bluuebunny/crossref_metadata_2025 huggingface dataset:
DETERMINANTS OF EARLY DISCONTINUATION OF IUCD USE IN RURAL NORTHERN DISTRICT OF INDIA: A MULTIVARIATE ANALYSIS AND ITS VALIDATION
Authors: TRIPATHI VRIJESH , NANDAN DEOKI , SALHAN SUDHA
Published: April 2005

The purpose of this study was to examine the determinants for early discontinuation among IUCD users in a rural district of northern India. Multivariate analysis indicated several significant predictors of early discontinuation of IUCD use. The risk of discontinuation increased more than two times in the presence of factors such as more than usual amount of menstrual flow before insertion and intermenstrual bleeding after insertion. Similarly, residence or alternatively those coming from villages without health centres were nearly two times more likely to discontinue. Menstrual disturbance increased the risk nearly three-fold. If only those women who report normal menstrual cycles had IUCDs inserted, it is very likely that the high discontinuation rate due to menstrual disturbance could be reduced. Knowledge about the IUCD and its effectiveness decreased the risk of early discontinuation but was not a statistically significant factor in multivariate analysis. Validation of the developed model was done by using the bootstrapping method and the model was found to be 18% noisy. These findings may help family planning providers in counselling and practice.
ARE GENDER DIFFERENCES IN HIGH ACHIEVEMENT DISAPPEARING? A TEST IN ONE INTELLECTUAL DOMAIN
Authors: HOWARD ROBERT W.
Published: April 2005

Males traditionally predominate at upper achievement levels. One general view holds that this is due only to various social factors such as the ‘glass ceiling’ and lack of female role models. Another view holds that it occurs partly because of innate ability differences, with more males being at upper ability levels. In the last few decades, women have become more achievement focused and competitive and have gained many more opportunities to achieve. The present study examined one intellectual domain, international chess, to quantify its gender differences in achievement and to see if these have been diminishing with the societal changes. Chess is a good test domain because it is a meritocracy, it has objective performance measures, and longitudinal data of a whole population are available. Performance ratings overall and in the top 10, 50 and 100 players of each sex show large gender differences and little convergence over the past three decades, although a few females have become high achievers. The distribution of performance ratings on the January 2004 list shows a higher male mean and evidence for more male variation, just as with traits such as height. Career patterns of players first on the list between 1985 and 1989 show that top males and females entered the list at about the same age but females tend to play fewer games and have shorter careers. In this domain at least, the male predominance is large and has remained roughly constant despite societal changes.
MALE PARTICIPATION IN FAMILY PLANNING: RESULTS FROM A QUALITATIVE STUDY IN MPIGI DISTRICT, UGANDA
Authors: KAIDA ANGELA , KIPP WALTER , HESSEL PATRICK , KONDE-LULE JOSEPH
Published: April 2005

The aim of this study was to determine men’s perceptions about family planning and how they participate or wish to participate in family planning activities in Mpigi District, central Uganda. Four focus group discussions were conducted with married men and with family planning providers from both the government and private sector. In addition, seven key informants were interviewed using a semi-structured interview guide. The results indicate that men have limited knowledge about family planning, that family planning services do not adequately meet the needs of men, and that spousal communication about family planning issues is generally poor. However, almost all men approved of modern family planning and expressed great interest in participating. The positive change of the beliefs and attitudes of men towards family planning in the past years has not been recognized by family planning programme managers, since available services are not in line with current public attitudes. A more couple-oriented approach to family planning is needed. Measures could include, for example, recruiting males as family planning providers, offering more family planning counselling for couples, and promoting female-oriented methods with men and vice versa.
Stability and Change in Emotional Intelligence: Exploring the Transition to Young Adulthood
Authors: Parker James D.A. , Saklofske Donald H. , Wood Laura M. , Eastabrook Jennifer M. , Taylor Robyn N.
Published: April 2005

Abstract. The concept of emotional intelligence (EI) has attracted growing interest from researchers working in various fields. The present study examined the long-term stability (32 months) of EI-related abilities over the course of a major life transition (the transition from high school to university). During the first week of full-time study, a large group of undergraduates completed the EQ-i:Short; 32 months later a random subset of these students (N = 238), who had started their postsecondary education within 24 months of graduating from high school, completed the measures for a second time. The study found EI scores to be relatively stable over the 32-month time period. EI scores were also found to be significantly higher at Time 2; the overall pattern of change in EI-levels was more than can be attributed to the increased age of the participants.
Personality Characteristics as Risk Indications of Alcohol Use and Violent Behavior in Male and Female Adolescents
Authors: Eklund Jenny M. , af Klinteberg Britt
Published: April 2005

Abstract. The present study focused on personality characteristics in adolescent boys (n = 414) and girls (n = 552) in 8th grade with self-reported violent behavior and risky alcohol use. Adolescents with indications of violent behavior and/or risky alcohol use, compared to others, were generally more impulsive, had a stronger need for change and action, were less adjusted and socially conforming, as well as more aggressive. The findings pointed toward a clustering of problem behaviors. Furthermore, adolescents with a combination of violent behavior and alcohol use had more pronounced personality scores than subjects who reported only one of these behaviors. The main finding was that among girls these behaviors appeared to be associated with more deviant levels of the personality characteristics in focus.
The Relationship of Cortical Activity and Personality in a Reinforced Go-Nogo Paradigm
Authors: Hewig Johannes , Hagemann Dirk , Seifert Jan , Naumann Ewald , Bartussek Dieter
Published: April 2005

