bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic mechanical measurements on fresh-water ice during freezing and thawing: preliminary results
Authors: Fitzgerald E R 
Published: May 2003

An automated measurement system for elastic (J' ) and viscous (J'' ) components of complex shear compliance, J* = J'  iJ'', and the elastic (G' ) and viscous (G'' ) components of complex shear modulus, G* = G' + iG'' = 1/J*, has been used to obtain these material parameters for fresh-water ice during freezing and thawing. The system is reviewed briefly and yields mechanical loss tangents, J''/J' = G''/G', the shear-wave velocity and attenuation, in addition to shear compliance and modulus, at sinusoidal vibration frequencies from 2 to 10 000 Hz at temperatures between 25 and 150°C. Results reported here are chiefly at temperatures from 10 to 10°C. The required sample disk pairs, which are clamped to a central drive plate, are prepared outside the apparatus for solids and gels. Liquids of known volume are inserted between the drive plate and surrounding clamps at a separation distance, h, by a syringe to form sample disks of area, A = Volume / h. Measurements at 58 frequencies between 2 and 10 000 Hz require 3.5 min; several measurements at each temperature were made to test for equilibrium. Results for both tap and distilled water above freezing revealed high values of elastic (J' ) compliance that decreased sharply at 100 Hz and higher frequencies. Tap-water samples with 4 to 6% by volume air bubbles were less compliant ("stiffer") above freezing than samples with 0 to 1% by volume air, but when frozen, the samples with the smaller volume of air bubbles were less compliant, that is, had higher modulus values than the samples with high air-bubble volumes. Dynamic mechanical property changes in the transition from water to ice are compared to changes previously found during phase transitions in other materials. Further investigation on the effects of air-bubble volumes on dynamic mechanical properties of both water and ice is planned. PACS Nos.: 62.30+d, 62.40+i
The effect of HCl adsorption on the structure and dynamics of the ice surface
Authors: Suzanne J , Ferry D , Demirdjian B , Girardet C , Toubin C , Picaud S , Hoang P NM 
Published: May 2003

Neutron diffraction and quasi-elastic neutron scattering experiments together with molecular dynamics simulations were performed to investigate the effect of HCl adsorption in the sub-monolayer range on the structure and dynamics of a thin ice Ih film deposited on a MgO (100) substrate. We show that surface melting occurs in the supported pure-ice film down to about 8 K below the normal melting temperature of bulk ice Ih. Upon HCl adsorption, the surface melting temperature is still lowered by 15 K at HCl amounts corresponding to 0.3 and 0.6 monolayer. Results of simulations can satisfactorily interpret the lowering of the melting temperature due to the support and to HCl adsorption. Upon adsorption of one HCl monolayer, HCl dihydrate is formed at 220 K and the film becomes amorphous at 250 K. The results are discussed within the context of stratospheric and upper tropospheric/lower stratospheric chemistry. PACS Nos.: 68.55-a, 61.12-q, 31.15Qg, 82.33Tb
Dependence of the normal modes on the electronic structure of various phases of ice as calculated by ab initio methods
Authors: Jenkins S , Kirk S R , Côté A S , Ross D K , Morrison I 
Published: May 2003

The charge-density distribution in various phases of ice is used to explore the information that can be obtained about the preferred directions of motion of atoms so as to investigate the possibility of the creation of more efficient and computationally cost-effective dynamical matrices. PACS Nos.: 63.20Dj, 31.90+s, 71.10-w
A new approach to the study of interfacial melting of ice: infrared spectroscopy
Authors: Sadtchenko V , Ewing G E 
Published: May 2003

