-CyD as the internal standard with a UV detector at 231 nm. In method D, the per[1-14C]acetate of beta-CyD was fractionated on a silica column with n-hexane-ethanol containing 1% of water and the radioactivity of each fraction was measured with a liquid scintillation counter. gamma-CyD was used as the internal standard. Interfering plasma proteins were removed by centrifugal ultrafiltration with an MPS-1 micro-partition system. Method B was superior to the other methods with respect to ease of sample preparation, sensitivity and time required for analysis. The cumulative amount of beta-CyD in the mesenteric vein absorbed from the rat intestinal lumen after administration of phenobarbital-beta-CyD complex in a closed loop method was determined by the use of method B. PMID:4019695

  9. Influence of combined alpha, beta and gamma radionuclide contamination on the frequency of waxy-reversions in barley pollen.

    PubMed

    Bubryak, I; Vilensky, E; Naumenko, V; Grodzisky, D

    1992-02-01

    The mutagenic effectiveness of chronic, combined alpha-, beta-, and gamma-irradiation caused by radionuclide contamination of the biogeocenosis was studied in comparison with chronic gamma-irradiation from an external 60Co source. The waxy-test on barley pollen proved to be sufficiently sensitive to evaluate the increase in waxy-reversion frequencies in plants exposed to a 3 mSv dose. A dose of 50-200 mSv from external irradiation was needed to double the mutation rate in barley pollen. Moreover, the smaller doses (dose rates) were more harmful than the higher doses if measured as the increase in mutation frequency per unit of irradiation. Higher genotoxicity was observed from combined irradiation due to radionuclide contamination than from similar doses from an external gamma source. We concluded that mutagenic effects in plant cells, in the case of radionuclide contamination of the biogeocenosis, could not be extrapolated only on the basis of measured dose, but separate investigations should be carried out to establish the genotoxicity of specific radionuclide mixtures and possible toxic chemical synergisms. PMID:1574702

  10. High-frequency filtering of strong-motion records

    USGS Publications Warehouse

    Douglas, J.; Boore, D.M.

    2011-01-01

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

  11. A second mutation associated with apparent [beta]-hexosaminidase A pseudodeficiency: Identification and frequency estimation

    SciTech Connect

    Cao, Z.; Chabot, T.; Triggs-Raine, B.L. ); Natowicz, M.R.; Prence, E.M. Harvard Medical School, Boston, MA ); Kaback, M.M.; Lim-Steele, S.T.; Brown, D. Univ. of California, San Diego, CA )

    1993-12-01

    Deficient activity of [beta]-hexosaminidase A (Hex A), resulting from mutations in the HEXA gene, typically causes Tay-Sachs disease. However, healthy individuals lacking Hex A activity against synthetic substrates (i.e., individuals who are pseudodeficient) have been described. Recently, an apparently benign C[sub 739]-to-T (Arg247Trp) mutation was found among individuals with Hex A levels indistinguishable from those of carriers of Tay-Sachs disease. This allele, when in compound heterozygosity with a second [open quotes]disease-causing[close quotes] allele, results in Hex A pseudodeficiency. The authors examined the HEXA gene of a healthy 42-year-old who was Hex A deficient but did not have the C[sub 739]-to-T mutation. The HEXA exons were PCR amplified, and the products were analyzed for mutations by using restriction-enzyme digestion or single-strand gel electrophoresis. A G[sub 805]-to-A (Gly269Ser) mutation associated with adult-onset G[sub m2] gangliosidosis was found on one chromosome. A new mutation, C[sub 745]-to-T (Arg 249Trp), was identified on the second chromosome. This mutation was detected in an additional 4/63 (6%) non-Jewish and 0/218 Ashkenazi Jewish enzyme-defined carriers. Although the Arg249Trp change may result in a late-onset form of G[sub M2] gangliosidosis, any phenotype must be very mild. This new mutation and the benign C[sub 739]-to-T mutation together account for [approximately]38% of non-Jewish enzyme-defined carriers. Because carriers of the C[sub 739]-to-T and C[sub 745]-to-T mutations cannot be differentiated from carriers of disease-causing alleles by using the classical biochemical screening approaches, DNA-based analyses for these mutations should be offered for non-Jewish enzyme-defined heterozygotes, before definitive counseling is provided. 46 refs., 5 figs., 2 tabs.

