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Journal articles on the topic 'Lock-In spectroscopy'

Author: Grafiati

Published: 29 February 2024

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1

Koresawa, Hidenori, Kyuki Shibuya, Takeo Minamikawa, Akifumi Asahara, Ryo Oe, Takahiko Mizuno, Masatomo Yamagiwa, et al. "Lock-in-detection dual-comb spectroscopy." OSA Continuum 2, no. 6 (June 12, 2019): 1998. http://dx.doi.org/10.1364/osac.2.001998.

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2

Chernyshov, A. K., and E. A. Chernyshova. "Diode-laser derivative spectroscopy without lock-in amplifier." Physics of Wave Phenomena 19, no. 2 (May 25, 2011): 89–92. http://dx.doi.org/10.3103/s1541308x11020038.

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3

Ball, C. A. B., and A. B. Conibear. "Simulated lock‐in amplifier deep level transient spectroscopy." Review of Scientific Instruments 62, no. 11 (November 1991): 2831–32. http://dx.doi.org/10.1063/1.1142169.

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4

Zhang, Qinduan, Jun Chang, Zhenhua Cong, Zongliang Wang, and Fupeng Wang. "Dual Path Lock-In System for Elimination of Residual Amplitude Modulation and SNR Enhancement in Photoacoustic Spectroscopy." Sensors 18, no. 12 (December 4, 2018): 4255. http://dx.doi.org/10.3390/s18124255.

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A technique for elimination of residual amplitude modulation (ERAM) in photoacoustic spectroscopy based on dual path lock-in was proposed and experimentally demonstrated. There are two lock-in amplifiers, one is for gas concentration demodulation and another for residual amplitude modulation (RAM) measurement by tuning the reference signal in different phases, and then a dual path lock-in technique based on subtraction is applied to RAM removal, improving the second harmonic profile significantly. In this system, the signal to noise ratio (SNR) increases about two times based on our dual path lock-in technique compared to one distributed feedback laser diode (DFB-LD). The system achieved a good linear response (R-square = 0.99887) in a concentration range from 100 ppmv to 2400 ppmv and a minimum detection limit (MDL) of 1.47 ppmv.

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5

Holcomb, M. J., and W. A. Little. "Cascading lock‐in amplification: Application to wavelength modulation spectroscopy." Review of Scientific Instruments 63, no. 12 (December 1992): 5570–75. http://dx.doi.org/10.1063/1.1143383.

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6

Fonsêca, Hugo, Diego Rativa, and Ricardo Lima. "In-Loco Optical Spectroscopy through a Multiple Digital Lock-In on a Linear Charge-Coupled Device (CCD) Array." Sensors 23, no. 16 (August 16, 2023): 7195. http://dx.doi.org/10.3390/s23167195.

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Accurate and reliable measurements of optical properties are crucial for a wide range of industrial and commercial applications. However, external illumination fluctuations can often make these measurements challenging to obtain. This work proposes a new technique based on digital lock-in processing that enables the use of CCD spectrometers in optical spectroscopy applications, even in uncontrolled lighting conditions. This approach leverages digital lock-in processing, performed on each pixel of the spectrometer’s CCD simultaneously, to mitigate the impact of external optical interferences. The effectiveness of this method is demonstrated by testing and recovering the spectrum of a yellow LED subjected to other light sources in outdoor conditions, corresponding to a Signal-to-Noise Ratio of −70.45 dB. Additionally, it was possible to demonstrate the method’s applicability for the spectroscopic analysis of gold nanoparticles in outdoor conditions. These results suggest that the proposed technique can be helpful for a wide range of optical measurement techniques, even in challenging lighting conditions.

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7

Yanju Liu, Jianhui Song, Liang Chen, and Sheng Pan. "Design of Lock-in Amplifier Used on the Photoacoustic Spectroscopy." Journal of Convergence Information Technology 8, no. 6 (March 31, 2013): 942–49. http://dx.doi.org/10.4156/jcit.vol8.issue6.112.

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8

Karami, Mohammad, Zahra Heydarinasab, and Farrokh Sarreshtedari. "Sub-Doppler dichroism as a useful tool in alkali atom hyperfine spectroscopy." Laser Physics 33, no. 12 (October 30, 2023): 125701. http://dx.doi.org/10.1088/1555-6611/ad04c7.

