bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploration of the free‐energy surface of a three‐helix peptide with stochastic optimization methods
Authors: Herges T. , Schug A. , Wenzel W.
Published: May 2004

We report our recent efforts to develop all‐atom forcefields that can be used to predict the three‐dimensional, tertiary structure of proteins using stochastic optimization methods. We have analyzed an approximate free‐energy surface of the 36‐residue headpiece of the villin protein and found configurations that were lower in energy than the NMR configuration. We adjusted the parameters of the solvent model to stabilize the NMR structure using a decoy approach. We arrived at a free‐energy surface that is characterized by a deep folding funnel populated by different three‐helix structures, one of which is very similar to the NMR structure. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Orientational ordering in physisorbed molecular layers induced by surface geometry and confinement
Authors: Ramseyer C. , Pouthier V. , Humbert J. , Girardet C.
Published: May 2004

Monte Carlo calculations are performed to study the orientational ordering of a model two‐dimensional molecular admonolayer confined between two monatomic steps of a square substrate. Aside from the orientational influence of the substrate on the molecular axes, we show strong competition between the lateral interactions and the confinement potential due to the steps, which is responsible for more or less abrupt orientational transitions depending on the strength of the various interactions, the width of the confinement, and the temperature. An application to the adsorption of N2monolayer adsorbed on Cu/CuO stripe substrate is discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Reversible coagulation–fragmentation processes and random combinatorial structures: Asymptotics for the number of groups
Authors: Erlihson Michael M. , Granovsky Boris L.
Published: May 2004

The equilibrium distribution of a reversible coagulation‐fragmentation process (CFP) and the joint distribution of components of a random combinatorial structure (RCS) are given by the same probability measure on the set of partitions. We establish a central limit theorem for the number of groups (= components) in the case a(k) = qkp−1, k ≥ 1, q, p > 0, where a(k), k ≥ 1, is the parameter function that induces the invariant measure. The result obtained is compared with the ones for logarithmic RCS's and for RCS's, corresponding to the case p < 0. © 2004 Wiley Periodicals, Inc. Random Struct. Alg. 2004
Is constraint satisfaction over two variables always easy?
Authors: Engebretsen Lars , Guruswami Venkatesan
Published: May 2004

By the breakthrough work of Håstad [J ACM 48(4) (2001), 798–859], several constraint satisfaction problems are now known to have the following approximation resistance property: Satisfying more clauses than what picking a random assignment would achieve is NP‐hard. This is the case for example for Max E3‐Sat, Max E3‐Lin, and Max E4‐Set Splitting. A notable exception to this extreme hardness is constraint satisfaction over two variables (2‐CSP); as a corollary of the celebrated Goemans‐Williamson algorithm [J ACM 42(6) (1995), 1115–1145], we know that every Boolean 2‐CSP has a nontrivial approximation algorithm whose performance ratio is better than that obtained by picking a random assignment to the variables. An intriguing question then is whether this is also the case for 2‐CSPs over larger, non‐Boolean domains. This question is still open, and is equivalent to whether the generalization of Max 2‐SAT to domains of size d, can be approximated to a factor better than (1 − 1/d2). In an attempt to make progress towards this question, in this paper we prove, first, that a slight restriction of this problem, namely, a generalization of linear inequations with two variables per constraint, is not approximation resistant, and, second, that the Not‐All‐Equal Sat problem over domain size d with three variables per constraint, is approximation resistant, for every d ≥ 3. In the Boolean case, Not‐All‐Equal Sat with three variables per constraint is equivalent to Max 2‐SAT and thus has a nontrivial approximation algorithm; for larger domain sizes, Max 2‐SAT can be reduced to Not‐All‐Equal Sat with three variables per constraint. Our approximation algorithm implies that a wide class of 2‐CSPs called regular 2‐CSPs can all be approximated beyond their random assignment threshold. © 2004 Wiley Periodicals, Inc. Random Struct. Alg. 2004
A behavioral type system and its application in Ptolemy II
Authors: Lee Edward A. , Xiong Yuhong
Published: May 2004

Interface automata [deH01] have been introduced as an interface theory [deH01a] capable of functioning as a behavioral type system. Behavioral type systems describe dynamic properties of components and their compositions. Like traditional (data) type systems, behavioral type systems can be used to check compatibility of components. In this paper, we use interface automata to devise a behavioral type system for Ptolemy II, leveraging the contravariant and optimistic properties of interface automata to achieve behavioral subtyping and polymorphism. Ptolemy II is a software framework supporting concurrent component composition according to diverse models of computation. In this paper, we focus on representing the communication protocols used in component communication within the behavioral type system. In building this type system, we identify two key limitations in interface automata formalisms; we overcome these limitations with two extensions, transient states and projection automata. In addition to static type checking, we also propose to extend the use of interface automata to the on-line reflection of component states and to run-time type checking, which enable dynamic component creation, morphing application structure, and admission control. We discuss the trade-offs in the design of behavioral type systems.
Pedunculated Neurilemmoma of the Tongue Base
Authors: Bassichis Benjamin A. , McClay John E.
Published: May 2004

