bluuebunny/crossref_metadata_2025 huggingface dataset:
Can SAPS II Predict Operative Mortality More Accurately Than POSSUM and P‐POSSUM in Patients with Colorectal Carcinoma Undergoing Resection?
Authors: Can Mehmet F. , Yagci Gohkan , Tufan Turgut , Ozturk Erkan , Zeybek Nazif , Cetiner Sadettin
Published: January 2008

Background

This study assessed the APACHE II (Acute Physiology and Chronic Health Evaluation II), SAPS II (Simplified Acute Physiology Score‐II), POSSUM (Physiologic and Operative Severity Score for Enumeration of Morbidity and Mortality), and P‐POSSUM (Portsmouth‐POSSUM) in patients with colorectal cancer undergoing curative or palliative resection.

Methods

Predicted mortality rates and the observed/expected mortality ratio were computed by means of each scoring system. The results were compared between survivors and nonsurvivors and between elective and emergency operations. Each model was assessed for its accuracy to predict the risk of death using receiver operator characteristic (ROC) curve analysis, and risk stratification was generated as well.

Results

Some 224 patients were enrolled in the study. The overall 30‐day mortality rate was 3.6% (n = 8). Predicted mortality rates generated by APACHE II, SAPS II, POSSUM, and P‐POSSUM were 9.1%, 3.7%, 13.4%, and 5.2%, respectively. All the scoring systems assigned higher scores to those patients who died than to those who survived. Areas under the curve calculated by ROC curve analysis for APACHE II, SAPS II, POSSUM, and P‐POSSUM were 0.786, 0.854, 0.793, and 0.831, respectively. Best stratification was achieved by the SAPS II score.

Conclusions

SAPS II and P‐POSSUM were determined to be better predictors for patients with colorectal cancer undergoing resection. SAPS II also was found to have a higher degree of discriminatory power in colorectal resection for carcinoma. The predictive value of this useful severity score in several surgical subgroups must be examined to evaluate its routine use in risk‐adjusted audit.
Graft‐dependent Renal Hyperparathyroidism Despite Successful Kidney Transplantation
Authors: Schlosser K. , Rothmund M. , Maschuw K. , Barth P. J. , Vahl T. P. , Suchan K. L. , Fernández E. Domínguez
Published: January 2008

Introduction

Only a few reports can be found on the recurrence or persistence of hyperparathyroidism after total parathyroidectomy and autotransplantation (PTX + AT) following kidney transplantation (KTX). The objective of the present study was to assess the frequency and pathophysiological mechanisms responsible for the development of graft‐dependent renal hyperparathyroidism (rHPT) after KTX.

Patients and methods

Between 1986 and 2006, 69 patients underwent surgery for rHPT after KTX at our institution. Patients with reoperations at the parathyroid autograft (AT) were identified. Kidney graft function (KGF) was assessed by the glomerular filtration rate (GFR). Representative parts of the parathyroid gland chosen for autotransplantation during the initial parathyroidectomy and of the excised AT at reoperation were reanalyzed according to the morphologic pattern and the proliferative index.

Results

Eight of the 69 patients underwent reoperation of the AT. All patients had undergone initial PTX + AT before KTX. The GFR before parathyroid reoperation was 66.6 ± 9.6 ml/min per1.73 m² (mean ± SEM). Histopathological re‐examination revealed nodular hyperplasia in the parathyroid tissue for autotransplantation and in the excised parathyroid autografts. The Ki67 index was increased in the glands chosen for autotransplantation prior to KTX, but was overall low in the excised autografts.

Discussion

Although not reported in the literature to date, tertiary hyperparathyroidism (tHPT) may arise from parathyroid autografts even in patients with a good KGF. In these cases, graft‐dependent tHPT represents the inability of autonomous, nodular parathyroid tissue to regress despite the recovery of renal function. Non‐nodular tissue should be selected for parathyroid autotransplantation to decrease the incidence of graft‐dependent recurrent rHPT.
The Value of Positron Emission Tomography in the Surgical Management of Recurrent Papillary Thyroid Carcinoma
Authors: Grant Clive S. , Thompson Geoffrey B. , Farley David R. , Richards Melanie L. , Mullan Brian P. , Hay Ian D.
Published: January 2008

Background

Patients with papillary thyroid carcinoma (PTC) may suffer recurrence despite thyroidectomy and complete radioiodine (RAI) ablation. Reoperation is vitally dependent on accurate and complete disease localization, typically utilizing cervical ultrasonography (US) and/or computed tomography. Our aim was to determine the comparative value of F18‐fluorodeoxyglucose positron emission tomography (PET) to US for localization of locoregional recurrence in patients who underwent reoperation for recurrent PTC.

Methods

From 1999 to 2004, 30 patients who underwent re‐exploration and 100 nonoperated patients who were investigated with PET for possible recurrent PTC were reviewed. The surgical group [9 males, 21 females; mean age = 50 years (range = 18–84 years)] all had received RAI ablation. Preoperative thyroid‐stimulating hormone (TSH), thyroglobulin (Tg), and location of metastasis were recorded for each imaging study and surgical exploration. All separate sites that contained disease pathologically must have been identified by imaging for a patient to be considered true positive (TP).

Results

PET scans were TP in 43%, false positive in 7%, false negative (FN) in 50%, and had a sensitivity of 46%. Comparable US results were 86%, 10%, 3%, and 96%. Of the 15 patients with FN PET scans, 13 had lymph node metastasis less than 2 cm in diameter, 11 had Tg ≤ 10 μg/L, and the TSH < 20 in 13. In only 3 of the 30 (10%) patients was PET deemed to add value.

