bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution, ecology and conservation of an endangered Andean hummingbird: the Violet-throated Metaltail (Metallura baroni)
Authors: TINOCO BORIS A. , ASTUDILLO PEDRO X. , LATTA STEVEN C. , GRAHAM CATHERINE H.
Published: March 2009

The Violet-throated MetaltailMetallura baroniis a high altitude hummingbird endemic to south-central Ecuador currently considered globally ‘Endangered’. Here we present the first detailed assessment of its distribution, ecology and conservation. We first used a maximum entropy model (Maxent model) to create a predicted distribution for this species based on very limited species occurrence data. We used this model to guide field surveys for the species between April and October 2006. We found a positive relationship between model values and species presence, indicating that the model was a useful tool to predict species occurrence and guide exploration. In the sites where the metaltail was found we gathered data on its habitat requirements, food resources and behaviour. Our results indicate that Violet-throated Metaltail is restricted to the Western Cordillera of the Andes Mountains in Azuay and Cañar provinces of Ecuador, with an area of extent of less than 2,000 km2. Deep river canyons to the north and south, lack of suitable habitat, and potential interspecific competition in the east may limit the bird's distribution. The species occurred in three distinct habitats, includingPolylepiswoodland, the upper edge of the montane forest, and in shrubby paramo, but we found no difference in relative abundance among these habitats. The metaltail seems to tolerate moderate human intervention in its habitats as long as some native brushy cover is maintained. We found thatBrachyotumsp.,Berberissp., andBarnadesiasp. were important nectar resources. The ‘Endangered’ status of this species is supported due to its restricted distribution in fragmented habitats which are under increasing human pressures.
A NOTE ON INFLATION PERSISTENCE IN A FAIR WAGE MODEL OF THE BUSINESS CYCLE
Authors: de la Croix David , de Walque Gregory , Wouters Rafael
Published: March 2009

We generalize existing fair wage models to allow effort to vary over the business cycle. When effort is variable, wage fluctuations are partially compensated for by endogenous effort fluctuations, so that the sensitivity of marginal cost to output and employment variations is decreased. This new mechanism decreases the need for sluggishness to explain the observed high inflation persistence.
The Italian National Food Consumption Survey INRAN-SCAI 2005–06: main results in terms of food consumption
Authors: Leclercq Catherine , Arcella Davide , Piccinelli Raffaela , Sette Stefania , Le Donne Cinzia ,   Aida Turrini on behalf of the INRAN-SCAI 2005–06 Study Group
Published: March 2009

Objective

The current paper aims to present the main results of the Italian National Food Consumption Survey INRAN-SCAI 2005–06.

Design

A cross-sectional study was performed. Households were randomly selected after geographical stratification of the national territory. Food consumption was assessed on three consecutive days through individual estimated dietary records.

Setting

Italy.

Subjects

The final study sample comprised 3323 subjects (1501 males and 1822 females) aged 0·1 to 97·7 years belonging to 1329 households: fifty-two infants (0–2·9 years), 193 children (3–9·9 years), 247 teenagers (10–17·9 years), 2313 adults (18–64·9 years) and 518 elderly (65 years and above).

Results

Participation rate was 33 %. The mean ratio of estimated energy intake to estimated BMR was 1·41 in adults. Indicators of mean and high individual consumption are presented for fifteen large categories and fifty-one subcategories of foods and beverages, in the total population and in consumers, by age and sex categories. The overall consumption of fruit and vegetables was 418 g/d. The consumption of red meat was approximately 700 g/week, expressed as raw weight. Some specific aspects of the Italian food consumption pattern were confirmed: a large contribution from bread, pasta and pizza to cereals, from olive oil to fats and from wine to alcoholic beverages.

Conclusions

The database obtained from the survey will be the key reference for Italian food consumption during the coming years and will be utilized for a variety of purposes including the assessment of nutrient intakes and risk analysis.
The relationship between BMI and iron status in iron-deficient adolescent Iranian girls
Authors: Eftekhari MH , Mozaffari-Khosravi H , Shidfar F
Published: March 2009

Objective

Many Iranian adolescent girls are Fe-deficient, but it is unclear whether Fe deficiency is associated with other nutritional risk indicators. The present study aimed to investigate the association between Fe deficiency and weight status (measured as BMI) among a representative sample of adolescent girls.

Design

A cross-sectional study. Fe-deficient high-school girls (with or without anaemia) were selected by systematic random sampling among all students in grades 1 to 4 from high schools for girls. Blood samples were collected and analysed for Hb, haematocrit, serum ferritin, Fe and total Fe binding capacity. Weight and height were measured. BMI was calculated and compared with age- and gender-specific BMI reference values.

Setting

South Iran.

Subjects

A total of 431 adolescent girls aged 13–20 years.

Results

Some 15·3 % of the participants were at risk for overweight and 9·5 % of them were overweight. An inverse association was found between serum ferritin and BMI (r = −0·38, β = −0·21, P < 0·001). Anaemia was more prevalent among overweight Fe-deficient adolescents than among those Fe-deficient and at risk for overweight or normal weight (34·1 % v. 28·8 % v. 27·8 %, respectively; P < 0·001).

