bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of viruses in the onset of asthma and allergy: lessons from animal modelsSupported by the Medical Research Council of Canada (MT‐13766).
Authors: Hegele R. G.
Published: November 2010

There are several potential mechanisms by which viral respiratory tract infections in childhood might trigger the onset of sensitization to allergens and asthma. To study these potential mechanisms, researchers have developed a number of animal models. In this paper, results of animal experiments are discussed under three headings: (i) chronic sequelae of acute viral infections; (ii) viral infections and sensitization to aeroallergens; and (iii) persistent viral infections. The use of animal models to study the role of viral infections in the induction of allergic sensitization and airway responsiveness has provided intriguing new insights that may be relevant to the pathogenesis of human disease.
Interaction between haemopoietic regulation and airway inflammation
Authors: O'byrne P. M. , Gauvreau G. M. , Wood L. J.
Published: November 2010

Asthma is characterized by reversible airway narrowing, by airway hyperresponsiveness, and by airway inflammation. Inhaled allergens are the most important of the stimuli known to cause asthma. Methods for studying inhaled allergen in the laboratory have been well standardized and extensively used for the investigation of the pathophysiology and the pharmacological modulation of allergen‐induced airway responses. Allergen inhalation by a sensitized subject results in an early asthmatic response, and, in the majority of subjects, a late asthmatic response and airway hyperresponsiveness. The late response and airway hyperresponsiveness are associated with increases in airway eosinophils and metachromatic cells. Allergen‐induced airway inflammation in dogs (predominantly neutrophilic) is associated with increased granulocyte‐macrophage progenitors in bone marrow, which is dependent on the effects of a circulating serum factor stimulating the bone marrow. The newly formed cells traffic to the airways. These increases in granulocyte‐macrophage progenitors are blocked by inhaled corticosteroids. In human subjects, allergen‐induced eosinophilic inflammation is associated with increases in Eo/B progenitors, mediated through up‐regulation if the IL‐5 receptor on progenitors and increases responsiveness to IL‐5. Inhaled corticosteroids also attenuate all allergen‐induced physiological responses and airway inflammation, an effect possibly mediated, in part, through inhibition of eosinophil and basophil maturation or release from the bone marrow.
The paradigm of type 1 and type 2 antigen‐presenting cells. Implications for atopic allergy
Authors: Kapsenberg M. L. , Hilkens C. M. U. , Wierenga E. A. , Kalinski P.
Published: November 2010

Optimal clearance of the various pathogen types encountered by the human body requires the selective activation of particular cellular and/or humoral immune responses. The orchestration of the types of effector responses is directed by Th cells through the production of type 1 (Th1 cell‐associated) and type 2 (Th2 cell‐associated) cytokines. The way in which the Th cell cytokine profile is matched to the type of invading pathogen, and why these profiles sometimes derail and lead to disease, is not well understood. Here, we will discuss the concept that antigen‐presenting cells (APC) provide Th cells not only with antigen and costimulatory signals, but also with a polarizing signal (signal 3). This signal can be mediated by many APC‐derived factors, but IL‐12 and PGE2 seem to be of major importance. The Th2‐biased responses in atopic allergy appeared to be associated with monocytes with a decreased IL‐12/PGE2 ratio and, consequently, with the down‐regulation of type 1 cytokine production in Th cells. As for Th cells, APC can be functionialy polarized. In vitro experiments with monocyte‐derived dendritic cells (DC) showed that the presence of IFN‐γ during activation of immature DC primes for mature DC with the ability of high IL‐12 production and, consequently, a Th1‐driving capacity (APC1 or DC1). In contrast, PGE2 primes for a low IL‐12 production ability and a Th2‐driving capacity (APC2 or DC2). These findings suggest that pathogens provoke either Th1‐ or Th2‐cell development by inducing the production of a certain pattern of inflammatory DC‐polarizing mediators (e.g. IFN‐γ and PGE2) at the site of infection. The type of immune polarization will not only depend on the type of pathogen, but also varies with the type of infected tissue, i.e. that different tissues produce different mediators in response to the same pathogen. In the case of atopic allergy, this concept implies that the Th2‐cell bias may be related to low levels of cross‐regulatory infections, to Th1 cell‐inducing pathogens, or to an aberrant function of stromal cells in peripheral tissues.
Experimental models in rhinitis
Authors: Demoly P. , Campbell A. , Lebel B. , Bousquet J.
Published: November 2010

Nasal challenge with allergen or mediators is a useful model to understand the pathophysiology of allergic rhinitis. Some mechanisms have thereby been clearly clarified. Different methods have been proposed to mimic the natural allergen exposure and to measure the clinical and biological responses. Nasal challenges can also be used in clinical practice, mainly when there is a discrepancy between results of skin tests and in vitro or when occupational allergens are involved. Nasal challenges are also valuable to assess the efficacy of specific immunotherapy or some drugs.
Effect of antihistamines on epithelial cells
Authors: Devalia J. L. , Davies R. J.
Published: November 2010

