bluuebunny/crossref_metadata_2025 huggingface dataset:
Association between childhood maltreatment and adult emotional dysregulation in a low-income, urban, African American sample: Moderation by oxytocin receptor gene
Authors: Bradley Bekh , Westen Drew , Mercer Kristina B. , Binder Elisabeth B. , Jovanovic Tanja , Crain Daniel , Wingo Aliza , Heim Christine
Published: April 2011

The ability to effectively regulate emotions and a secure attachment style are critical for maintaining mental health across the life span. The experience of childhood maltreatment interferes with normal development of emotional regulation and dramatically increases risk for a wide range of psychiatric disorders in adulthood. The central nervous system oxytocin systems are critically involved in mediating social attachment and buffering psychophysiological responses to stress. We therefore investigated the impact of childhood maltreatment and an oxytocin receptor (OXTR) single nucleotide polymorphism (rs53576) and their interaction on emotional dysregulation and attachment style in adulthood in a sample of low-income, African American men and women recruited from primary care clinics of an urban, public hospital. Consistent with prior research, we found that the severity of childhood maltreatment was associated with increased levels of emotional dysregulation in adulthood. Childhood maltreatment was also positively associated with ratings of disorganized/unresolved adult attachment style and negatively associated with ratings of secure adult attachment style. There was no direct association betweenrs53576and emotional dysregulation or ratings of adult attachment style. However, there were significant interactions betweenrs53576and childhood maltreatment in predicting level of adult emotional dysregulation and attachment style. Specifically, G/G genotype carriers were at risk for increased emotional dysregulation when exposed to three or more categories of childhood abuse. In addition, G/G genotype carriers exhibited enhanced disorganized adult attachment style when exposed to severe childhood abuse compared to A/A and A/G carriers. Our findings suggest that A allele carriers ofOXTR rs53576are resilient against the effects of severe childhood adversity, by protection against emotional dysregulation and disorganized attachment.
The impact of sexual abuse on female development: Lessons from a multigenerational, longitudinal research study
Authors: Trickett Penelope K. , Noll Jennie G. , Putnam Frank W.
Published: April 2011

This is a report on the research design and findings of a 23-year longitudinal study of the impact of intrafamilial sexual abuse on female development. The conceptual framework integrated concepts of psychological adjustment with theory regarding how psychobiological factors might impact development. Participants included 6- to 16-year-old females with substantiated sexual abuse and a demographically similar comparison group. A cross-sequential design was used and six assessments have taken place, with participants at median age 11 at the first assessment and median age 25 at the sixth assessment. Mothers of participants took part in the early assessments and offspring took part at the sixth assessment. Results of many analyses, both within circumscribed developmental stages and across development, indicated that sexually abused females (on average) showed deleterious sequelae across a host of biopsychosocial domains including: earlier onsets of puberty, cognitive deficits, depression, dissociative symptoms, maladaptive sexual development, hypothalamic–pituitary–adrenal attenuation, asymmetrical stress responses, high rates of obesity, more major illnesses and healthcare utilization, dropping out of high school, persistent posttraumatic stress disorder, self-mutilation,Diagnostic and Statistical Manual of Mental Disordersdiagnoses, physical and sexual revictimization, premature deliveries, teen motherhood, drug and alcohol abuse, and domestic violence. Offspring born to abused mothers were at increased risk for child maltreatment and overall maldevelopment. There was also a pattern of considerable within group variability. Based on this complex network of findings, implications for optimal treatments are elucidated. Translational aspects of extending observational research into clinical practice are discussed in terms that will likely have a sustained impact on several major public health initiatives.
Resilience in children threatened by extreme adversity: Frameworks for research, practice, and translational synergy
Authors: Masten Ann S.
Published: April 2011

This article delineates parallel frameworks that grew out of the research on risk and resilience over the past four decades, a framework for research and a framework for practice, and then discusses the promise of an emerging synthesis. The research framework defined the meaning, models, and methods that successfully guided four waves of research to date on the nature and processes involved in human resilience. The applied framework emerged in response to urgent needs of children and families faced by adversity and those charged with helping them, resulting in guidelines for translating the unfolding but incomplete research evidence into action. The application of a resilience approach transformed practice in many fields concerned with promoting resilience in people at risk for problems, revolutionizing the mission, models, measures, and methods of practice to align with the emphasis on positive adaptation and strengths defining a resilience-based approach. Yet these interventions rarely translated back to inform and refine resilience theory in ways that would accelerate progress to promote resilience more effectively. The concluding section on translational synergy discusses the potential for a synthesis of basic and applied resilience frameworks as the next steps toward realizing the original objective and promise of resilience science.
Mother–child relationships, family context, and child characteristics as predictors of anxiety symptoms in middle childhood
Authors: Kerns Kathryn A. , Siener Shannon , Brumariu Laura E.
Published: April 2011

The goal of the study was to examine several factors that may explain the development of anxiety symptoms in middle childhood. Using data from the NICHD Study of Early Child Care (n = 1,364 families), we examined mother–child relationships, other aspects of family context, and child characteristics as predictors of anxiety in preadolescence. Latent growth curve analyses revealed that children who were more anxious at the beginning of middle childhood had been more behaviorally inhibited as preschoolers, and in middle childhood lived in families who experienced more negative life events and had mothers who were more anxious. Children who became more anxious across middle childhood were less behaviorally inhibited as preschoolers and in middle childhood perceived less security in their attachments to their mothers, experienced more negative life events, and had mothers who were more anxious. The findings illustrate the need to include a broad set of risk factors in etiological models of anxiety. In addition, the evidence for cumulative effects suggests several possible points of intervention with anxious children and their parents.
Preventing falls and fractures in long-term care
Authors: Wallis Stephen J , Campbell Gordon A
Published: April 2011