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Abstract Analytical modeling of the sub-Doppler dichroic atomic vapor laser lock error signal shows that the slope of this error signal could be of interest for the identification of transitions in alkali atom hyperfine spectroscopy. Among four D1 line transitions of alkali atoms, the slope sign of the sub-Doppler error signal is different only for the case when the Landé g-factor is negative for both the ground and excited states. The analytical model used, which includes all sublevel transitions, shows very good agreement with the experimental spectroscopy results. The use of this technique allows us to accurately characterize hyperfine transitions in alkali atoms without the need for advanced spectroscopic tools.

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9

Schlierf, Michael, Felix Berkemeier, and Matthias Rief. "Direct Observation of Active Protein Folding Using Lock-in Force Spectroscopy." Biophysical Journal 93, no. 11 (December 2007): 3989–98. http://dx.doi.org/10.1529/biophysj.107.114397.

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10

Ardekani, Hossein, Ryan L. Wilmington, Mounika Vutukuru, Zhuofa Chen, Ryan Brandt, Anna k. Swan, and Kenan Gundogdu. "Broadband micro-transient absorption spectroscopy enabled by improved lock-in amplification." Review of Scientific Instruments 92, no. 10 (October 1, 2021): 104706. http://dx.doi.org/10.1063/5.0060244.

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11

Walther, Frans J., and Alan J. Waring. "Structure and Function of Canine SP-C Mimic Proteins in Synthetic Surfactant Lipid Dispersions." Biomedicines 12, no. 1 (January 12, 2024): 163. http://dx.doi.org/10.3390/biomedicines12010163.

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Lung surfactant is a mixture of lipids and proteins and is essential for air breathing in mammals. The hydrophobic surfactant proteins B and C (SP-B and SP-C) assist in reducing surface tension in the lung alveoli by organizing the surfactant lipids. SP-B deficiency is life-threatening, and a lack of SP-C can lead to progressive interstitial lung disease. B-YL (41 amino acids) is a highly surface-active, sulfur-free peptide mimic of SP-B (79 amino acids) in which the four cysteine residues are replaced by tyrosine. Mammalian SP-C (35 amino acids) contains two cysteine-linked palmitoyl groups at positions 5 and 6 in the N-terminal region that override the β-sheet propensities of the native sequence. Canine SP-C (34 amino acids) is exceptional because it has only one palmitoylated cysteine residue at position 4 and a phenylalanine at position 5. We developed canine SP-C constructs in which the palmitoylated cysteine residue at position 4 is replaced by phenylalanine (SP-Cff) or serine (SP-Csf) and a glutamic acid-lysine ion-lock was placed at sequence positions 20–24 of the hydrophobic helical domain to enhance its alpha helical propensity. AI modeling, molecular dynamics, circular dichroism spectroscopy, Fourier Transform InfraRed spectroscopy, and electron spin resonance studies showed that the secondary structure of canine SP-Cff ion-lock peptide was like that of native SP-C, suggesting that substitution of phenylalanine for cysteine has no apparent effect on the secondary structure of the peptide. Captive bubble surfactometry demonstrated higher surface activity for canine SP-Cff ion-lock peptide in combination with B-YL in surfactant lipids than with canine SP-Csf ion-lock peptide. These studies demonstrate the potential of canine SP-Cff ion-lock peptide to enhance the functionality of the SP-B peptide mimic B-YL in synthetic surfactant lipids.

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12

Balgos, M. H., N. Hayazawa, M. Tani, and T. Tanaka. "Megahertz repetition rate-based lock-in detection scheme for rapid data acquisition in terahertz time domain spectroscopy." Review of Scientific Instruments 94, no. 4 (April 1, 2023): 043002. http://dx.doi.org/10.1063/5.0138938.

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We report a fast pump modulation scheme in a terahertz time domain spectroscopy (THz-TDS) system by utilizing the intensity modulation from the megahertz repetition rate of the pump pulse for lock-in detection. In conventional THz-TDS, the modulation required for the high signal-to-noise ratio lock-in detection is achieved through the use of an optical chopper or an AC bias. Here, we propose the use of an electro-optic modulator (EOM), operated as a pulse picker, to vary the repetition rate of the pump pulse, relative to the probe pulse, allowing us to directly use the megahertz laser repetition rate as the reference modulation frequency for lock-in detection. Our proposed scheme is applicable to all types of pulsed THz emitters, including those that cannot be electronically biased. Since the maximum allowable modulation frequency is limited only by the laser repetition rate and/or by the bandwidth of the EOM, megahertz modulation rates, and, consequently, rapid data acquisition times, become possible. Using our technique, we were able to detect an oscillating signal with frequencies up to 10 kHz, using ∼1 µs integration time per point, ∼100× faster than previously reported values for THz-TDS systems.

