bluuebunny/crossref_metadata_2025 huggingface dataset:
Customised acrylic nasal stents following recanalisation of modified Young's procedure
Authors: Pavithran P , Pujary K , Mahesh S G , Parul P , Aziz B
Published: April 2010

Introduction:

Maintaining the patency of the nasal vestibule following recanalisation of a modified Young's procedure can be a difficult task, as restenosis is quite common.

Materials and methods:

Sixteen patients underwent recanalisation of a modified Young's procedure, between January 2005 and December 2007, in the ENT – head and neck surgery department of a tertiary centre. Three different stent types were used following recanalisation: silicone suction tube tips, dental wax plate stents and customised acrylic stents.

Results:

The silicone suction tube stents prevented restenosis. They were visible in the post-operative period, and there appeared to be some blunting of the nasal valve region, with no functional impairment. Dental wax plates had a high rate of restenosis and were uncomfortable and unsightly. The customised acrylic stents were more acceptable in the post-operative period, and enabled nasal valve angulation to be maintained.

Conclusion:

The customised acrylic stent described was a superior alternative to such stenting methods as repeated packing, silicone suction tubes and dental wax plates, following recanalisation of a modified Young's procedure.
Potential impacts of tourist developments in St Lucia on the Endangered White-breasted ThrasherRamphocinclus brachyurus
Authors: YOUNG RICHARD P. , JN BAPTISTE TIMOTHEUS , DORNELLY ALWIN , TEMPLE HELEN , WHITEHEAD HESTER , YOUNG H. GLYN , MORTON MATTHEW N.
Published: April 2010

A rapidly developing tourism industry, concentrated in coastal regions, is suspected to seriously impact upon biodiversity in the global conservation priority of the insular Caribbean. In St Lucia, construction of tourism infrastructure in the coastal dry forest threatens the Endangered White-breasted ThrasherRamphocinclus brachyurus. Long-term protection of habitat is vital, but design of such conservation action is constrained by lack of data on the species' distribution and population responses to habitat change and fragmentation. Distance sampling surveys were conducted in 2006 and 2007 to estimate numbers and map the distribution of the two remaining sub-populations. White-breasted Thrashers in St Lucia were estimated to number around 1,200 individuals, with roughly 1,050 birds occupying just over 600 ha of dry forest in the Mandelé area. We demonstrate that tourist development companies will likely soon own land constituting around 40% of the species' extent of occurrence on St Lucia, and nearly 35% globally, and that ongoing and planned tourist developments threaten around one third of the St Lucian White-breasted Thrasher population. Given the size of these potential impacts, it is vital that patches of dry forest to the west and north of a development site in the Mandelé area are safeguarded. These sites support White-breasted Thrashers at high density and are contiguous with an existing forest reserve. Other important conservation measures include preserving stands of connected mature dry and riparian forest inside the tourist development sites, alongside invasive predator control.
What Might Bring Regular Order Back to the House?
Authors: Green Matthew , Burns Daniel
Published: April 2010

It is not hard to find critics of how the U.S. Congress operates today. Two of the most prominent, Thomas Mann and Norman Ornstein, have bemoaned in particular Congress's failure to follow “regular order,” which in their 2006 bookThe Broken Branchthey describe as a legislative process that incorporates “discussion, debate, negotiation, and compromise” (Mann and Ornstein 2006, 170).
Blackberries, Tweets, and YouTube: Technology and the Future of Communicating with Congress
Authors: Shogan Colleen J.
Published: April 2010

From the establishment of the United States Postal Service and the invention of the telegram, to the introduction of C-SPAN and the explosion of the Internet, the development of new communication technologies has always affected the functioning of Congress. Not surprisingly, recent innovations such as e-mail and social networking have spurred Congress to alter the way it operates as an institution, and rethink the manner in which it engages the public. In this brief examination, I discuss recent changes in congressional behavior and practices due to technological innovation, specifically the proliferation of social networking Web sites. Then, I cautiously predict future trends in the use of social networking and related technologies as they become more integrated in congressional offices and increase the capacity for more robust internal and constituent communications over time.
Stump Speeches and Road Trips: The Impact of State Campaign Appearances in Presidential Elections
Authors: Hill Jeffrey S. , Rodriquez Elaine , Wooden Amanda E.
Published: April 2010

Travel, stump speeches, and pressing-the-flesh make up a large part of any presidential electoral campaign. Obviously, candidates feel that their appearances are important, as they make hundreds of appearances between Labor Day and Election Day. But are they right? Well over 100 million people cast ballots in November, but only the tiniest fraction of voters meets or catches a glimpse of either of the candidates. Do candidate appearances and contact sway voters in some way? In this article, we use changes in weekly state tracking polls to determine the impact of candidate appearances in battleground and non-battleground states. Using polling data from the 2000, 2004, and 2008 elections, we find that campaign appearances can change a candidate's polling percentages, and that the impact varies by candidate and location (battleground state, safe Democratic state, or safe Republican state). We also find that the selection of a vice-presidential candidate is important, because of this candidate's ability to campaign effectively.
Political Theorists
Authors: Moore Matthew J.
Published: April 2010

