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1

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

2

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

3

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

4

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

5

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

6

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

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

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

9

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

10

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

11

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

12

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

13

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

14

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

15

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

16

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

17

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

18

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

19

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

20

Experiments with a quartz resonator  

NASA Astrophysics Data System (ADS)

Experiments with a quartz resonator are described: (i) the frequency response, the quality factor, and the transient processes; (ii) the temperature dependence of the resonance frequency; and (iii) the parameters of the equivalent impedance. A popular quartz resonator designed for generating oscillations of frequency 32?768 Hz (= 215) serves as an example. A new data-acquisition system from PASCO Scientific is used for the measurements. The experiments employ 1 ppm frequency resolution, but are well suited for undergraduate laboratories.

Kraftmakher, Yaakov

2013-09-01

21

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

22

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

23

INSTRUMENTS AND METHODS OF INVESTIGATION: New technologies: nuclear quadrupole resonance as an explosive and narcotic detection technique  

NASA Astrophysics Data System (ADS)

Possibilities of detecting nuclear quadrupole resonance (NQR) signals in explosives and drugs are considered. Direct and indirect NQR techniques for searching substances are described and the potentialities of various experimental methods are compared.

Grechishkin, Vadim S.; Sinyavskii, Nikolai Ya

1997-04-01

24

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

25

Evidence of Antiferromagnetic Ordering in La/sub 2/CuO/sub 4/: Re-Interpretation of /sup 139/La Nuclear Quadrupole Resonance (NQR) Data.  

National Technical Information Service (NTIS)

A re-interpretation of the result of recent /sup 139/La nuclear quadrupole resonance measurements on La/sub 2/CuO/sub 4/ reveals an antiferromagnetic order in this material at low temperature. The magnitude and the direction of the local field at the La p...

I. Furo A. Janossy

1987-01-01

26

14N pulsed nuclear quadrupole resonance. 1. Nutation experiments in the case of an axially symmetric electric field gradient tensor  

Microsoft Academic Search

An exact theory based on density matrix calculations is provided for assessing the nuclear quadrupole resonance (NQR) behaviour of a spin 1 (14N) subjected to a single radio-frequency pulse. It concerns a powder sample in zero magnetic field with the assumption of an axially symmetric electric field gradient tensor. Theoretical results, in terms of signal evolution as a function of

B. Cordier; D. Grandclaude; A. Retournard; L. Merlat; D. Canet

2005-01-01

27

(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

28

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

29

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

30

Radiative widths of resonances (experiments)  

SciTech Connect

After a hiatus of several years, this conference brings us considerable new data on resonance production in photon photon interactions. I will first discuss the contributions concerning the tensor, pseudoscalar and scalar mesons, then review the current status of the (c/ovr string/c /eta//sub c/) and finally summarize the exciting new results concerning the spin 1 mesons. 40 refs., 21 figs., 7 tabs.

Gidal, G.

1988-07-01

31

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

32

Experience with the ALPI linac resonators  

NASA Astrophysics Data System (ADS)

The medium ? section of the linac accelerator ALPI [G. Fortuna et al., Nucl. Instr. and Meth. A 328 (1993) 236] is now in operation: beams of 32S, 37Cl, 58Ni, 76Ge, 81Br were accelerated for nuclear physics experiments in the first half of 1995. The medium ? section of ALPI includes 12 cryostats containing four accelerating quarter-wave resonators each (? = 0.11,f = 160 MHz). Two similar resonators are installed in a buncher cryostat and two in a rebuncher unit. Accelerating fields around 2.5 MV/m are available. The experience in cavity preparation, installation, conditioning and operation is described.

Porcellato, A. M.; Bisoffi, G.; Gustaffsson, S.; Boscagli, L.; Carlucci, D.; Chiurlotto, F.; Morvillo, M.; Stivanello, F.

1996-02-01

33

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

34

Undergraduate Electron-Spin-Resonance Experiment.  

ERIC Educational Resources Information Center

|Describes the basic procedures for use of an electron-spin resonance spectrometer and potassium azide (KN3) in an experiment which extends from the phase of sample preparation (crystal growth, sample mounting, and orientation) through data taking to the stages of calculation and theoretical explanation. (Author/DS)|

Willis, James S.

1980-01-01

35

Undergraduate Electron-Spin-Resonance Experiment.  

ERIC Educational Resources Information Center

Describes the basic procedures for use of an electron-spin resonance spectrometer and potassium azide (KN3) in an experiment which extends from the phase of sample preparation (crystal growth, sample mounting, and orientation) through data taking to the stages of calculation and theoretical explanation. (Author/DS)

Willis, James S.

1980-01-01

36

Superconducting microwave resonators for physics experiments  

NASA Astrophysics Data System (ADS)

Superconducting resonators at K-band frequencies have been developed for different applications in general physics. Niobium pillbox cavities have been built for the one-atom maser experiment by which the interaction of Rydberg atoms with single microwave photons has been investigated. At 21.5 GHz and 1.3 K, quality factors of up to 10 to the 11th were obtained. Coating of the cavity with Nb3Sn resulted in quality factors of 6 x 108 at 4.2 K and 6 x 10 9th at 2 K. A superconducting Fabry-Perot resonator consisting of two spherically curved niobium mirrors was also investigated. The quality factor of 1.8 x 10 to the 7th measured at 25 GHz and 4.2 K was found to be two orders of magnitude higher than for a corresponding copper resonator. Fabry-Perot resonators can be used for detecting small position changes for one mirror with respect to another caused by gravitational forces. First experiments with copper Fabry-Perot mirrors suspended in a vacuum chamber provided a maximum sensitivity for a gravitational acceleration of one mirror of 4 x 10 to the -11th m/sec sq. These results are promising for a possible fifth force detector based on a superconducting Fabry-Perot resonator.

Klein, N.; Mueller, G.; Piel, H.; Schurr, J.

1989-03-01

37

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

38

Undergraduate electron-spin-resonance experiment  

NASA Astrophysics Data System (ADS)

For institutions which have an electron-spin-resonance spectrometer available to them, potassium azide (KN3) is a material which provides a unique opportunity for a student to conduct an experiment which extends from the phase of sample preparation (crystal growth, sample mounting, and orientation) through data taking to the stages of calculation and theoretical explanation. Through the desires and imagination of the teacher, the level of sophistication can be varied widely, but at any level the student can have the satisfaction of doing a complete experiment which reenforces the lessons of many courses in physics. This paper describes the basic procedures of this experiment and gives sample results for instructor reference.

Willis, James S.

1980-09-01

39

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

40

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

41

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

42

Resonance Structure with Polarization Experiments at MAMI  

NASA Astrophysics Data System (ADS)

The Mainz Microtron MAMI is an ideal facility to study the hadron structure with the electromagnetic probe. With the new accelerator stage, the Harmonic Double-Sided Microtron (HDSM), which is in operation since 2007, high-intensity polarized electron and photon beams with energies up to 1.6 GeV are delivered to the experiments. Polarized proton, deuteron, 3He targets, and recoil proton polarimeters are available to allow a broad range of polarization observables for low-mass nucleon resonances to be measured. In this talk, an overview over selected recent double polarization experiments at MAMI is given.

Arends, Hans-Jrgen

2011-10-01

43

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

44

Land mine detection by nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) combines the compound specific detection capability offered by chemical detection techniques with the spatial localization capability and convenience of an induction coil metal detector. In the 16 years since NQR was last applied to mine detection in the U.S., there has been considerable improvement in the basic techniques. This paper reviews the progress achieved under a recent initiative to detect landmines by NQR. Two basic technical developments are summarized: the design of a detection coil suitable for probing the ground for landmines buried at typical depths, and an increase in the NQR signal obtained from the explosive TNT. In addition, we report the sensitivity of an NQR detection system to detect the electromagnetic response of metal-cased landmines.

Hibbs, Andrew D.; Barrall, Geoffrey A.; Czipott, Peter V.; Lathrop, Daniel K.; Lee, Y. K.; Magnuson, Erik E.; Matthews, Robert; Vierkoetter, S. A.

1998-09-01

45

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

46

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

47

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

48

Simulations of pulsed nuclear magnetic resonance experiments  

SciTech Connect

In order to help elucidate various aspects of pulsed nuclear magnetic resonance (NMR) experiments in the liquid state, a consistent mathematical treatment based on density matrix formalism was developed and implemented in a computer program, RELAX. Relaxation effects stemming from dipolar, chemical shift anisotropy (CSA), and random field mechanisms are accounted for, including contributions from dipole-CSA cross-correlation. The program was utilized to study para-fluorophenyl spin systems in dynamical regimes characteristic of both small and large molecules. Theory demonstrates that dipole-CSA cross-correlation can have pronounced effects in these systems and suggests that analysis of these effects will be useful in the study of protein conformation and dynamics.

Smith, S.A.

1991-01-01

49

Neutron interferometric double-resonance experiment  

SciTech Connect

In continuation of previous work explicitly demonstrating the basic quantum-mechanical principles of the static and the time-dependent superposition of spinors, a new double-resonance coil experiment is described, where a spin-flip process associated with an exchange of energy quanta happens in both beams of a perfect-crystal neutron interferometer. It is shown that under the given circumstances of neutron self-interference coherence is preserved in spite of the energy transfer to every neutron, which may stimulate renewed epistemological discussions about the interpretation of quantum mechanics. Furthermore quantum beating on a macroscopic time scale has been observed by introducing an exceedingly small energy difference of 8.6 x 10/sup -17/ eV between the two interfering beams. According to the statistical accuracy of the data thereby an energy sensitivity of 2.7 x 10/sup -19/ eV has been achieved.

Badurek, G.; Rauch, H.; Tuppinger, D.

1986-10-01

50

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

51

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

52

Nuclear quadrupole resonance study of hydrogen bonded solid materials.  

PubMed

Nuclear quadrupole resonance is presented as a method for the study of solid hydrogen bonded materials. NQR study of hydrogen bonds in ferroelectric and paraelectric KH2PO4, antiferroelectric and paraelectric squaric acid, ferroelectric croconic acid and antiferroelectric and paraelectric cocrystal 5'-dimethyl-2, 2'-bipyridine - chloranilic acid (1:1) are discussed in more details. A 14N NQR study of the strong short O-HKN hydrogen bond in two polymorphic forms of cocrystal isonicotinamide-oxalic acid (2:1) is presented as well. Various correlations between the NQR parameters and between the NQR and structural parameters have been observed. These correlations may be used to determine the proton position in a hydrogen bond and some other structural parameters from the NQR data. PMID:24062106

Seliger, Janez

2011-09-01

53

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

54

Miniature Magnet for Electron Spin Resonance Experiments  

ERIC Educational Resources Information Center

|Describes commercially available permanent magnets that have been incorporated in a compact and inexpensive structure providing both field sweep and modulation suitable for electron spin resonance at microwave frequencies. (MLH)|

Rupp, L. W.; And Others

1976-01-01

55

Miniature Magnet for Electron Spin Resonance Experiments  

ERIC Educational Resources Information Center

Describes commercially available permanent magnets that have been incorporated in a compact and inexpensive structure providing both field sweep and modulation suitable for electron spin resonance at microwave frequencies. (MLH)

Rupp, L. W.; And Others

1976-01-01

56

Weak Magnetic Order in Bilayered-Hydrate NaxCoO2\\\\cdotyH2O Structure Probed by Co Nuclear Quadrupole Resonance Proposed Phase Diagram in Superconducting NaxCoO2\\\\cdotyH2O---  

Microsoft Academic Search

A weak magnetic order was found in a nonsuperconducting bilayered-hydrate NaxCoO2\\\\cdotyH2O sample by Co nuclear quadrupole resonance (NQR) measurement. The nuclear spin-lattice relaxation rate divided by temperature 1\\/T_1T shows a prominent peak at 5.5 K, below which a Co NQR peak splits due to an internal field at the Co site. From the analyses of the Co NQR spectrum at

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

2005-01-01

57

Experiments on Acoustic Resonance in Heat Exchanger Tube Bundles  

NASA Astrophysics Data System (ADS)

A series of experiments have been made on aeroacoustic tones produced by flow over tubes in a duct. The sound is characterized by the onset of a loud and persistent acoustic resonance. The acoustic resonance occurs at the frequency of the acoustic modes. The magnitude and extent of the resonance are functions of tube pattern and tube pitch. The sound levels increase in proportion to Mach number, dynamic head and pressure drop.

Blevins, R. D.; Bressler, M. M.

1993-07-01

58

Parity assignments in nuclear resonance fluorescence experiments using compton polarimeters  

Microsoft Academic Search

Measurements of the linear polarization of resonantly scattered photons have been used for model-independent parity determinations in nuclear resonance fluorescence experiments. Two different Compton polarimeters, a five Ge detector arrangement and a sectored Ge(Li) detector, have been installed at the bremsstrahlung facility of the Stuttgart Dynamitron Accelerator. The following spin and parity assignments have been achieved to excited states (excitation

R. D. Heil; B. Kasten; W. Scharfe; P. A. Butler; H. Friedrichs; S. D. Hoblit; U. Kneissl; S. Lindenstruth; M. Ludwig; G. Mller; H. H. Pitz; K. W. Rose; M. Schumacher; U. Seemann; J. Simpson; P. von Brentano; Th. Weber; C. Wesselborg; A. Zilges

1990-01-01

59

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

60

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

61

Ressonancia de quadrupolo nuclear da arsenolita. (Nuclear quadrupole resonance of arsenolite).  

National Technical Information Service (NTIS)

A pulsed Nuclear Quadrupole Resonance (NQR) spectrometer was constructed using imported Matec units. Peripherical components were specially assembled and tested for the implantation of the spin-echo technique in the Laboratorio de Centros de Cor of IFUSP....

R. Madarazo

1988-01-01

62

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

63

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

64

Acoustic flow in the resonator throat: Experiment and computational modeling  

NASA Astrophysics Data System (ADS)

This paper is devoted to the study of acoustic flow in the Helmholtz resonator throat. The presented results of a complex investigation on the basis of data of a physical experiment and a mathematical modeling, their comparative analysis, and comparison with theoretical estimations provide a rather complete image of the acoustic flow formation and, in particular, enable one to obtain qualitative and quantitative dependences of the averaged velocity component in the resonator throat at different powers of an exciting sound wave.

Duben', A. P.; Kozubskaya, T. K.; Korolev, S. I.; Maslov, V. P.; Mironov, A. K.; Mironova, D. A.; Shakhparonov, V. M.

2012-01-01

65

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments  

SciTech Connect

The focus of this work is to determine the resonance parameters for stable hafnium isotopes in the 0.005 - 200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. Accurate hafnium cross sections and resonance parameters are needed in order to quantify the effects of hafnium found in zirconium, a metal commonly used in reactors. The accuracy of the cross sections and the corresponding resonance parameters used in current nuclear analysis tools are rapidly becoming the limiting factor in reducing the overall uncertainty on reactor physics calculations. Experiments measuring neutron capture and transmission are routinely performed at the Rensselaer Polytechnic Institute (RPI) LINAC using the time-of flight technique. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m, respectively. Capture experiments were performed using a sixteen section NaI multiplicity detector at a flight path length of 25 m. These experiments utilized several thicknesses of metallic and isotope-enriched liquid Hf samples. The liquid Hf samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analyses were performed using the R-matrix Bayesian code SAMMY. A combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005 - 200 eV. Additionally, resonance integrals were calculated, along with errors for each hafnium isotope, using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previous values. The {sup 176}Hf resonance integral, based on this work, is approximately 73% higher than the ENDF/B-VI value. This is due primarily to the changes to resonance parameters in the 8 eV resonance, the neutron width presented in this work is more than twice that of the previous value. The calculated elemental hafnium resonance integral however, changed very little.

Trbovich, M J; Barry, D P; Slovacek, R E; Danon, Y; Block, R C; Francis, N C; Lubert, M; Burke, J A; Drindak, N J; Lienweber, G; Ballad, R

2007-02-06

66

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

67

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

68

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

69

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

70

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments  

SciTech Connect

The focus of this work is to determine resonance parameters for stable hafnium isotopes in the 0.005-200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. The large neutron cross section of hafnium, combined with its corrosion resistance and excellent mechanical properties, make it a useful material for controlling nuclear reactions. Experiments measuring neutron capture and transmission were performed at the Rensselaer Polytechnic Institute (RPI) electron linear accelerator (LINAC) using the time of flight method. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m. Capture experiments were done using a sixteen section NaI(Tl) multiplicity detector at a flight path length of 25 m. These experiments utilized various thicknesses of metallic and isotopically-enriched liquid samples. The liquid samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analysis was done using the R-matrix Bayesian code SAMMY version M6 beta. SAMMY is able to account for experimental resolution effects for each of the experimental setups at the RPI LINAC, and also can correct for multiple scattering effects in neutron capture yield data. The combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005-200 eV. Resonance integrals were calculated along with errors for each hafnium isotope using the NJOY [1] and INTER [2] codes. The isotopic resonance integrals calculated were significantly different than previously published values; however the calculated elemental hafnium resonance integral changed very little.

MJ Trbovich; DP Barry; RE Slovacck; Y Danon; RC Block; JA Burke; NJ Drindak; G Leinweber; RV Ballad

2004-10-13

71

Hafnium Resonance Parameter Analysis using Neutron Capture and Transmission Experiments  

SciTech Connect

The focus of this work is to determine resonance parameters for stable hafnium isotopes in the 0.005-200 eV region, with special emphasis on the overlapping 176Hf and 178Hf resonances near 8 eV. The large neutron cross section of hafnium, combined with its corrosion resistance and excellent mechanical properties, make it a useful material for controlling nuclear reactions.Experiments measuring neutron capture and transmission were performed at the Rensselaer Polytechnic Institute (RPI) electron linear accelerator (LINAC) using the time of flight method. 6Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m. Capture experiments were done using a sixteen-section NaI(Tl) multiplicity detector at a flight path length of 25 m. These experiments utilized various thicknesses of metallic and isotopically enriched liquid samples. The liquid samples were designed to provide information on the 176Hf and 178Hf contributions to the 8-eV doublet without saturation.Data analysis was done using the R-matrix Bayesian code SAMMY version M6 beta. SAMMY is able to account for experimental resolution effects for each of the experimental setups at the RPI LINAC, and also can correct for multiple scattering effects in neutron capture yield data. The combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005-200 eV. Resonance integrals were calculated along with errors for each hafnium isotope using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previously published values; however the calculated elemental hafnium resonance integral changed very little.

Trbovich, Michael J.; Barry, Devin P.; Burke, John A.; Drindak, Noel J.; Leinweber, Greg; Ballad, Robert V. [Lockheed Martin Corporation, P.O. Box 1072, Schenectady, New York 12301-1072 (United States); Slovacek, Rudy E.; Danon, Yaron; Block, Robert C. [Rensselaer Polytechnic Institute, Mechanical, Aerospace and Nuclear Engineering Department, Troy, New York 12180-3590 (United States)

2005-05-24

72

Nuclear quadrupole resonance of norephedrine.  

PubMed

Toward searching for illegal drugs, we investigated the pulsed nuclear quadrupole resonance (NQR) response of 14N in (1R,2S)-(-)-norephedrine, based on the predictions of quantum chemical calculations. Two pairs of spectral lines (?+=3.089, 3.093 MHz and ?-=2.594, 2.608 MHz) were observed despite its molecule structure having only a single nitrogen atom. This indicates that the molecular crystal has two nonequivalent nitrogen atoms in the unit cell. The temperature dependence of the NQR frequencies and relaxation properties were investigated for the purpose of accurate remote sensing of the drugs. The NQR frequency shift was approximately 0.23 kHz/K around room temperature. The spin-lattice relaxation and spin-phase memory times were 5.2-10.2 ms and 0.6-1.5 ms, respectively. PMID:21924876

Shinohara, Junichiro; Kobayashi, Kazuhiko; Sato-Akaba, Hideo; Itozaki, Hideo

2011-09-06

73

^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

74

Closing supersymmetric resonance regions with direct detection experiments  

NASA Astrophysics Data System (ADS)

In order for neutralino dark matter to avoid being overproduced in the early Universe, these particles must annihilate (or coannihilate) rather efficiently. Neutralinos with sufficiently large couplings to annihilate at such high a rate (such as those resulting from gaugino-Higgsino mixing, as in well-tempered or focus point scenarios), however, have become increasingly disfavored by the null results of XENON100 and other direct detection experiments. One of the few remaining ways that neutralinos could potentially evade such constraints is if they annihilate through a resonance, as can occur if 2m?0 falls within about 10% of either mA/H, mh, or mZ. If no signal is observed from upcoming direct detection experiments, the degree to which such a resonance must be tuned will increase significantly. In this paper, we quantify the degree to which such a resonance must be tuned in order to evade current and projected constraints from direct detection experiments. Assuming a future rate of progress among direct detection experiments that is similar to that obtained over the past decade, we project that within 7 years the light Higgs and Z pole regions will be entirely closed, while the remaining parameter space near the A/H resonance will require that 2m?0 be matched to the central value (near mA) to within less than 4%. At this rate of progress, it will be a little over a decade before multiton direct detection experiments will be able to close the remaining, highly tuned, regions of the A/H resonance parameter space.

Hooper, Dan; Kelso, Chris; Sandick, Pearl; Xue, Wei

2013-07-01

75

Magnetic Field Gradient Calibration as an Experiment to Illustrate Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

|A nuclear magnetic resonance (NMR) spectroscopy experiment for the undergraduate physical chemistry laboratory is described that encompasses both qualitative and quantitative pedagogical goals. Qualitatively, the experiment illustrates how images are obtained in magnetic resonance imaging (MRI). Quantitatively, students experience the

Seedhouse, Steven J.; Hoffmann, Markus M.

2008-01-01

76

Magnetic Field Gradient Calibration as an Experiment to Illustrate Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

A nuclear magnetic resonance (NMR) spectroscopy experiment for the undergraduate physical chemistry laboratory is described that encompasses both qualitative and quantitative pedagogical goals. Qualitatively, the experiment illustrates how images are obtained in magnetic resonance imaging (MRI). Quantitatively, students experience the

Seedhouse, Steven J.; Hoffmann, Markus M.

2008-01-01

77

A versatile computer-controlled pulsed nuclear quadrupole resonance spectrometer  

NASA Astrophysics Data System (ADS)

A new, pulsed nuclear quadrupole resonance (NQR) spectrometer capable of performing a variety of pulsed and swept experiments is described. The spectrometer features phase locked, superheterodyne detection using a commercial spectrum analyzer and a fully automatic, computer-controlled tuning and matching network. The tuning and matching network employs stepper motors which turn high power air gap capacitors in a ``moving grid'' optimization strategy to minimize the reflected power from a directional coupler. In the duplexer circuit, digitally controlled relays are used to switch different lengths of coax cable appropriate for the different radio frequencies. A home-built pulse programmer card controls the timing of radio frequency pulses sent to the probe, while data acquisition and control software is written in Microsoft Quick Basic. Spin-echo acquisition experiments are typically used to acquire the data, although a variety of pulse sequences can be employed. Scan times range from one to several hours depending upon the step resolution and the spectral range required for each experiment. Pure NQR spectra of NaNO2 and 3-aminopyridine are discussed.

Fisher, Gregory; Macnamara, Ernesto; Santini, Robert E.; Raftery, Daniel

1999-12-01

78

Experiments on statistical mechanics using resonance ionization spectroscopy  

SciTech Connect

Five different fluctuation phenomena at the atomic and molecular levels have been studied by resonance ionization spectroscopy techniques with one-atom detection sensitivity. The Poisson distribution described the observed frequency distributions suggesting random behavior. In addition, a gedanken experiment suggested by Einstein and Furth on the diffusion of atoms was performed in order to test the equality between time and ensemble averages. The obtained results confirmed the ergodicity of the studied system.

Iturbe, J.; Allman, S.L.; Hurst, G.S.; Payne, M.G.

1984-04-01

79

Nitrogen-detected CAN and CON experiments as alternative experiments for main chain NMR resonance assignments  

PubMed Central

Heteronuclear direct-detection experiments, which utilize the slower relaxation properties of low ? nuclei, such as 13C have recently been proposed for sequence-specific assignment and structural analyses of large, unstructured, and/or paramagnetic proteins. Here we present two novel 15N direct-detection experiments. The CAN experiment sequentially connects amide 15N resonances using 13C? chemical shift matching, and the CON experiment connects the preceding 13C? nuclei. When starting from the same carbon polarization, the intensities of nitrogen signals detected in the CAN or CON experiments would be expected four times lower than those of carbon resonances observed in the corresponding 13C-detecting experiment, NCA-DIPAP or NCO-IPAP (Bermel et al. 2006b; Takeuchi et al. 2008). However, the disadvantage due to the lower ? is counteracted by the slower 15N transverse relaxation during detection, the possibility for more efficient decoupling in both dimensions, and relaxation optimized properties of the pulse sequences. As a result, the median S/N in the 15N observe CAN experiment is 16% higher than in the 13C observe NCA-DIPAP experiment. In addition, significantly higher sensitivity was observed for those residues that are hard to detect in the NCA-DIPAP experiment, such as Gly, Ser and residues with high-field C? resonances. Both CAN and CON experiments are able to detect Pro resonances that would not be observed in conventional proton-detected experiments. In addition, those experiments are free from problems of incomplete deuterium-to-proton back exchange in amide positions of perdeuterated proteins expressed in D2O. Thus, these features and the superior resolution of 15N-detected experiments provide an attractive alternative for main chain assignments. The experiments are demonstrated with the small model protein GB1 at conditions simulating a 150 kDa protein, and the 52 kDa glutathione S-transferase dimer, GST.

Takeuchi, Koh; Heffron, Gregory; Sun, Zhen-Yu J.; Frueh, Dominique P.

2010-01-01

80

A set of BEST triple-resonance experiments for time-optimized protein resonance assignment  

Microsoft Academic Search

A series of sequential, intra-residue, and bi-directional BEST HNCA, HNCO, and HNCB pulse sequences is presented that extends the BEST concept introduced recently for fast multidimensional protein NMR [Schanda et al., J. Am. Chem. Soc. 128 (2006) 9042] to the complete set of experiments required for sequential resonance assignment. We demonstrate for the protein ubiquitin that 3D BEST HNC correlation

Ewen Lescop; Paul Schanda; Bernhard Brutscher

2007-01-01

81

Meson photoproduction and baryon resonances at MAMBO experiment  

NASA Astrophysics Data System (ADS)

Photoproduction of mesons within the framework of the MAMBO experiment (BGO-OD at Bonn plus MAMI at Mainz) was studied. The results on the operative work of the cryogenic H2/D2 target system during the last commissioning beam times at the March and June 2012 are shown. Investigation of the single charged pion photoproduction was provided using a polarized 3He target at the tagged photon facility of the MAMI accelerator. Unpolarized and helicity dependent cross sections are presented for channels ?N ? ?X in the ?(1232) baryon resonance region.

Romaniuk, Mariia

2013-03-01

82

Laboratory experiments for exploring the surface plasmon resonance  

NASA Astrophysics Data System (ADS)

The surface plasmon wave is a surface wave confined at the interface between a dielectric and a metal. The excitation of the surface plasmon resonance (SPR) on a gold thin film is discussed within the Kretschmann configuration, where the coupling with the excitation light is achieved by means of a prism in total reflection. The electromagnetic principles are detailed and a simple experimental setup is described that can be used for laboratory experiments for senior students in the third or fourth year of university. This experiment allows accurate determination of the angle of plasmon extinction and discussion of the principles of biosensors based on the SPR. A slight modification of the setup allows the investigation of the dependence of SPR on wavelength and illustrates the damping of SPR due to its coupling with the interband transitions of the gold thin film.

Pluchery, Olivier; Vayron, Romain; Van, Kha-Man

2011-03-01

83

A set of BEST triple-resonance experiments for time-optimized protein resonance assignment.  

PubMed

A series of sequential, intra-residue, and bi-directional BEST H-N-CA, H-N-CO, and H-N-CB pulse sequences is presented that extends the BEST concept introduced recently for fast multidimensional protein NMR [Schanda et al., J. Am. Chem. Soc. 128 (2006) 9042] to the complete set of experiments required for sequential resonance assignment. We demonstrate for the protein ubiquitin that 3D BEST H-N-C correlation spectra can be recorded on a 600MHz NMR spectrometer equipped with a cryogenic probe in only a few minutes of acquisition time with sufficient sensitivity to detect all expected cross peaks. PMID:17468025

Lescop, Ewen; Schanda, Paul; Brutscher, Bernhard

2007-04-13

84

A set of BEST triple-resonance experiments for time-optimized protein resonance assignment  

NASA Astrophysics Data System (ADS)

A series of sequential, intra-residue, and bi-directional BEST H N CA, H N CO, and H N CB pulse sequences is presented that extends the BEST concept introduced recently for fast multidimensional protein NMR [Schanda et al., J. Am. Chem. Soc. 128 (2006) 9042] to the complete set of experiments required for sequential resonance assignment. We demonstrate for the protein ubiquitin that 3D BEST H N C correlation spectra can be recorded on a 600 MHz NMR spectrometer equipped with a cryogenic probe in only a few minutes of acquisition time with sufficient sensitivity to detect all expected cross peaks.

Lescop, Ewen; Schanda, Paul; Brutscher, Bernhard

2007-07-01

85

Optical Resonators in Current and Future Experiments of the ALPS Collaboration  

SciTech Connect

The ALPS collaboration runs a 'light shining through a wall' (LSW) experiment to search for weakly interacting sub-eV particles (WISPs). Its sensitivity is significantly enhanced by the incorporation of a large-scale production resonator and a small-scale high-power resonant second harmonic generator. Here we report on important experimental details and limitations of these resonators and derive recommendations for further experiments. A very promising improvement for a future ALPS experiment is the incorporation of an additional large-scale regeneration resonator. We present a rough sketch of how to combine a regeneration resonator with a single-photon counter (SPC) as detector for regenerated photons.

Meier, T. [Max-Planck-Institute for Gravitational Physics, Albert-Einstein-Institute (Germany) and Institut fuer Gravitationsphysik, Leibniz Universitaet Hannover, Callinstr. 38, D-30167 Hannover (Germany)

2010-08-30

86

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

87

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

88

Electron cyclotron resonance heating in the microwave tokamak experiment  

NASA Astrophysics Data System (ADS)

This paper presents the results from a series of Electron Cyclotron Resonance Heating (ECRH) experiments on the Microwave Tokamak Experiment (MTX). On-axis heating at B(sub T) = 5T (f(sub ce) = 140 GHz) has been performed at electron densities up to cutoff. We have used both a long-pulse gyrotron (approximately 200 kW, approximately 0.1s) and a pulsed Free Electron Laser (FEL) as microwave sources. Gyrotron experiments with power densities corresponding to 4 MW m(exp -3) are presented. A far infrared (FIR) polarimeter measured peaking of plasma current profiles in some discharges during the ECRH pulse. During high-power single-pulse FEL experiments, single-pass microwave transmission measurements show nonlinear effects (i.e., higher transmission than predicted by linear theory). A corrugated-wall duct was used in the tokamak port to increase the gradient of the parallel refractive index n(sub parallel) of the incident wave, and increased absorption was observed. Evidence of electron tail heating during FEL pulses was observed on soft x-ray and ECE diagnostics. These results are in agreement with predictions of nonlinear theory; extrapolation of this theory to reactor-like conditions indicates efficient absorption and heating. A Laser Assisted Particle Probe Spectroscopy (LAPPS) diagnostic provided estimates of the vacuum electric field of the FEL which were consistent with the measured power. Multiple pulse operation of the ETA-2 accelerator for the FEL has also been demonstrated indicating the feasibility of high-average power FEL operation.

Allen, S. L.; Casper, T. A.; Fenstermacher, M. E.; Foote, J. H.; Hooper, E. B.; Hoshino, K.; Lasnier, C. J.; Lopez, P.; Makowski, M. A.; Marinak, M. M.

1992-09-01

89

Electron cyclotron resonance heating in the microwave tokamak experiment  

SciTech Connect

This paper presents the results from a series of Electron Cyclotron Resonance Heating (ECRH) experiments on the Microwave Tokamak Experiment (MTX). On-axis heating at B{sub T} = 5T (f{sub ce} = 140 GHz) has been performed at electron densities up to cutoff. We have used both a long-pulse gryotron ({approximately}200 kW, {approximately}0.1s) and a pulsed Free Electron Laser (FEL) as microwave sources. Gyrotron experiments with power densities corresponding to 4 MW m{sup {minus}3}. A far infrared (FIR) polarimeter measured peaking of plasma current profiles in some discharges during the ECRH pulse. During high-power single-pulse FEL experiments, single-pass microwave !transmission measurements show nonlinear effects; i.e., higher transmission than predicted by linear theory. A corrugated-wall duct was used in the tokamak port to increase the gradient of the parallel refractive index n{sub parallel} of the incident wave, and increased absorption was observed. Evidence of electron tail heating during FEL pulses was observed on soft x-ray and ECE diagnostics. These results are in agreement with predictions of nonlinear theory; extrapolation of this theory to reactor-like conditions indicates efficient absorption and heating. A Laser Assisted Particle Probe Spectroscopy (LAPPS) diagnostic provided estimates of the vacuum electric field of the FEL which were consistent with the measured power. Multiple pulse operation of the ETA-II accelerator for the FEL has also been demonstrated, indicating the feasibility of high-average power FEL operation.

Allen, S.L.; Casper, T.A.; Fenstermacher, M.E. [and others

1992-09-01

90

Versatile resonance-tracking circuit for acoustic levitation experiments.  

PubMed

Objects can be levitated by radiation pressure forces in an acoustic standing wave. In many circumstances it is important that the standing wave frequency remain locked on an acoustic resonance despite small changes in the resonance frequency. A self-locking oscillator circuit is described which tracks the resonance frequency by sensing the magnitude of the transducer current. The tracking principle could be applied to other resonant systems. PMID:18699064

Baxter, K; Apfel, R E; Marston, P L

1978-02-01

91

Resonant solar neutrino oscillation versus laboratory neutrino oscillation experiments  

SciTech Connect

The interplay between resonant solar neutrino oscillations and neutrino oscillations in laboratory experiments is investigated in a 3 generation model. Due to the assumed hierarchy of neutrino masses, together with our choice of a convenient parameterization of the 3 generation mixing matrix, we can derive a simple analytic formula which reduces the solar neutrino problem to an effective 2 generation problem. The reduction makes it apparent that the allowed range of mixing and mass parameters crucially depend on whether the survival probability of solar neutrinos S satisfies S greater than or equal to 1/3 or not. The formulae for probabilities of laboratory neutrino oscillations are also greatly simplified. We argue that a combination of the observed solar neutrino depletion and data obtained from reactor experiments seems to rule out some range of neutrino masses. If a sizable nu/sub ..mu../ ..-->.. nu/sub e/ oscillation is observed at accelerators, as suggested at this Workshop, it severely restricts the range of 2 mixing angles.

Lim, Chong-Sa

1987-02-01

92

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

93

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

94

Structure of light nuclei in resonance scattering experiments  

NASA Astrophysics Data System (ADS)

Resonance scattering with rare isotope beams provides direct access to continuum properties of exotic nuclei and can serve as a stringent test for modern theoretical approaches. Properties of neutron deficient isotope 8B, that were studied using resonance scattering of protons of 7Be, are discussed and compared to the predictions of the ab initio theories. New experimental data on clustering in 10Be studied using 6He+? resonance elastic scattering is presented.

Rogachev, G. V.; Avila, M.; Baby, L. T.; Blackmon, J.; Goldberg, V. Z.; Johnson, E. D.; Matos, M.; Macon, K.; Mitchell, J. P.; Linhardt, L.; Kuchera, A.; Koshchiy, E.; Kemper, K.; Santiago-Gonzales, D.; Volya, A.; Wiedenhoever, I.

2013-04-01

95

Advanced Undergraduate-Laboratory Experiment on Electron Spin Resonance in Single-Crystal Ruby  

ERIC Educational Resources Information Center

An electron-spin-resonance experiment which has been successfully performed in an advanced undergraduate physics laboratory is described. A discussion of that part of the theory of magnetic resonance necessary for the understanding of the experiment is also provided in this article. (DT)

Collins, Lee A.; And Others

1974-01-01

96

The Effect of Resonance Absorption in OMEGA Direct-Drive Designs and Experiments  

SciTech Connect

Resonance absorption enhances the early time laser absorption in direct-drive inertial confinement fusion implosions, affecting the performance of imploding capsules. In this paper, resonance absorption is studied both theoretically and experimentally for a lambda = 351-nm laser. Simulations demonstrate an important contribution of the resonance absorption during both the short laser picket (~100 ps) and the first 200-300 ps in the long laser pulse. Planar reflection light experiments on OMEGA were conducted to validate theoretical results. There is a generally good agreement between simulation and experimental results. As an additional diagnostic of resonance absorption, shock-timing experiments employing OMEGA drive beams of different polarization are proposed.

Igumenshchev, I.V.; Goncharov, V.N.; Seka, W.; Edgell, D.; Boehly, T.R.

2007-10-04

97

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

98

Ferromagnetic resonance of isotropic heterogeneous magnetic materials: theory and experiments  

Microsoft Academic Search

Experimental variations of the ferromagnetic resonance (FMR) recorded on soft composite bodies are presented and their interpretation is undertaken. A successful application is performed for the Kittel expression of the FMR, initially written for an ellipsoid placed in vacuum, to a magnetic inclusion of the composite. This model includes the demagnetizing effects due to the magnetic inclusions.

Alexis Chevalier; Jean-Luc Mattei; Marcel Le Floc'h

2000-01-01

99

Laboratory Experiments for Exploring the Surface Plasmon Resonance  

ERIC Educational Resources Information Center

|The surface plasmon wave is a surface wave confined at the interface between a dielectric and a metal. The excitation of the surface plasmon resonance (SPR) on a gold thin film is discussed within the Kretschmann configuration, where the coupling with the excitation light is achieved by means of a prism in total reflection. The electromagnetic

Pluchery, Olivier; Vayron, Romain; Van, Kha-Man

2011-01-01

100

Peptide backbone orientation and dynamics in spider dragline silk and two-photon excitation in nuclear magnetic and quadrupole resonance  

NASA Astrophysics Data System (ADS)

In the first part of the dissertation, spider dragline silk is studied by solid state NMR techniques. The dependence of NMR frequency on molecular orientation is exploited using the DECODER experiment to determine the orientation of the protein backbone within the silk fibre. Practical experimental considerations require that the silk fibres be wound about a cylindrical axis perpendicular to the external magnetic field, complicating the reconstruction of the underlying orientation distribution and necess-itating the development of numerical techniques for this purpose. A two-component model of silk incorporating static b-sheets and polyglycine II helices adequately fits the NMR data and suggests that the b-sheets are well aligned along the silk axis (20 FWHM) while the helices are poorly aligned (68 FWHM). The effects of fibre strain, draw rate and hydration on orientation are measured. Measurements of the time-scale for peptide backbone motion indicate that when wet, a strain-dependent frac-tion of the poorly aligned component becomes mobile. This suggests a mechanism for the supercontraction of silk involving latent entropic springs that undergo a local strain-dependent phase transition, driving supercontraction. In the second part of this dissertation a novel method is developed for exciting NMR and nuclear quadrupole resonance (NQR) by rf irradiation at multiple frequencies that sum to (or differ by) the resonance frequency. This is fundamentally different than traditional NMR experiments where irradiation is applied on-resonance. With excitation outside the detection bandwidth, two-photon excitation allows for detection of free induction signals during excitation, completely eliminating receiver dead-time. A theoretical approach to describing two-photon excitation is developed based on average Hamiltonian theory. An intuition for two-photon excitation is gained by analogy to the coherent absorption of multiple photons requiring conservation of total energy and momentum. It is shown that two-photon excitation efficiency impro-ves when the two applied rf frequencies deviate from half-resonance. For two-photon NQR, it is shown that observable magnetization appears perpendicular to the excita-tion coil, requiring a second coil for detection, and that double quantum coherences are also generated. Several model systems and experimental geometries are used to demonstrate the peculiarities of two-photon excitation in NMR and NQR.

