bluuebunny/crossref_metadata_2025 huggingface dataset:
Carotid Endarterectomy: Surgical Techniques, Emboli, and Outcomes
Authors: Naylor A. Ross
Published: July 2008

Carotid endarterectomy (CEA) is now the single most commonly performed peripheral vascular procedure in the western world, and is one of the few surgical procedures to be evaluated in level 1 randomized trials. Yet, despite that it has a proven role in selected patients it still remains a source of continuing debate. At pres ent, there is little consensus on many of the individual aspects of the procedure, such as the role of patching, shunting, and general anesthesia. More recently, there has been an increasing interest in the role of periopera tive monitoring, largely because of increasing aware ness that most strokes follow inadvertent surgeon error. This article reviews the surgical aspects of CEA together with an overview of the evolution of a monitor ing program, which has contributed to a 60% reduction in operative risk.
Strategies to Protect the Brain During Cardiac Surgery
Authors: Newman Mark F. , Stanley Timothy O. , Grocott Hilary P.
Published: July 2008

Despite significant advances in cardiopulmonary by pass (CPB) technology, surgical techniques, and anes thetic management, central nervous system (CNS) com plications remain a common and costly problem after CPB. Stroke is often considered a rare and unprevent able complication of cardiac surgery. Recent studies have shown that through the use of echocardiography and historical risk stratification strategies, we can de fine which patients are at substantially greater risk for CNS injury. Through enhanced understanding of the etiology of stroke and perioperative factors, which are associated with potential for neuroprotection or injury extension, there now exists a greater potential than ever to substantially reduce neurological injury associ ated with cardiac surgery. Strategies and theories of stratifying patients at risk and secondarily reducing that risk are described, as well as consideration for early postoperative assessment to allow treatment when events occur.
Effect of dust charge fluctuation on the propagation of dust-ion acoustic waves in inhomogeneous mesospheric dusty plasma
Authors: Mowafy A. E. , El-Shewy E. K. , Moslem W. M. , Zahran M. A.
Published: July 2008

Investigation of positive and negative dust charge fluctuations on the propagation of dust-ion acoustic waves (DIAWs) in a weakly inhomogeneous, collisionless, unmagnetized dusty plasmas consisting of cold positive ions, stationary positively and negatively charged dust particles and isothermal electrons. The reductive perturbation method is employed to reduce the basic set of fluid equations to the variable coefficients Korteweg–de Varies (KdV) equation. At the critical ion density, the KdV equation is not appropriate for describing the system. Hence, a new set of stretched coordinates is considered to derive the modified variable coefficients KdV equation. It is found that the presence of positively charged dust grains does not only significantly modify the basic properties of solitary structure, but also changes the polarity of the solitary profiles. In the vicinity of the critical ion density, neither KdV nor the modified KdV equation is appropriate for describing the DIAWs. Therefore, a further modified KdV equation is derived, which admits both soliton and double layer solutions.
Polymer surface and thin film vibrational dynamics of poly(methyl methacrylate), polybutadiene, and polystyrene
Authors: Freedman Miriam A. , Becker James S. , Rosenbaum A. W. , Sibener S. J.
Published: July 2008

Inelastic helium atom scattering has been used to investigate the vibrational dynamics at the polymer vacuum interface of poly(methyl methacrylate), polystyrene, and polybutadiene thin films on SiOx∕Si(100). Experiments were performed for a large range of surface temperatures below and above the glass transition of these three polymers. The broad multiphonon feature that arises in the inelastic scattering spectra at surface temperatures between 175 and 500K is indicative of the excitation of a continuum of surface vibrational modes. Similarities exist in the line shapes of the scattering spectra, indicating that helium atoms scatter from groups of similar mass on the surface of these polymer thin films. The line shapes obtained were further analyzed using a semiclassical scattering model. This study has shown that quite different polymer thin films can have similar interfacial dynamics at the topmost molecular layer.
Charge trapping induced current instability in pentacene thin film transistors: Trapping barrier and effect of surface treatment
Authors: Miyadera T. , Wang S. D. , Minari T. , Tsukagoshi K. , Aoyagi Y.
Published: July 2008

The current instability of pentacene thin film transistors is described by the energetic distribution of the barrier height for the trapping of mobile charges at the organic/insulator interface. The trapping energy was quantitatively analyzed by measuring the temperature dependence of current decay, which follows a stretched exponential function. The distribution of the barrier becomes higher and narrower by the use of a self assembled monolayer (SAM) on the insulator surface, whereas the pentacene film morphology has little influence on the trapping barriers. The increase in the barrier height in the SAM-treated device suppresses charge trapping, resulting in stable device operation.
Reverse-magnetic-field reciprocity in conductive samples with extended contacts
Authors: Cornils Martin , Paul Oliver
Published: July 2008

This paper reports on the extension of the reverse-magnetic-field reciprocity (RMFR) principle to electrically linear devices with arbitrary shape and extended contacts. The RMFR principle is a consequence of Onsager’s relation for the conductivity tensor depending on the magnetic field. It states the identity of resistance measurements on linearly conductive four-contact samples in a magnetic field B upon contact switching and magnetic field reversal. The previously available proof was restricted to samples with pointlike contacts and thus did not directly apply to real devices. Implications for two-contact and three-contact structures, for planar and symmetric devices, and the use of the structures as magnetic sensors are discussed. Experimental results obtained with complementary metal oxide semiconductor test structures of different geometries are in excellent agreement with the theoretical findings.
Switching from ⟨110⟩ to ⟨100⟩ orientation increases both the on current and off current of p-channel metal-oxide semiconductor transistors
Authors: Yang Peizhen , Lau W. S. , Ho V. , Lim B. K. , Siah S. Y. , Chan L.
Published: July 2008

