Accurate measurements of transition frequencies and isotope shifts of laser-trapped francium.
Sanguinetti, S; Calabrese, R; Corradi, L; Dainelli, A; Khanbekyan, A; Mariotti, E; de Mauro, C; Minguzzi, P; Moi, L; Stancari, G; Tomassetti, L; Veronesi, S
2009-04-01
An interferometric method is used to improve the accuracy of the 7S-7P transition frequencies of three francium isotopes by 1 order of magnitude. The deduced isotope shifts for 209-211Fr confirm the ISOLDE data. The frequency of the D2 transition of 212Fr--the accepted reference for all Fr isotope shifts--is revised, and a significant difference with the ISOLDE value is found. Our results will be a benchmark for the accuracy of the theory of Fr energy levels, a necessary step to investigate fundamental symmetries. PMID:19340162
Highly Accurate and Precise Infrared Transition Frequencies of the H_3^+ Cation
NASA Astrophysics Data System (ADS)
Perry, Adam J.; Markus, Charles R.; Hodges, James N.; Kocheril, G. Stephen; McCall, Benjamin J.
2016-06-01
Calculation of ab initio potential energy surfaces for molecules to high accuracy is only manageable for a handful of molecular systems. Among them is the simplest polyatomic molecule, the H_3^+ cation. In order to achieve a high degree of accuracy (<1 wn) corrections must be made to the to the traditional Born-Oppenheimer approximation that take into account not only adiabatic and non-adiabatic couplings, but quantum electrodynamic corrections as well. For the lowest rovibrational levels the agreement between theory and experiment is approaching 0.001 wn, whereas the agreement is on the order of 0.01 - 0.1 wn for higher levels which are closely rivaling the uncertainties on the experimental data. As method development for calculating these various corrections progresses it becomes necessary for the uncertainties on the experimental data to be improved in order to properly benchmark the calculations. Previously we have measured 20 rovibrational transitions of H_3^+ with MHz-level precision, all of which have arisen from low lying rotational levels. Here we present new measurements of rovibrational transitions arising from higher rotational and vibrational levels. These transitions not only allow for probing higher energies on the potential energy surface, but through the use of combination differences, will ultimately lead to prediction of the "forbidden" rotational transitions with MHz-level accuracy. L.G. Diniz, J.R. Mohallem, A. Alijah, M. Pavanello, L. Adamowicz, O.L. Polyansky, J. Tennyson Phys. Rev. A (2013), 88, 032506 O.L. Polyansky, A. Alijah, N.F. Zobov, I.I. Mizus, R.I. Ovsyannikov, J. Tennyson, L. Lodi, T. Szidarovszky, A.G. Császár Phil. Trans. R. Soc. A (2012), 370, 5014 J.N. Hodges, A.J. Perry, P.A. Jenkins II, B.M. Siller, B.J. McCall J. Chem. Phys. (2013), 139, 164201 A.J. Perry, J.N. Hodges, C.R. Markus, G.S. Kocheril, B.J. McCall J. Molec. Spectrosc. (2015), 317, 71-73.
Accurate frequency noise measurement of free-running lasers.
Schiemangk, Max; Spiessberger, Stefan; Wicht, Andreas; Erbert, Götz; Tränkle, Günther; Peters, Achim
2014-10-20
We present a simple method to accurately measure the frequency noise power spectrum of lasers. It relies on creating the beat note between two lasers, capturing the corresponding signal in the time domain, and appropriately postprocessing the data to derive the frequency noise power spectrum. In contrast to methods already established, it does not require stabilization of the laser to an optical reference, i.e., a second laser, to an optical cavity or to an atomic transition. It further omits a frequency discriminator and hence avoids bandwidth limitation and nonlinearity effects common to high-resolution frequency discriminators.
High Frequency QRS ECG Accurately Detects Cardiomyopathy
NASA Technical Reports Server (NTRS)
Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds
2005-01-01
High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing
Accurate transition rates for intercombination lines of singly ionized nitrogen
Tayal, S. S.
2011-01-15
The transition energies and rates for the 2s{sup 2}2p{sup 2} {sup 3}P{sub 1,2}-2s2p{sup 3} {sup 5}S{sub 2}{sup o} and 2s{sup 2}2p3s-2s{sup 2}2p3p intercombination transitions have been calculated using term-dependent nonorthogonal orbitals in the multiconfiguration Hartree-Fock approach. Several sets of spectroscopic and correlation nonorthogonal functions have been chosen to describe adequately term dependence of wave functions and various correlation corrections. Special attention has been focused on the accurate representation of strong interactions between the 2s2p{sup 3} {sup 1,3}P{sub 1}{sup o} and 2s{sup 2}2p3s {sup 1,3}P{sub 1}{sup o}levels. The relativistic corrections are included through the one-body mass correction, Darwin, and spin-orbit operators and two-body spin-other-orbit and spin-spin operators in the Breit-Pauli Hamiltonian. The importance of core-valence correlation effects has been examined. The accuracy of present transition rates is evaluated by the agreement between the length and velocity formulations combined with the agreement between the calculated and measured transition energies. The present results for transition probabilities, branching fraction, and lifetimes have been compared with previous calculations and experiments.
Accurate Determination of Conformational Transitions in Oligomeric Membrane Proteins
Sanz-Hernández, Máximo; Vostrikov, Vitaly V.; Veglia, Gianluigi; De Simone, Alfonso
2016-01-01
The structural dynamics governing collective motions in oligomeric membrane proteins play key roles in vital biomolecular processes at cellular membranes. In this study, we present a structural refinement approach that combines solid-state NMR experiments and molecular simulations to accurately describe concerted conformational transitions identifying the overall structural, dynamical, and topological states of oligomeric membrane proteins. The accuracy of the structural ensembles generated with this method is shown to reach the statistical error limit, and is further demonstrated by correctly reproducing orthogonal NMR data. We demonstrate the accuracy of this approach by characterising the pentameric state of phospholamban, a key player in the regulation of calcium uptake in the sarcoplasmic reticulum, and by probing its dynamical activation upon phosphorylation. Our results underline the importance of using an ensemble approach to characterise the conformational transitions that are often responsible for the biological function of oligomeric membrane protein states. PMID:26975211
How Accurate Are Transition States from Simulations of Enzymatic Reactions?
2015-01-01
The rate expression of traditional transition state theory (TST) assumes no recrossing of the transition state (TS) and thermal quasi-equilibrium between the ground state and the TS. Currently, it is not well understood to what extent these assumptions influence the nature of the activated complex obtained in traditional TST-based simulations of processes in the condensed phase in general and in enzymes in particular. Here we scrutinize these assumptions by characterizing the TSs for hydride transfer catalyzed by the enzyme Escherichia coli dihydrofolate reductase obtained using various simulation approaches. Specifically, we compare the TSs obtained with common TST-based methods and a dynamics-based method. Using a recently developed accurate hybrid quantum mechanics/molecular mechanics potential, we find that the TST-based and dynamics-based methods give considerably different TS ensembles. This discrepancy, which could be due equilibrium solvation effects and the nature of the reaction coordinate employed and its motion, raises major questions about how to interpret the TSs determined by common simulation methods. We conclude that further investigation is needed to characterize the impact of various TST assumptions on the TS phase-space ensemble and on the reaction kinetics. PMID:24860275
Accurate Evaluation Method of Molecular Binding Affinity from Fluctuation Frequency
NASA Astrophysics Data System (ADS)
Hoshino, Tyuji; Iwamoto, Koji; Ode, Hirotaka; Ohdomari, Iwao
2008-05-01
Exact estimation of the molecular binding affinity is significantly important for drug discovery. The energy calculation is a direct method to compute the strength of the interaction between two molecules. This energetic approach is, however, not accurate enough to evaluate a slight difference in binding affinity when distinguishing a prospective substance from dozens of candidates for medicine. Hence more accurate estimation of drug efficacy in a computer is currently demanded. Previously we proposed a concept of estimating molecular binding affinity, focusing on the fluctuation at an interface between two molecules. The aim of this paper is to demonstrate the compatibility between the proposed computational technique and experimental measurements, through several examples for computer simulations of an association of human immunodeficiency virus type-1 (HIV-1) protease and its inhibitor (an example for a drug-enzyme binding), a complexation of an antigen and its antibody (an example for a protein-protein binding), and a combination of estrogen receptor and its ligand chemicals (an example for a ligand-receptor binding). The proposed affinity estimation has proven to be a promising technique in the advanced stage of the discovery and the design of drugs.
Accurate measurement of intestinal transit in the rat
Miller, M.S.; Galligan, J.J.; Burks, T.F.
1981-11-01
A new method for quantifying intestinal transit was evaluated by comparison with two other popular techniques. The distribution of radiochromium (51Cr) throughout the small intestine of rats previously treated with saline (1.0 ml/kg s.c.), capsaicin (10 mg/kg s.c.), hexamethonium (20 mg/kg i.p.), D-ala2-met-enkephalinamide (1.0 microgram i.c.v.), or neostigmine (0.1 mg/kg i.p.) was quantified by (1) measuring the most distal intestinal segment reached by chromium, (2) calculating the slope produced by linear regression analysis on cumulative percent chromium that had passed through each segment, and (3) determining the geometric center of the distribution of chromium throughout the small intestine. It was concluded that the geometric center methods for quantifying intestinal transit provides the most sensitive and reliable measure of intestinal transit. Less sensitive techniques often fail to detect important effects of drugs on intestinal transit.
Rotational frequencies of transition metal hydrides for astrophysical searches in the far-infrared
NASA Technical Reports Server (NTRS)
Brown, John M.; Beaton, Stuart P.; Evenson, Kenneth M.
1993-01-01
Accurate frequencies for the lowest rotational transitions of five transition metal hydrides (CrH, FeH, CoH, NiH, and CuH) in their ground electronic states are reported to help the identification of these species in astrophysical sources from their far-infrared spectra. Accurate frequencies are determined in two ways: for CuH, by calculation from rotational constants determined from higher J transitions with an accuracy of 190 kHz; for the other species, by extrapolation to zero magnetic field from laser magnetic resonance spectra with an accuracy of 0.7 MHz.
Importance of level mixing on accurate [Fe II] transition rates
NASA Astrophysics Data System (ADS)
Deb, N. C.; Hibbert, A.
2010-12-01
Context. In a very recent measurement Gurell et al. (2009, A&A, 508, 525) commented that while the theoretical lifetime of a 4G5.5 is approximately one tenth of the lifetime of b 2H5.5 the corresponding measurement shows this to be close to one fifth. This large discrepancy is attributed to the effect of inadequate level mixing in the theoretical calculations. Aims: The aim of this work is to make a detailed analysis of these level mixing effects on transitions from various lower levels to the a 4G5.5 and b 2H5.5 levels given in three previous calculations and in the present more extensive CI calculation. Methods: The CIV3 structure codes of Hibbert (1975, Comput. Phys. Commun., 9, 141) and Hibbert et al. (1991, Comput. Phys. Commun., 64, 455) are used in the present work, combined with our “fine-tuning” extrapolation process. Results: The calculated mixing between the upper levels, obtained in previous calculations, is shown to be too weak. The stronger mixing determined in our work gives rise to a calculated lifetime for b 2H5.5 within 3% of the measured value. On the other hand our calculated lifetime for a 4G5.5 is around 20% lower than the measured value, which has fairly wide error bars. Conclusions: Our enhanced calculations explain the difference between previous calculations of the b 2H5.5 lifetime and the recent measured value and confirm the latter. We also suggest a somewhat higher value than experiment for the lifetime of a 4G5.5.
NASA Technical Reports Server (NTRS)
Wintucky, Edwin G.; Simons, Rainee N.
2014-01-01
This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from two dissimilar waveguides is capable of isolating the power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT). In addition to accurate power measurements at harmonic frequencies, a potential application of the MDC is in the design of a beacon source for atmospheric propagation studies at millimeter-wave frequencies.
A fast and accurate frequency estimation algorithm for sinusoidal signal with harmonic components
NASA Astrophysics Data System (ADS)
Hu, Jinghua; Pan, Mengchun; Zeng, Zhidun; Hu, Jiafei; Chen, Dixiang; Tian, Wugang; Zhao, Jianqiang; Du, Qingfa
2016-10-01
Frequency estimation is a fundamental problem in many applications, such as traditional vibration measurement, power system supervision, and microelectromechanical system sensors control. In this paper, a fast and accurate frequency estimation algorithm is proposed to deal with low efficiency problem in traditional methods. The proposed algorithm consists of coarse and fine frequency estimation steps, and we demonstrate that it is more efficient than conventional searching methods to achieve coarse frequency estimation (location peak of FFT amplitude) by applying modified zero-crossing technique. Thus, the proposed estimation algorithm requires less hardware and software sources and can achieve even higher efficiency when the experimental data increase. Experimental results with modulated magnetic signal show that the root mean square error of frequency estimation is below 0.032 Hz with the proposed algorithm, which has lower computational complexity and better global performance than conventional frequency estimation methods.
An Accurate ab initio Quartic Force Field and Vibrational Frequencies for CH4 and Isotopomers
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Martin, Jan M. L.; Taylor, Peter R.
1995-01-01
A very accurate ab initio quartic force field for CH4 and its isotopomers is presented. The quartic force field was determined with the singles and doubles coupled-cluster procedure that includes a quasiperturbative estimate of the effects of connected triple excitations, CCSD(T), using the correlation consistent polarized valence triple zeta, cc-pVTZ, basis set. Improved quadratic force constants were evaluated with the correlation consistent polarized valence quadruple zeta, cc-pVQZ, basis set. Fundamental vibrational frequencies are determined using second-order perturbation theory anharmonic analyses. All fundamentals of CH4 and isotopomers for which accurate experimental values exist and for which there is not a large Fermi resonance, are predicted to within +/- 6 cm(exp -1). It is thus concluded that our predictions for the harmonic frequencies and the anharmonic constants are the most accurate estimates available. It is also shown that using cubic and quartic force constants determined with the correlation consistent polarized double zeta, cc-pVDZ, basis set in conjunction with the cc-pVQZ quadratic force constants and equilibrium geometry leads to accurate predictions for the fundamental vibrational frequencies of methane, suggesting that this approach may be a viable alternative for larger molecules. Using CCSD(T), core correlation is found to reduce the CH4 r(e), by 0.0015 A. Our best estimate for r, is 1.0862 +/- 0.0005 A.
Monitoring of cache miss rates for accurate dynamic voltage and frequency scaling
NASA Astrophysics Data System (ADS)
Singleton, Leo C.; Poellabauer, Christian; Schwan, Karsten
2005-01-01
Modern mobile processors offer dynamic voltage and frequency scaling, which can be used to reduce the energy requirements of embedded and real-time applications by exploiting idle CPU resources, while still maintaining all applications' real-time characteristics. However, accurate predictions of task run-times are key to computing the frequencies and voltages that ensure that all tasks' real-time constraints are met. Past work has used feedback-based approaches, where applications' past CPU utilizations are used to predict future CPU requirements. Inaccurate predictions in these approaches can lead to missed deadlines, less than expected energy savings, or large overheads due to frequent voltage and frequency changes. Previous solutions ignore other `indicators' of future CPU requirements, such as the frequency of I/O operations, memory accesses, or interrupts. This paper addresses this shortcoming for memory-intensive applications, where measured task run-times and cache miss rates are used as feedback for accurate run-time predictions. Cache miss rates indicate the frequency of memory accesses and enable us to derive the latencies introduced by these operations. The results shown in this paper indicate improvements in the number of deadlines met and the amount of energy saved.
Monitoring of cache miss rates for accurate dynamic voltage and frequency scaling
NASA Astrophysics Data System (ADS)
Singleton, Leo C.; Poellabauer, Christian; Schwan, Karsten
2004-12-01
Modern mobile processors offer dynamic voltage and frequency scaling, which can be used to reduce the energy requirements of embedded and real-time applications by exploiting idle CPU resources, while still maintaining all applications' real-time characteristics. However, accurate predictions of task run-times are key to computing the frequencies and voltages that ensure that all tasks' real-time constraints are met. Past work has used feedback-based approaches, where applications' past CPU utilizations are used to predict future CPU requirements. Inaccurate predictions in these approaches can lead to missed deadlines, less than expected energy savings, or large overheads due to frequent voltage and frequency changes. Previous solutions ignore other `indicators' of future CPU requirements, such as the frequency of I/O operations, memory accesses, or interrupts. This paper addresses this shortcoming for memory-intensive applications, where measured task run-times and cache miss rates are used as feedback for accurate run-time predictions. Cache miss rates indicate the frequency of memory accesses and enable us to derive the latencies introduced by these operations. The results shown in this paper indicate improvements in the number of deadlines met and the amount of energy saved.
NASA Astrophysics Data System (ADS)
Dong, J. W.; Wang, B.; Gao, C.; Wang, L. J.
2016-09-01
An accurate and fast fiber transfer delay measurement method is demonstrated. As a key technique, a simple ambiguity resolving process based on phase discrimination and frequency measurement is used to overcome the contradiction between measurement accuracy and system complexity. The system achieves a high measurement accuracy of 0.2 ps with a 0.1 ps measurement resolution and a large dynamic range up to 50 km as well as no dead zone.
NASA Astrophysics Data System (ADS)
Peng, Qin; Jinbo, Li; Jian, Kang; Xiaoyong, Li; Jianjun, Zhou
2014-09-01
A low noise phase locked loop (PLL) frequency synthesizer implemented in 65 nm CMOS technology is introduced. A VCO noise reduction method suited for short channel design is proposed to minimize PLL output phase noise. A self-calibrated voltage controlled oscillator is proposed in cooperation with the automatic frequency calibration circuit, whose accurate binary search algorithm helps reduce the VCO tuning curve coverage, which reduces the VCO noise contribution at PLL output phase noise. A low noise, charge pump is also introduced to extend the tuning voltage range of the proposed VCO, which further reduces its phase noise contribution. The frequency synthesizer generates 9.75-11.5 GHz high frequency wide band local oscillator (LO) carriers. Tested 11.5 GHz LO bears a phase noise of-104 dBc/Hz at 1 MHz frequency offset. The total power dissipation of the proposed frequency synthesizer is 48 mW. The area of the proposed frequency synthesizer is 0.3 mm2, including bias circuits and buffers.
NASA Astrophysics Data System (ADS)
Cao, Cheng-Hao; Zhang, Hong-Bing; Pan, Yi-Xin; Teng, Xin-Bao
2016-03-01
Local fluid flow (LFF) at the mesoscopic scale is the main dissipation mechanism of seismic waves in heterogeneous porous media within the seismic frequency band. LFF is easily influenced by the structure and boundary conditions of the porous media, which leads to different behaviors of the peak frequency of attenuation. The associated transition frequency can provide detailed information about the trend of LFF; therefore, research on the transition frequency of LFF and its relationship with the peak frequency of the corresponding attenuation (i.e., inverse of quality factor) facilitates the detailed understanding of the effect of inner structures and boundary conditions in porous media. In this study, we firstly obtain the transition frequency of fluid flux based on Biot's theory of poroelasticity and the fast Fourier transform algorithm in a sample containing one repeating unit cell (RUC). We then analyze changes of these two frequencies in porous media with different porous properties. Finally, we extend our analysis to the influence of the undrained boundary condition on the transition frequency and peak frequency in porous media with multiple RUCs. This setup can facilitate the understanding of the effect from the undrained boundary condition. Results demonstrate that these two frequencies have the same trend at low water saturation, but amplitude variations differ between the frequencies as the amount of saturation increases. However, for cases of high water saturation, both the trend and the amplitude variation of these two frequencies fit well with each other.
Distributed fiber sensing system with wide frequency response and accurate location
NASA Astrophysics Data System (ADS)
Shi, Yi; Feng, Hao; Zeng, Zhoumo
2016-02-01
A distributed fiber sensing system merging Mach-Zehnder interferometer and phase-sensitive optical time domain reflectometer (Φ-OTDR) is demonstrated for vibration measurement, which requires wide frequency response and accurate location. Two narrow line-width lasers with delicately different wavelengths are used to constitute the interferometer and reflectometer respectively. A narrow band Fiber Bragg Grating is responsible for separating the two wavelengths. In addition, heterodyne detection is applied to maintain the signal to noise rate of the locating signal. Experiment results show that the novel system has a wide frequency from 1 Hz to 50 MHz, limited by the sample frequency of data acquisition card, and a spatial resolution of 20 m, according to 200 ns pulse width, along 2.5 km fiber link.
Accurate measurement of the 12.6 GHz "clock" transition in trapped (171)Yb(+) ions.
Fisk, P H; Sellars, M J; Lawn, M A; Coles, G
1997-01-01
We have measured the frequency of the (171)Yb(+) 12.6 GHz M(F)=0-->0 ground state hyperfine "clock" transition in buffer gas-cooled ion clouds confined in two similar, but not identical, linear Paul traps. After correction for the known differences between the two ion traps, including significantly different second-order Doppler shifts, the frequencies agree within an uncertainty of less than 2 parts in 10(13). Our best value, based on an analytic model for the second-order Doppler shift, for the frequency of the clock transition of an isolated ion at zero temperature, velocity, electric field and magnetic field, is 12642812118.466+0.002 Hz.
Switch over to the high frequency rf systems near transition
Brennan, J.M.; Wei, J.
1988-01-01
The purpose of this note is to point out that since bunch narrowing naturally occurs in the acceleration process in the vicinity of transition, it should be possible to switch over to the high frequency system close to transition when the bunch has narrowed enough to fit directly into the high frequency bucket. The advantage of this approach is the simplicity, no extra components or gymnastics are required of the low frequency system. The disadvantage, of course, is for protons which do not go through transition. But on the other hand, there is no shortage of intensity for protons and so it should be possible to keep the phase space area low for protons, and then matching to the high frequency bucket should be easily accomplished by adiabatic compression. 3 refs., 7 figs.
Ustinov, E A
2014-10-01
Commensurate-incommensurate (C-IC) transition of krypton molecular layer on graphite received much attention in recent decades in theoretical and experimental researches. However, there still exists a possibility of generalization of the phenomenon from thermodynamic viewpoint on the basis of accurate molecular simulation. Recently, a new technique was developed for analysis of two-dimensional (2D) phase transitions in systems involving a crystalline phase, which is based on accounting for the effect of temperature and the chemical potential on the lattice constant of the 2D layer using the Gibbs-Duhem equation [E. A. Ustinov, J. Chem. Phys. 140, 074706 (2014)]. The technique has allowed for determination of phase diagrams of 2D argon layers on the uniform surface and in slit pores. This paper extends the developed methodology on systems accounting for the periodic modulation of the substrate potential. The main advantage of the developed approach is that it provides highly accurate evaluation of the chemical potential of crystalline layers, which allows reliable determination of temperature and other parameters of various 2D phase transitions. Applicability of the methodology is demonstrated on the krypton-graphite system. Analysis of phase diagram of the krypton molecular layer, thermodynamic functions of coexisting phases, and a method of prediction of adsorption isotherms is considered accounting for a compression of the graphite due to the krypton-carbon interaction. The temperature and heat of C-IC transition has been reliably determined for the gas-solid and solid-solid system.
Ustinov, E. A.
2014-10-07
Commensurate–incommensurate (C-IC) transition of krypton molecular layer on graphite received much attention in recent decades in theoretical and experimental researches. However, there still exists a possibility of generalization of the phenomenon from thermodynamic viewpoint on the basis of accurate molecular simulation. Recently, a new technique was developed for analysis of two-dimensional (2D) phase transitions in systems involving a crystalline phase, which is based on accounting for the effect of temperature and the chemical potential on the lattice constant of the 2D layer using the Gibbs–Duhem equation [E. A. Ustinov, J. Chem. Phys. 140, 074706 (2014)]. The technique has allowed for determination of phase diagrams of 2D argon layers on the uniform surface and in slit pores. This paper extends the developed methodology on systems accounting for the periodic modulation of the substrate potential. The main advantage of the developed approach is that it provides highly accurate evaluation of the chemical potential of crystalline layers, which allows reliable determination of temperature and other parameters of various 2D phase transitions. Applicability of the methodology is demonstrated on the krypton–graphite system. Analysis of phase diagram of the krypton molecular layer, thermodynamic functions of coexisting phases, and a method of prediction of adsorption isotherms is considered accounting for a compression of the graphite due to the krypton–carbon interaction. The temperature and heat of C-IC transition has been reliably determined for the gas–solid and solid–solid system.
Ustinov, E A
2014-10-01
Commensurate-incommensurate (C-IC) transition of krypton molecular layer on graphite received much attention in recent decades in theoretical and experimental researches. However, there still exists a possibility of generalization of the phenomenon from thermodynamic viewpoint on the basis of accurate molecular simulation. Recently, a new technique was developed for analysis of two-dimensional (2D) phase transitions in systems involving a crystalline phase, which is based on accounting for the effect of temperature and the chemical potential on the lattice constant of the 2D layer using the Gibbs-Duhem equation [E. A. Ustinov, J. Chem. Phys. 140, 074706 (2014)]. The technique has allowed for determination of phase diagrams of 2D argon layers on the uniform surface and in slit pores. This paper extends the developed methodology on systems accounting for the periodic modulation of the substrate potential. The main advantage of the developed approach is that it provides highly accurate evaluation of the chemical potential of crystalline layers, which allows reliable determination of temperature and other parameters of various 2D phase transitions. Applicability of the methodology is demonstrated on the krypton-graphite system. Analysis of phase diagram of the krypton molecular layer, thermodynamic functions of coexisting phases, and a method of prediction of adsorption isotherms is considered accounting for a compression of the graphite due to the krypton-carbon interaction. The temperature and heat of C-IC transition has been reliably determined for the gas-solid and solid-solid system. PMID:25296827
An Accurate Quartic Force Field and Vibrational Frequencies for HNO and DNO
NASA Technical Reports Server (NTRS)
Dateo, Christopher E.; Lee, Timothy J.; Schwenke, David W.
1994-01-01
An accurate ab initio quartic force field for HNO has been determined using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, CCSD(T), in conjunction with the correlation consistent polarized valence triple zeta (cc-pVTZ) basis set. Improved harmonic frequencies were determined with the cc-pVQZ basis set. Fundamental vibrational frequencies were determined using a second-order perturbation theory analysis and also using variational calculations. The N-0 stretch and bending fundamentals are determined well from both vibrational analyses. The H-N stretch, however, is shown to have an unusually large anharmonic correction, and is not well determined using second-order perturbation theory. The H-N fundamental is well determined from the variational calculations, demonstrating the quality of the ab initio quartic force field. The zero-point energy of HNO that should be used in isodesmic reactions is also discussed.
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Arnold, James O. (Technical Monitor)
1996-01-01
The vibrational frequencies and infrared intensities of naphthalene neutral and cation are studied at the self-consistent-field (SCF), second-order Moller-Plesset (MP2), and density functional theory (DFT) levels using a variety of one-particle basis sets. Very accurate frequencies can be obtained at the DFT level in conjunction with large basis sets if they are scaled with two factors, one for the C-H stretches and a second for all other modes. We also find remarkably good agreement at the B3LYP/4-31G level using only one scale factor. Unlike the neutral PAHs where all methods do reasonably well for the intensities, only the DFT results are accurate for the PAH cations. The failure of the SCF and MP2 methods is caused by symmetry breaking and an inability to describe charge delocalization. We present several interesting cases of symmetry breaking in this study. An assessment is made as to whether an ensemble of PAH neutrals or cations could account for the unidentified infrared bands observed in many astronomical sources.
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Langhoff, Stephen R. (Technical Monitor)
1996-01-01
Due to advances in quantum mechanical methods over the last few years, it is now possible to determine ab initio potential energy surfaces in which fundamental vibrational frequencies are accurate to within +/- 8 cm(sup -1) on average, and molecular bond distances are accurate to within +/- 0.001-0.003 A, depending on the nature of the bond. That is, the potential energy surfaces have not been scaled or empirically adjusted in any way, showing that theoretical methods have progressed to the point of being useful in analyzing spectra that are not from a tightly controlled laboratory environment, such as rovibrational spectra from the interstellar medium. Some recent examples demonstrating this accuracy win be presented and discussed. These include the HNO, CH4, C2H4, and ClCN molecules. The HNO molecule is interesting due to the very large H-N anharmonicity, while ClCN has a very large Fermi resonance. The ab initio studies for the CH4 and C2H4 molecules present the first accurate full quartic force fields of any kind (i.e., whether theoretical or empirical) for a five-atom and six-atom system, respectively.
Ab Initio Potential Energy Surfaces and the Calculation of Accurate Vibrational Frequencies
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Dateo, Christopher E.; Martin, Jan M. L.; Taylor, Peter R.; Langhoff, Stephen R. (Technical Monitor)
1995-01-01
Due to advances in quantum mechanical methods over the last few years, it is now possible to determine ab initio potential energy surfaces in which fundamental vibrational frequencies are accurate to within plus or minus 8 cm(exp -1) on average, and molecular bond distances are accurate to within plus or minus 0.001-0.003 Angstroms, depending on the nature of the bond. That is, the potential energy surfaces have not been scaled or empirically adjusted in any way, showing that theoretical methods have progressed to the point of being useful in analyzing spectra that are not from a tightly controlled laboratory environment, such as vibrational spectra from the interstellar medium. Some recent examples demonstrating this accuracy will be presented and discussed. These include the HNO, CH4, C2H4, and ClCN molecules. The HNO molecule is interesting due to the very large H-N anharmonicity, while ClCN has a very large Fermi resonance. The ab initio studies for the CH4 and C2H4 molecules present the first accurate full quartic force fields of any kind (i.e., whether theoretical or empirical) for a five-atom and six-atom system, respectively.
Robust Blind Frequency and Transition Time Estimation for Frequency Hopping Systems
NASA Astrophysics Data System (ADS)
Fu, Kuo-Ching; Chen, Yung-Fang
2010-12-01
In frequency hopping spread spectrum (FHSS) systems, two major problems are timing synchronization and frequency estimation. A blind estimation scheme is presented for estimating frequency and transition time without using reference signals. The scheme is robust in the sense that it can avoid the unbalanced sampling block problem that occurs in existing maximum likelihood-based schemes, which causes large errors in one of the estimates of frequency. The proposed scheme has a lower computational cost than the maximum likelihood-based greedy search method. The estimated parameters are also used for the subsequent time and frequency tracking. The simulation results demonstrate the efficacy of the proposed approach.
Lee, Myung W.
2007-01-01
The amplitude of a bottom simulating reflection (BSR), which occurs near the phase boundary between gas hydrate-bearing sediments and underlying gas-filled sediments, strongly depends on the frequency content of a seismic signal, as well as the impedance contrast across the phase boundary. A strong-amplitude BSR, detectable in a conventional seismic profile, is a good indicator of the presence of free gas beneath the phase boundary. However, the BSR as observed in low-frequency multichannel seismic data is generally difficult to identify in high-frequency, single-channel seismic data. To investigate the frequency dependence of BSR amplitudes, single-channel seismic data acquired with an air gun source at Blake Ridge, which is located off the shore of South Carolina, were analyzed in the frequency range of 10-240 Hz. The frequency-dependent impedance contrast caused by the velocity dispersion in partially gas saturated sediments is important to accurately analyze BSR amplitude. Analysis indicates that seismic attenuation of gas hydrate-bearing sediments, velocity dispersion, and a transitional base all contribute to the frequency-dependent BSR amplitude variation in the frequency range of 10-500 Hz. When velocity dispersion is incorporated into the BSR amplitude analysis, the frequency-dependent BSR amplitude at Blake Ridge can be explained with gas hydrate-bearing sediments having a quality factor of about 250 and a transitional base with a thickness of about 1 meter.
Conflict Frequency and Relationship Quality across the Transition to Parenthood
ERIC Educational Resources Information Center
Kluwer, Esther S.; Johnson, Matthew D.
2007-01-01
Longitudinal data from 293 Dutch couples were used to examine the association between conflict frequency and relationship quality across the transition to parenthood, which is known as one of the most challenging events in the early stages of marriage. More frequent conflict during pregnancy was related to lower levels of relationship quality…
Accurate formula for dissipative interaction in frequency modulation atomic force microscopy
NASA Astrophysics Data System (ADS)
Suzuki, Kazuhiro; Kobayashi, Kei; Labuda, Aleksander; Matsushige, Kazumi; Yamada, Hirofumi
2014-12-01
Much interest has recently focused on the viscosity of nano-confined liquids. Frequency modulation atomic force microscopy (FM-AFM) is a powerful technique that can detect variations in the conservative and dissipative forces between a nanometer-scale tip and a sample surface. We now present an accurate formula to convert the dissipation power of the cantilever measured during the experiment to damping of the tip-sample system. We demonstrated the conversion of the dissipation power versus tip-sample separation curve measured using a colloidal probe cantilever on a mica surface in water to the damping curve, which showed a good agreement with the theoretical curve. Moreover, we obtained the damping curve from the dissipation power curve measured on the hydration layers on the mica surface using a nanometer-scale tip, demonstrating that the formula allows us to quantitatively measure the viscosity of a nano-confined liquid using FM-AFM.
Accurate formula for dissipative interaction in frequency modulation atomic force microscopy
Suzuki, Kazuhiro; Matsushige, Kazumi; Yamada, Hirofumi; Kobayashi, Kei; Labuda, Aleksander
2014-12-08
Much interest has recently focused on the viscosity of nano-confined liquids. Frequency modulation atomic force microscopy (FM-AFM) is a powerful technique that can detect variations in the conservative and dissipative forces between a nanometer-scale tip and a sample surface. We now present an accurate formula to convert the dissipation power of the cantilever measured during the experiment to damping of the tip-sample system. We demonstrated the conversion of the dissipation power versus tip-sample separation curve measured using a colloidal probe cantilever on a mica surface in water to the damping curve, which showed a good agreement with the theoretical curve. Moreover, we obtained the damping curve from the dissipation power curve measured on the hydration layers on the mica surface using a nanometer-scale tip, demonstrating that the formula allows us to quantitatively measure the viscosity of a nano-confined liquid using FM-AFM.
National Institute of Standards and Technology Data Gateway
SRD 116 NIST Recommended Rest Frequencies for Observed Interstellar Molecular Microwave Transitions - 2002 Revision (Web, free access) Critically evaluated transition frequencies for the molecular transitions detected in interstellar and circumstellar clouds are presented.
NASA Astrophysics Data System (ADS)
Gerges, Meana; Foldes, Emily L.; Ackermann, D. Michael; Bhadra, Narendra; Bhadra, Niloy; Kilgore, Kevin L.
2010-12-01
High-frequency alternating currents (HFAC) have proven to be a reversible and rapid method of blocking peripheral nerve conduction, holding promise for treatment of disorders associated with undesirable neuronal activity. The delivery of HFAC is characterized by a transient period of neural firing at its inception, termed the 'onset response'. The onset response is minimized for higher frequencies and higher amplitudes, but requires larger currents. However, the complete block can be maintained at lower frequencies and amplitudes, using lower currents. In this in vivo study on whole mammalian peripheral nerves, we demonstrate a method to minimize the onset response by initiating the block using a stimulation paradigm with a high frequency and large amplitude, and then transitioning to a low-frequency and low-amplitude waveform, reducing the currents required to maintain the conduction block. In five of six animals, it was possible to transition from a 30 kHz to a 10 kHz waveform without inducing any transient neural firing. The minimum transition time was 0.03 s. Transition activity was minimized or eliminated with longer transition times. The results of this study show that this method is feasible for achieving a nerve block with minimal onset responses and current amplitude requirements.
Measurement of the lowest millimeter-wave transition frequency of the CH radical
Truppe, S.; Hendricks, R. J.; Hinds, E. A.; Tarbutt, M. R.
2014-01-01
The CH radical offers a sensitive way to test the hypothesis that fundamental constants measured on Earth may differ from those observed in other parts of the universe. The starting point for such a comparison is to have accurate laboratory frequencies. Here, we measure the frequency of the lowest millimeter-wave transition of CH, near 535 GHz, with an accuracy of 0.6 kHz. This improves the uncertainty by roughly two orders of magnitude over previous determinations and opens the way for sensitive new tests of varying constants.
The 10 Hz Frequency: A Fulcrum For Transitional Brain States
Garcia-Rill, E.; D’Onofrio, S.; Luster, B.; Mahaffey, S.; Urbano, F. J.; Phillips, C.
2016-01-01
A 10 Hz rhythm is present in the occipital cortex when the eyes are closed (alpha waves), in the precentral cortex at rest (mu rhythm), in the superior and middle temporal lobe (tau rhythm), in the inferior olive (projection to cerebellar cortex), and in physiological tremor (underlying all voluntary movement). These are all considered resting rhythms in the waking brain which are “replaced” by higher frequency activity with sensorimotor stimulation. That is, the 10 Hz frequency fulcrum is replaced on the one hand by lower frequencies during sleep, or on the other hand by higher frequencies during volition and cognition. The 10 Hz frequency fulcrum is proposed as the natural frequency of the brain during quiet waking, but is replaced by higher frequencies capable of permitting more complex functions, or by lower frequencies during sleep and inactivity. At the center of the transition shifts to and from the resting rhythm is the reticular activating system, a phylogenetically preserved area of the brain essential for preconscious awareness. PMID:27547831
Towards more accurate numerical modeling of impedance based high frequency harmonic vibration
NASA Astrophysics Data System (ADS)
Lim, Yee Yan; Kiong Soh, Chee
2014-03-01
The application of smart materials in various fields of engineering has recently become increasingly popular. For instance, the high frequency based electromechanical impedance (EMI) technique employing smart piezoelectric materials is found to be versatile in structural health monitoring (SHM). Thus far, considerable efforts have been made to study and improve the technique. Various theoretical models of the EMI technique have been proposed in an attempt to better understand its behavior. So far, the three-dimensional (3D) coupled field finite element (FE) model has proved to be the most accurate. However, large discrepancies between the results of the FE model and experimental tests, especially in terms of the slope and magnitude of the admittance signatures, continue to exist and are yet to be resolved. This paper presents a series of parametric studies using the 3D coupled field finite element method (FEM) on all properties of materials involved in the lead zirconate titanate (PZT) structure interaction of the EMI technique, to investigate their effect on the admittance signatures acquired. FE model updating is then performed by adjusting the parameters to match the experimental results. One of the main reasons for the lower accuracy, especially in terms of magnitude and slope, of previous FE models is the difficulty in determining the damping related coefficients and the stiffness of the bonding layer. In this study, using the hysteretic damping model in place of Rayleigh damping, which is used by most researchers in this field, and updated bonding stiffness, an improved and more accurate FE model is achieved. The results of this paper are expected to be useful for future study of the subject area in terms of research and application, such as modeling, design and optimization.
Infrared and far-infrared transition frequencies for the CH2 radical. [in interstellar gas clouds
NASA Technical Reports Server (NTRS)
Sears, T. J.; Mckellar, A. R. W.; Bunker, P. R.; Evenson, K. M.; Brown, J. M.
1984-01-01
A list of frequencies and intensities for transitions of CH2 in the middle and far infrared regions is presented which should aid in the detection of CH2 and provide valuable information on the local physical and chemical environment. Results are presented for frequency, vacuum wavelength, and line strength for rotational transition frequencies and for the transition frequencies of the v(2) band.
Precise Measurement of ^{40}CaH^{+} Vibrational Transition Frequency
NASA Astrophysics Data System (ADS)
Kajita, Masatoshi; Abe, Minori
2013-06-01
Small number of molecular ions in a linear trap can be sympathetically cooled with atomic ions and form a string crystal at the position, where the electric field is zero. Molecular ions in a strinc crystal are advantageous to measure the transition frequencies without Stark shift induced by the trap electric field, but it is required to localize small number of molecular ions in a single quantum state. ^{40}CaH^{+} molecular ion is advantageous to solve this problem, because (1) molecular ion with rotational constant of 141 GHz is localized in the vibrational-rotational ground state when the surrounding temperature is lower than 10 K, and (2) there is no hyperfine splitting in the J=0 state. In this presentation, we porpose to measure the ^{40}CaH^{+} X^{1}% Σ( v,N,F,M) =(0,0,1/2,±1/2) → (v_{u},0,1/2,±1/2) (v_{u}=1,2,3,,,) transition with the uncertainty lower than 10^{-16}. With these transitions, Zeeman shift is less than 10^{-16}/G (given by the slight dependence of schielding effect by electron cloud on the vibrational state) and electric quadrupole shift is zero because of F=1/2. The J=0→0 transition is one-photon forbidden, and it can be observed also by Raman transition using two lasers. Stark shift induced by Raman lasers actually dominates the measurement uncertainty. When v=0→1 transition is observed using Raman lasers in the 6000-15000 /cm, Stark shift with saturation power is of the order of 1.5×10^{-14} and it is higher for overtone transitions. With the following Raman laser frequencies, total Stark shift induced by two Raman lasers is zero. v=0→1 24527 /cm and 23079 /cm v=0→2 24600 /cm and 21745 /cm v=0→3 26237 /cm and 22017 /cm v=0→4 25354 /cm and 19814 /cm The ^{40}CaH^{+} X^{1}Σ( v,N,F,M) =(0,0,1/2,±1/2) →(v_{u},0,1/2,±1/2) (v_{u}=1,2,3,,,) transition can be measured with the uncertainty lower than 10^{-16}, and it is useful to test the variation in the proton-to-electron mass ratio.
Accurate Estimation of Carotid Luminal Surface Roughness Using Ultrasonic Radio-Frequency Echo
NASA Astrophysics Data System (ADS)
Kitamura, Kosuke; Hasegawa, Hideyuki; Kanai, Hiroshi
2012-07-01
It would be useful to measure the minute surface roughness of the carotid arterial wall to detect the early stage of atherosclerosis. In conventional ultrasonography, the axial resolution of a B-mode image depends on the ultrasonic wavelength of 150 µm at 10 MHz because a B-mode image is constructed using the amplitude of the radio-frequency (RF) echo. Therefore, the surface roughness caused by atherosclerosis in an early stage cannot be measured using a conventional B-mode image obtained by ultrasonography because the roughness is 10-20 µm. We have realized accurate transcutaneous estimation of such a minute surface profile using the lateral motion of the carotid arterial wall, which is estimated by block matching of received ultrasonic signals. However, the width of the region where the surface profile is estimated depends on the magnitude of the lateral displacement of the carotid arterial wall (i.e., if the lateral displacement of the arterial wall is 1 mm, the surface profile is estimated in a region of 1 mm in width). In this study, the width was increased by combining surface profiles estimated using several ultrasonic beams. In the present study, we first measured a fine wire, whose diameter was 13 µm, using ultrasonic equipment to obtain an ultrasonic beam profile for determination of the optimal kernel size for block matching based on the correlation between RF echoes. Second, we estimated the lateral displacement and surface profile of a phantom, which had a saw tooth profile on its surface, and compared the surface profile measured by ultrasound with that measured by a laser profilometer. Finally, we estimated the lateral displacement and surface roughness of the carotid arterial wall of three healthy subjects (24-, 23-, and 23-year-old males) using the proposed method.
Accurate nonrelativistic ground-state energies of 3d transition metal atoms
Scemama, A.; Applencourt, T.; Giner, E.; Caffarel, M.
2014-12-28
We present accurate nonrelativistic ground-state energies of the transition metal atoms of the 3d series calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC). Selected multi-determinantal expansions obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) method and including the most prominent determinants of the full configuration interaction expansion are used as trial wavefunctions. Using a maximum of a few tens of thousands determinants, fixed-node errors on total DMC energies are found to be greatly reduced for some atoms with respect to those obtained with Hartree-Fock nodes. To the best of our knowledge, the FN-DMC/(CIPSI nodes) ground-state energies presented here are the lowest variational total energies reported so far. They differ from the recently recommended non-variational values of McCarthy and Thakkar [J. Chem. Phys. 136, 054107 (2012)] only by a few percents of the correlation energy. Thanks to the variational property of FN-DMC total energies, our results provide exact lower bounds for the absolute value of all-electron correlation energies, |E{sub c}|.
Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms
Zhang, S. Y.; Wu, J. T.; Zhang, Y. L.; Leng, J. X.; Yang, W. P.; Zhang, Z. G.; Zhao, J. Y.
2015-01-01
Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios. PMID:26459877
Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms.
Zhang, S Y; Wu, J T; Zhang, Y L; Leng, J X; Yang, W P; Zhang, Z G; Zhao, J Y
2015-10-13
Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios.
Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms.
Zhang, S Y; Wu, J T; Zhang, Y L; Leng, J X; Yang, W P; Zhang, Z G; Zhao, J Y
2015-01-01
Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios. PMID:26459877
Measurements of the frequency spectrum of transition radiation
NASA Technical Reports Server (NTRS)
Cherry, M. L.; Mueller, D.
1977-01-01
We report a measurement of the frequency spectrum of X-ray transition radiation. X rays were generated by electrons of 5 and 9 GeV in radiators of multiple polypropylene foils, and detected in the range 4 to 30 keV with a calibrated single-crystal Bragg spectrometer. The experimental results closely reproduce the features of the theoretically predicted spectrum. In particular, the pronounced interference pattern of multifoil radiators and the expected hardening of the radiation with increasing foil thickness are clearly observed. The overall intensity of the radiation is somewhat lower than predicted by calculations.
Frequency Comb Assisted IR Measurements of H_3^+, H_2D^+ and D_2H^+ Transitions
NASA Astrophysics Data System (ADS)
Jusko, Pavol; Asvany, Oskar; Schlemmer, Stephan
2016-06-01
We present recent measurements of the fundamental transitions of H_3^+, H_2D^+ and D_2H^+ in a 4 K 22-pole trap by action spectroscopic techniques. Either Laser Induced Inhibition of Cluster Growth (He attachment at T≈4 K), endothermic reaction of H_3^+ with O_2, or deuterium exchange has been used as measurement scheme. We used a 3 μm optical parametric oscillator coupled to a frequency comb in order to achieve accuracy generally below 1 MHz. Five transitions of H_3^+, eleven of H_2D^+ and ten of D_2H^+ were recorder in our spectral range. We compare our H_3^+ results with two previous frequency comb assisted works. Moreover, accurate determination of the frequency allows us to predict pure rotational transitions for H_2D^+ and D_2H^+ in the THz range. P. Jusko, C. Konietzko, S. Schlemmer, O. Asvany, J. Mol. Spec. 319 (2016) 55 O. Asvany, S. Brünken, L. Kluge, S. Schlemmer, Appl. Phys. B 114 (2014) 203 O. Asvany, J. Krieg, S. Schlemmer, Rev. Sci. Instr. 83 (2012) 093110 J.N. Hodges, A.J. Perry, P.A. Jenkins, B.M. Siller, B.J. McCall, J. Chem. Phys. 139 (2013) 164201 H.-C. Chen, C.-Y. Hsiao, J.-L. Peng, T. Amano, J.-T. Shy, Phys. Rev. Lett. 109 (2012) 263002
A Proposed Frequency Synthesis Approach to Accurately Measure the Angular Position of a Spacecraft
NASA Technical Reports Server (NTRS)
Bagri, D. S.
2005-01-01
This article describes an approach for measuring the angular position of a spacecraft with reference to a nearby calibration source (quasar) with an accuracy of a few tenths of a nanoradian using a very long baseline interferometer of two antennas that measures the interferometer phase with a modest accuracy. It employs (1) radio frequency phase to determine the spacecraft position with high precision and (2) multiple delay measurements using either frequency tones or telemetry signals at different frequency spacings to resolve ambiguity of the location of the fringe (cycle) containing the direction of the spacecraft.
ACCURATE ESTIMATIONS OF STELLAR AND INTERSTELLAR TRANSITION LINES OF TRIPLY IONIZED GERMANIUM
Dutta, Narendra Nath; Majumder, Sonjoy E-mail: sonjoy@gmail.com
2011-08-10
In this paper, we report on weighted oscillator strengths of E1 transitions and transition probabilities of E2 transitions among different low-lying states of triply ionized germanium using highly correlated relativistic coupled cluster (RCC) method. Due to the abundance of Ge IV in the solar system, planetary nebulae, white dwarf stars, etc., the study of such transitions is important from an astrophysical point of view. The weighted oscillator strengths of E1 transitions are presented in length and velocity gauge forms to check the accuracy of the calculations. We find excellent agreement between calculated and experimental excitation energies. Oscillator strengths of few transitions, wherever studied in the literature via other theoretical and experimental approaches, are compared with our RCC calculations.
NASA Astrophysics Data System (ADS)
Sellers, Michael; Lisal, Martin; Brennan, John
2015-06-01
Investigating the ability of a molecular model to accurately represent a real material is crucial to model development and use. When the model simulates materials in extreme conditions, one such property worth evaluating is the phase transition point. However, phase transitions are often overlooked or approximated because of difficulty or inaccuracy when simulating them. Techniques such as super-heating or super-squeezing a material to induce a phase change suffer from inherent timescale limitations leading to ``over-driving,'' and dual-phase simulations require many long-time runs to seek out what frequently results in an inexact location of phase-coexistence. We present a compilation of methods for the determination of solid-solid and solid-liquid phase transition points through the accurate calculation of the chemical potential. The methods are applied to the Smith-Bharadwaj atomistic potential's representation of cyclotrimethylene trinitramine (RDX) to accurately determine its melting point (Tm) and the alpha to gamma solid phase transition pressure. We also determine Tm for a coarse-grain model of RDX, and compare its value to experiment and atomistic counterpart. All methods are employed via the LAMMPS simulator, resulting in 60-70 simulations that total 30-50 ns. Approved for public release. Distribution is unlimited.
NASA Astrophysics Data System (ADS)
Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.
2008-12-01
A global potential energy surface (PES) that includes short and long range terms has been determined for the NH3 molecule. The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations and the internally contracted averaged coupled-pair functional electronic structure methods have been used in conjunction with very large correlation-consistent basis sets, including diffuse functions. Extrapolation to the one-particle basis set limit was performed and core correlation and scalar relativistic contributions were included directly, while the diagonal Born-Oppenheimer correction was added. Our best purely ab initio PES, denoted "mixed," is constructed from two PESs which differ in whether the ic-ACPF higher-order correlation correction was added or not. Rovibrational transition energies computed from the mixed PES agree well with experiment and the best previous theoretical studies, but most importantly the quality does not deteriorate even up to 10300cm-1 above the zero-point energy (ZPE). The mixed PES was improved further by empirical refinement using the most reliable J =0-2 rovibrational transitions in the HITRAN 2004 database. Agreement between high-resolution experiment and rovibrational transition energies computed from our refined PES for J =0-6 is excellent. Indeed, the root mean square (rms) error for 13 HITRAN 2004 bands for J =0-2 is 0.023cm-1 and that for each band is always ⩽0.06cm-1. For J =3-5 the rms error is always ⩽0.15cm-1. This agreement means that transition energies computed with our refined PES should be useful in the assignment of new high-resolution NH3 spectra and in correcting mistakes in previous assignments. Ideas for further improvements to our refined PES and for extension to other isotopolog are discussed.
WWVB: A Half Century of Delivering Accurate Frequency and Time by Radio
Lombardi, Michael A; Nelson, Glenn K
2014-01-01
In commemoration of its 50th anniversary of broadcasting from Fort Collins, Colorado, this paper provides a history of the National Institute of Standards and Technology (NIST) radio station WWVB. The narrative describes the evolution of the station, from its origins as a source of standard frequency, to its current role as the source of time-of-day synchronization for many millions of radio controlled clocks. PMID:26601026
TTVFast: An efficient and accurate code for transit timing inversion problems
Deck, Katherine M.; Agol, Eric; Holman, Matthew J.; Nesvorný, David
2014-06-01
Transit timing variations (TTVs) have proven to be a powerful technique for confirming Kepler planet candidates, for detecting non-transiting planets, and for constraining the masses and orbital elements of multi-planet systems. These TTV applications often require the numerical integration of orbits for computation of transit times (as well as impact parameters and durations); frequently tens of millions to billions of simulations are required when running statistical analyses of the planetary system properties. We have created a fast code for transit timing computation, TTVFast, which uses a symplectic integrator with a Keplerian interpolator for the calculation of transit times. The speed comes at the expense of accuracy in the calculated times, but the accuracy lost is largely unnecessary, as transit times do not need to be calculated to accuracies significantly smaller than the measurement uncertainties on the times. The time step can be tuned to give sufficient precision for any particular system. We find a speed-up of at least an order of magnitude relative to dynamical integrations with high precision using a Bulirsch-Stoer integrator.
NASA Astrophysics Data System (ADS)
Małolepsza, Edyta; Witek, Henryk A.; Morokuma, Keiji
2005-09-01
An optimization technique for enhancing the quality of repulsive two-body potentials of the self-consistent-charge density-functional tight-binding (SCC-DFTB) method is presented and tested. The new, optimized potentials allow for significant improvement of calculated harmonic vibrational frequencies. Mean absolute deviation from experiment computed for a group of 14 hydrocarbons is reduced from 59.0 to 33.2 cm -1 and maximal absolute deviation, from 436.2 to 140.4 cm -1. A drawback of the new family of potentials is a lower quality of reproduced geometrical and energetic parameters.
NASA Astrophysics Data System (ADS)
Lamouroux, Julien; Gamache, Robert R.
2013-06-01
A model for the prediction of the vibrational dependence of CO_2 half-widths and line shifts for several broadeners, based on a modification of the model proposed by Gamache and Hartmann, is presented. This model allows the half-widths and line shifts for a ro-vibrational transition to be expressed in terms of the number of vibrational quanta exchanged in the transition raised to a power p and a reference ro-vibrational transition. Complex Robert-Bonamy calculations were made for 24 bands for lower rotational quantum numbers J'' from 0 to 160 for N_2-, O_2-, air-, and self-collisions with CO_2. In the model a Quantum Coordinate is defined by (c_1 Δν_1 + c_2 Δν_2 + c_3 Δν_3)^p where a linear least-squares fit to the data by the model expression is made. The model allows the determination of the slope and intercept as a function of rotational transition, broadening gas, and temperature. From these fit data, the half-width, line shift, and the temperature dependence of the half-width can be estimated for any ro-vibrational transition, allowing spectroscopic CO_2 databases to have complete information for the line shape parameters. R. R. Gamache, J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transfer. {{83}} (2004), 119. R. R. Gamache, J. Lamouroux, J. Quant. Spectrosc. Radiat. Transfer. {{117}} (2013), 93.
Highly Accurate Frequency Calculations of Crab Cavities Using the VORPAL Computational Framework
Austin, T.M.; Cary, J.R.; Bellantoni, L.; /Argonne
2009-05-01
We have applied the Werner-Cary method [J. Comp. Phys. 227, 5200-5214 (2008)] for extracting modes and mode frequencies from time-domain simulations of crab cavities, as are needed for the ILC and the beam delivery system of the LHC. This method for frequency extraction relies on a small number of simulations, and post-processing using the SVD algorithm with Tikhonov regularization. The time-domain simulations were carried out using the VORPAL computational framework, which is based on the eminently scalable finite-difference time-domain algorithm. A validation study was performed on an aluminum model of the 3.9 GHz RF separators built originally at Fermi National Accelerator Laboratory in the US. Comparisons with measurements of the A15 cavity show that this method can provide accuracy to within 0.01% of experimental results after accounting for manufacturing imperfections. To capture the near degeneracies two simulations, requiring in total a few hours on 600 processors were employed. This method has applications across many areas including obtaining MHD spectra from time-domain simulations.
O`Brien, E.; Lissauer, D.; McCorkle, S.; Polychronakos, V.; Takai, H.; Chi, C.Y.; Nagamiya, S.; Sippach, W.; Toy, M.; Wang, D.; Wang, Y.F.; Wiggins, C.; Willis, W.; Cherniatin, V.; Dolgoshein, B.; Bennett, M.; Chikanian, A.; Kumar, S.; Mitchell, J.T.; Pope, K.
1991-12-31
We describe the results of a test ran involving a Transition Radiation Detector that can both distinguish electrons from pions which momenta greater titan 0.7 GeV/c and simultaneously track particles passing through the detector. The particle identification is accomplished through a combination of the detection of Transition Radiation from the electron and the differences in electron and pion energy loss (dE/dx) in the detector. The dE/dx particle separation is most, efficient below 2 GeV/c while particle ID utilizing Transition Radiation effective above 1.5 GeV/c. Combined, the electron-pion separation is-better than 5 {times} 10{sup 2}. The single-wire, track-position resolution for the TRD is {approximately}230 {mu}m.
Kajita, Masatoshi; Gopakumar, Geetha; Abe, Minori; Hada, Masahiko
2011-08-15
Transition frequencies of cold molecules must be accurately evaluated to test the variance in the proton-to-electron mass ratio. Measuring the X {sup 2}{Sigma}(v,N)=(0,0){yields}(1,0) transition frequency of optically trapped {sup 174}Yb{sup 6}Li molecules is a promising method for achieving this goal. The Stark shifts induced by trap and probe (for the Raman transition) lasers are eliminated by choosing appropriate frequencies (magic frequencies) during the construction of the optical lattice. In the far-off resonance region, the Stark shift is found to be less than 10{sup -16} even when the laser frequencies are detuned from the magic frequencies by {approx}1 MHz.
Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.
1993-01-01
The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbation estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10, 472 +/- 5, and 2051 +/- 10 cm(exp -1) for omega(sub 1), omega(sub 2), and omega(sub 3), respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental nu(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.
Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.
1993-01-01
The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbational estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10,472 +/- 5, and 2051 +/-10/cm for omega1, omega2, and omega3, respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental v(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.
Accurate CO{sub 2} laser frequencies and molecular constants of regular and new hot-band lines
Chou, Che-Chung; Shy, Jow-Tsong; Maki, A.G.
1994-12-31
A new, high-resolution, highly efficient, cw, CO{sub 2} laser oscillating on more than 250 lines including over 40 lines in the new 9 {mu}m hot band has been built at NIST, Boulder. The frequencies of the 9 and 10 {mu}m hot band lines and high J (to J=66) regular band lines of {sup 12}C{sup 16}O{sub 2} , which now fill the gap between the 9 and 10 {mu}m regions, have been locked to saturated fluorescence signals in CO{sub 2}, and measured. New molecular constants and more accurate frequencies of the four common isotopes of CO{sub 2} have been obtained.
Kowzan, Grzegorz; Lee, Kevin F; Paradowska, Magdalena; Borkowski, Mateusz; Ablewski, Piotr; Wójtewicz, Szymon; Stec, Kamila; Lisak, Daniel; Fermann, Martin E; Trawiński, Ryszard S; Masłowski, Piotr
2016-03-01
We present a cavity-enhanced direct optical frequency comb spectroscopy system with a virtually imaged phased array (VIPA) spectrometer and either a dither or a Pound-Drever-Hall (PDH) locking scheme used for stable transmission of the comb through the cavity. A self-referenced scheme for frequency axis calibration is shown along with an analysis of its accuracy. A careful comparison between both locking schemes is performed based on near-IR measurements of the carbon monoxide ν=3←0 band P branch transitions in a gas sample with known composition. The noise-equivalent absorptions (NEA) for the PDH and dither schemes are 9.9×10(-10) cm(-1) and 5.3×10(-9) cm(-1), respectively.
A Simple, Accurate Model for Alkyl Adsorption on Late Transition Metals
Montemore, Matthew M.; Medlin, James W.
2013-01-18
A simple model that predicts the adsorption energy of an arbitrary alkyl in the high-symmetry sites of late transition metal fcc(111) and related surfaces is presented. The model makes predictions based on a few simple attributes of the adsorbate and surface, including the d-shell filling and the matrix coupling element, as well as the adsorption energy of methyl in the top sites. We use the model to screen surfaces for alkyl chain-growth properties and to explain trends in alkyl adsorption strength, site preference, and vibrational softening.