Conclusions

At least with suppressed TSH, PET scanning in reoperative PTC patients appears to offer modest benefit beyond high‐resolution US.
Long‐term Outcome after Parathyroidectomy in Patients with Advanced Primary Hyperparathyroidism and Associated Vitamin D Deficiency
Authors: Pradeep P. V. , Mishra Anjali , Agarwal Gaurav , Agarwal Amit , Verma A. K. , Mishra S. K.
Published: January 2008

Introduction

Primary hyperparathyroidism (PHPT) is increasingly being recognized in the developing world, but long‐term recovery of affected organs after successful parathyroidectomy, remains unaddressed. A study was therefore undertaken to elucidate this aspect of care among our patients.

Methods

Retrospective analysis was done on 82 PHPT patients who underwent parathyroidectomy between 1991 and 2004. Appropriate biochemical and radiological investigations revealed the recovery pattern in target organs.

Results

Follow‐up ranged between 2 years and 13 years. Bone pain and muscle weakness disappeared quickly in all patients. Radiographs revealed vigorous but disorderly remineralization in lesions that healed within a median period of 3 months. Mean 25‐OH vitamin D levels in the preoperative and postoperative period were 11.6 ± 8.7 and 16.94 ± 12.77 ng/ml, respectively. Twenty‐four of 32 (75%) patients remained persistently vitamin D deficient (mean level 12.15 ± 5.45 ng/ml) postoperatively and in the long term (2–13 years; median: 3 years). Kidney disease occurred in 43 patients, and 74% of them became symptom free; in 9 patients it remained static and in 3 others it progressed to end‐stage renal disease (ESRD). Seven patients had pancreatitis, 5 became symptom free, and 2 had no relief after failed exploration (n = 1) and recurrence (n = 1). Overall recurrence and persistence rates were 2.7% each. Of the 5 deaths in the follow‐up period, three were due to ESRD and one was due to cerebral metastasis.

Conclusions

In India, PHPT presents at an advanced stage and is associated with vitamin D deficiency. Persistent vitamin D deficiency after operation delays bone recovery. Replenishment of vitamin D stores in the follow‐up has to be continuously ensured. Recovery from renal disease is gradual and may never occur in some patients; in others, it may progress to ESRD. Patients recover fully from pancreatitis.
Estimation of linear wave polarization of the auroral kilometric radiation
Authors: Panchenko M. , Hanasz J. , Rucker H. O.
Published: January 2008

There is a general view that the auroral kilometric radiation (AKR) polarization is fully circular with dominating right‐hand extraordinary mode and some admixture of the left‐hand ordinary mode. Most of up‐to‐date determinations of the wave modes of the AKR have been based on measurements of the circular component of the wave polarization, leaving the linear polarization parameters unknown. In space observations the polarimeter is usually not directed to the AKR source. However, having determined the polarization parameters in each of the three perpendicular planes, one is able to determine the polarization ellipse in the 3‐D space. Results of statistical estimations of the AKR polarization parameters in the wave plane are presented. Data were provided by the Interball‐2/Polrad triaxial polarimeter. It is the first time the dynamic spectra of all four Stokes parameters of the AKR are displayed in the wave plane. The AKR polarization is mostly circular with an estimated mean value of the semiaxes ratio of 0.99 ± 0.10 rms error, with a small contribution of the linear component at a level of 0.07 ± 0.09 rms error, and an unpolarized component at a level of 0.10 ± 0.08. The uncertainties of these estimations are too large to definitely conclude on presence or absence of some small contributions of the linear and upolarized components in the AKR. However, in the limits of the above uncertainties these estimations do not contradict expectations that the linear polarization is absent in the AKR. Some small contribution of the unpolarized component can be explained by a relatively high level of noise and board interefences.
Synoptic controls upon δ18O in southern Tasmanian precipitation
Authors: Barras Vaughan J. I. , Simmonds Ian
Published: January 2008

An event‐based record of 18O in precipitation at Margate in Tasmania, Australia, was analysed using 3d Lagrangian trajectories and composites of ERA40 850hPa geopotential height for the years 1994–2002. Trajectory analysis found that moisture entrainment occurs during the 48 hour period prior to arrival for all precipitating air masses at Margate. The rate of entrainment was greatest for events of high rainfall/high depletion, contributing up to 19% of vapour in the air mass in summer and up to 47% in winter. The majority of air masses were found to be advected from the Southern Ocean, however, for high rainfall/high depletion events during summer 30% of air masses were found to approach from the Tasman Sea (east of 155E longitude). Mean isotope ratios were less depleted by 1.4‰ for these events indicating mixing with less depleted air. High rainfall/high depletion events were also associated with negative geopotential anomalies east of Tasmania.
Discrete visco‐elastic lattice methods for seismic wave propagation
Authors: O'Brien G. S.
Published: January 2008