Eles, Philip Thomas

101

Auditory perception of 3D size: Experiments with synthetic resonators  

Microsoft Academic Search

For representing complex data through auditory display, the ecological approach to sound perception, if combined with the most advanced techniques for physical modeling, seems to form a good strategy to translate information into sound by composition of auditory scenes and to create an object-based auditory information space.We examine the auditory perception of one feature of simulated 3D resonators: the size.

Laura Ottaviani; Davide Rocchesso

2004-01-01

102

Nuclear quadrupole resonance single-pulse echoes.  

PubMed

We report the first detection of a spin echo after excitation of a powder sample by a single pulse at the resonance frequency during nuclear quadrupole resonance (NQR). These echoes can occur in samples that have an inhomogeneously broadened line, in this case due to the distribution of electric field gradients. The echoes are easily detectable when the Rabi frequency approaches the linewidth and the average effective tipping angle is close to 270 degrees. When limited by a weak radio-frequency field, the single-pulse echo can be used to increase the signal to noise ratio over conventional techniques. These effects can be used to optimize the NQR detection of contraband containing quadrupole nuclei and they are demonstrated with glycine hemihydrochloride and hexhydro-1,3,5-trinitro-1,3,5-triazine (RDX). PMID:18571445

Prescott, David W; Miller, Joel B; Tourigny, Chris; Sauer, Karen L

2008-05-29

103

Sparsely sampled high-resolution 4-D experiments for efficient backbone resonance assignment of disordered proteins.  

PubMed

Intrinsically disordered proteins (IDPs) play important roles in many critical cellular processes. Due to their limited chemical shift dispersion, IDPs often require four pairs of resonance connectivities (H(?), C(?), C(?) and CO) for establishing sequential backbone assignment. Because most conventional 4-D triple-resonance experiments share an overlapping C(?) evolution period, combining existing 4-D experiments does not offer an optimal solution for non-redundant collection of a complete set of backbone resonances. Using alternative chemical shift evolution schemes, we propose a new pair of 4-D triple-resonance experiments--HA(CA)CO(CA)NH/HA(CA)CONH--that complement the 4-D HNCACB/HN(CO)CACB experiments to provide complete backbone resonance information. Collection of high-resolution 4-D spectra with sparse sampling and FFT-CLEAN processing enables efficient acquisition and assignment of complete backbone resonances of IDPs. Importantly, because the CLEAN procedure iteratively identifies resonance signals and removes their associating aliasing artifacts, it greatly reduces the dependence of the reconstruction quality on sampling schemes and produces high-quality spectra even with less-than-optimal sampling schemes. PMID:21277815

Wen, Jie; Wu, Jihui; Zhou, Pei

2011-01-04

104

Resonance  

NSDL National Science Digital Library

For advanced undergraduate students: Observe resonance in a collection of driven, damped harmonic oscillators. Vary the driving frequency and amplitude, the damping constant, and the mass and spring constant of each resonator. Notice the long-lived transients when damping is small, and observe the phase change for resonators above and below resonance.

Simulations, Phet I.; Dubson, Michael; Loeblein, Patricia; Olson, Jonathan; Perkins, Kathy; Gratny, Mindy

2011-07-20

105

Neutron-multiwave-interference experiments with many resonance coils  

SciTech Connect

Neutron-multiwave-interference phenomena based on Ramsey's resonance method of ''separated oscillating fields'' are studied. A neutron passes through N successive resonant coils (({Dirac_h}/2{pi}){omega}{sub 0}=2{mu}{sub n}B{sub 0}), which flip the neutron spin with a probability {rho} smaller than 1. These coils are separated by path lengths L over which a homogeneous field B{sub 1} is present. Because the spin-flip probability {rho} is smaller than 1, the number of waves for a neutron is doubled after each flipper, so as to produce 2{sup N} neutron waves at the end of the setup. The phase difference between any pair of waves is a multiple of a ''phase quantum'' determined by the line integral of the field difference B{sub 1}-B{sub 0} over the length L. Highly regular patterns of the quantum-mechanical probability R in (B{sub 1},{rho}) space appear due to pair interference between individual waves. Possible applications of this phenomenon, such as a direct measurement of n-particle correlation function, are pointed out.

Grigoriev, S. V. [Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188350, Russia (Russian Federation); Interfacultair Reactor Instituut, TU-Delft, 2629 JB Delft, The Netherlands (Netherlands); Chetverikov, Yu. O.; Syromyatnikov, A. V. [Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188350, Russia (Russian Federation); Kraan, W. H.; Rekveldt, M. Th. [Interfacultair Reactor Instituut, TU-Delft, 2629 JB Delft, The Netherlands (Netherlands)

2003-09-01

106

Detection of ammonium nitrate inside vehicles by nuclear quadrupole resonance  

Microsoft Academic Search

The development of a system for the detection of ammonium nitrate (AN) in vehicles by nuclear quadrupole resonance (NQR) is\\u000a described. The results from studies of the penetration of radiofrequency (RF) magnetic fields inside certain metal enclosures,\\u000a including full-scale vehicles, were critical in the design of a novel high-Q resonant probe. The probe was shaped not only for optimal penetration

J. Barras; M. J. Gaskell; N. Hunt; R. I. Jenkinson; K. R. Mann; D. A. G. Pedder; G. N. Shilstone; J. A. S. Smith

2004-01-01

107

Resonance Raman Spectroscopy of Beta-Carotene and Lycopene: A Physical Chemistry Experiment.  

ERIC Educational Resources Information Center

Discusses the theory of resonance Raman (RR) spectroscopy as it applies to beta-carotene and lycopene pigments (found in tomatoes and carrots, respectively). Also discusses an experiment which demonstrates the theoretical principles involved. The experiment has been tested over a three-year period and has received excellent acceptance by physical

Hoskins, L. C.

1984-01-01

108

Resonance Raman Spectroscopy of Beta-Carotene and Lycopene: A Physical Chemistry Experiment.  

ERIC Educational Resources Information Center

|Discusses the theory of resonance Raman (RR) spectroscopy as it applies to beta-carotene and lycopene pigments (found in tomatoes and carrots, respectively). Also discusses an experiment which demonstrates the theoretical principles involved. The experiment has been tested over a three-year period and has received excellent acceptance by physical

Hoskins, L. C.

1984-01-01

109

Near-field optical experiments on low-symmetry split-ring-resonator arrays.  

PubMed

Effective symmetric and antisymmetric eigenmodes of coupled plasmonic resonances play a crucial role in many photonic metamaterials. Recently, we discussed a particular arrangement of metallic split-ring resonators that is planar, hence enabling direct experimental access to the different eigenmodes via near-field optical microscopy. In this Letter, corresponding optical experiments are presented and compared with simple theoretical modeling, providing a direct confirmation of our previous, more indirect conclusions. PMID:21042383

Diessel, Daniela; Decker, Manuel; Linden, Stefan; Wegener, Martin

2010-11-01

110

Mechanism and experiment study on photothermally excited bilayer silicon microcantilever resonators  

NASA Astrophysics Data System (ADS)

Silicon micro-cantilever resonators are typical elements in micro-electro-mechanical systems. Basing on the photothermally excited micro-cantilever resonators, many optical microsystems can be realized, such as micro-swichtes,mciro-modulators and microsensors etc. In this paper, mechanism and experiment study is given on photo-thermally excited bi-layered silicon micro-cantilever resonators, and relative results can be served as the basis of further applications. When coating is put on the surface of micro-cantilever to increase the optically exciting efficiency, the whole resonator becomes bi-layered structure, and the mechanism of this bi-layered resonator is very different from those of single material resonators. In this paper, photo-thermally excited mechanism of bi-layered silicon micro-cantilever was presented and a corresponding photo-thermal theoretical model was set up based on the photo-thermal effect. The first three resonant modes of the silicon micro-cantilever were detected successfully by using piezoelectric resistors fabricated as a Wheat-stone sensing bridge on the micro-cantilever. A novel method was presented to excite and detect the microresonator at the same time by using only one optical source , and this novel method was demonstrated by detecting the first resonant mode of the micro-cantilever.

Zhang, Shaojun; Liu, Yueming

2004-12-01

111

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

112

A set of triple-resonance nuclear magnetic resonance experiments for structural characterization of organophosphorus compounds in mixture samples.  

PubMed

The (1)H, (13)C correlation NMR spectroscopy utilizes J(CH) couplings in molecules, and provides important structural information from small organic molecules in the form of carbon chemical shifts and carbon-proton connectivities. The full potential of the (1)H, (13)C correlation NMR spectroscopy has not been realized in the Chemical Weapons Convention (CWC) related verification analyses due to the sample matrix, which usually contains a high amount of non-related compounds obscuring the correlations of the relevant compounds. Here, the results of the application of (1)H, (13)C, (31)P triple-resonance NMR spectroscopy in characterization of OP compounds related to the CWC are presented. With a set of two-dimensional triple-resonance experiments the J(HP), J(CH) and J(PC) couplings are utilized to map the connectivities of the atoms in OP compounds and to extract the carbon chemical shift information. With the use of the proposed pulse sequences the correlations from the OP compounds can be recorded without significant artifacts from the non-OP compound impurities in the sample. Further selectivity of the observed correlations is achieved with the application of phosphorus band-selective pulse in the pulse sequences to assist the analysis of multiple OP compounds in mixture samples. The use of the triple-resonance experiments in the analysis of a complex sample is shown with a test mixture containing typical scheduled OP compounds, including the characteristic degradation products of nerve agents sarin, soman, and VX. The viability of the approach in verification analysis is demonstrated in the analysis of the 30th OPCW Proficiency Test sample. PMID:23084058

Koskela, Harri

2012-09-25

113

Charge-inhomogeneity doping relations in Y Ba2 Cu3 Oy detected by angle-dependent nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

The origin of charge inhomogeneity in YBa2Cu3Oy is investigated using an experimental method designed to determine the nuclear quadrupole resonance (NQR) asymmetry parameter ? for very wide NQR lines at different positions on the line. The method is based on the measurement of the echo intensity as a function of the angle between the radio frequency field H1 and the principal axis of the electric field gradient. Static charge inhomogeneity deduced from ?>0 is found in this compound, but only in conjunction with oxygen deficiency. This limits considerably the possible forms of charge inhomogeneity in bulk YBa2Cu3Oy .

Ofer, Rinat; Levy, Shahar; Kanigel, Amit; Keren, Amit

2006-01-01

114

4D experiments measured with APSY for automated backbone resonance assignments of large proteins.  

PubMed

Detailed structural and functional characterization of proteins by solution NMR requires sequence-specific resonance assignment. We present a set of transverse relaxation optimization (TROSY) based four-dimensional automated projection spectroscopy (APSY) experiments which are designed for resonance assignments of proteins with a size up to 40 kDa, namely HNCACO, HNCOCA, HNCACB and HN(CO)CACB. These higher-dimensional experiments include several sensitivity-optimizing features such as multiple quantum parallel evolution in a 'just-in-time' manner, aliased off-resonance evolution, evolution-time optimized APSY acquisition, selective water-handling and TROSY. The experiments were acquired within the concept of APSY, but they can also be used within the framework of sparsely sampled experiments. The multidimensional peak lists derived with APSY provided chemical shifts with an approximately 20 times higher precision than conventional methods usually do, and allowed the assignment of 90 % of the backbone resonances of the perdeuterated primase-polymerase ORF904, which contains 331 amino acid residues and has a molecular weight of 38.4 kDa. PMID:23625454

Krhenbhl, Barbara; Boudet, Julien; Wider, Gerhard

2013-04-30

115

Doppler effect experiment of resonance materials for rock like oxide fuels  

Microsoft Academic Search

A Doppler effect experiment of resonance materials such as erbium, tungsten, thorium and uranium was carried out in the Fast Critical Assembly of Japan Atomic Energy Research Institute. Cylindrical shaped samples of 150 mm in stack length and 23 mm in diameter were fabricated. The sample was contained in capsules and placed at the center of the core. Temperature of

Y. Nakano; M. Andoh; S. Okajima; H. Takano; H. Akie

2001-01-01

116

Ion Cyclotron Resonant Heating slot antenna for the Tandem Mirror Experiment-Upgrade  

SciTech Connect

The Ion Cyclotron Resonant Heating (ICRH) slot antenna has been a part of the ion and electron plasma heating system in the central cell region of the Tandem Mirror Experiment-Upgrade (TMX-U). This paper presents the mechanical design and arrangement of the antenna, coax feed lines, feedthroughs, and matching network for the slot antenna.

Brooksby, C.A.; Calderson, M.O.; Cummins, W.F.; Ferguson, S.W.; Williamson, V.L.

1985-11-14

117

Transverse relaxation optimized triple-resonance NMR experiments for nucleic acids  

Microsoft Academic Search

Triple resonance HCN and HCNCH experiments are reliable methods of establishing sugar-to-base connectivity in the NMR spectra of isotopicaly labeled oligonucleotides. However, with larger molecules the sensitivity of the experiments is drastically reduced due to relaxation processes. Since the polarization transfer between 13C and 15N nuclei relies on rather small heteronuclear coupling constants (1112Hz), the long evolution periods (up to

Radovan Fiala; Ji? Czernek; Vladimr Sklen?

2000-01-01

118

Transverse relaxation optimized triple-resonance NMR experiments for nucleic acids  

Microsoft Academic Search

Triple resonance HCN and HCNCH experiments are reliable methods of establishing sugar-to-base connectivity in the NMR spectra of isotopicaly labeled oligonucleotides. However, with larger molecules the sensitivity of the experiments is drastically reduced due to relaxation processes. Since the polarization transfer between 13 Ca nd 15N nuclei relies on rather small heteronuclear coupling constants (11-12 Hz), the long evolution periods

Radovan Fiala

2000-01-01

119

TROSY in Triple-Resonance Experiments: New Perspectives for Sequential NMR Assignment of Large Proteins  

Microsoft Academic Search

The NMR assignment of 13C, 15N-labeled proteins with the use of triple resonance experiments is limited to molecular weights below ~ 25,000 Daltons, mainly because of low sensitivity due to rapid transverse nuclear spin relaxation during the evolution and recording periods. For experiments that exclusively correlate the amide proton (1HN), the amide nitrogen (15N), and 13C atoms, this size limit

Michael Salzmann; Konstantin Pervushin; Gerhard Wider; Hans Senn; Kurt Wuthrich

1998-01-01

120

Resonance  

NSDL National Science Digital Library

All About Circuits is a website that âprovides a series of online textbooks covering electricity and electronics.â Written by Tony R. Kuphaldt, the textbooks available here are wonderful resources for students, teachers, and anyone who is interested in learning more about electronics. This specific section, Resonance, is the sixth chapter in the Volume II textbook. Topics covered in this chapter include: electric pendulum, simple parallel resonance, simple series resonance, resonance in series-parallel circuits, and Q and bandwidth of a resonant circuit. Diagrams and detailed descriptions of concepts are included throughout the chapter to provide users with a comprehensive lesson. Visitors to the site are also encouraged to discuss concepts and topics using the All About Circuits discussion forums (registration with the site is required to post materials).

Kuphaldt, Tony R.

2008-07-07

121

Ionization resonances for H atoms in a strong (static + microwave) field: Experiment vs.theory  

NASA Astrophysics Data System (ADS)

Following up onfootnote E. Galvez et al., previous abstract, this meeting, take, e.g., H(n_0=40) atoms in collinear static and 8.105 GHz fields (amplitudes Fs and F_?, respectively). At F_? = 220 V/cm (n_0^4F_?=0.110) the survival probability P_surv decreases sharply at Fs ~= k \\cdot 50 V/cm, k=1,ldots,5. Raising F_? from zero, higher- (lower-)k resonances first appear at lower (higher) F_?. A given resonance disappears at certain F_?. Though in linear Stark effect approximation (LSEA) k ? = 3n_0Fs (in a.u.) gives energy matching for the splitting between same-|m|, adjacent Stark substates at k \\cdot 52.8 V/cm, this cannot explain these (multiphoton) resonances because in LSEA the transition matrix element is zero. (Finite quantum defects affected matrix elements in previous alkali atom experimentsfootnote T.F. Gallagher, Rydberg Atoms (CUP, Cambridge, 1994), Chap. 10.) Numerical simulations based on classical dynamics reproduce all distinctive features of the (F_? + F_s) resonances data with 3d H atoms. Classically and quantally we use an adiabatic model to view the dynamics as a case of parametric resonance. We explain the disappearance of the resonances and achieve quantitative agreement with experiment.

Koch, P.; Richards, D.; Galvez, E.; Zelazny, S.

1998-05-01

122

Search for N* Resonances in Double-Polarization Experiments using CLAS  

SciTech Connect

At medium energies where the strong coupling constant is very large and perturbative methods can no longer be applied, the nature of confinement remains one of the key challenges in our present understanding of QCD. A necessary step is undoubtedly to identify the relevant degrees of freedom in this energy regime and the effective forces between them. Thus, a precise knowledge of the spectrum of baryon resonances and their properties is needed. A large number of states has been found in different analyses. However, only a few of them are well established and confirmed by different experiments. It has been shown that particular resonances have large effects on polarization observables. At Jefferson Laboratory, a major program has been proposed to perform a large set of photoproduction experiments using linearly- and circularly-polarized tagged photon beams as well as longitudinally and transversely-polarized targets. In double-pion production, a major obstacle in the determination of the couplings of baryon resonances are the considerable contributions from non-resonant mechanisms, m this case, polarization observables, which are sensitive to very small resonance contributions, will be helpful in the evaluation of N* properties.

Volker Crede

2007-06-01

123

Third interger resonance slow extraction schemem for a mu->e experiment at Fermilab  

SciTech Connect

The current design of beam preparation for a proposed mu->e conversion experiment at Fermilab is based on slow resonant extraction of protons from the Debuncher. The Debuncher ring will have to operate with beam intensities of 3 x 10{sup 12} particles, approximately four orders of magnitude larger than its current value. The most challenging requirements on the beam quality are the spill uniformity and low losses in the presence of large space charge and momentum spread. We present results from simulations of third integer resonance extraction assisted by RF knock-out (RFKO), a technique developed for medical accelerators. Tune spreads up to 0.05 have been considered.

Nagaslaev, V.; Amundson, J.; Johnstone, J.; Michelotti, L.; Park, C.S.; Werkema, S.; /Fermilab; Syphers, M.; /Michigan State U.

2010-09-01

124

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

125

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

126

Results of Resonant Activation and Macroscopic Quantum Tunneling Experiments in Magnesium Diboride Thin Film Josephson Junctions  

NASA Astrophysics Data System (ADS)

The Josephson junction is an experimental testbed widely used to study resonant activation and macroscopic quantum tunneling. These phenomena have been observed in junctions based on conventional low-temperature superconductors such as Nb and Al, and even in high-Tc, intrinsic superconductors. We report results of superconducting-to normal state switching experiments below 1 K using MgB2-based Josephson heterojunctions with Pb and Nb counter-electrodes. Measurements were made with and without RF excitation. With microwaves, we see evidence of a resonant peak, in addition to the primary escape (from ground state) peak -- consistent with resonant activation. We also observe features suggestive of macroscopic quantum tunneling including peaks in the escape rate enhancements and an ``elbow'' in the graph of calculated escape temperatures Tesc versus sample temperature.

Ramos, Roberto; Carabello, Steve; Lambert, Joseph; Mlack, Jerome; Dai, Wenqing; Shen, Yi.; Li, Qi; Cunnane, Daniel; Zhuang, C. G.; Chen, Ke; Xi, X. X.

2012-02-01

127

Detection of ammonium nitrate inside vehicles by Nuclear Quadrupole Resonance  

Microsoft Academic Search

\\u000a Nuclear quadrupole resonance (NQR) has been demonstrated for the detection of explosives in a number of potential applications,\\u000a including baggage screening, mail screening and landmine detection. A further highly desirable application concerns the detection\\u000a of explosives concealed within a vehicle, which from the point of view of RF penetration can be considered as a large metal\\u000a box with holes in

J. Barras; M. J. Gaskell; N. Hunt; R. I. Jenkinson; K. Mann; D. Peddar; G. N. Shilstone; J. A. S. Smith

128

Infrared analogs of heteronuclear nuclear magnetic resonance coherence transfer experiments in peptides  

NASA Astrophysics Data System (ADS)

Using short pulses whose bandwidth covers only one amide band and that are resonant with either the amide I or the amide II band, we propose two-color multiple pulse infrared experiments that are analogs of heteronuclear nuclear magnetic resonance (NMR) experiments for probing the structure of peptides and proteins. These pulse sequences yield simpler spectra of nonoverlapping vibrational bands with fewer overlapping peaks than one-color techniques, and open new ways to more sophisticated control over coherence transfer pathways. Differences between NMR and IR techniques stemming from the different initial conditions and the pulse field strengths are taken into account. We find that in several cases, ? pulses commonly used in NMR to simplify the spectra can be avoided in vibrational spectroscopy due to the low temperature initial condition (i.e., vibrational energies are large compared to kT).

Scheurer, C.; Mukamel, S.

2002-04-01

129

The 7-gap-resonator-accelerator for the REX-ISOLDE-experiment at CERN  

NASA Astrophysics Data System (ADS)

The Radioactive Beam Experiment at ISOLDE (REX-ISOLDE-Experiment) which presently is being developed and under construction at CERN serves to investigate exotic, very neutron rich, radioactive nuclei [1] (Radioactive beam EXperiment at ISOLDE: Coulomb Excitation and Neutron Transfer Reactions of Exotic Nuclei, Proposal to the ISOLDE commitee, CERNSIC94-25). A linear accelerator delivers radioactive ions which are produced by the isotope separator ISOLDE with energies between 0.85 and 2.2MeV/u. The Linac will consist of a RFQ-accelerator, an interdigital H-Structure (IH) and three 7-gap-resonators with variable energy. While the LMU Munich is responsible for the frontpart of the accelerator, the backpart is being built by the MPI [2] (H. Podlech, Master Thesis, MPI-H-V21-1997, Heidelburg, 1997). After estimation of the voltage of one resonator to 1.75MV at 90kW, the design velocities were fixed to 5.4%, 6.0% and 6.6% of the velocity of light. Three downscaled models (1:2.5) were built in order to optimize the shuntimpedance and the field-distribution at the operation frequency of the amplifiers of 101.28MHz. The optimization of all low power resonators is now successfully finished. Extensive beam dynamic calculations were made in order to optimize the transmission of the beam up to the target. It turned out that final energies between 0.85 and 2.2MeV/u with nearly 100% transmission can be achieved. The acceptance in the x-plane is 1.2?mm mrad (norm.) and in the y-plane 3.0?mm mrad (norm.). The bunchlength of the fully accelerated beam (2.2MeV/u) is 2.4ns at the target. The development of the resonators was accompanied by extensive MAFIA calculations. It could be demonstrated that spiral-resonators like 7-gap-resonators can be calculated with MAFIA with an accuracy of 1% in comparison with experimental results. Presently, the tanks and the half shells of the power type resonators are manufactured in the workshops of the MPI.

Podlech, H.; Grieser, M.; von Hahn, R.; Papureanu, S.; Repnow, R.; Schwalm, D.

1998-04-01

130

Protein carbon-13 spin systems by a single two-dimensional nuclear magnetic resonance experiment  

Microsoft Academic Search

By applying a two-dimensional double-quantum carbon-13 nuclear magnetic resonance experiment to a protein uniformly enriched to 26% carbon-13, networks of directly bonded carbon atoms were identified by virtue of their one-bond spin-spin couplings and were classified by amino acid type according to their particular single- and double-quantum chemical shift patterns. Spin systems of 75 of the 98 amino acid residues

B. H. Oh; W. M. Westler; P. Darba; J. L. Markley

1988-01-01

131

Variable-pitch rectangular cross-section radiofrequency coils for the nitrogen-14 nuclear quadrupole resonance investigation of sealed medicines packets.  

PubMed

The performance of rectangular radio frequency (RF) coils capable of being used to detect nuclear quadrupole resonance (NQR) signals from blister packs of medicines has been compared. The performance of a fixed-pitch RF coil was compared with that from two variable-pitch coils, one based on a design in the literature and the other optimized to obtain the most homogeneous RF field over the whole volume of the coil. It has been shown from (14)N NQR measurements with two medicines, the antibiotic ampicillin (as trihydrate) and the analgesic medicine Paracetamol, that the latter design gives NQR signal intensities almost independent of the distribution of the capsules or pills within the RF coil and is therefore more suitable for quantitative analysis. PMID:23057555

Barras, Jamie; Katsura, Shota; Sato-Akaba, Hideo; Itozaki, Hideo; Kyriakidou, Georgia; Rowe, Michael D; Althoefer, Kaspar A; Smith, John A S

2012-10-26

132

Resonance Frequency Tuning of a Double Ring Resonator in GaInAsP/InP: Experiment and Simulation  

NASA Astrophysics Data System (ADS)

A racetrack shaped double ring resonator (DRR) filter is demonstrated with radii of 200 ?m. The double ring resonator contains two -3 dB multimode interference (MMI) couplers for I/O coupling and a -13 dB codirectional coupler in between the rings. A free spectral range of 50 GHz has been realized. A simulation model has been developed to describe the DRR. As fabrication tolerances do not allow the realization of two identical rings with required nm-circumference accuracy in the resonator, a frequency alignment of the resonator is indispensable. The resonance frequency tuning is performed thermally using platinum resistors which have been placed on top of the waveguides in both rings. An on-off ratio increase has been achieved of more than 3 dB, resulting in a total on-off ratio larger than 18 dB. The frequency alignment is inevitable in the case of multiple coupled micro ring resonators.

Rabus, Dominik Gerhard; Hamacher, Michael; Heidrich, Helmut

2002-02-01

133

PiC simulations of the anomalous Doppler resonance for a scaled laboratory experiment  

NASA Astrophysics Data System (ADS)

The anomalous Doppler resonance occurs due to coupling between a negative harmonic of the electron cyclotron frequency and an electromagnetic wave, as such this regime is only applicable in slow-wave media like a plasma or dielectric loaded waveguide. In nuclear fusion devices the generation of fast electrons by Lower Hybrid Current Drive or in extreme cases Dreicer acceleration, can lead to the criterion for the anomalous Doppler resonance being fulfilled. The anomalous Doppler resonance is also relevant in the nature of pulsar radio emission. Simulations have been developed to study non-thermal electrons drifting at relativistic velocities along a magnetic field with a background plasma acting as the slow-wave media. The simulations will be used to inform the design of a scaled laboratory experiment at Strathclyde, the results of which will be used to compare with the prediction of the numerical simulations and analytical theory. Once benchmarked by the experiment simulations will investigate regimes relevant to tokamak and astrophysical plasmas.

Bryson, R.; Spiers, D. C.; King, M.; Phelps, A. D. R.; McConville, S. L.; Gillespie, K. M.; Ronald, K.; Vorgul, I.; Cairns, R. A.; Bingham, R.

2012-10-01

134

Numerical experiment and analysis of the differential acoustic resonance spectroscopy for elastic property measurements  

NASA Astrophysics Data System (ADS)

Differential acoustic resonance spectroscopy (DARS) was recently developed to estimate the elastic parameters of rock samples with a resonant frequency perturbation caused by a test sample at kilohertz frequency. In the derivation of the DARS theory, the wave inside the cavity is assumed to be a harmonic acoustic plane wave, which may be a source of measurement errors. A simulation program may help researchers to understand the mechanism of this device and to find out whether the assumption in the theory derivation is correct. In this paper, we develop a simulation program based on the elastic wave equation in cylindrical coordinates, and model the DARS system. The modeled power spectrum agrees well with that obtained by the laboratory measurement. An analysis of the wave field snapshots and the pressure distribution curves shows that the standing wave inside the cavity along its long axis is asymmetrical. This study also investigates the relationships between the resonant frequencies and the density, the compressibility and the P-wave and S-wave velocities of the samples. By numerical experiments, this paper finds that only the compressibility can be estimated with the resonant frequency, when the sample is located at the velocity node. But when the sample is located at other positions, the P-wave and S-wave velocities can alter the shape of the vibration curve, though they have no impact on the resonant power spectrum. This implies that it may be possible to estimate the P-wave and S-wave velocities by using the full waveform of the vibration curve.

Dong, Chunhui; Wang, Shangxu; Zhao, Jianguo; Tang, Genyang

2013-10-01

135

Low-frequency acoustic absorption of localized resonances: Experiment and theory  

NASA Astrophysics Data System (ADS)

The idea of localized resonance in phononic crystals is introduced to improve the low-frequency acoustic absorption of viscoelastic materials, which are widely used underwater to absorb the unwanted noise and meet a difficult challenge to enhance low-frequency absorption. Experimental measurements for acoustic absorptances of various viscoelastic polymer slabs embedded with locally resonant scatterers, i.e., heavy spheres coated by soft silicon rubber, are reported. Theoretical investigations using a layer-multiple-scattering method show good agreement with the experiment results, which supports unambiguously the observed low-frequency absorption phenomenon. The physical mechanism for the low-frequency absorption is also investigated by referring the elements of the Mie scattering matrix. The observations suggest that the scattered energy tends to remain in transverse waves, which enhance the multiple scattering, damp rapidly in viscoelastic polymer and dominate the acoustic absorption.

Zhao, Honggang; Wen, Jihong; Yu, Dianlong; Wen, Xisen

2010-01-01

136

Rabi and Larmor nuclear quadrupole double resonance of spin-1 nuclei  

NASA Astrophysics Data System (ADS)

We demonstrate the creation of two novel double-resonance conditions between spin-1 and spin-1/2 nuclei in a crystalline solid. Using a magnetic field oscillating at the spin-1/2 Larmor frequency, the nuclear quadrupole resonance (NQR) frequency is matched to the Rabi or Rabi plus Larmor frequency, as opposed to the Larmor frequency as is conventionally done. We derive expressions for the cross-polarization rate for all three conditions in terms of the relevant secular dipolar Hamiltonian, and demonstrate with these expressions how to measure the strength of the heterogenous dipolar coupling using only low magnetic fields. In addition, the combination of different resonance conditions permits the measurement of the spin-1/2 angular momentum vector using spin-1 NQR, opening up an alternate modality for the monitoring of low-field nuclear magnetic resonance. We use ammonium nitrate to explore these resonance conditions, and furthermore use the oscillating field to increase the signal-to-noise ratio per time by a factor of 3.5 for NQR detection of this substance.

Prescott, D. W.; Malone, M. W.; Douglass, S. P.; Sauer, K. L.

2012-12-01

137

Photon production through multi-step processes important in nuclear resonance fluorescence experiments  

NASA Astrophysics Data System (ADS)

We present calculations describing the production of photons through multi-step processes occurring when a beam of gamma-rays interacts with a macroscopic material. These processes involve the creation of energetic electrons through Compton scattering, photo-absorption and pair production, the subsequent scattering of these electrons, and the creation of energetic photons occurring as these electrons are slowed through Bremsstrahlung emission. Unlike single Compton collisions, during which an energetic photon that is scattered through a large angle loses most of its energy, these multi-step processes result in a sizable flux of energetic photons traveling at large angles relative to an incident photon beam. These multi-step processes are also a key background in experiments that measure nuclear resonance fluorescence by shining photons on a thin foil and observing the spectrum of back-scattered photons. Effective cross sections describing the production of back-scattered photons are presented in a tabular form that allows simple estimates of backgrounds expected in a variety of experiments. Incident photons with energies between 0.5 MeV and 8 MeV are considered. These calculations of effective cross sections may be useful for those designing NRF experiments or systems that detect specific isotopes in well-shielded environments through observation of resonance fluorescence.

Hagmann, C.; Pruet, J.

2007-06-01

138

Resonant X-ray Scattering Experiments on the Ordering of Electronic Degrees of Freedom  

NASA Astrophysics Data System (ADS)

Resonant X-ray scattering (RXS) has been developed as a powerful technique for observing orderings of electronic degrees of freedom: charge, spin, orbital, and multipoles. After a brief introduction of the RXS technique, we review some RXS experiments on the orderings in d and f electron systems with a strong correlation between electrons. The basic concept of RXS and the recent developments of the technique are described in this review paper. We also present future prospects of the studies using RXS for users.

Matsumura, Takeshi; Nakao, Hironori; Murakami, Youichi

2013-02-01

139

Limiting effects on laser compression by resonant backward Raman scattering in modern experiments  

SciTech Connect

Through resonant backward Raman scattering, the plasma wave mediates the energy transfer between long pump and short seed laser pulses. These mediations can result in pulse compression at extraordinarily high powers. However, both the overall efficiency of the energy transfer and the duration of the amplified pulse depend upon the persistence of the plasma wave excitation. At least with respect to the recent state-of-the-art experiments, it is possible to deduce that at present the experimentally realized efficiency of the amplifier is likely constrained mainly by two effects, namely, the pump chirp and the plasma wave wavebreaking.

Yampolsky, Nikolai A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Fisch, Nathaniel J. [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States)

2011-05-15

140

Dynamic analysis of mechanical model for three-dimensional resonant trigger probe and experiment  

NASA Astrophysics Data System (ADS)

A novel three-dimensional resonant trigger probe, which is fabricated with force sensitive components with good resonant characteristics and an integrated micro-stem and microsphere, is a new type of probe for micro/nano coordinating measuring machine (micro/nano CMM). In this paper, its triggering mechanical models are proposed to simulate the nano interaction between sample surface and the microsphere tip of the probe. In the models, the interaction between the sample surface and microsphere tip in Z direction is presumed in tapping mode (TM) and the interactions in X and Y directions are presumed in friction mode (FM). Taking account of air damping, energy dissipation, restoring force of elastic deformation, nanoscale interface friction, interface adhesion and van der Waals force, the models of the interactions between the microsphere tip and the sample surface in X(Y) direction and Z direction are deduced and constructed respectively. Based on the proposed models, the dynamic analysis on the triggering mechanism of the probe is presented. By experiment, the three-dimensional approaching curves of the probe are observed and they are proven to be suitable for the triggering signals of the probe. Preliminary experimental results show that the trigger resolution of the probe is about 0.24 nm in X direction, 0.20 nm in Y direction and 0.18 nm in Z direction. The theoretical analysis and experimental results demonstrate the validity of the novel resonant trigger probe.

Yu, Huijuan; Huang, Qiang-Xian; Li, Zhibo; Wang, Maocui; Wei, Jin-Peng

2013-01-01

141

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

142

Evaluation of Possible Nuclear Magnetic Resonance Diagnostic Techniques for Tokamak Experiments  

SciTech Connect

Potential applications of nuclear magnetic resonance (NMR) diagnostic techniques to tokamak experiments are evaluated. NMR frequencies for hydrogen isotopes and low-Z nuclei in such experiments are in the frequency range approximately equal to 20-200 MHz, so existing RF [radio-frequency] antennas could be used to rotate the spin polarization and to make the NMR measurements. Our tentative conclusion is that such measurements are possible if highly spin polarized H or (superscript)3He gas sources (which exist) are used to fuel these plasmas. In addition, NMR measurements of the surface layers of the first wall (without plasma) may also be possible, e.g., to evaluate the inventory of tritium inside the vessel.

S.J. Zweben; T.W. Kornack; D. Majeski; G. Schilling; C.H. Skinner; R. Wilson

2002-08-05

143

Update on Seeded SM-LWFA and Pseudo-Resonant LWFA Experiments -- (STELLA-LW)  

SciTech Connect

The Staged Electron Laser Acceleration -- Laser Wakefield (STELLA-LW) experiment is investigating two new methods for laser wakefield acceleration (LWFA) using the TW CO2 laser available at the Brookhaven National Laboratory Accelerator Test Facility. The first is seeded self-modulated LWFA where an ultrashort electron bunch (seed) precedes the laser pulse to generate a wakefield that the laser pulse subsequently amplifies. The second is pseudo-resonant LWFA where nonlinear pulse steepening of the laser pulse occurs in the plasma allowing the laser pulse to generate significant wakefields. The status of these experiments is reviewed. Evidence of wakefield generation caused by the seed bunches has been obtained as well as preliminary energy gain measurements of a witness bunch following the seeds. Comparison with a 1-D linear model for the wakefield generation appears to agree with the data.

Kimura, W. D. [STI Optronics, Inc., Bellevue, WA 98004 (United States); Andreev, N. E.; Kuznetsov, S. V.; Pogosova, A. A. [Institute for High Energy Densities, Russian Academy of Sciences, Moscow 125412, Russia (Russian Federation); Babzien, M.; Kusche, K. P.; Stolyarov, D.; Yakimenko, V. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Cline, D. B.; Ding, X. [UCLA, Los Angeles, CA 90095 (United States); Hooker, S. M.; Pavlishin, I. V.; Pogorelsky, I. V. [University of Oxford, Oxford, OX1 3PU (United Kingdom); Kallos, E.; Katsouleas, T. C.; Muggli, P. [University of Southern California, CA 90089 (United States); Steinhauer, L. C. [University of Washington, Redmond Plasma Physics Laboratory, Redmond, WA 98052 (United States); Ting, A. [Naval Research Laboratory, Washington, DC 20375 (United States); Zigler, A. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Zhou, F. [Stanford Linear Accelerator Center, Stanford CA 94025 (United States)

2006-11-27

144

Initial Experience with the Resonance Metallic Stent for Antegrade Ureteric Stenting  

SciTech Connect

Background and purpose. We describe our initial experience with a new metallic ureteric stent which has been designed to provide long-term urinary drainage in patients with malignant ureteric strictures. The aim is to achieve longer primary patency rates than conventional polyurethane ureteric stents, where encrustation and compression by malignant masses limit primary patency. The Resonance metallic double-pigtail ureteric stent (Cook, Ireland) is constructed from coiled wire spirals of a corrosion-resistant alloy designed to minimize tissue in-growth and resist encrustation, and the manufacturer recommends interval stent change at 12 months. Methods. Seventeen Resonance stents were inserted via an antegrade approach into 15 patients between December 2004 and March 2006. The causes of ureteric obstruction were malignancies of the bladder (n = 4), colon (n = 3), gynecologic (n = 5), and others (n = 3). Results. One patient had the stent changed after 12 months, and 3 patients had their stents changed at 6 months. These stents were draining adequately with minimal encrustation. Four patients are still alive with functioning stents in situ for 2-10 months. Seven patients died with functioning stents in place (follow-up periods of 1 week to 8 months). Three stents failed from the outset due to bulky pelvic malignancy resulting in high intravesical pressure, as occurs with conventional plastic stents. Conclusion. Our initial experience with the Resonance metallic ureteric stent indicates that it may provide adequate long-term urinary drainage (up to 12 months) in patients with malignant ureteric obstruction but without significantly bulky pelvic disease. This obviates the need for regular stent changes and would offer significant benefit for these patients with limited life expectancy.

Wah, Tze M., E-mail: Tze.Wah@leedsth.nhs.uk; Irving, Henry C. [St. James's University Hospital, Department of Radiology (United Kingdom); Cartledge, Jon [St. James's University Hospital, Department of Urology (United Kingdom)

2007-07-15

145

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

146

Identification of Copper(II) Complexes in Aqueous Solution by Electron Spin Resonance: An Undergraduate Coordination Chemistry Experiment.  

