bluuebunny/crossref_metadata_2025 huggingface dataset:
The Hebrew Version ofDe celo et mundoAttributed to Ibn Sīnā
Authors: Glasner Ruth
Published: October 2008

The Hebrew textOn the Heavens and the World, ascribed to Ibn Sīnā, is an interesting and intriguing composition. It dates from the 13th century and was quite influential. It is not a translation of any text of Ibn Sīnā known to us, but is related to the (pseudo-Avicennian) LatinDe celo et mundo, which appears in the 1508 Venice edition of translations of Ibn Sīnā. The Latin and Hebrew texts differ widely and the relation between them is far from being clear. Both are in sixteen chapters, the titles of the chapters are the same, but the texts are only roughly similar. The Hebrew text often offers short, incomplete summaries of the Latin arguments. On the other hand it includes many passages which have no parallel in the Latin. There are two possible explanations of the perplexing relationship between the two texts: either that there was more than one version of the Latin (or of the original Arabic) text, or that the translator, Shlomo ben Moshe of Laguiri wrote a kind of paraphrase. The paper shows that the second explanation is correct and offers a preliminary study of the sources and the aims of the Hebrew text.
Le commentaire par al-Kindī de l'Optiqued'euclide: un traité jusqu'ici inconnu
Authors: Rashed Roshdi
Published: October 2008

After he wrote his well-knownDe aspectus, al-Kindī wrote a substantial critical commentary on Euclid'sOptics: the “Rectification of error and difficulties due to Euclid's book: theOptics.” This previously ignored work enriches our knowledge of the optics not only of the geometers of the mid-9th century, but also of late antiquity. This is the first known commentary on Euclid's treatise, and it raises again the questions of its textual traditions, their multiplicity, and the role of Theon of Alexandria; it also poses the problem of the survival of al-Kindī's thought through his successors, such as Ahmad b. 'Īsā. The article examines these and related issues.
The Relation Between Averroes' Middle and long commentaries on theDe Anima
Authors: Davidson Herbert A.
Published: October 2008

Where Averroes' commentaries on Aristotle can be dated, the Middle Commentary on a given work can be seen to predate the Long Commentary. As an accompaniment to his fine edition of Averroes' Middle Commentary on theDe anima, A. Ivry has maintained that in this instance matters are reversed and the Middle Commentary on the De anima is “an abridged and revised version” of the Long Commentary on the same work. Ivry develops his thesis most fully inArabic Sciences and Philosophy5. There he argues that two passages in the Middle Commentary on theDe animarefer to the Long Commentary by name, that a third passage alludes to the Long Commentary, and that in other passages the Middle and Long Commentaries use similar phraseology and the former can be seen to have abridged the latter. The present article replies as follows: The pair of passages in the Middle Commentary which Ivry reads as referring explicitly to the Long Commentary can plausibly be read as cross-references within the Middle Commentary itself. The passage that he takes as alluding to the Long Commentary does not in fact allude to that work, but is an unambiguous reference to a later section of the Middle Commentary. And there is no justification for regarding the passages in the Middle Commentary cited by Ivry which use phraseology similar to that of the Long Commentary as borrowings from the latter. In the course of his arguments, Ivry refers to Averroes' position on the nature of the human material intellect, the issue that gave Averroes the most trouble in his commentaries on Aristotle'sDe animaand that has most intrigued students of Averroes ever since. The present article points out that on the subject of the human material intellect, neither the Middle nor the Long Commentary on theDe animaborrows from the other, for the conceptions of the material intellect which they espouse are different and incompatible.
Response
Authors: Ivry Alfred L.
Published: October 2008

Herbert Davidson's critique of my thesis regarding the relation between Averroes' Middle and Long commentaries on De anima contrasts my reading and translation of Middle Commentary passages with his own. I leave it to the informed reader to judge whether one translation is more “neutral” than the other, excluding the specific denotation which I give to sharh, which is the point at issue.
Über den lateinischen Euklid im Mittelalter
Authors: Busard Hubert L. L.
Published: October 2008

In diesem Aufsatz möchte ich einen Überblick über unser heutiges Wissen bezüglich der Übersetzung derElementeEuklids ins Lateinische geben. Cicero hat als Quästor in Sizilien (im Jahre 75 v. Chr.) das Grab des Archimedes aufgesucht und instandsetzen lassen, er nennt gelegentlich Euklid und Archimedes (De oratoreIII, 33, 132) und er zitiert inAcademicaI, Buch II, § 116, die Definitionen von Punkt und Linie. Vor dem 6.
The Computation of Planetary Longitudes in the Zīj of Ibn al-Bannā'
Authors: Samsó Julio , Millás Eduardo
Published: October 2008

Ibn al-Bannā' of Marrakesh (1256–1321) is the author of one of the four extant “editions” of the unfinished zīj of Ibn Isḥāq (fl. Tunis and Marrakesh ca. 1193–1222): it contains a selection of his tables accompanied by a collection of canons, easy to understand, which makes the zīj accessible for the computation of planetary longitudes. The present paper studies some modifications of the structure of the tables the purpose of which is to make calculations easier. The tables of the planetary and lunar equations of the centre are “displaced." The tables of the equation of the anomaly of Mars, Venus and Mercury, are standard, while, in the cases of Jupiter and Saturn, the equation of the anomaly is calculated in the same way as that for the Moon. Ibn al-Bannā' appears as a clever adapter, who displays a clear ingenuity allowing him to introduce formal modifications which give his work an appearance of novelty which does not correspond to reality.
Porphyry, Universal Soul and the Arabic Plotinus
Authors: Costa Cristina D'Ancona
Published: October 2008