If the on current of p-channel metal-oxide semiconductor (PMOS) transistors fabricated on (100) silicon substrate can be easily increased by switching from ⟨110⟩ to ⟨100⟩ orientation because of faster hole transport in the “on state,” it is natural to expect that this switching can also increase the off current because of faster hole transport in the “off state.” Indeed we managed to observe this experimentally for relatively long PMOS transistors. In this letter, we will also show that there is an overall performance improvement in PMOS transistors despite the increase in both on current and off current.
Polarization dependence of optical properties of metallodielectric gratings with subwavelength grooves in classical and conical mounts
Authors: Vengurlekar Arvind S.
Published: July 2008

We report optical transmission and reflection spectral measurements in the visible and near infrared on a one-dimensional transmission grating having a metal film deposited on deep rectangular subwavelength grooves etched in quartz. Measurements are made for both classical and conical diffraction geometry by varying the azimuthal angles (φ) between the plane of incidence and the grating vector. Strong differences for transverse electric (TE) and transverse magnetic (TM) polarized light are seen. We find conditions under which the transmission is negligible irrespective of light polarization and angle of incidence. The transmission spectra show deep dips corresponding to excitation of surface plasmons by TM polarized light when φ=0°, by both TE and TM light when 0°<φ<90° and by TE light for φ=90°. We also examine the reciprocity behavior of the optical properties for incidence from the metal and substrate sides and dependence on light polarization.
Lead-free piezoelectric ceramics derived from the K0.5Na0.5NbO3–AgNbO3 solid solution system
Authors: Lei Chao , Ye Zuo-Guang
Published: July 2008

A lead-free solid solution between potassium sodium niobate and silver niobate, (1−x)K0.5Na0.5NbO3–xAgNbO3 (KNN-AN, with x=0–0.36), has been prepared in the form of ceramics by solid state reaction under O2 atmosphere. The crystal chemical study shows that Ag+ ion diffuses into the KNN lattices to form a solid solution of perovskite structure with x up to 0.30. The substitution of Ag+ ion for (K0.5Na0.5)+ ion results in linear decreases in the ferroelectric Curie temperature (TC), from 420°C in KNN down to 325°C in 0.70KNN-0.30AN, and in the tetragonal to orthorhombic phase transition temperature (TT-O), from 190 down to 150°C. The relative density of the KNN-AN ceramics reaches 94%. The optimum piezoelectric properties are found in the ceramics of 0.82KNN-0.18AN, with a piezocoefficient d33=186pC∕N, an electromechanical coupling factor kp=42.5%, and a TC=355°C. For the ceramics with x=0.24, the remanent polarization reaches a maximum value of Pr=20μC∕cm2, with a reduced coercive field Ec=6.4kV∕cm and a TC=340°C. It is shown that the (1−x)KNN-xAN ceramics exhibit piezoelectric properties which are comparable or superior to the hot-pressed KNN ceramics and other KNN-based systems. In particular, the piezoelectric properties exhibit very a good thermal stability up to high temperature, which is a significant improvement from other KNN-based piezoceramics.
Electron Landé g factor in GaAs–(Ga,Al)As quantum wells under applied magnetic fields: Effects of Dresselhaus spin splitting
Authors: Reyes-Gómez E. , Porras-Montenegro N. , Perdomo-Leiva C. A. , Brandi H. S. , Oliveira L. E.
Published: July 2008

The effects of the Dresselhaus spin splitting on the Landé g factor associated with conduction electrons in GaAs–(Ga,Al)As quantum wells are studied by using the nonparabolic Ogg–McCombe effective Hamiltonian. The g factor and cyclotron effective mass are calculated as functions of applied magnetic fields (along both the growth and in-plane directions) and GaAs well widths of the heterostructure. Present calculations indicate that in GaAs–(Ga,Al)As heterostructures, the inclusion of the Dresselhaus term leads to very small corrections in the effective Landé factor. Taking into account the effects of nonparabolic and anisotropic terms in the Hamiltonian is fundamental in obtaining quantitative agreement with experimental measurements. Moreover, the present results suggest that previous theoretical work on the Dresselhaus spin-splitting effects on the effective Landé factor should be viewed with caution if nonparabolic and anisotropic effects are not taken into account.
Optimal control in a noisy system
Authors: Asenjo F. , Toledo B. A. , Muñoz V. , Rogan J. , Valdivia J. A.
Published: July 2008

We describe a simple method to control a known unstable periodic orbit (UPO) in the presence of noise. The strategy is based on regarding the control method as an optimization problem, which allows us to calculate a control matrix A. We illustrate the idea with the Rossler system, the Lorenz system, and a hyperchaotic system that has two exponents with positive real parts. Initially, a UPO and the corresponding control matrix are found in the absence of noise in these systems. It is shown that the strategy is useful even if noise is added as control is applied. For low noise, it is enough to find a control matrix such that the maximum Lyapunov exponent λmax<0, and with a single non-null entry. If noise is increased, however, this is not the case, and the full control matrix A may be required to keep the UPO under control. Besides the Lyapunov spectrum, a characterization of the control strategies is given in terms of the average distance to the UPO and the control effort required to keep the orbit under control. Finally, particular attention is given to the problem of handling noise, which can affect considerably the estimation of the UPO itself and its exponents, and a cleaning strategy based on singular value decomposition was developed. This strategy gives a consistent manner to approach noisy systems, and may be easily adapted as a parametric control strategy, and to experimental situations, where noise is unavoidable.
Neutron production from interactions of high-intensity ultrashort pulse laser with a planar deuterated polyethylene target
Authors: Petrov G. M. , Davis J.
Published: July 2008

