bluuebunny/crossref_metadata_2025 huggingface dataset:
Purification of tocopherols and phytosterols by a two‐step in situ enzymatic reaction
Authors: Watanabe Yomi , Nagao Toshihiro , Hirota Yoshinori , Kitano Motohiro , Shimada Yuji
Published: November 2006

The purification of tocopherols and phytosterols (referred to as sterols) from soybean oil deodorizer distillate (SODD) was attempted. Tocopherols and sterols in the SODD were first recovered by short‐path distillation, which was named sODD tocopherol/sterol concentrate (SODDTSC). The SODD‐TSC contained MAG, DAG, FFA, and unidentified hydrocarbons in addition to the two substances of interest. It was then treated with Candida rugosa lipase to convert sterols to FA steryl esters, acylglycerols to FFA, and FFA to FAME. Methanol (MeOH), however, inhibited esterification of the sterols. Hence, a two‐step in situ reaction was conducted: SODDTSC was stirred with 20 wt% water and 200 U/g mixture of C. rugosa lipase at 30°C, and 2 moles of MeOH per mole of FFA was added to the reaction mixture after 16h. The lipase treatment for 40 h in total achieved 80% conversion of the initial sterols to FA steryl esters, complete hydrolysis of the acylglycerols, and a 78% decrease in the initial FFA content by methyl esterification. Tocopherols did not change throughout the process. To enhance the degree of steryl and methyl esterification, the reaction products, FA steryl esters and FAME, were removed by short‐path distillation, and the resulting fraction containing tocopherols, sterols, and FFA was treated with the lipase again. Distillation of the reaction mixture purified tocopherols to 76.4% (recovery, 89.6%) and sterols to 97.2% as FA steryl esters (recovery, 86.3%).
Fatty acid selectivity of microbial lipase and lipolytic enzymes from salmonid fish intestines toward astaxanthin diesters
Authors: Halldorsson Arnar , Haraldsson Gudmundur G.
Published: November 2006

The objective of the work described in this paper was to study a possible FA selectivity of digestive lipolytic enzymes isolated from salmon and trout intestines toward astaxanthin diesters of various FA composition and compare it with the FA selectivity of microbial lipase. Astaxanthin diesters of varying FA composition were prepared in excellent yields (>90%) by chemical esterification using a carbodiimide coupling aget. The astaxanthin diesters were screened in a hydrolysis reaction by various commercially available lipases. The highest conversion rates were observed with the Candida rugosa lipase, which discriminated against n−3 PUFA. The rate of hydrolysis was determined by HPLC. Digestive lipolytic enzymes isolated from salmon and rainbow trout intestines displayed reversed FA selectivity. Thus, astaxanthin diesters highly enriched with n−3 PUFA including EPA and DHA were observed to be hydrolyzed at a considerably higher rate than the more saturated esters. Similar trends in FA selectivity were observed in the hydrolysis of fish oil TAG by the digestive lipolytic enzyme mixtures.
Oxidative stability during storage of structured lipids produced from fish oil and caprylic acid
Authors: Nielsen Nina Skall , Xu Xuebing , Timm‐Heinrich Maike , Jacobsen Charlotte
Published: November 2006

Structured lipids produced by enzymatic or chemical methods for different applications have been receiving considerable attention. The oxidative stability of a randomized structured lipid (RFO), produced by chemical interesterification from fish oil (FO) and tricaprylin, and a specific structured lipid (SFO), produced by enzymatic interesterification from the same oil and caprylic acid, was compared with the stability of FO. Oils were stored at 2°C for 11 wk followed by storage at 20°C for 6 wk. In addition, the antioxidative effect of adding the metal chelators EDTA or citric acid to SFO was investigated. FO contained the largest amount of PUFA and RFO the lowest. However, SFO had a higher PV initially and during storage at 2°C, whereas the PV of FO was highest during storage at 20°C. The level of volatile oxidation products was highest in SFO during the entire storage period, and off‐flavors were more pronounced in SFO. The lower oxidative stability of SFO was probably related to the initially lower quality (regarding oxidation products), which is apparently a result of the long production procedure required. Addition of metal chelators did not reduce the oxidation of the SFO.
Temperature effect on the viscosities of palm oil and coconut oil blended with diesel oil
Authors: Tangsathitkulchai C. , Sittichaitaweekul Y. , Tangsathitkulchai M.
Published: November 2006

One of the major difficulties in using crude vegetable oils as substitute fuels in diesel engines is their relatively high viscosities. Increasing the temperature of the crude vegetable oil, blending it with diesel oil, or the combination of both offers a simple and effective means of controlling and lowering the viscosities of vegetable oils. This work reports viscosity data, determined with a rotational bob‐and‐cup viscometer, for crude palm oil and cononut oil blended with diesel oil over the temperature range of 20–80°C and for different mixture compositions. All the test oil samples showed a time‐independent newtonian type of flow behavior. The reduction of viscosity with increasing liquid temperature followed an exponential relationship, with the two constants of the equation being a function of the volume percentage of the vegetable oil in the mixture. A single empirical equation was developed for predicting the viscosity of these fuel mixtures under varying temperatures and blend compositions.
Direct analysis of Ca, P, and Fe in oleochemicals by inductively coupled plasma MS
Authors: Wiedemann Sophie C. C. , Abbes Henkjan , Hansen Wei G.
Published: November 2006

