bluuebunny/crossref_metadata_2025 huggingface dataset:
Trust, confidence and social environment in post-communist societies
Authors: Sapsford Roger , Abbott Pamela
Published: February 2006

This paper looks at trust and confidence in people and institutions in eight of the countries that have undergone transformation since the breakup of the Soviet Union. While the questions are not identical to those asked in previous research in post-Soviet societies, our findings are comparable—greatest trust in relatives and friends, less in people in general and least in politicians and institutions of social control. Levels of trust are not high, and there are interesting differences between the countries, giving support to the view that trust and confidence are eroded by sudden and dramatic negatively perceived change.
Variation of biomechanical, structural, and compositional properties along the tendon to bone insertion site
Authors: Thomopoulos Stavros , Williams Gerald R. , Gimbel Jonathan A. , Favata Michele , Soslowsky Louis J.
Published: February 2006

The tendon to bone insertion site is a complex transitional region that links two very different materials. The insertion site must transfer a complex loading environment effectively to prevent injury and provide proper joint function. In order to accomplish this load transfer effectively, the properties of the insertion site were hypothesized to vary along its length. The quasilinear viscoelastic (QLV) Model was used to determine biomechanical properties, polarized light analysis was used to quantitate collagen orientation (structure), and in situ hybridization was used to determine the expression of extracellular matrix genes (composition). All assays were performed at two insertion site locations: the tendon end of the insertion and the bony end of the insertion. Biomechanically, the apparent properties of peak strain, the coefficients (A and B) that describe the elastic component of the QLV model, and one of the coefficients (τ1) of the viscous component of the model were significantly higher, while another of the coefficients (C) of the viscous component was significantly lower at the tendon insertion compared to the bony insertion. The collagen was significantly more oriented at the tendon insertion compared to the bony insertion. Finally, collagen types II, IX, and X, and aggrecan were localized only to the bony insertion, while decorin and biglycan were localized only to the tendon insertion. Thus, the tendon to bony insertion site varies dramatically along its length in terms of its viscoelastic properties, collagen structure, and extracellular matrix composition.

© 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.
The HPA and immune axes in stress: the involvement of the serotonergic system
Authors: Leonard B.E.
Published: February 2006

The impact of acute and chronic stress on the hypothalamic-pituitary-adrenal (HPA) axis is reviewed and evidence presented that corticotrophin releasing factor (CRF) is the stress neurotransmitter which plays an important role in the activation of the central sympathetic and serotonergic systems. The activity of CRF is expressed through specific receptors (CRF 1 and 2) that are antagonistic in their actions and widely distributed in the limbic regions of the brain, as well as in the hypothalamus, and on immune cells.

The mechanism whereby chronic stress, via the CRF induced activation of the dorsal raphe nucleus, can induce a change in the serotonergic system, involves an increase in the 5HT2A and a decrease in the 5HT1A receptor mediated function. Such changes contribute to the onset of anxiety and depression. In addition, the hypersecretion of glucocorticoids that is associated with chronic stress and depression desensitises the central glucocorticoid receptors to the negative feedback inhibition of the HPA axis. This indirectly results in the further activation of the HPA axis.

The rise in pro-inflammatory cytokines that usually accompanies the chronic stress response results in a further stimulation of the HPA axis thereby adding to the stress response. While CRF would appear to play a pivotal role, evidence is provided that simultaneous changes in the serotonergic and noradrenergic systems, combined with the activation of peripheral and central macrophages that increase the pro-inflammatory cytokine concentrations in the brain and blood, also play a critical role in predisposing to anxiety and depression. Neurodegenerative changes in the brain that frequently occur in the elderly patient with major depression, could result from the activation of indoleaminedioxygenase (IDO), a widely distributed enzyme that converts tryptophan via the kynenine pathway to for the neurotoxic end product quinolinic acid.
Quality of life measures in schizophrenia
Authors: Bobes J. , García-Portilla P. , Sáiz P.A. , Bascarán T. , Bousoño M.
Published: February 2006

The recognition of the importance of evaluating the quality of life of patients with schizophrenia highlighted the importance ofdeveloping appropriate instruments. In this paper we review the available quality of life instruments focusing on their conceptual framework, structure, administration and psychometric properties. First, we address the generic instruments that have been validated for schizophrenic populations, namely the World Health Organization Quality of Life Assessment (WHOQOL), the Medical Outcome Study (MOS) 36-Item Short-Form Health Survey (SF-36) and the EuroQoL-5 Dimensions (EQ-5D). Then, we focus on instruments that have been specifically developed for patients with schizophrenia and other or severe mentally illness such as the Quality of Life Scale (QLS), the Quality of Life Interview (QoLI), the Lancashire Quality of Life Profile (LQoLP), the Sevilla Quality of Life Questionnaire (SQLQ), the Personal Evaluation of Transitions in Treatment (PETIT), and the Quality of Life Questionnaire in Schizophrenia (S-QoL).
Schizophrenia and diabetes: Epidemiological data
Authors: Rouillon F. , Sorbara F.
Published: February 2006