Conclusions

An inverse association was found between BMI and serum ferritin. Overweight adolescents demonstrated an increased prevalence of Fe-deficiency anaemia. It seems that both abnormalities of weight and Fe status should simultaneously be targeted in overweight female adolescents.
The receptor for advanced glycation endproducts (RAGE) and cardiovascular disease
Authors: Yan Shi Fang , Ramasamy Ravichandran , Schmidt Ann Marie
Published: March 2009

Recent and compelling investigation has expanded our view of the biological settings in which the products of nonenzymatic glycation and oxidation of proteins and lipids – the advanced glycation endproducts (AGEs) – form and accumulate. Beyond diabetes, natural ageing and renal failure, AGEs form in inflammation, oxidative stress and in ischaemia–reperfusion. The chief signal transduction receptor for AGEs – the receptor for AGEs (RAGE) – is a multiligand-binding member of the immunoglobulin superfamily. In addition to AGEs, RAGE binds certain members of the S100/calgranulin family, high-mobility group box 1 (HMGB1), and β-amyloid peptide and β-sheet fibrils. Recent studies demonstrate beneficial effects of RAGE antagonism and genetic deletion in rodent models of atherosclerosis and ischaemia–reperfusion injury in the heart and great vessels. Experimental evidence is accruing that RAGE ligand generation and release during ischaemia–reperfusion may signal through RAGE, thus suggesting that antagonism of this receptor might provide a novel form of therapeutic intervention in heart disease. However, it is plausible that innate, tissue-regenerative roles for these RAGE ligands may also impact the failing heart – perhaps through RAGE and/or distinct receptors. In this review, we focus on RAGE and the consequences of its activation in the cardiovasculature.
Influence of aperture field heterogeneity and anisotropy on dispersion regimes and dispersivity in single fractures
Authors: Zheng Q. , Dickson S. , Guo Y.
Published: March 2009

A 33 factorial experimental design was implemented to numerically investigate the interactive effect of the mean (μb), standard deviation (σb), and anisotropic ratio (AR) (λbx/λby) of single‐fracture apertures on dispersion regimes (specifically Taylor dispersion and geometric dispersion) and dispersivity. The Reynolds equation was solved to obtain the flow fields in each computer‐generated fracture, and the random walk particle tracking method was used to simulate solute transport. The simulation results show that (1) for a fixed hydraulic gradient, the dominant dispersion regime is controlled by μb, and to a lesser degree, σb, and geometric dispersion becomes more dominant as the coefficient of variation (COV) (σb/μb) increases; (2) for a fixed mean aperture, the dispersivity and the spread in dispersivity for varying ARs increases with the COV; and (3) the AR has a significant effect on dispersivity only when the COV is large (≳0.2).
A sporadic layer in the Venus lower ionosphere of meteoric origin
Authors: Pätzold M. , Tellmann S. , Häusler B. , Bird M. K. , Tyler G. L. , Christou A. A. , Withers P.
Published: March 2009

The Venus Express Radio Science (VeRa) experiment aboard Venus Express has detected, by means of radio occultation, distinct, low‐lying layers of electron density below the base (115 km altitude) of the ionosphere of Venus. A plausible origin of these lowest layers is ionization by the influx of meteoroids into the atmosphere. The layers appeared only occasionally during the 2006 and 2007 Venus Express occultation seasons, could be identified only on the dayside and seem to be geographically localized as they usually occur in either the northern or southern hemisphere of the same orbit; they are detected at all latitudes, but only at solar zenith angles between 55° and 90°. Typical peak plasma densities of 1010 m−3 are reached between 110 and 120 km altitude. Peak meteor layer electron densities increase with decreasing solar zenith angle. Layer shapes are symmetric with respect to peak altitude. The present observational statistics and lack of dedicated models prevents definite statements to be made on the origin of the source meteoroids.
Left‐hand rule for synoptic eddy feedback on low‐frequency flow
Authors: Kug Jong‐Seong , Jin Fei‐Fei
Published: March 2009

In this study, scale interaction between synoptic eddies and low‐frequency flow is investigated. The synoptic eddy feedback is a key process in sustaining the low‐frequency flow. We show clear evidence using NCEP reanalysis data that there is a general underlying rule—the “left‐hand rule”, governing the synoptic eddy feedback onto low‐frequency flow. This rule states that eddy‐vorticity fluxes are directed preferentially about 90 degrees toward their left‐hand side, so that they converge into cyclonic flow and diverge from anticyclonic flow. Therefore, the eddy vorticity flux plays a positive role in reinforcing low‐frequency flow.
Some inferences on the role of lower positive charge region in facilitating different types of lightning
Authors: Nag Amitabh , Rakov Vladimir A.
Published: March 2009

It is generally thought that the lower positive charge region serves to enhance the electric field at the bottom of the main negative charge region and thereby facilitate the launching of a negatively‐charged leader toward ground. On the other hand, the presence of excessive lower positive charge region may prevent the occurrence of negative cloud‐to‐ground discharges by “blocking” the progression of descending negative leader from reaching ground and thus “converting” the potential cloud‐to‐ground flash to an intracloud (or cloud‐to‐air) one. Assuming that the preliminary breakdown pulse train is a manifestation of interaction of a downward‐extending negative leader channel with the lower positive charge region, we qualitatively examine the inferred dependence of lightning type on the magnitude of this charge region.
MHD model of the flapping motions in the magnetotail current sheet
Authors: Erkaev N. V. , Semenov V. S. , Kubyshkin I. V. , Kubyshkina M. V. , Biernat H. K.
Published: March 2009

