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Articoli di riviste sul tema "NQR Spectrometer"

Autore: Grafiati

Pubblicato: 12 ottobre 2024

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1

Hemnani, Preeti, A. K. Rajarajan, Gopal Joshi e S. V. G. Ravindranath. "Design of probe for NQR/NMR detection". International Journal of Electrical and Computer Engineering (IJECE) 10, n. 4 (1 agosto 2020): 3468. http://dx.doi.org/10.11591/ijece.v10i4.pp3468-3475.

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Nuclear Magnetic Resonance (NMR) is a RF technique that is able to detect any compound by sensing the excited resonance signals from atomic nuclei having non-zero spin. NQR is similar to NMR but the only difference is NMR needs a DC magnetic field and due to this its application in the field is limited. A FPGA based NQR spectrometer is designed using a single FPGA chip to perform the digital tasks required for NQR spectrometer. Design of Probe for NMR/NQR spectrometer is researched. Parallel tuned and series tuned Probes are discussed and simulated.14N NQR from NaNO2 is observed from spectrometer designed with parallel tuned probe.

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2

Bielecki, A., D. B. Zax, K. W. Zilm e A. Pines. "Zero‐field NMR and NQR spectrometer". Review of Scientific Instruments 57, n. 3 (marzo 1986): 393–403. http://dx.doi.org/10.1063/1.1138898.

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3

Hemnani, Preeti, A. K. Rajarajan, Gopal Joshi e S. V. G. Ravindranath. "The Building of Pulsed NQR/NMR Spectrometer". International Journal of Electrical and Computer Engineering (IJECE) 8, n. 3 (1 giugno 2018): 1442. http://dx.doi.org/10.11591/ijece.v8i3.pp1442-1450.

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<p>NQR spectrometer designed is composed of four modules; Transmitter, Probe, Receiver and computer controlled (FPGA & Software) module containing frequency synthesizer, synchronous demodulator, pulse programmer and display. The function of the Transmitter module is to amplify the RF pulse sequence to about 200 W power level into the probe (50 Ohm) which is a parallel resonance circuit with a tapped capacitor. The probe excites the nucleus and picks-up the signal emitted from the nuclei. The nuclear signal at the same frequency as the excitation, which is typically in the range of a few microvolts is amplified, demodulated and filtered (1 kHz to 100 kHz) by receiver module. 14N NQR, 1H and 2H NMR signals are observed from the spectrometer.As the SNR of NQR signal is very low, NQR signal processing based on Adaptive Line Enhancement is presented.</p>

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4

Blanz, M., T. J. Rayner e J. A. S. Smith. "A fast field-cycling NMR/NQR spectrometer". Measurement Science and Technology 4, n. 1 (1 gennaio 1993): 48–59. http://dx.doi.org/10.1088/0957-0233/4/1/009.

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5

Mano, Koichi, e Masao Hashimoto. "Computer Enhanced SRO NQR-Spectrometer". Zeitschrift für Naturforschung A 41, n. 1-2 (1 febbraio 1986): 445–48. http://dx.doi.org/10.1515/zna-1986-1-287.

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An automatic computer supported SRO NQR spectrometer system was constructed for the measurement of time dependent NQR signal intensities. The system has several functions: fast scanning (500 kH z/25 s), averaging, smoothing, automatic noise level estimation, automatic peak detection, etc. The process of the ß → α phase transition of p-dichlorobenzene is illustrated by the 3-dimensional spectrum .

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6

Schiano, J. L., e M. D. Ginsberg. "A Pulsed Spectrometer Designed for Feedback NQR". Zeitschrift für Naturforschung A 55, n. 1-2 (1 febbraio 2000): 61–66. http://dx.doi.org/10.1515/zna-2000-1-212.

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A pulsed NQR spectrometer specifically designed to facilitate real-time tuning of pulse sequence parameters is described. A modular approach based on the interconnection of several rack-mounted blocks provides easy access to all spectrometer signals and simplifies the task of modifying the spectrometer design. We also present experimental data that demonstrates the ability of the spectrometer to increase the signal to noise ratio of NQR measurements by automatically adjusting the pulse width in the strong off-resonant comb pulse sequence.

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7

Hemnani, Preeti, A. K. Rajarajan, Gopal joshi e S. V. G. Ravindranath. "FPGA Based RF Pulse Generator for NQR/NMR Spectrometer". Procedia Computer Science 93 (2016): 161–68. http://dx.doi.org/10.1016/j.procs.2016.07.196.

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8

Khusnutdinov, R. R., G. V. Mozzhukhin, N. R. Khusnutdinova e B. M. Salakhutdinov. "High-Q litz wire NQR sensor for medical applications". Power engineering: research, equipment, technology 25, n. 3 (21 agosto 2023): 3–11. http://dx.doi.org/10.30724/1998-9903-2023-25-3-3-11.

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RELEVANCE. The design and development of radio frequency (RF) coil sensors is an important engineering and, at the same time, fundamental task for those radio spectroscopic instruments that require an increase in sensitivity, measured as a signal-to-noise ratio (SNR). Radio spectroscopy of nuclear quadrupole resonance (NQR), especially in nitrogen compounds, in which the resonant frequency is very low and ranges from a few megahertz or lower to hundreds of kilohertz, requires the use of special solutions to increase the sensitivity. PURPOSE. Theoretical substantiation and search for a technical solution that allows achieving high sensitivity on standard equipment through the use of a high-quality sensor. METHODS. Methods for optimizing the design of sensors for NQR/NMR spectrometers are considered. The design of the sensor for the NQR spectrometer, which contains an inductance coil wound with a Litz wire, has been calculated and designed. RESULTS. A high-quality coil for the spectrometer sensor was made, which gives an increase in the quality factor by about 1.5 times. The use of a spectrometer with this coil made it possible to confidently record weak noisy signals of paracetamol at a low duty cycle. The sensitivity of the sensor made it possible to distinguish preparations from different manufacturers by their spectral characteristics. CONCLUSIONS. A solenoid sensor has been developed, modeled and manufactured, which has a high quality factor and allows recording quadrupole resonance signals of drugs (paracetamol) by a non-destructive method directly through the package. The possibility of using such a sensor for quality control of medicines, detection of falsified and counterfeit medicines is shown.