ERIC Educational Resources Information Center

Background, procedures, and results are provided for an experiment which examines, through electron spin resonance spectroscopy, complex species formed by cupric and 2,6-dihydroxybenzoate ions in aqueous solutions. The experiment is illustrative of several aspects of inorganic and coordination chemistry, including the identification of species

Micera, G.; And Others

1984-01-01

147

Focal magnetic resonance guided focused ultrasound for prostate cancer: Initial North American experience  

PubMed Central

The treatment of low-risk prostate cancer is a common clinical dilemma between standard curative whole gland therapy (and its associated quality of life diminishing side effects) and active surveillance (and its low, but real, risk of progression). The goal of focal therapy in low-risk prostate cancer is to achieve the best balance between cancer control and maintenance of quality of life. Magnetic resonance-guided focused ultrasound (MRgFUS) surgery is a non-invasive thermal ablation method that integrates magnetic resonance imaging for target identification, treatment planning and closed-loop control of thermal deposition and focused ultrasound for thermal ablation of the tumour target. This novel transrectal system allows for tumour localization, targeting and monitoring of tumour target ablation in real time, while simultaneously preserving adjacent normal tissue thereby minimizing the side effects of standard curative surgical or radiation therapy. We report the first North American clinical experience of treatment of localized prostate cancer with focal MR-guided transrectal focused ultrasound (clinicaltrial.gov identifier NCT01226576).

Lindner, Uri; Ghai, Sangeet; Spensieri, Paula; Hlasny, Eugen; Van der Kwast, Theodorus H.; McCluskey, Stuart A.; Haider, Masoom A.; Kucharczyk, Walter; Trachtenberg, John

2012-01-01

148

Electron Spin Resonance Experiments on Donors in Silicon. I. Electronic Structure of Donors by the Electron Nuclear Double Resonance Technique  

Microsoft Academic Search

The ground-state wave function of the antimony, phosphorus, and arsenic impurities in silicon has been investigated by means of the electron nuclear double resonance (ENDOR) method. By this method the hyperfine interactions of the donor electron with the Si29 nuclei situated at different lattice sites were obtained. The isotropic part of the hyperfine interaction agreed with the theory of Kohn

G. Feher

1959-01-01

149

The design, fabrication, and testing of beryllium capsules for resonant ultrasound experiments  

SciTech Connect

Inertial Confinement Fusion (ICF) ignition targets require smooth and well-characterized deuterium/tritium (DT) ice layers. Los Alamos is developing Resonant Ultrasound Spectroscopy (RUS) to measure the internal pressure in the targets at room temperature after filling with DT. RUS techniques also can detect and measure the amplitudes of low modal surface roughness perturbations of the target shell interior. The experiments required beryllium capsules with a nominal inside radius of 1 mm and a spherical outside radius of 3 mm. The capsules have various spherical harmonic contours up to mode 12 machined into their interior surfaces. The capsules are constructed from hemispheres using an epoxy adhesive and then filled to {approximately}270 atm with helium or deuterium gas. This paper describes the adhesive joint design, machining techniques, and interior geometry inspection techniques. It also describes the fixtures needed to assemble, fill, and pressure test the capsules.

Salazar, M.A.; Salzer, L.; Day, R. [Los Alamos National Lab., NM (United States)

1999-03-01

150

A tetrode based fast pulsed microwave source for electron cyclotron resonance breakdown experiments  

NASA Astrophysics Data System (ADS)

To study electron cylotron resonance (ECR) breakdown and afterglow plasma in an experimental linear plasma system, a pulsed microwave source with rapid rise and fall of microwave power is desired. A pulsed microwave source with fast rise and fall capability for ECR breakdown experiments has been designed and tested for performance in the system. A tetrode, controlled by a modulator card, is used as a fast switch to initiate microwave power from a conventional magnetron operating at 2.45 GHz. The typical rise time of microwave power is ~3 ?s and a fall time of ~10 ?s. Using this scheme in a realistic pulsed microwave source at 800 W power, ECR breakdown of neutral gas is achieved and the plasma delay and fall time are observed from the plasma density measurements using a Langmuir probe. The design details of the fast rise pulsed microwave source are presented in this article with initial experimental results.

Yadav, Vipin K.; Sathyanarayana, K.; Purohit, D.; Bora, D.

2007-02-01

151

A tetrode based fast pulsed microwave source for electron cyclotron resonance breakdown experiments  

SciTech Connect

To study electron cylotron resonance (ECR) breakdown and afterglow plasma in an experimental linear plasma system, a pulsed microwave source with rapid rise and fall of microwave power is desired. A pulsed microwave source with fast rise and fall capability for ECR breakdown experiments has been designed and tested for performance in the system. A tetrode, controlled by a modulator card, is used as a fast switch to initiate microwave power from a conventional magnetron operating at 2.45 GHz. The typical rise time of microwave power is {approx}3 {mu}s and a fall time of {approx}10 {mu}s. Using this scheme in a realistic pulsed microwave source at 800 W power, ECR breakdown of neutral gas is achieved and the plasma delay and fall time are observed from the plasma density measurements using a Langmuir probe. The design details of the fast rise pulsed microwave source are presented in this article with initial experimental results.

Yadav, Vipin K.; Sathyanarayana, K.; Purohit, D.; Bora, D. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat - 382 428 (India)

2007-02-15

152

Resonant spin amplification of hole spin dynamics in two-dimensional hole systems: experiment and simulation  

NASA Astrophysics Data System (ADS)

Spins in semiconductor structures may allow for the realization of scalable quantum bit arrays, an essential component for quantum computation schemes. Specifically, hole spins may be more suited for this purpose than electron spins, due to their strongly reduced interaction with lattice nuclei, which limits spin coherence for electrons in quantum dots. Here, we present resonant spin amplification (RSA) measurements, performed on a p-modulation doped GaAs-based quantum well at temperatures below 500 mK. The RSA traces have a peculiar, butterfly-like shape, which stems from the initialization of a resident hole spin polarization by optical orientation. The combined dynamics of the optically oriented electron and hole spins are well-described by a rate equation model, and by comparison of experiment and model, hole spin dephasing times of more than 70 ns are extracted from the measured data.

Korn, T.; Kugler, M.; Hirmer, M.; Schuh, D.; Wegscheider, W.; Schller, C.

2011-12-01

153

Detailed design of a resonantly enhanced axion-photon regeneration experiment  

SciTech Connect

A resonantly enhanced photon-regeneration experiment to search for the axion or axionlike particles is described. This experiment is a shining light through walls study, where photons traveling through a strong magnetic field are (in part) converted to axions; the axions can pass through an opaque wall and convert (in part) back to photons in a second region of strong magnetic field. The photon regeneration is enhanced by employing matched Fabry-Perot optical cavities, with one cavity within the axion generation magnet and the second within the photon-regeneration magnet. Compared to simple single-pass photon regeneration, this technique would result in a gain of (F/{pi}){sup 2}, where F is the finesse of each cavity. This gain could feasibly be as high as 10{sup 10}, corresponding to an improvement in the sensitivity to the axion-photon coupling, g{sub a{gamma}}{sub {gamma}}, of order (F/{pi}){sup 1/2}{approx}300. This improvement would enable, for the first time, a purely laboratory experiment to probe axion-photon couplings at a level competitive with, or superior to, limits from stellar evolution or solar axion searches. This report gives a detailed discussion of the scheme for actively controlling the two Fabry-Perot cavities and the laser frequencies, and describes the heterodyne signal detection system, with limits ultimately imposed by shot noise.

Mueller, Guido; Sikivie, Pierre; Tanner, D. B.; Bibber, Karl van [Department of Physics, University of Florida, Gainesville, Florida 32611 (United States); Naval Postgraduate School, Monterey, California 93943 (United States)

2009-10-01

154

Parity violating asymmetries in the G0 experiment: Pion photoproduction on the delta resonance  

NASA Astrophysics Data System (ADS)

Symmetry tests and more precisely parity violation experiments using the properties of the weak interaction give us unique insight into the internal hadronic structure of matter. The G0 experiment at Jefferson Laboratory used parity violating electron scattering to probe the strange quark contribution to the electromagnetic nucleon form factors, GsM and GsE as well as the axial contribution, GeA . The data taken during the experiment provide further information on the axial transition form factor of the N - Delta transition, GAND , as well as the scale of the low energy constant d Delta characterizing the parity violating gammaNDelta coupling. The analysis of backward angle G0 data taken with a liquid deuterium target to deduce the parity violating asymmetry for pion photoproduction on the Delta resonance, and the first experimental constraint on the value of dDelta, are reported in this thesis. The results showed that dDelta = (8.3 +/- 25.3)gpi where the uncertainty is dominated by statistics, and that 75% of the theory range would be excluded by this measurement at 1 sigma.

Coppens, Alexandre F. C.

155

1 H? 13 C? 27 Al triple resonance transfer of populations in double resonance experiments for the detection of 13 C? 27 Al dipolar interactions  

Microsoft Academic Search

A 13C{1H} CPMAS {27Al} TRAPDOR NMR experiment is reported with the aim of detecting 13C?27Al proximities and distances in solids. The 13C and 27Al pulses are applied to the same probe channel, because their resonance frequencies lie extremely close to each other. The study of the heteronuclear dipolar interaction between these two nuclei, which are of fundamental importance in solid

Leo van Wllen

1998-01-01

156

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

157

Slow muon experiment by laser resonant ionization method at RIKEN-RAL muon facility  

Microsoft Academic Search

We report first results of the slow muon generation from pulsed surface muon beam using a method of resonant laser ionization of muonium. The muonium is produced from the muon beam by electron capture near the surface of thin tungsten foil heated to 2100 K. The ionization is resonantly enhanced by using a vacuum-ultraviolet (VUV) radiation resonant with 2P state

P. Bakule; Y. Matsuda; Y. Miyake; P. Strasser; K. Shimomura; S. Makimura; K. Nagamine

2003-01-01

158

Magnetic resonance angiography at 3.0 Tesla: initial clinical experience.  

PubMed

Magnetic resonance (MR) angiography has undergone significant development over the past decade. It has gone from being a novelty application of MR with limited clinical use to replacing catheter angiography in some clinical applications. One of the principal limitations inherent to all MR angiographic techniques is that they remain signal limited when pushed to the limits of higher resolution and short acquisition time. Developments in magnetic gradient hardware, coil design, and pulse sequences now are well optimized for MR angiography obtained at 1.5-T main magnetic field (B-field) strength, with acquisition times and imaging matrix size near their optimal limits, respectively. Recently, the United States Food and Drug Administration (FDA) approved use of clinical magnetic resonance imaging with main magnetic field strengths of up to 4 T. Before FDA approval, use of MR with magnetic field strengths much greater than 1.5 T was essentially reserved for investigational or research applications. The main advantage of high B-field imaging is a significant improvement in the signal-to-noise ratio (SNR), which increases in an approximately linear fashion with field strength in the range of 1.5 to 3.0 T. This increased SNR is directly available when performing MR angiographic acquisitions at higher magnetic field strengths, allowing for better resolution and conspicuity of vessels with similar acquisition times. Little has been reported on the benefits of performing MR angiography at magnetic field strengths >1.5 T. The purpose of this article is to summarize our current experience with intracranial and cervical MR angiographic techniques at 3.0 T. PMID:11432577

Campeau, N G; Huston, J; Bernstein, M A; Lin, C; Gibbs, G F

2001-06-01

159

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

160

Resonant Detection of Light Pressure by a Torsion Pendulum in Air-An Experiment for Underclass Laboratories  

Microsoft Academic Search

A mirror suspended by a torsion fiber in air may be driven at resonance by the force from an interrupted light beam to reach a detectable oscillation amplitude. The radiometer forces which compete with the true light force may be separated experimentally. The method was tested as a laboratory experiment by a small freshman class and proved to be workable

Robert E. Pollock

1963-01-01

161

On the second harmonic electron cyclotron resonance heating and current drive experiments on T-10 and D3-D  

Microsoft Academic Search

Studies of electron cyclotron current drive at the second harmonic resonance have been performed both on the D3-D and T-10 tokamaks at injected power levels of approximately 0.5 MW. The D3-D experiment used high held launch of the extraordinary mode at an angle of 15 deg to the radial. In this experiment, with pulse lengths approximately equal to 500 msec,

J. Lohr; C. B. Forest; Y. R. Lin-Liu; T. C. Luce; R. W. Harvey; E. A. Downs; R. A. James; A. A. Bagdasarov; A. A. Borshegovskii; V. V. Chistyakov; M. M. Dremin; A. V. Gorshkov; Y. A. Gorelov; Y. V. Esipchuk; N. V. Ivanov; A. Y. Kislov; D. A. Kislov; S. E. Lysenko; A. A. Medvedev; V. Y. Mirenskii; G. E. Notkin; V. V. Parail; Y. D. Pavlov; K. A. Razumova; I. N. Roi; P. V. Savrukhin; V. V. Sannikov; A. V. Sushkov; V. M. Trukhin; N. L. Vasin; V. V. Volkov; G. G. Denisov; M. I. Petelin; V. A. Flyagin

1993-01-01

162

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

163

Detection of TNT and RDX landmines by standoff nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) combines the compound specific detection capability offered by chemical offered by chemical detection techniques with the spatial coating capability and convenience of an induction coil metal detector. In this paper we present the first results of the detection of TNT by NQR with sufficient for detection of many antipersonnel mines and essentially all antitank mines. In addition, we review the result of a blind in-field demonstration of the system in detecting RDX in which 28 out of 31 RDX-only targets were found with 1 false alarm in a 110 m test lane, and a second test in which 21 out of 21 RDX mines were found with zero false alarms at a clearance rate of 1.1 m2 per minute.

Hibbs, Andrew D.; Barrall, Geoffrey A.; Czipott, Peter V.; Drew, A. J.; Gregory, Dave; Lathrop, Daniel K.; Lee, Y. K.; Magnuson, Erik E.; Matthews, Robert; Skvoretz, D. C.; Vierkoetter, Stephie A.; Walsh, David O.

1999-08-01

164

Heavy Fermion Superconductor Ce2PdIn8 studied by 115In Nuclear Quadrupole Resonance  

NASA Astrophysics Data System (ADS)

We have performed nuclear quadrupole resonance (NQR) measurements on a recently-discovered heavy-fermion superconductor Ce2PdIn8 with superconducting critical temperature Tc = 0.64 K. Below coherent temperature Tcoh ~ 30 K, the spin-lattice relaxation rate 1/T1 decreases with decreasing temperature T and is proportional to T1/2 between Tc and Tcoh. This is clearly different from the Fermi-liquid behavior in which the T dependence is proportional to T, and indicates that Ce2PdIn8 is located on the verge of antiferromagnetic quantum critical point from the view point of the NQR. Below Tc, 1/T1 shows no coherence peak and is proportional to T3. This is clear evidence for the realization of unconventional superconductivity with line nodes in this compound.

Fukazawa, H.; Nagashima, R.; Shimatani, S.; Kohori, Y.; Kaczorowski, D.

2013-07-01

165

Experiments and modification on electron cyclotron resonance ion sources at the Institute of Modern Physics  

SciTech Connect

Uranium ion beams were produced from electron cyclotron resonance (ECR) ion sources by sputtering method this year at the Institute of Modern Physics. At first, we chose the Lanzhou ECR No. 3 ion source to implement the production experiment of U ion beams. Finally, 11 e {mu}A of U{sup 28+}, 5 e {mu}A of U{sup 32+}, and 1.5 e {mu}A of U{sup 35+} were obtained. A U{sup 26+} ion beam produced by the LECR2 ion source was accelerated successfully by the cyclotron. This means that the Heavy Ion Research Facility in Lanzhou (HIRFL) has accomplished the acceleration of the ion beam of the heaviest element according to the designed parameters. The Lanzhou ECR ion source No. 2 (LECR2), which was built in 1997, has served the HIRFL for eight years and needed to be upgraded to provide more intense high charge state ion beams for HIRFL cooling storage ring. We started the upgrading project of LECR2 last year, and the modified design just has been finished.

Zhang, Z.M.; Zhao, H.W.; Sun, L.T.; Cao, Y.; Zhang, X.Z.; Guo, X.H.; Li, X.X.; Li, J.Y.; Feng, Y.C.; Wang, H.; Ma, B.H.; Zhao, H.Y.; He, W.; Shang, Y. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China and Graduate School of the Chinese Academy of Science, Beijing 100039 (China); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China and Graduate School of the Chinese Academy of Science, Beijing, 100039 (China)

2006-03-15

166

Optically detected magnetic resonance experiments on native defects in ZnGeP2  

NASA Astrophysics Data System (ADS)

In order to investigate the defects responsible for the sub-band-gap absorption in ZnGeP2 optically detected magnetic resonance (ODMR) using the magnetic circular dichroism of the absorption (MCDA) as detection channel was applied. This is the first ODMR study of defects in II-IV-V2 chalcopyrites. The experiments exhibit that three different native defects contribute to the absorption in the spectral range from 0.5eV to the band-gap energy of about 2.0eV. The Ge antisite defects show a dominant transition near the band edge. Zn vacancies show strong MCD above 1.6eV and below 1eV, and the P vacancies are detected over the complete spectral range. In combination with photoinduced EPR studies these results reveal the contributions of the different defects to the broad absorption band. Peculiarities in the MCD of the Zn-vacancies are explained in terms of long spin-lattice relaxation times.

Hofmann, D. M.; Romanov, N. G.; Gehlhoff, W.; Pfisterer, D.; Meyer, B. K.; Azamat, D.; Hoffmann, A.

2003-12-01

167

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

168

Frequency Response of an Air Resonance Tube--Some Computer-Interfaced Experiments.  

ERIC Educational Resources Information Center

|Describes a measurement system for recording the frequency response of acoustic systems. The computer interface detects the characteristic modes, their relative strengths, and resonant shapes over a broad range of frequencies. Includes experimental data for tubes and analyzes the data to determine the optimal functional form for the resonant

Jolly, Pratibha; And Others

1993-01-01

169

Finite-Element Analysis and Corresponding Experiments of Resonant Energy Transfer for Wireless Transmission Devices  

Microsoft Academic Search

A wireless energy transfer system based on resonant energy transfer technology for power transmission and recharging of electrical devices is studied. The relationship between the energy transfer efficiency and several key parameters of the system is analyzed using finite-element method. Thin film resonant cells, consisting of a tape coil on one layer, which is separated by an insulation layer to

Junhua Wang; Siu Lau Ho; Weinong Fu; Cheung Tsz Kit; Mingui Sun

2011-01-01

170

Frequency Response of an Air Resonance Tube--Some Computer-Interfaced Experiments.  

ERIC Educational Resources Information Center

Describes a measurement system for recording the frequency response of acoustic systems. The computer interface detects the characteristic modes, their relative strengths, and resonant shapes over a broad range of frequencies. Includes experimental data for tubes and analyzes the data to determine the optimal functional form for the resonant

Jolly, Pratibha; And Others

1993-01-01

171

Preliminary experience with cardiovascular magnetic resonance in evaluation of fetal cardiovascular anomalies  

PubMed Central

Background The cardiovascular system is the part of the fetal anatomy that most frequently suffers from congenital pathology. This study shows our preliminary experience with fetal cardiovascular magnetic resonance (CMR) to evaluate congenital cardiovascular abnormalities. Methods Between January 2006 and June 2011, Prenatal routine obstetric ultrasound (US), echocardiography and CMR data from 68 pregnant women carrying fetuses with congenital cardiovascular anomalies were compared with postnatal diagnoses (postnatal imagings, surgery and autopsy). All prenatal CMR was performed at 1.5?T. Imaging sequences included steady-state free-precession (SSFP) sequences, real-time SSFP and single-shot turbo spin echo (SSTSE) sequences. The images were analyzed with an anatomic segmental approach by two radiologists. Results Fetal CMR yielded the same diagnosis as postnatal findings in 79% (54/68) of patients. The diagnostic sensitivity of routine obstetric US for cardiac anomalies was 46% (31/68). The diagnostic sensitivity of fetal echocardiographic examination by a fetal cardiac specialist was 82% (56/68). In 2 (3%) of 68 cases, diagnoses with both echocardiography and CMR were incorrect when compared with postnatal diagnosis. In ten (15%) cases, diagnosis at echocardiography was incorrect and that at CMR was correct. In twelve (18%) cases, diagnosis at echocardiography was correct and that at CMR was incorrect. Ten cases missed or misdiagnosed by echocardiography but correctly diagnosed by fetal CMR included asplenia syndrome (n?=?2), interrupted inferior vena cava of polysplenia syndrome (n?=?1), tricuspid incompetence (n?=?1), double outlet right ventricle (n?=?2), double aortic arch (n?=?1), right pulmonary artery hypoplasia (n?=?1), right-sided aortic arch of tetralogy of Fallot (n?=?1) and hypoplastic left heart syndrome of a twin fetus (n?=?1). Conclusion Fetal CMR is a promising diagnostic tool for assessment of congenital cardiovascular abnormalities, especially in situations that limit echocardiography.

2013-01-01

172

Blood-Brain Barrier Experiments with Clinical Magnetic Resonance Imaging and an Immunohistochemical Study  

PubMed Central

Objective The purpose of study was to evaluate the feasibility of brain magnetic resonance (MR) images of the rat obtained using a 1.5T MR machine in several blood-brain barrier (BBB) experiments. Methods Male Sprague-Dawley rats were used. MR images were obtained using a clinical 1.5T MR machine. A microcatheter was introduced via the femoral artery to the carotid artery. Normal saline (group 1, n = 4), clotted autologous blood (group 2, n = 4), triolein emulsion (group 3, n = 4), and oleic acid emulsion (group 4, n = 4) were infused into the carotid artery through a microcatheter. Conventional and diffusion-weighted images, the apparent coefficient map, perfusion-weighted images, and contrast-enhanced MR images were obtained. Brain tissue was obtained and triphenyltetrazolium chloride (TTC) staining was performed in group 2. Fluorescein isothiocyanate (FITC)-labeled dextran images and endothelial barrier antigen (EBA) studies were performed in group 4. Results The MR images in group 1 were of good quality. The MR images in group 2 revealed typical findings of acute cerebral infarction. Perfusion defects were noted on the perfusion-weighted images. The MR images in group 3 showed vasogenic edema and contrast enhancement, representing vascular damage. The rats in group 4 had vasogenic edema on the MR images and leakage of dextran on the FITC-labeled dextran image, representing increased vascular permeability. The immune reaction was decreased on the EBA study. Conclusion Clinical 1.5T MR images using a rat depicted many informative results in the present study. These results can be used in further researches of the BBB using combined clinical MR machines and immunohistochemical examinations.

Park, Jun Woo; Kim, Hak Jin; Han, Hyung Soo

2010-01-01

173

Non-invasive magnetic resonance imaging-guided focused ultrasound treatment for uterine fibroids early experience  

Microsoft Academic Search

ObjectiveTo describe early results regarding efficacy and safety of magnetic resonance imaging-guided focused ultrasound surgery (MRgFUS) for the treatment of uterine leiomyomas among a population of Japanese women.

Yutaka Morita; Naoki Ito; Hiromi Hikida; Sawako Takeuchi; Kouji Nakamura; Hirofumi Ohashi

2008-01-01

174

Low-frequency acoustic absorption of localized resonances: Experiment and theory  

Microsoft Academic Search

The idea of localized resonance in phononic crystals is introduced to improve the low-frequency acoustic absorption of viscoelastic materials, which are widely used underwater to absorb the unwanted noise and meet a difficult challenge to enhance low-frequency absorption. Experimental measurements for acoustic absorptances of various viscoelastic polymer slabs embedded with locally resonant scatterers, i.e., heavy spheres coated by soft silicon

Honggang Zhao; Jihong Wen; Dianlong Yu; Xisen Wen

2010-01-01

175

Simulation Aspects of the Code Benchmarking Based on the CERN-PS ``Montague-resonance''Experiment  

NASA Astrophysics Data System (ADS)

Measurements of emittance exchange due to the Montague resonance in the CERN Proton Synchrotron in 2003 have provided detailed data, which are suitable for benchmarking of different simulation codes for high-intensity accelerators. We present here some characteristic features of the Montague resonance by using first simulations obtained with MICROMAP and IMPACT under simplifying conditions. The challenges for the planned code benchmarking are discussed.

Hofmann, I.; Franchetti, G.; Giovannozzi, M.; Martini, M.; Metral, E.; Qiang, J.; Ryne, R. D.

2005-06-01

176

Low-power stimulated emission nuclear quadrupole resonance detection system utilizing Rabi transitions  

NASA Astrophysics Data System (ADS)

The application of CW radar techniques to Nuclear Quadrupole Resonance (NQR) detection of nitrogen based explosives and chlorine based narcotics enables the use of low power levels, in the range of 10's of watts, to yield high signal strengths. By utilizing Rabi transitions the nucleus oscillates between states one and two under the time dependent incident electromagnetic field and alternately absorbs energy from the incident field while emitting coherent energy via stimulated emission. Through the application of a cancellation algorithm the incident field is eliminated from the NQR response, allowing the receive signal to be measured while transmitting. The response signal is processed using matched filters of the NQR response which enables the direct detection of explosives. This technology has applicability to the direct detection of explosives and narcotics for security screening, all at safe low power levels, opposed to the current XRay and Millimeter wave screening systems that detect objects that may contain explosives and utilize high power. The quantum mechanics theoretical basis for the approach and an application for a system for security screening are described with empirical results presented to show the effects observed.

Apostolos, John; Mouyos, William; Feng, Judy; Chase, Walter

2013-06-01

177

WURST-QCPMG sequence and "spin-lock" in ?N nuclear quadrupole resonance.  

PubMed

?N nuclear quadrupole resonance (NQR) is a promising method for the analysis of pharmaceuticals or for the detection of nitrogen based illicit compounds, but so far, the technique is still not widely used, mostly due to the very low sensitivity. This problem is already acute in the preliminary NQR stage, when a compound is being examined for the first time and the NQR frequencies are being searched for, by scanning a wide frequency range step-by-step. In the present work, we experimentally show how to increase the efficiency of this initial stage by using a combination of a wideband excitation achieved with frequency swept pulses (WURST) and a "spin-lock" state obtained with a quadrupolar-CPMG (QCPMG) sequence. In the first part we show that WURST pulses provide a much larger excitation bandwidth compared to common rectangular pulses. This increased bandwidth allows to increase the frequency step and reduces the total number of steps in a scanning stage. In the second part we show that the "spin-lock" decay time T2eff obtained with the WURST-QCPMG combination is practically identical with the T2eff obtained with the most common "spin-lock" sequence, the SLSE, despite a very different nature and length of excitation pulses. This allows for a substantial S/N increase through echo averaging in every individual step and really allows to exploit all the advantages of the wider excitation in the NQR frequency scanning stage. Our experimental results were obtained on a sample of trinitrotoluene, but identical behavior is expected for all compounds where a "spin-lock" state can be created. PMID:23793057

Gregorovi?, Alan; Apih, Toma

2013-06-04

178

A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments  

NASA Astrophysics Data System (ADS)

The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 ?m diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner.

Smith, Doran D.; Alexson, Dimitri A.; Garbini, Joseph L.

2013-09-01

179

Using nitrogen-14 nuclear quadrupole resonance and electric field gradient information for the study of radiation effects  

SciTech Connect

Nitrogen-14 nuclear quadrupole resonance (NQR) was used in an attempt to detect the effects of ionizing radiation on organic material. Previously reported resonances for urea were detected at 2,913.32 {+-} 0.01 kHz and 2,347.88 {+-} 0.08 kHz with associated T{sub 2}* values 780 {+-} 20 {micro}s and 523 {+-} 24 {micro}s, respectively. The previously unreported {nu}{sub {minus}} line for urea-d{sup 4} was detected at 2,381 {+-} 0.04 Khz and used to determine accurately for the first time the values for the nuclear quadrupole coupling constant {chi} (3,548.74 {+-} 0.03 kHz) and the asymmetry parameter {eta} (0.31571 {+-} 0.00007) for urea-d{sup 4}. The inverse linewidth parameter T{sub 2}* for {nu}{sub +} was measured at 928 {+-} 23 {micro}s and for {nu}{sub {minus}} at 721 {+-} 12 {micro}s. Townes and Dailey analysis was performed and urea-d{sup 4} exhibits a 0.004 increase in lone pair electronic density and a slight decrease in N-H bond electronic density, as compared to urea, probably due to the mass difference. A relationship is proposed, referred to as NQR linewidth analysis, between the dynamic spin relaxation times T{sub 2} and T{sub 2}* and the widths of the distributions of the NQR parameters. Linewidth analysis is presented as a tool for possible use in future NQR work in all area, not just radiation effects. This relationship is tested using sodium nitrite T{sub 2} and T{sub 2}* values for {nu}{sub {minus}} and {nu}{sub {minus}} as a function of temperature.

Iselin, L.H.

1995-12-01

180

Surface Channeling Experiments at 20 MeV and Resonant Coherent Excitation of N6+ Ions  

NASA Astrophysics Data System (ADS)

Surface channeling of 21.8 and 23 MeV N6+ ions of a Pt(110) surface is experimentally verified. At 21.8 MeV resonant coherent excitation is observed leading to enhanced ionization when the ions scatter along the [110] surface half channels.

Hatke, N.; Dirska, M.; Grether, M.; Luderer, E.; Robin, A.; Nrmann, A.; Heiland, W.

1997-11-01

181

Resonant Character of Edge Plasma Parameters in Stochastic Boundary Experiments at DIII-D and TEXTOR  

Microsoft Academic Search

Dependence of electron pressure pe profiles on the edge safety factor during resonant magnetic perturbations (RMPs) is analyzed and compared to heat and particle fluxes. For TEXTOR, a strong reduction of pe and an increase of target fluxes is measured when the inward penetration of the vacuum stochastic layer is maximized. For DIII-D, target heat and particle fluxes follow the

O. Schmitz; B. D. Bray; N. H. Brooks; T. E. Evans; A. W. Leonard; T. H. Osborne; W. P. West; M. E. Fenstermacher; M. Groth; C. J. Lasnier; H. Frerichs; M. Lehnen; B. Unterberg; M. W. Jakubowski; R. A. Moyer; J. G. Watkins

2008-01-01

182

Animal and human imaging experiments in magnetic resonance electrical impedance tomography (MREIT)  

Microsoft Academic Search

Cross-sectional imaging of an electrical conductivity distribution inside the human body has been an active research topic in the field of impedance imaging. This paper describes the recent progress in magnetic resonance electrical impedance tomography (MREIT) where conductivity imaging with a spatial resolution of a few mm is pursued. After the early studies on its theory and image reconstruction algorithms,

Eung Je Woo

2009-01-01

183

Optimizing ion-cyclotron resonance frequency heating for ITER: dedicated JET experiments  

Microsoft Academic Search

In the past years, one of the focal points of the JET experimental programme was on ion-cyclotron resonance heating (ICRH) studies in view of the design and exploitation of the ICRH system being developed for ITER. In this brief review, some of the main achievements obtained in JET in this field during the last 5 years will be summarized. The

E Lerche; D Van Eester; J Ongena; M-L Mayoral; M Laxaback; F Rimini; A Argouarch; P Beaumont; T Blackman; V Bobkov; D Brennan; A Brett; G Calabro; M Cecconello; I Coffey; L Colas; A Coyne; K Crombe; A Czarnecka; R Dumont; F Durodie; R Felton; D Frigione; M Gatu Johnson; C Giroud; G Gorini; M Graham; C Hellesen; T Hellsten; S Huygen; P Jacquet; T Johnson; V Kiptily; S Knipe; A Krasilnikov; P Lamalle; M Lennholm; A Loarte; R Maggiora; M Maslov; A Messiaen; D Milanesio; I Monakhov; M Nightingale; C Noble; M Nocente; L Pangioni; I Proverbio; C Sozzi; M Stamp; W Studholme; M Tardocchi; T W Versloot; V Vdovin; M Vrancken; A Whitehurst; E Wooldridge; V Zoita

2011-01-01

184

Energy Levels, Selection Rules, and Line Intensities for Molecular Beam Electric Resonance Experiments with Diatomic Molecules  

Microsoft Academic Search

In the molecular beam electric resonance method the energy levels in an electric field of a diatomic molecule which is in the ground electronic state, and a low vibrational and rotational state are studied. Transitions are produced between states with different space quantization of the molecule relative to the electric field and with different couplings of the angular momenta of

Vernon Hughes; Ludwig Grabner

1950-01-01

185

Myocardial perfusion imaging: clinical experience and recent progress in radionuclide scintigraphy and magnetic resonance imaging  

Microsoft Academic Search

In the past 20 years, radionuclide scintigraphy has proven to be a sensitive clinical tool in the assessment of myocardial perfusion abnormalities. Magnetic resonance imaging may also be used to study myocardial perfusion, but its potential value still has to emerge in the clinical setting. This review addresses the potential and achievements of both methods in clinical cardiology.

Cess A. Visser; Jan T. Keijer; Jeroen J. Bax; Albert C. van Rossum; Frans C. Visser

1997-01-01

186

Dissociating Confidence and Accuracy: Functional Magnetic Resonance Imaging Shows Origins of the Subjective Memory Experience  

Microsoft Academic Search

Successful memory typically implies both objective accuracy and subjective confidence, but there are instances when confidence and accuracy diverge. This dissociation suggests that there may be distinct neural patterns of activation related to confidence and accuracy. We used event-related functional magnetic resonance imaging to study the encoding of novel facename associations, assessed with a postscan memory test that included objective

Elizabeth F. Chua; Erin Rand-Giovannetti; Daniel L. Schacter; Marilyn S. Albert; Reisa A. Sperling

2004-01-01

187

Amplifier linearization using compact microstrip resonant cell-theory and experiment  

Microsoft Academic Search

This paper presents a novel technique for reducing the intermodulation distortions (IMDs) in power amplifiers. In this method, both second- and third-harmonic components generated by the transistor are reflected back simultaneously by the compact microstrip resonant cell (CMRC) at the input port with proper phases to mix with the fundamental signal for the reduction of IMDs. A rigorous mathematical analysis

Tsz Yin Yum; Quan Xue; Chi Hou Chan

2004-01-01

188

HCCCH Experiment for Through-Bond Correlation of Thymine Resonances in ^13C-Labeled DNA Oligonucleotides  

NASA Astrophysics Data System (ADS)

Application of heteronuclear magnetic resonance pulse methods to ^13C,^15N-labeled nucleic acids is important for the accurate structure determination of larger RNA and DNA oligonucleotides and protein-nucleic acid complexes. These methods have been applied primarily to RNA, due to the availability of labeled samples. The two major differences between DNA and RNA are at the C2' of the ribose and deoxyribose and the additional methyl group on thymine versus uracil. We have enzymatically synthesized a ^13C,^15N-labeled 32 base DNA oligonucleotide that folds to form an intramolecular triplex. We present two- and three-dimensional versions of a new HCCCH-TOCSY experiment that provides intraresidue correlation between the thymine H6 and methyl resonances via the intervening carbons (H6-C6-C5-Cme-Hme).

Sklen? , Vladimr; Masse, James E.; Feigon, Juli

1999-04-01

189

Linkage Isomerization by Two-Dimensional 31P Nuclear Magnetic Resonance Spectroscopy. An Undergraduate Inorganic Laboratory Experiment  

NASA Astrophysics Data System (ADS)

An application of two-dimensional 31P NMR spectroscopy is demonstrated through the characterization of linkage isomers of tetraammine(triphosphato)cobalt(III) chelates and metal-promoted hydrolysis of inorganic triphosphate ion. Unambiguous assignments of 31P resonances for two isomers, a,g and b,g chelates, were achieved by the direct through-bond connectivities among the three phosphate groups. The lack of such connectivity also helped to identify cobalt(III)-catalyzed hydrolysis products, orthophosphate and pyrophosphate ions. The experiment provides background information on 2-D NMR spectroscopy including the significance of pulse calibration, relaxation, evolution and mixing times, data processing, and finally, hands-on training for performing 2-D NMR experiments. The experiment is ideally suited for a senior laboratory course and may be included in the core inorganic curriculum required for a certified ACS B.S. degree.

Bose, Rathindra N.; Al-Ajlouni, Ahmad M.; Volckova, Erika

2001-01-01

190

The Giant Dipole Resonance built on highly excited states - results of the MEDEA experiment  

NASA Astrophysics Data System (ADS)

Gamma-rays, light charged particles and evaporation residues emitted from hot nuclei formed in the 36Ar + 90Zr reaction at 27 MeV/u have been measured with a nearly 4? barium fluoride multidetector. It is shown that hot Sn-like nuclei with a range of excitation energies between 300 and 600 MeV are produced. The ?-ray yield from the decay of the Giant Dipole Resonance in these nuclei is shown to remain constant over this excitation energy range. The measured ?-ray spectra are compared with statistical calculations encompassing several recent theoretical models for the quenching of gamma-ray emission from the dipole resonance at very high temperatures.

Suomijrvi, T.; Le Faou, J. H.; Blumenfeld, Y.; Piattelli, P.; Agodi, C.; Alamanos, N.; Alba, R.; Auger, F.; Bellia, G.; Chomaz, Ph.; Coniglione, R.; del Zoppo, A.; Finocchiaro, P.; Frascaria, N.; Gaardhje, J. J.; Garron, J. P.; Gillibert, A.; Lamehi-Rachti, M.; Liguori-Neto, R.; Maiolino, C.; Migneco, E.; Russo, G.; Roynette, J. C.; Santonocito, D.; Sapienza, P.; Scarpaci, J. A.; Smerzi, A.

1994-03-01

191

Ferromagnetic resonance experiments in partially devitrified Co-based metallic glass  

Microsoft Academic Search

Properties of nanocrystalline magnets exhibiting low Curie temperature of the residual amorphous matrix, obtained by partial crystallization of CoNbCuSiB melt-spun ribbon, were studied by means of ferromagnetic resonance (FMR) as well as conventional magnetometry. The results acquired in FMR measurements, performed at the temperature ranging from 4.2 up to 300K for a series of samples significantly differing in the volume

M. Kuzminski; H. K. Lachowicz; L. Lezama; J. M. Barandiarn; P. Didukh; A. ?lawska-Waniewska

2001-01-01

192

A set of 4D NMR experiments of enhanced resolution for easy resonance assignment in proteins  

NASA Astrophysics Data System (ADS)

This paper presents examples of techniques based on the principle of random sampling that allows acquisition of NMR spectra featuring extraordinary resolution. This is due to increased dimensionality and maximum evolution time reached. The acquired spectra of CsPin protein and maltose binding protein were analyzed statistically with the aim to evaluate each technique. The results presented include exemplary spectral cross-sections. The spectral data provided by the proposed techniques allow easy assignment of backbone and side-chain resonances.

Zawadzka-Kazimierczuk, Anna; Kazimierczuk, Krzysztof; Ko?mi?ski, Wiktor

2010-01-01

193

Use of a double resonance electron capture dissociation experiment to probe fragment intermediate lifetimes  

Microsoft Academic Search

The relative abundances of fragment ions in electron capture dissociation (ECD) are often greatly affected by the secondary\\u000a and tertiary structures of the precursor ion, and have been used to derive the gas-phase conformations of the protein ions.\\u000a In this study, it is found that resonance ejection of the charge reduced molecular ion during ECD resulted in significant\\u000a changes in

Cheng Lin; Jason J. Cournoyer; Peter B. OConnor

2006-01-01

194

Continuous-wave, two-crystal, singly-resonant optical parametric oscillator: theory and experiment.  

PubMed

We present theoretical and experimental study of a continuous-wave, two-crystal, singly-resonant optical parametric oscillator (T-SRO) comprising two identical 30-mm-long crystals of MgO:sPPLT in a four- mirror ring cavity and pumped with two separate pump beams in the green. The idler beam after each crystal is completely out-coupled, while the signal radiation is resonant inside the cavity. Solving the coupled amplitude equations under undepleted pump approximation, we calculate the maximum threshold reduction, parametric gain acceptance bandwidth and closest possible attainable wavelength separation in arbitrary dual-wavelength generation and compare with the experimental results. Although the T-SRO has two identical crystals, the acceptance bandwidth of the device is equal to that of a single-crystal SRO. Due to the division of pump power in two crystals, the T-SRO can handle higher total pump power while lowering crystal damage risk and thermal effects. We also experimentally verify the high power performance of such scheme, providing a total output power of 6.5 W for 16.2 W of green power at 532 nm. We verified coherent energy coupling between the intra-cavity resonant signal waves resulting Raman spectral lines. Based on the T-SRO scheme, we also report a new technique to measure the temperature acceptance bandwidth of the single-pass parametric amplifier across the OPO tuning range. PMID:23609663

Samanta, G K; Aadhi, A; Ebrahim-Zadeh, M

2013-04-22

195

A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments.  

