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• Thermochemical methods allowed the study of two arylguanidines. • Combustion calorimetry was used to obtain formation enthalpies of arylguanidines. • Phase transitions were studied with DSC, and thermogravimetry. • The energetic-structural relationships for arylguanidines are presented. In the present work some thermochemical properties of 1,3-diphenylguanidine and 1,3-di- o -tolylguanidine were determined experimentally. To achieve this goal, differential scanning calorimetry was used to obtain purities, temperatures of fusion, enthalpies of fusion, entropies of fusion and heat capacities of the crystal phase as a function of temperature. Using thermogravimetry, the loss rate mass was measured for the crystal phase, and by applying the Langmuir equation the vapor pressure was estimated as a function of temperature, the enthalpy of sublimation was calculated by means of the Clausius-Clapeyron equation. Additionally, the entropy of sublimation and the Gibbs energy of sublimation were derived. With combustion calorimetry in a static bomb, the massic combustion energy was obtained and the standard molar enthalpy of formation in the crystal phase was determined. By combining the enthalpy of formation in the crystal phase and the enthalpy of sublimation, the standard molar enthalpy of formation in the gaseous phase was obtained for two arylguanidines. With the experimental data, the energetic effect due to the presence of two methyl groups in 1,3-di- o -diphenylguanidine was analyzed. [ABSTRACT FROM AUTHOR]

Nitrogen, carbon monoxide, and methane are key materials in the far outer Solar System where their high volatility enables them to sublimate, potentially driving activity at very low temperatures. Knowledge of their vapor pressures and latent heats of sublimation at relevant temperatures is needed to model the processes involved. We describe a method for using a quartz crystal microbalance to measure the sublimation flux of these volatile ices in the free molecular flow regime, accounting for the simultaneous sublimation from and condensation onto the quartz crystal to derive vapor pressures and latent heats of sublimation. We find vapor pressures to be somewhat lower than previous estimates in literature, with carbon monoxide being the most discrepant of the three species, almost an order of magnitude lower than had been thought. These results have important implications across a variety of astrophysical and planetary environments. • New vapor pressure measurements for N2, CO, and CH4 ices. • Uses quartz crystal microbalance to measure sublimation. • Accounts for simultaneous deposition from surrounding gas. • CO ice has lower vapor pressure than previously thought. [ABSTRACT FROM AUTHOR]

• Vapor pressure of drug were determined and sublimation thermodynamics were evaluated. • Solubility of nifedipine was measured in buffers (pH 2.0 and 7.4), n-hexane and 1-octanol. • Thermodynamic parameters of solubility and solvation were calculated. • Solid state of compound was characterized by DSC and PXRD. • Transfer process nifedipine between aqueous and organic phases was discussed. The saturated vapour pressure of the cardiovascular drug nifedipine is measured within the temperature range (390.15–404.15) K by the inert gas-carrier method. The thermodynamic functions of sublimation of the compounds are calculated at a reference temperature. The standard molar enthalpy of nifedipine sublimation is found to be equal to 144.8 kJ∙mol−1. The drug solubility in solvents modeling various media of the human body is determined in the temperature range (293.15–313.15) K. In the ascending order of solubility values of the studied compound, the solvents can be arranged as follows: buffer pH 7.4, buffer pH 2.0, n -hexane, 1-octanol. The solute–solvent intermolecular interactions are discussed based on the thermodynamic functions of solubility, solvation and transfer. [ABSTRACT FROM AUTHOR]

Highlights • Phenyl-substituted ureas were studied by combustion calorimetry. • Vapor pressures were measured by transpiration method. • Enthalpies of sublimation and vaporization were derived. • Enthalpies of fusion were measured by DSC. • G3MP2 gas phase enthalpies of formation were in agreement with experiment. • Regularities in energetics due to introduction of phenyl substituent revealed. Abstract Standard molar enthalpies of formation of 1-phenyl-3-isopropyl-urea and 1-phenyl-3-tert-butyl-urea were derived from results of high-precision combustion calorimetry. Standard molar enthalpies of sublimation of these compounds and of phenyl-urea were derived from their vapour pressure – temperature dependences measured by the transpiration method. Thermal behaviour of phenyl substituted ureas was studied by DSC. Thermochemical data on phenyl-substituted ureas available in the literature were collected, evaluated, and combined with our own experimental results. We have evaluated and recommended for further thermochemical calculations a set of sublimation, vaporization, fusion and formation enthalpies for the phenyl-substituted ureas at 298.15 K. A computational procedure was developed to support the experimental gas-phase enthalpies of formation. The theoretical gas phase molar enthalpies of formation of the phenyl-substituted ureas calculated by the high-level quantum-chemical G3MP2 method were in a good agreement with the recommended experimental data. General regularities in energetics due to introduction of phenyl substituent in the alkyl-substituted ureas have been revealed and used for validation of the experimental and theoretical data. Additivity methods were developed to estimate the thermochemical properties of organic compounds containing the carbamide moiety. [ABSTRACT FROM AUTHOR]

Highlights • Enthalpy of formation of N-phenylcarbazole measured by combustion calorimetry. • Vapor pressures measured by transpiration method. • Enthalpies of sublimation and vaporization were derived. • G4 gas phase enthalpy of formation was in agreement with experiment. • Hydrogenation enthalpy was derived and compared with other LOHC. Abstract The liquid organic hydrogen carriers (LOHCs) are promising materials for hydrogen storage. The standard molar enthalpy of formation, Δ f H m o (cr, 298.15 K) = (196.0 ± 4.9) kJ·mol−1, of N-phenyl-carbazole was obtained from high-precision combustion calorimetry. The standard molar enthalpy of sublimation Δ c r g H m o (298.15 K) = (116.1 ± 1.7) kJ·mol−1 and vaporisation Δ l g H m o (298.15 K) = (100.5 ± 1.6) kJ·mol−1 of N-phenyl-carbazole were derived from the vapour pressure temperature dependences measured by the transpiration method. The standard molar enthalpy of fusion Δ c r l H m o = (19.4 ± 0.3) kJ·mol−1 at T fus = 367.9 K was measured by DSC. Gas phase molar enthalpy of formation of N-phenyl-carbazole calculated by the high-level quantum-chemical method G4 Δ f H m o (g, 298.15 K) = (312.9 ± 3.5) kJ·mol−1, was in an excellent agreement with the experimental result (312.1 ± 5.2) kJ·mol−1. The hydrogenation/dehydrogenation reaction enthalpy result (−519.3 ± 6.6) kJ·mol−1 of N-phenyl-carbazole was calculated and compared with the data for other potential liquid organic hydrogen carriers. Phase transition enthalpies were validated with the help of empirical methods. A set of thermodynamic properties of N-phenyl-carbazole were recommended as reliable benchmark properties for thermochemical calculations. Due to the high hydrogen storage capacity, as well as the ability to form overcooled liquid even by room temperature, this compound could be considered as seminal candidate for LOHC. [ABSTRACT FROM AUTHOR]

Highlights • Vapor pressures of Clonixin were determined by transpiration method. • The solubility of drug in four solvents were measured at different temperatures. • The distribution coefficients of Clonixin in system 1-octanol/ buffer were obtained. • Thermodynamics parameters of solubility, solvation and transfer for Clonixin were calculated. Abstract The saturated vapor pressure of Clonixin has been measured by the transpiration method in the temperature range of 419.15–443.15 К, and the thermodynamic functions of sublimation have been calculated. It has been found that the energy of the compound crystal lattice is equal to 108.4 kJ·mol−1. The drug solubility in solvents imitating biological media of the body (buffer pH 2.0 and 7.4, 1-octanol, hexane) and the distribution coefficients in the systems 1-octanol/buffer (pH 2.0 and 7.4) have been determined by the shake-flask method in the temperature range of 293.15–313.15 К. The compound solubility values in these solvents lie within the interval from 1.78·10−4 to 8.01·10−2 mol/l. The coefficients of the drug distribution from buffer pH 2.0 in 1-octanol are one order of magnitude higher than from buffer pH 7.4. Based on the experimental data, the thermodynamic functions of the drug dissolution, transfer and solvation have been calculated in the chosen solvents. [ABSTRACT FROM AUTHOR]

