Nitrogen Ice Research Articles

Thickness of Pluto's Ice Shell from elastic deformation of the Sputnik Planitia forebulge: Response to infill load or vestige of impact event?

Load on a planet's lithosphere can often form a well-defined flexural bulge, including a permanent (or long-lasting) forebulge, which preserves important information on the force of the load and properties of the lithosphere itself. On Pluto, aspects of the outer ice shell (i.e. the lithosphere) have become increasingly ascertainable, as recent work using data from the New Horizons space probe has revealed evidence of ongoing surface cryovolcanism and a subsurface water ocean. However, the precise thickness and elasticity of the ice shell has yet to be fully established. Sputnik Planitia, one of the largest surface features on Pluto, is an elliptical depression that may have formed during an impact event and subsequently infilled with nitrogen ice. It is characterized by a smooth, radially asymmetrical, forebulge which has been retained in places along the border of the depression. However, the proportion of influence on the formation of the forebulge between the impact load and the load induced by the infill remains unknown. Here, we report results from the analysis of the forebulge of Sputnik Planitia to explore the characteristics of the ice shell and the nitrogen infill. By utilizing multiple Converging Monte Carlo (CMC) simulations within the material and environmental parameters of Pluto, the best fit flexure surface was able to replicate the topography of the flexure (including the forebulge) from ten profiles. Results show an ice shell thickness ranging from 65 to 90 km, with an average of 78 km. The density of the ice shell is 50 kg/m3 less than the density of the subsurface water ocean. We demonstrate that if the formation of the forebulge occurs solely from the nitrogen ice infill load, the infill must reach >18 km of thickness. Furthermore, a southeast-northwest central load symmetry may have been produced by an impacting object with a southeast-northwest trajectory.

Research on the Structural Performance of Liquid Nitrogen Ice Plugs on Nuclear Power Pipes

Research on the Structural Performance of Liquid Nitrogen Ice Plugs on Nuclear Power Pipes

Constraints on the evolution of the Triton atmosphere from occultations: 1989–2022

Context. In about 2000, the south pole of Triton experienced an extreme summer solstice that occurs every ∼650 years, when the subsolar latitude reached about 50°S. Bracketing this epoch, a few occultations probed the Triton atmosphere in 1989, 1995, 1997, 2008, and 2017. A recent ground-based stellar occultation observed on 6 October 2022 provides a new measurement of the atmospheric pressure on Triton. This is presented here. Aims. The goal is to constrain the volatile transport models (VTMs) of the Triton atmosphere. The atmosphere is basically in vapor pressure equilibrium with the nitrogen ice at its surface. Methods. Fits to the occultation light curves yield the atmospheric pressure of Triton at the reference radius 1400 km, from which the surface pressure is deduced. Results. The fits provide a pressure p1400 = 1.211 ± 0.039 μbar at radius 1400 km (47 km altitude), from which a surface pressure of psurf = 14.54 ± 0.47 μbar is deduced (1σ error bars). To within the error bars, this is identical to the pressure derived from the previous occultation of 5 October 2017, p1400 = 1.18 ± 0.03 μbar and psurf = 14.1 ± 0.4 μbar, respectively. Based on recent models of the volatile cycles of Triton, the overall evolution of the surface pressure over the last 30 years is consistent with N2 condensation taking place in the northern hemisphere. However, models typically predict a steady decrease in the surface pressure for the period 2005-2060, which is not confirmed by this observation. Complex surface-atmosphere interactions, such as ice albedo runaway and formation of local N2 frosts in the equatorial regions of Triton, could explain the relatively constant pressure between 2017 and 2022.