2D and 3D discrete particle or lattice methods for the simulation of seismic waves are presented for different visco‐elastic media. It is demonstrated that a numerical implementation of the method is capable of modelling visco‐elastic seismic wave propagation. Lattice methods represent the medium under investigation as particles or nodes interacting through local force rules. Three schemes are developed, a Maxwell body, a Kelvin‐Voigt body and a Zener Body (or standard linear solid). The force acting between particles is chosen to represent each of these different rheologies. Each of these schemes was tested against analytical solutions for wave propagation in 2D and 3D unbounded visco‐elastic media. The seismograms generated for each different rheology fit well with the expected theoretical seismograms with the maximum misfit error energy being less than 3% for each different rheology. As such, lattice methods offer an alternative approach to seismic wave modelling in elastic and visco‐elastic media.
Single-shot measurement of ultrafast time-varying phase modulation induced by femtosecond laser pulses with arbitrary polarization
Authors: Hartinger Klaus , Bartels Randy A.
Published: January 2008

We demonstrate a single-shot measurement of the transient phase modulation due to field free molecular alignment at the revival times of a rotational wave packet. The wave packet is excited by an arbitrarily polarized ultrashort laser pulse in CO2 at room temperature. With this technique the time dependence along the eigenpolarization directions of the linear susceptibility tensor, i.e., the time dependence of its principle components, can be directly observed with high sensitivity.
Formation of an ion beam in an elementary cell with inhomogeneous emission current density
Authors: Kotelnikov I. A. , Davydenko V. I. , Ivanov A. A. , Tiunov M. A.
Published: January 2008

A well-known Pierce solution that allows focusing a beam of charged particles using properly shaped electrodes outside the beam aperture is generalized to the case of an accelerating system with inhomogeneous emission current density. It is shown that the defocusing effect of the space charge can, in principle, be evenly compensated over the entire cross section of the beam. In contrast to the beam with a uniform emission current density, both the electric potential and the transverse electric field must be controlled along the beam boundary in order to eliminate the angular divergence. However, eliminating the angular spread evenly across the beam constitutes a mathematically ill-posed problem which needs to be solved with the use of one or another method of regularization. An alternative way of diminishing beam emittance is proposed for the beam where the emission current is uniform across the entire aperture except for a narrow beam edge layer and a simple formula for the Pierce electrodes is derived. Numerical simulation has proved the reasonable accuracy of our analytical theory.
Dynamic Hohlraums as x-ray sources in high-energy density science
Authors: Hansen J. F. , Glendinning S. G. , Heeter R. F. , Brockington S. J. E.
Published: January 2008

The first demonstration of laser driven dynamic Hohlraums (LDDH) as a spectrally smooth backlighter source for opacity and temperature measurements through absorption spectrometry of materials in local thermodynamic equilibrium at temperatures >150eV has been made. This is a crucial temperature regime for future astrophysics and ignition fusion experiments at the nearly completed National Ignition Facility (NIF) [E. I. Moses and C. R. Wuest, Fusion Sci. Technol. 47, 314 (2005)] at the Lawrence Livermore National Laboratory. The new backlighter consists of a LDDH filled with either krypton or argon that implodes to create an x-ray flash. The properties of this x-ray flash have been measured in experiments at the Omega laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] at the Laboratory for Laser Energetics in Rochester, New York, satisfying all requirements imposed by future experiments: (1) the emission spectrum extends to at least 5.5keV, well above the maximum x-ray energy (∼3.5keV) obtained from the previously “best” opacity backlighters (uranium M-shell emission backlighters); (2) the spectrum is smooth and featureless (intensity variation <6%rms), allowing absorption spectrometry through experimental samples; (3) the emission source size is sufficiently small (<50μm) for projection backlighting through future samples; (4) the emission is bright enough (and twice as bright as imploding hydrogen-filled capsules) for gated spectrometer measurements; (5) the emission duration is optimized (≈100ps) for the current and future generations of spectrometers; and (6) by using only a small number of beams with limited energy and symmetry for the backlighter (10 out of 60 beams in the Omega experiments), the majority of laser beams are left available for heating sample materials to >150eV.
Refractory rf ovens and sputter probes for electron cyclotron resonance ion source
Authors: Cavenago M. , Galatá A. , Kulevoy T. , Petrenko S. , Sattin M. , Facco A.
Published: January 2008

Beams from electron cyclotron resonance ion source (ECRIS) with radio frequency ovens for refractory material (using a Mo coil) were recently demonstrated; results for Ti and V are here discussed, with temperature Ts⩾2300K stably maintained and extracted current of about 1000nA for V8+ and V9+. The status of sputter probes is also reported, and the reason why trapping efficiency may be lower than in the oven case are investigated. The simple tubular probe concept show typical currents of Sn18+ about 250nA, for the most abundant isotopes, but an operating pressure of about 300μPa may be required. Some preliminary experiments were performed with Penning probes, showing that transmission of Sn or Pr from Penning cathode to ECRIS plasma is limited. Placement of tin onto anticathode and use of collimator between Penning and ECRIS are also discussed.
Calculated electronic transitions of the water ammonia complex
Authors: Lane Joseph R. , Vaida Veronica , Kjaergaard Henrik G.
Published: January 2008

We have calculated vertical excitation energies and oscillator strengths of the low lying electronic transitions in H2O, NH3, and H2O∙NH3 using a hierarchy of coupled cluster response functions [coupled cluster singles (CCS), second order approximate coupled cluster singles and doubles (CC2), coupled cluster singles and doubles (CCSD), and third order approximate coupled cluster singles, doubles, and triples (CC3)] and correlation consistent basis functions (n-aug-cc-pVXZ, where n=s,d,t and X=D,T,Q). Our calculations indicate that significant changes in the absorption spectra of the photodissociative states of H2O and NH3 monomers occur upon complexation. In particular, we find that the electronic transitions originating from NH3 are blueshifted, whereas the electronic transitions originating from H2O are redshifted.
Crystal growth kinetics exhibit a fragility-dependent decoupling from viscosity
Authors: Ediger M. D. , Harrowell Peter , Yu Lian
Published: January 2008

