Deuterium Signal Research Articles

Determination of the radial position of zero density for profile reflectometry on experimental advanced superconducting tokamak

The Experimental Advanced Superconducting Tokamak (EAST) reflectometry is a Frequency-Modulated Continuous-Wave monostatic system with the transmission lines similar to the ITER reflectometer design. One of the most significant and common problems for reflectometry to reconstruct the density profile is the determination of initialization, i.e. zero density position (R start), which could be determined by the extraordinary mode (X-mode) reflectometry. The main source of noise still comes from the wave scattering of plasmas despite the sweeping period of around 10 microseconds. It is found that to reduce the random noise of R start, averaging on 25 periods is the optimal solution. During the L-mode discharges with only lower hybrid wave (LHW) heating, R start would move outwards and its fluctuation and the high frequency components of turbulence around R start would be obviously increased when the 2.45 GHz system is switched on, while no obvious change is observed in the 4.6 GHz case. These phenomena are consistent with that 2.45 GHz LHW has less current drive ability than 4.6 GHz LHW on EAST. During ELMy H-mode, the peak of R start is consistent with Deuterium signal and the maximum displacement is about 3 cm. The comparison of density profiles from reflectometry and Lithium beam emission spectroscopy (Li-BES) suggests that setting the density at R start to (4 ± 2)× 1017 m-3 is much better than zero, while this value is somewhat empirical and closely related to the amplitude threshold for determining the first probing frequency corresponding to R start.

Poly(arylisocyanides) as Versatile, Enantiodiscriminating Alignment Media for Small Molecules.

Lyotropic liquid crystalline (LLC) phases of amino acid derived polyarylisocyanides were employed as chiral alignment media for the measurement of residual dipolar couplings (RDCs) of small chiral organic molecules. Anisotropic samples in CDCl3 displayed quadrupolar splittings of the deuterium signal in the range of several hundreds of Hertz. The LLC phases showed excellent orienting properties for a broad range of analytes bearing various functional groups. The precise extraction of RDCs in the range of up to ±40 Hertz from F2-coupled HSQC spectra was possible. Additionally, the chiral environment offers the opportunity for diastereomorphous interactions with the enantiomers of chiral analytes leading to two different sets of RDCs. This differential order effect was particularly pronounced with ketones and alcohols.

Proton/Deuterium Magnetic Resonance Imaging of Rodents at 9.4T Using Birdcage Coils

The purpose of the present study was to fabricate a volume coil for proton/deuterium magnetic resonance imaging (MRI) in rodents at 9.4 T. Two birdcage radiofrequency (RF) coils have been designed for proton/deuterium MRI: the rungs of two concentric birdcages were azimuthally interleaved with each other for better decoupling, and the two coils were tuned to 400.3 and 61.4 MHz for 1 H/2 H resonance at 9.4 T. Compared to a commercially available coil, the proposed 1 H/2 H RF coil provides reasonable transmission efficiency and imaging signal-to-noise ratio (SNR); the relationships among imaging parameters such as SNR, voxel size, and deuterium oxide concentrations have been quantitatively studied, and the linear correlation results together with the spectroscopic data in vivo indicate its feasibility in deuterium metabolic imaging (DMI) in vivo. Our study indicates that using the birdcage design for MRI signal excitation combined with surface coil array for signal reception can facilitate DMI investigations more effectively towards future pre-clinical and clinical applications. As a noninvasive method by measuring nonhydrogen nuclear deuterium signals to reflect metabolite information, DMI will feature prominently in future precision medicine through the whole process of diagnosis, treatment, and prognosis. © 2021 Bioelectromagnetics Society.

