bluuebunny/crossref_metadata_2025 huggingface dataset:
Genesis of twin tropical cyclones as revealed by a global mesoscale model: The role of mixed Rossby gravity waves
Authors: Shen Bo‐Wen , Tao Wei‐Kuo , Lin Yuh‐Lang , Laing Arlene
Published: June 2012

In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden‐Julian Oscillation (MJO). This is shown by analyzing observational data, including NCEP reanalysis data and METEOSAT 7 IR satellite imagery, and performing numerical simulations using a global mesoscale model. A 10‐day control run is initialized at 0000 UTC 1 May 2002 with grid‐scale condensation but no sub‐grid cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non‐developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and thus the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8–10 day period. Five additional 10‐day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres, leading to the formation of the TCs. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (1) wave deepening (intensification) associated with a reduction in wavelength and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with boundary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low‐ and mid‐level cyclonic circulations associated with a specific gyre.
Investigation on the maximum content of vacancy at the B sites in La0.75Sr0.25Mn1−xO3 perovskite manganites
Authors: Ji D. H. , Tang G. D. , Li Z. Z. , Han Q. J. , Hou X. , Bian R. R. , Liu S. R.
Published: June 2012

The effects of the vacancy at the B sites on the structural and magnetic properties of perovskite manganites with a nominal composition La0.75Sr0.25Mn1−xO3 (0.0 ≤  x ≤ 0.13), prepared by the sol-gel method, were investigated. X-ray diffraction patterns indicate that there is a ABO3 perovskite structure single phase in the samples with x ≤ 0.08; however, there are second and third phases containing La, except ABO3 perovskite phase, in the samples with x ≥ 0.10. Magnetic measurement indicates that the sample with x = 0.08 has the lowest Curie temperature. By a quantitative phase analysis, we believe that there is a maximum value of vacancy content at the B sites in ABO3 perovskite manganites.
Some algebraic properties of differential operators
Authors: Carpentier Sylvain , De Sole Alberto , Kac Victor G.
Published: June 2012

First, we study the subskewfield of rational pseudodifferential operators over a differential field \documentclass[12pt]{minimal}\begin{document}${\mathcal K}$\end{document}K generated in the skewfield \documentclass[12pt]{minimal}\begin{document}${\mathcal K}((\partial ^{-1}))$\end{document}K((∂−1)) of pseudodifferential operators over \documentclass[12pt]{minimal}\begin{document}${\mathcal K}$\end{document}K by the subalgebra \documentclass[12pt]{minimal}\begin{document}${\mathcal K}[\partial ]$\end{document}K[∂] of all differential operators. Second, we show that the Dieudonnè determinant of a matrix pseudodifferential operator with coefficients in a differential subring \documentclass[12pt]{minimal}\begin{document}${\mathcal A}$\end{document}A of \documentclass[12pt]{minimal}\begin{document}${\mathcal K}$\end{document}K lies in the integral closure of \documentclass[12pt]{minimal}\begin{document}${\mathcal A}$\end{document}A in \documentclass[12pt]{minimal}\begin{document}${\mathcal K}$\end{document}K, and then we give an example of a 2 × 2 matrix with entries in \documentclass[12pt]{minimal}\begin{document}${\mathcal A}[\partial ]$\end{document}A[∂] whose Dieudonnè determinant does not lie in \documentclass[12pt]{minimal}\begin{document}${\mathcal A}$\end{document}A.
Density dependence of the entropy and the solvation shell structure in supercritical water via molecular dynamics simulation
Authors: Ma Haibo
Published: June 2012

We perform molecular dynamics simulations of supercritical water (SCW) with a wide range of densities along a near critical isotherm using the simple point charge extended (SPC/E) pair potential in order to study the entropy and the solvation shell structure around a central water molecule. It is shown that both the translational and orientational two-particle correlation entropy terms can serve as the metrics of the translational-orientational structural orders in water and it is revealed that the translational structural order is very sensitive to the density variation in the gas-like and liquid-like region, while the orientational structural order is much more dependent upon compression in the medium-density SCW region. The comparison of the magnitudes of the full thermodynamic excess entropy and two-particle correlation entropy confirms the recent findings that the many-body terms other than two-body ones also present significant and non-neglectable contributions to the full excess entropy for the highly anomalous fluids like water. The analysis of entropy terms as a function of intermolecular distance and the orientational distribution functions as well as the three-dimensional spatial distribution functions indicate that the structural order occurs only in a much more diffused first solvation shell due to the elongated hydrogen bonds under supercritical conditions. It is revealed that no obvious second or higher neighbor shells occur in SCW, in contrast with the feature of normal liquid water that the anomalous decrease of translational order upon compression occurs mainly in the second shell.
Revisiting the melting temperature of NpO2 and the challenges associated with high temperature actinide compound measurements
Authors: Böhler R. , Welland M. J. , Bruycker F. De , Boboridis K. , Janssen A. , Eloirdi R. , Konings R. J. M. , Manara D.
Published: June 2012