Saturated CO{sub 2} absorption near 1.6 μm for kilohertz-accuracy transition frequencies
Burkart, Johannes Romanini, Daniele; Campargue, Alain; Kassi, Samir; Sala, Tommaso; Marangoni, Marco
2015-05-21
Doppler-free saturated-absorption Lamb dips were measured on weak rovibrational lines of {sup 12}C{sup 16}O{sub 2} between 6189 and 6215 cm{sup −1} at sub-Pa pressures using optical feedback frequency stabilized cavity ring-down spectroscopy. By referencing the laser source to an optical frequency comb, transition frequencies for ten lines of the 30013←00001 band P-branch and two lines of the 31113←01101 hot band R-branch were determined with an accuracy of a few parts in 10{sup 11}. Involving rotational quantum numbers up to 42, the data were used for improving the upper level spectroscopic constants. These results provide a highly accurate reference frequency grid over the spectral interval from 1599 to 1616 nm.
Hou, Dong; Wu, Jiutao; Zhang, Shuangyou; Ren, Quansheng; Zhang, Zhigang; Zhao, Jianye
2014-03-17
We demonstrate an approach to create a stable erbium-fiber-based frequency comb at communication band by directly locking the combs to two rubidium atomic transitions resonances (electromagnetically induced transparency absorption and two-photon absorption), respectively. This approach directly transfers the precision and stability of the atomic transitions to the comb. With its distinguishing feature of compactness by removing the conventional octave-spanning spectrum and f-to-2f beating facilities and the ability to directly control the comb's frequency at the atomic transition frequency, this stable optical comb can be widely used in optical communication, frequency standard, and optical spectroscopy and microscopy.
Towards an accurate treatment of σ∗ ← σ transitions: Moving onto N6.-
NASA Astrophysics Data System (ADS)
Dumont, Élise; Ferré, Nicolas; Monari, Antonio
2013-08-01
Dimeric σ∗ radical anions are ubiquitous, and their formation, spectroscopy and outcome can often be elucidated by density functional theory. But for shorter interfragment distances, three-electron two-center systems can be reluctant to a single-determinant description, such as the hexanitrogen radical anion. For N6.-, we show that multireference configuration interactions calculations are required to recover its characteristic electronic excitation energy, while TDDFT fails even with modern exchange-correlation functionals. The effects of vibronic couplings on the absorption spectrum are delineated based on a full quantum mechanical dynamical treatment; this study opens the door towards an accurate description of the subtle solvatochromism of hemi-bonded systems.
NASA Astrophysics Data System (ADS)
Vu, Thanh-Tung; Higuchi, Masato; Aketagawa, Masato
2016-10-01
We propose the use of the sinusoidal frequency modulation technique to improve both the frequency stability of an external cavity laser diode (ECLD) and the measurement accuracy and range of a displacement-measuring interferometer. The frequency of the ECLD was modulated at 300 kHz by modulating the injection current, and it was locked to the b21 hyperfine component of the transition 6-3, P(33), 127I2 (633 nm) by the null method. A relative frequency stability of 6.5 × 10-11 was achieved at 100 s sampling time. The stabilized ECLD was then utilized as a light source for an unbalanced Michelson interferometer. In the interferometer, the displacement and direction of the target mirror can be determined using a Lissajous diagram based on two consecutive and quadrant-phase harmonics of the interference signal. Generally, the measurement range of the interferometer by the proposed method is limited by the modulation index and the signal-to-noise ratio of the harmonics. To overcome this drawback, suitable consecutive harmonic pairs were selected for the specific measurement ranges to measure the displacement. The displacements determined in the specific ranges by the proposed method were compared with those observed by a commercial capacitive sensor. From the comparison, the proposed method has high precision to determine the displacement. The measurement range was also extended up to 10 m by selecting a suitable modulation index and suitable consecutive pairs of harmonics.
Jiang, Puqing; Huang, Bin; Koh, Yee Kan
2016-07-01
Accurate measurements of the cross-plane thermal conductivity Λcross of a high-thermal-conductivity thin film on a low-thermal-conductivity (Λs) substrate (e.g., Λcross/Λs > 20) are challenging, due to the low thermal resistance of the thin film compared with that of the substrate. In principle, Λcross could be measured by time-domain thermoreflectance (TDTR), using a high modulation frequency fh and a large laser spot size. However, with one TDTR measurement at fh, the uncertainty of the TDTR measurement is usually high due to low sensitivity of TDTR signals to Λcross and high sensitivity to the thickness hAl of Al transducer deposited on the sample for TDTR measurements. We observe that in most TDTR measurements, the sensitivity to hAl only depends weakly on the modulation frequency f. Thus, we performed an additional TDTR measurement at a low modulation frequency f0, such that the sensitivity to hAl is comparable but the sensitivity to Λcross is near zero. We then analyze the ratio of the TDTR signals at fh to that at f0, and thus significantly improve the accuracy of our Λcross measurements. As a demonstration of the dual-frequency approach, we measured the cross-plane thermal conductivity of a 400-nm-thick nickel-iron alloy film and a 3-μm-thick Cu film, both with an accuracy of ∼10%. The dual-frequency TDTR approach is useful for future studies of thin films. PMID:27475589
Jiang, Puqing; Huang, Bin; Koh, Yee Kan
2016-07-01
Accurate measurements of the cross-plane thermal conductivity Λcross of a high-thermal-conductivity thin film on a low-thermal-conductivity (Λs) substrate (e.g., Λcross/Λs > 20) are challenging, due to the low thermal resistance of the thin film compared with that of the substrate. In principle, Λcross could be measured by time-domain thermoreflectance (TDTR), using a high modulation frequency fh and a large laser spot size. However, with one TDTR measurement at fh, the uncertainty of the TDTR measurement is usually high due to low sensitivity of TDTR signals to Λcross and high sensitivity to the thickness hAl of Al transducer deposited on the sample for TDTR measurements. We observe that in most TDTR measurements, the sensitivity to hAl only depends weakly on the modulation frequency f. Thus, we performed an additional TDTR measurement at a low modulation frequency f0, such that the sensitivity to hAl is comparable but the sensitivity to Λcross is near zero. We then analyze the ratio of the TDTR signals at fh to that at f0, and thus significantly improve the accuracy of our Λcross measurements. As a demonstration of the dual-frequency approach, we measured the cross-plane thermal conductivity of a 400-nm-thick nickel-iron alloy film and a 3-μm-thick Cu film, both with an accuracy of ∼10%. The dual-frequency TDTR approach is useful for future studies of thin films.
NASA Astrophysics Data System (ADS)
Jiang, Puqing; Huang, Bin; Koh, Yee Kan
2016-07-01
Accurate measurements of the cross-plane thermal conductivity Λcross of a high-thermal-conductivity thin film on a low-thermal-conductivity (Λs) substrate (e.g., Λcross/Λs > 20) are challenging, due to the low thermal resistance of the thin film compared with that of the substrate. In principle, Λcross could be measured by time-domain thermoreflectance (TDTR), using a high modulation frequency fh and a large laser spot size. However, with one TDTR measurement at fh, the uncertainty of the TDTR measurement is usually high due to low sensitivity of TDTR signals to Λcross and high sensitivity to the thickness hAl of Al transducer deposited on the sample for TDTR measurements. We observe that in most TDTR measurements, the sensitivity to hAl only depends weakly on the modulation frequency f. Thus, we performed an additional TDTR measurement at a low modulation frequency f0, such that the sensitivity to hAl is comparable but the sensitivity to Λcross is near zero. We then analyze the ratio of the TDTR signals at fh to that at f0, and thus significantly improve the accuracy of our Λcross measurements. As a demonstration of the dual-frequency approach, we measured the cross-plane thermal conductivity of a 400-nm-thick nickel-iron alloy film and a 3-μm-thick Cu film, both with an accuracy of ˜10%. The dual-frequency TDTR approach is useful for future studies of thin films.
NASA Technical Reports Server (NTRS)
Huang, Xinchuan; Taylor, Peter R.; Lee, Timothy J.
2011-01-01
High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C H + molecular cation, referred to as c-C H + and I-C H +. Specifically the 33 3333 singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants using both vibrational 2nd-order perturbation theory and variational methods to solve the nuclear Schroedinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C H +, 33 obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C H + 33 and I-C H + are the most reliable available for the free gas-phase species and it is hoped that 33 these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations.
Huang, Xinchuan; Taylor, Peter R; Lee, Timothy J
2011-05-19
High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C(3)H(3)(+) molecular cation, referred to as c-C(3)H(3)(+) and l-C(3)H(3)(+). Specifically, the singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit, and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants by use of both vibrational second-order perturbation theory and variational methods to solve the nuclear Schrödinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C(3)H(3)(+), obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C(3)H(3)(+) and l-C(3)H(3)(+) are the most reliable available for the free gas-phase species, and it is hoped that these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations. PMID:21510653
NASA Technical Reports Server (NTRS)
Ellison, Donald; Conway, Bruce; Englander, Jacob
2015-01-01
A significant body of work exists showing that providing a nonlinear programming (NLP) solver with expressions for the problem constraint gradient substantially increases the speed of program execution and can also improve the robustness of convergence, especially for local optimizers. Calculation of these derivatives is often accomplished through the computation of spacecraft's state transition matrix (STM). If the two-body gravitational model is employed as is often done in the context of preliminary design, closed form expressions for these derivatives may be provided. If a high fidelity dynamics model, that might include perturbing forces such as the gravitational effect from multiple third bodies and solar radiation pressure is used then these STM's must be computed numerically. We present a method for the power hardward model and a full ephemeris model. An adaptive-step embedded eight order Dormand-Prince numerical integrator is discussed and a method for the computation of the time of flight derivatives in this framework is presented. The use of these numerically calculated derivatieves offer a substantial improvement over finite differencing in the context of a global optimizer. Specifically the inclusion of these STM's into the low thrust missiondesign tool chain in use at NASA Goddard Spaceflight Center allows for an increased preliminary mission design cadence.
Živković, Daniel; Steinrücken, Matthias; Song, Yun S.; Stephan, Wolfgang
2015-01-01
Advances in empirical population genetics have made apparent the need for models that simultaneously account for selection and demography. To address this need, we here study the Wright–Fisher diffusion under selection and variable effective population size. In the case of genic selection and piecewise-constant effective population sizes, we obtain the transition density by extending a recently developed method for computing an accurate spectral representation for a constant population size. Utilizing this extension, we show how to compute the sample frequency spectrum in the presence of genic selection and an arbitrary number of instantaneous changes in the effective population size. We also develop an alternate, efficient algorithm for computing the sample frequency spectrum using a moment-based approach. We apply these methods to answer the following questions: If neutrality is incorrectly assumed when there is selection, what effects does it have on demographic parameter estimation? Can the impact of negative selection be observed in populations that undergo strong exponential growth? PMID:25873633
NASA Astrophysics Data System (ADS)
Wang, Xinxin; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue
2016-08-01
The potential energy curves were calculated for the 21 states (X2Π, A2Π, 32Π, 42Π, 52Π, 12Σ+, 22Σ+, 32Σ+, 12Σ-, 22Σ-, 32Σ-, 12Δ, 22Δ, 32Δ, 12Φ, 14Σ+, a4Σ-, 24Σ-, 14Π, 24Π and 14Δ), which originated from the two lowest dissociation channels of ClO radical. The calculations were done for internuclear separations approximately from 0.08 to 1.10 nm using the CASSCF method, which was followed by the icMRCI approach with the aug-cc-pV5Z basis set. Of these 21 states, the 14Π, 24Π, 32Δ, 42Π, 52Π, 12Φ, 32Σ+, 14Δ and 24Σ- states are repulsive. The 12Δ, 12Σ-, 14Σ+, 22Σ-, 12Σ+, 22Σ+, 22Δ and 32Σ- states are very weakly bound. Only the A2Π state has one barrier. The avoided crossing exists between the A2Π and the 32Π state. However, the avoided crossing does not generate any double wells. Core- valence correlation correction was accounted for at the level of an aug-cc-pCVQZ basis set. Scalar relativistic correction was included by the third-order Douglas-Kroll Hamiltonian approximation at the level of an aug-cc-pVQZ basis set. All the potential energy curves were extrapolated to the complete basis set limit. The spectroscopic parameters were determined. The 12Σ-, 22Σ-, 32Σ- and 14Σ+ states may be very difficult to be detected in an experiment, since each of these Λ-S states has only one or two vibrational states. The Franck-Condon factors and radiative lifetimes were calculated for several low vibrational levels of the A2Π - X2Π, 32Π - a4Σ-, 22Δ - a4Σ- and 32Σ- - 12Σ- transitions. The spin-orbit coupling effect on the spectroscopic parameters of the X2Π, A2Π, 32Π, a4Σ- and 22Σ+ states were discussed. The spectroscopic properties reported here can be expected to be reliably predicted ones.
Mifflin, Amanda L.; Velarde Ruiz Esparza, Luis A.; Ho, Junming; Psciuk, Brian; Negre, Christian; Ebben, Carlena J.; Upshur, Mary Alice; Lu, Zhou; Strick, Benjamin; Thomson, Regan; Batista, Victor; Wang, Hongfei; Geiger, Franz M.
2015-02-26
Room temperature sub-wavenumber high-resolution broadband sum frequency generation (HR-BB-SFG) spectra of the common terpene (+)-α-pinene reveal ten peaks in the C–H stretching region. The spectral resolution exceeds that of Fourier transform infrared, femtosecond stimulated Raman, and traditional BB-SFG and scanning SFG spectroscopy of the same molecule. Experiment and simulation show the spectral lineshapes to be accurate. Homogeneous vibrational decoherence lifetimes of up to 1.7 psec are assigned to specific oscillators and compare favorably to lifetimes computed from density functional tight binding molecular dynamics calculations, while phase-resolved spectra yield orientation information for them. We propose the new spectroscopy as an attractive alternative to time-resolved vibrational spectroscopy or heterodyne-detection schemes for studying vibrational energy relaxation and vibrational coherences in molecules.
NASA Astrophysics Data System (ADS)
Farlin, J.; Maloszewski, P.
2013-05-01
Baseflow recession analysis and groundwater dating have up to now developed as two distinct branches of hydrogeology and have been used to solve entirely different problems. We show that by combining two classical models, namely the Boussinesq equation describing spring baseflow recession, and the exponential piston-flow model used in groundwater dating studies, the parameters describing the transit time distribution of an aquifer can be in some cases estimated to a far more accurate degree than with the latter alone. Under the assumption that the aquifer basis is sub-horizontal, the mean transit time of water in the saturated zone can be estimated from spring baseflow recession. This provides an independent estimate of groundwater transit time that can refine those obtained from tritium measurements. The approach is illustrated in a case study predicting atrazine concentration trend in a series of springs draining the fractured-rock aquifer known as the Luxembourg Sandstone. A transport model calibrated on tritium measurements alone predicted different times to trend reversal following the nationwide ban on atrazine in 2005 with different rates of decrease. For some of the springs, the actual time of trend reversal and the rate of change agreed extremely well with the model calibrated using both tritium measurements and the recession of spring discharge during the dry season. The agreement between predicted and observed values was however poorer for the springs displaying the most gentle recessions, possibly indicating a stronger influence of continuous groundwater recharge during the summer months.
NASA Astrophysics Data System (ADS)
Tao, Jianmin; Mo, Yuxiang; Tian, Guocai; Ruzsinszky, Adrienn
2016-08-01
Long-range van der Waals (vdW) interaction is critically important for intermolecular interactions in molecular complexes and solids. However, accurate modeling of vdW coefficients presents a great challenge for nanostructures, in particular for fullerene clusters, which have huge vdW coefficients but also display very strong nonadditivity. In this work, we calculate the coefficients between fullerenes, fullerene and sodium clusters, and fullerene and alkali atoms with the hollow-sphere model within the modified single-frequency approximation (MSFA). In the MSFA, we assume that the electron density is uniform in a molecule and that only valence electrons in the outmost subshell of atoms contribute. The input to the model is the static multipole polarizability, which provides a sharp cutoff for the plasmon contribution outside the effective vdW radius. We find that the model can generate C6 in excellent agreement with expensive wave-function-based ab initio calculations, with a mean absolute relative error of only 3 % , without suffering size-dependent error. We show that the nonadditivities of the coefficients C6 between fullerenes and C60 and sodium clusters Nan revealed by the model agree remarkably well with those based on the accurate reference values. The great flexibility, simplicity, and high accuracy make the model particularly suitable for the study of the nonadditivity of vdW coefficients between nanostructures, advancing the development of better vdW corrections to conventional density functional theory.
Thom, Joseph; Wilpers, Guido; Riis, Erling; Sinclair, Alastair G
2013-08-12
We demonstrate a system for fast and agile digital control of laser phase, amplitude and frequency for applications in coherent atomic systems. The full versatility of a direct digital synthesis radiofrequency source is faithfully transferred to laser radiation via acousto-optic modulation. Optical beatnotes are used to measure phase steps up to 2π, which are accurately implemented with a resolution of ≤ 10 mrad. By linearizing the optical modulation process, amplitude-shaped pulses of durations ranging from 500 ns to 500 ms, in excellent agreement with the programmed functional form, are demonstrated. Pulse durations are limited only by the 30 ns rise time of the modulation process, and a measured extinction ratio of > 5 × 10(11) is achieved. The system presented here was developed specifically for controlling the quantum state of trapped ions with sequences of multiple laser pulses, including composite and bichromatic pulses. The demonstrated techniques are widely applicable to other atomic systems ranging across quantum information processing, frequency metrology, atom interferometry, and single-photon generation.
Frequency transitions in odor-evoked neural oscillations.
Ito, Iori; Bazhenov, Maxim; Ong, Rose Chik-ying; Raman, Baranidharan; Stopfer, Mark
2009-12-10
In many species, sensory stimuli elicit the oscillatory synchronization of groups of neurons. What determines the properties of these oscillations? In the olfactory system of the moth, we found that odors elicited oscillatory synchronization through a neural mechanism like that described in locust and Drosophila. During responses to long odor pulses, oscillations suddenly slowed as net olfactory receptor neuron (ORN) output decreased; thus, stimulus intensity appeared to determine oscillation frequency. However, changing the concentration of the odor had little effect upon oscillatory frequency. Our recordings in vivo and computational models based on these results suggested that the main effect of increasing odor concentration was to recruit additional, less well-tuned ORNs whose firing rates were tightly constrained by adaptation and saturation. Thus, in the periphery, concentration is encoded mainly by the size of the responsive ORN population, and oscillation frequency is set by the adaptation and saturation of this response.
NASA Astrophysics Data System (ADS)
Tadokoro, K.; Yasuda, K.; Taniguchi, S.; Uemura, Y.; Matsuhiro, K.
2015-12-01
The GPS/acoustic sea-floor crustal deformation measurement system has developed as a useful tool to observe tectonic deformation especially at subduction zones. One of the factors preventing accurate GPS/acoustic sea-floor crustal deformation measurement is horizontal heterogeneity of sound speed in the ocean. It is therefore necessary to measure the gradient directly from sound speed structure. We report results of high-frequency CTD measurements using Underway CTD (UCTD) in the Kuroshio region. We perform the UCTD measurements on May 2nd, 2015 at two stations (TCA and TOA) above the sea-floor benchmarks installed across the Nankai Trough, off the south-east of Kii Peninsula, middle Japan. The number of measurement points is six at each station along circles with a diameter of 1.8 nautical miles around the sea-floor benchmark. The stations TCA and TOA are located on the edge and the interior of the Kuroshio current, respectively, judging from difference in sea water density measured at the two stations, as well as a satellite image of sea-surface temperature distribution. We detect a sound speed gradient of high speeds in the southern part and low speeds in the northern part at the two stations. At the TCA station, the gradient is noticeable down to 300 m in depth; the maximum difference in sound speed is +/- 5 m/s. The sound speed difference is as small as +/- 1.3 m/s at depths below 300 m, which causes seafloor benchmark positioning error as large as 1 m. At the TOA station, the gradient is extremely small down to 100 m in depth. The maximum difference in sound speed is less than +/- 0.3 m/s that is negligible small for seafloor benchmark positioning error. Clear gradient of high speed is observed to the depths; the maximum difference in sound speed is +/- 0.8-0.9 m/s, causing seafloor benchmark positioning error of several tens centimeters. The UCTD measurement is effective tool to detect sound speed gradient. We establish a method for accurate sea
Cueto, M.; Herrero, V. J.; Tanarro, I.; Doménech, J. L.; Cernicharo, J.; Barlow, M. J.; Swinyard, B. M.
2014-03-01
The protonated argon ion, {sup 36}ArH{sup +}, was recently identified in the Crab Nebula from Herschel spectra. Given the atmospheric opacity at the frequency of its J = 1-0 and J = 2-1 rotational transitions (617.5 and 1234.6 GHz, respectively), and the current lack of appropriate space observatories after the recent end of the Herschel mission, future studies on this molecule will rely on mid-infrared observations. We report on accurate wavenumber measurements of {sup 36}ArH{sup +} and {sup 38}ArH{sup +} rotation-vibration transitions in the v = 1-0 band in the range 4.1-3.7 μm (2450-2715 cm{sup –1}). The wavenumbers of the R(0) transitions of the v = 1-0 band are 2612.50135 ± 0.00033 and 2610.70177 ± 0.00042 cm{sup –1} (±3σ) for {sup 36}ArH{sup +} and {sup 38}ArH{sup +}, respectively. The calculated opacity for a gas thermalized at a temperature of 100 K and with a linewidth of 1 km s{sup –1} of the R(0) line is 1.6 × 10{sup –15} × N({sup 36}ArH{sup +}). For column densities of {sup 36}ArH{sup +} larger than 1 × 10{sup 13} cm{sup –2}, significant absorption by the R(0) line can be expected against bright mid-IR sources.
Van Yperen-De Deyne, A; Pauwels, E; Van Speybroeck, V; Waroquier, M
2012-08-14
In this paper an overview is presented of several approximations within Density Functional Theory (DFT) to calculate g-tensors in transition metal containing systems and a new accurate description of the spin-other-orbit contribution for high spin systems is suggested. Various implementations in a broad variety of software packages (ORCA, ADF, Gaussian, CP2K, GIPAW and BAND) are critically assessed on various aspects including (i) non-relativistic versus relativistic Hamiltonians, (ii) spin-orbit coupling contributions and (iii) the gauge. Particular attention is given to the level of accuracy that can be achieved for codes that allow g-tensor calculations under periodic boundary conditions, as these are ideally suited to efficiently describe extended condensed-phase systems containing transition metals. In periodic codes like CP2K and GIPAW, the g-tensor calculation schemes currently suffer from an incorrect treatment of the exchange spin-orbit interaction and a deficient description of the spin-other-orbit term. In this paper a protocol is proposed, making the predictions of the exchange part to the g-tensor shift more plausible. Focus is also put on the influence of the spin-other-orbit interaction which becomes of higher importance for high-spin systems. In a revisited derivation of the various terms arising from the two-electron spin-orbit and spin-other-orbit interaction (SOO), new insight has been obtained revealing amongst other issues new terms for the SOO contribution. The periodic CP2K code has been adapted in view of this new development. One of the objectives of this study is indeed a serious enhancement of the performance of periodic codes in predicting g-tensors in transition metal containing systems at the same level of accuracy as the most advanced but time consuming spin-orbit mean-field approach. The methods are first applied on rhodium carbide but afterwards extended to a broad test set of molecules containing transition metals from the fourth
Quantum dynamics of a two-level emitter with a modulated transition frequency
NASA Astrophysics Data System (ADS)
Macovei, Mihai; Keitel, Christoph H.
2014-10-01
The resonant quantum dynamics of an excited two-level emitter is investigated via classical modulation of its transition frequency while simultaneously the radiator interacts with a broadband electromagnetic field reservoir. The frequency of modulation is selected to be of the order of the bare-state spontaneous decay rate. In this way, one can induce quantum interference effects, and consequently, quantum coherences among multiple decaying transition pathways. Depending on the modulation depth and its absolute phase, both the spontaneous emission and the frequency shift may be conveniently modified and controlled.
Matyugin, Yu A; Ignatovich, S M; Kuznetsov, Sergei A; Nesterenko, M I; Okhapkin, M V; Pivtsov, V S; Skvortsov, Mikhail N; Bagaev, Sergei N
2012-03-31
We report high-precision frequency measurements of the separate hyperfine structure (HFS) components of the emission B - X system transitions of {sup 127}I{sub 2} molecules in the 982 - 985 nm range. To resolve the HFS of the emission lines, advantage was taken of the method of three-level laser spectroscopy. The function of exciting radiation was fulfilled by the second harmonic of a cw Nd : YAG laser, and the probe radiation in the 968 - 998 nm range was generated by an external-cavity diode laser. The output Nd : YAG laser frequency was locked to an HFS component of the absorption transition and the probing laser radiation to the emission transition component. When both frequencies were locked to HFS components with a common upper level, the output diode laser frequency was precisely equal to the emission transition frequency. The output frequency of the thus stabilised diode laser was measured with the help of a femtosecond optical frequency synthesiser based on a Ti : sapphire laser. We present the results of the absolute frequency measurements of 20 HFS components belonging to six vibrational - rotational transitions of the B - X system of iodine [R56(32 - 48)a1, P58(32 - 48)a1, P85(33 - 48)a1, R87(33 - 48a1, R88(33 - 48)a10] and all 15 components of the R86(33 - 48) line. The relative measurement uncertainty is equal to 7 Multiplication-Sign 10{sup -10} and is determined by the frequency instability of the diode laser radiation.
The Frequency of Binary Star Interlopers Amongst Transitional Disks.
NASA Astrophysics Data System (ADS)
Ruíz-Rodríguez, D.; Ireland, M.; Cieza, L.; Kraus, A.
2016-09-01
Using Non-Redundant Mask interferometry (NRM), we searched for binary companions to objects previously classified as Transitional Disks (TD). These objects are thought to be an evolutionary stage between an optically thick disk and optically thin disk. We investigate the presence of a stellar companion as a possible mechanism of material depletion in the inner region of these disks, which would rule out an ongoing planetary formation process in distances comparable to the binary separation. For our detection limits, we implement a new method of completeness correction using a combination of randomly sampled binary orbits and Bayesian inference. The selected sample of 24 TDs belong to the nearby and young star forming regions: Ophiuchus (˜ 130 pc), Taurus-Auriga (˜ 140 pc) and IC348 ( ˜ 220 pc). These regions are suitable to resolve faint stellar companions with moderate to high confidence levels at distances as low as 2 au from the central star. With a total of 31 objects, including 11 known TDs and circumbinary disks from the literature, we have found that a fraction of 0.38 ± 0.09 of the SEDs of these objects are likely due to the tidal interaction between a close binary and its disk, while the remaining SEDs are likely the result of other internal processes such as photoevaporation, grain growth, planet disk interactions. In addition, we detected four companions orbiting outside the area of the truncation radii and we propose that the IR excesses of these systems are due to a disk orbiting a secondary companion
NASA Astrophysics Data System (ADS)
Farlin, J.; Maloszewski, P.
2012-12-01
Baseflow recession analysis and groundwater dating have up to now developed as two distinct branches of hydrogeology and were used to solve entirely different problems. We show that by combining two classical models, namely Boussinesq's Equation describing spring baseflow recession and the exponential piston-flow model used in groundwater dating studies, the parameters describing the transit time distribution of an aquifer can be in some cases estimated to a far more accurate degree than with the latter alone. Under the assumption that the aquifer basis is sub-horizontal, the mean residence time of water in the saturated zone can be estimated from spring baseflow recession. This provides an independent estimate of groundwater residence time that can refine those obtained from tritium measurements. This approach is demonstrated in a case study predicting atrazine concentration trend in a series of springs draining the fractured-rock aquifer known as the Luxembourg Sandstone. A transport model calibrated on tritium measurements alone predicted different times to trend reversal following the nationwide ban on atrazine in 2005 with different rates of decrease. For some of the springs, the best agreement between observed and predicted time of trend reversal was reached for the model calibrated using both tritium measurements and the recession of spring discharge during the dry season. The agreement between predicted and observed values was however poorer for the springs displaying the most gentle recessions, possibly indicating the stronger influence of continuous groundwater recharge during the dry period.
Non-Maxwellian to Maxwellian transitions of atmospheric microplasmas at microwave frequencies
NASA Astrophysics Data System (ADS)
Lee, M. U.; Jeong, S. Y.; Won, I. H.; Sung, S. K.; Yun, G. S.; Lee, J. K.
2016-07-01
Particle-in-cell/Monte Carlo simulations and numerical analysis of a single particle motion are performed for atmospheric He microplasmas at microwave frequencies to determine the characteristics of non-Maxwellian to Maxwellian transition. The left and the right regimes of Paschen curve, divided by this transition, reveal that the transition frequencies depend on the gap of electrodes and the neutral gas pressure to follow scaling laws for a new extended Paschen law. The fluid models are reasonable at the right-side regime of Paschen breakdown areas, but not on the left side, which is highly kinetic for electrons. The plasmas driven by weaker electric fields of high enough frequencies at the right-side Paschen regime breed more energetic electrons.
Frequency tuning of single photons from a whispering-gallery mode resonator to MHz-wide transitions
NASA Astrophysics Data System (ADS)
Schunk, G.; Vogl, U.; Sedlmeir, F.; Strekalov, D. V.; Otterpohl, A.; Averchenko, V.; Schwefel, H. G. L.; Leuchs, G.; Marquardt, Ch.
2016-11-01
Quantum repeaters rely on interfacing flying qubits with quantum memories. The most common implementations include a narrowband single photon matched in bandwidth and central frequency to an atomic system. Previously, we demonstrated the compatibility of our versatile source of heralded single photons, which is based on parametric down-conversion in a triply resonant whispering-gallery mode resonator, with alkaline transitions [Schunk et al., Optica 2015, 2, 773]. In this paper, we analyse our source in terms of phase matching, available wavelength-tuning mechanisms and applications to narrowband atomic systems. We resonantly address the D1 transitions of caesium and rubidium with this optical parametric oscillator pumped above its oscillation threshold. Below threshold, the efficient coupling of single photons to atomic transitions heralded by single telecom-band photons is demonstrated. Finally, we present an accurate analytical description of our observations. Providing the demonstrated flexibility in connecting various atomic transitions with telecom wavelengths, we show a promising approach to realize an essential building block for quantum repeaters.
Direct CW - NMR observation of forbidden transitions at double larmor frequency in hydrogen
NASA Astrophysics Data System (ADS)
Skrbek, L.; Sebek, J.; Safrata, R. S.
1990-08-01
By means of the classical transverse continuous wave nuclear magnetic resonance (NMR) the forbidden transitions at double Larmor frequency for hydrogen have been observed. The NMR spectra have been measured directly by scanning the external magnetic field up to 10 mT at temperatures about 30 mK. The intensity of the forbidden transition at double Larmor frequency I 2 is of the same order of magnitude as the intensity I 1 of the main Larmor line under these conditions. The intensity ratio I 1/I 2 depends on the external magnetic field in accordance with Cheng theory and NMR-SQUID measurements of Kohl and coworkers.
Frequency measurement of the J = 1-0 rotational transition of HD
Evenson, K.M.; Jennings, D.A.; Brown, J.M.; Zink, L.R.; Leopold, K.R.
1988-07-01
The frequency of the astronomically important J = 1-0 rotational transition of HD at 2.7 THz (90/cm) has been measured with tunable FIR radiation with an accuracy of 150 kHz. This frequency is now known to sufficient accuracy for use in future astrophysical heterodyne observations of HD in planetary atmospheres (reported by Bezard et al., 1986) and in the interstellar medium (reported by Bussoletti et al., 1975). 14 references.
Biomechanical mechanism for transitions in phase and frequency of arm and leg swing during walking.
Kubo, Masayoshi; Wagenaar, Robert C; Saltzman, Elliot; Holt, Kenneth G
2004-08-01
As humans increase walking speed, there are concurrent transitions in the frequency ratio between arm and leg movements from 2:1 to 1:1 and in the phase relationship between the movements of the two arms from in-phase to out-of-phase. Superharmonic resonance of a pendulum with monofrequency excitation had been proposed as a potential model for this phenomenon. In this study, an alternative model of paired pendulums with multiple-frequency excitations is explored. It was predicted that the occurrence of the concurrent transitions was a function of (1) changes in the magnitude ratio of shoulder accelerations at step and stride frequencies that accompany changes in walking speed and (2) proximity of these frequencies to the natural resonance frequencies of the arms modeled as a pair of passive pendulums. Model predictions were compared with data collected from 14 healthy young subjects who were instructed to walk on a treadmill. Walking speeds were manipulated between 0.18 and 1.52 m/s in steps of 0.22 m/s. Kinematic data for the arms and shoulders were collected using a 3D motion analysis system, and simulations were conducted in which the movements of a double-pendulum system excited by the accelerations at the suspension point were analyzed to determine the extent to which the arms acted as passive pendulums. It was confirmed that the acceleration waveforms at the shoulder are composed primarily of stride and step frequency components. Between the shoulders, the stride frequency components were out-of-phase, while the step frequency components were in-phase. The amplitude ratio of the acceleration waveform components at the step and stride frequencies changed as a function of walking speed and were associated with the occurrence of the transitions. Simulation results using these summed components as excitatory inputs to the double-pendulum system were in agreement with actual transitions in 80% of the cases. The potential role of state-dependent active muscle
NASA Astrophysics Data System (ADS)
Toyota, Koudai
2016-10-01
The method of the envelope Hamiltonian [K. Toyota, U. Saalmann, and J. M. Rost, New J. Phys. 17, 073005 (2015), 10.1088/1367-2630/17/7/073005] is applied to further study a detachment dynamics of a model negative ion in one dimension in the high-frequency regime. This method is based on the Floquet approach, but the time dependency of an envelope function is explicitly kept for arbitrary pulse durations. Therefore, it is capable of describing not only a photon absorption or emission, but also a nonadiabatic transition which is induced by the time-varying envelope of the pulse. It was shown that the envelope Hamiltonian accurately retrieves the results obtained by the time-dependent Schrödinger equation, and the underlying physics were well understood by the adiabatic approximation based on the envelope Hamiltonian. In this paper, we explore two more aspects of the detachment dynamics, which were not considered in our previous work. First, we determine the features of both a spatial and temporal interference of photoelectron wave packets in a photon-absorption process. We conclude that both of the interference mechanisms are universal in ionization dynamics in the high-frequency regime. Second, we extract a pulse duration which maximizes a yield of the nonadiabatic transition as a function of a pulse duration. It is shown that it becomes maximum when the pulse duration is comparable to a time scale of an electron.
Yu, Yang; Zhang, Fan; Gao, Ming-Xin; Li, Hai-Tao; Li, Jing-Xing; Song, Wei; Huang, Xin-Sheng; Gu, Cheng-Xiong
2013-01-01
OBJECTIVES Intraoperative transit time flow measurement (TTFM) is widely used to assess anastomotic quality in coronary artery bypass grafting (CABG). However, in sequential vein grafting, the flow characteristics collected by the conventional TTFM method are usually associated with total graft flow and might not accurately indicate the quality of every distal anastomosis in a sequential graft. The purpose of our study was to examine a new TTFM method that could assess the quality of each distal anastomosis in a sequential graft more reliably than the conventional TTFM approach. METHODS Two TTFM methods were tested in 84 patients who underwent sequential saphenous off-pump CABG in Beijing An Zhen Hospital between April and August 2012. In the conventional TTFM method, normal blood flow in the sequential graft was maintained during the measurement, and the flow probe was placed a few centimetres above the anastomosis to be evaluated. In the new method, blood flow in the sequential graft was temporarily reduced during the measurement by placing an atraumatic bulldog clamp at the graft a few centimetres distal to the anastomosis to be evaluated, while the position of the flow probe remained the same as in the conventional method. This new TTFM method was named the flow reduction TTFM. Graft flow parameters measured by both methods were compared. RESULTS Compared with the conventional TTFM, the flow reduction TTFM resulted in significantly lower mean graft blood flow (P < 0.05); in contrast, yielded significantly higher pulsatility index (P < 0.05). Diastolic filling was not significantly different between the two methods and was >50% in both cases. Interestingly, the flow reduction TTFM identified two defective middle distal anastomoses that the conventional TTFM failed to detect. Graft flows near the defective distal anastomoses were improved substantially after revision. CONCLUSIONS In this study, we found that temporary reduction of graft flow during TTFM seemed to
Gyüre, B.; Márkus, B. G.; Bernáth, B.; Simon, F.; Murányi, F.
2015-09-15
We present a novel method to determine the resonant frequency and quality factor of microwave resonators which is faster, more stable, and conceptually simpler than the yet existing techniques. The microwave resonator is pumped with the microwave radiation at a frequency away from its resonance. It then emits an exponentially decaying radiation at its eigen-frequency when the excitation is rapidly switched off. The emitted microwave signal is down-converted with a microwave mixer, digitized, and its Fourier transformation (FT) directly yields the resonance curve in a single shot. Being a FT based method, this technique possesses the Fellgett (multiplex) and Connes (accuracy) advantages and it conceptually mimics that of pulsed nuclear magnetic resonance. We also establish a novel benchmark to compare accuracy of the different approaches of microwave resonator measurements. This shows that the present method has similar accuracy to the existing ones, which are based on sweeping or modulating the frequency of the microwave radiation.
Gyüre, B; Márkus, B G; Bernáth, B; Murányi, F; Simon, F
2015-09-01
We present a novel method to determine the resonant frequency and quality factor of microwave resonators which is faster, more stable, and conceptually simpler than the yet existing techniques. The microwave resonator is pumped with the microwave radiation at a frequency away from its resonance. It then emits an exponentially decaying radiation at its eigen-frequency when the excitation is rapidly switched off. The emitted microwave signal is down-converted with a microwave mixer, digitized, and its Fourier transformation (FT) directly yields the resonance curve in a single shot. Being a FT based method, this technique possesses the Fellgett (multiplex) and Connes (accuracy) advantages and it conceptually mimics that of pulsed nuclear magnetic resonance. We also establish a novel benchmark to compare accuracy of the different approaches of microwave resonator measurements. This shows that the present method has similar accuracy to the existing ones, which are based on sweeping or modulating the frequency of the microwave radiation. PMID:26429462
Haasl, Ryan J; Payseur, Bret A
2010-12-01
Theoretical work focused on microsatellite variation has produced a number of important results, including the expected distribution of repeat sizes and the expected squared difference in repeat size between two randomly selected samples. However, closed-form expressions for the sampling distribution and frequency spectrum of microsatellite variation have not been identified. Here, we use coalescent simulations of the stepwise mutation model to develop gamma and exponential approximations of the microsatellite allele frequency spectrum, a distribution central to the description of microsatellite variation across the genome. For both approximations, the parameter of biological relevance is the number of alleles at a locus, which we express as a function of θ, the population-scaled mutation rate, based on simulated data. Discovered relationships between θ, the number of alleles, and the frequency spectrum support the development of three new estimators of microsatellite θ. The three estimators exhibit roughly similar mean squared errors (MSEs) and all are biased. However, across a broad range of sample sizes and θ values, the MSEs of these estimators are frequently lower than all other estimators tested. The new estimators are also reasonably robust to mutation that includes step sizes greater than one. Finally, our approximation to the microsatellite allele frequency spectrum provides a null distribution of microsatellite variation. In this context, a preliminary analysis of the effects of demographic change on the frequency spectrum is performed. We suggest that simulations of the microsatellite frequency spectrum under evolutionary scenarios of interest may guide investigators to the use of relevant and sometimes novel summary statistics.
Absolute molecular transition frequencies measured by three cavity-enhanced spectroscopy techniques
NASA Astrophysics Data System (ADS)
Cygan, A.; Wójtewicz, S.; Kowzan, G.; Zaborowski, M.; Wcisło, P.; Nawrocki, J.; Krehlik, P.; Śliwczyński, Ł.; Lipiński, M.; Masłowski, P.; Ciuryło, R.; Lisak, D.
2016-06-01
Absolute frequencies of unperturbed 12C16O transitions from the near-infrared (3-0) band were measured with uncertainties five-fold lower than previously available data. The frequency axis of spectra was linked to the primary frequency standard. Three different cavity enhanced absorption and dispersion spectroscopic methods and various approaches to data analysis were used to estimate potential systematic instrumental errors. Except for a well established frequency-stabilized cavity ring-down spectroscopy, we applied the cavity mode-width spectroscopy and the one-dimensional cavity mode-dispersion spectroscopy for measurement of absorption and dispersion spectra, respectively. We demonstrated the highest quality of the dispersion line shape measured in optical spectroscopy so far. We obtained line positions of the Doppler-broadened R24 and R28 transitions with relative uncertainties at the level of 10-10. The pressure shifting coefficients were measured and the influence of the line asymmetry on unperturbed line positions was analyzed. Our dispersion spectra are the first demonstration of molecular spectroscopy with both axes of the spectra directly linked to the primary frequency standard, which is particularly desirable for the future reference-grade measurements of molecular spectra.
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Martin, Jan M. L.; Dateo, Christopher E.; Taylor, Peter R.
1995-01-01
The XCN and XNC (X = F, Cl) isomers have been investigated using the CCSD(T) method in conjunction with correlation consistent basis sets. Equilibrium geometries, harmonic frequencies, anharmonic constants, fundamental frequencies, and heats of formation have been evaluated. Agreement with experiment for the fundamental frequencies is very good, even for nu(sub 2), for CICN, which is subject to a strong Fermi resonance with 2nu(sub 3). It is also shown that a second-order perturbation theory approach to solving the nuclear Schroedinger equation gives results in excellent agreement with essentially exact variational calculations. This is true even for nu(sub 2) of ClCN, provided that near-singular terms are eliminated from the perturbation theory formulas and the appropriate Fermi interaction energy matrix is then diagonalized. A band at 615/cm, tentatively assigned as the Cl-N stretch in ClNC in matrix isolation experiments, is shown not to be due to ClNC. Accurate atomization energies are determined and are used to evaluate accurate heats of formation (3.1 +/- 1.5, 33.2 +/- 1.5, 72.6 +/- 1.5, and 75.9 +/- 1.5 kcal/mol for FCN, ClCN, FNC, and ClNC, respectively). It is expected that the theoretical heats of formation for FCN, FNC, and ClNC are the most accurate available.
Dual-axis vapor cell for simultaneous laser frequency stabilization on disparate optical transitions
Jayakumar, Anupriya Plotkin-Swing, Benjamin; Jamison, Alan O.; Gupta, Subhadeep
2015-07-15
We have developed a dual-axis ytterbium (Yb) vapor cell and used it to simultaneously address the two laser cooling transitions in Yb at wavelengths 399 nm and 556 nm, featuring the disparate linewidths of 2π × 29 MHz and 2π × 182 KHz, respectively. By utilizing different optical paths for the two wavelengths, we simultaneously obtain comparable optical densities suitable for saturated absorption spectroscopy for both the transitions and keep both the lasers frequency stabilized over several hours. We demonstrate that by appropriate control of the cell temperature profile, two atomic transitions differing in relative strength across a large range of over three orders of magnitude can be simultaneously addressed, making the device adaptable to a variety of spectroscopic needs. We also show that our observations can be understood with a simple theoretical model of the Yb vapor.
Madej, Alan A.; Bernard, John E.; John Alcock, A.; Czajkowski, Andrzej; Chepurov, Sergei
2006-04-15
Absolute frequency measurements, with up to 1x10{sup -11} level accuracies, are presented for 60 lines of the P and R branches for the {nu}{sub 1}+{nu}{sub 3} band of {sup 13}C{sub 2}H{sub 2} at 1.5 {mu}m (194 THz). The measurements were made using cavity-enhanced, diode-laser-based saturation spectroscopy. With one laser system stabilized to the P(16) line and a second laser system stabilized to the line whose frequency was to be determined, a Cr:YAG frequency comb was employed to accurately measure the tetrahertz level frequency intervals. The results are compared with recent work from other groups and indicate that these lines would form a basis for a high-quality atlas of reference frequencies for this region of the spectrum.
Quantum versus classical phase-locking transition in a frequency-chirped nonlinear oscillator
Barth, I.; Friedland, L.; Gat, O.; Shagalov, A. G.
2011-07-15
Classical and quantum-mechanical phase-locking transition in a nonlinear oscillator driven by a chirped-frequency perturbation is discussed. Different limits are analyzed in terms of the dimensionless parameters P{sub 1}={epsilon}/{radical}(2m({Dirac_h}/2{pi}){omega}{sub 0}{alpha}) and P{sub 2}=(3({Dirac_h}/2{pi}){beta})/(4m{radical}({alpha})) ({epsilon}, {alpha}, {beta}, and {omega}{sub 0} being the driving amplitude, the frequency chirp rate, the nonlinearity parameter, and the linear frequency of the oscillator). It is shown that, for P{sub 2}<
>P{sub 1}+1, the transition involves quantum-mechanical energy ladder climbing (LC). The threshold for the phase-locking transition and its width in P{sub 1} in both AR and LC limits are calculated. The theoretical results are tested by solving the Schroedinger equation in the energy basis and illustrated via the Wigner function in phase space.
Versolato, O. O.; Wansbeek, L. W.; Jungmann, K.; Timmermans, R. G. E.; Willmann, L.; Wilschut, H. W.
2011-04-15
We explore the potential of the electric quadrupole transitions 7s {sup 2}S{sub 1/2}-6d {sup 2}D{sub 3/2}, 6d {sup 2}D{sub 5/2} in radium isotopes as single-ion optical frequency standards. The frequency shifts of the clock transitions due to external fields and the corresponding uncertainties are calculated. Several competitive {sup A}Ra{sup +} candidates, with A= 223-229, are identified. In particular, we show that the transition 7s {sup 2}S{sub 1/2} (F=2,m{sub F}=0)-6d {sup 2}D{sub 3/2} (F=0,m{sub F}=0) at 828 nm in {sup 223}Ra{sup +}, with no linear Zeeman and electric quadrupole shifts, stands out as a relatively simple case, which could be exploited as a compact, robust, and low-cost atomic clock operating at a fractional frequency uncertainty of 10{sup -17}. With more experimental effort, the {sup 223,225,226}Ra{sup +} clocks could be pushed to a projected performance reaching the 10{sup -18} level.
NASA Astrophysics Data System (ADS)
Versolato, O. O.; Wansbeek, L. W.; Jungmann, K.; Timmermans, R. G. E.; Willmann, L.; Wilschut, H. W.
2011-04-01
We explore the potential of the electric quadrupole transitions 7s2S1/2-6d2D3/2, 6d2D5/2 in radium isotopes as single-ion optical frequency standards. The frequency shifts of the clock transitions due to external fields and the corresponding uncertainties are calculated. Several competitive ARa+ candidates, with A= 223-229, are identified. In particular, we show that the transition 7s2S1/2(F=2,mF=0)-6d2D3/2(F=0,mF=0) at 828 nm in Ra223+, with no linear Zeeman and electric quadrupole shifts, stands out as a relatively simple case, which could be exploited as a compact, robust, and low-cost atomic clock operating at a fractional frequency uncertainty of 10-17. With more experimental effort, the Ra223,225,226+ clocks could be pushed to a projected performance reaching the 10-18 level.
Transitive responding in pigeons: influences of stimulus frequency and reinforcement history.
Siemann, M; Delius, J D; Wright, A A
1996-09-01
Fersen et al. (1991) (J. Exp. Psychol.: Anim. Behav. Process., 17: 334-341) trained pigeons to discriminate four overlapping pairs of stimuli A + B -, B + C -, C + D - and D + E - (+ rewarded, - penalized). When subsequently tested with a pair BD the pigeons showed a strong preference for stimulus B. A special value transfer theory was offered as an explanation for this transitive responding. A simpler reinforcement ratio account based on certain inequalities factually affecting the accuracy performance on training pairs is proposed. To explore its implications an experiment employing a novel grit-grain conditioning method was carried out. The presentation frequencies of the training pairs were biased so that the choice accuracies obtained at the end of training were approximately equal for all pairs. Testing with pair BD still yielded high preference for B, documenting the robustness of the transitive responding phenomenon. When suitably adjusted to the training design the reinforcement ratio account was still viable. The transitive responding with the BD and other test pairs could also be simulated with a simple reinforcement based conditioning model. Some of the subjects were then retrained with modified presentation frequencies so that the subjects ended up with an even overall exposure to all training pairs. Test pairs continued to yield strong transitive responding. It is concluded that this behavioral effect is a robust phenomenon which is largely unaffected by training design modifications.
Blackbody radiation shift of the {sup 133}Cs hyperfine transition frequency
Micalizio, Salvatore; Godone, Aldo; Calonico, Davide; Levi, Filippo; Lorini, Luca
2004-05-01
We report the theoretical evaluations of the static scalar polarizability of the {sup 133}Cs ground state and of the blackbody radiation shift induced on the transition frequency between the two hyperfine levels with m{sub F}=0. This shift is of fundamental importance in the evaluation of the accuracy of the primary frequency standards based on atomic fountains and is employed in the realization of the SI second in the International Atomic Time scale at the level of 1x10{sup -15}. Our computed value for the polarizability is {alpha}{sub 0}=(6.600{+-}0.016)x10{sup -39}C m{sup 2}/V in agreement at the level of 1x10{sup -3} with recent theoretical and experimental values. As regards the blackbody radiation shift we find for the relative hyperfine transition frequency {beta}=(-1.49{+-}0.07)x10{sup -14} at T=300 K in agreement with frequency measurements reported by our group and by Bauch and Schroeder [Phys. Rev. Lett. 78, 622 (1997)]. This value is lower by 2x10{sup -15} than that obtained with measurements based on the dc Stark shift and than the value commonly accepted up to now.
Kim, Sang-Yoon; Lim, Woochang
2015-08-01
We are interested in characterization of synchronization transitions of bursting neurons in the frequency domain. Instantaneous population firing rate (IPFR) [Formula: see text], which is directly obtained from the raster plot of neural spikes, is often used as a realistic collective quantity describing population activities in both the computational and the experimental neuroscience. For the case of spiking neurons, a realistic time-domain order parameter, based on [Formula: see text], was introduced in our recent work to characterize the spike synchronization transition. Unlike the case of spiking neurons, the IPFR [Formula: see text] of bursting neurons exhibits population behaviors with both the slow bursting and the fast spiking timescales. For our aim, we decompose the IPFR [Formula: see text] into the instantaneous population bursting rate [Formula: see text] (describing the bursting behavior) and the instantaneous population spike rate [Formula: see text] (describing the spiking behavior) via frequency filtering, and extend the realistic order parameter to the case of bursting neurons. Thus, we develop the frequency-domain bursting and spiking order parameters which are just the bursting and spiking "coherence factors" [Formula: see text] and [Formula: see text] of the bursting and spiking peaks in the power spectral densities of [Formula: see text] and [Formula: see text] (i.e., "signal to noise" ratio of the spectral peak height and its relative width). Through calculation of [Formula: see text] and [Formula: see text], we obtain the bursting and spiking thresholds beyond which the burst and spike synchronizations break up, respectively. Consequently, it is shown in explicit examples that the frequency-domain bursting and spiking order parameters may be usefully used for characterization of the bursting and the spiking transitions, respectively.
NASA Technical Reports Server (NTRS)
Currie, Thayne; Sicilia-Aguilar, Auora
2011-01-01
We present Spitzer 3.6-24 micron photometry and spectroscopy for stars in the 1-3 Myr-old Coronet Cluster, expanding upon the survey of Sicilia-Aguilar et al. (2008). Using sophisticated radiative transfer models, we analyze these new data and those from Sicilia-Aguilar et al. (2008) to identify disks with evidence for substantial dust evolution consistent with disk clearing: transitional disks. We then analyze data in Taurus and others young clusters - IC 348, NGC 2362, and eta Cha -- to constrain the transitional disk frequency as a function of time. Our analysis confirms previous results finding evidence for two types of transitional disks -- those with inner holes and those that are homologously depleted. The percentage of disks in the transitional phase increases from approx.15-20% at 1-2 Myr to > 50% at 5-8 Myr; the mean transitional disk lifetime is closer to approx. 1 Myr than 0.1-0.5 Myr, consistent with previous studies by Currie et al. (2009) and Sicilia-Aguilar et al. (2009). In the Coronet Cluster and IC 348, transitional disks are more numerous for very low-mass M3--M6 stars than for more massive K5-M2 stars, while Taurus lacks a strong spectral type-dependent frequency. Assuming standard values for the gas-to-dust ratio and other disk properties, the lower limit for the masses of optically-thick primordial disks is Mdisk approx. 0.001-0.003 M*. We find that single color-color diagrams do not by themselves uniquely identify transitional disks or primordial disks. Full SED modeling is required to accurately assess disk evolution for individual sources and inform statistical estimates of the transitional disk population in large samples using mid-IR colors.
Currie, Thayne; Sicilia-Aguilar, Aurora
2011-05-01
We present Spitzer 3.6-24 {mu}m photometry and spectroscopy for stars in the 1-3 Myr old Coronet Cluster, expanding upon the survey of Sicilia-Aguilar et al. Using sophisticated radiative transfer models, we analyze these new data and those from Sicilia-Aguilar et al. to identify disks with evidence for substantial dust evolution consistent with disk clearing: transitional disks. We then analyze data in Taurus and others young clusters-IC 348, NGC 2362, and {eta} Cha-to constrain the transitional disk frequency as a function of time. Our analysis confirms previous results finding evidence for two types of transitional disks-those with inner holes and those that are homologously depleted. The percentage of disks in the transitional phase increases from {approx}15%-20% at 1-2 Myr to {>=}50% at 5-8 Myr; the mean transitional disk lifetime is closer to {approx}1 Myr than 0.1-0.5 Myr, consistent with previous studies by Currie et al. and Sicilia-Aguilar et al. In the Coronet Cluster and IC 348, transitional disks are more numerous for very low mass M3-M6 stars than for more massive K5-M2 stars, while Taurus lacks a strong spectral-type-dependent frequency. Assuming standard values for the gas-to-dust ratio and other disk properties, the lower limit for the masses of optically thick primordial disks is M{sub disk} {approx} 0.001-0.003 M{sub *}. We find that single color-color diagrams do not by themselves uniquely identify transitional disks or primordial disks. Full spectral energy distribution modeling is required to accurately assess disk evolution for individual sources and inform statistical estimates of the transitional disk population in large samples using mid-IR colors.
NASA Astrophysics Data System (ADS)
Choi, Jun-Ho; Cho, Minhaeng
2013-05-01
The Hessian matrix reconstruction method initially developed to extract the basis mode frequencies, vibrational coupling constants, and transition dipoles of the delocalized amide I, II, and III vibrations of polypeptides and proteins from quantum chemistry calculation results is used to obtain those properties of delocalized O-H stretch modes in liquid water. Considering the water symmetric and asymmetric O-H stretch modes as basis modes, we here develop theoretical models relating vibrational frequencies, transition dipoles, and coupling constants of basis modes to local water configuration and solvent electric potential. Molecular dynamics simulation was performed to generate an ensemble of water configurations that was in turn used to construct vibrational Hamiltonian matrices. Obtaining the eigenvalues and eigenvectors of the matrices and using the time-averaging approximation method, which was developed by the Skinner group, to calculating the vibrational spectra of coupled oscillator systems, we could numerically simulate the O-H stretch IR spectrum of liquid water. The asymmetric line shape and weak shoulder bands were quantitatively reproduced by the present computational procedure based on vibrational exciton model, where the polarization effects on basis mode transition dipoles and inter-mode coupling constants were found to be crucial in quantitatively simulating the vibrational spectra of hydrogen-bond networking liquid water.
Lim, Chee Wei; Tai, Siew Hoon; Lee, Lin Min; Chan, Sheot Harn
2012-07-01
The current food crisis demands unambiguous determination of mycotoxin contamination in staple foods to achieve safer food for consumption. This paper describes the first accurate LC-MS/MS method developed to analyze tricothecenes in grains by applying multiple reaction monitoring (MRM) transition and MS(3) quantitation strategies in tandem. The tricothecenes are nivalenol, deoxynivalenol, deoxynivalenol-3-glucoside, fusarenon X, 3-acetyl-deoxynivalenol, 15-acetyldeoxynivalenol, diacetoxyscirpenol, and HT-2 and T-2 toxins. Acetic acid and ammonium acetate were used to convert the analytes into their respective acetate adducts and ammonium adducts under negative and positive MS polarity conditions, respectively. The mycotoxins were separated by reversed-phase LC in a 13.5-min run, ionized using electrospray ionization, and detected by tandem mass spectrometry. Analyte-specific mass-to-charge (m/z) ratios were used to perform quantitation under MRM transition and MS(3) (linear ion trap) modes. Three experiments were made for each quantitation mode and matrix in batches over 6 days for recovery studies. The matrix effect was investigated at concentration levels of 20, 40, 80, 120, 160, and 200 μg kg(-1) (n = 3) in 5 g corn flour and rice flour. Extraction with acetonitrile provided a good overall recovery range of 90-108% (n = 3) at three levels of spiking concentration of 40, 80, and 120 μg kg(-1). A quantitation limit of 2-6 μg kg(-1) was achieved by applying an MRM transition quantitation strategy. Under MS(3) mode, a quantitation limit of 4-10 μg kg(-1) was achieved. Relative standard deviations of 2-10% and 2-11% were reported for MRM transition and MS(3) quantitation, respectively. The successful utilization of MS(3) enabled accurate analyte fragmentation pattern matching and its quantitation, leading to the development of analytical methods in fields that demand both analyte specificity and fragmentation fingerprint-matching capabilities that are
Li, H; Yan, G
2008-01-01
To portably monitor the motility of the total GI tract, a method for assessing GI motility by simultaneously measuring transit time and contraction frequency is put forward. The portable monitoring system is composed of a swallowable telemetric capsule, a portable recorder, magnetizing coils deposited in vitro, and workstation for data processing. The transit time and contraction frequency of the GI tract are deduced by analysing the variation of the position and orientation angles of a telemetric capsule in time domain and frequency domain. AC electromagnetic localization method is used to determine the position and orientation of the telemetric capsule in vivo. In the paper, the localization model based on a quasi-static magnetic field, the method of monitoring GI motility and the set-up of the monitoring system are detailed. Then from static and dynamic experiments, the performances of the system including the accuracy and dynamic response are evaluated. Finally, the electromagnetic safety of the system is verified by simulating electromagnetic radiation to the human body. PMID:19005962
Liquid-glass transition as the freezing of characteristic acoustic frequencies
Sanditov, D. S.
2010-11-15
Half-quantum interpretation is proposed for the liquid-glass transition as the freezing of characteristic acoustic frequencies (degrees of freedom) that are related to the molecular mobility of delocalized excited kinetic units, namely, linear quantum oscillators. There exists a correlation between the energy quantum of an elementary excitation (atom delocalization energy) and the glass transition temperature, which is proportional to the characteristic Einstein temperature. By analogy with the Einstein theory of the heat capacity of solids, the temperature range of the concentration of excited atoms in an amorphous medium is divided into the following two regions: a high-temperature region with a linear temperature dependence of this concentration and a low-temperature region, where the concentration of excited atoms decreases exponentially to the limiting minimum value (about 3%). At this value, the viscosity increases to a critical value (about 10{sup 12} Pa s), which corresponds to the glass transition temperature, i.e., the temperature of freezing the mobility of excited kinetic units. The temperature dependence of the free activation energy of viscous flow in the glass transition range is specified by the temperature dependence of the relative number of excited atoms.
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Martin, Jan M. L.; Kwak, Dochan (Technical Monitor)
2002-01-01
The CCSD(T) method has been used to compute a highly accurate quartic force field and fundamental frequencies for all N-14 and N-15 isotopomers of the high energy density material T(sub d)N(sub 4). The computed fundamental frequencies show beyond doubt that the bands observed in a matrix isolation experiment by Radziszewski and coworkers are not due to different isotopomers of T(sub d)N(sub 4). The most sophisticated thermochemical calculations to date yield a N(sub 4) -> 2N(sub 2) heat of reaction of 182.22 +/- 0.5 kcal/mol at 0 K (180.64 +/- 0.5 at 298 K). It is hoped that the data reported herein will aid in the ultimate detection of T(sub d)N(sub 4).
NASA Technical Reports Server (NTRS)
Decrossas, Emmanuel; Glover, Michael D.; Porter, Kaoru; Cannon, Tom; Mantooth, H. Alan; Hamilton, M. C.
