bluuebunny/crossref_metadata_2025 huggingface dataset:
Species barrier of HIV‐1 and its jumping by virus engineering
Authors: Nomaguchi Masako , Doi Naoya , Kamada Kazuya , Adachi Akio
Published: April 2008

Monkey infection models are absolutely necessary for studies of human immunodeficiency virus type 1 (HIV‐1) pathogenesis and of developing drugs/vaccines against HIV‐1. In addition, currently unknown roles of its accessory proteins for in vivo replication await elucidation by experimental approaches. Due to the fact that HIV‐1 is tropic only for chimpanzees and humans, studies of this line have been impeded for a long time, although various investigations have been carried out utilising genetically related SIV and SIV/HIV chimeric virus (SHIV) as pathogens. Recent findings of anti‐HIV‐1 innate factors such as tripartite motif protein 5α (TRIM5α) and APOBEC3G/F prompted us to re‐initiate an old and vital research project which would, as a result, confer the capability to overcome the species barrier on the HIV‐1. We currently have obtained, by virus engineering through genetic manipulation and adaptation, some new and promising HIV‐1 clones for in vivo studies in macaque monkeys as mentioned above. In this review, we summarise the past, present and future of HIV‐1/SIV chimeric viruses with special reference to relevant basic HIV‐1/SIV studies. Copyright © 2008 John Wiley & Sons, Ltd.
What is the furthest graph from a hereditary property?
Authors: Alon Noga , Stav Uri
Published: April 2008

For a graph property P, the edit distance of a graph G from P, denoted EP(G), is the minimum number of edge modifications (additions or deletions) one needs to apply to G to turn it into a graph satisfying P. What is the furthest graph on n vertices from P and what is the largest possible edit distance from P? Denote this maximal distance by ed(n,P). This question is motivated by algorithmic edge‐modification problems, in which one wishes to find or approximate the value of EP(G) given an input graph G. A monotone graph property is closed under removal of edges and vertices. Trivially, for any monotone property, the largest edit distance is attained by a complete graph. We show that this is a simple instance of a much broader phenomenon. A hereditary graph property is closed under removal of vertices. We prove that for any hereditary graph property P, a random graph with an edge density that depends on P essentially achieves the maximal distance from P, that is: ed(n,P) = EP(G(n,p(P))) + o(n2) with high probability. The proofs combine several tools, including strengthened versions of the Szemerédi regularity lemma, properties of random graphs and probabilistic arguments. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008
Community resilience and contemporary agri‐ecological systems: reconnecting people and food, and people with people
Authors: King Christine A.
Published: April 2008

Alternative agricultural systems that emphasize ecological and community resilience provide a bridge between traditional agriculture and natural resource management. These can be referred to as agri‐ecological systems and include systems such as Organic Agriculture, Biodynamics, Community Supported Agriculture (CSA), Permaculture, Farmers Markets and Community Gardens. This paper reports on current research by the author to explore a range of these systems and how they contribute to agri‐ecological and community resilience. For example, resiliency can be seen as a system's ability to adapt and respond to external impacts on a system, and farmers markets show resiliency to sudden market changes (such as price or consumer preferences toward organics, through direct sale and the involvement of a range of consumers and producers offering a broad range of organic produce). That is, this paper reviews these alternative approaches to food production in relation to key concepts from ecological systems thinking, such as ecological resilience, biodiversity and holism. More specifically, the paper explores how agri‐ecological systems contribute to more sustainable and resilient communities, through community development processes such as relationship building, genuine participation, inclusiveness, resource mobilization and creating space for knowledge sharing. The paper concludes by comparing ecological systems models to agri‐ecological systems, and suggests how ecological systems theories and concepts might contribute to thinking about the future of community‐based agri‐ecological resilience. Copyright © 2008 John Wiley & Sons, Ltd.
Organizations advocating for youth: The local advantage
Authors: Deschenes Sarah , McLaughlin Milbrey , Newman Anne
Published: April 2008

Youth occupy a unique place in our democratic society. They must primarily rely on others to speak on their behalf as decisions are made about the allocation of resources within and across various youth‐serving institutions. Advocacy organizations comprise crucial representational assets for all youth, but America's poorest children and youth especially need an effective voice to speak for and about them. Yet advocates for youth in urban areas face tough challenges since urban voters typically have few positive connections to youth. This article draws on three years of research focused on three organizations in the San Francisco Bay Area that have successfully advocated for better policies for youth. The authors explore the strategies that these organizations have employed to overcome the challenges they face, with particular attention to the advantages that follow from advocating at the local rather than at the state or federal level.
Youth organizing: From youth development to school reform
Authors: Warren Mark R. , Mira Meredith , Nikundiwe Thomas
Published: April 2008

Over the past twenty years, youth organizing has grown across the country. Through organizing, young people identify issues of concern and mobilize their peers to build action campaigns to achieve their objectives. Youth organizing has been appreciated for its contributions to youth and community development. The authors use two case studies to trace the more recent emergence of youth organizing as an important force for school reform. The Boston‐based Hyde Square Task Force began with a focus on afterschool programming, but its youth leaders now organize to get Boston Public Schools to adopt a curriculum addressing sexual harassment. Meanwhile, the Baltimore Algebra Project began as a peer‐to‐peer tutoring program but now also organizes to demand greater funding for Baltimore schools. These cases illustrate a broader phenomenon where students reverse the deficit paradigm by acting out of their own self‐interest to become agents of institutional change.
Negotiating reform: Young people's leadership in the educational arena
Authors: Shah Seema , Mediratta Kavitha
Published: April 2008