Feasibility of deuterium magnetic resonance spectroscopy of 3-O-Methylglucose at 7 Tesla

Deuterium Magnetic Resonance Spectroscopy (DMRS) is a non-invasive technique that allows the detection of deuterated compounds in vivo. DMRS has a large potential to analyze uptake, perfusion, washout or metabolism, since deuterium is a stable isotope and therefore does not decay during biologic processing of a deuterium labelled substance. Moreover, DMRS allows the distinction between different deuterated substances. In this work, we performed DMRS of deuterated 3-O-Methylglucose (OMG). OMG is a non-metabolizable glucose analog which is transported similar to D-glucose. DMRS of OMG was performed in phantom and in vivo measurements using a preclinical 7 Tesla MRI system. The chemical shift (3.51 ± 0.1 ppm) and relaxation times were determined. OMG was injected intravenously and spectra were acquired over a period of one hour to monitor the time evolution of the deuterium signal in tumor-bearing rats. The increase and washout of OMG could be observed. Three different exponential functions were compared in terms of how well they describe the OMG washout. A mono-exponential model with offset seems to describe the observed time course best with a time constant of 1910 ± 770 s and an offset of 2.5 ± 1.2 mmol/l (mean ± std, N = 3). Chemical shift imaging could be performed with a voxel size of 7.1 mm x 7.1 mm x 7.9 mm. The feasibility of DMRS with deuterium labelled OMG could be demonstrated. These data might serve as basis for future studies that aim to characterize glucose transport using DMRS.

NanoSIMS analysis of hydrogen and deuterium in metallic alloys: Artefacts and best practice

Hydrogen embrittlement can cause catastrophic failure of high strength alloys, yet determining localised hydrogen in the microstructure is analytically challenging. NanoSIMS is one of the few techniques that can map hydrogen and deuterium in metal samples at microstructurally relevant length scales. Therefore it is essential to understand the artefacts and determine the optimum methodology for its reliable detection. An experimental methodology/protocol for NanoSIMS analysis of deuterium (as a proxy for hydrogen) has been established uncovering unreported artefacts and a new approach is presented to minimise these artefacts in mapping hydrogen and deuterium in alloys. This method was used to map deuterium distributions in electrochemically charged austenitic stainless steel and precipitation hardened nickel-based alloys. Residual deuterium contamination was detected in the analysis chamber as a result of deuterium outgassing from the samples, and the impact of this deuterium contamination was assessed by a series of NanoSIMS experiments. A new analysis protocol was developed that involves mapping deuterium in the passive oxide layer thus mitigating beam damage effects that may prevent the detection of localised deuterium signals when the surface is highly deuterated.

LIBS study of ITER relevant tungsten–oxygen coatings exposed to deuterium plasma in Magnum-PSI

We discuss the applicability of laser induced breakdown spectroscopy (LIBS) for deuterium retention analysis in compact and porous tungsten-oxide (W-O) coatings. Deuterium loading was performed by exposing the coatings to deuterium plasma in Magnum-PSI linear plasma device.The deuterium signals obtained by ex-situ LIBS had sufficiently good signal-to-noise ratio for reliable separation of essentially broadened hydrogen and deuterium lines as well as for comparison of the lateral and depth distributions of deuterium in the coatings. Strong deuterium signal was obtained for the first laser shot which corresponded to the surface layer of the W-O coatings whereas deeper in the coating the signal decreased to noise level. In addition, the deuterium signal was highest in the central region of compact W-O coating. For both coatings, depth profiles of elements obtained by LIBS match with those recorded by secondary ion mass spectroscopy (SIMS) in the lateral direction along the sample surface. The results of LIBS and SIMS results were supported by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) data which showed that the exposure to deuterium plasma resulted in remarkable changes in the surface morphology along the sample surface. The study demonstrates the LIBS potential in deuterium retention measurements in plasma facing components.

Quantitative analysis of proton solubility in YSZ using SIMS

The solubilities of protons in 8YSZ single crystal and polycrystals at 600 °C were investigated using secondary ion mass spectrometry (SIMS). As a measure of proton solubility, deuteron solubility in YSZ was measured because of its lower background level in SIMS measurements. It became possible to quantitatively determine the solubility using a new analytical method proposed here, which includes a procedure to remove the small background signal included in the deuterium signal. The new method was employed for determining the solubilities in YSZ single crystal and polycrystals. Although the solubility in the single crystal was below the detection limit of SIMS (~1016 cm−3), the solubilities in the polycrystals were significantly larger than that in the single crystal. The solubility shows a proportional relationship with the grain boundary density, which strongly suggests that deuterons incorporate mainly into the grain boundaries in YSZ. The deuteron solubility per unit grain boundary area was determined to be 3.2 × 1013 cm−2.

Is Nickel Hydroxide Charging Only Skin-Deep?