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13

Liu, Yan Li, and Rui Zhang. "AD630 Lock-In Amplifier Circuit for Weak Signal." Advanced Materials Research 482-484 (February 2012): 975–80. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.975.

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Lock-in amplifying (LIA) is one of important techniques of picking up weak signals buried in the noise, and is the core component of Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology. Then we design a small size, dual phase lock-in amplifier (LIA) integrated circuit. This paper is based on the phase-sensitive detector AD630, together with the phase-locked loop (PLL) circuit (74HC4046) and the active filter (MAX275) the value of Q and the center frequency of which could be adjusted. The output signals were collected by A/D converter and dedicated high-resolution data acquisition card. The range of frequency is 500Hz-100 kHz, the dynamic range of acquisition signal is greater than 100dB, the signal-to-noise ratio is up to 60dB, and the overall area of circuit is only 14cm × 14.8cm. Experiments show that the design meets the requirements of integration into the system.

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14

Borkowski, Maciej, Ewa B. Skrodzka, and Bogumił B. J. Linde. "COMPARISON OF SINGLE AND DUAL-PHASE LOCK-IN AMPLIFIERS FOR PHOTOACOUSTIC SPECTROSCOPY." Instrumentation Science & Technology 42, no. 4 (May 9, 2014): 469–74. http://dx.doi.org/10.1080/10739149.2014.888671.

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15

Albertini, A., and W. Kleemann. "Analogue and digital lock-in techniques for very-low-frequency impedance spectroscopy." Measurement Science and Technology 8, no. 6 (June 1, 1997): 666–72. http://dx.doi.org/10.1088/0957-0233/8/6/014.

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16

Ragni, A., G. Sciortino, M. Sampietro, G. Ferrari, and D. Polli. "Multi-channel lock-in based differential front-end for broadband Raman spectroscopy." Integration 67 (July 2019): 44–49. http://dx.doi.org/10.1016/j.vlsi.2019.03.001.

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17

Fangnon, Eric, Evgenii Malitckii, Yuriy Yagodzinskyy, and Pedro Vilaça. "Improved Accuracy of Thermal Desorption Spectroscopy by Specimen Cooling during Measurement of Hydrogen Concentration in a High-Strength Steel." Materials 13, no. 5 (March 10, 2020): 1252. http://dx.doi.org/10.3390/ma13051252.

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Thermal desorption spectroscopy (TDS) is a powerful method for the measurement of hydrogen concentration in metallic materials. However, hydrogen loss from metallic samples during the preparation of the measurement poses a challenge to the accuracy of the results, especially in materials with high diffusivity of hydrogen, like ferritic and ferritic-martensitic steels. In the present paper, the effect of specimen cooling during the experimental procedure, as a tentative to reduce the loss of hydrogen during air-lock vacuum pumping for one high-strength steel of 1400 MPa, is evaluated. The results show, at room temperature, the presence of a continuous outward hydrogen flux accompanied with the redistribution of hydrogen within the measured steel during its exposure to the air-lock vacuum chamber under continuous pumping. Cooling of the steel samples to 213 K during pumping in the air-lock vacuum chamber before TDS measurement results in an increase in the measured total hydrogen concentration at about 14%. A significant reduction in hydrogen loss and redistribution within the steel sample improves the accuracy of hydrogen concentration measurement and trapping analysis in ferritic and martensitic steels.

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18

BELLINI, M., S. CAVALIERI, C. CORSI, and M. MATERAZZI. "Towards high-resolution spectroscopy in the XUV with phase-locked harmonic pulses." Laser and Particle Beams 19, no. 1 (January 2001): 29–33. http://dx.doi.org/10.1017/s0263034601191044.

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We report the results of measurements aimed to check the phase lock of time-delayed, collinear, harmonic pulses and to verify the possibility of performing Ramsey-like spectroscopy in the XUV. We demonstrate that for harmonics of medium order and for the peak intensities available with our laser system, the generation of collinear phase-locked harmonic pulses is indeed possible and that such pulses can be used to achieve high-resolution spectroscopy in the short-wavelength region.