This work revisits the melting behaviour of neptunium dioxide, an actinide compound which can be produced in the nuclear fuel during operation, and which has an important impact on the nuclear fuel and waste radioactivity especially on the very long term. The present experimental approach employs remote laser heating under controlled atmosphere and fast pyrometry. This technique circumvents problems encountered by more traditional heating techniques, in particular, the reaction between sample and containment at temperatures beyond 2500 K. In addition, only a small amount of sample material is required, which is an advantage with respect to the radioactivity and limited availability of neptunium. The NpO2 melting/freezing temperature has been measured to be 3070 K ± 62 K, much higher than previous values (around 2830 K) obtained by more traditional thermal analysis methods. The large amount of experimental data collected allowed a consistent statistical analysis. It seems likely, although not fully evident from the present results, that the high oxygen potential at temperatures around melting leads to a slightly hypo-stoichiometric congruent melting composition, as already observed in other actinide (ThO2, PuO2) and lanthanide oxides (e.g., CeO2). Finally, a recently developed phase-field model was used for the simulation of the observed thermograms, allowing a deeper insight in material properties that are difficult to directly measure. For example, a polaron contribution to the high-temperature thermal conductivity, well accepted for the commonly studied actinide oxide UO2, is shown here to likely be present in NpO2.
Electrocaloric properties of epitaxial strontium titanate films
Authors: Zhang J. , Misirlioglu I. B. , Alpay S. P. , Rossetti G. A.
Published: June 2012

The electrocaloric (EC) response of strontium titanate thin films is computed as a function of misfit strain, temperature, electric field strength, and electrode configuration using a nonlinear thermodynamic theory. For films in a capacitor configuration on compressive substrates, the transition between paraelectric and strain-induced ferroelectric tetragonal phases produces a large adiabatic temperature change, ΔT = 5 K, at room temperature for electric field changes ΔE = 1200 kV/cm. For films on tensile substrates, the transition between the paraelectric and strain-induced ferroelectric orthorhombic phases can also be accessed using inter-digitated electrodes (IDEs). The maximum EC response occurs for IDEs with a [110] orientation.
Simple and exact approach to the electronic polarization effect on the solvation free energy: Formulation for quantum-mechanical/ molecular-mechanical system and its applications to aqueous solutions
Authors: Takahashi Hideaki , Omi Atsushi , Morita Akihiro , Matubayasi Nobuyuki
Published: June 2012

We present a simple and exact numerical approach to compute the free energy contribution δμ in solvation due to the electron density polarization and fluctuation of a quantum-mechanical solute in the quantum-mechanical/molecular-mechanical (QM/MM) simulation combined with the theory of the energy representation (QM/MM-ER). Since the electron density fluctuation is responsible for the many-body QM-MM interactions, the standard version of the energy representation method cannot be applied directly. Instead of decomposing the QM-MM polarization energy into the pairwise additive and non-additive contributions, we take sum of the polarization energies in the QM-MM interaction and adopt it as a new energy coordinate for the method of energy representation. Then, it is demonstrated that the free energy δμ can be exactly formulated in terms of the energy distribution functions for the solution and reference systems with respect to this energy coordinate. The benchmark tests were performed to examine the numerical efficiency of the method with respect to the changes in the individual properties of the solvent and the solute. Explicitly, we computed the solvation free energy of a QM water molecule in ambient and supercritical water, and also the free-energy change associated with the isomerization reaction of glycine from neutral to zwitterionic structure in aqueous solution. In all the systems examined, it was demonstrated that the computed free energy δμ agrees with the experimental value, irrespective of the choice of the reference electron density of the QM solute. The present method was also applied to a prototype reaction of adenosine 5′-triphosphate hydrolysis where the effect of the electron density fluctuation is substantial due to the excess charge. It was demonstrated that the experimental free energy of the reaction has been accurately reproduced with the present approach.
Fragmentation cross sections of protonated water clusters
Authors: Zamith Sébastien , Labastie Pierre , L'Hermite Jean-Marc
Published: June 2012

We have measured fragmentation cross sections of protonated water cluster cations (H2O)n=30−50H+ by collision with water molecules. The clusters have well-defined sizes and internal energies. The collision energy has been varied from 0.5 to 300 eV. We also performed the same measurements on deuterated water clusters (D2O)n=5−45D+ colliding with deuterated water molecules. The main fragmentation channel is shown to be a sequential thermal evaporation of single molecules following an initial transfer of relative kinetic energy into internal energy of the cluster. Unexpectedly, that initial transfer is very low on average, of the order of 1% of collision energy. We evaluate that for direct collisions (i.e., within the hard sphere radius), the probability for observing no fragmentation at all is more than 35%, independently of cluster size and collision energy, over our range of study. Such an effect is well known at higher energies, where it is attributed to electronic effects, but has been reported only in a theoretical study of the collision of helium atoms with sodium clusters in that energy range, where only vibrational excitation occurs.
Aperiodic arrays of active nanopillars for radiation engineering
Authors: Lawrence Nate , Trevino Jacob , Dal Negro Luca
Published: June 2012