The prevalence of falls and associated injuries increases with age and dependency. The highest occurs among individuals living in long-term care institutions. Preventing falls results in reduced physical and psychological morbidity as well as having cost-saving implications. This review explores both uni- and multifactorial approaches to reducing fall rates and risk in individuals in long-term care, as well as highlighting the differences in this group from community-dwelling individuals.
A Bayesian Approach to Parameter Estimation for Kernel Density Estimation via Transformations
Authors: Liu Qing , Pitt David , Zhang Xibin , Wu Xueyuan
Published: April 2011

In this paper, we present a Markov chain Monte Carlo (MCMC) simulation algorithm for estimating parameters in the kernel density estimation of bivariate insurance claim data via transformations. Our data set consists of two types of auto insurance claim costs and exhibits a high-level of skewness in the marginal empirical distributions. Therefore, the kernel density estimator based on original data does not perform well. However, the density of the original data can be estimated through estimating the density of the transformed data using kernels. It is well known that the performance of a kernel density estimator is mainly determined by the bandwidth, and only in a minor way by the kernel. In the current literature, there have been some developments in the area of estimating densities based on transformed data, where bandwidth selection usually depends on pre-determined transformation parameters. Moreover, in the bivariate situation, the transformation parameters were estimated for each dimension individually. We use a Bayesian sampling algorithm and present a Metropolis-Hastings sampling procedure to sample the bandwidth and transformation parameters from their posterior density. Our contribution is to estimate the bandwidths and transformation parameters simultaneously within a Metropolis-Hastings sampling procedure. Moreover, we demonstrate that the correlation between the two dimensions is better captured through the bivariate density estimator based on transformed data.
Quality management in the prophylaxis of venous thrombembolism - Results of a survey including 464 medical and surgical patients
Authors: Klein-Weigel  , Richter  , Arendt  , Gerdsen  , Härtwig  , Gutsche-Petrak  , Walter  , Santarelli  , Glöckner  , Hannemann  , Hermanns  , Leimbach  , Rakob  , Hullmeine  , Jordan  , Wiegand  , Lenke  , Lochmann  , Grunwald  , Brackertz  , Jäger  , Bublak  , Brand  , Alsen
Published: April 2011

Background: We surveyed the quality of risk stratification politics and monitored the rate of entries to our company-wide protocol for venous thrombembolism (VTE) prophylaxis in order to identify safety concerns. Patients and methods: Audit in 464 medical and surgical patients to evaluate quality of VTE prophylaxis. Results: Patients were classified as low 146 (31 %), medium 101 (22 %), and high risk cases 217 (47 %). Of these 262 (56.5 %) were treated according to their risk status and in accordance with our protocol, while 9 more patients were treated according to their risk status but off-protocol. Overtreatment was identified in 73 (15.7 %), undertreatment in 120 (25,9 %) of all patients. The rate of incorrect prophylaxis was significantly different between the risk categories, with more patients of the high-risk group receiving inadequate medical prophylaxis (data not shown; p = 0.038). Renal function was analyzed in 392 (84.5 %) patients. In those patients with known renal function 26 (6.6 %) received improper medical prophylaxis. If cases were added in whom prophylaxis was started without previous creatinine control, renal function was not correctly taken into account in 49 (10.6 %) of all patients. Moreover, deterioration of renal function was not excluded within one week in 78 patients (16.8 %) and blood count was not re-checked in 45 (9.7 %) of all patients after one week. There were more overtreatments in surgical (n = 53/278) and more undertreatments in medical patients (n = 54/186) (p = 0.04). Surgeons neglected renal function and blood controls significantly more often than medical doctors (p-values for both < 0.05). Conclusions: We found a low adherence with our protocol and substantial over- and undertreatment in VTE prophylaxis. Besides, we identified disregarding of renal function and safety laboratory examinations as additional safety concerns. To identify safety problems associated with medical VTE prophylaxis and hot spots quality management-audits proved to be valuable instruments.
Cystic medial necrosis Erdheim Gsell as a rare reason for spontaneous rupture of the ascending aorta
Authors: Gary  , Seinost  , Hafner  , Gorkiewicz  , Brodmann
Published: April 2011

Spontaneous rupture of the ascending aorta is a life-threatening condition requiring immediate intervention. The rupture usually leads to sudden death as a result of hemopericardium or hemothorax. The underlying histopathological condition in the cases described so far was mostly an atheromatous plaque. Some other rare underlying conditions were also described. We report a case of cystic medial necrosis Erdheim Gsell as a reason for fatal spontaneous rupture of the ascending aorta.
Impact of climate change on the hydroclimatology of Lake Tana Basin, Ethiopia
Authors: Setegn Shimelis G. , Rayner David , Melesse Assefa M. , Dargahi Bijan , Srinivasan Raghavan
Published: April 2011

