bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in dung beetle communities along a gradient of tropical forest disturbance in South-East Asia
Authors: Lee Janice Ser Huay , Lee Ian Qian Wei , Lim Susan Lee-Hong , Huijbregts Johannes , Sodhi Navjot S.
Published: October 2009

With increasing conversion of South-East Asian forests to human-dominated landscapes, dramatic changes in biodiversity are likely to have ramifications on ecosystem processes (Sodhi & Brook 2006). Dung beetles (Coleoptera: Scarabaeidae) have been used to investigate how biodiversity changes affect ecosystem functions (Larsenet al. 2005, Sladeet al. 2007). Dung beetles provide important ecosystem services such as dung removal and secondary seed dispersal (Nicholset al. 2008) and have been shown to be reliable indicators of tropical forest disturbance (Gardneret al. 2008, Klein 1989). Here, we determine the effects of forest disturbance on the species richness of dung beetles and ecosystem functions they perform in Peninsular Malaysia and Singapore. As far as we know, there has been no known study published on dung beetle ecology on the Malay Peninsula. In this study, we test the hypothesis that old-growth forests contain dung beetle communities of higher species richness, abundance, biomass and larger body size. Previous studies have shown that changes in dung beetle communities have the potential to disrupt ecosystem services in natural habitats (Larsenet al. 2005, Mittal 1993). We also investigate whether dung removal is affected by forest disturbance and test the hypothesis that dung removal is reduced in more disturbed forests compared with less-disturbed forests.
Phylogenetic constraints on fine-scale patterns of habitat use by eight primate species in eastern Ecuador
Authors: Sheth Seema Nayan , Loiselle Bette A. , Blake John G.
Published: October 2009

Lowland forests of western Amazonia contain the most species-rich primate communities in the Neotropics, which begs the question of what mechanisms operate to promote species coexistence. This study examines habitat occupancy and its relationship to phylogeny in a primate community in Amazonian Ecuador. First, as potential factors that shape community structure, we determined whether (1) mean height in the forest canopy differed among species; (2) within each species, habitat occupancy was disproportional to habitat availability; and (3) species diverged in habitat occupancy. We then tested hypotheses regarding ecological distance and its relationship to phylogenetic distance among species pairs within this community. We tested these hypotheses primarily with data derived from 15 censuses of primate species on two 100-ha plots in eastern Ecuador. In these censuses, we observed eight primate species over nearly 200 encounters. We observed larger species at greater heights in the forest canopy than smaller ones. Although they occupied habitat types at frequencies proportionate to their availability in the study area, species diverged in habitat occupancy. Although a clear relationship was not observed between phylogenetic and ecological distances among species pairs, this study suggests that ecological differences among the species in this community facilitate their coexistence.
Reproductive variation corresponding to breeding season length in three tropical frog species
Authors: Sheridan Jennifer A.
Published: October 2009

Several South-East Asian anuran species can breed year-round near the equator (due to abundant rainfall in all months in Singapore, for example) but are limited to a 6-mo breeding season in other areas (including central Thailand). In order to investigate the extent to which such differences in breeding season length are associated with differences in reproductive measures such as clutch size, reproduction of three common species,Polypedates leucomystax,Microhyla heymonsiandHylarana erythraea, was compared in Singapore and Thailand over a 2-y period. All three species produce nearly twice as many eggs per clutch in seasonal environments compared with aseasonal environments, although annual fecundity may be similar in both environments. InPolypedates leucomystax, increased clutch size and volume are associated with larger female size, but in the other two species female size is unchanged with respect to latitude. InH. erythraea, the increased clutch size in Thailand was observed early in the breeding season; later clutches were not significantly different between sites. Collectively, these data suggest that these widespread species have adapted to shortened breeding season length by increasing clutch size.
Population dynamics of the black-cheeked gnateater (Conopophaga melanops, Conopophagidae) in southern Brazil
Authors: de Lima André Magnani Xavier , Roper James Joseph
Published: October 2009

Population structure and dynamics of the black-cheeked gnateater (Conopophaga melanops) were studied at Salto Morato Nature Reserve, in Paraná, southern Brazil, from October 2006 to September 2007. Territory size and population density, breeding season (timing and length), reproductive success and annual survival rates were estimated from sightings of 18 marked adult birds and the success of 18 nesting attempts. The black-cheeked gnateater is socially monogamous and territorial, with a breeding-season length of approximately 3 mo beginning in early October. Predation caused most nest failures, nest survival was 0.96 d−1and apparent annual nesting success was 22%, resulting in annual productivity of 0.36 individuals per adult. Apparent adult annual survival was ~0.44 y−1. Seventy-five per cent of fledglings survived at least 2 mo after fledging. Two methods of estimating population growth rate suggest very different rates: r = −0.04 (~ stable), or λ varies between 0.475–0.616 (declining). Yet, low apparent adult survival suggests that territories are not permanent, perhaps abandoned after nest failure. We find that by estimating population growth, even in short-term studies, testable hypotheses can be generated that will allow better understanding of population dynamics.
For the Reconciliation and Unity of the Anglican Communion: A Japanese Perspective Post Lambeth 2008
Authors: Nishihara Renta
Published: October 2009

