bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological, ecological and genetic variability of Lavandula luisieri (Rozeira) Rivas-Martínez in central eastern Portugal
Authors: Delgado Fernanda , Ribeiro Sílvia , Alves Álvaro , Bettencourt Eliseu , Dias Sónia
Published: March 2010

The morphological characterisation and data analysis of germplasm accessions of wild Portuguese Lavandula luisieri (Rozeira) Rivas-Martínez from the southern Beira Interior region of central eastern Portugal are described. The study, based on seeds and cultivated plants, was conducted in 2005, 2006 and 2008 among populations selected from four sites (I, II, III and IV). Quantitative and qualitative phenotypic data relating to a set of 35 morphological traits were analysed using canonical discriminant analysis. Genetic similarity among accessions was assessed using amplified fragment length polymorphism molecular markers. The traits contributing most to the variability among studied populations were related to plant density, leaf colour, seed weight and various spike and flower characteristics. Plant populations from each of the four test sites were statistically distinct, exhibiting unique characteristics when compared with one another; however, populations from Sites II, III and IV showed greater genetic similarity and differed substantially from the population of Site I. Altitude and temperature were found to be the most significant environmental variables influencing plant traits, yet the morphological variability of L. luisieri was also influenced by soil pH levels, suggesting that the expressed variability is not only a result of genetic characteristics but also of existing ecological conditions.
Serum Retinol, α-tocopherol, and Lipid Peroxide Concentrations in Low-income Indian Pregnant Mothers
Authors: Lohia Neha , Udipi Shobha , Ghugre Padmini , Deshpande Kishori
Published: March 2010

Serum α-tocopherol, retinol, and malondialdehyde concentrations were measured at 7th month of pregnancy in 122 women from low socio-economic background. Maternal anthropometric measurements, 24-hour nutrient intakes, and pregnancy outcome were recorded. One-third (34.3 %) of mothers had low birth weight babies and 10 % delivered preterm. Maternal diets were inadequate in all the nutrients, the most limiting being vitamin A. Three-fourths of mothers had intakes less than 25 % of the Indian recommended daily intake (RDI) of 600 µg retinol equivalents/day. Serum α-tocopherol concentrations of 98 % were indicative of deficiency and almost half the mothers had low serum retinol concentrations (≤10 µg/dL). Mean malondialdehyde level was 7.0 ± 1.4 nmoles/mL. These values are higher than reports in the literature and were attributable to poor intake of most dietary antioxidants. Malondialdehyde concentrations were negatively correlated with serum α-tocopherol. Birth weight was positively correlated with maternal weight and biceps skinfold thickness, macronutrient intakes, serum retinol, and α-tocopherol concentrations. Preterm delivery was associated with low anthropometric measurements and low nutrient intakes especially vitamin A. Mothers who delivered preterm had significantly lower malondialdehyde concentrations than those who delivered at term. The role of antioxidant nutrients, especially vitamin A and oxidative stress in relation to fetal growth and pregnancy outcome among mothers from low socioeconomic settings requires attention.
Antioxidant Activity of Olive Polyphenols in Humans: a Review
Authors: Raederstorff Daniel
Published: March 2010

In vitro and animal studies show that polyphenols from olives have potent antioxidant activities; 50 % of the phenolic compounds contained in olives and virgin olive oil are hydroxytyrosol and derivatives thereof. Hydroxytyrosol is the major olive polyphenol consumed and well absorbed in humans. It is considered to have the highest antioxidant potency compared to the other olive polyphenols. Review of the human intervention studies showed that olive polyphenols decreased the levels of oxidized-LDL in plasma and positively affected several biomarkers of oxidative damage. The antioxidant effects of olive polyphenols on low-density lipoprotein (LDL) oxidation are observed after a dietary intake of about 10 mg per day. The overall evidence from in vitro assays, and animal and human studies support the antioxidant effect of olive polyphenols. However, further larger human studies are needed to clarify the effect of olive polyphenols on markers of oxidative stress, particularly DNA damage and plasma isoprostane levels.
Fasting and Post-methionine Homocysteine Levels in Alzheimers Disease and Vascular Dementia
Authors: Villa Paola , Bosco Paolo , Ferri Raffaele , Perri Concetta , Suriano Rosanna , Costantini Barbara , Macrì Francesca , Proto Caterina , Cento Rosa Maria , Lanzone Antonio
Published: March 2010

The aim of the study is to compare the basal homocysteine levels in patients with impairment of cognitive status, and in controls, to evaluate if the methionine loading test is able to identify any differences between patients with Alzheimers disease and patients with vascular dementia. We enrolled 56 subjects, 20 with Alzheimers disease, 18 with vascular dementia, and 18 normal controls. The data shown that plasma homocysteine levels both basal and post-methionine load were significantly higher in the two groups of demented patients than in the control group. No significant differences were found between Alzheimers patients and vascular dementia patients. The homocysteine percent increase after a methionine loading test was significantly higher in the controls with respect to the two groups of demented patients. Only in Alzheimers patients were vitamin B12 basal levels negatively correlated with basal homocysteine levels (p<0.05), while positively correlated with the homocysteine percent increase after load (p<0.05). The study confirms the possible role of chronically elevated homocysteinemia in neuronal degeneration in demented patients. Even if the methionine loading test revealed an abnormal homocysteine metabolism in demented patients, it didnt show any difference among patients with Alzheimers disease and vascular dementia.
The Effect of 4 Weeks Treatment with a 2-gram Daily Dose of Pyruvate on Body Composition in Healthy Trained Men
Authors: Ostojic Sergej M. , Ahmetovic Zlatko
Published: March 2010