2013-01-01
Various stripline structures and flip chip interconnect designs for high-speed digital communication systems implemented in low temperature co-fired ceramic (LTCC) substrates are studied in this paper. Specifically, two different transition designs from edge launch 2.4 millimeter connectors to stripline transmission lines embedded in LTCC are discussed. After characterizing the DuPont (sup trademark) 9K7 green tape, different designs are proposed to improve signal integrity for high-speed digital data. The full-wave simulations and experimental data validate the presented designs over a broad frequency band from Direct Current to 50 gigahertz and beyond.
Nudds, Robert L.; Taylor, Graham K.; Thomas, Adrian L. R.
2004-01-01
The wing kinematics of birds vary systematically with body size, but we still, after several decades of research, lack a clear mechanistic understanding of the aerodynamic selection pressures that shape them. Swimming and flying animals have recently been shown to cruise at Strouhal numbers (St) corresponding to a regime of vortex growth and shedding in which the propulsive efficiency of flapping foils peaks (St approximately fA/U, where f is wingbeat frequency, U is cruising speed and A approximately bsin(theta/2) is stroke amplitude, in which b is wingspan and theta is stroke angle). We show that St is a simple and accurate predictor of wingbeat frequency in birds. The Strouhal numbers of cruising birds have converged on the lower end of the range 0.2 < St < 0.4 associated with high propulsive efficiency. Stroke angle scales as theta approximately 67b-0.24, so wingbeat frequency can be predicted as f approximately St.U/bsin(33.5b-0.24), with St0.21 and St0.25 for direct and intermittent fliers, respectively. This simple aerodynamic model predicts wingbeat frequency better than any other relationship proposed to date, explaining 90% of the observed variance in a sample of 60 bird species. Avian wing kinematics therefore appear to have been tuned by natural selection for high aerodynamic efficiency: physical and physiological constraints upon wing kinematics must be reconsidered in this light. PMID:15451698
NASA Technical Reports Server (NTRS)
Chatfield, David C.; Friedman, Ronald S.; Lynch, Gillian C.; Truhlar, Donald G.; Schwenke, David W.
1993-01-01
Accurate quantum mechanical dynamics calculations are reported for the reaction probabilities of O(3P) + H2 yields OH + H with zero total angular momentum on a single potential energy surface. The results show that the reactive flux is gated by quantized transition states up to the highest energy studied, which corresponds to a total energy of 1.90 eV. The quantized transition states are assigned and compared to vibrationally adiabatic barrier maxima; their widths and transmission coefficients are determined; and they are classified as variational, supernumerary of the first kind, and supernumerary of the second kind. Their effects on state-selected and state-to-state reactivity are discussed in detail.
Martins, Raphael P.; Kaur, Kuljeet; Hwang, Elliot; Ramirez, Rafael J.; Willis, B. Cicero; Filgueiras-Rama, David; Ennis, Steven R.; Takemoto, Yoshio; Ponce-Balbuena, Daniela; Zarzoso, Manuel; O’Connell, Ryan P.; Musa, Hassan; Guerrero-Serna, Guadalupe; Avula, Uma Mahesh R.; Swartz, Michael F.; Bhushal, Sandesh; Deo, Makarand; Pandit, Sandeep V.; Berenfeld, Omer; Jalife, José
2014-01-01
Background Little is known about the mechanisms underlying the transition from paroxysmal to persistent atrial fibrillation (AF). In an ovine model of long-standing persistent AF (LS-PAF) we tested the hypothesis that the rate of electrical and/or structural remodeling, assessed by dominant frequency (DF) changes, determines the time at which AF becomes persistent. Methods and Results Self-sustained AF was induced by atrial tachypacing. Seven sheep were sacrificed 11.5±2.3 days after the transition to persistent AF and without reversal to sinus rhythm (SR); 7 sheep were sacrificed after 341.3±16.7 days of LS-PAF. Seven sham-operated animals were in SR for 1 year. DF was monitored continuously in each group. RT-PCR, western blotting, patch-clamping and histological analyses were used to determine changes in functional ion channel expression and structural remodeling. Atrial dilatation, mitral valve regurgitation, myocyte hypertrophy, and atrial fibrosis occurred progressively and became statistically significant after the transition to persistent AF, with no evidence for left ventricular dysfunction. DF increased progressively during the paroxysmal-to-persistent AF transition and stabilized when AF became persistent. Importantly, the rate of DF increase (dDF/dt) correlated strongly with the time to persistent AF. Significant action potential duration (APD) abbreviation, secondary to functional ion channel protein expression changes (CaV1.2, NaV1.5 and KV4.2 decrease; Kir2.3 increase), was already present at the transition and persisted for one-year follow up. Conclusions In the sheep model of LS-PAF, the rate of DF increase predicts the time at which AF stabilizes and becomes persistent, reflecting changes in APD and densities of sodium, L-type calcium and inward rectifier currents. PMID:24463369
Liu, Hong; Wang, Jie; Xu, Xiangyang; Song, Enmin; Wang, Qian; Jin, Renchao; Hung, Chih-Cheng; Fei, Baowei
2014-11-01
A robust and accurate center-frequency (CF) estimation (RACE) algorithm for improving the performance of the local sine-wave modeling (SinMod) method, which is a good motion estimation method for tagged cardiac magnetic resonance (MR) images, is proposed in this study. The RACE algorithm can automatically, effectively and efficiently produce a very appropriate CF estimate for the SinMod method, under the circumstance that the specified tagging parameters are unknown, on account of the following two key techniques: (1) the well-known mean-shift algorithm, which can provide accurate and rapid CF estimation; and (2) an original two-direction-combination strategy, which can further enhance the accuracy and robustness of CF estimation. Some other available CF estimation algorithms are brought out for comparison. Several validation approaches that can work on the real data without ground truths are specially designed. Experimental results on human body in vivo cardiac data demonstrate the significance of accurate CF estimation for SinMod, and validate the effectiveness of RACE in facilitating the motion estimation performance of SinMod.
NASA Astrophysics Data System (ADS)
Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.
2009-06-01
A further refined, global potential energy surface (PES) is computed for the C_{3v} symmetry isotopologues of ammonia, including ^{14}NH_3, ^{15}NH_3, ^{14}ND_3 and ^{14}NT_3. The refinement procedure was similar to that used in our previously reported PES, but now extends to higher J energy levels and other isotopologues. Both the diagonal Born-Oppenheimer correction and the non-adiabatic correction were included. J=0-6 rovibrational energy levels and transition frequencies of ^{14}NH_3 computed on this PES are in excellent agreement with HITRAN data. Statistics on nearly 4100 transitions and more than 1000 energy levels demonstrate the accuracy achieved by the state-of-the-art "Best Theory + Experiment" strategy. Most transition frequencies are of ±0.01-0.02 cm^{-1} accuracy. Similar accuracy has been found on ^{15}NH_3 J=0-3 rovibrational energy levels. Several transitions and energy levels in HITRAN have been identified as unreliable or suspicious, and some have been re-assigned. For ^{14}ND_3 and ^{14}NT_3, J=0-3 calculations have been performed. Agreement for pure rotation-inversion transitions is nearly perfect, with more reliable energy levels presented. On the other hand, our J=0 results suggest a re-analysis on the ^{14}ND_3 ν_1 band origin is needed. Finally, we will discuss possible future refinements leading to an even better final PES for Ammonia. X. Huang, D.W. Schwenke, and T.J. Lee, J. Chem. Phys. 129, 214304 (2008).
Nez, F.; Plimmer, M.D.; Bourzeix, S.; Julien, L.; Biraben, F. ); Felder, R. )
1993-06-10
We have performed a new measurement of the Rydberg constant by frequency comparison of the 2S--8S and 2S--8D two-photon transitions in hydrogen with the difference of two optical standards connected to a frequency chain. Our result is: R[sub [infinity
Xu, Zhongnan; Kitchin, John R.; Joshi, Yogesh V.; Raman, Sumathy
2015-04-14
We validate the usage of the calculated, linear response Hubbard U for evaluating accurate electronic and chemical properties of bulk 3d transition metal oxides. We find calculated values of U lead to improved band gaps. For the evaluation of accurate reaction energies, we first identify and eliminate contributions to the reaction energies of bulk systems due only to changes in U and construct a thermodynamic cycle that references the total energies of unique U systems to a common point using a DFT + U(V ) method, which we recast from a recently introduced DFT + U(R) method for molecular systems. We then introduce a semi-empirical method based on weighted DFT/DFT + U cohesive energies to calculate bulk oxidation energies of transition metal oxides using density functional theory and linear response calculated U values. We validate this method by calculating 14 reactions energies involving V, Cr, Mn, Fe, and Co oxides. We find up to an 85% reduction of the mean average error (MAE) compared to energies calculated with the Perdew-Burke-Ernzerhof functional. When our method is compared with DFT + U with empirically derived U values and the HSE06 hybrid functional, we find up to 65% and 39% reductions in the MAE, respectively.
NASA Astrophysics Data System (ADS)
Dai, Shaoyang; Xia, Wei; Zhang, Yin; Zhao, Jianye; Zhou, Dawei; Wang, Qing; Yu, Qi; Li, Kunqian; Qi, Xianghui; Chen, Xuzong
2016-11-01
The femtosecond fiber-based optical frequency combs have been proved to be powerful tools for investigating the energy levels of atoms and molecules. In this paper, an Er-doped fiber femtosecond optical frequency comb has been implemented for studying the polarization dependence of 5S-5D two-photon transitions in thermal gas of atomic rubidium 87 using an entirely symmetrical optical configuration. By changing the polarization states of the counter-propagating light beams, the polarization dependence of direct two photon transition spectrum is demonstrated, and a dramatic variation (up to 5.5 times) of the two-photon transitions strength has been observed. The theory for the polarization dependence of two photon transition based on the second-order perturbation was established, which is in good agreement with the experimental results. The measurement results indicate that the polarization state manipulation with the existing frequency comb is used for femtosecond optical frequency comb based two photon transition spectroscopic purposes, which will improve the precision measurement of the absolute transition frequency and related applications.
Layering effects on low frequency modes in n-layered MX2 transition metal dichalcogenides.
Cammarata, Antonio; Polcar, Tomas
2016-02-14
n-Layered (n = 2, 3, 4) MX2 transition metal dichalcogenides (M = Mo, W; X = S, Se, Te) have been studied using DFT techniques. Long-range van der Waals forces have been modeled using the Grimme correction to capture interlayer interactions. We study the dynamic and electronic dependence of atomic displacement on the number of layers. We find that the displacement patterns mainly affected by a change in the layer number are low-frequency modes at Γ and A k-points; such modes are connected with the intrinsic tribological response. We disentangle electro-phonon coupling by combining orbital polarization, covalency and cophonicity analysis with phonon band calculations. We find that the frequency dependence on the number of layers and the atomic type has a non-trivial relation with the electronic charge distribution in the interlayer region. We show that the interlayer electronic density can be adjusted by appropriately tuning M-X cophonicity, acting as a knob to control vibrational frequencies, hence the intrinsic frictional response. The present results can be exploited to study the electro-phonon coupling effects in TMD-based materials beyond tribological applications. PMID:26806673
NASA Astrophysics Data System (ADS)
Nishiyama, A.; Nakashima, K.; Matsuba, A.; Misono, M.
2015-12-01
We performed Doppler-free two-photon absorption spectroscopy of naphthalene using an optical frequency comb as a frequency reference. Rotationally resolved rovibronic spectra were observed, and absolute frequencies of the rovibronic transitions were determined with an uncertainty of several tens of kHz. The resolution and precision of our system are finer than the natural width of naphthalene. We assigned 1466 lines of the Q (Ka) Q (J) transition and calculated molecular constants. We attribute systematic spectral line shifts to the Coriolis interaction, and discuss the origin of the spectral linewidths.
VizieR Online Data Catalog: CH3NCO (methyl isocyanate) transition frequencies (Halfen+,
NASA Astrophysics Data System (ADS)
Halfen, D. T.; Ilyushin, V. V.; Ziurys, L. M.
2016-02-01
In order to establish accurate rest frequencies in the 3mm window, which lies above 40GHz, we conducted a new analysis of CH3NCO using the previous data of Koput (1986JMoSp.115..131K) and new spectra measured in the Ziurys laboratory in the 60-88GHz range with the FTmmW spectrometer. See table 1 and section 2 for further details. Observations of CH3NCO were performed as part of the spectral survey of Sgr B2(N). The data were collected during 2002 September-2014 March using the ARO 12m telescope on Kitt Peak, Arizona, and the Submillimeter Telescope (SMT) on Mount Graham. (2 data files).
Phase transition studies in barium and strontium titanates at microwave frequencies
NASA Technical Reports Server (NTRS)
Dahiya, Jai N.
1993-01-01
The objectives were the following: to understand the phase transformations in barium and strontium titanates as the crystals go from one temperature to the other; and to study the dielectric behavior of barium and strontium titanate crystals at a microwave frequency of 9.12 GHz and as a function of temperature. Phase transition studies in barium and strontium titanate are conducted using a cylindrical microwave resonant cavity as a probe. The cavity technique is quite successful in establishing the phase changes in these crystals. It appears that dipole relaxation plays an important role in the behavior of the dielectric response of the medium loading the cavity as phase change takes place within the sample. The method of a loaded resonant microwave cavity as applied in this work has proven to be sensitive enough to monitor small phase changes of the cavity medium.
NASA Astrophysics Data System (ADS)
Fogarasi, Géza; Boggs, James E.; Pulay, Péter
Ab initio calculations with the 6-311 G** basis set and all single and double excitations in the CI treatment have been carried out to determine the structure of the HCC radical. The theoretical geometry of R(CC) = 1·209, r(CH) = 1·067 Å (or 1·205 and 1·063, respectively, if corrected for residual errors) is in excellent accordance with the experimental rotational constant. The calculated harmonic vibrational frequencies are v1 ⋍ 3450, v2 ⋍ 540 and v3 ⋍ 2040 cm-1. An extremely low energy around 2000 cm-1 is obtained for the first electronic transition A2II ← X 2∑. Results for the excited state are also given. The theoretical vibrational frequencies, with all possible errors taken into account, are inconsistent with the accepted interpretations of the few experimental results. It is shown, however, that a complete reinterpretation of the spectroscopic observations is possible, by which the present calculations fit with the recent gas phase infrared laser spectroscopic data but remain in definite contradiction with the infrared matrix results.
Okubo, Sho; Nakayama, Hirotaka; Iwakuni, Kana; Inaba, Hajime; Sasada, Hiroyuki
2011-11-21
We determine the absolute frequencies of 56 rotation-vibration transitions of the ν(3) band of CH(4) from 88.2 to 90.5 THz with a typical uncertainty of 2 kHz corresponding to a relative uncertainty of 2.2 × 10(-11) over an average time of a few hundred seconds. Saturated absorption lines are observed using a difference-frequency-generation source and a cavity-enhanced absorption cell, and the transition frequencies are measured with a fiber-laser-based optical frequency comb referenced to a rubidium atomic clock linked to the international atomic time. The determined value of the P(7) F(2)((2)) line is consistent with the International Committee for Weights and Measures recommendation within the uncertainty.
NASA Technical Reports Server (NTRS)
Voorhies, Coerte V.; Conrad, Joy
1996-01-01
The geomagnetic spatial power spectrum R(sub n)(r) is the mean square magnetic induction represented by degree n spherical harmonic coefficients of the internal scalar potential averaged over the geocentric sphere of radius r. McLeod's Rule for the magnetic field generated by Earth's core geodynamo says that the expected core surface power spectrum (R(sub nc)(c)) is inversely proportional to (2n + 1) for 1 less than n less than or equal to N(sub E). McLeod's Rule is verified by locating Earth's core with main field models of Magsat data; the estimated core radius of 3485 kn is close to the seismologic value for c of 3480 km. McLeod's Rule and similar forms are then calibrated with the model values of R(sub n) for 3 less than or = n less than or = 12. Extrapolation to the degree 1 dipole predicts the expectation value of Earth's dipole moment to be about 5.89 x 10(exp 22) Am(exp 2)rms (74.5% of the 1980 value) and the expected geomagnetic intensity to be about 35.6 (mu)T rms at Earth's surface. Archeo- and paleomagnetic field intensity data show these and related predictions to be reasonably accurate. The probability distribution chi(exp 2) with 2n+1 degrees of freedom is assigned to (2n + 1)R(sub nc)/(R(sub nc). Extending this to the dipole implies that an exceptionally weak absolute dipole moment (less than or = 20% of the 1980 value) will exist during 2.5% of geologic time. The mean duration for such major geomagnetic dipole power excursions, one quarter of which feature durable axial dipole reversal, is estimated from the modern dipole power time-scale and the statistical model of excursions. The resulting mean excursion duration of 2767 years forces us to predict an average of 9.04 excursions per million years, 2.26 axial dipole reversals per million years, and a mean reversal duration of 5533 years. Paleomagnetic data show these predictions to be quite accurate. McLeod's Rule led to accurate predictions of Earth's core radius, mean paleomagnetic field
ERIC Educational Resources Information Center
Plotner, Anthony J.; Trach, John S.; Strauser, David R.
2012-01-01
Vocational rehabilitation (VR) professionals are critical partners in the transition process for students with disabilities; therefore, they are required to develop transition service delivery proficiencies. VR professional perceptions of transition competencies are seldom examined due to the perception that transition falls mainly on school-based…
Mifflin, Amanda L; Velarde, Luis; Ho, Junming; Psciuk, Brian T; Negre, Christian F A; Ebben, Carlena J; Upshur, Mary Alice; Lu, Zhou; Strick, Benjamin L; Thomson, Regan J; Batista, Victor S; Wang, Hong-Fei; Geiger, Franz M
2015-02-26
Despite the importance of terpenes in biology, the environment, and catalysis, their vibrational spectra remain unassigned. Here, we present subwavenumber high-resolution broad-band sum frequency generation (HR-BB-SFG) spectra of the common terpene (+)-α-pinene that reveal 10 peaks in the C-H stretching region at room temperature. The high spectral resolution resulted in spectra with more and better resolved spectral features than those of the Fourier transform infrared, femtosecond stimulated Raman spectra in the bulk condensed phase and those of the conventional BB-SFG and scanning SFG spectroscopy of the same molecule on a surface. Experiment and simulation show the spectral line shapes with HR-BB-SFG to be accurate. Homogeneous vibrational decoherence lifetimes of up to 1.7 ps are assigned to specific oscillators and compare favorably to lifetimes computed from density functional tight binding molecular dynamics calculations. Phase-resolved spectra provided their orientational information. We propose the new spectroscopy as an attractive alternative to time domain vibrational spectroscopy or heterodyne detection schemes for studying vibrational energy relaxation and vibrational coherences in molecules at molecular surfaces or interfaces.
Johnston, M; Jung, Y
2014-06-01
Purpose: Arterial spin labeling (ASL) is an MRI perfusion imaging method from which quantitative cerebral blood flow (CBF) maps can be calculated. Acquisition with variable post-labeling delays (PLD) and variable TRs allows for arterial transit time (ATT) mapping and leads to more accurate CBF quantification with a scan time saving of 48%. In addition, T1 and M0 maps can be obtained without a separate scan. In order to accurately estimate ATT and T1 of brain tissue from the ASL data, variable labeling durations were invented, entitled variable-bolus ASL. Methods: All images were collected on a healthy subject with a 3T Siemens Skyra scanner. Variable-bolus Psuedo-continuous ASL (PCASL) images were collected with 7 TI times ranging 100-4300ms in increments of 700ms with TR ranging 1000-5200ms. All boluses were 1600ms when the TI allowed, otherwise the bolus duration was 100ms shorter than the TI. All TI times were interleaved to reduce sensitivity to motion. Voxel-wise T1 and M0 maps were estimated using a linear least squares fitting routine from the average singal from each TI time. Then pairwise subtraction of each label/control pair and averaging for each TI time was performed. CBF and ATT maps were created using the standard model by Buxton et al. with a nonlinear fitting routine using the T1 tissue map. Results: CBF maps insensitive to ATT were produced along with ATT maps. Both maps show patterns and averages consistent with literature. The T1 map also shows typical T1 contrast. Conclusion: It has been demonstrated that variablebolus ASL produces CBF maps free from the errors due to ATT and tissue T1 variations and provides M0, T1, and ATT maps which have potential utility. This is accomplished with a single scan in a feasible scan time (under 6 minutes) with low sensivity to motion.
Godun, R M; Nisbet-Jones, P B R; Jones, J M; King, S A; Johnson, L A M; Margolis, H S; Szymaniec, K; Lea, S N; Bongs, K; Gill, P
2014-11-21
Singly ionized ytterbium, with ultranarrow optical clock transitions at 467 and 436 nm, is a convenient system for the realization of optical atomic clocks and tests of present-day variation of fundamental constants. We present the first direct measurement of the frequency ratio of these two clock transitions, without reference to a cesium primary standard, and using the same single ion of 171Yb+. The absolute frequencies of both transitions are also presented, each with a relative standard uncertainty of 6×10(-16). Combining our results with those from other experiments, we report a threefold improvement in the constraint on the time variation of the proton-to-electron mass ratio, μ/μ=0.2(1.1)×10(-16) yr(-1), along with an improved constraint on time variation of the fine structure constant, α/α=-0.7(2.1)×10(-17) yr(-1). PMID:25479482
Yoshimi, Satoshi; Ochi, Hidenori; Murakami, Eisuke; Uchida, Takuro; Kan, Hiromi; Akamatsu, Sakura; Hayes, C Nelson; Abe, Hiromi; Miki, Daiki; Hiraga, Nobuhiko; Imamura, Michio; Aikata, Hiroshi; Chayama, Kazuaki
2015-01-01
Daclatasvir and asunaprevir dual oral therapy is expected to achieve high sustained virological response (SVR) rates in patients with HCV genotype 1b infection. However, presence of the NS5A-Y93H substitution at baseline has been shown to be an independent predictor of treatment failure for this regimen. By using the Invader assay, we developed a system to rapidly and accurately detect the presence of mutant strains and evaluate the proportion of patients harboring a pre-treatment Y93H mutation. This assay system, consisting of nested PCR followed by Invader reaction with well-designed primers and probes, attained a high overall assay success rate of 98.9% among a total of 702 Japanese HCV genotype 1b patients. Even in serum samples with low HCV titers, more than half of the samples could be successfully assayed. Our assay system showed a better lower detection limit of Y93H proportion than using direct sequencing, and Y93H frequencies obtained by this method correlated well with those of deep-sequencing analysis (r = 0.85, P <0.001). The proportion of the patients with the mutant strain estimated by this assay was 23.6% (164/694). Interestingly, patients with the Y93H mutant strain showed significantly lower ALT levels (p=8.8 x 10-4), higher serum HCV RNA levels (p=4.3 x 10-7), and lower HCC risk (p=6.9 x 10-3) than those with the wild type strain. Because the method is both sensitive and rapid, the NS5A-Y93H mutant strain detection system established in this study may provide important pre-treatment information valuable not only for treatment decisions but also for prediction of disease progression in HCV genotype 1b patients. PMID:26083687
Wu, Ping; Deng, Yuqun; Fan, Juping; Teng, Yan; Shi, Yanchao; Sun, Jun
2014-10-15
This paper presents an efficient approach to realizing the frequency tunability of a relativistic backward wave oscillator (RBWO) over three frequency bands by mode transition without changing the slow wave structure (SWS). It is figured out that the transition of the operation mode in the RBWO can be efficiently achieved by using the strong end reflection of the SWS. This mode transition results in the tunability of the RBWO over three frequency bands at high power and high efficiency without changing the SWS. In numerical simulation, the output frequency of the RBWO can jump over 7.9 GHz in C-band, 9.9 GHz in X-band, and 12.4 GHz in Ku-band with output power exceeding 3.0 GW and conversion efficiency higher than 35% by just reasonably transforming the structures of the front and post resonant reflectors which provide the strong end reflection for the SWS.
NASA Astrophysics Data System (ADS)
Bazinette, R.; Paillol, J.; Massines, F.
2016-06-01
The aim of this paper is to better understand the transition from Townsend to radio-frequency homogeneous dielectric barrier discharge (DBD) at atmospheric pressure. The study is done in an Ar/NH3 Penning mixture for an electrode configuration adapted to roll-to-roll plasma surface treatment. The study was led in a frequency range running from 50 kHz up to 8.3 MHz leading to different DBD modes with a 1 mm gas gap: Glow (GDBD), Townsend (TDBD), and Radio-frequency (RF-DBD). In the frequency range between TDBD and RF-DBD, from 250 kHz to 2.3 MHz, additional discharges are observed outside the inter-electrode gas gap. Because each high voltage electrode are inside a dielectric barrel, these additional discharges occur on the side of the barrel where the gap is larger. They disappear when the RF-DBD mode is attained in the 1 mm inter-electrode gas gap, i.e., for frequencies equal or higher than 3 MHz. Fast imaging and optical emission spectroscopy show that the additional discharges are radio-frequency DBDs while the inter-electrode discharge is a TDBD. The RF-DBD discharge mode is attained when electrons drift becomes low enough compared to the voltage oscillation frequency to limit electron loss at the anode. To check that the additional discharges are due to a larger gas gap and a lower voltage amplitude, the TDBD/RF-DBD transition is investigated as a function of the gas gap and the applied voltage frequency and amplitude. Results show that the increase in the frequency at constant gas gap or in the gas gap at constant frequency allows to obtain RF-DBD instead of TDBD. At low frequency and large gap, the increase in the applied voltage allows RF-DBD/TDBD transition. As a consequence, an electrode configuration allowing different gap values is a solution to successively have different discharge modes with the same applied voltage.
NASA Astrophysics Data System (ADS)
Liu, X. Y.; Hu, J. T.; Liu, J. H.; Xiong, Z. L.; Liu, D. W.; Lu, X. P.; Shi, J. J.
2012-07-01
The discharge mode transition from uniform plasma across the gas gap to the α mode happens at the rising phase of the pulsed radio frequency capacitively coupled plasma (PRF CCP). This transition is attributed to the fast increasing stochastic heating at the edge of sheath. In the second stage with the stable current and voltage amplitude, the consistency between experimental and numerical spatial-temporal 777 nm emission profile suggests that He* and He2* dominate the production of O(5p1) through dissociation and excitation of O2. Finally, the sterilization efficiency of PRF CCP is found to be higher than that of plasma jet.
Gong, W.; Peng, X. Li, W.; Guo, H.
2014-07-15
Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.
NASA Astrophysics Data System (ADS)
Gong, W.; Peng, X.; Li, W.; Guo, H.
2014-07-01
Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable 4He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10-12@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.
Frequency of close companions among Kepler planets—a transit time variation study
Xie, Ji-Wei; Wu, Yanqin; Lithwick, Yoram E-mail: wu@astro.utoronto.ca
2014-07-10
A transiting planet exhibits sinusoidal transit time variations (TTVs) if perturbed by a companion near a mean-motion resonance. We search for sinusoidal TTVs in more than 2600 Kepler candidates, using the publicly available Kepler light curves (Q0-Q12). We find that the TTV fractions rise strikingly with the transit multiplicity. Systems where four or more planets transit enjoy a TTV fraction that is roughly five times higher than those where a single planet transits, and about twice as high as those for doubles and triples. In contrast, models in which all transiting planets arise from similar dynamical configurations predict comparable TTV fractions among these different systems. One simple explanation for our results is that there are at least two different classes of Kepler systems, one closely packed and one more sparsely populated.
NASA Astrophysics Data System (ADS)
Boisvert, J.-S.; Margot, J.; Massines, F.
2016-08-01
In this paper, we investigate DBDs in the medium frequency range (MF, 0.3-3 MHz). More precisely, for a 2 inter-dielectric gap in helium at atmospheric pressure, the frequency is varied from 1.0 to 2.7 MHz. The generated discharge shows similarities with both the low-frequency atmospheric-pressure glow discharge (APGD) and the atmospheric pressure capacitively coupled radio-frequency (CCRF) discharge. In the frequency range under investigation, two diffuse discharge modes can be observed depending on the voltage applied between the electrodes. At low applied voltage, the discharge emissions are barely visible and are concentrated in the center of the gas gap similarly to CCRF discharges in the Ω mode where the electron density is concentrated in the bulk. Ohmic heating is the main power transfer mechanism. At higher applied voltage, the discharge emissions are 10 times more intense and are closer to the dielectric surfaces similarly to the more common radio-frequency α mode. These two discharge modes can be observed in the same experimental conditions with the amplitude of the applied voltage as sole control parameter. The gas temperature obtained from N2 impurities rotational spectrum increases from room temperature to about 500 K while the power density rises from 10-1 to 101 W cm-3 when the applied voltage is increased. In addition, when the discharge transits back and forth from the Ω to the α mode, a hysteresis is observed. The transition from the Ω to the α mode occurs abruptly with a large RMS current increase while the transition from the α to the Ω mode is rather smooth with no significant discontinuity in the RMS current.
NASA Astrophysics Data System (ADS)
Boisvert, J.-S.; Margot, J.; Massines, F.
2016-08-01
In this paper, we investigate DBDs in the medium frequency range (MF, 0.3–3 MHz). More precisely, for a 2 inter-dielectric gap in helium at atmospheric pressure, the frequency is varied from 1.0 to 2.7 MHz. The generated discharge shows similarities with both the low-frequency atmospheric-pressure glow discharge (APGD) and the atmospheric pressure capacitively coupled radio-frequency (CCRF) discharge. In the frequency range under investigation, two diffuse discharge modes can be observed depending on the voltage applied between the electrodes. At low applied voltage, the discharge emissions are barely visible and are concentrated in the center of the gas gap similarly to CCRF discharges in the Ω mode where the electron density is concentrated in the bulk. Ohmic heating is the main power transfer mechanism. At higher applied voltage, the discharge emissions are 10 times more intense and are closer to the dielectric surfaces similarly to the more common radio-frequency α mode. These two discharge modes can be observed in the same experimental conditions with the amplitude of the applied voltage as sole control parameter. The gas temperature obtained from N2 impurities rotational spectrum increases from room temperature to about 500 K while the power density rises from 10‑1 to 101 W cm‑3 when the applied voltage is increased. In addition, when the discharge transits back and forth from the Ω to the α mode, a hysteresis is observed. The transition from the Ω to the α mode occurs abruptly with a large RMS current increase while the transition from the α to the Ω mode is rather smooth with no significant discontinuity in the RMS current.
Frequency measurement of the 2S(1/2)-2D(3/2) electric quadrupole transition in a single 171Yb+ ion.
Webster, Stephen; Godun, Rachel; King, Steven; Huang, Guilong; Walton, Barney; Tsatourian, Veronika; Margolis, Helen; Lea, Stephen; Gill, Patrick
2010-03-01
We report on precision laser spectroscopy of the 2S(1/2)(F = 0)-2D(3/2) (F = 2, m(F) = 0) clock transition in a single ion of 171Yb+. The absolute value of the transition frequency, determined using an optical frequency comb referenced to a hydrogen maser, is 688358979309310 +/- 9 Hz. This corresponds to a fractional frequency uncertainty of 1.3 x 10(-14).
ERIC Educational Resources Information Center
Field, David; And Others
1992-01-01
Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)
Hubert, Sébastien; Briancon, Stéphanie; Hedoux, Alain; Guinet, Yannick; Paccou, Laurent; Fessi, Hatem; Puel, François
2011-11-25
The phase transition of a model API, caffeine Form I, was studied during tableting process monitored with an instrumented press. The formulation used had a plastic flow behavior according to the Heckel model in the compression pressure range of 70-170 MPa. The quantitative methods of analysis used were Differential Scanning Calorimetry (DSC) and low frequency Micro Raman Spectroscopy (MRS) which was used for the first time for the mapping of polymorphs in tablets. They brought complementary contributions since MRS is a microscopic spectral analysis with a spatial resolution of 5 μm(3) and DSC takes into account a macroscopic fraction (10mg) of the tablet. Phase transitions were present at the surfaces, borders and center of the tablets. Whatever the pressure applied during the compression process, the transition degree of caffeine Form I toward Form II was almost constant. MRS provided higher transition degrees (50-60%) than DSC (20-35%). MRS revealed that caffeine Form I particles were partially transformed in all parts of the tablets at a microscopic scale. Moreover, tablet surfaces showed local higher transition degree compared to the other parts.
NASA Astrophysics Data System (ADS)
Calkins, Keith Gordon
The fine-structure constant or electromagnetic coupling constant, alpha e, is a dimensionless ratio which unites many physics subfields. Although known precisely via experiments in each subfield, there is disagreement within and between subfields. In particular, precise values obtained via electron ge - 2 experiments which depend heavily on QED calculations have not always been in agreement with those obtained via muon g mu - 2 experiments. Also, solid state measurements (quantum hall effect and AC Josephson effect) often disagree with neutronic hmn measurements. alphae is often said to vary with energy but the question remains as to whether or not its low energy value is stable now or has been stable over the history of the universe. Improved precision helps resolve these issues as they relate to physics, possibly beyond the standard model. The Optical Frequency Measurements group in the Time and Frequency Division at the National Institute of Science and Technology (NIST, Boulder, CO) developed and maintains a femtosecond laser frequency comb which is calibrated with respect to the cesium fountain clock implementation of the second. A single frequency component of the femtosecond laser comb is used together with a solid state diode laser and cesium thermal beam to precisely measure the cesium D1 F ∈ {3,4} transition frequencies. The value of fD1centroid = 335 116 048 748.1(2.4) kHz obtained for the transition centroid is over fifteen times more precise than the most recent previous measurement. A precise value for the cesium D1 hyperfine splitting fHFe = 1 167 723.6(4.7) kHz is reported as well. This value is also over fifteen times more precise than the most recent previous measurement. These new neutral 133Cs 6s 2 S½ → 6p 2 P½ transition (D1) frequencies, when combined with the 2002 CODATA values of the Rydberg, proton/electron mass ratio, cesium atomic mass, and cesium recoil frequency, provide an almost QED-free value of alpha: alphae = 1/137.036 0000
Calculation of Transition Frequencies and Line Strengths of Water for Cool Star Opacities
NASA Astrophysics Data System (ADS)
Miller, S.; Tennyson, J.; Fernley, J.
1992-03-01
First principles calculations for water, using a number of electronic potential surfaces, are presented as a first step towards the computation of an accurate water opacity for cool stars such as M dwarfs. Key word : MOLECULAR PROCESSES - OPACITIES - STARS: ATMOSPHERES - STARS: LATE-TYPE - STARS: LOW-MASS
Demmel, F; Doster, W; Petry, W; Schulte, A
1997-01-01
The contribution of hydrogen bonds to protein-solvent interactions and their impact on structural flexibility and dynamics of myoglobin are discussed. The shift of vibrational peak frequencies with the temperature of myoglobin in sucrose/water and glycerol/water solutions is used to probe the expansion of the hydrogen bond network. We observe a characteristic change in the temperature slope of the O-H stretching frequency at the glass transition which correlates with the discontinuity of the thermal expansion coefficient. The temperature-difference spectra of the amide bands show the same tendency, indicating that stronger hydrogen bonding in the bulk affects the mainchain solvent interactions in parallel. However, the hydrogen bond strength decreases relative to the bulk solvent with increasing cosolvent concentration near the protein surface, which suggests preferential hydration. Weaker and/or fewer hydrogen bonds are observed at low degrees of hydration. The central O-H stretching frequency of protein hydration water is red-shifted by 40 cm-1 relative to the bulk. The shift increases towards lower temperatures, consistent with contraction and increasing strength of the protein-water bonds. The temperature slope shows a discontinuity near 180 K. The contraction of the network has reached a critical limit which leads to frozen-in structures. This effect may represent the molecular mechanism underlying the dynamic transition observed for the mean square displacements of the protein atoms and the heme iron of myoglobin. PMID:9378100
NASA Astrophysics Data System (ADS)
Birkenmeier, G.; Cavedon, M.; Conway, G. D.; Manz, P.; Stroth, U.; Fischer, R.; Fuchert, G.; Happel, T.; Laggner, F. M.; Maraschek, M.; Medvedeva, A.; Nikolaeva, V.; Prisiazhniuk, D.; Pütterich, T.; Ryter, F.; Shao, L. M.; Willensdorfer, M.; Wolfrum, E.; Zohm, H.; the ASDEX Upgrade Team
2016-08-01
Limit-cycle oscillations (LCOs) close to the power threshold of L- to H-mode transitions are investigated in plasmas of ASDEX Upgrade. During this phase, referred to as I-phase, a strong magnetic activity in the poloidal magnetic field {{\\overset{\\centerdot}{{B}} }θ} with an up–down asymmetry is found. In some cases, the regular LCOs during I-phase transition smoothly into a phase with intermittent bursts which have similar properties to type-III edge localised modes (ELMs). Indications of precursors during the intermittent phase as well as in the regular LCO phase point to a common nature of the I-phase and type-III ELMs. The LCO frequency measured in a set of discharges with different plasma currents and magnetic fields scales as f∼ ≤ft(B\\text{t}1/2I\\text{p}3/2\\right)/(nT) .
NASA Astrophysics Data System (ADS)
Speranskiy, Kirill; Kurnikova, Maria
2004-07-01
We propose a hierarchical approach to model vibrational frequencies of a ligand in a strongly fluctuating inhomogeneous environment such as a liquid solution or when bound to a macromolecule, e.g., a protein. Vibrational frequencies typically measured experimentally are ensemble averaged quantities which result (in part) from the influence of the strongly fluctuating solvent. Solvent fluctuations can be sampled effectively by a classical molecular simulation, which in our model serves as the first, low level of the hierarchy. At the second high level of the hierarchy a small subset of system coordinates is used to construct a patch of the potential surface (ab initio) relevant to the vibration in question. This subset of coordinates is under the influence of an instantaneous external force exerted by the environment. The force is calculated at the lower level of the hierarchy. The proposed methodology is applied to model vibrational frequencies of a glutamate in water and when bound to the Glutamate receptor protein and its mutant. Our results are in close agreement with the experimental values and frequency shifts measured by the Jayaraman group by the Fourier transform infrared spectroscopy [Q. Cheng et al., Biochem. 41, 1602 (2002)]. Our methodology proved useful in successfully reproducing vibrational frequencies of a ligand in such a soft, flexible, and strongly inhomogeneous protein as the Glutamate receptor.
Bansal, Kanika; Datta, Shouvik; Henini, Mohamed; Alshammari, Marzook S.
2014-09-22
We observed qualitatively dissimilar frequency dependence of negative capacitance under high charge injection in two sets of functionally different junction diodes: III-V based light emitting and Si-based non-light emitting diodes. Using an advanced approach based on bias activated differential capacitance, we developed a generalized understanding of negative capacitance phenomenon which can be extended to any diode based device structure. We explained the observations as the mutual competition of fast and slow electronic transition rates which are different in different devices. This study can be useful in understanding the interfacial effects in semiconductor heterostructures and may lead to superior device functionality.
Coello Pérez, Eduardo A.; Papenbrock, Thomas F.
2015-07-27
In this paper, we present a model-independent approach to electric quadrupole transitions of deformed nuclei. Based on an effective theory for axially symmetric systems, the leading interactions with electromagnetic fields enter as minimal couplings to gauge potentials, while subleading corrections employ gauge-invariant nonminimal couplings. This approach yields transition operators that are consistent with the Hamiltonian, and the power counting of the effective theory provides us with theoretical uncertainty estimates. We successfully test the effective theory in homonuclear molecules that exhibit a large separation of scales. For ground-state band transitions of rotational nuclei, the effective theory describes data well within theoreticalmore » uncertainties at leading order. To probe the theory at subleading order, data with higher precision would be valuable. For transitional nuclei, next-to-leading-order calculations and the high-precision data are consistent within the theoretical uncertainty estimates. In addition, we study the faint interband transitions within the effective theory and focus on the E2 transitions from the 02+ band (the “β band”) to the ground-state band. Here the predictions from the effective theory are consistent with data for several nuclei, thereby proposing a solution to a long-standing challenge.« less
NASA Astrophysics Data System (ADS)
Coello Pérez, E. A.; Papenbrock, T.
2015-07-01
We present a model-independent approach to electric quadrupole transitions of deformed nuclei. Based on an effective theory for axially symmetric systems, the leading interactions with electromagnetic fields enter as minimal couplings to gauge potentials, while subleading corrections employ gauge-invariant nonminimal couplings. This approach yields transition operators that are consistent with the Hamiltonian, and the power counting of the effective theory provides us with theoretical uncertainty estimates. We successfully test the effective theory in homonuclear molecules that exhibit a large separation of scales. For ground-state band transitions of rotational nuclei, the effective theory describes data well within theoretical uncertainties at leading order. To probe the theory at subleading order, data with higher precision would be valuable. For transitional nuclei, next-to-leading-order calculations and the high-precision data are consistent within the theoretical uncertainty estimates. We also study the faint interband transitions within the effective theory and focus on the E 2 transitions from the 02+ band (the "β band") to the ground-state band. Here the predictions from the effective theory are consistent with data for several nuclei, thereby proposing a solution to a long-standing challenge.
Coello Pérez, Eduardo A.; Papenbrock, Thomas F.
2015-07-27
In this paper, we present a model-independent approach to electric quadrupole transitions of deformed nuclei. Based on an effective theory for axially symmetric systems, the leading interactions with electromagnetic fields enter as minimal couplings to gauge potentials, while subleading corrections employ gauge-invariant nonminimal couplings. This approach yields transition operators that are consistent with the Hamiltonian, and the power counting of the effective theory provides us with theoretical uncertainty estimates. We successfully test the effective theory in homonuclear molecules that exhibit a large separation of scales. For ground-state band transitions of rotational nuclei, the effective theory describes data well within theoretical uncertainties at leading order. To probe the theory at subleading order, data with higher precision would be valuable. For transitional nuclei, next-to-leading-order calculations and the high-precision data are consistent within the theoretical uncertainty estimates. In addition, we study the faint interband transitions within the effective theory and focus on the E2 transitions from the 0_{2}^{+} band (the “β band”) to the ground-state band. Here the predictions from the effective theory are consistent with data for several nuclei, thereby proposing a solution to a long-standing challenge.
NASA Astrophysics Data System (ADS)
Gilliland, Ronald L.
Transits of the planets Mercury and especially Venus have been exciting events in the development of astronomy over the past few hundred years. Just two years ago the first transiting extra-solar planet, HD 209458b, was discovered, and subsequent studies during transit have contributed fundamental new knowledge. From the photometric light curve during transit one obtains a basic confirmation that the radial velocity detected object is indeed a planet by allowing precise determination of its mass and radius relative to these stellar quantities. From study of spectroscopic changes during transit it has been possible to probe for individual components of the transiting planets atmosphere. Planet transits are likely to become a primary tool for detection of new planets, especially other Earth-like planets with the Kepler Discovery Mission. Looking ahead, the additional aperture of the James Webb Space Space Telescope promises to allow the first possibility of studying the atmosphere of extra-solar Earth-analogue planets, perhaps even providing the first evidence of direct relevance to the search for signs of life on other planets.
Hansen, Michael G; Ernsting, Ingo; Vasilyev, Sergey V; Grisard, Arnaud; Lallier, Eric; Gérard, Bruno; Schiller, Stephan
2013-11-01
We demonstrate a robust and simple method for measurement, stabilization and tuning of the frequency of cw mid-infrared (MIR) lasers, in particular of quantum cascade lasers. The proof of principle is performed with a quantum cascade laser at 5.4 µm, which is upconverted to 1.2 µm by sum-frequency generation in orientation-patterned GaAs with the output of a standard high-power cw 1.5 µm fiber laser. Both the 1.2 µm and the 1.5 µm waves are measured by a standard Er:fiber frequency comb. Frequency measurement at the 100 kHz-level, stabilization to sub-10 kHz level, controlled frequency tuning and long-term stability are demonstrated.
Zhou, M; Andrews, L; Bauschlicher, C W
2001-07-01
Figure 18 presents the C-O stretching vibrational frequencies of the first-row transition-metal monocarbonyl cations, neutrals, and anions in solid neon; similar diagrams have been reported for neutral MCO species in solid argon, but three of the early assignments have been changed by recent work and one new assignment added. The laser-ablation method produces mostly neutral atoms with a few percent cations and electrons for capture to make anions; in contrast, thermal evaporation gives only neutral species. Hence, the very recent neon matrix investigations in our laboratory provide carbonyl cations and anions for comparison to neutrals on a level playing field. Several trends are very interesting. First, for all metals, the C-O stretching frequencies follow the order cations > neutrals > anions with large diagnostic 100-200 cm-1 separations, which is consistent with the magnitude of the metal d to CO pi * donation. Second, for a given charge, there is a general increase in C-O stretching vibrational frequencies with increasing metal atomic number, which demonstrates the expected decrease in the metal to CO pi * donation with increasing metal ionization potential. Some of the structure in this plot arises from the extra stability of the filled and half-filled d shell and from the electron pairing that occurs at the middle of the TM row; the plot resembles the "double-humped" graph found for the variation in properties across a row of transition metals. For the anions, the variation with metal atom is the smallest since all of the metals can easily donate charge to the CO ligand. Third, for the early transition-metal Ti, V, and Cr families, the C-O stretching frequencies decrease when going down the family, but the reverse relationship is observed for the late transition-metal Fe, Co, and Ni families. In most of the present discussion, we have referred to neon matrix frequencies; however, the argon matrix frequencies are complementary, and useful information can be
Schunter, C; Garza, J C; Macpherson, E; Pascual, M
2014-01-01
Single nucleotide polymorphisms (SNPs) are rapidly becoming the marker of choice in population genetics due to a variety of advantages relative to other markers, including higher genomic density, data quality, reproducibility and genotyping efficiency, as well as ease of portability between laboratories. Advances in sequencing technology and methodologies to reduce genomic representation have made the isolation of SNPs feasible for nonmodel organisms. RNA-seq is one such technique for the discovery of SNPs and development of markers for large-scale genotyping. Here, we report the development of 192 validated SNP markers for parentage analysis in Tripterygion delaisi (the black-faced blenny), a small rocky-shore fish from the Mediterranean Sea. RNA-seq data for 15 individual samples were used for SNP discovery by applying a series of selection criteria. Genotypes were then collected from 1599 individuals from the same population with the resulting loci. Differences in heterozygosity and allele frequencies were found between the two data sets. Heterozygosity was lower, on average, in the population sample, and the mean difference between the frequencies of particular alleles in the two data sets was 0.135 ± 0.100. We used bootstrap resampling of the sequence data to predict appropriate sample sizes for SNP discovery. As cDNA library production is time-consuming and expensive, we suggest that using seven individuals for RNA sequencing reduces the probability of discarding highly informative SNP loci, due to lack of observed polymorphism, whereas use of more than 12 samples does not considerably improve prediction of true allele frequencies.
Transit-time devices as local oscillators for frequencies above 100 GHz
NASA Technical Reports Server (NTRS)
Eisele, H.; Kidner, C.; Haddad, G. I.
1992-01-01
Very promising preliminary experimental results have been obtained from GaAs IMPATT diodes at F-band frequencies (75 mW, 3.5 percent at 111.1 GHz and 20 mW, 1.4 percent at 120.6 GHz) and from GaAs TUNNETT diodes at W-band frequencies (26 mW, 1.6 percent at 87.2 GHz and 32 mW, 2.6 percent at 93.5 GHz). These results indicate that IMPATT, MITATT and TUNNETT diodes have the highest potential of delivering significant amounts of power at Terahertz frequencies. As shown recently, the noise performance of GaAs W-band IMPATT diodes can compete with that of Gunn devices. Since TUNNETT diodes take advantage of the quieter tunnel injection, they are expected to be especially suited for low-noise local oscillators. This paper will focus on the two different design principles for IMPATT and TUNNETT diodes, the material parameters involved in the design and some aspects of the present device technology. Single-drift flat-profile GaAs D-band IMPATT diodes had oscillations up to 129 GHz with 9 mW, 0.9 percent at 128.4 GHz. Single-drift GaAs TUNNETT diodes had oscillations up to 112.5 GHz with 16 mW and output power levels up to 33 mW and efficiencies up to 3.4 percent around 102 GHz. These results are the best reported so far from GaAs IMPATT and TUNNETT diodes.
VizieR Online Data Catalog: Propenal (CH2CHCHO) transition frequencies (Daly+,
NASA Astrophysics Data System (ADS)
Daly, A. M.; Bermudez, C.; Kolesnikova, L.; Alonso, J. L.
2015-08-01
A commercially available sample of liquid propenal (b.p.=125°C) was used without further purification. Propenal spectrum was acquired using two different spectrometers. A recently upgraded Stark-modulation spectrometer employing 33kHz modulation frequency and phase-sensitive detection was used to cover the 26-110GHz range. Millimeter- and submillimeter-wave measurements, over the 50-660GHz range, were performed using a direct absorption spectrometer recently constructed at the University of Valladolid. See section 2 for further details. (2 data files).
NASA Astrophysics Data System (ADS)
2015-11-01
The H 3+molecular ion has served as a long-standing benchmark for state-of-the-art ab initio calculations of molecular potentials and variational calculations of rovibrational energy levels. However, the accuracy of such calculations would not have been confirmed if not for the wealth of spectroscopic data that has been made available for this molecule. Recently, a new high-precision ion spectroscopy technique was demonstrated by Hodges et al., which led to the first highly accurate and precise (∼MHz) H 3+transition frequencies. As an extension of this work, we present ten additional R-branch transitions measured to similar precision as a next step toward the ultimate goal of producing a comprehensive high-precision survey of this molecule, from which rovibrational energy levels can be calculated.
NASA Astrophysics Data System (ADS)
Manbachi, Amir; Lee, Mike; Foster, F. Stuart; Ginsberg, Howard J.; Cobbold, Richard S. C.
2014-03-01
In 2012 approximately 800,000 spinal fusion surgeries were performed in the United States, requiring the insertion of screws into the pedicles. Their exact placement is critical and made complex due to limited visibility of the spine, continuous bleeding in the exposed regions, and variability in morphologies. The alarmingly high rate of screw misplacements (up to 20%) reported in the literature is of major concern since such misplacements can place the surrounding vital structures at risk. A potential guidance method for determining the best screw trajectory is by the use of real-time ultrasound imaging similar to that used for intravascular imaging. An endovascular transducer could be inserted into the pedicle to image the anatomy from within and identify bone boundaries. A major challenge of imaging within bone is high signal attenuation. The rapid increase of attenuation with frequency requires much lower frequencies (1-3 MHz) than those used in intravascular imaging. This study describes the custom design and fabrication of 2 MHz ultrasound probes (3.5 mm diameter/ 11 Fr) for pedicle screw guidance. Three transducer designs are explored to provide improved sensitivity and signal to noise ratio, compared to the previously tested transducer within the pedicle. Experimental measurements are compared with the results obtained using various simulation tools. The work reported in this paper represents the first stage in our ultimate goal of developing a 32- element phased array that is capable of generating a radial B-mode image.
NASA Astrophysics Data System (ADS)
Alvarez-Martinez, R.; Martinez-Mekler, G.; Cocho, G.
2011-01-01
The behavior of rank-ordered distributions of phenomena present in a variety of fields such as biology, sociology, linguistics, finance and geophysics has been a matter of intense research. Often power laws have been encountered; however, their validity tends to hold mainly for an intermediate range of rank values. In a recent publication (Martínez-Mekler et al., 2009 [7]), a generalization of the functional form of the beta distribution has been shown to give excellent fits for many systems of very diverse nature, valid for the whole range of rank values, regardless of whether or not a power law behavior has been previously suggested. Here we give some insight on the significance of the two free parameters which appear as exponents in the functional form, by looking into discrete probabilistic branching processes with conflicting dynamics. We analyze a variety of realizations of these so-called expansion-modification models first introduced by Wentian Li (1989) [10]. We focus our attention on an order-disorder transition we encounter as we vary the modification probability p. We characterize this transition by means of the fitting parameters. Our numerical studies show that one of the fitting exponents is related to the presence of long-range correlations exhibited by power spectrum scale invariance, while the other registers the effect of disordering elements leading to a breakdown of these properties. In the absence of long-range correlations, this parameter is sensitive to the occurrence of unlikely events. We also introduce an approximate calculation scheme that relates this dynamics to multinomial multiplicative processes. A better understanding through these models of the meaning of the generalized beta-fitting exponents may contribute to their potential for identifying and characterizing universality classes.
Madej, Alan A.; Alcock, A. John; Czajkowski, Andrzej; Bernard, John E.; Chepurov, Sergei
2006-10-15
Absolute frequency measurements, with uncertainties as low as 2 kHz (1x10{sup -11}), are presented for the {nu}{sub 1}+{nu}{sub 3} band of {sup 12}C{sub 2}H{sub 2} at 1.5 {mu}m (194-198 THz). The measurements were made using cavity-enhanced, diode-laser-based saturation spectroscopy. With one laser system stabilized to the P(16) line of {sup 13}C{sub 2}H{sub 2} and a system stabilized to the line in {sup 12}C{sub 2}H{sub 2} whose frequency was to be determined, a Cr:YAG laser-based frequency comb was employed to measure the frequency intervals. The systematic uncertainty is notably reduced relative to that of previous studies, and the region of measured lines has been extended. Improved molecular constants are obtained.
NASA Astrophysics Data System (ADS)
Bozkaya, Uǧur; Sherrill, C. David
2013-08-01
Orbital-optimized coupled-electron pair theory [or simply "optimized CEPA(0)," OCEPA(0), for short] and its analytic energy gradients are presented. For variational optimization of the molecular orbitals for the OCEPA(0) method, a Lagrangian-based approach is used along with an orbital direct inversion of the iterative subspace algorithm. The cost of the method is comparable to that of CCSD [O(N6) scaling] for energy computations. However, for analytic gradient computations the OCEPA(0) method is only half as expensive as CCSD since there is no need to solve the λ2-amplitude equation for OCEPA(0). The performance of the OCEPA(0) method is compared with that of the canonical MP2, CEPA(0), CCSD, and CCSD(T) methods, for equilibrium geometries, harmonic vibrational frequencies, and hydrogen transfer reactions between radicals. For bond lengths of both closed and open-shell molecules, the OCEPA(0) method improves upon CEPA(0) and CCSD by 25%-43% and 38%-53%, respectively, with Dunning's cc-pCVQZ basis set. Especially for the open-shell test set, the performance of OCEPA(0) is comparable with that of CCSD(T) (ΔR is 0.0003 Å on average). For harmonic vibrational frequencies of closed-shell molecules, the OCEPA(0) method again outperforms CEPA(0) and CCSD by 33%-79% and 53%-79%, respectively. For harmonic vibrational frequencies of open-shell molecules, the mean absolute error (MAE) of the OCEPA(0) method (39 cm-1) is fortuitously even better than that of CCSD(T) (50 cm-1), while the MAEs of CEPA(0) (184 cm-1) and CCSD (84 cm-1) are considerably higher. For complete basis set estimates of hydrogen transfer reaction energies, the OCEPA(0) method again exhibits a substantially better performance than CEPA(0), providing a mean absolute error of 0.7 kcal mol-1, which is more than 6 times lower than that of CEPA(0) (4.6 kcal mol-1), and comparing to MP2 (7.7 kcal mol-1) there is a more than 10-fold reduction in errors. Whereas the MAE for the CCSD method is only 0.1 kcal
Bozkaya, Uğur; Sherrill, C David
2013-08-01
Orbital-optimized coupled-electron pair theory [or simply "optimized CEPA(0)," OCEPA(0), for short] and its analytic energy gradients are presented. For variational optimization of the molecular orbitals for the OCEPA(0) method, a Lagrangian-based approach is used along with an orbital direct inversion of the iterative subspace algorithm. The cost of the method is comparable to that of CCSD [O(N(6)) scaling] for energy computations. However, for analytic gradient computations the OCEPA(0) method is only half as expensive as CCSD since there is no need to solve the λ2-amplitude equation for OCEPA(0). The performance of the OCEPA(0) method is compared with that of the canonical MP2, CEPA(0), CCSD, and CCSD(T) methods, for equilibrium geometries, harmonic vibrational frequencies, and hydrogen transfer reactions between radicals. For bond lengths of both closed and open-shell molecules, the OCEPA(0) method improves upon CEPA(0) and CCSD by 25%-43% and 38%-53%, respectively, with Dunning's cc-pCVQZ basis set. Especially for the open-shell test set, the performance of OCEPA(0) is comparable with that of CCSD(T) (ΔR is 0.0003 Å on average). For harmonic vibrational frequencies of closed-shell molecules, the OCEPA(0) method again outperforms CEPA(0) and CCSD by 33%-79% and 53%-79%, respectively. For harmonic vibrational frequencies of open-shell molecules, the mean absolute error (MAE) of the OCEPA(0) method (39 cm(-1)) is fortuitously even better than that of CCSD(T) (50 cm(-1)), while the MAEs of CEPA(0) (184 cm(-1)) and CCSD (84 cm(-1)) are considerably higher. For complete basis set estimates of hydrogen transfer reaction energies, the OCEPA(0) method again exhibits a substantially better performance than CEPA(0), providing a mean absolute error of 0.7 kcal mol(-1), which is more than 6 times lower than that of CEPA(0) (4.6 kcal mol(-1)), and comparing to MP2 (7.7 kcal mol(-1)) there is a more than 10-fold reduction in errors. Whereas the MAE for the CCSD method is
Systems for low frequency seismic and infrasound detection of geo-pressure transition zones
Shook, G. Michael; LeRoy, Samuel D.; Benzing, William M.
2007-10-16
Methods for determining the existence and characteristics of a gradational pressurized zone within a subterranean formation are disclosed. One embodiment involves employing an attenuation relationship between a seismic response signal and increasing wavelet wavelength, which relationship may be used to detect a gradational pressurized zone and/or determine characteristics thereof. In another embodiment, a method for analyzing data contained within a response signal for signal characteristics that may change in relation to the distance between an input signal source and the gradational pressurized zone is disclosed. In a further embodiment, the relationship between response signal wavelet frequency and comparative amplitude may be used to estimate an optimal wavelet wavelength or range of wavelengths used for data processing or input signal selection. Systems for seismic exploration and data analysis for practicing the above-mentioned method embodiments are also disclosed.
Shook, G. Michael; LeRoy, Samuel D.; Benzing, William M.
2006-07-18
Methods for determining the existence and characteristics of a gradational pressurized zone within a subterranean formation are disclosed. One embodiment involves employing an attenuation relationship between a seismic response signal and increasing wavelet wavelength, which relationship may be used to detect a gradational pressurized zone and/or determine characteristics thereof. In another embodiment, a method for analyzing data contained within a response signal for signal characteristics that may change in relation to the distance between an input signal source and the gradational pressurized zone is disclosed. In a further embodiment, the relationship between response signal wavelet frequency and comparative amplitude may be used to estimate an optimal wavelet wavelength or range of wavelengths used for data processing or input signal selection. Systems for seismic exploration and data analysis for practicing the above-mentioned method embodiments are also disclosed.
NASA Astrophysics Data System (ADS)
Wang, Xinxin; Shi, Deheng; Zhou, Dan; Zhu, Zunlue; Sun, Jinfeng
2015-11-01
The potential energy curves of 10 Λ-S states of BS+ yielded from the first four dissociation limits are calculated by the internally contracted multireference configuration interaction approach with the Davidson correction. The core-valence correlation and scalar relativistic corrections are included. Basis on the calculated potential energy curves, the spectroscopic parameters are evaluated. All the PECs are extrapolated to the complete basis set limit. The spin-orbit coupling are taken into account by the state interaction method with the Breit-Pauli Hamiltonian. Finally, the transition dipole moments, Franck-Condon Factors and radiative lifetimes of transitions from the 23Π0-, 23Π0+, 23Σ0- and 23Σ1- states to ground state 13Π2 are predicted for future experiment.
