bluuebunny/crossref_metadata_2025 huggingface dataset:
Adventitious presence of other varieties in oilseed rape (Brassica napus) from seed banks and certified seed
Authors: Jørgensen Tina , Hauser Thure Pavlo , Jørgensen Rikke Bagger
Published: May 2007

To obtain information on possible sources of contamination of the seed harvest of oilseed rape (Brassica napus L., spp. napus) by other varieties (adventitious presence), we investigated the purity of certified seed lots; the abundance and origin of volunteers; and longevity and origin of seeds in the soil seed-bank. This information was acquired through DNA analysis of volunteers collected in the field and seedlings derived from the soil seed-bank. DNA profiles of the volunteers and seedlings were obtained using Inter Simple Sequence Repeat (ISSR) markers, and the profiles were compared with ISSR profiles from an assortment of 14 of the most commonly cultivated oilseed rape varieties from 1985 to 2004. This comparison was performed using the assignment program, AFLPOP. The age of the seed bank germinating to become volunteers was assumed from information on previously cultivated oilseed rape varieties at the site and the year of cultivation. The results showed that plants or seeds belonged to varieties cultivated at the site 4–17 years earlier, suggesting a long persistence of volunteer populations. High volunteer frequencies (6%, 29% and 32%) were found in the three oilseed rape fields analysed and, from soil cores, their soil seed-bank was estimated to be 50–100 seeds m− 2. The ISSR analysis of the 14 reference varieties showed that three of the certified seed lots contained other varieties above the allowed threshold. Our findings are discussed in the context of the coexistence between GM (genetically modified) and non-GM oilseed rape, and future levels of seed purity.
Reduced embryo sensitivity to abscisic acid in a sprouting-susceptible sorghum (Sorghum bicolor) variety is associated with altered ABA signalling
Authors: Gualano Nicolás , Carrari Fernando , Verónica Rodríguez María , Pérez-Flores Laura , Sánchez Rodolfo , Iusem Norberto , Benech-Arnold Roberto
Published: May 2007

In the work reported in this paper, we attempted to elucidate the nature of the different abscisic acid (ABA) sensitivities presented by developing embryos from sorghum [Sorghum bicolor (L.) Moench] lines with contrasting pre-harvest sprouting (PHS) behaviour (Redland B2, susceptible; IS 9530, resistant). We explored two different hypotheses for a possible mechanism: (1) a different functionality of the ABA signalling pathway, and (2) a different rate of ABA degradation/conjugation in the apoplast of embryos from these genotypes. To assess the first possibility, we used an ABA-responsive gene (Rab17) as a reporter of changes in endogenous ABA content, which were artificially induced in embryos from both genotypes by means of fluridone application immediately after anthesis, to reduce ABA content, and embryo incubation in the presence of ABA. A defect in ABA signalling should be seen as a level of Rab17 expression that is independent of endogenous ABA content. For testing the second possibility at two stages of development, embryos from both lines were isolated and incubated in water for different periods. ABA concentrations in embryos and the incubation media were quantified through radioimmunoassay. In contrast to our findings for the resistant IS 9530 line, Rab17 expression did not respond to changes in ABA levels in sensitive Redland B2 embryos. The ABA degradation/conjugation rates in embryos and incubation media did not show clear differences between sorghum lines for any of the developmental stages analysed. These results suggest that a disruption in the ABA signal transduction pathway in Redland B2 underlies the low ABA sensitivity shown by embryos from this line.
Kalziumsupplementation in der Schwangerschaft – ein Muss (?)
Authors: Beinder
Published: May 2007

Obwohl im Verlauf der Schwangerschaft täglich zwischen 50 und 330 mg Kalzium von der Mutter an den Feten transferiert werden, gibt es keine Evidenz, dass dadurch bei Frauen mit einer ausgewogenen Ernährung Langzeitrisiken für eine Osteoporose auftreten. Es gibt auch keine gesicherte Evidenz, dass bei gesunden Schwangeren die Supplementation mit Kalzium einen günstigen Einfluss für das ungeborene Kind hätte. Die empfohlene Kalziumzufuhr liegt nach der Deutschen und Österreichischen Gesellschaft für Ernährung (DGE und ÖGE), der Schweizerischen Gesellschaft für Ernährungsforschung (SGE) und der Schweizerische Vereinigung für Ernährung (SVE) bei 1000 mg/die und sollte 2000 mg/die nicht überschreiten. Diese Menge an Kalzium ist durch eine ausgewogene Ernährung, die 3–4 Portionen Milch- und Milchprodukte beinhaltet, gut zu erreichen. Weitere ergiebige Kalziumquellen sind kalziumreiche Mineralwässer, Nüsse und Vollkornprodukte. Eine Substitution von Kalzium in der Schwangerschaft ist somit bei gesunden Schwangeren kein Muss. Hingegen bei Schwangeren mit Laktoseintoleranz, veganer Ernährung, chronisch entzündlichen Autoimmunerkrankungen und bei Behandlung mit niedermolekularen Heparinen in der Schwangerschaft kann die Kalziumzufuhr oder -resorption die empfohlenen Werte unterschreiten. Diese Schwangeren sollten großzügig mit 500 bis 1000 mg/die Kalzium substituiert werden. Die Prophylaxe der Präeklampsie mit Kalzium ist nur bei Frauen mit einem anamnestisch hohen Risiko für eine Präeklampsie und ungenügender Kalziumzufuhr in der Nahrung möglich. Berichte, nach denen die Kalziumsubstitution in der Schwangerschaft einen günstigen Einfluss auf das fetale Wachstum hat und den Blutdruck der Nachkommen senkt, sind noch präliminär.
Kalzium und Blutdruck
Authors: Simonetti  , Mohaupt
Published: May 2007

