bluuebunny/crossref_metadata_2025 huggingface dataset:
Intercomparison of the primal and dual formulations of variational data assimilation
Authors: El Akkraoui Amal , Gauthier Pierre , Pellerin Simon , Buis Samuel
Published: June 2008

Two approaches can be used to solve the variational data assimilation problem. The primal form corresponds to the 3D/4D‐Var used now in many operational NWP centres. An alternative approach, called dual or 3D/4D‐PSAS, consists in solving the problem in the dual of observation space. Both forms use the same basic operators so that once one method is developed, it should be possible to obtain the other easily provided these operators have a modular form. It has been shown that, with proper conditioning of the minimization problem, the two algorithms should have similar convergence rates and computational performances. In the presence of nonlinearities, the incremental form of 3D/4D‐Var extends the equivalence to the so‐called 3D/4D‐PSAS. The first objective of this paper is to present results obtained with the variational data assimilation of the Meteorological Service of Canada to show the equivalence between the 3D‐Var and the PSAS systems. This exercise has forced us to have a close look at the modularity of the operational 3D/4D‐Var which then makes it possible to obtain the 3D‐PSAS scheme. This paper then focuses on these two quadratic problems that show similar convergence rates. However, the minimization of 3D‐PSAS is examined more thoroughly as some parameters are shown to be determining elements in the minimization process. Lastly, preconditioning properties are studied and the Hessians of the two problems are shown to be directly related to one another through their singular vectors, which makes it possible to cycle the Hessian of the PSAS form. Copyright © 2008 Royal Meteorological Society
Electrochemical mass spectrometric studies on 1‐cyclopropyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine
Authors: Castagnoli Neal , Bissel Philippe , Jurva Ulrik , Ashraf‐Khorasani Mehdi
Published: June 2008

Mechanistic studies on chemical and biological one‐electron oxidations of cyclic tertiary allylamines are being pursued with the aid of an electrochemical‐electrospray ionization mass spectrometric based assay. The results of previous studies on the electrochemical oxidation of 1‐cyclopropyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine have documented a two‐electron oxidative N‐decyclopropylation pathway. The present paper describes the characterization of a second pathway involving an overall four‐electron oxidation of this cyclopropylamine. The results document more completely the fate of cyclopropylaminyl radical cations that are thought to be intermediates in enzyme‐catalyzed oxidations of aminyl substrates and that may lead to chemically reactive metabolites. Copyright © 2008 John Wiley & Sons, Ltd.
Zur Leistungsfähigkeit, korrekten Anwendung und Kontrolle von EDV‐Programmen für die Berechnung räumlicher Stabwerke im Stahlbau (Teil 1)
Authors: Gensichen Volker , Lumpe Günter
Published: June 2008

Räumliche Stabwerke aus Stahl werden in der Regel mit Hilfe von Statik‐Programmen berechnet, die auf einer baustatischen Theorie zweiter oder höherer Ordnung basieren. Im vorliegenden Beitrag wird unter besonderer Berücksichtigung der Ersatzimperfektionen geklärt, ob diese vereinfachten Theorien ausreichen und welche Erweiterungen erforderlich sind, um in allen Fällen für die Baupraxis hinreichend genaue Ergebnisse zu erzielen. Für Programm‐Hersteller und ‐Nutzer werden einfache Systeme angegeben, an denen die grundsätzliche Leistungsfähigkeit eines Statikprogramms mit geringem Aufwand überprüft werden kann. Ferner werden Hinweise zur korrekten Anwendung von Statikprogrammen gegeben.
Learning contexts, black Cultural Ethos, and the science achievement of African American students in an urban middle school
Authors: Parsons Eileen Carlton
Published: June 2008

As other countries vigorously promote rapid advancement in science, optimizing the participation of all students in the United States in science is imperative. This study focused on African American students and examined their science achievement in relation to Black Cultural Ethos (BCE), a construct rooted in psychology. Via qualitative and quantitative data obtained from a non‐random control group design, the study addressed three questions: (1) With respect to BCE, what characterizes the natural instructional contexts of two middle school science teachers? (2) What characterizes the achievement of African American students in contexts that incorporate BCE and contexts that do not? (3) What achievement patterns, if any, exist in BCE and non‐BCE instructional contexts? With regard to the natural contexts, the teachers did not incorporate BCE even when the opportunities were available to do so. Within these non‐BCE contexts, the group's mean scores on the study‐specific test that aligned with instruction decreased from pretest to posttest with approximately one‐third of the students' scores improving. When a context was altered with a moderate effect size of 0.47 to include BCE, the group's mean scores on the aforementioned test increased from pretest to posttest with two‐thirds of the students' scores improving. An illustration of the interplay between BCE and context and a consideration of the interplay as a mediating factor in research involving African American students encapsulate the significance and implications of the study's findings. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 665–683, 2008
S‐nitrosocysteine (RSNO), an effective antioxidant in cured meat
Authors: Kanner J.
Published: June 2008

S‐nitrosocysteine (RSNO), a compound which has been shown to be generated during the curing process of meat, was found to act as an antioxidant. The antioxidative activity of RSNO in an aqueous linoleate model system, in the presence of myoglobin, was compared with that of other known antioxidants, such as BHT and α‐tocopherol. The results indicated that RSNO has an antioxidative activity only slightly lower than that of BHT. During the initial stage of the reaction, RSNO acted not only as an inhibitor of linoleic acid oxidation, but also as a hydroperoxide decomposer. The high inhibitory effect of added RSNO (1mM/kg meat) on lipid oxidation in ground cooked turkey meat was demonstrated in the product itself.
Gas chromatographic determination of free fatty acids in vegetable oils by a modified esterification procedure
Authors: Chapman G. W.
Published: June 2008