Youth organizing within the institutional context of community‐based organizations has grown exponentially. Drawing on interviews with more than eighty organizers, youth, and educators, this article examines young people's experiences as they organize to expand educational opportunities for themselves and their peers in urban school districts. The authors explore educator responses to youth organizing and analyze how race‐ and class‐based assumptions about youth leadership, as well as differing cultural norms between schools and youth organizing groups, pose challenges for young people fighting for education reform. The authors describe three strategies youth organizing groups use to address these challenges: intensive leadership development, targeted relationship building with district administrators, and alliance building. Implications for both educators and youth organizing groups are discussed.
Developing the field of youth organizing and advocacy: What foundations can do
Authors: Yee Sylvia M.
Published: April 2008

For more than a decade, the Evelyn and Walter Haas, Jr. Fund has seeded many San Francisco Bay Area youth organizing and advocacy programs. Now that the field is maturing, argues the fund's vice president of programs, foundations have a critical programmatic and capacity‐building role to play. The author offers analysis and strategies for integrating youth development grant making across foundation interest areas. The programs described illustrate the diversity of youth organizing and advocacy programs that could be supported by funders, whether or not any particular philanthropic institution has a grant‐making focus on youth development or youth organizing. The article ends with an in‐depth portrait of the self‐reported needs of youth organizing and advocacy programs and concrete strategies for foundations seeking to more effectively enable youth organizing and advocacy to play an important role in bringing about a more vibrant, diverse, and effective democratic culture.
The RISC ProofNavigator: a proving assistant for program verification in the classroom
Authors: Schreiner Wolfgang
Published: April 2008

This paper gives an overview of the RISC ProofNavigator, an interactive proving assistant for the area of program verification. The assistant combines the user-guided top-down decomposition of proofs with the automatic simplification and closing of proof states by an external satisfiability solver. The software exhibits a modern graphical user interface which has been developed with a focus on simplicity in order to make the software suitable for educational scenarios. Nevertheless, some use cases of a certain level of complexity demonstrate that it may be also appropriate for various realistic applications.
Erratum to: The state of the art in the analysis of two-dimensional gel electrophoresis images
Authors: Berth Matthias , Moser Frank Michael , Kolbe Markus , Bernhardt Jörg
Published: April 2008

Due to a technical error, the article “The state of the art in the analysis of two-dimensional gel electrophoresis images” carries an incorrect copyright line. The copyright of the article is with DECODON GmbH, not with Springer-Verlag.”
Expertise and aging: maintaining skills through the lifespan
Authors: Horton Sean , Baker Joseph , Schorer Jörg
Published: April 2008

As lifespan continues to increase in many developed countries, so too does the age at which we see extraordinary achievements from older adults. Examples from running, golf, and other domains continue to redefine what is possible as we age. Evidence suggests, however, that progression through adulthood is associated with a dramatic decline in all manner of physical and cognitive abilities, from physiological capacities (e.g., VO2 max) to cognitive and perceptual functions (e.g., IQ scores, reaction time). In the face of such precipitous decline in specific abilities, how do we account for maintenance of skilled performance and expertise amongst those supposedly well along the age-decline curve? Expert performers are seemingly able to sustain high levels of achievement in the face of an overall deterioration in general capacities. Moreover, experts maintain this performance in spite of reduced involvement in their field. There are three primary explanations for the ability of experts to maintain superior performance in spite of an overall decline in abilities: (a) preserved differentiation, (b) compensation, and (c) selective maintenance. Overall, research into the high achievements of older adults may reveal a great deal with respect to skill preservation and how to best counter age-related decline.
The mammalian Nek1 kinase is involved in primary cilium formation
Authors: Shalom Ohad , Shalva Nechama , Altschuler Yoram , Motro Benny
Published: April 2008

Recent studies implicate primary cilium (PC) proteins in the etiologies of various polycystic kidney diseases (PKD). NIMA‐related kinases (NRKs) are conserved serine/threonine kinases, which are usually defined as ‘mitotic kinases’. Murine mutants for the NRKs, nek1 (kat mice) suffer from PKD, suggesting that it may be involved in cilium control. We demonstrated herein that Nek1 is localized to basal body region and that Nek1 overexpression inhibits ciliogenesis in Madin–Darby canine kidney epithelial cells. The number of primary cilia is dramatically reduced in kat2J mouse embryonic fibroblasts culture. It is thus hypothesized that Nek1 links cell cycle progression and the PC cycle.
Osteoclastic-like giant cell tumour in a cat
Authors: Chang Shih-Chieh , Liao Jiunn-Wang , Liu Cheng-I. , Wong Min-Liang , Cheng Feng-Pang
Published: April 2008

