Note: This page contains sample records for the topic 35cl nqr frequency from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Isotope effect on the temperature dependence of the 35Cl NQR frequency in (NH4)2RuCl6  

NASA Astrophysics Data System (ADS)

35Cl NQR of (NH4)2RuCl6, (ND4)2RuCl6, (NH4)2SnCl6, and (ND4)2SnCl6 was measured.Isotope effect on the spatial distribution of hydrogen atoms is discussed.Tunneling splittings of torsional ground state of ammonium ions were estimated.Origin of T1Q anomaly previously reported in (NH4)2SnCl6 and (ND4)2SnCl6 was revealed.

Kume, Yoshio; Amino, Daiki; Asaji, Tetsuo

2013-07-01

2

Electronic structure and biological activity of chosen DDT-type insecticides studied by 35Cl-NQR.  

PubMed

A correlation between the electronic structure and biological activity of chosen dichlorodiphenyltrichloroethane (DDT)-type insecticides: 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane, 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene, 2,2-bis(4-chlorophenyl)ethanoic acid and 4,4'-dichlorobenzophenone (used in agriculture) has been analysed on the basis of the (35)Cl-nuclear quadrupole resonance (NQR) spectroscopy. The (35)Cl-NQR resonance frequencies measured at 77 K have been correlated with the lethal dose (LD(50)) parameter that characterises the biological activity of these insecticides. PMID:18942076

Jadzyn, Maciej; Nogaj, Boles?aw

2009-02-01

3

A Study of Transition-Metal Organometallic Complexes Combining (35) Cl Solid-State NMR Spectroscopy and (35) Cl?NQR Spectroscopy and First-Principles DFT Calculations.  

PubMed

A series of transition-metal organometallic complexes with commonly occurring metal?chlorine bonding motifs were characterized using (35) Cl solid-state NMR (SSNMR) spectroscopy, (35) Cl nuclear quadrupole resonance (NQR) spectroscopy, and first-principles density functional theory (DFT) calculations of NMR interaction tensors. Static (35) Cl ultra-wideline NMR spectra were acquired in a piecewise manner at standard (9.4?T) and high (21.1?T) magnetic field strengths using the WURST-QCPMG pulse sequence. The (35) Cl electric field gradient (EFG) and chemical shielding (CS) tensor parameters were readily extracted from analytical simulations of the spectra; in particular, the quadrupolar parameters are shown to be very sensitive to structural differences, and can easily differentiate between chlorine atoms in bridging and terminal bonding environments. (35) Cl?NQR spectra were acquired for many of the complexes, which aided in resolving structurally similar, yet crystallographically distinct and magnetically inequivalent chlorine sites, and with the interpretation and assignment of (35) Cl?SSNMR spectra. (35) Cl?EFG tensors obtained from first-principles DFT calculations are consistently in good agreement with experiment, highlighting the importance of using a combined approach of theoretical and experimental methods for structural characterization. Finally, a preliminary example of a (35) Cl?SSNMR spectrum of a transition-metal species (TiCl4 ) diluted and supported on non-porous silica is presented. The combination of (35) Cl?SSNMR and (35) Cl?NQR spectroscopy and DFT calculations is shown to be a promising and simple methodology for the characterization of all manner of chlorine-containing transition-metal complexes, in pure, impure bulk and supported forms. PMID:23907813

Johnston, Karen E; O'Keefe, Christopher A; Gauvin, Rgis M; Trbosc, Julien; Delevoye, Laurent; Amoureux, Jean-Paul; Popoff, Nicolas; Taoufik, Mostafa; Oudatchin, Konstantin; Schurko, Robert W

2013-08-01

4

Sodium and potassium salts of dichloroisocyanuric acid and their hydrates as antimicrobials agents studied by 35Cl-NQR spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

The electronic structure of dichloroisocyanuric acid derivatives was analysed by 35Cl-NQR spectroscopy and DFT calculations. Here we concentrate our attention on three different factors: type of metallic substituent (sodium and potassium), temperature of the sample (liquid nitrogen and room) and degree of hydration (an amount of water molecules attached to analysed compounds). In particular, all the variations in 35Cl-NQR frequencies upon hydration of salts containing sodium and potassium ions are explained as a consequence of H-bonds formation and accompanied effects of charge redistribution. Our studies can be useful in searching for the derivatives of dichloroisocyanuric acid revealing higher antimicrobial activity.

Walczak, A.; Brycki, B.; Kaczmarek, M.; Poleshchuk, O. Kh.; Ostafin, M.; Nogaj, B.

2006-06-01

5

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

6

Supramolecular synthon pattern in solid clioquinol and cloxiquine (APIs of antibacterial, antifungal, antiaging and antituberculosis drugs) studied by 35 Cl NQR, 1 H- 17 O and 1 H- 14 N NQDR and DFT\\/QTAIM  

Microsoft Academic Search

The quinolinol derivatives clioquinol (5-chloro-7-iodo-8-quinolinol, Quinoform) and cloxiquine (5-chloro-8-quinolinol) were\\u000a studied experimentally in the solid state via 35Cl NQR, 1H-17O and 1H-14N NQDR spectroscopies, and theoretically by density functional theory (DFT). The supramolecular synthon pattern of OHN\\u000a hydrogen bonds linking dimers and ?? stacking interactions were described within the QTAIM (quantum theory of atoms in molecules)\\u000a \\/DFT (density functional theory)

Jolanta Natalia Latosi?ska; Magdalena Latosi?ska; Marzena Agnieszka Tomczak; Janez Seliger; Veselko agar

7

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 CCl in more than 20 clathrates have been measured in the range 4-200 K. The crystal structures of CCl\\/Dianin's compound (1), CCl\\/Fe(AcAc) (3), CCl\\/Ni(SCN)(3-MePy) (4), and CCl\\/Ni(exan)(4,4-dm-2,2-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

8

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

9

Radio-frequency tunable atomic magnetometer for detection of solid-state NQR  

NASA Astrophysics Data System (ADS)

We constructed a potassium atomic magnetometer which resonantly detects rf magnetic fields with subfemtotesla sensitivity. The resonance frequency is set by the Zeeman resonance of the potassium atoms in a static magnetic field applied to the magnetometer cell. Strong optical pumping of the potassium atoms into a stretched state reduces spin-exchange broadening of the Zeeman resonance, resulting in relatively small linewidth of about 200 Hz (half-width at half-maximum). The magnetometer was used to detect ^14N NQR signal from powdered ammonium nitrate at 423 kHz, with sensitivity an order of magnitude higher than with a conventional room temperature pickup coil with comparable geometry. The demonstrated sensitivity of 0.24 fT/Hz^1/2 can be improved by several means, including use of higher power lasers for pumping and probing. Our technique can potentially be used to develop a mobile, open-access NQR spectrometer for detection of nitrogen-containing solids of interest in security applications.

Lee, S.-K.; Sauer, K. L.; Seltzer, S. J.; Alem, O.; Romalis, M. V.

2007-06-01

10

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.; agar, V.; Kazimierczuk, Z.

2009-07-01

11

Superdeformation and ?-cluster structure in 35Cl  

NASA Astrophysics Data System (ADS)

A superdeformed (SD) band has been identified in a non-?-conjugate nucleus 35Cl. It crosses the negative-parity ground band above 11/2? and becomes the yrast at 15/2?. Lifetimes of all relevant states have been measured to follow the evolution of collectivity. Enhanced B(E2), B(E1) values as well as energetics provide evidence for superdeformation and existence of parity doublet cluster structure in an odd-A nucleus in the A?40 region. Large-scale shell-model calculations assign (sd)16(pf)3 as the origin of these states. Calculated spectroscopic factors correlate the SD states in 35Cl to those in 36Ar.

Bisoi, Abhijit; Sarkar, M. Saha; Sarkar, S.; Ray, S.; Basu, M. Roy; Kanjilal, Debasmita; Nag, Somnath; Selvakumar, K.; Goswami, A.; Madhavan, N.; Muralithar, S.; Bhowmik, R. K.

2013-09-01

12

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, M. L.; Yesinowski, J. P.; Miller, J. B.; Krauss, Ronald A.

1994-10-01

13

35Cl quadrupole resonance study of the thermally activated motion of the nitro group in chlorinated nitrobenzenes  

NASA Astrophysics Data System (ADS)

The results of NQR studies of the thermoactivated motion of NO2 groups in chlorine-containing nitrobenzenes are presented. A procedure for analyzing the experimental data is suggested. It uses the characteristic temperature of the minimum of the modulation contribution to the temperature dependence of the spin-lattice relaxation time T 1 of the resonant probe nuclei (35Cl) bonded with the moving group by nonvalent interactions. The activation energy of the thermoactivated motion was correlated with the temperature of the minimum. The possibility of a temperature dependence of the activation energy of the NO2 group was examined.

Kyuntsel, I. A.

2013-05-01

14

Radio-frequency tunable atomic magnetometer for detection of solid-state NQR  

Microsoft Academic Search

We constructed a potassium atomic magnetometer which resonantly detects rf magnetic fields with subfemtotesla sensitivity. The resonance frequency is set by the Zeeman resonance of the potassium atoms in a static magnetic field applied to the magnetometer cell. Strong optical pumping of the potassium atoms into a stretched state reduces spin-exchange broadening of the Zeeman resonance, resulting in relatively small

S.-K. Lee; K. L. Sauer; S. J. Seltzer; O. Alem; M. V. Romalis

2007-01-01

15

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

16

Dynamic orientational disorder of the nitro group in 2-chloro-nitrobenzene revealed through 35 Cl nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

In the present paper we analyse the contributions of nitro group movements in 2-chloro-nitrobenzene to the nuclear quadrupole resonance (NQR) parameters of the chlorine nucleus in the molecule. We found two contributions to the spin-lattice relaxation time (T1) and the NQR frequency (?Q) due to the onset of nitro group movements in the molecule. One of these contributions is the well-known semirotation of the nitro group around the N-C axis. The other one is attributed to some tilting or tipping of the nitro plane away from the benzene ring introducing some dynamic orientational disorder of this group in the crystal only observed as a contribution from the temperature dependence of T1 and ?Q. Its activation energy is similar to that of the nitro group reorientation (21.9 and 23.6 kJ mol-1 for the two processes) and may arise from competing crystalline and steric chlorine nucleus effects. The present investigation shows that in chloronitrobenzenes the NO2 group dynamic orientational disorder can produce modulation effects on the chlorine T1 which are large enough to be observed by means of the NQR.

Brunetti, Aldo H.

2002-09-01

17

Mid-Infrared Diode Laser Spectroscopy of/X~1A' HC35Cl  

NASA Astrophysics Data System (ADS)

The observation of the C-Cl stretching fundamental of HC35Cl in its ground/X~1A' state is reported. HCCl was formed in a continuous flow system by the excimer laser photolysis of CHBr2Cl at 193 nm and the transient absorption recorded by infrared diode laser spectroscopy. The band hasa-type character and the fundamental vibrational frequency is found to be 811.5963 cm-1. No evidence was found for perturbations in either the ground or vibrationally excited states, implying that the excited tripleta~3A'' states lies above the C-Cl stretching level in HCCl. The observed rotation-vibration transitions were well fit by a standard asymmetric rotor Hamiltonian. There is a decrease in theArotational constant on vibrational excitation, suggesting that some bend-C-Cl stretch coupling is present.

Chang, Bor-Chen; Fei, Ruian; Sears, Trevor J.

1997-06-01

18

Signal processing for NQR discrimination of buried land mines  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole resonance (NQR) is a technique that discriminates mines from clutter by exploiting unique properties of explosives, rather than the attributes of the mine that exist in many forms of anthropic clutter. After exciting the explosive with a properly designed electromagnetic-induction (EMI) system, one attempts to sense late-time spin echoes, which are characterized by radiation at particular frequencies. It is this narrow-band radiation that indicates the presence of explosives, since this effect is not seen in most clutter, both natural and anthropic. However, this problem is complicated by several issues. First, the late-time radiation if often very weak, particularly for TNT, and therefore the signal-to-noise ratio must be high for extracting the NQR response. Further, the frequency at which the explosive radiates is often a strong function of the background environment, and therefore in practice the NQR radiation frequency is not known a priori. Finally, at the frequencies of interest, there is a significant amount of background radiation, which induces radio frequency interference (RFI). In this paper we discuss several signal processing tools we have developed to enhance the utility of NQR explosives detection. In particular, with regard to the RFI, we exposure least-mean-squares algorithms which have proven well suited to extracting background interference. Algorithm performance is assessed through consideration of actual measured data. With regard to the detection of the NQR electromagnetic echo, we consider a Bayesian discrimination algorithm. The performance of the Bayesian algorithm is presented, again using measured NQR data.

Tantum, Stacy L.; Collins, Leslie M.; Carin, Lawrence; Gorodnitsky, Irina; Hibbs, Andrew D.; Walsh, David O.; Barrall, Geoffrey A.; Gregory, Dave; Matthews, Robert; Vierkoetter, Stephie A.

1999-08-01

19

Semiempirical quantum mechanical calculations of electronic distribution and NQR parameters of bromine atoms in some organic and inorganic compounds  

Microsoft Academic Search

The Br electric field gradient (EFG) for some organic and inorganic compounds was calculated using a semi-empirical method. The nuclear quadrupole resonance (NQR) frequencies and asymmetry parameters of the bromine atoms in these compounds have also been evaluated. Quantitative correlation of the NQR frequencies and asymmetry parameters of the EFG of bromine nuclei with the population of p orbitals of

N. L Hadipour; S Javadian

2000-01-01

20

Quadrupole Coupling Parameters and Structural Aspects of Crystalline and Amorphous Solids by NMR and Nqr.  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole interaction is very sensitive to the local electron distribution and chemical bondings. NMR and NQR techniques have been combined to obtain the quadrupole coupling constant ({Qcc}) and asymmetry parameter (eta) and extract structural information for several borate, gallate, and metavanadate compounds and glasses. ^{71}Ga and ^{69}Ga NMR has been used to study crystalline beta-Ga _2O_3 and several gallate glasses. Quadrupole parameters were acquired for GaO_6 and GaO_4 units in beta-Ga_2 O_3 by the computer simulation of the NMR powder patterns. A sensitive CW NQR spectrometer was built to detect NQR resonances below 2 MHz. The spectrometer includes a modified Robinson oscillator-detector, a new bi-symmetric square wave Zeeman modulator and a computerized data acquisition system. ^{51}V (I = 7/2) NQR resonances below 850 kHz have been detected for several metavanadates at both room temperature and liquid nitrogen temperature. Quadrupole parameters thus obtained are an order of magnitude more accurate than values obtained by previous NMR studies. For a spin 3/2 nucleus, the pure NQR frequency {Q_{cc}over 2}sqrt{1+{eta^2over 3}}is insufficient to determine either Q_{cc} or eta. However, two methods, Zeeman perturbed NQR powder pattern and ^{10}B NQR, can be employed to obtain both Q_{cc } and eta. An example is given for ^{11}B in CaO-B_2O_3. With a double coil tank circuit design, pure ^ {11}B NQR was used to determine the fraction of borons in BO_3 and BO _4 configurations in hydrated zinc borates. ^{11}B NMR and NQR were also used to study lead borate glasses. Small changes in Q_{cc} (less than 2%) and eta (less than 0.1) suggest that BO_3 units with non-bridging oxygens are not present in the lead borate glasses.

Mao, Degen

21

Dissociation dynamics of higher-order He2I35Cl(B,v? = 3) complexes  

NASA Astrophysics Data System (ADS)

The dissociation dynamics of He2I35Cl complexes prepared with varying amounts of intermolecular vibrational excitation within the 2He + I35Cl(B,v? = 3) potential energy surface are reported. For the intermolecular level associated with one He atom in an energetically excited, delocalized state and the other localized in the lowest-energy, T-shaped potential minimum, the higher-energy He atom dissociates preferentially. The binding energy of the ground-state He2I35Cl(X,v? = 0) conformer with a police nightstick geometry (one He atom in the T-shaped minimum and the second in the linear well) is measured to be 38.6(9) cm1.

Darr, Joshua P.; Loomis, Richard A.

2013-10-01

22

Enhancing nuclear quadrupole resonance (NQR) signature detection leveraging interference suppression algorithms  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole resonance (NQR) is a radio frequency (RF) magnetic spectroscopic technique that has been shown to detect and identify a wide range of explosive materials containing quadrupolar nuclei. The NQR response signal provides a unique signature of the material of interest. The signal is, however, very weak and can be masked by non-stationary RF interference (RFI) and thermal noise, limiting detection distance. In this paper, we investigate the bounds on the NQR detection range for ammonium nitrate. We leverage a low-cost RFI data acquisition system composed of inexpensive B-field sensing and commercial-off-the-shelf (COTS) software-defined radios (SDR). Using collected data as RFI reference signals, we apply adaptive filtering algorithms to mitigate RFI and enable NQR detection techniques to approach theoretical range bounds in tactical environments.

DeBardelaben, James A.; Miller, Jeremy K.; Myrick, Wilbur L.; Miller, Joel B.; Gilbreath, G. Charmaine; Bajramaj, Blerta

2012-05-01

23

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

24

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

25

Nqrs Data for C26H35Cl2CuNP (Subst. No. 1604)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Substances Containing C10H16 Zn' of Volume 48 'Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Brnstein - Group III 'Condensed Matter'. It contains an extract of Section '3.2 Data tables' of the Chapter '3 Nuclear quadrupole resonance data' providing the NQRS data for C26H35Cl2CuNP (Subst. No. 1604)

Chihara, H.; Nakamura, N.

26

37 Cl- 35 Cl variations in a diffusion-controlled groundwater system  

NASA Astrophysics Data System (ADS)

Groundwaters in the low-permeability Quaternary glacial deposits of southwestern Ontario commonly exhibit increasing Cl - concentrations with depth. Because these deposits were formed in a freshwater glacial environment and because Cl - is not derived from weathering of these deposits, previous investigations hypothesized that upward diffusion of saline formation waters from the shallow bedrock caused this Cl - trend. This hypothesis was tested by measuring 37 Cl / 35 Cl ratios in the groundwaters from two typical sites and comparing the results with theoretically derived isotopic distributions produced by diffusion. 37 Cl measurements, expressed relative to standard mean ocean chloride (SMOC), ranged from -0.8 to +2.2% and vertical profiles showed a gradual enrichment in 35 Cl relative to 37 Cl with increasing distance upward from the bedrock-till interface. 537 Cl distributions were simulated with a mathematical solute transport model incorporating the effects of kinetic isotopic partitioning. A sensitivity analysis indicated that the model results were affected by the groundwater velocity, the isotope enrichment factor and diffusion times. Agreement between the simulated and observed Cl - isotope profiles was obtained using a groundwater velocity of 0, an isotopic enrichment factor of 1.0012 and diffusion times ranging from 14,000 to 16,000 years. Based on these results, we conclude that the isotopic enrichment in 35 Cl was caused by upward diffusion over a period of about 15,000 years. This diffusion period is consistent with what is known about the Quaternary history of the area.

Desaulniers, Donald E.; Kaufmann, Ronald S.; Cherry, John A.; Bentley, Harold W.

1986-08-01

27

SQUID detected NMR and NQR. Superconducting Quantum Interference Device.  

PubMed

The dc Superconducting QUantum Interference Device (SQUID) is a sensitive detector of magnetic flux, with a typical flux noise of the order 1 muphi0 Hz(-1/2) at liquid helium temperatures. Here phi0 = h/2e is the flux quantum. In our NMR or NQR spectrometer, a niobium wire coil wrapped around the sample is coupled to a thin film superconducting coil deposited on the SQUID to form a flux transformer. With this untuned input circuit the SQUID measures the flux, rather than the rate of change of flux, and thus retains its high sensitivity down to arbitrarily low frequencies. This feature is exploited in a cw spectrometer that monitors the change in the static magnetization of a sample induced by radio frequency irradiation. Examples of this technique are the detection of NQR in 27Al in sapphire and 11B in boron nitride, and a level crossing technique to enhance the signal of 14N in peptides. Research is now focused on a SQUID-based spectrometer for pulsed NQR and NMR, which has a bandwidth of 0-5 MHz. This spectrometer is used with spin-echo techniques to measure the NQR longitudinal and transverse relaxation times of 14N in NH4ClO4, 63+/-6 ms and 22+/-2 ms, respectively. With the aid of two-frequency pulses to excite the 359 kHz and 714 kHz resonances in ruby simultaneously, it is possible to obtain a two-dimensional NQR spectrum. As a third example, the pulsed spectrometer is used to study NMR spectrum of 129Xe after polariza-tion with optically pumped Rb. The NMR line can be detected at frequencies as low as 200 Hz. At fields below about 2 mT the longitudinal relaxation time saturates at about 2000 s. Two recent experiments in other laboratories have extended these pulsed NMR techniques to higher temperatures and smaller samples. In the first, images were obtained of mineral oil floating on water at room temperature. In the second, a SQUID configured as a thin film gradiometer was used to detect NMR in a 50 microm particle of 195Pt at 6 mT and 4.2 K. PMID:9650797

Augustine, M P; TonThat, D M; Clarke, J

1998-03-01

28

{sup 35}Cl+{sup 12}C asymmetrical fission excitation functions  

SciTech Connect

The fully energy-damped yields from the {sup 35}Cl+{sup 12}C reaction have been systematically investigated using particle-particle coincidence techniques at a {sup 35}Cl bombarding energy of {approximately}8 MeV/nucleon. The fragment-fragment correlation data show that the majority of events arises from a binary-decay process with rather large numbers of secondary light-charged particles emitted from the two excited exit fragments. No evidence is observed for ternary break-up events. The binary-process results of the present measurement, along with those of earlier, inclusive experimental data obtained at several lower bombarding energies are compared with predictions of two different kinds of statistical model calculations. These calculations are performed using the transition-state formalism and the extended Hauser-Feshbach method and are based on the available phase space at the saddle point and scission point of the compound nucleus, respectively. The methods give comparable predictions and are both in good agreement with the experimental results thus confirming the fusion-fission origin of the fully damped yields. The similarity of the predictions for the two models supports the claim that the scission point configuration is very close to that of the saddle point for the light {sup 47}V compound system. The results also give further support for the specific mass-asymmetry-dependent fission barriers needed in the transition-state calculation. {copyright} {ital 1996 The American Physical Society.}

Beck, C.; Mahboub, D.; Nouicer, R.; Matsuse, T.; Djerroud, B.; Freeman, R.M.; Haas, F.; Hachem, A.; Morsad, A.; Youlal, M. [Centre de Recherches Nucleaires, Institut National de Physique Nucleaire et de Physique des Particules--Centre National de la Recherche Scientifique/Universite Louis Pasteur, B.P.28, F-67037 Strasbourg Cedex 2 (France); Sanders, S.J. [Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045 (United States); Dayras, R.; Wieleczko, J.P.; Berthoumieux, E.; Legrain, R.; Pollacco, E. [DAPNIA/SPhN, C.E. Saclay, F-91191 Gif sur Yvette Cedex (France); Cavallaro, S.; De Filippo, E.; Lanzano, G.; Pagano, A.; Sperduto, M.L. [Dipartimento di Fisica dell`Universita di Catania, INFN and LNS Catania, I-95129 Catania (Italy)

1996-07-01

29

Gamma-ray energies from the reaction 35Cl(n,?)  

NASA Astrophysics Data System (ADS)

A two-axis flat-crystal spectrometer has been used to measure accurately gamma-ray energies up to 2 MeV from the reaction 35Cl(n,?). This represents a fourfold extension of the range of direct optically based gamma-ray energies. The crystals and spectrometer have performed in a manner which demonstrates that sub-ppm measurements are possible at energies >~2 MeV. The reported transition energies (in eV) are 517 077.41+/-0.23, 786 311.32+/-0.38, 788 437.43+/-0.44, 1 164 885.74+/-0.48, 1 951 197.06+/-0.58, and 1 959 413.45+/-8.45. The sum rule is satisfied by three of the lines (786 keV+1165 keV=1951 keV) within an uncertainty of ~1 ppm.

Kessler, E. G., Jr.; Greene, G. L.; Deslattes, R. D.; Brner, H. G.

1985-08-01

30

Gamma ray energies and 36Cl level scheme from the reaction 35Cl(n, ?)  

NASA Astrophysics Data System (ADS)

The ?-ray spectrum emitted after thermal neutron capture in 35Cl has been studied by use of the crystal and pair spectrometers installed at the ILL high flux reactor. We identified about 400 transitions in this reaction 326 of which were placed into the 36C1 level scheme; several new states were found. The level energies up to 3.5 MeV were measured with a precision of 5-20 eV relative to the 412 keV 198Au standard, those above 3.5 MeV with a precision of 10ppm. The neutron binding energy was determined to be EB = 8579.68(9) keV.

Krusche, B.; Lieb, K. P.; Daniel, H.; von Egidy, T.; Barreau, G.; Brner, H. G.; Brissot, R.; Hofmeyr, C.; Rascher, R.

1982-09-01

31

(75)As, (63)Cu NMR and NQR characterization of selected arsenic minerals.  

PubMed

The direct measurement and identification of solid state arsenic phases using (75)As NMR is made difficult by the simultaneous conditions of large quadrupole moment and low coordination symmetry in many compounds. However, specific arsenic minerals can efficiently be detected and discriminated via nuclear quadrupolar resonance (NQR). We report on the first NMR and NQR measurements in the natural minerals enargite (Cu3AsS4), niccolite (NiAs), arsenopyrite (FeAsS) and loellingite (FeAs2). The NQR frequencies have been determined from both high-field NMR powder patterns and via zero-field frequency sweeps. Density functional theory (DFT) based ab initio calculations support the experimental results. The compounds studied here are common in terms of the known set of As-containing minerals. They are sometimes encountered in the context of base metal or gold mining. The study represents a significant addition to the list of arsenic minerals that can now be detected with NQR techniques. PMID:23706610

Lehmann-Horn, J A; Miljak, D G; Bastow, T J

2013-05-14

32

NQR investigation and characterization of cocrystals and crystal polymorphs  

NASA Astrophysics Data System (ADS)

The application of 14N NQR to the study of cocrystals and crystal polymorphs is reviewed. In ferroelectric and antiferroelectric organic cocrystals 14N NQR is used to determine proton position in an N-H...O hydrogen bond and proton displacement below TC. In cocrystal isonicitinamide - oxalic acid (2:1) 14N NQR is used to distinguish between two polymorphs and to determine the type of the hydrogen bond (N-...H-O). The difference in the 14N NQR spectra of cocrystal formers and cocrystal is investigated in case of carbamazepine, saccharin and carbamazepine - saccharin (1:1). The experimental resolution allows an unambiguous distinction between the 14N NQR spectrum of the cocrystal and the 14N NQR spectra of the cocrystal formers. The possibility of application of NQR and double resonance for the determination of the inhomogeneity of the sample and for the study of the life time of an unstable polymorph is discussed.

Seliger, Janez; agar, Veselko; Asaji, Tetsuo

2013-05-01

33

133Cs and 35Cl NMR spectroscopy and molecular dynamics modeling of Cs + and Cl ? complexation with natural organic matter  

Microsoft Academic Search

Interaction of dissolved aqueous species with natural organic matter (NOM) is thought to be important in sequestering some species and enhancing the transport of others, but little is known about these interactions on a molecular scale. This paper describes a combined experimental 133Cs and 35Cl nuclear magnetic resonance (NMR) and computational molecular dynamics (MD) modeling study of the interaction of

Xiang Xu; Andrey G. Kalinichev; R. James Kirkpatrick

2006-01-01

34

133Cs and 35Cl NMR spectroscopy and molecular dynamics modeling of Cs+ and Cl complexation with natural organic matter  

Microsoft Academic Search

Interaction of dissolved aqueous species with natural organic matter (NOM) is thought to be important in sequestering some species and enhancing the transport of others, but little is known about these interactions on a molecular scale. This paper describes a combined experimental 133Cs and 35Cl nuclear magnetic resonance (NMR) and computational molecular dynamics (MD) modeling study of the interaction of

Xiang Xu; Andrey G. Kalinichev; R. James Kirkpatrick

2006-01-01

35

Application of a dc SQUID to rf amplification: NQR  

SciTech Connect

Superconducting QUantum Interference Devices (SQUIDs) have been used for more than a decade for the detection of magnetic resonance. Until recently, these devices had mostly been confined to operation in the audiofrequency range, so that experiments have been restricted to measurements of resonance at low frequencies, or of changes in the static susceptibility of a sample induced by rf irradiation at the resonant frequency. However, the recent extension of the operating range of low noise dc SQUIDs to radiofrequencies (rf) allows one to detect magnetic resonance directly at frequencies up to several hundred megahertz. In this paper, we begin by summarizing the properties of dc SQUIDs as tuned rf amplifers. We then describe first, the development of a SQUID system for the detection of pulsed nuclear quadrupole resonance (NQR) at about 30 MHz and second, a novel technique for observing magnetic resonances in the absence of any externally applied rf fields.

Hilbert, C.; Clarke, J.; Sleator, T.; Hahn, E.L.

1985-05-01

36

Factors affecting the NQR line width in nitramine explosives  

Microsoft Academic Search

A number of factors associated with crystal quality contribute to the nuclear quadrupole resonance (NQR) line width. Imperfections\\u000a such as dislocations, voids, strain and impurities can be electrical sources that distort the electric field gradient at nearby\\u000a quadrupolar nuclei and broaden the observed NQR line. We measured the14N NQR line widths in powdered samples of the nitramine explosives hexahydro-1,3,5-trinitro-s-triazine (RDX),

M. L. Buess; S. M. Caulder

2004-01-01

37

Coulomb excitation of ground bands in 160,162,164Dy with 20Ne and 35Cl ions  

Microsoft Academic Search

Multiple Coulomb excitation of states up to Jpi=12+ in the ground band was measured to test the rigid-rotor prediction for intraband B(E2) ratios. The deexcitation gamma rays were observed in singles and in the particle- gamma coincident mode following excitation by 20Ne or 35Cl ions from the Oak Ridge isochronous cyclotron. B(E2) values were extracted by comparing experimental excitation probabilities

R. O. Sayer; E. Eichler; Noah R. Johnson; D. C. Hensley; L. L. Riedinger

1974-01-01

38

Gamma-ray angular correlation and polarization measurements in the reaction 35Cl(p, gamma)36Ar  

Microsoft Academic Search

Triple angular correlation measurements have been performed at eight resonances in the reaction 35Cl(p, ?)36Ar, with protons in the energy range Ep = 7332595 keV. A number of multiple cascades, from the decay of high-spin levels, has been investigated. Appropriate methods of analysis of triple correlation measurements are discussed. Polarization measurements have been performed at three of the resonances. The

F. C. Ern

1966-01-01

39

Detection of Cl- binding to band 3 by double-quantum-filtered 35Cl nuclear magnetic resonance.  

PubMed Central

We have applied double-quantum-filtered (DQF) NMR of 35Cl to study binding of Cl- to external sites on intact red blood cells, including the outward-facing anion transport sites of band 3, an integral membrane protein. A DQF 35Cl NMR signal was observed in cell suspensions containing 150 mM KCl, but the DQF signal can be totally eliminated by adding 500 microM 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS), an inhibitor that interferes with Cl- binding to the band 3 transport site. Therefore, it seems that only the binding of Cl- to transport sites of band 3 can give rise to a 35Cl DQF signal from red blood cell suspensions. In accordance with this concept, analysis of the single quantum free induction decay (FID) revealed that signals from buffer and DNDS-treated cells were fitted with a single exponential function, whereas the FID signals of untreated control cells were biexponential. The DQF signal remained after the cells were treated with eosin-5-maleimide (EM), a noncompetitive inhibitor of chloride exchange. This result supports previous reports that EM does not block the external chloride binding site. The band 3-dependent DQF signal is shown to be caused at least in part by nonisotropic motions of Cl- in the transport site, resulting in incompletely averaged quadrupolar couplings.

Liu, D; Knauf, P A; Kennedy, S D

1996-01-01

40

Spatial electron density distribution of the chlorine atoms in organic and complex compounds as studied by NQR and MNDO  

Microsoft Academic Search

Quantitative correlation of the NQR frequencies and asymmetry parameters of the EFG at nuclei having spin I = 32 with the population of the indicator atom (at Npx = 2) and nonaxiality of its electron distribution has been obtained. The Npy and Npz populations of the Cl atoms in some chloro-containing organic and coordination compounds have been calculated using the

V. P. Feshin; M. Yu. Konshin

1995-01-01

41

[sup 81]Br and [sup 35]Cl NMR investigation of sodium, silver, halo-sodalite semiconductor supralattices  

SciTech Connect

[sup 81]Br and [sup 35]Cl NMR yields, respectively, bromide and chloride site-specific information pertinent to the structural and electronic properties of Na[sub 8-n-p]Ag[sub n]X[sub 2-p]-sodalite, semiconductor cluster supralattices, where X = Br, Cl; 0 [le] n [le] 8; 0 [le] p [le] 2. The [sup 81]Br and [sup 35]Cl MAS chemical shifts and line shapes observed for encapsulated Na[sub 4]X and Ag[sub 4]X clusters within the sodalite cavities provide insight into the nature of the intracluster bonding (ionic-covalent character) and the extent of intercavity coupling. Substantial nuclear shielding is observed for encapsulated Ag[sub 4]X clusters in sodalite materials with high loading of Ag[sub 4]Br clusters, whereas no NMR signal is detected from silver-bromide clusters isolated within sodalite lattices. Spin-lattice and spin-spin relaxation measurements yield information on intracavity coupling and motion within the sodalite cages. The results enable one to explore the transition from isolated clusters to an expanded Ag[sub 4]X supralattice, through the compositional and temperature dependence of the NMR spectra of the sodalite halide anions. 22 refs., 10 figs.

Jelinek, R. (Lawrence Berkeley Lab., CA (United States)); Stein, A.; Ozin, G.A. (Univ. of Toronto, Ontario (Canada))

1993-03-24

42

The ground and ?6=1 vibrational levels of HC35Cl3: The first high-resolution analysis of the ?6 fundamental band  

NASA Astrophysics Data System (ADS)

The paper reports on the first high-resolution study of the weak ?6 fundamental rovibrational band of monoisotopic chloroform HC35Cl3. More than 4500 infrared transitions pertaining to the ?6 band have been assigned, spanning the rotational states J=095 and ?73?K?K?89. The new Fourier transform infrared data were combined with accurate submillimeter-wave transition frequencies in the v6=1 state measured previously [Journal of Molecular Structure 795; 2006: 157162] in a simultaneous fit. The existence of resonance crossings due to the ?k=1,?l=?2l-type resonance in the v6=1 state, which generated perturbation-allowed rotational transitions, provided independent values of the C and C?6 constants. When we combined them with the wavenumbers of the fundamental ?6 band, we were able to determine accurately the axial rotational constants in the vibrational ground state C0=0.05715783 (20) cm?1, DK0=2.759 (63)10?8 cm?1, and even HK0=?8.27 (75)10?14 cm?1.

Pracna, Petr; Ceausu-Velcescu, Adina; Horneman, Veli-Matti

2012-07-01

43

Site-directed mutagenesis of conserved cysteine residues in NqrD and NqrE subunits of Na+-translocating NADH:quinone oxidoreductase.  