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9

Zhenye, Feng, Edwin A. C. Lücken e Jacques Diolot. "A Computer-controlled, Fully Automatic NMR/NQR Double Resonance Spectrometer". Zeitschrift für Naturforschung A 47, n. 1-2 (1 febbraio 1992): 395–400. http://dx.doi.org/10.1515/zna-1992-1-266.

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AbstractA completely automatic computer-controlled NMR/NQR double resonance spectrometer is described. It features automatic tuning of the low, variable frequency power amplifier, thus permitting untended use over long periods, with high sensitivity and signal reproducibility. The sample is transferred between the low-frequency, zero-field region and the high-field region using compressed air and the possibility of switching on a field of several tens of gauss during the transfer of the sample is also included

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10

Osokin, D. Ya, e R. R. Khusnutdinov. "A two-frequency coherent pulse NQR spectrometer". Instruments and Experimental Techniques 52, n. 1 (gennaio 2009): 85–89. http://dx.doi.org/10.1134/s0020441209010138.

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11

Beguš, Samo, Vojko Jazbinšek, Janez Pirnat e Zvonko Trontelj. "A miniaturized NQR spectrometer for a multi-channel NQR-based detection device". Journal of Magnetic Resonance 247 (ottobre 2014): 22–30. http://dx.doi.org/10.1016/j.jmr.2014.08.002.

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12

Zikumaru, Yushi. "NQR Spectrometer with a Two Integrated Circuits Radio Frequency Head". Zeitschrift für Naturforschung A 45, n. 3-4 (1 aprile 1990): 591–94. http://dx.doi.org/10.1515/zna-1990-3-467.

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Abstract An NQR spectrometer has been constructed using two linear integrated circuits in its oscillator-detector. This is very simple and compact and works in range 3-65 MHz. The radio frequency voltage can be varied from 10 mVp-p to 15 V p-p by changing the supply-voltage of an integrated circuit μA 733. The utility of the spectrometer is demonstrated by recording 35Cl NQR spectra in p-C6H4Cl2 , NaClO3 , and KClO3 .

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13

Lee, Donghoon, S. J. Gravina e P. J. Bray. "NQR Studies of Atomic Arrangements and Chemical Bonding in Glasses". Zeitschrift für Naturforschung A 45, n. 3-4 (1 aprile 1990): 268–72. http://dx.doi.org/10.1515/zna-1990-3-412.

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Abstract A very high sensitivity continuous wave NQR spectrometer was developed to detect pure NQR transitions at low frequencies (down to 200 kHz). A signal-to-noise ratio of more than 100 to 1 has been achieved at about 1.36 MHz for crystalline B 2 0 3 . Two large n B responses have been found in vitreous B 2 0 3 (NMR detected only one site) with linewidths of less than 30 kHz. 27 A1 NQR spectra were obtained for OC-A1203 (Corundum), the mineral andalusite (a form of A1203 • Si0 2), and a glass having the composition of anorthite (CaO • A1203 • 2Si0 2).

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Choi, K., e I. Yu. "Inductive detection of piezoelectric resonance by using a pulse NMR/NQR spectrometer". Review of Scientific Instruments 60, n. 10 (ottobre 1989): 3249–52. http://dx.doi.org/10.1063/1.1140560.

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15

Pirnat, J., J. Lužnik e Z. Trontelj. "Iodine NQR and Phase Transitions in [N(CH3)4]2 ZnI4". Zeitschrift für Naturforschung A 45, n. 3-4 (1 aprile 1990): 349–52. http://dx.doi.org/10.1515/zna-1990-3-423.

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Abstract Using a superregenerative NQR spectrometer, the temperature dependence of 127I NQR spectra in [N(CH3)4]2ZnI4 was measured between 167 and 335 K. The measurements confirm two known structural phase transitions at 219 and 257.5 K. The correspondence between the distinct regions of iodine NQR spectra and the crystal structure is discussed. The relation of [N(CH3)4]2ZnI4 to the incommensurate family with the general formula X2YZ4 and the high temperature (paraphase) crystal space group D162h (Pmcn) is studied.

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16

Hotra, Oleksandra, e Andriy Samila. "A Low-Cost Digital Pulsed Coherent Spectrometer for Investigation of NQR in Layered Semiconductor GaSe and InSe Crystals". Electronics 9, n. 12 (25 novembre 2020): 1996. http://dx.doi.org/10.3390/electronics9121996.

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A low-cost digital pulsed nuclear quadrupole resonance (NQR) radio-spectrometer is proposed, all main modules of digital processing and synthesis of which on the field-programmable gate array (FPGA) are implemented. The input sensitivity of the device is of the order of 3 μV to 5 μV which allows conducting NQR studies in samples of relatively small dimensions. The application of the developed methods of NQR pulsed radio spectroscopy made it possible to increase spectral resolution, improve spectral shape and significantly reduce the time of research. In the case of studying InSe and GaSe crystals, spectra with signal-to-noise ratio (SNR) values of 41.9 dB were observed in samples with a volume of 0.1 cm3. As the results of the research have shown, the characteristics of the proposed spectrometer make it effective when used to observe free induction decay (FID) signals of a significant number of isotopes of elements with quadrupolar nuclei.