In this paper we establish the temperature dependence of the kinetic coefficient associated with crystal growth into the supercooled liquid for a wide range of organic and inorganic materials. We show that the kinetic coefficient for crystal growth scales with the shear viscosity η as η−ξ and that the exponent depends systematically on the fragility of the liquid. The greater the fragility (i.e., deviation away from an Arrhenius temperature dependence for η), the larger the difference 1−ξ. We argue that this breakdown in scaling between the crystal growth kinetics and the viscosity is a manifestation of heterogeneous dynamics in supercooled liquids. In addition, we show that the absolute growth rate at intermediate viscosities is correlated with the entropy difference between the liquid and the crystal.
A remarkable shape-catalytic effect of confinement on the rotational isomerization of small hydrocarbons
Authors: Santiso Erik E. , Buongiorno Nardelli Marco , Gubbins Keith E.
Published: January 2008

As part of an effort to understand the effect of confinement by porous carbons on chemical reactions, we have carried out density functional theory calculations on the rotational isomerization of three four-membered hydrocarbons: n-butane, 1-butene, and 1,3-butadiene. Our results show that the interactions with the carbon walls cause a dramatic change on the potential energy surface for pore sizes comparable to the molecular dimensions. The porous material enhances or hinders reactions depending on how similar is the shape of the transition state to the shape of the confining material. The structure of the stable states and their equilibrium distributions are also drastically modified by confinement. Our results are consistent with a doubly exponential behavior of the reaction rates as a function of pore size, illustrating how the shape of a catalytic support can dramatically change the efficiency of a catalyst.
Theoretical study of the surface reactivity of alkaline earth oxides: Local density of states evaluation of the local softness
Authors: Cárdenas Carlos , De Proft Frank , Chamorro Eduardo , Fuentealba Patricio , Geerlings Paul
Published: January 2008

The local softness of MgO, CaO, SrO, and BaO (100) surfaces has been studied using a model based on the local density of states. In all the species, the local softness (chemical reactivity) of oxygen atoms at the surface is enhanced as compared to the bulk. The results for the local and the global softness are in agreement with the ionic pattern of the metal-oxygen bond of the series.
Progress in modeling and numerical simulation of negative hydrogen ion sources (invited)
Authors: Hatayama A.
Published: January 2008

Recent progress in numerical modeling of H− ion sources has been reviewed. The following two topics are mainly the focus: (1) the origin of the nonuniformity of H− production and H− beam in large H− sources and (2) extraction physics, especially the role of the “weak” transverse magnetic field on H− extraction. The present understanding of the origin of H− beam nonuniformity is reviewed and discussed with the results by a series of Monte Carlo transport modeling of electrons, neutrals, and H− ions. Also, the physical mechanism of the large enhancement of H− extraction due to the weak transverse magnetic field is discussed with the particle in cell modeling. In addition, some new results on the effect of surface H− production on the electric potential structure near the extraction aperture are presented and discussed.
Spectroscopic studies of the phase transition in ammonia borane: Raman spectroscopy of single crystal NH3BH3 as a function of temperature from 88to330K
Authors: Hess Nancy J. , Bowden Mark E. , Parvanov Vencislav M. , Mundy Chris , Kathmann Shawn M. , Schenter Gregory K. , Autrey Tom
Published: January 2008

Raman spectra of single crystal ammonia borane, NH3BH3, were recorded as a function of temperature from 88to300K using Raman microscopy and a variable temperature stage. The orthorhombic to orientationally disordered tetragonal phase transition at 225K was clearly evident from the decrease in the number of vibrational modes. However, some of the modes in the orthorhombic phase appeared to merge 10–12K below the phase transition perhaps suggesting the presence of an intermediate phase. Factor group analysis of vibrational spectra for both orthorhombic and tetragonal phase is provided. In addition, electronic structure calculations are used to assist in the interpretation and assignment of the normal modes.
New ab initio potential energy surface and the vibration-rotation-tunneling levels of (H2O)2 and (D2O)2
Authors: Huang X. , Braams Bastiaan J. , Bowman Joel M. , Kelly Ross E. A. , Tennyson Jonathan , Groenenboom Gerrit C. , van der Avoird Ad
Published: January 2008

We report a new full-dimensional potential energy surface (PES) for the water dimer, based on fitting energies at roughly 30 000 configurations obtained with the coupled-cluster single and double, and perturbative treatment of triple excitations method using an augmented, correlation consistent, polarized triple zeta basis set. A global dipole moment surface based on Møller-Plesset perturbation theory results at these configurations is also reported. The PES is used in rigorous quantum calculations of intermolecular vibrational frequencies, tunneling splittings, and rotational constants for (H2O)2 and (D2O)2, using the rigid monomer approximation. Agreement with experiment is excellent and is at the highest level reported to date. The validity of this approximation is examined by comparing tunneling barriers within that model with those from fully relaxed calculations.
Groundstate dispersion interaction between π-conjugated polymers
Authors: Barford William , Xu Xibai
Published: January 2008