Die Regulation des Blutdrucks ist komplex und verschiedenen Organen unterstellt. Das intrazelluläre Kalzium spielt eine zentrale Rolle in der Regulation kardiovaskulärer Funktionen: Ein vermehrter Kalzium-Influx in die glatten Gefäßmuskelzellen führt zu einem erhöhten Muskeltonus mit einer darausfolgenden Zunahme des peripheren Gefäßwiderstandes, und als Konsequenz davon zu einem Blutdruckanstieg. Parathormon spielt dabei eine permissive Rolle: Unter dem Einfluss von Parathormon ist Kalzium besser in der Lage in die Zellen einzutreten und somit wird der vasokonstriktorische Effekt verstärkt. Eine positive Korrelation zwischen Parathormon-Spiegel und Blutdruck konnte sowohl bei primärem als auch bei sekundärem Hyperparathyroidismus gezeigt werden. Patienten mit essentieller Hypertonie haben erhöhte Parathormon-Spiegel bereits vor Entwicklung einer offensichtlichen Hypertonie. Eine vermehrte Kalzium-Einnahme führt im geringen Ausmaß zu einer Blutdrucksenkung. Dieser positive Effekt könnte durch eine Parathormon-Suppression mit darausfolgender Erniedrigung des intrazellulären Kalziums zu erklären sein. Eine kalziumreiche Diät wirkt zudem positiv auf das Fettgewebe mit einer Hemmung der Lipogenese.
Die Hyperkalzämie im Verlauf der Sarkoidose – Fallbeispiel, Prävalenz, Pathophysiologie und Therapiemöglichkeiten
Authors: Ackermann
Published: May 2007

Die Einführung in die Thematik erfolgt mit einem Fallbeispiel. Die Hyperkalzämie ist eine häufige Komplikation der Sarkoidose. Ungefähr 10% der Sarkoidosepatienten haben im beobachteten Zeitraum eine Hyperkalzämie. Die Hyperkalziurie ist ungefähr doppelt so häufig, weswegen am ehesten von einem Hyperkalzämie/Hyperkalziurie-Syndrom gesprochen werden sollte. Die Hyperkalziurie sollte bei diesen Patienten auch systematisch gesucht werden. Die Ursache der Hyperkalzämie bei Sarkoidosepatienten ist die unkontrollierte Bildung von 1,25-Dihydroxyvitamin D3 in Makrophagen von Granulomen, was einerseits zu einer vermehrten Absorption von Kalzium im Darm und andererseits zu einer vermehrten Resorption im Knochen führt. Die Höhe des Serumkalziums und die Persistenz der Hyperkalzämie bestimmen die Behandlung. Diese besteht neben einer genügenden Flüssigkeitszufuhr hauptsächlich in der Vermeidung der Zufuhr von Kalzium und Vitamin D sowie in der Reduktion der inadäquaten Produktion des 1,25-Dihydroxyvitamin D3. Kortikosteroide beeinflussen die unkontrollierte Aktvität der 1 α-Hydroxylase der Granulommakrophagen, führen allerdings auch zu Osteoporose. Wenn Glukokortikosteroide nicht eingesetzt werden können, kann auch mit Chloroquin oder Ketoconazol, eine alleinige Hyperkalziurie jedoch auch nur mit einem Thiaziddiuretikum behandelt werden.
Pathophysiologie und Diagnostik der Nephrokalzinose
Authors: Fuster
Published: May 2007

Bei der Nephrokalzinose handelt es ich um eine generalisierte Verkalkung des Nierenparenchyms, hervorgerufen durch eine Vielzahl von hereditären oder erworbenen Störungen. Ursächlich sind Störungen des Kalzium-, Phosphat- oder Oxalatstoffwechsels. Häufig ist die Nephrokalzinose von einer Nephrolithiasis begleitet und eine rezidivierende Nephrolithiasis ist oft das einzige Krankheitssymptom. Unbehandelt kann die Nephrokalzinose zu einer progredienten Nierenfunktionsverschlechterung führen. Die Ätiologie jeder Nephrokalzinose muss daher gesucht und eine entsprechende kausale Therapie eingeleitet werden.
High temporal resolution Mg/Ca and Ba/Ca records in modern Porites lobata corals
Authors: Allison Nicola , Finch Adrian A.
Published: May 2007

Secondary ion mass spectrometry (SIMS) was used to determine Mg/Ca and Ba/Ca variations across two skeletal structures (the fasciculi and the centers of calcification, COCs) in two Porites lobata corals of different linear extension rates, from Oahu, Hawaii. Both corals exhibit large Mg and Ba heterogeneity, which is not related to sea surface temperature (SST) or composition. Higher concentrations of Ba occur in the fasciculi and higher Mg in the COCs of the slowly extending coral compared to the fast growing coral. Mg and Ba concentrations are significantly higher in the COCs of both corals compared to the fasciculi. Trace element variations may reflect changes in the calcifying fluid composition or changes in skeletal trace element incorporation. Regressions between Mg, Ba, and Sr (reported in a prior publication) indicate that the skeletal incorporation of each element is affected by a different factor or combination of factors. Smoothed SIMS records of Ba/Ca variations across the fasciculi of the fast growing coral follow the seasonal trend predicted from SST and expected seawater chemistry variations. Smoothed SIMS Mg/Ca records do not correlate with SST, indicating that SIMS Mg/Ca records cannot be used to estimate past SSTs.
Absorption of MARSIS radar signals: Solar energetic particles and the daytime ionosphere
Authors: Espley Jared R. , Farrell William M. , Brain David A. , Morgan David D. , Cantor Bruce , Plaut Jeffrey J. , Acuña Mario H. , Picardi Giovanni
Published: May 2007