The deuteron acceleration from a planar uniform deuterated polyethylene (CD2) target was studied with a two-dimensional electromagnetic particle-in-cell method in the ultrarelativistic regime for peak laser intensities between 1023 and 1025W∕m2. Under identical conditions the deuteron energy and angular distributions are very different when compared to that produced from a double-layer target. The neutron production from D(d,n)–He3 nuclear fusion reactions was also investigated with a three-dimensional Monte Carlo ion beam-target deposition model. The neutron yield and its angular distribution were studied as a function of peak laser intensity and laser pulse duration. A neutron yield of 104–106neutronsperJoule laser energy is inferred from simulations of a 4 μm thick planar uniform CD2 target. The angular scattering of neutrons is found to be nonisotropic and has a significant component in the forward (laser propagation) direction.
Nanoporous SiO2/Si thin layers produced by ion track etching: Dependence on the ion energy and criterion for etchability
Authors: Dallanora A. , Marcondes T. L. , Bermudez G. G. , Fichtner P. F. P. , Trautmann C. , Toulemonde M. , Papaléo R. M.
Published: July 2008

Vitreous SiO2 thin films thermally grown onto Si wafers were bombarded by Au ions with energies from 0.005 to 11.1 MeV/u and by ions at constant velocity (0.1 MeV/u A197u, T130e, A75s, S32, and F19). Subsequent chemical etching produced conical holes in the films with apertures from a few tens to ∼150 nm. The diameter and the cone angle of the holes were determined as a function of energy loss of the ions. Preferential track etching requires a critical electronic stopping power Seth∼2 keV/nm, independent of the value of the nuclear stopping. However, homogeneous etching, characterized by small cone opening angles and narrow distributions of pore sizes and associated with a continuous trail of critical damage, is only reached for Se>4 keV/nm. The evolution of the etched-track dimensions as a function of specific energy (or electronic stopping force) can be described by the inelastic thermal spike model, assuming that the etchable track results from the quenching of a zone which contains sufficient energy for melting. The model correctly predicts the threshold for the appearance of track etching Seth if the radius of the molten region has at least 1.6 nm. Homogeneous etching comes out only for latent track radii larger than 3 nm.
Electromigration-induced extrusion failures in Cu/low-k interconnects
Authors: Wei Frank L. , Gan Chee Lip , Tan Tam Lyn , Hau-Riege Christine S. , Marathe Amit P. , Vlassak Joost J. , Thompson Carl V.
Published: July 2008

Electromigration experiments were conducted to investigate the thresholds required for electromigration-induced extrusion failures in Cu/low-k interconnect structures. Extrusions at the anode were observed after long periods of void growth. Characterization of failure sites was carried out using scanning and transmission electron microscopy, which showed that failures occurred through delamination at the interface between the silicon-nitride-based capping layer diffusion barrier and the underlying Cu, Ta liner, and interlevel dielectric (ILD) materials. This interface is subjected to near tensile (mode I) loading with a mode mixity angle between 4° and 7°, estimated using finite-element-method analysis, as electromigration leads to a compressive stress in the underlying Cu. Comparisons of the fracture toughness for interfaces between the capping layer and individual underlayer materials indicate that the extrusion process initially involves plane-strain crack propagation. As Cu continues to extrude, the crack geometry evolves to become elliptical. An analysis of the critical stress required for extrusions based on these observations leads to a value of approximately 710 MPa, which agrees well with the value determined through estimation of the volume of material extruded and the required stress to accomplish this extrusion. The analysis of the critical stress required for extrusion formation also indicates that sparsely packed, intermediate to wide interconnect lines are most susceptible to electromigration-induced extrusion damage, and that extrusion failures are favored by ILDs with low stiffness (low elastic moduli) and thin liners, both of which are needed in future interconnect systems.
Simultaneous resonant enhanced multiphoton ionization and electron avalanche ionization in gas mixtures
Authors: Shneider Mikhail N. , Zhang Zhili , Miles Richard B.
Published: July 2008

Resonant enhanced multiphoton ionization (REMPI) and electron avalanche ionization (EAI) are measured simultaneously in Ar:Xe mixtures at different partial pressures of mixture components. A simple theory for combined REMPI+EAI in gas mixture is developed. It is shown that the REMPI electrons seed the avalanche process, and thus the avalanche process amplifies the REMPI signal. Possible applications are discussed.
Band structures of GaAs, InAs, and InP: A 34 k⋅p model
Authors: Saïdi I. , Ben Radhia S. , Boujdaria K.
Published: July 2008

