bluuebunny/crossref_metadata_2025 huggingface dataset:
Introduction
Authors: Müller Rolf
Published: November 2011

The topic of this book is the interdependence of stratospheric ozone depletion and climate change. The purpose of this introductory chapter is to lay the foundations, which are necessary for the understanding of the specialized chapters constituting the central portion of this book. In this chapter the basics of stratospheric chemistry are described; ozone production and ozone loss through catalytic cycles and the distribution of ozone in the stratosphere resulting from the interaction of stratospheric ozone chemistry with the stratospheric circulation (the so called Brewer-Dobson circulation). The anthropogenic release of chlorofluorocarbons and other ozone-depleting substances has led to a strong perturbation of the ozone layer. The temporal development of the major ozone-depleting substances in the atmosphere is discussed, focusing both on the rapid increase in ozone-depleting substances in the atmosphere since 1960 and the decline observed today and projected to continue due to the success of the Montreal Protocol and its adjustments and amendments in reducing global production and consumption of these substances. One consequence of the accumulation of ozone-depleting substances in the atmosphere is the ozone depletion observed today in the upper stratosphere peaking at 40km with a decline between 1980 and 1996 of about 10%. The most severe ozone depletion, however, is observed in the Antarctic “ozone hole”, where mean column ozone has been about 40% below 1980 values for the past 15 years. Severe ozone depletion is also observed in recent cold Arctic winters, with the hitherto strongest loss having occurred in winter 2010–2011. Polar ozone depletion occurs because a set of chemical and meteorological processes interact in a way leading eventually to precipitous chemical loss of ozone in springtime. In response to reductions in ozone depleting substances in future decades, stratospheric ozone is projected to recover. However, ozone recovers differently in different regions and at different altitudes in the stratosphere. Further, ozone will not simply recover to 1980 or 1960 values, rather the development of stratospheric ozone over the coming decades will be determined by both substantial reductions in ozone-depleting substances and changes in the stratosphere caused by climate change. Finally, model studies indicate that, had no controls on ozone depleting substances been put into effect, by the middle of this century a severe global depletion of ozone (reductions by more than a factor of two globally) would have developed.
Polar Stratospheric Clouds and Sulfate Aerosol Particles: Microphysics, Denitrification and Heterogeneous Chemistry
Authors: Peter Thomas , Grooß Jens-Uwe
Published: November 2011

Clouds and aerosol particles play important roles in the chemistry of the polar winter stratosphere. Under extremely cold conditions their surfaces host heterogeneous chemical reactions, which—depending on temperature and aerosol loading—may lead to a very fast transformation of chlorine containing reservoir compounds into active, ozone destroying chlorine. Furthermore, polar stratospheric clouds (PSCs) may generate large nitric-acid-containing particles, which sediment rapidly, thereby denitrifying the stratospheric air and disabling reactive nitrogen species to deactivate the ozone-destroying chlorine. Both processes, heterogeneous chemistry and denitrification provide the basis for chlorine-catalyzed ozone destruction, which under sustained cold conditions leads to the ozone hole over the Antarctic and substantial ozone depletion over the Arctic. While the principles of these polar ozone loss mechanisms have long been recognized, very recently new measurements and modeling of PSCs have cast serious doubts on our understanding of some of the most fundamental processes of PSC formation and heterogeneous chemistry. One important open question is whether the nucleation of nitric acid hydrates and subsequent denitrification are governed predominantly by ice-assisted or ice-free processes. A number of previously discussed processes appear to be unlikely from today's perspective, such as homogeneous nucleation of hydrates in supercooled liquid solution droplets, nucleation of hydrates in glassy aerosols or pseudo-heterogeneous nucleation at a droplet/vapor interface. However, while heterogeneous nucleation of hydrates on water ice is accepted in the light of laboratory experiments and field observations, an unidentified ice-free heterogeneous nucleation process, e.g. on dust particles, appears to be required in order to explain a number of very recent field observations, in particular by the downward-looking LiDAR on the CALIPSO satellite in the Arctic winter 2009–2010. This result is perplexing and reverses the previous understanding of PSC formation, because there is currently no conclusive laboratory evidence supporting this finding. There are also open issues concerning chlorine activation on solid and liquid PSC and cold stratospheric aerosol particles. In particular, activation reaction rates on nitric acid hydrate particles retain an uncertainty of almost two orders of magnitude. However, while this uncertainty remains a physico-chemical flaw, it appears not to hamper our ability to understand and predict chlorine activation and ozone loss, as liquid particles are usually the dominant chlorine processors. Liquid phase heterogeneous and multi-phase chemistry is much less uncertain. It appears that under many circumstances, the formation of PSCs is not even required for rapid chlorine activation, rather the heterogeneous chemistry on sufficiently cold background aerosol ensures the dissolution and activation of chlorine reservoir species such as HCl.
Ozone Loss in the Polar Stratosphere
Authors: Harris Neil R. P. , Rex Markus
Published: November 2011