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19

Matsuoka, Leo. "Artifact side peaks in saturated absorption spectroscopy caused by inappropriate lock-in amplification." Japanese Journal of Applied Physics 62, no. 10 (October 1, 2023): 108006. http://dx.doi.org/10.35848/1347-4065/ad03a6.

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Abstract Saturated absorption spectroscopy is a powerful technique that provides valuable information about gas-phase atomic targets, including not only the precise positions of transitions but also the effects of velocity-changing collisions, which manifest as changes in the shape of the peaks. However, using a lock-in amplifier inappropriately can generate artifact side peaks, potentially leading to a misinterpretation of results. To investigate the emergence of these artifacts, we conducted numerical calculations based on the basic Lambert–Beer’s law. Our model reproduced the artifact side peaks and revealed that these artifacts become more significant as the transmittance of the probe laser decreases.

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20

Erskine, Steven R., C. Michael Foley, and Donald R. Bobbitt. "Single-Laser, Single-Beam Pump/Probe Thermal Lens Spectroscopy." Applied Spectroscopy 41, no. 7 (September 1987): 1189–93. http://dx.doi.org/10.1366/0003702874447716.

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A unique design for a thermal lens photometer based on a single-laser/single-beam configuration is presented. The system is compatible with lock-in detection and uses a pair of acoustooptic modulators to temporally separate the pump and probe events. A minimum measurable absorbance of 6 × 10−6 cm−1 is reported. Limitations to the use of acoustooptic modulation at high absorbances are discussed.

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21

Waddington, John L., Eadbhard O'Callaghan, Conall Larkin, Oonagh Redmond, John Stack, and Joseph T. Ennis. "Magnetic Resonance Imaging and Spectroscopy in Schizophrenia." British Journal of Psychiatry 157, S9 (December 1990): 56–65. http://dx.doi.org/10.1192/s000712500029185x.

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In this new era of structural and functional neuroimaging technologies, it is the unsurpassed anatomical resolution of magnetic resonance imaging (MRI) (Andreasen, 1989; and Besson, this supplement) that has resulted in a new generation of studies on cerebral morphology in schizophrenia. With the recent development of whole-body magnets of very high (⩾ 1.5T) and uniform field strength, it has become possible to extend the scope of this approach to include measurement of certain fundamental neurochemical processes, via magnetic resonance spectroscopy (MRS: Hubesch et al, 1989; Lock et al, this supplement). The purpose of this article is to introduce and review critically the existing literature on the application of MRI and MRS to schizophrenia, and to give a preliminary account of some of our own recent studies in these areas.

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22

Sciortino, Giuseppe, Andrea Ragni, Alejandro De la Cadena, Marco Sampietro, Giulio Cerullo, Dario Polli, and Giorgio Ferrari. "Four-Channel Differential Lock-in Amplifiers With Autobalancing Network for Stimulated Raman Spectroscopy." IEEE Journal of Solid-State Circuits 56, no. 6 (June 2021): 1859–70. http://dx.doi.org/10.1109/jssc.2020.3046484.

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23

Wang, Wubin, Dong Chen, Wenxi Yao, Wei Chen, and Zhengyu Lu. "Fast lock-in amplifier electrochemical impedance spectroscopy for big capacity lead-acid battery." Journal of Energy Storage 40 (August 2021): 102693. http://dx.doi.org/10.1016/j.est.2021.102693.

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24

Wojtkiewicz, Stanislaw, Karolina Bejm, and Adam Liebert. "Lock-in functional near-infrared spectroscopy for measurement of the haemodynamic brain response." Biomedical Optics Express 13, no. 4 (March 4, 2022): 1869. http://dx.doi.org/10.1364/boe.448038.

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25

Uhl, D., L. Bruder, and F. Stienkemeier. "A flexible and scalable, fully software-based lock-in amplifier for nonlinear spectroscopy." Review of Scientific Instruments 92, no. 8 (August 1, 2021): 083101. http://dx.doi.org/10.1063/5.0059740.

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26

Li, Nan, Wei Wang, Hui Xu, Hongqi Yu, Jietao Diao, and David D. U. Li. "Wide-Bandwidth Biological Impedance Spectroscopy System Based on the Digital Lock-In Technique." Spectroscopy Letters 46, no. 7 (October 3, 2013): 476–82. http://dx.doi.org/10.1080/00387010.2012.705801.

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27

Scott, J. F. "New results in incommensurate crystals: Kink diffusion and long-period lock-in phases." Journal of Raman Spectroscopy 17, no. 1 (February 1986): 151–54. http://dx.doi.org/10.1002/jrs.1250170130.