The band structure of direct-band gap semiconductors (GaAs, InAs, InP) is described theoretically by using a 34×34 k⋅p model. We extend the sp3d5 basis functions by the inclusion of sV∗ orbitals. We find that the sp3d5s∗ k⋅p model is sufficient to describe the electronic structure of all materials investigated over a wide energy range, obviating the use of any d valence orbitals. Finally, our results show that Luttinger parameters, the κ valence band parameter, the effective Landé factor g∗, and the effective-masses in the X and L valleys are in good agreement with available experimental data. In particular, the adjustment of the k⋅p Hamiltonian parameters proved that g∗ of GaAs, InAs, and InP are, respectively, −0.41, −15.82, and 1.35, which are in good agreement with the experimental values of −0.44, −14.90, and 1.26.
High mobility electron-conducting thin-film transistors by organic vapor phase deposition
Authors: Rolin C. , Vasseur K. , Schols S. , Jouk M. , Duhoux G. , Müller R. , Genoe J. , Heremans P.
Published: July 2008

In this letter, we report on the growth of thin films of N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13H27) by organic vapor phase deposition (OVPD). Uniform films are deposited with a material utilization efficiency of 59±4% and deposition rates up to 15Å∕s. Top-contact transistors based on OVPD-grown PTCDI-C13H27 show high n-type mobilities (up to 0.3cm2∕Vs) and reproducible characteristics. The influence of deposition parameters on electrical properties is discussed.
Reversible resistive switching behaviors in NiO nanowires
Authors: Kim Sung In , Lee Jae Hak , Chang Young Wook , Hwang Sung Sic , Yoo Kyung-Hwa
Published: July 2008

We have investigated resistive switching phenomena in NiO nanowires fabricated using anodized aluminum oxide membranes. We show that NiO nanowires exhibit reversible and bistable resistive switching behaviors like those in NiO thin films. However, compared to NiO thin films, electroforming in NiO nanowires takes place at much lower electric fields. Thus, a 1-μm-long NiO nanowire device operates under 2.5V and even a 25-μm-long NiO nanowire array operates under 20V. These results suggest the possibility of developing nanowire-based resistance memory devices.
Effects of water and methanol on the molecular organization of 1-butyl-3-methylimidazolium tetrafluoroborate as functions of pressure and concentration
Authors: Chang Hai-Chou , Jiang Jyh-Chiang , Liou You-Chang , Hung Chao-Hsin , Lai Ting-Yun , Lin Sheng Hsien
Published: July 2008

The structural organization in mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4])/water or methanol was studied by infrared spectroscopy. No drastic change in the concentration dependence of the alkyl C–H band frequency was observed at high concentration of the ionic liquid. This behavior indicates a clustering of the ionic liquid in alkyl regions. Nevertheless, the presence of methanol significantly perturbs the ionic liquid–ionic liquid associations in the imidazolium region. On the basis of the responses to change in pressure and concentration, two different types of O–H species, i.e., free O–H and bonded O–H, were observed in the O–H stretching region. For [bmim][BF4]/water mixtures, the compression leads to loss of the free O–H band intensity. It is likely that free O–H is switched to bonded O–H as high pressures are applied. For [bmim][BF4]/methanol mixtures, the free O–H is still stable under high pressures.
Back-gate ZnO nanowire field-effect transistors each with a top Ω shaped Au contact
Authors: Yang W. Q. , Dai L. , Ma R. M. , Liu C. , Sun T. , Qin G. G.
Published: July 2008

We have fabricated depletion and enhancement modes (D-mode and E-mode) back-gate metal-insulator-semiconductor field-effect-transistors (MISFETs), using two kinds of ZnO nanowires (NWs) labeled as A and B, respectively. The NWs A and B were synthesized via the vapor phase transport method with ZnO∕C admixture and Zn as the sources, respectively. Each of the MISFETs has a top Ω shaped Au contact on the conductive channel. Compared to that without any top Au contact, the on/off ratio (∼106) of the ZnO NW A MISFET increases by a factor of 103, and is the highest one among the back-gate ZnO NW MISFETs ever reported; while the ZnO NW B MISFET changes from D-mode to E-mode when a top Au contact is added. The effects of the Au∕ZnO NW contacts on the performances of the NW A and B MISFETs were discussed.
Holographic fabrication of diamondlike photonic crystal template using two-dimensional diffractive optical elements
Authors: Xu Di , Chen Kevin P. , Ohlinger Kris , Lin Yuankun
Published: July 2008

This letter demonstrates holographic fabrication of three-dimensional diamondlike photonic crystal templates in SU8 photoresist using a single diffractive optical element. Five coherent laser beams produced by a two-dimensional phase mask were used to construct face-centered-cubic or tetragonal interference patterns. The superposition of two interference patterns through double exposures yields diamondlike photonic crystal templates in SU8. Photonic bandgap calculation reveals a full bandgap in inverse structures based on the template. The utilization of the two-dimensional phase mask simplifies the fabrication configuration in multiple beam holographic lithography for three-dimensional photonic fabrication.
Formation of thin films using pulse power and electromagnetic repulsion forces
Authors: Sekiya Yoshihisa , Yamada Tadahiko , Kondo Yoshitaka
Published: July 2008

Thin metal films that can strongly adhere to a plastic surface were formed from a metal plasma produced by applying pulse power. The associated electromagnetic repulsion force drives the metal plasma toward the plastic surface. In this paper, we present the properties of metal plasmas and thin metal films having strong adhesion to plastic surfaces.
In situ metal-organic chemical vapor deposition atomic-layer deposition of aluminum oxide on GaAs using trimethyaluminum and isopropanol precursors
Authors: Cheng Cheng-Wei , Fitzgerald Eugene A.
Published: July 2008