The role of Pluto's ocean's salinity in supporting nitrogen ice loads within the Sputnik Planitia basin

The existence of a subsurface water ocean on Pluto has been inferred on numerous grounds. The characteristics of such an ocean are vital inputs for various types of models that are carried out to illuminate the interior structure and evolution of Pluto, especially in light of the complementary relationship between the dimensions of the ocean and an outer water ice shell. In particular, models of loading of the Sputnik Planitia (SP) impact basin by nitrogen ice infill require knowledge of ocean properties such as density, and previous studies did not consider the potential densification of Pluto's ocean from salinity. Here we carry out analytic and Finite Element Method (FEM) modeling of loading deformations and stresses in an ice shell lithosphere, to determine the conditions, including ocean density, that best account for the observed distributions of tectonic features around the SP basin. Our results, while generally consistent with those of previous studies, provide more complete constraints on the initial basin depth (no deeper than 6 km, with most likely values in the 3–4 km range). Further, we find that increasing density (salinity) generally increases disagreement between model tectonic predictions and observations, and therefore we infer modest salinity-based densification of Pluto's ocean (ρocean < 1100 kg/m3) relative to values seen or inferred on other worlds.

Properties of water, carbon dioxide, and nitrogen ices in planetary surface environments

Numerous investigations have measured and identified properties of water and exotic ices. These properties are measured at various pressures and temperatures; however, these disparate studies are sometimes difficult to find, confusing, or even contradictory. Here, we amass and present a catalogue of some temperature dependent equations on ice density, latent heat of fusion, constant values for latent heat of sublimation, specific heat capacity at constant pressure, thermal conductivity, and Arrhenius flow law parameters for water ice, carbon dioxide ice, and solid nitrogen. The equations are either directly cited from the sources or are fitted from data in past publications.

E–I characteristics and critical currents of small Bi-2223/Ag coil thermally stabilized by solid and liquid nitrogen compared to water ice

A small-sized coil of helically wound Bi-2223/Ag tape was measured in liquid/solid nitrogen (LN2/SN2), and also in water (H2O) ice at external fields of 0–8 T and in a temperature range of 10–77 K. This work is especially focused on the coil stability for current amplitudes above the critical current criterion of 1 µV cm−1. While the E–I characteristics measured under the critical current criterion did not show any substantial variances at these different cooling conditions, significant differences were observed above the critical current magnitude, mainly upon cooling by solid nitrogen and water ice. The results confirm improved thermal stability for the coil measured in sub-cooled water ice compared to solid nitrogen. Consequently, cooling by water ice could be interesting for future applications of high-temperature superconducting coils.

The formation and evolution of Pluto's Sputnik basin prior to nitrogen ice fill

We simulate Sputnik Planitia (SP), Pluto's largest impact basin, from formation through cooling and relaxation prior to loading of the basin with N2 ice. To assess potential conditions for Pluto's interior that permit the formation of an SP-like basin in terms of depth and diameter, we consider impacts into targets that possess a subsurface ocean with variable ice shell thicknesses and thermal structures. We use a shock physics code to model excavation and transient crater collapse. Then, using the final temperature and density structure from the shock physics code as initial conditions, we simulate the subsequent cooling and viscoelastic relaxation of basin topography using a finite element model (FEM). We show that a thin ice shell (on the order of 100 km) overlying a thick ocean (on the order of 228 km) produces an SP-like basin in terms of diameter and pre-N2 depth. A basin formed in a much thicker ice shell (200 km) overlying a thin ocean (128 km) can reproduce SP if the ice shell is relatively warm and possesses a strong rheology. Our results suggest that SP was not a mascon basin prior to subsequent loading by N2 ice, but rather close to isostatically compensated. We find that SP could have developed into a mascon basin following N2 loading if the ice shell is thin, conductive and possesses a lithosphere capable of supporting the N2 load.