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17

Reddy, Narsimha, Arun Bhavsar e P. T. Narasimhan. "Microprocessor-Controlled Pulsed NQR Spectrometer for Automatic Acquisition of Zeeman Perturbed Nuclear Quadrupole Spin Echo Envelope Modulations (ZSEEM )". Zeitschrift für Naturforschung A 41, n. 1-2 (1 febbraio 1986): 449–52. http://dx.doi.org/10.1515/zna-1986-1-288.

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A simple microprocessor-controlled pulsed NQR spectrometer system has been developed with the capability to acquire Zeeman perturbed spin echo envelope modulations (ZSEEM). The CPU of the system is based on the Intel Corporation 8085 A microprocessor. The performance of the spectrometer is illustrated with the presentation of ZSEEM spectra of NaClO3 and KClO3.

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18

Samila, Andriy, Alexander Khandozhko, Ivan Hryhorchak, Leonid Politans’kyy e Taras Kazemirskiy. "A CONTROL UNIT FOR A PULSED NQR-FFT SPECTROMETER". Informatics, Control, Measurement in Economy and Environment Protection 5, n. 4 (28 ottobre 2015): 55–58. http://dx.doi.org/10.5604/20830157.1176577.

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19

Хандожко, Александр Григорьевич, Виктор Александрович Хандожко e Андрей Петрович Самила. "A pulse coherent nqr spectrometer with effective transient suppression". Eastern-European Journal of Enterprise Technologies 6, n. 12(66) (28 dicembre 2013): 21. http://dx.doi.org/10.15587/1729-4061.2013.19700.

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20

Monea, Cristian, Gabriel V. Iana, Silviu Ionita, Laurentiu M. Ionescu, Sandel A. Zaharia, Stelian Ilie e Nicu Bizon. "An optimized NQR spectrometer for detection of prohibited substances". Measurement 151 (febbraio 2020): 107158. http://dx.doi.org/10.1016/j.measurement.2019.107158.

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21

Trontelj, Zvonko, Janez Pirnat, Vojko Jazbinšek, Janko Lužnik, Stane Srčič, Zoran Lavrič, Samo Beguš, Tomaž Apih, Veselko Žagar e Janez Seliger. "Nuclear Quadrupole Resonance (NQR)—A Useful Spectroscopic Tool in Pharmacy for the Study of Polymorphism". Crystals 10, n. 6 (31 maggio 2020): 450. http://dx.doi.org/10.3390/cryst10060450.

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Nuclear Quadrupole Resonance (NQR) spectroscopy has been known for 70 years. It is suitable for the study of measured (poly)crystalline chemical compounds containing quadrupole nuclei (nuclei with spin I ≥ 1) where the characteristic NQR frequencies represent the fingerprints of these compounds. In several cases, 14N NQR can distinguish between the polymorphic crystalline phases of active pharmaceutical ingredients (APIs). In order to further stimulate 14N NQR studies, we review here several results of API polymorphism studies obtained in Ljubljana laboratories: (a) In sulfanilamide, a clear distinction between three known polymorphs (α, β, γ) was demonstrated. (b) In famotidine, the full spectra of all seven different nitrogen positions were measured; two polymorphs were distinguished. (c) In piroxicam, the 14N NQR data helped in confirming the new polymorphic form V. (d) The compaction pressure in the tablet production of paracetamol, which is connected with linewidth change, can be used to distinguish between producers of paracetamol. We established that paracetamol in the tablets of six different manufacturers can be identified by 14N NQR linewidth. (e) Finally, in order to get an extremely sensitive 14N NQR spectrometer, the optical detection of the 14N NQR signal is mentioned.

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22

Ostafin, Michał, Mariusz Maćkowiak e Marek Bojarski. "Automatically Tuned Probe Head System for Pulsed NQR Spectroscopy in Extreme Thermodynamic Conditions". Zeitschrift für Naturforschung A 49, n. 1-2 (1 febbraio 1994): 42–46. http://dx.doi.org/10.1515/zna-1994-1-210.

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Abstract A complete N Q R probe-head system operating in the frequency ranges 0.5 -150 and 150- 300 MHz is described. The head is particularly suited for NQR experiments carried out at a remote location, for example in a low-temperature cryostat or high-pressure chamber. Moreover, the head system includes a microprocessor-controller for automated tuning of the probe to the operating frequency of the associated NQR spectrometer. The controller can be easily interfaced to a PC via standard serial port.

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23

Honda, H., A. Sasane, K. Miyagi, A. Ishikawa e Y. Mori. "81Br NQR for Uncoordinated Br ions in trans-[CoBr2(en)2][H5O2]Br2 and trans-[CoBr2(en)2] [D5O2]Br2". Zeitschrift für Naturforschung A 49, n. 1-2 (1 febbraio 1994): 209–12. http://dx.doi.org/10.1515/zna-1994-1-232.

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AbstractThe temperature dependence of the 81Br NQR frequencies (vD) for uncoordinated Br- ions in trans-[CoBr2(en)2] [D5O2]Br2(D) has been determined by a continuous-wave spectrometer. vD amounted to 16.200 MHz at 273 K. This is lower by 418 kHz than the 81Br NQR frequency (vH) for trans-[CoBr2 (en2] [H5O2 ]Br2 (H). The frequency difference (Δv = vH -vD) remained almost constant in the temperature range studied. A shortening of the O-H bond length caused by deuteration could explain the magnitude and the sign of Av on the basis of a point charge model calculation. The compounds D and H yielded 81Br NQR lines in the range 110-320 K and 90-343 K, respectively. As to the 59Co NQR frequencies (7/2 - 5/2), the observed isotope frequency shifts (Δv1 = v1H - v1D) between D and H were smaller than 5 kHz. Below 160 K, 59Co resonances were only available by pulsed experiments. 59Co NQR spin-lattice relaxation times T1Q of 0.54 ms at 194 K and 4.8 s at 77 K for H have been observed.