We present observations from the subsurface sounding mode of the MARSIS instrument onboard Mars Express that imply radar wave absorption because of increased amounts of ionization in the upper Martian atmosphere during the fall of 2005. On at least two occasions these radar disruptions lasted for several days and we find that these periods are correlated with periods when other instruments indicate elevated levels of solar energetic particles. Another disruption lasted for over a month and we find that it was likely caused by a combination of solar activity and observing through the daytime ionosphere. There is no evidence in the present results for the constant ionospheric layer predicted to be created by the normal infall of cosmic dust, although the effects of enhanced infall during meteor showers remains uncertain. The effects of dust activity also remain uncertain but will be tested during the 2007 dust season.
Seismic evidence for whole lithosphere separation between Saxothuringian and Moldanubian tectonic units in central Europe
Authors: Heuer B. , Kämpf H. , Kind R. , Geissler W. H.
Published: May 2007

The Bohemian Massif is part of the Variscan belt of central Europe. We carried out a high resolution mapping of lithospheric thickness beneath central Europe by investigating 264 teleseismic events recorded at 80 broad band stations in the western Bohemian Massif with the method of S receiver function analysis. A negative phase beneath the Saxothuringian and northeastern Teplá‐Barrandian units at about 9–10 s before the S onset is interpreted as caused by the lithosphere‐asthenosphere boundary (LAB) at 80–90 km depth. In the Moldanubian unit, the negative phase occurs at 13–15 s before the S onset, corresponding to lithospheric thickness of 120–130 km. The boundary between the domains is oriented E‐W and probably marks the northern extension of Moldanubian lithosphere. The Moho also deepens from the Saxothuringian to the Moldanubian unit. The observed crustal/lithospheric domains could represent two distinct microplates with a relatively sharp boundary cutting through the whole lithosphere.
Extreme polar cap density enhancements along magnetic field lines during an intense geomagnetic storm
Authors: Tu J.‐N. , Dhar M. , Song P. , Reinisch B. W. , Green J. L. , Benson R. F. , Coster A. J.
Published: May 2007

Sounding measurements from the radio plasma imager (RPI) on the IMAGE satellite are used to derive electron number density distributions along magnetic field lines in the polar cap magnetosphere during an intense magnetic storm. It is shown that electron densities along magnetic field lines in the polar cap magnetosphere were greatly enhanced on both the dayside and nightside during the storm, compared to the electron density profiles measured during periods of lower geomagnetic activities. The electron density enhancements were observed extending to 7 Earth radii (RE) in altitude on the dayside, with the electron density value reaching about 10 cm−3 at 7 RE altitude. The observed density enhancements were likely due to the enhanced cleft ion fountain during the storm although some of nightside density enhancements might be caused by the increased ion outflows locally in the polar cap. The strongest electron density enhancements observed on the dayside are possibly further associated with storm‐time transport of plasma from the midlatitude ionosphere and plasmasphere to high latitudes, which manifests as a plasma plume intruding to dayside high latitudes as seen from total electron content (TEC) maps. With an enhanced source population supplied by the plasma plume, acceleration and heating processes in the dayside cusp/auroral region may produce a large flux of outflowing plasma along magnetic field lines while the outflowing plasma is convected anti‐sunward toward the polar cap. These processes lead to strongly enhanced cleft ion fountain and thus greatly raised electron densities at magnetospheric altitudes in the polar cap. The present study captures an event of a massive redistribution of the magnetospheric and ionospheric plasma during a geomagnetic storm caused by extreme solar wind/interplanetary magnetic field (IMF) conditions.
Time, location, and scale dependence of soil nitrous oxide emissions, soil water, and temperature using wavelets, cross‐wavelets, and wavelet coherency analysis
Authors: Yates T. T. , Si B. C. , Farrell R. E. , Pennock D. J.
Published: May 2007

Soil N2O emission measurements have high‐spatial and temporal variability that results in poor field scale predictive relationships, and this leads to high uncertainty in estimates of flux. Correlation between variables may be location and scale dependent. This needs to be understood to identify at what scales or locations predictive relationships may be used to reduce uncertainty in estimates. The purpose of this study was to describe the scale and location dependency of N2O emission on soil water and temperature using wavelet coherency and their change through time. Measurements of N2O flux, soil water content, and temperature were made multiple times from a 128‐point transect on a hummocky, agricultural landscape in the Dark Brown soil zone of Saskatchewan, Canada. Using three sampling dates in the spring of 2004, the local wavelet, cross‐wavelet, and wavelet coherency spectra were generated. In late March, the spatial pattern of wavelet coherency between soil N2O flux and temperature was scale dependent. At the end of April, there was no significant relationship between N2O and temperature. Instead, a location‐dependent spatial pattern existed between flux and water‐filled pore space. By late June, there were no significant scale‐ or location‐dependent relationships. The results indicate that N2O emission models for this landscape cannot rely on a single predictive relationship, but may have to adjust between scale‐ and location‐dependent relationships at different times of the year.
Mesopause structure from Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED)/Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) observations
Authors: Xu Jiyao , Liu H.‐L. , Yuan W. , Smith A. K. , Roble R. G. , Mertens C. J. , Russell J. M. , Mlynczak M. G.
Published: May 2007

Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED)/Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) temperature observations are used to study the global structure and variability of the mesopause altitude and temperature. There are two distinctly different mesopause altitude levels: the higher level at 95–100 km and the lower level below ∼86 km. The mesopause of the middle‐ and high‐latitude regions is at the lower altitude in the summer hemisphere for about 120 days around summer solstice and is at the higher altitude during other seasons. At the equator the mesopause is at the higher altitude for all seasons. In addition to the seasonal variation in middle and high latitudes, the mesopause altitude and temperature undergo modulation by diurnal and semidiurnal tides at all latitudes. The mesopause is about 1 km higher at most latitudes and 6–9 K warmer at middle to high latitudes around December solstice than it is around June solstice. These can also be interpreted as hemispheric asymmetry between mesopause altitude and temperature at solstice. Possible causes of the asymmetry as related to solar forcing and gravity wave forcing are discussed.
Ultraviolet and visible radiation at Barrow, Alaska: Climatology and influencing factors on the basis of version 2 National Science Foundation network data
Authors: Bernhard Germar , Booth Charles R. , Ehramjian James C. , Stone Robert , Dutton Ellsworth G.
Published: May 2007

Spectral ultraviolet (UV) and visible irradiance has been measured near Barrow, Alaska (71°N, 157°W), between 1991 and 2005 with a SUV‐100 spectroradiometer. The instrument is part of the U.S. National Science Foundation's UV Monitoring Network. Here we present results based on the recently produced “version 2” data release, which supersedes published “version 0” data. Cosine error and wavelength‐shift corrections applied to the new version increased biologically effective UV dose rates by 0–10%. Corrected clear‐sky measurements of different years are typically consistent to within ±3%. Measurements were complemented with radiative transfer model calculations to retrieve total ozone and surface albedo from measured spectra and for the separation of the different factors influencing UV and visible radiation. A climatology of UV and visible radiation was established, focusing on annual cycles, trends, and the effect of clouds. During several episodes in spring of abnormally low total ozone, the daily UV dose at 305 nm exceeded the climatological mean by up to a factor of 2.6. Typical noontime UV Indices during summer vary between 2 and 4; the highest UV Index measured was 5.0 and occurred when surface albedo was unusually high. Radiation levels in the UV‐A and visible exhibit a strong spring‐autumn asymmetry. Irradiance at 345 nm peaks on approximately 20 May, 1 month before the solstice. This asymmetry is caused by increased cloudiness in autumn and high albedo in spring, when the snow covered surface enhances downwelling UV irradiance by up to 57%. Clouds reduce UV radiation at 345 nm on average by 4% in March and by more than 40% in August. Aerosols reduce UV by typically 5%, but larger reductions were observed during Arctic haze events. Stratospheric aerosols from the Pinatubo eruption in 1991 enhanced spectral irradiance at 305 nm for large solar zenith angles. The year‐to‐year variations of spectral irradiance at 305 nm and of the UV Index are mostly caused by variations in total ozone and cloudiness. Changes in surface albedo that may occur in the future can have a marked impact on UV levels between May and July. No statistically significant trends in monthly mean noontime irradiance were found.
True triaxial strength and deformability of the siltstone overlying the Chelungpu fault (Chi‐Chi earthquake), Taiwan
Authors: Oku Haruyuki , Haimson Bezalel , Song Sheng‐Rong
Published: May 2007

We conducted true triaxial compression tests to examine the effect of the intermediate principal stress (σ2) on brittle failure and deformability of the siltstone overlying the Chelungpu fault, Taiwan. For constant minimum stress (σ3) a pattern of increased strength (σ1) as a function of σ2, unpredicted by common strength criteria, was observed. Strength data are well fitted by a Mogi‐modified Nadai criterion relating the octahedral shear stress at failure to the mean normal stress on the induced shear fracture or fault. The induced fault strikes subparallel to σ2 and dips steeply in the direction of σ3. Significantly, fault dip angle steadily increases as σ2 rises for unchanged σ3. SEM inspection of tested specimens reveals only sporadic localized intergranular microcracks associated with the creation of the fault. The modulus of elasticity and the onset of dilatancy exhibit a similar behavior to that of σ1, as they increase with σ2 when subjected to a constant σ3.
Adaptation and spectral tuning in divergent marine proteorhodopsins from the eastern Mediterranean and the Sargasso Seas
Authors: Sabehi Gazalah , Kirkup Benjamin C , Rozenberg Mira , Stambler Noga , Polz Martin F , Béjà Oded
Published: May 2007