The question of the role of normative or historical political theory within the broader discipline of political science has been controversial at least since the founding of the American Political Science Association (see Gunnell 2006 for a brief overview). Perhaps it goes without saying that during that same period people who think of themselves as engaged in political theory have disagreed among themselves about the core concerns of the field, the appropriate kinds of graduate training, the relative value of various authors and texts, and, of course, about theory's role within political science.
Theory Survey or Survey Theory?
Authors: Dean Jodi
Published: April 2010

Matthew Moore's survey of political theorists in U.S. American colleges and universities is an impressive contribution to political science (Moore 2010). It is the first such survey of political theory as a subfield, the response rate is very high, and the answers to the survey questions provide new information about how political theorists look when compared to political scientists overall. We are roughly the same age, for example, and are slightly more likely to be female. The survey also gives us a picture of political theorists' conditions of employment: about half of us get jobs in the first year upon receiving our Ph.D.s; most of us teach at schools that range from 1,000 to 10,000 students; most of us are not at Ph.D.-granting institutions.
Political Theory Today: Who's Teaching What to Whom? Some Reflections
Authors: Ackelsberg Martha
Published: April 2010

Matthew Moore's survey and analysis reflect an enormous amount of work, for which all of us who study or teach political theory should be grateful. They offer us a fascinating snapshot of who is teaching political theory today, of how they understand and think about what they are doing, and of how they think others think about theory. Much that is included in his analysis (and especially in the longer paper from which the report here is selected) is well worth further study and debate, as it opens a door to the ways political science in general (and not theory alone) is being taught around the country: what political scientists think they are doing when they/we teach their material, what training they/we have, and even what modal teaching loads are.
Gender Equality in the Academy: The Pipeline Problem
Authors: Monroe Kristen Renwick , Chiu William F.
Published: April 2010

As part of the ongoing work by the Committee on the Status of Women in the Profession (CSWP), we offer an empirical analysis of the pipeline problem in academia. The image of a pipeline is a commonly advanced explanation for persistent discrimination that suggests that gender inequality will decline once there are sufficient numbers of qualified women in the hiring pool. The CSWP believes that it is important to ask whether this phenomenon is actually occurring, because the implication is that we can explain inequality as a function of insufficient numbers of trained women in the pool, rather than as a result of ongoing discrimination that requires alternate remedies. Data from the American Association of University Professors suggests that merely increasing the pool of qualified women has not led to a commensurate number of women rising to the top in academia. Women are still ending up in lower paid jobs, and they continue to earn less than men in comparable positions. More aggressive policies to end discrimination are required.
Aquí Estamos? A Survey of Latino Portrayal in Introductory U.S. Government and Politics Textbooks
Authors: Monforti Jessica Lavariega , McGlynn Adam
Published: April 2010

The breadth of material covered in introductory U.S. government and politics survey courses creates a situation in which the textbooks used may serve as the primary source of information students receive about the country's political system. At the same time, their content represents a conscious choice by the authors, editors, and publishers of these textbooks regarding what topics and content are necessary and worthy of publication, which socializes students to accept particular viewpoints of the formation and operation of the U.S. government. Oftentimes, the information presented in textbooks across subdisciplines ignores the political experiences and influence of racial, ethnic, and other minority groups. We test this premise by engaging in a study of 29 introductory U.S. government and politics textbooks to assess the level of coverage and treatment of Latinos/as, the fastest growing racial/ethnic group in the country. We find that the discussion of Latinos in these textbooks is incredibly brief and often limited to the civil rights chapters. Furthermore, Latinos are primarily mentioned in the discussion of immigration, while their overall contributions to the political development of the United States are largely ignored.
America's Financial Future, Civic Engagement, and the Public University: Editor's Introduction
Authors: Galatas Steven
Published: April 2010

In July of 2008, the American Association of State Colleges and Universities (AACSU) selected a handful of public universities to begin an initiative to promote civic engagement among students, faculty, and wider communities regarding the issues of the national debt and budget deficit issues. Named the America's Future Initiative, the project developed pilot programs on university campuses as part of AASCU's American Democracy Project, an effort to promote civic engagement on America's public university campuses. Moreover, the initiative linked the participating universities to Public Agenda, a nonprofit, nonpartisan organization aimed at raising awareness about a number of public policy issues. The universities selected to participate in the America's Future Initiative varied tremendously in terms of geographic location and student enrollment.
Standardizing Citizenship: The Potential Influence of State Curriculum Standards on the Civic Development of Adolescents
Authors: Journell Wayne
Published: April 2010

The rise of state-mandated standards in public education have allowed legislators to answer the question of what constitutes a proper civic education, a debate that has existed in the United States since the turn of the twentieth century. Through the content they employ in their standards, states may indirectly influence the type of citizenship education students receive in the classroom. The present study focuses on the Virginia Standards of Learning for two courses, civics and economics and U.S. and Virginia government, which are commonly taught to eighth graders and high school seniors, respectively. A content analysis of the essential knowledge found in the standards for these courses categorizes instructional content into seven forms of citizenship: civic republicanism, character education, deliberative, social justice, participatory, transnational, and cosmopolitan. Although the results are specific to the Virginia Standards of Learning, the nature of how citizenship is portrayed within the standards may transfer to other states with similar forms of standards-based education within their social studies curricula.
A Pilgrimage to the Disneyland of Faith
Authors: Crowe Justin , McWilliams Susan , Beienburg Sean
Published: April 2010

