Artykuły w czasopismach: „Spin noise signal”

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Shi Ping, Ma Jian, Qian Xuan, Ji Yang i Li Wei. "Signal-to-noise ratio of spin noise spectroscopy in rubidium vapor". Acta Physica Sinica 66, nr 1 (2017): 017201. http://dx.doi.org/10.7498/aps.66.017201.

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Chaudhari, Abhijit P., Shane P. Kelly, Riccardo J. Valencia-Tortora i Jamir Marino. "Zeno crossovers in the entanglement speed of spin chains with noisy impurities". Journal of Statistical Mechanics: Theory and Experiment 2022, nr 10 (1.10.2022): 103101. http://dx.doi.org/10.1088/1742-5468/ac8e5d.

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Abstract We use a noisy signal with finite correlation time to drive a spin (dissipative impurity) in the quantum XY spin chain and calculate the dynamics of entanglement entropy (EE) of a bipartition of spins, for a stochastic quantum trajectory. We compute the noise averaged EE of a bipartition of spins and observe that its speed of spreading decreases at strong dissipation, as a result of the Zeno effect. We recover the Zeno crossover and show that noise averaged EE can be used as a proxy for the heating and Zeno regimes. Upon increasing the correlation time of the noise, the location of the Zeno crossover shifts at stronger dissipation, extending the heating regime.

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Ma, Yintao, Zhixia Qiao, Mingzhi Yu, Yanbin Wang, Yao Chen, Guoxi Luo, Ping Yang i in. "Single-beam integrated hybrid optical pumping spin exchange relaxation free magnetometer for biomedical applications". Applied Physics Letters 121, nr 11 (12.09.2022): 114001. http://dx.doi.org/10.1063/5.0105945.

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An ingenious approach to accomplish the high signal strengthen and relatively homogeneous spin polarization has been presented in a hybrid optical pumping spin-exchange-relaxation-free atomic magnetometer only utilizing single-beam configuration. We have experimentally demonstrated an approximately three-fold enhancement of the output signal at the optimal spin polarization by optically pumping the thin vapor due to the same spin evolution behavior of the two different kinds of vapor atoms. Eventually, a measuring sensitivity of 30 fT/Hz1/2 was achieved combined with the homemade differential detection system for attenuating large background offset and suppressing optical power noise. This scheme provides a prospect for the development of ultra-highly sensitive and chip-scale atomic magnetometer for the applications that desire both high signal-to-noise ratio and uniform spin polarization, such as magnetocardiography and magnetoencephalography.

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Mokhtari, S. Abolfazl, i Mehdi Sabzehparvar. "Spin flight mode identification with OEEMD algorithm". Aircraft Engineering and Aerospace Technology 91, nr 4 (1.04.2019): 582–600. http://dx.doi.org/10.1108/aeat-12-2017-0280.

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Purpose The paper aims to present an innovative method for identification of flight modes in the spin maneuver, which is highly nonlinear and coupled dynamic. Design/methodology/approach To fix the mode mixing problem which is mostly happen in the EMD algorithm, the authors focused on the proposal of an optimized ensemble empirical mode decomposition (OEEMD) algorithm for processing of the flight complex signals that originate from FDR. There are two improvements with the OEEMD respect to the EEMD. First, this algorithm is able to make a precise reconstruction of the original signal. The second improvement is that the OEEMD performs the task of signal decomposition with fewer iterations and so with less complexity order rather than the competitor approaches. Findings By applying the OEEMD algorithm to the spin flight parameter signals, flight modes extracted, then with using systematic technique, flight modes characteristics are obtained. The results indicate that there are some non-standard modes in the nonlinear region due to couplings between the longitudinal and lateral motions. Practical implications Application of the proposed method to the spin flight test data may result accurate identification of nonlinear dynamics with high coupling in this regime. Originality/value First, to fix the mode mixing problem in EMD, an optimized ensemble empirical mode decomposition algorithm is introduced, which disturbed the original signal with a sort of white Gaussian noise, and by using white noise statistical characteristics the OEEMD fix the mode mixing problem with high precision and fewer calculations. Second, by applying the OEEMD to the flight output signals and with using the systematic method, flight mode characteristics which is very important in the simulation and controller designing are obtained.

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Dai, Weiying, Gopal Varma, Rachel Scheidegger i David C. Alsop. "Quantifying fluctuations of resting state networks using arterial spin labeling perfusion MRI". Journal of Cerebral Blood Flow & Metabolism 36, nr 3 (5.11.2015): 463–73. http://dx.doi.org/10.1177/0271678x15615339.

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Blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) has been widely used to investigate spontaneous low-frequency signal fluctuations across brain resting state networks. However, BOLD only provides relative measures of signal fluctuations. Arterial Spin Labeling (ASL) MRI holds great potential for quantitative measurements of resting state network fluctuations. This study systematically quantified signal fluctuations of the large-scale resting state networks using ASL data from 20 healthy volunteers by separating them from global signal fluctuations and fluctuations caused by residual noise. Global ASL signal fluctuation was 7.59% ± 1.47% relative to the ASL baseline perfusion. Fluctuations of seven detected resting state networks vary from 2.96% ± 0.93% to 6.71% ± 2.35%. Fluctuations of networks and residual noise were 6.05% ± 1.18% and 6.78% ± 1.16% using 4-mm resolution ASL data applied with Gaussian smoothing kernel of 6mm. However, network fluctuations were reduced by 7.77% ± 1.56% while residual noise fluctuation was markedly reduced by 39.75% ± 2.90% when smoothing kernel of 12 mm was applied to the ASL data. Therefore, global and network fluctuations are the dominant structured noise sources in ASL data. Quantitative measurements of resting state networks may enable improved noise reduction and provide insights into the function of healthy and diseased brain.

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Wilson, Richard H., Rachel McArdle, Kelly L. Watts i Sherri L. Smith. "The Revised Speech Perception in Noise Test (R-SPIN) in a Multiple Signal-to-Noise Ratio Paradigm". Journal of the American Academy of Audiology 23, nr 08 (wrzesień 2012): 590–605. http://dx.doi.org/10.3766/jaaa.23.7.9.