An 11-year-old neutered male domestic shorthair cat was presented with an epulis. A hemispherical mass, 8 mm in maximum diameter, without a peduncle and bright reddish in colour, was observed on the gingiva of the left mandible. Radiography failed to show any infiltrating osteolysis. The epulis was surgically removed via gingival incision around the margin to the depth of connective tissue layer. Histopathological examination indicated that the epulis contained a large number of multinucleated giant cells (MGCs) intermixed with mononuclear mesenchymal cells in a loose fibrovascular stroma. Mitotic cells were found, mainly in the centre of the mass. MGCs were stained positive by the tartrase resistant acid phosphatase (TRAP) staining, indicating osteoclasts activity. Immunohistochemical staining for proliferating-cell nuclear antigen (PCNA) was observed within the majority of mononucleated cells, whereas multinucleated cells did not stain. An osteoclast-like giant cell tumour was concluded in this case. The origin of epulis is likely from the periosteal tissue. The cat recovered uneventfully and no recurrence has been noted for 3 years thereafter.
Molecular aspects of tumour hypoxia
Authors: Rademakers Saskia E. , Span Paul N. , Kaanders Johannes H.A.M. , Sweep Fred C.G.J. , van der Kogel Albert J. , Bussink Johan
Published: April 2008

Hypoxia is an important feature of the microenvironment of a wide range of solid tumours. Its critical role in radio‐ and chemoresistance and its significance as an adverse prognostic factor have been well established over the last decades. On a cellular level, hypoxia evokes a complex molecular response with a central role for the HIF‐1 pathway. The cellular processes under control of HIF‐1 contain important prognostic information and comprise potential candidates for directing hypoxia‐modifying therapies. This review will provide an overview of the current knowledge on the molecular aspects of tumour hypoxia and the link to clinical practice.
Classification of fault breccias and related fault rocks
Authors: WOODCOCK N. H. , MORT K.
Published: April 2008

Despite extensive research on fault rocks, and on their commercial importance, there is no non-genetic classification of fault breccias that can easily be applied in the field. The present criterion for recognizing fault breccia as having no ‘primary cohesion’ is often difficult to assess. Instead we propose that fault breccia should be defined, as with sedimentary breccia, primarily by grain size: with at least 30% of its volume comprising clasts at least 2 mm in diameter. To subdivide fault breccias, we advocate the use of textural terms borrowed from the cave-collapse literature – crackle, mosaic and chaotic breccia – with bounds at 75% and 60% clast content. A secondary breccia discriminant, more difficult to apply in the field, is the ratio of cement to matrix between the clasts. Clast-size issues concerning fault gouge, cataclasite and mylonite are also discussed.
Expansion of Human Neural Precursor Cells in Large‐Scale Bioreactors for the Treatment of Neurodegenerative Disorders
Authors: Baghbaderani Behnam A. , Mukhida Karim , Sen Arindom , Hong Murray , Mendez Ivar , Behie Leo A.
Published: April 2008

The transplantation of in vitro expanded human neural precursor cells (hNPCs) represents a potential new treatment alternative for individuals suffering from incurable neurodegenerative disorders such as Parkinson's disease (PD) and Huntington's disease (HD). However, in order for cell restorative therapy to have widespread therapeutic significance, it will be necessary to generate unlimited quantities of clinical grade hNPCs in a standardized method. We report here that we have developed a serum‐free medium and scale‐up protocols that allow for the generation of clinical quantities of human telencephalon‐derived hNPCs in 500‐mL computer‐controlled suspension bioreactors. The average hNPC aggregate diameter in the bioreactors was maintained below a target value of 500 μm by controlling the liquid shear field. The human cells, which were inoculated at 105 cells/mL, exhibited a doubling time of 84 h, underwent a 36‐fold expansion over the course of 18 days, and maintained an average viability of over 90%. The bioreactor‐derived hNPCs retained their nestin expression following expansion and were able to differentiate into glial and neuronal phenotypes under defined conditions. It has also been demonstrated that these hNPCs differentiated to a GABAergic phenotype that has recently been shown to be able to restore functional behavior in rat models of HD and neuropathic pain (Mukhida, K. et al. Stem Cells 2007; DOI 10.1634/stemcells.2007–0326). This study demonstrates that clinical quantities of hNPCs can be successfully and reproducibly generated under standardized conditions in computer‐controlled suspension bioreactors.
Rotation in der Anästhesiepflege – Eine Analyse der Wirkungen auf Wissens- und Lernprozesse
Authors: Jordan Silvia , Brauner Elisabeth
Published: April 2008

Basierend auf organisationstheoretischen Ansätzen zu so genannten High Reliability Organisationen – Hochrisiko-Organisationen, in denen zuverlässige Leistung lebensentscheidend sein kann – und sozialpsychologischen Ansätzen zu Wissens- und Lernprozessen (transactive knowledge systems) wird in diesem Beitrag die organisatorische Maßnahme der job rotation hinsichtlich ihrer Wirkung auf Wissens- und Lernprozesse in der Anästhesiepflege diskutiert. Die empirischen Daten wurden im Rahmen eines Forschungsprojekts zur Einarbeitung von Anästhesiepflegenovizen an der Universitätsklinik Innsbruck von September 2003 bis Juni 2005 erhoben. Im Sinne eines mixed method Designs wurden Beobachtungs- und Interviewdaten mit einer Fragebogenstudie zu Transaktivem Wissen und Zusammenarbeit unter Anästhesiepflegepersonen und Anästhesisten/Anästhesistinnen ergänzt. Die Auswertung der qualitativen Daten erfolgte mit Hilfe des computerunterstützten Verfahrens GABEK, jene der quantitativen Daten anhand einer statistischen Analyse in SPSS. Die Ergebnisse der Analyse zeichnen ein ambivalentes Bild der job rotation, da sie einerseits Lernfähigkeit und Bewusstsein eigener Wissensgrenzen fördern, andererseits jedoch Vertrauen, Gruppenzusammenhalt und soziales Metawissen – also relevante Faktoren zuverlässiger interdisziplinärer Zusammenarbeit – behindern kann. Stabilisierung und Veränderung sind somit bei der organisatorischen Gestaltung von Pflegetätigkeit gleichermaßen zu bedenken.
Inzidenz und Risikoerfassung von Dekubitus – Ergebnisse einer Qualitätsmessung des Verein Outcome in Schweizer Akutspitälern
Authors: Gehrlach Christoph , Otzen Ina , Küttel Rolf , Heller Regula , Lerchner Martina
Published: April 2008

