bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Optical Imaging Reveals the Dependence of Particle Geometry on Interactions Between CdSe Quantum Dots and Immune Cells
Authors: Aaron Jesse S. , Greene Adrienne C. , Kotula Paul G. , Bachand George D. , Timlin Jerilyn A.
Published: December 2010

The biocompatibility and possible toxicological consequences of engineered nanomaterials, including quantum dots (QDs) due to their unique suitability for biomedical applications, remain intense areas of interest. We utilized advanced imaging approaches to characterize the interactions of CdSe QDs of various sizes and shapes with live immune cells. Particle diffusion and partitioning within the plasma membrane, cellular uptake kinetics, and sorting of particles into lysosomes were all independantly characterized. Using high‐speed total internal reflectance fluorescence (TIRF) microscopy, we show that QDs with an average aspect ratio of 2.0 (i.e., rod‐shaped) diffuse nearly an order of magnitude slower in the plasma membrane than more spherical particles with aspect ratios of 1.2 and 1.6, respectively. Moreover, more rod‐shaped QDs were shown to be internalized into the cell 2‐3 fold more slowly. Hyperspectral confocal fluorescence microscopy demonstrates that QDs tend to partition within the cell membrane into regions containing a single particle type. Furthermore, data examining QD sorting mechanisms indicate that endocytosis and lysosomal sorting increases with particle size. Together, these observations suggest that both size and aspect ratio of a nanoparticle are important characteristics that significantly impact interactions with the plasma membrane, uptake into the cell, and localization within intracellular vesicles. Thus, rather than simply characterizing nanoparticle uptake into cells, we show that utilization of advanced imaging approaches permits a more nuanced and complete examination of the multiple aspects of cell‐nanoparticle interactions that can ultimately aid understanding possible mechanisms of toxicity, resulting in safer nanomaterial designs.
Coloring, a versatile technique for implementing object‐oriented languages
Authors: Ducournau Roland
Published: December 2010

Late binding and subtyping create run‐time overhead for object‐oriented languages. Dynamic typing and multiple inheritance create even more overhead. Static typing and single inheritance lead to two major invariants, of reference and position, that make the implementation as efficient as possible. Coloring is a technique that preserves these invariants for dynamic typing or multiple inheritance at minimal spatial cost. Coloring has been independently proposed for method invocation under the name ofselector coloring, for subtype tests under the name ofpack encoding, and for attribute access and object layout. This paper reviews a number of uses of coloring for optimizing object‐oriented programming, generalizes them, and specifies several variations, such as bidirectional andn‐directional coloring. Coloring is NP‐hard, hence compilers that use it depend on heuristics. The paper describes two families of heuristics and presents some experimental results which indicate that coloring is both efficient and tractable and that bidirectional coloring gives the best results. Copyright © 2010 John Wiley & Sons, Ltd.
Using meta‐modeling in design and implementation of component‐based systems: the SOFA case study
Authors: Hnětynka Petr , Plášil František
Published: December 2010

To allow efficient and user‐friendly development of a component‐based application, component systems have to provide a rather complex development infrastructure, including a tool for component composition, component repository, and a run‐time infrastructure. In this paper, we present and evaluate benefits of using meta‐modeling during the process of defining a component system and also during creation of the development and run‐time infrastructures. Most of the presented arguments are based on a broad practical experience with designing the component systems SOFA and SOFA 2; the former designed in a classical ad hoc ‘manual’ way, whereas the latter with the help of meta‐modeling. Copyright © 2010 John Wiley & Sons, Ltd.
A group‐oriented secure multiagent platform
Authors: Such Jose M. , Alberola Juan M. , Espinosa Agustin , Garcia‐Fornes Ana
Published: December 2010

Security is becoming a major concern in multiagent systems, since an agent's incorrect or inappropriate behaviour may cause non‐desired effects, such as money and data loss. Some multiagent platforms (MAP) are now providing baseline security features, such as authentication, authorization, integrity and confidentiality. However, they fail to support other features related to the sociability skills of agents such as agent groups. What is more, none of the listed MAPs provide a mechanism for preserving the privacy of the users (regarding their identities) that run their agents on such MAPs. In this paper, we present the security infrastructure (SI) of the Magentix MAP, which supports agent groups and preserves user identity privacy. The SI is based on identities that are assigned to all the different entities found in Magentix (users, agents and agent groups). We also provide an evaluation of the SI describing an example application built on top of Magentix and a performance evaluation of it. Copyright © 2010 John Wiley & Sons, Ltd.
Mitochondrial Function Controls Proliferation and Early Differentiation Potential of Embryonic Stem Cells
Authors: Mandal Sudip , Lindgren Anne G. , Srivastava Anand S. , Clark Amander T. , Banerjee Utpal
Published: December 2010

Pluripotent stem cells hold significant promise in regenerative medicine due to their unlimited capacity for self-renewal and potential to differentiate into any cell type of the body. In this study, we demonstrate that proper mitochondrial function is essential for proliferation of undifferentiated ESCs. Attenuating mitochondrial function under self-renewing conditions makes these cells more glycolytic-dependent, and it is associated with an increase in the mRNA reserves of Nanog, Oct4, and Sox2. In contrast, attenuating mitochondrial function during the first 7 days of differentiation results in normal repression of Oct4, Nanog, and Sox2. However, differentiation potential is compromised as revealed by abnormal transcription of multiple Hox genes. Furthermore, under differentiating conditions in which mitochondrial function is attenuated, tumorigenic cells continue to persist. Our results, therefore establish the importance of normal mitochondrial function in ESC proliferation, regulating differentiation, and preventing the emergence of tumorigenic cells during the process of differentiation.
Combining trust with location information for routing in wireless sensor networks
Authors: Leligou H. C. , Trakadas P. , Maniatis S. , Karkazis P. , Zahariadis T.
Published: December 2010

