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1

Studies of the electronic structure and biological activity of chosen 1,4-benzodiazepines by 35Cl NQR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

Selected derivatives of 1,4-benzodiazepine: lorazepam, lormetazepam, oxazepam and temazepam, used as active substances in anxiolytic drugs, have been studied by 35Cl NQR method in order to find the correlation between electronic structure and biological activity. The 35Cl NQR resonance frequencies ( ?Q) measured at 77 K have been correlated with the following parameters characterising their biological activity: biological half-life period ( t0.5), affinity to benzodiazepine receptor (IC 50) and mean dose equivalent. The results of experimental study of some benzodiazepine derivatives by nuclear quadrupole resonance of 35Cl nuclei are compared with theoretical results based on DFT calculations which were carried out by means of Gaussian'98 W software.

Bronisz, K.; Ostafin, M.; Poleshchuk, O. Kh.; Mielcarek, J.; Nogaj, B.

2006-11-01

2

Application of nuclear quadrupole resonance to the study of clathrates. sup 35 Cl NQR and crystallography of clathrated CCl sub 4  

SciTech Connect

The {sup 35}Cl nuclear quadrupole resonance (NQR) spectra of CCl{sub 4} in more than 20 clathrates have been measured in the range 4-200 K. The crystal structures of CCl{sub 4}/Dianin's compound (1), CCl{sub 4}/Fe(AcAc){sub 3} (3), CCl{sub 4}/Ni(SCN){sub 2}(3-MePy){sub 4} (4), and CCl{sub 4}/Ni(exan){sub 2}(4,4{prime}-dm-2,2{prime}-bpy) (19) clathrates are also reported. Site symmetry and site multiplicity of the guest molecule in clathrates were determined by NQR spectroscopy and by x-ray crystallography. The degree of host-guest interaction was estimated from the NQR frequency shifts. The libration frequencies of the guest molecules in trigonal cavities were determined from NQR frequencies by Bayer-Kushida theory analysis.

Pang, Li; Lucken, E.A.C.; Bernardinelli, G. (Univ. de Geneve (Switzerland))

1990-11-21

3

35Cl NQR spectra of certain chlorine-containing chromium compounds  

NASA Astrophysics Data System (ADS)

The coordination of chlorobenzene to Cr(CO)3 and ClC6H5Cr+ fragments is shown to result in a considerable rise in the NQR frequency of chlorine atoms. The field constant in (chlorobenzene)chromium tricarbonyl was found to grow markedly, relative to pure chlorobenzene.

Kuznetsov, S. I.; Bryukhova, E. V.; Semin, G. K.

2015-03-01

4

35Cl NQR Spectra of several 2,2-bis- p-chlorophenyl chloroethane derivatives  

NASA Astrophysics Data System (ADS)

Measurement of NQR line frequency at 77 K have been performed for the following compounds: 1-chloro-2,2-bis-(p-chlorophenyl) ethylene (DDMU), 1,1-dichloro-2,2-bis-(p-chlorophenyl) ethylene (DDE), 1,1-dichloro-2,2-bis-(p-chlorophenyl) ethane (ODD), 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT). An attempt to assign spectrum lines to particular Cl nuclei in a molecule has been made. Molecular and crystallographic inequivalences occurring in these compounds have been considered. Comparison of the NQR and crystallographic data revealed the influence of phenyl rings conformation on electric charge distribution in the studied molecules.

Nogaj, B.; Pietrzak, J.; Wielopolska, E.; Schroeder, G.; Jarczewski, A.

5

Motion of Water Molecules and Hydrogen Bonds in Zinc Hexachlorostannate (IV) Hexahydrate as Studied by 1H NMR and 35Cl NQR  

NASA Astrophysics Data System (ADS)

The 1H NMR spin-lattice relaxation time T1, 35Cl NQR frequency ?Q, and 35Cl NQR spin-lattice relaxation time T1Q of [Zn(H2O)6] [SnCl6] (zinc hexachlorostannate(IV) hexahydrate) have been measured at temperatures between 77 and 350 K. The NQR spin echo signal with ?Q = 15.689 MHz at 77 K showed a positive temperature coefficient attributable to O-H-Cl type H-bonds in the crystal. ?Q at 77 K is strongly correlated with the electronegativity ?M of the metal M in the series of stannates [M(H2O)6] [SnCl6] (M = Mg, Ca, Mn, Co, Ni, Zn). A T1 minimum observed for the Zn salt is ascribed to 180° flips of water molecules with an activation energy of 20 kJ mol-1. The motion is influenced by repulsive forces among the water molecules within a cation rather than by attractive forces between the H-bonded H and CI atoms. T1Q proved to be mainly governed by lattice vibrations, weakly modulated by the fluctuating electric field gradient caused by the 180° flip motions.

Ishikawa, A.; Sasane, A.; Hirakawa, Y.; Mori, Y.

1996-06-01

6

Detection of {sup 14}N and {sup 35}Cl in cocaine base and hydrochloride using NQR, NMR, and SQUID techniques  

SciTech Connect

Results from {sup 14}N pure NQR of cocaine in the free base form (cocaine base) yield a nuclear quadrupole coupling constant (NQCC) e{sup 2}Qq/h of 5.0229 ({+-}0.0001) MHz and an asymmetry parameter {eta} of 0.0395 ({+-}0.0001) at 295 K, with corresponding values of 5.0460 ({+-}0.0013) MHz and 0.0353 ({+-}0.0008) at 77 K. Both pure NQR (at 295-77 K) and a superconducting quantum interference device (SQUID) detector (at 4.2 K) were used to measure the very low (<1 MHz) {sup 14}N transition frequencies in cocaine hydrochloride; at 295 K the NQCC is 1.1780 ({+-}0.0014) MHz and the asymmetry parameter is 0.2632 ({+-}0.0034). Stepping the carrier frequency enables one to obtain a powder pattern without the severe intensity distortions that otherwise arise from finite pulse power. A powder pattern simulation using an NQCC value of 5.027 MHz and an asymmetry parameter {eta} of 0.2 agrees reasonably well with the experimental stepped-frequency spectrum. The use of pure NQR for providing nondestructive, quantitative, and highly specific detection of crystalline compounds is discussed, as are experimental strategies. 31 refs., 8 figs., 1 tab.

Yesinowski, J.P.; Buess, M.L.; Garroway, A.N. [Naval Research Lab., Washington, DC (United States); Ziegeweid, M.; Pines, A. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States)

1995-07-01

7

35Cl-NQR and DFT study of electronic structure of amlodipine and felodipine vascular-selective drugs from the dihydropyridine Ca ++ antagonists group  

NASA Astrophysics Data System (ADS)

Amlodipine (AM) and felodipine (FL) have been studied in solid state by the nuclear quadrupole resonance (NQR) and density functional theory (DFT). The results have shown that NQR data do not permit a differentiation between R and S enantiomers, which is a consequence of the symmetry of the 4-aryl ring, whereas they permit a differentiation between free bases and salts. The HOMO-LUMO gap is smaller for AM than for FL, which suggests smaller energy of excitation for AM. The absolute hardness, chemical potential and electrophilicity of both AM enantiomers are lower than the corresponding values for FL enantiomers, suggesting that AM should be more reactive than FL in unimolecular reactions.

Latosi?ska, J. N.; Latosi?ska, M.; Kasprzak, J.

2008-09-01

8

Application of nuclear quadrupole resonance to the study of clathrates. sup 35 Cl NQR and crystallography of clathrated CCl sub 4  

Microsoft Academic Search

The ³⁵Cl nuclear quadrupole resonance (NQR) spectra of CClâ in more than 20 clathrates have been measured in the range 4-200 K. The crystal structures of CClâ\\/Dianin's compound (1), CClâ\\/Fe(AcAc)â (3), CClâ\\/Ni(SCN)â(3-MePy)â (4), and CClâ\\/Ni(exan)â(4,4â²-dm-2,2â²-bpy) (19) clathrates are also reported. Site symmetry and site multiplicity of the guest molecule in clathrates were determined by NQR spectroscopy and by x-ray crystallography.

Li Pang; E. A. C. Lucken; G. Bernardinelli

1990-01-01

9

Frequency selective detection of nuclear quadrupole resonance (NQR) spin echoes  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) is a radio frequency (RF) technique that can be used to detect the presence of quadrupolar nuclei, such as the 14N nucleus prevalent in many explosives and narcotics. The technique has been hampered by low signal-to-noise ratios and is further aggravated by the presence of RF interference (RFI). To ensure accurate detection, proposed detectors should exploit the rich form of the NQR signal. Furthermore, the detectors should also be robust to any remaining residual interference, left after suitable RFI mitigation has been employed. In this paper, we propose a new NQR data model, particularly for the realistic case where multiple pulse sequences are used to generate trains of spin echoes. Furthermore, we refine two recently proposed approximative maximum likelihood (AML) detectors, enabling the algorithm to optimally exploit the data model of the entire echo train and also incorporate knowledge of the temperature dependent spin-echo decay time. The AML-based detectors ensure accurate detection and robustness against residual RFI, even when the temperature of the sample is not precisely known, by exploiting the dependencies of the NQR resonant lines on temperature. Further robustness against residual interference is gained as the proposed detector is frequency selective; exploiting only those regions of the spectrum where the NQR signal is expected. Extensive numerical evaluations based on both simulated and measured NQR data indicate that the proposed Frequency selective Echo Train AML (FETAML) detector offers a significant improvement as compared to other existing detectors.

Somasundaram, Samuel D.; Jakobsson, Andreas; Smith, John A. S.; Althoefer, Kaspar A.

2006-05-01

10

35Cl Nuclear Quadrupole Resonance and Thermally Activated Molecular Motion in the 2:1 Crystalline Complex of Antimony Trichloride with Benzene  

Microsoft Academic Search

Nuclear quadrupole resonance (NQR) spectra of chlorine and antimony in the 2SbCl3 · C6H6 complex and their temperature behavior between 77 K and the melting point were studied. The spectral lines of two nonequivalent SbCl3 moieties are compared with available X-ray diffraction data. An analysis of the temperature dependence of the resonant frequency and the spin–lattice relaxation time for 35Cl

V. A. Mokeeva

2002-01-01

11

Molecular structure and nuclear quadrupole coupling tensors of 14N and 35Cl in 1-chloro-2,4-dinitrobenzene. Phase I  

Microsoft Academic Search

The crystal structure of the orthorhombic, stable phase of 1-chloro-2,4-dinitrobenzene was studied at T=295 K by x-ray diffraction; space group D102h=Pccn; a=893.0(1) pm, b=1104.5(2) pm, c=1567.6(2) pm, Z=8, &rgr;calc=1.740 Mg m?3, all atoms in position 8(e). The Zeeman split single crystal 35Cl NQR gives e2&Fgr;zzQh?1(35Cl)=74.287(4) MHz, &eegr;(35Cl)=0.1636(18) at T=295 K. At 110 K the values are: e2&Fgr;zzQh?1(35Cl)=75.183(4) MHz, &eegr;(35Cl)=0.1572(20). &Fgr;zz(35Cl)

Surendra Sharma; Norbert Weiden; Alarich Weiss

1989-01-01

12

Electron density distribution in cladribine (2-chloro-2?-deoxyadenosine) - A drug against leukemia and multiple sclerosis - Studied by multinuclear NQR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

2-Chloro-2'-deoxyadenosine (Cladribine) chemotherapeutic drug has been studied experimentally in solid state by 35Cl NQR and NMR-NQR double resonance and theoretically by the Density Functional Theory. Fifteen resonance frequencies on 14N have been detected and assigned to particular nitrogen sites in the 2-CdA molecule. The effects of tautomerism, regioisomerism, conformations and molecular aggregations, related to intermolecular hydrogen bond formation, on the NQR parameters have been analysed within the DFT and AIM ( Atoms in Molecules) formalism. The properties of the whole molecule, the so-called global reactivity descriptors, have been calculated for a comparison of both syn and anti conformations of 2-CdA molecule to check the effect of crystal packing on molecular conformation.

Latosi?ska, J. N.; Latosi?ska, M.; Seliger, J.; Žagar, V.; Kazimierczuk, Z.

2009-07-01

13

Zeeman Effect of the Nuclear Quadrupole Resonance of 81Br in para-Bromophenol and 35Cl in paraChlorophenol  

Microsoft Academic Search

The Zeeman effect of the 81Br and 35Cl nuclear quadrupole resonance has been studied with high precision on single crystals of para-bromophenol and para-chlorophenol, respectively. The results substantially agree with previous x-ray and NQR studies of para-chlorophenol (x-ray studies are known only for this substance). In p-bromophenol, four physically inequivalent sites were found, instead of two, as reported by other

P. Bucci; P. Cecchi; A. Colligiani

1969-01-01

14

Explosives detection by nuclear quadrupole resonance (NQR)  

NASA Astrophysics Data System (ADS)

Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a laboratory prototype NQR explosives detector which interrogates a volume of 300 liters (10 ft3). This paper presents abbreviated results from a demonstration of the laboratory prototype NQR explosives detector conducted at the Federal Aviation Administration Technical Center in May 1994 on RDX-based explosives.

Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.; Krauss, Ronald A.

1994-10-01

15

H/D isotope effect of 1H MAS NMR spectra and 79Br NQR frequencies of piperidinium p-bromobenzoate and pyrrolidinium p-bromobenzoate  

NASA Astrophysics Data System (ADS)

H/D isotope effects onto 79Br NQR frequencies of piperidinium p-bromobenzoate were studied by deuterium substitution of hydrogen atoms which form two kinds of N-H?O type hydrogen bonds, and the isotope shift of ca. 100 kHz were detected for a whole observed temperature range. In addition, 1H MAS NMR spectra measurements of piperidinium and pyrrolidinium p-bromobenzoate were carried out and little isotope changes of NMR line shape were detected. In order to reveal effects of molecular arrangements into the obtained isotope shift of NQR frequencies, single-crystal X-ray measurement of piperidinium p-bromobenzoate- d2 and density-functional-theory calculation were carried out. Our estimation showed the dihedral-angle change between piperidine and benzene ring contributes to isotope shift rather than those of N-H lengths by deuterium substitution.

Honda, Hisashi; Kyo, Shinshin; Akaho, Yousuke; Takamizawa, Satoshi; Terao, Hiromitsu

2010-04-01

16

A miniaturized NQR spectrometer for a multi-channel NQR-based detection device.  

PubMed

A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting (14)N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring (14)N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel (14)N NQR based detection device. PMID:25233110

Beguš, Samo; Jazbinšek, Vojko; Pirnat, Janez; Trontelj, Zvonko

2014-10-01

17

A miniaturized NQR spectrometer for a multi-channel NQR-based detection device  

NASA Astrophysics Data System (ADS)

A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting 14N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring 14N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel 14N NQR based detection device.

Beguš, Samo; Jazbinšek, Vojko; Pirnat, Janez; Trontelj, Zvonko

2014-10-01

18

I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics  

SciTech Connect

NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity'of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting QUantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of {sup 14}N via the quadrupolar interaction. Because {sup 14}N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe {sup 14}N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional {sup 13}C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}({eta}{sup 1}-C{sub 5}H{sub 5}){sub 2}, Zr({eta}{sup 5}-C{sub 5}H{sub 5}){sub 3}({eta}{sup 1}-C{sub 5}H{sub 5}) and Sn({eta}{sup 1}-C{sub 5}H{sub 5}){sub 4}. This work was undertaken in the hope of gaining insight into the intramolecuhrr dynamics, specifically which fluxional processes exist in the solid state, by what mechanism rearrangements are occurring, and the activation energies by which these processes are governed.

Ziegeweid, M.A.

1995-11-29

19

Two-dimensional NQR using ultra-broadband electronics.  

PubMed

We have recently developed an ultra-broadband instrument that can effectively excite and detect NMR and NQR signals over a wide frequency range. Our current system operates between 100 kHz and 3.2 MHz using an un-tuned sample coil. The major benefits of this instrument compared to conventional NQR/NMR systems include increased robustness, ease of use (in particular for multi-frequency experiments), and elimination of the need for tuning adjustments in the hardware. Here we describe its use for performing two-dimensional (2D) scans, which allow improved interpretation of complex NQR spectra by detecting the connected resonances. Our method relies on population transfers between the three energy levels of spin-1 nuclei (such as (14)N) by using multi-frequency excitation and a single RF coil. Experimental results on pure samples and mixtures are also presented. PMID:24495675

Mandal, S; Song, Y-Q

2014-03-01

20

Studies of the Predissociated, Quasilinear B^{1}A^' State of CH^{35}Cl and CD^{35}Cl by Optical-Optical Double Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

Last year at this meeting, we reported studies of the predissociated, quasilinear B^{1}A^' state of fluorocarbene (CHF and CDF) using a fluorescence dip detected optical-optical double resonance technique via the A^{1}A^'' state. Recently, we have extended these observations to chlorocarbene, measuring OODR spectra of both CH^{35}Cl and CD^{35}Cl. By recording OODR spectra of both isotopomers, we are able to pinpoint the origin of the B^{1}A^' state, while lies near 22 400 cm^{-1}. In contrast to CHF, the B^{1}A^' origin in chlorocarbene lies below the energetic threshold of the lowest dissociation channel, C(^{3}P) + HCl. However, at higher energies several channels open up, including C-H and C-Cl bond fission, and the OODR spectra show significant lifetime broadening. Trends in the measured linewidths with energy will be discussed. C. Tao, S. A. Reid, T. W. Schmidt, and S. H. Kable, J. Chem. Phys. 125, 051105 (2007).

Tao, C.; Mukarakate, C.; Reid, S. A.

2009-06-01

21

Structure of Cl-containing silicate and aluminosilicate glasses: A 35Cl MAS-NMR study  

NASA Astrophysics Data System (ADS)

Chlorine-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were collected at 14.1 and 18.8 Tesla fields to determine the atomic scale structural environments of the chloride ions in anhydrous and hydrous silicate and aluminosilicate glasses containing 0.2 to 0.7 wt% Cl. NMR peaks are broad and featureless, but are much narrower than the total chemical shift range for the nuclide in inorganic chlorides. Peak widths are primarily due to quadrupole interactions and to a lesser extent to chemical shift distributions. Peak positions are quite different for the Na- and Ca-containing glasses, suggesting that most Cl - coordination environments contain network modifier cations. Comparison of peak positions and shapes for silicate and aluminosilicate glasses containing either Na or Ca suggests that there is no obvious contribution from Cl - bonded to Al, and relative quantitation of peak areas indicates that there is no systematic undercounting of 35Cl spins in the aluminous vs. the Al-free samples. In Ca-Na silicate glasses with varying Ca/(Ca + Na), the mixed-cation glasses have intermediate chemical shifts between those of the end members, implying that there is not a strong preference of either Ca 2+ or of Na + around Cl -. Hydrous Na-aluminosilicate glasses with H 2O contents up to 5.9 wt% show a shift to higher frequency NMR signal with increasing H 2O content, while the quadrupole coupling constant ( CQ) remains constant at ˜3.3 MHz. However, the change in frequency is much smaller than that expected if H 2O systematically replaced Na + in the first-neighbor coordination shell around Cl -. A series of hydrous Ca-aluminosilicate glasses with H 2O contents up to 5.5 wt% show no shift in NMR signal with increasing H 2O content. The CQ remains constant at ˜4.4 MHz, again suggesting no direct interaction between Cl - and H 2O in these samples.

Sandland, Travis O.; Du, Lin-Shu; Stebbins, Jonathan F.; Webster, James D.

2004-12-01

22

NQR study of chalcogenide glasses Ge-As-Se.  

PubMed

A three-component Ge-As-Se system is studied by the nuclear quadrupole resonance (NQR) method on (75)As nuclei and by the nutation NQR spectroscopy. The NQR (75)As spectra of the glasses Ge(0.021) As(0.375) Se(0.604), Ge(0.043) As(0.348) Se(0.609) and Ge(0.068) As(0.318) Se(0.614) reveal broad lines with two peaks assigned to the main structural unit of As(2)Se(3). With increasing average coordination number ( ?r), the spectrum signals are shifted towards higher frequencies. At ?r > 2.54, the spectrum becomes complex, which is a consequence of formation of more complex molecular structures in the glasses of high content of germanium. At fixed frequencies the asymmetry parameter ? of the samples studied is determined. PMID:21452350

Glotova, Olga; Korneva, Irina; Sinyavsky, Nikolay; Ostafin, Michal; Nogaj, Boleslaw

2011-07-01

23

Downregulation of Na(+)-NQR complex is essential for Vibrio alginolyticus in resistance to balofloxacin.  

PubMed

Increasingly isolated frequency of antibiotic-resistant V. alginolyticus strains in clinic and aquaculture has been reported, but the mechanisms of V. alginolyticus antibiotic resistance are largely absent. In the present study, native/SDS-PAGE based proteomics, which may provide information on protein-protein interaction, was utilized to investigate differential proteins of V. alginolyticus in resistance to balofloxacin. Ten proteins were altered, in which V12G01_04671, V12G01_00457, V12G01_15927, V12G01_15240, NqrA (spot 26), and NqrF (spot 30) were downregulated, while V12G01_22043, TolC, V12G01_15130, V12G01_19297 were upregulated. Importantly, the two components of Na(+)-NQR complex, NqrA and NqrF, were vertically lined and was further investigated. Western blotting assay indicated that downregulation of the two proteins contrasted sharply with upregulation of a control protein TolC, which was consistent with the result obtained from 2-DE gel analysis. Furthermore, overexpression of NqrA, NqrF and TolC resulted in decrease and elevation of bacterial survival ability in medium with balofloxacin, respectively. These results indicate that downregulation of Na(+)-NQR complex is essential for V. alginolyticus resistance to balofloxacin. This is the first report on the role of Na(+)-NQR complex in antibiotic resistance. This finding highlights the way to an understanding of antibiotic-resistant mechanisms in content of metabolic regulation. PMID:22465713

Li, Peipei; Liu, Xianjie; Li, Hui; Peng, Xuan-Xian

2012-05-17

24

A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La  

E-print Network

An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1/10th scale test of the design for the forthcoming n+p->d+gamma experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current mode readout, measurements were made of asymmetries in gamma-ray emission following neutron capture on 35Cl, 113Cd, and 139La targets. Upper limits on the parity-allowed asymmetry $s_n \\cdot (k_{\\gamma} \\times k_n)$ were set at the level of 7 x 10^-6 for all three targets. Parity-violating asymmetries $s_n \\cdot k_{\\gamma}$ were observed in 35Cl, A_gamma = (-29.1 +- 6.7) x 10^-6, and 139La, A_gamma = (-15.5 +- 7.1) x 10^-6, values consistent with previous measurements.

G. S. Mitchell; C. S. Blessinger; J. D. Bowman; T. E. Chupp; K. P. Coulter; M. T. W. Gericke; G. L. Jones; M. B. Leuschner; H. Nann; S. A. Page; S. I. Penttila; T. B. Smith; W. M. Snow; W. S. Wilburn

2004-01-08

25

The 35Cl/37Cl isotopic ratio in dense molecular clouds: HIFI observations of hydrogen chloride towards W3A  

E-print Network

We report on the detection with the HIFI instrument on board the Herschel satellite of the two hydrogen chloride isotopologues, H35Cl and H37Cl, towards the massive star-forming region W3A. The J=1-0 line of both species was observed with receiver 1b of the HIFI instrument at 625.9 and 624.9 GHz. The different hyperfine components were resolved. The observations were modeled with a non-local, non-LTE radiative transfer model that includes hyperfine line overlap and radiative pumping by dust. Both effects are found to play an important role in the emerging intensity from the different hyperfine components. The inferred H35Cl column density (a few times 1e14 cm^-2), and fractional abundance relative to H nuclei (~7.5e^-10), supports an upper limit to the gas phase chlorine depletion of ~200. Our best-fit model estimate of the H35Cl/H37Cl abundance ratio is ~2.1+/-0.5, slightly lower, but still compatible with the solar isotopic abundance ratio (~3.1). Since both species were observed simultaneously, this is the...

Cernicharo, J; Daniel, F; Agundez, M; Caux, E; de Graauw, T; De Jonge, A; Kester, D; Leduc, H G; Steinmetz, E; Stutzki, J; Ward, J S

2010-01-01

26

Application of 14N NQR to the study of piroxicam polymorphism.  

PubMed

A study was conducted to test the capability of the (14)N nuclear quadrupole resonance (NQR) method to discriminate qualitatively and quantitatively among different forms of piroxicam. Samples of commercial piroxicam form I and its monohydrate were obtained on the local market. Additionally, samples of form I and II were prepared by recrystallization in 1,2-dichloroethane and ethanol, respectively. DSC and FT-IR were employed as reference methods. A (14)N NQR spectrometer was used to measure samples of different forms and mixtures of piroxicam at 2587 and 3439 ?kHz. DSC and FT-IR clearly confirmed differences between the different piroxicam forms. Measurements of (14)N NQR signals of different forms of piroxicam at 2587 ?kHz detected only spectral peaks of form I. The dependence of (14)N NQR signal intensity on the concentration of form I in mixtures with the monohydrate showed a clear linear relationship at both measured frequencies, though the scattering of data was greater at 3439 ?kHz due to the lower S/N ratio. The (14)N NQR method has the potential to become an additional and important spectroscopic tool in the study of solid-state forms, not only of pure active pharmaceutical ingredients or excipients, but also of their mixtures. This ability lends the method to a possible successful utilization at different levels of pharmaceutical manufacturing and product quality control. PMID:20597116

Lavri?, Zoran; Pirnat, Janez; Lužnik, Janko; Seliger, Janez; Zagar, Veselko; Trontelj, Zvonko; Sr?i?, Stane

2010-12-01

27

Copper valence, structural separation and lattice dynamics in tennantite (fahlore): NMR, NQR and SQUID studies  

NASA Astrophysics Data System (ADS)

Electronic and magnetic properties of tennantite subfamily of tetrahedrite-group minerals have been studied by copper nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and SQUID magnetometry methods. The temperature dependences of copper NQR frequencies and line-width, nuclear spin-lattice relaxation rate T {1/-1} and nuclear spin-echo decay rate T {2/-1} in tennantite samples in the temperature range 4.2-210 K is evidence of the presence of field fluctuations caused by electronic spins hopping between copper CuS3 positions via S2 bridging atom. The analysis of copper NQR data at low temperatures points to the magnetic phase transition near 65 K. The magnetic susceptibility in the range 2-300 K shows a Curie-Weiss behavior, which is mainly determined by Fe2+ paramagnetic substituting ions.

Gainov, R. R.; Dooglav, A. V.; Pen'kov, I. N.; Mukhamedshin, I. R.; Savinkov, A. V.; Mozgova, N. N.

2008-01-01

28

Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.  

PubMed

Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined ?iso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and ?33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (?11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements. PMID:24581866

Peri?, Berislav; Gautier, Régis; Pickard, Chris J; Bosio?i?, Marko; Grbi?, Mihael S; Požek, Miroslav

2014-01-01

29

Methyl quantum tunneling and nitrogen-14 NQR NMR studies using a SQUID magnetic resonance spectrometer  

SciTech Connect

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) techniques have been very successful in obtaining molecular conformation and dynamics information. Unfortunately, standard NMR and NQR spectrometers are unable to adequately detect resonances below a few megahertz due to the frequency dependent sensitivity of their Faraday coil detectors. For this reason a new spectrometer with a dc SQUID (Superconducting Quantum Interference Device) detector, which has no such frequency dependence, has been developed. Previously, this spectrometer was used to observe {sup 11}B and {sup 27}Al NQR resonances. The scope of this study was increased to include {sup 23}Na, {sup 51}V, and {sup 55}Mn NQR transitions. Also, a technique was presented to observe {sup 14}N NQR resonances through cross relaxation of the nitrogen polarization to adjacent proton spins. When the proton Zeeman splitting matches one nitrogen quadrupoler transition the remaining two {sup 14}N transitions can be detected by sweeping a saturating rf field through resonance. Additionally, simultaneous excitation of two nitrogen resonances provides signal enhancement which helps to connect transitions from the same site. In this way, nitrogen-14 resonances were observed in several amino acids and polypeptides. This spectrometer has also been useful in the direct detection of methyl quantum tunneling splittings at 4.2 K. Tunneling, frequencies of a homologous series of carboxylic acids were measured and for solids with equivalent crystal structures, an exponential correlation between the tunneling frequency and the enthalpy of fusion is observed. This correlation provides information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

Black, B.E. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)

1993-07-01

30

14 N NQR spectrum of sildenafil citrate  

NASA Astrophysics Data System (ADS)

The 14N nuclear quadrupole resonance (NQR) spectrum of sildenafil citrate tablets has been recorded allowing the quadrupole coupling constants and asymmetry parameters of all six unique nitrogen atoms in its structure to be determined. A density function calculation gives results that are largely in agreement with the experimental values.

Stephenson, David; Singh, Nadia

2014-10-01

31

Species selection for phytoremediation of 36Cl/35Cl using angiosperm phylogeny and inter-taxa differences in uptake.  

PubMed

High concentrations of 35Cl and the radioisotope 36Cl (produced naturally by cosmic radiation and anthropogenically by U fission and the use of neutron sources) can be problematic in soil, but are potentially amenable to phytoremediation if appropriate plants can be found. Here, results are reported that might aid the selection of plants with unusually high or low uptake of 36Cl A residual maximum likelihood analysis was used to estimate, from 13 experiments, relative 36Cl uptake by 106 species across the angiosperm phylogeny. Nested analysis of variance, coded using a recent angiosperm phylogeny, showed that there were significant inter-species differences in 36Cl uptake and that species behavior was not independent; but linked through theirphylogeny. Eudicots had significantly higher 36Cl uptake than Monocots and related clades and, in particular the Orders Caryophyllales, Apiales, and Cucurbitales had high uptake while the Poales, Lillales, Brassicales, and Fabales had low uptake. Overall, 35% of the inter-taxa variation in 36Cl was attributed to the taxonomic ranks of Order and above, a significant phylogenetic effect compared with other elements for which similar analyses have been published. The implications of these findings for selecting plants for phytoremediation of soil contaminated with 35/36Cl are discussed. PMID:16463542

Willey, Neil; Fawcett, Kathy

2005-01-01

32

Fragmentation Cross Sections of Medium-Energy 35Cl, 40Ar, and 48TiBeams on Elemental Targets  

SciTech Connect

Charge-changing and fragment production cross sections at 0degrees have been obtained for interactions of 290, 400, and 650MeV/nucleon 40Ar beams, 650 and 1000 MeV/nucleon 35Cl beams, and a 1000MeV/nucleon 48Ti beam. Targets of C, CH2, Al, Cu, Sn, and Pb were used.Using standard analysis methods, we obtain fragment cross sections forcharges as low as 8 for Cl and Ar beams, and as low as 10 for the Tibeam. Using data obtained with small-acceptance detectors, we reportfragment production cross sections for charges as low as 5, corrected foracceptance using a simple model of fragment angular distributions. Withthe lower-charged fragment cross sections, we cancompare the data topredictions from several models (including NUCFRG2, EPAX2, and PHITS) ina region largely unexplored in earlier work. As found in earlier workwith other beams, NUCFRG2 and PHITS predictions agree reasonably wellwith the data for charge-changing cross sections, but do not accuratelypredict the fragment production cross sections. The cross sections forthe lightest fragments demonstrate the inadequacy of several models inwhich the cross sections fall monotonically with the charge of thefragment. PHITS, despite not agreeing particularly well with the fragmentproduction cross sections on average, nonetheless qualitativelyreproduces somesignificant features of the data that are missing from theother models.

Zeitlin, C.; Guetersloh, S.; Heilbronn, L.; Miller, J.; Fukumura,A.; Iwata, Y.; Murakami, T.; Sihver, L.; Mancusi, D.

2007-12-08

33

The dissociation dynamics of He...I 35Cl(B,v'=2,3) complexes with varying amounts of internal energy.  

PubMed

The He...I (35)Cl intermolecular vibrational levels with n'=0-6 that are bound within the He+ICl(B,v'=3) potential [A. B. McCoy, J. P. Darr, D. S. Boucher, P. R. Winter, M. D. Bradke, and R. A. Loomis, J. Chem. Phys. 120, 2677 (2004)] are identified in laser-induced fluorescence experiments performed at very low temperatures within a supersonic expansion. Comparisons of the positions and intensities of these lines with the excitation spectra, calculated using potential surfaces to describe the interactions between the helium atom and ICl in its ground and excited state, assist in the assignments. Based on these comparisons the excited state potential was rescaled so that the experimental and calculated J'=0 energies agree to within the experimental uncertainties for all but the lowest, n'=0, intermolecular level. Two-laser, action, and pump-probe spectroscopy experiments indicate that the bound He...I (35)Cl(B,v'=3) intermolecular vibrational levels undergo vibrational predissociation forming rotationally excited I (35)Cl(B,v'=2,j') products with distributions that depend upon the initial intermolecular vibrational level excited. Action spectra recorded in the ICl B-X, 2-0 region while monitoring the Deltav=0, I (35)Cl(B,v'=2) channel reveal two additional dissociation mechanisms for the He...I (35)Cl(B,v') excited state complexes: rotational predissociation of discrete metastable states lying slightly above the He+I (35)Cl(B,v'=2) asymptote and direct dissociation that occurs when the linear conformer is excited to the continuum of states above the same asymptote. The rotational predissociation pathway forms I (35)Cl(B,v'=2,j') products in all of the rotational states energetically accessible. The direct dissociation mechanism yields very cold rotational product state distributions; for instance, the average rotational energy in the product state distribution measured when the linear complexes are prepared 20 cm(-1) above the dissociation limit is only 1.51 cm(-1), representing only 7.6% of the available energy. PMID:15740259

Darr, Joshua P; Loomis, Richard A; McCoy, Anne B

2005-01-22

34

NQR Study of Dynamics in Incommensurate Phases  

NASA Astrophysics Data System (ADS)

Dynamic processes in solids exhibiting structurally incommensurate phases are briefly reviewed, and the application of NMR and NQR is discussed. The unique utility of these methods, - arising due to, on one hand, the microscopic resonant nature of the probe used and, on the other, the presence of periodic, though incommensurable, structure - , is brought out by presenting recent results in a prototype system (Rb2ZnCl4) in the presence of randomly quenched disorder. In particular, the interesting new methodology of measuring, by analysing NQR spin echo modulation, ultra-slow diffusion like collective motions of ensembles of atoms in the presence of pinning effects due to disorder is illustrated with new results.

Sastry, V. S. S.; Venu, K.; Maheswari, S. Uma; Subramanian, R. K.

2000-02-01

35

Improved line parameters for the Chi 2Pi-Chi 2Pi (1-0) bands of (35)ClO and (37)ClO  

NASA Technical Reports Server (NTRS)

Improved line parameters at 296 K for the Chi 2Pi-Chi 2Pi (1-0) bands of (35)ClO and (37)ClO have been calculated with J up to 43.5. The integrated intensity for the 2048 lines in the main and satellite bands has been normalized to 9.68-sq cm/atm at 296K.

Goldman, Aaron; Gillis, James R.; Rinsland, Curtis P.; Burkholder, James B.

1994-01-01

36

93Nb- and 27Al-NMR/NQR studies of the praseodymium based PrNb2Al20  

NASA Astrophysics Data System (ADS)

We report a study of 93Nb- and 27Al-nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) in a praseodymium based compound PrNb2Al20. The observed NMR line at around 3 T and 30 K shows a superposition of typical powder patterns of one Nb signal and at least two Al signals. 93Nb-NMR line could be reproduced by using the previously reported NQR frequency ?Q ? 1.8MHz and asymmetry parameter ? ? 0 [Kubo T et al 2014 JPS Conf. Proc. 3 012031]. From 27Al-NMR/NQR, NQR parameters are obtained to be ?Q,A ? 1.53 MHz, and ?A ? 0.20 for the site A, and ?Q,B ? 2.28 MHz, and ?B ? 0.17 for the site B. By comparing this result with the previous 27Al-NMR study of PrT2Al20 (T = Ti, V) [Tokunaga Y et al 2013 Phys. Rev. B 88 085124], these two Al site are assigned to the two of three crystallographycally inequivalent Al sites.