The line-dipole approximation is used to investigate the scaling of the groundstate dispersion interaction, EW, between parallel conjugated polymers of length L and transverse separation D. Both a second-order perturbation theory calculation using the Mott-Wannier exciton model of excited states and a semiclassical analysis of distributed dipoles indicate that at L∼D there is a crossover from the point-dipole approximation result of EW∼L2∕D6 for L⪡D to the thermodynamically expected result of EW∼L∕D5 for L⪢D.
Bias-stress induced contact and channel degradation in staggered and coplanar organic field-effect transistors
Authors: Richards Tim , Sirringhaus Henning
Published: January 2008

We have investigated the dependence of bias-stress induced degradation in organic field-effect transistors on the device configuration. We show that separation of contact and channel effects is essential for understanding bias-stress instabilities. In coplanar device configurations, an increase in source contact resistance during current flow is primarily responsible for a rapid device degradation. In contrast, in staggered device configurations, the significantly slower reduction in current is primarily due to charge trapping in the channel leading to an increase in threshold voltage, while the contacts themselves do not exhibit significant degradation.
Design and characterization of bridged loop-gap resonators for use in electron paramagnetic resonance measurements
Authors: da Silva Fernanda R. , Sartori José Carlos , Romero Murilo A. , Nascimento Otaciro R.
Published: January 2008

This paper revisits the design of L and S band bridged loop-gap resonators (BLGRs) for electron paramagnetic resonance applications. A novel configuration is described and extensively characterized for resonance frequency and quality factor as a function of the geometrical parameters of the device. The obtained experimental results indicate higher values of the quality factor (Q) than previously reported in the literature, and the experimental analysis data should provide useful guidelines for BLGR design.
Easy control of the size and composition of FePt nanoparticles with Improved synthesis
Authors: Kang S. , Shi S. , Nikles D. E. , Harrell J. W.
Published: January 2008

A new synthesis of FePt nanoparticles with tunable size and composition has been developed. Unlike conventional synthesis methods with which it is difficult to simultaneously control the size and chemical composition of FePt nanoparticles, the new synthesis offers a convenient way to tune FePt nanoparticles with different sizes and compositions. The synthesis involves the simultaneous decomposition of Fe3(CO)12 and reduction of Pt(acac)2 in diethylene glycol. Fe3(CO)12 is a powder (nonvolatile) which is critical in governing the FePt particle size and composition. By varying the amount of surfactants and precursors ratio [Fe3(CO)12∕Pt(acac)2], FePt particles with tunable composition and particle size (2–8nm) can be obtained. After high temperature annealing (∼600°C), Fe50Pt50 nanoparticles are partially transformed to the L10 phase as indicated by the soft and hard components in the hysteresis loops. The coercivity ranges from a few kilo-Oersted to more than 15kOe, depending on the particle size. Dynamic coercivity measurements reveal that the large FePt particles are easier to chemically order than the small FePt particles under the same annealing condition.
Iterative compensation for hysteresis effects in positioning and tracking problems
Authors: Tseng C. , Mayergoyz I. , McAvoy P. , Krafft C.
Published: January 2008

An iterative algorithm for hysteresis compensation in micropositioning applications is presented. It is demonstrated that this algorithm has a geometric rate of convergence. The results of the testing of this iterative algorithm in tracking problems related to magnetic recording are reported.
Single and multidomain characteristics of GaMnAs investigated by magnetotransport measurements
Authors: Kim Jungtaek , Shin D. Y. , Yoo Taehee , Kim Hyungchan , Lee Sanghoon , Liu X. , Furdyna J. K.
Published: January 2008

We have investigated the magnetization reorientation process of GaMnAs ferromagnetic films by changing external field direction in planar Hall effect (PHE) measurement. While the angular dependences of PHE data taken with clockwise and counterclockwise under strong magnetic field (i.e., above 400Oe) are completely overlapped without hysteresis, they are significantly different under small magnetic field (i.e., below 50Oe) by exhibiting nonabrupt hysteresis. We have analyzed such angular dependence of PHE using the magnetic free energy based on Stoner-Wohlfarth model. The behavior observed under the high field was well understood in terms of coherent rotation of magnetization in the form of single domain. However, the nonabrupt hysteric behavior observed with low field cannot be explained by a single domain picture and requires involvement of multidomain structures.
Magnetic anisotropy of NaxCoO2 single crystals
Authors: Chen D. P. , Wang Xiaolin , Lin C. T. , Dou S. X.
Published: January 2008

We report the magnetic properties of single crystals of NaxCoO2 (x=0.42, 0.82, and 0.87). The magnetic susceptibility measurements revealed considerable anisotropy along H∥ab and H∥c for the as-grown single crystals. It was found that an antiferromagnetic transition with a Neel temperature TN=21K occurred for the x=0.82 sample, and there was a paramagnetic phase for the x=0.87 sample over a wide temperature range from 2to300K, but the sample with x=0.42 shows a monotonic increase of χ with increasing temperature above ∼100K. In addition, the x=0.82 sample has the largest derived anisotropic g-factor ratio (gab∕gc∼1.30), whereas the sample with x=0.42 is nearly isotropic (gab∕gc∼0.96).
A two-site bipolaron model for organic magnetoresistance
Authors: Wagemans W. , Bloom F. L. , Bobbert P. A. , Wohlgenannt M. , Koopmans B.
Published: January 2008

The recently proposed bipolaron model for large “organic magnetoresistance” (OMAR) at room temperature is extended to an analytically solvable two-site scheme. It is shown that even this extremely simplified approach reproduces some of the key features of OMAR, viz., the possibility to have both positive and negative magnetoresistance, as well as its universal line shapes. Specific behavior and limiting cases are discussed. Extensions of the model, to guide future experiments and numerical Monte Carlo studies, are suggested.
The magnetism and its pressure dependence of europium interlanthanide chalcogenides
Authors: Guertin Robert P. , Choi E. S. , Jin G. B. , Albrecht-Schmitt T. E.
Published: January 2008

