Bacterial and eukaryotic intact polar lipids in the eastern subtropical South Pacific: Water-column distribution, planktonic sources, and fatty acid composition

Fatty acids are generally the most abundant lipid molecules in plankton, and thus play a central role in the cycling of organic matter in the upper ocean. These fatty acids are primarily derived from intact polar diacylglycerolipids (IP-DAGs), which compose cell membranes in plankton. The molecular diversity of IP-DAGs in the upper ocean remains to be fully characterized, and the advent of high performance liquid chromatography/electrospray ionization-mass spectrometry (HPLC/ESI-MS) approaches have now provided the opportunity to readily analyze IP-DAGs from marine planktonic communities. We used HPLC/ESI-MS to determine the concentrations of three classes of phospholipids (phosphatidlyglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC)), three classes of betaine lipids (diacylglyceryl trimethylhomoserine (DGTS), diacylglyceryl hydroxymethyl-trimethyl-β-alanine (DGTA), and diacylglyceryl carboxyhydroxymethylcholine (DGCC)), and three classes of glycolipids (monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG)) in plankton filtered (>0.2 μm) from seawater collected within the euphotic zone of the eastern South Pacific. The distributions of these IP-DAGs along the cruise transect provided important new insights on their tentative planktonic sources. Complementary data from our cruise, a principle components analysis of our IP-DAG concentrations, observed fatty acid compositions of IP-DAG classes and published IP-DAG distributions in pure cultures of plankton suggest that heterotrophic bacteria were the dominant sources of PG and PE, while MGDG and SQDG originated primarily from Prochlorophytes. The origins of the other classes of IP-DAGs were less clear, although it is likely that PC, DGTS, DGTA, and DGCC were derived primarily from eukaryotic phytoplankton. The molecular distributions of fatty acids attached to the different classes of IP-DAGs were generally distinct from one another, and suggest that reported distributions of total fatty acids (as analyzed by gas chromatography) in the literature should be regarded as homogenized mixtures of distinct molecular pools of fatty acids.     

Realistic triaxial density–potential–force profiles for stellar systems and dark matter haloes

Popular models for describing the luminosity–density profiles of dynamically hot stellar systems (e.g. Jaffe, Hernquist, Dehnen) were constructed to match the deprojected form of de Vaucouleurs' R ^1/4 light-profile. However, we now know that elliptical galaxies and bulges display a mass-dependent range of structural profiles. To compensate this, the model in Terzić & Graham was designed to closely match the deprojected form of Sérsic R ^{1/ n} light-profiles, including deprojected exponential light-profiles and galaxies with partially depleted cores. It is thus applicable for describing bulges in spiral galaxies, dwarf elliptical galaxies, both 'power-law' and 'core' elliptical galaxies, also dark matter haloes formed from Λ cold dark matter cosmological simulations. In this paper, we present a new family of triaxial density–potential–force triplets, which generalizes the spherical model reported in Terzić & Graham to three dimensions. If the (optional) power-law core is present, it is a five-parameter family, while in the absence of the core it reduces to three parameters. The isodensity contours in the new family are stratified on confocal ellipsoids and the potential and forces are expressed in terms of integrals which are easy to evaluate numerically. We provide the community with a suite of numerical routines for orbit integration, which feature: optimized computations of potential and forces for this family; the ability to run simulations on parallel platforms; and modular and easily editable design.     

The concentration control of soluble copper in a mine tailings stream

Comparison of decreasing total copper content and increasing pH of an abandoned copper mine drainage stream to the stability fields of malachite, tenorite, and cupric hydroxide indicates that soluble copper is not lost by precipitation but by sorption on the stream sediments.     