Kubo, Tetsuro; Kotegawa, Hisashi; Tou, Hideki; Higashinaka, Ryuji; Nakama, Akihiro; Aoki, Yuji; Sato, Hideyuki

2015-03-01

37

Exploiting temperature dependency in the detection of NQR signals  

Microsoft Academic Search

Nuclear quadrupole resonance (NQR) offers an unequivocal method of detecting and identifying land mines. Unfortunately, the practical use of NQR is restricted by the low signal-to-noise ratio (SNR), and the means to improve the SNR are vital to enable a rapid, reliable, and convenient system. In this paper, an approximate maximum-likelihood detector (AML) is developed, exploiting the temperature dependency of

Andreas Jakobsson; Magnus Mossberg; Michael D. Rowe; John A. S. Smith

2006-01-01

38

Zero-field NMR and NQR studies of magnetically ordered state in charge-ordered EuPtP  

NASA Astrophysics Data System (ADS)

EuPtP undergoes two valence transitions and has two kinds of valence states of Eu ions at low temperatures. In the charge-ordered state, this compound shows an antiferromagnetic order ascribed to magnetic divalent Eu ions. We investigated the antiferromagnetically ordered state of EuPtP by nuclear magnetic resonance (NMR) measurement and nuclear quadrupole resonance (NQR) measurement in a zero external magnetic field. The observed 153Eu NMR signals of a magnetic divalent state and Eu,153151 NQR signals of a nonmagnetic trivalent state clearly demonstrate that the spins order in the hexagonal basal plane and the internal magnetic field is not canceled out, even at the Eu3 + layers which are in the middle of magnetic Eu2 + layers. In addition, the observation of 31P and 195Pt NMR spectra allowed us to discuss a possible magnetic structure. We also evaluated the nuclear quadrupole frequencies for both Eu2 + and Eu3 + ion states.

Koyama, T.; Maruyama, T.; Ueda, K.; Mito, T.; Mitsuda, A.; Umeda, M.; Sugishima, M.; Wada, H.

2015-03-01

39

Detection of chloronium and measurement of the 35Cl/37Cl isotopic ratio at z = 0.89 toward PKS 1830-211  

NASA Astrophysics Data System (ADS)

We report the first extragalactic detection of chloronium (H2Cl+) in the z = 0.89 absorber in front of the lensed blazar PKS 1830-211. The ion is detected through its 111-000 line along two independent lines of sight toward the North-East and South-West images of the blazar. The relative abundance of H2Cl+ is significantly higher (by a factor ~7) in the NE line of sight, which has a lower H2/H fraction, indicating that H2Cl+ preferably traces the diffuse gas component. From the ratio of the H235Cl+ and H237Cl+ absorptions toward the SW image, we measure a 35Cl/37Cl isotopic ratio of 3.1-0.2+0.3 at z = 0.89, similar to that observed in the Galaxy and the solar system.

Muller, S.; Black, J. H.; Guélin, M.; Henkel, C.; Combes, F.; Gérin, M.; Aalto, S.; Beelen, A.; Darling, J.; Horellou, C.; Martín, S.; Menten, K. M.; V-Trung, Dinh; Zwaan, M. A.

2014-06-01

40

Rapid detection of arsenic minerals using portable broadband NQR  

NASA Astrophysics Data System (ADS)

The remote real-time detection of specific arsenic species would significantly benefit in minerals processing to mitigate the release of arsenic into aquatic environments and aid in selective mining. At present, there are no technologies available to detect arsenic minerals in bulk volumes outside of laboratories. Here we report on the first room-temperature broadband 75As nuclear quadrupole resonance (NQR) detection of common and abundant arsenic ores in the Earth crust using a large sample (0.78 L) volume prototype sensor. Broadband excitation aids in detection of natural minerals with low crystallinity. We briefly discuss how the proposed NQR detector could be employed in mining operations.

Lehmann-Horn, J. A.; Miljak, D. G.; O'Dell, L. A.; Yong, R.; Bastow, T. J.

2014-10-01

41

K-shell ionization and radiative electron capture in 0.75-2.5 MeV u-1 32S, 35Cl + Cu atomic collisions  

NASA Astrophysics Data System (ADS)

From the measured target thickness dependence of the K x-ray and radiative electron capture (REC) yields in the 0.75-2.5 MeV u-1 32S, 35Cl + Cu collisions, the cross sections for K x-ray production and REC, in dependence on collision energy, have been determined. In comparison with theory, we find simple models that describe rather well some of the present results. The target (Cu) K x-ray production cross sections are in fair agreement with ECPSSR model predictions. The REC theoretical calculations (Stobbe model times 11, the number of loosely bound electrons in Cu) are in agreement with the present data for Cl + Cu collision, but overestimate the data for S + Cu collision by approximately a factor of 2. Large enhancements for the projectile K-shell fluorescence yields, up to 10 for S and 6 for Cl, as well as for K-shell vacancy lifetimes, up to 16 for S and 21 for Cl, are reported.

Scafe?, A. C.; Ciortea, C.; Dumitriu, D. E.; Enulescu, A.; Fluera?u, D.; Gugiu, M. M.; Pen?ia, M.; Piticu, I.

2013-09-01

42

Triphenylsilyl perchlorate revisited: /sup 29/Si and /sup 35/Cl NMR spectroscopy and x-ray crystallography showing covalent nature in both solution and the solid state. Difficulties in observing long-lived silyl cations in the condensed state  

SciTech Connect

/sup 29/Si and /sup 35/Cl NMR spectroscopic and X-ray crystallographic study of triphenylsilyl perchlorate shows it to be a covalent perchloryl ester in both solution and the solid state. The results are in accord with earlier studies notably those of Wannagat but contrast the recent claim by Lambert etal. (J. Am. Chem. Soc. 1986, 108, 2482) for NMR observation of long-lived ionic triphenylsilyl perchlorate.

Prakash, G.K.S.; Keyaniyan, S.; Aniszfeld, R.; Heiliger, L.; Olah, G.A.; Stevens, R.C.; Choi, H.K.; Bau, R.

1987-08-19

43

NQR Investigation of Anion Dynamics in Rb2Zn(Cl1 - xBrx)4  

NASA Astrophysics Data System (ADS)

The structural stability of Rb2Zn(Cl1 - xBrx)4 (x = 1% and 3%) is investigated using the 35Cl quadrupole resonance frequency and spin lattice relaxation time (T1Q) in the paraelectric (PE) phase. The PE to incommensurate (IC) phase transition temperature T1, observed at 302 K in the pure compound, is lowered to 300 K for x = 1 % and to 293 K for x = 3%. These effects are smaller than in the earlier reported case of 3% Cs substitution in Rb2ZnCl4 , which reduces T1 by 25 K. While bigger cation substitution affects only the barrier for anion dynamics about directions perpendicular to the a-axis (direction of low temperature IC modulation wave), bigger anion substitution is found to affect the barrier for anion dynamics about the a-axis as well. The present study also indicates that the cusp like dip in T1Q observed while approaching T1 from above (characterizing the soft mode condensation associated with the structural phase transition) is essentially unaffected by anion impurity substitution, in contrast to the case where bigger cation substitution tends to smear the transitional effects. These results seem to suggest the dominant role played by cations in stabilizing the PE phase of these A2BX4 systems, in comparison to anions.

Subramanian, R. K.; Maheswari, S. Uma; Venu, K.; Sastry, V. S. S.

1996-06-01

44

Localization and Function of the Membrane-bound Riboflavin in the Na+-translocating NADH:Quinone Oxidoreductase (Na+-NQR) from Vibrio cholerae*  

PubMed Central

The sodium ion-translocating NADH:quinone oxidoreductase (Na+-NQR) from the human pathogen Vibrio cholerae is a respiratory membrane protein complex that couples the oxidation of NADH to the transport of Na+ across the bacterial membrane. The Na+-NQR comprises the six subunits NqrABCDEF, but the stoichiometry and arrangement of these subunits are unknown. Redox-active cofactors are FAD and a 2Fe-2S cluster on NqrF, covalently attached FMNs on NqrB and NqrC, and riboflavin and ubiquinone-8 with unknown localization in the complex. By analyzing the cofactor content and NADH oxidation activity of subcomplexes of the Na+-NQR lacking individual subunits, the riboflavin cofactor was unequivocally assigned to the membrane-bound NqrB subunit. Quantitative analysis of the N-terminal amino acids of the holo-complex revealed that NqrB is present in a single copy in the holo-complex. It is concluded that the hydrophobic NqrB harbors one riboflavin in addition to its covalently attached FMN. The catalytic role of two flavins in subunit NqrB during the reduction of ubiquinone to ubiquinol by the Na+-NQR is discussed. PMID:20558724

Casutt, Marco S.; Huber, Tamara; Brunisholz, René; Tao, Minli; Fritz, Günter; Steuber, Julia

2010-01-01

45

A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35 Cl , 113 Cd , and 139 La  

Microsoft Academic Search

An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1\\/10th scale test of the design for the forthcoming n?+p?d+? experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current

G. S. Mitchell; C. S. Blessinger; J. D. Bowman; T. E Chupp; K. P Coulter; M. Gericke; G. L Jones; M. B Leuschner; H. Nann; S. A Page; S. I. Penttilä; T. B Smith; W. M Snow; W. S. Wilburn

2004-01-01

46

Solid-State NMR/NQR and First-Principles Study of Two Niobium Halide Cluster Compounds  

E-print Network

1 Solid-State NMR/NQR and First-Principles Study of Two Niobium Halide Cluster Compounds Berislav : 10.1016/j.ssnmr.2014.02.001 #12;2 Abstract Two hexanuclear niobium halide cluster compounds solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were

Boyer, Edmond

47

A computational NQR study on the hydrogen-bonded lattice of cytosine-5-acetic acid.  

PubMed

A computational study at the level of density functional theory (DFT) employing 6-311++G** standard basis set was carried out to evaluate nuclear quadrupole resonance (NQR) spectroscopy parameters in cytosine-5-acetic acid (C5AA). Since the electric field gradient (EFG) tensors are very sensitive to the electrostatic environment at the sites of quadruple nuclei, the most possible interacting molecules with the target one were considered in a five-molecule model system of C5AA using X-ray coordinates transforming. The hydrogen atoms positions were optimized and two model systems of original and H-optimized C5AA were considered in NQR calculations. The calculated EFG tensors at the sites of (17)O, (14)N, and (2)H nuclei were converted to their experimentally measurable parameters, quadrupole coupling constants and asymmetry parameters. The evaluated NQR parameters reveal that the nuclei in original and H-optimized systems contribute to different hydrogen bonding (HB) interaction. The comparison of calculated parameters between optimized isolated gas-phase and crystalline monomer also shows the relationship between the structural deformation and NQR parameters in C5AA. The basis set superposition error (BSSE) calculations yielded no significant errors for employed basis set in the evaluation of NQR parameters. All the calculations were performed by Gaussian 98 package of program. PMID:17926341

Mirzaei, Mahmoud; Hadipour, Nasser L

2008-04-15

48

C-Cl activation of the weakly coordinating anion [B(3,5-Cl2C6H3)4]- at a Rh(I) centre in solution and the solid-state.  

PubMed

Addition of H2 to [Rh((i)Bu2PCH2CH2P(i)Bu2)(NBD)][BAr(Cl)4] (NBD = norbornadiene, Ar(Cl) = 3,5-Cl2C6H3) in the solid-state results in the rapid formation of zwitterionic [Rh((i)Bu2PCH2CH2P(i)Bu2){(?(6)-C6H3Cl2)BAr(Cl)3}] by a gas/solid reaction. This undergoes slow C-Cl bond cleavage in the solid-state to ultimately afford the dimeric Rh(III) complex [RhCl((i)Bu2PCH2CH2P(i)Bu2){C6H3Cl(BAr(Cl)3)}]2. This reactivity is mirrored in solution (CH2Cl2). Kinetic data for the C-Cl activation in both the solid-state and solution are reported. PMID:23884210

Pike, Sebastian D; Weller, Andrew S

2013-09-28

49

NQR investigation of pressure-induced charge transfer in oxygen-deficient YBa sub 2 Cu sub 3 O sub 7-. delta. (. delta. = 0. 38)  

SciTech Connect

Measurements of the pressure dependence of {sup 63}Cu nuclear quadrupole frequency in YBa{sub 2}Cu{sub 3}O{sub 6.62} from ambient pressure up to 1.5 GPa at 4k have been performed. {Tc} was found to increase with pressure: d{Tc}/dp {approximately} 5 K/GPa. All observed NQR lines are linear in pressure: dln{nu}{sub Q}/dp=z. We found positive z for the empty chain sites, consistent with ionic (Cu{sup 1+}) configuration in which the atom simply feels a squeezing lattice. Planar coppers close to the empty chains have positive z, while those that are close to full chains have z {approximately} 0. We present an analysis of the NQR result on the basis of the charge transfer model in which the mobile charges migrate from the chain to the plane sites. We deduced that a transfer of 0.021 holes to the O(2,3) sites would explain the result in YBa{sub 2}Cu{sub 3}O{sub 6.62}, whereas only 0.007 holes transfer in fully oxygenated YBa{sub 2}Cu{sub 3}O{sub 7}.

Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H. (Los Alamos National Lab., NM (United States)); Takigawa, M. (International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center)

1992-01-01

50

Low-frequency nuclear quadrupole resonance with a dc SQUID  

SciTech Connect

Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.

Chang, J.W.

1991-07-01

51

Genomic Plasticity of the rrn-nqrF Intergenic Segment in the Chlamydiaceae?  

PubMed Central

In Chlamydiaceae, the nucleotide sequence between the 5S rRNA gene and the gene for subunit F of the Na+-translocating NADH-quinone reductase (nqrF or dmpP) has varied lengths and gene contents. We analyzed this site in 45 Chlamydiaceae strains having diverse geographical and pathological origins and including members of all nine species. PMID:17158668

Liu, Zhi; Rank, Roger; Kaltenboeck, Bernhard; Magnino, Simone; Dean, Deborah; Burall, Laurel; Plaut, Roger D.; Read, Timothy D.; Myers, Garry; Bavoil, Patrik M.

2007-01-01

52

Z .Solid State Nuclear Magnetic Resonance 11 1998 139156 SQUID detected NMR and NQR  

E-print Network

Z .Solid State Nuclear Magnetic Resonance 11 1998 139­156 SQUID detected NMR and NQR Matthew P dc Superconducting QUantum Interference Device SQUID is a sensitive detector of magnetic flux to a thin film superconducting coil deposited on the SQUID to form a flux transformer. With this untuned

Augustine, Mathew P.

53

Weakly first-order behavior in ferromagnetic transition of UCoGe revealed by 59Co-NQR studies  

NASA Astrophysics Data System (ADS)

We have performed 59Co nuclear quadrupole resonance (NQR) measurements on ferromagnetic (FM) superconductor UCoGe, in which ferromagnetism occurs at TCurie ˜ 2.5 K. By measuring NQR spectrum at various temperatures, we investigated the development of local magnetic moment around TCurie, and suggest that FM transition possesses weakly first-order character. This first-order behavior is consistent with the theoretical prediction that the low temperature FM transition in itinerant magnets is generically of first-order.

Hattori, T.; Ishida, K.; Nakai, Y.; Ohta, T.; Deguchi, K.; Sato, N. K.; Satoh, I.

2010-12-01

54

Mass and charge distributions in chlorine-induced nuclear reactions. [[sup 35]Cl at E/A = 15 MeV, [sup 37]Cl at E/A = 7. 3 MeV  

SciTech Connect

Projectile-like fragments were detected and characterized in terms of A, Z, and energy for the reactions [sup 37]Cl on [sup 40]Ca and [sup 209]Bi at E/A = 7.3 MeV, and [sup 35]Cl, on [sup 209]Bi at E/A = 15 MeV, at angles close to the grazing angle. Mass and charge distributions were generated in the N-Z plane as a function of energy loss, and have been parameterized in terms of their centroids, variances, and coefficients of correlation. Due to experimental problems, the mass resolution corresponding to the [sup 31]Cl on [sup 209]Bi reaction was very poor. This prompted the study and application of a deconvolution technique for peak enhancement. The drifts of the charge and mass centroids for the system [sup 37]Cl on [sup 40]Ca are consistent with a process of mass and charge equilibration mediated by nucleon exchange between the two partners, followed by evaporation. The asymmetric systems show a strong drift towards larger asymmetry, with the production of neutron-rich nuclei. It was concluded that this is indicative of a net transfer of protons from the light to the heavy partner, and a net flow of neutrons in the opposite direction. The variances for all systems increase with energy loss, as it would be expected from a nucleon exchange mechanism; however, the variances for the reaction [sup 37]Cl on [sup 40]Ca are higher than those expected from that mechanism. The coefficients of correlation indicate that the transfer of nucleons between projectile and target is correlated. The results were compared to the predictions of two current models based on a stochastic nucleon exchange mechanism. In general, the comparisons between experimental and predicted variances support this mechanism; however, the need for more realistic driving forces in the model calculations is indicated by the disagreement between predicted and experimental centroids.

Marchetti, A.A.

1991-01-01

55

NQR Line Broadening Due to Crystal Lattice Imperfections and Its Relationship to Shock Sensitivity  

NASA Astrophysics Data System (ADS)

The hydrodynamic hot spot model is used to explain the difference between shock sensitive and shock insensitive explosives. Among the major factors that influence the shock sensitivity of energetic compounds are the quality and particle size of the energetic crystals used to formulate the cast plastic bonded explosive. As do all energetic compounds, RDX and HMX exhibit internal crystal defects the magnitude and type of which depend on the manufacturing process used to synthesize and re-crystallize the energetic compound. Nuclear Quadrupole Resonance (NQR) spectroscopy was used to determine the crystal quality of RDX, HMX and CL-20 obtained from various manufacturers. The NQR experimental results are discussed. Cast plastic bonded explosives were made using the RDX and HMX obtained from the various manufacturers and subsequently subjected to the NOL large-scale gap test (LSGT). The results of the LSGT are discussed and correlated with the NQR results. A relationship between the crystal defect density and shock initiation pressure of the plastic bonded explosive is developed and discussed.

Caulder, S. M.; Buess, M. L.; Garroway, A. N.; Miller, P. J.

2004-07-01

56

NQR investigation of pressure-induced charge transfer in oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} ({delta} = 0.38)  

SciTech Connect

Measurements of the pressure dependence of {sup 63}Cu nuclear quadrupole frequency in YBa{sub 2}Cu{sub 3}O{sub 6.62} from ambient pressure up to 1.5 GPa at 4k have been performed. {Tc} was found to increase with pressure: d{Tc}/dp {approximately} 5 K/GPa. All observed NQR lines are linear in pressure: dln{nu}{sub Q}/dp=z. We found positive z for the empty chain sites, consistent with ionic (Cu{sup 1+}) configuration in which the atom simply feels a squeezing lattice. Planar coppers close to the empty chains have positive z, while those that are close to full chains have z {approximately} 0. We present an analysis of the NQR result on the basis of the charge transfer model in which the mobile charges migrate from the chain to the plane sites. We deduced that a transfer of 0.021 holes to the O(2,3) sites would explain the result in YBa{sub 2}Cu{sub 3}O{sub 6.62}, whereas only 0.007 holes transfer in fully oxygenated YBa{sub 2}Cu{sub 3}O{sub 7}.

Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H. [Los Alamos National Lab., NM (United States); Takigawa, M. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center

1992-03-01

57

Roles of the Sodium-Translocating NADH:Quinone Oxidoreductase (Na+-NQR) on Vibrio cholerae Metabolism, Motility and Osmotic Stress Resistance  

PubMed Central

The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ?nqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ?nqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ?nqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology. PMID:24811312

Minato, Yusuke; Halang, Petra; Quinn, Matthew J.; Faulkner, Wyatt J.; Aagesen, Alisha M.; Steuber, Julia; Stevens, Jan F.; Häse, Claudia C.

2014-01-01

58

Roles of the sodium-translocating NADH:quinone oxidoreductase (Na+-NQR) on vibrio cholerae metabolism, motility and osmotic stress resistance.  

PubMed

The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ?nqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ?nqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ?nqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology. PMID:24811312

Minato, Yusuke; Fassio, Sara R; Kirkwood, Jay S; Halang, Petra; Quinn, Matthew J; Faulkner, Wyatt J; Aagesen, Alisha M; Steuber, Julia; Stevens, Jan F; Häse, Claudia C

2014-01-01

59

On the crystal structures of some protonic complexes of oxo-ligands with tetrachloroauric acid, [(RO) n H][AuCl 4] (R: Py, Ph 3As; n: 1, 2), prepared from deuterated and non-deuterated solvent systems  

Microsoft Academic Search

The possible structural change of the dimeric cations [(RO)nH]+ (R=Py, Ph3As) in [(RO)nH][AuCl4] crystals due to the lowering of temperature or hydrogen–deuterium exchange was studied by 35Cl NQR and powder X-ray diffraction measurements. Temperature dependence of the nuclear quadrupole resonance (NQR) frequencies of [(Ph3AsO)2H][AuCl4] and [(PyO)2H][AuCl4] suggested the symmetric hydrogen bond was retained down to 4.2 K. A crystalline polymorph

Tetsuo Asaji; Fukue Tajima; Masao Hashimoto

2002-01-01

60

Defective BN Nanotubes: A Density Functional Theory Study of B-11 and N-14 NQR Parameters  

NASA Astrophysics Data System (ADS)

A density functional theory (DFT) study is performed to investigate the influence of structural defects on the electronic structure properties of perfect boron nitride nanotubes (BNNTs). To this aim, as representative models, the single-walled (6,0) BNNT consisting of 36 boron, 36 nitrogen, and 12 hydrogen atoms and the single-walled (4,4) BNNT consisting of 36 boron, 36 nitrogen, and 16 hydrogen atoms are considered. The nuclear quadrupole resonance (NQR) parameters are calculated and compared in two perfect and defective models of the considered BNNTs. The results indicate that due to formation of non-hexagonal rings in the defective model because of removing a B-N bond, the NQR parameters at the sites of first neighbouring nuclei are significantly influenced by imposed perturbation, however, the sites of other nuclei, farther from perturbation, remain almost unchanged. The calculations are performed at the level of the BLYP method and 6-31G* standard basis set using the GAUSSIAN 98 package

Giahi, Masoud; Mirzaei, Mahmoud

2009-04-01

61

Ru-NQR Study for Novel Phase Transition in CeRu2Al10  

NASA Astrophysics Data System (ADS)

We have performed Ru-NQR measurements on CeRu2Al10 exhibiting novel phase transition at an abnormally high temperature T0 = 27.3 K and on NdRu2Al10 with a magnetic transition temperature Tm = 2.4 K as a reference RKKY system. The splitting of the NQR line due to internal fields below T0 shows a mean-field-like monotonic increase, indicating no change in the magnetic structure below T0. The internal field strength is one order larger than those at Al sites in CeRu2Al10, and is comparable to that at the Ru site in NdRu2Al10 despite the sevenfold smaller magnitude of the 4f moment, being indicative of an enhanced conduction electron polarization at the Ru site. One of the causes of the high T0 might be the enhanced exchange coupling through the Ce–Ru–Ce path mediated by the enhanced conduction electron polarization. Being similar to that in the Al site, the nuclear spin–lattice relaxation rate 1/T1 shows a gap-like decrease below T0 without enhancement owing to a critical slowing down at T0, in contrast to the mean field 2nd-order transition.

Matsumura, Masahiro; Tomita, Naoya; Matsuoka, Junichirou; Kishimoto, Yasuki; Kato, Harukazu; Kitagawa, Kentaro; Nishioka, Takashi; Tanida, Hiroshi; Sera, Masafumi

2014-10-01

62

A mutation in Na(+)-NQR uncouples electron flow from Na(+) translocation in the presence of K(+).  

PubMed

The sodium-pumping NADH:ubiquinone oxidoreductase (Na(+)-NQR) is a bacterial respiratory enzyme that obtains energy from the redox reaction between NADH and ubiquinone and uses this energy to create an electrochemical Na(+) gradient across the cell membrane. A number of acidic residues in transmembrane helices have been shown to be important for Na(+) translocation. One of these, Asp-397 in the NqrB subunit, is a key residue for Na(+) uptake and binding. In this study, we show that when this residue is replaced with asparagine, the enzyme acquires a new sensitivity to K(+); in the mutant, K(+) both activates the redox reaction and uncouples it from the ion translocation reaction. In the wild-type enzyme, Na(+) (or Li(+)) accelerates turnover while K(+) alone does not activate. In the NqrB-D397N mutant, K(+) accelerates the same internal electron transfer step (2Fe-2S ? FMNC) that is accelerated by Na(+). This is the same step that is inhibited in mutants in which Na(+) uptake is blocked. NqrB-D397N is able to translocate Na(+) and Li(+), but when K(+) is introduced, no ion translocation is observed, regardless of whether Na(+) or Li(+) is present. Thus, this mutant, when it turns over in the presence of K(+), is the first, and currently the only, example of an uncoupled Na(+)-NQR. The fact the redox reaction and ion pumping become decoupled from each other only in the presence of K(+) provides a switch that promises to be a useful experimental tool. PMID:25486106

Shea, Michael E; Mezic, Katherine G; Juárez, Oscar; Barquera, Blanca

2015-01-20

63

Structural and Functional Investigation of Flavin Binding Center of the NqrC Subunit of Sodium-Translocating NADH:Quinone Oxidoreductase from Vibrio harveyi.  

PubMed

Na+-translocating NADH:quinone oxidoreductase (NQR) is a redox-driven sodium pump operating in the respiratory chain of various bacteria, including pathogenic species. The enzyme has a unique set of redox active prosthetic groups, which includes two covalently bound flavin mononucleotide (FMN) residues attached to threonine residues in subunits NqrB and NqrC. The reason of FMN covalent bonding in the subunits has not been established yet. In the current work, binding of free FMN to the apo-form of NqrC from Vibrio harveyi was studied showing very low affinity of NqrC to FMN in the absence of its covalent bonding. To study structural aspects of flavin binding in NqrC, its holo-form was crystallized and its 3D structure was solved at 1.56 Å resolution. It was found that the isoalloxazine moiety of the FMN residue is buried in a hydrophobic cavity and that its pyrimidine ring is squeezed between hydrophobic amino acid residues while its benzene ring is extended from the protein surroundings. This structure of the flavin-binding pocket appears to provide flexibility of the benzene ring, which can help the FMN residue to take the bended conformation and thus to stabilize the one-electron reduced form of the prosthetic group. These properties may also lead to relatively weak noncovalent binding of the flavin. This fact along with periplasmic location of the FMN-binding domains in the vast majority of NqrC-like proteins may explain the necessity of the covalent bonding of this prosthetic group to prevent its loss to the external medium. PMID:25734798

Borshchevskiy, Valentin; Round, Ekaterina; Bertsova, Yulia; Polovinkin, Vitaly; Gushchin, Ivan; Ishchenko, Andrii; Kovalev, Kirill; Mishin, Alexey; Kachalova, Galina; Popov, Alexander; Bogachev, Alexander; Gordeliy, Valentin

2015-01-01

64

Structural and Functional Investigation of Flavin Binding Center of the NqrC Subunit of Sodium-Translocating NADH:Quinone Oxidoreductase from Vibrio harveyi  

PubMed Central

Na+-translocating NADH:quinone oxidoreductase (NQR) is a redox-driven sodium pump operating in the respiratory chain of various bacteria, including pathogenic species. The enzyme has a unique set of redox active prosthetic groups, which includes two covalently bound flavin mononucleotide (FMN) residues attached to threonine residues in subunits NqrB and NqrC. The reason of FMN covalent bonding in the subunits has not been established yet. In the current work, binding of free FMN to the apo-form of NqrC from Vibrio harveyi was studied showing very low affinity of NqrC to FMN in the absence of its covalent bonding. To study structural aspects of flavin binding in NqrC, its holo-form was crystallized and its 3D structure was solved at 1.56 Å resolution. It was found that the isoalloxazine moiety of the FMN residue is buried in a hydrophobic cavity and that its pyrimidine ring is squeezed between hydrophobic amino acid residues while its benzene ring is extended from the protein surroundings. This structure of the flavin-binding pocket appears to provide flexibility of the benzene ring, which can help the FMN residue to take the bended conformation and thus to stabilize the one-electron reduced form of the prosthetic group. These properties may also lead to relatively weak noncovalent binding of the flavin. This fact along with periplasmic location of the FMN-binding domains in the vast majority of NqrC-like proteins may explain the necessity of the covalent bonding of this prosthetic group to prevent its loss to the external medium. PMID:25734798

Bertsova, Yulia; Polovinkin, Vitaly; Gushchin, Ivan; Ishchenko, Andrii; Kovalev, Kirill; Mishin, Alexey; Kachalova, Galina; Popov, Alexander; Bogachev, Alexander; Gordeliy, Valentin

2015-01-01

65

A study of hydrogen bond of imidazole and its 4-nitro derivative by ab initio and DFT calculated NQR parameters  

Microsoft Academic Search

Nuclear quadrupole resonance (NQR) parameters of 14N, 2H of N2H groups are calculated for imidazole and 4-nitroimidazole using HF and B3LYP methods. These computations are performed on the basis of X-ray and neutron diffraction structural data which are collected at 100, 103, 123 and 293 K temperatures. In order to take into account intermolecular hydrogen bonds and the van der

S. K. Amini; N. L. Hadipour; F. Elmi

2004-01-01

66

Emission spectroscopy, harmonic vibrational frequencies, and improved ground state structures of jet-cooled monochloro- and monobromosilylene (HSiCl and HSiBr)  

Microsoft Academic Search

The ground state harmonic frequencies of gas phase H\\/DSi35Cl and H\\/DSi79Br have been determined by exciting single vibronic bands of the A~ 1A''-X~ 1A' electronic transition and recording the dispersed fluorescence. The jet-cooled radicals were produced in a pulsed discharge jet using H\\/DSiX3 (X=Cl or Br) precursors. The emission data were fitted to an anharmonic model and a normal coordinate

David A. Hostutler; Nicholas Ndiege; Dennis J. Clouthier; Steven W. Pauls

2001-01-01

67

Superconducting state of filled-skutterudite RPt4Ge12 (R = La, Pr): 73Ge-NQR studies  

NASA Astrophysics Data System (ADS)

We report 73Ge-NQR studies on filled-skutterudite superconductors LaPt4Ge12 and PrPt4Ge12 under zero external field. In PrPt4Ge12, the measurement of the nuclear spin-lattice relaxation rate 1/T1 has revealed a distinct coherence peak just below Tc followed by an exponential decrease well below Tc, evidencing that PrPt4Ge12 is an s-wave superconductor with the isotropic gap in a weak-coupling regime. In LaPt4Ge12, the 1/T1 exhibits the exponential decrease well below Tc, suggesting the isotropic s-wave superconductivity. Even though 73Ge-NQR-1/T1 in LaPt4Ge12 has been measured under zero field, its coherence peak was absent, which contrasts with the result in Pr-compound. This may point to a possible anisotropy in the Fermi surface and/or some damping effect of quasiparticles in association with electron-phonon interactions.

Kanetake, F.; Mukuda, H.; Kitaoka, Y.; Sugawara, H.; Magishi, K.; Itoh, K. M.; Haller, E. E.

2010-12-01

68

Noise-resilient multi-frequency surface sensor for nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

A planar nuclear quadrupole resonance (NQR) sensor has been developed. The sensor is resilient to environmental noise and is capable of simultaneous independent multi-frequency operation. The device was constructed as an open multimodal birdcage structure, in which the higher modes, generally not used in magnetic resonance, are utilized for NQR detection. These modes have smooth distributions of the amplitudes of the corresponding radiofrequency magnetic fields everywhere along the sensor's surface. The phases of the fields, on the other hand, are cyclically shifted across the sensor's surface. Noise signals coming from distant sources, therefore, induce equal-magnitude cyclically phase-shifted currents in different parts of the sensor. When such cyclically phase-shifted currents arrive at the mode connection point, they destructively interfere with each other and are cancelled out. NQR signals of polycrystalline or disordered substances, however, are efficiently detected by these modes because they are insensitive to the phases of the excitation/detection. No blind spots exist along the sensor's surface. The sensor can be used for simultaneous detection of one or more substances in locations with environmental noise.

Peshkovsky, A. S.; Cattena, C. J.; Cerioni, L. M.; Osán, T. M.; Forguez, J. G.; Peresson, W. J.; Pusiol, D. J.

2008-10-01

69

An ultra-broadband low-frequency magnetic resonance system.  

PubMed

MR probes commonly employ resonant circuits for efficient RF transmission and low-noise reception. These circuits are narrow-band analog devices that are inflexible for broadband and multi-frequency operation at low Larmor frequencies. We have addressed this issue by developing an ultra-broadband MR probe that operates in the 0.1-3MHz frequency range without using conventional resonant circuits for either transmission or reception. This "non-resonant" approach significantly simplifies the probe circuit and allows robust operation without probe tuning while retaining efficient power transmission and low-noise reception. We also demonstrate the utility of the technique through a variety of NMR and NQR experiments in this frequency range. PMID:24632101

Mandal, S; Utsuzawa, S; Cory, D G; Hürlimann, M; Poitzsch, M; Song, Y-Q

2014-05-01

70

An ultra-broadband low-frequency magnetic resonance system  

NASA Astrophysics Data System (ADS)

MR probes commonly employ resonant circuits for efficient RF transmission and low-noise reception. These circuits are narrow-band analog devices that are inflexible for broadband and multi-frequency operation at low Larmor frequencies. We have addressed this issue by developing an ultra-broadband MR probe that operates in the 0.1-3 MHz frequency range without using conventional resonant circuits for either transmission or reception. This “non-resonant” approach significantly simplifies the probe circuit and allows robust operation without probe tuning while retaining efficient power transmission and low-noise reception. We also demonstrate the utility of the technique through a variety of NMR and NQR experiments in this frequency range.

Mandal, S.; Utsuzawa, S.; Cory, D. G.; Hürlimann, M.; Poitzsch, M.; Song, Y.-Q.

2014-05-01

71

Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat  

NASA Technical Reports Server (NTRS)

La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for x ranging from 0 up to 0.3, with particular emphasis on the effect of doping on the Cu(2+) magnetic correlations and dynamics, are reviewed. In the low doping limit, x less than or equal to 0.05, the results can be interpreted consistently in terms of a simple phenomenological 'two-fluids' model whereby the effect of thermally-activated mobile O(2p) holes is the one of disrupting locally the Cu(2+) spin correlations. For x greater than or equal to 0.1, the results indicate the onset, as T approaches T(sub c)(+), of a strong coupling between Cu(2+) spins and the Fermi liquid of O(2p) holes leading to the apparent disappearance of localized Cu(2+) moment in connection with the opening of a superconducting gap.

Borsa, F.; Rigamonti, A.

1991-01-01

72

Electronic properties of Y-Ba-Cu-O superconductors as seen by Cu and O NMR/NQR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) allow the investigation of electronic properties at the atomic level. The authors will report on such studies of typical members of the the Y-Ba-Cu-O family such as YBa2Cu30(6 + x) (1-2-3-(6 + x)), YBa2Cu4O8 (1-2-4) and Y2Ba4Cu7015 (2-4-7) with many examples of recent work performed in their laboratory. In particular, they will deal with Knight shift and relaxation studies of copper and oxygen. They will discuss important issues of current studies such as: (1) Existence of a common electronic spin-susceptibility in the planes (and perhaps in the chains) of 1-2-4; (2) Strong evidence for the existence of a pseudo spin-gap of the antiferromagnetic fluctuations in 1-2-4 and 2-4-7; (3) Evidence for d-wave pairing in 1-2-4; (4) Strong coupling of inequivalent Cu-O planes in 2-4-7 and possible origin for the high Tc value of this compound; and (5) The possibility to describe NMR data in the framework of a charge-excitation picture.