A new kind of magnetohydrodynamic waves is analyzed for a current sheet in the presence of a small normal magnetic field component (Bz) varying along the sheet. For the initial undisturbed state, a simplified model of the current sheet is considered with a Harris‐like current density distribution across the sheet. Within the framework of this model, an analytical solution is obtained for the flapping‐type wave oscillations and instability, related to the gradient of the normal magnetic field component along the current sheet. The flapping wave frequency is found to be a function of the wave number, which has an asymptotic saturation for large wave numbers. This frequency is pure real in a stable situation for the magnetotail current sheet, when the Bz component increases toward Earth. The current sheet becomes unstable in some regions, where the Bz component decreases locally toward Earth. In the stable region, the “kink”‐like wave oscillations are calculated for an initial Gaussian perturbation localized to the center of the current sheet. The flapping wave propagations are analyzed for two cases: (1) the initial perturbation is fixed, and (2) the source is moving toward Earth. In the last case, the Mach cone is obtained for the propagating flapping waves. The source for the flapping waves is associated with the fast plasma flow originated from the reconnection region.
Geoid and gravity anomaly data of conjugate regions of Bay of Bengal and Enderby Basin: New constraints on breakup and early spreading history between India and Antarctica
Authors: Krishna K. S. , Michael Laju , Bhattacharyya R. , Majumdar T. J.
Published: March 2009

Timing of breakup of the Indian continent from eastern Gondwanaland and evolution of the lithosphere in the Bay of Bengal still remain as ambiguous issues. Geoid and free‐air gravity data of Bay of Bengal and Enderby Basin are integrated with shipborne geophysical data to investigate the early evolution of the eastern Indian Ocean. Geoid and gravity data of the Bay of Bengal reveal five N36°W fracture zones (FZs) and five isolated NE‐SW structural rises between the Eastern Continental Margin of India (ECMI) and the 85°E Ridge/86°E FZ. The FZs meet the 86°E FZ at an angle of ∼39°. The rises are associated with low‐gravity and geoid anomalies and are oriented nearly orthogonal to the FZs trend. The geoid and gravity data of the western Enderby Basin reveal a major Kerguelen FZ and five N4°E FZs. The FZs discretely converge to the Kerguelen FZ at an angle of ∼37°. We interpret the FZs identified in Bay of Bengal and western Enderby Basin as conjugate FZs that trace the early Cretaceous rifting of south ECMI from Enderby Land. Structural rises between the FZs of Bay of Bengal may either represent fossil ridge segments, possibly have extinct during the early evolution of the Bay of Bengal lithosphere or may have formed later by the volcanic activity accreted the 85°E Ridge. Two different gravity signatures (short‐wavelength high‐amplitude negative gravity anomaly and relatively broader low‐amplitude negative gravity anomaly) are observed on south and north segments of the ECMI, respectively. The location of continent‐ocean boundary (COB) is at relatively far distance (100–200 km) from the coastline on north ECMI than that (50–100 km) on the south segment. On the basis of geoid, gravity, and seismic character and orientation of conjugate FZs in Bay of Bengal and western Enderby Basin, we believe that transform motion occurred between south ECMI and Enderby Land at the time of breakup, which might have facilitated the rifting process in the north between combined north ECMI‐Elan Bank and MacRobertson Land and in the south between southwest Sri Lanka and Gunnerus Ridge region of East Antarctica. Approximately during the period between the anomalies M1 and M0 and soon after detachment of the Elan Bank from north ECMI, the rifting process possibly had reorganized in order to establish the process along the entire eastern margins of India and Sri Lanka.
Reflection seismic waveform tomography
Authors: Wang Yanghua , Rao Ying
Published: March 2009

In seismic waveform tomography, if using reflection data with limited source‐receiver offsets, it is difficult to reconstruct the deep part of the subsurface velocity model. We present two approaches to tackle this problem: layer stripping and weighted updating. In a layer‐stripping procedure, we replace the top portion of seismic data with synthetics generated from the previous‐layer inversion and make the current inversion focus on the minimization of the data misfit corresponding to the deep part of the model. To improve efficiency, we use only sparsely sampled frequency data in the deeper‐layer inversions, unlike the first‐layer inversion where we use densely sampled frequency data as usual. The sparsely sampled frequencies together have the full wave number coverage for effective imaging. Combined use of dense and sparse sampling in frequency is a compromise between resolution and efficiency, as it reduces the number of iterations needed in layer‐stripping inversion while still producing a good image. In the second scheme, we apply depth‐dependent weights to model updates in order to improve the convergence in an iterative solution. The weighting is inversely proportional to the ray density variation along the depth and is mathematically equivalent to the application of an inverse Hessian matrix which sharpens the gradient vector for model updating. For real seismic data, we transfer point source shot records to line source records, by partial amplitude compensation and phase adjusting, before inputting it to the waveform tomography. We perform traveltime inversion to generate a reliable layered velocity model and then waveform tomography to produce a high‐resolution image of the subsurface model through frequency domain iteration.
Ozone ensemble forecast with machine learning algorithms
Authors: Mallet Vivien , Stoltz Gilles , Mauricette Boris
Published: March 2009