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24

Scharfetter, Hermann, Markus Bödenler e Dominik Narnhofer. "A cryostatic, fast scanning, wideband NQR spectrometer for the VHF range". Journal of Magnetic Resonance 286 (gennaio 2018): 148–57. http://dx.doi.org/10.1016/j.jmr.2017.12.004.

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25

Sullivan, E. P. A. "Estimating relaxation times with a very simple ratemeter-type NQR spectrometer". Journal of Molecular Structure 319 (marzo 1994): 285–88. http://dx.doi.org/10.1016/0022-2860(93)07925-m.

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26

Garcia, Maria L. S., e Edwin A. C. Lucken. "(CH3)3CCOOSbCl4: Structure Determination by Zeeman Perturbed NQR". Zeitschrift für Naturforschung A 41, n. 1-2 (1 febbraio 1986): 129–33. http://dx.doi.org/10.1515/zna-1986-1-219.

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A single crystal of tetrachloro(0,0-pivaloylato)antimony(V) has been studied at 77 K, byZeeman perturbed 35Cl NQR, using a FT-NQR pulsed spectrometer. The four lines at zero-field, ν1 = 27.6468, ν2= 27.3070, ν3= 25.7341 and ν4= 25.3438 MHz yield eight EFG tensors in themagnetic field, related by a twofold symmetry element in the crystal. The correspondingasymmetry parameters are η1, = 0.134, η2 = 0.13, η3= 0.07, and η4 = 0.09. The molecular structurededuced from the relative orientations of the principal Z-axes of the EFG tensors confirms that thehigher quadrupole coupling constants are associated with the chlorine atoms in equatorial positions,relative to the plane of the organic ligand, as predicted from NQR powder studies. It is concludedthat the crystal structure is monoclinic with two (class m or 2) or four (class 2/m) moleculesper unit cell. The molecular packing is such that the planes formed by equatorial or axial chlorineatoms are approximately at right angles to their symmetry related images.

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27

Maćkowiak, Mariusz, e Piotr Kątowski. "Enhanced Information Recovery in 2D On-and Off-Resonance Nutation NQR using the Maximum Entropy Method". Zeitschrift für Naturforschung A 51, n. 5-6 (1 giugno 1996): 337–47. http://dx.doi.org/10.1515/zna-1996-5-605.

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Abstract Two-dimensional zero-field nutation NQR spectroscopy has been used to determine the full quadrupolar tensor of spin - 3/2 nuclei in serveral molecular crystals containing the 3 5 Cl and 7 5 As nuclei. The problems of reconstructing 2D-nutation NQR spectra using conventional methods and the advantages of using implementation of the maximum entropy method (MEM) are analyzed. It is shown that the replacement of conventional Fourier transform by an alternative data processing by MEM in 2D NQR spectroscopy leads to sensitivity improvement, reduction of instrumental artefacts and truncation errors, shortened data acquisition times and suppression of noise, while at the same time increasing the resolution. The effects of off-resonance irradiation in nutation experiments are demonstrated both experimentally and theoretically. It is shown that off-resonance nutation spectroscopy is a useful extension of the conventional on-resonance experiments, thus facilitating the determination of asymmetry parameters in multiple spectrum. The theoretical description of the off-resonance effects in 2D nutation NQR spectroscopy is given, and general exact formulas for the asymmetry parameter are obtained. In off-resonance conditions, the resolution of the nutation NQR spectrum decreases with the spectrometer offset. However, an enhanced resolution can be achieved by using the maximum entropy method in 2D-data reconstruction.

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28

Rudakov, T. N., V. V. Fedotov, A. V. Belyakov e V. T. Mikhal’tsevich. "Suppression of transient processes in the oscillatory circuit of the NQR spectrometer". Instruments and Experimental Techniques 43, n. 1 (gennaio 2000): 78–81. http://dx.doi.org/10.1007/bf02759003.

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Samila, A. P., e А. П. Саміла. "Hardware and software implementation of data acquisition system for pulsed NQR spectrometer". Технология и конструирование в электронной аппаратуре, n. 1-2 (aprile 2017): 16–22. http://dx.doi.org/10.15222/tkea2017.1-2.16.

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Clarke, John. "Low Frequency Nuclear Quadrupole Resonance with SQUID Amplifiers". Zeitschrift für Naturforschung A 49, n. 1-2 (1 febbraio 1994): 5–13. http://dx.doi.org/10.1515/zna-1994-1-204.

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Abstract The dc SQUID (Superconducting QUantum Interference Device) can be configured as an amplifier of spin-echos with a noise temperature of approximately 10 mK (f/1 M Hz) at an operating temperature of 1.5 K. A Fourier transform spectrometer based on a SQUID with a superconducting input circuit and operated in a flux-locked loop is used to obtain nuclear quadrupole resonance (NQR) spectra in a broadband m ode over the bandwith 0 -1 M Hz. Spin-echo spectra of 14N in NH4ClO4 reveal sharp NQR resonances, obtained simultaneously, at 17.4, 38.8 and 56.2 kHz. At 1.5 K, the measured longitudinal and transverse relaxation times T1 and T2 for the 38.8 kHz transition are 63 ± 3 ms and 22±2 ms, respectively.