Brinkmann, D.

1995-04-01

73

Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat  

NASA Technical Reports Server (NTRS)

La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for O = to or less than 0.3 and in the temperature range 1.6 + 450 K are analyzed in terms of Cu(++) magnetic correlations and dynamics. It is described how the magnetic correlations that would result from Cu-Cu exchange are reduced by mobile charge defects related to x-doping. A comprehensive picture is given which explains satisfactorily the x and T dependence of the correlation time, of the correlation length and of the Neel temperature T(sub n)(x) as well as being consistent with known electrical resistivity and magnetic susceptibility measurements. It is discussed how, in the superconducting samples, the mobile defects also cause the decrease, for T yields T(sub c)(+) of the hyperfine Cu electron-nucleus effective interaction, leading to the coexistence of quasi-localized, reduced magnetic moments from 3d Cu electrons and mobile oxygen p-hole carriers. The temperature dependence of the effective hyperfine field around the superconducting transition yields an activation energy which could be related to the pairing energy. New specific heat measurements are also presented and discussed in terms of the above picture.

Borsa, F.; Rigamonti, A.

1990-01-01

74

Electronic properties of Y-Ba-Cu-O superconductors as seen by Cu and O NMR/NQR  

NASA Technical Reports Server (NTRS)

Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) allow the investigation of electronic properties at the atomic level. We will report on such studies of typical members of the the Y-Ba-Cu-O family such as YBa2Cu30(6 + x) (1-2-3-(6 + x)), YBa2Cu4O8 (1-2-4) and Y2Ba4Cu7015 (2-4-7) with many examples of recent work performed in our laboratory. In particular, we will deal with Knight shift and relaxation studies of copper and oxygen. We will discuss important issues of current studies such as: (1) Existence of a common electronic spin-susceptibility in the planes (and perhaps in the chains) of 1-2-4; (2) Strong evidence for the existence of a pseudo spin-gap of the antiferromagnetic fluctuations in 1-2-4 and 2-4-7; (3) Evidence for d-wave pairing in 1-2-4; (4) Strong coupling of inequivalent Cu-O planes in 2-4-7 and possible origin for the high Tc value of this compound; and (5) The possibility to describe NMR data in the framework of a charge-excitation picture.

Brinkmann, D.

1995-01-01

75

Evidence for low-temperature internal dynamics in Cu 12As 4S 13 according to copper NQR and nuclear relaxation  

NASA Astrophysics Data System (ADS)

63,65Cu nuclear quadrupole resonance (NQR) was applied to study the natural mineral Cu 12As 4S 13 (tennantite) in the temperature range 4.2-210 K. The obtained results point to the presence of field fluctuations caused by internal motions in tennantite. Consistently with the crystal structure, the experimental data can be described by an occurrence of a magnetic phase transition, which takes place near 65 K. The low-temperature phase is characterized by Cu(II) electron magnetic moments freezing in the form of a spin-glass-like constitution.

Gainov, R. R.; Dooglav, A. V.; Pen'kov, I. N.

2006-12-01

76

Density functional calculations of 14N and 11B NQR parameters in the H-capped (6,0) and (4,4) single-walled BN nanotubes  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) calculations were performed to calculate nitrogen-14 and boron-11 nuclear quadrupole resonance (NQR) spectroscopy parameters in the representative considered models of zigzag and armchair boron nitride nanotubes (BNNTs) for the first time. The considered models consisting of 1 nm length of H-capped (6,0) and (4,4) single-walled BNNT were first allowed to fully relax and then the NQR calculations were performed on the geometrically optimized models. The evaluated nuclear quadrupole coupling constants and asymmetry parameters for the mentioned nuclei reveal that the considered models can be divided into four layers of nuclei with an equivalent electrostatic environment where those nuclei at the ends of tubes have a very strong electrostatic environment compared to the other nuclei along the length of tubes. Those nuclei at the center of the tube length also have an equivalent electrostatic environment. The calculations were performed based on the B3LYP DFT method and 6-311G** and 6-311++G** standard basis sets using the Gaussian 98 package of program.

Mirzaei, Mahmoud; Hadipour, Nasser L.

2008-02-01

77

Coexistence of multiple charge-density waves and superconductivity in SrPt2As2 revealed by 75As-NMR /NQR and 195Pt-NMR  

NASA Astrophysics Data System (ADS)

The relationship between charge-density wave (CDW) orders and superconductivity in arsenide superconductor SrPt2As2 with Tc=5.2 K which crystallizes in the CaBe2Ge2 -type structure was studied by 75As nuclear magnetic resonance (NMR) measurements up to 520 K, and 75As nuclear quadrupole resonance (NQR) and 195Pt-NMR measurements down to 1.5 K. At high temperature, 75As-NMR spectrum and nuclear-spin-relaxation rate (1 /T1) have revealed two distinct CDW orders, one realized in the As-Pt-As layer below TCDWAs (1 )=410 K and the other in the Pt-As-Pt layer below TCDWAs (2 )=255 K . The 1 /T1 measured by 75As-NQR shows a clear Hebel-Slichter peak just below Tc and decreases exponentially well below Tc. Concomitantly, 195Pt Knight shift decreases below Tc. Our results indicate that superconductivity in SrPt2As2 is in the spin-singlet state with an s -wave gap and is robust under the two distinct CDW orders in different layers.

Kawasaki, Shinji; Tani, Yoshihiko; Mabuchi, Tomosuke; Kudo, Kazutaka; Nishikubo, Yoshihiro; Mitsuoka, Daisuke; Nohara, Minoru; Zheng, Guo-qing

2015-02-01

78

Suppression of electron correlations in the collapsed tetragonal phase of CaFe2As2 under ambient pressure demonstrated by As75 NMR/NQR measurements  

SciTech Connect

The static and the dynamic spin correlations in the low-temperature collapsed tetragonal and the high-temperature tetragonal phase in CaFe2As2 have been investigated by As75 nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. Through the temperature (T) dependence of the nuclear spin lattice relaxation rates (1/T1) and the Knight shifts, although stripe-type antiferromagnetic (AFM) spin correlations are realized in the high-temperature tetragonal phase, no trace of the AFM spin correlations can be found in the nonsuperconducting, low-temperature, collapsed tetragonal (cT) phase. Given that there is no magnetic broadening in As75 NMR spectra, together with the T-independent behavior of magnetic susceptibility ? and the T dependence of 1/T1T?, we conclude that Fe spin correlations are completely quenched statically and dynamically in the nonsuperconducting cT phase in CaFe2As2.

Furukawa, Yuji [Ames Laboratory; Roy, Beas [Ames Laboratory; Ran, Sheng [Ames Laboratory; Budko, Sergey L. [Ames Laboratory; Canfield, Paul C. [Ames Laboratory

2014-03-20

79

Multinuclear NMR/NQR study of HgBa 2CuO 4+ xF y superconductors with different oxygen and fluorine content  

NASA Astrophysics Data System (ADS)

We have measured 63,65Cu NMR/NQR spectra, 199Hg and 19F NMR spectra and spin-lattice relaxation rate on a series of powder HgBa 2CuO 4+ xF y samples with different oxygen and fluorine content. Comparison of 63Cu and 199Hg relaxation data to numerical calculations for several types of the order parameter symmetry gives the best coincidence with the d-wave symmetry. 19F NMR line width and relaxation rate are strongly influenced by the magnetic flux-line motion. The 19F magnetization recovery curve is described by a stretched exponential function. The 19F spin-lattice relaxation strongly depends on the fluorine content evidencing that at higher doping level part of F atoms occupy the apical O2 position.

Gippius, A. A.; Antipov, E. V.; Klein, O.; Lüders, K.

2000-07-01

80

Structure of Cl-containing silicate and aluminosilicate glasses: A 35Cl MAS-NMR study  

Microsoft Academic Search

Chlorine-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were collected at 14.1 and 18.8 Tesla fields to determine the atomic scale structural environments of the chloride ions in anhydrous and hydrous silicate and aluminosilicate glasses containing 0.2 to 0.7 wt% Cl. NMR peaks are broad and featureless, but are much narrower than the total chemical shift range for

Travis O. Sandland; Lin-Shu Du; Jonathan F. Stebbins; James D. Webster

2004-01-01

81

Frequency noise in frequency swept fiber laser.  

PubMed

This Letter presents a measurement of the spectral content of frequency shifted pulses generated by a lightwave synthesized frequency sweeper. We found that each pulse is shifted in frequency with very high accuracy. We also discovered that noise originating from light leaking through the acousto- optical modulators and forward propagating Brillouin scattering appear in the spectrum. PMID:23546253

Pedersen, Anders Tegtmeier; Rottwitt, Karsten

2013-04-01

82

HIV Testing Frequency  

MedlinePLUS

... Testing : HIV Testing Frequency Translate Text Size Print HIV Testing Frequency Testing Frequency How often should you ... local health department for proper care and information. HIV Testing HIV Test Locations HIV Test Types HIV ...

83

Chlorine transfer out of a very low permeability clay sequence (Paris Basin, France): 35Cl and 37Cl evidence  

NASA Astrophysics Data System (ADS)

The marine Callovo-Oxfordian clay formation is found at a depth around 410m in the eastern part of the Paris Basin (France). It is a very low permeability formation investigated by the French agency for nuclear waste management (ANDRA) to study the feasibility of a radioactive waste disposal. Examining hydrogeological and geochemical characteristics of the clay sequence may test confinement properties of this formation. This study uses chlorine isotopes to investigate long-term transport processes which may carry chemical elements out of the clay layer to the surrounding rocks. Detailed chlorine concentration and ? 37Cl depth profiles are examined using pore waters and aquifer waters sampled in the clay formation and its surrounding aquifers (the Dogger at the bottom and the Oxfordian/Kimmeridgian/Tithonian unit at the top). They are discussed in terms of chlorine budget and hydrogeological processes. Clay pore waters and aquifer waters show strong chlorine concentration depletion (<3000 mg/L) relative to the original marine interstitial water (˜19000 mg/L). This probably results from an early dilution by meteoric water in limestones (as also indicated by oxygen and hydrogen isotopes). A steep Cl-concentration gradient from the Dogger at ˜500m in depth (˜2500 mg/L) to the Oxfordian/Kimmeridgian/Tithonian aquifer near the surface (? 10 mg/L) is associated to a 'v-shaped' profile of the ? 37Cl values. Modelling Cl transport shows that a hydrodynamic dispersion process explains Cl concentration and ? 37Cl profiles in Oxfordian Limestone. This process implies a mean upward flux of chloride in the 2.6 10 -8-8.2 10 -8 mole/m 2/yr range from the clay formation towards upper limestones where a westward advective flow disperses the chloride. The modelling and knowledge of underground water transfer suggest a maximum effective Cl-hydrodynamic vertical dispersion coefficient (= vertical Cl-transport coefficient) of ˜7.6 10 -10 m 2/s. Chlorine transfer through the Callovo-Oxfordian clay, since deposition 160My ago, can be mainly described by the interplay of an early dilution and a later hydrodynamic dispersion event which has apparently erased most of the isotopic effects of diagenetic events (such as early diffusion, ion filtration etc.).

Lavastre, Véronique; Jendrzejewski, Nathalie; Agrinier, Pierre; Javoy, Marc; Evrard, Marc

2005-11-01

84

Converting Frequency Responses to Daily Frequency  

Cancer.gov

Frequency information on the DSQ in NHANES 2009-2010 was collected using a rate and time unit (e.g., 3 times per week). A different response format consisting of a set number of frequency categories is used in the self-administered paper questionnaire (link to questionnaire) ,. In both cases, the frequency responses are converted to a common unit of time, i.e. times per day.

85

Generalized frequency modulation  

E-print Network

In frequency modulation (FM) systems, a continuous-time information signal is modulated onto a sinusoidal carrier wave by using the information signal to modulate the frequency of the carrier wave. In this thesis, a more ...

Torres, Wade Patrick

2001-01-01

86

Physical Activity Frequency & Health  

MedlinePLUS Videos and Cool Tools

... hand corner of the player. Physical Activity Frequency & Health HealthDay February 20, 2015 Related MedlinePlus Pages Exercise ... in a study on physical activity frequency and health. They reported their level of activity at the ...

87

Frequency stability review  

NASA Technical Reports Server (NTRS)

Certain aspects of the description and measurement of oscillator stability are treated. Topics covered are time and frequency deviations, Allan variance, the zero-crossing counter measurement technique, frequency drift removal, and the three-cornered hat.

Greenhall, C. A.

1987-01-01

88

Frequency comb swept lasers  

E-print Network

We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep ...

Tsai, Tsung-Han

89

Frequency Measurement & Analysis Service  

E-print Network

NIST Frequency Measurement & Analysis Service #12;A Complete Solution To All Frequency Measurement & Calibration Problems The NIST Frequency Measurement and Analysis Service makes it easy to measure, and are traceable to NIST at an uncertainty of 2.5 x 10-13 per day. Subscribers to the NIST service receive

Magee, Joseph W.

90

High frequency nonlinear imaging  

Microsoft Academic Search

Nonlinear imaging has already shown improved image resolution compared to fundamental imaging at lower frequencies (2-4 MHz). The required steps to obtain nonlinear images at high frequencies are presented here. The transmit frequency was from 20 to 60 MHz and on receive, pulse-inversion, the first, second, and the third harmonic were used for imaging. Experiments were conducted using a wire

Jens K. Poulsen

2001-01-01

91

Eastern Frequency Response Study  

SciTech Connect

This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.

Miller, N.W.; Shao, M.; Pajic, S.; D'Aquila, R.

2013-05-01

92

Channelizers and frequency encoders  

NASA Astrophysics Data System (ADS)

Three different types of frequency channelizers for EW receivers are described according to their outputs. They are (1) the video signal channelizer, (2) RF channelizers with a different frequency available from each channel, and (3) a receiver in which the same RF is available from different channels. Different kinds of frequency encoders are used to determine the center frequencies of the input signals. The general properties of these encoders are discussed. It is concluded that the best approach to channelized receiver design is to consider the channelizer and the frequency encoder as one unit and to design them as an interactive system.

Tsui, James B. Y.

1989-09-01

93

Frequency Bin Entangled Photons  

E-print Network

A monochromatic laser pumping a parametric down conversion crystal generates frequency entangled photon pairs. We study this experimentally by addressing such frequency entangled photons at telecommunication wavelengths (around 1550 nm) with fiber optics components such as electro-optic phase modulators and narrow band frequency filters. The theory underlying our approach is developed by introducing the notion of frequency bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate a Bell inequality adapted to our setup by more than five standard deviations.

L. Olislager; J. Cussey; A. T. Nguyen; Ph. Emplit; S. Massar; J. -M. Merolla; K. Phan Huy

2010-02-10

94

Frequency selective infrared sensors  

DOEpatents

A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

Davids, Paul; Peters, David W

2013-05-28

95

Frequency selective infrared sensors  

DOEpatents

A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

Davids, Paul; Peters, David W

2014-11-25

96

Frequency detector for fast frequency lock of digital PLLs  

E-print Network

Frequency detector for fast frequency lock of digital PLLs V. Kratyuk, P.K. Hanumolu, U.-K. Moon and K. Mayaram A new frequency detector, which allows for a fast frequency lock of phase-locked loops the frequency difference. The proposed frequency detector provides frequency difference informa- tion at each

Moon, Un-Ku

97

Radio frequency detection assembly and method for detecting radio frequencies  

DOEpatents

A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

Cown, Steven H. (Rigby, ID); Derr, Kurt Warren (Idaho Falls, ID)

2010-03-16

98

Frequency conversion system  

NASA Technical Reports Server (NTRS)

A frequency conversion system comprises first and second gain sources providing first and second frequency radiation outputs where the second gain source receives as input the output of the first gain source and, further, the second gain source comprises a Raman or Brillouin gain fiber for wave shifting a portion of the radiation of the first frequency output into second frequency radiation output to provided a combined output of first and second frequencies. Powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

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

2001-01-01

99

Analysis of nuclear-quadrupole-resonance spectrum of incommensurate phases: The case of bis(4-chlorophenyl) sulfone  

Microsoft Academic Search

In this work, previous experimental studies of the 35Cl nuclear-quadrupole-resonance (NQR) line shape in the incommensurate phase of bis(4-chlorophenyl) sulfone were extended. The broad spectra in the incommensurate phase (IC) were measured using the Fourier transform of the nuclear signal to avoid systematic errors committed in some studies of this compound. The results were interpreted within the framework of the

J. Schneider; C. Schürrer; A. Wolfenson; A. Brunetti

1998-01-01

100

Frequencies of solar oscillations  

NASA Technical Reports Server (NTRS)

Solar oscillations have been observed at three different spatial scales at Big Bear Solar Observatory during 1986-1987 and, using three data sets, a new and more accurate table of solar oscillation frequencies has been compiled. The oscillations, which are presented as functions of radial order n and spherical harmonic degree l, are averages over azimuthal order and therefore approximate the normal mode frequencies of a nonrotating, spherically symmetric sun, near solar minimum. The table contains frequencies for most of the solar p and f modes with l between 0 and 1860, n between 0 and 26, and oscillation mode frequencies between 1.0 and 5.3.

Libbrecht, K. G.; Woodard, M. F.; Kaufman, J. M.

1990-01-01

101

Nonlinear Frequency Compression  

PubMed Central

Frequency lowering technologies offer an alternative amplification solution for severe to profound high frequency hearing losses. While frequency lowering technologies may improve audibility of high frequency sounds, the very nature of this processing can affect the perceived sound quality. This article reports the results from two studies that investigated the impact of a nonlinear frequency compression (NFC) algorithm on perceived sound quality. In the first study, the cutoff frequency and compression ratio parameters of the NFC algorithm were varied, and their effect on the speech quality was measured subjectively with 12 normal hearing adults, 12 normal hearing children, 13 hearing impaired adults, and 9 hearing impaired children. In the second study, 12 normal hearing and 8 hearing impaired adult listeners rated the quality of speech in quiet, speech in noise, and music after processing with a different set of NFC parameters. Results showed that the cutoff frequency parameter had more impact on sound quality ratings than the compression ratio, and that the hearing impaired adults were more tolerant to increased frequency compression than normal hearing adults. No statistically significant differences were found in the sound quality ratings of speech-in-noise and music stimuli processed through various NFC settings by hearing impaired listeners. These findings suggest that there may be an acceptable range of NFC settings for hearing impaired individuals where sound quality is not adversely affected. These results may assist an Audiologist in clinical NFC hearing aid fittings for achieving a balance between high frequency audibility and sound quality. PMID:23539261

Scollie, Susan; Glista, Danielle; Seelisch, Andreas

2013-01-01

102

Frequency Response Analysis Tool  

SciTech Connect

Frequency response has received a lot of attention in recent years at the national level, which culminated in the development and approval of North American Electricity Reliability Corporation (NERC) BAL-003-1 Frequency Response and Frequency Bias Setting Reliability Standard. This report is prepared to describe the details of the work conducted by Pacific Northwest National Laboratory (PNNL) in collaboration with the Bonneville Power Administration and Western Electricity Coordinating Council (WECC) Joint Synchronized Information Subcommittee (JSIS) to develop a frequency response analysis tool (FRAT). The document provides the details on the methodology and main features of the FRAT. The tool manages the database of under-frequency events and calculates the frequency response baseline. Frequency response calculations are consistent with frequency response measure (FRM) in NERC BAL-003-1 for an interconnection and balancing authority. The FRAT can use both phasor measurement unit (PMU) data, where available, and supervisory control and data acquisition (SCADA) data. The tool is also capable of automatically generating NERC Frequency Response Survey (FRS) forms required by BAL-003-1 Standard.

Etingov, Pavel V.; Kosterev, Dmitry; Dai, T.

2014-12-31

103

Stabilized radio frequency quadrupole  

DOEpatents

A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

Lancaster, Henry D. (Orinda, CA); Fugitt, Jock A. (Berkeley, CA); Howard, Donald R. (Danville, CA)

1984-01-01

104

Optical frequency metrology  

Microsoft Academic Search

Extremely narrow optical resonances in cold atoms or single trapped ions can be measured with high resolution. A laser locked to such a narrow optical resonance could serve as a highly stable oscillator for an all-optical atomic clock. However, until recently there was no reliable clockwork mechanism that could count optical frequencies of hundreds of terahertz. Techniques using femtosecond-laser frequency

Th. Udem; R. Holzwarth; T. W. Hänsch

2002-01-01

105

Dialysis dose and frequency  

Microsoft Academic Search

Background. From the beginning of the dialysis era, the issue of optimal dialysis dose and frequency has been a central topic in the delivery of dialysis treatment. Methods. We undertook a discussion to achieve a consensus on key points relating to dialysis dose and frequency, focusing on the relationships with clinical and patient outcomes. Results. Traditionally, dialysis adequacy has been

Francesco Locatelli; Umberto Buoncristiani; Bernard Canaud; Hans Kohler; Thierry Petitclerc; Pietro Zucchelli; Ospedale A. Manzoni; CHU Montpellier; Schwerpunkt Nephrologie

2004-01-01

106

Microfabricated ion frequency standard  

DOEpatents

A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.

Schwindt, Peter (Albuquerque, NM); Biedermann, Grant (Albuquerque, NM); Blain, Matthew G. (Albuquerque, NM); Stick, Daniel L. (Albuquerque, NM); Serkland, Darwin K. (Albuquerque, NM); Olsson, III, Roy H. (Albuquerque, NM)

2010-12-28

107

Laser Frequency Stabilization  

NASA Technical Reports Server (NTRS)

Laser ranging and interferometry are essential technologies allowing for many astounding new spacebased missions such as the Laser Interferometer Space Antenna (LISA) to measure gravitational radiation emitted from distant super massive black hole mergers or distributed aperture telescopes with unprecedented angular resolution in the NIR or visible regime. The requirements on laser frequency noise depend on the residual motion and the distances between the spacecraft forming the interferometer. The intrinsic frequency stability of commercial lasers is several orders of magnitude above these requirements. Therefore, it is necessary for lasers to be stabilized to an ultrastable frequency reference so that they can be used to sense and control distances between spacecraft. Various optical frequency references and frequency stabilization schemes are considered and investigated for the applicability and usefulness for space-based interferometry missions.

Donelan, Darsa; Mueller, Guido; Thorpe, James; Livas, Jeffrey

2011-01-01

108

Powerline frequency measurement  

SciTech Connect

A microcomputer has been used to measure powerline frequency with a precision of six decimal digits (0.0001 Hz) using an averaging time of 3 to 4 min. The algorithm for frequency measurement requires no multiplication or division operations, so a very simple microprocessor can be used. The frequency measurement is sensitive enough to permit detection of small, controlled changes in generation, hence in powerline frequency. Thus, the results of the frequency measurement can be applied to the load-management field. Methods based on these principles have the potential of providing an inexpensive communications path between the power supplier and the industrial user for purposes of shedding load during peak power usage.

Rochelle, R.B.; Rochelle, R.W.; Adams, R.K.

1986-05-01

109

Frequency comb swept lasers  

PubMed Central

We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a ~?1.2dB sensitivity roll off over ~3mm range, compared to conventional swept source and FDML lasers which have ?10dB and ?5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0–3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed. PMID:19997365

Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C.; Fujimoto, James G.

2010-01-01

110

A beat frequency buncher  

SciTech Connect

A superconducting high energy buncher operating at 13/12 times the linac frequency has been built and installed, to combine with the low energy buncher operating at 1/12 the linac frequency. The system is synchronized so the linac and high energy buncher beat frequency remains in phase with the low energy buncher. On linac cycles not corresponding to a primary bunch, the high energy buncher bunches residual beam away from the linac longitudinal acceptance rather than into it. The resonator for the new high energy buncher was constructed by shortening an existing low-{beta} resonator.

Storm, D.W.; Corcoran, D.T.; Harper, G.C.

1995-09-01

111

Quantum frequency downconversion experiment  

E-print Network

We report the first quantum frequency downconversion experiment. Using the difference frequency generation process in a periodically poled lithium niobate waveguide, we successfully observed the phase-preserved frequency downconversion of a coherent pulse train with an average photon number per pulse of $<$1, from the 0.7-$\\mu$m visible wavelength band to the 1.3-$\\mu$m telecom band. We expect this technology to become an important tool for flexible photonic quantum networking, including the realization of quantum repeater systems over optical fiber using atom-photon entanglement sources for the visible wavelength bands.

Hiroki Takesue

2010-06-02

112

Squeezing frequency combs  

E-print Network

We have developed the full theory of a synchronously pumped type I optical parametric oscillator (SPOPO). We derive expressions for the oscillation threshold and the characteristics of the generated mode-locked signal beam. We calculate the output quantum fluctuations of the device, and find that, in the degenerate case (coincident signal and idler set of frequencies), perfect squeezing is obtained when one approaches threshold from below for a well defined "super-mode', or frequency comb, consisting of a coherent linear superposition of signal modes of different frequencies which are resonant in the cavity.

German J. De Valcarcel; Giuseppe Patera; Nicolas Treps; Claude Fabre

2006-05-15

113

Name That Frequency  

NSDL National Science Digital Library

This activity was designed for blind learners, but all types of learners can model how vibrating particles, such as in a sound wave, bump into other particles causing them to vibrate, and that the vibrations travel. The chain reaction of sound waves will be demonstrated using old video cassettes (in a way similar to a dominoes game). Learners with visual impairments as well as sighted learners will have the chance to create tactile diagrams of varying wave frequencies. The activity includes setting up the row of tapes at various “frequencies,” closer together for higher frequency, farther apart for lower.

Perkins School for the Blind

2012-06-26

114

Roll Out the Frequency  

NSDL National Science Digital Library

In this activity, students use marks on a 1.4 m strip of paper to simulate light wave frequencies and measure the time it takes for different frequencies to pass through the "viewer" made from a manila folder. Students learn that different colors of light have different wave frequencies. The resource is part of the teacher's guide accompanying the video, NASA Why Files: The Case of the Mysterious Red Light. Lesson objectives supported by the video, additional resources, teaching tips and an answer sheet are included in the teacher's guide.

2012-08-03

115

Frequency Domain Controller Design 9.2 Frequency Response Characteristics  

E-print Network

Frequency Domain Controller Design 9.2 Frequency Response Characteristics The frequency transfer functions are defined for sinusoidal inputs having all possible frequencies . They are obtained from (9.1) by simply setting , that is (9.1) Typical diagrams for the magnitude and phase of the open-loop frequency

Gajic, Zoran

116

Supernova frequency estimates  

SciTech Connect

Estimates of the frequency of type I and II supernovae occurring in galaxies of different types are derived from observational material acquired by the supernova patrol of the Shternberg Astronomical Institute.

Tsvetkov, D.Y.

1983-01-01

117

Acoustic emission frequency discrimination  

NASA Technical Reports Server (NTRS)

In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

Sugg, Frank E. (inventor); Graham, Lloyd J. (inventor)

1988-01-01

118

A digital frequency synthesizer  

Microsoft Academic Search

A digital frequency synthesizer has been designed and constructed based on generating digital samples ofexp [j(2^{pi}nk\\/N)]at timenT. The real and imaginary parts of this exponential form samples of quadrature sinusoids where the frequency indexkis allowed to vary(-N\\/4) leq K < (N\\/4). The digital samples drive digital to analog converters followed by low-pass interpolating filters to produce analog sinusoids. The method

JOSEPH TIERNEY; CHARLES M. RADER; B. Gold

1971-01-01

119

Twirling Rope Frequency  

NSDL National Science Digital Library

In this activity (page 1 of the PDF), learners will stand twelve feet apart swinging a rope at the slowest tempo possible while someone uses a stopwatch to record the number of twirls per minute. Based on this frequency, learners will predict whether the tempo will speed up or slow down when the twirlers move closer to each other. Use this activity to introduce the terms frequency and period. Relates to the linked video, DragonflyTV: Double Dutch.

Twin Cities Public Television, Inc.

2006-01-01

120

On letter frequency effects.  

PubMed

In four experiments we examined whether the frequency of occurrence of letters affects performance in the alphabetic decision task (speeded letter vs. pseudo-letter classification). Experiments 1A and 1B tested isolated letters and pseudo-letters presented at fixation, and Experiments 2A and 2B tested the same stimuli inserted at the 1st, 3rd, or 5th position in a string of Xs. Significant negative correlations between letter frequency and response times to letter targets were found in all experiments. The correlations were found to be stronger for token frequency counts compared with both type frequency and frequency rank, stronger for frequency counts based on a book corpus compared with film subtitles, and stronger for measures counting occurrences as the first letter of words compared with inner letters and final letters. Correlations for letters presented in strings of Xs were found to depend on letter case and position-in-string. The results are in favor of models of word recognition that implement case-specific and position-specific letter representations. PMID:21855049

New, Boris; Grainger, Jonathan

2011-10-01

121

Frequency conversion system  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

122

Hg(+) Frequency Standards  

NASA Technical Reports Server (NTRS)

In this paper we review the development of Hg(+) microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3 x 10(exp -14)/nu(sub tau) when a cryogenic oscillator of stability 2-3 x 10(exp 15) was used a the local oscillator. The trapped ion frequency standard employs a Hg-202 discharge lamp to optically pump the trapped Hg(+)-199 clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg(+) ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At approx. 10(exp -12), the 2nd order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10(exp -14) or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, alpha = e(exp 2)/2(pi)hc, at the level of 10(exp -20)/year as predicted in some Grand Unified String Theories.

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

2000-01-01

123

Frequency Tunable Wire Lasers  

NASA Technical Reports Server (NTRS)

The present invention provides frequency tunable solid-state radiation-generating devices, such as lasers and amplifiers, whose active medium has a size in at least one transverse dimension (e.g., its width) that is much smaller than the wavelength of radiation generated and/or amplified within the active medium. In such devices, a fraction of radiation travels as an evanescent propagating mode outside the active medium. It has been discovered that in such devices the radiation frequency can be tuned by the interaction of a tuning mechanism with the propagating evanescent mode.

Hu, Qing (Inventor)

2013-01-01

124

Frequency division multiplex technique  

NASA Technical Reports Server (NTRS)

A system for monitoring a plurality of condition responsive devices is described. It consists of a master control station and a remote station. The master control station is capable of transmitting command signals which includes a parity signal to a remote station which transmits the signals back to the command station so that such can be compared with the original signals in order to determine if there are any transmission errors. The system utilizes frequency sources which are 1.21 multiples of each other so that no linear combination of any harmonics will interfere with another frequency.

Brey, H. (inventor)

1973-01-01

125

Using Suffix Arrays to Compute Term Frequency and Document Frequency  

E-print Network

Using Suffix Arrays to Compute Term Frequency and Document Frequency for All Substrings in a Corpus with much longer ngrams. Suffix arrays were first introduced to compute the frequency and location of a substring (ngram) in a sequence (corpus) of length N. To compute frequencies over all N(N +1)/2 substrings

Church, Kenneth W.

126

Low frequency phase signal measurement with high frequency squeezing  

E-print Network

We calculate the utility of high-frequency squeezed-state enhanced two-frequency interferometry for low-frequency phase measurement. To use the high-frequency sidebands of the squeezed light, a two-frequency intense laser is used in the interferometry instead of a single-frequency laser as usual. We find that the readout signal can be contaminated by the high-frequency phase vibration, but this is easy to check and avoid. A proof-of-principle experiment is in the reach of modern quantum optics technology.

Zehui Zhai; Jiangrui Gao

2011-08-24

127

Flood Frequency Analysis  

NSDL National Science Digital Library

This assignment asks students to do a flood frequency analysis to determine the size and stage of various floods and determine if the town of Crawford, OH is likely to be flooded or not. Outcomes: learn to work with quantitative data, learn to use Excel, be able to use USGS data.

Sheila Roberts

128

Radio frequency identification (RFID)  

Microsoft Academic Search

First conceived in 1948, Radio Frequency Identification (RFID) has taken many years for the technology to mature to the point where it is sufficiently affordable and reliable for widespread use. From Electronic Article Surveillance (EAS) for article (mainly clothing) security to more sophisticated uses, RFID is seen by some as the inevitable replacement for bar codes. With increasing use comes

C. M. Roberts

2006-01-01

129

Rotating Phasors- Negative Frequencies  

NSDL National Science Digital Library

This interactive phasor page allows you to control the values of a rotating phasor and see a visualization of each change that is done. You can control: one, pos/neg, two, beats, delta, sawtooth, square, triangle, time, zoom, plus you can put into five different values: Frequency (rel, HZ, mHZ), Amplitude (raw, rel), and Phases (Deg, Rad, unitrad).

130

Endless frequency shifting of optical frequency comb lines.  

PubMed

The functional principle of a novel technique for frequency shifting lines of an optical frequency comb is demonstrated. The underlying principle is to shift the carrier frequency by changing the carrier phase within the time span between subsequent pulses of a mode-locked laser used as comb generator. This universal frequency shifter does not require intrusion into the comb generator and provides high agility for arbitrary temporal frequency evolutions. PMID:23482149

Benkler, Erik; Rohde, Felix; Telle, Harald R

2013-03-11

131

NMR and NQR parameters of ethanol crystal  

E-print Network

Electric field gradients and chemical shielding tensors of the stable monoclinic crystal phase of ethanol are computed. The projector-augmented wave (PAW) and gauge-including projector-augmented wave (GIPAW) models in the periodic plane-wave density functional theory are used. The crystal data from X-ray measurements, as well as the structures where either all atomic, or only hydrogen atom positions are optimized in the density functional theory are analyzed. These structural models are also studied by including the semi-empirical Van der Waals correction to the density functional theory. Infrared spectra of these five crystal models are calculated.

Milinkovic, M

2012-01-01

132

Multiple chatter frequencies in millingprocesses  

Microsoft Academic Search

Analytical and experimental identifications of the chatter frequencies in millingprocesses are presented. In the case of milling, there are several frequency sets arising from the vibration signals, as opposed to the single well-defined chatter frequency of the unstable turning process. Frequency diagrams are constructed analytically and attached to the stability charts of mechanical models of high-speed milling. The correspondingquasiperiodic solutions

P. V. Bayly; B. P. Mann

133

Judged frequency of lethal events  

Microsoft Academic Search

A series of 5 experiments with 660 adult Ss studied how people judge the frequency of death from various causes. The judgments exhibited a highly consistent but systematically biased subjective scale of frequency. Two kinds of bias were identified: (a) a tendency to overestimate small frequencies and underestimate larger ones; and (b) a tendency to exaggerate the frequency of some

Sarah Lichtenstein; Baruch Fischhoff; Mark Layman; Barbara Combs

1978-01-01

134

Extended frequency turbofan model  

NASA Technical Reports Server (NTRS)

The fan model was developed using two dimensional modeling techniques to add dynamic radial coupling between the core stream and the bypass stream of the fan. When incorporated into a complete TF-30 engine simulation, the fan model greatly improved compression system frequency response to planar inlet pressure disturbances up to 100 Hz. The improved simulation also matched engine stability limits at 15 Hz, whereas the one dimensional fan model required twice the inlet pressure amplitude to stall the simulation. With verification of the two dimensional fan model, this program formulated a high frequency F-100(3) engine simulation using row by row compression system characteristics. In addition to the F-100(3) remote splitter fan, the program modified the model fan characteristics to simulate a proximate splitter version of the F-100(3) engine.