In situ atomic-layer deposition (ALD) of Al2O3 on p-GaAs in metal-organic chemical vapor deposition system is demonstrated in this article. Isopropanol was chosen as the oxygen source for Al2O3 ALD, instead of common H2O. The ALD mechanism is discussed and it is proposed that water does not form in the process. The saturation growth rate of Al2O3 is about 0.8Å∕cycle. X-ray photoetectron spectroscopy depth profiles were performed and no arsenic oxide is observed at the interface. The capacitance-voltage measurements show a small accumulation capacitance dispersion and voltage shift in the depletion region. The interfacial defect density near the midgap of the GaAs bandgap has been determined with the conductance-frequency method. The interfacial defect density is determined as 2.5×1011eV−1cm−2 at the midgap of the GaAs.
Simultaneous closure of multiple high voltage parallel spark channels without switch: A parametric study
Authors: Raote Pallavi , Patil Gautam , Nilaya J. Padma , Biswas Dhruba J.
Published: July 2008

Results of a detailed parametric study of a self-switched mutually inductively coupled high voltage parallel spark preionizer are presented. The maximal behavior exhibited by the breakdown voltage of the parallel gaps with respect to the number of mutually coupled turns has been explained. It has been found that there exists a threshold rise time of the current pulse beyond which simultaneous closure of the parallel gaps is not possible and that this threshold value is independent of the nature and geometry of the cores used for the mutual coupling. The degree of simultaneity of the closure of the self-switched parallel gaps matched that of the conventional operation of such gaps.
Field driven ferromagnetic phase nucleation and propagation in antiferromagnetically coupled multilayer films with perpendicular anisotropy
Authors: Hauet T. , Günther C. M. , Hovorka O. , Berger A. , Im M.-Y. , Fischer P. , Eimüller T. , Hellwig O.
Published: July 2008

We investigate the reversal process in {[Co∕Pt]X−1Co∕Ru}×16∕[Co∕Pt]X multilayer films by magnetometry and magnetic transmission x-ray microscopy. After demagnetization, a stable one-dimensional ferromagnetic (FM) stripe domain phase (tiger-tail phase) for a thick sample (X=7) is imaged, while metastable sharp antiferromagnetic domain walls are observed in the remanent state for a thinner stack sample (X=6). When applying an external magnetic field the sharp domain walls of the thinner sample gradually transform into the FM phase via separate nucleation of many isolated FM domains all along the domain boundary. We present energy calculations that reveal the underlying energetics driving the overall reversal mechanism.
Controlled rotation of the exchange-bias direction in IrMn∕Cu∕Co via ion irradiation
Authors: Schafer D. , Geshev J. , Nicolodi S. , Pereira L. G. , Schmidt J. E. , Grande P. L.
Published: July 2008

Co ∕ Cu ∕ Ir Mn films were irradiated with 40keV He+ ions varying the fluence and the current, with magnetic field applied at 120° with respect to the original exchange-bias direction. The angular variations of the exchange-bias field of the irradiated samples were compared with those of the as-made and the thermally annealed films. Gradual deviation of the exchange-bias direction with the fluence increase was observed. Complete reorientation of the easy axes of both ferromagnet and antiferromagnet toward that of the field applied during irradiation was achieved for fluences higher than 1×1015ions∕cm2, accompanied with a significant enhancement of the exchange-bias field.
Role of structural defects in the unipolar resistive switching characteristics of Pt∕NiO∕Pt structures
Authors: Park Chanwoo , Jeon Sang Ho , Chae Seung Chul , Han Seungwu , Park Bae Ho , Seo Sunae , Kim Dong-Wook
Published: July 2008

We investigated the resistive switching characteristics of two types of Pt∕NiO∕Pt structures with epitaxial and polycrystalline NiO layers. Both of these Pt∕NiO∕Pt structures exhibited unipolar resistive switching. Pt/epitaxial-NiO∕Pt showed unstable switching or no resistance state change after several repeated runs. Pt/polycrystalline-NiO∕Pt showed very reproducible switching. The experimental data indicated that microstructural defects (e.g., grain boundaries) played crucial roles in the reliability of the unipolar resistive switching behavior. This was further supported by first-principles calculations.
Highly efficient nonresonant two-photon absorption in ZnO pellets
Authors: Mani S. , Jang J. I. , Ketterson J. B.
Published: July 2008

In this article, we report direct evidence for efficient nonresonant two-photon absorption-induced luminescence in ZnO pellets at 2K and room temperature. Stimulated emission near the band edge is observed at room temperature employing this form of excitation under low excitation levels over a broad range of excitation wavelengths. The steady-state population dynamics based on the time-integrated photoluminescence spectra at 2K indicates that this nonresonant two-photon excitation is much more efficient in creating excitonic matter, compared with the traditional one-photon excitation method.
Reverse-bias-induced bipolar resistance switching in Pt∕TiO2∕SrTi0.99Nb0.01O3∕Pt devices
Authors: Wu S. X. , Xu L. M. , Xing X. J. , Chen S. M. , Yuan Y. B. , Liu Y. J. , Yu Y. P. , Li X. Y. , Li S. W.
Published: July 2008