As part of a course considering “American Democracy in Theory and Practice,” we took 36 students to Rick Warren's Saddleback Church in Lake Forest, California. During that visit, students observed a community that seeks self-sufficiency and yet proves to be simultaneously responsive to and reflective of American democracy more broadly. Specifically, in a few short hours, they were able to see the virtues of civic association, the difficulty of respecting individualism in large-scale polities, the influence of regional identity, and the two-way interaction between politics and culture—all themes that featured prominently in our course. We offer this reflection to suggest the pedagogical benefits of showing the tensions of American politics in action and to encourage colleagues to consider integrating similar ventures into their own courses.
Rock and Roll Will Never Die: Using Music to Engage Students in the Study of Political Science
Authors: Soper Christopher
Published: April 2010

Popular music is ubiquitous in the lives of our students, music is used by politicians at virtually every one of their campaign events, and musicians are increasingly active in politics, but music has never been considered as a pedagogical tool in teaching political science classes. This article describes the use of music in an introduction to American politics class. I argue that playing music in class can increase student interest, reinforce important concepts, and actively engage the students in the learning process. Finally, using popular culture connects meaningfully with the way that many of our undergraduate students are experiencing politics.
ALICE FLEETWOOD BARTEE
Authors: Connor George E.
Published: April 2010

Dr. Alice Fleetwood Bartee served on the faculty of the Department of Political Science at Missouri State University from 1973 until her retirement in 2008. During her 35 years of service, she compiled an outstanding record in the areas of teaching, research, and service. I was privileged to be her colleague for almost 20 years. A year and half ago, faculty, administrators, students, and members of the community gathered to celebrate her legacy at a touching retirement dinner. A few weeks ago, many of those same people came together again to celebrate her life, a life that was truly remarkable.
ARTHUR KALLEBERG
Authors: Yarwood Dean L. , Wood David M. , Leuthold David A. , Dohm Richard R.
Published: April 2010

Our friend and colleague, Arthur Kalleberg, passed away peacefully on October 3, 2009, at the age of 78. He had been in retirement for the past 15 years. He was born in 1931 in Minneapolis and spent his youth there. After serving in the Navy during the Korean Conflict, he attended the University of Minnesota, where he received his BA (with honors), MA, and Ph.D.
STANLEY KELLEY, JR.
Authors: Bartels Larry M. , Geer John G. , Greenstein Fred I.
Published: April 2010

Stanley Kelley, Jr., a creative scholar and legendary teacher at Princeton University, died on January 17, 2010, at the age of 83.
LEONARD S. ROBINS
Authors: Holt Robert T.
Published: April 2010

Dr. Leonard S. Robins died on November 9, 2009, at the age of 71, from complications following major surgery. Lenny, as he was known to his friends and colleagues, received his undergraduate degree in political science at the University of Minnesota and went on to study public affairs at the University of Michigan. After several years working in public service and research organizations, he returned to the University of Minnesota for his Ph.D., which was awarded in 1975. In 1982, he took a position in public administration at Roosevelt University in Chicago, where he stayed until his retirement in 2003.
ROBERT E. WARD
Authors: Gerson Ralph J.
Published: April 2010

Professor Emeritus Robert E. Ward of Stanford University died at the age of 93 on December 7, 2009, in Portola Valley, California. Dr. Ward was a professor of political science and the first director of the Center for Research in International Studies at Stanford University from 1973 to 1987. He was also a senior fellow of the Hoover Institution. Dr. Ward received his B.A. degree from Stanford University in 1936 and his Ph.D. from the University of California (Berkeley) in 1948. During World War II, he served in U.S. Naval Intelligence, receiving the Legion of Merit award. From 1948 to 1973, Dr. Ward was on the faculty of the University of Michigan. Professor Ward joined the Stanford faculty in 1973, serving as a professor of political science from 1973 to 1987 and Director of the Center for Japanese Studies from 1965 to 1968 and 1971 to 1973.
106th Annual Meeting in Washington, DC, September 2–5, 2010
Authors: Pewett Melissa
Published: April 2010

For over one hundred years, APSA's Annual Meeting and Exhibition has provided scholars a unique opportunity to share research, present papers, and network with colleagues. And although each meeting has provided a distinct and worthwhile experience, the 106th Annual Meeting and Exhibition promises to bring one of the most stirring meeting programs yet. Aptly convening in the nation's capital, Washington, DC, more than 7,000 attendees will discuss the latest political science research and theory as it relates to the theme of “hard times” facing the world economy. Program chairs Lisa Martin, University of Wisconsin–Madison, and Andrea Campbell, Massachusetts Institute of Technology, developed a theme that raises questions across many areas of specialization. With more than eight hundred panels organized by 50 thematic divisions, 60 related groups, APSA committees, and presidential task forces, these questions will be explored over the course of the four day event.
Report of the Editors of the American Political Science Review, 2008–2009
Authors: Rogowski Ronald
Published: April 2010