RNAlater facilitates remote sampling of aquaculture Atlantic salmon liver for proteomic analysis

AbstractDuring sample collection and transport, high‐quality nucleic acids, proteins and metabolites are preserved by snap‐freezing (SF) samples in liquid nitrogen or dry ice. In remote aquaculture facilities, SF materials are not readily available and can be hazardous during sampling and transport. RNAlater is widely used in aquaculture for transcriptome studies, but its effect on proteome stability needs further investigation. Here, we used proteomics to demonstrate that RNAlater (RL) preserved liver samples similarly to SF samples. Additionally, 69 proteins (∼2.6%) comprising ribosomal proteins, transcription cofactors, translational factors, proteases and transmembrane proteins were significantly less abundant in the RL proteome. These proteins are expected to be denatured by RL and are cellular components of ribosomes and nucleosomes and involved in proteolysis, transcription and translation. We also demonstrated that RL did not influence abundance of important proteins originally identified in liver samples from salmon reared under heat stress, hypoxia or specific feeding regimes. These findings suggest that preserving samples in RL is suitable for proteomics and offer a safer and effective preservation technology for use in remote aquaculture locations.

Transport measurement of MgB2 wire under the sub-cooled water ice compared to other cooling conditions

The standard DC transport measurements of MgB2 composite conductors were done in vacuum, low-pressure helium gas, sub-cooled solid nitrogen and water ice. The effect of these coolants on electro-thermal behaviour was studied at self-field and temperature range from 32 K to 36.5 K. The obtained results show that even small volume of Helium gas enhances the sample thermal stability during the I–V measurement in comparison to those obtained in vacuum. The cooling by solid nitrogen improves the sample stability in contrast to helium gas. The measurements performed inn water ice exhibits an excellent and stable behavior of superconducting wire carrying high transport current below and above the quench as well. Consequently, water ice shows simple, safe, and promising He-free mode of cooling for future superconducting systems.

Tectonism and Enhanced Cryovolcanic Potential Around a Loaded Sputnik Planitia Basin, Pluto

AbstractSputnik Planitia on Pluto is a vast plain consisting of a nitrogen ice deposit filling a broad topographic depression, likely an impact basin. The basin displays a broad, raised rim and is surrounded by numerous extensional fault systems, each with characteristic orientations with respect to the basin center. The nitrogen ice exerts a large mechanical load on the water ice outer shell crust (here also containing the lithosphere). We calculate models of stress and deformation related to this load, varying dimensional, mechanical, and boundary condition properties of the load and Pluto's lithosphere, in order to constrain the conditions that led to the formation of the observed tectonic and topographic signals. We demonstrate that the tectonic configuration is diagnostic of a particular set of conditions that hold for the Sputnik basin and Pluto, including moderate elastic lithosphere thickness (40–75 km, with higher values favored if initial basin topography is compensated) and a basin that was pan‐shaped and shallow (∼3 km) at the time of nitrogen deposition initiation. These tectonic systems show the contributions of both flexural (bending) and membrane (stretching) responses of the lithosphere, with the latter dominating in proportion to the importance of spherical geometry effects. Rim topography may also show an influence of primordial annular trans‐basin ice shell thickening from the impact process. Analysis of stress‐driven cryomagma transport shows that loading stresses can facilitate ascent of cryomagmas in annular zones around the basin, the locations of which overlap the observed distances from Sputnik of several candidate cryovolcanic sites.

Identification of a prismatic P3N3 molecule formed from electron irradiated phosphine-nitrogen ices

Polyhedral nitrogen containing molecules such as prismatic P3N3 - a hitherto elusive isovalent species of prismane (C6H6) - have attracted particular attention from the theoretical, physical, and synthetic chemistry communities. Here we report on the preparation of prismatic P3N3 [1,2,3-triaza-4,5,6-triphosphatetracyclo[2.2.0.02,6.03,5]hexane] by exposing phosphine (PH3) and nitrogen (N2) ice mixtures to energetic electrons. Prismatic P3N3 was detected in the gas phase and discriminated from its isomers utilizing isomer selective, tunable soft photoionization reflectron time-of-flight mass spectrometry during sublimation of the ices along with an isomer-selective photochemical processing converting prismatic P3N3 to 1,2,4-triaza-3,5,6-triphosphabicyclo[2.2.0]hexa-2,5-diene (P3N3). In prismatic P3N3, the P–P, P–N, and N–N bonds are lengthened compared to those in, e.g., diphosphine (P2H4), di-anthracene stabilized phosphorus mononitride (PN), and hydrazine (N2H4), by typically 0.03–0.10 Å. These findings advance our fundamental understanding of the chemical bonding of poly-nitrogen and poly-phosphorus systems and reveal a versatile pathway to produce exotic, ring-strained cage molecules.