Scholars working in the field of Graeco-Arabic Neoplatonism often discuss the role Porphyry, the editor of Plotinus, must be credited with in the formation of the Arabic Plotiniancorpus. A note in thiscorpusapparently suggests that Porphyry provided a commentary to the so-calledTheology of Aristotle, i.e., parts of some treatises ofEnneadsIV-VI. Consequently, Porphyry has been considered as responsible for the (sometimes relevant) doctrinal shifts which affect the Arabic Plotinian paraphrase with respect to the original text. This article aims at submitting this hypothesis to trial on a specific doctrinal point where Porphyry parts company with Plotinus: the relationship between the Demiurgic Intellect and World Soul. The ancient doxographical sources testify that Porphyry, in his conviction to be in agreement with Plotinus, in fact parted company with him in so far as he merged the World Soul into the Demiurgic Intellect, while Plotinus always kept them apart. There are in theEnneadssome baffling passages where the role of Intellect as the Demiurge of the sensible world is not clearly distinguishable from the role of World Soul. Notwithstanding that, these passages in the Arabic paraphrase do not bear any trace of the characteristically Porphyrian merging of World Soul into Intellect. The Arabic paraphrase of Plotinus’ writings never confuses Intellect and World Soul, as Porphyry did. This fact seems to disprove, at least on this point, the hypothesis of Porphyry's intervention as the explanation for the doctrinal differences between the original Plotinus’ text and its Arabic tradition.
Les commentaires d'al-Māhānī et d'un anonyme du Livre X des Éléments d'Euclide
Authors: Miled Marouane Ben
Published: October 2008

This paper presents the first edition, translation and analyse of al-Māhānī’s commentary of the Book X of Euclid’s Elements (9th century, the most ancient to have reached us) and of an anonymous’ one (prior to 968, among the first algebraic commentaries). For the first time, irrational numbers are defined and classified. The algebraisation of Elements’ X-91 to 102, on the basis of al-Khwārizmī’s Algebra, shows irrational numbers as solution to algebraic quadratic equations. The algebraic calculus makes here the first steps. On this occasion, negative numbers and their calculation rules appears. Simplifications imposed by the algebraic writings are sometimes in opposition with the conclusions of propositions conceived in a purely geometrical framework, revealing a contradiction between geometrical and algebraic goals. It will be resolved by the independant way algebra will take with mathematicians belonging to the tradition of al-Karajī and al-Samaw’al from the 11th-12th centuries on.
Static stress changes induced by the magmatic intrusions during the 2002–2003 Etna eruption
Authors: Currenti Gilda , Del Negro Ciro , Ganci Gaetana , Williams Charles A.
Published: October 2008

The shallow intrusive processes that occurred during 2002–2003 Etna eruption, as well as the complex interaction between the magma intrusive events and the tectonic response of the volcano's eastern flank, are investigated with numerical deformation modeling and the estimation of changes in the static Coulomb stress. Ground deformation and volcanologic evidence clearly indicate a composite mechanism of intrusion on both the southern and northeastern flanks of the volcano. Geodetic data inversions have been based on a homogeneous elastic half‐space model, although geological data and seismic tomography indicate that Mt. Etna is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of the deformation field. To account for topographic effects, as well as a complicated distribution of material properties, we use the finite element method (FEM) to provide a more realistic model. The presence of medium heterogeneity strongly affects the amplitudes of the static stress changes. Seismicity matches well the areas of positive increase in the static stress caused by the intrusive events along the southern and northeastern flanks. The changes in the state of stress generated by the southern dike produce an extensional stress field that favors magma propagation along the north‐east Rift. The highest seismic releases were associated with the activation of two fault systems, the Timpe Fault System and the Pernicana Fault. The static stress changes resolved onto these faults indicate that the magma intrusions on the southern and northeastern flanks encouraged these seismogenic structures to slip.
East Greenland Ridge in the North Atlantic Ocean: An integrated geophysical study of a continental sliver in a boundary transform fault setting
Authors: Døssing Arne , Dahl‐Jensen T. , Thybo H. , Mjelde R. , Nishimura Y.
Published: October 2008

The combined Greenland‐Senja Fracture Zones (GSFZ) represent a first‐order plate tectonic feature in the North Atlantic Ocean. The GSFZ defines an abrupt change in the character of magnetic anomalies with well‐defined seafloor spreading anomalies in the Greenland and Norwegian basins to the south but ambiguous and weak magnetic anomalies in the Boreas Basin to the north. Substantial uncertainty exists concerning the plate tectonic evolution of the latter area, including the role of the East Greenland Ridge, which is situated along the Greenland Fracture Zone. In 2002, a combined ocean‐bottom seismometer and multichannel seismic (MCS) survey acquired two intersecting wide‐angle reflection and coincident MCS profiles across and along the East Greenland Ridge. We present the results of integrated reflection seismic interpretation, first‐arrival tomography, 2D kinematic raytracing, full‐wave amplitude modeling, and gravity modeling of the intersecting profiles. The results show that (1) the Greenland Basin is characterized by a normal oceanic crustal velocity structure, (2) the velocity structure of the East Greenland Ridge is of overall continental type, and (3) a major faulted basin province above highly extended continental crust exists to the NE of the ridge. The results further suggest that a zone of extremely thin and faulted continental crust above partially serpentinized mantle peridotite defines the NW edge of the East Greenland Ridge and the transition to the NE Greenland margin.
The formation of Tharsis on Mars: What the line‐of‐sight gravity is telling us
Authors: Williams Jean‐Pierre , Nimmo Francis , Moore William B. , Paige David A.
Published: October 2008