Abstract. The reinforcement sensitivity theory proposes two biological systems for the regulation of emotion, motivation, and personality: the behavioral activation system (BAS), which responds to stimuli related to positive and negative reinforcement, and the behavioral inhibition system (BIS), which responds to conditioned stimuli of punishment and nonreward. Recent findings provided evidence for increased bilateral frontal cortical trait activity in high BAS subjects. We hypothesized that increased bilateral frontal cortical state activity might be found in high BAS subjects in response to stimuli related to positive and negative reinforcement. The cortical reaction of 38 subjects to a reinforced Go-Nogo task was analyzed. A trial consisted of three subsequent stimuli: a cue stimulus (indicating positive, negative, or no reinforcement), an imperative stimulus (Go or Nogo/Inhibition), and a feedback stimulus (success/failure). Alpha power was extracted as a measure of cortical activity. In addition, BAS and BIS were measured using questionnaires. There was an increased cortical activity in response to the cues for reinforcement. High BAS subjects showed an even higher bilateral frontal cortical activity in response to the cues for positive and negative reinforcement as compared to neutral trials. This finding further corroborates a relation of bilateral frontal cortical activity and the BAS, which has now been demonstrated for cortical trait and state activity.
Analysis and characterization of the vertical accuracy of digital elevation models from the Shuttle Radar Topography Mission
Authors: Falorni Giacomo , Teles Vanessa , Vivoni Enrique R. , Bras Rafael L. , Amaratunga Kevin S.
Published: April 2005

The first near‐global high‐resolution digital elevation model (DEM) of the Earth has recently been released following the successful Shuttle Radar Topography Mission (SRTM) of 2000. This data set will have applications in a wide range of fields and will be especially valuable in the Earth sciences. Prior to widespread dissemination and use, it is important to acquire knowledge regarding the accuracy characteristics. In this work a comprehensive analysis of the vertical errors present in the data set and the assessment of their effects on different hydrogeomorphic products is performed. In particular, the work consisted of (1) measuring the vertical accuracy of the data set in two areas with different topographic characteristics; (2) characterizing the error structure by comparing elevation residuals with terrain attributes; (3) assessing a wavelet‐based filter for removing speckle; and (4) assessing the effects of vertical errors on hydrogeomorphic products and on slope stability modeling. The results indicate that in the two sites, relief has a strong effect on the vertical accuracy of the SRTM DEM. In the high‐relief terrain, large errors and data voids are frequent, and their location is strongly influenced by topography, while in the low‐ to medium‐relief site, errors are smaller, although the hilly terrain still produces an effect on the sign of the errors. Speckling generates deviations in the drainage network in one of the investigated areas, but the application of a wavelet filter proved to be an effective tool for removing vertical noise, although further fine tuning is necessary. Vertical errors cause differences in automatically extracted hydrogeomorphic products that range between 4 and 1090.
Plate boundary slip associated with the 2003 Off‐Tokachi earthquake based on small repeating earthquake data
Authors: Matsubara Makoto , Yagi Yuji , Obara Kazushige
Published: April 2005

Plate boundary slip associated with the 2003 Off‐Tokachi earthquake, northern Japan is determined by analysis of repeating earthquakes in the source region. A total of 251 repeating earthquake groups consisting of 666 events are identified in and around the aftershock region from October 1, 2000 to May 31, 2004. Although a number of the repeating earthquakes in this region occurred before the main shock, there are many events that occurred after the main event. The repeating earthquakes are located in the major afterslip region and distributed to the southeast. Based on this analysis, it is estimated that the areas to the east and southeast of the coseismic area undergone approximately 50 cm of slip over three months following the earthquake, and less than 5 cm over the three years prior to the earthquake. Repeating earthquakes can provide afterslip data in offshore areas where resolution from land‐based GPS is poor.
Nucleation in synoptically forced cirrostratus
Authors: Lin R.‐F. , Starr D. O. , Reichardt J. , DeMott P. J.
Published: April 2005

Formation and evolution of cirrostratus in response to weak, uniform, and constant synoptic forcing is simulated using a one‐dimensional numerical model with explicit microphysics, in which the particle size distribution in each grid box is fully resolved. A series of tests of the model response to nucleation modes (homogeneous‐freezing‐only/heterogeneous nucleation) and heterogeneous nucleation parameters are performed. In the case studied here, nucleation is first activated in the prescribed moist layer. A continuous cloud‐top nucleation zone with a depth depending on the vertical humidity gradient and one of the nucleation parameters is developed afterward. For the heterogeneous nucleation cases, intermittent nucleation zones in the mid‐upper portion of the cloud form where the relative humidity is on the rise because existent ice crystals falling from higher nucleation zones do not efficiently deplete the excess water vapor and ice nuclei are available. Vertical resolution as fine as 1 m is required for realistic simulation of the homogeneous‐freezing‐only scenario, while the model resolution requirement is more relaxed in the cases where heterogeneous nucleation dominates. Bulk microphysical and optical properties are evaluated and compared. Ice particle number flux divergence, which is due to the vertical gradient of the gravity‐induced particle sedimentation, is constantly and rapidly changing the local ice number concentration, even in the nucleation zone. When the depth of the nucleation zone is shallow, particle number concentration decreases rapidly as ice particles grow and sediment away from the nucleation zone. When the depth of the nucleation zone is large, a region of high ice number concentration can be sustained. The depth of nucleation zone is an important parameter to be considered in parametric treatments of ice cloud generation.
Multidecadal changes in near‐global cloud cover and estimated cloud cover radiative forcing
Authors: Norris Joel R.
Published: April 2005