Highlights • Vinalia and Cerealia Faculae on Ceres have a common carbonate composition and a variety of morphologies and topographies. • We considered the ejection and deposition of carbonate grains by three possible materials: ice, gas and brine. • We find that brine eruption is the most likely formation mechanism explaining bright mantling and central structures. Abstract Vinalia and Cerealia Faculae are bright and salt-rich localized areas in Occator crater on Ceres. The predominance of the near-infrared signature of sodium carbonate on these surfaces suggests their original material was a brine. Here we analyze Dawn Framing Camera's images and characterize the surfaces as composed of a central structure, either a possible depression (Vinalia) or a central dome (Cerealia), and a discontinuous mantling. We consider three materials enabling the ascent and formation of the faculae: ice ascent with sublimation and carbonate particle lofting, pure gas emission entraining carbonate particles, and brine extrusion. We find that a mechanism explaining the entire range of morphologies, topographies, as well as the common composition of the deposits is brine fountaining. This process consists of briny liquid extrusion, followed by flash freezing of carbonate and ice particles, particle fallback, and sublimation. Subsequent increase in briny liquid viscosity leads to doming. Dawn observations did not detect currently active water plumes, indicating the frequency of such extrusions is longer than years. [ABSTRACT FROM AUTHOR]

Abstract Evolution of the surfaces of cometary nuclei is determined by the sublimation of ice. The rate of sublimation is commonly calculated using the simple Hertz–Knudsen formula, which should be corrected by a temperature dependent sublimation coefficient α s (Kossacki et al., 1999; Gundlach et al., 2011; Kossacki and Leliwa-Kopystynski, 2014). In Kossacki et al. (2017) the temperature dependence of α s for water ice with acetone and methanol present in comets was analyzed. In this work the influence of propanal at the temperature ~195–~230 K and formamide at the temperature ~200–~235 K were investigated. Experiments were performed with slab ice and porous fine-grained ice. It is found, that the presence of propanal reduces the sublimation coefficient at T < 207 K and enhances at T > 208 K. The presence of formamide reduced the sublimation coefficient in the whole investigated temperature range. Porous fine-grained ice sublimed up to four times slower than non-porous one. [ABSTRACT FROM AUTHOR]

Highlights • New thermophysical data for anthracene were measured and calculated. • Recommended sublimation pressures and enthalpies for anthracene were developed. • Recommended values for thermophysical properties are presented. Abstract Anthracene (CAS RN: 120-12-7) is recommended as a primary standard for sublimation enthalpy measurements and it is also frequently used for testing apparatus for vapour pressure measurements. Two recent recommendations by ICTAC for sublimation enthalpy at 298.15 K obtained by extrapolation can be found in the literature. However, no recommended vapour pressure equation and sublimation enthalpy as a function of temperature were reported. The following steps were performed to develop recommended sublimation pressure and enthalpy data for anthracene in the temperature range in which the calibrations are typically performed: (i) analysis and reconciliation of the literature values on vapour pressures and examination of their thermodynamic consistency with related thermal properties; (ii) new extensive vapour pressure measurements in the temperature range (343–373) K; (iii) calculation of ideal-gas thermodynamic properties combining statistical thermodynamics and quantum chemistry methods, and (iv) multi-property correlation of selected vapour pressure and thermal data. The quality and range of available data needed for the multi-property correlation allowed to establish the recommended sublimation pressure equation in the temperature range (200–373) K while at higher temperatures and for the liquid phase only tentative data are provided. Recommended values at 298.15 K are (0.91 ± 0.09) mPa for sublimation pressure and (101.01 ± 0.52) kJ·mol−1 for sublimation enthalpy; the recommended enthalpy of sublimation at 0 K is (104.4 ± 0.9) kJ mol−1. Based on the recommended sublimation pressures, super cooled liquid vapour pressures required for environmental modeling were also calculated. [ABSTRACT FROM AUTHOR]

Abstract The Martian climate is governed by an annual cycle, that results in the condensation of CO 2 ice during winter, up to a meter thick at the pole and thousands of kilometers in extension. Water and dust may be trapped during the condensation and freed during the sublimation. In addition, ice may be translucent or granular depending on the deposition process (snow vs direct condensation), annealing efficiency, and dust sinking process. The determination of ice translucency is of particular interest to confirm or reject the cold jet model (also known as Kieffer model). This work is focused on the dune field of Richardson Crater (72° S, 180° W)in which strong interactions between the water, dust and CO 2 cycles are observed. We analyzed CRISM hyperspectral images in the near IR using radiative transfer model inversion. We demonstrate that among the states of CO 2 ice, the translucent state is observed most frequently. The monitoring of surface characteristics shows a decrease in the thickness of the ice during the spring consistently with climate models simulations. We estimate a very low dust content of a few ppmv into the CO 2 ice, consistent with the formation scenario of cold jets. The water impurities is around 0.1%v, almost stable during the spring, suggesting a water escape from the surface of subliming CO 2 ice layer. The water ice grain size varies in a range 1 to 50 microns. From these results, we propose the following new mechanism of small water ice grain suspension: as a cold jet occurs, water ice grains of various sizes are lifted from the surface. These jets happen during daytime, when the general upward gas flux from the subliming CO 2 ice layer is strong enough to carry the smaller grains, while the bigger fall back on the CO 2 ice layer. The smaller water grains are carried away and integrated to the general atmospheric circulation. [ABSTRACT FROM AUTHOR]

Galaxias Chaos is a region of low plateaus separated by narrow fractures – a chaotic terrain. Galaxias Mensae and Galaxias Colles are characterised by mesa and knobby terrains of individual landforms, or small assemblages, separated by plains. Galaxias Chaos has been attributed to ground disturbance due to sublimation in shallow subsurface ice-rich deposits, Galaxias Mensae and Galaxias Colles to sublimation and degradation of icy surface materials, without production of chaotic terrain. Liquid water has not been regarded as a product of the degradation of these icy terrains. This paper asks two research questions: (1) what was the total extent of the different modes of landscape degradation, especially chaotic terrain, involved in producing the present landscapes of Galaxias Chaos and Galaxias Mensae–Colles; (2) can the generation of liquid water as a product of landscape degradation be ruled-out? Using a morphological-statistical approach, including power spectrum analysis of relief, our observations and analyses show that present mesa-knobby terrains of Galaxias Mensae–Colles evolved from a landscape that had the same directional pattern and relief as presently found in Galaxias Chaos. This terrain extended across ∼440,000 km 2 but ∼22,000 km 3 (average thickness, 77 m) have been lost across ∼285,000 km 2 . This represents a significant loss of ice-bearing deposits. Moreover, this surface degradation was spatially partitioned by landforms associated with elevated ground heating and the transmission of a fluid in the shallow subsurface towards a distal channel. In answer to research question 2, it cannot be determined definitively if the fluid involved was groundwater, generated by the thermal destabilisation of the icy deposits, or low viscosity lava. However, it is likely that the degradation of Galaxias Mensae–Colles was not a consequence of sublimation alone. These findings underscore the significance of cryo-volcanic interactions in the cycling of water between the Martian surface and the atmosphere. [ABSTRACT FROM AUTHOR]