‘Oumuamua May Be an Icy Fragment of a Pluto-Like Exoplanet

Researchers favor nitrogen ice as the most likely material for the mysterious interstellar object’s composition.

Assessment of the Dynamics of Temperature Changes in the Knee Joint Area in Response to Selected Cooling Agents in Thermographic Tests.

Although local cryotherapy (LC) is performed with various cooling agents (CAg) such as ice, water, and gasses, in clinical practice, it is mostly performed with cooling gasses. Presently, LC with cooling gasses is very popular but the inference about the thermal (stimulus) effect on the tissues is mainly based on research carried out using ice packs. The proposed objective of the study was to evaluate the dynamics of temperature changes in the knee joint area in response to a 3-min exposure to liquid nitrogen vapors (LNVs), cold air (CA) and ice bag (IB). The study group included 23 healthy volunteers with an average age of 26.67 ± 4.56. The exposed (ROIE) and contralateral (ROINE) areas of the knee joint after exposure to CAg were observed. Immediately after 3 min of LC, the ROIE temperature dropped by 10.11 ± 0.91 °C after LNV, 7.59 ± 0.14 °C after IB and 6.76 ± 1.3 °C after CA. Significant tissue cooling was maintained up to 15 min after LNV (p < 0.01), 10 min after IB (p < 0.05) and 5 min after CA (p < 0.05). LC causes significant temperature changes both in ROIE and ROINE. The greatest cooling potential was demonstrated for LNV and the lowest for CA.

Can Triton's Internal Heat Be Inferred From Its Ice Cap?

AbstractNeptune's moon Triton is among the Solar System's most geologically active bodies, allowing for study of its internal dynamics through surface features. Here, I consider whether the unusually great extent of its nitrogen ice cap constrains its geothermal heat. I find that viscous spreading alone can result in a hemispheric‐scale ice sheet, which only yields a loose constraint on geothermal heat flow ≥2 mW/m2. However, if the ice cap's great extent is additionally aided by basal melting, heat flow would be constrained between 5 and 18 mW/m2. This latter range would require a significant heat source beyond radiogenic heating and be sufficient to drive vigorous geological activity, providing an explanation for the moon's youthful surface and strengthening the case for Triton as an ocean world. High‐resolution images and topographic data from a new spacecraft mission at Triton would allow for testing of these possibilities and constraints on the moon's internal heat.

Validation of a Novel, Flash-Freezing Method: Aluminum Platform.

Stored biological materials should have minimal pre‐analytical variations in order to provide researchers with high‐quality samples that will give reliable and reproducible results, yet methods of storage should be easy to implement, with minimal cost and health hazard. Frozen tissue samples are a valuable biological resource. Here we compare different methods, such as liquid nitrogen (LN) or dry ice (DI), to a cheap and safe alternative using an aluminum platform (AP). Murine fresh liver and pancreas tissues were used with varying lengths of warm ischemia time. Quality assessment was based on histological evaluation, DNA and RNA extraction and quantification, and RNA degradation analysis, as well preservation of antigens for immunofluorescence, in a blinded manner. Both in superficial and deep tissue sections, based on histological assessment, AP is superior to DI, or as good as LN techniques in terms of presence of ice crystals, cutting artifacts, and overall quality/structural preservation. DNA and RNA were successfully extracted in reasonable quantities from all freezing techniques, but RNA degradation was seen for pancreas samples across all techniques. Immunofluorescence with cytokeratin8 (CK‐8), alpha smooth muscle actin (αSMA), CD3, and B220 shows equally good outcomes for AP and LN, which are better than DI. The aluminum platform is a cheap, yet reliable method to freeze samples, rapidly preserving histological, antigenic, and DNA/RNA quality. Wider testing is required across different sample types. © 2020 The Authors. Basic Protocol: Flash‐freezing fresh tissue with aluminum platform Alternate Protocol 1: Freezing fresh tissue with liquid nitrogen Alternate Protocol 2: Freezing fresh tissue with dry ice