Proteorhodopsins (PRs) phototrophy was recently discovered in oceanic surface waters. PRs have been observed in different marine environments and in diverse taxa, including the ubiquitous marine alphaproteobacterial SAR11 group and the uncultured gammaproteobacterial SAR86 group. Previously, two SAR86 PR subgroups, discovered in the Pacific Ocean, were shown to absorb light with different maxima, λmax 527 nm (green) and λmax 490 nm (blue) and their distribution was explained by prevailing light conditions – green pigments at the surface and blue in deeper waters. Here, we show that PRs display high diversity in geographically distinct patterns despite similar physical water column properties such as mixing and light penetration. We compared summer and winter samples representing stratified and mixed conditions from both the Mediterranean and Sargasso Sea. As expected, in the Mediterranean Sea, green pigments were mainly confined to the surface and the percentage of blue pigments increased toward deeper samples; in the Sargasso Sea, unexpectedly, all PRs were of the blue type. As an additional result, both locations show seasonal dependence in the distribution of different PR families. Finally, spectral tuning was not restricted to a single PR family as previously reported but occurs across the sampled PR families from various microbial taxa. The distribution of tunable PRs across the PR tree suggests that ready adaptability has been distributed widely among microorganisms, and may be a reason that PRs are abundant and taxonomically widely dispersed.
GeoChip: a comprehensive microarray for investigating biogeochemical, ecological and environmental processes
Authors: He Zhili , Gentry Terry J , Schadt Christopher W , Wu Liyou , Liebich Jost , Chong Song C , Huang Zhijian , Wu Weimin , Gu Baohua , Jardine Phil , Criddle Craig , Zhou Jizhong
Published: May 2007

Owing to their vast diversity and as-yet uncultivated status, detection, characterization and quantification of microorganisms in natural settings are very challenging, and linking microbial diversity to ecosystem processes and functions is even more difficult. Microarray-based genomic technology for detecting functional genes and processes has a great promise of overcoming such obstacles. Here, a novel comprehensive microarray, termed GeoChip, has been developed, containing 24 243 oligonucleotide (50 mer) probes and covering >10 000 genes in >150 functional groups involved in nitrogen, carbon, sulfur and phosphorus cycling, metal reduction and resistance, and organic contaminant degradation. The developed GeoChip was successfully used for tracking the dynamics of metal-reducing bacteria and associated communities for an in situ bioremediation study. This is the first comprehensive microarray currently available for studying biogeochemical processes and functional activities of microbial communities important to human health, agriculture, energy, global climate change, ecosystem management, and environmental cleanup and restoration. It is particularly useful for providing direct linkages of microbial genes/populations to ecosystem processes and functions.
Long-term ecological impacts of antibiotic administration on the human intestinal microbiota
Authors: Jernberg Cecilia , Löfmark Sonja , Edlund Charlotta , Jansson Janet K
Published: May 2007

Antibiotic administration is known to cause short-term disturbances in the microbiota of the human gastrointestinal tract, but the potential long-term consequences have not been well studied. The aims of this study were to analyse the long-term impact of a 7-day clindamycin treatment on the faecal microbiota and to simultaneously monitor the ecological stability of the microbiota in a control group as a baseline for reference. Faecal samples from four clindamycin-exposed and four control subjects were collected at nine different time points over 2 years. Using a polyphasic approach, we observed highly significant disturbances in the bacterial community that persisted throughout the sampling period. In particular, a sharp decline in the clonal diversity of Bacteroides isolates, as assessed by repetitive sequence-based PCR (rep-PCR) and long-term persistence of highly resistant clones were found as a direct response to the antibiotic exposure. The Bacteroides community never returned to its original composition during the study period as assessed using the molecular fingerprinting technique, terminal restriction fragment length polymorphism (T-RFLP). Furthermore, using real-time PCR we found a dramatic and persistent increase in levels of specific resistance genes in DNA extracted from the faeces after clindamycin administration. The temporal variations in the microbiota of the control group were minor compared to the large and persistent shift seen in the exposed group. These results demonstrate that long after the selection pressure from a short antibiotic exposure has been removed, there are still persistent long term impacts on the human intestinal microbiota that remain for up to 2 years post-treatment.
Microbial ecology meets electrochemistry: electricity-driven and driving communities
Authors: Rabaey Korneel , Rodríguez Jorge , Blackall Linda L , Keller Jurg , Gross Pamela , Batstone Damien , Verstraete Willy , Nealson Kenneth H
Published: May 2007

Bio-electrochemical systems (BESs) have recently emerged as an exciting technology. In a BES, bacteria interact with electrodes using electrons, which are either removed or supplied through an electrical circuit. The most-described type of BES is microbial fuel cells (MFCs), in which useful power is generated from electron donors as, for example, present in wastewater. This form of charge transport, known as extracellular electron transfer, was previously extensively described with respect to metals such as iron and manganese. The importance of these interactions in global biogeochemical cycles is essentially undisputed. A wide variety of bacteria can participate in extracellular electron transfer, and this phenomenon is far more widespread than previously thought. The use of BESs in diverse research projects is helping elucidate the mechanism by which bacteria shuttle electrons externally. New forms of interactions between bacteria have been discovered demonstrating how multiple populations within microbial communities can co-operate to achieve energy generation. New environmental processes that were difficult to observe or study previously can now be simulated and improved via BESs. Whereas pure culture studies make up the majority of the studies performed thus far, even greater contributions of BESs are expected to occur in natural environments and with mixed microbial communities. Owing to their versatility, unmatched level of control and capacity to sustain novel processes, BESs might well serve as the foundation of a new environmental biotechnology. While highlighting some of the major breakthroughs and addressing only recently obtained data, this review points out that despite rapid progress, many questions remain unanswered.
Rapidly rotating Bose-Einstein condensates in strongly anharmonic traps
Authors: Correggi M. , Rindler-Daller T. , Yngvason J.
Published: May 2007