This study examines variability in zonal mean surface‐observed upper‐level (combined midlevel and high‐level) and low‐level cloud cover over land during 1971–1996 and over ocean during 1952–1997. These data were averaged from individual synoptic reports in the Extended Edited Cloud Report Archive (EECRA). Although substantial interdecadal variability is present in the time series, long‐term decreases in upper‐level cloud cover occur over land and ocean at low and middle latitudes in both hemispheres. Near‐global upper‐level cloud cover declined by 1.5%‐sky‐cover over land between 1971 and 1996 and by 1.3%‐sky‐cover over ocean between 1952 and 1997. Consistency between EECRA upper‐level cloud cover anomalies and those from the International Satellite Cloud Climatology Project (ISCCP) during 1984–1997 suggests the surface‐observed trends are real. The reduction in surface‐observed upper‐level cloud cover between the 1980s and 1990s is also consistent with the decadal increase in all‐sky outgoing longwave radiation reported by the Earth Radiation Budget Satellite (ERBS). Discrepancies occur between time series of EECRA and ISCCP low‐level cloud cover due to identified and probable artifacts in satellite and surface cloud data. Radiative effects of surface‐observed cloud cover anomalies, called “cloud cover radiative forcing (CCRF) anomalies,” are estimated based on a linear relationship to climatological cloud radiative forcing per unit cloud cover. Zonal mean estimated longwave CCRF has decreased over most of the globe. Estimated shortwave CCRF has become slightly stronger over northern midlatitude oceans and slightly weaker over northern midlatitude land areas. A long‐term decline in the magnitude of estimated shortwave CCRF occurs over low‐latitude land and ocean, but comparison with ERBS all‐sky reflected shortwave radiation during 1985–1997 suggests this decrease may be underestimated.
A minimum gradient algorithm for phased‐array null formation
Authors: Kogan Leonid
Published: April 2005

Formation of the null at the phased‐array beam pattern pointed toward the source of a radio frequency interference (RFI) can serve to mitigate the effects of that RFI. Several algorithms for creating a null at the phased‐array beam pattern have been designed. On the basis of an array side lobe minimization algorithm (Kogan, 2000), a new method for creating a null at the phased‐array beam pattern is described here. The algorithm is a straightforward one and can have an advantage in creating wide‐area nulls, especially for phased arrays with a small number of antennas. We have tested this algorithm for a possible Square Kilometre Array antenna station configured as a phased array of 19 antennas and for the Very Large Array configuration D (VLA‐D), working as a phased array for very long baseline interferometry experiments. The null is created at the given area around the given direction. The narrow null (∼0.1 ) deeper than 100 dB level can be achieved at the cost of a 2% decrease in the signal‐to‐noise ratio in the main direction. The creation of such a deep null can be impractical for many reasons, however, first and foremost because the phases and weights would have to be specified with impractical precision. Rounding the phase and weights to 1° and 0.01, respectively raises the null up to ∼50 dB.
Temperature dependence of vortex configuration by honeycomb hole arrays in a superconducting Nb film
Authors: Wu T. C. , Wang J. C. , Horng Lance , Wu J. C. , Yang T. J.
Published: April 2005

A honeycomb array of submicrometer holes in a Nb superconducting thin film has been fabricated to investigate the flux pinning effect. It is found that the minima positions reveal two regimes characterized by the matching fields and the fractional ones. It is believed that the complex behavior may come from more than one vortex being captured per pinning site. Furthermore, the temperature dependence of the saturation number of vortices per pinning site together with vortex-vortex interaction gives the complex vortex configurations.
Magnetic properties of thulium aluminoboride TmAlB4
Authors: Mori Takao , Okada Shigeru , Kudou Kunio
Published: April 2005

Magnetic properties of thulium aluminoboride TmAlB4 were investigated. Strong anisotropic behavior is observed with the c axis indicated to be the easy axis. The Curie–Weiss temperatures showed a very large anisotropy with θp‖=−5.3K and θp⊥=−62K. χ‖c exhibits a drop around TN=5.8K indicating an antiferromagnetic transition. Magnetic transitions have not been observed for any of the other known aluminoboride phases. Successive sharp metamagnetic transitions were also observed at HC1=11kG and HC2=24.5kG with H‖c. The magnetic behavior has interesting similarities to the well known REB4 system with possible multiple transitions occurring below TN, but the ordering behavior may be even more complex.
Magnetic field study of the “hidden transition” in UCd11
Authors: Rotundu C. R. , Andraka B. , Stewart G. R. , Takano Y. , Fisk Z.
Published: April 2005

The specific heat of UCd11 was measured in magnetic fields to 27T. Besides the antiferromagnetic transition, there is a second transition that can be clearly resolved in fields between 14 and 20T. This second transition (at Tm) extrapolates to a broad shoulder in C∕T in zero field. The two lines of transitions cross somewhere between 20 and 23T. Tm displays unusually weak dependence on the strength of the magnetic field. Our results argue for the intrinsic origin of this “hidden” transition.
Anisotropic exchange
Authors: Skomski R. , Kashyap A. , Zhou J. , Sellmyer D. J.
Published: April 2005

The origin and physical nature anisotropic exchange interactions is investigated. Emphasis is on nonrelativistic exchange anisotropies, as encountered, for example, in intermetallics with layered crystal structures. The summation of site-resolved exchange interactions is analyzed, and it is shown that Ruderman–Kittel-type long-range exchange yield converging exchange-stiffness expressions down to atomic length scales. In general, the resulting exchange stiffness is anisotropic, even if the interaction is mediated by an isotropic free electron gas. The determination of the mean-field Curie temperature from pair-exchange interactions requires the diagonalization of an interaction matrix, as opposed to simple site averaging.
Magnetic structure of the local-moment antiferromagnet CeCuSn
Authors: Chang S. , Janssen Yuri , Garlea V. O. , Zarestky J. , Nakotte H. , McQueeney R. J.
Published: April 2005