Climate change has the potential to reduce water resource availability in the Nile Basin countries in the forthcoming decades. We investigated the sensitivity of water resources to climate change in the Lake Tana Basin, Ethiopia, using outputs from global climate models (GCMs). First, we compiled projected changes in monthly precipitation and temperature in the basin from 15 GCMs. Although the GCMs uniformly suggest increases in temperature, the rainfall projections are not consistent. Second, we investigated how changes in daily temperature and precipitation might translate into changes in streamflow and other hydrological components. For this, we generated daily climate projections by modifying the historical data sets to represent the changes in the GCM climatologies and calculated hydrological changes using the Soil and Water Assessment Tool (SWAT). The SWAT model itself was calibrated and validated using the flows from four tributaries of Lake Tana. For the Special Report on Emissions Scenarios A2 scenario, four of the nine GCMs investigated showed statistically significant declines in annual streamflow for the 2080–2100 period. We interpret our results to mean that anthropogenic climate changes may indeed alter the water balance in the Lake Tana Basin during the next century but that the direction of change cannot be determined with confidence using the current generation of GCMs.
Direct measurement of internal quantum efficiency in light emitting diodes under electrical injection
Authors: Matioli Elison , Weisbuch Claude
Published: April 2011

A method is presented for the direct measurement of the internal quantum efficiency in light emitting diodes (LEDs), based on the ratio of the measured external quantum efficiency and the calculated light extraction efficiency. The external quantum efficiency is measured from a single facet of the device in a simple, well-defined geometry, for which the light extraction efficiency can be calculated with good accuracy. In the proposed method, all LED facets are coated with highly absorbing material which suppresses any light that is not directly emitted into a small aperture on the top facet of the LED. We present a full wave optical model for a multilayer LED structure, from which we derive and validate an approximate model to easily calculate the extraction efficiency through the top facet of the LED. Because a current spreading electrode, often metallic, is required for uniform injection, we show that its impact on the extraction efficiency can be simply modeled through a separate transmission function calculated from the complex index of refraction of the electrode material. The various assumptions made to justify the direct emission model through a single facet (absence of photon backscatter, no photon recycling, simplified device layer model) are discussed and evaluated. The model is applied to a specific GaN LED structure.
Synthesis and magnetic properties of Co–Ti–Bi codoped M-type barium ferrite
Authors: Jia Lijun , Zhang Huaiwu , Yin Shuiming , Bai Feiming , Liu Baoyuan , Wen Qiye , Shen Jian
Published: April 2011

The effects of Co2+, Ti4+, and Bi3+ substitution on the microstructures and properties of low-temperature fired M-type barium hexaferrites have been studied in order to adapt the development of low-temperature cofired ferrites technology and produce gyromagnetic devices with a multilayer process. It is found that Bi3+ ions can enter into the 2a sublattice and consequently enhance the grain growth and densification due to the activation of the lattice, which in turn first lead to an increase and then a decrease of Ms. The substitution of Bi3+ ions is beneficial to forming the M phase and lowers the sintering temperature to about 900 °C, which is ideal for cofiring with silver paste. Scanning electron microscope and x-ray diffraction analysis have shown that the samples have excellent crystalline grains with a uniform size about 1–2 μm. Moreover, nonmagnetic Ti4+ ions prefer to enter the 4fVI octahedral sites, giving rise to the weakening of the strong 12k-4fVI superexchange path and thus the isotropic exchange energy approaches the other second-order terms on the magnetic Hamiltonian, such as the antisymmetric interaction or even the magnetocrystalline anisotropy. With increasing the substitution content, some Co2+ ions, which locate in octahedral 12k sites, give a strong planar contribution to the anisotropy. Therefore, Ms and Hc decrease with the Co–Ti-substitution.
Magnetoresistance effect of tunnel junctions using Co2(Ti, Mn)Z (Z = Al, Si) Heusler alloys
Authors: Sasaki A. , Tezuka N. , Jiang L. , Sugimoto S.
Published: April 2011

We investigated postannealing temperature dependence of the structural and magnetic properties of Co2Ti0.5Mn0.5Al and Co2Ti0.5Mn0.5Si films. It was observed that the Co2Ti0.5Mn0.5Al film formed an ordered L21 structure and an ordered B2 structure after postannealing at above 873 K and below 773 K, respectively. The Co2Ti0.5Mn0.5Si film deposited with substrate heating at above 473 K formed an ordered L21 structure. The obtained magnetoresistance ratio for a junction using an L21 ordered Co2Ti0.5Mn0.5Si electrode was 12.5% at room temperature (RT). The estimated spin polarization of the Co2Ti0.5Mn0.5Si film was 0.14 at RT. The magnetoresistance ratios of a junction using a B2 ordered Co2Ti0.5Mn0.5Al electrode were 65.8% at RT and 128.4% at 7 K. The estimated spin polarizations of the Co2Ti0.5Mn0.5Al film were 0.56 at RT and 0.78 at 7 K.
Defect and impurity effects in exchange bias systems
Authors: Vallejo-Fernandez G. , Kaeswurm B. , O’Grady K.
Published: April 2011