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Sikorsky, Tomas, Andrzej Pelczar, Stephan Schneider e Thorsten Schumm. "Integrating superregenerative principles in a compact, power-efficient NMR/NQR spectrometer: A novel approach with pulsed excitation". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1062 (maggio 2024): 169239. http://dx.doi.org/10.1016/j.nima.2024.169239.

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Manallah, B. "Delayed Double Resonance Between Quadrupolar Levels: Observation of a Nuclear Spin Emission Signal in s-Triazine". Zeitschrift für Naturforschung A 41, n. 1-2 (1 febbraio 1986): 396–98. http://dx.doi.org/10.1515/zna-1986-1-276.

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A delayed double resonance experiment was carried out using a Robinson-type continuous wave spectrometer. The sample chosen was s-triazine at liquid helium temperature, where the relaxation times are of the order of ten hours. Line pairings between the two Nitrogen-14 NQR sites were confirmed. Emission signals from ν- transitions were observed after successively saturating first the ν- line and then the ν+ line. The results are understood in terms of a simple model of spin population dynamics.

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Ganal, P., T. Butz, A. Lerf, M. Naito e H. Nishihara. "The 181Ta Nuclear Quadrupole Interaction in the Charge Density Wave Phases of 1T-TaS2". Zeitschrift für Naturforschung A 45, n. 3-4 (1 aprile 1990): 439–44. http://dx.doi.org/10.1515/zna-1990-3-439.

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Abstract With a high resolution time differential perturbed angular correlation spectrometer we investigated the nuclear quadrupole interaction of Ta in 1T-TaS2 . The results obtained for the commensurate charge density wave phase lead to a revised assignment of the previously observed 181Ta NQR resonances. Differences in the intracluster architecture of the 13-atom Star of David cluster between 1T-TaS2 and 1T-TaSe2 could be responsible for the metal to semiconductor transition which occurs in lT-TaS2 but not in lT-TaSe2 .

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Samila, A., V. Khandozhko e L. Politansky. "Energy efficiency increase of NQR spectrometer transmitter at pulse resonance excitation with noise signals". Solid State Nuclear Magnetic Resonance 87 (ottobre 2017): 10–17. http://dx.doi.org/10.1016/j.ssnmr.2017.06.001.

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Trepanier, R. J., e M. A. Whitehead. "Line Width Narrowing with 14N Nuclear Quadrupole Resonance Lines at 296 K and 77 K Using a High Powered Pulsed Spectrometer". Zeitschrift für Naturforschung A 41, n. 1-2 (1 febbraio 1986): 386–91. http://dx.doi.org/10.1515/zna-1986-1-274.

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The dependence of the NQR line width on the RF pulse intensity and period using a continuous steady state pulse train for polycrystalline 14N compounds shows a dependence on the asymmetry parameter η, the temperature, and the crystal structure.

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Rozorinov, Heorhii, Olena Nenia, Nataliia Bereznenko e Petro Mamotenko. "Simulation of Radio Pulse Generator of NQR Spectrometer for the Detection of Explosives and Narcotic Substances". Modern Special Technics 61, n. 2 (2020): 151–61. http://dx.doi.org/10.36486/mst2411-3816.2020.2(61).15.

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Horiuchi, Keizo, Ryuichi Ikeda e Daiyu Nakamura. "Phase transition and anionic motion in solid [(CH3)2NH2]2SnCl6as studied by the temperature dependence of35Cl NQR frequencies and chlorine nuclear relaxation times determined with a pulsed NQR spectrometer". Berichte der Bunsengesellschaft für physikalische Chemie 91, n. 12 (dicembre 1987): 1351–59. http://dx.doi.org/10.1002/bbpc.19870911209.

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Harbison, Gerard S., e Andris Slokenbergs. "Two-dimensional Nutation Echo Nuclear Quadrupole Resonance Spectroscopy". Zeitschrift für Naturforschung A 45, n. 3-4 (1 aprile 1990): 575–80. http://dx.doi.org/10.1515/zna-1990-3-464.

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Abstract We discuss two new two-dimensional nuclear quadrupole resonance experiments, both based on the principle of nutation spectroscopy, which can be used to determine the asymmetry parameter, and thus the full quadrupolar tensor, of spin-3/2 nuclei at zero applied magnetic field. The first experiment is a simple nutation pulse sequence in which the first time period (t1) is the duration of the radiofrequency exciting pulse; and the second (t2) is the normal free-precession of a quadrupolar nucleus at zero-field. After double Fourier-transformation, the result is a 2 D spectrum in which the first frequency dimension is the nutation spectrum for the quadrupolar nucleus at zero-field. For polycrystalline samples this sequence generates powder lineshapes; the position of the singularities, in these lineshapes can be used to determine the asymmetry parameters η in a very straightforward manner, η has previously only been obtainable using Zeeman perturbed NQR methods. The second sequence is the same nutation experiment with a spin-echo pulse added. The virtue of this refocussing pulse is that it allows acquisition of nutation spectra from samples with arbitrary inhomogeneous linewidth; thus, asymmetry parameters can be determined even where the quadrupolar resonance is wider than the bandwidth of the spectrometer. Experimental examples of 35Cl, 81Br and 63Cu nutation and nutation-echo spectra are presented.

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Jonsen, Paul. "5036279 Portable NMR and NQR spectrometers". Magnetic Resonance Imaging 11, n. 2 (gennaio 1993): V. http://dx.doi.org/10.1016/0730-725x(93)90057-k.