We report on single-crystal neutron diffraction studies of the local-moment antiferromagnet CeCuSn. The ground-state magnetic structure is characterized by a magnetic wave vector k=(0.115,0,0). The onset of antiferromagnetic order occurs around 12K with an inflection in the temperature dependence of the magnetic intensities at about 8K. This is in contrast to bulk measurements, which only show broad features at 8–10K. The ordered moments are likely reduced from the free-ion moment for Ce.
Third harmonics due to surface barrier in high-temperature superconductor
Authors: Xu X. B. , Zhang L. , Leng X. , Ding S. Y. , Liu H. K. , Wang X. L. , Dou S. X. , Lin Z. W. , Zhu J. G.
Published: April 2005

The influence of surface barrier on the third harmonics ac susceptibility (χ3) is studied numerically. The surface barrier is described by a critical current density in surfaces which are higher than the inside one. The model can act as the critical state one, the flux creep one, or the flux flow one when temperature (or field) changes. The numerical results based on the model are more close to the popular experimental data probing the harmonics as a function of temperature (or field). Besides, the surface barrier will lead to new peaks in the real and imaginary parts of the third harmonics, which are the finger signature of the surface barrier. Comparison of the peaks with those of the real part of elemental harmonic shows that they are located at the same temperature where dips in χ′ caused by the surface barrier occur, which is in well agreement with experiments.
Detection of spin and charge states in centrosymmetric materials by nonlinear optics
Authors: Satoh Takuya , Lottermoser Thomas , Fiebig Manfred , Ogimoto Yasushi , Tamaru Hiroharu , Izumi Makoto , Miyano Kenjiro
Published: April 2005

Nonlinear optics is applied to two types of centrosymmetric magnetic materials and shown to be a powerful complement to linear optics. (i) For the investigation of centrosymmetric bulk compounds resonance-enhanced sum-frequency generation is introduced and found to be particularly useful for the investigation of antiferromagnets. The technique is demonstrated on antiferromagnetic NiO. (ii) The interfaces of centrosymmetric thin films are investigated on manganite heterostructures by interface-sensitive second-harmonic generation. Maker fringes reveal a valence difference of Mn ions at the heterointerface. Comparison with a model calculation shows good agreement.
Effects of sample size on magnetic properties of Bi2Sr2CaCu2O8+δ
Authors: Fleger Y. , Kalisky B. , Shaulov A. , Yeshurun Y.
Published: April 2005

The magnetic moment and relaxation rates in Bi2Sr2CaCu2O8+δ crystals exhibit remarkable dependence on the sample size in the vicinity of the vortex order–disorder phase transition line. Specifically, we find that: (1) the magnitude of the normalized magnetic moment increases as the sample size decreases, (2) the relaxation rate increases with the sample size, and (3) the difference between the relaxation rates in samples of different size, decreases with temperature and field. These phenomena are attributed to dynamic coexistence of quasi-ordered and metastable disordered vortex states in the samples, in the temperature and field range near the vortex phase transition.
Magnetic structure of NdScGe
Authors: Cadogan J. M. , Ryan D. H. , Gagnon R. , Voyer C. J.
Published: April 2005

We have determined the magnetic structure of NdScGe (tetragonal I4∕mmm) by high-resolution neutron powder diffraction, ac-susceptibility and magnetometry. The magnetic ordering temperature is 194(2)K and the magnetic structure is characterized by ferromagnetic order of the Nd sublattice, lying in or close to the tetragonal basal plane. The Nd moment at 4K is 3.2(2)μB and, in contrast to the claims of a recent Perturbed Angular Correlation study, we find no evidence for a lattice softening effect suggested to occur around the Curie temperature.
Quasilinear temperature dependence of resistivity due to nested Fermi surface
Authors: Schlottmann P.
Published: April 2005

Following an approach by Virosztek and Ruvalds [Phys. Rev. B 42, 4064 (1990)] we calculate the quasiparticle damping close to a quantum critical point (QCP). The model consists of nested Fermi surfaces of an electron pocket and a hole pocket separated by a wave vector Q, which give rise to itinerant antiferromagnetism for a repulsive interaction between the particles. The order can gradually be suppressed by mismatching the nesting and a QCP is obtained as the critical temperature tends to zero. The damping is quasilinear in T yielding a quasilinear T dependence of the resistivity.
Crossover of pinning mechanism in La1.85Sr0.15CuO4 crystals
Authors: Bruckental Y. , Kalisky B. , Shaulov A. , Yeshurun Y.
Published: April 2005

The pinning mechanism in La1.85Sr0.15CuO4 (LaSCO) was investigated by analyzing the critical current dependence on field and temperature. Unlike other high temperature superconductors such as YBa2Cu3O7, DyBa2Cu3O7−δ, and Nd1.85Ce0.15CuO4−δ, which exhibit a single pinning mechanism over wide temperature and magnetic field ranges, our data in LaSCO show a clear crossover from δl to δTc pinning with temperature or field. While δl pinning is effective at low fields or low temperatures, δTc pinning dominates at high fields or high temperatures. Implications of the pinning mechanism crossover on the unique behavior of the second magnetization peak in LaSCO are discussed.
High pressure high temperature synthesis and magnetization of magneto-superconducting RuSr2(LnCe2)Cu2O12.25 (Ru-1232) compounds (Ln=Y and Dy)
Authors: Awana V. P. S. , Kishan H. , Kawashima T. , Takayama-Muromachi E. , Cardoso C. A.
Published: April 2005