We use a strong domain wall pinning model to interpret previous results on the effects of dopants and defects in the loop shift Hex of exchange bias systems. The effects of defects and dopants leads to a peak in the value of Hex as a function of the concentration, which was interpreted on the basis of the domain state model. We consider a strong domain wall pinning model such that the strength of the pins can lead to the formation of quasi-single domain grains. These single domain grains then behave as Stoner–Wohlfarth entities subject to thermal activation. This model provides excellent agreement with reported experimental data predicting the peak with concentration and the correct form of the variation in the peak shape with temperature.
Theoretical analyses on effective magnetoelectric coupling coefficients in piezoelectric/piezomagnetic laminates
Authors: Cui Xiaoxi , Dong Shuxiang
Published: April 2011

In previous theoretical analyses, magnetoelectric (ME) coupling coefficient αME of piezoelectric/piezomagnetic laminates for static and dynamic modes is usually regarded as one that is not related to laminates’ sizes (length and width). In micrometer or sub-millimeter ME laminates, the decrease in ME coupling was normally attributed to the substrate’s clamping effect. Here, we report an effective ME coefficient αME,eff including sizes’ effect based on magnetic circuit method including the size induced demagnetization effect, which predicted that as sizes of ME laminates decrease from 100 mm to 10−3 mm, αME,eff will dramatically decreases from ∼5 V/cm-Oe to 0.08 V/cm-Oe. Size decrease in ME laminates will result in a decrease in effective magnetic induction Bμ inside piezomagnetic phase in an applied magnetic field H. Our analyses further disclose a degenerate mode occurred between the longitudinal and transverse resonance modes, which may cause a weakened ME coupling. Finally, our analyses indicate that a thin and long ME laminate will exhibit a stronger ME coupling, which was then confirmed by our experimental results.
Determination of band offsets in strained InAsxP1−x/InP quantum well by capacitance voltage profile and photoluminescence spectroscopy
Authors: Dixit V. K. , Singh S. D. , Porwal S. , Kumar Ravi , Ganguli Tapas , Srivastava A. K. , Oak S. M.
Published: April 2011

InAsxP1−x/InP quantum wells (QWs) with excellent crystalline and interfacial quality are grown by metal organic vapor phase epitaxy as confirmed from the cross-sectional transmission electron microscopy, high resolution x-ray diffraction and photoluminescence measurements. The electron confinement in InAsxP1−x/InP QW states is determined by capacitance voltage measurements, where we find that the electron accumulation increases with increasing QWs thickness and arsenic composition. This is explained by the variation of the band offset and hence the effective change in the position of the electronic energy level from Fermi level with QWs composition and thickness. The conduction band offset (ΔEc) for InAsxP1−x/InP QWs has been obtained by solving the self consistent set of Schrodinger and Poisson equations and fitting the theoretical carrier density profile with the apparent carrier density measured from experiments. The ΔEc values in strained InAsxP1−x/InP QWs have been obtained which fits to the expression ΔEc(x) = 402-350(1−x)meV for 0.38 <x <0.62.
Polymer-bonded NiZn ferrite magnetic cores mixed with titanium (IV) isopropoxide (C12H28O4Ti)
Authors: Cheng K. W. E. , Ding Kai , Ho S. L. , Fu W. N. , Wang Junhua , Wang Shuxiao
Published: April 2011

For decades, the technology and engineering domains have been constantly demanding high-performance magnetic materials. Recently, polymer bonded NiZn ferrite magnetic materials mixed with titanium (IV) isopropoxide (C12H28O4Ti) for power converter applications have been found to be very promising in reducing the loss, cost, and material weight when compared to their conventional counterparts using air-core technology, conventional soft ferrites, and powder iron. The proposed magnetic core is flexible in both size and shape and is not brittle. The design of a high-frequency transformer for a 100 W two-transistor forward converter-based electric vehicle battery charger operating at a switching frequency of 360 kHz is reported in this paper. Printed circuit board prototyping and experimental results as well as comparisons with conventional converters are provided to validate the application feasibility of the proposed materials.
Extendibility of traditional perpendicular magnetic recording for hard disk drives
Authors: Bain James A. , Vijaya Kumar B. V. K. , Cai Yu , Jeon Seungjune , Mai Ken , Messner William , Hin Sim Cheow , Wang Yiming , Zhu Jian-Gang
Published: April 2011

We present an analysis of the extendability of traditional perpendicular recording based on micromagnetic recording simulation and channel cost/performance analysis. The analysis indicates that head field gradient is the single most important factor in realizing densities above 1.0 Tb/in2. The conclusion of this analysis is that 1.5 Tb/in2 may be possible with this technology, but 2 Tb/in2 will be extremely challenging, perhaps impossible even with powerful channel chips. We also examine the extendibility of servo systems, and conclude that either actuator bandwidth must be increased by a factor of 2 from today’s drives or integrated disturbance power spectrum must be decreased by a factor of 2 to reach densities of 2 Tb/in2 and beyond.
The influence of media optical properties on the efficiency of optical power delivery for heat assisted magnetic recording
Authors: Powell Stephen P. , Black Eric J. , Schlesinger Tuviah E. , Bain James A.
Published: April 2011