A theory of concentric, kink and sinusoidal folding and of monoclinal flexuring of compressible, elastic multilayers: VII. development of folds within Huasna Syncline, San Luis Obispo County, California

Folds in the Huasna area of the southern Coast Ranges of California provide an opportunity to study different fold forms and to estimate dimensional and relative rheological properties of rocks at the time of folding. Plunging, concentric-like and chevron-like folds with wavelengths ranging from about 0.1 to 1 km are clearly visible in natural exposures at the south end of the Huasna syncline, which has a wavelength of 12–16 km. Examination of two fresh roadcut exposures in the Miocene Monterey Formation suggests that folding within part of the Monterey was accommodated primarily by layer-parallel slip between structural layers with thicknesses ranging from 30 to 43 m, even though lithologic layers range from a few mm to a few dm in thickness. This part of the Monterey is folded into a series of concentric-like folds, with chevron-like folds at their cores and with a ratio of wavelength to total thickness of layers of about . Theoretical analysis of multilayers, comprised of identical, elastic or elastic—plastic layers with frictionless contacts, indicates that the effective, or weighted-average thickness of structural layers corresponding with an ratio of 0.42 is about 41 m. Thus, the theoretical predictions are roughly in agreement with available data concerning these folds.Thicknesses of structural units in other folds of this area are inadequately known to closely check theoretical predictions, but most of the data are consistent with predictions. An exception is the Huasna syncline which has a larger wavelength than we would predict. There are several likely explanations for this discrepancy. Layers in the underlying Franciscan complex may have taken part in the folding, making our estimates of total thickness too small. The basement rocks may have been much softer, relative to the overlying sedimentary rocks, than we assumed. The Huasna syncline could be partly a result of gravitational instability of relatively low density, Miocene siliceous and porcelaneous shales, overlain by relatively high density, Pliocene sandstones.The Huasna syncline and some of the smaller folds in the Miocene rocks are doubly in the northwest—southeast direction. Further, the maximum compression was approximately normal to the traces of the large faults in this part of California.     

Franciscan melanges compared with olistostromes of Taiwan and Italy

Details of origin of Franciscan melanges are unknown, although subduction is accepted as the controlling process. Some melanges near plate boundaries in Taiwan and Italy are evidently olistostromes. How do Franciscan melanges compare with these? The Lichi melange and units of “argille scagliose” type in the Northern Apennines rest upon normal marine sediments. The time of accumulation was brief, as shown by limiting time brackets. These key types of evidence for olistostrome origin are rare or absent in the Franciscan, but the pervasive shearing would probably have obliterated such evidence.Similarities between the above-cited olistostromes and Franciscan melanges include the following: argillaceous matrix; large and small blocks of sedimentary rocks and ophiolites; phacoidal and joint-block shapes; soft-sediment deformation in some sandstone; rotation of blocks; extreme dispersal of distinctive rocks; reappearance of older rocks at younger levels. Collectively, these similarities suggest that Franciscan melanges were originally assembled by olistostrome accumulation.Differences between presumed olistostromes and the Franciscan include the following, in addition to stratigraphic relations mentioned above. The Lichi melange shows faint original gross layering where shearing is minimal. Franciscan melanges show various compositional units, but shearing allows tectonic explanations. Blueschist metamorphism is rare or absent in olistostromes of Taiwan and the Northern Apennines. It occurs in the Franciscan not only in random blocks, but also as extensive units of schist and phyllite near the structural top of the complex, toward the “hanging wall” (Great Valley sequence). In the structurally lowest levels, only zeolite facies metamorphism is prevalent. Similar generalities apply to ages of rocks at highest and lowest structural levels. The age distribution would be just the opposite if the entire Franciscan were simply an east-dipping pile of olistostromes.It is concluded that neither subduction alone nor olistostromes alone could have produced all the features of Franciscan melanges, but both played an important role. Critical original features of olistostromes have been modified or destroyed by recurrent underthrusting.     