The association of diabetes mellitus and mental illness, in particular, schizophrenia, has been remarked upon for over a century. Recentepidemiological studies have shown the age- and sex-matched prevalence of diabetes in patients with schizophrenia to be 1.5–2 times those in the general population. This difference is particularly noticeable in younger patients. The explanation for this finding probably resides in both environmental and biological factors. Patients with schizophrenia tend to be sedentary and have a poor diet, which are both known risk factors for diabetes. However, familial studies have indicated a heritable component to the risk of diabetes in patients with schizophrenia. A number of biological mechanisms have been proposed to explain this, including neuroendocrine changes and neurodevelopmental anomalies, but none are entirely satisfactory. In addition, it has been suggested that treatment with antipsychotic medication may potentially increase the risk of diabetes and account for some of the increased prevalence seen in patients with schizophrenia. It has been suggested that different antipsychotic drugs may differ in their ability to facilitate the emergence of poor glycaemic control in patients with schizophrenia. However, the situation is far from clear and more work is required to accurately assess the potential risk associated with different antipsychotic drugs.
Evidence for rapid environmental changes in low latitudes during the Late Silurian Lau Event: the Burgen-1 drillcore, Gotland, Sweden
Authors: CALNER MIKAEL , ERIKSSON MÅRTEN J.
Published: February 2006

Erosional outliers are an important component of the Ludlow (Late Silurian) stratigraphy of Gotland, Sweden. However, due to the poor degree of exposure, outcrop studies have not revealed a detailed section from any of these outliers. The first complete stratigraphy of such an erosional remnant, the Burgen outlier, is presented here, based on the recently recovered Burgen-1 drillcore. Stratigraphical units encountered are, from oldest to youngest, the uppermost Hemse Group (>35 m), Eke Formation (0.4 m), Burgsvik Formation (3.4 m) and the basal Hamra Formation (12 m preserved). Based on carbon stable isotopes and lithological correlation to nearby outcrops that are zoned by conodonts, it can be concluded that the most profound late Ludlow sedimentary changes took place shortly after the onset of the globally recognized Lau Event (δ13C values reach 8.7 ‰ in the lower Hamra Formation). Sedimentary changes include development of discontinuity surfaces, widespread occurrence of an intraclastic conglomerate, increased microbial activity (Rothpletzella and Wetheredella), and influx of clastics to the basin. These changes are linked to substantial base-level changes during the event. A general comparison with the Prague basin suggests contemporaneous sedimentary changes on Baltica and on cratonic elements from peri-Gondwana during the event.
Impacts of breeding on international collaborative wheat improvement
Authors: REYNOLDS M. P. , BORLAUG N. E.
Published: February 2006

For over 40 years a collaborative network of publicly funded international wheat scientists has made a significant contribution to food security in the developing world. Thousands of modern wheat varieties (MVs) have been released for use in both favourable and marginal environments on well over 50 million hectares. The yield increases associated with genetic improvement in yield potential and adaptation to biotic and abiotic stresses are well documented. Millions of small-scale farmers in the developing world have benefited. While this so-called ‘Green Revolution’ displaced landraces in favour of more productive MVs, these and other genetic resources, held in trust by international organizations, have been utilized to improve the inherent genetic diversity of modern varieties. Furthermore, the result of increased yields reduced the need to bring natural ecosystems under cultivation, by as much as a billion hectares.

Although international wheat breeding has its origins in the 1940s, recognition of a common scientific basis of agricultural problems worldwide was highlighted by the creation of International Agricultural Research Centres (IARCs) which included the International Maize and Wheat Improvement Centre (CIMMYT) established in 1965. This grew into a larger network called the Consultative Group for International Agricultural Research (CGIAR) now comprising 15 IARCs, including the International Centre for Agricultural Research in the Dry Areas (ICARDA) established in Syria in 1977, another key player in the international wheat and barley breeding network. Two of the major coordination responsibilities of CIMMYT are maintaining the world collection of wheat genetic resources – a public good protected by international treaty – and the facilitation of the International Wheat Nurseries.

After the initial impact of the Green Revolution in high production zones through exploitation of Rht-B1 and Rht-D1 dwarfing genes in conjunction with disease resistance, international breeding encompassed more challenging environments through, for example, international shuttle breeding between Brazil and Mexico to overcome problems associated with acid soils that restricted adoption of MVs. Another example is drought, which affects at least 30 million ha of wheat in the developing world. The approach focused initially on exploiting the inherent yield potential and disease resistance of MVs and later combined this with new stress-adaptive traits from wild wheat ancestors through wide crossing techniques. Adoption of modern varieties has increased substantially in drier areas between 1990 and 1997. In all environments, possibly the greatest threat to productivity is disease, especially those caused by fungal pathogens. International wheat breeding has placed great emphasis on genetic control of disease since resource-poor farmers generally lack the means to control diseases chemically.
Implications of increased susceptibility to predation for managing the sylvatic cycle ofEchinococcus multilocularis
Authors: VERVAEKE M. , DAVIS S. , LEIRS H. , VERHAGEN R.
Published: February 2006

