bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermotropic Mesomorphism via Self‐Assembly of Cationic Dendritic Polymers with an Anionic Polar Carboxylic Acid
Authors: Hernández‐Ainsa Silvia , Barberá Joaquín , Marcos Mercedes , Romero Pilar , Serrano José Luis
Published: December 2011

The synthesis and characterization of ionic liquid crystalline dendritic polymers based on the ammonium salts of commercially available poly(propylene imine) (PPI), poly(amidoamine) (PAMAM), poly(ethyleneimine) (PEI), and the fully methylated PEI (PEIMe) with 5‐(4‐cyanobiphenoxy)pentanoic acid (CBPA) are reported. The occurrence of proton transfer from the carboxylic acid to the amine groups is confirmed using IR and NMR techniques. The mesomorphic behavior is investigated by means of differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffractometry. Although CBPA exhibits monotropic nematic mesomorphism, all ionic complexes display enantiotropic liquid crystal properties. The relationship between the mesomorphism of the complexes and their structure is discussed.
Occupational risk factors and pancreatic cancer: A review of recent findings
Authors: Andreotti Gabriella , Silverman Debra T.
Published: December 2011

Several occupational exposures have been linked to excess risk of pancreatic cancer; however, most associations are not well established. The objective of this review article is to report on the more recently published studies (1998–2010), and provide a summary of the most consistently reported occupational risk factors for pancreatic cancer, including exposure to chlorinated hydrocarbon compounds, pesticides, polycyclic aromatic hydrocarbons (PAHs), metals, nitrosamines, radiation, various airborne particles, and employment in sedentary occupations. We conclude that the strongest and most consistent findings linking occupational exposures with pancreatic cancer risk to date are for chlorinated hydrocarbons and PAHs. © 2011 Wiley Periodicals, Inc.
Pancreatic cancer risk: Associations with meat‐derived carcinogen intake in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort
Authors: Anderson Kristin E. , Mongin Steven J. , Sinha Rashmi , Stolzenberg‐Solomon Rachael , Gross Myron D. , Ziegler Regina G. , Mabie Jerome E. , Risch Adam , Kazin Sally S. , Church Timothy R.
Published: December 2011

Background

Epidemiological studies report positive associations between high‐temperature cooked meat intake and pancreatic cancer. We assessed associations between dietary intake of heterocyclic amines (HCAs) and benzo(a)pyrene (BaP)—mutagens formed in meat cooked at high temperatures—and incident exocrine pancreatic cancer in a prospective cohort.

Methods

The 62 581 subjects randomized to screening in the Prostate, Lung, Colorectal, and Ovarian Screening Trial (PLCO) who completed an initial dietary survey that assessed meat intake, cooking methods, and doneness preferences defined the cohort. Subjects were surveyed annually for incident cancers through 2007. A National Cancer Institute research database (CHARRED) was used to estimate HCA and BaP intake and a Mutagenic Activity Index (MAI) from survey data. Proportional hazard ratios (HRs) for risk of pancreatic cancer were estimated from multi‐variate Cox regression models by quintile of intake, with the lowest quintile as the referent.

Results

During follow‐up (median: 10 yr), 248 cases of exocrine pancreatic cancer were confirmed. Preferences for well and very well done meat were generally associated with increased risks. Significant elevations in pancreatic cancer risk were found in upper quintiles of MAI, and individual mutagens 2‐amino‐3,4,8‐trimethylimidazo[4,5‐f]quinoxaline (DiMeIQx) and 2‐amino‐3,8‐dimethylimidazo[4,5‐f]quinoxaline (MeIQx). Compared to the lowest quintile of MAI, the third and fifth quintiles brought HRs of 1.86 (1.22, 2.85) and 1.87 (1.16, 3.02), respectively. These three exposures exhibited significant (P‐trend: 0.01–0.03) positive trends in risk as their levels increased

Conclusion

Consuming well‐done meat cooked at high temperatures, which contains high mutagen levels, appears to confer increased risk of pancreatic cancer. © 2011 Wiley Periodicals, Inc.
Selected medical conditions and risk of pancreatic cancer
Authors: Olson Sara H.
Published: December 2011

We review the current evidence for associations of several medical conditions with risk of pancreatic cancer, including allergies, pancreatitis, gall bladder disease, cholecystectomy, ulcers, gastrectomy, appendectomy, and tonsillectomy. There are consistent findings of reduced risk associated with presence of self‐reported allergies, particularly hay fever but not asthma; data on other allergies are limited and inconclusive. Several studies provide evidence that patients with pancreatic cancer are more likely than comparison groups to report pancreatitis. Those studies that investigated the time between onset of pancreatitis and diagnosis of pancreatic cancer found that risk estimates declined with longer periods of time; however, increased risks were noted for long‐term pancreatitis, indicating that this condition is both a risk factor and a sign of early disease. Increased risk was reported in association with cholelithiasis, but the few studies that considered time before diagnosis of cancer did not find increased risk for cholelithiasis diagnosed in the more distant past. There is weak evidence that cholecystectomy 2 or more years before cancer diagnosis is related to risk, but this is based on only a few studies. There is no consistent association between ulcers and risk, while gastrectomy may increase risk. Overall, study of these conditions, particularly those that are rare, presents methodologic challenges. Time between diagnoses is likely to be important but is not considered in most studies. Lack of adequate control in several studies for risk factors such as smoking and heavy alcohol use also makes it difficult to draw firm conclusions about these results. © 2011 Wiley Periodicals, Inc.
Direct B0 field monitoring and real‐time B0 field updating in the human breast at 7 tesla
Authors: Boer Vincent O. , vd Bank Bart L. , van Vliet Gerard , Luijten Peter R. , Klomp Dennis W. J.
Published: December 2011

