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158 results on '"D. A. P."'

2. Valence shell photoelectron angular distributions and vibrationally resolved spectra of imidazole:a combined experimental–theoretical study

Author

Patanen, M. (M.), Abid, A. R. (A. R.), Pratt, S. T. (S. T.), Kivimäki, A. (A.), Trofimov, A. B. (A. B.), Skitnevskaya, A. D. (A. D.), Grigoricheva, E. K. (E. K.), Gromov, E. V. (E. V.), Powis, I. (I.), and Holland, D. M. (D. M. P.)

Subjects
Physics::Atomic and Molecular Clusters
Abstract

Linearly polarized synchrotron radiation has been used to record polarization dependent valence shell photoelectron spectra of imidazole in the photon energy range 21–100 eV. These have allowed the photoelectron angular distributions, as characterized by the anisotropy parameter β, and the electronic state intensity branching ratios to be determined. Complementing these experimental data, theoretical photoionization partial cross sections and β-parameters have been calculated for the outer valence shell orbitals. The assignment of the structure appearing in the experimental photoelectron spectra has been guided by vertical ionization energies and spectral intensities calculated by various theoretical methods that incorporate electron correlation and orbital relaxation. Strong orbital relaxation effects have been found for the 15a’, nitrogen lone-pair orbital. The calculations also predict that configuration mixing leads to the formation of several low-lying satellite states. The vibrational structure associated with ionization out of a particular orbital has been simulated within the Franck–Condon model using harmonic vibrational modes. The adiabatic approximation appears to be valid for the X 2A″ state, with the β-parameter for this state being independent of the level of vibrational excitation. However, for all the other outer valence ionic states, a disparity occurs between the observed and the simulated vibrational structure, and the measured β-parameters are at variance with the behavior expected at the level of the Franck–Condon approximation. These inconsistencies suggest that the excited electronic states may be interacting vibronically such that the nuclear dynamics occur over coupled potential energy surfaces.

Published
2021

3. An experimental and theoretical study of the photoelectron spectra of cis-dichloroethene:valence shell vertical ionization and vibronic coupling in the low-lying cationic states

Author

Trofimov, A. B. (A. B.), Powis, I. (I.), Menzies, R. C. (R. C.), Holland, D. M. (D. M. P.), Antonsson, E. (E.), Patanen, M. (M.), Nicolas, C. (C.), Miron, C. (C.), Skitnevskaya, A. D. (A. D.), Gromov, E. V. (E. V.), and Köppel, H. (H.)

Subjects
Physics::Atomic and Molecular Clusters
Abstract

The valence shell photoelectron spectrum of cis-dichloroethene has been studied both experimentally and theoretically. Photoelectron spectra have been recorded with horizontally and vertically plane polarized synchrotron radiation, thereby allowing the anisotropy parameters, characterizing the angular distributions, to be determined. The third-order algebraic-diagrammatic construction approximation scheme for the one-particle Green’s function has been employed to compute the complete valence shell ionization spectrum. In addition, the vertical ionization energies have been calculated using the outer valence Green’s function (OVGF) method and the equation-of-motion coupled-cluster, with single and double substitutions for calculating ionization potentials (EOM-IP-CCSD) model. The theoretical results have enabled assignments to be proposed for most of the structure observed in the experimental spectra, including the inner-valence regions dominated by satellite states. The linear vibronic coupling model has been employed to study the vibrational structure of the lowest photoelectron bands, using parameters obtained from ab initio calculations. The ground state optimized geometries and vibrational frequencies have been computed at the level of the second-order Møller-Plesset perturbation theory, and the dependence of the ionization energies on the nuclear configuration has been evaluated using the OVGF method. While the adiabatic approximation holds for the X̃ ²B₁ state photoelectron band, the à ²B₂, B̃ ²A₁, and C̃ ²A₂ states interact vibronically and form a complex photoelectron band system with four distinct maxima. The D̃ ²B₁ and Ẽ ²B₂ states also interact vibronically with each other. The potential energy surface of the D̃ ²B₁ state is predicted to have a double-minimum shape with respect to the out-of-plane a₂ deformations of the molecular structure. The single photoelectron band resulting from this interaction is characterized by a highly irregular structure, reflecting the non-adiabatic nuclear dynamics occurring on the two coupled potential energy surfaces forming a conical intersection close to the minimum of the Ẽ ²B₂ state.