This paper presents the use of inductively coupled plasma MS (ICP‐MS) for direct elemental analysis in oleochemicals (long‐chain fatty acid derivative). It focuses on Ca, P, and Fe, which are key elements for many industrial applications and which are known to be challenging for MS technology. The instrument is operated with a “shield torch” interface under “high‐power cool plasma.” In addition, oxygen is blended with argon to prevent buildup of carbon on both torch and cones. The extra sensitivity of the ICP‐MS technology permits high dilution factors, thereby minimizing any potential matrix effects. The contents of Ca, P, and Fe are quantified by standard addition. There is no need to resort to interference corrections for P, because it is measured as its oxide PO+. Detection limits lie in the sub‐ppm for Ca and P and in the low‐ppb for Fe. Accuracy of the method has been demonstrated for our products by a recovery test.
Cross‐linkers control the viscoelastic properties of soybean oil‐based biomaterials
Authors: Xu Jingyuan , Liu Zengshe , Erhan Sevim Z. , Carriere Craig J.
Published: November 2006

Because of environmental concerns, biodegradable materials have been of increasing research interest over the last several years. Previously, we reported on a biobased material developed from epoxidized soybean oil (ESO) that displayed viscoelastic behavior similar to synthetic rubbers or plastics. In this work, the viscoelastic properties of several biomaterials made from ESO cross‐linked by different amounts of two different cross‐linking agents were investigated. The composites exhibited different glass transition temperatures and viscoelastic behaviors depending on the type and amount of cross‐linker used. Higher glass transition temperatures and stronger viscoelastic properties of the materials were found with a greater amount of cross‐linker. Comparing agent triethylene glycol diamine (TGD) with agent triethylenetriamine (TETA), we found that the material cross‐linked by TETA had a higher glass transition temperature and stronger viscoelastic solid properties than the material cross‐linked by the agent TGD.
Commercial spread optimization using experimental design and sensory data
Authors: Wikström Malin , Sjöström Michael
Published: November 2006

The cost and quality of food products are issues that concern both the consumer and producer. In this research, the process used for the production of a commercial spread was subjected to a statistical experimental design for the purpose of reducing the cost of production while maintaining or improving the sensory quality. Three factors—the amount of oil added (x1), the speed of puddling (x2), and the temperature treatment (A or B; x3)—were varied according to a full‐factorial design at two levels. The experiments were performed over 2 d, and the factorial design was complemented with three replicates for temperature treatments A and B, which were performed on different days. The products were evaluated with both sensory and physicochemical measurements. Special attention was paid to the hardness of the product since it was permissible to reduce it slightly. In contrast, sensory quality aspects of the product including butter‐aroma and off‐flavor, as well as other quality properties such as spreadability, shine, and meltability, had to be maintained at the present level or improved. Statistical evaluation of the data showed that it was possible to add high amounts of oil (x1) without impairing the sensory quality of the product and, hence, reduce the cost of production. The hardness of the product was also slightly reduced when using the high level of oil. In maintaining other sensory qualities such as shine and spreadability at the present levels, the choice of temperature treatment (x3) was important.
Fractionation of crude soybean lecithin with aqueous ethanol
Authors: Wu Yingzi , Wang Tong
Published: November 2006

Aqueous ethanol was used to fractionate soybean PC and PI, which have dissimilar solubilities in this solvent. The effects of oil and moisture contents of the crude lecithin, ethanol‐to‐lecithin ratio, and dispersion temperature on the efficiency of phospholipid (PL) fractionation were investigated. Yield, purity, recovery, and PL class composition were examined. Yield was defined as the amount of fractionated material, divided by the acetone‐insoluble (AI) matter in the starting material; purity was the percentage of PL (PC+PE+PI) as quantified by HPLC in the fraction; and recovery was the amount of PL quantified relative to the quantity of AI matter. Higher oil contents significantly increased the yield of the PC fraction, but they significantly decreased yield, purity, and recovery of the PI fraction. They also significantly affected the PL composition of the PC fraction. Higher moisture contents significantly decreased the yield but slightly increased the purity of PC fractions. Higher temperatures significantly increased the yield and recovery of the PC fraction. They also affected the relative proportion of PL classes in the PC and PI fractions. The ethanol‐to‐lecithin ratio significantly affected yield, purity, and recovery as well as the relative proportions of PL in both PC and PI fractions. A combination of multiple fractionation and high‐low temperature treatment was also examined. Fractionating twice with ethanol increased the purity of the PC fraction. High‐low temperature fractionation increased the purity and PC percentage in the PC fraction.
“Adventuring through the Pieces of a still Unorganized Mosaic”: Reading Jean Toomer's Collage Aesthetic in Cane
Authors: FAREBROTHER RACHEL
Published: November 2006

In Cane the reader is immediately struck by Jean Toomer's bold manipulation of a collage technique; he abandons progressive plotting, instead assembling a variety of disparate forms and genres. As well as signalling the heterogeneity of the collage elements through typographical layout, he stretches and scrambles familiar forms, breaking them, splitting them open and stitching them onto other genres. In a letter to Toomer on 25 April 1922, Waldo Frank describes the effect of these broken forms: “in the reading the mind does not catch on to a uniformly moving Life that conveys it whole to the end, but rather steps from piece to piece as if adventuring through the pieces of a still unorganized mosaic.” As Frank points out, Toomer abandons linear narrative and “uniform” progression, subjecting the reader to chaotic surprises and unexpected truths revealed through the process of piecing together the meaning of seemingly random fragments.
The property theory of Lord Kames (Henry Home)
Authors: Rahmatian Andreas
Published: November 2006