We engineer aperiodic nanostructures for enhanced omnidirectional light extraction and coupling of 1.55 μm radiation to distinctive optical resonances carrying of orbital angular momentum (OAM) using light emitting Si-based materials. By systematically studying nanopillar arrays with varying pillar separations and increasing degree of rotational symmetry in Fourier space, we show that omnidirectional extraction is achieved with circularly symmetric Fourier space, leading to best light emission enhancement from planar devices such as LEDs or lasers. To demonstrate the potential of active aperiodic structures with azimuthally isotropic k-space, we fabricate nanopillar arrays of erbium doped silicon-rich nitride using electron beam lithography and reactive ion etching. Experimental results obtained using leaky-mode photoluminescence spectroscopy prove over 10 times extraction enhancement at 1.55 μm from aperiodic golden angle spirals (GA spirals), in good agreement with design based on analytical Bragg scattering and finite difference time domain calculations. In addition, by imaging Er radiation in direct and reciprocal space, we demonstrate that GA spiral arrays support angularly isotropic emission patterns and distinctive optical resonances with a well-defined azimuthal structure carrying OAM. These findings offer unique opportunities for the engineering of novel active structures that leverage isotropic emission patterns and structured light for secure optical communication, sensing, imaging, and light sources on a Si platform.
Juxtaposing density matrix and classical path-based wave packet dynamics
Authors: Aghtar Mortaza , Liebers Jörg , Strümpfer Johan , Schulten Klaus , Kleinekathöfer Ulrich
Published: June 2012

In many physical, chemical, and biological systems energy and charge transfer processes are of utmost importance. To determine the influence of the environment on these transport processes, equilibrium molecular dynamics simulations become more and more popular. From these simulations, one usually determines the thermal fluctuations of certain energy gaps, which are then either used to perform ensemble-averaged wave packet simulations, also called Ehrenfest dynamics, or to employ a density matrix approach via spectral densities. These two approaches are analyzed through energy gap fluctuations that are generated to correspond to a predetermined spectral density. Subsequently, density matrix and wave packet simulations are compared through population dynamics and absorption spectra for different parameter regimes. Furthermore, a previously proposed approach to enforce the correct long-time behavior in the wave packet simulations is probed and an improvement is proposed.
Annealed InGaN green light-emitting diodes with graphene transparent conductive electrodes
Authors: Zhang Yiyun , Wang Liancheng , Li Xiao , Yi Xiaoyan , Zhang Ning , Li Jing , Zhu Hongwei , Wang Guohong
Published: June 2012

Multi-layer graphene (MLG) films were transferred onto p-GaN layer as transparent conductive electrodes in InGaN green light-emitting diodes (MLG-GLEDs), and their optoelectronic properties were investigated. The interdiffusion between metal atoms from metal pads and Ga atoms from p-GaN had a strong effect on the contact barrier at graphene/p-GaN interface, resulting in substantial changes in transport characteristics of MLG-GLEDs and deterioration of the electrical contact between graphene and p-GaN. A high temperature annealing treatment was employed to improve the light-emitting performance of MLG-GLEDs.
On the nature of the coefficient of friction of diamond-like carbon films deposited on rubber
Authors: Martinez-Martinez D. , van der Pal J. P. , Schenkel M. , Shaha K. P. , Pei Y. T. , De Hosson J. Th. M.
Published: June 2012

In this paper, the nature of the coefficient of friction (CoF) of diamond-like carbon (DLC)-protected rubbers is studied. The relative importance of the viscoelastic and adhesive contributions to the overall friction is evaluated experimentally by modifying the contact load and the adhesive strength between the surface and the counterpart. The results indicate that the increase of CoF during the tribotests under non-lubricated conditions is caused by the increase of the adhesive contribution to friction motivated by the growth of the contact area during the test. In the case of oil lubricating condition, the adhesive force is minimized and the CoF is observed to decrease during the tribotest. This is caused by the reduction of the viscoelastic contribution due to the variation of the shape of the contact area. The role of the microstructure of the DLC film on the efficiency of the oil lubrication is also discussed.
Coherent periodic activity in excitatory Erdös-Renyi neural networks: The role of network connectivity
Authors: Tattini Lorenzo , Olmi Simona , Torcini Alessandro
Published: June 2012

In this article, we investigate the role of connectivity in promoting coherent activity in excitatory neural networks. In particular, we would like to understand if the onset of collective oscillations can be related to a minimal average connectivity and how this critical connectivity depends on the number of neurons in the networks. For these purposes, we consider an excitatory random network of leaky integrate-and-fire pulse coupled neurons. The neurons are connected as in a directed Erdös-Renyi graph with average connectivity 〈k〉 scaling as a power law with the number of neurons in the network. The scaling is controlled by a parameter γ, which allows to pass from massively connected to sparse networks and therefore to modify the topology of the system. At a macroscopic level, we observe two distinct dynamical phases: an asynchronous state corresponding to a desynchronized dynamics of the neurons and a regime of partial synchronization (PS) associated with a coherent periodic activity of the network. At low connectivity, the system is in an asynchronous state, while PS emerges above a certain critical average connectivity 〈k〉c. For sufficiently large networks, 〈k〉c saturates to a constant value suggesting that a minimal average connectivity is sufficient to observe coherent activity in systems of any size irrespectively of the kind of considered network: sparse or massively connected. However, this value depends on the nature of the synapses: reliable or unreliable. For unreliable synapses, the critical value required to observe the onset of macroscopic behaviors is noticeably smaller than for reliable synaptic transmission. Due to the disorder present in the system, for finite number of neurons we have inhomogeneities in the neuronal behaviors, inducing a weak form of chaos, which vanishes in the thermodynamic limit. In such a limit, the disordered systems exhibit regular (non chaotic) dynamics and their properties correspond to that of a homogeneous fully connected network for any γ-value. Apart for the peculiar exception of sparse networks, which remain intrinsically inhomogeneous at any system size.
Numerical study of the onset of thermosolutal convection in rotating spherical shells
Authors: Net Marta , Garcia Ferran , Sánchez Juan
Published: June 2012