Pluto’s landscape is shaped by the endless condensation and sublimation cycles of the volatile ices covering its surface. In particular, the Sputnik Planitia ice sheet, which is thought to be the main reservoir of nitrogen ice, displays a large diversity of terrains, with bright and dark plains, small pits and troughs, topographic depressions and evidences of recent and past glacial flows. Outside Sputnik Planitia, New Horizons also revealed numerous nitrogen ice deposits, in the eastern side of Tombaugh Regio and at mid-northern latitudes. These observations suggest a complex history involving volatile and glacial processes occurring on different timescales. We present numerical simulations of volatile transport on Pluto performed with a model designed to simulate the nitrogen cycle over millions of years, taking into account the changes of obliquity, solar longitude of perihelion and eccentricity as experienced by Pluto. Using this model, we first explore how the volatile and glacial activity of nitrogen within Sputnik Planitia has been impacted by the diurnal, seasonal and astronomical cycles of Pluto. Results show that the obliquity dominates the N 2 cycle and that over one obliquity cycle, the latitudes of Sputnik Planitia between 25°S-30°N are dominated by N 2 condensation, while the northern regions between 30°N and -50°N are dominated by N 2 sublimation. We find that a net amount of 1 km of ice has sublimed at the northern edge of Sputnik Planitia during the last 2 millions of years. It must have been compensated by a viscous flow of the thick ice sheet. By comparing these results with the observed geology of Sputnik Planitia, we can relate the formation of the small pits and the brightness of the ice at the center of Sputnik Planitia to the sublimation and condensation of ice occurring at the annual timescale, while the glacial flows at its eastern edge and the erosion of the water ice mountains all around the ice sheet are instead related to the astronomical timescale. We also perform simulations including a glacial flow scheme which shows that the Sputnik Planitia ice sheet is currently at its minimum extent at the northern and southern edges. We also explore the stability of N 2 ice deposits outside the latitudes and longitudes of the Sputnik Planitia basin. Results show that N 2 ice is not stable at the poles but rather in the equatorial regions, in particular in depressions, where thick deposits may persist over tens of millions of years, before being trapped in Sputnik Planitia. Finally, another key result is that the minimum and maximum surface pressures obtained over the simulated millions of years remain in the range of milli-Pascals and Pascals, respectively. This suggests that Pluto never encountered conditions allowing liquid nitrogen to flow directly on its surface. Instead, we suggest that the numerous geomorphological evidences of past liquid flow observed on Pluto’s surface are the result of liquid nitrogen that flowed at the base of thick ancient nitrogen glaciers, which have since disappeared. [ABSTRACT FROM AUTHOR]

Impact craters in the mid-latitudes of Mars are commonly filled to variable degrees with some combination of ice, dust, and rocky debris. Concentric surface features visible in these craters have been linked to debris transportation and glacial and periglacial processes. Concentric crater fill (CCF) observed today are interpreted to be the remains of repeated periods of accumulation and sublimation during the last tens to hundreds of million years. Previous work suggests that during phases of high obliquity, ice accumulates in crater interiors and begins to flow down steep crater slopes, slowly filling the crater. During times of low obliquity ice is protected from sublimation through a surface debris layer consisting of dust and rocky material. Here, we use an ice flow line model to understand the development of concentric crater fill. In a regional study of Utopia Planitia craters, we address questions about the influence of crater size on the CCF formation process, the time scales needed to fill an impact crater with ice, and explore commonly described flow features of CCF. We show that observed surface debris deposits as well as asymmetric flow features can be reproduced with the model. Using surface mass balance data from global climate models and a credible obliquity scenario, we find that craters less than 80 km in diameter can be entirely filled in less than 8 My, beginning as recently as 40 Ma ago. Uncertainties in input variables related to ice viscosity do not change the overall behavior of ice flow and the filling process. We model CCF for the Utopia Planitia region and find subtle trends for crater size versus fill level, crater size versus sublimation reduction by the surface debris layer, and crater floor elevation versus fill level. [ABSTRACT FROM AUTHOR]

We report precise experimental values of the enthalpy of sublimation (Δ H s ) of quenched condensed films of neon (Ne), nitrogen (N 2 ), oxygen (O 2 ), argon (Ar), carbon dioxide (CO 2 ), krypton (Kr), xenon (Xe), and water (H 2 O) vapour using a single consistent measurement platform. The experiments are performed well below the triple point temperature of each gas and fall in the temperature range where existing experimental data is very limited. A 6 cm 2 and 400 µm thick double paddle oscillator (DPO) with high quality factor (Q ≈ 4 × 10 5 at 298 K) and high frequency stability (33 parts per 10 −9 ) is utilized for the measurements. The enthalpies of sublimation are derived by measuring the rate of mass loss during temperature programmed desorption. The mass change is detected due to change in the resonance frequency of the self-tracking oscillator. Our measurements typically remain within 10% of the available literature, theory, and National Institute of Standards and Technology (NIST) Web Thermo Tables ( WTT ) values, but are performed using an internally consistent method across different gases. [ABSTRACT FROM AUTHOR]

Nine recently discovered long-period comets were observed by the Solar Wind Anisotropies (SWAN) Lyman-alpha all-sky camera on board the Solar and Heliosphere Observatory (SOHO) satellite during the period of 2013 to 2016. These were C/2012 K1 (PanSTARRS), C/2013 US10 (Catalina), C/2013 V5 (Oukaimeden), C/2013 R1 (Lovejoy), C/2014 E2 (Jacques), C/2014 Q2 (Lovejoy), C/2015 G2 (MASTER), C/2014 Q1 (PanSTARRS) and C/2013 XI (PanSTARRS). Of these 9 comets 6 were long-period comets and 3 were possibly dynamically new. Water production rates were calculated from each of the 885 images using our standard time-resolved model that accounts for the whole water photodissociation chain, exothermic velocities and collisional escape of H atoms. For most of these comets there were enough observations over a broad enough range of heliocentric distances to calculate power-law fits to the variation of production rate with heliocentric distances for pre- and post-perihelion portions of the orbits. Comet C/2014 Q1 (PanSTARRS), with a perihelion distance of only ∼0.3 AU, showed the most unusual variation of water production rate with heliocentric distance and the resulting active area variation, indicating that when the comet was within 0.7 AU its activity was dominated by the continuous release of icy grains and chunks, greatly increasing the active sublimation area by more than a factor of 10 beyond what it had at larger heliocentric distances. A possible interpretation suggests that a large fraction of the comet's mass was lost during the apparition. [ABSTRACT FROM AUTHOR]

Io has an atmosphere produced by volcanism and sublimation of frosts deposited around active volcanoes. However, the time variation of atomic oxygen escaping Io's atmosphere is not well known. In this paper, we show a significant increase in atomic oxygen around Io during a volcanic event. Brightening of Io's extended sodium nebula was observed in the spring of 2015. We used the Hisaki satellite to investigate the time variation of atomic oxygen emission around Io during the same period. This investigation reveals that the duration of atomic oxygen brightness increases from a volcanically quiet level to a maximum level during the same approximate time period of 30 days as the observed sodium brightness. On the other hand, the recovery of the atomic oxygen brightness from the maximum to the quiet level (60 days) was longer than that of the sodium nebula decreasing (40 days). Additionally, a dawn-dusk asymmetry of the atomic oxygen emission is observed. [ABSTRACT FROM AUTHOR]

A weekly time-series of oxygen isotope (δ 18 O) measurements was collected over a 16-month period from near-surface (1 m) and near-bottom (60 m) waters of Bedford Basin, a coastal fjord adjacent to the Scotian Shelf, off eastern Canada. The time-series was complemented with δ 18 O measurements of local precipitation (rain and snow), river, and wastewater runoff. The isotopic composition of precipitation displayed strong seasonality with an average (volume-weighted) δ 18 O value of −5.39‰ (±0.96) for summer and a depleted value of −10.37‰ (±2.96) over winter. Winter precipitation exhibited more depleted and variable δ 18 O of solid precipitation relative to rainfall. The annual, amount-weighted average δ 18 O of Sackville River discharge (−6.49‰ ± 0.82) was not statistically different from precipitation (−7.24‰ ± 0.92), but exhibited less seasonal variation. Freshwater end-members (zero-salinity intercepts) estimated from annual and seasonal regressions of δ 18 O versus salinity (S) for Bedford Basin near-surface samples were consistent with the δ 18 O of summer precipitation and the annual, amount-weighted average for the Sackville River. However, the isotopically depleted signature of winter precipitation was not observed clearly in near-surface waters of Bedford Basin, which might reflect isotope enrichment during sublimation from accumulated snowfall prior to melting and discharge, or retention and mixing within the drainage basin. In near bottom waters, most of the δ 18 O-S variation (average freshwater end-member: 7.47‰ ± 2.17) could be explained by vertical mixing with near-surface waters (average freshwater end-member: −6.23‰ ± 0.34) and hence with locally-derived freshwater. However the near-bottom δ 18 O-S variation suggested an additional contribution of a freshwater end-member with a δ 18 O of −15.55‰ ± 2.3, consistent with a remotely-derived freshwater end-member identified previously for the Scotian Shelf. Residuals from a long-term regression of δ 18 O-S were generally within the range expected due to analytical uncertainty (±0.05); however near-surface waters exhibited seasonal variability of small amplitude, which was consistent with the timing and δ 18 O variability of local freshwater inputs. [ABSTRACT FROM AUTHOR]