We apply machine learning algorithms to perform sequential aggregation of ozone forecasts. The latter rely on a multimodel ensemble built for ozone forecasting with the modeling system Polyphemus. The ensemble simulations are obtained by changes in the physical parameterizations, the numerical schemes, and the input data to the models. The simulations are carried out for summer 2001 over western Europe in order to forecast ozone daily peaks and ozone hourly concentrations. On the basis of past observations and past model forecasts, the learning algorithms produce a weight for each model. A convex or linear combination of the model forecasts is then formed with these weights. This process is repeated for each round of forecasting and is therefore called sequential aggregation. The aggregated forecasts demonstrate good results; for instance, they always show better performance than the best model in the ensemble and they even compete against the best constant linear combination. In addition, the machine learning algorithms come with theoretical guarantees with respect to their performance, that hold for all possible sequences of observations, even nonstochastic ones. Our study also demonstrates the robustness of the methods. We therefore conclude that these aggregation methods are very relevant for operational forecasts.
Theory, analytical investigation, and performance of the complementary derivatives method for reducing reflection errors from nonuniform grid domains in finite difference methods
Authors: Kermani Mohammad H. , Ramahi Omar M.
Published: March 2009

The central finite difference is used very often to approximate first‐order differential equations, and it results in a second‐order truncation error for a uniform grid size. Nonuniform grids are used for simulating structures with large aspect ratios or problems with large field gradients in order to improve computational efficiency. However, changing the grid size increases the truncation error at the interface between domains having different grid sizes. The error at the interface is manifested as a spurious reflection from the grid boundary, thus decreasing the simulation accuracy. The complementary derivatives method (CDM) was originally introduced as a robust discretization technique to eliminate any spurious errors arising from the changing grid sizes. In this paper, we review the theory of the CDM. We investigate the CDM analytically for the one‐dimensional case and derive the fundamental modes of propagation in the numerical solution of the differential equation. Then, we calculate the reflection coefficient from the interface of two domains having different grid sizes with and without the CDM. Different representative numerical examples also demonstrate the efficiency of the CDM in reducing the reflection from the grid boundary and improving the simulation results in different applications.
Measurements of geomagnetically induced current in a power grid in Hokkaido, Japan
Authors: Watari S. , Kunitake M. , Kitamura K. , Hori T. , Kikuchi T. , Shiokawa K. , Nishitani N. , Kataoka R. , Kamide Y. , Aso T. , Watanabe Y. , Tsuneta Y.
Published: March 2009

There have been numerous reports showing that space weather affects power grids through a geomagnetically induced current (GIC). Generally, power grids consist of power lines connected to transformers, of which neutral points are directly grounded. The GIC flows into those transformers through the neutral points if geomagnetic variations cause a ground level potential. These currents can damage power grids, especially transformers. It has been tacitly assumed, however, that the effect of the GIC is minor in Japan because of the country's location at geomagnetically lower latitudes. To examine the GIC effect in Japan, we conducted approximately 2 years of GIC measurements in Hokkaido, Japan. It is found that GICs associated with substorms can be detected in Japan even at the solar minimum although intense GICs do occur mostly during geomagnetic storms. Temporal variations of GICs show high correlation with geomagnetic field variations, rather than time derivatives of the geomagnetic field.
Maternal Feeding Practices Become More Controlling After and Not Before Excessive Rates of Weight Gain
Authors: Rhee Kyung E. , Coleman Sharon M. , Appugliese Danielle P. , Kaciroti Niko A. , Corwyn Robert F. , Davidson Natalie S. , Bradley Robert H. , Lumeng Julie C.
Published: March 2009

It is unclear whether controlling maternal feeding practices (CMFPs) lead to or are a response to increases in a child's BMI. Our goal was to determine the direction of this relationship. Data were obtained from National Institute of Child Health and Human Development's Study of Early Child Care and Youth Development. Child BMI z‐score (zBMI) was calculated from measured weight and height. CMFP was defined by, “Do you let your child eat what he/she feels like eating?”. Change in child zBMI was calculated between 4–7 years and 7–9 years, and dichotomized into “increasing” vs. “no change or decreasing”. Change in CMFP was calculated over the same time periods, and dichotomized into “more controlling” vs. “no change or less controlling.” Multiple logistic regression, stratified by gender and controlling for race, maternal education, maternal weight status, and baseline child weight status, was used for analysis. A total of 789 children were included. From 4 to 9 years, mean zBMI increased (P = 0.02) and mothers became more controlling (P < 0.001). Increasing CMFP between 4 and 7 years was associated with decreased odds of increasing zBMI between 7 and 9 years in boys (odds ratio = 0.52, 95% confidence interval = 0.27–1.00). There was no relationship in girls. Increasing zBMI between 4 and 7 years was associated with increasing CMFPs between 7 and 9 years in girls (odds ratio = 1.72, 95% confidence interval = 1.08–2.74), but not boys. Early increases in CMFP were not associated with later increases in zBMI for boys or girls. However, early increases in zBMI among girls were associated with later increases in CMFP. Clarifying the relationship between maternal feeding practices and child weight will inform future recommendations.
Estimating Activity‐related Energy Expenditure Under Sedentary Conditions Using a Tri‐axial Seismic Accelerometer
Authors: van Hees Vincent T. , van Lummel Rob C. , Westerterp Klaas R.
Published: March 2009