Zurawski, Jonathan; Flinn, Ashley; Sklover, Lindsay; Sloane, Jacob A
2016-08-01
Risk of relapse after natalizumab (NAT) cessation and switch to dimethyl fumarate (DMF) is unknown. The objective of this paper is to identify the risk and associated risk factors for relapse after switching from NAT to DMF in relapsing-remitting multiple sclerosis. Patients (n = 30) were treated with NAT for ≥12 months and then switched to DMF in a mean of 50 days. Patient age, annualized relapse rates (ARR), Expanded Disability Status Scale scores (EDSS), and lymphocyte counts were assessed. Overall, eight patients (27 %) had relapses after switching to DMF. Five patients (17 %) suffered severe relapses with multifocal clinical and radiological findings. New lesions by MRI (T2 hyperintense or enhancing) were observed in 35 % of patients. Relapses occurred at a mean of 3.5 months after NAT cessation. Patient age and elevated ARR prior to NAT use were significantly associated with risk of relapse after switch to DMF. Once on DMF for 4 months prior to relapse, lymphocyte count decreased more significantly in patients without relapses than those with relapses. Switching from NAT to DMF correlated with increased relapses. Young patient age, high ARR and stability of lymphocyte counts were risk factors for relapse after transition from NAT to DMF. PMID:27193310
Detection of low-frequency lambda-doublet transitions of the free 12CH and 13CH radicals
McCarthy, M. C.; Mohamed, S.; Brown, J. M.; Thaddeus, P.
2006-01-01
By Fourier transform microwave spectroscopy, lambda-doubling transitions of 12CH and 13CH in the lowest rotational levels of the X2∏1/2 ground state have been directly detected, which has not been done previously. For both radicals, hyperfine-split lines have been measured to an accuracy of better than 1 ppm between 3 and 15 GHz, an improvement of at least 2 orders of magnitude over previous laboratory data. The measured frequencies have been combined with all previous data for CH and 13CH in the v = 0 level of the X2∏ electronic state to determine improved hyperfine parameters. The production of CH from various gases also has been studied and, with methanol, the yield of CH relative to OH. Astronomical studies of CH in higher rotational levels and 13CH can now be undertaken on the basis of the present work. PMID:16894169
Zaka-ul-Islam, M.; Niemi, K.; Gans, T.; O'Connell, D.
2011-07-25
Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.
Schunk, F M; Rand, D; Rose-Petruck, C
2015-12-14
The evaporation and condensation of water on multi-walled carbon nanotube (MWCNT) surfaces was studied as a function of temperature and time using X-ray spatial frequency heterodyne imaging (SFHI). SFHI is an imaging modality that produces an absorption and scatter image in a single exposure, and has increased sensitivity to variations in electron density relative to more common place X-ray imaging techniques. Differing features exhibited in the temporal scatter intensity profiles recorded during evaporation and condensation revealed the existence of an absorption-desorption hysteresis. Effects on the aforementioned phenomena due to chemical functionalization of the carbon nanotube surfaces were also monitored. The increased interaction potential between the functionalized MWCNT walls and water molecules altered the evaporation event time scale and increased the temperature at which condensation could take place. Theoretical calculations were used to correlate the shape of the observed scatter profiles during condensation to changes in the MWCNT cross section geometry and configuration of the contained water volume. Changes in evaporation time scales with temperature coincided with the boiling point for confined water predicted by the Kelvin equation, indicating that a thermodynamic description of mesoscopic confined water is permissible in some instances. PMID:26549826
Zheng, Huiyong; Avis, Nancy E.; Greendale, Gail A.; Harlow, Siobán D.
2015-01-01
Objective: To determine whether reproductive hormones are related to sexual function during the menopausal transition. Design: The Study of Women's Health Across the Nation (SWAN) is a multiethnic cohort study of the menopausal transition located at seven US sites. At baseline, the 3302 community-based participants, aged 42–52, had an intact uterus and at least one ovary and were not using exogenous hormones. Participants self-identified as White, Black, Hispanic, Chinese, or Japanese. At baseline and at each of the 10 follow-up visits, sexual function was assessed by self-administered questionnaires, and blood was drawn to assay serum levels of T, estradiol, FSH, SHBG, and dehydroepiandrosterone sulfate. Main Outcome Measures: Self-reported frequency of masturbation, sexual desire, sexual arousal, orgasm, and pain during intercourse. Results: Masturbation, sexual desire, and arousal were positively associated with T. Masturbation, arousal, and orgasm were negatively associated with FSH. Associations were modest. Estradiol was not related to any measured sexual function domain. Pain with intercourse was not associated with any hormone. Conclusions: Reproductive hormones were associated with sexual function in midlife women. T was positively associated, supporting the role of androgens in female sexual function. FSH was negatively associated, supporting the role of menopausal status in female sexual function. The modest associations in this large study suggest that the relationships are subtle and may be of limited clinical significance. PMID:25412335
NASA Astrophysics Data System (ADS)
Chen, Yeong-Shu; Cheng, Ye-Dar; Yang, Tachung; Koai, Kwang-Lu
2010-03-01
In this paper, an identification technique in the dynamic analyses of rotor-bearing-foundation systems called the pseudo mode shape method (PMSM) was improved in order to enhance the accuracy of the identified dynamic characteristic matrices of its foundation models. Two procedures, namely, phase modification and numerical optimisation, were proposed in the algorithm of PMSM to effectively improve its accuracy. Generally, it is always necessary to build the whole foundation model in studying the dynamics of a rotor system through the finite element analysis method. This is either unfeasible or impractical when the foundation is too complicated. Instead, the PMSM uses the frequency response function (FRF) data of joint positions between the rotor and the foundation to establish the equivalent mass, damping, and stiffness matrices of the foundation without having to build the physical model. However, the accuracy of the obtained system's FRF is still unsatisfactory, especially at those higher modes. In order to demonstrate the effectiveness of the presented methods, a solid foundation was solved for its FRF by using both the original and modified PMSM, as well as the finite element (ANSYS) model for comparisons. The results showed that the accuracy of the obtained FRF was improved remarkably with the modified PMSM based on the results of the ANSYS. In addition, an induction motor resembling a rotor-bearing-foundation system, with its housing treated as the foundation, was taken as an example to verify the algorithm experimentally. The FRF curves at the bearing supports of the rotor (armature) were obtained through modal testing to estimate the above-mentioned equivalent matrices of the housing. The FRF of the housing, which was calculated from the equivalent matrices with the modified PMSM, showed satisfactory consistency with that from the modal testing.
NASA Astrophysics Data System (ADS)
Thorne, J. H.; Schwartz, M. W.; Holguin, A. J.; Moritz, M.; Batllori, E.; Folger, K.; Nydick, K.
2013-12-01
Ecological systems may respond in complex manners as climate change progresses. Among the responses, site-level climate conditions may cause a shift in vegetation due to the physiological tolerances of plant species, and the fire return interval may change. Natural resource managers challenged with maintaining ecosystem health need a way to forecast how these processes may affect every location, in order to determine appropriate management actions and prioritize locations for interventions. We integrated climate change-driven vegetation type transitions with projected change in fire frequency for 45,203 km2 of the southern Sierra Nevada, California, containing over 10 land management agencies as well as private lands. This Magnitude of Change (MOC) approach involves classing vegetation types in current time according to their climate envelopes, and identifying which sites will in the future have climates beyond what that vegetation currently occurs in. Independently, fire models are used to determine the change in fire frequency for each site. We examined 82 vegetation types with >50 grid cell occurrences. We found iconic resources such as the giant sequoia, lower slope oak woodlands, and high elevation conifer forests are projected as highly vulnerable by models that project a warmer drier future, but not as much by models that project a warmer future that is not drier than current conditions. Further, there were strongly divergent vulnerabilities of these forest types across land ownership (National Parks versus US Forest Service lands), and by GCM. For example, of 50 giant sequoia (Sequoiadendron giganteum) groves and complexes, all but 3 (on Sierra National Forest) were in the 2 highest levels of risk of climate and fire under the GFDL A2 projection, while 15 groves with low-to-moderate risk were found on both the National Parks and National Forests 18 in the 2 under PCM A2. Landscape projections of potential MOC suggest that the region is likely to experience
Mack, Markus; Karlewski, Florian; Hattermann, Helge; Hoeckh, Simone; Jessen, Florian; Cano, Daniel; Fortagh, Jozsef
2011-05-15
We report the measurement of absolute excitation frequencies of {sup 87}Rb to nS and nD Rydberg states. The Rydberg transition frequencies are obtained by observing electromagnetically induced transparency on a rubidium vapor cell. The accuracy of the measurement of each state is < or approx. 1 MHz, which is achieved by frequency stabilizing the two diode lasers employed for the spectroscopy to a frequency comb and a frequency comb calibrated wavelength meter, respectively. Based on the spectroscopic data we determine the quantum defects of {sup 87}Rb, and compare it with previous measurements on {sup 85}Rb. We determine the ionization frequency from the 5S{sub 1/2}(F=1) ground state of {sup 87}Rb to 1010.029 164 6(3)THz, providing the binding energy of the ground state with an accuracy improved by two orders of magnitude.
NASA Astrophysics Data System (ADS)
Domenech, Jose Luis; Cueto, Maite; Herrero, Victor Jose; Tanarro, Isabel; Cernicharo, Jose; Drouin, Brian
2015-06-01
HCl^+ is a key intermediate in the interstellar chemistry of chlorine. It has been recently identified in space from Herschel's spectra and it has also been detected in the laboratory through its optical emission, infrared and mm-wave spectra. Now that Hershchel is decomissioned, further astrophysical studies on this radical ion will likely rely on ground-based observations in the mid-infrared. We have used a difference frequency laser spectrometer coupled to a hollow cathode discharge to measure the absorption spectrum of H35Cl^+ and H37Cl^+ in the v=0-1 band of the ^2Π state with Dopppler limited resolution. The accuracy of the individual measurements (˜ 10 MHz (3σ)) relies on a solid state wavemeter referenced to an iodine-stabilized Ar^+ laser. The new data are being fit using the CALPGM software from JPL, and the current status will be presented. M. De Luca et al., Astrophys. J. Lett. 751, L37 (2012) W. D. Sheasley and C. W. Mathews, J. Mol. Spectrosc. 47, 420 (1973) P. B. Davies, P. A. Hamilton, B. A. Johnson, Mol. Phys. 57, 217 (1986) H. Gupta, B. J. Drouin, and J. C. Pearson, Astrophys. J. Lett. 751, L37 (2012)
NASA Astrophysics Data System (ADS)
Rúa, Armando; Fernández, Félix E.; Hines, Melissa A.; Sepúlveda, Nelson
2010-03-01
Vanadium dioxide (VO2) thin films were grown on silicon microcantilevers and companion test substrates by pulsed laser deposition followed by in situ annealing in an oxidizing atmosphere, with annealing times used to control crystallite sizes. Annealing times of 18 min produced VO2 films with average crystallite sizes of ˜10 nm or less, while those annealed for 35 min had crystallites of average size ˜90 nm, comparable to sample thickness. X-ray diffraction and x-ray photoelectron spectroscopy studies of the samples showed that films with crystallite sizes ˜40 nm or greater consisted of substoichiometric VO2 in its monoclinic phase, with preferential orientation with (011) planes parallel to the sample surface, while finer structured samples had a substantially similar composition, but showed no clear evidence of preferential orientation and were probably partially amorphous. Forced vibration experiments were performed with the cantilevers as they were thermally cycled through the VO2 insulator-to-metal transition (IMT). Very large reversible changes in the resonant frequencies of up to 5% (3.6 kHz) as well as hysteretic behavior were observed, which depend strongly on film crystallite size. The average value of Young's modulus for VO2 films with crystallite sizes of ˜90 nm was estimated from the mechanical resonance data at room temperature to be ˜120 GPa, but the large tensile stresses which develop between film and substrate through the IMT impede a similar determination for the VO2 tetragonal phase, since the commonly used relationships for cantilever frequencies derived from elasticity theory are not applicable for strongly curved composite beams. The results presented show that VO2 thin films can be useful in novel microscale and nanoscale electromechanical resonators in which effective stiffness can be tuned thermally or optically. This response can provide additional functionality to VO2—based devices which take advantage of other property changes
Watzky, M.A.; Endicott, J.F.; Song, X.
1996-06-05
Patterns in the cyanide stretching frequencies have been examined in several series of monometal- and CN{sup {minus}} bridged transition metal complexes. Metal-to-cyanide back-bonding can be identified as a major factor contributing to red shifts of v{sub CN} in monometal complexes. This effect is complicated in cyanide-bridged complexes in two ways: (a) when both metals can back-bond to cyanide, the net interaction is repulsive and results in a blue shift of v{sub CN}: and (b) when a donor and acceptor are bridged, V{sub CN} undergoes a substantial red shift (sometimes more than 60 cm{sup {minus}1} lower in energy than the parent monometal complex). These effects can be described by simple perturbational models for the electronic interactions. Monometal cyanide complexes and CN{sup {minus}}-bridged backbonding metals can be treated in terms of their perturbations of the CN{sup {minus}} {pi} and {pi}* orbitals by using a simple, Hueckel-like, three-center perturbational treatment of electronic interactions. However, bridged donor-acceptor pairs are best described by a vibronic model in which it is assumed that the extent of electronic delocalization is in equilibrium with variations of some nuclear coordinates. Consistent with this approach, it is found that (a) the oscillator strength of the donor-acceptor charge transfer (DACT) absorption is roughly proportional to the red shift of v{sub CN} and (b) there are strong symmetry constraints on the coupling.
de Beauvoir, B.; Nez, F.; Julien, L.; Cagnac, B.; Biraben, F.; Touahri, D.; Hilico, L.; Acef, O.; Clairon, A.; Zondy, J.
1997-01-01
We have performed a pure optical frequency measurement of the 2S-8S/D two-photon transitions in atomic hydrogen and deuterium. These frequencies are directly compared to a new frequency standard, a diode laser stabilized to a two-photon transition at 778nm in rubidium. We deduce a new value for the Rydberg constant, R{sub {infinity}}=109737.3156859(10)cm{sup -1} with an uncertainty of 9{times}10{sup -12}. From the isotope shift, we derive a precise value of the 2S Lamb shift in deuterium [L{sub 2S-2P}=1059.230(9)MHz] and the difference of the quadratic charge radii of deuteron and proton. {copyright} {ital 1997} {ital The American Physical Society}
NASA Technical Reports Server (NTRS)
Brown, John M.; Evenson, Kenneth M.; Zink, Lyndon R.
1994-01-01
The J = 0 left arrow 1 fine-structure transition in atomic sulfur (S I) in its ground (3)P state has been detected in the laboratory by far-infrared laser magnetic resonance. The fine-structure interval has been measured accurately as 5,322,492.9 +/- 2.8 MHz which corresponds to a wavelength of 56.325572 +/- 0.000030 micrometers.
NASA Astrophysics Data System (ADS)
Bogdanova, Kh. G.; Bulatov, A. R.; Golenishchev-Kutuzov, V. A.; Mamin, R. F.; Potapov, A. A.
2007-03-01
The specific features of a phase transition from a disordered orbital state to an ordered orbital state in an La0.875Sr0.125MnO3 single crystal are investigated using acoustic methods at a frequency f = 500 MHz. The phase transition is accompanied by a distortion of MnO6 octahedra due to the cooperative Jahn-Teller effect and is a first-order phase transition, as judged from the sharp change observed in the damping of acoustic pulses, the acoustic wave velocity, and the temperature hysteresis. It is revealed that the parameters of the acoustic waves change significantly throughout the temperature range of existence of the cooperatively distorted structure. In an external magnetic field, the structural phase transition is shifted toward lower temperatures.
NASA Astrophysics Data System (ADS)
Uzpen, Brian Robert
spectroscopy is obtained for a large subset of the mid-IR excess sources for the purpose of stellar and circumstellar characterization. Finally, a statistical analysis of a complete stellar sample is investigated to determine that the frequency of dusty mid-IR debris disks is 0.3±0.3% and transition disks is 1.2±0.6%. The frequencies of these mid-IR excess sources are used to constrain disk lifetimes to 5±2 Myr.
NASA Astrophysics Data System (ADS)
Chen, Y.; Gu, Y. J.; Hung, S. H.
2014-12-01
Based on finite-frequency theory and cross-correlation teleseismic relative traveltime data from the USArray, Canadian National Seismograph Network (CNSN) and Canadian Rockies and Alberta Network (CRANE), we present a new tomographic model of P-wave velocity perturbations for the lithosphere and upper mantle beneath the Cordillera-cration transition region in southwestern Canada. The inversion procedure properly accounts for the finite-volume sensitivities of measured travel time residuals, and the resulting model shows a greater resolution of upper mantle velocity heterogeneity beneath the study area than earlier approaches based on the classical ray-theoretical approach. Our model reveals a lateral change of P velocities from -0.5% to 0.5% down to ~200-km depth in a 50-km wide zone between the Alberta Basin and the foothills of the Rocky Mountains, which suggests a sharp structural gradient along the Cordillera deformation front. The stable cratonic lithosphere, delineated by positive P-velocity perturbations of 0.5% and greater, extends down to a maximum depth of ~180 km beneath the Archean Loverna Block (LB). In comparison, the mantle beneath the controversial Medicine Hat Block (MHB) exhibits significantly higher velocities in the uppermost mantle and a shallower (130-150 km depth) root, generally consistent with the average depth of the lithosphere-asthenosphere boundary beneath Southwest Western Canada Sedimentary Basin (WCSB). The complex shape of the lithospheric velocities under the MHB may be evidence of extensive erosion or a partial detachment of the Precambrian lithospheric root. Furthermore, distinct high velocity anomalies in LB and MHB, which are separated by 'normal' mantle block beneath the Vulcan structure (VS), suggest different Archean assembly and collision histories between these two tectonic blocks.
NASA Astrophysics Data System (ADS)
Koroleva, L. A.; Tyulin, V. I.; Matveev, V. K.; Pentin, Yu. A.
2013-05-01
B3LYP, MP2, CCSD(T), and MP4/MP2 in the 6-311G( d, p), 6-311++G( d, p), cc-pVTZ, aug-cc-pVTZ bases used to calculate the transition frequencies of torsional vibration of trans- and cis-isomers of acrolein in the ground electronic state ( S 0) are analyzed. It is found that for trans-isomers, all methods of calculation except for B3LYP in the cc-pVTZ basis yield good agreement between the calculated and experimental values. It is noted that for the cis-isomer of acrolein, no method of calculation confirms the experimental value of the frequency of torsional vibration (138 cm-1). It is shown that the calculated and experimental values for obertones at 273.0 cm-1 and other transitions of torsional vibration are different for this isomer in particular. However, it is established that in some calculation methods (B3LYP, MP2), the frequency of the torsional vibration of the cis-isomer coincides with another experimental value of this frequency (166.5 cm-1). It is concluded that in analyzing the vibrational structure of the UV spectrum, the calculated and experimental values of its obertone (331.3 cm-1) coincide, along with its frequency. It is also noted that the frequency of torsional vibration for the cis-isomer (166.5 cm-1) can also be found in other experimental works if we change the allocation of torsional transition 18{1/1}.
NASA Astrophysics Data System (ADS)
Mondelain, D.; Kassi, S.; Sala, T.; Romanini, D.; Gatti, D.; Campargue, A.
2016-08-01
The line position of the very weak S(2) transition of deuterium in the 2-0 band has been measured with a Comb-Assisted Cavity Ring Down spectrometer. The high sensitivity spectra were recorded at 5 and 10 mbar with a Noise Equivalent Absorption, αmin, of 8 × 10-11 cm-1. The line positions at 5 and 10 mbar were measured with sub-MHz accuracy (460 and 260 kHz, respectively). After correction of the line pressure-shift, the frequency at zero pressure of the S(2) transition of the first overtone band was determined to be 187 104 299.51 ± 0.50 MHz. This value agrees within 1.7 MHz with the frequency obtained from the best available ab initio calculations and corresponds to only 15% of the claimed theoretical uncertainty.
Radio frequency-power and the ring-mode to red-mode transition in an inductively coupled plasma
NASA Astrophysics Data System (ADS)
Coffer, J. G.; Camparo, J. C.
2012-04-01
The optical output of an alkali-metal inductively coupled plasma (alkali-ICP) plays an important role in both atomic magnetometers and atomic clocks, producing these devices' atomic signals through optical pumping. Unfortunately, though the alkali-ICP's optical pumping efficiency grows exponentially with temperature, at relatively high temperatures (˜140 °C) the discharge transitions from "ring mode" to "red mode," which is a spectral change in the plasma's output that corresponds broadly to a transition from "good emission" for optical pumping to "poor emission." Recently, evidence has accumulated pointing to radiation trapping as the mechanism driving the ring-mode to red-mode transition, suggesting that the phenomenon is primarily linked to the alkali vapor's temperature. However, observations of the transition made in the 1960 s, demonstrating that the ICP temperature associated with the transition depended on rf-power, would appear to cast doubt on this mechanism. Here, we carefully investigate the influence of rf-power on the ring-mode to red-mode transition, finding that rf-power only affects the transition through discharge heating. Thus, the present work shows that the primary effect of rf-power on the ring-mode to red-mode transition can be understood in terms of the radiation trapping mechanism.
Radio frequency-power and the ring-mode to red-mode transition in an inductively coupled plasma
Coffer, J. G.; Camparo, J. C.
2012-04-15
The optical output of an alkali-metal inductively coupled plasma (alkali-ICP) plays an important role in both atomic magnetometers and atomic clocks, producing these devices' atomic signals through optical pumping. Unfortunately, though the alkali-ICP's optical pumping efficiency grows exponentially with temperature, at relatively high temperatures ({approx}140 deg. C) the discharge transitions from ''ring mode'' to ''red mode'', which is a spectral change in the plasma's output that corresponds broadly to a transition from ''good emission'' for optical pumping to ''poor emission.'' Recently, evidence has accumulated pointing to radiation trapping as the mechanism driving the ring-mode to red-mode transition, suggesting that the phenomenon is primarily linked to the alkali vapor's temperature. However, observations of the transition made in the 1960 s, demonstrating that the ICP temperature associated with the transition depended on rf-power, would appear to cast doubt on this mechanism. Here, we carefully investigate the influence of rf-power on the ring-mode to red-mode transition, finding that rf-power only affects the transition through discharge heating. Thus, the present work shows that the primary effect of rf-power on the ring-mode to red-mode transition can be understood in terms of the radiation trapping mechanism.
Huang, Xinchuan; Valeev, Edward F; Lee, Timothy J
2010-12-28
One-particle basis set extrapolation is compared with one of the new R12 methods for computing highly accurate quartic force fields (QFFs) and spectroscopic data, including molecular structures, rotational constants, and vibrational frequencies for the H(2)O, N(2)H(+), NO(2)(+), and C(2)H(2) molecules. In general, agreement between the spectroscopic data computed from the best R12 and basis set extrapolation methods is very good with the exception of a few parameters for N(2)H(+) where it is concluded that basis set extrapolation is still preferred. The differences for H(2)O and NO(2)(+) are small and it is concluded that the QFFs from both approaches are more or less equivalent in accuracy. For C(2)H(2), however, a known one-particle basis set deficiency for C-C multiple bonds significantly degrades the quality of results obtained from basis set extrapolation and in this case the R12 approach is clearly preferred over one-particle basis set extrapolation. The R12 approach used in the present study was modified in order to obtain high precision electronic energies, which are needed when computing a QFF. We also investigated including core-correlation explicitly in the R12 calculations, but conclude that current approaches are lacking. Hence core-correlation is computed as a correction using conventional methods. Considering the results for all four molecules, it is concluded that R12 methods will soon replace basis set extrapolation approaches for high accuracy electronic structure applications such as computing QFFs and spectroscopic data for comparison to high-resolution laboratory or astronomical observations, provided one uses a robust R12 method as we have done here. The specific R12 method used in the present study, CCSD(T)(R12), incorporated a reformulation of one intermediate matrix in order to attain machine precision in the electronic energies. Final QFFs for N(2)H(+) and NO(2)(+) were computed, including basis set extrapolation, core-correlation, scalar
NASA Astrophysics Data System (ADS)
Caretta, Antonio; Miranti, Rany; Havenith, Remco W. A.; Rampi, Elia; Donker, Michiel C.; Blake, Graeme R.; Montagnese, Matteo; Polyakov, Alexey O.; Broer, Ria; Palstra, Thomas T. M.; van Loosdrecht, Paul H. M.
2014-01-01
The ferroelectric phase transition at TC=340K in (C6H5CH2CH2NH3)2CuCl4 is studied by means of temperature-dependent low-frequency Raman scattering, focusing on the coupling of a low-energy librational mode to the order parameter of the transition. Analysis of the symmetry and characteristics of this mode links the dipolar order to the tilt angle of the organic cations. The thermal evolution of the Raman spectrum demonstrates the displacive component of the phase transition in combination with order-disorder phenomena and the importance of the organic-inorganic interplay to the physical properties of the compound. The ferroelectric properties investigated here can be generalized to the family of layered organic-inorganic hybrids.
NASA Astrophysics Data System (ADS)
Pamfiloff, Eugene
2006-10-01
A process of high frequency stimulation of nucleons can be utilized for the accelerated fission, decay or controlled transition of unstable isotopes. For example ^238U could be persuaded to transition promptly into ^206Pb, where portions of the total mass difference of 29873.802 MeV per nucleus becomes available energy. The proposals of this paper describe an effective system for nuclei stimulation configured to accelerate such a series of 14 transitions over several milliseconds, instead of 4.47 x 10^9 years. Positive ions or ionized capsules of fuel suspended by magnetic fields and subjected to the system of correlated frequency modulation of multiple beam lines, tailored to the specific target, will emit sufficient energy to stimulate subsequent targets. The system can be applied to all radioisotopes, including ^232Th, nuclear waste product isotopes such as ^239Pu, and a variety of other suitable unstable or stable nuclei. Through the proposed confinement system and application of high frequency stimulation in the 10^22 to 10^24 Hz regime, the change in rest mass can be applied to both the fragmentation of subsequent, periodically injected targets, and the production of heat, making a continuous supply of energy possible. The system allows the particle fragmentation process to be brought into the laboratory and provides potential solutions to the safe disposal of fissile material.
NASA Astrophysics Data System (ADS)
Pamfiloff, Eugene
2006-10-01
A process of high frequency stimulation of nucleons can be utilized for the accelerated fission, decay or controlled transition of unstable isotopes. ^238U could be persuaded to transition promptly into the stable ^206Pb isotope, where a portion of the total mass difference of 29873.802 MeV per nucleus becomes available energy. The proposals of this paper describe an effective system for nuclei stimulation configured to accelerate such a series of 14 transitions over several milliseconds, instead of 4.47 x 10^9 years. Positive ions or ionized capsules of fuel suspended by magnetic fields and subjected to the system of correlated frequency modulation of multiple beam lines, tailored to the specific target, will emit sufficient energy to stimulate subsequent targets. The system can be applied to all radioisotopes, nuclear waste product isotopes such as ^239Pu, and a variety of other suitable unstable or stable nuclei. Through the proposed confinement system and application of high frequency stimulation in the 10^22 to 10^24 Hz regime, the change in mass can be applied to both the fragmentation of subsequent, periodically injected targets, and the production of heat, making a continuous supply of energy possible. The system allows the particle fragmentation process to be brought into the lab and provides potential solutions to the safe disposal of fissile material.
NASA Astrophysics Data System (ADS)
Pamfiloff, Eugene
2006-11-01
A process of high frequency stimulation of nucleons can be utilized for the accelerated fission, decay or controlled transition of unstable isotopes. ^238U could be persuaded to transition promptly into the stable ^206Pb isotope, where a portion of the total mass difference of 29873.802 MeV per nucleus becomes available energy. The proposals of this paper describe an effective system for nuclei stimulation configured to accelerate such a series of 14 transitions over several milliseconds, instead of 4.47 x 10^9 years. Positive ions or ionized capsules of fuel suspended by magnetic fields and subjected to the system of correlated frequency modulation of multiple beam lines, tailored to the specific target, will emit sufficient energy to stimulate subsequent targets. The system can be applied to all radioisotopes, nuclear waste product isotopes such as ^239Pu, and a variety of other suitable unstable or stable nuclei. Through the proposed confinement system and application of high frequency stimulation in the 10^22 to 10^24 Hz regime, the change in mass can be applied to both the fragmentation of subsequent, periodically injected targets, and the production of heat, making a continuous supply of energy possible. The system allows the particle fragmentation process to be brought into the lab and provides potential solutions to the safe disposal of fissile material.
Accurate quantum chemical calculations
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.
1989-01-01
An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.
NASA Astrophysics Data System (ADS)
Vergent'ev, T. Yu.; Koroleva, E. Yu.; Kurdyukov, D. A.; Naberezhnov, A. A.; Filimonov, A. V.
2013-01-01
The behavior of the specific conductivity of composites based on silver iodide embedded in porous glasses with an average pore diameter of 7 ± 1 nm and in artificial opals with a pore diameter of 40-100 nm has been investigated in the temperature range from 300 to 500 K. It has been shown that a decrease in the characteristic pore size does not lead to a change in the order of the phase transition and that the temperature of the transition to the superionic state of silver iodide in a porous glass and in an opal upon heating is close to the phase transition temperature T c in the bulk material (˜420 K). Upon cooling, the phase transition temperature T c significantly decreases, and the phase transition becomes diffuse. With a decrease in the pore size, the region of the temperature hysteresis of the phase transition increases. The dc conductivities of the composites have been estimated from the impedance diagrams. The temperature dependence of the dc conductivity of both composites has a thermally activated nature, and the slope of the curve σ(1/ T) changes near the phase transition, which indicates a change in the activation energy. The activation energies in the low-temperature and high-temperature phases have been estimated at ˜450-470 and ˜100 meV, respectively. The equivalent electrical circuit describing the charge transfer processes in the studied samples has been proposed.
Ding, Z. F.; Yuan, G. Y.; Gao, W.; Sun, J. C.
2008-06-15
In inductively coupled plasma sources, discharge transitions from electrostatic mode (E mode) to electromagnetic mode (H mode) and from H mode to E mode occur. In previous studies, only a few works paid attention to the effects of the impedance matching network. Cunge et al. [Plasma Sources Sci. Technol. 8, 576 (1999)] investigated the E-H and H-E mode transitions under two different impedance matching situations, but no physical mechanism or interpretation was presented. This issue is remained to be systematically and quantitatively investigated, and the underlying mechanism to be unveiled. In this paper, the effects of the impedance matching network were experimentally studied in electropositive argon gas by varying the series capacitance in an inversely L-shaped matching network. The positive and negative feedback regions are established according to the effect of varying the series capacitance on the output power of the rf power supply. It was found that under the same experimental parameters, the discharge mode transitions are apt to be discontinuous and continuous in the positive and negative feedback regions, respectively. In addition, the critical coil rf current (or applied power) at the mode transition, the hysteretic loop width, and the difference in applied power during the discharge mode transition vary with the series capacitance. The critical coil rf current at the E-H mode transition is not always higher than that at the H-E mode transition.
Hoyt, C.W.; Barber, Z.W.; Oates, C.W.; Fortier, T.M.; Diddams, S.A.; Hollberg, L.
2005-08-19
We report the direct excitation of the highly forbidden (6s{sup 2}){sup 1}S{sub 0}{r_reversible}(6s6p){sup 3}P{sub 0} optical transition in two odd isotopes of neutral ytterbium. As the excitation laser frequency is scanned, absorption is detected by monitoring the depletion from an atomic cloud at {approx}70 {mu}K in a magneto-optical trap. The measured frequency in {sup 171}Yb (F=1/2) is 518 295 836 591.6{+-}4.4 kHz. The measured frequency in {sup 173}Yb (F=5/2) is 518 294 576 847.6{+-}4.4 kHz. Measurements are made with a femtosecond-laser frequency comb calibrated by the National Institute of Standards and Technology cesium fountain clock and represent nearly a 10{sup 6}-fold reduction in uncertainty. The natural linewidth of these J=0 to J=0 transitions is calculated to be {approx}10 mHz, making them well suited to support a new generation of optical atomic clocks based on confinement in an optical lattice.
Zheng, Rui; Zheng, Limin; Lu, Yunpeng; Yang, Minghui
2015-10-21
Theoretical studies of the potential energy surface (PES) and bound states are performed for the N2-N2O van der Waals (vdW) complex. A four-dimensional intermolecular PES is constructed at the level of single and double excitation coupled-cluster method with a non-iterative perturbation treatment of triple excitations [CCSD(T)] with aug-cc-pVTZ basis set supplemented with bond functions. Two equivalent T-shaped global minima are located, in which the O atom of N2O monomer is near the N2 monomer. The intermolecular fundamental vibrational states are assigned by inspecting the orientation of the nodal surface of the wavefunctions. The calculated frequency for intermolecular disrotation mode is 23.086 cm(-1), which is in good agreement with the available experimental data of 22.334 cm(-1). A negligible tunneling splitting with the value of 4.2 MHz is determined for the ground vibrational state and the tunneling splitting increases as the increment of the vibrational frequencies. Rotational levels and transition frequencies are calculated for both isotopomers (14)N2-N2O and (15)N2-N2O. The accuracy of the PES is validated by the good agreement between theoretical and experimental results for the transition frequencies and spectroscopic parameters.
Zheng, Rui; Zheng, Limin; Yang, Minghui E-mail: yangmh@wipm.ac.cn; Lu, Yunpeng E-mail: yangmh@wipm.ac.cn
2015-10-21
Theoretical studies of the potential energy surface (PES) and bound states are performed for the N{sub 2}–N{sub 2}O van der Waals (vdW) complex. A four-dimensional intermolecular PES is constructed at the level of single and double excitation coupled-cluster method with a non-iterative perturbation treatment of triple excitations [CCSD(T)] with aug-cc-pVTZ basis set supplemented with bond functions. Two equivalent T-shaped global minima are located, in which the O atom of N{sub 2}O monomer is near the N{sub 2} monomer. The intermolecular fundamental vibrational states are assigned by inspecting the orientation of the nodal surface of the wavefunctions. The calculated frequency for intermolecular disrotation mode is 23.086 cm{sup −1}, which is in good agreement with the available experimental data of 22.334 cm{sup −1}. A negligible tunneling splitting with the value of 4.2 MHz is determined for the ground vibrational state and the tunneling splitting increases as the increment of the vibrational frequencies. Rotational levels and transition frequencies are calculated for both isotopomers {sup 14}N{sub 2}–N{sub 2}O and {sup 15}N{sub 2}–N{sub 2}O. The accuracy of the PES is validated by the good agreement between theoretical and experimental results for the transition frequencies and spectroscopic parameters.
Schmidt, S.C.; Schiferl, D.; Zinn, A.S.; Ragan, D.D.; Moore, D.S.
1989-01-01
Coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman spectroscopy have been used to obtain vibrational spectra of shock-compressed and static high-pressure fluid nitrogen, respectively. Vibrational frequencies were obtained from the CARS data using a semiclassical model for these spectra. Spontaneous Raman vibrational frequencies were determined by fitting data using a Lorentz shape line. A functional form was found for the dependence of the vibrational frequency on pressure and temperature to 40 GPa and 5000 K, respectively. The result is compared to a recent theoretical model. 6 refs., 2 figs., 1 tab.
Lisovskiy, V.; Booth, J.-P.; Landry, K.; Douai, D.; Cassagne, V.; Yegorenkov, V.
2006-10-15
This paper reports current-voltage characteristics and pressure-voltage transition curves from the weak-current {alpha}-mode to the strong-current {gamma}-mode for rf capacitive discharges in N{sub 2}O at frequencies of 2 MHz, 13.56 MHz, and 27.12 MHz. At 2 MHz the rf discharge is mostly resistive whereas at 13.56 MHz and 27.12 MHz it is mostly capacitive. The weak-current {alpha}-mode was found to exist only above a certain minimum gas pressure for all frequencies studied. N. Yatsenko [Sov. Phys. Tech. Phys. 26, 678 (1981)] previously proposed that the {alpha}-{gamma} transition corresponds to breakdown of the sheaths. However, we show that this is the case only for sufficiently high gas pressures. At lower pressure there is a smooth transition from the weak-current {alpha}-mode to a strong-current {gamma}-mode, in which the sheaths produce fast electrons but the sheath has not undergone breakdown.
Liu, X. Y.; Hu, J. T.; Liu, J. H.; Xiong, Z. L.; Liu, D. W.; Lu, X. P.; Shi, J. J.
2012-07-23
The discharge mode transition from uniform plasma across the gas gap to the {alpha} mode happens at the rising phase of the pulsed radio frequency capacitively coupled plasma (PRF CCP). This transition is attributed to the fast increasing stochastic heating at the edge of sheath. In the second stage with the stable current and voltage amplitude, the consistency between experimental and numerical spatial-temporal 777 nm emission profile suggests that He* and He{sub 2}* dominate the production of O({sup 5}p{sub 1}) through dissociation and excitation of O{sub 2}. Finally, the sterilization efficiency of PRF CCP is found to be higher than that of plasma jet.
NASA Technical Reports Server (NTRS)
Titarchuk, Lev; Fiorito, Ralph
2004-01-01
Recent studies have shown that strong correlations are observed between the low frequencies (1-10 Hz) of quasiperiodic oscillations (QPOs) and the spectral power law index of several Black Hole (BH) candidate sources, in low hard states, steep power-law (soft) states and in transition between these states. The observations indicate that the X-ray spectrum of such state (phases) show the presence of a power-law component and are sometimes related to simultaneous radio emission indicated the probable presence of a jet. Strong QPOs (less than 20% rms) are present in the power density spectrum in the spectral range where the power-law component is dominant ( i.e. 60-90% ). This evidence contradicts the dominant long standing interpretation of QPOs as a signature of the thermal accretion disk. We present the data from the literature and our own data to illustrate the dominance of power-law index-QPO frequency correlations. We provide a model, that identifies and explains the origin of the QPOs and how they are imprinted on the properties of power-law flux component. We argue the existence of a bounded compact coronal region which is a natural consequence of the adjustment of Keplerian disk flow to the innermost sub-Keplerian boundary conditions near the central object and that ultimately leads to the formation of a transition layer (TL) between the adjustment radius and the innermost boundary. The model predicts two phases or states dictated by the photon upscattering produced in the TL: (1) hard state, in which the TL is optically thin and very hot (kT approx. greater than 50 keV) producing photon upscattering via thermal Componization; the photon spectrum index Gamma appprox.1.5 for this state is dictated by gravitational energy release and Compton cooling in an optically thin shock near the adjustment radius; (2) a soft state which is optically thick and relatively cold (approx. less than 5 keV); the index for this state, Gamma approx. 2.8 is determined by soft
NASA Astrophysics Data System (ADS)
Titarchuk, L.; Fiorito, R.
2004-08-01
Recent studies have shown that strong correlations are observed between the low frequencies (1-10 Hz) of quasiperiodic oscillations (QPOs) and the spectral power law index of several Black Hole (BH) candidate sources, in low hard state, steep power-law (soft) state and in transition between these states. Strong QPOs (> 20% rms) are present in the power density spectrum in the spectral range where the power-law component is dominant ( i.e. 60-90 %). This evidence contradicts the dominant long standing interpretation of QPOs as a signature of the thermal accretion disk. We present the data from the literature and our own data to illustrate the dominance of power-law index-QPO frequency correlations. We provide a model, that identifies and explains the origin of the QPOs and how they are imprinted on the properties of power-law flux component. We argue the existence of a bounded compact coronal region which is a natural consequence of the adjustment of Keplerian disk flow to the innermost sub-Keplerian boundary conditions near the central object and that ultimately leads to the formation of a transition layer (TL) between the adjustment radius and the innermost boundary. The model predicts two phases or states dictated by the photon upscattering produced in the TL: (1) hard state, in which the TL is optically thin and very hot (kT ˜ 50 keV) producing photon upscattering via thermal Componization; the photon spectrum index Γ ˜ 1.7 for this state is dictated by gravitational energy release and Compton cooling in an optically thin shock near the adjustment radius; (2) a soft state which is optically thick and relatively cold ( kT ˜ 5 keV); the index for this state, Γ ˜ 2.8 is determined by soft-photon upscattering and photon trapping in converging flow into BH. In the TL model for corona the QPO frequency ν high is related to the gravitational (close to Keplerian) frequency ν {K} at the outer (adjustment) radius and ν low is related to the TL's normal mode
NASA Astrophysics Data System (ADS)
Titarchuk, Lev; Fiorito, Ralph
2004-09-01
Recent studies have shown that strong correlations are observed between the low frequencies (1-10 Hz) of quasi-periodic oscillations (QPOs) and the spectral power law index of several black hole (BH) candidate sources, in low (hard) states, steep power law (soft) states, and transitions between these states. The observations indicate that the X-ray spectra of such state (phases) show the presence of a power-law component and are sometimes related to simultaneous radio emission, indicating the probable presence of a jet. Strong QPOs (>20% rms) are present in the power density spectrum in the spectral range where the power-law component is dominant (i.e., 60%-90%). This evidence contradicts the dominant, long-standing interpretation of QPOs as a signature of the thermal accretion disk. We present the data from the literature and our own data to illustrate the dominance of power-law index-QPO frequency correlations. We provide a model that identifies and explains the origin of the QPOs and how they are imprinted on the properties of the power-law flux component. We argue for the existence of a bounded compact coronal region that is a natural consequence of the adjustment of the Keplerian disk flow to the innermost sub-Keplerian boundary conditions near the central object and that ultimately leads to the formation of a transition layer (TL) between the adjustment radius and the innermost boundary. The model predicts two phases or states dictated by the photon upscattering produced in the TL: (1) a hard state, in which the TL is optically thin and very hot (kT>~50 keV), producing photon upscattering via thermal Comptonization (the photon spectrum index Γ~1.7 for this state is dictated by gravitational energy release and Compton cooling in an optically thin shock near the adjustment radius), and (2) a soft state that is optically thick and relatively cold (kT<~5 keV; the index for this state, Γ~2.8, is determined by soft-photon upscattering and photon trapping in a
NASA Astrophysics Data System (ADS)
Titarchuck, Lev; Fiorito, Ralph
2006-02-01
Recent studies have shown that strong correlations are observed between the low frequencies (1-10 Hz) of quasiperiodic oscillations (QPOs) and the spectral power law index of several Black Hole (BH) candidate sources, in low hard state, steep power-law (soft) state and in transition between these states. The observations indicate that the X-ray spectrum of such state (phases) show the presence of a power-law component and are sometimes related to simultaneous radio emission indicated the probable presence of a jet. Strong QPOs (> 20% rms) are present in the power density spectrum in the spectral range where the power-law component is dominant (i.e. 60-90%). This evidence contradicts the dominant long standing interpretation of QPOs as a signature of the thermal accretion disk. We present the data from the literature and our own data to illustrate the dominance of power-law index-QPO frequency correlations. We provide a model, that identifies and explains the origin of the QPOs and how they are imprinted on the properties of power-law flux component. We argue the existence of a bounded compact coronal region which is a natural consequence of the adjustment of Keplerian disk flow to the innermost sub-Keplerian boundary conditions near the central object and that ultimately leads to the formation of a transition layer (TL) between the adjustment radius and the innermost boundary. The model predicts two phases or states dictated by the photon upscattering produced in the TL: (1) hard state, in which the TL is optically thin and very hot (kT ≳ 50 keV) producing photon upscattering via thermal Componization; the photon spectrum index Γ ~ 1.7 for this state is dictated by gravitational energy release and Compton cooling in an optically thin shock near the adjustment radius; (2) a soft state which is optically thick and relatively cold (kT ≲ 5 keV); the index for this state, Γ ~ 2.8 is determined by soft-photon upscattering and photon trapping in converging flow into
Ferguson, Katie A.; Huh, Carey Y. L.; Amilhon, Bénédicte; Williams, Sylvain; Skinner, Frances K.
2013-01-01
The coupling of high frequency oscillations (HFOs; >100 Hz) and theta oscillations (3–12 Hz) in the CA1 region of rats increases during REM sleep, indicating that it may play a role in memory processing. However, it is unclear whether the CA1 region itself is capable of providing major contributions to the generation of HFOs, or if they are strictly driven through input projections. Parvalbumin-positive (PV+) interneurons may play an essential role in these oscillations due to their extensive connections with neighboring pyramidal cells, and their characteristic fast-spiking. Thus, we created mathematical network models to investigate the conditions under which networks of CA1 fast-spiking PV+ interneurons are capable of producing high frequency population rhythms. We used whole-cell patch clamp recordings of fast-spiking, PV+ cells in the CA1 region of an intact hippocampal preparation in vitro to derive cellular properties, from which we constrained an Izhikevich-type model. Novel, biologically constrained network models were constructed with these individual cell models, and we investigated networks across a range of experimentally determined excitatory inputs and inhibitory synaptic strengths. For each network, we determined network frequency and coherence. Network simulations produce coherent firing at high frequencies (>90 Hz) for parameter ranges in which PV-PV inhibitory synaptic conductances are necessarily small and external excitatory inputs are relatively large. Interestingly, our networks produce sharp transitions between random and coherent firing, and this sharpness is lost when connectivity is increased beyond biological estimates. Our work suggests that CA1 networks may be designed with mechanisms for quickly gating in and out of high frequency coherent population rhythms, which may be essential in the generation of nested theta/high frequency rhythms. PMID:24155715
NASA Astrophysics Data System (ADS)
Yu, S.; Pei, X.; Hasnain, Q.; Nie, L.; Lu, X.
2016-02-01
In this paper, we investigate the temporally resolved evolution of the nanosecond pulsed dielectric barrier discharge (DBD) in a moderate 6 mm discharge gap under various pressures and pulse repetition frequencies (PRFs) by intensified charge-coupled device (ICCD) images, using dry air and its components oxygen and nitrogen. It is found that the pressures are very different when the mode transits between uniform and filamentary in air, oxygen, and nitrogen. The PRFs can also obviously affect the mode-transition. The transition mechanism in the pulsed DBD is not Townsend-to-Streamer, which is dominant in the traditional alternating-voltage DBD. The pulsed DBD in a uniform mode develops in the form of plane ionization wave due to overlap of primary avalanches, while the increase in pressure disturbs the overlap and discharge develops in streamer, corresponding to the filamentary mode. Increasing the initial electron density by pre-ionization may contribute to discharge uniformity at higher pressures. We also found that the dependence of homogeneity upon PRF is a non-monotonic one.
Madej, A.A.; Bernard, J.E.; Dube, P.; Marmet, L.; Windeler, R.S.
2004-07-01
A Cs referenced optical frequency comb system has been used to measure the center frequency of the 5s {sup 2}S{sub 1/2}-4d {sup 2}D{sub 5/2} transition at 445 THz in a single, trapped, and laser-cooled {sup 88}Sr{sup +} ion. The transition frequency {nu}{sub SD}=444 779 044 095 510 Hz{+-}50 Hz (1{sigma}) is obtained, when corrected for systematic shifts. A detailed calculation of the estimated systematic shifts is presented which yields improved values for the various shift parameters including blackbody and electric quadrupole moment shifts.
Zheng, Wenjun; Brooks, Bernard R; Thirumalai, D
2006-05-16
By representing the high-resolution crystal structures of a number of enzymes using the elastic network model, it has been shown that only a few low-frequency normal modes are needed to describe the large-scale domain movements that are triggered by ligand binding. Here we explore a link between the nearly invariant nature of the modes that describe functional dynamics at the mesoscopic level and the large evolutionary sequence variations at the residue level. By using a structural perturbation method (SPM), which probes the residue-specific response to perturbations (or mutations), we identify a sparse network of strongly conserved residues that transmit allosteric signals in three structurally unrelated biological nanomachines, namely, DNA polymerase, myosin motor, and the Escherichia coli chaperonin. Based on the response of every mode to perturbations, which are generated by interchanging specific sequence pairs in a multiple sequence alignment, we show that the functionally relevant low-frequency modes are most robust to sequence variations. Our work shows that robustness of dynamical modes at the mesoscopic level is encoded in the structure through a sparse network of residues that transmit allosteric signals.
NASA Astrophysics Data System (ADS)
Mürtz, P.; Zink, L. R.; Evenson, K. M.; Brown, J. M.
1998-12-01
Thirteen new rotational transitions of H2O+ in the (0,0,0) level of the X˜ 2B1 state have been measured in the wavenumber region between 80 and 200 cm-1 (50 and 120 μm) by far-infrared laser magnetic resonance (LMR) spectroscopy. LMR data measured previously between 25 and 90 cm-1 (110 and 400 μm), as well as optical and infrared combination differences, have been combined with the new LMR data in a weighted least-squares analysis using an A-reduced expression of the rotational-fine structure Hamiltonian. Thirty-two molecular constants were simultaneously determined, some sextic centrifugal distortion parameters and some quartic and sextic spin-rotation parameters for the first time. From this improved set of molecular parameters, very accurate calculations of rotational term values and zero-field predictions of the 111-000 transition, including hyperfine structure, have been performed. Moreover, the electronic g-tensors and the hyperfine coupling constants are consistent with ab initio calculations which had been carried out for these constants.
Frequency discriminating laser
Thomas, M.D.
1987-10-20
A laser is described for discriminating between a higher gain transition and a lower gain transition to permit the laser to lase at the lower gain transition. It consists of: a laser cavity, including more than two mirrors each of which is highly transmissive at the frequency of the higher gain transition, one of which is partially reflective at the frequency of the lower gain transition, and all but the one of which are highly reflective at the frequency of the lower gain transition; an active laser medium disposed within the cavity; and means for pumping the active laser medium.
NASA Astrophysics Data System (ADS)
Lisin, V. N.; Shegeda, A. M.; Samartsev, V. V.
2015-09-01
A relative phase shift between the different groups of excited dipoles, which appears as result of its frequency splitting due to action of a pulse of electric or magnetic fields, depends on a time, if the pulse overlaps in time with echo-pulse. As а consequence, the echo waveform is changed. The echo time form is modulated. The inverse modulation period well enough approximates Zeeman and pseudo-Stark splitting in the cases of magnetic and, therefore, electrical fields. Thus the g-factors of ground 4I15/2 and excited 4F9/2 optical states of Er3+ ion in LuLiF4 and YLiF4 have been measured and pseudo-Stark shift of R1 line in ruby has been determined.
Absolute frequency of an atomic hydrogen maser clock
NASA Technical Reports Server (NTRS)
Peters, H. E.; Hall, R. G.; Percival, D. B.
1972-01-01
An accurate determination was made of the unperturbed atomic hydrogen ground state hyperfine transition frequency (F=1,m=0 - F=0,m=0) in reference to present world wide realizations of internationally defined time interval. In relation to the international atomic time system, the composite value is 1,420,405,751.7755 plus or minus 0.0031 HZ.
NASA Technical Reports Server (NTRS)
Huang, Xinchuan; Fortenberry, Ryan Clifton; Lee, Timothy J.
2013-01-01
Very recently, molecular rotational transitions observed in the photon-dominated region of the Horsehead nebula have been attributed to l-C3H+. In an effort to corroborate this finding, we employed state-of-the art and proven high-accuracy quantum chemical techniques to compute spectroscopic constants for this cation and its isotopologues. Even though the B rotational constant from the fit of the observed spectrum and our computations agree to within 20 MHz, a typical level of accuracy, the D rotational constant differs by more than 40%, while the H rotational constant differs by three orders of magnitude. With the likely errors in the rotational transition energies resulting from this difference in D on the order of 1 MHz for the lowest observed transition (J = 4 yields 3) and growing as J increases, the assignment of the observed rotational lines from the Horsehead nebula to l-C3H+ is questionable.
Huang Xinchuan; Fortenberry, Ryan C.; Lee, Timothy J.
2013-05-10
Very recently, molecular rotational transitions observed in the photon-dominated region of the Horsehead nebula have been attributed to l-C{sub 3}H{sup +}. In an effort to corroborate this finding, we employed state-of-the-art and proven high-accuracy quantum chemical techniques to compute spectroscopic constants for this cation and its isotopologues. Even though the B rotational constant from the fit of the observed spectrum and our computations agree to within 20 MHz, a typical level of accuracy, the D rotational constant differs by more than 40%, while the H rotational constant differs by three orders of magnitude. With the likely errors in the rotational transition energies resulting from this difference in D on the order of 1 MHz for the lowest observed transition (J = 4 {yields} 3) and growing as J increases, the assignment of the observed rotational lines from the Horsehead nebula to l-C{sub 3}H{sup +} is questionable.
NASA Technical Reports Server (NTRS)
Titarchuk, Lev; Fiorito, Ralph
2004-01-01
Recent studies have shown that strong correlations are observed between the low frequencies (1-10 Hz) of quasi-periodic oscillations (QPOs) and the spectral power law index of several black hole (BH) candidate sources, in low (hard) states, steep power law (soft) states, and transitions between these states. The observations indicate that the X-ray spectra of such state (phases) show the presence of a power-law component and are sometimes related to simultaneous radio emission, indicating the probable presence of a jet. Strong QPOs (>20% rms) are present in the power density spectrum in the spectral range where the power-law component is dominant (i.e., 60%90%). This evidence contradicts the dominant, long-standing interpretation of QPOs as a signature of the thermal accretion disk. We present the data from the literature and our own data to illustrate the dominance of power-law index-QPO frequency correlations. We provide a model that identifies and explains the origin of the QPOs and how they are imprinted on the properties of the power-law flux component. We argue for the existence of a bounded compact coronal region that is a natural consequence of the adjustment of the Keplerian disk flow to the innermost sub-Keplerian boundary conditions near the central object and that ultimately leads to the formation of a transition layer (TL) between the adjustment radius and the innermost boundary. The model predicts two phases or states dictated by the photon upscattering produced in the TL: (1) a hard state, in which the TL is optically thin and very hot (kT approximately greater than 50 keV), producing photon upscattering via thermal Comptonization (the photon spectrum index Gamma approximates 1.7 for this state is dictated by gravitational energy release and Compton cooling in an optically thin shock near the adjustment radius), and (2) a soft state that is optically thick and relatively cold (kT approximately less than 5 keV the index for this state, Gamma
Li, Qi; Song, Xiaodong; Wu, Dingjun
2014-05-01
Predicting structure-borne noise from bridges subjected to moving trains using the three-dimensional (3D) boundary element method (BEM) is a time consuming process. This paper presents a two-and-a-half dimensional (2.5D) BEM-based procedure for simulating bridge-borne low-frequency noise with higher efficiency, yet no loss of accuracy. The two-dimensional (2D) BEM of a bridge with a constant cross section along the track direction is adopted to calculate the spatial modal acoustic transfer vectors (MATVs) of the bridge using the space-wave number transforms of its 3D modal shapes. The MATVs calculated using the 2.5D method are then validated by those computed using the 3D BEM. The bridge-borne noise is finally obtained through the MATVs and modal coordinate responses of the bridge, considering time-varying vehicle-track-bridge dynamic interaction. The presented procedure is applied to predict the sound pressure radiating from a U-shaped concrete bridge, and the computed results are compared with those obtained from field tests on Shanghai rail transit line 8. The numerical results match well with the measured results in both time and frequency domains at near-field points. Nevertheless, the computed results are smaller than the measured ones for far-field points, mainly due to the sound radiation from adjacent spans neglected in the current model.
NASA Astrophysics Data System (ADS)
Ishida, R.; Hiramatsu, Y.; Obara, K.; Matsuzawa, T.
2011-12-01
In southwestern Japan, non-volcanic deep low-frequency (DLF) tremors (e.g., Obara, 2002) and short-term slow slip events (S-SSEs; e.g., Obara et al., 2004) occur in temporal and spatial coincidence with the active stages of DLF tremors (Obara et al., 2004). Based on this feature, Hiramatsu et al. (2008) proposed a method to monitor slip at the transition zone between the locked and aseismic slip zones on the plate interface using DLF tremors. In this study, we applied the method as the same way of previous studies (Hiramatsu et al., 2008; Hirose et al., 2010) and estimated the long-term average slip rate at the transition zone from DLF tremors in southwestern Japan. We also estimated the slip distributions of S-SSEs from DLF tremors using the modified envelope correlation method (ECM) tremor catalog (Maeda and Obara, 2009) and the hourly centroid tremor catalog (Obara et al., 2010) along with the ECM tremor catalog (Obara, 2002) in southwestern Japan. The modified ECM applied both the differential travel time and the spatial distribution of mean square amplitudes to estimate a tremor's spatial location and radiation energy. The hourly centroid tremor catalog is constructed using a clustering process to estimate centroid locations, revealing clear depth-dependent behavior of the tremor activity. The cumulative seismic moment from 2001 to 2009 increases at a constant rate, indicating a constant moment release rate in the long-term average. We estimated slip rate at the transition zone using the formula ˙ {M0} = μ S_˙ {U}, where ˙ {M0} is the moment release rate, μ the rigidity, S the fault area that is related to the slip of S-SSEs in each region, and ˙ {U} the slip rate. We obtained the slip rates of 4.1 ± 0.5 cm/yr, 3.7 ± 0.6 cm/yr, and 2.6 ± 0.2 cm/yr in the western Shikoku, northern Kii peninsula, and Tokai regions, respectively, at the transition zone through the analyzed period. The slip deficit rate at the transition zone in each region is 2.6cm/yr, 2
NASA Astrophysics Data System (ADS)
Creager, K. C.; Sweet, J.; Vidale, J. E.; Houston, H.
2012-12-01
Using data from the Array of Arrays and CAFE experiments, we have identified eight Low-Frequency Earthquake (LFE) families on the subduction plate interface, under the Olympic Peninsula, Washington State. We analyze the time history of each during the time interval 2007-2012. The updip-most family (LFE1) only lights up during the well-known northern Cascadia Episodic Tremor and Slip (ETS) events that recur every 15 months. The recurrence intervals shorten from updip LFE1 to the downdip-most family (LFE4), which repeats every 14 days; 30 times more frequently. This presentation focuses on the downdip family. See the Sweet presentation, this session, for an analysis of the updip-most LFE family. LFEs from family 4 typically have durations of about one hour, with as many as 100 repeats during that time. Unlike their updip counterparts, they occur as discrete events without other LFEs or tremor visible during that time. They are strongly modulated by tidal shear stress. Twice as many LFEs occur during encouraging shear stress as during discouraging times. In contrast, these same LFEs occur when tidal normal stress is compressive which should inhibit slip. To reconcile LFE occurrence with favorable tidal Coulomb stress requires that the friction coefficient be less than 0.2 .This extreme sensitivity to very small shear stresses also suggests near lithostatic pore fluid pressures. We propose that the bursts of LFEs in this family correspond to discrete slow-slip events that occur with remarkable regularity. To add up to plate rates, each burst would correspond to a little more than 1 mm of slip, and each individual LFE to a little less than 0.1 mm, assuming all the slip occurs in the form of LFE activity and each LFE ruptures the same spot. One of these event sequences was captured by our 1-km aperture 80-element Big Skidder Array in 2008. Careful stacked correlation functions from 32 LFEs relative to a reference event showed S-P times varied only up to 0.02s, which
Frequency Standards and Metrology
NASA Astrophysics Data System (ADS)
Maleki, Lute
2009-04-01
imaging an event horizon (Invited) / S. Doeleman. Optically-pumped space cesium clock for Galileo: results of the breadboard / R. Ruffieux ... [et al.] -- pt. IV. Optical clocks I: lattice clocks. Optical lattice clock: seven years of progress and next steps (Invited) / H. Katori, M. Takamoto and T. Akatsuka. The Yb optical lattice clock (Invited) / N. D. Demke ... [et al.]. Optical Lattice clock with Sr atoms (Invited) / P. G. Westergaard ... [et al.]. Development of an optical clock based on neutral strontium atoms held in a lattice trap / E. A. Curtis ... [et al.]. Decoherence and losses by collisions in a [symbol]Sr lattice clock / J. S. R. Vellore Winfred ... [et al.]. Lattice Yb optical clock and cryogenic Cs fountain at INRIM / F. Levi ... [et al.] -- pt. V. Optical clocks II: ion clocks. [Symbol]Yb+ single-ion optical frequency standards (Invited) / Chr. Tamm ... [et al.]. An optical clock based on a single trapped [symbol]Sr+ ion (Invited) / H. S. Margolis ... [et al.]. A trapped [symbol]Yb+ ion optical frequency standard based on the [symbol] transition (Invited) / P. Gill ... [et al.]. Overview of highly accurate RF and optical frequency standards at the National Research Council of Canada (Invited) / A. A. Madej ... [et al.] -- pt. VI. Optical frequency combs. Extreme ultraviolet frequency combs for spectroscopy (Invited) / A. Ozawa ... [et al.]. Development of an optical clockwork for the single trapped strontium ion standard at 445 THz / J. E. Bernard ... [et al.]. A phase-coherent link between the visible and infrared spectral ranges using a combination of CW OPO and femtosecond laser frequency comb / E. V. Kovalchuk and A. Peters. Improvements to the robustness of a TI: sapphire-based femtosecond comb at NPL / V. Tsatourian ... [et al.] -- pt. VII. Atomic microwave standards. NIST FI and F2 (Invited) / T. P. Heavner ... [et al.]. Atomic fountains for the USNO master clock (Invited) / C. Ekstrom ... [et al.]. The transportable cesium fountain clock NIM5
Fast stabilization of a CO{sub 2} laser for a frequency standard at 10 {mu}m
Pisani, M.Q.; Sassi, M.P.; Zucco, M.