Free fatty acids in small vegetable oil samples were determined by gas liquid chromatography after a modified BCl3 or BF3/methanol esterification procedure with methylurea. This compound was found to sufficiently reduce triacylglyceride transesterification during free fatty acid esterification with BC13 or BF3 methanol. Good results were obtained using this new procedure on neutral lipid oils containing known amounts of free fatty acids. Good agreement between the new method and the A.O.C.S. titration method was also demonstrated on commercial and laboratory‐extracted crude oils. Because very small oil samples (200 mg) can be analyzed, the new method could be applicable for oilseed physiological studies.
Lipid composition of oats (Avena sativa L.)
Authors: Sahasrabudhe M. R.
Published: June 2008

Compositions of lipids extracted from a sample of Hinoat oat by seven solvent systems and that extracted with chloroform/methanol (2:1 v/v) from six selected cultivars representing high and low lipid contents are reported. Lipid components (steryl esters, triglycerides, partial glycerides, free fatty acids, glycolipids and phospholipids) were separated by silicic acid column chromatography and thin layer chromatography and quantitated by GLC analysis of fatty acids and phosphorus determinations. Twelve oat cultivars were examined for the fatty acid composition of lipid extracted with n‐hexane. Lipids extracted from Hinoat by different solvent systems ranged from 5.6 to 8.8%. Quantitative distribution of lipid components extracted with chloroform/methanol from six cultivars containing 4.6 to 11.6% lipid showed a significant correlation (γ=0.99) between the total lipid and the neutral lipid content. Phospholipid content was similar in all cultivars, but glycolipids showed a two‐fold increase in high lipid oats. Triglycerides contained less palmitic and more oleic acid than the glycolipids or phospholipids. Nine glycolipids and 11 phospholipids have been identified, and the polar lipid composition of Hinoat oat is presented.
Familial occurrence of complex regional pain syndrome
Authors: de Rooij Annetje M. , de Mos Marissa , Sturkenboom Miriam C.J.M. , Marinus Johan , van den Maagdenberg Arn M.J.M. , van Hilten Jacobus J.
Published: June 2008

Genetic factors are suggested to play a role in complex regional pain syndrome (CRPS), but familial occurrence has not been extensively studied. In the present study we evaluated familial occurrence in Dutch patients with CRPS.

Families were recruited through the Dutch Association of CRPS patients and through referral by clinicians. The number of affected members per family, the phenotypic expression and inheritance were assessed. Demographic and clinical characteristics of familial CRPS (fCRPS) patients were compared with those of sporadic CRPS (sCRPS) patients from a Dutch population‐based study and with a group of sCRPS patients that was proportionally matched for referral center of the fCRPS probandi to control for referral bias.

Thirty‐one CRPS families with two or more affected relatives were identified, including two families with five, four with four, eight with three and 17 with two affected relatives. In comparison with sCRPS patients, fCRPS patients had a younger age at onset and more often had multiple affected extremities and dystonia.

We conclude that CRPS may occur in a familial form, but did not find a clear inheritance pattern. Patients with fCRPS develop the disease at a younger age and have a more severe phenotype than sporadic cases, suggesting a genetic predisposition to develop CRPS.
The p53 target protein Wig‐1 binds hnRNP A2/B1 and RNA Helicase A via RNA
Authors: Prahl Magdalena , Vilborg Anna , Palmberg Carina , Jörnvall Hans , Asker Charlotte , Wiman Klas G.
Published: June 2008

MINT‐6542926, MINT‐6542899:

WIG1 (uniprotkb:Q9HA38) physically interacts (MI:0218) with hnRNP A2/B1 (uniprotkb:P22626) by anti bait coimmunoprecipitation (MI:0006)

MINT‐6542945:

RHA (uniprotkb:Q08211) physically interacts (MI:0218) with hnRNP A2/B1 (uniprotkb:P22626) by anti bait coimmunoprecipitation (MI:0006)

MINT‐6542918, MINT‐6542891:

WIG1 (uniprotkb:Q9HA38) physically interacts (MI:0218) with RHA (uniprotkb:Q08211) by anti bait coimmunoprecipitation (MI:0006)

MINT‐6542867:

WIG1 (uniprotkb:Q9HA38) physically interacts (MI:0218) with RHA (uniprotkb:Q08211) by anti tag coimmunoprecipitation (MI:0007)

MINT‐6542879:

WIG1 (uniprotkb:Q9HA38) physically interacts (MI:0218) with hnRNP A2/B1(uniprotkb:P22626) by anti tag coimmunoprecipitation (MI:0007)
The tumour suppressor RASSF1A is a novel substrate of PKC
Authors: Verma Sunil K. , Ganesan Trivadi S. , Parker Peter J.
Published: June 2008