As the applications of wireless sensor networks proliferate, the efficiency in supporting large sensor networks and offering security guarantees becomes an important requirement in the design of the relevant networking protocols. Geographical routing has been proven to efficiently cope with large network dimensions while trust management schemes have been shown to assist in defending against routing attacks. Once trust information is available for all network nodes, the routing decisions can take it into account, i.e. routing can be based on both location and trust attributes. In this paper, we investigate different ways to incorporate trust in location‐based routing schemes and we propose a novel way of balancing trust and location information. Computer simulations show that the proposed routing rule exhibits excellent performance in terms of delivery ratio, latency time and path optimality. Copyright © 2010 John Wiley & Sons, Ltd.
On centralized schedulers for 802.11e WLANs distributionversusgrouping of resources allocation
Authors: Mur Daniel Camps , Pérez‐Costa Xavier , Marchenko Vladimir , Ribes Sebastià Sallent
Published: December 2010

Wireless LAN is becoming a pervasive wireless access technology that can be found in almost any mobile device such as laptops, PDAs, portable game consoles and mobile phones. Each of these groups of devices have a different set of requirements according to their intended use and applications but most of them share two main requirements: QoS support to satisfy applications' demands and power saving functionality to achieve an operating time according to users' expectations. IEEE 802.11e defines two centralized solutions in order to address these problems: Hybrid Coordination Channel Access (HCCA) for QoS and Scheduled Automatic Power Save Delivery (S‐APSD) for power saving. The focus of our work in this paper is the analysis and evaluation of a proposed centralized scheduler that makes use of both aforementioned IEEE 802.11e QoS and power saving solutions. Our contributions are as follows: (i) Design and analytical modeling of a proposed centralized scheduler (DRA) that maximizes the minimum distance between the resource allocations with pseudo‐polynomial complexity, (ii) Extensive performance evaluation of the QoS and power saving benefits of theDistributionproposal (DRA) as compared to a genericGroupingone (GRA), and (iii) Evaluation of the complexity and scalability of the proposal to assess its feasibility in practice. Copyright © 2010 John Wiley & Sons, Ltd.
Power efficient scheduling over fading channel for cross‐layer optimization
Authors: Bai Xiaofeng , Shami Abdallah , Primak Serguei
Published: December 2010

We consider the minimization of long‐term average power consumption for packet transmission between a mobile station and the base station over Nakagami‐m fading channel. Power consumption is minimized by intelligent transmission scheduling design, with the average queuing delay and joint packet loss across MAC and physical layers being confined below certain levels. The problem is formulated as an infinite horizon constrained Markov decision problem and solved by linear programming (LP) method. The primary intention of this paper is to provide a visible paradigm on using LP method to optimize the performance of mobile wireless communication systems. We elaborate the detailed mathematical solution with consistent simulation experiments and emphasize the effectiveness of adaptive transmission scheduling for cross‐layer QoS provisioning. Copyright © 2010 John Wiley & Sons, Ltd.
Adaptive paging schemes for group calls in mobile broadband cellular systems
Authors: Gállego José Ramón , Canales María , Hernández‐Solana Ángela , Valdovinos Antonio
Published: December 2010

In this paper, we analyze the problem of efficient paging for group call searches under realistic mobility patterns. Taking as a basis a location update scheme, based on the definition of an adaptive macro‐location area, adapted to the mobility pattern of the terminals, we characterize the residence probabilities in each location area of a generic macro‐area. With this information, we propose and evaluate different sequential group paging strategies, also taking into account their computational cost. Results show the suitability of some of the proposals (semiadaptive and hybrid schemes) and its applicability to new packet‐based broadband cellular systems. Copyright © 2010 John Wiley & Sons, Ltd.
Interference mitigation in WSN by means of directional antennas and duty cycle control
Authors: Staniec Kamil , Debita Grzegorz
Published: December 2010

Network spanning algorithms, such as ZigBee‐native and Stojmenovič, constitute a crucial element in the wireless sensor network design, by determining its potential for reliability and fault‐tolerance. The interconnections between nodes have a great impact on the radio interference level present in such a network and may create a serious electromagnetic compatibility issue in some cases. It can be proved that the total interference incurred by a statistical node can be diminished in two ways: either by using directional antennas or by setting an upper limit on the duty cycle of each network node. Copyright © 2010 John Wiley & Sons, Ltd.
Extraction of airfoil data using PIV and pressure measurements
Authors: Yang Hua , Shen Wen Zhong , Sørensen Jens Nørkær , Zhu Wei Jun
Published: December 2010