How the Nippon Sei Ko Kai (NSKK), the Anglican Church in Japan, can respond to the discussion at the Lambeth Conference 2008? The NSKK celebrates its 150th anniversary of its missionary, beginning this year (2009). The NSKK is a diverse church where high and low, broad and liberal co-existed from the beginning, which in a way represented the epitome of the Anglican Communion. The NSKK officially expressed its position regarding the ‘Anglican Covenant’, at an early stage when the Windsor Report 2004 was issued; owning a binding force as in ‘Anglican Covenant’ does not match the spirit of Anglicanism which values the unity of diversity and autonomy of each province and diocese, and ‘Chicago-Lambeth Quadrilateral’ is enough for a guideline for the unity of Anglican Identity. The NSKK is a church, which values the principles of the consensus fidelium in the Anglicanism and focuses on the Anglican Consultative Council as the center.
‘That They May All Be One’: Anglican Communion in Prayer
Authors: Wolf Geralyn
Published: October 2009

The bishops of the Anglican Communion gathered at the Lambeth Conference, 2008, at a time when some constituent provinces and dioceses had already crossed the threshold of discontent, deciding not to attend the gathering, and when further division loomed ahead. This article examines the challenges of living into a generous diversity while holding fast to the historic Christian faith. The author reveals a cautious hope rooted in Jesus’ prayer for unity and the mystery of the Pascha, Christ’s death and resurrection. As the Communion drifts into greater autonomy, she calls for a disposition of reconciliation, paving the way for reunification in the future.
Mirror instability and L‐mode electromagnetic ion cyclotron instability: Competition in the Earth's magnetosheath
Authors: Shoji Masafumi , Omura Yoshiharu , Tsurutani Bruce T. , Verkhoglyadova Olga P. , Lembege Bertrand
Published: October 2009

We performed both two‐ and three‐dimensional hybrid simulations of the competing processes between the L‐mode electromagnetic ion cyclotron (EMIC) and mirror instabilities, assuming anisotropic energetic ions with T⊥/T∥ = 4.0. In the two‐dimensional model, the energy of the EMIC waves is higher at the linear growth phase because its growth rate is larger than that of the mirror mode. In the three‐dimensional model, however, the energy of the mirror mode waves is larger than that of the EMIC waves for all times because the wave number spectra of mirror mode waves form torus‐like structures. We also theoretically derived a necessary condition for the dominance of the mirror instability. As the mirror mode waves relax the temperature anisotropy effectively, the linear growth rates of the EMIC waves become smaller before saturation. The EMIC waves cause heating of protons trapped by the nonlinear potentials due to coexistence of forward and backward propagating waves and inverse cascading. They terminate the linear growth of EMIC waves. Because of these parallel heatings, the temperature anisotropy decreases to the threshold of the mirror instability and thus the mirror mode wave saturates. At the nonlinear stage, coalescence of the mirror mode waves takes place in both models. The quick dissipation of the EMIC waves occurs due to the heating by the nonlinear processes. On the other hand, the coalescence is a much slower process than the nonlinear processes of EMIC waves, and thus the mirror mode waves remain in the three‐dimensional model.
Positive Indian Ocean Dipole events precondition southeast Australia bushfires
Authors: Cai W. , Cowan T. , Raupach M.
Published: October 2009

The devastating “Black Saturday” bushfire inferno in the southeast Australian state of Victoria in early February 2009 and the “Ash Wednesday” bushfires in February 1983 were both preceded by a positive Indian Ocean Dipole (pIOD) event. Is there a systematic pIOD linkage beyond these two natural disasters? We show that out of 21 significant bushfires seasons since 1950, 11 were preceded by a pIOD. During Victoria's wet season, particularly spring, a pIOD contributes to lower rainfall and higher temperatures exacerbating the dry conditions and increasing the fuel load leading into summer. Consequently, pIODs are effective in preconditioning Victoria for bushfires, more so than El Niño events, as seen in the impact on soil moisture on interannual time scales and in multi‐decadal changes since the 1950s. Given that the recent increase in pIOD occurrences is consistent with what is expected from global warming, an increased bushfire risk in the future is likely across southeast Australia.
Contemporaneous deposition of phyllosilicates and sulfates: Using Australian acidic saline lake deposits to describe geochemical variability on Mars
Authors: Baldridge A. M. , Hook S. J. , Crowley J. K. , Marion G. M. , Kargel J. S. , Michalski J. L. , Thomson B. J. , de Souza Filho C. R. , Bridges N. T. , Brown A. J.
Published: October 2009

Studies of the origin of the Martian sulfate and phyllosilicate deposits have led to the hypothesis that there was a marked, global‐scale change in the Mars environment from circum‐neutral pH aqueous alteration in the Noachian to an acidic evaporitic system in the late Noachian to Hesperian. However, terrestrial studies suggest that two different geochemical systems need not be invoked to explain such geochemical variation. Western Australian acidic playa lakes have large pH differences separated vertically and laterally by only a few tens of meters, demonstrating how highly variable chemistries can coexist over short distances in natural environments. We suggest diverse and variable Martian aqueous environments where the coetaneous formation of phyllosilicates and sulfates at the Australian sites are analogs for regions where phyllosilicates and sulfates coexist on Mars. In these systems, Fe and alkali earth phyllosilicates represent deep facies associated with upwelling neutral to alkaline groundwater, whereas aluminous phyllosilicates and sulfates represent near‐surface evaporitic facies formed from more acidic brines.
An operational method for shock arrival time prediction by one‐dimensional CESE‐HD solar wind model
Authors: Feng X. S. , Zhang Y. , Yang L. P. , Wu S. T. , Dryer M.
Published: October 2009