Activity‐related energy expenditure (AEE) is difficult to quantify, especially under sedentary conditions. Here, a model was developed using the detected type of physical activity (PA) and movement intensity (MI), based on a tri‐axial seismic accelerometer (DynaPort MiniMod; McRoberts B.V., The Hague, the Netherlands), with energy expenditure for PA as a reference. The relation between AEE (J/min/kg), MI, and the type of PA was determined for standardized PAs as performed in a laboratory including: lying, sitting, standing, and walking. AEE (J/min/kg) was calculated from total energy expenditure (TEE) and sleeping metabolic rate (SMR) as assessed with indirect calorimetry ((TEE × 0.9) ‐ SMR). Subsequently, the model was validated over 23‐h intervals in a respiration chamber. Subjects were 15 healthy women (age: 22 ± 2 years; BMI: 24.0 ± 4.0 kg/m2). Predicted AEE in the chamber was significantly related to measured AEE both within (r2 = 0.81 ± 0.06, P < 0.00001) and between (r2 = 0.70, P < 0.001) subjects. The explained variation in AEE by the model was higher than the explained variation by MI alone. This shows that a tri‐axial seismic accelerometer is a valid tool for estimating AEE under sedentary conditions.
Visceral and Subcutaneous Adiposity and Brachial Artery Vasodilator Function
Authors: Parikh Nisha I. , Keyes Michelle J. , Larson Martin G. , Pou Karla M. , Hamburg Naomi M. , Vita Joseph A. , O'Donnell Christopher J. , Vasan Ramachandran S. , Mitchell Gary F. , Hoffmann Udo , Fox Caroline S. , Benjamin Emelia J.
Published: March 2009

Endothelial dysfunction may link obesity to cardiovascular disease (CVD). We tested the hypothesis that visceral abdominal tissue (VAT) as compared with subcutaneous adipose tissue (SAT) is more related to endothelium‐dependent vasodilation. Among Framingham Offspring and Third Generation cohorts (n = 3,020, mean age 50 years, 47% women), we used multivariable linear regression adjusted for CVD and its risk factors to relate computed tomography (CT)‐assessed VAT and SAT, BMI, and waist circumference (WC), with brachial artery measures. In multivariable‐adjusted models, BMI, WC, VAT, and SAT were positively related to baseline artery diameter and baseline mean flow velocity (all P < 0.001), but not hyperemic mean flow velocity. In multivariable‐adjusted models, BMI (P = 0.002), WC (P = 0.001), and VAT (P = 0.01), but not SAT (P = 0.24) were inversely associated with percentage of flow‐mediated dilation (FMD%). However, there was little incremental increase in the proportion of variability explained by VAT (R2 = 0.266) as compared to SAT (R2 = 0.265), above and beyond traditional risk factors. VAT, but not SAT was associated with FMD% after adjusting for clinical covariates. Nevertheless, the differential association with VAT as compared to SAT was minimal.
Rise in Extracellular Fluid Volume During High Sodium Depends on BMI in Healthy Men
Authors: Visser Folkert W. , Krikken Jan A. , Muntinga Jaap H.J. , Dierckx Rudi A. , Navis Gerjan J.
Published: March 2009

A high sodium (HS) intake is associated to increased cardiovascular and renal risk, especially in overweight subjects. We hypothesized that abnormal sodium and fluid handling is involved, independent of hypertension or insulin resistance. Therefore, we studied the relation between BMI and sodium‐induced changes in extracellular fluid volume (ECFV; distribution volume of 125I‐iothalamate) in 78 healthy men, not selected for BMI. A total of 78 subjects with a median BMI of 22.5 (range: 19.2–33.9 kg/m2) were studied after 1 week on a low sodium (LS) diet (50 mmol Na+/d) and after 1 week on HS (200 mmol Na+/d). The change from LS to HS resulted in an increase in ECFV of 1.2 ± 1.8 l. Individual changes in ECFV were correlated to BMI (r = 0.361, P < 0.01). Furthermore, in response to HS, a higher BMI was associated to a higher rise in filtered load of sodium (FLNa+ = [Na+] × GFR, r = 0.281, P < 0.05). Thus, a shift to HS leads to a larger rise in ECFV in healthy subjects with higher BMI, associated with an elevated FLNa+ during HS. Although no hypertension occurred in these healthy subjects, our data provide a potential explanation for the interaction of sodium intake and BMI on cardiovascular and renal risk. Exaggerated fluid retention may be an early pathogenic factor in the cardiorenal complications of overweight.
Distinction and correlation between magnetization switchings driven by spin transfer torque and applied magnetic field
Authors: Zhu Xiaochun , Kang Seung H.
Published: March 2009

The dynamics of the magnetization switching in magnetic tunnel junctions (MTJs) designed for spin-transfer-torque (STT) magnetoresistive random access memory (MRAM) was investigated using micromagnetic simulations. It was found that for short pulses (<∼10ns), the switching current threshold does not correlate with the switching field threshold and it is, therefore, essentially insensitive to MTJ shape (aspect ratio) and edge roughness. However, if the magnetization reversal is thermally activated for longer pulses, the switching current and the switching field are directly correlated. For a relatively large MTJ, the distribution is wide due to the excitation of high-order spin wave modes.
Back-hopping after spin torque transfer induced magnetization switching in magnetic tunneling junction cells
Authors: Min T. , Sun J. Z. , Beach R. , Tang D. , Wang P.
Published: March 2009