A newly developed technique for determining the angle of attack (AOA) on a rotating blade is used to extract AOAs and airfoil data from measurements obtained during the MEXICO (Model rotor EXperiments in COntrolled conditions) rotor experiment. Detailed surface pressure and Particle Image Velocimetry (PIV) flow fields at different rotor azimuth positions are examined for determining sectional airfoil data. The AOA is derived locally by determining the local circulation on the blade from pressure data and subtracting the induction of the bound circulation from the local velocity. The derived airfoil data are compared to 2D data from wind tunnel experiments and XFOIL computations. The comparison suggests that the rotor is subject to severe 3D effects originating from the geometry of the rotor, and explains why the Blade Element Momentum technique with 2D airfoil data over‐predicts the loading of the rotor. The extraction technique is verified by employing the derived airfoil characteristics as input to computations using the BEM technique and comparing the calculated axial and tangential forces to the measured data. The comparison also demonstrates that the used technique of determining the AOA is a reliable tool to extract airfoil data from experimental data. Copyright © 2010 John Wiley & Sons, Ltd.
Crystal Engineering with Oxo‐ and Cyanocarbon Anions: Synthesis and Structural Characterization of Triorganotin(IV) Pentacyanopropenides and Hexacyanoazapentadienides
Authors: Asrial   , Olbrich Falk , Spoida Marlies , Fischer Axel , Edelmann Frank T.
Published: December 2010

The first triorganotin(IV) pentacyanopropenides, [R3Sn(H2O)2][C3(CN)5] (R = Me (2), nBu (3), Ph (4) were prepared by treatment of Ag[C3(CN)5] (1) with equimolar amounts of R3SnCl in reagent grade THF. In a similar manner, dark red [R3Sn(H2O)2][N{C(CN)C(CN)2}2] (6) containing the hexacyanoazapentadienyl anion was prepared in 55 % yield. The molecular structure of [Ph3Sn(H2O)2][C3(CN)5] (4) was determined by X‐ray diffraction. The crystal structure consists of separated trigonal‐bipyramidal [Ph3Sn(H2O)2]+ cations and nearly planar [C3(CN)5]– anions which are linked through O–H···N hydrogen bonds to give a three‐dimensional network.
Regular [Tl6]6– Cluster in Cs4Tl2O Exhibiting Closed‐Shell Configuration and Energetic Stabilization due to Relativistic Spin–Orbit Coupling
Authors: Saltykov Vyacheslav , Nuss Jürgen , Wedig Ulrich , Jansen Martin
Published: December 2010

Cs4Tl2O was synthesized by reaction of the binary compounds CsTl and Cs2O at 573 K, followed by slow cooling to room temperature. According to single‐crystal X‐ray analysis, the title compound crystallizes in a new structure type (trigonal, space group R$\bar{3}$m (no. 166), a = 11.986(1), c = 20.370(2) Å, Z = 9). It consists of isolated [Tl6]6– octahedra, being regular with respect to the equality of all three main diagonals (4.546(5) Å), and of [Cs12O3]6+ triple octahedra extending along the c direction.The electronic structure of Cs4Tl2O was examined by relativistic density functional calculations including spin–orbit coupling and compared to the one of Rb10Tl6O2, which exhibits a highly distorted [Tl6]6– octahedra. In the latter case the closed‐shell electronic structure is the result of a Jahn–Teller distortion. In contrast, the regular one in Cs4Tl2O corresponds to a closed‐shell configuration, in accordance with diamagnetic properties, only if spin–orbit coupling is considered.
Is it Possible to Train Surgeons for Rural Africa? A Report of a Successful International Program
Authors: Pollock Jonathan D. , Love Timothy P. , Steffes Bruce C. , Thompson David C. , Mellinger John , Haisch Carl
Published: December 2010

Background

The critical shortage of surgeons and access to surgical care in Africa is increasingly being recognized as a global health crisis. Across Africa, there is only one surgeon for every 250,000 people and only one for every 2.5 million of those living in rural areas. Surgical diseases are responsible for approximately 11.2% of the total global burden of disease. Even as the importance of treating surgical disease is being recognized, surgeons in sub‐Saharan Africa are leaving rural areas and their countries altogether to practice in more desirable locations.

Methods

The Pan‐African Academy of Christian Surgeons (PAACS) was formed in 1997 as a strategic response to this profound need for surgical manpower. It is training surgical residents through a 5‐year American competency‐based model. Trainees are required to be of African origin and a graduate of a recognized medical school.

Results

To date, PAACS has established six training programs in four countries. During the 2009–2010 academic year, there were 35 residents in training. A total of 18 general surgeons and one pediatric surgeon have been trained. Two more general surgeons are scheduled to finish training in 2011. Four graduates have gone on to subspecialty training, and the remaining graduates are practicing general surgery in rural and underserved urban centers in Angola, Guinea‐Conakry, Ghana, Cameroon, Republic of Congo, Kenya, Ethiopia, and Madagascar.

Conclusions

The PAACS has provided rigorous training for 18 African general surgeons, one of whom has also completed pediatric surgery training. To our knowledge, this is the only international rural‐based surgical training program in Africa.
Diagnostic hysteroscopy and saline infusion sonography in the diagnosis of intrauterine abnormalities: an assessment of patient preference
Authors: van Dongen Heleen , Timmermans Anne , Jacobi Cathrien E. , Elskamp Trudy , de Kroon Cor D. , Jansen Frank Willem
Published: December 2010