With the purpose of operational real‐time forecasting for arrival times of flare/coronal mass ejection associated shocks in the vicinity of the Earth, a one‐dimensional hydrodynamic (HD) shock propagation model is established by a novel numerical scheme, the space‐time conservation element and solution element (CESE) method. The required observational data inputs to this new one‐dimensional CESE‐HD model are the low coronal radio Type II drift speed, the duration estimation, and the background solar wind speed for a solar eruptive event. Applying this model to 137 solar events during the period of February 1997 to August 2002, it is found that our model could be practically equivalent to the STOA, ISPM, HAFv.2, and SPM models in forecasting the shock arrival time. The absolute error in the transit time from our model is not larger than those of the other four models for the same set of events. These results may demonstrate the potential capability of our model in terms of improving real‐time forecasting because the CESE method can be extended to three‐dimensional magnetohydrodynamics (3D‐MHD) from the solar photosphere to any heliospheric position.
Vortex Rossby waves in mesoscale dipoles
Authors: Rodríguez‐Marroyo R. , Viúdez A.
Published: October 2009

Mesoscale oceanic vortex dipoles are stable coherent vortex structures formed by two closely packed regions of opposite sign vertical vorticity. The authors investigate periodic oscillations in the vortices that make barotropic and baroclinic dipoles depart from a complete steady state. These oscillations are a pair of vortex Rossby waves (VRWs) and are numerically simulated using a three‐dimensional, Boussinesq, and f‐plane model. The evolution of balanced (void of inertia‐gravity waves), static, and inertially stable dipoles is examined under different initial conditions. These initial conditions include the vortex potential vorticity (PV) geometry, initial distance between vortices, and PV extrema. The numerical results show that each VRW is an oscillation with azimuthal wave number 2 that amplifies preferentially at two vortex locations and has an angular phase speed of the same sign as the vortex vertical vorticity. The VRWs in the dipole (dipole VRWs) imply an oscillation in the dipole speed of displacement and, in baroclinic dipoles, interchange between kinetic and potential energy as well. In the absence of any external forcing, the amplitude, periodicity, and phase speed of the dipole VRWs depend on the initial conditions, especially on the PV extrema, vortex geometry, and initial distance between vortices. It is found that steady dipoles are possible but their steadiness is not robust in the sense that any small perturbation will cause the development of VRWs.
An oceanic cyclonic eddy on the lee side of Lanai Island, Hawai'i
Authors: Dong Changming , Mavor Timothy , Nencioli Francesco , Jiang Songnian , Uchiyama Yusuke , McWilliams James C. , Dickey Tommy , Ondrusek Michael , Zhang Hongchun , Clark Dennis K.
Published: October 2009

A young cold core cyclonic eddy displaying a significant increase in surface chlorophyll was observed offshore Lanai Island, Hawai'i, where the Marine Optical Buoy (MOBY) is located. During one of its deployments, MOBY broke free from its mooring. In the course of its 3‐day free drifting period, MOBY followed a cyclonic eddy, which is manifested by satellite remote sensing data, chlorophyll data from Moderate Resolution Imaging Spectroradiometer, and sea surface temperature (SST) from a Geostationary Operational Environmental Satellite. The time series of the SST show that the cold core eddy was in a formative stage. It existed as a stand‐alone eddy for about 9 days before it merged with cold water south of Oahu Island. A high‐resolution numerical model simulation reproduces similar eddies in terms of location, size, and intensity. An eddy detection algorithm is described and applied to locate and track the modeled eddies. The results demonstrate that mesoscale and submesoscale eddies are frequently generated on and pass through the lee side of Lanai Island and the statistical analysis quantifies the general features of eddies in the area.
Perception of Exercise Difficulty Predicts Weight Regain in Formerly Overweight Women
Authors: Brock David W. , Chandler‐Laney Paula C. , Alvarez Jessica A. , Gower Barbara A. , Gaesser Glenn A. , Hunter Gary R.
Published: October 2009

It has been previously reported that overweight and obese individuals perceive exercise as more difficult than their lean counterparts, and this difference may not be solely attributed to physiological differences. Therefore, we tested the hypothesis that individual differences in the perception of exercise difficulty during exercise, independent of concurrently measured physiological markers of exertion, are predictive of weight regain, after completion of a weight loss program. A total of 113 formerly overweight women who had previously completed a weight‐loss program to achieve a normal body weight (BMI <25 kg/m2) underwent a submaximal aerobic exercise task while measures of physiological and perceived exertion (rating of perceived exertion (RPE)) were recorded. Weight gain was assessed following a subsequent 1‐year free‐living period. Average weight regain 1 year following the intervention was 5.46 ± 3.95 kg. In regression modeling, RPE (β = 0.21, P = 0.01), but not physiological exertion (β = 0.02, P = 0.81), during the submaximal exercise task was positively associated with 1‐year weight regain following weight loss in premenopausal women, independent of measured confounding variables. The association between RPE and weight regain suggests that perception of exercise difficulty is an important predictor of weight regain following a weight‐loss intervention.
Parenting Characteristics in the Home Environment and Adolescent Overweight: A Latent Class Analysis
Authors: Berge Jerica M. , Wall Melanie , Bauer Katherine W. , Neumark‐Sztainer Dianne
Published: October 2009