Line‐of‐sight (LOS) spacecraft acceleration profiles from the Radio Science Experiment and topography from the Mars Orbiter Laser Altimeter (MOLA) instrument of the Mars Global Surveyor (MGS) are analyzed to estimate the effective elastic thickness (Te) for various regions of Tharsis. We identify a buried basin flanking the Thaumasia Highlands at the southeastern margin of Tharsis. Assuming that this basin results from lithospheric flexure from surface loading by the Thaumasia Highlands, we fit LOS profiles across the feature with a thin‐shell, elastic flexure model and find the mountain belt to reflect a value of Te ∼ 20 km consistent with a Noachian formation age. We also determine admittances from LOS profiles for five regions across Tharsis and fit them with theoretical admittances calculated using the flexural model. Crater density, surface density, and predominant surface age are found to vary systematically across Tharsis while Te does not. The highest surface density and lowest Te values are obtained for the western portion of Tharsis where crater densities are lowest. Our results imply the majority of the topographic rise was emplaced within the Noachian irrespective of the surface ages. Topographic loading and resurfacing (i.e., volcanic activity) persisted into the Amazonian while becoming increasingly confined to the western margin where the youngest surface ages are found and the eruptive style transitioned from effusive volcanism to shield‐forming volcanism as Te increased.
Coupled sea surface temperature–seawater δ18O reconstructions in the Arabian Sea at the millennial scale for the last 35 ka
Authors: Anand Pallavi , Kroon Dick , Singh Arun Deo , Ganeshram Raja S. , Ganssen Gerald , Elderfield Henry
Published: October 2008

Two sediment cores from the western (905; 10.46°9′N, 51.56°4′E, water depth 1586 m) and eastern (SK17; 15°15′N, 72°58′E, water depth 840 m) Arabian Sea were used to study past sea surface temperatures (SST) and seawater δ18O (δ18Ow) variations for the past 35 ka. We used coupled Mg/Ca‐δ18O calcite variability in two planktonic foraminiferal species: Globigerinoides ruber, which thrives throughout the year, and Globigerina bulloides, which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing. SSTs in both areas based on Mg/Ca in G. ruber were ∼3 to 4°C lower during the Last Glacial Maximum (LGM; ∼21 ka) than today and the Holocene period. The SST records based on G. bulloides also indicate general cooling, down to 18°C in both areas. SSTs in the western Arabian Sea based on G. bulloides were always lower than those based on G. ruber, indicating the presence of strong seasonal temperature contrast during the Holocene and LGM. We interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling (SW monsoon) and winter convective mixing (NE monsoon) in the western Arabian Sea. In the eastern Arabian Sea, G. bulloides‐based SSTs were slightly lower (about 1°C) than G. ruber‐based SSTs during the Holocene, indicating the almost absence of a seasonal temperature gradient, similar to today. However, a large seasonal temperature contrast occurred during the LGM which favors the assumption that strong NE monsoon winds forced winter upwelling or convective mixing offshore Goa. SST and δ18Ow reconstructions reveal evidence of millennial‐scale cycles, particularly in the eastern Arabian Sea. Here, the stadial periods (Northern Hemisphere cold periods such as Younger Dryas and Heinrich events) are marked by increasing SSTs and salty sea surface conditions relative to those during the interstadial periods. Indeed, the δ18Ow record shows evidence of low‐saline surface waters during interstadial periods, indicating increased freshwater runoff from the Western Ghats as a consequence of enhanced SW monsoon intensity.
Message From Fred Spilhaus to AGU Members
Authors: Spilhaus Fred
Published: October 2008

My service as AGU's executive director will end in mid‐2009. I understand the Union is committed to a worldwide search for my successor. My contract ends on 30 June 2009, after which I anticipate stepping into an emeritus status. I have indicated my willingness to serve, at the Union's request, in whatever capacity necessary to assure a smooth transition and the continuing growth and success of AGU.
Defining the geochemical composition of the EPICA Dome C ice core dust during the last glacial‐interglacial cycle
Authors: Marino F. , Castellano E. , Ceccato D. , De Deckker P. , Delmonte B. , Ghermandi G. , Maggi V. , Petit J. R. , Revel‐Rolland M. , Udisti R.
Published: October 2008

The major element composition of the insoluble, windborne long‐range dust archived in the European Project for Ice Coring in Antarctica Dome C ice core has been determined by Particle Induced X‐ray Emission analyses. The geochemistry of dust from the last glacial maximum (LGM) and from the Holocene is discussed in terms of past environmental changes, throughout the last climatic cycle. Antarctic dust from glacial and interglacial climate clearly reveals different geochemical compositions. The weathered crustal‐like signature of LGM dust is characterized by a low compositional variability, suggesting a dominant source under the glacial regime. The close correspondence between the major element composition of Antarctic glacial dust and the composition of southern South American sediments supports the hypothesis of a dominant role of this area as major dust supplier during cold conditions. Conversely, the major element composition of Holocene dust displays high variability and high Al content on average. This implies that an additional source could also play some role. Comparison with size‐selected sediments suggests that a contribution from Australia is likely during warm times, when a reduced glacial erosion decreases the primary dust production and a more intense hydrological cycle and larger vegetation cover inactivates dust mobility in a large part of southern South America, weakening its contribution as a massive dust supplier to Antarctica.
Monsoon‐like winds reverse oceanic circulation in the Panama Bight
Authors: Devis‐Morales Andrea , Schneider Wolfgang , Montoya‐Sánchez Raúl A. , Rodríguez‐Rubio Efraín
Published: October 2008