Faraday observed in 1850 "that a particle of water which could retain the liquid state whilst touching ice on only one side, could not retain the liquid if it were touched by ice on both" (M. Faraday, Royal Institution Discourse, June 7, 1850; Experimental Researches in Chemistry and Physics (Taylor and Francis, New York, 1991)). Thus began the concept of interfacial melting, and the presence of a liquid water film on the surface of ice at temperatures of 0°C and below. Over the past few decades, there have been a number of measurements of interfacial melting. In some studies, the thickness of the thin film, variously called the quasi-liquid layer (QLL), liquid-like layer, surface melting layer, or premelting layer, has been determined. The results of these measurements demonstrate a striking variation depending on the experimental method and the nature of the ice samples. For example, at 0.1°C, the thickness values range over two orders of magnitude from around 1 to 100 nm. Although the disagreement can be partially explained by the differences in ice samples, the experimental techniques employed in measurements of the QLL thickness are based on different physical principals, and involve a web of assumptions for their deconvolution. We describe here the technique of infrared attenuated total reflection (ATR) spectroscopy that has been directed to the study of interfacial melting of ice for the first time. PACS No.: 83.50Lh
On the thermodynamic stability of clathrate hydrates
Authors: Tanaka H 
Published: May 2003

The thermodynamic stability of clathrate hydrates is investigated by theoretically examining the free energy of formation of clathrate hydrates encaging propane and argon. The total free energy is divided into several contributions: the interaction between water and guest molecules, the entropic contribution arising from the combinations of cage occupancy, and the free energy due to intermolecular vibrations. The method introduced here removes some of the assumptions of the van der Waals and Platteeuw theory. It is shown that the shift of the vibrational frequency of the host lattice destabilizes the clathrate hydrates thermodynamically. PACS No.: 61.50Ah
The surface physics of ice in thunderstorms
Authors: Dash J G , Wettlaufer J S 
Published: May 2003

Laboratory and field studies have shown that thunderstorm electrification is principally due to rebounding collisions between ice particles and hail. Recent studies have provided clues for an understanding of the microphysics of the charging mechanism, involving the dynamics of vapor growth, molecular diffusion, and collisionally modified surface melting. The theory is in quantitative agreement with the systematic dependence of charge and mass transfer on growth rate, collision speed, and temperature. PACS Nos.: 05.70-a, 64.10+h, 64.70-p, 63.35
Photon emission accompanying deformation and fracture of ice
Authors: Mizuno Y , Mizuno T 
Published: May 2003

We observed photon emission during deformation and fracture of axially loaded polycrystalline ice. Emission of visible photons (300650 nm) was correlated with crack generation and fracture, based on time-resolved photon emission signals taken during load changes. Emission intensity, including the entire spectra ranging from 300 to 650 nm, was roughly correlated with increasing strain energy released by fracturing, while considerable scattering of the intensity data implied that emission intensity also depended on the characteristics of each individual crack. Correlation was taken between simultaneous emissions detected with two photomultiplier tubes with different ranges of spectral sensitivity. Brief, intense emissions were clearly associated with load drops, and these probably included wavelengths shorter than 320 nm, indicating that near ultraviolet light is also emitted. On the other hand, weak but continuous signals with wavelengths longer than 650 nm were emitted the entire time the ice was subjected to a load. Emission intensity and spectra may be attributed to microprocesses during fracturing. Experimental evidence for emission of visible photons indicates that the generated electric charges on crack surfaces and at crack tips have energy ranging from 2 to 6 eV. PACS No.: 46.50
Reduction of ice adhesion to metal by using self-assembling monolayers (SAMs)
Authors: Petrenko V F , Peng S 
Published: May 2003

A new method has been developed to study the role of hydrogen bonding in ice adhesion and to minimize the effect of this mechanism on ice adhesion. Metals were coated with a mono-molecular layer that had either strong hydrophobic properties or strong hydrophilic properties. Self-assembling monolayers (SAMs) of varying degrees of hydrophobicity/hydrophilicity were created by mixing the hydrophobic and hydrophilic components. The SAM structure and quality were examined using atomic force microscopy, and the degree of the SAM hydrophobicity/hydrophilicity was characterized by the contact angle of water on the monolayer surfaces. Then, water was frozen on the top of the SAM and the shear strength of the interface between ice and SAM was measured. A good correlation between the contact angle of water and the ice adhesion strength was shown and the fraction of ice adhesion caused by hydrogen bonding was determined. It is revealed that hydrogen bonding significantly enhances ice adhesion. PACS No.: 61
Three-dimensional simulation of ice growth in the presence of antifreeze proteins
Authors: Wathen B , Kuiper M J , Walker V K , Jia Z 
Published: May 2003