The ability to increase the chances that infectious prey are taken by predators is an observed feature of many parasites that rely on one or more predator-prey relationships to complete their life-cycle. In the sylvatic life-cycle ofEchinococcus multilocularis– the causative agent of human alveolar echinococcosis – foxes are the final host, with voles acting as intermediate hosts. Here we review the evidence thatE. multiloculariscauses increased susceptibility to predation and present a general mathematical model for the sylvatic life-cycle. The ability to increase susceptibility to predation in the intermediate host reduces the sensitivity of the parasite population to adverse conditions. For example, there is no critical density of foxes below which the parasite is expected to die out, even if the effect of the parasite on infected prey is very small. We suggest that increased susceptibility to predation is a plausible explanation for the observed resilience ofE. multilocularisduring and following field trials of praziquantel baiting.
The spectrum of congenital cardiac malformations encountered in six children with Kabuki syndrome
Authors: McMahon Colin J. , Reardon William
Published: February 2006

We investigated the prevalence and forms of congenital cardiac malformations in six children with Kabuki syndrome. There were three girls and three boys, diagnosed at a median age of 1.7 years, with a range from 0.7 to 11.1 years. Cardiac lesions were present in five children (83%), specifically complete transposition, tetralogy of Fallot, coarctation of the aorta, ventricular septal defect, and patency of the arterial duct. Characteristic dysmorphic findings were noted in all patients, as well as a strong predisposition to severe problems with feeding in the neonatal period, and developmental delay. Cardiologists should be alert to this syndrome in children who present with the aforementioned constellation of findings, as patients with mild expression of Kabuki syndrome may go unrecognized for a considerable time.
Exercise performance in children and adolescents after the Ross procedure
Authors: Marino Bradley S. , Pasquali Sara K. , Wernovsky Gil , Bockoven John R. , McBride Michael , Cho Catherine J. , Spray Thomas L. , Paridon Stephen M.
Published: February 2006

Objectives:The Ross procedure is increasingly utilized in the treatment of aortic valvar disease in children and adolescents. Our purpose was to compare pre- and post-operative exercise state in this population.Methods:We included patients who underwent the Ross procedure at our institution between January, 1995, and December, 2003, and in whom we had performed pre- and post-operative exercise stress tests. We used a ramp bicycle protocol to measure consumption of oxygen and production of carbon dioxide. Cardiac output was estimated from effective pulmonary blood flow by the helium acetylene re-breathing technique.Results:We studied 26 patients, having a median age at surgery of 15.7 years, with a range from 7.5 to 24.1 years. The primary indication for surgery in two-thirds was combined aortic stenosis and insufficiency. Median time from the operation to the post-operative exercise stress test was 17.4 months, with a range from 6.7 to 30.2 months. There was a trend toward lower maximal consumption of oxygen after the procedure, at 36.3 plus or minus 7.6 millilitres per kilogram per minute (83.9% predicted) as opposed to 38.6 plus or minus 8.4 millilitres per kilogram per minute (88.5% predicted, p equal to 0.06). Patients after the procedure, however, had significantly increased adiposity, so that there was no difference in maximal consumption of oxygen indexed to ideal body weight before and after the operation. In 20 of the patients, aerobic capacity improved or was stable after the operation. There was no post-operative chronotropic impairment.Conclusions:In the majority of patients following the Ross procedure, exercise performance is stable and within the normal range of a healthy age and sex matched population, despite sedentary lifestyles and increased adiposity.
Post-mortem magnetic resonance imaging provides the diagnosis following aortic rupture in an infant with treated aortic interruption
Authors: Taylor Andrew M. , Jones Rod , Derrick Graham
Published: February 2006

In the United Kingdom, there has been a steady decline in the number of conventional autopsies performed in children. For cardiovascular disease, structural and not pathological considerations are often more important in defining the cause of death. Magnetic resonance imaging is now often used in the assessment of congenital cardiac malformations during life. In this case report, we demonstrate how post-mortem magnetic resonance imaging was able to establish the diagnosis of aortic rupture in a patient who had undergone surgical repair of aortic interruption. In this patient, the parents had declined conventional histopathological autopsy, but were happy to consent to magnetic resonance post-mortem assessment.
Schumann resonances as a tool to study the lower ionospheric structure of Mars
Authors: Molina‐Cuberos G. J. , Morente J. A. , Besser B. P. , Portí J. , Lichtenegger H. , Schwingenschuh K. , Salinas A. , Margineda J.
Published: February 2006

The study of the propagation of extremely low frequency (ELF) waves is essential for electromagnetic sounding investigations planned for some of the future Martian missions. Future surface stations will have the possibility of continuously recording low‐frequency electromagnetic field fluctuations. Natural electromagnetic waves produced near the surface by electrostatic discharges in dust storms (dust devils) or by geological activity can be trapped in the resonant cavity formed by the surface and lower ionosphere as it occurs on the Earth. Low‐frequency electromagnetic waves can also travel along the magnetic field lines of the recently discovered magnetic anomalies from the magnetosphere to the surface and may produce resonant structures in the cavity. The structure of the resonant frequencies, also called Schumann frequencies, is mainly determined by the geometry of the cavity and by the global electrical conductivity of the ionosphere/atmosphere. Measurements of Schumann frequencies by surface stations can be used for remote sensing of the electrical conductivity of the lower ionosphere/atmosphere. We present a numerical model of electromagnetic wave propagation based on the transmission line modeling (TLM) method with the aim of calculating the resonance frequencies on Mars and their dependence on solar activity and various possible ionization sources like meteoroids. The model has been previously validated by application to the terrestrial case. The numerical results obtained for the Earth are very close to the experimental ones, which supports our predictions on Mars. Our model can be used to study the global atmospheric conductivity using future real ELF measurements by surface stations or even balloons on Mars.
Unusual magnetic signature of the Hadriaca Patera Volcano: Implications for early Mars
Authors: Lillis R. J. , Manga M. , Mitchell D. L. , Lin R. P. , Acuna M. H.
Published: February 2006