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40

Shen, Zefang, Haylee D'Agui, Lewis Walden, Mingxi Zhang, Tsoek Man Yiu, Kingsley Dixon, Paul Nevill et al. "Miniaturised visible and near-infrared spectrometers for assessing soil health indicators in mine site rehabilitation". SOIL 8, n. 2 (18 luglio 2022): 467–86. http://dx.doi.org/10.5194/soil-8-467-2022.

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Abstract. Mining can cause severe disturbances to the soil, which underpins the viability of terrestrial ecosystems. Post-mining rehabilitation relies on measuring soil properties that are critical indicators of soil health. Soil visible–near-infrared (vis–NIR) spectroscopy is rapid, accurate, and cost-effective for estimating a range of soil properties. Recent advances in infrared detectors and microelectromechanical systems (MEMSs) have produced miniaturised, relatively inexpensive spectrometers. Here, we evaluate the spectra from four miniaturised visible and NIR spectrometers, some combinations, and a full-range vis–NIR spectrometer for modelling 29 soil physical, chemical, and biological properties used to assess soil health at mine sites. We collected topsoil samples from reference, undisturbed native vegetation, and stockpiles from seven mines in Western Australia. We evaluated the spectrometers' repeatability and the accuracy of spectroscopic models built with seven statistical and machine learning algorithms. The spectra from the visible spectrometer could estimate sand, silt, and clay with similar or better accuracy than the NIR spectrometers. However, the spectra from the NIR spectrometers produced better estimates of soil chemical and biological properties. By combining the miniaturised visible and NIR spectrometers, we improved the accuracy of their soil property estimates, which were similar to those from the full-range spectrometer. The miniaturised spectrometers and combinations predicted 24 of the 29 soil properties with moderate or greater accuracy (Lin's concordance correlation, ρc≥0.65). The repeatability of the NIR spectrometers was similar to that of the full-range, portable spectrometer. The miniaturised NIR spectrometers produced comparably accurate soil property estimates to the full-range portable system which is an order of magnitude more expensive, particularly when combined with the visible range sensor. Thus, the miniaturised spectrometers could form the basis for a rapid, cost-effective soil diagnostic capacity to support mine site rehabilitation and deliver significant positive economic and environmental outcomes.

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Zhu, Chenxi, Xiaping Fu, Jianyi Zhang, Kai Qin e Chuanyu Wu. "Review of portable near infrared spectrometers: Current status and new techniques". Journal of Near Infrared Spectroscopy 30, n. 2 (9 marzo 2022): 51–66. http://dx.doi.org/10.1177/09670335211030617.

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Near infrared (NIR) spectroscopy is a non-destructive detection technology involving NIR spectral data acquisition and chemometric treatment. The use of an NIR spectrometer is evidently crucial in this regard; however, traditional benchtop NIR spectrometers considerably limit usage scenarios. Accordingly, the miniaturization of spectrometers with high level performance has become a research trend. Various commercial products have been developed, and new techniques have been applied to produce more portable NIR spectrometers. This paper reviews the main types of commercial portable NIR spectrometers and summarizes as well as compares their specifications. Moreover, new techniques for promoting miniaturization and the prospects for future development are introduced.

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42

Rukundo, Isaac R., Mary-Grace C. Danao, Robert B. Mitchell, Steven D. Masterson e Curtis L. Weller. "Comparing the Use of Handheld and Benchtop NIR Spectrometers in Predicting Nutritional Value of Forage". Applied Engineering in Agriculture 37, n. 1 (2021): 171–81. http://dx.doi.org/10.13031/aea.14157.

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HighlightsA transportable spectrometer performed similarly to benchtop spectrometers to predict forage quality.Absorption bands in the second and third overtone regions were used to predict forage quality with ample accuracy.A low-cost handheld spectrometer was useful for routine screening of forage for nitrogen content. Abstract. Assessing the nutritional composition of animal feed and forage materials is important to achieve high animal productivity and wellness. Precision nutrition programs that use NIR technology can determine the nutritional composition of feed and forage quickly and simply, generating actionable information such as total nitrogen (N), acid detergent fiber (ADF), neutral detergent fiber (NDF), and acid detergent lignin (ADL) contents, as well as in vitro dry matter digestibility (IVDMD). Recent advances in optics and microelectronics have allowed for the development of handheld spectrometers that are portable, robust, and user-friendly. However, are the handheld units accurate enough to predict nutritional content of animal feed? In this study, the performance of two handheld NIR spectrometers to predict the nutritional content of forage based on N, ADF, NDF, ADL, and IVDMD was evaluated by comparing them to two benchtop NIR spectrometers often used in feed and forage analysis. The forage samples comprised switchgrass (Panicum virgatum L), big bluestem (Andropogon gerardi), and Indiangrass (Sorghastrum nutans). The first handheld spectrometer covers 780-2500 nm with a spectral interval (??) of 1 nm, while the second handheld spectrometer is a palm-sized smartphone spectrometer covering 900-1700 nm with ?? = 4 nm. The benchtop spectrometers both cover 400-2500 nm with ?? = 2 nm. Forage samples were scanned on each spectrometer and divided into calibration (n = 143) and validation (n = 35) sets. Partial least squares (PLS) regression was used to calibrate all spectrometers using mean-centered spectral data that had been preprocessed using Savitzky-Golay first derivative (SG1) or second derivative (SG2) algorithm with 9-63 smoothing points. Results showed that PLS models that best predicted N using the benchtop spectrometers had lower standard error of prediction (SEP = 1.24-1.28 g kg-1) and higher ratio of prediction to deviation (RPD = 3.66-3.78) compared to the models developed based on spectra collected from the handheld spectrometers (SEP = 1.46-1.78 g kg-1; RPD = 2.39-2.84). ADF, NDF, and ADL were variable and generally poorly predicted using spectra from the benchtop spectrometers (SEP = 10.02-33.19 g kg-1;RPD = 1.71-2.24), and even more so using the handheld spectrometers (SEP = 10.63-32.57 g kg-1;RPD = 1.64-2.47). Predicting IVDMD was similar for both sets of benchtop (SEP = 40.00-41.73 g kg-1; RPD = 2.24-2.34) and handheld (SEP = 34.46-40.84 g kg-1; RPD = 2.29-2.72) spectrometers. These results show that the handheld devices can be used for screening of forage samples based on N, which is a closely monitored component in animal feed and forage, as well as IVDMD, an important forage quality index. Keywords: Forage, Portable spectrometer, Spectroscopy, Screenin, Ruminant nutrition.