This study was conducted to assess whether women would prefer to undergo saline infusion sonography (SIS) or office hysteroscopy for the investigation of the uterine cavity. In a randomised controlled trial, 100 patients underwent SIS or office hysteroscopy for assessing patients' pain scores. After the investigation, 92 of them were asked to fill out an anonymous questionnaire addressing their preference regarding the method of evaluation and treatment of the uterine cavity. A control group, consisting of 50 women who never underwent SIS or office hysteroscopy, was also asked to complete an identical questionnaire. The questionnaire was completed by 113 women (83.7%). Twenty-four (21.2%) women would opt for SIS, whereas 52 (46.0%) would opt for office hysteroscopy, and 37 (32.7%) had no preference. If therapy would be necessary, 48.7% of the women would opt for an outpatient treatment, whereas 33.0% of the women would prefer treatment under general anaesthesia. Despite the fact that SIS is less painful, the majority of the women prefer office hysteroscopy. Additionally, therapy in an outpatient setting is preferred to a day case setting.
Stability of Rice Bran Oil in Terms of Oryzanol, Tocopherols, Tocotrienols and Sterols
Authors: Afinisha Deepam L. S. , Sundaresan A. , Arumughan C.
Published: December 2010

The effect of oryzanol, tocopherols and tocotrienols (tocols) and sterols individually and as combinations of two were analyzed for DPPH radical scavenging activity and antioxidant activity. Oryzanol, tocols and sterols were isolated by using column chromatography and then added at known concentrations in stripped RBO. The results showed that tocol added samples are more stable than with oryzanol and sterol as individual additions. Among them T1 (sample having 0.04% tocols) is more stable than T2 (sample having 0.08% tocols). Comparing T1 and T2 with control oil, T1 had a peroxide value almost similar to control oil (T1, 5.68 mequiv/kg : control oil, 5.52 mequiv/kg) showing the antioxidant activity of tocols even in the absence of other micronutrients. The diene value of both T1 (4.27) and T2 (4.03) is lower than control oil (6.14). While analyzing combinations, prevention of oxidation was significantly better for oryzanol and tocols combinations, OT1 had a peroxide value of 10.57 mequiv/kg, OT2, 10.42 mequiv/kg when compared to the control sample (52.25 mequiv/kg). Similarly the diene value 5.86 (OT1) and 7.1 (OT2), the p‐anisidine value 53.8 and 63 for OT1 and OT2, respectively. The DPPH activity of samples T2 (0.08% tocols) and OT2 (sample having 0.8% oryzanol + 0.08% tocols) had a lower IC50 on the initial day and the IC50 was lowest for T1 (0.04% tocols) and OT1 (sample having 1.6% oryzanol + 0.04% tocols) on the final day.
Minimum loss multiplicative routing metrics for wireless mesh networks
Authors: Passos Diego , de Albuquerque Célio Vinicius N. , Campista Miguel Elias M. , Costa Luís Henrique M. K. , Duarte Otto Carlos M. B.
Published: December 2010

Wireless mesh networks are low-cost self-configurable multihop networks. This work presents a study about the main routing metrics used in this kind of network, pointing out their virtues and limitations. It also proposes, implements, and analyzes alternative multiplicative metrics. To evaluate the performance of the proposed metrics, comparative measurements over real mesh testbeds were conducted. A case study of a production mesh network using a multiplicative routing metric is also evaluated. Results show that, in various scenarios, the network performance with the proposed multiplicative routing metrics has been improved in terms of routing stability, packet loss rate, end-to-end delay, and throughput.
Storage alters feline bronchoalveolar lavage fluid cytological analysis
Authors: Nafe Laura A. , DeClue Amy E. , Reinero Carol R.
Published: December 2010

Bronchoalveolar lavage fluid (BALF) collection is a valuable respiratory diagnostic procedure in cats. This study evaluated effects of BALF storage on total nucleated cell counts (TNCCs) and differential cell counts (DCC), cell morphology, and cytological diagnosis. Forty-five research cats with neutrophilic, eosinophilic, and mixed inflammation, and healthy controls were enrolled. BALF samples were processed within 1 h (baseline) or stored at 4°C (4C24) or room temperature (RT24) for 24 h, or 4°C (4C48) or room temperature (RT48) for 48 h before processing. Stored BALF at RT48 had decreased TNCC compared to baseline. The RT24 and RT48 samples had greater eosinophil % and the RT24, 4C48, and RT48 samples had decreased neutrophil % compared with baseline. Cellular morphology deteriorated in all stored samples. Storage resulted in a change in cytological diagnosis in up to 57% of stored samples. We conclude that cytological analysis of BALF in cats should be performed promptly for optimal results.
Nasaler Heroinkonsum in Österreich
Authors: Busch Martin , Eggerth Alexander
Published: December 2010

Ziel: Einschätzung der Bedeutung des nasalen Heroinkonsums in Österreich. Methodik: Analyse der Daten aus dem nationalen Dokumentationssystems der Klientinnen und Klienten der Drogenhilfe des Klientenjahrganges 2007 mit Leitdroge Heroin (N = 2.211) mit dem Fokus auf die Variablen «vorwiegende Einnahmeform», «injizierende Applikation» und Einstiegsalter in den Heroinkonsum bzw. in die injizierende Applikation. Ergebnisse: Nasaler Heroinkonsum stellt bei jungen Klientinnen und Klienten der Drogenhilfe die häufigste Applikationsform von Heroin dar. Ein nicht unerheblicher Teil der Personen mit Leitdroge Heroin steigt im Laufe der Drogenkarriere vom nasalen auf den injizierenden Heroinkonsum um. Schlussfolgerungen: Die Bedeutung des nasalen Heroinkonsums wurde in Österreich bisher unterschätzt. Überlegungen zur Verhinderung des Umstiegs von nasalen auf intravenösen Heroinkonsum im Sinne der Schadensminimierung scheinen angebracht.
Die Umsetzung eines Rauchverbots im Maßregelvollzug
Authors: Hofstetter Volker , Rohner Anne , Müller-Isberner Rüdiger
Published: December 2010