Antihistamines have mostly been used in the management of allergic rhinitis, primarily for their symptomatic relief. Recent studies, however, have suggested that the non‐sedating second‐generation antihistamines also possess anti‐inflammatory activity, and consequently may be useful in the management of inflammation in allergic airways disease. Several in vivo studies have demonstrated that antihistamines decrease inflammatory cell infiltration in allergic disease, mediator release from mast/basophil cells, and the expression of adhesion molecules on epithelial cells. Similarly, in vitro studies have demonstrated that antihistamines decrease the migration and activation of eosinophils and the release of pro‐inflammatory mediators from mast/basophil cells, induced by immunological and non‐immunological stimuli. More recent evidence suggests that the antihistamines may modulate airway inflammation by influencing the activity of airway epithelial cells, which due to their spatial arrangement and predominance in the airways, are thought to play a pivotal role in the aetiology of airway disease. We and others have demonstrated that antihistamines attenuate allergen‐ or chemical‐induced expression and/or release of mediators which influence the activity of inflammatory cells, such as eosinophils, mast cells, basophils and lymphocytes, known to be involved in the pathogenesis of allergic airway diseases. Collectively, these studies suggest that second‐generation H1‐histamine receptor antagonists may have potential use either as safe anti‐inflammatory alternatives to corticosteroids, or as rescue medication in combination with corticosteroids, for the management of severe airway disease.
Polyisotypic antipeanut‐specific humoral responses in peanut‐allergic individuals
Authors: Kolopp‐Sarda M. N. , Moneret‐Vautrin D. A. , Gobert B. , Kanny G. , Guerin L. , Faure G. C. , Béné M. C.
Published: November 2010

Background

Peanut‐containing food products may induce severe clinical reactions in sensitized subjects, and high levels of antipeanut IgE have been reported in the literature. Immunotherapy, proposed for the prevention of severe accidents, is often ill‐tolerated and only partly efficient. This could be due to the spontaneous development of polyisotypic antipeanut antibodies.

Objective

To appreciate the presence and reactivity of other isotypes other than IgE of peanut‐specific antibodies in serum samples from peanut‐sensitized subjects.

Methods

Serum samples were obtained from 20 non‐sensitized subjects and 23 sensitized patients divided in three groups according to their response to peanut oral challenge (no response or response to high or low doses, respectively). Peanut‐specific IgG, IgG subclasses, IgA and IgM were assayed using an ELISA, and their reactivity against peanut proteins tested using Western Blot.

Results

A large dispersion of antipeanut antibody levels was observed in the three groups of patients, high levels of IgG, IgG1, IgG4 and IgA usually correlating with highly positive radioallergosorbent test (RAST). Such high levels were observed at onset in four patients who underwent peanut immunotherapy who had side effects and poor efficiency. Western blotting demonstrated that the polyisotypic response observed was directed to several peanut antigens, including the major allergens, Ara h1 and Ara h2.

Conclusion

Peanut‐sensitized patients who spontaneously develop specific IgE, display polyisotypic‐specific antibody responses, whatever their response to oral challenge. This might explain the poor efficiency of peanut rush immunotherapy attempts.
An investigation into the association among preterm birth, cytokine gene polymorphisms and periodontal disease
Authors: Moore S. , Ide M. , Randhawa M. , Walker J.J. , Reid J.G. , Simpson N.A.B.
Published: November 2010

Objective  To investigate a putative relationship between preterm delivery and the carriage of polymorphic genes that code for the cytokines interleukin‐1β (IL‐1β) at codon +3953 and tumour necrosis factor‐α (TNF‐α) at codon −308 in a group of postpartum women and to elucidate if the concurrent presence of periodontal disease increased the risk of preterm delivery in this group.

Design  Case–control study

Setting  Postnatal wards at Guy's and St Thomas' Hospital Trust.

Population  Postpartum women from southeast London, UK.

Methods  Case subjects were defined as those who experienced a birth at less than 37 weeks of gestation. Control subjects gave birth at term. Demographic data were collected and a periodontal examination was performed. Blood samples were collected and analysed by restriction fragment length polymerase techniques for the presence of each of the allelic variants.

Main outcome measures  The level of periodontal disease and the carriage of allelic variants of IL‐1β+3953 and TNF‐α−308 genes.

Results  Forty‐eight case subjects and 82 control subjects were assessed. There was no statistically significant difference in the carriage of the IL‐1β+3953 allelic variant between cases and controls (29%versus 18%, P= 0.112). However, 23 (48%) of the case subjects and 24 (29%) of controls were heterozygous or homozygous for the variant TNF‐α−308 gene (odds ratio [OR] 2.2, 95% confidence interval [CI] 1.0–5.0, P= 0.026). There was no association between the carriage of either the polymorphic IL‐1β+3953 or TNF‐α−308 variant and the severity of periodontal disease. The combination of periodontal disease and the allelic variant did not increase the risk of preterm delivery.

Conclusions  In this study, a higher proportion of women who delivered preterm carried the polymorphic TNF‐α−308 gene. There did not appear to be any interaction between either of the genotypes and periodontal disease with preterm delivery as has been reported for bacterial vaginosis and the TNF‐α−308 polymorphic gene.
Maternal mortality as an indicator of obstetric care in Europe
Authors: Wildman Katherine , Bouvier‐Colle Marie‐Hélène ,   the MOMS group
Published: November 2010

Objective  This analysis considers the usefulness of maternal mortality ratio (MMR) as an indicator of obstetric care in the context of low overall maternal mortality. We explore whether variation in the level of MMR among European countries reflects differences in obstetric care.