Ras association domain family 1A (RASSF1A) is a tumour suppressor that contains an amino‐terminal cysteine‐rich region, similar to the diacylglycerol (DAG)‐binding domain (C1 domain) found in the protein kinase C (PKC) family of proteins, and a carboxy‐terminal Ras‐association (RA) domain. In the present study, RASSF1A was identified as a substrate for PKC. Using classical biochemical approaches, it was established that S197 and S203 within the RA domain of RASSF1A are phosphorylated by PKC in vitro and in vivo. Unlike the WT protein, the S197, 203D double mutant of RASSF1A failed to modulate microtubule organization and perinuclear vimentin collapse. By contrast, the equivalent AA mutant of RASSF1A phenocopied the WT protein. These findings indicate that PKC phosphorylation of RASSF1A regulates its ability to reorganize the microtubule network.
AML1‐ETO interacts with Sp1 and antagonizes Sp1 transactivity through RUNT domain
Authors: Wei Hui , Liu Xiangrong , Xiong Xiujuan , Wang Yang , Rao Qing , Wang Min , Wang Jianxiang
Published: June 2008

MINT‐6549474: AML1‐ETO (genbank_protein_gi:AAB34820) physically interacts (MI:0218) with Sp1 (uniprotkb:P08047) by anti bait coimmunoprecipitation (MI:0006)

MINT‐6549439: Sp1 (uniprotkb:P08047) physically interacts (MI:0218) with AML1‐ETO (uniprotkb:AAB34820) by anti tag coimmunoprecipitation (MI:0007)

MINT‐6549458: Sp1 (uniprotkb:P08047) physically interacts (MI:0218) with AML1a (uniprotkb:Q01196‐2) by anti tag coimmunoprecipitation (MI:0007)
Oceanography in northwestern Europe during the last interglacial from intrashell δ18O ranges in Littorina Littorea gastropods
Authors: Burman Johan , Påsse Tore
Published: June 2008

Coastal sea-surface temperature (SST) and sea-surface salinity (SSS), including seasonality, in northwest (NW) Europe during the early phase of the Eemian interglacial ca. 125 ka ago were reconstructed from Littorina littorea (common periwinkle) gastropods. The results were based on intra-annual δ18O analyses in recent and fossil shells, mainly originating from the sea of Kattegat (Sweden) and the English Channel (United Kingdom), and confined to intertidal settings. The Eemian L. littorea shells indicated annual SSTs in the range 8–18°C for the English Channel and 8–26°C for Kattegat. All specimens from the Eemian sites experienced summer SSTs of ca. 1–3°C above recent conditions. The estimated winter SST in the English Channel during the Eemian was comparable to modern measurements of ca. 8°C. However, the Kattegat region displayed Eemian winter SST approximately 8°C warmer than today, and similar to conditions in the western English Channel. The recent-fossil isotope analogue approach indicated high SSS above 35 practical salinity units (psu) for a channel south of England in full contact with the North Atlantic Ocean during the last interglacial. In addition, the Kattegat shells indicated a SSS of ca. 29 psu, which points out a North Sea affinity for this region during the Eemian.
Stressor-induced changes to the protoscoleces ofEchinococcus granulosusof Indian buffalo origin
Authors: Pan D. , Bhattacharya D. , Bera A.K. , Gudewar J. , De S. , Das S.K.
Published: June 2008

In the present study viable protoscoleces ofEchinococcus granulosuswere exposed toin vitroanthelmintic treatment to observe efficacy against Indian buffalo isolates. Evaluation criteria included morphological changes, viability scores and expression of peptides as a product of prestressed protoscoleces. Protoscolex changes included presence of bladder-like structure and morphological distortion. Two peptides of relative molecular weight (Mr) 40 and 70 kDa were visualized when proteins were separated by discontinuous gel electrophoresis. These two peptides seemed to be products of prestressed protoscoleces.
Orthogonal Latin Rectangles
Authors: HÄGGKVIST ROLAND , JOHANSSON ANDERS
Published: June 2008

We use a greedy probabilistic method to prove that, for every ε > 0, every m × n Latin rectangle on n symbols has an orthogonal mate, where m = (1 − ε)n. That is, we show the existence of a second Latin rectangle such that no pair of the mn cells receives the same pair of symbols in the two rectangles.
Sensitivity of pore‐scale dispersion to the construction of random bead packs
Authors: Maier Robert S. , Schure Mark R. , Gage Justin P. , Seymour Joseph D.
Published: June 2008

Pore‐scale simulations of flow and transport offer the possibility of modeling laboratory‐scale experiments without averaging the properties of the porous medium. Comparisons between simulation and experiment are complicated, however, by the difficulty of reproducing the exact geometry of the experimental porous medium in a simulation. Flow and dispersion are affected by differences in packing density, random packing variation, inhomogeneities, and confining walls. It is therefore important to understand the magnitude of such effects when comparing simulation and experiment. We quantify the sensitivity of pore‐scale simulations of flow and dispersion to variations in packing density, the random packing algorithm, and selective sphere removal for the case of randomly packed spheres. The results allow us to interpret differences in dispersion between pore‐scale simulations and NMR spectroscopy measurements in packed cylinders. Dispersion is analyzed in terms of the time‐dependent dispersion coefficient and by the propagator function (i.e., the density function of solute mass versus mass propagation distance). The simulation and experimental propagator functions share important qualitative features, and there are no obvious problems such as an incorrect center of mass. However, the simulation underestimates experimental dispersion, and the underestimate is greater than can be explained by possible differences in packing density and random packing between the NMR and simulated sphere packings. An examination of NMR images of the experimental packing reveals regularities in packing structure and raises the possibility that nonrandom ordering could account for the difference in dispersion.
Predicting interplanetary shock arrivals at Earth, Mars, and Venus: A real‐time modeling experiment following the solar flares of 5–14 December 2006
Authors: McKenna‐Lawlor S. M. P. , Dryer M. , Fry C. D. , Smith Z. K. , Intriligator D. S. , Courtney W. R. , Deehr C. S. , Sun W. , Kecskemety K. , Kudela K. , Balaz J. , Barabash S. , Futaana Y. , Yamauchi M. , Lundin R.
Published: June 2008