Stoichiometric single-crystalline TiO2 thin films were grown on SrTi0.99Nb0.01O3 (Nb:STO) substrates by oxygen plasma-assisted molecular beam epitaxy. The Pt∕TiO2∕Nb:STO∕Pt devices showed extremely weak resistance switching hysteresis without applying reverse bias. However, when the reverse bias increased above −2V, the hysteresis became more and more prominent. Further, it was found that the low (high) resistance state can be set by applying sufficient reverse (forward) bias. The origin of the reverse-bias-induced bipolar switching behavior should be attributed to the modulation of Schottky-like barrier width by electrochemical migration of oxygen vacancies.
Temperature dependence of ordered GeSi island growth on patterned Si (001) substrates
Authors: Zhong Zhenyang , Chen Peixuan , Jiang Zuimin , Bauer Guenther
Published: July 2008

Statistical information on GeSi islands grown on two-dimensionally pit-patterned Si substrates at different temperatures is presented. Three growth regimes on patterned substrates are identified: (i) kinetically limited growth at low growth temperatures, (ii) ordered island growth in an intermediate temperature range, and (iii) stochastic island growth within pits at high temperatures. A qualitative model based on growth kinetics is proposed to explain these phenomena. It can serve as a guidance to realize optimum growth conditions for ordered islands on patterned substrates.
Enhancement of thermoelectric properties of sputtered Bi–Sb–Te thin films by electric current stressing
Authors: Liao Chien-Neng , Liou Kuen-Ming , Chu Hsu-Shen
Published: July 2008

Both electrical conductivity and Seebeck coefficient of sputtered Bi–Sb–Te films were enhanced by introducing a high density of electric current through the films during thermal annealing. The electrically stressed Bi–Sb–Te films were found to have lower carrier concentration but much higher mobility than the films thermally treated at the same temperatures. A mechanism based on electromigration-induced preferential Sb diffusion is proposed to explain the observed electrical transport properties and precipitation of Sb-rich phase in the electrically stressed Bi–Sb–Te films. The study shall lead to an effective strategy of improving thermoelectric properties of Bi–Sb–Te films by electric current stressing.
Electronic structures of boron nanoribbons
Authors: Ding Yi , Yang Xiaobao , Ni Jun
Published: July 2008

Using first principles calculations, we investigate the electronic properties of boron nanoribbons. The boron nanoribbons are constructed from the stable boron sheet. The bare boron nanoribbons with different edges are metals. The boron nanoribbons with two-hydrogen passivated on the zigzag edges become semiconductors and are more stable than the one-hydrogen passivated ones. The band gaps are within the range of 0.5eV and there is an oscillatory variation in the band gaps with the change of widths due to the even-odd number of nanoribbon widths.
Hildegard E. Peplau: The Psychiatric Nursing Legacy of a Legend
Authors: Haber Judith
Published: July 2008

Hildegard Peplau is remembered by nurses worldwide as the "mother of psychiatric nursing." Her scope of influence transcended her psychiatric nursing specialty and had a profound effect on the nursing profession, nursing science, and nursing practice. Peplau played a leadership role by influencing and emphasizing the advancement ofprofessional educational, and practice standards, and the importance of professional self-regulation through credentialing. She made a major contribution to nursing science, professional nursing and, of course, to the psychiatric nursing specialty through development of the Interpersonal Relations paradigm, a mid-range theory that has influenced the importance with which the nurse-patient relationship is regarded. The essential nature of the nursepatient relationship and its significance as a therapeutic modality operationalizes Peplau's scholarship and provides the basis for both the art and science of nursing practice. Peplau would challenge psychiatric nurses to thrive in the new millennium through continued commitment to the importance of the nurse-patient relationship, engagement in evidence-based practice, support of competence in information technology, and provision of leadership in influencing the health care paradigm shift to community-based health care delivery.
Canola (Brassica napus L.) seedbank declines rapidly in farmer-managed fields in South Australia
Authors: Baker Jeanine , Preston Christopher
Published: July 2008

Canola is an important crop in southern Australia, where it is used as part of the crop rotation to manage cereal diseases, improve wheat yields, and assist in integrated weed management programs. The potential release of herbicide-tolerant transgenic cultivars into Australia has raised concerns that volunteer canola may itself become an uncontrollable weed. This study examined the persistence of the canola seedbank in farmer-managed fields in 3 geographical areas of the South Australian cropping region for up to 3.5 years after the last canola crop was grown. In total, 66 fields from minimum- and no-tillage farms were sampled for number of canola seed/m2 and the percentage of those that germinated. ANOVA analysis indicated that time since the last harvest and cultivation method were both significant factors affecting the number of seed/m2 present. Neither time since harvest nor cultivation method was significant for number of germinated canola seeds, although time since harvest approached significance at the 5% level. This demonstrates that the canola seedbank and the number of volunteers decline rapidly in managed cropping systems in southern Australia. Therefore, it is unlikely that herbicide-tolerant canola will become a major weed if volunteers are managed carefully.
Consumption and Social Life in Cities: Evidence from Germany
Authors: Borck Rainald
Published: July 2008

This paper examines social agglomeration externalities. Using survey data from the German Socioeconomic Panel, it examines the link between city size and different measures of consumption, social interaction and social capital. There is strong evidence of agglomeration effects in consumption, while positive effects of city size on social interaction and social capital variables seem to some extent to be driven by sorting. Further, using responses to satisfaction questions, the paper analyses whether individuals are compensated for diseconomies of agglomeration by positive agglomeration externalities in other areas. This hypothesis cannot be rejected.
Functional Polycentricity: A Formal Definition in Terms of Social Network Analysis
Authors: Green Nick
Published: July 2008

