12 research outputs found
Generating and sustaining long-lived spin states in 15N,15N′-azobenzene
Long-Lived spin States (LLSs) hold a great promise for sustaining non-thermal spin order and investigating various slow processes by Nuclear Magnetic Resonance (NMR) spectroscopy. Of special interest for such application are molecules containing nearly equivalent magnetic nuclei, which possess LLSs even at high magnetic fields. In this work, we report an LLS in trans-15N,15N′-azobenzene. The singlet state of the 15N spin pair exhibits a long-lived character. We solve the challenging problem of generating and detecting this LLS and further increase the LLS population by converting the much higher magnetization of protons into the 15N singlet spin order. As far as the longevity of this spin order is concerned, various schemes have been tested for sustaining the LLS. Lifetimes of 17 minutes have been achieved at 16.4 T, a value about 250 times longer than the longitudinal relaxation time of 15N in this magnetic field. We believe that such extended relaxation times, along with the photochromic properties of azobenzene, which changes conformation upon light irradiation and can be hyperpolarized by using parahydrogen, are promising for designing new experiments with photo-switchable long-lived hyperpolarization
The effect of agro-reclamation techniques on water-physical characteristics of light chestnut heavy loamy soil during rice cultivation against the background of sprinkling under the conditions of the Lower Volga region
Purpose: scientific substantiation of the use of agro-reclamation tillage practices of light chestnut heavy loamy soils in rice cultivation with periodic irrigation by sprinkling.
Materials and methods. The research was conducted at the experimental site of the All-Russian Research Institute of Irrigated Agriculture in 2022–2023 with Stalingrad 1 rice crops in a two-factor experiment: factor A (soil water regime) – two options and factor B (tillage) – three options. Generally accepted methods of laying and conducting field research were used.
Results. Immediately after rice sowing, the soil density in the layer of 0.0–0.6 m, varied in the range of 1.19–1.41 t/cubic m depending on the tillage practice. The minimum value of soil density in the layer of 0.0–0.6 m was formed in the A2B3 variant and amounted to 1.23 t/cubic m. The maximum soil compaction in this layer of 1.34 t/cubic m was observed in variant A1B1. During the period of full ripeness of the grain, soil compaction occurred in all tillage options. Its minimum compaction (1.34 t/cubic m), compared with the control (winter plowing), was noted with a combination of winter plowing and spring deep loosening. The minimum values of the water consumption coefficient and irrigation water loss were obtained in the A2B3 variant, and their numerical values were 851.7 and 703.6 cubic m/t, respectively.
Conclusions. It was found that winter plowing to a depth of 0.25–0.27 m in combination with spring deep loosening to a depth of 0.40 m, in comparison with traditional winter plowing in one step, provides a decrease in soil density in a layer of 0.0–0.4 m by 0.10 (after sowing) and 0.12 t/cubic m (during the period of full ripeness of grain), which contributes to the yield increase to 6.95 t/ha and a reduction in irrigation water loss by 112.4 cubic m for the formation of 1 ton of grain
No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations
The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere, which-given methane's lifetime of several centuries-predicts an even, well mixed distribution of methane. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally
Martian dust storm impact on atmospheric H<sub>2</sub>O and D/H observed by ExoMars Trace Gas Orbiter
Global dust storms on Mars are rare but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere, primarily owing to solar heating of the dust. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes, as well as a decrease in the water column at low latitudes. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere
Integral methods of measuring the population life quality in local communities of the region
The presented article discusses the method of constructing an integral indicator of measuring the life quality. An important problem in assessing the life quality of the population is the complex nature of this concept, covering a variety of quantitative and qualitative characteristics. Currently, in the absence of the possibility of conducting scientific research on a wide range of indicators at once, selective methods are used using a small number of indicators for assessing the life quality of the population. The authors propose to use a three-stage procedure for constructing an integral indicator based on the calculation of primary indicators, the procedure for their normalization and the construction of the final integral indicator for assessing the life quality of the population. Such a technique opens up wide opportunities for further scientific regional research, since it allows conducting research in the context of local territories of the region, as well as on the entire region scale
Algorithmic cooling of nuclear spins using long-lived singlet order
Algorithmic cooling methods manipulate an open quantum system in order to lower its temperature below that of the environment. We achieve significant cooling of an ensemble of nuclear spin-pair systems by exploiting the long-lived nuclear singlet state, which is an antisymmetric quantum superposition of the "up" and "down" Zeeman states. The effect is demonstrated by nuclear magnetic resonance (NMR) experiments on a molecular system containing a coupled pair of near-equivalent 13C nuclei. The populations of the system are subjected to a repeating sequence of cyclic permutations separated by relaxation intervals. The long-lived nuclear singlet order is pumped well beyond the unitary limit. The pumped singlet order is converted into nuclear magnetization which is enhanced by 21% relative to its thermal equilibrium value
Fast destruction of singlet order in NMR experiments
Some nuclear spin systems support long-lived states, which display greatly extended relaxation times relative to the relaxation time of nuclear spin magnetization. In spin-1/2 pairs, such a long-lived state is given by singlet order, representing the difference of the population of the nuclear singlet state and the mean population of the three triplets. In many cases, the experiments with long-lived singlet order are very time-consuming because of the need to wait for singlet order decay before the experiment can be repeated; otherwise, spin order remaining from a previous measurement may lead to experimental artifacts. Here, we propose techniques for fast and efficient singlet order destruction. These methods exploit coherent singlet-triplet conversion; in some cases, multiple conversion steps are introduced. We demonstrate that singlet order destruction enables a dramatic reduction of the waiting time between consecutive experiments and suggest to use this approach in singlet-state Nuclear Magnetic Resonance (NMR) experiments with nearly equivalent spins.<br/
Fused 1,2-Diboraoxazoles Based on closo-Decaborate Anion–Novel Members of Diboroheterocycle Class
The novel members of the 1,2-diboraoxazoles family have been obtained. In the present work, we have carried out the intramolecular ring-closure reaction of borylated iminols of general type [B10H9N=C(OH)R]− (R = Me, Et, nPr, iPr, tBu, Ph, 4-Cl-Ph). This process is conducted in mild conditions with 83–87% yields. The solid-state structures of two salts of 1,2-diboraoxazoles were additionally investigated by X-ray crystallography. In addition, the phenomena of bonding interactions in the 1,2-diboraoxazole cycles have been theoretically studied by the Quantum Theory of Atoms in Molecules analysis. Several local and integral topological properties of the electron density involved in these interactions have been computed