Hypothermic storage of sturgeon sperm: methodology and ongoing history

Hypothermic storage of sperm in a liquid state without freezing, without the use of either liquid nitrogen or dry ice as well as special cryological equipment is an interesting and attractive research line in reproductive biology in terms of practical application. Historically, hypothermia is the very first approach to the preservation of genetic material, but, despite this, the methods of hypothermic storage of gametes and embryos have not received proper development and application in animal husbandry, giving way to cryopreservation. One of the main reasons for this is the high species-specific resistance to cold storage. The technologies for hypothermic storage of sperm existing today and recommended for use in fish farming and in sturgeon breeding in particular are still not effective enough and require further improvement. This short review outlines the history of the development of technologies for the hypothermic storage of sturgeon sperm, considers a number of methodological approaches, concepts and ideas behind these developments. The male reproductive system in sturgeons, the structure and physiology of spermatozoa have a number of features that distance them from teleost fishes, but partly relate to amphibians and higher vertebrates. This made it possible to apply to sturgeons some successful approaches and achievements in the development of methods for hypothermic storage of mammalian (mouse and human) sperm. Thus, the most effective and possibly promising approach is partial or complete replacement of seminal plasma with salt-free isotonic solutions based on sugars (oligosaccharides) and albumin. The purpose of this review is to draw the attention of fish farmers and researchers to developments and advances in hypothermic sperm storage.

Downhill sledding at 40 AU: Mobilizing Pluto's chaotic mountain blocks

We present a force-balance analysis of the mobilization and emplacement of the large mountain block chains observed on the western rim of Pluto's Sputnik Planitia basin. These mountain blocks are likely disrupted pieces of Pluto's water ice crust that are grounded in the nitrogen ice that fills the basin. After fracturing from the basin rim, they could have slid downslope into the basin under their own weight on timescales as short as hundreds to thousands of years, collecting into the observed ranges where the basin slope shallows below a critical value. This movement would require a lubricating fluid, most likely nitrogen, to be present at the base of the blocks.Traction from flowing nitrogen glaciers could have initiated or aided transport for blocks that are small enough to be at least halfway immersed by the nitrogen. Lateral convective forces within the nitrogen ice sheet did not play a significant role in the mobilization of all but the smallest of the observed blocks that likely float buoyantly in the nitrogen ice.If the blocks did emplace by basal sliding, the requirement that liquid nitrogen be present to provide lubrication provides a key to Pluto's past climate history. This work adds to the body of evidence that erosional features and other surface modification could have been driven by the surface or near-surface flow of liquid nitrogen resulting from global climate change on Pluto.

Biopsie musculaire

Muscle biopsy is an invasive procedure consisting in the removal of skeletal muscle tissue, sometimes of the fascia, for histological and sometimes biochemical and molecular examinations. The indications are suspicions of myopathy, vasculitis and fasciitis. The diagnosis of muscle tumors is not cover in this review. If the procedure is relatively simple, the diagnostic efficient depends on the quality of the indication, the choice of muscle, the tissue preparation technique and the pathological analysis guided by clinical and paraclinical data. These elements require peculiar clinical, technical and histopathological expertises. For these reasons, muscle biopsy must be carried out in an expert center in this field. Open muscle biopsy is the most common technique in France. Bergström needle biopsies and conchotome are sometimes used. The preparation of the sample, after the biopsy and before its pathological analysis, involves the freezing of a fragment in isopenthane, the inclusion of a fragment in paraffin and the inclusion of a fragment in glutaraldehyde. Pathological examination includes the study of standard stains, histoenzymology, immunostaining and sometimes electron microscopy. Sample preparation for biochemistry and molecular biology studies requires its direct freezing in nitrogen or dry ice. The collection of an informed and signed consent by the patient is necessary for the realization of genetic analyzes and for the conservation of the remaining tissue in a center of biological resource approved by the National Commission of computing and freedoms (CNIL). Some of these techniques are systematic and others are guided by clinical suspicion.