Design  The data presented in this article were collected as part of the European Concerted Action on Mothers' Mortality and Severe morbidity (MOMS). In this study, a panel of experts followed a protocol to determine cause of death and whether it was pregnancy‐related. This analysis uses the expert panel's confirmation of cause of death and obstetric attribution.

Setting  All maternal deaths within 11 European countries.

Population  Two hundred and ninety obstetric deaths occuring between 1992 and 1995.

Methods  We present the results of a multivariable analysis that controls for cause of death, moment of death, place of death, pregnancy outcome, women's age and nationality.

Main outcome measures  We test the hypothesis that countries with higher MMR would have proportionally more cases of direct obstetric death due to thromboembolism, hypertension, haemorrhage or infection compared with other countries in the study. We examine timing of death and maternal age to measure whether there are differences between country groups for older mothers.

Results  We find distinct patterns in cause and timing of death and age‐specific mortality ratios between countries with different levels of MMR.

Conclusions  Despite low rates of maternal mortality in Europe, between‐country differences follow patterns with respect to cause and timing of death and maternal age. In addition to representing an important indicator of health status in a country, differences in MMR among European countries provide insight to where obstetric care plays a role maternal deaths.
Prevalence of bladder neck mobility in asymptomatic non‐pregnant nulliparous volunteers
Authors: Reed H. , Freeman R.M. , Waterfield A. , Adekanmi O.
Published: November 2010

Antenatal bladder neck mobility is known to be associated with postpartum stress incontinence. Whether this represents a normal feature of pregnancy or a pathological process is unclear. Forty‐eight nulliparous volunteers had perineal ultrasound scans to assess bladder neck mobility. Using previously defined cutoffs (for incontinence), 50% had increased linear movement and 39% increased angle of rotation. This suggests that bladder neck mobility is common in asymptomatic nulliparous women. Furthermore, it could represent a risk factor for stress incontinence after pregnancy and in the longer term.
Vascular MRI in the Diagnosis and Therapy of the High Risk Atherosclerotic Plaque
Authors: WENTZEL JOLANDA J. , AGUIAR SILVIA H. , FAYAD ZAHI A.
Published: November 2010

Disruption of a high risk plaque is known as the primary cause of cardiovascular events. Characterization of arterial wall components has become an essential adjunct in the identification of patients with plaques prone to rupture. Magnetic Resonance Imaging (MRI) has been revealed as one of the noninvasive tools possibly capable of identifying and characterizing high risk atherosclerotic plaque. MRI may facilitate diagnosis, and guide and serially monitor interventional and pharmacological treatment of atherosclerotic disease. In addition, it permits the simultaneous assessment of the anatomy, morphology, and hemodynamics for the study of flow‐induced atherogenesis. It possibly will identify asymptomatic patients with subclinical atherosclerosis. This has potential significance for the improvement of strategies in primary and secondary prevention. (J Interven Cardiol 2003;16:129–142)
Magnetic Resonance Imaging Guided Cardiovascular Interventions in Congenital Heart Diseases
Authors: RICKERS CARSTEN , SEETHAMRAJU RAVI TEJA , JEROSCH‐HEROLD MICHAEL , WILKE NORBERT M.
Published: November 2010

The purpose of this article is to present some recent applications of diagnostic and interventional MRI in congenital heart disease. To date x‐ray‐based techniques have been the norm for most diagnostic and therapeutic applications. With the advent of ultrafast MRI and the development of MRI‐compatible catheters and guide wires, the goal of achieving real‐time guidance by MRI for interventions in congenital heart diseases has proven feasible. We briefly review the latest advances in cardiovascular MRI, and the development of MR‐compatible devices for diagnostic and therapeutic applications such as ASD closure and pulmonary artery dilation. (J Interven Cardiol 2003;16:143–147)
Advantages and Disadvantages of Coils for Transcatheter Closure of Patent Ductus Arteriosus
Authors: Galal M. OMAR
Published: November 2010

Different coils have been used to close the patent ductus arteriosus (PDA). In small‐ and moderate‐sized PDA, coils are an adequate alternative to surgery and/or to other devices. The aim of the study is to review and discuss the advantages and disadvantages of using coils (excluding PFM coils PFM Medical, Germany) to close PDA. Cambier was the first to successfully close a PDA using a Gianturco coil. To date, thousands of patients worldwide have undergone transcatheter closure of PDA using this or other types of coils. The use of coils is analyzed with regard to costs in comparison with other therapeutic modalities; techniques—anterograde, retrograde approach, selection of coil size—in relation to the size of the PDA and the available sizes of coils; efficacy of the rate of complete occlusion and the need for reocclusion; and safety in relation to embolization rate, other complications including hemolysis, left pulmonary artery LPA stenosis and coarctation. It is concluded that coils are a cheap alternative for the occlusion of PDA in the small‐to‐moderate PDA. The technique can be learned quite quickly, it has a high rate of complete occlusion, and has an acceptable rate of safety. The disadvantages include a moderate rate of coil embolization and of hemolysis in patients with residual shunt after coil occlusion in large PDAs. When more than one coil is used, the potential for developing LPA stenosis is high. (J Interven Cardiol 2003;16:157–163)
Fully electromagnetic gyrokinetic eigenmode analysis of high-beta shaped plasmas
Authors: Belli E. A. , Candy J.
Published: November 2010