PubMed

Each of two hydrophobic subunits of Na+-translocating NADH:quinone oxidoreductase (NQR), NqrD and NqrE, contain a pair of strictly conserved cysteine residues within their transmembrane alpha-helices. Site-directed mutagenesis showed that substitutions of these residues in NQR of Vibrio harveyi blocked the Na+-dependent and 2-n-heptyl-4-hydroxyquinoline N-oxide-sensitive quinone reductase activity of the enzyme. However, these mutations did not affect the interaction of NQR with NADH and menadione. It was demonstrated that these conserved cysteine residues are necessary for the correct folding and/or the stability of the NQR complex. Mass and EPR spectroscopy showed that NQR from V. harveyi bears only a 2Fe-2S cluster as a metal-containing prosthetic group. PMID:18298367

Fadeeva, M S; Bertsova, Y V; Verkhovsky, M I; Bogachev, A V

2008-02-01

44

Zero field NMR and NQR  

SciTech Connect

Methods are described and demonstrated for detecting the coherent evolution of nuclear spin observables in zero magnetic field with the full sensitivity of high field NMR. The principle motivation is to provide a means of obtaining solid state spectra of the magnetic dipole and electric quadrupole interactions of disordered systems without the line broadening associated with random orientation with respect to the applied magnetic field. Comparison is made to previous frequency domain and high field methods. A general density operator formalism is given for the experiments where the evolution period is initiated by a sudden switching to zero field and is terminated by a sudden restoration of the field. Analytical expressions for the signals are given for a variety of simple dipolar and quadrupolar systems and numerical simulations are reported for up to six coupled spin-1/2 nuclei. Experimental results are reported or reviewed for /sup 1/H, /sup 2/D, /sup 7/Li, /sup 13/C, and /sup 27/Al nuclei in a variety of polycrystalline materials. The effects of molecular motion and bodily sample rotation are described. Various extensions of the method are discussed, including demagnetized initial conditions and correlation by two-dimensional Fourier transformation of zero field spectra with themselves or with high field spectra.

Zax, D.B.; Bielecki, A.; Zilm, K.W.; Pines, A.; Weitekamp, D.P.

1985-11-15

45

Behavior and structure of the band 3 anion transport site: a /sup 35/Cl and /sup 37/Cl NMR study  

SciTech Connect

The present thesis focuses on band 3, the most heavily used ion transport protein in typical vertebrate systems. The strategy employed involves /sup 35/Cl NMR, which is shown to be a sensitive probe of (1) Cl/sup -/ migration from solution to a binding site, (2) Cl/sup -/ binding to the site, and (3) the sidedness of a membrane-bound site. Both low-affinity (K/sub D >> 0.5 M) and high-affinity (K/sub D/ = 80 +/- 20 mM) sites are observed on both surfaces of isolated red cell membranes. The latter sites are identified as band 3 transport sites by their affinity for a variety of anions. The transport sites on both sides on both sides of the membrane together behave like a homogeneous population under varying (pCl/sup -/), (Br/sup -/), or pH. These results support the ping-pong model for the transport cycle. The rates of Cl/sup -/ binding and dissociation at the inward- and outward-facing sites are shown by /sup 35/Cl and /sup 37/Cl NMR to exceed 10/sup 5/ events sec/sup -1/ site/sup -1/. Three classes of inhibitors are found: (1) niflumic acid has no effect on Cl/sup -/ migration or binding to the transport site - this inhibitor slows the translocation of bound Cl/sup -/ during both influx and efflux; (2) 1.2-cyclohexanedione (CHD) slows the migration of Cl/sup -/ between the transport site and solution; and (3) phenylglyoxal (PG) modifies an essential transport site arginine. The transport site remains intact following a variety of stripping and proteolytic treatments. Together these results indicate that the transport site is buried in the membrane, where access to solution is provided by a channel that can be blocked by CHD. All essential transport site and channel residues lie on the papain-generated fragments. A model involving a sliding hydrophobic barrier is presented for the ion translocation event.

Falke, J.J.

1985-01-01

46

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

47

NQR study of local structures and cooling rate dependent superconductivity in La sub 2 CuO sub 4+. delta  

SciTech Connect

Structural properties of oxygen-annealed polycrystals of La{sub 2}CuO{sub 4 + {delta}} ({delta}{approximately}0.03) have been studied using {sup 139}La NQR spectroscopy. Superconducting critical temperatures were found to depend on the rate of cooling through a narrow temperature range at about 195K. Preliminary analysis of the {sup 139}La NQR spectra suggest that the oxygen-rich phase-separated region is composed of two structurally distinct phases, both of which are metallic and super-conducting. One phase has a structure closely related to the stoichiometric oxygen-poor compound. The second shows a considerable amount of apical oxygen disorder, a large shift in NQR frequency {nu}{sub Q}, and a volume fraction which increases with cooling rate. The formation of the second phase below {minus}200K is indicative of the freezing Of CuO{sub 6} octahedral tilting. Abrupt shifts in {nu}{sub Q} above {Tc} were also observed for both phases, suggestive of a local structural anomaly or charge transfer to the Cu-O plane.

Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H.; Thompson, J.D.; Canfield, P.C.; Fisk, Z. (Los Alamos National Lab., NM (United States)); Schirber, J.E. (Sandia National Labs., Albuquerque, NM (United States))

1992-01-01

48

Direct studies of low-energy resonances in 31P(p, ) 28Si and 35Cl(p, )32S  

SciTech Connect

Low-energy resonances in 31P(p,a)28Si and 35Cl(p,a)32S were studied directly in order to gain a better understanding of reaction cycling in the Si-Ar region in novae, supernovae, and X-ray bursts. Resonance strengths at Ec:m = 600 and 622 keV in 31P(p,a)28Si were measured as well as the Ec:m: = 611 keV resonance in 35Cl(p,a)32S, the lowest energy that any resonance in this reaction has been observed. The strengths of these resonances were found to be lower than previously determined through indirect methods, resulting in weak cycling in the Si-Ar region.

Moazen, Brian [University of Tennessee, Knoxville (UTK); Matei, Catalin [Oak Ridge Associated Universities (ORAU); Bardayan, Daniel W [ORNL; Blackmon, Jeff C [ORNL; Chae, K. Y. [University of Tennessee, Knoxville (UTK); Chipps, K. [Colorado School of Mines, Golden; Hatarik, Robert [Rutgers University; Jones, K. L. [University of Tennessee, Knoxville (UTK); Kozub, R. L. [Tennessee Technological University; Matos, M. [Louisiana State University; Nesaraja, Caroline D [ORNL; O'Malley, Patrick [Rutgers University; Pain, S. D. [Rutgers University; Pelham, T. [University of Surrey, UK; Pittman, S. T. [University of Tennessee, Knoxville (UTK); Smith, Michael Scott [ORNL

2011-01-01

49

The single NqrB and NqrC subunits in the Na(+)-translocating NADH: quinone oxidoreductase (Na(+)-NQR) from Vibrio cholerae each carry one covalently attached FMN.  

PubMed

The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is the prototype of a novel class of flavoproteins carrying a riboflavin phosphate bound to serine or threonine by a phosphodiester bond to the ribityl side chain. This membrane-bound, respiratory complex also contains one non-covalently bound FAD, one non-covalently bound riboflavin, ubiquinone-8 and a [2Fe-2S] cluster. Here, we report the quantitative analysis of the full set of flavin cofactors in the Na(+)-NQR and characterize the mode of linkage of the riboflavin phosphate to the membrane-bound NqrB and NqrC subunits. Release of the flavin by ?-elimination and analysis of the cofactor demonstrates that the phosphate group is attached at the 5'-position of the ribityl as in authentic FMN and that the Na(+)-NQR contains approximately 1.7mol covalently bound FMN per mol non-covalently bound FAD. Therefore, each of the single NqrB and NqrC subunits in the Na(+)-NQR carries a single FMN. Elimination of the phosphodiester bond yields a dehydro-2-aminobutyrate residue, which is modified with ?-mercaptoethanol by Michael addition. Proteolytic digestion followed by mass determination of peptide fragments reveals exclusive modification of threonine residues, which carry FMN in the native enzyme. The described reactions allow quantification and localization of the covalently attached FMNs in the Na(+)-NQR and in related proteins belonging to the Rhodobacter nitrogen fixation (RNF) family of enzymes. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). PMID:22366169

Casutt, Marco S; Schlosser, Andreas; Buckel, Wolfgang; Steuber, Julia

2012-02-16

50

NQR spin-echo methods at very low temperatures  

NASA Astrophysics Data System (ADS)

Pulsed methods may be successfully used in very low temperature NMR or NQR experiments provided good thermal anchoring of the sample is achieved. In order to reduce heating effects, it is advantageous to use rf pulses that are shorter than the standard magnetization tipping pulses used at higher temperatures. The present work describes the use of short nonstandard rf pulses in NQR spin-echo experiments on powdered samples. Theoretical density matrix calculations have been carried out, and the resulting expression for the echo amplitude confirmed by experiment. Measurements were made on a powder sample of high-purity semimetallic arsenic using a sample probe designed for use in a dilution refrigerator. Preliminary spin-lattice relaxation-time measurements show that the Korringa relation holds in arsenic down to 150 mK.

Goudemond, I. P.; Keartland, J. M.; Hoch, M. J. R.

1991-03-01

51

Preparation and crystal structure determination of Eu 27Ti 20X 2S 54O 12 (X ? I 0.35 Cl 0.65)  

Microsoft Academic Search

The structure of the new compound Eu27T20X2S54O12 (X ? I0.35 Cl0.65), prepared by solid state reaction, contains ?2[(Ti4S2O4)(Ti2S10)4\\/2] planes built up from rutile-like chains that cross perpendicularly. Two [TiS6] octahedra separate the [Ti4S2O4] clusters at the chain intersections. These planes are separated by a corrugated layer of [Ti3S8O4] triplets of face-sharing Ti-centered octahedra. Five crystallographically independent europium ions are seven-

Laurent Cario; Jason A. Cody; Catherine Deudon; Alain Meerschaut

1998-01-01

52

14 N NQR spectra of complexes between hexamethylenetetramine and the crystalline hydrates of salts  

Microsoft Academic Search

Nuclear quadrupole resonance has recently been used more and more effective along with such traditional methods as vibrational spectroscopy and proton magnetic resonance to investigate hydrogen bonding. The NQR method on 14N nuclei has been put into practice at a later date than on the chlorine nuclei. This is explained by the low intensity of the 14N NQR signals and

. O. Azizov; V. S. Grechishkin; T. G. Balicheva; I. V. Pologikh

1979-01-01

53

Quadrupole coupling parameters and structural aspects of crystalline and amorphous solids by NMR and NQR  

SciTech Connect

NMR and NQR techniques were combined to obtain the quadrupole coupling constant (Qcc) and asymmetry parameter ({eta}) and extract structural information for several borate, gallate, and metavanadate compounds and glasses. {sup 71}Ga and {sup 69}Ga NMR was used to study crystalline {beta}-Ga{sub 2}O{sub 3} and several gallate glasses. Quadrupole parameters were acquired for GaO{sub 6} and GaO{sub 4} units in {beta}-Ga{sub 2}O{sub 3} by the computer simulation of the NMR powder patterns. A sensitive CW NQR spectrometer was built to detect NQR resonances below 2 MHz. The spectrometer includes a modified Robinson oscillator-detector, a new bi-symmetric square wave Zeeman modulator and a computerized data acquisition system. {sup 51}V (I = 7/2) NQR resonances below 850 kHz were detected for several metavanadates at both room temperature and liquid nitrogen temperature. Two methods, Zeeman perturbed NQR powder pattern and {sup 10}B NQR, can be employed to obtain both Qcc and {eta}. With a double coil tank circuit design, pure {sup 11}B NQR was used to determine the fraction of borons in BO{sub 3} and BO{sub 4} configurations in hydrated zinc borates. {sup 11}B NMR and NQR were also used to study lead borate glasses.

Mao, Degen.

1991-01-01

54

Direct Measurement of Low-Energy Resonances in ^31P(p,?)^28Si and ^35Cl(p,?)^32S  

NASA Astrophysics Data System (ADS)

Reaction cycles in explosive hydrogen burning in novae and X-ray bursts influence both the energy generation and the processing of material to higher masses. The ^31P(p,?)^28Si and ^35Cl(p,?)^32S reactions are thought to lead to the formation of reaction cycles in the Si-Ar region, but the strength of these cycles depends on the (p,?)/(p,?) reaction rate ratio. Previous attempts to measure the strength of low-energy resonances in ^32S and ^36Ar have relied on indirect methods or resulted only in setting upper limits for a number of the resonances of interest. We have measured the strength of low-energy resonances in ^32S and ^36Ar at Oak Ridge National Laboratory by using stable ^31P and ^35Cl beams and a differentially pumped windowless hydrogen gas target to detect p-? coincidences in arrays of silicon strip detectors. Details of the experimental configuration and results will be presented. ^*This work is supported in part by the U.S. DOE and NSF.

Matei, Catalin; Moazen, B. H.; Chae, K. Y.; Jones, K. L.; Kapler, R. W.; Pittman, S. T.; Bardayan, D. W.; Nesaraja, C. D.; Pain, S. D.; Smith, M. S.; Allen, J.; Chipps, K. A.; Hatarik, R.; Matthews, C.; O'Malley, P. D.; Pelham, T.; Peters, W. A.; Blackmon, J. C.; Matos, M.; Kozub, R. L.; Rogers, J.; Sissom, D. J.

2009-05-01

55

Complete and incomplete fusion in the reaction {sup 35}Cl+{sup 12}C at the energy range 70{endash}154 MeV  

SciTech Connect

Velocity spectra of evaporation residues produced in the {sup 35}Cl+{sup 12}C reaction have been measured at bombarding energies of 125, 140, and 154 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate complete fusion and incomplete fusion components. The results show the presence of small contributions of incomplete fusion components which appear to be due to a cluster transfer reaction mechanism. Angular distributions and total and complete fusion evaporation residue cross sections were extracted at 70, 90, 110, 125, 140, and 154 MeV. The complete fusion cross sections and the deduced critical angular momenta are compared with other experimental data and the predictions of existing models. {copyright} {ital 1997} {ital The American Physical Society}

Pirrone, S.; Aiello, S.; Arena, N.; Cavallaro, S.; Femino, S.; Lanzalone, G.; Politi, G.; Porto, F.; Romano, S.; Sambataro, S. [Dipartimento di Fisica, Universita di Catania, Universita di Messina, Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Gruppo Collegato di Messina and Laboratorio Nazionale del Sud, I-95129 Catania (Italy)

1997-05-01

56

5Trifluoromethyl1,2-dimethyl-1H-pyrazolium chlorides: synthesis and 1 H , 13 C , 19 F and 35 Cl NMR chemical shifts  

Microsoft Academic Search

The one-pot synthesis of nine novel 5-trifluoromethyl-1,2-dimethyl-1H-pyrazolium chlorides 2 from the cyclocondensation of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones 1 [CF3C(O)CH=C(R1)OR, where R1=H, Me, n-Pr, n-Hex, Ph, 4-Me-C6H4, 4-F-C6H4, 4-Cl-C6H4, 4-NO2-C6H4, and R=Me, Et] with 1-2-dimethyl hydrazine, in quantitative yields, is reported. The 1H, 13C, 19F and 35Cl NMR chemical shifts of compounds 2 also are described.

Marcos A. P Martins; Rogrio F Blanco; Claudio M. P Pereira; Paulo Beck; Sergio Brondani; Wilson Cunico; Nilo E. K Zimmermann; Helio G Bonacorso; Nilo Zanatta

2002-01-01

57

NQR study of local structures and cooling rate dependent superconductivity in La{sub 2}CuO{sub 4+{delta}}  

SciTech Connect

Structural properties of oxygen-annealed polycrystals of La{sub 2}CuO{sub 4 + {delta}} ({delta}{approximately}0.03) have been studied using {sup 139}La NQR spectroscopy. Superconducting critical temperatures were found to depend on the rate of cooling through a narrow temperature range at about 195K. Preliminary analysis of the {sup 139}La NQR spectra suggest that the oxygen-rich phase-separated region is composed of two structurally distinct phases, both of which are metallic and super-conducting. One phase has a structure closely related to the stoichiometric oxygen-poor compound. The second shows a considerable amount of apical oxygen disorder, a large shift in NQR frequency {nu}{sub Q}, and a volume fraction which increases with cooling rate. The formation of the second phase below {minus}200K is indicative of the freezing Of CuO{sub 6} octahedral tilting. Abrupt shifts in {nu}{sub Q} above {Tc} were also observed for both phases, suggestive of a local structural anomaly or charge transfer to the Cu-O plane.

Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H.; Thompson, J.D.; Canfield, P.C.; Fisk, Z. [Los Alamos National Lab., NM (United States); Schirber, J.E. [Sandia National Labs., Albuquerque, NM (United States)

1992-10-01

58

Possible stripe fluctuations in La2 - x - yNdySrxCuO4 at room temperature observed by 63Cu NQR spectroscopy  

NASA Astrophysics Data System (ADS)

63Cu nuclear quadrupole resonance (NQR) studies at room temperature were reported on six Nd-doped La2 - xSrxCuO4 samples. The NQR spectrum for La1.48Nd0.4Sr0.12CuO4 has a different line shape compared with those from the other samples, which is similar to the case of the insulating La2CuO4. This may suggest that the stripe fluctuations at such a special Nd and Sr doping fall into the frequency window of 63Cu NQR. The spectra of the other five samples were analysed by pairs of 63Cu and 65Cu Gaussians at A and B sites. The full width of half-maxim (FWHM) for 63Cu at B sites is anomalously large for La1.45Nd0.4Sr0.15CuO4, which was considered to be related to the stripe fluctuations.

Zhang, Q.-M.; Ying, X. N.; Gu, M.; Wang, Y. N.

2005-04-01

59

^63Cu NQR relaxation in the p-type transparent conductor CuScO_2:Mg  

NASA Astrophysics Data System (ADS)

Transparent conducting oxides with p-type conductivity are of interest as electronic complements to the more familiar n-type transparent conductors. This paper reports the first results of a study of carrier spin dynamics in p-type CuScO_2:Mg using ^63Cu nuclear spin-lattice relaxation measurements. Relaxation rates 1/T1 have been measured by nuclear quadrupole resonance (NQR) over the range 280 K to 400 K. The ^63Cu NQR frequency is found to be 28,135 5 kHz at 300 K and to decrease linearly with temperature over the experimental range. The value of 1/T1 at 300 K is 130 10 s-1. The rate is weakly dependent on temperature and increases by only about 15 % up to 400 K. This behavior contrasts sharply with results obtained previously(1. A. Rajabzadeh, J. Tate and W. Warren, Bull. Am. Phys. Soc. 48, 1009 (2003).) for the related material CuYO_2:Ca. In that material, relaxation rates for ^63Cu and ^65Cu were strongly temperature dependent, being approximately thermally-activated with activation energy 152 10 meV. The nuclear relaxation properties of CuScO_2:Mg are suggestive of more conventional metallic transport in CuScO_2:Mg compared with CuYO_2:Ca.

Rossi, Vincent; Tate, Janet; Warren, William; Li, Jun; Sleight, Arthur

2003-05-01

60

Sb NQR in filled skutterudites MFe 4Sb 12 (M=Na, Ca, La)  

Microsoft Academic Search

Temperature-dependent nuclear quadrupole resonance (NQR) investigations on the 121,123Sb nuclei in filled skutterudites MFe4Sb12 (M=Na, Ca, La) are reported. These new compounds show a nice interplay of ferromagnetic and antiferromagnetic correlations best seen in the relaxation rate. Substructures observed in the 121,123Sb NQR spectra give strong evidence for static (or dynamic) disorder on the filler site. Therefore, we performed ab-initio

A. A. Gippius; E. N. Morozova; K. S. Okhotnikov; E. A. Alkaev; A. V. Shevelkov; M. Baenitz; A. Leithe-Jasper; H. Rosner; R. Viennois; Yu. Grin; F. Steglich

2006-01-01

61

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

62

Oxidant-induced formation of a neutral flavosemiquinone in the Na+-translocating NADH:Quinone oxidoreductase (Na+-NQR) from Vibrio cholerae.  

PubMed

The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) from the human pathogen Vibrio cholerae is a respiratory flavo-FeS complex composed of the six subunits NqrA-F. The Na(+)-NQR was produced as His(6)-tagged protein by homologous expression in V. cholerae. The isolated complex contained near-stoichiometric amounts of non-covalently bound FAD (0.78 mol/mol Na(+)-NQR) and riboflavin (0.70 mol/mol Na(+)-NQR), catalyzed NADH-driven Na(+) transport (40 nmol Na(+)min(-1) mg(-1)), and was inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide. EPR spectroscopy showed that Na(+)-NQR as isolated contained very low amounts of a neutral flavosemiquinone (10(-3) mol/mol Na(+)-NQR). Reduction with NADH resulted in the formation of an anionic flavosemiquinone (0.10 mol/mol Na(+)-NQR). Subsequent oxidation of the Na(+)-NQR with ubiquinone-1 or O(2) led to the formation of a neutral flavosemiquinone (0.24 mol/mol Na(+)-NQR). We propose that the Na(+)-NQR is fully oxidized in its resting state, and discuss putative schemes of NADH-triggered redox transitions. PMID:18454933

Tao, Minli; Casutt, Marco S; Fritz, Gnter; Steuber, Julia

2008-04-11

63

NQR, NMR and Crystal Structure Studies of [C(NH2)3]2HgX4 (X = Br, I)  

NASA Astrophysics Data System (ADS)

The crystal structure of [C(NH2)3]2HgBr4 has been determined at room temperature: monoclinic, space group C2/c, with a = 10.035(2), b = 11.164(2), c = 13.358(3) , ? = 111.67(3), and Z = 4. The crystal consists of planar [C(NH2)3]+ and distorted tetrahedral [HgBr4]2- ions. The Hg atom is located on a two-fold axis such that two sets of inequivalent Br atoms exist in an [HgBr4]2- ion. In accordance with the crystal structure, two 81Br NQR lines widely separated in frequency were observed between 77 and ca. 380 K. [C(NH2)3]2HgI4 yielded four 127I NQR lines ascribable to m = 1/2 ? 3/2 transitions, indicating that its crystal structure is different from the bromide complex. The 1H NMR T 1 measurements showed a single minimum for the bromide but two minima for the iodide. The analyses based on the C3 reorientations of the planar [C(NH2)3]+ ions gave the activation energies of 29.8 kJ mol-1 for the bromide, and 30.2 and 40.0 kJ mol-1 for the iodide.

Furukawa, Y.; Terao, H.; Ishihara, H.; Gesing, T. M.; Buhl, J.-C.

2004-12-01

64

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

65

Determination of the electric field gradient tensor by 2D NQR  

Microsoft Academic Search

For a full specification of the Electric Field Gradient (EFG) tensor, five independent parameters are necessary: the asymmetry parameter (?), the largest component of the EFG (eq), and three angles which determine the orientation of the EFG principal axis with respect to the crystallographic frame. The parameters eq and ? can be determined independently by pure Nuclear Quadrupole Resonance (NQR)

C. R. Hernn; S. R. Rabbani; Christovam Mendona

1997-01-01

66

Structureactivity study of thiazides by magnetic resonance methods (NQR, NMR, EPR) and DFT calculations  

Microsoft Academic Search

The paper presents a comprehensive analysis of the relationship between the electronic structure of thiazides and their biological activity. The compounds of interest were studied in solid state by the resonance methods nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) and quantum chemistry (ab inito and DFT) methods. Detailed parallel analysis of the spectroscopic parameters

J. N. Latosi?ska

2005-01-01

67

In-Situ Real Time Detection of Explosive/Chemical Compounds in Mines Using Nuclear Quadrupole Resonance (NQR).  

National Technical Information Service (NTIS)

This program was part of DARPA's 'Dog Nose' initiative to develop land mine detection technology based upon the chemical signature of the mine explosive charge. Nuclear quadrupole resonance (NQR) was the only technology pursued that detects the bulk explo...

A. D. Hibbs

2001-01-01

68

Feasibility of nuclear quadrupole resonance as a novel dosimetry tool  

Microsoft Academic Search

Nuclear quadrupole resonance (N.Q.R) frequencies are influenced by the symmetry of the charge distribution of a compound around the site of interest. Damage by ionizing radiation causes changes in this charge symmetry which can be detected by standard pulsed N.Q.R. methods. Previous work done on various chlorates of [sup 35]Cl at room temperature (Vargas et al., 1978) shows a linear

L. H. Iselin; D. E. Hintenlang; S. J. Epperson; G. A. Higgins; K. Jamil

1990-01-01

69

Study of local magnetic fields in the oxide ?-Bi 2 O 3 by NQR and ? SR techniques  

Microsoft Academic Search

NQR and?SR investigations of the local magnetic field in?-Bi2O3 were performed. In theNQR experiments on?-Bi2O3 which is usually considered as diamagnetic, the splitting of the spectral lines revealed a local field on the bismuth nuclei. The internal magnetic field obtained by?SR significantly exceeds the dipole field from Bi nuclear magnetic moments. A possible source of the local magnetic fields is

V. N. Duginov; V. G. Grebinnik; T. N. Mamedov; V. G. Olshevsky; V. Yu. Pomjakushin; V. A. Zhukov; B. F. Kirillov; B. A. Nikolsky; V. G. Orlov; A. V. Pirogov; A. N. Ponomarev; V. A. Suetin; E. A. Kravchenko

1994-01-01

70

Antiferromagnetic properties of a water-vapor-inserted YBa2 Cu3 O6.5 compound studied byNMR, NQR, and muSR  

Microsoft Academic Search

We present a detailed NQR, nuclear magnetic resonance (NMR), and muSR study of the magnetic phase obtained during a topotactic chemical reaction of YBa2Cu3O6.5 high-temperature superconductor with low-pressure water vapor. Cu65 -enriched samples have been used for NQR\\/NMR studies which allows to get a good resolution in the Cu(1) NQR and Cu(2) zero field NMR (ZFNMR) spectra. It is shown

A. V. Dooglav; A. V. Egorov; I. R. Mukhamedshin; A. V. Savinkov; H. Alloul; J. Bobroff; W. A. Macfarlane; P. Mendels; G. Collin; N. Blanchard; P. G. Picard; P. J. C. King; J. Lord

2004-01-01

71

Stopping cross sections of atomic layer deposited Al2O3 and Ta2O5 and of Si3N4 for 12C, 16O, 35Cl, 79Br and 127I ions  

NASA Astrophysics Data System (ADS)

Stopping cross sections of atomic layer deposited Al2O3 and Ta2O5 and of Si3N4 for 0.03-1 MeV/u 12C, 16O, 35Cl, 79Br and 127I ions have been measured by the transmission technique employing a Time of Flight-Elastic Recoil Detection Analysis (ToF-ERDA) setup. Simulation of experimental slowing down energy spectra was employed to obtain stopping cross section curves over a continuous energy range. The experimental results are compared with the predictions of the SRIM2012 parameterization and literature data.

Mizohata, K.; Risnen, J.; Keinonen, J.; Hrknen, E.; Palmans, J.; Ritala, M.

2013-04-01

72

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

73

Measurement of in-situ stress in salt and rock using NQR techniques  

Microsoft Academic Search

A discussion of how stress and strain affect the quantities which can be measured in an NQR experiment shows that, for stresses of the magnitude to be expected at depths up to about 10,000 feet, quadrupole coupling constants will fall in the range of 1 to 10 kHz for both the sodium and chloride ions in NaCl. The most promising

E. Schempp; T. Hirschfeld; S. Klainer

1980-01-01

74

Basic aspects and main results of NMR-NQR spectroscopies in high-temperature superconductors  

NASA Astrophysics Data System (ADS)

After a mention of the structural, magnetic and electronic properties of high-temperature superconductors (HTSC), the basic principles of NMR-NQR experiments in these compounds are presented, emphasizing the marked differences and the novel aspects of the latter systems in comparison with metals and conventional superconductors. It follows a review of NMR-NQR spectra and relaxation rates in two-dimensional quantum antiferromagnets (particularly 0034-4885/61/10/002/img1) driven towards the superconducting state by charge doping. The main results obtained in the normal state of HTSC are summarized, while the problems of the spin-gap and of the superconducting fluctuations are discussed to a certain extent, by including the most recent contributions. An overview is given on the main conclusions derived from NMR-NQR experiments in the superconducting state. A section is devoted to the insights into the vortex lattice and the flux lines motion that have been obtained from NMR line narrowing, 0034-4885/61/10/002/img2 and echo dephasing. This review deals mostly with three systems, 0034-4885/61/10/002/img3, 0034-4885/61/10/002/img4 and 0034-4885/61/10/002/img5.

Rigamonti, A.; Borsa, F.; Carretta, P.

1998-10-01

75

A correlation of spectroscopic parameters from different magnetic resonance spectroscopies for thiazides: a study by NQR, NMR, EPR and DFT methods  

Microsoft Academic Search

A Letter is devoted to a detailed parallel analysis of the spectroscopic parameters such as quadrupole coupling constant (NQR), chemical shift, chemical shift anisotropy, asymmetry parameter (NMR) and hyperfine coupling constant (EPR) for thiazides. The compounds were studied in solid state by the resonance (NQR, NMR and EPR) and density functional theory (DFT) methods. The spectroscopic parameters determined at room

J. N. Latosi?ska

2004-01-01

76

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

2013-07-25

77

63,65Cu NQR study of Zn and Ni doped YBa 2Cu 3O 7  

Microsoft Academic Search

63,65Cu NQR measurements have been performed on Zn and Ni doped YBCO (YBa2Cu3?xMxO7, M?Zn or Ni, x=0.0 ? 0.09). Distinctive differences due to the nonmagnetic Zn and the magnetic Ni dopants substituted for copper are compared microscopically based on the plane and the chain 63,65Cu NQR data. Both spin-lattice and spin-spin relaxation rates decrease for Zn doped YBCO whereas they

K. S. Han; B. J. Mean; K. H. Lee; D. H. Kim; S. W. Seo; Moohee Lee; W. C. Lee; J. S. Cho

2000-01-01

78

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

79

Study of local magnetic fields in the oxide alpha-Bi2O3 by NQR and muSR techniques  

Microsoft Academic Search

NQR and muSR investigations of the local magnetic field in alpha-Bi2O3 were performed. In the NQR experiments on alpha-Bi2O3 which is usually considered as diamagnetic, the splitting of the spectral lines revealed a local field on the bismuth nuclei. The internal magnetic field obtained by muSR significantly exceeds the dipole field from Bi nuclear magnetic moments. A possible source of

V. N. Duginov; V. G. Grebinnik; T. N. Mamedov; V. G. Olshevsky; V. Yu. Pomjakushin; V. A. Zhukov; B. F. Kirillov; B. A. Nikolsky; V. G. Orlov; A. V. Pirogov; A. N. Ponomarev; V. A. Suetin; E. A. Kravchenko

1994-01-01

80

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

81

First-principles study of (75)As NQR in arsenic-chalcogenide compounds.  

PubMed

We present a theoretical study of the nuclear quadrupole interaction, ?(Q), of (75)As in crystalline and amorphous materials containing sulfur and selenium, and compare them with experiment. We studied a combination of hydrogen-terminated molecular clusters and periodic cells at various levels of quantum chemical theory. The results show clearly that the standard density functional theory (DFT) approximations, LDA and GGA, underestimate the nuclear quadrupole (NQR) interaction systematically, while Hartree-Fock theory overestimates it to an even greater degree. However, various levels of configuration interaction and the B3LYP hybrid exchange-correlation functional, which includes some exact exchange, give very good quantitative agreement for As bonded only to the chalcogen species. As-As bonds require highly converged basis sets. We have performed a systematic study of the effect of local distortions around an arsenic atom on ?(Q) and ?. Using a simple, semiclassical model, we have combined our total energy results with our NQR calculations to predict ?(Q) lineshapes for bond angle and bond length distortions. Our predictions for lineshape, including first and second moments, are in excellent agreement with the results of Su et al for a-As(2)S(3), a-As(2)Se(3) and a-AsSe. We offer new insight into the distortions that led to this inhomogeneous broadening. Our results show clearly that, for trivalent arsenic atoms with zero or one arsenic nearest neighbor, symmetric bond stretching is the predominant contributor to the ?(Q) linewidth. However, in the presence of two arsenic nearest neighbors, distortions of the As-As-As apex angle dominates and, in fact, leads to a much larger second moment, in agreement with experiment. PMID:21406910

Edwards, Arthur H; Taylor, P C; Campbell, Kristy A; Pineda, Andrew C

2011-01-19

82

Sb NQR study of the filled skutterudite CeFe4Sb12 synthesized under high pressure  

NASA Astrophysics Data System (ADS)

We report the results of Sb nuclear quadrupole resonance (NQR) measurements on the filled skutterudite CeFe4Sb12 synthesized under high pressure (HP) and compare them with those for the sample synthesized under ambient pressure (AP) to understand the influence of the Ce-site filling fraction. The NQR spectra for the HP sample are much sharper than those for the AP sample, suggesting that the Ce filling fraction is higher. Also, the nuclear spin-lattice relaxation rate 1/ T 1 follows an exponential decrease 1/ T 1 ? exp(-?/ k B T), with the gap being ?/ k B = 270 K at temperatures above 100 K, which is larger than that for the AP sample. This result suggests that the c- f hybridization is enhanced by increasing the Ce-site filling fraction.

Magishi, Ko-ichi; Takahashi, Masahiro; Saito, Takahito; Koyama, Kuniyuki; Sugawara, Hitoshi; Saito, Takashi; Tatsuoka, Sho; Tanaka, Kenya; Sato, Hideyuki

2013-08-01

83

Ab initio DFT study of bisphosphonate derivatives as a drug for inhibition of cancer: NMR and NQR parameters.  

PubMed

DFT computations were carried out to characterize the (17)Oand (2)H electric field gradient, EFG, in various bisphosphonate derivatives. The computations were performed at the B3LYP level with 6-311++G (d,P) standard basis set. Calculated EFG tensors were used to determine the (17)O and (2)H nuclear quadrupole coupling constant, ? and asymmetry parameter, ?. For better understanding of the bonding and electronic structure of bisphosphonates, isotropic and anisotropic NMR chemical shieldings were calculated for the (13)C, (17)O and (31)P nuclei using GIAO method for the optimized structure of intermediate bisphosphonates at B3LYP level of theory using 6-311++G (d, p) basis set. The results showed that various substituents have a strong effect on the nuclear quadrupole resonance (NQR) parameters (?, ?) of (17)O in contrast with (2)H NQR parameters. The NMR and NQR parameters were studied in order to find the correlation between electronic structure and the activity of the desired bisphosphonates. In addition, the effect of substitutions on the bisphosphonates polarity was investigated. Molecular polarity was determined via the DFT calculated dipole moment vectors and the results showed that substitution of bromine atom on the ring would increase the activity of bisphosphonates. PMID:21633790

Aghabozorg, Hussein; Sohrabi, Beheshteh; Mashkouri, Sara; Aghabozorg, Hamid Reza

2011-06-02

84

Korormicin insensitivity in Vibrio alginolyticus is correlated with a single point mutation of Gly-140 in the NqrB subunit of the Na(+)-translocating NADH-quinone reductase.  