Typically, Martian volcanoes show either a total absence of crustal magnetism or a local magnetic mimimum. Hadriaca Patera is the only volcano on Mars with a clear positive magnetic anomaly directly over the volcanic edifice, as determined by electron reflection magnetometry. Hadriaca's topography, lava flow crater ages, gravity anomaly, position relative to the Hellas rim and past aqueous environment provide geological constraints on possible scenarios to explain this unusual magnetic signature. The two most probable scenarios are a) pre‐Hellas thermoremanent magnetization (TRM) of a deep‐seated magma body followed by post‐Hellas intrusive partial thermal demagnetization and b) post‐Hellas emplacement of the volcano and TRM in a global magnetic field. It is thus likely that Mars had at least one of the following: highland volcanism in pre‐Hellas times (older than any datable volcanic feature on the planet) or an active dynamo some time after the Hellas impact.
Projected changes in mean and extreme precipitation over the Mediterranean region from a high resolution double nested RCM simulation
Authors: Gao Xuejie , Pal Jeremy S. , Giorgi Filippo
Published: February 2006

Results are presented from high resolution climate change simulations over the Mediterranean region using the ICTP Regional Climate Model, RegCM3. Two sets of multi‐decadal simulations are performed at 20‐km grid spacing for present day and future climate (IPCC A2 scenario). We analyze changes in precipitation mean and extremes and find that the change signal shows seasonally dependent fine scale structure in response to the topographic forcing and changes in circulation, especially over the Alpine region and the Iberian, Italian and Hellenic peninsulas. In winter, the mean precipitation change is positive in the Northern Mediterranean regions and negative in the Southern Mediterranean, while precipitation in the other seasons mostly decreases (especially in summer), except over some localized areas. Changes in extreme precipitation events and dry spells suggest not only shifts, but also a broadening, of the precipitation distribution, with an increased probability of occurrence of events conducive to both floods and droughts.
Crystal structure and equation of state of MgSiO3 perovskite
Authors: Vanpeteghem C. B. , Zhao J. , Angel R. J. , Ross N. L. , Bolfan‐Casanova N.
Published: February 2006

We have re‐examined the crystal structure and equation of state of MgSiO3 perovskite by single‐crystal X‐ray diffraction up to 10 GPa. We have determined an isothermal bulk modulus K0 = 253(1) GPa with K′0 = 4, which is in excellent agreement with the adiabatic bulk moduli reported in recent studies by Brillouin spectroscopy and ultrasonic interferometry. We confirm that the compressibility of perovskite is anisotropic with the b‐axis being the least compressible direction. On compression, the bond lengths and angles on Mg‐site and Si‐site decrease continuously, indicating that the structure gets more distorted as pressure increases. This is supported by a general model for perovskites that predicts that the octahedra become more tilted at lower mantle pressures.
Energy flux of nonlinear internal waves in northern South China Sea
Authors: Chang Ming‐Huei , Lien Ren‐Chieh , Tang Tswen Yung , D'Asaro Eric A. , Yang Yiing Jang
Published: February 2006

We analyze three sets of ADCP measurements taken on the Dongsha plateau, on the shallow continental shelf, and on the steep continental slope in the northern South China Sea (SCS). The data show strong divergences of energy and energy flux of nonlinear internal waves (NLIW) along and across waves' prevailing westward propagation path. The NLIW energy flux is 8.5 kW m−1 on the plateau, only 0.25 kW m−1 on the continental shelf 220 km westward along the propagation path, and only 1 kW m−1 on the continental slope 120 km northward across the propagation path. Along the wave path on the plateau, the average energy flux divergence of NLIW is ∼0.04 W m−2, which corresponds to a dissipation rate of O(10−7−10−6) W kg−1. Combining the present with previous observations and model results, a scenario of NLIW energy flux in the SCS emerges. NLIWs are generated east of the plateau, propagate predominantly westward across the plateau along a beam of ∼100 km width that is centered at ∼21°N, and dissipate nearly all their energy before reaching the continental shelf.
Processing of Mars Exploration Rover imagery for science and operations planning
Authors: Alexander Douglass A. , Deen Robert G. , Andres Paul M. , Zamani Payam , Mortensen Helen B. , Chen Amy C. , Cayanan Michael K. , Hall Jeffrey R. , Klochko Vadim S. , Pariser Oleg , Stanley Carol L. , Thompson Charles K. , Yagi Gary M.
Published: February 2006