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Background: The Revised Speech Perception in Noise Test (R-SPIN; Bilger, 1984b) is composed of 200 target words distributed as the last words in 200 low-predictability (LP) and 200 high-predictability (HP) sentences. Four list pairs, each consisting of two 50-sentence lists, were constructed with the target word in a LP and HP sentence. Traditionally the R-SPIN is presented at a signal-to-noise ratio (SNR, S/N) of 8 dB with the listener task to repeat the last word in the sentence. Purpose: The purpose was to determine the practicality of altering the R-SPIN format from a single SNR paradigm into a multiple SNR paradigm from which the 50% points for the HP and LP sentences can be calculated. Research Design: Three repeated measures experiments were conducted. Study Sample: Forty listeners with normal hearing and 184 older listeners with pure-tone hearing loss participated in the sequence of experiments. Data Collection and Analysis: The R-SPIN sentences were edited digitally (1) to maintain the temporal relation between the sentences and babble, (2) to establish the SNRs, and (3) to mix the speech and noise signals to obtain SNRs between –1 and 23 dB. All materials were recorded on CD and were presented through an earphone with the responses recorded and analyzed at the token level. For reference purposes the Words-in-Noise Test (WIN) was included in the first experiment. Results: In Experiment 1, recognition performances by listeners with normal hearing were better than performances by listeners with hearing loss. For both groups, performances on the HP materials were better than performances on the LP materials. Performances on the LP materials and on the WIN were similar. Performances at 8 dB S/N were the same with the traditional fixed level presentation and the descending presentation level paradigms. The results from Experiment 2 demonstrated that the four list pairs of R-SPIN materials produced good first approximation psychometric functions over the –4 to 23 dB S/N range, but there were irregularities. The data from Experiment 2 were used in Experiment 3 to guide the selection of the words to be used at the various SNRs that would provide homogeneous performances at each SNR and would produce systematic psychometric functions. In Experiment 3, the 50% points were in good agreement for the LP and HP conditions within both groups of listeners. The psychometric functions for List Pairs 1 and 2, 3 and 4, and 5 and 6 had similar characteristics and maintained reasonable separations between the HP and LP functions, whereas the HP and LP functions for List Pair 7 and 8 bisected one another at the lower SNRs. Conclusions: This study indicates that the R-SPIN can be configured into a multiple SNR paradigm. A more in-depth study with the R-SPIN materials is needed to develop lists that are systematic and reasonably equivalent for use on listeners with hearing loss. The approach should be based on the psychometric characteristics of the 200 HP and 200 LP sentences with the current R-SPIN lists discarded. Of importance is maintaining the synchrony between the sentences and their accompanying babble.

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Adilakshmi, D., Kousik Chandra i K. V. Ramanathan. "Enhancement of the Nuclear Spin Noise Signal Using Wavelet Transform". ChemPhysChem 20, nr 3 (4.12.2018): 456–62. http://dx.doi.org/10.1002/cphc.201800938.

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Ginthör, Stephan J., Judith Schlagnitweit, Matthias Bechmann i Norbert Müller. "Nuclear spin noise tomography in three dimensions with iterative simultaneous algebraic reconstruction technique (SART) processing". Magnetic Resonance 1, nr 2 (6.08.2020): 165–73. http://dx.doi.org/10.5194/mr-1-165-2020.

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Abstract. We report three-dimensional spin noise imaging (SNI) of nuclear spin density from spin noise data acquired by Faraday detection. Our approach substantially extends and improves the two-dimensional SNI method for excitation-less magnetic resonance tomography reported earlier (Müller and Jerschow, 2006). This proof of principle was achieved by taking advantage of the particular continuous nature of spin noise acquired in the presence of constant magnitude magnetic field gradients and recent advances in nuclear spin noise spectroscopy acquisition as well as novel processing techniques. In this type of projection–reconstruction-based spin noise imaging the trade-off between signal-to-noise ratio (or image contrast) and resolution can be adjusted a posteriori during processing of the original time-domain data by iterative image reconstruction in a unique way not possible in conventional rf-pulse-dependent magnetic resonance imaging (MRI). The 3D SNI is demonstrated as a proof of concept on a commercial 700 MHz high-resolution NMR spectrometer, using a 3D-printed polymeric phantom immersed in water.

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KRAWIECKI, A., S. MATYJAŚKIEWICZ, J. A. HOŁYST i K. KACPERSKI. "FRACTAL SPECTROSCOPY BY NOISE-FREE STOCHASTIC MULTIRESONANCE AT HIGHER HARMONICS". International Journal of Bifurcation and Chaos 14, nr 01 (styczeń 2004): 141–59. http://dx.doi.org/10.1142/s0218127404009235.

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Noise-free stochastic resonance is investigated in two chaotic maps with periodically modulated control parameter close to a boundary crisis: the Hénon map and the kicked spin model. Response of the maps to the periodic signal at the fundamental frequency and its higher harmonics is examined. The systems show noise-free stochastic multiresonance, i.e. multiple maxima of the signal-to-noise ratio at the fundamental frequency as a function of the control parameter. The maxima are directly related to the fractal structure of the attractors and basins of attraction colliding at the crisis point. The signal-to-noise ratios at higher harmonics show more maxima, as well as dips where the signal-to-noise ratio is zero. This opens a way to use noise-free stochastic resonance to probe the fractal structure of colliding sets by a method which can be called "fractal spectroscopy". Using stochastic resonance at higher harmonics can reveal smaller details of the fractal structures, but the interpretation of results becomes more difficult. Quantitative theory based on a model of a colliding fractal attractor and a fractal basin of attraction is derived which agrees with numerical results for the signal-to-noise ratio at the fundamental frequency and at the first two harmonics, quantitatively for the Hénon map, and qualitatively for the kicked spin model. It is also argued that the maps under study belong to a more general class of threshold-crossing stochastic resonators with a modulated control parameter, and qualitative discussion of conditions under which stochastic multiresonance appears in such systems is given.

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Strakholis, Andrey A., Vladimir T. Oleynikov i Andrey N. Petrenko. "Noise-like signals and their conversion used in radio communication systems". T-Comm 16, nr 7 (2022): 14–20. http://dx.doi.org/10.36724/2072-8735-2022-16-7-14-20.

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The actual problem of determining the principle of the transmission signal formation and its transformation into an initial signal providing stable radio communication in a radio interference situation is considered. This is typical when organizing the management of fire extinguishing units, especially in forests and steppes. The subject of the study is the use of a reprogrammable matched filter (PPSF), in which a spin echo processor with a working substance 59Co is used to convert phase-manipulated noise-like signals. The purpose of the work is to propose the use of a spin processor in the PPSF, which ensures the conversion of FM SHPS even in the presence of dynamically changing multipath. With this configuration of the radio-transmitting device, it becomes possible to organize multicast radio communication without deploying a base station. The results of the study include the results of machine modeling of the conversion of FM SHPS to PPSF under unfavorable conditions of formation of a three-beam signal at the input of a radio receiver. The structural diagrams of the FM SHPS and PPSF shaper of the laboratory installation on which the research was carried out are given. The obtained results of laboratory studies within the permissible error, when removing the results and in measuring instruments coincide with the results of machine modeling. Therefore, the considered principle of converting FM SHPS into PPSF, which is based on the principle of converting FM SHPS into a primary signal, can be successfully implemented in radio stations used by units of the Ministry of Emergency Situations of Russia in fire extinguishing areas.