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Wikus, Patrick, Wolfgang Frantz, Rainer Kümmerle e Patrik Vonlanthen. "Commercial gigahertz-class NMR magnets". Superconductor Science and Technology 35, n. 3 (20 gennaio 2022): 033001. http://dx.doi.org/10.1088/1361-6668/ac4951.

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Abstract Nuclear magnetic resonance (NMR) spectroscopy is a wide-spread analytical technique which is used in a large range of different fields, such as quality control, food analysis, material science and structural biology. In the widest sense, NMR is an analytical technique to determine the structure of molecules. At the time of writing this manuscript, commercial NMR spectrometers with a proton resonance frequency ⩾900 MHz are only available from Bruker. In 2019, Bruker installed the first 1.1 GHz (25.8 T) NMR spectrometer at the St. Jude Children Research Hospital in Memphis, Tennessee, followed by the installation of the first 1.2 GHz (28.2 T) NMR spectrometer at the University of Florence in Italy in 2020. These were the first commercial NMR spectrometers operating at magnetic fields in excess of what can be achieved with conventional low temperature superconductors, and which depend on high temperature superconductors to generate the required magnetic field. In this paper, the requirements on commercial NMR magnets are discussed and the history of high-field NMR magnets is reviewed. Bruker’s R&D program for 1.1 and 1.2 GHz NMR magnets and spectrometers will be described, and some of the key properties of these first commercial NMR magnets with high-temperature superconductors are reported.

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Tu, Zhiyang (Stan), Joseph Irudayaraj e Youngsoo Lee. "Characterizing Spray-Dried Powders through NIR Spectroscopy: Effect of Two Preparation Strategies for Calibration Samples and Comparison of Two Types of NIR Spectrometers". Foods 12, n. 3 (19 gennaio 2023): 467. http://dx.doi.org/10.3390/foods12030467.

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Emerging portable near infrared (NIR) spectroscopic approaches coupled with data analysis and chemometric techniques provide opportunities for the rapid characterization of spray-dried products and process optimization. This study aimed to enhance the understanding of applying NIR spectroscopy in spray-dried samples by comparing two sample preparation strategies and two spectrometers. Two sets of whey protein–maltodextrin matrixes, one with a protein content gradient and one with a consistent protein content, were spray-dried, and the effect of the two preparation strategies on NIR calibration model development was studied. Secondly, a portable NIR spectrometer (PEAK) was compared with a benchtop NIR spectrometer (CARY) for the moisture analysis of prepared samples. When validating models with the samples with focused protein contents, the best PLS protein models established from the two sample sets had similar performances. When comparing two spectrometers, although CARY outperformed PEAK, PEAK still demonstrated reliable performance for moisture analysis, indicating that it is capable as an inline sensor.

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Chakrapani, Sneha B., Michael J. Minkler e Bryan S. Beckingham. "Low-field 1H-NMR spectroscopy for compositional analysis of multicomponent polymer systems". Analyst 144, n. 5 (2019): 1679–86. http://dx.doi.org/10.1039/c8an01810c.

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46

Wehlburg, Christine M., David M. Haaland e David K. Melgaard. "New Hybrid Algorithm for Transferring Multivariate Quantitative Calibrations of Intra-Vendor Near-Infrared Spectrometers". Applied Spectroscopy 56, n. 7 (luglio 2002): 877–86. http://dx.doi.org/10.1366/000370202760171554.

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A new prediction-augmented classical least-squares/partial least-squares (PACLS/PLS) hybrid algorithm is ideally suited for use in transferring multivariate calibrations between spectrometers. Spectral variations such as instrument response differences can be explicitly incorporated into the algorithm through the use of subset sample spectra collected on both spectrometers. Two current calibration transfer methods, subset recalibration and piecewise direct standardization (PDS), also utilize subset sample spectra to facilitate transfer of calibration. The three methods were applied to the transfer of quantitative multivariate calibration models for near-infrared (NIR) data of organic samples containing chlorobenzene, heptane, and toluene between a primary and three secondary spectrometers that were all the same model, called intra-vendor transfer of calibration. The hybrid PACLS/PLS method outperformed subset recalibration and provided predictions equivalent to PDS with additive background correction on the two secondary spectrometers whose instrument drift appeared to be dominated by simple linear baseline variations. One of the secondary spectrometers had complex instrument drift that was captured by repeatedly measuring the spectrum of a single repeat sample. In calculating a transfer function to correct prediction spectra, PDS assumes no instrumental drift on the secondary spectrometer. Therefore, PDS was unable to directly accommodate both the subset samples and the use of a single repeat sample to transfer and maintain a calibration on that secondary instrument. In order to implement the transfer of calibration with PDS in the presence of complex instrument drift, recalibrated PLS models that included the repeat spectra from the secondary spectrometer were used to predict the spectra transformed by PDS. The importance of correcting for drift on the secondary spectrometer during calibration transfer was illustrated by the improvements in prediction for all three methods vs. using only the instrument response differences derived from the subset sample spectra. When the effects of instrument drift were complex on the secondary spectrometer, the PACLS/PLS hybrid algorithm outperformed both PDS and subset recalibration. Through the explicit incorporation of spectral variations, due to instrument response differences and drift on the secondary spectrometer, the PACLS/PLS algorithm was successful at intra-vendor transfer of calibrations between NIR spectrometers.

