bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of acetyl, docosahexaenoyl‐glycerophosphocholine and its characterization using nuclear magnetic resonance
Authors: Polette A. , Deshayes C. , Chantegrel B. , Croset M. , Armstrong J. M. , Lagarde M.
Published: November 2006

Docosahexaenoic acid (DHA) circulates in mammals in lipoproteins and bound to serum albumin as a nonesterified fatty acid as well as esterified in lysophosphatidylcholine (lysoPC). 1‐Lyso,2‐DHA‐glycerophosphocholine (GPC) is an unstable isomer because of a primary alcohol at the sn‐1 position. To keep DHA at the sn‐2 position of lysoPC, its usual position for the corresponding lysoPC to be acylated into PC in tissues, we synthesized 1‐acetyl,2‐DHA‐GPC and confirmed its structure by use of nuclear magnetic resonance (NMR) spectroscopy in comparison with its positional isomer, 1‐DHA,2‐acetyl‐GPC. 1‐Lyso,2‐DHA‐GPC was prepared from 1‐stearoyl,2‐DHA‐GPC by enzymatic hydrolysis and purified by high‐performance liquid chromatography. The isomerization of 1‐lyso,2‐DHA‐GPC into 1‐DHA,2‐lyso‐GPC was obtained by keeping the former overnight at room temperature under nitrogen. Both lysoPC isomers were acetylated by acetic anhydride into 1‐acetyl,2‐DHA‐GPC and 1‐DHA,2‐acetyl‐GPC, respectively, and the resulting phospholipids were fully characterized by NMR. In particular, the 1,2 substitution pattern of the acetyl and DHA chains could be easily detected by 2D heteronuclear multibond correlation. We conclude that 1‐acetyl,2‐DHA‐GPC might be considered as a stable form of 1‐lyso,2‐DHA‐GPC for its delivery to tissues, if the latter exhibits acetyl hydrolase activity.
n−3 and n−6 fatty acid enrichment by dietary fish oil and phospholipid sources in brain cortical areas and nonneural tissues of formula‐fed piglets
Authors: Goustard‐Langelier Bénédicte , Guesnet Philippe , Durand Georges , Antoine Jean‐Michel , Alessandri Jean‐Marc
Published: November 2006

Sufficient availability of both n‐3 and n‐6 long‐chain polyunsaturated fatty acids (LCPUFA) is required for optimal structural and functional development in infancy. The question has been raised as to whether infant formulae would benefit from enrichment with 20 and 22 carbon fatty acids. To address this issue, we determined the effect of fish oil and phospholipid (LCPUFA) sources on the fatty acid composition of brain cortical areas and nonneural tissues of newborn piglets fed artificially for 2 wk. They were fed sow milk, a control formula, or the formula enriched with n‐3 fatty acids from a low‐20:5n‐3 fish oil added at a high or a low concentration, or the formula enriched with n‐3 and n‐6 fatty acids from either egg yolk‐ or pig brain‐phospholipids. Both the fish oil‐ and the phospholipid‐enriched formula produced significantly higher plasma phospholipid 22:6n‐3 concentrations than did the control formula. The 22:6n‐3 levels in the brain, hepatic, and intestinal phospholipids were significantly correlated with plasma values, whereas cardiac 22:6n‐3 content appeared to follow a saturable dose‐response. Feeding sow milk resulted in a much higher 20:4n‐6 content in nonneural tissues than did feeding formula. Supplementation with egg phospholipid increased the 20:4n‐6 content in the heart, red blood cells, plasma, and intestine in comparison to the control formula, while pig brain phospholipids exerted this effect in the heart only. The addition of 4.5% fish oil in the formula was associated with a decline in 20:4n‐6 in the cortex, cerebellum, heart, liver, and plasma phospholipids, whereas using this source at 1.5% limited the decline to the cerebellum, liver, and plasma. Whatever the dietary treatment, the phosphatidylethanolamine 20:4n‐6 level was 10–20% higher in the brain temporal lobe than in the parietal, frontal, and occipital lobes in the temporal lobe by administering the formula enriched with egg or brain phospholipids.

In conclusion, feeding egg phospholipids to neonatal pigs increased both the 22:6n‐3 content in the brain and the 20:4n‐6 content in the temporal lobe cortex. This source also increased the 22:6n‐3 levels in nonneural tissues with only minor alterations of 20:4n‐6. These data support the notion that infant formulae should be supplemented with both 22:6n‐3 and 20:4n‐6 rather than with 22:6n‐3 alone.
Abnormal serum lysophospholipids in multiple myeloma patients
Authors: Sasagawa Takayo , Okita Misako , Murakami Jun , Kato Tsutomu , Watanabe Akiharu
Published: November 2006

Lysophosphatidylcholine (LPC) and lysophosphatidic acid (LPA) mediate various kinds of biological activities and play an important role in cellular signal transduction. We analyzed serum phospholipids obtained from 16 multiple myeloma (MM) patients and observed that serum LPA level was significantly higher in MM patients (5.3±0.5 nmol/mL) than in normal controls (1.7±0.3 nmol/mL). LPC level was also higher than that in normal controls, and it correlated significantly with the concentration of LPA (r=0.678, P<0.01). In MM patients, palmitic acid/linoleic acid ratios in phosphatidylcholine and LPC were higher than those in normal controls. In the 12‐mon follow‐up study of two patients with the immune globulin G type, we recognized that the increase of LPC, LPA, and arachidonic acid/linoleic acid ratio in phosphatidylinositol corresponded with a decline in the serum albumin level and choline esterase activity.
Differential effect of N‐ethyl maleimide on Δ6‐desaturase activity in human fetal liver toward fatty acids of the n−6 and n−3 series
Authors: Rodriguez Annie , Sarda Pierre , Boulot Pierre , Leger Claude Louis , Descomps Bernard
Published: November 2006