Dramatic springtime ozone losses have occurred over the Antarctic every year since the early 1980s. During a six-week period between mid-August and the end of September, more than 99% of the ozone is destroyed in a layer 3–5km deep at altitudes between 15 and 21km. With the exception of one year (2002) the ozone loss has remained until at least the end of October and sometimes into December, depending on the stability of the Antarctic vortex in each particular year. In contrast, the ozone loss that occurs over the Arctic varies enormously from year to year. In some years there is little or no loss; in other years as much as 60% or 70% of the ozone is lost at some altitudes. This chapter looks in some detail at the main factors that determine the ozone loss over the two poles using a mixture of observational and modeling studies.
Mid-latitude Ozone Depletion
Authors: Chipperfield M. P.
Published: November 2011

The abundance of ozone at mid-latitudes (35°–60° N and S) is controlled by a combination of chemical and dynamical processes. Observations have shown that mid-latitude column ozone decreased in both hemispheres from about 1980 onwards. The column depletion in the southern hemisphere was larger and increased through to 2000; in the north the depletion peaked around 1993. In the profile, ozone loss was observed in both the lower (∼20km) and upper (∼40km) stratosphere. There is strong evidence that this observed depletion in mid-latitude ozone was largely driven by increases in stratospheric chlorine and bromine. The basic fingerprint of modeled loss matches those observations in terms of profile and latitudinal variations and long-term variations. However, there is also strong evidence that dynamical changes have contributed to changes in northern mid-latitudes, which have been more extensively studied that the south. In the north, about 1/3 of the ozone trend over the last few decades can be ascribed to dynamical changes. Stratospheric chlorine and bromine is now starting to decrease following a peak in the late 1990s. This should cause a recovery of the ozone layer, but other factors (e.g. greenhouse gas-induced climate change) will modulate this. Although ozone has been observed to increase over the past decade (in both the column and profile) it has not yet been possible to ascribe this change unequivocally to recovery from depletion casued by chlorine and bromine species.
Impact of Climate Change on the Stratospheric Ozone Layer
Authors: Dameris Martin , Baldwin Mark P.
Published: November 2011

The purpose of this chapter is to give an overview about effects of climate change on the temporal evolution of the stratospheric ozone layer. Climate change is affecting the ozone layer through changes in air mass transport, chemical composition, and temperature. In turn, changes to the ozone layer are influencing climate through radiative processes; consequential changes in temperature gradients are modifying atmospheric dynamics. Therefore, climate change and the evolution of the ozone layer are coupled. Understanding all of the processes involved is made more complex by the fact that many of the feedbacks between physical, dynamical and chemical processes in Earth's atmosphere are nonlinear. Investigations of the relationships and feedbacks between ozone depletion and climate change processes have demonstrated that it is not possible to achieve a complete understanding of long-term changes of stratospheric ozone content without the consideration of climate change.
Stratospheric Ozone in the 21st Century
Authors: Waugh D. W. , Eyring V. , Kinnison D. E.
Published: November 2011

This chapter discusses the future evolution of stratospheric ozone and its return to historical values from state-of-the-art three-dimensional coupled chemistry-climate models. These models have been developed by international research groups and evaluated by the atmospheric science community over the last two decades and include a detailed representation of the physical, dynamical, and chemical processes of the atmosphere, with a focus on the stratosphere. This chapter describes the models and shows examples on how these models are evaluated with observations. Factors that affect stratospheric ozone abundance, specifically ones that relate to uncertainties in the return of ozone to historical values (e.g., stratospheric halogen loading, and climate-induced temperature and transport trends) are discussed. The projected evolution of ozone is shown for different latitude regions (e.g., tropics, mid-latitudes, and polar), for different altitudes and for the total column. Hemispheric differences are also highlighted. In general models that have a better representation of transport processes measured by the models ability to represent the mean age of air and inorganic chlorine abundances are better suited to project the evolution of ozone in the 21st century. Uncertainties in current modelling approaches and recommendations for future projection simulations are also discussed.
Dissociation of ERK signalling inhibition from the anti-amyloidogenic action of synthetic ceramide analogues
Authors: Li Hongyun , Evin Genevieve , Hill Andrew F. , Hung Ya Hui , Bush Ashley I. , Garner Brett
Published: November 2011

Inhibition of GSL (glycosphingolipid) synthesis reduces Aβ (amyloid β-peptide) production in vitro. Previous studies indicate that GCS (glucosylceramide synthase) inhibitors modulate phosphorylation of ERK1/2 (extracellular-signal-regulated kinase 1/2) and that the ERK pathway may regulate some aspects of Aβ production. It is not clear whether there is a causative relationship linking GSL synthesis inhibition, ERK phosphorylation and Aβ production. In the present study, we treated CHO cells (Chinese-hamster ovary cells) and SH-SY5Y neuroblastoma cells, that both constitutively express human wild-type APP (amyloid precursor protein) and process this to produce Aβ, with GSL-modulating agents to explore this relationship. We found that three related ceramide analogue GSL inhibitors, based on the PDMP (D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol) structure, reduced cellular Aβ production and in all cases this was correlated with inhibition of pERK (phosphorylated ERK) formation. Importantly, the L-threo enantiomers of these compounds (that are inferior GSL synthesis inhibitors compared with the D-threo-enantiomers) also reduced ERK phosphorylation to a similar extent without altering Aβ production. Inhibition of ERK activation using either PD98059 [2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one] or U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene) had no impact on Aβ production, and knockdown of endogenous GCS using small interfering RNA reduced cellular GSL levels without suppressing Aβ production or pERK formation. Our data suggest that the alteration in pERK levels following treatment with these ceramide analogues is not the principal mechanism involved in the inhibition of Aβ generation and that the ERK signalling pathway does not play a crucial role in processing APP through the amyloidogenic pathway.
Reflux in Children and Its Effects on Assessment and Management of Voice Disorders From a Speech-Language Pathologist's Perspective
Authors: Theis Shannon M.
Published: November 2011