We report here on the journal's operations during the year from July 1, 2008, to June 30, 2009. In doing so, we want first to express our thanks to the APSA: its staff, Council, and Publications Committee, both for good advice and for important material support. The impact of both is documented, albeit only partially, in the following article. The APSR Editorial Board and its Executive Committee have also been invaluable, and we have benefited particularly from the concentrated counsel that a subcommittee provided during a two-day site visit to UCLA in July. Editorial Board members have also given unstintingly of their time to serve as guest editors on UCLA-connected submissions that might otherwise raise conflicts of interest. We owe very special debts of gratitude to our Senior Editor, Joseph Riser, whose serene and wise disposition seems never to falter; our graduate editorial assistants (EAs), Megan Gallagher, Diana Ichpekova, Rebekah Sterling, and Matt Spence; two of our original co-editors, Kathleen Bawn and Michael Chwe, who gave extraordinarily dedicated service but decided to leave the group effective July 1, 2009; and Gary Cox (UCSD) and Arthur Lupia (Michigan), who agreed to join our weekly meetings via videoconference—in Gary's case, for the long term; in Skip's, temporarily. Finally, we thank the authors of the nearly 700 papers submitted to us and the over 2,000 referees who gave, unremunerated and anonymously as always, their astute and often admirably detailed counsel.
Susanne Hoeber Rudolph: Remarks on Receiving the “Grain of Sand” Award
Authors: Rudolph Susanne Hoeber
Published: April 2010

I'm happy to be the recipient of an award recognizing the work of scholars who deploy literary and experiential resources in pursuit of meaning. And I am delighted that there is a conference-related group institutionalizing this honor. On this auspicious occasion, I thought I would offer a few remarks about my current work.
The Many Seats at the Round Table of Knowledge: Lloyd I. Rudolph Remarks on Receiving the Grain of Sand Award
Authors: Rudolph Lloyd I.
Published: April 2010

The many years Susanne Rudolph and I spent editing and interpreting Amar Singh's diary for our book, Reversing the Gaze, led us to reflect on the multiplicity of forms of knowledge, starting with Amar Singh's first-person, subjective knowledge and extending to the situational truths of Gandhi's satyagrahas.
Diversity among different populations of a locally common rice (Oryza sativa L.) landrace from north-western Indian Himalayas
Authors: Kumar S. , Pandey A. , Bisht I. S. , Bhat K. V. , Mehta P. S.
Published: April 2010

Genetic structure of five populations of a locally common rice (Oryza sativa L.) landrace Jaulia from parts of Uttarakhand state of India was studied using sequence tagged microsatellite site (STMS) markers. Of these, four populations were on-farm managed, assembled from different niche environments, and one population was conserved ex situ and represented static conservation. The 16 STMS primer pairs fully differentiated the inter- and intrapopulation diversity. A total of 72 alleles were recorded with a mean of 4.5 alleles per locus. Population wise, the total number of alleles ranged from 21 to 41, with maximum number of alleles for population IC 548358 and minimum number of alleles for population IC 100051 representing static conservation. A greater number of alleles specific to populations under farmer management could be recorded. Changes in yield parameters also seemed to be affected under farmer management besides other environmental adaptations for qualitative morphological characters. The marker diversity using STMS primer pairs indicates the genetic differentiation among populations resulting from joint effects of several evolutionary forces operating within the historical and biological context of the crop landrace. The variations in adaptations, on the other hand, indicate the degree to which populations are adapted to their environments and their potential for continued performance or as donors of characters in plant breeding. Both biotic and abiotic aspects of the environment are involved.
GaN for space application: almost ready for flight
Authors: Muraro Jean-Luc , Nicolas Guillaume , Nhut Do Minh , Forestier Stéphane , Rochette Stéphane , Vendier Olivier , Langrez Dominique , Cazaux Jean-Louis , Feudale Marziale
Published: April 2010

On the last years, gallium nitride (GaN) technology has made a remarked breakthrough in the world of microwave electronics. Power transistors are now available. How this GaN technology would impact space-borne units is now a priority concern. Although the power capability of GaN technology is the first obvious profit, GaN could also be used for other applications like low noise amplifiers, mixers, and probably more. The high sustainable temperature of GaN transistors is most striking advantage for in-flight use. This is connected to packaging design which is also experiencing a lot of activities and quick progresses. Of course, space application is dependent upon the full demonstration of reliability and this constitutes another field of investigation. Finally, after 8 years of GaN studies, experimental results are presented: they open wide the road a revolution inside space-borne electronics: the rise of GaN.
Multiple overshoot and rebound of a bursty bulk flow
Authors: Panov E. V. , Nakamura R. , Baumjohann W. , Angelopoulos V. , Petrukovich A. A. , Retinò A. , Volwerk M. , Takada T. , Glassmeier K.‐H. , McFadden J. P. , Larson D.
Published: April 2010

Chen and Wolf (1999) used a thin‐filament theory to construct a 2D model of a bursty bulk flow (BBF) motion inside the plasma sheet. The modeling revealed that the low‐entropy filament overshoots its equilibrium position and executes a heavily damped oscillation about that position. In this letter we demonstrate, for the first time, the multiple overshoot and rebound of a BBF observed by the five THEMIS probes on 17 March 2008 just after 10:22 UT. We found that the BBF oscillatory braking was accompanied by interlaced enhancements and depletions of radial pressure gradients. The earthward and tailward flow bursts caused formation of vortices with opposite sense of rotation.
A sensitivity study of the Enceladus torus
Authors: Fleshman B. L. , Delamere P. A. , Bagenal F.
Published: April 2010