Seasonal circulation and three‐dimensional thermohaline structure within the Panama Bight are examined by employing satellite‐derived sea surface winds and dense in‐situ hydrographic datasets. The northerly Panama wind jet, associated with a dipole structure of wind stress curl that is positive (negative) on its eastern (western) flank, dominates the bight in winter. This wind jet generates a cyclonic eddy with mean geostrophic velocities of 60 cm s−1, including the poleward flowing coastal Colombia Current, and induces a well pronounced thermocline dome. As a result, temperature (salinity) in the bight is much colder (saltier) than in its surrounding waters. Winds blow from southwesterly directions in summer and the bight is dominated by an anticyclonic eddy associated with a thermocline bowl. Mean geostrophic velocities are on the order of 40 cm s−1 and the Colombia Current is not observed. Temperature (salinity) in the bight is much warmer (fresher) than in its surrounding waters.
Regional conductivity structure of Cascadia: Preliminary results from 3D inversion of USArray transportable array magnetotelluric data
Authors: Patro Prasanta K. , Egbert Gary D.
Published: October 2008

In conjunction with the USArray component of EarthScope, long period magnetotelluric (MT) data are being acquired in a series of arrays across the continental US. Initial deployments in 2006 and 2007 acquired data (10–10,000 s) at 110 sites covering the US Pacific Northwest, distributed with the same nominal spacing as the USArray seismic transportable array (∼75 km). The most striking and robust features revealed by initial three‐dimensional inversion of this dataset are extensive areas of high conductivity in the lower crust beneath all of southeastern Oregon, and beneath the Cascade Mountains, contrasting with very resistive crust in Siletzia and the Columbia Embayment. Significant variations in upper mantle conductivity are also revealed by the inversions, with the most conductive mantle beneath the Washington backarc, and the most resistive corresponding to subducting oceanic mantle.
Satellite traces: An ionogram signature for large‐scale wave structure and a precursor for equatorial spread F
Authors: Tsunoda Roland T.
Published: October 2008

Although the source that controls day‐to‐day variability in the occurrence of equatorial plasma structure (i.e., equatorial spread F, or ESF) remains to be identified, progress is being made. There is evidence that the appearance of large‐scale wave structure (LSWS) in the bottomside F layer, around the time of its post‐sunset rise (PSSR), is a more‐direct precursor of ESF than the PSSR itself. The bulk of the evidence, however, is in the form of “satellite” F traces in ionograms, which may be viewed as less than convincing, because these signatures have not been shown to be causally related to LSWS. In this paper, incoherent‐scatter radar and ionosonde data, both collected on 24 July 1979 from the Kwajalein atoll, Marshall Islands, are used to show that this is indeed the case.
Dust generation and drought patterns in Africa from helium‐4 in a modern Cape Verde coral
Authors: Mukhopadhyay S. , Kreycik P.
Published: October 2008

We show that helium‐4 (4He) concentrations in a modern Porites coral from Cape Verde provides a robust reconstruction of mineral dust loading over the Eastern Tropical Atlantic from mid‐1950's to mid‐1990's. The 4He record demonstrates pronounced increases in dust emission from North Africa associated with the severe droughts in the Sahel. Our record provides direct evidence that dust emission rates in the 1950's, prior to the onset of the Sahel droughts, were a factor of nine lower than during 1980–84. This large change in dust emission rate indicates global aerosol contents would have increased by ∼45% over this period, which may have contributed to a reduction in solar radiation reaching the Earth's surface. We find that dust emission from North Africa is most closely related to drought patterns, rather than to changes in atmospheric circulation patterns resulting from climate oscillations, such as North Atlantic Oscillations and El Nino/Southern Oscillation.
Observations of an atmospheric chemical equator and its implications for the tropical warm pool region
Authors: Hamilton Jacqueline F. , Allen Grant , Watson Nicola M. , Lee James D. , Saxton Julie E. , Lewis Alastair C. , Vaughan Geraint , Bower Keith N. , Flynn Michael J. , Crosier Jonathan , Carver Glenn D. , Harris Neil R. P. , Parker Robert J. , Remedios John J. , Richards Nigel A. D.
Published: October 2008