We report simulation of optical power delivery for heat assisted magnetic recording that examines the effect of the medium optical properties. Power is delivered to the medium using a near field transducer (NFT), creating a hot spot with a full width at half maximum of 50 nm. Efficiency is computed as the ratio of power dissipated in the medium within the full width at half maximum of the spot to the reference power level incident on the NFT. This efficiency was computed for a range of real and imaginary indices of refraction (n and k, respectively) of the medium ranging from 0 to 5 at a free space wavelength of 828 nm. The results indicate a maximum coupling of 4% of the power within the hot spot for the relatively low n and k values of 1.2 and 0.6, respectively. A simple model of termination impedance is used to explain these n and k values.
Effect of initial particle size on phase transformation temperature of surfactant capped Fe3O4 nanoparticles
Authors: Ayyappan S. , Panneerselvam G. , Antony M. P. , Rama Rao N. V. , Thirumurugan N. , Bharathi A. , Philip John
Published: April 2011

We investigate the effect of particle size on reduction temperatures in surfactant capped fine iron oxide (Fe3O4) nanoparticles in size ranging from 7 to 3 nm using in situ high temperature X-ray diffraction (HTXRD). The 7 nm size particles are reduced to metallic α-Fe and FeO phase at 400°C and remains stable up to 600°C. On further heating, α-Fe phase grows at the expense of FeO and the growth process completes at 800°C. Above 900°C, α-Fe is converted to γ-Fe phase and at 1000°C, a part of γ-Fe phase is converted to α-Fe2O3. As the size is decreased from 7 to 3 nm, the onset of reduction to metallic Fe and FeO is enhanced by 100 to 200°C, due to the increased surface spin disorder. Irrespective of the initial particle size, the final phase obtained after annealing at 1000°C and cooled back to room temperature was a mixed phase of α-Fe and α-Fe2O3. Thermo Gravimetric Analysis coupled Mass Spectra (TGA-MS) confirm that the evolved carbon from the oleic acid assist the removal of oxygen atom from Fe3O4 lattice, facilitating the reduction of Fe3O4 into α-Fe and FeO. The magnetization data of the final products before and after vacuum annealing are consistent with final phases observed in the XRD.
The collapse of a bubble against infinite and finite rigid boundaries for underwater laser propulsion
Authors: Chen Jun , Han Bing , Li Bei-bei , Shen Zhong-Hua , Lu Jian , Ni Xiao-Wu
Published: April 2011

In order to investigate the influence of a bubble on underwater laser propulsion, the analytical formula of the bubble collapse time near rigid boundary is deduced from Rayleigh collapse time and Rattray prolongation factor. Experiments and numerical simulations are employed to validate the collapse time formula. The collapsing features of a bubble, including the maximum bubble radius Rmax, the collapse time of the bubble TCR, the shock wave and liquid jet emitted during the bubble collapse, are obtained near infinite and finite rigid boundaries. The theoretical, numerical and experimental results for the dimensionless distance γ > 1 all illuminate that TCR increases with Rmax near the rigid boundary. Rmax and TCR increase with the laser energy first, then begin to level out as the laser energy continues to increase, thus it is impossible to increase the propelling force just through increasing the laser pulse energy continuously. In addition, TCR is smaller, and the shock wave pressure and the liquid jet velocity are larger near the finite rigid boundary than that near the infinite rigid boundary, which means that the bubble collapses fiercer in the former case, in other words the finite rigid boundary gets more propelling force.
Effect of the tip–contact interaction on the MFM image of magnetic nanocontact
Authors: Kaneko Tomoaki , Imamura Hiroshi
Published: April 2011

MFM images of magnetic nanocontacts fabricated in nano-oxide layers are evaluated with special attention to the tip–contact interaction. We show that a sharp ring or arc signal with a diameter on the order of 100 nm appears while the diameter of the contact is on the order of 1 nm. We also show that the position of the sharp signal is determined by the competition between the forces due to the magnetic anisotropy in the contact and due to the tip–contact interaction.
Influence of asymmetric disks on control over the existence of vortex in submicrometer-scaled Permalloy disks
Authors: Huang Chao-Hsien , Wu Kuo-Ming , Wang Chih-Yi , Wu Jong-Ching , Horng Lance
Published: April 2011

The influence of the degree of asymmetry of a Py disk in a vortex configuration by changing an excised angle is studied in this paper. Samples of 40 nm thick NiFe disk arrays, with excised angles varying from 15° to 90° and diameters of 800, 500, and 300 nm, were investigated to observe the dependence of vortex nucleation and annihilation fields on the asymmetry and dimensions. Linear relations of vortex nucleation and annihilation fields to aspect ratio were found, and are useful mainly for controlling the nucleation and annihilation fields. Relationships between the vortex existence field and the aspect ratio, a thickness and diameter were found, and these should be taken into account when designing single vortex element applications.
Viscous fingering of a miscible reactive A+B→C interface for an infinitely fast chemical reaction: Nonlinear simulations
Authors: Nagatsu Y. , De Wit A.
Published: April 2011

Nonlinear dynamics of miscible viscous fingering is analyzed numerically for a reactive system when a solution containing a reactant A is displacing another miscible solution containing another reactant B. A simple A+B→C reaction takes place upon contact of the solutions. The viscosity of the fluid depends on the concentration of the various chemicals. The nonlinear fingering dynamics is studied numerically for an infinite Damköhler number Da, i.e., for an infinitely fast reaction as a function of the log-mobility ratios Rb and Rc quantifying the viscosity ratios of the solutions of B and C, respectively, versus that of the solution of A. If Rb>0, i.e., if the system is genuinely viscously unstable because the displacing solution of A is less viscous than the displaced solution of B, we analyze the changes to classical nonreactive viscous fingering induced by the reaction. If on the contrary Rb<0, which corresponds to a hydrodynamically stable case in absence of reactions, we study chemically driven viscous fingering occurring when the chemical reaction triggers a nonmonotonic viscosity profile. Comparison between the present simulation results and corresponding linear stability analysis and experiments is also conducted.
Nonlinear phononic crystals based on chains of disks alternating with toroidal structures
Authors: Spadoni A. , Daraio C. , Hurst W. , Brown M.
Published: April 2011