Ru Sr 2 ( Ln Ce 2 ) Cu 2 O 12.25 (Ru-1232) compounds with Ln=Y and Dy being synthesized by high pressure high temperature (6GPa, 1200°C) solid state synthesis route crystallize in space group P4∕mmm in near single phase form with small quantities of SrRuO3 and RuSr2(RE1.5Ce0.5)Cu2O10 (Ru-1222). Both samples exhibit magnetic transitions (Tmag.) at ∼90K with significant branching of zero-field-cooled (ZFC) and field-cooled (FC) magnetization and a sharp cusp in ZFC at ∼70K, followed by superconducting transitions at ∼30K. Both compounds show typical ferromagnetic hysteresis loops in magnetic moment (M) versus field (H) magnetization right up to Tmag. i.e., <90K. To our knowledge these are the first successfully synthesized Ru-1232 compounds in near single phase with lanthanides including Y and Dy. The results are compared with widely reported Gd∕Ru-1222 and Ru-1212 (RuSr2GdCu2O8) compounds. In particular, it seems that the Ru moments magnetic ordering temperature (Tmag.) scales in the c-direction distance between magnetic RuO6 octahedras in Ru-1212∕1222 or 1232 systems.
Electronic and magnetic structures of CeTe2
Authors: Shim J. H. , Youn S. J. , Park Min Sik , Min B. I.
Published: April 2005

We have investigated electronic structures of CeTe2 to explore the correlation between the magnetic, charge density wave, and superconducting phases by using the local spin density approximation (LSDA) and LSDA+U (U=on-site Coulomb interaction) methods. We have found that the contribution near EF from Ce 4f states is negligible, suggesting that Ce 4f electrons are not the superconducting carriers. The total energy calculation indicates that the ABBA-type antiferromagnetic configuration is the most stable, while the stability is weakened by pressure. We have discussed the possible superconducting mechanism in the magnetic phase of CeTe1.82.
Magnetic field effects in UNi1∕3Ru2∕3Al
Authors: Alsmadi A. M. , El-Khatib S. , de Châtel P. F. , Nakotte H. , Lacerda A. H. , Jung M. H. , Andreev A. V. , Honda F. , Sechovsky V.
Published: April 2005

We report on the electronic properties of a UNi1∕3Ru2∕3Al single crystal as a function of temperature and magnetic field. Our specific-heat, magnetization, and resistivity data provide strong evidence that the uranium 5f moments order ferromagnetically below TC=74K. Magnetic measurements reveal that the c axis is the easy magnetization direction with a saturation moment of about 0.78μB∕U-atom. Our neutron diffraction studies on UNi1∕3Ru2∕3Al provide strong evidence that Ni occupies the 1b (and Ru the 2c) positions of the ZrNiAl structure. We argue that such preferential occupation of Ni and Ru atoms is responsible for the observed ferromagnetic ground state.
Magnetization and specific heat in U1−xLaxGa2 and magnetocaloric effect in UGa2
Authors: da Silva L. M. , Gandra F. G. , Medina A. N. , dos Santos A. O. , Cardoso L. P.
Published: April 2005

We have investigated the properties of the ferromagnetic series U1−xLaxGa2. The magnetization results show a reduction of μeff and of Tc when x is increased. The electronic coefficient γ of the specific heat increases to a maximum of 260mJ∕UmolK2 at x=0.75. This behavior is probably consequence of delocalization of 5f electrons, causing enhancement of the density of states. For x=0.9 the ordering disappears and a non-Fermi-liquid behavior is observed. UGa2 also presented a significant magnetocaloric effect of ΔSmag=−3.5J∕kgK at 120K and H=7T which can be modified by chemical pressure.
Anomalous magnetoresistance at low temperatures (T⩽10K) in a single crystal of GdB4
Authors: Cho B. K. , Rhyee Jong-Soo , Kim J. Y. , Emilia M. , Canfield P. C.
Published: April 2005

We successfully synthesized pure single crystals of GdB4, which reveals RRR=550, defined as RRR≡ρ(300K)∕ρ(2K). The temperature derivative of resistivity dρ(T)∕dT shows a transitionlike change of electronic property at Ta≈10K, in addition to the known antiferromagnetic transition at TN=42K. We also found that the ρ(T) shows an anomalous increase under the applied magnetic fields H below Ta, which leads to a positive magnetoresistance ratio MR≡[ρ(H,T)−ρ(0,T)]∕ρ(0,T)=58800% at T=2K and H=7T. Furthermore, the electronic feature near Ta manifests itself by a broad bump near T≈10K in a specific heat measurement, which indicates that the transition at Ta is a bulk property. We found that the positive and large magnetoresistance can be described by an empirical function, based on Kohler’s rule for the electron dynamics of a pure simple metal.
Electrical and magnetic properties of La2∕3Ca1∕3MnO3∕YBa2Cu3O7−δ∕La2∕3Ca1∕3MnO3 trilayers
Authors: Perez F. , Baca E. , Saldarriaga W. , Castro L. F. , Gomez M. E. , Prieto P. , Shi H. , Lederman D.
Published: April 2005