A new, more efficient method to compute unstable linear gyrokinetic eigenvalues and eigenvectors has been developed for drift-wave analysis of plasmas with arbitrary flux-surface shape, including both transverse and compressional magnetic perturbations. In high-beta, strongly shaped plasmas like in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)], numerous branches of closely spaced unstable eigenmodes exist. These modes are difficult and time-consuming to adequately resolve with the existing linear initial-value solvers, which are further limited to the most unstable eigenmode. The new method is based on an eigenvalue approach and is an extension of the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)], reusing the existing discretization schemes in both real and velocity-space. Unlike recent methods, which use an iterative solver to compute eigenvalues of the relatively large gyrokinetic response matrix, the present scheme computes the zeros of the much smaller Maxwell dispersion matrix using a direct method. In the present work, the new eigensolver is applied to gyrokinetic stability analysis of a high-beta, NSTX-like plasma. We illustrate the smooth transformation from ion-temperature-gradient (ITG)-like to kinetic-ballooning (KBM)-like modes, and the formation of hybrid ITG/KBM modes, and further demonstrate the existence of high-k Alfvénic drift-wave “cascades” for which the most unstable mode is a higher excited state along the field line. A new compressional electron drift wave, which is driven by a combination of strong beta and pressure gradient, is also identified for the first time. Overall, we find that accurate calculation of stability boundaries and growth rates cannot, in general, ignore the compressional component δB∥ of the perturbation.
Calculation of the electron mobility in III-V inversion layers with high-κ dielectrics
Authors: O’Regan T. P. , Fischetti M. V. , Sorée B. , Jin S. , Magnus W. , Meuris M.
Published: November 2010

We calculate the electron mobility for a metal-oxide-semiconductor system with a metallic gate, high-κ dielectric layer, and III-V substrate, including scattering with longitudinal-optical (LO) polar-phonons of the III-V substrate and with the interfacial excitations resulting from the coupling of insulator and substrate optical modes among themselves and with substrate plasmons. In treating scattering with the substrate LO-modes, multisubband dynamic screening is included and compared to the dielectric screening in the static limit and with the commonly used screening model obtained by defining an effective screening wave vector. The electron mobility components limited by substrate LO phonons and interfacial modes are calculated for In0.53Ga0.47As and GaAs substrates with SiO2 and HfO2 gate dielectrics. The mobility components limited by the LO-modes and interfacial phonons are also investigated as a function of temperature. Scattering with surface roughness, fixed interface charge, and nonpolar-phonons is also included to judge the relative impact of each scattering mechanism in the total mobility for In0.53Ga0.47As with HfO2 gate dielectric. We show that InGaAs is affected by interfacial-phonon scattering to an extent larger than Si, lowering the expected performance, but probably not enough to question the technological relevance of InGaAs.
On the determination of intensities for electron photodetachment and photoionization spectra involving states coupled by conical intersections: Total integral cross sections for polyatomic molecules
Authors: Han Seungsuk , Yarkony David R.
Published: November 2010

The formal underpinning is derived for the computational determination of electron photodetachment and photoionization total integral cross sections for molecules in which the residual species, which can be a neutral or an ion, has states that are strongly coupled by conical intersections. The theory takes full account of the requisite antisymmetry of all the electrons and the potential nonorthogonality of the orbital for the scattering electron to the occupied molecular orbitals of the residual. The breakdown of the Born–Oppenheimer approximation requires significant modifications to the standard adiabatic state theory. The developed theory builds on ideas from theories of low-energy electron scattering, in which the scattered electron is described by an orbital taken as channel dependent, but independent of nuclear coordinates. The derived computational approach is based on the accurate description of the vibronic levels of the residual species using the nonadiabatic vibronic coupling theory of Köppel, Domcke, and Cederbaum. The electron scattering problem is solved using the complex rotation L2 method of Han and Reinhardt. This approach has the advantage that both Coulomb and free electron boundary conditions can be treated in the same approach.
Autofocused, enhanced proton acceleration from a nanometer-scale bulged foil
Authors: Wang H. Y. , Yan X. Q. , Lu Y. R. , Zheng F. L. , Guo Z. Y. , Ma W. J. , He X. T. , Tajima T. , Habs D. , Chen J. E.
Published: November 2010

We report an autofocused, enhanced proton acceleration by the interaction of an intense laser pulse with a bulged target. These results are obtained from two-dimensional particle-in-cell simulations using a real Gaussian laser pulse, normally incident on a bulged/planar, 60 nm thick foil (C:H=1:1). When the laser pulse hits the precurved target, energetic protons are converged on the axis automatically. For the bulged foil, due to oblique incidence at the wing region, the efficient vacuum heating at larger incidence angles will result in more energetic hot electrons than from the flat foil. The enhancement of hot electron temperature and density will result in a larger longitudinal field, which contributes to an enhancement of proton energy. The maximum proton energy of 124 MeV is attained from a bulged target irradiated by a linear polarized laser pulse at an intensity of 1.3×1020 W/cm2, which is two times higher than from the planar target (61 MeV).
Self-propelled motion of a torus rotating about its centerline in a viscous incompressible fluid
Authors: Moshkin N. P. , Suwannasri Pairin
Published: November 2010