Parenting style and parental support and modeling of physical activity and healthy dietary intake have been linked to youth weight status, although findings have been inconsistent across studies. Furthermore, little is known about how these factors co‐occur, and the influence of the coexistence of these factors on adolescents' weight. This article examines the relationship between the co‐occurrence of various parenting characteristics and adolescents' weight status. Data are from Project EAT (eating among teens), a population‐based study of 4,746 diverse adolescents. Theoretical and latent class groupings of parenting styles and parenting practices were created. Regression analyses examined the relationship between the created variables and adolescents' BMI. Having an authoritarian mother was associated with higher BMI in sons. The co‐occurrence of an authoritarian mother and neglectful father was associated with higher BMI for sons. Daughters' whose fathers did not model or encourage healthy behaviors reported higher BMIs. The co‐occurrence of neither parent modeling healthy behaviors was associated with higher BMIs for sons, and incongruent parental modeling and encouraging of healthy behaviors was associated with higher BMIs in daughters. Although, further research into the complex dynamics of the home environment is needed, findings indicate that authoritarian parenting style is associated with higher adolescent weight status and incongruent parenting styles and practices between mothers and fathers are associated with higher adolescent weight status.
Early Response to Sibutramine in Patients Not Meeting Current Label Criteria: Preliminary Analysis of SCOUT Lead‐in Period
Authors: Caterson Ian , Coutinho Walmir , Finer Nick , Van Gaal Luc , Maggioni Aldo , Torp‐Pedersen Christian , Sharma Arya M. , Ge Hong , Santoro Donatella , Shepherd Gillian , James Philip ,   SCOUT Investigators
Published: October 2009

The Sibutramine Cardiovascular Outcomes (SCOUT) trial protocol defines a patient population predominantly outside current European Union label criteria. This article explores responses to sibutramine during the 6‐week, single‐blind, lead‐in period between patients who conformed to the label requirements (“conformers”) and those who did not (“nonconformers”). SCOUT is an ongoing, randomized, double‐blind, placebo‐controlled outcome trial in overweight/obese patients at high risk of a cardiovascular event. In total, 10,742 patients received sibutramine and weight management during the lead‐in period. Initial responses were assessed post hoc in label conformers and nonconformers. Of that 8.1% patients met label criteria; 91.9%, the majority with cardiovascular disease and/or blood pressure >145/90 mm Hg, were nonconformers. Conformers and nonconformers had similar reductions in body weight (median change −2.2 kg) and waist circumference (women: −2.0 cm for both groups; men: −1.5 cm vs. −2.0 cm for conformers and nonconformers, respectively) over the 6‐week period. Greater blood pressure falls were evident in nonconformers (median change −3.5/−1.0 vs. −1.0/0.0 mm Hg). Both groups had small pulse rate increases; median 1.5 bpm (nonconformers) vs. 3.0 bpm (conformers). There was a low incidence of serious adverse events (conformers: 1.0%; nonconformers: 2.8%) and ∼93% of patients in both groups completed the 6‐week period. The SCOUT lead‐in period evaluating weight management with sibutramine confirms its good tolerability and efficacy in patients who meet current label criteria. Preliminary data from high‐risk patients for whom sibutramine is currently contraindicated suggest a low discontinuation rate and few serious adverse events but confirmation from the SCOUT outcome data is needed.
Retinol‐binding Protein 4 (RBP4) Protein Expression Is Increased in Omental Adipose Tissue of Severely Obese Patients
Authors: Kelly Karen R. , Kashyap Sangeeta R. , O'Leary Valerie B. , Major Jennifer , Schauer Philip R. , Kirwan John P.
Published: October 2009

Visceral fat has been linked to insulin resistance and type 2 diabetes mellitus (T2DM); and emerging data links RBP4 gene expression in adipose tissue with insulin resistance. In this study, we examined RBP4 protein expression in omental adipose tissue obtained from 24 severely obese patients undergoing bariatric surgery, and 10 lean controls (4 males/6 females, BMI = 23.2 ± 1.5 kg/m2) undergoing elective abdominal surgeries. Twelve of the obese patients had T2DM (2 males/10 females, BMI: 44.7 ± 1.5 kg/m2) and 12 had normal glucose tolerance (NGT: 4 males/8 females, BMI: 47.6 ± 1.9 kg/m2). Adipose RBP4, glucose transport protein‐4 (GLUT4), and p85 protein expression were determined by western blot. Blood samples from the bariatric patients were analyzed for serum RBP4, total cholesterol, triglycerides, and glucose. Adipose RBP4 protein expression (NGT: 11.0 ± 0.6; T2DM: 11.8 ± 0.7; lean: 8.7 ± 0.8 arbitrary units) was significantly increased in both NGT (P = 0.03) and T2DM (P = 0.005), compared to lean controls. GLUT4 protein was decreased in both NGT (P = 0.02) and T2DM (P = 0.03), and p85 expression was increased in T2DM subjects, compared to NGT (P = 0.03) and lean controls (P = 0.003). Regression analysis showed a strong correlation between adipose RBP4 protein and BMI for all subjects, as well as between adipose RBP4 and fasting glucose levels in T2DM subjects (r = 0.76, P = 0.004). Further, in T2DM, serum RBP4 was correlated with p85 expression (r = 0.68, P = 0.01), and adipose RBP4 protein trended toward an association with p85 protein (r = 0.55, P = 0.06). These data suggest that RBP4 may regulate adiposity, and p85 expression in obese‐T2DM, thus providing a link to impaired insulin signaling and diabetes in severely obese patients.
The Longitudinal Association From Obesity to Depression: Results From the 12‐year National Population Health Survey
Authors: Gariepy Genevieve , Wang JianLi , Lesage Alain D. , Schmitz Norbert
Published: October 2009