Fragestellung: Entwicklung einer Strategie zur Umsetzung des am 1. Oktober 2007 in Kraft getretenen Hessischen Nichtraucherschutzgesetzes in der Vitos Klinik für forensische Psychiatrie Haina. Methoden: Nach einer umfassenden Literaturrecherche zur Bedeutung des Tabakkonsums im Zusammenhang mit psychischen Erkrankungen wurde ein komplettes Rauchverbot für die gesamte Klinik und sämtlichen dazugehörigen Außenflächen implementiert. Ergebnisse: Das Rauchverbot führte nicht zu der befürchteten Zunahme des aggressiven Verhaltens der Patienten und Verstöße gegen das Verbot nahmen in den folgenden 18 Monaten kontinuierlich ab. Das Rauchverbot stieß jedoch auf ein negatives Medienecho und gerichtliche Eingaben der Patienten zwangen die Klinik dazu, das Rauchen im Außenbereich wieder zu gestatten. Fazit: Grundsätzlich ist die Umsetzung eines kompletten Rauchverbots in einer forensisch psychiatrischen Klinik möglich, ohne dass eine Zunahme aggressiven Verhaltens der Patienten zu erwarten ist. Eine Verbesserung der Akzeptanz eines solchen Rauchverbots wäre durch entsprechende Qualifikation von Mitarbeitern, mehr finanziellen Ressourcen und größerem zeitlichem Spielraum mit mehr Vorbereitungszeit zu erzielen.
Beurteilung der Fahreignung bei Drogenkonsum
Authors: Bork Stephan
Published: December 2010

In der folgenden Übersichtsarbeit werden die Grundlagen der Beurteilung der Fahreignung in Zusammenhang mit Drogenkonsum erläutert. Die Ausführungen orientieren sich an der Begutachtungsleitlinie zur Kraftfahrereignung ( BAST, 2000 ). Zusätzlich wird auf die Beurteilung der Fahreignung bei Substitutionsbehandlung eingegangen und das Problem der ärztlichen Schweigepflicht im therapeutischen Kontext erörtert.
Seismic anisotropy beneath the Afar Depression and adjacent areas: Implications for mantle flow
Authors: Gao Stephen S. , Liu Kelly H. , Abdelsalam Mohamed G.
Published: December 2010

Shear wave splitting is a robust tool to infer the direction and strength of seismic anisotropy in the lithosphere and underlying asthenosphere. Previous shear wave splitting studies in the Afar Depression and adjacent areas concluded that either Precambrian sutures or vertical magmatic dikes are mostly responsible for the observed anisotropy. Here we report results of a systematic analysis of teleseismic shear wave splitting using all the available broadband seismic data recorded in the Afar Depression, Main Ethiopian Rift (MER), and Ethiopian Plateau. We found that while the ∼450 measurements on the Ethiopian Plateau and in the MER show insignificant azimuthal variations with MER‐parallel fast directions and thus can be explained by a single layer of anisotropy, the ∼150 measurements in the Afar Depression reveal a systematic azimuthal dependence of splitting parameters with a π/2 periodicity, suggesting a two‐layer model of anisotropy. The top layer is characterized by a relatively small (0.65 s) splitting delay time and a WNW fast direction that can be attributed to magmatic dikes within the lithosphere, and the lower layer has a larger (2.0 s) delay time and a NE fast direction. Using the spatial coherency of the splitting parameters obtained in the MER and on the Ethiopian Plateau, we estimated that the optimal depth of the source of anisotropy is centered at about 300 km, i.e., in the asthenosphere. The spatial and azimuthal variations of the observed anisotropy can best be explained by a NE directed flow in the asthenosphere beneath the MER and the Afar Depression.
Hydrothermal plumes imaged by high‐resolution side‐scan sonar on a cruising AUV, Urashima
Authors: Kumagai Hidenori , Tsukioka Satoshi , Yamamoto Hiroyuki , Tsuji Takeshi , Shitashima Kiminori , Asada Miho , Yamamoto Fujio , Kinoshita Masataka
Published: December 2010

An autonomous underwater vehicle (AUV) is an ideal platform that enables a closer approach to the seafloor than other platforms. The AUV provides remarkable advancement not only in imaging small‐scale bathymetry with high resolution but also in imaging the spatial distribution of scattering signals within a water column. Acoustic echoes can be recorded continuously by AUVs, potentially providing information related to hydrothermal plumes within a water column. In May 2007, such an AUV, Urashima, of the Japan Agency for Marine–Earth Science and Technology, captured fantastic acoustic images within the water column above an active hydrothermal field, the Iheya‐North field, off Okinawa. Numerous filamentous and hyperbolic echoes were recorded on the side‐scan sonar images. According to the temperature and geochemical anomaly, the scattering signals within the water column were hydrothermal plumes upwelling from the vent area. This proof of concept has implications for long‐range exploration for vent field with AUVs.
First oceanic measurements of ethanol and propanol
Authors: Beale R. , Liss P. S. , Nightingale P. D.
Published: December 2010