The principal aim of this study was to determine the effects of short-term (28 days) pyruvate supplementation on body composition in young healthy men. Twenty-two young (mean age, 22.2 ± 2.7 years) male soccer players were allocated to two randomly assigned groups in a placebo-controlled, double-blind design. Subjects in the pyruvate group orally ingested tablets that contained pyruvate at a dose of 2 g per day in two equal doses for 4 weeks. There were no statistically significant changes in weight and body-mass index (BMI) within or between groups (p>0.05) after the supplementation protocol. Percentage of body fat decreased similarly in both pyruvate and placebo groups after the supplementation protocol (p>0.05). There were no changes in waist-to-hip ratio (WHR), arm fat index (AFI), and total or regional muscle mass within or between groups (p>0.05). No subject reported any side effects from pyruvate or placebo treatment. The results of the present study indicate that supplementation with pyruvate during training does not significantly alter the body mass, fat, and muscle mass in healthy trained men. Pyruvate supplementation appears to be ineffective as a fat loss strategy in young athletes.
Bio-discrimination of α-tocopherol Stereoisomers in Rearing and Veal Calves Fed Milk Replacer Supplemented with All-rac-α-tocopheryl Acetate
Authors: Dersjant-Li  , Jensen  , Bos  , Peisker
Published: March 2010

This study evaluated the biological discrimination of different α-tocopherol stereoisomers (i. e. RRR-, RRS-, RSR-, RSS- and the four 2S-α-tocopherols) from all-rac-α-tocopheryl acetate supplementation in milk replacer for rearing and veal calves respectively, in practical farming conditions. Two experiments were conducted. In experiment 1, six rearing calves were fed milk replacer supplemented with 80 mg/kg all-rac-α-tocopheryl acetate for a period of 9 weeks. The calves were supplied calf starter concentrate from 1 to 12 weeks. In experiment 2, six veal calves were fed milk replacer supplemented with 80 mg/kg all-rac-α-tocopheryl acetate for a period of 24 weeks. Blood samples were taken at the start and every 4 weeks until 12 weeks for rearing calves in experiment 1, and until slaughter (24 weeks) for veal calves in experiment 2. Liver, adipose, muscle, and brain samples were taken at slaughter of the six veal calves in experiment 2. The distribution of different α-tocopherol stereoisomers in feed, plasma, and tissues was analyzed. In both experiments, it was observed that RRR-α-tocopherol was the dominant stereoisomer in plasma and tissues. The average percentage of the RRR-α-tocopherol stereoisomer was 64 %, and 39 % of the total α-tocopherol in plasma for rearing and veal calves, respectively. The higher RRR-α-tocopherol stereoisomer proportion as percentage of the total α-tocopherol in rearing calves was related to higher dietary natural vitamin E intake. Other 2R-α-tocopherol stereoisomers had lower utilization efficiency than RRR-α-tocopherol stereoisomer. 2S-α-tocopherol stereoisomers were basically not utilized by calves.
Vitamin B6 Compounds are Capable of Reducing the Superoxide Radical and Lipid Peroxide Levels Induced by H2O2 in Vascular Endothelial Cells in Culture
Authors: Mahfouz Mohamedain M. , Zhou Sherry Q. , Kummerow Fred A.
Published: March 2010

Pyridoxamine, pyridoxine, and pyridoxal phosphate were tested to examine if they have antioxidant properties. Endothelial cells exposed to 0.5 mM H2O2 for 2 hours increased the superoxide anion and lipid peroxide levels as biomarkers of oxidative stress. The increase of superoxide was mainly due to the activation of NADPH-oxidase by H2O2. Preincubation of the endothelial cells with 0.1 or 1.0 mM of pyridoxamine or pyridoxal phosphate for one-half hour before H2O2 exposure significantly reduced the superoxide and lipid peroxide compared to the cells exposed to H2O2 only. Preincubation of the cells with 0.1 or 1.0 mM of pyridoxine also significantly reduced the lipid peroxide but did not significantly affect the superoxide level unless the preincubation time was extended to 24 hours. The prostacyclin release by endothelial cells was also significantly inhibited by H2O2. However, the preincubation of endothelial cells with 1.0 mM of pyridoxamine, pyridoxine, or pyridoxal phosphate did not prevent that inhibition. These results indicate that pyridoxamine, pyridoxine, and pyridoxal phosphate acted as antioxidants and reduced the superoxide and lipid peroxides induced by H2O2, but did not protect the cells from the effects directly related to H2O2 itself.
Perinatal Vitamin A Status in Relation to Neurodevelopmental Outcome at two Years of Age
Authors: Zhang Xuan , Chen Ke , Wei Xiao-Ping , Qu Ping , Liu You-Xue , Chen Jie , Li Ting-Yu
Published: March 2010