Prior observational studies have investigated the association between obesity and depression but evidence remains weak and mixed. There has been a call for high‐quality longitudinal studies to elucidate the etiologic relationship from obesity to depression. The main objective of this study was therefore to investigate whether obesity was a risk factor for depression in a nationally representative sample followed for 12 years. Seven waves of data collection (1994–1995 to 2006–2007) were obtained from the National Population Health Survey (NPHS). Our analyses included 10,545 adults without depression at baseline. Past‐year major depression episode (MDE) was assessed from the Composite International Diagnostic Interview‐Short Form for Major Depression (CIDI‐SFMD). Obesity was estimated using baseline BMI from self‐reported weight and height (obesity: BMI ≥30 kg/m2). Kaplan–Meier survival curves were generated and Cox proportional hazard regression modeling was used to estimate the risk of MDE by obesity status, controlling for sociodemographic and health and lifestyle variables. We found that obesity at baseline did not significantly predict subsequent MDE in women (adjusted hazard ratio (AHR): 1.03, 95% confidence interval (CI) 0.84–1.26) and negatively predicted MDE in men (HR: 0.71, CI 0.51–0.98), after adjusting for important confounders. In summary, our findings suggest that obesity is a significant (negative) predictor of depression in adult men but not in women. These results moderate prior evidence supporting a positive link from obesity to depression.
No evidence of direct binding between ursodeoxycholic acid and the p53 DNA-binding domain
Authors: Amaral Joana D. , Correia Ana R. , Steer Clifford J. , Gomes Cláudio M. , Rodrigues Cecília M.P.
Published: October 2009

UDCA (ursodeoxycholic acid) is used increasingly for the treatment of cholestatic liver diseases. Among other cytoprotective effects, this endogenous bile acid is a potent inhibitor of apoptosis, interfering with both intrinsic and extrinsic apoptotic pathways. In previous studies, we have demonstrated that the transforming growth factor β1-induced E2F-1/Mdm2 (murine double minute 2)/p53 apoptotic pathway was an upstream molecular target of UDCA. In agreement with this, we have recently established p53 as a key molecular target in UDCA prevention of cell death. The tumour suppressor p53 is a well-described transcription factor that induces the expression of multiple different pro-apoptotic gene products. Its regulation involves a variety of signalling proteins and small molecules, and occurs at multiple levels, including transcription, translation and post-translation levels. In the present study, by using different biophysical techniques, we have investigated the possibility of a direct interaction between the p53 core domain, also referred to as the DNA-binding domain, and UDCA. Our in vitro analysis did not provide any evidence for direct binding between the bile acid UDCA and the p53 core domain.
Integrability and superintegrability of the generalized n-level many-mode Jaynes–Cummings and Dicke models
Authors: Skrypnyk T.
Published: October 2009

We analyze symmetries of the integrable generalizations of Jaynes–Cummings and Dicke models associated with simple Lie algebras g and their reductive subalgebras gK [T. Skrypnyk, “Generalized n-level Jaynes-Cummings and Dicke models, classical rational r-matrices and nested Bethe ansatz,” J. Phys. A: Math. Theor. 41, 475202 (2008)]. We show that their symmetry algebras contain commutative subalgebras isomorphic to the Cartan subalgebras of g, which can be added to the commutative algebras of quantum integrals generated with the help of the quantum Lax operators. We diagonalize additional commuting integrals and constructed with their help the most general integrable quantum Hamiltonian of the generalized n-level many-mode Jaynes–Cummings and Dicke-type models using nested algebraic Bethe ansatz.
Huge ac magnetoresistance of La0.7Sr0.3MnO3 in subkilogauss magnetic fields
Authors: Rebello A. , Naik V. B. , Mahendiran R.
Published: October 2009

We report the electrical and magnetotransport behavior of a ferromagnetic metallic oxide, La0.7Sr0.3MnO3, in response to radio frequency current passing through the sample. We have studied the temperature dependence of the ac resistance (R) and inductive reactance (X) under different dc bias magnetic fields (Hdc=0–1 kOe) for different frequencies (f) of radio frequency current from f=0.1 to 5 MHz. The zero field R, which decreases smoothly around the Curie temperature TC for f=100 kHz, transforms into a peak for f=0.5–5 MHz. The peak decreases in amplitude, broadens, shifts downward in temperature as the bias field increases, and is completely suppressed under Hdc=1 kOe when f=0.5 MHz. The ac magnetoresistance and magnetoinductance exhibit a peak close to the TC. A huge low-field ac magnetoresistance (ΔR/R=40%) and magnetoinductance (ΔX/X=12%) are found in a field of Hdc=700 Oe and f=2 MHz. It has been suggested that the observed ac magnetoresistance has its origin in the suppression of spin fluctuation near TC and the enhancement of magnetic skin depth under the external magnetic field. The huge ac magnetoresistance reported in this work can be exploited for magnetic field sensors and other applications.
Absolute nitrogen atom density measurements by two-photon laser-induced fluorescence spectroscopy in atmospheric pressure dielectric barrier discharges of pure nitrogen
Authors: Es-Sebbar Et-Touhami , Sarra-Bournet Christian , Naudé Nicolas , Massines Françoise , Gherardi Nicolas
Published: October 2009