The role of the ocean in the cycling of ethanol and propanol remains unanswered due to a total lack of data on their concentrations in seawater. We report the first measurements of these low molecular mass alcohols made during two field experiments in the Atlantic Ocean. Ethanol concentrations ranged from 2–33 nM. Our analytical technique allowed the separation of the two propanol isomers and concentrations of 1‐ and 2‐propanol varied between 2–22 nM and 1–19 nM respectively. Global extrapolation of the sea ‐ air fluxes indicate that the ocean may be an important source for these compounds to the atmosphere and suggest that the magnitude of the fluxes may be enhanced in natural upwelling regions.
The 2010 Maule, Chile earthquake: Downdip rupture limit revealed by space geodesy
Authors: Tong Xiaopeng , Sandwell David , Luttrell Karen , Brooks Benjamin , Bevis Michael , Shimada Masanobu , Foster James , Smalley Robert , Parra Hector , Báez Soto Juan Carlos , Blanco Mauro , Kendrick Eric , Genrich Jeff , Caccamise Dana J.
Published: December 2010

Radar interferometry from the ALOS satellite captured the coseismic ground deformation associated with the 2010 Mw 8.8 Maule, Chile earthquake. The ALOS interferograms reveal a sharp transition in fringe pattern at ∼150 km from the trench axis that is diagnostic of the downdip rupture limit of the Maule earthquake. An elastic dislocation model based on ascending and descending ALOS interferograms and 13 near‐field 3‐component GPS measurements reveals that the coseismic slip decreases more or less linearly from a maximum of 17 m (along‐strike average of 6.5 m) at 18 km depth to near zero at 43–48 km depth, quantitatively indicating the downdip limit of the seismogenic zone. The depth at which slip drops to near zero appears to be at the intersection of the subducting plate with the continental Moho. Our model also suggests that the depth where coseismic slip vanishes is nearly uniform along the strike direction for a rupture length of ∼600 km. The average coseismic slip vector and the interseismic velocity vector are not parallel, which can be interpreted as a deficit in strike‐slip moment release.
Heliosheath fluctuations near the perpendicular termination shock: Two‐dimensional hybrid simulations
Authors: Liu Kaijun , Gary S. Peter , Winske Dan
Published: December 2010

The two‐dimensional Los Alamos hybrid simulation code is used to study the excitation of fluctuations and the associated ion dynamics at the high Alfvén‐Mach heliospheric termination shock and in the near‐shock heliosheath. This simulation represents the electrons as a zero‐mass fluid, addresses only a perpendicular shock, and considers the upstream ions to consist of a cool solar wind component and a more energetic pickup component. The shock yields two strongly heated downstream components: the more dense thermals and the more tenuous suprathermals, each with strong T⊥ > T∥ anisotropies. In the downstream, relatively homogeneous sheath plasma, linear dispersion theory predicts that each component anisotropy drives both the Alfvén‐cyclotron instability and the proton mirror instability. The simulation demonstrates that Alfvén‐cyclotron modes dominate mirror‐like modes in the downstream, in contrast to earlier two‐dimensional hybrid simulations of high‐Mach quasi‐perpendicular shocks without pickup ions, in which the Alfvén‐cyclotron and mirror modes were excited to comparable intensities. A hypothesis is presented that the presence of pickup ions implies a relatively low magnetosonic Mach number at termination shocks, thereby favoring the excitation of the Alfvén‐cyclotron instability. The primary consequence of wave‐particle interactions from this instability is pitch angle scattering, so the energetic part of the ion perpendicular velocity distribution in the heliosheath is depleted by comparison with the distribution computed from a comparable one‐dimensional hybrid simulation.
Proton velocity distribution in thin current sheets: Cluster observations and theory of transient trajectories
Authors: Artemyev A. V. , Petrukovich A. A. , Nakamura R. , Zelenyi L. M.
Published: December 2010

The structure of thin current sheets in the Earth magnetotail is studied on the basis of 43 crossings by Cluster spacecraft. Current sheet embedding is described as the ratio of the magnitudes of magnetic field at the thin current sheet boundary and in the lobe. This ratio is found to be ∼0.4 on average. The proton population consists of the current‐carrying particles with density ∼10%–20% of the total density, and the background plasma. This current‐carrying distribution is found to have a half‐ring structure in the (vx, vy) plane, which is consistent with the theory of transient particle motion (so‐called Speiser‐type trajectories). The main parameter of the thin current sheet models, the flow anisotropy ɛ, is estimated to be ɛ ≥ 0.3–0.5. The E × B drift of the background plasma due to the presence of an earthward ambipolar electric field can weaken the total proton current density (in the magnetospheric rest frame) by a factor of ∼(1 − Tenp/TpnΔ), where Te and Tp are electron and proton temperatures and nΔ and np are the density of the current‐carrying particles and the total plasma density, respectively.
Nonspecular meteor trail altitude distributions and durations observed by a 50 MHz high‐power radar
Authors: Sugar G. , Oppenheim M. M. , Bass E. , Chau J. L.
Published: December 2010

High‐power large‐aperture (HPLA) radars frequently observe nonspecular meteor trail echoes that result from plasma turbulence driven by the intense pressure gradients on the trail edges. This paper analyzes the altitude range, duration, and dependence on head echo strength of nonspecular trails using two large data sets from the 50 MHz HPLA radar at the Jicamarca Radio Observatory. Over 2100 trails were used to build altitude profiles that extend from 86 km to 120 km altitude, with 97% of events occurring between 90 km and 110 km. Longer‐duration trails tend to form at lower altitudes than shorter‐duration echoes. The peak of the altitude distribution of trails lasting at least 5 s can be up to 12 km lower than the peak of the distribution of trails shorter than 5 s. Further, the data show a clear power law relationship for the frequency of both head echo and nonspecular trail power. An improved knowledge of nonspecular trails will allow researchers to better understand meteor trail evolution and their use in monitoring lower thermospheric winds.
Long‐lasting goodshielding at the equatorial ionosphere
Authors: Wei Yong , Pu Zuyin , Hong Minghua , Zong Qiugang , Liu Jianjun , Guo Jianpeng , Ridley Aaron , Wan Weixing
Published: December 2010

