bluuebunny/crossref_metadata_2025 huggingface dataset:
SSTR5 ablation in islet results in alterations in glucose homeostasis in mice
Authors: Wang X.P. , Yang J. , Norman M.A. , Magnusson J. , DeMayo F.J. , Brunicardi F.C.
Published: May 2005

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (βSSTR5Kd) using the Cre‐lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, βSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST‐28 stimulation in the βSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in βSSTR5Kd mice pancreata. In addition, βSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in βSSTR5Kd mice. Further studies of βSSTR5Kd mice had revealed elevated serum C‐peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.
Role change of design engineers in product development
Authors: Hong Paul , Vonderembse Mark A. , Doll William J. , Nahm Abraham Y.
Published: May 2005

Product development is recognized as cross‐functional, knowledge‐intensive work that has become increasingly important in the fast‐paced, globally competitive environment. Researchers and practicing managers contend that design engineers may play an important role in product development efforts. However, their effect on the product development process is not well understood and the extent of their impact on product development performance has not been adequately accessed. This research defines the changing role of design engineers, and it discusses their impact on setting clear project targets and sharing knowledge about customers. The study investigates the impact of these variables on product development productivity. Data collected from 205 manufacturing firms were used to create valid and reliable instruments to assess role change of design engineers, clarity of project targets, shared knowledge about customers and product development productivity. Results from structural equation modeling indicate that as the role of design engineers expands the clarity of project targets increase. This increase impacts the extent of shared knowledge about customers. Increases in the clarity of project targets and shared knowledge about customers appear to enhance product development productivity.
Uncemented short‐length diaphyseal segmental replacement prosthesis fixation—Finite element analysis and long‐term results
Authors: Werner C. M. L. , Jacob H. A. C. , Ramseier L. E. , Favre P. , Exner G. U.
Published: May 2005

Introduction: Extensively porous coated segmental replacement prostheses with intramedullary cementless fixation to bone over the whole length of stem often exhibit resorption of the surrounding bone due to stress‐shielding. This makes them particularly susceptible to aseptic loosening.

Study: A finite element analysis of the state of loading of a short‐length fixation in a new prosthetic stem design has shown a definite advantage over long‐length fixation. The stress pattern within the bone surrounding the prosthesis confirmed that shortening of the ongrowth area in length increases the stress values at the resection level significantly. This stem (Endlock) has been used for diaphyseal anchorage in the treatment of tumors in combination with an artificial joint of proven design in order to reduce stress shielding.

Results: No Endlock stem fractures or aseptic loosenings were observed at recent follow‐up. The early clinical results comply with the theoretical assumptions.

Conclusions: A short‐length fixation system based on intramedullary anchorage of segmental replacement endoprostheses would possibly support physiologic adaptive processes more than fixation over the full length of the stem. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
An historical and genomic view of schistosome conjugal biology with emphasis on sex-specific gene expression
Authors: HOFFMANN K. F.
Published: May 2005

The genetic programmes associated with the sexual biology of dioecious schistosomes remain a critically important but significantly understudied area of parasitology. Throughout the last four decades, progress has been slow in describing the gross antigenic and proteomic differences linked to sexually mature schistosomes and in characterizing some of the sex-associated transcripts and regulatory mechanisms induced during developmental maturation. These investigations have been severely hindered by the lack of complete EST/genomic information, as well as corresponding post- and functional-genomic tools for studying these pathogenic parasites. As near complete transcriptomes forSchistosoma japonicumandS. mansonihave recently been reported, and both DNA microarrays and post-transcriptional gene silencing have been applied to schistosomes, the tools and techniques for the high-throughput identification and characterization of transcripts involved in conjugal biology are now readily available. Here, an historical review is presented that summarizes some of the most significant findings associated with schistosome sex and sexual maturation during the last several decades. Following this discussion is a current overview of some modern day genomic approaches used to study schistosomes, which illustrates how major advances in the field of conjugal biology will be achieved.
The use ofCaenorhabditis elegansin parasitic nematode research
Authors: GILLEARD J. S.
Published: May 2005

There is increasing interest in the use of the free-living nematodeCaenorhabditis elegansas a tool for parasitic nematode research and there are now a number of compelling examples of its successful application.C. eleganshas the potential to become a standard tool for molecular helminthology researchers, just as yeast is routinely used by molecular biologists to study vertebrate biology. However, in order to exploitC. elegansin a meaningful manner, we need a detailed understanding of the extent to which different aspects ofC. elegansbiology have been conserved with particular groups of parasitic nematodes. This review first considers the current state of knowledge regarding the conservation of genome organisation across the nematode phylum and then discusses some recent evolutionary development studies in free-living nematodes. The aim is to provide some important concepts that are relevant to the extrapolation of information fromC. elegansto parasitic nematodes and also to the interpretation of experiments that useC. elegansas a surrogate expression system. In general, examples have been specifically chosen because they highlight the importance of careful experimentation and interpretation of data. Consequently, the focus is on the differences that have been found between nematode species rather than the similarities. Finally, there is a detailed discussion of the current status ofC. elegansas a heterologous expression system to study parasite gene function and regulation using successful examples from the literature.
ProbingTrypanosoma cruzibiology with DNA microarrays
Authors: BURLEIGH B. A.
Published: May 2005