Large dynamic fluctuations of the static magnetic field (B0) are observed in the human body during MR scanning, compromising image quality and detection sensitivity in several MR imaging and spectroscopy sequences. Partially, these dynamic B0 fluctuations are due to physiological motion such as breathing, but other sources of temporal B0 field fluctuations are also present in the MR system (e.g., eddy currents). Especially at ultrahigh field (≥7 T), the increased susceptibility effects lead to large B0 field variations over time. Direct measurement and correction of these temporal field variations of up to 70 Hz will lead to a significant reduction of artifacts and improved measurement stability/reproducibility. For direct measurement of the temporally changing B0 field, a simple field probe was developed, that was placed in proximity to the tissue of interest. In this work, it is shown how such a field probe system can be used to monitor temporal B0 field variations in the human body during MRI and magnetic resonance spectroscopy. Furthermore, it is shown how the acquired temporal B0 field information can drive a dynamic shim module to directly correct the B0 magnetic field in real time. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Efficient variational constitutive updates by means of a novel parameterization of the flow rule
Authors: Bleier Nikolaus , Mosler Jörn
Published: December 2011

Analogously to the classical return‐mapping algorithm, so‐called variational constitutive updates are numerical methods allowing to compute the unknown state variables such as the plastic strains and the stresses for material models showing an irreversible mechanical response. In sharp contrast to standard approaches in computational inelasticity, the state variables follow naturally and jointly from energy minimization in case of variational constitutive updates. This leads to significant advantages from a numerical, mathematical as well as from a physical point of view. However, while the classical return‐mapping algorithm has been being developed for several decades, and thus, it has already reached a certain maturity, variational constitutive updates have drawn attention only relatively recently. This is particularly manifested in the numerical performance of such algorithms. Within the present paper, the numerical efficiency of variational constitutive updates is critically analyzed. It will be shown that a naive approximation of the flow rule causes a singular Hessian within the respective Newton–Raphson scheme. However, by developing a novel parameterization of the flow rule, an efficient algorithm is derived. Its performance is carefully compared to that of the classical return‐mapping scheme. This comparison clearly shows that the novel variationally consistent implementation is, at least, as efficient as the classical return‐mapping algorithm. Copyright © 2011 John Wiley & Sons, Ltd.
OpenCL‐based implementation of an unstructured edge‐based finite element convection‐diffusion solver on graphics hardware
Authors: Mossaiby F. , Rossi R. , Dadvand P. , Idelsohn S.
Published: December 2011

The solution of problems in computational fluid dynamics (CFD) represents a classical field for the application of advanced numerical methods. Many different approaches were developed over the years to address CFD applications. Good examples are finite volumes, finite differences (FD), and finite elements (FE) but also newer approaches such as the lattice‐Boltzmann (LB), smooth particle hydrodynamics or the particle finite element method. FD and LB methods on regular grids are known to be superior in terms of raw computing speed, but using such regular discretization represents an important limitation in dealing with complex geometries. Here, we concentrate on unstructured approaches which are less common in the GPU world. We employ a nonstandard FE approach which leverages an optimized edge‐based data structure allowing a highly parallel implementation. Such technique is applied to the ‘convection‐diffusion’ problem, which is often considered as a first step towards CFD because of similarities to the nonconservative form of the Navier–Stokes equations. In this regard, an existing highly optimized parallel OpenMP solver is ported to graphics hardware based on the OpenCL platform. The optimizations performed are discussed in detail. A number of benchmarks prove that the GPU‐accelerated OpenCL code consistently outperforms the OpenMP version. Copyright © 2011 John Wiley & Sons, Ltd.
Directly resolving particles in an electric field: local charge, force, torque, and applications
Authors: Liu Qianlong
Published: December 2011

Prosperetti's seminal Physalis method for fluid flows with suspended particles is extended to electric fields to directly resolve finite‐sized particles and to investigate accurately the mutual fluid–particle, particle–particle, and particle–boundary interactions. The present paper shows the straightforward extension of the two dimensions [Liu, Q., 2011,J. Comput. Phys.230:8256–8274] to three dimensions as one of the important advantages. The method can be used for uncharged/charged dielectrics, uncharged/charged conductors, conductors with specified voltage, and general weak and strong discontinuous interface conditions. These general interface conditions can be in terms of field variable, its gradients, and surface integration, which has not been addressed by other numerical methods. In addition, for the first time, we rigourously derive the force and torque on the finite‐sized particles resulting from the interactions between harmonics. The method, for the first time, directly resolves the particles with accurate local charge distribution, force, and torque on the particles, making many applications in engineering, mechanics, physics, chemistry, and biology possible, such as heterogeneous materials, microfluidics, electrophotography, electric double‐layer capacitors, and microstructures of nanodispersions. In the present paper, the accuracy of the coefficients in the general analytical solutions is extensively investigated. The method is numerically verified to be accurate even for very strong jump in the weak and strong discontinuous interface conditions, which have not yet been investigated in any other numerical methods. The efficiency of the method is demonstrated with up to 100,000 3D particles, which suggests that the method can be used for many important engineering applications of broad interest. Copyright © 2011 John Wiley & Sons, Ltd.
A numerical test of long‐time stability for rigid body integrators
Authors: Ortolan Giulia , Saccon Alessandro
Published: December 2011

