bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-phase modulation of a laser in self created plasma channel
Authors: Panwar A. , Sharma A.K.
Published: March 2009

An analytical formalism of self focusing and self-phase modulation of an intense short pulse laser in a plasma due to relativistic and ponderomotive nonlinearities is developed. In the paraxial ray approximation, the pulse retains its Gaussian radial profile, however, its spot size varies with the distance of propagation in a periodic manner. It is influenced by self focusing. The frequency of the laser undergoes red shift. For a tanhyperbolic temporal profile of pulse, the red-shift is maximum at the foot of the pulse and decreases slowly as one goes to higher and higher intensity portions. The effect of ponderomotive nonlinearity is very significant in this respect. The maximum downshift occurs at a distance at which the laser acquires a minimum spot size. With retarded time normalized axial intensity increases more atz ~ Rdand the radial intensity is also more narrowly peaked atz ~ Rd, whereRd = 2πr02/λ is the Rayleigh length,r0and λ are the spot size and wavelength of the laser pulse respectively.
Surface plasmon enhanced electron acceleration with few-cycle laser pulses
Authors: Dombi P. , Rácz P. , Bódi B.
Published: March 2009

Surface plasmon enhanced electron acceleration is a recently discovered efficient particle acceleration phenomenon in the nanoscale-confined field of surface electromagnetic waves. For the generation and spatial/spectral control of keV-energy electrons generated, this way few-cycle laser pulses can be utilized particularly well. We present numerical results based on a simple model of this phenomenon analogous to the three-step model of high harmonic generation. We identify those parameter regimes where the emitted electron beam is highly directional and monoenergetic opening the door to novel ultrafast applications and methods.
On-line Detection of Tracking Loss in Aviation GPS Receivers Using Frequency-Lock Loops
Authors: So Hyoungmin , Choi Sujin , Jeon Sanghoon , Kee Changdon
Published: March 2009

For high-precision real-time kinematics (RTK) and safety-of-life Global Navigation Satellite Systems (GNSS), it is critical to track the carrier reliably without interruptions. We develop hardware-oriented robust on-line cycle slip and loss detection logic for a single-frequency stand-alone aviation receiver. The moving average statistics of time-differenced frequency-lock loop (FLL) are shown to provide a robust and fixed detection threshold for cycle loss detection. A Monte-Carlo simulation shows that the detection performance remains robust when aviation dynamics from minimum operational performance standard (MOPS) are added to a simulated strong scintillation.
SESAR: R&D and Project Portfolios for Airline Business Needs
Authors: Brooker Peter
Published: March 2009

‘Even the longest journey must begin where you stand.

Lao-tzu

‘In the long run, we're all dead’

J. M. Keynes

A version of this paper was first presented at the Royal Institute of Navigation NAV 08 Conference held at Church House, Westminster, London in October 2008.

SESAR is Europe's ‘Single European Sky Air traffic Research system’, targeted at post-2020. The vision is to integrate and implement new technologies to improve air traffic management (ATM) performance. The focus for planning and executing system operations will increasingly be aircraft navigating high-quality 4D trajectories: a 4D trajectory is the aircraft path, three space dimensions plus time, from gate-to-gate, i.e. including the path along the ground at the airport. A 20+year ATM plan has to use limited information on the success of innovations and the development of large-scale, often safety critical, software, which by its nature can take markedly longer and cost markedly more than early estimates. SESAR must be sufficiently flexible in deployment to maximise financial benefits to individual stakeholdersusing their specific financial criteria. Airline needs are the main ATM system/business drivers. Airlines do not want to commit to developing an ‘ultra-modern system’per se, but rather to one that makes business-sensible investments in new technologies that are indispensable for achieving improved safety and meeting projected capacity requirements. The approach has been to use simple corporate finance ideas to examine the different viewpoints and business environments of air traffic service suppliers (ANSPs) and individual airlines. The key decision-making point is that ANSPs act as an agent for airlines as a whole. The key financial point is that a typical airline has to work hard to survive and needs quick paybacks on investment. The design of the SESAR R&D and project portfolios can learn lessons from information technology systems design and deployment. ‘Real option analysis’ of systems can increase business value by improving the sequencing and partitioning of projects, helping to ensure that the system is adaptable to technological innovation and changes in business needs.
Recent decline of the St Helena Wirebird Charadrius sanctaehelenae
Authors: McCULLOCH NEIL
Published: March 2009

The Wirebird Charadrius sanctaehelenae, a plover, is the only surviving bird species endemic to the South Atlantic Island of St Helena. The species is currently dependent on habitats that are wholly anthropogenic or extensively modified by human activity. A census carried out during 2005–2006 showed that the Wirebird has undergone a decline of more than 40% over a five-year period to a total of 235 individuals. The species now qualifies for re-classification as ‘Critically Endangered’. Vegetation surveys support the results of a previous study in suggesting that the decline may be associated with degradation of the Wirebird's favoured grassland habitat due to reduction of livestock numbers. Predation by introduced mammals and birds is also likely to be a factor but this remains unquantified. The Wirebird may face additional threats to its habitat in the future unless potential tourism-related development associated with the proposed construction of an airport on the island is closely regulated.
Low calcium intake is associated with increased bone resorption in postmenopausal Japanese women: Yokogoshi Study
Authors: Nakamura Kazutoshi , Saito Toshiko , Yoshihara Akihiro , Ishikawa Miki , Tsuchiya Yasuo , Oshiki Rieko , Kobayashi Ryosaku , Maruyama Keiko , Hyodo Keiko , Nashimoto Mitsue , Tsugawa Naoko , Okano Toshio , Oyama Mari , Yamamoto Masaharu
Published: March 2009

Objective

Low Ca intake is common among Japanese women, but its effect on bone metabolism has not been fully elucidated. The aim of the present study was to determine the relationship between Ca intake and serum markers of bone turnover in postmenopausal Japanese women.