In this paper, we investigate numerically the problem of the motion of a self-propelled torus in a viscous incompressible fluid. The surface of the torus rotates with constant velocity around its centerline. The flow patterns are analyzed for the range of moderate Reynolds numbers 20≤Re≤40 (Reynolds number defined by the velocity of uniform stream and smaller diameter of the torus), the range of the aspect ratios 1.5≤Ar≤20 (aspect ratio is defined as the ratio of torus diameter to cross-section diameter of the torus), and the range of rotational rate α, 0≤α≤2.5 (α is defined as the ratio of tangential tank-treading motion of the torus surface to the uniform far-field velocity).
Two-dimensional Legendre polynomial modeling of composite bulk acoustic wave resonators
Authors: Raherison A. , Lefebvre J. E. , Ratolojanahary F. E. , Elmaimouni L. , Gryba T.
Published: November 2010

A bidimensional analysis of 6 mm hexagonal resonators is described using a double orthonormal basis set for the expansion of field quantities. The analysis takes into account the electrical voltage source and by means of a unique formalism along with a single calculation restitutes all the types of resonance whatever the thickness to width ratio value through either modal solutions or electrical impedance. An illustrative example gives the capabilities of the method to investigate spurious modes in laterally bounded resonators.
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mid infrared light sources using InGaAs/GaAsSb “W” type quantum wells on InP substrates
Authors: Pan C. H. , Lin S. D. , Lee C. P.
Published: November 2010

We have investigated the InGaAs/GaAsSb/InAlGaAs/InAlAs type-II “W” quantum wells (QWs) grown on InP substrates by molecular beam epitaxy. The photoluminescence (PL) emission wavelength longer than 2.56 μm at room temperature (RT) is demonstrated for the first time in this material system. The PL emission peaks of our designed samples can cover a wide range from 2 to 2.5 μm at cryogenic temperature. The samples show good optical quality that the reduction in integrated PL intensity is only around one order of magnitude from 35 K to RT. We found that the integrated PL intensity decreased as the emission wavelength increased, which is due to the reduction in the electron-hole wave function overlap. This is consistent with the calculated result. In the power dependent PL measurements, the emission peak of “W” type QWs show blue shifts with the excitation power (Pex) but does not follow the Pex1/3 rule as predicted by type-II band bending model. The localized states filling effect gives reasonable explanations for the observed phenomena.
Quantitative modeling of forces in electromagnetic tweezers
Authors: Bijamov Alex , Shubitidze Fridon , Oliver Piercen M. , Vezenov Dmitri V.
Published: November 2010

This paper discusses numerical simulations of the magnetic field produced by an electromagnet for generation of forces on superparamagnetic microspheres used in manipulation of single molecules or cells. Single molecule force spectroscopy based on magnetic tweezers can be used in applications that require parallel readout of biopolymer stretching or biomolecular binding. The magnetic tweezers exert forces on the surface-immobilized macromolecule by pulling a magnetic bead attached to the free end of the molecule in the direction of the field gradient. In a typical force spectroscopy experiment, the pulling forces can range between subpiconewton to tens of piconewtons. In order to effectively provide such forces, an understanding of the source of the magnetic field is required as the first step in the design of force spectroscopy systems. In this study, we use a numerical technique, the method of auxiliary sources, to investigate the influence of electromagnet geometry and material parameters of the magnetic core on the magnetic forces pulling the target beads in the area of interest. The close proximity of the area of interest to the magnet body results in deviations from intuitive relations between magnet size and pulling force, as well as in the force decay with distance. We discuss the benefits and drawbacks of various geometric modifications affecting the magnitude and spatial distribution of forces achievable with an electromagnet.
A kind of two-dimensional electroconvection at ultralow electric frequency
Authors: Xiang Ying , Liu Yi-Kun , Xie Xiang-Sheng , Li Jia-Ming , Wang Jia-Hui , Cai Zhi-Gang
Published: November 2010

We report a kind of two-dimensional (2D) electroconvection (EC) domain observed in a negative dielectric anisotropy nematic liquid crystal (LC) in a parallel-rubbed alignment cell. The domain is excited by an ac electric field with ultralow frequency, and can be transformed into a one-dimensional (1D) EC domain at low amplitude electric fields. We conclude that the 1D domain is a kind of Williams domain, while the 2D domain is induced by flexoelectric effect, the corresponding 2D texture coming from superposition of two sets of symmetrical 1D stripes oblique to the initial LC orientation.
Demonstration of long-range surface plasmon-polariton waveguide sensors with asymmetric double-electrode structures
Authors: Joo Yang Hyun , Song Seok Ho , Magnusson Robert
Published: November 2010

We demonstrate a long-range surface plasmon-polaritons (LRSPP) refractive-index sensor using an asymmetric double-electrode LRSPP waveguide configuration. The LRSPP sensor is inherently self-referencing by virtue of two Bragg wavelengths in the transmission spectrum generated by a Bragg grating. The measured sensitivity is about 130 nm/RIU and 27 pm/K, which means a sensing resolution of ∼10−6 RIU and a temperature determination with an inaccuracy of 0.04 K under measurement accuracy of the Bragg wavelength of 1 pm. The sensor dimensions of 1.95 mm in total length and submicrometer in fluidic-channel thickness may be desirable for highly integrated sensors based on LRSPP.
Nanogap electrodes formed at the exposed edge of Au/self-assembled monolayer/Al2O3/Au tunnel structures grown by atomic layer deposition
Authors: Hu Bing , Yao Jingyuan , Hinds Bruce J.
Published: November 2010