The influence of an externally enforced compositional gradient on the onset of convection of a mixture of two components in a rotating fluid spherical shell is studied for Ekman numbers E = 10−3 and E = 10−6, Prandtl numbers σ = 0.1, 0.001, Lewis numbers τ = 0.01, 0.1, 0.8, and radius ratio η = 0.35. The Boussinesq approximation of the governing equations is derived by taking the denser component of the mixture for the equation of the concentration. Differential and internal heating, an external compositional gradient, and the Soret and Dufour effects are included in the model. By neglecting these two last effects, and by considering only differential heating, it is found that the critical thermal Rayleigh number \documentclass[12pt]{minimal}\begin{document}$R_{e}^c$\end{document}Rec depends strongly on the direction of the compositional gradient. The results are compared with those obtained previously for pure fluids of the same σ. The influence of the mixture becomes significant when the compositional Rayleigh number Rc is at least of the same order of magnitude as the known \documentclass[12pt]{minimal}\begin{document}$R_{e}^c$\end{document}Rec computed without mixture. For positive and sufficiently large compositional gradients, \documentclass[12pt]{minimal}\begin{document}$R_e^c$\end{document}Rec decreases and changes sign, indicating that the compositional convection becomes the main source of instability. Then the critical wave number mc decreases, and the drifting waves slow down drastically giving rise to an almost stationary pattern of convection. Negative gradients delay the onset of convection and determine a substantial increase of mc and ωc for Rc sufficiently high. Potential laws are obtained numerically from the dependence of \documentclass[12pt]{minimal}\begin{document}$R_{e}^c$\end{document}Rec and of the critical frequency ωc on Rc, for the moderate and small Ekman numbers explored.
Apparatus for the high temperature measurement of the Seebeck coefficient in thermoelectric materials
Authors: Martin Joshua
Published: June 2012

The Seebeck coefficient is a physical parameter routinely measured to identify the potential thermoelectric performance of a material. However, researchers employ a variety of techniques, conditions, and probe arrangements to measure the Seebeck coefficient, resulting in conflicting materials data. To compare and evaluate these methodologies, and to identify optimal Seebeck coefficient measurement protocols, we have developed an improved experimental apparatus to measure the Seebeck coefficient under multiple conditions and probe arrangements (300 K–1200 K). This paper will describe in detail the apparatus design and instrumentation, including a discussion of its capabilities and accuracy as measured through representative diagnostics. In addition, this paper will emphasize the techniques required to effectively manage uncertainty in high temperature Seebeck coefficient measurements.
Microwave-induced nonequilibrium temperature in a suspended carbon nanotube
Authors: Hortensius H. L. , Öztürk A. , Zeng P. , Driessen E. F. C. , Klapwijk T. M.
Published: June 2012

Antenna-coupled suspended single carbon nanotubes exposed to 108 GHz microwave radiation are shown to be selectively heated with respect to their metal contacts. This leads to an increase in the conductance as well as to the development of a power-dependent DC voltage. The increased conductance stems from the temperature dependence of tunneling into a one-dimensional electron system. The DC voltage is interpreted as a thermovoltage, due to the increased temperature of the electron liquid compared to the equilibrium temperature in the leads.
Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates
Authors: Yao Yingbang , Chen Long , Wang Zhihong , Alshareef Husam , Zhang X. X.
Published: June 2012

(001)-oriented BiFeO3 (BFO) thin films were grown on SrxCa1−xRuO3- (SCRO; x = 1, 0.67, 0.33, 0) buffered SrTiO3 (001) substrates using pulsed laser deposition. The microstructural, electrical, ferroelectric, and piezoelectric properties of the thin films were considerably affected by the buffer layers. The interface between the BFO films and the SCRO-buffer layer was found to play a dominant role in determining the electrical and piezoelectric behaviors of the films. We found that films grown on SrRuO3-buffer layers exhibited minimal electrical leakage while films grown on Sr0.33Ca0.67RuO3-buffer layers had the largest piezoelectric response. The origin of this difference is discussed.
Comparative studies of yield strength and elastic compressibility between nanocrystalline and bulk cobalt
Authors: Yu Xiaohui , Zhang Jianzhong , Zhang Yingying , Wang Liping , Zhao Yusheng
Published: June 2012

Comparative studies of yield strength and elastic compressibility between nanocrystalline and bulk cobalt were conducted using synchrotron x-ray diffraction under tri-axial pressure loading-unloading conditions. Relative to micron Co, nano Co exhibits higher flow stress (2.9 GPa compared with 2.1 GPa in micro Co), extra degree of strain-induced peak broadening during loading yet a better strain recoverability after unloading. These observations suggest different deformation mechanisms with intergranular strains dominated in nano Co and intragranular strains in micron Co. The determined bulk modulus for nano Co is 216 GPa, ∼17% higher than that of micron Co (185 GPa). This finding supports a generalized model of nanocrystals with pre-compressed surface layers and indicates that the grain-size induced elastic strengthening and weakening are primarily determined by the nature of internal stress (compressed vs. tensile) present in the surface layer of a nanocrystal.
Communication: Fast and local predictors of the violation of the Stokes-Einstein law in polymers and supercooled liquids
Authors: Puosi F. , Leporini D.
Published: June 2012