Mason, J. R.; Park, J. W.; Jaekel, R. F.

1980-01-01

135

Flood Frequency Analysis  

NSDL National Science Digital Library

The Flood Frequency Analysis module offers an introduction to the use of flood frequency analysis for flood prediction and planning. Through use of rich illustrations, animations, and interactions, this module explains the basic concepts, underlying issues, and methods for analyzing flood data. Common concepts such as the 100-year flood and return periods as well as issues affecting the statistical representation of floods are discussed. Common flood data analysis methods as well as an overview of design events are also covered. As a foundation topic for the Basic Hydrologic Science course, this module may be taken on its own, but it will also be available as a supporting topic providing factual scientific information to support students in completion of the case-based forecasting modules.

2014-09-14

136

High frequency reference electrode  

DOEpatents

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.

Kronberg, James W. (Aiken, SC)

1994-01-01

137

Rapid frequency scan EPR.  

PubMed

In rapid frequency scan EPR with triangular scans, sufficient time must be allowed to insure that the magnetization in the x, y plane decays to baseline at the end of the scan, which typically is about 5T(2) after the spins are excited. To permit relaxation of signals excited toward the extremes of the scan the total scan time required may be much longer than 5T(2). However, with periodic, saw-tooth excitation, the slow-scan EPR spectrum can be recovered by Fourier deconvolution of data recorded with a total scan period of 5T(2), even if some spins are excited later in the scan. This scan time is similar to polyphase excitation methods. The peak power required for either polyphase excitation or rapid frequency scans is substantially smaller than for pulsed EPR. The use of an arbitrary waveform generator (AWG) and cross loop resonator facilitated implementation of the rapid frequency scan experiments reported here. The use of constant continuous low B(1), periodic excitation waveform, and constant external magnetic field is similar to polyphase excitation, but could be implemented without the AWG that is required for polyphase excitation. PMID:21664848

Tseitlin, Mark; Rinard, George A; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

2011-08-01

138

Frequency shifts of high frequency p-modes  

NASA Technical Reports Server (NTRS)

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.

Jain, Rekha

1995-01-01

139

Frequency Domain Identification Toolbox  

NASA Technical Reports Server (NTRS)

This report documents software written in MATLAB programming language for performing identification of systems from frequency response functions. MATLAB is a commercial software environment which allows easy manipulation of data matrices and provides other intrinsic matrix functions capabilities. Algorithms programmed in this collection of subroutines have been documented elsewhere but all references are provided in this document. A main feature of this software is the use of matrix fraction descriptions and system realization theory to identify state space models directly from test data. All subroutines have templates for the user to use as guidelines.

Horta, Lucas G.; Juang, Jer-Nan; Chen, Chung-Wen

1996-01-01

140

Novel polar frequency discriminator  

NASA Astrophysics Data System (ADS)

An alternative layout for a polar frequency discriminator (PFD) is introduced. This simpler configuration requires no crossover, so that the PFD is easily integrated in its entirety. Since only one quadrature coupler is required, the circuit is less sensitive to 3 dB coupling and 90 deg phase deviations which occur within these components in wideband applications. Only three detectors are required, reducing cost and errors that arise if detectors do not track each other exactly. The disadvantages are the slightly more complex video processing and additional power loss.

Rachman, D. M.; Downing, B. J.

1985-11-01

141

Microwave Frequency Polarizers  

NASA Technical Reports Server (NTRS)

This article describes the fabrication and analysis of microwave frequency polarizing grids. The grids are designed to measure polarization from the cosmic microwave background. It is effective in the range of 500 to 1500 micron wavelength. It is cryogenic compatible and highly robust to high load impacts. Each grid is fabricated using an array of different assembly processes which vary in the types of tension mechanisms to the shape and size of the grids. We provide a comprehensive study on the analysis of the grids' wire heights, diameters, and spacing.

Ha, Vien The; Mirel, Paul; Kogut, Alan J.

2013-01-01

142

Hurricane Frequency and Intensity  

NSDL National Science Digital Library

In recent years more and more attention has been paid to the Earth's climate and how it is evolving. When studying hurricanes it is important to understand that, for a hurricane to grow, warm water is an absolute necessity. So if the Earth continues to warm, what does that mean for hurricanes and their intensity? In this lesson, the student will look at past hurricane data by researching the intensity and frequency of hurricanes using the Live Access Server and several Internet sites found in the Lesson Links section.

143

Signal Frequency Spectra with Audacity®  

NASA Astrophysics Data System (ADS)

The primary objective of the activity presented here is to allow students to explore the frequency components of various simple signals, with the ultimate goal of teaching them how to remove unwanted noise from a voice signal. Analysis of the frequency components of a signal allows students to design filters that remove unwanted components of a signal while conserving the shape and magnitude of the relevant portion of a signal. For example, signal noise is often contained in higher frequency (fast-changing) components whereas signal drift is contained in lower frequency (slow-changing) components of the signal. A low-pass filter allows lower frequency components below a cutoff frequency to pass through, whereas a high-pass filter allows higher frequency components above a cutoff frequency to pass through. With activities such as the one presented here, students are introduced to real-world problem-solving applications of physics concepts that go beyond simple theory and equations.

Gailey, Alycia

2015-04-01

144

SECURING RADIO FREQUENCY IDENTIFICATION (RFID)  

E-print Network

May 2007 SECURING RADIO FREQUENCY IDENTIFICATION (RFID) SYSTEMS SECURING RADIO FREQUENCY IDENTIFICATION (RFID) SYSTEMS Karen Scarfone, EditorKaren Scarfone, Editor Computer Security Division of Standards and Technology National Institute of Standards and Technology RFID is a form of automatic

145

Time, Frequency and Physical Measurement.  

ERIC Educational Resources Information Center

Describes several developments in atomic clocks and frequency standards pointing out the feasibility and practicality in adopting a unified standard of time and frequency to replace other base standards of length, mass, and temperature. (GA)

Hellwig, Helmut; And Others

1978-01-01

146

The Future Teachers' Frequency Vocabulary.  

ERIC Educational Resources Information Center

Describes the compilation of the Future Teachers' Frequency Vocabulary, based on 236 written compositions by students at a teacher training college in Belgrade. Results were compared with the Child Frequency Vocabulary compiled in 1983, based on children's compositions. (LET)

Knaflic, Vladislava

1992-01-01

147

Malaria haplotype frequency estimation.  

PubMed

We present a Bayesian approach for estimating the relative frequencies of multi-single nucleotide polymorphism (SNP) haplotypes in populations of the malaria parasite Plasmodium falciparum by using microarray SNP data from human blood samples. Each sample comes from a malaria patient and contains one or several parasite clones that may genetically differ. Samples containing multiple parasite clones with different genetic markers pose a special challenge. The situation is comparable with a polyploid organism. The data from each blood sample indicates whether the parasites in the blood carry a mutant or a wildtype allele at various selected genomic positions. If both mutant and wildtype alleles are detected at a given position in a multiply infected sample, the data indicates the presence of both alleles, but the ratio is unknown. Thus, the data only partially reveals which specific combinations of genetic markers (i.e. haplotypes across the examined SNPs) occur in distinct parasite clones. In addition, SNP data may contain errors at non-negligible rates. We use a multinomial mixture model with partially missing observations to represent this data and a Markov chain Monte Carlo method to estimate the haplotype frequencies in a population. Our approach addresses both challenges, multiple infections and data errors. PMID:23609602

Wigger, Leonore; Vogt, Julia E; Roth, Volker

2013-09-20

148

Laser frequency multiplication  

NASA Astrophysics Data System (ADS)

A high quality mode locked pulse train was obtained at 9.55 microns, the CO2 wavelength chosen for frequency doubling into the atmospheric window at 4.8 microns. The pulse train consists of a 3 micro sec burst of 1.5 nsec pulses separated by 40 nsec, in a TEM (sub 00) mode and with a total energy of 100 mJ. The pulse intensity without focussing is about 3 MW/sq.cm., already quite close to the target intensity of 10 MW/sq.cm. for frequency doubling in a AgGaSe2 crystal. The mode-locked train is obtained by intracavity modulation at 12.5 MHz using a germanium crystal driven with a power of about 30 Watts. Line selection is achieved firstly by the use of a 0.92 mm thick CaF2 plate at the Brewster angle within the cavity, which completely suppresses 10.6 micron band radiation. Secondly, a particular rotational line, the P20 at 9.55 micron, is selected by the injection of a continuous beam is mode-matched to the pulsed laser cavity using a long focal length lens, and for best line-locking it is necessary to fine tune the length of the pulsed laser resonator. Injection causes substantial depression of the gain switched spike.

1991-11-01

149

High-frequency ECG  

NASA Technical Reports Server (NTRS)

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

Tragardh, Elin; Schlegel, Todd T.

2006-01-01

150

Digital frequency-offset detector  

NASA Technical Reports Server (NTRS)

Simple, low-cost device with designer-selectable tolerances provides accurate frequency comparison with minimal circuitry and ease of adjustment. Warning alerts if frequencies being compared fall outside selected tolerance. Device can be applied to any electronic system where accurate timing or frequency control is important.

Bogart, R. W.; Juengst, M. J.

1977-01-01

151

Frequency-bin entangled photons  

SciTech Connect

A monochromatic laser pumping a parametric down-conversion crystal generates frequency-entangled photon pairs. We study this experimentally by addressing such frequency-entangled photons at telecommunication wavelengths (around 1550 nm) with fiber-optics components such as electro-optic phase modulators and narrow-band frequency filters. The theory underlying our approach uses the notion of frequency-bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate by more than five standard deviations a Bell inequality adapted to our setup.

Olislager, L.; Emplit, P. [Service OPERA-Photonique, CP 194/5, Universite Libre de Bruxelles, Avenue F.D. Roosevelt 50, B-1050 Brussels (Belgium); Cussey, J. [SmartQuantum SA, Espace Phoenix, Route du Radome, FR-22560 Pleumeur-Bodou (France); Nguyen, A. T. [Service de Physique et Electricite, Institut Meurice, Haute Ecole Lucia de Brouckere, Avenue Emile Gryzon 1, B-1070 Brussels (Belgium); Massar, S. [Laboratoire d'Information Quantique, CP 225, Universite Libre de Bruxelles, Boulevard du Triomphe, B-1050 Brussels (Belgium); Merolla, J.-M.; Huy, K. Phan [Departement d'Optique P. M. Duffieux, Institut Franche-Comte Electronique Mecanique Thermique et Optique-Sciences et Technologies, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 6174, Universite de Franche-Comte, FR-25030 Besancon (France)

2010-07-15

152

Frequency sensitivity for video compression  

NASA Astrophysics Data System (ADS)

We investigate the frequency sensitivity of the human visual system, which reacts differently at different frequencies in video coding. Based on this observation, we used different quantization steps for different frequency components in order to explore the possibility of improving coding efficiency while maintaining perceptual video quality. In other words, small quantization steps were used for sensitive frequency components while large quantization steps were used for less sensitive frequency components. We performed subjective testing to examine the perceptual video quality of video sequences encoded by the proposed method. The experimental results showed that a reduction in bitrate is possible without causing a decrease in perceptual video quality.

Seo, Guiwon; Lee, Jonghwa; Lee, Chulhee

2014-03-01

153

Flying radio frequency undulator  

NASA Astrophysics Data System (ADS)

A concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The "flying" undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the -1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton's photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particles and the co-propagating rf pulse.

Kuzikov, S. V.; Savilov, A. V.; Vikharev, A. A.

2014-07-01

154

Frequency doubling crystals  

DOEpatents

A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

Wang, Francis (Danville, CA); Velsko, Stephan P. (Livermore, CA)

1989-01-01

155

Matsubara Frequency Sums  

E-print Network

We cannot use directly the results of zero-temperature at finite temperature, for at finite temperature the average is to be carried over all highly degenerate excited states unlike zero-temperature average is only on unique ground state. One of the formal way to take into account the finite temperature into quantum field theory is due to Matsubara, to replace temporal component of eigenvalues $k_{4}$ by $\\omega_{n}=\\frac{2\\pi n}{\\beta}$ $(\\frac{2\\pi (n+{1/2})}{\\beta})$ with summation over all integer values of $n$. The summation is done with the infinite series expansion of $\\coth (\\pi y)$. With the chemical potential $\\mu$, $\\omega_{n}$ will be replaced by $\\omega_{n} - \\mu$ in the eigenvalues and the summation over $n$ cannot be done easily. Various methods exist to evaluate it. We use the infinite series expansion of $\\coth (\\pi y)$ to work operationally for such Matsubara frequency sums.

Alok Kumar

2010-02-25

156

Flying radio frequency undulator  

SciTech Connect

A concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the ?1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton's photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particles and the co-propagating rf pulse.

Kuzikov, S. V.; Vikharev, A. A. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Savilov, A. V. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod (Russian Federation)

2014-07-21

157

Radio frequency coaxial feedthrough  

DOEpatents

An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

Owens, Thomas L. (Kingston, TN)

1989-01-17

158

Frequency mixing crystal  

DOEpatents

In a laser system for converting infrared laser light waves to visible light comprising a source of infrared laser light waves and means of harmoic generation associated therewith for production of light waves at integral multiples of the frequency of the original wave, the improvement of said means of harmonic generation comprising a crystal having the chemical formula X.sub.2 Y(NO.sub.3).sub.5 .multidot.2 nZ.sub.2 o wherein X is selected from the group consisting of Li, Na, K, Rb, Cs, and Tl; Y is selected from the group consisting of Sc, Y, La, Ce, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In; Z is selected from the group consisting of H and D; and n ranges from 0 to 4.

Ebbers, Christopher A. (Livermore, CA); Davis, Laura E. (Manteca, CA); Webb, Mark (Salida, CA)

1992-01-01

159

Mid-infrared frequency combs  

E-print Network

Laser frequency combs are coherent light sources that emit a broad spectrum consisting of discrete, evenly spaced narrow lines, each having an absolute frequency measurable within the accuracy of an atomic clock. Their development, a decade ago, in the near-infrared and visible domains has revolutionized frequency metrology with numerous windfalls into other fields such as astronomy or attosecond science. Extension of frequency comb techniques to the mid-infrared spectral region is now under exploration. Versatile mid-infrared frequency comb generators, based on novel laser gain media, nonlinear frequency conversion or microresonators, promise to significantly expand the tree of applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the fingerprint region, with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may spark off new discoveries in the various fields relevant to molecular sciences.

Schliesser, Albert; Hänsch, Theodor W

2012-01-01

160

Ab initio potential energy and dipole moment surfaces, infrared spectra, and vibrational predissociation dynamics of the 35Cl-⋯H2/D2 complexes  

NASA Astrophysics Data System (ADS)

Three-dimensional potential energy and dipole moment surfaces of the Cl--H2 system are calculated ab initio by means of a coupled cluster method with single and double excitations and noniterative correction to triple excitations with augmented correlation consistent quadruple-zeta basis set supplemented with bond functions, and represented in analytical forms. Variational calculations of the energy levels up to the total angular momentum J=25 provide accurate estimations of the measured rotational spectroscopic constants of the ground van der Waals levels n=0 of the Cl-⋯H2/D2 complexes although they underestimate the red shifts of the mid-infrared spectra with v=0?v=1 vibrational excitation of the monomer. They also attest to the accuracy of effective radial interaction potentials extracted previously from experimental data using the rotational RKR procedure. Vibrational predissociation of the Cl-⋯H2/D2(v=1) complexes is shown to follow near-resonant vibrational-to-rotational energy transfer mechanism so that more than 97% of the product monomers are formed in the highest accessible rotational level. This mechanism explains the strong variation of the predissociation rate with isotopic content and nuclear spin form of the complex. Strong deviation of the observed relative abundances of ortho and para forms of the complexes from those of the monomers is qualitatively explained by the secondary ligand exchange reactions in the ionic beam, within the simple thermal equilibrium model. Positions and intensities of the hot v=0, n=1?v=1, n=1 and combination v=0, n=0?v=1, n=1 bands are predicted, and implications to the photoelectron spectroscopy of the complex are briefly discussed.

Buchachenko, A. A.; Grinev, T. A.; K?os, J.; Bieske, E. J.; Szcz??niak, M. M.; Cha?asi?ski, G.

2003-12-01

161

A technique for orthogonal frequency division multiplexing frequency offset correction  

Microsoft Academic Search

This paper discusses the effects of frequency offset on the performance of orthogonal frequency division multiplexing (OFDM) digital communications. The main problem with frequency offset is that it introduces interference among the multiplicity of carriers in the OFDM signal. It is shown, and confirmed by simulation, that to maintain signal-to-interference ratios of 20 dB or greater for the OFDM carriers,

P. H. Moose

1994-01-01

162

Speech enhancement via frequency bandwidth extension using line spectral frequencies  

Microsoft Academic Search

This paper contributes to narrowband speech enhancement by means of frequency bandwidth extension. A new algorithm is proposed for generating synthetic frequency components in the high-band (i.e., 4-8 kHz) given the low-band ones (i.e., 0-4 kHz) for wide-band speech synthesis. It is based on linear prediction (LPC) analysis-synthesis. It consists of a spectral envelope extension using efficiently line spectral frequencies

S. Chennoukh; A. Gerrits; G. Miet; R. Sluijter

2001-01-01

163

Radio Frequency Identification  

NSDL National Science Digital Library

A wealth of information about RFID is available at this site (1), ranging from background material to case studies. A discussion highlighting the myriad of uses for RFID is included. Transponder News (2) offers several articles that explore the technology in greater detail. Two in particular look at current and future trends, while others are editorial essays and technical notes. Pacific Northwest National Laboratory (3) is involved in the development of advanced tags for RFID systems. The project's homepage outlines current research efforts for three different types of radio frequency tags, which are being designed for varying degrees of sophistication and functionality. While RFID technology can be very useful, the fact that information about items is collected remotely raises concerns about privacy and security. This issue is addressed in a research paper from the Massachusetts Institute of Technology (4). The authors review current RFID systems and their operation, and then propose a number of security mechanisms that could reduce the risk associated with their use. A paper presented at the 2002 European Wireless Conference (5) compares the performance of RFID systems that use ultra-high frequency (UHF) communications to those that use microwave communications. It is argued that although microwave-based devices, such as Bluetooth, are suitable for worldwide operation, systems that communicate in the UHF range have greater range and less interference. The introduction of RFID smart tags in goods is discussed in this article (6). Now that these tags are cheap enough to be attached to thousands of items, stores will be able to track goods as they are transferred from storehouses to retail shelves, thereby minimizing the possibility of loss or theft. RFID technology has found another use in the war with Iraq. An article from May 20, 2003 (7) describes wristbands embedded with an RFID chip. The status and position of a wounded soldier who is wearing such a wristband can be monitored while he or she is recovering at a medical facility. For additional updates on the development of RFID technology, RFID News (8) maintains current news about emerging standards, innovative applications, and general issues.

Leske, Cavin.

164

Magic Frequencies for Cesium Primary-Frequency Standard  

SciTech Connect

We consider microwave hyperfine transitions in the ground state of cesium and rubidium atoms which are presently used as the primary and the secondary frequency standards. The atoms are confined in an optical lattice generated by a circularly polarized laser field. We demonstrate that applying an external magnetic field with appropriately chosen direction may cancel dynamic Stark frequency shift making the frequency of the clock transition insensitive to the strengths of both the laser and the magnetic fields. This can be attained for practically any laser frequency which is sufficiently distant from a resonance.

Flambaum, V. V.; Dzuba, V. A.; Derevianko, A. [School of Physics, University of New South Wales, Sydney 2052 (Australia); Department of Physics, University of Nevada, Reno, Nevada 89557 (United States)

2008-11-28

165

Flood frequency in Alaska  

USGS Publications Warehouse

Records of peak discharge at 183 sites were used to study flood frequency in Alaska. The vast size of Alaska, its great ranges of physiography, and the lack of data for much of the State precluded a comprehensive analysis of all flood determinants. Peak stream discharges, where gaging-station records were available, were analyzed for 2-year, 5-year, 10-year, 25-year, and 50-year average-recurrence intervals. A regional analysis of the flood characteristics by multiple-regression methods gave a set of equations that can be used to estimate floods of selected recurrence intervals up to 50 years for any site on any stream in Alaska. The equations relate floods to drainage-basin characteristics. The study indicates that in Alaska the 50-year flood can be estimated from 10-year gaging- station records with a standard error of 22 percent whereas the 50-year flood can be estimated from the regression equation with a standard error of 53 percent. Also, maximum known floods at more than 500 gaging stations and miscellaneous sites in Alaska were related to drainage-area size. An envelope curve of 500 cubic feet per second per square mile covered all but 2 floods in the State.

Childers, J.M.

1970-01-01

166

The limit of frequency estimation  

NASA Technical Reports Server (NTRS)

In phase and frequency measurements, the measured phase and frequency are not the true phase and frequency but the ones which are disturbed by noises, due to the effects of the noise processes. The effects of three noise processes, i.e., White PM, White FM, and Random Walk FM, on the estimations of phase and frequency is discussed. It is indicated that the properties of these two estimations are very different. In phase estimation, the error can be reduced by properly selecting suitable smoothing length NT and smaple interval T. But in frequency estimation, the error cannot be reduced arbitrarily by means of improving estimator or measurement equipment. The precision of frequency is limited by the intrinsic noises in the clock.

Guo, Wei

1993-01-01

167

Effective switching frequency multiplier inverter  

DOEpatents

A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

Su, Gui-Jia (Oak Ridge, TN); Peng, Fang Z. (Okemos, MI)

2007-08-07

168

Flood Frequency Analysis: International Edition  

NSDL National Science Digital Library

Flood frequency analysis uses historical flow records to both estimate the frequency with which floods of a certain magnitude may occur and predict the possible flood magnitude over a certain time period. This module offers a thorough introduction to appropriately constructing the necessary historical data series, calculating the flooding probabilities, and gauging the reliability of the resulting probability values. Methods for assessing flood frequency in basins with limited data are also discussed.

COMET

2010-08-31

169

Frequency Regularities in ? Scuti Stars  

NASA Astrophysics Data System (ADS)

Space missions have produced an incredibly large database on pulsating stars. The light curves via the frequency content contain a detailed description of each star. The critical point is the identification of modes, especially in the non-asymptotic regime. The best derived parameters from the frequency content of a pulsating star light curve are the frequency differences and ratios. This presentation focuses on the potential of period ratios in mode identification.

Paparó, M.; Benk?, J. M.

2013-12-01

170

Frequency-Shift Hearing Aid  

NASA Technical Reports Server (NTRS)

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

Weinstein, Leonard M.

1994-01-01

171

International Frequency Control Symposium. Proceedings.  

NASA Astrophysics Data System (ADS)

The following topics are dealt with: sensors; atomic clocks; space applications; GPS; stability; synchronisation; time keeping; BAW resonators; SAW resonators; STW; frequency control; oscillators; and aging.

172

Statistics of atomic frequency standards  

Microsoft Academic Search

Abstract-A theoretical development,is presented,which,results in a relationship,between,the,expectation,value,of the standard deviation,of the frequency,fluctuations,for any finite number,of data samples and the infinite time average value of the standard deviation, which,provides,an invariant,measure,of an important,quality factor of a frequency,standard. A practical and,straightforward,method,of determining,the power,spectral density of the frequency,fluctuations from the variance of the frequency fluctuations, the sampling time, the number of samples taken, and

W. Allan

1996-01-01

173

Frequency response method in pharmacokinetics.  

PubMed

The paper presents the demonstration of applicability of the frequency response method in a bioavailability study. The frequency response method, common in system engineering, is based on an approximation of the frequency response of a linear dynamic system, calculated from input-output measurements, by a frequency model of the system transfer function in the frequency domain. In general, the influence of the system structure on the form of the system frequency response is much more distinct than on the form of the system output. This is of great advantage in modeling the system frequency response instead of the system output, commonly used in pharmacokinetics. After a brief theoretical section, the method is demonstrated on the estimation of the rate and extent of gentamicin bioavailability after intratracheal administration to guinea pigs. The optimal frequency model of the system describing the gentamicin pathway into the systemic circulation and point estimates of its parameters were selected by the approximation of the system frequency response in the frequency domain, using a noniterative algorithm. Two similar estimates of the system weighing function were independently obtained: the weighting function of the selected frequency model and the weighting function estimated by the numerical deconvolution procedure. Neither of the estimates of the weighting function does decrease monotonously after the maximum of about 2.2-2.5 unit of dose hr-1 recorded approximately 0.1 hr after drug administration. Both estimates show a marked additional peak approximately at 0.3 hr after administration and possible peaks in the further time period. We hypothesized that the loop found in the frequency response calculated and in the selected optimal frequency model, the high-order of this model, and several peaks identified in the estimates of the system weighting function indicated the complexity of the system and the presence of time delays. Three estimates of the extent of gentamicin intratracheal bioavailability obtained by the three different ways: directly from the calculated frequency response, calculated using the selected frequency model, and by the deconvolution method were 0.950, 0.934, and 0.907 respectively. Thus the conclusion can be made that gentamicin injected intratracheally to guinea pigs is almost completely available. PMID:7699584

Dedík, L; Durisová, M

1994-08-01

174

Image restoration using fast Fourier and wavelet transforms  

NASA Astrophysics Data System (ADS)

Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a proof-of-concept NQR explosives detector which interrogates a volume of 300 liters (10 ft3). With minimal modification to the existing explosives detector, we can detect operationally relevant quantities of (free base) cocaine within the 300-liter inspection volume in 6 seconds. We are presently extending this approach to the detection of heroin base and also examining 14N and 35,37Cl pure NQR for detection of the hydrochloride forms of both materials. An adaptation of this NQR approach may be suitable for scanning personnel for externally carried contraband and explosives. We first outline the basics of the NQR approach, highlighting strengths and weaknesses, and then present representative results for RDX and cocaine detection. We also present a partial compendium of relevant NQR parameters measured for some materials of interest.

Harrod, William J.; Nagy, James G.; Plemmons, Robert J.

1994-02-01

175

Narcotics and explosives detection by 14N pure nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a proof-of-concept NQR explosives detector which interrogates a volume of 300 liters (10 ft3). With minimal modification to the existing explosives detector, we can detect operationally relevant quantities of (free base) cocaine within the 300-liter inspection volume in 6 seconds. We are presently extending this approach to the detection of heroin base and also examining 14N and 35,37Cl pure NQR for detection of the hydrochloride forms of both materials. An adaptation of this NQR approach may be suitable for scanning personnel for externally carried contraband and explosives. We first outline the basics of the NQR approach, highlighting strengths and weaknesses, and then present representative results for RDX and cocaine detection. We also present a partial compendium of relevant NQR parameters measured for some materials of interest.

Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.

1994-03-01

176

Acoustic resonance frequency locked photoacoustic spectrometer  

DOEpatents

A photoacoustic spectroscopy method and apparatus for maintaining an acoustic source frequency on a sample cell resonance frequency comprising: providing an acoustic source to the sample cell, the acoustic source having a source frequency; repeatedly and continuously sweeping the source frequency across the resonance frequency at a sweep rate; and employing an odd-harmonic of the source frequency sweep rate to maintain the source frequency sweep centered on the resonance frequency.

Pilgrim, Jeffrey S.; Bomse, David S.; Silver, Joel A.

2003-09-09

177

Hydrogen-maser frequency standard  

NASA Technical Reports Server (NTRS)

Wall shift in frequency of proposed variable-shift maser that is caused by collisions between hydrogen atoms and container walls, could easily be determined, thereby allowing building of frequency standard with accuracy of 1 part in 10 to 14th power.

Reinhardt, V.; Cervenka, P.

1979-01-01

178

Pitch Extraction and Fundamental Frequency  

E-print Network

Report TR-CS 2003-06 November, 2003 c David Gerhard Department of Computer Science University of Regina is to extract the fundamental frequency (f0) from a sound signal, which is usually the lowest frequency of Pitch The musical pitch of an audio signal is a perceptual feature, relevant only in the context

Regina, University of

179

Lexical Frequency in Sign Languages  

ERIC Educational Resources Information Center

Measures of lexical frequency presuppose the existence of corpora, but true machine-readable corpora of sign languages (SLs) are only now being created. Lexical frequency ratings for SLs are needed because there has been a heavy reliance on the interpretation of results of psycholinguistic and neurolinguistic experiments in the SL research…

Johnston, Trevor

2012-01-01

180

Statistics of atomic frequency standards  

Microsoft Academic Search

A theoretical development is presented which results in a relationship between the expectation value of the standard deviation of the frequency fluctuations for any finite number of data samples and the infinite time average value of the standard deviation, which provides an invariant measure of an important quality factor of a frequency standard. A practical and straightforward method of determining

DAVID W. ALLAN

1966-01-01

181

Gaming Frequency and Academic Performance  

ERIC Educational Resources Information Center

There are numerous claims that playing computer and video games may be educationally beneficial, but there has been little formal investigation into whether or not the frequency of exposure to such games actually affects academic performance. This paper explores the issue by analysing the relationships between gaming frequency--measured as the…

Ip, Barry; Jacobs, Gabriel; Watkins, Alan

2008-01-01

182

ML radio frequency attenuating connector  

Microsoft Academic Search

In the increasingly harsh radio frequency environment associated with modern aerospace and missile systems, it is essential that safety standards are maintained or improved where electrically initiated explosive devices are involved. The Radio Frequency Attenuating Connector (RFAC) effectively protects igniters from electromagnetic interference both in hand held and installed modes. The RFAC provides a highly reliable pinless connector interface utilizing

M. G. Prewett

1982-01-01

183

Reconfigurable infrared frequency selective surfaces  

Microsoft Academic Search

In this paper, a new reconfigurable frequency selective surface (RFSS) design concept is introduced. A grid of simple metallic patches interconnected by a matrix of switches is proposed as the unit cell of an RFSS. The switches are independently addressable and provide significant transmission and reflection flexibility over a large range of frequencies. This flexibility is exploited by optimizing the

J. A. Bossard; D. H. Werner; T. S. Mayer; R. P. Drupp

2004-01-01

184

Frequency Conversion of Entangled State  

E-print Network

The quantum characteristics of sum-frequency process in an optical cavity with an input signal optical beam, which is a half of entangled optical beams, are analyzed. The calculated results show that the quantum properties of the signal beam can be maintained after its frequency is conversed during the intracavity nonlinear optical interaction. The frequency-conversed output signal beam is still in an entangled state with the retained other half of initial entangled beams. The resultant quantum correlation spectra and the parametric dependences of the correlations on the initial squeezing factor, the optical losses and the pump power of the sum-frequency cavity are calculated. The proposed system for the frequency conversion of entangled state can be used in quantum communication network and the calculated results can provide direct references for the design of experimental systems.

Aihong Tan; Xiaojun Jia; Changde Xie

2006-03-01

185

Single-frequency tunable laser for pumping cesium frequency standards  

SciTech Connect

A single-frequency tunable laser for pumping the cesium frequency standard is studied. It is shown experimentally that the laser emits at a single frequency despite the fact that a few longitudinal modes of the external cavity fall within the reflection band of a fibre Bragg grating (FBG) written in the optical fibre. The laser wavelength can be tuned by varying the pump current of the laser, its temperature, and the FBG temperature. The laser linewidth does not exceed 2 MHz for 10 mW of output power. (lasers)

Zhuravleva, O V; Ivanov, Andrei V; Leonovich, A I; Kurnosov, V D; Kurnosov, K V; Chernov, Roman V; Shishkov, V V [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation); Pleshanov, S A [Federal State Unitary Enterprise 'Istok Research and Production Association', Fryazino, Moscow region (Russian Federation)

2006-08-31

186

Laser frequency stabilization for LISA  

NASA Technical Reports Server (NTRS)

The requirement on laser frequency noise in the Laser Interferometer Space Antenna (LISA) depends on the velocity and our knowledge of the position of each spacecraft of the interferometer. Currently it is assumed that the lasers must have a pre-stabilized frequency stability of 30Hz/square root of Hz over LISA'S most sensitive frequency band (3 mHz - 30 mHz). The intrinsic frequency stability of even the most stable com- mercial lasers is several orders of magnitude above this level. Therefore it is necessary to stabilize the laser frequency to an ultra-stable frequency reference which meets the LISA requirements. The baseline frequency reference for the LISA lasers are high finesse optical cavities based on ULE spacers. We measured the stability of two ULE spacer cavities with respect to each other. Our current best results show a noise floor at, or below, 30 Hz/square root of Hz above 3 mHz. In this report we describe the experimental layout of the entire experiment and discuss the limiting noise sources.

Mueller, Guido; McNamara, Paul; Thorpe, Ira; Camp, Jordan

2005-01-01

187

A study of high-frequency regenerative frequency dividers  

Microsoft Academic Search

A comprehensive analytical study of high-frequency regenerative frequency dividers (RFD) is presented. The study includes two fundamental modes of operation in RFDs, namely stable and pulled operation modes. Differential equations characterizing the RFD behavior for both operation modes are derived. Next, an RFD circuit is designed and simulated in a 0.18µ µ µ µm standard CMOS process. Simulations verify the

Amin Q. Safarian; Payam Heydari

2005-01-01

188

Pulsed optically pumped frequency standard  

SciTech Connect

We reconsider the idea of a pulsed optically pumped frequency standard conceived in the early 1960s to eliminate the light-shift effect. The development of semiconductor lasers and of pulsed electronic techniques for atomic fountains and new theoretical findings allow an implementation of this idea which may lead to a frequency standard whose frequency stability is limited only by the thermal noise in the short term and by the temperature drift in the long term. We shall also show both theoretically and experimentally the possibility of doubling the atomic quality factor with respect to the classical Ramsey technique approach.

Godone, Aldo; Micalizio, Salvatore; Levi, Filippo [Istituto Elettrotecnico Nazionale Galileo Ferraris, Strada delle Cacce 91, 10135 Torino (Italy)

2004-08-01

189

Frequency coded sensors incorporating tapers  

NASA Technical Reports Server (NTRS)

A surface acoustic wave device includes a piezoelectric substrate on which is formed a transducer that generates acoustic waves on the surface of the substrate from electrical waves received by the transducer. The waves are carried along an acoustic track to either a second transducer or a reflector. The transducers or transducer and reflector are formed of subsections that are constructed to operate at mutually different frequencies. The subsections of at least one of the transducers or transducer and reflector are out of alignment with respect to one another relative to the transverse of the propagation direction. The out of aligned subsections provide not only a frequency component but also a time to the signal output signal. Frequency response characteristics are improved. An alternative embodiment provides that the transducers and/or reflectors are continuously tapered instead of having discrete frequency subsections.

Hines, Jacqueline H. (Inventor); Solie, Leland P. (Inventor)

2010-01-01

190

AUTO ID FUTURE - FREQUENCY AGNOSTIC  

E-print Network

Identification of information is one key to the development of intelligent decision systems of the future. Frequency agnostic automatic identification is only one step in the physical world to make physical objects identify ...

DATTA, SHOUMEN

191

Low-Frequency Radioastronomy Basics  

NASA Astrophysics Data System (ADS)

With the many large instruments in construction or in project, the present epoch corresponds to a renewal of low-frequency radioastronomy. The field will attract new researchers and students not expert of the radioastronomy techniques. With this audience in mind, we present here a very brief introduction to radioastronomy basics, including propagation and polarization of low-frequency radio waves as well as instrumental aspects. Basic formulas are given. The references and internet links will allow the interested reader to go further.

Zarka, P.