Voice disorders in the pediatric population are common, but have been understudied. Inflammation, trauma, and neurologic and congenital anomalies all can result in childhood dysphonia. Laryngopharyngeal reflux, an extraesophageal variation of gastroesophageal reflux, has been associated with laryngeal symptoms of dysphonia, globus sensation, throat clearing, and chronic cough in children. This article reviews the current evaluation and treatment techniques of reflux and the effects of laryngopharyngeal reflux on voice quality in children. A case study illustrates the importance of treating laryngeal inflammation to achieve an accurate diagnosis.
Extra-Esophageal Reflux and Laryngeal Disease: Update From a Translational Research Team
Authors: Bock Jonathan M. , Johnston Nikki , Toohill Robert J. , Koszewski Ian J. , Samuels Tina L. , Blumin Joel H.
Published: November 2011

Extraesophageal reflux (EER) has been implicated in a variety of different otorhinolaryngologic disorders including otitis media, chronic sinusitis, globus pharyngeus, laryngeal neoplasia, and many benign laryngeal disorders. New technologies such as multichannel intraluminal impedance studies have revolutionized our ability to detect the prevalence of EER, and the role of biomarker detection in diagnosing ongoing EER is evolving. Gastric refluxate contains not only hydrochloric acid, but also bile salts and digestive enzymes such as pepsin. Analysis of pepsin levels in both tissues and secretions is emerging as a useful adjunct in the diagnosis of EER and work to evaluate the role of pepsin in the promotion of laryngeal inflammation and neoplasia is ongoing. This review discusses the recent literature regarding the diagnosis and treatment of EER, and describes the controversies that can perhaps be further elucidated by ongoing clinical and translational research.
Organizational Design of it Supplier Relationship Management: A Multiple Case Study of Five Client Companies
Authors: Kaiser Jasmin , Buxmann Peter
Published: November 2011

This papers shows that the management of contractual relationships in IS/IT outsourcing is not only receiving greater attention in academic research, but that it has also moved into focus of companies with high outsourcing degrees. This shift of management attention is accompanied by observable changes in IT organizations’ design, revealing an underrepresented but promising research topic. While prior research has predominantly explored single aspects, for example, supplier selection or relationship building, this article takes a more holistic approach on IT supplier relationship management (SRM) with a focus on organizational design. A conceptual framework, covering three core elements of organizational design, strategy, structure and process, guided the multiple case study on IT SRM in five client IT organizations. One key finding from sourcing strategy is that IT organizations have in parts significantly and abruptly reduced their number of suppliers in the last years, a phenomenon typically well known in the automobile industry. With regard to structure, different organizational models are presented, varying upon their degree of centralization and mode of sourcing. The concept of a hybrid (centralized-decentralized) structure, where a central unit fulfills SRM activities, was shown to be the predominant model within our case organizations. Design and potential benefits of this barely examined model are discussed in detail and empirical examples are provided respectively. As a third organizational design component, formal processes and lateral connections are presented as a means to bridge barriers between organizational entities central to IT SRM. Finally, various opportunities for future research are illustrated.
Flow structure and acoustics of supersonic jets from conical convergent-divergent nozzles
Authors: Munday D. , Gutmark E. , Liu J. , Kailasanath K.
Published: November 2011

Conical convergent-divergent (CCD) nozzles represent an important category of supersonic jet-engine nozzles which require variable throat areas and variable exit areas to adapt to a range of operating conditions. CCD nozzles with design Mach numbers of 1.3, 1.5, and 1.65 are examined experimentally over a range of fully expanded Mach numbers from 1.22 to 1.71. The characteristics of the flow and acoustic fields from these nozzles are explored. Shadowgraph, Particle Image Velocimetry, far-field and near-field acoustic surveys are presented. Results of a Monotonically Integrated Large Eddy Simulation are presented for the Mach 1.5 nozzle at an underexpanded condition. The agreement between simulations and measurements is excellent. It is shown that these nozzles differ from traditional smoothly contoured method-of-characteristics nozzles in that they never achieve a shock free condition. Furthermore it is shown that these nozzles produce a “double diamond” pattern in which two sets of shock diamonds are generated with an axial displacement between them. The cause of this phenomenon is explored. It is further shown that as a consequence they are never free from shock-associated noise even when operated at perfect expansion. In spite of this difference, it is found that CCD nozzles behave like traditional convergent-divergent nozzles in that they produce the same shock-cell size, broadband shock-associated noise peak frequency, and screech frequency as traditional convergent-divergent nozzles. The apparent source regions for mixing noise, broadband shock associated noise and screech are all similar to those from traditional convergent-divergent nozzles.
Microfabrication of controlled-geometry samples for the laser-heated diamond-anvil cell using focused ion beam technology
Authors: Pigott Jeffrey S. , Reaman Daniel M. , Panero Wendy R.
Published: November 2011

