bluuebunny/crossref_metadata_2025 huggingface dataset:
Article Commentary: Hearing aids and cochlear damage: The case against fitting the pure tone audiogram
Authors: Halpin Chris , Rauch Steven D.
Published: March 2009

Herein we propose a different approach to hearing aids, an approach that flows logically from the pathophysiology of cochlear disorders. This approach challenges some central tenets of the industry by 1) suggesting that many, if not most, cases would be better served by flat, undistorted gain across all frequencies rather than by “fitting” gain to the audiogram; and 2) suggesting that most of the improvements in hearing aid technology are targeted at reducing patient complaints as opposed to increasing measurable word recognition performance. We recommend that it is better to accommodate the damaged cochlea in these cases than to attempt to reverse‐engineer the audiometric test results.
Effects of a tongue‐holding maneuver during swallowing evaluated by high‐resolution manometry
Authors: Umeki Hiroshi , Takasaki Kenji , Enatsu Kaori , Tanaka Fujinobu , Kumagami Hidetaka , Takahashi Haruo
Published: March 2009

Objective

This study aimed to investigate the effects of a tongue‐holding maneuver (THM) during swallowing using a novel high‐resolution manometry (HRM) system.

Study Design

Case series with planned data collection.

Materials and Methods

Thirty‐three asymptomatic Japanese adults were studied. A solid‐state HRM assembly with 36 circumferential sensors spaced 1‐cm apart was positioned to record pressures from the velopharynx to the upper esophagus at rest and during swallowing. The maximum values of the dry swallowing pressures at the velopharynx, mesohypopharynx, upper esophageal sphincter (UES), and distance from the nostril to each point of maximum values with and without the THM were measured.

Results

The distance from the nostril to the UES was statistically shorter when swallowing with the THM than without the THM (paired t test, P = 0.009). The maximum pressure at UES was greater when swallowing with the THM than without the THM, although there was no statistically significant difference (paired t test, P = 0.051). There was no difference in the pressures and the distance between swallowing with or without the THM at any other site.

Conclusions

These findings suggest that the THM may not have a potential to facilitate compensatory swallowing power when swallowing.
Quality of life in patients treated with PDMS injection for swallowing disorders
Authors: Molteni Gabriele , Ghidini Angelo , Bergamini Giuseppe , Alicandri‐Ciufelli Matteo , Mattioli Francesco , Luppi Maria Pia , Presutti Livio
Published: March 2009

Objective

To document the efficacy of polydimethylsiloxane (PDMS) injections in patients with swallowing disorders after partial supracricoid laryngectomy; to assess the importance of quality‐of‐life (QOL) outcome in oncologic patients.

Subjects and Methods

The study included 11 patients with swallowing disorders after partial laryngectomy and appropriate rehabilitation. They were treated with endoscopic injection of PDMS; QOL was investigated with four questionnaires (M.D. Anderson Dysphagia Inventory, Performance Status Scale for Head and Neck Cancer, Performance Karnofsky Scale, and Voice Handicap Index‐10) before and after surgical treatment and further rehabilitation.

Results

A significant improvement in QOL of all 11 patients was seen after endoscopic injection. The impact of this treatment on the social life of patients was considerable.

Conclusion

Swallowing disorders and speech problems are quite common complications of partial laryngectomy. QOL in oncologic patients is a mandatory outcome measure. PDMS injection showed an improvement in the everyday life of selected patients.
The effects of molar tooth involvement in mandibular angle fractures treated with rigid fixation
Authors: Ramakrishnan Jeevan , Shingleton Alexander , Reeves Dawn , Key J. Michael , Vural Emre
Published: March 2009

Objective

To determine whether the presence of a tooth in the line of mandibular angle fracture increases the incidence of complications and whether removing these teeth has an effect on complication rates.

Design

Case series with chart review.

Subjects and Methods

The analysis was performed on 83 patients who underwent open reduction and internal fixation for mandibular angle fractures. Lower molar teeth involved in the fracture line were extracted if they were loose, fractured, or grossly infected or prevented satisfactory reduction. Data regarding demographics, involvement of a molar tooth, management of the involved tooth, and postoperative outcome were analyzed. Statistical analysis was performed by using likelihood ratio χ2 and logistic regression.

Results

The revision surgery in fractures with molar tooth involvement was 28.9 percent, compared to 12.9 percent when no tooth was involved (P = 0.084). When a tooth was involved in the fracture, the revision surgery rate was 25 percent when it was removed and 30% when it was preserved (P = 0.734).