Pluto's Beating Heart Regulates the Atmospheric Circulation: Results From High‐Resolution and Multiyear Numerical Climate Simulations

AbstractPluto's atmosphere is mainly nitrogen and is in solid‐gas equilibrium with the surface nitrogen ice. As a result, the global nitrogen ice distribution and the induced nitrogen condensation‐sublimation flows strongly control the atmospheric circulation. It is therefore essential for Global Climate Models to accurately account for the global nitrogen ice distribution in order to realistically simulate Pluto's atmosphere. Here we present a set of new numerical simulations of Pluto's atmosphere in 2015 performed with a Global Climate Model using a 50‐km horizontal resolution (3.75° 2.5°) and taking into account the latest topography and ice distribution data, as observed by the New Horizons spacecraft. In order to analyze the seasonal evolution of Pluto's atmosphere dynamics, we also performed simulations at coarser resolution (11.25° 7.5°) but covering three Pluto years. The model predicts a near‐surface western boundary current inside the Sputnik Planitia basin in 2015, which is consistent with the dark wind streaks observed in this region. We find that this atmospheric current could explain the differences in ice composition and color observed in the northwestern regions of Sputnik Planitia, by significantly impacting the nitrogen ice sublimation rate in these regions through processes possibly involving conductive heat flux from the atmosphere, transport of dark materials by the winds, and surface albedo positive feedbacks. In addition, we find that this current controls Pluto's general atmospheric circulation, which is dominated by a retrorotation, independently of the nitrogen ice distribution outside Sputnik Planitia. This exotic circulation regime could explain many of the geological features and longitudinal asymmetries in ice distribution observed all over Pluto's surface.

Distribution and energy balance of Pluto’s nitrogen ice, as seen by New Horizons in 2015

Pluto’s surface is geologically complex because of volatile ices that are mobile on seasonal and longer time scales. Here we analyzed New Horizons LEISA spectral data to globally map the nitrogen ice, including nitrogen with methane diluted in it. Our goal was to learn about the seasonal processes influencing ice redistribution, to calculate the globally averaged energy balance, and to place a lower limit on Pluto’s N2 inventory. We present the average latitudinal distribution of nitrogen and investigate the relationship between its distribution and topography on Pluto by using maps that include the shifted bands of methane in solid solution with nitrogen (which are much stronger than the 2.15-μm nitrogen band) to more completely map the distribution of the nitrogen ice. We find that the global average bolometric albedo is 0.83±0.11, similar to that inferred for Triton, and that a significant fraction of Pluto’s N2 is stored in Sputnik Planitia. We also used the encounter-hemisphere distribution of nitrogen ice to infer the latitudinal distribution of nitrogen over the rest of Pluto, allowing us to calculate the global energy balance. Under the assumption that Pluto’s nitrogen-dominated 11.5μbar atmosphere is in vapor pressure equilibrium with the nitrogen ice, the ice temperature is 36.93±0.10 K, as measured by New Horizons’ REX instrument. Combined with our global energy balance calculation, this implies that the average bolometric emissivity of Pluto’s nitrogen ice is probably in the range 0.47–0.72. This is consistent with the low emissivities estimated for Triton based on Voyager results, and may have implications for Pluto’s atmospheric seasonal variations, as discussed below. The global pattern of volatile transport at the time of the encounter was from north to south, and the transition between condensation and sublimation within Sputnik Planitia is correlated with changes in the grain size and CH4 concentration derived from the spectral maps. The low emissivity of Pluto’s N2 ice suggests that Pluto’s atmosphere may undergo an extended period of constant pressure even as Pluto recedes from the Sun in its orbit.