In some cases such as junctions with low magnetic thermal activation energy, the magnetization of the free layer in MgO-based magnetic tunnel junctions (MTJs) can back hop to its original direction after successful spin torque induced switching. The back-hopping is observed in both current directions corresponding to parallel-to-antiparallel and antiparallel-to-parallel switchings. For bias voltage pulses with increasing pulse width, the threshold voltage for back-hopping appears to decrease together with spin-torque switching and junction breakdown thresholds, but its rate of decrease is less. Increasing the anisotropy field Hk by increasing the MTJ aspect ratio can raise the threshold voltage of back-hopping significantly.
Magnetic ground state at the ytterbium site in YbNiAl4
Authors: Saensunon Banchachit , Nishimura Katsuhiko , Voyer C. J. , Ryan D. H. , Hutchison Wayne D. , Stewart Glen A.
Published: March 2009

Magnetic, specific heat, and Y170b-Mössbauer spectroscopy measurements are presented for polycrystalline YbNiAl4. Although the low temperature specific heat data are consistent with the early stages of a magnetic transition, there is no clear evidence for magnetic order down to the lowest experimental temperature of 1.5 K. It is concluded that this is due to an even stronger quenching effect than is predicted by the current crystal field theory.
Development of heparin-coated magnetic nanoparticles for targeted drug delivery applications
Authors: Khurshid H. , Kim S. H. , Bonder M. J. , Colak L. , Ali Bakhtyar , Shah S. I. , Kiick K L. , Hadjipanayis G. C.
Published: March 2009

We have designed a potential drug delivery system by combining low-molecular-weight heparin to iron oxide magnetic nanoparticles with an average size of 20 nm. The particles were synthesized by the NaBH4 reduction of FeCl2 and then coated with poly-L-lysine. Heparin was noncovalently conjugated on these nanoparticles via the interactions between the negatively charged sulfate and carboxylate groups of heparin and the positively charged amine group of poly-L-lysine. The nanoparticles were examined by using transmission electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and zeta potential measurements. The data provide direct evidence that the heparin was immobilized at the surface of poly-L-lysine-coated iron oxide nanoparticles. Magnetic measurements revealed the particles are ferromagnetic with a saturation magnetization of 31 emu/g.
L
1
0
ordering of FePt thin films using sub-10 ms laser pulses
Authors: Inaba Y. , Kang S. , Izatt J. R. , Harrell J. W. , Thompson G. B. , Kubota Y. , Klemmer T. J.
Published: March 2009

The structural and magnetic properties of 10 nm FePt thin films annealed using a 1064 nm wavelength laser with 10, 7.5, 5.0, and 2.5 ms pulses have been examined. The A1 to L10 phase transformation was confirmed by x-ray diffraction (XRD). The maximum order parameter of 0.53 and coercivity of 5.36 kOe can be obtained with 10 ms pulse width laser annealing at a laser energy fluence of 10 J/cm2. The order parameter of the furnace annealed samples was approximately 1.0 suggesting that 10 ms is insufficient to obtain a fully ordered phase. The laser annealed grain size, as measured by in-plane XRD analysis, is 24 % smaller than that of furnace annealed sample for an equivalent order parameter demonstrating the merit of short time annealing.
Temperature stability of field induced anisotropy in soft ferromagnetic Fe,Co-based amorphous and nanocomposite ribbons
Authors: Ohodnicki P. R. , Laughlin D. E. , McHenry M. E. , Keylin V. , Huth J.
Published: March 2009

The temperature stability of field induced uniaxial anisotropy (KU) was investigated by thermomagnetic treatments of (Co1−xFex)89Zr7B4 amorphous ribbons after field annealing below and above the crystallization temperature. We conclude: (1) Field annealing treatments are necessary to properly investigate the temperature stability of KU, (2) KU of field crystallized alloys exhibit improved temperature stability relative to alloys remaining amorphous after field annealing, and (3) larger KU is obtained for field crystallization treatments as compared to zero-field crystallization followed by field reannealing. Field crystallization may be required for elevated temperature applications when field induced anisotropy is critical for performance.
The effect of boron addition on the atomic structure and microwave magnetic properties of FeGaB thin films
Authors: Gao Jinsheng , Yang Aria , Chen Yajie , Kirkland J. P. , Lou Jing , Sun Nian X. , Vittoria Carmine , Harris Vincent G.
Published: March 2009

Varying amounts of boron were added to the host FeGa alloy to investigate its impact upon local atomic structure and magnetic and microwave properties. The impact of B upon the local atomic structure in FeGaB films was investigated by extended x-ray absorption fine structure (EXAFS) analysis. The EXAFS fitting results revealed a contraction of lattice parameters with the introduction of B. The Debye–Waller factor determined from EXAFS fitting increases as a function of boron addition and abruptly changes during the structural evolution from crystalline to amorphous that occurs near 9% B. Upon the onset of this transition the static and microwave magnetic properties became exceptionally soft, with values of coercivity and ferromagnetic linewidth reducing to less than 1 Oe and 25 Oe, respectively.
Differential destructive interference of the circular polarization eigenmodes of scattered soft x rays at the grazing incidence in magnetic thin films
Authors: Jeong Dae-Eun , Kim Sang-Koog
Published: March 2009