The effect of N‐ethyl‐maleimide (NEM) on Δ5‐and Δ6‐desaturase activities and the incorporation of substrates and products into different microsomal lipid classes and phospholipid (PL) subclasses were studied in human fetal liver microsomes, obtained after legally approved therapeutic abortion. Desaturase activities were measured by a radiochemical method using reversed‐phase high‐performance liquid chromatography (HPLC). After nonphospholipid (NPL) and PL separation on silica cartridges, the radioactivity in different lipids of the NPL group was assessed by two‐dimensional thin‐layer chromatography, and their fatty acid (FA) composition by gas‐liquid chromatography. The PL subclasses were separated, and the distribution of radioactivity between products and substrates was determined in PL subclasses. NEM inhibited the Δ5‐ and Δ6‐desaturase activities in the n−6 series of FA but not the Δ6‐desaturase activity in the n−3 series, which suggests the existence of two distinct Δ6‐desaturases, one for the n−6 series and another for the n−3 series. Whether NEM was present or absent, most of the radioactivity was recovered in the free FA form (about 80%). The desaturation products, obtained in the presence or absence of NEM, were preferentially incorporated into PL, suggesting a channeling of the newly synthesized FA toward microsomal PL. The comparison of the distribution of substrates and products incorporated into the different PL classes showed that most of the labeled FA were incorporated into phosphatidylcholine and to a lesser degree into phosphatidylethanolamine.
Biosynthesis and localization of phosphatidyl‐scyllo‐inositol in barley aleurone cells
Authors: Carstensen Sven , Pliska‐Matyshak Gay , Bhuvarahamurthy Narasimhan , Robbins Kim M. , Murthy Pushpalatha P. N.
Published: November 2006

A novel isomer of phosphatidylinositol (PI), phosphatidyl‐scyllo‐inositol, was characterized in the aleurone cells of barley seeds. In this investigation, the subcellular localization of scyllo‐PI and the relative rates of biosynthesis and accumulation of [32P]phosphoric acid ([32Pi])‐labeled scyllo‐ and myo‐phosphoinositides in the plasma membrane and intracellular membrane pools were investigated. About 25% of the [32Pi]‐labeled phospholipids were present in plasma membrane and 75% in intracellular membranes. Incorporation of [32Pi] into scyllo‐PI was greater than into myo‐PI in both the plasma membranes and intracellular membranes at all time points investigated, thus suggesting a higher rate of biosynthesis; however, the data do not preclude reduced breakdown of labeled scyllo‐PI as a contributing factor. In vitro studies were conducted to investigate the presence of cytidinediphosphate diacylglycerol (CDP‐DG):scyllo‐inositol 3‐phosphatidyltransferase (scyllo‐PI synthase) and to optimize enzymatic activity. The inclusion of nonionic detergents (Brij 58 and Triton X‐100) effected significant enhancement in the biosynthesis of scyllo‐PI, whereas anionic, cationic, and zwitterionic detergents had little or no effect. This is the first evidence for CDP‐DG:scyllo‐inositol 3‐phosphatidyltransferase activity.
The isolation and characterization of right‐side‐out plasma membrane vesicles from barley aleurone cells
Authors: Robbins Kim M. , Bhuvarahamurthy Narasimhan , Pliska‐Matyshak Gay , Murthy Pushpalatha P. N.
Published: November 2006

Examination of organelle‐ and membrane‐specific processes such as signal transduction necessitates the use of plasma membrane vesicles with cytoplasmic side‐in orientation. we are interested in the structural identity and subcellular localization of in vivo [32P]phosphoric acid ([32Pi])‐labeled phosphoinositides, including the recently discovered phosphatidyl‐scyllo‐inositol, for signal transduction studies. In the first part of this investigation, plasma membrane vesicles from barley aleurone cells were isolated employing the aqueous polymer (Dextran and polyethylene glycol) two‐phase partition method. The membrane vesicles that partitioned into the upper and lower phases of the aqueous polymer two‐phase system were characterized and the purity of the vesicles ascertained by assaying for two marker enzymes, K+‐stimulated, Mg2+‐dependent adenosine triphosphatase (EC 3.6.1.3, ATPase), localized in the plasma membranes, and cytochrome c oxidase, localized in the mitochondria. Inhibitors for ATPases such as azide, molybdate, and vanadate were used to distinguish between plasma membrane‐associated and intracellular membrane‐as‐sociated ATPases. These inhibitor studies suggest that the plasma membrane preparation contained about 7% of intracellular membrane vesicles and the intracellular membrane fraction contained about 6% of plasma membrane vesicles. Orientation of the plasma membrane vesicles was ascertained by measuring the latent ATPase activity. These latency studies suggest that about 95% of the plasma membrane vesicles were of cytoplasmic side‐in orientation. In the second part of this investigation, intracellular distribution and in vivo [32Pi] labeling of phosphoinositides in the plasma membranes and intracellular membranes were investigated. Preferential accumulation of [32Pi]‐labeled phosphatidyl‐myo‐inositol monophosphate (myo‐PIP) and phosphatidyl‐myo‐inositol bisphosphate (myo‐PIP2) was observed in the plasma membrane. However, scyllo‐phosphatidylinositol (scyllo‐PI) was detected in both the plasma membrane and the intracellular membranes. The cellular concentration of myo‐phosphoinositides was determined, and, after 24 h of labeling with [32Pi], the ratio of radiolabel in myo‐PI, PIP, and PIP2 paralleled the relative concentrations in aleurone cells.
Principal component analysis of measured quantities during degradation of hydroperoxides in oxidized vegetable oils
Authors: Héberger Károly , Keszler Ágnes , Gude Michael
Published: November 2006