The twin Mars Exploration Rovers (MER) delivered an unprecedented array of image sensors to the Mars surface. These cameras were essential for operations, science, and public engagement. The Multimission Image Processing Laboratory (MIPL) at the Jet Propulsion Laboratory was responsible for the first‐order processing of all of the images returned by these cameras. This processing included reconstruction of the original images, systematic and ad hoc generation of a wide variety of products derived from those images, and delivery of the data to a variety of customers, within tight time constraints. A combination of automated and manual processes was developed to meet these requirements, with significant inheritance from prior missions. This paper describes the image products generated by MIPL for MER and the processes used to produce and deliver them.
Behavior of a drop on an oscillating solid plate
Authors: Lyubimov Dmitry V. , Lyubimova Tatyana P. , Shklyaev Sergey V.
Published: February 2006

Oscillations of a nominally hemispherical, inviscid drop on a solid plate are considered accounting for the contact line dynamics. Hocking boundary conditions hold on the contact line: the velocity of the contact line is proportional to the deviation of the contact angle from its equilibrium value. Natural oscillations of a drop are studied, and both eigenfrequencies and damping ratios are determined for the axisymmetric modes. The linear oscillations caused by normal vibration of the substrate are considered. Well-pronounced resonant phenomena are revealed. The nonlinear oscillations of a drop are studied.
Enhanced strain of InAs quantum dots by an InGaAs ternary layer in a GaAs matrix
Authors: Shin Hyunho , Kim Jong-Bong , Yoo Yo-Han , Lee Woong , Yoon Euijoon , Yu Young-Moon
Published: February 2006

The present work demonstrates via numerical analysis that the presence of a thin InGaAs ternary layer around InAs quantum dots (QDs) reinforces the in-plane (εrr) and vertical (εzz) strain components of InAs quantum dots as compared to the QDs embedded directly in GaAs matrix, contrary to the general belief of strain relief. It has been further shown that such reinforced εrr and εzz states yields a decreased band-gap energy, i.e., the experimentally observed redshift in the literature.
The application of a vacuum-ultraviolet Fourier transform spectrometer and synchrotron-radiation source to measurements of bands of NO. VII. The final report
Authors: Yoshino K. , Thorne A. P. , Murray J. E. , Cheung A. S.-C. , Wong A. L. , Imajo T.
Published: February 2006

Photoabsorption measurements of NO bands have been made by vacuum-ultraviolet Fourier transform spectrometry with a resolution of 0.12cm−1 in the wavelength region of 166.2–196.2 nm. Accurate line positions are obtained for the δ(υ,0) bands with υ=2, 3, the ϵ(υ,0) bands with υ=2, 3, and the β(υ,0) bands with υ=10,12,14. Absolute term values are found for the corresponding upper levels C(2,3), D(2,3), and B(10,12,14). Accurate rotational line integrated cross sections have also been obtained for the lines in these bands. Integrated cross sections reported in our earlier papers [J. Chem. Phys. 109, 1751 (1998); 112, 2251 (2000); 115, 3719 (2001); 116, 155 (2002); 117, 10621 (2002); 119, 8373 (2003)] have been revised, and the results reported here comprise the δ(υ,0) bands with υ=0–3, the ϵ(υ,0) bands with υ=0–3, the β(υ,0) bands with υ=6,7,9–12,14, and the γ(3,0) band. For each band, the band oscillator strength is obtained from the sum of the line strengths of all rotational lines, and these are compared with other published values.
On unidirectional flight of a free flapping wing
Authors: Vandenberghe Nicolas , Childress Stephen , Zhang Jun
Published: February 2006

We study the dynamics of a rigid, symmetric wing that is flapped vertically in a fluid. The motion of the wing in the horizontal direction is not constrained. Above a critical flapping frequency, forward flight arises as the wing accelerates to a terminal state of constant speed. We describe a number of measurements which supplement our previous work. These include (a) a study of the initial transition to forward flight near the onset of the instability, (b) the separate effects of flapping amplitude and frequency, (c) the effect of wing thickness, (d) the effect of asymmetry of the wing planform, and (e) the response of the wing to an added resistance. Our results emphasize the robustness of the mechanisms determining the forward-flight speed as observed in our previous study.
Flow of evaporating, gravity-driven thin liquid films over topography
Authors: Gaskell P. H. , Jimack P. K. , Sellier M. , Thompson H. M.
Published: February 2006

The effect of topography on the free surface and solvent concentration profiles of an evaporating thin film of liquid flowing down an inclined plane is considered. The liquid is assumed to be composed of a resin dissolved in a volatile solvent with the associated solvent concentration equation derived on the basis of the well-mixed approximation. The dynamics of the film is formulated as a lubrication approximation and the effect of a composition-dependent viscosity is included in the model. The resulting time-dependent, nonlinear, coupled set of governing equations is solved using a full approximation storage multigrid method. The approach is first validated against a closed-form analytical solution for the case of a gravity-driven, evaporating thin film flowing down a flat substrate. Analysis of the results for a range of topography shapes reveal that although a full-width, spanwise topography such as a step-up or a step-down does not affect the composition of the film, the same is no longer true for the case of localized topography, such as a peak or a trough, for which clear nonuniformities of the solvent concentration profile can be observed in the wake of the topography.
Binary Ni–Nb bulk metallic glasses
Authors: Xia L. , Li W. H. , Fang S. S. , Wei B. C. , Dong Y. D.
Published: February 2006