Design

A cross-sectional study.

Setting

A community setting.

Subjects

Subjects were 595 home-dwelling postmenopausal Japanese women. Ca intake was assessed by a validated FFQ. Serum type I collagen cross-linked N-telopeptides (NTX) and osteocalcin were measured as markers of bone turnover. The relationships between demographic characteristics, lifestyles, serum Ca, vitamin D and intact serum parathyroid hormone and bone turnover were also assessed.

Results

The average age of the subjects was 64·5 (sd 5·8) years and the mean Ca intake was 527 (sd 160) mg/d. Ca intake was significantly associated with serum NTX (P = 0·0104), but not with serum osteocalcin. Mean serum NTX concentration in the lowest quartile of Ca intake (<417 mg/d) was significantly higher than in the fourth, referent quartile. Among these Japanese postmenopausal women, very low Ca intake (less than ∼400 mg/d) was associated with increased bone resorption but not bone formation.

Conclusions

Increased bone resorption may be one mechanism by which this Ca-depleted population normalizes bone metabolism and prevents osteoporosis.
Selenium level is associated withapoE ε4in rural elderly Chinese
Authors: Gao Sujuan , Jin Yinlong , Hall Kathleen S , Liang Chaoke , Unverzagt Frederick W , Ma Feng , Cheng Yibin , Shen Jianzhao , Cao Jingxiang , Matesan Janetta , Li Ping , Bian Jianchao , Hendrie Hugh C , Murrell Jill R
Published: March 2009

Objective

Se is an essential trace element in human nutrition associated with antioxidant activity. Previous studies on predictors of toenail Se or serum Se have mostly concentrated on demographic factors such as age and gender. The present paper examines the association betweenapoEgenotype and Se levels in nail samples in a rural elderly Chinese cohort.

Design

Two thousand Chinese aged 65 years and over from four counties in China were enrolled in a cohort to study the association of Se with cognitive decline. Nail samples were collected from each participant and analysed for Se levels. Dietary Se intake was estimated from an FFQ using Se contents measured in food items collected from each village. Blood samples on filter cards were collected and analysed forapoEgenotype. Mixed-effect models were constructed with nail Se level as the dependent variable and each village as the random effect, which controlled for the potential confounding effect from correlation in Se measures obtained from participants residing in the same village.

Results

In this elderly Chinese cohort, carriers of theapoE ε4allele had significantly lower Se levels measured in nail samples than non-carriers after adjusting for other significant covariates and controlling for estimated dietary Se intake. There was no significant difference between the two genotypes on estimated Se dietary intake (P= 0·6451).

Conclusions

Future studies are needed to examine the mechanism underlying the association between theapoE ε4allele and Se levels, including the role of oxidative stress and that of reduced lipid metabolism in theapoE ε4carriers.
Carbon accumulation in peatlands of West Siberia over the last 2000 years
Authors: Beilman David W. , MacDonald Glen M. , Smith Laurence C. , Reimer Paula J.
Published: March 2009

We use a network of cores from 77 peatland sites to determine controls on peat C content and peat C accumulation over the last 2000 years (since 2 ka) across Russia's West Siberian Lowland (WSL), the world's largest wetland region. Our results show a significant influence of fossil plant composition on peat C content, with peats dominated by Sphagnum having a lower C content. Radiocarbon‐derived C accumulation since 2 ka at 23 sites is highly variable from site to site, but displays a significant N–S trend of decreasing accumulation at higher latitudes. Northern WSL peatlands show relatively small C accumulation of 7 to 35 kg C m−2 since 2 ka. In contrast, peatlands south of 60°N show larger accumulation of 42 to 88 kg C m−2. Carbon accumulation since 2 ka varies significantly with modern mean annual air temperature, with maximum C accumulation found between −1 and 0°C. Rates of apparent C accumulation since 2 ka show no significant relationship to long‐term Holocene averages based on total C accumulation. A GIS‐based extrapolation of our site data suggests that a substantial amount (∼40%) of total WSL peat C has accumulated since 2 ka, with much of this accumulation south of 60°N. The large peatlands in the southern WSL may be an important component of the Eurasian terrestrial C sink, and future warming could result in a shift northward in long‐term WSL C sequestration.
Kinematic behavior of southern Alaska constrained by westward decreasing postglacial slip rates on the Denali Fault, Alaska
Authors: Mériaux A.‐S. , Sieh K. , Finkel R. C. , Rubin C. M. , Taylor M. H. , Meltzner A. J. , Ryerson F. J.
Published: March 2009