2011-04-01

192

Tables of molecular vibrational frequencies  

Microsoft Academic Search

Fundamental vibrational frequencies of 109 molecular forms of 38 polyatomic chain molecules consisting of the CH3, CD3, CH2 CD2, CHD, O, and S groups are given as an extension of tables of molecular vibrational frequencies published in the NSRDS-NBS publication series and in this journal. On preparing the tables in this part, an approach, different from that in the previous

Takehiko Shimanouchi; Hiroatsu Matsuura; Yoshiki Ogawa; Issei Harada

1978-01-01

193

Frequency dependencies of power noise  

Microsoft Academic Search

In this paper, frequency dependencies of delta-I noise caused by variations of the on-chip switching activity have been analyzed by simulations for a complex computer system board with multi-chip module, especially the impact of coincidences with resonances of the power distribution system. The switching frequency and the noise source waveform have been varied in case of a single delta-I step.

Bernd Garben; Roland Frech; Jochen Supper; Michael F. McAllister

2002-01-01

194

Frequency chirping in external modulators  

Microsoft Academic Search

A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an ?-parameter that contributes to frequency chirping

Fumio Koyama; KENICHI IGA

1988-01-01

195

Decimation & Expansion (Frequency Domain View)  

E-print Network

1/12 Decimation & Expansion (Frequency Domain View) Need to look at: ­ Z- Transform ­ DTFT #12-3-6 1 C3(m) M-Fold Decimation ­ Frequency-Domain 2 /j M MW e #12;3/12 ][][ ][][)( nMcnMx nMxnx M M = = Now... use the comb function to write decimation: Doesn't Really Do Anything Here... But Later it Will

Fowler, Mark

196

Frequency regulator for synchronous generators  

DOEpatents

The present invention is directed to a novel frequency regulator which controls a generator output frequency for variations in both the input power to the generator and the power supplied to an uncontrolled external load. The present invention further includes over current and current balance protection devices which are relatively inexpensive to manufacture, which may be encapsulated to provide protection from the operating environment and which respond more quickly than previously known electromechanical devices. 11 figs.

Karlicek, R.F.

1982-08-10

197

Stepped frequency ground penetrating radar  

DOEpatents

A stepped frequency ground penetrating radar system is described comprising an RF signal generating section capable of producing stepped frequency signals in spaced and equal increments of time and frequency over a preselected bandwidth which serves as a common RF signal source for both a transmit portion and a receive portion of the system. In the transmit portion of the system the signal is processed into in-phase and quadrature signals which are then amplified and then transmitted toward a target. The reflected signals from the target are then received by a receive antenna and mixed with a reference signal from the common RF signal source in a mixer whose output is then fed through a low pass filter. The DC output, after amplification and demodulation, is digitized and converted into a frequency domain signal by a Fast Fourier Transform. A plot of the frequency domain signals from all of the stepped frequencies broadcast toward and received from the target yields information concerning the range (distance) and cross section (size) of the target.

Vadnais, Kenneth G. (Ojai, CA); Bashforth, Michael B. (Buellton, CA); Lewallen, Tricia S. (Ventura, CA); Nammath, Sharyn R. (Santa Barbara, CA)

1994-01-01

198

Combining information across frequency regions in fundamental frequency discrimination.  

PubMed

Sensitivity to fundamental frequency (F0) differences was measured for two complex tones, A and B, which had the same F0 but were filtered into two different frequency regions. Tones were presented either alone or together. A signal-detection analysis was used to predict effects of combining F0 information across frequency regions. For 400-ms tones containing only unresolved harmonics, the first experiment showed that performance (in terms of d(')) for the combined presentation was better than for the isolated tones but was not optimal (assuming independent channels and noises) and was independent of the relative timing of pulses in the envelopes of tones A and B (varied by changing the starting phase of components of tone B relative to those of tone A). The nonoptimal performance was shown not to be due to peripheral masking (experiment II), or to listeners paying attention mainly to one frequency region (experiment III), nor was it specific to conditions where all harmonics were unresolved (experiment IV). In contrast, optimal performance in F0 discrimination for combined presentation was observed for 50-ms tones (experiment V). The results may reflect the limited ability of the human auditory system to integrate information simultaneously in the time and the frequency domains. PMID:20370030

Gockel, Hedwig E; Carlyon, Robert P; Plack, Christopher J

2010-04-01

199

Frequency Stability of Atomic Frequency Standards beyond Quantum Projection Noise  

E-print Network

In this paper we describe that the optically pumped frequency standards can have frequency stability beyond the quantum noise limit by detecting the Ramsey resonance through the squeezed light. In this paper we report that instead of considering the interaction of entangled atoms in the microwave region, it will be more practical to create the entanglement of the atoms in the detection region using the squeezed light, which is also used for the detection of the Ramsey resonance. The advantage of squeezing can be derived when the technical noises have been removed.

G. M. Saxena

2011-04-07

200

Frequency tracked gated pulse technique for ultrasonic frequency  

NASA Technical Reports Server (NTRS)

A tracking generator 21 is slaved to a spectrum analyzer 23 to produce an input signal having a frequency that follows the frequency of the spectrum analyzer sweeping local oscillator 22. The input signal is gated to a transducer 26 by a transmitter gate 25 to produce ultrasonic waves in the sample 28. The resulting ultrasonic echoes are converted into electrical signals by the transducer and then gated into the spectrum analyzer by receiver gate 29. This arrangement produces spectra that are equivalent to shock-exciting the transducer with a true delta function shock-excitation.

Cantrell, Jr., John H. (Inventor); Heyman, Joseph S. (Inventor)

1983-01-01

201

Frequency response of ice streams  

PubMed Central

Changes at the grounding line of ice streams have consequences for inland ice dynamics and hence sea level. Despite substantial evidence documenting upstream propagation of frontal change, the mechanisms by which these changes are transmitted inland are not well understood. In this vein, the frequency response of an idealized ice stream to periodic forcing in the downstream strain rate is examined for basally and laterally resisted ice streams using a one-dimensional, linearized membrane stress approximation. This reveals two distinct behavioural branches, which we find to correspond to different mechanisms of upstream velocity and thickness propagation, depending on the forcing frequency. At low frequencies (centennial to millennial periods), slope and thickness covary hundreds of kilometres inland, and the shallow-ice approximation is sufficient to explain upstream propagation, which occurs through changes in grounding-line flow and geometry. At high frequencies (decadal to sub-decadal periods), penetration distances are tens of kilometres; while velocity adjusts rapidly to such forcing, thickness varies little and upstream propagation occurs through the direct transmission of membrane stresses. Propagation properties vary significantly between 29 Antarctic ice streams considered. A square-wave function in frontal stress is explored by summing frequency solutions, simulating some aspects of the dynamical response to sudden ice-shelf change. PMID:23197934

Williams, C. Rosie; Hindmarsh, Richard C. A.; Arthern, Robert J.

2012-01-01

202

Active Faraday optical frequency standard.  

PubMed

We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 ?W. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks. PMID:25361349

Zhuang, Wei; Chen, Jingbiao

2014-11-01

203

Spatial frequencies and emotional perception.  

PubMed

It has been suggested that, during evolution, specific mechanisms developed in order to optimize the detection of threats and opportunities even in perceptually degraded conditions. A naturalistic example of perceptual degradation can be found in blurry images, which contain the coarsest elements of a scene (low spatial frequencies) but lack the fine-grained details (high spatial frequencies). In the past decade, several studies have examined the relation between spatial frequencies and emotions, using a variety of methods, stimuli, and rationales. Here, we conduct a literature survey on the studies that have examined the relation between emotion and spatial frequencies. Some studies have suggested that the low spatial frequencies of emotional stimuli may be processed by a subcortical neural pathway, eventually eliciting emotional responses. However, the evidence provided by the reviewed studies does not support this possibility, for conceptual and methodological reasons (e.g., mistaking the processing of a fuzzy stimulus for subcortical processing). Here, the conceptual and methodological problems present in the reviewed studies are analyzed and discussed, along with suggestions for future research. PMID:23183741

De Cesarei, Andrea; Codispoti, Maurizio

2013-01-01

204

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2010-10-01

205

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

2010-10-01

206

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2011-10-01

207

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Frequencies. 87.303 Section 87.303 Telecommunication...SERVICES Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight...

2010-10-01

208

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

2010-10-01

209

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

2011-10-01

210

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Frequencies. 87.303 Section 87.303 Telecommunication...SERVICES Flight Test Stations § 87.303 Frequencies. (a) These frequencies are available for assignment to flight...

2011-10-01

211

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

2011-10-01

212

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2010-10-01

213

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2011-10-01

214

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2011-10-01

215

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2010-10-01

216

47 CFR 87.263 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequencies. 87.263 Section 87.263 Telecommunication...Aeronautical Enroute Stations § 87.263 Frequencies. (a) Domestic VHF service. (1) Frequencies in the 128.8125-132.125...

2011-10-01

217

47 CFR 95.1111 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...information: (1) Specific frequencies or frequency range(s) used; (2) Modulation...provider (name, title, office, phone number, fax number, e-mail...care provider shall notify the frequency coordinator whenever a...

2010-10-01

218

47 CFR 95.1111 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...information: (1) Specific frequencies or frequency range(s) used; (2) Modulation...provider (name, title, office, phone number, fax number, e-mail...care provider shall notify the frequency coordinator whenever a...

2011-10-01

219

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2014 CFR

...deviate from the following frequencies in that it should correspond to the actual center of stacked channels. When stacking an odd number of channels, the center frequency specified will correspond to one of the following frequencies....

2014-10-01

220

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2011 CFR

...deviate from the following frequencies in that it should correspond to the actual center of stacked channels. When stacking an odd number of channels, the center frequency specified will correspond to one of the following frequencies....

2011-10-01

221

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2010 CFR

...deviate from the following frequencies in that it should correspond to the actual center of stacked channels. When stacking an odd number of channels, the center frequency specified will correspond to one of the following frequencies....

2010-10-01

222

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2013 CFR

...deviate from the following frequencies in that it should correspond to the actual center of stacked channels. When stacking an odd number of channels, the center frequency specified will correspond to one of the following frequencies....

2013-10-01

223

47 CFR 74.502 - Frequency assignment.  

Code of Federal Regulations, 2012 CFR

...deviate from the following frequencies in that it should correspond to the actual center of stacked channels. When stacking an odd number of channels, the center frequency specified will correspond to one of the following frequencies....

2012-10-01

224

47 CFR 74.561 - Frequency tolerance.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency tolerance. 74.561 Section 74...Broadcast Auxiliary Stations § 74.561 Frequency tolerance. In the bands above 944 MHz, the operating frequency of the transmitter shall be...

2014-10-01

225

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2012-10-01

226

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2014 CFR

... 2014-10-01 2014-10-01 false Frequency stability. 24.135 Section 24.135 ...COMMUNICATIONS SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be...

2014-10-01

227

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2013-10-01

228

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

2013-10-01

229

47 CFR 22.863 - Frequency stability.  

Code of Federal Regulations, 2014 CFR

...2 2014-10-01 2014-10-01 false Frequency stability. 22.863 Section 22.863 ...Commercial Aviation Air-Ground Systems § 22.863 Frequency stability. The frequency stability of equipment used under this...

2014-10-01

230

47 CFR 87.263 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequencies. 87.263 Section 87.263 Telecommunication...Aeronautical Enroute Stations § 87.263 Frequencies. (a) Domestic VHF service. (1) Frequencies in the 128.8125-132.125...

2013-10-01

231

47 CFR 24.129 - Frequencies.  

Code of Federal Regulations, 2014 CFR

... 2014-10-01 2014-10-01 false Frequencies. 24.129 Section 24.129 Telecommunication...COMMUNICATIONS SERVICES Narrowband PCS § 24.129 Frequencies. The following frequencies are available for narrowband PCS:...

2014-10-01

232

47 CFR 74.661 - Frequency tolerance.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency tolerance. 74.661 Section 74...Auxiliary Stations § 74.661 Frequency tolerance. Stations in this service shall maintain the carrier frequency of each authorized transmitter...

2014-10-01

233

47 CFR 90.715 - Frequencies available.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequencies available. 90.715 Section 90...Regulations Governing Licensing and Use of Frequencies in the 220-222 MHz Band § 90.715 Frequencies available. (a) The following...

2013-10-01

234

47 CFR 5.303 - Frequencies.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequencies. 5.303 Section 5.303 Telecommunication...Experimental Radio Licenses § 5.303 Frequencies. Licensees may operate in any frequency band, except for the following:...

2014-10-01

235

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

2012-10-01

236

47 CFR 27.54 - Frequency stability.  

Code of Federal Regulations, 2014 CFR

...2 2014-10-01 2014-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication...SERVICES Technical Standards § 27.54 Frequency stability. The frequency stability shall be sufficient to ensure that...

2014-10-01

237

47 CFR 87.305 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency coordination. 87.305 Section... Flight Test Stations § 87.305 Frequency coordination. (a)(1) Each...existing license concerning flight test frequencies, except as provided in...

2012-10-01

238

47 CFR 24.229 - Frequencies.  

Code of Federal Regulations, 2014 CFR

...2 2014-10-01 2014-10-01 false Frequencies. 24.229 Section 24.229 Telecommunication...COMMUNICATIONS SERVICES Broadband PCS § 24.229 Frequencies. The frequencies available in the Broadband PCS service are...

2014-10-01

239

47 CFR 87.263 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequencies. 87.263 Section 87.263 Telecommunication...Aeronautical Enroute Stations § 87.263 Frequencies. (a) Domestic VHF service. (1) Frequencies in the 128.8125-132.125...

2012-10-01

240

47 CFR 87.41 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequencies. 87.41 Section 87.41...Applications and Licenses § 87.41 Frequencies. (a) Applicant responsibilities. The applicant must propose frequencies to be used by the station...

2013-10-01

241

47 CFR 78.111 - Frequency tolerance.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency tolerance. 78.111 Section 78...Technical Regulations § 78.111 Frequency tolerance. Stations in this service shall maintain the carrier frequency of each authorized transmitter...

2014-10-01

242

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2012-10-01

243

47 CFR 80.513 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency coordination. 80.513 Section 80...Marine Utility Stations § 80.513 Frequency coordination. (a) Except as...located in an area having a recognized frequency coordinating committee must be...

2012-10-01

244

47 CFR 73.754 - Frequency monitors.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency monitors. 73.754 Section 73...International Broadcast Stations § 73.754 Frequency monitors. (a) The licensee of...international broadcast station shall operate a frequency monitor at the transmitter...

2014-10-01

245

47 CFR 24.235 - Frequency stability.  

Code of Federal Regulations, 2014 CFR

...2 2014-10-01 2014-10-01 false Frequency stability. 24.235 Section 24.235 ...COMMUNICATIONS SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure...

2014-10-01

246

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Frequencies. 87.349 Section 87.349 Telecommunication...Aeronautical Utility Mobile Stations § 87.349 Frequencies. (a) The frequency assigned to an aeronautical utility...

2013-10-01

247

47 CFR 74.503 - Frequency selection.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency selection. 74.503 Section 74...Broadcast Auxiliary Stations § 74.503 Frequency selection. (a) Each application...station shall be specific with regard to frequency. In general, the lowest...

2014-10-01

248

Cavity-Enhanced Direct Frequency Comb Spectroscopy  

E-print Network

Cavity-Enhanced Direct Frequency Comb Spectroscopy: Technology and Applications Florian Adler-molecule spectroscopy, ultrasensitive spectroscopy, frequency-domain ultrafast spectroscopy Abstract Cavity-enhanced direct frequency comb spectroscopy combines broad band- width, high spectral resolution, and ultrahigh

249

Frequency translation method for low frequency variable gain amplification and filtering  

E-print Network

This thesis discusses an innovative solution to an industry challenge. A frequency translation method is designed to shift low frequency signals to intermediate frequencies in order to utilize higher-frequency components. ...

Feng, Mabel Y

2007-01-01

250

Variable frequency microprocessor clock generator  

SciTech Connect

A microprocessor-based system is described comprising: a digital central microprocessor provided with a clock input and having a rate of operation determined by the frequency of a clock signal input thereto; memory means operably coupled to the central microprocessor for storing programs respectively including a plurality of instructions and addressable by the central microprocessor; peripheral device operably connected to the central microprocessor, the first peripheral device being addressable by the central microprocessor for control thereby; a system clock generator for generating a digital reference clock signal having a reference frequency rate; and frequency rate reduction circuit means connected between the clock generator and the clock input of the central microprocessor for selectively dividing the reference clock signal to generate a microprocessor clock signal as an input to the central microprocessor for clocking the central microprocessor.

Branson, C.N.

1989-04-04

251

Swept Frequency Laser Metrology System  

NASA Technical Reports Server (NTRS)

A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

Zhao, Feng (Inventor)

2010-01-01

252

Partnership Concurrency and Coital Frequency  

PubMed Central

National HIV prevalence estimates across sub-Saharan Africa range from less than 1 percent to over 25 percent. Recent research proposes several explanations for the observed variation, including prevalence of male circumcision, levels of condom use, presence of other sexually transmitted infections, and practice of multiple concurrent partnerships. However, the importance of partnership concurrency for HIV transmission may depend on how it affects coital frequency with each partner. The coital dilution hypothesis suggests that coital frequency within a partnership declines with the addition of concurrent partners. Using sexual behavior data from rural Malawi and urban Kenya, we investigate the relationship between partnership concurrency and coital frequency, and find partial support for the coital dilution hypothesis. We conclude the paper with a discussion of our findings in light of the current literature on concurrency. PMID:23695523

Reniers, Georges; Helleringer, Stéphane

2013-01-01

253

Variable frequency microwave heating apparatus  

DOEpatents

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

Bible, Don W. (Clinton, TN); Lauf, Robert J. (Oak Ridge, TN); Johnson, Arvid C. (Lake in the Hills, IL); Thigpen, Larry T. (Angier, NC)

1999-01-01

254

Atomic frequency standards at NICT  

NASA Astrophysics Data System (ADS)

Various activities of atomic frequency standards studied in National Institute of Information and Communications Technology (NICT) are briefly reviewed. After BIPM accepted the first cesium fountain clock in NICT as a reference to determine International Atomic Time (TAI), efforts to further reduce the uncertainty of collision shifts are ongoing. A second fountain clock using atomic molasses is being built to enable the operation with less atomic density. Single ion clock using calcium has been pursued for several years in NICT. The absolute frequency measured in 2008 has CIPM to adopt the Ca+ clock transition as a part of the list of radiation (LoR) to realize the meter. Sr lattice clock has started its operation last year. The absolute frequency agreed well with those obtained in other institutes. Study of stable cavities to stabilize clock lasers are also introduced.

Ido, T.; Fujieda, M.; Hachisu, H.; Hayasaka, K.; Kajita, M.; Kojima, R.; Kumagai, M.; Locke, C.; Li, Y.; Matsubara, K.; Nogami, A.; Shiga, N.; Yamaguchi, A.; Koyama, Y.; Hosokawa, M.; Hanado, Y.

2011-10-01

255

An ironless low frequency subwoofer functioning under its resonance frequency.  

E-print Network

frequency loudspeaker (10Hz-100Hz) is described. Its structure is totally ironless in order to avoid of the loudspeaker lead to its high efficiency. Efforts have been made for reducing the non-linearities of the loudspeaker for a more accurate sound reproduction. In particular we have developed a motor totally made

Paris-Sud XI, Université de

256

47 CFR 101.1005 - Frequencies available.  

Code of Federal Regulations, 2010 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Local Multipoint Distribution Service § 101.1005 Frequencies available. (a) The following frequencies are...

2010-10-01

257

Hg{sup +} frequency standards  

SciTech Connect

In this paper we review the development of Hg{sup +} microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3x10{sup -14}/{radical}{tau} when a cryogenic oscillator of stability 2-3x10{sup -15} was used as the local oscillator. The trapped ion frequency standard employs a {sup 202}Hg discharge lamp to optically pump the trapped {sup 199}Hg{sup +} clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg{sup +} ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At {approx}10{sup -12}, the 2{sup nd} order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10{sup -14} or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, {alpha}=e{sup 2}/2{pi}hc, at the level of 10{sup -20}/year as predicted in some Grand Unified String Theories.

Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute [California Institute of Technology, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Building 298, Pasadena, California 91104 (United States)

1999-01-15

258

Power enhanced frequency conversion system  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

259

ML radio frequency attenuating connector  

NASA Astrophysics Data System (ADS)

In the increasingly harsh radio frequency environment associated with modern aerospace and missile systems, it is essential that safety standards are maintained or improved where electrically initiated explosive devices are involved. The Radio Frequency Attenuating Connector (RFAC) effectively protects igniters from electromagnetic interference both in hand held and installed modes. The RFAC provides a highly reliable pinless connector interface utilizing inductive coupling techniques and eliminates the need to use high-power bridgewires typically driven from a 28V dc aircraft or missile power bus. The conventional triggering circuits and data bussing can be replaced in the RFAC by fiber optics.

Prewett, M. G.

260

Metamaterial frequency-selective superabsorber.  

PubMed

Using transformation optics a frequency-selective superabsorber can be constructed that consists of an absorbing core material coated with a shell of isotropic double negative metamaterial. For a fixed volume its absorption cross section can be made arbitrarily large at one frequency. The double-negative shell serves to amplify the evanescent tail of the high-order cylindrical waves, which induces strong scattering and absorption. Our conclusion is supported by both analytical Mie theory and numerical finite-element simulation. Interesting applications of such a device are discussed. PMID:19252579

Ng, Jack; Chen, Huanyang; Chan, C T

2009-03-01

261

Modeling of EEG Signal Sound Frequency Characteristic Using Time Frequency Analysis  

Microsoft Academic Search

This paper presents the study of sound frequency characteristic based on Electroencephalography (EEG) signals. The study includes feature extraction of the EEG signals with respect to different sound frequencies, covering low frequency (40 Hz), mid-range frequency (5000 Hz), and high frequency (15000 Hz). Human brain activities are expected to be different when exposed to different sound frequencies, and can be

R. Sudirman; A. K. Chee; W. B. Daud

2010-01-01

262

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.10 Missing 1 0.95 Missing 1 0.95 Response Frequency Percent Response Frequency Percent Course Materials were 44.76 5 45 42.86 Missing 1 0.95 Missing 1 0.95 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

263

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.94 Missing 1 1.89 Missing 1 1.89 Response Frequency Percent Response Frequency Percent Course Materials were.15 5 32 60.38 Missing 1 1.89 Missing 1 1.89 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

264

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.48 Missing 2 1.90 Missing 2 1.90 Response Frequency Percent Response Frequency Percent Course Materials were.62 5 65 61.90 Missing 2 1.90 Missing 2 1.90 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

265

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.63 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were.81 5 32 59.26 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

266

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.90 Missing 4 3.45 Missing 4 3.45 Response Frequency Percent Response Frequency Percent Course Materials were.28 5 63 54.31 Missing 2 1.72 Missing 2 1.72 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

267

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.19 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were.56 5 43 79.63 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

268

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.00 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were 40.00 5 15 37.50 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

269

Response Frequency Percent Response Frequency Percent I have learned and understood the subject matter in  

E-print Network

Response Frequency Percent Response Frequency Percent I have learned and understood the subject.67 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent Course Materials were.14 5 12 57.14 Missing 0 0.00 Missing 0 0.00 Response Frequency Percent Response Frequency Percent

Walters, Bradley B.

270

Frequency Separation Locking and Synchronization for FDM Optical Sources Using Widely Frequency Tunable Laser Diodes  

Microsoft Academic Search

A laser diode (LD) frequency separation locking method (called the reference pulse method) is proposed. This method has advantageous features for frequency division multiplexing (FDM) networks from the viewpoint of frequency separation stability with a strict frequency separation standard, modulation format independence, controllability over a large number of LDs, and frequency synchronization capability. Frequency locking experiments, using four and ten

Naoki Shimosaka; Kazuhisa Kaede; Masahiko Fujiwara; Shuntaro Yamazaki; Shigeru Murata; Makoto Nishio

1990-01-01

271

Connecting colors to flexible frequencies  

NASA Astrophysics Data System (ADS)

Here is a simple way to reinforce the relationships among wavelength, frequency, and color in the visible light spectrum. All that is required is a 3-ft section of plastic or metal electric dryer venting hose, cans of red and violet spray paint, a couple of 5-in elastic bands, and a metric ruler.

Shaw, Mike

2010-11-01

272

Low-frequency acoustic microscope  

Microsoft Academic Search

Low-frequency acoustic microscopy has demonstrated a tremendous potential for the nondestructive evaluation of metals, composite materials, and structural ceramics. This proposal allowed us to build a new, improved instrument with which can make not only amplitude, but also phase, measurements. The addition of the phase measurement capability allows us to do two dimensional image processing to extract more information from

B. T. Khuri-Yakub; Butrus T

1986-01-01

273

Original article Frequency and evolution  

E-print Network

Original article Frequency and evolution of Melampsora larici-populina Klebahn races in north Champenoux, France (Received 11 February 1991; accepted 7 September 1991) Summary — Race populations in M larici-populina were studied for 4 years (nearly 7 000 identifica- tions). Race E1 is ubiquitous

Boyer, Edmond

274

PRIMARY FREQUENCY STANDARDS AT NIST  

Microsoft Academic Search

NIST has a more than 50-year history of developing ever more accurate atomic frequency standards. For most of that time, the technology was based on thermal atomic beams of cesium atoms, and the accuracy improvement was approximately a factor of 10 every 7 years. To put this into some kind ofperspective, both the period of this history and the rate

Robert Drullinger

275

High-frequency welding trials.  

PubMed

The high-frequency weldability of a new family of polyolefin films is compared with that of conventional films made of other polymers. A comparison of the optimum weld parameters of all the films and the results of performance testing of all the pouches produced are reported. PMID:15326740

Kelch, R

2000-09-01

276

Frequency agile optical parametric oscillator  

DOEpatents

The frequency agile OPO device converts a fixed wavelength pump laser beam to arbitrary wavelengths within a specified range with pulse to pulse agility, at a rate limited only by the repetition rate of the pump laser. Uses of this invention include Laser radar, LIDAR, active remote sensing of effluents/pollutants, environmental monitoring, antisensor lasers, and spectroscopy.

Velsko, Stephan P. (Livermore, CA)

1998-01-01

277

Frequency agile optical parametric oscillator  

DOEpatents

The frequency agile OPO device converts a fixed wavelength pump laser beam to arbitrary wavelengths within a specified range with pulse to pulse agility, at a rate limited only by the repetition rate of the pump laser. Uses of this invention include Laser radar, LIDAR, active remote sensing of effluents/pollutants, environmental monitoring, antisensor lasers, and spectroscopy. 14 figs.

Velsko, S.P.

1998-11-24

278

Frequency diversity and its applications  

Microsoft Academic Search

Adaptive shared resource methods may be the only available effective countermeasures to rain-induced attenuation in satellite communication systems above 20 GHz. Two of these methods, frequency diversity (FDV) and burst length control (BLC) are examined and compared by using a unified approach. The fundamental statistical relationships between unassisted and assisted conditions are derived, and optimum values are identified. It is

F. Carassa; G. Tartara; E. Matricciani

1988-01-01

279

Frequency Allocation; The Radio Spectrum.  

ERIC Educational Resources Information Center

The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

Federal Communications Commission, Washington, DC.

280

Antenna arrays with frequency compensation  

NASA Astrophysics Data System (ADS)

It is shown that the principle of least ordered sequences can be used to design linear nonequidistant arrays with suppression of additional diffraction peaks of the radiation pattern. This provides for a uniform sidelobe level and a stable directive gain in a wide frequency range. The range and directivity properties of such arrays are analyzed, and an efficient method of array synthesis is proposed.

Chaplin, A. F.; Koval', B. V.

1988-02-01

281

Protein alphabet reduction based on frequency dictionaries  

E-print Network

Protein alphabet reduction based on frequency dictionaries Misha Kudryashev with Tatyana Popova, ..., k} #12;11 Frequency dictionary Let X be a "q-letter word ensemble." Then P(X) is the q-th frequency dictionary for a text: it is a function that associates with each string of letters qiiif ...21 its frequency

Gorban, Alexander N.

282

Multiple chatter frequencies in milling processes  

Microsoft Academic Search

Analytical and experimental identifications of the chatter frequencies in milling processes are presented. In the case of milling, there are several frequency sets arising from the vibration signals, as opposed to the single well-defined chatter frequency of the unstable turning process. Frequency diagrams are constructed analytically and attached to the stability charts of mechanical models of high-speed milling. The corresponding

T. Insperger; G. Stépán; P. V. Bayly; B. P Mann

2003-01-01

283

Chapter Nine Frequency Domain Controller Design  

E-print Network

Chapter Nine Frequency Domain Controller Design 9.1 Introduction Frequency domain techniques physical system driven by a sinusoidal input with a broad range of frequencies. The controller design;382 FREQUENCY DOMAIN CONTROLLER DESIGN gain stability margins and steady state errors. It is also possible

Gajic, Zoran

284

Time-Frequency localization of Multiband signals  

E-print Network

Time-Frequency localization of Multiband signals University of Arkansas, November 7, 2008 Joe Lakey (w Scott Izu)1 November 3, 2008 Joe Lakey (w Scott Izu) Time-frequency multiband #12;Time and frequency localization Fourier transform: f () = R f (t) e-2it dt Joe Lakey (w Scott Izu) Time-frequency

Lakey, Joseph D.

285

Time-Frequency localization of Multiband signals  

E-print Network

Time-Frequency localization of Multiband signals FFT, Norbert Wiener Center, February 20, 2009 Joe Lakey (w Scott Izu)1 February 20, 2009 Joe Lakey (w Scott Izu) Time-frequency multiband #12;Time and frequency localization Fourier transform: f () = R f (t) e-2it dt Joe Lakey (w Scott Izu) Time-frequency

Lakey, Joseph D.

286

NRL Low-Frequency Antenna Development  

E-print Network

NRL Low-Frequency Antenna Development Brian Hicks W. Erickson, K. Stewart #12;NRL Low Frequency Antenna Development Our goal has been to research and develop wide- bandwidth low-frequency antennas.g. Galactic drift scans, solar bursts, and other strong sources) #12;NRL Low Frequency Antenna Development

Ellingson, Steven W.

287

47 CFR 74.761 - Frequency tolerance.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency tolerance. 74.761 Section 74...and TV Booster Stations § 74.761 Frequency tolerance. The licensee of a low...shall maintain the transmitter output frequencies as set forth below. The frequency...

2014-10-01

288

Infrared frequency standard using electrically trapped molecules  

Microsoft Academic Search

This paper discusses the possibility of developing a frequency standard using molecular vibrational transition frequencies, which are useful in optical communications. Cold molecules (<300muK) are trapped by microwave or infrared laser light, whose frequency is chosen so that the Stark shift on the transition frequency is significantly reduced. Microwave trapping is much more advantageous than infrared trapping for measuring the

Masatoshi Kajita

2008-01-01

289

Optical Frequency Synthesizer for Precision Spectroscopy  

Microsoft Academic Search

We have used the frequency comb generated by a femtosecond mode-locked laser and broadened to more than an optical octave in a photonic crystal fiber to realize a frequency chain that links a 10 MHz radio frequency reference phase-coherently in one step to the optical region. By comparison with a similar frequency chain we set an upper limit for the

R. Holzwarth; Th. Udem; T. W. Hänsch; J. C. Knight; W. J. Wadsworth; P. St. J. Russell

2000-01-01

290

Coverage Improvement for Dual Frequency SBAS  

E-print Network

Coverage Improvement for Dual Frequency SBAS Todd Walter, Juan Blanch & Per Enge Stanford #12;3 Dual Frequency Two civil frequencies in the ARNS bands allow aircraft to directly estimate equation targeting single satellite faults #12;4 Single SV Fault VPL Single frequency VPL well suited

Stanford University

291

New measurement solutions for low frequency systems  

NASA Astrophysics Data System (ADS)

Many physical phenomena occur in the low frequency area (vibration, acoustics and electrical signal analysis) that the measurement of these frequencies remain vital. The spectrum analyzer is used as an example of the use of low frequencies. It is used in sonar development, low frequency data links, production testing of torpedoes, transfer function of servo-systems, troop movement detection, flow studies in nuclear reactor cooling and harmonic distortion. The application of the spectrum analyzer to low frequency measurement is reviewed.

Siegerman, H.

292

Monochromatic radio frequency accelerating cavity  

DOEpatents

A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

Giordano, Salvatore (Port Jefferson, NY)

1985-01-01

293

Monochromatic radio frequency accelerating cavity  

DOEpatents

A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

Giordano, S.

1984-02-09

294

Frequency response of electrochemical cells  

NASA Technical Reports Server (NTRS)

Impedance concepts can be applied to the analysis of battery electrodes, yielding information about the structure of the electrode and the processes occurring in the electrode. Structural parameters such as the specific area (surface area per gram of electrode) can be estimated. Electrode variables such as surface overpotential, ohmic losses, and diffusion limitations may be studied. Nickel and cadmium electrodes were studied by measuring the ac impedance as a function of frequency, and the specific areas that were determined were well within the range of specific areas determined from BET measurements. Impedance spectra were measured for the nickel and cadmium electrodes, and for a 20 A-hr NiCd battery as functions of the state of charge. More work is needed to determine the feasibility of using frequency response as a nondestructive testing technique for batteries.

Thomas, Daniel L.

1989-01-01

295

High frequency power distribution system  

NASA Technical Reports Server (NTRS)

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.

Patel, Mikund R.

1986-01-01

296

Uranus smooth low frequency emission  

NASA Astrophysics Data System (ADS)

For the Uranus smooth low frequency emission (SLF) two different (and contradictory) source locations (one polar, one equatorial) have been reported in the literature. Visibility studies show that polar source locations within a limited magnetic longitude range can be singled out, whereas a polar source distributed along the whole range of magnetic longitudes is compatible with observations. In this study we have computed intensity contours for comparison with the observed emission. Profiles obtained by a geometrical beaming model favor the equatorial source location.

Rabl, G. K. F.; Ladreiter, H. P.; Rucker, H. O.; Leblanc, Y.

1992-08-01

297

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

Padamsee, Hasan S.

2014-10-01

298

Firewater system inadvertent actuation frequency  

SciTech Connect

The purpose of this analysis was to determine generic and plant-specific firewater inadvertent actuation frequencies for wetpipe and preaction firewater systems at the Advanced Test Reactor (ATR). Firewater systems of both kinds are installed throughout the ATR facility. When installed for the protection of reactor equipment, firewater systems may also adversely affect the equipment they are meant to protect. This occurs when inadvertent actuation of a firewater system causes wetting and subsequent damage to equipment.

Schroeder, J.A.; Eide, S.A.

1991-08-01

299

User-Driven Frequency Scaling  

Microsoft Academic Search

We propose and evaluate User-Driven Fre- quency Scaling (UDFS) for improved power management on processors that support Dynamic Voltage and Fre- quency Scaling (DVFS), e.g, those used in current laptop and desktop computers. UDFS dynamically adapts CPU frequency to the individual user and the workload through a simple user feedback mechanism, unlike currently-used DVFS methods which rely only on CPU

Arindam Mallik; Bin Lin; Gokhan Memik; Peter A. Dinda; Robert P. Dick

2006-01-01

300

Dynamic optical frequency domain reflectometry.  

