bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on radiation generation and symmetrization in two-side irradiated heavy-ion beam Hohlraums
Authors: Ermolovich V.F. , Remizov G.N. , Romanov Yu. A. , Ryabikina N.A. , Shagaliev R.M. , Vakhlamova L.L. , Vatulin V.V. , Vinokurov O.A. , Kang K.-H. , Maruhn J.A. , Bockf R.
Published: March 2009

The properties of heavy-ion induced fusion targets with two-sided illumination and with the converters placed completely inside the Hohlraum have been investigated using integrated simulations based on the SATURN and MIMOZA code packages in order to check the results obtained with the view-factor method in previous work, which is briefly reviewed. Separate converter simulations show the importance of an accurate treatment of radiation transport but also demonstrate that a converter efficiency of 40–80% can be achieved easily depending on the detailed converter material and geometry. For the complete target, a gas fill is shown to be necessary, and it turned out to be very important to allow some of the radiation shields to become partially transparent during the evolution. In the most favorable case, an asymmetry in the temperature on the capsule of about 5% was achieved, leading to a reduction of the neutron yield by a factor of 7 compared to an ideally symmetric situation.
Modification of materials surface using plasma enhanced ion beams
Authors: Bystritskii V. , Kharlov A. , Lavernia E. , Peng X. , Yankelevich Y. , Garate E. , Grigoriev V.
Published: March 2009

The paper presents experimental results on the application of microsecond plasma opening switch (MPOS) technology for materials surface modification. The ion beam parameters generated by the MPOS are up to 250 keV energy and current density and energy densities of up to 150 A/cm2 and 2.2 J/cm2, respectively. Characterization of the treated samples showed structural changes to a depth of several microns. The small ion range (few microns) and fast cooling of the upper melted layer (up to 1010 K/s) result in formation of fine-grain structures characterized by improved corrosion and erosion properties. Measurements indicate an increase in microhardness of a factor of about 3 for carbon steel samples. Corrosion resistance increase for the treated samples of at least 3, as measured by mass loss and potentiodynamic methods, has been measured for Al alloys. Microstructural changes in the surface morphology indicate a reduction in grain size for the treated samples and the appearance of shallow craters. Results of numeric simulations are given for the temperature distribution in materials due to ion beam heating.
Quantum coherence in the control of molecular processes
Authors: Brumer Paul , Shapiro Moshe
Published: March 2009

Coherent control of molecular processes provides a means of controlling the dynamics of molecules, and of molecular processes, via laser-induced quantum interference. We briefly review this approach, provide relevant references, and highlight recent advances in the control of molecular processes.
Laser-pumped and laser-cooled atomic clocks for space applications
Authors: Buell Walter F.
Published: March 2009

Highly stable atomic frequency standards are of increasing importance for a variety of space applications, ranging from communication to navigation and time transfer to tests of fundamental science. We present a discussion of the improvements possible with laser pumping of vapor cell clocks, including applying coherent population trapping (CPT) techniques. We also present our progress toward a cold atom clock based on magneto-optically trapped atoms for space applications.
Nonlinear optics in solid hydrogen
Authors: Katsuragawa M. , Suzuki M. , Sihombing R.S.D. , Li J.Z. , Hakuta K.
Published: March 2009

We show through experiments of stimulated Raman scattering how solid hydrogen (parahydrogen) can open new perspectives on nonlinear optics. Two phenomena are described: One is the self-induced phase matching in parametric anti-Stokes stimulated Raman scattering (SRS) in which the phase matching is self-organized automatically without the stringent restriction of refractive-index dispersion of the medium, and the other is the extremely slow coherence decay behavior for the Raman transition that may result in the Raman width of 80 kHz full width at half maximum (FWHM).
THE LIMITS OF ECONOMETRICS: NONPARAMETRIC ESTIMATION IN HILBERT SPACES
Authors: Chichilnisky Graciela
Published: March 2009

We extend Bergstrom's 1985 results on nonparametric (NP) estimation in Hilbert spaces to unbounded sample sets. The motivation is to seek the most general possible framework for econometrics, NP estimation with no a priori assumptions on the functional relations nor on the observed data. In seeking the boundaries of the possible, however, we run against a sharp dividing line, which defines anecessary and sufficient conditionfor NP estimation. We identify this condition somewhat surprisingly with a classic statistical assumption on the relative likelihood of bounded and unbounded events (DeGroot, 2004). Other equivalent conditions are found in other fields: decision theory and choice under uncertainty (monotone continuity axiom (Arrow, 1970), insensitivity to rare events (Chichilnisky, 2000), and dynamic growth models (dictatorship of the present; Chichilnisky, 1996). When the crucial condition works, NP estimation can be extended to the sample spaceR+. Otherwise the estimators, which are based on Fourier coefficients, do not converge: the underlying distributions are shown to have “heavy tails” and to contain purely finitely additive measures. Purely finitely additive measures are not constructible, and their existence has been shown to be equivalent to the axiom of choice in mathematics. Statistics and econometrics involving purely finitely additive measures are still open issues, which suggests the current limits of econometrics.
Effective results for points on certain subvarieties of tori
Authors: BÉRCZES ATTILA , GYŐRY KÁLMÁN , EVERTSE JAN-HENDRIK , PONTREAU CORENTIN
Published: March 2009

The combined conjecture of Lang-Bogomolov for tori gives an accurate description of the set of those pointsxof a given subvarietyof$\mathbb{G}_{\bf m}^N(\oQ )=(\oQ^*)^N$, that with respect to the height are “very close” to a given subgroup Γ of finite rank of$\mathbb{G}_{\bf m}^N(\oQ)$. Thanks to work of Laurent, Poonen and Bogomolov, this conjecture has been proved in a more precise form.