PubMed

Na(+)-translocating NADH-quinone reductase (NQR) from the marine Vibrio alginolyticus is strongly inhibited by a new antibiotic korormicin. Korormicin specifically inhibits the Na(+)-dependent reaction of the NQR complex and acts as a purely non-competitive inhibitor for Q-1 with the inhibitor constant of 82 pM. Korormicin-resistant mutants were isolated from V. alginolyticus and the NQR complex was purified from a mutant KR2. Similar to 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO), korormicin acted as a purely noncompetitive inhibitor to the NQR complex from the mutant KR2, but the inhibitor constant increased to 8 microM, which is 10(5)-fold higher than that of the wild-type NQR complex. The inhibitor constant of HQNO, however, was only slightly affected by the acquisition of korormicin resistance. The spontaneous mutation was caused by a single mutation of G-422 to T-422 in the nucleotide sequence of the nqrB gene, which resulted in the conversion of Gly-140 to Val-140. Thus, Gly-140 seems to play an important role for the binding of korormicin to the NqrB subunit. The fact that korormicin is a purely noncompetitive inhibitor for Q-1 strongly supports the presence of one of Q-1 binding sites in the NqrB subunit, which also has a covalently bound FMN at Thr-235. PMID:12054467

Hayashi, Maki; Shibata, Naoaki; Nakayama, Yuji; Yoshikawa, Kazuhiro; Unemoto, Tsutomu

2002-05-15

85

NMR and NQR parameters of the SiC-doped on the (4,4) armchair single-walled BPNT: a computational study.  

PubMed

The structural properties, NMR and NQR parameters in the pristine and silicon carbide (SiC) doped boron phosphide nanotubes (BPNTs) were calculated using DFT methods (BLYP, B3LYP/6-31G) in order to evaluate the influence of SiC-doped on the (4,4) armchair BPNTs. Nuclear magnetic resonance (NMR) parameters including isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (13)C, (29)Si, (11)B, and (31)P atoms and quadrupole coupling constant (C ( Q )), and asymmetry parameter (? ( Q )) at the sites of various (11)B nuclei were calculated in pristine and SiC- doped (4,4) armchair boron phosphide nanotubes models. The calculations indicated that doping of (11)B and (31)P atoms by C and Si atoms had a more significant influence on the calculated NMR and NQR parameters than did doping of the B and P atoms by Si and C atoms. In comparison with the pristine model, the SiC- doping in Si(P)C(B) model of the (4,4) armchair BPNTs reduces the energy gaps of the nanotubes and increases their electrical conductance. The NMR results showed that the B and P atoms which are directly bonded to the C atoms in the SiC-doped BPNTs have significant changes in the NMR parameters with respect to the B and P atoms which are directly bonded to the Si atoms in the SiC-doped BPNTs. The NQR results showed that in BPNTs, the B atoms at the edges of nanotubes play dominant roles in determining the electronic behaviors of BPNTs. Also, the NMR and NQR results detect that the Fig. 1b (Si(P)C(B)) model is a more reactive material than the pristine and the Fig. 1a (Si(B)C(p)) models of the (4,4) armchair BPNTs. PMID:21625895

Baei, Mohammad T; Sayyad-Alangi, S Zahra; Moradi, Ali Varasteh; Torabi, Parviz

2011-05-28

86

Electronic properties of LaO1-xFxFeAs in the normal state probed by NMR/NQR  

NASA Astrophysics Data System (ADS)

We report 139La, 57Fe and 75As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements on powders of the new LaO1-xFxFeAs superconductor for x=0 and 0.1 at temperatures up to 480 K, and compare our measured NQR spectra with local density approximation (LDA) calculations. For all three nuclei in the x=0.1 material, it is found that the local Knight shift increases monotonically with an increase in temperature, and scales with the macroscopic susceptibility, suggesting a single magnetic degree of freedom. Surprisingly, the spin lattice relaxation rates for all nuclei also scale with one another, despite the fact that the form factors for each site sample different regions of q-space. This result suggests a lack of any q-space structure in the dynamical spin susceptibility that might be expected in the presence of antiferromagnetic correlations. Rather, our results are more compatible with simple quasi-particle scattering. Furthermore, we find that the increase in the electric field gradient at the As cannot be accounted for by LDA calculations, suggesting that structural changes, in particular the position of the As in the unit cell, dominate the NQR response.

Grafe, H.-J.; Lang, G.; Hammerath, F.; Paar, D.; Manthey, K.; Koch, K.; Rosner, H.; Curro, N. J.; Behr, G.; Werner, J.; Leps, N.; Klingeler, R.; Klauss, H.-H.; Litterst, F. J.; Bchner, B.

2009-03-01

87

Field-tuned critical fluctuations in YFe2Al10: Evidence from magnetization, 27Al NMR, and NQR investigations  

NASA Astrophysics Data System (ADS)

We report magnetization, specific heat, and NMR investigations on YFe2Al10 over a wide range of temperature and magnetic field and zero field (NQR) measurements. Magnetic susceptibility, specific heat, and spin-lattice relaxation rate divided by T(1/T1T) follow a weak power law (T-0.4) temperature dependence, which is a signature of the critical fluctuations of Fe moments. The value of the Sommerfeld-Wilson ratio and the linear relation between 1/T1T and ? suggest the existence of ferromagnetic correlations in this system. No magnetic ordering down to 50 mK in Cp(T)/T and the unusual T and H scaling of the bulk and NMR data are associated with a magnetic instability which drives the system to quantum criticality. The magnetic properties of the system are tuned by field wherein ferromagnetic fluctuations are suppressed and a crossover from quantum critical to Fermi-liquid behavior is observed with increasing magnetic field.

Khuntia, P.; Strydom, A. M.; Wu, L. S.; Aronson, M. C.; Steglich, F.; Baenitz, M.

2012-12-01

88

Antiferromagnetic properties of a water-vapor-inserted YBa2 Cu3 O6.5 compound studied byNMR, NQR, and ?SR  

NASA Astrophysics Data System (ADS)

We present a detailed NQR, nuclear magnetic resonance (NMR), and ?SR study of the magnetic phase obtained during a topotactic chemical reaction of YBa2Cu3O6.5 high-temperature superconductor with low-pressure water vapor. Cu65 -enriched samples have been used for NQR/NMR studies which allows to get a good resolution in the Cu(1) NQR and Cu(2) zero field NMR (ZFNMR) spectra. It is shown that the NQR spectrum of the starting material transforms progressively under insertion of water, and almost completely disappears when about one H2O molecule is inserted per unit cell. Similarly, a Cu65 ZFNMR signal characteristic of this water inserted material appears and grows with increasing water content, which indicates that the products of the reaction are nonsuperconducting antiferromagnetic phases in which the copper electronic magnetic moments in the CuO2 bilayers are ordered. The use of Cu65 -enriched samples allowed us to reliably resolve three different copper resonances which correspond to different internal magnetic fields. The antiferromagnetic phases are also felt by proton NMR which reveals two sites with static internal fields of 150 and about 15 Gauss, respectively. ?SR studies performed on a series of samples prepared in the same way as the C65u -enriched ones reveal two muon sites with the same local fields as the proton sites, which vanish at T?400K . This indicates that muons preferentially occupy proton vacancy sites, and that the magnetic phases have similar Nel temperatures as the other bilayer undoped cuprate compounds. An analysis of the internal fields on the different spin probes suggests that they can be all assigned to a single magnetic phase at large water content in which the Cu(1) electron spins order with those of the Cu(2) . The detailed evolution of the spectra with the progressive increase of water content is shown to be compatible with a coexistence of phases during the early stages ot the reaction. It appears that even samples packed in paraffin underwent a transformation of a substantial part of the sample after 6 years storage in atmosphere. Samples packed in Stycast epoxy resin heated moderately to a temperature (200C) undergo a reaction with epoxy decomposition products which yield the formation of the same final compound. It is clear that such effects should be considered quite seriously and avoided in experiments attempting to resolve tiny effects in these materials, such as those performed in some recent neutron scattering experiments.

Dooglav, A. V.; Egorov, A. V.; Mukhamedshin, I. R.; Savinkov, A. V.; Alloul, H.; Bobroff, J.; Macfarlane, W. A.; Mendels, P.; Collin, G.; Blanchard, N.; Picard, P. G.; King, P. J. C.; Lord, J.

2004-08-01

89

/sup 79/ /sup 81/Br NQR spectra of bromochalcogenide complexes of Au(III), Pt(IV), and Pd(II)  

SciTech Connect

The structure of bromochalcogenide complexes of gold, platinum, and palladium, viz., AuBr/sub 4/ x SeBr/sub 3/, PtBr/sub 6/(SeBr/sub 3/)/sub 2/, PtBr/sub 6/(TeBr/sub 3/)/sub 2/, and PdBr/sub 2/(SeBr/sub 2/)/sub 2/, has been established with the aid of the NQR spectra of the bromine atoms. In the compounds of gold and platinum investigated SeBr/sub 3/ groupings are coordinated as ligands, and in the palladium complex SeBr/sub 2/ groupings serve as ligands.

Fokina, Z.A.; Kuznetsov, S.I.; Timoshchenko, N.I.; Bryukhova, E.V.

1987-01-10

90

NMR and NQR study of the electronic and structural properties of Al-Cu-Fe and Al-Cu-Ru quasicrystals  

SciTech Connect

[sup 27]Al and [sup 63,65]Cu NMR is reported for powdered stable Al-Cu-Fe and Al-Cu-Ru icosahedral quasicrystals and crystalline approximants, and for an Al-Pd-Mn single-grain quasicrystal. [sup 27]Al NQR spectra at 4.2 K were observed in Al-Cu-Fe and Al-Cu-Ru samples. From quadrupole-perturbed NMR spectra at different magnetic fields, and from zero-field NQR spectra, a wide distribution of local electric-field gradient (EFG) tensor components and principal-axis-system orientations was found at the Al site. A model EFG calculation based on a 1/1 Al-Cu-Fe approximant successfully explained the observed NQR spectra. The average local gradient is largely determined by the [ital p]-electron wave function at the Al site, while the width of the distribution is due to EFG lattice contribution. Comparison of [sup 63]Cu and [sup 27]Al NMR shows the EFG distribution at the two sites is similar, but the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more [ital s]-type wave function of the conduction electrons. Overall spread of EFG values is well reproduced by calculation based on the approximant. However, the experimental spectra indicate a much larger number of nonequivalent sites when compared with the simulated NQR spectra based on the 1/1 approximant. The short-range, local chemical order is well represented by the approximant, but differences in coordination must be included at intermediate range in the quasicrystal. Measured [sup 27]Al Knight shift, magnetic susceptibility, and nuclear spin-lattice relaxation time as a function of temperature indicate reduced density of states at the Fermi level by a factor of 7 or 8 from the value in Al metal, consistent with the notion of a pseudogap for these quasicrystals. No differences in measured parameters were detected as a function of composition of the quasicrystalline alloys.

Shastri, A.; Borsa, F.; Torgeson, D.R.; Shield, J.E.; Goldman, A.I. (Ames Laboratory, U.S. Department of Energy and Department of Physics Astronomy, Iowa State University, Ames, Iowa 50011 (United States))

1994-12-01

91

Measurement of the 14N nuclear quadrupole resonance frequencies by the solid effect  

NASA Astrophysics Data System (ADS)

1H 14N nuclear quadrupole double resonance using magnetic field cycling between high and low magnetic field and solid effect in the low magnetic field is analyzed in details. The transition probabilities per unit time for the solid-effect transitions are calculated. The double resonance spectra are calculated in the limiting cases of fast and slow nitrogen spin lattice relaxation. The double resonance spectra are measured in histamine and quinolinic acid. The experimental spectra are analyzed and the 14N NQR frequencies are determined.

Seliger, J.; agar, V.

2008-07-01

92

NMR and NQR study of Si-doped (6,0) zigzag single-walled aluminum nitride nanotube as n or P-semiconductors.  

PubMed

Density functional theory (DFT) calculations were performed to investigate the electronic structure properties of pristine and Si-doped aluminum nitride nanotubes as n or P-semiconductors at the B3LYP/6-31G* level of theory in order to evaluate the influence of Si-doped in the (6,0) zigzag AlNNTs. We extended the DFT calculation to predict the electronic structure properties of Si-doped aluminum nitride nanotubes, which are very important for production of solid-state devices and other applications. To this aim, pristine and Si-doped AlNNT structures in two models (Si(N) and Si(Al)) were optimized, and then the electronic properties, the isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (27)Al and (14)N atoms, NQR parameters for the sites of various of (27)Al and (14)N atoms, and quantum molecular descriptors were calculated in the optimized structures. The optimized structures, the electronic properties, NMR and NQR parameters, and quantum molecular descriptors for the Si(N) and Si(Al) models show that the Si(N) model is a more reactive material than the pristine or Si(Al) model. PMID:22588584

Baei, Mohammad T; Peyghan, Ali Ahmadi; Tavakoli, Khadijeh; Babaheydari, Ali Kazemi; Moghimi, Masoumeh

2012-05-16

93

NMR and NQR study of the tetrahedral frustrated quantum spin system Cu2Te2O5Br2 in its paramagnetic phase  

NASA Astrophysics Data System (ADS)

The quantum antiferromagnet Cu2Te2O5Br2 was investigated by NMR and nuclear quadrupole resonance (NQR). The T125e NMR investigation showed that there is a magnetic transition around 10.5 K at 9 T, in agreement with previous studies. From the divergence of the spin-lattice relaxation rate, we ruled out the possibility that the transition could be governed by a one-dimensional divergence of the spin-spin correlation function. The observed anisotropy of the T125e shift was shown to be due to a spin polarization of the 5s2 E doublet of the [TeO3E] tetrahedra, highlighting the importance of tellurium in the exchange paths. In the paramagnetic state, Br NQR and NMR measurements led to the determination of the Br hyperfine coupling and the electric field gradient tensor, and to the spin polarization of Brp orbitals. The results demonstrate the crucial role of bromine in the interaction paths between Cu spins.

Comment, Arnaud; Mayaffre, Hadrien; Mitrovi?, Vesna; Horvati?, Mladen; Berthier, Claude; Grenier, Batrice; Millet, Patrice

2010-12-01

94

Local magnetic and structural properties of the low-temperature orthorhombic to low-temperature tetragonal transition: A 139La NQR study in lightly hole-doped La1.8-xEu0.2SrxCuO4  

Microsoft Academic Search

139La nuclear quadrupole resistance (NQR) and relaxation measurements in lightly hole-doped La1.8-xEu0.2SrxCuO4 have been used to investigate the microscopic properties of the low-temperature orthorhombic to low-temperature tetragonal transition. The transition is characterized by a sharp peak in 139La NQR relaxation rate, indicating phonon softening. We find that the structural phase transition is accompanied by a modification of the spin state.

B. J. Suh; P. C. Hammel; M. Hcker; B. Bchner

1999-01-01

95

^63Cu NMR and NQR study of the stripe phase in La_1.6-xNd_0.40Sr_xCuO_4  

NASA Astrophysics Data System (ADS)

We find that the integrated intensity of ^63Cu NQR in La_1.6-xNd_0.40Sr_xCuO4 decreases dramatically below the stripe ordering temperature.(P.M. Singer et al.),Phys. Rev. B 60, 15345 (1999).(A.W. Hunt et al.),Phys. Rev. Lett. 82, 4300 (1999). Comparison with scattering results indicates that the missing signal represents the stripe order parameter. We observe that the loss of signal is sharpest for x ~1/8, indicating that x ~1/8 is the optimal concentration for stripe formation. This work was supported by the National Science Foundation (DMR 99-71266, DMR 98-08941), the A.P. Sloan Foundation, the Mitsui Foundation, and the Platzman Fund.

Singer, Philip M.; Hunt, Allen W.; Cederstrm, Agneta F.; Imai, Takashi

2000-03-01

96

NMR and NQR Studies on Non-centrosymmetric Superconductors Re7B3, LaBiPt, and BiPd  

NASA Astrophysics Data System (ADS)

We report the nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements for non-centrosymmetric superconductors Re7B3, LaBiPt, and BiPd containing heavy elements. For all three compounds, the spin--lattice relaxation rate 1/T1 shows a coherence peak just below Tc and decreases exponentially at low temperatures, which indicates that an isotropic superconducting gap is dominant in these compounds. In BiPd, the height of the coherence peak just below Tc is much suppressed, which suggests that there exists a substantial component of gap with nodes in this compound. Our results indicate that heavy element is not the only factor, but the extent of inversion symmetry breaking is also important to induce a large spin--orbit coupling and an unconventional superconducting state.

Matano, Kazuaki; Maeda, Satoki; Sawaoka, Hiroki; Muro, Yuji; Takabatake, Toshiro; Joshi, Bhanu; Ramakrishnan, Srinivasan; Kawashima, Kenji; Akimitsu, Jun; Zheng, Guo-qing

2013-08-01

97

Frequency Spectrum.  

National Technical Information Service (NTIS)

Uses a pictorial representation of the frequency spectrum to identify power frequencies, audio frequencies, radio frequencies, VhF, UhF, and microwaves. Given a specific wavelength, calculates the frequency. Given either frequency or wavelength, calculate...

1994-01-01

98

Local magnetic and structural properties of the low-temperature orthorhombic to low-temperature tetragonal transition: A ¹³⁹La NQR study in lightly hole-doped La{sub 1.8-x}Eu{sub 0.2}SrCuO  

Microsoft Academic Search

¹³⁹La nuclear quadrupole resistance (NQR) and relaxation measurements in lightly hole-doped La{sub 1.8-x}Eu{sub 0.2}SrCuO have been used to investigate the microscopic properties of the low-temperature orthorhombic to low-temperature tetragonal transition. The transition is characterized by a sharp peak in ¹³⁹La NQR relaxation rate, indicating phonon softening. We find that the structural phase transition is accompanied by a modification of the

B. J. Suh; P. C. Hammel; M. Huecker; B. Buechner

1999-01-01

99

Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We report detailed 17O, 139La, and 63,65Cu Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La1.875Ba0.125CuO4 single crystal and in oriented powder samples of La1.8- x Eu0.2Sr x CuO4. We observe a partial wipeout of the 17O NMR intensity and a simultaneous drop of the 17O electric field gradient (EFG) at low temperatures where the spin stripe order sets in. In contrast, the 63,65Cu intensity is completely wiped out at the same temperature. The drop of the 17O quadrupole frequency is compatible with a charge stripe order. The 17O spin lattice relaxation rate shows a peak similar to that of the 139La, which is of magnetic origin. This peak is doping dependent and is maximal at x ? 1/8.

Grafe, H.-J.; Curro, N. J.; Young, B. L.; Vyalikh, A.; Vavilova, J.; Gu, G. D.; Hcker, M.; Bchner, B.

2010-10-01

100

209Bi NMR and NQR investigation of the small-gap semiconductor Ce3Bi4Pt3  

Microsoft Academic Search

We report measurements of the temperature dependence of the 209Bi nuclear quadrupole resonance frequency nuQ, the Knight shift K, and the spin-lattice relaxation rate 1\\/T1 in the small-gap semiconductor Ce3Bi4Pt3 between 1.8 and 300 K. Corresponding measurements also are reported for the nonmagnetic metallic isomorph La3Bi4Pt3. The nuQ data in the Ce compound show a characteristic departure from metallic-to-insulating behavior

A. P. Reyes; R. H. Heffner; P. C. Canfield; J. D. Thompson; Z. Fisk

1994-01-01

101

209Bi NMR and NQR investigation of the small-gap semiconductor Ce3Bi4Pt3  

NASA Astrophysics Data System (ADS)

We report measurements of the temperature dependence of the 209Bi nuclear quadrupole resonance frequency ?Q, the Knight shift K, and the spin-lattice relaxation rate 1/T1 in the small-gap semiconductor Ce3Bi4Pt3 between 1.8 and 300 K. Corresponding measurements also are reported for the nonmagnetic metallic isomorph La3Bi4Pt3. The ?Q data in the Ce compound show a characteristic departure from metallic-to-insulating behavior when the sample is cooled below TM=80 K, the temperature of the susceptibility maximum, attributable to a loss of low-frequency vibrational modes in the insulating state. The Knight shift has both isotropic and axial components; this anisotropy originates from the presence of Ce via a transferred hyperfine coupling between Ce 4f and conduction electrons. An s-f exchange constant >=0.4 eV is found, consistent with hybridization in other rare-earth intermetallic compounds. A change in the scaling between the susceptibility and both the isotropic and axial Knight shifts at temperature TM provides evidence that hybridization between the Ce 4f orbitals and the conduction electrons is responsible for the gap structure. The temperature dependence of the 1/T1 data is consistent with a model electronic density of states possessing a temperature-independent gap ? of 180 K and a bandwidth of the order of 1600 K. The temperature dependence of 1/T1 can also be fit well with a temperature-dependent gap with ?(0) also ~=180 K.

Reyes, A. P.; Heffner, R. H.; Canfield, P. C.; Thompson, J. D.; Fisk, Z.

1994-06-01

102

Frequency curves  

USGS Publications Warehouse

This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.

Riggs, H. C.

1968-01-01

103

Frequency Synthesizer.  

National Technical Information Service (NTIS)

Dual phase lock loops are used to provide a rapid switching, low power, low spurious and fine resolution frequency synthesizer for various radio applications. The first phase lock loop provides for coarse frequency adjustment, and the second phase lock lo...

E. J. Nossen

1978-01-01

104

Lifetimes of the first 7 ? \\/2 levels in 35 Cl and 37 Cl  

Microsoft Academic Search

An interesting research line in the ld~ subshell is that of establishing the M2-transition strength from the first ~- states (generally described as single-particle states) to the ~- ground state. These data can help one to make a choice among the proposed models for these nuclei; i.e. various kinds of shell-model calculations, weak or strong coupling (1.a). We have been

F. Brandolini; M. De Poli; C. Rossi Alvarez

1973-01-01

105

Local distortions in the BiO6-octahedra sublattice of BaPbxBi1-xO3 as seen by a137Ba NMR/NQR  

NASA Astrophysics Data System (ADS)

The a137Ba NMR and NQR spectra as well as the spin-lattice relaxation rate were measured for the first time in the BaPbxBi1-xO3 samples with x = 0.91 (normal metal), x = 0.75 (superconductor) and x = 0.64 (semiconductor). The strong quadrupole broadening of the NMR lines with lowering temperature was found for all the samples. An evolution of static distortions in the BiO6-octahedra sublattice along with asymmetry of the electric field gradient at the Ba-sites is discussed. This asymmetry caused by the nearest non-cubic surrounding of barium is originated from the temperature dependent tilt of BiO6-octahedra. Spin-lattice relaxation rate of a137Ba is monitored by fluctuating part of electric field gradient at the Ba-site and its exponential growth at low temperatures evidences the thermally activated collective rotations of BiO6-octahedra around their static tilt. An activation energy and a strength of these dynamic distortions are evaluated and found to increase in going from metallic to semiconducting phase of BaPbxBi1-xO3.

Verkhovskii, S. V.; Gerashenko, A. P.; Zhdanov, Yu. I.; Mikhalev, K. N.; Sagaradze, I. V.; Medvedev, Eu. Yu.; Cheshnitskii, S. M.; Pletnev, R. N.; Kumagai, K.; Piskunov, Yu. V.; Yakubovskii, A. Yu.

1997-02-01

106

Single-spin fluid, spin gap, and [ital d]-wave pairing in YBa[sub 2]Cu[sub 4]O[sub 8]: A NMR and NQR study  

SciTech Connect

We present results of [sup 17]O and [sup 63,65]Cu nuclear magnetic resonance (NMR) and nuclear quadrupolar resonance (NQR) studies in the normal and superconducting state of the 82-K superconductor YBa[sub 2]Cu[sub 4]O[sub 8]. The various components of the Cu and O Knight-shift tensors show strong but similar temperature dependences over the temperature range from 8.5 to 300 K in both the CuO[sub 2] planes and the chains, supporting the picture that there is only one spin component in the planes and the chains, although with different susceptibilities. The oxygen data obey the Korringa relation. This may be interpreted as Fermi-liquid behavior of the electronic system far away from the antiferromagnetic wave vector. The temperature dependence of both the planar Cu and O shift tensors and the planar Cu spin-lattice relaxation rate suggest the opening of a pseudo-spin-gap well above [ital T][sub [ital c

Bankay, M.; Mali, M.; Roos, J.; Brinkmann, D. (Physik-Institut, Universitaet Zuerich, 8057 Zuerich (Switzerland))

1994-09-01

107

Temperature-Induced Change in the Magnitude of the Effective Density of States: A NQR/NMR Study of the A-Site-Ordered Perovskite System CaCu3Ru4O12  

NASA Astrophysics Data System (ADS)

NQR/NMR measurements, including spin-lattice relaxation rate (1/T1) and Knight shift (K) evaluations, have been carried out for Cu and Ru nuclear spins in the A-site ordered perovskite system CaCu3Ru4O12, which exhibits a mass-enhancement-like behavior although it possesses no f electrons. The temperature evolution of T1 for Cu, which was measured up to 700 K, exhibits 1/T1T = constant behavior at high enough temperatures. This clearly denies the existence of a Cu localized moment, which was previously suggested as the origin of the mass enhancement in a dense Kondo scenario. Furthermore, K and (1/T1T) for Cu exhibit significant temperature dependences with two characteristic temperatures TF=20 K and TX=180 K, suggesting a temperature-induced transition of microscopic electronic character at TF and TX. We propose a two-band model, where the effective density of states for one of the bands shows a significant temperature dependence in TF

Kato, Harukazu; Tsuruta, Takuya; Matsumura, Masahiro; Nishioka, Takashi; Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, Russell E.

2009-05-01

108

Nuclear magnetic resonance with dc SQUID (Super-conducting QUantum Interference Device) preamplifiers  

SciTech Connect

Sensitive radio-frequency (rf) amplifiers based on dc Superconducting QUantum Interface Devices (SQUIDS) are available for frequencies up to 200 MHz. At 4.2 K, the gain and noise temperature of a typical tuned amplifier are 18.6 +- 0.5 dB and 1.7 +- 0.5 K at 93 MHz. These amplifiers are being applied to a series of novel experiments on nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR). The high sensitivity of these amplifiers was demonstrated in the observation of ''nuclear spin noise'', the emission of photons by /sup 35/Cl nuclei in a state of zero polarization. In the more conventional experiments in which one applies a large rf pulse to the spins, a Q-spoiler, consisting of a series array of Josephson junctions, is used to reduce the Q of the input circuit to a very low value during the pulse. The Q-spoiler enables the circuit to recover quickly after the pulse, and has been used in an NQR experiment to achieve a sensitivity of about 2 /times/ 10/sup 16/ nuclear Bohr magnetons in a single free precession signal with a bandwidth of 10 kHz. In a third experiment, a sample containing /sup 35/Cl nuclei was placed in a capacitor and the signal detected electrically using a tuned SQUID amplifier and Q-spoiler. In this way, the electrical polarization induced by the precessing Cl nuclear quadrupole moments was detected: this is the inverse of the Stark effect in NQR. Two experiments involving NMR have been carried out. In the first, the 30 MHz resonance in /sup 119/Sn nuclei is detected with a tuned amplifier and Q-spoiler, and a single pulse resolution of 10/sup 18/ nuclear Bohr magnetons in a bandwidth of 25 kHz has been achieved. For the second, a low frequency NMR system has been developed that uses an untuned input circuit coupled to the SQUID. The resonance in /sup 195/Pt nuclei has been observed at 55 kHz in a field of 60 gauss. 23 refs., 11 figs.

Fan, N.Q.; Heaney, M.B.; Clark, J.; Newitt, D.; Wald, L.; Hahn, E.L.; Bierlecki, A.; Pines, A.

1988-08-01

109

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, Vronique; Jendrzejewski, Nathalie; Agrinier, Pierre; Javoy, Marc; Evrard, Marc

2005-11-01

110

Polyvinylidene fluoride microfilter formation by 35Cl9+, 58Ni10+, and 63Cu11+ ion bombardment and alkali etching  

NASA Astrophysics Data System (ADS)

We have studied the process of producing microfilters of polyvinylidene fluoride by Cl, Ni, and Cu ion bombardment and alkali etching. The effects of ion energy and mass on the resulting hole diameters were examined. The hole diameter perforated in PVDF increases with increasing mass and decreases with increasing kinetic energy of the ions. The hole diameters on the surface of the film change little, but the effective hole diameter, which depends on the narrowest site along the long tube, decreases with increasing kinetic energy of ion. This is inferred from the angle of taper in the canal. The axial and lateral etching rates of the long canal were obtained by measurements of gaseous flow through the holes. Clear-cut entrances for the holes were observed by SEM and the cylindrical and parallel canals were shown by TEM. The doses per film are calculated to be about 2-6 Mrad at a hole density of 3 108/cm2.

Yoshihide, Komaki; Niro, Ishikawa; Tsutomu, Sakurai; Norio, Morishita; Matae, Iwasaki

1988-09-01

111

Radio frequency interference  

Microsoft Academic Search

The article consists of a Powerpoint presentation on radio frequency interference. The areas discussed include: radio frequency interference; electromagnetic interference; mobile Internet device and wireless sensitivity requirement.

H. Skinner; K. Slattery

2008-01-01

112

High Frequency Via.  

National Technical Information Service (NTIS)

Techniques that enable the transitioning of high frequency signals on a printed wiring board processed in accordance with industry standards (such as the IPC specifications) are disclosed. One embodiment provides a high frequency via structure for a print...

J. S. Greeley

2004-01-01

113

Direct SAW Frequency Synthesizer.  

National Technical Information Service (NTIS)

A frequency synthesizer utilizing three elementary direct synthesizers to achieve fast frequency hopping among 219 tones is described. The elementary synthesizers used for the two 9-channel sets of tones consist of a comb generator followed by a surface a...

A. J. Budreau P. H. Carr

1978-01-01

114

Minimax frequency invariant beamforming  

Microsoft Academic Search

Introduction: The frequency invariant beamformer (FIB) is a beam-former of which the response is approximately invariant for a designed frequency range. The technique mostly used for the design of an FIB is FIR or IIR filter coefficient optimisation that employs some analytical relations between frequency responses of filters located on different antenna array elements of the FIB, with utilisation of

I. D. Dotlic?

2004-01-01

115

Laser frequency standards  

Microsoft Academic Search

This paper gives a brief review of the present status of the problem of developing optical frequency standards. The basic principles of laser-frequency stabilization based on narrow nonlinear optical resonances are presented. The basic physical factors determining the shape and the shift of narrow resonances are discussed. The design of the modern laser frequency standard, based on the use of

Sergei N Bagaev; V P Chebotaev

1986-01-01

116

Femtosecond Optical Frequency Combs  

NASA Astrophysics Data System (ADS)

A laser frequency comb allows the conversion of the very rapid oscillations of visible light down to frequencies that can be handled with conventional electronics. This has enabled the most precise laser spectroscopy experiments yet, to determine fundamental constants and to limit their possible slow drift. Using an optical frequency reference in combination with a laser frequency comb has made it possible to construct all optical atomic clocks. Frequency combs are also used to calibrate astronomical spectrographs and might reach an accuracy that is sufficient to observe the change of the expansion rate of the universe in real time.

Udem, Thomas; Holzwarth, Ronald; Hnsch, Theodor

117

Co Nuclear-Quadrupole-Resonance Measurements on NaxCoO2.yH2O - Phase Diagram for Bilayered-Hydrate System  

Microsoft Academic Search

Co nuclear quadrupole resonance (NQR) measurements were performed on several superconducting (SC) NaxCoO2.yH2O samples with different values of a SC transition temperature (Tc). The measurements were done for the investigation of the relationship between Tc and microscopic physical quantities derived from the Co NQR. We measured Co-NQR frequency nuQ and the nuclear-lattice relaxation rate 1\\/T1 the Co site, and found

Yoshihiko Ihara; Hideo Takeya; Kenji Ishida; Chishiro Michioka; Kazuyoshi Yoshimura; Kazunori Takada; Takayoshi Sasaki; Hiroya Sakurai; Eiji Takayama-Muromachi

2006-01-01

118

Frequency Selective Buildings Through Frequency Selective Surfaces  

Microsoft Academic Search

This paper proposes the deployment of frequency selective surfaces (FSS) in indoor wireless environments and investigates their effect on radio wave propagation. FSS can be deployed to selectively confine radio propagation in indoor areas, by artificially increasing the radio transmission loss naturally caused by building walls. FSS can also be used to channel radio signals into other areas of interest.

Marios Raspopoulos; Stavros Stavrou

2011-01-01

119

Frequency Dependence of Vibrothermography  

NASA Astrophysics Data System (ADS)

It has long been postulated that vibrothermographic heating-the heating of cracks due to sound or vibration-induced rubbing-may be frequency dependent. It has been difficult to factor out the innate frequency dependence of the heat-generation process from the geometry-dependent mode structure. We present experiments showing the heating of cracks in slender Inconel/Titanium specimens at transverse resonance. Different resonant modes vibrate at different frequencies but load the crack in the same way (Mode I). The results show a clear increase of heating with vibration frequency.

Zhang, Wenjun; Holland, Stephen D.; Renshaw, Jeremy

2010-02-01

120

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. Hnsch

2002-01-01

121

Improving Food Frequency Questionnaires  

Microsoft Academic Search

In an attempt to improve data quality and ease of administration of standard self-administered food frequency questionnaires, various alternative approaches were tried for inquiring about frequency of consumption, portion size, seasonal intake, and food preparation. Evaluation consisted of a cognitive interviewing method in which respondents verbalize their thought process while completing several variations of a questionnaire. Interviewers observed and asked

AMY F SUBAR; FRANCES E THOMPSON; ALBERT F SMITH; JARED B JOBE; REGINA G ZIEGLER; NANCY POTISCHMAN; ARTHUR SCHATZKIN; ANNE HARTMAN; CHRISTINE SWANSON; LAURA KRUSE; RICHARD B HAYES; DENISE RIEDEL LEWIS; LINDA C HARLAN

1995-01-01

122

Master International Frequency List.  

National Technical Information Service (NTIS)

The International Frequency List, in magnetic tape format, contains particulars of radio frequency assignments between 10 kHz and 40,000 gHz and of assignments to broadcasting stations in Regions 1, 2 and 3, as recorded in the Master International Frequen...

1971-01-01

123

IGBT high frequency operation  

Microsoft Academic Search

IGBT (insulated gate bipolar transistor) devices have been designed into low frequency (<20 kHz) power controls for many types of equipment. This equipment includes: high voltage applications such as 120 V to 440 V motor controls; AC power line conditioning; and automotive ignition systems. It can be quite disconcerting to have an IGBT power control design that generates radio frequency

R. J. Valentine

1996-01-01

124

Frequency Control Devices.  

National Technical Information Service (NTIS)

The objective of the program was to explore advanced concepts in the design and manufacture of frequency control devices. The program was designed to lead to low cost mass production, high performance components, increased levels of communication system c...

K. M. Lakin

1995-01-01

125

Radio Frequency Radiation Hazards.  

National Technical Information Service (NTIS)

Explains the biological (personnel) and non-biological (feed and fuel) effects of RF radiation. The frequency spectrum is explained and the difference between ionizing and non-ionizing radiation is illustrated.

1994-01-01

126

Effective Frequency Technique.  

National Technical Information Service (NTIS)

An effective monochromatic frequency technique is described to represent the effects of finite spectral bandwidth for active and passive measurements centered on an absorption line, a trough region, or a slowly varying spectral feature. For Gaussian and r...

C. L. Korb C. Y. Weng

2003-01-01

127

Homodyne Frequency Multiplier Concept.  

National Technical Information Service (NTIS)

The technical note describes experiments conducted with broadband single ended, single balanced and double balanced mixers connected through a hybrid device to allow both the Radio Frequency (RF) and Local Oscillator (LO) ports to be driven by the same si...