We have developed a homogeneous model of physical chemistry to investigate the neutral‐dominated, water‐based Enceladus torus. Electrons are treated as the summation of two isotropic Maxwellian distributions: a thermal component and a hot component. The effects of electron impact, electron recombination, charge exchange, and photochemistry are included. The mass source is neutral H2O, and a rigidly corotating magnetosphere introduces energy via pickup of freshly ionized neutrals. A small fraction of energy is also input by Coulomb collisions with a small population (<1%) of suprathermal electrons. Mass and energy are lost due to radial diffusion, escaping fast neutrals produced by charge exchange and recombination, and a small amount of radiative cooling. We explore a constrained parameter space spanned by water source rate, ion radial diffusion, hot electron temperature, and hot electron density. The key findings are as follows: (1) radial transport must take longer than 12 days; (2) water is input at a rate of 100–180 kg s−1; (3) hot electrons have energies between 100 and 250 eV; (4) neutrals dominate ions by a ratio of 40:1 and continue to dominate even when thermal electrons have temperatures as high as ≈5 eV; (5) hot electrons do not exceed 1% of the total electron population within the torus; (6) if hot electrons alone drive the observed longitudinal variation in thermal electron density, then they also drive a significant variation in ion composition.
Proof of concept of regional scale hydrologic simulations at hydrologic resolution utilizing massively parallel computer resources
Authors: Kollet Stefan J. , Maxwell Reed M. , Woodward Carol S. , Smith Steve , Vanderborght Jan , Vereecken Harry , Simmer Clemens
Published: April 2010

We present the results of a unique, parallel scaling study using a 3‐D variably saturated flow problem including land surface processes that ranges from a single processor to a maximum number of 16,384 processors. In the applied finite difference framework and for a fixed problem size per processor, this results in a maximum number of approximately 8 × 109 grid cells (unknowns). Detailed timing information shows that the applied simulation platform ParFlow exhibits excellent parallel efficiency. This study demonstrates that regional scale hydrologic simulations on the order of 103 km2 are feasible at hydrologic resolution (∼100–101 m laterally, 10−2–10−1 m vertically) with reasonable computation times, which has been previously assumed to be an intractable computational problem.
Tearing stability of a multiscale magnetotail current sheet
Authors: Sitnov M. I. , Schindler K.
Published: April 2010

The sufficient stability criterion of the collisionless ion tearing mode in the magnetotail current sheet, which was first obtained by Lembege and Pellat in 1982, is considered. For many conventional 2D current sheet equilibria, this criterion is satisfied within the WKB approximation, which is commonly interpreted as stability of those equilibria with respect to tearing. However, this is not necessarily the case for equilibria with more than two characteristic spatial scales. An example for substantial tearing destabilization of an equilibrium with accumulation of the magnetic flux at the tailward end of a thin current sheet is presented. Similar equilibria are reported in Geotail and THEMIS observations prior to onsets of magnetospheric substorms and dipolarization fronts associated with bursty bulk flows.
The effect of precipitate size on magnetic domain behavior in grain-oriented electrical steels
Authors: Turner Steven , Moses Anthony , Hall Jeremy , Jenkins Keith
Published: April 2010

Precipitates in the form of grain growth inhibitors play an essential role in the production of grain-oriented electrical steels, as they promote the development of Goss texture during secondary recrystallization. However, the presence of precipitates in the final material can have a detrimental effect on loss and permeability, as they impede domain wall motion during the magnetization process. In previous work [K. Jenkins and M. Lindenmo, J. Magn. Magn. Mater. 320, 2423 (2008)], a conventional grain-oriented electrical steel was presented that contained very fine precipitates, which did not damage the bulk magnetic properties. In this article the influence of precipitate size is investigated by comparing local Barkhausen noise measurements and electron backscatter diffraction analysis for a number of grain-oriented electrical steels, which are metallurgically similar except for the size and abundance of precipitates.
Magnetic field simulation of magnetic phase detection sensor for steam generator tube in nuclear power plants
Authors: Ryu Kwon-sang , Son Derac , Park Duck-gun , Kim Yong-il
Published: April 2010

Magnetic phases and defects are partly produced in steam generator tubes by stress and heat, because steam generator tubes in nuclear power plants are used under high temperature, high pressure, and radioactivity. The magnetic phases induce an error in the detection of the defects in steam generator tubes by the conventional eddy current method. So a new method is needed for detecting the magnetic phases in the steam generator tubes. We designed a new U-type yoke which has two kinds of coils and simulated the signal by the magnetic phases and defects in the Inconnel 600 tube.
Effect of Fe partial substitution for Co on the magnetic properties of Y(Co,Fe)5 from first-principles
Authors: Liu X. B. , Altounian Z. , Yue M.
Published: April 2010

The structure, magnetization and exchange interaction in Y(Co1−xFex)5 with x=0 to 0.3 are studied from a first-principles density functional calculation. The cohesive energy calculations indicate that Fe prefers to occupy the 3g site and the lattice constants increase with Fe Content. The magnetization increases from 7.50 to 8.97μB with increasing x from 0 to 0.3 as the calculations show that Fe has a much larger moment (about 2.4μB) than that of Co (about 1.5μB). The exchange parameters between Fe and Co are larger than those for Co–Co and Fe–Fe pairs, and are responsible for the higher TC of Y(Co1−xFex)5. The estimated TC from the calculated exchange parameters increases from about 1065 to 1298 K with increasing x from 0 to 0.3 using a multisublattices mean-field model.
Anisotropic SmCo5 nanoflakes by surfactant-assisted high energy ball milling
Authors: Cui B. Z. , Gabay A. M. , Li W. F. , Marinescu M. , Liu J. F. , Hadjipanayis G. C.
Published: April 2010