Die Vermeidung von Dekubitus gehört zu den zentralen Aufgaben der Pflege. Eine geringe Dekubitusrate ist ein Indikator für die Qualität der Versorgung der Patienten. Bei einer Qualitätsmessung des Verein Outcome (Schweiz) wurden Daten zur Dekubitusinzidenz in 51 Spitälern (n = 88 636) erhoben. Im Rahmen der Auswertungen sowie weiterer Sekundäranalysen wurden diese Daten auf Inzidenz, Schweregrade und Risiko von Dekubitus sowie auf die prädiktive Validität der Norton-Skala ausgewertet. Die Inzidenzrate war mit 3,1% vergleichsweise niedrig. 2,6% der Patienten brachten einen vorbestehenden Dekubitus mit. 3,8% der Patienten hatten zum Zeitpunkt der Entlassung einen Dekubitus. Trotz einer – im Vergleich mit internationalen Zahlen – relativ niedrigen Inzidenzrate konnten die Spitäler Handlungsbedarf in Bezug auf Qualitätsverbesserungen ableiten. Unter Verwendung der Norton-Skala wurde bei 9,5% der Patienten ein Dekubitusrisiko diagnostiziert, aber nur 14% dieser Gruppe entwickelte tatsächlich einen Dekubitus. Festzustellen ist daher, dass das Dekubitusrisiko mittels Norton-Skala tendenziell überschätzt wurde. Die Sensitivität der Norton-Skala lag bei 42,4%, die Spezifität bei 91,5%. Da ein nachvollziehbares Risikoassessment der erste Schritt für die Zuteilung prophylaktischer Maßnahmen ist, erscheint eine Weiterentwicklung der Norton-Skala sinnvoll.
Single Doppler radar observation of the concentric eyewall in Typhoon Saomai, 2006, near landfall
Authors: Zhao Kun , Lee Wen‐Chau , Jou Ben Jong‐Dao
Published: April 2008

Landfalling Typhoon Saomai (2006) was observed by the CINRAD WSR‐98D radar on the southeast coast of China. This study documents the formation and evolution of a concentric eyewall episode using the axisymmetric circulation derived from the ground‐based velocity track display technique. Saomai's outer eyewall formed after reaching its peak intensity, ∼5 hours before landfall. Updraft, tangential wind maximum and shallow low‐level inflow coincided with the high reflectivity and voriticity ring in both inner and outer eyewalls, surrounding a moat region characterized by weak downward motion and lower reflectivity. The subsidence and rain‐free moat region between the two eyewalls was filled with rain and upward motion prior to landfall, indicating a breakdown in the outer eyewall which was a barrier to radial inflow. Meanwhile, the outer vorticity maximum flattened and the central pressure dropped 9 hPa. The eyewall replacement cycle didn't complete probably due to the landfall.
Properties of magnetosheath mirror modes observed by Cluster and their response to changes in plasma parameters
Authors: Soucek Jan , Lucek Elizabeth , Dandouras Iannis
Published: April 2008

Mirror modes are large amplitude nonpropagating compressive structures frequently observed in the magnetosheath. They appear in the form of quasi‐sinusoidal oscillations in the magnetic field, profound magnetic decreases (dips) or magnetic enhancements (peaks), accompanied by a corresponding anticorrelated signature in plasma density. In this study we present an analysis of the properties of mirror mode structures in the magnetosheath of the Earth based on a database of Cluster observations and also a detailed case study of one magnetosheath traversal. We focused primarily on the identification of conditions associated with the magnetic dips and magnetic peaks. It is shown that the character of mirror structures is related to the local degree of instability of the plasma with respect to the mirror instability threshold: peaks are typically observed in an unstable plasma, while mirror structures observed deep within the stable region appear almost exclusively as dips. This observation is found to be consistent with recent theoretical and numerical studies. An abrupt transition of mirror structures from peaks to dips at an approximate distance of 2 Earth radii from the magnetopause was identified by multispacecraft analysis and we interpret this effect as a consequence of plasma expansion in the vicinity of the magnetopause locally changing the plasma conditions towards a more stable state.
Characteristics of low‐latitude Pc1 pulsations during geomagnetic storms
Authors: Bortnik J. , Cutler J. W. , Dunson C. , Bleier T. E. , McPherron R. L.
Published: April 2008