1994-12-31
A CO{sub 2} laser has been frequency stabilized to an OsO{sub 4} transition with a control bandwidth of 10 kHz. The obtained spectral purity of the laser is 100 Hz. The realization of very accurate frequency standards and experiments of high resolution spectroscopy in the 10 {mu}m region are made possible by this source.
NASA Astrophysics Data System (ADS)
Yamashita, Y.; Yakiwara, H.; Shimizu, H.; Uchida, K.; Hirano, S.; Miyamachi, H.; Umakoshi, K.; Nakamoto, M.; Fukui, M.; Kamizono, M.; Kanehara, H.; Yamada, T.; Shinohara, M.; Obara, K.
2014-12-01
To understand the shallow part of plate interface between megathrust seismogenic zone and trench axis is very important for development of huge earthquake rupture and generation of tsunami. Monitoring of offshore seismicity near the Nankai trough by temporal ocean bottom seismographic observation in 2013 revealed that low-frequency tremor occurred associated with shallow very-low-frequency earthquakes (VLFEs) in the shallow part of plate interface. The shallow tremor episode lasted for approximately 1 month, which is almost consistent with the shallow VLFE activity observed from land broad-band seismic stations [Asano, 2014]. The horizontal location of shallow tremor estimate by envelope correlation method [Obara, 2002] shows a belt-like distribution along trench strike with narrow width than the deep tremor. The most remarkable feature of the shallow tremor activity is migration. There are two migration modes including diffusive slower migration and rapid tremor reversal (RTR), which are very similar to the deep tremor as a part of the ETS. This strongly indicates a possibility of the occurrence of episodic slow slip event in the shallow transition zone. That is to say, the migration of shallow tremor is supposed to be caused by migrating rupture front of SSE. In addition, the migration was detouring around the subducted Kyushu-Palau ridge. This suggests that the occurrence of tremor is sensitive to change in the shape of plate interface and seeks to propagate along almost the same depth range, in other word, a specified temperature and pressure condition. The narrow width distribution of shallow tremor also indicates that the shallow tremor is strongly related to dehydration process of a specified mineral under a narrow limited range of temperature and pressure condition compared to the deep tremor.
Accurate monotone cubic interpolation
NASA Technical Reports Server (NTRS)
Huynh, Hung T.
1991-01-01
Monotone piecewise cubic interpolants are simple and effective. They are generally third-order accurate, except near strict local extrema where accuracy degenerates to second-order due to the monotonicity constraint. Algorithms for piecewise cubic interpolants, which preserve monotonicity as well as uniform third and fourth-order accuracy are presented. The gain of accuracy is obtained by relaxing the monotonicity constraint in a geometric framework in which the median function plays a crucial role.
Accurate Finite Difference Algorithms
NASA Technical Reports Server (NTRS)
Goodrich, John W.
1996-01-01
Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.
Magic wavelengths for terahertz clock transitions
Zhou Xiaoji; Xu Xia; Chen Xuzong; Chen Jingbiao
2010-01-15
Magic wavelengths for laser trapping of boson isotopes of alkaline-earth metal atoms Sr, Ca, and Mg are investigated while considering terahertz clock transitions between the {sup 3}P{sub 0}, {sup 3}P{sub 1}, and {sup 3}P{sub 2} metastable triplet states. Our calculation shows that magic wavelengths for laser trapping do exist. This result is important because those metastable states have already been used to make accurate clocks in the terahertz frequency domain. Detailed discussions for magic wavelengths for terahertz clock transitions are given in this article.
NASA Astrophysics Data System (ADS)
Terra, Osama; Hussein, Hatem
2016-02-01
In this study, we report the development of a frequency standard for optical fiber communication applications based on a two-photon transition in rubidium at 385.2 THz. This standard kills two birds with one stone in the sense it is capable of providing us with two highly stable serviceable wavelengths at 778.1 and 1556.2 nm. In this system, we exploit the narrow line-width of a fiber laser emitting at 1556.2 nm in conjunction with an erbium-doped fiber amplifier to generate a sufficient second harmonic laser beam at 778.1 nm in a periodically polled lithium niobate waveguide mixer in order to probe and frequency-lock the laser to the 5S1/2 ( F g = 3)-5D5/2 ( F e = 5) hyperfine two-photon transition component in 85Rb. The metrological performance of the standard is evaluated with the aid of an optical frequency comb synthesizer. Allan variance measurement shows a stability of 4 × 10-12 at 1 s (limited by the comb stability), reaching a floor of 6.8 × 10-13 at 1000 s. After correction of all the major systematic frequency shifts including the light shift, the absolute frequency is found to be 385 285 142 374.0 (5.0) kHz. Moreover, the absolute frequencies of most of the hyperfine components of the 5S1/2-5D5/2 transition of the two naturally existing rubidium isotopes are measured using a femtosecond frequency comb synthesizer after stabilizing a laser on each component.
Absolute frequencies of the {sup 6,7}Li 2S {sup 2}S{sub 1/2}{yields}3S {sup 2}S{sub 1/2} transitions
Lien, Yu-Hung; Lo, Kuan-Ju; Chen, Jun-Ren; Liu, Yi-Wei; Chen, Hsuan-Chen; Tian, Jyun-Yu; Shy, Jow-Tsong
2011-10-15
The measurement of the absolute frequencies of the 2S{yields}3S of atomic lithium is reported. To reduce systematic effects, we employed a frequency-comb-stabilized excitation laser, a weakly collimated atomic beam, and the cascading 2P{yields}2S 670 nm fluorescence as the signal. The transition frequencies, including two isotopes ({sup 6,7}Li), were measured to an accuracy of < 330 kHz. In comparison with the previous GSI Group experiment, the frequency of the 2S{sub 1/2}{yields}3S{sub 1/2} transition of {sup 7}Li is 815 618 181.45(9) MHz, which is improved by a factor of 2. The resultant hyperfine constants of the 3S state and the deduced difference of the nuclear charge radii {delta}
NASA Astrophysics Data System (ADS)
Park, Chang Yong; Yu, Dai-Hyuk; Lee, Won-Kyu; Eon Park, Sang; Kim, Eok Bong; Lee, Sun Kyung; Cho, Jun Woo; Yoon, Tai Hyun; Mun, Jongchul; Jong Park, Sung; Kwon, Taeg Yong; Lee, Sang-Bum
2013-04-01
We measured the absolute frequency of the optical clock transition 1S0(F = 1/2)-3P0(F = 1/2) of 171Yb atoms confined in a one-dimensional optical lattice and it was determined to be 518 295 836 590 863.5(8.1) Hz. The frequency was measured against Terrestrial Time (TT; the SI second on the geoid) using an optical frequency comb of which the frequency was phase-locked to an H-maser as a flywheel oscillator traceable to TT. The magic wavelength was also measured as 394 798.48(79) GHz. The results are in good agreement with two previous measurements of other institutes within the specified uncertainty of this work.
Accurate Optical Reference Catalogs
NASA Astrophysics Data System (ADS)
Zacharias, N.
2006-08-01
Current and near future all-sky astrometric catalogs on the ICRF are reviewed with the emphasis on reference star data at optical wavelengths for user applications. The standard error of a Hipparcos Catalogue star position is now about 15 mas per coordinate. For the Tycho-2 data it is typically 20 to 100 mas, depending on magnitude. The USNO CCD Astrograph Catalog (UCAC) observing program was completed in 2004 and reductions toward the final UCAC3 release are in progress. This all-sky reference catalogue will have positional errors of 15 to 70 mas for stars in the 10 to 16 mag range, with a high degree of completeness. Proper motions for the about 60 million UCAC stars will be derived by combining UCAC astrometry with available early epoch data, including yet unpublished scans of the complete set of AGK2, Hamburg Zone astrograph and USNO Black Birch programs. Accurate positional and proper motion data are combined in the Naval Observatory Merged Astrometric Dataset (NOMAD) which includes Hipparcos, Tycho-2, UCAC2, USNO-B1, NPM+SPM plate scan data for astrometry, and is supplemented by multi-band optical photometry as well as 2MASS near infrared photometry. The Milli-Arcsecond Pathfinder Survey (MAPS) mission is currently being planned at USNO. This is a micro-satellite to obtain 1 mas positions, parallaxes, and 1 mas/yr proper motions for all bright stars down to about 15th magnitude. This program will be supplemented by a ground-based program to reach 18th magnitude on the 5 mas level.
High-precision frequency measurement of the 423-nm Ca i line
Salumbides, E. J.; Maslinskas, V.; Dildar, I. M.; Wolf, A. L.; Duijn, E.-J. van; Eikema, K. S. E.; Ubachs, W.
2011-01-15
We have performed an accurate frequency calibration of the 4s{sup 2} {sup 1}S{sub 0{yields}}4s4p {sup 1}P{sub 1} principal resonance line of the neutral calcium atom at 423 nm. Doppler-free cw excitation on a Ca atomic beam was performed by utilizing a Sagnac geometry in the alignment of the excitation beams. From frequency calibrations against a frequency comb, stabilized to a global positioning system (GPS) disciplined Rb standard, the transition frequency is determined at 709 078 373.01(35) MHz for the main {sup 40}Ca isotope. Slightly lower accuracies are obtained for the transition frequencies of the less abundant isotopes. The achieved fractional uncertainty of 5x10{sup -10} exceeds the requirements for including this transition in investigations that aim to probe a possible variation in the fine-structure constant {alpha} on cosmological time scales.
NASA Astrophysics Data System (ADS)
Surdi, Harshad
Kinetic inductance springs from the inertia of charged mobile carriers in alternating electric fields and it is fundamentally different from the magnetic inductance which is only a geometry dependent property. The magnetic inductance is proportional to the volume occupied by the electric and magnetic fields and is often limited by the number of turns of the coil. Kinetic inductance on the other hand is inversely proportional to the density of electrons or holes that exert inertia, the unit mass of the charge carriers and the momentum relaxation time of these charge carriers, all of which can be varied merely by modifying the material properties. Highly sensitive and broadband signal amplifiers often broaden the field of study in astrophysics. Quantum-noise limited travelling wave kinetic inductance parametric amplifiers offer a noise figure of around 0.5 K +/- 0.3 K as compared to 20 K in HEMT signal amplifiers and can be designed to operate to cover the entire W-band (75 GHz -- 115 GHz). The research cumulating to this thesis involves applying and exploiting kinetic inductance properties in designing a W-band orthogonal mode transducer, quadratic gain phase shifter with a gain of ~49 dB over a meter of microstrip transmission line. The phase shifter will help in measuring the maximum amount of phase shift Deltaφmax(I) that can be obtained from half a meter transmission line which helps in predicting the gain of a travelling wave parametric amplifier. In another project, a microstrip to slot line transition is designed and optimized to operate at 150 GHz and 220 GHz frequencies, that is used as a part of horn antenna coupled microwave kinetic inductance detector proposed to operate from 138 GHz to 250 GHz. In the final project, kinetic inductance in a 2D electron gas (2DEG) is explored by design, simulation, fabrication and experimentation. A transmission line model of a 2DEG proposed by Burke (1999), is simulated and verified experimentally by fabricating a
Suen, Wu; Spiro, Thomas G.; Sowers, Lawrence C.; Fresco, Jacques R.
1999-01-01
UV resonance Raman spectroscopy was used to detect and estimate the frequency of the unfavored imino tautomer of the transition mutagen 5-hydroxy-2′-deoxycytidine (HO5dCyt) in its anionic form. In DNA, this 2′-deoxycytidine analog arises from the oxidation of 2′-deoxycytidine and induces C → T transitions with 102 greater frequency than such spontaneous transitions. An imino tautomer marker carbonyl band (≈1650 cm−1) is enhanced at ≈65°C against an otherwise stable spectrum of bands associated with the favored amino tautomer. This band is similarly present in the UV resonance Raman spectra of the imino cytidine analogs N3-methylcytidine at high pH and N4-methoxy-2′-deoxycytidine at pH 7 and displays features attributable to the imino form of C residues and their derivatives. The fact that the imino tautomer of HO5dCyt occurs at a frequency consistent with its high mutagenic enhancement lends strong support to the hypothesis that unfavored base tautomers play important roles in the mispair intermediates of replication leading to substitution mutations. PMID:10200291
NASA Astrophysics Data System (ADS)
Ottino-Löffler, Bertrand; Strogatz, Steven H.
2016-09-01
We study the dynamics of coupled phase oscillators on a two-dimensional Kuramoto lattice with periodic boundary conditions. For coupling strengths just below the transition to global phase-locking, we find localized spatiotemporal patterns that we call "frequency spirals." These patterns cannot be seen under time averaging; they become visible only when we examine the spatial variation of the oscillators' instantaneous frequencies, where they manifest themselves as two-armed rotating spirals. In the more familiar phase representation, they appear as wobbly periodic patterns surrounding a phase vortex. Unlike the stationary phase vortices seen in magnetic spin systems, or the rotating spiral waves seen in reaction-diffusion systems, frequency spirals librate: the phases of the oscillators surrounding the central vortex move forward and then backward, executing a periodic motion with zero winding number. We construct the simplest frequency spiral and characterize its properties using analytical and numerical methods. Simulations show that frequency spirals in large lattices behave much like this simple prototype.
Accurate maser positions for MALT-45
NASA Astrophysics Data System (ADS)
Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven
2013-10-01
MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.
Accurate maser positions for MALT-45
NASA Astrophysics Data System (ADS)
Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven
2013-04-01
MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.
Frequency Standards and Metrology
NASA Astrophysics Data System (ADS)
Maleki, Lute
2009-04-01
imaging an event horizon (Invited) / S. Doeleman. Optically-pumped space cesium clock for Galileo: results of the breadboard / R. Ruffieux ... [et al.] -- pt. IV. Optical clocks I: lattice clocks. Optical lattice clock: seven years of progress and next steps (Invited) / H. Katori, M. Takamoto and T. Akatsuka. The Yb optical lattice clock (Invited) / N. D. Demke ... [et al.]. Optical Lattice clock with Sr atoms (Invited) / P. G. Westergaard ... [et al.]. Development of an optical clock based on neutral strontium atoms held in a lattice trap / E. A. Curtis ... [et al.]. Decoherence and losses by collisions in a [symbol]Sr lattice clock / J. S. R. Vellore Winfred ... [et al.]. Lattice Yb optical clock and cryogenic Cs fountain at INRIM / F. Levi ... [et al.] -- pt. V. Optical clocks II: ion clocks. [Symbol]Yb+ single-ion optical frequency standards (Invited) / Chr. Tamm ... [et al.]. An optical clock based on a single trapped [symbol]Sr+ ion (Invited) / H. S. Margolis ... [et al.]. A trapped [symbol]Yb+ ion optical frequency standard based on the [symbol] transition (Invited) / P. Gill ... [et al.]. Overview of highly accurate RF and optical frequency standards at the National Research Council of Canada (Invited) / A. A. Madej ... [et al.] -- pt. VI. Optical frequency combs. Extreme ultraviolet frequency combs for spectroscopy (Invited) / A. Ozawa ... [et al.]. Development of an optical clockwork for the single trapped strontium ion standard at 445 THz / J. E. Bernard ... [et al.]. A phase-coherent link between the visible and infrared spectral ranges using a combination of CW OPO and femtosecond laser frequency comb / E. V. Kovalchuk and A. Peters. Improvements to the robustness of a TI: sapphire-based femtosecond comb at NPL / V. Tsatourian ... [et al.] -- pt. VII. Atomic microwave standards. NIST FI and F2 (Invited) / T. P. Heavner ... [et al.]. Atomic fountains for the USNO master clock (Invited) / C. Ekstrom ... [et al.]. The transportable cesium fountain clock NIM5
NASA Astrophysics Data System (ADS)
Armstrong, William D.; Shanmugham, Manikantan; Bailey, Harold
2004-07-01
The present paper presents cyclic strain amplitude and longitudinal strain measurements of longitudinally compressed Terfenol-D particle samples subjected to magneto-strain cycling. A comparison is made of the responses of material strain cycle tested at temperatures near the matrix glass transition start temperature, and material strain cycle tested at a temperature near the matrix glass transition finish temperature. The cyclic strain amplitude of the material was significantly larger when tested at a temperature near the matrix glass transition finish temperature. A useful range of longitudinal applied stress exists where the composite suffers little apparent degradation. Beyond this range the composite exhibits steadily decreasing cyclic strain amplitude with increases in longitudinal compressive stress magnitude.
High density terahertz frequency comb produced by coherent synchrotron radiation.
Tammaro, S; Pirali, O; Roy, P; Lampin, J-F; Ducournau, G; Cuisset, A; Hindle, F; Mouret, G
2015-07-20
Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10(-10) and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile.
High density terahertz frequency comb produced by coherent synchrotron radiation
Tammaro, S.; Pirali, O.; Roy, P.; Lampin, J.-F.; Ducournau, G.; Cuisset, A.; Hindle, F.; Mouret, G.
2015-01-01
Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10−10 and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile. PMID:26190043
Autonomous Rubidium Clock Weak Frequency Jump Detector for Onboard Navigation Satellite System.
Khare, Akshay; Arora, Rajat; Banik, Alak; Mehta, Sanjay D
2016-02-01
Frequency jumps are common in rubidium frequency sources. They affect the estimation of user position in navigational satellite systems. These jumps must be detected and corrected immediately as they have direct impact on the navigation system integrity. A novel weak frequency jump detector is proposed based on a Kalman filter with a multi-interval approach. This detector can be applied for both "sudden" and "slow" frequency transitions. In this detection method, noises of clock data are reduced by Kalman filtering, for accurate estimation of jump size with less latency. Analysis on in-orbit rubidium atomic frequency standard (RAFS) phase telemetry data shows that the detector can be used for fast detection and correction of weak frequency jumps. Furthermore, performance comparison of different existing frequency jump detection techniques with the proposed detector is discussed. A multialgorithm-based strategy is proposed depending on the jump size and latency for onboard navigation satellites having RAFS as the primary frequency source.
Autonomous Rubidium Clock Weak Frequency Jump Detector for Onboard Navigation Satellite System.
Khare, Akshay; Arora, Rajat; Banik, Alak; Mehta, Sanjay D
2016-02-01
Frequency jumps are common in rubidium frequency sources. They affect the estimation of user position in navigational satellite systems. These jumps must be detected and corrected immediately as they have direct impact on the navigation system integrity. A novel weak frequency jump detector is proposed based on a Kalman filter with a multi-interval approach. This detector can be applied for both "sudden" and "slow" frequency transitions. In this detection method, noises of clock data are reduced by Kalman filtering, for accurate estimation of jump size with less latency. Analysis on in-orbit rubidium atomic frequency standard (RAFS) phase telemetry data shows that the detector can be used for fast detection and correction of weak frequency jumps. Furthermore, performance comparison of different existing frequency jump detection techniques with the proposed detector is discussed. A multialgorithm-based strategy is proposed depending on the jump size and latency for onboard navigation satellites having RAFS as the primary frequency source. PMID:26685233
NASA Astrophysics Data System (ADS)
Mills, Andrew A.; Ford, Kyle B.; Kreckel, Holger; Perera, Manori; Crabtree, Kyle N.; McCall, Benjamin J.
2009-06-01
With the advent of Herschel and SOFIA, laboratory methods capable of providing molecular rest frequencies in the terahertz and sub-millimeter regime are increasingly important. As of yet, it has been difficult to perform spectroscopy in this wavelength region due to the limited availability of radiation sources, optics, and detectors. Our goal is to provide accurate THz rest frequencies for molecular ions by combining previously recorded microwave transitions with combination differences obtained from high precision mid-IR spectroscopy. We are constructing a Sensitive Resolved Ion Beam Spectroscopy setup which will harness the benefits of kinematic compression in a molecular ion beam to enable very high resolution spectroscopy. This ion beam is interrogated by continuous-wave cavity ringdown spectroscopy using a home-made widely tunable difference frequency laser that utilizes two near-IR lasers and a periodically-poled lithium niobate crystal. Here, we report our efforts to optimize our ion beam spectrometer and to perform high-precision and high-accuracy frequency measurements using an optical frequency comb. footnote
NASA Technical Reports Server (NTRS)
Cooksy, A. L.; Saykally, R. J.; Brown, J. M.; Evenson, K. M.
1986-01-01
Accurate values are presented for the fine-structure intervals in the 3P ground state of neutral atomic C-12 and C-13 as obtained from laser magnetic resonance spectroscopy. The rigorous analysis of C-13 hyperfine structure, the measurement of resonant fields for C-12 transitions at several additional far-infrared laser frequencies, and the increased precision of the C-12 measurements, permit significant improvement in the evaluation of these energies relative to earlier work. These results will expedite the direct and precise measurement of these transitions in interstellar sources and should assist in the determination of the interstellar C-12/C-13 abundance ratio.
NNLOPS accurate associated HW production
NASA Astrophysics Data System (ADS)
Astill, William; Bizon, Wojciech; Re, Emanuele; Zanderighi, Giulia
2016-06-01
We present a next-to-next-to-leading order accurate description of associated HW production consistently matched to a parton shower. The method is based on reweighting events obtained with the HW plus one jet NLO accurate calculation implemented in POWHEG, extended with the MiNLO procedure, to reproduce NNLO accurate Born distributions. Since the Born kinematics is more complex than the cases treated before, we use a parametrization of the Collins-Soper angles to reduce the number of variables required for the reweighting. We present phenomenological results at 13 TeV, with cuts suggested by the Higgs Cross section Working Group.
Gliksman, N R; Skibbens, R V; Salmon, E D
1993-01-01
Microtubules (MTs) in newt mitotic spindles grow faster than MTs in the interphase cytoplasmic microtubule complex (CMTC), yet spindle MTs do not have the long lengths or lifetimes of the CMTC microtubules. Because MTs undergo dynamic instability, it is likely that changes in the durations of growth or shortening are responsible for this anomaly. We have used a Monte Carlo computer simulation to examine how changes in the number of MTs and changes in the catastrophe and rescue frequencies of dynamic instability may be responsible for the cell cycle dependent changes in MT characteristics. We used the computer simulations to model interphase-like or mitotic-like MT populations on the basis of the dynamic instability parameters available from newt lung epithelial cells in vivo. We started with parameters that produced MT populations similar to the interphase newt lung cell CMTC. In the simulation, increasing the number of MTs and either increasing the frequency of catastrophe or decreasing the frequency of rescue reproduced the changes in MT dynamics measured in vivo between interphase and mitosis. Images PMID:8298190
Fleming, Donald G; Arseneau, Donald J; Sukhorukov, Oleksandr; Brewer, Jess H; Mielke, Steven L; Truhlar, Donald G; Schatz, George C; Garrett, Bruce C; Peterson, Kirk A
2011-11-14
The neutral muonic helium atom (4)Heμ, in which one of the electrons of He is replaced by a negative muon, may be effectively regarded as the heaviest isotope of the hydrogen atom, with a mass of 4.115 amu. We report details of the first muon spin rotation (μSR) measurements of the chemical reaction rate constant of (4)Heμ with molecular hydrogen, (4)Heμ + H(2) → (4)HeμH + H, at temperatures of 295.5, 405, and 500 K, as well as a μSR measurement of the hyperfine coupling constant of muonic He at high pressures. The experimental rate constants, k(Heμ), are compared with the predictions of accurate quantum mechanical (QM) dynamics calculations carried out on a well converged Born-Huang (BH) potential energy surface, based on complete configuration interaction calculations and including a Born-Oppenheimer diagonal correction. At the two highest measured temperatures the agreement between the quantum theory and experiment is good to excellent, well within experimental uncertainties that include an estimate of possible systematic error, but at 295.5 K the quantum calculations for k(Heμ) are below the experimental value by 2.1 times the experimental uncertainty estimates. Possible reasons for this discrepancy are discussed. Variational transition state theory calculations with multidimensional tunneling have also been carried out for k(Heμ) on the BH surface, and they agree with the accurate QM rate constants to within 30% over a wider temperature range of 200-1000 K. Comparisons between theory and experiment are also presented for the rate constants for both the D + H(2) and Mu + H(2) reactions in a novel study of kinetic isotope effects for the H + H(2) reactions over a factor of 36.1 in isotopic mass of the atomic reactant.
Microfabricated ion frequency standard
Schwindt, Peter; Biedermann, Grant; Blain, Matthew G.; Stick, Daniel L.; Serkland, Darwin K.; Olsson, III, Roy H.
2010-12-28
A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.
Slabko, V V; Tsipotan, A S; Aleksandrovsky, A S
2013-05-31
The influence of the oscillation phases of the dipole moments induced in metal nanoparticles and quantum dots by an external laser field on their interaction energy is considered. It is shown that a difference in resonant frequencies leads to the formation of additional minima and maxima, which are absent in the spectral dependence of the interaction energy of identical particles at similar orientations of the pair of particles with respect to the plane of polarisation of radiation. These features are due to the fact that the oscillation phase difference of the induced dipole moments of particles reaches values close to {pi}. (interaction of laser radiation with matter. laser plasma)
NASA Astrophysics Data System (ADS)
Bräuniger, Thomas; Ramaswamy, Kannan; Madhu, P. K.
2004-01-01
We here report on using fast amplitude-modulated (FAM) pulse trains with constantly incremented pulse durations (SW-FAM) for signal enhancement in one-dimensional nuclear magnetic resonance spectra of quadrupolar nuclei with half-integer spin. In such systems, a FAM pulse train leads to a redistribution of populations across the spin levels, which results in a substantial gain for the central-transition signal. Compared to fixed-duration FAM pulse trains, SW-FAM delivers about the same signal enhancement for spinning samples, but gives much better performance in the static case. This is demonstrated for several compounds, observing the nuclei 23Na ( I=3/2), 27Al ( I=5/2), and 45Sc ( I=7/2).
NASA Astrophysics Data System (ADS)
Droege, A. T.; Engelking, P. C.
1984-06-01
The (0,0), (1,1), and (2,2) vibrational bands of the weak, spin forbidden b 1Σ+ → X 3Σ- transition of the PH radical have been observed in a flowing afterglow of PH3 in He. The spectra yield the following constants for the upper b state: Te =(14 325.5±0.1) cm-1, Be =(8.587±0.003) cm-1, we =(2403.0±0.1) cm-1, Dv =(4.0±0.05×10-4) cm-1, αe =(0.0253±0.003) cm-1, and re =(1.4178±0.0004) Å. The intensity distribution is consistent with the mixing of the b 1Σ+ state almost exclusively with the A 3Π state.
NASA Astrophysics Data System (ADS)
Havey, Daniel K.; Hodges, Joseph T.; Long, David A.; Okumura, Mitchio; Miller, Charles E.
2009-06-01
The reliability of high-J line parameters in spectroscopic databases can affect the uncertainty budget of experiments aiming to utilize optical probing to study highly rotationally excited molecules. Ultra-cold collision dynamics of O_2(E_{rot}), specifically, has recently been suggested as an intriguing but experimentally demanding system. One possibility would be to directly probe absorption transitions of O_2 as it trickles down a ladder of rotational states via collisional relaxation following rotational excitation. In certain cases, another strategy might be to utilize optical absorption to probe the collision partner for O_2. Both of these experimental approaches require an understanding of the spectroscopy of elevated rotational states, and in particular the intensities and widths are important for quantifying molecular dynamics. In the case of rotationally excited species, these data would have to be obtained by extrapolation of line parameters from existing databases. Subtle deviations from the database line parameters, as revealed by experiments, may be amplified depending on how far in J the data are extrapolated. Our goals in this study are (I) to provide the highest-J spectroscopic measurements of line intensities and widths for the primary isotope of O_2 in the A-band region and (II) to understand how the line parameters compare to, and build on, what is contained in the widely used HITRAN database. The experiments presented here are challenging because these lines are some of the weakest ever observed in the laboratory, thus requiring extremely sensitive optical detection methods. We have measured transitions between J' = 32 and 50 (self-broadened) and J' = 32 and 42 (air-broadened) and have demonstrated a minimum detectable line intensity of ˜2×10^{-31} cm molec.^{-1}. Our highest J measurements probe lower states having rotational energies of ˜3775 cm^{-1}, 40% higher than the most extensive measurements to date.
Degenhardt, Carsten; Stoehr, Hardo; Lisdat, Christian; Wilpers, Guido; Schnatz, Harald; Lipphardt, Burghard; Nazarova, Tatiana; Pottie, Paul-Eric; Sterr, Uwe; Helmcke, Juergen; Riehle, Fritz
2005-12-15
An optical frequency standard based on an ensemble of neutral calcium atoms laser-cooled to 12 {mu}K has been realized. By using ultracold atoms, one major previous source of uncertainty, the residual Doppler effect, was reduced. We show that cold collisions contribute a negligible amount to the uncertainty. The influence of a temporal evolution of the phase of the laser pulses used to interrogate the clock transition was measured and corrected for. The frequency of the clock transition at 657 nm was referenced to the caesium fountain clock of PTB utilizing a femtosecond comb generator with a fractional uncertainty of 1.2x10{sup -14}. The transition frequency was determined to be (455 986 240 494 144{+-}5.3) Hz, making the calcium clock transition one of the most accurately known optical transitions. A frequency stability of 3x10{sup -15} at 100 s averaging time was achieved and the noise contributions that limit to the observed stability were analyzed in detail. Additionally, the natural linewidth of the clock transition has been determined.
Accurate free energy calculation along optimized paths.
Chen, Changjun; Xiao, Yi
2010-05-01
The path-based methods of free energy calculation, such as thermodynamic integration and free energy perturbation, are simple in theory, but difficult in practice because in most cases smooth paths do not exist, especially for large molecules. In this article, we present a novel method to build the transition path of a peptide. We use harmonic potentials to restrain its nonhydrogen atom dihedrals in the initial state and set the equilibrium angles of the potentials as those in the final state. Through a series of steps of geometrical optimization, we can construct a smooth and short path from the initial state to the final state. This path can be used to calculate free energy difference. To validate this method, we apply it to a small 10-ALA peptide and find that the calculated free energy changes in helix-helix and helix-hairpin transitions are both self-convergent and cross-convergent. We also calculate the free energy differences between different stable states of beta-hairpin trpzip2, and the results show that this method is more efficient than the conventional molecular dynamics method in accurate free energy calculation.
Profitable capitation requires accurate costing.
West, D A; Hicks, L L; Balas, E A; West, T D
1996-01-01
In the name of costing accuracy, nurses are asked to track inventory use on per treatment basis when more significant costs, such as general overhead and nursing salaries, are usually allocated to patients or treatments on an average cost basis. Accurate treatment costing and financial viability require analysis of all resources actually consumed in treatment delivery, including nursing services and inventory. More precise costing information enables more profitable decisions as is demonstrated by comparing the ratio-of-cost-to-treatment method (aggregate costing) with alternative activity-based costing methods (ABC). Nurses must participate in this costing process to assure that capitation bids are based upon accurate costs rather than simple averages. PMID:8788799
Puzzarini, Cristina; Biczysko, Malgorzata; Bloino, Julien; Barone, Vincenzo
2015-01-01
In an effort to provide an accurate spectroscopic characterization of oxirane, state-of-the-art computational methods and approaches have been employed to determine highly accurate fundamental vibrational frequencies and rotational parameters. Available experimental data were used to assess the reliability of our computations, and an accuracy on average of 10 cm−1 for fundamental transitions as well as overtones and combination bands has been pointed out. Moving to rotational spectroscopy, relative discrepancies of 0.1%, 2%–3%, and 3%–4% were observed for rotational, quartic, and sextic centrifugal-distortion constants, respectively. We are therefore confident that the highly accurate spectroscopic data provided herein can be useful for identification of oxirane in Titan’s atmosphere and the assignment of unidentified infrared bands. Since oxirane was already observed in the interstellar medium and some astronomical objects are characterized by very high D/H ratios, we also considered the accurate determination of the spectroscopic parameters for the mono-deuterated species, oxirane-d1. For the latter, an empirical scaling procedure allowed us to improve our computed data and to provide predictions for rotational transitions with a relative accuracy of about 0.02% (i.e., an uncertainty of about 40 MHz for a transition lying at 200 GHz). PMID:26543240
Peters, Norman E.; Burns, Douglas A.; Aulenbach, Brent T.
2014-01-01
Many previous investigations of mean streamwater transit times (MTT) have been limited by an inability to quantify the MTT dynamics. Here, we draw on (1) a linear relation (r 2 = 0.97) between groundwater 3H/3He ages and dissolved silica (Si) concentrations, combined with (2) predicted streamwater Si concentrations from a multiple-regression relation (R 2 = 0.87) to estimate MTT at 5-min intervals for a 23-year time series of streamflow [water year (WY) 1986 through 2008] at the Panola Mountain Research Watershed, Georgia. The time-based average MTT derived from the 5-min data was ~8.4 ± 2.9 years and the volume-weighted (VW) MTT was ~4.7 years for the study period, reflecting the importance of younger runoff water during high flow. The 5-min MTTs are normally distributed and ranged from 0 to 15 years. Monthly VW MTTs averaged 7.0 ± 3.3 years and ranged from 4 to 6 years during winter and 8–10 years during summer. The annual VW MTTs averaged 5.6 ± 2.0 years and ranged from ~5 years during wet years (2003 and 2005) to >10 years during dry years (2002 and 2008). Stormflows are composed of much younger water than baseflows, and although stormflow only occurs ~17 % of the time, this runoff fraction contributed 39 % of the runoff during the 23-year study period. Combining the 23-year VW MTT (including stormflow) with the annual average baseflow for the period (~212 mm) indicates that active groundwater storage is ~1,000 mm. However, the groundwater storage ranged from 1,040 to 1,950 mm using WY baseflow and WY VW MTT. The approach described herein may be applicable to other watersheds underlain by granitoid bedrock, where weathering is the dominant control on Si concentrations in soils, groundwater, and streamwater.
Practical aspects of spatially high accurate methods
NASA Technical Reports Server (NTRS)
Godfrey, Andrew G.; Mitchell, Curtis R.; Walters, Robert W.
1992-01-01
The computational qualities of high order spatially accurate methods for the finite volume solution of the Euler equations are presented. Two dimensional essentially non-oscillatory (ENO), k-exact, and 'dimension by dimension' ENO reconstruction operators are discussed and compared in terms of reconstruction and solution accuracy, computational cost and oscillatory behavior in supersonic flows with shocks. Inherent steady state convergence difficulties are demonstrated for adaptive stencil algorithms. An exact solution to the heat equation is used to determine reconstruction error, and the computational intensity is reflected in operation counts. Standard MUSCL differencing is included for comparison. Numerical experiments presented include the Ringleb flow for numerical accuracy and a shock reflection problem. A vortex-shock interaction demonstrates the ability of the ENO scheme to excel in simulating unsteady high-frequency flow physics.
A Plan for Dealing with Transition.
ERIC Educational Resources Information Center
Arin-Krupp, Judy
1984-01-01
The author describes her plan for dealing with life transitions. The plan has three steps. First, the individual in transition must accurately perceive the situation; second, respond to the situation, change, or transition; and third, reassess his or her perception of the transition. (CT)
Accurate documentation and wound measurement.
Hampton, Sylvie
This article, part 4 in a series on wound management, addresses the sometimes routine yet crucial task of documentation. Clear and accurate records of a wound enable its progress to be determined so the appropriate treatment can be applied. Thorough records mean any practitioner picking up a patient's notes will know when the wound was last checked, how it looked and what dressing and/or treatment was applied, ensuring continuity of care. Documenting every assessment also has legal implications, demonstrating due consideration and care of the patient and the rationale for any treatment carried out. Part 5 in the series discusses wound dressing characteristics and selection.
Trans-Ionospheric High Frequency Signal Ray Tracing
NASA Astrophysics Data System (ADS)
Wright, S.; Gillespie, R. J.
2012-09-01
All electromagnetic radiation undergoes refraction as it propagates through the atmosphere. Tropospheric refraction is largely governed by interaction of the radiation with bounded electrons; ionospheric refraction is primarily governed by free electron interactions. The latter phenomenon is important for propagation and refraction of High Frequency (HF) through Extremely High Frequency (EHF) signals. The degree to which HF to EHF signals are bent is dependent upon the integrated refractive effect of the ionosphere: a result of the signal's angle of incidence with the boundaries between adjacent ionospheric regions, the magnitude of change in electron density between two regions, as well as the frequency of the signal. In the case of HF signals, the ionosphere may bend the signal so much that it is directed back down towards the Earth, making over-the-horizon HF radio communication possible. Ionospheric refraction is a major challenge for space-based geolocation applications, where the ionosphere is typically the biggest contributor to geolocation error. Accurate geolocation requires an algorithm that accurately reflects the physical process of a signal transiting the ionosphere, and an accurate specification of the ionosphere at the time of the signal transit. Currently implemented solutions are limited by both the algorithm chosen to perform the ray trace and by the accuracy of the ionospheric data used in the calculations. This paper describes a technique for adapting a ray tracing algorithm to run on a General-Purpose Graphics Processing Unit (GPGPU or GPU), and using a physics-based model specifying the ionosphere at the time of signal transit. This technique allows simultaneous geolocation of significantly more signals than an equivalently priced Central Processing Unit (CPU) based system. Additionally, because this technique makes use of the most widely accepted numeric algorithm for ionospheric ray tracing and a timely physics-based model of the ionosphere
Gravitationally induced quantum transitions
NASA Astrophysics Data System (ADS)
Landry, A.; Paranjape, M. B.
2016-06-01
In this paper, we calculate the probability for resonantly inducing transitions in quantum states due to time-dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultracold neutrons, which are organized according to the energy levels of the Schrödinger equation in the presence of the Earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency ω . The driving force is created by oscillating a macroscopic mass in the neighborhood of the system of neutrons. The neutron lifetime is approximately 880 sec while the probability of transitions increases as t2. Hence, the optimal strategy is to drive the system for two lifetimes. The transition amplitude then is of the order of 1.06 ×10-5, and hence with a million ultracold neutrons, one should be able to observe transitions.
SPLASH: Accurate OH maser positions
NASA Astrophysics Data System (ADS)
Walsh, Andrew; Gomez, Jose F.; Jones, Paul; Cunningham, Maria; Green, James; Dawson, Joanne; Ellingsen, Simon; Breen, Shari; Imai, Hiroshi; Lowe, Vicki; Jones, Courtney
2013-10-01
The hydroxyl (OH) 18 cm lines are powerful and versatile probes of diffuse molecular gas, that may trace a largely unstudied component of the Galactic ISM. SPLASH (the Southern Parkes Large Area Survey in Hydroxyl) is a large, unbiased and fully-sampled survey of OH emission, absorption and masers in the Galactic Plane that will achieve sensitivities an order of magnitude better than previous work. In this proposal, we request ATCA time to follow up OH maser candidates. This will give us accurate (~10") positions of the masers, which can be compared to other maser positions from HOPS, MMB and MALT-45 and will provide full polarisation measurements towards a sample of OH masers that have not been observed in MAGMO.
Impedance Scaling for Small Angle Transitions
Stupakov, G.; Bane, Karl; Zagorodnov, I.; /DESY
2010-10-27
Based on the parabolic equation approach to Maxwell's equations we have derived scaling properties of the high frequency impedance/short bunch wakefields of structures. For the special case of small angle transitions we have shown the scaling properties are valid for all frequencies. Using these scaling properties one can greatly reduce the calculation time of the wakefield/impedance of long, small angle, beam pipe transitions, like one often finds in insertion regions of storage rings. We have tested the scaling with wakefield simulations of 2D and 3D models of such transitions, and found that the scaling works well. In modern ring-based light sources one often finds insertion devices having extremely small vertical apertures (on the order of millimeters) to allow for maximal undulator fields reaching the beam. Such insertion devices require that there be beam pipe transitions from these small apertures to the larger cross-sections (normally on the order of centimeters) found in the rest of the ring. The fact that there may be many such transitions, and that these transitions introduce beam pipe discontinuities very close to the beam path, means that their impedance will be large and, in fact, may dominate the impedance budget of the entire ring. To reduce their impact on impedance, the transitions are normally tapered gradually over a long distance. The accurate calculation of the impedance or wakefield of these long transitions, which are typically 3D objects (i.e. they do not have cylindrical symmetry), can be quite a challenging numerical task. In this report we present a method of obtaining the impedance of a long, small angle transition from the calculation of a scaled, shorter one. Normally, the actual calculation is obtained from a time domain simulation of the wakefield in the structure, where the impedance can be obtained by performing a Fourier transform. We shall see that the scaled calculation reduces the computer time and memory requirements
Accurate thickness measurement of graphene
NASA Astrophysics Data System (ADS)
Shearer, Cameron J.; Slattery, Ashley D.; Stapleton, Andrew J.; Shapter, Joseph G.; Gibson, Christopher T.
2016-03-01
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
Accurate thickness measurement of graphene.
Shearer, Cameron J; Slattery, Ashley D; Stapleton, Andrew J; Shapter, Joseph G; Gibson, Christopher T
2016-03-29
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
Holland, J J; de la Torre, J C; Steinhauer, D A; Clarke, D; Duarte, E; Domingo, E
1989-01-01
Monoclonal antibody-resistant mutants have been widely used to estimate virus mutation frequencies. We demonstrate that standard virion neutralization inevitably underestimates monoclonal antibody-resistant mutant genome frequencies of vesicular stomatitis virus, due to phenotypic masking-mixing when wild-type (wt) virions are present in thousandsfold greater numbers. We show that incorporation of antibody into the plaque overlay medium (after virus penetration at 37 degrees C) can provide accurate estimates of genome frequencies of neutral monoclonal antibody-resistant mutant viruses in wt clones. By using this method, we have observed two adjacent G----A base transition frequencies in the I3 epitope to be of the order of 10(-4) in a wt glycine codon. This appears to be slightly lower than the frequencies observed at other sites for total (viable and nonviable) virus genomes when using a direct sequence approach. Images PMID:2479770
ERIC Educational Resources Information Center
Statfeld, Jenna L.
2011-01-01
Post-school transition is the movement of a child with disabilities from school to activities that occur after the completion of school. This paper provides information about: (1) post-school transition; (2) transition plan; (3) transition services; (4) transition planning; (5) vocational rehabilitation services; (6) services that are available…
Hyperfine structure and isotope shifts of transitions in neutral and singly ionized ytterbium
NASA Technical Reports Server (NTRS)
Berends, R. W.; Maleki, L.
1992-01-01
The present experimental investigation of the hyperfine structure and isotopic shifts of transitions in neutral and singly-ionized Yb, which constitute a system of some interest to microwave-frequency standards, used counterpropagating pump and probe laser beams directed through a hollow-cathode discharge lamp. The results obtained are in agreement with previous measurements except in the case of the Yb-173(+) 6 2P0 sub 3/2 state, which is more accurately determined.
NASA Astrophysics Data System (ADS)
Osinowo, Olawale O.; Idowu Olayinka, A.
2012-08-01
Groundwater exploration in either a basement or sedimentary environment is often fairly well defined and focuses on delineating weathered/fractured rocks or saturated formations, respectively. Conversely, unique geological structures, the complex coexistence of different rock types and poorly defined basal/lateral contacts between basement and sedimentary rocks make groundwater development in a geological transition environment very challenging. Ijebu-Ode and its environs lie within such a problematic transition zone, between the Precambrian basement rocks and Cretaceous sediments of the Dahomey Basin, in southwestern Nigeria, where associated acute groundwater development challenges require adequate subsurface information to maximize its groundwater resource potential. This study integrated very low frequency electromagnetic (VLF-EM) and electrical resistivity (ER) geophysical prospecting techniques for a detailed terrain study of Ijebu-Ode in order to establish the reasons for the low groundwater resource potential in the area. Thirty five VLF-EM profiles, 140 vertical electrical soundings (VES) and relevant hydrogeological data were acquired along grids and profiles. Data were filtered, inverted and enhanced using appropriate software packages. The current density and geoelectric parameters of the VLF-EM and VES data were employed to generate terrain maps, the conductivity distribution and a subsurface basement model of the study area. Current density plots and geoelectric parameters identified up to three layers in the basement complex terrain which comprised lateritic topsoil, weathered basement and fresh basement rocks. The five layers encountered in the sedimentary terrain were topsoil, a lateritic unit, a dry sandy unit, a saturated sandy unit and fresh basement rocks. The hydraulic conductivity of the thick (3-18 m) lateritic unit was determined to be 1.32 × 10-5 mm s-1, while that of the underlying sandy units ranged from 2.65 × 10-4 to 1.36 × 10-3 mm
NASA Astrophysics Data System (ADS)
Haswell, Carole A.
2010-07-01
1. Our solar system from afar; 2. Exoplanet discoveries by the transit method; 3. What the transit lightcurve tells us; 4. The transiting exoplanet population; 5. Transmission spectroscopy and Rossiter-McLaughlin effect; 6. Secondary eclipses and phase variations; 7. Transit timing variations and orbital dynamics; 8. Brave new worlds: the future; Index.
Library preparation for highly accurate population sequencing of RNA viruses
Acevedo, Ashley; Andino, Raul
2015-01-01
Circular resequencing (CirSeq) is a novel technique for efficient and highly accurate next-generation sequencing (NGS) of RNA virus populations. The foundation of this approach is the circularization of fragmented viral RNAs, which are then redundantly encoded into tandem repeats by ‘rolling-circle’ reverse transcription. When sequenced, the redundant copies within each read are aligned to derive a consensus sequence of their initial RNA template. This process yields sequencing data with error rates far below the variant frequencies observed for RNA viruses, facilitating ultra-rare variant detection and accurate measurement of low-frequency variants. Although library preparation takes ~5 d, the high-quality data generated by CirSeq simplifies downstream data analysis, making this approach substantially more tractable for experimentalists. PMID:24967624
Note-accurate audio segmentation based on MPEG-7
NASA Astrophysics Data System (ADS)
Wellhausen, Jens
2003-12-01
Segmenting audio data into the smallest musical components is the basis for many further meta data extraction algorithms. For example, an automatic music transcription system needs to know where the exact boundaries of each tone are. In this paper a note accurate audio segmentation algorithm based on MPEG-7 low level descriptors is introduced. For a reliable detection of different notes, both features in the time and the frequency domain are used. Because of this, polyphonic instrument mixes and even melodies characterized by human voices can be examined with this alogrithm. For testing and verification of the note accurate segmentation, a simple music transcription system was implemented. The dominant frequency within each segment is used to build a MIDI file representing the processed audio data.
Accurate Parameter Estimation for Unbalanced Three-Phase System
Chen, Yuan
2014-01-01
Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS. PMID:25162056
Accurate parameter estimation for unbalanced three-phase system.
Chen, Yuan; So, Hing Cheung
2014-01-01
Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS.
Differential equation based method for accurate approximations in optimization
NASA Technical Reports Server (NTRS)
Pritchard, Jocelyn I.; Adelman, Howard M.
1990-01-01
A method to efficiently and accurately approximate the effect of design changes on structural response is described. The key to this method is to interpret sensitivity equations as differential equations that may be solved explicitly for closed form approximations, hence, the method is denoted the Differential Equation Based (DEB) method. Approximations were developed for vibration frequencies, mode shapes and static displacements. The DEB approximation method was applied to a cantilever beam and results compared with the commonly-used linear Taylor series approximations and exact solutions. The test calculations involved perturbing the height, width, cross-sectional area, tip mass, and bending inertia of the beam. The DEB method proved to be very accurate, and in most cases, was more accurate than the linear Taylor series approximation. The method is applicable to simultaneous perturbation of several design variables. Also, the approximations may be used to calculate other system response quantities. For example, the approximations for displacements are used to approximate bending stresses.
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
38 CFR 4.46 - Accurate measurement.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
Efficient Geometric Probabilities of Multi-Transiting Exoplanetary Systems from CORBITS
NASA Astrophysics Data System (ADS)
Brakensiek, Joshua; Ragozzine, Darin
2016-04-01
NASA’s Kepler Space Telescope has successfully discovered thousands of exoplanet candidates using the transit method, including hundreds of stars with multiple transiting planets. In order to estimate the frequency of these valuable systems, it is essential to account for the unique geometric probabilities of detecting multiple transiting extrasolar planets around the same parent star. In order to improve on previous studies that used numerical methods, we have constructed an efficient, semi-analytical algorithm called the Computed Occurrence of Revolving Bodies for the Investigation of Transiting Systems (CORBITS), which, given a collection of conjectured exoplanets orbiting a star, computes the probability that any particular group of exoplanets can be observed to transit. The algorithm applies theorems of elementary differential geometry to compute the areas bounded by circular curves on the surface of a sphere. The implemented algorithm is more accurate and orders of magnitude faster than previous algorithms, based on comparisons with Monte Carlo simulations. We use CORBITS to show that the present solar system would only show a maximum of three transiting planets, but that this varies over time due to dynamical evolution. We also used CORBITS to geometrically debias the period ratio and mutual Hill sphere distributions of Kepler's multi-transiting planet candidates, which results in shifting these distributions toward slightly larger values. In an Appendix, we present additional semi-analytical methods for determining the frequency of exoplanet mutual events, i.e., the geometric probability that two planets will transit each other (planet–planet occultation, relevant to transiting circumbinary planets) and the probability that this transit occurs simultaneously as they transit their star. The CORBITS algorithms and several worked examples are publicly available.
Efficient Geometric Probabilities of Multi-Transiting Exoplanetary Systems from CORBITS
NASA Astrophysics Data System (ADS)
Brakensiek, Joshua; Ragozzine, Darin
2016-04-01
NASA’s Kepler Space Telescope has successfully discovered thousands of exoplanet candidates using the transit method, including hundreds of stars with multiple transiting planets. In order to estimate the frequency of these valuable systems, it is essential to account for the unique geometric probabilities of detecting multiple transiting extrasolar planets around the same parent star. In order to improve on previous studies that used numerical methods, we have constructed an efficient, semi-analytical algorithm called the Computed Occurrence of Revolving Bodies for the Investigation of Transiting Systems (CORBITS), which, given a collection of conjectured exoplanets orbiting a star, computes the probability that any particular group of exoplanets can be observed to transit. The algorithm applies theorems of elementary differential geometry to compute the areas bounded by circular curves on the surface of a sphere. The implemented algorithm is more accurate and orders of magnitude faster than previous algorithms, based on comparisons with Monte Carlo simulations. We use CORBITS to show that the present solar system would only show a maximum of three transiting planets, but that this varies over time due to dynamical evolution. We also used CORBITS to geometrically debias the period ratio and mutual Hill sphere distributions of Kepler's multi-transiting planet candidates, which results in shifting these distributions toward slightly larger values. In an Appendix, we present additional semi-analytical methods for determining the frequency of exoplanet mutual events, i.e., the geometric probability that two planets will transit each other (planet-planet occultation, relevant to transiting circumbinary planets) and the probability that this transit occurs simultaneously as they transit their star. The CORBITS algorithms and several worked examples are publicly available.
Accurate Optical Lattice Clock with {sup 87}Sr Atoms
Le Targat, Rodolphe; Baillard, Xavier; Fouche, Mathilde; Brusch, Anders; Tcherbakoff, Olivier; Rovera, Giovanni D.; Lemonde, Pierre
2006-09-29
We report a frequency measurement of the {sup 1}S{sub 0}-{sup 3}P{sub 0} transition of {sup 87}Sr atoms in an optical lattice clock. The frequency is determined to be 429 228 004 229 879(5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical clocks with neutral atoms in free fall. The two previous measurements of this transition were found to disagree by about 2x10{sup -13}, i.e., almost 4 times the combined error bar and 4 to 5 orders of magnitude larger than the claimed ultimate accuracy of this new type of clocks. Our measurement is in agreement with one of these two values and essentially resolves this discrepancy.
Blackbody radiation shift in the {sup 87}Rb frequency standard
Safronova, M. S.; Jiang Dansha; Safronova, U. I.
2010-08-15
The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature, of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in {sup 87}Rb using the relativistic all-order method and carried out a detailed evaluation of the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly excited states. Our predicted value for the Stark coefficient, k{sub S}=-1.240(4)x10{sup -10} Hz/(V/m){sup 2}, is three times more accurate than the previous calculation [E. J. Angstman, V. A. Dzuba, and V. V. Flambaum, Phys. Rev. A 74, 023405 (2006)].
Mapping the QCD Phase Transition with Accreting Compact Stars
Blaschke, D.; Poghosyan, G.; Grigorian, H.
2008-10-29
We discuss an idea for how accreting millisecond pulsars could contribute to the understanding of the QCD phase transition in the high-density nuclear matter equation of state (EoS). It is based on two ingredients, the first one being a ''phase diagram'' of rapidly rotating compact star configurations in the plane of spin frequency and mass, determined with state-of-the-art hybrid equations of state, allowing for a transition to color superconducting quark matter. The second is the study of spin-up and accretion evolution in this phase diagram. We show that the quark matter phase transition leads to a characteristic line in the {omega}-M plane, the phase border between neutron stars and hybrid stars with a quark matter core. Along this line a drop in the pulsar's moment of inertia entails a waiting point phenomenon in the accreting millisecond pulsar (AMXP) evolution: most of these objects should therefore be found along the phase border in the {omega}-M plane, which may be viewed as the AMXP analog of the main sequence in the Hertzsprung-Russell diagram for normal stars. In order to prove the existence of a high-density phase transition in the cores of compact stars we need population statistics for AMXPs with sufficiently accurate determination of their masses, spin frequencies and magnetic fields.
Moons over Jupiter: transits and shadow transits
NASA Astrophysics Data System (ADS)
Rogers, J. H.; et al.
2003-06-01
There is no more beautiful illustration of orbital motions than the movements of Jupiter's satellites. Every six years, their movements are most strikingly displayed, when the jovian system is presented edge-on to Earth. This means that there is a higher frequency of multiple transits over the face of the planet, as all the moons transit across the equatorial zone, whereas in other years Ganymede and Callisto transit near the poles or not at all. Also, for a few months, the satellites pass in front of each other, displaying mutual eclipses and occultations. In 2002/2003 we have been able to observe a fine series of these multiple and mutual events. On the cover, and on these pages, are some of the highest-resolution images received.
Accurate heart rate estimation from camera recording via MUSIC algorithm.
Fouladi, Seyyed Hamed; Balasingham, Ilangko; Ramstad, Tor Audun; Kansanen, Kimmo
2015-01-01
In this paper, we propose an algorithm to extract heart rate frequency from video camera using the Multiple SIgnal Classification (MUSIC) algorithm. This leads to improved accuracy of the estimated heart rate frequency in cases the performance is limited by the number of samples and frame rate. Monitoring vital signs remotely can be exploited for both non-contact physiological and psychological diagnosis. The color variation recorded by ordinary cameras is used for heart rate monitoring. The orthogonality between signal space and noise space is used to find more accurate heart rate frequency in comparison with traditional methods. It is shown via experimental results that the limitation of previous methods can be overcome by using subspace methods. PMID:26738015
Laser-frequency stabilization using forward scattering
NASA Astrophysics Data System (ADS)
Fellman, T.; Lindberg, Å.; Ståhlberg, B.
1994-12-01
Frequency stabilization of a single-mode dye laser is demonstrated using a simple magneto-optical forward scattering method. The dye laser was locked to the 2p4-3ss2, λ = 633 nm neon transition. Heterodyne beat-frequency measurements against a127I2-He-Ne meter standard laser showed a frequency stability of a few MHz.
Extracting transition rates from zero-polarizability spectroscopy
NASA Astrophysics Data System (ADS)
Zuhrianda, Zuhrianda; Safronova, Marianna S.; Safronova, Ulyana I.; Clark, Charles W.
2016-05-01
Accurate knowledge of atomic properties has been critical for the design and interpretation of experiments, quantifying and reducing uncertainties and decoherence, and development of concepts for next-generation experiments and precision measurement techniques. We predict a sequence of magic-zero wavelengths for which ac Stark shift vanishes for the Sr excited 5 s 5p3P0 state, and provide a general roadmap for extracting transition matrix elements using precise frequency measurements. We demonstrate that such measurements can serve as a best global benchmark of the spectroscopic accuracy that is required for the development of high-precision predictive methods. These magic-zero wavelengths are also needed for state-selective atom manipulation for implementation of quantum logic operations. We also identify five magic wavelengths of the 5s21S0 - 5 s 5 p3P0 Sr clock transition between 350 nm and 500 nm which can also serve as precision benchmarks.
Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien; Cimino, Paola; Penocchio, Emanuele; Puzzarini, Cristina
2015-09-01
The structures and relative stabilities as well as the rotational and vibrational spectra of the three low-energy conformers of pyruvic acid (PA) have been characterized using a state-of-the-art quantum-mechanical approach designed for flexible molecules. By making use of the available experimental rotational constants for several isotopologues of the most stable PA conformer, Tc-PA, the semiexperimental equilibrium structure has been derived. The latter provides a reference for the pure theoretical determination of the equilibrium geometries for all conformers, thus confirming for these structures an accuracy of 0.001 Å and 0.1 deg for bond lengths and angles, respectively. Highly accurate relative energies of all conformers (Tc-, Tt-, and Ct-PA) and of the transition states connecting them are provided along with the thermodynamic properties at low and high temperatures, thus leading to conformational enthalpies accurate to 1 kJ mol(-1). Concerning microwave spectroscopy, rotational constants accurate to about 20 MHz are provided for the Tt- and Ct-PA conformers, together with the computed centrifugal-distortion constants and dipole moments required to simulate their rotational spectra. For Ct-PA, vibrational frequencies in the mid-infrared region accurate to 10 cm(-1) are reported along with theoretical estimates for the transitions in the near-infrared range, and the corresponding infrared spectrum including fundamental transitions, overtones, and combination bands has been simulated. In addition to the new data described above, theoretical results for the Tc- and Tt-PA conformers are compared with all available experimental data to further confirm the accuracy of the hybrid coupled-cluster/density functional theory (CC/DFT) protocol applied in the present study. Finally, we discuss in detail the accuracy of computational models fully based on double-hybrid DFT functionals (mainly at the B2PLYP/aug-cc-pVTZ level) that avoid the use of very expensive CC
Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien; Cimino, Paola; Penocchio, Emanuele; Puzzarini, Cristina
2015-09-01
The structures and relative stabilities as well as the rotational and vibrational spectra of the three low-energy conformers of pyruvic acid (PA) have been characterized using a state-of-the-art quantum-mechanical approach designed for flexible molecules. By making use of the available experimental rotational constants for several isotopologues of the most stable PA conformer, Tc-PA, the semiexperimental equilibrium structure has been derived. The latter provides a reference for the pure theoretical determination of the equilibrium geometries for all conformers, thus confirming for these structures an accuracy of 0.001 Å and 0.1 deg for bond lengths and angles, respectively. Highly accurate relative energies of all conformers (Tc-, Tt-, and Ct-PA) and of the transition states connecting them are provided along with the thermodynamic properties at low and high temperatures, thus leading to conformational enthalpies accurate to 1 kJ mol(-1). Concerning microwave spectroscopy, rotational constants accurate to about 20 MHz are provided for the Tt- and Ct-PA conformers, together with the computed centrifugal-distortion constants and dipole moments required to simulate their rotational spectra. For Ct-PA, vibrational frequencies in the mid-infrared region accurate to 10 cm(-1) are reported along with theoretical estimates for the transitions in the near-infrared range, and the corresponding infrared spectrum including fundamental transitions, overtones, and combination bands has been simulated. In addition to the new data described above, theoretical results for the Tc- and Tt-PA conformers are compared with all available experimental data to further confirm the accuracy of the hybrid coupled-cluster/density functional theory (CC/DFT) protocol applied in the present study. Finally, we discuss in detail the accuracy of computational models fully based on double-hybrid DFT functionals (mainly at the B2PLYP/aug-cc-pVTZ level) that avoid the use of very expensive CC
Benchmarking accurate spectral phase retrieval of single attosecond pulses
NASA Astrophysics Data System (ADS)
Wei, Hui; Le, Anh-Thu; Morishita, Toru; Yu, Chao; Lin, C. D.