Polycentricity is often used descriptively with regard to a regional system of settlements, usually referred to as a polycentric urban region (PUR). Although presented in much of the literature as in essence a morphological concept, polycentricity possesses a functional element that receives less attention. Polycentricity is also seen as a normative concept. However, it has not been rigorously defined using formal techniques. This paper argues that defining polycentricity in terms of both morphology and function is possible by drawing on techniques originating in social network analysis. The paper sets out a formal definition and derivation of functional polycentricity based on these techniques, which is then extended to a derivation of an index of regional functional polycentricity. The paper sets out worked examples to show how the techniques described might be utilised. The paper closes with a discussion of issues that may arise when putting these definitions into practice.
Studying the Effects of the Intensity of US State Growth Management Approaches on Land Development Outcomes
Authors: Howell-Moroney Michael
Published: July 2008

Driven by negative externalities from suburban sprawl, many states in the US have adopted comprehensive growth management legislation in an effort to regulate land development more directly. Most extant scholarship evaluating the effects of growth management programmes employs a design that averages growth management's effect across all of the growth management states. Yet, this approach largely ignores descriptive analyses of individual state growth management approaches which show large variation in both the methods and intensity of means by which states manage growth. This paper seeks to ascertain if differences in growth management intensity yield different evaluative outcomes. Analysis of panel data for nine growth management states using fixed effects regressions, across eight different model specifications, shows that only states with the strongest growth management intensity experience consistent success at reducing the expansion of urban land and increasing population densities.
A Theoretical Framework and Methodology for Characterising National Urban Systems on the Basis of Flows of People: Empirical Evidence for France and Germany
Authors: Limtanakool Narisra , Dijst Martin , Schwanen Tim
Published: July 2008

In advanced economies, flows play an important part in connecting urban nodes. This paper sets up a framework for identifying and classifying the pattern of the urban systems from an interaction perspective. Three S-dimensions are proposed (that is, the strength of interaction, the symmetry of interaction and the structure of the network) and a set of indices that are important for characterising network configurations. Using the European long-distance mobility database (DATELINE), the framework is applied to examine the pattern of interaction between functional urban areas (FURs) in France and Germany. The analysis is carried out separately for three journey purposes: business, holiday and leisure. The results reveal that national urban systems embrace a wide variety of constellations and that considerable variation in these constellations can be observed across journey purposes and countries. Overall, the authors are confident that the proposed framework provides a useful analytical tool for characterising the configurations of urban systems.
Mast Cell Density, Hepatic Stellate Cell Activation and TGF-β1 Transcripts in the Aging Sprague-Dawley Rat During Early Acute Liver Injury
Authors: Grizzi F. , Franceschini B. , Gagliano N. , Moscheni C. , Annoni G. , Vergani C. , Hermonat P.L. , Chiriva-Internati M. , Dioguardi N.
Published: July 2008

Mast cells (MCs) have been indicated as a source of various inflammatory cytokines, chemokines and growth factors. This study evaluates liver tissue MC density as a quantitative marker of acute liver inflammation in 2- and 19-month old rats treated with carbon tetrachloride (CCl4) to assess the relationships between MC density, hepatocellular damage, mRNA encoding TGF- β1, hepatic stellate cell (HSC) activation and collagen levels. Consecutive histological sections from each age group were stained with toluidine blue to identify granulated MCs, Direct Red 80 to recognize collagen matrix, and by immunohistochemistry to identify activated hepatic stellate cells (HSCs), which were subsequently counted by means of a computer-aided image analysis. Histology showed hepatocellular necrosis with inflammatory cell infiltration and collagen matrix deposition. Two and 24 hours after intoxication, MC density had considerably increased in the younger rats, but less in those aged 19 months. Although the untreated older rats had a larger area occupied by activated HSCs than the untreated younger rats, the increase in the number of HSCs was greater in the younger rats both two and 24 hours after intoxication. The greater MC density in younger rats suggests that older rats have a reduced immune response or recruit fewer MCs. The activated HSCs and TGF- β1 transcripts did not increase significantly during the study period, thus indicating that these are later events in chemically induced hepatic toxicity. In conclusion, MC density may be an index of acute liver inflammation after CCl4 intoxication.
Interlaboratory Comparison of Short-Term Carcinogenicity Studies Using CB6F1-rasH2 Transgenic Mice
Authors: Takaoka Masaya , Sehata Shinya , Maejima Takanori , Imai Toshio , Tor Mikinori , Satoh Hiroshi , Toyosawa Kaoru , Tanakamaru Zen-Yo , Adachi Tamiko , Hisada Shigeru , Ueda Makoto , Ogasawara Hiroyuki , Matsumoto Masahiro , Kobayashi Kiyoshi , Mutai Mamoru , Usui Toshimi
Published: July 2008