Information about the effect of antioxidant vitamins nutrition during pregnancy on offsprings intellectual development is extremely limited. Objective: To investigate the correlation of antioxidant vitamins (Vitamin A, E and C) at delivery and the neurodevelopment of early childhood. Method: A total of 158 paired maternal-neonatal subjects were recruited. The serum concentrations of vitamin A, E and C in maternal and cord blood after delivery were determined and intellectual development was evaluated by Gesell Development Schedule (GDS) at two years old. Result: After adjusting for potential confounders, vitamin A placental transport ratio (VA-PTR) was positively associated with motor area development quotients (DQ) and average DQ(p<0.01). Cord VA level was positively related with language area and social area DQ (p<0.05). Nevertheless, there was no significant association between cord VE, VC levels, VE PTR or VC PTR and GDS. The adaptive area and average DQ in high cord VA group was higher than those in low VA group (p<0.05). Cord VA level and VA-PTR were positively associated with birth head circumference and birth weight, respectively. Conclusion: Our data suggested that adequate vitamin A at delivery had beneficial influence on neonatal birth outcomes and childrens neurodevelopment in later childhood.
Effect of Vitamin E Supplementation on Oxidative Stress in a Rat Model of Diet-induced Obesity
Authors: Shen XiuHua , Tang QingYa , Wu Jiang , Feng Yi , Huang Juan , Cai Wei
Published: March 2010

Objective: To evaluate the effect of vitamin E on the level of oxidative stress in diet-induced obese Sprague-Dawley rats. Methods: Thirty weaning male rats were placed into three groups with 10 animals each: a control group with normal chow, a diet-induced obesity group (DIO) with high-fat diet, and an intervention group with high-fat diet supplemented with vitamin E (VE, 350 mg/kg). Blood and adipose tissue were collected from rats after 10 weeks. Biomarkers of oxidative stress were detected for plasma 8-epi-prostaglandin- F2α (8-epi-PGF2α), thiobarbituric acid-reactive substances (TBARS), total anti-oxidative capacity (TAOC), α-tocopherol, superoxide dismutase (SOD) activity, and glutathione peroxidase activity (GPx). Lipid and glucose metabolism parameters such as plasma glucose, insulin, and triacylglycerol (TG) were also analyzed. Results: After 10 weeks, all obese rats (both the DIO and VE groups) had higher plasma 8-epi-PGF2α and TBARS levels than the controls. Their plasma-adjusted α-tocopherol, SOD, and GPx activities were lower than the control levels but insulin was higher (p<0.01). The VE intervention increased plasma SOD, GPx, and T-AOC, and decreased 8-epi-PGF2α (p<0.05). VE intervention also decreased plasma glucose, insulin, and TG levels (p<0.05). Conclusions: Increased oxidative stress could be an important target for the prevention of obesity-related diseases. Vitamin E has moderate effects for improvement of oxidative stress status and glucose metabolism in the animal model of diet-induced obesity.
Glioblastoma multiforme – Neue Hoffnungen dank moderner Therapieansätze
Authors: Gautschi  , Cadosch  , Collen  , Land  , Hoederath  , Hildebrandt  , Fournier  , Hundsberger
Published: March 2010

Das Glioblastoma multiforme (GBM) ist der häufigste maligne, hirneigene Tumor und hat trotz moderner Therapieoptionen eine fatale Prognose. Mehr als die Hälfte aller Patienten versterben innerhalb des ersten Jahres nach Diagnosestellung. Fokale neurologische Ausfälle, epileptische Anfälle, Persönlichkeitsveränderungen sowie neurokognitive Störungen zählen zu den typischen Symptomen eines GBM. Die Verdachtsdiagnose wird anhand zerebraler bildgebender Verfahren gestellt und histopathologisch mittels Biopsie oder Resektion bestätigt. Die chirurgische Exstirpation, gefolgt von einer zeitgleichen Kombination aus Radiotherapie und Chemotherapie mit Temozolomid und anschliessender adjuvanter Chemotherapie mit Temozolomid, gilt derzeit als Standardtherapie. Aktuell wird weltweit eine Vielzahl an interdisziplinären Studien mit Glioblastompatienten durchgeführt mit dem gemeinsamen Ziel, die Prognose der betroffenen Patienten weiter zu verbessern.
Myoclonies chez une personne très âgée: une cause fréquente et réversible
Authors: Gardiol  , Lamy  , Humbert
Published: March 2010

Nous rapportons le cas d'une personne âgée de 98 ans hospitalisée pour des myoclonies généralisées. Le laboratoire montre une hypocalcémie ainsi qu'une vitamine D abaissée. Nous posons donc le diagnostic de troubles neuromusculaires sur hypocalcémie dans un contexte d'hypovitaminose D. Les symptômes s'amendent rapidement après substitution intraveineuse puis orale. Ce cas illustre l'importance du bilan électrolytique, surtout chez la personne âgée, lors de manifestations neuromusculaires.
Gravitational circulation and its response to the variation in river discharge in the Seto Inland Sea, Japan
Authors: Kobayashi Shiho , Zenitani Hiromu , Nagamoto Kazuhisa , Futamura Akira , Fujiwara Tateki
Published: March 2010