Aneurilemmoma, also referred to as a schwannoma or neurimoma, is a benign, encapsulated tumor of the Schwann cells of the nerve sheath. Of the extracranial neurilemmomas, 25% affect the head and neck, with the lateral cervical region and mouth being the most common sites. Intraoral neurilemmomas may arise from both soft tissue and bone. The soft tissue lesions usually present as an asymptomatic, submucosal swelling in the tongue, lip, cheek, and palate. We report the case of a 9‐year‐old boy who presented with a symptomatic, exophytic, and pedunculated lesion at the tongue base, appearing papillomatous. Complete excision and pathologic evaluation revealed a neurilemmoma.
Entamoeba histolyticaGal/GalNAc lectin depletes antioxidant defences of target epithelial cells
Authors: RAWAL S. , MAJUMDAR S. , DHAWAN V. , VOHRA H.
Published: May 2004

Among the variety of virulence factors ofEntamoeba histolytica, an adherence lectin (Gal/GalNAc, 260 kDa) is known to mediate colonization and subsequent host responses. Gal/GalNAc lectin is universally recognized by the immune sera of patients with amoebic liver abscess. It plays a crucial role in cytolysis and phagocytosis of human and rat colonic mucin glycoproteins. The objective of the present study was to elucidate the role of antioxidants inE. histolyticaGal/GalNAc lectin-induced signals in the target epithelial cells. We have attempted to define a pathway in target cells, Henle-407 cells (human intestinal epithelial cell line), that could link this immunodominant antigen to a known biological pathway for target cell activation and triggering of subsequent disease pathology/parasite survival. Since several workers have demonstrated that cAMP and cGMP may act as important cellular signals for altering ion transport, so in the present study, cAMP and cGMP levels were measured in Henle-407 cells which showed significant increase at 15 min after stimulation. Elevated cAMP and cGMP levels are implicated in altered electrolyte transport and conductance. Results showed that there were increased levels of ROS and RNI which led to reduced activities of antioxidant enzymes – catalase, superoxide dismutase and glutathione peroxidase. Despite the increased glutathione (reduced) levels, the enzymes were not able to combat the damage caused by ROS and RNI. Thus, there was an increased local concentration of the free radicals and reduced activities of all the three enzymes which could damage the target cell in terms of cytoskeleton and permeability changes.
Foreword: ontologies for distributed systems
Authors: STUCKENSCHMIDT HEINER
Published: May 2004

The benefits of using ontologies have been recognised in many areas such as knowledge and content management, electronic commerce and recently the emerging field of the Semantic Web. These new applications can be seen as a great success of research in ontologies. On the other hand, moving into real application comes with new challenges that need to be addressed on a principled level rather than for specific applications. This special issue will be devoted to less well-explored topics that have come into focus recently as a response to the new problems we face when trying to use ontologies in heterogeneous distributed environments. These environments include the use of ontologies in peer-to-peer and pervasive computing systems.
Use of ontologies in a pervasive computing environment
Authors: RANGANATHAN ANAND , McGRATH ROBERT E , CAMPBELL ROY H , MICKUNAS M DENNIS
Published: May 2004

Ontologies are entering widespread use in many areas such as knowledge and content management, electronic commerce and the Semantic Web. In this paper we show how the use of ontologies has helped us overcome some important problems in the development of pervasive computing environments. We have integrated ontologies and Semantic Web technology into our pervasive computing infrastructure. Our investigations have shown that Semantic Web technology can be integrated into our CORBA-based infrastructure to augment several important services. This work suggests a number of requirements for future research in the development of ontologies, reasoners, languages and interfaces.
Can “Tax-for-Fee” Reform Reduce Rural Tension in China? The Process, Progress and Limitations
Authors: Yep Ray
Published: May 2004

This article questions the effectiveness and viability of the fiscal response to rural stability adopted by the Chinese state. Tax-for-fee reform (feigaishui) has been heralded as a possible solution to the cancer of excessive fiscal predation by local government. While the experiment may have achieved in relief of peasant burden, the success is simply based on central government financial sponsorship and is thus hardly sustainable as a national programme. And unless there is fundamental reform of fiscal redistribution, the new scheme will ironically hurt rather than help the poorest peasants. Putting all the blame on local cadres is politically expedient, but the central government needs to admit that the present crisis is a result of the systemic discrimination against peasants and the consequent deficit in financing rural governance. The ultimate solution entails a full-scale eradication of structural bias against the peasantry.
The Political Thought of Sun Yat-sen: Development and Impact. By Audrey Wells. [London: Palgrave Macmillan, 2001. 256 pp. £50.00. ISBN 0-333-77787-5.]
Authors: Myers Ramon H.
Published: May 2004

What, another book about Sun Yat-sen? The sceptical reader should not be deterred. He or she will learn much by reading this informative, lucid history of Sun Yat-sen's career, his thinking, and his influence on China as well as on various leaders of developing nations of the last century.

Wells portrays Sun as a rare, humane revolutionary who could have unified China and facilitated China's transition to a peaceful, modern society and state. Such achievements were well in his grasp but the foreign leaders of Sun's time preferred a weak, divided China and ignored his pleas for assistance.

