Presence Of Atmospheric Water Research Articles

Degradation processes of iron-sulfides and calcite containing aggregates from asphaltic mixtures

Iron-sulfide and calcite containing aggregates used for preparation of asphalt mixtures underwent degradation processes under atmospheric conditions. Four locations with specific secondary mineral phases situated on highways and roads from Transylvania (Romania) were investigated. The mineralogical investigations performed on aggregates as well as on the resulted secondary phases revealed the presence of two types of degradation processes: sulfate precipitation, and carbonation. Iron sulfides such as pyrite and marcasite of hydrothermal origin identified in aggregate grains are the source for iron and acidity. During the wet and warm season, in the presence of atmospheric water and oxygen, in a relatively short time (up to two months) iron-sulfides are transformed and sulfate minerals such as melanterite, rozenite, szomolmokite, copiapite, halotrichite and gypsum precipitate. They are associated with secondary calcite, clay minerals and sulfur. Secondary calcite is the result of carbonation process which is mainly controlled by the acid environment generated by atmospheric CO2 dissolved in the rain water. Another source of acidity is the presence of sulfuric acid resulted during the iron-sulfides degradation process. All secondary products are accompanied by Fe-oxihydroxides of rusty color. Thereafter, the resulted sulfate minerals, which later are easily leached by rainwater, progressively consume the iron-sulfides from the aggregate. This process leads to mechanical disintegration of the grains, progressive stripping and potholes. Secondary calcite is found filling the pores of the asphalt mixture or coating the aggregate grains. Later, it could be dissolved by rainwater.

Detection of Carbonates in Martian Weathering Profiles

AbstractNoachian surfaces on Mars exhibit vertical assemblages of weathering horizons termed as weathering profiles; this indicates that surface water caused alteration of the rocks that required a different, warmer climate than today. Evidence of this early Martian climate with CO2 vapor as the main component causing greenhouse warming has been challenged by the lack of carbonate in these profiles. Here we report the analysis of Compact Reconnaissance Imaging Spectrometer for Mars L‐detector data leading to the detections of carbonates using a spectral signature exclusively attributed to them. The carbonates are collocated with hydroxylated minerals in weathering profiles over the Martian surface. The origin of CO2 for the formation of carbonates could be the atmosphere. The widespread distribution of weathering profiles with carbonates over the surface of the planet suggest global interactions between fluids containing carbonate/bicarbonate ions with the surface of Mars in the presence of atmospheric water until around 3.7 billion years ago.

Revisión y mejora de la caracterización del grado de impermeabilidad requerido por el CTE DB-HS1 para fachadas de edificación

The Spanish Technical Building Code published in 2006 regulates the basic requirements of building facades to prevent the inadequate presence of atmospheric water inside Spanish buildings. The moisture exposure estimate, based on several climate parameters, allows adjusting these requirements for every location and facade. However, the parameters used by the Spanish Code can be improved, resulting in a more appropriate estimate of the required water tightness degree and thus in an improvable allocations of the necessary design conditions. This paper reviews these parameters, presenting other internationally applied, and analyses the moisture exposure in the Spanish territory, which would allow improving the subsequent performance of the basic requirements imposed to the facades.

All-aromatic polyetherimide and polyamide-imide thin films deposited by the infrared laser ablation

The thermo-oxidative stability and molecular weight were determined for polyimide and polyamide-imide thin films, deposited by resonant infrared laser ablation (RIR-LA). RIR-LA films were deposited at various wavelengths and compared with the traditional solution-cast films using thermogravimetric analysis. The RIR-LA films showed slightly lower oxidation temperatures, but the initial weight loss temperatures were greater. Since molecular weight is directly correlated with the physical and mechanical properties of the polymer, multiangle laser light scattering was employed to ascertain the weight-average molecular weight of the polymers before and after LA. The RIR-LA films exhibited slightly reduced weight-average molecular weight. This degradation has three possible sources: bond scission during LA, reduced solvent transfer leading to lower chain extension and hydrolysis caused by the presence of atmospheric water.