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Dutsov, Chavdar, Timothy Hume i Philipp Schmidt-Wellenburg. "Systematic effects in the search for the muon electric dipole moment using the frozen-spin technique". EPJ Web of Conferences 282 (2023): 01013. http://dx.doi.org/10.1051/epjconf/202328201013.

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At the Paul Scherrer Institute (PSI) we are developing a high precision instrument to measure the muon electric dipole moment (EDM). The experiment is based on the frozen-spin method in which the spin precession induced by the anomalous magnetic moment is suppressed, thus increasing the signal-to-noise ratio for EDM signals to achieve a sensitivity otherwise unattainable using conventional g - 2 muon storage rings. The expected statistical sensitivity for the EDM after a year of data taking is 6 10−23e cm with the p = 125 MeV/c muon beam available at the PSI. Reaching this goal necessitates a comprehensive analysis on spurious effects that mimic the EDM signal. This work discusses a quantitative approach to study systematic effects for the frozen-spin method when searching for the muon EDM. Equations for the motion of the muon spin in the electromagnetic fields of the experimental system are analytically derived and validated by simulation.

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Nausner, Martin, Michael Goger, Eli Bendet-Taicher, Judith Schlagnitweit, Alexej Jerschow i Norbert Müller. "Signal enhancement in protein NMR using the spin-noise tuning optimum". Journal of Biomolecular NMR 48, nr 3 (6.10.2010): 157–67. http://dx.doi.org/10.1007/s10858-010-9446-4.

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Indrati, Rini, Heriansyah Heriansyah i Wakhrudin Wakhrudin. "Analisis Variasi Time Repetition (TR) terhadap Signal to Noise Ratio dan Contrast to Noise Ratio pada Pemeriksaan MRI Cervical T2 Weighted Fast Spin Echo (FSE) Potongan Sagital". Jurnal Imejing Diagnostik (JImeD) 2, nr 1 (11.01.2016): 119–23. http://dx.doi.org/10.31983/jimed.v2i1.3168.

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Background: Time Repetition (TR) is one parameter that can affect the value of Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR). The purpose of this research is to know the effect of variation of TR value on SNR and CNR on cervical MRI examination with Sagital T2 Weighted Fast Spin Echo sequence and to know the most optimal TR value from the variation of TR value to SNR and CNR on cervical MRI examination with Sagital T2 Weighted Fast Spin Echo.Methods: The type of this study was experimental study. The study was conducted using MRI 1.5 Tesla at Kasih Ibu Denpasar Hospital. Data were 40 MRI cervical images of sagital Fast Spin Echo from 10 volunteers with four variations of TR (2500 ms, 3000 ms, 3500 ms, and 4000 ms). The SNR and CNR values are measured by identifying the Region of Interest (ROI) in the corpus, discus, cerebro spinal fluid (CSF), and medula spinalis regions to obtain the average signals and compared with the mean deviation of the background. Data was analyzed by regression test to know the influence and by Anova test.Results: The result of the research showed that there was the influence of TR value to SNR and CNR of MRI Cervical Sagital T2 FSE. There was a strong correlation between the variation of TR values with SNR and CNR Cervical with p-value 0.05, the optimal TR value obtained in Cervical Sagital T2 FSE anatomical image on MRI 1,5 Tesla modality was 3500 ms.Conclusion: Time Repetition affected the signal to noise ratio and contrast to noise ratio. TR 3500 ms produced the most optimal cervical MRI image quality.

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Ferraro, Elena, i Marco De Michielis. "Bandwidth-Limited and Noisy Pulse Sequences for Single Qubit Operations in Semiconductor Spin Qubits". Entropy 21, nr 11 (26.10.2019): 1042. http://dx.doi.org/10.3390/e21111042.

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Spin qubits are very valuable and scalable candidates in the area of quantum computation and simulation applications. In the last decades, they have been deeply investigated from a theoretical point of view and realized on the scale of few devices in the laboratories. In semiconductors, spin qubits can be built confining the spin of electrons in electrostatically defined quantum dots. Through this approach, it is possible to create different implementations: single electron spin qubit, singlet–triplet spin qubit, or a three-electron architecture, e.g., the hybrid qubit. For each qubit type, we study the single qubit rotations along the principal axis of Bloch sphere including the mandatory non-idealities of the control signals that realize the gate operations. The realistic transient of the control signal pulses are obtained by adopting an appropriate low-pass filter function. In addition. the effect of disturbances on the input signals is taken into account by using a Gaussian noise model.

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Wang, Xiao Fei, i Ji Min Li. "The Unique Property in Magnetic Noise of Spin Modulated Atomic Magnetometer". Key Engineering Materials 787 (listopad 2018): 75–80. http://dx.doi.org/10.4028/www.scientific.net/kem.787.75.

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This paper presents a spin modulated atomic magnetometer, different from other kinds of atomic magnetometers, the conversion coefficient between the polarization signal and the magnetic field to be measured is independent of the transverse relaxation time, which means that the higher sensitivity can be achieved when polarization is kept constant. For better understanding, the magnetic noise of spin modulated magnetometer is demonstrated and compared to SERF magnetometer. The magnetic noise measurement experiment is designed, the experimental results are consistent with the theoretical prediction. This paper validate the unique property of spin modulated magnetometer and this property will play an important role in guiding the optimization of future experiments.

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Hendrick, R. Edward. "Sampling time effects on signal-to-noise and contrast-to-noise ratios in spin-echo MRI". Magnetic Resonance Imaging 5, nr 1 (styczeń 1987): 31–37. http://dx.doi.org/10.1016/0730-725x(87)90481-4.

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Mizushima, K., K. Kudo, T. Nagasawa i R. Sato. "Signal-to-noise ratios in high-signal-transfer-rate read heads composed of spin-torque oscillators". Journal of Applied Physics 107, nr 6 (15.03.2010): 063904. http://dx.doi.org/10.1063/1.3294653.

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Bei, Y., i E. W. Hill. "Dependence of signal-to-noise ratio on excitation current and signal frequency in spin valve sensors". Journal of Applied Physics 93, nr 10 (15.05.2003): 8391–93. http://dx.doi.org/10.1063/1.1558095.

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Hoult, D. I., i N. S. Ginsberg. "The Quantum Origins of the Free Induction Decay Signal and Spin Noise". Journal of Magnetic Resonance 148, nr 1 (styczeń 2001): 182–99. http://dx.doi.org/10.1006/jmre.2000.2229.

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Stoyanov, Bozhidar, i Borislav Stoyanov. "BOOST: Medical Image Steganography Using Nuclear Spin Generator". Entropy 22, nr 5 (26.04.2020): 501. http://dx.doi.org/10.3390/e22050501.

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In this study, we present a medical image stego hiding scheme using a nuclear spin generator system. Detailed theoretical and experimental analysis is provided on the proposed algorithm using histogram analysis, peak signal-to-noise ratio, key space calculation, and statistical package analysis. The provided results show good performance of the brand new medical image steganographic scheme.