Although Sun was famous in China immediately after his death, Sun's “synthesis of Eastern and Western ideas” attracted few outstanding Chinese leaders to his cause. As Ssu-yu Teng and John K. Fairbank stated in their China's Response to the West: A Documentary Survey, 1839–1923 (p. 276) “the doom of the Kuomintang was sealed from the time when Dr. Sun failed to convince the scholars of Peita that his “Three People's Principles” could give them intellectual leadership.” Why Sun's political thought did not attract a broad segment of the leading elite to agree with his message and follow his revolutionary path is still a puzzle.
Love-Letters and Privacy in Modern China: The Intimate Lives of Lu Xun and Xu Guangping. By Bonnie S. McDougall. [Oxford: Oxford University Press, 2002. 305 pp. $125.00. ISBN 0-19-925679-9.]
Authors: Chou Eva Shan
Published: May 2004

This is an important work from a scholar who has already made wide-ranging contributions to our understanding of modern Chinese literature. With Love-Letters and Privacy in Modern China, Bonnie S. McDougall now adds a valuable study of its most prominent figure, Lu Xun (1881–1936), contributing in particular to the fast-growing scholarship on the private life of this modern icon. Her study focuses on his relationship with Xu Guangping (1898–1968), the student who became his partner, mother of his son, and for three decades after his death, editor and memoirist.

Two wider aims, named in the title, are to examine love letters as a literary genre and privacy as a social variable. Such research performs the task of bringing Chinese data to issues of general concern. The matter is not just a territorial one. As the author says of investigating privacy in modern China, “privacy is a human rights issue: deny a sense of privacy . . . , or claim that it is substantially different, and we deny the people of that culture basic rights of association and communication” (p. 209).
Multilingualism in China: The Politics of Writing Reforms for Minority Languages 1949–2002. By Minglang Zhou. [Berlin and New York: Mouton de Gruyter, 2003. xxiv+458 pp. €94.00. ISBN 3-11-017896-6.]
Authors: Mackerras Colin
Published: May 2004

This book is a detailed examination of reform in the writing of minority languages under the PRC, including the adaptation of languages to scripts never before used to write them. Considering how closely language is related to culture and society, this entails a good deal of treatment of issues such as PRC politics, external influences, such as from the Soviet Union and the West, the impact of modernization and factors like education and religion. Of course, there is quite a bit about China's spoken minority languages as well.

The book is generally well written, though there are places where the language becomes dense and difficult to follow. The source material for the book is four summers of fieldwork in China's minority areas (1997–2000) and a vast amount of printed material. The list of references takes up no less than 40 pages (pp. 407–446). All items are in Chinese or English. The author makes judicious use of this array of material to mould his own viewpoints on specific issues.

My only real problem with this book as a work of scholarship is the lack of clarity in the aims and central argument. The introduction gives extensive historical background on China's ethnic relations and policies, including in the PRC. It also forecasts the topics of the individual chapters, concluding with the author's hope that China's experiences in multilingualism will “facilitate the maintenance and development of minority languages in the world community” (p. 35). The conclusion summarizes answers to some of the crucial questions the book tackles, and again returns to the hope that the Chinese experience will be of use to the world as a whole.
Incoherent scatter Faraday rotation measurements on a radar with single linear polarization
Authors: Shpynev Boris G.
Published: May 2004

This paper outlines an application of the incoherent scatter technique to the Irkutsk (Russia) VHF radar system, which has an antenna with a single, strictly linear polarization. Owing to ionospheric Faraday rotation, determination of wave plane polarization angle is essential to obtain electron density. We describe a new technique for electron density determination on a radar with single polarization based on the radar equation. This technique does not require additional external density calibration using other instruments such as ionosondes.
Reducing the height of a circular array of monopoles using top hats and dielectric coatings
Authors: Janapsatya Januar , Bialkowski Marek E.
Published: May 2004

Using a Radial Guide Field Matching Method, an investigation is performed into reducing the height of an electronically steered circular array of monopole antennas composed of a central active element surrounded by passive elements being either short‐ or open‐circuited. It is shown that a considerable height reduction can be achieved using top hats attached to monopoles ends and by applying dielectric coating underneath the top hats. The trade‐off in achieving height reduction is narrower impedance bandwidth.
Role of local wind circulation in plume monitoring at Mt. Etna volcano (Sicily): Insights from a mesoscale numerical model
Authors: Favalli Massimiliano , Mazzarini Francesco , Pareschi Maria Teresa , Boschi Enzo
Published: May 2004

Mesoscale simulations at Mt. Etna volcano (Sicily, Italy), validated by measurements, highlight the fundamental role played by the local wind field in the dispersion of a gaseous volcanic plume. During the night, downslope surface winds (over‐hill flow and katabatic breezes) force the plume to follow the steep morphology, whereas during the day very frequent NNW synoptic winds crash into the cone and are contrasted by SE strong sea breezes and anabatic winds, with the consequent formation of convective ascendant currents. The local mesoscale wind reconstruction can provide useful improvements in gaseous flux estimation. Far away synoptic wind velocities, often used in these flux evaluations, might be inadequate. We propose a 3D numerical mesoscale wind reconstruction to evaluate plume dynamics (and from it plume flux and potential hazard) throughout all the hours of the day.
Geotail encounter with reconnection diffusion region in the Earth's magnetotail: Evidence of multiple X lines collisionless reconnection?
Authors: Deng X. H. , Matsumoto H. , Kojima H. , Mukai T. , Anderson R. R. , Baumjohann W. , Nakamura R.
Published: May 2004