Published
2018

4. Wavelength-extended photovoltaic infrared photodetectors

Author

Suraj P. Khanna, P. K. D. D. P. Pitigala, Lianhe Li, A. G. Unil Perera, Edmund H. Linfield, and Yan-Feng Lao

Subjects
Materials science, Physics and Astronomy (miscellaneous), Infrared, business.industry, Photovoltaic system, Detector, Photodetector, Heterojunction, Specific detectivity, 7. Clean energy, Gallium arsenide, Wavelength, chemistry.chemical_compound, Optics, chemistry, Optoelectronics, business
Abstract

We report the incorporation of a long-wavelength photovoltaic response (up to 8 μm) in a short-wavelength p-type GaAs heterojunction detector (with the activation energy of EA∼0.40 eV), operating at 80 K. This wavelength-extended photovoltaic response is enabled by employing a non-symmetrical band alignment. The specific detectivity at 5 μm is obtained to be 3.5 × 1012 cm Hz1∕2/W, an improvement by a factor of 105 over the detector without the wavelength extension.

Published
2014

5. Performance improvements of a split-off band infra-red detector using a graded barrier

Author

A. G. U. Perera, Yan-Feng Lao, P. K. D. D. P. Pitigala, H. C. Liu, Edmund H. Linfield, and Lianhe Li

Subjects
010302 applied physics, Range (particle radiation), Materials science, Infrared, business.industry, Superlattice, Detector, General Physics and Astronomy, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Peak response, Responsivity, Optics, 0103 physical sciences, Image force, Optoelectronics, 0210 nano-technology, business, Common emitter
Abstract

Uncooled split-off band infrared detectors have been demonstrated with an operational device response in the 3–5 μm range. We have shown that it is possible to enhance this device response through reducing the recapture rate by replacing one of the commonly used flat barriers in the device with a graded barrier, which was grown using a “digital alloying” approach. Responsivity of approximately 80 μA/W (D* = 1.4 × 108 Jones) were observed at 78 K under a 1 V applied bias, with a peak response at 2.8 μm. This is an improvement by a factor of ∼25 times compared to an equivalent device with a flat barrier. This enhancement is due to improved carrier transport resulting from the superlattice structure, and a low recapture rate enabled by a reduced distance to the image force potential peak in the graded barrier. The device performance can be further improved by growing a structure with repeats of the single emitter layer reported here.

Published
2014

6. Benefit of contralateral routing of signals for unilateral cochlear implant users.

Author

Taal, C. H., van Barneveld, D. C. P. B. M., Soede, W., Briaire, J. J., and Frijns, J. H. M.

Subjects
*COCHLEAR implants, *INTELLIGIBILITY of speech, *MICROPHONES, *NOISE, *AUDITORY perception, *POWER spectra, *PATIENTS
Abstract

One way to improve speech understanding in noise for HI with a unilateral hearing loss is by contralateral routing of signals (CROS). Such a CROS-system captures sounds with an additional microphone at the worst hearing ear and transmits these to the better one. The better ear is then provided with a mix of signals originating from both ears. The goal of this study is to quantify the effect of a CROS-system on speech reception thresholds (SRTs) with unilaterally implanted CI-users in diffuse and directional noise as a function of speaker location. Listening tests are performed and an accurate directional intelligibly model is proposed used for further analysis. In diffuse noise it is concluded that the use of a CROS system results in a maximum gain in SRT of 7.9 dB when speech comes from the CROS side compared to a maximum loss in SRT of 2.1 dB when speech comes from the implanted side. In the case of directional noise, the effect of the CROS is symmetric and the maximum loss or gain in SRT was around 9 dB. The study therefore shows a clear potential of using the CROS system in diffuse noise. [ABSTRACT FROM AUTHOR]

Published
2016
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7. Spin-stand imaging of overwritten data and its comparison with magnetic force microscopy

Author

Mayergoyz, I. D. and Mayergoyz, I. D.