Lord Kames (Henry Home) (1696–1782) was a well-known jurist, philosopher and judge in the Scottish Enlightenment, whose writings on aesthetics and literary criticism, especially, were very significant in the eighteenth century and later, not only in Britain and the United States, but also in France and Germany. His works on law and legal history were important mainly during his lifetime, but at least one aspect of his legal writings deserves special attention today: his concept of property, which he never stated as one comprehensive theory. Nevertheless, it pervades most of his work. This article seeks to extract and piece together, from a number of his legal and non-legal works, the elements of this quite original property theory which comprises legal-doctrinal, philosophical-theoretical, historical, sociological and psychological, aesthetic-moral and economic aspects. Together these elements can be restated as a surprisingly coherent property system, which may enrich discussions in modern property theory.
Rechtsseitige Unterbauchschmerzen zwei Wochen postpartal
Authors: Fahrni  , Hohl  , Stutz  , Schwendinger  , Kubik-Huch
Published: November 2006

Wir berichten über die CT-Bildgebung bei einer 33-jährigen Patientin, welche wegen seit fünf Tagen zunehmenden rechtsseitigen Unterbauchschmerzen und Schüttelfrost auf den Notfall zugewiesen wurde. Zwei Wochen zuvor hatte sie nach Einleitung in der 39. SSW problemlos entbunden. Zwei Tage postpartal wurde eine Sterilisation durchgeführt. Klinisch bestand initial der Verdacht auf eine Appendizitis. Eine zur Bestätigung der Diagnose ergänzend durchgeführte Computertomographie zeigte jedoch keine Appendizitis sondern eine rechtsseitige Ovarialvenenthrombose. Es wurde unverzüglich eine antibiotische Behandlung in Kombination mit niedermolekularem Heparin in therapeutischer Dosierung begonnen.
Characterization of Ze and LDR of nonspherical and inhomogeneous ice particles for 95‐GHz cloud radar: Its implication to microphysical retrievals
Authors: Sato Kaori , Okamoto Hajime
Published: November 2006

Effect of density, shape, and orientation on radar reflectivity factor (Ze) and linear depolarization ratio (LDR) at 95 GHz are investigated by using the discrete dipole approximation (DDA) for ice cloud studies. We consider hexagonal plate, hollow hexagonal column, and hollow bullet rosette in horizontal (2‐D) or three‐dimensional (3‐D) random orientation. We first validate a widely used method to take into account the density and shape effects by the combinational use of Mie theory with the Maxwell‐Garnett mixing rule (the MG‐Mie method). It is found that the MG‐Mie method underestimates Ze and its applicability is limited to sizes smaller than 40 μm. On the basis of the DDA, it is possible to separately treat density, aspect ratio, orientation, and shape. Effect of density turns out to be minor. Orientation and shape are the major controlling factors for Ze especially at effective radius reff > 100 μm and LDR except for very large sizes where the effect of orientation in LDR diminishes. Comparison between the DDA results and the analytical solution for 3‐D Rayleigh spheroids show that LDR in the small size range is characterized by the target boundary and aspect ratio. In the large size range, LDR reveals features of a single target element; for example, LDR of bullet rosette is similar to that of a single branch of the particle. Combinational use of Ze and LDR is effective in microphysics retrieval for LDR < −23 dB. For LDR > −23 dB, additional information such as Doppler velocity is required.
Subsurface ice on Mars with rough topography
Authors: Aharonson Oded , Schorghofer Norbert
Published: November 2006

High‐latitude ground ice on Mars discovered by the Gamma Ray Spectrometer suite is thought to be thermally stable owing to the presence of vapor in the Martian atmosphere. However, local slopes can alter surface and subsurface temperatures substantially, and hence allow ground ice to persist at locations where it would otherwise be unstable. Global statistics of the topography of Mars are computed, processed, and extrapolated to derive a description of surface roughness on spatial scales to which ground ice should be sensitive. This slope distribution is convolved with a new thermal model for the dependence of subsurface ice on slope, to produce a prediction of the global ice distribution that includes the effect of topographic roughness. In the highest latitudes, slopes reduce the amount of buried ice, while in lower latitudes the ice fraction increases, widening the geographic boundary of the ice table. At the high latitudes, where ice is stable beneath horizontal ground, the estimated reduction of ice is small compared to the existing ice volume. Areas in the midlatitudes with high surface roughness that have previously been predicted to be ice free are predicted to contain quantities of ice that may be detectable at present and accessible in the future. Slopes cause ground ice to be stable to latitudes of about 25 degrees in both hemispheres, including, for example, areas within the northern Olympus Mons aureole deposits, Hecates Tholus, and Hellas basin. Ice is unstable at equatorial latitudes, even when accounting for surface slopes.
Dynamics of a river channel confluence with discordant beds: Flow turbulence, bed load sediment transport, and bed morphology
Authors: Boyer Claudine , Roy André G. , Best James L.
Published: November 2006