On 11 December 1994 the Geotail spacecraft encountered an active reconnection diffusion region around the X line in the Earth's magnetotail. Three interesting features were observed. One is quadrupole pattern of the out‐of‐plane By magnetic field component during the passage of magnetic islands and the crossing of the neutral sheet. The second is a direction reversal of the electron beams in the vicinity of the separatrix of the magnetic topology of reconnection. The third is a clear plasma flow reversal. By combining the observations of plasma, magnetic field, particles, and waves, this report may provide evidence of multiple X lines collisionless reconnection in the magnetotail at the microscopic level.
Theory of magnetized Rossby waves in the ionospheric E layer
Authors: Kaladze T. D. , Aburjania G. D. , Kharshiladze O. A. , Horton W. , Kim Y.‐H.
Published: May 2004

For the weakly ionized E layer plasma, a generalized Charney‐Obukhov equation for magnetized Rossby waves is derived. This magnetized Rossby wave is produced by the dynamo electric field and represents the ionospheric generalization of tropospheric Rossby waves in a rotating atmosphere by the spatially inhomogeneous geomagnetic field. The basic characteristics of the wave are given. The modified Rossby velocity and Rossby‐Obukhov radius are introduced. The mechanism of self‐organization into solitary vortical nonlinear structures is examined. The mechanism of a self‐organization of solitary structures is the result of the mutual compensation of wave dispersion and interaction through the scalar and Poisson bracket convective nonlinearities in the nonlinear wave equation. As a result, the solitary structures are anisotropic, containing a circular vortex superimposed on a dipole perturbation. The degree of anisotropy sharply increases when the vortex size approaches the so‐called intermediate geostrophic size.
Cluster observations of finite amplitude Alfvén waves and small‐scale magnetic filaments downstream of a quasi‐perpendicular shock
Authors: Alexandrova O. , Mangeney A. , Maksimovic M. , Lacombe C. , Cornilleau‐Wehrlin N. , Lucek E. A. , Décréau P. M. E. , Bosqued J.‐M. , Travnicek P. , Fazakerley A. N.
Published: May 2004

The Cluster satellites crossed the Earth's bow shock several times on 31 March 2001. For all these crossings the bow shock was supercritical and quasi‐perpendicular. We present here the results of a detailed analysis of the magnetic field fluctuations observed downstream of the shock. We use data from the four Cluster spacecraft to determine the behavior and the geometry of these fluctuations with good accuracy. Shortly after the ramp crossing, we observed a large‐amplitude nonlinear Alfvén wave, propagating along the downstream average magnetic field with a spectrum peaking at two frequencies below the proton and the alpha ion cyclotron frequencies. Farther downstream in the magnetosheath the magnetic field fluctuations took the form of three‐dimensional structures which can be interpreted as cylindrical field‐aligned current tubes. It is the first time that such current tubes have been observed downstream of a quasi‐perpendicular shock, and they are closely associated with a quasi‐monochromatic, finite amplitude Alfvén wave. We suggest that a close relation exists between the nonlinear Alfvén wave and the current tubes as a result of a filamentation instability which is expected to occur at β ≥ 1 and for frequencies comparable to the ion cyclotron frequencies.
Dynamics of ring current ions as obtained from IMAGE HENA and MENA ENA images
Authors: Perez J. D. , Zhang X.‐X. , C:son Brandt P. , Mitchell D. G. , Jahn J.‐M. , Pollock C. J.
Published: May 2004

Ion distributions from three storms in the year 2000 have been obtained from HENA and MENA ENA images at 27–39 keV and 5–12 keV, respectively. The observed motion of the ring current is compared with calculations of expected radial and angular drift speeds made using a combination of the Tsyganenko 89 magnetic field model and the Weimer 2001 electric field model. In one case between 1000 and 1100 UT on 10 June 2000 that had already been reported, the westward drift of the 33 keV ions is as expected. Comparisons with speeds inferred from the motion of peaks in the ion distributions, however, often did not agree with the model predictions. Examination of the predicted paths showed that the ions are expected to experience significant energy changes as they drift so that they quickly move out of the observed energy channel. Thus we are able to conclude that the observed motion is consistent with equatorial electric fields in the inner magnetosphere of a few tenths of a mV/m on 10 June 2000, several mV/m on 12 August 2000, and ≤1 mV/m on 4 October 2000 as predicted. Other interesting observations include (1) the suggestion of a two step injection process during the main phase of the 4 October 2000 storm, (2) the unexplained disappearance of the 33 keV protons when their drift motion brings them to noon in the recovery phase of the 10 June 2000 storm, (3) the apparent subtle changes in the electric potential pattern in the equator early in the 4 October 2000 storm, and (4) the energy dependence of the spatial source of the injected particles in the plasma sheet during the strong storm on 12 August 2000.
Observational constraints on the fracture energy of subduction zone earthquakes
Authors: Venkataraman Anupama , Kanamori Hiroo
Published: May 2004