Long‐term slip rates for the Denali Fault in southern Alaska are derived using 10Be cosmogenic radionuclide (CRN) dating of offset glacial moraines at two sites. Correction of 10Be CRN model ages for the effect of snow shielding uses historical, regional snow cover data scaled to the site altitudes. To integrate the time variation of snow cover, we included the relative changes in effective wetness over the last 11 ka, derived from lake‐level records and δ18O variations from Alaskan lakes. The moraine CRN model ages are normally distributed around an average of 12.1 ± 1.0 ka (n = 22, ± 1σ). The slip rate decreases westward from ∼13 mm/a at 144°49′W to about 7 mm/a at 149°26′W. The data are consistent with a kinematic model in which southern Alaska translates northwestward at a rate of ∼14 mm/a relative to a stable northern Alaska with no rotation. This suggests progressive slip partitioning between the Denali Fault and the active fold and thrust belt at the northern front of the Alaska range, with convergence rates increasing westward from ∼4 mm/a to 11 mm/a between ∼149°W and 145°W. As the two moraines sampled for this study were emplaced synchronously, our suggestion of a westward decrease in the slip rate of the Denali Fault relies largely upon the measured offsets at both sites, regardless of any potential systematic uncertainty in the CRN model ages.
A thermomechanical numerical model for crustal accretion of medium to fast spreading mid‐ocean ridges
Authors: Machetel P. , Garrido C. J.
Published: March 2009

We propose a new thermomechanical numerical model of mid‐ocean ridge accretion aimed at investigating asymmetric spreading rates, diverse configurations of lens and sill magma injections, crystallization and depth, and on‐ and off‐axis patterns of hydrothermal cooling. The numerical algorithm iteratively resolves temperature and motion equations until it reaches a stationary solution. The motion equation was written in a vorticity‐stream function formalism, with boundary and internal conditions applied to the stream function to impose the style of magma injection. Unlike in previous models, our model does not assume an a priori shape for the temperature field, which is initiated by an initial half‐space cooling according to the left and right spreading rates. Complex patterns of hydrothermal cooling are simulated by enhanced thermal diffusivity. The model succeeds in describing the dynamic and thermal effects of spreading rates, the style of magma intrusion, and the hydrothermal cooling. Accurate descriptions of these are essential to study the cooling histories of crustal rocks and geophysical observables.
Coral reefs may start dissolving when atmospheric CO2 doubles
Authors: Silverman Jacob , Lazar Boaz , Cao Long , Caldeira Ken , Erez Jonathan
Published: March 2009

Calcification rates in stony corals are expected to decline significantly in the near future due to ocean acidification. In this study we provide a global estimate of the decline in calcification of coral reefs as a result of increase in sea surface temperature and partial pressure of CO2. This estimate, unlike previously reported estimates, is based on an empirical rate law developed from field observations for gross community calcification as a function of aragonite degree of saturation (Ωarag), sea surface temperature and live coral cover. Calcification rates were calculated for more than 9,000 reef locations using model values of Ωarag and sea surface temperature at different levels of atmospheric CO2. The maps we produced show that by the time atmospheric partial pressure of CO2 will reach 560 ppm all coral reefs will cease to grow and start to dissolve.
Daytime low‐altitude quasi‐periodic echoes at Gadanki: Understanding of their generation mechanism in the light of their Doppler characteristics
Authors: Patra A. K. , Venkateswara Rao N. , Choudhary R. K.
Published: March 2009

In this paper, we investigate the genesis of low‐altitude quasi‐periodic (LQP) E region echoes observed during daytime by the Gadanki radar. We show that such echoes reflect much wider Doppler spectra compared to that of typical daytime low‐altitude E‐region echoes. Further, the Doppler spread resembles that of meteor induced spread echoes. Considering that the meteor spread echoes are generated by the gradient drift instability on the sharp density gradient associated with the plasma trail, we invoke plasma density gradient and a similar physical process to account for the LQP spread echoes. Taking into account all the pertinent issues related to the formation of plasma density structures in the collision dominated lower E region, we surmise that the required plasma density structures are generated by a weakly driven Kelvin‐Helmholtz instability. These structures get polarized by the background electric field or neutral wind and become gradient drift unstable manifesting LQP echoes.
Tracking eruptive phenomena by infrasound: May 13, 2008 eruption at Mt. Etna
Authors: Cannata A. , Montalto P. , Privitera E. , Russo G. , Gresta S.
Published: March 2009

Active volcanoes produce inaudible infrasound due to the coupling between surface magmatic processes and the atmosphere. Monitoring techniques based on infrasound measurements have been proved capable of producing information during volcanic crises. We report observations collected from an infrasound network on Mt. Etna which enabled us to detect and locate a new summit eruption on May 13, 2008 when poor weather inhibited direct observations. Three families of signals were identified that allowed the evolution of the eruption to be accurately tracked in real‐time. Each family is representative of a different active vent, producing different waveforms due to their varying geometry. Several competitive models have been developed to explain the source mechanisms of the infrasonic events, but according to our studies we demonstrate that two source models coexist at Mt. Etna during the investigated period. Such a monitoring system represents a breakthrough in the ability to monitor and understand volcanic phenomena.
Anomalous ocean load tide signal observed in lake‐level variations in Tierra del Fuego
Authors: Richter A. , Hormaechea J. L. , Dietrich R. , Perdomo R. , Fritsche M. , Del Cogliano D. , Liebsch G. , Mendoza L.
Published: March 2009