G. J. Rast T. A. Barley

1971-01-01

128

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

129

Fiber optic frequency transfer link  

Microsoft Academic Search

A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an

Lori E. Primas; Richard L. Sydnor; George F. Lutes

1991-01-01

130

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

131

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, M. L.; Yesinowski, J. P.; Miller, J. B.

1994-03-01

132

Optical frequency standards  

NASA Astrophysics Data System (ADS)

The evolution of atomic frequency standards since Essen's atomic clock fifty years ago has been considerable both in respect of microwave and optical standards. In particular, the development of trapping and laser cooling techniques for both atoms and ions has played a major role. This paper reviews the status of the development of single cold trapped ion and cold trapped atom optical frequency standards. Recent results show comb measurements of trapped ion optical frequency standards with accuracies close to Cs fountain limited operation. The factors affecting future stability and reproducibility are discussed. The opportunities for future standards capable of approaching reproducibility at the 10-18 level are outlined, together with the likely limitations arising.

Gill, Patrick

2005-06-01

133

Novel superconducting characteristics and unusual normal-state properties in iron-based pnictide superconductors: 57FeNMR and 75AsNQR/NMR studies in REFeAsO1-y (RE = La, Pr, Nd) and Ba0.6K0.4Fe2As2  

NASA Astrophysics Data System (ADS)

We discuss the novel superconducting characteristics and unusual normal-state properties of iron (Fe)-based pnictide superconductors REFeAsO1-y (RE = La, Pr, Nd) and Ba0.6K0.4Fe2As2 (Tc = 38 K) by means of 57FeNMR and 75AsNQR/NMR. In the superconducting state of LaFeAsO0.7 (Tc = 28 K), the spin component of the 57Fe-Knight shift decreases to almost zero at low temperatures, which provide firm evidence of the superconducting state formed by spin-singlet Cooper pairing. The nuclear spin-lattice relaxation rates (1/T1) in LaFeAsO0.7 and Ba0.6K0.4Fe2As2 exhibit a T3-like dependence without a coherence peak just below Tc, indicating that an unconventional superconducting state is commonly realized in these Fe-based pnictide compounds. All these events below Tc are consistently argued in terms of an extended s-wave pairing with a sign reversal of the order parameter among Fermi surfaces. In the normal state, 1/T1T decreases remarkably upon cooling for both the Fe and As sites of LaFeAsO0.7. In contrast, it gradually increases upon cooling in Ba0.6K0.4Fe2As2. Despite the similarity between the superconducting properties of these compounds, a crucial difference was observed in their normal-state properties depending on whether electrons or holes are doped into the FeAs layers. These results may provide some hint to address a possible mechanism of Fe-based pnictide superconductors.

Mukuda, H.; Terasaki, N.; Yashima, M.; Nishimura, H.; Kitaoka, Y.; Iyo, A.

2009-05-01

134

Frequency division multiplexed imaging  

NASA Astrophysics Data System (ADS)

In this paper, we describe frequency division multiplexed imaging (FDMI), where multiple images are captured simultaneously in a single shot and can later be extracted from the multiplexed image. This is achieved by spatially modulating the images so that they are placed at different locations in the Fourier domain. The technique assumes that the images are band-limited and they are placed at non-overlapping frequency regions through the modulation process. The FDMI technique can be used for extracting sub-exposure information and in applications where multiple cameras or captures are needed, such as high-dynamic-range and stereo imaging. We present experimental results to illustrate the FDMI idea.

Gunturk, Bahadir K.; Feldman, Martin

2013-01-01

135

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.

Blind, Perkins S.

2012-06-26

136

The microwave frequency method  

NASA Astrophysics Data System (ADS)

We present new results showing that when sufficient microwave power is employed the grains carrying the natural remanent moment (NRM) that are able to absorb microwaves reach their blocking temperature in less than 10 ms, and the sample temperature at the end of this very short time has only increased by about 30 C. We also show that because large gaps exist in the spin-wave frequency of small particles, some grains are unable to absorb because they are too small, and others because they are too large. A large number of results have been published, that were obtained using frequencies close to 14 GHz, using what has been called the microwave Thellier method. However, as Biggin has pointed out [Biggin, A.J., et al., 2007. A comparison of a quasi-perpendicular method of absolute palaeointensity determination with other thermal and microwave techniques. Earth Planet. Sci. Lett. 257, 564-581] the microwaves constitute a marginal improvement on thermal methods, with the attendant alteration problems. We wish to propose a radically new method here, the microwave frequency method, where the microwave frequency is varied, selectively magnetizing and demagnetizing grains of different sizes thereby keeping the sample temperature so low that alteration is avoided completely.

Walton, Derek; Boehnel, Harald N.

2008-04-01

137

LOW FREQUENCY NOISE LEGISLATION  

Microsoft Academic Search

Introduction. Legislation regarding low frequency noise (LFN, <500 Hz including infrasound), when existent, is highly deficient. Not only is it expressed in dBA, actually defeating the purpose of evaluating LFN, but no concrete measures are prescribed if excessive LFN is identified. The status quo notion that acoustical phenomena are only harmful when perceived by humans cannot be sustained given current

Mariana Alves-Pereira; Jersy Motylewski; Elzbieta Kotlicka; Nuno A. A. Castelo

138

Bounce frequency fishbone analysis  

Microsoft Academic Search

Large amplitude bursting modes are observed on NSTX, which are identified as bounce frequency fishbone modes(PDX Group, Princeton Plasma Physics Lab, Phys Rev. Lett) 50, 891 (1983)^,(L. Chen, R. B. White, and M. N. Rosenbluth Phys Rev. Lett) 52, 1122 (1984). The identification is carried out using numerical equilibria obtained from TRANSP( R. V. Budny, M. G. Bell A. C.

Roscoe White; Eric Fredrickson; Liu Chen

2002-01-01

139

Dual frequency optical cavity  

DOEpatents

Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a "T" configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

George, E. Victor (Livermore, CA); Schipper, John F. (Palo Alto, CA)

1985-01-01

140

Low frequency electromagnetic devices  

Microsoft Academic Search

The design, simulation and implementation of low frequency electromagnetic devices on planar structures are given. Planar devices and components are designed and built on a ceramic-based material that allowed a surface-mount (SMT) application. Method of moment based electromagnetic field solvers are used to verify the design of the devices. Planar devices and components are then implemented and tested. Simulation results

Abdullah Eroglu

2009-01-01

141

Riser High Frequency Response  

Microsoft Academic Search

Offshore risers' susceptibility to high frequency response increases with the water depth i.e. the length of the riser. Whereas it is well- known that fatigue damage due to vortex induced vibrations needs to be accounted for in the riser design the effect of vessel springing is less acknowledged. An analysis of a flexible riser hydrodynamic behavior induced by springing high

Jelena Vidic-Perunovic; Niels J Rishj Nielsen

142

Improved Frequency Standard Design.  

National Technical Information Service (NTIS)

The purpose of this program is two-fold: to improve the performance of the Frequency Standard and to reduce its cost through the further use of integrated circuits and Master Slice design of special purpose integrated circuits. Work is progressing satisfa...

1967-01-01

143

HF (High Frequency) Communications Frequency-Management Procedure for Forecasting the Frequency of Optimum Transmission.  

National Technical Information Service (NTIS)

This report describes a procedure for forecasting the Frequency of Optimum Transmission (FOT) on a high-frequency communications path when the Maximum Observable Frequency (MOF) on another path and an historical record of the correlations of MOFs measured...

M. Daehler

1984-01-01

144

Low frequency ultrasounds in medicine  

Microsoft Academic Search

Ultrasound energy at frequency lower than 200 kHz has been used recently in medical field for transdermal drug transport and therapy with experimental results better than high frequency ultrasound at few MHz. As a consequence, the low frequency ultrasounds are gained more interest in the medical field. In the paper we review the most promising application of low frequency ultrasounds

A. S. Fiorillo; D. Grimaldi; S. A. Pullano

2009-01-01

145

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

146

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. 4 figs.

Kronberg, J.W.

1994-05-31

147

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, J.W.

1991-03-05

148

Frequency steerable acoustic transducers  

NASA Astrophysics Data System (ADS)

Structural health monitoring (SHM) is an active research area devoted to the assessment of the structural integrity of critical components of aerospace, civil and mechanical systems. Guided wave methods have been proposed for SHM of plate-like structures using permanently attached piezoelectric transducers, which generate and sense waves to evaluate the presence of damage. Effective interrogation of structural health is often facilitated by sensors and actuators with the ability to perform electronic, i.e. phased array, scanning. The objective of this research is to design an innovative directional piezoelectric transducer to be employed for the localization of broadband acoustic events, or for the generation of Lamb waves for active interrogation of structural health. The proposed Frequency Steerable Acoustic Transducers (FSATs) are characterized by a spatial arrangement of active material which leads to directional characteristics varying with frequency. Thus FSATs can be employed both for directional sensing and generation of guided waves without relying on phasing and control of a large number of channels. The analytical expression of the shape of the FSATs is obtained through a theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. The FSAT configurations analyzed in this work are a quadrilateral array and a geometry which corresponds to a spiral in the wavenumber domain. The quadrilateral array is experimentally validated, confirming the concept of frequency-dependent directionality. Its limited directivity is improved by the Wavenumber Spiral FSAT (WS-FSAT), which, instead, is characterized by a continuous frequency dependent directionality. Preliminary validations of the WS-FSAT, using a laser doppler vibrometer, are followed by the implementation of the WS-FSAT as a properly shaped piezo transducer. The prototype is first used for localization of acoustic broadband sources. Signal processing algorithms and related imaging techniques for damage location are also presented. Finally, the WS-FSAT has also been experimentally validated in generation.

Senesi, Matteo

149

Rapid Frequency Scan EPR  

PubMed Central

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 5 T2 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 5 T2. 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 5 T2, 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 B1, 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.

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

2011-01-01

150

Fiber optic frequency transfer link  

NASA Astrophysics Data System (ADS)

A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an adjustable phase. A fiber optic transmitter at the reference unit modulates a light beam with the reference frequency and transmits the light beam into the fiber optic cable. A 50/50 reflector at the remote unit reflects a first portion of the light beam from the reference unit back into the fiber optic cable to the reference unit. A first fiber optic receiver disposed at the remote unit receives a second portion of the light beam and demodulates the reference frequency to be used at the remote unit. A second fiber optic receiver disposed at the reference unit receives the first portion of the light beam and demodulates a reference frequency component. A phase conjugator is connected to the frequency source for comparing the phase of the reference frequency component to the phase of the reference frequency modulating the light beam being transmitted from the reference unit to maintain a conjugate (anti-symmetric) relationship between the reference frequency component and the reference frequency modulating the light beam where virtually no phase difference exists between the phase of the reference frequency component and the phase of the reference frequency modulating the light beam.

Primas, Lori E.; Sydnor, Richard L.; Lutes, George F.

1991-07-01

151

Reductive dechlorination of TCE by chemical model systems in comparison to dehalogenating bacteria: insights from dual element isotope analysis (13C/12C, 37Cl/35Cl).  

PubMed

Chloroethenes like trichloroethene (TCE) are prevalent environmental contaminants, which may be degraded through reductive dechlorination. Chemical models such as cobalamine (vitamin B12) and its simplified analogue cobaloxime have served to mimic microbial reductive dechlorination. To test whether in vitro and in vivo mechanisms agree, we combined carbon and chlorine isotope measurements of TCE. Degradation-associated enrichment factors ?(carbon) and ?(chlorine) (i.e., molecular-average isotope effects) were -12.2 0.5 and -3.6 0.1 with Geobacter lovleyi strain SZ; -9.1 0.6 and -2.7 0.6 with Desulfitobacterium hafniense Y51; -16.1 0.9 and -4.0 0.2 with the enzymatic cofactor cobalamin; -21.3 0.5 and -3.5 0.1 with cobaloxime. Dual element isotope slopes m = ??(13)C/ ??(37)Cl ? ?(carbon)/?(chlorine) of TCE showed strong agreement between biotransformations (3.4 to 3.8) and cobalamin (3.9), but differed markedly for cobaloxime (6.1). These results (i) suggest a similar biodegradation mechanism despite different microbial strains, (ii) indicate that transformation with isolated cobalamin resembles in vivo transformation and (iii) suggest a different mechanism with cobaloxime. This model reactant should therefore be used with caution. Our results demonstrate the power of two-dimensional isotope analyses to characterize and distinguish between reaction mechanisms in whole cell experiments and in vitro model systems. PMID:23627862

Cretnik, Stefan; Thoreson, Kristen A; Bernstein, Anat; Ebert, Karin; Buchner, Daniel; Laskov, Christine; Haderlein, Stefan; Shouakar-Stash, Orfan; Kliegman, Sarah; McNeill, Kristopher; Elsner, Martin

2013-05-28

152

Trapped Ion Frequency Standards  

NASA Astrophysics Data System (ADS)

Trapped ions form the basis for a high performance frequency standard since long interrogation times are possible in a nearly perturbation free environment. At JPL, approximately 2x10^6 ^199Hg+ ions are confined in a Linear Ion Trap (LIT)(J.D. Prestage, G.J. Dick, L. Maleki, J.Appl. Phys. 66, 1013 (1989).) and cooled to near room temperature by collisions with a helium buffer gas. Atomic state selection is accomplished by optical pumping using 194 nm light from a ^202Hg lamp and the 40.5 GHz ground state hyperfine transition is interrogated using Ramsey successive oscillatory fields. With an interrogation time of 8 seconds, the measured fractional frequency stability is ?_y(?)=6.5x10-14/ ?^1/2, where ? is the averaging interval in seconds. The frequency stability measured between two Hg^+ ion standards currently exceeds other standards between 10,000 seconds and 1 month. (R.L. Tjoelker, J.D. Prestage, L. Maleki, in Symp. on Freq. Standards & Metrology, Woods Hole MA,(1995).) The long term differential drift between an ion standard and a cavity tuned hydrogen maser over a 5 month interval was measured to be (2.1 0.8)x10-16/day. A new two segment linear ion trap currently under development separates the ion loading and atomic state selection region from the microwave interrogation region. Initial measurements indicate a stability of ?_y(?)=5.6x10-14/ ?^1/2. Operating at reduced linear ion densities, this configuration should allow for improved accuracy and long term stability.

Tjoelker, R. L.

1996-03-01

153

RADIO FREQUENCY ATTENUATOR  

DOEpatents

A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

Giordano, S.

1963-11-12

154

Pronunciation and the Frequency Meaningfulness Effect in Children's Frequency Discrimination.  

ERIC Educational Resources Information Center

|In an absolute frequency judgment task, 130 sixth graders received either high-frequency (Hi-F), low-frequency, high-meaningfulness (Lo-F/Hi-M), or low-frequency, low-meaningfulness (Lo-F/Lo-M) words selected from the 1944 Thorndike-Lorge list. Subjects were asked to either pronounce the words aloud, listen to the examiner prounounce the written

Ghatala, Elizabeth S.; And Others

155

HF (High Frequency) Maximum Usable Frequency (MUF) Model Uncertainty Assessment.  

National Technical Information Service (NTIS)

A statistical analysis of observed oblique sounder median maximum observed frequencies (MOF) and predicted maximum usable frequencies (MUF) was used to assess the accuracy of high-frequency MUF prediction. A database of 13,054 hours of oblique sounder MOF...

T. N. Roy D. B. Sailors

1987-01-01

156

Frequency selective bolometers.  

PubMed

We propose a concept for radiometry in the millimeter, the submillimeter, and the far-IR spectral regions, the frequency selective bolometer (FSB). This system uses a bolometer as a coupled element of a tuned quasi-optical interference filter in which the absorption, the transmission, and the reflection characteristics of the filter depend on the frequency in a controlled manner. Several FSB's can be cascaded within a straight light pipe to produce a high-efficiency, compact, multiband radiometer. A prototype design is presented together with its anticipated performance based on a one-dimensional transmission-line model. Instruments based on FSB technology should have several advantages over current multiband bolometric radiometers including smaller and more compact cryogenic optics, reduced demands on cryostat size and weight, high coupling efficiency, minimum constraints on the geometry in the focal plane. An FSB system can be configured as a multiband, close-packed focal-plane array, permitting efficient use of the throughput of a telescope. PMID:21127568

Kowitt, M S; Fixsen, D J; Goldin, A; Meyer, S S

1996-10-01

157

Laser-frequency multiplication  

SciTech Connect

A high quality mode locked pulse train was obtained at 9.55 micrometers, the CO2 wavelength chosen for frequency doubling into the atmospheric window at 4.8 micrometers. The pulse train consists of a 3 micro sec burst of 1.5 nsec pulses separated by 40 nsec, in a TEM(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 micrometer band radiation. Secondly, a particular rotational line, the P20 at 9.55 micrometers, 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.

Not Available

1991-11-01

158

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. Copyright 2013 John Wiley & Sons, Ltd. PMID:23609602

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

2013-04-23

159

Frequency selective bolometers  

NASA Astrophysics Data System (ADS)

We propose a concept for radiometry in the millimeter, the submillimeter, and the far-IR spectral regions, the frequency selective bolometer (FSB). This system uses a bolometer as a coupled element of a tuned quasi-optical interference filter in which the absorption, the transmission, and the reflection characteristics of the filter depend on the frequency in a controlled manner. Several FSB's can be cascaded within a straight light pipe to produce a high-efficiency, compact, multiband radiometer. A prototype design is presented together with its anticipated performance based on a one-dimensional transmission-line model. Instruments based on FSB technology should have several advantages over current multiband bolometric radiometers including smaller and more compact cryogenic optics, reduced demands on cryostat size and weight, high coupling efficiency, minimum constraints on the geometry in the focal plane. An FSB system can be configured as a multiband, close-packed focal-plane array, permitting efficient use of the throughput of a telescope.

Kowitt, M. S.; Fixsen, D. J.; Goldin, A.; Meyer, S. S.

1996-10-01

160

Firewater system inadvertent actuation frequencies  

SciTech Connect

This paper presents some recommended generic values for fire protection system inadvertent actuation frequencies. The frequencies are based on actual data from Department of Energy and commercial reactor plant facilities.

Schroeder, J.A. [EG and G Idaho, Inc., Idaho Falls, ID (United States); Eide, S.A. [Los Alamos Technical Associates, Inc., Albuquerque, NM (United States)

1993-04-01

161

Firewater system inadvertent actuation frequencies  

SciTech Connect

This paper presents some recommended generic values for fire protection system inadvertent actuation frequencies. The frequencies are based on actual data from Department of Energy and commercial reactor plant facilities.

Schroeder, J.A. (EG and G Idaho, Inc., Idaho Falls, ID (United States)); Eide, S.A. (Los Alamos Technical Associates, Inc., Albuquerque, NM (United States))

1993-01-01

162

Frequency Standards for Radar Transponders.  

National Technical Information Service (NTIS)

The frequency standards given here were derived by the Frequency Coordination Working Group of the Inter-Range Instrumentation Group, with the assistance of members of the Electronic Trajectory Measurements Working Group and development groups of the thre...

1965-01-01

163

Frequency-Hopping Communication Systems.  

National Technical Information Service (NTIS)

This report presents a current review and analysis of the most important aspects of frequency-hopping communication systems. Frequency synthesis and other implementation issues are discussed. The effects and suitability of various modulations is examined....

D. Torrieri

2003-01-01

164

A Frequency Hopping Synchronization System.  

National Technical Information Service (NTIS)

Frequency hopping is one of several spread spectrum communication techniques which offer some immunity to jamming as well as some rejection of multipath interference. Synchronization of the frequency hopping transmitter and receiver is necessary in an ope...

R. J. McDevitt

1980-01-01

165

Dual-frequency patch antennas  

Microsoft Academic Search

Dual-frequency patch antennas may provide an alternative to large-bandwidth planar antennas, in applications in which large bandwidth is really needed for operating at two separate transmit-receive bands. When the two operating frequencies are far apart, a dual-frequency patch structure can be conceived to avoid the use of separate antennas. In this paper, a critical overview of possible solutions for dual-frequency

S. Maci; G. BifJi Gentili

1997-01-01

166

Fiber Optic Frequency Transfer Link.  

National Technical Information Service (NTIS)

A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the...

L. Primas R. Sydnor G. Lutes

1989-01-01

167

Optical frequency standards and clocks  

Microsoft Academic Search

Optical frequency standards based on single trapped ions or ensembles of neutral atoms have recently demonstrated stability and accuracy superior to that of the current generation of microwave primary frequency standards, with significant potential for further improvements. When combined with femtosecond optical frequency combs, these standards can be operated as optical clocks generating a direct microwave output signal, raising the

H. S. Margolis

2010-01-01

168

Predictability of low frequency modes  

Microsoft Academic Search

Summary In this paper we propose a procedure for the extended integration of low frequency modes of the time scale of 30 to 50 days. A major limitation of the extended integrations arise from a contamination of low frequency modes as a result of energy exchanges from the higher frequency modes. In this study we show an example on the

T. N. Krishnamurti; M. Subramaniam; D. K. Oosterhof; G. Daughenbaugh

1990-01-01

169

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 harmonic 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} {center dot} 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, C.A.; Davis, L.E.; Webb, M.

1990-10-16

170

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 harmonic 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} {center_dot} 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, C.A.; Davis, L.E.; Webb, M.

1990-10-16

171

Bounce frequency fishbone analysis  

NASA Astrophysics Data System (ADS)

Large amplitude bursting modes are observed on NSTX, which are identified as bounce frequency fishbone modes(PDX Group, Princeton Plasma Physics Lab, Phys Rev. Lett) 50, 891 (1983)^,(L. Chen, R. B. White, and M. N. Rosenbluth Phys Rev. Lett) 52, 1122 (1984). The identification is carried out using numerical equilibria obtained from TRANSP( R. V. Budny, M. G. Bell A. C. Janos et al), Nucl Fusion 35, 1497 (1995) and the numerical guiding center code ORBIT( R.B. White, Phys. Fluids B 2)(4), 845 (1990). These modes are important for high energy particle distributions which have large average bounce angle, such as the nearly tangentially injected beam ions in NSTX and isotropic alpha particle distributions. They are particularly important in high q low shear advanced plasma scenarios. Different ignited plasma scenarios are investigated with these modes in view.

White, Roscoe; Fredrickson, Eric; Chen, Liu

2002-11-01

172

High frequency nanotube oscillator  

DOEpatents

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

Peng, Haibing (Houston, TX); Zettl, Alexander K. (Kensington, TX)

2012-02-21

173

Radio frequency picosecond phototube  

SciTech Connect

We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a ''head-on'' geometry is investigated by means of Monte Carlo simulation.

A. Margaryan; R. Carlini; R. Ent; N. Grigoryan; K. Gyunashyan; O. Hashimoto; K. Hovater; M. Ispiryan; S. Knyazyan; B. Kross; S. Majewski; G. Marikyan; M. Mkrtchyan; L. Parlakyan; V. Popov; L. Tang; H. Vardanyan; C. Yan; S. Zhamkochyan; C. Zorn

2006-10-01

174

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

175

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

176

FREQUENCY STABILIZING SYSTEM  

DOEpatents

An electronic control circuit is described in which a first signal frequency is held in synchronization with a second varying reference signal. The circuit receives the first and second signals as inputs and produces an output signal having an amplitude dependent upon rate of phase change between the two signals and a polarity dependent on direction of the phase change. The output may thus serve as a correction signal for maintaining the desired synchronization. The response of the system is not dependent on relative phase angle between the two compared signals. By having practically no capacitance in the circuit, there is minimum delay between occurrence of a phase shift and a response in the output signal and therefore very fast synchronization is effected.

Kerns, Q.A.; Anderson, O.A.

1960-05-01

177

Mid-infrared frequency combs  

NASA Astrophysics Data System (ADS)

Laser frequency combs are coherent light sources that emit a broad spectrum of discrete, evenly spaced narrow lines whose absolute frequency can be measured to within the accuracy of an atomic clock. Their development in the near-infrared and visible domains has revolutionized frequency metrology while also providing numerous unexpected opportunities in other fields such as astronomy and attosecond science. Researchers are now exploring how to extend frequency comb techniques to the mid-infrared spectral region. Versatile mid-infrared frequency comb generators based on novel laser gain media, nonlinear frequency conversion or microresonators promise to significantly expand the 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 lead to new discoveries in the various fields relevant to molecular science.

Schliesser, Albert; Picqu, Nathalie; Hnsch, Theodor W.

2012-07-01

178

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.

179

Towards VECSEL frequency combs  

NASA Astrophysics Data System (ADS)

Significant progress has been made over the last year towards generating frequency combs using VECSELs. Here, I will discuss recent progress made generating < 4kW peak power femtosecond pulse VECSELs, where we have achieved 3.3 W average power with 400 fs pulse duration at 1.7 GHz repetition rate. This has been achieved by exploiting the rapid power scaling progress made in the field of CW VECSELs [1]. The gain structure used here is grown and processed by the University of Marburg, and the window layer is etched for anti-resonance to increase the gain bandwidth and reduce the dispersion [2]. We have used this to generate supercontinuum, achieving 45 % throughput in a 2.2 micron core photonic crystal fiber when the VECSEL produced 1 W average output power. A continuum with a width of 175 nm is generated. At higher average powers heating of the fiber tip reduces coupling efficiency which limits the supercontinuum bandwidth and we will discuss measures to avoid this. Finally, I will outline approaches to further reduce the pulse length, whilst maintaining the average power, to a point where generating coherent octave spanning supercontinuum, suitable for F-2F stabilization should become a reality.

Wilcox, Keith G.

2013-02-01

180

X-band frequency synthesizer with high frequency resolution  

Microsoft Academic Search

A high frequency resolution X-band frequency source composed of a direct digital synthesizer (DDS) and a phase locked loop (PLL) is proposed in the paper. The DDS provides signals as the reference of the PLL, which generates a stable and low phase noise X-band signal. Hardware design is given with an ADF4002 and an AD9858. Experimental measurements of the frequency

Shengwu Yu; Jinping Xu; Zhihao Shen

2012-01-01

181

Frequency standard using hydrogen maser  

SciTech Connect

A frequency standard is described comprising: frequency-generating means for generating electromagnetic energy at variable frequencies; a hydrogen maser adapted to generate electromagnetic energy at hydrogen resonance frequency; and electronic means connecting the hydrogen maser to the frequency-generating means to lock and maintain the frequency of the frequency-generating means at an accurate, stable, standard frequency with the electromagnetic energy generated by the hydrogen maser at hydrogen resonance frequency. The hydrogen maser comprises: a microwave cavity assembly comprising a dielectric container having outer and inner surfaces. The outer surface of the container defines a microwave cavity tuned to about the hydrogen resonance frequency. The container has an aperture therein for open communication between the inner and outer portions of the container, and has on an end wall a discontinuous conductive coating with a predetermined configuration to suppress undesirable oscillation of the microwave cavity; a dissociator having a chamber for generating hydrogen atoms with an opening serving as an exit and forming a narrow beam of the hydrogen atoms and yieldable member means; and means for moving the yieldable member means to align the narrow beam of hydrogen atoms with the aperture.

Stein, S.R.; Smith, T.E.; Lewis, L.L.

1987-11-10

182

Characterization of the frequency stability of frequency-hopping sources.  

PubMed

A method that applies time-domain stability measures, hitherto used only in the context of fixed-frequency sources, to the characterization of frequency-hopped sources is introduced. This method has been successfully applied to the testing of a novel practical frequency-hopping synthesizer. It is shown that despite the fact that hopping sources exhibit an orders-of-magnitude larger amount of short term noise than stable free-running frequency sources, some of the techniques used to estimate the noise of stable sources are also applicable to hopping voltage-controlled oscillator systems. PMID:18267604

Kalivas, G A; Harrison, R G

1991-01-01

183

Frequency hopping millimeter wave reflectometer  

SciTech Connect

Reflectometry techniques are employed to study density fluctuations in fusion plasmas either using one channel or two channels with slightly different frequencies, to probe simultaneously closely spaced plasma layers (for radial correlation studies). The present article describes a novel system with increasing measuring capability utilizing only one single frequency that can be hopped during the discharge. This broadband fast hopping mm-wave reflectometer (BFHR) has been developed for both ASDEX upgrade (Max Plank Institute-Garching-Germany) and TJ-II stellarator (CIEMAT-Spain). The BFHR incorporates frequency synthesizers at microwave frequencies multiplied into the millimeter-wave range and uses heterodyne detection for sensitive phase and amplitude measurements.

Cupido, L.; Sanchez, J.; Estrada, T. [EURATOM/IST Association, Centro de Fusao Nuclear Instituto-Superior Tecnico, 1049-001 Lisbon (Portugal); Laboratorio Nacional de Fusion, Associacion Euratom CIEMAT, 28040 Madrid (Spain)

2004-10-01

184

Nuclear Quadrupole Resonance Studies of Charge Distributions in Molecular Solids.  

NASA Astrophysics Data System (ADS)

A detailed description of an NMR-NQR double resonance spectrometer designed and constructed in this laboratory is given, including some instruction on its use. ('14)N NQR data obtained by pulse methods for six classes of nitrogen-containing compounds are presented and analyzed in the framework of the Townes and Dailey theory. A study of the anti-cancer drugs cyclophosphamide, isophosphamide and triphosphamide suggests the existence of a correlation between the substance's chemotherapeutic efficacy and the (pi) - (sigma)(,NP) charge density at the trigonal nitrogen. Satisfactory correlations of the NQR spectra of 22 monosubstituted anilines with both the Hammett (sigma) parameters and the in vitro biological activities of the corresponding sulfanilamides have been found, indicating that the nitrogen lone-pair orbital is more sensitive than the nitrogen-carbon sigma orbital is to substituent effects. NQR spectra of several N-acetyl amino acids and related compounds are reported. The inductive effect of the chloroacetyl group on the nitrogen is discussed. A positive correlation between the (pi) - (sigma)(,NC) electron density at the nitrogen and the Taft inductive parameter (sigma)* is observed, suggesting that the nitrogen (pi) -charge density in the N-acetyl amino acids does not vary appreciably. Both ('14)N and ('35)Cl NQR data have been obtained for a series of compounds containing nitrogen directly bonded to chlorine. The existence of a linear correlation between the ('14)N and ('35)Cl quadrupole coupling constants is interpreted in terms of a simple model dealing with charge excesses and deficiencies at the respective nuclei. A study of two complexes of 4-aminopyridine (4AP) addresses the loss of pyridine nitrogen lone-pair charge upon formation of the strong and asymmetric N-H-N bond characteristic of these complexes. Evidence of hydrogen bonding interactions involving the amino nitrogens is found to be in agreement with a published neutron diffraction study. ('14)N NQR data for seven organic dye cations and one free base are presented. The cations are weakly paramagnetic at 77 K, exhibiting broad and featureless EPR spectra characteristic of weak charge-transfer complexes. The positive charge in the cations is largely delocalized. The existence of a simple relationship between the ('14)N NQR data and optical properties for three cyanine laser dyes is discussed.

Greenbaum, Steven Garry

185

Optical frequency\\/wavelength references  

Microsoft Academic Search

For more than 100 years, optical atomic\\/molecular frequency references have played important roles in science and technology, and provide standards enabling precision measurements. Frequency-stable optical sources have been central to experimental tests of Einstein's relativity, and also serve to realize our base unit of length. The technology has evolved from atomic discharge lamps and interferometry, to narrow atomic resonances in

L. Hollberg; C. W. Oates; G. Wilpers; C. W. Hoyt; Z. W. Barber; S. A. Diddams; W. H. Oskay; J. C. Bergquist

2005-01-01

186

Meal Frequency and Childhood Obesity  

Microsoft Academic Search

Objective: Previous studies have demonstrated an inverse association between meal frequency and the prevalence of obesity in adulthood. The aim of this study was to assess the relationship between meal frequency and childhood obesity.Research Methods and Procedures: Stature and weight of 4370 German children ages 5 to 6 years were determined in six Bavarian (Germany) public health offices during the

Andr M. Toschke; Helmut Kchenhoff; Berthold Koletzko; Rdiger von Kries

2005-01-01

187

High Frequency Magnetic Force Microscopy  

Microsoft Academic Search

Image magnetization dynamics on all time scales, including the ultra-short regime, is an important subject that needs to be addressed by advanced magnetic force microscopy. High frequency (microwave) and fast time-domain phenomena are fundamental properties that are also closely related to applications such as magnetic data storage. In practice, the ability to evaluate high frequency performance of magnetic recording heads

Shaoping Li

188

Frequency shaped sliding mode synthesis  

SciTech Connect

A sliding mode design method based on frequency shaped quadratic optimal control formulation is proposed in this paper. This method is applied to the design of a VSC controller for a flexible link robot arm. Simulation results show that the excitation of the link deformations can be minimized by introducing frequency-shaping in the synthesis of sliding mode. 7 refs., 19 figs.

Young, K.D. (Lawrence Livermore National Lab., CA (USA)); Oezguener, U. (Ohio State Univ., Columbus, OH (USA). Dept. of Electrical Engineering)

1990-03-01

189

Blackbody Radiation: Frequency and Wavelength  

NSDL National Science Digital Library

The Blackbody Radiation: Frequency and Wavelength model simulates the blackbody radiation curves of Planck both as a function of frequency and as a function of wavelength to allow for comparison of the two functions. The Planck radiation law can be derived both as a function of frequency and as a function of wavelength. In doing so, one gets two slightly different expressions for the energy density per frequency (wavelength) as a function of frequency (wavelength. Shown in the main window is a schematic of a blackbody cavity showing (on the right) the color of the radiation emitted. The graph plots the energy density per frequency (wavelength) as a function of frequency (wavelength and shows the visible spectrum. One can switch between the two functions by using the radio buttons provided. A slider alows the twmperature to be set or changed. The Blackbody Radiation: Frequency and Wavelength model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_blackbody_fw.jar file will run the program if Java is installed.

Palop, Jose I.

2010-12-12

190

Negative-Frequency Resonant Radiation  

NASA Astrophysics Data System (ADS)

Optical solitons or solitonlike states shed light to blueshifted frequencies through a resonant emission process. We predict a mechanism by which a second propagating mode is generated. This mode, called negative resonant radiation, originates from the coupling of the soliton mode to the negative-frequency branch of the dispersion relation. Measurements in both bulk media and photonic-crystal fibers confirm our predictions.

Rubino, E.; McLenaghan, J.; Kehr, S. C.; Belgiorno, F.; Townsend, D.; Rohr, S.; Kuklewicz, C. E.; Leonhardt, U.; Knig, F.; Faccio, D.

2012-06-01

191

Contour Integration across Spatial Frequency  

ERIC Educational Resources Information Center

|Association field models of contour integration suggest that local band-pass elements are spatially grouped to global contours within limited bands of spatial frequency (Field, Hayes, & Hess, 1993). While results for local orientation and spacing variation render support for AF models, effects of spatial frequency (SF) have rarely been addressed.

Persike, Malte; Olzak, Lynn A.; Meinhardt, Gunter

2009-01-01

192

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

193

Pitch perception: dissociating frequency from fundamental-frequency discrimination.  