We relate seismologically observable parameters such as radiated energy, seismic moment, rupture area, and rupture speed to the dynamics of faulting. To achieve this objective, we computed the radiated energy for 23 subduction zone earthquakes recorded between 1992 and 2001; most of these earthquakes have a magnitude Mw > 7.5, but we also included some smaller (Mw ∼ 6.7) well‐studied subduction zone earthquakes and six crustal earthquakes. We compiled static stress drop estimates for these 29 earthquakes from literature and used a slip‐weakening model to determine the radiation efficiency of these earthquakes. We also determined the rupture speed of these earthquakes from literature. From fracture mechanics, fracture energy, and hence radiation efficiency, can be related to the rupture speed. The radiation efficiencies estimated from the partitioning of energy as given by the slip‐weakening model are consistent with the rupture speed estimated for these earthquakes. Most earthquakes have radiation efficiencies between 0.25 and 1 and are hence efficient in generating seismic waves, but tsunami earthquakes and two deep earthquakes, the 1994 Bolivia and the 1999 Russia‐China border earthquakes, have very small radiation efficiencies (<0.25) and hence dissipate a large amount of energy during faulting. We suggest that differences in the radiation efficiencies of different types of earthquakes could be due to fundamental differences in their rupture mechanics. In deep events, the energy is probably dissipated in thermal processes in the fault zone, while it is possible that the morphology of the trench causes large energy dissipation during the rupture process of tsunami earthquakes.
Location and geometry of the Wellington Fault (New Zealand) defined by detailed three‐dimensional georadar data
Authors: Gross Ralf , Green Alan G. , Horstmeyer Heinrich , Begg John H.
Published: May 2004

Earthquakes with surface‐wave magnitudes of 7.3–7.9 are estimated to be associated with the rupture of the Wellington Fault at relatively regular intervals of 500–770 years. The last such earthquake probably happened between AD 1510 and 1660. Along its southern segment, the Wellington Fault passes through Wellington, New Zealand's capital, and the densely populated Hutt Valley. It is considered to be a highly hazardous structure. To map the shallow geometry of the Wellington Fault, we have collected 3‐D ground‐penetrating radar (georadar) data at two sites along the fault in the Hutt Valley. At one site, the first ever georadar fault plane reflections from an active strike‐slip fault are observed. They coincide with conspicuous diffractions generated by abrupt truncations of structures against the fault plane. These georadar data provide the most vivid shallow images of any active fault surveyed to date. At the second site, apparent offsets of lineaments in the sedimentary sections on either side of the fault are consistent with ∼20 m of dextral displacement estimated from the offset of a nearby terrace riser. The dips and minimum depth extents of the primary zones of fault displacement at the two sites are 55–75°SE and ∼20 m and 72–84°SE and ∼12 m, respectively. Although the georadar‐defined zones of faulting are a few meters wide, prominent reflection fabrics suggest that shearing, fracturing, and crushing extend for several tens of meters on either side of the fault.
GPS measurements of current crustal movements along the Dead Sea Fault
Authors: Wdowinski S. , Bock Y. , Baer G. , Prawirodirdjo L. , Bechor N. , Naaman S. , Knafo R. , Forrai Y. , Melzer Y.
Published: May 2004

A network of 11 continuous GPS stations was constructed in Israel between 1996 and 2001 to monitor current crustal movements across the Dead Sea Fault (DSF). Analysis of the GPS measurements with respect to the ITRF2000 Reference Frame yields time series of daily site positions containing both secular and seasonal variations. Horizontal secular variations (station velocities) are evaluated with respect to the main tectonic element in the region, the DSF. We use six velocity vectors west of the DSF to define the ITRF2000 pole of the Sinai sub‐plate, and rotate the velocity field for all stations into the Sinai reference frame (SRF). The velocity vectors reveal that (1) relative station movements are less than 4 mm/yr; (2) the nine stations located west of the DSF show no statistically significant motion with respect to the SRF; and (3) the two stations located in the Golan Heights (KATZ and ELRO) and a station in Damascus, Syria (UDMC) show 1.7–2.8 mm/yr northward motion with respect to Sinai, indicating a left‐lateral motion along the DSF. Using locked‐fault models, we estimate the current slip rate across the DSF as 3.3 ± 0.4 mm/yr. If we exclude the northern sites (ELRO and UDMC), which are located adjacent to the compressional jog of Mount Hermon, our estimate increases to 3.7 ± 0.4 mm/yr. The calculated ITRF2000 Sinai, Eurasia, and Nubia poles and a published pole for Arabia allow us to calculate the current relative plate motion of Sinai‐Arabia and Sinai‐Nubia.
Decomposition of methane hydrates in sand, sandstone, clays, and glass beads
Authors: Uchida Tsutomu , Takeya Satoshi , Chuvilin Evgene M. , Ohmura Ryo , Nagao Jiro , Yakushev Vladimir S. , Istomin Vladimir A. , Minagawa Hideki , Ebinuma Takao , Narita Hideo
Published: May 2004

Decomposition conditions of methane hydrates in sediments were measured during formation‐decomposition cycles. As test sediments, we used silica sand, sandstone, and clays (kaoline and bentonite), which are typical natural materials known as hydrate bearing sediments, and the range of samples cover a range of water saturating abilities. To better understand the results, we also used uniformly sized glass beads. Pore effects on decomposition of these materials were investigated by analyzing the pore‐space distributions of the materials and by varying the initial water content of the samples. The results obtained for sand and sandstone samples indicated that the final decomposition temperatures were shifted lower than those for bulk hydrates at the same pressure. Temperature shifts were more negative for smaller initial water contents with the maximum shift being approximately −0.5 K. The results were consistent with those measured for glass beads with nearly the same particle size. For kaoline clays, the shift was at most −1.5 K. We conclude that the decomposition conditions are mainly affected by the pore sizes. The surface textures and mineral components had less influence on the results. We confirmed that glass beads mimic the effect of sediments for sand, sandstone, and kaoline clays, which have little to no swelling when put in contact with water. On the other hand, for bentonite particles, the results indicated that methane hydrates formed not only between the particles but also in the interlayers. A thermodynamic promoting effect was found for dilute bentonite solutions, although the positive decomposition‐temperature shift was at most +0.5 K.
Asymptotic solution of static displacements caused by dislocations in a spherically symmetric Earth
Authors: Sun Wenke
Published: May 2004