Recently, the authors found that an additional magneto-optical effect that linearly polarized soft x rays incident on a single magnetic layer on a nonmagnetic substrate can be converted to any states among the linearly s- and p- and circularly left- and right-handed polarizations by changing the grazing angle of incidence in specular reflection geometry. In this article, the authors report that the physical origin of such an effect is the differential interference of the circular polarization eigenmodes of scattered soft x rays at the grazing incidence. Totally destructive interference takes place selectively for one helicity but not for the other one at a certain grazing angle and in a specific energy region just below the absorption edges, thus leading to differential circular reflectivity. Numerical calculations using an iterative method of transmission, reflection, and propagation matrices allow us not only to verify the underlying mechanism but also to find the necessary specific conditions of photon energy and incidence angle where such a phenomenon can occur.
A flux-mnemonic permanent magnet brushless machine for wind power generation
Authors: Yu Chuang , Chau K. T. , Jiang J. Z.
Published: March 2009

In this paper, the concept of flux mnemonics is newly extended to the wind power generator. By incorporating a small magnetizing winding into an outer-rotor doubly salient AlNiCo permanent magnet (PM) machine, a new flux-mnemonic PM brushless wind power generator is proposed and implemented. This generator can offer effective and efficient air-gap flux control. First, the characteristics of the proposed generator are analyzed by using the finite element method. Second, the closed-loop flux control is devised to achieve a constant generated voltage under time-varying wind speeds. Finally, the experimental results are given to verify the validity of the proposed generator and control system.
Assessment of shot peening uniformity by magnetic drag force measurements
Authors: Garshelis Ivan. J. , Tollens Stijn P. L. , Hollander Marnix E. , Kari Ryan J. , Cuseo James M.
Published: March 2009

The effects of varying shot peening process parameters on drag force signatures are examined. The salient features of such signatures are found to compare favorably with those expected from consideration of the effects of peening on magnetic properties combined with analysis of the actual force sources. The potential utility of the drag force method for automatic assessment of peening quality and uniformity is encouraged by experimental results.
Switching volume change and recording performance correlation for weakly coupled exchange spring media
Authors: Ikeda Yoshihiro , Choe Gunn , Zhang Kezhao , Takano Kentaro
Published: March 2009

We employed a new field sweep ratio dependence analysis method on the polar Kerr loop of exchange spring media to estimate the short time switching field, H0, and thermal stability factor, KUV/kBT, at various normalized Kerr signal levels, M, using modified Sharrock’s equation. For weakly coupled media, we observed that large switching volume changes around a “kink” in the Kerr loops. We observed a rapid increase in the KUV/kBT values before the kink, which suggests rapid switching of large areas of the soft layer via domain wall propagation. Small interfacial decoupling in exchange spring media between the soft and hard layers showed large degradation in media writability.
Analysis of the proximity effect and the interface transparency with perpendicular current in Ni/Nb system
Authors: Huang S. Y. , Chiu Y. C. , Liang J. J. , Lin L. K. , Tsai T. C. , Hsu S. Y. , Lee S. F.
Published: March 2009

We quantitatively study the interface resistance in Ni/Nb multilayers fabricated by sputtering system. For a fixed Ni layer thickness in Ni/Nb/Ni trilayers, the superconducting temperature Tc decreases with decreasing Nb thickness. By analyzing the data with the proximity effect, the critical thickness below which superconductivity vanished was deduced. From current perpendicular to plane (CPP) measurement interpreted with a one-band series-resistor model, we obtained the CPP resistivities of Nb and Ni and the unit area resistances of 4.2±0.2 and 1.5±0.4 fΩ m2 for superconducting and normal Ni/Nb interfaces. The transparency parameter is directly calculated in terms of interface resistance.
High temperature magnetic properties of nanocrystalline PrCo5 and YCo5 alloys obtained by mechanical milling
Authors: Galindo J. T. Elizalde , Gómez F. J. Rivera , Aquino J. A. Matutes
Published: March 2009

Enhanced hard magnetic properties were obtained in nanostructured PrCo5 and YCo5 intermetallic compounds processed by mechanical milling for 240 min, and subsequent annealing in high vacuum at 1103 K for 1.0 and 2.5 min, respectively, followed by quenching in water. X-ray diffraction data demonstrate that the annealing has produced an average grain size ⟨D⟩ below 20 nm for both compounds, as a consequence magnetic measurements at room temperature showed a coercivity (HC) higher than 0.79 MA/m, and enhanced remanence (σr/σmax>0.5). High temperature magnetic measurements showed a temperature dependence of HC and remanent magnetization σr for both compounds, where the temperature coefficient of coercivity for PrCo5 is bigger than for YCo5. Such behavior is consistent with the intrinsic temperature variation of magnetocrystalline anisotropy for PrCo5 and YCo5 intermetallic compounds.
Thickness dependence of structure and magnetic properties of annealed [Fe/Pt]n multilayer films
Authors: Yao Bo , Coffey Kevin R.
Published: March 2009

The L10 FePt phase material has potential applications for magnetic recording and permanent magnets due to its high magnetocrystalline anisotropy energy density. The heat treatment of [Fe/Pt]n multilayer films is one approach to form the L10 FePt phase at a lower processing temperature, which is highly desirable for its applications. This paper reports the influence of film total thickness (8–100 nm) on the structure and magnetic properties of annealed [Fe/Pt]n multilayer films. A novel technique based on hollow cone dark field transmission electron microscopy is used to determine the L10 phase fraction and grain size in the annealed films. It was found that the L10 phase fraction and grain size, ordering, and magnetic properties are strongly dependent on the total film thicknesses. An L10 FePt phase fraction close to 100% is achieved for a thick [Fe/Pt]n multilayer film (100 nm) annealed at 400 °C for 1 h, while a value of only 36% is achieved for a thin film (8 nm) annealed at the same condition. In this work the L10 FePt phase nucleation density is also presented. These results suggest that the L10 phase formation is nucleation limited, and that the subsequent growth of L10 phase grains also strongly influences the structure and magnetic properties of the annealed films.
Anisotropic properties in Fe–Pt thick film magnets
Authors: Nakano M. , Shibata S. , Yanai T. , Fukunaga H.
Published: March 2009