PubMed

The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 ?m diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner. PMID:24089869

Smith, Doran D; Alexson, Dimitri A; Garbini, Joseph L

2013-09-01

196

Dual-room 1.5-T intraoperative magnetic resonance imaging suite with a movable magnet: implementation and preliminary experience  

Microsoft Academic Search

We hereby report our initial clinical experience of a dual-room intraoperative magnetic resonance imaging (iMRI) suite with\\u000a a movable 1.5-T magnet for both neurosurgical and independent diagnostic uses. The findings from the first 45 patients who\\u000a underwent scheduled neurosurgical procedures with iMRI in this suite (mean age, 41.3??12.0years; intracranial tumors, 39\\u000a patients; cerebral vascular lesions, 5 patients; epilepsy surgery, 1

Xiaolei Chen; Bai-nan Xu; Xianghui Meng; Jun Zhang; Xingguang Yu; Dingbiao Zhou

197

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

198

Magnetic resonance for evaluation of toxic encephalopathies: implications from animal experiments.  

PubMed

Examinations of brain of rats intoxicated with hexachlorophene or acrylamide with ultrahigh-field (4.7 T) proton magnetic resonance (MR) showed alterations consistent with clinical pictures in humans and morphological findings in experimental animals. On the other hand, conventional biochemical analyses have revealed that ethylene oxide, methyl bromide, and acrylamide inhibit creatine kinase (CK; an enzyme catalyzing the reaction: ATP+creatine<-->ADP+phosphocreatine) activities in the brain of animals. Thus, 31P MR combined with magnetization transfer may be utilized to monitor living humans (or animals) intoxicated with these chemicals by determining CK activities in the target organ. PMID:16797711

Igisu, Hideki; Kinoshita, Yoshimasa

2006-05-22

199

Magnetic resonance imaging-guided focused ultrasound ablation of uterine fibroids: early clinical experience  

Microsoft Academic Search

PurposeThe aim of this study was to assess the feasibility and effectiveness of magnetic resonance (MRI)-guided focused ultrasound\\u000a (MRIgFUS) ablation for uterine fibroids and to identify the candidates for this treatment.\\u000a \\u000a \\u000a \\u000a Materials and methodsA total of 48 patients with a symptomatic uterine fibroid underwent MRIgFUS. The percent ablation volume was calculated, and\\u000a the patients characteristics and the MR imaging features

Koji Mikami; Takamichi Murakami; Atsuya Okada; Keigo Osuga; Kaname Tomoda; Hironobu Nakamura

2008-01-01

200

Magnetic Resonance-Guided Percutaneous Cryoablation of Uterine Fibroids: Early Clinical Experiences  

Microsoft Academic Search

PurposeUterine fibroids (leiomyomas) are the most common tumors of the uterus. The present study evaluated the feasibility and effectiveness\\u000a of magnetic resonance (MR)-guided percutaneous cryoablation for uterine fibroids as a minimally invasive treatment alternative.\\u000a \\u000a \\u000a \\u000a MethodsFrom August 2001 to June 2002, MR-guided percutaneous cryoablation was performed on seven uterine fibroids in 6 patients who\\u000a displayed clinical symptoms related to tumors. Using

Yusuke Sakuhara; Tadashi Shimizu; Yoshihisa Kodama; Akihiro Sawada; Hideho Endo; Daisuke Abo; Tenshu Hasegawa; Kazuo Miyasaka

2006-01-01

201

Magnetic resonance experiments on the green emission in undoped ZnO crystals  

NASA Astrophysics Data System (ADS)

Optically detected magnetic resonance shows that a broad, green emission band in ZnO at 2.45eV originates from a spintriplet-recombination characterised by g||c=1.984 and g?c=2.025 (parallel and perpendicular to the crystallographic c-axis, respectively) and a zero-field splitting of /D=26010-4cm-1. These parameters and the polarisation properties of the emission are very similar to the anion vacancies in CaO but not compatible with the Zeeman results on ZnO:Cu.

Leiter, F.; Zhou, H.; Henecker, F.; Hofstaetter, A.; Hofmann, D. M.; Meyer, B. K.

2001-12-01

202

On the possibility of low-threshold anomalous absorption in tokamak 2nd-harmonic electron cyclotron resonance heating experiments  

NASA Astrophysics Data System (ADS)

The parametric decay of an extraordinary electron cyclotron pump wave to electron Bernstein (EB) wave and ion Bernstein wave leading to anomalous absorption in 2nd-harmonic electron cyclotron resonance heating (ECRH) experiments is analyzed. It is shown that in an axisymmetric system, like tokamak, excitation of the low-threshold absolute parametric decay instability (PDI) is possible in the case of non-monotonic behaviour of plasma density in radial direction and due to poloidal magnetic-field inhomogeneity. The threshold of the absolute PDI instability determined by linear dissipation of the EB wave is shown to be substantially exceeded in nowadays 2nd-harmonic ECRH experiments in tokamaks that provide an explanation for the mysterious ion acceleration effect observed there.

Gusakov, E.; Popov, A.

2012-07-01

203

Extracting protein folding kinetics in single-pair fluorescence resonance energy transfer experiment based on wavelet analysis  

NASA Astrophysics Data System (ADS)

Dynamic structural changes of protein folding and biological macromolecules undergoing biochemical reactions can be monitored and studied using the single-pair fluorescence resonance energy transfer (sp-FRET) spectroscopy tool. In this work, we have simulated a single-pair FRET photoemission process as an illustrative model example, where a FRET pair resides on a folding protein that undergoes diffusion in water. And then we apply the wavelet analysis method, which is a widely used method in many fields, such as the digital signal processing, noise reduction and the data compression (JPEG2000), to deal with the case of fluorescence resonance energy transfer (FRET) experiment for protein folding. It is shown that the wavelet analysis filter facilitates the detection of various intermediate conformational states in a noisy trajectory. Thus it is finally suggested that it is particularly suitable for sp-FRET spectroscopy studies of protein folding and can be of use for directly extracting the folding energy landscape. Our study establishes potentially useful data analysis technique and theoretical guidelines for the study of sp-FRET spectroscopy experiments.

Shan, Guangcun; Huang, Wei

2007-01-01

204

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

205

Magnetic resonance imaging in medical education: a demonstration experiment for students  

Microsoft Academic Search

A demonstration experiment is described, which illustrates fundamental physical processes with NMR and MRI. The terms precession, Larmor frequency, gyromagnetic ratio, 90 degrees pulse, relaxation time, and echo signal are explained with it. The experiment can be set up with the usual laboratory means, at low cost.

O. Ennemoser; W. Ambach

1991-01-01

206

Power instability of singly resonant optical parametric oscillators: theory and experiment.  

PubMed

We present a theoretical model on the effects of mechanical perturbations on the output power instability of singly-resonant optical parametric oscillators (SR-OPOs). Numerical simulations are performed based on real experimental parameters associated with a SR-OPO designed in our laboratory, which uses periodically-poled LiNbO3 (PPLN) as the nonlinear crystal, where the results of the theoretical model are compared with the measurements. The out-coupled power instability is simulated for a wide range of input pump powers the SR-OPO oscillation threshold. From the results, maximum instability is found to occur at an input pump power of ~1.5 times above the OPO threshold. It is also shown theoretically that the idler instability is susceptible to variations in the cavity length caused by vibrations, with longer cavities capable of generating more stable output power. The validity of the theoretical model is verified experimentally by using a mechanical vibrator in order to vary the SR-OPO resonator length over one cavity mode spacing. It is found that at 1.62 times threshold, the out-coupled idler suffers maximum instability. The results of experimental measurements confirm good agreement with the theoretical model. An intracavity etalon is finally used to improve the idler output power by a factor of ~2.2 at an input pump power of 1.79 times oscillation threshold. PMID:23262694

Sabouri, Saeed Ghavami; Khorsandi, Alireza; Ebrahim-Zadeh, Majid

2012-12-01

207

Dissociating confidence and accuracy: functional magnetic resonance imaging shows origins of the subjective memory experience.  

PubMed

Successful memory typically implies both objective accuracy and subjective confidence, but there are instances when confidence and accuracy diverge. This dissociation suggests that there may be distinct neural patterns of activation related to confidence and accuracy. We used event-related functional magnetic resonance imaging to study the encoding of novel face--name associations, assessed with a postscan memory test that included objective measures of accuracy and subjective measures of confidence. We showed specific neural activity in the left inferior prefrontal cortex associated with trials when subjects expressed high confidence that they had chosen the correct name for the face and made a correct identification. Moreover, we found that this region was also associated with imparting high confidence when subjects chose the incorrect name. However, medial temporal lobe regions showed activity only for high-confidence correct trials. Many functional magnetic resonance imaging studies have shown that the medial temporal lobe and left prefrontal regions are particularly important for the successful formation of memories by using a combination of subjective and objective measures. Our findings suggest that these regions may be differentially involved in the objective and subjective components of memory and that the origins of confidence-accuracy dissociations may be related to incomplete activation of the neural pattern seen in successful encoding. These findings may also aid understanding of eyewitness misidentifications and memory distortions. PMID:15453969

Chua, Elizabeth F; Rand-Giovannetti, Erin; Schacter, Daniel L; Albert, Marilyn S; Sperling, Reisa A

2004-09-01

208

Fourier Transform Nuclear Magnetic Resonance Spectroscopy Experiment for Undergraduate and Graduate Students  

NASA Astrophysics Data System (ADS)

Many NMR experiments in analytical chemistry courses utilize commercial Fourier transform (FT) instruments that do little in teaching the students about the components of the spectrometer. We have designed a FT-NMR spectrometer composed of self-contained components (i.e. mixers, switches, amplifiers) that has been successfully incorporated into laboratory experiments for both undergraduate and graduate students. The undergraduate instrumental analysis experiment allows students to examine the spectrometer on a component by component basis. The individual components of the spectrometer were mounted on a board and connected by coaxial cables, which easily permits changes in the configuration of the spectrometer. Topics covered in the experiment included filtering, amplification, phase cycling, and quadrature detection as well as quantitative determination of the amount of ethanol in an unknown sample. In the graduate analog instrumentation course, the graduate students were required to take the same components used in the undergraduate experiment and construct a working spectrometer.

Doscotch, Matthew A.; Evans, John F.; Munson, Eric J.

1998-08-01

209

Structure and Nuclear Magnetic Resonance. An Experiment for the General Chemistry Laboratory  

NASA Astrophysics Data System (ADS)

We have developed an experiment that introduces freshman chemistry students to NMR. Students are trained to work on the instrument, analyze 1H and 13C spectra, and identify simple organic molecules. They are also introduced to the idea of functional groups and they use concepts learned in class about Lewis structures to distinguish among spectra of isomers of C3H8O. As part of this exercise students submit written reports and complete a survey evaluating the experiment. The lab experiment, survey results, and findings are presented.

Dvila, Rosa M.; Widener, R. K.

2002-08-01

210

Whistler mode resonance-cone transmissions at 100 kHz in the OEDIPUS-C experiment  

NASA Astrophysics Data System (ADS)

A radio transmitter was operated at one end of the tethered sounding rocket double payload OEDIPUS C, and a synchronized receiver at the other end. Both the transmitter and the receiver were connected to "double-V" dipoles. On the flight downleg after the tether had been cut, direct bistatic propagation experiments were carried out successfully with the transmitter-receiver pair. This paper addresses the transmission of 300-?s pulses at a carrier frequency of 100 kHz between the dipoles over distances of about 1200 m. The waves of interest propagate in the whistler mode close to its resonance cone, where the transmitter is situated in the cone apex. The radiated field under these conditions is computed as well as the resonance response of the receiving antenna, i.e., its effective length. In the whistler mode, the influence of the plasma is important and it results in qualitative changes in the structure of the radiated field and in the value of the receiving antenna effective length as compared to the free space case. Our main concern is the excitation and reception of a pulsed signal when time and space dispersion play important roles in both the delay and spreading of such a signal.

Chugunov, Y. V.; Fiala, V.; Hayosh, M.; James, H. G.

2012-12-01

211

Focusing twist reflector for electron-cyclotron resonance heating in the Tandem Mirror Experiment-Upgrade  

SciTech Connect

A twist reflector plate is described that linearly polarizes and focuses the TE/sub O/sub 1// circular waveguide mode for heating hot electrons in the thermal barrier of the Tandem Mirror Experiment-Upgrade (TMX-U). The plate polarizing efficiency is 95%, and it has operated satisfactorily at 150 kW power level.

Stallard, B.W.; Coffield, F.E.; Felker, B.; Taska, J.; Christensen, T.E.; Gallagher, N.C. Jr.; Sweeney, D.W.

1984-05-01

212

Magnetic Resonance-Guided Percutaneous Cryoablation of Uterine Fibroids: Early Clinical Experiences  

SciTech Connect

Purpose. Uterine fibroids (leiomyomas) are the most common tumors of the uterus. The present study evaluated the feasibility and effectiveness of magnetic resonance (MR)-guided percutaneous cryoablation for uterine fibroids as a minimally invasive treatment alternative. Methods. From August 2001 to June 2002, MR-guided percutaneous cryoablation was performed on seven uterine fibroids in 6 patients who displayed clinical symptoms related to tumors. Using a horizontal-type open MR system, cryoablation probes were percutaneously placed in fibroids. Fibroids were ablated, and the site and size of ice balls were monitored on MR imaging. Postoperatively, patients completed a questionnaire to assess changes in presenting clinical symptoms, and MR images were obtained for all patients at follow-up. Changes in clinical symptoms and tumor volume were evaluated in each patient. Results. All treated patients showed reductions in tumor size. Mean volume reduction rate was 40.3% at 6 weeks postoperatively, and 79.4% at 9-12 months. All patients reported fever after treatment. Surgical drainage was required for abscess in the probe channel in one patient, and transient liver damage occurred in another. Subjective symptoms improved in all patients except one who had multiple tumors, and no patient complained of new symptoms after cryoablation during follow-up. Conclusion. MR-guided percutaneous cryoablation represents a feasible and effective treatment for uterine fibroids.

Sakuhara, Yusuke, E-mail: YRB03514@nifty.com; Shimizu, Tadashi; Kodama, Yoshihisa; Sawada, Akihiro [Hokkaido University School of Medicine, Department of Radiology (Japan); Endo, Hideho [Kitami Red Cross Hospital, Department of Radiology (Japan); Abo, Daisuke [Hokkaido University School of Medicine, Department of Radiology (Japan); Hasegawa, Tenshu [Asahikawa Red Cross Hospital, Department of Obstetrics and Gynecology (Japan); Miyasaka, Kazuo [Hokkaido University School of Medicine, Department of Radiology (Japan)

2006-08-15

213

In Utero Detection of Retinoblastoma with Fetal Magnetic Resonance and Ultrasound: Initial Experience  

PubMed Central

Purpose?Our aim was to evaluate and compare the ability of prenatal ultrasound (US) and fetal magnetic resonance imaging (MRI) to detect retinoblastoma lesions in utero. Methods?Fetuses at risk for having bilateral retinoblastoma were enrolled in this prospective study. High-resolution US of the fetal eye was performed at 16 to 18 weeks' gestation, every 4 weeks until 32 weeks, then every 2 weeks until delivery. Fetal MRIs were performed every 8 weeks starting at 16 to 18 weeks of gestation. An exam under anesthesia (EUA) was performed postnatally, the gold standard of this study. Lesions were classified as being elevated or minimally elevated based upon their morphology. Results?Of six fetuses suspected or confirmed to be at risk for developing bilateral retinoblastoma, one had tumors on her first postnatal EUA exam. A total of two minimally elevated lesions were seen by the EUA but not detected prenatally by imaging. One elevated lesion (2?mm in height) identified by postnatal EUA was initially identified by prenatal US. Fetal MRI did not detect any lesions. Conclusion?Both prenatal US and fetal MRI are limited in the detection of minimally elevated retinoblastoma lesions. Prenatal US appears to be more sensitive than fetal MRI in the detection of elevated retinoblastoma lesions.

Paquette, Lisa B.; Miller, David; Jackson, Hollie A.; Lee, Thomas; Randolph, Linda; Murphree, A. Lynn; Panigrahy, Ashok

2012-01-01

214

Observation of lobes near the X point in resonant magnetic perturbation experiments on MAST.  

PubMed

The application of nonaxisymmetric resonant magnetic perturbations (RMPs) with a toroidal mode number n = 6 in the MAST tokamak produces a significant reduction in plasma energy loss associated with type-I edge localized modes (ELMs), the first such observation with n > 3. During the ELM mitigated stage clear lobe structures are observed in visible-light imaging of the X-point region. These lobes or manifold structures, that were predicted previously, have been observed for the first time in a range of discharges and their appearance is correlated with the effect of RMPs on the plasma; i.e., they only appear above a threshold when a density pump out is observed or when the ELM frequency is increased. They appear to be correlated with the RMPs penetrating the plasma and may be important in explaining why the ELM frequency increases. The number and location of the structures observed can be well described using vacuum modeling. Differences in radial extent and poloidal width from vacuum modeling are likely to be due to a combination of transport effects and plasma screening. PMID:23004608

Kirk, A; Harrison, J; Liu, Yueqiang; Nardon, E; Chapman, I T; Denner, P

2012-06-20

215

On the use of Cramr-Rao minimum variance bounds for the design of magnetic resonance spectroscopy experiments.  

PubMed

Localized Magnetic Resonance Spectroscopy (MRS) is in widespread use for clinical brain research. Standard acquisition sequences to obtain one-dimensional spectra suffer from substantial overlap of spectral contributions from many metabolites. Therefore, specially tuned editing sequences or two-dimensional acquisition schemes are applied to extend the information content. Tuning specific acquisition parameters allows to make the sequences more efficient or more specific for certain target metabolites. Cramr-Rao bounds have been used in other fields for optimization of experiments and are now shown to be very useful as design criteria for localized MRS sequence optimization. The principle is illustrated for one- and two-dimensional MRS, in particular the 2D separation experiment, where the usual restriction to equidistant echo time spacings and equal acquisition times per echo time can be abolished. Particular emphasis is placed on optimizing experiments for quantification of GABA and glutamate. The basic principles are verified by Monte Carlo simulations and in vivo for repeated acquisitions of generalized two-dimensional separation brain spectra obtained from healthy subjects and expanded by bootstrapping for better definition of the quantification uncertainties. PMID:23933043

Bolliger, Christine S; Boesch, Chris; Kreis, Roland

2013-08-08

216

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

217

High-resolution solid-state nuclear magnetic resonance experiments on highly radioactive ceramics  

NASA Astrophysics Data System (ADS)

A triple-containment magic-angle spinning rotor insert system has been developed and a sample handling procedure formulated for safely analyzing highly radioactive solids by high-resolution solid-state NMR. The protocol and containment system have been demonstrated for magic-angle spinning (MAS) experiments on ceramic samples containing 5-10 wt % 239Pu and 238Pu at rotation speeds of 3500 Hz. The technique has been used to demonstrate that MAS NMR experiments can be used to measure amorphous atomic number fractions produced by accelerated internal radiation damage. This will allow incorporated ?-emitters with short half-lives to be used to model the long-term radiation tolerance of potential ceramic radioactive waste forms. This is an example of MAS NMR spectroscopy on samples containing fissionable isotopes.

Farnan, Ian; Cho, Herman; Weber, William J.; Scheele, Randall D.; Johnson, Nigel R.; Kozelisky, Anne E.

2004-12-01

218

Pituitary Magnetic Resonance Imaging for Sellar and Parasellar Masses: Ten-Year Experience in 2598 Patients  

PubMed Central

Context: Sellar and parasellar masses present with overlapping clinical and radiological features ranging from asymptomatic incidental presentations and hormonal effects to compressive local mass effects. Pituitary masses are diagnosed with increased frequency with magnetic resonance imaging (MRI) advancements and availability, but indications and diagnostic outcomes of MRI screening for sellar lesions are not defined. Although pituitary adenomas are the most frequently encountered sellar mass lesions, other etiologies should be considered in the differential diagnosis of a sellar mass. Setting: The study was conducted at a tertiary pituitary center. Patients: This study was a retrospective review of 2598 subjects undergoing at least one pituitary MRI scan from 1999 to 2009. Main Outcome Measure: Prevalence and diagnosis of specific sellar and parasellar masses as screened by pituitary MRI. Results: The most common indications for pituitary imaging, excluding known mass follow-up, were for evaluation of hyperprolactinemia or hypogonadism. A normal pituitary gland was reported in 47% of subjects undergoing pituitary MRI. The most common pituitary adenomas initially identified by MRI included prolactinoma (40%), nonfunctioning adenoma (37%), and GH adenoma (13%). Nonadenomatous sellar masses accounted for 18% of visible lesions, of which the most common were Rathke's cleft cyst (19%), craniopharyngioma (15%), and meningioma (15%). Metastases accounted for 5% of nonpituitary lesions and breast cancer was the most common primary source. Conclusions: Half of all pituitary MRI scans performed in a large patient population yielded no visible lesion. Nonadenomatous pituitary lesions should be considered in the diagnosis of sellar masses observed on MRI, and a high clinical suspicion is required to exclude the presence of a nonfunctioning pituitary adenoma.

Famini, Pouyan; Maya, Marcel M.

2011-01-01

219

Detuned resonances of Tollmien-Schlichting waves in an airfoil boundary layer: Experiment, theory, and direct numerical simulation  

NASA Astrophysics Data System (ADS)

Transition prediction in two-dimensional laminar boundary layers developing on airfoil sections at subsonic speeds and very low turbulence levels is still a challenge. The commonly used semi-empirical prediction tools are mainly based on linear stability theory and do not account for nonlinear effects present unavoidably starting with certain stages of transition. One reason is the lack of systematic investigations of the weakly nonlinear stages of transition, especially of the strongest interactions of the instability modes predominant in non-self-similar boundary layers. The present paper is devoted to the detailed experimental, numerical, and theoretical study of weakly nonlinear subharmonic resonances of Tollmien-Schlichting waves in an airfoil boundary layer, representing main candidates for the strongest mechanism of these initial nonlinear stages. The experimental approach is based on phase-locked hot-wire measurements under controlled disturbance conditions using a new disturbance source being capable to produce well-defined, complex wave compositions in a wide range of streamwise and spanwise wave numbers. The tests were performed in a low-turbulence wind tunnel at a chord Reynolds number of Re = 0.7 106. Direct numerical simulations (DNS) were utilized to provide a detailed comparison for the test cases. The results of weakly nonlinear theory (WNT) enabled a profound understanding of the underlying physical mechanisms observed in the experiments and DNS. The data obtained in experiment, DNS and WNT agree basically and provide a high degree of reliability of the results. Interactions occurring between components of various initial frequency-wavenumber spectra of instability waves are investigated by systematic variation of parameters. It is shown that frequency-detuned and spanwise-wavenumber-detuned subharmonic-type resonant interactions have an extremely large spectral width. Similar to results obtained for self-similar base flows it is found that the amplification factors in the frequency-detuned resonances can be even higher than in tuned cases, in spite of the strong base-flow non-self-similarity. An explanation of this unusual phenomenon is found based on the theoretical analysis and comparison of experimental, theoretical, and DNS data.

Wrz, W.; Sartorius, D.; Kloker, M.; Borodulin, V. I.; Kachanov, Y. S.; Smorodsky, B. V.

2012-09-01

220

139La nuclear magnetic resonance characterisation of La2O3 and La1-xSrxMO3 where M = Cr, Mn or Co.  

PubMed

139La Nuclear magnetic resonance (NMR) spectra have been used to obtain nuclear quadrupole coupling parameters for La2O3 and a series of perovskites La1-xSrxMO3 (where M = Cr, Mn or Co). Depending on the doping level of SrO2 these materials are either paramagnetic or ferromagnetic at room temperature. Magnetic transferred hyperfine effects are strongly in evidence in the Mn compounds. A 59Co NMR spectrum was observed in LaCoO3. A precision measurement of the nuclear quadrupole coupling constant in La2O3 was made by nuclear quadrupole resonance (NQR) spectroscopy. PMID:7827974

Bastow, T J

1994-02-01

221

Proton and deuterium NMR experiments in zero field. [Perdeuterated p-demethoxybenzene, perdeuterated malonic acid, diethyl terephthalate-d4, nonadecane-2,2'-D2, sodium propionate-D2  

SciTech Connect

High field solid-state NMR lineshapes suffer from inhomogeneous broadening since resonance frequencies are a function of molecular orientation. Time domain zero field NMR is a two-dimensional field-cycling technique which removes this broadening by probing the evolution of the spin system under zero applied field. The simplest version, the sudden transition experiment, induces zero field evolution by the sudden removal of the applied magnetic field. Theory and experimental results of this experiment and several variations using pulsed dc magnetic fuelds to initiate zero field evolution are presented. In particular, the pulsed indirect detection method allows detection of the zero field spectrum of one nuclear spin species via another (usually protons) by utilizing the level crossings which occur upon adiabatic demagnetization to zero field. Experimental examples of proton/deuteron systems are presented which demonstrate the method results in enhanced sensitivity relative to that obtained in sudden transition experiments performed directly on deuterium. High resolution /sup 2/H NQR spectra of a series of benzoic acid derivatives are obtained using the sudden transition and indirect detection methods. Librational oscillations in the water molecules of barium chlorate monohydrate are studied using proton and deuterium ZF experiments. 177 refs., 88 figs., 2 tabs.

Millar, J.M.

1986-02-01

222

s-wave superconductivity in superconducting BaTi2Sb2O revealed by 121/123Sb-NMR/nuclear quadrupole resonance measurements  

NASA Astrophysics Data System (ADS)

We report the 121/123Sb-NMR/nuclear quadrupole resonance (NQR) measurements on the superconductor BaTi2Sb2O with a two-dimensional Ti2O square-net layer formed with Ti3+ (3d1). NQR measurements revealed that the in-plane four-fold symmetry is broken at the Sb site below TA40 K, without an internal field appearing at the Sb site. These exclude a spin-density wave (SDW)/ charge density wave (CDW) ordering with incommensurate correlations, but can be understood with the commensurate CDW ordering at TA. The spin-lattice relaxation rate 1/T1, measured at the four-fold symmetry breaking site, decreases below superconducting (SC) transition temperature Tc, indicative of the microscopic coexistence of superconductivity and the CDW/SDW phase below TA. Furthermore, 1/T1 of 121Sb-NQR shows a coherence peak just below Tc and decreases exponentially at low temperatures. These results are in sharp contrast with those in cuprate and iron-based superconductors, and strongly suggest that its SC symmetry is classified to an ordinary s-wave state.

Kitagawa, S.; Ishida, K.; Nakano, K.; Yajima, T.; Kageyama, H.

2013-02-01

223

Real time polarization monitor developed for high power electron cyclotron resonance heating and current drive experiments in large helical device  

NASA Astrophysics Data System (ADS)

The polarization state of a wave is an important factor in electron cyclotron resonance heating (ECRH) and current drive (ECCD), for it strongly affects the propagation and absorption of the wave in the plasma. A real-time monitor of the polarization of the EC beam has been developed for use in ECRH/ECCD experiments in large helical device (LHD). Two orthogonal components of the wave field are measured in one of the miter-bends by use of a specially designed coupler and a waveguide circuit with a 0-90 phase switch to deduce the polarization parameters: the polarization angle ? and the ellipticity ?. Since fast-response pin diodes are used for the switches, the polarization is determined every 3 ms, facilitating real time acquisition of the polarization. This article reports on the design and the principle of this monitor as well as on the algorithm used to calculate ? and ?. This article also reports on the method of calibration, for the accuracy of this measurement depends on it. Finally, a comparison is made between polarization parameters measured by a monitor actually installed on one of the ECRH transmission lines on LHD and the value set by the polarizer in ECRH experiments.

Notake, T.; Idei, H.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Kobayashi, S.; Mizuno, Y.; Ito, S.; Takita, Y.; Ohkubo, K.; Kasparek, W.; Watari, T.; Kumazawa, R.

2005-02-01

224

Reduced fluorescence lifetime heterogeneity of 5-fluorotryptophan in comparison to tryptophan in proteins: implication for resonance energy transfer experiments.  

PubMed

Tryptophan (Trp), an intrinsically fluorescent residue of proteins, has been used widely as an energy donor in fluorescence resonance energy transfer (FRET) experiments aimed at measuring intramolecular distances and distance distributions in protein folding-unfolding reactions. However, the high level of heterogeneity associated with the fluorescence lifetime of tryptophan, even in single-tryptophan proteins, imposes restrictions on its use as the energy donor. A search for a tryptophan analogue having reduced lifetime heterogeneity when compared to tryptophan led us to 5-fluorotryptophan (5F-Trp). A single tryptophan-containing mutant form of barstar, a small 89-residue bacterial protein, has multiple lifetime components in its various structural forms including the unfolded state, similar to observations made with several other proteins. Biosynthetic incorporation of 5F-Trp in place of Trp in the mutant barstar resulted in a significant decrease in the level of heterogeneity of fluorescence decay when compared to Trp-barstar, in the native state as well as in the denatured state. Importantly, observation of a major decay component of more than 80% in both the states makes 5F-Trp a significantly better candidate for being the energy donor in FRET experiments, as compared to Trp. This is expected to enable an unambiguous estimation of intramolecular distance distributions during protein folding and unfolding. The sequence insensitivity of the fluorescence decay kinetics of 5F-Trp in proteins was demonstrated by observing the decay kinetics of 5F-Trp incorporated in several synthetic peptides. PMID:21574591

Sarkar, Saswata Sankar; Udgaonkar, Jayant B; Krishnamoorthy, G

2011-05-16

225

Mapping the conformational stability of maltose binding protein at the residue scale using nuclear magnetic resonance hydrogen exchange experiments.  

PubMed

Being able to differentiate local fluctuations from global folding-unfolding dynamics of a protein is of major interest for improving our understanding of structure-function determinants. The maltose binding protein (MBP), a protein that belongs to the maltose transport system, has a structure composed of two globular domains separated by a rigid-body "hinge bending". Here we determined, by using hydrogen exchange (HX) nuclear magnetic resonance experiments, the apparent stabilization free energies of 101 residues of MBP bound to ?-cyclodextrin (MBP-?CD) under native conditions. We observed that the last helix of MBP (helix ?14) has a lower protection factor than the rest of the protein. Further, HX experiments were performed using guanidine hydrochloride under subdenaturing conditions to discriminate between local fluctuations and global unfolding events and to determine the MBP-?CD energy landscape. The results show that helix ?4 and a part of helices ?5 and ?6 are clearly grouped into a subdenaturing folding unit and represent a partially folded intermediate under native conditions. In addition, we observed that amide protons located in the hinge between the two globular domains share similar ?G(gu)(app) and m values and should unfold simultaneously. These observations provide new points of view for improving our understanding of the thermodynamic stability and the mechanisms that drive folding-unfolding dynamics of proteins. PMID:23046344

Merstorf, Cline; Maciejak, Olek; Math, Jrme; Pastoriza-Gallego, Manuela; Thiebot, Bndicte; Clment, Marie-Jeanne; Pelta, Juan; Auvray, Loc; Curmi, Patrick A; Savarin, Philippe

2012-10-24

226

Low-energy physical properties of high- Tc superconducting Cu oxides: A comparison between the resonating valence bond and experiments  

NASA Astrophysics Data System (ADS)

In a recent review by Anderson and co-workers, it was pointed out that an early resonating valence bond (RVB) theory is able to explain a number of unusual properties of high-temperature superconducting (SC) Cu oxides. Here we extend previous calculations to study more systematically the low-energy physical properties of the plain vanilla d -wave RVB state, and to compare the results with the available experiments. We use a renormalized mean-field theory combined with variational Monte Carlo and power Lanczos methods to study the RVB state of an extended t-J model in a square lattice with parameters suitable for the hole-doped Cu oxides. The physical observable quantities we study include the specific heat, the linear residual thermal conductivity, the in-plane magnetic penetration depth, the quasiparticle energy at the antinode (?,0) , the superconducting energy gap, the quasiparticle spectra, and the Drude weights. The traits of nodes (including kF , the Fermi velocity vF , and the velocity along Fermi surface v2 ), and the SC order parameter are studied. Comparisons of the theory and the experiments in cuprates show an overall qualitative agreement, especially on their doping dependences.

Yang, Kai-Yu; Shih, C. T.; Chou, C. P.; Huang, S. M.; Lee, T. K.; Xiang, T.; Zhang, F. C.

2006-06-01

227

The influence of signal noise on the accuracy of kinetic constants measured by surface plasmon resonance experiments.  

PubMed

An analysis is carried out to investigate the accuracy of kinetic parameters obtained using surface plasmon resonance methodology with a BIAcore instrument. The Cramer Rao lower bound for the least possible variance of an estimator of the kinetic parameters is determined. Using simulations it is shown that the standard least-squares estimation technique provides estimates that achieve this bound. The theoretical and simulation results are compared with experimental data obtained from an analysis of the interaction of the myc peptide with the anti-myc antibody, 9E10. This investigation indicates that the accuracy of the results depends on the signal level which has particular relevance to the design of experiments with low signal levels. It is shown how the accuracy of the estimates of the kinetic constants depends on the kinetic constants themselves and how the accuracy of the association constants depends on the concentration of the analyte that is used in the experiment. In addition, the effects of increasing the number of data points in the analysis of dissociation data on the accuracy of the estimates are quantitated. It is also demonstrated that signal averaging of data derived from repeat sensorgrams can result in a significant decrease in the standard deviation of the estimates. PMID:10452798

Ober, R J; Ward, E S

1999-08-15

228

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

229

/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

230

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

231

Field experiment provides ground truth for surface nuclear magnetic resonance measurement  

USGS Publications Warehouse

The need for sustainable management of fresh water resources is one of the great challenges of the 21st century. Since most of the planet's liquid fresh water exists as groundwater, it is essential to develop non-invasive geophysical techniques to characterize groundwater aquifers. A field experiment was conducted in the High Plains Aquifer, central United States, to explore the mechanisms governing the non-invasive Surface NMR (SNMR) technology. We acquired both SNMR data and logging NMR data at a field site, along with lithology information from drill cuttings. This allowed us to directly compare the NMR relaxation parameter measured during logging, T 2, to the relaxation parameter T 2 * measured using the SNMR method. The latter can be affected by inhomogeneity in the magnetic field, thus obscuring the link between the NMR relaxation parameter and the hydraulic conductivity of the geologic material. When the logging T 2 data were transformed to pseudo-T 2 * data, by accounting for inhomogeneity in the magnetic field and instrument dead time, we found good agreement with T 2 * obtained from the SNMR measurement. These results, combined with the additional information about lithology at the site, allowed us to delineate the physical mechanisms governing the SNMR measurement. Such understanding is a critical step in developing SNMR as a reliable geophysical method for the assessment of groundwater resources. Copyright 2012 by the American Geophysical Union.

Knight, R.; Grunewald, E.; Irons, T.; Dlubac, K.; Song, Y.; Bachman, H. N.; Grau, B.; Walsh, D.; Abraham, J. D.; Cannia, J.

2012-01-01

232

Nuclear Quadrupole Resonance Studies of the Sorc Sequence and Nuclear Magnetic Resonance Studies of Polymers.  

NASA Astrophysics Data System (ADS)

The behavior of induction signals during steady -state pulse irradiation in ^{14} N NQR was investigated experimentally. Because Strong Off-resonance Comb (SORC) signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these steady-state SORC signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the method. Also as part of the NQR work, Cocaine base has been detected using conventional NQR techniques. The experimental results show that SORC detection can be of sufficient sensitivity to form the basis of narcotics screening devices for both mail and airline baggage. A new NMR technique, to obtain the correlation time of the random thermal motion of a polymer at temperatures near the glass transition has been introduced. The temperature dependence is a result of thermal motion. For slow-motion of a polymer chain near the glass transition, the CSA parameter begins to decrease. This motional narrowing can be interpreted to yield the correlation time of the thermal motion. In this work Nitrocellulose isotopically highly enriched with ^{15}N was studied at four different temperatures between 27^ circ and 120^circ Celsius and the correlation times for polymer backbone motions were obtained. Nafion films containing, water (D_2 O and H_2^{17}O) and methanol (CH_3OD, CH _3^{17}OH), have been studied using Deuteron and Oxygen-17 NMR spectroscopy. Glassy behavior of the water domains at low temperature is evidenced by the specific nature of the ^2H NMR lineshapes. Activation energies extracted from ^2H spin-lattice relaxation data on the high temperature side of the T_1 minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra of both unstretched and stretched samples reflect considerable anisotropy of the host polymer. Activation volumes corresponding to a specific dynamical process were obtained from measurements of spin-lattice relaxation vs. pressure. From the NMR measurements of Nafion films containing methanol, it was found that the molecular motion is much more rapid than the molecular motion of water in Nafion membranes.

Jayakody, Jayakody R. Pemadasa

1993-01-01

233

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

234

Stochastic resonance  

NASA Astrophysics Data System (ADS)

Over the last two decades, stochastic resonance has continuously attracted considerable attention. The term is given to a phenomenon that is manifest in nonlinear systems whereby generally feeble input information (such as a weak signal) can be be amplified and optimized by the assistance of noise. The effect requires three basic ingredients: (i) an energetic activation barrier or, more generally, a form of threshold; (ii) a weak coherent input (such as a periodic signal); (iii) a source of noise that is inherent in the system, or that adds to the coherent input. Given these features, the response of the system undergoes resonance-like behavior as a function of the noise level; hence the name stochastic resonance. The underlying mechanism is fairly simple and robust. As a consequence, stochastic resonance has been observed in a large variety of systems, including bistable ring lasers, semiconductor devices, chemical reactions, and mechanoreceptor cells in the tail fan of a crayfish. In this paper, the authors report, interpret, and extend much of the current understanding of the theory and physics of stochastic resonance. They introduce the readers to the basic features of stochastic resonance and its recent history. Definitions of the characteristic quantities that are important to quantify stochastic resonance, together with the most important tools necessary to actually compute those quantities, are presented. The essence of classical stochastic resonance theory is presented, and important applications of stochastic resonance in nonlinear optics, solid state devices, and neurophysiology are described and put into context with stochastic resonance theory. More elaborate and recent developments of stochastic resonance theory are discussed, ranging from fundamental quantum properties-being important at low temperatures-over spatiotemporal aspects in spatially distributed systems, to realizations in chaotic maps. In conclusion the authors summarize the achievements and attempt to indicate the most promising areas for future research in theory and experiment.

Gammaitoni, Luca; Hnggi, Peter; Jung, Peter; Marchesoni, Fabio

1998-01-01

235

Design and fabrication of circular and rectangular components for electron-cyclotron-resonant heating of tandem mirror experiment-upgrade  

SciTech Connect

The electron-cyclotron-resonant heating (ECRH) systems of rectangular waveguides on Tandem Mirror Experiment-Upgrade (TMX-U) operated with a overall efficiency of 50%, each system using a 28-GHz, 200-kW pulsed gyrotron. We designed and built four circular-waveguide systems with greater efficiency and greater power-handling capabilities to replace the rectangular waveguides. Two of these circular systems, at the 5-kG second-harmonic heating locations, have a total transmission efficiency of >90%. The two systems at the 10-kG fundamental heating locations have a total transmission efficiency of 80%. The difference in efficiency is due to the additional components required to launch the microwaves in the desired orientation and polarization with respect to magnetic-field lines at the 10-kG points. These systems handle the total power available from each gyrotron but do not have the arcing limitation problem of the rectangular waveguide. Each system requires several complex components. The overall physical layout and the design considerations for the rectangular and circular waveguide components are described here.

Felker, B.; Calderon, M.O.; Chargin, A.K.; Coffield, F.E.; Lang, D.D.; Rubert, R.R.; Pedrotti, L.R.; Stallard, B.W.; Gallagher, N.C. Jr.; Sweeney, D.W.