  12. Gyrotron: A high-frequency microwave amplifier

    NASA Technical Reports Server (NTRS)

    Kupiszewski, A.

    1979-01-01

    A proposed microwave amplifier mechanism for future generations of millimeter high power uplinks to spacecraft and planetary radar transmitters is introduced. Basic electron-electromagnetic field interaction theory for RF power gain is explained. The starting point for general analytical methods leading to detailed design results is presented.

  13. Schlieren metrology for high frequency medical ultrasound.

    PubMed

    Zanelli, Claudio I; Howard, Samuel M

    2006-12-22

    The increased use of medical ultrasound above 40 MHz poses the challenge of measuring beam features that may be less than 40 microm. We have successfully used the optical Schlieren technique for transducers operating as high as 110 MHz. After a brief discussion of the technique, results are presented, including comparisons to state-of-the-art hydrophones and wire targets. PMID:16949117

  14. Modular low-aspect-ratio high-beta torsatron

    DOEpatents

    Sheffield, G.V.

    1982-04-01

    A fusion-reactor device is described which the toroidal magnetic field and at least a portion of the poloidal magnetic field are provided by a single set of modular coils. The coils are arranged on the surface of a low-aspect-ratio toroid in planed having the cylindrical coordinate relationship phi = phi/sub i/ + kz, where k is a constant equal to each coil's pitch and phi/sub i/ is the toroidal angle at which the i'th coil intersects the z = o plane. The toroid defined by the modular coils preferably has a race track minor cross section. When vertical field coils and, preferably, a toroidal plasma current are provided for magnetic-field-surface closure within the toroid, a vacuum magnetic field of racetrack-shaped minor cross section with improved stability and beta valves is obtained.

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

    DOEpatents

    De La Cruz, Jose; Lacey, Paul

    2003-04-15

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

  16. Yellow maize with high (beta)-carotene is an effective source of vitamin A in healthy Zimbabwean men

    Technology Transfer Automated Retrieval System (TEKTRAN)

    BACKGROUND: The bioconversion efficiency of yellow maize Beta-carotene to retinol in humans is unknown. OBJECTIVE: The objective of this study was to determine the vitamin A value of yellow maize Beta-carotene in humans. DESIGN: High Beta-carotene-containing yellow maize was grown in a hydroponic...

  17. Yellow maize with high beta-carotene is an effective source of vitamin A in healthy Zimbabwean men

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The bioconversion efficiency of yellow maize beta-carotene to retinol in humans is unknown. Thus, the objective of this study was to determine the vitamin A value of yellow maize beta-carotene in humans. A high beta-carotene containing yellow maize was grown in a hydroponic medium with 23 atom% 2H2O...

  18. 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.

  19. Deuterium-tritium TFTR plasmas in the high poloidal beta regime

    SciTech Connect

    Sabbagh, S.A.; Mauel, M.E.; Navratil, G.A.

    1995-03-01

    Deuterium-tritium plasmas with enhanced energy confinement and stability have been produced in the high poloidal beta, advanced tokamak regime in TFTR. Confinement enhancement H {triple_bond} {tau}{sub E}/{tau}{sub E ITER-89P} > 4 has been obtained in a limiter H-mode configuration at moderate plasma current I{sub p} = 0.85 {minus} 1.46 MA. By peaking the plasma current profile, {beta}{sub N dia} {triple_bond} 10{sup 8} < {beta}{sub t{perpendicular}} > aB{sub 0}/I{sub p} = 3 has been obtained in these plasma,s exceeding the {beta}{sub N} limit for TFTR plasmas with lower internal inductance, l{sub i}. Fusion power exceeding 6.7 MW with a fusion power gain Q{sub DT} = 0.22 has been produced with reduced alpha particle first orbit loss provided by the increased l{sub i}.