Decomposition of hydroperoxides in sunflower oil under strictly oxygen‐free conditions was followed by measuring peroxide values against time, absorbance values at 232 and 268 nm, para‐anisidine values, and by quantitative analyses of volatile products using various additives. The results were arranged in a matrix form and subjected to principal component analysis. Three principal components explained 89–97% of the total variance in the data. The measured quantities and the effect of additives were closely related. Characteristic plots showed similarities among the measured quantities (loading plots) and among the additives (score plots). Initial decomposition rate of hydroperoxides and the amount of volatile products formed were similar to each other. The outliers, the absorbance values, were similar to each other but carried independent information from the other quantities. Para‐anisidine value (PAV) was a unique parameter. Since PAV behaved differently during the course of hydroperoxide degradation, it served as a kinetic indicator. Most additives were similar in their effects on the mentioned quantities, but two outliers were also observed. Rotation of the principal component axes did not change the dominant patterns observed. The investigations clearly showed which variables were worth measuring to evaluate different additives.
Long‐term behavior of oil‐based varnishes and paints. Photo‐ and thermooxidation of cured linseed oil
Authors: Mallégol Jacky , Gardette Jean‐Luc , Lemaire Jacques
Published: November 2006

Thermooxidation at 100°C and photooxidation at wavelengths above 300 nm of dried oil films were evaluated. The chemical modifications of the networks were determined by infrared analysis coupled with gaseous treatments (NO, SF4, and NH3). The dried films are rather stable in thermooxidation, whereas in photooxidation, important degradation of the network occurs with many chain scissions. This photoinstability results from the presence of crosslinks that are sensitive to radical attack because of the lability of the hydrogen atom on the tertiary carbons. The photooxidation reactions are fully described in this paper. Yellowing of the cured samples, observed with ultraviolet‐visible and fluorescence spectrometries, rapidly is decreased by irradiation because the oil contaminants that are mainly responsible for the yellowness are photooxidized. On the contrary, yellowing slowly but continuously increases during thermooxidation at 100°C.
Preparation of conjugated soybean oil and other natural oils and fatty acids by homogeneous transition metal catalysis
Authors: Larock Richard C. , Dong Xiaoyang , Chung Steven , Reddy Ch. Kishan , Ehlers Laurie E.
Published: November 2006

The use of as little as 0.1 mol% [RhCl(C8H14)2]2, 0.25 mol% PtCl2(PPh3)2, or 0.5 mol% RuHCl(CO)(PPh3)3, where Ph = phenyl, catalyzes the isomerization of soybean oil to conjugated soybean oil under mild reaction conditions and in high yields. No hydrogenation products are detected with any of these catalysts. Preliminary physical tests have shown that the conjugated soybean oil has exceptional drying properties and the resulting coatings exhibit good solvent resistance. The [RhCl(C8H14)2]2 catalyst provides similarly high yields of other conjugated vegetable oils, conjugated linoleic acid, and conjugated ethyl linoleate. Other rhodium catalysts, such as RhCl(PPh3)3, have also been found to be effective for the conjugation of ethyl linoleate.
Detection of DNA during the refining of soybean oil
Authors: Gryson N. , Ronsse F. , Messens K. , De Loose M. , Verleyen T. , Dewettinck K.
Published: November 2006

The isolation of DNA from foodstuffs is the first step in the detection of genetically modified organisms. Refining processes, however, have an irrevocable influence on the quality and quantity of DNA and make detection in refined oil impossible. In order to determine the most significant step in removing DNA from crude soybean oil, two refining processes were considered: chemical refining and physical refining. Although conducted on a lab scale, quality parameters showed that the refining processes were good simulations of the industrial refining. From samples drawn at various refining stages, DNA was extracted with a protocol originally developed for the extraction of DNA from lecithin. The polymerase chain reaction results prove that the protocol was sufficiently useful for extracting DNA from soybean oil. The amplified DNA revealed that degumming is the most important step in removing DNA from crude soybean oil. After degumming, DNA was concentrated in the water fraction; no DNA could be amplified in the oil fractions. During physical degumming, degradation of DNA was observed.
Simultaneous detection of tocopherols, carotenoids, and chlorophylls in vegetable oils by direct injection C30 RP‐HPLC with coulometric electrochemical array detection
Authors: Puspitasari‐Nienaber Ni Luh , Ferruzzi Mario G. , Schwartz Steven J.
Published: November 2006