The application of genome-scale approaches to studyTrypanosoma cruzi–host interactions at different stages of the infective process is becoming possible with sequencing and assembly of theT. cruzigenome nearing completion and sequence information available for both human and mouse genomes. Investigators have recently begun to exploit DNA microarray technology to analyze host transcriptional responses toT. cruziinfection and dissect developmental processes in the complexT. cruzilife-cycle. Collectively, information generated from these and future studies will provide valuable insights into the molecular requirements for establishment ofT. cruziinfection in the host and highlight the molecular events coinciding with disease progression. While the field is in its infancy, the availability of genomic information and increased accessibility to relatively high-throughput technologies represents a significant advancement toward identification of novel drug targets and vaccine candidates for the treatment and prevention of Chagas' disease.
Integrating genetics and genomics to identify new leads for the control ofEimeriaspp.
Authors: SHIRLEY M. W. , BLAKE D. , WHITE S. E. , SHERIFF R. , SMITH A. L.
Published: May 2005

Eimerian parasites display a biologically interesting range of phenotypic variation. In addition to a wide spectrum of drug-resistance phenotypes that are expressed similarly by many other parasites, theEimeriaspp. present some unique phenotypes. For example, unique lines ofEimeriaspp. include those selected for growth in the chorioallantoic membrane of the embryonating hens egg or for faster growth (precocious development) in the mature host. The many laboratory-derived egg-adapted or precocious lines also share a phenotype of a marked attenuation of virulence, the basis of which is different as a consequence of thein ovoorin vivoselection procedures used. Of current interest is the fact that some wild-type populations ofEimeria maximaare characterized by an ability to induce protective immunity that is strain-specific. The molecular basis of phenotypes that defineEimeriaspp. is now increasingly amenable to investigation, both through technical improvements in genetic linkage studies and the availability of a comprehensive genome sequence for the caecal parasiteE. tenella. The most exciting phenotype in the context of vaccination and the development of new vaccines is the trait of strain-specific immunity associated withE. maxima. Recent work in this laboratory has shown that infection of two inbred lines of White Leghorn chickens with the W strain ofE. maximaleads to complete protection to challenge with the homologous parasite, but to complete escape of the heterologous H strain, i.e. the W strain induces an exquisitely strain-specific protective immune response with respect to the H strain. This dichotomy of survival in the face of immune-mediated killing has been examined further and, notably, mating between a drug-resistant W strain and a drug-sensitive H strain leads to recombination between the genetic loci responsible for the specificity of protective immunity and resistance to the anticoccidial drug robenidine. Such a finding opens the way forward for genetic mapping of the loci responsible for the induction of protective immunity and integration with the genome sequencing efforts.
Faulting and volcanism in the axial valley of the slow‐spreading center of the Mariana back arc basin from Wadatsumi side‐scan sonar images
Authors: Deschamps Anne , Fujiwara Toshiya , Asada Miho , Montési Laurent , Gente Pascal
Published: May 2005

We analyzed in detail the geology of the median valley floor of the Mariana Basin slow‐spreading ridge using sea surface geophysical data and a high‐resolution deep‐tow side‐scan sonar survey over one spreading segment. Analysis of surface magnetic data indicates highly asymmetric accretion, with the half‐spreading rate on the western side of the basin being two to three times larger than on the eastern side. Surface magnetic and reflectivity data together suggest that asymmetric spreading is accomplished through eastward ridge jumps of ∼10 km of amplitude. Deep‐tow backscatter data indicate along‐axis variations of the volcanic processes with the emplacement of smooth and hummocky flows at the segment center and end, respectively. This variation likely relates to changes in the effusion rate due to the deepening or even disappearance of the magma chamber toward the segment end. Concerning tectonic processes, we find a power law distribution of the fractures, with an exponent of 1.74. This suggests that within the inner valley floor, fracture growth prevails over fracture nucleation and coalescence and that fractures accommodate less than 8% of the strain. According to our calculation based on a ratio of 0.02 to 0.03 between the vertical displacement and the length of faults, the amount of tectonic strain accommodated in the inner valley floor would consistently be ∼1.1–3.4%. Data also show two distinct sets of fractures. One trend is parallel to the rift direction at the segment center (∼N160°E) and perpendicular to the plate separation direction. Another set trends ∼17° oblique to this direction (∼N175°E) and is located over the eastern part of the valley, in the vicinity of a major bounding fault also trending ∼N175°E, that is, obliquely to the direction of plate motion. We modeled the stress field near a major fault that is oblique to the regional stress field associated with plate separation using a three‐dimensional boundary element approach. We found that the orientation of the predicted fissuring near the oblique fault is locally rotated by ∼15° due to a flexure of the bending plate close to this fault.
Solar source of the largest geomagnetic storm of cycle 23
Authors: Gopalswamy N. , Yashiro S. , Michalek G. , Xie H. , Lepping R. P. , Howard R. A.
Published: May 2005