The depth of charging in Ni(OH)2-coated electrodes treated with paraffin wax to remove porosity has been investigated using time-of-flight secondary-ion mass spectrometry after charging and discharging in deuterated solvent at pH 14. The proportion of deuterium uptake was found to be dependent on the number of charge/discharge cycles, showing that the measured deuterium signal was indeed dependent on the electrochemical redox activity of the sample. Sputter craters were characterized using atomic force microscopy to find the sputter rate. This then allowed the maximum depth of charging to be found to be approximately 20 nm. This confirmed a surface “skin” in which charging occurs with the rest of the bulk inactive.

Valine derived poly (acetylenes) as versatile chiral lyotropic liquid crystalline alignment media for RDC-based structure elucidations.

Anisotropic samples of lyotropic liquid crystalline (LLC) phases of valine derived polyaryl acetylenes were employed as chiral alignment media for the measurement of residual dipolar couplings (RDCs) of 12 small, chiral, organic molecules. The quadrupolar splitting of the deuterium signal of CDCl3 can be adjusted by temperature and concentration changes from 0 to 350 Hz. The LLC phases showed excellent orienting properties for all analytes bearing various functional groups. The precise extraction of RDCs in the range of up to ±30 Hz from F2-coupled HSQC spectra was possible. Additionally, the chiral environment led to diastereomorphous interactions with the enantiomers of chiral analytes leading to two different sets of RDCs. This differential order effect was particularly pronounced with H-bond donors like alcohols and 2° amines.

First GD-OES results on various deuterium ion fluences implanted in tungsten

Glow discharge optical emission spectroscopy (GD-OES) was used to investigate the deep depth profile of deuterium in tungsten exposed to deuterium ions at various fluences. Deuterium was found to continue to decrease in intensity at depths 10–20 µm, even at the lowest fluences, well beyond the probing depths of conventional deuterium measurement techniques. The detection sensitivity was sufficient to allow for definite separation in spectra for all fluences used in the present experiments. The integrated deuterium signal from GD-OES measurement was compared with total deuterium content for samples implanted with deuterium with fluences ranging from 1.0 × 1020 D/m2 to 1.0 × 1022 D/m2. The result showed a clear trend, where the intensity scales with implanted deuterium fluence to the 0.25 power. These results motivate further experiments and calibration of the system for future absolute retention measurements using GD-OES.

Deuterium permeation through metals under γ-ray irradiation

Tritium handling in fusion reactors is important for economical fuel cycles and radiological safety; however, the extremely limited number of studies on tritium permeation through structural materials under irradiation conditions has been reported. In this study, γ-ray irradiation effect on tritium permeation has been investigated using three kinds of metals with different permeation properties including palladium, platinum, and austenitic stainless steel. An increase of deuterium signal on the quadrupole mass spectrometer during irradiation consisted of an increase of deuterium permeation flux and an electrical noise, and both were separately detected. The increase rate of permeation flux for all materials became lower as the test temperature increased. Dose rate dependence of the increase rate was confirmed. Oxidation of the austenitic stainless steel indicates a decrease of not only the deuterium permeation flux but also the irradiation effect.

Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

Abstract. Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d–6. Therefore, we hypothesize that the causes of the DFO2006–AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d–6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δDice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, −230 years (minimum) at MIS 7a and +60 to +126 years on average.

Atom probe tomography observation of hydrogen in high-Mn steel and silver charged via an electrolytic route

Abstract We investigate an electrolytic route for hydrogen charging of metals and its detection in Atom Probe Tomography (APT) experiments. We charge an austenitic Fe-30Mn-8Al-1.2C (wt.%) weight reduced high-Mn steel and subsequently demonstrate the detectability of deuterium in an APT experiment. The experiment is repeated with a deposited Ag film upon an APT tip of a high-Mn steel. It is shown that a detectable deuterium signal can be seen in the high-Mn steel, and a D:H ratio of 0.84 can be reached in Ag films. Additionally, it was found that the predicted time constraint on detectability of D in APT was found to be lower than predicted by bulk diffusion for the high-Mn steel.