Detection and quantification of tocopherols, carotenoids, and chlorophylls in vegetable oil have been used to aid their authentication. Their importance in influencing the oxidative stability of vegetable oils and their possible health benefits have been shown in numerous studies. Therefore, the need for a rapid and reliable analysis method has become increasingly important. This study demonstrates the application of C30 RP‐HPLC with electrochemical detection for the simultaneous analysis of tocopherols, carotenoids, and chlorophylls in vegetable oils. Aliquots of vegetable oils were dissolved in appropriate solvents and injected directly without saponification, thus preventing sample loss or component degradation. Effective separation of tocopherols, carotenoids, and chlorophylls was achieved. Detection was performed using a coulometric electrochemical array detector set between 200 and 620 mV. For a 25‐μL injection, the respective detection limits for carotenoids, tocopherols, and chlorophylls were 1 fmol, 0.15 pmol, and 0.5 pmol, representing 1000‐, 25‐, and 5‐fold enhancement over the UV‐vis methodology. The detector response was linear between 0.01 and 2.00 μg/mL for all compounds studied. Within‐day variations (CV) were between 2.0 and 6.3%, whereas between‐day variations were between 2.7 and 7.4%. This method can be applied for rapid and sensitive analysis in the study of oil quality and adulteration.
Multivariate model for the prediction of total phenolic acids in crude extracts of polyphenols from canola and rapessed meals: A preliminary study
Authors: Naczk M. , Pink J. , Zadernowski R. , Pink D.
Published: November 2006

The feasibility of using UV spectrophotometry to develop multivariate models for prediction of total phenolic acids content in crude polyphenol extracts from defatted canola and rapeseed meals was investigated. The polyphenols were extracted from the meals with methanol/acetone/water (7∶7∶6, by vol). Partial least squares regression was used to correlate the spectral data of the crude polyphenols in methanol between 320 and 355 nm with the total phenolic acid content in canola and rapeseed meals. The Folin‐Denis assay was used to provide reference data for creating the model. The predictive ability of the model is good, as indicated by the RPD value (the ratio of the SD of data to the standard error of calibration) of 3.84.
Optimization of the composition of low‐fat oil‐in‐water emulsions stabilized by white lupin protein
Authors: Raymundo A. , Franco J. M. , Empis J. , Sousa I.
Published: November 2006

The effect of composition (protein, xanthan gum, and oil content) of lupin protein‐stabilized emulsions on their physical properties—droplet size distribution, rheological behavior, and texture—was studied. Droplet size distribution was measured by laser light‐scattering experiments, rheological parameters were determined from oscillatory and steady‐state flow measurements, and texture responses were obtained from texture profile analysis. Response surface methodology was used to optimize the emulsion composition using commercial mayonnaise parameters as a standard. An increase in protein, xanthan gum, or oil content produced, in the experimental range considered, an increase in the rheological and textural parameters studied, as well as a decrease in the average oil droplet diameter. It was possible to produce stable lupin protein‐stabilized emulsions with physical properties similar to those of commercial mayonnaise for a wide variety of protein, xanthan gum, and oil concentration values, which may be designed to suit market specifications.
Preparation of plastic fats with zero trans FA from palm oil
Authors: Jeyarani T. , Yella Reddy S.
Published: November 2006

A series of plastic fats containing no trans FA and having varying melting or plastic ranges, suitable for use in bakery, margarines, and for cooking purposes as vanaspati, were prepared from palm oil. The process of fractionating palm oil under different conditions by dry and solvent fractionation processes produced stearins of different yields. Melting characteristics of stearin fractions varied depending on the yield and the process. The lower‐yield stearins were harder and had a wider plastic range than those of higher yields. The fractions with yields of about 35% had melting profiles similar to those of commercial vanaspati. The plastic range of palm stearins was further improved by blending them with corresponding oleins and with other vegetable oils. The plasticity or solid fat content varied depending on the proportion of stearin. Blends with higher proportions of stearins were harder than those with lower proportions. the melting profiles of some blends, especially those containing 40–60% stearin of about 25% yield and 40–60% corresponding oleins or mahua or rice bran oils, were similar to those of commercial vanaspati and bakery shortenings. These formulations did not contain any trans FA, unlike those of commercial hydrogenated fats. Thus, by fractionation and blending, plastic fats with no trans acids could be prepared for different purposes to replace hydrogenated fats, and palm oil could be utilized to the maximum extent.
Influence of shearing and time on the rheological properties of milk chocolate during tempering
Authors: Briggs J. L. , Wang T.
Published: November 2006

The quality of chocolate is highly dependent on proper tempering. During tempering, crystals are formed as the chocolate is subjected to shear. The aim of this work was to evaluate the applicability of traditional rheological techniques to gain a better understanding of the relationship between rheological properties and the degree of shearing and time of tempering. Treatments of two shearing rates (15 and 30 s−1) covering four tempering times (0, 400, 600, and 800 s) were investigated. As samples were cooled from a melt temperature of 50°C, the apparent viscosity followed the Arrhenius equation. An induction time, which was affected by shear rate, was observed during tempering, followed by an increase in apparent viscosity, caused by formation of crystalline structures. Various characteristics of the rewarming curve were attributed to polymorphism. Steady‐shear constitutive models assessed after rewarming showed that the yield stress was dependent on shear and tempering time. Collectively, findings showed that traditional rheological methods may be used as tools to investigate crystallization and flow properties of molten chocolate indirectly during tempering.
Compatibility in the Biomphalaria glabrata/Echinostoma caproni model: new candidate genes evidenced by a suppressive subtractive hybridization approach
Authors: BOUCHUT A. , COUSTAU C. , GOURBAL B. , MITTA G.
Published: November 2006