In this study gravitational circulation and its response to the variation in river discharge have been investigated in the Seto Inland Sea, Japan. Monthly hydrographic surveys have been conducted from 2002 to 2006 in Hiuchi‐Nada, a basin located between two straits. Horizontal salinity gradients along the channel varied as the 9/10 power of the river discharge into one end of the basin. Significant volume fluxes which were proportional to the horizontal salinity gradients were found. The relationship between river discharge (R m3 s−1) and the volume flux (Q m3 s−1) was represented as Q = 13.9R0.88. When river discharge increased, vertical density gradients were intensified and then along‐channel horizontal density gradients were gradually enhanced due to vertical mixing at the western strait. These gradients drove gravitational circulations along the channel. The gravitational circulations were not uniform across the channel and accompanied by horizontal circulations. In the northern part of the basin, low‐salinity water at the eastern end of the basin was directed toward the west and high‐salinity water was directed toward the east. The eastward flows arising from the intrusion of relatively heavy water at the western strait extended from the bottom to the surface. In the southern part, low‐salinity water was directed toward the west. The westward flows arising from the intrusion of relatively light water at the eastern strait concentrated in the middle layer and formed a plume‐like structure, accompanied by the eastward flow under the plume. These situations were responsible for the development of the bulk exchange flux.
Radial anisotropy and prior petrological constraints: A comparative study
Authors: Beghein C.
Published: March 2010

Radial seismic anisotropy models are traditionally obtained using empirical constraints based on laboratory experiments and petrological considerations. We tested the hypothesis that such petrological constraints affect the uppermost mantle models of S wave anisotropy using a statistical approach. In addition, we were able to determine which model features are constrained by the data and which are dominated by the prior. We focused on large‐scale models and found that the most likely models obtained in both cases are highly correlated. This demonstrates that for the best data‐fitting solution, the geometry of uppermost mantle radial anisotropy is not strongly affected by prior petrological constraints. The amplitude of the anomalies, however, can change significantly: The best data‐fitting model obtained without petrological constraints displays stronger amplitudes than the one obtained with prior. This could become an issue when quantitatively interpreting seismic anisotropy models, and thus emphasizes the importance of accurately accounting for parameter uncertainties and trade‐offs, and of understanding whether the seismic data or the prior constraints the model. We showed that model uncertainties are strongly affected by the prior as the relative RMS uncertainties were reduced by a factor of 2. In addition, we showed that while the model distributions are not necessarily Gaussian a priori, imposing petrological constraints can force the distributions to be narrower and more Gaussian‐like, as expected from inverse theory. Finally, we demonstrated that the age dependence of seismic wave velocities is robust and independent of prior constraints. A similar age signal exists for anisotropy, but with larger uncertainties without prior constraints.
Slab window migration and terrane accretion preserved by low‐temperature thermochronology of a magmatic arc, northern Antarctic Peninsula
Authors: Guenthner William R. , Barbeau David L. , Reiners Peter W. , Thomson Stuart N.
Published: March 2010

Existing paleogeographic reconstructions indicate that the northern Antarctic Peninsula was central to several Mesozoic and Cenozoic tectonic events that have implications for ocean circulation and continental margin evolution. To evaluate the exhumational record of these processes, we collected new samples and measured fission track and (U‐Th)/He cooling ages of apatite and zircon from 13 Jurassic and Cretaceous granitoids in western Graham Land between the northern tip of the peninsula and the Antarctic Circle. Apatite He data reveal distinct ages and systematic age patterns north and south of Anvers Island, near the midpoint of the study area: To the south, apatite He ages range from 16 to 8 Ma and young northward, whereas to the north they range between 65 and 24 Ma (with one exception at 11 Ma) and young southward. Thermal histories inferred from the ages and closure temperatures of multiple thermochronometers in single samples indicate distinct histories for northern and southern Graham Land. Northern sites reveal a Late Cretaceous pulse of rapid cooling (>7°C/Myr) followed by very slow cooling (∼1°C/Myr) to the Recent, whereas southern sites record either a pulse of rapid mid‐Miocene cooling (∼8°C/Myr) or steady and moderate cooling (∼3°C/Myr) from the Late Cretaceous to the Recent. We interpret the Late Cretaceous rapid cooling in the northern part of the study area as a possible manifestation of terrane accretion associated with the Palmer Land event. We interpret the systematic spatial trends in apatite He ages and contrasting thermal histories along the peninsula as recording progressive Late Cenozoic northward opening of a slab window south of Anvers Island. This is consistent with a time transgressive pulse of ∼2–3 km of rock uplift and exhumation in the upper plate following ridge‐trench collision, cessation of subduction, and opening of the slab window, presumably caused by increased asthenospheric upwelling beneath the overriding plate.
Delamination or slab detachment beneath Vrancea? New arguments from local earthquake tomography
Authors: Koulakov Ivan , Zaharia Bogdan , Enescu Bogdan , Radulian M. , Popa M. , Parolai Stefano , Zschau J.
Published: March 2010