A 3‐D, kinematic, solar wind model (Hakamada‐Akasofu‐Fry version 2 (HAFv.2)) is used to predict interplanetary shock arrivals at Venus, Earth, and Mars during a sequence of significant solar events that occurred in the interval 5–14 December 2006. Mars and Venus were on the opposite side of the Sun from Earth during this period. The shocks from the first two east limb events (5 and 6 December) were predicted to interact to form a single disturbance before reaching Earth and Venus. A single shock was indeed recorded at Earth only about 3 h earlier than had been predicted. The composite shock was predicted by HAFv.2 to arrive at Venus on 8 December at ∼0500 UT. Solar energetic particles (SEPs) were detected in Venus Express Analyzer of Space Plasmas and Energetic Atoms‐4 data for some 3 d (from <0530 UT on 6 December), and an energetic storm particle (ESP) event signaled the arrival of a single shock wave at 0900 UT on 7 December. SEPs were correspondingly recorded at Mars. However, the eastern flank of the composite shock was predicted to decay to an MHD wave prior to reaching this location, and no shock signature was observed in the available data. The shocks generated in association with two flare events that occurred closer to the West Limb on 13 and 14 December were predicted by HAFv.2 to remain separate when they arrived at Earth but to combine thereafter before reaching Mars. Each was expected to decay to MHD waves before reaching Venus, which was at that time located behind the Sun. Separated shocks were observed to arrive at L1 (ACE) only 8 min earlier than and 5.3 h later than their predicted times. The western flank of the combined shocks was predicted to arrive at Mars early on 20 December 2006. An indication of the passage of this shock was provided by a signature of ion heating in Mars Express IMA (ion mass‐resolving analyzer) data from <0424 UT on 20 December. The predictions of the HAFv.2 model for Earth were each well within the ±11 h. RMS error earlier found, on the basis of significant statistics, to apply at 1 AU during the rise and maximum phases of solar cycle 23. Overall, the model is demonstrated to be capable of predicting the effects produced by shocks and by the background solar wind at Venus, Earth, and Mars. It is suggested that the continuous presence of solar wind monitors (plasma and interplanetary magnetic field observations) at “benchmark planets” can constitute a necessary and valuable component of ongoing and future space weather programs for the validation of solar wind models such as HAFv.2.
Downward current electron beam observed by Cluster and FAST
Authors: Wright Andrew N. , Owen Christopher J. , Chaston Christopher C. , Dunlop Malcolm W.
Published: June 2008

We report observations from a conjunction of FAST and Cluster during an interval of downward current at an MLT of 3–4 h on field lines mapping to the PSBL. Both spacecraft see upgoing electrons with an energy of a few hundred eV, suggesting substantial acceleration has occurred below FAST's altitude of 3200 km. At Cluster, isolated bursts of electrons are seen, and modeling indicates that the current mapped from the ionosphere exists as a collection of current filaments at Cluster (4–5 RE). The current filaments are aligned with the background magnetic field and have a perpendicular scale at Cluster of about 100 km (which maps to 10–20 km in the ionosphere), and is similar to the mapped width observed by FAST. The electron beams are quasi‐steady during a Cluster spacecraft transit time of 1 min. The field aligned current densities at FAST and Cluster are of the order of a few μAms−2 and 0.05 μAm−2, respectively, and j/B is conserved along a current filament.
Dependence of radar signal strength on frequency and aspect angle of nonspecular meteor trails
Authors: Close S. , Hamlin T. , Oppenheim M. , Cox L. , Colestock P.
Published: June 2008

When a meteoroid penetrates Earth's atmosphere, it forms a high‐density ionized plasma column immersed in the ionosphere between approximately 70 and 140 km altitude. High‐power, large‐aperture (HPLA) radars detect nonspecular trails when VHF or UHF radio waves reflect off structures in a turbulent meteor trail. These trails persist from a few milliseconds to many minutes and the return from these trails is referred to as nonspecular trails or range‐spread trail echoes. In this paper, we present analysis of nonspecular trails detected with ALTAIR, which is an HPLA radar operating simultaneously at 160 MHz and 422 MHz on the Kwajalein Atoll. First, we investigate the aspect sensitivity of nonspecular trails and show that as the angle between the radar beam and the background magnetic field increases, the signal strength falls off 3 to 4 dB per degree at 160 MHz. For ALTAIR, this means that the aspect angle must be within approximately 12 degrees in order to detect nonspecular trails using the chosen waveforms. Second, we compare and contrast the meteoroids that form nonspecular trails and find that the meteoroid energy causes much of the variability in the nonspecular trail's signal‐to‐noise ratio (SNR) for a given aspect angle. In addition, we show two range‐resolved fragmentation events that also affect the SNR. Finally, we determine the dependence of SNR on wavelength using two wavelengths and show that the maximum nonspecular trail SNR scales as approximately λ6, with a variation that depends upon altitude.
Response of the inner magnetosphere and the plasma sheet to a sudden impulse
Authors: Keika K. , Nakamura R. , Baumjohann W. , Runov A. , Takada T. , Volwerk M. , Zhang T. L. , Klecker B. , Lucek E. A. , Carr C. , Rème H. , Dandouras I. , André M. , Frey H.
Published: June 2008