In order to elucidate mechanisms underlying snail/echinostome compatibility, numerous molecular studies comparing transcripts and proteins of Biomphalaria glabrata susceptible or resistant to Echinostoma caproni were undertaken. These studies focused on plasma and haemocytes of the two strains and revealed that some transcripts and/or proteins were differentially expressed between strains. The aim of the present study was to develop a complementary transcriptomic approach by constructing subtractive libraries. This work revealed some candidate transcripts already identified in previous studies (calcium-binding proteins and glycolytic enzymes) as well as novel candidate transcripts that were differentially represented between strains of B. glabrata. Among these newly identified genes, we revealed several genes potentially involved in immune processes encoding proteases, protease inhibitors, a lectin, an aplysianin-like molecule, and cell adhesion molecules.
Nitrogen availability and soil N2O emissions following conversion of forests to coffee in southern Sumatra
Authors: Verchot Louis V. , Hutabarat Lusida , Hairiah Kurniatun , van Noordwijk Meine
Published: November 2006

Changes in land use impact on the N cycle with both local and global consequences. We examined how conversion of forest to agriculture in one catchment in southern Sumatra altered N availability and soil N2O emission. Measurements were made along a chronosequence of forest land converted to coffee gardens. A number of different management practices were also examined. Inorganic N stocks and N cycling rates were highest in the forest and lower in the coffee gardens. The forest and young conversion sites appeared to be N limited, whereas the older agricultural sites and the more intensively managed sites were not as strongly N limited. N2O emissions were low in the forest (<2 kgN ha−1yr−1) and increased sharply following deforestation. Emissions on recently cleared land were 4.6 kgN ha−1yr−1 and 8.4 kgN ha−1yr−1 in a 1‐year‐old coffee garden. Emissions in the older coffee gardens were lower with the lowest flux observed in a 10 year old site (1.8 kgN ha−1yr−1). We explored the effects of different types of management approaches that farmers are using in this landscape. Emissions in an 18‐year‐old multistrata coffee garden with a significant overstory of N fixing trees were 5 times greater (15.5 kg ha−1yr−1) than emissions from forests. We also found that intensive organic matter management produced high emissions. To understand the spatial and temporal variability of the N2O emissions we used the hole‐in‐the‐pipe conceptual model. N2O fluxes were lowest on N limited sites. Soil water content also played an important role and emissions were highest when water filled pore space (WFPS) was between 85 and 95%. A number of formulations of this model have been applied in different ways over the years to explain spatial and temporal variation in the soil N‐oxide flux, and in this study we found the mechanistic explanation useful. Our study suggests that land use change and intensification of agriculture in N limited highland landscapes may significantly increase the biosphere to atmosphere flux of N gases.
Restraining segments and reactivation of the Santa Monica–Dume–Malibu Coast fault system, offshore Los Angeles, California
Authors: Sorlien Christopher C. , Kamerling Marc J. , Seeber Leonardo , Broderick Kris G.
Published: November 2006

A regional west striking system of surface and blind faults transects northern metropolitan Los Angeles, separating the Santa Monica Mountains from two deep sedimentary basins. The surface faults include the Santa Monica, Dume, and Malibu Coast faults. The three‐dimensional (3‐D) geometries of these faults and deformed dated strata were examined in order to determine how oblique shortening is accommodated, how structural relief grows along a mountain front, and how block translation is related to block rotation. Industry seismic reflection, well, and outcrop data were used to construct digital structure‐contour maps of several of these faults and three stratigraphic horizons that intersect them. These maps, swath bathymetry, digital elevation models, and seismicity were incorporated into a 3‐D digital database. Modeling included new approaches to determining strike‐slip displacement by separate analyses of shortening and structural relief in a restraining double bend. Stratigraphic thicknesses indicate Miocene extension across the Santa Monica and Dume faults, which have been reactivated as a single or linked moderately dipping arcuate fault that accommodates one coherent block motion via left‐lateral and left‐reverse displacement. Modeling indicates 5 km (+8/−1 km) of left‐lateral displacement on part of the Santa Monica–Dume fault and ∼11° of clockwise rotation of the Santa Monica Mountains during the last ∼4 ± 1 m.y. Modern displacement rates modeled from GPS data are similar to our modeled post‐∼4 Ma rates of westward escape and clockwise rotation of the Santa Monica Mountains.
Evaluation of lava effusion rate and viscosity from other flow parameters
Authors: Tallarico A. , Dragoni M. , Zito G.
Published: November 2006

The effusion rate of lava from a volcanic vent is an important quantity controlling the length of the ensuing lava flow. The ability to evaluate the effusion rate is therefore of importance to estimate the hazard connected with the flow. In the present paper we provide formulae giving the effusion rate and the lava viscosity for two‐ and three‐dimensional (3‐D) Newtonian and Bingham flows. In order to keep the difference between the actual lava effusion rate and the model estimation within 10%, the 3‐D model must be used if the ratio between the width and the thickness of the lava flow does not exceed the value 13. The Bingham model must be used if the ratio between the plug thickness and the thickness of the lava flow exceeds the value 0.07. An analogous consideration can be made for viscosity.
Magnetostratigraphy of Cenozoic sediments from the Xining Basin: Tectonic implications for the northeastern Tibetan Plateau
Authors: Dai Shuang , Fang Xiaomin , Dupont‐Nivet Guillaume , Song Chunhui , Gao Junping , Krijgsman Wout , Langereis Cor , Zhang Weilin
Published: November 2006