In this paper we prove, for certain special classes of varieties, effective versions of the Lang-Bogomolov conjecture, giving explicit upper bounds for the heights and degrees of the pointsxunder consideration. The main feature of our results is that the points we consider do not have to lie in a prescribed number field. Our main tools are Baker-type logarithmic forms estimates and Bogomolov-type estimates for the number of points on the varietywith very small height.
Einstein metrics, complex surfaces, and symplectic 4-manifolds
Authors: LeBRUN CLAUDE
Published: March 2009

Which smooth compact 4-manifolds admit an Einstein metric with non-negative Einstein constant? A complete answer is provided in the special case of 4-manifolds that also happen to admit either a complex structure or a symplectic structure.
Fingerprint recognition to assist daily identification of radiotherapy patients
Authors: Palmgren J.-E. , Lahtinen T.
Published: March 2009

A system to assist daily identification of radiotherapy patients and to prevent accidental exposures to mis-indentified patients was developed. The fingerprint-based biometric system was chosen because of its high sensitivity in identification and suitability for hospital use. In a 6-month survey, 85.7% of the daily treatment fractions were identified successfully; 5.5% of the unsuccessful identifications were overridden by the staff and the remaining 8.8% were due to poor-quality fingerprints. No false identifications occurred so that patient was identified as a different person. During the past 2.5 years and 47,000 treatment fractions, the system has been well accepted by the patients and radiation technologists and misidentified patients have not been treated since the installation.
Tracing Gender Equality Cultures: Elite Perceptions of Gender Equality in Norway and Sweden
Authors: Teigen Mari , Wängnerud Lena
Published: March 2009

Cultural explanations are frequent in social science research. In gender studies, they are especially common in cross-country comparative research that attempts to explain variations in everyday life situations for women and men. A noticeable example is found in the book Rising Tide: Gender Equality and Cultural Change Around the World, by Ronald Inglehart and Pippa Norris (2003). Inglehart and Norris construct a gender-equality scale from measurements on attitudes among citizens regarding women as political leaders, women's professional and educational rights, and women's traditional role as mother. The results show that Finland, Sweden, West Germany, Canada, and Norway are the countries most influenced by egalitarian values. At the other end of the spectrum countries like Nigeria, Morocco, Egypt, Bangladesh, and Jordan are found (p. 33). The authors demonstrate that egalitarian values are systematically related to the actual conditions of women's and men's lives. They conclude that modernization underpins cultural change, that is, attitudinal change from traditional to gender-equal values, and that these cultural changes have major impact on gender-equality processes.
Women Acting for Women? An Analysis of Gender and Debate Participation in the British House of Commons 2005–2007
Authors: Catalano Ana
Published: March 2009

The recent push for more women parliamentarians around the world via positive action measures such as gender quotas naturally begs the question of whether the increased descriptive representation of women in parliament is making a substantive difference, in terms of the types of policies passed, behavioral norms, and procedures. How does the substantive representation of women take place? One way of measuring gendered impacts in politics is to look at the participation of Members of Parliament (MPs) in formal, parliamentary debate on key policy issues. It is reasonable to assume that one (though certainly not the only) measure of a good MP is his or her ability to contribute his or her voice and thoughts to public policy debates in parliament. Furthermore, if we consider women MPs representative of women in particular as a marginalized group, making their voices heard in parliamentary debates is perhaps one of the best ways of acting for women. As Melissa Williams (1998, 138) argues, the unique voice of women is a necessary component for women's political equality:

It is not enough that women communicate their perspectives to men; a full respect for women's agency, and a full protection of their interests, requires that they act on their own behalf. Only through their legislative presence can women be sure that the “woman's point of view” on each policy issue is formulated and expressed.
Sexism and Gender Bias in Election 2008: A More Complex Path for Women in Politics
Authors: Lawless Jennifer L.
Published: March 2009

When Hillary Clinton announced her presidential candidacy, questions about the role of gender in presidential politics immediately surfaced. Would gender stereotyping and sexism pervade the electoral environment? Would the media treat Clinton differently than her competitors in the Democratic primary field? Would Clinton's candidacy mobilize women of all types, simply by virtue of its historic nature? And when Clinton lost the Democratic nomination, new questions quickly arose. Was America just not ready to elect a female president? To what extent did Bill Clinton account for Senator Clinton's successes and failures? How would the 18 million women and men who cast their ballots for Clinton vote in the general election? With so many interesting unknowns, political scientists will likely spend the next several years examining Hillary Clinton's campaign and assessing the extent to which her sex affected her experiences and contributed to her primary loss.
Group Politics Redux: Race and Gender in the 2008 Democratic Presidential Primaries
Authors: Huddy Leonie , Carey Tony E.
Published: March 2009