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28

Qin, Jianhuan, Zhiming Huang, Yujian Ge, Yun Hou, and Junhao Chu. "Tandem demodulation lock-in amplifier based on digital signal processor for dual-modulated spectroscopy." Review of Scientific Instruments 80, no. 3 (March 2009): 033112. http://dx.doi.org/10.1063/1.3098948.

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29

Bertrand, Mathieu, Aleksandr Shlykov, Mehran Shahmohamadi, Mattias Beck, Stefan Willitsch, and Jérôme Faist. "High-Power, Narrow-Linewidth Distributed-Feedback Quantum-Cascade Laser for Molecular Spectroscopy." Photonics 9, no. 8 (August 19, 2022): 589. http://dx.doi.org/10.3390/photonics9080589.

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Quantum cascade lasers are versatile light sources in the mid-infrared range for molecular spectroscopy which find a wide range of applications from high-resolution studies to sensing. While devices with either high power or narrow spectral linewidth have previously been reported, there is still a lack of sources combining both of these characteristics which are particularly important for precision measurements of weak spectroscopic transitions. In this article, we describe and characterize a novel master-oscillator power-amplifier distributed-feedback quantum cascade laser designed to fill this gap. At an output power of 300 mW, the device features a free-running linewidth of 1.3 MHz, measured with a frequency discriminator technique, at an emission wavenumber of 2185 cm−1. This linewidth is sufficiently narrow to enable a further reduction by a tight lock to a high-Q oscillator.

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30

Erskine, Steven R., and Donald R. Bobbitt. "Theoretical and Experimental Investigation of the Relationship between Aperture Dimension and Signal-to-Noise Optimization in Thermal Lens Spectroscopy." Applied Spectroscopy 42, no. 2 (February 1988): 331–35. http://dx.doi.org/10.1366/0003702884428257.

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The effect of three types of experimental laser noise on conventional thermal lens spectroscopy are considered. Theoretical calculations of noise and signal-to-noise ratio as a function of aperture size are included to determine ideal aperture dimensions for systems limited by laser pointing instabilities, flicker noise, and/or shot noise. Experimentally determined noise curves are also presented and discussed in the context of the theoretical results. The results show that for most thermal lens configurations based on lock-in detection, optimum S/N is obtained at an aperture-to-beam-size ratio of 0.6.

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31

KOBAYASHI, Hiroyuki. "Reducing Particle Contamination During Pump-down in Load Lock Chamber." Journal of the Vacuum Society of Japan 53, no. 10 (2010): 568–72. http://dx.doi.org/10.3131/jvsj2.53.568.

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32

Rico, Felix, Andreas Russek, Laura González, Helmut Grubmüller, and Simon Scheuring. "Heterogeneous and rate-dependent streptavidin–biotin unbinding revealed by high-speed force spectroscopy and atomistic simulations." Proceedings of the National Academy of Sciences 116, no. 14 (March 19, 2019): 6594–601. http://dx.doi.org/10.1073/pnas.1816909116.

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Receptor–ligand interactions are essential for biological function and their binding strength is commonly explained in terms of static lock-and-key models based on molecular complementarity. However, detailed information on the full unbinding pathway is often lacking due, in part, to the static nature of atomic structures and ensemble averaging inherent to bulk biophysics approaches. Here we combine molecular dynamics and high-speed force spectroscopy on the streptavidin–biotin complex to determine the binding strength and unbinding pathways over the widest dynamic range. Experiment and simulation show excellent agreement at overlapping velocities and provided evidence of the unbinding mechanisms. During unbinding, biotin crosses multiple energy barriers and visits various intermediate states far from the binding pocket, while streptavidin undergoes transient induced fits, all varying with loading rate. This multistate process slows down the transition to the unbound state and favors rebinding, thus explaining the long lifetime of the complex. We provide an atomistic, dynamic picture of the unbinding process, replacing a simple two-state picture with one that involves many routes to the lock and rate-dependent induced-fit motions for intermediates, which might be relevant for other receptor–ligand bonds.

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33

Chugh, Vinit Kumar, Kai Wu, Venkatramana D. Krishna, Arturo di Girolamo, Robert P. Bloom, Yongqiang Andrew Wang, Renata Saha, Shuang Liang, Maxim C.-J. Cheeran, and Jian-Ping Wang. "Magnetic Particle Spectroscopy with One-Stage Lock-In Implementation for Magnetic Bioassays with Improved Sensitivities." Journal of Physical Chemistry C 125, no. 31 (July 30, 2021): 17221–31. http://dx.doi.org/10.1021/acs.jpcc.1c05126.