The largest geomagnetic storm of solar cycle 23 occurred on 2003 November 20 with a Dst index of −472 nT, due to a coronal mass ejection (CME) from active region 0501. The CME near the Sun had a sky‐plane speed of ∼1660 km/s, but the associated magnetic cloud (MC) arrived with a speed of only 730 km/s. The MC at 1 AU (ACE Observations) had a high magnetic field (∼56 nT) and high inclination to the ecliptic plane. The southward component of the MC's magnetic field was made up almost entirely of its axial field because of its east‐south‐west (ESW) chirality. We suggest that the southward pointing strong axial field of the MC reconnected with Earth's front‐side magnetic field, resulting in the largest storm of the solar cycle 23.
Multi‐year measurements of cloud base heights at South Pole by lidar
Authors: Mahesh Ashwin , Campbell James R. , Spinhirne James D.
Published: May 2005

The Micropulse Lidar Network has operated a full‐time lidar measurement program at South Pole Station since 2000. Observations from this instrument are an important multi‐year record of clouds over the Antarctic plateau. Earlier South Pole observations relied mostly on passive measurements to characterize clouds; the lidar's active profiles present an opportunity to validate current understanding of Antarctic clouds, as well as study properties that are not adequately captured in passive measurements. Lidar observations show clouds to be present roughly 40 percent of the time, and often appearing in wind‐swept layers immediately above ground‐based scattering layers such as blowing snow and suspended ice particles. There is very little indication of seasonal variability in cloud base heights; this contradicts earlier observations from an interferometer made in 1992 when it was determined that the distribution of cloud base heights in the summer months was different from that seen at other times. Those observations had also indicated that cloud base heights over the high plateau are distributed bimodally, with many near‐surface clouds, and a second mode of other clouds well above the surface–based inversion. The lidar observations, however, suggest that this may be true only of the optically thicker clouds and even then only in the spring.
Quasi‐spherical approach for seismic wave modeling in a 2‐D slice of a global Earth model with lateral heterogeneity
Authors: Toyokuni Genti , Takenaka Hiroshi , Wang Yanbin , Kennett Brian L. N.
Published: May 2005

For iterative calculations of synthetic seismograms with limited computer resources, a fast and accurate modeling method is needed. Axisymmetric modeling has often been used in global seismology to restrict computational time and storage. This approach can correctly model 3‐D geometrical spreading effects with computational times comparable to 2‐D methods, but cannot treat asymmetric structures about the source axis. To overcome this problem, a new approach is proposed for seismic wave propagation in a 2‐D slice through a global Earth model with lateral heterogeneity. The elastodynamic equation for spherical coordinates is not solved in the conventional spherical domain but instead in the “quasi‐spherical domain” using the finite‐difference method. The validity and efficiency of this technique is illustrated with numerical examples including subduction zone structures.
Evidence for self‐similar, triangular slip distributions on earthquakes: Implications for earthquake and fault mechanics
Authors: Manighetti I. , Campillo M. , Sammis C. , Mai P. M. , King G.
Published: May 2005

We characterize average slip distributions on earthquakes beyond their individual heterogeneity. For that, we analyze a large number of seismic slip distributions both measured at the surface after earthquakes (44 profiles) and derived from slip inversion models (76 models). Investigating the overall shape of these slip profiles, we find that they are roughly triangular both along strike and dip, and most of them (70–80%) are asymmetric. Long linear slopes and high slip gradients therefore are the key ingredients to describe earthquake slip profiles. The scaling relations between maximum displacement and length (or width) suggest furthermore that the triangular slip profiles are self‐similar. Such slip patterns make earthquakes dominated by one major zone of maximum slip hence one major “asperity.” Analyzing the position of hypocenters with respect to these “asperities,” we find that earthquakes nucleate at a distance from them that averages 20–30% of their total length. Compiling observations on 56 earthquakes, we show that this distance (i.e., the asperity size) is structurally defined. We then compare the earthquake slip profiles to cumulative slip profiles measured on long‐term faults of various ages and sizes and find that all profiles have a similar shape, triangular and asymmetric. Hence combining data for a large number of earthquakes leads to point out average, generic characteristics of the coseismic slip that are similar to those that emerge from the accumulation of events with time on a single fault. This suggests that these characteristics result from robust physical properties.
X‐ray diffraction study of the single‐crystal elastic moduli of ε‐Fe up to 30 GPa
Authors: Merkel Sébastien , Shu Jinfu , Gillet Philippe , Mao Ho‐Kwang , Hemley Russell J.
Published: May 2005

Room temperature investigations of the single‐crystal elastic moduli and anisotropy of the ε phase of iron are performed up to 30.3 GPa using the radial X‐ray diffraction technique. The accuracy of the calculated elastic moduli has improved compared to previous measurements using similar techniques because of an increase in accuracy of the measurement, confinement of the sample to limit the effect of plasticity, and better calibration of the stress conditions. The aggregate shear modulus that we obtain is in good agreement with a variety of other experimental deductions but differs from first‐principles calculations. The effects of the calibration of stress and micromechanical model on the deduction of elastic moduli and elastic anisotropy are discussed in detail. The anisotropy we obtain has the same order of magnitude as first‐principles calculations but the direction is reversed, with a weaker amplitude that previous measurements.
Cirrus cloud optical, microphysical, and radiative properties observed during the CRYSTAL‐FACE experiment: A lidar‐radar retrieval system
Authors: Mitrescu C. , Haynes J. M. , Stephens G. L. , Miller S. D. , Heymsfield G. M. , McGill M. J.
Published: May 2005