1983-11-18

236

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

237

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

238

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

239

Utilization of pure nuclear quadrupole resonance spectroscopy for the study of pharmaceutical crystal forms.  

PubMed

Solid-state physical characterization of a pharmaceutical substance is necessary for successful development and approval of the final product. Different physical analytical techniques are available to do so: X-ray diffraction (XRD), IR, Raman, DSC, TG and NMR. Moreover, all of them detect the presence of excipients perturbing the analysis of the pure substance in low doses. In order to study polymorphism and pseudo polymorphism of drug, this paper introduces possible applications of pure nuclear quadrupole resonance, as a non-destructive technique in qualitative and quantitative approaches. Chlorpropamide and diclofenac sodium were used as examples. Unlike the mentioned techniques, the nuclear quadrupole resonance (NQR) signal of pharmaceutical compounds is not perturbed by the presence of solid excipient or other substances unless they possess resonance frequencies in the same frequency range of the compound studied. PMID:15913931

Prez, S C; Cerioni, L; Wolfenson, A E; Faudone, S; Cuffini, S L

2005-07-14

240

Variation of the resonance width of HOCl(6{nu}{sub OH}) with total angular momentum: Comparison between {ital ab initio} theory and experiment  

SciTech Connect

Complex L{sup 2} calculations of the variation of (very narrow) resonance widths of the 6{nu}{sub OH} state of HOCl with total angular momentum are reported, using a recently developed, accurate {ital ab initio} potential energy surface [S. Skokov, J. M. Bowman, and K. A. Peterson, J. Chem. Phys. {bold 109}, 2662 (1998)]. The calculations are carried out within the adiabatic rotation approximation for the overall rotation and a truncation/recoupling method for the vibrational states. Comparisons with recent double-resonance experiments of the Rizzo and Sinha groups are made. The variation of resonance width with {ital J} for {ital K}=0 is shown to be due to rotation-induced coupling of the 6{nu}{sub OH} state with a dense set of states with large excitation in the dissociative coordinate. {copyright} {ital 1999 American Institute of Physics.}

Skokov, S.; Bowman, J.M. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)

1999-05-01

241

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

242

Space charge effect of the high intensity proton beam during the resonance extraction for the Mu2e experiment at Fermilab  

SciTech Connect

The proposed Mu2e experiment to search for direct {mu} {yields} e conversion at Fermilab plans slow, resonant extraction of a beam with 3 x 10{sup 12} protons from the Debuncher ring. Space charge of this high intensity beam is a critical factor, since it induces significant betatron tune spread and consequently affects resonance extraction processes, such as spill uniformity and beam losses. This study shows the multi-particle simulation results in the early stages of resonance extraction and spill uniformity in the presence of 2D and 3D space charge effects. We have presented the results of the third-integer resonance extraction in early stage for the Mu2e experiment in the presence of space charge effects. In order to track particles and to calculate self-consistent space charge effects, Synergia2 was used, which is capable of parallel computing. The space charge tune shift was computed and was reasonable value compared with the analytical calculation. Locations of the septum and Lambertson were chosen so that particles are kicked and extracted efficiently. The spill rates for with and without space charge effects were uniform, but should be improved for the early stage after the sextupole field ramping.

Park, Chong Shik; Amundson, James; Johnstone, John; Michelotti, Leo; Nagaslaev, Vladimir; Werkema, Steve; /Fermilab

2011-03-01

243

In vivo nuclear Overhauser effect in sup 31 P-(1H) double-resonance experiments in a 1. 5-T whole-body MR system  

SciTech Connect

In {sup 31}P-(1H) MR experiments of humans in a 1.5-T whole-body system, signal intensity enhancements of {sup 31}P resonances of up to 68 +/- 4% (for phosphocreatine of the calf muscle) have been observed upon irradiation at proton frequency. This observation is explained as a nuclear Overhauser effect due to the dipolar coupling between {sup 1}H and {sup 31}P spins.

Bachert-Baumann, P.; Ermark, F.; Zabel, H.J.; Sauter, R.; Semmler, W.; Lorenz, W.J. (Institut fuer Radiologie and Pathophysiologie, Heidelberg (Germany, F.R.))

1990-07-01

244

A pilot study using magnetic resonance imaging to determine the pattern of muscle group recruitment by rowers with different levels of experience  

Microsoft Academic Search

Objective. To determine whether it was possible using magnetic resonance imaging (MRI) to define the pattern of muscle recruitment in\\u000a a specific sport (rowing) and to see whether there were differences in this pattern between athletes of different experience.\\u000a \\u000a \\u000a Design and method. It has been shown that during vigorous exercise the water content of muscle increases transiently. This can be

R. A. R. Green; D. J. Wilson

2000-01-01

245

Electron Spin Resonance Experiments on Donors in Silicon. III. Investigation of Excited States by the Application of Uniaxial Stress and Their Importance in Relaxation Processes  

Microsoft Academic Search

The excited states of the antimony, phosphorus, and arsenic impurities in silicon have been investigated by subjecting samples to a uniaxial stress and observing the change in the electron spin resonance spectrum. The experiments were performed at 1.25K and ~9000 Mc\\/sec on silicon samples subjected to strains up to 10-3. From the reduction in the hyperfine splitting and the observed

D. K. Wilson; G. Feher

1961-01-01

246

An ultrahigh-vacuum apparatus for resonant diffraction experiments using soft x rays (h{nu}=300-2000 eV)  

SciTech Connect

We have developed an ultrahigh-vacuum instrument for resonant diffraction experiments using polarized soft x rays in the energy range of h{nu}=300-2000 eV at beamline BL17SU of SPring-8. The diffractometer consists of modified differentially pumped rotary feedthroughs for {theta}-2{theta} stages, a sample manipulator with motor-controlled x-y-z-, tilt ({chi})-, and azimuth ({phi})-axes, and a liquid helium flow-type cryostat for temperature dependent measurements between 30 and 300 K. Test results indicate that the diffractometer exhibits high reproducibility (better than 0.001 deg.) for a Bragg reflection of {alpha}-quartz 100 at a photon energy of h{nu}=1950 eV. Typical off- and on-resonance Bragg reflections in the energy range of 530-1950 eV could be measured using the apparatus. The results show that x-ray diffraction experiments with energy-, azimuth-, and incident photon polarization-dependence can be reliably measured using soft x rays in the energy range of {approx}300-2000 eV. The facility can be used for resonant diffraction experiments across the L-edge of transition metals, M-edge of lanthanides, and up to the Si K-edge of materials.

Takeuchi, T.; Chainani, A.; Takata, Y.; Tanaka, Y.; Oura, M. [RIKEN SPring-8 Center, 1-1-1 Kouto Sayo-cho Sayo-gun, Hyogo 679-5148 (Japan); Tsubota, M. [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto Sayo-cho Sayo-gun, Hyogo 679-5148 (Japan); Senba, Y.; Ohashi, H. [JASRI/SPring-8, 1-1-1 Kouto Sayo-cho Sayo-gun, Hyogo 679-5148 (Japan); Mochiku, T.; Hirata, K. [Superconducting Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Shin, S. [RIKEN SPring-8 Center, 1-1-1 Kouto Sayo-cho Sayo-gun, Hyogo 679-5148 (Japan); ISSP, The University of Tokyo, 5-1-5 Kashiwanoha Kashiwa, Chiba 277-8581 (Japan)

2009-02-15

247

NMR experiments for resonance assignments of 13 C, 15 N doubly-labeled flexible polypeptides: Application to the human prion protein hPrP(23230)  

Microsoft Academic Search

A combination of three heteronuclear three-dimensional NMR experiments tailored for sequential resonance assignments in uniformly 15N, 13C-labeled flexible polypeptide chains is described. The 3D (H)N(CO-TOCSY)NH, 3D (H)CA(CO-TOCSY)NH and 3D (H)CBCA(CO-TOCSY)NH schemes make use of the favorable 15N chemical shift dispersion in unfolded polypeptides, exploit the slow transverse 15N relaxation rates of unfolded polypeptides in high resolution constant-time [1H, 15N]-correlation experiments,

Aizhuo Liu; Roland Riek; Gerhard Wider; Christine von Schroetter; Ralph Zahn; Kurt Wthrich

2000-01-01

248

^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

249

Experiments of high-amplitude and shock-free oscillations of air column in a tube with array of Helmholtz resonators  

NASA Astrophysics Data System (ADS)

This experimental study is made to verify the weakly nonlinear theory for high-amplitude and shock-free oscillations of an air column developed in the previous paper [Sugimoto et al., J. Acoust. Soc. Am., 114, 1772-1784 (2003)]. The experiments use a new tube and resonators designed so as to not only avoid higher harmonic resonances and evanescences but also reduce the values of the coefficient of Q in the amplitude equation, and a rubber diaphragm sandwiched by circular plates to drive the air column. The steady-state pressure field in the tube and in the cavities of the resonators is measured, from which Fourier coefficients are obtained. In spite of nonlinearity, higher harmonics are suppressed significantly as designed, and the frequency response measured shows quantitatively good agreement with the one predicted up to about 170 dB (SPL). The first harmonics and the nonoscillatory component in the pressure field are well predicted, though the second harmonics show a quantitative discrepancy with the theory. In view of the good agreement of the frequency response, it is concluded that the theory is valid and useful enough to provide guidelines in designing the tube with the array of resonators.

Masuda, M.; Sugimoto, N.

2005-07-01

250

Open-loop operation experiments in a resonator fiber-optic gyro using the phase modulation spectroscopy technique.  

PubMed

A detection system in the resonator fiber-optic gyro is set up by the phase modulation (PM) spectroscopy technique. The slope of the demodulated curve near the resonant point is found to affect the ultimate sensitivity of the gyro. To maximize the demodulated signal slope, the modulation frequency and index are optimized by the expansion of the Bessel function and optical field overlapping method. Using different PM frequencies for the light waves, the open-loop gyro output signal is observed. The modulation frequency in this PM technique is limited only by the cutoff frequency of the LiNbO3 phase modulators, which can reach several gigahertz. This detection technique and system can be applied to the resonator micro-optic gyro with a less than 10 cm long integrated optical ring. PMID:17068533

Zhang, Xu-lin; Ma, Hui-Iian; Jin, Zhong-he; Ding, Chun

2006-11-01

251

Nuclear magnetic resonance spectroscopy  

Microsoft Academic Search

Magnetic resonance spectroscopy is a valuable method for the non-invasive investigation of metabolic processes and can now be combined with conventional magnetic resonance imaging in patients. This article gives a brief introduction into the principles and physiological and clinical applications of in vivo proton magnetic resonance spectroscopy, surveys experiences in healthy volunteers and presents exemplary results in patients suffering from

Armin Ettl; Christa Fischer-Klein; Andreas Chemelli; Albert Daxer; Stephan Felber

1994-01-01

252

14N nuclear quadrupole resonance of picolinic, nicotinic, isonicotinic and dinicotinic acids  

NASA Astrophysics Data System (ADS)

The 14N nuclear quadrupole resonance (NQR) quadrupole coupling tensors of picolinic, nicotinic, isonicotinic and dinicotinic acids have been determined. Two different 14N quadrupole coupling constants 1007 kHz and 4159 kHz have been observed for picolinic acid demonstrating the presence of both protonated and non-protonated nitrogen atoms in this system in the solid. Only one set of non-protonated 14N NQR lines has been observed in other pyridinecarboxylic acids demonstrating the absence of the protonated zwitter ion forms observed in picolinic acid. The non-protonated 14N quadrupole coupling constant is the highest for the non-protonated nitrogen in picolinic acid and decreases to 3774 kHz in nicotinic acid and 3570 kHz in isonicotinic acid. It is the lowest in dinicotinic acid where the corresponding 14N quadrupole coupling constant is 2794 kHz. The observed anomalous decrease in the 14N quadrupole coupling constant of dinicotinic acid with decreasing temperature is tentatively explained as reflecting the increase in the residence time of the N-H⋯O bonded proton in the potential well close to the nitrogen.

Seliger, J.; agar, V.; Zidanek, A.; Blinc, R.

2006-12-01

253

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

254

The Role of High-Resolution Magnetic Resonance in Atypical and Intractable Benign Paroxysmal Positional Vertigo: Our Preliminary Experience  

Microsoft Academic Search

Background: The diagnosis of benign paroxysmal positional vertigo (BPPV) is easy when typical nystagmus is present. However, diagnostic doubts arise when faced with cases presenting atypical features of the positional paroxysmal nystagmus as well as the clinical course and disease evolution. Methods: A morphological evaluation of inner ear structures via high-resolution magnetic resonance (HR-MR) studies has been performed in 2

Iacopo Dallan; Luca Bruschini; Emanuele Neri; Andrea Nacci; Giovanni Segnini; Ferdinando Rognini; Augusto Pietro Casani

2007-01-01

255

Surface-Enhanced Resonance Raman Scattering and Visible Extinction Spectroscopy of Copper Chlorophyllin: An Upper Level Chemistry Experiment  

ERIC Educational Resources Information Center

|Advanced chemistry students are introduced to surface-enhanced resonance Raman scattering (SERRS) by studying how sodium copper chlorophyllin (CuChl) adsorbs onto silver colloids (CuChl/Ag) as a function of pH. Using both SERRS and visible extinction spectroscopy, the extent of CuChl adsorption and colloidal aggregation are monitored. Initially

Schnitzer, Cheryl S.; Reim, Candace Lawson; Sirois, John J.; House, Paul G.

2010-01-01

256

Preliminary tests for the electron cyclotron resonance ion source coupled to a laser ion source for charge state enhancement experiment  

Microsoft Academic Search

At the Laboratori Nazionali del Sud we have designed a hybrid ion source, consisting of a laser ion source as first stage, which gives intense currents of electrons and of multiply charged ions, followed by an electron cyclotron resonance (ECR) ion source as a second stage, which should act as a charge state multiplier. The ECR ion source coupled to

S. Gammino; G. Ciavola; L. Torrisi; L. Celona; J. Wolowski; E. Woryna; P. Parys; L. Lska; J. Krsa; G. D. Shirkov

2000-01-01

257

T-matrix studies of aerosol particle shape effects on IR resonance spectral line profiles and comparison with an experiment  

Microsoft Academic Search

Experimental infrared resonance absorption line profiles are compared with results from T-matrix theory calculations for several mineral components of atmospheric dust (illite, kaolinite, montmorillonite, quartz, and calcite). The model results are used to infer general characteristics of the aerosol particle shape distribution. For the silicate clays the spectral line profiles are best fit by a shape distribution of highly eccentric

P. D. Kleiber; V. H. Grassian; M. A. Young; Paula K. Hudson

2009-01-01

258

Determination of ?-v-j vector correlations in photodissociation experiments using 2+n resonance-enhanced multiphoton ionization with time-of-flight mass spectrometer detection  

NASA Astrophysics Data System (ADS)

A practical method is described for 2+n resonance-enhanced multiphoton-ionization probing of photofragment ?-v-j correlations arising in molecular photodissociation on a linearly polarized single-photon electric-dipole transition. The scheme uses polarized spectroscopy on the two-photon resonant transition with velocity detection by time-of-flight mass spectrometry. The technique is based on the theory of Kummel, Sitz, and Zare for polarized two-photon detection of angular momentum alignment and orientation and Dixon's bipolar moment description of vector correlations. Optimal experimental and polarization geometries are described for selective measurement of targeted bipolar moments. The utility of the technique is demonstrated in experiments using 2+1 REMPI to probe methyl radical vector correlations in the 266 nm photodissociation of methyl iodide.

Pisano, Patrick J.; Cline, Joseph I.

2000-04-01

259

Long-lived frequency shifts observed in a magnetic resonance force microscope experiment following microwave irradiation of a nitroxide spin probe  

NASA Astrophysics Data System (ADS)

We introduce a spin-modulation protocol for force-gradient detection of magnetic resonance that enables the real-time readout of longitudinal magnetization in an electron spin resonance experiment involving fast-relaxing spins. We applied this method to observe a prompt change in longitudinal magnetization following the microwave irradiation of a nitroxide-doped perdeuterated polystyrene film having an electron spin-lattice relaxation time of T1~1ms. The protocol allowed us to discover a large, long-lived cantilever frequency shift. Based on its magnitude, lifetime, and field dependence, we tentatively attribute this persistent signal to deuteron spin magnetization created via transfer of polarization from nitroxide spins.

Chen, Lei; Longenecker, Jonilyn G.; Moore, Eric W.; Marohn, John A.

2013-04-01

260

Extending the direct laser modulation bandwidth by exploiting the photon-photon resonance: modeling, simulations and experiments  

NASA Astrophysics Data System (ADS)

The direct laser modulation bandwidth can be extended substantially by introducing a supplementary photon-photon resonance (PPR) at a higher frequency than the carrier-photon resonance (CPR). The paper presents a modified rate equation model that takes into account the PPR by treating the longitudinal confinement factor as a dynamic variable. The conditions required for obtaining a strong PPR and an enhancement of the small-signal modulation bandwidth are analyzed and experimental results confirming the model are presented. Since the small-signal modulation bandwidth may not be indicative of the large-signal modulation capability, particularly in case of a small-signal modulation response with substantial variations across the bandwidth, we have also analyzed the influence of the PPR-enhanced small-signal modulation response shape on the large-signal modulation capability as well as the methods that can be employed to flatten the small-signal modulation transfer function between the CPR and PPR.

Dumitrescu, M.; Laakso, A.; Viheriala, J.; Kamp, M.; Bardella, P.; Eisenstein, G.

2013-03-01

261

Ferromagnetic resonance studies of Fe\\/Ni and Fe\\/CoNbZr multilayers: Model and experiments  

Microsoft Academic Search

Ferromagnetic resonance (FMR) studies were carried out on Fe\\/Ni and Fe\\/CoNbZr multilayers. A simple model taking into consideration the multilayered nature of the film was used to calculate the field positions and mode intensities of the experimental spectra. The complicated intensity patterns of the modes observed in the FMR spectra of the multilayers were explained in terms of model calculations.

B. Ramamurthy Acharya; Shiva Prasad; N. Venkataramani; M. Kaabouchi; R. Krishnan; C. Sella

1995-01-01

262

Electric-energy generation using variable-capacitive resonator for power-free LSI: efficiency analysis and fundamental experiment  

Microsoft Academic Search

A power generator based on a vibration-to-electric energy converter using a variable-resonating capacitor is experimentally demonstrated. The generator consists of a complete system with a mechanical-variable capacitor, a charge-transporting LC tank circuit and an externally powered timing-capture controller. A practical design methodology to maximize the efficiency of the vibration-to-electric energy generation system is also described. The efficiency of the generator

Masayuki Miyazaki; Hidetoshi Tanaka; Goichi Ono; Tomohiro Nagano; Norio Ohkubo; Takayuki Kawahara; Kazuo Yano

2003-01-01

263

IR theory of weak H-bonds: Davydov coupling, Fermi resonances and direct relaxations. II. General trends, from numerical experiments  

Microsoft Academic Search

The theoretical model proposed in the precedent paper [Chem. Phys. 248 (1999) 53] which was dealing with the X-H??Y stretching mode of a cyclic dimer susceptible of Davydov coupling, and involving weak H-bonds and Fermi resonances, is applied. The basis of this theory was an extension of the quantum model of Wjcik [Mol. Phys. 36 (1978) 1757] in which has

D. Chamma; O. Henri-Rousseau

1999-01-01

264

On the role of graphite chamber-wall lining in experiments on the ion-cyclotron resonance plasma heating in the globus-M spherical tokamak  

NASA Astrophysics Data System (ADS)

Comparative results of experiments on the ion-cyclotron resonance (ICR) heating of plasma in the Globus-M spherical tokamak using a hydrogen-deuterium mixture are presented. The experimental data are analyzed over a long period of time during which the internal surface of the chamber walls was gradually coated with graphite plates. The observed monotonic decrease in the efficiency of ICR plasma heating in the chamber with increasing graphite coverage can be explained by a growth in the high-frequency power absorption in the coating material. Results of numerical simulation of this process are reported.

Ayushin, B. B.; Varfolomeev, V. I.; Gusev, V. K.; D'Yachenko, V. V.; Petrov, Yu. V.; Sakharov, N. V.; Khitrov, S. A.; Chernyshev, F. V.; Shcherbinin, O. N.

2009-01-01

265

NMR experiments for resonance assignments of 13C, 15N doubly-labeled flexible polypeptides: Application to the human prion protein hPrP(23-230)  

Microsoft Academic Search

A combination of three heteronuclear three-dimensional NMR experiments tailored for sequential resonance as- signments in uniformly 15N, 13C-labeled flexible polypeptide chains is described. The 3D (H)N(CO-TOCSY)NH, 3D (H)CA(CO-TOCSY)NH and 3D (H)CBCA(CO-TOCSY)NH schemes make use of the favorable 15N chemical shift dispersion in unfolded polypeptides, exploit the slow transverse 15N relaxation rates of unfolded polypep- tides in high resolution constant-time (

Aizhuo Liu; Roland Riek; Gerhard Wider; Christine von Schroetter; Ralph Zahn; Kurt Wthrich

2000-01-01

266

Resonant Auger decay of Xe* 4 d -1 5/2 6p : A contribution to the complete experiment from fluorescence polarization studies  

NASA Astrophysics Data System (ADS)

Fluorescence polarimetry has been used to determine the relative partial-wave Auger decay widths for transitions to states of the XeII 5p46p multiplet after photoexcitation of the Xe*4d5/2-16p(J*=1) resonance by linearly and circularly polarized synchrotron radiation. Combination with data on the angular distribution and spin polarization of the Auger electrons, providing information on the relative phases of the amplitudes, constitutes the complete experiment on the Auger decay. Multiconfiguration relativistic calculations of the amplitudes have been performed and compared to the measurements.

O'Keeffe, P.; Alose, S.; Fritzsche, S.; Lohmann, B.; Kleiman, U.; Meyer, M.; Grum-Grzhimailo, A. N.

2004-07-01

267

Nuclear magnetic resonance studies on yeast tRNAPhe I. Assignment of the iminoproton resonances of the acceptor and D stem by means of Nuclear Overhauser Effect experiments at 500 MHz.  

PubMed Central

Resonances of the water exchangeable iminoprotons of the acceptor and D stem of yeast tRNAPhe have been assigned by means of Nuclear Overhauser Effects (NOE's). Assignments were made for spectra recorded from tRNA dialysed against a buffer with 110 mM sodium and 5 mM magnesium ions and against a buffer with 430 mM sodium and no magnesium ions. Remarkable is the assignment of a resonance at 13.6 - 13.7 ppm to the iminoproton of C11G24. This assignment as well as those of G1C72, G3C70, U7A66, U12A23 and C13G22 are different from those made previously on the basis of less direct evidence. NOE experiments performed at 45 degrees C support the view that the D stem together with the tertiary interaction U8A14 is one of the most stable parts of the molecule in the presence of magnesium ions. A comparison of the spectra recorded under the two different buffer conditions shows that an excess of 320 mM sodium ions is not capable to force the tRNA in the same conformation as 5 mM magnesium ions can do.

Heerschap, A; Haasnoot, C A; Hilbers, C W

1982-01-01

268

Resonances and resonance widths  

SciTech Connect

Two-dimensional betatron resonances are much more important than their simple one-dimensional counterparts and exhibit a strong dependence on the betatron phase advance per cell. A practical definition of ''width'' is expanded upon in order to display these relations in tables. A primarily pedagogical introduction is given to explain the tables, and also to encourage a wider capability for deriving resonance behavior and wider use of ''designer'' resonances.

Collins, T.

1986-05-01

269

Sequential backbone assignment of uniformly 13C-labeled RNAs by a two-dimensional P(CC)H-TOCSY triple resonance NMR experiment.  

PubMed

A new 1H-13C-31P triple resonance experiment is described which allows unambiguous sequential backbone assignment in 13C-labeled oligonucleotides via through-bond coherence transfer from 31P via 13C to 1H. The approach employs INEPT to transfer coherence from 31P to 13C and homonuclear TOCSY to transfer the 13C coherence through the ribose ring, followed by 13C to 1H J-cross-polarisation. The efficiencies of the various possible transfer pathways are discussed. The most efficient route involves transfer of 31Pi coherence via C4'i and C4'i-1, because of the relatively large JPC4' couplings involved. Via the homonuclear and heteronuclear mixing periods, the C4'i and C4'i-1 coherences are subsequently transferred to, amongst others, H1'i and H1'i-1, respectively, leading to a 2D 1H-31P spectrum which allows a sequential assignment in the 31P-1H1' region of the spectrum, i.e. in the region where the proton resonances overlap least. The experiment is demonstrated on a 13C-labeled RNA hairpin with the sequence 5'(GGGC-CAAA-GCCU)3'. PMID:7533569

Wijmenga, S S; Heus, H A; Leeuw, H A; Hoppe, H; van der Graaf, M; Hilbers, C W

1995-01-01

270

Real-time magnetic resonance-guided high-intensity focused ultrasound focal therapy for localised prostate cancer: preliminary experience.  

PubMed

Five patients with unifocal, biopsy-proven prostate cancer (PCa) evident on multiparametric magnetic resonance imaging (MRI) were treated with magnetic resonance-guided focused ultrasound (MRgFUS) ablation before radical prostatectomy (RP). An endorectal probe featuring a phased-array focused ultrasound transducer was positioned for lesion ablation under MRI guidance. The tissue temperature and accumulation of thermal damage in the target zone was monitored during the procedure by MRI thermometry. Overlap between the ablation area and the devascularisation of the target lesion was evaluated by contrast-enhanced MRI performed immediately after treatment. The procedure was uneventful, and no adverse events were observed. RP was safely performed without significant surgical difficulties in relation to the previous MRgFUS treatment. The histopathology report showed extensive coagulative necrosis, with no residual tumour in the ablated area. Significant bilateral residual tumour, not evident on pretreatment MRI, was observed outside the treated area in two patients. MRgFUS ablation of focal localised PCa is feasible and, if confirmed in appropriate studies, could represent a valid option for the focal treatment of localised PCa. PMID:23159454

Napoli, Alessandro; Anzidei, Michele; De Nunzio, Cosimo; Cartocci, Gaia; Panebianco, Valeria; De Dominicis, Carlo; Catalano, Carlo; Petrucci, Federico; Leonardo, Costantino

2012-11-12

271

J-substitution algorithm in magnetic resonance electrical impedance tomography (MREIT): phantom experiments for static resistivity images.  

PubMed

Recently, a new static resistivity image reconstruction algorithm is proposed utilizing internal current density data obtained by magnetic resonance current density imaging technique. This new imaging method is called magnetic resonance electrical impedance tomography (MREIT). The derivation and performance of J-substitution algorithm in MREIT have been reported as a new accurate and high-resolution static impedance imaging technique via computer simulation methods. In this paper, we present experimental procedures, denoising techniques, and image reconstructions using a 0.3-tesla (T) experimental MREIT system and saline phantoms. MREIT using J-substitution algorithm effectively utilizes the internal current density information resolving the problem inherent in a conventional EIT, that is, the low sensitivity of boundary measurements to any changes of internal tissue resistivity values. Resistivity images of saline phantoms show an accuracy of 6.8%-47.2% and spatial resolution of 64 x 64. Both of them can be significantly improved by using an MRI system with a better signal-to-noise ratio. PMID:12166867

Khang, Hyun Soo; Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyoung; Kwon, Ohin; Yoon, Jeong Rock; Seo, Jin Keun

2002-06-01

272

Calculation of the nuclear quadrupole resonance spectra of YBa/sub 2/Cu/sub 3/O/sub 7/minus/x/  

SciTech Connect

Nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) studies on /sup 63,65/Cu have demonstrated the the resonance properties of these nuclei can give important information about the electronic structure of the high temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/minus/x/ as well as the exchange coupling energy between the Cu(2) sites. Measurements for various oxygen stoichiometries have given insight into the effect of oxygen content on the valence state of the Cu. In the work reported here, the electric field gradient (EFG) tensors at the Cu(1) and Cu(2) sites in YBa/sub 2/Cu/sub 3/O/sub 7/minus/x/, have been determined from calculations on large clusters for x = 0 and 1. 13 refs., 2 tabs.

Winter, N.W.; Violet, C.E.

1989-06-01

273

Magnetic resonance of the chest: initial experience with imaging and in vivo T1 and T2 calculations  

SciTech Connect

Magnetic resonance (MR) imaging of the chest was performed in 33 patients; 28 patients had a variety of malignant tumors and five had benign processes involving the pleura, chest wall, mediastinum, hila, and pulmonary parenchyma. In addition, in vivo T1 and T2 calculations were performed on 17 malignancies and 2 benign processes. Of the 18 patients examined with both MR and computed tomography (CT), 15 MR examinations were considered to be as diagnostic as CT in demonstrating abnormalities. It is concluded that, with current technology without respiratory or cardiac gating, MR offers little improvement in diagnosis over contrast-enhanced CT. Furthermore, it does not appear possible to predict tissue type based on T1 and T2 measurements because of a wide overlap in these values.

Ross, J.S.; O'Donovan, P.B.; Novoa, R.; Mehta, A.; Buonocore, E.; MacIntyre, W.J.; Golish, J.A.; Ahmad, M.

1984-07-01

274

Iterated finite-orbit Monte Carlo simulations with full-wave fields for modeling tokamak ion cyclotron resonance frequency wave heating experiments  

SciTech Connect

The five-dimensional finite-orbit Monte Carlo code ORBIT-RF[M. Choi et al., Phys. Plasmas 12, 1 (2005)] is successfully coupled with the two-dimensional full-wave code all-orders spectral algorithm (AORSA) [E. F. Jaeger et al., Phys. Plasmas 13, 056101 (2006)] in a self-consistent way to achieve improved predictive modeling for ion cyclotron resonance frequency (ICRF) wave heating experiments in present fusion devices and future ITER [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)]. The ORBIT-RF/AORSA simulations reproduce fast-ion spectra and spatial profiles qualitatively consistent with fast ion D-alpha [W. W. Heidbrink et al., Plasma Phys. Controlled Fusion 49, 1457 (2007)] spectroscopic data in both DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] and National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] high harmonic ICRF heating experiments. This work verifies that both finite-orbit width effect of fast-ion due to its drift motion along the torus and iterations between fast-ion distribution and wave fields are important in modeling ICRF heating experiments.

Choi, M.; Chan, V. S.; Lao, L. L.; Pinsker, R. I. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Green, D.; Berry, L. A.; Jaeger, F.; Park, J. M. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); Heidbrink, W. W.; Liu, D.; Podesta, M. [University of California-Irvine, Irvine, California 92697 (United States); Harvey, R. [CompX, P.O. Box 2672, Del Mar, California 92014-5672 (United States); Smithe, D. N. [Tech-X Corporation, Boulder, Colorado 80303 (United States); Bonoli, P. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2010-05-15

275

Magnetic resonance imaging (MRI) scanning for research: the experiences of healthy volunteers and patients with remitted depressive illness  

Microsoft Academic Search

We report the findings from a study exploring the experiences of individuals undergoing MRI scanning for research. Semi-structured interviews took place before and after scanning with 17 participants; 12 were healthy volunteers and five were patients with a diagnosis of remitted depression. Themes of apprehension and curiosity prior to scanning were common in both groups. Patients were often confused about

Victoria Tischler; Emma Bronjewski; Katherine OConnor; Tim Calton

2009-01-01

276

A resonance broadening kinetic theory of the modified two-stream instability: Implications for radar auroral backscatter experiments  

SciTech Connect

The kinetic theory of the modified two-stream instability (MTSI) is usually considered more accurate than the corresponding fluid theory, for the purpose of interpreting VHF and UHF coherent radar backscatter measurements. However, recent developments in the nonlinear theory of the MTSI have retained the fluid theory formalism and consequently may not be entirely valid in the short-wavelength regime where VHF and UHF radars operate. In this paper, a nonlinear kinetic theory dispersion relation which takes account of the nonlinear resonance broadening effects is developed. With the aid of this dispersion relation, the phase speeds of the short wavelength plasma waves are calculated, as functions of wavelength, aspect angle, and flow angle. The results indicate that phase speeds tend to increase with increasing drift speed, at all wavelengths. Furthermore, under given flow conditions, the phase speeds are relatively insensitive to the flow angle and aspect angle but vary considerably with altitude. However, unlike long-wavelength fluid type waves, short-wavelength MTSI waves are moderately dispersive, the shorter wavelengths having the larger phase speeds. Finally, these kinetic theory calculations are also used to estimate the form of the k spectrum of saturated MTSI waves, and the results are compared with previously published fluid theory predictions of spectral density.

Robinson, T.R.; Honary, F. (Univ. of Leicester (England))

1990-02-01

277

Simulation of non-resonant internal kink mode with toroidal rotation in the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

Plasmas in spherical and conventional tokamaks, with weakly reversed shear q profile and minimum q above but close to unity, are susceptible to an non-resonant (m,n) = (1,1) internal kink mode. This mode can saturate and persist and can induce a (2,1) seed island for Neoclassical Tearing Mode. [Breslau et al. Nucl. Fusion 51, 063027 (2011)]. The mode can also lead to large energetic particle transport and significant broadening of beam-driven current. Motivated by these important effects, we have carried out extensive nonlinear simulations of the mode with finite toroidal rotation using parameters and profiles of an NTSX plasma with a weakly reversed shear profile. The numerical results show that, at the experimental level, plasma rotation has little effect on either equilibrium or linear stability. However, rotation can significantly influence the nonlinear dynamics of the (1,1) mode and the induced (2,1) magnetic island. The simulation results show that a rotating helical equilibrium is formed and maintained in the nonlinear phase at finite plasma rotation. In contrast, for non-rotating cases, the nonlinear evolution exhibits dynamic oscillations between a quasi-2D state and a helical state. Furthermore, the effects of rotation are found to greatly suppress the (2,1) magnetic island even at a low level.

Wang, Feng; Fu, G. Y.; Breslau, J. A.; Tritz, Kevin; Liu, J. Y.

2013-07-01

278

Resolving the Role of Plant Glutamate Dehydrogenase. I. in vivo Real Time Nuclear Magnetic Resonance Spectroscopy Experiments  

PubMed Central

In higher plants the glutamate dehydrogenase (GDH) enzyme catalyzes the reversible amination of 2-oxoglutarate to form glutamate, using ammonium as a substrate. For a better understanding of the physiological function of GDH either in ammonium assimilation or in the supply of 2-oxoglutarate, we used transgenic tobacco (Nicotiana tabacum L.) plants overexpressing the two genes encoding the enzyme. An in vivo real time 15N-nuclear magnetic resonance (NMR) spectroscopy approach allowed the demonstration that, when the two GDH genes were overexpressed individually or simultaneously, the transgenic plant leaves did not synthesize glutamate in the presence of ammonium when glutamine synthetase (GS) was inhibited. In contrast we confirmed that the primary function of GDH is to deaminate Glu. When the two GDH unlabeled substrates ammonium and Glu were provided simultaneously with either [15N]Glu or 15NH4+ respectively, we found that the ammonium released from the deamination of Glu was reassimilated by the enzyme GS, suggesting the occurrence of a futile cycle recycling both ammonium and Glu. Taken together, these results strongly suggest that the GDH enzyme, in conjunction with NADH-GOGAT, contributes to the control of leaf Glu homeostasis, an amino acid that plays a central signaling and metabolic role at the interface of the carbon and nitrogen assimilatory pathways. Thus, in vivo NMR spectroscopy appears to be an attractive technique to follow the flux of metabolites in both normal and genetically modified plants.

Labboun, Soraya; Terce-Laforgue, Therese; Roscher, Albrecht; Bedu, Magali; Restivo, Francesco M.; Velanis, Christos N.; Skopelitis, Damianos S.; Moshou, Panagiotis N.; Roubelakis-Angelakis, Kalliopi A.; Suzuki, Akira; Hirel, Bertrand

2009-01-01

279

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

280

Experiments on the influence of low frequency sound on the acoustic resonances in a corrugated flow pipe  

Microsoft Academic Search

It is well known that an air flow in a corrugated pipe might excite the\\u000alongitudinal acoustic modes of the pipe. In this letter is reported experiments\\u000awhere a low frequency, oscillating flow with velocity magnitudes of the same\\u000aorder as the air flow has been added. Depending on the oscillation strength, it\\u000amight silence the pipe or move the

Ulf R. Kristiansen; Pierre-Olivier Mattei; Cdric Pinhde; Muriel Amielh

2010-01-01

281

The value of magnetic resonance imaging in the early diagnosis of Creutzfeldt-Jakob disease - own experience  

PubMed Central

Summary Background: Creutzfeldt-Jakob disease (CJD) is a rare progressive neurodegenerative disorder, caused by the deposition of the pathological isoform of prion protein PrPsc in the central nervous system. The classic triad of symptoms consists of: rapidly progressive dementia, myoclonus and typical electroencephalographic findings (intermittent rhythmic delta activity and periodic sharp wave complexes). Detection of 14-3-3 protein in the cerebrospinal fluid plays an important diagnostic role as well. Magnetic resonance (MR) images of the brain have been recently incorporated into the diagnostic criteria of sporadic Creutzfeldt-Jakob disease. Case Report: MR examinations were performed in a 65-year-old man and a 54-year-old woman with delusional disorder and cognitive dysfunction, respectively. Diffusion restriction (hyperintense signal in DWI) was shown in the cortex of the left parietal and occipital lobe in the first patient and symmetrically in the cortex of both cerebral hemispheres except for precentral gyri in the second one. In both cases, the first examinations were misread, with the suspicion of ischemic infarcts as the first differential diagnosis. Consultations and subsequent MR examinations in which lesions in subcortical nuclei appeared allowed for a diagnosis of probable CJD. In the first case it was confirmed by clinical picture, EEG and finally autopsy. In the second case, EEG was not typical for CJD but the clinical course of the disease confirmed that diagnosis. Conclusions: The authors present the cases of two patients with characteristic MR images that allowed early diagnosis of probable Creutzfeldt-Jakob disease before the characteristic clinical picture appeared. Early diagnosis is nowadays important for the prevention of disease transmission and in the future hopefully for early treatment.

Bekiesinska-Figatowska, Monika; Kuczynska-Zardzewialy, Arleta; Pomianowska, Barbara; Kajdana, Katarzyna; Szpak, Grazyna M.; Iwanowska, Beata; Madzik, Jaroslaw

2012-01-01

282

Hyperemic stress myocardial perfusion cardiovascular magnetic resonance in mice at 3 Tesla: initial experience and validation against microspheres  

PubMed Central

Background Dynamic first pass contrast-enhanced myocardial perfusion is the standard CMR method for the estimation of myocardial blood flow (MBF) and MBF reserve in man, but it is challenging in rodents because of the high temporal and spatial resolution requirements. Hyperemic first pass myocardial perfusion CMR during vasodilator stress in mice has not been reported. Methods Five C57BL/6J mice were scanned on a clinical 3.0 Tesla Achieva system (Philips Healthcare, Netherlands). Vasodilator stress was induced via a tail vein catheter with an injection of dipyridamole. Dynamic contrast-enhanced perfusion imaging (Gadobutrol 0.1mmol/kg) was based on a saturation recovery spoiled gradient echo method with 10-fold k-space and time domain undersampling (k-t PCA). One week later the mice underwent repeat anaesthesia and LV injections of fluorescent microspheres at rest and at stress. Microspheres were analysed using confocal microscopy and fluorescence-activated cell sorting. Results Mean MBF at rest measured by Fermi-function constrained deconvolution was 4.1??0.5ml/g/min and increased to 9.6??2.5ml/g/min during dipyridamole stress (P?=?0.005). The myocardial perfusion reserve was 2.4 ?0.54. The mean count ratio of stress to rest microspheres was 2.4 ?0.51 using confocal microscopy and 2.6??0.46 using fluorescence. There was good agreement between cardiovascular magnetic resonance CMR and microspheres with no significant difference (P?=?0.84). Conclusion First-pass myocardial stress perfusion CMR in a mouse model is feasible at 3 Tesla. Rest and stress MBF values were consistent with existing literature and perfusion reserve correlated closely to microsphere analysis. Data were acquired on a 3 Tesla scanner using an approach similar to clinical acquisition protocols, potentially facilitating translation of imaging findings between rodent and human studies.