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Johnsen, Peter C., Sinéad A. Ryan, Christian Gentry, Anya Grafov, Henry Kapteyn i Margaret Murnane. "A beamline for ultrafast extreme ultraviolet magneto-optical spectroscopy in reflection near the shot noise limit". Review of Scientific Instruments 94, nr 3 (1.03.2023): 033001. http://dx.doi.org/10.1063/5.0127119.

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High harmonic generation (HHG) makes it possible to measure spin and charge dynamics in materials on femtosecond to attosecond timescales. However, the extreme nonlinear nature of the high harmonic process means that intensity fluctuations can limit measurement sensitivity. Here we present a noise-canceled, tabletop high harmonic beamline for time-resolved reflection mode spectroscopy of magnetic materials. We use a reference spectrometer to independently normalize the intensity fluctuations of each harmonic order and eliminate long term drift, allowing us to make spectroscopic measurements near the shot noise limit. These improvements allow us to significantly reduce the integration time required for high signal-to-noise (SNR) measurements of element-specific spin dynamics. Looking forward, improvements in the HHG flux, optical coatings, and grating design can further reduce the acquisition time for high SNR measurements by 1–2 orders of magnitude, enabling dramatically improved sensitivity to spin, charge, and phonon dynamics in magnetic materials.

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Kim, Subin, Sungwha You, Myoung Eun Sohn, Woojae Han, Jae-Hyun Seo i Yonghee Oh. "A Comparison Between the Korean Digits-in-Noise Test and the Korean Speech Perception-in-Noise Test in Normal-Hearing and Hearing-Impaired Listeners". Journal of Audiology and Otology 25, nr 4 (10.10.2021): 171–77. http://dx.doi.org/10.7874/jao.2021.00045.

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Background and Objectives: The purpose of the present study was to validate the performance and diagnostic efficacy of the Korean digits-in-noise (K-DIN) test in comparison to the Korean speech perception-in-noise (K-SPIN) test, which is the representative speech-in-noise test in clinical practice.Subjects and Methods: Twenty-seven subjects (15 normal-hearing and 12 hearing-impaired listeners) participated. The recorded Korean 0-9 digits were used to form quasirandom digit triplets; 50 target digit triplets were presented at the most comfortable level of each subject while presenting speech-shaped background noise at various levels of signal-to-noise ratios (-12.5, -10, -5, or +5 dB). Subjects were then instructed to listen to both target and noise masker unilaterally and bilaterally through a headphone. K-SPIN test was also conducted using the same procedure as the K-DIN. After calculating their percent correct responses, K-DIN and K-SPIN results were compared using a Pearson-correlation test.Results: Results showed a statistically significant correlation between K-DIN and K-SPIN in all hearing conditions (left: r=0.814, p<0.001; right: r=0.788, p<0.001; bilateral: r=0.727, p<0.001). Moreover, the K-DIN test achieved better testing efficacy, shorter average listening time (5 min vs. 30 min), and easier performance of task according to participants’ qualitative reports than the K-SPIN test.Conclusions: In this study, the Korean version of digit triplet test was validated in both normal-hearing and hearing-impaired listeners. The findings suggest that the K-DIN test can be used as a simple and time-efficient hearing-in-noise test in audiology clinics in Korea.

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Hittmair, K., S. Trattnig, C. J. Herold, M. Breitenseher i J. Kramer. "Comparison between Conventional and Fast Spin-Echo Stir Sequences". Acta Radiologica 37, nr 3P2 (maj 1996): 943–49. http://dx.doi.org/10.1177/02841851960373p2100.

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Purpose: To evaluate the common characteristics and differences in contrast behavior of short-TI-inversion-recovery (STIR) and short-TI-inversion-recovery fast spin-echo (TurboSTIR) sequences. Material and Methods: Phantoms doped with increasing doses of Gd-DTPA and a pork-fat phantom were used to evaluate the dependence of the STIR and TurboSTIR signals on the T1 relaxation time. Clinical TurboSTIR images were obtained from 30 patients with musculoskeletal abnormalities and compared to conventional STIR images in 15 cases and to postcontrast TurboSTIR images in another 15 cases. Results: In the phantom measurements, a significantly shorter inversion time (TI) was needed to achieve fat suppression on TurboSTIR images, and, with an identical number of signal averages, contrast-to-noise ratios were lower on TurboSTIR images. These differences between STIR and TurboSTIR can be attributed to the contribution of stimulated echoes to overall TurboSTIR signal and can be compensated by a shorter TI and a higher number of signal averages for TurboSTIR, respectively. With these adaptations, clinical TurboSTIR and STIR images showed an identical contrast behavior with fat suppression and a high sensitivity to pathological lesions but TurboSTIR saved a significant amount of scan time and reduced some types of artifacts. Contrast uptake impaired lesion conspicuity on TurboSTIR images. Conclusion: TurboSTIR sequences should replace conventional STIR sequences and should be performed before contrast administration.

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Chen, Jiaxuan, Ryosho Nakane, Gouhei Tanaka i Akira Hirose. "Film-penetrating transducers applicable to on-chip reservoir computing with spin waves". Journal of Applied Physics 132, nr 12 (28.09.2022): 123902. http://dx.doi.org/10.1063/5.0102974.

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We have proposed a spin-wave transducer structure named film-penetrating transducers (FPTs). FPTs penetrate an on-chip magnetic film for a spin-wave transmission medium and allow flexible spatial arrangements of many exciters/detectors due to their zero-dimensional feature. We constructed four device models with different spatial arrangements of FPT/conventional exciters using a 10-nm-thick ferrimagnetic garnet film with a central FPT detector. We performed numerical experiments that combine electromagnetics with micromagnetics including thermal noise at 300 K. We evaluated important device features of FPTs, such as the signal-to-noise ratios (SNRs), input/output signal transmission efficiencies, and nonlinear phenomena of spin waves. We applied in-phase sinusoidal input currents with various amplitudes and frequencies and altered the damping strengths near the film boundaries. We obtained sufficient SNRs for the practical use of FPTs and revealed that FPTs have both higher transmission efficiencies and nonlinear strengths than conventional antennas, as the input frequency approaches the ferromagnetic resonance frequency of the film. Moreover, we observed and analyzed various nonlinear phenomena of spin waves, including beats in the time-domain waveform, components of integer harmonic frequencies, wide-range scatterings of inter-harmonic frequencies, and frequency doubling in spin precession. These characteristics probably originate from various device effects: FPTs effectively excite dipolar spin waves with large-angle precession, propagating spin waves reflect from the film boundaries, and spin waves dynamically and nonlinearly interfere with each other. This study demonstrated that FPTs have promising features for both their applications to reservoir computing and the studies on the physics of nonlinear and space-varying spin waves.