This paper reports observations of a tropospheric chemical equator in the Western Pacific region during the Austral monsoon season, separating the polluted Northern Hemisphere from the cleaner Southern Hemisphere. Measurements of carbon monoxide, ozone, aerosol size/composition, and non‐methane hydrocarbons were made from aircraft, flying north from Darwin, Australia as part of the Aerosol and Chemical Transport In tropical conVEction (ACTIVE) campaign. A chemical equator, defined as a sharp gradient in the chemical background, was found not to be coincident with the Intertropical Convergence Zone during this period. A pronounced interfacial region was identified between 8.5 and 10°S, where tracer mixing ratios increased rapidly within the boundary layer, e.g. CO from 40 ppbv to 160 ppbv within 0.5° latitude (50 km), with inhibited inter‐hemispheric mixing. These measurements are discussed in context using a combination of meteorological and Earth‐observing satellite imagery, back trajectory analysis and chemical model data with the conclusion that air flowing into and subsequently uplifted by the active convection of the Tropical Warm Pool (TWP) region in the Western Pacific is likely to be highly polluted, and will perturb the composition of the Tropical Tropopause Layer. The main source of CO and other pollutants within the TWP region is expected to be biomass burning, with extensive fires in North Sumatra and Thailand during this period. The sharp gradient in composition at the chemical equator seen here results from extensive burning to the north, contrasting with pristine maritime air advected from the Southern Indian Ocean by a strong land‐based cyclone over the Northern Territory of Australia.
Microscopy capabilities of the Microscopy, Electrochemistry, and Conductivity Analyzer
Authors: Hecht M. H. , Marshall J. , Pike W. T. , Staufer U. , Blaney D. , Braendlin D. , Gautsch S. , Goetz W. , Hidber H.‐R. , Keller H. U. , Markiewicz W. J. , Mazer A. , Meloy T. P. , Morookian J. M. , Mogensen C. , Parrat D. , Smith P. , Sykulska H. , Tanner R. J. , Reynolds R. O. , Tonin A. , Vijendran S. , Weilert M. , Woida P. M.
Published: October 2008

The Phoenix microscopy station, designed for the study of Martian dust and soil, consists of a sample delivery system, an optical microscope, and an atomic force microscope. The combination of microscopies facilitates the study of features from the millimeter to nanometer scale. Light‐emitting diode illumination allows for full color optical imaging of the samples as well as imaging of ultraviolet‐induced visible fluorescence. The atomic force microscope uses an array of silicon tips and can operate in both static and dynamic mode.
How important are Southern Hemisphere wind changes for low glacial carbon dioxide? A model study
Authors: Tschumi T. , Joos F. , Parekh P.
Published: October 2008

The response of atmospheric CO2 to modifications in the strength and position of Southern Hemisphere westerlies is examined with the Bern3D ocean model. The model responds more sensitively to changes in the wind amplitude than to variations in latitudinal position. Depending on the model setup, a 50% reduction in wind strength leads to a CO2 drawdown of 3–34 ppm, while a 50% increase results in a rise of 10–24 ppm. A poleward shift of 5° lowers CO2 by 2–16 ppm whereas an equatorward shift of 5° induces a CO2 increase of 2–14 ppm. Physical and biological mechanisms equally contribute to the modeled changes in atmospheric CO2. Our results are in conflict with the hypothesis that Southern Hemisphere wind changes are responsible for the low atmospheric CO2 concentrations during glacial periods.
Gas binding to Au13, Au12Pd, and Au11Pd2 nanoclusters in the context of catalytic oxidation and reduction reactions
Authors: Wells Brad A. , Chaffee Alan L.
Published: October 2008

The ability of Au13, Au12Pd, and Au11Pd2 nanoclusters to bind species typically found in the oxidation and reduction of small hydrocarbon has been investigated by means of atom centered density functional theory calculations. Binding energies of CO2, H2, CO, O2, CH4, H2O, O⋅, H⋅, C⋅HO, C⋅O2H, and O⋅H have been calculated. For pure gold nanoclusters, CO2, H2, and CH4 were found to not bind, and O2 and H2O bound weakly with binding energies less than 15kcalmol−1, with the rest binding strongly with binding energies in the range 26–68kcalmol−1. Binding additional gas molecules did not greatly reduce the binding energy. Adding palladium to the clusters created binding sites for all of the test gases. Binding to the palladium atom generally increased the binding energy of molecules but decreased the binding energy of radicals.
Self-association of urea in aqueous solutions: A Voronoi polyhedron analysis study
Authors: Idrissi Abdenacer , Damay Pierre , Yukichi Kitamura , Jedlovszky Pal
Published: October 2008

Molecular dynamics simulation of the aqueous solutions of urea of seven different concentrations (including neat water as a reference system) has been performed on the isothermal-isobaric (N,p,T) ensemble. The ability of the urea molecules of self-association is investigated by means of the method of Voronoi polyhedra. For this purpose, all the analyses are repeated by removing one of the two components from the sample configurations and considering only the other one. In this way, the analysis of self-aggregation is reduced to the analysis of voids, a problem that can routinely be addressed by means of Voronoi analysis. The obtained results show that the urea molecules exhibit self-association behavior, which is found to be the strongest at the urea mole fraction of 0.23. However, the size of these urea aggregates is found to be rather limited; on average, they are built up by 3–4 molecules, and never exceed the size of 20–25 molecules.
Characteristics of CoxTi1−xO2 thin films deposited by metal organic chemical vapor deposition
Authors: McClure Adam , Kayani A. , Idzerda Y. U. , Arenholz E. , Cruz E.
Published: October 2008

This paper deals with the growth and characterization of ferromagnetic cobalt doped TiO2 thin films deposited by liquid precursor metal organic chemical vapor deposition using a combination of the source materials Co(TMHD)3, tetrahydrofuran, and titanium isopropoxide. An array of experiments reveals the intrinsic ferromagnetic nature of the grown films and suggests that the magnetism is not generated by oxygen vacancies.
Iterative Monte Carlo for quantum dynamics
Authors: Jadhao Vikram , Makri Nancy
Published: October 2008