This study presents an asymptotic solution of static displacements excited by a point dislocation in a spherical symmetric Earth model as an approximation of the dislocation theory for a spherical Earth model [Sun et al., 1996]. The solution is mathematically simple and physically reasonable since it reflects Earth sphericity and radial structure. Comparison of the asymptotic results with both the exact results and the corresponding flat Earth results shows that for any distance the exact results are approximated better by the asymptotic results than by the flat Earth results. For a homogeneous sphere, both theoretical and numerical investigations indicate that the solution is valid for all types of seismic sources and for an epicentral distance of at least 20° with a relative error less than 1% compared to results calculated for a spherical Earth model [Sun et al., 1996]. For a vertical strike‐slip source, the asymptotic solution is valid for the entire Earth surface. For the 1066A Earth model, it is found that the asymptotic solutions are sensitive to the vertical derivatives of model parameters. The sensitivity can be used to study the vertical structure of the Earth. It is also found that the sphericity effect can be well reflected in the asymptotic solution, and can reach 20% discrepancy in the near field for a deep source. Owing to its mathematical simplicity, this solution can be applied easily to calculate coseismic displacement, just as the theory for a half‐space Earth model like Okada's [1985].
Shock‐compressed MgSiO3 glass, enstatite, olivine, and quartz: Optical emission, temperatures, and melting
Authors: Luo Sheng‐Nian , Akins Joseph A. , Ahrens Thomas J. , Asimow Paul D.
Published: May 2004

Optical emission of MgSiO3 glass, enstatite, olivine, and quartz under shock wave compression was investigated with optical pyrometry at discrete wavelengths ranging from visible to near infrared. We develop a new analysis of optical emission that does not require a gray body assumption. Instead, at each wavelength, the optical linear absorption coefficients (a) and blackbody spectral radiances (Lλb) of shocked and unshocked materials were obtained by nonlinear fitting to the time‐resolved radiance from the target assembly. The absorption spectra of unshocked samples corresponding to the measured values of a reproduce those from independent static optical spectroscopic measurements. The measured values of a (ranging from 7 to 56 mm−1) for shocked samples indicate that shock‐induced high‐pressure phases (including melt) can be regarded essentially as black bodies in the optical range investigated, although starting phases such as enstatite and olivine have band‐like spectra at ambient conditions. The effect of emission from the air gap at the driver sample interface on the recorded radiance can be resolved, but a and Lλb cannot be separated for this component of the signal. The shock velocity‐particle velocity relationships of these silicates derived from radiance history are in accord with previous investigations using independent techniques. Given the limited amount of shock wave data, possible high‐pressure melting curves of Mg‐perovskite and its assemblage with periclase are deduced; their melting temperatures near the core‐mantle boundary (CMB) being 6000 ± 500 K and 4000 ± 300 K, respectively. It is proposed that Mg‐perovskite melts with density increase at the CMB pressure.
Efficient analysis of electromagnetic scattering and radiation from patches on finite, arbitrarily curved, grounded substrates
Authors: Yuan Ning , Yeo Tat Soon , Nie Xiao Chun , Li Le Wei , Gan Yeow Beng
Published: May 2004

A precorrected‐fast Fourier transform (FFT) accelerated surface integral equation approach formulated using the homogeneous medium Green's function is presented for the analysis of patch arrays on finite, arbitrarily shaped, grounded substrate. The integral equation is solved by the method of moments, and the precorrected‐FFT method is applied to reduce the memory requirement and computational complexity of the solution procedure. The memory required for this algorithm is O(N1.5), and the computational complexity is NiterN1.5log N, where N is the number of unknowns and Niter is the iteration number. Numerical results are presented to demonstrate the accuracy and capability of the method.
On the detection of summertime terrestrial photosynthetic variability from its atmospheric signature
Authors: Bonfils Céline , Fung Inez , Doney Scott , John Jasmin
Published: May 2004

We identify the climatic signatures of the summertime terrestrial photosynthesis variability using a long simulation of pre‐industrial climate performed with the NCAR coupled global climate‐carbon model. Since plant physiology controls simultaneously CO2 uptake and surface fluxes of water, changes in photosynthesis are accompanied by changes in numerous climate variables: daily maximum temperature, diurnal temperature range, Bowen ratio, canopy temperature and tropospheric lapse rate. Results show that these climate variables may be used as powerful proxies for photosynthesis activity for subtropical vegetation and for tropical vegetation when photosynthetic variability may be limited by water availability.
Monitoring change in volcanic interiors using coda wave interferometry: Application to Arenal Volcano, Costa Rica
Authors: Snieder Roel , Hagerty Mike
Published: May 2004