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Holtås, S., F. Ståhlberg, H. Nilsson, E. M. Larsson i A. Ericsson. "Low Flip Angle Gradient Echo Magnetic Resonance Imaging of the Cervical Spine at 0.3 Tesla". Acta Radiologica 30, nr 4 (lipiec 1989): 343–48. http://dx.doi.org/10.1177/028418518903000402.

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The influence of flip angle and TR on signal to noise ratio and contrast between cerebrospinal fluid (CSF) and cord was evaluated in cervical spine imaging in 5 volunteers, using gradient echo technique. All experiments were performed on a 0.3 tesla Fonar β-3000 M scanner using solenoidal surface coils. The most useful sequence was considered to be TR/TE=300/12 ms and 10° flip angle. This sequence provided images with a ‘myelographic appearance’ with good delineation of cord, CSF and epidural space. The grey and white matter was also regularly visualized. The acquisition time was considerably shorter than would have been necessary if a long TR/TE spin echo sequence had been used to obtain the same contrast pattern and the sequence was not as sensitive to motion as was the spin echo sequence. The sequence was also evaluated in 10 patients with degenerative disease and in 5 with lesions in the cord. The gradient echo sequence was found to be equal to or better than short and long TR/TE spin echo sequences in demonstrating narrowing of the spinal canal and cord lesions. The drawback is the limited signal to noise ratio.

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Guest, Jamie, Peter Kiraly, Mathias Nilsson i Gareth A. Morris. "Signal-to-noise ratio in diffusion-ordered spectroscopy: how good is good enough?" Magnetic Resonance 2, nr 2 (6.10.2021): 733–39. http://dx.doi.org/10.5194/mr-2-733-2021.

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Abstract. Diffusion-ordered NMR spectroscopy (DOSY) constructs multidimensional spectra displaying signal strength as a function of Larmor frequency and of diffusion coefficient from experimental measurements using pulsed field gradient spin or stimulated echoes. Peak positions in the diffusion domain are determined by diffusion coefficients estimated by fitting experimental data to some variant of the Stejskal–Tanner equation, with the peak widths determined by the standard error estimated in the fitting process. The accuracy and reliability of the diffusion domain in DOSY spectra are therefore determined by the uncertainties in the experimental data and thus in part by the signal-to-noise ratio of the experimental spectra measured. Here the Cramér–Rao lower bound, Monte Carlo methods, and experimental data are used to investigate the relationship between signal-to-noise ratio, experimental parameters, and diffusion domain accuracy in 2D DOSY experiments. Experimental results confirm that sources of error other than noise put an upper limit on the improvement in diffusion domain accuracy obtainable by time averaging.

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Provost, Terrence J., i R. Edward Hendrick. "Maximizing signal-to-noise and contrast-to-noise ratios in spin-echo imaging using non-standard flip angles". Magnetic Resonance Imaging 4, nr 2 (styczeń 1986): 105–6. http://dx.doi.org/10.1016/0730-725x(86)90916-1.

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SHAPIRO, I. I., E. C. LORENZINI, J. ASHENBERG, C. BOMBARDELLI, P. N. CHEIMETS, V. IAFOLLA, D. M. LUCCHESI, S. NOZZOLI, F. SANTOLI i S. GLASHOW. "TESTING THE PRINCIPLE OF EQUIVALENCE IN AN EINSTEIN ELEVATOR". International Journal of Modern Physics D 16, nr 12a (grudzień 2007): 2227–43. http://dx.doi.org/10.1142/s0218271807011693.

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Improving the level of accuracy in testing the principle of equivalence (PE) requires reliably extracting a very small signal from an instrument's intrinsic noise and the noise associated with the instrument's motion. In fact, the spin velocity required to modulate a PE-violating signal produces a relatively high level of motion-related noise and modulation of gravity gradients at various frequencies. In the test of the PE in an Einstein elevator under development by our team, the differential acceleration detector free-falls while spinning around a horizontal axis inside an evacuated, comoving capsule released from a stratospheric balloon. The accuracy goal of the experiment is to test the PE at an accuracy of a few parts in 1015, a limit set by the expected white-noise sources in our detector. The extraction of a very small signal from the prevailing noise sources is necessary for the experiment to succeed. In this paper, we discuss different detector configurations and describe a particular design that is able to provide a remarkable attenuation and frequency separation of the effects of motion and gravity gradients with respect to a PE-violating signal. Numerical simulations of the detector's dynamics in the presence of relevant perturbations, realistic errors, and construction imperfections show the merits of this configuration for the differential acceleration detector.

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Malthouse, J. P. G., i P. Phelan. "Effect of magnetic field strength on the linewidth and spin-lattice relaxation time of the thiocyanate carbon of cyanylated β-lactoglobulin B: optimization of the experimental parameters for observing thiocyanate carbons in proteins". Biochemical Journal 306, nr 2 (1.03.1995): 531–35. http://dx.doi.org/10.1042/bj3060531.

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The linewidths and spin-lattice relaxation times of the 13C-n.m.r. signal at 109.7 p.p.m. due to the thiocyanate carbon of intact [cyanato-13C]cyanylated-beta-lactoglobulin-B have been determined at magnetic field strengths of 1.88, 6.34 and 11.74 T as well as the spin-lattice relaxation times of its backbone alpha-carbon atoms. The linewidths were directly proportional to the square of the magnetic field strength and we conclude that, at magnetic field strengths of 6.34 T or above, more than 70% of the linewidth will be determined by chemical-shift anisotropy. We estimate that the spin-lattice relaxation time resulting from the chemical-shift anisotropy of the thiocyanate carbon is 1.52 +/- 0.1 s and we conclude that for magnetic field strengths of 6.34 T and above the observed spin-lattice relaxation time of the thiocyanate carbon will be essentially independent of magnetic field strength. Using the rigid-rotor model we obtain estimates of the rotational correlation time of [cyanato-13C]cyanylated-beta-lactoglobulin-B and of the chemical-shift anisotropy shielding tensor of its thiocyanate carbon. We have calculated the linewidths and spin-lattice relaxation times of thiocyanate carbons at magnetic field strengths of 1.88-14.1 T in proteins with M(r) values in the range 10,000-400,000. The effects of magnetic field strength on the resolution and signal-to-noise ratios of the signals due to thiocyanate carbons attached to proteins of M(r) greater than 10,000 are discussed.

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Chandra, Ramesh, i Henry Rusinek. "Long term study of random noise and signal uniformity in spin-echo brain imaging". Medical Physics 20, nr 4 (lipiec 1993): 1071–75. http://dx.doi.org/10.1118/1.597003.

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Wrachtrup, J., i A. Gruber. "Projection noise in the optically detected magnetic resonance signal of a single electron spin". Solid State Nuclear Magnetic Resonance 11, nr 1-2 (marzec 1998): 59–64. http://dx.doi.org/10.1016/s0926-2040(97)00096-9.