The pioneering of x-ray diffraction with in situ laser heating in the diamond-anvil cell has revolutionized the field of high-pressure mineral physics, expanding the ability to determine high-pressure, high-temperature phase boundaries and equations of state. Accurate determination of high-pressure, high-temperature phases and densities in the diamond-anvil cell rely upon collinearity of the x-ray beam with the center of the laser-heated spot. We present the development of microfabricated samples that, by nature of their design, will have the sample of interest in the hottest portion of the sample. We report initial successes with a simplified design using a Pt sample with dimensions smaller than the synchrotron-based x-ray spot such that it is the only part of the sample that absorbs the heating laser ensuring that the x-rayed volume is at the peak hotspot temperature. Microfabricated samples, synthesized using methods developed at The Ohio State University's Mineral Physics Laboratory and Campus Electron Optics Facility, were tested at high P-T conditions in the laser-heated diamond-anvil cell at beamline 16 ID-B of the Advanced Photon Source. Pt layer thicknesses of ≤0.8 μm absorb the laser and produce accurate measurements on the relative equations of state of Pt and PtC. These methods combined with high-purity nanofabrication techniques will allow for extension by the diamond-anvil cell community to multiple materials for high-precision high-pressure, high-temperature phase relations, equations of state, melting curves, and transport properties.
Surface piezoelectricity: Size effects in nanostructures and the emergence of piezoelectricity in non-piezoelectric materials
Authors: Dai Shuangxing , Gharbi Mohamed , Sharma Pradeep , Park Harold S.
Published: November 2011

In this work, using a combination of a theoretical framework and atomistic calculations, we highlight the concept of “surface piezoelectricity,” which can be used to interpret the piezoelectricity of nanostructures. Focusing on three specific material systems (ZnO, SrTiO3, and BaTiO3), we discuss the renormalization of apparent piezoelectric behavior at small scales. In a rather interesting interplay of symmetry and surface effects, we show that nanostructures of certain non-piezoelectric materials may also exhibit piezoelectric behavior. Finally, for the case of ZnO, using a comparison with first principles calculations, we also comment on the fidelity of the widely used core–shell interatomic potentials to capture non-bulk electro-mechanical response.
Organic light-emitting devices with polymethylmethacrylate interfacial layer: Role of organic internal interface on electric field distribution
Authors: Ainsebaa Abdelmalek , Fave Jean-Louis , Schott Michel
Published: November 2011

Organic light-emitting devices (OLEDs) are studied, containing polyvinylcarbazole and bathocuproine layers, with or without insertion of a polymethylmethacrylate layer at the organic interface. The latter efficiently blocks electrons but not holes. Large currents flowing in the diodes are limited by the interplay of transmission of holes through the organic heterojunction and space charge limitation in the anodic part of the diode. Minority electron currents are always small. An illustrative analytical model is presented, showing the evolution of fields in the anodic and cathodic compartments and the possibility of two physically acceptable solutions. Electroluminescence is observed only in the diodes without polymethylmethacrylate above a threshold V ∼ 7 V. Quantum yields of both phosphorescence and fluorescence and the triplet lifetime of BCP have also been determined.
Influence of source and drain contacts on the properties of the indium-zinc oxide thin-film transistors based on anodic aluminum oxide gate dielectrics
Authors: Lan Linfeng , Xu Miao , Peng Junbiao , Xu Hua , Li Min , Luo Dongxiang , Zou Jianhua , Tao Hong , Wang Lei , Yao Rihui
Published: November 2011

Thin-film transistors (TFTs) based on indium-zinc oxide (IZO) active layer and anodic aluminum oxide (Al2O3) gate dielectric layer were fabricated. The influence of source and drain (S/D) contacts on TFT performance was investigated by comparing IZO–TFTs with different S/D electrodes. The TFT with Mo S/D electrodes had higher output current and lower threshold voltage, but had poorer subthreshold swing and lower effective electron mobility compared to that with ITO S/D electrodes. By using x-ray photoelectron spectroscopy (XPS) depth profile analyzing method, it was observed that Mo was diffusing seriously into IZO, resulting in the variation of the effective channel length, thereby causing serious short-channel effect, poor subshreshold swing, and bad uniformity of the TFTs with Mo S/D electrodes.
Photoelectron spectroscopic study of iron-pyrene cluster anions
Authors: Li Xiang , Bowen Kit H. , Jena Puru , Kandalam Anil K.
Published: November 2011

Iron-pyrene cluster anions, [Fem(pyrene)n]− (m = 1–2, n = 1–2) were studied in the gas phase by photoelectron spectroscopy, resulting in the determination of their electron affinity and vertical detachment energy values. Density functional theory calculations were also conducted, providing the structures and spin multiplicities of the neutral clusters and their anions as well as their respective electron affinity and vertical detachment energy values. The calculated magnetic moments of neutral Fe1(pyrene)1 and Fe2(pyrene)1 clusters suggest that a single pyrene molecule could be a suitable template on which to deposit small iron clusters, and that these in turn might form the basis of an iron cluster-based magnetic material. A comparison of the structures and corresponding photoelectron spectra for the iron-benzene, iron-pyrene, and iron-coronene cluster systems revealed that pyrene behaves more similarly to coronene than to benzene.
Surface-acoustic-wave-driven spin pumping in Y3Fe5O12/Pt hybrid structure
Authors: Uchida Ken-ichi , An Toshu , Kajiwara Yosuke , Toda Masaya , Saitoh Eiji
Published: November 2011