We demonstrate the application of a 100 km long lake as a sensor for studying the tidal effects on Tierra del Fuego main island. The lake‐level variations observed in Lago Fagnano reflect both the direct response to the tidal potential and the indirect effect of the ocean tidal loading. Modeling both contributions explains the observed tidal signal in the lake to about 70%. Underestimated model load tide amplitudes are found to be probably responsible for the remaining difference. We interpret this discrepancy as a hint for regional elastic lithosphere properties differing substantially from those represented by currently available global models.
Identification and spatiotemporal organization of aftershocks
Authors: Bottiglieri M. , Lippiello E. , Godano C. , de Arcangelis L.
Published: March 2009

We propose a fast method able to discriminate between Poissonian independent earthquakes and aftershocks. The method is based on the evaluation of the variability coefficient, defined as the ratio between the standard deviation and the average value of the interoccurrence time between two successive earthquakes. We apply this technique to the California and a properly constructed synthetic catalogue in order to estimate the level of background seismicity and identify seismic sequences. We then investigate the spatiotemporal organization of aftershocks focusing on the distributions of interevent times and interevent distances between two successive events. We find evidence for the existence of a characteristic spatial length scale, related to the size of the aftershock zone, whereas no typical timescale is detected.
Radiosonde‐based trends in precipitable water over the Northern Hemisphere: An update
Authors: Durre Imke , Williams Claude N. , Yin Xungang , Vose Russell S.
Published: March 2009

In an effort to update previous analyses of long‐term changes in column‐integrated water vapor, we have analyzed trends in surface‐to‐500‐hPa precipitable water (PW) calculated from radiosonde measurements of dew point depression, temperature, and pressure at approximately 300 stations in the Northern Hemisphere for the period 1973–2006. Inhomogeneities were addressed by applying a homogenization algorithm that adjusts for both documented and undocumented change points. The trends of the adjusted PW time series are predominantly upward, with a statistically significant trend of 0.45 mm decade−1 for the Northern Hemisphere land areas included in the analysis. Particularly significant increases are found in all seasons over the islands of the western tropical Pacific, and trends are also positive and statistically significant for the year as a whole and in at least one season in Japan and the United States. These results indicate that the widespread increases in tropospheric water vapor, which earlier studies had reported and shown to be physically consistent with concurrent increases in temperature and changes in moisture transport, have continued in recent years.
Inter- and intra-habitat bacterial diversity associated with cold-water corals
Authors: Schöttner Sandra , Hoffmann Friederike , Wild Christian , Rapp Hans Tore , Boetius Antje , Ramette Alban
Published: March 2009

The discovery of large ecosystems of cold-water corals (CWC), stretching along continental margins in depths of hundreds to thousands of meters, has raised many questions regarding their ecology, biodiversity and relevance as deep-sea hard-ground habitat. This study represents the first investigation that explicitly targets bacterial diversity from distinct microbial habitats associated with the cosmopolitan reef-building coral Lophelia pertusa, and also compares natural (fjord) and controlled (aquarium) conditions. Coral skeleton surface, coral mucus, ambient seawater and reef sediments clearly showed habitat-specific differences in community structure and operational taxonomic unit (OTU) number. Especially in the natural environment, bacterial communities associated with coral-generated habitats were significantly more diverse than those present in the surrounding, non-coral habitats, or those in artificial coral living conditions (fjord vs aquarium). These findings strongly indicate characteristic coral–microbe associations and, furthermore, suggest that the variety of coral-generated habitats within reef systems promotes microbial diversity in the deep ocean.
Despite strong seasonal responses, soil microbial consortia are more resilient to long-term changes in rainfall than overlying grassland
Authors: Cruz-Martínez Karelyn , Suttle K Blake , Brodie Eoin L , Power Mary E , Andersen Gary L , Banfield Jillian F
Published: March 2009

Climate change impacts on soil microbial communities could alter the structure of terrestrial ecosystems and biogeochemical cycles of the Earth. We used 16S rRNA gene microarrays to evaluate changes in the composition of grassland soil microbial communities under rainfall amendments simulating alternative climate change scenarios, and to compare these to responses of overlying plants and invertebrates. Following 5 years of rainfall manipulation, soil bacteria and archaea in plots where natural rain was supplemented differed little from ambient controls, despite profound treatment-related changes in the overlying grassland. During the sixth and seventh year, seasonal differences in bacterial and archaeal assemblages emerged among treatments, but only when watering exacerbated or alleviated periods of particularly aberrant conditions in the ambient climate. In contrast to effects on plants and invertebrates, effects on bacteria and archaea did not compound across seasons or years, indicating that soil microbial communities may be more robust than associated aboveground macroorganisms to certain alterations in climate.
Presence of Aspergillus sydowii, a pathogen of gorgonian sea fans in the marine sponge Spongia obscura
Authors: Ein-Gil Neta , Ilan Micha , Carmeli Shmuel , Smith Garriet W , Pawlik Joseph R , Yarden Oded
Published: March 2009

The fungus Aspergillus sydowii is the causative agent of epidemics that affect gorgonian corals (sea fans) and has significantly affected their populations in the Caribbean Sea. We have isolated a strain of A. sydowii from healthy marine sponges (Spongia obscura) collected in Bahamian inshore waters. After its identification on the basis of morphology, molecular markers and chemical profiling followed by pathogenicity tests, we found this strain to be highly similar to a strain isolated from diseased coral, and have shown the capacity of this fungus to persist in sponge environment. Our findings suggest that sponges have the possibility of being reservoirs of a potential marine pathogen.
Obesity and Television Watching in Preschoolers in Greece: The GENESIS Study
Authors: Manios Yannis , Kourlaba Georgia , Kondaki Katerina , Grammatikaki Evangelia , Anastasiadou Anastasia , Roma‐Giannikou Eleytheria
Published: March 2009