During magnetic storm times, a dawnward electric field may build up at the Alfven layer in the inner magnetosphere to cancel an enhanced duskward magnetospheric convection electric field. This effect is known as “shielding” because the dawnward electric field prevents the duskward electric field from penetrating into the inner magnetosphere. The term “goodshielding” refers to the perfect shielding status, in which the penetration electric field is almost completely canceled by shielding electric field. Observational evidence of goodshielding has rarely been reported before. Here we present two long‐lasting (16 and 23 min) goodshielding cases as unambiguous evidence. Both cases show similar historical patterns of shielding status: long‐duration electric field penetration (undershielding), goodshielding, and then overshielding. The goodshielding time periods, featuring quiet‐level ionospheric electric field at the dayside equator, are not directly related to the changes of interplanetary magnetic field (IMF) BZ, but the transitions from goodshielding to overshielding coincide with reduction of convection electric field. Both cases show that the equatorial electric field does not significantly respond to convection electric field enhancements during goodshielding, indicating that the shielding electric field may quickly adjust to shield newly enhanced convection electric fields. The quick shielding is possibly attributed to the fact that the ring current has become stronger and has been brought closer to the Earth. These new features may provide some clues to understand the magnetosphere‐ionosphere coupling processes during storm times.
On the relationship between thermosphere density and solar wind parameters during intense geomagnetic storms
Authors: Guo Jianpeng , Feng Xueshang , Forbes Jeffrey M. , Lei Jiuhou , Zhang Jie , Tan Chenming
Published: December 2010

Total mass density measurements at 72°S, 0°, and 72°N latitude from the CHAMP satellite near 400 km altitude are used to provide a quantitative assessment of the relationship between solar wind energy input and density variations during intense (Dst ≤ −100 nT) geomagnetic storms that occurred between August 2001 and December 2006. Correlations between the thermosphere density variations and various solar wind parameters and coupling functions representing the energy input into the thermosphere reveal significantly different characteristics during different geomagnetic storms. Statistical analysis shows that, out of the chosen solar wind parameters including coupling functions, the Borovsky parameter correlates best with the global scale density variations. The correlations at the equator are significantly higher than those at high latitudes. Moreover, the correlations on the dayside are almost the same as those on the nightside at 72°S and 0° latitude, whereas the correlation on the nightside is slightly higher than that on the dayside at 72°N latitude. These results indicate that it might be possible to use solar wind measurements to improve predictions of thermosphere density perturbations and the resulting changes in satellite drag.
Effect of dust storms on the D region of the Martian ionosphere: Atmospheric electricity
Authors: Haider S. A. , Sheel V. , Smith M. D. , Maguire W. C. , Molina‐Cuberos G. J.
Published: December 2010

We have used dust opacity values observed by the Thermal Emission Imaging System onboard Mars Odyssey to estimate the effect of dust aerosols in the D region of the Martian ionosphere. An ion‐dust aerosol model has been developed to calculate ion concentrations and conductivity at midlatitudes during a dust storm in the Southern Hemisphere. We report that the concentration of the water cluster ions H+(H2O)n, NO2−(H2O)n, and CO3−(H2O)n are reduced by 2 orders of magnitude in the presence of dust aerosols. This indicates that during a dust storm, when the optical depth changes considerably, a large hole in the ion concentrations may appear until this anomalous condition returns to the normal condition after a period of about a few days. During such dust storms, the total ion conductivity is reduced by an order of magnitude.
Thick dyke emplacement and internal flow: A structural and magnetic fabric study of the deep‐seated dolerite dyke of Foum Zguid (southern Morocco)
Authors: Silva Pedro F. , Marques Fernando O. , Henry Bernard , Madureira Pedro , Hirt Ann M. , Font Eric , Lourenço Nuno
Published: December 2010

Knowledge on forced magma injection and magma flow in dykes is crucial for the understanding of how magmas migrate through the crust to the Earth's surface. Because many questions still persist, we used the long, thick, and deep‐seated Foum Zguid dyke (Morocco) to investigate dyke emplacement and internal flow by means of magnetic methods, structural analysis, petrography, and scanning electron microscopy. We also investigated how the host rocks accommodated the intrusion. Regarding internal flow: 1. Important variations of the rock magnetic properties and magnetic fabric occur with distance from dyke wall; 2. anisotropy of anhysteretic remanent magnetization reveals that anisotropy of magnetic susceptibility (AMS) results mainly from the superposition of subfabrics with distinct coercivities and that the imbrication between magnetic foliation and dyke plane is more reliable to deduce flow than the orientation of the AMS maximum principal axis; and 3. a dominant upward flow near the margins can be inferred. The magnetic fabric closest to the dyke wall likely records magma flow best due to fast cooling, whereas in the core the magnetic properties have been affected by high‐temperature exsolution and metasomatic effects due to slow cooling. Regarding dyke emplacement, this study shows that the thick forceful intrusion induced deformation by homogeneous flattening and/or folding of the host sedimentary strata. Dewatering related to heat, as recorded by thick quartz veins bordering the dyke in some localities, may have also helped accommodating dyke intrusion. The spatial arrangement of quartz veins and their geometrical relationship with the dyke indicate a preintrusive to synintrusive sinistral component of strike slip.
Three‐dimensional computational axial tomography scan of a volcano with cosmic ray muon radiography
Authors: Tanaka Hiroyuki K. M. , Taira Hideaki , Uchida Tomihisa , Tanaka Manobu , Takeo Minoru , Ohminato Takao , Aoki Yosuke , Nishitama Ryuichi , Shoji Daigo , Tsuiji Hiroshi
Published: December 2010