PubMed

We describe a dynamic Optical Frequency Domain Reflectometry (OFDR) system which enables real time, long range, acoustic sensing at high sampling rate. The system is based on a fast scanning laser and coherent detection scheme. Distributed sensing is obtained by probing the Rayleigh backscattered light. The system was tested by interrogation of a 10 km communication type single mode fiber and successfully detected localized impulse and sinusoidal excitations. PMID:24787772

Arbel, Dror; Eyal, Avishay

2014-04-21

301

Variable frequency microwave furnace system  

DOEpatents

A variable frequency microwave furnace system (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34) for testing or other selected applications. The variable frequency microwave furnace system (10) includes a microwave signal generator (12) or microwave voltage-controlled oscillator (14) for generating a low-power microwave signal for input to the microwave furnace. A first amplifier (18) may be provided to amplify the magnitude of the signal output from the microwave signal generator (12) or the microwave voltage-controlled oscillator (14). A second amplifier (20) is provided for processing the signal output by the first amplifier (18). The second amplifier (20) outputs the microwave signal input to the furnace cavity (34). In the preferred embodiment, the second amplifier (20) is a traveling-wave tube (TWT). A power supply (22) is provided for operation of the second amplifier (20). A directional coupler (24) is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

Bible, Don W. (Clinton, TN); Lauf, Robert J. (Oak Ridge, TN)

1994-01-01

302

Mid-IR frequency measurement using an optical frequency comb and a long-distance remote frequency reference  

E-print Network

We have built a frequency chain which enables to measure the absolute frequency of a laser emitting in the 28-31 THz frequency range and stabilized onto a molecular absorption line. The set-up uses an optical frequency comb and an ultrastable 1.55 $\\mu$m frequency reference signal, transferred from LNE-SYRTE to LPL through an optical link. We are now progressing towards the stabilization of the mid-IR laser via the frequency comb and the extension of this technique to quantum cascade lasers. Such a development is very challenging for ultrahigh resolution molecular spectroscopy and fundamental tests of physics with molecules.

Bruno Chanteau; Olivier Lopez; Wei Zhang; Giorgio Santarelli; Yann Le Coq; Frédéric Auguste; Benoît Darquié; Christian Chardonnet; Anne Amy-Klein

2012-10-13

303

Frequency-frequency correlation functions and apodization in two-dimensional infrared vibrational echo spectroscopy  

E-print Network

Frequency-frequency correlation functions and apodization in two-dimensional infrared vibrational is to monitor the dynamical evolution of a molecular system by reporting the time dependent frequency fluctuations of an ensemble of vibrational probes. The vibrational frequency-frequency correlation function

Fayer, Michael D.

304

A tunable dual frequency dye laser - dual frequency oscillator design  

NASA Technical Reports Server (NTRS)

The pulsed dye laser offers a tunable oscillator, followed by three amplifiers. It is pumped by a dual frequency Nd:YAG laser. Tuning and spectral width are controlled by a holographic network connected to a high power telescope. The modified two wavelength dye laser allows for absorption lidar techniques for remote sensing of the atmosphere. Line switching is achieved by electrooptical commutation. A feasibility experiment was performed with the original oscillator. A model was then built, and tested with different dyes. After a few modifications were made to improve the conversion efficiency, this oscillator was inserted in the laser to check whether the amplifier stages were correctly adjusted.

Abury, Y.

1983-01-01

305

Multi-frequency communication system and method  

DOEpatents

A multi-frequency RFID remote communication system is provided that includes a plurality of RFID tags configured to receive a first signal and to return a second signal, the second signal having a first frequency component and a second frequency component, the second frequency component including data unique to each remote RFID tag. The system further includes a reader configured to transmit an interrogation signal and to receive remote signals from the tags. A first signal processor, preferably a mixer, removes an intermediate frequency component from the received signal, and a second processor, preferably a second mixer, analyzes the IF frequency component to output data that is unique to each remote tag.

Carrender, Curtis Lee; Gilbert, Ronald W.

2004-06-01

306

A low power prescaler, phase frequency detector, and charge pump for a 12 ghz frequency synthesizer  

E-print Network

A low power implementation of a CMOS frequency synthesizer at 12 GHz is an important step to improve the efficiency of a wireless transceiver in this frequency band. Since synthesizers are often employed as reference frequency sources such as local...

Eschenko, Evan Lee

2009-05-15

307

Low Radio Frequency Picosatellite Missions  

NASA Astrophysics Data System (ADS)

The dramatic advances in cubesat and other picosatellite capabilities are opening the door for scientifically important observations at low radio frequencies. Because simple antennas are effective at low frequencies, and receiver technology allows low mass and low power instruments, these observations are an ideal match for very small spacecraft. A workshop on cubesat missions for low frequency radio astronomy was held at the Kiss Institute for Space Sciences, Caltech, to explore mission concepts involving one up to hundreds of picosatellites. One result from this workshop was that there are opportunities for viable missions throughout this large range. For example, the sky-integrated spectral signature of highly redshifted neutral hydrogen from the dark ages and cosmic dawn epochs can be measured by a single antenna on a single spacecraft. There are challenging issues of calibration, foreground removal, and RF interference that need to be solved, but the basic concept is appealingly simple. At the other extreme, imaging of angular structure in the high-redshift hydrogen signal will require an interferometer array with a very large number of antennas. In this case the primary requirement is a sufficiently low individual spacecraft mass that hundreds can be launched affordably. The technical challenges for large arrays are long-term relative station keeping and high downlink data rates. Missions using several to a few tens of picosatellites can image and track bright sources such as solar and planetary radio bursts, and will provide essential validation of technologies needed for much larger arrays.This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Jones, Dayton L.

2014-06-01

308

Intensity-duration-frequency curves  

NASA Astrophysics Data System (ADS)

Intensity-duration-frequency (IDF) curves, or tables, are perhaps the most commonly used method for presentation of the characteristics of extreme rainfall events. This chapter provides an historical overview of developments in modeling and representation of IDF curves. Direction is provided to sources of information for IDF curve estimation, and alternative methods of modeling and representation of IDF relationships are discussed. Finally, this chapter provides an overview of contemporary IDF studies that are currently underway, as well as brief discussions of some emerging technologies that are leading to improvements in IDF curve estimation.

Durrans, S. Rocky

309

Planet frequency from microlensing observations  

NASA Astrophysics Data System (ADS)

Galactic gravitational microlensing is a very efficient technique to detect brown dwarfs and extrasolar planets at large orbital distances from their stars, and down to Earth-mass planets. More than 50 planets have been discovered so far, with 31 already published. Recent statistical results on the frequency of exoplanets based on several years of microlensing observations find that planets should be the rule rather than the exception, and confirm that super-Earth are much more frequent that giant planets in the Galaxy.

Cassan, A.; Ranc, C.

2014-12-01

310

Grouping Separated Frequency Components by Estimating Propagation Model Parameters in Frequency-Domain Blind Source Separation  

Microsoft Academic Search

This paper proposes a new formulation and optimization procedure for grouping frequency components in frequency-domain blind source separation (BSS). We adopt two separation techniques, independent component analysis (ICA) and time-frequency (T-F) masking, for the frequency-domain BSS. With ICA, grouping the frequency components corresponds to aligning the permutation ambiguity of the ICA solution in each frequency bin. With T-F masking, grouping

Hiroshi Sawada; Shoko Araki; Ryo Mukai; Shoji Makino

2007-01-01

311

Relativistic Frequency Synthesis of Light Fields  

E-print Network

Waveform shaping and frequency synthesis based on waveform modulation is ubiquitous in electronics, telecommunication technology, and optics. For optical waveforms, the carrier frequency is on the order of several hundred THz, while the modulation frequencies used in conventional devices like electro- or acousto-optical modulators are orders of magnitude lower. As a consequence, any new frequencies are typically very close to the fundamental. The synthesis of new frequencies in the extreme ultraviolet (XUV), e.g. by using relativistic oscillating mirrors, requires modulation frequencies in the optical regime or even in the extreme ultraviolet. The latter has not been proven possible to date. Here we demonstrate that individual strong harmonics can indeed be generated by reflecting light off a plasma surface that oscillates at XUV frequencies. The strong harmonics are explained by nonlinear frequency mixing of near-infrared light and a laser-driven plasma oscillation in the extreme ultra-violet mediated by a relativistic non-linearity.

C. Rödel; E. Eckner; J. Bierbach; M. Yeung; B. Dromey; T. Hahn; S. Fuchs; A. Galestian Pour; M. Wünsche; S. Kuschel; D. Hemmers; O. Jäckel; G. Pretzler; M. Zepf; G. G. Paulus

2013-10-29

312

Frequency synthesis using MEMS piezoelectric resonators  

E-print Network

(cont.) Ultimately, this thesis presents two approaches to frequency synthesizer design. The first uses frequency windows of approximately 200 MHz. The 800 MHz to 1 GHz matching network is presented in detail along with ...

Calhoun, Paul Jacob, 1979-

2004-01-01

313

Infants' Attentional Responses to Frequency Modulated Sweeps.  

ERIC Educational Resources Information Center

Reports on three experiments that assessed the attentional responses of 4-month-old infants to frequency-modulated sweeps corresponding to the frequency range of adult-to-infant and adult-to-adult intonational patterns. (HOD)

Colombo, John; Horowitz, Frances Degen

1986-01-01

314

Frequency Conversion Activation on the Mercury Laser  

Microsoft Academic Search

High efficiency frequency conversion while operating at average power is critical for the Mercury laser. We will demonstrate average power frequency conversion of face-cooled DKDP and YCOB crystals using a sapphire heat spreader approach.

A J Bayramian; R J Beach; C Bibeau; R Campbell; C A Ebbers; B L Freitas; R Kent; D Van Lue; Z Liao; T Landron; S A Payne; K I Schaffers; S Sutton; Y Fei; B Chai

2004-01-01

315

Fifty Years of Atomic Frequency Standards  

Microsoft Academic Search

This brief review of the history of atomic frequency standards includes: atomic beam magnetic resonance, microwave absorption and optical pumping, atomic masers, lasers, laser cooling and laser cooled atoms and ions at optical frequencies.

Norman F. Ramsey

2002-01-01

316

Frequency selective surfaces for Terahertz applications   

E-print Network

This thesis presents both theoretical and experimental investigations of the performance and capabilities of frequency selective surfaces (FSS) applied at THz frequencies. The aim is to explore and extend the use of FSS, ...

Sanz Fernandez, Juan Jose; Fernandez, Juan Jose Sanz

2012-11-29

317

Transition frequencies in the neuronal oscillator  

NASA Astrophysics Data System (ADS)

I present dynamical mechanisms responsible for transition frequencies, which are hidden in the homoclinic (HC) to supercritical Andronov-Hopf (AH) bifurcation switching in the two-dimensional Hindmarsh-Rose (2DHR) oscillator. For this purpose, I derive frequency gradients with respect to the input current and timescale in the 2DHR oscillator. The frequency gradients are formulated with phase response curves (PRCs) by expanding the firing frequency with small perturbations of the input current and timescale on the one-dimensional phase space of the 2DHR oscillator. I thus find two different types of striking breaks in the frequency plot with respect to the timescale, the sigmoid functional frequency and the discontinuous frequency. I also show effects of the unique PRC change on these transition frequencies.

Sato, Yasuomi D.

2013-06-01

318

Dual frequency piezoelectric transducer for medical applications  

NASA Astrophysics Data System (ADS)

Recent advances in the field of medical ultrasound requires a dual frequency transducer capable of operation at two frequencies. This is usually achieved by having a broadband transducer which can be excited at two different frequencies. Such frequency characteristics will allow echo-amplitude imaging at the higher frequency where a high resolution is required and color flow imaging (CFI) at the lower frequency for improved sensitivity. In this paper a novel dual frequency transducer design, demonstrating two distinct resonance, is presented. This is achieved by varying the geometry of the piezoelectric ceramic in a manner which results in two distinct thickness mode resonance. The results showing the temporal characteristics of such transducer are presented. The parameters influencing the temporal response of this transducer are discussed. It is also shown that the two resonance frequencies are independent. Finally, the advantages of this new design over the conventional techniques are discussed.

Bolorforosh, M. S.

1992-11-01

319

Substructure coupling in the frequency domain  

NASA Technical Reports Server (NTRS)

Frequency domain analysis was found to be a suitable method for determining the transient response of systems subjected to a wide variety of loads. However, since a large number of calculations are performed within the discrete frequency loop, the method loses it computational efficiency if the loads must be represented by a large number of discrete frequencies. It was also discovered that substructure coupling in the frequency domain work particularly well for analyzing structural system with a small number of interface and loaded degrees of freedom. It was discovered that substructure coupling in the frequency domain can lead to an efficient method of obtaining natural frequencies of undamped structures. It was also found that the damped natural frequencies of a system may be determined using frequency domain techniques.

1985-01-01

320

Low frequency AC waveform generator  

DOEpatents

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Bilharz, Oscar W. (Scotia, NY)

1986-01-01

321

Low frequency ac waveform generator  

DOEpatents

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Bilharz, O.W.

1983-11-22

322

Latency represents sound frequency in mouse IC  

Microsoft Academic Search

Frequency is one of the fundamental parameters of sound. The frequency of an acoustic stimulus can be represented by a neural\\u000a response such as spike rate, and\\/or first spike latency (FSL) of a given neuron. The spike rates\\/frequency function of most\\u000a neurons changes with different acoustic amplitudes, whereas FSL\\/frequency function is highly stable. This implies that FSL\\u000a might represent the

Qiang Qiu; Jie Tang; ZuLin Yu; Juan Zhang; YingJie Zhou; ZhongJu Xiao; JunXian Shen

2007-01-01

323

Atomic quantum memory for multimode frequency combs  

E-print Network

We propose a Raman quantum memory scheme that uses several atomic ensembles to store/retrieve the multimode highly entangled state of an optical quantum frequency comb, such as the one produced by parametric down-conversion of a pump frequency comb. We analyse the efficiency and the fidelity of such a quantum memory. Results show that our proposal may be helpful to multimode information processing using the different frequency bands of an optical frequency comb.

Z. Zheng; O. Mishina; N. Treps; C. Fabre

2015-01-27

324

Atomic quantum memory for multimode frequency combs  

NASA Astrophysics Data System (ADS)

We propose a Raman quantum memory scheme that uses several atomic ensembles to store and retrieve the multimode highly entangled state of an optical quantum frequency comb, such as the one produced by parametric down-conversion of a pump frequency comb. We analyze the efficiency and the fidelity of such a quantum memory. Results show that our proposal may be helpful to multimode information processing using the different frequency bands of an optical frequency comb.

Zheng, Zhan; Mishina, Oxana; Treps, Nicolas; Fabre, Claude

2015-03-01

325

Spatial averaging of time-frequency distributions  

Microsoft Academic Search

This paper presents a novel approach based on time-frequency distributions (TFDs) for separating signals received by a multiple antenna array. This approach provides a significant improvement in performance over the previously introduced spatial time-frequency distributions, specifically for signals with close time-frequency signatures. In this approach, spatial averaging of the time-frequency distributions of the sensor data is performed to eliminate the

Yimin Zhang; Moeness G. Amin

1999-01-01

326

Frequency Response Measurement for Periodic Test Signals  

Microsoft Academic Search

\\u000a The frequency response measurement with periodic test signals allows the determination of the relevant frequency range for\\u000a linear systems for certain, discrete points in the frequency spectrum. Typically, one uses sinusoidal signals at fixed frequencies,\\u000a see Sect. 5.1. However, one can also use other periodic signals such as e.g. rectangular, trapezoidal, or triangular signals\\u000a as shown in Sect. 5.2. The

Rolf Isermann; Marco Münchhof

327

Neural analysis of sound frequency in insects  

Microsoft Academic Search

Summary Insects, like other hearing animals, must extract information from the sounds they hear so that they may respond appropriately. One parameter of sound that carries information is its frequency content. Insects analyze sound frequency to identify mates, to judge the distance to potential competitors, and to detect predators and prey. We review how frequency is analyzed in the insect

Gerald S. Pollack; Kazuo Imaizumi

1999-01-01

328

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2010-10-01

329

47 CFR 2.1507 - Test frequencies.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Test frequencies. 2.1507 Section 2.1507 Telecommunication...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Test Procedures § 2.1507 Test frequencies. Testing of an EPIRB for...

2010-10-01

330

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2011-10-01

331

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2010-10-01

332

47 CFR 90.213 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency stability. 90.213 Section 90...General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere...governed by this part must have a minimum frequency stability as specified in the...

2011-10-01

333

47 CFR 90.213 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency stability. 90.213 Section 90...General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere...governed by this part must have a minimum frequency stability as specified in the...

2010-10-01

334

47 CFR 2.1507 - Test frequencies.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Test frequencies. 2.1507 Section 2.1507 Telecommunication...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Test Procedures § 2.1507 Test frequencies. Testing of an EPIRB for...

2011-10-01

335

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2011-10-01

336

Indoor propagation measurements at DECT frequencies  

Microsoft Academic Search

Broadband measurements of the indoor radio propagation channel, performed on the office floor of a factory, are described. The sounded frequency band has been 1.7-2.2 GHz, since several mobile and cordless telephone systems, and in particular DECT, operate within that frequency range. The frequency domain technique, proposed by Howard and Pahlavan (1990), based upon the use of a network analyzer,

F. Babich; G. Lombardi; L. Tomasi; E. Valentinuzzi

1996-01-01

337

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2013-10-01

338

47 CFR 90.613 - Frequencies available.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01false Frequencies available.90.613 Section 90...Regulations Governing Licensing and Use of Frequencies in the 806-824, 851-869, 896-901...Applications and the Selection and Assignment of Frequencies for Use in the 806-824 Mhz,...

2012-10-01

339

47 CFR 74.1202 - Frequency assignment.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency assignment. 74.1202 Section 74...Broadcast Booster Stations § 74.1202 Frequency assignment. (a) An applicant...application must be specific with regard to the frequency requested. Only one output channel...

2014-10-01

340

47 CFR 90.213 - Frequency stability.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency stability. 90.213 Section 90...General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere...governed by this part must have a minimum frequency stability as specified in the...

2013-10-01

341

47 CFR 90.213 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency stability. 90.213 Section 90...General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere...governed by this part must have a minimum frequency stability as specified in the...

2012-10-01

342

47 CFR 18.301 - Operating frequencies.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Operating frequencies. 18.301 Section 18.301 Telecommunication...Technical Standards § 18.301 Operating frequencies. ISM equipment may be operated on any frequency above 9 kHz except as indicated...

2014-10-01

343

47 CFR 74.1261 - Frequency tolerance.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency tolerance. 74.1261 Section 74...Broadcast Booster Stations § 74.1261 Frequency tolerance. (a) The licensee of...watts or less shall maintain the center frequency at the output of the translator...

2014-10-01

344

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2012-10-01

345

47 CFR 74.762 - Frequency measurements.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency measurements. 74.762 Section...and TV Booster Stations § 74.762 Frequency measurements. (a) The licensee...booster station must measure the carrier frequencies of its output channel as often...

2014-10-01

346

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency stability. 90.539 Section 90...Regulations Governing the Licensing and Use of Frequencies in the 758-775 and 788-805 MHz Bands § 90.539 Frequency stability. Transmitters...

2013-10-01

347

47 CFR 74.802 - Frequency assignment.  

Code of Federal Regulations, 2010 CFR

...One or more adjacent 25 kHz segments within the assignable frequencies...frequencies in a particular market(s) in the 700 MHz band...in the 700 MHz band in those market(s) will be required to...specified frequencies in the market in which the low power...

2010-10-01

348

Derivational Morphology and Base Morpheme Frequency  

ERIC Educational Resources Information Center

Morpheme frequency effects for derived words (e.g. an influence of the frequency of the base "dark" on responses to "darkness") have been interpreted as evidence of morphemic representation. However, it has been suggested that most derived words would not show these effects if family size (a type frequency count claimed to reflect semantic…

Ford, M. A.; Davis, M. H.; Marslen-Wilson, W. D.

2010-01-01

349

Magnetic MEMS reconfigurable frequency-selective surfaces  

Microsoft Academic Search

A reconfigurable frequency-selective electromagnetic filter implemented by integrating hard magnetic materials with microelectromechanical systems (MEMS) provides a new variation of reconfigurable frequency-selective surfaces (FSS). By incorporating magnetically actuated dipole elements that are capable of being tilted away from the supporting surface, we can tune the FSSs operating frequency without having to physically alter the dimensions of the dipole elements. The

Joe M. Zendejas; John P. Gianvittorio; Yahya Rahmat-Samii; Jack W. Judy

2006-01-01

350

Judging the Frequency of English Words  

ERIC Educational Resources Information Center

Given the lack of empirical corpus-based frequency counts in many languages, it would be useful and of theoretical interest if judgements of relative frequency of words in a language by proficient speakers of that language could substitute objective frequency counts for the purposes of devising language teaching materials, tests, and research…

Alderson, J. Charles

2007-01-01

351

Dual frequency selective reflectarray for propagation improvement  

Microsoft Academic Search

This paper proposes a novel dual frequency selective reflectarray that can control reflected beams independently at dual frequencies using two different polarizations. The reflectarray improves propagation by controlling the scattered beams to achieve high speed in broadband wireless mobile communication systems at a high frequency. The reflectarray comprises cross-dipole arrays and double square loops. Measurement and analysis results show the

T. Maruyama; T. Furuno; T. Ohya; Y. Oda; Qiang Chen; K. Sawaya

2010-01-01

352

High Frequency Dynamic Nuclear Polarization  

PubMed Central

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-? 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 temperature MAS probes were developed that permit in-situ microwave irradiation of the samples. And, finally, biradical polarizing agents were developed that increased the efficiency of DNP experiments by factors of ~4 at considerably lower paramagnet concentrations. Collectively these developments have made it possible to apply DNP on a routine basis to a number of different scientific endeavors, most prominently in the biological and material sciences. This Account reviews these developments, including the primary mechanisms used to transfer polarization in high frequency DNP, and the current choice of microwave sources and biradical polarizing agents. In addition, we illustrate the utility of the technique with a description of applications to membrane and amyloid proteins that emphasizes the unique structural information that is available in these two cases. PMID:23597038

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

353

Preferred frequencies for three unconsolidated earth materials  

SciTech Connect

Exploring near-surface mechanical wave propagation through cohesive and noncohesive soils is important for detecting buried objects (i.e., landmines and unexploded ordnance). Here, we determine that certain preferred frequencies travel through specific soils more efficiently. A controlled-frequency acoustic seismic source was developed to modulate the applied frequency and amplitude. Surface response due to continuous waves traveling through soils was recorded both instantaneously and after a finite load time. Preferred frequencies for sand, clay loam, and silt loam were measured to be 300-330, 100-140, and 140-260 Hz, respectively. Observed frequency shifts were dependent upon applied amplitude and load time.

Gilcrist, Laura E.; Baker, Gregory S.; Sen, Surajit [Department of Geology, State University of New York at Buffalo, Buffalo, New York 14260 (United States); Department of Earth and Planetary Science, University of Tennessee, Knoxville, Tennessee 37996 (United States); Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260 (United States)

2007-12-17

354

Frequency comb generation in superconducting resonators.  

PubMed

We have generated frequency combs spanning 0.5 to 20 GHz in superconducting ?/2 resonators at T=3??K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 10(8). The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves. PMID:25396390

Erickson, R P; Vissers, M R; Sandberg, M; Jefferts, S R; Pappas, D P

2014-10-31

355

Frequency Comb Generation in Superconducting Resonators  

NASA Astrophysics Data System (ADS)

We have generated frequency combs spanning 0.5 to 20 GHz in superconducting ? /2 resonators at T =3 K . Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 1 08. The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves.

Erickson, R. P.; Vissers, M. R.; Sandberg, M.; Jefferts, S. R.; Pappas, D. P.

2014-10-01

356

Multiple frequency method for operating electrochemical sensors  

DOEpatents

A multiple frequency method for the operation of a sensor to measure a parameter of interest using calibration information including the steps of exciting the sensor at a first frequency providing a first sensor response, exciting the sensor at a second frequency providing a second sensor response, using the second sensor response at the second frequency and the calibration information to produce a calculated concentration of the interfering parameters, using the first sensor response at the first frequency, the calculated concentration of the interfering parameters, and the calibration information to measure the parameter of interest.

Martin, Louis P. (San Ramon, CA)

2012-05-15

357

Lightweight, high-frequency transformers  

NASA Technical Reports Server (NTRS)

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.

Schwarze, G. E.

1983-01-01

358

Frequency domain optical parametric amplification  

PubMed Central

Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43?mJ two-cycle pulses at 1.8??m wavelength. PMID:24805968

Schmidt, Bruno E.; Thiré, Nicolas; Boivin, Maxime; Laramée, Antoine; Poitras, François; Lebrun, Guy; Ozaki, Tsuneyuki; Ibrahim, Heide; Légaré, François

2014-01-01

359

Magnetic Earth Ionosphere Resonant Frequencies  

NASA Technical Reports Server (NTRS)

The Community College Division is pleased to report progress of NASA funded research at West Virginia State College. During this reporting period, the project research group has continued with activities to develop instrumentation capability designed to monitor resonant cavity frequencies in the atmospheric region between the Earth's surface and the ionosphere. In addition, the project's principal investigator, Dr. Craig Spaniol, and NASA technical officer, Dr. John Sutton, have written and published technical papers intended to expand the scientific and technical framework needed for project research. This research continues to provide an excellent example of government and education working together to provide significant research in the college environment. This cooperative effort has provided many students with technical project work which compliments their education.

Spaniol, Craig

1994-01-01

360

A radio frequency coaxial feedthrough  

DOEpatents

An improved radio frequency coaxial transmission line vacuum feedthrough is provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflection from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits the voltage and power handling capabilities of a feedthrough.

Owens, T.L.

1987-12-07

361

Annular symmetry nonlinear frequency converters  

NASA Astrophysics Data System (ADS)

We present a new type of two-dimensional nonlinear structure for quasi-phase matching. This structure has continuous rotational symmetry, and in contrary to the commonly used periodic structures, is not lattice shaped and has no translation symmetry. It is shown that this annular symmetry structure possesses interesting phase matching attributes that are significantly different than those of periodic structures. In particular, it enables simultaneous phase-matched frequency doubling of the same pump into several different directions. Moreover, it has extremely wide phase-mismatch tolerance, since a change in the phase matching conditions does not change the second harmonic power, but only changes its propagation direction. Several structures were fabricated using either the indirect e-beam method in LiNbO3 or the electric field poling method in stoichiometric LiTaO3, and their conversion efficiencies, as well as angular and thermal dependencies, were characterized by second harmonic generation.

Kasimov, Dror; Arie, Ady; Winebrand, Emil; Rosenman, Gil; Bruner, Ariel; Shaier, Pnina; Eger, David

2006-10-01

362

Dermatomycosis Frequency and Localization Sites  

PubMed Central

Introduction: Since the prevalence of skin mycotic infections is changing and is area depended we aimed to analyze the frequency of the skin myocotic infections and the appearance sites. Material and Methods: There were involved 560 patients referred to the Dermatology Clinic of University Clinical Center of Kosova during a period of one year. Results: The mean age of our study group was around thirties with a predominance of female and rural patients. Although most of cases presented with single site disease localization, we observed the increase in number of cases with more than one site localization with age. Conclusion: The increased prevalence skin mycotic infections, as well as more than one place of localization deserve a multidimensional approach.

Koçinaj, Allma Ferizi; Kotori, Merita Grajqevci; Koraqi, Andi; Fida, Monika

2015-01-01

363

Frequency stabilization of algaas lasers  

SciTech Connect

Performances of semiconductor lasers have been remarkably improved by the demand of the optical communications industry. Recently, a single longitudinal mode, CW oscillation at room temperature has been realized. The price of each laser has been reduced as low as $250. These lasers are mostly oscillated in the near-infrared, and the coherent lights of 0.83 micrometers and 1.3-1.6 micrometers in wavelengths are obtained by AlGaAs lasers and InGaAsP lasers, respectively. Since few number of other kind of lasers oscillates in these wavelength regions, these semiconductor lasers could be conveniently used not only in optical communications but in many fields of application, e.g., laser spectroscopy, optical pumping, frequency and length standards, laser radar, air-borne gyroscope, etc.

Ohtsu, M.; Tsuchida, H.; Tako, T.

1982-01-01

364

Coping with Radio Frequency Interference  

NASA Astrophysics Data System (ADS)

The radio spectrum is a finite resource, on which humanity makes many demands. And pressure on it is ever increasing with the development of new technology and ideas for radio services. After all, we all benefit from wifi and cell phones. Radio astronomers have a small percentage of the spectrum allocated to them at octave intervals in the metre-centimetre bands, and at important frequencies, such as that of the 21cm line of HI. Signals from other services, as well as from our own poorly-engineered equipment, sometimes contaminate our bands: these signals constitute RFI. These may totally obliterate the astronomical signal, or, in the case of CLOUDSAT, may be capable of completely destroying a receiver, which introduces us to the new possibility of 'destructive interference'. A geo-stationary satellite can block access to a piece of sky from one site. Good equipment design eliminates self-inflicted interference, while physical separation often provides adequate practical mitigation at many frequencies. However, new observatories end up being located in the West Australian desert or Antarctica. In future they may be on the back side of the Moon. But there is no Earth-bound protection via physical separation against satellite signals. Some mitigation can be achieved by frequent data dumps and the excision of RFI, or by real-time detection and blanking of the receiver, or by more sophisticated algoriths. Astronomers of necessity aim to achieve mitigation via coordination, at the local level, and by participating in spectrum management at the national and international levels. This involves them spending a lot of time in Geneva at the International Telegraphic Union protecting their access to spectrum, and access to clean spectrum from the L3 point and the far side of the Moon.

Lewis, B. M.

2009-01-01

365

High-Dynamic Frequency Tracking Using Wavelets  

NASA Astrophysics Data System (ADS)

In this article, we investigate the use of wavelets for frequency tracking in the presence of high dynamics. In particular, we construct automatic frequency control loops that are based on correlating the incoming sinusoidal signal with Fourier-based functions and with Daubechies-4 wavelet functions. Both loops are compared based on their abilities to track an input frequency with varying degrees of frequency rate. For each loop, we show the steady-state frequency error and corresponding steady-state variance as a function of the frequency rate of the input signal. The results indicate that when the input frequency rate is close to zero (nearly constant frequency input), the Fourier-based loop achieves lower variance than does the wavelet-based loop. As the frequency rate increases (high dynamics), the performance of the Fourier-based loop degrades, and ultimately the Fourier-based loop ceases to track. Meanwhile, the wavelet-based loop achieves a lower steady-state error and continues to successfully track in frequency rate ranges where the Fourier-based loop breaks down. Thus, this study suggests that wavelets can be a viable alternative to traditional Fourier-based frequency tracking loops when the input is undergoing high dynamics. This type of dynamics could be found in applications such as space probes descending through a turbulent and unpredictable planetary atmosphere. However, during normal spacecraft cruise, more traditional Fourier-based loops will outperform wavelet-based loops.

Hamdan, K.; Tsou, H.; Hinedi, S. M.

1996-10-01

366

Radio Frequency Power Load and Associated Method  

NASA Technical Reports Server (NTRS)

A radio frequency power load and associated method. A radio frequency power load apparatus may include a container with an ionized fluid therein. The apparatus may include one conductor immersed in a fluid and another conductor electrically connected to the container. A radio frequency transmission system may include a radio frequency transmitter, a radio frequency amplifier connected to the transmitter and a radio frequency power load apparatus connected to the amplifier. The apparatus may include a fluid having an ion source therein, one conductor immersed in a fluid, and another conductor electrically connected to the container. A method of dissipating power generated by a radio frequency transmission system may include constructing a waveguide with ionized fluid in a container and connecting the waveguide to an amplifier of the transmission system.

Srinivasan, V. Karthik (Inventor); Freestone, Todd M. (Inventor); Sims, William Herbert, III (Inventor)

2014-01-01

367

Space-frequency correlation of classical waves in disordered media: High-frequency and  

E-print Network

OFFPRINT Space-frequency correlation of classical waves in disordered media: High-frequency) 14005 www.epljournal.org doi: 10.1209/0295-5075/80/14005 Space-frequency correlation of classical waves in disordered media: High-frequency and small-scale asymptotics A. C. Fannjiang Department of Mathematics

Fannjiang, Albert

368

On the Carrier Frequency Offset Estimation for Frequency Hopping Burst Mode Mobile Radio  

E-print Network

On the Carrier Frequency Offset Estimation for Frequency Hopping Burst Mode Mobile Radio G¨okhan M evaluate the Cramer-Rao bounds (CRB) for the estimation of the carrier frequency offset (CFO) for general QAM modulations with no knowledge of the transmitted sequence (blind operation) in frequency hopping

Yýlmaz, �zgür

369

Phase-stabilized 167 MHz Repetition Frequency Carbon Nanotube Fiber Laser Frequency Comb  

E-print Network

Phase-stabilized 167 MHz Repetition Frequency Carbon Nanotube Fiber Laser Frequency Comb Jinkang@phys.ksu.edu Abstract: The frequency comb generated by a high repetition frequency erbium-doped fiber ring laser using.3930) Metrological instrumentation; (320.7090) Ultrafast lasers; (060.5295) Photonic crystal fibers 1. Introduction

Washburn, Brian

370

Elimination of pump-induced frequency jitter on fiber-laser frequency combs  

E-print Network

Elimination of pump-induced frequency jitter on fiber-laser frequency combs J. J. McFerran, W. C. ID 68330) Optical frequency combs generated by femtosecond fiber lasers typically exhibit significant- veloped with Ti:sapphire lasers, frequency combs have been recently demonstrated with mode-locked fiber

Washburn, Brian

371

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

372

Single-frequency approximation of the coupling ray theory  

E-print Network

Single-frequency approximation of the coupling ray theory Ludek Klimes & Petr Bulant Department­ray­theory Green tensor is frequency dependent, and is usually calculated for many frequencies. This frequency this frequency dependence. In the vicinity of a given prevailing frequency, we approximate the frequency­ domain

Cerveny, Vlastislav

373

Frequency comparison and absolute frequency measurement of I 2-stabilized lasers at 532 nm  

Microsoft Academic Search

A frequency comparison and an absolute frequency measurement of iodine stabilized frequency-doubled Nd:YAG lasers at 532 nm has been performed at the Max-Planck-Institute for Quantum Optics. Two independent I2-stabilized laser systems, one assembled at the Institute of Laser Physics, Novosibirsk, Russia, the other at the Physikalisch-Technische Bundesanstalt, Braunschweig, Germany were investigated. Using a phase-coherent frequency chain, the absolute frequency of

A. Yu. Nevsky; R. Holzwarth; J. Reichert; Th. Udem; T. W. Hänsch; J. von Zanthier; H. Walther; H. Schnatz; F. Riehle; P. V. Pokasov; M. N. Skvortsov; S. N. Bagayev

2001-01-01

374

Simulation of multi-frequency ECRH  

SciTech Connect

We use a test particle simulation code to investigate electron cyclotron heating in a magnetic mirror well. A comparison is made between heating with one frequency and heating with two closely spaced frequencies. The code follows electron orbits in the presence of one or two monochromatic ECRH waves using guiding center equations and an equation for the electron gyrophase. Coulomb collisions with electrons and ions are simulated as a Monte Carlo scattering process. We find for the parameters of SM-1 that at the fundamental resonance the heating rate, or velocity rf diffusion coefficient, begins to decrease significantly from the quasilinear value for epsilon/sub e/ greater than or equal to 10 keV due to superadiabatic effects. As suggested by Howard et al., using multiple frequencies pushes the superadiabatic boundary to higher energies. For a given energy, the optimum frequency separations for two frequencies are those which cause the axial bounce resonances to interlace; i.e., odd multiples of the bounce frequency, ..omega../sub b/. This interlacing increases the chance of resonance overlap and thus stochasticity. If the frequency difference is equal to an even multiple of ..omega../sub b/, the diffusion coefficient returns to near its one frequency value. More generally, for more than two frequencies one should choose the frequency separation such that the bounce resonances interlace evenly. Detailed calculations are presented for SM-1 parameters.

Rognlien, T.D.