A spin current generated from a surface acoustic wave (SAW) was observed in an Y3Fe5O12 (YIG)/Pt hybrid structure. At the YIG/Pt interface, a SAW generated in the YIG layer was found to pump a spin current into the Pt layer, which was detected through the inverse spin-Hall effect in the Pt. The YIG/Pt lateral structure combined with a piezoelectric wedge transducer enables the systematic investigation of the spin-voltage distribution due to the SAW in the YIG. Since the observed phenomenon has high affinity with SAW-based electronics, it will pave the way for constructing spintronic SAW devices.
Kinetic energy principle and neoclassical toroidal torque in tokamaks
Authors: Park Jong-Kyu
Published: November 2011

It is shown that when tokamaks are perturbed, the kinetic energy principle is closely related to the neoclassical toroidal torque by the action invariance of particles. Especially when tokamaks are perturbed from scalar pressure equilibria, the imaginary part of the potential energy in the kinetic energy principle is equivalent to the toroidal torque by the neoclassical toroidal viscosity. A unified description therefore should be made for both physics. It is also shown in this case that the potential energy operator can be self-adjoint and thus the stability calculation can be simplified by minimizing the potential energy.
Numerical investigation and evaluation of optimum hydrodynamic performance of a horizontal axis hydrokinetic turbine
Authors: Subhra Mukherji Suchi , Kolekar Nitin , Banerjee Arindam , Mishra Rajiv
Published: November 2011

The hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkTs) under different turbine geometries and flow conditions is discussed. Hydrokinetic turbines are a class of zero-head hydropower systems which utilize kinetic energy of flowing water to drive a generator. However, such turbines very often suffer from low-efficiency which is primarily due to its operation in a low tip-speed ratio (≤4) regime. This makes the design of a HAHkT a challenging task. A detailed computational fluid dynamics study was performed using the k-ω shear stress transport turbulence model to examine the effect of various parameters like tip-speed ratio, solidity, angle of attack, and number of blades on the performance HAHkTs having power capacities of ∼12 kW. For this purpose, a three-dimensional numerical model was developed and validated with experimental data. The numerical studies estimate optimum turbine solidity and blade numbers that produce maximum power coefficient at a given tip speed ratio. Simulations were also performed to observe the axial velocity ratios at the turbine rotor downstream for different tip speed ratios which provide quantitative details of energy loss suffered by each turbine at an ambient flow condition. The velocity distribution provides confirmation of the stall-delay phenomenon due to the effect of rotation of the turbine and a further verification of optimum tip speed ratio corresponding to maximum power coefficient obtained from the solidity analysis.
X-ray diffraction and surface acoustic wave analysis of BST/Pt/TiO2/SiO2/Si thin films
Authors: Mseddi Souhir , Njeh Anouar , Schneider Dieter , Fuess Hartmut , Hédi Ben Ghozlen Mohamed
Published: November 2011

High dielectric constant and electrostriction property of (Ba, Sr)Ti03 (BST) thin films result in an increasing interest for dielectric devices and microwave acoustic resonator. Barium strontium titanate (Ba0.645Sr0.355TiO3) films of about 300 nm thickness are grown on Pt(111)/TiO2/SiO2/Si(001) substrates by rf magnetron sputtering deposition techniques. X-ray diffraction is applied for the microstructural characterization. The BST films exhibit a cubic perovskite structure with a dense and smooth surface. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in the BST films. Young’s modulus E and the Poisson ratio ν of TiO2, Pt and BST films in different propagation directions are derived from the measured dispersion curves. Estimation of BST elastics constants are served in SAW studies. Impact of stratification process on SAW, propagating along [100] and [110] directions of silicon substrate, has been interpreted on the basis of ordinary differential equation (ODE) and stiffness matrix method (SMM). A good agreement is observed between experimental and calculated dispersion curves. The performed calculations are strongly related to the implemented crystallographic data of each layer. Dispersion curves are found to be sensitive to the SAW propagation direction and the stratification process for the explored frequency ranges 50−250 MHz, even though it corresponds to a wave length clearly higher than the whole films thickness.
Symmetry of flexoelectric coefficients in crystalline medium
Authors: Shu Longlong , Wei Xiaoyong , Pang Ting , Yao Xi , Wang Chunlei
Published: November 2011

Flexoelectric effect, which is defined as strain gradient–induced polarization or electric gradient–induced strain in crystalline solids, can be presented as a fourth-rank tensor. The symmetry of the flexoelectric coefficients in matrix form is studied. The results indicate that the direct flexoelectric coefficients should be presented in 3 × 18 form and the converse flexoelectric coefficients in 6 × 9 form, rather than 6 × 6 form, like elastic constants. In addition, non-zero and independent elements in the matrices have been calculated for 32 point groups and 7 Ci groups. These results will provide valuable reference to the theoretical and application studies of flexoelectric effect.
Domain matching epitaxy of ferrimagnetic CoFe2O4 thin films on Sc2O3/Si(111)
Authors: Sánchez F. , Bachelet R. , de Coux P. , Warot-Fonrose B. , Skumryev V. , Tarnawska L. , Zaumseil P. , Schroeder T. , Fontcuberta J.
Published: November 2011