Multiply scattered waves are a new tool for monitoring changes in the earth's subsurface. In this study we use the air pressure and displacement recorded at the Arenal Volcano to detect temporal changes. The pressure pulses emitted by the volcano are associated with a complex displacement signal of overlapping coda waves. By deconvolving the ground motion with the air pressure for different time intervals we obtain a highly repeatable displacement signal that has the character of diffusive wave propagation. This deconvolved displacement signal changes with the time interval analyzed in the employed data. This change can be explained by a shift in the point of excitation of the elastic waves over a distance of about 15 meters.
In‐situ measurements of velocity structure within turbidity currents
Authors: Xu J. P. , Noble M. A. , Rosenfeld L. K.
Published: May 2004

Turbidity currents are thought to be the main mechanism to move ∼500,000 m3 of sediments annually from the head of the Monterey Submarine Canyon to the deep‐sea fan. Indirect evidence has shown frequent occurrences of such turbidity currents in the canyon, but the dynamic properties of the turbidity currents such as maximum speed, duration, and dimensions are still unknown. Here we present the first‐ever in‐situ measurements of velocity profiles of four turbidity currents whose maximum along‐canyon velocity reached 190 cm/s. Two turbidity currents coincided with storms that produced the highest swells and the biggest stream flows during the year‐long deployment.
Towards European Procedural Primacy in National Legal Systems
Authors: Delicostopoulos John S.
Published: May 2004

Abstract: In the polycentric judicial architecture of the Community, there is a rich, constant interplay between national procedural rules and European interventions. In the making of the European legal order, EC law depends on national procedural law and therefore, substantive EC supremacy depends, existentially, on procedure. In this context, the author argues that the traditional sharply defined dichotomy of national procedural autonomy versus Community law effectiveness no longer reflects the implicit course of action laid down by the Court of Justice. Instead, the European legal order has moved, as a praxis, from national procedural autonomy to a more subtle combination of national procedural competence and European procedural primacy. The rationale behind this trend testifies both to the importance of the interrelationship between procedure and substantive law in the making of Europe and to the flexibility of procedural law; EC law depends on procedural law and procedure readily submits to the demands of a new legal order. In doing so, it also creates new choices and venues for European supremacy.
Ions in water: The microscopic structure of concentrated NaOH solutions
Authors: Botti A. , Bruni F. , Imberti S. , Ricci M. A. , Soper A. K.
Published: May 2004

A neutron diffraction experiment with isotopic H/D substitution on four concentrated NaOH/H2O solutions is presented. The full set of partial structure factors is extracted, by combining the diffraction data with a Monte Carlo simulation. These allow to investigate both the changes of the water structure in the presence of ions and their solvation shells. It is found that the interaction with the solute affects the tetrahedral network of hydrogen bonded water molecules in a manner similar to the application of high pressure to pure water. The solvation shell of the OH− ions has an almost concentration independent structure, although with concentration dependent coordination numbers. The hydrogen site coordinates a water molecule through a weak bond, while the oxygen site forms strong hydrogen bonds with a number of molecules that is on the average very close to four at the higher water concentrations and decreases to about three at the lowest one. The competition between hydrogen bond interaction and Coulomb forces in determining the orientation of water molecules within the cation solvation shell is visible in the behavior of the gNaHw(r) function.
Prototype reflectivity analyses of hydrogen storage levels in single-walled carbon nanotubes
Authors: Tran Nick E. , Lambrakos S. G. , Moore P. G. , Ashraf Imam M. , Dulcey C. S.
Published: May 2004

A prototype case study is presented that examines the level of hydrogen content in H-SWNTs using the Surface Plasmon Resonance technique. The damping effect and the angular shift in the resonance minimum of an SWNT–gold interface due to the presence of hydrogen is analyzed using a parametric model, which is based on the concept of an effective permittivity. The new approach provides for a non-invasive analysis of the level of hydrogen content in H-SWNTs and is potentially extendable to other carbon-based hydrogen storage materials.
A theoretical study of the fine and hyperfine interactions in the NCO and CNO radicals
Authors: Prasad Rajendra
Published: May 2004

The geometries, the harmonic vibrational frequencies, and the Renner–Teller parameter have been reported for the NCO+(X̃ 3Σ−), NCO(X̃ 2Π,Ã 2Σ+,B̃ 2Π,2 2Σ+), NCO−(X̃ 1Σ+), CNO+(X̃), CNO(X̃ 2Π,Ã 2Σ+,B̃ 2Π,2 2Σ+), and CNO−(X̃ 1Σ+) systems at the full valence–complete active space self-consistent-field (fv–CASSCF) level of theory. The Π2 electronic states of the NCO and CNO radicals have two distinct real vibrational frequencies for the bending modes and these states are subject to the type A Renner–Teller effect. The total energy of CNO+ without zero point energy correction of the linear geometry is ∼31 cm−1 higher than the bent geometry at the fv–CASSCF level and the inversion barrier vanishes after the zero point energy correction; therefore, the ground state of the CNO+ may possess a quasilinear geometry. The spin–orbit coupling constants estimated using atomic mean field Hamiltonian at the fv–CASSCF level of theory are in better agreement with the experimental values. The excitation energies, the electron affinity, and the ionization potential have been computed at the complete active space second order perturbation theory (CASPT2) and the multireference singles and doubles configuration (MRSD–CI) levels of theory. The computed values of the electric hyperfine coupling constants for the N14 atom in the ground state of the NCO radical agree well with the experimental data. The magnetic hyperfine coupling constants (HFCC’s) have been estimated employing the configuration selected MRSD–CI and the multireference singles configuration interaction (MRS–CI) methods using iterative natural orbitals (ino) as one particle basis. Sufficiently accurate value of the isotropic contribution to the HFCC’s can be obtained using an MRS–CI–ino procedure.
Decomposition of nuclear magnetic resonance spin–spin coupling constants into active and passive orbital contributions
Authors: Gräfenstein Jürgen , Tuttle Tell , Cremer Dieter
Published: May 2004