We use search‐coil magnetometer data from a low‐latitude station in Parkfield, California (L = 1.77) to study the occurrence of Pc1 pulsations associated with geomagnetic storms. The Pc1 pulsations and storms are identified using automatic algorithms, and the statistical distributions are examined using a superposed epoch analysis technique, as a function of local time, time relative to storm main phase, and storm intensity. Results show that Pc1 pulsations are 2–3 times more likely (than normal) to be observed in the 2–4 d following moderate storms and 4–5 times more likely in the 2–7 d following intense storms. The Pc1 frequencies are higher in moderate storms than they are in nonstorm times and become even higher and occupy a greater range of local times as the strength of the storms increase. These results are consistent with the idea that the source of EMIC waves extends to lower L values as storm intensity increases.
Density‐driven exchange flow in terms of the Kelvin and Ekman numbers
Authors: Valle‐Levinson Arnoldo
Published: April 2008

The pattern of density‐induced flow influenced by basin's width, friction, and Earth's rotation is investigated as a function of the Ekman (Ek) and Kelvin (Ke) numbers. A semianalytical solution is used to determine the conditions under which the density‐induced exchange flow is vertically sheared or horizontally sheared. Solutions are obtained over diverse laterally varying bathymetries. It is found that the exchange flow is horizontally sheared under high frictional conditions (Ek > 1) independently of the width of the basin (Ke). The horizontally sheared pattern describes inflow in the channel and outflow over shoals, with the inflow occupying the entire water column. The exchange flow pattern is also horizontally sheared under weak friction (Ek → 0) and in wide (Ke > 2) basins. In that case, however, the outflow is concentrated on the left (looking into the basin in the Northern Hemisphere) portion of the cross section and inflow appears on the right. Also, under weak friction, the exchange pattern becomes more vertically sheared, with outflow at surface and inflow underneath as the width of the basin becomes small (Ke < 1). Bathymetry is not very influential in the weak friction exchange patterns. Finally, under moderate friction (0.01 < Ek < 0.1), the exchange pattern is both horizontally and vertically sheared for all widths. The horizontally sheared pattern is best defined in wide basins (high Ke), whereas the vertically sheared pattern practically dominates in narrow basins (low Ke). These findings allow classification of various estuaries in the Ek‐Ke parameter space.
Non‐ideal liquidus curve in the Fe‐S system and Mercury's snowing core
Authors: Chen Bin , Li Jie , Hauck Steven A.
Published: April 2008

We conducted multi‐anvil experiments to investigate the melting behavior of the iron‐sulfur system at moderate pressures. Our data reveal a positive departure from ideal solution behavior at 14 GPa, as indicated by the presence of two inflection points on the liquidus curve of iron‐rich compositions. In contrast, the shape of the liquidus curve at 10 GPa is consistent with nearly ideal mixing between end‐member components. Combined with existing data at lower pressures and above 20 GPa, our results suggest a negative liquidus temperature gradient under conditions found at shallow depths in Mercury's core. At the present time, the core is most likely precipitating solid iron in the form of snow, at a single depth or in two distinct zones. Formation and segregation of iron snow would alter the thermal and chemical state of the core and influence the origin and surface expression of the planet's magnetic field.>
Systems Pharmacology
Authors: Iyengar Ravi
Published: April 2008

The slides are from a presentation given by Professor Ravi Iyengar from Mount Sinai School of Medicine at the Drug Forum Meeting 9 that took place in Washington, DC on February 20-21, 2008. The slides describe two projects: one that was published last year, and the other unpublished. These projects used network analysis to explore the relationships between FDA approved drugs and a human protein-protein interaction network.
Glucagon and hyperglycaemia in diabetes
Authors: Cryer Philip E.
Published: April 2008

Glucagon, in the setting of absolute or relative insulin deficiency, is thought to contribute to the pathogenesis of hyperglycaemia in diabetes, but much of the evidence is extrapolated from short-term studies to the long-term condition. In the present issue of Clinical Science, Li and co-workers report that infusion of glucagon raised fasting plasma glucose concentrations and impaired glucose tolerance over 4 weeks in mice, thus demonstrating a sustained glycaemic effect of hyperglucagonaemia. Nonetheless, compelling evidence that glucagon contributes to the pathogenesis of hyperglycaemia in diabetes awaits long-term selective reduction of glucagon secretion or action in humans.
Integrated on-chip inductors using magnetic material (invited)
Authors: Gardner Donald S. , Schrom Gerhard , Hazucha Peter , Paillet Fabrice , Karnik Tanay , Borkar Shekhar , Hallstein Roy , Dambrauskas Tony , Hill Charles , Linde Clark , Worwag Wojciech , Baresel Robert , Muthukumar Sriram
Published: April 2008

On-chip inductors with magnetic material are integrated into both advanced 130 and 90nm complementary metal-oxide semiconductor processes. The inductors use aluminum or copper metallization and amorphous CoZrTa magnetic material. Increases in inductance of up to 28 times corresponding to inductance densities of up to 1.3 μH/mm2 were obtained, significantly greater than prior values for on-chip inductors. With such improvements, the effects of eddy currents, skin effect, and proximity effect become clearly visible at higher frequencies. The CoZrTa was chosen for its good combination of high permeability, good high-temperature stability (>250°C), high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatibility with silicon technology. The CoZrTa alloy can operate at frequencies up to 9.8GHz, but trade-offs exist between frequency, inductance, and quality factor. The effects of increasing the magnetic thickness on the permeability spectra were measured and modeled. The inductors use magnetic vias and elongated structures to take advantage of the uniaxial magnetic anisotropy. Techniques are presented to extract a sheet inductance and examine the effects of magnetic vias on the inductors. The inductors with thick copper and thicker magnetic films have resistances as low as 0.04 Ω, and quality factors up to 8 at frequencies as low as 40 MHz.
Ferromagnetic resonance of ultrathin Co∕Ag superlattices on Si(111)
Authors: Kakazei G. N. , Martin P. P. , Ruiz A. , Varela M. , Alonso M. , Paz E. , Palomares F. J. , Cebollada F. , Rubinger R. M. , Carmo M. C. , Sobolev N. A.
Published: April 2008