River channel confluences play a major role in the dynamics of all fluvial systems, and yet our understanding of bed load routing at these sites is very sparse. The dynamics of confluences are a function of the momentum ratio between the combining flows and the three‐dimensional geometry of the junction. Recent experiments have shown that discordance in bed height between the confluent rivers increases turbulence intensity and enhances upwelling of flow within the confluence. However, the significance of these flow characteristics on sediment transport is still unknown. To examine the relations between flow and sediment transport, we have measured near‐bed flow turbulence, bed load transport rates, and changes in bed morphology for eight different flow conditions at a sand bed discordant confluence. Detailed analysis of the near‐bed flow patterns reveals that within the shear layer, low mean flow velocities are combined with the highest values of Reynolds shear stresses and that turbulence generation is associated with intense upward movements of flow. High sediment transport rates are found at the edges of the shear layer region where horizontal‐vertical cross stresses (ρUw′) are high. These patterns match changes in bed morphology where erosion occurs along the shear layer. The relation between the shear layer and sediment transport confirms the role of bed discordance on the dynamics of the confluence. Migration of the shear layer into the confluence, as a result of a change in momentum ratio, modifies local near‐bed flow characteristics, sediment transport rates, and the spatial distribution of deposition and erosion zones.
A GEOCLIM simulation of climatic and biogeochemical consequences of Pangea breakup
Authors: Donnadieu Y. , Goddéris Y. , Pierrehumbert R. , Dromart G. , Fluteau F. , Jacob R.
Published: November 2006

Large fluctuations in continental configuration occur throughout the Mesozoic. While it has long been recognized that paleogeography may potentially influence atmospheric CO2via the continental silicate weathering feedback, no numerical simulations have been done, because of the lack of a spatially resolved climate‐carbon model. GEOCLIM, a coupled numerical model of the climate and global biogeochemical cycles, is used to investigate the consequences of the Pangea breakup. The climate module of the GEOCLIM model is the FOAM atmospheric general circulation model, allowing the calculation of the consumption of atmospheric CO2through continental silicate weathering with a spatial resolution of 7.5°long × 4.5°lat. Seven time slices have been simulated. We show that the breakup of the Pangea supercontinent triggers an increase in continental runoff, resulting in enhanced atmospheric CO2consumption through silicate weathering. As a result, atmospheric CO2falls from values above 3000 ppmv during the Triassic down to rather low levels during the Cretaceous (around 400 ppmv), resulting in a decrease in global mean annual continental temperatures from about 20°C to 10°C. Silicate weathering feedback and paleogeography both act to force the Earth system toward a dry and hot world reaching its optimum over the last 260 Myr during the Middle‐Late Triassic. In the super continent case, given the persistent aridity, the model generates high CO2values to produce very warm continental temperatures. Conversely, in the fragmented case, the runoff becomes the most important contributor to the silicate weathering rate, hence producing a CO2drawdown and a fall in continental temperatures. Finally, another unexpected outcome is the pronounced fluctuation in carbonate accumulation simulated by the model in response to the Pangea breakup. These fluctuations are driven by changes in continental carbonate weathering flux. Accounting for the fluctuations in area available for carbonate platforms, the simulated ratio of carbonate deposition between neritic and deep sea environments is in better agreement with available data.
Persistent transport barrier on the West Florida Shelf
Authors: Olascoaga M. J. , Rypina I. I. , Brown M. G. , Beron‐Vera F. J. , Koçak H. , Brand L. E. , Halliwell G. R. , Shay L. K.
Published: November 2006

Analysis of drifter trajectories in the Gulf of Mexico has revealed the existence of a region on the southern portion of the West Florida Shelf (WFS) that is not visited by drifters that are released outside of the region. This so‐called “forbidden zone” (FZ) suggests the existence of a persistent cross‐shelf transport barrier on the southern portion of the WFS. In this letter a year‐long record of surface currents produced by a Hybrid‐Coordinate Ocean Model simulation of the WFS is used to compute Lagrangian coherent structures (LCSs), which reveal the presence of a persistent cross‐shelf transport barrier in approximately the same location as the boundary of the FZ. The location of the cross‐shelf transport barrier undergoes a seasonal oscillation, being closer to the coast in the summer than in the winter. A month‐long record of surface currents inferred from high‐frequency (HF) radar measurements in a roughly 60 km × 80 km region on the WFS off Tampa Bay is also used to compute LCSs, and these also reveal the presence of transient transport barriers. While the HF‐radar‐derived transport barriers cannot be unambiguously linked to the boundary of the FZ, this analysis does demonstrate the feasibility of monitoring transport barriers on the WFS using a HF‐radar‐based measurement system. The implications of a persistent cross‐shelf transport barrier on the WFS for the development of harmful algal blooms on the shoreward side of the barrier are considered.
Two types of the Asian continental blocking and their relation to the east Asian monsoon during the boreal winter
Authors: Lee Hyun‐Soo , Jhun Jong‐Ghap
Published: November 2006

The relationships between two types of blocking over the Asian continent (60E–140E) during northern winter are examined by using both the NCEP‐NCAR and the ECMWF reanalysis data for the period 1958–2005. Both the Ω‐type blocking occurring over the region of 60E–100E and the dipole‐type blocking occurring over the region of 100E–140E contribute to a stronger than normal east Asian winter monsoon (EAWM). However, their blocking frequency shows rather different interannual variation. In addition, the dipole‐type blocking frequency is negatively correlated with ENSO activity. While the blocking frequency of the Ω type is positively correlated with the snow cover during the preceding autumn over the Siberian High region and far eastern Russia, that of the dipole type is negatively correlated with the Eurasian snow cover. Thus, the combination of the variation in tropical SST and snow cover may exert a favorable influence on a relatively strong EAWM by the generation and maintenance of blocking patterns.
On the variability of the shape‐slope parameter relations of the gamma raindrop size distribution model
Authors: Narayana Rao T. , Kirankumar N. V. P. , Radhakrishna B. , Narayana Rao D.
Published: November 2006