The aim of the current work was to evaluate the effect of preschoolers' television (TV) watching time on the prevalence of obesity even after controlling for their total energy intake and their physical activity status. A representative sample of 2,374 Greek children aged 1–5 years was examined (“Growth, Exercise and Nutrition Epidemiological Study in preSchoolers”, GENESIS study). Children's TV watching time on a usual weekday and at a usual weekend was recorded. The overall mean of children's TV viewing time was 1.32 h/day. The majority of participants (74.0%) spent <2 h/day watching TV whereas only 3.1% spent >4 h/day in front of a TV set. Overall, 65.2% of participants were normal weight, 17.2% were overweight, and the rest 17.6% were obese. The prevalence of obesity was significantly higher among those with TV viewing time ≥2 h/day (21.7%) compared to those watching TV <2 h/day (16.1%, P = 0.003). TV viewing time remained significantly associated with the likelihood of being obese even after controlling for potential confounders (i.e., socio demographic and other characteristics and physical activity status) only among children aged 3–5 years. However, further adjusting for children's total energy intake revealed that the association between the TV viewing time and the probability of being obese was no longer statistically significant. On the other hand, physical activity status continued to be an independent factor of being obese. The current findings support the hypothesis that the effect of TV viewing time on childhood obesity is independent of physical activity status and may be attributed to the increased total energy intake during TV watching.
Differential Responses of Orexigenic Neuropeptides to Fasting in Offspring of Obese Mothers
Authors: Chen Hui , Morris Margaret J.
Published: March 2009

Maternal obesity due to long‐term high‐fat diet (HFD) consumption leads to faster growth in offspring during suckling, and increased adiposity at 20 days of age. Decreased expression of the orexigenic neuropeptide Y (NPY) and increased anorexigenic proopiomelanocortin (POMC) mRNA expression were observed in the fed state. However, hunger is the major drive to eat and hypothalamic appetite regulators change in response to meals. Therefore, it is important to compare both satiated and fasting states. Female Sprague–Dawley rats (8 weeks old) were fed a cafeteria‐style HFD (15.33 kJ/g) or chow for 5 weeks before mating, with the same diet continuing throughout gestation and lactation. At postnatal day 20, male pups were killed either after overnight fasting or in the fed state. Pups from obese dams were hyperphagic during both pre‐ and postweaning periods. Pups from obese dams had higher hypothalamic mRNA expression of POMC and NPY Y1 receptor, but lower hypothalamic melanocortin‐4 receptor (MC4R) and its downstream target single‐minded gene 1 (Sim1), in the fed state. Overnight fasting reduced circulating glucose, insulin, and leptin and increased hypothalamic NPY Y1 receptor mRNA in pups from both lean and obese dams. Hypothalamic NPY and agouti‐related protein (AgRP) were only increased by fasting in pups from obese dams; reductions in MC4R and Sim1 were only seen in pups from lean dams. At weaning, the suppressed orexigenic signals in offspring from obese dams were normalized after overnight fasting, although anorexigenic signaling appeared impaired in these animals. This may contribute to their hyperphagia and faster growth.
Cardiorespiratory Fitness and the Risk of Overweight in Youth: The Healthy Hearts Longitudinal Study of Cardiometabolic Health
Authors: McGavock Jonathan M. , Torrance Brian D. , McGuire K. Ashlee , Wozny Paul D. , Lewanczuk Richard Z.
Published: March 2009

The primary objective of this longitudinal study was to determine the association between cardiorespiratory fitness and the risk of overweight status in youth. To accomplish this aim we analyzed data from annual school‐based surveys of cardiorespiratory fitness and anthropometry conducted between 2004 and 2006. The first analysis was performed on a cohort of 902 youth aged 6–15 years followed for 12 months to assess the association between cardiorespiratory fitness levels determined from a graded maximal field test and the risk of becoming overweight. The second analysis was conducted on a cohort of 222 youth followed for 2 years to assess the continuous association between annual changes fitness and weight gain. Children with low cardiorespiratory fitness were characterized by higher waist circumference and disproportionate weight gain over the 12‐month follow‐up period (P < 0.05). Within the entire cohort, the 12‐month risk of overweight classification was 3.5‐fold (95% confidence = 2.0–6.0, P < 0.001) higher in youth with low cardiorespiratory fitness, relative to fit peers. A time series mixed effects regression model revealed that reductions in cardiorespiratory fitness were significantly and independently associated with increasing BMI (r = −0.18, P < 0.05) in youth. Accordingly, low cardiorespiratory fitness and reductions in fitness over time are significantly associated with weight gain and the risk of overweight in children 6–15 years old. An assessment of cardiorespiratory fitness using a common field test may prove useful for the identification of youth at risk of overweight and serve as a potential target for obesity prevention.
“Dead layer” characteristics based on a correlation of the ferroelectric polarization under relevant boundary conditions in a parallel plate capacitor
Authors: Vendik Orest G. , Zubko Svetlana P. , Medvedeva Natalia Yu.
Published: March 2009