In the context of Hamiltonian ODEs, a necessary condition for an integrator to be symplectic or conjugate‐symplectic is that it nearly preserves the exact Hamiltonian. This paper introduces a numerical test of this necessity for rigid body methods. It turns out that several rigid body integrators proposed in literature fail this test. Hence, these integrators should be used with caution for long‐time simulation. Copyright © 2011 John Wiley & Sons, Ltd.
Efficient implicit simulation of incremental sheet forming
Authors: Hadoush A. , van den Boogaard A.H.
Published: December 2011

In single point incremental forming (SPIF), the sheet is incrementally deformed by a small spherical tool following a lengthy tool path. The simulation by the ﬁnite element method of SPIF requires extremely long computing times that limit the application to simple academic cases. The main challenge is to perform thousands of load increments modelling the lengthy tool path with elements that are small enough to model the small contact area. Because of the localised deformation in the process, a strong nonlinearity is observed in the vicinity of the tool. The rest of the sheet experiences an elastic deformation that introduces only a weak nonlinearity because of the change of shape. The standard use of the implicit time integration scheme is ineﬃcient because it applies an iterative update (Newton–Raphson) strategy for the entire system of equations. The iterative update is recommended for the strong nonlinearity that is active in a small domain but is not required for the large part with only weak nonlinearities. It is proposed in this paper to split the ﬁnite element mesh into two domains. The ﬁrst domain models the plastically deforming zone that experiences the strong nonlinearity. It applies a full nonlinear update for the internal force vector and the stiﬀness matrix every iteration. The second domain models the large elastically deforming zone of the sheet. It applies a pseudolinear update strategy based on a linearization at the beginning of each increment. Within the increment, it reuses the stiﬀness matrix and linearly updates the internal force vector. The partly linearized update strategy is cheaper than the full nonlinear update strategy, resulting in a reduction of the overall computing. Furthermore, in this paper, adaptive reﬁnement is combined with the two domain method. It results in accelerating the standard SPIF implicit simulation of 3200 shell elements by a factor of 3.6. Copyright © 2011 John Wiley & Sons, Ltd.
Adjoint‐based optimal variable stiffness mesh deformation strategy based on bi‐elliptic equations
Authors: Wang Qiqi , Hu Rui
Published: December 2011

There are many recent advances in mesh deformation methods for computational fluid dynamics simulation in deforming geometries. We present a method of constructing dynamic mesh around deforming objects by solving the bi‐elliptic equation, an extension of the biharmonic equation. We show that introducing a stiffness coefficient field a(x) in the bi‐elliptic equation can enable mesh deformation for very large boundary movements. An indicator of the mesh quality is constructed as an objective function of a numerical optimization procedure to find the best stiffness coefficient field a(x). The optimization is efficiently solved using steepest descent along adjoint‐based, integrated Sobolev gradients. A multiscenario optimization procedure is performed to calculate the optimal stiffness coefficient field a蜧(x) for a priori unpredictable boundary movements. Copyright © 2011 John Wiley & Sons, Ltd.
Optical switching with isotropic liquid crystals
Authors: Costache Florenta , Blasl Martin
Published: December 2011

Optical communication networks and remote optical sensing applications must include, in their architecture, optical switches to dynamically control the optical path connection. Optical switches with no moving parts can warrant high stability and reliability. This is just one of the reasons to employ electrooptical waveguides based on isotropic liquid crystals in optical switching devices. Furthermore of advantage is that, since these devices are fabricated by means of high precision silicon wafer planar technology, they can be tailored to the specific needs of a given application and are suitable for high volume manufacturing.
Laser direct writing
Authors: Häfner Matthias , Pruss Christof , Osten Wolfgang
Published: December 2011

Diffractive optics are compact and flexible optical elements with attractive properties that conventional refractive or reflective surfaces cannot deliver. While their fabrication is still challenging, the developments over the past years in both replication and mastering have advanced their application in fields like illumination shaping, metrology, laser beam forming, polarization shaping or fraud protection. A powerful tool for mastering is the technology of laser direct writing, initially developed for applications like mask production for lithography or mastering for optical data storage. In this contribution we present recent developments in laser direct writing technology for diffractive optics.
The effect of loading rates and particle geometry on compressive properties of polypropylene/zinc oxide nanocomposites: Experimental and numerical prediction
Authors: Omar Mohd Firdaus , Akil Hazizan Md , Ahmad Zainal Arifin , Mahmud Shahrom
Published: December 2011

Compressive properties, of particulate filled polymer matrix composites, are affected (to a certain extent) by the geometry of the particles, as well as the loadingrates. Therefore, this article presents the results on the compressive properties of polypropylene/zinc oxide nanocomposites across strain rates from 10−2 to 10−3 s−1. The specimens were tested using a Universal Testing Machine for static loading and a conventional Split Hopkinson Pressure Bar apparatus for dynamic loading. Results show that the yield stress and 2.5% flow stress, of both PP/ZnO nanocomposites, showed a positive increment with increasing strain rates. However, the yield strain shows a contradictory pattern, where it decreased with increasing strain rates. PP/ZnO‐white seal recorded higher strain rate sensitivity, dissipation energy, stiffness, and strength properties, than that of PP/ZnO‐pharmaceutical, over a wide range of strain rates investigated. Interestingly, the Eyring theory almost agreed with the experimental results. Overall, based on the experimental and numerical results, we do believe that particle geometry, as well as strain rates, has a significant influence on the compressive properties of polypropylene/zinc oxide nanocomposites specimens. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
Evaluation of interfacial properties and microfailure mechanisms in single fiber‐reinforced epoxy composites at low temperature
Authors: Park Joung‐Man , Wang Zuo‐Jia , Kwon Dong‐Jun , Gu Ga‐Young , Um Moon‐Kwang , DeVries K. Lawrence
Published: December 2011