The violation of the Stokes-Einstein (SE) law is investigated in a melt of linear chains by extensive molecular-dynamics simulations. It is found that the SE breakdown is signaled (with 5% uncertainty) by the monomer mean-square displacement ⟨u2⟩ on the picosecond time scale. On this time scale the displacements of the next-next-nearest neighbors are uncorrelated. It is shown that: (i) the SE breakdown occurs when ⟨u2⟩ is smaller than the breadth of the distribution of the square displacements to escape from the first-neighbors cage, (ii) the dynamical heterogeneity affects the form of the master curve of the universal scaling between the structural relaxation and ⟨u2⟩.
Disorder enhanced intrinsic electroresistance in Sm0.60Sr0.40Mn1−xFexO3
Authors: Mahmud S. T. , Saber M. M. , Alagoz H. S. , Biggart K. , Bouveyron R. , Khan Mahmud , Jung J. , Chow K. H.
Published: June 2012

The intrinsic electroresistance (ER) of polycrystalline Sm0.60Sr0.40Mn1−xFexO3 (0 ≤ x ≤ 0.02) have been investigated by magnetotransport measurements. It is found that the ER increases with x while it is suppressed by a magnetic field. These observations imply that the ER increases dramatically with the inhomogeneity in the samples. The possible mechanisms responsible for the observed behavior are discussed.
Hall effect enhanced low-field sensitivity in a three-contact extraordinary magnetoresistance sensor
Authors: Sun Jian , Kosel Jürgen
Published: June 2012

An extraordinary magnetoresistance (EMR) device with a 3-contact geometry has been fabricated and characterized. A large enhancement of the output sensitivity at low magnetic fields compared to the conventional EMR device has been found, which can be attributed to an additional influence coming from the Hall effect. Output sensitivities of 0.19 mV/T at zero-field and 0.2 mV/T at 0.01 T have been measured in the device, which is equivalent to the ones of the conventional EMR sensors with a bias of ∼0.04 T. The exceptional performance of EMR sensors in the high field region is maintained in the 3-contact device.
Selective area growth and characterization of InGaN nano-disks implemented in GaN nanocolumns with different top morphologies
Authors: Albert S. , Bengoechea-Encabo A. , Lefebvre P. , Barbagini F. , Sanchez-Garcia M. A. , Calleja E. , Jahn U. , Trampert A.
Published: June 2012

This work reports on the morphology control of the selective area growth of GaN-based nanostructures on c-plane GaN templates. By decreasing the substrate temperature, the nanostructures morphology changes from pyramidal islands (no vertical m-planes), to GaN nanocolumns with top semipolar r-planes, and further to GaN nanocolumns with top polar c-planes. When growing InGaN nano-disks embedded into the GaN nanocolumns, the different morphologies mentioned lead to different optical properties, due to the semi-polar and polar nature of the r-planes and c-planes involved. These differences are assessed by photoluminescence measurements at low temperature and correlated to the specific nano-disk geometry.
Enhanced Wnt/β‐catenin signalling during tooth morphogenesis impedes cell differentiation and leads to alterations in the structure and mineralisation of the adult tooth
Authors: Aurrekoetxea Maitane , Lopez Jon , García Patricia , Ibarretxe Gaskon , Unda Fernando
Published: June 2012

Background information

Previous studies have indicated that over‐activation of the wingless interaction site (Wnt)/β‐catenin signalling pathway has important implications for tooth development, at the level of cell differentiation and morphology, as well as for the production of supernumerary teeth. Here, we provide evidence for a crucial role of this signalling pathway during the stage of tooth morphogenesis. We have developed an in vitro model consisting of 14.5‐day‐old mouse embryo first molars, in which the Wnt pathway is overactivated by the glycogen synthase kinase‐3 inhibitor 6‐bromoindirubin‐3′‐oxime (BIO; 20 µM).

Results

We found that over‐activation of the Wnt/β‐catenin pathway delayed the differentiation and growth of the inner dental epithelium. In addition, in contrast to controls in which Nestin protein expression was restricted to differentiated odontoblasts, in BIO‐treated molars, Nestin expression spread through sub‐odontoblastic cellular layers. This alteration appears to be related to: (i) the over‐expression of Bmp4 in the same region, (ii) the delay in odontoblast precursor cell differentiation and (iii) increased proliferation of mesenchymal cells. Furthermore, treatments longer than 6 days induced the malformation of typical dental structures and led to a total lack of cell differentiation. Finally, over‐activation of the Wnt route during odontogenesis resulted in adult teeth which presented altered size, morphology and mineralisation.

Conclusions

Our results indicate that Wnt/β‐catenin over‐activation during tooth morphogenesis is sufficient to cause dramatic alterations in the adult tooth, by delaying cellular differentiation and stimulating proliferation of the dental mesenchyme of developing teeth.
Columnar‐lined oesophagus without intestinal metaplasia: results from a cohort with a mean follow‐up of 7 years
Authors: Dias Pereira A. , Chaves P.
Published: June 2012

Background

The definition of Barrett's oesophagus lacks consensus, particularly the requirement of intestinal metaplasia for diagnosis. Scarce information exists on the prevalence and natural history of columnar‐lined oesophagus without intestinal metaplasia.

Aim

To evaluate the demographics and natural history of columnar‐lined oesophagus without intestinal metaplasia ≥2 cm in length.