The earliest political behavior researchers documented the powerful effects of group attachments and other socioeconomic factors on vote choice and partisan identification in the 1940s and 1950s (Berelson, Lazarsfeld, and McPhee 1954; Campbell et al. 1960). Yet, research interest in the group-based origins of political behavior has waxed and waned in the intervening decades (Huddy 2003). The existence of both an African-American and female frontrunner for the Democratic presidential nomination in 2008 provides an opportunity to consider the contemporary electoral consequences of in-group loyalties and out-group antipathies. We take advantage of select survey and poll data collected during the 2008 Democratic primaries to evaluate the power of gender and race as both positive and negative influences on voter calculus in an election in which the two major candidates were differentiated less by their issue positions and beliefs than by their skin color and gender.
An Untraditional Intersectional Analysis of the 2008 Election
Authors: Hancock Ange-Marie
Published: March 2009

Most will agree that scholars of political science will examine the two-year cycle of this American presidential election for generations to come. The essays in this symposium are “first reads,” and due to time and space constraints can only identify a handful of trends. Suffice it to say that Senator Hillary Clinton and Governor Sarah Palin's candidacies are a boon to women and politics scholars, offering a wide swath of research questions and data to mine. The use of gender as an analytical category (Hawkesworth 2006; Scott 1986) will enhance examinations of the vast difference in Clinton's and Palin's ideologies, candidacies, and gendered performances in a way that illuminates, rather than obscures, the ideological diversity among women in the United States (see Schreiber 2008). Yet the deep attention paid to Clinton and Palin has so far focused on gender despite the candidates' own allusions to race and class identities as complicating factors in their gendered self-presentations. To focus solely on their positions as female candidates obscures some important macro-level questions about the 2008 election as a watershed moment, whether the focus is on “18 million cracks in the glass ceiling” or the shift in target voters from soccer moms into hockey moms.
Cirrus cloud optical and microphysical properties determined from AIRS infrared spectra
Authors: Yue Qing , Liou K. N.
Published: March 2009

We developed an efficient thermal infrared radiative transfer model on the basis of the delta‐four‐stream approximation to facilitate high‐spectral‐resolution remote sensing applications under cirrus cloudy conditions in the Atmospheric Infrared Sounder (AIRS) data. Numerical experiments demonstrated that sensitivity in the 800‐1130 cm−1 thermal infrared window spectral region is sufficiently distinct for the inference of cirrus optical depth and ice crystal mean effective size and shape factor. We analyzed 312 nighttime cirrus pixels in two AIRS granules over ARM TWP sites and applied the radiative transfer model to these cases to determine cirrus optical depth and ice crystal mean effective size, based on a look‐up table approach. The retrieval program has been evaluated through an error budget analysis and validation effort by comparing AIRS‐retrieved results with those determined from ground‐based millimeter‐wave cloud radar data at ARM TWP sites, for five AIRS pixels that were collocated and coincident with ground‐based measurements.
Hydrometeor‐enhanced tephra sedimentation: Constraints from the 18 May 1980 eruption of Mount St. Helens
Authors: Durant A. J. , Rose W. I. , Sarna‐Wojcicki A. M. , Carey S. , Volentik A. C. M.
Published: March 2009

Uncertainty remains on the origin of distal mass deposition maxima observed in many recent tephra fall deposits. In this study the link between ash aggregation and the formation of distal mass deposition maxima is investigated through reanalysis of tephra fallout from the Mount St. Helens 18 May 1980 (MSH80) eruption. In addition, we collate all the data needed to model distal ash sedimentation from the MSH80 eruption cloud. Four particle size subpopulations were present in distal fallout with modes at 2.2 Φ, 4.2 Φ, 5.9 Φ, and 8.3 Φ. Settling rates of the coarsest subpopulation closely matched predicted single‐particle terminal fall velocities. Sedimentation of particles <100 μm was greatly enhanced, predominantly through aggregation of a particle subpopulation with modal diameter 5.9 ± 0.2 Φ (19 ± 3 μm). Mammatus on the MSH80 cloud provided a mechanism to transport very fine ash particles, with predicted atmospheric lifetimes of days to weeks, from the upper troposphere to the surface in a matter of hours. In this mechanism, ash particles initiate ice hydrometeor formation high in the troposphere. Subsequently, the volcanic cloud rapidly subsides as mammatus develop from increased particle loading and cloud base sublimation. Rapid fallout occurs as the cloud passes through the melting level in a process analogous to snowflake aggregation. Aggregates sediment en masse and form the distal mass deposition maxima observed in many recent volcanic ash fall deposits. This work provides a data resource that will facilitate tephra sedimentation modeling and allow model intercomparisons.
Evaluation of a coastal ocean circulation model for the Columbia River plume in summer 2004
Authors: Liu Yonggang , MacCready Parker , Hickey Barbara M. , Dever Edward P. , Kosro P. Michael , Banas Neil S.
Published: March 2009