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Vallatos, Antoine, Lesley Gilmour, Anthony J. Chalmers i William M. Holmes. "Multiple boli arterial spin labeling for high signal-to-noise rodent brain perfusion imaging". Magnetic Resonance in Medicine 79, nr 2 (17.05.2017): 1020–30. http://dx.doi.org/10.1002/mrm.26706.

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Lewis, H. Donell, Vernon A. Benignus, Keith E. Muller, Carolin M. Malott i Curtis N. Barton. "Babble and Random-Noise Masking of Speech in High and Low Context Cue Conditions". Journal of Speech, Language, and Hearing Research 31, nr 1 (marzec 1988): 108–14. http://dx.doi.org/10.1044/jshr.3101.108.

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"Perceptual" masking of speech by multitalker speech (babble) has been widely reported but poorly quantified. Furthermore, the validity of the construct of perceptual masking is questionable. This report describes an experiment using a newly standardized test of speech perception in noise (SPIN) with both babble and spectrally matched random-noise maskers. Classical psychophysieal ogive curves were used to model speech recognition as a function of signal-to-noise ratio (S/N). The two maskers yielded speech recognition functions of the same steepness but different locations on the S/N axis. The high-context items of SPIN yielded speech recognition curves with steeper slope and different locations on the S/N axis than the low-context items. These data are used to argue that perceptual masking was not documented (under certain assumptions) and that the superior masking of babble may be explained in purely acoustical terms. Speculations are offered about the possible acoustical differences that could be responsible for the differences in masking effect.

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Suzuki, Yoshiharu, Teruo Kanki, Hidekazu Tanaka, Tomotaka Inoue, Naoki Wada, Kiyohiko Matsubara i Naoki Asakawa. "Stochastic Resonance in Bioinspired Electronic Device Using Polymer Field Effect Transistors". Key Engineering Materials 790 (listopad 2018): 20–27. http://dx.doi.org/10.4028/www.scientific.net/kem.790.20.

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Stochastic resonance (SR) phenomenon is emerged in organic field effect transistors (OFETs) using $\pi$-conjugated polymer, where application of external noise to the OFET system enhances signal/information processing performance which is often found in biological systems.The channel conductivity of the OFET is slightly increased by spin-coating using heated semiconductor polymer solution with heated glass substrate.In order to improve frequency responses of OFET, optimal width of the gate electrode is explored. Furthermore, it turns out that scratching and removing semiconductor film outside the source-drain electrodes and the channel enhances the On-Off current ratio of the device. These fabrication processes lead to steeper nonlinearity on the $I_{\rm DS}$ {\it vs.} $V_{\rm GS}$ curve, resulting in emergence of SR, which is fingerprinted in increase of correlation value between input and output signals with increase of intensity of external noise.

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35

Novick, Marni L., Ruth A. Bentler, Andrew Dittberner i Gregory A. Flamme. "Effects of Release Time and Directionality on Unilateral and Bilateral Hearing Aid Fittings in Complex Sound Fields". Journal of the American Academy of Audiology 12, nr 10 (listopad 2001): 534–44. http://dx.doi.org/10.1055/s-0042-1745644.

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AbstractIn studies to date, the effectiveness of the directional microphone has been investigated independently of the signal processing scheme used in the hearing aid. In addition, the number and placement of the background noise speakers can create an advantage for a particular polar pattern (i.e., cardioid, supercardioid, and hypercardioid) in any laboratory design. With these considerations in mind, the purpose of this investigation was twofold: (1) to determine the effect of different amplitude-compression release times on speech perception ability in noise, measured with directional microphone hearing aids, and (2) to determine the impact of environment (classroom vs anechoic chamber) on those measures. Ten subjects with mild to moderate sensorineural hearing loss participated. Using an eight-speaker complex sound field, speech perception was assessed in an anechoic chamber and a typical classroom environment. None of the release times resulted in superior performance in either the anechoic or classroom environment. Abbreviations: ANOVA = analysis of variance, BTE = behind the ear, HINT = Hearing in Noise Test, ITE = in the ear, KEMAR = Knowles Electronics Mannikin for Acoustic Research, RBCF = randomized blocks completely factorial, RT = reverberation time, SNR = signal-to-noise ratio, SPIN = Speech Perception in Noise (test), TR = release time

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Yang, Shu-Cheng, Hui-Jiao Luo, Yuan-Hao Zhang i Chen Zhang. "Measurement of the Central Galactic Black Hole by Extremely Large Mass-Ratio Inspirals". Symmetry 14, nr 12 (3.12.2022): 2558. http://dx.doi.org/10.3390/sym14122558.

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In the galaxy, extremely large mass-ratio inspirals (X-MRIs) composed of brown dwarfs and the massive black hole at the galactic center are expected to be promising gravitational wave sources for space-borne detectors. In this work, we simulate the gravitational wave signals from twenty X-MRI systems by an axisymmetric Konoplya–Rezzolla–Zhidenko metric with varied parameters. We find that the mass, spin, and deviation parameters of the Kerr black hole can be determined accurately (∼10−5−10−6) with only one X-MRI event with a high signal-to-noise ratio. The measurement of the above parameters could be improved with more X-MRI observations.

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Zhu, Saike, Lidan Wang, Zhekang Dong i Shukai Duan. "Convolution Kernel Operations on a Two-Dimensional Spin Memristor Cross Array". Sensors 20, nr 21 (31.10.2020): 6229. http://dx.doi.org/10.3390/s20216229.

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In recent years, convolution operations often consume a lot of time and energy in deep learning algorithms, and convolution is usually used to remove noise or extract the edges of an image. However, under data-intensive conditions, frequent operations of the above algorithms will cause a significant memory/communication burden to the computing system. This paper proposes a circuit based on spin memristor cross array to solve the problems mentioned above. First, a logic switch based on spin memristors is proposed, which realizes the control of the memristor cross array. Secondly, a new type of spin memristor cross array and peripheral circuits is proposed, which realizes the multiplication and addition operation in the convolution operation and significantly alleviates the computational memory bottleneck. At last, the color image filtering and edge extraction simulation are carried out. By calculating the peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) of the image result, the processing effects of different operators are compared, and the correctness of the circuit is verified.

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38

Nakamura, Yuki, Hideyuki Watanabe, Hitoshi Sumiya, Kohei M. Itoh, Kento Sasaki, Junko Ishi-Hayase i Kensuke Kobayashi. "Optimization of optical spin readout of the nitrogen-vacancy center in diamond based on spin relaxation model". AIP Advances 12, nr 5 (1.05.2022): 055215. http://dx.doi.org/10.1063/5.0090450.