Ferrimagnetic spinel CoFe2O4 (CFO) films are integrated with Si(111) using Sc2O3 buffer layers. The huge lattice mismatch (17%) between CFO and Sc2O3 is accommodated by domain matching, and CFO grows epitaxially with (111) out-of-plane orientation and coexistence of A- and B-type in-plane crystal variants. CFO films have low roughness of 4 Å and saturation magnetization of about 300 emu/cm3. These properties make CFO films on Sc2O3-buffered Si(111) comparable to those grown on oxide single crystals and thus extend the possibilities of using spinel oxides in electronic devices.
Analysis of the minority carrier response of n-type and p-type Au/Ni/Al2O3/In0.53Ga0.47As/InP capacitors following an optimized (NH4)2S treatment
Authors: O’Connor É. , Monaghan S. , Cherkaoui K. , Povey I. M. , Hurley P. K.
Published: November 2011

The electrical properties of metal-oxide-semiconductor capacitors incorporating atomic layer deposited Al2O3 on n-type and p-type In0.53Ga0.47As were investigated. A clear minority carrier response was observed for both n-type and p-type Au/Ni/Al2O3/In0.53Ga0.47As devices following an optimized ammonium sulfide (NH4)2S treatment. Capacitance-voltage and conductance-voltage measurements performed at varying temperatures allowed an Arrhenius extraction of activation energies for the minority carrier response, indicating a transition from a generation-recombination regime to a diffusion controlled response.
Polarity-driven nickel oxide precipitation in LaNiO3-LaAlO3 superlattices
Authors: Detemple E. , Ramasse Q. M. , Sigle W. , Cristiani G. , Habermeier H.-U. , Benckiser E. , Boris A. V. , Frano A. , Wochner P. , Wu M. , Keimer B. , van Aken P. A.
Published: November 2011

We have studied the microstructure of LaNiO3-LaAlO3 superlattices using transmission electron microscopy in combination with electron energy loss spectroscopy. In superlattices grown on non-polar SrTiO3 substrates, nanometer-sized NiO precipitates form directly at the interface between the substrate and the initial LaNiO3 layer, while control measurements on polar substrates show no NiO. Because of the drastically different electronic properties of NiO and LaNiO3, such precipitates can strongly affect measurements on atomically thin LaNiO3-based films and multilayers on SrTiO3. In general, polarity-driven secondary phase formation should be carefully evaluated as a possible consequence of the polarity mismatch at metal-oxide interfaces.
Optical near-field induced visible response photoelectrochemical water splitting on nanorod TiO2
Authors: Huong Le Thu Hac , Mawatari Kazuma , Pihosh Yuriy , Kawazoe Tadashi , Yatsui Takashi , Ohtsu Motoichi , Tosa Masahiro , Kitamori Takehiko
Published: November 2011

Here we report a way to induce the visible response of non-doped TiO2 in the photocatalytic electrochemical water splitting, which is achieved by utilizing the optical near-field (ONF) generated on nanorod TiO2. The visible response is attributed to the ONF-induced phonon-assisted excitation process, in which TiO2 is excited by sub-bandgap photons via phonon energy. Our approach directly gets involved in the excitation process without chemical modification of materials; accordingly it is expected to have few drawbacks on the photocatalytic performance. This study may offer another perspective on the development of solar harvesting materials.
A threshold for laser-driven linear particle acceleration in unbounded vacuum
Authors: Jie Wong Liang , Kärtner Franz X.
Published: November 2011

We hypothesize that a charged particle in unbounded vacuum can be substantially accelerated by a force linear in the electric field of a propagating electromagnetic wave only if the accelerating field is capable of bringing the particle to a relativistic energy in its initial rest frame during the interaction. We consequently derive a general formula for the acceleration threshold of such schemes and support our conclusion with the results of numerical simulations over a broad range of parameters for different kinds of pulsed laser beams.
A Model for Contact Binary EP Andromedae
Authors: Manzoori Davood
Published: November 2011

This paper presents the first comprehensive study of the EP And system, a contact binary. In this work the solution of the standard V light curve was obtained using the phoebe program (version 0.3c). Absolute parameters of the stellar components were then determined, enabling us to discuss the structure and evolutionary status of the close binary EP And. The times of minima data (‘O–C curve’) were analyzed. It was found that a third body with a period of 41.20 yr and mass 0.15 M⊙ is orbiting around the system. Also a modulating period of an 11.72-yr cycle along with a relative period increase of = 1.79 × 10−7 were obtained, which were attributed to the magnetic activity cycle and mass transfer with rate = 9.98 × 10−8 yr−1 between the components, respectively.
Restore and sequester: estimating biomass in native Australian woodland ecosystems for their carbon-funded restoration
Authors: Jonson J. H. , Freudenberger D.
Published: November 2011