In order to evaluate a short-term carcinogenicity testing system using CB6F1-Tg rasH2 ( rasH2-Tg) mice carrying a human prototype c-Ha- ras gene, 26-week studies were conducted in 12 different facilities as a part of an International Life Science Institute Health and Environmental Science Institute (ILSI HESI) international collaborative project. In each study N-methyl- N-nitrosourea (MNU) was administered to a separate group of rasH2-Tg mice by single intraperitoneal injection (75 mg/kg) as a positive control. We herein have summarized the mortality, body weight change, and neoplastic and nonneoplastic lesions detected in these positive control groups as representative historical positive control data. Also, we performed an interlaboratory comparison of the response of rasH2-Tg mice to MNU based on the data of 11 positive control groups from these studies. Although the body weight of rasH2-Tg mice showed lower values than that of non-Tg mice during the experimental period, body weight gain in the rasH2-Tg mice was similar to that in non-Tg mice. The mortality of rasH2-Tg mice during the study period was very low, the same as for the non-Tg mice. Incidences of spontaneous alveolar/bronchiolar adenomas and splenic hemangiomas/hemangiosarcomas were also low in the rasH2-Tg mice. Nonneoplastic lesions detected in the rasH2-Tg mice were similar to those in non-Tg mice, excluding the incidence of myopathy. There were interlaboratory differences in mortality and incidence of some lesions in the MNU-treated groups. However, the causes of death were common among the 11 laboratories and almost all the MNU-treated rasH2-Tg mice developed forestomach squamous cell papillomas/carcinomas or malignant lymphomas. This suggests that there is no appreciable difference in the response of the rasH2-Tg mouse to MNU used as a positive control. Therefore, it is concluded that MNU would be an adequate positive control compound in this testing system.
Tumorigenesis in High-Dose Total Body Irradiated Rhesus Monkeys—A Life Span Study
Authors: Hollander Carel F. , Zurcher Chris , Broerse Johan J.
Published: July 2008

In the early sixties, studies have been performed at the TNO-Institutes for Health Research on acute effects of high dose total body irradiation (TBI) with X-rays and fission neutrons in Rhesus monkeys and the protective effect of autologous bone marrow transplantation (BMT). The surviving animals of this study were kept to investigate late radiation effects, ie, tumorigenesis. TBI in combination with chemotherapy, followed by rescue with BMT is increasingly used for the treatment of hematological malignancies and refractory autoimmune disease. The risk of radiation carcinogenesis after this treatment is of growing concern in man. Studies on tumor induction in nonhuman primates are of relevance in this context since the response of this species to radiation does not differ much from that in man. The group of long-term surviving monkeys comprised nine neutron irradiated animals (average total body dose 3.4 Gy, range 2.3—4.4 Gy) and 20 X-irradiated monkeys (average total body dose 7.1 Gy, range 2.8—8.6 Gy). A number of 21 age-matched nonirradiated Rhesus monkeys served as a control-group. All animals were regularly screened for the occurrence of tumors. Complete necropsies were performed after natural death or euthanasia. At postirradiation intervals of 4—21 years an appreciable number of malignant tumors was observed. In the neutron irradiated group eight out of nine animals died with 1 or more malignant tumors. In the X-irradiated group this fraction was 10 out of 20. The tumors in the control group, in seven out of 21 animals, appeared at much older age compared with those in the irradiated cohorts. The histogenesis of the malignant tumors was diverse, as was the case for benign tumors. The observed shortening of latency periods and life span, as well as, the increase of mean number of tumors per tumor bearing animal for benign neoplasms parallels the trend observed for malignant tumors. The results of this study were compared to other radiation late effects after TBI followed by different BMT treatment modalities in Rhesus monkeys. The observation that the carcinogenic risk of TBI in the Rhesus monkeys is similar to that derived from the studies of the Japanese atomic bomb survivors and the increase of the risk by a factor of 8 emphasizes the need for regular screening for secondary radiation-induced tumors in long-term surviving patients after TBI followed by BMT.
The Monkey (Macaca fascicularis) Heart Neural Structures and Conducting System: An Immunochemical Study of Selected Neural Biomarkers and Glutamate Receptors
Authors: Mueller Ruedi W. , Gill Santokh S. , Pulido Olga M.
Published: July 2008

The neural markers, protein gene product 9.5 (PGP 9.5), neurofilaments (NF) and glutamate receptors (GluRs) were visualized by immunohistochemistry in the monkey heart. PGP 9.5 showed the greatest affinity for intramural ganglia cells and nerve fibres. Structural components of the conducting system were also stained, particularly the bundle of His, AV node and Purkinje fibres. Anti-NF 200 and NF 160 showed strong, preferential affinity to nerve fibres and ganglia throughout the heart. Further studies concentrated on the presence and the distribution of glutamate receptors: NMDAR 1, GluR 1, GluR 2/3, GluR 5/6/7, mGluR 2/3, and mGluR 5. Positive immunoreactivity of GluRs was evident in nerve terminals within the atrium, myocardium, intramural ganglia and elements of the conducting system. The intensity of the stain varied for each antibody according to the anatomical distribution within neural structures and conducting system. The specificity of immunolabelling was confirmed by absorption studies with each corresponding peptide. There is preferential affinity to and differential distribution of staining with PGP 9.5, NFs and several subtypes of GluRs in the various components of the cardiac conducting system in adult monkeys. The expression of specific neural markers and glutamate receptors common to nerve fibers and ganglia cells is consistent to our previous report in rodents. These expressions suggests that such structures in the heart share common characteristics with a variety of neural tissues and hence are potential targets for neurotoxins. Furthermore, the strong affinity and specific distribution of several subtypes of GluRs in the monkey heart fosters our view that these receptors may be able to influence the physiology and pathophysiology of cardiac rhythm and excitation. Hence as in the brain, the GluRs may be involved in the mediation of excitatory effects in the heart.