2013-01-01

283

Development of exp 239 Pu Total Cross Section Multilevel Parameters Determination Technique by Analysing Experiments on Neutron Transmission in Resolved Resonance Region.  

National Technical Information Service (NTIS)

The aim of this work is development of S-matrix multilevel resonance parameters determination technique with neutron transmission data used in resolved resonance region. Experimental transmission data values were obtained for the Pu-239 thickness range 0....

T. Bakalov G. Il'chev S. Toshkov V. F. Ukraintsev Chan Khan Maj

1981-01-01

284

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

285

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

286

NMR and NQR studies of the heavy fermion superconductors CeTIn{sub 5} (T=Co and Ir)  

SciTech Connect

We have carried out {sup 115}In and {sup 59}Co nuclear quadrupole resonance and nuclear magnetic resonance measurements on CeCoIn{sub 5} and CeIrIn{sub 5}. The temperature T dependence of the nuclear spin-lattice relaxation rate 1/T{sub 1} of {sup 115}In in the normal state indicates that CeCoIn{sub 5} is located just at an antiferromagnetic instability, and CeIrIn{sub 5} is in the nearly antiferromagnetic region. In the superconducting state, 1/T{sub 1} has no Hebel-Slichter coherence peak just below T{sub C} and a power-law T dependence (close to T{sup 3}) at very low temperatures, which indicates the existence of line nodes in the superconducting energy gap. The {sup 115}In (Ce-In plane) Knight shift in CeCoIn{sub 5} decreases for both parallel and perpendicular directions to the tetragonal c axis in the superconducting state, which shows that the spin susceptibility decreases in all directions. These results indicate that CeCoIn{sub 5} and CeIrIn{sub 5} exhibit non-s-wave even parity (probably d-wave) superconductivity.

Kohori, Y.; Yamato, Y.; Iwamoto, Y.; Kohara, T.; Bauer, E. D.; Maple, M. B.; Sarrao, J. L.

2001-10-01

287

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

288

A general method for assigning NMR spectra of denatured proteins using 3D HC(CO)NH-TOCSY triple resonance experiments  

Microsoft Academic Search

A general approach for assigning the resonances of uniformly 15N- and 13C-labeled proteins in their unfolded state is presented. The assignment approach takes advantage of the spectral dispersion of the amide nitrogen chemical shifts in denatured proteins by correlating side chain and backbone carbon and proton frequencies with the amide resonances of the same and adiacent residues. The 1H resonances

Timothy M. Logan; Edward T. Olejniczak; Robert X. Xu; Stephen W. Fesik

1993-01-01

289

Development of a compact fast CCD camera and resonant soft x-ray scattering endstation for time-resolved pump-probe experiments.  

PubMed

The designs of a compact, fast CCD (cFCCD) camera, together with a resonant soft x-ray scattering endstation, are presented. The cFCCD camera consists of a highly parallel, custom, thick, high-resistivity CCD, readout by a custom 16-channel application specific integrated circuit to reach the maximum readout rate of 200 frames per second. The camera is mounted on a virtual-axis flip stage inside the RSXS chamber. When this flip stage is coupled to a differentially pumped rotary seal, the detector assembly can rotate about 100/360 in the vertical/horizontal scattering planes. With a six-degrees-of-freedom cryogenic sample goniometer, this endstation has the capability to detect the superlattice reflections from the electronic orderings showing up in the lower hemisphere. The complete system has been tested at the Advanced Light Source, Lawrence Berkeley National Laboratory, and has been used in multiple experiments at the Linac Coherent Light Source, SLAC National Accelerator Laboratory. PMID:21806178

Doering, D; Chuang, Y-D; Andresen, N; Chow, K; Contarato, D; Cummings, C; Domning, E; Joseph, J; Pepper, J S; Smith, B; Zizka, G; Ford, C; Lee, W S; Weaver, M; Patthey, L; Weizeorick, J; Hussain, Z; Denes, P

2011-07-01

290

Development of a compact fast CCD camera and resonant soft x-ray scattering endstation for time-resolved pump-probe experiments  

NASA Astrophysics Data System (ADS)

The designs of a compact, fast CCD (cFCCD) camera, together with a resonant soft x-ray scattering endstation, are presented. The cFCCD camera consists of a highly parallel, custom, thick, high-resistivity CCD, readout by a custom 16-channel application specific integrated circuit to reach the maximum readout rate of 200 frames per second. The camera is mounted on a virtual-axis flip stage inside the RSXS chamber. When this flip stage is coupled to a differentially pumped rotary seal, the detector assembly can rotate about 100/360 in the vertical/horizontal scattering planes. With a six-degrees-of-freedom cryogenic sample goniometer, this endstation has the capability to detect the superlattice reflections from the electronic orderings showing up in the lower hemisphere. The complete system has been tested at the Advanced Light Source, Lawrence Berkeley National Laboratory, and has been used in multiple experiments at the Linac Coherent Light Source, SLAC National Accelerator Laboratory.

Doering, D.; Chuang, Y.-D.; Andresen, N.; Chow, K.; Contarato, D.; Cummings, C.; Domning, E.; Joseph, J.; Pepper, J. S.; Smith, B.; Zizka, G.; Ford, C.; Lee, W. S.; Weaver, M.; Patthey, L.; Weizeorick, J.; Hussain, Z.; Denes, P.

2011-07-01

291

Labeling interacting configurations through an analysis of excitation dynamics in a resonant photoemission experiment: the case of rutile TiO2.  

PubMed

A detailed study of resonant photoemission at Ti L(2,3) edges of insulating rutile TiO(2-x) thin film is presented. Pure TiO(2) resonating structures, defect-related resonances, resonant Raman-Auger and normal LVV Auger emissions are tracked, including an unpredicted two-hole correlated satellite below the non-bonding part of the valence band. The analysis of excitation dynamics unambiguously addresses the origin of these features and, in particular, the extent of charge transfer effects on the Ti-O bonding in the valence band of rutile, disclosing further applications to the more general case of, formally, d(0) oxides. PMID:23328648

Drera, G; Sangaletti, L; Bondino, F; Malvestuto, M; Malavasi, L; Diaz-Fernandez, Y; Dash, S; Mozzati, M C; Galinetto, P

2013-01-17

292

Microscopic magnetic nature of water absorbed Na0.35CoO2 investigated by NMR, NQR and ?+SR  

NASA Astrophysics Data System (ADS)

In order to clarify the variation of the microscopic magnetic nature with the carrier density in NaxCoO2yHO, we have measured positive muon-spin rotation/relaxation (?+SR) spectra for H2O as well as D2O absorbed samples. Based on the zero field (ZF-) ?+SR measurements, there was no clear difference between the two superconducting phases (SC-I and SC-II). Furthermore, the ZF-spectrum for the H2O absorbed sample exhibits a clear oscillation in the whole T range measured (1.4-100 K), suggesting the formation of [H3O]+-like H2?+O ions in the sample. Further, the absence of an oscillation in the D2O absorbed sample also evidences the presence of H2?+O. We also measured 59Co nuclear quadrupole resonance spectra of magnetic sample. The temperature dependence of spectra shows that there is no evidence of charge ordering and CDW ordering around magnetic transition temperature.

Ohta, Hiroto; Mnsson, Martin; Ikedo, Yutaka; Sugiyama, Jun; Michioka, Chishiro; Yoshimura, Kazuyoshi; Brewer, Jess H.; Ansaldo, Eduardo J.; Stubbs, Scott L.; Chow, Kim H.; Lord, James S.

2010-12-01

293

Cyclotron resonance and quasiparticles  

SciTech Connect

This introductory paper contains personal perspectives about the importance of cyclotron resonance in forming our modern view of solids. The papers following this one will discuss the discovery, refinements, and some of the latest developments. Although I will touch on some of these subjects, I leave the details to the other authors and in the main focus on the conceptual impact of the work. I propose that it was experiments based on cyclotron resonance which established the quasiparticle concept.

Cohen, Marvin L.

2005-01-15

294

Atomic resonance and scattering  

SciTech Connect

Experiments were conducted in the following areas: mapping of energy levels of a Rydberg lithium atom in a strong magnetic field in the vicinity of a crossing between levels from different principle quantum numbers, electrodynamics in a cavity, resonance enhanced multiphoton ionization, velocity dependence of rotational rainbow structure in Na2-Ar, high precision mass measurement on single ions using cyclotron resonance, low temperature energy transfer, trapping of neutral atoms, and vibrationally inelastic collisions.

Kleppner, D.; Pritchard, D.E.; Ahmad-Bitar, R.; Ducas, T.; Kelleher, D.; Ligare, M.; Lyyra, A.M.; Moskowitz, P.; Saenger, K.L.; Smith, N.

1984-01-01

295

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

296

Feshbach resonances in ultracold gases  

SciTech Connect

Feshbach resonances are the essential tool to control the interaction between atoms in ultracold quantum gases. They have found numerous experimental applications, opening up the way to important breakthroughs. This review broadly covers the phenomenon of Feshbach resonances in ultracold gases and their main applications. This includes the theoretical background and models for the description of Feshbach resonances, the experimental methods to find and characterize the resonances, a discussion of the main properties of resonances in various atomic species and mixed atomic species systems, and an overview of key experiments with atomic Bose-Einstein condensates, degenerate Fermi gases, and ultracold molecules.

Chin Cheng; Grimm, Rudolf; Julienne, Paul; Tiesinga, Eite [Department of Physics and James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States); Center for Quantum Physics and Institute of Experimental Physics, University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck (Austria) and Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Otto-Hittmair-Platz 1, 6020 Innsbruck (Austria); Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, 100 Bureau Drive, Gaithersburg, Maryland 20899-8423 (United States)

2010-04-15

297

The search for missing baryon resonances  

SciTech Connect

Experiments with electromagnetic probes are promising to search for baryon resonances that have been predicted by quark models but have not yet been observed. Data sets from different experiments show interesting resonance structures possibly due to so far unknown states. This might indicate that at least some of the missing baryon resonances start to show up.

Thoma, U. [2. Physikalisches Institut, University of Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany)

2005-05-06

298

Assessment of the McMaster KN Accelerator for Nuclear Resonance Absorption and Fluorescence Experiments with 28Si Nucleus Induced by 27Al(p, gamma)28Si Capture Reaction  

Microsoft Academic Search

This thesis represents a detailed assessment of the McMaster KN Accelerator site for the performance of a nuclear resonance absorption and flourescence phenomenon in the 28Si nucleus. The main focus of this work is the 27Al(p, ?) 28Si reaction, although other nuclear reactions are explored, such as: 27Al(p, p'?) 27Al and 27Al( p, ??)24Mg. The gamma yield experiments from all

Jovica Atanackovic

2011-01-01

299

Resonance Pacemakers in Excitable Media  

NASA Astrophysics Data System (ADS)

Chemical waves are initiated in an excitable medium by resonance with local periodic forcing of the excitability. Experiments are carried out with a photosensitive Belousov-Zhabotinsky medium, in which the excitability is varied according to the intensity of the imposed illumination. Complex resonance patterns are exhibited as a function of the amplitude and frequency of the forcing. Local resonance-induced wave initiation transforms the medium globally from a quiescent excitable steady state to a periodic state of successive traveling waves.

Chigwada, Tabitha Ruvarashe; Parmananda, P.; Showalter, Kenneth

2006-06-01

300

Resonating microbridge mass flow sensor  

Microsoft Academic Search

A resonating microbridge mass flow sensor with a frequency output is presented, based on standard IC and thin-film technologies, and on front-side anisotropic etching. The operation, realization, theory and experiments are described. The sensitivity is compared with that of a resonating membrane prototype. Preliminary results show a base resonance frequency of 85 kHz at a temperature elevation of the microbridge

Siebe Bouwstra; Rob Legtenberg; Harrie A. C. Tilmans; Miko Elwenspoek

1990-01-01

301

Localized ferromagnetic resonance using Magnetic Resonance Force Microscopy  

Microsoft Academic Search

Magnetic Resonance Force Microscopy (MRFM) is a novel approach to scanned probe imaging, combining the advantages of Magnetic Resonance Imaging (MRI) with Scanning Probe Microscopy (SPM) [1]. It has extremely high sensitivity that has demonstrated detection of individual electron spins [2] and small numbers of nuclear spins [3]. Here we describe our MRFM experiments on Ferromagnetic thin film structures. Unlike

Jongjoo Kim

2008-01-01

302

Microwave permittivity and permeability experiments in high-loss dielectrics: Caution with implicit Fabry-Prot resonance for negative imaginary permeability  

NASA Astrophysics Data System (ADS)

Various materials have been examined to obtain permittivity and permeability values required for detailed investigations on functional materials like microwave-absorbing and high-permittivity dielectrics. We call for caution when samples exhibit negative imaginary permeability, whether containing a resonance peak or not. In the retrieval procedure, the Fabry-Prot resonance (FPR) can produce a negative imaginary permeability, which should be classified as an extrinsic rather than an intrinsic physical attribute. In particular, for high-loss materials, the implicit FPR would bring a plausible negative imaginary permeability. Here we have listed a dielectric dispersion of FPR behavior for BiFeO3 samples.

Hou, Zhi-Ling; Zhang, Min; Kong, Ling-Bao; Fang, Hui-Min; Li, Zhong-Jun; Zhou, Hai-Feng; Jin, Hai-Bo; Cao, Mao-Sheng

2013-10-01

303

Dibaryon Resonances.  

National Technical Information Service (NTIS)

New degrees of freedom, like mesons and baryonic resonance on one band, or quarks and color on the other hand, can lead to possible exotic states of baryonic number 2. Large resonances have indeed been observed in both elastic and inelastic nucleon-nucleo...

B. Mayer

1987-01-01

304

A Suite of Solid-State NMR Experiments for RNA Intranucleotide Resonance Assignment in a 21?kDa Protein-RNA Complex.  

PubMed

Intranucleotide resonance of the 26mer box C/D RNA in complex with the L7Ae protein were assigned by solid-state NMR (ssNMR; see picture) spectroscopy. This investigation opens the way for studying RNA in large protein-RNA complexes by ssNMR spectroscopy. PMID:23893717

Marchanka, Alexander; Simon, Bernd; Carlomagno, Teresa

2013-07-26

305

Resonant interactions of diatomic molecules with intense laser fields: time-independent multi-channel Green function theory and application to experiment  

Microsoft Academic Search

The resonant interactions of diatomic molecules with UV and VUV intense laser radiation are investigated within an original non-perturbative approach of multi-channel nuclear wave functions and Green's functions. The interactions are considered in a quantum-electrodynamic picture where the laser field and molecule are treated as quantum objects. The presented theoretical approach is formulated as a multi-quantum technique to calculate analytically

Alexander I. Pegarkov

2000-01-01

306

Postmortem computed tomography and magnetic resonance imaging in a case of terminal-stage small cell lung cancer: an experience of autopsy imaging in tumor-related death  

Microsoft Academic Search

We report a case of terminal-stage small-cell lung cancer with multiple metastases in which postmortem computed tomography\\u000a and magnetic resonance imaging (collectively called autopsy imaging) were performed and correlated with conventional autopsy\\u000a findings. In this case, autopsy imaging provided contemporaneous data that supported conventional autopsy findings. Autopsy\\u000a imaging revealed the process of primary tumor growth, changes in metastatic lesions, and

Go Ikeda; Ryoo Yamamoto; Masatsune Suzuki; Hiroichi Ishikawa; Kazunori Kikuchi; Seiji Shiotani

2007-01-01

307

Resonant Auger decay of Xe* 4 d -1 5\\/2 6p : A contribution to the complete experiment from fluorescence polarization studies  

Microsoft Academic Search

Fluorescence polarimetry has been used to determine the relative partial-wave Auger decay widths for transitions to states of the XeII 5p46p multiplet after photoexcitation of the Xe*4d5\\/2-16p(J*=1) resonance by linearly and circularly polarized synchrotron radiation. Combination with data on the angular distribution and spin polarization of the Auger electrons, providing information on the relative phases of the amplitudes, constitutes the

P. O'Keeffe; S. Aloiese; S. Fritzsche; B. Lohmann; U. Kleiman; M. Meyer; A. N. Grum-Grzhimailo

2004-01-01

308

Piezoelectric d33 coefficients in foamed and layered polymer piezoelectrets from dynamic mechano-electrical experiments, electro-mechanical resonance spectroscopy and acoustic-transducer measurements  

NASA Astrophysics Data System (ADS)

Piezoelectrets are novel transducer materials which can be widely applied in sensors and actuators. Here, three techniques for determining piezoelectric d33 coefficients of piezoelectrets are reviewed and compared. Two types of piezoelectrets, polyethylene-naphthalate (PEN) polymer-foam piezoelectrets and fluorinated ethylene-propylene (FEP) copolymer-layer piezoelectrets, have been prepared and measured by means of dynamic, resonance, and acoustical methods. The dynamic measurements show that the d33 coefficient of PEN-foam samples clearly decreases with increasing stress, but 80% of the initial d33 can be retained after 1800 cycles of a continuous dynamic measurement in a mechanical fatigue test. The resonance measurements demonstrate that both PEN-foam and FEP-layer samples exhibit clear electro-mechanical resonances. PEN-foam samples show elastic moduli in the range from 1 to 12 MPa and d33 values up to 500 pC N-1, while FEP-layer samples show homogeneous elastic moduli of about 0.3 MPa and d33 values of about 280 pC N-1. The acoustical measurements reveal that both PEN-foam and FEP-layer samples exhibit stable frequency responses in the range from 5.7 to 20 kHz. In addition, d33 coefficients obtained with different experimental methods are in good agreement with each other, which confirms the reliability of all three techniques.

Fang, Peng; Hollnder, Lars; Wirges, Werner; Gerhard, Reimund

2012-03-01

309

Resonant Excitation of Plasma Wakefields  

SciTech Connect

We describe characteristics of the bunch train and plasma source used in a resonant plasma wakefield experiment at the Brookhaven National Laboratory Accelerator Test Facility. The bunch train has the proper correlated spread to unambiguously observe the expected energy gain by the witness bunch at resonance. The plasma density in the capillary discharge is sufficiently high to reach the resonance with the typical bunch train spacing of this experiment. It is also uniform over more than 3/4 of the 2 cm-long capillary.

Muggli, P.; Allen, B. [University of Southern California, Los Angeles, CA 90089 (United States); Yakimenko, V.; Fedurin, M.; Kusche, K.; Babzien, M. [Brookhaven National Laboratory, Upton, NY 11973 (United States)

2010-11-04

310

Resonant Auger decay of Xe{sup *} 4d{sub 5/2}{sup -1}6p: A contribution to the complete experiment from fluorescence polarization studies  

SciTech Connect

Fluorescence polarimetry has been used to determine the relative partial-wave Auger decay widths for transitions to states of the Xe II 5p{sup 4}6p multiplet after photoexcitation of the Xe{sup *} 4d{sub 5/2}{sup -1}6p(J{sup *}=1) resonance by linearly and circularly polarized synchrotron radiation. Combination with data on the angular distribution and spin polarization of the Auger electrons, providing information on the relative phases of the amplitudes, constitutes the complete experiment on the Auger decay. Multiconfiguration relativistic calculations of the amplitudes have been performed and compared to the measurements.

O'Keeffe, P. [LURE, Centre Universitaire Paris--Sud, Batiment 209D, F-91898 Orsay Cedex (France); Aloiese, S.; Meyer, M. [LURE, Centre Universitaire Paris--Sud, Batiment 209D, F-91898 Orsay Cedex (France); CEA/DRECAM/SPAM, CEN Saclay, F-91105 Gif-sur-Yvette (France); Fritzsche, S. [Fachbereich Physik, Universitaet Kassel, Heinrich-Plett Strasse 40, D-34132 Kassel (Germany); Lohmann, B. [Institut fuer Theoretische Physik, Westfaelische Wilhelms-Universitaet Muenster, Wilhelm-Klemm-Strasse 9, D-48149 Muenster (Germany); Kleiman, U. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Grum-Grzhimailo, A. N. [LURE, Centre Universitaire Paris--Sud, Batiment 209D, F-91898 Orsay Cedex (France); Institute of Nuclear Physics, Moscow State University, Moscow 119899 (Russian Federation)

2004-07-01

311

Conference report: functional magnetic resonance imaging for beginners--a review of the fMRI experience IV, 13-14 May 2002, Natcher Conference Center, National Institutes of Health, Bethesda, MD.  

PubMed

The fourth fMRI Experience meeting was held at the Bethesda, Maryland campus of the National Institutes of Health on May 13th and 14th, 2002. The purpose of the meeting was to provide a platform for students working with functional magnetic resonance imaging (fMRI) to pres ent their research to an international audience of peers. This year"s meeting featured special lectures from Dr. Leslie Ungerleider ("Imaging Mechanisms of Visual Attention") and Dr. Daniel Weinberger ("Genetic Variation and fMRI Response"). PMID:12920320

Caggiano, Daniel; Joffily, Mateus

2002-06-27

312

Closed solution to the Baker-Campbell-Hausdorff problem: exact effective Hamiltonian theory for analysis of nuclear-magnetic-resonance experiments.  

PubMed

A closed solution to the Baker-Campbell-Hausdorff problem is described. The solution, which is based on the Cayley-Hamilton theorem, allows the entanglement between exponential operators to be described by an exact finite series expansion. Addressing specifically the special unitary Lie groups SU(2), SU(3), and SU(4), we derive expansion formulas for the entangled exponential operator as well as for the effective Hamiltonian describing the net evolution of the quantum system. The capability of our so-called exact effective Hamiltonian theory for analytical and numerical analysis is demonstrated by evaluation of multiple-pulse methods within liquid- and solid-state nuclear-magnetic-resonance spectroscopy. The examples include composite pulses for inversion, decoupling, and dipolar recoupling, as well as coherence-order- and spin-state-selective double- to single-quantum conversion, homonuclear dipolar decoupling, finite rf excitation for quadrupolar nuclei, heteronuclear coherence transfer, and gates for quantum computation. PMID:11863504

Untidt, Thomas S; Nielsen, Niels Chr

2002-01-23

313

Fundamental mode rectangular waveguide system for electron-cyclotron resonant heating (ECRH) for tandem mirror experiment-upgrade (TMX-U)  

SciTech Connect

We present a brief history of TMX-U's electron cyclotron resonant heating (ECRH) progress. We emphasize the 2-year performance of the system, which is composed of four 200-kW pulsed gyrotrons operated at 28 GHz. This system uses WR42 waveguide inside the vacuum vessel, and includes barrier windows, twists, elbows, and antennas, as well as custom-formed waveguides. Outside the TMX-U vessel are directional couplers, detectors, elbows, and waveguide bends in WR42 rectangular waveguide. An arc detector, mode filter, eight-arm mode converter, and water load in the 2.5-in. circular waveguide are attached directly to the gyrotron. Other specific areas discussed include the operational performance of the TMX-U pulsed gyrotrons, windows and component arcing, alignment, mode generation, and extreme temperature variations. Solutions for a number of these problems are described.

Rubert, R.R.; Felker, B.; Stallard, B.W.; Williams, C.W.

1983-12-01

314

A Dual Pass Band Filter with Embedded CPW Resonator  

Microsoft Academic Search

A dual passband filter using both microstrip and CPW resonators is proposed. The CPW resonators are embedded into the microstrip resonators to miniaturize the filter size. The cross coupling between the input and output resonators is introduced to exhibit a pair of transmission zeros in the two sides of the pass band, thus increasing the selectivity. An experiment has done

Bo-Chun Chen; Tze-Min Shen; Ting-Yi Huang; Ruey-Beei Wu

2007-01-01

315

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

316

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

317

Determination of the Parameters of the Electric Field Gradient Tensor for Nuclei with Half Integral Spin from Zeeman-Split NQR Spectra  

Microsoft Academic Search

A new method is proposed for determining the magnitude of the coupling constant, the asymmetry parameter and the orientation of the principal axes of the electric field gradient tensor at the site of a quadrupole nucleus with half integral spin. A function is constructed from the first order splitting of the nuclear quadrupole resonance absorption line produced by a small

S. Sengupta; R. Roy; A. K. Saha

1972-01-01

318

Resonant behavior of dielectric objects (electrostatic resonances).  

PubMed

Resonant behavior of dielectric objects occurs at certain frequencies for which the object permittivity is negative and the free-space wavelength is large in comparison with the object dimensions. Unique physical features of these resonances are studied and a novel technique for the calculation of resonance values of permittivity, and hence resonance frequencies, is proposed. Scale invariance of resonance frequencies, unusually strong orthogonality properties of resonance modes, and a two-dimensional phenomenon of "twin" spectra are reported. The paper concludes with brief discussions of optical controllability of these resonances in semiconductor nanoparticles and a plausible, electrostatic resonance based, mechanism for nucleation and formation of ball lightning. PMID:14754117

Fredkin, D R; Mayergoyz, I D

2003-12-19

319

Estimation of the age of human bloodstains by electron paramagnetic resonance spectroscopy: long-term controlled experiment on the effects of environmental factors.  

PubMed

In this study, we examined the efficacy and limitations of electron paramagnetic resonance (EPR) for estimating the age of human bloodstains. At 77K, human bloodstains give four striking EPR signals in the g=6.2 (g6), 4.3 (g4), 2.27 (H) and 2.005 (R) regions due to ferric high-spin, ferric non-heme, ferric low-spin and free radical species, respectively. We found that plotting double logarithms of the EPR intensity ratio of H/g4 versus days past bleeding gave a linear correlation up to 432 days with an error range within 25% of the actual number of days under controlled conditions. However, environmental factors such as differences of absorbent, light exposure and fluctuations of storage temperature affected the changes of these EPR-active compounds, which result in misestimation of the time since bleeding occurred. Therefore, one should take such factors into account in estimating the period since bleeding by this method. PMID:15939175

Fujita, Yoshihiko; Tsuchiya, Koichiro; Abe, Shinji; Takiguchi, Yoshiharu; Kubo, Shin-ichi; Sakurai, Hiromu

2005-04-22

320

Magnetic resonance fingerprinting.  

PubMed

Magnetic resonance is an exceptionally powerful and versatile measurement technique. The basic structure of a magnetic resonance experiment has remained largely unchanged for almost 50?years, being mainly restricted to the qualitative probing of only a limited set of the properties that can in principle be accessed by this technique. Here we introduce an approach to data acquisition, post-processing and visualization--which we term 'magnetic resonance fingerprinting' (MRF)--that permits the simultaneous non-invasive quantification of multiple important properties of a material or tissue. MRF thus provides an alternative way to quantitatively detect and analyse complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to identify the presence of a specific target material or tissue, which will increase the sensitivity, specificity and speed of a magnetic resonance study, and potentially lead to new diagnostic testing methodologies. When paired with an appropriate pattern-recognition algorithm, MRF inherently suppresses measurement errors and can thus improve measurement accuracy. PMID:23486058

Ma, Dan; Gulani, Vikas; Seiberlich, Nicole; Liu, Kecheng; Sunshine, Jeffrey L; Duerk, Jeffrey L; Griswold, Mark A

2013-03-14

321

Investigations of the radial propagation of blob-like structure in a non-confined electron cyclotron resonance heated plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak  

SciTech Connect

A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E x B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed.

Ogata, R.; Liu, H. Q.; Ishiguro, M.; Ikeda, T. [Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Hanada, K.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A. [Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Nishino, N. [Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University (Japan); Collaboration: QUEST Group

2011-09-15

322

Enhanced spin fluctuations in the As-based filled skutterudite LaFe4As12 : A L139a NMR and A75s NQR study  

NASA Astrophysics Data System (ADS)

We have grown single crystals of the itinerant-electron weak ferromagnet LaFe4As12 (TC=3.8K) and refined its crystal structure parameters. We report experimental results of magnetic susceptibility and nuclear magnetic resonance at the La site and nuclear quadrupole resonance at the As site in the paramagnetic state for this compound. The temperature dependences of the static magnetic susceptibility, the L139a Knight shift, and the reciprocal of the product of the spin-lattice relaxation time and temperature (1/T1T) of both L139a and A75s nuclei can be consistently understood in terms of self-consistent renormalization theory of spin fluctuations for weak itinerant-electron ferromagnets.

Nowak, B.; ?oga?, O.; Pietraszko, A.; Baumbach, R. E.; Maple, M. B.; Henkie, Z.

2009-06-01

323

Cl-NQR study of the structural order-disorder transition in (CH3NH3)2MnCl4  

Microsoft Academic Search

The temperature dependence of the Cl nuclear quadrupole resonance for the two chemically inequivalent chlorine sites in the perovskitic layer structure compound (CH3NH3)2 MnCl4 has been measured around the second order phase transition at 393.7 K. A value of the critical exponent ? of the order parameter was determined to be ? = 0.250 0.005 which is intermediate between

R. Kind; J. Roos

1976-01-01

324

Gravitoelectromagnetic resonances  

NASA Astrophysics Data System (ADS)

The interaction between gravitational and electromagnetic radiation has a rather long research history. It is well known, in particular, that gravity-wave distortions can drive propagating electromagnetic signals. Since forced oscillations provide the natural stage for resonances to occur, gravitoelectromagnetic resonances have been investigated as a means of more efficient gravity-wave detection methods. In this report, we consider the coupling between the Weyl and the Maxwell fields on a Minkowski background, which also applies to astrophysical environments where gravity is weak, at the second perturbative level. We use covariant methods that describe gravitational waves via the transverse component of the shear, instead of pure-tensor metric perturbations. The aim is to calculate the properties of the electromagnetic signal, which emerges from the interaction of its linear counterpart with an incoming gravitational wave. Our analysis shows how the wavelength and the amplitude of the gravitationally driven electromagnetic wave vary with the initial conditions. More specifically, for certain initial data, the amplitude of the induced electromagnetic signal is found to diverge. Analogous, diverging, gravitoelectromagnetic resonances were also reported in cosmology. Given that, we extend our Minkowski space study to cosmology and discuss analogies and differences in the physics and in the phenomenology of the Weyl-Maxwell coupling between the aforementioned two physical environments.

Tsagas, Christos G.

2011-08-01

325

Correlation of primary relaxations and high-frequency modes in supercooled liquids. I. Theoretical background of a nuclear magnetic resonance experiment.  

PubMed

The question regarding a possible correlation of the time scales of primary and secondary relaxations in supercooled liquids is formulated quantitatively. It is shown how this question can be answered using spin-lattice relaxation weighted stimulated-echo experiments, which are presented in an accompanying paper [A. Nowaczyk, B. Geil, G. Hinze, and R. Bhmer, Phys. Rev. E 74, 041505 (2006)]. General theoretical expressions relevant for the description of such experiments in the presence of correlation effects are derived. These expressions are analyzed by Monte Carlo integration for various correlation scenarios also including exchange processes, which are the hallmark of dynamical heterogeneity. The results of these numerical simulations provide clear signatures that allow one to distinguish uncorrelated from differently correlated cases. Since modified spin-lattice relaxation effects occur in the presence of nonexponential magnetization recovery, it is shown how to correct for them to a good approximation. PMID:17155062

Geil, B; Diezemann, G; Bhmer, R

2006-10-30

326

Re-examination of metabolic fluxes in Escherichia coli during anaerobic fermentation of glucose using 13 C labeling experiments and 2-dimensional nuclear magnetic resonance (NMR) spectroscopy  

Microsoft Academic Search

Improved design of metabolic flux estimation using mixed label 13C labeling experiments and identifiability analysis motivated re-examination of metabolic fluxes during anaerobic fermentation\\u000a in the Escherichia coli. Comprehensive metabolic flux maps were determined by using a mixture of differently labeled glucose and compared to conventional\\u000a flux maps obtained using extracellular measurements and comprehensive metabolic flux maps obtained using only U-13C

Madhuresh K. Choudhary; Jong Moon Yoon; Ramon Gonzalez; Jacqueline V. Shanks

2011-01-01

327

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

Microsoft Academic Search

We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSR) which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of MSR of a homogeneous object

Yaroslav Urzhumov; Wenchen Chen; Chris Bingham; Willie Padilla; David R. Smith

2011-01-01

328

Magnetic Resonance Studies of Defects in GaN With Reduced Dislocation Densities.  

National Technical Information Service (NTIS)

Magnetic resonance experiments, including optically detected magnetic resonance (ODMR) and electron paramagnetic resonance (EPR), have been performed on Si-doped homoepitaxial GaN layers grown by MOCVD and on high quality, free-standing (approximately 200...

E. Glasera G. C. Braga J. J. Freitas M. E. Twigg W. E. Carlos

2001-01-01

329

Saw Blades and Resonance  

NASA Astrophysics Data System (ADS)

This paper describes an inexpensive, classroom experiment that allows students to quantitatively investigate resonance using a hacksaw blade. The blade clamped to the edge of a table forms a cantilever that may vibrate at any of a number of preferred frequencies. A small cylindrical magnet is fixed to the saw blade. An electromagnetic coil powered by a frequency generator causes large-amplitude vibrations of the saw blade at the resonant frequencies. Vibrations of a similar system, a vibrating car antenna, have been discussed by Newburgh and Newburgh.1 The dramatic increases in the oscillation amplitude are both instructive and fascinating. Analogies may be drawn to systems ranging from a child on a swing to the Tacoma Narrows bridge.

Liebl, Michael

2005-05-01

330

Surface Plasmon Resonance Laboratory  

NSDL National Science Digital Library

This lab focuses on the optical generation and modeling of Surface Plasmons, in particular the attempt of predicting and generating a resonance condition in a three layer system; glass, metal and air. The lab is designed to easily create a film and test its resonance with minimal cost and time to prepare the setup between testing. This concept can be demonstrated in a more elaborate setup, but is not necessary unless this demonstration will be used as a research instrument afterwards. This lab is comprised of four main parts: 1. Understanding the theory of SPR, through deriving the Fresnel equations from Maxwell Equations. 2. Determining the optimal conditions for the Prism Coating (Modeling). 3. Fabricating the coated prism with a deposition system. 4. Comparing modeling and experiment, explain error.

Snchez, Erik

2010-11-24

331

All-resonant control of superconducting resonators.  

PubMed

An all-resonant method is proposed to control the quantum state of superconducting resonators. This approach uses a tunable artificial atom linearly coupled to resonators, and allows for efficient routes to Fock state synthesis, qudit logic operations, and synthesis of NOON states. This resonant approach is theoretically analyzed, and found to perform significantly better than existing proposals using the same technology. PMID:23215585

Strauch, Frederick W

2012-11-20

332

All-Resonant Control of Superconducting Resonators  

NASA Astrophysics Data System (ADS)

An all-resonant method is proposed to control the quantum state of superconducting resonators. This approach uses a tunable artificial atom linearly coupled to resonators, and allows for efficient routes to Fock state synthesis, qudit logic operations, and synthesis of NOON states. This resonant approach is theoretically analyzed, and found to perform significantly better than existing proposals using the same technology.

Strauch, Frederick W.

2012-11-01

333

If It's Resonance, What is Resonating?  

ERIC Educational Resources Information Center

|The phenomenon under the name "resonance," which, is based on the mathematical analogy between mechanical resonance and the behavior of wave functions in quantum mechanical exchange phenomena was described. The resonating system does not have a structure intermediate between those involved in the resonance, but instead a structure which is

Kerber, Robert C.

2006-01-01

334

Electroexcitation of nucleon resonances  

NASA Astrophysics Data System (ADS)

We review recent progress in the investigation of the electroexcitation of nucleon resonances, both in experiment and in theory. We describe current experimental facilities, the experiments performed on ? and ? electroproduction off protons, and theoretical approaches used for the extraction of resonance contributions from the experimental data. The status of 2?, K?, and K? electroproduction is also presented. The most accurate results have been obtained for the electroexcitation amplitudes of the four lowest excited states, which have been measured in a range of Q2 up to 8 and 4.5 GeV 2 for ?(1232)P33, N(1535)S11 and N(1440)P11, N(1520)D13, respectively. These results have been confronted with calculations based on lattice QCD, large-Nc relations, perturbative QCD (pQCD), and QCD-inspired models. The amplitudes for the ?(1232) indicate large pion-cloud contributions at low Q2 and do not show any sign of approaching the pQCD regime for Q2<7GeV. Measured for the first time, the electroexcitation amplitudes of the Roper resonance, N(1440)P11, provide strong evidence for this state as a predominantly radial excitation of a three-quark (3q) ground state, with additional non-3-quark contributions needed to describe the low Q2 behavior of the amplitudes. The longitudinal transition amplitude for the N(1535)S11 was determined and has become a challenge for quark models. Explanations may require large meson-cloud contributions or alternative representations of this state. The N(1520)D13 clearly shows the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2>0.5GeV, confirming a long-standing prediction of the constituent quark model. The interpretation of the moments of resonance transition form factors in terms of transition transverse charge distributions in infinite momentum frame is presented.

Aznauryan, I. G.; Burkert, V. D.

2012-01-01

335

Ringing phenomenon of the fiber ring resonator.  

PubMed

A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well. PMID:17676092

Ying, Diqing; Ma, Huilian; Jin, Zhonghe

2007-08-01

336

Sequential resonant tunneling in quantum cascade lasers  

SciTech Connect

A model of sequential resonant tunneling transport among two-dimensional subbands that takes into account explicitly elastic scattering is investigated. It is compared to transport measurements performed on quantum cascade lasers, where resonant tunneling processes are known to be dominating. Excellent agreement is found between experiment and theory over a large range of current, temperature, and device structures.

Terazzi, Romain; Gresch, Tobias; Wittmann, Andreas; Faist, Jerome [Quantum Optoelectronics Group, Institute for Quantum Electronics, ETH, 8086 Zuerich (Switzerland)

2008-10-15

337

Multiple Ferromagnetic Resonance in Ferrite Spheres  

Microsoft Academic Search

Ferromagnetic resonance experiments have been performed on single crystal spheres of manganese and manganese-zinc ferrites placed in field configurations having large gradients in the rf magnetic field at the sample site. Five major and several minor resonant absorptions are observed extending over a region of 700 oersteds at room temperature. The line spacings are essentially independent of sphere size. The

Robert L. White; Irvin H. Solt

1956-01-01

338

An Active Microwave Filter with Dielectric Resonator  

Microsoft Academic Search

An active microwave filter has been newly developed by using dielectric resonators combined with active elements. The purpose of this paper is to describe about the new technique and the performance of the active filter at 6 GHz band. The value of the equivalent unloaded Q of the resonant element exceeds 37,000 in our experiment.

H. Matsumura; Y. Konishi

1979-01-01

339

Dendritic versus somatic resonance  

Microsoft Academic Search

Here, we investigate to what extent and under which circumstances cells with dendritic resonance may be misclassified as nonresonant by somatic measurement of resonance properties. We use simple conductance-based multicompartmental models to analyze the effect of dendritic resonance on somatic input (and hence resonance estimates based on somatic recordings). We find that indeed, even a strong dendritic resonance may not

Ekaterina A Zhuchkova; Susanne Schreiber

2011-01-01

340

Resonant charging  

NASA Astrophysics Data System (ADS)

It has been shown (Athas et al., 1994) that adiabatic switching can significantly reduce the dynamic power dissipation in an integrated circuit. Due to the overhead in the realization of adiabatic logic blocks (Saas et al., 2000) the best results are achieved when it is used only for charging dominant loads in an integrated circuit (Voss and Glessner, 2001). It has been demonstrated (Saas et al., 2001) that a multi stage driver is needed for minimal power dissipation. In this article a complete three stage driver including the generation of oscillating supply is described. To obtain a minimal power dissipation during synchronization the resonant frequency has to be constant. Therefore the waveforms for the logic states of the signal and the realization of a single stage differ from those presented in (Saas et al., 2001). In the H-SPICE simulations losses of the inductor are taken into account. This allows to estimate the power reduction that is achievable in a real system.

Saas, C.; Nossek, J. A.