1981-11-23

375

VCO PLL Frequency Synthesizers for Spacecraft Transponders  

NASA Technical Reports Server (NTRS)

Two documents discuss a breadboard version of advanced transponders that, when fully developed, would be installed on future spacecraft to fly in deep space. These transponders will be required to be capable of operation on any deepspace- communications uplink frequency channel between 7,145 and 7,235 MHz, and any downlink frequency channel between 8,400 and 8,500 MHz. The document focuses on the design and operation of frequency synthesizers for the receiver and transmitter. Heretofore, frequency synthesizers in deep-space transponders have been based on dielectric resonator oscillators (DROs), which do not have the wide tuning bandwidth necessary to tune over all channels in the uplink or downlink frequency bands. To satisfy the requirement for tuning bandwidth, the present frequency synthesizers are based on voltage-controlled-oscillator (VCO) phase-locked loops (PLLs) implemented by use of monolithic microwave integrated circuits (MMICs) implemented using inGaP heterojunction bipolar transistor (HBT) technology. MMIC VCO PLL frequency synthesizers similar to the present ones have been used in commercial and military applications but, until now, have exhibited too much phase noise for use in deep-space transponders. The present frequency synthesizers contain advanced MMIC VCOs, which use HBT technology and have lower levels of flicker (1/f) phase noise. When these MMIC VCOs are used with high-speed MMIC frequency dividers, it becomes possible to obtain the required combination of frequency agility and low phase noise.

Smith, Scott; Mysoor, Narayan; Lux, James; Cook, Brian

2007-01-01

376

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

Microsoft Academic Search

Results of extremely low frequency\\/very low frequency (ELF\\/VLF) wave generation by intensity-modulated high frequency (HF) heaters of 3.2 MHz in Gakona, Alaska, near local solar noon during a geomagnetic quiet time, are presented to support an electrojet-independent ELF\\/VLF wave generation mechanism. The modulation was set by splitting the HF transmitter array into two subarrays; one was run at cw full

Spencer Kuo; Arnold Snyder; Chia-Lie Chang

2010-01-01

377

Detecting body cavity bombs with nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) is a technology with great potential for detecting hidden explosives. Past NQR research has studied the detection of land mines and bombs concealed within luggage and packages. This thesis focuses on an NQR application that has received less attention and little or no publicly available research: detecting body cavity bombs (BCBs). BCBs include explosives that have been ingested, inserted into orifices, or surgically implanted. BCBs present a threat to aviation and secure facilities. They are extremely difficult to detect with the technology currently employed at security checkpoints. To evaluate whether or not NQR can be used to detect BCBs, a computational model is developed to assess how the dielectric properties of biological tissue affect the radio frequency magnetic field employed in NQR (0.5-5MHz). The relative permittivity of some biological tissue is very high (over 1,000 at 1MHz), making it conceivable that there is a significant effect on the electromagnetic field. To study this effect, the low-frequency approximation known as the Darwin model is employed. First, the electromagnetic field of a coil is calculated in free space. Second, a dielectric object or set of objects is introduced, and the free-space electric field is modified to accommodate the dielectric object ensuring that the relevant boundary conditions are obeyed. Finally, the magnetic field associated with the corrected electric field is calculated. This corrected magnetic field is evaluated with an NQR simulation to estimate the impact of dielectric tissue on NQR measurements. The effect of dielectric tissue is shown to be small, thus obviating a potential barrier to BCB detection. The NQR model presented may assist those designing excitation and detection coils for NQR. Some general coil design considerations and strategies are discussed.

Collins, Michael London

378

[Low-Frequency Flow Oscillation  

NASA Technical Reports Server (NTRS)

The results of the research conducted under this grant are presented in detail in three Master theses, by Heinrich, Balow, and Broeren. Additional analysis of the experimental data can be found in two AIAA Journal articles and two conference papers. Citations for all of the studies' publications can be found in the bibliography which is attached. The objective of Heinrich's study was to document the low-frequency flow oscillation on the LRN-1007 airfoil, which had been previously observed at low Reynolds number, to determine its origin, and explore the phenomenon at higher Reynolds number. Heinrich performed detailed flow visualization on the airfoil using surface fluorescent oil and laser-sheet off-body visualization. A large leading-edge separation bubble and trailing-edge separation was identified on the airfoil just prior to the onset of the unsteady stall flow oscillation. From the laser-sheet data, the unsteady flow appeared as a massive boundary-layer separation followed by flow reattachment. Hot-wire data were taken in the wake to identify the presence of the flow oscillation and the dominant frequency. The oscillation was found in the flow from a Reynolds number of 0.3 to 1.3 x 10 exp 6. The Strouhal number based on airfoil projected height was nominally 0.02 and increased slightly with increasing Reynolds number and significantly with increasing airfoil angle of attack. Balow focused his research on the leading-edge separation bubble which was hypothesized to be the origin of the low-frequency oscillation. Initially, experimental measurements in the bubble at the onset of the low-frequency oscillation were attempted to study the characteristics of the bubble and explain possible relationships to the shear-layer-flapping phenomena. Unfortunately, the bubble proved to be extremely sensitive to the probe interference and it drastically reduced the size of the bubble. These detailed measurements were then abandoned by Balow. However, this led to a series of tests where the leading-edge bubble and trailing-edge separation were altered and the affect on the flow-oscillation studied. Balow found that by tripping the airfoil boundary-layer with "zigzag" tape ahead of bubble separation, the bubble was effectively eliminated mid the oscillation suppressed. Wake survey drag measurements showed a drastic reduction in airfoil drag when the bubble and oscillation were eliminated. Using the "zigzag" tape, the trailing-edge separation was moved downstream approximately 5 percent chord. This was found to reduce the amplitude of the oscillation, particularly in the onset stage at low angle of attack (around 14 degrees). Through detailed analysis of the wake behind the airfoil during the unsteady flow oscillation, Balow provided a better understanding of the wake flowfield. Broeren studied the oscillating flowfield in detail at Reynolds number equal 3 x 10 exp 5 and an angle of attack of 15 degrees using laser Doppler velocimetry (LDV). Two-dimensional LDV data were acquired at 687 grid points above the model upper surface while hot-wire data were taken simultaneously in the wake. Using the hot-wire signal, the LDV data were phase averaged into 24 bins to represent a single ensemble average of one oscillation cycle. The velocity data showed a flowfield oscillation that could be divided into three flow regimes. In the first regime, the flow over the airfoil was completely separated initially, the flowfield reattached from the leading edge and the reattachment point moved downstream with increasing time or phase. Broeren referred to this as the reattachment regime. The bubble development regime followed, where a leading-edge separation bubble formed at the leading edge and grew with increasing time. During the initial part of this regime the trailing-edge separation continued to move downstream. However, during the last 30 degrees of phase the trailing-edge separation moved rapidly forward and appeared to merge with the leading-edge bubble. During the third regime, the separation regime, the flow was segmented f

Bragg, Michael B.

1997-01-01

379

Integrally formed radio frequency quadrupole  

DOEpatents

An improved radio frequency quadrupole (10) is provided having an elongate housing (11) with an elongate central axis (12) and top, bottom and two side walls (13a-d) symmetrically disposed about the axis, and vanes (14a-d) formed integrally with the walls (13a-d), the vanes (14a-d) each having a cross-section at right angles to the central axis (12) which tapers inwardly toward the axis to form electrode tips (15a-d) spaced from each other by predetermined distances. Each of the four walls (13a-d), and the vanes (14a-d) integral therewith, is a separate structural element having a central lengthwise plane (16) passing through the tip of the vane, the walls (13a-d) having flat mounting surfaces (17, 18) at right angles to and parallel to the control plane (16), respectively, which are butted together to position the walls and vane tips relative to each other.

Abbott, Steven R. (Concord, CA)

1989-01-01

380

Cluster analysis of word frequency dynamics  

NASA Astrophysics Data System (ADS)

This paper describes the analysis and modelling of word usage frequency time series. During one of previous studies, an assumption was put forward that all word usage frequencies have uniform dynamics approaching the shape of a Gaussian function. This assumption can be checked using the frequency dictionaries of the Google Books Ngram database. This database includes 5.2 million books published between 1500 and 2008. The corpus contains over 500 billion words in American English, British English, French, German, Spanish, Russian, Hebrew, and Chinese. We clustered time series of word usage frequencies using a Kohonen neural network. The similarity between input vectors was estimated using several algorithms. As a result of the neural network training procedure, more than ten different forms of time series were found. They describe the dynamics of word usage frequencies from birth to death of individual words. Different groups of word forms were found to have different dynamics of word usage frequency variations.

Maslennikova, Yu S.; Bochkarev, V. V.; Belashova, I. A.

2015-01-01

381

Frequency Control Performance Measurement and Requirements  

SciTech Connect

Frequency control is an essential requirement of reliable electric power system operations. Determination of frequency control depends on frequency measurement and the practices based on these measurements that dictate acceptable frequency management. This report chronicles the evolution of these measurements and practices. As technology progresses from analog to digital for calculation, communication, and control, the technical basis for frequency control measurement and practices to determine acceptable performance continues to improve. Before the introduction of digital computing, practices were determined largely by prior experience. In anticipation of mandatory reliability rules, practices evolved from a focus primarily on commercial and equity issues to an increased focus on reliability. This evolution is expected to continue and place increased requirements for more precise measurements and a stronger scientific basis for future frequency management practices in support of reliability.

Illian, Howard F.

2010-12-20

382

Wide band stepped frequency ground penetrating radar  

DOEpatents

A wide band ground penetrating radar system (10) embodying a method wherein a series of radio frequency signals (60) is produced by a single radio frequency source (16) and provided to a transmit antenna (26) for transmission to a target (54) and reflection therefrom to a receive antenna (28). A phase modulator (18) modulates those portion of the radio frequency signals (62) to be transmitted and the reflected modulated signal (62) is combined in a mixer (34) with the original radio frequency signal (60) to produce a resultant signal (53) which is demodulated to produce a series of direct current voltage signals (66) the envelope of which forms a cosine wave shaped plot (68) which is processed by a Fast Fourier Transform unit 44 into frequency domain data (70) wherein the position of a preponderant frequency is indicative of distance to the target (54) and magnitude is indicative of the signature of the target (54).

Bashforth, Michael B. (Buellton, CA); Gardner, Duane (Santa Maria, CA); Patrick, Douglas (Santa Maria, CA); Lewallen, Tricia A. (Ventura, CA); Nammath, Sharyn R. (Santa Barbara, CA); Painter, Kelly D. (Goleta, CA); Vadnais, Kenneth G. (Alexandria, VA)

1996-01-01

383

Wide band stepped frequency ground penetrating radar  

DOEpatents

A wide band ground penetrating radar system is described embodying a method wherein a series of radio frequency signals is produced by a single radio frequency source and provided to a transmit antenna for transmission to a target and reflection therefrom to a receive antenna. A phase modulator modulates those portions of the radio frequency signals to be transmitted and the reflected modulated signal is combined in a mixer with the original radio frequency signal to produce a resultant signal which is demodulated to produce a series of direct current voltage signals, the envelope of which forms a cosine wave shaped plot which is processed by a Fast Fourier Transform Unit 44 into frequency domain data wherein the position of a preponderant frequency is indicative of distance to the target and magnitude is indicative of the signature of the target. 6 figs.

Bashforth, M.B.; Gardner, D.; Patrick, D.; Lewallen, T.A.; Nammath, S.R.; Painter, K.D.; Vadnais, K.G.

1996-03-12

384

Frequency of radiculopathies in motor vehicle accidents.  

PubMed

This retrospective study compared the frequency of electrodiagnostically confirmed cervical and lumbar radiculopathies in a motor vehicle accident (MVA) population to that of a non-MVA population in 24,651 consecutive initial electrodiagnostic reports. The frequency of cervical radiculopathy was slightly but significantly increased in 8% of the MVA compared to 6% of the non-MVA patients. The frequency of plexopathy was significantly increased in the MVA (3%) compared to the non-MVA patients (2%). The frequency of lumbar radiculopathy was not significantly increased (12% for both groups). Nineteen percent of the MVA patients and 18% of the non-MVA patients had cervical and/or lumbar radiculopathy. This shows that the frequency of cervical and lumbar radiculopathies is low after MVAs. MVA appears to cause a small but significant increase in the frequency of cervical radiculopathy and plexopathy. PMID:19260059

Braddom, Randall L; Spitz, Lawrence; Rivner, Michael H

2009-04-01

385

Explaining the gender difference in nightmare frequency.  

PubMed

A recent meta-analysis showed a robust gender difference in nightmare frequency of medium effect size in adolescents and young adults: Women tend to report nightmares more frequently than men. The present study, carried out in an unselected student sample, indicates that 2 factors mediate the gender difference in nightmare frequency: neuroticism and overall dream recall frequency. The effect of neuroticism on the gender difference and the finding that the gender difference in nightmare frequency emerges at an age of about 10 years suggest that gender-specific socialization processes may play an important role in explaining the gender differences in nightmare frequency in adolescents and young to middle-aged adults. This idea is supported by the previous finding that nightmare frequency is related to sex role orientation. However, longitudinal studies are necessary to validate these hypotheses. PMID:24934011

Schredl, Michael

2014-01-01

386

Finite Element Model Updating Using Antiresonant Frequencies  

NASA Astrophysics Data System (ADS)

This paper uses antiresonant frequencies in the finite element model updating of an experimental 6-m aluminum truss and analyzes the physical correctness of the updated model by using it to detect damage. Rigid elements are used to simplify the modelling of welded joints, and their dimensions are used as parameters in an iterative update based on eigenvalue and antiresonance sensitivities. An update using both natural frequencies and antiresonant frequencies is shown to produce a 48% better correlation to experimental frequency response functions (FRFs) than an update that uses only natural frequencies. The antiresonant updated model is used to predict FRFs for the truss in 112 damaged configurations. Pattern classification and curve-fit algorithms for damage detection are tested. The curve-fit method correctly identified damage 92·6% of the time compared to 76·1% for the pattern classifier. The high quality of the model is attributed to the use of rigid elements that are updated using antiresonant frequencies.

JONES, K.; TURCOTTE, J.

2002-05-01

387

Beat frequency interference pattern characteristics study  

NASA Technical Reports Server (NTRS)

The frequency spectra and corresponding beat frequencies created by the relative motions between multiple Solar Power Satellites due to solar wind, lunar gravity, etc. were analyzed. The results were derived mathematically and verified through computer simulation. Frequency spectra plots were computer generated. Detailed computations were made for the seven following locations in the continental US: Houston, Tx.; Seattle, Wa.; Miami, Fl.; Chicago, Il.; New York, NY; Los Angeles, Ca.; and Barberton, Oh.

Ott, J. H.; Rice, J. S.

1981-01-01

388

Operation of Graphene Transistors at Gigahertz Frequencies  

Microsoft Academic Search

Top-gated graphene transistors operating at high frequencies (GHz) have been fabricated and their characteristics analyzed. The measured intrinsic current gain shows an ideal 1\\/f frequency dependence, indicating an FET-like behavior for graphene transistors. The cutoff frequency fT is found to be proportional to the dc transconductance gm of the device. The peak fT increases with a reduced gate length, and

Yu-Ming Lin; Keith A. Jenkins; Alberto Valdes-Garcia; Joshua P. Small; Damon B. Farmer; Phaedon Avouris

2009-01-01

389

Frequency modulation drive for a piezoelectric motor  

DOEpatents

A piezoelectric motor has peak performance at a specific frequency f.sub.1 that may vary over a range of frequencies. A drive system is disclosed for operating such a motor at peak performance without feedback. The drive system consists of the motor and an ac source connected to power the motor, the ac source repeatedly generating a frequency over a range from f.sub.1 -.DELTA.x to f.sub.1 +.DELTA.y.

Mittas, Anthony (Albuquerque, NM)

2001-01-01

390

Apparatus for measuring high frequency currents  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

391

Precision frequency measurements with entangled states  

E-print Network

We demonstrate how quantum entanglement can be used for precision frequency measurements with trapped ions. In particular, we show how to suppress linear Zeeman shifts in optical frequency measurements by using maximally entangled states of two ions even if the individual ions do not have any field-independent transition. In addition, this technique allows for an accurate measurement of small external field frequency shifts such as the electric quadrupole shift which are important for ion clock experiments.

C. F. Roos

2005-08-19

392

Digital, matrix and intermediate-frequency scanning  

Microsoft Academic Search

This paper describes circuit configurations for phased arrays which to some degree circumvent the difficulty of obtaining simple electronically-controlled phase shifters for UHF and Microwave frequencies. These configurations include phase shifters operating at an intermediate (i-f) frequency, frequency-scanning systems, within-pulse scanning, switched-multiple-beam antennas, switched-delay-line phase shifters, and digital-processing delay techniques.

JESSE L. BUTLER

1965-01-01

393

Widely tunable extreme UV frequency comb generation.  

PubMed

Extreme UV (XUV) frequency comb generation in the wavelength range of 51 to 85 nm is reported based on high-order harmonic generation of two consecutive IR frequency comb pulses that were amplified in an optical parametric chirped pulse amplifier. The versatility of the system is demonstrated by recording direct XUV frequency comb excitation signals in He, Ne, and Ar with visibilities of up to 61%. PMID:21633437

Pinkert, T J; Kandula, D Z; Gohle, C; Barmes, I; Morgenweg, J; Eikema, K S E

2011-06-01

394

Novel modulation technique for microwave frequencies  

NASA Astrophysics Data System (ADS)

A novel modulation technique is presented which facilitates the transmission of high frequency, fractional bandwidth signals in fibers. This approach uses the advantages of modelocked semiconductor lasers and external modulators. Narrow band (about 10 GHz) modulation can be readily achieved at high center frequencies. Experimental realization of this concept is demonstrated with an acoustooptic modulation of modelocked optical pulses from a GaAs laser diode at a center frequency of 2.05 GHz and a bandwidth of 68.7 MHz.

Yu, P. K. L.; Kellner, A. L.; Lam, B. C.; Yan, G. S.

1989-09-01

395

Laser frequency stabilization using Zeeman effect  

Microsoft Academic Search

We describe a new and easy to handle method to stabilize the laser frequency on an atomic transition. This method, based on Zeeman effect, involves the circular dichroism of an atomic vapour submitted to a magnetic field. It is applied to the frequency stabilization of a single frequency LNA laser on (2 (2 ^3S1-2 ^3P0) helium transition. Nous décrivons une

B. Chéron; H. Gilles; J. Hamel; O. Moreau; H. Sorel

1994-01-01

396

High Frequency AC Power Distribution Platforms  

Microsoft Academic Search

High Frequency AC (HFAC) power distribution system concerns the delivery of power at multi-kHz frequency via electric cables.\\u000a Early work on HFAC has demonstrated the many potential benefits of HFAC systems in terms of flexibility to meet loads at different\\u000a voltage levels, ease of electrical isolation using compact high frequency transformers, and the prospect of significant savings\\u000a in component count

Patrick Chi-Kwong Luk; Andy Seng Yim Ng

397

Advances in microwave acoustic frequency sources  

NASA Astrophysics Data System (ADS)

This paper reviews the principal advances with microwave frequency sources that use mechanical vibrations and waves in their frequency-controlling elements. Specifically, the review discusses the direction microwave acoustic technology has taken in the utilization of bulk acoustic-wave (BAW), surface acoustic-wave (SAW), shallow bulk acoustic-wave (SBAW), thin-film membrane, and composite structures to generate stable microwave frequency sources in the range from 100 MHz to 1 GHz and above.

Gerber, E. A.; Lukaszek, T.; Ballato, A.

1986-10-01

398

Frequency difference beyond behavioral limen reflected by frequency following response of human auditory Brainstem  

PubMed Central

Background The present study investigated whether the frequency-following response (FFR) of the auditory brainstem can represent individual frequency-discrimination ability. Method We measured behavioral frequency-difference limens (FDLs) in normal hearing young adults. Then FFRs were evoked by two pure tones, whose frequency difference was no larger than behavioral FDL. Discrimination of FFRs to individual frequencies was conducted as the neural representation of stimulus frequency difference. Participants were 15 Chinese college students (ages 19–25; 3 males, 12 females) with normal hearing characteristics. Results According to discriminative neural representations of individual frequencies, FFRs accurately reflected individual FDLs and detected stimulus-frequency differences smaller than behavioral threshold (e.g., 75% of FDL). Conclusions These results suggest that when a frequency difference cannot be behaviorally distinguished, there is still a possibility of it being detected physiologically. PMID:25108552

2014-01-01

399

Local frequency dependence and global coexistence.  

PubMed

In sessile organisms such as plants, interactions occur locally so that important ecological aspects like frequency dependence are manifest within local neighborhoods. Using probabilistic cellular automata models, we investigated how local frequency-dependent competition influenced whether two species could coexist. Individuals of the two species were randomly placed on a grid and allowed to interact according to local frequency-dependent rules. For four different frequency-dependent scenarios, the results indicated that over a broad parameter range the two species could coexist. Comparisons between explicit spatial simulations and the mean-field approximation indicate that coexistence occurs over a broader region in the explicit spatial simulation. PMID:10366552

Molofsky, J; Durrett, R; Dushoff, J; Griffeath, D; Levin, S

1999-06-01

400

Multiple chatter frequencies in milling processes  

NASA Astrophysics Data System (ADS)

Analytical and experimental identifications of the chatter frequencies in milling processes are presented. In the case of milling, there are several frequency sets arising from the vibration signals, as opposed to the single well-defined chatter frequency of the unstable turning process. Frequency diagrams are constructed analytically and attached to the stability charts of mechanical models of high-speed milling. The corresponding quasiperiodic solutions of the governing time-periodic delay-differential equations are also identified with some milling experiments in the case of highly intermittent cutting.

Insperger, T.; Stépán, G.; Bayly, P. V.; Mann, B. P.

2003-04-01

401

Frequency spectrum analyzer with phase-lock  

SciTech Connect

A frequency-spectrum analyzer with phase-lock for analyzing the frequency and amplitude of an input signal is comprised of a voltage controlled oscillator (VCO) which is driven by a ramp generator, and a phase error detector circuit. The phase error detector circuit measures the difference in phase between the VCO and the input signal, and drives the VCO locking it in phase momentarily with the input signal. The input signal and the output of the VCO are fed into a correlator which transfers the input signal to a frequency domain, while providing an accurate absolute amplitude measurement of each frequency component of the input signal.

Boland, T.J.

1981-07-29

402

Frequency spectrum analyzer with phase-lock  

DOEpatents

A frequency-spectrum analyzer with phase-lock for analyzing the frequency and amplitude of an input signal is comprised of a voltage controlled oscillator (VCO) which is driven by a ramp generator, and a phase error detector circuit. The phase error detector circuit measures the difference in phase between the VCO and the input signal, and drives the VCO locking it in phase momentarily with the input signal. The input signal and the output of the VCO are fed into a correlator which transfers the input signal to a frequency domain, while providing an accurate absolute amplitude measurement of each frequency component of the input signal.

Boland, Thomas J. (Idaho Falls, ID)

1984-01-01

403

Subjective frequency ratings for 432 ASL signs.  

PubMed

Given the importance of lexical frequency for psycholinguistic research and the lack of comprehensive frequency data for sign languages, we collected subjective estimates of lexical frequency for 432 signs in American Sign Language (ASL). Our participants were 59 deaf signers who first began to acquire ASL at ages ranging from birth to 14 years old and who had a minimum of 10 years of experience. Subjective frequency estimates were made on a scale ranging from 1 = rarely see the sign to 7 = always see the sign. The mean subjective frequency ratings for individual signs did not vary in relation to age of sign language exposure (AoLE), chronological age, or length of ASL experience. Nor did AoLE show significant effects on the response times (RTs) for making the ratings. However, RTs were highly correlated with mean frequency ratings. These results suggest that the distributions of subjective lexical frequencies are consistent across signers with varying AoLEs. The implications for research practice are that subjective frequency ratings from random samples of highly experienced deaf signers can provide a reasonable measure of lexical control in sign language experiments. The Appendix gives the mean and median subjective frequency ratings and the mean and median log(RT) of the ASL signs for the entire sample; the supplemental material gives these measures for the three AoLE groups: native, early, and late. PMID:23943581

Mayberry, Rachel I; Hall, Matthew L; Zvaigzne, Meghan

2014-06-01

404

23 CFR 650.311 - Inspection frequency.  

Code of Federal Regulations, 2012 CFR

...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

2012-04-01

405

23 CFR 650.311 - Inspection frequency.  

Code of Federal Regulations, 2011 CFR

...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

2011-04-01

406

23 CFR 650.311 - Inspection frequency.  

Code of Federal Regulations, 2010 CFR

...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

2010-04-01

407

23 CFR 650.311 - Inspection frequency.  

Code of Federal Regulations, 2014 CFR

...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

2014-04-01

408

23 CFR 650.311 - Inspection frequency.  

Code of Federal Regulations, 2013 CFR

...FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS BRIDGES, STRUCTURES, AND HYDRAULICS National Bridge Inspection Standards § 650.311 Inspection frequency. (a) Routine inspections. (1)...

2013-04-01

409

Phononic Frequency Combs through Nonlinear Resonances  

NASA Astrophysics Data System (ADS)

We explore an analogue of optical frequency combs in driven nonlinear phononic systems, and present a mechanism for generating phononic frequency combs through nonlinear resonances. In the underlying process, a set of phonon modes is simultaneously excited by the external driving which yields frequency combs with an array of discrete and equidistant spectral lines of each nonlinearly excited phonon mode. Frequency combs through nonlinear resonance of different orders are investigated, and in particular the possibility of correlation tailoring in higher-order cases is revealed. We suggest that our results can be applied in various nonlinear acoustic processes, such as phonon harvesting, and can also be generalized to other nonlinear systems.

Cao, L. S.; Qi, D. X.; Peng, R. W.; Wang, Mu; Schmelcher, P.

2014-02-01

410

Frequency doubled, cavity dumped feedback laser  

NASA Technical Reports Server (NTRS)

Higher efficiency in cavity dumping and frequency doubling in a laser used to produce modulated output beam pulses is achieved by deflecting light out of the resonant cavity to a third mirror through a frequency doubler using an electro-optic modulator and a polarizing beamsplitter in the resonant cavity, or using just an acousto-optic modulator to deflect light out of the laser cavity in response to a control signal (electric or acoustic). The frequency doubler in front of the third mirror rotates the frequency doubled light so that it will pass out of the laser cavity through the polarizing beamsplitter, while undoubled frequency light is reflected by the polarizing beamsplitter back into the gain medium of the laser. In the case of using a type-II frequency doubler, a dichroic beamsplitter deflects out the frequency doubled light and passes the undoubled frequency light to the polarizing beamsplitter for return to the laser gain medium. If an acousto-optic modulator is used, it deflects light out of the primary laser cavity, so a polarizing beamsplitter is not needed, and only a dichroic beamsplitter is needed to separate frequency doubled light out of the path from the third mirror.

Sipes, Jr., Donald L. (Inventor); Robinson, Deborah L. (Inventor)

1989-01-01

411

Frequency spectrum analyzer with phase-lock  

SciTech Connect

A frequency-spectrum analyzer with phase-lock for analyzing the frequency and amplitude of an input signal is comprised of a voltage controlled oscillator (VCO) which is driven by a ramp generator, and a phase error detector circuit. The phase error detector circuit measures the difference in phase between the VCO and the input signal, and drives the VCO locking it in phase momentarily with the input signal. The input signal and the output of the VCO are fed into a correlator which transfers the input signal to a frequency domain, while providing an accurate absolute amplitude measurement of each frequency component of the input signal.

Boland, T.J.

1984-02-07

412

Time-Frequency Analysis May 25, 2012  

E-print Network

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.5 The Fragility of Fourier Transform Methods Curvelets 49 6.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 6.2 Frequency-Based Curvelet Construction

Grohs, Philipp

413

47 CFR 87.195 - Frequencies.  

Code of Federal Regulations, 2013 CFR

... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

2013-10-01

414

47 CFR 87.195 - Frequencies.  

Code of Federal Regulations, 2011 CFR

... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

2011-10-01

415

47 CFR 87.195 - Frequencies.  

Code of Federal Regulations, 2014 CFR

... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

2014-10-01

416

47 CFR 87.195 - Frequencies.  

Code of Federal Regulations, 2012 CFR

... Section 87.195 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aircraft Stations Emergency Locator Transmitters § 87.195 Frequencies. (a)...

2012-10-01

417

Isomorphism and disorder in o-chlorohalobenzenes studied by NQR.  

PubMed

In this work we present experimental results that allow to characterize different solid modifications found in o-chlorohalobenzenes. Three disordered phases have been found in o-chlorobromobenzene. The stable phase at high temperature (phase I) is also obtained by quenching the sample at 77 K. Slow cooling allow to obtain the low temperature phase III which, on heating, transforms to phase II at 183 K and this, in turns, transforms to phase I at T~210 K. The disorder evidenced through the Nuclear Quadrupole Resonance spectra, is attributed to a random occupation of chlorine and bromine sites. In all phases there is evidence of molecular reorientations out of the benzene ring plane around the pseudo-symmetry axis between the atoms of Cl and Br. In o-chlorofluorobenzene two phases have been found depending on the cooling rate. One phase is disordered due to the random exchange of the occupation of Cl and F sites. In this case, there is also evidence of molecular reorientations out of the benzene ring plane, but in this case the reorientation is around the pseudo-symmetry axis that pass through the C-Cl bonds. Comparisons with the behavior of o-dichlorobenzene are also made. PMID:24440588

Pérez, Silvina C; Wolfenson, Alberto; Zuriaga, Mariano

2014-01-01

418

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

2011-10-01

419

47 CFR 2.1055 - Measurements required: Frequency stability.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Measurements required: Frequency stability. 2.1055 Section 2...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS... § 2.1055 Measurements required: Frequency stability. (a) The frequency...

2011-10-01

420

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

2010-10-01

421

47 CFR 76.1804 - Aeronautical frequencies: leakage monitoring (CLI).  

Code of Federal Regulations, 2014 CFR

...2014-10-01 false Aeronautical frequencies: leakage monitoring (CLI). 76...Filings § 76.1804 Aeronautical frequencies: leakage monitoring (CLI). ...cable distribution system on any new frequency or frequencies in the aeronautical...

2014-10-01

422

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

2012-10-01

423

47 CFR 2.1055 - Measurements required: Frequency stability.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Measurements required: Frequency stability. 2.1055 Section 2...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS... § 2.1055 Measurements required: Frequency stability. (a) The frequency...

2013-10-01

424

47 CFR 2.1055 - Measurements required: Frequency stability.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Measurements required: Frequency stability. 2.1055 Section 2...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS... § 2.1055 Measurements required: Frequency stability. (a) The frequency...

2012-10-01

425

47 CFR 2.1055 - Measurements required: Frequency stability.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 false Measurements required: Frequency stability. 2.1055 Section 2...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS... § 2.1055 Measurements required: Frequency stability. (a) The frequency...

2014-10-01

426

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

2013-10-01

427

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Frequency and wavelength bands. 2.101 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and...

2014-10-01

428

47 CFR 80.377 - Frequencies for ship earth stations.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

2014-10-01

429

47 CFR 80.377 - Frequencies for ship earth stations.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

2011-10-01

430

47 CFR 80.377 - Frequencies for ship earth stations.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

2013-10-01

431

47 CFR 80.377 - Frequencies for ship earth stations.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

2012-10-01

432

47 CFR 80.377 - Frequencies for ship earth stations.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Frequencies for ship earth stations. 80.377 Section 80.377 ...THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency band...

2010-10-01

433

A precision millimeter-wave measurement of the Rydberg frequency  

E-print Network

The Rydberg frequency, cR[infinity], sets the frequency scale for the spectrum of hydrogen atoms. From a frequency measurement of one transition in hydrogen, cR[infinity] can be extracted and the frequency of any other ...

De Vries, Joel Christopher, 1971-

2001-01-01

434

Gradual adaptation to auditory frequency mismatch.  

PubMed

What is the best way to help humans adapt to a distorted sensory input? Interest in this question is more than academic. The answer may help facilitate auditory learning by people who became deaf after learning language and later received a cochlear implant (a neural prosthesis that restores hearing through direct electrical stimulation of the auditory nerve). There is evidence that some cochlear implants (which provide information that is spectrally degraded to begin with) stimulate neurons with higher characteristic frequency than the acoustic frequency of the original stimulus. In other words, the stimulus is shifted in frequency with respect to what the listener expects to hear. This frequency misalignment may have a negative influence on speech perception by CI users. However, a perfect frequency-place alignment may result in the loss of important low frequency speech information. A trade-off may involve a gradual approach: start with correct frequency-place alignment to allow listeners to adapt to the spectrally degraded signal first, and then gradually increase the frequency shift to allow them to adapt to it over time. We used an acoustic model of a cochlear implant to measure adaptation to a frequency-shifted signal, using either the gradual approach or the "standard" approach (sudden imposition of the frequency shift). Listeners in both groups showed substantial auditory learning, as measured by increases in speech perception scores over the course of fifteen one-hour training sessions. However, the learning process was faster for listeners who were exposed to the gradual approach. These results suggest that gradual rather than sudden exposure may facilitate perceptual learning in the face of a spectrally degraded, frequency-shifted input. This article is part of a Special Issue entitled . PMID:25445816

Svirsky, Mario A; Talavage, Thomas M; Sinha, Shivank; Neuburger, Heidi; Azadpour, Mahan

2014-11-01

435

Predicting the Frequency of Senior Center Attendance.  

ERIC Educational Resources Information Center

Used data from 1984 Supplement on Aging of the National Health Interview Survey to examine frequency of senior center attendance. Estimated multinomial logistic regression model to distinguish between persons who rarely, sometimes, and frequently attend. Found that more frequent users are older. Greater frequency was associated with lower income…

Miner, Sonia; And Others

1993-01-01

436

High frequency scattering by convex curvilinear polygons  

E-print Network

High frequency scattering by convex curvilinear polygons S. Langdon ,, M. Mokgolele and S. N therein). Much recent work has focused on reducing this cost by incorporating the high frequencyAX, UK Abstract We consider scattering of a time-harmonic acoustic incident plane wave by a sound

437

Asthma and the High Frequency Sound Environment  

Microsoft Academic Search

ASTHMA is a disturbance of the respiratory mechanism involving reversible, partial obstruction of the airway. One symptom is a raised sensitivity in human relationships. In a previous communication it has been shown that sufferers from asthma are unusually sensitive to high frequency sound waves between 10 and 30 kHz1. In this communication, an investigation of the high frequency sound environment

R. K. Mason

1968-01-01

438

High Frequency Sound Radiation from a Diaphragm  

Microsoft Academic Search

Calculation of the intensity of the high frequency sound radiation from a circular oscillator.-By a hydrodynamical-acoustical method a calculation is made of the intensity of the high frequency sound radiation from a circular piston-like oscillator at a distance from the oscillator greater than 2a, where a is the radius. It is shown that there is no parallel \\

R. B. Lindsay

1928-01-01

439

High frequency scattering by convex curvilinear polygons  

E-print Network

High frequency scattering by convex curvilinear polygons S. Langdon , M. Mokgolele and S. N has focused on reducing this cost by incorporating the high frequency asymptotics of the solutionAX, UK Abstract We consider scattering of a time-harmonic acoustic incident plane wave by a sound

Langdon, Stephen

440

Minimum Separation of Line Spectral Frequencies  

Microsoft Academic Search

We provide a theoretical lower limit on the distance of line spectral frequencies for both the line spectrum pair decomposition and the immittance spectrum pair decomposition. The result applies to line spectral frequencies computed from linear predictive polynomials with all roots within a zero-centered circle of radius r<1

Tom Bäckström; Carlo Magi; Paavo Alku

2007-01-01

441

Lightning protection devices for high frequencies equipments  

SciTech Connect

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

Pierre, J.

1983-01-01

442

Amplitude Frequency Response Measurement: A Simple Technique  

ERIC Educational Resources Information Center

A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…

Satish, L.; Vora, S. C.