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34

Al Mohtar, A., J. Vaillant, Z. Sedaghat, M. Kazan, L. Joly, C. Stoeffler, J. Cousin, A. Khoury, and A. Bruyant. "Generalized lock-in detection for interferometry: application to phase sensitive spectroscopy and near-field nanoscopy." Optics Express 22, no. 18 (September 5, 2014): 22232. http://dx.doi.org/10.1364/oe.22.022232.

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35

Messerle, Barbara A., Gerhard Wider, Gottfried Otting, Christoph Weber, and Kurt Wüthrich. "Solvent suppression using a spin lock in 2D and 3D NMR spectroscopy with H2O solutions." Journal of Magnetic Resonance (1969) 85, no. 3 (December 1989): 608–13. http://dx.doi.org/10.1016/0022-2364(89)90252-7.

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36

OTTING, G. "ChemInform Abstract: Use of High Power Spin-Lock Purge Pulses in High Resolution NMR Spectroscopy." ChemInform 29, no. 41 (June 19, 2010): no. http://dx.doi.org/10.1002/chin.199841313.

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37

Monteiro, Fábio D. R., and Peter Stallinga. "Using an Off-the-Shelf Lock-In Detector for Admittance Spectroscopy in the Study of Plants." Agricultural Sciences 11, no. 04 (2020): 390–416. http://dx.doi.org/10.4236/as.2020.114023.

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38

Gaddy, M., V. Kuryatkov, V. Meyers, D. Mauch, J. Dickens, A. Neuber, and S. Nikishin. "Structural, Morphological, Optical and Electrical Properties of Bulk (0001) GaN:Fe Wafers." MRS Advances 3, no. 3 (2018): 179–84. http://dx.doi.org/10.1557/adv.2018.234.

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ABSTRACTCharacterization of three vendor’s bulk semi-insulating GaN:Fe wafers, grown by either hydride vapor phase epitaxy or the ammonothermal method, was performed using: scanning electron microscopy, secondary ion mass spectroscopy, high resolution X-ray diffraction, cathodoluminescence, photoluminescence, and high voltage testing. Although the Fe doping level is significantly different for each growth method, both are promising for the fabrication of PCSS devices operating in the lock-on mode.

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39

Bellaiche-Sharpe, P., K. M. Gough, B. J. Schattka, T. MaCdonald, J. Rustenburg, A. Struyk, and G. McDonnell. "Real-Time Photoacoustic Signal Analysis in a Gas-Phase Spectrophone: A Feasibility Study." Applied Spectroscopy 50, no. 11 (November 1996): 1366–72. http://dx.doi.org/10.1366/0003702963904647.

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A digital signal processing (DSP) system has been constructed for the acquisition of intracavity dye laser photoacoustic spectra (ICL-PAS). The DSP system permits observation of the real-time PA pulse, an arrangement which facilitates the adjustment of all spectral acquisition parameters as well as signal processing for noise reduction. Sample spectra of the real-time PA pulse illustrate the improvements possible with Fourier filtering and time-averaging. Spectra of the region of the fifth CH stretching overtone of ethene, benzene, and propane in the gas phase are presented. The system offers significant potential advantages in signal quality, signal processing, and construction cost over the more conventional lock-in amplifier detection method.

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40

Andersson, Mats, Linda Persson, Tomas Svensson, and Sune Svanberg. "Flexible lock-in detection system based on synchronized computer plug-in boards applied in sensitive gas spectroscopy." Review of Scientific Instruments 78, no. 11 (November 2007): 113107. http://dx.doi.org/10.1063/1.2813346.

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41

Jäger, Martin, Paul Schuler, Hartmut B. Stegmann, and Antal Rockenbauer. "Molecular Recognition Analyzed by Observing Intramolecular Interconversion with EPR Spectroscopy." Zeitschrift für Naturforschung B 53, no. 12 (December 1, 1998): 1511–19. http://dx.doi.org/10.1515/znb-1998-1215.