The mountains of Jupiter's volcanic moon Io are tall, steep, and tectonic in origin, yet their precise modes of formation and their associations with volcanic paterae are not fully understood. Global spatial statistics of paterae and mountains and their associated lineations reveal that both types of features are more common at low latitudes and tectonic lineations have preferred orientations, whereas straight patera margins are randomly oriented. Additionally, structurally controlled lineations tend to cluster with each other, and in areas of high concentrations these tectonic lineations are shorter in length than their global average. These results indicate that global-scale (rather than local or regional) processes are involved in forming Io's tectonic structures, but that the diversity of mountain characteristics and the collapse of paterae adjacent to mountain complexes are more locally controlled. Regional structural mapping of the Hi'iaka, Shamshu, Tohil, and Zal regions reveals Io's mountains reside in large, fault-bounded crustal blocks that have undergone modification through local responses of subsurface structures to variable stresses. Strike-slip motion along reactivated faults led to the formation of transpressional and transtensional features, creating tall peaks and low basins, some of which are now occupied by paterae. We propose Io's mountains result from a combination of crustal stresses involving global and local-scale processes, dominantly volcanic loading and tidal flexing. These stresses sometimes are oriented at oblique angles to pre-existing faults, reactivating them as reverse, normal, or strike-slip faults, modifying the large, cohesive crustal blocks that many of Io's mountains reside in. Further degradation of mountains and burial of faults has occurred from extensive volcanism, mass wasting, gravitational collapse, and erosion by sublimation and sapping of sulfur-rich layers. This model of fault-bounded blocks being modified by global stresses and local structural response accounts for the variation and patterns of mountain sizes, shapes, and orientations, along with their isolation and interactions with other features. It also provides a context for the operation and extent of global and regional stresses in shaping Io's surface. [ABSTRACT FROM AUTHOR]

In the present work two methods of determination of sublimation enthalpies at 298.15 K based on solution enthalpies at 298.15 K and fusion enthalpies at the melting temperatures were applied for aromatic amines. The sublimation enthalpies of 17 substituted anilines and 1- and 2-naphthylamines at 298.15 K were calculated using their fusion enthalpies at the melting temperatures found in the literature, the solvation enthalpies in benzene and vaporization enthalpy of aniline. Additionally, the sublimation enthalpies of 9 substituted anilines and 1- and 2-naphthylamines were determined from their solution and solvation enthalpies. In this work we measured the solution enthalpies of aniline, its five derivatives and 2-naphthylamine in benzene while the solution enthalpies of other five aromatic amines were taken from the literature. The solvation enthalpies were calculated by means of the group-additivity scheme. The sublimation enthalpies values obtained as such were compared to the reference data. This method showed the good congruence with both direct experiment and solution calorimetry approach. In most cases the divergence does not exceed 2–3%. The consistency between independently determined sublimation enthalpies values validates the reliability of the relationship between the sublimation enthalpy at 298.15 K and fusion enthalpy at the melting temperature. [ABSTRACT FROM AUTHOR]

Io’s volcanic plumes are the ultimate source of its SO 2 atmosphere, but past eruptions have covered the moon in surface frost which sublimates in sunlight. Today, Io’s atmosphere is a result of some combination of volcanism and sublimation, but it is unknown exactly how these processes work together to create the observed atmosphere. We use the direct simulation Monte Carlo (DSMC) method to model the interaction of giant plumes with a sublimation atmosphere. Axisymmetric plume/atmosphere simulations demonstrate that the total mass of SO 2 above Io’s surface is only poorly approximated as the sum of independent volcanic and sublimated components. A simple analytic model is developed to show how variation in the mass of erupting gas above Io’s surface can counteract variation in the mass of its hydrostatic atmosphere as surface temperature changes over a Jupiter year. Three-dimensional, unsteady simulations of giant plumes over an Io day are also presented, showing how plume material becomes suspended in the sublimation atmosphere. We find that a plume which produces some total mass above Io’s surface at night will cause a net increase in the noon-time atmosphere of only a fraction of the night-time value. However, as much as seven times the night-side mass of the plume will become suspended in the sublimation atmosphere, altering its composition and displacing sublimated material. [ABSTRACT FROM AUTHOR]

Evolution of the surfaces of cometary nuclei is determined by the sublimation of ice. The rate of sublimation is commonly calculated using the simple Hertz–Knudsen formula, which should be corrected by a temperature dependent sublimation coefficient α s (Kossacki et al., 1999; Gundlach et al., 2011; Kossacki and Leliwa–Kopystynski, 2014). In this work influence of C 3 H 6 O (acetone), and CH 3 OH (methanol) present in cometary ice on the sublimation coefficient is investigated. We have found, that the mass fraction of admixtures ≤ 2% in water ice is sufficient for an increase of α s by a factor about 5, depending on the temperature. The sublimation coefficient is sensitive to very small concentrations of admixtures. When the admixture is acetone and the mass fraction f = 0.005 is α s (215  K ) ∼ 0.46 instead of ∼ 0.18 for pure water ice. When f = 0.01 is α s (215  K ) ∼ 0.74, and when f = 0.02 is α s (215  K ) ∼ 0.78. The presence of 0.01 mass fraction of methanol has similar influence on the sublimation coefficient as the presence of 0.01 mass fraction of acetone. At temperatures T > 235 K for all investigated compositions of ice α s ∼ 0.15. [ABSTRACT FROM AUTHOR]

Detailed images of highly porous small bodies show variety of the surface. One of the interesting findings is that the depressions on comets look shallower than the simple craters such as on the moon, that is the depth-to-diameter ratio of the depressions is smaller than ∼0.2. Although the mechanisms for the formation of the depression are controversial; such as collapse after the sublimation of the sub-surface volatile or activities after impact such as sublimation and viscous relaxation, the shape of the cavity formed on the highly-porous surface by impact itself has not been studied much. We performed impact experiments of sintered glass-bead targets with porosities of ∼94% and 87%, as well as gypsum targets with a porosity of ∼50%, and pumice targets with that of 74%. The cavity formed in the porous target by the impact has maximum diameter at some depth from the target surface. This type of cavity is called bulb-shape cavity. In addition to the results of this study, we also compiled the results of previous impact experiments for cavity sizes in which the targets with porosity larger than 30% were used. Then new empirical scaling relations for the maximum diameter and the bulb depth for the wide range of target porosity were obtained. We applied the relations to comets and showed that the surface strength and the particle size of the comet 9P/Tempel 1 are estimated to be of the orders of 10 1 –10 3 Pa, and, with the assumption of ice grains consisted of monodisperse spheres, to be larger than ∼90 µm, respectively. The ratio of bulb depth to the maximum diameter on a comet derived from the extrapolation of scaling relations expects that the ratio on the weak surface with the strength less than 10 2 Pa was 0.10 or below, which is smaller than the depth-to-diameter ratio of simple craters, ∼0.2. It suggests a possibility that shallow depressions on comets could be formed only by impact without the need for subsequent activities, such as sublimation and viscous relaxation. [ABSTRACT FROM AUTHOR]