We studied the glass forming ability of Ni–Nb binary alloys and found that some of the alloys can be prepared into bulk metallic glasses by a conventional Cu-mold casting. The best glass former within the compositional range studied is off-eutectic Ni62Nb38 alloy, which is markedly different from those predicted by the multicomponent and deep eutectic rules. The glass formation mechanism for binary Ni–Nb alloys was studied from the thermodynamic point of view and a parameter γ* was proposed to approach the ability of glass formation against crystallization.
Dielectric and magnetic properties of sol-gel-derived lead iron niobate ceramics
Authors: Majumder S. B. , Bhattacharyya S. , Katiyar R. S. , Manivannan A. , Dutta P. , Seehra M. S.
Published: February 2006

In this work, we report the synthesis of sol-gel-derived lead iron niobate [Pb1.10(Fe0.5Nb0.5)O3] (PFN) powders and sintered ceramics. The PFN powders were calcined at (Ta), 973, 1073, 1173, 1273, and 1373 K for 3 h in air. As envisaged from x-ray-diffraction analyses, PFN powder calcined at 1173 K was crystallized into pure monoclinic perovskite phase whereas powders calcined at all other temperatures had varied amounts of retained pyrochlore (Pb3Nb4O13) phase coexisted with dominant monoclinic perovskite phase. The PFN pellet (prepared using the phase pure powder calcined at 1173 K) sintered at 1373 K for 4 h in air also had a minute quantity of retained pyrochlore phase coexisting with desired perovskite phase. From the temperature dependence of measured capacitance and loss tangent at different frequencies, the ferroelectric to paraelectric phase-transition temperature of PFN ceramics was observed at Tc≈370K. The diffused nature of this transition and high dielectric constant of PFN is related to the cation disorder at the B site of A(BI+3BII+5)O3 lattice. For PFN powders, calcined at different temperatures, the temperature dependence of the magnetic susceptibility (χ) was measured in a temperature range of 2–360 K, whereas the magnetic hysteresis loops and electron magnetic resonance (EMR) spectra were measured at room temperature. Room-temperature ferromagnetism is observed in all the calcined powder samples and it was found that the magnetization increases with the increase in calcination temperature (Ta). The symmetric EMR line shape with g≈2.01 observed in all calcined samples was identified to be due to Fe3+ ions. It is suggested that the observed weak ferromagnetism, which increases with an increase in Ta, may be due to canting of the Fe3+ spins. These observations suggest PFN to be a very attractive single-phase ferroelectric/ferromagnetic material for room-temperature applications.
Drain current overshoot transient in polycrystalline silicon transistors: The effect of hole generation mechanism
Authors: Exarchos M. , Papaioannou G. J. , Kouvatsos D. N. , Voutsas A. T.
Published: February 2006

We have investigated the overshoot effect of switch-on transients of polycrystalline silicon thin-film transistors. The investigation has been performed with devices fabricated on laterally grown polycrystalline silicon films having very long crystal domains. These films were crystallized by excimer-laser annealing and had a thickness in the range of 30–100 nm. The measurement of the switch-on transients reveals that the device transient behavior depends significantly on both temperature and illumination conditions. The temperature dependence, under dark state or under illumination, suggests that the mechanism accountable for the transient behavior of thin-film transistors cannot be attributed only to carrier trapping, but rather to a more complex mechanism involving carrier generation and recombination in the device body. This allows the estimation of the dependence of generation lifetime on the polycrystalline film thickness.
Galerkin analysis of kinematic dynamos in the von Kármán geometry
Authors: Marié L. , Normand C. , Daviaud F.
Published: February 2006

We investigate dynamo action by solving the kinematic dynamo problem for velocity fields of the von Kármán type between two coaxial counter-rotating propellers in a cylinder. A Galerkin method is implemented that takes advantage of the symmetries of the flow and their subsequent influence on the nature of the magnetic field at the dynamo threshold. Distinct modes of instability have been identified that differ by their spatial and temporal behaviors. Our calculations give the result that a stationary and antisymmetric mode prevails at the dynamo threshold. We then present a quantitative analysis of the results based on the parametric study of four interaction coefficients obtained by reduction of our initially large eigenvalue problem. We propose these coefficients to measure the relative importance of the different mechanisms at play in the von Kármán kinematic dynamo.
Effect of overall drop deformation on flow-induced coalescence at low capillary numbers
Authors: Baldessari Fabio , Leal L. Gary
Published: February 2006

