Water Mass Density Research Articles

Fingerprints of Amorphous Icelike Behavior in the Vibrational Density of States of Protein Hydration Water

The low-frequency modes of protein hydration water are investigated by inelastic neutron scattering. Experiments on both protonated and fully deuterated maltose binding protein samples allow us to unambiguously single out the contribution from water. The low-energy vibrational density of states of hydration water at 100 K is similar to the density of states of high- and low-density amorphous ice, and quite different from that of simple forms of crystalline ice. This result can be related to the picture of hydration water mass density depending on the protein surface curvature, which supports its glassy behavior.

Instability of stagnation line icing

A high Reynolds number analysis is used to investigate the stability of an ice surface lying beneath a low Mach number stagnation-line air flow. The ice surface is covered by a thin water film, whose thickness is consistent with the water mass densities typically encountered in aircraft icing cloud conditions. A multiple scales stability analysis is used to show that the ice surface can become unstable near the stagnation line. The ice surface is found to admit strongly three-dimensional linear instabilities, and increasing the Mach number suppresses the instability.

Water mass characteristics in the Cenomanian US Western Interior seaway as indicated by stable isotopes of calcareous organisms

Stable oxygen isotopes taken from taxon-specific planktic foraminifera are potential sources of water mass density proxy data and paleoclimate information. Material suitable for stable isotope analysis is uncommon in the middle to late Cenomanian strata of the Western Interior of the USA. However, well preserved material from 17 correlative horizons at five localities across SE Montana and NE Wyoming has provided an opportunity to obtain reliable δ 18O data from foraminiferal samples, fine-fraction carbonate (e.g. calcareous nannofossils) and inoceramid prisms. With the exception of inoceramids, which for a benthic organism have stable isotopic compositions resembling surface-dwelling calcareous organisms, these data indicate that the water column was vertically stratified and water masses were anomalously depleted in 18O. Within samples, planktic and benthic foraminifera display strong vertical gradients in δ 18O and δ 13C of several per mil. The vertical gradient of δ 18O ranges from more negative nearer the sea surface to less negative at the sea floor, with a gradient of about 4‰. This implies less saline/warmer waters near the surface with increasingly more saline/colder waters with depth. This isotopic distribution indicates a stably stratified water column at least seasonally. In addition, a persistent vertical carbon isotope gradient of 2–3‰ suggests a strong nutrient gradient that if mixed would result in high surface water fertility. Preservation of high amounts of organic carbon in the sediments corroborates this inference. Although the water column was stratified overall, the nutrients necessary to promote high productivity were clearly renewed at least seasonally. Nutrient renewal could have been achieved by (1) winter cooling of the upper layer allowing deeper seasonal mixing with nutrient-rich deep waters, (2) seasonal shallowing of the pycnocline into the photic zone, (3) entrainment and decomposition of organic matter at the previously proposed frontal convergence, (4) upwelling of nutrient-rich deep waters along the previously proposed oceanic front, or (5) mixing of ‘shelf’ waters with more oceanic waters across an oceanic front.

A semi-empirical backscattering model at L-band and C-band for a soybean canopy with soil moisture inversion

Radar backscatter measurements of a pair of adjacent soybean fields at L-band and C-band are reported. These measurements, which are fully polarimetric, took place over the entire growing season of 1996. To reduce the data acquisition burden, these measurements were restricted to 45/spl deg/ in elevation and to 45/spl deg/ in azimuth with respect to the row direction. Using the first order radiative transfer solution as a form for the model of the data, four parameters were extracted from the data for each frequency/polarization channel to provide a least squares fit to the model. For inversion, particular channel combinations were regressed against the soil moisture and area density of vegetation water mass. Using L-band cross-polarization and VV-polarization, the vegetation water mass can be regressed with an R/sup 2/=0.867 and a root mean square error (RMSE) of 0.0678 kg/m/sup 2/. Similarly, while a number of channels, or combinations of channels, can be used to invert for soil moisture, the best combination observed, namely, L-band VV-polarization, C-band HV- and VV-polarizations, can achieve a regression coefficient of R/sup 2/=0.898 and volumetric soil moisture RMSE of 1.75%.

Determination of the reactivity of clay-fluid systems using liquid limit data

The reactivity coefficient, defined as lambda = rhowGsSatheta (rhow is the mass density of water, Gs is the specific gravity, Sa is the specific surface, and theta is the double-layer thickness), has been proposed as a parameter to assess the sensitivity of a clay-fluid system to changes in physical and chemical properties of the pore fluid. In this study, the liquid limit of a clay-fluid mixture, wL, is shown to be related to the reactivity coefficient. Double-layer theory is applied to determine the void ratio at the liquid limit, which is assumed to occur at a stress close to 10 kPa. Liquid limit data were measured for a bentonite clay at different pore-fluid concentrations; other data were collected from the literature. Both measured and collected data followed the proposed simple expression, suggesting that there is a unique relationship between wL and lambda, at least for the three-layer sheet minerals (or for clays with wL > 50). The proposed expression can be used as a simple approach to determine the sensitivity of clay-fluid systems. A parametric study based on the lambda-wL relationship is presented to study the effects of temperature and pore-fluid concentration on the liquid limit.Key words: clay, specific surface, pore fluid, ion concentration, double layer.