The passage of an interplanetary shock caused a sudden compression of the magnetosphere between 0900 UT and 0915 UT on 24 August 2005. An estimate of the shock normal from solar wind data obtained by Geotail upstream of the bow shock indicates symmetric compression with respect to the noon‐midnight meridian. Compression‐related disturbances of the magnetic and electric field and plasma motion were observed by Double Star Program (DSP) Tan Ce 1 (TC1) and Tan Ce 2 (TC2) in the inner magnetosphere and by the Cluster spacecraft in the dawnside plasma sheet. DSP/TC1 and TC2 observations suggest that the disturbances in the inner magnetosphere are propagating from the dayside magnetopause. Cluster S/C 4 observations indicate that the front normal of the disturbances in the dawnside plasma sheet is ϕ ∼ 180° at 0902:50 UT and ϕ = 107° at 0904:34 UT, where ϕ is the longitude in GSM coordinates, if we assume that the measured electric field is on the front plane and the normal lies on the X–Y plane. The timing analysis applied to magnetic field data from the four Cluster spacecraft independently gives a front normal, which is calculated to be ϕ = 131° at about 0904:20 UT. Shock‐associated magnetic and electric field disturbances propagating from both the dayside and flank magnetopauses are detected in the plasma sheet; the latter makes the dominant contribution. Substorms are, however, not triggered at the passage of the disturbances.
Direct video and hydrophone observations of submarine explosive eruptions at NW Rota‐1 volcano, Mariana arc
Authors: Chadwick W. W. , Cashman K. V. , Embley R. W. , Matsumoto H. , Dziak R. P. , de Ronde C. E. J. , Lau T. K. , Deardorff N. D. , Merle S. G.
Published: June 2008

Extraordinary video and hydrophone observations of a submarine explosive eruption were made with a remotely operated vehicle in April 2006 at a depth of 550–560 m on NW Rota‐1 volcano in the Mariana arc. The observed eruption evolved from effusive to explosive, while the eruption rate increased from near zero to 10–100 m3/h. During the peak in activity, cyclic explosive bursts 2–6 min long were separated by shorter non‐eruptive pauses lasting 10–100 s. The size of the ejecta increased with the vigor of the explosions. A portable hydrophone deployed near the vent recorded sounds correlated with the explosive bursts; the highest amplitudes were ∼50 dB higher than ambient noise at frequencies between 10 and 50 Hz. The acoustic data allow us to quantify the durations, amplitudes, and evolution of the eruptive events over time. The low eruption rate, high gas/lava ratio, and rhythmic eruptive behavior at NW Rota‐1 are most consistent with a Strombolian eruptive style. We interpret that the eruption was primarily driven by the venting of magmatic gases, which was also the primary source of the sound recorded during the explosive bursts. The rhythmic nature of the bursts can be explained by partial gas segregation in the conduit and upward migration in a transitional regime between bubbly flow and fully developed slug flow. The strongest explosive bursts were accompanied by flashes of red glow and oscillating eruption plumes in the vent, apparently caused by magma‐seawater interaction and rapid steam formation and condensation. This is the first time submarine explosive eruptions have been witnessed with simultaneous near‐field acoustic recordings.
Features of aerosol optical depths over the Bay of Bengal and the Arabian Sea during premonsoon season: Variabilities and anthropogenic influence
Authors: Kedia Sumita , Ramachandran S.
Published: June 2008

Spectral aerosol optical depths (AOD) measured on board a cruise over the Bay of Bengal and the Arabian Sea during March–May 2006 are analyzed. Mean 0.5 μm AOD over the Bay of Bengal is higher (0.36) than the Arabian Sea (0.25). AODs obtained from MODIS Terra and Aqua are found to track well the Sun photometer AODs. A comparison between Sun photometer and MODIS AODs yielded a correlation coefficient of 0.96. MODIS fine mode fraction over the Bay of Bengal is higher (0.71) when compared to the Arabian Sea value of 0.60. Ångström exponent (α) over the Bay of Bengal is higher at 1.12, indicating the dominance of smaller size aerosols in the aerosol columnar distribution than the Arabian Sea (0.73), while Ångström coefficient (β) is comparable at 0.15 and 0.16 for the Bay of Bengal and the Arabian Sea. Background AODs are higher over the Bay of Bengal and the Arabian Sea indicating a strong continental influence. The scaling distance is lower over the Bay of Bengal due to nearly similar AODs, while the scaling distance over the Arabian Sea is about 2000 km. The anthropogenic influence in AODs over the Bay of Bengal and the Arabian Sea estimated using wind speed dependent AODs and maritime clean AODs are found to agree within ±1σ of the anthropogenic fraction obtained from MODIS AODs and FMFs. The mean anthropogenic contribution to the AODs estimated from the three methods is higher over the Bay of Bengal (68–75%) than the Arabian Sea (51–65%).
Intrusion of recent air in midlatitude stratosphere revealed by in situ tracer measurements and trajectory calculations
Authors: Pirre M. , Pisso I. , Marécal V. , Catoire V. , Mébarki Y. , Robert C.
Published: June 2008