The magnetic and electrical properties of ferromagentic∕superconducting∕ferromagnetic trilayers as a function of the thickness of the superconducting (SC) layer (between 5 and 15 monolayers) were measured. La2∕3Ca1∕3MnO3∕YBa2Cu3O7−δ∕La2∕3Ca1∕3MnO3 trilayered films were fabricated in situ on (001) SrTiO3 single-crystal substrates using dc sputtering with high oxygen pressures (3.5mbar). The crystalline quality of the trilayers was analyzed by x-ray diffraction. Transport and magnetic measurements revealed a weak dependence of the ferromagnet’s (FMs) Curie temperature TFMC and the FM magnetization on the thickness of the SC layer, and a strong dependence of the superconducting transition temperature TC.
Magnetic and optical properties of rare earth doped Sn0.95RE0.05O2−δ (RE=Gd, Dy, Er)
Authors: Mohan Kant K. , Chandrasekaran K. , Ogale S. B. , Venkatesan T. , Sethupathi K. , Rao M. S. R.
Published: April 2005

The magnetic and optical properties of rare earth (Gd, Dy, and Er) ion doped SnO2 bulk and optical properties of thin films are investigated. The bulk samples were found to show an upturn in ac magnetic susceptibility at low temperatures TU and exhibited a paramagnetic moment at room temperature. The band gap of the bulk samples was found to be independent of the rare earth (RE) ions while for the thin films it varied from 3.48 eV to 3.58 eV. The observed low temperature upturn suggests an interesting magnetic property in SnO2 with RE doping.
Thermal annealing effect on magnetic properties of Fe nanoparticles implanted in yttrium-stabilized zirconia
Authors: Zhu Xiaobin , Blois C. , Buchanan K. S. , Liu Z. , Meldrum A. , Freeman M. R.
Published: April 2005

The magnetic properties of thermally annealed Fe nanocrystals prepared through ion implantation in single crystal yttrium-stabilized zirconia (Y0.2Zr0.8O19) were studied by quasistatic hysteresis loop measurements and by pulsed ferromagnetic resonance. The change of coercivity and the shape of hysteresis loops at different annealing temperature can be interpreted through the size increase of the nanocrystals. Magnetostatic coupling must be taken into account to understand the rise times of the ferromagnetic resonance, especially for the samples annealed at higher temperature.
Spin dynamics simulations of BCC iron
Authors: Tao Xiuping , Landau D. P. , Schulthess T. C. , Stocks G. M.
Published: April 2005

Using spin dynamics simulations we investigated the magnetic excitations in paramagnetic iron with a Heisenberg model considering four shells of interacting neighbors. We determined the dynamic structure factor S(q,ω) and found two peaks in “constant-E” scans and three peaks in “constant-q” scans for the paramagnetic regime. Fitting of “constant-q” scans shows that peaks centered at ±ω0 are due to propagating modes for moderate ∣q∣. Our results indicate that spin wave excitations persist above Tc.
Magnetoreresistance of PrOs4Sb12: Search for the evidence of heavy fermion behavior
Authors: Rotundu C. R. , Andraka B.
Published: April 2005

Electrical resistivity of PrOs4Sb12 was measured at temperatures down to 20 mK and in fields to 18 T. The resistivity is dominated by low-energy crystalline electric-field effects. Our analysis of the resistivity in magnetic fields provides a support for the heavy fermion state.
Rotational spectrum and carbon-13 hyperfine structure of the C3H, C5H, C6H, and C7H radicals
Authors: McCarthy M. C. , Thaddeus P.
Published: April 2005

By means of Fourier transform microwave spectroscopy of a supersonic molecular beam, we have detected the singly substituted carbon-13 isotopic species of C5H, C6H, and C7H. Hyperfine structure in the rotational transitions of the lowest-energy fine structure component (Π1∕22 for C5H and C7H, and Π3∕22 for C6H) of each species was measured between 6 and 22GHz, and precise rotational, centrifugal distortion, Λ-doubling, and C13 hyperfine coupling constants were determined. In addition, resolved hyperfine structure in the lowest rotational transition (J=3∕2→1∕2) of the three C13 isotopic species of C3H was measured by the same technique. By combining the centimeter-wave measurements here with previous millimeter-wave data, a complete set of C13 hyperfine coupling constants were derived to high precision for each isotopic species. Experimental structures (r0) have been determined for C5H and the two longer carbon-chain radicals, and these are found to be in good agreement with the predictions of high-level coupled-cluster calculations. C3H, C5H, and C7H exhibit a clear alternation in the magnitude and sign of the C13 hyperfine coupling constants along the carbon-chain backbone. Because the electron spin density is nominally zero at the central carbon atom of C3H, C5H, and C7H, and at alternating sets of carbon atoms of C5H and C7H, owing to spin polarization, almost all of the C13 coupling constants at these atoms are small in magnitude and negative in sign. Spin-polarization effects are known to be important for the Fermi-contact (bF) term, but prior to the work here they have generally been neglected for the hyperfine terms a, c, and d.
Magnetically driven isentropic compression to multimegabar pressures using shaped current pulses on the Z accelerator
Authors: Davis Jean-Paul , Deeney Christopher , Knudson Marcus D. , Lemke Raymond W. , Pointon Timothy D. , Bliss David E.
Published: April 2005

A technique has previously been developed on the Z accelerator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] to generate ramped compression waves in condensed matter for equation-of-state studies [C. A. Hall, J. R. Asay, M. D. Knudson, W. A. Stygar, R. B. Spielman, T. D. Pointon, D. B. Reisman, A. Toor, and R. C. Cauble, Rev. Sci. Instrum. 72, 3587 (2001)] by using the Lorentz force to push on solid electrodes rather than to drive a Z pinch. This technique has now been extended to multimegabar pressures by shaping the current pulse on Z to significantly increase the sample thickness through which the compression wave can propagate without forming a shock. Shockless, free-surface velocity measurements from multiple sample thicknesses on a single experiment can be analyzed using a backward integration technique [D. B. Hayes, C. A. Hall, J. R. Asay, and M. D. Knudson, J. Appl. Phys. 94, 2331 (2003)] to extract an isentropic loading curve. At very high pressures, the accuracy of this method is dominated by relative uncertainty in the transit time between two thicknesses. This paper discusses in some detail the issues involved with accurate measurement of a multimegabar isentrope, including experiment design trade-offs and mechanics of pulse shaping on Z.
Filamentation instability of an electromagnetic wave in flowing magnetized homogeneous plasma
Authors: Ghanshyam R. , Tripathi V. K. , Burnwal A. P. , Jayaswal S. K.
Published: April 2005