The gamma parameters have been derived on the ground with the disdrometer and aloft with VHF and UHF radar measurements made at Gadanki in the southwest monsoon season. They have been used to study the variability of the shape‐slope (μ ‐ Λ) relation with the climatic regime and also as a function of height. The μ ‐ Λ relation obtained at Gadanki differs from that derived at Florida and Oklahoma indicating climatic differences in the relation, which could be due to the microphysical differences in the rain DSD at these two locations. However, these differences could also arise due to the use of different type of disdrometers at these locations. For the first time, an attempt has been made to study the variation of this relation with height, and the analysis clearly reveals a significant variation in the coefficients of the relation with height. The vertical variability of the relation has been ascribed to the microphysical processes occurring in the height region concerned in the present study. These results suggest that for accurate retrieval of drop size distribution from polarimetric measurements and also for studies on the microphysics of rain systems, the vertical variability of the relation needs to be accounted, in particular in an environment where the DSD variations are considerable. In addition, the reduction of the scatter in the μ ‐ Λ plot after filtering light rain events, suggests that the μ ‐ Λ relation may be pertinent to moderate to heavy rain corroborating some of the earlier reports.
Low‐ to middle‐latitude X‐ray emission from Jupiter
Authors: Bhardwaj Anil , Elsner Ronald F. , Gladstone G. Randall , Waite J. Hunter , Branduardi‐Raymont Graziella , Cravens Thomas E. , Ford Peter G.
Published: November 2006

The Chandra X‐ray Observatory (CXO) observed Jupiter during the period 24–26 February 2003 for ∼40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS‐S) and the imaging array of the High‐Resolution Camera (HRC‐I). Two ACIS‐S exposures, each ∼8.5 hours long, were separated by an HRC‐I exposure of ∼20 hours. The low‐ to middle‐latitude nonauroral disk X‐ray emission is much more spatially uniform than the auroral emission. However, the low‐ to middle‐latitude X‐ray count rate shows a small but statistically significant hour angle dependence and depends on surface magnetic field strength. In addition, the X‐ray spectra from regions corresponding to 3–5 gauss and 5–7 gauss surface fields show significant differences in the energy band 1.26–1.38 keV, perhaps partly due to line emission occurring in the 3–5 gauss region but not the 5–7 gauss region. A similar correlation of surface magnetic field strength with count rate is found for the 18 December 2000 HRC‐I data, at a time when solar activity was high. The low‐ to middle‐latitude disk X‐ray count rate observed by the HRC‐I in the February 2003 observation is about 50% of that observed in December 2000, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low‐ to middle‐latitude X‐ray emission does not show any oscillations similar to the ∼45 min oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's nonauroral X‐ray emission exhibits similarities to variations in solar X‐ray flux observed by GOES and TIMED/SEE. The two ACIS‐S 0.3–2.0 keV low‐ to middle‐latitude X‐ray spectra are harder than the auroral spectrum and are different from each other at energies above 0.7 keV, showing variability in Jupiter's nonauroral X‐ray emission on a timescale of a day. The 0.3–2.0 keV X‐ray power emitted at low to middle latitudes is 0.21 GW and 0.39 GW for the first and second ACIS‐S exposures, respectively. We suggest that X‐ray emission from Jupiter's disk may be largely generated by the scattering and fluorescence of solar X rays in its upper atmosphere, especially at times of high incident solar X‐ray flux. However, the dependence of count rate on surface magnetic‐field strength may indicate the presence of some secondary component, possibly ion precipitation from radiation belts close to the planet.
Configurational anisotropy in single‐domain and pseudosingle‐domain grains of magnetite
Authors: Williams Wyn , Muxworthy Adrian R. , Paterson Greig A.
Published: November 2006

In classical domain theory, single‐domain (SD) grains change their magnetization by coherent rotation, where the energy barrier to domain reversal is provided by the magnetocrystalline anisotropy or by shape anisotropy for elongated grains. However, numerical micromagnetic models have shown that domain structure in SD grains is rarely perfectly uniform. For example, magnetite has significant “flowering” of its magnetization even in grains that approach the room temperature superparamagnetic (SP) size of ∼30 nm. The flowering deforms slightly to accommodate the grain shape and thereby produces anisotropy independent of magnetocrystalline effects but dependent on magnetization direction within the grain. This can be similar in magnitude to that of magnetocrystalline anisotropy, even for equidimensional grains (where distance from the centroid to the grain faces is equal). The interaction of the domain structure and grain geometry is termed configurational anisotropy and has been studied mainly in relation to man‐made isotropic magnetic media but received little attention in rock magnetism. In this paper we examine configurational anisotropy in SD to pseudo‐single‐domain (PSD) grains of magnetite using a three‐dimensional finite element/boundary integral (FEBI) micromagnetic model. Equidimensional grains of magnetite of three different shapes are considered: a cube, an octahedron, and a regular tetrahedron, and in each case the effects magnetocrystalline anisotropy were removed in order to isolate the configurational anisotropy. The numerical models predict that very large coercivities are possible even for SD equidimensional grains. For tetrahedral grains coercivities of ∼120 mT were obtained, which otherwise would require a grain elongation of ∼1:1.75. Depending on the orientation of the principle crystalline axis to the grain shape, the configurational anisotropy may increase or decrease the overall energy barrier to domain reversal.
Reactivity and loss mechanisms of NO3 and N2O5 in a polluted marine environment: Results from in situ measurements during New England Air Quality Study 2002
Authors: Aldener Mattias , Brown Steven S. , Stark Harald , Williams Eric J. , Lerner Brian M. , Kuster William C. , Goldan Paul D. , Quinn Patricia K. , Bates Timothy S. , Fehsenfeld Frederick C. , Ravishankara A. R.
Published: November 2006