Cosmic ray muon radiography can measure the density distribution within a volcano. Unidirectional radiography shows a precise cross‐sectional view of a conduit and a magma body through a volcano parallel to the plane of the detector. However, it only resolves the average density distribution along individual muon paths. Precise size and shape of underground structure, such as a conduit or a magma body, provide clear and pervasive information on understanding dynamics of volcanic eruption. Here we show a highly resolved three‐dimensional tomographic image of an active volcano Asama in Japan. Specifically, we developed a portable power‐effective muon radiography telescope that can be operated stable with a realistically sized solar panel so as to place it around an active volcano where commercial electric power is not available. The resulting image below the crater floor shows that a local low‐density region accumulates sufficient gas pressure to cause Vulcanian eruption. The present muon computational axial tomography scan has a resolving power with a resolution of 100 m, allowing it to see great detail in volcanoes.
On preconditioning of coastal upwelling in the eastern Great Australian Bight
Authors: Kämpf Jochen
Published: December 2010

Using a high‐resolution hydrodynamic model, this work explores the formation of a subsurface pool of cold and nutrient‐rich water on the continental shelf southwest of Kangaroo Island, South Australia. Findings reveal that localized upwelling in shelf break canyons south of Kangaroo Island play an important role in the pool's formation. Supported by observational evidence, this study suggests a direct link between canyon upwelling, pool formation, and the appearance of coastal upwelling centers in austral summer. The shelf and slope circulation establishing during this season creates a particularly deep canyon upwelling from an average depth of ∼310 m, which is much deeper than previously suggested. Results indicate that model applications, not resolving the shelf break canyons, underestimate upwelling‐related volume fluxes across the shelf break by a factor of 3.5 and nitrate fluxes by a factor of 5.
Validation of v1.022 mesospheric water vapor observed by the Solar Occultation for Ice Experiment instrument on the Aeronomy of Ice in the Mesosphere satellite
Authors: Rong Pingping , Russell James M. , Gordley Larry L. , Hervig Mark E. , Deaver Lance , Bernath Peter F. , Walker Kaley A.
Published: December 2010

Water vapor measured by the Solar Occultation for Ice Experiment (SOFIE) instrument on the Aeronomy of Ice in the Mesosphere satellite has been validated in the vertical range 45–95 km. Precision estimates for SOFIE v1.022 H2O are ∼0.2%–2.5% up to 80 km and degrade to ∼20% at ∼90 km. The SOFIE total systematic error from the retrieval analysis remains at ∼3%–4% throughout the lower to middle mesosphere and increases from ∼9% at 85 km to ∼16% at 95 km. Comparisons with Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer (ACE‐FTS) and Microwave Limb Sounder (MLS) H2O show excellent agreement (0%–2%) up to 80 km in the Northern Hemisphere with rare exceptions. Percentage differences above ∼85 km increase to ∼20% or worse due largely to the low H2O volume mixing ratios in the upper mesosphere. For the Southern Hemisphere SOFIE is consistently biased low by 10%–20% relative to both ACE‐FTS and MLS H2O. Slopes of SOFIE daily mean H2O isopleths on an altitude versus time cross section are used as an indicator of upwelling air motion. In the lower to middle mesosphere, the slope is the largest from mid‐May to mid‐June (maximum of ∼1.5 cm/s), and then in July and August, it is reduced significantly. Both SOFIE and MLS daily mean H2O volume mixing ratios at the polar mesospheric cloud height increase rapidly from ∼2.0 to ∼5.0 ppmv prior to the solstice and then approach a near‐constant but slightly increasing level (6.0–6.5 ppmv) throughout the season.
Increasing rain intensity over Okinawa, 1982–2005, and the link to changes in characteristics of northwest Pacific typhoons
Authors: Ikema Takeharu , Bigg Grant R. , Bryant Robert G.
Published: December 2010

Daily rainfall variation over the strategically situated western Pacific island of Okinawa is investigated for 1982–2005. Although no trend in the annual rainfall was observed, analyses using a probability distribution function for each year revealed that the frequency of light (0–3 mm d−1) and heavy (26–50 mm d−1) rainfall events have a statistically significant decreasing trend, while extreme (>75 mm d−1) rainfall events have been increasing. Such events are associated with typhoons. An analysis of typhoons passing near Okinawa during 1982–2005 revealed that a cause of the increasing trend in heavy rainfall was increased rainfall amounts per typhoon rather than a rising number of strong typhoons approaching the island. In particular, typhoons which passed to the west of Okinawa, or which approached the island within 100 km, during the peak typhoon month of September showed a statistically significant increase in total rainfall of 6.5 mm y−1 over this time period. This is partially due to a slowing of the typhoon speeds in the latter half of the record. This work supports other recent studies that suggest changes to characteristics of stronger tropical storms are not restricted to the North Atlantic although, owing to the limited length of the record, we are not able to determine at this time whether the observed trends are unusual compared with natural multidecadal variability.