Carbon dioxide has been detected on the trailing hemispheres of several Uranian satellites, but the exact nature and distribution of the molecules remain unknown. One such satellite, Umbriel, has a prominent high albedo annulus-shaped feature within the 131-km-diameter impact crater Wunda. We hypothesize that this feature is a solid deposit of CO 2 ice. We combine thermal and ballistic transport modeling to study the evolution of CO 2 molecules on the surface of Umbriel, a high-obliquity (∼98°) body. Considering processes such as sublimation and Jeans escape, we find that CO 2 ice migrates to low latitudes on geologically short (100s–1000 s of years) timescales. Crater morphology and location create a local cold trap inside Wunda, and the slopes of crater walls and a central peak explain the deposit's annular shape. The high albedo and thermal inertia of CO 2 ice relative to regolith allows deposits 15-m-thick or greater to be stable over the age of the solar system. We conclude that Wunda, located at low latitude (7.9° S) and near the center of the trailing hemisphere where CO 2 detections are strongest, likely contains a solid CO 2 ice deposit. We discuss prospects for similar CO 2 ice deposits on crater floors on the other major Uranian moons, and predict that they are present on Ariel, Titania, and possibly Oberon (but not Miranda or smaller satellites). Such deposits have likely not been observed due to the limited nature of Voyager 2 image coverage. [ABSTRACT FROM AUTHOR]

Enthalpies of vaporization at T = 298.15 K of cis and trans -whiskey lactone have been evaluated by correlation gas chromatography to be (68.4 ± 1.7) kJ·mol −1 and (67.5 ± 1.7) kJ·mol −1 , respectively. The enthalpies of vaporization of isomintlactone and mintlactone also evaluated by correlation gas chromatography have been found to have vaporization enthalpies of (74.2 ± 1.8) kJ·mol −1 and (73.2 ± 1.8) kJ·mol −1 respectively. The vapor pressures for cis and trans -whiskey lactone at T = 298.15 K have been evaluated as (1.5 ± 0.09) Pa and (2.0 ± 0.1) Pa using vapor pressures of a series of lactones as standards. Vapor pressures for isomintlactone and mintlactone were evaluated as (0.26 ± 0.012) Pa and (0.33 ± 0.02) Pa, respectively. Fusion and sublimation enthalpies for (+)-isomintlactone as well as the vapor pressure of the solid have been estimated. [ABSTRACT FROM AUTHOR]

Fields of pits, both large and small, in Tombaugh Regio (Sputnik Planitia, and the Pitted Uplands to the east), and along the scarp of Piri Rupes, are examples of landscapes on Pluto where we conclude that sublimation drives their formation and evolution. Our heuristic modeling closely mimics the form, spacing, and arrangement of a variety of Tombaugh Regio's pits. Pluto's sublimation modified landforms appear to require a significant role for (diffusive) mass wasting as suggested by our modeling. In our models, the temporal evolution of pitted surfaces is such that initially lots of time passes with little happening, then eventually, very rapid development of relief and rapid sublimation. Small pits on Sputnik Planitia are consistent with their formation in N 2 -dominated materials. As N 2 -ice readily flows, some other ``stiffer'' volatile ice may play a role in supporting the relief of sublimation degraded landforms that exhibit several hundred meters of relief. A strong candidate is CH 4 , which is spectroscopically observed to be associated with these features, but the current state of rheological knowledge for CH 4 ice at Pluto conditions is insufficient for a firm assessment. [ABSTRACT FROM AUTHOR]

Vapor pressure of thioacetazone (TAZ) has been determined in the temperature range of 404.15–429.15 K by the transpiration method. The obtained data were used to calculate the standard molar enthalpy of sublimation that was found to be 164.1 kJ/mol at T = 298.15 K. The drug solubility was measured at seven temperatures from 288.15 to 318.15 K in modeling solvents: octanol, hexane and aqueous buffers pH 2.0 and 7.4 by the saturation shake-flask method by using spectrophotometric analysis. It has been found that TAZ has poor solubility in hexane and buffer solutions and limited solubility in octanol. The experimental data were well correlated by van’t Hoff and modified Apelblat equations. A temperature dependence of TAZ partition coefficient in the octanol/buffer pH 7.4 system has been derived. The partition coefficient value in this system (logP = 1.82) refers to the optimal interval for oral absorption drugs. The thermodynamic parameters of sublimation, solubility, solvation and transfer have been determined based on experimental data. The dominant effect of enthalpy and entropy contributions to the Gibbs energy of the investigated processes has been revealed. [ABSTRACT FROM AUTHOR]

Recent observations have suggested that there is water ice present on the surfaces of 24 Themis and 1 Ceres. We present upper limits on the H 2 O production rate on these bodies derived using a search for [O I]6300 Å emission. For Themis, the water production is less than 4.5 × 10 27 mol s − 1 , while for Ceres our derived upper limit is 4.6 × 10 28 mol s − 1 . The derived limits imply a very low fraction of the surface area of each asteroid is active ( < 2 × 10 − 4 ), though this estimate varies by as much as an order of magnitude depending on thermal properties of the surface. This is much lower than seen for comets, which have active areas of 10 − 2 –10 − 1 . We discuss possible implications for our findings on the nature of water ice on Themis and Ceres. [ABSTRACT FROM AUTHOR]

Experiments of sublimation of pure water ice have been performed in the temperature range −105   °C to −30   °C and atmospheric partial pressures ranging from 10 −6 to 10 −1 mb. Sampling of both vapour and residual ice fractions has been performed with the use of a vacuum line designed for the extraction and purification of gases before the measurement of their D/H ratios. Sublimation was responsible for sizable isotopic fractionation factors in the range 0.969–1.123 for temperatures lying between −105   °C and −30   °C. The fractionation factor exhibits a cross-over at temperatures around −50   °C with the water vapour fraction being D-depleted relative to the residual ice fraction at T < −50   °C (α ice-vapour =  0.969–0.995). This cross-over has implications for the understanding of the atmospheric water cycle of some terrestrial planets such as the Earth or Mars. The magnitude of deuterium enrichment or depletion between ice and water vapour cannot explain the differences in the D/H ratios amongst Jupiter comets and long–period comets families nor those that have been documented between Earth's and cometary water. [ABSTRACT FROM AUTHOR]

The transpiration method was used to measure the vapor pressures as a function of temperature of the following antimicrobial drugs: ciprofloxacin, enrofloxacin, norfloxacin and levofloxacin. Based on these results standard molar enthalpies, entropies and Gibbs energies of sublimation at T = 298.15 K were calculated and a correlation between the crystal lattice energy and the saturation vapor pressure in a number of fluoroquinolones was found. The thermophysical characteristics of the compounds studied were determined by DSC. The influence of different structural fragments of molecules substituents and the effects of hydrogen bonds in crystal lattices on the sublimation enthalpy was discussed. [ABSTRACT FROM AUTHOR]

Scalloped depressions in the Martian mid-latitudes are likely formed by sublimation of ice-rich ground. The stability of subsurface ice changes with the planetary obliquity, generally becoming less stable at lower axial tilt. As a result, the relative rates of sublimation and creep change over time. A landscape evolution model shows that these variations produce internal structure in scalloped depressions, commonly in the form of arcuate ridges, which emerge as depressions resume growth after pausing or slowing. In other scenarios, the formation of internal structure is minimal. Significant uncertainties in past climate and model parameters permit a range of scenarios. Ridges observed in some Martian scalloped depressions could date from obliquity lows or periods of low ice stability occurring <5 Ma, suggesting that the pits are young features and may be actively evolving. [ABSTRACT FROM AUTHOR]