In this preliminary study, micromechanical techniques were used to compare the interfacial properties of both carbon and glass fiber composites with two structurally different epoxy matrices (YD‐114 and YDF‐175) at ambient and relatively low temperatures (25°C and −10°C). Tensile modulus of elasticity for both epoxies was higher at lower temperature. Although both fibers exhibited more bimodality at lower temperature than at ambient temperature, glass fiber composites exhibited a statistically greater improvement in tensile strength. This may be attributed to differences in inherent flaws and rigidity. A decrement in stress was observed for YDF‐175 epoxy composites under cyclic loadings at both temperatures, which was attributed to lower interfacial shear strength (IFSS). In contrast to the IFSS of conventional YD‐114 epoxy composites, the IFSS of both the carbon and glass fibers/YDF‐175 epoxy composites studied was higher at the lower temperature. The microfailure pattern observed in microdroplet pullout tests was consistent with the other IFSS results. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
Bio‐assay Guided Isolation of α‐Glucosidase Inhibitory Constituents from Hibiscus Mutabilis Leaves
Authors: Kumar Deepak , Kumar Hemanth , Vedasiromoni J. R. , Pal Bikas C.
Published: December 2011

Introduction

The increasing demand for natural‐product‐based medicines and health‐care products for the management of diabetes encouraged investigation of this commonly available Indian plant.

Objectives

To establish the anti‐diabetic (α‐glucosidase inhibitory) activity of H. mutabilis leaf extract, isolate and identify the constituents responsible for the activity, and validate a HPLC method for quantification of the active constituents for standardisation of the extract.

Material and methods

The methanolic extract of leaves was partitioned between water, n‐butanol and ethyl acetate. Bio‐assay guided fractionation, based on inhibition of α‐glucosidase, allowed isolation and identification of the active components. The active components were quantified using RP‐HPLC‐DAD validated for linearity, limit of detection, limit of quantification, precision, accuracy and robustness for this plant extract and the partitioned fractions.

Results

Ferulic acid and caffeic acid were identified as the α‐glucosidase inhibitors present in H. mutabilis. They were partitioned into an ethyl acetate fraction. The HPLC‐DAD calibration curve showed good linearity (r2 > 0.99). For the recovery studies the %RSD was less than 2%. The interday and intraday variations were found to be less than 4% RSD for retention time and response.

Conclusion

The identification of α‐glucosidase inhibition activity in H. mutabilis supports further investigations into the possible use of the plant for the management of diabetes. The HPLC method validated for these extracts will be useful in future research with the plant. Copyright © 2011 John Wiley & Sons, Ltd.
Proteomics reveals selective regulation of proteins in response to memory‐related serotonin stimulation in Aplysia californica ganglia
Authors: Monje Francisco J. , Birner‐Gruenberger Ruth , Darnhofer Barbara , Divisch Isabella , Pollak Daniela D. , Lubec Gert
Published: December 2011

The marine mollusk Aplysia californica (Aplysia) is a powerful model for learning and memory due to its minimalistic nervous system. Key proteins, identified to be regulated by the neurotransmitter serotonin in Aplysia, have been successfully translated to mammalian models of learning and memory. Based upon a recently published large‐scale analysis of Aplysia proteomic data, the current study investigated the regulation of protein levels 24 and 48 h after treatment with serotonin in Aplysia ganglia using a 2‐D gel electrophoresis approach. Protein spots were quantified and protein‐level changes of selected proteins were verified by Western blotting. Among those were Rab GDP dissociation inhibitor alpha (RabGDIα), synaptotagmin‐1 and deleted in azoospermia‐associated protein (DAZAP‐1) in cerebral ganglia, calreticulin, RabGDIα, DAZAP‐1, heterogeneous nuclear ribonucleoprotein F (hnRNPF), RACK‐1 and actin‐depolymerizing factor (ADF) in pleural ganglia and DAZAP‐1, hnRNPF and ADF in pedal ganglia. Protein identity of the majority of spots was confirmed by a gel‐based mass spectrometrical method (FT‐MS). Taken together, protein‐level changes induced by the learning‐related neurotransmitter serotonin in Aplysia ganglia are described and a role for the abovementioned proteins in synaptic plasticity is proposed.
A chemical switch for detecting insect infestation
Authors: Weerakoon Kanchana A , Chin Bryan A
Published: December 2011

BACKGROUND: Plants emit phytochemicals as a defensive mechanism against herbivores. A small sensor switch that responds to these chemicals could be used to stop insect infestation at early stages.

RESULTS: Polyethylene‐co‐vinyl acetate was chosen as the best polymer for this particular application, based on its swelling response to plant volatiles. When the carbon concentration of the active layer was low enough to be near the percolation threshold, the sensor could be used as a ‘chemical switch’. The resistance of the sensor increased significantly, mimicking a ‘switch‐off’ response when exposed to the analyte vapor. When the analyte vapor was no longer present, the sensor returned back to its original condition, showing a ‘switch‐on’ response. The percolation point was obtained when the carbon concentration of the polymer/carbon composite was kept at 2.5 wt%.