Using a novel flux growth technique, we have synthesized polycrystalline samples of the ternary interlanthanide chalcogenide system EuLn2X4 (X=S and Se) for several heavy lanthanides, Ln. The magnetic properties of these materials, all of which are antiferromagnetic below a few Kelvin, are related to the complex crystal structure. In this paper, we describe the crystal structure of EuLn2X4 and measurements of their magnetic properties, mostly at low temperatures. For X=Se and Ln=Ho, Tm, and Lu, we present the hydrostatic pressure dependence of the antiferromagnetic ordering temperatures, TN, and the low temperature (∼2K) high field magnetization to 9T. Similar results are presented for the isomorphic sulfide EuLu2S4.
Magnetization behaviors for FeRh single crystal thin films
Authors: Cao Jiangwei , Nam Nguyen T. , Inoue Sho , Ko Hnin Yu Yu , Phuoc Nguyen N. , Suzuki Takao
Published: January 2008

The structural and magnetic phase transition in FeRh thin films are investigated. The (001) oriented single crystal FeRh thin films fabricated onto MgO (100) substrate possess lattice parameter a smaller than c, because of the compressive stress along the a axis from MgO substrate. With increasing annealing temperature, paramagnetic FeRh thin films transform into ferromagnetic and then antiferromagnetic-ferromagnetic (AF-FM) stages. The transition temperature of AF-FM increases with annealing temperature, while the thermal hysteresis width decreases. The M-H loops of the film annealed at 700°C show an opening at high magnetic fields during the transition state. Note that the opening in M-H loops disappears when AF phase has transformed into FM phase. The origin of the opening is not known but possibly due to the combination of hysteresis loops of FM and AF phases, where FM phase is soft magnetic and the AF phase FeRh shows a hysteresis behavior with coercivity due to the reduction of magnetic anisotropy at high temperatures. The abrupt change of coercivity along the perpendicular direction during the AF-FM transition suggests that a stress-induced magnetic anisotropy exists in FeRh thin films due to the volume expansion in the phase transition process.
Improvement of soft magnetic properties of [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4 bulk metallic glass by B2O3 flux melting
Authors: Bitoh T. , Shibata D.
Published: January 2008

The effect of the B2O3 flux melting, which improves the glass-forming ability of bulk metallic glasses (BMGs), on the soft magnetic properties of the cast [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4 BMG has been investigated. The ring-shaped bulk specimens prepared by the B2O3 flux melting and copper mold casting exhibit the better soft magnetic properties than those of the ones prepared by the conventional copper mold casting. It probably originates for eliminating the nonmetallic inclusions which behave the pinning sites of magnetic domain walls by the B2O3 flux melting. The B2O3 flux melting is effective for improvement of the soft magnetic properties of BMGs.
Magnetization reversal mechanism of ultra thin Nd2Fe14B films with perpendicular magnetic anisotropy
Authors: Liu Xiaoxi , Shiozaki Yoshiaki , Morisako Akimitsu
Published: January 2008

The crystallographic and magnetic properties of sub-10-nm Nd2Fe14B films have been investigated. It is found that the magnetization reversal mechanism is changed in Nd–Fe–B films with the decrease of film thickness. Films with thickness greater than 10nm show domain-wall-motion type of behavior. Strong exchange coupling between the grains makes the magnetic domain wall easily propagate in the films. Films with thickness of 4nm show the Stoner-Wohlfarth particle behavior. The initial magnetization process is magnetization rotation. This is also verified by angular dependence of the coercivity.
Microstructure and magnetocaloric effect of melt-spun Y2Fe17 ribbons
Authors: Fang Y. K. , Chang C. W. , Yeh C. C. , Chang H. W. , Li W. , Chang W. C.
Published: January 2008

The phase constitution, microstructure, and magnetocaloric effect (MCE) in low-cost iron-based binary Y2Fe17 ribbons have been investigated by using x-ray diffraction, transmission electron microscopy, and measuring their magnetic properties, respectively. It is found that the crystal structure of the as-spun ribbons is hexagonal Th2Ni17 type with the wheel speed ranging from 10to40m∕s because of the week glass-forming ability. The ribbon prepared at 20m∕s shows a magnetic entropy change of 1.89J∕kgK under magnetic field change of 10kOe. The low-cost, easy-synthesis, and considerable MCE properties make Y2Fe17 alloys in ribbon form as suitable room temperature MCE materials.
Domain wall ratchet effect in a magnetic wire with asymmetric notches
Authors: Himeno A. , Kondo K. , Tanigawa H. , Kasai S. , Ono T.
Published: January 2008

Current-driven domain wall (DW) motion in a magnetic wire with asymmetric notches under an external magnetic field was investigated by means of magnetic force microscopy. It was found that the reduction rate in the critical current density by the application of a magnetic field depended on the direction of the DW propagation. This suggests the existence of the asymmetric pinning potential in the notch, resulting in the DW ratchet effect.
Extension and comparison of neoclassical models for poloidal rotation in tokamaks
Authors: Stacey W. M.
Published: January 2008