Atomic layer deposition of high quality Al2O3 thin films onto Au electrodes was enabled by surface modification with a self-assembled monolayer of –OH groups that react with a monolayer of trimethylaluminum gas source. Ar ion milling was then used to expose the edge of the Au/insulator/Au structure for molecular electrode contacts. The junctions are characterized by atomic force microscope and tunnel current properties. The Au/self-assembled monolayer/Al2O3/Au tunnel junction, with a very thin oxide insulator layer (15.4 Å), is stable and has a small tunneling current density of about 0.20–0.75 A/cm2 at 0.5 V.
Influence of device geometry in the electrical behavior of all organic ambipolar field effect transistors
Authors: Cosseddu P. , Bonfiglio A.
Published: November 2010

Microcontact printing has been used for realizing all organic, highly flexible, ambipolar field effect transistors based on a pentacene-C60 heterojunction. The contacts were patterned using poly(ethylenedioxythiophene):poly(styrenesulfonate) as conductive polymer. We have compared three different device architectures, bottom contact, top contact, and middle contact, and demonstrated in the last case that a perfect balance between n- and p-type mobilities may be obtained, being source ad drain directly interfaced with both semiconductors. This led to a significant improvement of the electrical performances, which, in turn, allowed the realization of all organic complementary inverters.
Intermolecular electronic coupling in organic molecular thin films measured by temperature modulation spectroscopy
Authors: Yadav A. , Jin Y. , Chan P. K. L. , Shtein M. , Pipe K. P.
Published: November 2010

Temperature modulation spectroscopy is used to obtain the temperature dependences of oscillator strength, exciton transition energy, and linewidth for a copper phthalocyanine thin film. With increasing temperature, the oscillator strength exhibits a pronounced decrease for charge transfer (CT) excitons, making this technique suitable for differentiating exciton types. From the measured magnitude and temperature dependence of the CT oscillator strength, we obtain estimates for the intermolecular electronic coupling and its exponential decay coefficient.
Three-dimensional instability of dust ion-acoustic solitary waves in a magnetized dusty plasma with two different types of nonisothermal electrons
Authors: Shalaby M. , EL-Labany S. K. , EL-Shamy E. F. , Khaled M. A.
Published: November 2010

The nonlinear propagation of dust ion-acoustic solitary waves (DIASWs) in a magnetized dusty plasma which consists of two different types of nonisothermal electrons, hot adiabatic inertial ions fluid and immobile negatively charged dust particles is studied. The modified Zakharov–Kuznetsov (MZK) equation, describing the small but finite amplitude DIASWs, is derived using a reductive perturbation method. The combined effects of the external magnetic field, obliqueness (i.e., the propagation angle), and the two-temperature nonisothermal electrons, which are found to significantly modify the basic properties of DIASWs, are explicitly examined. The three-dimensional instability of DIASWs is also analyzed using the small-k (long wavelength plane wave) perturbation expansion technique. The results show that the external magnetic field, the propagation angle, and the two-temperature nonisothermal electrons have strong effects on the instability criterion as well as the growth rate.
Multiscale molecular simulations of argon vapor condensation onto a cooled substrate with bulk flow
Authors: Gu Kai , Watkins Charles B. , Koplik Joel
Published: November 2010

A hybrid simulation method is employed to study the condensation of saturated argon vapor flowing tangentially across a stationary cooled substrate, at nanoscale resolution. The method combines a direct simulation Monte Carlo treatment of the bulk vapor phase with a nonequilibrium molecular dynamics treatment of the condensed liquid and interphase regions; it provides an efficient simulation procedure for a heterogeneous system with a large ratio of vapor to liquid length scales. Starting from a bare, crystalline solid wall, the condensation process evolves from a transient unsteady state to a quasisteady state, where interfacial properties and heat and mass transfer parameters are analyzed. The Knudsen layer structure from the hybrid simulation is compared with kinetic theory predictions from a modified moment method analysis and from pure DSMC simulation. The effects of condensation strength and a tangential flow velocity that is on the order of the condensation velocity are examined. A comparison is made between the nonequilibrium results and equilibrium results for the interphase transition between liquid and vapor. The results reveal the structure of the interphase for such phenomena as inverted temperature, drift flux, and heat transfer. Heat transfer phenomena at the substrate surface are also described.
Evaluation of long carrier lifetimes in thick 4H silicon carbide epitaxial layers
Authors: Miyazawa Tetsuya , Ito Masahiko , Tsuchida Hidekazu
Published: November 2010

The carrier lifetime of ∼265 μm thick n-type 4H silicon carbide epilayers prepared using the carbon-implantation/annealing method was evaluated. An extraordinarily long minority carrier lifetime of 18.5 μs and a high injection lifetime of 19.2 μs were evaluated from time-resolved photoluminescence and microwave photoconductivity decay measurements, respectively. Based on the relationship between the epilayer thickness and carrier lifetime, the influence of surface recombination on the carrier lifetime was eliminated, and the bulk lifetime and hole diffusion constant were discussed.
Optically generated adaptive localized structures in confined chiral liquid crystals doped with fullerene
Authors: Trushkevych O. , Ackerman P. , Crossland W. A. , Smalyukh I. I.
Published: November 2010