Effects of atmospheric water and surface wind on passive microwave retrievals of sea ice concentration: a simulation study

The atmospheric effects on the retrieval of sea ice concentration from passive microwave sensors were examined using simulated data typical for the Arctic summer. The simulation includes atmospheric contributions of cloud liquid water (CLW), water vapour (WV) and surface wind on the microwave signatures. A plane parallel radiative transfer model was used to compute brightness temperatures at SSM/I frequencies over surfaces that contained open water, first‐year (FY) ice, multi‐year (MY) ice and their combinations. Synthetic retrievals were performed using the NASA Team (NT) algorithm for the estimation of sea ice concentrations. Our results show that if the satellite sensor's field of view is filled with only FY ice, the retrieval is hardly affected by the atmospheric conditions because of the high contrast between emission signals from the FY ice surface and the atmosphere. Pure MY ice concentration is generally underestimated because of the low MY ice surface emissivity, which results in the enhancement of emission signals from the atmosphere. In marginal ice areas, the atmospheric and surface effects tend to degrade the accuracy at low sea ice concentrations. FY ice concentration is overestimated and MY ice concentration is underestimated in the presence of atmospheric water and surface wind at low ice concentration. Moreover, strong surface wind appears to be more important than atmospheric water in contributing to the retrieval errors of total ice concentrations over marginal ice zones.

Theoretical Spectra and Light Curves of Close‐in Extrasolar Giant Planets and Comparison with Data

We present theoretical atmosphere, spectral, and light-curve models for extrasolar giant planets (EGPs) undergoing strong irradiation for which Spitzer planet/star contrast ratios or light curves have been published (circa 2007 June). These include HD 209458b, HD 189733b, TrES-1, HD 149026b, HD 179949b, and υ And b. By comparing models with data, we find that a number of EGP atmospheres experience thermal inversions and have stratospheres. This is particularly true for HD 209458b, HD 149026b, and υ And b. This finding translates into qualitative changes in the planet/star contrast ratios at secondary eclipse and in close-in EGP orbital light curves. Moreover, the presence of atmospheric water in abundance is fully consistent with all the Spitzer data for the measured planets. For planets with stratospheres, water absorption features invert into emission features and mid-infrared fluxes can be enhanced by a factor of 2. In addition, the character of near-infrared planetary spectra can be radically altered. We derive a correlation between the importance of such stratospheres and the stellar flux on the planet, suggesting that close-in EGPs bifurcate into two groups: those with and without stratospheres. From the finding that TrES-1 shows no signs of a stratosphere, while HD 209458b does, we estimate the magnitude of this stellar flux breakpoint. We find that the heat redistribution parameter, Pn, for the family of close-in EGPs assumes values from ~0.1 to ~0.4. This paper provides a broad theoretical context for the future direct characterization of EGPs in tight orbits around their illuminating stars.

One‐Dimensional Chains Formed by First‐Row Transition Metal(II) Nitrates and Pyrimidine – Influence of Water Coordination on Structural Reliability

AbstractAn isostructural family of one‐dimensional coordination polymers, [M(NO3)2(pym)(H2O)2]∞ [M = Mn (1), Co (2), Ni (3), Zn (4); pym = pyrimidine], has been prepared and their phase purity assessed. It is shown that in contrast to otherM(NO3)2–pyrimidine coordination polymers, 1–4 show a surprising preference for the structure reported herein rather the wide variety of other possible product architectures. It is also shown that a related complex [Ni(NO3)2(pym)(MeCN)2]∞ (5), in which water ligands observed in 1–4 are replaced by MeCN molecules, can also be prepared. However, 5 is highly hygroscopic and readily converts to 3 in the presence of atmospheric water. The implication of the uniformity of structure is discussed in relation to the serendipitous coordination of water molecules to the metal centres. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Geminal poly(silyl ester)s: Highly labile degradable polymers

Geminal silyl ester linkages were used for the backbone construction of linear polymers, which exhibit rapid cleavage in the presence of atmospheric water. A series of poly(gem-silyl ester)s with two ester groups flanking each silicon atom were synthesized, in order to probe the effects of different silyl-substituted side-chain groups upon the physical and chemical properties. The transsilylation condensation reaction of bis(trimethylsilyl) terephthalate with dichlorodiisopropylsilane, dichlorodicyclohexylsilane, dichloromethyl-n-octadecylsilane, and dichloromethyl-4-methylphenethylsilane gave the four poly(gem-silyl ester)s with two isopropyl, two cyclohexyl, one methyl plus one octadecyl, and one methyl plus one 4-methyl-phenethyl side-chain groups per silicon, respectively. The polymers were characterized by NMR (1H, 13C, and 29Si), infrared spectroscopy (IR), size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Hydrolytic degradation studies of the polymers solvated in tetrahydrofuran and as bulk samples in the solid state were performed in the presence of atmospheric water as the nucleophilic cleavage agent, and the molecular weight loss was monitored by SEC. Poly(diisopropylsilyl terephthalate) (1a) and poly(dicyclohexylsilyl terephthalate) (1b) were found to be more stable towards nucleophilic degradation in comparison to poly(methyl-n-octadecylsilyl terephthalate) (1c) and poly(methyl-4-methylphenethylsilyl terephthalate) (1d), due to the presence of sterically bulky isopropyl or cyclohexyl groups attached to the silicon atoms. All of the polymers degraded into small molecules upon hydrolysis, with the exception that the degradation products of 1c and 1d self-condensed in the solid state to form the respective polysiloxanes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3606–3613, 1999