Two approaches to modeling the size effect in a ferroelectric parallel plate capacitor are considered: (i) spatial correlation of polarization under the influence of boundary conditions on electrodes of the capacitor and (ii) “dead layer” model. For the description of the spatial correlation, the Landau–Ginzburg–Devonshire equation is used. The characteristic feature of the spatial correlation approach is a correlation parameter α. The dead layer model was first mentioned in 1959 as “a series capacitor model.” Phenomenological characteristics of the dead layer are the thickness hd and dielectric constant εd of the layer. The dead layer model could be useful for practical use as a basis of simulations. Nevertheless one should take into account that the description of the size effect and definitions of the dead layer parameters are based on the correlation of the dynamic ferroelectric polarization in conjunction with the relevant boundary conditions. The estimating of α can be found by processing the experimental data obtained from inelastic neutron scattering. The size effect will be considered without an assumption of any charge transfer and formation of the depletion layers.
Effect of boron on the field-induced magnetic anisotropy in Fe-based soft magnetic nanostructures
Authors: Ito N. , Suzuki K. , Garitaonandia J. S. , Cashion J. D.
Published: March 2009

The field-induced magnetic anisotropy (Ku) and the hyperfine interactions in nanocrystalline Fe94−xNb6Bx (x=10, 12, and 14) alloys have been investigated with particular attention paid to the origin of Ku in the bcc-Fe/amorphous soft magnetic nanostructures. The Fe57 Mössbauer spectra from the Fe–Nb–B alloys suggest that the solute content in the residual amorphous phase remains unchanged while the volume fraction of the residual amorphous phase (Vam), increases linearly with B content. This indicates that Vam is governed by the lever rule over the partial equilibrium between the primary bcc-Fe and the residual amorphous phases. Both the saturation magnetization (Js) and Ku were confirmed to vary linearly with Vam and they are well described by taking into account the volume-weighted average of Js=2.1T and Ku=127J∕m3 for the bcc-Fe nanocrystallites and Js=1.0T and Ku=76J∕m3 for the residual amorphous matrix. The relatively large Ku value estimated for the bcc nanocrystallites may be attributed to a possible local tetragonal distortion induced by the interstitial B atoms.
The search for quantum critical scaling in a classical system
Authors: Lamsal Jagat , Gaddy John , Petrovic Marcus , Montfrooij Wouter , Vojta Thomas
Published: March 2009

Order-disorder phase transitions in magnetic metals that occur at zero temperature have been studied in great detail. Theorists have advanced scenarios for these quantum critical systems in which the unusual response can be seen to evolve from a competition between ordering and disordering tendencies, driven by quantum fluctuations. Unfortunately, there is a potential disconnect between the real systems that are being studied experimentally, and the idealized systems that theoretical scenarios are based upon. Here we discuss how disorder introduces a change in morphology from a three-dimensional system to a collection of magnetic clusters, and we present neutron scattering data on a classical system, Li[Mn1.96Li0.04]O4, that show how magnetic clusters by themselves can lead to scaling laws that mimic those observed in quantum critical systems.
Dzyaloshinski–Moriya micromagnetics of magnetic surface alloys
Authors: Skomski R. , Honolka J. , Bornemann S. , Ebert H. , Enders A.
Published: March 2009

The magnetism of magnetic surface alloys such as Fe–Pt on Pt(997) has been investigated by micromagnetic model calculations. A unique feature of some of these systems is that interatomic exchange, magnetocrystalline anisotropy, and Dzyaloshinski–Moriya (DM) interactions are all of comparable magnitude, of the order of 0.5 meV. This leads to an intriguing nanoscale interplay between ordinary magnetization states and noncollinear spin structures. We identify two cases where the latter dominate. First, for sufficiently strong DM interaction, the zero-field spin structures change from uniform to a canted state with an incommensurate wave vector. Second, a similar transition occurs for weak DM interaction when the reverse external field approaches the nucleation field.
Planar patterned media fabricated by ion irradiation into CrPt3 ordered alloy films
Authors: Kato T. , Iwata S. , Yamauchi Y. , Tsunashima S. , Matsumoto K. , Morikawa T. , Ozaki K.
Published: March 2009

Planar patterned media using CrPt3 ordered alloy films were fabricated by Ar+ or Kr+ ion irradiation through nanoimprinted or electron beam lithography made masks. CrPt3 ordered alloy film on fused quartz substrate exhibits a large perpendicular anisotropy of 5×106 erg/cc and a large coercivity of 12 kOe, and we found that its magnetic order (magnetization) was completely suppressed by a quite low Ar+ or Kr+ ion dose of about 1–2×1014 ions/cm2. Magnetic force microscope image of the ion-beam patterned CrPt3 with a bit size of 90×90 nm showed clear magnetic contrast in nonirradiated regions, while no magnetic contrast in irradiated regions. The read-back waveform taken from an ion-beam patterned CrPt3 disk with 600 nm patterning pitch showed sharp signal transition between irradiated and nonirradiated regions, which indicates the possibility of high-density planar patterned media using CrPt3 ordered alloy.
Calculated electronic and magnetic structure of rutile phase V1−xCrxO2
Authors: Williams M. E. , Butler W. H. , Mewes C. K. , Sims H. , Chshiev M. , Sarker S. K.
Published: March 2009