Evaluation of Surface-Related Phenomena Using Sedimentation Tests

Abstract Sedimentation tests are suggested to assess the sensitivity of clay-water systems to environmental changes. A simple framework based on a parallel structure assumption was developed to analyze data from sedimentation tests. The slope of the relationship between the final sediment volume and the ionic concentration, plotted on a log-log scale, is related to the specific surface Sa, the double layer thickness ϑ, and to the specific gravity Gs. A new parameter, λ, the reactivity coefficient, where λ = Sa · ϑ · Gs · ρw, is introduced to help identification of reactive clay-water systems. High values of λ identify systems that are sensitive to changes in pore fluid characteristics. An experimental procedure is suggested to acquire relevant sedimentation parameters. Data collected during sedimentation tests of kaolinite, bentonite, and disaggregated Pierre shale, Mancos shale, and Queenston shale are used to verify the model. Agreement between experimental data and the model suggests that this simple technique can be used to identify reactive shales in the field. Other applications arise in tailing pond modeling, drilling mud management, and clay liner reliability assessment.

Faunal and geochemical evidence for changes in intermediate water temperature and salinity in the western Coral Sea (northeast Australia) during the Late Quaternary

Abstract Ostracod assemblages and geochemical analyses of valves of specific ostracod taxa are used to reconstruct, both qualitatively and quantitatively, bottom-water temperatures (BWT) for the last 100,000 years in the western Coral Sea. The investigated core (51GC21) is situated in the lower reaches of the Antarctic Intermediate Water, at 1630 m water depth. First, we ran a Principal Coordinate Analysis (PCoA) of 42 surface samples from the Coral Sea, and then compared fossil assemblages with results of the PCoA. In addition, we selected well preserved speciments of the two genera Krithe and Bythocypris for Mg Ca analyses. The Mg Ca is used to infer past changes in BWT for intermediate waters of the western Coral Sea; results indicate large temperature fluctuations over the last 100,000 years. Of interest is the documentation that the BWT was similar to the present-day temperature during part of Isotope Stage 3. Comparison between our temperature record and the benthic foraminifer δ18O record of core 51GC21, and with the δ18O variations in seawater, as reconstructed by Labeyrie et al. (1987), allowed assessment of past changes in BWT salinity and density. Thus, we identify for the western Coral Sea three distinct periods on the basis of water mass density changes (i.e. for Isotope Stage 1, Stages 2, 3 and 4, and Stage 5). Our temperature record also indicates a good correlation with the 60°S summer insolation calculations for the period between 25,000 yr B.P. and 75,000 yr B.P. Comparison of our results from this study with other records from the western Pacific (the Ontong Java Plateau in particular) reveal the role of New Guinea as an oceanographic barrier. A wet phase recorded on continental Australia coincides with our high bottom-water temperature record for isotopic Stage 3.

SI Conversion

This paper assists engineers in the conversion of the complicated foot‐pound‐second (FPS) system to the simplified System International (SI), expressed in meters‐newtons‐seconds. It is useful in both analytical and dimensional domains. A short history of the methods is given for general information. The masses of some elements, compounds, liquids, and gases are given, and are expressed in “dimensionless” units as ratios of their unit mass densities, and those of the unit mass density of water, which equal unity. Eight examples are given, showing the precise method of conversion. The examples also provide analyses to be used for checking the answers to the problems. This method of conversion will help engineers acquire the skill of its application, and also will provide a basis for checking and controlling the creation of formulas that are elaborated upon in the analytical and dimension domains. Furthermore, a new parameter of solidity is also introduced as a ratio of the volume of solids to that of the total unit volume. Solidity is inversely proportional to porosity.

A Classroom Demonstration of Thermohaline Circulation

The movement of deep and bottom waters in the sea is largely a function of the thermohaline circulation. This circulation is important in influencing geologic processes ranging from the dissolution of biogenic siliceous and calcareous sediments to the formation of erosional unconformities. The thermohaline circulation is driven by differences in water mass density produced at high latitudes. This density-driven deep circulation is difficult to visualize but can be dynamically demonstrated by using the simple technique described.

General Criteria for the Validity of the Buckingham‐Darcy Flow Law

AbstractA detailed, first‐principles study is undertaken on the exact equation of linear momentum balance for water in an unsaturated soil. First, it is shown that an approximate momentum balance equation, presented originally by Raats and Klute, can be used to demonstrate unequivocably that the flow of water through a rigid, homogeneous, isotropic, unsaturated soil will obey the Buckingham‐Darcy law within 10−12 to 10−5 sec after a gradient in the total potential of soil water has been applied. Next, an exact equation of motion for the Fourier component of the water mass flux density vector is derived using standard methods in nonequilibrium statistical mechanics. This exact equation is employed to deduce the general physical criteria required for the Raats‐Klute equation to be an accurate expression. The results of the investigation lead to the conclusion that the Raats‐Klute equation will be accurate if: (i) the water mass density and mass flux density vector constitute a complete set of strongly coupled, macroscopic dynamical variables; and (ii) the time scale over which these two variables change significantly is much longer than that over which any other dynamical quantities vary. If these two conditions are met, then, according to statistical mechanics, the flow of water through unsaturated soil will be described accurately over all macroscopic time intervals by the Buckingham‐Darcy law.

MEASUREMENT OF THERMAL CONDUCTIVITY OF DAIRY PRODUCTS AND MARGARINES

ABSTRACTA line heat source thermal conductivity probe was used to measure the thermal conductivity of 28 dairy products and margarines at 0, 20, and 40†C. Water and fat contents and mass density of each sample were also measured and correlated to thermal conductivity.There was a strong positive correlation between thermal conductivity and water content, and an inverse correlation between thermal conductivity and fat content. Temperature did not appear to be a significant factor over the limited temperature range studied. Although there was some correlation between mass density and non‐fat solids fraction, no correlation was observed between mass density and thermal conductivity.