We study experimentally the acoustic response of a load-bearing, phononic crystal composed of alternating steel disks, and polytetrafluoroethylene o-rings under precompression. The crystal allows for axial, rocking, and shear-polarized wavemodes when excited by a broad-band signal applied off-axis. Finite element analysis is employed to determine the system’s wave modes. The nonlinear interaction between disks and o-rings supports a dynamic response that is tunable with variations in static precompression, leading to controllable frequency shifts in a large band gap. A modal analysis reveals that four of the six principal wave modes are susceptible to external precompression while two modes are not.
Critical tensile and compressive strains for cracking of Al2O3 films grown by atomic layer deposition
Authors: Jen Shih-Hui , Bertrand Jacob A. , George Steven M.
Published: April 2011

Al2O3 atomic layer deposition (ALD) is a model ALD system and Al2O3 ALD films are excellent gas diffusion barrier on polymers. However, little is known about the response of Al2O3 ALD films to strain and the potential film cracking that would restrict the utility of gas diffusion barrier films. To understand the mechanical limitations of Al2O3 ALD films, the critical strains at which the Al2O3 ALD films will crack were determined for both tensile and compressive strains. The tensile strain measurements were obtained using a fluorescent tagging technique to image the cracks. The results showed that the critical tensile strain is higher for thinner thicknesses of the Al2O3 ALD film on heat-stabilized polyethylene naphthalate (HSPEN) substrates. A low critical tensile strain of 0.52% was measured for a film thickness of 80 nm. The critical tensile strain increased to 2.4% at a film thickness of 5 nm. In accordance with fracture mechanics modeling, the critical tensile strains and the saturation crack densities scaled as (1/h)1/2 where h is the Al2O3 ALD film thickness. The fracture toughness for cracking, KIC, of the Al2O3 ALD film was also determined to be KIC = 2.30 MPa m1/2. Thinner Al2O3 ALD film thicknesses also had higher critical strains for cracking from compressive strains. Field-emission scanning electron microscopy (FE-SEM) images revealed that Al2O3 ALD films with thicknesses of 30–50 nm on Teflon fluorinated ethylene propylene (FEP) substrates cracked at a critical compressive strain of ∼1.0%. The critical compressive strain increased to ∼2.0% at a film thickness of ∼20 nm. A comparison of the critical tensile strains on HSPEN substrates and critical compressive strains on Teflon FEP substrates revealed some similarities. The critical strain was ∼1.0% for film thicknesses of 30–50 nm for both tensile and compressive strains. The critical compressive strain then increased more rapidly than the critical tensile strain for thinner films with thicknesses < 30 nm. The high critical tensile and compressive strains for thin Al2O3 ALD films should be very useful for flexible gas diffusion barriers on polymers.
Electroabsorption modulators based on bulk GaN films and GaN/AlGaN multiple quantum wells
Authors: Kao Chen-Kai , Bhattacharyya Anirban , Thomidis Christos , Paiella Roberto , Moustakas Theodore D.
Published: April 2011

Ultraviolet electroabsorption modulators based on bulk GaN films and on GaN/AlGaN multiple quantum wells were developed and characterized. In both types of devices, the absorption edge at room temperature is dominated by excitonic effects and can be strongly modified through the application of an external electric field. In the bulk devices, the applied voltage causes a broadening and quenching of the excitonic absorption, leading to enhanced transmission. In the quantum-well devices, the external field partially cancels the built-in polarization-induced electric fields in the well layers, thereby increasing the absorption. Unlike optical modulators based on smaller-bandgap zinc blende semiconductors, the bulk devices here are shown to provide similar performance levels as the quantum well devices, which is mainly a consequence of the uniquely large exciton binding energies of nitride semiconductors.
Tunable semiconductor vertical-cavity surface-emitting laser with an intracavity liquid crystal layer
Authors: Castany O. , Dupont L. , Shuaib A. , Gauthier J. P. , Levallois C. , Paranthoën C.
Published: April 2011

A tunable vertical-cavity surface-emitting laser is fabricated where tunability is achieved with an intracavity layer of nematic liquid crystal and gain is provided by a semiconductor quantum well structure. The anisotropic liquid crystal layer enables a continuously tunable single-mode emission along the extraordinary axis of the layer. Polarization control is achieved when the layer thickness is such that the ordinary modes are out of the spectral gain region. Laser emission in the 1.5μm telecom wavelength range is demonstrated under optical pumping with a tuning range of more than 30 nm for an applied voltage of less than 3 V.
Nonlinear capacitance and electrochemical response of ionic liquid-ionic polymers
Authors: Davidson Jacob D. , Goulbourne N. C.
Published: April 2011