PubMed

High-frequency pure tones (>6 kHz), which alone do not produce salient melodic pitch information, provide melodic pitch information when they form part of a harmonic complex tone with a lower fundamental frequency (F0). We explored this phenomenon in normal-hearing listeners by measuring F0 difference limens (F0DLs) for harmonic complex tones and pure-tone frequency difference limens (FDLs) for each of the tones within the harmonic complexes. Two spectral regions were tested. The low- and high-frequency band-pass regions comprised harmonics 6-11 of a 280- or 1,400-Hz F0, respectively; thus, for the high-frequency region, audible frequencies present were all above 7 kHz. Frequency discrimination of inharmonic log-spaced tone complexes was also tested in control conditions. All tones were presented in a background of noise to limit the detection of distortion products. As found in previous studies, F0DLs in the low region were typically no better than the FDL for each of the constituent pure tones. In contrast, F0DLs for the high-region complex were considerably better than the FDLs found for most of the constituent (high-frequency) pure tones. The data were compared with models of optimal spectral integration of information, to assess the relative influence of peripheral and more central noise in limiting performance. The results demonstrate a dissociation in the way pitch information is integrated at low and high frequencies and provide new challenges and constraints in the search for the underlying neural mechanisms of pitch. PMID:23716218

Oxenham, Andrew J; Micheyl, Christophe

2013-01-01

194

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

195

Nuclear Quadrupole Coupling Constants in Niobium Pentachloride and Related Compounds (I) Halogen Nuclei  

NASA Astrophysics Data System (ADS)

35Cl NQR spectrum in NbCl5 has been investigated from 4.2 K to 480 K. The lines of about 7 MHz have larger multiplicity and show positive temperature dependence in contrast to the usual negative one for the line of about 13 MHz. The former lines are further separated into two groups having different temperature dependences. The expressions for the chlorine coupling constant are derived according to Townes-Daileys method on the basis of the p?-d? bond. The NQR data are analysed and the lines are assigned to the axial, equatorial and bridging chlorine atoms in the Nb2Cl10 dimer. The theory is applied to other related compounds.

Okubo, Noriaki

1982-02-01

196

Aeronautical Frequency Assignments Near Cable Television Carrier Frequencies.  

National Technical Information Service (NTIS)

This report contains lists and geographical locations of aeronautical radio stations operating near frequencies commonly used for visual, aural, or pilot carriers by cable television systems. These lists are provided to assist cable television system oper...

1982-01-01

197

Resolving Frequency Ambiguities in Step-Frequency Compressive Receivers.  

National Technical Information Service (NTIS)

Present Compressive Receiver implementations are limited due to their analog implementation and the necessity for digital processing of the serial output data. Previous research has shown that a stepped-frequency digital design using sub-Nyquist sampling ...

O. Ceylan

1999-01-01

198

Time-frequency-distribution analysis of frequency dispersive targets  

NASA Astrophysics Data System (ADS)

In the analysis of scattering targets, it is common to obtain time domain profiles by a Fourier transformation of the frequency response. In this process, wide-band frequency data are used to generate an approximation of the impulse response of the target via an inverse Fourier transform (IFT). The peaks in this impulse response then correspond to scattering centers of the target. In this paper, the authors show that an analysis of scattering from frequency dispersive structures can be accomplished by time-frequency distribution (TFD) techniques. Three TFDs are investigated, and applied to the scattering analysis of a circular waveguide cavity. This paper comprises a brief description of the applied TFDs, and a detailed comparison of the TFD results for scattering analysis. We shall show that for some targets, such as the cavity, TFD is an effective method for description of the properties of the target. For the waveguide cavity, propagating modes and cutoff frequencies can readily be determined from the TFD, whereas neither time nor frequency representations will provide such information.

Walton, E. K.; Moghaddar, A.

1993-01-01

199

GHz band frequency hopping PLL-based frequency synthesizers  

NASA Astrophysics Data System (ADS)

In this paper we describe a full-integrated circuit containing all building blocks of a completed PLL-based synthesizer except for low pass filter (LPF). The frequency synthesizer is designed for a frequency hopping (FH) transceiver operating up to 1.5 GHz as a local oscillator. The architecture of Voltage Controlled Oscillator (VCO) is optimized to get better performance, and a phase noise of -111.85-dBc/Hz @ 1 MHz and a tuning range of 250 MHz are gained at a centre frequency of 1.35 GHz. A novel Dual-Modulus Prescaler (DMP) is designed to achieve a very low jitter and a lower power. The settling time of PLL is 80 ?s while the reference frequency is 400 KHz. This monolithic frequency synthesizer is to integrate all main building blocks of PLL except for the low pass filter, with a maximum VCO output frequency of 1.5 GHz, and is fabricated with a 0.18 ?m mixed signal CMOS process. Low power dissipation, low phase noise, large tuning range and fast settling time are gained in this design.

Xu, Yong; Wang, Zhi-Gong; Guan, Yu; Xu, Zhi-Jun; Qiao, Lu-Feng

2005-11-01

200

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

201

Booster synchrotron frequency below transition  

SciTech Connect

The dipole mode synchrotron frequency is a basic beam parameter; it and a few similarly basic quantities measured at small time intervals serve to characterize the longitudinal beam dynamics throughout the acceleration cycle. The effective accelerating voltage, in conjunction with the amount of rf voltage required for the acceleration, is important for the estimate of the beam energy loss per turn. The dipole mode frequency can be used to obtain the effective accelerating rf voltage, providing that it can be measured precisely. The synchrotron frequency measured from the synchrotron phase detector signal (SPD) generally agrees well with calculation, and it can be applied for such purposes as inferring the effective rf voltage.

Xi Yang et al.

2004-04-21

202

Frequency modulated thermal wave imaging  

NASA Astrophysics Data System (ADS)

Pulsed thermography (PT), being simple and fast, remains one of the most popular thermographic NDE techniques, though it has intrinsic limitations. An alternative method is suggested and named frequency modulated thermal wave imaging (FMTWI), where the heating waveform phase relations are adjusted over a bandwidth (B) in such a way, that a chirp (frequency modulated) signal of duration T, with much reduced peak power is produced. FMTWI, while retaining all characteristics of lock-in thermography, has the added advantage of overcoming the blind frequency problem. It can be processed by matched filtering (pulse compression) to improve sensitivity.

Tuli, S.; Chatterjee, K.

2012-05-01

203

Discussion of human resonant frequency  

NASA Astrophysics Data System (ADS)

Human bodies are often exposed to vertical vibrations when they are in the workplace or on vehicles. Prolonged exposure may cause undue stress and discomfort in the human body especially at its resonant frequency. By testing the response of the human body on a vibrating platform, many researchers found the human whole-body fundamental resonant frequency to be around 5 Hz. However, in recent years, an indirect method has been prosed which appears to increase the resonant frequency to approximately 10 Hz. To explain this discrepancy, experimental work was carried out in NTU. The study shows that the discrepancy lies in the vibration magnitude used in the tests. A definition of human natural frequency in terms of vibration magnitude is proposed.

Brownjohn, James M.; Zheng, Xiahua

2001-06-01

204

Chemically Polished High Frequency Resonators.  

National Technical Information Service (NTIS)

The upper frequency limit of quartz resonators is determined by the physical properties of quartz and restrictions imposed by processing techniques. More often than not, the processing limitations are reached long before the physical limitations. Mechanic...

W. P. Hanson

1983-01-01

205

Economic Areawise Load Frequency Control.  

National Technical Information Service (NTIS)

The report describes a proposed solution for the generation control problem which unifies economic dispatch, load frequency control and statistical load forecasting. This solution retains the decentralized character of the Area Control Principle but updat...

J. Zaborszky T. Ying Chiang

1975-01-01

206

METAS Time & Frequency Metrology Report.  

National Technical Information Service (NTIS)

METAS is the National Metrology Institute (NMI) for Switzerland. The Time & Frequency Laboratory (TFL) is responsible for the generation and dissemination of precise time and performs calibrations for customers. This paper reports on current or recent act...

A. Stefanov C. Schlunegger L. Bernier

2009-01-01

207

METAS Time & Frequency Metrology Report.  

National Technical Information Service (NTIS)

METAS is the Swiss Federal Office of Metrology and Accreditation. The METAS Time & Frequency Laboratory (T&F Lab) operates a cesium primary standard, maintains the Swiss national time scales, disseminates precise time and performs calibrations for custome...

C. Schlunegger G. Dudle L. Bernier

2005-01-01

208

Artful waveguides for frequency doubling  

Microsoft Academic Search

Two kinds of poled polymer systems, DR1\\/PMMA and p-NA\\/PVA were set in artfully designed frequency doubling multi-layered waveguides. (Ti2O5)x\\/(SiO2)y glass which was adjustable on refractive index by varying the ratio, x\\/y was inserted between poled polymer nonlinear optical layer and glass substrate to optimize conversion efficiency of frequency doubling. Also a face-to-face structure of poled polymer film was applied to

Keisuke Sasaki; G. J. Zhang; S. Horinouchi

1994-01-01

209

Digital Channelizing Radio Frequency Receiver  

Microsoft Academic Search

HYPRES is developing a class of digital receivers featuring direct digitization at radio frequency (RF). Such a receiver consists of a wideband analog-to-digital converter (ADC) modulator and multiple digital channelizer units to extract different frequency bands-of-interest within the broad digitized spectrum. The single-bit oversampled data, from either a lowpass delta or bandpass delta-sigma modulator, are applied to one or more

Deepnarayan Gupta; Timur V. Filippov; Alexander F. Kirichenko; Dmitri E. Kirichenko; Igor V. Vernik; Anubhav Sahu; Saad Sarwana; Pavel Shevchenko; Andrei Talalaevskii; Oleg A. Mukhanov

2007-01-01

210

Frequency modulated ultrasonic Doppler flowmeter  

Microsoft Academic Search

A new ultrasonic Doppler flowmeter based on the concept of a frequency-modulated wave rather than a continuous single frequency\\u000a is described. Results are presented showing that the flowmeter can accurately measure vessel diameter and range, volume flow\\u000a remote from the probe, and flow direction, and can, by tracking the probe along the vessel, visualise the internal diameter.\\u000a The possibility of

K. McCarty; J. P. Woodcock

1975-01-01

211

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

212

Off-resonance effects and selectivity profiles in pulsed nitrogen-14 nuclear quadrupole resonance.  

PubMed

In order to alleviate base-line distortions in nitrogen-14 NQR spectra originating from pulse breakthrough, low power radio-frequency (rf) pulses were applied. It is recalled that the required power is four times lower than that for an equivalent NMR experiment. This is easily explained by the fact that, in NMR, half the amplitude of the rf field is active. Moreover, the selectivity profile (i.e. the peak amplitude as a function of the difference between the carrier frequency and the resonance frequency) exhibits a shape which is, in most cases, more favorable in NQR than in NMR. An appropriate theory has been developed for explaining these experimental observations. It is concluded that low power NQR is perfectly feasible and should even be recommended for most applications, provided that the line-width of the NQR signal is not too large. PMID:23063174

Guendouz, L; Robert, A; Retournard, A; Leclerc, S; Aissani, S; Canet, D

2012-09-01

213

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

214

1,3,4-Diazaphosphorine from n-acetylurea  

SciTech Connect

In continuation of the authors study of phosphorylation of acetamides we found that N-acetylurea reacts readily with both a solution and with a dispersion of PCl/sub 5/ in benzene to form 2,6-dichloro-1,3,4-diazaphosphorine (I), a crystalline compound which is stable during distillation in vacuo, but which hydrolyzes in air. Compound (I) is soluble in benzene, diethyl ether, and chloroform. The elemental analysis and /sup 31/P, /sup 1/H, and /sup 13/C NMR and /sup 35/Cl NQR spectroscopy data conform well with the proposed structure of compound (I).

Rozinov, V.G.; Dmitrichenko, M.Yu.; Donskikh, V.I.; Dolgushin, G.V.; Feshin, V.P.

1987-07-10

215

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.

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

2012-01-01

216

Variable frequency drive applications guide  

SciTech Connect

Traditionally, fans and pumps have been designed to be capable of handling the maximum demand of the system in which they are installed. However, quite often the actual demand can vary and it can be much lower than the original design capacity. These situations have been corrected in the past through additions of outlet dampers to fans or throttling valves to pumps. While these can be effective and simple controls they severely affect the efficiency of the system. Variable frequency (speed) is the most efficient means of capacity control. The most cost effective method of achieving variable speed capacity control is using AC adjustable frequency drives. AC adjustable frequency controls convert any fixed speed AC motor into an adjustable speed device. Adjusting the speed of a motor, by controlling the frequency of the AC power to that motor, reduces its horsepower requirements. According to pump and fan laws, capacity is proportional to speed while horsepower is proportional to the cube of the speed. Therefore, by reducing the speed of an AC motor by 20 percent the horsepower requirement is reduced by nearly 50 percent. Reduced speed through variable frequency control allows for flexibility of meeting changing weather and comfort requirements without operating costly equipment at full capacity.

Laloudakis, D.J.

1991-10-01

217

Artful waveguides for frequency doubling  

NASA Astrophysics Data System (ADS)

Two kinds of poled polymer systems, DR1/PMMA and p-NA/PVA were set in artfully designed frequency doubling multi-layered waveguides. (Ti2O5)x/(SiO2)y glass which was adjustable on refractive index by varying the ratio, x/y was inserted between poled polymer nonlinear optical layer and glass substrate to optimize conversion efficiency of frequency doubling. Also a face-to-face structure of poled polymer film was applied to frequency doubling waveguide in Cerenkov-type phase matching. In this structure d33:-d33 counter-parallel distribution was effective for overlapping of both fields. Finally ridge-type channel waveguide was prepared for high efficiency SHG waveguide.

Sasaki, Keisuke; Zhang, G. J.; Horinouchi, S.

1994-09-01

218

An ellipsoidal frequency selective surface  

NASA Astrophysics Data System (ADS)

The frequency selective surface (FSS) considered reflects radio waves within a small frequency band, but it is nearly transparent to radio waves outside this band. The ellipsoidal FSS represents an ordered arrangement of dipole-like elements on an elliptical surface. Attention is given to the theory of FSS operation, the approach used in the design process, the techniques considered for fabricating the flat surface FSS, the test chamber, the transfer of the design for the flat FSS to the ellipsoidal curved surface, and the test results. The frequency-selective response of the FSS shows that the FSS is highly reflective near 9 GHz and is relatively transparent above 1.05 GHz and below 7.5 GHz.

Dick, M. J.

219

Partnership concurrency and coital frequency.  

PubMed

National HIV prevalence estimates across sub-Saharan Africa range from less than 1 percent to over 25percent. 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

Gaydosh, Lauren; Reniers, Georges; Helleringer, Stphane

2013-09-01

220

High frequency gyrokinetic particle simulation  

SciTech Connect

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

Kolesnikov, R. A.; Lee, W. W.; Qin, H.; Startsev, E. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)

2007-07-15

221

Variable frequency microwave heating apparatus  

SciTech Connect

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, D.W.; Lauf, R.J.; Johnson, A.C.; Thigpen, L.T.

1999-10-05

222

Intercontinental Frequency Comparison by Very Low-Frequency Radio Transmission  

Microsoft Academic Search

Studies of signals from Rugby, England, at 16 kc and 60 kc have given evidence that a single source of standard frequency can be made available at vlf on a world-wide basis. At a distance of 5200 km the Doppler effects in transmission seldom exceed 3 parts in 109, and a measurement can be made to 1 part in 109

John Pierce

1957-01-01

223

Radio frequency interference at passive microwave earth observation frequencies  

Microsoft Academic Search

The retrieval of geophysical parameters of the Earth and its atmosphere from satellite observations fundamentally relies upon the accuracy of the measurements. The growth in communication technologies has led to the exploitation of regions of the electromagnetic spectrum hitherto primarily used for Earth observation. This article describes and maps the distribution of radio frequency interference in the microwave portion of

C. Kidd

2006-01-01

224

47 CFR 74.661 - Frequency tolerance.  

Code of Federal Regulations, 2011 CFR

...the carrier frequency of each authorized transmitter...the following percentage of the assigned frequency...700 0.003 1 Television translator relay stations...a frequency tolerance of 0.002%. 2 Stations...2005, for tolerance values exceeding those...

2011-10-01

225

47 CFR 74.661 - Frequency tolerance.  

Code of Federal Regulations, 2012 CFR

...the carrier frequency of each authorized transmitter...the following percentage of the assigned frequency...700 0.003 1 Television translator relay stations...a frequency tolerance of 0.002%. 2 Stations...2005, for tolerance values exceeding those...

2012-10-01

226

47 CFR 87.475 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...transmitter. (e) Frequencies available for differential GPS stations. Frequencies in the 112-118 MHz band may be...Special Category I (SCAT-I) ground stations for differential GPS data links. (1) The frequencies available are...

2011-10-01

227

47 CFR 87.475 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...transmitter. (e) Frequencies available for differential GPS stations. Frequencies in the 112-118 MHz band may be...Special Category I (SCAT-I) ground stations for differential GPS data links. (1) The frequencies available are...

2012-10-01

228

Analog Frequency Modulated Laser Using Magnetostriction.  

National Technical Information Service (NTIS)

The present invention relates to an analog frequency modulatable laser. The radiation of the lasing medium is analog frequency modulated by change of the optical path length by movement of reflective mirrors forming the resonant cavity at the frequency of...

L. T. Kabacoff

1985-01-01

229

47 CFR 27.54 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication... Technical Standards § 27.54 Frequency stability. The frequency stability shall be sufficient to ensure that the...

2012-10-01

230

47 CFR 24.135 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency stability. 24.135 Section 24.135 Telecommunication...SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained...

2012-10-01

231

47 CFR 24.235 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency stability. 24.235 Section 24.235 Telecommunication...SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the...

2011-10-01

232

47 CFR 27.54 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication... Technical Standards § 27.54 Frequency stability. The frequency stability shall be sufficient to ensure that the...

2011-10-01

233

47 CFR 24.235 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Frequency stability. 24.235 Section 24.235 Telecommunication...SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the...

2012-10-01

234

47 CFR 5.101 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

... 1 2012-10-01 2012-10-01 false Frequency stability. 5.101 Section 5.101 Telecommunication FEDERAL...Standards and Operating Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency...

2012-10-01

235

47 CFR 87.529 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Automatic Weather Stations (AWOS/ASOS) § 87.529 Frequencies...frequency. Normally, frequencies available for air traffic control operations set forth in subpart E will be assigned to...

2011-10-01

236

47 CFR 87.529 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Automatic Weather Stations (AWOS/ASOS) § 87.529 Frequencies...frequency. Normally, frequencies available for air traffic control operations set forth in subpart E will be assigned to...

2012-10-01

237

DSS 13 frequency stability tests  

NASA Astrophysics Data System (ADS)

In a previous article, the results of frequency stability tests at DSS 13 were presented in table form for tau = 1000 s for the test period May 1985 through March 1986. This article is a continuation of that initial report and presents specially selected Allan sigma (square root of variance) plots of each of the subsystem test previously reported. An additional result obtained from tests performed during July 1986 was included for completeness. The Allan sigma plots are useful in that frequency stability information is not only given for tau = 1000 s, but for tau values in the regions of 1, 100, 500, and 2000 s as well.

Otoshi, T. Y.; Franco, M. M.

1987-05-01

238

Shaping frequency-entangled qudits  

NASA Astrophysics Data System (ADS)

We demonstrate the creation, characterization, and manipulation of frequency-entangled qudits by shaping the energy spectrum of entangled photons. The generation of maximally entangled qudit states is verified up to dimension d=4 through tomographic quantum-state reconstruction. Subsequently, we measure Bell parameters for qubits and qutrits as a function of their degree of entanglement. In agreement with theoretical predictions, we observe that for qutrits the Bell parameter is less sensitive to a varying degree of entanglement than for qubits. For frequency-entangled photons, the dimensionality of a qudit is ultimately limited by the bandwidth of the pump laser and can be on the order of a few millions.

Bernhard, Christof; Bessire, Bnz; Feurer, Thomas; Stefanov, Andr

2013-09-01

239

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention Remember the warnings. Statistics. N. ... Remember the warnings. Frequency. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

240

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention Time spent reading ... Time spent reading food label (seconds). Frequency. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

241

Measurement method of frequency agile radar synthesis detection unit's frequency tracking accuracy  

NASA Astrophysics Data System (ADS)

Frequency agile radar synthesis detection unit works in frequency hopping state in radio frequency (RF) band. For the limitation of the accuracy of instantaneous frequency measurement (IFM) technology, the frequency tracking accuracy can't be examined directly. The system design method proposed by the paper examines the frequency tracking accuracy of the frequency agile radar synthesis detection unit (FARSDU) at intermediate frequency. The method is realized in engineering and good performance has been got.

Han, Jianhui; Jiang, Yonghua

2005-11-01

242

Sparse time-frequency representations  

PubMed Central

Auditory neurons preserve exquisite temporal information about sound features, but we do not know how the brain uses this information to process the rapidly changing sounds of the natural world. Simple arguments for effective use of temporal information led us to consider the reassignment class of time-frequency representations as a model of auditory processing. Reassigned time-frequency representations can track isolated simple signals with accuracy unlimited by the time-frequency uncertainty principle, but lack of a general theory has hampered their application to complex sounds. We describe the reassigned representations for white noise and show that even spectrally dense signals produce sparse reassignments: the representation collapses onto a thin set of lines arranged in a froth-like pattern. Preserving phase information allows reconstruction of the original signal. We define a notion of consensus, based on stability of reassignment to time-scale changes, which produces sharp spectral estimates for a wide class of complex mixed signals. As the only currently known class of time-frequency representations that is always in focus this methodology has general utility in signal analysis. It may also help explain the remarkable acuity of auditory perception. Many details of complex sounds that are virtually undetectable in standard sonograms are readily perceptible and visible in reassignment.

Gardner, Timothy J.; Magnasco, Marcelo O.

2006-01-01

243

Frequency steering of hydrogen masers  

Microsoft Academic Search

The two Master Clock (MC) systems at USNO are steered in frequency so as to equalize their times with that of a mean timescale produced by an ensemble of hydrogen masers and cesium standards weighted dynamically and revised by post-processing. Occasional steers are also made to keep UTC (USNO) close to TAI. Experiments have been made with different steering algorithms

Lee A. Breakiron; Paul Koppang

1996-01-01

244

Single Frequency Networks in DTV  

Microsoft Academic Search

Single Frequency Networks (SFNs) offer many advantages including better coverage, less interference, less power, and higher reliability. SFNs can also free up extra TV channels, resulting in more efficient use of the spectrum. The paper presents an overview of the advantages of SFNs and some basics about how to implement them. The significantly improved Signal to Interference performance and less

Anders Mattsson

2005-01-01

245

Radio Frequency and Optical Metamaterials.  

National Technical Information Service (NTIS)

This research encompassed of study radio frequency (RF) and optical metamaterials. The RF study of metamaterials focuses on the polarization behavior of split-ring resonators (SRR) and wire-post (WP) elements and the spatially dispersive behavior of the S...

A. D. Drehman B. Turchinetz E. E. Crisman J. S. Derov T. H. O'Donnell

2013-01-01

246

Accumulator and Debuncher Revolution Frequencies  

SciTech Connect

The purpose of this note is to identify what parameters determine the proper setting of the Accumulator and Debuncher dipole buses, and what the {bar p} revolution frequencies should be under these circumstances. As will be seen, certain parameters of the Main Ring lead to very tight tolerances in these bus setting.

Shafer, R.

1985-09-09

247

Echo frequency reduction in pyroelectrics  

NASA Astrophysics Data System (ADS)

This study focuses on the frequency characteristics of Lithium Niobate (LiNbO3) as a pyroelectric detector. Four lithium niobate samples of varying thickness were studied. Each sample had the same cross-sectional area (approximately 1 mm by 1 mm square) and was irradiated with laser pulse energy under the same conditions. The echo frequency was defined as the efficient conversion of mechanical energy into electrical energy with a voltage modulation on the signal pulse. To test the theory if there would be a reduction in the echo frequency, two samples were cut with the same dimension, but different cut angle. The measurements of four different sample thicknesses under two widely different laser wavelengths (UV laser and IR laser) were tested. Illumination was accomplished by irradiating the samples "head on" toward a 1 mm by 1 mm sample cross section. Illumination was further studied under the same conditions but with a black ink coating which was composed of n-propanol, n-butanol, and diacetone alcohol. In all cases a change in echo frequency was observed and was stronger for the IR laser radiation case. Deeper penetration of the IR laser wavelength into the samples could have caused more homogenous bulk heating (versus the UV laser wavelength) which led to larger geometrical changes in material volume. Changes in material volume require mechanical displacements and the piezoelectric effect couples these mechanical displacements with excess charge creation at the electrodes.

Sorbel, Scott Randall

248

Frequency Effects, Noticing, and Creativity  

ERIC Educational Resources Information Center

Ellis's target article suggests that language processing is based on frequency and probabilistic knowledge and that language learning is implicit. These findings are consistent with those of SLA researchers working within a variationist framework (e.g., Tarone, 1985; Bayley & Preston, 1996). This paper provides a brief overview of this research

Tarone, Elaine

2002-01-01

249

A globally convergent frequency estimator  

Microsoft Academic Search

Online estimation of the frequency of a sinusoidal signal is a classical problem in systems theory that has many practical applications. In this paper the authors provide a solution to the problem of ensuring a globally convergent estimation. More specifically, they propose a new adaptive notch filter whose dynamic equations exhibit the following remarkable features: 1) all signals are globally

Liu Hsu; Romeo Ortega; G. Damm

1999-01-01

250

Frequency and Phase Lock Loop  

Microsoft Academic Search

A new electronic subsystem has been developed: The frequency and phase lock loop. It has an extended acquisition range compared to the standard phase lock loop. It will be advantageous to use this new loop in all applications where a simultaneous need for large acquisition range and a narrow tracking bandwidth can justify the added complexity of the new loop.

Richard Citta

1977-01-01

251

Radio Frequency Plasma in Water  

Microsoft Academic Search

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500 K. Spectroscopic measurements show

Tsunehiro Maehara; Hiromichi Toyota; Makoto Kuramoto; Atsushi Iwamae; Atsushi Tadokoro; Shinobu Mukasa; Hiroshi Yamashita; Ayato Kawashima; Shinfuku Nomura

2006-01-01

252

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.

253

Low Frequency Acoustic Resonance Studies  

Microsoft Academic Search

Fluid phase transitions in porous media are a powerful probe of the effect of confinement and disorder on phase transitions. Aerogel may provide a model system in which to study the effect of dilute impurities on a variety of phase transitions. In this paper we present a series of low frequency acoustic experiments on the effect of aerogel on the

Tobias Herman; John R. Beamish

2005-01-01

254

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

255

Spatial frequency domain error budget  

SciTech Connect

The aim of this paper is to describe a methodology for designing and characterizing machines used to manufacture or inspect parts with spatial-frequency-based specifications. At Lawrence Livermore National Laboratory, one of our responsibilities is to design or select the appropriate machine tools to produce advanced optical and weapons systems. Recently, many of the component tolerances for these systems have been specified in terms of the spatial frequency content of residual errors on the surface. We typically use an error budget as a sensitivity analysis tool to ensure that the parts manufactured by a machine will meet the specified component tolerances. Error budgets provide the formalism whereby we account for all sources of uncertainty in a process, and sum them to arrive at a net prediction of how "precisely" a manufactured component can meet a target specification. Using the error budget, we are able to minimize risk during initial stages by ensuring that the machine will produce components that meet specifications before the machine is actually built or purchased. However, the current error budgeting procedure provides no formal mechanism for designing machines that can produce parts with spatial-frequency-based specifications. The output from the current error budgeting procedure is a single number estimating the net worst case or RMS error on the work piece. This procedure has limited ability to differentiate between low spatial frequency form errors versus high frequency surface finish errors. Therefore the current error budgeting procedure can lead us to reject a machine that is adequate or accept a machine that is inadequate. This paper will describe a new error budgeting methodology to aid in the design and characterization of machines used to manufacture or inspect parts with spatial-frequency-based specifications. The output from this new procedure is the continuous spatial frequency content of errors that result on a machined part. If the machine does not meet specifications, the procedure identifies the sources of the critical errors. We would then evaluate these errors and either reduce the errors through design improvements or modifications to cutting parameters (spindle speed, feed, etc.) or select a different candidate machine if improvements were not practical.

Hauschildt, H; Krulewich, D

1998-08-27

256

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

257

Stereo channels with different temporal frequency tunings.  

PubMed

To investigate the spatial and temporal frequency tunings for stereopsis, we measured the contrast sensitivity for depth discrimination with variable spatiotemporal frequencies and disparities using drifting sinusoidal gratings. The results showed that the contrast sensitivity changed with the stimulus disparity and the disparity tuning function varied with the spatial frequency. The disparity in the peak sensitivity decreased proportionally with the spatial frequency (size-disparity correlation). Although the temporal frequency exhibited a limited influence on the peak disparity, the temporal frequency tuning varied with the spatial frequency. The shape of the temporal frequency tuning function was lowpass for higher spatial frequencies, whereas it was bandpass for low spatial frequencies. These results suggest that more than one channel with different temporal as well as spatial frequency tunings contribute to stereopsis. PMID:17184805

Lee, Seungbae; Shioiri, Satoshi; Yaguchi, Hirohisa

2006-12-20

258

Low frequency and high-frequency cochlear nonlinearity in humans  

PubMed Central

Low- and high-frequency cochlear nonlinearity was studied by measuring DPOAE I/O functions at 0.5 and 4 kHz in 103 normal-hearing subjects. Behavioral thresholds at both f2's were used to set L2 in dB SL for each subject. Primary levels were optimized by determining the L1 resulting in the largest Ldp for each L2 for each subject and both f2's. DPOAE I/O functions were measured using L2 inputs from ?10 dB SL (0.5 kHz) or ?20 dB SL (4 kHz) to 65 dB SL (both frequencies). Mean DPOAE I/O functions, averaged across subjects, differed between the two frequencies, even when threshold was taken into account. The slopes of the I/O functions were similar at 0.5 and 4 kHz for high-level inputs, with maximum compression ratios of about 4:1. At both frequencies, the maximum slope near DPOAE threshold was approximately 1, which occurred at lower levels at 4 kHz, compared to 0.5 kHz. These results suggest that there is a wider dynamic range and perhaps greater cochlear-amplifier gain at 4 kHz, compared to 0.5 kHz. Caution is indicated, however, because of uncertainties in the interpretation of slope and because the confounding influence of differences in noise level could not be completely controlled.

Gorga, Michael P.; Neely, Stephen T.; Dierking, Darcia M.; Kopun, Judy; Jolkowski, Kristin; Groenenboom, Kristin; Tan, Hongyang; Stiegemann, Bettina

2008-01-01

259

Feasibility of nuclear quadrupole resonance as a novel dosimetry tool  

Microsoft Academic Search

Nuclear quadrupole resonance (N.Q.R) frequencies are influenced by the symmetry of the charge distribution of a compound around the site of interest. Damage by ionizing radiation causes changes in this charge symmetry which can be detected by standard pulsed N.Q.R. methods. Previous work done on various chlorates of ³⁵Cl at room temperature (Vargas et al., 1978) shows a linear effect

L. H. Iselin; D. E. Hintenlang; S. J. Epperson; G. A. Higgins; K. Jamil

1990-01-01

260

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. Hnsch; J. C. Knight; W. J. Wadsworth; P. St. J. Russell

2000-01-01

261

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Frequency stability. 90.539 Section 90.539 Telecommunication...793-805 MHz Bands § 90.539 Frequency stability. Transmitters designed to operate...frequency bands must meet the frequency stability requirements in this section....

2012-10-01

262

47 CFR 90.539 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Frequency stability. 90.539 Section 90.539 Telecommunication...793-805 MHz Bands § 90.539 Frequency stability. Transmitters designed to operate...frequency bands must meet the frequency stability requirements in this section....

2011-10-01

263

Development of high frequency medical ultrasound arrays  

Microsoft Academic Search

Recent progress in the development of high frequency linear and phased arrays has resulted in a number of devices that operate at and above 20 MHz. The highest frequency commercial arrays that are presently available rely on mechanical dicing and operate at a maximum frequency of 20 MHz. For higher frequencies novel approaches are required. Several researchers have fabricated fine-scale

T. A. Ritter; T. R. Shrout; K. K. Shung

2001-01-01

264

Multi-frequency Electrokinetic Micromixing  

NASA Astrophysics Data System (ADS)

We report an electrokinetic process to rapidly mix micro and nanoliter volume solutions for microfluidics applications. The method consists in initiating a flow instability that will rapidly stir the microflow streams. The effect occurs by applying multi-frequency alternative current signals in a periodic array of planar microelectrodes. The device was manufactured using bulk titanium microfabrication. It consists of an array of 24 electrodes sitting on the bottom of 200 microns wide, 30 microns deep and 6 millimeters long titanium channel. The electrodes are 20 to 40 microns wide with a pitch of 40 to 80 microns depending on the configuration studied. The device is very versatile and can be used for micro-nano particles concentration, cells sorting and micromixing depending on the input signal applied. In the present study we present some measurements of the mixing behavior. We discuss the advantage of the multi-frequency electrokinetic micromixing and show some quantitative results.

Bottausci, Frederic; Mezic, Igor

2006-11-01

265

Surface acoustic wave frequency comb  

NASA Astrophysics Data System (ADS)

We investigate opto-mechanical oscillation (OMO) and subsequent generation of acoustic wave frequency combs in monolithic crystalline whispering gallery mode (WGM) resonators. The OMO is observed in resonators made of electro-optic (lithium tantalate), non-electro-optic birefringent (magnesium fluoride), and non-birefringent (calcium fluoride) materials. The phenomenon manifests itself as generation of optical harmonics separated by the eigenfrequency of a surface acoustic wave (SAW) mechanical mode of the same WGM resonator. We show that the light escaping the resonator and demodulated on a fast photodiode produces a spectrally pure radio frequency (RF) signal. For instance, we demonstrate generation of 200 MHz signals with instantaneous linewidth of 0.2 Hz.

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

2012-02-01

266

Radio Frequency Charge Parity Meter  

NASA Astrophysics Data System (ADS)

We demonstrate a total charge parity measurement by detecting the radio frequency signal that is reflected by a lumped-element resonator coupled to a single InAs nanowire double quantum dot. The high frequency response of the circuit is used to probe the effects of the Pauli exclusion principle at interdot charge transitions. Even parity charge transitions show a striking magnetic field dependence that is due to a singlet-triplet transition, while odd parity transitions are relatively insensitive to a magnetic field. The measured response agrees well with cavity input-output theory, allowing accurate measurements of the interdot tunnel coupling and the resonator-charge coupling rate gc/2?17MHz.

Schroer, M. D.; Jung, M.; Petersson, K. D.; Petta, J. R.

2012-10-01

267

High Frequency Instabilities in Sheaths  

NASA Astrophysics Data System (ADS)

Sheaths occur on interfaces between plasmas and solid bodies such as spacecraft. Sheath potential structures are assumed to be stable but there are many exceptions where sheaths become unstable. These have been studied in laboratory plasmas. When an electrode is biased positively the sheath-plasma instability near the electron plasma frequency is observed. When a gridded sphere is biased positively the plasma bubble exhibits electron transit time oscillations. When the same sphere is biased negatively an instability near the ion plasma frequency is observed. In a magnetic field a ring of energetic electrons is formed around a positively biased electrode. Electron drift wave instabilities are observed. Such instabilities are important for correctly interpreting signals from antennas or tethers in space. (Work supported by DOE/NSF.)

Stenzel, R. L.; Urrutia, J. M.