2015-02-01
A single extreme-ultraviolet (XUV) attosecond pulse or pulse train in the time domain is fully characterized if its spectral amplitude and phase are both determined. The spectral amplitude can be easily obtained from photoionization of simple atoms where accurate photoionization cross sections have been measured from, e.g., synchrotron radiations. To determine the spectral phase, at present the standard method is to carry out XUV photoionization in the presence of a dressing infrared (IR) laser. In this work, we examine the accuracy of current phase retrieval methods (PROOF and iPROOF) where the dressing IR is relatively weak such that photoelectron spectra can be accurately calculated by second-order perturbation theory. We suggest a modified method named swPROOF (scattering wave phase retrieval by omega oscillation filtering) which utilizes accurate one-photon and two-photon dipole transition matrix elements and removes the approximations made in PROOF and iPROOF. We show that the swPROOF method can in general retrieve accurate spectral phase compared to other simpler models that have been suggested. We benchmark the accuracy of these phase retrieval methods through simulating the spectrogram by solving the time-dependent Schrödinger equation numerically using several known single attosecond pulses with a fixed spectral amplitude but different spectral phases.
Accurate energy levels for singly ionized platinum (Pt II)
NASA Technical Reports Server (NTRS)
Reader, Joseph; Acquista, Nicolo; Sansonetti, Craig J.; Engleman, Rolf, Jr.
1988-01-01
New observations of the spectrum of Pt II have been made with hollow-cathode lamps. The region from 1032 to 4101 A was observed photographically with a 10.7-m normal-incidence spectrograph. The region from 2245 to 5223 A was observed with a Fourier-transform spectrometer. Wavelength measurements were made for 558 lines. The uncertainties vary from 0.0005 to 0.004 A. From these measurements and three parity-forbidden transitions in the infrared, accurate values were determined for 28 even and 72 odd energy levels of Pt II.
NASA Astrophysics Data System (ADS)
Elliott, Ben; Sung, Keeyoon; Brown, Linda; Miller, Charles
2014-06-01
The proliferation and increased abilities of remote sensing missions for the monitoring of planetary atmospheric gas species has spurred the need for complete and accurate spectroscopic reference standards. As a part of our ongoing effort toward creating a global carbon dioxide (CO2) frequency reference standard, we report new FTS measurements of the 17O enriched isotopologues of CO2. The first measurements were taken in the ν3 region (2200 - 2450 cm-1, 65 - 75 THz), have absolute calibration accuracies of 100 kHz (3E-6 cm-1), comparable to the uncertainties for typical sub-millimeter/THz spectroscopy. Such high absolute calibration accuracy has become regular procedure for the cases of linear molecules such as CO2 and CO for FTS measurements at JPL, and enables us to produce measured transition frequencies for entire bands with accuracies that rival those of early heterodyne measurements for individual beat notes. Additionally, by acquiring spectra of multiple carbon dioxide isotopologues simultaneously, we have begun to construct a self-consistent frequency grid based on CO2 that extends from 20 - 200 THz. These new spectroscopic reference standards are a significant step towards minimizing CO2 retrieval errors from remote sensing applications, especially those involving targets with predominantly CO2 atmospheres such as Mars, Venus and candidate terrestrial exoplanets where minor isotopologues will make significant contributions to the radiance signals.
Transition States and transition state analogue interactions with enzymes.
Schramm, Vern L
2015-04-21
Enzymatic transition states have lifetimes of a few femtoseconds (fs). Computational analysis of enzyme motions leading to transition state formation suggests that local catalytic site motions on the fs time scale provide the mechanism to locate transition states. An experimental test of protein fs motion and its relation to transition state formation can be provided by isotopically heavy proteins. Heavy enzymes have predictable mass-altered bond vibration states without altered electrostatic properties, according to the Born-Oppenheimer approximation. On-enzyme chemistry is slowed in most heavy proteins, consistent with altered protein bond frequencies slowing the search for the transition state. In other heavy enzymes, structural changes involved in reactant binding and release are also influenced. Slow protein motions associated with substrate binding and catalytic site preorganization are essential to allow the subsequent fs motions to locate the transition state and to facilitate the efficient release of products. In the catalytically competent geometry, local groups move in stochastic atomic motion on the fs time scale, within transition state-accessible conformations created by slower protein motions. The fs time scale for the transition state motions does not permit thermodynamic equilibrium between the transition state and stable enzyme states. Isotopically heavy enzymes provide a diagnostic tool for fast coupled protein motions to transition state formation and mass-dependent conformational changes. The binding of transition state analogue inhibitors is the opposite in catalytic time scale to formation of the transition state but is related by similar geometries of the enzyme-transition state and enzyme-inhibitor interactions. While enzymatic transition states have lifetimes as short as 10(-15) s, transition state analogues can bind tightly to enzymes with release rates greater than 10(3) s. Tight-binding transition state analogues stabilize the rare but
Extratropical Transitions in Atlantic Canada: Impacts and Adaptive Responses
NASA Astrophysics Data System (ADS)
Masson, Athena; Catto, Norm
2013-04-01
. Storm surge damage occurred along the north shore of the Bonavista Peninsula. Similar effects, differing only in the size of the affected areas, have resulted from several extratropical transitions which have impacted Atlantic Canada since July 1989. Extratropical transition "Leslie" impacted Newfoundland on 10-11 September 2012. Although the area affected was comparable to "Igor", wind velocities and rainfall totals were less, fortunately limiting damage. Preparation, advance warning to the population, proaction, and response efforts all showed significant improvement, however, indicating that the experience gained from coping with "Igor" had been successfully applied in adaptation to "Leslie". Extratropical transitions pose a significantly different set of challenges for adaptation in comparison to purely tropical hurricanes, and responses and adaptation strategies should be tailored to address these specific events. Calculating the frequency, magnitude and intensity of potential shifts is important for accurate forecasting and public awareness, safety management, preparedness, and adaptation. Available data indicate an increase in extratropical frequency and severity in Atlantic Canada since 1991, but there are difficulties in establishing the extent and nature of transition for previous storm events. A cautionary policy would assume no significant changes in extratropical transition frequency for Atlantic Canada, but would also acknowledge that large events remain probable.
Influence of modulation frequency in rubidium cell frequency standards
NASA Technical Reports Server (NTRS)
Audoin, C.; Viennet, J.; Cyr, N.; Vanier, J.
1983-01-01
The error signal which is used to control the frequency of the quartz crystal oscillator of a passive rubidium cell frequency standard is considered. The value of the slope of this signal, for an interrogation frequency close to the atomic transition frequency is calculated and measured for various phase (or frequency) modulation waveforms, and for several values of the modulation frequency. A theoretical analysis is made using a model which applies to a system in which the optical pumping rate, the relaxation rates and the RF field are homogeneous. Results are given for sine-wave phase modulation, square-wave frequency modulation and square-wave phase modulation. The influence of the modulation frequency on the slope of the error signal is specified. It is shown that the modulation frequency can be chosen as large as twice the non-saturated full-width at half-maximum without a drastic loss of the sensitivity to an offset of the interrogation frequency from center line, provided that the power saturation factor and the amplitude of modulation are properly adjusted.
Detection and accurate localization of harmonic chipless tags
NASA Astrophysics Data System (ADS)
Dardari, Davide
2015-12-01
We investigate the detection and localization properties of harmonic tags working at microwave frequencies. A two-tone interrogation signal and a dedicated signal processing scheme at the receiver are proposed to eliminate phase ambiguities caused by the short signal wavelength and to provide accurate distance/position estimation even in the presence of clutter and multipath. The theoretical limits on tag detection and localization accuracy are investigated starting from a concise characterization of harmonic backscattered signals. Numerical results show that accuracies in the order of centimeters are feasible within an operational range of a few meters in the RFID UHF band.
Mill profiler machines soft materials accurately
NASA Technical Reports Server (NTRS)
Rauschl, J. A.
1966-01-01
Mill profiler machines bevels, slots, and grooves in soft materials, such as styrofoam phenolic-filled cores, to any desired thickness. A single operator can accurately control cutting depths in contour or straight line work.
ERIC Educational Resources Information Center
Naylor, Mary; Keating, Stacen A.
2008-01-01
Transitional care encompasses a broad range of services and environments designed to promote the safe and timely passage of patients between levels of health care and across care settings. High-quality transitional care is especially important for older adults with multiple chronic conditions and complex therapeutic regimens, as well as for their…
Graves, Barbara W; Haley, Mary Mumford
2013-01-01
The transition from intrauterine to extrauterine life is a complex adaptation. Although, in a sense, the entire time in utero is in preparation for this transition, there are many specific anatomic and physiologic changes that take place in the weeks and days leading up to labor that facilitate a healthy transition. Some, including increasing pulmonary vasculature and blood flow, are part of an ongoing process of maturation. Others, such as a reversal in the lung from secreting fluid to absorbing fluid and the secretion of pulmonary surfactant, are associated with the hormonal milieu that occurs when spontaneous labor is impending. Interventions such as elective cesarean birth or induction of labor may interfere with this preparation for birth. Postnatal interventions such as immediate clamping of the umbilical cord and oropharyngeal suction may also compromise the normal process of newborn transition. This article reviews the physiology of the fetal to newborn transition and explores interventions that may facilitate or hinder the optimal process.
Electrical Conductivity in Transition Metals
ERIC Educational Resources Information Center
Talbot, Christopher; Vickneson, Kishanda
2013-01-01
The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence…
Active Faraday optical frequency standard.
Zhuang, Wei; Chen, Jingbiao
2014-11-01
We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks. PMID:25361349
Active Faraday optical frequency standard.
Zhuang, Wei; Chen, Jingbiao
2014-11-01
We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks.
NASA Astrophysics Data System (ADS)
Sun, Wenjun; Jiang, Song; Xu, Kun; Li, Shu
2015-12-01
This paper presents an extension of previous work (Sun et al., 2015 [22]) of the unified gas kinetic scheme (UGKS) for the gray radiative transfer equations to the frequency-dependent (multi-group) radiative transfer system. Different from the gray radiative transfer equations, where the optical opacity is only a function of local material temperature, the simulation of frequency-dependent radiative transfer is associated with additional difficulties from the frequency-dependent opacity. For the multiple frequency radiation, the opacity depends on both the spatial location and the frequency. For example, the opacity is typically a decreasing function of frequency. At the same spatial region the transport physics can be optically thick for the low frequency photons, and optically thin for high frequency ones. Therefore, the optical thickness is not a simple function of space location. In this paper, the UGKS for frequency-dependent radiative system is developed. The UGKS is a finite volume method and the transport physics is modeled according to the ratio of the cell size to the photon's frequency-dependent mean free path. When the cell size is much larger than the photon's mean free path, a diffusion solution for such a frequency radiation will be obtained. On the other hand, when the cell size is much smaller than the photon's mean free path, a free transport mechanism will be recovered. In the regime between the above two limits, with the variation of the ratio between the local cell size and photon's mean free path, the UGKS provides a smooth transition in the physical and frequency space to capture the corresponding transport physics accurately. The seemingly straightforward extension of the UGKS from the gray to multiple frequency radiation system is due to its intrinsic consistent multiple scale transport modeling, but it still involves lots of work to properly discretize the multiple groups in order to design an asymptotic preserving (AP) scheme in all
NASA Astrophysics Data System (ADS)
Beach, R.; Albrecht, G.; Mitchell, S.; Comaskey, B.; Solarz, R.; Krupke, William F.; Brandle, C.; Berkstresser, G.
1990-01-01
A ground state depleted (GSD) laser has been demonstrated at 912 nm in the form of a Q-switched oscillator operating on the Nd(3+) F-4(sub 3/2) - I-4(sub 9/2) transition in Y2SiO5. Samarium scandium gallium garnet has been demonstrated effective at selectively suppressing the competing and much stronger F-4(sub 3/2) - I-4(sub 11/2) lasing transition. Efficient harmonic generation has been demonstrated using non-critically phase matched KNbO3.
Beach, R.; Albrecht, G.; Mitchell, S.; Comaskey, B.; Solarz, R.; Krupke, W. ); Brandle, C.; Berkstresser, G. )
1990-01-01
A ground state depleted (GSD) laser has been demonstrated at 912 nm in the form of a Q-switched oscillator operating on the Nd{sup 3+}{sup 4}F{sub 3/2}-{sup 4}I{sub 9/2} transition in Y{sub 2}SiO{sub 5}. Samarium scandium gallium garnet has been demonstrated effective at selectively suppressing the competing and much stronger {sup 4}F{sub 3/2}-{sup 4}I{sub 11/2} lasing transition. Efficient harmonic generation has been demonstrated using non-critically phase matched KNbO{sub 3}. 15 refs., 15 figs., 3 tabs.
Laboratory rotational ground state transitions of NH3D+ and CF+
NASA Astrophysics Data System (ADS)
Stoffels, A.; Kluge, L.; Schlemmer, S.; Brünken, S.
2016-09-01
Aims: This paper reports accurate laboratory frequencies of the rotational ground state transitions of two astronomically relevant molecular ions, NH3D+ and CF+. Methods: Spectra in the millimetre-wave band were recorded by the method of rotational state-selective attachment of He atoms to the molecular ions stored and cooled in a cryogenic ion trap held at 4 K. The lowest rotational transition in the A state (ortho state) of NH3D+ (JK = 10-00), and the two hyperfine components of the ground state transition of CF+ (J = 1-0) were measured with a relative precision better than 10-7. Results: For both target ions, the experimental transition frequencies agree with recent observations of the same lines in different astronomical environments. In the case of NH3D+ the high-accuracy laboratory measurements lend support to its tentative identification in the interstellar medium. For CF+ the experimentally determined hyperfine splitting confirms previous quantum-chemical calculations and the intrinsic spectroscopic nature of a double-peaked line profile observed in the J = 1-0 transition towards the Horsehead photon-dominated region (PDR).
The Supported Teen: Transitioning to High School
ERIC Educational Resources Information Center
Dorman, Benton
2012-01-01
Transition plans for students with special needs provide support for social and academic success while giving students an accurate picture of what to expect in high school. The Texas Comprehensive Center recommends that schools develop a comprehensive transition plan district-wide. This district plan must include the cooperation of staff from the…
Middle Grades Transition Programs around the Globe
ERIC Educational Resources Information Center
Andrews, Colin; Bishop, Penny
2012-01-01
Transitions into and out of the middle grades can be challenging for many reasons. Students need to acclimate to new policies, practices, and buildings; teachers require accurate data about their new students' capacities; and families must navigate relationships with new personnel. All school transitions present different and, at times, puzzling…
NASA Astrophysics Data System (ADS)
Chun, Byung Jae; Kang, Hyun Jay; Kim, Young-Jin; Kim, Seung-Woo
2016-03-01
Generating multiple optical frequencies referenced to the frequency standard is an important task in optical clock dissemination and optical communication. An apparatus for frequency-comb-referenced generation of multiple optical frequencies is demonstrated for high-precision free-space transfer of multiple optical frequencies. The relative linewidth and frequency instability at each channel corresponds to sub-1 Hz and 1.06×10-15 at 10 s averaging time, respectively. During the free-space transfer, the refractive index change of transmission media caused by atmospheric turbulences induces phase and frequency noise on optical frequencies. These phase and frequency noise causes induced linewidth broadening and frequency shift in optical frequencies which can disturb the accurate frequency transfer. The proposed feedback loop with acousto-optic modulator can monitor and compensate phase/frequency noise on optical frequencies. As a result, a frequency-comb-referenced single optical mode is compensated with a high signal to noise ratio (SNR) of 80 dB. By sharing the same optical paths, this feedback loop is confirmed to be successfully transferred to the neighboring wavelength channels (a 100 GHz spaced channel). This result confirms our proposed system can transfer optical frequencies to the remote site in free-space without performance degradation.
Can blind persons accurately assess body size from the voice?
Pisanski, Katarzyna; Oleszkiewicz, Anna; Sorokowska, Agnieszka
2016-04-01
Vocal tract resonances provide reliable information about a speaker's body size that human listeners use for biosocial judgements as well as speech recognition. Although humans can accurately assess men's relative body size from the voice alone, how this ability is acquired remains unknown. In this study, we test the prediction that accurate voice-based size estimation is possible without prior audiovisual experience linking low frequencies to large bodies. Ninety-one healthy congenitally or early blind, late blind and sighted adults (aged 20-65) participated in the study. On the basis of vowel sounds alone, participants assessed the relative body sizes of male pairs of varying heights. Accuracy of voice-based body size assessments significantly exceeded chance and did not differ among participants who were sighted, or congenitally blind or who had lost their sight later in life. Accuracy increased significantly with relative differences in physical height between men, suggesting that both blind and sighted participants used reliable vocal cues to size (i.e. vocal tract resonances). Our findings demonstrate that prior visual experience is not necessary for accurate body size estimation. This capacity, integral to both nonverbal communication and speech perception, may be present at birth or may generalize from broader cross-modal correspondences. PMID:27095264
Differential equation based method for accurate approximations in optimization
NASA Technical Reports Server (NTRS)
Pritchard, Jocelyn I.; Adelman, Howard M.
1990-01-01
This paper describes a method to efficiently and accurately approximate the effect of design changes on structural response. The key to this new method is to interpret sensitivity equations as differential equations that may be solved explicitly for closed form approximations, hence, the method is denoted the Differential Equation Based (DEB) method. Approximations were developed for vibration frequencies, mode shapes and static displacements. The DEB approximation method was applied to a cantilever beam and results compared with the commonly-used linear Taylor series approximations and exact solutions. The test calculations involved perturbing the height, width, cross-sectional area, tip mass, and bending inertia of the beam. The DEB method proved to be very accurate, and in msot cases, was more accurate than the linear Taylor series approximation. The method is applicable to simultaneous perturbation of several design variables. Also, the approximations may be used to calculate other system response quantities. For example, the approximations for displacement are used to approximate bending stresses.
A variable-frequency local oscillator for the frequency-hopping technique
NASA Technical Reports Server (NTRS)
Stitt, G. R.; Johnson, L. J.
1986-01-01
The frequency hopping technique described elsewhere requires the use of a local oscillator whose output frequency may be rapidly and accurately changed by a fixed frequency increment. Such a device, capable of producing 16 different frequencies separated by 50 kHz over the range of 35.02 to 35.77 MHz, has been built for the Urbana MST (mesosphere stratosphere troposphere) radar facility. The design and construction of that device is described and illustrated.
EMR Gage Would Measure Coal Thickness Accurately
NASA Technical Reports Server (NTRS)
King, J. D.; Rollwitz, W. L.
1982-01-01
Laboratory tests indicate electron magnetic resonance (EMR) would be effective in measuring thickness of coal overlying rock substrate. In prototype dual-frequency EMR system, Sample is irradiated by two radio frequencies. Signals are mixed, producing sum and difference output frequencies that are detected by receiver. Magnetic field is varied to scan resonant spot through sample. In system designed for field use, electromagnet is U-shaped, so that sample can be adjacent to, rather than inside the probe. Same coil is used for transmitting and receiving.
Observation of transitions in lithiumlike germanium
NASA Technical Reports Server (NTRS)
Behring, W. E.; Seely, J. F.; Brown, C. M.; Feldman, U.; Knauer, J. P.
1989-01-01
Transitions of the type n = 2-2, n = 2-3 and n = 3-4 in Li-like Ge(29+) have been observed in the spectrum from a laser-produced plasma. The energy levels and ionization energy of Ge(29+) were derived from the observed wavelengths. The wavelength of the 2s 2S1/2-2p 2P3/2 transition is sufficiently accurate to determine the quantum-electrodynamic contribution to the transition energy.
Modified chemiluminescent NO analyzer accurately measures NOX
NASA Technical Reports Server (NTRS)
Summers, R. L.
1978-01-01
Installation of molybdenum nitric oxide (NO)-to-higher oxides of nitrogen (NOx) converter in chemiluminescent gas analyzer and use of air purge allow accurate measurements of NOx in exhaust gases containing as much as thirty percent carbon monoxide (CO). Measurements using conventional analyzer are highly inaccurate for NOx if as little as five percent CO is present. In modified analyzer, molybdenum has high tolerance to CO, and air purge substantially quenches NOx destruction. In test, modified chemiluminescent analyzer accurately measured NO and NOx concentrations for over 4 months with no denegration in performance.
NASA Technical Reports Server (NTRS)
Audoin, Claude; Dimarcq, N.; Giordano, V.; Viennet, J.
1990-01-01
When observed in a cesium beam frequency standard, the hyperfine transition frequency of the atoms differs slightly from the invariant transition frequency of the unperturbed atoms at rest. The various physical and technical origins of the frequency offsets are stated. They relate to fundamental physical effects, to the method of probing the atomic resonance and to the frequency control of the slaved oscillator. The variation of the frequency offsets under a change of the value of the internal operating characteristics is considered. The sensitivity to a change of the magnetic induction, the microwave power, and the temperature is given. A comparison is made of the sensitivity of cesium beam frequency standards of the commercially available type, making use of magnetic state selection, and of devices under study, in which the state preparation and detection is accomplished optically. The pathways between the external stimuli and the physical origin of the frequency offsets are specified.
Can Appraisers Rate Work Performance Accurately?
ERIC Educational Resources Information Center
Hedge, Jerry W.; Laue, Frances J.
The ability of individuals to make accurate judgments about others is examined and literature on this subject is reviewed. A wide variety of situational factors affects the appraisal of performance. It is generally accepted that the purpose of the appraisal influences the accuracy of the appraiser. The instrumentation, or tools, available to the…
Accurate pointing of tungsten welding electrodes
NASA Technical Reports Server (NTRS)
Ziegelmeier, P.
1971-01-01
Thoriated-tungsten is pointed accurately and quickly by using sodium nitrite. Point produced is smooth and no effort is necessary to hold the tungsten rod concentric. The chemically produced point can be used several times longer than ground points. This method reduces time and cost of preparing tungsten electrodes.
Accurate oscillator strengths for interstellar ultraviolet lines of Cl I
NASA Technical Reports Server (NTRS)
Schectman, R. M.; Federman, S. R.; Beideck, D. J.; Ellis, D. J.
1993-01-01
Analyses on the abundance of interstellar chlorine rely on accurate oscillator strengths for ultraviolet transitions. Beam-foil spectroscopy was used to obtain f-values for the astrophysically important lines of Cl I at 1088, 1097, and 1347 A. In addition, the line at 1363 A was studied. Our f-values for 1088, 1097 A represent the first laboratory measurements for these lines; the values are f(1088)=0.081 +/- 0.007 (1 sigma) and f(1097) = 0.0088 +/- 0.0013 (1 sigma). These results resolve the issue regarding the relative strengths for 1088, 1097 A in favor of those suggested by astronomical measurements. For the other lines, our results of f(1347) = 0.153 +/- 0.011 (1 sigma) and f(1363) = 0.055 +/- 0.004 (1 sigma) are the most precisely measured values available. The f-values are somewhat greater than previous experimental and theoretical determinations.
Accurate finite difference methods for time-harmonic wave propagation
NASA Technical Reports Server (NTRS)
Harari, Isaac; Turkel, Eli
1994-01-01
Finite difference methods for solving problems of time-harmonic acoustics are developed and analyzed. Multidimensional inhomogeneous problems with variable, possibly discontinuous, coefficients are considered, accounting for the effects of employing nonuniform grids. A weighted-average representation is less sensitive to transition in wave resolution (due to variable wave numbers or nonuniform grids) than the standard pointwise representation. Further enhancement in method performance is obtained by basing the stencils on generalizations of Pade approximation, or generalized definitions of the derivative, reducing spurious dispersion, anisotropy and reflection, and by improving the representation of source terms. The resulting schemes have fourth-order accurate local truncation error on uniform grids and third order in the nonuniform case. Guidelines for discretization pertaining to grid orientation and resolution are presented.
AN ACCURATE FLUX DENSITY SCALE FROM 1 TO 50 GHz
Perley, R. A.; Butler, B. J. E-mail: BButler@nrao.edu
2013-02-15
We develop an absolute flux density scale for centimeter-wavelength astronomy by combining accurate flux density ratios determined by the Very Large Array between the planet Mars and a set of potential calibrators with the Rudy thermophysical emission model of Mars, adjusted to the absolute scale established by the Wilkinson Microwave Anisotropy Probe. The radio sources 3C123, 3C196, 3C286, and 3C295 are found to be varying at a level of less than {approx}5% per century at all frequencies between 1 and 50 GHz, and hence are suitable as flux density standards. We present polynomial expressions for their spectral flux densities, valid from 1 to 50 GHz, with absolute accuracy estimated at 1%-3% depending on frequency. Of the four sources, 3C286 is the most compact and has the flattest spectral index, making it the most suitable object on which to establish the spectral flux density scale. The sources 3C48, 3C138, 3C147, NGC 7027, NGC 6542, and MWC 349 show significant variability on various timescales. Polynomial coefficients for the spectral flux density are developed for 3C48, 3C138, and 3C147 for each of the 17 observation dates, spanning 1983-2012. The planets Venus, Uranus, and Neptune are included in our observations, and we derive their brightness temperatures over the same frequency range.
Accurate estimators of correlation functions in Fourier space
NASA Astrophysics Data System (ADS)
Sefusatti, E.; Crocce, M.; Scoccimarro, R.; Couchman, H. M. P.
2016-08-01
Efficient estimators of Fourier-space statistics for large number of objects rely on fast Fourier transforms (FFTs), which are affected by aliasing from unresolved small-scale modes due to the finite FFT grid. Aliasing takes the form of a sum over images, each of them corresponding to the Fourier content displaced by increasing multiples of the sampling frequency of the grid. These spurious contributions limit the accuracy in the estimation of Fourier-space statistics, and are typically ameliorated by simultaneously increasing grid size and discarding high-frequency modes. This results in inefficient estimates for e.g. the power spectrum when desired systematic biases are well under per cent level. We show that using interlaced grids removes odd images, which include the dominant contribution to aliasing. In addition, we discuss the choice of interpolation kernel used to define density perturbations on the FFT grid and demonstrate that using higher order interpolation kernels than the standard Cloud-In-Cell algorithm results in significant reduction of the remaining images. We show that combining fourth-order interpolation with interlacing gives very accurate Fourier amplitudes and phases of density perturbations. This results in power spectrum and bispectrum estimates that have systematic biases below 0.01 per cent all the way to the Nyquist frequency of the grid, thus maximizing the use of unbiased Fourier coefficients for a given grid size and greatly reducing systematics for applications to large cosmological data sets.
Improved calculations of the lowest vibrational transitions in HeH{sup +}
Bubin, Sergiy; Stanke, Monika; Kedziera, Dariusz; Adamowicz, Ludwik
2007-08-15
More accurate variational calculations of the lowest three pure vibrational states (v=0,1,2) of the {sup 4}HeH{sup +} molecular ion have been carried out without assuming the Born-Oppenheimer approximation. In the calculations we included the complete set of {alpha}{sup 2} relativistic corrections, i.e., mass-velocity, Darwin, spin-spin, and orbit-orbit. This allowed us to improve the agreement between the theory and the experiment for the vibrational frequencies of the 1{yields}0 and 2{yields}1 transitions as compared to our previous calculations [Stanke et al., Phys. Rev. Lett. 96, 233002 (2006)].
A new model for broadband waveguide to microstrip transition design
NASA Technical Reports Server (NTRS)
Ponchak, George E.; Downey, Alan N.
1986-01-01
A new model is presented which permits the prediction of the resonant frequencies created by antipodal finline waveguide to microstrip transitions. The transition is modeled as a tapered transmission line in series with an infinite set of coupled resonant circuits. The resonant circuits are modeled as simple microwave resonant cavities of which the resonant frequencies are easily determined. The model is developed and the resonant frequencies determined for several different transitions. Experimental results are given to confirm the models.
Estimations of uncertainties of frequencies
NASA Astrophysics Data System (ADS)
Eyer, Laurent; Nicoletti, Jean-Marc; Morgenthaler, Stephan
2015-08-01
Diverse variable phenomena in the Universe are periodic. Astonishingly many of the periodic signals present in stars have timescales coinciding with human ones (from minutes to years). The periods of signals often have to be deduced from time series which are irregularly sampled and sparse, furthermore correlations between the brightness measurements and their estimated uncertainties are common.The uncertainty on the frequency estimation is reviewed. We explore the astronomical and statistical literature, in both cases of regular and irregular samplings. The frequency uncertainty is depending on signal to noise ratio, the frequency, the observational timespan. The shape of the light curve should also intervene, since sharp features such as exoplanet transits, stellar eclipses, raising branches of pulsation stars give stringent constraints.We propose several procedures (parametric and nonparametric) to estimate the uncertainty on the frequency which are subsequently tested against simulated data to assess their performances.
Kinetic simulation of the sheath dynamics in the intermediate radio frequency regime
NASA Astrophysics Data System (ADS)
Shihab, M.; Elgendy, A. T.; Korolov, I.; Derzsi, A.; Schulze, J.; Eremin, D.; Mussenbrock, T.; Donkó, Z.; Brinkmann, R. P.
2013-10-01
The dynamics of temporally modulated plasma boundary sheaths is studied in the intermediate radio frequency regime where the applied radio frequency and the ion plasma frequency (or the reciprocal of the ion transit time) are comparable. Two fully kinetic simulation algorithms are employed and their results are compared. The first is a realization of the well-known particle-in-cell technique with Monte Carlo collisions and simulates the entire discharge, a planar radio frequency capacitively coupled plasma with an additional ionization source. The second code is based on the recently published scheme Ensemble-in-Spacetime (EST); it resolves only the sheath and requires the time-resolved voltage across and the ion flux into the sheath as input. Ion inertia causes a temporal asymmetry (hysteresis) of the charge-voltage relation; other ion transit time effects are also found. The two algorithms are in good agreement, both with respect to the spatial and temporal dynamics of the sheath and with respect to the ion energy distributions at the electrodes. It is concluded that the EST scheme may serve as an efficient post-processor for fluid or global simulations and for measurements: it can rapidly and accurately calculate ion distribution functions even when no genuine kinetic information is available.
ERIC Educational Resources Information Center
Badami, Rokhsareh; VaezMousavi, Mohammad; Wulf, Gabriele; Namazizadeh, Mahdi
2012-01-01
One purpose of the present study was to examine whether self-confidence or anxiety would be differentially affected by feedback from more accurate rather than less accurate trials. The second purpose was to determine whether arousal variations (activation) would predict performance. On Day 1, participants performed a golf putting task under one of…
Accurate Anharmonic IR Spectra from Integrated Cc/dft Approach
NASA Astrophysics Data System (ADS)
Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien; Carnimeo, Ivan; Puzzarini, Cristina
2014-06-01
The recent implementation of the computation of infrared (IR) intensities beyond the double harmonic approximation [1] paved the route to routine calculations of infrared spectra for a wide set of molecular systems. Contrary to common beliefs, second-order perturbation theory is able to deliver results of high accuracy provided that anharmonic resonances are properly managed [1,2]. It has been already shown for several small closed- and open shell molecular systems that the differences between coupled cluster (CC) and DFT anharmonic wavenumbers are mainly due to the harmonic terms, paving the route to introduce effective yet accurate hybrid CC/DFT schemes [2]. In this work we present that hybrid CC/DFT models can be applied also to the IR intensities leading to the simulation of highly accurate fully anharmonic IR spectra for medium-size molecules, including ones of atmospheric interest, showing in all cases good agreement with experiment even in the spectral ranges where non-fundamental transitions are predominant[3]. [1] J. Bloino and V. Barone, J. Chem. Phys. 136, 124108 (2012) [2] V. Barone, M. Biczysko, J. Bloino, Phys. Chem. Chem. Phys., 16, 1759-1787 (2014) [3] I. Carnimeo, C. Puzzarini, N. Tasinato, P. Stoppa, A. P. Charmet, M. Biczysko, C. Cappelli and V. Barone, J. Chem. Phys., 139, 074310 (2013)
NASA Technical Reports Server (NTRS)
Constantinides, E. D.; Marhefka, R. J.
1992-01-01
The incomplete Airy integrals serve as canonical functions for the uniform ray optical solutions to several high frequency scattering and diffraction problems that involve a class of integrals characterized by two stationary points that are arbitrarily close to one another or to an integration endpoint. Integrals of such analytical properties describe transition region phenomena associated with composite shadow boundaries. An efficient and accurate method for computing the incomplete Airy functions would make the solutions to such problems useful for engineering purposes. Here, a convergent series solution form for the incomplete Airy functions is derived. Asymptotic expansions involving several terms were also developed and serve as large argument approximations. The combination of the series solution form with the asymptotic formulae provides for an efficient and accurate computation of the incomplete Airy functions. Validation of accuracy is accomplished using direct numerical integration data.
Badami, Rokhsareh; VaezMousavi, Mohammad; Wulf, Gabriele; Namazizadeh, Mahdi
2012-06-01
One purpose of the present study was to examine whether self-confidence or anxiety would be differentially affected byfeedback from more accurate rather than less accurate trials. The second purpose was to determine whether arousal variations (activation) would predict performance. On day 1, participants performed a golf putting task under one of two conditions: one group received feedback on the most accurate trials, whereas another group received feedback on the least accurate trials. On day 2, participants completed an anxiety questionnaire and performed a retention test. Shin conductance level, as a measure of arousal, was determined. The results indicated that feedback about more accurate trials resulted in more effective learning as well as increased self-confidence. Also, activation was a predictor of performance. PMID:22808705
Cerebral cortical activity associated with non-experts' most accurate motor performance.
Dyke, Ford; Godwin, Maurice M; Goel, Paras; Rehm, Jared; Rietschel, Jeremy C; Hunt, Carly A; Miller, Matthew W
2014-10-01
This study's specific aim was to determine if non-experts' most accurate motor performance is associated with verbal-analytic- and working memory-related cerebral cortical activity during motor preparation. To assess this, EEG was recorded from non-expert golfers executing putts; EEG spectral power and coherence were calculated for the epoch preceding putt execution; and spectral power and coherence for the five most accurate putts were contrasted with that for the five least accurate. Results revealed marked power in the theta frequency bandwidth at all cerebral cortical regions for the most accurate putts relative to the least accurate, and considerable power in the low-beta frequency bandwidth at the left temporal region for the most accurate compared to the least. As theta power is associated with working memory and low-beta power at the left temporal region with verbal analysis, results suggest non-experts' most accurate motor performance is associated with verbal-analytic- and working memory-related cerebral cortical activity during motor preparation. PMID:25058623
NASA Technical Reports Server (NTRS)
1992-01-01
This report describes NASA's metric transition in terms of seven major program elements. Six are technical areas involving research, technology development, and operations; they are managed by specific Program Offices at NASA Headquarters. The final program element, Institutional Management, covers both NASA-wide functional management under control of NASA Headquarters and metric capability development at the individual NASA Field Installations. This area addresses issues common to all NASA program elements, including: Federal, state, and local coordination; standards; private industry initiatives; public-awareness initiatives; and employee training. The concluding section identifies current barriers and impediments to metric transition; NASA has no specific recommendations for consideration by the Congress.
Two highly accurate methods for pitch calibration
NASA Astrophysics Data System (ADS)
Kniel, K.; Härtig, F.; Osawa, S.; Sato, O.
2009-11-01
Among profiles, helix and tooth thickness pitch is one of the most important parameters of an involute gear measurement evaluation. In principle, coordinate measuring machines (CMM) and CNC-controlled gear measuring machines as a variant of a CMM are suited for these kinds of gear measurements. Now the Japan National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) and the German national metrology institute the Physikalisch-Technische Bundesanstalt (PTB) have each developed independently highly accurate pitch calibration methods applicable to CMM or gear measuring machines. Both calibration methods are based on the so-called closure technique which allows the separation of the systematic errors of the measurement device and the errors of the gear. For the verification of both calibration methods, NMIJ/AIST and PTB performed measurements on a specially designed pitch artifact. The comparison of the results shows that both methods can be used for highly accurate calibrations of pitch standards.
Accurate guitar tuning by cochlear implant musicians.
Lu, Thomas; Huang, Juan; Zeng, Fan-Gang
2014-01-01
Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼ 30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task. PMID:24651081
Accurate Guitar Tuning by Cochlear Implant Musicians
Lu, Thomas; Huang, Juan; Zeng, Fan-Gang
2014-01-01
Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task. PMID:24651081
Preparation and accurate measurement of pure ozone.
Janssen, Christof; Simone, Daniela; Guinet, Mickaël
2011-03-01
Preparation of high purity ozone as well as precise and accurate measurement of its pressure are metrological requirements that are difficult to meet due to ozone decomposition occurring in pressure sensors. The most stable and precise transducer heads are heated and, therefore, prone to accelerated ozone decomposition, limiting measurement accuracy and compromising purity. Here, we describe a vacuum system and a method for ozone production, suitable to accurately determine the pressure of pure ozone by avoiding the problem of decomposition. We use an inert gas in a particularly designed buffer volume and can thus achieve high measurement accuracy and negligible degradation of ozone with purities of 99.8% or better. The high degree of purity is ensured by comprehensive compositional analyses of ozone samples. The method may also be applied to other reactive gases. PMID:21456766
Accurate guitar tuning by cochlear implant musicians.
Lu, Thomas; Huang, Juan; Zeng, Fan-Gang
2014-01-01
Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼ 30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task.
Accurate modeling of parallel scientific computations
NASA Technical Reports Server (NTRS)
Nicol, David M.; Townsend, James C.
1988-01-01
Scientific codes are usually parallelized by partitioning a grid among processors. To achieve top performance it is necessary to partition the grid so as to balance workload and minimize communication/synchronization costs. This problem is particularly acute when the grid is irregular, changes over the course of the computation, and is not known until load time. Critical mapping and remapping decisions rest on the ability to accurately predict performance, given a description of a grid and its partition. This paper discusses one approach to this problem, and illustrates its use on a one-dimensional fluids code. The models constructed are shown to be accurate, and are used to find optimal remapping schedules.
Line gas sampling system ensures accurate analysis
Not Available
1992-06-01
Tremendous changes in the natural gas business have resulted in new approaches to the way natural gas is measured. Electronic flow measurement has altered the business forever, with developments in instrumentation and a new sensitivity to the importance of proper natural gas sampling techniques. This paper reports that YZ Industries Inc., Snyder, Texas, combined its 40 years of sampling experience with the latest in microprocessor-based technology to develop the KynaPak 2000 series, the first on-line natural gas sampling system that is both compact and extremely accurate. This means the composition of the sampled gas must be representative of the whole and related to flow. If so, relative measurement and sampling techniques are married, gas volumes are accurately accounted for and adjustments to composition can be made.
Accurate mask model for advanced nodes
NASA Astrophysics Data System (ADS)
Zine El Abidine, Nacer; Sundermann, Frank; Yesilada, Emek; Ndiaye, El Hadji Omar; Mishra, Kushlendra; Paninjath, Sankaranarayanan; Bork, Ingo; Buck, Peter; Toublan, Olivier; Schanen, Isabelle
2014-07-01
Standard OPC models consist of a physical optical model and an empirical resist model. The resist model compensates the optical model imprecision on top of modeling resist development. The optical model imprecision may result from mask topography effects and real mask information including mask ebeam writing and mask process contributions. For advanced technology nodes, significant progress has been made to model mask topography to improve optical model accuracy. However, mask information is difficult to decorrelate from standard OPC model. Our goal is to establish an accurate mask model through a dedicated calibration exercise. In this paper, we present a flow to calibrate an accurate mask enabling its implementation. The study covers the different effects that should be embedded in the mask model as well as the experiment required to model them.
Accurate Molecular Polarizabilities Based on Continuum Electrostatics
Truchon, Jean-François; Nicholls, Anthony; Iftimie, Radu I.; Roux, Benoît; Bayly, Christopher I.
2013-01-01
A novel approach for representing the intramolecular polarizability as a continuum dielectric is introduced to account for molecular electronic polarization. It is shown, using a finite-difference solution to the Poisson equation, that the Electronic Polarization from Internal Continuum (EPIC) model yields accurate gas-phase molecular polarizability tensors for a test set of 98 challenging molecules composed of heteroaromatics, alkanes and diatomics. The electronic polarization originates from a high intramolecular dielectric that produces polarizabilities consistent with B3LYP/aug-cc-pVTZ and experimental values when surrounded by vacuum dielectric. In contrast to other approaches to model electronic polarization, this simple model avoids the polarizability catastrophe and accurately calculates molecular anisotropy with the use of very few fitted parameters and without resorting to auxiliary sites or anisotropic atomic centers. On average, the unsigned error in the average polarizability and anisotropy compared to B3LYP are 2% and 5%, respectively. The correlation between the polarizability components from B3LYP and this approach lead to a R2 of 0.990 and a slope of 0.999. Even the F2 anisotropy, shown to be a difficult case for existing polarizability models, can be reproduced within 2% error. In addition to providing new parameters for a rapid method directly applicable to the calculation of polarizabilities, this work extends the widely used Poisson equation to areas where accurate molecular polarizabilities matter. PMID:23646034
Accurate phase-shift velocimetry in rock.
Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R; Holmes, William M
2016-06-01
Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models. PMID:27111139
Accurate phase-shift velocimetry in rock
NASA Astrophysics Data System (ADS)
Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R.; Holmes, William M.
2016-06-01
Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.
Accurate phase-shift velocimetry in rock.
Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R; Holmes, William M
2016-06-01
Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.
Polishing-To-Figuring Transition In Turned Optics
NASA Astrophysics Data System (ADS)
Brown, Norman J.; Baker, Phillip C.; Parks, Robert E.
1982-03-01
The spatial frequency response of elastic backed flexible lapping belts is examined. The transition from planing off to propagating sinusoidal ripple is shown to be extremely sensitive to ripple frequency.
Generating clock signals for a cycle accurate, cycle reproducible FPGA based hardware accelerator
Asaad, Sameth W.; Kapur, Mohit
2016-01-05
A method, system and computer program product are disclosed for generating clock signals for a cycle accurate FPGA based hardware accelerator used to simulate operations of a device-under-test (DUT). In one embodiment, the DUT includes multiple device clocks generating multiple device clock signals at multiple frequencies and at a defined frequency ratio; and the FPG hardware accelerator includes multiple accelerator clocks generating multiple accelerator clock signals to operate the FPGA hardware accelerator to simulate the operations of the DUT. In one embodiment, operations of the DUT are mapped to the FPGA hardware accelerator, and the accelerator clock signals are generated at multiple frequencies and at the defined frequency ratio of the frequencies of the multiple device clocks, to maintain cycle accuracy between the DUT and the FPGA hardware accelerator. In an embodiment, the FPGA hardware accelerator may be used to control the frequencies of the multiple device clocks.
Repumping and spectroscopy of laser-cooled Sr atoms using the (5s5p)3P2-(5s4d)3D2 transition
NASA Astrophysics Data System (ADS)
Mickelson, P. G.; Martinez de Escobar, Y. N.; Anzel, P.; De Salvo, B. J.; Nagel, S. B.; Traverso, A. J.; Yan, M.; Killian, T. C.
2009-12-01
We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms using the (5s5p)3P2-(5s4d)3D2 transition. Atom number in a magneto-optical trap is enhanced by driving this transition because Sr atoms that have decayed into the (5s5p)3P2 dark state are repumped back into the (5s2)1S0 ground state. Spectroscopy of 84Sr, 86Sr, 87Sr and 88Sr improves the value of the (5s5p)3P2-(5s4d)3D2 transition frequency and determines the isotope shifts for the transition accurately enough to guide laser-cooling experiments with less abundant isotopes.
Spectroscopically Accurate Line Lists for Application in Sulphur Chemistry
NASA Astrophysics Data System (ADS)
Underwood, D. S.; Azzam, A. A. A.; Yurchenko, S. N.; Tennyson, J.
2013-09-01
Monitoring sulphur chemistry is thought to be of great importance for exoplanets. Doing this requires detailed knowledge of the spectroscopic properties of sulphur containing molecules such as hydrogen sulphide (H2S) [1], sulphur dioxide (SO2), and sulphur trioxide (SO3). Each of these molecules can be found in terrestrial environments, produced in volcano emissions on Earth, and analysis of their spectroscopic data can prove useful to the characterisation of exoplanets, as well as the study of planets in our own solar system, with both having a possible presence on Venus. A complete, high temperature list of line positions and intensities for H32 2 S is presented. The DVR3D program suite is used to calculate the bound ro-vibration energy levels, wavefunctions, and dipole transition intensities using Radau coordinates. The calculations are based on a newly determined, spectroscopically refined potential energy surface (PES) and a new, high accuracy, ab initio dipole moment surface (DMS). Tests show that the PES enables us to calculate the line positions accurately and the DMS gives satisfactory results for line intensities. Comparisons with experiment as well as with previous theoretical spectra will be presented. The results of this study will form an important addition to the databases which are considered as sources of information for space applications; especially, in analysing the spectra of extrasolar planets, and remote sensing studies for Venus and Earth, as well as laboratory investigations and pollution studies. An ab initio line list for SO3 was previously computed using the variational nuclear motion program TROVE [2], and was suitable for modelling room temperature SO3 spectra. The calculations considered transitions in the region of 0-4000 cm-1 with rotational states up to J = 85, and includes 174,674,257 transitions. A list of 10,878 experimental transitions had relative intensities placed on an absolute scale, and were provided in a form suitable
Theoretical Studies of Atomic Transitions
Charlotte Froese Fischer
2005-07-08
Atomic structure calculations were performed for properties such as energy levels, binding energies, transition probabilities, lifetimes, hyperfine structure, and isotope shifts. Accurate computational procedures were devised so that properties could be predicted even when they could not be obtained from experiment, and to assist in the identification of observed data. The method used was the multiconfiguration Hartree-Fock (MCHF) method, optionally corrected for relativistic effects in the Breit-Pauli approximation. Fully relativistic Dirac-Fock calculations also were performed using the GRASP code A database of energy levels, lifetimes, and transition probabilities was designed and implemented and, at present, includes many results for Be-like to Ar-like.
X-Ray Transition Energies Database
National Institute of Standards and Technology Data Gateway
SRD 128 X-Ray Transition Energies Database (Web, free access) This X-ray transition table provides the energies and wavelengths for the K and L transitions connecting energy levels having principal quantum numbers n = 1, 2, 3, and 4. The elements covered include Z = 10, neon to Z = 100, fermium. There are two unique features of this data base: (1) a serious attempt to have all experimental values on a scale consistent with the International System of measurement (the SI) and (2) inclusion of accurate theoretical estimates for all transitions.
Mixing and Transition Control Studied
NASA Technical Reports Server (NTRS)
1996-01-01
Considerable progress in understanding nonlinear phenomena in both unbounded and wallbounded shear flow transition has been made through the use of a combination of high- Reynolds-number asymptotic and numerical methods. The objective of this continuing work is to fully understand the nonlinear dynamics so that ultimately (1) an effective means of mixing and transition control can be developed and (2) the source terms in the aeroacoustic noise problem can be modeled more accurately. Two important aspects of the work are that (1) the disturbances evolve from strictly linear instability waves on weakly nonparallel mean flows so that the proper upstream conditions are applied in the nonlinear or wave-interaction streamwise region and (2) the asymptotic formulations lead to parabolic problems so that the question of proper out-flow boundary conditions--still a research issue for direct numerical simulations of convectively unstable shear flows--does not arise. Composite expansion techniques are used to obtain solutions that account for both mean-flow-evolution and nonlinear effects. A previously derived theory for the amplitude evolution of a two-dimensional instability wave in an incompressible mixing layer (which is in quantitative agreement with available experimental data for the first nonlinear saturation stage for a plane-jet shear layer, a circular-jet shear layer, and a mixing layer behind a splitter plate) have been extended to include a wave-interaction stage with a three-dimensional subharmonic. The ultimate wave interaction effects can either give rise to explosive growth or an equilibrium solution, both of which are intimately associated with the nonlinear self-interaction of the three dimensional component. The extended theory is being evaluated numerically. In contrast to the mixing-layer situation, earlier comparisons of theoretical predictions based on asymptotic methods and experiments in wall-bounded shear-flow transition have been somewhat lacking
Isomerism of Cyanomethanimine: Accurate Structural, Energetic, and Spectroscopic Characterization.
Puzzarini, Cristina
2015-11-25
The structures, relative stabilities, and rotational and vibrational parameters of the Z-C-, E-C-, and N-cyanomethanimine isomers have been evaluated using state-of-the-art quantum-chemical approaches. Equilibrium geometries have been calculated by means of a composite scheme based on coupled-cluster calculations that accounts for the extrapolation to the complete basis set limit and core-correlation effects. The latter approach is proved to provide molecular structures with an accuracy of 0.001-0.002 Å and 0.05-0.1° for bond lengths and angles, respectively. Systematically extrapolated ab initio energies, accounting for electron correlation through coupled-cluster theory, including up to single, double, triple, and quadruple excitations, and corrected for core-electron correlation and anharmonic zero-point vibrational energy, have been used to accurately determine relative energies and the Z-E isomerization barrier with an accuracy of about 1 kJ/mol. Vibrational and rotational spectroscopic parameters have been investigated by means of hybrid schemes that allow us to obtain rotational constants accurate to about a few megahertz and vibrational frequencies with a mean absolute error of ∼1%. Where available, for all properties considered, a very good agreement with experimental data has been observed.
Accurately Mapping M31's Microlensing Population
NASA Astrophysics Data System (ADS)
Crotts, Arlin
2004-07-01
We propose to augment an existing microlensing survey of M31 with source identifications provided by a modest amount of ACS {and WFPC2 parallel} observations to yield an accurate measurement of the masses responsible for microlensing in M31, and presumably much of its dark matter. The main benefit of these data is the determination of the physical {or "einstein"} timescale of each microlensing event, rather than an effective {"FWHM"} timescale, allowing masses to be determined more than twice as accurately as without HST data. The einstein timescale is the ratio of the lensing cross-sectional radius and relative velocities. Velocities are known from kinematics, and the cross-section is directly proportional to the {unknown} lensing mass. We cannot easily measure these quantities without knowing the amplification, hence the baseline magnitude, which requires the resolution of HST to find the source star. This makes a crucial difference because M31 lens m ass determinations can be more accurate than those towards the Magellanic Clouds through our Galaxy's halo {for the same number of microlensing events} due to the better constrained geometry in the M31 microlensing situation. Furthermore, our larger survey, just completed, should yield at least 100 M31 microlensing events, more than any Magellanic survey. A small amount of ACS+WFPC2 imaging will deliver the potential of this large database {about 350 nights}. For the whole survey {and a delta-function mass distribution} the mass error should approach only about 15%, or about 6% error in slope for a power-law distribution. These results will better allow us to pinpoint the lens halo fraction, and the shape of the halo lens spatial distribution, and allow generalization/comparison of the nature of halo dark matter in spiral galaxies. In addition, we will be able to establish the baseline magnitude for about 50, 000 variable stars, as well as measure an unprecedentedly deta iled color-magnitude diagram and luminosity
Accurate upwind methods for the Euler equations
NASA Technical Reports Server (NTRS)
Huynh, Hung T.
1993-01-01
A new class of piecewise linear methods for the numerical solution of the one-dimensional Euler equations of gas dynamics is presented. These methods are uniformly second-order accurate, and can be considered as extensions of Godunov's scheme. With an appropriate definition of monotonicity preservation for the case of linear convection, it can be shown that they preserve monotonicity. Similar to Van Leer's MUSCL scheme, they consist of two key steps: a reconstruction step followed by an upwind step. For the reconstruction step, a monotonicity constraint that preserves uniform second-order accuracy is introduced. Computational efficiency is enhanced by devising a criterion that detects the 'smooth' part of the data where the constraint is redundant. The concept and coding of the constraint are simplified by the use of the median function. A slope steepening technique, which has no effect at smooth regions and can resolve a contact discontinuity in four cells, is described. As for the upwind step, existing and new methods are applied in a manner slightly different from those in the literature. These methods are derived by approximating the Euler equations via linearization and diagonalization. At a 'smooth' interface, Harten, Lax, and Van Leer's one intermediate state model is employed. A modification for this model that can resolve contact discontinuities is presented. Near a discontinuity, either this modified model or a more accurate one, namely, Roe's flux-difference splitting. is used. The current presentation of Roe's method, via the conceptually simple flux-vector splitting, not only establishes a connection between the two splittings, but also leads to an admissibility correction with no conditional statement, and an efficient approximation to Osher's approximate Riemann solver. These reconstruction and upwind steps result in schemes that are uniformly second-order accurate and economical at smooth regions, and yield high resolution at discontinuities.
Accurate measurement of unsteady state fluid temperature
NASA Astrophysics Data System (ADS)
Jaremkiewicz, Magdalena
2016-07-01
In this paper, two accurate methods for determining the transient fluid temperature were presented. Measurements were conducted for boiling water since its temperature is known. At the beginning the thermometers are at the ambient temperature and next they are immediately immersed into saturated water. The measurements were carried out with two thermometers of different construction but with the same housing outer diameter equal to 15 mm. One of them is a K-type industrial thermometer widely available commercially. The temperature indicated by the thermometer was corrected considering the thermometers as the first or second order inertia devices. The new design of a thermometer was proposed and also used to measure the temperature of boiling water. Its characteristic feature is a cylinder-shaped housing with the sheath thermocouple located in its center. The temperature of the fluid was determined based on measurements taken in the axis of the solid cylindrical element (housing) using the inverse space marching method. Measurements of the transient temperature of the air flowing through the wind tunnel using the same thermometers were also carried out. The proposed measurement technique provides more accurate results compared with measurements using industrial thermometers in conjunction with simple temperature correction using the inertial thermometer model of the first or second order. By comparing the results, it was demonstrated that the new thermometer allows obtaining the fluid temperature much faster and with higher accuracy in comparison to the industrial thermometer. Accurate measurements of the fast changing fluid temperature are possible due to the low inertia thermometer and fast space marching method applied for solving the inverse heat conduction problem.
The first accurate description of an aurora
NASA Astrophysics Data System (ADS)
Schröder, Wilfried
2006-12-01
As technology has advanced, the scientific study of auroral phenomena has increased by leaps and bounds. A look back at the earliest descriptions of aurorae offers an interesting look into how medieval scholars viewed the subjects that we study.Although there are earlier fragmentary references in the literature, the first accurate description of the aurora borealis appears to be that published by the German Catholic scholar Konrad von Megenberg (1309-1374) in his book Das Buch der Natur (The Book of Nature). The book was written between 1349 and 1350.
New law requires 'medically accurate' lesson plans.
1999-09-17
The California Legislature has passed a bill requiring all textbooks and materials used to teach about AIDS be medically accurate and objective. Statements made within the curriculum must be supported by research conducted in compliance with scientific methods, and published in peer-reviewed journals. Some of the current lesson plans were found to contain scientifically unsupported and biased information. In addition, the bill requires material to be "free of racial, ethnic, or gender biases." The legislation is supported by a wide range of interests, but opposed by the California Right to Life Education Fund, because they believe it discredits abstinence-only material.
Accurate density functional thermochemistry for larger molecules.
Raghavachari, K.; Stefanov, B. B.; Curtiss, L. A.; Lucent Tech.
1997-06-20
Density functional methods are combined with isodesmic bond separation reaction energies to yield accurate thermochemistry for larger molecules. Seven different density functionals are assessed for the evaluation of heats of formation, Delta H 0 (298 K), for a test set of 40 molecules composed of H, C, O and N. The use of bond separation energies results in a dramatic improvement in the accuracy of all the density functionals. The B3-LYP functional has the smallest mean absolute deviation from experiment (1.5 kcal mol/f).
New law requires 'medically accurate' lesson plans.
1999-09-17
The California Legislature has passed a bill requiring all textbooks and materials used to teach about AIDS be medically accurate and objective. Statements made within the curriculum must be supported by research conducted in compliance with scientific methods, and published in peer-reviewed journals. Some of the current lesson plans were found to contain scientifically unsupported and biased information. In addition, the bill requires material to be "free of racial, ethnic, or gender biases." The legislation is supported by a wide range of interests, but opposed by the California Right to Life Education Fund, because they believe it discredits abstinence-only material. PMID:11366835
Universality: Accurate Checks in Dyson's Hierarchical Model
NASA Astrophysics Data System (ADS)
Godina, J. J.; Meurice, Y.; Oktay, M. B.
2003-06-01
In this talk we present high-accuracy calculations of the susceptibility near βc for Dyson's hierarchical model in D = 3. Using linear fitting, we estimate the leading (γ) and subleading (Δ) exponents. Independent estimates are obtained by calculating the first two eigenvalues of the linearized renormalization group transformation. We found γ = 1.29914073 ± 10 -8 and, Δ = 0.4259469 ± 10-7 independently of the choice of local integration measure (Ising or Landau-Ginzburg). After a suitable rescaling, the approximate fixed points for a large class of local measure coincide accurately with a fixed point constructed by Koch and Wittwer.
NASA Astrophysics Data System (ADS)
Twagirayezu, Sylvestre; Cich, Matthew J.; Sears, Trevor J.; McRaven, Christopher P.; Hall, Gregory E.
2015-10-01
Doppler-free transition frequencies for v4- and v5-excited hot bands have been measured in the v1 + v3 band region of the spectrum of acetylene using saturation dip spectroscopy with an extended cavity diode laser referenced to a frequency comb. The frequency accuracy of the measured transitions, as judged from line shape model fits and comparison to known frequencies in the v1 + v3 band itself, is between 3 and 22 kHz. This is some three orders of magnitude improvement on the accuracy and precision of previous line position estimates that were derived from the analysis of high-resolution Fourier transform infrared absorption spectra. Comparison to transition frequencies computed from constants derived from published Fourier transform infrared spectra shows that some upper rotational energy levels suffer specific perturbations causing energy level shifts of up to several hundred MHz. These perturbations are due to energy levels of the same rotational quantum number derived from nearby vibrational levels that become degenerate at specific energies. Future identification of the perturbing levels will provide accurate relative energies of excited vibrational levels of acetylene in the 7100-7600 cm-1 energy region.
Tasinato, Nicola; Duxbury, Geoffrey; Langford, Nigel; Hay, Kenneth G
2010-01-28
Information about intermolecular potentials is usually obtained through the analysis of the absorption line shapes recorded in the frequency domain. This approach is also adopted to study the effects of motional narrowing and speed dependence of the pressure broadening coefficients. On the other hand, time domain measurements are directly related to molecular collisions and are therefore frequently employed to study molecular relaxation rates, as well as the effects of velocity changing collisions and the speed dependence of the absorption cross sections. Intrapulse quantum cascade laser spectrometers are able to produce both saturation and molecular alignment of the gas sample. This is due to the rapid sweep of the radiation through the absorption features. In the present work the frequency down-chirped radiation emitted by an intrapulsed quantum cascade laser operating near 7.8 mum is employed to investigate the collisional relaxation processes, and the collisional narrowing, in the 15(0,15)<--16(1,16) and 15(1,15)<--16(0,16) doublet in the water vapor nu(2) band. The effects of He, Ne, Ar, N(2), and CO(2) as collisional partners are investigated. The experimental results clearly indicate the dependence of the collisional cross sections upon the chirp rate. They also demonstrate that by using different chirp rates it is possible to gain information about the intermolecular processes driving the molecular collisions and the related energy transfer.
Frequency spectrum analyzer with phase-lock
Boland, Thomas J.
1984-01-01
A frequency-spectrum analyzer with phase-lock for analyzing the frequency and amplitude of an input signal is comprised of a voltage controlled oscillator (VCO) which is driven by a ramp generator, and a phase error detector circuit. The phase error detector circuit measures the difference in phase between the VCO and the input signal, and drives the VCO locking it in phase momentarily with the input signal. The input signal and the output of the VCO are fed into a correlator which transfers the input signal to a frequency domain, while providing an accurate absolute amplitude measurement of each frequency component of the input signal.