  20. Advanced high frequency partial discharge measuring system

    NASA Technical Reports Server (NTRS)

    Karady, George G.

    1994-01-01

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

  1. High frequency single mode traveling wave structure for particle acceleration

    NASA Astrophysics Data System (ADS)

    Ivanyan, M. I.; Danielyan, V. A.; Grigoryan, B. A.; Grigoryan, A. H.; Tsakanian, A. V.; Tsakanov, V. M.; Vardanyan, A. S.; Zakaryan, S. V.

    2016-09-01

    The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM01 mode in a metallic tube with internally coated low conductive thin layer are examined.

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

    PubMed

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

    2016-01-01

    Vowel identification in noise using consonant-vowel-consonant (CVC) logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4-8 kHz). CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz) and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception. PMID:26730702

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

    PubMed Central

    2016-01-01

    Vowel identification in noise using consonant-vowel-consonant (CVC) logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4–8 kHz). CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz) and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception. PMID:26730702

  4. Interface Strategy To Achieve Tunable High Frequency Attenuation.

    PubMed

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

    2016-03-16

    Among all polarizations, the interface polarization effect is the most effective, especially at high frequency. The design of various ferrite/iron interfaces can significantly enhance the materials' dielectric loss ability at high frequency. This paper presents a simple method to generate ferrite/iron interfaces to enhance the microwave attenuation at high frequency. The ferrites were coated onto carbonyl iron and could be varied to ZnFe2O4, CoFe2O4, Fe3O4, and NiFe2O4. Due to the ferrite/iron interface inducing a stronger dielectric loss effect, all of these materials achieved broad effective frequency width at a coating layer as thin as 1.5 mm. In particular, an effective frequency width of 6.2 GHz could be gained from the Fe@NiFe2O4 composite. PMID:26918285

  5. Radio-frequency electromagnetic emissions from materials under high-frequency mechanical excitation

    NASA Astrophysics Data System (ADS)

    Sorensen, Christian; Moore, David

    2015-06-01

    Direct contact piezoelectric transducers were used to excite compacted polycrystalline dielectric material samples with high amplitude but short duration ultrasound through a frequency range of 50 kHz to 10 MHz, while near field RF emissions were measured in 12 frequency bands from 18 to 750 GHz using a suite of detectors. Emissions were observed only in three detectors, covering the 40-75 GHz, 110-170 GHz, and 170-260 GHz frequency ranges. Emission amplitudes appear to rise nonlinearly with applied ultrasound amplitude, and the emission amplitudes versus ultrasound frequency are different than the thermal responses of these samples. Data comparing thermal responses and electromagnetic emissions versus ultrasound frequency and amplitude for several sample types (oxidizers and energetic materials) will be presented. LA-UR-15-20605.

  6. High frequency energy cascades in inviscid hydrodynamics

    NASA Astrophysics Data System (ADS)

    Costa, Adam Smith N.; de Araújo, J. M.; Cohen, Nir; Lucena, Liacir S.; Viswanathan, G. M.

    2014-04-01

    With the aim of gaining insight into the notoriously difficult problem of energy and vorticity cascades in high dimensional incompressible flows, we take a simpler and very well understood low dimensional analog and approach it from a new perspective, using the Fourier transform. Specifically, we study, numerically and analytically, how kinetic energy moves from one scale to another in solutions of the hyperbolic or inviscid Burgers equation in one spatial dimension (1D). We restrict our attention to initial conditions which go to zero as x→±∞. The main result we report here is a Fourier analytic way of describing the cascade process. We find that the cascade proceeds by rapid growth of a crossover scale below which there is asymptotic power law decay of the magnitude of the Fourier transform.