We study a rotating Bose-Einstein condensate in a strongly anharmonic trap (flat trap with a finite radius) in the framework of two-dimensional Gross-Pitaevskii theory. We write the coupling constant for the interactions between the gas atoms as 1∕ε2 and we are interested in the limit ε→0 (Thomas-Fermi limit) with the angular velocity Ω depending on ε. We derive rigorously the leading asymptotics of the ground state energy and the density profile when Ω tends to infinity as a power of 1∕ε. If Ω(ε)=Ω0∕ε a “hole” (i.e., a region where the density becomes exponentially small as 1∕ε→∞) develops for Ω0 above a certain critical value. If Ω(ε)⪢1∕ε the hole essentially exhausts the container and a “giant vortex” develops with the density concentrated in a thin layer at the boundary. While we do not analyze the detailed vortex structure we prove that rotational symmetry is broken in the ground state for const∣logε∣<Ω(ε)≲const∕ε.
The effect of Ar neutral beam treatment of screen-printed carbon nanotubes for enhanced field emission
Authors: Kyung Se Jin , Park Jae Beom , Park Byung Jae , Min Kyung Seok , Lee June Hee , Yeom Geun Young , Shin Yong Sook , Park Chong Yun
Published: May 2007

This study examined the effectiveness of an Ar neutral beam as a surface treatment for improving the field emission properties of screen-printed carbon nanotubes (CNTs). A short period of the neutral beam treatment on tape-activated CNTs enhanced the emission properties of the CNTs, showing a decrease in the turn-on field and an increase in the number of emission sites. The neutral beam treatment appeared to render the CNT surfaces more actively by exposing more CNTs from the CNT paste without cutting or kinking the already exposed long CNT emitters. The treated CNTs emitted more electrons than the CNTs treated using other methods. When the field emission properties were measured after the neutral beam treatment, the turn-on field decreased from 1.65to0.60V∕μm and the emission field at 1mA∕cm2 decreased from 3.10to2.41V∕μm. After the neutral beam treatment for 10s, there was an improvement in the stability of the emission current at a constant electric field. It is expected that the neutral beam treatment introduced in this study will provide an easy way of improving the emission intensity and stability of screen-printed CNT emitters.
Stress dependence of the polarized Raman spectrum of polycrystalline lead zirconate titanate
Authors: Deluca Marco , Sakashita Tatsuo , Zhu Wenliang , Chazono Hirokazu , Pezzotti Giuseppe
Published: May 2007

The stress dependence of the Raman spectrum of a relaxor-based polycrystalline ferroelectric lead zirconate titanate–lead nickel niobate–lead zinc niobate (PZT–PNN–PZN) has been investigated using polarized Raman microprobe spectroscopy. Emphasis has been placed on explicitly working out the second harmonic equations that relate Raman intensities to the angle between the laser polarization direction and selected crystalline axes. Based on these assessments, the effect under polarized light of crystal orientation on the intensity of selected Raman modes has been rationalized and the obtained experimental data interpreted. Raman spectra were collected with both parallel and cross polarization filters and their dependence on stress calibrated with loading the PZT–PNN–PZN samples in a four-point flexural jig. The use of polarized light allowed us to clarify the effect of domain orientation on the Raman spectrum of PZT–PNN–PZN and to perform precise calibrations of the stress dependence of the A1(TO4) Raman mode, independent of domain orientation in both poled and unpoled PZT–PNN–PZN samples. This study demonstrates the feasibility of microscopic stress (in addition to local domain orientation) evaluations in PZT materials using a polarized Raman microprobe.
Magnetophotorefractive effect of holographic recording in LiNbO3:Fe crystals
Authors: Qi Jiwei , Xu Jingjun , Li Yudong , Kong Fanlei , Sun Qian , Rupp Romano A.
Published: May 2007

An experimental investigation of the magnetophotorefractive effect for different holographic recording configurations is presented. Our results show that the diffraction efficiency of holographic grating strongly depends on the applied magnetic field for each configuration, since the magnetophotorefractive effect induces a change of the electric current. The diffraction efficiencies of the refractive-index gratings decrease markedly for all configurations we investigated. The reason for our results is discussed.
Diffusion and Brownian motion in Lagrangian coordinates
Authors: Fyrillas Marios M. , Nomura Keiko K.
Published: May 2007

In this paper we consider the convection-diffusion problem of a passive scalar in Lagrangian coordinates, i.e., in a coordinate system fixed on fluid particles. Both the convection-diffusion partial differential equation and the Langevin equation are expressed in Lagrangian coordinates and are shown to be equivalent for uniform, isotropic diffusion. The Lagrangian diffusivity is proportional to the square of the relative change of surface area and is related to the Eulerian diffusivity through the deformation gradient tensor. Associated with the initial value problem, we relate the Eulerian to the Lagrangian effective diffusivities (net spreading), validate the relation for the case of linear flow fields, and infer a relation for general flow fields. Associated with the boundary value problem, if the scalar transport problem possesses a time-independent solution in Lagrangian coordinates and the boundary conditions are prescribed on a material surface/interface, then the net mass transport is proportional to the diffusion coefficient. This can be also shown to be true for large Péclet number and time-periodic flow fields, i.e., closed pathlines. This agrees with results for heat transfer at high Péclet numbers across closed streamlines.
Residual stress relaxation in the film/substrate system due to creep deformation
Authors: Zhang X. C. , Xu B. S. , Wang H. D. , Wu Y. X.
Published: May 2007