A method of retrieving cloud microphysical properties using combined observations from both cloud radar and lidar is introduced. The description of the lidar‐radar model accounts for nonspherical effects of the ice crystals, with a treatment for multiple scattering and Mie effects. This retrieval makes use of an improvement to the traditional optimal estimation retrieval method, whereby a series of corrections are applied to the state vector during the search for an iterative solution. This allows faster convergence to a solution and is less processor intensive. The retrieval method is applied to radar and lidar observations from the CRYSTAL‐FACE experiment, and vertical profiles of ice crystal characteristic diameter, number concentration, and ice water content are retrieved for a cirrus cloud layer observed 1 day of that experiment. Empirical relationships between ice water content and radar reflectivity as well as between particle number concentrations and characteristic diameter are also examined. The results indicate that a distinct and robust relationship exists between the latter two parameters, offering insight into the nature of cirrus microphysical processes.
Debris‐bed friction of hard‐bedded glaciers
Authors: Cohen D. , Iverson N. R. , Hooyer T. S. , Fischer U. H. , Jackson M. , Moore P. L.
Published: May 2005

Field measurements of debris‐bed friction on a smooth rock tablet at the bed of Engabreen, a hard‐bedded, temperate glacier in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction of up to 500 kPa. The corresponding bulk friction coefficient between the dirty basal ice and the tablet was between 0.05 and 0.08. A model of friction in which nonrotating spherical rock particles are held in frictional contact with the bed by bed‐normal ice flow can account for these measurements if the power law exponent for ice flowing past large clasts is 1. A small exponent (n < 2) is likely because stresses in ice are small and flow is transient. Numerical calculations of the bed‐normal drag force on a sphere in contact with a flat bed using n = 1 show that this force can reach values several hundred times that on a sphere isolated from the bed, thus drastically increasing frictional resistance. Various estimates of basal friction are obtained from this model. For example, the shear traction at the bed of a glacier sliding at 20 m a−1 with a geothermally induced melt rate of 0.006 m a−1 and an effective pressure of 300 kPa can exceed 100 kPa. Debris‐bed friction can therefore be a major component of sliding resistance, contradicting the common assumption that debris‐bed friction is negligible.
Impact of new laboratory studies of N2O5 hydrolysis on global model budgets of tropospheric nitrogen oxides, ozone, and OH
Authors: Evans M. J. , Jacob D. J.
Published: May 2005

We investigate the impact of new laboratory studies of N2O5 hydrolysis in aerosols on global model simulations of tropospheric chemistry. We use data from these new studies to parameterize the reaction probability (γN2O5) in the GEOS‐CHEM global model as a function of local aerosol composition, temperature, and relative humidity. We find a much lower global mean γN2O5 (0.02) than commonly assumed in models (0.1). Relative to a model simulation assuming a uniform γN2O5 = 0.1, we find increases in mass‐averaged tropospheric NOx, O3, and OH concentrations of 7%, 4%, and 8% respectively. The increases in NOx and O3 concentrations bring the GEOS‐CHEM simulation in better agreement with climatological observations.
Integrated equivalent latitude as a proxy for dynamical changes in ozone column
Authors: Wohltmann I. , Rex M. , Brunner D. , Mäder J.
Published: May 2005

It is well known that short‐term variability in ozone column at a given location is almost solely caused by dynamical changes connected to tropospheric pressure systems. Long‐term trends and interannual variability of ozone are also influenced by these dynamical changes. We address two questions, which are still under discussion: What is the impact of these dynamical changes on the observed long‐term trend of ozone, and what is the quantitative contribution of the physical processes standing behind the dynamical variability to the trends and short‐term variability? These processes are identified as horizontal isentropic transport and the vertical displacement of isentropes. We use a multiple regression model to analyze the variability of the total ozone column. The model includes a newly introduced explanatory variable based on the equivalent latitude profile at a given location. Ozone column data are taken from 8 high quality stations of the European Dobson spectrometer network. Results show that vertical displacements are the main contributor to short‐term variability, and that 30%–50% of the long‐term trend can be explained by long‐term pressure changes.
Observations of infrasound from surf in southern California
Authors: Arrowsmith Stephen J. , Hedlin Michael A. H.
Published: May 2005

We observe 10,000's of infrasound signals annually, in the frequency range from 1–5 Hz, at the I57US infrasound array in Southern California. 75% of these signals arrive at I57US at azimuths between 260 and 320 degrees. There is a good correlation between the amplitudes of signals from 260–320° and wave height measurements offshore Southern California, providing firm evidence that the signals from these azimuths are caused by surf action. By modeling the propagation of infrasound for specific time periods (using 3D ray‐tracing and up‐to‐date atmospheric models), we show that amplitudes of signals recorded at I57US are also dependent upon atmospheric winds. The modeled rays that return in the stratosphere fit observations more closely than modeled rays that return in the troposphere, suggesting the signals are from stratospheric returns. Our findings are the first observations of surf infrasound at a long‐range from the source region. This suggests that surf signals might serve as a probe of the atmosphere, much like microbarom signals are used to probe the atmosphere at greater range.
Introduction to special section: Stress transfer, earthquake triggering, and time‐dependent seismic hazard
Authors: Steacy Sandy , Gomberg Joan , Cocco Massimo
Published: May 2005