Several neoclassical models for the calculation of poloidal rotation in tokamaks were rederived within a common framework, extended to include additional physics and numerically compared. The importance of new physics phenomena not usually included in poloidal rotation calculations (e.g., poloidal electric field, V×B force resulting from enhanced radial particle flow arising from the ionization of recycling neutrals) was examined. Extensions of the Hirshman–Sigmar, Kim–Diamond–Groebner, and Stacey–Sigmar poloidal rotation models are presented.
Magnetism and superconductivity in the superconductor/quasimagnet/ferromagnet Nb∕Pd∕Fe system
Authors: Potenza A. , Gabureac M. S. , Marrows C. H.
Published: January 2008

We have studied the superconducting properties of sputtered multilayers of Nb∕Pd∕Fe. This structure is expected to exhibit a double proximity effect as both superconducting and ferromagnetic orders propagate into the Pd layer from the interfaces with Nb and Fe, respectively. By measuring samples with varying Pd thickness, we estimated that double proximity is present in the Pd layers with thickness up to 40Å. Measurements of structural, superconducting, and magnetic behaviors, in samples with varying Fe thickness showed that the Pd spacer removes the alloying between Nb and Fe opening the way for the occurrence of reentrant superconducting effects in this system.
Fe-based nanocrystalline alloy powder cores with excellent high frequency magnetic properties
Authors: Kim Yoon B. , Jee K. K. , Choi G. B.
Published: January 2008

Toroidal shape FeSiBNbCu nanocrystalline alloy powder cores were prepared by compaction at room temperature after creating Cu-oxide layer as an insulator on the surface of FeSiBNbCu nanocrystalline alloy powder. The characteristics of the Cu-oxide layer and its effect on the high frequency magnetic properties of the compacted cores were investigated. A Cu-oxide layer was successively synthesized by electroless plating of Cu on the FeSiBNbCu nanocrystalline alloy powder and subsequent thermal oxidation. FeSiBNbCu nanocrystalline alloy powder core prepared from the powder having Cu-oxide layer exhibits a high value of quality factor and a stable permeability up to high frequency range over 10MHz. The core loss could be reduced remarkably and the dc-bias property could be improved significantly by synthesizing Cu-oxide layer on the FeSiBNbCu nanocrystalline alloy powder. Effective insulation by Cu-oxide layer between the FeSiBNbCu nanocrystalline alloy powder could be attributed to the improvement in high-frequency properties of the FeSiBNbCu nanocrystalline alloy powder cores
Improved model for transport driven by drift modes in tokamaks
Authors: Halpern Federico D. , Eriksson Annika , Bateman Glenn , Kritz Arnold H. , Pankin Alexei , Wolfe Christopher M. , Weiland Jan
Published: January 2008

A comparison is made between two versions of the Weiland model for computing anomalous transport driven by drift modes such as the ion temperature gradient (ITG) and trapped electron mode (TEM) in tokamak plasmas. Both are quasilinear fluid models that include physical effects resulting from finite β, magnetic shear, electron-ion collisions, impurities, and fast ions. An outline of the derivation is presented for the newer Weiland19 model, which includes a more accurate description of the effects of finite β, low and negative magnetic shear, plasma elongation, varying correlation lengths, particle pinch, and momentum transport. It is shown that the two models produce nearly the same ion thermal diffusivity as a function of normalized temperature gradient in a circular plasma with moderate magnetic shear, low β, and moderately low density gradient. The models differ significantly at low magnetic shear and in elongated plasmas with high β. In addition, the two models differ significantly in the behavior of the transition between moderate transport driven by ITG/TEM modes at low β and large transport driven by magnetohydrodynamic instabilities at high β. In the older Weiland14 model, the transition occurs at a low value of β that is insensitive to plasma elongation and magnetic shear. In the newer Weiland19 model, the transition occurs at a relatively large value of β that is a sensitive function of plasma elongation and magnetic shear.
Monomial integrals on the classical groups
Authors: Gorin T. , López G. V.
Published: January 2008

This paper presents a powerful method to integrate general monomials on the classical groups with respect to their invariant (Haar) measure. The method has first been applied to the orthogonal group by one of the authors, Gorin [J. Math. Phys., 43, 3342 (2002)], and is here used to obtain similar integration formulas for the unitary and the unitary symplectic group. The integration formulas are all recursive, where the recursion parameter is the number of column (row) vectors from which the elements in the monomial are taken. This is an important difference to other integration methods. The integration formulas are easily implemented in a computer algebra environment, which allows us to compute a given monomial integral very efficiently. The result is always a rational function of the matrix dimension.
Formation of periodic magnetic structure by localized amorphization of crystalline Co2MnSi using femtosecond laser
Authors: Baek Kwang H. , Park Jun H. , Kim Jung H. , Kim Chang K. , Yoon Chong S. , Lee Geon Joon , Lee Young Pak
Published: January 2008

Femtosecond laser-interference induced amorphization (FLIA) was used to form a spatially periodic magnetic structure by selectively amorphizing the surface of bulk Co2MnSi. Regularly spaced alternating lines with a periodicity of 2μm were produced by FLIA. Magnetic force microscopy of the samples clearly revealed one-dimensional periodic magnetic domains resulting from the modulated surface structure which was confirmed by transmission electron microscopy. The periodicity of the modulated structure can be further decreased or the process can be modified to write two-dimensional pattern so that the resulting magnetic structure can be potentially utilized for a permanent magnetic identification.
A flux-mnemonic permanent magnet brushless motor for electric vehicles
Authors: Yu Chuang , Chau K. T. , Liu Xinhua , Jiang J. Z.
Published: January 2008