Concentrations of NO3 and N2O5 were measured using an in situ instrument aboard the NOAA research vessel Ronald H. Brown in the marine boundary layer along the United States east coast as part of the New England Air Quality Study (NEAQS) in the summer of 2002. We analyze the results in terms of the loss partitioning and sink budgets for both of these compounds. Analysis of the data on nights with large N2O5 losses allowed for a determination of its heterogeneous uptake coefficient and gave γ(N2O5) = 0.03 ± 0.02. Reactions of NO3 with terrestrially emitted biogenic volatile organic compounds (isoprene and monoterpenes), advected into the marine boundary layer, and with DMS emitted from the ocean surface were also important. In general, loss of NO3 and N2O5 was rapid, and the partitioning between NO3 and N2O5 losses was roughly equal. Because rapid N2O5 loss consumes NOx at twice the rate of the reaction of NO2 with O3, whereas rapid NO3 loss leads to NOx removal at the same rate, the equal partitioning of losses indicates a nocturnal NOx loss rate of approximately 1.5 times the rate of NO2 + O3. Activation of halogens from the uptake of NO3 and N2O5 on sea salt was calculated to have produced substantial amounts of active Cl on some mornings through the nocturnal formation and sunrise photolysis of ClNO2 if the process proceeded at the rate determined by laboratory studies. However, there was no direct observational evidence to test the magnitude of the predicted source.
Nature and origin of the hematite‐bearing plains of Terra Meridiani based on analyses of orbital and Mars Exploration rover data sets
Authors: Arvidson R. E. , Poulet F. , Morris R. V. , Bibring J.‐P. , Bell J. F. , Squyres S. W. , Christensen P. R. , Bellucci G. , Gondet B. , Ehlmann B. L. , Farrand W. H. , Fergason R. L. , Golombek M. , Griffes J. L. , Grotzinger J. , Guinness E. A. , Herkenhoff K. E. , Johnson J. R. , Klingelhöfer G. , Langevin Y. , Ming D. , Seelos K. , Sullivan R. J. , Ward J. G. , Wiseman S. M. , Wolff M.
Published: November 2006

The ∼5 km of traverses and observations completed by the Opportunity rover from Endurance crater to the Fruitbasket outcrop show that the Meridiani plains consist of sulfate‐rich sedimentary rocks that are largely covered by poorly‐sorted basaltic aeolian sands and a lag of granule‐sized hematitic concretions. Orbital reflectance spectra obtained by Mars Express OMEGA over this region are dominated by pyroxene, plagioclase feldspar, crystalline hematite (i.e., concretions), and nano‐phase iron oxide dust signatures, consistent with Pancam and Mini‐TES observations. Mössbauer Spectrometer observations indicate more olivine than observed with the other instruments, consistent with preferential optical obscuration of olivine features in mixtures with pyroxene and dust. Orbital data covering bright plains located several kilometers to the south of the landing site expose a smaller areal abundance of hematite, more dust, and a larger areal extent of outcrop compared to plains proximal to the landing site. Low‐albedo, low‐thermal‐inertia, windswept plains located several hundred kilometers to the south of the landing site are predicted from OMEGA data to have more hematite and fine‐grained olivine grains exposed as compared to the landing site. Low calcium pyroxene dominates spectral signatures from the cratered highlands to the south of Opportunity. A regional‐scale model is presented for the formation of the plains explored by Opportunity, based on a rising ground water table late in the Noachian Era that trapped and altered local materials and aeolian basaltic sands. Cessation of this aqueous process led to dominance of aeolian processes and formation of the current configuration of the plains.
Changes in carbon cycling ascertained by stable isotopic analyses in a hypersaline microbial mat
Authors: Kelley Cheryl A. , Prufert‐Bebout Leslie E. , Bebout Brad M.
Published: November 2006