We report the facile optical creation of switchable localized structures in chiral liquid crystals doped with fullerene. In a cholesteric cell unwound by vertical boundary conditions, the initially dispersed fullerenes are deposited from the bulk to the surface of confining glass plates by low-intensity illumination. This alters the surface boundary conditions and allows for the creation of localized particlelike structures with twist-bound defects (dubbed Torons) that are controlled by electric fields and arranged into patterns of interest for photonic and electro-optic applications.
Effect of deposition conditions and thermal annealing on the charge trapping properties of SiNx films
Authors: Ren Yongling , Weber Klaus J. , Nursam Natalita M. , Wang Da
Published: November 2010

The density of charge trapping centers in SiNx:H films deposited by plasma enhanced chemical vapor deposition is investigated as a function of film stoichiometry and postdeposition annealing treatments. In the as-deposited films, the defect density is observed to increase with an increasing N/Si ratio x in the range of 0.89–1.45, and to correlate with the N–H bond density. Following the annealing in the temperature range of 500–800 °C, the defect density increases for all N/Si ratios, with the largest increase observed in the most Si rich samples. However, the defect density always remains highest in the most N rich films. The better charge storage ability suggests the N rich films are more suitable for the creation of negatively charged nitride films on solar cells.
Formation of substoichiometric GeOx at the Ge–HfO2 interface
Authors: Broqvist Peter , Binder Jan Felix , Pasquarello Alfredo
Published: November 2010

The stability of oxygen vacancies across the Ge–HfO2 interface is studied through semilocal and hybrid density-functional calculations. On the semiconductor side, the formation energies are obtained for substoichiometric GeOx of varying x through the use of a bond-energy model. On the hafnium oxide side, the interface is modeled through bulk models with aligned band structures. Formation energies are compared for different charge states and Fermi energy levels. The oxygen vacancy is found to be most stable in the interfacial germanium oxide layer for both p-type and n-type doping. This favors the formation of substoichiometric GeOx, consistent with experimental observations.
Development and performance of wheat roots above shallow saline groundwater
Authors: Rose D. A. , Ghamarnia H. M. , Gowing J. W.
Published: November 2010

Shallow saline groundwater can meet part of a crop’s water requirement by capillary rise (i.e. sub-irrigation) when supplemented by surface irrigation with water of better quality. Proper management of deficit irrigation under these conditions requires better understanding of direct water use by crops from the shallow saline groundwater. This in turn requires information on development and performance of root systems. We therefore studied the development of wheat roots in lysimeters with water-tables maintained at 1 m under a combination of surface and sub-irrigation, each with 3 levels of salinity, by core sampling and with minirhizotrons. Compared to crops grown with adequate rainfall, root systems were shallow, rarely penetrating below 45 cm, and sparse, with maximum root-length densities (RLDs) of 0.5–1.8 cm/cm3 in the top 10 cm of the soil. Downward growth slowed continuously as time passed. Ultimate depths of penetration and RLDs at all depths decreased as the salinities of both surface and sub-irrigation increased. RLDs were inversely proportional to depth rather than decreasing exponentially below the surface. Estimates of RLD from cores exceeded those from minirhizotrons in the top 10 cm but were smaller at greater depth, as expected from the literature. Total root length ranged between 1 and 3 km/m2, around an order of magnitude smaller than for winter wheat in north-west Europe. Grain yields were likewise small, 0.4–1.2 t/ha, but yields per unit root length of 40–50 g/km were comparable to those from high-yielding crops. Roots in the top 10 cm comprised more than half the total root length and were most closely correlated with total water use, which included surface irrigation. Below 10 cm, the correlation was strongest with water extracted from the profile. As demand on global water resources inevitably rises, saline groundwater will increasingly be needed as a component in crop production, particularly in semi-arid parts of the world. The shallow roots found under our experimental conditions indicate a need for frequent irrigation, but the adoption of such a strategy would be likely to restrict uptake from the water-table and at the same time increase non-beneficial evaporation. We present our results as a contribution to finding an optimal irrigation strategy under these conditions.
Spatial variability of soil carbon, nitrogen, and phosphorus content and storage in an alpine wetland in the Qinghai - Tibet Plateau, China
Authors: Bai Junhong , Ouyang Hua , Xiao Rong , Gao Junqin , Gao Haifeng , Cui Baoshan , Huang Laibin
Published: November 2010