2011-12-01

268

Frequency response of electrochemical cells  

NASA Astrophysics Data System (ADS)

The main objective was to examine the feasibility of using frequency response techniques (1) as a tool in destructive physical analysis of batteries, particularly for estimating electrode structural parameters such as specific area, porosity, and tortuosity and (2) as a non-destructive testing technique for obtaining information such as state of charge and acceptability for space flight. The phenomena that contribute to the frequency response of an electrode include: (1) double layer capacitance; (2) Faradaic reaction resistance; (3) mass transfer of Warburg impedance; and (4) ohmic solution resistance. Nickel cadmium cells were investigated in solutions of KOH. A significant amount of data was acquired. Quantitative data analysis, using the developed software, is planned for the future.

Thomas, Daniel L.

1990-10-01

269

Integrated optical-frequency mixers  

Microsoft Academic Search

Optical frequency (OF) mixers based on periodically poled lithium mobate (PPLN) waveguides are among the most efficient nonlinear optical devices available today. An attractive technology for communications applications, OF mixers have been used to demonstrate many important all-optical signal-processing functions including wavelength conversion, dispersion compensation by spectral inversion, and 160 Gbit\\/s optical time-division multiplexing. Integrated-optic structures extend the functionality of

Jonathan R. Kurz

2004-01-01

270

Ultra-High-Frequency Oscillography  

Microsoft Academic Search

Starting from the transit-time effects of the first and second kind, occurring in a cathode-ray tube, two methods are described for the oscillographic examination of ultra-high-frequency oscillations. First, we have the inversion spectrograph which supplies, by means of a white and spectrally dispersed electron beam, sinusoidal and complex inversion spectrograms. Second, we may use ultradynamic Lissajous figures which differ from

H. E. Hollmann

1940-01-01

271

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

272

Wireless charging using radio frequency  

Microsoft Academic Search

Wireless technologies such as mobiles, PDAs, laptops, pagers, sensors, embedded controllers etc. have become an integral part of an individual's day-to-day life. Everyone would have faced the problem of their devices going out of charge. This paper explores the possibilities of charging your cell phones wirelessly i. e. radio waves (30 KHz-30MHz). It is observed that the RF frequency can

Prashant Vikram; Sujay Shetty; Sujay Paralikar

2011-01-01

273

FAST low frequency pulsar survey  

NASA Astrophysics Data System (ADS)

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is under construction and will be commissioned in September 2016. A low frequency 7-beam receiver working around 400 MHz is proposed for FAST early science. It will be optimized for a whole FAST sky drift-scan pulsar survey. Simulations show that about 1500 new normal pulsars will be discovered, as while as about 200 millisecond pulsars.

Yue, Youling; Li, Di; Nan, Rendong

2013-03-01

274

Bivariate Instantaneous Frequency and Bandwidth  

Microsoft Academic Search

The generalizations of instantaneous frequency and instantaneous bandwidth to\\u000aa bivariate signal are derived. These are uniquely defined whether the signal\\u000ais represented as a pair of real-valued signals, or as one analytic and one\\u000aanti-analytic signal. A nonstationary but oscillatory bivariate signal has a\\u000anatural representation as an ellipse whose properties evolve in time, and this\\u000arepresentation provides a

Jonathan M. Lilly; Sofia C. Olhede

2009-01-01

275

47 CFR 73.1540 - Carrier frequency measurements.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Carrier frequency measurements. 73.1540 Section 73.1540...Stations § 73.1540 Carrier frequency measurements. (a) The carrier frequency...standard of frequency for radio frequency measurements is the standard frequency...

2011-10-01

276

Variable frequency microwave furnace system  

DOEpatents

A variable frequency microwave furnace system designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity for testing or other selected applications. The variable frequency microwave furnace system includes a microwave signal generator or microwave voltage-controlled oscillator for generating a low-power microwave signal for input to the microwave furnace. A first amplifier may be provided to amplify the magnitude of the signal output from the microwave signal generator or the microwave voltage-controlled oscillator. A second amplifier is provided for processing the signal output by the first amplifier. The second amplifier outputs the microwave signal input to the furnace cavity. In the preferred embodiment, the second amplifier is a traveling-wave tube (TWT). A power supply is provided for operation of the second amplifier. A directional coupler is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load. 5 figs.

Bible, D.W.; Lauf, R.J.

1994-06-14

277

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

278

The Frequency Agile Solar Radiotelescope  

NASA Astrophysics Data System (ADS)

The Frequency Agile Solar Radiotelescope (FASR) is a Fourier synthesis telescope designed to perform broadband imaging spectroscopy over an extremely broad frequency range ( 0.1-30 GHz). The frequency, temporal, and angular resolution of the instrument will be optimized for the many and varied radio phenomena produced by the Sun. Consequently, FASR will the most powerful and versatile radioheliograph ever built. FASR was recommended by the NAS/NRC Astronomy and Astrophysics Survey Committee for construction in the coming decade and is currently under review by the decadal survey of Solar and Space Physics. An NSF-funded study of the instrument concept is currently under way. FASR will probe all phenomena in the solar atmosphere from the mid-chromosphere to the outer corona. The range of science that FASR will address is correspondingly broad. The design and function of FASR offer several unique capabilities, to which several key science goals are well-matched: 1- The nature and evolution of coronal magnetic fields, including direct measurement of coronal magnetic fields; the temporal and spatial evolution of coronal fields; inference of coronal electric currents; the storage and release of magnetic energy. 2- Transient energetic phenomena such as energy release in flares; plasma heating; particle acceleration; electron transport; the formation and destabilization of large scale structures (filaments, coronal mass ejections). 3- Quantitative diagnostics of the three-dimensional solar atmosphere; the quiet Sun and coronal holes; origin of the solar wind; coronal heating; formation of filaments. In addition, FASR will be a powerful tool for synoptic programs and for forecasting activities. The operational model for FASR will make the data widely available for immediate use by the wider scientific community. This talk will introduce the instrument, the science drivers, and the current status and plans for the project.

Bastian, T. S.

2002-05-01

279

TUTORIAL: Frequency metrology and clocks  

NASA Astrophysics Data System (ADS)

Transitions between discrete energy levels in well-isolated atomic systems are highly reproducible and therefore make ideal references for highly accurate frequency standards or clocks. In particular, a single laser-cooled ion confined in a radiofrequency ion trap closely approximates the spectroscopic ideal of a particle at rest in a perturbation-free environment. Narrow optical transitions in such systems are therefore very promising for the realization of optical clocks with accuracy around 2 orders of magnitude higher than current microwave primary standards. In this paper the fundamental aspects, current performance and applications of trapped ion optical clocks are reviewed and the potential for future improvements is considered.

Margolis, H. S.

2009-08-01

280

Introduction to Configural Frequency Analysis  

NASA Astrophysics Data System (ADS)

This is a comprehensive introduction to configural frequency analysis, its rationale, and various modifications. When more individuals than expected display a pattern of characteristics, these individuals belong to a type. When fewer individuals than expected display a pattern they belong to an antitype. This book deals with methods that focus on groups of subjects in contingency tables. A many-faceted statistical method, CFA is useful whenever categorical variables are analyzed. The original contribution of this text is the linking of CFA to log-linear modeling and the general linear model, enabling the reader to relate CFA to a well-known statistical background.

von Eye, Alexander

1990-05-01

281

Formulae for Insect Wingbeat Frequency  

PubMed Central

A formula is developed connecting the wingbeat frequency of insects with their masses and wing areas. It is derived first theoretically, using dimensional analysis, and then it is compared with published measurements. The formula discovered involves two parameters which dimensional analysis alone cannot determine. One of these is evaluated using one among many proposed semi-empirical relationships (the only one that stands scrutiny); the other by fitting a published dataset. It is found that the resulting equation, applying to insects in general, accords well with observation, and indeed is very close to being optimal (in a sense to be defined).

Deakin, Michael A B

2010-01-01

282

The CEBAF Frequency Distribution System  

SciTech Connect

The RF system for the CEBAF accelerator requires that two frequencies, 70.000 and 499.000 MHz, be distributed throughout the accelerator site. Proper operation of the multipass beam requires an energy spread of less than 2.5 {times} 10{sup {minus}5}. This imposes stringent constraints on the allowed slow phase error, in turn implying that there must be active regulation of the phase of the distributed reference frequencies. There are several methods already in use that regulate the phase of a distributed signal. A SLAC type pulsed microwave interferometer was not readily applicable, as this method uses the off time in a pulsed accelerator to perform its phase correction and measurement; CEBAF is a continuous device with every RF bucket filled. Since the CEBAF system requires amplifiers in the distribution line, a diplexed reference signal such as that used at LANL would require a series of discrete control loops, tied together with an overall control loop. It was felt that a less compl

Krycuk, Anton; Mahoney, Kelly; Simrock, Stefan

1991-05-01

283

Forward masking of frequency modulationa  

PubMed Central

Forward masking of sinusoidal frequency modulation (FM) was measured with three types of maskers: FM, amplitude modulation (AM), and a masker created by combining the magnitude spectrum of an FM tone with random component phases. For the signal FM rates used (5, 20, and 40?Hz), an FM masker raised detection thresholds in terms of frequency deviation by a factor of about 5 relative to without a masker. The AM masker produced a much smaller effect, suggesting that FM-to-AM conversion did not contribute substantially to the FM forward masking. The modulation depth of an FM masker had a nonmonotonic effect, with maximal masking observed at an intermediate value within the range of possible depths, while the random-phase FM masker produced less masking, arguing against a spectrally-based explanation for FM forward masking. Broad FM-rate selectivity for forward masking was observed for both 4-kHz and 500-Hz carriers. Thresholds measured as a function of the masker-signal delay showed slow recovery from FM forward masking, with residual masking for delays up to 500?ms. The FM forward-masking effect resembles that observed for AM [Wojtczak and Viemeister (2005). J. Acoust. Soc. Am. 188, 31983210] and may reflect modulation-rate selective neural adaptation to FM.

Byrne, Andrew J.; Wojtczak, Magdalena; Viemeister, Neal F.

2012-01-01

284

47 CFR 74.602 - Frequency assignment.  

Code of Federal Regulations, 2011 CFR

...BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Television Broadcast Auxiliary Stations § 74.602 Frequency...following frequencies are available for assignment to television pickup, television STL, television relay and television...

2011-10-01

285

47 CFR 74.602 - Frequency assignment.  

Code of Federal Regulations, 2012 CFR

...BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Television Broadcast Auxiliary Stations § 74.602 Frequency...following frequencies are available for assignment to television pickup, television STL, television relay and...

2012-10-01

286

Hydrogen Masers with Cavity Frequency Switching Servos.  

National Technical Information Service (NTIS)

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. Two automatic approaches to cavity stabilization have been used successfully in f...

H. B. Owings H. E. Peters P. A. Koppang

1990-01-01

287

47 CFR 74.464 - Frequency tolerance.  

Code of Federal Regulations, 2011 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...Remote Pickup Broadcast Stations § 74.464 Frequency...operating frequency of each station in accordance with the...Tolerance (percent) Base station Mobile station...

2011-10-01

288

47 CFR 74.464 - Frequency tolerance.  

Code of Federal Regulations, 2012 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...Remote Pickup Broadcast Stations § 74.464 Frequency...operating frequency of each station in accordance with the...Tolerance (percent) Base station Mobile station...

2012-10-01

289

47 CFR 87.263 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...least 288 kilometers (180 miles) from the Gulf of Mexico shoreline (outside the Gulf of Mexico region). The frequencies 136.900...frequency 136.750 MHz is available in the Gulf of Mexico Region to serve domestic routes over...

2011-10-01

290

High power, high frequency lasertron rf sources.  

National Technical Information Service (NTIS)

High power rf sources have historically been limited to frequencies at which intense electron beams could be efficiently modulated. We have been exploring the power, frequency and efficiency limitations associated with the use of lasertrons for generating...

J. Norem E. Chojnacki R. Konecny

1990-01-01

291

47 CFR 87.421 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Airport Control Tower Stations § 87.421 Frequencies. The Commission will assign VHF frequencies after coordination...

2011-10-01

292

47 CFR 87.421 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Airport Control Tower Stations § 87.421 Frequencies. The Commission will assign VHF frequencies after coordination...

2012-10-01

293

Compact Acoustic Surface Wave Frequency Multiplexers.  

National Technical Information Service (NTIS)

The design of low cost, compact surface acoustic wave frequency multiplexers is described. The frequency selective properties of surface wave filters are used to achieve low inband (high-Q) loss and high outband rejection. Observations made on measured tr...

K. R. Laker A. J. Budreau P. H. Carr

1974-01-01

294

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.349... (a) The frequency assigned to an aeronautical utility station at an airport...to the ground control frequency, an aeronautical utility station at an airport...

2012-10-01

295

47 CFR 87.217 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Advisory Stations (Unicoms) § 87.217 Frequencies. (a) Only one unicom frequency will be assigned at...

2012-10-01

296

47 CFR 87.351 - Frequency changes.  

Code of Federal Regulations, 2012 CFR

...COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.351 Frequency changes. When the aeronautical utility frequency is required to be changed because of an action by the FAA...

2012-10-01

297

47 CFR 87.351 - Frequency changes.  

Code of Federal Regulations, 2011 CFR

...COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.351 Frequency changes. When the aeronautical utility frequency is required to be changed because of an action by the FAA...

2011-10-01

298

47 CFR 87.217 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Advisory Stations (Unicoms) § 87.217 Frequencies. (a) Only one unicom frequency will be assigned at...

2011-10-01

299

47 CFR 87.349 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...RADIO SERVICES AVIATION SERVICES Aeronautical Utility Mobile Stations § 87.349... (a) The frequency assigned to an aeronautical utility station at an airport...to the ground control frequency, an aeronautical utility station at an airport...

2011-10-01

300

Performance Analysis of a Frequency Hopping Modem.  

National Technical Information Service (NTIS)

The report summarizes an analysis of a wide band modem in the presence of Gaussian noise or CW interference. The modem incorporates time division as the multiple access technique, multiple frequency keying as the modulation technique, frequency hopping as...

A. L. Covitt

1972-01-01

301

47 CFR 27.5 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...frequency assignments. The frequencies available in the Broadband Radio Service (BRS) and Educational Broadband Service (EBS) are...licensee has the right to inspect the construction or installation work. [62 FR 9658, Mar. 3, 1997, as amended at 65 FR...

2011-10-01

302

Time Domain Frequency Stability Calculated from the Frequency Domain Description: Use of the SIGINT Software Package to Calculate Time Domain Frequency Stability from the Frequency Domain.  

National Technical Information Service (NTIS)

The authors describe the use of SIGINT, an interactive software package developed by the National Institute of Standards and Technology, which facilitates the calculation of time domain frequency stability from frequency domain data as a function of measu...

F. L. Walls J. Gary A. O'Gallagher R. Sweet L. Sweet

1991-01-01

303

REVIEW: Optical frequency standards and femtosecond lasers  

NASA Astrophysics Data System (ADS)

A review is presented of the state of the art in a new direction in quantum electronics based on the use of femtosecond lasers for precision frequency measurements and the development of optical frequency and time standards.

Baklanov, E. V.; Pokasov, P. V.

2003-05-01

304

Frequency Converter, 60 Cps to 400 Cps.  

National Technical Information Service (NTIS)

The specification covers the requirements for a shipboard motor alternator, 60 cps to 400 cps frequency converter. The specifications define the frequency converter physical configuration and performance characteristics. (Author)

H. Clark

1965-01-01

305

Long Range Communications at Extremely Low Frequencies.  

National Technical Information Service (NTIS)

Extremely low frequencies (ELF) are ideal for communicating with deeply submerged submarines because, below 100 Hz, electromagnetic waves penetrate deeply into seawater. Propagation at these frequencies takes place in the 'waveguide' formed between the ea...

S. L. Bernstein M. L. Burrows J. E. Evans A. S. Griffiths D. A. McNeill

1973-01-01

306

Fine Synchronization of Coherent Frequency Hopping Signals.  

National Technical Information Service (NTIS)

A method for precise synchronization of receiver timing with a phase coherent frequency hopping signal has been developed. It is assumed that initial synchronization by other techniques has aligned the receiver frequency hopping sequence with the signal w...

A. F. Thornhill

1975-01-01

307

47 CFR 87.323 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...aircraft in the airport area. These frequencies must not be used for air traffic control purposes or to transmit information pertaining to runway, wind or weather conditions. (d) The frequency 3281.0 kHz is available for assignment...

2011-10-01

308

47 CFR 87.323 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...aircraft in the airport area. These frequencies must not be used for air traffic control purposes or to transmit information pertaining to runway, wind or weather conditions. (d) The frequency 3281.0 kHz is available for assignment...

2012-10-01

309

Reduction of frequency noise and frequency shift by phase shifting elements in frequency modulation atomic force microscopy  

SciTech Connect

We recently reported the analysis of the frequency noise in the frequency modulation atomic force microscopy (FM-AFM) both in high-Q and low-Q environments [Rev. Sci. Instrum. 80, 043708 (2009)]. We showed in the paper that the oscillator noise, the frequency fluctuation of the oscillator, becomes prominent in the modulation frequency lower than f{sub 0}/2Q, where f{sub 0} and Q are the resonance frequency and Q-factor. The magnitude of the oscillator noise is determined by the slope of the phase versus frequency curve of the cantilever at f{sub 0}. However, in actual FM-AFM in liquids, the phase versus frequency curve may not be always ideal because of the existence of various phase shifting elements (PSEs). For example, the spurious resonance peaks caused by the acoustic excitation and a band-pass filter in the self-oscillation loop increase the slope of the phase versus frequency curve. Due to those PSEs, the effective Q-factor is often increased from the intrinsic Q-factor of the cantilever. In this article, the frequency noise in the FM-AFM system with the PSEs in the self-oscillation loop is analyzed to show that the oscillator noise is reduced by the increase of the effective Q-factor. It is also shown that the oscillation frequency deviates from the resonance frequency due to the increase of the effective Q-factor, thereby causing the reduction in the frequency shift signal with the same factor. Therefore the increase of the effective Q-factor does not affect the signal-to-noise ratio in the frequency shift measurement, but it does affect the quantitativeness of the measured force in the FM-AFM. Furthermore, the reduction of the frequency noise and frequency shift by the increase of the effective Q-factor were confirmed by the experiments.

Kobayashi, Kei [Office of Society-Academia Collaboration for Innovation, Kyoto University, Katsura, Nishikyo, Kyoto 615-8520 (Japan); Yamada, Hirofumi; Matsushige, Kazumi [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan)

2011-03-15

310

A Physically Based Flood Frequency Distribution  

NASA Astrophysics Data System (ADS)

The geomorphoclimatic instantaneous unit Hydrograph theory, the joint probability density function of storm duration and intensity, and Philip's representation of the infiltration process are used to derive a flood frequency distribution that could be used in regions with no streamflow records. The resulting flood frequency distribution is in analytical form containing only few climatologic and physiographic parameters of the catchment. This frequency distribution was tested against frequency distributions calculated from historic records for arid and wet climates, with good and reasonable results, respectively.

DAz-Granados, M. A.; Valdes, J. B.; Bras, R. L.

1984-07-01

311

High frequency dynamic nuclear polarization.  

PubMed

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 = 1/2 species (13)C or (15)N. The difficulty is still greater when quadrupolar nuclei, such as (17)O or (27)Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime, roughly 150-660 GHz, and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades, scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low 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

2013-04-18

312

Frequency synchronization for generalized OFDMA uplink  

Microsoft Academic Search

In orthogonal frequency division multiple access (OFDMA), the total spectral resource is partitioned into multiple orthogonal subcarriers. These subcarriers are assigned to different users for simultaneous transmission. OFDMA is very sensitive to frequency synchronization errors. In an unsynchronized OFDMA uplink, each user has a different carrier frequency offset (CFO) relative to the common uplink receiver. The orthogonality among subcarriers is

Zhongren Cao; Ufuk Tureli; Yu-Dong Yao; Patrick Honan

2004-01-01

313

High-Frequency Power for Fluorescent Lighting.  

National Technical Information Service (NTIS)

High-frequency power for fluorescent lighting offers many advantages over the standard 60-Hertz frequency, such as reduced operating cost, less heat per lumen and, from 400 Hertz to about 5 kHz, less radio frequency interference. Economic factors, however...

L. J. Elliott S. J. Wooten

1968-01-01

314

Landau damping with high frequency impedance  

SciTech Connect

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

Blaskiewicz,M.

2009-05-04

315

Frequency-variation method for system identification  

Microsoft Academic Search

A frequency-variation method is established for identifying a linear system transfer function from a single set of frequency response data. The method generally applies three different Cauer continued fraction forms. Based on the real and imaginary parts of the frequency response data, a corresponding transfer function can be identified. The identification processes can be carried out with a digital computer.

Leang-San Shieh; JOSE MARIANO NAVARRO

1974-01-01

316

Mutant gene frequencies in cats of Cyprus  

Microsoft Academic Search

Three areas of the island of Cyprus have been sampled for frequency of nine mutant genes among the domestic cat population. The significance of the observed frequencies are discussed with particular reference to the existence of world-wide clines for O (orange) and tb (blotched tabby). The frequencies for Cyprus seems to be intermediate to those reported for European and Asian

Roy Robinson

1972-01-01

317

Look at Motion in the Frequency Domain.  

National Technical Information Service (NTIS)

A moving image can be specified by a contrast distribution, c(x,y,t), over the dimensions of space x,y, and time t. Alternatively, it can be specified by the distribution C(u,v,w) over spatial frequency u,v and temporal frequency w. The frequency represen...

A. B. Watson A. J. Ahumada

1983-01-01

318

High frequency EMI filter parasitic characterization  

Microsoft Academic Search

Design of electrical EMI filters requires an in-depth understanding of the desired frequency response. While low frequency filter performance (below 2-5 MHz) often matches the expected response, at higher frequencies the actual filter attenuation is generally much worse than expected. Traditional explanations involve the self parasitics of the reactive devices, equivalent series inductance (ESL) of capacitors, and equivalent parallel capacitance

Michael Schutten; Satish Prabhakaran; David Karipides; Jeff Nasadoski; Robert Thomas

2011-01-01

319

Frequency-switched heterodyne cavity ringdown spectroscopy  

Microsoft Academic Search

When the frequency of light coupled into a cavity is suddenly shifted, the radiation emanating from the input port of the previously excited cavity can beat with the ref lection of the frequency-shifted input on the surface of a photodetector. When the beat frequency is stable, the time decay of the resulting optical heterodyne signal can be used to measure

M. D. Levenson; B. A. Paldus; T. G. Spence; C. C. Harb; R. N. Zare; M. J. Lawrence; R. L. Byer

2000-01-01

320

Wafer Probing Issues at Millimeter Wave Frequencies  

Microsoft Academic Search

With increased wafer probing activity at millimeter wave frequencies, and the maturing of wafer probing technology itself, new issues have arisen. Many of these issues involve phenomena which, although present at lower frequencies, do not cause significant perturbation at measured data below 40 GHz. At higher frequencies wafer probe systems begin to experience the effects of phenomena such as surface

Edward M. Godshalk

1992-01-01

321

A Passive Hydrogen Maser Frequency Standard  

Microsoft Academic Search

Basic principles, circuit details, and measurements on a passive hydrogen maser frequency standard are presented. The perturbations to the output frequency are discussed and it is shown that the temperature coefficient of the microwave cavity is negligible in this system. Thus the fractional change in the output frequency is about 10-13\\/K determined by the second order Doppler shift and the

F. L. Walls; D. A. Howe

1978-01-01

322

Annular symmetry nonlinear frequency converters.  

PubMed

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 LiNbO(3) or the electric field poling method in stoichiometric LiTaO(3), and their conversion efficiencies, as well as angular and thermal dependencies, were characterized by second harmonic generation. PMID:19529321

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

2006-10-01

323

Radio Frequency Plasma in Water  

NASA Astrophysics Data System (ADS)

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500 K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.

Maehara, Tsunehiro; Toyota, Hiromichi; Kuramoto, Makoto; Iwamae, Atsushi; Tadokoro, Atsushi; Mukasa, Shinobu; Yamashita, Hiroshi; Kawashima, Ayato; Nomura, Shinfuku

2006-11-01

324

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

325

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

326

Radio-frequency characteristics of graphene oxide  

NASA Astrophysics Data System (ADS)

We confirm graphene oxide, a two-dimensional carbon structure at the nanoscale level can be a strong candidate for high-efficient interconnector in radio-frequency range. In this paper, we investigate high frequency characteristics of graphene oxide in range of 0.5-40 GHz. Radio-frequency transmission properties were extracted as S-parameters to determine the intrinsic ac transmission of graphene sheets, such as the impedance variation dependence on frequency. The impedance and resistance of graphene sheets drastically decrease as frequency increases. This result confirms graphene oxide has high potential for transmitting signals at gigahertz ranges.

Kim, Whan Kyun; Jung, Young Mo; Cho, Joon Hyong; Kang, Ji Yoong; Oh, Ju Yeong; Kang, Hosung; Lee, Hee-Jo; Kim, Jae Hun; Lee, Seok; Shin, H. J.; Choi, J. Y.; Lee, S. Y.; Kim, Y. C.; Han, I. T.; Kim, J. M.; Yook, Jong-Gwan; Baik, Seunghyun; Jun, Seong Chan

2010-11-01

327

FREQUENCY CONTROL OF CELL CYCLE OSCILLATORS  

PubMed Central

SUMMARY The cell cycle oscillator, based on a core negative feedback loop and modified extensively by positive feedback, cycles with a frequency that is regulated by environmental and developmental programs to encompass a wide range of cell cycle times. We discuss how positive feedback allows frequency tuning, how size and morphogenetic checkpoints regulate oscillator frequency, and how extrinsic oscillators such as the circadian clock gate cell cycle frequency. The master cell cycle regulatory oscillator in turn controls the frequency of peripheral oscillators controlling essential events. A recently proposed phase-locking model accounts for this coupling.

Oikonomou, Catherine; Cross, Frederick R.

2010-01-01

328

[Morphophysiological effects of an ultrahigh frequency field].  

PubMed

The influence of ultrahigh-frequency field on a honey bee vitality was investigated. Different velocity of heating under the ultrahigh-frequency field action was found for the head, chest and abdomen parts of adult bees. The heating of the body was dependent upon the stage of their development as well. Ultrahigh-frequency field depressed life capacity and induced morphological abnormalities. Modifying influence of ultrahigh-frequency field on morphogenesis events was possible in the case of discrete ultrahigh-frequency action, that had not induced life-dangerous heating of maturing bee body. PMID:8843357

Es'kov, E K

329

Research on semiconductor laser frequency stabilization  

NASA Astrophysics Data System (ADS)

Narrow linewidth and high stability of frequency are extremely necessary in modern precision experiments. The frequency of a free running semiconductor laser will drift several GHz per day, far too much to fulfill the demands in atomic and laser physics. In order to overcome this disadvantage, a variety of technologies for frequency stabilization are researched. The experimental realizations of frequency stabilization based on 780nm semiconductor laser are described in detail. Meanwhile, the performance and capabilities of the various frequency stabilization technologies are analyzed.

Han, Shun-li; Hu, Wei-liang

2013-09-01

330

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

331

WIDE BAND REGENERATIVE FREQUENCY DIVIDER AND MULTIPLIER  

DOEpatents

A regenerative frequency divider and multiplier having wide band input characteristics is presented. The circuit produces output oscillations having frequencies related by a fixed ratio to input oscillations over a wide band of frequencies. In accomplishing this end, the divider-multiplier includes a wide band input circuit coupled by mixer means to a wide band output circuit having a pass band related by a fixed ratio to that of the input circuit. A regenerative feedback circuit derives a fixed frequency ratio feedback signal from the output circuit and applies same to the mixer means in proper phase relation to sustain fixed frequency ratio oscillations in the output circuit.

Laine, E.F.

1959-11-17

332

Optical Frequency Comb Refernced Sub-Doppler Resolution Difference-Frequency Infrared Spectrometer  

NASA Astrophysics Data System (ADS)

We have determined absolute frequencies of 56 transition of the ?_3 band of 12CH_4 and 13CH_4 with at a typical uncertainty level of 2 kHz. While the frequency of the difference-frequency-generation (DFG) source is stabilized to the Lamb dip of the methane transition, the frequencies of the pump and signal source are measured with a 1.5-?m optical frequency comb (OFC). The determined value is consistent with the International Committee for Weight and Measures recommendation within the uncertainty. We have also developed OFC-referenced frequency sweep, which allow us to accumulate spectral data for long time without any frequency drift and to determine the frequency of the transition which are too weak to use the frequency reference for the frequency stabilization.

Iwakuni, K.; Okubo, S.; Nakayama, H.; Sasada, H.; Inaba, H.

2012-06-01

333

Nonlinear cloaking at microwave frequencies  

NASA Astrophysics Data System (ADS)

The ideas of employing the unique properties of metamaterials for cloaking and invisibility applications has been recently suggested and investigated by several groups, because they may find numerous applications in physics and technology. While many of the recent designs of the cloaking structures are based on the transformation optics and exact formulas, the original concept suggested by Tretyakov employed the periodical set of parallel-plate waveguides with the height smoothly varying from H to h in order to reduce drastically the total scattering cross-section of a given object and to obtain broadband cloaking effect. Our paper is devoted to improvement of this design to make tunability and nonlinear effect. The Tretyakov's design was scaled for Ku-band frequencies and the cloak was placed into rectangular waveguide. The broad transmission band ("invisibility region") was obtained. The tunability of transmission band was realized by addition the capacitors into the cloak, between metallic plates. The cloaking system was simulated numerically by CST Microwave Studio. The possibility of invisibility switching on/off was shown by changing of capacity of varactor diodes from 0.4 to 3.4 pF by incident power. The nonlinear cloak behavior was shown at microwaves.

Gurvitz, E. A.; Sedykh, E. A.; Khodzitskiy, M. K.

334

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

335

Infralow-frequency digital phase meter  

NASA Astrophysics Data System (ADS)

Digital methods of measuring phase shifts in the infralow-frequency range are most effective, in terms of high speed and insensitivity to frequency changes in the input signal, but the output signal depends on the frequency of the input signal voltage. This drawback can be overcome by various means such as synchronization or special correction. Precise multiplication of the input signal frequency by a given factor and subsequent filling with the high-frequency of the entire time interval generated by a start-stop module will yield the optimum performance characteristics without additional calibration or correction. Such an instrument consists of two amplifier-limiter stages producing rectangular pulses with a 0.5 duty factor, a mode selector shaping pulses with either of the corresponding two durations, a high-frequency frequency signal generator, a trigger, a frequency divider, a digital period meter, a transcriber, a reversible counter, an OR circuit, two AND circuits, a counter, and three driven multivibrators. In order to cover a wide frequency range, it is necessary to use multidigit devices or, simpler, to generate a set of frequencies not higher than a certain multiple of the pulse repetition rate at the mode selectro output.

Anepir, A. A.; Anepir, Y. A.; Gutorov, O. I.; Zainchkovskiy, V. N.; Mikhaylov, Y. G.

1984-09-01

336

The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency  

SciTech Connect

Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz-13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I-V curves that the higher driving frequency induced higher discharge currents, and the gas temperature was increased as the driving frequency was increased.

Kim, Dan Bee [Division of Physical Metrology, Korea Research Institute of Standards and Science, 209 Gajeongno, Yuseong-gu, Daejeon 305-340 (Korea, Republic of); Jung, H.; Gweon, B.; Rhee, J. K.; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Moon, S. Y. [LG Electronics Advanced Research Institute, 16 Woomyeon-Dong, Seocho-Gu, Seoul 137-724 (Korea, Republic of)

2011-04-15

337

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

338

Frequency response of sampled-data systems  

Microsoft Academic Search

This paper introduces the concept of frequency response for sampled-data systems and explores some basic properties as well as its computational procedures. It is shown that 1) by making use of the lifting technique, the notion of frequency response can be naturally introduced to sampled-data systems in spite of their time-varying characteristics, 2) it represents a frequency domain steady-state behaviour,

Yutaka Yamamoto; Pramod P. Khargonekar

1996-01-01

339

Two low frequency surveys of radio galaxies  

Microsoft Academic Search

High resolution, low frequency observations are very efficient for surveying radio galaxies because of: (1) the wide field of view; and (2) the bias toward steep spectrum (lobe dominated) emission. Here I present preliminary results from two ongoing low frequency radio surveys: the 4 Meter All Sky Survey (4MASS) and the low frequency counterpart to the XMM-Large Scale Structure (XMM-LSS)

A. S Cohen; T. J. W Lazio; N. E Kassim; R. A Perley; W. D Cotton; J. Condon; H. J. A Rttgering; R. Wilman; P. Best; M. Pierre; M. Birkinshaw; A. Zanichelli

2003-01-01

340

Ciliary beat frequency in newborn infants.  

PubMed Central

The ciliary beat frequencies of 31 newborns and 14 adults were measured in vitro by a photodiode method at body temperature (37 degrees C). The mean (SD) neonatal ciliary beat frequency (12.7 (0.82) Hz) was faster than that in adults (11.1 (0.84) Hz) (p less than 0.01). Increased ciliary beat frequency may be advantageous during the neonatal period.

O'Callaghan, C; Smith, K; Wilkinson, M; Morgan, D; Priftis, K

1991-01-01

341

On the frequency scalings of RF guns  

SciTech Connect

A frequency scaling law for RF guns is derived from the normalized Vlasov-Maxwell equations. It shows that higher frequency RF guns can generate higher brightness beams under the assumption that the accelerating gradient and all beam and structure parameters are scaled with the RF frequency. Numerical simulation results using MAGIC confirm the scaling law. A discussion of the range of applicability of the law is presented. {copyright} 1995 {ital American Institute of Physics}.

Lin, L.C.; Chen, S.C.; Wurtele, J.S. [Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1995-06-01

342

Stabilized fiber-optic frequency distribution system  

Microsoft Academic Search

A technique for stabilizing reference frequencies transmitted over fiber-optic cable in a frequency distribution system is discussed. The distribution system utilizes fiber-optic cable as the transmission medium to distribute precise reference signals from a frequency standard to remote users. The stability goal of the distribution system is to transmit a 100-MHz signal over a 22-km fiber-optic cable and maintain a

L. E. Primas; G. F. Lutes; R. L. Sydnor

1989-01-01

343

Dual vibrational high frequency magnetic force microscopy  

Microsoft Academic Search

The ability to evaluate high frequency writer performance is crucial to the write-head designs for high data rate application. To quantify the write-head performance at high frequency (~1 GHz), a new high frequency detection approach has been implemented. The essence of the method is to utilize a two-step signal mixing process to produce the force harmonics, which are not only

Shaoping Li; Scott Stokes; Y. Liu; Sheryl Foss-Schroder; W. Zhu; Dean Palmer

2002-01-01

344

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

345

Power system frequency monitoring network (FNET) implementation  

Microsoft Academic Search

Frequency dynamics is one of the most important measures of an electrical power system status. To better understand power system dynamics, an accurately measured wide-area frequency is needed. The concept of building an Internet-based real-time GPS-synchronized wide-area frequency monitoring network (FNET) was proposed in 2000 by Qiu et al., and this concept has been realized. The FNET system consists of

Zhian Zhong; Chunchun Xu; Bruce J. Billian; Li Zhang; Shu-Jen Steven Tsai; Richard W. Conners; Virgilio A. Centeno; Arun G. Phadke; Yilu Liu

2005-01-01

346

A novel frequency-scanned reflector antenna  

Microsoft Academic Search

Theoretical and experimental results are presented for a frequency-scanned antenna composed of a line source and a frequency-scanned reflection grating that is shaped to a cylindrical reflector. The principle considered is to select the grating geometry such that the first higher-order diffracted wave propagates and serves as the frequency-scanned beam. An analytical solution for the cylindrical reflector geometry that gives

F. Stefan Johansson; Lars G. Josefsson; Torlid Lorentzon

1989-01-01

347

Frequency-switched heterodyne cavity ringdown spectroscopy.  