We present a fully quantum mechanical methodology for calculating complex-time correlation functions by evaluating the discretized path integral expression iteratively on a grid selected by a Monte Carlo procedure. Both the grid points and the summations performed in each iteration utilize importance sampling, leading to favorable scaling with the number of particles, while the stepwise evaluation of the integrals circumvents the exponential growth of statistical error with time.
Memory effect near transition temperature in Sm C∗ phase in nonsurface stabilized ferroelectric liquid crystals
Authors: Coondoo I. , Malik A. , Choudhary A. , Kumar A. , Biradar A. M.
Published: October 2008

Memory behavior in the ferroelectric liquid crystal (FLC) material, Felix 17/100, has been investigated by electro-optical, dielectric, and hysteresis methods at different temperatures ranging from room temperature to near ferro-paraelectric phase transition. Memory effect has been observed in the studied material near the transition temperature in Sm C∗ phase in the cells having thickness greater than the pitch value of the material. This is in contrast to the memory effect observed in conventional FLCs where thickness of the cell has to be less than the pitch value of the material. Electrical conductivity measurements elucidate that the steep increase in the conductivity near the transition temperature in Sm C∗ phase enhances the motion of free ions and probably weakens the depolarization field in the material, thereby showing memory effect.
Comparison of the effect of cyanoacrylate- and polyurethane-based adhesives on a longitudinal strain solitary wave in layered polymethylmethacrylate waveguides
Authors: Dreiden G. V. , Khusnutdinova K. R. , Samsonov A. M. , Semenova I. V.
Published: October 2008

We study the effect of two types of adhesive bonding on the propagation of a localized longitudinal strain wave in two- and three-layered elastic bars. The detectable variation in the decay rate of the wave at relatively long distances of propagation is observed. It is proposed that such variation can be used as an indicator of the type of an interface.
A new type of thermoelectric material, EuZn2Sb2
Authors: Zhang Hui , Zhao Jing-Tai , Grin Yu. , Wang Xiao-Jun , Tang Mei-Bo , Man Zhen-Yong , Chen Hao-Hong , Yang Xin-Xin
Published: October 2008

Polycrystalline EuZn2Sb2 is prepared by direct reaction of the elements. Its composition, structure, magnetism, heat capacity, and thermoelectric properties have been investigated. EuZn2Sb2 crystallizes in p3¯m space group with a=4.4932(7)Å and c=7.6170(10)Å. Antiferromagnetic ordering is detected at the Nèel temperature of 13.06K, and the saturation magnetization reaches 6.87μB∕Eu at 2K and 7T. Eu ion has +2 valence. Its Hall effects are characterized by a high positive Hall coefficient of +0.226cm3∕C, proper carrier concentration of 2.77×1019∕cm3, and high carrier mobility of 257cm2∕Vs at 300K. This compound shows high p-type Seebeck coefficient (+122to+181μV∕K), low lattice thermal conductivity (1.60–0.40W∕mK), and high electrical conductivity (1137–524S∕cm). The obtained figure of merit and powder factor reach 0.92 and 20.72μW∕cmK2, respectively. The thermoelectric properties of EuZn2Sb2 are encouraging.
Planar polymer photovoltaic cells with millimeter interelectrode spacing
Authors: Gao Jun , Hui Jin , Hou Yanbing , Alem Salima
Published: October 2008

We present the photovoltaic measurements of planar photovoltaic cells with extremely large interelectrode spacing based on either pure polymers or polymer∕fullerene blends. The planar configuration allows for both uniform and site-selective illuminations. As expected, cells with identical electrodes do not exhibit any photovoltaic action under uniform illumination. On the other hand, open-circuit voltage (VOC) greater than 1V has been observed in pure polymer cells with dissimilar gold∕calcium electrodes, which decreases when calcium is replaced with aluminum or when a fullerene derivative is added. In addition, all asymmetric cells exhibit photovoltaic action when the illumination is only applied to the anode half, the cathode, or the middle section of the cell. Our results provide unambiguous support to the metal∕insulator∕metal interpretation of polymer photovoltaic response.
Influence of Si concentration on the magnetization dynamics in as-sputtered FeCoSiN thin films at high frequencies
Authors: Xu Feng , Chen Xin , Ma Yungui , Phuoc N. N. , Zhang Xiaoyu , Ong C. K.
Published: October 2008

In this work, the high-frequency magnetic permeability spectra of as-sputtered FeCoSiN films with various Si concentrations were investigated. The soft magnetic properties with an induced in-plane uniaxial anisotropy can only be obtained within some composition ranges because of the formation of different granular microstructures. The permeability spectra measured without any external fields (He) were well fitted based on the phenomenological Landau–Lifshitz–Gilbert equation. Results show that with the increase in Si concentration, the saturated magnetization 4πMs, the resonance frequency fr, the permeability μ, and the qualify factor Q values decrease, while the damping coefficient α and resonant frequency linewidth Δf increase. The increase in Gilbert damping coefficient α or G is ascribed to the increase in mosaicity or magnetic ripples with higher volume proportion of Si-rich matrix. The investigations on Δf-He relations indicate the extrinsic damping contribution from the two-magnon scattering in FeCoSiN, which is suggested to be due to the change in the granular microstructures compared with FeCoN.
A frequency stabilization technique for diode lasers based on frequency-shifted beams from an acousto-optic modulator
Authors: Gunawardena Mevan , Hess Paul W. , Strait Jared , Majumder P. K.
Published: October 2008