Crystallographically anisotropic SmCo5 nanoflakes were fabricated directly by one-step surfactant-assisted high energy ball milling (HEBM) of Sm17Co83 ingot powders for 5 h in heptane and oleic acid (OA) without preprocessing or further annealing. The SmCo5 nanoflakes have a strong [001] out-of-plane texture. The thickness of nanoflakes is in the range of 8–80 nm while their length is 0.5–8 μm. The surfactant OA plays an important role in the formation of SmCo5 nanoflakes. HEBM of SmCo5 ingots in heptane without OA resulted in the formation of magnetically isotropic more or less equiaxed SmCo5 particles with a size of 2–30 μm. Closely packed “kebablike” SmCo5 nanoflakes were formed by HEBM in heptane with 15 wt % OA. HEBM in 150 wt % OA led to well-separated nanoflakes instead of the closely packed kebablike nanostructure. This resulted in the enhanced [001] out-of-plane texture. In-plane transmission electron microscope examination showed that the SmCo5 nanoflakes were composed of grains with sizes in the range of 4–8 nm. Coercivities of about 18.0 kOe were obtained for the anisotropic SmCo5 nanoflakes.
Preparation of PrCo5 bulk magnets using nanograin powders made by surfactant-assisted high energy milling
Authors: Shen Y. , Huang M. Q. , Higgins A. K. , Liu S. , Horwath J. C. , Chen C. H.
Published: April 2010

PrCo 5 nanograin powders used for making bulk magnets were produced by surfactant-assisted high energy ball milling. Using a special compaction technique at 200–525 °C, PrCo5 bulk magnets were successfully prepared using the nanoflake powders. This kind of bulk magnet has a cluster microstructure and is nanocrystalline. The coercivity of the bulk magnet pressed at 200 °C is 5.22 kOe. It is found that the density of the bulk increases with the compaction temperature. Bulk magnet density up to 92% of the theoretical value has been obtained.
Angular dependence of magnetization reversal process in exchange biased epitaxial MnPd/Fe bilayers
Authors: Zhan Qing-feng , Krishnan Kannan M.
Published: April 2010

We investigated the angular dependence of magnetization reversal in epitaxial MnPd/Fe bilayers grown on MgO(001) using combined longitudinal and transverse magneto-optical Kerr effect. Square loops, asymmetrically shaped loops, and double-shifted loops were observed as the field orientation was varied from parallel to perpendicular to the bias direction. Additionally, including the effect of an induced uniaxial anisotropy in the ferromagnetic layers, an improved effective field model was used to interpret the complex angular dependence of the magnetic switching fields. The fitting shows good agreement with the experimental results for the samples with different thicknesses.
Thermal stability of exchange bias nanostructures
Authors: Vallejo-Fernandez G. , Chapman J. N.
Published: April 2010

The thermal stability of an array of square exchange bias nanoelements has been investigated as a function of both the element size and the microstructure of the antiferromagnetic layer. The thermal stability of the nanostructures is measured in terms of their median blocking temperature ⟨TB⟩. It is shown that, generally, ⟨TB⟩ is lower for nanostructures than for the equivalent thin film system. However, the opposite behavior can be observed depending on the measurement conditions, specifically the temperature of measurement and the setting temperature. These results emphasize the importance/limitations of the setting process in exchange bias systems.
Monte Carlo study of a bilayer model for exchange bias using a magnetic glass exhibiting random magnetic anisotropy
Authors: Nguyen Ha M. , Hsiao Pai-Yi , Phan Manh-Huong
Published: April 2010

An extensive Monte Carlo simulation is conducted to investigate a bilayer model of ferromagnet (FM)/amorphous magnet (AM). The random magnetic anisotropy (RMA) of the AM layer is demonstrated to be a new source for positive and negative exchange bias. Our simulated results show usual and unusual dependencies on cooling field, temperature, and RMA strength. These phenomena demand novel appropriate mechanisms to understand. Nevertheless, this FM/AM bilayer model opens a new avenue, other than those of FM/antiferromagnet and FM/spin glass bilayers, for magnetism of the exchange bias and for its applications.
Spin alignment in, and electronic and magnetic properties of small Co–O molecules
Authors: Pozhar Liudmila A. , Mavromichalis Constantine
Published: April 2010

Magnetoelectronic properties of small atomic clusters composed of Co and O atoms have been calculated from the first principles in the Hartree–Fock (HF) approximation. It has been found that the smallest Co–O molecules are “antiferromagnetic” singlets, with uncompensated electron spins localized on Co atoms, while somewhat larger Co–O molecules are “ferromagnetic,” with parallel spins localized on Co atoms. The stretchable O–O bond in such Co–O molecules can accommodate small geometrical changes that may facilitate spin realignment in antiferromagnetic HF singlet Co–O molecules converting such molecules to ferromagnetic HF triplets and pentets. Such spin realignment is energetically favorable and can lead to reconstruction of the antiferromagnet-ferromagnet interface to provide for minimization of the surface energy in exchange-biased core-shell Co/Co–O nanoclusters. In its turn, this interface reconstruction may lead to a loss of exchange bias in small Co–O nanoclusters.
[
Pt
/
Co
]
4
/
NiO
thin film perpendicular magnetic anisotropy dependence on Co layer thickness
Authors: Lin K.-W. , Volobuev V. V. , Guo J.-Y. , Chung S.-H. , Ouyang H. , van Lierop J.
Published: April 2010