An electromagnetic wave propagating at an angle θO to the flow velocity νb in a supersonically flowing homogeneous plasma with a background magnetic field is susceptible to filamentation instability. It is found that the dominant contribution arises for this instability from the plasma flow. The flow velocity introduces finite real frequency to the low frequency ion quasimode. The low frequency mode grows temporally at the cost of free energy available from the plasma flow velocity and hence the pump wave is broken into filaments and trapped into the density troughs of the growing ion quasimode. The nonlinearity arises through the ponderomotive force and the growth rate is sensitive to the angle of the pump and flow velocity νb. It can be concluded from the calculations that the growth rate increases and the instability in k space widens with plasma flow velocity and the angle of incidence.
Measurement of edge currents in DIII-D and their implication for pedestal stability
Authors: Thomas D. M. , Leonard A. W. , Groebner R. J. , Osborne T. H. , Casper T. A. , Snyder P. B. , Lao L. L.
Published: April 2005

The present performance limits of tokamak discharges are strongly coupled to the stability and transport properties of the edge plasma. Both experimental and modeling efforts have shown a clear connection between the edge pressure pedestal height and core plasma confinement. The key to understanding the stability and performance limits of the pedestal revolves around an accurate knowledge of the plasma current in this region. Using the Zeeman effect in an injected 30keV lithium beam, we have measured the currents in the edge of the DIII-D [J. L. Luxon, Nucl. Fusion 42, 6114 (2002)] tokamak for various confinement modes. This method of determining j(r) is insensitive to the large electric fields which coexist in the pedestal region and which complicate motional Stark effect measurements. For the high confinement cases, where substantial pedestal pressures exist, we find large (~MA∕m2), localized (ΔR∼1–2cm) currents in the pedestal region, located near the maximum in the pressure gradient. These values are consistent with calculations of edge bootstrap current using the neoclassical NCLASS [W. A. Houlberg, K. C. Shaing, S. P. Hirshman, and M. C. Zarnstorff, Phys. Plasmas 4, 3230 (1997)] and Sauter [O. Sauter, C. Angioni, and Y. R. Lin-Lin, Phys. Plasmas 6, 2834 (1999)] models and the measured pedestal density and temperature profiles. The apparent consistency of the measured jEDGE with neoclassical predictions occurs despite the violation of one of the fundamental tenets of the theory, namely, ε=ρi∕LP⪡1, where ρi is the ion poloidal gyroradius and Lp is the pressure gradient scale length. The measured jEDGE has also been used to generate self-consistent reconstructions using the free boundary equilibrium solvers CORSICA [T. A. Casper, T. B. Kaiser, R. A. Jong, L. L. LoDestro, J. Moller, and L. D. Pearlstein, Plasma Phys. Controlled Fusion 45, 1193 (2003)] and EFIT [L. L. Lao, H. E. St. John, R. D. Stambough, A. G. Kellman, and W. Pfeiffer, Nucl. Fusion 25, 1611 (1985)]. These equilibria allow us, in conjunction with the edge localized instabilities in tokamak experiments [P. B. Snyder, H. R. Wilson, J. R. Ferron, L. L. Lao, A. W. Leonard, T. H. Osborne, A. D. Turnbull, D. Mossessian, M. Murakami, and X. Q. Xu, Phys. Plasmas 9, 2037 (2002); H. R. Wilson, P. B. Snyder, G. T. A. Huysmans, and R. L. Miller, Phys. Plasmas 9, 1277 (2002)] magnetohydrodynamic stability code, to assess the linear stability of the edge to peeling∕ballooning modes. These results are then compared to the measured edge localized mode onset conditions and again good agreement is found between the experimental and model limits on the maximum permissible jEDGE.
Modeling fluid instabilities in inertial confinement fusion hydrodynamics codes
Authors: Zalesak Steven T. , Schmitt Andrew J. , Velikovich A. L. , Gardner J. H.
Published: April 2005

The numerical tools typically used to model the evolution of fluid instabilities in inertial confinement fusion hydrodynamics codes are examined, and some are found to have properties which would seem to be incompatible with the accurate modeling of small-amplitude perturbations, i.e., perturbations in the linear stage of evolution. In particular a “differentiability condition” which is satisfied by the physics in such situations is not necessarily satisfied by the numerical algorithms in typical use. It is demonstrated that it is possible to remove much of the nondifferentiability in many cases, and that substantial improvement in one’s ability to accurately model the evolution of small-amplitude perturbations can result. First a simple example involving a nondifferentiable radiation transport algorithm is shown, and then the nondifferentiabilities introduced by the use of upwind and “high resolution” hydrodynamics algorithms are analyzed.
First-principles study of the adsorption of cesium on Si(001)(2×1) surface
Authors: Xiao H. Y. , Zu X. T. , Zhang Y. F. , Yang L.
Published: April 2005