An analytical model is developed to estimate the effect of creep deformation on the stress relaxation and distribution in the film/substrate bilayer structure during prolonged exposure to high temperature. In the model, either the film or the substrate subjecting to high-temperature creep is considered. Closed-form solutions for the residual stresses in the film and the substrate are derived. A relationship between the stress relaxation rate in the film/substrate system and the relaxation time is obtained. Case studies show that the ratios of the biaxial modulus and the thickness of the film to those of the substrate, the creep parameters, and the exposure temperature have significant influence on the residual stress relaxation rate.
Thermal effects on the electrical properties of (methyl orange)/ (polyvinyl alcohol) composites
Authors: de Oliveira Helinando P. , de Melo Celso P.
Published: May 2007

We have used electrical impedance spectroscopy to determine the dielectric characteristics of polymeric films prepared by incorporating varying amounts of methyl orange (MO), an azobenzene dye, into solid films of polyvinyl alcohol (PVA), an insulating polymer. By mapping the variation of relevant parameters such as the dielectric relaxation time, we have analyzed how thermal effects would affect the charge transport and polarization processes in the MO/PVA composite samples as the frequency of an applied external field and the temperature were varied in a controlled manner. We interpret the results in terms of number and size of the dye aggregates in the polymeric matrix, by correlating thermal and polarization effects to the temperature and the relative amount of MO in the composite films. Finally, we show that the electrical characteristics of the MO/PVA samples can be modified by light incidence, a fact that confirms the possibility of using these composites in (light written)-(electrically read) solid-state memory devices.
Tunnel magnetoresistance in fully epitaxial magnetic tunnel junctions with a full-Heusler alloy thin film of Co2Cr0.6Fe0.4Al and a MgO tunnel barrier
Authors: Marukame Takao , Yamamoto Masafumi
Published: May 2007

Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with a full-Heusler alloy Co2Cr0.6Fe0.4Al (CCFA) thin film and a MgO tunnel barrier. Pseudo-spin-valve-type, fully epitaxial CCFA∕MgO∕Co50Fe50 MTJs with a CCFA film composition close to the stoichiometric one demonstrated high tunnel magnetoresistance (TMR) ratios of 90% at room temperature (RT) and 240% at 4.2K. These high TMR ratios were attributed to the increased spin polarization at the Fermi level due to the increased ratio of the B2 region to the A2 region in CCFA films achieved by bringing the CCFA film composition close to the stoichiometric one. Fully epitaxial CCFA∕MgO∕Co50Fe50 MTJs with exchange biasing were also fabricated, where a Co50Fe50 upper electrode was used in a synthetic ferrimagnetic Co50Fe50∕Ru∕Co90Fe10 trilayer exchange-biased with an IrMn layer through the Co90Fe10∕IrMn interface. These exchange-biased CCFA∕MgO∕Co50Fe50 MTJs exhibited further enhanced TMR ratios of 109% at RT and 317% at 4.2K. We suggested enhancement of the TMR ratio by a coherent tunneling contribution for fully epitaxial CCFA∕MgO∕Co50Fe50 MTJs.
Computational study of the melting-freezing transition in the quantum hard-sphere system for intermediate densities. I. Thermodynamic results
Authors: Sesé Luis M.
Published: May 2007

The points where the fluid-solid (face-centered-cubic) transition takes place in the quantum hard-sphere system, for reduced densities 0.85>ρN*>0.5 (reduced de Broglie wavelengths λB*⩽0.8), have been determined via calculations of Helmholtz free energies. A number of complementary methods have been utilized, namely, path-integral Monte Carlo simulations for fixing the basic thermodynamic and structural quantities, Ornstein-Zernike computations of the fluid isothermal compressibilities using the centroid correlations, and applications of the Einstein crystal technique. Attention is paid to the evaluation of the statistical uncertainties in the isothermal compressibilities and also to the quantum implementation of the Einstein crystal technique by including explicitly the constraint of fixed center of mass. The equation of state along the fluid λB* branches studied has been determined with two methods, one based on the isothermal compressibilities and the other on the usual virial estimator. Along the solid λB* branches the equation of state has been fixed with the virial estimator. The results indicate that the phase transition investigated is governed by entropic effects and that the fluid-solid coexistence densities are arranged along a straight line ρFCC*=ρ(ρF*), a behavior which at least holds even for λB*<2, as revealed by completing the present analysis with data available in the literature.
A destabilizing effect of rotation shear on magnetohydrodynamic ballooning modes
Authors: Connor J. W. , Hastie R. J. , Webster A. J.
Published: May 2007

The destabilization of ideal magnetohydrodynamic ballooning modes at finite rotation shear is demonstrated for the model s-α equilibrium by exploiting low magnetic shear, s, to simplify the two-dimensional stability problem to a one-dimensional eigenvalue problem. This simpler calculation captures the same features as exhibited by a full two-dimensional treatment, namely that stable values in the s-α stability diagram become unstable above a critical rotation shear. The first and second stability boundaries at low s are calculated as functions of rotation shear.
Compositional effects on the shock-compression response of alumina-filled epoxy
Authors: Setchell R. E. , Anderson M. U. , Montgomery S. T.
Published: May 2007