In this paper, two-photon absorption laser induced fluorescence spectroscopy is used to follow the nitrogen atom density in flowing dielectric barrier discharges fed with pure nitrogen and operating at atmospheric pressure. Two different dielectric barrier discharge regimes are investigated: the Townsend regime, which is homogeneous although operating at atmospheric pressure, and the more common filamentary regime. In both regimes, densities as high as 3×1014∕cm3 are detected. However, the N atoms kinetic formation depends on the discharge regime. The saturation level is reached more rapidly with a filamentary discharge. For a given discharge regime, the N atom density depends strongly on the energy dissipated in the plasma between the gas inlet and the measurement position, whether the energy is varied by varying the position of the measurements, the gas flow, or the dissipated power. Experiments performed in the postdischarge show that the N atom decay cannot be simply attributed to three-body recombination of atomic nitrogen with nitrogen molecules, meaning that other mechanisms such as surface recombination or gas impurities play a role.
Epitaxial growth and picosecond carrier dynamics of GaInAs/GaInNAs superlattices
Authors: Martin M. , Mangeney J. , Travers L. , Minot C. , Harmand J. C. , Mauguin O. , Patriarche G.
Published: October 2009

We study GaInAs/GaInNAs superlattice structures grown on InP substrate as potential candidates for photoconductive terahertz devices or saturable absorbers working at 1.55 μm wavelength. The N-rich GaInNAs layers are flat, with no three-dimensional islanding, and act as trapping layers where carriers can recombine rapidly. The carrier lifetime in GaInAs/GaInNAs superlattice was measured for various growth parameters using time-resolved differential transmission experiments at 1.55 μm wavelength. The carrier lifetime is found to depend strongly on N content and can be reduced down to 3.8 ps for samples with 14% of N. The mechanisms involved in the capture process of photocarriers are discussed.
Structure, spectroscopic properties, and photochemistry of the hydroxymethoxy radical
Authors: Eisfeld Wolfgang , Francisco Joseph S.
Published: October 2009

The hydroxymethoxy (HMO) radical is proposed to be the primary product of photodissociation of the atmospherically important hydroxymethyl hydroperoxide (HMHP). This transient species is still unknown and the present study provides theoretical predictions of properties, spectroscopy, and photochemistry of this radical for the first time. Structures, harmonic frequencies, vertical and vibrationally resolved absorption spectra are computed for several electronic states, using state-of-the-art ab initio electronic structure methods. The lowest excited state, absorbing in the mid to near infrared, seems to be the most promising candidate for spectroscopic identification of HMO. The electron affinity of 2.232 eV and the characteristic photodetachment spectrum is also predicted to be suitable for experimental investigations. By contrast, the B̃ state absorbing around 3.5 eV is proposed to undergo fast photodissociation, forming CH2O and OH, and thus appears less useful for spectroscopic detection of HMO. However, the photodissociation may be important for the atmospheric chemistry of HMHP. Ionization of HMO will also lead to dissociation or rearrangement of the cation and will yield only unspecific spectra.
A unified probability density function formulation to model turbulence modification in two-phase flow
Authors: Anand Gaurav , Jenny Patrick
Published: October 2009

In the present study, a unified probability density function formulation for capturing the phenomena of turbulence modification of the continuous phase due to the dispersed phase turbulence is presented. A stochastic model based on dispersed phase turbulence length scale has been proposed for the purpose. The model has been validated with experimental data [Poelma , “Particle fluid interactions in grid-generated turbulence,” J. Fluid Mech.589, 315 (2007)] on the decay of turbulence of the flow seeded with ceramic particles in a vertical recirculating water channel. The obtained simulation results are in good agreement with the experimental data. Numerical experiments have been performed to investigate the influence of gravity on the decay of the continuous phase Reynolds stresses. For comparison, the influence of dispersed phase turbulence on the continuous phase turbulence without taking gravity into consideration has also been studied.

At the request of the authors, this article is being retracted effective 22 June 2012.
Determination of refractive indices and thicknesses of Ba0.7Sr0.3TiO3 films with and without MgO (001) buffer layer on silicon substrate
Authors: Yin Y. , Ye H. , Zhang C. , Shen W. D. , Liu X.
Published: October 2009

Ba 0.7 Sr 0.3 TiO 3 (BST30) thin films, deposited on single crystal Si (100) substrates with or without a MgO(001) buffer layer by the sol-gel method, have been investigated for their optical properties with a visible reflection spectrophotometer. An improved simplex numerical optimization method based on the reflectance spectra fitting is utilized to obtain the refractive indices and thicknesses of the thin films. Two models for the refractive index variations of the films (with or without a MgO buffer layer) together with a resemble double-layer structure are used to describe the films. The crystallization and microstructure of the films are characterized by the field emission scanning electron microscopy, which indicates that the MgO(001) buffer layer can significantly hold up the interdiffusion between the BST30 layer and the Si substrate, acuminate the interfaces, and improve the crystallinity of the BST thin film deposited on it. Furthermore, due to the large difference between the refractive index of the BST30 thin film and that of the MgO(001) buffer layer, which results in a strong beam confinement, a desirable waveguide structure could be constructed.
Increase in the Curie temperature and magnetic anisotropy in FePd/Pt–iron oxide core-shell nanoparticles
Authors: Fleurier R. , Bhattacharyya S. , Saboungi M.-L. , Raimboux N. , Simon P. , Kliava J. , Magrez A. , Feher T. , Forro L. , Salvetat J.-P.
Published: October 2009