Vrancea, located at the southeastern Carpathians Arc bend, is one of the areas in the Alpine‐Himalayan belt that features strong earthquakes occurring at intermediate depths (60–200 km). In this study we investigated the crustal and lithospheric structure beneath the Vrancea seismic area using a local earthquake tomography approach. We used an updated and revised catalog, spanning from 1982 to 2006 that uses data from both permanent and temporary networks in the target area. Simultaneous tomographic inversion for the Vp and Vs anomalies and the Vp/Vs ratio and source locations was done using the LOTOS code. The reliability and robustness of the results were rigorously checked using various tests (e.g., by studying the role of different parameters on the results of the inversion, performing the inversion using random data subsets, and synthetic modeling). The tomography results clearly indicate the presence of a high‐velocity material beneath Vrancea at a depth interval of about 60–200 km that coincides with the distribution of intermediate‐depth seismicity. This result agrees generally with previous tomographic studies. We compare two scenarios leading to this structure: (1) subduction and slab detachment and (2) “drop forming” or delamination. The latter mechanism presumes that the thickening of the crust due to continent‐continent collision causes transformation of the mafic lower crust into denser eclogite. This material accumulates until it reaches a critical mass, at which point it forms a large drop that begins to fall down. We propose that the high‐velocity anomaly we observe in our tomogram might represent the descending eclogitic lower crust material enveloped by the entrained lithosphere. It is possible that a similar delamination process can be observed in other parts of the Alpine‐Himalayan belt, such as in the Pamir Hindu‐Kush area.
Active shoreline of Ontario Lacus, Titan: A morphological study of the lake and its surroundings
Authors: Wall S. , Hayes A. , Bristow C. , Lorenz R. , Stofan E. , Lunine J. , Le Gall A. , Janssen M. , Lopes R. , Wye L. , Soderblom L. , Paillou P. , Aharonson O. , Zebker H. , Farr T. , Mitri G. , Kirk R. , Mitchell K. , Notarnicola C. , Casarano D. , Ventura B.
Published: March 2010

Of more than 400 filled lakes now identified on Titan, the first and largest reported in the southern latitudes is Ontario Lacus, which is dark in both infrared and microwave. Here we describe recent observations including synthetic aperture radar (SAR) images by Cassini's radar instrument (λ = 2 cm) and show morphological evidence for active material transport and erosion. Ontario Lacus lies in a shallow depression, with greater relief on the southwestern shore and a gently sloping, possibly wave‐generated beach to the northeast. The lake has a closed internal drainage system fed by Earth‐like rivers, deltas and alluvial fans. Evidence for active shoreline processes, including the wave‐modified lakefront and deltaic deposition, indicates that Ontario is a dynamic feature undergoing typical terrestrial forms of littoral modification.
A simple method for the estimation of thermal inertia
Authors: Wang J. , Bras R. L. , Sivandran G. , Knox R. G.
Published: March 2010

A simple method for estimating thermal inertia using daily amplitude of surface soil heat flux and temperature is proposed. Based on an analytical solution of the diffusion equation where the soil temperature is idealized as a sinusoidal function, the thermal inertia is expressed as a proportional coefficient in a linear equation relating the amplitudes of surface soil (ground) heat flux and temperature. Tests of the proposed method demonstrate that this simple method is potentially useful in the Earth and extra‐terrestrial remote sensing.
Variability of Indian summer monsoon in a new upper tropospheric humidity data set
Authors: Xavier Prince K. , John Viju O. , Buehler S. A. , Ajayamohan R. S. , Sijikumar S.
Published: March 2010

Using a new data set we demonstrate the variability of upper troposphere humidity (UTH) associated with the Indian Summer Monsoon (ISM). The main advantage of the new data set is its all‐sky representation which is essential to capture the full variability of humidity even in cloudy areas. We show that UTH undergoes significant variations during the active/break phases of the monsoon and discuss the mechanisms. The interannual variations of monsoon are also well reflected in the UTH. A preliminary investigation into the cause of the 2009 monsoon failure reveals anomalous subsidence and suppressed convection over the monsoon region due to anomalous warm conditions in the equatorial Pacific throughout the summer. The large scale drying of the upper troposphere may also have contributed to a negative feedback in suppressing convection.
What are the dominant features of rainfall leading to realistic large‐scale crop yield simulations in West Africa?
Authors: Berg Alexis , Sultan Benjamin , de Noblet‐Ducoudré Nathalie
Published: March 2010

A large‐scale crop model is forced by a range of climate datasets over West Africa to test the sensitivity of simulated yields to errors in input rainfall. The model skill, defined as the correlation between observed and simulated yield anomalies over 1968–1990 at the country scale, is used for assessment. We show that there are two essential rainfall features for the model to skillfully simulate interannual yield variability at the country scale: cumulative annual variability and frequency. At such a scale, providing additional information on intraseasonal variability, such as the chronology of rain events, does not improve the model skill. We suggest that such information is relevant at smaller spatial scales but is not spatially consistent enough to impact large‐scale yield variability.
Numerical estimates of drift loss and Dst effect for outer radiation belt relativistic electrons with arbitrary pitch angle
Authors: Kim Kyung Chan , Lee D.‐Y. , Kim H.‐J. , Lee E. S. , Choi C. R.
Published: March 2010