The Xining subbasin of the Longzhong basin holds the longest continuous Cenozoic stratigraphic record at the margin of the northeastern Tibetan Plateau. Despite a rich biostratigraphic content (including the Xiejia mammal fauna), the tectonic evolution of the basin is largely unconstrained. In this study we present stratigraphic, biostratigraphic, and magnetostratigraphic results that provide a basis for reconstructing the Cenozoic tectonic evolution of the Xining basin with respect to adjacent regions of the northeastern Tibetan Plateau. Magnetostratigraphic analysis from three red bed sections in the Xining basin indicates continuous deposition at low and nearly constant accumulation rates (average 2.2 cm/kyr) from 52.0 to 17.0 Ma. We interpret this result to indicate that no major regional tectonic event implying large sediment accumulation variations has affected the Xining basin deposition during this considerable time window. In detail, accumulation rate variations outline a three‐stage evolution with 1.8 cm/kyr from 52.0 Ma to 34.5 Ma, 4.1 cm/kyr from 34.5 to 31.0 Ma, and 2.3 cm/kyr from 31.0 to 17.0 Ma. The second‐order increase between 34.5 and 31.0 Ma can be interpreted to result from either a distal tectonic event or to be of climatic origin. Although the region was tectonically quiescent for much of the Cenozoic, tectonic activity occurred during basin initiation (or reactivation) at circa 55.0–52.5 Ma and during intense basin deformation after 17.0 Ma.
Gas age–ice age differences and the chronology of the Vostok ice core, 0–100 ka
Authors: Bender M. L. , Floch G. , Chappellaz J. , Suwa M. , Barnola J.‐M. , Blunier T. , Dreyfus G. , Jouzel J. , Parrenin F.
Published: November 2006

Gas is trapped in polar ice at depths of ∼50–120 m and is therefore significantly younger than the ice in which it is embedded. The age difference is not well constrained for slowly accumulating ice on the East Antarctic Plateau, introducing a significant uncertainty into chronologies of the oldest deep ice cores (Vostok, Dome Fuji, and Dome C). We recorrelate the gas records of Vostok and Greenland Ice Sheet Project 2 (GISP2) cores in part on the basis of new CH4 data and use these records to construct six Vostok chronologies that use different assumptions to calculate gas age–ice age differences. We then evaluate these chronologies by comparing times of climate events at Vostok with correlative events in the well‐dated Byrd ice core (West Antarctica). From this evaluation we identify two leading chronologies for the Vostok core that are based on recent models of firn temperature, firn densification, and thinning of upstream ice. One chronology involves calculating gas age–ice age differences from these models. The second, new, approach involves calculating ice depths in the core that are contemporaneous with depths in the same ice core whose gas ages are well constrained. This latter approach circumvents problems associated with highly uncertain accumulation rates in the Vostok core. The uncertainty in Vostok chronologies derived by correlating into the GISP2 gas record remains about ±1 kyr, and high‐precision correlations continue to be difficult.
Evolution of ozone, particulates, and aerosol direct radiative forcing in the vicinity of Houston using a fully coupled meteorology‐chemistry‐aerosol model
Authors: Fast Jerome D. , Gustafson William I. , Easter Richard C. , Zaveri Rahul A. , Barnard James C. , Chapman Elaine G. , Grell Georg A. , Peckham Steven E.
Published: November 2006

A new fully coupled meteorology‐chemistry‐aerosol model is used to simulate the urban‐ to regional‐scale variations in trace gases, particulates, and aerosol direct radiative forcing in the vicinity of Houston over a 5 day summer period. Model performance is evaluated using a wide range of meteorological, chemistry, and particulate measurements obtained during the 2000 Texas Air Quality Study. The predicted trace gas and particulate distributions were qualitatively similar to the surface and aircraft measurements with considerable spatial variations resulting from urban, power plant, and industrial sources of primary pollutants. Sulfate, organic carbon, and other inorganics were the largest constituents of the predicted particulates. The predicted shortwave radiation was 30 to 40 W m−2 closer to the observations when the aerosol optical properties were incorporated into the shortwave radiation scheme; however, the predicted hourly aerosol radiative forcing was still underestimated by 10 to 50 W m−2. The predicted aerosol radiative forcing was larger over Houston and the industrial ship channel than over the rural areas, consistent with surface measurements. The differences between the observed and simulated aerosol radiative forcing resulted from transport errors, relative humidity errors in the upper convective boundary layer that affect aerosol water content, secondary organic aerosols that were not yet included in the model, and uncertainties in the primary particulate emission rates. The current model was run in a predictive mode and demonstrates the challenges of accurately simulating all of the meteorological, chemical, and aerosol parameters over urban to regional scales that can affect aerosol radiative forcing.
Seasonally varying modes in long‐term variability of European precipitation during the 20th century
Authors: Zveryaev Igor I.
Published: November 2006