CONCLUSION: A low‐mass‐fraction carbon composite sensor has been designed and fabricated to detect γ‐terpinene, α‐pinene, p‐cymene, farnesene, limonene and cis‐hexenyl acetate. The sensor is inexpensive, easy to fabricate and highly stable in air. Copyright © 2011 Society of Chemical Industry
Optimization of AlGaN‐based spacer layer for InAlN/GaN interfaces
Authors: Akazawa M. , Gao B. , Hashizume T. , Hiroki M. , Yamahata S. , Shigekawa N.
Published: December 2011

AlGaN‐based spacer layers for lattice‐matched and nearly lattice matched InAlN/GaN interfaces were examined in Al2O3/InAlN/AlGaN/AlN/GaN structures. An Al2O3 overlayer was deposited to investigate the characteristics under positive bias by capacitance‐voltage (C‐V) measurement. The C‐V characteristic for a sample with an Al0.38Ga0.62N/AlN double spacer layer indicated unfavorable electron accumulation at the InAlN/AlGaN interface inside the barrier under positive bias. To suppress the unfavorable accumulation, attempts were made to increase the Al molar fraction of the AlGaN layer to reduce the conduction band discontinuity and interface charge at InAlN/AlGaN interface. An Al0.44Ga0.56N/AlN double spacer layer and an Al0.44Ga0.56N single spacer layer of almost the same total thickness were investigated. Although both spacer layers result in normal C‐V characteristics without the indication of unfavorable electron accumulation, the InAlN layer on a 1.5‐nm‐thick Al0.44Ga0.56N single spacer layer exhibited superior surface morphology without deteriorating the mobility of the two‐dimensional electron gas despite the absence of the AlN layer. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study of UV electro‐absorption modulators based on bulk III‐nitride films and multiple quantum wells
Authors: Kao Chen‐kai , Bhattacharyya A. , Thomidis C. , Moldawer A. , Paiella R. , Moustakas T. D.
Published: December 2011

In this paper we present studies and compare the performance of UV electroabsorption modulators based on bulk GaN films and GaN/AlGaN multiple quantum wells. In both types of devices, the absorption edge at room temperature is dominated by excitonic effects and can be strongly modified through the application of an external electric field. We find that when similar active layer thicknesses and device geometries are employed, the electroabsorption modulators based on bulk nitride films can provide similar performance levels as those of GaN/AlGaN multiple quantum well devices. This should be compared to the case of arsenide, phosphide, or antimonide semiconductors, where the electroabsorption effect in quantum wells is an order of magnitude stronger than in the bulk. This is primarily due to the strong ionic character of the nitride semiconductors, which lead to very large exciton binding energies at room temperature (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of inversion domain formation in AlN grown on sapphire by MOVPE
Authors: Kueller Viola , Knauer Arne , Brunner Frank , Mogilatenko Anna , Kneissl Michael , Weyers Markus
Published: December 2011

For certain growth conditions pronounced roughening has been observed for AlN layers grown on c‐plane sapphire by metal‐organic vapour phase epitaxy. TEM investigations revealed inversion domains correlated with the rough regions of the wafer. Al‐polar material was found at hillocks and N‐polar AlN in the valleys. We have investigated the early stages of growth and found three determining factors for the polarity development in AlN on c‐plane sapphire: substrate treatment by NH3 (nitridation) or TMAl preflow, substrate treatment by annealing under H2 atmosphere and the influence of parasitic depositions in the reactor. We propose a correlation between the sapphire surface termination and the polarity of AlN. Oxygen termination of sapphire is suggested to lead to N‐polarity and aluminium termination to Al‐polar AlN. By optimising the reactor condition, substrate treatment and growth conditions, smooth Al‐polar AlN layers were obtained for the subsequent growth of deep UV‐LED heterostructures. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of vertically propagating convectively coupled equatorial waves using observations and a non‐hydrostatic Boussinesq model on the equatorial beta‐plane
Authors: Roundy Paul E. , Janiga Matthew A.
Published: December 2011

A non‐hydrostatic model on the equatorial beta‐plane is solved for the most basic solutions of vertically and zonally propagating internal plane waves. Solutions tilt in the vertical and propagate upward, with buoyancy as a principal restoring force. Results indicate that when frequency is of the same order of magnitude as a reduced buoyancy frequency, the shallow‐water model equivalent depth depends on frequency. One consequence of this dependence is that Kelvin waves become dispersive at high frequencies. In a complementary observational analysis, linear regression and a space‐time wavelet spectrum analysis of observed convectively coupled mixed Rossby gravity (MRG) waves are applied to estimate vertical wavelengths that are consistent with the strongest signals associated with observed convectively coupled waves at specific zonal wave numbers and frequencies. Substitution of these dispersion parameters into the model yields theoretical structures characterized by vertical and horizontal wavenumbers and frequencies similar to those observed in the lower and middle troposphere. These model solutions demonstrate that the Coriolis terms associated with the horizontal component of the earth's angular momentum explain substantial meridional tilts and phase shifts between quantities associated with observed convectively coupled waves, especially proximate to the surface of the Earth. Copyright © 2011 Royal Meteorological Society
Boundary‐layer flow within and above a forest canopy of variable density
Authors: Ross Andrew N.
Published: December 2011