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For quantum sensing, it is vital to develop an efficient technique for determining the quantum state of the sensor. We optimize the weighting of the photoluminescence intensity for readout of the spin state of the nitrogen-vacancy (NV) center in diamond. We find that adopting a physical model that considers the optical transitions and relaxations of the NV center allows for an efficient readout. Our method improves the signal-to-noise ratio of the readout by 5.4% in a short time of 3 s, while the existing methods typically require 1 min of integration time. We also show that our technique enhances the readout of the nuclear spin memory. The demonstrated way is helpful for a wide range of measurements, from a few minutes to several days.

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Tiwari, Dhananjay. "Improving signal-to-noise ratio of magnetic tunnel junction based radio frequency detector via spin-torque ferromagnetic resonance". Review of Scientific Instruments 93, nr 5 (1.05.2022): 053904. http://dx.doi.org/10.1063/5.0087860.

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This article focuses on the spin-torque ferromagnetic resonance (STFMR) technique, which was developed and optimized to investigate spin-transfer effects in magnetic tunnel junctions (MTJ) and spin Hall effect phenomena in ferromagnet/non-magnetic heavy metal bilayer systems. The devices for STFMR are typically fabricated with co-planar waveguides with contact pads for applying radio frequency or direct current, Irf(Idc). The device under investigation was a CoFeB/MgO/CoFeB based MTJ with a resistance-area product of 1.5 Ω ( μm)2 having a circular cross section with a diameter of 180 nm and tunneling magneto-resistance in the range of 60%–80%. The development of the STFMR setup and its optimization for achieving higher signal-to-noise ratio (SNR) is discussed using two modulation schemes, namely, radio-frequency modulation and field modulation (FM). The FM-STFMR method reduces frequency-dependent noise and offers a higher SNR of 30 dB compared to other modulation schemes in the literature. In addition, a vector network analyzer based STFMR technique is developed, which provides a simple and fast means for characterizing MTJ devices. Furthermore, to calculate the exact power reaching the MTJ, impedance mismatch is calculated using the de-embedding method. The magnitude of in-plane torkance and out-of-plane torkance with dc bias is measured, and the results are found to be consistent with the results of STFMR techniques. The results show that the magnitude of out-of-plane torkance is substantially smaller than that of in-plane torkance in MTJ.

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40

Constable, R. Todd, Robert C. Smith i John C. Gore. "Signal-to-Noise and Contrast in Fast Spin Echo (FSE) and Inversion Recovery FSE Imaging". Journal of Computer Assisted Tomography 16, nr 1 (styczeń 1992): 41–47. http://dx.doi.org/10.1097/00004728-199201000-00008.

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Siegel, Renée, Thomas T. Nakashima i Roderick E. Wasylishen. "Signal-to-noise enhancement of NMR spectra of solids using multiple-pulse spin-echo experiments". Concepts in Magnetic Resonance Part A 26A, nr 2 (2005): 62–77. http://dx.doi.org/10.1002/cmr.a.20038.

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Prato, F. S., D. J. Drost, T. Keys, P. Laxon, B. Comissiong i E. Sestini. "Optimization of signal-to-noise ratio in calculatedT1 images derived from two spin-echo images". Magnetic Resonance in Medicine 3, nr 1 (luty 1986): 63–75. http://dx.doi.org/10.1002/mrm.1910030109.

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Ziegler, A., i M. Decorps. "Signal-to-Noise Improvement in in Vivo Spin-Echo Spectroscopy in the Presence of Motion". Journal of Magnetic Resonance, Series B 102, nr 1 (sierpień 1993): 26–34. http://dx.doi.org/10.1006/jmrb.1993.1058.

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Campbell, Julia, Mashhood Nielsen, Alison LaBrec i Connor Bean. "Sensory Inhibition Is Related to Variable Speech Perception in Noise in Adults With Normal Hearing". Journal of Speech, Language, and Hearing Research 63, nr 5 (22.05.2020): 1595–607. http://dx.doi.org/10.1044/2020_jslhr-19-00261.

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Purpose Speech perception in noise (SPiN) varies widely in individuals with normal hearing, which may be attributed to factors that are not reflected in the audiogram, such as inhibition. However, inhibition is involved at both sensory and cognitive stages of auditory perception, and while inhibition at the cognitive level has been shown to be a significant factor in SPiN processes, it is unknown whether sensory inhibition may also contribute to SPiN variability. Therefore, the goal of this study was to evaluate sensory inhibition in adults with normal hearing and mild SPiN impairment. Method Cortical auditory evoked potentials (CAEPs) were recorded in 49 adults via high-density electroencephalography using an auditory gating paradigm. Participants were categorized according to a median signal-to-noise ratio (SNR) loss of 1.5 dB: typical SNR loss ≤ 1.5 dB ( n = 32), mild SNR loss > 1.5 dB ( n = 17). CAEP gating responses were compared and correlated with SNR loss and extended high-frequency thresholds. Current density reconstructions were performed to qualitatively observe underlying cortical inhibitory networks in each group. Results In comparison to adults with typical SPiN ability, adults with mild SPiN impairment showed an absence of the gating response. A CAEP gating component (P2) reflected decreased sensory inhibition and correlated with increased SNR loss. Extended high-frequency thresholds were also found to correlate with SNR loss, but not gating function. An atypical cortical inhibitory network was observed in the mild SNR loss group, with reduced frontal and absent prefrontal activation. Conclusion Sensory inhibition appears to be atypical and related to SPiN deficits in adults with mild impairment. In addition, cortical inhibitory networks appear to be incomplete, with a possible compensatory parietal network. Further research is needed to delineate between types or levels of central inhibitory mechanisms and their contribution to SPiN processes.

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45

Chaidaungsri, Nuttapon, Arkom Kaewrawang, Komkrit Chooruang i Damrongsak Tongsomporn. "Investigation of Perpendicular Magnetic Recording Footprint by Spin-Stand Microscopy". Applied Mechanics and Materials 781 (sierpień 2015): 215–18. http://dx.doi.org/10.4028/www.scientific.net/amm.781.215.

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The characteristics of magnetic recording are necessary to understand in order to increase the areal densities and improve the perfermance of recording system. Therefore, experimental tools must be developed to help researchers to carry out signal and noise recording experiments on different heads and media combinations. In this paper, the perpendicular magnetic recording footprint using spin-stand microscopy is demonstrated. It was found experimentally that the magnetic footprint can precisely catch some recording dynamics of the write heads during the write gate off conditions and also provide useful insight information of the recording performance.

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Huy, Ho Hoang, Julian Sasaki, Nguyen Huynh Duy Khang, Shota Namba, Pham Nam Hai, Quang Le, Brian York i in. "Large inverse spin Hall effect in BiSb topological insulator for 4 Tb/in² magnetic recording technology". Applied Physics Letters 122, nr 5 (30.01.2023): 052401. http://dx.doi.org/10.1063/5.0135831.