Satellite observations often show that relativistic electron fluxes that decrease during a geomagnetic storm main phase do not recover their prestorm level even when the storm has substantially recovered. A possible explanation for such sustained flux dropout is that the electrons that move to larger shells (L shells) aided by the disturbance storm time (Dst) effect associated with the main phase geomagnetic field depression may be suffering drift loss to the magnetopause, resulting in irreversible (nonadiabatic) flux decreases during a geomagnetic storm. In this study, we have numerically evaluated the drift loss effect by combining it with the Dst effect and including off‐equatorially mirroring electrons for three different storm conditions obtained by averaging 95 geomagnetic storms that occurred from 1997 to 2002. Using the Tsyganenko T02 model and our own simplified method, we estimated the storm time flux changes based on the guiding center orbit dynamics. Assuming that there is no competing source mechanism taking place at the same time, our calculations of the electron fluxes at equatorial midnight suggest that the drift loss when combined with the Dst effect can be responsible for flux dropouts, which can be seen even inside the geosynchronous orbit during storm periods. Specifically, by evaluating omnidirectional flux values at three specific times that correspond to the storm onset time, the time of minimum Dst value, and the end of the Dst recovery, we have obtained the following numerical results. First, for the strong storm with −150 nT < Dstmin ≤ −100 nT, the combined drift loss and Dst effect can cause a complete dropout of the electron flux for r ≥ ∼5 RE at the end of the storm recovery. A nearly full recovery of the particle flux by the adiabatic Dst effect is seen only for r < ∼5 RE. For the moderate storm with −100 nT < Dstmin ≤ −50 nT, the overall flux decrease level at the end of the storm recovery is less significant compared to that of the strong storm. However, the combined loss effect can still penetrate into r ∼ 5 RE, leading to some partial dropout of the flux. For the severe storm with Dstmin ≤ −150 nT, the flux dropout is far more significant than for the other two storms, indicating that the combined drift loss and Dst effect can even reduce the flux level at an inner region of r ∼ 4 RE. But in this case, the solar wind dynamic pressure is so high that the dayside magnetopause can cross the geosynchronous orbit. Consequently, the flux dropouts seen in actual observations can be primarily attributed to a fast and direct loss to the magnetopause at times when the magnetopause crosses the geosynchronous orbit. It is possible that our numerical results may quantitatively change to some extent with different magnetospheric models and assumptions and may also change depending on the validity of the fully adiabatic invariants assumption.
Tandem afterslip on connected fault planes following the 2008 Nima‐Gaize (Tibet) earthquake
Authors: Ryder I. , Bürgmann R. , Sun J.
Published: March 2010

On 9 January 2008 a M 6.4 normal‐faulting earthquake occurred in central Tibet, near the border of Nima and Gaize counties and just north of the Bangong‐Nujiang suture zone. A week later, a M 5.9 aftershock occurred a few kilometers to the northwest of the main shock. Here we consider interferometric synthetic aperture radar (InSAR) data from the Japanese ALOS and European Envisat satellites, covering both the coseismic phase and 9 months of postseismic deformation. The coseismic interferograms clearly show surface deformation resulting from both main shock and aftershock ruptures, and data inversions using elastic dislocation models suggest that two northwest dipping faults form a synthetic system, with the more steeply dipping aftershock plane meeting the main shock plane at depth. Postseismic interferograms show first‐order similarities with their coseismic counterparts, indicating that afterslip occurred on both main shock and aftershock rupture surfaces during the months following the earthquakes. The afterslip occurred at comparable depths to the coseismic slip, but the amount of slip was about an order of magnitude smaller. A slip template method is used to obtain moment release estimates at different postseismic time intervals and hence document the time dependence of the postseismic transient. The exponential decay time of the afterslip is 34 days, and the moment release due to the afterslip was about 10% of the coseismic moment. Models of viscoelastic stress relaxation in a Maxwell half‐space place a strong lower bound on midcrust to lower crustal viscosity of 3 × 1017 Pa s. Postseismic data covering a longer time span have the potential to improve this constraint.
Correlation of earthquake source parameters inferred from dynamic rupture simulations
Authors: Schmedes Jan , Archuleta Ralph J. , Lavallée Daniel
Published: March 2010

We analyzed 315 dynamic strike‐slip rupture models computed up to 5.0 Hz to get a quantitative understanding of the correlation and amplitude distributions of parameters describing the earthquake source, such as slip and rupture velocity. To account for the epistemic uncertainty of the problem, we constructed a database of dynamic ruptures computed by ourselves and other authors. This database contains ruptures computed using different models of initial stress, peak stress, and critical slip‐weakening distance. Using the set of computed ruptures, we constructed probability density functions (pdfs) for the amplitude distributions of the source parameters and for the correlation between the source parameters. We tried to extract parameter pairs that showed a small variability in the spatial correlation given the large epistemic uncertainty in the input. We only analyzed the areas on the fault with subshear propagation speed. The principal findings are as follows: (1) Final slip amplitude does not show correlation with the local rupture velocity. (2) Final slip amplitude correlates well with risetime. (3) Rupture velocity correlates well with peak slip rate and the duration of the impulsive part of the slip rate function. (4) The pdf of rupture velocity, risetime, and peak slip rate depends on the distance from the nucleation zone. (5) Fracture energy is not the single controlling factor for the rupture velocity; the slope of the linear slip‐weakening curve has a significant effect on the rupture velocity. (6) The crack length (length that is slipping at a given time) decreases with the distance from the nucleation zone.
On the fast decay of Agulhas rings
Authors: van Sebille Erik , van Leeuwen Peter Jan , Biastoch Arne , de Ruijter Wilhelmus P. M.
Published: March 2010