Realistic hindcast of the Columbia River estuarine‐plume‐shelf circulation in summer 2004 using the Regional Ocean Modeling System nested within the Navy Coastal Ocean Model (NCOM) is quantitatively evaluated with an extensive set of observations. The model has about equal skill at tidal and subtidal properties. Tidal circulation and water properties are best simulated in the estuary, which is strongly forced and damped, but worst on the shelf. Subtidal currents are again best in the estuary. However, subtidal temperature and salinity are best simulated in the surface waters on the shelf, even inside the river plume. A comprehensive skill assessment method is proposed to evaluate the cross‐scale modeling system with a focus on the plume. The model domain is divided into five dynamical regions: estuary, near‐ and far‐field plume, near surface and deep layers. A skill score is obtained for each region by averaging the skills of different physical variables, and an overall skill is obtained by averaging the skills across the five regions. This weighting metric results in more skill weight per unit volume in the near surface layer where the plume is trapped and in the estuary. It is also demonstrated, through model/data comparison and skill assessment, that by nesting within NCOM, some important remote forcing, e.g., coastal trapped waves, are added to our model; on the other hand, some biases are also received. With a finer grid and more realistic forcing, our regional model improves skill over a larger‐scale model in modeling the shelf‐plume circulation.
Stratigraphy of Promethei Lingula, south polar layered deposits, Mars, in radar and imaging data sets
Authors: Milkovich S. M. , Plaut J. J. , Safaeinili A. , Picardi G. , Seu R. , Phillips R. J.
Published: March 2009

The south polar layered deposits (SPLD) of Mars have been studied through imagery for decades. Now, two subsurface sounding radar instruments have collected data: the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on Mars Express and the Shallow Radar (SHARAD) instrument on Mars Reconnaissance Orbiter are observing the SPLD at multiple frequencies (1.8–5 and 20 MHz, respectively). Both instruments detect subsurface reflections in the Promethei Lingula region of the SPLD. MARSIS detects up to three reflections within Promethei Lingula, in addition to detecting the basal contact between the SPLD and the underlying plains. SHARAD detects 10s of reflections without penetrating to the base of the SPLD. MARSIS reflections likely correlate to the boundaries of packets of reflections in the SHARAD data; whatever change in composition of the SPLD that causes the SHARAD reflections to occur in packets may also be the source of the MARSIS reflections. In several locations, SHARAD reflections can be compared directly with images of layers; an individual reflection corresponds to 3–7 layers in images at resolutions of 6 m/pixel. Reflection surfaces are calculated using the radar observations and extrapolated to the SPLD margins where they are compared to the stratigraphy observed in images. We find that the MARSIS reflections, and thus the packet structure within the SHARAD observations, are likely related to distinctive groups of layers rather than individual layers. The radar data sets allow us to confirm several predictions concerning the interior of the SPLD from stratigraphic studies of images, including that most of the layers extend throughout the region and that they decrease in elevation toward the margin of the SPLD.
Irradiation of olivine by 4 keV He+: Simulation of space weathering by the solar wind
Authors: Loeffler M. J. , Dukes C. A. , Baragiola R. A.
Published: March 2009

We have studied the effects of 4 keV He+ ion irradiation on olivine while measuring, in situ, changes in the near‐infrared (NIR) reflectance and in the chemical composition of the surface. The observed changes in reflectance are reddening and the attenuation of the Fe‐3d absorption bands in the NIR. Spectral reddening of irradiated olivine powder (<45 μm) correlates with the amount of metallic iron formed by ion impact, consistent with the idea that space‐weathering effects in the reflectance of olivine‐bearing S type asteroids are due to the formation of metallic iron. The metallization rate of the powder is about half that of a sectioned rock of olivine, which we propose is a consequence of redeposition of sputtered material. The NIR spectral changes observed in ion irradiation experiments are similar to those observed in our previous experiments on vapor redeposition, indicating that different space weathering mechanisms can lead to similar final effects on reflectance. Finally, we estimate that at 1 AU the spectral reddening caused by the solar wind saturates approximately 2 orders of magnitude faster than comparable reddening caused by micrometeorite impacts.
Eriksonian Lifespan Theory and Life History Theory: An Integration Using the Example of Identity Formation
Authors: Dunkel Curtis S. , Sefcek Jon A.
Published: March 2009

Furthering the cause of consilience in the social sciences a model is proposed in which Eriksonian life span theory and life history theory are integrated. The model explains individual differences in the Eriksonian developmental stages as a function of the individual differences in developmental trajectories of life history theory as conceptualized by Belsky, Steinberg, and Draper (1991) . Erikson's fifth stage of identity formation is used to examine the model, with the results of three studies presented to illustrate the viability of the model. Future research should examine other aspects of the model and the relationship between the developmental trajectories in life history theory and the Eriksonian stages in greater detail.
Beyond Big and Little: The Four C Model of Creativity
Authors: Kaufman James C. , Beghetto Ronald A.
Published: March 2009

Most investigations of creativity tend to take one of two directions: everyday creativity (also called “little-c”), which can be found in nearly all people, and eminent creativity (also called “Big-C”), which is reserved for the great. In this paper, the authors propose a Four C model of creativity that expands this dichotomy. Specifically, the authors add the idea of “mini-c,” creativity inherent in the learning process, and Pro-c, the developmental and effortful progression beyond little-c that represents professional-level expertise in any creative area. The authors include different transitions and gradations of these four dimensions of creativity, and then discuss advantages and examples of the Four C Model.
Gender Differences in Domain-Specific Self-Esteem: A Meta-Analysis
Authors: Gentile Brittany , Grabe Shelly , Dolan-Pascoe Brenda , Twenge Jean M. , Wells Brooke E. , Maitino Alissa
Published: March 2009