  7. High-frequency multimodal atomic force microscopy

    PubMed Central

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

    2014-01-01

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

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

    PubMed

    Cunningham, Kane A; Reichmuth, Colleen

    2016-01-01

    Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism. PMID:26519092

  9. Factors Affecting the Benefits of High-Frequency Amplification

    ERIC Educational Resources Information Center

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

    2008-01-01

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

  10. High frequency eddy current device for near surface material characterizations

    NASA Astrophysics Data System (ADS)

    Hillmann, S.; Heuer, H.; Meyendorf, N.

    2009-03-01

    For near surface characterization a new high frequency eddy current device was been developed. By using a measurement frequency up to 100 MHz information of near surface areas can be acquired. Depending on the investigated material high resolution depth profiles can be derived. The obtained data with the new device were compared to those obtained with a high precision impedance analyser. It could be demonstrated that the new device measures the eddy current conductivity signal in the high frequencies much better than the impedance analyser. By sweeping the frequency from 100 kHz up to 100 MHz the technique delivers a depth profile of the electrical conductivity of the material. This kind of high frequency eddy current technique can be used for quality assurance, surface contamination control or near surface material characterization e.g. microstructure and cold work influences. It can be a powerful tool to obtain information for process control or a good / bad decision in mass production processes like for example rolling, coating, and surface treatments. The big advantage of the high frequency eddy current method is that it is fast und precise. This paper presents results with a new developed prototype Eddy-Current-Device for measurement frequencies up to 100 MHz which is first time suitable in rough industrial environment and makes expensive lab network analysers unnecessary for this kind of investigations.

  11. Residual absorption of high temperature superconductors at THz frequencies

    SciTech Connect

    Keller, P.; Barowski, H.S.; Prenninger, M.; Pechen, E.V.; Renk, K.F.

    1996-12-31

    The authors report on a study of the residual absorption of high temperature superconductors (HTS) at THz frequencies. Using transmission Fabry-Perot interferometry, they determined both, real and imaginary part of the conductivity. They especially studied YBCO thin films. They found that the dynamical conductivity varied strongly from sample to sample. As a main result, they find that the absorptivity increases at frequencies above 1 THz much weaker than quadratically, i.e., the {omega}{sup 2} behavior of the absorptivity at microwave frequencies is not continued in the THz frequency range.

  12. Increased Low- and High-Frequency Oscillatory Activity in the Prefrontal Cortex of Fibromyalgia Patients

    PubMed Central

    Lim, Manyoel; Kim, June Sic; Kim, Dajung J.; Chung, Chun Kee

    2016-01-01

    Recent human neuroimaging studies have suggested that fibromyalgia (FM), a chronic widespread pain disorder, exhibits altered thalamic structure and function. Since the thalamus has extensive reciprocal connection with the cortex, structural and functional thalamic alterations in FM might be linked to aberrant thalamocortical oscillation. This study investigated the presence of abnormal brain rhythmicity in low- and high-frequency bands during resting state in patients with FM and their relationship to clinical pain symptom. Spontaneous magnetoencephalography (MEG) activity was recorded in 18 females with FM and 18 age- and sex-matched healthy control (HC) subjects. The most remarkable finding was that FM patients had general increases in theta, beta and gamma power along with a slowing of the dominant alpha peak. Increased spectral powers in the theta-band were primarily localized to the left dorsolateral prefrontal (DLPFC) and orbitofrontal cortex (OFC). Beta and gamma over-activation were localized to insular, primary motor and primary and secondary somatosensory (S2) cortices, as well as the DLPFC and OFC. Furthermore, enhanced high-frequency oscillatory activities in the DLPFC and OFC were associated with higher affective pain scores in patients with FM. Our results demonstrate that FM patients feature enhanced low- and high-frequency oscillatory activity in the brain areas related to cognitive and emotional modulation of pain. Increased low- and high-frequency activity of the prefrontal cortex may contribute to persistent perception of pain in FM. Therapeutic intervention based on manipulating neural oscillation to restore normal thalamocortical rhythmicity may be beneficial to pain relief in FM. PMID:27014041

  13. High performance vapour-cell frequency standards

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  14. Pigeons use high spatial frequencies when memorizing pictures.