The theory of the J–OC–PSP (decomposition of J into orbital contributions using orbital currents and partial spin polarization) method is derived to distinguish between the role of active, passive, and frozen orbitals on the nuclear magnetic resonance (NMR) spin–spin coupling mechanism. Application of J–OC–PSP to the NMR spin–spin coupling constants of ethylene, which are calculated using coupled perturbed density functional theory in connection with the B3LYP hybrid functional and a [7s,6p,2d/4s,2p] basis set, reveal that the well-known π mechanism for Fermi contact (FC) spin coupling is based on passive π orbital contributions. The π orbitals contribute to the spin polarization of the σ orbitals at the coupling nuclei by mediating spin information between σ orbitals (spin-transport mechanism) or by increasing the spin information of a σ orbital by an echo effect. The calculated FC(π) value of the SSCC J(CC)1 of ethylene is 4.5 Hz and by this clearly smaller than previously assumed.
Intra- and intermolecular energy transfer in highly excited ozone complexes
Authors: Ivanov Mikhail V. , Grebenshchikov Sergy Yu. , Schinke Reinhard
Published: May 2004

The energy transfer of highly excited ozone molecules is investigated by means of classical trajectories. Both intramolecular energy redistribution and the intermolecular energy transfer in collisions with argon atoms are considered. The sign and magnitude of the intramolecular energy flow between the vibrational and the rotational degrees of freedom crucially depend on the projection Ka of the total angular momentum of ozone on the body-fixed a axis. The intermolecular energy transfer in single collisions between O3 and Ar is dominated by transfer of the rotational energy. In accordance with previous theoretical predictions, the direct vibrational de-excitation is exceedingly small. Vibration–rotation relaxation in multiple Ar+O3 collisions is also studied. It is found that the relaxation proceeds in two clearly distinguishable steps: (1) During the time between collisions, the vibrational degrees of freedom are “cooled” by transfer of energy to rotation; even at low pressure equilibration of the internal energy is slow compared to the time between collisions. (2) In collisions, mainly the rotational modes are “cool” by energy transfer to argon.
Jahn–Teller effect in van der Waals complexes; Ar–C6H6+ and Ar–C6D6+
Authors: van der Avoird Ad , Lotrich Victor F.
Published: May 2004

The two asymptotically degenerate potential energy surfaces of argon interacting with the X̃ 2E1g ground state benzene+ cation were calculated ab initio from the interaction energy of the neutral Ar–benzene complex given by Koch et al. [J. Chem. Phys. 111, 198 (1999)] and the difference of the geometry-dependent ionization energies of the complex and the benzene monomer computed by the outer valence Green’s function method. Coinciding minima in the two potential surfaces of the ionic complex occur for Ar on the C6v symmetry axis of benzene+ (the z axis) at ze=3.506 Å. The binding energy De of 520 cm−1 is only 34% larger than the value for the neutral Ar–benzene complex. The higher one of the two surfaces is similar in shape to the neutral Ar–benzene potential, the lower potential is much flatter in the (x,y) bend direction. Nonadiabatic (Jahn–Teller) coupling was taken into account by transformation of the two adiabatic potentials to a two-by-two matrix of diabatic potentials. This transformation is based on the assumption that the adiabatic states of the Ar–benzene+ complex geometrically follow the Ar atom. Ab initio calculations of the nonadiabatic coupling matrix element between the adiabatic states with the two-state-averaged CAS-SCF(5,6) method confirmed the validity of this assumption. The bound vibronic states of both Ar–C6H6+ and Ar–C6D6+ were computed with this two-state diabatic model in a basis of three-dimensional harmonic oscillator functions for the van der Waals modes. The binding energy D0=480 cm−1 of the perdeuterated complex agrees well with the experimental upper bound of 485 cm−1. The ground and excited vibronic levels and wave functions were used, with a simple model dipole function, to generate a theoretical far-infrared spectrum. Strong absorption lines were found at 10.1 cm−1 (bend) and 47.9 cm−1 (stretch) that agree well with measurements. The unusually low bend frequency is related to the flatness of the lower adiabatic potential in the (x,y) direction. The van der Waals bend mode of e1 symmetry is quadratically Jahn–Teller active and shows a large splitting, with vibronic levels of A1, E2, and A2 symmetry at 1.3, 10.1, and 50.2 cm−1. The level at 1.3 cm−1 leads to a strong absorption line as well, which could not be measured because it is too close to the monomer line. The level at 50.2 cm−1 gives rise to weaker absorption. Several other weak lines in the frequency range of 10 to 60 cm−1 were found.