This meta-analysis examines gender differences in 10 specific domains of self-esteem across 115 studies, including 428 effect sizes and 32,486 individuals. In a mixed-effects analysis, men scored significantly higher than women on physical appearance ( d = 0.35), athletic ( d = 0.41), personal self ( d = 0.28), and self-satisfaction self-esteem ( d = 0.33). Women scored higher than men on behavioral conduct ( d = −0.17) and moral–ethical self-esteem ( d = −0.38). The gender difference in physical appearance self-esteem was significant only after 1980 and was largest among adults. No significant gender differences appeared in academic, social acceptance, family, and affect self-esteem. The results demonstrate the influence of reflected appraisals on self-esteem.
Does a Long-Term Relationship Kill Romantic Love?
Authors: Acevedo Bianca P. , Aron Arthur
Published: March 2009

This article examines the possibility that romantic love (with intensity, engagement, and sexual interest) can exist in long-term relationships. A review of taxonomies, theory, and research suggests that romantic love, without the obsession component typical of early stage romantic love, can and does exist in long-term marriages, and is associated with marital satisfaction, well-being, and high self-esteem. Supporting the separate roles of romantic love and obsession in long-term relationships, an analysis of a moderately large data set of community couples identified independent latent factors for romantic love and obsession and a subsample of individuals reporting very high levels of romantic love (but not obsession) even after controlling for social desirability. Finally, a meta-analysis of 25 relevant studies found that in long- and short-term relationships, romantic love (without obsession) was strongly associated with relationship satisfaction; but obsession was negatively correlated with it in long-term and positively in short-term relationships.
Personal Intelligence Expressed: A Theoretical Analysis
Authors: Mayer John D.
Published: March 2009

An individual's cumulative life decisions help determine that person's well-being. To make good decisions requires knowing something about who one is and who one wants to be. It seems plausible that personality may draw on a specifically tailored intelligence that supports its own self-understanding and contributes to such life decisions. This personal intelligence (PI) helps the individual meet his or her own personal needs and to fit in with (or stand out from) the environment. What are people high in PI actually like relative to those lower in the skills? Drawing on a 2008 theory of PI-related abilities, the author reviews several literatures to examine what features distinguish the behavior of people high in PI from those lower in such skills. The feature list sets the stage for future research in distinguishing high-PI individuals from low-PI individuals according to their life expressions.
Hotel Companies' Contribution to Improving the Quality of Life of Local Communities and the Well-Being of Their Employees
Authors: Bohdanowicz Paulina , Zientara Piotr
Published: March 2009

The aim of this paper is to discuss the question of how hotel companies contribute to improving the quality of life in host communities and the well-being of their employees. A number of research techniques were employed, which allowed to see what the hospitality sector has done to further the aforesaid end. The findings are placed into the context of corporate social responsibility (CSR), and it is argued that, in recent years, hotel companies have gone to great lengths to improve the quality of life in local communities and the well-being of their employees. Critically, by presenting concrete initiatives and highlighting their rationale, it is shown that a growing number of hotels have embedded the idea of CSR into their business models. The paper concludes by asserting that international hotel companies can play an important role in the development of host communities.
Transport and Tourism Destination Development: An Indonesian Perspective
Authors: Henderson Joan
Published: March 2009

The manner in which countries develop as international tourist destinations is a dynamic and complex phenomenon, to which multiple parties and forces contribute. Safe and efficient transport, affording accessibility from abroad and mobility on arrival, is a critical consideration to facilitate progress whereas its absence acts as a barrier. The paper discusses these issues with reference to Indonesia and the implications of a European Union ban on Indonesian airlines.
Optical stability of shape-engineered InAs/InAlGaAs quantum dots
Authors: Yang Youngsin , Jo Byounggu , Kim Jaesu , Lee Cheul-Ro , Kim Jin Soo , Oh Dae Kon , Kim Jong Su , Leem Jae-Young
Published: March 2009

The optical properties of shape-engineered InAs/InAlGaAs quantum dots (SEQDs) were investigated by temperature-dependent and excitation-power-dependent photoluminescence (PL) spectroscopy and compared with those of the conventionally grown InAs QDs (CQDs). The emission wavelength of the InAs/InAlGaAs SEQDs at 240 K was redshifted by 18 nm from that at 15 K, which was relatively smaller than that of the InAs CQDs (97 nm). The PL yield at 240 K was reduced to 1/86 and 1/65 of that measured at 15 K for the InAs CQDs and the InAs/InAlGaAs SEQDs, respectively. The emission wavelength for the InAs CQDs was blueshifted by 76 nm with increasing excitation power from 0.56 to 188 mW, compared to only by 7 nm for the InAs/InAlGaAs SEQDs. These results indicated that the InAs/InAlGaAs SEQDs were optically more stable than the InAs CQDs mainly due to the enhancement of the carrier confinement in the vertical direction and the improvement in the size uniformity.
Permeability and losses in ferrites from dc to the microwave regime
Authors: Fiorillo F. , Coïsson M. , Beatrice C. , Pasquale M.
Published: March 2009