2003-05-01

341

Controlling chaos in ferromagnetic resonance  

Microsoft Academic Search

The chaotic response of yttirum iron garnet (YIG) films in high-power ferromagnetic resonance (FMR) has been successfully controlled in experiments using a time-delayed control method. The ac component of the FMR signal was delayed and used to perturb a system parameter, the static magnetic field. The application of the perturbations initially modified the chaotic oscillations in the FMR absorption signal,

P. E. Wigen; M. Ye; D. W. Peterman

1995-01-01

342

Resonance phenomena in fluid media  

Microsoft Academic Search

Studies were made to detect the presence of a memory in fluid media. The experiments revealed that the effect of electromagnetic radiation on fluid media can be explained by the phenomenon of resonant response of the system receiving the radiation. Studies were made on plant seeds and yeasts, accompanied by catalytic chemical reactions and several physical and chemical tests. Sorption

A. T. Lukyanov; V. M. Inyushin; A. P. Gorokhov

1987-01-01

343

Airborne surface plasmon resonance biosensing  

Microsoft Academic Search

On March 14, 2003 an experimental aircraft fitted with surface plasmon resonance (SPR) biosensors connected to an air sampling system performed a 90-minute flight over Renton, Washington, demonstrating the first-ever use of SPR sensors for airborne biodetection. In this paper, we describe the instrumentation constructed for this purpose, the experiment conducted, and the results obtained. Instrumentation was based on Texas

Timothy M. Chinowsky; Alexei Naimushin; Scott Soelberg; Charles Spinelli; Peter Kauffman; Sinclair S. Yee; Clement E. Furlong

2004-01-01

344

Notes on Experiments.  

ERIC Educational Resources Information Center

|Describes four physics experiments including "Investigation of Box Resonances Using a Micro"; "A Direct Reading Wattmeter, DC or AC"; "Exercises in the Application of Ohm's Law"; and "Hysteresis on Gas Discharges." Discusses procedures, instrumentation, and analysis in each example. (CW)|

Physics Education, 1988

1988-01-01

345

Sonic resonance in a sandwiched electrorheological panel  

NASA Astrophysics Data System (ADS)

We have studied the sound transmission properties of a flexible sandwiched electrorheological (ER) panel. It shows that, at a frequency range of 80-150 Hz, the sound pressure level spectrum exhibits a resonant peak. The resonant peak makes a shift to high frequency and the phase of the transmitted wave changes with an increase of the applied electric field. A vibration-radiation model is set up to simulate the sound radiating process and verifies a resonant effect in the ER panel in qualitative agreement with experiments. The tunable resonance effect in the ER panel would be useful in constructing tunable phononic crystals and other acoustic devices.

Tang, Hong; Luo, Chunrong; Zhao, Xiaopeng

2005-07-01

346

Empathy in schizophrenia: impaired resonance.  

PubMed

Resonance is the phenomenon of one person unconsciously mirroring the motor actions as basis of emotional expressions of another person. This shared representation serves as a basis for sharing physiological and emotional states of others and is an important component of empathy. Contagious laughing and contagious yawning are examples of resonance. In the interpersonal contact with individuals with schizophrenia we can often experience impaired empathic resonance. The aim of this study is to determine differences in empathic resonance-in terms of contagion by yawning and laughing-in individuals with schizophrenia and healthy controls in the context of psychopathology and social functioning. We presented video sequences of yawning, laughing or neutral faces to 43 schizophrenia outpatients and 45 sex- and age-matched healthy controls. Participants were video-taped during the stimulation and rated regarding contagion by yawning and laughing. In addition, we assessed self-rated empathic abilities (Interpersonal Reactivity Index), psychopathology (Positive and Negative Syndrome Scale in the schizophrenia group resp. Schizotypal Personality Questionnaire in the control group), social dysfunction (Social Dysfunction Index) and executive functions (Stroop, Fluency). Individuals with schizophrenia showed lower contagion rates for yawning and laughing. Self-rated empathic concern showed no group difference and did not correlate with contagion. Low rate of contagion by laughing correlated with the schizophrenia negative syndrome and with social dysfunction. We conclude that impaired resonance is a handicap for individuals with schizophrenia in social life. Blunted observable resonance does not necessarily reflect reduced subjective empathic concern. PMID:19377866

Haker, Helene; Rssler, Wulf

2009-04-18

347

Coherent Nuclear Resonance Fluorescence  

NASA Astrophysics Data System (ADS)

For a long time, the impact of ideas with respect to coherency and scattering on the art and science of Mssbauer spectroscopy was not very essential. The main line of development of Mssbauer experiments rested in the frame of absorption spectroscopy. Mssbauer physicists dealt mostly with absorption spectra taken either in traditional transmission experiments or in measurements of the conversion electron yield. For the interpretation and description of these spectra, it was appropriate to use the picture of interaction of ?-quantum with an individual nucleus where the nuclear resonant absorption cross-section was applied. The coherent properties of radiation and those of the interaction mechanism were not explicitly involved in these studies. In the meantime, coherent phenomena with Mssbauer ?-rays were thoroughly investigated, starting soon after Mssbauer's discovery. The present paper is aimed to illuminate this side of the Mssbauer story.

Smirnov, G. V.

348

A wireless power telemetry with self-calibrated resonant frequency  

Microsoft Academic Search

A wireless power telemetry with self-calibrated resonant frequency is presented. The proposed calibration scheme adjusts the resonant frequency of inductively secondary coil to match the incident frequency of inductively primary coil. To adjust the resonant frequency of the secondary coil, the received power efficiency is improved. By experimented results, the overall power efficiency with frequency calibration is improved by a

Wei-Jen Huang; Chein-Lung Chen; Shen-Iuan Liu

2009-01-01

349

Optically detected magnetic resonance (ODMR) of photoexcited triplet states  

Microsoft Academic Search

Optically Detected Magnetic Resonance (ODMR) is a double resonance technique which combines optical measurements (fluorescence,\\u000a phosphorescence, absorption) with electron spin resonance spectroscopy. After the first triplet-state ODMR experiments in\\u000a zero magnetic field reported in 1968 by Schmidt and van der Waals, the number of double resonance studies on excited triplet\\u000a states grew rapidly. Photosynthesis has proven to be a fruitful

Donatella Carbonera

2009-01-01

350

Electroexcitation of nucleon resonances  

SciTech Connect

We review recent progress in the investigation of the electroexcitation of nucleon resonances, both in experiment and in theory. The most accurate results have been obtained for the electroexcitation amplitudes of the four lowest excited states, which have been measured in a range of Q2 up to 8 and 4.5 GeV2 for the Delta(1232)P33, N(1535)S11 and N(1440)P11, N(1520)D13, respectively. These results have been confronted with calculations based on lattice QCD, large-Nc relations, perturbative QCD (pQCD), and QCD-inspired models. The amplitudes for the Delta(1232) indicate large pion-cloud contributions at low Q2 and don't show any sign of approaching the pQCD regime for Q2<7 GeV2. Measured for the first time, the electroexcitation amplitudes of the Roper resonance, N(1440)P11, provide strong evidence for this state as a predominantly radial excitation of a three-quark (3q) ground state, with additional non-3-quark contributions needed to describe the low Q2 behavior of the amplitudes. The longitudinal transition amplitude for the N(1535)S11 was determined and has become a challenge for quark models. Explanations may require large meson-cloud contributions or alternative representations of this state. The N(1520)D13 clearly shows the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 > 0.5 GeV2, confirming a long-standing prediction of the constituent quark model. The interpretation of the moments of resonance transition form factors in terms of transition transverse charge distributions in infinite momentum frame is presented.

Inna Aznauryan, Volker D. Burkert

2012-01-01

351

Potential of Delayed Gadolinium Enhancement Magnetic Resonance for Quantification of Reverse Remodeling of the Peri-Infarct Zone in Patients with Ischemic Cardiomyopathy Treated with Chronic Vasodilator Therapy: Initial Experience  

PubMed Central

Purpose The peri-infarct zone represents the morphological substrate for re-entry ventricular tachycardia after myocardial infarction (MI) and its extent is a strong predictor of major cardiac events. Although delayed gadolinium enhancement magnetic resonance (DGE-MRI) was shown to allow for detailed characterization of MI by quantifying infarct core zone and peri-infarct zone volume, potentials of DGE-MRI for measuring changes in peri-infarct zone volume are unknown. Therefore, we aimed to assess changes in volume of the peri-infarct zone among patients with ischemic cardiomyopathy treated with chronic vasodilator therapy. Materials and Methods Core and peri-infarct zone volumes as assessed with DGE-MRI were measured in 5 patients at baseline and following 6 months treatment with sustained-release dipyridamole. Results Core zone volume remained stable during follow-up [median(range): 19ml(942) vs. 16ml(1146); p=0.785]. The ratio between the peri-infarct zone and the core zone volume decreased significantly at 6 month as compared to baseline [median(range): 0.22(0.190.42) vs. 0.18(0.090.32); p=0.043], and a trend towards reduction in peri-infarct zone volume was found [median(range): 5ml(28) vs. 3ml(26); p=0.059]. The peri-infarct zone volume decreased in all but 1 patient over the follow-up. Conclusions This initial experience suggests that reverse remodeling of the peri-infarct zone with reduction in peri-infarct zone volume may take place in patients with ischemic cardiomyopathy. Quantification of this process may be feasible with DGE-MRI, but further studies are needed to confirm this hypothesis and to further clarify the role of DGE-MRI for the assessment of changes in peri-infarct zone volume in patients with ischemic cardiomyopathy.

Muzzarelli, Stefano; Ordovas, Karen Gomes; Cannavale, Giuseppe; Naeger, David; Michaels, Andrew D.; Higgins, Charles B.

2011-01-01

352

Chapter 1 Magnetic Resonance Contributions to Other Sciences  

Microsoft Academic Search

In 1947, I.I. Rabi invented the molecular beam magnetic resonance method for the important, but limited purpose, of measuring nuclear magnetic moments and five of us working in his laboratory immediately began such experiments. The first experiments with LiCl gave the expected single resonance for each nucleus, but we were surprised to discover six resonances for the proton in H2,

Norman F. Ramsey

2008-01-01

353

Ferromagnetic resonance force microscopy of a permalloy film  

Microsoft Academic Search

We describe Ferromagnetic Resonance Force Microscopy (FMRFM) experiments performed on a 50 nm thick permalloy film. We have studied the evolution of the FMRFM force spectra as a function of temperature. The temperature-dependent studies show a decrease of the ferromagnetic resonance field with increasing temperature which we attribute to the temperature-dependent changes of the saturation magnetization. The experiments demonstrate the

E. Nazaretski; I. Martin; R. Movshovich; D. V. Pelekhov; M. Zalalutdinov; J. W. Baldwin; T. Mewes; B. Houston

2007-01-01

354

Instrumental Analysis Experiments  

NSDL National Science Digital Library

This site features laboratory experiments for undergraduate instrumental analysis. Topics include data acquisition, control of instrumentation (gas chromatography, polarography, voltammetry, atomic absorption, robots), infrared spectroscopy, liquid chromatography, and nuclear magnetic resonance. Extensive use of LabView, Excel, and computers. Experiments are available for download in PDF format.

Walters, John P.

2011-04-20

355

Magnetic resonance of ferrite nanoparticles  

Microsoft Academic Search

Ferromagnetic resonance (FMR) experiments at 9.26GHz on non-interacting maghemite (?-Fe2O3) nanoparticles of ferrofluids are performed as a function of temperature (3.5300K) and particle diameter (4.810nm). The orientational mobility of the particles inside the fluid is employed to monitor the orientational distribution of the anisotropy axes by solidifying the MF matrix under the external field. On those textured suspensions, angular analysis

F. Gazeau; J. C Bacri; F. Gendron; R. Perzynski; Yu. L Raikher; V. I. Stepanov; E. Dubois

1998-01-01

356

Hadronic Resonances from Lattice QCD  

SciTech Connect

The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.

John Bulava; Robert Edwards; George Fleming; K. Jimmy Juge; Adam C. Lichtl; Nilmani Mathur; Colin Morningstar; David Richards; Stephen J. Wallace

2007-06-16

357

Hadronic Resonances from Lattice QCD  

SciTech Connect

The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.

Lichtl, Adam C. [RBRC, Brookhaven National Laboratory, Upton, NY 11973 (United States); Bulava, John; Morningstar, Colin [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Edwards, Robert; Mathur, Nilmani; Richards, David [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Fleming, George [Yale University, New Haven, CT 06520 (United States); Juge, K. Jimmy [Department of Physics, University of the Pacific, Stockton, CA 95211 (United States); Wallace, Stephen J. [University of Maryland, College Park, MD 20742 (United States)

2007-10-26

358

Magnetic resonance of a single molecular spin  

NASA Astrophysics Data System (ADS)

THE introduction of optical detection methods for observing magnetic resonance transitions in metastable paramagnetic states1-4 has contributed enormously to our understanding of the properties of photoexcited molecules in condensed phases. In such experiments the luminescence intensity is recorded as a function of the frequency of an applied microwave field. At resonance with transitions between sublevels of a metastable paramagnetic state, the lifetime of the metastable state is altered and a consequent change in the luminescence intensity is observed. Here we report the observation of such optically detected magnetic resonance transitions for the triplet state of a single pentacene molecule embedded in a p-terphenyl host crystal. This result has been obtained by combining the conventional optical detection technique for observing magnetic resonance transitions1-4 with the new single-molecule optical detection methods developed recently5,6. This observation opens the way for magnetic resonance studies in condensed phases with single-molecule sensitivity.

Khler, J.; Disselhorst, J. A. J. M.; Donckers, M. C. J. M.; Groenen, E. J. J.; Schmidt, J.; Moerner, W. E.

1993-05-01

359

Integral data analysis for resonance parameters determination  

SciTech Connect

Neutron time-of-flight experiments have long been used to determine resonance parameters. Those resonance parameters have then been used in calculations of integral quantities such as Maxwellian averages or resonance integrals, and results of those calculations in turn have been used as a criterion for acceptability of the resonance analysis. However, the calculations were inadequate because covariances on the parameter values were not included in the calculations. In this report an effort to correct for that deficiency is documented: (1) the R-matrix analysis code SAMMY has been modified to include integral quantities of importance, (2) directly within the resonance parameter analysis, and (3) to determine the best fit to both differential (microscopic) and integral (macroscopic) data simultaneously. This modification was implemented because it is expected to have an impact on the intermediate-energy range that is important for criticality safety applications.

Larson, N.M.; Leal, L.C.; Derrien, H.

1997-09-01

360

Electronically Tunable Surface-Coil-Type Resonator for L-Band EPR Spectroscopy  

Microsoft Academic Search

The automatic frequency control (AFC) circuit in conventional electron paramagnetic resonance (EPR) spectrometers automatically tunes the microwave source to the resonance frequency of the resonator. The circuit works satisfactorily for samples stable enough that the geometric relations in the resonance structure do not change in a significant way. When EPR signals are measured during in vivo experiments with small rodents,

Hiroshi Hirata; Tadeusz Walczak; Harold M Swartz

2000-01-01

361

Excitation of the l=12 cyclotron resonance in the NRL modified betatron accelerator  

Microsoft Academic Search

The basic periodicity in the NRL device is twelve-fold. There are twelve toroidal field coils, twelve sectors, and so on. For a long time, the l equals 12 resonance was the dominant resonance in the experiment. To test the importance of the l equals 12 resonance, we have intentionally introduces an l equals 12 field error using twelve resonant coils.

Lek K. Len; T. Smith; Peter Loschialpo; Joseph Mathew; S. J. Marsh; Demos Dialetis; Jeffry Golden; Jeng-Hsien Chang; Christos A. Kapetanakos

1992-01-01

362

Solid-state NMR triple-resonance backbone assignments in a protein  

Microsoft Academic Search

Triple-resonance solid-state NMR spectroscopy is demonstrated to sequentially assign the 13C' and 15N amide backbone resonances of adjacent residues in an oriented protein sample. The observed 13C' chemical shift frequency provides an orientational constraint complementary to those measured from the 1H and 15N amide resonances in double-resonance experiments.

Wee Meng Tan; Zhengtian Gu; Ana Carolina Zeri

1999-01-01

363

Theory and applications of surface plasmon resonance, resonant mirror, resonant waveguide grating, and dual polarization interferometry biosensors.  

PubMed

Biosensors have been used extensively in the scientific community for several purposes, most notably to determine association and dissociation kinetics, protein-ligand, protein-protein, or nucleic acid hybridization interactions. A number of different types of biosensors are available in the field, each with real or perceived benefits over the others. This review discusses the basic theory and operational arrangements of four commercially available types of optical biosensors: surface plasmon resonance, resonant mirror, resonance waveguide grating, and dual polarization interferometry. The different applications these techniques offer are discussed from experiments and results reported in recently published literature. Additionally, recent advancements or modifications to the current techniques are also discussed. PMID:22163431

Daghestani, Hikmat N; Day, Billy W

2010-11-01

364

Unstable resonators with excited converging wave  

SciTech Connect

This paper reports the properties of unstable resonators with an additional mirror inside or outside the resonator investigated, both experimentally and theoretically. The additional mirror excites the converging wave, and by this, output coupling is decreased without affecting beam quality. Experiments were performed with a pulsed Nd:YAG system. The theoretical model was based on the coupled Kirchhoff integrals and solved numerically. Agreement between theory and experiments indicates that this kind of resonator provides high focusability and maximum extraction efficiency simultaneously, even with low-gain media. This enables one to apply unstable resonators to solid-state lasers with low small-signal gain, like alexandrite or CW-pumped Nd:YAG.

Hodgson, N. (Optisches Institut, Technische Universitat Berlin, Strasse des 17. Juni 135, 1000 Berlin 12 (DE)); Weber, H. (Festkoerper-Laser-Institut Berlin GmbH, Strasse des 17, Juni 135, 1000 Berlin (DE))

1990-04-01

365

Cyclotron resonance heating systems for SST1  

Microsoft Academic Search

RF systems in the ion cyclotron resonance frequency (ICRF) range and electron cyclotron resonance frequency (ECRF) range are in an advanced stage of commissioning, to carry out pre-ionization, breakdown, heating and current drive experiments on the steady-state superconducting tokamak SST-1. Initially the 1.5 MW continuous wave ICRF system would be used to heat the SST-1 plasma to 1.0 keV during

D. Bora; Sunil Kumar; Raj Singh; K. Sathyanarayana; S. V. Kulkarni; A. Mukherjee; B. K. Shukla; J. P. Singh; Y. S. S. Srinivas; P. Khilar; M. Kushwah; Rajnish Kumar; R. Sugandhi; P. Chattopadhyay; Singh Raghuraj; H. M. Jadav; B. Kadia; Manoj Singh; Rajan Babu; P. Jatin; G. Agrajit; P. Biswas; A. Bhardwaj; D. Rathi; G. Siju; K. Parmar; A. Varia; S. Dani; D. Pragnesh; C. Virani; Harsida Patel; P. Dharmesh; A. R. Makwana; P. Kirit; M. Harsha; J. Soni; V. Yadav; D. S. Bhattacharya; M. Shmelev; V. Belousov; V. Kurbatov; Yu. Belov; E. Tai

2006-01-01

366

Resonant thermal transport in semiconductor barrier structures  

NASA Astrophysics Data System (ADS)

I report that thermal single-barrier (TSB) and thermal double-barrier (TDB) structures (formed, for example, by inserting one or two regions of a few Ge monolayers in Si) provide both a suppression of the phonon transport as well as a resonant-thermal-transport effect. I show that high-frequency phonons can experience a traditional double-barrier resonant tunneling in the TDB structures while the formation of Fabry-Perot resonances (at lower frequencies) causes quantum oscillations in the temperature variation of both the TSB and TDB thermal conductances ?TSB and ?TDB.

Hyldgaard, P.

2004-05-01

367

Versatile Magnetic Resonance Spectrometer  

Microsoft Academic Search

A Pound-Knight-Watkins marginal oscillator has been modified by the addition of a vibrating capacitor in parallel with the tuning capacitor to produce a simple circuit which may be used to observe paramagnetic resonance at low fields, nuclear magnetic resonance, and nuclear quadrupole resonance. Suggestions are made as to the type of information which may be obtained in an undergraduate laboratory

J. A. Cowen; W. H. Tanttila

1958-01-01

368

VERSATILE MAGNETIC RESONANCE SPECTROMETER  

Microsoft Academic Search

A Pound-Knight-Watkins marginal osciliator was modified by the addition ; of a vibrating capacitor in parallel with the tuning capacitor to produce a ; simple circuit which may be used to observe paramagnetic resonance at low fields, ; nuclear magnetic resonance, and nuclear quadrupole resonance. Suggestions are ; mnde as to the type of information which may be obtained in

J. A. Cowen; W. H. Tanttila

1958-01-01

369

N+CPT clock resonance  

SciTech Connect

In a typical compact atomic time standard a current modulated semiconductor laser is used to create the optical fields that interrogate the atomic hyperfine transition. A pair of optical sidebands created by modulating the diode laser become the coherent population trapping (CPT) fields. At the same time, other pairs of optical sidebands may contribute to other multiphoton resonances, such as three-photon N-resonance [Phys. Rev. A 65, 043817 (2002)]. We analyze the resulting joint CPT and N-resonance (hereafter N+CPT) analytically and numerically. Analytically we solve a four-level quantum optics model for this joint resonance and perturbatively include the leading ac Stark effects from the five largest optical fields in the laser's modulation comb. Numerically we use a truncated Floquet solving routine that first symbolically develops the optical Bloch equations to a prescribed order of perturbation theory before evaluating. This numerical approach has, as input, the complete physical details of the first two excited-state manifolds of {sup 87}Rb. We test these theoretical approaches with experiments by characterizing the optimal clock operating regimes.

Crescimanno, M. [Department of Physics and Astronomy, Youngstown State University, Youngstown, Ohio 44555 (United States); Hohensee, M. [MS-59, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, Massachusetts 02138 (United States)

2008-12-15

370

Gallium nitride nanowire electromechanical resonators  

NASA Astrophysics Data System (ADS)

Nanoscale mechanical resonators are of great interest for high-resolution sensing applications, where the small resonator mass and high quality factor (Q, defined as resonance frequency f0 over full width at half maximum power) lead to unprecedented sensitivity. Here, we investigate gallium nitride (GaN) nanowire (NW) resonators. The single-crystal, c-axis NWs are 5 mum -- 20 mum long, with diameters from 50 nm -- 500 nm, and grow essentially free of defects. Our initial experiments involve measuring the resonances of as-grown NWs in a scanning electron microscope, where we observe exceptionally high Q values of 10 4 -- 105, one to two orders of magnitude higher than most NWs of comparable size. Using a single NW as a mass sensor, we then demonstrate a sub-attogram mass sensitivity. To provide a more flexible measurement technique that avoids electron-microscope detection, we fabricate doubly clamped NWs with an entirely electronic drive and readout scheme using a combination of lithographic patterning and dielectrophoresis. An electrostatic gate induces vibration, while readout utilizes the piezoresistivity of GaN. Observed resonances range from 9--36 MHz with Q values typically around 103 at room temperature and 10 -4 Pa. We use the behavior of f0 and Q to sense the NW's local environment, such as the additional sources of energy dissipation not present in the as-grown NWs. By cooling the device to 8 K, Q increases by an order of magnitude to above 104, with a highest value to date of 26,000 under vacuum. We explore additional NW properties through the thermal noise in the NW's mechanical motion and the exponential decay of mechanical motion in the presence of burst drive. Finally, we investigate the low-frequency 1/f parameter noise displayed by f0. We show that the noise in f0 is consistent with noise in the NW's resistance leading to temperature noise from local Joule heating, which in turn generates resonance frequency noise. For sensor applications, there will be optimal drive conditions that balance the f 0 noise with the signal-to-noise ratio of the system. With these insights, along with the simple drive and readout technique, these GaN-NW doubly clamped resonators have significant potential for high-resolution sensing applications.

Gray, Jason Michael

371

Resonant and non-resonant magnetic scattering  

SciTech Connect

The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

1991-12-31

372

Resonant and non-resonant magnetic scattering  

SciTech Connect

The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

1991-01-01

373

The three principal secular resonances nu(5), nu(6), and nu(16) in the asteroidal belt  

NASA Astrophysics Data System (ADS)

Theoretical and numerical results obtained for secular resonant motion in the asteroidal belt are reviewed. William's (1969) theory yields the locations of the principal secular resonances nu(5), Nu(6), and nu(16) in the asteroidal belt. Theories by Nakai and Kinoshita (1985) and by Yoshikawa (1987) make it possible to model the basic features of orbital evolution at the secular resonances nu(16) and nu(6), respectively. No theory is available for the secular resonance nu(5). Numerical experiments by Froeschle and Scholl yield quantitative and new qualitative results for orbital evolutions at the three principal secular resonances nu(5), nu(6), and nu(16). These experiments indicate possible chaotic motion due to overlapping resonances. A secular resonance may overlap with another secular resonance or with a mean motion resonance. The role of the secular resonances as possible sources of meteorites is discussed.

Froeschle, Ch.; Scholl, H.

1989-09-01

374

Hadronic resonances at ALICE  

NASA Astrophysics Data System (ADS)

Measurements of the ratios of hadronic resonance yields to non-resonance yields can be used to study the properties of the hadronic phase of high-energy heavy-ion collisions. A change in resonance masses or widths could be an indication of chiral symmetry restoration. Measurements of resonances in proton-proton collisions provide an important baseline for measurements in heavy-ion collisions as well as data for tuning QCD-inspired particle production models. The ALICE collaboration has measured the K*(892)0 and phi(1020) resonances in Pb-Pb collisions at = 2.76 TeV and the K*(892)0, phi(1020), and ?*(1385) resonances in pp collisions at = 7 TeV. These measurements - including transverse momentum spectra, ratios to non-resonances, masses, and widths - are discussed and compared to theoretical predictions.

Knospe, A. G.; Alice Collaboration

2013-09-01

375

Localized ferromagnetic resonance using Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Force Microscopy (MRFM) is a novel approach to scanned probe imaging, combining the advantages of Magnetic Resonance Imaging (MRI) with Scanning Probe Microscopy (SPM) [1]. It has extremely high sensitivity that has demonstrated detection of individual electron spins [2] and small numbers of nuclear spins [3]. Here we describe our MRFM experiments on Ferromagnetic thin film structures. Unlike ESR and NMR, Ferromagnetic Resonance (FMR) is defined not only by local probe field and the sample structures, but also by strong spin-spin dipole and exchange interactions in the sample. Thus, imaging and spatially localized study using FMR requires an entirely new approach. In MRFM, a probe magnet is used to detect the force response from the sample magnetization and it provides local magnetic field gradient that enables mapping of spatial location into resonance field. The probe field influences on the FMR modes in a sample, thus enabling local measurements of properties of ferromagnets. When sufficiently intense, the inhomogeneous probe field defines the region in which FMR modes are stable, thus producing localized modes. This feature enables FMRFM to be important tool for the local study of continuous ferromagnetic samples and structures. In our experiments, we explore the properties of the FMR signal as the strength of the local probe field evolves from the weak to strong perturbation limit. This underlies the important new capability of Ferromagnetic resonance imaging, a powerful new approach to imaging ferromagnet. The new developed FMR imaging technique enables FMR imaging and localized FMR spectroscopy to combine spectroscopy and lateral information of ferromagnetic resonance images [4][5]. Our theoretical approach agrees well with spatially localized spectroscopy and imaging results. This approach also allows analysis and reconstruction of FMR modes in a sample. Finally we consider the effect of strong probe fields on FMR modes. In this regime the probe field significantly modifies the FMR modes. In particular we observe the complete local suppression of the FMR mode under the probe. This provides as a new tool for local study of continuous ferromagnetic thin films and microstructures.

Kim, Jongjoo

376

Parity nonconservation in neutron resonances  

NASA Astrophysics Data System (ADS)

Experiments to observe the parity nonconserving effects in 81Br, 111Cd, 117Sn, 127I, 139La and 238U are described. The measurements were performed with a beam of polarized neutrons from the pulsed reactor IBR-30 at Dubna. A dependence of total cross sections on neutron helicity was discovered in the following resonances: 0.88 eV 81Br, 4.53 eV 111Cd, 1.33 eV 117Sn, and 0.75 eV 139La. The effect has a resonance character and is in agreement with theoretical predictions made in the framework of the model of mixing compound states. The paper contains experimental estimates for the mixing coefficients and matrix elements.

Alfimenkov, V. P.; Borzakov, S. B.; van Thuan, Vo; Mareev, Yu. D.; Pikelner, L. B.; Khrykin, A. S.; Sharapov, E. I.

1983-04-01

377

Searches for resonances decaying to top  

SciTech Connect

Searches for resonances decaying to top pairs in p{anti p} collisions at {radical}s = 1.96 TeV are presented. An upper limit on the production of a narrow width resonance is given using 2.1 fb{sup -1} data collected by the D0 experiment. Limits on the couplings of a massive gluon are given and a measurement of the differential cross section d{sigma}/dM{sub t{anti t}} is presented using 1.9 fb{sup -1} data collected by the CDF experiment.

Meyer, Jorg; /Gottingen U.

2008-04-01

378

Superconducting coplanar waveguide resonators for low temperature pulsed electron spin resonance spectroscopy.  

PubMed

We discuss the design and implementation of thin film superconducting coplanar waveguide micro-resonators for pulsed electron spin resonance experiments. The performance of the resonators with P doped Si epilayer samples is compared to waveguide resonators under equivalent conditions. The high achievable filling factor even for small sized samples and the relatively high Q-factor result in a sensitivity of 4.5 10(8) spins per shot, which is superior to that of conventional waveguide resonators, in particular to spins close to the sample surface. The peak microwave power is on the order of a few milliwatts, which is compatible with measurements at ultra-low temperatures. We also discuss the effect of the nonuniform microwave magnetic field on the Hahn echo power dependence. PMID:23464260

Malissa, H; Schuster, D I; Tyryshkin, A M; Houck, A A; Lyon, S A

2013-02-01

379

Superconducting coplanar waveguide resonators for low temperature pulsed electron spin resonance spectroscopy  

NASA Astrophysics Data System (ADS)

We discuss the design and implementation of thin film superconducting coplanar waveguide micro-resonators for pulsed electron spin resonance experiments. The performance of the resonators with P doped Si epilayer samples is compared to waveguide resonators under equivalent conditions. The high achievable filling factor even for small sized samples and the relatively high Q-factor result in a sensitivity of 4.5 108 spins per shot, which is superior to that of conventional waveguide resonators, in particular to spins close to the sample surface. The peak microwave power is on the order of a few milliwatts, which is compatible with measurements at ultra-low temperatures. We also discuss the effect of the nonuniform microwave magnetic field on the Hahn echo power dependence.

Malissa, H.; Schuster, D. I.; Tyryshkin, A. M.; Houck, A. A.; Lyon, S. A.

2013-02-01

380

The resonant body transistor.  

PubMed

This paper introduces the resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body. Combining the benefits of FET sensing with the frequency scaling capabilities and high quality factors (Q) of internal dielectrically transduced bar resonators, the resonant body transistor achieves >10 GHz frequencies and can be integrated into a standard CMOS process for on-chip clock generation, high-Q microwave circuits, fundamental quantum-state preparation and observation, and high-sensitivity measurements. An 11.7 GHz bulk-mode RBT is demonstrated with a quality factor Q of 1830, marking the highest frequency acoustic resonance measured to date on a silicon wafer. PMID:20180594

Weinstein, Dana; Bhave, Sunil A

2010-04-14

381

Artificial Dielectric Resonator Made of Spherical Metal Particles  

NASA Astrophysics Data System (ADS)

A microwave resonator is fabricated by a lump of spherical metal particles for the first time. It is the evidence that those particles constitute artificial dielectrics. The effective permittivity is calculated numerically together with the permeability. Resonant mode frequencies in the experiment are compared with the theoretical result obtained by the effective material constants above. Their reasonable agreement indicates the validity of material constant extraction. The unique diamagnetism of spherical particles could be utilized for improvement of spurious property of a resonator.

Awai, Ikuo; Mizue, Osamu; Saha, Arun Kumar

382

Feshbach resonances in ultracold atom-diatom scattering  

SciTech Connect

Quantum-mechanical scattering calculations of Feshbach resonances arising from van der Waals molecule formation are used to determine vibrational and rotational predissociation lifetimes. A multichannel effective range theory is used to establish the relationship between predissociation and the zero-temperature limit of collisional quenching for resonances lying close to the thresholds for dissociation. The elastic scattering Feshbach resonances may be measurable in ultracold atom-molecule experiments. {copyright} {ital 1998} {ital The American Physical Society}

Forrey, R.C.; Balakrishnan, N.; Kharchenko, V.; Dalgarno, A. [Institute for Theoretical Atomic and Molecular Physics, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

1998-10-01

383

Surface spin wave resonator  

Microsoft Academic Search

Consideration is given to the properties of a surface spin wave converter of meander type consisting of a YIG film deposited on a single-crystal ferrite substrate. The impedance of the device is determined, and the resonant frequency and q-factor of a resonator based on such a converter are evaluated. Results are presented for a YIG\\/ferrite resonator whose q-factor is of

G. A. Vugalter

1980-01-01

384

Dynamically generated hadron resonances  

SciTech Connect

As an example of dynamically generated resonances we mention the interaction of vector mesons with baryons within the local hidden gauge formalism which gives rise to a large amount of such states, many of which can be associated to known resonances, while others represent predictions for new resonances. The width of these states coming from decay into pseudoscalar baryon is also addressed. We also mention recent states coming from {rho}{pi} interaction obtained with Faddeev equations.

Oset, E.; Gonzalez, P. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacion de Paterna, Aptd. 22085, 46071 Valencia (Spain); Ramos, A. Torres [Departament d'Estructura i Constituents de la Materia, Universitat de Barcelona (Spain); Martinez, A. [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Garzon, E. J.; Xie, Ju Jun

2011-10-21

385

Resonant Optical Antennas  

Microsoft Academic Search

We have fabricated nanometer-scale gold dipole antennas designed to be resonant at optical frequencies. On resonance, strong field enhancement in the antenna feed gap leads to white-light supercontinuum generation. The antenna length at resonance is considerably shorter than one-half the wavelength of the incident light. This is in contradiction to classical antenna theory but in qualitative accordance with computer simulations

P. Mhlschlegel; H.-J. Eisler; O. J. F. Martin; B. Hecht; D. W. Pohl

2005-01-01

386

Adiabatic microring resonators.  

PubMed

A class of whispering-gallery-mode resonators, herein referred to as adiabatic microring resonators, is proposed and numerically demonstrated. Adiabatic microrings enable electrical and mechanical contact to be made to the resonator without inducing radiation, while supporting only a single radial mode and therein achieving an uncorrupted free spectral range (FSR). Rigorous finite-difference time-domain simulations indicate that adiabatic microrings with outer diameters as small as 4 ?m can achieve resonator quality factors (Qs) as high as Q = 88,000 and an FSR of 8.2 THz, despite large internal contacts. PMID:20890343

Watts, Michael R

2010-10-01

387

Ferromagnetic Resonance Force Microscopy  

Microsoft Academic Search

The magnetic resonance force microscope(MRFM) is anovel scanning probe instrument that combines the three-dimensional imaging\\u000a capabilities of magnetic resonance imaging(MRI) with the high sensitivity and resolution of atomic force microscopy(AFM).\\u000a In the nuclear magnetic resonance (NMR) mode or the electron spin resonance(ESR) mode it will enable nondestructive, chemical-specific,\\u000a high-resolution microscopic studies and imaging of subsurface properties of abroad range of

Philip E. Wigen; Michael L. Roukes; Peter C. Hammel

388

Giant resonance decay  

SciTech Connect

Decay studies of giant multipole resonances are discussed, emphasizing the role of Coulomb excitation with intermediate energy heavy ions, which can provide very large cross sections for both isoscalar and isovector resonances. We discuss measurement of the photon decay of one and two phonon giant resonances, reporting results where available. It is pointed out throughout the presentation that the use of E1 photons as a tag'' provides a means to observe weakly excited resonances that cannot be observed in the singles spectra. 30 refs., 16 figs., 1 tab.

Beene, J.R.; Bertrand, F.E.

1990-01-01

389

Investigation of nuclear quadrupole resonance in the series of bromine- and iodine-containing disubstituted benzenes  

Microsoft Academic Search

The results of Br m and I t27 NOR determinations in the series of disubstituted halobenzenes are given. It Is shown that a correlation, very roughly linear, can be found between the NQR frequencies and the Hammett constant o. The possible causes of the deviations of this relationship from ltnearity are discussed. It is pointed out that the analytical potentialities

G. K. Semin

1962-01-01

390

Evaluation of a new Spin-echo diffusion-weighted sequence on a 0.35T open magnetic resonance imaging (MRI)-system: first experiences within 3h after acute stroke  

Microsoft Academic Search

In acute stroke, diffusion-weighted magnetic resonance imaging helps to select patients who are eligible for thrombolysis, but is almost exclusively implemented on closed-bore scanners, which make monitoring of patients difficult. We developed and tested a cardiac gated Spin-echo diffusion-weighted sequence with prescan finetrim and motion correction on an open system with 0.35T. Nineteen stroke patients appropriate for thrombolytic therapy by

W. A. Wohlgemuth; G. Schulte-Altedorneburg; T. Becker; L. Zha; D. Kramer; K. Kirchhof

2005-01-01

391

Pitch sensation involves stochastic resonance.  

PubMed

Pitch is a complex hearing phenomenon that results from elicited and self-generated cochlear vibrations. Read-off vibrational information is relayed higher up the auditory pathway, where it is then condensed into pitch sensation. How this can adequately be described in terms of physics has largely remained an open question. We have developed a peripheral hearing system (in hardware and software) that reproduces with great accuracy all salient pitch features known from biophysical and psychoacoustic experiments. At the level of the auditory nerve, the system exploits stochastic resonance to achieve this performance, which may explain the large amount of noise observed in the working auditory nerve. PMID:24045830

Martignoli, Stefan; Gomez, Florian; Stoop, Ruedi

2013-09-18

392

Parity nonconservation in neutron resonances  

Microsoft Academic Search

Experiments to observe the parity nonconserving effects in 81Br, 111Cd, 117Sn, 127I, 139La and 238U are described. The measurements were performed with a beam of polarized neutrons from the pulsed reactor IBR-30 at Dubna. A dependence of total cross sections on neutron helicity was discovered in the following resonances: 0.88 eV 81Br, 4.53 eV 111Cd, 1.33 eV 117Sn, and 0.75

V. P. Alfimenkov; S. B. Borzakov; Vo van Thuan; Yu. D. Mareev; L. B. Pikelner; A. S. Khrykin; E. I. Sharapov

1983-01-01

393

The Experimental Status of Baryon Resonances  

NASA Astrophysics Data System (ADS)

Nucleons are complex systems of confined quarks and exhibit characteristic spectra of excited states. Highly excited nucleon states are sensitive to details of quark confinement which is poorly understood within Quantum Chromodynamics (QCD), the fundamental theory of strong interactions. Thus, measurements of excited nucleon states and the corresponding determination of their properties are needed to come to a better understanding of how confinement works in nucleons. However, the excited states of the nucleon cannot simply be inferred from cleanly separated spectral lines. Quite the contrary, a spectral analysis in nucleon resonance physics is challenging because of the fact that these resonances are broadly overlapping states which decay into a multitude of final states involving mesons and baryons. To provide a consistent and complete picture of an individual nucleon resonance, the various possible production and decay channels must eventually be treated in a multi-channel framework that permits separating resonance from background contributions. A long-standing question in hadron physics is whether the large number of so-called missing baryon resonances really exists, i.e. experimentally not established baryon states which are predicted by quark models based on three constituent quark effective degrees of freedom. It is important to emphasize that nearly all existing data on non-strange production of baryon resonances result from ?N scattering experiments. However, quark models predict strong couplings of these missing states to ?p rendering the study of these resonances in photo-induced reactions a very promising approach. Several new states have in fact been proposed in recent experiments. Current and upcoming experiments at Jefferson Laboratory will determine polarization (or spin) observables for photoproduction processes involving baryon resonances. Differences between the predictions for these observables can be large, and so conversely they provide strong constraints on the analysis. An interesting question is whether it is possible to design a complete set of experiments which will uniquely determine the scattering amplitude for a given process. The current effort with the CLAS detector at Jefferson Lab is to utilize highly-polarized frozen-spin (butanol) and deuterium targets in combination with polarized photon beams. In particular, the very successful FROST experiment took the first double-polarization data from November '07 to February '08 paving the way for a complete experiment in K? and K? photoproduction. This contribution will review recent results and also discuss open questions and perspectives in N^* physics.