A gridded monthly terrestrial gauge‐based precipitation for 1901–2000 from the Climatic Research Unit, University of East Anglia, set is used to investigate leading seasonal modes in the long‐term precipitation variability over Europe and their links to atmospheric circulation. Performed empirical orthogonal function (EOF) analysis has shown that the leading modes of precipitation variability over Europe are clearly season‐dependent. The character of the links between regional precipitation and atmospheric circulation also features essential seasonality. The first EOF modes of the winter, spring, and summer seasonal mean precipitation over Europe are associated with the North Atlantic Oscillation (NAO). However, because the summer NAO differs significantly from the winter and spring NAO, the first EOF mode of the summer precipitation has a spatial‐temporal structure which is principally different from those of the winter and spring seasons. The first EOF mode of the fall precipitation is not associated with the NAO. This mode demonstrates a strong link to the Scandinavian teleconnection pattern. The second EOF modes of the winter and fall precipitation are linked to the east Atlantic and the NAO teleconnection patterns, respectively. Analysis of running correlations between the principal components of the leading EOF modes of precipitation and the NAO index has revealed nonstationarity of the links between European precipitation and the NAO. Moreover, there is evident seasonality in the character of the long‐term changes of the above links.
Uncertainties in, and interpretation of, carbon flux estimates using the eddy covariance technique
Authors: Loescher H. W. , Law B. E. , Mahrt L. , Hollinger D. Y. , Campbell J. , Wofsy S. C.
Published: November 2006

Whole ecosystem carbon dioxide (CO2) exchange estimated with the eddy covariance (EC) technique has been central to studies on the responses of terrestrial ecosystems to disturbance and intra‐annual and interannual variations in climate, but challenges exist in understanding and reducing the uncertainty in estimates of net ecosystem exchange (NEE) of CO2. We review the potential uncertainties associated with the eddy covariance technique, including systematic errors from insensitivity to high‐frequency turbulence, random errors from inadequate sample size associated with averaging period, vertical and horizontal advection issues, and selection criteria for removing periods of inadequate mixing from further analyses. We also discuss benefits and caveats of using independent measurements to evaluate EC‐derived NEE, such as comparisons of EC‐derived annual NEE and allometric net ecosystem production estimates (NEP) and interpretation of nighttime NEE with scaled chamber‐based estimates of ecosystem respiration.
Modeling ice growth on Canadian lakes using artificial neural networks
Authors: Seidou O. , Ouarda T. B. M. J. , Bilodeau L. , Hessami M. , St‐Hilaire A. , Bruneau P.
Published: November 2006

This paper presents artificial neural network (ANN) models designed to predict ice in Canadian lakes and reservoirs during the early winter ice thickness growth period. The models fit ice thickness measurements at one or more monitored lakes and predict ice thickness during the growth period either at the same locations for dates without measurements (local ANN models) or at any site in the region (regional ANN model), provided that the required meteorological input variables are available. The input variables were selected after preliminary assessments and were adapted from time series of daily mean air temperature, rainfall, cloud cover, solar radiation, and average snow depth. The results of the ANN models compared well with those of the deterministic physics‐driven Canadian Lake Ice Model (CLIMO) in terms of root‐mean‐square error and in terms of relative root‐mean‐square errors. The ANN models predictions were also marginally more precise than a revised version of Stefan's law (RSL), presented herein. They reproduced some intrawinter and interannual growth rate fluctuations that were not accounted for by RSL. The performance of the models results in good part from a careful choice of input variables, inspired from the work on deterministic models such as CLIMO. ANN models of ice thickness show good potential for the use in contexts where ad hoc adjustments are desirable because of the limited availability of measurements and where poor data nature, availability, and quality precludes using deterministic physics‐driven models.
Sensitivity of top‐down estimates of CO sources to GCTM transport
Authors: Arellano Avelino F. , Hess Peter G.
Published: November 2006

Estimates of CO sources derived from inversions using satellite observations still exhibit discrepancies. Here, we conduct controlled inverse analyses to elucidate the influence of model transport on the robustness of regional CO source estimates. We utilized Model of Ozone and Related chemical Tracers global chemical transport models (GCTM) driven by National Centers for Environmental Prediction and European Centre for Medium‐Range Weather Forecast reanalyses, and GEOS‐Chem GCTM driven by Global Modeling and Assimilation Office assimilated meteorology to generate response functions for prescribed regional CO sources. We find that inter‐model differences in CO due to differences in transport are within 10–30% of inter‐model mean CO concentration. However, these differences can translate to regionally significant spread in source estimates. While we find that CO source estimates for East Asia and North Africa are reasonably robust, we find inconsistencies and inter‐model spread of greater than 40% in our source estimates for Indonesia, South America, Europe and Russia. This indicates the need for rigorous assessment on uncertainties in top‐down source estimates through model inter‐comparisons and ensemble approaches.
Multi‐scale/multi‐fluid simulations of the post plasmoid current sheet in the terrestrial magnetosphere
Authors: Harnett E. M. , Winglee R. M. , Paty C.
Published: November 2006

Multi‐scale/multi‐fluid simulations are used to provide the first high resolution (∼120 km) simulations of a thin tail current sheet within the global framework of the Earth's magnetosphere during southward IMF. The current sheet in the tail is shown to thin to 1200 km in the wake of a plasmoid. A hydrogen boundary layer forms on the outside of the current sheet with a thickness on the order of 900 km. Kinks form in the cross‐tail direction in the thin current sheet with a wavelength on the order of 1 RE. The amplitude grows up to 0.5 RE before the kinks become unstable, leading to the reformation of a thicker current sheet. These kinks initiate just earthward of the reconnection region and propagate both tailward, and earthward until they reach dipolar fieldlines. These processes occur as the result of the coupling between cross‐tail flows in O+ and field‐aligned flows in ionospheric H+.
Origins of horizontal divergence in the auroral thermosphere: A modelling study
Authors: Cooper S. L. , Conde M.
Published: November 2006