Fluxmetric and transmission line methods have been combined in the wideband characterization of Mn–Zn and Ni–Zn soft ferrites. The real μ′(f) and imaginary μ″(f) permeability components and the energy loss W(Jp,f) have been obtained in ring samples, for defined values of the peak polarization Jp up to 1 GHz. The role of an increasing dc magnetic field 0≤Hdc⊥≤140 kA/m transverse to the ring plane on the frequency dependence of μ′(f), μ″(f), and W(Jp,f) has also been investigated. Permeability and energy losses are interpreted applying the statistical theory of losses to the case where spin damping is the leading cause of the magnetic energy dissipation. The separate roles of domain wall processes and rotations are consequently put in evidence and predicted by associating them to relaxation and ferromagnetic resonance effects, respectively. The rotational susceptibility is obtained, as a solution of the linear Landau–Lifshitz–Gilbert equation, averaged over a distribution of effective anisotropy fields and the loss is calculated accordingly.
A new approach to (quasi) periodic boundary conditions in micromagnetics: The macrogeometry
Authors: Fangohr Hans , Bordignon Giuliano , Franchin Matteo , Knittel Andreas , de Groot Peter A. J. , Fischbacher Thomas
Published: March 2009

We present a new method to simulate repetitive ferromagnetic structures. This macrogeometry approach combines treatment of short-range interactions (i.e., the exchange field) as for periodic boundary conditions with a specification of the arrangement of copies of the primary simulation cell in order to correctly include effects of the demagnetizing field. This method (i) solves a consistency problem that prevents the naive application of three-dimensional periodic boundary conditions in micromagnetism and (ii) is well suited for the efficient simulation of repetitive systems of any size.
Molecular biosensor based on a coordinated iron complex
Authors: Salazar-Salinas Karim , Jauregui Luis A. , Kubli-Garfias Carlos , Seminario Jorge M.
Published: March 2009

A sensor model based on the porphyrin nucleus of the soluble guanylate cyclase enzyme is modeled and tested with nitric oxide and carbon monoxide. Molecular oxygen is tested as a possible interferer. Geometries and electronic structures of the model are assessed by density functional theory. Vibrational circular dichroism (VCD), infrared, and Raman spectra are obtained for the iron complexes uncoordinated and coordinated with the gas moieties. The sensor is capable of detecting the ligands to different extents. Carbon monoxide is less detectable than nitric oxide due to the adopted position of the molecule in the sensor; carbon oxide is aligned with the iron atom, while nitric oxide and molecular oxygens bend with an angle detectable by the VCD. It is suggested that pollutants may be detected and measured with the proposed biosensors
Magnetic field-dependent resistance measurements in the superconducting ferromagnet (Ru1−xNbx)Sr2Eu1.4Ce0.6Cu2O10
Authors: Botello-Zubiate M. E. , Ayala-Valenzuela O. E. , Matutes-Aquino J. A. , Jaime M.
Published: March 2009

Polycrystalline samples of Ru1−xNbxSr2Eu1.4Ce0.6Cu2O10−δ(x=0,0.2,0.4,0.6,0.8,1) were prepared by conventional solid state reaction using stoichiometric amounts of high purity RuO2, Nb2O5, SrCO3, Eu2O3, CeO2, and CuO powders. The phase evolution during the solid state reaction was followed by x-ray diffraction and randomly oriented particles in laminates form with a size between 1–3 μm were observed by scanning electron microscopy. Temperature-dependent resistance measurements were made with applied magnetic fields of 0, 2, 5, 10, and 15 T. All compositions except x=1 were superconducting without applied magnetic field for the lowest measuring temperatures. Onset, intergrain and intragrain transition, and TR=0 transition temperatures were determined. These critical temperatures depend on Nb content, microstructure, and applied magnetic field.
Thermal asperity suppression based on least-squares fitting in perpendicular magnetic recording systems
Authors: Kovintavewat Piya , Koonkarnkhai Santi
Published: March 2009

Thermal asperity (TA) causes a major problem in data detection process. Without the TA detection and correction algorithm, the system performance (even with perfect synchronization) can be unacceptable, depending on how severe the TA effect is. This paper proposes a new method to suppress the TA effects in perpendicular magnetic recording channels. The TA detection is a threshold-based approach, while the TA correction is done by averaging the readback signal and applying a least-squares fitting technique to estimate the TA signal. Then, the corrected readback signal is obtained by subtracting the TA-affected readback signal by the reconstructed TA signal. Results indicate that the proposed method performs better than the existing one in terms of bit-error rate and is robust to changes in the peak TA amplitude.
Room temperature multiferroic properties of Eu doped BiFeO3
Authors: Uniyal P. , Yadav K. L.
Published: March 2009

We have studied the multiferroic properties of Bi1−xEuxFeO3, x=0.03, 0.05, 0.07, and 0.1 ceramics prepared by conventional solid state reaction method. The substitution of Eu in place of Bi increases the magnetization at room temperature. An anomaly in the dielectric constant is observed at ∼400 °C which corresponds to TN. Room-temperature dielectric polarization–electric field (P-E) curves indicate that higher doped compositions exhibit saturated P-E loops with Pr (remnant polarization) of these BFO-based samples increasing with the degree of Eu modification. As a result, improved multiferroic properties of the Bi0.9Eu0.1FeO3 ceramics with remnant polarization and magnetization (Pr and Mr) of 11 μC/cm2 and 0.0347 emu/g, respectively, were obtained. The evidence of weak ferromagnetism and saturated ferroelectric hysteresis loops in Bi1−xEuxFeO3 system at room temperature makes it a good candidate for potential applications.
Effect of rare-earth doping on the superconducting properties of MgB2
Authors: Ojha N. , Varma G. D. , Singh H. K. , Awana V. P. S.
Published: March 2009