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Tian, Jing, Xinyu Chen, Zhennan Liang, Wenliang Qi, Xiaohuan Zheng, Daoli Lu e Bin Chen. "Application of NIR Spectral Standardization Based on Principal Component Score Evaluation in Wheat Flour Crude Protein Model Sharing". Journal of Food Quality 2022 (12 aprile 2022): 1–10. http://dx.doi.org/10.1155/2022/9009756.

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Abstract (sommario):

In order to explore spectral standardization methods for spectra collected by different NIR spectrometers, to reduce spectral differences, and to realize model sharing among different instruments, the crude protein content of 154 wheat flour samples was measured using one grating and three Fabry-Perot tunable filter NIR spectrometers in wavelength. At the same wavelength range and wavelength interval, three algorithms, namely, direct standardization (DS), piecewise direct standardization (PDS), and simple linear regression direct standardization (SLRDS), were used to standardize spectra collected by different instruments from the same samples. Spectral standardization error rate (SSER), principal component score error rate (PCSER), and other indicators were employed to analyze the spectral differences between the master and the target spectra, and the effect of model sharing was evaluated using parameters including prediction correlation coefficient (Rp), root mean square error of prediction (RMSEP), and relative prediction deviation (RPD). The results show the following: (1) The difference between spectra can be quantitatively evaluated through analyzing SSER and PCSER. (2) After standardization by the three algorithms, the spectral difference between the three target and the master spectrometers is significantly reduced and the prediction effect of the master model is greatly improved. (3) Among the three algorithms, DS algorithm had the smallest error rate in standardizing spectra from three target spectrometers. After standardization by the DS algorithm, the master model had the best effect. Its prediction accuracy was greatly improved compared with that before standardization. (4) The standard model established based on the S450 spectrometer can be applied to the same spectrometer as the N500 spectrometer with the same resolution and different wavelength ranges, so as to achieve model sharing. Therefore, DS, PDS, and SLRDS algorithms can effectively reduce the spectral differences between different instruments and realize the sharing of NIR calibration models for wheat flour crude protein measurement.

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Priori, Simone, Nada Mzid, Simone Pascucci, Stefano Pignatti e Raffaele Casa. "Performance of a Portable FT-NIR MEMS Spectrometer to Predict Soil Features". Soil Systems 6, n. 3 (8 agosto 2022): 66. http://dx.doi.org/10.3390/soilsystems6030066.

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Abstract (sommario):

NIR spectrometers based on micro-electromechanical systems (MEMS) have become available in the market, with lower prices and smaller dimensions than traditional spectrometers. MEMS technology allows for miniaturizing and reduces the cost of the spectrometers, allowing a wider use for agricultural consultants, technicians, and scientific researchers. The aim of this work was to evaluate an innovative FT-NIR MEMS spectrometer, namely the Neospectra Scanner (NS), covering the range from 1350 to 2500 nm. The assessment was performed by comparing the accuracy of prediction of soil organic carbon, texture fractions, and total calcium carbonate, obtained with NS, with that of a standard full VIS-NIR spectrometer, namely the ASD-Fieldspec Fr Pro (AF). A dataset of 182 soil samples, dried and sieved at 2 mm, collected from 4 different agricultural areas of Italy were scanned with both devices. AF showed slightly higher R2 and lower prediction error (RMSEP) than NS for all soil features, but the accuracy of the two instruments can be considered comparable. Removing the 350–1350 nm range from VIS-NIR spectra of AF, i.e., as to have the same spectral range of NS, made the prediction accuracy of AF reduced spectra (1350–2500 nm) slightly lower than that of NS. This demonstrates that the lower accuracy of the NS in soil features prediction is not due to the lower resolution of the spectra, but probably due to the lack of visible and beginning of the NIR range (350–1300 nm).

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Akay, Cengiz, e Aytaç Yalçiner. "A New Weak Field Double Resonance NMR Spectrometer". Zeitschrift für Naturforschung A 50, n. 2-3 (1 marzo 1995): 177–85. http://dx.doi.org/10.1515/zna-1995-2-309.

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Abstract (sommario):

Abstract Weak field NMR and double resonance spectrometers are mostly homemade. In this work, some electronic units of such a spectrometer operating at 1.437 mT were designed and realized by including new integrated circuits: an audio generator, digital sweep generator, digital additional field and delay unit, Quartz generator, NMR detector(Q-meter), AF-narrowband amplifier, phase shifter and phase sensitive detector.

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Gomes, Bruna, Carlos Lobo e Luiz Colnago. "Monitoring Electrochemical Reactions in Situ with Low Field NMR: A Mini-Review". Applied Sciences 9, n. 3 (1 febbraio 2019): 498. http://dx.doi.org/10.3390/app9030498.

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Abstract (sommario):

The number of applications of time domain NMR using low-field spectrometers in research and development has been steadily increasing in recent years with applications ranging from quality control of industrial products to the study of physical and chemical properties of a wide array of solid and liquid samples to, most recently, electrochemical studies. In this mini-review we summarize the progress that has been achieved in the coupling between time domain NMR (using low-field spectrometers) and electrochemistry and how the challenges that this coupling poses have been overcome over the years. We also highlight the effect that the static magnetic field of the NMR spectrometer has on the electrochemical systems.

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