In the south-western region of Australia, allometric relationships between tree dimensional measurements and total tree biomass were developed for estimating carbon sequestered in native eucalypt woodlands. A total of 71 trees representing eight local native species from three genera were destructively sampled. Within this sample set, below ground measurements were included for 51 trees, enabling the development of allometric equations for total biomass applicable to small, medium, and large native trees. A diversity of tree dimensions were recorded and regressed against biomass, including stem diameter at 130 cm (DBH), stem diameter at ground level, stem diameter at 10 cm, stem diameter at 30 cm, total tree height, height of canopy break and mean canopy diameter. DBH was consistently highly correlated with above ground, below ground and total biomass. However, measurements of stem diameters at 0, 10 and 30 cm, and mean canopy diameter often displayed equivalent and at times greater correlation with tree biomass. Multi-species allometric equations were also developed, including ‘Mallee growth form’ and ‘all-eucalypt’ regressions. These equations were then applied to field inventory data collected from three locally dominant woodland types and eucalypt dominated environmental plantings to create robust relationships between biomass and stand basal area. This study contributes the predictive equations required to accurately quantify the carbon sequestered in native woodland ecosystems in the low rainfall region of south-western Australia.
The role of terrestrially derived organic carbon in the coastal ocean: A changing paradigm and the priming effect
Authors: Bianchi Thomas S.
Published: November 2011

One of the major conundrums in oceanography for the past 20 y has been that, although the total flux of dissolved organic carbon (OC; DOC) discharged annually to the global ocean can account for the turnover time of all oceanic DOC (ca. 4,000–6,000 y), chemical biomarker and stable isotopic data indicate that there is very little terrestrially derived OC (TerrOC) in the global ocean. Similarly, it has been estimated that only 30% of the TerrOC buried in marine sediments is of terrestrial origin in muddy deltaic regions with high sedimentation rates. If vascular plant material—assumed to be highly resistant to decay—makes up much of the DOC and particulate OC of riverine OC (along with soil OC), why do we not see more TerrOC in coastal and oceanic waters and sediments? An explanation for this “missing” TerrOC in the ocean is critical in our understanding of the global carbon cycle. Here, I consider the origin of vascular plants, the major component of TerrOC, and how their appearance affected the overall cycling of OC on land. I also examine the role vascular plant material plays in soil OC, inland aquatic ecosystems, and the ocean, and how our understanding of TerrOC and “priming” processes in these natural systems has gained considerable interests in the terrestrial literature, but has largely been ignored in the aquatic sciences. Finally, I close by postulating that priming is in fact an important process that needs to be incorporated into global carbon models in the context of climate change.
Mutually facilitated dispersal between the nonmotile fungus
Aspergillus fumigatus
and the swarming bacterium
Paenibacillus vortex
Authors: Ingham Colin J. , Kalisman Oren , Finkelshtein Alin , Ben-Jacob Eshel
Published: November 2011

In the heterogeneous environment surrounding plant roots (the rhizosphere), microorganisms both compete and cooperate. Here, we show that two very different inhabitants of the rhizosphere, the nonmotile fungus
Aspergillus fumigatus
and the swarming bacterium
Paenibacillus vortex
, can facilitate each other's dispersal.
A. fumigatus
conidia (nonmotile asexual fungal spores) can be transported by
P. vortex
swarms over distances of at least 30 cm and at rates of up to 10.8 mm h
−1
. Moreover, conidia can be rescued and transported by
P. vortex
from niches of adverse growth conditions. Potential benefit to the bacteria may be in crossing otherwise impenetrable barriers in the soil: fungal mycelia seem to act as bridges to allow
P. vortex
to cross air gaps in agar plates. Transport of conidia was inhibited by proteolytic treatment of conidia or the addition of purified
P. vortex
flagella, suggesting specific contacts between flagella and proteins on the conidial surface. Conidia were transported by
P. vortex
into locations where antibiotics inhibited bacteria growth, and therefore, growth and sporulation of
A. fumigatus
were not limited by bacterial competition. Conidia from other fungi, similar in size to those fungi from
A. fumigatus
, were not transported as efficiently by
P. vortex
. Conidia from a range of fungi were not transported by another closely related rhizosphere bacterium,
Paenibacillus polymyxa
, or the more distantly related
Proteus mirabilis
, despite both being efficient swarmers.
Beta structure motifs of islet amyloid polypeptides identified through surface-mediated assemblies
Authors: Mao Xiao-Bo , Wang Chen-Xuan , Wu Xing-Kui , Ma Xiao-Jing , Liu Lei , Zhang Lan , Niu Lin , Guo Yuan-Yuan , Li Deng-Hua , Yang Yan-Lian , Wang Chen
Published: November 2011

We report here the identification of the key sites for the beta structure motifs of the islet amyloid polypeptide (IAPP) analogs by using scanning tunneling microscopy (STM). Duplex folding structures in human IAPP
8–37
(hIAPP
8–37
) assembly were observed featuring a hairpin structure. The multiplicity in rIAPP assembly structures indicates the polydispersity of the rat IAPP
8–37
(rIAPP
8–37
) beta-like motifs. The bimodal length distribution of beta structure motifs for rIAPP
8–37
R18H indicates the multiple beta segments linked by turns. The IAPP
8–37
analogs share common structure motifs of IAPP
8–17
and IAPP
26–37
with the most probable key sites at positions around Ser
19
/Ser
20
and Gly
24
. These observations reveal the similar amyloid formation tendency in the C and N terminus segments because of the sequence similarity, while the differences in specific amino acids at each key site manifest the effect of sequence variations. The results could be beneficial for studying structural polymorphism of amyloidal peptides with multiple beta structure motifs.
Functional traits determine trade-offs and niches in a tropical forest community
Authors: Sterck Frank , Markesteijn Lars , Schieving Feike , Poorter Lourens
Published: November 2011