The bulk polycrystalline samples with nominal compositions Mg1−x(Eu2O3)x/2B2 and Mg1−x(Pr6O11)x/6B2 (where x=0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) have been prepared via standard solid-state reaction route. The x-ray diffraction (XRD) results of both series of materials reveal the presence of secondary phases MgO and REB6(RE=Eu/Pr) besides the main hexagonal phase of MgB2. The magnetic and electrical measurements show that transition temperatures (Tc) of both Eu2O3 and Pr6O11-doped MgB2 samples decrease from 39 to 37 K when values of x increase from 0.0 to 0.05. Improvement in critical current density (Jc) at 10 K has been observed at higher fields (>4 T) for Eu2O3-doped samples of composition x=0.04 and in entire field range (0–5 T) in the case of Pr6O11-doped samples of composition x=0.03 as compared to the Jc values of other compositions. The Jc values at 5 T field and 10 K of undoped, x=0.03 for Pr6O11-doped and x=0.04 for Eu2O3-doped MgB2 samples are 2.21×103, 1.15×104, and 1.10×104 A/cm2, respectively. Improvement in Hc2 and Hirr has also been observed in doped samples.
A new stator-flux orientation strategy for flux-switching permanent magnet motor based on current-hysteresis control
Authors: Hua Wei , Cheng Ming , Lu Wei , Jia Hongyun
Published: March 2009

A stator-flux orientation strategy based on current hysteresis for the flux-switching permanent magnet (FSPM) motor is proposed, in which the stator-PM FSPM motor is considered as a conventional rotor-PM surface-mounted motor and an equivalent rotor-orientated dq-axes synchronous reference frame is built although there are actually no rotary magnetic motive force produced by the stator magnets in the FSPM motor. Based on the proposed model, a vector-control strategy with current hysteresis for the FSPM motor drive is investigated and implemented on a dSPACE-based platform, and both the simulated and experimental results validate the effectiveness. It should be emphasized that the proposed stator-flux orientation strategy can be applied to other stator-PM machines (including doubly salient and flux-reversal PM machines) and other control methods (including space-vector pulsed-width-modification and direct torque control).
Tunnel magnetoresistance for magnetic tunnel junctions with Co2FeAl0.5Si0.5 full Heusler electrodes fabricated by molecular beam epitaxy system
Authors: Tezuka N. , Ikeda N. , Mitsuhashi F. , Sugimoto S.
Published: March 2009

The authors fabricated Co2FeAl0.5Si0.5 full Heusler alloy thin films by using a molecular beam epitaxy system on Cr buffered MgO single crystal substrates and investigated their structural and magnetic properties. It was revealed that Co2FeAl0.5Si0.5 films formed ordered L21 and B2 structures after annealing above 500 °C and below 400 °C, respectively. Then magnetic tunnel junctions with these electrodes and Al-oxide or MgO barriers were also fabricated, and the bias voltage dependence of tunnel magnetoresistance ratio was investigated. It was found that the tunnel magnetoresistance ratio of the junction with Al-oxide barrier has a larger asymmetric bias voltage dependence compared with that with MgO barrier, and the negative tunnel magnetoresistance ratio at high negative bias voltage is observed for both junctions.
MgO-based double barrier magnetic tunnel junctions with thin free layers
Authors: Feng G. , van Dijken Sebastiaan , Coey J. M. D.
Published: March 2009

The free layer thickness (tfree) in double barrier magnetic tunnel junctions (DMTJs) based on crystalline MgO barriers and CoFeB ferromagnetic layers has been varied from 0.5 to 3.0 nm in order to investigate its effect on the magnetic and electrical properties. One obvious feature of DMTJs with tfree≤1 nm is the absence of sharp free layer switching in the TMR curves, which can be explained by the superparamagnetic nature of discontinuous CoFeB layer, which breaks into nanodots when it is very thin. Normal free layer switch is observed when tfree=2.0 and 3.0 nm. Another difference is a rapid increase in junction resistance and tunnel magnetoresistance at low temperature for DMTJs with thin tfree, which is attributed to the Coulomb blockade effect. We also observed a small conductance peak in the dI/dV curve at low bias only in the parallel configuration and at temperatures below 100 K. This is related to the Kondo scattering process on the nanodots, which constitutes the discontinuous free layer. We found no Coulomb staircase existing in the I-V curves; this may be due to the microsize of the junctions.
Large magnetic refrigerant capacity in Gd71Fe3Al26 and Gd65Fe20Al15 amorphous alloys
Authors: Dong Q. Y. , Shen B. G. , Chen J. , Shen J. , Wang F. , Zhang H. W. , Sun J. R.
Published: March 2009