Alumina-filled epoxies are composites having constituents with highly dissimilar mechanical properties, resulting in complex behavior during shock compression and release. A previous study examined the shock properties of a particular composition in some detail. In the current study, the effects of compositional variations on shock properties were examined. Planar-impact experiments producing states of nearly equal strain were conducted to investigate the effects of changes in the size and shape of alumina particles, and in the total volume fraction of alumina. Laser interferometry and wave timing were used to obtain transmitted wave profiles, Hugoniot states, and release wave velocities. In addition, wave profiles and velocities were obtained in “thin-pulse” experiments that examined the combined effects of compression and release properties in different compositions. Changes in the size and shape of alumina particles were found to have little effect except in the viscous spreading of wave profiles during shock compression. Increasing the volume fraction of alumina resulted in steadily increasing Hugoniot states, wave rise times, and release wave velocities. An important observation was that differences between release wave and shock wave velocities increased significantly as the alumina loading was increased. Consequences of this effect were evident in the thin-pulse experiments, which showed that increased alumina loading resulted in stronger wave attenuation.
Scattering loss in electro-optic particulate composite materials
Authors: Mackay Tom G. , Lakhtakia Akhlesh
Published: May 2007

The effective permittivity dyadic of a composite material containing particulate constituent materials with one constituent having the ability to display the Pockels effect is computed, using an extended version of the strong-permittivity-fluctuation theory which takes account of both the distributional statistics of the constituent particles and their sizes. Scattering loss, thereby incorporated in the effective electromagnetic response of the homogenized composite material, is significantly affected by the application of a low-frequency (dc) electric field.
Oxygen-octahedral phonon properties of xBaTiO3+(1−x)Ba(Mg1∕3Ta2∕3)O3 and xCa(Sc1∕2Nb1∕2)O3+(1−x)Ba(Sc1∕2Nb1∕2)O3 microwave ceramics
Authors: Chia Chih-Ta , Chang Pi-Jung , Chen Mei-Yu , Lin I.-Nan , Ikawa Hiroyuki , Lin L.-J.
Published: May 2007

Oxygen-octahedral A1g(O) phonons for both 1:2 ordered xBaTiO3+(1−x)Ba(Mg1∕3Ta2∕3)O3 (0≤x≤ 0.05) and 1:1 ordered xCa(Sc1∕2Nb1∕2)O3+(1−x)Ba(Sc1∕2Nb1∕2)O3 (0≤x≤ 0.25) ceramics were investigated using Raman scattering. Lineshapes of A1g(O) phonons directly reflect structural characteristic of TiO6, TaO6, ScO6, and NbO6 octahedral cages that are strongly correlated with microwave performance of the samples. The larger width of stretching A1g(O) phonon, implies poor crystalline structure and short phonon lifetime, giving us lower value of Q×f. The atomic polarizabilities of Ta5+, Ti4+, Ca2+, Sc3+, and Nb5+ have a strong influence on the structure of oxygen octahedron that dominates microwave performance of xBaTiO3+(1−x)Ba(Mg1∕3Ta2∕3)O3 and xCa(Sc1∕2Nb1∕2)O3+(1−x)Ba(Sc1∕2Nb1∕2)O3 ceramics.
THz transmission characteristics of dielectric-filled parallel-plate waveguides
Authors: Mendis Rajind
Published: May 2007

THz transmission characteristics of dielectric-filled (DF) metallic parallel-plate waveguides (PPWGs) are experimentally and theoretically investigated via the propagation of sub-ps THz pulses. It is found that a PPWG having a high-resistivity (>10 kΩ cm) silicon filling can, in fact, exhibit a higher transmission loss compared to one having a polythene filling, despite the significantly lower THz absorption in the bulk silicon. Consequently, it is shown that the key to achieving low-loss transmission in DF-PPWGs is to use a dielectric filling having not only a low absorption, but also a low refractive index. The application of this guided-wave geometry for THz spectroscopy of minute (film) substances is also predicted.
Effects of low-fluence swift iodine ion bombardment on the crystallization of ion-beam-synthesized silicon carbide
Authors: Intarasiri S. , Yu L. D. , Singkarat S. , Hallén A. , Lu J. , Ottosson M. , Jensen J. , Possnert G.
Published: May 2007

Ion beam synthesis using high-fluence carbon ion implantation in silicon in combination with subsequent or in situ thermal annealing has been shown to be able to form nanocrystalline cubic SiC (3C-SiC) layers in silicon. In this study, a silicon carbide layer was synthesized by 40-keV C12+ implantation of a p-type (100) Si wafer at a fluence of 6.5×1017 ions∕cm2 at an elevated temperature. The existence of the implanted carbon in Si substrate was investigated by time-of-flight energy elastic recoil detection analysis. The SiC layer was subsequently irradiated by 10–30 MeV I127 ions to a very low fluence of 1012 ions∕cm2 at temperatures from 80 to 800 °C to study the effect on the crystallization of the SiC layer. Infrared spectroscopy and Raman scattering measurement were used to monitor the formation of SiC and detailed information about the SiC film properties was obtained by analyzing the peak shape of the Si-C stretching mode absorption. The change in crystallinity of the synthesized layer was probed by glancing incidence x-ray diffraction measurement and transmission electron microscopy was also used to confirm the results and to model the crystallization process. The results from all these measurements showed in a coherent way that the synthesized structure was a polycrystalline layer with nanometer sized SiC crystals buried in a-Si matrix. The crystallinity of the SiC layer was enhanced by the low-fluence swift heavy ion bombardment and also favored by higher energy, higher fluence, and higher substrate temperature. It is suggested that electronic stopping plays a dominant role in the enhancement.