In the midlatitude stratosphere the mean circulation is downward leading to relatively old air. Mixing between this old air and more recent air from the troposphere or the tropical stratosphere can nevertheless occur. In particular, mixing between the lower part of the tropical stratospheric reservoir and the midlatitude stratosphere was reported in the so‐called “tropically controlled transition region” which extends from the tropics to midlatitudes between the isentropic surfaces 380 K and 450 K (15–18 km altitude). O3/CO and HCl/O3 relations derived from the measurements of the in situ tunable lasers (TDLAS) balloon‐borne instrument Spectroscopie Infrarouge par Absorption de Lasers Embarqués (SPIRALE), and 3D air parcels trajectories are used to analyze the characteristics of this region at the time and location of SPIRALE. These measurements took place above Aire sur l'Adour (43.6°N, 0°E) in October 2002. Two‐month 3D backward trajectories ending around each individual measurement recorded with a time step of 1 s are computed on the basis of European Centre for Medium‐Range Weather Forecasts (ECMWF) wind fields. The region is found to extend from 380 K to 465 K, and mixing is found to take place 1 to 2 months before the SPIRALE measurements. The region is composed of two layers with different characteristics. In the 380–405 K layer the recent air is uplifted from below the 380 K isentropic surface, and the percentage of recent air is high (minimum estimate 32%). In the 405–465 K layer the origin of recent air is the tropical stratosphere, and the percentage of the recent air is lower (minimum estimate 12%).
Spatial and temporal distribution of soil organic carbon in nonsorted striped patterned ground of the High Arctic
Authors: Horwath Jennifer L. , Sletten Ronald S. , Hagedorn Birgit , Hallet Bernard
Published: June 2008

The role of periglacial processes on soil carbon distribution is examined at a High Arctic site in northwest Greenland. A 16‐m trench dug across a series of nonsorted stripes at Thule Air Base revealed sand‐rich wedges underlying striped, vegetated troughs, and organic‐rich soil horizons buried at depth. The site has sparse prostrate vegetation and is estimated to contain 9.4 kg/m2 of soil organic carbon (SOC) in the active layer. The distribution of carbon is variable with nearly half (49%) stored in the sand wedges, which only account for 10% of the trench area. Additionally, 62% of the total SOC was found below 25 cm, highlighting the significant role of cryoturbation and physical redistribution of carbon in permafrost‐affected soils. Carbon in the active sand‐rich wedges dates from modern at the surface (65 ± 35 radiocarbon years) to 2695 ± 40 radiocarbon years at depth, and carbon turnover time appears to be ∼450 years. Buried organic horizons found at 50–70 cm depth have radiocarbon ages of 27,480–31,900 BP. A conceptual model is proposed in which the active sand wedges have developed in an approximately 30 ka surface containing buried soils preserved in permafrost or under a cold‐based glacier. As the ice retreated and soils warmed, soil development and active cryoturbation resumed forming nonsorted stripes in the modern surface.
A map analysis of patterned‐ground along a North American Arctic Transect
Authors: Raynolds Martha K. , Walker Donald A. , Munger Corinne A. , Vonlanthen Corinne M. , Kade Anja N.
Published: June 2008

Arctic patterned‐ground features have been described individually, but never examined as parts of integrated landscape/ecosystems that vary along the Arctic climate gradient. Here we examine the complex interrelationships between patterned ground, climate, vegetation and soil along a north‐south transect through all five bioclimate subzones of the North American Arctic. We mapped the vegetation, biomass, end‐of‐summer thaw depths, and snow cover on twenty 10 × 10‐m grids. The vegetation maps illustrate the transition of vegetation types and patterns from north to south. Biomass maps showed lower biomass in the centers of patterned‐ground features than in areas between features, and increasing biomass from north to south. Thaw‐depth maps showed deeper thaw in the centers of features than between features, and shallow thaw on the north and south ends of the transect. Snow depth maps showed less snow on patterned‐ground features subject to differential frost heave compared to areas between features which did not heave, and a north‐south gradient of increasing snow depth. The maps also documented the change from small nonsorted polygons to larger nonsorted circles from north to south, and increasing pattern size with moisture. Principal components analysis revealed underlying relationships between patterned‐ground landscapes and measured vegetation and environmental variables. Climate in combination with the vegetation was the most important factor affecting patterned ground on zonal sites, but soil moisture, texture and chemistry were also important.
Variability in atmospheric O2 and CO2 concentrations in the southern Pacific Ocean and their comparison with model estimates
Authors: Thompson Rona L. , Gloor Manuel , Manning Andrew C. , Lowe David C. , Rödenbeck Christian , Le Quéré Corinne
Published: June 2008

We examine ship‐based observations of atmospheric O2 and CO2 in the southern Pacific Ocean made during two voyages: in February 2003 and in April 2004. We found, for the Austral late summer to autumn, evidence of a maximum in Atmospheric Potential Oxygen (APO) (an atmospheric tracer that is conservative with respect to terrestrial biological activity, APO ≈ O2 + CO2) centered around 50°S owing to biologically driven O2 outgassing (associated with strong productivity in the Sub‐Tropical Convergence Zone) and evidence in the February voyage of a decreasing APO trend from 57°S south toward the Antarctic coast. The observed APO variability appears to be primarily determined by the interplay between atmospheric transport and the spatial distribution of O2 air‐sea flux resulting from regional differences in biological production. Comparisons of these observations with APO derived from coupling the TM3 atmospheric transport model with flux estimates from (1) the PISCES‐T ocean biogeochemistry model, and (2) O2 and CO2 climatologies, show that both PISCES‐T and the climatology reproduce the observed gradient and curvature of APO but underestimate the magnitude of the observed APO maximum in the mid southern latitudes. Although the temporal limitation of our data does not permit us to calculate the annual mean APO gradient, the results support previous model predictions of a decreasing APO trend from the mid to high southern latitudes.
Influence of sediment settling velocity on mechanistic soil erosion modeling
Authors: Tromp‐van Meerveld H. J. , Parlange J.‐Y. , Barry D. A. , Tromp M. F. , Sander G. C. , Walter M. T. , Parlange M. B.
Published: June 2008