In this paper, a new permanent magnet (PM) brushless motor is proposed for electric vehicles. The key is to incorporate the concept of memory motors, namely, the online tunable flux-mnemonic PMs, into the stator doubly fed doubly salient PM motor, hence achieving effective air-gap flux control. By further employing the outer-rotor and double-layer-stator topology, the proposed motor takes the definite advantages of compact structure, low armature reaction, and direct-drive capability. Increasingly, this motor can offer the unique features of pole dropping and pole reversing. Finite element analysis and, hence, computer simulation are given to verify the validity of the proposed motor.
Magnetic dipole based systems for probing optical magnetism
Authors: Noginova N. , Zhu G. , Mavy M. , Noginov M. A.
Published: January 2008

Recent advances in plasmonic-based metamaterials show that the magnetic component of an optical field can be strongly affected by the material’s properties and geometry of metallic nanostructures, leading to such interesting effects as negative magnetic permeability and magnetic resonance in the optical range. To probe such effects experimentally, systems containing Eu3+ ions can be used as spectroscopic tools. The study of the magnetic dipole-related transition at ∼590nm in comparison with the electric dipole-related transition at ∼615nm can reveal information on the relative distribution of magnetic and electric fields as well as effective permeability and permittivity. We report the development of such systems, demonstrating very high emission efficiency, and the first experimental results.
Assembly of high-quality colloidal crystals under negative pressure
Authors: Zhang Jianhui , Liu Huaiyong , Wang Zhenlin , Ming Naiben
Published: January 2008

High-quality colloidal crystals with deep photonic band gap of up to 78% and steep photonic band edge of up to 5.2%∕nm are fabricated by only using the quasimonodisperse spheres with polydispersity of 2.5%–3.1%. By controlling the self-assembly of spheres in the neck region of a Bunsen flask under negative pressure, all the reported limits of the popular vertical deposition method are simultaneously solved, and the damage of the polydispersity, impurity, and surface roughness of spheres to the crystal quality is effectively reduced. Even the impure spheres with large polydispersity of up to 10% and the rough large silica@Ag core-shell particles can be assembled into the well-ordered structures. The superior assembly ability of colloidal spheres as well as the good optical quality demonstrated here may find their broad applications in nanoassembly, templating synthesis, optical, physicochemical applications, etc.
Generation of excess Si species at Si∕SiO2 interface and their diffusion into SiO2 during Si thermal oxidation
Authors: Ibano Kenzo , Itoh Kohei M. , Uematsu Masashi
Published: January 2008

Si self-diffusion in thermally grown SiO2 near the SiO2∕Si interface during thermal oxidation process was studied using isotopic heterostrucutures (SinatO2∕Si28) as a function of the oxidation temperature, the oxidation time, and the fraction of oxygen in the ambient gas. The Si self-diffusivity near the SiO2∕Si interface during oxidation was found to be larger than the thermal Si self-diffusivity by more than one order of magnitude. This enhancement indicates that Si species are emitted from the SiO2∕Si interface and diffused into SiO2 during oxidation, as has been predicted by recent theoretical studies.
Sound controlled rotation of a cluster of small particles on an ultrasonically vibrating metal strip
Authors: Zhang Xueyi , Zheng Yun , Hu Junhui
Published: January 2008

We show that a vibrating metal strip, mechanically driven by an ultrasonic transducer, can rotate a cluster of small particles around a fixed point, and the diameter of the cluster of small particles can reach a stable value (steady diameter) for a given driving condition. The rotation is very stable when the vibration of the metal strip is appropriate. The revolution speed, its direction, and steady diameter of the particle cluster can be controlled by the operating frequency of the ultrasonic transducer. For shrimp eggs, a revolution speed up to 360rpm can be obtained.
In situ preparation of CdS nanoparticles imbedded in a polyelectrolyte multilayer for photocurrent generation
Authors: Lee Wonjoo , Min Sun-Ki , Shin Seunghoon , Han Sung-Hwan , Lee Soo-Hyoung
Published: January 2008

CdS nanoparticles (NPs) were prepared and imbedded in polyelectrolyte multilayers (PEMs) in situ and applied to the photocurrent generation. The PEM films of the poly(propylviologen)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) were prepared using layer-by-layer deposition. The Br− ions of the viologen groups were exchanged with S2− ion by dipping the PEMs films in a Na2S solution. Then, the films were dipped in a solution containing Cd2+ to give CdS NPs of less than 10nm in size. The CdS NP-PEM films form an efficient acceptor-sensitizer dyad system, which showed a good photocurrent of 70nA∕cm2 at 380nm for a 3.5 bilayer sample.
Dielectric relaxation and magnetodielectric response in epitaxial thin films of La2NiMnO6
Authors: Padhan P. , Guo H. Z. , LeClair P. , Gupta A.
Published: January 2008

Frequency and magnetic field dependent dielectric measurements have been performed on epitaxial thin films of the double perovskite La2NiMnO6, revealing a dielectric relaxation and magnetodielectric effect. The films are grown on Nb-doped and SrRuO3-coated SrTiO3 substrates using the pulsed laser deposition technique. While a rapid dielectric relaxation is observed at ∼300K, the relaxation rate increases dramatically at lower temperatures. Below the Curie temperature of La2NiMnO6, the dielectric constant increases in a magnetic field for a range of temperature. This temperature range depends on magnetic field and measurement frequency. The results are explained by the influence of a magnetic field on the dipolar relaxation.