We have examined the dependence of the magnetism from perpendicular magnetic anisotropy with Co thickness in [Pt/Co] multilayers coupled to a NiO layer. We measure a perpendicular exchange bias field that changes polarity with Co thickness and find that with 2 nm of Co the perpendicular magnetic anisotropy is no longer present. Further evidence of the change in the Co layers preferred orientation is offered by zero field cooled susceptometry, where the low temperature susceptibility is negative for thin Co layers (0.9–1.2 nm) and becomes positive with increasing Co thickness (1.5–2.0 nm). Thin Co layered films also exhibit a compensation point around 100 K. These results indicate that the Co and NiO interface moments are coupled strongly and that there is competition between Pt/Co and Co/Ni at the film layer interfaces that sets the overall anisotropy from perpendicular and parallel configurations.
Anomalous temperature dependence of training effect in specular spin valve using ultrathin Cr2O3-nano-oxide layer with magnetoelectric effect
Authors: Sawada Kazuya , Shimomura Naoki , Doi Masaaki , Sahashi Masashi
Published: April 2010

Exchange bias from antiferromagnetic (AFM) oxides with a magnetoelectric (ME) effect has been studied for controlling ferromagnetic (FM) magnetizations by an applying electric field. However, thick ME oxides are needed for realizing the electrically controlled exchange biasing. Therefore, in this study the temperature dependencies of the training effect for the Cr2O3-nano-oxide-layer (NOL) are investigated for confirming the ME effect of the Cr2O3-NOL. The anomalous temperature tendencies of system dependent constant for exchange bias and magnetoresistance (MR), κHex and κMR, were observed, which are probably originated from the ME effect of the Cr2O3-NOL because (1) these anomalous temperature tendencies could not be obtained in the CoO-NOL spin valve and (2) the κHex and κMR are defined as the strength of the coupling between FM and AFM spins. It is remarkable result for us to confirm the possibility of the ME effect from the ultrathin Cr2O3 layer (less than 1 nm) because the ME effect was observed in only thick ME materials.
Temperature dependence of the spontaneous remagnetization in Nd60Fe30Al10 and Nd60Fe20Co10Al10 bulk amorphous ferromagnets
Authors: Collocott S. J.
Published: April 2010

Time dependent behavior of the magnetization, i.e., magnetic viscosity, in ferromagnetic materials is well known. Less well known is the phenomenon of spontaneous remagnetization, where following a magnetic history that results in the dc demagnetized state, a ferromagnetic material spontaneously develops a magnetic moment as a function of time. Spontaneous remagnetization behavior of the bulk amorphous ferromagnets Nd60Fe30Al10 and Nd60Fe20Co10Al10 is investigated as a function of temperature from 50 to 400 K. At all temperatures the spontaneous remagnetization, Mspon, follows the relationship Mspon=Sspon ln(t+t0), where Sspon is a measure of the spontaneous remagnetization processes, t is the time, and t0 is a reference time. Sspon is strongly temperature dependent, increasing approximately linearly with temperature from 50 to ≈300 K, where it reaches a peak, before decreasing rapidly. This behavior is similar to that observed for the magnetic viscosity coefficient, S, in ferromagnetic materials.
Magnetic field induced enhancement in thermal conductivity of magnetite nanofluid
Authors: Parekh Kinnari , Lee Hyo Sook
Published: April 2010

Magnetite nanofluid is synthesized using continuous chemical process. Powder x-ray diffraction and transmission electron microscopy show single phase spinel structure with size of 9.83 and 9.9 nm, respectively. Thermal conductivity of magnetite nanofluid has been studied as a function of transverse magnetic field and temperature. We found almost 30% enhancements in thermal conductivity for 4.7% volume fraction under transverse magnetic field. This result is explained on the basis of formation of continuous three-dimensional zipperlike structure of magnetic nanoparticles inside magnetic fluid. The temperature dependent thermal conductivity shows no enhancement in the temperature region of 25–65 °C.
Minimizing oxygen inclusion when electroplating high saturation density CoFe for microelectromechanical system
Authors: Chen Jue , Flick Eva , Gatzen Hans H.
Published: April 2010

Co–Fe alloys with a high saturation flux density Bs are used as soft magnetic materials in various microelectromechanical system applications. The electroplating process to deposit this material was widely researched. This paper describes experimental investigations to optimize the Co–Fe electroplating process. Besides the high saturation flux density Bs and other magnetic properties, mechanical and chemical properties like low film stress and good corrosion resistance also have to be considered. In these experiments, test electrolytes with different additives were used. The main purpose of those additives is to avoid the oxidation of Fe2+ to Fe3+ in the electrolyte to minimize the formation of Fe(OH)3 and its integration in the deposited film. Vibrating sample magnetometer measurements were applied to characterize the magnetic properties. The composition of Fe and Co in the deposited film was determined by energy dispersive x-ray spectroscopy. An electron probe microanalyzer was used to determine the impurities (O, S, and B) in the deposits. The results show different efficiencies of the applied additives improving the plating process.
Chemical synthesis of monodisperse γ-Fe–Ni magnetic nanoparticles with tunable Curie temperatures for self-regulated hyperthermia
Authors: McNerny K. L. , Kim Y. , Laughlin D. E. , McHenry M. E.
Published: April 2010