Signal Processing for the Measurement of the Deuterium/Hydrogen Ratio in the Local Interstellar Medium

We report on a comprehensive signal processing procedure for very low signal levels for the measurement of neutral deuterium in the local interstellar medium from a spacecraft in Earth orbit. The deuterium measurements were performed with the IBEX-Lo camera on NASA’s Interstellar Boundary Explorer (IBEX) satellite. Our analysis technique for these data consists of creating a mass relation in three-dimensional time of flight space to accurately determine the position of the predicted D events, to precisely model the tail of the H events in the region where the H tail events are near the expected D events, and then to separate the H tail from the observations to extract the very faint D signal. This interstellar D signal, which is expected to be a few counts per year, is extracted from a strong terrestrial background signal, consisting of sputter products from the sensor’s conversion surface. As reference we accurately measure the terrestrial D/H ratio in these sputtered products and then discriminate this terrestrial background source. During the three years of the mission time when the deuterium signal was visible to IBEX, the observation geometry and orbit allowed for a total observation time of 115.3 days. Because of the spinning of the spacecraft and the stepping through eight energy channels the actual observing time of the interstellar wind was only 1.44 days. With the optimised data analysis we found three counts that could be attributed to interstellar deuterium. These results update our earlier work.

Modelling stable water isotopes in monsoon precipitation during the previous interglacial

Changes in the tropical hydrological cycle have been recorded world wide in speleothem records dating back more than 200,000 years for some areas. Numerous empirical and modelling studies have demonstrated a strong link between the intensity of the northern hemisphere monsoon and the precessional insolation cycle (∼23 ka (thousand years)). Here we present simulations of the climate conditions of the previous interglacial, the Eemian (115–130 ka BP), using a general circulation model. We focus on changes in the tropical hydrological cycle and in the monsoon in particular. The model is equipped with a module for computing the water isotopic composition of all water reservoirs represented by the model. Our analysis of the simulated water isotope signals indicates that this key palaeo-proxy, i.e. the 18O or Deuterium signal in precipitation, is controlled by varying factors in different tropical areas: The main control on 18O for the Indian summer monsoon is the local precipitation amount, in accordance with the traditional interpretation, while the main control of 18O for East Asia is downwind depletion of 18O in vapour along the transport path. Over Africa the model simulates a strong gradient in the 18O anomalies during the Eemian climatic optimum, with depleted values in the east and relatively enriched 18O content in the west. This pattern is the result of a combination of the local “amount effect” and an anomalous zonal moisture transport. The influence of the SSTs anomalies on the placement of the Intertropical Convergence Zone (ITCZ) is found to be of major importance for the precipitation amount in the coastal regions of tropical South America. For the western part of South America a decrease in precipitation is seen for the Eemian climatic optimum, while an increase is seen for the eastern part. Our results underline the importance of reviewing the mechanisms causing isotopic changes in proxy records and further investigating the causes for past shifts in the ITCZ.

Polyacetylenes as a new alignment medium to measure residual dipolar couplings for chiral organic molecules

Liquid crystal solutions derived from polyacetylenes are used as an alignment medium to measure residual dipolar couplings (RDCs) in NMR for chiral organic molecules such as strychnine or menthol. The advantages of this new medium are the straightforward and easy synthesis and a reasonable small quadrupolar splitting of the deuterium signal indicating the desired alignment behavior. The obtained RDCs can be back calculated and used for structure verification. The spectra of the two enantiomers of menthol reveal different RDCs.

Stable isotope ratios in winter-grown feathers of Great Reed Warblers Acrocephalus arundinaceus, Clamorous Reed Warblers A. stentoreus and their hybrids in a sympatric breeding population in Kazakhstan