In this paper we present a physics-based model for the electrochemical response of ionic liquid-ionic polymer transducers (IPTs) and show how the mobile ionic liquid ions influence the charging characteristics and actuation performance of a device. It is assumed that a certain fraction of the ionic liquid ions exist as “free,” making for a total of 3 mobile ions. This leads to predictions of distinctly different charging characteristics for ionic liquid versus water-based IPTs, since for the latter there is only a single mobile ion. The large ionic liquid ions are modeled by including steric effects in a set of modified Nernst-Planck/Poisson equations, and the resulting system of equations is solved using the method of matched asymptotic expansions (MAE). The inclusion of steric effects allows for a realistic description of boundary layer composition near actuator operating voltages (~1 V). Analytical expressions for the charge transferred and differential capacitance are derived as a function of the fraction of free ionic liquid ions, influence of steric effects in formation of the electric double layer, and applied voltage. It is shown that the presence of free ionic liquid ions tends to increase the overall amount of charge transferred, and also leads to a nonmonotonic capacitance-voltage curve. We suggest that these results could be used to experimentally identify the extent of free ionic liquid ion movement and to test the validity of the assumptions made in the underlying theory. A comparison with numerical results shows that while the MAE solution procedure gives valid results for capacitance and charge transferred, it cannot predict the dynamic response due to the presence of multiple time scales in the current decay. This is in contrast to previous results in analyzing water-based IPTs, where the MAE solution is in good agreement with numerical results at all times and applied voltages due to the presence of only a single mobile ion. By examining the structure of the electric double layer in the ionic liquid IPT, it is shown that although the additional mobile ions lead to more charge transferred, they likely do not increase the bending moment generated by a cantilevered IPT because of the increase in symmetry in boundary layer charge density profiles. These results are in good qualitative agreement with recent experiments.
Modeling and simulations of the spreading and destabilization of nematic droplets
Authors: Cummings L. J. , Lin T.-S. , Kondic L.
Published: April 2011

A series of experiments [C. Poulard and A. M. Cazabat, “Spontaneous spreading of nematic liquid crystals,” Langmuir 21, 6270 (2005)] on spreading droplets of nematic liquid crystal (NLC) reveals a surprisingly rich variety of behaviors. Small droplets can either be arrested in their spreading, spread stably, destabilize without spreading (corrugated surface), or spread with a fingering instability and corrugated free surface. In this work, we discuss the problem of NLC drops spreading in a simplified two-dimensional (2D) geometry. The model that we present is based on a long-wavelength approach for NLCs by Ben Amar and Cummings [“Fingering instabilities in driven thin nematic films,” Phys. Fluids 13, 1160 (2001); L. J. Cummings, “Evolution of a thin film of nematic liquid crystal with anisotropic surface energy,” Eur. J. Appl. Math. 15, 651 (2004)]. The improvements in the model here permit fully nonlinear time-dependent simulations. These simulations, for the appropriate choice of parameter values, exhibit 2D versions of most of the phenomena mentioned above.
Anomalous Hall effect in electron-doped Nd2−xCexCuO4+δ superconductor with nonstoichiometric disorder
Authors: Charikova T. B. , Shelushinina N. G. , Harus G. I. , Neverov V. N. , Petukhov D. S. , Sochinskaya O. E. , Ivanov A. A.
Published: April 2011

Magnetoresistivity and the Hall effect measured in magnetic fields up to B=9T (B∥c,J∥ab) in electron-doped Nd2−xCexCuO4+δ single crystal films with x=0.14, 0.15, and 0.18 and different oxygen contents (δ) were studied for temperatures in the range 0.4–4.2K. The behavior of the resistivity and Hall coefficient in the mixed state are discussed in terms of a flux-flow model including a vortex counterflow owing to pinning forces.
Occupation preferences in doped CmIm′ multinaries by correlated analysis of EXAFS and FTIR data
Authors: Robouch B. V. , Marcelli A. , Robouch P. , Kisiel A.
Published: April 2011

We discuss x-ray absorption fine structure (EXAFS) data for binary doped CmIm′ compound structures which can be deconvolved to determine elemental bond distances and the deviations from random configurations owing to site preference occupations (SOPs). The SOP-deviation estimates can be confirmed further by independent Fourier transform infrared (FTIR) data. The limits of our model are discussed.
Bose-Einstein condensation of dipolar excitons in lateral traps
Authors: Timofeev V. B. , Gorbunov A. V. , Demin D. A.
Published: April 2011

The phase diagram of Bose-Einstein condensates of dipolar excitons accumulated in lateral electrostatic traps is determined. Spatially periodic luminescence structures of the exciton Bose condensate and their critical dependence on pump level and temperature are observed. Coherence in the dipolar exciton Bose-Einstein condensates is studied by direct measurement of the 1-st and 2-nd order correlators with variations in pump level and temperature. These results are indicative of large-scale coherence of the exciton Bose condensate.
Gate-controlled current and inelastic electron tunneling spectrum of benzene: A self-consistent study
Authors: Liang Y. Y. , Chen H. , Mizuseki H. , Kawazoe Y.
Published: April 2011