It has widely been presumed that most horizontal divergence in Earth's thermospheric wind field results from pressure gradients established by localized heating. A simplified local‐scale, three‐dimensional, time‐dependent, finite element model has been used to determine other possible sources of horizontal divergence over spatial scales of less than 200 km. In a limited study to test the hypothesis that inertial processes contribute to the generation of horizontal divergence, a non‐divergent, time‐varying ion convection pattern was used to deposit momentum. Divergent neutral winds resulted. Divergence was induced by both localized heating and time varying momentum deposition. Further, for the geometries considered, thermal expansion resulting from heating was the dominant driver of the horizontal gradient perpendicular to the background flow, whereas inertial processes dominated the horizontal gradient parallel to the background flow.
Methane and carbon dioxide emissions from tropical reservoirs: Significance of downstream rivers
Authors: Guérin Frédéric , Abril Gwenaël , Richard Sandrine , Burban Benoît , Reynouard Cécile , Seyler Patrick , Delmas Robert
Published: November 2006

Methane (CH4) and carbon dioxide (CO2) concentrations and water‐air fluxes were measured in three tropical reservoirs and their respective rivers downstream of the dams. From reservoirs, CH4 and CO2 flux were in the range of 3 ± 2 and 254 ± 392 mmol.m−2.d−1, respectively. Rivers downstream of dams were significantly enriched in CH4 and CO2 originating from reservoir hypolimnions. From rivers, CH4 and CO2 flux were in the range of 60 ± 38 and 859 ± 400 mmol.m−2.d−1, respectively. Despite their relatively small surfaces, rivers downstream of dams accounted for a significant fraction (9–33% for CH4 and 7–25% for CO2) of the emissions across the reservoir surfaces classically taken into account for reservoirs. A significant fraction of CH4 appeared to degas at the vicinity of the dam (turbines and spillways), although it could not be quantified.
Outward radial diffusion driven by losses at magnetopause
Authors: Shprits Y. Y. , Thorne R. M. , Friedel R. , Reeves G. D. , Fennell J. , Baker D. N. , Kanekal S. G.
Published: November 2006

Loss mechanisms responsible for the sudden depletions of the outer electron radiation belt are examined based on observations and radial diffusion modeling, with L*‐derived boundary conditions. SAMPEX data for October–December 2003 indicate that depletions often occur when the magnetopause is compressed and geomagnetic activity is high, consistent with outward radial diffusion for L* > 4 driven by loss to the magnetopause. Multichannel Highly Elliptical Orbit (HEO) satellite observations show that depletions at higher L occur at energies as low as a few hundred keV, which excludes the possibility of the electromagnetic ion cyclotron (EMIC) wave‐driven pitch angle scattering and loss to the atmosphere at L* > 4. We further examine the viability of the outward radial diffusion loss by comparing CRRES observations with radial diffusion model simulations. Model‐data comparison shows that nonadiabatic flux dropouts near geosynchronous orbit can be effectively propagated by the outward radial diffusion to L* = 4 and can account for the main phase depletions of outer radiation belt electron fluxes.
Stability of arc lower crust: Insights from the Talkeetna arc section, south central Alaska, and the seismic structure of modern arcs
Authors: Behn Mark D. , Kelemen Peter B.
Published: November 2006

One process for the formation of continental crust is the accretion of arc terranes at continental margins. A longstanding problem with this model is that although the composition of the continental crust is andesitic, the majority of arc lavas are basaltic. Moreover, those arc lavas that are andesitic tend to be evolved (lower Mg #) compared to the continental crust. Continental crust can be produced through mixing of basaltic and silicic arc lava compositions, assuming that mafic cumulates formed during generation of the silicic component are removed. If these cumulates are denser than the underlying mantle, removal can occur via foundering of lower arc crust. Indeed, field observations of the Talkeetna arc section in south central Alaska, combined with modeling of fractionation in primitive arc magmas, suggest that large amounts of primitive gabbronorite and pyroxenite are missing from the lower crust. Using rock compositions from the Talkeetna section and the free energy minimization program Perple_X, we calculated equilibrium mineral assemblages for a range of gabbroic and ultramafic compositions at P, T, oxygen fugacity (fO2), and H2O contents appropriate for arc lower crust. The quartz‐olivine‐garnet‐free mineral assemblage found in the Talkeetna gabbronorites (and in the similar Kohistan section in Pakistan) defines a narrow range of fO2 centered on NNO+2 (±1 log unit). Predicted mineral assemblages calculated under these conditions were used to estimate the density and seismic structure of the arc lower crust. We find that the missing gabbroic and ultramafic rocks from the Talkeetna section were likely denser than the underlying mantle, while the gabbronorites that remain are either neutrally or slightly positively buoyant. Generalizing, we show that lower crustal Vp > 7.4 km/s in modern arcs is indicative of lower crust that is convectively unstable relative to the underlying mantle. However, most lower crust in modern arcs is observed to have Vp < 7.4 km/s, implying that gravitationally unstable material must founder rapidly on geologic timescales, or high Vp plutonic rocks crystallize beneath the Moho.