Ferromagnetic resonance (FMR) is used to probe the magnetic properties of Co∕Ag superlattices (SLs) with ultrathin Co layers (2–6Å). Different series of 5×[Ag∕Co] multilayers have been grown by molecular beam epitaxy on Si(111) substrates, monitoring the growth by reflection high energy electron diffraction. Cross-section transmission electron microscopy confirms the growth of local areas with the designed SL periodicity, a sharp compositional modulation, well defined Ag–Co interfaces, and a perfect fcc (111) stacking. FMR spectra have been recorded at various polar angles in the 0°–90° range. A single and extremely broad resonance peak is observed in all cases. While SLs with Ag layers thinner than 10Å exhibit similar values of the perpendicular anisotropy, a clear reduction is observed for samples with Ag layers about 14Å thick. Possible causes for this change are discussed.
The torque ripple reduction of a concentrated winding synchronous reluctance motor according to stator and rotor structure variations using response surface methodology
Authors: Choi Yun-Chul , Lee Jung-Ho , Hong Jung Pyo
Published: April 2008

This paper deals with optimum design criteria to minimize the torque ripple of a concentrated winding synchronous reluctance motor (SynRM) using response surface methodology (RSM). The feasibility of using RSM with the finite element method in practical engineering problem is investigated with computational examples and comparison between the fitted response and the results obtained from an analytical solution according to the design variables of stator and rotor in concentrated winding SynRM (6slot).
Branching laws for endomorphisms of fermions and the Cuntz algebra O2
Authors: Abe Mitsuo , Kawamura Katsunori
Published: April 2008

Fermions are expressible in terms of polynomials in the canonical generators and their ∗-conjugates of the Cuntz algebra O2. A canonical construction of such fermions is called a recursive fermion system. In this paper, various unital ∗-endomorphisms of the algebra of fermions are explicitly constructed by using the recursive fermion system. We investigate how such endomorphisms transform the Fock representation, the infinite wedge representation, and their duals.
Diffusion at the liquid-vapor interface
Authors: Duque Daniel , Tarazona Pedro , Chacón Enrique
Published: April 2008

Recently, the intrinsic sampling method has been developed in order to obtain, from molecular simulations, the intrinsic structure of the liquid-vapor interface that is presupposed in the classical capillary wave theory. Our purpose here is to study dynamical processes at the liquid-vapor interface, since this method allows tracking down and analyzing the movement of surface molecules, thus providing, with great accuracy, dynamical information on molecules that are “at” the interface. We present results for the coefficients for diffusion parallel and perpendicular to the liquid-vapor interface of the Lennard-Jones fluid, as well as other time and length parameters that characterize the diffusion process in this system. We also obtain statistics of permanence and residence time. The generality of our results is tested by varying the system size and the temperature; for the latter case, an existing model for alkali metals is also considered. Our main conclusion is that, even if diffusion coefficients can still be computed, the turnover processes, by which molecules enter and leave the intrinsic surface, are as important as diffusion. For example, the typical time required for a molecule to traverse a molecular diameter is very similar to its residence time at the surface.
Spontaneous L-mode plasma rotation scaling in the TCV tokamak
Authors: Duval B. P. , Bortolon A. , Karpushov A. , Pitts R. A. , Pochelon A. , Sauter O. , Scarabosio A. , Turri G. ,   the TCV Team
Published: April 2008

Predicting intrinsic plasma rotation and its shear, which often help stabilize plasma instabilities affecting plasma performance, is important for prospective fusion grade devices. Although rotation in ITER-like scenarios has been extrapolated from measured experimental plasma rotation data, little is understood about the underlying mechanisms governing either the generation or dissipation of momentum in a tokamak plasma. This paper reports on studies of intrinsic toroidal and poloidal plasma rotation from charge exchange spectroscopy using a low power diagnostic beam on the TCV tokamak [Tonetti et al., in Proceedings of the Symposium on Fusion Technology (1991), p. 587] that drives negligible toroidal velocity. In TCV, plasma behavior can be separated by the core and edge regions. In limited configurations, the core rotates in the counter-current direction and can reverse to the co-current direction with a <10% increase in the plasma density. This is different for diverted configurations where the core rotates in the co-current direction reversing to the counter-current direction at higher plasma densities. For all these situations, core toroidal momentum is strongly transported by plasma sawteeth oscillations. In contrast, the toroidal edge rotation is close to stationary for limited discharges but evolves with plasma density for diverted configurations. Theoretical models that predict a change in momentum transport from turbulence have previously been suggested to provide a mechanism that might explain these phenomena. In this paper, mode activity that changes at the toroidal velocity reversal, is identified as a new possible candidate. In the absence of an available model that can explain these basic phenomena, this paper presents observations and, where possible, scaling of the rotation profiles with some of the major plasma parameters such as current, density and shape to guide the development of a physics model for use in improving the extrapolation of the rotation amplitude and profiles to future devices.
Optimization methods for finding minimum energy paths
Authors: Sheppard Daniel , Terrell Rye , Henkelman Graeme
Published: April 2008