In this introduction, we review much of the recent work related to stress transfer, earthquake triggering, and time‐dependent seismic hazard in order to provide context for the special section on these subjects. Considerable advances have been made in the past decade, and we focus on our understanding of stress transfer at various temporal and spatial scales, review recent studies of the role of fluids in earthquake triggering, describe evidence for the connection between volcanism and earthquake triggering, examine observational evidence for triggering at all scales, and finally discuss the link between earthquake triggering and time‐dependent seismic hazard. We conclude by speculating on future areas of research in the next decade.
On the Readability of Graphs Using Node-Link and Matrix-Based Representations: A Controlled Experiment and Statistical Analysis
Authors: Ghoniem Mohammad , Fekete Jean-Daniel , Castagliola Philippe
Published: May 2005

In this article, we describe a taxonomy of generic graph related tasks along with a computer-based evaluation designed to assess the readability of two representations of graphs: matrix-based representations and node-link diagrams. This evaluation encompasses seven generic tasks and leads to insightful recommendations for the representation of graphs according to their size and density. Typically, we show that when graphs are bigger than twenty vertices, the matrix-based visualization outperforms node-link diagrams on most tasks. Only path finding is consistently in favor of node-link diagrams throughout the evaluation.
dc noise enhancement due to correlations between grain size and switching field
Authors: Marrow Marcus , Neal Bertram H.
Published: May 2005

A mechanism for dc noise enhancement in the presence of a reverse dc field is presented. In particular, only in a medium where the grain switching fields increase monotonically with increasing grain size does the dc noise exhibit a spatially correlated amplification with respect to the dc erased state as has been recently observed in spin-stand measurements. The effect of this correlation was explored by generating media with random grains using a Monte Carlo grain growth model. In our study the media are assumed to be perfectly oriented and have a fixed nonmagnetic intergranular spacing. The magnetization is initially saturated in one direction and grains are reversed to simulate the application of a reverse dc field. The dc noise maximum occurs when the medium is in the zero net magnetization state. The noise power for the case of grain-size-correlated switching is approximately twice that (3dB) for the case of uncorrelated switching, in reasonable agreement with the experiment.
Co
–
Pt
∕
Pt
thin films with perpendicular magnetization and a high coercivity prepared by gas flow sputtering
Authors: Mifuji Shiro , Sakuma Hiroshi , Ishii Kiyoshi
Published: May 2005

Pt underlayers were deposited on an SiO2 glass substrate by magnetron sputtering, and then Co–Pt alloy films were deposited on them at 50 °C by gas flow sputtering. Perpendicular magnetization was realized at a composition ranging from 0 to 55 at % Pt. Their structure and magnetic properties were studied as a function of Pt content and annealing temperature from 200 to 400 °C. For as-sputtered Co–Pt(30nm)∕Pt(200nm) films, it was found that the perpendicular coercivity increased with increase in Pt content and had a maximum value of 4.7 kOe at 25 at % Pt. At this composition, the perpendicular anisotropy constant was 1.8×106erg∕cc. Post-annealing of the films in an Ar atmosphere resulted in increases in both coercivity and anisotropy constant. At 300 °C, they reached maximum values of 7.0 kOe and 4.0×106erg∕cc, respectively.
Perpendicular recording media using phase-separated AlSi films
Authors: Yasui N. , Nakamura T. , Fukutani K. , Saito T. , Aiba T. , Ohashi Y. , Den T.
Published: May 2005

We have developed perpendicular recording media with nanosized cylindrical Co particles. The diameter and period of these particles are less than 10 and 12 nm, respectively. Al cylinders were grown in an a-Si matrix during AlSi film deposition due to the eutectic phase separation. The Al cylinders can be removed by chemical etching to form nanoporous templates. The pores were filled with Co by electrodeposition method via a metal underlayer as an electrode. These films show perpendicular anisotropy with Hc of 4.1 kOe.
Effect of MgO and Al2O3 on the microstructure and magnetic properties of CoCrPt-oxide perpendicular recording media
Authors: Park S. H. , Hong D. H. , Lee T. D.
Published: May 2005

MgO, Al2O3 and SiO2 incorporated CoCrPt thin films (20 nm) have been fabricated on the Ru underlayer to study the role of different oxides on magnetic isolation of CoCrPt grains. Unlike the SiO2 incorporated case, the MgO and Al2O3 incorporated specimens do not show higher coercivity and squareness. Microstructural analysis of MgO and Al2O3 cases shows quite different morphology than that of SiO2. MgO and Al2O3 are segregated within the grains as well as grain boundaries in a patch form. The differences in magnetic properties are speculated in terms of different kinetics for the different chemical species.
Microstructure and magnetic properties of rapidly annealed FePt (001) and FePt–MgO (001) films
Authors: Chen J. S. , Zhou T. J. , Ding Y. F. , Lim B. C. , Liu B.
Published: May 2005