A Monte Carlo computational method for simulating the growth of entire ice crystals from the liquid phase has been developed specifically to study the inhibition of ice-crystal growth by antifreeze proteins (AFPs). AFPs are found in the fluids of certain organisms that inhabit freezing environments and constrain ice-crystal growth by adsorbtion to the ice surface, but their inhibition mechanism is still poorly understood. Thus, it was of interest to incorporate these molecules into the dynamic ice simulations to examine the inhibition phenomenon on a whole-crystal basis. We have undertaken simulations with AFPs from two different organisms that differ in activity; the insect AFP has up to 100 times the activity of the fish AFP on a molar basis. Simulations involving insect and fish AFPs have achieved ice-growth inhibition at simulation temperatures within reported activity ranges for both fish and insect AFPs, accompanied by resulting ice morphologies similar to those observed experimentally. These results, as well as other studies on ice-etching patterns and ice burst growth at temperatures below known AFP ice-growth inhibition abilities suggest that AFP activity is dominated by the AFP ice-binding position rather than AFP ice-binding strength. PACS No.: 07.05T
Measured temperature and pressure dependence of Vp and Vs in compacted, polycrystalline sI methane and sII methaneethane hydrate
Authors: Helgerud M B , Waite W F , Kirby S H , Nur A 
Published: May 2003

We report on compressional- and shear-wave-speed measurements made on compacted polycrystalline sI methane and sII methaneethane hydrate. The gas hydrate samples are synthesized directly in the measurement apparatus by warming granulated ice to 17°C in the presence of a clathrate-forming gas at high pressure (methane for sI, 90.2% methane, 9.8% ethane for sII). Porosity is eliminated after hydrate synthesis by compacting the sample in the synthesis pressure vessel between a hydraulic ram and a fixed end-plug, both containing shear-wave transducers. Wave-speed measurements are made between 20 and 15°C and 0 to 105 MPa applied piston pressure. PACS No.: 61.60Lj
Measurements of physical properties of gas hydrates and in situ observations of formation and decomposition processes via Raman spectroscopy and X-ray diffraction
Authors: Uchida T , Takeya S , Wilson L D , Tulk C A , Ripmeester J A , Nagao J , Ebinuma T , Narita H 
Published: May 2003

Gas hydrate properties and phase transition kinetics were studied using Raman spectroscopic and X-ray diffraction methods. These techniques have the advantage of measuring physical properties such as crystal structure, gas composition, and cage occupancy of gas molecules without decomposing the sample. In situ observations using these techniques are indicative of formation and decomposition processes in gas hydrates. Raman spectroscopy is used for the analysis of gas concentrations and gas compositions of gas hydrates. The ν1 symmetrical CH stretching vibration mode of methane molecules in the hydrate phase shows a doublet, and the relative intensity of the peaks determines the cage-occupancy ratio. However, as the Raman method is not standard for this application, we evaluated the method by analyzing the same methane hydrate sample using NMR and Raman scattering in a laboratory in Canada and also comparing the data with the Raman measurements made on the same sample in a laboratory in Japan. The data were consistent with all three measurements. In addition, in situ measurements of hydrate formation and decomposition were done by X-ray diffraction. The transformation of ice into CO2 hydrates occurred in two steps: at first a CO2 hydrate layer rapidly formed a coating on the ice surface and then the CO2 hydrate slowly grew according to the diffusion rates of CO2 and H2O molecules through the hydrate layer to the reaction sites. The same methods were used to observe the self-preservation effect of methane hydrates. PACS Nos.: 82.80Ch, 61.10Nz
Temperature, pressure, and compositional effects on anomalous or "self" preservation of gas hydrates
Authors: Stern L A , Circone S , Kirby S H , Durham W B 
Published: May 2003