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Abstract Molecular recognition between Rebek’s cleft R and 4-(2-benzimidazolyl)-aminomethyl-2,6-di-rm-butyl-phenol (Bi) is investigated by means of EPR spectroscopy. Their specific inter-molecular interactions are distinguished from non-specific interactions represented by mere protonation on addition of benzoic acid. Both interactions are related to intramolecular in terconversions at the C∞-atom of Bi*, where a two-jump mechanism is found for free and protonated Bi* and a two-site exchange for the complexed ligand. While NMR spectroscopy indicates the existence of 1:1 and 1:2 receptor-substrate complexes, the faster time scale of EPR spectroscopy allows to identify one 1 : 2 as well as three 1 : 1 associates and to elucidate their formation conditions. Based upon the corresponding hf parameters, binding modes and sites are proposed for the key-in-the-lock system.

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42

Zhou, Lu Jun, Qiang Chen, and Jian Qing Fang. "Acoustic Resonance Spectroscopy for Hazards Materials Classification." Applied Mechanics and Materials 427-429 (September 2013): 686–90. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.686.

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In this paper, a measure system based on acoustic resonance is developed for hazards materials classification. It employs the lock-in amplifier as core processor to collect the acoustic resonance spectroscopy (ARS) of sealed containers which storied hazards materials. The transmitter and receiver are coupled externally to the wall of the container. The transmitter generates the sound by using a swept frequency source. The receiver on the opposite side of the wall of the container can detect the transmitted signal. The acoustic properties of hazards materials such as velocity and attenuation can be learned from the observed spectrum signal. Then multivariate methods are used to evaluate pretreatment methods, such as normalization, and classification possibilities of data collected by ARS in a laboratory environment. Principal component analysis (PCA) shows that it is possible to observe differences between samples using the data acquired from the ARS system. Further results obtained from Linear Discriminant Analysis (LDA) show that the identification rates for hazards materials classification are 100%.It is concluded that the ARS system has significant potential in the hazards materials classification.

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43

Augulis, Ramūnas, and Donatas Zigmantas. "Two-dimensional electronic spectroscopy with double modulation lock-in detection: enhancement of sensitivity and noise resistance." Optics Express 19, no. 14 (June 22, 2011): 13126. http://dx.doi.org/10.1364/oe.19.013126.

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Mahnke, Peter. "Characterization of a commercial software defined radio as high frequency lock-in amplifier for FM spectroscopy." Review of Scientific Instruments 89, no. 1 (January 2018): 013113. http://dx.doi.org/10.1063/1.4999552.

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Zhao, Bo, Alexandar L. Hansen, and Qi Zhang. "Characterizing Slow Chemical Exchange in Nucleic Acids by Carbon CEST and Low Spin-Lock FieldR1ρNMR Spectroscopy." Journal of the American Chemical Society 136, no. 1 (December 18, 2013): 20–23. http://dx.doi.org/10.1021/ja409835y.

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Dethomas, F. A., Cecil Dybowski, and Harvey S. Gold. "Effect of Modulation Source Properties upon Signal-To-Noise Ratios of Inelastic Electron Tunneling Spectra." Applied Spectroscopy 40, no. 8 (November 1986): 1180–83. http://dx.doi.org/10.1366/0003702864507585.

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Lock-in amplification using ac modulation and second-harmonic detection is routinely employed in such techniques as ac polarography, ac voltammetry, and inelastic electron tunneling spectroscopy (IETS). Properties of the modulation source are shown in the present IET studies to limit the obtainable signal-to-noise ratio of a spectrum. A single inelastic electron tunneling junction is used to demonstrate the effect of various commercial modulation sources on the IET spectrum of benzoic acid on alumina. With all other parameters being held constant, the signal-to-noise ratio of the IET spectrum is found to be inversely correlated with the total harmonic distortion of the modulation source.

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Rezaeian, Khatereh, Hamid Khanmohammadi, and Nafiseh Shabani. "Sequential Detection of CN- and HSO4- Anions in an Aqueous Environment Utilizing a New Colorimetric Azoimine Receptor: Mimicking Logic Gate Behaviour and a Security Keypad Lock." Australian Journal of Chemistry 71, no. 5 (2018): 389. http://dx.doi.org/10.1071/ch18048.