Methods

Patients with columnar‐lined oesophagus ≥2 cm in length and no intestinal metaplasia in biopsy specimens from two consecutive endoscopies with at least a 1‐year interval were prospectively followed. A cohort of Barrett's oesophagus patients was used as a control.

Results

Columnar‐lined oesophagus without intestinal metaplasia (n = 15) had a similar gender distribution, reflux symptoms prevalence and length as those of Barrett's oesophagus (n = 205). Patients were significantly younger (28.6 vs. 60 years, P < 0.0001) and accounted for 48% of patients aged <40 years in the two cohorts, but only 1% of those aged >40 years (P < 0.001). Patient distribution in both cohorts in 5 age brackets (0–19, 20–29, 30–39, 40–49, and >50 years) was significantly different, except for patients aged 40–49 years. Intestinal metaplasia was documented in 60% of the cohort after a mean follow‐up of 7.1 years.

Conclusions

Columnar‐lined oesophagus without intestinal metaplasia ≥2 cm is infrequent in the setting of a systematic biopsy protocol, is associated with a younger age in comparison with Barrett's oesophagus, and appears to be an intermediate step between squamous and intestinal lining of the oesophagus.
High prevalence of exon 8 G533C mutation in apparently sporadic medullary thyroid carcinoma in Greece
Authors: Sarika H. L. , Papathoma A. , Garofalaki M. , Vasileiou V. , Vlassopoulou B. , Anastasiou E. , Alevizaki M.
Published: June 2012

Objective

Genetic screening for ret mutation has become routine practice in the evaluation of medullary thyroid carcinoma (MTC). Approximately 25% of these tumours are familial, and they occur as components of the multiple endocrine neoplasia type 2 syndromes (MEN 2A and 2B) or familial MTC. In familial cases, the majority of mutations are found in exons 10, 11, 13, 14 or 15 of the ret gene. A rare mutation involving exon 8 (G533C) has recently been reported in familial cases of MTC in Brazil and Greece; some of these cases were originally thought to be sporadic. The aim of this study was to re‐evaluate a series of sporadic cases of MTC, with negative family history, and screen them for germline mutations in exon 8.

Design and patients

Genomic DNA was extracted from peripheral lymphocytes in 129 unrelated individuals who had previously been characterized as ‘sporadic’ based on the negative family history and negative screening for ret gene mutations. Samples were analysed in Applied Biosystems 7500 real‐time PCR and confirmed by sequencing.

Measurements and results

The G533C exon 8 mutation was identified in 10 of 129 patients with sporadic MTC. Asymptomatic gene carriers were subsequently identified in other family members.

Conclusion

In our study, we found that 7·75% patients with apparently sporadic MTC do carry G533C mutation involving exon 8 of ret. We feel that there is now a need to include exon 8 mutation screening in all patients diagnosed as sporadic MTC, in Greece.
Candida albicans survival and biofilm formation under starvation conditions
Authors: Ning Y. , Hu X. , Ling J. , Du Y. , Liu J. , Liu H. , Peng Z.
Published: June 2012

Aim

To investigate the survival and biofilm formation capacity of Candida albicans in starvation and under anaerobic conditions.

Methodology

Candida albicans growth and survival were monitored in vitro for up to 8 months. Fungal suspensions from late exponential, stationary and starvation phases were incubated on human dentine, polystyrene and glass slides. Scanning electron microscopy (SEM) was used to observe the process of biofilm formation. 2,3‐bis(2‐Methoxy‐4‐nitro‐5‐sulfophenyl)‐2H‐tetrazolium‐5‐carboxyanilide inner salt (XTT) reduction assay was performed to quantify the biofilm formation capability, and confocal laser scanning microscopy (CLSM) was used to study and make semi‐quantitative comparisons of the ultrastructure of biofilms formed on human dentine. ‘XTT bioactivity’ and ‘COMSTAT results’ were analysed by two‐way analysis of variance (ANOVA) and one‐way ANOVA, respectively.

Results

Candida albicans survived for over six months. SEM demonstrated that starving C. albicans produced mature biofilms on different substrata. C. albicans of the same growth phase incubated on human dentine displayed significantly higher biofilm formation capability than on polystyrene or glass slides (P < 0.05). Biofilm formation capability by starving cells was significantly lower than that in exponential or stationary phases (P < 0.05). CLSM revealed that biofilms formed by starvation‐phase cells were less complex, had a higher roughness coefficient and surface/volume ratio (P < 0.05).

Conclusions

Candida albicans cells can survive and form biofilms in anaerobic and nutrient‐limited conditions and may pose a treatment challenge.
Kidney transplant ureteroneocystostomy: comparison of full‐thickness vs. Lich–Gregoir techniques
Authors: Kayler Liise , Zendejas Ivan , Molmenti Ernesto , Chordia Poorvi , Schain Denise , Magliocca Joseph
Published: June 2012