We previously reported on a thermal regime where pure, polycrystalline methane hydrate is preserved metastably in bulk at up to 75 K above its nominal temperature stability limit of 193 K at 0.1 MPa, following rapid release of the sample pore pressure. Large fractions (>50 vol.% ) of methane hydrate can be preserved for 23 weeks by this method, reflecting the greatly suppressed rates of dissociation that characterize this "anomalous preservation" regime. This behavior contrasts that exhibited by methane hydrate at both colder (193240 K) and warmer (272290 K) isothermal test conditions, where dissociation rates increase monotonically with increasing temperature. Here, we report on recent experiments that further investigate the effects of temperature, pressure, and composition on anomalous preservation behavior. All tests conducted on sI methane hydrate yielded self-consistent results that confirm the highly temperature-sensitive but reproducible nature of anomalous preservation behavior. Temperature-stepping experiments conducted between 250 and 268 K corroborate the relative rates measured previously in isothermal preservation tests, and elevated pore-pressure tests showed that, as expected, dissociation rates are further reduced with increasing pressure. Surprisingly, sII methaneethane hydrate was found to exhibit no comparable preservation effect when rapidly depressurized at 268 K, even though it is thermodynamically stable at higher temperatures and lower pressures than sI methane hydrate. These results, coupled with SEM imaging of quenched sample material from a variety of dissociation tests, strongly support our earlier arguments that ice-"shielding" effects provided by partial dissociation along hydrate grain surfaces do not serve as the primary mechanism for anomalous preservation. The underlying physical-chemistry mechanism(s) of anomalous preservation remains elusive, but appears to be based more on textural or morphological changes within the hydrate material itself, rather than on compositional zoning or ice-rind development. PACS Nos.: 82.30Lp, 81.40Gh, 81.40Vw, 68.37Hk, 83.80Nb
Raman spectroscopic observations of methane-hydrate formation and hydrophobic hydration around methane molecules in solution
Authors: Uchida T , Okabe R , Gohara K , Mae S , Seo Y , Lee H , Takeya S , Nagao J , Ebinuma T , Narita H 
Published: May 2003

To reveal the hydrophobic hydration process of methane molecules dissolved in water, Raman spectra of dissolved methane (CH4) in water were measured under various conditions. The conditions include water saturated with CH4 gas, waterCH4 solution with CH4 hydrate crystals in equilibrium, and also during hydrate decomposition. The symmetric CH stretching mode of the CH4 molecule in water is a single peak at 2910 cm1 with a half-width of approximately 5 cm1. These results indicate that the size of the space for the CH4 molecules, called the hydration shell, is between the large and small cages of the hydrate crystal, but it has a broad size distribution. To better understand the CH4-molecule vibrations, its spectrum in water was compared with its spectra in liquid carbon dioxide (CO2) and in liquid ethane (C2H6). These spectra were very similar to those observed in water, except that the peak widths were sharper than those in water. This suggests that the broadening of the shell-size distribution is due to the way the CH4 molecules affect the hydration shell. On the other hand, when the system included hydrate crystals, a double CH4 peak arose due to structure in the aqueous solution near the crystal surface. This indicates that a cage-like structure can exist in the water phase. Compared with the decomposition experiment, the cage-like structure is likely due to the presence of the bulk hydrate crystal and is different from the hydration shell for the dissolved CH4 molecules. PACS Nos.: 81.10Dn, 33.20Fb
Effect of direct- and alternating-current electric fields on friction between ice and metals
Authors: Arakawa M , Petrenko V F , Chen C 
Published: May 2003

We report an extremely strong effect of direct and alternating current on the friction of steel sliding on ice. Under the most favorable conditions, the friction force increased by a factor of 33 when 520 V of 60 Hz voltage was applied. The effects on this phenomenon of both temperature and voltage were studied. Electrostatic pressure and field-stimulated growth of the ice/metal contact area appear to be the most likely causes of this effect. PACS No.: 81.40Pq
Observation of crack propagation in saline ice and freshwater ice with fluid inclusion
Authors: Arakawa M , Petrenko V F 
Published: May 2003