An analytical model is developed for flow within and above a forest canopy with a slowly varying canopy density. Results are compared with existing analytical models for flow over a surface with slowly varying roughness length, and also with numerical simulations. The results show that the analytical solution is successful in capturing the behaviour of the flow for small and slowly changing variations in canopy density. Previous models which only vary the roughness length and neglect changes in displacement height fail to capture the near‐surface flow accurately. Including changes in displacement height as well as roughness length changes gives results closer to those obtained with the full canopy model, but even then the flow induced in the canopy leads to significant differences. The analytical model also highlights the sensitivity of the results to the parametrization of the vertical component of the turbulent stress tensor, τzz. For shorter wavelength variations in the canopy density, the analytical model breaks down as the more rapid changes in density induce larger flow perturbations which lead to increased flow into and out of the canopy. This kind of idealised analytical study provides important insights into the role of canopy heterogeneities on boundary‐layer flow. This is important both for understanding near‐surface winds and transport, and also for parametrizing the effects of surface heterogeneities in large‐scale weather and climate models. Copyright © 2011 Royal Meteorological Society
Wave‐breaking characteristics of midlatitude blocking
Authors: Masato G. , Hoskins B. J. , Woollings T. J.
Published: December 2011

In this article, Northern Hemisphere winter midlatitude blocking is analysed through its wave‐breaking characteristics. Rossby wave breaking is identified as a key process in blocking occurrence, as it provides the mechanism for the meridional reversal pattern typical of blocking. Two indices are designed to detect the major properties of wave breaking, i.e. the orientation (cyclonic/anticyclonic–direction of breaking or DB index) and the relative contribution of air masses (warm/cold–relative intensity or RI index). The use of the DB index differentiates between the anticyclonic cases over Europe and Asia and the cyclonic events over the oceanic basins. One of the three regions displaying cyclonic type was found over the Atlantic Ocean, the other two being over the Pacific Ocean. The first of these is located over the western side of the Pacific and is dominated by warm air extrusions, whereas the second is placed northward of the exit region of the jet stream, where the meridional θ gradient is much weaker. Two European blocking types have been detected using the RI index, which separates out the cases dominated by warm and cold air masses. The latter cases in particular exhibited a well‐structured dipole, with associated strong anomalies in both temperature and precipitation. Copyright © 2011 Royal Meteorological Society
High open‐circuit voltage of graphene‐based photovoltaic cells modulated by layer‐by‐layer transfer
Authors: Ihm Kyuwook , Lee Kyung‐Jae , Lim Jong Tae , Kang Tai‐Hee , Chung Sukmin , Hong Byung Hee , Yeom Geun Young
Published: December 2011

Graphene has shown great application opportunities in future nanoelectronic devices because of its outstanding electronic properties. Moreover, its impressive optical properties have been attracting the interest of researchers, and, recently, the photovoltaic effects of a heterojunction structure embedded with few layer graphene (FLG) have been demonstrated. Here, we report the photovoltaic response of graphene–semiconductor junctions and the controlled open‐circuit voltage (Voc) with varying numbers of graphene layers. After unavoidably adsorbed contaminants were removed from the FLGs by means of in situ annealing, prepared by layer‐by‐layer transfer of the chemically grown graphene layer, the work functions of FLGs showed a sequential increase as the graphene layers increase, despite random interlayer‐stacking, resulting in the modulation of photovoltaic behaviors of FLGs/Si interfaces. The surface photovoltaic effects observed here show an electronic realignment in the depth direction in the FLG heterojunction systems, indicating future potential toward solar devices utilizing the excellent transparency and flexibility of FLG. Copyright © 2011 John Wiley & Sons, Ltd.
Characterization of Ar ion etching induced damage for GaN
Authors: Kataoka Keita , Kimoto Yasuji , Horibuchi Kayo , Nonaka Takamasa , Takahashi Naoko , Narita Tetsuo , Kanechika Masakazu , Dohmae Kazuhiko
Published: December 2011

We studied the overall picture of the etching‐induced damage for GaN films. By using Ar ion etching, we characterized the damage for GaN from various perspectives by AES, transmission electron microscopy, X‐ray absorption spectroscopy, and cathode luminescence. From AES results, it was found that N on GaN surface is selectively etched. After air exposure, the near surface layer within the damage layer was oxidized by the existence of the chemically active dangling bonds. The thickness of the damage layer was observed by cross‐sectional transmission electron microscopy as the dimmed layer, which is caused by the absence of translation symmetry, in other words, degradation of the crystallinity introduced by crystal defects and/or transformation into an amorphous phase in nanoscale. Total reflection X‐ray absorption near‐edge structure spectrum indicated the gradual change from GaN to Ga oxide with higher Ar ion acceleration voltage. Moreover, the etching‐induced nonradiative defects were detected by comparing the cathode luminescence intensities. The various phenomena of the damage can be comprehensively evaluated by using these methods, and the overall picture of etching‐induced damage for GaN was revealed. Copyright © 2011 John Wiley & Sons, Ltd.
How to deal with double partial verification when evaluating two index tests in relation to a reference test?
Authors: van Geloven Nan , Broeze Kimiko A. , Opmeer Brent C. , Mol Ben Willem , Zwinderman Aeilko H.
Published: December 2011