The microstructure and magnetic properties of (FePt)100−x(MgO)x films annealed at different temperature for different time were investigated. The (FePt)100−x(MgO)x films in situ deposited at 350°C show (001) preferred orientation. The coercivity increases with the annealing temperature for all films. For FePt and (FePt)95 (MgO)5 films, the coercivity first increases with the increase of the annealing time from 10to30s, but decreases dramatically with further increment of the annealing time. For the FePt–(MgO)10 film, the effect of annealing time on coercivity is not obvious. The domain size decreases with the increase of the MgO content and post-annealing can reduce the domain size effectively.
Understanding and optimizing laminated recording media (invited)
Authors: Margulies D. T. , Supper N. , Do H. , Schabes M. E. , Berger A. , Moser A. , Rice P. M. , Arnett P. , Madison M. , Lengsfield B. , Rosen H. , Tang K. , Polcyn A. , Fullerton Eric E.
Published: May 2005

We find subnanometer spacer layers are sufficient to decorrelate the transition noise of the layers in laminated longitudinal recording media, thus improving the media signal-to-noise ratio. These results are surprising given that the layers remain structurally correlated due to their epitaxial growth, and therefore the noise in the layers may be expected to be correlated as well. Experimental results suggest that the reduced transition noise is produced by a slight shift between the transition locations in the layers. This shift is created by the recording head and allows the transitions to sample a different microstructure, thus decorrelating the transition noise.
Optical switching between bistable phases in rubidium manganese hexacyanoferrate at room temperature
Authors: Tokoro Hiroko , Matsuda Tomoyuki , Hashimoto Kazuhito , Ohkoshi Shin-ichi
Published: May 2005

The phase transition from Fe(II)(S=0)–CN–Mn(III)(S=2) to Fe(III)(S=1∕2)–CN–Mn(II)(S=5∕2) in Rb0.98Mn1.01[Fe(CN)6]∙0.2H2O was observed at room temperature with a one-shot-laser-pulse (λ=532nm; pulse width: 6ns) irradiation. The quantum yield (Φ) depended on the laser power density (P) and Φ=38 was achieved with a 24mJcm−2pulse−1. In this photochemical reaction, only when the P value was above 6mJcm−2pulse−1 (Pth), the low-temperature phase was converted to the high-temperature phase. The threshold in laser power density and large Φ value were thermodynamically considered using a mean field model that contains cooperative interaction.
Saturation magnetostriction coefficient measurement of CoCrPt alloy thin films using a highly sensitive optical deflection-detecting system
Authors: Im Mi-Young , Jeong Jong-Ryul , Shin Sung-Chul
Published: May 2005

We report on the saturation magnetostriction coefficient of 500Å(Co82Cr18)100−xPtx and xÅ(Co82Cr18)79Pt21 alloy thin films with perpendicular magnetic anisotropy. The CoCrPt alloy films were prepared by dc magnetron sputtering and the magnetostriction coefficients were measured via a highly sensitive optical deflection-detecting system using a one-dimensional position sensitive detector. The saturation magnetostriction coefficient is increased from −7.23×10−6 to 8.5×10−6 and from −8×10−6 to 14×10−6 with increasing the Pt concentration from 0to35at.% and the film thickness from 400to800Å, respectively. X-ray diffractometry study revealed that crystalline orientation in CoCrPt alloy film, which depends on the Pt concentration and the CoCrPt film thickness, strongly influences the evolution of saturation magnetostriction coefficient.
Enhancement of ferromagnetic ordering in dielectric BaFe1−xZrxO3−δ (x=0.5–0.8) single-crystal films by pulsed laser-beam deposition
Authors: Matsui T. , Taketani E. , Fujimura N. , Tsuda H. , Morii K.
Published: May 2005

The effect of Zr substitution on the magnetic and dielectric properties of the BaFe1−xZrxO3−δ epitaxial grown films was investigated. The Zr substitution significantly improved the dielectric properties of the films. In addition to this, the saturation magnetization for the x=0.7 sample was determined to be 0.98μB∕Fen+, in contrast to 0.09μB∕Fen+ for the x=0.5 sample. This implies that the magnetic ordering for the x=0.7 sample has been greatly enhanced, possibly due to the ferromagnetic spin alignment of Fe ions. We will discuss the magnetization behavior in conjunction with the valence state of the Fe ions in the samples.
A spectroscopic comparison between several high-symmetry S=10 Mn12 single-molecule magnets
Authors: Hill S. , Anderson N. , Wilson A. , Takahashi S. , Chakov N. E. , Murugesu M. , North J. M. , Dalal N. S. , Christou G.
Published: May 2005

We report angle-dependent high-field electron-paramagnetic-resonance data collected for single-crystal samples of Mn12–Ac. The spectra reveal fine structures associated with various Mn12 species corresponding to different disordered local environments. Each of the fine structures exhibits a distinct dependence on the field orientation, thereby highlighting the discrete nature of the disorder. We compare these data with the spectra obtained for two recently discovered analogs of Mn12–Ac, differing only in their ligand and solvent molecules. None of the fine structures seen for Mn12–Ac are found for the recently discovered Mn12 complexes, thus confirming that the solvent significantly influences the magnetization dynamics in Mn12–Ac.
Dynamic magnetomechanical properties of Terfenol-D/epoxy pseudo 1-3 composites
Authors: Or Siu Wing , Li Tongle , Chan Helen Lai Wa
Published: May 2005