Analyses of the stable isotope composition of feathers can provide significant insight into the spatial structure of bird migration. We collected feathers from Great Reed Warblers Acrocephalus arundinaceus, Clamorous Reed Warblers A. stentoreus and a small sample of their hybrids in a sympatric breeding population in Kazakhstan to assess natural variation in stable isotope signatures and delineate wintering sites. The Great Reed Warbler is a long-distance migrant that overwinters in sub-Saharan Africa, whereas the Clamorous Reed Warbler performs a short-distance migration to the Indian sub-continent. Carbon (δ13C), nitrogen (δ15N) and deuterium (δD) isotope signatures were obtained from winter-grown feathers of adult birds. There were highly significant differences in δD and less significant differences in δ13C between Great and Clamorous Reed Warblers. Thus, our results show that the stable isotope technique, and in particular the deuterium (δD) signal, resolves continental variation in winter distribution between these closely related Acrocephalus species with sympatric natal origin. The isotope signatures of hybrid Great × Clamorous Reed Warblers clustered with those of the Great Reed Warblers. Hence, a parsimonious suggestion is that the hybrids undergo moult in Afrotropical wintering grounds, as do the Great Reed Warblers. The observed δD values fell within the range of expected values based on available precipitation data collected at precipitation stations across the wintering continents of each species. However, the power to predict the winter origin of birds in our study system using these data was weak as the expected values ranged widely at this broad continental scale.

Enantiomeric analysis using natural abundance deuterium 3D NMR spectroscopy in polypeptide chiral oriented media

The use of natural abundance deuterium (NAD) three-dimensional (3D) NMR experiment in chiral liquid crystals (CLC) is reported and discussed. This homonuclear autocorrelation 3D experiment allows assigning deuterium signals of weakly aligned molecules at natural isotopic abundance. It provides an efficient strategy for identifying the spectral enantio-discriminations on NAD spectra. We demonstrate that NAD 3D NMR is feasible within reasonable experimental times (14h) using the 3D Quadrupole Double-Quantum NMR sequence [O. Lafon, P. Lesot, Chem. Phys. Lett. 404 (2005) 90] and a 14.1T NMR spectrometer equipped with a selective 5mm deuterium NMR cryoprobe. The analytical potentialities of this technique are illustrated in the case of (±)-but-2-yn-1-ol dissolved in poly-γ-benzyl-l-glutamate/CHCl3 mesophase.

Methoxyl groups of plant pectin as a precursor of atmospheric methane: evidence from deuterium labelling studies

* The observation that plants produce methane (CH4) under aerobic conditions has caused considerable controversy among the scientific community and the general public. It led to much discussion and debate not only about its contribution to the global CH4 budget but also about the authenticity of the observation itself. Previous results suggested that methoxyl groups of the abundant plant structural component pectin might play a key role in the in situ formation process of CH4. Here, this effect is investigated using an isotope labelling study. * Polysaccharides, pectin and polygalacturonic acid, with varying degrees of trideuterium-labelled methyl groups in the methoxyl moieties, were investigated for CH4 formation under UV irradiation and heating. * A strong deuterium signal in the emitted CH4 was observed from these labelled polysaccharides. * Results clearly demonstrate that ester methyl groups of pectin can serve as a precursor of CH4, supporting the idea of a novel chemical route of CH4 formation in plants under oxic environmental conditions.

Cores and pH-dependent Dynamics of Ferredoxin-NADP+ Reductase Revealed by Hydrogen/Deuterium Exchange

NMR-detected hydrogen/deuterium (H/D) exchange of amide protons is a powerful way for investigating the residue-based conformational stability and dynamics of proteins in solution. Maize ferredoxin-NADP(+) reductase (FNR) is a relatively large protein with 314 amino acid residues, consisting of flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide phosphate (NADP(+))-binding domains. To address the structural stability and dynamics of FNR, H/D exchange of amide protons was performed using heteronuclear NMR at pD(r) values 8.0 and 6.0, physiologically relevant conditions mimicking inside of chloroplasts. At both pD(r) values, the exchange rate varied widely depending on the residues. The profiles of protected residues revealed that the highly protected regions matched well with the hydrophobic cores suggested from the crystal structure, and that the NADP(+)-binding domain can be divided into two subdomains. The global stability of FNR obtained by H/D exchange with NMR was higher than that by chemical denaturation, indicating that H/D exchange is especially useful for analyzing the residue-based conformational stability of large proteins, for which global unfolding is mostly irreversible. Interestingly, more dynamic conformation of the C-terminal subdomain of the NADP(+)-binding domain at pD(r) 8.0, the daytime pH in chloroplasts, than at pD(r) 6.0 is likely to be involved in the increased binding of NADP(+) for elevating the activity of FNR. In light of photosynthesis, the present study provides the first structure-based relationship of dynamics with function for the FNR-type family in solution.