PubMed

When the frequency of light coupled into a cavity is suddenly shifted, the radiation emanating from the input port of the previously excited cavity can beat with the reflection of the frequency-shifted input on the surface of a photodetector. When the beat frequency is stable, the time decay of the resulting optical heterodyne signal can be used to measure intracavity absorption spectra with near quantum-limited sensitivity. PMID:18064227

Levenson, M D; Paldus, B A; Spence, T G; Harb, C C; Zare, R N; Lawrence, M J; Byer, R L

2000-06-15

348

Instantaneous frequency based newborn EEG seizure characterisation  

NASA Astrophysics Data System (ADS)

The electroencephalogram (EEG), used to noninvasively monitor brain activity, remains the most reliable tool in the diagnosis of neonatal seizures. Due to their nonstationary and multi-component nature, newborn EEG seizures are better represented in the joint time-frequency domain than in either the time domain or the frequency domain. Characterising newborn EEG seizure nonstationarities helps to better understand their time-varying nature and, therefore, allow developing efficient signal processing methods for both modelling and seizure detection and classification. In this article, we used the instantaneous frequency (IF) extracted from a time-frequency distribution to characterise newborn EEG seizures. We fitted four frequency modulated (FM) models to the extracted IFs, namely a linear FM, a piecewise-linear FM, a sinusoidal FM, and a hyperbolic FM. Using a database of 30-s EEG seizure epochs acquired from 35 newborns, we were able to show that, depending on EEG channel, the sinusoidal and piecewise-linear FM models best fitted 80-98% of seizure epochs. To further characterise the EEG seizures, we calculated the mean frequency and frequency span of the extracted IFs. We showed that in the majority of the cases (>95%), the mean frequency resides in the 0.6-3 Hz band with a frequency span of 0.2-1 Hz. In terms of the frequency of occurrence of the four seizure models, the statistical analysis showed that there is no significant difference( p = 0.332) between the two hemispheres. The results also indicate that there is no significant differences between the two hemispheres in terms of the mean frequency ( p = 0.186) and the frequency span ( p = 0.302).

Mesbah, Mostefa; O'Toole, John M.; Colditz, Paul B.; Boashash, Boualem

2012-12-01

349

A cesium fountain frequency standard: preliminary results  

Microsoft Academic Search

An atomic frequency standard based on a fountain of cold cesium atoms has been in operation in our laboratory for a few months. Ramsey fringes as narrow as 0.7 Hz have been obtained. The short-term frequency stability, measured against an H-maser, is 3 10-13 ?-1\\/2, probably limited by the local oscillator frequency noise. A preliminary evaluation of some systematic effects

A. Clairon; P. Laurent; G. Santarelli; S. Ghezali; S. N. Lea; M. Bahoura

1995-01-01

350

Environmental factors and hydrogen maser frequency stability  

Microsoft Academic Search

It is necessary to have a complete understanding of the environmental sensitivities of cavity-tuned hydrogen masers to obtain optimum frequency stability and to avoid common-mode frequency fluctuations. Measurements of environmental sensitivities (temperature, relative humidity, atmospheric pressure, line voltage and magnetic field) made at the National Institute of Standards and Technology have demonstrated that the frequency stability of a cavity-tuned, active

Thomas E. Parker

1999-01-01

351

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

352

Single frequency and tunable laser diodes  

Microsoft Academic Search

The state-of-the-art technologies for single-frequency and frequency-tunable laser diodes are reviewed. Spectral linewidth characteristics for distributed-feedback laser diodes are discussed, based on experimentally observed discrepancies from the theory and improvements obtained with quantum-well active regions. Frequency-tunable mechanisms are reviewed mainly for monolithic tunable laser diodes with distributed-Bragg-reflector (DBR) or distributed-feedback configurations

Kohroh Kobayashi; Ikuo Mito

1988-01-01

353

Resonant frequency multiplication in microscopic magnetic dots  

NASA Astrophysics Data System (ADS)

We demonstrate the phenomenon of nonlinear frequency multiplication in sub-micrometer Permalloy dots. The efficiency of multiplication is strongly enhanced when the harmonic is resonant with the normal dynamical modes of the dot. We find that the characteristics of resonant enhancement are dependent on the spatial symmetry of the dynamical mode and are different for the double- and the triple-frequency harmonics. The resonant frequency tripling is particularly efficient, providing a practical route for the implementation of microscopic integrated microwave frequency multipliers.

Demidov, V. E.; Ulrichs, H.; Urazhdin, S.; Demokritov, S. O.; Bessonov, V.; Gieniusz, R.; Maziewski, A.

2011-07-01

354

Psychophysical tuning curves at very high frequencies  

NASA Astrophysics Data System (ADS)

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

Yasin, Ifat; Plack, Christopher J.

2005-10-01

355

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

356

A DPTD frequency standard comparison system.  

PubMed

A dual phase-coincidence-detection time difference (DPTD) system for frequency standard comparison is proposed in this paper. Based on the concept of the greatest common factor frequency and a high-stability common frequency source, a high-resolution phase comparison between frequency standards can be implemented by utilizing the phase coincidence detection approach. The resolution of this simple instrument is better than 10 ps and the resolution of theoretical analysis is much higher than 10 ps. Compared with dualmixer time difference systems, a comparison system based on this method is simple in structure and low in cost. PMID:23192802

Wang, Hai; Zhang, Min; Li, Li

2012-11-01

357

47 CFR 87.279 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Enroute and Aeronautical Fixed Stations Aeronautical Fixed Stations § 87.279 Frequencies. (a) United States (except...

2011-10-01

358

47 CFR 87.279 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Enroute and Aeronautical Fixed Stations Aeronautical Fixed Stations § 87.279 Frequencies. (a) United States (except...

2012-10-01

359

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

360

Frequencies for Pain Reliever Questionnaire Items: Divided ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Divided Attention Time spent reading food label (seconds). Statistics. N. Valid. Missing. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

361

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention Recognize any adverse (bad) reactions. Statistics. N. Valid. Missing. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

362

Comparison between Ramp Pulse Modulation (RPM) and constant frequency modulation for the beat frequency oscillation in voltage regulators  

Microsoft Academic Search

In the voltage regulator (VR) applications, the load frequency varies in a very wide range from several kHz to several MHz. When the load transient frequency approaches to the switching frequency of VR, there is a low frequency oscillation in the system, which is the beat frequency oscillation between the load transient frequency and the switching frequency of VR. When

Kisun Lee; Han Zou

2010-01-01

363

Life span of ventricular fibrillation frequencies.  

PubMed

The nature and organization of electrical activity during ventricular fibrillation (VF) are important and controversial subjects dominated by 2 competing theories: the wavebreak and the dominant mother rotor hypothesis. To investigate spatiotemporal characteristics of ventricular fibrillation (VF), transmembrane potentials (V(m)) were recorded from multiple sites of perfused rabbit hearts using a voltage-sensitive dye and a photodiode array or a CCD camera, and the time-frequency characteristics of V(m) were analyzed by short-time fast Fourier transform (FFT) or generalized time-frequency representation with a cone-shaped kernel. The analysis was applied to all pixels to track VF frequencies in time and space. VF consisted of blobs, which are groups of contiguous pixels with a common frequency and an ill-defined shape. At any time t, several VF frequency blobs coexisted in the field of view, and the number of coexisting blobs was on average 5.9+/-2.1 (n=8 hearts) as they appeared and disappeared discontinuously with time and were not fixed in space. The life span of frequency blobs from birth to either annihilation or breakup to another frequency had a half-life of 0.39+/-0.13 second (n=4 hearts). The Ca2+ channel blocker nifedipine increased the stability of VF frequencies and reduced the number of frequency blobs progressing to a single frequency. In conclusion, VF consists of dynamically changing frequency blobs, which have a short life span and can be modified by pharmacological interventions, suggesting that VF is maintained by dynamically changing multiple wavelets. PMID:12193467

Choi, Bum-Rak; Nho, Wonchul; Liu, Tong; Salama, Guy

2002-08-23

364

Orbiting Low Frequency Array for radio astronomy  

Microsoft Academic Search

Recently new and interesting science drivers have emerged for very low frequency radio astronomy from 0.3 MHz to 30 MHz. However Earth bound radio observations at these wavelengths are severely hampered by ionospheric distortions, man made interference, solar flares and even complete reflection below 10 MHz. OL- FAR is Orbiting Low Frequency ARray, a project whose aim is to develop

Raj Thilak Rajan; Steven Engelen; Mark Bentum; Chris Verhoeven

2011-01-01

365

Multiridge detection and time-frequency reconstruction  

Microsoft Academic Search

The ridges of the wavelet transform, the Gabor transform, or any time-frequency representation of a signal contain crucial information on the characteristics of the signal. Indeed, they mark the regions of the time-frequency plane where the signal concentrates most of its energy. We introduce a new algorithm to detect and identify these ridges. The procedure is based on an original

R. A. Carmona; Wen L. Hwang; B. Torresani

1999-01-01

366

47 CFR 74.1261 - Frequency tolerance.  

Code of Federal Regulations, 2012 CFR

...booster station with an authorized transmitter power output of 10 watts or less shall maintain the center frequency at the output of...station with an authorized transmitter power output greater than 10 watts shall maintain the center frequency at the output of the...

2012-10-01

367

Detection and frequency tracking of chirping signals  

SciTech Connect

This paper discusses several methods to detect the presence of and track the frequency of a chirping signal in broadband noise. The dynamic behavior of each of the methods is described and tracking error bounds are investigated in terms of the chirp rate. Frequency tracking and behavior in the presence of varying levels of noise are illustrated in examples. 11 refs., 29 figs.

Elliott, G.R.; Stearns, S.D.

1990-08-01

368

Frequencies for Cough/ Cold Questionnaire Items - Label ...  

Center for Drug Evaluation (CDER)

... Frequencies for Cough/ Cold Questionnaire Items - Label Ranked #12. Label ranked #12. Frequency. ... 687, 15, 3.3, 3.3, 95.4. 241, 12, 2.6, 2.6, 98.0. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

369

Frequency of severe storms and global warming  

Microsoft Academic Search

We use five years of data from the Atmospheric Infrared Sounder (AIRS) to develop a correlation between the frequency of Deep Convective Clouds (DCC) and the zonal mean tropical surface temperature. AIRS data show that the frequency of DCC in the tropical oceans is very temperature sensitive, increasing 45% per 1 K increase of the zonal mean surface temperature. The

Hartmut H. Aumann; Alexander Ruzmaikin; Joao Teixeira

2008-01-01

370

On Resonant Heating Below the Cyclotron Frequency  

SciTech Connect

Resonant heating of particles by an electrostatic wave propagating perpendicular to a confining uniform magnetic field is examined. It is shown that, with a sufficiently large wave amplitude, significant perpendicular stochastic heating can be obtained with wave frequency at a fraction of the cyclotron frequency.

Liu Chen; Zhihong Lin; White, R.

2001-02-02

371

Uncertainties in Adaptive Maximum Entropy Frequency Estimators.  

National Technical Information Service (NTIS)

For a real sinusoid in white noise, the weight vector noise associated with an adaptive maximum entropy frequency estimator causes the peak of the spectrum estimator to shift away from the input frequency. For a long adaptive filter and a normalized frequ...

R. J. Keeler

1979-01-01

372

Calibration of current transducers at high frequencies  

Microsoft Academic Search

The transfer impedances of current transducers are estimated using a special calibration fixture, which is often assumed to be perfectly matched at its coaxial ports. However, the errors inherent in this approximation increase with frequency, making the measurement of cable currents increasingly inaccurate at higher frequencies. A one-dimensional (1-D) transmission line model is proposed to account for such errors in

Alastair R. Ruddle; Simon C. Pomeroy; David D. Ward

2001-01-01

373

New Frequency for Piezoelectric Resonator Measurement.  

National Technical Information Service (NTIS)

When a quartz crystal resonator unit is used in a reflectance bridge to stabilize the frequency of an oscillator it is found that the frequency is insensitive to the length of the cable between the crystal unit and the bridge. Properties of the reflection...

W. H. Horton R. C. Smythe

1983-01-01

374

DQPSK Receiver tolerance to transmitter frequency stability  

Microsoft Academic Search

In case of Differential Quadrature Phase Shift Keying transmission, the diode laser frequency instability affects the quality of the received signal. Free-running transmitters are employed to experimentally evaluate the tolerance of the interferometric DQPSK receiver to this instability. Heterodyne measure of the frequency offset is discussed for different transmitters. Experimental data are related both with BER performance and power penalty.

Lucia Marazzi; Paola Parolari; Pierpaolo Boffi; Rocco Siano; Matteo Feroldi; M. Martinelli

2006-01-01

375

Note on Frequency Shifts in Dispersing Media  

Microsoft Academic Search

The propagation of a light wave through a dispersing medium is discussed. The absorption frequencies of the medium are shown to be the absorption frequencies of the coupled system formed by molecules contained in a cavity elongated in the direction of the electric intensity of the incident wave. The cavity is supposed to contain a large number of molecules and

G. Breit; E. O. Salant

1930-01-01

376

Text Genre Detection Using Common Word Frequencies  

Microsoft Academic Search

In this paper we present a method for detecting the text genre quickly and easily following an approach originally proposed in authorship attribution studies which uses as style markers the frequencies of occurrence of the most frequent words in a training corpus (Burrows, 1992). In contrast to this approach we use the frequencies of occurrence of the most frequent words

Efstathios Stamatatos; Nikos Fakotakis; George K. Kokkinakis

2000-01-01

377

Frequency agile stepped OFDM waveform for HRR  

Microsoft Academic Search

High range resolution (HRR) is an important feature for radar, aiming at target classification. The range resolution is inversely proportional to the bandwidth of the transmitted signal. Pulse burst waveforms can achieve HRR at low expenses when the carrier frequency increases from one pulse to the next, stepping and synthesizing the wide bandwidth. In such a stepped frequency approach the

Gabriel Lellouch; Radmila Pribic; Piet van Genderen

2009-01-01

378

Frequency interference between two quartz crystal microbalances  

Microsoft Academic Search

Multichannel quartz crystal microbalances (MQCM) are very attractive for biosensor applications because these devices can be miniaturized using microelectromechanical systems micromachining technology, leading to substantial reductions in cost, diagnostic time, and sample volumes. However, the miniaturization also brings about frequency interference between adjacent microbalances and the measuring accuracy will thus be affected by the extent of frequency coupling. In this

Feng Shen; Kwok Hong Lee; Sean J. O'Shea; Pin Lu; Teng Yong Ng

2003-01-01

379

High frequency measurement of multilayer ceramic capacitors  

Microsoft Academic Search

The monolithic ceramic capacitor (MLC) is small and has good high frequency performance. It is used in various high frequency circuits for impedance matching, DC block, filter and bypass functions. For the best performance in these applications, low equivalent series resistance (ESR) and equivalent series inductance (ESL) is required. We have developed the testing method to compare the performance of

Yukio Sakabe; Masami Hayashi; Takefumi Ozaki; James P. Canner

1996-01-01

380

Frequency Reliability Sensitivity for Dynamic Structural Systems  

Microsoft Academic Search

Parameter uncertainty of structural systems is inherent in most engineering problems. Therefore, reliability analysis of uncertain structural systems is of great significance, and frequency reliability analysis is important to uncertain vibration structure systems. Based on the frequency reliability theory, this article introduces an approach to calculate the reliability of a mechanical structure under dynamic excitation. With the criterion that the

Yimin Zhang; Chunmei L; Na Zhou; Changqing Su

2010-01-01

381

Resonant Magnetic Field Sensor With Frequency Output  

Microsoft Academic Search

This paper presents a novel type of resonant magnetic field sensor exploiting the Lorentz force and providing a frequency output. The mechanical resonator, a cantilever structure, is embedded as the frequency-determining element in an electrical oscillator. By generating an electrical current proportional to the position of the cantilever, a Lorentz force acting like an additional equivalent spring is exerted on

Robert Sunier; Tobias Vancura; Yue Li; Kay-Uwe Kirstein; Henry Baltes; Oliver Brand

2006-01-01

382

Natural frequencies of simply supported circular plates  

Microsoft Academic Search

Although the problem of finding the natural frequencies of free vibration of a simply supported circular plate has a straightforward solution, very few numerical results are available in the literature. In the present work accurate (six significant figure) non-dimensional frequency parameters (lambda2) are given for all values of n + s <= 10, where n and s are the numbers

A. W. Leissa; Y. Narita

1980-01-01

383

Natural frequencies of clamped orthotropic skew plates  

Microsoft Academic Search

Approximate formulae are proposed for estimating natural frequencies of isotropic and specially orthotropic skew plates with clamped sides. It has been shown previously that one can estimate a natural frequency of a generally orthotropic skew plate with clamped sides by using an approximate formula for the isotropic plate which one can relate to the orthotropic one by applying a previously

T. Sakata; T. Hayashi

1982-01-01

384

Frequency domain modeling of nanophotonic devices  

Microsoft Academic Search

Several problems in nanophotonics are uniquely suitable for frequency domain modeling methods. We first present a new method for sensitivity analysis of nanophotonic devices. The algorithm is based on the finite-difference frequency-domain method and uses the adjoint variable method and perturbation theory techniques. We show that our method is highly efficient and accurate and can be applied to the calculation

Georgios Veronis; Shanhui Fan

2006-01-01

385

Low Frequency Electromagnetic Cross-Borehole Imaging.  

National Technical Information Service (NTIS)

Most of the research in cross-borehole electromagnetic (EM) imaging has been done at high frequencies (17 to 200 Mhz). At these frequencies, the propagation distance through-the-earth is limited to less than 8 meters and the attenuation of the signal depe...

M. Pihlman P. E. Harben

1988-01-01

386

Single-layer dual frequency patch antenna  

Microsoft Academic Search

A configuration for a slotted patch antenna is introduced which allows two separate operating frequencies. Both of these frequencies are associated with a radiating mode almost identical to that of a standard patch. The two resonances are related to the patch width and the slot\\/patch length, respectively.

S. Maci; Gentili Biffi; G. Avitabile

1993-01-01

387

Amplitude Frequency Response Measurement: A Simple Technique  

Microsoft Academic Search

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 is operated in the Envelope acquisition mode. Under these

L. Satish; Santosh C. Vora

2010-01-01

388

Detection of Partial Discharges at High Frequencies  

Microsoft Academic Search

This paper details a partial discharge measurement detection model that has been used to produce a test circuit suitable for detection of partial discharge at high frequencies. The circuit is designed to identify partial discharges in different insulating samples stressed by non-standard (including high frequency sine-waves and square waves). This is particularly important for the testing of equipment used in

F. Alrumayan; I. Cotton

2006-01-01

389

Physics of Radio-Frequency Plasmas  

NASA Astrophysics Data System (ADS)

1. Introduction; 2. Plasma dynamics and equilibrium; 3. Bounded plasmas; 4. Radiofrequency sheaths; 5. Single frequency capacitively-coupled plasmas; 6. Multi-frequency capacitively-coupled plasmas; 7. Inductively-coupled plasmas; 8. Helicon plasmas; 9. Real plasmas; 10. Electrical measurements; Index.

Chabert, Pascal; Braithwaite, Nicholas

2011-02-01

390

High power radio frequency attenuation device  

Microsoft Academic Search

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling

Q. A. Kerns; H. W. Miller

1984-01-01

391

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

392

47 CFR 90.213 - Frequency stability.  

Code of Federal Regulations, 2011 CFR

...base stations with a 12.5 kHz channel bandwidth must have a frequency stability of...base stations with a 6.25 kHz channel bandwidth must have a frequency stability of 1...designed to operate with a 12.5 kHz channel bandwidth or designed to operate on a...

2011-10-01

393

47 CFR 90.213 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...base stations with a 12.5 kHz channel bandwidth must have a frequency stability of...base stations with a 6.25 kHz channel bandwidth must have a frequency stability of 1...designed to operate with a 12.5 kHz channel bandwidth or designed to operate on a...

2012-10-01

394

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 Bckstrm; Carlo Magi; Paavo Alku

2007-01-01

395

Steady state frequency response of STATCOM  

Microsoft Academic Search

The paper develops analytical expressions for the admittances and impedances of a static synchronous compensator (STATCOM) as a function of frequency. The expressions include the conventional positive and negative sequence admittance as well as transfer admittances where a positive sequence current generates a negative sequence voltage at another frequency. These results are then corroborated using the tool of electromagnetic transients

M. Mohaddes; A. M. Gole; Sladjana Elez

2001-01-01

396

High Frequency Fatigue of Turbine Blade Material.  

National Technical Information Service (NTIS)

This increased fatigue crack growth rate at elevated temperature due to high frequency loading is examined. The crack growth rate is found to depend upon major cycle stress intensity factor, hold-time and minor cycle frequency, and amplitude for a given t...

R. C. Goodman A. M. Brown

1982-01-01

397

Frequency distribution for suspended sediment loads  

Microsoft Academic Search

A method is described for deriving a frequency distribution for suspended sediment loads. The method uses a curvilinear regression relation between the logarithm of annual flood peaks and the logarithm of suspended sediment loads associated with that flood peak. It combines this relation with a log-Pearson type III distribution for annual floods to produce a sediment load frequency distribution. Suspended

R. S. Parker; Brent M. Troutman

1989-01-01

398

HIGH FREQUENCY ULTRASONIC IMAGING AND TISSUE CHARACTERIZATION  

Microsoft Academic Search

High frequency ultrasonic imaging is considered by many to be the next frontier in ultrasonic imaging. It has many clinical applications ranging from imaging the eye and skin to small animal imaging. Small animal imaging has recently generated intense interest for the purpose of evaluating the efficacy of drugs and gene therapy. Commercial high frequency scanners often termed \\

K. K. Shung

399

Circular-edge spatial frequency response test  

Microsoft Academic Search

A new method for testing the resolution of digital cameras has been developed. The new method is an extension of the ISO 12233 Slanted-edge Spatial Frequency Response test. The new method computes the spatial frequency response along the edge of a circle. It is especially well adapted to inexpensive imaging systems with rotationally symmetric blur and lens distortion. In addition

Richard L. Baer

2003-01-01

400

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...STATIONS IN THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency...

2011-10-01

401

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...STATIONS IN THE MARITIME SERVICES Frequencies Ship Earth Stations § 80.377 Frequencies for ship earth stations. The frequency...

2012-10-01

402

Metal mesh resonant filters for terahertz frequencies.  

PubMed

The interest in terahertz photometric and imaging measurements has motivated the development of bandpass resonant filters to be coupled to multiple-pixel devices such as bolometer arrays. Resonant grids are relatively simple to fabricate, exhibiting high transmission at the central frequency, a narrow bandpass, and good rejection of the side frequencies of the spectrum. We have fabricated filters centered at different frequencies between 0.4 and 10 THz, using photolithography and electroforming techniques. Transmission measurements have shown center frequencies and bandwidths close to the design predictions. The performance of the filters was found not to be critically dependent on small physical deformations in the mesh, becoming more noticeable at higher frequencies (i.e., for smaller physical sizes). Wider bandwidths, needed to attain higher sensitivities in the continuum, were obtained by changing the design parameters for filters at 2 and 3 THz. PMID:19002231

Melo, Arline M; Kornberg, Mariano A; Kaufmann, Pierre; Piazzetta, Maria H; Bortolucci, Emlio C; Zakia, Maria B; Bauer, Otto H; Poglitsch, Albrecht; da Silva, Alexandre M P Alves

2008-11-10

403

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

404

Ultrasonic Atomization Amount for Different Frequencies  

NASA Astrophysics Data System (ADS)

The mass flow rate of ultrasonic atomization was estimated by measuring the vaporization amount from a bulk liquid with a fountain. The effects of ultrasonic frequency and intensity on the atomization characteristics were investigated when the directivities of the acoustic field from a transducer were almost the same. The sample was distillated water and the ultrasonic frequencies were 0.5, 1.0, and 2.4 MHz. The mass flow rate of ultrasonic atomization increased with increasing ultrasonic intensity and decreasing ultrasonic frequency. The fountain was formed at the liquid surface where the effective value of acoustic pressure was above atmospheric pressure. The fountain height was strongly governed by the acoustic pressure at the liquid surface of the transducer center. At the same ultrasonic intensity, the dependence of ultrasonic frequency on the number of atomized droplets was small. At the same apparent surface area of the fountain, the number of atomized droplets became larger as the ultrasonic frequency increased.

Yasuda, Keiji; Honma, Hiroyuki; Xu, Zheng; Asakura, Yoshiyuki; Koda, Shinobu

2011-07-01

405

A Two-Frequency RF Photocathode Gun  

SciTech Connect

In this paper we resurrect an idea originally proposed by Serafini[1] in 1992 for an RF photocathode gun capable of operating simultaneously at the fundamental frequency and a higher frequency harmonic. Driving the gun at two frequencies with the proper field ratio and relative phase produces a beam with essentially no rf emittance and a linear longitudinal phase space distribution. Such a gun allows a completely new range of operating parameters for controlling space charge emittance growth. In addition, the linear longitudinal phase space distribution aids in bunch compression. This paper will compare results of simulations for the two-frequency gun with the standard rf gun, and the unique properties of the two-frequency gun will be discussed.

Dowell, D.

2004-11-05

406

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

407

Frequency conversion of an entangled state  

SciTech Connect

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 the 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 the entangled state can be used in quantum communication network and the calculated results can provide direct references for the design of experimental systems.

Tan Aihong; Jia Xiaojun; Xie Changde [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University Taiyuan 030006 (China)

2006-03-15

408

Phase-stabilized 167 MHz repetition frequency carbon nanotube fiber laser frequency comb  

Microsoft Academic Search

The frequency comb generated by a high repetition frequency erbium-doped fiber ring laser using carbon nanotube saturable absorber is phase-stabilized for the first time. The comb's stability is compared a photonic crystal fiber acetylene reference.

Jinkang Lim; Kevin Knabe; Yishan Wang; Rodrigo Amezcua-Correa; Franois Couny; Philip S. Light; Fetah Benabid; Jonathan C. Knight; Kristan L. Corwin; Jeffrey W. Nicholson; Brian R. Washburn

2009-01-01

409

Optimum frequency band for radio polarization observations  

NASA Astrophysics Data System (ADS)

Polarized radio synchrotron emission from interstellar, intracluster and intergalactic magnetic fields is affected by frequency-dependent Faraday depolarization. The maximum polarized intensity depends on the physical properties of the depolarizing medium. New-generation radio telescopes such as Low Frequency Array (LOFAR), the Square Kilometre Array (SKA) and its precursors need a wide range of frequencies to cover the full range of objects. The optimum frequency of maximum polarized intensity (PI) is computed for the cases of depolarization in magneto-ionic media by regular magnetic fields (differential Faraday rotation) or by turbulent magnetic fields (internal or external Faraday dispersion), assuming that the Faraday spectrum of the medium is dominated by one component or that the medium is turbulent. Polarized emission from bright galaxy discs, spiral arms and cores of galaxy clusters are best observed at wavelengths below a few centimetres (at frequencies beyond about 10 GHz), haloes of galaxies and clusters around decimetre wavelengths (at frequencies below about 2 GHz). Intergalactic filaments need observations at metre wavelengths (frequencies below 300 MHz). Sources with extremely large intrinsic rotation measure | RM | or RM dispersion can be searched with mm-wave telescopes. Measurement of the PI spectrum allows us to derive the average Faraday | RM | or the Faraday dispersion within the source, as demonstrated for the case of the spiral galaxy NGC 6946. Periodic fluctuations in PI at low frequencies are a signature of differential Faraday rotation. Internal and external Faraday dispersion can be distinguished by the different slopes of the PI spectrum at low frequencies. A wide band around the optimum frequency is important to distinguish between varieties of depolarization effects.

Arshakian, Tigran G.; Beck, Rainer

2011-12-01

410

Single and Multiple Frequency Fiber Lasers  

NASA Astrophysics Data System (ADS)

Single frequency, low intensity noise, widely tunable lasers operating in the 1.5 ?m region have potential applications in future wavelength division multiplexed optical communications systems, fiber sensor arrays and high resolution spectroscopic measurements. A single frequency fiber laser having these characteristics will be described in detail. The laser cavity contains an erbium doped fiber gain module, fiber isolators to ensure unidirectional travelling wave operation and two fiber Fabry-Perot filters acting in tandem, which provide broadband tunability (1530 nm-1560 nm) combined with stable single frequency operation. Shot noise limited operation of this laser has been observed at frequencies greater than 300 MHz. At lower frequencies (1-300 MHz) the intensity noise has been characterized in terms of sidemode suppression (>60 dB of minimum sidemode suppression has been realized). Lower still (10 kHz-1 MHz) the intensity noise is dominated by the laser's relaxation resonance (30 kHz @ 1 mW output, -105 dBc/Hz). The linewidth of this laser has been measured to be less than 4 kHz using a loss compensated recirculating delayed self -heterodyne interferometer (RDSHI). The RDSHI is an improvement over the standard delayed self-heterodyne interferometer in that the effective delay line can be increased by a factor of 30 over the standard method, increasing the resolution by a corresponding amount. The RDSHI also allows measurement of the short term frequency jitter of a laser. In order to reduce laser frequency jitter, the Pound-Drever technique was employed to lock the laser frequency to an external fiber Fabry-Perot. The same technique also permitted the internal mode selection filter to track the laser frequency, completely eliminating residual mode hopping due to thermal length changes of the laser cavity. Finally, fiber laser configurations that allow multiple frequencies to be simultaneously produced in one laser cavity will be described.

Dawson, Jay Walter

411

The high-resolution infrared spectrum of nitryl chloride: Rotational analysis of the [sup 35]ClNO[sub 2] [nu][sub 4] band around 6 [mu]m  

Microsoft Academic Search

Nitryl chloride (ClNO[sub 2]) is involved in heterogeneous stratospheric chemistry by the reaction of HCl with N[sub 2]O[sub 5] on polar stratospheric cloud particles. The present work reports the first high-resolution infrared absorption spectra of nitryl chloride. The authors have recorded two infrared absorption spectra of ClNO[sub 2] at room temperature between 450 and 2,450 cm[sup [minus]1] with a stepping-mode

J. Orphal; M. Morillon-Chapey; G. Guelachvili

1994-01-01

412

Recent results of measurements of the 14N(n,p)14C, 35Cl(n,p)35S, 36Cl(n,p)36S, and 36Cl(n,?)33P reaction cross sections  

Microsoft Academic Search

Experiments are reported for measuring the cross section of the 14N(n,p)14C reaction over the neutron energy range from thermal energy to 150 keV at the IBR-30 pulsed booster at JNR, Dubna and the WWR-M reactor at INR, Kiev. The reaction cross section values were found for the thermal energy and for the neutron energies of 24 keV, 54 keV, 144

Yu. M. Gledenov; V. I. Salatski; P. V. Sedyshev; M. V. Sedysheva; P. E. Koehler; V. A. Vesna; I. S. Okunev

1995-01-01

413

A New Frequency Partitioning and Allocation of Subcarriers for Fractional Frequency Reuse in Mobile Communication Systems  

NASA Astrophysics Data System (ADS)

Some OFDMA-based wireless commuication systems, e. g., Wireless Broadband Internet (WiBro) or Worldwide interoperability for Microwave Access (WiMAX), support frequency reuse of 1 to maximize spectral efficiency. One of the efficient methods to reduce co-channel interference (CCI) caused by frequency reuse is fractional frequency reuse (FFR). In this paper, we propose and validate a novel frequency partitioning method and subcarrier assignment mechanism to improve system and individual capacity of mobile systems using FFR.

Han, Seung Su; Park, Jongho; Lee, Tae-Jin; Ahn, Hyun Gi; Jang, Kyunghun

414

Frequency Bistability of a Semiconductor Laser under a Frequency-Dependent Feedback  

NASA Astrophysics Data System (ADS)

The emission frequency of a diode laser submitted to a frequency-dependent optoelectronic feedback is observed to have more than one stable operation point together with a stable power emission. This is, to our knowledge, the first observation of bistability exclusively in the frequency of an optical system. The experiment was carried out with a semiconductor laser coupled to the cesium D2 line by an orthogonally polarized frequency-sensitive optical feedback.

Farias, B.; Passerat de Silans, T.; Chevrollier, M.; Ori, M.

2005-05-01

415

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

416

Event synchronous sinusoidal model based on frequency-to-instantaneous frequency mapping  

Microsoft Academic Search

We describe a glottal event synchronous sinusoidal model for speech analysis and synthesis. The sinusoidal components are event synchronously estimated using a mapping from linearly spaced filter center frequencies to the instantaneous frequencies of the filter outputs. Frequency domain fixed points of this mapping correspond to the constituent sinusoidal components of the input signal. A robust technique based on a

Parham Zolfaghari; Hideki Banno; Fumitada Itakura; Hideki Kawahara

2002-01-01

417

Modified fast inhomogeneous plane wave algorithm from low frequency to microwave frequency [computational electromagnetics  

Microsoft Academic Search

Computational electromagnetics (CEM) is facing increasingly more complex geometries calling for more sophisticated solutions. Hence efficient fast algorithms are urgently needed and studied. Among the developed methods, the MLFMA (multi-level fast multipole algorithm) is an attractive way to solve problems with the large number of unknowns. MLFMA algorithms work well at high frequencies or low frequencies but there are low-frequency

L. J. Jiang; W. C. Chew

2003-01-01

418

Frequency synchronization algorithms for OFDM systems suitable for communication over frequency selective fading channels  

Microsoft Academic Search

In this paper, the problem of carrier synchronization of OFDM systems in the presence of a substantial frequency offset is considered. New frequency estimation algorithms for the data aided (DA) mode are presented. The resulting two stage structure is able to cope with frequency offsets in the order of multiples of the spacing between subchannels. Key features of the novel

Ferdinand Classen; Heinrich Meyr

1994-01-01

419

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

420

Using Suffix Arrays to Compute Term Frequency and Document Frequency for All Substrings in a Corpus  

Microsoft Academic Search

Bigrams and trigrams are commonly used in statistical natural language processing; this paper will describe techniques for working with much longer -grams with high mutual information (MI) where the joint term frequency is higher than what would be expected by chance, assuming that the parts of the n-gram combine independently. Residual inverse document frequency (RIDF) compares document frequency to another

Mikio Yamamoto; Kenneth Ward Church

2001-01-01

421

Using Suffix Arrays to Compute Term Frequency and Document Frequency for All Substrings in a Corpus  

Microsoft Academic Search

Mutual Information (MI) and similar measures are often used in corpus-based linguistics to find interesting ngrams. MI looks for bigrams whose term frequency () is larger than chance. Residual Inverse Document Frequency (RIDF) is similar, but it looks for ngrams whose document frequency (df) is larger than chance. Previous studies have tended to focus on relatively short ngrams, typically bigrams

Mikio Yamamoto; Kenneth W. Church

1998-01-01

422

Low-Frequency Oscillations in Rotating Stars  

NASA Astrophysics Data System (ADS)

We review the properties of low-frequency oscillations in uniformly rotating stars. Rotation not only yields a new class of modes, like inertial modes and r-modes, but also significantly modifies the properties of low-frequency g-modes. For slow rotation rates where |?/?|?1, we can treat the rotation frequency ? as a small parameter for perturbation analysis, but for |\\varOmega/?|not?1, we have to properly solve the oscillation equation given as a set of partial differential equations, taking account of the effects of the Coriolis force and the centrifugal force, where ? stands for the oscillation frequency observed in the corotating frame of the star. The Coriolis force couples modes having different spherical harmonic degrees l, and the centrifugal force deforms the equilibrium structure. Rapid rotation affects the stability and the frequency of low-frequency modes. We discuss perturbation theory, the traditional approximation, linear mode coupling, series expansion methods, and weakly nonlinear calculations, which are applied to low-frequency modes in rotating stars.