Despite a variety of urinary tract reconstructive techniques, urinary complications are the most frequent technical adverse event following kidney transplantation. We examined outcomes of two ureteroneocystostomy techniques, the full‐thickness (FT) technique and the Lich–Gregoir (LG) technique in 634 consecutive kidney‐alone transplants (327 FT and 307 LG) between December 2006 and December 2010. Urological complications at one yr post‐transplantation occurred in 27 cases (4.3%) including 16 ureteral strictures (2.5%), four ureteral obstructions (0.6%) owing to donor‐derived stones or intrinsic hematoma, and seven urine leaks (1.1%). Compared with LG, the FT technique was associated with similar proportions of ureteral complications overall (3.9% vs. 4.6%, p = 0.70), ureteral strictures (3.7% vs. 1.3%, p = 0.08), urinary stones/hematoma (1.0% vs. 0.3%, p = 0.36), and overall urinary leaks (1.6% vs. 0.6%, p = 0.22); however, the FT technique was associated with somewhat fewer urine leaks at the ureterovesical junction (0% vs. 1.3%, p = 0.05). There were no differences between the two groups in terms of length of stay, delayed graft function, urinary tract infection with the first post‐transplant year, estimated glomerular filtration rate, and overall graft and patient survival. The FT technique of ureteroneocystostomy is technically simple to perform and has a similar incidence of urinary complications compared with the LG technique.
A CD3+ count‐based thymoglobulin induction regimen permits delayed introduction of calcineurin inhibitors in kidney transplantation
Authors: Wang Connie J. , Tuffaha Ahmad , Zhang Da , Diederich Dennis A. , Wetmore James B.
Published: June 2012

Background

Withholding calcineurin inhibitors (CNIs) can be considered when graft function is inadequate following kidney transplantation (KT). Thymoglobulin (rATG) can be used to prevent acute rejection while CNIs are being withheld. Here, we report our results of a novel CNI‐sparing induction protocol, which utilizes a CD3+ cell count‐based rATG treatment regimen when delayed graft function (DGF) develops in the immediate postoperative period.

Methods

In a cohort of 153 consecutive deceased‐donor KT recipients, all received a single intraoperative dose of basiliximab; 84 subsequently developed DGF and therefore received rATG (rATG+ group), while 69 demonstrated immediate graft function and received CNIs (rATG− group).

Results

In the rATG+ group, mean duration of therapy was 8.5 ± 6.0 d, permitting CNI initiation to be delayed until postoperative day 10.3 ± 6.2. Cumulative dose of rATG was only 5.1 ± 4.5 mg/kg while targeting CD3+ counts of ≤30 cells/mm3. CD3+ counts were reduced to a mean of 16.7 ± 17.0 cells/mm3 during therapy. At one yr, patient and graft survival rates were 97.6% and 92.9%, respectively, while the frequency of infections and malignancies were not significantly increased compared to the rATG− group.

Conclusion

A unique induction regimen successfully delayed CNI initiation by using modest doses of rATG to deplete CD3+ cells, while yielding excellent long‐term graft outcome without increased risk of infection or malignancy.
An unusual presentation of alveolar echinococcosis in a 12‐yr‐old immunocompetent child
Authors: Oral Akgun , Ozturk Gurkan , Aydinli Bülent , Kantarci Mecit , Bedii Salman Ahmet
Published: June 2012

Oral A, Ozturk G, Aydinli B, Kantarci M, Salman AB. An unusual presentation of alveolar echinococcosis in a 12‐yr‐old immunocompetent child.

Abstract:  AE is a parasitic disease caused by Echinococcus multilocularis (E.m.). AE is a rare form of echinococcosis and mostly seen in 50‐ to 70‐yr‐old patients. Its asymptomatic invasive tumor‐like lesion development period, which lasts as much as 20 yr, is too long. Hence, this disease is very rare in children. Herein, we report an AE in a 12‐yr‐old girl who was not eligible for surgical treatment because of a radiological evaluation of non‐resectable lesion and was scheduled for a LT.
Development of Badges of Status in Captive Male House Sparrows (Passer domesticus) in Relation to the Relative Ornamentation of Flock‐Mates
Authors: Laucht Silke , Dale James
Published: June 2012

The development of quality signals is expected to be largely influenced by environmental conditions among which the social environment could be an important factor, particularly in gregarious animals. Here, we investigated the role of the presumed social environment on the development of badge size in moulting male House Sparrows (Passer domesticus) over a 3‐yr time span. House Sparrow badges are testosterone‐dependent ornaments that are typically argued to be ‘badges of status’ –that is, signals of competitive ability and aggression. Immediately prior to moult, we created several groups of males, either with similarly sized badges or with badges of different sizes, and we measured each male's badge size before and after moult. The former groups were presumed to have a less clear social hierarchy than the latter groups because of group members advertising relatively similar competitive ability (and thus were expected to more frequently challenge one another in order to establish dominance). Conversely, the latter groups were presumed to have relatively higher social stability because birds would less frequently encounter rivals advertising similar agonistic threat. We predicted in groups of birds with similarly sized badges, both (1) larger changes (i.e. increases or decreases) in badge sizes and (2) higher increases in between‐individual variation within groups. The first prediction was supported in one of the 3 yrs, but there was no support for the second prediction in any year. We conclude that social environment has an effect on the development of badges of status, but that it is highly contingent on the specific nature and timing of group interactions.
Late diagnosis of ectodermal dysplasia syndrome
Authors: Granger Robert H , Marshman Gillian , Liu Lu , McGrath John A
Published: June 2012