We present a simple method for diode laser frequency stabilization that makes use of a Doppler-broadened vapor cell absorption signals of two frequency-shifted laser beams. Using second-order-diffracted, double-passed beams from an acousto-optic modulator, we achieve a frequency separation roughly equal to the Doppler half width. The differential transmission signals of the two beams provide an error signal with a very large linear feature, allowing frequency stabilization over a range of greater than 1 GHz by means of standard proportional-integral-derivative servo feedback to the piezoelectric control of the grating in our external cavity diode laser. We have applied this technique to two different diode laser systems, one used to lock to the 410 nm E1 transition in indium and another for locking to the M1/E2 transition in thallium at 1283 nm. In both cases the technique reduces frequency fluctuation to roughly 1 MHz over time scales from 10−3 to 102 s.
Energy gap reduction in dilute nitride GaAsSbN
Authors: Lin Yan-Ting , Ma Ta-Chun , Chen Tsung-Yi , Lin Hao-Hsiung
Published: October 2008

The energy gap of dilute nitride GaAsSbN has been studied. We found that the energy gap reduction induced by nitrogen incorporation is nearly independent of the Sb composition of the alloy, indicating that the conduction band and the valence band can be independently manipulated by incorporating N and Sb, respectively. A “double” band anticrossing (BAC) model, which is a combination of a BAC model for GaAsN and a valence BAC model for GaAsSb with the localized levels and hybridization parameters reported in literatures, has been proposed to fit the energy gap of annealed GaAsSbN samples. The as-grown samples, however, are with lower energy gaps, most likely resulting from the existence of substitutional N pairing and clustering in the alloys.
Tunable graphene system with two decoupled monolayers
Authors: Schmidt H. , Lüdtke T. , Barthold P. , McCann E. , Fal’ko V. I. , Haug R. J.
Published: October 2008

The use of two truly two-dimensional gapless semiconductors, monolayer and bilayer graphene, as current-carrying components in field-effect transistors (FETs) gives access to special types of nanoelectronic devices. Here, we report on the development of graphene-based FETs containing two decoupled graphene monolayers manufactured from a single one folded during the exfoliation process. The transport characteristics of these devices differ markedly from those manufactured from a single-crystal bilayer. By analyzing Shubnikov–de Haas oscillations, we demonstrate the possibility to independently control the carrier densities in both layers using top and bottom gates, despite there being only a nanometer scale separation between them.
Piezoelectric response and origin in (001) Pb(Mg1/3Nb2/3)0.70Ti0.30O3 crystal
Authors: Tu C.-S. , Hsieh C.-M. , Schmidt V. Hugo , Chien R. R. , Luo H.
Published: October 2008

Converse and direct piezoelectric coefficients (d33C and d33D) of (001)-cut Pb(Mg1/3Nb2/3)0.70Ti0.30O3 (PMN-30%PT) single crystals have been investigated as a function of poling electric (E) field. E-field-dependent domain structures were observed by using a polarizing microscope. Both d33C and d33D exhibit a rapid increase at E=1–2 kV/cm and reach maxima at E=2.5–4 kV/cm. This study suggests that polarization rotation from rhombohedral to monoclinic MA phases plays an important role while the high piezoelectric response builds up. Overpoling phenomenon evidenced by a sudden reduction in piezoelectric coefficient with increasing field is very sensitive to Ti content.
Fully transparent nonvolatile memory employing amorphous oxides as charge trap and transistor’s channel layer
Authors: Yin Huaxiang , Kim Sunil , Kim Chang Jung , Song Ihun , Park Jaechul , Kim Sangwook , Park Youngsoo
Published: October 2008

A fully transparent nonvolatile memory with the conventional sandwich gate insulator structure was demonstrated. Wide band gap amorphous GaInZnO (a-GIZO) thin films were employed as both the charge trap layer and the transistor channel layer. An excellent program window of 3.5 V with a stressing time of 100 ms was achieved through the well-known Fowler–Nordheim tunneling method. Due to the similar energy levels extracted from the experimental data, the asymmetrical program/erase characteristics are believed to be the result of the strong trapping of the injected negative charges in the shallow donor levels of the GIZO film.
Photoluminescence lifetime and potential fluctuation in wurtzite Zn1−xCdxO alloy films
Authors: Yamamoto Kenji , Ohashi Toshiya , Tawara Takehiko , Gotoh Hideki , Nakamura Atsushi , Temmyo Jiro
Published: October 2008

Carrier recombination dynamics in wurtzite Zn1−xCdxO alloy films has been studied by time-resolved photoluminescence (PL) to evaluate the potential fluctuation. Typical PL lifetime τ2 in Zn1−xCdxO is around 200 ps and gradually increases with a Cd content of up to 0.19. At a Cd content over 0.3, τ2 becomes roughly 50 ns. The degree of potential fluctuation E0 is increased from 9 to 157 meV with an increment in Cd content of 0.19. In contrast, at a Cd content over 0.3, E0 decreases to 35 meV with a Cd content of 0.55. This suggests that the potential fluctuation in Zn1−xCdxO with a high Cd content is greatly improved, which is qualitatively supported by the Zimmermann’s model [R. Zimmermann, J. Cryst. Growth 101, 346 (1990)].
Summative evaluation of climate application activities with pastoralists in western Queensland
Authors: Cobon D. H. , Bell K. L. , Park J. N. , Keogh D. U.
Published: October 2008