In this paper, standard molar energies of combustion of 2-oxazolidinone and 3-acetyl-2-oxazolidinone are reported. The experimental values, obtained from static-bomb combustion calorimetry, are −(1465.42 ± 0.52) kJ·mol −1 and −(2350.86 ± 0.84) kJ·mol −1 , respectively. Using these combustion energy values, the standard molar enthalpies of formation, in crystalline phase, for the aforesaid compounds were calculated. These values were also determined, and the corresponding values are −(430.30 ± 0.96) kJ·mol −1 and −(617.72 ± 1.58) kJ·mol −1 , respectively. The standard molar enthalpies of sublimation at T = 298.15 K were experimentally obtained by using the well-known Knudsen effusion method. The obtained values are (84.20 ± 3.22) kJ·mol −1 and (82.36 ± 1.84) kJ·mol −1 , respectively. From the above experimental results, the standard molar enthalpies of formation in gas-phase of the compounds were derived. The values are: −(346.10 ± 3.36) kJ·mol −1 and −(535.36 ± 2.43) kJ·mol −1 , respectively. To support the consistency of the experimental results presented here, enthalpies of formation in gas-phase, using the G4 composite method, were carried out as well. Experimental results suggest that the formation of intermolecular hydrogen bonds between the nitrogen (at ring’s position 3, see Fig. 1) with the oxygen (at ring’s position 2, see Fig. 1) contributes to the values of temperature and enthalpy of fusion, enthalpy of sublimation, and enthalpy of formation in solid phase. [ABSTRACT FROM AUTHOR]

Complex of rhodium(III) with acetylacetone (Rh(acac) 3 ) was synthesized, purified and identified for thermochemical study. Vapor pressures of the compound were measured by static and transpiration methods in the temperature range from 398 to 521 K. Thermodynamic characteristics of sublimation process Δ sub H 459.6 and Δ sub S ° 459.6 were determined from the experimental data. Heat capacity in the temperature range from 188 to 465 K was measured by using DSC for the first time. Using experimental results, Δ sub H 298.15 and Δ sub S° 298.15 of the compound were derived. [ABSTRACT FROM AUTHOR]

A key outstanding question in Martian science is “are the polar caps gaining or losing mass and what are the implications for past, current and future climate?” To address this question, we use observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of the north polar cap during late summer for multiple Martian years, to monitor the summertime water cycle in order to place quantitative limits on the amount of water ice deposited and sublimed in late summer. We establish here for the first time the summer cycle of water ice absorption band signatures on the north polar cap. We show that in a key region in the interior of the north polar cap, the absorption band depths grow until L s = 120, when they begin to shrink, until they are obscured at the end of summer by the north polar hood. This behavior is transferable over the entire north polar cap, where in late summer regions 'flip' from being net sublimating into net condensation mode. This transition or 'mode flip' happens earlier for regions closer to the pole, and later for regions close to the periphery of the cap. The observations and calculations presented herein estimate that on average a water ice layer ∼70 microns thick is deposited during the L s = 135–164 period. This is far larger than the results of deposition on the south pole during summer, where an average layer 0.6–6 microns deep has been estimated by Brown et al. (2014) Earth Planet. Sci. Lett., 406, 102–109. [ABSTRACT FROM AUTHOR]

Unusually low reflectance material, within which depressions known as hollows appear to be actively forming by sublimation, is a major component of Mercury's surface geology. The observation that this material is exhumed from depth by large impacts has the intriguing implication that the planet's lower crust or upper mantle contains a significant volatile-rich, low-reflectance layer, the composition of which will be key for developing our understanding of Mercury's geochemical evolution and bulk composition. Hollows provide a means by which the composition of both the volatile and non-volatile components of the low-reflectance material (LRM) can be constrained, as they result from the loss of the volatile component, and any remaining lag can be expected to be formed of the non-volatile component. However, previous work has approached this by investigating the spectral character of hollows as a whole, including that of bright deposits surrounding the hollows, a unit of uncertain character. Here we use high-resolution multispectral images, obtained as the MESSENGER spacecraft approached Mercury at lower altitudes in the latter part of its mission, to investigate reflectance spectra of inactive hollow floors where sublimation appears to have ceased, and compare this to those of the bright surrounding products and the parent material. This analysis reveals that the final lag after hollow-formation has a flatter spectral slope than that of any other unit on the planet and reflectance approaching that of more space-weathered parent material. This indicates firstly that the volatile material lost has a steeper spectral slope and higher reflectance than the parent material, consistent with (Ca,Mg) sulfides, and secondly, that the low-reflectance component of LRM is non-volatile and may be graphite. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive experimental and computational study of the thermodynamic properties of 2,7-di- tert -butylfluorene. The standard ( p o = 0.1 MPa) molar enthalpy of formation in the crystalline phase was derived from the standard molar energy of combustion, measured by static bomb combustion calorimetry. The enthalpies and temperatures of transition between condensed phases were determined from DSC experiments. The vapour pressures of the crystalline and liquid phases were measured between (349.14 and 404.04) K, using two different experimental methods. From these results the standard molar enthalpies, entropies and Gibbs energies of sublimation and of vaporization were derived. The enthalpy of sublimation was also determined using Calvet microcalorimetry. The thermodynamic stability of 2,7-di- tert -butylfluorene in the crystalline and gaseous phases was evaluated by the determination of the standard Gibbs energies of formation, at the temperature 298.15 K, and compared with the ones reported in the literature for fluorene. A computational study at the G3(MP2)//B3LYP and G3 levels has been carried out. A conformational analysis has been performed and the enthalpy of formation of 2,7-di- tert -butylfluorene has been calculated, using atomization and isodesmic reactions. The calculated enthalpies of formation have been compared to the experimental values. [ABSTRACT FROM AUTHOR]

The present work deals with the investigation of thermal properties of two volatile scandium(III) beta-diketonates with 2,2,6,6-tetramethyl-4-fluoro-3,5-heptanedione and 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione which have been synthesized and purified. Using the static method with glass membrane gauge-manometer the temperature dependencies of saturated and unsaturated vapor pressure were measured for the first time. The temperatures and enthalpies of melting were measured for these compounds by differential scanning calorimetry. The standard thermodynamic characteristics of enthalpy and entropy for sublimation, vaporization and melting processes were derived. [ABSTRACT FROM AUTHOR]

The standard ( p o = 0.1 MPa) molar enthalpies of formation in the condensed phase, Δ f H m o , of 2,4-dichloro-5-methylpyrimidine, 2,4-dichloro-6-methylpyrimidine, 4,6-dichloro-2-methylpyrimidine and 4,6-dichloro-5-methylpyrimidine were derived from the standard molar energies of combustion, Δ c U m o , in oxygen, to yield CO 2 (g), N 2 (g) and HCl·600H 2 O (l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation, Δ cr, l g H m o , for these compounds, at T = 298.15 K were determined by high temperature Calvet microcalorimetry. Combining these values, the following enthalpies of formation in the gas phase, at T = 298.15 K, were then derived: 2,4-dichloro-5-methylpyrimidine, (79.6 ± 4.1) kJ mol −1 , 2,4-dichloro-6-methylpyrimidine, (70.5 ± 3.0) kJ mol −1 , 4,6-dichloro-2-methylpyrimidine, (68.7 ± 3.3) kJ mol −1 , and 4,6-dichloro-5-methylpyrimidine, (78.1 ± 2.5) kJ mol −1 . The gas-phase enthalpies of formation were also estimated by G3 theoretical calculations, which were extended to the computation of gas-phase enthalpies of formation of the other dichloromethylpyrimidine isomers, namely, 2,5-dichloro-4-methylpyrimidine, 4,5-dichloro-2-methylpyrimidine and 4,5-dichloro-6-methylpyrimidine, whose experimental study was not performed. [ABSTRACT FROM AUTHOR]

The sublimation processes of hydroxyl amino acids, L-serine and L-threonine, were investigated by Knudsen’s effusion method with mass spectrometric vapor composition control. Fragmentation of molecules under electron ionization was discussed. For these compounds, the molar enthalpies of sublimation were derived from the Clausius–Clapeyron equation. Using values for the heat capacity differences between the gas and crystal phases of the compounds the molar standard enthalpies of sublimation at T = 298.15 K, were obtained. The molar enthalpies of solvation in water at infinite dilution (i.d.) were derived from the molar enthalpies of solution of amino acids in water at i.d. and the molar standard enthalpies of sublimation obtained. Correlations between the enthalpies of sublimation/solvation and some molecular descriptors of amino acids were discussed. Conformational analysis of Thr was made by using B3LYP/6-31++G(d,p). Analysis of natural bond orbitals (NBO) has been carried out for the conformers of Ser, Thr and Tyr. It was shown that the side chain of molecule had an influence on formation intramolecular H-bond. [ABSTRACT FROM AUTHOR]