Magnetic entropy change and refrigerant capacity of Gd-based amorphous Gd71Fe3Al26 and Gd65Fe20Al15 alloys are investigated. The refrigerant capacities reach 750 and 726 J kg−1 for Gd71Fe3Al26 and Gd65Fe20Al15, respectively, which are much larger than those of all magnetocaloric materials ever reported. The peak values of magnetic entropy change under a field change of 0–5 T are 7.4 J kg−1 K−1 at 117.5 K and 5.8 J kg−1 K−1 at 182.5 K for Gd71Fe3Al26 and Gd65Fe20Al15, respectively. A very large refrigerant capacity and a considerable magnetic entropy change jointly make them attractive candidates for magnetic refrigerant.
Effect of the temperature history on the magnetism of (110) europium films
Authors: Bataille A. M. , Dumesnil K. , Gukasov A. , Dufour C.
Published: March 2009

Neutron scattering experiments using a two-dimensional detector have been performed to measure simultaneously a nuclear Bragg peak and its six surrounding magnetic satellites in a 2 μm thick (110)europium film. This technique enables the investigation of the three helical orders propagating along different directions, which gives a complete information on the magnetic configuration at a given temperature. Important variations in temperature and hysteretic effects have been observed for the magnetic population, in good agreement with a previous structural analysis. The thermal history of the film appears also to have dramatic consequences on the magnetic configurations, correlated with lattice clamping effects persisting above the magnetic ordering temperature.
Fabrication of Heuslar Fe3Si nanoparticles
Authors: Jing Ying , Xu Yunhao , Wang Jian-Ping
Published: March 2009

Magnetic nanoparticles have promising applications in spintronics, for example, to make single particle spintronic devices. The combination of widely accessible Fe and Si makes up a system of great interest and potential. Fe3Si phase is considered to be similar with Heuslar alloy, which could lead to high spin polarization, a desirable feature for spintronic devices. Fe3Si nanoparticles were fabricated by a unique gas condensation sputtering technique. Faceted Fe3Si nanoparticles with D03 crystal structure were obtained and exhibited ferromagnetic behavior at room temperature. The anisotropy constant K1 was estimated to be 8.0×105 ergs/cm3 by fitting the magnetization curve based on the law of approach to saturation.
Photodissociation of the linear Ar–I2 van der Waals complex: Velocity-map imaging of the I2 fragment
Authors: Zhang Yongwei , Vidma Konstantin , Parker David H. , Loomis Richard A.
Published: March 2009

Photodissociation of the Ar–I2 1:1 linear van der Waals complex is studied over the 490–520 nm region using the velocity-map imaging technique. Molecular iodine, and both the T-shaped and linear Ar–I2(X,v″=0) ground-state complexes absorb strongly in this range, and these transitions access both the bound and dissociative regions of the I2(B) state. We measure the angle-speed distribution of vibrationally excited I2(B,v′) state products by resonant 1+1 ionization via the E and f ion-pair states, forming I2+, which is imaged under velocity-mapping conditions. The images show a strong angular anisotropy, which is the same for all excitation energies, spanning from the bound region to above the molecular dissociation limit. The observed angular anisotropy of the I2 fragments is consistent with a direct dissociation of linear Ar–I2 complexes promoted to the inner repulsive potential wall of the Ar+I2(B,v′) potential energy surface.
Design and construction of a novel rotary magnetostrictive motor
Authors: Zhou Nanjia , Blatchley Charles C. , Ibeh Christopher C.
Published: March 2009

Magnetostriction can be used to induce linear incremental motion, which is effective in giant magnetostrictive inchworm motors. Such motors possess the advantage of combining small step incremental motion with large force. However, continuous rotation may be preferred in practical applications. This paper describes a novel magnetostrictive rotary motor using terfenol-D (Tb0.3Dy0.7Fe1.9) material as the driving element. The motor is constructed of two giant magnetostrictive actuators with shell structured flexure-hinge and leaf springs. These two actuators are placed in a perpendicular position to minimize the coupling displacement of the two actuators. The principal design parameters of the actuators and strain amplifiers are optimally determined, and its static analysis is undertaken through finite element analysis software. The small movements of the magnetostrictive actuators are magnified by about three times using oval shell structured amplifiers. When two sinusoidal wave currents with 90° phase shift are applied to the magnetostrictive actuators, purely rotational movement can be produced as in the orbit of a Lissajous diagram in an oscillograph, and this movement is used to drive the rotor of the motor. A prototype has been constructed and tested.
Quantifying mixing using equilibrium reactions
Authors: Wheat Philip M. , Posner Jonathan D.
Published: March 2009

A method of quantifying equilibrium reactions in a microchannel using a fluorometric reaction of Fluo-4 and Ca2+ ions is presented. Under the proper conditions, equilibrium reactions can be used to quantify fluid mixing without the challenges associated with constituent mixing measures such as limited imaging spatial resolution and viewing angle coupled with three-dimensional structure. Quantitative measurements of CaCl and calcium-indicating fluorescent dye Fluo-4 mixing are measured in Y-shaped microchannels. Reactant and product concentration distributions are modeled using Green’s function solutions and a numerical solution to the advection-diffusion equation. Equilibrium reactions provide for an unambiguous, quantitative measure of mixing when the reactant concentrations are greater than 100 times their dissociation constant and the diffusivities are equal. At lower concentrations and for dissimilar diffusivities, the area averaged fluorescence signal reaches a maximum before the species have interdiffused, suggesting that reactant concentrations and diffusivities must be carefully selected to provide unambiguous, quantitative mixing measures. Fluorometric equilibrium reactions work over a wide range of pH and background concentrations such that they can be used for a wide variety of fluid mixing measures including industrial or microscale flows.