    PubMed

    Murphy, Matthew S; Brooks, Daniel I; Cook, Robert G

    2015-07-01

    The ability of animals to visually memorize and categorize a large number of pictures is well established. Determining the kinds of information animals use to accomplish these goals has been more difficult. This experiment examined the contribution of spatial frequency information to picture memorization by pigeons. A series of grayscale pictures were notch-filtered to eliminate different portions of the spatial frequency spectrum of memorized pictures. The results indicated that the higher spatial frequencies in the pictures were most important to accurate recognition, suggesting that the detection of fine detail at the high range of pigeon visual acuity was a critical component to their memorized representations. Subsequent tests with band-pass and hybrid conflict stimuli confirmed this conclusion. It is suggested that cognitive and task demands may determine how spatial frequency is used by pigeons, with higher frequencies more important to item memorization, while lower spatial frequencies may contribute to categorization in other types of discrimination tasks. PMID:25915753

  15. High-Frequency Subband Compressed Sensing MRI Using Quadruplet Sampling

    PubMed Central

    Sung, Kyunghyun; Hargreaves, Brian A

    2013-01-01

    Purpose To presents and validates a new method that formalizes a direct link between k-space and wavelet domains to apply separate undersampling and reconstruction for high- and low-spatial-frequency k-space data. Theory and Methods High- and low-spatial-frequency regions are defined in k-space based on the separation of wavelet subbands, and the conventional compressed sensing (CS) problem is transformed into one of localized k-space estimation. To better exploit wavelet-domain sparsity, CS can be used for high-spatial-frequency regions while parallel imaging can be used for low-spatial-frequency regions. Fourier undersampling is also customized to better accommodate each reconstruction method: random undersampling for CS and regular undersampling for parallel imaging. Results Examples using the proposed method demonstrate successful reconstruction of both low-spatial-frequency content and fine structures in high-resolution 3D breast imaging with a net acceleration of 11 to 12. Conclusion The proposed method improves the reconstruction accuracy of high-spatial-frequency signal content and avoids incoherent artifacts in low-spatial-frequency regions. This new formulation also reduces the reconstruction time due to the smaller problem size. PMID:23280540

  16. Generation of Large-Scale Zonal Structures by Drift Flute Waves in High-Beta HED Plasmas

    NASA Astrophysics Data System (ADS)

    Yasin, Essam; Sotnikov, Vladmir; Kindel, Joseph; Onishchenko, O. G.; Leboeuf, J. N.

    2009-05-01

    Our aim is to develop a more general analysis of nonlinear dynamics of drift-flute waves, applicable to arbitrary plasma beta and arbitrary spatial scales in comparison with the ion Larmor radius. This study is of interest for fundamental plasma theory as well as for the interpretation of Z-pinch and laboratory astrophysics experiments. Description of low-frequency waves and in particular drift flute waves in a high beta plasma, generally speaking, requires a kinetic approach, based on the Vlasov-Maxwell set of equations. In the present work we show that the alternative two-fluid description can adequately describe the ion perturbations with arbitrary ratio of the characteristic spatial scales to the ion Larmor radius in so-called Pade approximation. For this purpose reduced two-fluid hydrodynamic equations which describe nonlinear dynamics of the flute waves with arbitrary spatial scales and arbitrary plasma beta are derived. The linear dispersion relation of the flute waves and the Rayleigh-Taylor instability are analyzed. A general nonlinear dispersion relation which describes generation of large-scale zonal structures by the flute waves is presented and analyzed.