Modern microbial mats have been used as analogs for early life because of the longevity of microbial life on Earth. Mats collected from hypersaline salterns in Baja California were maintained for over a year and a half under both normal (85 ppt salinity, 50 mM SO42−) and reduced salinity (35 ppt salinity; near modern seawater) and sulfate concentrations (20 mM, ≤1 mM SO42−) to assess carbon processing under sulfate conditions more similar to the Archean oceans. As sulfate was removed from the mats by diffusion out into the overlying water, methane concentrations within the mats increased. Highest methane concentrations occurred in mats with reduced salinity and little sulfate. The δ13C values of bulk particulate organic matter in all of the mats averaged −11‰, similar to what had been observed previously for these Microcoleus mats. In mats with sulfate, pore water concentrations of dissolved inorganic carbon (DIC) δ13C values averaged about −3‰. However, in the mats with ≤1 mM sulfate concentrations, the DIC δ13C values increased substantially with depth, from about −1‰ in the overlying water to +10‰ by 20 mm depth. Rates of methanogenesis, calculated from pore water dissolved methane concentration profiles, were too low to account for the total increase in DIC δ13C values. These positive isotopic signatures, however, are also consistent with the occurrence of acetogenesis, as are the higher acetate concentrations in the low‐sulfate mats. Acetogens may be poised to become successful competitors for substrates in these mats, given the right environmental conditions.
Combined experimental-theoretical study of the lower excited singlet states of paravinyl phenol, an analog of the paracoumaric acid chromophore
Authors: de Groot Mattijs , Buma Wybren Jan , Gromov Evgeniy V. , Burghardt Irene , Köppel Horst , Cederbaum Lorenz S.
Published: November 2006

The low-lying excited singlet states of paravinyl phenol (pVP) are investigated experimentally and theoretically paying attention to their similarity to excited states of paracoumaric acid, the chromophore of the photoactive yellow protein (PYP). Resonance enhanced multiphoton ionization and laser induced fluorescence spectroscopic techniques are employed to obtain supersonically cooled, vibrationally resolved excitation and emission spectra related to the lowest A′1(V′) excited state of pVP. Comprehensive analyses of the spectral structures are carried out by means of the equation-of-motion coupled cluster singles and doubles and time dependent density functional theory methods in combination with the linear vibronic coupling model and Franck-Condon calculations. The assignments of the spectral patterns are given, mostly in terms of excitations of totally symmetric modes. Weak activity of the non-totally-symmetric modes indicates low probability of photochemical processes in the Franck-Condon region of the A′1(V′) state. The second A′1(V) and third A″1(Ryd) excited states of pVP are characterized with regard to their electronic structure, properties, and effects of geometry relaxations. The lengthening of the double bond relevant to the trans-cis isomerization of the PYP chromophore is found for the A′1(V) state. A possibility of photochemical processes and strong vibronic interactions in this state can be expected. The theoretical results for the A″1(Ryd) state predict that dissociation with respect to the O–H bond is possible.
Scaled particle theory for hard sphere pairs. I. Mathematical structure
Authors: Stillinger Frank H. , Debenedetti Pablo G. , Chatterjee Swaroop
Published: November 2006

We develop an extension of the original Reiss-Frisch-Lebowitz scaled particle theory that can serve as a predictive method for the hard sphere pair correlation function g(r). The reversible cavity creation work is analyzed both for a single spherical cavity of arbitrary size, as well as for a pair of identical such spherical cavities with variable center-to-center separation. These quantities lead directly to a prediction of g(r). Smooth connection conditions have been identified between the small-cavity situation where the work can be exactly and completely expressed in terms of g(r), and the large-cavity regime where macroscopic properties become relevant. Closure conditions emerge which produce a nonlinear integral equation that must be satisfied by the pair correlation function. This integral equation has a structure which straightforwardly generates a solution that is a power series in density. The results of this series replicate the exact second and third virial coefficients for the hard sphere system via the contact value of the pair correlation function. The predicted fourth virial coefficient is approximately 0.6% lower than the known exact value. Detailed numerical analysis of the nonlinear integral equation has been deferred to the subsequent paper.
Scaled particle theory for hard sphere pairs. II. Numerical analysis
Authors: Chatterjee Swaroop , Debenedetti Pablo G. , Stillinger Frank H.
Published: November 2006

We use the extension of scaled particle theory presented in the accompanying paper [F. H. Stillinger et al., J. Chem. Phys. 125, 204504 (2006)] to calculate numerically the pair correlation function of the hard sphere fluid over the density range 0⩽ρσ3⩽0.96. Comparison with computer simulation results reveals that the new theory is able to capture accurately the fluid’s structure across the entire density range examined. The pressure predicted via the virial route is systematically lower than simulation results, while that obtained using the compressibility route is lower than simulation predictions for ρσ3⩽0.67 and higher than simulation predictions for ρσ3⩾0.67. Numerical predictions are also presented for the surface tension and Tolman length of the hard sphere fluid.
Optical and thermal properties of Co2+:ZnWO4 crystal
Authors: Yang Fugui , Wang Hongyan , Wei Yanping , Lu Xiuai , Tu Chaoyang , Jia Guohua , You Zhenyu , Wang Yan , Zhu Zhaojie , Li Jianfu
Published: November 2006

The crystal of ZnWO4 doped with Co2+ has been grown by the Czochralski technique. The orientation procedure was presented. Along the crystallographic axes, the principal coefficients of thermal expansion and absorption spectra were measured and discussed. Based on the data, the crystal field parameter 10Dq, Racah parameter B, as well as the absorption cross sections were calculated. The nonlinear dependence of optical absorption on concentration of cobalt ions was found and discussed in single crystal Co2+:ZnWO4. The results indicate that inner defects such as natural cleavage or slip faces in crystal are important in the study of optical and thermal properties.
Atomic contributions to bond dissociation energies in aliphatic hydrocarbons
Authors: Matta Chérif F. , Castillo Norberto , Boyd Russell J.
Published: November 2006