Crede, Volker

2010-11-01

394

Interparticle Coupling Effects on Plasmon Resonances of Nanogold Particles  

Microsoft Academic Search

The collaborative oscillation of conductive electrons in metal nanoparticles results in a surface plasmon resonance that makes them useful for various applications including biolabeling. We investigate the coupling between pairs of elliptical metal particles by simulations and experiments. The results demonstrate that the resonant wavelength peak of two interacting particles is red-shifted from that of a single particle because of

K.-H. Su; Q.-H. Wei; X. Zhang; J. J. Mock; D. R. Smith; S. Schultz

2003-01-01

395

Resonant inelastic x-ray scattering from molecules and atoms  

SciTech Connect

X-ray fluorescence spectroscopy is one of the most powerful methods for the understanding of the electronic structure of matter. We report here on fluorescence experiments in the 2 to 6 keV photon energy range using tunable synchrotron radiation and the resulting experimental programs on resonant inelastic scattering in atoms and on polarization measurements in resonant molecular excitations.

Arp, U.; Deslattes, R.D. [National Institute of Standards and Technology, Gaithersburg, MD (United States); Miyano, K.E. [Brooklyn College, Brooklyn, NY (United States); Southworth, S.H. [and others

1995-12-31

396

Characterization of microwave magnetic narrow band filters by ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

Ferromagnetic resonance cavity and microstrip excitation experiments have been performed on a straight edge yttrium iron garnet resonator. Both excitation systems have been modeled as band-stop configurations and a mapping from the swept bias magnetic field domain to the frequency domain has been elaborated to compare them in terms of the dispersion and the amplitude of the magnetostatic wave modes.

Bousbahi, Khaled; Marcelli, Romolo

2000-05-01

397

Modification of piezoelectric vibratory gyroscope resonator parameters by feedback control  

Microsoft Academic Search

A method for analyzing the effect of feedback control on the dynamics of piezoelectric resonators used in vibratory gyroscopes has been developed. This method can be used to determine the feasibility of replacing the traditional mechanical balancing operations, used to adjust the resonant frequency, by displacement feedback and for determining the velocity feedback required to produce a particular bandwidth. Experiments

Philip W. Loveday; Craig A. Rogers

1998-01-01

398

Magnetic resonance imaging and spectroscopy  

SciTech Connect

This book contains 17 selections. Some of the chapter titles are: Basic Principles of Magnetic Resonance Imaging;Evaluation of Demyelinating Diseases;Respiratory Gating in Magnetic Resonance Imaging;Magnetic Resonance Imaging of the Abdomen;Contrast Agents in Magnetic Resonance Imaging;and Economic Considerations in Magnetic Resonance Imaging.

Mettler, F.A.; Muroff, L.R.; Kulkarni, M.V.

1986-01-01

399

Off-resonance slow light  

NASA Astrophysics Data System (ADS)

We consider the propagation of a light pulse in a medium with a single resonance. If the frequency of the pulse is tuned far from resonance and the pulse duration is much shorter than the lifetime of the excited state of the resonant particles in the medium (atoms in a gas, impurity ions in a solid, etc.), the group velocity of the pulse is appreciably reduced. It is shown that the slowing down of the group velocity of the pulse is accompanied with a pulse chirp, which produces a pulse broadening in time. It is proposed to use two samples in sequence with opposite chirps (up chirp and down chirp or vice versa) compensating the pulse broadening. Then the pulse can be delayed with almost no losses, distortion, and broadening. However, there is a maximum distance, beyond which the pulse experiences corruption. Pumping with an auxiliary laser beam can control the delay time of the light pulse in the medium. Conditions to eliminate the contribution of the dephasing processes in the pulse propagation are considered.

Shakhmuratov, R. N.; Odeurs, J.

2008-12-01

400

Single Molecule Electron Paramagnetic Resonance  

NASA Astrophysics Data System (ADS)

Electron paramagnetic resonance (EPR) is a powerful spectroscopic tool for studying the dynamics of biomolecular systems. EPR measurements on bulk samples using a commercial X-band spectrometer provide insight into atomic-scale structure and dynamics of ensembles of biomolecules. Separately, single molecule measurements of biomolecular systems allow researchers to capture heterogeneous behaviors that have revealed the molecular mechanisms behind many biological processes. We are merging these two powerful techniques to perform single molecule EPR. In this experiment, we selectively label double-stranded DNA molecules with nitrogen-vacancy (NV) center nanodiamonds and optically detect the magnetic resonance of the NV probe. Shifts and broadening of our EPR peaks indicate the changing position of the attached DNA relative to the applied magnetic field. Using this new technique, we have successfully measured the first EPR spectrum of a single biomolecule. By controlling the geometry of the diamond and the applied magnetic field, we will quantitatively determine the rotational and translational dynamics of single biomolecules. This research provides the foundation for an advanced single molecule magnetic resonance approach to studies of complex biomolecular systems.

Teeling-Smith, Richelle M.; Johnston-Halperin, Ezekiel; Poirier, Michael G.; Hammel, P. Chris

2013-03-01

401

High-Q Bandpass Resonators Utilizing Bandstop Resonator Pairs.  

National Technical Information Service (NTIS)

A high-Q bandpass resonators utilizing composite bandstop resonator pairs is reported. The bandstop resonator pairs are formed of composite series or parallel connected realizable transmission line elements. The elements are exclusively either quarter-wav...

H. C. Okean

1973-01-01

402

An NMR Kinetics Experiment.  

ERIC Educational Resources Information Center

Outlines advantages of and provides background information, procedures, and typical student data for an experiment determining rate of hydration of p-methyoxyphenylacetylene (III), followed by nuclear magnetic resonance spectroscopy. Reaction rate can be adjusted to meet time framework of a particular laboratory by altering concentration of

Kaufman, Don; And Others

1982-01-01

403

An NMR Kinetics Experiment.  

ERIC Educational Resources Information Center

|Outlines advantages of and provides background information, procedures, and typical student data for an experiment determining rate of hydration of p-methyoxyphenylacetylene (III), followed by nuclear magnetic resonance spectroscopy. Reaction rate can be adjusted to meet time framework of a particular laboratory by altering concentration of

Kaufman, Don; And Others

1982-01-01

404

Measurements of Parity Violation in a Search for Candidate Resonances for a Test of Time Reversal Invariance in Neutron Absorption  

Microsoft Academic Search

Parity violation in neutron resonance absorption has been used in a search for candidate resonances for a new class of tests of time reversal invariance. Time reversal non-invariant effects in neutron absorption could be enhanced under the same conditions which lead to enhanced parity violation. This experiment therefore searched for parity violation in p-wave resonances to identify resonances appropriate for

Kevin Patrick Coulter

1989-01-01

405

Resonance seeking control  

Microsoft Academic Search

An adaptive control method that seeks the unknown resonant frequency of a load and drives it at its resonant frequency to achieve optimal performance is proposed and investigated. The method is based on estimating the derivative of the average power delivered to the load with respect to the driving frequency and using this estimate to adaptively control the driving frequency.

C. Gokcek

2005-01-01

406

The Concept of Resonance  

ERIC Educational Resources Information Center

|A general example of a delocalization system associated with a higher energy than the localized one, which suggests that it is wrong to consider delocalization as equivalent to resonance stabilization, is presented. The meaning of resonance energy as it appears in valence bond theory is described as the lowering of the calculated ground-state

Truhlar, Donald G.

2007-01-01

407

Adaptive resonance associative map  

Microsoft Academic Search

This article introduces a neural architecture termed Adaptive Resonance Associative Map ( ARAM) that extends unsupervised Adaptive Resonance Theory (ART) systems for rapid, yet stable, heteroassociative learning. ARAM can be visualized as two overlapping ART networks sharing a single category field. Although ARAM is simpler in architecture than another class of supervised ART models known as ARTMAP, it produces classification

Ah-hwee Tan

1995-01-01

408

Supervised adaptive resonance networks  

Microsoft Academic Search

Adaptive Resonance Theory (ART) has been used to design a number of massively-parallel, unsupervised, pattern recognition machines. ART networks learn a set of recognition codes by ensuring that input vectors match or resonate with one of a learned set of template vectors. A novelty detector determines whether or not an input vector is new or familiar. Novel input vectors lead

Robert A. Baxter

1991-01-01

409

Surface plasmon resonance immunosensors: sensitivity considerations  

Microsoft Academic Search

Some aspects of improving surface plasmon resonance response in immunosensing applications are considered. Both from calculations and experiments, it was found that maximum sensitivity is obtained for a silver layer about 55 nm thick in direct contact with the species to be quantified. Application of an intermediate layer with high permittivity can be useful in suppressing background responses. Experimentally, a

R. P. H. Kooyman; H. Kolkman; J. Van Gent; J. Greve

1988-01-01

410

Magnetic resonance measurements of polar sea ice  

Microsoft Academic Search

A Nuclear Magnetic Resonance (NMR) sensor system has been developed to measure the brine fraction profile of polar sea ice. The system is based on a 0.3 T Halbach permanent magnet array and has significantly more sensitivity than earlier Earth's field NMR systems deployed in Antarctica. Brine fraction experiments were performed in November 2009 near Ross Island, Antarctica and the

Robin Dykstra; Achim Gadke

2011-01-01

411

Magnetic Resonance Imaging (MRI) of the Kidney.  

National Technical Information Service (NTIS)

The thesis reflects experience with Magnetic Resonance Imaging (MRI) in the diagnosis of kidney disease. Initial results were obtained on a 0.15 T resistive and a 0.5 T superconducting prototype MR scanner (Philips, Best, the Netherlands). Further clinica...

L. Te Strake

1987-01-01

412

Resonant snubber inverter  

DOEpatents

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

Lai, Jih-Sheng (Knoxville, TN); Young, Sr., Robert W. (Oak Ridge, TN); Chen, Daoshen (Knoxville, TN); Scudiere, Matthew B. (Oak Ridge, TN); Ott, Jr., George W. (Knoxville, TN); White, Clifford P. (Knoxville, TN); McKeever, John W. (Oak Ridge, TN)

1997-01-01

413

Resonant snubber inverter  

DOEpatents

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 14 figs.

Lai, J.S.; Young, R.W. Sr.; Chen, D.; Scudiere, M.B.; Ott, G.W. Jr.; White, C.P.; McKeever, J.W.

1997-06-24

414

Effect of internal resistance of a Helmholtz resonator on acoustic energy reduction in enclosures.  

PubMed

The effect of internal resistance of a Helmholtz resonator on acoustic energy reduction in an enclosure and the multimodal coupling-based Helmholtz resonator design are investigated. Using the analytical solution of a resonator-enclosure interaction model, an energy reduction index is defined in a frequency band to optimize the resonator resistance. The dual process of energy dissipation and radiation of the resonator is quantified. Optimal resistance of the resonator and its physical effect on the resonator-enclosure interaction are numerically evaluated and categorized in terms of frequency bandwidths. Predictions on the resonator performance are confirmed by experiments. Comparisons with existing models based on different optimization criteria are also performed. It is shown that the proposed model serves as an effective design tool to determine the internal resistance of the resonator in order to achieve sound reduction in the frequency band enclosing acoustic resonances. PMID:19206783

Yu, Ganghua; Li, Deyu; Cheng, Li

2008-12-01

415

Polarization Near Isobaric Analogue Resonances.  

National Technical Information Service (NTIS)

For the purpose of analysing isobaric analogue resonances, a single-level resonance formula has been incorporated into nuclear scattering amplitudes found with an optical-model potential. The inclusion of the resonance term leads to polarization magnitude...

J. L. Adams W. J. Thompson D. Robson

1966-01-01

416

Behavioral and Biological Effects of Resonant Electromagnetic Absorption in Rats.  

National Technical Information Service (NTIS)

Past experiments of this project utilizing three separate and distinct radiation facilities have determined the whole body and distribution within the body of resonant electromagnetic power absorption for both man models and laboratory rodents. The absorp...

O. P. Gandhi J. A. D'Andrea M. J. Hagmann J. L. Lords K. Sedigh

1976-01-01

417

Combined nuclear-molecular resonance inelastic scattering of x rays.  

PubMed

We report on theoretical and experimental studies of nuclear inelastic scattering in a molecular crystal, whose atoms experience both molecular and lattice vibrations. In this case scattering proceeds as combined nuclear-molecular resonance inelastic scattering. The lattice vibrations give rise to inelastic scattering around the molecular resonances with an energy dependence identical to that around the nuclear resonance. The incoherent nature of the scattering in the molecular resonances results in a proper balance of elastic and inelastic components, which has important implications for studies of heterogeneous systems. PMID:15245079

Kohn, V G; Chumakov, A I; Rffer, R

2004-06-15

418

Neutron Resonance Spin Determination Using Multi-Segmented Detector DANCE  

NASA Astrophysics Data System (ADS)

A sensitive method to determine the spin of neutron resonances is introduced based on the statistical pattern recognition technique. The new method was used to assign the spins of s-wave resonances in 155Gd. The experimental neutron capture data for these nuclei were measured with the DANCE (Detector for Advanced Neutron Capture Experiment) calorimeter at the Los Alamos Neutron Science Center. The highly segmented calorimeter provided detailed multiplicity distributions of the capture ?-rays. Using this information, the spins of the neutron capture resonances were determined. With these new spin assignments, level spacings are determined separately for s-wave resonances with J? = 1- and 2-.

Baramsai, B.; Mitchell, G. E.; Agvaanluvsan, U.; Becvar, F.; Bredeweg, T. A.; Couture, A.; Chyzh, A.; Dashdorj, D.; Haight, R. C.; Jandel, M.; Keksis, A. L.; Krticka, M.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Walker, C.; Wouters, J. M.

2011-06-01

419

Nuclear quadrupole resonance of amidinium tetrachlorophosphorates  

SciTech Connect

The /sup 35/Cl NQR spectra and relaxation parameters of the cyclic amidinium tetrachlorophosphorates PCl/sub 4/(NCH/sub 3/)/sub 2/CX, where X = C/sub 6/H/sub 5/ (1), CCl/sub 3/ (2), and CF/sub 3/ (3), have been studied at 77/sup 0/K. The crystal of (3) has been found to contain two coexisting phases of the compound, which consist, respectively, and zwitterionic molecules of a hexacoordinated phosphorus atom with square-pyramidal symmetry of the PCl/sub 4/ group and molecules of chlorotropic isomers with a trigonal-bipyramidal environment for the phosphorus atom. The structural features of the crystalline state and the nature of the phosphorus-ligand bonds have been discussed.

Romanenko, E.A.; Kal'chenko, V.I.; Rudyi, R.B.

1986-05-01

420

Localized ferromagnetic resonance force microscopy of permalloy-cobalt films  

SciTech Connect

We report the Ferromagnetic Resonance Force Microscopy (FMRFM) experiments on a combined permalloy-cobalt continuous film. Our studies demonstrate the capability of FMRFM to perform local spectroscopy of different ferromagnetic materials. Theoretical analysis of the uniform resonance mode at the edge of the film provides good quantitative agreement with the experimental data. Our experiments demonstrate the micron scale lateral resolution and allow to extract local magnetic properties in continuous ferromagnetic samples.

Nazaretski, Evgueni [Los Alamos National Laboratory; Movshovich, Roman [Los Alamos National Laboratory; Martin, Ivar [Los Alamos National Laboratory; Cha, Kitty V [Los Alamos National Laboratory; Akhadov, Elshan A [Los Alamos National Laboratory; Obukhov, Yu [OH STATE U; Pelekhov, D C [OH STATE U; Hammel, P C [OH STATE U

2008-01-01

421

LABCOM resonator Phase 3  

SciTech Connect

The purpose of this project was to develop quartz crystal resonator designs, production processes, and test capabilities for 5-MHz, 6.2-MHz, and 10-MHz resonators for Tactical Miniature Crystal Oscillator (TMXO) applications. GE Neutron Devices (GEND) established and demonstrated the capability to produce and test quartz crystal resonators for use in the TMXO developed by the US Army ERADCOM (now LABCOM). The goals in this project were based on the ERADCOM statement of work. The scope of work indicated that the resonator production facilities for this project would not be completely independent, but that they would be supported in part by equipment and processes in place at GEND used in US Department of Energy (DOE) work. In addition, provisions for production test equipment or or eventual technology transfer costs to a commercial supplier were clearly excluded from the scope of work. The demonstrated technical capability of the deep-etched blank design is feasible and practical. It can be manufactured in quantity with reasonable yield, and its performance is readily predictable. The ceramic flatpack is a very strong package with excellent hermeticity. The four-point mount supports the crystal to reasonable shock levels and does not perturb the resonator's natural frequency-temperature behavior. The package can be sealed with excellent yields. The high-temperature, high-vacuum processing developed for the TMXO resonator, including bonding the piezoid to its mount with conductive polyimide adhesive, is consistent with precision resonator fabrication. 1 fig., 6 tabs.

Keres, L.J.

1990-11-01

422

Modelling resonant planetary systems  

NASA Astrophysics Data System (ADS)

Many discovered multi-planet systems are in meanmotion resonances. The aim of this work is to study dynamical processes leading to the formation of resonant configurations on the basis of a unified model described earlier [1]. The model includes gravitational interactions of planets and migration of planets due to the presence of a gas disc. For the observed systems 24 Sex, HD 37124, HD 73526, HD 82943, HD 128311, HD 160691, Kepler 9, NN Ser with planets moving in the 2:1 resonance, it is shown that the capture in this resonance occurs at very wide ranges of parameters of both type I and type II migration. Conditions of migration leading to the formation of the resonant systems HD 45364 ? HD 200964 (3:2 and 4:3, respectively) are obtained. Formation scenarios are studied for the systems HD 102272, HD 108874, HD 181433, HD 202206 with planets in high order resonances. We discuss also how gravitational interactions of planets and planetesimal discs lead to the breakup of resonant configurations and the formation of systems similar to the 47 UMa system.

Emel'yanenko, V.

2012-09-01

423

Resonant quantum transitions in trapped antihydrogen atoms.  

PubMed

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves. PMID:22398451

Amole, C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C ; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S

2012-03-07

424

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

NASA Astrophysics Data System (ADS)

We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSRs), which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of the MSR of a homogeneous object to include anisotropic metamaterials and consider the most extreme case of anisotropy, where the permeability is negative in one direction but positive in the others. It is shown that deeply subwavelength objects made of such indefinite (hyperbolic) media exhibit a pronounced magnetic dipole resonance that couples strongly to uniform or weakly inhomogeneous magnetic field and provides strong enhancement of the magnetic force, enabling applications such as enhanced magnetic levitation.

Urzhumov, Yaroslav; Chen, Wenchen; Bingham, Chris; Padilla, Willie; Smith, David R.

2012-02-01

425

Study on Dynamic Alignment Technology of COIL Resonator  

NASA Astrophysics Data System (ADS)

The performance of great power chemical oxygen-iodine laser (COIL) beam is decided mostly by resonator mirror maladjustment and environment vibration. To improve the performance of light beam, an auto-alignment device is used in COIL resonator, the device can keep COIL resonator collimating by adjusting the optical components of resonator. So the coupling model of COIL resonator is present. The multivariable self study fuzzy uncoupling arithmetic and six-dimensional micro drive technology are used to design a six-input-three-output uncoupling controller, resulting in the realization of the high precision dynamic alignment. The experiments indicate that the collimating range of this system is 8 mrad, precision is 5 urad and frequency response is 20Hz, which meet the demand of resonator alignment system.

Xiong, M. D.; Zou, X. J.; Guo, J. H.; Jia, S. N.; Zhang2, Z. B.

2006-10-01

426

Atomic pseudospin resonance.  

PubMed

A new type of resonance is discovered in Rydberg atoms placed in a constant magnetic field -->B and a transient electric field that rotates at the constant frequency -->omega in a plane perpendicular to -->B. The dynamics is explained in terms of two pseudoparticles with spin 1 / 2 in two generalized magnetic fields. The resonance frequency is predicted and found at -->omega = (e/2m)-->B, where -e/m is the electron's charge-to-(reduced)mass ratio. We discuss the applicability of the resonance to accurate magnetic field measurements and the prospects for determining e/m with improved precision. PMID:11736397

Fregenal, D; Ehrenreich, T; Henningsen, B; Horsdal-Pedersen, E; Nyvang, L; Ostrovsky, V N

2001-11-09

427

Spin resonance strength calculations  

SciTech Connect

In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.

Courant,E.D.

2008-10-06

428

Investigation on methods of eliminating acoustic resonance in small wattage high-intensity-discharge (HID) lamps  

Microsoft Academic Search

In this paper, a detailed theoretical prediction and experimental verification of acoustic resonance frequency distribution in a small wattage metal-halide (MH) lamp is presented. Extensive experiments have been conducted on 35 W MH lamps to investigate different methods for avoiding acoustic resonance. The results indicate that a randomized switching scheme cannot eliminate arc instabilities caused by acoustic resonances in small

Wei Yan; Y. K. E. Ho; S. Y. R. Hui

2000-01-01

429

Spectroscopy of Baryon Resonances at Elsa  

NASA Astrophysics Data System (ADS)

Current and upcoming experiments at the ELectron Stretcher Accelerator (ELSA) facility will determine polarization (or spin) observables for photoproduction processes involving baryon resonances. Differences between the predictions for these observables can be large, and so conversely they provide strong constraints in the analyses that aim at studying the properties of known resonances and at searching for hitherto unobserved states. The current effort with the Crystal Barrel/TAPS detector at ELSA is to utilize highly-polarized frozen-spin (butanol) and deuterium targets in combination with polarized photon beams. I will discuss recent spectroscopy results and present a brief status of the polarization program.

Crede, Volker

430

rf-field-induced Feshbach resonances  

SciTech Connect

A rigorous quantum theory of atomic collisions in the presence of radio frequency (rf) magnetic fields is developed and applied to elucidate the effects of combined dc and rf magnetic fields on ultracold collisions of Rb atoms. We show that rf fields can be used to induce Feshbach resonances, which can be tuned by varying the amplitude and frequency of the rf field. The rf-induced Feshbach resonances occur also in collisions of atoms in low-field-seeking states at moderate rf field strengths easily available in atom chip experiments, which opens up the world of tunable interactions to magnetically trappable atomic quantum gases.

Tscherbul, T. V.; Dalgarno, A. [Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138 (United States); ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Calarco, T. [Institute of Quantum Information Processing, Ulm University, D-89081 Ulm (Germany); Lesanovsky, I. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Krems, R. V. [Department of Chemistry, University of British Columbia, Vancouver BC, V6T 1Z1 (Canada); Schmiedmayer, J. [Atominstitut, TU-Wien, Stadionallee 2, 1020 Vienna (Austria)

2010-05-15

431

Simple Microwave Resonance Spectrometer  

Microsoft Academic Search

A relatively simple and inexpensive apparatus for the observation of electron paramagnetic resonance at microwave frequencies is described. The apparatus is designed for the undergraduate laboratory but, with some modification, may be used as a research tool.

E. S. Gravlin; J. A. Cowen

1959-01-01

432

Magnetic resonance imaging  

SciTech Connect

This book contains the following four major sections: physics and chemistry, relaxation/relaxometry, instrumentation, research areas. The authors discuss instrumentation and technical approaches in magnetic resonance (MR) imaging.

Partain, C.L.; Price, R.R.; Patton, J.A.; Kulkarni, M.V.; James, A.E.

1988-01-01

433

Magnetic Resonance Imaging (MRI).  

National Technical Information Service (NTIS)

Magnetic resonance imaging (MRI) is a method of graphically representing the distribution of water and other hydrogen-rich molecules in the human body. Imaging parameters are complex. Although MR images may demonstrate anatomy as do conventional radiograp...

E. Feigenbaum

1985-01-01

434

Micro-machined resonator  

DOEpatents

A micro-machined resonator, typically quartz, with upper and lower micro-machinable support members, or covers, having etched wells which may be lined with conductive electrode material, between the support members is a quartz resonator having an energy trapping quartz mesa capacitively coupled to the electrode through a diaphragm; the quartz resonator is supported by either micro-machined cantilever springs or by thin layers extending over the surfaces of the support. If the diaphragm is rigid, clock applications are available, and if the diaphragm is resilient, then transducer applications can be achieved. Either the thin support layers or the conductive electrode material can be integral with the diaphragm. In any event, the covers are bonded to form a hermetic seal and the interior volume may be filled with a gas or may be evacuated. In addition, one or both of the covers may include oscillator and interface circuitry for the resonator.

Godshall, N.A.; Koehler, D.R.; Liang, A.Y.; Smith, B.K.

1993-03-30

435

New Microscopic Mechanism for Secondary Relaxation in Glasses  

SciTech Connect

The dynamics of simple molecular systems showing glassy properties has been explored by dielectric spectroscopy and nuclear quadrupole resonance (NQR) on the halogenomethanes CBr{sub 2}Cl{sub 2} and CBrCl{sub 3} in their low-temperature monoclinic phases. The dielectric spectra display features which correspond to alpha- and beta-relaxation processes, commonly observed in canonical glass formers. NQR experiments, also performed in the ergodic monoclinic phase of CCl{sub 4}, enable the determination of the microscopic mechanism underlying the beta dynamics in these simple model glasses: Molecules that are nonequivalent with respect to their molecular environment perform reorientational jumps at different time scales. Thus our findings reveal another mechanism that can give rise to typical beta-relaxation behavior, raising some doubt about the existence of a universal explanation of this phenomenon.

Zuriaga, M. [IFFAMAF, Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Pardo, L. C.; Tamarit, J. Ll.; Veglio, N.; Barrio, M. [Grup de Caracteritzacio de Materials, Departament de Fisica i Enginyeria Nuclear, ETSEIB, Universitat Politecnica de Catalunya, Diagonal 647, 08028 Barcelona, Catalonia (Spain); Lunkenheimer, P.; Loidl, A. [Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg (Germany); Bermejo, F. J. [CSIC-Department of Electricity and Electronics, University of the Basque Country, P.O. Box 664, 48080 Bilbao (Spain)

2009-08-14

436

New Microscopic Mechanism for Secondary Relaxation in Glasses  

NASA Astrophysics Data System (ADS)

The dynamics of simple molecular systems showing glassy properties has been explored by dielectric spectroscopy and nuclear quadrupole resonance (NQR) on the halogenomethanes CBr2Cl2 and CBrCl3 in their low-temperature monoclinic phases. The dielectric spectra display features which correspond to ?- and ?-relaxation processes, commonly observed in canonical glass formers. NQR experiments, also performed in the ergodic monoclinic phase of CCl4, enable the determination of the microscopic mechanism underlying the ? dynamics in these simple model glasses: Molecules that are nonequivalent with respect to their molecular environment perform reorientational jumps at different time scales. Thus our findings reveal another mechanism that can give rise to typical ?-relaxation behavior, raising some doubt about the existence of a universal explanation of this phenomenon.

Zuriaga, M.; Pardo, L. C.; Lunkenheimer, P.; Tamarit, J. Ll.; Veglio, N.; Barrio, M.; Bermejo, F. J.; Loidl, A.

2009-08-01

437

resonant Auger decay  

Microsoft Academic Search

The Ar resonant Auger spectra have been recorded in Raman conditions at a photon energy of 249 eV corresponding to the Ar 2p1\\/2 ? 3d excitation. The high experimental resolution allowed us to resolve the fine structure in the resonant Auger spectra in much greater detail than obtained previously. Experimental individual angular anisotropy ? parameter values of the Ar 2p?1

S Osmekhin; S Fritzsche; A N Grum-Grzhimailo; H Aksela; S Aksela

438

Nuclear magnetic resonance gyroscope  

SciTech Connect

A nuclear magnetic resonance gyro using two nuclear magnetic resonance gases, preferably xenon 129 and xenon 131, together with two alkaline metal vapors, preferably rubidium, potassium or cesium, one of the two alkaline metal vapors being pumped by light which has the wavelength of that alkaline metal vapor, and the other alkaline vapor being illuminated by light which has the wavelength of that other alkaline vapor.

Grover, B.C.

1984-02-07

439

Resonance searches with the $t\\overline{t}$ Invariant Mass Distribution measured with the D\\O\\, Experiment at $\\sqrt{s}=1.96\\,\\textrm{TeV}  

SciTech Connect

Understanding the universe, its birth and its future is one of the biggest motivations in physics. In order to understand the cosmos, the fundamental particles forming the universe, the components our matter is built of need to be known and understood. Over time physicists have built a theory which describes the physics of the known fundamental particles very well: the Standard Model (SM) of particle physics. The SM describes the particles, their interactions and phenomena with high precision. So far no proven deviations from the SM have been found, though recently evidence for possible physics beyond the SM has been observed. The SM is not describing the mass of the elementary particles however and even with the addition of the Higgs mechanism giving mass to the particles, we have no full theory for all four fundamental forces. We know the model needs to be extended or replaced by another one, as gravitation is not included in the SM. Having a theory which describes all fundamental particles found so far and all but one fundamental interaction is a great success. However, all this describes about 4% of the universe we live in. 23% is dark matter and 73% is dark energy. Dark matter is believed to interact only through gravity and maybe the weak force, which makes it hardly observable. Dark energy is even more elusive. Among other theories the cosmologic constant and scalar fields are discussed to describe it. One should also note that other models exist which for example modify the Newtonian law of gravity. The Higgs mechanism has become the most popular model for mass generation. Alternative theories like Super Symmetry (SUSY), large Extra Dimensions, Technicolor, String Theory, to name just a few, have spread to describe the necessary mass generation or new particles. As proof for new physics beyond the SM has not been found yet, one assumes that new physics will manifest itself at a larger energy scale and therefore a higher particle mass. Particles with high masses are therefore presumed to be a window to test the SM for deviations caused by new physics. The heaviest fundamental particle which is in our reach is the top quark. Its mass is almost as large as that of a complete tungsten atom. It is so heavy, that it decays faster than it can hadronize. It seems the perfect probe to study new physics at the moment. In this analysis the top quark is used as a probe to search for a new resonance, whose properties are similar to a SM Z boson but is much more massive. This analysis will study t{bar t} decays to search for an excess in the invariant mass distribution of the t{bar t} pairs. Resonant states are suggested for massive Z-like bosons in extended gauge theories, Kaluza Klein states of the gluon or Z, axigluons, topcolor, and other beyond the Standard Model theories. Independent of the exact model a resonant production mechanism should be visible in the t{bar t} invariant mass distribution. In this thesis a model-independent search for a narrow-width heavy resonance X decaying into t{bar t} is performed. In the SM, the top quark decays into a W boson and a b quark nearly 100% of the time, which has been proven experimentally, too. The t{bar t} event signature is fully determined by the W boson decay modes. In this analysis, only the lepton+jets final state, which results from the leptonic decay of one of the W bosons and the hadronic decay of the other, is considered. The event signature is an isolated electron or muon with high transverse momentum, large transverse energy imbalance due to the undetected neutrino, and at least three jets, two of which result from the hadronization of b quarks.

Schliephake, Thorsten Dirk; /Wuppertal U.

2010-06-01

440

Resonant nonlinear ultrasound spectroscopy  

DOEpatents

Components with defects are identified from the response to strains applied at acoustic and ultrasound frequencies. The relative resonance frequency shift .vertline..DELTA..function./.function..sub.0.vertline., is determined as a function of applied strain amplitude for an acceptable component, where .function..sub.0 is the frequency of the resonance peak at the lowest amplitude of applied strain and .DELTA..function. is the frequency shift of the resonance peak of a selected mode to determine a reference relationship. Then, the relative resonance frequency shift .vertline..DELTA..function./.function..sub.0 is determined as a function of applied strain for a component under test, where fo .function..sub.0 the frequency of the resonance peak at the lowest amplitude of applied strain and .DELTA..function. is the frequency shift of the resonance peak to determine a quality test relationship. The reference relationship is compared with the quality test relationship to determine the presence of defects in the component under test.

Johnson, Paul A. (Santa Fe, NM); TenCate, James A. (Los Alamos, NM); Guyer, Robert A. (Amherst, MA); Van Den Abeele, Koen E. A. (Sint-Niklaas, BE)

2001-01-01

441

Resonantly driven wobbling kinks.  

PubMed

The amplitude of oscillations of the freely wobbling kink in the varphi(4) theory decays due to the emission of second-harmonic radiation. We study the compensation of these radiation losses (as well as additional dissipative losses) by the resonant driving of the kink. We consider both direct and parametric driving at a range of resonance frequencies. In each case, we derive the amplitude equations which describe the evolution of the amplitude of the wobbling and the kink's velocity. These equations predict multistability and hysteretic transitions in the wobbling amplitude for each driving frequency--the conclusion verified by numerical simulations of the full partial differential equation. We show that the strongest parametric resonance occurs when the driving frequency equals the natural wobbling frequency and not double that value. For direct driving, the strongest resonance is at half the natural frequency, but there is also a weaker resonance when the driving frequency equals the natural wobbling frequency itself. We show that this resonance is accompanied by the translational motion of the kink. PMID:19792274

Oxtoby, O F; Barashenkov, I V

2009-08-31

442

Schumann Resonances in Lightning Research  

Microsoft Academic Search

Schumann resonances (SR) are global electromagnetic resonances excited primarily by lightning discharges. This review is aimed at the reader generally unfamiliar with Schumann resonances. Our goal is to give some historical context to SR research, and to show the extensive use of Schumann resonances in a variety of lightning-related studies in recent years, ranging from estimates of the spatial and

Colin Price; Olga Pechony; Eran Greenberg

2007-01-01

443

Enhanced terahertz transmission by surface plasmon resonance  

NASA Astrophysics Data System (ADS)

The surface plasmon resonance (SPR) between metal and dielectric material has a good enhancement on electromagnetic wave transmission. In this paper, a series of two-dimension (2D) metal gratings and spiral structures with different geometrical size were experimentally tested by Terahertz time-domain spectroscopy (THz-TDS). The experiment results show that the 2D metal gratings have almost 70% increment on terahertz transmission than the pure silicon substrate in the range of 0.2-2.5THz, which indicates a strong coupling in the terahertz range, and the resonance mode shows a blue shift. On the other hand, the influence of different radiation directions was analyzed. It presents that the slightly higher transmission can be achieved when terahertz wave radiate from the front side than the back side. It reveals that surface plasmon resonance can enhance the terahertz transmission efficiently and has potential applications in security imaging, biological analysis and spectroscopy.

Wen, Yongzheng; Yang, Jiancheng; Yu, Xiaomei; Zhao, Yuejin; Liu, Xiaohua; Dong, Liquan

2012-02-01

444

QUASI-RESONANT THEORY OF TIDAL INTERACTIONS  

SciTech Connect

When a spinning system experiences a transient gravitational encounter with an external perturber, a quasi-resonance occurs if the spin frequency of the victim roughly matches the peak angular speed of the perturber. Such encounters are responsible for the formation of long tails and bridges during galaxy collisions. For high-speed encounters, the resulting velocity perturbations can be described by the impulse approximation. The traditional impulse approximation, however, does not distinguish between prograde and retrograde encounters, and therefore completely misses the resonant response. Here, we modify the impulse approximation to include the effects of quasi-resonant phenomena on stars orbiting within a disk. Explicit expressions are derived for the velocity and energy changes to the stars induced by tidal forces from an external gravitational perturber passing either on a straight line or a parabolic orbit. Comparisons with numerical-restricted three-body calculations illustrate the applicability of our analysis.

D'Onghia, Elena; Vogelsberger, Mark; Faucher-Giguere, Claude-Andre; Hernquist, Lars, E-mail: edonghia@cfa.harvard.ed [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2010-12-10

445

Magnetically-excited flexural plate wave resonator  

SciTech Connect

A flexural plate wave (FPW) resonator was constructed by patterning current lines on a silicon nitride membrane suspended on a rectangular silicon frame. Eigenmodes of the rectangular membrane were excited using Lorentz forces generated between alternating surface currents and a static in-plane magnetic field. The magnetic field strength required for these devices can be achieved with small permanent magnets ({approx} 1 cm{sup 3}). Preferential coupling to a particular membrane mode was achieved by positioning current lines along longitudinal mode antinodes. An equivalent-circuit model was derived that characterizes the input impedance of a one-port device and the transmission response of a two-port device over a range of frequencies near a single membrane resonance. Experiments were performed to characterize the effects of varying magnetic field, ambient gas, gas pressure, and input power. To the authors` knowledge, this is the first experimental demonstration of a resonant FPW device.

Martin, S.J.; Butler, M.A.; Spates, J.J.; Schubert, W.K.; Mitchell, M.A. [Sandia National Labs., Albuquerque, NM (United States). Microsensor Research and Development Dept.

1997-08-01

446

Euclidean resonance in a magnetic field  

NASA Astrophysics Data System (ADS)

An analogy is found between Wigner resonant tunneling and tunneling across a static potential barrier in a static magnetic field. Whereas in the process of Wigner tunneling an electron encounters a classically allowed region where a discrete energy level coincides with its energy, in the magnetic field the potential barrier is constant in the direction of tunneling. Along the tunneling path, certain regions are formed where, in the classical language, the kinetic energy of the motion perpendicular to tunneling is negative. These regions play the role of potential wells, where a discrete energy level can coincide with the electron energy. This phenomenon, which occurs at a certain magnetic field, is called Euclidean resonance and substantially depends on the shape of the potential forces in the direction perpendicular to tunneling. Under conditions of Euclidean resonance, a long-distance underbarrier motion is possible, which can be observed in experiments.

Ivlev, B.

2007-08-01

447

Mass loading induced dephasing in nanomechanical resonators.  

PubMed

This paper presents a study of dephasing of an underdamped nanomechanical resonator subject to random mass loading of small particles. A frequency noise model is presented which describes dephasing due to the attachment and detachment of particles at random points and particle diffusion along the resonator. This situation is commonly encountered in current mass measurement experiments using nanoelectromechanical (NEM) resonators. The conditions which can lead to inhomogeneous broadening and fine structure in the modes' absorption spectra are discussed. It is also shown that the spectra of the higher-order cumulants of the (complex) vibrational mode amplitude are sensitive to the parameters characterizing the frequency noise process. Hence, measurement of these cumulants can provide information not only about the mass but also about other parameters of the particles (diffusion coefficient and attachment-detachment rates). PMID:23104872

Atalaya, Juan

2012-10-26

448

Tens Femtogram Resoluble Piezoresistive Cantilever Sensors with Optimized High-Mode Resonance Excitation  

Microsoft Academic Search

Ultra-sensitive mass sensor is demanded for bio\\/chemical molecular detection. A piezoresistive resonant cantilever sensor with optimized is developed with an optimized electromagnetic excitation for high-mode flexure resonance. In our experiment, it has been proved that the quality factor of the resonant sensor can be improved by this optimized high-mode resonance exciting technique. Experimental results have shown that the optimized excitation

Dazhong Jin; Jian Liu; Xinxin Li; Min Liu; Guomin Zuo; Yuelin Wang; Haitao Yu; Xiaohong Ge

2006-01-01

449

Strongly driven electron spins using a K(u) band stripline electron paramagnetic resonance resonator.  

PubMed

This article details our work to obtain strong excitation for electron paramagnetic resonance (EPR) experiments by improving the resonator's efficiency. The advantages and application of strong excitation are discussed. Two 17 GHz transmission-type, stripline