  17. Disruption of microalgal cells using high-frequency focused ultrasound.

    PubMed

    Wang, Meng; Yuan, Wenqiao; Jiang, Xiaoning; Jing, Yun; Wang, Zhuochen

    2014-02-01

    The objective of this study was to evaluate the effectiveness of high-frequency focused ultrasound (HFFU) in microalgal cell disruption. Two microalgal species including Scenedesmus dimorphus and Nannochloropsis oculata were treated by a 3.2-MHz, 40-W focused ultrasound and a 100-W, low-frequency (20kHz) non-focused ultrasound (LFNFU). The results demonstrated that HFFU was effective in the disruption of microalgal cells, indicated by significantly increased lipid fluorescence density, the decrease of cell sizes, and the increase of chlorophyll a fluorescence density after treatments. Compared with LFNFU, HFFU treatment was more energy efficient. The combination of high and low frequency treatments was found to be even more effective than single frequency treatment at the same processing time, indicating that frequency played a critical role in cell disruption. In both HFFU and LFNFU treatments, the effectiveness of cell disruption was found to be dependent on the cell treated. PMID:24374364

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

    PubMed Central

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

    2015-01-01

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

  19. Shift of the shadow boundary in high frequency scattering

    NASA Astrophysics Data System (ADS)

    Zworski, Maciej

    1991-02-01

    The microlocal theory of diffraction is used to establish the conjecture of Keller and Rubinow relating the shift of the shadow boundary in high frequency scattering to the directional curvatures of a strictly convex obstacle.

  20. High-frequency matrix converter with square wave input

    SciTech Connect

    Carr, Joseph Alexander; Balda, Juan Carlos

    2015-03-31

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

  1. High frequency jet ventilation in fat embolism syndrome.

    PubMed

    Lee, A; Simpson, D

    1986-11-01

    The use of high frequency jet ventilation in the management of a patient with fat embolism syndrome is described. Its principal advantage over conventional intermittent positive pressure ventilation is a reduction in the amount of sedation necessary. PMID:3789371

  2. Relic gravitational waves with a running spectral index and its constraints at high frequencies

    SciTech Connect

    Tong, M. L.; Zhang, Y.

    2009-10-15

    We study the impact of a running index {alpha}{sub t} on the spectrum of relic gravitational waves (RGWs) over the whole range of frequency (10{sup -18}{approx}10{sup 10}) Hz and reveal its implications in RGWs detections and in cosmology. Analytical calculations show that, although the spectrum of RGWs on low frequencies is less affected by {alpha}{sub t}{ne}0, on high frequencies, the spectrum is modified substantially. Investigations are made toward potential detections of the {alpha}{sub t}-modified RGWs for several kinds of current and planned detectors. The Advanced LIGO will likely be able to detect RGWs with {alpha}{sub t}{>=}0 for inflationary models with the inflation index {beta}=-1.956 and the tensor-scalar ratio r=0.55. The future LISA can detect RGWs for a much broader range of ({alpha}{sub t},{beta},r), and will have a better chance to break a degeneracy between them. Constraints on {alpha}{sub t} are estimated from several detections and cosmological observations. Among them, the most stringent one is from the bound of the big bang nucleosynthesis, and requires {alpha}{sub t}<0.008 rather conservatively for any reasonable ({beta},r), preferring a nearly power-law spectrum of RGWs. In light of this result, one would expect the scalar running index {alpha}{sub s} to be of the same magnitude as {alpha}{sub t}, if both RGWs and scalar perturbations are generated by the same scalar inflation.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  4. SEPP-ZVS High Frequency Inverter Incorporating Auxiliary Switch

    NASA Astrophysics Data System (ADS)

    Ogiwara, Hiroyuki; Itoi, Misao; Nakaoka, Mutsuo

    This paper presents a novel circuit topology to attain ZVS operation of a high frequency inverter over a wide range output power regulation using a PWM control technique by connecting an auxiliary switch to the conventional single ended push-pull (SEPP) ZVS high frequency inverter. A switching current is injected into the main switches via the auxiliary switch only during the short period between its turn-on and off times to supply a current required for its ZVS operation.

  5. Soft Switching SEPP High Frequency Inverter for Induction Heating

    NASA Astrophysics Data System (ADS)

    Ogiwara, Hiroyuki; Nakaoka, Mutsuo

    This paper presents a novel circuit topology to attain soft switching operation of a high frequency inverter. Its output power is regulated over a wide range using a PWM control technique by connecting an auxiliary resonant circuit to the conventional single ended push pull (SEPP) high frequency inverter for induction heating. All switching devices in the proposed inverter are operated soft switching mode. This paper describes its circuit constitution and obtained experimental results from a practical point of view.