Low frequency acoustic and electromagnetic scattering
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Maccamy, R. C.
1986-01-01
This paper deals with two classes of problems arising from acoustics and electromagnetics scattering in the low frequency stations. The first class of problem is solving Helmholtz equation with Dirichlet boundary conditions on an arbitrary two dimensional body while the second one is an interior-exterior interface problem with Helmholtz equation in the exterior. Low frequency analysis show that there are two intermediate problems which solve the above problems accurate to 0(k/2/ log k) where k is the frequency. These solutions greatly differ from the zero frequency approximations. For the Dirichlet problem numerical examples are shown to verify the theoretical estimates.
Low frequency acoustic and electromagnetic scattering
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Maccamy, R. C.
1983-01-01
This paper deals with two classes of problems arising from acoustics and electromagnetics scattering in the low frequency stations. The first class of problem is solving Helmholtz equation with Dirichlet boundary conditions on an arbitrary two dimensional body while the second one is an interior-exterior interface problem with Helmholtz equation in the exterior. Low frequency analysis show that there are two intermediate problems which solve the above problems accurate to 0(k(2) log k) where k is the frequency. These solutions greatly differ from the zero frequency approximations. For the Dirichlet problem numerical examples are shown to verify the theoretical estimates.
Mattei, Jean-François; Troit, Virginie
2016-02-01
In two centuries, modern humanitarian action has experienced several fractures often linked to crises. Although its professionalism and intervention force remain indisputable, it faces, since the 2000s, a new context that limits its ability to act and confronts it with new dilemmas, even though it must deal with needs for aid of unprecedented scale. These difficulties reveal a humanitarian transition period that was not anticipated. This transition period reflects the change from a dominant paradigm of North-South solidarity of Western origin to a much more complex model. This article provides a summary of the current mutations that are dominated by the States' assertion of sovereignty. Among the possible solutions, it argues for an ethical approach and a better integration of the research carried out in the Global South, prerequisites for building a true partnership and placing the victims at the heart of the operations which involve them. PMID:26936180
ERIC Educational Resources Information Center
Gallick, Barb; Lee, Lisa
2010-01-01
Adults often find themselves transitioning from one activity to another in a short time span. Most of the time, they do not feel they have a lot of control over their schedules, but wish that they could carve out extended time to relax and focus on one project. Picture a group of children in the block area who have spent 15 or 20 minutes building…
Improved Tracking of an Atomic-Clock Resonance Transition
NASA Technical Reports Server (NTRS)
Prestage, John D.; Chung, Sang K.; Tu, Meirong
2010-01-01
An improved method of making an electronic oscillator track the frequency of an atomic-clock resonance transition is based on fitting a theoretical nonlinear curve to measurements at three oscillator frequencies within the operational frequency band of the transition (in other words, at three points within the resonance peak). In the measurement process, the frequency of a microwave oscillator is repeatedly set at various offsets from the nominal resonance frequency, the oscillator signal is applied in a square pulse of the oscillator signal having a suitable duration (typically, of the order of a second), and, for each pulse at each frequency offset, fluorescence photons of the transition in question are counted. As described below, the counts are used to determine a new nominal resonance frequency. Thereafter, offsets are determined with respect to the new resonance frequency. The process as described thus far is repeated so as to repeatedly adjust the oscillator to track the most recent estimate of the nominal resonance frequency.
Accurate shear measurement with faint sources
Zhang, Jun; Foucaud, Sebastien; Luo, Wentao E-mail: walt@shao.ac.cn
2015-01-01
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.
Accurate basis set truncation for wavefunction embedding
NASA Astrophysics Data System (ADS)
Barnes, Taylor A.; Goodpaster, Jason D.; Manby, Frederick R.; Miller, Thomas F.
2013-07-01
Density functional theory (DFT) provides a formally exact framework for performing embedded subsystem electronic structure calculations, including DFT-in-DFT and wavefunction theory-in-DFT descriptions. In the interest of efficiency, it is desirable to truncate the atomic orbital basis set in which the subsystem calculation is performed, thus avoiding high-order scaling with respect to the size of the MO virtual space. In this study, we extend a recently introduced projection-based embedding method [F. R. Manby, M. Stella, J. D. Goodpaster, and T. F. Miller III, J. Chem. Theory Comput. 8, 2564 (2012)], 10.1021/ct300544e to allow for the systematic and accurate truncation of the embedded subsystem basis set. The approach is applied to both covalently and non-covalently bound test cases, including water clusters and polypeptide chains, and it is demonstrated that errors associated with basis set truncation are controllable to well within chemical accuracy. Furthermore, we show that this approach allows for switching between accurate projection-based embedding and DFT embedding with approximate kinetic energy (KE) functionals; in this sense, the approach provides a means of systematically improving upon the use of approximate KE functionals in DFT embedding.
Accurate determination of characteristic relative permeability curves
NASA Astrophysics Data System (ADS)
Krause, Michael H.; Benson, Sally M.
2015-09-01
A recently developed technique to accurately characterize sub-core scale heterogeneity is applied to investigate the factors responsible for flowrate-dependent effective relative permeability curves measured on core samples in the laboratory. The dependency of laboratory measured relative permeability on flowrate has long been both supported and challenged by a number of investigators. Studies have shown that this apparent flowrate dependency is a result of both sub-core scale heterogeneity and outlet boundary effects. However this has only been demonstrated numerically for highly simplified models of porous media. In this paper, flowrate dependency of effective relative permeability is demonstrated using two rock cores, a Berea Sandstone and a heterogeneous sandstone from the Otway Basin Pilot Project in Australia. Numerical simulations of steady-state coreflooding experiments are conducted at a number of injection rates using a single set of input characteristic relative permeability curves. Effective relative permeability is then calculated from the simulation data using standard interpretation methods for calculating relative permeability from steady-state tests. Results show that simplified approaches may be used to determine flowrate-independent characteristic relative permeability provided flow rate is sufficiently high, and the core heterogeneity is relatively low. It is also shown that characteristic relative permeability can be determined at any typical flowrate, and even for geologically complex models, when using accurate three-dimensional models.
How Accurately can we Calculate Thermal Systems?
Cullen, D; Blomquist, R N; Dean, C; Heinrichs, D; Kalugin, M A; Lee, M; Lee, Y; MacFarlan, R; Nagaya, Y; Trkov, A
2004-04-20
I would like to determine how accurately a variety of neutron transport code packages (code and cross section libraries) can calculate simple integral parameters, such as K{sub eff}, for systems that are sensitive to thermal neutron scattering. Since we will only consider theoretical systems, we cannot really determine absolute accuracy compared to any real system. Therefore rather than accuracy, it would be more precise to say that I would like to determine the spread in answers that we obtain from a variety of code packages. This spread should serve as an excellent indicator of how accurately we can really model and calculate such systems today. Hopefully, eventually this will lead to improvements in both our codes and the thermal scattering models that they use in the future. In order to accomplish this I propose a number of extremely simple systems that involve thermal neutron scattering that can be easily modeled and calculated by a variety of neutron transport codes. These are theoretical systems designed to emphasize the effects of thermal scattering, since that is what we are interested in studying. I have attempted to keep these systems very simple, and yet at the same time they include most, if not all, of the important thermal scattering effects encountered in a large, water-moderated, uranium fueled thermal system, i.e., our typical thermal reactors.
Accurate Stellar Parameters for Exoplanet Host Stars
NASA Astrophysics Data System (ADS)
Brewer, John Michael; Fischer, Debra; Basu, Sarbani; Valenti, Jeff A.
2015-01-01
A large impedement to our understanding of planet formation is obtaining a clear picture of planet radii and densities. Although determining precise ratios between planet and stellar host are relatively easy, determining accurate stellar parameters is still a difficult and costly undertaking. High resolution spectral analysis has traditionally yielded precise values for some stellar parameters but stars in common between catalogs from different authors or analyzed using different techniques often show offsets far in excess of their uncertainties. Most analyses now use some external constraint, when available, to break observed degeneracies between surface gravity, effective temperature, and metallicity which can otherwise lead to correlated errors in results. However, these external constraints are impossible to obtain for all stars and can require more costly observations than the initial high resolution spectra. We demonstrate that these discrepencies can be mitigated by use of a larger line list that has carefully tuned atomic line data. We use an iterative modeling technique that does not require external constraints. We compare the surface gravity obtained with our spectral synthesis modeling to asteroseismically determined values for 42 Kepler stars. Our analysis agrees well with only a 0.048 dex offset and an rms scatter of 0.05 dex. Such accurate stellar gravities can reduce the primary source of uncertainty in radii by almost an order of magnitude over unconstrained spectral analysis.
Different ways to active optical frequency standards
NASA Astrophysics Data System (ADS)
Pan, Duo; Xue, Xiaobo; Zhang, Xiaogang; Chen, Jingbiao
2016-06-01
Active optical frequency standard, or active optical clock, is a new concept of optical frequency standard, where a weak feedback with phase coherence information in optical bad-cavity limitation is formed, and the continuous self-sustained coherent stimulated emission between two atomic transition levels with population inversion is realized. Through ten years of both theoretical and experimental exploration, the narrow linewidth and suppression of cavity pulling effect of active optical frequency standard have been initially proved. In this paper, after a simple review, we will mainly present the most recent experimental progresses of active optical frequency standards in Peking University, including 4-level cesium active optical frequency standards and active Faraday optical frequency standards. The future development of active optical frequency standards is also discussed.
Hermetic optical-fiber iodine frequency standard.
Light, Philip S; Anstie, James D; Benabid, Fetah; Luiten, Andre N
2015-06-15
We have built an optical-frequency standard based on interrogating iodine vapor that has been trapped within the hollow core of a hermetically sealed kagome-lattice photonic crystal fiber. A frequency-doubled Nd:YAG laser locked to a hyperfine component of the P(142)37-0 I_{2}127 transition using modulation transfer spectroscopy shows a frequency stability of 3×10(-11) at 100 s. We discuss the impediments in integrating this all-fiber standard into a fully optical-fiber-based system, and suggest approaches that could improve performance of the frequency standard substantially.
An impedimetric approach for accurate particle sizing using a microfluidic Coulter counter
NASA Astrophysics Data System (ADS)
Jagtiani, Ashish V.; Carletta, Joan; Zhe, Jiang
2011-04-01
In this paper, we present the design, impedimetric characterization and testing of a microfabricated Coulter counter for particle size measurement that uses a pair of thin film coplanar Au/Ti electrodes. An electrical equivalent circuit model of the designed device is analyzed. Accurate measurement of particle size was achieved by operating the device at a frequency for which the overall impedance is dominated by the channel resistance. A combination of design features, including the use of a pair of sensing electrodes with a surface area of 100 µm by 435 µm, a spacing of 1785 µm between the two sensing electrodes and a 350 µm long microchannel, ensures that this resistance dominates over a range of relatively low frequencies. The device was characterized for NaCl electrolyte solutions with different ionic concentrations ranging from 10-5 to 0.1 M. Results proved that the resistive behavior of the sensor occurs over a range of relatively low frequencies for all tested concentrations. The Coulter counter was then used to detect 30 µm polystyrene particles at a selected excitation frequency. Testing results demonstrated that the device can accurately measure particle sizes with small error. The design can be extended to ac Coulter counters with sub-micron sensing channels. Analysis of three designs of ac Coulter counters including sub-micron sensing channels using the electrical equivalent circuit model predicts that they can be operated at even lower frequencies, to accurately size nanoscale particles.
RSRM Chamber Pressure Oscillations: Transit Time Models and Unsteady CFD
NASA Technical Reports Server (NTRS)
Nesman, Tom; Stewart, Eric
1996-01-01
Space Shuttle solid rocket motor low frequency internal pressure oscillations have been observed since early testing. The same type of oscillations also are present in the redesigned solid rocket motor (RSRM). The oscillations, which occur during RSRM burn, are predominantly at the first three motor cavity longitudinal acoustic mode frequencies. Broadband flow and combustion noise provide the energy to excite these modes at low levels throughout motor burn, however, at certain times during burn the fluctuating pressure amplitude increases significantly. The increased fluctuations at these times suggests an additional excitation mechanism. The RSRM has inhibitors on the propellant forward facing surface of each motor segment. The inhibitors are in a slot at the segment field joints to prevent burning at that surface. The aft facing segment surface at a field joint slot burns and forms a cavity of time varying size. Initially the inhibitor is recessed in the field joint cavity. As propellant burns away the inhibitor begins to protrude into the bore flow. Two mechanisms (transit time models) that are considered potential pressure oscillation excitations are cavity-edge tones, and inhibitor hole-tones. Estimates of frequency variation with time of longitudinal acoustic modes, cavity edge-tones, and hole-tones compare favorably with frequencies measured during motor hot firing. It is believed that the highest oscillation amplitudes occur when vortex shedding frequencies coincide with motor longitudinal acoustic modes. A time accurate computational fluid dynamic (CFD) analysis was made to replicate the observations from motor firings and to observe the transit time mechanisms in detail. FDNS is the flow solver used to detail the time varying aspects of the flow. The fluid is approximated as a single-phase ideal gas. The CFD model was an axisymmetric representation of the RSRM at 80 seconds into burn.Deformation of the inhibitors by the internal flow was determined
NASA Astrophysics Data System (ADS)
Rudin, Stephen; Divani, Afshin; Wakhloo, Ajay K.; Lieber, Baruch B.; Granger, William; Bednarek, Daniel R.; Yang, Chang-Ying J.
1998-07-01
Detailed cerebrovascular blood flow can be more accurately determined radiographically from the new droplet tracking method previously introduced by the authors than from standard soluble contrast techniques. For example, arteriovenous malformation (AVM) transit times which are crucial for proper glue embolization treatments, were shown to be about half when using droplets compared to those measured using soluble contrast techniques. In this work, factors such as x-ray pulse duration, frame rate, system spatial resolution (focal spot size), droplet size, droplet and system contrast parameters, and system noise are considered in relation to their affect on the accurate determination of droplet location and velocity.
Highly accurate articulated coordinate measuring machine
Bieg, Lothar F.; Jokiel, Jr., Bernhard; Ensz, Mark T.; Watson, Robert D.
2003-12-30
Disclosed is a highly accurate articulated coordinate measuring machine, comprising a revolute joint, comprising a circular encoder wheel, having an axis of rotation; a plurality of marks disposed around at least a portion of the circumference of the encoder wheel; bearing means for supporting the encoder wheel, while permitting free rotation of the encoder wheel about the wheel's axis of rotation; and a sensor, rigidly attached to the bearing means, for detecting the motion of at least some of the marks as the encoder wheel rotates; a probe arm, having a proximal end rigidly attached to the encoder wheel, and having a distal end with a probe tip attached thereto; and coordinate processing means, operatively connected to the sensor, for converting the output of the sensor into a set of cylindrical coordinates representing the position of the probe tip relative to a reference cylindrical coordinate system.
Toward Accurate and Quantitative Comparative Metagenomics.
Nayfach, Stephen; Pollard, Katherine S
2016-08-25
Shotgun metagenomics and computational analysis are used to compare the taxonomic and functional profiles of microbial communities. Leveraging this approach to understand roles of microbes in human biology and other environments requires quantitative data summaries whose values are comparable across samples and studies. Comparability is currently hampered by the use of abundance statistics that do not estimate a meaningful parameter of the microbial community and biases introduced by experimental protocols and data-cleaning approaches. Addressing these challenges, along with improving study design, data access, metadata standardization, and analysis tools, will enable accurate comparative metagenomics. We envision a future in which microbiome studies are replicable and new metagenomes are easily and rapidly integrated with existing data. Only then can the potential of metagenomics for predictive ecological modeling, well-powered association studies, and effective microbiome medicine be fully realized. PMID:27565341
Apparatus for accurately measuring high temperatures
Smith, Douglas D.
1985-01-01
The present invention is a thermometer used for measuring furnace temperaes in the range of about 1800.degree. to 2700.degree. C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.
Apparatus for accurately measuring high temperatures
Smith, D.D.
The present invention is a thermometer used for measuring furnace temperatures in the range of about 1800/sup 0/ to 2700/sup 0/C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.
Micron Accurate Absolute Ranging System: Range Extension
NASA Technical Reports Server (NTRS)
Smalley, Larry L.; Smith, Kely L.
1999-01-01
The purpose of this research is to investigate Fresnel diffraction as a means of obtaining absolute distance measurements with micron or greater accuracy. It is believed that such a system would prove useful to the Next Generation Space Telescope (NGST) as a non-intrusive, non-contact measuring system for use with secondary concentrator station-keeping systems. The present research attempts to validate past experiments and develop ways to apply the phenomena of Fresnel diffraction to micron accurate measurement. This report discusses past research on the phenomena, and the basis of the use Fresnel diffraction distance metrology. The apparatus used in the recent investigations, experimental procedures used, preliminary results are discussed in detail. Continued research and equipment requirements on the extension of the effective range of the Fresnel diffraction systems is also described.
Accurate metacognition for visual sensory memory representations.
Vandenbroucke, Annelinde R E; Sligte, Ilja G; Barrett, Adam B; Seth, Anil K; Fahrenfort, Johannes J; Lamme, Victor A F
2014-04-01
The capacity to attend to multiple objects in the visual field is limited. However, introspectively, people feel that they see the whole visual world at once. Some scholars suggest that this introspective feeling is based on short-lived sensory memory representations, whereas others argue that the feeling of seeing more than can be attended to is illusory. Here, we investigated this phenomenon by combining objective memory performance with subjective confidence ratings during a change-detection task. This allowed us to compute a measure of metacognition--the degree of knowledge that subjects have about the correctness of their decisions--for different stages of memory. We show that subjects store more objects in sensory memory than they can attend to but, at the same time, have similar metacognition for sensory memory and working memory representations. This suggests that these subjective impressions are not an illusion but accurate reflections of the richness of visual perception.
Accurate Thermal Stresses for Beams: Normal Stress
NASA Technical Reports Server (NTRS)
Johnson, Theodore F.; Pilkey, Walter D.
2003-01-01
Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of the three-dimensional thermal stress problem to a two-dimensional one. Numerical results from the general theory of thermoelasticity are compared to those obtained from strength of materials. It is concluded that the theory of thermoelasticity for prismatic beams proposed in this paper can be used instead of strength of materials when precise stress results are desired.
Accurate Thermal Stresses for Beams: Normal Stress
NASA Technical Reports Server (NTRS)
Johnson, Theodore F.; Pilkey, Walter D.
2002-01-01
Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of the three-dimensional thermal stress problem to a two-dimensional one. Numerical results from the general theory of thermoelasticity are compared to those obtained from strength of materials. It is concluded that the theory of thermoelasticity for prismatic beams proposed in this paper can be used instead of strength of materials when precise stress results are desired.
Accurate metacognition for visual sensory memory representations.
Vandenbroucke, Annelinde R E; Sligte, Ilja G; Barrett, Adam B; Seth, Anil K; Fahrenfort, Johannes J; Lamme, Victor A F
2014-04-01
The capacity to attend to multiple objects in the visual field is limited. However, introspectively, people feel that they see the whole visual world at once. Some scholars suggest that this introspective feeling is based on short-lived sensory memory representations, whereas others argue that the feeling of seeing more than can be attended to is illusory. Here, we investigated this phenomenon by combining objective memory performance with subjective confidence ratings during a change-detection task. This allowed us to compute a measure of metacognition--the degree of knowledge that subjects have about the correctness of their decisions--for different stages of memory. We show that subjects store more objects in sensory memory than they can attend to but, at the same time, have similar metacognition for sensory memory and working memory representations. This suggests that these subjective impressions are not an illusion but accurate reflections of the richness of visual perception. PMID:24549293
Accurate Telescope Mount Positioning with MEMS Accelerometers
NASA Astrophysics Data System (ADS)
Mészáros, L.; Jaskó, A.; Pál, A.; Csépány, G.
2014-08-01
This paper describes the advantages and challenges of applying microelectromechanical accelerometer systems (MEMS accelerometers) in order to attain precise, accurate, and stateless positioning of telescope mounts. This provides a completely independent method from other forms of electronic, optical, mechanical or magnetic feedback or real-time astrometry. Our goal is to reach the subarcminute range which is considerably smaller than the field-of-view of conventional imaging telescope systems. Here we present how this subarcminute accuracy can be achieved with very cheap MEMS sensors and we also detail how our procedures can be extended in order to attain even finer measurements. In addition, our paper discusses how can a complete system design be implemented in order to be a part of a telescope control system.
Toward Accurate and Quantitative Comparative Metagenomics
Nayfach, Stephen; Pollard, Katherine S.
2016-01-01
Shotgun metagenomics and computational analysis are used to compare the taxonomic and functional profiles of microbial communities. Leveraging this approach to understand roles of microbes in human biology and other environments requires quantitative data summaries whose values are comparable across samples and studies. Comparability is currently hampered by the use of abundance statistics that do not estimate a meaningful parameter of the microbial community and biases introduced by experimental protocols and data-cleaning approaches. Addressing these challenges, along with improving study design, data access, metadata standardization, and analysis tools, will enable accurate comparative metagenomics. We envision a future in which microbiome studies are replicable and new metagenomes are easily and rapidly integrated with existing data. Only then can the potential of metagenomics for predictive ecological modeling, well-powered association studies, and effective microbiome medicine be fully realized. PMID:27565341
The importance of accurate atmospheric modeling
NASA Astrophysics Data System (ADS)
Payne, Dylan; Schroeder, John; Liang, Pang
2014-11-01
This paper will focus on the effect of atmospheric conditions on EO sensor performance using computer models. We have shown the importance of accurately modeling atmospheric effects for predicting the performance of an EO sensor. A simple example will demonstrated how real conditions for several sites in China will significantly impact on image correction, hyperspectral imaging, and remote sensing. The current state-of-the-art model for computing atmospheric transmission and radiance is, MODTRAN® 5, developed by the US Air Force Research Laboratory and Spectral Science, Inc. Research by the US Air Force, Navy and Army resulted in the public release of LOWTRAN 2 in the early 1970's. Subsequent releases of LOWTRAN and MODTRAN® have continued until the present. Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact author_help@spie.org with any questions or concerns. The paper will demonstrate the importance of using validated models and local measured meteorological, atmospheric and aerosol conditions to accurately simulate the atmospheric transmission and radiance. Frequently default conditions are used which can produce errors of as much as 75% in these values. This can have significant impact on remote sensing applications.
Accurate Weather Forecasting for Radio Astronomy
NASA Astrophysics Data System (ADS)
Maddalena, Ronald J.
2010-01-01
The NRAO Green Bank Telescope routinely observes at wavelengths from 3 mm to 1 m. As with all mm-wave telescopes, observing conditions depend upon the variable atmospheric water content. The site provides over 100 days/yr when opacities are low enough for good observing at 3 mm, but winds on the open-air structure reduce the time suitable for 3-mm observing where pointing is critical. Thus, to maximum productivity the observing wavelength needs to match weather conditions. For 6 years the telescope has used a dynamic scheduling system (recently upgraded; www.gb.nrao.edu/DSS) that requires accurate multi-day forecasts for winds and opacities. Since opacity forecasts are not provided by the National Weather Services (NWS), I have developed an automated system that takes available forecasts, derives forecasted opacities, and deploys the results on the web in user-friendly graphical overviews (www.gb.nrao.edu/ rmaddale/Weather). The system relies on the "North American Mesoscale" models, which are updated by the NWS every 6 hrs, have a 12 km horizontal resolution, 1 hr temporal resolution, run to 84 hrs, and have 60 vertical layers that extend to 20 km. Each forecast consists of a time series of ground conditions, cloud coverage, etc, and, most importantly, temperature, pressure, humidity as a function of height. I use the Liebe's MWP model (Radio Science, 20, 1069, 1985) to determine the absorption in each layer for each hour for 30 observing wavelengths. Radiative transfer provides, for each hour and wavelength, the total opacity and the radio brightness of the atmosphere, which contributes substantially at some wavelengths to Tsys and the observational noise. Comparisons of measured and forecasted Tsys at 22.2 and 44 GHz imply that the forecasted opacities are good to about 0.01 Nepers, which is sufficient for forecasting and accurate calibration. Reliability is high out to 2 days and degrades slowly for longer-range forecasts.
The high cost of accurate knowledge.
Sutcliffe, Kathleen M; Weber, Klaus
2003-05-01
Many business thinkers believe it's the role of senior managers to scan the external environment to monitor contingencies and constraints, and to use that precise knowledge to modify the company's strategy and design. As these thinkers see it, managers need accurate and abundant information to carry out that role. According to that logic, it makes sense to invest heavily in systems for collecting and organizing competitive information. Another school of pundits contends that, since today's complex information often isn't precise anyway, it's not worth going overboard with such investments. In other words, it's not the accuracy and abundance of information that should matter most to top executives--rather, it's how that information is interpreted. After all, the role of senior managers isn't just to make decisions; it's to set direction and motivate others in the face of ambiguities and conflicting demands. Top executives must interpret information and communicate those interpretations--they must manage meaning more than they must manage information. So which of these competing views is the right one? Research conducted by academics Sutcliffe and Weber found that how accurate senior executives are about their competitive environments is indeed less important for strategy and corresponding organizational changes than the way in which they interpret information about their environments. Investments in shaping those interpretations, therefore, may create a more durable competitive advantage than investments in obtaining and organizing more information. And what kinds of interpretations are most closely linked with high performance? Their research suggests that high performers respond positively to opportunities, yet they aren't overconfident in their abilities to take advantage of those opportunities.
Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas
Waskoenig, J.; Gans, T.
2010-05-03
Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.
Using Nice-Ohvms Lineshapes to Study Relaxation Rates and Transition Dipole Moments
NASA Astrophysics Data System (ADS)
Hodges, James N.; McCall, Benjamin J.
2016-06-01
Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy (NICE-OHVMS) is a successful technique that we have developed to sensitively, precisely, and accurately record transitions of molecular ions. It has been used exclusively as a method for precise transition frequency measurement via saturation and fitting of the resultant Lamb dips. NICE-OHVMS has been employed to improve the uncertainties on H_3^+, CH_5^+, HeH^+, and OH^+, reducing the transition frequency uncertainties by two orders of magnitude. Because NICE-OHVMS is a saturation technique, this provides a unique opportunity to access information about the ratio of the transition dipole moment to the relaxation rate of the transition. This can be done in two ways, either through comparison of Lamb dip depth to the transition profile or comparison of the absorption intensity and dispersion intensity. Due to the complexity of the modulation scheme, there are many parameters that affect the apparent intensity of the recorded lineshape. A complete understanding of the lineshape is required to make the measurements of interest. Here we present a model that accounts for the heterodyne modulation and velocity modulation, assuming that the fundamental lineshape is represented by a Voigt profile. Fits to data are made and interpreted in order to extract the saturation parameter. K.N. Crabtree et al., Chem. Phys. Lett. 551, 1 (2012). J.N. Hodges et al., J. Chem. Phys. 139, 164201 (2013). A.J. Perry et al., J. Mol. Spectrosc. 317, 71 (2015). A.J. Perry et al., J. Chem. Phys. 141, 101101 (2014). C.R. Marcus et al., Astrophys. J. 817, 138 (2016).
40 CFR 93.104 - Frequency of conformity determinations.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 40 Protection of Environment 21 2013-07-01 2013-07-01 false Frequency of conformity determinations..., Funded or Approved Under Title 23 U.S.C. or the Federal Transit Laws § 93.104 Frequency of conformity... implementation plan. (b) Frequency of conformity determinations for transportation plans. (1) Each...
40 CFR 93.104 - Frequency of conformity determinations.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 21 2012-07-01 2012-07-01 false Frequency of conformity determinations..., Funded or Approved Under Title 23 U.S.C. or the Federal Transit Laws § 93.104 Frequency of conformity... implementation plan. (b) Frequency of conformity determinations for transportation plans. (1) Each...
40 CFR 93.104 - Frequency of conformity determinations.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 20 2014-07-01 2013-07-01 true Frequency of conformity determinations..., Funded or Approved Under Title 23 U.S.C. or the Federal Transit Laws § 93.104 Frequency of conformity... implementation plan. (b) Frequency of conformity determinations for transportation plans. (1) Each...
The Weather - Climate Transition, the Spectral Plateau and the Emergent Climate Regime (Invited)
NASA Astrophysics Data System (ADS)
Lovejoy, S.; Schertzer, D. J.
2010-12-01
Analysis of planetary scale satellite radiances, in situ aircraft data and meteorological reanalyses and model outputs shows that they accurately have spatial cascade structures starting at 5000 - 20000 km scales. This is compatible with anisotropic scaling weather processes driven by solar energy flux inputs modulated by scaling cloud fields which predict that the lifetime of planetary scale structures is T ≈ 10 days. We argue that this is indeed the origin of the ubiquitous “spectral plateau” observed in all the state variables (wind, temperature, humidity, rain etc.), but also in the energy fluxes, global satellite temperature estimates, reanalyses and in climate indices. We show that the space-time scaling Fractionally Integrated Flux (FIF) model - which accurately models the weather scales τ< T - do indeed predict this as a “dimensional transition”. Evidence for this is given from turbulent flux analyses for frequencies down to (138 yrs)**-1 from the 700 mb 20th Century reanalysis product. However, the relatively spectrally flat “plateau” does not extend to the very low frequencies: paleotemperatures for example commonly display low frequency scaling regimes which are much steeper; for example for the temperature, E(ω) ≈ ω**-β with β ≈ 1.4 -1.8 for ω < ≈(3 - 10 yrs)**-1. It would appear that this is indeed the low frequency transition scale for an emergent climate regime proper. In this interpretation, the plateau is actually a broad regime transitional from weather to climate spanning roughly the range (10 days)**-1 to (3-10 yrs)**-1. This issue is important since it would imply strong long range statistical dependencies for frequencies <(3-10 yrs)**-1 but weaker dependencies in the higher frequency plateau transitional regime. In order to investigate this further we combine detailed analysis of the 138 year long 20th Century reanalysis fields (1.5o, 6 hour resolution) with published paleotemperature analyses extending the scaling
NASA Astrophysics Data System (ADS)
Zhao, Xiao-mei; Xie, Dong-fan; Li, Qi
2015-02-01
With the development of intelligent transport system, advanced information feedback strategies have been developed to reduce traffic congestion and enhance the capacity. However, previous strategies provide accurate information to travelers and our simulation results show that accurate information brings negative effects, especially in delay case. Because travelers prefer to the best condition route with accurate information, and delayed information cannot reflect current traffic condition but past. Then travelers make wrong routing decisions, causing the decrease of the capacity and the increase of oscillations and the system deviating from the equilibrium. To avoid the negative effect, bounded rationality is taken into account by introducing a boundedly rational threshold BR. When difference between two routes is less than the BR, routes have equal probability to be chosen. The bounded rationality is helpful to improve the efficiency in terms of capacity, oscillation and the gap deviating from the system equilibrium.
Rarefied Transitional Bridging of Blunt Body Aerodynamics
NASA Technical Reports Server (NTRS)
Wilmoth, R. G.; Blanchard, R. C.; Moss, J. N.
1998-01-01
The bridging procedures discussed provide an accurate engineering method for predicting rarefied transitional aerodynamics of spherically-blunted cone entry vehicles. The single-point procedure offers a way to improve the bridging procedures while minimizing the computational effort. However, the accuracy of these procedures ultimately depends on accurate knowledge of the aerodynamics in the free-molecular and continuum limits. The excellent agreement shown for DSMC predictions and bridging relations with the Viking flight data in transitional regime enhance the coincidence in these procedures.
A Catalog of Transit Timing Posterior Distributions for all Kepler Planet Candidate Transit Events
NASA Astrophysics Data System (ADS)
Montet, Benjamin Tyler; Becker, Juliette C.; Johnson, John Asher
2015-12-01
Kepler has ushered in a new era of planetary dynamics, enabling the detection of interactions between multiple planets in transiting systems for hundreds of systems. These interactions, observed as transit timing variations (TTVs), have been used to find non-transiting companions to transiting systems and to measure masses, eccentricities, and inclinations of transiting planets. Often, physical parameters are inferred by comparing the observed light curve to the result of a photodynamical model, a time-intensive process that often ignores the effects of correlated noise in the light curve. Catalogs of transit timing observations have previously neglected non-Gaussian uncertainties in the times of transit, uncertainties in the transit shape, and short cadence data. Here, I present a catalog of not only times of transit centers, but also posterior distributions on the time of transit for every planet candidate transit event in the Kepler data, developed through importance sampling of each transit. This catalog allows one to marginalize over uncertainties in the transit shape and incorporate short cadence data, the effects of correlated noise, and non-Gaussian posteriors. Our catalog will enable dynamical studies that reflect accurately the precision of Kepler and its limitations without requiring the computational power to model the light curve completely with every integration. I will also present our open-source N-body photodynamical modeling code, which integrates planetary and stellar orbits accounting for the effects of GR, tidal effects, and Doppler beaming.
Rainfall intensity-duration-frequency formulas.
Chen, C.-L.
1983-01-01
A new general rainfall intensity-duration-frequency formula is presented, utilizing a method similar to, but more accurate than one previously developed. The previously developed formula was based on the average depth-duration ratio of about 40% and the mean depth-frequency ratio of 1.48. It is shown that this formula is only a particular form of the writer's more general formulation. -from Author
Satellite time and frequency transfer (STIFT)
NASA Technical Reports Server (NTRS)
Vessot, R. F. C.
1983-01-01
The concept of placing a hydrogen maser high stability clock in Earth orbit to provide accurate time and frequency comparisons worldwide to major timing centers and to a large number of radio observatory antenna sites involved in VLBI measurements was studied. The proposal was chiefly directed toward studies and initial hardware designs for time comparisons between hydrogen maser frequency standards and to modifications of the hydrogen maser for long-term use in space.
Laser frequency stabilization using bichromatic crossover spectroscopy
Jeong, Taek; Seb Moon, Han
2015-03-07
We propose a Doppler-free spectroscopic method named bichromatic crossover spectroscopy (BCS), which we then use for the frequency stabilization of an off-resonant frequency that does not correspond to an atomic transition. The observed BCS in the 5S{sub 1/2} → 5P{sub 1/2} transition of {sup 87}Rb is related to the hyperfine structure of the conventional saturated absorption spectrum of this transition. Furthermore, the Doppler-free BCS is numerically calculated by considering all of the degenerate magnetic sublevels of the 5S{sub 1/2} → 5P{sub 1/2} transition in an atomic vapor cell, and is found to be in good agreement with the experimental results. Finally, we successfully achieve modulation-free off-resonant locking at the center frequency between the two 5S{sub 1/2}(F = 1 and 2) → 5P{sub 1/2}(F′ = 1) transitions using a polarization rotation of the BCS. The laser frequency stability was estimated to be the Allan variance of 2.1 × 10{sup −10} at 1 s.
Accurate VUV Laboratory Measurements of Fe III Transitions for Astrophysical Applications
NASA Technical Reports Server (NTRS)
Blackwell-Whitehead, R. J.; Pickering, J. C.; Smillie, D.; Nave, G.; Szabo, C. I.; Smith, Peter L.; Nielsen, K. E.; Peters, G.
2006-01-01
We report preliminary measurements of Fe III spectra in the 1150 to 2500 A wavelength interval. Spectra have been recorded with an iron-neon Penning discharge lamp (PDL) between 1600 and 2500 A at Imperial College (IC) using high resolution Fourier (FT) transform spectroscopy. These FT spectrometer measurements were extended beyond 1600 A to 1150 A using high-resolution grating spectroscopy at the National Institute of Standards and Technology (NIST). These recorded spectra represent the first radiometrically calibrated measurements of a doubly-ionized iron-group element spectrum combining the techniques of vacuum ultraviolet FT and grating spectroscopy. The spectral range of the new laboratory measurements corresponds to recent HST/STIS observations of sharp-lined B stars and of Eta Carinae. The new improved atomic data can be applied to abundance studies and diagnostics of astrophysical plasmas.
Accurate masses for dispersion-supported galaxies
NASA Astrophysics Data System (ADS)
Wolf, Joe; Martinez, Gregory D.; Bullock, James S.; Kaplinghat, Manoj; Geha, Marla; Muñoz, Ricardo R.; Simon, Joshua D.; Avedo, Frank F.
2010-08-01
We derive an accurate mass estimator for dispersion-supported stellar systems and demonstrate its validity by analysing resolved line-of-sight velocity data for globular clusters, dwarf galaxies and elliptical galaxies. Specifically, by manipulating the spherical Jeans equation we show that the mass enclosed within the 3D deprojected half-light radius r1/2 can be determined with only mild assumptions about the spatial variation of the stellar velocity dispersion anisotropy as long as the projected velocity dispersion profile is fairly flat near the half-light radius, as is typically observed. We find M1/2 = 3 G-1< σ2los > r1/2 ~= 4 G-1< σ2los > Re, where < σ2los > is the luminosity-weighted square of the line-of-sight velocity dispersion and Re is the 2D projected half-light radius. While deceptively familiar in form, this formula is not the virial theorem, which cannot be used to determine accurate masses unless the radial profile of the total mass is known a priori. We utilize this finding to show that all of the Milky Way dwarf spheroidal galaxies (MW dSphs) are consistent with having formed within a halo of a mass of approximately 3 × 109 Msolar, assuming a Λ cold dark matter cosmology. The faintest MW dSphs seem to have formed in dark matter haloes that are at least as massive as those of the brightest MW dSphs, despite the almost five orders of magnitude spread in luminosity between them. We expand our analysis to the full range of observed dispersion-supported stellar systems and examine their dynamical I-band mass-to-light ratios ΥI1/2. The ΥI1/2 versus M1/2 relation for dispersion-supported galaxies follows a U shape, with a broad minimum near ΥI1/2 ~= 3 that spans dwarf elliptical galaxies to normal ellipticals, a steep rise to ΥI1/2 ~= 3200 for ultra-faint dSphs and a more shallow rise to ΥI1/2 ~= 800 for galaxy cluster spheroids.
Henk, R.H.; Hubbard, S.M.; Lomax, T.J.; Shunk, G.A.
1995-07-01
This study involved the development of an index of transit service availability (ITSA). This index utilizes the factors which most effectively quantify the availability of public transit service (both bus and rail) in an urban area at a macroscopic planning level. The development of the index consisted of applying over 30 prospective measures of transit service availability of 228 urban area transit systems in the United States. The index utilizes three specific measures which quantify transit service coverage, frequency of transit service, and transit system capacity. The index developed in this study is designed to serve as a planning tool -- it is not intended for use in assessing transit system efficiency and/or performance.
Quantifying evolutionary dynamics from variant-frequency time series.
Khatri, Bhavin S
2016-01-01
From Kimura's neutral theory of protein evolution to Hubbell's neutral theory of biodiversity, quantifying the relative importance of neutrality versus selection has long been a basic question in evolutionary biology and ecology. With deep sequencing technologies, this question is taking on a new form: given a time-series of the frequency of different variants in a population, what is the likelihood that the observation has arisen due to selection or neutrality? To tackle the 2-variant case, we exploit Fisher's angular transformation, which despite being discovered by Ronald Fisher a century ago, has remained an intellectual curiosity. We show together with a heuristic approach it provides a simple solution for the transition probability density at short times, including drift, selection and mutation. Our results show under that under strong selection and sufficiently frequent sampling these evolutionary parameters can be accurately determined from simulation data and so they provide a theoretical basis for techniques to detect selection from variant or polymorphism frequency time-series. PMID:27616332
Frequency response and design parameters for differential microbarometers.
Mentink, Johan H; Evers, Läslo G
2011-07-01
The study of infrasound is experiencing a renaissance since it was chosen as a verification technique for the Comprehensive Nuclear-Test-Ban Treaty. Source identification is one of the main topics of research which involves detailed knowledge on the source time function, the atmosphere as medium of propagation, and the measurement system. Applications are also foreseen in using infrasound as passive probe for the upper atmosphere, taking the field beyond its monitoring application. Infrasound can be conveniently measured with differential microbarometers. An accurate description of the instrument response is an essential need to be able to attribute the recorded infrasound to a certain source or atmospheric properties. In this article, a detailed treatment is given of the response of a differential microbarometer to acoustic signals. After an historical introduction, a basic model for the frequency response is derived with its corresponding poles and zeros. The results are explained using electric analogs. In addition, thermal conduction is added to the model in order to capture the transition between adiabatic and isothermal behavior. Also discussed are high-frequency effects and the effect of external temperature variations. Eventually, the design parameters for differential microbarometers are derived. PMID:21786875
Frequency response and design parameters for differential microbarometers.
Mentink, Johan H; Evers, Läslo G
2011-07-01
The study of infrasound is experiencing a renaissance since it was chosen as a verification technique for the Comprehensive Nuclear-Test-Ban Treaty. Source identification is one of the main topics of research which involves detailed knowledge on the source time function, the atmosphere as medium of propagation, and the measurement system. Applications are also foreseen in using infrasound as passive probe for the upper atmosphere, taking the field beyond its monitoring application. Infrasound can be conveniently measured with differential microbarometers. An accurate description of the instrument response is an essential need to be able to attribute the recorded infrasound to a certain source or atmospheric properties. In this article, a detailed treatment is given of the response of a differential microbarometer to acoustic signals. After an historical introduction, a basic model for the frequency response is derived with its corresponding poles and zeros. The results are explained using electric analogs. In addition, thermal conduction is added to the model in order to capture the transition between adiabatic and isothermal behavior. Also discussed are high-frequency effects and the effect of external temperature variations. Eventually, the design parameters for differential microbarometers are derived.
Quantifying evolutionary dynamics from variant-frequency time series
NASA Astrophysics Data System (ADS)
Khatri, Bhavin S.
2016-09-01
From Kimura’s neutral theory of protein evolution to Hubbell’s neutral theory of biodiversity, quantifying the relative importance of neutrality versus selection has long been a basic question in evolutionary biology and ecology. With deep sequencing technologies, this question is taking on a new form: given a time-series of the frequency of different variants in a population, what is the likelihood that the observation has arisen due to selection or neutrality? To tackle the 2-variant case, we exploit Fisher’s angular transformation, which despite being discovered by Ronald Fisher a century ago, has remained an intellectual curiosity. We show together with a heuristic approach it provides a simple solution for the transition probability density at short times, including drift, selection and mutation. Our results show under that under strong selection and sufficiently frequent sampling these evolutionary parameters can be accurately determined from simulation data and so they provide a theoretical basis for techniques to detect selection from variant or polymorphism frequency time-series.
Quantifying evolutionary dynamics from variant-frequency time series
Khatri, Bhavin S.
2016-01-01
From Kimura’s neutral theory of protein evolution to Hubbell’s neutral theory of biodiversity, quantifying the relative importance of neutrality versus selection has long been a basic question in evolutionary biology and ecology. With deep sequencing technologies, this question is taking on a new form: given a time-series of the frequency of different variants in a population, what is the likelihood that the observation has arisen due to selection or neutrality? To tackle the 2-variant case, we exploit Fisher’s angular transformation, which despite being discovered by Ronald Fisher a century ago, has remained an intellectual curiosity. We show together with a heuristic approach it provides a simple solution for the transition probability density at short times, including drift, selection and mutation. Our results show under that under strong selection and sufficiently frequent sampling these evolutionary parameters can be accurately determined from simulation data and so they provide a theoretical basis for techniques to detect selection from variant or polymorphism frequency time-series. PMID:27616332
Zhu, Guo-Zhu; Wang, Lai-Sheng
2015-12-14
Tetracyanoquinodimethane (TCNQ) is widely used as an electron acceptor to form highly conducting organic charge-transfer solids. Surprisingly, the electron affinity (EA) of TCNQ is not well known and has never been directly measured. Here, we report vibrationally resolved photoelectron spectroscopy (PES) of the TCNQ{sup −} anion produced using electrospray and cooled in a cryogenic ion trap. Photoelectron spectrum taken at 354.7 nm represents the detachment transition from the ground state of TCNQ{sup −} to that of neutral TCNQ with a short vibrational progression. The EA of TCNQ is measured accurately to be 3.383 ± 0.001 eV (27 289 ± 8 cm{sup −1}), compared to the 2.8 ± 0.1 eV value known in the literature and measured previously using collisional ionization technique. In addition, six vibrational peaks are observed in the photoelectron spectrum, yielding vibrational frequencies for three totally symmetric modes of TCNQ. Two-photon PES via a bound electronic excited state of TCNQ{sup −} at 3.100 eV yields a broad low kinetic energy peak due to fast internal conversion to vibrationally excited levels of the anion ground electronic state. The high EA measured for TCNQ underlies its ability as a good electron acceptor.
NASA Astrophysics Data System (ADS)
Zhu, Guo-Zhu; Wang, Lai-Sheng
2015-12-01
Tetracyanoquinodimethane (TCNQ) is widely used as an electron acceptor to form highly conducting organic charge-transfer solids. Surprisingly, the electron affinity (EA) of TCNQ is not well known and has never been directly measured. Here, we report vibrationally resolved photoelectron spectroscopy (PES) of the TCNQ- anion produced using electrospray and cooled in a cryogenic ion trap. Photoelectron spectrum taken at 354.7 nm represents the detachment transition from the ground state of TCNQ- to that of neutral TCNQ with a short vibrational progression. The EA of TCNQ is measured accurately to be 3.383 ± 0.001 eV (27 289 ± 8 cm-1), compared to the 2.8 ± 0.1 eV value known in the literature and measured previously using collisional ionization technique. In addition, six vibrational peaks are observed in the photoelectron spectrum, yielding vibrational frequencies for three totally symmetric modes of TCNQ. Two-photon PES via a bound electronic excited state of TCNQ- at 3.100 eV yields a broad low kinetic energy peak due to fast internal conversion to vibrationally excited levels of the anion ground electronic state. The high EA measured for TCNQ underlies its ability as a good electron acceptor.
Accurate lineshape spectroscopy and the Boltzmann constant
Truong, G.-W.; Anstie, J. D.; May, E. F.; Stace, T. M.; Luiten, A. N.
2015-01-01
Spectroscopy has an illustrious history delivering serendipitous discoveries and providing a stringent testbed for new physical predictions, including applications from trace materials detection, to understanding the atmospheres of stars and planets, and even constraining cosmological models. Reaching fundamental-noise limits permits optimal extraction of spectroscopic information from an absorption measurement. Here, we demonstrate a quantum-limited spectrometer that delivers high-precision measurements of the absorption lineshape. These measurements yield a very accurate measurement of the excited-state (6P1/2) hyperfine splitting in Cs, and reveals a breakdown in the well-known Voigt spectral profile. We develop a theoretical model that accounts for this breakdown, explaining the observations to within the shot-noise limit. Our model enables us to infer the thermal velocity dispersion of the Cs vapour with an uncertainty of 35 p.p.m. within an hour. This allows us to determine a value for Boltzmann's constant with a precision of 6 p.p.m., and an uncertainty of 71 p.p.m. PMID:26465085
Accurate SHAPE-directed RNA structure determination
Deigan, Katherine E.; Li, Tian W.; Mathews, David H.; Weeks, Kevin M.
2009-01-01
Almost all RNAs can fold to form extensive base-paired secondary structures. Many of these structures then modulate numerous fundamental elements of gene expression. Deducing these structure–function relationships requires that it be possible to predict RNA secondary structures accurately. However, RNA secondary structure prediction for large RNAs, such that a single predicted structure for a single sequence reliably represents the correct structure, has remained an unsolved problem. Here, we demonstrate that quantitative, nucleotide-resolution information from a SHAPE experiment can be interpreted as a pseudo-free energy change term and used to determine RNA secondary structure with high accuracy. Free energy minimization, by using SHAPE pseudo-free energies, in conjunction with nearest neighbor parameters, predicts the secondary structure of deproteinized Escherichia coli 16S rRNA (>1,300 nt) and a set of smaller RNAs (75–155 nt) with accuracies of up to 96–100%, which are comparable to the best accuracies achievable by comparative sequence analysis. PMID:19109441
Accurate adiabatic correction in the hydrogen molecule
NASA Astrophysics Data System (ADS)
Pachucki, Krzysztof; Komasa, Jacek
2014-12-01
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10-12 at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H2, HD, HT, D2, DT, and T2 has been determined. For the ground state of H2 the estimated precision is 3 × 10-7 cm-1, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
Fast and Provably Accurate Bilateral Filtering.
Chaudhury, Kunal N; Dabhade, Swapnil D
2016-06-01
The bilateral filter is a non-linear filter that uses a range filter along with a spatial filter to perform edge-preserving smoothing of images. A direct computation of the bilateral filter requires O(S) operations per pixel, where S is the size of the support of the spatial filter. In this paper, we present a fast and provably accurate algorithm for approximating the bilateral filter when the range kernel is Gaussian. In particular, for box and Gaussian spatial filters, the proposed algorithm can cut down the complexity to O(1) per pixel for any arbitrary S . The algorithm has a simple implementation involving N+1 spatial filterings, where N is the approximation order. We give a detailed analysis of the filtering accuracy that can be achieved by the proposed approximation in relation to the target bilateral filter. This allows us to estimate the order N required to obtain a given accuracy. We also present comprehensive numerical results to demonstrate that the proposed algorithm is competitive with the state-of-the-art methods in terms of speed and accuracy. PMID:27093722
Accurate, reliable prototype earth horizon sensor head
NASA Technical Reports Server (NTRS)
Schwarz, F.; Cohen, H.
1973-01-01
The design and performance is described of an accurate and reliable prototype earth sensor head (ARPESH). The ARPESH employs a detection logic 'locator' concept and horizon sensor mechanization which should lead to high accuracy horizon sensing that is minimally degraded by spatial or temporal variations in sensing attitude from a satellite in orbit around the earth at altitudes in the 500 km environ 1,2. An accuracy of horizon location to within 0.7 km has been predicted, independent of meteorological conditions. This corresponds to an error of 0.015 deg-at 500 km altitude. Laboratory evaluation of the sensor indicates that this accuracy is achieved. First, the basic operating principles of ARPESH are described; next, detailed design and construction data is presented and then performance of the sensor under laboratory conditions in which the sensor is installed in a simulator that permits it to scan over a blackbody source against background representing the earth space interface for various equivalent plant temperatures.
Fast and Accurate Exhaled Breath Ammonia Measurement
Solga, Steven F.; Mudalel, Matthew L.; Spacek, Lisa A.; Risby, Terence H.
2014-01-01
This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that uses a quantum cascade based laser. The monitor is coupled to a sampler that measures mouth pressure and carbon dioxide. The system is temperature controlled and specifically designed to address the reactivity of this compound. The sampler provides immediate feedback to the subject and the technician on the quality of the breath effort. Together with the quick response time of the monitor, this system is capable of accurately measuring exhaled breath ammonia representative of deep lung systemic levels. Because the system is easy to use and produces real time results, it has enabled experiments to identify factors that influence measurements. For example, mouth rinse and oral pH reproducibly and significantly affect results and therefore must be controlled. Temperature and mode of breathing are other examples. As our understanding of these factors evolves, error is reduced, and clinical studies become more meaningful. This system is very reliable and individual measurements are inexpensive. The sampler is relatively inexpensive and quite portable, but the monitor is neither. This limits options for some clinical studies and provides rational for future innovations. PMID:24962141
Accurate adiabatic correction in the hydrogen molecule
Pachucki, Krzysztof; Komasa, Jacek
2014-12-14
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10{sup −12} at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H{sub 2}, HD, HT, D{sub 2}, DT, and T{sub 2} has been determined. For the ground state of H{sub 2} the estimated precision is 3 × 10{sup −7} cm{sup −1}, which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels.
Accurate adiabatic correction in the hydrogen molecule.
Pachucki, Krzysztof; Komasa, Jacek
2014-12-14
A new formalism for the accurate treatment of adiabatic effects in the hydrogen molecule is presented, in which the electronic wave function is expanded in the James-Coolidge basis functions. Systematic increase in the size of the basis set permits estimation of the accuracy. Numerical results for the adiabatic correction to the Born-Oppenheimer interaction energy reveal a relative precision of 10(-12) at an arbitrary internuclear distance. Such calculations have been performed for 88 internuclear distances in the range of 0 < R ⩽ 12 bohrs to construct the adiabatic correction potential and to solve the nuclear Schrödinger equation. Finally, the adiabatic correction to the dissociation energies of all rovibrational levels in H2, HD, HT, D2, DT, and T2 has been determined. For the ground state of H2 the estimated precision is 3 × 10(-7) cm(-1), which is almost three orders of magnitude higher than that of the best previous result. The achieved accuracy removes the adiabatic contribution from the overall error budget of the present day theoretical predictions for the rovibrational levels. PMID:25494728
MEMS accelerometers in accurate mount positioning systems
NASA Astrophysics Data System (ADS)
Mészáros, László; Pál, András.; Jaskó, Attila
2014-07-01
In order to attain precise, accurate and stateless positioning of telescope mounts we apply microelectromechanical accelerometer systems (also known as MEMS accelerometers). In common practice, feedback from the mount position is provided by electronic, optical or magneto-mechanical systems or via real-time astrometric solution based on the acquired images. Hence, MEMS-based systems are completely independent from these mechanisms. Our goal is to investigate the advantages and challenges of applying such devices and to reach the sub-arcminute range { that is well smaller than the field-of-view of conventional imaging telescope systems. We present how this sub-arcminute accuracy can be achieved with very cheap MEMS sensors. Basically, these sensors yield raw output within an accuracy of a few degrees. We show what kind of calibration procedures could exploit spherical and cylindrical constraints between accelerometer output channels in order to achieve the previously mentioned accuracy level. We also demonstrate how can our implementation be inserted in a telescope control system. Although this attainable precision is less than both the resolution of telescope mount drive mechanics and the accuracy of astrometric solutions, the independent nature of attitude determination could significantly increase the reliability of autonomous or remotely operated astronomical observations.
Population variability complicates the accurate detection of climate change responses.
McCain, Christy; Szewczyk, Tim; Bracy Knight, Kevin
2016-06-01
The rush to assess species' responses to anthropogenic climate change (CC) has underestimated the importance of interannual population variability (PV). Researchers assume sampling rigor alone will lead to an accurate detection of response regardless of the underlying population fluctuations of the species under consideration. Using population simulations across a realistic, empirically based gradient in PV, we show that moderate to high PV can lead to opposite and biased conclusions about CC responses. Between pre- and post-CC sampling bouts of modeled populations as in resurvey studies, there is: (i) A 50% probability of erroneously detecting the opposite trend in population abundance change and nearly zero probability of detecting no change. (ii) Across multiple years of sampling, it is nearly impossible to accurately detect any directional shift in population sizes with even moderate PV. (iii) There is up to 50% probability of detecting a population extirpation when the species is present, but in very low natural abundances. (iv) Under scenarios of moderate to high PV across a species' range or at the range edges, there is a bias toward erroneous detection of range shifts or contractions. Essentially, the frequency and magnitude of population peaks and troughs greatly impact the accuracy of our CC response measurements. Species with moderate to high PV (many small vertebrates, invertebrates, and annual plants) may be inaccurate 'canaries in the coal mine' for CC without pertinent demographic analyses and additional repeat sampling. Variation in PV may explain some idiosyncrasies in CC responses detected so far and urgently needs more careful consideration in design and analysis of CC responses.
Accurate MTF measurement in digital radiography using noise response
Kuhls-Gilcrist, Andrew; Jain, Amit; Bednarek, Daniel R.; Hoffmann, Kenneth R.; Rudin, Stephen
2010-01-01
Purpose: The authors describe a new technique to determine the system presampled modulation transfer function (MTF) in digital radiography using only the detector noise response. Methods: A cascaded-linear systems analysis was used to develop an exact relationship between the two-dimensional noise power spectrum (NPS) and the presampled MTF for a generalized detector system. This relationship was then utilized to determine the two-dimensional presampled MTF. For simplicity, aliasing of the correlated noise component of the NPS was assumed to be negligible. Accuracy of this method was investigated using simulated images from a simple detector model in which the “true” MTF was known exactly. Measurements were also performed on three detector technologies (an x-ray image intensifier, an indirect flat panel detector, and a solid state x-ray image intensifier), and the results were compared using the standard edge-response method. Flat-field and edge images were acquired and analyzed according to guidelines set forth by the International Electrotechnical Commission, using the RQA 5 spectrum. Results: The presampled MTF determined using the noise-response method for the simulated detector system was in close agreement with the true MTF with an averaged percent difference of 0.3% and a maximum difference of 1.1% observed at the Nyquist frequency (fN). The edge-response method of the simulated detector system also showed very good agreement at lower spatial frequencies (less than 0.5 fN) with an averaged percent difference of 1.6% but showed significant discrepancies at higher spatial frequencies (greater than 0.5 fN) with an averaged percent difference of 17%. Discrepancies were in part a result of noise in the edge image and phasing errors. For all three detector systems, the MTFs obtained using the two methods were found to be in good agreement at spatial frequencies less than 0.5 fN with an averaged percent difference of 3.4%. Above 0.5 fN, differences increased to
ERIC Educational Resources Information Center
Brookes, Bertram C.; Griffiths, Jose M.
1978-01-01
Frequency, rank, and frequency rank distributions are defined. Extensive discussion on several aspects of frequency rank distributions includes the Poisson process as a means of exploring the stability of ranks; the correlation of frequency rank distributions; and the transfer coefficient, a new measure in frequency rank distribution. (MBR)
Accurate Free Vibration Analysis of the Completely Free Rectangular Mindlin Plate
NASA Astrophysics Data System (ADS)
Gorman, D. J.; Ding, Wei
1996-01-01
The superposition method is exploited to obtain accurate solutions for the natural frequencies and mode shapes of the completely free Mindlin plate. Computed eigenvalues are tabulated for a number of plate aspect and thickness ratios. Steps taken to avoid computational instability are described. Difficulties associated with choosing mode shape functions, particularly when free edges are involved, have always hindered researchers utilizing the Rayleigh-Ritz method. Such difficulties are obviated here. To the authors' knowledge, this represents the first accurate comprehensive solution to this important plate vibration problem.
A simple technique for accurate and complete characterisation of a Fabry-Perot cavity.
Locke, C R; Stuart, D; Ivanov, E N; Luiten, A N
2009-11-23
It has become a significant challenge to accurately characterise the properties of recently developed very high finesse optical resonators (F > 10(6)). A similar challenge is encountered when trying to measure the properties of cavities in which either the probing laser or the cavity length is intrinsically unstable. We demonstrate in this article the means by which the finesse, mode-matching, free spectral range, mirror transmissions and dispersion may be measured easily and accurately even when the laser or cavity has a relatively poor intrinsic frequency stability. PMID:19997438
Towards Accurate Application Characterization for Exascale (APEX)
Hammond, Simon David
2015-09-01
Sandia National Laboratories has been engaged in hardware and software codesign activities for a number of years, indeed, it might be argued that prototyping of clusters as far back as the CPLANT machines and many large capability resources including ASCI Red and RedStorm were examples of codesigned solutions. As the research supporting our codesign activities has moved closer to investigating on-node runtime behavior a nature hunger has grown for detailed analysis of both hardware and algorithm performance from the perspective of low-level operations. The Application Characterization for Exascale (APEX) LDRD was a project concieved of addressing some of these concerns. Primarily the research was to intended to focus on generating accurate and reproducible low-level performance metrics using tools that could scale to production-class code bases. Along side this research was an advocacy and analysis role associated with evaluating tools for production use, working with leading industry vendors to develop and refine solutions required by our code teams and to directly engage with production code developers to form a context for the application analysis and a bridge to the research community within Sandia. On each of these accounts significant progress has been made, particularly, as this report will cover, in the low-level analysis of operations for important classes of algorithms. This report summarizes the development of a collection of tools under the APEX research program and leaves to other SAND and L2 milestone reports the description of codesign progress with Sandia’s production users/developers.