Geminal poly(silyl ester)s: Highly labile degradable polymers

Geminal silyl ester linkages were used for the backbone construction of linear polymers, which exhibit rapid cleavage in the presence of atmospheric water. A series of poly(gem-silyl ester)s with two ester groups flanking each silicon atom were synthesized, in order to probe the effects of different silyl-substituted side-chain groups upon the physical and chemical properties. The transsilylation condensation reaction of bis(trimethylsilyl) terephthalate with dichlorodiisopropylsilane, dichlorodicyclohexylsilane, dichloromethyl-n-octadecylsilane, and dichloromethyl-4-methylphenethylsilane gave the four poly(gem-silyl ester)s with two isopropyl, two cyclohexyl, one methyl plus one octadecyl, and one methyl plus one 4-methyl-phenethyl side-chain groups per silicon, respectively. The polymers were characterized by NMR (1H, 13C, and 29Si), infrared spectroscopy (IR), size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Hydrolytic degradation studies of the polymers solvated in tetrahydrofuran and as bulk samples in the solid state were performed in the presence of atmospheric water as the nucleophilic cleavage agent, and the molecular weight loss was monitored by SEC. Poly(diisopropylsilyl terephthalate) (1a) and poly(dicyclohexylsilyl terephthalate) (1b) were found to be more stable towards nucleophilic degradation in comparison to poly(methyl-n-octadecylsilyl terephthalate) (1c) and poly(methyl-4-methylphenethylsilyl terephthalate) (1d), due to the presence of sterically bulky isopropyl or cyclohexyl groups attached to the silicon atoms. All of the polymers degraded into small molecules upon hydrolysis, with the exception that the degradation products of 1c and 1d self-condensed in the solid state to form the respective polysiloxanes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3606–3613, 1999

Structure–functionality relationships of grafted Ti-MCM41 silicas. Spectroscopic and catalytic studies

Detailed spectroscopic measurements have been used to elucidate the nature of Ti(IV)-centred active sites that were anchored to a mesoporous silica surface (MCM41) by two distinct routes from titanocene precursors. The catalyst prepared in dry argon (Ti-MCM41 [Ar]) is more active than that prepared in air (in the presence of water vapour) in its activity in the epoxidation of cyclohexene with tert-butylhydroperoxide (TBHP). The degree of loading of the titanium onto the silica support also influences the precise nature of the active sites. In Ti-MCM41 [Ar] samples containing less that 2 wt.% of Ti, the most abundant species are tetrahedrally bonded Ti(IV) active sites which absorb at 210–230 nm in diffuse reflectance (DR) UV–Vis spectra and exhibit an emission at 430 and 490 nm when excited with a 250 nm light. Samples of catalyst with greater than 4 wt.% loading are shown to contain TiO2-like microclusters. These species absorb at λ250 nm in the DR UV–Vis and emit very weakly in the 500–600 nm region. In the case of Ti-MCM41 [air] catalysts, which were prepared in the presence of atmospheric water at the MCM41 surface, even at the lowest Ti loading (e.g. ⩽0.5%) an incipient formation of oligomers occurs. It is proposed that dimers or very small oligomers which absorb at around 250 nm in the DR spectra are responsible for a very strong emission at around 500 nm in the photoluminescence spectra. The abundant presence of these species might well explain the lower catalytic performance of Ti-MCM41 [air] in comparison with that of Ti-MCM41 [Ar]. The anchoring of the Ti species at the surface silanol groups of MCM41 was in all cases followed by FTIR spectroscopy.

Atmospheric degradation of the high-temperature superconductor, YBa2Cu3O7−x

The superconducting oxides YBa2Cu3O7−x and HoBa2Cu3O7−x degrade in the presence of atmospheric water. Planar defects appear in the crystal lattice normal to c, followed by gross distortion of the lattice, then complete breakdown to give a mixture of insulating products. Corrosion is enhanced by increasing the relative humidity and temperature.