  6. High-flow frequencies for selected streams in Oklahoma

    USGS Publications Warehouse

    Huntzinger, Thomas L.

    1978-01-01

    Streamflow records are analyzed statistically to determine high-flow characteristics of selected streams in Oklahoma. Tables are included which show the 2-, 5-, 10-, 25-, 50-, and 100-year high-flow frequencies for durations of 1, 3, 7, 30, 90, and 365 days. The log-Pearson Type III frequency distribution was used in the computations. Streamflow records used include data extending from 1903 to 1974.

  7. High frequency ultrasound with color Doppler in dermatology*

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Wen, L.; Meng, L.

    2014-12-01

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

  9. High-frequency homogenization of zero-frequency stop band photonic and phononic crystals

    NASA Astrophysics Data System (ADS)

    Antonakakis, T.; Craster, R. V.; Guenneau, S.

    2013-10-01

    We present an accurate methodology for representing the physics of waves, in periodic structures, through effective properties for a replacement bulk medium: this is valid even for media with zero-frequency stop bands and where high-frequency phenomena dominate. Since the work of Lord Rayleigh in 1892, low-frequency (or quasi-static) behaviour has been neatly encapsulated in effective anisotropic media; the various parameters come from asymptotic analysis relying upon the ratio of the array pitch to the wavelength being sufficiently small. However, such classical homogenization theories break down in the high-frequency or stop band regime whereby the wavelength to pitch ratio is of order one. Furthermore, arrays of inclusions with Dirichlet data lead to a zero-frequency stop band, with the salient consequence that classical homogenization is invalid. Higher-frequency phenomena are of significant importance in photonics (transverse magnetic waves propagating in infinite conducting parallel fibres), phononics (anti-plane shear waves propagating in isotropic elastic materials with inclusions) and platonics (flexural waves propagating in thin-elastic plates with holes). Fortunately, the recently proposed high-frequency homogenization (HFH) theory is only constrained by the knowledge of standing waves in order to asymptotically reconstruct dispersion curves and associated Floquet-Bloch eigenfields: it is capable of accurately representing zero-frequency stop band structures. The homogenized equations are partial differential equations with a dispersive anisotropic homogenized tensor that characterizes the effective medium. We apply HFH to metamaterials, exploiting the subtle features of Bloch dispersion curves such as Dirac-like cones, as well as zero and negative group velocity near stop bands in order to achieve exciting physical phenomena such as cloaking, lensing and endoscope effects. These are simulated numerically using finite elements and compared to predictions

  10. High frequency source localization in a shallow ocean sound channel using frequency difference matched field processing.

    PubMed

    Worthmann, Brian M; Song, H C; Dowling, David R

    2015-12-01

    Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, particularly those involving high frequency signals, imperfect knowledge of the actual propagation environment prevents accurate propagation modeling and source localization via MFP fails. For beamforming applications, this actual-to-model mismatch problem was mitigated through a frequency downshift, made possible by a nonlinear array-signal-processing technique called frequency difference beamforming [Abadi, Song, and Dowling (2012). J. Acoust. Soc. Am. 132, 3018-3029]. Here, this technique is extended to conventional (Bartlett) MFP using simulations and measurements from the 2011 Kauai Acoustic Communications MURI experiment (KAM11) to produce ambiguity surfaces at frequencies well below the signal bandwidth where the detrimental effects of mismatch are reduced. Both the simulation and experimental results suggest that frequency difference MFP can be more robust against environmental mismatch than conventional MFP. In particular, signals of frequency 11.2 kHz-32.8 kHz were broadcast 3 km through a 106-m-deep shallow ocean sound channel to a sparse 16-element vertical receiving array. Frequency difference MFP unambiguously localized the source in several experimental data sets with average peak-to-side-lobe ratio of 0.9 dB, average absolute-value range error of 170 m, and average absolute-value depth error of 10 m. PMID:26723312