This paper explores the atomic contributions to the electronic vibrationless bond dissociation enthalpy (BDE) at 0K of the central C–C bond in straight-chain alkanes (CnH2n+2) and trans-alkenes (CnH2n) with an even number of carbon atoms, where n=2, 4, 6, 8. This is achieved using the partitioning of the total molecular energy according to the quantum theory of atoms in molecules by comparing the atomic energies in the intact molecule and its dissociation products. The study is conducted at the MP2(full)∕6-311++G(d,p) level of theory. It is found that the bulk of the electronic energy necessary to sever a single C–C bond is not supplied by these two carbon atoms (the α-carbons) but instead by the atoms directly bonded to them. Thus, the burden of the electronic part of the BDE is primarily carried by the two hydrogens attached to each of the α-carbons and by the β-carbons. The effect drops off rapidly with distance along the hydrocarbon chain. The situation is more complex in the case of the double bond in alkenes, since here the burden is shared between the α-carbons as well as the atoms directly bonded to them, namely, again the α-hydrogens and the β-carbons. These observations may lead to a better understanding of the bond dissociation process and should be taken into account when locally dense basis sets are introduced to improve the accuracy of BDE calculations.
Mixed quantum-classical description of spectroscopy of dissipative systems
Authors: Toutounji Mohamad
Published: November 2006

Mixed quantum-classical statistical mechanics is employed to calculate dipole moment correlation function and linear absorption spectra. A quantum two-level subsystem interacting with quantum vibrations (primary oscillators) which in turn are coupled to a classical bath composed of infinite set of harmonic oscillators is used as a dissipative system. Starting with mixed quantum-classical Liouville equation for the evaluation of the mixed quantum-classical dipole moment correlation function and using coherent states and the inverse of Baker-Campbell-Hausdorf formula to evaluate the trace over the primary oscillators, whereby, a closed analytical expression for the electronic dipole moment correlation function is obtained. Illustrations of several absorption spectra at different temperatures are provided. An approximate optical four-point correlation is obtained in the high temperature limit. A strategy for deriving an exact optical four-point correlation is suggested.
A crossover from metal to plasma in dense fluid hydrogen
Authors: Sumi Tomonari , Sekino Hideo
Published: November 2006

Thermodynamic properties in dense fluid hydrogen are studied by using a density-functional theory for electron-proton binary mixtures that is called quantal hypernetted-chain (QHNC) integral equation. A nonlocal approximation for the exchange-correlation potential in a finite-temperature Kohn-Sham equation is presented. Results obtained from the QHNC with the nonlocal approximation are compared with those obtained from the QHNC with a local density approximation. Temperature variation of thermodynamic quantities between 104 and 106K are investigated along an isochor specified by a dimensionless density parameter of rs=0.5. These quantities obtained from the QHNCs show that a crossover from metal to plasma occurs around a temperature of T=1.78×105K. Electrical resistivity Re of the dense fluid hydrogen evaluated from a Ziman formula [The Properties of Liquid Metals, edited by S. Takenohi (Wiley, New York, 1973)] extended to finite temperature is about 0.7μΩcm at T=104K. The dense fluid hydrogen at the temperature can be considered as a metallic fluid, because the value is smaller than typical values of Re in alkali metals at room temperature. The Re slightly increases with the temperature increase, and the temperature valuation of Re is monotonic. We clearly show that the contribution from the electronic excited states plays an important role for the sharp crossover from the metal to the plasma, and that the crossover is interpreted as a crossover from degenerate electron gas to nondegenerate electron gas.
Conductance of a single molecule anchored by an isocyanide substituent to gold electrodes
Authors: Kiguchi Manabu , Miura Shinichi , Hara Kenji , Sawamura Masaya , Murakoshi Kei
Published: November 2006

The effect of anchoring group on the electrical conductance of a single molecule bridging two Au electrodes was studied using disubstituted [isocyanide (CN–), thiol (S–), or cyanide (NC–)] benzene. The conductance of a single Au/1,4-diisocyanobenzene/Au junction anchored by isocyanide via a C atom (junction with the Au–CN bond) was 3×10−3G0(=2e2∕h). The value was comparable to 4×10−3G0 of a single Au/1,4-benzenedithiol/Au junction with the Au–S bond. The Au/1,4-dicyanobenzene/Au molecular junction with the Au–NC bond did not show well-defined conductance values. The metal-molecule bond strength was estimated by the distance over which the molecular junction was stretched before breakdown. The stretched length of the molecular junction with the Au–CN bond was comparable to that of the Au junction, indicating that the Au–CN bond was stronger than the Au–Au bond.
Correlating the Schottky barrier height with the interfacial reactions of Ir gates for InAlAs∕InGaAs high electron mobility transistors
Authors: Wang Liang , Zhao Weifeng , Adesida Ilesanmi
Published: November 2006

The characteristics of Ir on InAlAs and on InAlAs∕InGaAs∕InP high electron mobility transistor (HEMT) heterostructures were characterized. A maximum Schottky barrier height (φB) of 825meV was achieved for Ir∕InAlAs after annealing at 400°C. Transmission electron microscopy investigations confirmed that an amorphous layer (a layer) exists at the Ir∕InAlAs interface at that temperature. Results indicate that enhancement of φB is associated with the a layer, while beyond 400°C, the decrease of φB is due to the crystallization of the a layer and the formation of IrAs2. The enhancement of φB for Ir∕InAlAs and the slow diffusion of Ir in IrAlAs make it a superior thermally stable gate metal for InAlAs∕InGaAs HEMTs.