As-deposited Fe–Pt thick films prepared by a pulsed laser deposition method with the laser power higher than 5 W had L10 ordered phase without a substrate heating system. As the laser power increased, the properties of the obtained films changed from isotropic to anisotropic ones. It was also confirmed that x-ray diffraction analysis agrees with the anisotropic phenomenon in crystalline structure with increasing laser power.
Effect of temperature on hybridization and magnetism in UPdSn and UCuSn
Authors: Kothapalli Karunakar , Nasreen Farzana , Peterson Joe , Nakotte Heinz , El-Khatib Sami , Vogel Sven C. , Llobet Anna , Reiche Helmut , Swainson Ian , Brück Ekkehard
Published: March 2009

We measured the temperature dependence of the structural parameters and the occurrence of magnetism in UPdSn and UCuSn using neutron diffraction. The data were taken in an effort to understand the role of hybridization effects for the development of the uranium magnetic moment and the occurrence of long-range magnetic order in these two compounds. The shortest U–U distance provides a measure of delocalization due to direct 5f-5f overlap, while the U–Pd (or U–Cu, respectively) and U–Sn distances give a measure of the effects of 5f-ligand hybridization. Using Rietveld refinement of our neutron diffraction data, we determined the shortest interatomic distances for temperatures between 15 K and room temperature. The changes in the interatomic distances cause changes in the hybridization effects, which in turn leads to the formation of a magnetic ground state for both compounds.
Change in the direction of anisotropy in PLD-fabricated Sm-Co thick film magnets
Authors: Nakano M. , Yamaguchi K. , Yanai T. , Yamashita F. , Fukunaga H.
Published: March 2009

Pulsed laser deposition (PLD) method with a substrate heating system enabled us to obtain Sm-Co thick film magnets with the thickness of several ten microns. With increasing a substrate temperature from 673 to 1073 K, the direction of anisotropy changed from in-plane to perpendicular one. The observation of crystalline structure in the films indicated the agreement with the change in anisotropy.
Spin-polarized electronic structures and transport properties of Fe-Co alloys
Authors: Kota Yohei , Takahashi Tomohiro , Tsuchiura Hiroki , Sakuma Akimasa
Published: March 2009

The electrical resistivities of Fe-Co alloys owing to random alloy disorder are calculated using the Kubo-Greenwood formula. The obtained electrical resistivities agree well with experimental data quantitatively at low temperature. The spin polarization of Fe50Co50 estimated from the conductivity (86%) has opposite sign to that from the densities of the states at the Fermi level (−73%). It is found that the conductivity is governed mainly by s electrons, and the s electrons in the minority spin states are less conductive due to strong scattering by the large densities of the states of d electrons than the majority spin electrons.
Optically pumped lasing from a single pillar microcavity with InGaAs/GaAs quantum well potential fluctuation quantum dots
Authors: Sęk G. , Podemski P. , Misiewicz J. , Reitzenstein S. , Reithmaier J. P. , Forchel A.
Published: March 2009

Here, an optical study is presented on cuboidal single pillar microresonators with a quantum-dot-like emitter formed from local fluctuations in the InGaAs/GaAs quantum well potential. By means of microphotoluminescence, emission spectra as a function of the excitation power density were recorded. In the low excitation spectra a number of sharp lines corresponding to the single quantum dots photoluminescence was observed. With increasing excitation power the spectra become dominated by the microcavity modes, on the background of which an intensive and narrow line appears when a certain threshold excitation power is exceeded. A threshold power corresponding to the onset of the superlinear emission intensity power dependence was determined, which is accompanied by a strong decrease in the emission mode linewidth, where both are the distinctive features of the lasinglike behavior. The threshold power density and the exponent of the superlinear part of the input-output characteristic increase with the pillar lateral size (d) and the quality factor (Q), however, they both decrease when plotted as a function of Q/d2, which is the actual figure of merit of the spontaneous emission coupling factor (β). It shows the dominant influence of the volume change effect over the cavity Q (finesse). Thus, larger β values are assigned to the smaller micropillars, in spite of their lower Q values. A quantum dot character of the lasing has been confirmed in a temperature dependent experiment, which showed a number of emission intensity oscillations instead of the expected monotonic decay with the temperature increase, which is a fingerprint of the spectral tuning of the quantum dot emission spectrum through the optical cavity mode.
Reactance simulation for the defects in steam generator tube with outside ferrite sludge
Authors: Ryu Kwon-sang , Son Derac , Park Duck-gun , Jung Jae-kap , Kima Yong-il
Published: March 2009

A magnetic sludge is partly produced around the tube sheet outside a steam generator due to stress and heat. The sludge with magnetite is one of the important factors affecting eddy current signals. It causes trouble for the safety of the steam generator tubes and is difficult to detect by conventional eddy current methods. A new type of probe is needed to detect the signals for the magnetic sludge. We designed a new U-type yoke which has two kinds of coils—a magnetizing coil and the other a detecting coil—and we simulated the signal induced by the ferromagnetic sludge in the Inconel 600 tube.