A comparison of chain-of-states based methods for finding minimum energy pathways (MEPs) is presented. In each method, a set of images along an initial pathway between two local minima is relaxed to find a MEP. We compare the nudged elastic band (NEB), doubly nudged elastic band, string, and simplified string methods, each with a set of commonly used optimizers. Our results show that the NEB and string methods are essentially equivalent and the most efficient methods for finding MEPs when coupled with a suitable optimizer. The most efficient optimizer was found to be a form of the limited-memory Broyden-Fletcher-Goldfarb-Shanno method in which the approximate inverse Hessian is constructed globally for all images along the path. The use of a climbing-image allows for finding the saddle point while representing the MEP with as few images as possible. If a highly accurate MEP is desired, it is found to be more efficient to descend from the saddle to the minima than to use a chain-of-states method with many images. Our results are based on a pairwise Morse potential to model rearrangements of a heptamer island on Pt(111), and plane-wave based density functional theory to model a rollover diffusion mechanism of a Pd tetramer on MgO(100) and dissociative adsorption and diffusion of oxygen on Au(111).
Treatment of charged solutes in three-dimensional integral equation theory
Authors: Kloss Thomas , Kast Stefan M.
Published: April 2008

Periodicity artifacts, which occur within three-dimensional reference interaction site model integral equation theory for net-charged solute systems, are analyzed and corrected by means of a renormalization procedure for long range interactions. The method is formulated for solute-solvent and solute-solute variants of the theory. Both dielectric and electrolyte solvents are considered. Comparison of the results for atomic ions with one-dimensional reference computations shows that structural and thermodynamic artifacts are efficiently removed.
Fabrication of fully epitaxial Co2MnSi∕MgO∕Co2MnSi magnetic tunnel junctions
Authors: Ishikawa Takayuki , Hakamata Shinya , Matsuda Ken-ichi , Uemura Tetsuya , Yamamoto Masafumi
Published: April 2008

Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with full-Heusler alloy Co2MnSi thin films as both lower and upper electrodes and with a MgO tunnel barrier. The fabricated MTJs showed clear exchange-biased tunnel magnetoresistance (TMR) characteristics with high TMR ratios of 179% at room temperature (RT) and 683% at 4.2K. In addition, the TMR ratio exhibited oscillations as a function of the MgO tunnel barrier thickness (tMgO) at RT, having a period of 0.28nm, for tMgO ranging from 1.8to3.0nm.
Steering dissociation of Br2 molecules with two femtosecond pulses via wave packet interference
Authors: Han Yong-Chang , Yuan Kai-Jun , Hu Wen-Hui , Yan Tian-Min , Cong Shu-Lin
Published: April 2008

The dissociation dynamics of Br2 molecules induced by two femtosecond pump pulses are studied based on the calculation of time-dependent quantum wave packet. Perpendicular transition from XΣg+1 to AΠ1u+3 and Π1u+1 and parallel transition from XΣg+1 to BΠ0u+3, involving two product channels Br (P3∕22)+Br (P3∕22) and Br (P3∕22)+Br* (P1∕22), respectively, are taken into account. Two pump pulses create dissociating wave packets interfering with each other. By varying laser parameters, the interference of dissociating wave packets can be controlled, and the dissociation probabilities of Br2 molecules on the three excited states can be changed to different degrees. The branching ratio of Br*∕(Br+Br*) is calculated as a function of pulse delay time and phase difference.
Radio frequency resonator structure and diagnostic measurements for a laboratory simulation of Auroral Kilometric Radiation
Authors: Ronald K. , Speirs D. C. , McConville S. L. , Phelps A. D. R. , Robertson C. W. , Whyte C. G. , He W. , Gillespie K. M. , Cross A. W. , Bingham R.
Published: April 2008

Auroral Kilometric Radiation is emitted from regions of depleted plasma density in the Earth’s polar magnetosphere. The radiation frequency is close to the local electron cyclotron frequency, polarized in the X-mode with an efficiency of ∼1%, with power up to 1GW. Kinetic analysis of the instability in the descending auroral flux indicated that the phenomena scaled with the cyclotron frequency. Therefore, an experimental reproduction of the auroral geometry has been created scaled to laboratory dimensions by raising the radiation frequency to the microwave range. The experiment transports a 75–85keV electron beam through a region of increasing magnetic flux density, with a mirror ratio of up to 30. The experiments measured the mode, spectrum, power, and conversion efficiency of the emitted radiation as a function of the mirror ratio in two resonance regimes, with frequencies of 4.42 and 11.7GHz. The microwave diagnostics and measurements will be presented in this paper.
Solid-state NMR covariance of homonuclear correlation spectra
Authors: Hu Bingwen , Amoureux Jean-Paul , Trebosc Julien , Deschamps Michael , Tricot Gregory
Published: April 2008