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A new isonicotiamide-based azoimine receptor has been successfully devised and synthesised for dual-recognition of CN− and HSO4− anions in aqueous media (3 : 2 DMSO–water solution). The devised azomethine probe detected lethal cyanide ions under UV-vis spectroscopy through the rapid appearance of an orange colour. More importantly, the colour and spectroscopic changes of the devised chemosensor could be revived upon the addition of HSO4− to the sensor containing cyanide ions. Furthermore, other surveyed anions failed to induce a similar response. Interestingly, based on changes in absorption intensity at a particular wavelength in the presence of two aforementioned anions, as two chemical inputs, an INHIBIT logic gate has been elaborated. Moreover, the reversibility of the sensory system provided an opportunity to present a sequential logic circuit at a molecular level. In accession, the target chemosensor could operate as a molecular keypad lock with sequential chemical inputs of CN− and HSO4− anions.

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Zhang, Xueshi, Lixian Liu, Le Zhang, Xukun Yin, Huiting Huan, Lu Zhang, and Xiaopeng Shao. "A compact portable photoacoustic spectroscopy sensor for multiple trace gas detection." Journal of Applied Physics 131, no. 17 (May 7, 2022): 174501. http://dx.doi.org/10.1063/5.0088257.

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A compact, highly sensitive, and cost-effective photoacoustic spectroscopic sensor for multiple trace gas detection was reported with a self-designed compact distributed feedback laser array and a 2-channel dual phase field programmable gate array based digital lock-in amplifier, only twentieth in size and weight of the commercial instruments. The capability of the portable sensor was verified by measuring CH4 and C2H2 simultaneously. With an integrated nonlocal means algorithm denoising, noise-equivalent concentrations were achieved as 6.89 ppb for CH4 and 2.74 ppb for C2H2, respectively, corresponding to a normalized noise equivalent absorption coefficient of 1.1 × 10−10 cm−1 W/Hz−1/2, a 79 folds higher than the original data. The results demonstrate that the developed minimized sensor has the potential for sensitive and portable measurement of multiple trace gases.

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Shiraki, Takuma, Takashi S. Kodama, Sayaka Shiki, Tatsuo Nakagawa, and Hisato Jingami. "Spectroscopic analyses of the binding kinetics of 15d-PGJ2 to the PPARγ ligand-binding domain by multi-wavelength global fitting." Biochemical Journal 393, no. 3 (January 13, 2006): 749–55. http://dx.doi.org/10.1042/bj20050930.

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PPARγ (peroxisome proliferator-activated receptor γ) is a nuclear receptor that is activated by natural lipid metabolites, including 15d-PGJ2 (15-deoxy-Δ12,14-prostaglandin J2). We previously reported that several oxidized lipid metabolites covalently bind to PPARγ through a Michael-addition to activate transcription. To separate the ligand-entering (dock) and covalent-binding (lock) steps in PPARγ activation, we investigated the binding kinetics of 15d-PGJ2 to the PPARγ LBD (ligand-binding domain) by stopped-flow spectroscopy. We analysed the spectral changes of 15d-PGJ2 by multi-wavelength global fitting based on a two-step chemical reaction model, in which an intermediate state represents the 15d-PGJ2–PPARγ complex without covalent binding. The extracted spectrum of the intermediate state in wild-type PPARγ was quite similar to the observed spectrum of 15d-PGJ2 in the C285S mutant, which cannot be activated by 15d-PGJ2, indicating that the complex remains in the inactive, intermediate state in the mutant. Thus ‘lock’ rather than ‘dock’ is one of the critical steps in PPARγ activation by 15d-PGJ2.

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Yao, Yikun, Xinjia Zhao, Xiangqian Tang, Jianmei Li, Xinyan Shan, and Xinghua Lu. "Laser etching of 2D materials with single-layer precision up to ten layers." Journal of Laser Applications 34, no. 4 (November 2022): 042051. http://dx.doi.org/10.2351/7.0000848.

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Patterned 2D materials with layer-controlled thickness and precise lateral resolution are of great potential for many applications. Laser etching is a promising technique for large-scale patterning of 2D materials, but better control in film thickness is strongly desired. Here, we explore the dynamic characteristics in the laser etching process in which a local temperature lock phenomenon is observed as laser power reaches the etching threshold. A layer-by-layer etching strategy is then developed based on the temporal evolution of the local temperature as measured by in-situ Raman spectroscopy. Employing such a method in a typical layered material MoS2, we demonstrate thickness control up to ten layers in layer-by-layer laser etching. The local temperature lock during laser etching is explained by thermodynamic simulation of temperature distribution within the 2D material under laser illumination. The influence of substrate thermal conductivity on the thickness of the controlled laser etching has been revealed. The results are valuable for potential applications of 2D material devices built with complex layered structures.

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