A key process of crack propagation in saline ice is the interaction between the crack and fluid inclusions. We observed their interaction in freshwater ice using very high-speed photography (VHSP) and found that the low-density fluids (air and inert liquid, Fluorinert, 1.78 g/cm3) could not impede the crack effectively, interrupting the propagation for less than 10 µs. The high-density liquid mercury, (13.8 g/cm3) impeded the crack more effectively, stalling the development of the crack for more than 20 µs. The crack velocity in saline ice was measured using two different methods: electrical resistance method (ERM) and VHSP. These two methods returned very different mean velocities, 15 m/s for the ERM and 250 m/s for the VHSP. We found that in ice with conductive liquid inclusions, the ERM measured the time it took to break liquid bridges stretched across a crack rather than the crack velocity. Results from the VHSP show that the maximum crack velocity in saline ice was 500 m/s, which is one-half of that found in freshwater ice. From our results using freshwater ice with inclusions, we conclude that liquid inclusions in saline ice may play a role in this retardation. PACS No.: 62.20Mk
Neutron powder diffraction studies as a function of temperature of structure II hydrate formed from propane
Authors: Rawn C J , Rondinone A J , Chakoumakos B C , Circone S , Stern L A , Kirby S H , Ishii Y 
Published: May 2003

Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters. PACS No.: 61.12-q
Rate of decay of specific surface area of snow during isothermal experiments and morphological changes studied by scanning electron microscopy
Authors: Legagneux L , Lauzier T , Domin F , Kuhs W F , Heinrichs T , Techmer K 
Published: May 2003

The quantification of the specific surface area (SSA) of snow crystals and of its variation during metamorphism are essential to understand and model the exchange of reactive gases between the snowpack and the atmosphere. Therefore, the decay rate of SSA of five fresh snow samples was studied in the laboratory at 4, 10, and 15°C under isothermal conditions in closed systems. The time-evolution of the snow SSA can in all cases be very well described by an empirical law of the form, SSA =  A log(t + Δt) + B, where A, B, and Δt are adjustable parameters. B seems to be closely related to the initial SSA of the snow, and A describes the SSA decay rate. Our preliminary findings at 15°C suggest that a linear relationship exists between A and B, so that it may be possible to predict the decay rate of snow SSA from its initial value. For the first time, images obtained from scanning electron microscopy show that crystal rounding of snow is the main process taking place during isothermal metamorphism. New grain boundaries also form. More surprising, however, was the formation of new basal, prismatic, and pyramidal crystal faces, sometimes with very sharp angles, especially at 15°C. The growth of facets with sharp angles is not fully explained by current theories of snow metamorphism and has not been observed before. PACS Nos.: 68.35Md, 68.37Hk, 81.20Ev, 81.05Rm
Effects of temperature cycling on the phase transition of water in gas-saturated sediments
Authors: Chuvilin E M , Ebinuma T , Kamata Y , Uchida T , Takeya S , Nagao J , Narita H 
Published: May 2003

Experimental results on hydrate- and ice-formation conditions in the pores of sandy sediments that have undergone temperature cycles are presented. Thermodynamic parameters of gas hydrate and ice formation in porous space were determined for CH4 and CO2 saturated sandy sediments. The experiments indicate that temperature and freezing cycles affect the thermodynamics of hydrate and waterice in gas-saturated sediments. Temperature cycles increased the hydrate accumulation in the pore space of sediments and reduce the freezing temperature of the remaining pore water. PACS Nos.: 91.60Hg, 92.40Sn
Double-microtoming technique for snow studies
Authors: Satyawali P K , Sinha N K , Sethi D N 
Published: May 2003

Classification of snow samples based on the thick-section method presents difficulty in recognizing the types of snow having similar structure. Using a double-microtoming technique together with thermal etching, textural details of vertical and horizontal thin sections of different snow samples are obtained. It has allowed us to examine the texture of different types of snow, which was not possible using the thick-section technique. This technique is capable of bringing out the grain or sub-grain boundaries and clearly shows the type of bonds between crystals (geometric or crystalline) using polarized light for relatively large-angle boundaries and thermal etching for small-angle boundaries. This way, one can characterize the texture of various snow types. The texture of snow that has not been studied so far is added information that can further classify a snow sample in addition to the common classes of snow. PACS No.: 92.40Rm