Survey methods were engaged to measure the change in use and knowledge of climate information by pastoralists in western Queensland. The initial mail survey was undertaken in 2000–01 (n = 43) and provided a useful benchmark of pastoralists climate knowledge. Two years of climate applications activities were completed and clients were re-surveyed in 2003 (n = 49) to measure the change in knowledge and assess the effectiveness of the climate applications activities. Two methods were used to assess changes in client knowledge, viz., self-assessment and test questions. We found that the use of seasonal climate forecasts in decision making increased from 36% in 2001 (n = 42) to 51% in 2003 (n = 49) (P = 0.07). The self-assessment technique was unsatisfactory as a measure of changing knowledge over short periods (1–3 years), but the test question technique was successful and indicated an improvement in climate knowledge among respondents. The increased levels of use of seasonal climate forecasts in management and improved knowledge was partly attributed to the climate applications activities of the project.
Further, those who used seasonal forecasting (n = 25) didn’t understand key components of forecasts (e.g. probability, median) better than those who didn’t use seasonal forecasts (n = 24) (P > 0.05). This identifies the potential for misunderstanding and misinterpretation of forecasts among users and highlights the need for providers of forecasts to understand the difficulties and prepare simply written descriptions of forecasts and disseminate these with the maps showing probabilities.
The most preferred means of accessing climate information were internet, email, ‘The Season Ahead’ newsletter and newspaper. The least preferred were direct contact with extension officers and attending field days and group meetings. Eighty-six percent of respondents used the internet and 67% used ADSL broadband internet (April 2003). Despite these findings, extension officers play a key role in preparing and publishing the information on the web, in emails and newsletters. We also believe that direct contact with extension officers trained in climate applications is desirable in workshop-like events to improve knowledge of the difficult concepts underpinning climate forecasts, which may then stimulate further adoption.
The Western Australian Rangeland Monitoring System (WARMS) - operating a regional scale monitoring system
Authors: Novelly P. E. , Watson I. W. , Thomas P. W. E. , Duckett N. J.
Published: October 2008

The Western Australian Rangeland Monitoring System (WARMS), a state government monitoring activity, provides information on change in Western Australia’s pastoral rangelands. It consists of a set of permanent sites, on which measurements of perennial vegetation (direct census in shrublands and perennial grass frequency and woody cover in grasslands) and assessments of soil surface condition are recorded at either 3-year (grasslands) or 5-year (shrublands) intervals. Data collection is non-destructive. Site distribution is based on vegetation type, and WARMS reports at the vegetation type or regional level, not individual site or property level.
Operating WARMS requires a range of defined conventions to ensure that personnel changes and the interval between samplings at any one site do not lead to confounding of results through variation in how data are collected. The number of sites (1622) and program timeframe (decadal) mean that data storage and management issues are critical. Data interpretation, including the interpretive framework and use of ancillary data to assist in interpreting causality, and provision of information products relevant to a range of users are also important operational aspects. A companion paper addresses the institutional requirements for WARMS, system design and the rationale behind this design.
Feasibility of using template-based and object-based automated detection methods for quantifying black and hybrid imported fire ant (Solenopsis invicta and S. invicta×richteri) mounds in aerial digital imagery
Authors: Vogt James T. , Wallet Bradley
Published: October 2008

Imported fire ants construct earthen nests (mounds) that exhibit many characteristics which make them potentially good targets for remote sensing programs, including geographical orientation, topography, and bare soil surrounded by actively growing vegetation. Template-based features and object-based features extracted from aerial multispectral imagery of fire ant infested pastures were used to construct classifiers for automated fire ant mound detection. A classifier constructed using template-based features alone yielded a 79% probability of detection with a corresponding false positive rate of 9%. Addition of object-based features (compactness and symmetry) to the classifier yielded a 79% probability of detection with a corresponding false positive rate of 4%. Maintaining a 79% detection rate when applying the classifier to a second, unique pasture dataset with different seasonal and other environmental factors resulted in a false positive rate of 17.5%. Data demonstrate that automated detection of mounds with classifiers incorporating template- and object-based features is feasible, but it may be necessary to construct unique classifiers on a site-specific basis.
Crystal structure of poxvirus thymidylate kinase: An unexpected dimerization has implications for antiviral therapy
Authors: Caillat Christophe , Topalis Dimitri , Agrofoglio Luigi A. , Pochet Sylvie , Balzarini Jan , Deville-Bonne Dominique , Meyer Philippe
Published: October 2008

Unlike most DNA viruses, poxviruses replicate in the cytoplasm of host cells. They encode enzymes needed for genome replication and transcription, including their own thymidine and thymidylate kinases. Some herpes viruses encode only 1 enzyme catalyzing both reactions, a peculiarity used for prodrug activation to obtain maximum specificity. We have solved the crystal structures of vaccinia virus thymidylate kinase bound to TDP or brivudin monophosphate. Although the viral and human enzymes have similar sequences (42% identity), they differ in their homodimeric association and active-site geometry. The vaccinia TMP kinase dimer arrangement is orthogonal and not antiparallel as in human enzyme. This different monomer orientation is related to the presence of a canal connecting the edge of the dimer interface to the TMP base binding pocket. Consequently, the pox enzyme accommodates nucleotides with bulkier bases, like brivudin monophosphate and dGMP; these are efficiently phosphorylated and stabilize the enzyme. The brivudin monophosphate-bound structure explains the structural basis for this specificity, opening the way to the rational development of specific antipox agents that may also be suitable for poxvirus TMP kinase gene-based chemotherapy of cancer.