Magnetic nanoparticles (MNPs) possessing low Curie temperatures (TC’s) offer the possibility for self-regulated heating of cancer cells, where the TC acts as an upper limit to heating to prevent damage to neighboring healthy tissue. We report the synthesis of monodisperse metastable fcc γ-phase Fe–Ni MNPs possessing tunable TC’s, whose stoichiometries have been predicted from metastable extensions to an equilibrium Fe–Ni phase diagram. Metastable alloys have been predicted within the constructs of the T0 construction in the Fe–Ni eutectoid phase diagram. Fe–Ni MNPs have been synthesized via chemical reduction in Fe- and Ni-precursors with stoichiometries ranging from Fe90Ni10 to Fe70Ni30. Mn-precursors have been added to further reduce the alloy’s TC. MNP morphology and structure have been confirmed by x-ray diffraction and transmission electron microscopy while magnetic properties were investigated using vibrating sample magnetometry. Fe70Ni30 MNPs were found to have a TC of 82 °C and specific magnetization of 66 emu/g. Addition of 1 wt % Mn to Fe75Ni25 reduced the TC to 78 °C, which is the lowest reported for fcc Fe–Ni alloys. We also report a model for radio frequency self-regulated heating, in which the maximum achievable temperature of water-MNP suspensions (TC<100 °C) or octyl ether-MNP suspensions (TC>100 °C) is approximately the TC of the MNPs suspended in the solution.
Influence of Y substitutions on the magnetism of Gd5Ge4
Authors: Paudyal Durga , Mudryk Y. , Pecharsky V. K. , Misra S. , Miller G. J. , Gschneidner K. A.
Published: April 2010

The interrelation between the specific crystallographic positions and their influence on the magnetism of neighboring atoms is examined from first principles electronic structure calculations using the Gd5Ge4 compound as a model system. The predicted preferences of the specific occupations by nonmagnetic yttrium atoms and the resulting magnetism of substituted Gd5Ge4 have been confirmed, respectively, by single crystal x-ray diffraction and magnetization experiments.
Novel magnetic microwires-embedded composites for structural health monitoring applications
Authors: Qin F. X. , Pankratov N. , Peng H. X. , Phan M. H. , Panina L. V. , Ipatov M. , Zhukova V. , Zhukov A. , Gonzalez J.
Published: April 2010

We report the results of a systematic study of the magnetic, mechanical, magnetoimpedance and field tunable properties of glass-coated amorphous Co68.7Fe4Ni1B13Si11Mo2.3 microwires and composites containing these microwires. The magnetic microwires possess good magnetic and mechanical properties. The magnetoimpedance ratio in the gigahertz range varies sensitively with applied fields below the anisotropy field but becomes unchanged for higher applied fields. The good mechanical properties are retained in the magnetic microwires-embedded composites. The strong field dependences of the effective permittivity and transmission parameters in the gigahertz range indicate that the present composites are very promising candidate materials for structural health monitoring and self-sensing applications.
Effect of the Zn content in the structural and magnetic properties of ZnxMg1−xFe2O4 mixed ferrites monitored by Raman and Mössbauer spectroscopies
Authors: da Silva S. W. , Nakagomi F. , Silva M. S. , Franco A. , Garg V. K. , Oliveira A. C. , Morais P. C.
Published: April 2010

Samples of ZnxMg1−xFe2O4 (0≤x≤1) synthesized by the combustion reaction method were investigated by x-ray diffraction, Mössbauer spectroscopy, and Raman spectroscopy. All the samples are found to have a cubic spinel structure and the lattice parameter increases linearly with increasing Zn-content (x). The Mössbauer data showed that the replacement of Mg2+ ions for Zn2+ ions changes substantially the hyperfine parameter. Moreover, it was verified the presence of Fe3+ ions both in A and B sites. The Raman spectra showed five predicted Raman bands for the spinel structure and it was observed the splitting of the A1g Raman mode into tree branches, where each one have been attributed to peaks belonging to each ion (Zn, Mg, and Fe) in the tetrahedral positions.
Colossal magnetoresistance in the double perovskite oxide La2CoMnO6
Authors: Mahato Rabindra Nath , Sethupathi K. , Sankaranarayanan V.
Published: April 2010

Polycrystalline sample of La2CoMnO6 has been synthesized by sol-gel technique. The powder x-ray diffraction data confirm the single phase nature of the sample. This compound has monoclinic crystal structure (space group P21/n) at room temperature. The temperature dependence of magnetization in low field shows considerable variation between zero-field-cooled and field-cooled magnetization curve below ∼210 K (TC) and it follows Curie–Weiss law in the paramagnetic region. The hysteresis loop at 5 K indicates a coercive field of ∼6 kOe and remnant magnetization of ∼2.32 μB/f.u. The temperature dependence of the resistivity data shows semiconductorlike behavior in the temperature range of 5–350 K and follows variable range hopping conduction mechanism in the temperature range 215–350 K. A colossal magnetoresistance of ∼80% is observed at 5 K in an applied field of 80 kOe and MR has a negative sign.