Laboratory actinide partitioning: Whitlockite/liquid and influence of actinide concentration levels

Fission and alpha track radiography techniques have been used to measure partition coefficients (D) at trace (ppm) concentration levels for the actinide elements Th, U, and Pu between synthetic whitlockite and coexisting “haplobasaltic” silicate liquid at 1 bar pressure and 1250°C at oxygen fugacities from 10^?8.5 and 10^?0.7 bars. Pu is much more readily incorporated into crystalline phases than is U or Th under reducing conditions (fO₂ = 10^?8.5), because Pu is primarily trivalent, whereas U and Th are tetravalent. Definitive valence state assignments cannot be made, but our best estimates of corrected partition coefficients for Pu⁺³, Pu⁺⁴, Th⁺⁴, U⁺⁴, and U⁺⁶ are, for whitlockite 3.6/<?0.6/1.2/0.5/?0.002. The effect of changing pressure and liquidus temperature is relatively small, which probably reflects a weak temperature dependence for D (whitlockite) but possibly could be due to cancellation of opposing temperature and pressure effects. Comparison of experiments at trace U levels with those containing percent concentrations of UO₂ indicate that Si is involved in the substitution of U in whitlockite with U + 2Si ? Ca + 2P being the most likely mechanism. D_u is lower. 0.3 vs 0.5. at percent levels compared to 20 ppm. This is best explained by the effect of U on melt structure or by a decrease in the fraction of tetravalent U at high U concentrations.     

A comparison of a Hi/Lo GPS constellation with a populated conventional GPS constellation in support of RTK: A covariance analysis

This study makes an initial comparison of three GPS-like constellations. Starting with a simplified constellation of 25 GPS satellites as a reference, GPS(25), we determine what kinematic positioning improvements would result from a constellation comprising a Hi component of 16 GPS satellites (at roughly 16.8 earth radii) coupled with a Lo component of 49 GPS satellites (at roughly 2.1 earth radii). We also include a GPS constellation of 49 GPS satellites, GPS(49), which comprises orbits like the GPS(25) constellation. The GPS(49) and the Hi(16)/Lo(49) constellations have semi-major axes selected so that they have exactly the same average number of satellites above 7.5 degrees elevation (averaged over 24 hours). What motivated this study was a need to measure the benefits, to precision differential kinematic positioning methods (i.e., RTK), which result from the higher Doppler shifts (hence speedier integrated Doppler) generated by the Lo component. Quicker initial convergence was anticipated, of course.     

Isotope Dilution MC-ICP-MS Rare Earth Element Analysis of Geochemical Reference Materials NIST SRM 610, NIST SRM 612, NIST SRM 614, BHVO-2G, BHVO-2, BCR-2G, JB-2, WS-E, W-2, AGV-1 and AGV-2

We present data for the concentrations of eleven rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu) in eleven international geochemical reference materials obtained by isotope dilution multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We have analysed both rock powders and synthetic silicate glasses, and the latter provide precise data to support the use of these as reference materials for in situ trace element determination techniques. Our data also provide precise measurements of the abundance of mono-isotopic Pr in both glasses and powders, which allows more accurate constraints on the anomalous redox-related behaviour of Ce during geochemical processes. All materials were analysed in replicate providing data that typically reproduce to better than one percent. Sm/Nd ratios in all these materials also reproduce to better than 0.2% and are accurate to < 0.2% and can thus be used as calibrants for Sm-Nd geochronology. Our analyses agree well with existing data on these reference materials. In particular, for NIST SRM 610, USGS BHVO-2, AGV-1 and AGV-2, our measured REE abundances are typically within < 2% (and mostly 1%) of REE concentrations previously determined by isotope dilution analysis and thermal ionisation mass spectrometry, consistent with the higher degree of precision and accuracy obtained from isotope dilution techniques. Close agreement of results between basaltic glass reference materials USGS BHVO-2G and BCR-2G and the BHVO-2 and BCR-2 powders from which they were created suggests that little fractionation, concentration or dilution of REE contents occurred during glass manufacture.