Based on spectroscopic and photometric observations we analyzed the dust environment of two minor distant objects, P/2008 CL94 (Lemmon) and P/2011 S1 (Gibbs). Both targets demonstrated the comet-like activity beyond the “zone of water–ice sublimation”. Meanwhile the spectrum of P/2008 CL94 (Lemmon) did not reveal molecular emission features above reflected continuum in a spectral region of 4100–6800Å. Reddening of the continuum is linear along the dispersion with the mean normalized reflectivity gradient equals to 2.0% ± 0.4%. The normalized reflectivity of P/2011 S1 (Gibbs) derived from the V−R and R−I color indices equals 11% ± 9% and 26% ± 6% respectively. Both objects have likely small nuclei (about 2 and 4 km in the radii for P/2008 CL94 and P/2011 S1 respectively), which are consistent with nucleus sizes of ‘Jupiter-family’ comets. The level of physical activity of P/2008 CL94 and S/2011 S1 is characterized by R-Afρ quantity of 106 ± 3 cm and 76 ± 8 cm respectively. The Afρ values are resulted in dust production rates of about 1–2 kg/s, assuming the average geometric albedo of grains of 0.1 and the dust outflow velocities between 1 and 10 m/s. [ABSTRACT FROM AUTHOR]

The standard ( p o = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of methyl 1 H -indole-3-carboxylate and ethyl 1 H -indole-2-carboxylate, at T = 298.15 K, were derived from measurements of the standard massic energies of combustion using a static bomb combustion calorimeter. The Knudsen effusion technique was used to measure the vapour pressures as a function of the temperature, which allowed determining the standard molar enthalpies of sublimation of these compounds. The standard ( p o = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, were calculated by combining, for each compound, the standard molar enthalpy of formation, in the crystalline phase, and the standard molar enthalpy of sublimation, yielding −(207.6 ± 3.6) kJ·mol −1 and −(234.4 ± 2.4) kJ·mol −1 , for methyl 1 H -indole-3-carboxylate and ethyl 1 H -indole-2-carboxylate, respectively. Quantum chemical studies were also conducted, in order to complement the experimental study. The gas-phase enthalpies of formation were estimated from high level ab initio molecular orbital calculations, at the G3(MP2) level, for the compounds studied experimentally, extending the study to the methyl 1 H -indole-2-carboxylate and ethyl 1 H -indole-3-carboxylate. The results obtained were compared with the experimental data and were also analysed in terms of structural enthalpic group contributions. [ABSTRACT FROM AUTHOR]

The standard ( p ° = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of 6-azauracil, 6-azathymine and 6-aza-2-thiothymine at T = 298.15 K, were derived from the standard molar energies of combustion, in oxygen, measured by combustion calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, were measured by high temperature Calvet microcalorimetry. For 6-azauracil, the standard molar enthalpy of sublimation, at T = 298.15 K, was determined from the temperature-vapour pressure dependence, obtained by the Knudsen mass-loss effusion method. From the experimental studies, the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of the 6-azauracil, 6-azathymine and 6-aza-2-thiothymine were derived. The gas-phase enthalpies of formation were also estimated by G3 and G4 calculations which were further extended to the computation of the standard molar enthalpy of formation of 6-aza-2-thiouracil. We compare the values obtained computationally with the experimental data available and find a good agreement between them. [ABSTRACT FROM AUTHOR]

The surfaces of many objects in the Solar System comprise substantial quantities of water ice sometimes mixed with minerals and/or organic molecules. The sublimation of the ice changes the structural and optical properties of these objects. We present laboratory data on the evolution of the structure and the visible and near-infrared spectral reflectance of icy surface analogues of cometary ices, made of water ice, complex organic matter (tholins) and silicates, as they undergo sublimation under low temperature (<−70 °C) and pressure (10 −5 mbar) conditions inside the SCITEAS simulation chamber. As the water ice sublimated, we observed in situ the formation of a porous sublimation lag deposit, or sublimation mantle, at the top of the ice. This mantle is a network of filaments made of the non-volatile particles. Organics or phyllosilicates grains, able to interact via stronger inter-particulate forces than olivine grains, can form a foam-like structure having internal cohesiveness, holding olivine grains together. As this mantle builds-up, the band depths of the sub-surface water ice are attenuated until complete extinction under only few millimeters of mantle. Optically thick sublimation mantles are mainly featureless in the near infrared. The absorption bands of the minerals present in the mantle are weak, or even totally absent if minerals are mixed with organics which largely dominate the VIS–NIR reflectance spectrum. During sublimation, ejections of large fragments of mantle, triggered by the gas flow, expose ice particles to the surface. The contrast of brightness between mantled and ice-exposed areas depends on the wavelength range and the dust/ice ratio considered. We describe how the chemical nature of the non-volatiles, the size of their particles, the way they are mixed with the ice and the dust/ice mass ratio influence the texture, activity and spectro-photometric properties of the sublimation mantles. These data provide useful references for interpreting remote-sensing observations of comets and also icy satellites or trans-neptunian objects. [ABSTRACT FROM AUTHOR]

Sublimation, the direct transition from solid to gas phase, is a process responsible for shaping and changing the reflectance properties of many Solar System surfaces. In this study, we have characterized the evolution of the structure/texture and of the visible and near-infrared (VIS–NIR) spectral reflectance of surfaces made of water ice mixed with analogues of complex extraterrestrial organic matter, named tholins , under low temperature (<−70 °C) and pressure (10 −5 mbar) conditions. The experiments were carried out in the SCITEAS simulation setup recently built as part of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern (Pommerol, A. et al. [2015a]. Planet. Space Sci. 109–110, 106–122). As the water ice sublimated, we observed in situ the formation of a sublimation lag deposit made of a water-free porous (>90% porosity) network of organic filaments on top of the ice. The temporal evolution of the tholins and water ice spectral features (reflectance at the absorption bands wavelengths, red slope, from 0.40 to 1.90 μm) are analyzed throughout the sublimation of the samples. We studied how different mixtures of tholins with water (0.1 wt.% tholins as coating or inclusions within the water particles), and different ice particle sizes (4.5 ± 2.5 or 67 ± 31 μm) influence the morphological and spectral evolutions of the samples. The sublimation of the ice below the mantle produces a gas flow responsible for the ejection of mm to cm-sized fragments of the deposit in outbursts-like events. The results show remarkable differences between these samples in term of mantle structure, speed of mantle building, rates and surface area of mantle ejections. These data provide useful references for interpreting remote-sensing observations of icy Solar System surfaces, in particular the activity of comet nuclei where sublimation of organic-rich ices and deposition of organic-dust particles likely play a major role. Consequently, the data presented here could be of high interest for the interpretation of Rosetta, and also New Horizons, observations. [ABSTRACT FROM AUTHOR]

The cadmium tin telluride (CdSnTe) alloy was prepared by direct reaction of high purity elemental constituents using rotating furnace. Thin films of CdSnTe different thickness were prepared on glass substrates by vacuum closed space sublimation method. The films were subjected to XRD, SEM, EDAX and UV–vis–NIR studies. The crystalline structure of CdSnTe alloy was found to be face-centered cubic with lattice parameter 6.30 Å. EDAX studies confirmed the composition of the alloy as CdSnTe 2 compound. The UV–vis–NIR optical transmission spectra of thin films of different substrate temperatures were obtained. The energy band gap found to be in the order of 1.5 eV. The band gap is suitable for LEDs, optoelectronics and photovoltaic applications. First principle density functional theory calculations of CdSnTe 2 structure were performed by using Vienna ab-initio simulation package software. The results of theoretical calculations are in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