How numerous tree species can coexist in diverse forest communities is a key question in community ecology. Whereas neutral theory assumes that species are adapted to common field conditions and coexist by chance, niche theory predicts that species are functionally different and coexist because they are specialized for different niches. We integrated biophysical principles into a mathematical plant model to determine whether and how functional plant traits and trade-offs may cause functional divergence and niche separation of tree species. We used this model to compare the carbon budget of saplings across 13 co-occurring dry-forest tree species along gradients of light and water availability. We found that species ranged in strategy, from acquisitive species with high carbon budgets at highest resource levels to more conservative species with high tolerances for both shade and drought. The crown leaf area index and nitrogen mass per leaf area drove the functional divergence along the simulated light gradient, which was consistent with observed species distributions along light gradients in the forest. Stomatal coordination to avoid low water potentials or hydraulic failure caused functional divergence along the simulated water gradient, but was not correlated to observed species distributions along the water gradient in the forest. The trait-based biophysical model thus explains how functional traits cause functional divergence across species and whether such divergence contributes to niche separation along resource gradients.
Human embryonic stem cell-derived neurons adopt and regulate the activity of an established neural network
Authors: Weick Jason P. , Liu Yan , Zhang Su-Chun
Published: November 2011

Whether hESC-derived neurons can fully integrate with and functionally regulate an existing neural network remains unknown. Here, we demonstrate that hESC-derived neurons receive unitary postsynaptic currents both in vitro and in vivo and adopt the rhythmic firing behavior of mouse cortical networks via synaptic integration. Optical stimulation of hESC-derived neurons expressing Channelrhodopsin-2 elicited both inhibitory and excitatory postsynaptic currents and triggered network bursting in mouse neurons. Furthermore, light stimulation of hESC-derived neurons transplanted to the hippocampus of adult mice triggered postsynaptic currents in host pyramidal neurons in acute slice preparations. Thus, hESC-derived neurons can participate in and modulate neural network activity through functional synaptic integration, suggesting they are capable of contributing to neural network information processing both in vitro and in vivo.
Superstatistics in nanoscale electrochemical systems
Authors: García-Morales Vladimir , Krischer Katharina
Published: November 2011

Stochastic electrochemical reaction steps on nanosized electrodes are non-Markovian when externally driven by an applied voltage. We show that, compared to the Markovian case (when external driving is absent), nanoscale electrochemical systems obey a superstatistics characterized by a superposition of Tsallis’
q
indices. The distribution of Tsallis’
q
indices along stochastic trajectories can be calculated from the electrochemical master equation and normal distributions from Boltzmann–Gibbs thermostatistics are recovered in the thermodynamic limit (the infinite electrode size limit). Although on the nanoscale the external control makes intricate correlations between the microstates, in the superstatistical frame one can still address the microstates as if they were uncorrelated. The resulting superstatistical entropic form is additive in this frame and Tsallis’ indices have on the time-average values

, which is, indeed, an example of a superstatistical system where no ad hoc distribution has to be assumed for the fluctuations; rather, the distribution is directly calculated from a mesoscopic master equation without freely adjustable parameters.
High-resolution record of the Matuyama–Brunhes transition constrains the age of Javanese
Homo erectus
in the Sangiran dome, Indonesia
Authors: Hyodo Masayuki , Matsu'ura Shuji , Kamishima Yuko , Kondo Megumi , Takeshita Yoshihiro , Kitaba Ikuko , Danhara Tohru , Aziz Fachroel , Kurniawan Iwan , Kumai Hisao
Published: November 2011

A detailed paleomagnetic study conducted in the Sangiran area, Java, has provided a reliable age constraint on hominid fossil-bearing formations. A reverse-to-normal polarity transition marks a 7-m thick section across the Upper Tuff in the Bapang Formation. The transition has three short reversal episodes and is overlain by a thick normal polarity magnetozone that was fission-track dated to the Brunhes chron. This pattern closely resembles another high-resolution Matuyama–Brunhes (MB) transition record in an Osaka Bay marine core. In the Sangiran sediments, four successive transitional polarity fields lie just below the presumed main MB boundary. Their virtual geomagnetic poles cluster in the western South Pacific, partly overlapping the transitional virtual geomagnetic poles from Hawaiian and Canary Islands’ lavas, which have a mean
40
Ar/
39
Ar age of 776 ± 2 ka. Thus, the polarity transition is unambiguously the MB boundary. A revised correlation of tuff layers in the Bapang Formation reveals that the hominid last occurrence and the tektite level in the Sangiran area are nearly coincident, just below the Upper Middle Tuff, which underlies the MB transition. The stratigraphic relationship of the tektite level to the MB transition in the Sangiran area is consistent with deep-sea core data that show that the meteorite impact preceded the MB reversal by about 12 ka. The MB boundary currently defines the uppermost horizon yielding
Homo erectus
fossils in the Sangiran area.