First-principles calculations based on density functional theory–generalized gradient approximation method have been performed on cesium adsorption on Si(001)(2×1) surface. The optimized geometries and adsorption energies have been obtained and the preferred binding sites have been determined for the coverage (Θ) of one monolayer and half a monolayer. At Θ=0.5 ML the most stable adsorption site is shown to be T3 site. At Θ=1 ML two Cs atoms are adsorbed at HH and T3 sites, respectively. It was found that the saturation coverage of Cs for the Si(001)(2×1)–Cs surface is one monolayer instead of half a monolayer. This finding supports the majority of experimental observations but does not support recent coaxial impact collision ion scattering spectroscopy investigations [Surf. Sci. 531, L340 (2003)] and He+ Rutherford backscattering spectroscopy studies [Phys. Rev. B 62, 4545 (2000)]. Mulliken charge and overlap population analysis showed that the Cs–Si bond is indeed ionic rather than polarized covalent as generally assumed for alkali metal (AM) on Si(001)(2×1) surface. Geometrical structure analysis seems to have limitations in determining the nature of AM-substrate bond. We also found that the silicon surface is metallic and semiconducting for the coverages of 0.5 and 1 ML, respectively.
Magnetic entropy change of the layered perovskites La2−2xSr1+2xMn2O7
Authors: Wang Aihua , Cao Guohui , Liu Yang , Long Yi , Li Yang , Feng Zhaosheng , Ross Joseph H.
Published: April 2005

Magnetocaloric properties of perovskite-type manganese oxides with double Mn-O layers of composition La2−2xSr1+2xMn2O7 (x=0.33 and 0.4) have been investigated. A broad peak of magnetic entropy change (−ΔSM) was observed at the Curie temperature. The shape of −ΔSM is strongly dependent on the Sr concentration. In contrast to Ln1−xAxMnO3 perovskites, the distinct curvilinear shape of −ΔSM for perovskites with double Mn-O layers shows different magnetic mechanisms arising from magnetocrystalline anisotropy.
“Black spots” in a surfactant-rich Belousov–Zhabotinsky reaction dispersed in a water-in-oil microemulsion system
Authors: Kaminaga Akiko , Vanag Vladimir K. , Epstein Irving R.
Published: April 2005

The Belousov–Zhabotinsky (BZ) reaction dispersed in water-in-oil aerosol OT (AOT) microemulsion has been studied at small radius Rd of water nanodroplets (Rd(nm)≅0.17ω,ω=[H2O]∕[AOT]=9). Stationary spotlike and labyrinthine Turing patterns are found close to the fully oxidized state. These patterns, islands of high concentration of the reduced state of the Ru(bpy)32+ catalyst, can coexist either with “black” reduction waves or, under other conditions, with the “white” oxidation waves usually observed in the BZ reaction. The experimental observations are analyzed with the aid of a new Oregonator-like model and qualitatively reproduced in computer simulations.
Effect of monovacancies on the relative stability of fcc and hcp hard-sphere crystals
Authors: Kwak Sang Kyu , Kofke David A.
Published: April 2005

We report results of Monte Carlo simulations showing that the presence of vacancies does not affect the relative stability of stress-free fcc and hcp hard-sphere crystals.
The structures of m-benzyne and tetrafluoro-m-benzyne
Authors: Smith Christopher E. , Crawford T. Daniel , Cremer Dieter
Published: April 2005

The structures of m-benzyne and its fluorinated derivative, tetrafluoro-m-benzyne, were investigated using coupled cluster methods including triple excitations [CCSD(T) and CCSDT], different reference wave functions (spin-restricted Hartree–Fock, spin-unrestricted Hartree–Fock, and Brueckner), and different basis sets [6-31G(d,p) and correlation-consistent valence triple-zeta (cc-pVTZ)]. The inclusion of triple excitations in conjunction with d- and f-type polarization functions is paramount to correctly describe through-bond delocalization of the monocyclic form. At the highest level of theory, the C1–C3 distance of the minimum energy form of m-benzyne is 2.0Å and the profile of the potential energy surface along the C1–C3 distance is that of an asymmetric, single well, in agreement with previous density-functional theory and coupled cluster studies. In addition, the calculated CCSD(T) fundamental frequencies are in excellent agreement with the measured infrared frequencies, thus confirming the monocyclic form of m-benzyne. For tetrafluoro-m-benzyne, however, the increased eclipsing strain between the ring-external C–X bonds stabilizes the bicyclo[3.1.0]hexatriene form: the C1–C3 distance is calculated at the CCSD(T)/cc-pVTZ level to be approximately 1.75Å, which is in the range of elongated CC bonds. Computed harmonic vibrational frequencies compare reasonably well with the experimental neon-matrix difference spectrum and provide further evidence for the existence of a bicyclic form.
Relativistic effects determined using the Douglas–Kroll contracted basis sets and correlation consistent basis sets with small-core relativistic pseudopotentials
Authors: Yockel Scott , Wilson Angela K.
Published: April 2005

The coupled cluster approximation with single, double, and quasiperturbative triple excitations [CCSD(T)] was used in combination with the Douglas–Kroll contracted correlation consistent basis sets [cc-pVnZ-DK, where n=D(2), T(3), Q(4), and 5] and small-core relativistic pseudopotentials (PP) with correlation consistent polarized valence basis sets (cc-pVnZ-PP and aug-cc-pVnZ-PP) to investigate the impact of scalar relativistic corrections on energetic and structural properties of small molecules containing third-row (Ga–Kr) atoms. These molecules were taken from the Gaussian-2 extended test set for third-row atoms. Atomization energies, ionization energies, electron affinities, and proton affinities for molecules in the test set were determined and compared with nonrelativistic results which were obtained in a recent study in which the standard and augmented correlation consistent basis sets were used in combination with CCSD(T). Several schemes were used to extrapolate the energies to the complete basis set limit.