Lee, Umin

423

High frequency pressure oscillator for microcryocoolers  

NASA Astrophysics Data System (ADS)

Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80 K, delivering a cooling power of 10 mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5 MPa and compression volume of about 22.6 mm3 when operating the actuator with a peak-to-peak sinusoidal voltage of 100 V at a frequency of 1 kHz. The electrical power input was 2.73 W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

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

2008-04-01

424

Quantitative measurement of vertigo frequency: preliminary results.  

PubMed

Persons who experience vertigo often describe their symptoms as a sensation of oscillations. Based on such a description, a pilot study was performed to determine if the frequency of the vertigo sensation could be quantified in a manner analogous to tone matching in tinnitus treatment. Fifteen subjects were tested using a virtual image system that consisted of a head mounted display showing a scene that oscillated horizontally or vertically at an adjustable frequency. Subjects were asked to adjust the direction and frequency to match their typical vertigo sensation. Results show that most persons with chronic vertigo had symptoms that could be realistically simulated by vection induced by the oscillating scene and that matched to a consistent specific frequency. They reported an average frequency of 1.09 Hz (range 0.27 to 3.3 Hz, SD 0.25). The large majority (13 out of 15) matched to a horizontal stimulus. Subjects that gave particularly high subjective ratings of the similarity of the motion sensation (7-8 out of 10) from the vection to their vertigo had lower frequency matches (average 0.61 +/- 0.25). Repeated measurements in 4 subjects 8 to 27 days later showed consistent results. This vertigo measurement technique may be used in the future to assess the ability of vestibular rehabilitation to reduce chronic vertigo. Identification of a specific frequency of chronic vertigo may be important in the specification of rehabilitation exercises. PMID:14646024

Zalewski-Zaragoza, Robert Aureo; Viirre, Erik Scott

2003-01-01

425

Spread Spectrum Communication with Chaotic Frequency Modulation  

NASA Astrophysics Data System (ADS)

We describe two different approaches to employ chaotic signals in spread-spectrum (SS) communication systems with phase and frequency modulation. In the first one a chaotic signal is used as a carrier. We demonstrate that using a feedback loop controller, the local chaotic oscillator in the receiver can be synchronized to the transmitter. The information can be transmitted using phase or frequency modulation of the chaotic carrier signal. In the second system the chaotic signal is used for frequency modulation of a voltage controlled oscillator (VCO) to provide a SS signal similar to frequency hopping systems. We show that in a certain parameter range the receiver VCO can be synchronized to the transmitter VCO using a relatively simple phase lock loop (PLL) circuit. The same PLL is used for synchronization of the chaotic oscillators. The information signal can be transmitted using a binary phase shift key (BPSK) or frequency shift key (BFSK) modulation of the frequency modulated carrier signal. Using an experimental circuit operating at radio frequency band and a computer modeling we study the bit error rate (BER) performance in a noisy channel as well as multiuser capability of the system.

Volkovskii, Alexander R.; Tsimring, Lev S.; Rulkov, Nikolai F.; Langmore, Ian; Young, Stephen C.

426

On zero frequency magnetic fluctuations in plasmas  

SciTech Connect

A plasma sustains fluctuations of electromagnetic fields and particle density even in a thermal equilibrium and such fluctuations have a large zero frequency peak. The level of fluctuations in the plasma for a given wavelength and frequency of electromagnetic fields is calculated through the fluctuation-dissipation theorem. The frequency spectrum shows that the energy contained in this peak is complementary to the energy ``lost`` by the plasma cutoff effect. The level of the zero (or nearly zero) frequency magnetic is computed as {l_angle}B{sup 2}{r_angle}{sup 0}/ 8{pi} = 1/2{pi}{sup 3}T({omega}{sub p}/c){sup 3}, where T and {omega}{sub p} are the temperature and plasma frequency. The relation between the nonradiative and radiative fluctuations is elucidated. Both a simple collision model and a kinetic theoretic treatment are presented with essentially the same results. The size of the fluctuations is {lambda} {approximately} (c/{omega}{sub p})({eta}/{omega}){sup {1/2}}, where {eta} and {omega} are the collision frequency and the (nearly zero) frequency of magnetic fields oscillations. Perhaps the most dramatic application of the present theory, however, is to the cosmological plasma of early epoch. Implications of these magnetic fields in the early Universe are discussed. Quantum mechanical calculations are also carried out for degenerate plasmas.

Tajima, T.; Cable, S. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; Kulsrud, R.M. [Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences

1992-01-01

427

On zero frequency magnetic fluctuations in plasmas  

SciTech Connect

A plasma sustains fluctuations of electromagnetic fields and particle density even in a thermal equilibrium and such fluctuations have a large zero frequency peak. The level of fluctuations in the plasma for a given wavelength and frequency of electromagnetic fields is calculated through the fluctuation-dissipation theorem. The frequency spectrum shows that the energy contained in this peak is complementary to the energy lost'' by the plasma cutoff effect. The level of the zero (or nearly zero) frequency magnetic is computed as {l angle}B{sup 2}{r angle}{sup 0}/ 8{pi} = 1/2{pi}{sup 3}T({omega}{sub p}/c){sup 3}, where T and {omega}{sub p} are the temperature and plasma frequency. The relation between the nonradiative and radiative fluctuations is elucidated. Both a simple collision model and a kinetic theoretic treatment are presented with essentially the same results. The size of the fluctuations is {lambda} {approximately} (c/{omega}{sub p})({eta}/{omega}){sup {1/2}}, where {eta} and {omega} are the collision frequency and the (nearly zero) frequency of magnetic fields oscillations. Perhaps the most dramatic application of the present theory, however, is to the cosmological plasma of early epoch. Implications of these magnetic fields in the early Universe are discussed. Quantum mechanical calculations are also carried out for degenerate plasmas.

Tajima, T.; Cable, S. (Texas Univ., Austin, TX (United States). Inst. for Fusion Studies); Kulsrud, R.M. (Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences)

1992-01-01

428

Low frequency sound propagation in activated carbon.  

PubMed

Activated carbon can adsorb and desorb gas molecules onto and off its surface. Research has examined whether this sorption affects low frequency sound waves, with pressures typical of audible sound, interacting with granular activated carbon. Impedance tube measurements were undertaken examining the resonant frequencies of Helmholtz resonators with different backing materials. It was found that the addition of activated carbon increased the compliance of the backing volume. The effect was observed up to the highest frequency measured (500 Hz), but was most significant at lower frequencies (at higher frequencies another phenomenon can explain the behavior). An apparatus was constructed to measure the effective porosity of the activated carbon as well as the number of moles adsorbed at sound pressures between 104 and 118 dB and low frequencies between 20 and 55 Hz. Whilst the results were consistent with adsorption affecting sound propagation, other phenomena cannot be ruled out. Measurements of sorption isotherms showed that additional energy losses can be caused by water vapor condensing onto and then evaporating from the surface of the material. However, the excess absorption measured for low frequency sound waves is primarily caused by decreases in surface reactance rather than changes in surface resistance. PMID:22779473

Bechwati, F; Avis, M R; Bull, D J; Cox, T J; Hargreaves, J A; Moser, D; Ross, D K; Umnova, O; Venegas, R

2012-07-01

429

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

PubMed Central

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

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

2011-01-01

430

Frequency dependence of elastic wave speed  

NASA Astrophysics Data System (ADS)

Elastic wave speed is one of the essential rock properties, and it is important for locating earthquake sources and estimating Earths structure. Usual seismic records contain up to ~ 10 Hz, whereas elastic wave records from laboratory measurements with rock sample contain the frequency from ~ 100 kHz to ~ 2 MHz. It is unclear whether elastic wave speed is independent of frequency or not. It is important to measure the accurate elastic wave speed over a wide frequency range. In this study, we measure the transmitting wave through a rock sample from 100 kHz to a few MHz, and consider the method to estimate the frequency dependence of elastic wave speed. We prepared a cylindrical granite sample (50 mm in diameter, 100 mm long), and put P-wave type broadband transducers to the both sectional surfaces of sample. We applied one cycle of sinusoidal voltage signal of various frequencies to one of the transducers, and received the transmitting wave through the sample with the other transducer. The transducers were calibrated with a laser Doppler vibrometer (LDV) that can measure the absolute particle velocity of a vibrating plane with a flat sensitivity up to 6 MHz. The method to estimate frequency dependence of elastic wave speed has not been established. One of the reasons is that initial portion of a sinusoidal voltage signal rises gradually, so that it contains other frequency contents than a frequency of input sinusoidal wave. The other reason is that later phases than the initial phase contain scattering waves. To avoid these problems, we analyzed the frequency dependence of traveltime for the first peak or other phases in the first cycle.

Kawakata, H.; Doi, I.; Yoshimitsu, N.

2010-12-01

431

Scaling of Yb-Fiber Frequency Combs  

NASA Astrophysics Data System (ADS)

Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E.; Hartl, Ingmar

2010-06-01

432

Frequency-change aftereffect produced by adaptation to real and illusory unidirectional frequency sweeps.  

PubMed

It was examined whether illusory and real continuities induce the frequency-change aftereffect, in which repeated exposure to a frequency sweep results in a shift in the perceived frequency change direction of a subsequent test sound. The magnitude of the aftereffect for different types of adaptors ("real sweep," "illusory sweep," and "sweep with gap") was compared. Listeners judged the direction of a frequency change of the test sound and showed a significant aftereffect only for the "real sweep" adaptors. The results suggest that the illusory sweeps are processed after the stage of frequency-change detection. PMID:23862900

Masutomi, Keiko; Kashino, Makio

2013-07-01

433

Frequency doubling of a Raman fiber laser  

NASA Astrophysics Data System (ADS)

655 nm laser radiation with power of >60 mW is generated by frequency doubling of a broadband randomly-polarized 1.31-?m phosphosilicate Raman fiber laser (RFL). The red power appears to grow linearly with increasing RFL power up to 7 W at efficiency comparable with that for single-frequency lasers. It has been shown that multiple sum-frequency mixing processes involving different RFL modes provide the main contribution to the output, which is enhanced by 2 times due to the modes stochasticity.

Kablukov, S. I.; Babin, S. A.; Churkin, D. V.; Denisov, A. V.; Kharenko, D. S.

2010-02-01

434

Frequency tolerances and spurious emission limitations  

NASA Astrophysics Data System (ADS)

Values for frequency tolerances and spurious emission limitations, as fixed by the World Administrative Radio Conference (WARC-79), eventually will apply to every transmitter used by the International Telecommunication Union member nations ratifying their Final Acts, and will affect all transmitters manufactured in the world. New and more strict values of these tolerances and limits become effective after 1985. Attention is given to the Special Preparatory Meeting (SPM), SPM approaches to frequency tolerance, SPM discussions, a frequency tolerance table, and spurious emission limitations. The WARC-79 recognized the need to continue examining transmitter spurious emission levels in a number of areas, especially where agreements could not be reached.

Watson, R. T.; Luther, W. A.

1981-08-01

435

Optical performance of frequency-selective bolometers.  

PubMed

Frequency-selective bolometers (FSBs) are a new type of detector for millimeter and submillimeter wavelengths that are transparent to all but a narrow range of frequencies as set by characteristics of the absorber itself. Therefore stacks of FSBs tuned to different frequencies provide a low-loss compact method for utilizing a large fraction of the light collected by a telescope. Tests of prototype FSBs indicate that the absorption spectra are well predicted by models, that peak absolute absorption efficiencies of the order of 50% are attainable, and that their out-of-band transmission is high. PMID:17068598

Perera, T A; Downes, T P; Meyer, S S; Crawford, T M; Cheng, E S; Chen, T C; Cottingham, D A; Sharp, E H; Silverberg, R F; Finkbeiner, F M; Fixsen, D J; Logan, D W; Wilson, G W

2006-10-10

436

The Continuing Evolution of Femtosecond Frequency Combs  

NASA Astrophysics Data System (ADS)

Following their development in early 2000, femtosecond frequency combs found immediate application as reference rulers in optical frequency metrology. Stabilization of the frequency comb emitted by an ultrafast laser has also enabled production of carrier-envelope phase-stabilized femtosecond pulses, thereby spurring seminal work in attosecond metrology. As the comb technology itself has matured, new areas of application have emerged such as precise calibration of astronomical spectrographs, arbitrary optical waveform synthesis, and precision spectroscopy. In this talk, I will highlight these new developments and discuss related and current work at UBC on these topics.

Jones, David

2008-05-01

437

Frequency shift in the moving periodic structure  

SciTech Connect

The interaction between the electromagnetic wave and the moving periodic structure is analyzed. The main physical effect revealed by theoretical analysis is that the frequency shift of the scattered or transmitted mode is proportional to the speed and the mode order m over the period a. The frequency shift is independent of the incidence direction and the carrier frequency. The physical effect is verified by an experiment. The analysis released here is fundamental in speed measurement and may have certain significance in interdisciplinary fields.

Dong Tianlin; Xia Dan [Department of Electronics and Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

2008-09-15

438

Turbine bucket natural frequency tuning rib  

DOEpatents

A tuning rib is added preferably in the aft cavity of a cored turbine bucket to alter the bucket's natural frequencies. The tuning rib may be a solid rib or a segmented rib and is particularly suited for altering high order frequency modes such as 2T, 4F and 1-3S. As such, detrimental crossings of natural bucket frequencies and gas turbine stimuli can be avoided to thereby improve the reliability of a gas turbine without impacting other features of the bucket that are important to the performance of the gas turbine.

Wang, John Zhiqiang (Greenville, SC); Norton, Paul Francis (Greenville, SC); Barb, Kevin Joseph (Halfmoon, NY); Jacala, Ariel Caesar-Prepena (Simpsonville, SC)

2002-01-01

439

Prestin and high frequency hearing in mammals  

PubMed Central

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

Zhang, Shuyi; Liu, Yang

2011-01-01

440

Turbine bucket natural frequency tuning rib  

SciTech Connect

A tuning rib is added preferably in the aft cavity of a cored turbine bucket to alter the bucket's natural frequencies. The tuning rib may be a solid rib or a segmented rib and is particularly suited for altering high order frequency modes such as 2T, 4F and 1-3S. As such, detrimental crossings of natural bucket frequencies and gas turbine stimuli can be avoided to thereby improve the reliability of a gas turbine without impacting other features of the bucket that are important to the performance of the gas turbine.

Wang, John Zhiqiang (Greenville, SC); Norton, Paul Francis (Greenville, SC); Barb, Kevin Joseph (Halfmoon, NY); Jacala, Ariel Caesar-Prepena (Simpsonville, SC)

2002-01-01

441

High power radio frequency attenuation device  

DOEpatents

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

Kerns, Quentin A. (Bloomingdale, IL); Miller, Harold W. (Winfield, IL)

1984-01-01

442

Precision frequency measurements with interferometric weak values  

SciTech Connect

We demonstrate an experiment which utilizes a Sagnac interferometer to measure a change in optical frequency of 129 {+-} 7 kHz/{radical}(Hz) with only 2 mW of continuous-wave, single-mode input power. We describe the measurement of a weak value and show how even higher-frequency sensitivities may be obtained over a bandwidth of several nanometers. This technique has many possible applications, such as precision relative frequency measurements and laser locking without the use of atomic lines.

Starling, David J.; Dixon, P. Ben; Jordan, Andrew N.; Howell, John C. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States)

2010-12-15

443

Direct Frequency Comb Spectroscopy of Trapped Ions  

NASA Astrophysics Data System (ADS)

Direct frequency comb spectroscopy of trapped ions is demonstrated for the first time. It is shown that the 4sS1/22-4pP3/22 transition in calcium ions can be excited directly with a frequency comb laser that is up-converted to 393 nm. Detection of the transition is performed using a shelving scheme to suppress the background signal from nonresonant comb modes. The measured transition frequency of f=761905012.7(0.5)MHz presents an improvement in accuracy of more than 2 orders of magnitude.

Wolf, A. L.; van den Berg, S. A.; Ubachs, W.; Eikema, K. S. E.

2009-06-01

444

Residual phase noise of digital frequency dividers  

NASA Astrophysics Data System (ADS)

Many low noise synthesizers and phase-locked loops utilize frequency dividers to generate integer sub-multiple frequencies from available low noise sources. In order to preserve signal quality, it is desirable to use frequency dividers that exhibit the lowest residual noise properties. Since digital devices should suppress all AM noise, phase noise is of most interest. Residual phase noise measurements were made with similar devices from the four logic families of ECL, ACT, FAST and LS. Test conditions were held constant in order to provide comparative results. Test results indicate that ACT (CMOS) exhibits the lowest residual phase noise, followed by FAST, LS and ECL.

McClure, Mark R.

1992-03-01

445

Effects of low-frequency biasing on spontaneous otoacoustic emissions: Frequency modulation  

PubMed Central

It was previously reported that low-frequency biasing of cochlear structures can suppress and modulate the amplitudes of spontaneous otoacoustic emissions (SOAEs) in humans [Bian, L. and Watts, K. L. (2008). Effects of low-frequency biasing on spontaneous otoacoustic emissions: Amplitude modulation, J. Acoust. Soc. Am. 123, 887898]. In addition to amplitude modulation, the bias tone produced an upward shift of the SOAE frequency and a frequency modulation. These frequency effects usually occurred prior to significant modifications of SOAE amplitudes and were dependent on the relative strength of the bias tone and a particular SOAE. The overall SOAE frequency shifts were usually less than 2%. A quasistatic modulation pattern showed that biasing in either positive or negative pressure direction increased SOAE frequency. The instantaneous SOAE frequency revealed a W-shaped modulation pattern within one biasing cycle. The SOAE frequency was maximal at the biasing extremes and minimized at the zero crossings of the bias tone. The temporal modulation of SOAE frequency occurred with a short delay. These static and dynamic effects indicate that modifications of the mechanical properties of the cochlear transducer could underlie the frequency shift and modulation. These biasing effects are consistent with the suppression and modulation of SOAE amplitude due to shifting of the cochlear transducer operating point.

Bian, Lin

2008-01-01

446

47 CFR 78.36 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...modification thereto, the applicant must, by appropriate studies and analyses, select sites, transmitters, antennas and frequencies...dimension (ground elevation) with respect to the National Spacial Reference System. (iii) For transmitters employing...

2009-10-01

447

47 CFR 78.36 - Frequency coordination.  

Code of Federal Regulations, 2010 CFR

...modification thereto, the applicant must, by appropriate studies and analyses, select sites, transmitters, antennas and frequencies...dimension (ground elevation) with respect to the National Spacial Reference System. (iii) For transmitters employing...

2010-10-01

448

Frequencies for Pain Reliever Questionnaire Items: Divided ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Divided Attention People with liver disease should not take this product unless directed by a ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

449

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...RADIO SERVICES FIXED MICROWAVE SERVICES Local Television Transmission Service § 101.803 Frequencies...following bands are available for assignment to television pickup and television non-broadcast pickup stations in this...

2012-10-01

450

47 CFR 101.803 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...RADIO SERVICES FIXED MICROWAVE SERVICES Local Television Transmission Service § 101.803 Frequencies...following bands are available for assignment to television pickup and television non-broadcast pickup stations in this...

2011-10-01

451

Component external leakage and rupture frequency estimates  

SciTech Connect

In order to perform detailed internal flooding risk analyses of nuclear power plants, external leakage and rupture frequencies are needed for various types of components - piping, valves, pumps, flanges, and others. However, there appears to be no up-to-date, comprehensive source for such frequency estimates. This report attempts to fill that void. Based on a comprehensive search of Licensee Event Reports (LERs) contained in Nuclear Power Experience (NPE), and estimates of component populations and exposure times, component external leakage and rupture frequencies were generated. The remainder of this report covers the specifies of the NPE search for external leakage and rupture events, analysis of the data, a comparison with frequency estimates from other sources, and a discussion of the results.

Eide, S.A.; Khericha, S.T.; Calley, M.B.; Johnson, D.A.; Marteeny, M.L.

1991-11-01

452

33 CFR 401.61 - Assigned frequencies.  

Code of Federal Regulations, 2013 CFR

... SAINT LAWRENCE SEAWAY DEVELOPMENT CORPORATION, DEPARTMENT OF TRANSPORTATION SEAWAY REGULATIONS AND RULES Regulations Radio Communications § 401.61 Assigned frequencies. The Seaway stations operate on the following assigned VHF...

2013-07-01

453

47 CFR 87.187 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...is available for use by airborne doppler radars in the aeronautical radionavigation...9300-9500 MHz is limited to airborne radars and associated airborne beacons...13250-13400 MHz available for airborne doppler radar use. (x) The frequency...

2009-10-01

454

47 CFR 87.187 - Frequencies.  

Code of Federal Regulations, 2010 CFR

...is available for use by airborne doppler radars in the aeronautical radionavigation...9300-9500 MHz is limited to airborne radars and associated airborne beacons...13250-13400 MHz available for airborne doppler radar use. (x) The frequency...

2010-10-01

455

On the relativity of relative frequencies.  

PubMed

The most prominent models of numerical representation posit that numerical symbols are converted into a single internal, abstract representation prior to estimation and comparison processing. Here, we (1) provide a mathematical analysis of the predictions of the abstract-representation hypothesis, assuming the validity of the analog-representation hypothesis, (2) run a simulation to assess the patterns of data that result from our mathematical analysis, and (3) conduct two experiments to test the predictions of our model, using relative frequencies as inputs. We assess relative frequencies in a typical numerical distance task, whereby participants are presented with two relative frequencies and asked to identify the one that represents the larger quantity. Our data reveal that relative frequencies' numerical representations (1) are analog and (2) are scale-specific (i.e., nonabstract). PMID:23269517

Warren, Erin; Cohen, Dale J

2013-04-01

456

23 CFR 650.311 - Inspection frequency.  

Code of Federal Regulations, 2013 CFR

...twenty-four months. (2) Certain bridges require inspection at less...and frequency to which these bridges are inspected considering...deficiencies. (3) Certain bridges may be inspected at greater...considering such factors as construction material,...

2013-04-01

457

Linear and Quadratic Time-Frequency Representations.  

National Technical Information Service (NTIS)

This report is reviewing both linear and quadratic time-frequency representations. The linear representations discussed are Short-Time Fourier Transform and S-transform. The quadratic representation discussed is Wigner distribution. We outline the motivat...

T. Thayaparan

2000-01-01

458

Tools for Time-Frequency Analysis.  

National Technical Information Service (NTIS)

Together with students and postdocs, the PI has worked on the mathematical aspects and applications of various tools in time frequency or time scale analysis. they have brought a deeper understanding to the geometry of redundant representations (frames), ...

I. Daubechies

1997-01-01

459

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention This product may make ulcers worse. ... This product may make ulcers worse. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

460

Frequencies for Pain Reliever Questionnaire Items: Divided ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Divided Attention People who consume more than 3 alcohol-containing drinks per day should ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

461

Frequencies for Pain Reliever Questionnaire Items: Divided ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Divided Attention A person who is allergic to aspirin should not use this product. Statistics. N. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

462

Frequencies for Pain Reliever Questionnaire Items: Divided ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Divided Attention This product does not reduce fever. ... This product does not reduce fever. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

463

47 CFR 95.1111 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...PERSONAL RADIO SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions...providers who desire to use wireless medical telemetry devices must register all devices...frequency coordinator whenever a medical telemetry device is permanently taken...

2011-10-01

464

47 CFR 87.187 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...is available on a secondary basis for telemetry and telecommand associated with the...following frequencies are shared with flight telemetry mobile stations: 1444.5, 1453.5...to paragraph (p ): Aeronautical telemetry operations must protect...

2012-10-01

465

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...mobile service primarily for aeronautical telemetry and associated telecommand operations...Permissible uses of these bands include telemetry and associated telecommand operations...following frequencies are shared with flight telemetry mobile stations: 1444.5,...

2012-10-01

466

47 CFR 95.1111 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...PERSONAL RADIO SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions...providers who desire to use wireless medical telemetry devices must register all devices...frequency coordinator whenever a medical telemetry device is permanently taken...

2012-10-01

467

47 CFR 87.187 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...is available on a secondary basis for telemetry and telecommand associated with the...following frequencies are shared with flight telemetry mobile stations: 1444.5, 1453.5...to paragraph (p ): Aeronautical telemetry operations must protect...

2011-10-01

468

47 CFR 87.303 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...mobile service primarily for aeronautical telemetry and associated telecommand operations...Permissible uses of these bands include telemetry and associated telecommand operations...following frequencies are shared with flight telemetry mobile stations: 1444.5,...

2011-10-01

469

47 CFR 95.655 - Frequency capability.  

Code of Federal Regulations, 2012 CFR

...Services and Military Affiliate Radio System will not be certificated.) (b) All frequency determining circuitry (including crystals) and programming controls in each CB transmitter and in each GMRS transmitter must be internal to the transmitter and...

2012-10-01

470

47 CFR 95.655 - Frequency capability.  

Code of Federal Regulations, 2011 CFR

...Services and Military Affiliate Radio System will not be certificated.) (b) All frequency determining circuitry (including crystals) and programming controls in each CB transmitter and in each GMRS transmitter must be internal to the transmitter and...

2011-10-01

471

High Power, High Frequency Component Test Facility.  

National Technical Information Service (NTIS)

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

M. E. Roth W. Krawczonek

1990-01-01

472

With Weekly Exercise, Time Trumps Frequency  

MedlinePLUS

... on this page, please enable JavaScript. With Weekly Exercise, Time Trumps Frequency No matter how they spread ... Preidt Friday, July 12, 2013 Related MedlinePlus Page Exercise and Physical Fitness FRIDAY, July 12 (HealthDay News) -- ...

473

47 CFR 74.762 - Frequency measurements.  

Code of Federal Regulations, 2012 CFR

...SERVICES EXPERIMENTAL RADIO, AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Low Power TV, TV Translator, and TV Booster Stations § 74.762 Frequency measurements. (a) The licensee of a low power TV station, a...

2012-10-01

474

47 CFR 74.762 - Frequency measurements.  

Code of Federal Regulations, 2011 CFR

...SERVICES EXPERIMENTAL RADIO, AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Low Power TV, TV Translator, and TV Booster Stations § 74.762 Frequency measurements. (a) The licensee of a low power TV station, a...

2011-10-01

475

Frequency Spreading in Forward Surface Scattering.  

National Technical Information Service (NTIS)

An experimental study of frequency spreading in acoustic signals forward scattered from model tank wind driven water surfaces has been performed. The study employed wide band probing signals to doubly sample the surface scatter process. A high degree of p...

J. G. Zornig

1977-01-01

476

Predicting variability in joint frequencies from boreholes  

NASA Astrophysics Data System (ADS)

Joints in rock are not evenly spaced, but commonly show clustering. This suggests that boreholes that are a short distance apart can intersect very different numbers of joints. A simple 1D model is used to illustrate variability in joint frequencies from vertical wells intersecting steeply dipping joints. The model indicates that raw joint frequencies logged from core or borehole images can give unreliable inputs into reservoir models, especially when the joints are clustered and variations occur over scales that are much smaller than the resolution of seismic surveys or the grid blocks used in reservoir simulations. Variability in joint frequencies from deviated or horizontal wells can be used, however, to test the variability in joint frequencies from vertical wells.

Peacock, D. C. P.

2006-02-01

477

SRS Process Facility Significance Fire Frequency  

SciTech Connect

This report documents the method and assumptions of a study performed to determine a site generic process facility significant fire initiator frequency and explains the proper way this value should be used.

Sarrack, A.G. [Westinghouse Savannah River Company, AIKEN, SC (United States)

1995-10-01

478

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention When you first read the label, would you say your attention was focused ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

479

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention People with stomach ulcers can use this product. Statistics. N. Valid. Missing ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

480

47 CFR 101.507 - Frequency stability.  

Code of Federal Regulations, 2012 CFR

...101.507 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The...

2012-10-01

481

Frequency Multiplexed Water Leak Detection System.  

National Technical Information Service (NTIS)

The patent application relates to an active leak detector which uses frequency multiplexing to indicate the location of water leaks. The circuit is composed of any number of satellite leak detectors and a master indicator circuit which monitors all detect...

F. E. Hinkle

1976-01-01

482

47 CFR 87.241 - Frequencies.  

Code of Federal Regulations, 2012 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Multicom Stations § 87.241 Frequencies. (a) 121.500 MHz: emergency and distress only; (b) 122.850...

2012-10-01

483

47 CFR 87.241 - Frequencies.  

Code of Federal Regulations, 2011 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Aeronautical Multicom Stations § 87.241 Frequencies. (a) 121.500 MHz: emergency and distress only; (b) 122.850...

2011-10-01

484

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention Means a lot to me. Statistics. N. ... Means a lot to me, 303, 0. Means a lot to me. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

485

47 CFR 74.161 - Frequency tolerances.  

Code of Federal Regulations, 2011 CFR

...specified in the instrument of authorization. For modes of transmission that do not have a resting or center carrier frequency, the occupied bandwidth of the station transmissions may not exceed that specified in the...

2011-10-01

486

Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) Project.  

National Technical Information Service (NTIS)

The West Virginia State College Community College Division NASA Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) study is described. During this contract period, the two most significant and professionally rewarding events were the presentation of t...

C. Spaniol

1993-01-01

487

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention Imagine you have a child, age 15. ... 303, 0. Imagine you have a child, age 15. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

488

Extremely High Frequency RF Effects on Electronics.  

National Technical Information Service (NTIS)

The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of e...

A. Mar D. Vigliano G. A. Wouters G. M. Loubriel J. T. Williams L. D. Bacon P. D. Coleman

2012-01-01

489

Radio Frequency Motion Sensor Cable Studies.  

National Technical Information Service (NTIS)

The Radio Frequency Motion Sensor (RFMS) detects movement within interior areas by detecting the electromagnetic phase and amplitude changes caused by an intruder moving through an RF field. The RFMS consists of a transmitter, receiver, up to three transm...

R. D. Bailey

1985-01-01

490

47 CFR 95.1225 - Frequency coordinator.  

Code of Federal Regulations, 2012 CFR

...AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1225...frequency coordinator(s) to manage the operation of medical body area networks in the 2360 MHz -2390 MHz...

2012-10-01

491

Spectral narrowing induced by discrete frequency fluctuations  

NASA Astrophysics Data System (ADS)

We study an ensemble of two level systems coupled to an environment that randomly modulates their resonant frequency. We use Poissonian statistics for the random frequency jumps and derive a closed-from formula for the spectrum in terms of the inhomogeneous frequency distribution and the Poisson rate constant. We show that for a Gaussian distribution our result asymptotically reproduces the results of the well known Kubo model. Our formula holds for any frequency distribution. In particular we calculate the spectrum of atoms in a 3D trap harmonic trap and show that motional narrowing naturally emerges. We experimentally measure this spectrum with optically trapped ^87Rb atoms and obtain a good agreement to our theory without fitting parameters. Our theory apply to a wide range of systems such as atomic ensembles, nuclear magnetic resonance spectroscopy, single molecule spectroscopy and the line-shape of lasers.

Sagi, Yoav; Pugatch, Rami; Almog, Ido; Davidson, Nir

2010-03-01

492

Damped Oscillator with delta-Kicked Frequency.  

National Technical Information Service (NTIS)

Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.

O. V. Manko

1996-01-01

493

Cesium Beam Frequency Standard with Microprocessor Control.  

National Technical Information Service (NTIS)

The use of microprocessor based instrumentation in support of a cesium beam frequency standard is explored. Specific advantages and approaches are examined with the design goals of improved performance, enhanced system flexibility and increased reliabilit...

R. M. Garvey

1982-01-01

494

Laser Doppler vibrometer employing active frequency feedback  

SciTech Connect

We present a heterodyne Michelson interferometer for vibration measurement in which feedback is used to obviate the need to unwrap phase data. The Doppler shift of a vibrating target mirror is sensed interferometrically and compensated by means of a voltage-controlled oscillator driving an acousto-optic modulator. For frequencies within the servo bandwidth, the oscillator control voltage provides a direct measurement of the target velocity. Outside the servo bandwidth, phase-sensitive detection is used to evaluate high-frequency displacements. This approach is of great interest for the frequently-occurring situation where vibration amplitudes at low frequency exceed an optical wavelength, but knowledge of the vibration spectrum at high frequency is important as well.

Chijioke, Akobuije; Lawall, John

2008-09-20

495

Flood-frequency characteristics of Wisconsin streams  

USGS Publications Warehouse

Flood-frequency characteristics for 312 gaged sites on Wisconsin streams are presented for recurrence intervals of 2 to 100 years using flood-peak data collected through water year 2000. Equations of the relations between flood-frequency and drainage-basin characteristics were developed by multiple-regression analyses. Flood-frequency characteristics for ungaged sites on unregulated, rural streams can be estimated by use of these equations. The state was divided into five areas with similar physiographic characteristics. The most significant basin characteristics are drainage area, main-channel slope, soil permeability, storage, rainfall intensity, and forest cover. The standard error of prediction for the equation for the 100-year flood discharge ranges from 22 to 44 percent in the state. A graphical method for estimating flood-frequency characteristics of regulated streams was developed from the relation of discharge and drainage area. Graphs for the major regulated streams are presented.

Walker, John F.; Krug, William R.

2003-01-01

496

47 CFR 74.638 - Frequency coordination.  

Code of Federal Regulations, 2011 CFR

...applicants in the area whose facilities could affect or be affected by the new proposal in terms of frequency interference on active channels, applied-for channels, or channels coordinated for future growth. Coordination must be completed...

2011-10-01

497

47 CFR 74.638 - Frequency coordination.  

Code of Federal Regulations, 2012 CFR

...applicants in the area whose facilities could affect or be affected by the new proposal in terms of frequency interference on active channels, applied-for channels, or channels coordinated for future growth. Coordination must be completed...

2012-10-01

498

High Frequency Low Noise Amplifier Project.  

National Technical Information Service (NTIS)

The design of low noise high frequency amplifiers using S parameters for transistors is described. Simple equations are given for the design of the matching circuits and for determining the minimum noise figure parameters.

W. J. Fleming

1981-01-01

499

Frequencies for Pain Reliever Questionnaire Items: Focused ...  

Center for Drug Evaluation (CDER)

... Frequencies for Pain Reliever Questionnaire Items: Focused Attention Know when to stop taking the drug. ... Know when to stop taking the drug. ... More results from www.fda.gov/drugs/developmentapprovalprocess/developmentresources

500

Biological Effect of High-Frequency Ultrasound.  

National Technical Information Service (NTIS)

The effect of ultrasonic waves on tissues is related to a mechanical and vibratory action, and with high power and prolonged exposure -- to thermal and physicochemical action as well. A stream of high frequency ultrasonic waves (particularly when administ...

N. S. Arkhipov Y. N. Bogin

1969-01-01