Direct covariance NMR spectroscopy, which does not involve a Fourier transformation along the indirect dimension, is demonstrated to obtain homonuclear correlation two-dimensional (2D) spectra in the solid state. In contrast to the usual 2D Fourier transform (2D-FT) NMR, in a 2D covariance (2D-Cov) spectrum the spectral resolution in the indirect dimension is determined by the resolution along the detection dimension, thereby largely reducing the time-consuming indirect sampling requirement. The covariance method does not need any separate phase correction or apodization along the indirect dimension because it uses those applied in the detection dimension. We compare in detail the specifications obtained with 2D-FT and 2D-Cov, for narrow and broad resonances. The efficiency of the covariance data treatment is demonstrated in organic and inorganic samples that are both well crystallized and amorphous, for spin −1∕2 nuclei with C13, Si29, and P31 through-space or through-bond homonuclear 2D correlation spectra. In all cases, the experimental time has been reduced by at least a factor of 10, without any loss of resolution and signal to noise ratio, with respect to what is necessary with the 2D-FT NMR. According to this method, we have been able to study the silicate network of glasses by 2D NMR within reasonable experimental time despite the very long relaxation time of the Si29 nucleus. The main limitation of the 2D-Cov data treatment is related to the introduction of autocorrelated peaks onto the diagonal, which does not represent any actual connectivity.
Three-dimensional effects in shock-cylinder interactions
Authors: Weirs V. Gregory , Dupont Todd , Plewa Tomasz
Published: April 2008

The shock-cylinder interaction is important for understanding the mixing of fluids by impulsively accelerated material interfaces. The flowfield development is highly sensitive to the initial conditions, which can be difficult to fully characterize in experimental facilities. In this work, simulations based on experimental measurements are used to model the initial flowfield at the Los Alamos shocktube facility. While nominally two-dimensional, our simulations show the initial column has significant axial variation. These numerical solutions are then used as the initial conditions for three-dimensional simulations of the shock-cylinder interaction. A genuinely three-dimensional flowfield develops as a consequence of the initial, axial variation of the cylinder.
High-intensity laser-plasma interactions in the refluxing limit
Authors: Nilson P. M. , Theobald W. , Myatt J. , Stoeckl C. , Storm M. , Gotchev O. V. , Zuegel J. D. , Betti R. , Meyerhofer D. D. , Sangster T. C.
Published: April 2008

The interaction of intense laser pulses (5×1016W∕cm2<I<2×1019W∕cm2) with small-volume copper targets (20×20×2μm3<V<500×500×50μm3) is described. Electron refluxing causes Kα yields to be independent of laser intensity at I>1018W∕cm2, where the target is heated to less than 100eV. As target volume is reduced, efficient energy transfer by the refluxing electrons heats the targets to hundreds of eV. This affects L→K and M→K electronic transitions during ion de-excitation that probe the bulk plasma conditions during this rapid isochoric heating phase. Comparison of measured Kα yields in the cold-material limit with a Kα production model, and measured Kβ∕Kα variations with numerical target-heating calculations, provides a robust method for inferring the fast-electron energy content. Bulk electron temperatures of at least 200eV are inferred for the smallest mass targets.
Uniform and enhanced field emission from chromium oxide coated carbon nanosheets
Authors: Hou Kun , Outlaw Ronald A. , Wang Sigen , Zhu Mingyao , Quinlan Ronald A. , Manos Dennis M. , Kordesch Martin E. , Arp Uwe , Holloway Brian C.
Published: April 2008

Carbon nanosheets, a two-dimensional carbon nanostructure, are promising electron cathode materials for applications in vacuum microelectronic devices. This letter demonstrates a simple approach to improve the spatial emission uniformity of carbon nanosheets by coating them with a chromium oxide thin film. Photoelectron emission microscopy observations and in situ field emission tests revealed that chromium oxide coated carbon nanosheets not only have spatial uniformity but also have coating thickness dependent field emission properties. For example, a coating thickness of ∼1.5nm gave a substantially greater field emission than as-grown nanosheets or other thickness coatings.
Dynamics and generation mechanisms of mesoscale structures in tokamak edge plasmas
Authors: Krasheninnikov S. I. , Smolyakov A. I.
Published: April 2008

Intermittent convective-like plasma transport associated with mesoscale coherent structures extended along the magnetic field lines (“blobs”) is often dominant at the edge of tokamaks, stellarators, and linear devices. Blobs can travel a large distance toward the wall (∼10 cm and larger) and strongly enhance both edge plasma energy and particle transport and plasma-wall interactions. The dynamics of blobs and blob generation mechanisms are discussed in this paper.
Time-correlated force production measurements of the dielectric barrier discharge plasma aerodynamic actuator
Authors: Enloe C. L. , McHarg M. G. , McLaughlin T. E.
Published: April 2008

An atmospheric-pressure dielectric barrier discharge (DBD) plasma, operated as a surface-mode discharge with a single encapsulated electrode and an asymmetric electrode alignment, is known to couple momentum into the surrounding neutral fluid and through this coupling has shown considerable promise as an aerodynamic flow control device. Several different models, often with conflicting explanations, have been offered to explain the process of this momentum coupling. The DBD is known to proceed in two stages during the discharge cycle, one on the positive-going portion of the applied ac high-voltage waveform and the other on the negative-going portion. By using the actuator to drive a second-order mechanical system, we show here that the great majority (97%) of the momentum coupling occurs during the negative-going portion of the discharge cycle and we relate this behavior to dramatic differences in the structure of the discharge revealed with high-speed photography. This information is critical in evaluating descriptions of the momentum-coupling processes in the plasma.