Abstract

A new technique of magnetic imaging on a spin-stand [Mayergoyz et al., J. Appl. Phys. 87, 6824 (2000)] is further developed and extensively tested. The results of successful imaging of digital patterns overwritten with misregistration ranging from 0.3 to 0.07 mm are reported. The results are compared with magnetic force microscopy (MFM) images and the conclusion is reached that the spin-stand imaging technique can provide (at least) the same level of resolution and accuracy as the MFM imaging technique.

Published
2001

10. Quantification of magnetic force microscopy images using combined electrostatic and magnetostatic imaging

Author

Gomez, R. D. and Gomez, R. D.

Abstract

A method for calibrating the force gradients and probe magnetic moment in phase-contrast magnetic force microscopy ~MFM! is introduced. It is based upon the combined electrostatic force microscopy EFM and MFM images of a conducting non magnetic metal strip. The behavior of the phase contrast in EFM is analyzed and modeled as a finite area capacitor. This model is used in conjunction with the imaging data to derive the proportionality constant between the phase and the force gradient. This calibration is further used to relate the measured MFM images with the field gradient from the same conducting strip to derive the effective magnetic moment of the probe. The knowledge of the phase-force gradient proportionality constant and the probe’s effective moment is essential to directly quantify field derivatives in MFM images.

Published
1998

11. Magnetic imaging in the presence of external fields: Technique and applications (invited)

Author

Gomez, Romel D. and Gomez, Romel D.

Abstract

Magnetic force microscopy (MFM) in the presence of an external magnetic field has been developed. This has led to further understanding of image formation in MFM as well as new insights concerning the interaction of magnetic recording media with an external field. Our results confirm that, at low applied fields, image formation results from the interaction of the component by the local surface field along the direction of the probe’s magnetization. By reorienting the probe’s magnetization by an appropriate application of an external field, it is possible to selectively image specific components of the local field. At higher applied fields, the probe becomes saturated and the changes in the images may be attributed to magnetization reversal of the sample. We have observed the transformations that occur at various stages of the dc erasure of thin-film recording media. This technique has also been applied to conventional magneto-optical media to study domain collapse caused by increasing temperature with an external bias field. The methods, results, and their analysis are presented.

Published
1996

12. Switching characteristics of submicron cobalt islands

Author

Gomez, R. D. and Gomez, R. D.

Abstract

The magnetic characteristics of 0.230.430.02 mm3 cobalt islands were investigated using magnetic force microscopy in the presence of an applied field. The islands were noninteracting and showed a wide variety of single and multidomain configurations. The distribution of magnetization directions supports earlier models which suggest that crystalline anisotropy plays a dominant role in establishing a dispersion of easy axis directions about the long axis of the particles. The magnetic evolution, involving rotation and switching of individual islands, was observed at various points along the microscopic magnetization curve. A magnetization curve of an ensemble of islands was derived from the images and compares remarkably well with macroscopic M–H measurements.

Published
1996

15. Impulse measurements of impedance and propagation constant compared to rigid-frame and dual-wave predictions for foam.

Author

Lawrence, D. E. P. and Don, C. G.