Terfenol-D/epoxy pseudo 1-3 composites were fabricated by embedding and aligning Terfenol-D particles with a size distribution of 10–300μm in a passive epoxy matrix using six Terfenol-D volume fractions (υf) ranging from 0.22 to 0.72. The dependence of the dynamic relative permeability (μr33T), elastic modulus (E3H), and dynamic strain coefficient (d33) on υf was investigated as a function of magnetic bias field (HBias). The HBias response data showed that the built-in non-180° domain states related to residual compressive stresses in the composites result in a significant decrease in μr33T for HBias<40kA∕m in addition to a minimization of E3H and a maximization of d33 near HBias=40kA∕m. The υf dependent data revealed that μr33T is almost a linear function of υf; E3H increases gradually with increasing υf; and d33 increases initially, leveling off for υf>0.5. The present study provides a useful guide to optimize the composite properties for transducer design.
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magnetic anisotropy term of CoPtCr–SiO2 media for high density recording
Authors: Shimatsu T. , Sato H. , Mitsuzuka K. , Oikawa T. , Inaba Y. , Aoi H. , Muraoka H. , Nakamura Y. , Kitakami O. , Okamoto S.
Published: May 2005

Measurements of higher energy term of magnetic anisotropy, Ku2, in CoPtCr–SiO2 perpendicular recording media are described. It was revealed that the values of Ku2 and the first order energy term, Ku1, vary significantly according to the seed layer material used, however, no significant change in the ratio of Ku2∕Ku1 was observed on the addition of SiO2 to CoPtCr films. Ku2 increases and Ku1 decreases as the c∕a ratio of the hcp-CoPtCr lattice increases. It is concluded that CoPtCr films have sufficient potential in the values of Ku1 and Ku2 for high density perpendicular media.
Fabrication and magnetic property of MnB alloy
Authors: Zhu Hao , Ni Chaoying , Zhang Fengming , Du Youwei , Xiao John Q.
Published: May 2005

Manganese is a common dopant to achieve dilute magnetic semiconductors. Most magnetic semiconductors are hole-type and the Curie temperature is critically depending on the holes concentration. Boron can be used to increase the holes concentration and enhance the Curie temperature. In systems with both Mn and B dopants, one must consider the magnetic properties of MnB. In this study, single phase MnB alloy has been fabricated and characterized. Magnetic properties have been studied using superconducting quantum interference device and vibrating sample magnetometer over a broad temperature range. Very high magnetization of about 113emu∕g at room temperature has been observed, which is much higher than previous reports. The Curie temperature is around 306 °C, similar to previously reported value.
Magneto-optical enhancement by surface plasmon resonance in magnetic “nano-onions” with multicore-shell structures
Authors: Abe Masanori , Takeshi Suwa
Published: May 2005

Calculations based on the Maxwell–Garnett theory revealed a remarkable enhancement of the magneto-optical effect due to surface plasmon resonance excited in nanometer sized magnetic particles (“nano-onions”) with n-fold core-shell structures consisting of shell(s) and/or a core of noble metals such as Au and Ag. The Kerr effect was found to be greatly enhanced in a composite containing nano-onions of threefold Fe(orCoFe2O4)(core)∕dielectric(shell)∕Ag(shell) structure and also in a composite containing twofold Bi-YIG(core)∕Ag(shell) nano-onions. In the latter case, the Kerr rotation angle as large as 13.5° was obtained with a figure of merit, θKR=62°, (R is the reflectivity) at ℏω=2.6eV, which is much larger than the highest values of θK=19° and θKR=1.1°, reported for PtMnSb.
Ion beam induced destabilization of icosahedral structures in gas phase prepared FePt nanoparticles
Authors: Dmitrieva Olga , Rellinghaus Bernd , Kästner Jochen , Liedke Maciej Oskar , Fassbender Jürgen
Published: May 2005

Multiply twinned FePt nanoparticles with icosahedral structures were prepared by dc magnetron sputtering in argon. The icosahedral structure of these particles is known to be very stable against structural transformations into both the face-centered cubic phase (fcc, A1) and the chemically ordered tetragonal L10 phase upon in-flight or post-deposition thermal annealing. Irradiation of these multiply twinned FePt particles with 5keV He ions, however, resulted in a transformation into predominantly single crystalline fcc particles at high ion fluences of f>1017ions∕cm2. Adjacent particles were observed to coalesce under the effect of He irradiation, and the size of individual particles was found to be slightly reduced, which indicates a high atomic mobility owing to temporarily enhanced defect concentrations caused by the ion bombardment. Strikingly, there was no indication for the occurrence of L10 ordered FePt nanoparticles upon ion irradiation in these samples.
Relationship between the magnetocaloric effect and sequential magnetic phase transitions in Ni-Mn-Ga alloys
Authors: Zhou Xuezhi , Li Wei , Kunkel H. P. , Williams Gwyn , Zhang Shuihe
Published: May 2005