The Indian Ocean water that ends up in the Atlantic Ocean detaches from the Agulhas Current retroflection predominantly in the form of Agulhas rings and cyclones. Using numerical Lagrangian float trajectories in a high‐resolution numerical ocean model, the fate of coherent structures near the Agulhas Current retroflection is investigated. It is shown that within the Agulhas Current, upstream of the retroflection, the spatial distributions of floats ending in the Atlantic Ocean and floats ending in the Indian Ocean are to a large extent similar. This indicates that Agulhas leakage occurs mostly through the detachment of Agulhas rings. After the floats detach from the Agulhas Current, the ambient water quickly looses its relative vorticity. The Agulhas rings thus seem to decay and loose much of their water in the Cape Basin. A cluster analysis reveals that most water in the Agulhas Current is within clusters of 180 km in diameter. Halfway in the Cape Basin there is an increase in the number of larger clusters with low relative vorticity, which carry the bulk of the Agulhas leakage transport through the Cape Basin. This upward cascade with respect to the length scales of the leakage, in combination with a power law decay of the magnitude of relative vorticity, might be an indication that the decay of Agulhas rings is somewhat comparable to the decay of two‐dimensional turbulence.
African dust outbreaks: A satellite perspective of temporal and spatial variability over the tropical Atlantic Ocean
Authors: Huang Jingfeng , Zhang Chidong , Prospero Joseph M.
Published: March 2010

We describe the temporal evolution and spatial structure of extreme African dust outbreaks and their associated meteorological fields over West Africa and the tropical Atlantic using A‐Train data and a global reanalysis product. We used Aqua–Moderate Resolution Imaging Spectroradiometer daily aerosol optical depth (AOD) to identify major dust outbreaks, defined as AOD events one standard deviation above the background along the African coast. Dry air outbreaks were defined using water vapor data of the Aqua Atmospheric Infrared Sounder. Dry air outbreaks do not always coincide with dust outbreaks. Most boreal summer outbreaks reached the West Indies between 10°N and 20°N, some traveling on to the southeastern United States; winter outbreaks moved to South America between 0° and 10°N. Outbreaks travel westward at an average speed of 1000 km d−1, reaching the Caribbean or South America in a week's time. The advance of a dust front is associated with decreases in water vapor (up to −1.0 g kg−1) and increases in temperature (up to 1.0 K) and, behind the fronts, an anticyclonic circulation. We used Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data to characterize dust altitude distributions. The vertical distribution of warm dry air is similar to that of dust observed in CALIPSO. The dust layer altitude decreases during transport across the Atlantic and is significantly lower in boreal winter than summer. The study highlights the temporal and spatial variability of African dust outbreaks, which are important to improving our understanding of climate impacts of African dust and Atlantic climate variability in general.
Appearance of strong absorbers and fluorophores in limonene‐O3 secondary organic aerosol due to NH4+‐mediated chemical aging over long time scales
Authors: Bones David L. , Henricksen Dana K. , Mang Stephen A. , Gonsior Michael , Bateman Adam P. , Nguyen Tran B. , Cooper William J. , Nizkorodov Sergey A.
Published: March 2010

This study investigated long‐term chemical aging of model biogenic secondary organic aerosol (SOA) prepared from the ozonolysis of terpenes. Techniques including electrospray ionization mass spectrometry (ESI‐MS), UV‐visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, NMR, and three‐dimensional fluorescence were used to probe the changes in chemical composition of SOA collected by impaction on substrates and also of aqueous extracts of SOA. The addition of ammonium ions or amino acids to limonene SOA reproducibly produced orange‐colored species that strongly absorbed visible radiation and fluoresced at UV and visible wavelengths. Simultaneous addition of H2SO4 to the SOA aqueous extracts inhibited this color transformation. These observations suggest the existence of aging processes leading to heavily conjugated molecules containing organic nitrogen. The presence of nitrogen in the chromophores was confirmed by the dependence of the absorption and fluorescence spectra on the amino acids added. In contrast to the strong change in the absorption and fluorescence spectra, there was no significant change in the ESI‐MS, FTIR, and NMR spectra, suggesting that the chromophores were minor species in the aged SOA. Aqueous extracts of aged limonene + NH4+ SOA were characterized by an effective base‐e absorption coefficient of ∼3 L g−1 cm−1 at 500 nm. Assuming particulate matter concentrations typical of polluted rural air gives an upper limit of 0.2 M m−1 for the aerosol absorption coefficient due to the aged limonene oxidation products. Biogenic SOA can therefore become weakly absorbing if they undergo aging in the presence of NH4+‐containing aerosol.
Impedance and initial magnetic permeability of gadolinium
Authors: Fraga G. L. F. , Pureur P. , Cardoso L. P.
Published: March 2010

In the present work we report on measurements of the complex impedance and the magnetoimpedance of a textured sample of gadolinium metal. The preferential c -axis orientation of the Gd hexagonal structure is perpendicular to the long axis of the sample. From the experimental data, the complex initial magnetic permeability, μ=μ′+iμ″, was obtained as a function of temperature and frequency of the ac exciting current. We have found that the results for μ′(T) below the spin reorientation temperature may be described as a power law of the reduced temperature t=1−T/TSR, where TSR is the spin reorientation temperature. This behavior suggests that a genuine phase transition occurs at TSR. Although the impedance displays a weak anomaly at the Curie temperature, TC, magnetic measurements indicate that the ferromagnetic response of Gd extends up to this critical point. Thus, two different phases characterizes the cooperative magnetic state of this metal. The frequency dependent results for μ′ and μ″ were fitted to a modified Debye formula and the obtained parameters allow us to discriminate between the contributions from domain-wall motion and from magnetization rotation. We obtain that the dynamical properties of the domain walls in Gd are governed by a broad distribution of frequencies whose average value diverge at TSR. The isothermal magnetoimpedance measurements in temperatures smaller than TSR show an interesting plateau at low dc applied fields. This plateau is limited by a characteristic field HK whose magnitude decreases rapidly to nearly zero at TSR, giving further support for the phase transition scenario at this temperature.
An extension of the Wronskian technique for the multicomponent Wronskian solution to the vector nonlinear Schrödinger equation
Authors: Xu Tao , Tian Bo
Published: March 2010