Research into the diagnostic accuracy of clinical tests is often hampered by single or double partial verification mechanisms, that is, not all patients have their disease status verified by a reference test, neither do all patients receive all tests under evaluation (index tests). We show methods that reduce verification bias introduced when omitting data from partially tested patients. Adjustment techniques are well established when there are no missing index tests and when the reference test is ‘missing at random’. However, in practice, index tests tend to be omitted, and the choice of applying a reference test may depend on unobserved variables related to disease status, that is, verification may be missing not at random (MNAR). We study double partial verification in a clinical example from reproductive medicine in which we analyse the diagnostic values of the chlamydia antibody test and the hysterosalpingography in relation to a diagnostic laparoscopy. First, we plot all possible combinations of sensitivity and specificity of both index tests in two test ignorance regions. Then, we construct models in which we impose different assumptions for the verification process. We allow for missing index tests, study the influence of patient characteristics and study the accuracy estimates if an MNAR mechanism would operate. It is shown that data on tests used in the diagnostic process of the same population are preferably studied jointly and that the influence of an MNAR verification process was limited in a clinical study where more than half of the patients did not have the reference test. Copyright © 2011 John Wiley & Sons, Ltd.
Preparation of water‐soluble starch oligomers from variable starch species in 1‐allyl‐3‐methylimidazolium chloride
Authors: Lappalainen Katja , Kärkkäinen Johanna , Panula‐Perälä Johanna , Lajunen Marja
Published: December 2011

Native wheat, barley, rice, maize, wx maize, and potato starch species were modified by depolymerization in 1‐allyl‐3‐methylimidazolium chloride ([AMIM]Cl) ionic liquid (IL) using oil bath or microwave heating. Reactions were catalyzed with p‐toluenesulfonic acid (p‐TsOH). Reaction times varied depending on the starch species and its concentration, the heating method, and volume of the reaction mixture. Depolymerization products were analyzed with HPLC‐ELSD. All starch species mostly degraded into water‐soluble 1500–2000 Da‐sized starch oligomers. Glucose and other short‐chained sugars did not precipitate along with starch oligomers due to their high solubility in IL. This property was utilized in the purification of commercial maltodextrins. Produced water‐soluble, low MW starch oligomers might be used, e.g., in bacterial cultivations as a glucose source.
Gendiagnostikgesetz
Authors: Gillessen-Kaesbach G. , Glaubitz R. , Eiben B.
Published: December 2011

Die enormen Fortschritte im Bereich der Humangenetik tragen fast täglich zur Identifizierung neuer krankheitsverursachender Gene bei. Die Konsequenzen aus diesen genetischen Informationen haben eine erhebliche Bedeutung im Hinblick auf den persönlichen Umgang mit Krankheiten und auf die individuelle Lebensplanung. In der genetischen Beratung werden dem Ratsuchenden Informationen im Hinblick auf das Wesen der Erkrankung, der Bedeutung genetischer Befunde sowie Möglichkeiten der Prävention, Therapie und Diagnostik vermittelt, die dann Grundlage für eine autonome Entscheidung sind. Das am 1. Februar 2010 in Kraft getretene Gendiagnostikgesetz (GenDG) regelt den Umgang mit genetischen Untersuchungen sowie die Verwendung genetischer Proben und Daten beim Menschen und stellt die Anforderungen an die genetische Beratung dar. Ab dem 1. Februar 2012 dürfen nur Ärzte eine genetische Beratung durchführen, die eine entsprechende Qualifikation erworben haben.
Das Ersttrimesterscreening und die neue Risikoberechnungsoftware der Fetal Medicine Foundation Deutschland
Authors: Eiben B. , Thode C. , Merz E.
Published: December 2011

Das Ersttrimesterscreening zur Risikobestimmung für Trisomie 21, 18 und 13 hat sich in den letzten 10 Jahren in Deutschland etabliert. Die optimale Durchführung setzt die Einhaltung bestimmter Messkriterien voraus sowie die Benutzung evaluierter Risikoberechnungsprogramme. Die individuelle Risikoberechnung erfolgt im deutschsprachigen Raum meist mit dem Berechnungsprogramm PRC der Fetal Medicine Foundation Deutschland (FMF-D) unter Verwendung der Angaben zum maternalen Alter, zur Scheitel-Steiß-Länge, zur Nackentransparenz, zum freien β-HCG (Humanchoriongonadotropin) und zum PAPP-A („pregnancy-associated plasma protein-A“). PRC 2.0 berücksichtigt zusätzlich den Nikotinkonsum, die ethnische Herkunft und das mütterliche Gewicht. Durch die neuen Version des Berechnungsprogramms PRC 2.0 konnte die Trisomie-21-, -18- und -13-Detektionsrate erhöht werden bei gleichzeitiger Senkung der Falsch-positiv-Raten. Diese Ergebnisse werden verglichen mit den Ergebnissen aus der vorherigen Version von PRC und denen des englischen Algorithmus.
Nichtinvasive molekulargenetische Methoden in der pränatalen Diagnostik
Authors: Geigl J.B. , Speicher M.R.
Published: December 2011

Seit vielen Jahren wird an der Entwicklung nichtinvasiver pränataler Untersuchungen gearbeitet, um die Risiken für den Fetus bei der traditionellen Amniozentese oder Choriozottenbiopsie zu umgehen. Bis vor Kurzem waren die meisten Ansätze extrem aufwendig und nur auf ausgewählte Fragestellungen limitiert, sodass sie nicht über einen „Proof-of-principle-Status“ hinauskamen. Dies hat sich durch Einführung neuer Sequenzierverfahren grundlegend geändert, weil erste Studien belegten, dass fetale Aneuploidien aus mütterlicher Plasma-DNA korrekt identifiziert werden können. Darüber hinaus erlauben diese Techniken auch den Mutationsstatus des Fetus zu erheben, sodass sich einerseits in der pränatalen Diagnostik ganz neue Möglichkeiten ergeben, die andererseits aber auch mit erheblichen ethischen Herausforderungen verbunden sind. In dieser Übersicht wird die Entwicklung zu diesen neuen Verfahren dargestellt.
Präimplantationsdiagnostik für monogen vererbte Erkrankungen
Authors: Hehr A. , Paulmann B. , Seifert B. , Hehr U.
Published: December 2011