We report on a series of soil erosion experiments performed on the 2‐m × 6‐m EPFL erosion flume. Total sediment concentrations and the concentrations of seven size fractions (<2, 2–20, 20–50, 50–100, 100–315, 315–1000, and >1000 μm) were measured during 14 high‐intensity (47.5–52.5 mm/h) rainfall experiments on three different slopes (2.2–12.4%). The short‐time and long‐time analytical solutions for the Hairsine‐Rose erosion model were rewritten to account for infiltration. The newly collected data were used to test the model under conditions that had not been explored before (steeper slopes, infiltration, more realistic soil composition). The analytical solutions could predict the observed total sediment concentration well. However, the observed sediment concentrations for the individual size classes could be predicted only when adjusted settling velocities were used. The adjusted settling velocities were estimated through manual optimization. The optimized settling velocities for the smallest and midsize particles (<100 μm) were larger than calculated from Stokes' law or measured in a 0.47‐m tube, while the optimized settling velocities for the largest particles (>315 μm) were smaller than measured. The effective settling velocities could also be calculated from the calculated amount of material in the shield of each size class at the end of the experiments. This calculated settling velocity distribution agreed very well with the optimized settling velocities. This study moves the Hairsine‐Rose model another step closer to an operational soil erosion model for field applications.
On the incompleteness of the historical record of North Atlantic tropical cyclones
Authors: Solow Andrew R. , Beet Andrew R.
Published: June 2008

There is some question as to whether the historical record of observed North Atlantic tropical cyclones prior to the advent of satellite coverage is complete. This question is central to understanding the historical trend in tropical cyclone activity and the effect of environmental factors on it. To address this question, a statistical model of the relationship between annual cyclone counts between 1870 and 2004 and sea surface temperature and the state of the Southern Oscillation is extended to allow for non‐decreasing observation probability prior to 1966. The estimated observation probabilities increase from 0.72 in 1870 to 1 in 1964. Allowing for record incompleteness reduces the estimated effect of sea surface temperature on annual tropical cyclone activity.
Sunlight, water, and ice: Extreme Arctic sea ice melt during the summer of 2007
Authors: Perovich Donald K. , Richter‐Menge Jacqueline A. , Jones Kathleen F. , Light Bonnie
Published: June 2008

The summer extent of the Arctic sea ice cover, widely recognized as an indicator of climate change, has been declining for the past few decades reaching a record minimum in September 2007. The causes of the dramatic loss have implications for the future trajectory of the Arctic sea ice cover. Ice mass balance observations demonstrate that there was an extraordinarily large amount of melting on the bottom of the ice in the Beaufort Sea in the summer of 2007. Calculations indicate that solar heating of the upper ocean was the primary source of heat for this observed enhanced Beaufort Sea bottom melting. An increase in the open water fraction resulted in a 500% positive anomaly in solar heat input to the upper ocean, triggering an ice–albedo feedback and contributing to the accelerating ice retreat.
Toward better paleocarbonate ion reconstructions: New insights regarding the CaCO3 size index
Authors: Chiu Tzu‐Chien , Broecker Wallace S.
Published: June 2008

The reconstruction of paleocarbonate ion concentrations provides an important constraint on the contribution of the CaCO3 cycle to the decrease in atmospheric CO2 content during glacial time. Such reconstructions have been challenging because each of the existing paleo‐[CO32−] indices has serious limitations. In this study, we reexamine the Broecker‐Clark CaCO3 size index by analyzing the <20 μm, 20 to 38 μm, and 38 to 63 μm fractions in sediments from the Ontong‐Java Plateau and the Ceara Rise. Scanning electron microscope analyses demonstrate that the less than 20 μm CaCO3 is dominated by coccoliths and the greater than 20 μm CaCO3 is dominated by foraminifera. Our results clearly indicate that the coccoliths are far more resistant to dissolution than the foraminifera. Referenced to a core top sample from 2.31 km depth in a core top sample from 4.04 km depth on the Ontong‐Java Plateau, ∼70% of the foraminifera CaCO3 was dissolved as opposed to only ∼7% of the coccolith CaCO3. We found that the dissolution of foraminifera shells did not produce a significant amount of fragments smaller than 63 μm in size, and thus the Broecker‐Clark size index is not a measure of the extent of fragmentation. Rather, it is a measure of the extent of differential dissolution of foraminifera relative to coccoliths. On the basis of these results, we propose a new dissolution index which involves the ratio of dissolution‐susceptible foraminifera CaCO3 to total CaCO3.
A phenomenological fitting curve for the magnetocaloric effect of materials with a second-order phase transition
Authors: Dong Q. Y. , Zhang H. W. , Sun J. R. , Shen B. G. , Franco V.
Published: June 2008