The fundamental nature of the magnetic phase transitions in the Ni-Mn-Ga system is investigated quantitatively. By compositional tuning, the first-order metamagnetic/martensitic structural transition (occurring at TM≈200K in the parent compound Ni2MnGa) and the second-order/continuous transition (at TC≈375K in the parent) can be merged. This occurs for Ni55.2Mn18.6Ga26.2, where the entropy changes by ΔSM=−20.4Jkg−1K−1 (in a field of 5T near 317K), at a transition that displays both first- and second-order characteristics simultaneously.
Thermal expansion and Gruneisen parameters in some Pr–Ni–Si compounds
Authors: Song S. H. , Jiles D. C. , Snyder J. E. , Pecharsky A. O. , Wu D. , Dennis K. W. , Lograsso T. A. , McCallum R. W.
Published: May 2005

In this study, the thermal expansion and Gruneisen parameter of polycrystalline “Pr5Ni2Si3” and “Pr15Ni7Si10” were investigated over the temperature range of 5–300K. Calculations of the phonon contribution to thermal expansion were made, which allowed the magnetic contribution to thermal expansion to be calculated from the difference between the total thermal expansion and the phonon contribution. This resulted in a temperature-dependent magnetic contribution to thermal expansion that varied with the magnetic ordering of the material. The results show two magnetic transitions in each compound, the higher temperature transition corresponding to the Curie temperature and the lower temperature transition resulting from a spin reorientation.
The occurrence of avalanches in a single crystal of Mn12-acetate
Authors: Suzuki Yoko , Sarachik M. P. , Avraham N. , Myasoedov Y. , Shtrikman H. , Zeldov E. , Rumberger E. M. , Hendrickson D. N. , Christou G.
Published: May 2005

Recent studies of Mn12-acetate have focused on the possible observation of superradiance triggered by avalanches of the magnetic relaxation [J. Tejada, E. M. Chudnovsky, J. M. Hernandez, and R. Amigo, Appl. Phys. Lett. 84, 2373 (2004); M. Bal et al., Phys. Rev. B, 70, 140403 (2004)]. It is therefore of interest to determine the conditions for such avalanches. For several single crystals of Mn12-acetate of different dimensions, the distribution of magnetic fields at which magnetic avalanches occur at different temperatures is reported for field sweep rates of 5 and 10mT∕s. No avalanches were observed above 0.8K for these conditions. For temperatures below 0.8K, avalanches were found between 2.0 and 4.2T, with about half occurring below the field (3.2T) above which appreciable relaxation proceeds by ground state tunneling. At the level of statistics accumulated in these experiments, there appears to be no clear preference for an avalanche to occur at or near a resonant magnetic field, and a surprising number occur at fields below the expected onset of appreciable ground state tunneling in the absence of avalanches.
Magnetic and transport properties of MnGeP2 films grown on GaAs(001) by molecular beam epitaxy
Authors: Cui Y. , Mu W. , Lee J. , Song J. , Kim Y. , Ketterson J. B. , Cho S.
Published: May 2005

Mn Ge P 2 films were grown on undoped GaAs(001) substrates by molecular beam epitaxy. X-ray diffraction analysis reveals a film peak at 66.21°, corresponding to a c-axis of 1.128nm for the chalcopyrite structure. Superconducting quantum interference device magnetic measurements show ferromagnetic order in the film with a transition temperature around 325K and hysteresis loop measurements yield with coercive fields of about 1600Oe and 210Oe at 250K and 300K, respectively. The transport measurements exhibit nonmetallic behavior with p-type carriers and a carrier density increasing with temperature. The anomalous Hall effect (AHE) is observed in the film indicating spin polarized carriers. At low temperatures, the anomalous Hall resistance has a negative sign and decreases in magnitude with increasing temperature, changing sign around 150K. It then increases with temperature, reaching a maximum around 250K.
Magnetic anisotropy and phase transitions in single-crystal Tb5(Si2.2Ge1.8)
Authors: Han M. , Snyder J. E. , Tang W. , Lograsso T. A. , Schlagel D. L. , Jiles D. C.
Published: May 2005

The Tb5(SixGe4−x) alloy system has many features in common with the Gd5(SixGe4−x) system although it has a more complex magnetic and structural phase diagram. This paper reports on the magnetic anisotropy and magnetic phase transition of single-crystal Tb5(Si2.2Ge1.8) which has been investigated by the measurements of M-H and M-T along the a, b, and c axes. The variation of 1∕χ vs T indicates that there is a transition from paramagnetic to ferromagnetic at Tc=110K. Below this transition temperature M-H curves show very strong anisotropy, and it is believed that this is due to the complex spin configuration. M-H measurements at T=110K show that the a axis is the easy axis, and that the saturation magnetization is 200emu∕g. The b axis is the hard axis, which needs an external magnetic field much higher than 2T to saturate the magnetization in that direction, indicating a high magnetocrystalline anisotropy. The c axis is of intermediate hardness. The magnetic properties of this material are therefore very different from those of the related Gd5Si2Ge2 system, in which the b axis was found to be the easy axis and the magnitude of the anisotropy was smaller.