Recent experiments indicate that films of V1−xCrxO2 may be obtained which retain the tetragonal rutile phase to low temperature. In order to better understand this system we have calculated its electronic structure using density functional theory in the generalized gradient approximation and density functional theory with empirical on-site Coulomb correlations (LDA+U). Within these approximations we find that the ground state of rutile phase V1−xCrxO2 is quite simple. Both V and Cr are in the +4 state, implying that the V and Cr ions have moments of 1μB and 2μB, respectively. Similar to CrO2, V1−xCrxO2 is predicted to be ferromagnetic and half-metallic. Our results appear to be consistent with the experimental observations that VO2 is paramagnetic and metallic for temperatures above 340 K where it is stable. It is not clear, however, that these results are completely consistent with recent experimental observations of ferromagnetism at low temperature in V1−xCrxO2 for x=0.1 and x=0.2.
Synthesis of magnetic porous hollow silica nanotubes for drug delivery
Authors: Ma H. , Tarr J. , DeCoster M. A. , McNamara J. , Caruntu D. , Chen J. F. , O’Connor C. J. , Zhou W. L.
Published: March 2009

In this paper, we report a synthesis of magnetic porous hollow silica nanotubes (MPHSNTs) using sol-gel method. The MPHSNTs were fabricated by coating Fe3O4 nanoparticles and silica on surfactant hexadecyltrimethylammonium bromide (CTAB) modified CaCO3 nanoneedles surface under alkaline condition. CaCO3 nanoneedles and surfactant CTAB are introduced as nanotemplates to form the hollow and porous structures, respectively. After removing CTAB by calcination and etching CaCO3 nanoneedles away in diluted acetic acid, magnetic porous hollow silica nanotubes with Fe3O4 nanoparticles embedded in the silica shell were achieved. The products were characterized by scanning electron microscopy, transmission electron microscopy, and N2 adsorption-desorption isotherms. Superconducting quantum interference device measurement shows that the nanotubes exhibit superparamagnetism property at room temperature and ferromagnetism below the blocking temperature. Toxicity test was also performed for the magnetic nanocarriers, showing good bio-compatibility. Magnetic porous hollow silica nanotubes with advantages of high surface area, good bio-compatibility, and superparamagnetism are one of the novel drug nanocarriers for nanomedicine applications.
Observation of superspin glass state in magnetically textured ferrofluid (γ-Fe2O3)
Authors: Nakamae S. , Tahri Y. , Thibierge C. , L’Hôte D. , Vincent E. , Dupuis V. , Dubois E. , Perzynski R.
Published: March 2009

Magnetic properties in a magnetically textured ferrofluid made out of interacting maghemite (γ-Fe2O3) nanoparticles suspended in glycerin have been investigated. Despite the loss of uniform distribution of anisotropy axes, a superspin glass state exists at low temperature in a concentrated textured ferrofluid as in the case of its nontextured counterpart. The onset of superspin glass state was verified from the sample’s ac susceptibility. The influence of the anisotropy axis orientation on the aging behavior in the glassy states is also discussed.
Magnetic and structural properties of Co0.8MnxFe2.2−xO4 (x=0.2, 0.4, 0.6, 0.8) polycrystalline powders synthesized by sol-gel process
Authors: Lu Z. M. , Li Z. W. , Shen J. , Meng F. B. , Liu H. Y. , Li Y. X. , Li C. Y.
Published: March 2009

Co 0.8 Mn x Fe 2.2 − x O 4 (x=0.2, 0.4, 0.6, and 0.8) powders were prepared by a sol-gel process and annealed at different temperatures (Ta=600, 800, 1000, and 1200 °C). X-ray diffractometer results reveal that all the samples are inverse-type spinel with cubic structure. The magnetic properties were measured by vibrating sample magnetometer and the results indicate that the saturated magnetization (Ms) and coercivity (Hc) decrease with increasing Mn content x. The decrease in Ms is related to the magnetic moment of Mn3+ is lower than that of Fe3+. The decrease in Hc is ascribed to the content decrease in Co2+ on B sites. Increasing grain sizes at higher annealing temperature (Ta) also have an intensive influence on Hc.
Magnetic anisotropy of single Co atom on CuN surface
Authors: Shick A. B. , Máca F. , Lichtenstein A. I.
Published: March 2009

The magnetic anisotropy energy for a single Co atom on CuN/Cu(001) surface is investigated making use of the first-principles relativistic local spin density approximation (LSDA) calculations and the torque method. A single-ion character of the magnetic anisotropy is revealed, which originates mainly from the local magnetic moment of the Co atom. The effect of the orbital polarization beyond that given by the LSDA is studied making use of the different flavors of the LDA+U method. It is shown that the LDA+U induced orbital polarization affects the orbital component of the magnetic moment for different directions of the Co-atom magnetization and can modify substantially the magnetic anisotropy energy. Comparison with the available experimental data is discussed.
Anisotropy dispersion in the exchange-biased pinned layer of a spin valve prepared by 550 eV hydrogen-ion irradiation
Authors: Lee Soogil , Han Yoonsung , Kim Sanghoon , Hong Jongill
Published: March 2009