Partially oxidized fcc FePd and FePt nanoparticles with mean diameters of 5 and 3 nm, respectively, were synthesized by a reverse micelle polyol process. In situ measurements of magnetic and structural properties during annealing showed a large increase in the magnetocrystalline anisotropy and in the Curie temperature of the nanoparticles due to (i) a phase transition from A1 to L10 and (ii) a simultaneous phase separation between a metallic core and an iron oxide shell. These occurred at 675 K in the FePd nanoparticles and at above 850 K for the FePt. The Curie temperature of the nanoparticles was found to be about 850 K, an increase of more than 100 K from the bulk L10 phase. The ferromagnetic resonance results are discussed and compared with a phenomenological model that makes it possible to estimate the magnetocrystalline anisotropy as 1.6×105 and 1.5×106 J m−3 in FePd and FePt, respectively. Exchange coupling between the core and the shell explains both the high magnetocrystalline anisotropy of the core and the high Curie temperature of the shell.
Fast ignition of inertial fusion targets by laser-driven carbon beams
Authors: Honrubia J. J. , Fernández J. C. , Temporal M. , Hegelich B. M. , Meyer-ter-Vehn J.
Published: October 2009

Two-dimensional simulations of ion beam driven fast ignition are presented. Ignition energies of protons with Maxwellian spectrum and carbon ions with quasimonoenergetic and Maxwellian energy distributions are evaluated. The effect of the coronal plasma surrounding the compressed deuterium-tritium is studied for three different fuel density distributions. It is found that quasimonoenergetic ions have better coupling with the compressed deuterium-tritium and substantially lower ignition energies. Comparison of quasimonoenergetic carbon ions and relativistic electrons as ignitor beams shows similar laser energy requirements, provided that a laser to quasimonoenergetic carbon ion conversion efficiency around 10% can be achieved.
Influence of poling on far-infrared response of lead zirconate titanate ceramics
Authors: Simon E. , Hlinka J. , Kamba S. , Gregora I. , Erhart J.
Published: October 2009

The paper describes experiments revealing the anisotropy of the macroscopic dielectric response of poled lead zirconate titanate ceramics in the phonon frequency region. The results are discussed in terms of distinct polar phonon contributions and effective medium theory. The anisotropy probed in far-infrared experiments can be used to evaluate efficiency of the poling and/or depoling processes.
Structure, ionic conduction, and giant dielectric properties of mechanochemically synthesized BaSnF4
Authors: Ahmad Mohamad M. , Yamane Yohei , Yamada Koji
Published: October 2009

BaSnF 4 fluoride ion conductor has been prepared by mechanochemical milling technique at room temperature. The as-prepared material crystallizes in the cubic fluorite-type structure due to disordering of metal cations. The cubic phase transforms to tetragonal structure by annealing at 460 K. The ionic conductivity of the cubic phase is two to three orders of magnitude lower than the annealed sample. The complex conductivity of the investigated materials has been analyzed by a power-law model in order to extract the hopping rates and the concentration of mobile ions, the parameters that control the overall conduction behavior. The estimated values of the concentration of mobile ions are found to be of the same order, indicating that the conduction process is controlled by the mobility of charge carriers. BaSnF4 has been found to belong to a new class of nonoxidic giant dielectric constant materials with a value of ε′∼105, which is independent of temperature and frequency over wide ranges. It is found that the giant values of the dielectric constant are not due to surface barrier layer capacitance effects at the sample/electrode interface of the material.
Infrared absorption of GeNNO isolated in solid Ar
Authors: Jiang Zih-Min , Glatthaar Joerg , Lee Yuan-Pern
Published: October 2009

Codeposition of thermally generated atomic germanium vapor and nitrous oxide (N2O) in Ar onto a substrate at 11 K produced infrared absorption lines in several sets. The most prominent comprises intense lines at 1443.7, 1102.4, and 784.0 cm−1 that become diminished upon irradiation with UV or visible light. These lines are attributed to ν1 (NO stretching), ν2 (NN+GeN stretching), and ν3 (NNO bending+NN stretching) modes of singlet GeNNO. Two additional weak features at 1238.1 and 2859.2 cm−1 are assigned as ν3+ν4 and 2ν1 of GeNNO, respectively. Weak doublet features at 1259.3/1255.5 and 1488.9/1486.4 cm−1 are tentatively assigned to ν2 of triplet GeONN and ν1 of singlet cyc-Ge-η2 [NN(O)], respectively. Quantum-chemical calculations on the Ge+N2O system with density-functional theory (B3LYP /aug-cc-pVTZ) predict five stable structures: GeNNO (singlet and triplet), singlet cyc-Ge-η2 [NN(O)], triplet cyc-Ge-η2 (NNO), GeONN (singlet and triplet), and singlet GeNON. Vibrational wavenumbers, relative IR intensities, and N15-isotopic ratios for observed species are consistent with those computed. Irradiation of singlet GeNNO with λ=248 or 193 nm or λ>525 nm yields GeO.
Electric and magnetic resonances in symmetric pairs of split ring resonators
Authors: Kim In Kwang , Varadan Vasundara V.
Published: October 2009