This study considers the spatial variability of soil organic carbon, nitrogen, and phosphorus storage in a drained alpine wetland and the possible relationships with soil properties. Top 0–0.30 m soil samples were collected in a typical alpine wetland in the south-eastern Qinghai–Tibet plateau using grid sampling. There was high spatial variability for soil organic carbon density (SOCD), soil total nitrogen density (STND), and soil total phosphorous density (STPD) in the drained alpine wetland. Spherical models best described the structure of the semivariograms for SOCD and STPD, and an exponential model for STND, with the range parameter of <4 m. Similar spatial distribution with lower or higher patches of C, N, and P storage were observed. SOCD, STND, and STPD were significantly negatively correlated with soil moisture (P < 0.01), and significantly positively correlated with bulk density (P < 0.01). However, no significant correlations were observed between SOCD, STND, and STPD and soil pH values. Wetland drainage might lead to higher C, N, and P densities in top 0.30 m soils due to peat compaction; thus, it is necessary to incorporate water table fluctuations or the whole depth of peat layers to estimating precisely C, N and P storage.
Accelerated testing of nutrient release rates from fertiliser granules
Authors: Warrender Cristy M. , Warrender Garry W. , Smith Bradley , McKenzie Colin , Gilbert Robert G.
Published: November 2010

A method is developed for estimation of accelerated nutrient release rates into a soil from particulate fertiliser formulations, by carrying out release studies at elevated temperatures. This can provide time-saving targetting of samples to be subsequently used in field trials. The rate of total phosphorus leaching into water from a standard commercial fertiliser product embedded in grey, deep, sandy duplex soil was monitored using inductively coupled plasma-optical emission spectroscopy. The time dependence of phosphate concentration at a given temperature was found to obey simple first-order kinetics. These data fitted an Arrhenius relation within acceptable limits, enabling release rates at ambient field temperatures to be estimated significantly faster than by field experiment. A release rate calculated for the accelerated test, i.e. (1.2 ± 0.1) × 10−3/min, when compared with a more standard-type pot-trial leaching rate for the corresponding temperature of 2.3 × 10−4/min, gives a direct correlation of ~1 : 1 when corrected for concentration differences.
Ca
2
+
signaling by plant
Arabidopsis thaliana
Pep peptides depends on AtPepR1, a receptor with guanylyl cyclase activity, and cGMP-activated Ca
2+
channels
Authors: Qi Zhi , Verma Rajeev , Gehring Chris , Yamaguchi Yube , Zhao Yichen , Ryan Clarence A. , Berkowitz Gerald A.
Published: November 2010

A family of peptide signaling molecules (AtPeps) and their plasma membrane receptor AtPepR1 are known to act in pathogen-defense signaling cascades in plants. Little is currently known about the molecular mechanisms that link these signaling peptides and their receptor, a leucine-rich repeat receptor-like kinase, to downstream pathogen-defense responses. We identify some cellular activities of these molecules that provide the context for a model for their action in signaling cascades. AtPeps activate plasma membrane inwardly conducting Ca
2+
permeable channels in mesophyll cells, resulting in cytosolic Ca
2+
elevation. This activity is dependent on their receptor as well as a cyclic nucleotide-gated channel (CNGC2). We also show that the leucine-rich repeat receptor-like kinase receptor AtPepR1 has guanylyl cyclase activity, generating cGMP from GTP, and that cGMP can activate CNGC2-dependent cytosolic Ca
2+
elevation. AtPep-dependent expression of pathogen-defense genes (
PDF1.2
,
MPK3
, and
WRKY33
) is mediated by the Ca
2+
signaling pathway associated with AtPep peptides and their receptor. The work presented here indicates that extracellular AtPeps, which can act as danger-associated molecular patterns, signal by interaction with their receptor, AtPepR1, a plasma membrane protein that can generate cGMP. Downstream from AtPep and AtPepR1 in a signaling cascade, the cGMP-activated channel CNGC2 is involved in AtPep- and AtPepR1-dependent inward Ca
2+
conductance and resulting cytosolic Ca
2+
elevation. The signaling cascade initiated by AtPeps leads to expression of pathogen-defense genes in a Ca
2+
-dependent manner.
Transcription factor E4F1 is essential for epidermal stem cell maintenance and skin homeostasis
Authors: Lacroix Matthieu , Caramel Julie , Goguet-Rubio Perrine , Linares Laetitia K. , Estrach Soline , Hatchi Elodie , Rodier Geneviève , Lledo Gwendaline , de Bettignies Carine , Thépot Amélie , Deraison Céline , Chébli Karim , Hovnanian Alain , Hainaut Pierre , Dubus Pierre , Sardet Claude , Le Cam Laurent
Published: November 2010

A growing body of evidence suggests that the multifunctional protein E4F1 is involved in signaling pathways that play essential roles during normal development and tumorigenesis. We generated
E4F1
conditional knockout mice to address E4F1 functions in vivo in newborn and adult skin.
E4F1
inactivation in the entire skin or in the basal compartment of the epidermis induces skin homeostasis defects, as evidenced by transient hyperplasia in the interfollicular epithelium and alteration of keratinocyte differentiation, followed by loss of cellularity in the epidermis and severe skin ulcerations.
E4F1
depletion alters clonogenic activity of epidermal stem cells (ESCs) ex vivo and ends in exhaustion of the ESC pool in vivo, indicating that the lesions observed in the
E4F1
mutant skin result, at least in part, from cell-autonomous alterations in ESC maintenance. The clonogenic potential of
E4F1
KO ESCs is rescued by Bmi1 overexpression or by Ink4a/Arf or p53 depletion. Skin phenotype of
E4F1
KO mice is also delayed in animals with
Ink4a/Arf
and
E4F1
compound gene deficiencies. Our data identify a regulatory axis essential for ESC-dependent skin homeostasis implicating E4F1 and the Bmi1–Arf–p53 pathway.