Comparison of recent experimental results for flow-induced drop coalescence [H. Yang, C. C. Park, Y. T. Hu et al., “The coalescence of two equal-sized drops in a two-dimensional linear flow,” Phys. Fluids13, 1087 (2001)] with existing theory provides the motivation for an examination of the theory. Specifically, for head-on collisions, the experiments show a plateau in the dependence of drainage time versus capillary number at low capillary number that could not be explained by either the existing scaling analysis or the existing thin-film theory of the film drainage process previously described in the pioneering work of Davis and co-workers [S. G. Yiantsios and R. H. Davis, “Close approach and deformation of two viscous drops due to gravity and van der Waals forces,” J. Colloid Interface Sci. 144, 412 (1991); R. H. Davis, J. A. Schonberg, and J. M. Rallison, “The lubrication force between two viscous drops,” Phys. Fluids A 1, 77 (1989); M. A. Rother, A. Z. Zinchenko, and R. H. Davis, “Buoyancy-driven coalescence of slightly deformable drops,” J. Fluid Mech. 346, 117 (1997); S. G. Yiantsios and R. H. Davis, “On the buoyancy-driven motion of a drop towards a rigid surface or a deformable interface,” J. Fluid Mech. 217, 547 (1990)]. Both of these results indicate that the existing theories, while fundamentally correct in concept, are incomplete in providing a framework for a comprehensive explanation of the experimental results. In the present paper, we reexamine the thin-film theory of Davis et al. in the low capillary number limit. We find that a quasistatic model in which deformation is localized within the thin film is in general not sufficient to describe the leading-order asymptotic approximation of the flow-induced collision and coalescence of two slightly deformable drops at low capillary number. Instead, the overall deformation induced in the drops by the external flow plays a key role in determining the initial film thickness needed for numerical simulation of the thin-film dynamics via the existing theoretical framework. Also, we find that including retardation effects is important to be able to make quantitatively accurate predictions, especially at viscosity ratios below O(1).
Holographic particle image velocimetry measurements of hairpin vortices in a subcritical air channel flow
Authors: Svizher Alexander , Cohen Jacob
Published: February 2006

A holographic particle image velocimetry (HPIV) system is employed to study the evolution of coherent structures artificially generated in a plane Poiseuille air flow. As a first step the hot-wire technique and two-dimensional flow visualization are used to determine the generation conditions and dimensions of the coherent structures, their shedding frequency, trajectory, and convection velocity. Then, the HPIV method is utilized to obtain the instantaneous topology of the hairpin vortex and its associated three-dimensional distribution of the two (streamwise and spanwise) velocity components as well as the corresponding wall-normal vorticity. Finally, the experimental data are compared with results of related experimental and numerical studies. The present experimental results support the view that the generation of hairpins under various base flow conditions is governed by a basic mechanism, the important common elements of which are the shear of the base flow and an initial disturbance having a sufficiently large amplitude.
Quantum dots and etch-induced depletion of a silicon two-dimensional electron gas
Authors: Klein L. J. , Lewis K. L. M. , Slinker K. A. , Goswami Srijit , van der Weide D. W. , Blick R. H. , Mooney P. M. , Chu J. O. , Coppersmith S. N. , Friesen Mark , Eriksson M. A.
Published: February 2006

The controlled depletion of electrons in semiconductors is the basis for numerous devices. Reactive-ion etching provides an effective technique for fabricating both classical and quantum devices. However, Fermi-level pinning must be carefully considered in the development of small devices, such as quantum dots. Because of depletion, the electrical size of the device is reduced in comparison with its physical dimension. To investigate this issue in modulation-doped silicon single-electron transistors, we fabricate several types of devices in silicon-germanium heterostructures using two different etches, CF4 and SF6. We estimate the depletion width associated with each etch by two methods: (i) conductance measurements in etched wires of decreasing thickness (to determine the onset of depletion), and (ii) capacitance measurements of quantum dots (to estimate the size of the active region). We find that the SF6 etch causes a much smaller depletion width, making it more suitable for device fabrication.
Grain-boundary grooving by surface diffusion with asymmetric and strongly anisotropic surface energies
Authors: Min Donghong , Wong Harris
Published: February 2006

Grain-boundary migration controls grain growth, which is important in material processing and synthesis. When a vertical grain boundary ends at a horizontal free surface, a groove forms at the tip to reduce the combined grain-boundary and surface energies. The groove affects the migration of the grain boundary, and its effect must be understood. This work studies grain-boundary grooving by capillarity-driven surface diffusion with asymmetric and strongly anisotropic surface energies. The surface energies are described by the delta-function facet model that holds for temperatures above the roughening temperature of the bicrystal. Since the asymmetric anisotropy does not introduce a length scale, the asymmetric groove still grows with time t as t1∕4. Thus, the nonlinear partial differential equation that governs grooving is reduced by a self-similar transformation to an ordinary differential equation, which is then solved numerically by shooting methods. We vary systematically the crystallographic orientations of the bicrystal and the normalized grain-boundary energy. We find that the self-similar groove profile is faceted and asymmetric for most bicrystals. However, a few asymmetric bicrystals can also yield smooth and symmetric grooves. Some bicrystals may even form ridges instead of grooves. We also find that the asymmetric surface energies tilt the grain-boundary tip sideways, which induces the grain boundary to migrate. We show that anisotropic groove profiles measured in SrTiO3 and Ni can be well fitted by our model.
Replication of photonic crystals by soft ultraviolet-nanoimprint lithography
Authors: Belotti Michele , Torres Jérémi , Roy Emanuel , Pépin Anne , Chen Yong , Gerace Dario , Andreani Lucio Claudio , Galli Matteo
Published: February 2006