2010-01-01

443

HIGH FREQUENCY WAVES NEAR CUSP CAUSTICS  

E-print Network

HIGH FREQUENCY WAVES NEAR CUSP CAUSTICS E. Kalligiannaki 2;1 , Th. Katsaounis 3;1 & G.N. Makrakis 1 caustics. However, uniform expansions exist which are valid near and on the caustics, and reduce­Ludwig technique for computing high­frequency fields near cusp caustics. We compare these fields, with those

Katsaounis, Theodoros D.

444

Frequency response corrections for eddy correlation systems  

Microsoft Academic Search

Simplified expressions describing the frequency response of eddy correlation systems due to sensor response, path-length averaging, sensor separation and signal processing are presented. A routine procedure for estimating and correcting for the frequency response loss in flux and variance measurements is discussed and illustrated by application to the Institute of Hydrology's ‘Hydra’ eddy correlation system.

C. J. Moore

1986-01-01

445

Gravitational Bending of Light with Frequency Shifts  

E-print Network

Non-static gravitational fields generally introduce frequency shifts when bending light. In this paper, I discuss the frequency shifts induced in the bending of light by moving masses. As examples, I treat the recently discovered high-velocity pulsar PSR 2224+65 and a typical Einstein ring.

P. D. Morley

1993-11-15

446

Frequency doubled, cavity dumped feedback laser  

SciTech Connect

This patent describes an apparatus for efficient frequency doubling while cavity dumping a pumped laser in a resonator cavity in order to produce modulated output light pulses. The apparatus consists of: a laser having a pumped gain medium in the resonator cavity for emitting light at a first frequency on a fixed axis between two mirrors, modulating means placed between one of the two mirrors and the gain medium for deflecting light in the resonant cavity along a path at a fixed angle with respect to the fixed axis between the two mirrors in response to a cavity-dumping control signal, a third mirror placed to receive resonant cavity light deflected by the modulating means, and to redirect it back on the same path, frequency doubling means placed in the deflected light path between the modulating means and the third mirror, and beamsplitting means placed between the frequency doubling means and the modulating means for separating out frequency doubled light as a modulated output pulse, and passing undoubled frequency light through the modulating means and the gain medium, whereby light in the resonator cavity between the two mirrors experiences cavity dumping and frequency doubling while transmitting a modulated pulse of light reflected from the third mirror and redirection of undoubled frequency light into the resonator cavity while transmitting the modulated pulse of light for greater efficiency.

Sipes, D.L. Jr.; Robinson, D.L.

1989-06-20

447

Slender beams vibrations: Frequency jumps at buckling  

E-print Network

Slender beams vibrations: Frequency jumps at buckling S. Neukirch, J. Frelat, C. Maurini d controlled force vibrations slender elastic beam in the plane Influence of F, D on the frequencies ? #12.10 0.12 0.14 8 #12;Kirchhoff equations apply to : - slender bodies - not too bent 9 short review #12;F

Neukirch, Sébastien

448

2014 Amplifier -1 FREQUENCY RESPONSE OF  

E-print Network

2014 Amplifier - 1 FREQUENCY RESPONSE OF AN AUDIO AMPLIFIER The objectives of this experiment are amplifier · To thoroughly bore you APPARATUS: Audio Amplifier (Circuit Chip), Computer with FFTScope software, Speaker, Power supply, Interconnecting Cables good high fidelity amplifier will have frequency

Glashausser, Charles

449

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2014 CFR

...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

2014-10-01

450

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

2011-10-01

451

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

2012-10-01

452

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

2010-10-01

453

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2013 CFR

...frequency band is shared with stations in the earth-exploration satellite service. ...is shared with space stations (space to earth) in the fixed-satellite service...5) This frequency band is shared with earth stations (earth to space) in the...

2013-10-01

454

Electronic power generators for ultrasonic frequencies  

NASA Technical Reports Server (NTRS)

The design and construction of an ultrasonic frequency electronic power generator are discussed. The principle design elements of the generator are illustrated. The generator provides an inductive load with an output power of two kilowatts and a variable output frequency in the fifteen to thirty KiloHertz range. The method of conducting the tests and the results obtained with selected materials are analyzed.

Ciovica, D.

1974-01-01

455

New high-frequency weldable polyolefin films.  

PubMed

There is an increasing desire for plastic films that can be sealed using high-frequency energy. Tests on new high-frequency polyolefin film structures are reported, which compare them with the characteristics and performance of poly(vinyl chloride), ethylene-vinyl acetate and thermoplastic polyurethane films. PMID:11010316

Kelch, R

2000-05-01

456

LOFAR, a new low frequency radio telescope  

Microsoft Academic Search

LOFAR, the Low Frequency Array, is a large radio telescope consisting of approximately 100 soccer-field sized antenna stations spread over a region of 400 km in diameter. It will operate at frequencies from ?10 to 240 MHz, with a resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will allow for studies of a broad range of

Huub Röttgering

2003-01-01

457

Encoding frequency contrast in primate auditory cortex.  

PubMed

Changes in amplitude and frequency jointly determine much of the communicative significance of complex acoustic signals, including human speech. We have previously described responses of neurons in the core auditory cortex of awake rhesus macaques to sinusoidal amplitude modulation (SAM) signals. Here we report a complementary study of sinusoidal frequency modulation (SFM) in the same neurons. Responses to SFM were analogous to SAM responses in that changes in multiple parameters defining SFM stimuli (e.g., modulation frequency, modulation depth, carrier frequency) were robustly encoded in the temporal dynamics of the spike trains. For example, changes in the carrier frequency produced highly reproducible changes in shapes of the modulation period histogram, consistent with the notion that the instantaneous probability of discharge mirrors the moment-by-moment spectrum at low modulation rates. The upper limit for phase locking was similar across SAM and SFM within neurons, suggesting shared biophysical constraints on temporal processing. Using spike train classification methods, we found that neural thresholds for modulation depth discrimination are typically far lower than would be predicted from frequency tuning to static tones. This "dynamic hyperacuity" suggests a substantial central enhancement of the neural representation of frequency changes relative to the auditory periphery. Spike timing information was superior to average rate information when discriminating among SFM signals, and even when discriminating among static tones varying in frequency. This finding held even when differences in total spike count across stimuli were normalized, indicating both the primacy and generality of temporal response dynamics in cortical auditory processing. PMID:24598525

Malone, Brian J; Scott, Brian H; Semple, Malcolm N

2014-06-01

458

High frequency radar astronomy with HAARP  

Microsoft Academic Search

At high frequency, radio waves will interact with space plasmas and surfaces of local astronomical objects, producing an echo that can provide new diagnostic data. The availability at high power radars operating at high frequencies opens a window for the remote investigation of our surrounding space environment. We discuss and illustrate this technique with some specific examples.

Paul Rodriguez; Edward Kennedy; Paul Kossey

2003-01-01

459

Robust frequency and timing synchronization for OFDM  

Microsoft Academic Search

A rapid synchronization method is presented for an orthogonal frequency-division multiplexing (OFDM) system using either a continuous transmission or a burst operation over a frequency-selective channel. The presence of a signal can be detected upon the receipt of just one training sequence of two symbols. The start of the frame and the beginning of the symbol can be found, and

Timothy M. Schmidl; Donald C. Cox

1997-01-01

460

A frequency comb in the extreme ultraviolet  

Microsoft Academic Search

Since 1998, the interaction of precision spectroscopy and ultrafast laser science has led to several notable accomplishments. Femtosecond laser optical frequency `combs' (evenly spaced spectral lines) have revolutionized the measurement of optical frequencies and enabled optical atomic clocks. The same comb techniques have been used to control the waveform of ultrafast laser pulses, which permitted the generation of single attosecond

Christoph Gohle; Thomas Udem; Maximilian Herrmann; Jens Rauschenberger; Ronald Holzwarth; Hans A. Schuessler; Ferenc Krausz; Theodor W. Hänsch

2005-01-01

461

Fundamental frequency from classical molecular dynamics.  

PubMed

We give a theoretical validation for calculating fundamental frequencies of a molecule from classical molecular dynamics (MD) when its anharmonicity is small enough to be treated by perturbation theory. We specifically give concrete answers to the following questions: (1) What is the appropriate initial condition of classical MD to calculate the fundamental frequency? (2) From that condition, how accurately can we extract fundamental frequencies of a molecule? (3) What is the benefit of using ab initio MD for frequency calculations? Our analytical approaches to those questions are classical and quantum normal form theories. As numerical examples we perform two types of MD to calculate fundamental frequencies of H2O with MP2/aug-cc-pVTZ: one is based on the quartic force field and the other one is direct ab initio MD, where the potential energies and the gradients are calculated on the fly. From those calculations, we show comparisons of the frequencies from MD with the post vibrational self-consistent field calculations, second- and fourth-order perturbation theories, and experiments. We also apply direct ab initio MD to frequency calculations of C-H vibrational modes of tetracene and naphthalene. We conclude that MD can give the same accuracy in fundamental frequency calculation as second-order perturbation theory but the computational cost is lower for large molecules. PMID:25519091

Yamada, Tomonori; Aida, Misako

2015-02-01

462

A flexible dual frequency testbed for RFID  

Microsoft Academic Search

This paper presents the setup of a testbed developed for the fast evaluation of RFID systems in two frequency domains. At the one hand the 13.56 MHz and at the other hand the 868 MHz frequency domain are supported. The suggested design flow for configuring the testbed is highly automated and supports rapid evaluations of different designs and im- plementations

Christoph Angerer; Martin Holzer; Bastian Knerr; Markus Rupp

2008-01-01

463

Hydrogen masers with cavity frequency switching servos  

NASA Technical Reports Server (NTRS)

The stability of the free-running hydrogen maser is limited by pulling of the unperturbed hydrogen transition frequency due to instability of the cavity resonance frequency. While automatic spin-exchange tuning is in principle the more basic and accurate method, the required beam intensity switching and the long servo time constant result in reduced stability for measuring intervals up to 10(exp 6) seconds. More importantly, the spin-exchange tuning method requires a second stable frequency source as a reference, ideally a second hydrogen maser, to get the best results. The cavity frequency switching servo, on the other hand, has very little effect on the maser short term stability, and is fast enough to correct for cavity drift while maintaining the cavity at the spin-exchange tuned offset required to minimize instability due to beam intensity fluctuations. Not only does the cavity frequency switching servo not require a second stable frequency source, but the frequency reference is the atomic hydrogen radiated beam signal, so that no extra RF connections need be made to the cavity, and externally generated signals that would perturb the hydrogen atom need not be transmitted through the cavity. The operation of the cavity frequency switching stabilization method is discussed and the transient response of the servo and certain other aspects of the technique that have potential for achieving improved basic accuracy are illustrated.

Peters, Harry E.; Owings, H. B.; Koppang, Paul A.

1990-01-01

464

Status of Galileo Frequency and Signal Design  

Microsoft Academic Search

The paper presents the status of the Galileo frequency and signal structure, status Sept. 2002. The Galileo carrier frequency, modulation scheme and data rate of all 10 navigation signals are described as well as parameters of the search and rescue service. The navigation signals will support services addressed to three different types of users. The signal performance in terms of

Guenter W. Hein; Jeremie Godet; Jean-Luc Issler; Jean-Christophe Martin; Philippe Erhard; Rafael Lucas-Rodriguez; Tony Pratt

465

Mel Frequency Cepstral Coefficients for Music Modeling  

Microsoft Academic Search

We examine in some detail Mel Frequency Cepstral Coefficients (MFCCs) - the dominant features used for speech recognition - and investigate their applicability to modeling music. In particular, we examine two of the main assumptions of the process of forming MFCCs: the use of the Mel frequency scale to model the spectra; and the use of the Discrete Cosine Transform

Beth Logan

2000-01-01

466

Radio Frequency Fragment Separator at NSCL  

Microsoft Academic Search

A new device has been designed and built at NSCL which provides additional filtering of radioactive beams produced via projectile fragmentation. The Radio Frequency Fragment Separator (RFFS) uses the time micro structure of the beams accelerated by the cyclotrons to deflect particles according to their time-of-flight, in effect producing a phase filtering. The transverse RF (Radio Frequency) electric field of

D. Bazin; V. Andreev; A. Becerril; M. Doléans; P. F. Mantica; J. Ottarson; H. Schatz; J. B. Stoker; J. Vincent

2009-01-01

467

An active square loop frequency selective surface  

Microsoft Academic Search

An active frequency selective surface incorporating PIN diodes as switches is discussed. Waveguide simulation studies show that the frequency response of the surface can be electronically switched from that of a reflecting structure to a transmitting structure. A semi-empirical model based on a series-connected LC equivalent circuit approach gives agreement with measurements

T. K. Chang; R. J. Langley; E. Parker

1993-01-01

468

Microresonator-Based Optical Frequency Combs  

E-print Network

measure- ment (10), remote sensing, optical waveform (11) and microwave signal synthesis (12), and astro-locked lasers (1, 16). The frequency do- main spectrum of the output of a mode-locked laser constitutes an optical frequency comb. The comb arises from the periodic train of pulses emitted from such a laser (Fig

469

Flood Frequency Analysis of the Waimakariri River  

E-print Network

Flood Frequency Analysis of the Waimakariri River Robert Ware1 and Frank Lad2 Abstract Different approaches to flood frequency analysis are investigated, with par- ticular emphasis on estimating extreme hydrological events for a site, or group of sites. Frequentist approaches to flood estimation are examined. At

Reale, Marco

470

Climatic controls on the flood frequency distribution  

E-print Network

Climatic controls on the flood frequency distribution V. IACOBELLIS a , P. CLAPS b & M. FIORENTINO@unibas.it ABSTRACT Statistical models for flood frequency analysis present refined estimation and validation techniques but do not provide ultimate solutions to when regional analyses are required. More than

Poggi, Davide

471

Multi-dimensional ultra-high frequency passive radio frequency identification tag antenna designs  

E-print Network

In this thesis, we present the design, simulation, and empirical evaluation of two novel multi-dimensional ultra-high frequency (UHF) passive radio frequency identification (RFID) tag antennas, the Albano-Dipole antenna ...

Delichatsios, Stefanie Alkistis

2006-01-01

472

1 Pitch, Frequency, Musical Scales 1 1.1 Pitch and Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  

E-print Network

Contents ix 1 Pitch, Frequency, Musical Scales 1 1.1 Pitch and Frequency.2 Overtones, Pitch Equivalence, and Musical Scales . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2.1 Pitch Equivalence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1

Walker, James S.

473

Burst-by-burst laser frequency monitor  

NASA Technical Reports Server (NTRS)

The invention is a system for real-time frequency monitoring and display of an RF burst where the burst frequency is analyzed and displayed on a burst-by-burst basis in order to allow for frequency control. Although the invention was made for monitoring the laser frequency of a LIDAR system, it has other applications where realtime monitoring is required. The novelty of the invention resides in the use of a counter that is reset at the beginning of each unit time of monitoring and then gated for a unit of time. The invention also has an LED bar graph for displaying the measure of frequency at the end of each unit time in either a bar length mode or a moving dot mode. In the latter mode, the operator makes necessary adjustments to maintain the dot at the center of the bar graph.

Esproles, Carlos (inventor)

1994-01-01

474

High frequency characterization of graphene nanoribbon interconnects  

NASA Astrophysics Data System (ADS)

Interconnects and nanoscale transmission lines are critical components in the design of nanoelectronic systems. In this letter, we study the high frequency characteristics of chemical vapor deposition (CVD) graphene nanoribbon (GNR) interconnects and radio frequency propagation in GNRs embedded in a coplanar waveguide structure up to 20 GHz. An equivalent transmission line model is proposed to characterize the GNRs in high frequency regime. The strong agreement between fitting circuit parameters and measured data suggests that our model can be used in the design of nanoscale circuits in which GNRs are used to interconnect elements in the circuits. The fabricated GNRs show fairly constant characteristic impedance at high frequencies which could be useful for radio frequency interconnect applications. Our study provides an insight into microwave behavior of GNRs for developing high speed graphene devices.

Nguyen, Phuong Duc; Cong Nguyen, Thanh; Trong Huynh, Anh; Skafidas, Efstratios

2014-09-01

475

High frequency oscillations in brain hemodynamic response  

NASA Astrophysics Data System (ADS)

Tight autoregulation of vessel tone guarantees proper delivery of nutrients to the tissues. This regulation is maintained at a more delicate level in the brain since any decrease in the supply of glucose and oxygen to neuronal tissues might lead to unrecoverable injury. Functional near infrared spectroscopy has been proposed as a new tool to monitor the cerebrovascular response during cognitive activity. We have observed that during a Stroop task three distinct oscillatory patterns govern the control of the cerebrovascular reactivity: very low frequency (0.02-0.05 Hz), low frequency (0.08-0.12 Hz) and high frequency (0.12-0.18 Hz). High frequency oscillations have been shown to be related to stress level of the subjects. Our findings indicate that as the stress level is increased so does the energy of the high frequency component indicating a higher stimulation from the autonomic nervous system.

Akin, Ata; Bolay, Hayrunnisa

2007-07-01

476

Waveform Selectivity at the Same Frequency  

E-print Network

Electromagnetic properties depend on the composition of materials, i.e. either angstrom scales of molecules or, for metamaterials, subwavelength periodic structures. Each material behaves differently in accordance with the frequency of an incoming electromagnetic wave due to the frequency dispersion or the resonance of the periodic structures. This indicates that if the frequency is fixed, the material always responds in the same manner unless it has nonlinearity. However, such nonlinearity is controlled by the magnitude of the incoming wave or other bias. Therefore, it is difficult to distinguish different incoming waves at the same frequency. Here we present a new concept of circuit-based metasurfaces to selectively absorb or transmit specific types of waveforms even at the same frequency. The metasurfaces, integrated with schottky diodes as well as either capacitors or inductors, selectively absorb short or long pulses, respectively. The two types of the circuit elements are then combined to absorb or tran...

Wakatsuchi, Hiroki; Rushton, Jeremiah J; Gao, Fei; Kim, Sanghoon; Sievenpiper, Daniel F

2014-01-01

477

Detection and recognition of radial frequency patterns.  

PubMed

Detection thresholds for radial deformations of circular contours were measured using a range of radii and contour peak spatial frequencies. For radial frequencies above two cycles, thresholds were found to be a constant fraction of the mean radius across a four-octave range of pattern radii and peak spatial frequencies (mean Weber fraction: 0.003-0.004). At low radial frequencies, thresholds were unaffected by contrast reduction. In 167 ms presentations, subjects were able to identify radial frequencies of six cycles and below with an accuracy of over 90% correct even when phase was randomized. The extreme sensitivity of subjects to these radial deformations (as low as 2-4 s of arc) cannot be explained by local orientation or curvature analysis, and points instead to the global pooling of contour information at intermediate levels of form vision. PMID:9893789

Wilkinson, F; Wilson, H R; Habak, C

1998-11-01

478

Turbulence in unsteady flow at high frequencies  

NASA Technical Reports Server (NTRS)

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.

Kuhn, Gary D.

1990-01-01

479

Digitally enhanced optical fiber frequency reference.  

PubMed

We use digitally enhanced heterodyne interferometry to measure the stability of optical fiber laser frequency references. Suppression of laser frequency noise by over four orders of magnitude is achieved using post processing time delay interferometry, allowing us to measure the mechanical stability for frequencies as low as 100 ?Hz. The performance of the digitally enhanced heterodyne interferometer platform used here is not practically limited by the dynamic range or bandwidth issues that can occur in feedback stabilization systems. This allows longer measurement times, better frequency discrimination, a reduction in spatially uncorrelated noise sources and an increase in interferometer sensitivity. An optical fiber frequency reference with the stability reported here, over a signal band of 20 mHz-1 Hz, has potential for use in demanding environments, such as space-based interferometry missions and optical flywheel applications. PMID:24686596

McRae, Terry G; Ngo, Silvie; Shaddock, Daniel A; Hsu, Magnus T L; Gray, Malcolm B

2014-04-01

480

Low frequency signal in the GOLF measurements  

NASA Astrophysics Data System (ADS)

This paper shows the results obtained using a revisited method to normalize the velocity evaluation extracted from the measurements, for roughly 14 years of GOLF data. For the search of g modes, we calculate the low frequency power spectrum of the signal with 2 different approaches: • The classical calculation of the power spectrum of the velocity signal. • An alternative calculation, extracting first the variations along the time of the p-mode frequencies, then calculating the power spectrum of those frequency modulation [4]. Both spectra are compared to the g-mode frequency spectrum calculated for a solar model. Several observed frequencies are in close agreement with the calculated g modes. A careful statistical analysis of this result should now follow.

Grec, G.; Provost, J.; Renaud, C.

2011-01-01

481

Time-frequency transforms: a new approach to first heart sound frequency dynamics  

Microsoft Academic Search

The binomial joint time-frequency transform is used to test the hypothesis that first heart sound frequency rises during the isovolumic contraction period. Cardiac vibrations were recorded from eight open-chest dogs using an ultralight accelerometer cemented directly to the epicardium of the anterior left ventricle. Three characteristic time-frequency spectral patterns were evident in the animals investigated: (1) a frequency component that

John C. Wood; Andrew J. Buda; Daniel T. Barry

1992-01-01

482

Embedded controlled low-frequency AC to high-frequency AC converter fed induction heater  

Microsoft Academic Search

Purpose – The purpose of this paper is to present, a novel boost-active clamp bridge single stage high-frequency zero voltage soft-switching-pulse width modulation (ZVS-PWM) inverter, which converts the utility frequency AC power into high-frequency AC power with an embedded controller. This single stage high-frequency inverter is composed of a single-phase diode bridge rectifier, a non-smoothing filter, a boost-active clamp bridge

Kirubakaran Dhandapani; Rama Reddy Sathi

2011-01-01

483

Frequency Stabilization of X-Band Sources for Use in Frequency Synthesis into the Infrared  

Microsoft Academic Search

An X-band source of excellent frequency stability is needed in infrared frequency multiplication of high order. Such a source has been used in frequency multiplication by a factor of 401 using a point-contact Josephson junction as a frequency multiplier and mixer. Noise data on three X-band systems are reported. Two of these systems use klystrons as the source of X-band

Allan S. Risley; John H. Shoaf; J. Robert Ashley

1974-01-01

484

Frequency Stabilization of X-Band Sources For Use in Frequency Synthesis into the Infrared  

Microsoft Academic Search

Abstract-An X-band source of excellent frequency stability is needed in infrared frequency multiplication of high order. Such a source has been used in frequency multiplication by a factor of 401 using a point-contact Josephson junction as a frequency multiplier and mixer. Noise data on three X-band systems are reported. Two of these systems use klystrons as the source of X-band

JOHN H. SHOAF; ROBERT ASHLEY

1974-01-01

485

Relationship between wingbeat frequency and resonant frequency of the wing in insects.  

PubMed

In this study, we experimentally studied the relationship between wingbeat frequency and resonant frequency of 30 individuals of eight insect species from five orders: Odonata (Sympetrum flaveolum), Lepidoptera (Pieris rapae, Plusia gamma and Ochlodes), Hymenoptera (Xylocopa pubescens and Bombus rupestric), Hemiptera (Tibicen linnei) and Coleoptera (Allomyrina dichotoma). The wingbeat frequency of free-flying insects was measured using a high-speed camera while the natural frequency was determined using a laser displacement sensor along with a Bruel and Kjaer fast Fourier transform analyzer based on the base excitation method. The results showed that the wingbeat frequency was related to body mass (m) and forewing area (Af), following the proportionality f ~ m(1/2)/Af, while the natural frequency was significantly correlated with area density (f0 ~ mw/Af, mw is the wing mass). In addition, from the comparison of wingbeat frequency to natural frequency, the ratio between wingbeat frequency and natural frequency was found to be, in general, between 0.13 and 0.67 for the insects flapping at a lower wingbeat frequency (less than 100 Hz) and higher than 1.22 for the insects flapping at a higher wingbeat frequency (higher than 100 Hz). These results suggest that wingbeat frequency does not have a strong relation with resonance frequency: in other words, insects have not been evolved sufficiently to flap at their wings' structural resonant frequency. This contradicts the general conclusion of other reports--that insects flap at their wings' resonant frequency to take advantage of passive deformation to save energy. PMID:24166827

Ha, Ngoc San; Truong, Quang Tri; Goo, Nam Seo; Park, Hoon Cheol

2013-12-01

486

Frequency estimation method for measuring time-varying single frequency from digitized waveform  

Microsoft Academic Search

A frequency estimation method (ZFM: zero-crossing fitting method) for measuring time-varying single frequency is applied to determine the velocity of the mass for a space scale. The difference between the ZFM and conventional zero-crossing method used in typical electric frequency counters is discussed. The velocity derived from estimated Doppler frequency is evaluated with considerably lower level of noise using the

Koichi Maru; Yusaku Fujii; Jan Peter Hessling; Kazuhito Shimada

2009-01-01

487

High-frequency drive-power and frequency control for ultrasonic transducer operating at 3 MHz  

Microsoft Academic Search

This paper describes RF drive-power and frequency control for the ultrasonic cleaning system operating at a frequency of 3 MHz. The RF output power is maximized by the automatic frequency tuning of the PLL built in the full-bridge MOSFET DC-to-RF power inverter to the series resonating frequency of the ultrasonic transducer operating at 3 MHz. In addition, the full-bridge DC

Jun-ichi Ishikawa; Yoko Mizutani; Taiju Suzuki; Hiroaki Ikeda; Hirofumi Yoshida

1997-01-01

488

The frequency of planets in multiple systems  

E-print Network

The frequency of planets in binaries is an important issue in the field of extrasolar planet studies, because of its relevance in estimating of the global planet population of our Galaxy and the clues it can give to our understanding of planet formation and evolution. However, only preliminary estimates are available in the literature. We analyze and compare the frequency of planets in multiple systems to the frequency of planets orbiting single stars. We also try to highlight possible connections between the frequency of planets and the orbital parameters of the binaries (such as the periastron and mass ratio.) A literature search was performed for binaries and multiple systems among the stars of the sample with uniform planet detectability defined by Fischer & Valenti (2005), and 202 of the 850 stars of the sample turned out to be binaries, allowing a statistical comparison of the frequency of planets in binaries and single stars and a study of the run of the planet frequency as a function of the binary separation. We found that the global frequency of planets in the binaries of the sample is not statistically different from that of planets in single stars. Even conservatively taking the probable incompleteness of binary detection in our sample into account, we estimate that the frequency of planets in binaries can be no more than a factor of three lower than that of planets in single stars. There is no significant dependence of planet frequency on the binary separation, except for a lower value of frequency for close binaries. However, this is probably not as low as required to explain the presence of planets in close binaries only as the result of modifications of the binary orbit after the planet formation.

M. Bonavita; S. Desidera

2007-03-29

489

Beyond Phonotactic Frequency: Presentation Frequency Effects Word Productions in Specific Language Impairment  

ERIC Educational Resources Information Center

Phonotactic frequency effects on word production are thought to reflect accumulated experience with a language. Here we demonstrate that frequency effects can also be obtained through short-term manipulations of the input to children. We presented children with nonwords in an experiment that systematically manipulated English phonotactic frequency…

Plante, Elena; Bahl, Megha; Vance, Rebecca; Gerken, LouAnn

2011-01-01

490

Estimating minimum allele frequencies for DNA profile frequency estimates for PCR-based loci  

Microsoft Academic Search

In order that there can be confidence that DNA profile frequency estimates will not place undue bias against a defendant, 2 methods are described for estimating minimum allele frequency bounds for PCR-based loci. One approach estimates minimum allele frequencies for VNTR and STR loci using sample size and the observed heterozygosity at a locus, while the second approach, appropriate for

B. Budowle; K. L. Monson; R. Chakraborty

1996-01-01

491

THE COMPARISON OF SINGLE FREQUENCY AND DUAL FREQUENCY GPS FOR BRIDGE DEFLECTION AND VIBRATION MONITORING  

Microsoft Academic Search

The use of dual frequency code\\/carrier phase GPS data has been shown to be a feasible tool for bridge deflection monitoring. This is due to the quick On The Fly integer ambiguity resolution that is possible through using the dual frequency data in order to create the wide lane observable. The applications of OTF dual frequency data are numerous, whereby

Emily Cosser; Gethin W Roberts; Xiaolin Meng; Alan H Dodson

2003-01-01

492

Digital slip frequency generator and method for determining the desired slip frequency  

DOEpatents

The output frequency of an electric power generator is kept constant with variable rotor speed by automatic adjustment of the excitation slip frequency. The invention features a digital slip frequency generator which provides sine and cosine waveforms from a look-up table, which are combined with real and reactive power output of the power generator.

Klein, Frederick F. (Monroeville, PA)

1989-01-01

493

Describing the Frequency of Marijuana Use: Fuzziness and Context-Dependent Interpretation of Frequency Expressions.  

ERIC Educational Resources Information Center

A fuzzy set model is offered for interpreting vague frequency expressions, such as "rarely" and "sometimes." Results with 152 undergraduates reporting marijuana use reflect different frequency expressions for the same level of use and suggest that self-report validity may be enhanced by analyzing frequency expressions as fuzzy sets. (SLD)

Matt, Georg E.; Wilson, Sandra Jo

1994-01-01

494

SCADA based under frequency load shedding integrated with rate of frequency decline  

Microsoft Academic Search

Speed and accuracy of under frequency load shedding (UFLS) has a vital role in its effectiveness for preserving system stability. In any case load-shedding still remains the ultimate resource for emergency condition. Initial rate of change of frequency is a fast and potentially useful signal to detect the overload when a disturbance happens. In order to improve the under-frequency load

M. Parniani; A. Nasri

2006-01-01

495

Frequency compensation in an adaptive antenna system for frequency-hopping communications  

Microsoft Academic Search

For the full exploitation of an adaptive antenna system for wideband frequency-hopping communicatioms, some form of frequency compensation is necessary. Parameter-dependent, spectral, and anticipative processing are the three methods of frequency compensation that are examined; their strengths, limitations, and variations are discussed. The underlying adaptive algorithm is the Maximin algorithm, which has major advantages compared with other algorithms.

Don Torrieri; Kesh Bakhru

1987-01-01

496

Phase-stabilized Prism-based Cr:forsterite Laser Frequency Comb for Absolute Frequency Measurements  

E-print Network

Phase-stabilized Prism-based Cr:forsterite Laser Frequency Comb for Absolute Frequency Measurements., Somerset NJ 08873 Abstract: A prism-based Cr:forsterite frequency comb is stabilized, with a repetition rate of 116 MHz. The flexibility of the prism-based system aids in achieving the carrier

Washburn, Brian

497

Closed-form low frequency solutions for electromagnetic waves through a frequency selective surface  

Microsoft Academic Search

A simple closed-form approximate solution is given to the problem of transmission of a low-frequency electromagnetic wave through a frequency selective surface (FSS). The FSSs considered are periodic metal plates (or their complementary apertures) sandwiched between dielectric slabs. At low frequencies, the induced currents on the metal plates may be approximated by a known function with a constant coefficient to

Gino Zarrillo; Kevin Aguiar

1987-01-01

498

164-GHz MMIC HEMT Frequency Doubler  

NASA Technical Reports Server (NTRS)

A monolithic microwave integrated circuit (MMIC) that includes a high-electron-mobility transistor (HEMT) has been developed as a prototype of improved frequency doublers for generating signals at frequencies greater than 100 GHz. Signal sources that operate in this frequency range are needed for a variety of applications, notably including general radiometry and, more specifically, radiometric remote sensing of the atmosphere. Heretofore, it has been common practice to use passive (diode-based) frequency multipliers to obtain frequencies greater than 100 GHz. Unfortunately, diode-based frequency multipliers are plagued by high DC power consumption and low conversion efficiency. Moreover, multiplier diodes are not easily integrated with such other multiplier-circuit components as amplifiers and oscillators. The goals of developing the present MMIC HEMT frequency doubler were (1) to utilize the HEMT as an amplifier to increase conversion efficiency (more precisely, to reduce conversion loss), thereby increasing the output power for a given DC power consumption or, equivalently, reducing the DC power consumption for a given output power; and (2) to provide for the integration of amplifier and oscillator components on the same chip. The MMIC frequency doubler (see Figure 1) contains an AlInAs/GaInAs/InP HEMT biased at pinch-off to make it function as a class-B amplifier (meaning that it conducts in half-cycle pulses). Grounded coplanar waveguides (GCPWs) are used as impedance-matching transmission lines. Air bridges are placed at discontinuities to suppress undesired slot electromagnetic modes. Another combination of GCPWs also serves both as a low-pass filter to suppress undesired oscillations at frequencies below 60 GHz and as a DC blocker. Large decoupling capacitors and epitaxial resistors are added in the drain and gate lines to suppress bias oscillations. At the output terminal, the fundamental frequency is suppressed by a quarter-wave open stub, which presents a short circuit at the fundamental frequency and an open circuit at the second harmonic. At an input power of 7 mW, the output power and conversion loss at an output frequency of 164 GHz were found to be 5 dBm (approximately equal to 3.2 mW) and 2 dB, respectively, with a 3-dB output-power bandwidth of 14 GHz. This is the best performance reported to date for an MMIC HEMT frequency doubler above 100 GHz.

Samoska, Lorene; Radisic, Vesna; Micovic, Miro; Hu, Ming; Janke, Paul; Ngo, Catherine; Nguyen, Loi; Morgan, Matthew

2003-01-01

499

Frequency division using a micromechanical resonance cascade  

NASA Astrophysics Data System (ADS)

A coupled micromechanical resonator array demonstrates a mechanical realization of multi-stage frequency division. The mechanical structure consists of a set of N sequentially perpendicular microbeams that are connected by relatively weak elastic elements such that the system vibration modes are localized to individual microbeams and have natural frequencies with ratios close to 1:2:⋯:2N. Conservative (passive) nonlinear inter-modal coupling provides the required energy transfer between modes and is achieved by finite deformation kinematics. When the highest frequency beam is excited, this arrangement promotes a cascade of subharmonic resonances that achieve frequency division of 2j at microbeam j for j = 1, …, N. Results are shown for a capacitively driven three-stage divider in which an input signal of 824 kHz is passively divided through three modal stages, producing signals at 412 kHz, 206 kHz, and 103 kHz. The system modes are characterized and used to delineate the range of AC input voltages and frequencies over which the cascade occurs. This narrow band frequency divider has simple design rules that are scalable to higher frequencies and can be extended to a larger number of modal stages.

Qalandar, K. R.; Strachan, B. S.; Gibson, B.; Sharma, M.; Ma, A.; Shaw, S. W.; Turner, K. L.

2014-12-01

500

Method and apparatus for frequency spectrum analysis  

NASA Technical Reports Server (NTRS)

A method for frequency spectrum analysis of an unknown signal in real-time is discussed. The method is based upon integration of 1-bit samples of signal voltage amplitude corresponding to sine or cosine phases of a controlled center frequency clock which is changed after each integration interval to sweep the frequency range of interest in steps. Integration of samples during each interval is carried out over a number of cycles of the center frequency clock spanning a number of cycles of an input signal to be analyzed. The invention may be used to detect the frequency of at least two signals simultaneously. By using a reference signal of known frequency and voltage amplitude (added to the two signals for parallel processing in the same way, but in a different channel with a sampling at the known frequency and phases of the reference signal), the absolute voltage amplitude of the other two signals may be determined by squaring the sine and cosine integrals of each channel and summing the squares to obtain relative power measurements in all three channels and, from the known voltage amplitude of the reference signal, obtaining an absolute voltage measurement for the other two signals by multiplying the known voltage of the reference signal with the ratio of the relative power of each of the other two signals to the relative power of the reference signal.

Cole, Steven W. (inventor)

1992-01-01