Orientation of the gap of a split ring resonator determines whether the resonance is an electric or magnetic response. When the gap of a split ring resonator is parallel to the incident E-field, an electric resonance is excited, and when the gap is perpendicular to the E-field, a magnetic resonance is excited. In this paper, we show that strong coupling between adjacent symmetric split ring resonators can give rise to dual electric and magnetic resonances if the intercell spacing is small enough. By varying the interparticle spacing within a unit cell, we can position the dual resonances as desired. Inverting the simulated reflection and transmission coefficients of a periodic slab of symmetric pairs of split ring resonators, the permittivity and permeability can be extracted and are shown to result in negative properties at resonance. Through a careful analysis of the extracted and Lorentz model fits of the permittivity and permeability, together with the simulated S-parameters, we have established a clear guideline for identifying electric and magnetic resonances. We also present measurement data that agree well with our simulated data. Applications of this design to band-pass filters and microstrip antenna substrates are envisaged.
X-ray diffraction study of strain distribution in oxidized Si nanowires
Authors: Takeuchi Teruaki , Tatsumura Kosuke , Shimura Takayoshi , Ohdomari Iwao
Published: October 2009

Strain distributions in oxidized Si nanowires fabricated on a (001)-oriented silicon-on-insulator wafer have been determined by analyzing intensity profiles of the diffraction, caused by the nanowire periodicity, around the 111 Bragg point. In this analysis, theoretical diffraction curves, calculated by a kinematical treatment, are fitted to experimental ones, examining positions of the central and fringe maxima and their intensity ratios. Strains in oxidized samples are shown to be negative at the bottom surface and positive at the top surface of nanowires changing with depth in a concave way. The magnitudes of the strains at the bottom surface and at the top surface increase monotonically with increasing the oxidation time. The determined strain of a sample oxidized at 850 °C for 5 h is 0.50% at the top surface and −0.11% at the bottom surface.
Multistep damage evolution process in cubic zirconia irradiated with MeV ions
Authors: Moll S. , Thomé L. , Sattonnay G. , Debelle A. , Garrido F. , Vincent L. , Jagielski J.
Published: October 2009

This work reports the study, via the combination of Rutherford backscattering spectrometry and channeling, x-ray diffraction, and transmission electron microscopy experiments, of the damage formation in cubic yttria-stabilized zirconia single crystals irradiated with medium-energy (4 MeV) heavy (Au) ions. The damage buildup, which is accounted for in the framework of the multistep damage accumulation model, occurs in three steps. The first step at low fluences (up to 1015 cm−2), characterized by a regular increase in both the damage yield and the elastic strain, is related to the formation of small defect clusters. The second step in the intermediate fluence range (from 1015 to 5×1015 cm−2) leads to a sharp increase in the damage yield and to a large drop of the strain due to the formation of dislocation loops which collapse into a network of tangled dislocations. The third step at high fluences (above 5×1015 cm−2) exhibits a surprising decrease in the damage yield, which may be attributed to the reorganization of the dislocation network that leads to the formation of weakly damaged regions with a size of the order of 100 nm.
Spin torque-driven switching of exchange bias in a spin valve
Authors: Tang Xiao-Li , Zhang Huai-Wu , Su Hua , Jing Yu-Lan , Zhong Zhi-Yong
Published: October 2009

We show that the strength and direction of the exchange bias in a spin valve can be changed and recovered by applying a spin-polarized current pulse. In other words, once the exchange bias has been changed by a spin-polarized current pulse with the external magnetic field antiparallel to the exchange bias direction, it can be returned to the initial state by a current pulse of the same magnitude with reversal of the external field. Furthermore, the exchange bias field reverts to the same magnitude, irrespective of whether one or multiple current pulses are applied. Based on a model for spin-momentum transfer, the experimental observations can be rationalized in terms of changing micromagnetic distributions at the ferromagnet/antiferromagnet interface.
Electron-beam-induced current and cathodoluminescence study of dislocation arrays in 4H-SiC homoepitaxial layers
Authors: Chen Bin , Sekiguchi Takashi , Ohyanagi Takasumi , Matsuhata Hirofumi , Kinoshita Akimasa , Okumura Hajime
Published: October 2009

The electrical and optical properties of dislocation arrays (DAs) in 4H-SiC homoepitaxial layers were studied by using electron-beam-induced current (EBIC) and cathodoluminescence (CL) techniques. EBIC observations show that under electron-beam irradiation, the DAs are easily dissociated to form rhombic stacking faults (SFs), whereas the single threading dislocations are not. CL results demonstrate that a new peak (417 nm) appears at the formed SFs, which is the same as the phenomenon observed from dissociating basal plane dislocations. The dissociation mechanisms of DAs are proposed based on the assumption that small basal segments exist. The dissociation velocity of each dislocation in the DAs is discussed according to its recombination activity.
Pressure-induced phase transformations in cubic Gd2O3
Authors: Bai Ligang , Liu Jing , Li Xiaodong , Jiang Sheng , Xiao Wansheng , Li Yanchun , Tang Lingyun , Zhang Yufeng , Zhang Dechun
Published: October 2009

High-pressure transformation and compression behavior of Gd2O3 were investigated using synchrotron radiation x-ray diffraction in a diamond anvil cell up to 44 GPa at room temperature. The structural transformation from a cubic to a monoclinic phase occurred during the sample precompression process. Phase transitions from both the cubic and the monoclinic polymorphs to a hexagonal structure were observed. The hexagonal phase was stable up to the highest pressure in this study and was not quenchable and transformed to a monoclinic phase after pressure release. The bulk moduli of Gd2O3 for the cubic, monoclinic, and hexagonal phases were obtained by fitting the compression data to the Birch–Murnaghan equation of state. Moreover, an anomaly of the hexagonal type Gd2O3 was observed.