Nanoimprint lithography assisted by ultraviolet photopolymerization through a soft elastomer-based mold is applied to the fabrication of silicon-on-insulator slab photonic crystals for optical wavelengths. Variable angular reflectance is used to measure the dispersion of the photonic leaky modes. Experimental results are in good agreement with both theoretical calculations and previous results obtained by standard nanoimprint lithography as well as conventional nanofabrication techniques such as electron-beam lithography.
Low-noise La0.7Sr0.3MnO3 thermometers for uncooled bolometric applications
Authors: Yang Fan , Méchin Laurence , Routoure Jean-Marc , Guillet Bruno , Chakalov Radoslav A.
Published: February 2006

We report measurements of the temperature coefficient of the resistance (TCR) and the low-frequency noise of epitaxial La0.7Sr0.3MnO3 (LSMO) thin films deposited on SrTiO3 (STO) and (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates. An x-ray-diffraction study showed that the films were (001) oriented. A normalized Hooge parameter of 9×10−31m3 was measured at 300K in the case of a 10-μm-wide, 575-μm-long line patterned in the 200-nm-thick film grown on STO substrate. This value is among the lowest reported values for manganites and close to values measured in standard metals and semiconductors. The corresponding noise equivalent temperature (NET) was constant in the 300–340K range and equal to 6×10−7KHz−1∕2 at 10Hz and 150μA for a 10-μm-wide, 575-μm-long line patterned in a 200-nm-thick LSMO film. This very low NET value is comparable to the best published results for manganites and was even found to be lower than the NET of other uncooled thermometers such as amorphous semiconductors, vanadium oxides, or semiconducting YBa2Cu3O6+σ. This can easily be explained by the lower noise level of epitaxial manganites thin films compared to others. The results show that despite a TCR of only 0.017K−1 at 300K, and thanks to a very low-noise level, LSMO thin films are real potential material for uncooled thermometry and bolometry.
Analysis of leakage current mechanisms in Schottky contacts to GaN and Al0.25Ga0.75N∕GaN grown by molecular-beam epitaxy
Authors: Zhang H. , Miller E. J. , Yu E. T.
Published: February 2006

Temperature-dependent current-voltage measurements combined with conductive atomic force microscopy and analytical modeling have been used to assess possible mechanisms of reverse-bias leakage current flow in Schottky diodes fabricated from GaN and Al0.25Ga0.75N∕GaN structures grown by molecular-beam epitaxy. Below 150K, leakage current is nearly independent of temperature, indicating that conduction is dominated by tunneling transport. At higher temperatures, leakage current in both GaN and Al0.25Ga0.75N∕GaN diode structures is well described by a Frenkel-Poole emission model. Based on the inferred emission barrier heights and the observation that room-temperature leakage current is dominated by the presence of highly conductive dislocations, it is suggested that the key carrier transport process is emission of electrons from a trap state near the metal-semiconductor interface into a continuum of states associated with each conductive dislocation. In this model for leakage current flow, the emission barrier heights measured for the GaN and Al0.25Ga0.75N∕GaN diode structures indicate that the conductive dislocation states are aligned in energy between GaN and Al0.25Ga0.75N.
Phase transitions in epitaxial Ba0.5Sr0.5TiO3 thin films
Authors: Ríos S. , Scott J. F. , Lookman A. , McAneney J. , Bowman R. M. , Gregg J. M.
Published: February 2006

Ba 0.5 Sr 0.5 Ti O 3 (BST) thin-film capacitor structures with various thicknesses, (50–1200nm) and different strain conditions (on lanthanum strontium cobalt oxide La0.5Sr0.5CoO3 and strontium ruthenate SrRuO3 buffer layers) were made using pulsed laser deposition, and characterized by x-ray diffraction. The out-of-plane lattice parameter was followed as a function of temperature within the 100–300K temperature interval. The phase sequence (cubic-tetragonal-orthorhombic-rhombohedral) known to exist in the bulk analog is shown to be strongly affected by both the stress conditions imposed by the buffer layer and the thickness of the BST film itself. Thus, no phase transition was found for the in-plane compressed BST films. On the stress-free BST films, on the contrary, more phase transitions were observed. It appeared that the complexity of structural phase transitions increased as the film thickness in this system was reduced.
Current-limiting mechanisms in polymer diodes
Authors: Bohnenbuck Britta , von Hauff Elizabeth , Parisi Jürgen , Deibel Carsten , Dyakonov Vladimir
Published: February 2006

We examined the current-voltage (JV) characteristics of poly[2-methoxy,5-(3,7-dimethyloctyloxy)]- 1,4phenylenevinylene (MDMO-PPV) diodes in the framework of the model for space-charge- limited currents (SCLCs). The thickness of the MDMO-PPV layer was varied between samples, and the effect of using different metals for the cathode on the device performance was investigated. Since the SCLC model alone could not explain the experimental data, modifications to it were individually investigated: (1) a double Gaussian density of states to account for deep traps, (2) injection of electrons from the back contact resulting in a recombination current, and (3) the influence of the built-in potential resulting from the asymmetric work functions of the electrodes. Although the JV curves of organic diodes are often discussed in literature in the context of SCLC in the presence of traps, the introduction of deep traps into the SCLC model could not explain the observed cathode dependence. Considering recombination processes in the model could account for the cathode dependence of the experimental data, but not for the behavior observed when the thickness of the semiconducting layer was varied. The SCLC model in combination with a built-in potential and a parallel resistance was able to explain both the thickness and cathode dependence of the JV characteristics.