Accurate paleointensities - the multi-method approach
NASA Astrophysics Data System (ADS)
de Groot, Lennart
2016-04-01
The accuracy of models describing rapid changes in the geomagnetic field over the past millennia critically depends on the availability of reliable paleointensity estimates. Over the past decade methods to derive paleointensities from lavas (the only recorder of the geomagnetic field that is available all over the globe and through geologic times) have seen significant improvements and various alternative techniques were proposed. The 'classical' Thellier-style approach was optimized and selection criteria were defined in the 'Standard Paleointensity Definitions' (Paterson et al, 2014). The Multispecimen approach was validated and the importance of additional tests and criteria to assess Multispecimen results must be emphasized. Recently, a non-heating, relative paleointensity technique was proposed -the pseudo-Thellier protocol- which shows great potential in both accuracy and efficiency, but currently lacks a solid theoretical underpinning. Here I present work using all three of the aforementioned paleointensity methods on suites of young lavas taken from the volcanic islands of Hawaii, La Palma, Gran Canaria, Tenerife, and Terceira. Many of the sampled cooling units are <100 years old, the actual field strength at the time of cooling is therefore reasonably well known. Rather intuitively, flows that produce coherent results from two or more different paleointensity methods yield the most accurate estimates of the paleofield. Furthermore, the results for some flows pass the selection criteria for one method, but fail in other techniques. Scrutinizing and combing all acceptable results yielded reliable paleointensity estimates for 60-70% of all sampled cooling units - an exceptionally high success rate. This 'multi-method paleointensity approach' therefore has high potential to provide the much-needed paleointensities to improve geomagnetic field models for the Holocene.
Important Nearby Galaxies without Accurate Distances
NASA Astrophysics Data System (ADS)
McQuinn, Kristen
2014-10-01
The Spitzer Infrared Nearby Galaxies Survey (SINGS) and its offspring programs (e.g., THINGS, HERACLES, KINGFISH) have resulted in a fundamental change in our view of star formation and the ISM in galaxies, and together they represent the most complete multi-wavelength data set yet assembled for a large sample of nearby galaxies. These great investments of observing time have been dedicated to the goal of understanding the interstellar medium, the star formation process, and, more generally, galactic evolution at the present epoch. Nearby galaxies provide the basis for which we interpret the distant universe, and the SINGS sample represents the best studied nearby galaxies.Accurate distances are fundamental to interpreting observations of galaxies. Surprisingly, many of the SINGS spiral galaxies have numerous distance estimates resulting in confusion. We can rectify this situation for 8 of the SINGS spiral galaxies within 10 Mpc at a very low cost through measurements of the tip of the red giant branch. The proposed observations will provide an accuracy of better than 0.1 in distance modulus. Our sample includes such well known galaxies as M51 (the Whirlpool), M63 (the Sunflower), M104 (the Sombrero), and M74 (the archetypal grand design spiral).We are also proposing coordinated parallel WFC3 UV observations of the central regions of the galaxies, rich with high-mass UV-bright stars. As a secondary science goal we will compare the resolved UV stellar populations with integrated UV emission measurements used in calibrating star formation rates. Our observations will complement the growing HST UV atlas of high resolution images of nearby galaxies.
Accurate Thermal Conductivities from First Principles
NASA Astrophysics Data System (ADS)
Carbogno, Christian
2015-03-01
In spite of significant research efforts, a first-principles determination of the thermal conductivity at high temperatures has remained elusive. On the one hand, Boltzmann transport techniques that include anharmonic effects in the nuclear dynamics only perturbatively become inaccurate or inapplicable under such conditions. On the other hand, non-equilibrium molecular dynamics (MD) methods suffer from enormous finite-size artifacts in the computationally feasible supercells, which prevent an accurate extrapolation to the bulk limit of the thermal conductivity. In this work, we overcome this limitation by performing ab initio MD simulations in thermodynamic equilibrium that account for all orders of anharmonicity. The thermal conductivity is then assessed from the auto-correlation function of the heat flux using the Green-Kubo formalism. Foremost, we discuss the fundamental theory underlying a first-principles definition of the heat flux using the virial theorem. We validate our approach and in particular the techniques developed to overcome finite time and size effects, e.g., by inspecting silicon, the thermal conductivity of which is particularly challenging to converge. Furthermore, we use this framework to investigate the thermal conductivity of ZrO2, which is known for its high degree of anharmonicity. Our calculations shed light on the heat resistance mechanism active in this material, which eventually allows us to discuss how the thermal conductivity can be controlled by doping and co-doping. This work has been performed in collaboration with R. Ramprasad (University of Connecticut), C. G. Levi and C. G. Van de Walle (University of California Santa Barbara).
How flatbed scanners upset accurate film dosimetry
NASA Astrophysics Data System (ADS)
van Battum, L. J.; Huizenga, H.; Verdaasdonk, R. M.; Heukelom, S.
2016-01-01
Film is an excellent dosimeter for verification of dose distributions due to its high spatial resolution. Irradiated film can be digitized with low-cost, transmission, flatbed scanners. However, a disadvantage is their lateral scan effect (LSE): a scanner readout change over its lateral scan axis. Although anisotropic light scattering was presented as the origin of the LSE, this paper presents an alternative cause. Hereto, LSE for two flatbed scanners (Epson 1680 Expression Pro and Epson 10000XL), and Gafchromic film (EBT, EBT2, EBT3) was investigated, focused on three effects: cross talk, optical path length and polarization. Cross talk was examined using triangular sheets of various optical densities. The optical path length effect was studied using absorptive and reflective neutral density filters with well-defined optical characteristics (OD range 0.2-2.0). Linear polarizer sheets were used to investigate light polarization on the CCD signal in absence and presence of (un)irradiated Gafchromic film. Film dose values ranged between 0.2 to 9 Gy, i.e. an optical density range between 0.25 to 1.1. Measurements were performed in the scanner’s transmission mode, with red-green-blue channels. LSE was found to depend on scanner construction and film type. Its magnitude depends on dose: for 9 Gy increasing up to 14% at maximum lateral position. Cross talk was only significant in high contrast regions, up to 2% for very small fields. The optical path length effect introduced by film on the scanner causes 3% for pixels in the extreme lateral position. Light polarization due to film and the scanner’s optical mirror system is the main contributor, different in magnitude for the red, green and blue channel. We concluded that any Gafchromic EBT type film scanned with a flatbed scanner will face these optical effects. Accurate dosimetry requires correction of LSE, therefore, determination of the LSE per color channel and dose delivered to the film.
How flatbed scanners upset accurate film dosimetry.
van Battum, L J; Huizenga, H; Verdaasdonk, R M; Heukelom, S
2016-01-21
Film is an excellent dosimeter for verification of dose distributions due to its high spatial resolution. Irradiated film can be digitized with low-cost, transmission, flatbed scanners. However, a disadvantage is their lateral scan effect (LSE): a scanner readout change over its lateral scan axis. Although anisotropic light scattering was presented as the origin of the LSE, this paper presents an alternative cause. Hereto, LSE for two flatbed scanners (Epson 1680 Expression Pro and Epson 10000XL), and Gafchromic film (EBT, EBT2, EBT3) was investigated, focused on three effects: cross talk, optical path length and polarization. Cross talk was examined using triangular sheets of various optical densities. The optical path length effect was studied using absorptive and reflective neutral density filters with well-defined optical characteristics (OD range 0.2-2.0). Linear polarizer sheets were used to investigate light polarization on the CCD signal in absence and presence of (un)irradiated Gafchromic film. Film dose values ranged between 0.2 to 9 Gy, i.e. an optical density range between 0.25 to 1.1. Measurements were performed in the scanner's transmission mode, with red-green-blue channels. LSE was found to depend on scanner construction and film type. Its magnitude depends on dose: for 9 Gy increasing up to 14% at maximum lateral position. Cross talk was only significant in high contrast regions, up to 2% for very small fields. The optical path length effect introduced by film on the scanner causes 3% for pixels in the extreme lateral position. Light polarization due to film and the scanner's optical mirror system is the main contributor, different in magnitude for the red, green and blue channel. We concluded that any Gafchromic EBT type film scanned with a flatbed scanner will face these optical effects. Accurate dosimetry requires correction of LSE, therefore, determination of the LSE per color channel and dose delivered to the film.
Concrete bridge-borne low-frequency noise simulation based on train-track-bridge dynamic interaction
NASA Astrophysics Data System (ADS)
Li, Q.; Xu, Y. L.; Wu, D. J.
2012-05-01
Both the vibration of a railway bridge under a moving train and the associated bridge-borne noise are time-varying in nature. The former is commonly predicted in the time domain to take its time-varying and nonlinear properties into account, whereas acoustic computation is generally conducted in the frequency domain to obtain steady responses. This paper presents a general procedure for obtaining various characteristics of concrete bridge-borne low-frequency noise by bridging the gap between time-domain bridge vibration computation and frequency-domain bridge-borne noise simulation. The finite element method (FEM) is first used to solve the transient train-track-bridge dynamic interaction problem, with an emphasis on the local vibration of the bridge. The boundary element method (BEM) is then applied to find the frequency-dependent modal acoustic transfer vectors (MATVs). The time-domain sound pressure is finally obtained with the help of time-frequency transforms. The proposed procedure is applied to a real urban rail transit U-shaped concrete bridge to compute the bridge acceleration and bridge-borne noise, and these results are compared with the field measurement results. Both sets of results show the proposed procedure to be feasible and accurate and the dominant frequencies of concrete bridge-borne noise to range from 32 Hz to 100 Hz.
NASA Technical Reports Server (NTRS)
Sollner, T. C. L. G.; Brown, E. R.; Goodhue, W. D.; Le, H. Q.
1987-01-01
Recent observations of oscillation frequencies up to 56 GHz in resonant tunneling structures are discussed in relation to calculations by several authors of the ultimate frequency limits of these devices. It is found that calculations relying on the Wentzel-Kramers-Brillouin (WKB) approximation give limits well below the observed oscillation frequencies. Two other techniques for calculating the upper frequency limit were found to give more reasonable results. One method employs the solution of the time-dependent Schroedinger equation obtained by Kundrotas and Dargys (1986); the other uses the energy width of the transmission function for electrons through the double-barrier structure. This last technique is believed to be the most accurate since it is based on general results for the lifetime of any resonant state. It gives frequency limits on the order of 1 THz for two recently fabricated structures. It appears that the primary limitation of the oscillation frequency for double-barrier resonant-tunneling diodes is imposed by intrinsic device circuit parameters and by the transit time of the depletion layer rather than by time delays encountered in the double-barrier region.
Radioactive transitions in the helium isoelectronic sequence
NASA Technical Reports Server (NTRS)
Dalgarno, A.
1971-01-01
The principles of the atomic spectrum theory are used to quantitatively analyze radiation transitions in two-electron helium-like atomic systems. Quantum theoretical methods, describing absorption and emission of a single photon in a radiative transition between two stationary states of an atomic system, reproduced the energy level diagram for the low lying states of helium. Reliable values are obtained from accurate variationally determined two-electron nonrelativistic wave functions for radiative transition probabilities of 2 3p states in the helium isoelectric sequence, and for the 2 1s and 2 3s1 states of the helium sequence.
Accurate Ritz Wavelengths of Parity-forbidden [Co II] and [V II] Lines of Astrophysical Interest
NASA Astrophysics Data System (ADS)
Ruffoni, M. P.; Pickering, J. C.
2013-08-01
We report a comprehensive list of accurate Ritz wavelengths for parity-forbidden [Co II] and [V II] lines obtained from the analysis of energy levels measured in the laboratory with Fourier transform emission spectroscopy. Such lines, particularly those in the infrared, are in demand for the analysis of low-density astrophysical plasmas in and around objects such as planetary nebulae, star-forming regions, and active galactic nuclei. Transitions between all known metastable levels of Co II and V II are included in our analysis, producing wavelengths for 1477 [V II] lines and 782 [Co II] lines. Of these, 170 [V II] lines and 171 [Co II] lines arise from transitions with calculated transition probabilities greater than 1 × 10-2 s-1 and upper level excitations of less than 5 eV, and thus are likely to be observed in astrophysical spectra.
ACCURATE RITZ WAVELENGTHS OF PARITY-FORBIDDEN [Co II] AND [V II] LINES OF ASTROPHYSICAL INTEREST
Ruffoni, M. P.; Pickering, J. C.
2013-08-15
We report a comprehensive list of accurate Ritz wavelengths for parity-forbidden [Co II] and [V II] lines obtained from the analysis of energy levels measured in the laboratory with Fourier transform emission spectroscopy. Such lines, particularly those in the infrared, are in demand for the analysis of low-density astrophysical plasmas in and around objects such as planetary nebulae, star-forming regions, and active galactic nuclei. Transitions between all known metastable levels of Co II and V II are included in our analysis, producing wavelengths for 1477 [V II] lines and 782 [Co II] lines. Of these, 170 [V II] lines and 171 [Co II] lines arise from transitions with calculated transition probabilities greater than 1 Multiplication-Sign 10{sup -2} s{sup -1} and upper level excitations of less than 5 eV, and thus are likely to be observed in astrophysical spectra.
A time-accurate adaptive grid method and the numerical simulation of a shock-vortex interaction
NASA Technical Reports Server (NTRS)
Bockelie, Michael J.; Eiseman, Peter R.
1990-01-01
A time accurate, general purpose, adaptive grid method is developed that is suitable for multidimensional steady and unsteady numerical simulations. The grid point movement is performed in a manner that generates smooth grids which resolve the severe solution gradients and the sharp transitions in the solution gradients. The temporal coupling of the adaptive grid and the PDE solver is performed with a grid prediction correction method that is simple to implement and ensures the time accuracy of the grid. Time accurate solutions of the 2-D Euler equations for an unsteady shock vortex interaction demonstrate the ability of the adaptive method to accurately adapt the grid to multiple solution features.
NASA Astrophysics Data System (ADS)
Varma, Shikha
We have studied thin (1-7 monolayer) overlayers of Hg on Ag(100) and Cu(100) using angle-resolved photoemission and low energy electron diffraction. We have investigated the electronic states of well ordered, disordered and the liquid overlayers of mercury. We show that the electronic structure of the well ordered overlayers is very different than that of the disordered and the liquid overlayers. The well ordered overlayers of Hg on Ag(100) exhibit a new electronic state which is absent for the disordered overlayers of mercury as well as for gaseous mercury. We will argue that this new Hg state is a result of the interaction among the Hg-Hg atoms, when adsorbed on Ag(100). The strain among adlayer atoms also plays a crucial role in the development of the new electronic state. We have used the synchrotron radiation to study the partial cross-section and the branching ratio of the 5d electronic state of Hg. We have measured the partial cross-section and branching ratio of the well-ordered, disordered and liquid overlayers of mercury on Ag(100) and Cu(100). We have observed resonances in the photoemission intensities of the mercury 5d orbitals for thin films of mercury for incident photon energies near the 5p _{3/2}, 4f_{7/2 } and 4f_{5/2} thresholds. The results indicate that interband transitions from the 5p and 4f levels to the 5d orbitals can occur for a thin overlayer of mercury, as a result of final state 5f contributions, though such interband transitions are forbidden for the free isolated Hg atom. These resonances are attributed to the formation of a solid state band structure incorporating new itinerant mercury electronic state. These resonances are absent when the mercury film is disordered or melted. We have measured the branching ratio of the 5d orbital for thin mercury overlayers in the photon energy range between 26 to 105 eV. The branching ratios deviate from the nonrelativistic statistical value of 1.5, reaching values of 8.0. These results indicate
NASA Technical Reports Server (NTRS)
Weber, Arthur L.
1993-01-01
Life is composed principally of four classes of biomolecules - protein, nucleic acid, polysaccharide and lipid. Using 1) estimates of the reducing equivalents (electron pairs) needed to synthesize these biomolecules from carbon dioxide, and 2) measurements of the molecular composition of different organisms, we calculated the average number of electron pairs required for the reduction of carbon dioxide to biological carbon (electron pairs/carbon atom). These calculations showed that the carbon of the Earths biosphere is at the reduction level of formaldehyde that requires 2 electron pairs/carbon atom to be synthesized from carbon dioxide. This was also the reduction level of carbon of individual organisms, except for those that stored large amounts of fuel as lipid. Since this chemical property of life is easily discovered and probably universal, it's most likely known by other intelligent life in the universe. It could be the one thing we know about other carbon-based life in the universe, and the one thing that other intelligent life knows about us. We believe this common knowledge that formaldehyde represents the reduction level of life's carbon could lead to the selection of the 72.83814 GHz line of the 0,0,0,1,0,1 ground-state rotational transition of formaldehyde as a frequency for interstellar communication.
Accurate theoretical chemistry with coupled pair models.
Neese, Frank; Hansen, Andreas; Wennmohs, Frank; Grimme, Stefan
2009-05-19
Quantum chemistry has found its way into the everyday work of many experimental chemists. Calculations can predict the outcome of chemical reactions, afford insight into reaction mechanisms, and be used to interpret structure and bonding in molecules. Thus, contemporary theory offers tremendous opportunities in experimental chemical research. However, even with present-day computers and algorithms, we cannot solve the many particle Schrodinger equation exactly; inevitably some error is introduced in approximating the solutions of this equation. Thus, the accuracy of quantum chemical calculations is of critical importance. The affordable accuracy depends on molecular size and particularly on the total number of atoms: for orientation, ethanol has 9 atoms, aspirin 21 atoms, morphine 40 atoms, sildenafil 63 atoms, paclitaxel 113 atoms, insulin nearly 800 atoms, and quaternary hemoglobin almost 12,000 atoms. Currently, molecules with up to approximately 10 atoms can be very accurately studied by coupled cluster (CC) theory, approximately 100 atoms with second-order Møller-Plesset perturbation theory (MP2), approximately 1000 atoms with density functional theory (DFT), and beyond that number with semiempirical quantum chemistry and force-field methods. The overwhelming majority of present-day calculations in the 100-atom range use DFT. Although these methods have been very successful in quantum chemistry, they do not offer a well-defined hierarchy of calculations that allows one to systematically converge to the correct answer. Recently a number of rather spectacular failures of DFT methods have been found-even for seemingly simple systems such as hydrocarbons, fueling renewed interest in wave function-based methods that incorporate the relevant physics of electron correlation in a more systematic way. Thus, it would be highly desirable to fill the gap between 10 and 100 atoms with highly correlated ab initio methods. We have found that one of the earliest (and now
Gabor feature-based registration: accurate alignment without fiducial markers
NASA Astrophysics Data System (ADS)
Parra, Nestor A.; Parra, Carlos A.
2007-03-01
Accurate registration of diagnosis and treatment images is a critical factor for the success of radiotherapy. This study presents a feature-based image registration algorithm that uses a branch- and-bound method to search the space of possible transformations, as well as a Hausdorff distance metric to evaluate their quality. This distance is computed in the space of responses to a circular Gabor filter, in which, for each point of interest in both reference and subject images, a vector of complex responses to different Gabor kernels is computed. Each kernel is generated using different frequencies and variances of the Gabor function, which determines correspondent regions in the images to be registered, by virtue of its rotation invariance characteristics. Responses to circular Gabor filters have also been reported in literature as a successful tool for image classification; and in this particular application we utilize them for patient positioning in cranial radiotherapy. For test purposes, we use 2D portal images acquired with an electronic portal imaging device (EPID). Our method presents EPID-EPID registrations errors under 0.2 mm for translations and 0.05 deg for rotations (subpixel accuracy). We are using fiducial marker registration as the ground truth for comparisons. Registration times average 2.70 seconds based on 1400 feature points using a 1.4 GHz processor.
Baseline adjustment increases accurate interpretation of posturographic sway scores.
Tietäväinen, A; Corander, J; Hæggström, E
2015-09-01
Postural steadiness may be quantified using posturographic sway measures. These measures are commonly used to differentiate between a person's baseline balance and balance related to some physiological condition. However, the difference in sway scores between the two conditions may be difficult to detect due to large inter-subject variation. We compared detection accuracy provided by three models that linearly regress a sway measure (mean distance, velocity, or frequency) on the effect of eye closure on balance (eyes open (EO) vs. eyes closed (EC)). In Model 1 the dependent variable is a single sway score (EO or EC), whereas in Models 2 and 3 it is a change score (EO-EO or EC-EO). The independent variable is always the group (group=0: EO or group=1: EC). Model 3 also accounts for the regression to the mean effect (RTM), by considering the baseline value (EO) as a covariate. When differentiating between EO and EC conditions, 94% accuracy can be achieved when using mean velocity as sway measure and either Model 2 or 3. Thus by adjusting for baseline score one increases the accurate interpretation of posturographic sway scores.
Accurate measurement of RF exposure from emerging wireless communication systems
NASA Astrophysics Data System (ADS)
Letertre, Thierry; Monebhurrun, Vikass; Toffano, Zeno
2013-04-01
Isotropic broadband probes or spectrum analyzers (SAs) may be used for the measurement of rapidly varying electromagnetic fields generated by emerging wireless communication systems. In this paper this problematic is investigated by comparing the responses measured by two different isotropic broadband probes typically used to perform electric field (E-field) evaluations. The broadband probes are submitted to signals with variable duty cycles (DC) and crest factors (CF) either with or without Orthogonal Frequency Division Multiplexing (OFDM) modulation but with the same root-mean-square (RMS) power. The two probes do not provide accurate enough results for deterministic signals such as Worldwide Interoperability for Microwave Access (WIMAX) or Long Term Evolution (LTE) as well as for non-deterministic signals such as Wireless Fidelity (WiFi). The legacy measurement protocols should be adapted to cope for the emerging wireless communication technologies based on the OFDM modulation scheme. This is not easily achieved except when the statistics of the RF emission are well known. In this case the measurement errors are shown to be systematic and a correction factor or calibration can be applied to obtain a good approximation of the total RMS power.
ACCURATE CHARACTERIZATION OF HIGH-DEGREE MODES USING MDI OBSERVATIONS
Korzennik, S. G.; Rabello-Soares, M. C.; Schou, J.; Larson, T. P.
2013-08-01
We present the first accurate characterization of high-degree modes, derived using the best Michelson Doppler Imager (MDI) full-disk full-resolution data set available. A 90 day long time series of full-disk 2 arcsec pixel{sup -1} resolution Dopplergrams was acquired in 2001, thanks to the high rate telemetry provided by the Deep Space Network. These Dopplergrams were spatially decomposed using our best estimate of the image scale and the known components of MDI's image distortion. A multi-taper power spectrum estimator was used to generate power spectra for all degrees and all azimuthal orders, up to l = 1000. We used a large number of tapers to reduce the realization noise, since at high degrees the individual modes blend into ridges and thus there is no reason to preserve a high spectral resolution. These power spectra were fitted for all degrees and all azimuthal orders, between l = 100 and l = 1000, and for all the orders with substantial amplitude. This fitting generated in excess of 5.2 Multiplication-Sign 10{sup 6} individual estimates of ridge frequencies, line widths, amplitudes, and asymmetries (singlets), corresponding to some 5700 multiplets (l, n). Fitting at high degrees generates ridge characteristics, characteristics that do not correspond to the underlying mode characteristics. We used a sophisticated forward modeling to recover the best possible estimate of the underlying mode characteristics (mode frequencies, as well as line widths, amplitudes, and asymmetries). We describe in detail this modeling and its validation. The modeling has been extensively reviewed and refined, by including an iterative process to improve its input parameters to better match the observations. Also, the contribution of the leakage matrix on the accuracy of the procedure has been carefully assessed. We present the derived set of corrected mode characteristics, which includes not only frequencies, but line widths, asymmetries, and amplitudes. We present and discuss
Accurate measurement of cortical bone elasticity tensor with resonant ultrasound spectroscopy.
Bernard, Simon; Grimal, Quentin; Laugier, Pascal
2013-02-01
Resonant ultrasound spectroscopy (RUS) allows to accurately characterize the complete set of elastic constants of an anisotropic material from a set of measured mechanical resonant frequencies of a specimen. This method does not suffer from the drawbacks and limitations of the conventional sound velocity approach, but has been reported to fail to measure bone because of its strong viscoelastic damping. In this study, we take advantage of recent developments of RUS to overcome this limitation. The frequency response of a human cortical bone specimen (about 5 × 7 × 7 mm(3)) was measured between 100 and 280 kHz. Despite an important overlapping of the resonant peaks 20 resonant frequencies could be retrieved by using a dedicated signal processing method. The experimental frequencies were progressively matched to the frequencies predicted by a model of the sample whose elastic constants were adjusted. The determined diagonal elastic constants were in good agreement with concurrent sound velocity measurements performed in the principal directions of the specimen. This study demonstrates that RUS is suitable for an accurate measurement of cortical bone anisotropic elasticity. In particular, precision of measured Young and shear moduli is about 0.5%.
Accurate Determination of Torsion and Pure Bending Moment for Viscoelastic Measurements
NASA Astrophysics Data System (ADS)
Wang, Yun-Che; Ko, Chih-Chin; Shiau, Li-Ming
Measurements of time-dependent material properties in the context of linear viscoelasticity, at a given frequency and temperature, require accurate determination of both loading and deformation that are subjected to the testing materials. A pendulum-type viscoelastic spectroscopy is developed to experimentally measure loss tangent and the magnitude of dynamic modulus of solid materials. The mechanical system of the device is based on the behavior of the cantilever beam, and torsion and pure bending moment are generated from the interaction between a permanent magnet and the Helmholtz coils. The strength of the magnetic interactions may be determined with a material with known mechanical properties, such as aluminum 6061T4 alloy. The sensitivity of the torque measurement is on the order of one micro N-m level. With the high accurate torque measurement and deformation detection from a laser-based displacement measurement system, viscoelastic properties of materials can be experimentally measured in different frequency regimes. Sinusoidal driving signals are adopted for measuring complex modulus in the sub-resonant regime, and dc bias driving for creep tests in the low frequency limit. At structural resonant frequencies, the full-width-at-half-maximum (FWHM) method or Lorentzian curve fitting method is adopted to extract material properties. The completion of determining material properties in the wide frequency spectrum may help to identify the deformation mechanisms of the material and to create better models for simulation work.
Madebene, Bruno; Ulusoy, Inga; Mancera, Luis; Scribano, Yohann; Chulkov, Sergey
2011-01-01
Summary We present a theoretical framework for the computation of anharmonic vibrational frequencies for large systems, with a particular focus on determining adsorbate frequencies from first principles. We give a detailed account of our local implementation of the vibrational self-consistent field approach and its correlation corrections. We show that our approach is both robust, accurate and can be easily deployed on computational grids in order to provide an efficient computational tool. We also present results on the vibrational spectrum of hydrogen fluoride on pyrene, on the thiophene molecule in the gas phase, and on small neutral gold clusters. PMID:22003450
All-sky interferometry with spherical harmonic transit telescopes
Shaw, J. Richard; Pen, Ue-Li; Sigurdson, Kris; Sitwell, Michael; Stebbins, Albert
2014-02-01
In this paper, we describe the spherical harmonic transit telescope through the use of a novel formalism for the analysis of transit radio telescopes. This all-sky approach bypasses the curved-sky complications of traditional interferometry and so is particularly well-suited to the analysis of wide-field radio interferometers. It enables compact and computationally efficient representations of the data and its statistics, which allow new ways of approaching important problems like map-making and foreground removal. In particular, we show how it enables the use of the Karhunen-Loève transform as a highly effective foreground filter, suppressing realistic foreground residuals for our fiducial example by at least a factor 20 below the 21 cm signal, even in highly contaminated regions of the sky. This is despite the presence of the mode-mixing inherent in real-world instruments with frequency-dependent beams. We show, using Fisher forecasting, that foreground cleaning has little effect on power spectrum constraints compared to hypothetical foreground-free measurements. Beyond providing a natural real-world data analysis framework for 21 cm telescopes now under construction and future experiments, this formalism allows accurate power spectrum forecasts to be made that include the interplay of design constraints and realistic experimental systematics with 21st century 21 cm science.
Hees, A; Guéna, J; Abgrall, M; Bize, S; Wolf, P
2016-08-01
We use 6 yrs of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions, and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed. PMID:27541455
Hees, A; Guéna, J; Abgrall, M; Bize, S; Wolf, P
2016-08-01
We use 6 yrs of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions, and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed.
NASA Astrophysics Data System (ADS)
Hees, A.; Guéna, J.; Abgrall, M.; Bize, S.; Wolf, P.
2016-08-01
We use 6 yrs of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions, and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed.
Twagirayezu, Sylvestre; Cich, Matthew J.; Sears, Trevor J.; McRaven, Christopher P.; Hall, Gregory E.
2015-07-14
Doppler-free transition frequencies for v₄₋ and v₅₋excited hot bands have been measured in the v₁ + v₃ band region of the spectrum of acetylene using saturation dip spectroscopy with an extended cavity diode laser referenced to a frequency comb. The frequency accuracy of the measured transitions, as judged from line shape model fits and comparison to known frequencies in the v₁ + v₃ band itself, is between 3 and 22 kHz. This is some three orders of magnitude improvement on the accuracy and precision of previous line position estimates that were derived from the analysis of high-resolution Fourier transform infraredmore » absorption spectra. Comparison to transition frequencies computed from constants derived from published Fourier transform infrared spectra shows that some upper rotational energy levels suffer specific perturbations causing energy level shifts of up to several hundred MHz. These perturbations are due to energy levels of the same rotational quantum number derived from nearby vibrational levels that become degenerate at specific energies. Future identification of the perturbing levels will provide accurate relative energies of excited vibrational levels of acetylene in the 7100–7600 cm⁻¹ energy region.« less
Twagirayezu, Sylvestre; Cich, Matthew J.; Sears, Trevor J.; McRaven, Christopher P.; Hall, Gregory E.
2015-07-14
Doppler-free transition frequencies for v₄₋ and v₅₋excited hot bands have been measured in the v₁ + v₃ band region of the spectrum of acetylene using saturation dip spectroscopy with an extended cavity diode laser referenced to a frequency comb. The frequency accuracy of the measured transitions, as judged from line shape model fits and comparison to known frequencies in the v₁ + v₃ band itself, is between 3 and 22 kHz. This is some three orders of magnitude improvement on the accuracy and precision of previous line position estimates that were derived from the analysis of high-resolution Fourier transform infrared absorption spectra. Comparison to transition frequencies computed from constants derived from published Fourier transform infrared spectra shows that some upper rotational energy levels suffer specific perturbations causing energy level shifts of up to several hundred MHz. These perturbations are due to energy levels of the same rotational quantum number derived from nearby vibrational levels that become degenerate at specific energies. Future identification of the perturbing levels will provide accurate relative energies of excited vibrational levels of acetylene in the 7100–7600 cm⁻¹ energy region.
Experimental validation of sheath models at intermediate radio frequencies
NASA Astrophysics Data System (ADS)
Sobolewski, Mark
2013-09-01
Sheaths in radio-frequency (rf) discharges play a dominant role in determining important properties such as the efficiency of power delivery and utilization, plasma spatial uniformity, and ion energy distributions (IEDs). To obtain high quality predictions for these properties requires sheath models that have been rigorously tested and validated. We have performed such tests in capacitively coupled and rf-biased inductively coupled discharges, for inert as well as reactive gases, over two or more orders of magnitude in frequency, voltage, and plasma density. We measured a complete set of model input and output parameters including rf current and voltage waveforms, rf plasma potential measured by a capacitive probe, electron temperature and ion saturation current measured by Langmuir probe and other techniques, and IEDs measured by mass spectrometers and gridded energy analyzers. Experiments concentrated on the complicated, intermediate-frequency regime of ion dynamics, where the ion transit time is comparable to the rf period and the ion current oscillates strongly during the rf cycle. The first models tested used several simplifying assumptions including fluid treatment of ions, neglect of electron inertia, and the oscillating step approximation for the electron profile. These models were nevertheless able to yield rather accurate predictions for current waveforms, sheath impedance, and the peak energies in IEDs. More recently, the oscillating step has been replaced by an exact solution of Poisson's equation. This results in a modest improvement in the agreement with measured electrical characteristics and IED peak amplitudes. The new model also eliminates the need for arbitrary or nonphysical boundary conditions that arises in step models, replacing them with boundary conditions that can be obtained directly from measurements or theories of the presheath.
77 FR 3800 - Accurate NDE & Inspection, LLC; Confirmatory Order
Federal Register 2010, 2011, 2012, 2013, 2014
2012-01-25
... COMMISSION Accurate NDE & Inspection, LLC; Confirmatory Order In the Matter of Accurate NDE & Docket: 150... request ADR with the NRC in an attempt to resolve issues associated with this matter. In response, on August 9, 2011, Accurate NDE requested ADR to resolve this matter with the NRC. On September 28,...
NASA Technical Reports Server (NTRS)
Pujol, A., Jr.
1983-01-01
The development of an accurate close range (from 0.0 meters to 30.0 meters) radar system for Teleoperator Maneuvering Systems (TMS) is discussed. The system under investigation is a digital processor that converts incoming signals from the radar system into their related frequency spectra. Identification will be attempted by correlating spectral characteristics with accurate range determinataions. The system will utilize an analog to digital converter for sampling and converting the signal from the radar system into 16-bit digital words (two bytes) for RAM storage, data manipulations, and computations. To remove unwanted frequency components the data will be retrieved from RAM and digitally filtered using large scale integration (LSI) circuits. Filtering will be performed by a biquadratic routine within the chip which carries out the required filter algorithm. For conversion to a frequency spectrum the filtered data will be processed by a Fast Fourier Transform chip. Analysis and identification of spectral characteristics for accurate range determinations will be made by microcomputer computations.
Dynamic phase transition in diluted Ising model
NASA Astrophysics Data System (ADS)
Chattopadhyay, Sourav; Gorai, Gopal; Santra, S. B.
2015-06-01
Dynamic phase transition in disordered Ising model in two dimensions has been studied in presence of external time dependent oscillating magnetic field applying Glauber Monte Carlo techniques. Dynamic phase transitions are identified estimating dynamic order parameter against temperature for different concentrations of disorder. For a given field strength and frequency for which there was no hysteresis, it is observed that disorder is able induce hysteresis in the system. Effect of increasing concentration of disorder on hysteresis loop area has also been studied.
Transitions: A Personal Perspective.
ERIC Educational Resources Information Center
Wood, Ann Stace
1995-01-01
Distinguishes between unchosen transitions (children maturing and leaving, parents aging, companies downsizing) and chosen ones (moving, divorce, marriage, career changes). Describes the steps one goes through: uneasiness, renewed energy, complaining, exploration, partial transition, and the completed transition. (JOW)
Delay of Transition Using Forced Damping
NASA Technical Reports Server (NTRS)
Exton, Reginald J.
2014-01-01
Several experiments which have reported a delay of transition are analyzed in terms of the frequencies of the induced disturbances generated by different flow control elements. Two of the experiments employed passive stabilizers in the boundary layer, one leading-edge bluntness, and one employed an active spark discharge in the boundary layer. It is found that the frequencies generated by the various elements lie in the damping region of the associated stability curve. It is concluded that the creation of strong disturbances in the damping region stabilizes the boundary-layer and delays the transition from laminar to turbulent flow.
Explosive synchronization with asymmetric frequency distribution
NASA Astrophysics Data System (ADS)
Zhou, Wenchang; Chen, Lumin; Bi, Hongjie; Hu, Xin; Liu, Zonghua; Guan, Shuguang
2015-07-01
In this work, we study the synchronization in a generalized Kuramoto model with frequency-weighted coupling. In particular, we focus on the situations in which the frequency distributions of oscillators are asymmetric. For typical unimodal frequency distributions, such as Lorentzian, Gaussian, triangle, and even special Rayleigh, we find that the synchronization transition in the model generally converts from the first order to the second order as the central frequency shifts toward positive direction. We characterize two interesting coherent states in the system: In the former, two phase-locking clusters are formed, rotating with the same frequency. They correspond to those oscillators with relatively high frequencies while the oscillators with relatively small frequencies are not entrained. In the latter, two phase-locking clusters rotate with different frequencies, leading to the oscillation of the order parameter. We further conduct theoretical analysis to reveal the relation between the asymmetric frequency distribution and the conversion of synchronization type, and justify the coherent states observed in the system.
Estimating rapidly varying frequencies in the presence of noise
Machorro, E
2010-10-01
A variable window length least-squares fitting and the interpolated fast Fourier transform methods are used to estimate the rapidly changing frequency of a signal with measurement noise. The least-squares method is computationally more expensive, but provides more accurate frequency estimates
Precision Teaching, Frequency-Building, and Ballet Dancing
ERIC Educational Resources Information Center
Lokke, Gunn E. H.; Lokke, Jon A.; Arntzen, Erick
2008-01-01
This article reports the effectiveness of a brief intervention aimed at achieving fluency in basic ballet moves in a 9-year-old Norwegian girl by use of frequency-building and Precision Teaching procedures. One nonfluent ballet move was pinpointed, and instructional and training procedures designed to increase the frequency of accurate responding…
Transition to turbulence in pulsating pipe flow
NASA Astrophysics Data System (ADS)
Xu, Duo; Warnecke, Sascha; Hof, Bjoern; Avila, Marc
2014-11-01
We report an experimental investigation of the transition to turbulence in a pulsating pipe flow. This flow is a prototype of various pulsating flows in both nature and engineering, such as in the cardiovascular system where the onset of turbulence is often possibly related to various diseases (e.g., the formation of aneurysms). The experiments are carried out in a straight rigid pipe using water with a sinusoidal modulation of the flow rate. The governing parameters, Reynolds number, Womersley number α (dimensionless pulsating frequency) and the pulsating amplitude A, cover a wide range 3 < α < 23 and 0 < A < 1 . To characterize the transition to turbulence, we determine how the characteristic lifetime of turbulent spots (/puffs) are affected by the pulsation. While at high pulsation frequencies (α > 12) lifetimes of turbulent spots are entirely unaffected by the pulsation, at lower frequencies they are substantially affected. With decreasing frequency much larger Reynolds numbers are needed to obtain spots of the same characteristic lifetime. Hence at low frequency transition is delayed significantly. In addition the effect of the pulsation amplitude on the transition delay is quantified. Duo Xu would like to acknowledge the support from Humboldt Foundation.
Accurate Electron Affinity of Iron and Fine Structures of Negative Iron ions
Chen, Xiaolin; Luo, Zhihong; Li, Jiaming; Ning, Chuangang
2016-01-01
Ionization potential (IP) is defined as the amount of energy required to remove the most loosely bound electron of an atom, while electron affinity (EA) is defined as the amount of energy released when an electron is attached to a neutral atom. Both IP and EA are critical for understanding chemical properties of an element. In contrast to accurate IPs and structures of neutral atoms, EAs and structures of negative ions are relatively unexplored, especially for the transition metal anions. Here, we report the accurate EA value of Fe and fine structures of Fe− using the slow electron velocity imaging method. These measurements yield a very accurate EA value of Fe, 1235.93(28) cm−1 or 153.236(34) meV. The fine structures of Fe− were also successfully resolved. The present work provides a reliable benchmark for theoretical calculations, and also paves the way for improving the EA measurements of other transition metal atoms to the sub cm−1 accuracy. PMID:27138292
Accurate Electron Affinity of Iron and Fine Structures of Negative Iron ions
NASA Astrophysics Data System (ADS)
Chen, Xiaolin; Luo, Zhihong; Li, Jiaming; Ning, Chuangang
2016-05-01
Ionization potential (IP) is defined as the amount of energy required to remove the most loosely bound electron of an atom, while electron affinity (EA) is defined as the amount of energy released when an electron is attached to a neutral atom. Both IP and EA are critical for understanding chemical properties of an element. In contrast to accurate IPs and structures of neutral atoms, EAs and structures of negative ions are relatively unexplored, especially for the transition metal anions. Here, we report the accurate EA value of Fe and fine structures of Fe‑ using the slow electron velocity imaging method. These measurements yield a very accurate EA value of Fe, 1235.93(28) cm‑1 or 153.236(34) meV. The fine structures of Fe‑ were also successfully resolved. The present work provides a reliable benchmark for theoretical calculations, and also paves the way for improving the EA measurements of other transition metal atoms to the sub cm‑1 accuracy.
Accurate Electron Affinity of Iron and Fine Structures of Negative Iron ions.
Chen, Xiaolin; Luo, Zhihong; Li, Jiaming; Ning, Chuangang
2016-01-01
Ionization potential (IP) is defined as the amount of energy required to remove the most loosely bound electron of an atom, while electron affinity (EA) is defined as the amount of energy released when an electron is attached to a neutral atom. Both IP and EA are critical for understanding chemical properties of an element. In contrast to accurate IPs and structures of neutral atoms, EAs and structures of negative ions are relatively unexplored, especially for the transition metal anions. Here, we report the accurate EA value of Fe and fine structures of Fe(-) using the slow electron velocity imaging method. These measurements yield a very accurate EA value of Fe, 1235.93(28) cm(-1) or 153.236(34) meV. The fine structures of Fe(-) were also successfully resolved. The present work provides a reliable benchmark for theoretical calculations, and also paves the way for improving the EA measurements of other transition metal atoms to the sub cm(-1) accuracy. PMID:27138292
Measurement of Fracture Geometry for Accurate Computation of Hydraulic Conductivity
NASA Astrophysics Data System (ADS)
Chae, B.; Ichikawa, Y.; Kim, Y.
2003-12-01
Fluid flow in rock mass is controlled by geometry of fractures which is mainly characterized by roughness, aperture and orientation. Fracture roughness and aperture was observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wavelength of laser is 488nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The system improves resolution in the light axis (namely z) direction because of the confocal optics. The sampling is managed in a spacing 2.5 μ m along x and y directions. The highest measurement resolution of z direction is 0.05 μ m, which is the more accurate than other methods. For the roughness measurements, core specimens of coarse and fine grained granites were provided. Measurements were performed along three scan lines on each fracture surface. The measured data were represented as 2-D and 3-D digital images showing detailed features of roughness. Spectral analyses by the fast Fourier transform (FFT) were performed to characterize on the roughness data quantitatively and to identify influential frequency of roughness. The FFT results showed that components of low frequencies were dominant in the fracture roughness. This study also verifies that spectral analysis is a good approach to understand complicate characteristics of fracture roughness. For the aperture measurements, digital images of the aperture were acquired under applying five stages of uniaxial normal stresses. This method can characterize the response of aperture directly using the same specimen. Results of measurements show that reduction values of aperture are different at each part due to rough geometry of fracture walls. Laboratory permeability tests were also conducted to evaluate changes of hydraulic conductivities related to aperture variation due to different stress levels. The results showed non-uniform reduction of hydraulic conductivity under increase of the normal stress and different values of
Effects of Reduced Frequency on Network Configuration and Synchronization Transition
NASA Astrophysics Data System (ADS)
Liu-Hua, Zhu
2016-05-01
Not Available Supported by the Open Fund from Guangxi Colleges and Universities Key Laboratory of Complex System Optimization and Big Data Processing under Grant No 2015CSOBDP0101, and the National Natural Science Foundation of China under Grant No 11162019.
Laser transit anemometer experiences in supersonic flow
NASA Technical Reports Server (NTRS)
Hunter, William W., Jr.; Humphreys, William M., Jr.
1988-01-01
The purpose of this paper is to present examples of velocity measurements obtained in supersonic flow fields with the laser transit anemometer system. Velocity measurements of a supersonic jet exhausting in a transonic flow field, a cone boundary survey in a Mach 4 flow field, and a determination of the periodic disturbance frequencies of a sonic nozzle flow field are presented. Each of the above three cases also serves to illustrate different modes of laser transit anemometer operation. A brief description of the laser transit anemometer system is also presented.
Frequency-dependent viscous flow in channels with fractal rough surfaces
Cortis, A.; Berryman, J.G.
2010-05-01
The viscous dynamic permeability of some fractal-like channels is studied. For our particular class of geometries, the ratio of the pore surface area-to-volume tends to {infinity} (but has a finite cutoff), and the universal scaling of the dynamic permeability, k({omega}), needs modification. We performed accurate numerical computations of k({omega}) for channels characterized by deterministic fractal wall surfaces, for a broad range of fractal dimensions. The pertinent scaling model for k({omega}) introduces explicitly the fractal dimension of the wall surface for a range of frequencies across the transition between viscous and inertia dominated regimes. The new model provides excellent agreement with our numerical simulations.
Low frequency driven oscillations of cantilevers in viscous fluids at very low Reynolds number
NASA Astrophysics Data System (ADS)
Cranch, G. A.; Lane, J. E.; Miller, G. A.; Lou, J. W.
2013-05-01
The motion of submerged cantilevers driven by viscous fluids is experimentally investigated and a previously published theoretical model is verified over a broad range of Reynolds number covering 4×10-3≤Re≤2000 at frequencies up to 1 kHz. Both planar and cylindrical cantilevers are implemented using short length (few centimeters) fiber lasers, which are also used to measure the deflections. The driving forces are analyzed in detail illustrating how the dominant force transitions from a pressure related force to a viscous force depending on the Reynolds number of the fluid flow around the cantilever. Simplified, approximate expressions for the tip displacement of cantilevers oscillating in the highly viscous regime are also presented. These results will enable accurate, a priori, calculation of the motion of driven cantilevers over a range of dimensions, geometries, and fluid properties.
AUTOMATIC FREQUENCY CONTROL SYSTEM
Hansen, C.F.; Salisbury, J.D.
1961-01-10
A control is described for automatically matching the frequency of a resonant cavity to that of a driving oscillator. The driving oscillator is disconnected from the cavity and a secondary oscillator is actuated in which the cavity is the frequency determining element. A low frequency is mixed with the output of the driving oscillator and the resultant lower and upper sidebands are separately derived. The frequencies of the sidebands are compared with the secondary oscillator frequency. deriving a servo control signal to adjust a tuning element in the cavity and matching the cavity frequency to that of the driving oscillator. The driving oscillator may then be connected to the cavity.
Accurate ab initio quartic force fields for the ions HCO(+) and HOC(+)
NASA Technical Reports Server (NTRS)
Martin, J. M. L.; Taylor, Peter R.; Lee, Timothy J.
1993-01-01
The quartic force fields of HCO(+) and HOC(+) have been computed using augmented coupled cluster methods and basis sets of spdf and spdfg quality. Calculations on HCN, CO, and N2 have been performed to assist in calibrating the computed results. Going from an spdf to an spdfg basis shortens triple bonds by about 0.004 A, and increases the corresponding harmonic frequency by 10-20/cm, leaving bond distances about 0.003 A too long and triple bond stretching frequencies about 5/cm too low. Accurate estimates for the bond distances, fundamental frequencies, and thermochemical quantities are given. HOC(+) lies 37.8 +/- 0.5 kcal/mol (0 K) above HCO(+); the classical barrier height for proton exchange is 76.7 +/- 1.0 kcal/mol.
Sampling diffusive transition paths
F. Miller III, Thomas; Predescu, Cristian
2006-10-12
We address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.
Frequency to Voltage Converter Analog Front-End Prototype
NASA Technical Reports Server (NTRS)
Mata, Carlos; Raines, Matthew
2012-01-01
The frequency to voltage converter analog front end evaluation prototype (F2V AFE) is an evaluation board designed for comparison of different methods of accurately extracting the frequency of a sinusoidal input signal. A configurable input stage is routed to one or several of five separate, configurable filtering circuits, and then to a configurable output stage. Amplifier selection and gain, filter corner frequencies, and comparator hysteresis and voltage reference are all easily configurable through the use of jumpers and potentiometers.
13. EAST FACADE OF THE FREQUENCY CHANGER HOUSE. IT WAS ...
13. EAST FACADE OF THE FREQUENCY CHANGER HOUSE. IT WAS IN THIS BUILDING THAT 60 CYCLE AC POWER WAS CONVERTED TO 25 CYCLE DC POWER FOR USE IN CHICAGO'S TRANSIT SYSTEM; THE FREQUENCY CHANGER HOUSE IS PRESENTLY USED FOR STORAGE. LOOKING WEST. - Commonwealth Electric Company, Fisk Street Electrical Generating Station, 1111 West Cermak Avenue, Chicago, Cook County, IL
NASA Technical Reports Server (NTRS)
Greenhall, C. A.
1987-01-01
Certain aspects of the description and measurement of oscillator stability are treated. Topics covered are time and frequency deviations, Allan variance, the zero-crossing counter measurement technique, frequency drift removal, and the three-cornered hat.
Indium Single-Ion Frequency Standard
NASA Technical Reports Server (NTRS)
Nagourney, Warren
2001-01-01
A single laser-cooled indium ion is a promising candidate for an ultimate resolution optical time or frequency standard. It can be shown that single ions from group IIIA of the periodic table (indium, thallium, etc.) can have extremely small systematic errors. In addition to being free from Doppler, transit-time and collisional shifts, these ions are also quite insensitive to perturbations from ambient magnetic and electric fields (mainly due to the use of a J=0-0 transition for spectroscopy). Of all group IIIA ions, indium seems to be the most practical, since it is heavy enough to have a tolerable intercombination cooling transition rate and (unlike thallium) has transitions which are easily accessible with frequency multiplied continuous-wave lasers. A single indium ion standard has a potential inaccuracy of one part in 10(exp 18) for integration times of 10(exp 6) seconds. We have made substantial progress during the grant period in constructing a frequency standard based upon a single indium ion. At the beginning of the grant period, single indium ions were being successfully trapped, but the lasers and optical systems were inadequate to achieve the desired goal. We have considerably improved the stability of the dye laser used to cool the ions and locked it to a molecular resonance line, making it possible to observe stable cooling-line fluorescence from a single indium ion for reasonable periods of time, as required by the demands of precision spectroscopy. We have substantially improved the single-ion fluorescence signal with significant benefits for the detection efficiency of forbidden transitions using the 'shelving' technique. Finally, we have constructed a compact, efficient UV 'clock' laser and observed 'clock' transitions in single indium ions using this laser system. We will elaborate on these accomplishments.
An accurate single-electron pump based on a highly tunable silicon quantum dot.
Rossi, Alessandro; Tanttu, Tuomo; Tan, Kuan Yen; Iisakka, Ilkka; Zhao, Ruichen; Chan, Kok Wai; Tettamanzi, Giuseppe C; Rogge, Sven; Dzurak, Andrew S; Möttönen, Mikko
2014-06-11
Nanoscale single-electron pumps can be used to generate accurate currents, and can potentially serve to realize a new standard of electrical current based on elementary charge. Here, we use a silicon-based quantum dot with tunable tunnel barriers as an accurate source of quantized current. The charge transfer accuracy of our pump can be dramatically enhanced by controlling the electrostatic confinement of the dot using purposely engineered gate electrodes. Improvements in the operational robustness, as well as suppression of nonadiabatic transitions that reduce pumping accuracy, are achieved via small adjustments of the gate voltages. We can produce an output current in excess of 80 pA with experimentally determined relative uncertainty below 50 parts per million.
Modeling Frequency Comb Sources
NASA Astrophysics Data System (ADS)
Li, Feng; Yuan, Jinhui; Kang, Zhe; Li, Qian; Wai, P. K. A.
2016-06-01
Frequency comb sources have revolutionized metrology and spectroscopy and found applications in many fields. Stable, low-cost, high-quality frequency comb sources are important to these applications. Modeling of the frequency comb sources will help the understanding of the operation mechanism and optimization of the design of such sources. In this paper,we review the theoretical models used and recent progress of the modeling of frequency comb sources.
Accurate description of calcium solvation in concentrated aqueous solutions.
Kohagen, Miriam; Mason, Philip E; Jungwirth, Pavel
2014-07-17
Calcium is one of the biologically most important ions; however, its accurate description by classical molecular dynamics simulations is complicated by strong electrostatic and polarization interactions with surroundings due to its divalent nature. Here, we explore the recently suggested approach for effectively accounting for polarization effects via ionic charge rescaling and develop a new and accurate parametrization of the calcium dication. Comparison to neutron scattering and viscosity measurements demonstrates that our model allows for an accurate description of concentrated aqueous calcium chloride solutions. The present model should find broad use in efficient and accurate modeling of calcium in aqueous environments, such as those encountered in biological and technological applications.
Eastern Frequency Response Study
Miller, N.W.; Shao, M.; Pajic, S.; D'Aquila, R.
2013-05-01
This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.
Etingov, Pavel; Chassin, PNNL David; Zhang, PNNL Yu; PNNL,
2014-03-13
According to the North American Electric Reliability Corporation (NERC) definition: Frequency response is a measure of an Interconnections ability to stabilize frequency immediately following the sudden loss of generation or load, and is a critical component of the reliable operation of the Bulk-Power System, particularly during disturbances and recoveries. Failure to maintain frequency can disrupt the operation of equipment and initiate disconnection of power plant equipment to prevent it from being damaged, which could lead to wide-spread blackouts. Frequency Response Tool automates the power system frequency response analysis process. The tool performs initial estimation of the system frequency parameters (initial frequency, minimum frequency, settling point). User can visually inspect and adjust these parameters. The tool also calculates the frequency response performance metrics of the system, archives the historic events and baselines the system performance. Frequency response performance characteristics of the system are calculated using phasor measurement unit (PMU) information. Methodology of the frequency response performance assessment implemented in the tool complies with the NERC Frequency response standard.
2014-03-13
According to the North American Electric Reliability Corporation (NERC) definition: Frequency response is a measure of an Interconnections ability to stabilize frequency immediately following the sudden loss of generation or load, and is a critical component of the reliable operation of the Bulk-Power System, particularly during disturbances and recoveries. Failure to maintain frequency can disrupt the operation of equipment and initiate disconnection of power plant equipment to prevent it from being damaged, which could leadmore » to wide-spread blackouts. Frequency Response Tool automates the power system frequency response analysis process. The tool performs initial estimation of the system frequency parameters (initial frequency, minimum frequency, settling point). User can visually inspect and adjust these parameters. The tool also calculates the frequency response performance metrics of the system, archives the historic events and baselines the system performance. Frequency response performance characteristics of the system are calculated using phasor measurement unit (PMU) information. Methodology of the frequency response performance assessment implemented in the tool complies with the NERC Frequency response standard.« less
Puzzarini, Cristina; Ali, Ashraf; Biczysko, Malgorzata; Barone, Vincenzo
2015-01-01
An accurate spectroscopic characterization of protonated oxirane has been carried out by means of state-of-the-art computational methods and approaches. The calculated spectroscopic parameters from our recent computational investigation of oxirane together with the corresponding experimental data available were used to assess the accuracy of our predicted rotational and IR spectra of protonated oxirane. We found an accuracy of about 10 cm−1 for vibrational transitions (fundamentals as well as overtones and combination bands) and, in relative terms, of 0.1% for rotational transitions. We are therefore confident that the spectroscopic data provided herein are a valuable support for the detection of protonated oxirane not only in Titan’s atmosphere but also in the interstellar medium. PMID:26543241
Puzzarini, Cristina; Ali, Ashraf; Biczysko, Malgorzata; Barone, Vincenzo
2014-09-10
An accurate spectroscopic characterization of protonated oxirane has been carried out by means of state-of-the-art computational methods and approaches. The calculated spectroscopic parameters from our recent computational investigation of oxirane together with the corresponding experimental data available were used to assess the accuracy of our predicted rotational and IR spectra of protonated oxirane. We found an accuracy of about 10 cm{sup –1} for vibrational transitions (fundamentals as well as overtones and combination bands) and, in relative terms, of 0.1% for rotational transitions. We are therefore confident that the spectroscopic data provided herein are a valuable support for the detection of protonated oxirane not only in Titan's atmosphere but also in the interstellar medium.
The nature of transition blazars
Ruan, J. J.; Anderson, S. F.; Plotkin, R. M.; Brandt, W. N.; Schneider, D. P.; Burnett, T. H.; Myers, A. D.
2014-12-10
Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously transitioned' from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ∼0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.
NASA Astrophysics Data System (ADS)
Li, Jian
1995-11-01
Accurate measurements of isotope shifts, hyperfine splittings and Stark shifts are of interest for studying atomic structure. This thesis reports a new method to precisely measure small frequency intervals. This was done using an acousto-optic modulator to frequency shift part of a laser beam. The frequency shifted and unshifted laser beams were then superimposed and excited an atomic beam. The laser frequency was scanned across the transition while fluorescence produced by the radiative decay of the excited state was detected by a photomultiplier. Each transition generated two peaks in the spectrum separated by the acousto-optic modulation frequency, which permitted the frequency to be calibrated. This method was tested by measuring the isotope shifts and hyperfine splittings of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition at 555.6 nm. The shifts (MHz) relative to ^{176} Yb are: ^{173}Yb {it F}=7/2,-1432.1+/-1.2; ^{171}Yb {it F}=1/2, -1176.9+/-1.1; ^{174}Yb, 953.8+/-1.0; ^{172}Yb 1953.9+/-1.6; ^{170}Yb 3240.4+/-2.8; ^{173}Yb {it F}=5/2,3265.8+/-2.8; ^ {168}Yb, 4611.9+/-4.4; ^ {171,173}Yb {it F}=3/2,4760.1 +/-3.7 where the negative sign indicates that the transition occurs at a lower frequency than in ^{176}Yb. The magnetic dipole (a) and electric quadrupole (b) hyperfine coupling constants (MHz) of the (6s6p) ^3P_1 state for ^{171,173}Yb were determined to be a_{171}=3959.1 +/-3.0, a_{173}=-1094.44+/-0.84 and b_{173}=-827.89+/-0.85. These results were in agreement with the most accurate data found in the literature that were obtained by measuring frequency shifts using a Fabry Perot etalon whose length was stabilized with a helium neon laser locked to an iodine line. In contrast, our method uses cheaper and simpler apparatus. Next, the Stark shift of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition was measured by passing the atomic beam through a uniform electric field. The Stark shift rate was found to be -15.419+/-0.048 kHz/(kV/cm)^2. No
Bursting frequency prediction in turbulent boundary layers
LIOU,WILLIAM W.; FANG,YICHUNG
2000-02-01
The frequencies of the bursting events associated with the streamwise coherent structures of spatially developing incompressible turbulent boundary layers were predicted using global numerical solution of the Orr-Sommerfeld and the vertical vorticity equations of hydrodynamic stability problems. The structures were modeled as wavelike disturbances associated with the turbulent mean flow. The global method developed here involves the use of second and fourth order accurate finite difference formula for the differential equations as well as the boundary conditions. An automated prediction tool, BURFIT, was developed. The predicted resonance frequencies were found to agree very well with previous results using a local shooting technique and measured data.
A novel technique for highly accurate gas exchange measurements
NASA Astrophysics Data System (ADS)
Kalkenings, R. K.; Jähne, B. J.
2003-04-01
The Heidelberg Aeolotron is a circular wind-wave facility for investigating air-sea gas exchange. In this contribution a novel technique for measuring highly accurate transfer velocities k of mass transfer will be presented. Traditionally, in mass balance techniques the constant of decay for gas concentrations over time is measured. The major drawback of this concept is the long time constant. At low wind speeds and a water height greater than 1 m the period of observation has to be several days. In a gas-tight facility such as the Aeolotron, the transfer velocity k can be computed from the concentration in the water body and the change of concentration in the gas space. Owing to this fact, transfer velocities are gained while greatly reducing the measuring times to less than one hour. The transfer velocity k of a tracer can be parameterized as k=1/β \\cdot u_* \\cdot Sc^n, with the Schmidt Number Sc, shear velocity u_* and the dimensionless transfer resistance β. The Schmidt Number exponent n can be derived from simultaneous measurements of different tracers. Since these tracers are of different Schmidt number, the shear velocity is not needed. To allow for Schmidt numbers spanning a hole decade, in our experiments He, H_2, N_2O and F12 are used. The relative accuracy of measuring the transfer velocity was improved to less than 2%. In 9 consecutive experiments conducted at a wind speed of 6.2 m/s, the deviation of the Schmidt number exponent was found to be just under 0.02. This high accuracy will allow precisely determining the transition of the Schmidt number exponent from n=2/3 to n=0.5 from a flat to wavy water surface. In order to quantify gas exchange not only the wind speed is important. Surfactants have a pronounced effect on the wave field and lead to a drastic reduction in the transfer velocity. In the Aeolotron measurements were conducted with a variety of measuring devices, ranging from an imaging slope gauge (ISG) to thermal techniques with IR
Quantum Theory of Hyperfine Structure Transitions in Diatomic Molecules.
ERIC Educational Resources Information Center
Klempt, E.; And Others
1979-01-01
Described is an advanced undergraduate laboratory experiment in which radio-frequency transitions between molecular hyperfine structure states may be observed. Aspects of the quantum theory applied to the analysis of this physical system, are discussed. (Authors/BT)