Sublimating gas molecules scatter off of the surface of an icy body in the same manner as photons (Lambertian Scattering). This means that for every photon-driven body force, there should be a sublimation-driven analog that affects icy bodies. Thermal photons emitted from the surfaces of asymmetrically shaped bodies in the Solar System generate net torques that change the spin rates of these bodies over time. The long-term averaging of this torque is called the YORP effect. Here we propose a sublimation-driven analog to the YORP effect (Sublimation-YORP or SYORP), in which sublimating gas molecules emitted from the surfaces of icy bodies in the Solar System also generate net torques on the bodies. However, sublimating gas molecules carry ∼10 4 –10 5 times more momentum away from the body than thermal photons, resulting in much greater body torques. Previous studies of sublimative torques focused on emissions from highly localized sources on the surfaces of Jupiter Family Comet nuclei, and have therefore required extensive empirical observations to predict the resulting behavior of the body. By contrast, SYORP applies to non-localized emissions across the entire body, which likely dominates sublimation-drive torques on small icy chunks and dynamically young comets outside the Jupiter Family, and can therefore be applied without high-resolution spacecraft observations of their surfaces. Instead, we repurpose the well-tested mathematical machinery of the YORP effect to account for sublimation-driven torques. We show how an SYORP-driven mechanism best matches observations of the rarely observed, Sun-oriented linear features (striae) in the tails of comets, whose formation mechanism has remained enigmatic for decades. The SYORP effect naturally explains why striae tend to be observed between near-perihelion and ∼1 AU from the Sun for comets with perihelia less than 0.6 AU, and solves longstanding problems with moving enough material into the cometary tail to form visible striae. We show that the SYORP mechanism can form striae that match the striae of Comet West, estimate the sizes of the stria-forming chunks, and produce a power-law fit to these parent chunks with a power law index of - 1.4 - 0.6 + 0.3 . Lastly, we predict potential observables of this SYORP mechanism, which may appear as clouds or material that appear immediately prior to stria formation, or as a faint, wispy dust feature within the dust tail, between the nucleus and the striae. [ABSTRACT FROM AUTHOR]

Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of thousands of Mars years under conditions similar to the present, the model produces scallop-like features similar to those on the martian surface, starting from much smaller initial disturbances. The model also indicates crater expansion when impacts occur in surfaces underlain by excess ice to some depth, with morphologies similar to observed landforms on the martian northern plains. In order to produce these landforms by sublimation, substantial quantities of excess ice are required, at least comparable to the vertical extent of the landform, and such ice must remain in adjacent terrain to support the non-deflated surface. We suggest that martian thermokarst features are consistent with formation by sublimation, without melting, and that significant thicknesses of very clean excess ice (up to many tens of meters, the depth of some scalloped depressions) are locally present in the martian mid-latitudes. Climate conditions leading to melting at significant depth are not required. [ABSTRACT FROM AUTHOR]

Bi 2 O 3 thin films were deposited on ultrasonically-cleaned glass and mica substrates by close-spaced vacuum sublimation technique. Films surface morphology was studied using scanning electron microscopy (SEM). Structural study based on the transmission-electron microscopy (TEM) and selected-area electron diffraction (SAED) analysis has been shown that deposited films were polycrystalline with face-centered cubic structure. Optical study was carried out by spectral photometry analysis in the wavelengths range λ = 320–900 nm using the optical transmittance and absorbance measurements. For determination optical band gap E g the Tauc plot was used and the band gap energy E g is determined in the range of 3.50–3.62 eV, respectively. Fourier-transform infra-red (FTIR) analysis shown that obtained films are well-crystalline and have a good optical quality. [ABSTRACT FROM AUTHOR]

The enthalpies of solution, solvation and vaporization/sublimation are interrelated values combined in the simplest thermodynamic circle. Hence, experimental determination of vaporization/sublimation enthalpy can be substituted by experimentally simpler determination of solution enthalpy when solvation enthalpy is known. Previously it was found that solvation enthalpies of a wide range of unbranched aliphatic and aromatic solutes in saturated hydrocarbons are in good linear correlation with their molar refraction values. This allows to estimate the vaporization/sublimation enthalpy of any unbranched organic compound from its solution enthalpy in saturated hydrocarbon and molar refraction. In the present work this approach was modified for determination of vaporization/sublimation enthalpy of branched-chain alkyl aromatic and aliphatic compounds. Group contributions to the enthalpy of solvation due to the branching of carbon chain were evaluated. Enthalpies of solution at infinite dilution of 18 branched-chain aliphatic and alkyl aromatic compounds were measured at T = 298.15 K. Vaporization/sublimation enthalpies for 35 branched aliphatic and alkyl aromatic compounds were determined by using modified solution calorimetry approach. These values are in good agreement with available literature data on vaporization/sublimation enthalpies obtained by conventional methods. [ABSTRACT FROM AUTHOR]

We present the seasonal variation of the HDO/H 2 O ratio caused by sublimation–condensation processes in a global view of the martian water cycle. The HDO/H 2 O ratio was retrieved from ground-based observations using high-dispersion echelle spectroscopy of the Infrared Camera and Spectrograph (IRCS) of the Subaru telescope. Coordinated joint observations were made by the Planetary Fourier Spectrometer (PFS) onboard Mars Express (MEX). The observations were performed during the middle of northern spring ( Ls = 52°) and at the beginning of summer ( Ls = 96°) in Mars Year 31. The retrieved latitudinal mean HDO/H 2 O ratios are 4.1 ± 1.4 ( Ls = 52°) and 4.4 ± 1.0 ( Ls = 96°) times larger than the terrestrial Vienna Standard Mean Ocean Water (VSMOW). The HDO/H 2 O ratio shows a large seasonal variation at high latitudes. The HDO/H 2 O ratio significantly increases from 2.4 ± 0.6 wrt VSMOW at Ls = 52° to 5.5 ± 1.1 wrt VSMOW at Ls = 96° over the latitude range between 70°N and 80°N. This can be explained by preferential condensation of HDO vapor during the northern fall, winter, and spring and sublimation of the seasonal polar cap in the northern summer. In addition, we investigated the geographical distribution of the HDO/H 2 O ratio over low latitudes at the northern spring in the longitudinal range between 220°W and 360°W, including different local times from 10 h to 17 h. We found the HDO/H 2 O ratio has no significant variation (5.1 ± 1.2 wrt VSMOW) over the entire range. Our observations suggest that the HDO/H 2 O distribution in the northern spring and summer seasons is mainly controlled by condensation-induced fractionation between the seasonal northern polar cap and the atmosphere. [ABSTRACT FROM AUTHOR]

Two series of Fe and Al double substituted MnSi γ chimney ladders with a nominal valence electron count, VEC=14 per transition metal were prepared ( γ =1.75). Simultaneous replacement of Mn with Fe and Si with Al yielded the Mn 1− x Fe x Si 1.75− x Al x series while the second Mn 1− x Fe x Si 1.75–1.75 x Al 2 x series follows the pseudo-binary between MnSi 1.75 and FeAl 2 . Scanning electron microscopy and elemental mapping revealed that ~60% of the nominal Al content ends up in the product with the remainder lost to sublimation, and that up to 7% Al can be substituted in the main group sublattice. Profile analysis of X-ray powder diffraction data revealed gradual changes in the cell metrics, consistent with the simultaneous substitution of Fe and Al in a fixed ratio. All samples are p-type with VEC≈13.95 from the structural data and ~1×10 21 holes cm −3 from variable temperature Seebeck measurements. The substituted samples have lower electrical resistivities ( ρ 300 K =2–5 mΩ cm) due to an improved microstructure. This leads to increased thermoelectric power factors (largest S 2 / ρ =1.95 mW m − 1 K −2 ) compared to MnSi γ . The thermal conductivity for the Mn 0.95 Fe 0.05 Si 1.66 Al 0.1 sample is 2.7 W m −1 K −1 between 300 and 800 K, and is comparable to literature data for the parent material. [ABSTRACT FROM AUTHOR]