In this paper, the Wronskian technique is applied to the vector nonlinear Schrödinger equation with arbitrary m components, which arises from some applications in the multimode fibers, photorefractive materials, and Bose–Einstein condensates. Via the iterative algorithm based on the Darboux transformation, the (m+1)-component Wronskian solution is generated from the zero solution. The verification of the solution is finished by using the (m+1)-component Wronskian notation and new determinantal identities. With a set of N linearly independent solutions of the zero-potential Lax pair, the (m+1)-component Wronskian solution is found to be the representation of the bright N-soliton solution which contains (m+1)N parameters. For characterizing the asymptotic behavior of the generic bright N-soliton solution, an algebraic procedure is derived to obtain the explicit expressions of asymptotic solitons as t→∓∞.
Defect annealing in neutron and ion damaged silicon: Influence of defect clusters and doping
Authors: Fleming R. M. , Seager C. H. , Bielejec E. , Vizkelethy G. , Lang D. V. , Campbell J. M.
Published: March 2010

We have explored defect annealing in radiation damaged silicon in a regime characterized by defect clusters and higher doping. Several types of pnp and npn Si bipolar transistors have been irradiated with ions and neutrons, then isochronally annealed from 300 to 600 K to study the evolution of deep level transient spectroscopy (DLTS) defect signatures. Variations in these data with radiation environment, Fermi level, annealing temperature, and doping density have been used to separate the contributions of three dominant defects to the DLTS defect spectra. We find that the normal Si divacancy and a divacancylike defect with similar properties make similar contributions to a DLTS peak normally associated with transitions from the single minus charge state of the divacancy. However the latter defect is clearly associated with the presence of defect clusters. The vacancy-donor center can also contribute to this high temperature DLTS signature, and its relative importance can be quantitatively assessed by varying doping density and the bias applied to the sample p/n junctions during annealing, and also by the observation that another, donor-related defect grows in as this center anneals. The ratio of vacancy-donor and vacancy-oxygen pairs appears to accurately follow that seen in earlier studies of gamma-irradiated Si. Discussions are presented concerning the effects of defect clustering on the structure, appearance, and evolution of the defects we have identified.
Excitation rate dependence of Auger recombination in silicon
Authors: Hopkins Patrick E. , Barnat Edward V. , Cruz-Campa Jose L. , Grubbs Robert K. , Okandan Murat , Nielson Gregory N.
Published: March 2010

This work reports on measurements of the Auger recombination coefficients in silicon wafers with pump-probe thermoreflectance techniques operating at two different excitation rates: 250 kHz (low repetition rate) and 80 MHz (high repetition rate). The different excitation frequencies give rise to different thermoreflectance signals in the Si samples, which is ascribed to the excited number density in the conduction band. In the low repetition rate case, the excited carriers recombine via Auger processes before the next pump excitation is absorbed. However, in the high repetition rate case, the rate in which the pump excitations are absorbed at the sample surface is higher than the Auger recombination rate, indicating that the excited carrier densities in the high repetition rate experiments are much higher than in the low repetition rate measurements even though the pump fluences are comparable. This is ascribed to pulse accumulation in the high repetition rate measurements, and is quantified with rate equation and thermoreflectance models fit to the experimental data. Comparing the data taken at the two different excitation modulations gives insight into the excited carrier density when recombination rate are on the same order as excitation frequencies.
Optical properties of single-crystalline chalcopyrite semiconductor AgInSe2
Authors: Koitabashi Keisuke , Ozaki Shunji , Adachi Sadao
Published: March 2010

The optical properties of single-crystalline AgInSe2 have been studied by optical absorption, spectroscopic ellipsometry (SE), and photoreflectance (PR) spectroscopy. Optical absorption measurements suggest that AgInSe2 is a direct-gap semiconductor having an optical band gap of E0∼1.2 eV at T=15–300 K. The pseudodielectric-function spectra, ε(E)=ε1(E)+iε2(E), of AgInSe2 are determined by SE for light polarization perpendicular (E⊥c) and parallel to the c axis (E∥c) in the E=1.2–5.3 eV spectral region at room temperature. The measured SE spectra reveal distinct structures at energies of the critical points (En with n=0–8) in the Brillouin zone. The temperature-dependent PR spectra are obtained at T=15–300 K in the 1.2–1.7 eV spectral ranges. The lowest band-gap energy E0 of AgInSe2 shows unusual temperature dependence at T≤120 K. The resultant temperature coefficients dE0/dT are positive at T≤120 K and negative above 120 K, and are explained by considering the effects of thermal expansion and electron-phonon interaction. The spin-orbit and crystal-field splitting parameters are also determined to be Δso=321 meV and Δcr=−172 meV, respectively, and are discussed from an aspect of the electronic energy-band structure consequences.