The magnetic entropy change of polycrystalline samples Gd, La(Fe0.92Co0.08)11.83Al1.17, LaFe10.8Si2.2, Mn5Ge2.7Ga0.3, Nd2AlFe13Mn3, and TbCo2 with a second-order phase transition has been investigated. A uniform phenomenological function that describes the magnetic entropy change is found for these materials. This could be of great benefit for the design of magnetic refrigerators. The field dependence of the critical exponent for the variation in the maximum entropy change with field is studied. The critical exponent value of 2/3, which is predicted by the mean field theory, is only satisfied for moderate field values. The refrigerant capacity is analyzed and compared to the predictions of the fitting function.
Redshift of the excited state due to a nondegenerate biexciton in self-organized quantum dots
Authors: Kim K. , Norris T. B. , Hohenester U.
Published: June 2008

Using femtosecond differential transmission spectroscopy, we observed a “nondegenerate” biexciton, consisting of an electron-hole pair in the dot ground state and an electron-hole pair in the excited state, in InGaAs self-organized quantum dots. We resonantly pumped the ground state transition in the quantum dots and observed an induced resonance in the probe differential transmission spectrum near the first excited-state transition, which we attribute to the formation of a nondegenerate biexciton state. The binding energy of 15 meV does not change with excitation power, thus reflecting a genuine feature of few-particle states. Our theoretical model calculations show good agreement with these experimental results. When a prepulse is used to generate a population inversion in the quantum dots, we also observed the effects of nondegenerate biexcitonic correlations in differential transmission.
Modulating indium gallium zinc oxide transistor characteristics with discrete redox states of molecules embedded in the gate dielectric
Authors: Sarkar Smita , Suresh Arun , Myers Frank B. , Muth John F. , Misra Veena
Published: June 2008

A hybrid inorganic-organic device has been fabricated by incorporating redox active molecules in indium gallium zinc oxide thin film transistors. These devices show a clear modulation of source-drain current characteristics, which is associated with the quantized energy states of the redox active molecules. The molecules show discreet redox peaks in the current characteristics of transistors and a true-molecular-based charge transport has been demonstrated in a completely solid state device.
Linear and nonlinear quantum ion-acoustic waves in dense magnetized electron-positron-ion plasmas
Authors: Khan S. A. , Masood W.
Published: June 2008

The linear and nonlinear quantum ion-acoustic waves propagating obliquely in two dimensions in superdense, magnetized electron-positron-ion quantum plasma are investigated on the basis of quantum hydrodynamic model. It is found in linear analysis that the quantum corrections of diffraction are important in the very short wavelength regime that may be found in dense astrophysical plasmas. To investigate the solitary waves, the Zakharov-Kuznetsov equation is derived and the solution is presented in the small amplitude limit. By numerical analysis, it is found that the soliton structure of the ion acoustic wave depends upon quantum pressure, concentration of positrons, strength of magnetic field, and the propagation angle.
Delayed crack propagation in barium titanate single crystals in humid air
Authors: Jiang Bing , Bai Yang , Cao Jiang-Li , Su Yanjing , Shi San-Qiang , Chu Wuyang , Qiao Lijie
Published: June 2008

Domain witching of ferroelectrics under mechanical or electric load in vacuum or dry air has been intensively studied. However, the effects of environments on the domain switching in ferroelectrics have not been well understood. Here, we demonstrate that domain configurations in BaTiO3 single crystal under sustained load can be significantly affected by the humidity due to the decrease in surface energy and electrostatic energy upon adsorption of polar water molecules. Consequently, the crack propagation behaviors of the ferroelectrics under sustained load can be remarkably altered.
Potential formation in a one-dimensional bounded plasma system containing a two-electron temperature plasma: Kinetic model and PIC simulation
Authors: Gyergyek T. , Jurčič-Zlobec B. , Čerček M.
Published: June 2008

Potential formation in a bounded plasma system that contains electrons with a two-temperature velocity distribution and is terminated by a floating, electron emitting electrode (collector) is studied by a one-dimensional kinetic model. A method on how to determine the boundary conditions at the collector for the numerical solution of the Poisson equation is presented. The difference between the regular and the irregular numerical solutions of the Poisson equation is explained. The regular numerical solution of the Poisson equation fulfills the boundary conditions at the source and can be computed for any distance from the collector. The irregular solution does not fulfill the source boundary conditions and the computation breaks down at some distance from the collector. An excellent agreement of the values of the potential at the inflection point found from the numerical solution of the Poisson equation with the values predicted by the analytical model is obtained. Potential, electric field, and particle density profiles found by the numerical solution of the Poisson equation are compared to the profiles obtained with the particle in cell computer simulation. A very good quantitative agreement of the potential and electric field profiles is obtained. For certain values of the parameters the analytical model predicts three possible values of the potential at the inflection point. In such cases always only one of the corresponding numerical solutions of the Poisson equation is regular, while the other two are irregular. The regular numerical solution of the Poisson equation always corresponds to the solution of the model that predicts the largest ion flux to the collector.
Application of the method of increments to the adsorption of CO on the CeO2(110) surface
Authors: Müller Carsten , Herschend Björn , Hermansson Kersti , Paulus Beate
Published: June 2008

We have combined an embedded-cluster model with an extension of the method of increments to treat the adsorption of molecules on a surface. In this way we are able to investigate the physisorption of CO on CeO2(110) at the MP2, MP4(SDTQ), and CCSD(T) levels with only moderate computational costs. We find that, at the CCSD(T) level, 25% of the adsorption energy originates from electron correlation. The interactions of the CO molecule with its five nearest cerium and oxygen neighbors in the surface layer make the largest contributions to the electron correlation. Approximately 97% of the adsorption-induced electron correlation energy part of the adsorption energy is recovered by the method of increments (in our chosen expansion), at the MP2 level.