This case study reports the clinical, skin biopsy and molecular findings in a 56‐year‐old Filipino man with the autosomal recessive ectodermal dysplasia disorder, Schöpf‐Schulz‐Passarge syndrome, the precise nature of which was established only after reading of a similar case in this journal. In addition to the late diagnosis, successful clinical management of his acral hyperkeratosis and ulceration has been difficult, with oral retinoids exacerbating the skin fragility.
Extramammary Paget's disease of the vulva: An annotated review of the current literature
Authors: Delport Elsie Sophia
Published: June 2012

Extramammary Paget's disease is a rare and unusual neoplastic entity that presents mainly on apocrine gland‐bearing skin. The vulva is the most common site of involvement but any area of the anogenital skin can be affected. Due to its rarity, variable clinical course and deceptive histological appearance it has a high misdiagnosis rate and both gynaecologists and dermatologists have limited experience in its management. The significance of the disease lies in its association with underlying malignancy as well as its inherent ability to invade the dermis and metastasise. The management is notoriously complicated and recurrence rates are high despite aggressive surgeries. Several alternative modalities are being explored, with results that are often variable and unpredictable. This review summarises the histopathological, clinical and therapeutic features of extramammary Paget's disease of the vulva reported in recent years.
Management pathway of skin conditions presenting to an Australian tertiary hospital emergency department
Authors: Wallett Arabella , Sidhu Shireen
Published: June 2012

There have been limited published data on the management pathway of patients presenting to the emergency department with skin conditions. We report the pathway of patients presenting with skin conditions to a large tertiary hospital for 1 year and make recommendations to optimise the available dermatological services.
The spectrum of spitzoid tumours: A clinical study
Authors: Hafiji Juber , Rytina Ed , Burrows Nigel P
Published: June 2012

This study explores the relationship between different types of spitzoid tumours, spindle cell naevus of Reed and spitzoid melanomas. Clinical and histopathological data were retrospectively reviewed from our hospital database in Cambridge from January 2006 to July 2009. Clinical images, where available, were recorded. Search headings from our pathology database included ‘spitzoid tumours’, ‘Spitz naevi’, ‘atypical spitzoid tumours’, spitzoid tumours of uncertain malignant potential (‘STUMP’), ‘spindle cell naevus of Reed’ and ‘spitzoid melanomas’. The total number of spitzoid tumours was 118 comprising Spitz naevi (72), atypical spitzoid tumours (30), spitzoid melanomas (eight), and other naevi with spitzoid features (eight). In total, 60% of Spitz naevi were diagnosed clinically and 50% reported a history of change with spitzoid melanoma, compared with 32% with Spitz naevi. In all, 60% of Spitz naevi and atypical spitzoid tumours were pigmented in contrast with spitzoid melanomas (83%). Variegated pigmentation was found in 20% of Spitz naevi and atypical spitzoid tumours, however, no spitzoid melanomas had mixed pigmentation. There were 30 atypical spitzoid tumours (9 M : 21 F); 16 occurred on the lower limbs, peaking in the 20–30‐years age group. There were eight patients with spitzoid melanomas with a 7:1 F : M ratio, 50% of which were diagnosed clinically. Of the 34 spindle cell naevus of Reed (10 M : 24 F), 31 were misdiagnosed, most commonly as melanoma. Reed naevi peaked in the 30–40 year age group and on the upper limbs and lower limbs in the 20–30‐years age group. In summary, age and sex appeared helpful in distinguishing benign from malignant spitzoid tumours, however history was less discriminatory. Spitzoid melanomas, most of which were pigmented occurred more commonly in females. Atypical spitzoid tumours were more common in females and pathologists favoured malignancy in this group beyond 20 years of age.
A fatal neuromuscular disease in an adult patient after poliomyelitis in early childhood: Consideration of the pathology of post‐polio syndrome
Authors: Kosaka Takayuki , Kuroha Yasuko , Tada Mari , Hasegawa Arika , Tani Takashi , Matsubara Nae , Koike Ryoko , Toyoshima Yasuko , Takahashi Hitoshi
Published: June 2012

Post‐polio syndrome (PPS) characterized by new neuromuscular problems can appear many years after acute poliomyelitis in polio survivors. We report a 77‐year‐old man with antecedent poliomyelitis who newly developed neuromuscular disease with a clinical course of 27 years, the final 10 years of which were characterized by apparent progression, thus raising doubt as to the clinical diagnosis of amyotrophic lateral sclerosis (ALS) following PPS. Pathologically, plaque‐like, old poliomyelitis lesions were found almost exclusively in the lumbosacral cord, showing complete neuronal loss and glial scars in the anterior horns. Although less severe, neuronal loss and gliosis were also evident outside the old lesions, including the intermediate zone. Moreover, symmetrical degeneration of the corticospinal tracts, as evidenced by CD68 immunostaining, was a feature of the white matter of the lower spinal cord. In the motor cortex, loss of Betz cells was also confirmed. Synaptophysin immunostaining of the lumbosacral cord also revealed decreased expression outside the old lesions, excluding the posterior horn. Interestingly, decreased expression of synaptophysin was also evident in the cervical anterior horns, where no old lesions were observed. No Bunina bodies, TDP‐43 inclusions, or Golgi fragmentation were found. Neurogenic atrophy was evident in the iliopsoas and scalenus muscles, and inclusion body myositis‐like changes were also observed in these muscles and the tongue. Was it possible to have diagnosed this patient as having ALS? We consider that the features in this case may have represented the pathology of long‐standing and/or fatal PPS itself, and not ALS.