Die Präimplantationsdiagnostik (PID) für monogen vererbte Erkrankungen ist heute neben der Pränataldiagnostik als eine Möglichkeit der Realisierung des Kinderwunsches international fest etabliert. Die Schwangerschaftsraten entsprechen denen einer Behandlung mit intrazytoplasmatischer Spermieninjektion (ICSI) ohne genetische Testung im Rahmen der normalen Kinderwunschbehandlung. Sie erfordert vorab eine umfassende ergebnisoffene genetische und reproduktionsmedizinische Beratung interessierter Paare mit Darstellung der Möglichkeiten der PID, aber auch ihrer Risiken und ihrer begrenzten Erfolgschancen. Von Seiten des PID-Zentrums ist neben einer guten interdisziplinären medizinischen Betreuung ein Qualitätsmanagement für das genetische und In-vitro-Fertilisations(IVF)-Labor inklusive Schnittstellen zu etablieren, welches den Besonderheiten der Einzelzelldiagnostik Rechnung trägt.
Use of magnetic resonance analysis for clinical evaluation of the peripheral area of gestational sac in bleeding and non‐bleeding ectopic pregnancy cases
Authors: Kuroda Masako , Kuroda Keiji , Kuwatsuru Ryohei , Kitade Mari , Kikuchi Iwaho , Kumakiri Jun , Matsuoka Shozo , Takeda Satoru
Published: December 2011

Purpose

To evaluate preoperative magnetic resonance (MR) imaging features of bleeding and non‐bleeding ectopic pregnancy (EP) by comparison with surgical findings.

Methods

Eighteen suspected EP cases underwent preoperative MR imaging. We classified 8 cases as the bleeding group and 7 cases as the non‐bleeding group with or without intra‐abdominal bleeding and/or hematoma at the site of EP, and compared, retrospectively, gestational sac (GS)‐like structure, particularly the peripheral area of the GS via MR analysis. Excluded were 3 cases that were insufficient for assessing extrauterine GS‐like structure: ruptured tubal pregnancy and uterine horn pregnancy.

Results

GS‐like structures were typically observed as low intensity on T1‐weighted image (T1WI) and as high intensity on T2‐weighted image (T2WI). In non‐bleeding cases, most peripheral areas of the GS were of intermediate intensity on T1WI and high intensity on T2WI. Most bleeding cases were of high intensity on T1WI and low to high intensity on T2WI. Furthermore, the peripheral area of the GS was of higher intensity on T1WI with fat suppression than on T1WI.

Conclusions

It is clear that MR imaging is effective for diagnosis of cases of suspected EP. EP conditions may be predicted by signal intensity of the peripheral area of the GS via MR analysis.
Basaloid follicular hamartoma: A case report and review of the literature
Authors: Huang Shu‐Han , Hsiao Tien‐Fa , Lee Chin‐Cheng
Published: December 2011

Basaloid follicular hamartoma (BFH) is a rare, benign, skin adnexal tumor. Several clinical patterns have been reported, but they all share the same histopathological features. BFH may be hereditary or nonhereditary and can be accompanied by systemic diseases. Microscopic examination of BFH shows branching cords and anastomosing strands of basaloid cells in a loose, fibrous stroma. The most important pathological differential diagnosis is infundibulocystic basal cell carcinoma. These two lesions must be differentiated carefully based on clinical presentation and histopathological picture, and even molecular studies may be needed. We present a report of a 78‐year‐old woman with a solitary, asymptomatic, slow‐growing skin tumor on her left scalp. No associated systemic disorders were found. On the basis of an excisional biopsy performed on the tumor, a pathological diagnosis of sporadic BFH was made.
HERMITE–HADAMARD TYPE INEQUALITIES FOR FUNCTIONS WHEN A POWER OF THE ABSOLUTE VALUE OF THE FIRST DERIVATIVE IS P-CONVEX
Authors: BARANI A. , BARANI S.
Published: December 2011

In this paper we extend some estimates of the right-hand side of a Hermite–Hadamard type inequality for functions whose derivatives’ absolute values are P-convex. Applications to the trapezoidal formula and special means are introduced.
ESSENTIAL NORM OF EXTENDED CESÀRO OPERATORS FROM ONE BERGMAN SPACE TO ANOTHER
Authors: HU ZHANGJIAN
Published: December 2011

Let Ap(φ) be the pth Bergman space consisting of all holomorphic functions f on the unit ball B of ℂn for which $\|f\|^p_{p,\varphi }= \int _B |f(z)|^p \varphi (z) \,dA(z)\lt +\infty $, where φ is a given normal weight. Let Tg be the extended Cesàro operator with holomorphic symbol g. The essential norm of Tg as an operator from Ap (φ) to Aq (φ) is denoted by $\|T_g\|_{e, A^p (\varphi )\to A^q (\varphi )} $. In this paper it is proved that, for p≤q, with 1/k=(1/p)−(1/q) , where ℜg(z) is the radial derivative of g; and for p>q, with 1/s=(1/q)−(1/p) .