By investigating angular dependence of resistance and applying the Boltzmann distribution to the anisotropy dispersion of the magnetization in an exchange-biased pinned layer, we quantized the intrinsic anisotropy dispersion σγ of spin valves. The σγ was estimated to be 0.412° for the as-deposited spin valve and 0.183° for the ion-irradiated spin valve. This indicates that the dispersion indeed narrowed when the spin valve was field-annealed or irradiated by 550 eV hydrogen ions under a magnetic field, which is consistent with our previous attribution to the significant improvement in both exchange anisotropy and giant magnetoresistance of spin valves thus treated. Our methodology can be applied for other spin devices characterized by angular dependence of resistance to determine useful device properties such as the intrinsic anisotropy dispersion and the exchange bias of the exchange-biased reference layer.
Enhanced tunneling magnetoresistance of Fe3O4 in a Fe3O4-hexabromobenzene (C6Br6) composite system
Authors: Wang Wendong , He Jibao , Tang Jinke
Published: March 2009

Magnetotransport of Fe3O4-hexabromobenzene (C6Br6) composite has been studied. Powders of C6Br6 and Fe2O3 nanoparticles were mixed together. They were annealed in hydrogen flow. There was a phase transformation from Fe2O3 to Fe3O4 after annealing. Giant negative magnetoresistance (MR) was observed at room temperature and the MR ratio is about 13.4% in an applied field of 5 T. The maximum MR ratio is 21.5% at 130 K. The temperature dependence of the resistivity exhibits characteristics of intergranular tunneling in the samples. The enhancement of the MR ratio is attributed to the fact that the C6Br6 can act as barrier material and, more importantly, can prevent the oxidation of the surface of Fe3O4, which is believed to alter the half-metallic state at the surface.
Field induced resistivity anisotropy in SrRuO3 films
Authors: Shperber Yishai , Genish Isaschar , Reiner James W. , Klein Lior
Published: March 2009

SrRuO 3 is an itinerant ferromagnet with orthorhombic structure and uniaxial magnetocrystalline anisotropy—features expected to yield resistivity anisotropy. Here we explore changes in the resistivity anisotropy of epitaxial SrRuO3 films due to induced magnetization in the paramagnetic state by using the planar Hall effect. We find that the effect of the induced magnetization on the in-plane anisotropy is strongly angular dependent, and we provide a full description of this behavior at 160 K for induced magnetization in the (001) plane.
Magnetic entropy change of V substituted Ni–Mn–Ga Heusler alloy
Authors: Min S. G. , Zhang Y. D. , Malkinski L. , Yu S. C. , Lee K. W. , Kim Y. C.
Published: March 2009

The magnetization behaviors have been analyzed for Ni54Mn21−xVxGa25 (x=0,2,4) alloys which were prepared by conventional arc melting method in argon atmosphere. The Curie temperature TC was found to be 325, 300, and 265 K and the austenitic transition temperature TA on heating was found to be 315, 217, and 124 K for x=0, 2, and 4, respectively. The magnetic characteristics were performed with a Quantum Design superconducting quantum interference device magnetometer in the field of up to 20 kOe. A large magnetic entropy change ΔSM, which is calculated from H versus M curves associated with the ferromagnetic-paramagnetic transitions, has been observed. The maximum ΔSM for an applied field of 2.0 T is 2.49, 1.92, and 1.81 J/kg K for x=0, 2, and 4, respectively.
Outer shell structure in nearly zero magnetostrictive amorphous microwires
Authors: Óvári T.-A. , Chiriac H. , Lostun Mihaela
Published: March 2009

Nearly zero magnetostrictive microwires have been proven to be very versatile, due to their extremely soft magnetic properties, the changes in their magnetization mechanism with dimensions, and the appearance of sensitive application-related effects, such as the large Barkhausen and the giant magnetoimpedance effects. Their sensitive magnetoimpedance response originates in the specific domain structure, composed of an inner core and an outer shell (OS), since the OS with a circumferential easy axis is the main region involved in the magnetoimpedance effect. The circumferential OS is believed to display a bamboolike structure with consecutive rings circumferentially magnetized in opposite directions. However, earlier theoretical studies predicted a uniformly magnetized OS as being energetically favored. This paper aims to clarify this contradiction. The variation of the magnetostatic energy from the bamboo domain to the uniformly magnetized state has been calculated and it has been found to be null. Therefore, a uniformly magnetized OS has lower energy due to the absence of domain walls. Calculation results are supported by magneto-optical Kerr effect surface domain images and surface hysteresis loops. For large values of the metallic nucleus diameter, as well as for microwires with the glass coating removed, the OS vanishes, being replaced with a surface region with helical magnetization, which expands toward the microwire surface.
Magneto-optical studies of Cd1−x−yMnxCoyTe
Authors: Shen S. , Liu X. , Furdyna J. K. , Dobrowolska M. , Hwang Y. H. , Um Y. H.
Published: March 2009

We have investigated the optical absorption and magneto-optical properties of quaternary Cd1-x−yMnxCoyTe crystals (x=0.37, 0≤y≤0.009) grown by the vertical Bridgman method. The presence of Co showed a significant enhancement of magneto-optical effects as compared to ternary Cd0.63Mn0.37Te system with the same Mn content. Four features were observed in magnetic circular dichroism (MCD) spectra of these alloys, located near 1.37, 1.45, 1.82, and 2.13 eV. We present detailed temperature dependences of the position and intensity of these MCD features, and we discuss their possible origins.