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It is technically challenging to shrink the size of a tunneling magnetoresistance reader to below 20 nm for magnetic recording technology beyond 4 Tb/in2 due to its complex film stack. Recently, we proposed a reader architecture based on the inverse spin Hall effect to resolve those challenges, referred below as spin–orbit torque (SOT) reader, whose structure consists of a SOT layer and a ferromagnetic layer. However, the heavy metal-based SOT reader has small output voltage and low signal-to-noise ratio (SNR) due to the limited spin Hall angle θSH (< 1) of heavy metals. In this Letter, we demonstrate the integration of BiSb topological insulator with strong inverse spin Hall effect into the SOT reader that can significantly improve the output voltage and SNR. First, we theoretically calculate the noises in a 20 × 20 nm2 BiSb-based SOT reader to establish the relationships between SNR and θSH at various bias currents. We then demonstrate proof-of-concept BiSb-based SOT readers using CoFe/MgO/BiSb stack, which show large output voltages up to 15 mV at an input current of 9.4 kA/cm2 at room temperature. We project a giant θSH = 61 for BiSb. Our work demonstrates the potential of BiSb for SOT reader beyond 4 Tb/in2 magnetic recording technology.

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Trattnig, S., M. Breitenseher, G. Kontaxis, T. Helbich, T. Rand i H. Imhof. "Grase: Ultra-fast turbo gradient spin-echo sequence". Acta Radiologica 38, nr 5 (wrzesień 1997): 880–84. http://dx.doi.org/10.1080/02841859709172429.

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Purpose: Ultra-fast gradient and spin-echo (GRASE) imaging is a hybrid of turbo spin-echo (TSE) and echo-planar imaging (EPI). One scan consists of several spinechoes (SEs) (turbo factor, TF), each of which consists of a number of gradient echoes (EPI factor, EF). The aim of our study was to evaluate different combinations of TF and EF in GRASE imaging and to test its usefulness in musculoskeletal imaging. Material and Methods: On a 1.0 T MR unit, 11 GRASE sequences with different combinations of TF and EF (TR/TE 2150/120 ms) were evaluated in phantom studies with respect to signal-to-noise (S/N) ratio, nonuniformity of images, and geometrical distortion. From this study, the optimal GRASE-sequence was applied to 25 patients with different joint pathologies and compared to a T2-weighted TSE sequence (TR/TE 2855/130 ms). Lesion visualization, conspicuity, overall image quality, and artifacts were qualitatively analyzed by two observers independently of each other. Results: With respect to S/N ratio, signal nonuniformity, and geometrical distortion, the GRASE sequence with TF/EF 7/3 (S/N 47; signal nonuniformity 11.7%; distortion 1 pixel) proved to be superior to the other GRASE sequences within a scanning time of less than 120s. In a clinical study, the GRASE sequence proved superior to T2-weighted TSE (without fat suppression) in the visualization of bone-marrow and soft-tissue lesions ( p < 0.001) and ligamentous injuries, although the image quality was inferior.

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Guo, Qingqian, Changyu Ma, Xin Zhang, Yajie Xu, Meisheng Fan, Peng Yu, Tao Hu, Yan Chang i Xiaodong Yang. "SQUID-Based Magnetic Resonance Imaging at Ultra-Low Field Using the Backprojection Method". Concepts in Magnetic Resonance Part B, Magnetic Resonance Engineering 2020 (22.10.2020): 1–11. http://dx.doi.org/10.1155/2020/8882329.

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Ultra-low field magnetic resonance imaging (ULF MRI) is an effective imaging technique that applies the ultrasensitive detector of superconducting quantum interference device (SQUID) sensor to detect the MR signal at a microtesla field range. In this work, we designed and developed a SQUID-based ULF MRI system with a frequency-adjustable measurement field, the performance of which was characterized via water phantoms. In order to enhance the MR signals, a 500 mT Halbach magnet was used to prepolarize the magnetization of the sample prior to excitation. The signal-to-noise-ratio (SNR) of the spin-echo- (SE-) based pulse sequence can reach up to 70 in a single scan. The images were then reconstructed successfully by using the maximum likelihood expectation maximization (MLEM) algorithm based on the backprojection imaging method. It was demonstrated that an in-plane resolution of 1.8 × 1.8 mm2 can be achieved which indicated the feasibility of SQUID-based MRI at the ULF.

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Viola, Massimo. "The probability distribution of ellipticity: implications for weak lensing measurement". Proceedings of the International Astronomical Union 10, S306 (maj 2014): 94–98. http://dx.doi.org/10.1017/s174392131401360x.

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AbstractThe weak lensing effect generates spin-2 distortions, referred to as shear, on the observable shape of distant galaxies, induced by intervening gravitational tidal fields. Traditionally, the spin-2 distortion in the light distribution of distant galaxies is measured in terms of a galaxy ellipticity. This is a very good unbiased estimator of the shear field in the limit that a galaxy is measured at infinite signal-to-noise. However, the ellipticity is always defined as a ratio between two quantities (for example, between the polarisation and measurement of the galaxy size, or between the semi-major and semi-minor axis of the galaxy) and therefore requires some non-linear combination of the image pixels. This means, in any realistic case, this would lead to biases in the measurement of the shear (and hence in the cosmological parameters) whenever noise is present in the image. This type of bias can be understood from the particular shape of the 2D probability distribution of the ellipticity of an object measured from data. Moreover this probability distribution can be used to explore strategies for calibration of noise biases in present and future weak lensing surveys (e.g. KiDS, DES, HSC,Euclid, LSST...)

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Riccioli, L. Albini, A. F. Marliani, P. Ghedin, V. Clementi, R. Agati, D. Cevolani i M. Leonardi. "Magnetic Resonance Imaging of the Human Spine and Spinal Cord at 3 Tesla". Rivista di Neuroradiologia 18, nr 5-6 (grudzień 2005): 606–16. http://dx.doi.org/10.1177/197140090501800512.

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Investigation of the spinal cord with a high field strength MR system is hampered by the inhomogeneous magnetic field, physiological movements and the small size of the anatomical area. We describe normal and pathological neuroradiological findings and the parameters of optimized sequences for use with the new 3T MR systems. Thanks to its high spatial resolution, temporal resolution and signal/noise ratio, use of a 3 Tesla MR device (Signa EXCITE 3T) and a dedicated phased array coil has dramatically improved spine and spinal cord imaging, clearly displaying the anatomic details most difficult to examine. The longer T1 longitudinal tissue relaxation time with 3T MR systems is proportional to the strength of the external magnetic field B0. Tissue contrast between white matter, grey matter, CSF and bone tissue is not optimal with traditional spin echo and/or fast spin echo sequences. Hence they are often replaced by T1 Flair acquisitions (Fast Spin Echo–IR with average inversion times of 800–1000ms) which yield T1 weighted images with satisfactory contrast. Unlike images produced by systems using a lower magnetic field strength, 3T MR T2 sequences are highly diagnostic, disclosing the finest anatomical details.

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