Abstract

Acoustic impulse techniques are used to obtain measurements of propagation constant in three different foams and to determine both the characteristic impedance and the normal impedance at the surface of a hard-backed layer over the frequency range from 200 Hz to 10 kHz. A comparison is made of existing rigid-frame and dual-wave models of sound propagation in porous media, and predictions from both models are compared with experimental measurements. Both models give good agreement with the lower flow resistivity foam measurements, however, the dual-wave model better predicts the overall results for a foam with a flow resistivity of 25100 N s m-4, implying the need of the slow wave mode. The position of the maxima in the layer impedance results are particularly sensitive to the correct choice of tortuosity. An emphasis is placed on how the two models compare as the frame material becomes rigid and these ideas are used to consider the implication of a previous claim about the existence of a slow wave in foams. [ABSTRACT FROM AUTHOR]

Published
1995
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19. 43.66.Ts TELECOIL IN A DETACHABLE DIRECT AUDIO INPUT ACCESSORY.

Author

D. A. P.

Subjects
*PATENTS, *ACOUSTIC devices, *HEARING aids, *EQUIPMENT & supplies
Abstract

Information on a patent for a telecoil connected to a detachable Direct Audio Input (DAI) connector in a hearing aid is presented.

Published
2015

29. 9,408,003 43.66.Ts HEARING AID WITH AN ANTENNA.

Author

D. A. P.

Subjects
*HEARING aid design & construction, *ANTENNAS (Electronics), *PATENTS
Abstract

The article discusses U.S. patent 9,408,003, with is for a wireless hearing aid assembly that has an antenna.

Published
2017

30. 43.66.Ts HEARING AID WIRELESS NETWORK.

Author

D. A. P.

Subjects
*PATENTS, *HEARING aids, *EQUIPMENT & supplies
Abstract

The article reviews a U.S. patent for a hearing aid wireless network owned by Rene Rye Larsen, an assignor to medical device company GN ReSound A/S.

Published
2014

35. 43.66.Ts FEEDBACK PATH EVALUATION IMPLEMENTEDWITH LIMITED SIGNAL PROCESSING.

Author

D. A. P.

Subjects
*FEEDBACK control systems, *HEARING aids, *ADAPTIVE filters
Abstract

The article presents an abstract of the acoustical patent "Feedback evaluation implemented with limited signal processing" by Martin Evert Gustaf Hillbratt and Mats Höjlund, assignors to Cochlear Ltd.

Published
2016

37. 43.72.Gy IMMERSIVE AUDIO RENDERING SYSTEM.

Author

D. A. P.

Subjects
*AUDIO acoustics, *IMMERSIVE design
Abstract

The article presents an abstract of the acoustical patent "Immersive audio rendering system" by Alan D Kraemer and others, assignors to DTS LLC.

Published
2016

39. 43.71.Gv METHOD FOR TESTING HEARING AIDS.

Author

D. A. P.

Subjects
*HEARING aids, *GRAPHICAL user interfaces, *SIGNAL-to-noise ratio
Abstract

The article presents an abstract of the acoustical patent "Method for testing hearing aids" by Martina Bellanova and Mattias Latzel, assignors to Sivantos Pte.

Published
2016

40. 43.66.Ts HEARING AID HAVING LEVEL AND FREQUENCY-DEPENDENT GAIN.

Author

D. A. P.

Subjects
*HEARING aids, *SOUND pressure, *HEARING disorders
Abstract

The article presents an abstract of the acoustical patent "Hearing aid having level and frequency-dependent gain" by John D. Meyer and Toban A. Szuts, assignors to Meyer Sound Laboratories Inc.

Published
2016

41. 43.66.Ts AUTOMATIC POWER-OFF OF HEARING AID.

Author

D. A. P.

Subjects
*HEARING aids, *REMOTE control, *WIRELESS communications
Abstract

The article presents an abstract of the acoustical patent "Automatic power-off of hearing aid" by Morten Kroman, assignor to Widex A/S.

Published
2016

42. Network and method for providing a user interface for a simultaneous ring telecommunications service with automatic speech recognition capability.

Author

D. A. P.

Subjects
*PATENTS, *AUTOMATIC speech recognition, *USER interfaces, *TELECOMMUNICATION
Abstract

Evaluates a patent application for a network and method for providing a user interface in simultaneous ring telecommunications service, developed by BellSouth Intellectual Property Corporation. Capability of the network to recognize speech.

Published
2005
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