We use density functional theory based nonequilibrium Green's function to self-consistently study the current through the 1,4-benzenedithiol (BDT). The elastic and inelastic tunneling properties through this Au–BDT–Au molecular junction are simulated, respectively. For the elastic tunneling case, it is found that the current through the tilted molecule can be modulated effectively by the external gate field, which is perpendicular to the phenyl ring. The gate voltage amplification comes from the modulation of the interaction between the electrodes and the molecules in the junctions. For the inelastic case, the electron tunneling scattered by the molecular vibrational modes is considered within the self-consistent Born approximation scheme, and the inelastic electron tunneling spectrum is calculated.
Two-bit-per-dot patterned media combining in-plane and perpendicular-to-plane magnetized thin films
Authors: Moritz J. , Vinai G. , Auffret S. , Dieny B.
Published: April 2011

We demonstrate the possibility of doubling the areal density of information in magnetic patterned media by stacking decoupled in-plane and perpendicular-to-plane magnetized layers. Each dot can be set in four magnetostatically equivalent configurations, yielding a storage capability of two-bits per dot. Magnetic force microscopy analyses show that the magnetic signal from the out-of-plane magnetized layer is dominant right above the dots, whereas, the signal from the in-plane magnetized layers is largest above the spacing between dots. This results in an optimal use of the storage space and in an increase of the areal density with weak loss in readout signal-to-noise ratio.
Image reconstruction from sparse data in synchrotron-radiation-based microtomography
Authors: Xia D. , Xiao X. , Bian J. , Han X. , Sidky E. Y. , De Carlo F. , Pan X.
Published: April 2011

Synchrotron-radiation-based microcomputed-tomography (SR-μCT) is a powerful tool for yielding 3D structural information of high spatial and contrast resolution about a specimen preserved in its natural state. A large number of projection views are required currently for yielding SR-μCT images by use of existing algorithms without significant artifacts. When a wet biological specimen is imaged, synchrotron x-ray radiation from a large number of projection views can result in significant structural deformation within the specimen. A possible approach to reducing imaging time and specimen deformation is to decrease the number of projection views. In the work, using reconstruction algorithms developed recently for medical computed tomography (CT), we investigate and demonstrate image reconstruction from sparse-view data acquired in SR-μCT. Numerical results of our study suggest that images of practical value can be obtained from data acquired at a number of projection views significantly lower than those used currently in a typical SR-μCT imaging experiment.
Multireference state-specific Mukherjee's coupled cluster method with noniterative triexcitations using uncoupled approximation
Authors: Bhaskaran-Nair Kiran , Demel Ondřej , Šmydke Jan , Pittner Jiří
Published: April 2011

A new version of the multireference Mukherjee's coupled cluster method with perturbative triexcitations has been formulated, which is based on the uncoupled approximation applied to the triples equation. In contrast to the method developed by Evangelista et al. [J. Chem. Phys. 132, 074107 (2010)], the proposed approach does not require to solve the equation for T3 amplitudes iteratively, yet yields results of essentially the same quality. The method, abbreviated as MR MkCCSD(Tu), has been implemented in the ACES II program package and its assessment has been performed on the BeH2 model and on the tetramethyleneethane molecule.
Nonlinear dynamics of tapping-mode atomic force microscopy in liquid
Authors: Korayem M. H. , Ebrahimi N.
Published: April 2011

One problem in imaging is due to coexistence of double stable responses which can reduce the precision of the images. Our target is comparing coexistence of double responses in liquid with responses obtained in air. Contact forces have some differences in liquid in comparison to air in magnitude and in the formulation. Hydrodynamic forces are also applied on the cantilever. This may change the nonlinear dynamics of tapping-mode Atomic Force Microscopy (AFM) in liquid in comparison to air. In this paper, we have simulated a tapping-mode AFM (TMAFM) cantilever in liquid environment and explored the existence of multi responses in amplitude and phase diagrams. For modeling we have used a continuous beam model with its first mode and forward-time simulation method for the solution of its hybrid dynamics. Frequency response results of the simulation show a good agreement with experiments. The results for studying the nonlinear dynamics of an AFM microcantilever show that while there are two stable responses in air, in liquid just one response exists. Amplitude diagrams show that there is not any shift from low amplitude to high amplitude and both diagrams of sweeping up and down of the driving frequency coincide on each other. Average force diagrams show that in liquid there is not any repulsive regime and the magnitude of attractive force is small too. Sensitivity analysis for studying the effect of the free amplitude shows that in common setpoints double responses do not occur in liquid. Frequency response results show that just in driving frequencies larger than the resonance frequency of the microcantilever in liquid double responses can occur.
Robust high-temperature magnetic pinning induced by proximity in YBa2Cu3O7−δ/La0.67Sr0.33MnO3 hybrids
Authors: Chen C. Z. , Liu Z. Y. , Lu Y. M. , Zeng L. , Cai C. B. , Zeng R. , Dou S. X.
Published: April 2011

An elaborately designed bilayer consisting of superconducting YBa2Cu3O7−δ (YBCO) and ferromagnetic La0.67Sr0.33MnO3−δ (LSMO) was prepared on a single crystal LaAlO3 substrate by pulsed laser deposition (PLD), with a view to understanding the mechanism behind the influence of superconductor/ferromagnet proximity on the critical current density, Jc. The present bilayer system shows significant modifications in Jc, as evidenced by the suppressed decay of its temperature dependence, as well as the crossing behavior of the magnetic field dependence of Jc at high temperatures. This indicates that enhanced flux pinning emerges at high temperatures, and it is believed to arise from the special magnetic inhomogeneity, i.e., the ferromagnet/antiferromagnet clusters caused by phase separation due to the epitaxial stress between LSMO and the substrate.