Conclusion

Postoperative complications, especially the revision surgery rates, may not increase by involvement of lower molar teeth in the fracture line and selective removal of these teeth by using commonly accepted guidelines may not decrease complication rates in angle fractures.
Financial revolution and economic modernisation in Sweden
Authors: Ögren Anders
Published: March 2009

The development of a well-adapted financial system was a main part of the successful Swedish economic modernisation in the latter half of the nineteenth century. In this article it is shown that this development followed the pattern of a financial revolution. Major institutional and organisational changes that took place roughly between the late 1850s and early 1870s led to a rapid increase in liquidity and financial services. This financial revolution preceded the acceleration in economic growth in general and in the modern, industrial sector in particular. Monetisation especially encouraged growth, both in the industrial sector and in GDP as a whole. The basis of the financial system, measured as commercial bank assets and equity capital, affected overall GDP growth. The results also clearly promoted the importance of the development of the financial sector and monetisation as an interlinked and complementary process.
CONTEXTUAL LOGIC WITH MODALITIES FOR TIME AND SPACE
Authors: GAIFMAN HAIM
Published: March 2009

We develop a formal apparatus to be used as a tool in analyzing common kinds of context dependence in natural language, and their interaction with temporal and spatial modalities. It is based on context-operators, which act on wffs. The interplay between the various modalities and the context-operators is one of the main targets of the analysis. Statements made by different people at different times in different places, using the same personal temporal and spatial indexicals, can be represented in the system, and can be combined by sentential connectives and be subject to quantification. The use of spatial modality and the suggested treatment of adverbial phrases are new as far as we know. So is a certain variant of temporal modality. In the nontechnical part, consisting of Sections 1 and 2, we discuss the role that formalisms can, in principle, play in the analysis of linguistic usage; this is followed by a philosophical discussion of various kinds of context dependence. The semitechnical part, Section 3, introduces the system's components, the context, and the modal operators, and explains their use via natural language examples. In Section 4 the formal language and its semantics are defined, in full detail. The temporal and spatial sublanguages constitute separate sorts, which interact through the modal operators and the context-operators. A sound deductive system is given and a completeness result is stated, without proof.
Three‐dimensional simulation of the coupled Perkins and Es‐layer instabilities in the nighttime midlatitude ionosphere
Authors: Yokoyama Tatsuhiro , Hysell David L. , Otsuka Yuichi , Yamamoto Mamoru
Published: March 2009

Plasma density structures and associated irregularities in the nighttime midlatitude ionosphere are frequently observed as frontal structures elongated from northwest to southeast (NW‐SE) in the Northern Hemisphere. The frontal structures and the coupling process between the E and F regions are studied with a three‐dimensional numerical model, which can simulate two instability mechanisms: Perkins instability in the F‐region and sporadic‐E (Es)‐layer instability in the E region. The fastest growth of the coupled instability occurs when the unstable conditions on NW‐SE perturbation are satisfied in both regions. The perturbation of F‐region integrated conductivity grows much faster than the isolated Perkins instability. The meridional component of a rotational wind shear blows an existing Es layer southward, and the F‐region structure follows the E‐region drift velocity. The NW‐SE structure in the E region can be formed from random perturbation regardless of the F‐region condition. When the F region is unstable on the NW‐SE perturbation, however, the NW‐SE structure is formed in both regions with a common scale length. We conclude that (1) the Es‐layer instability plays a major role in seeding NW‐SE structure in the F region, and the Perkins instability is required to amplify its perturbation; (2) the rotational wind shear in the E region produces southwestward phase propagation of the NW‐SE structure in both the E and F regions; and (3) the coupling process has a significant effect on the scale of the Es‐layer perturbation rather than the growth rate of the Es‐layer instability.
A new empirical relation to estimate atmospheric electrical columnar resistance, effect of changing aerosol concentration and cosmic ray ionization on it: A quantitative study
Authors: Kulkarni M. N.
Published: March 2009

A new empirical relation is found among atmospheric electrical columnar resistance, aerosol concentration, and eddy diffusion coefficient. The methodology is reported for the first time. This empirical relation can be used regularly for estimating columnar resistance. As solar modulation of cosmic rays and consequent changes in columnar resistance of global atmospheric electric circuit convey solar influence on lower atmospheric meteorological phenomena, a quantitative comparison of percent change in columnar resistance due to change in cosmic ray ionization and that due to change in aerosol concentration is made, which shows that 20% change in cosmic ray ionization causes more (about two times) change in columnar resistance over ocean but less (about 1/3) change over land as compared to that caused by 20% change in aerosol concentration. This confirms that over ocean, ionization due to cosmic rays and over land, atmospheric aerosol concentration mainly determine columnar resistance. This land‐ocean contrast gets reduced with atmospheric turbulence. It is found that, for small heights of the boundary layer (low eddy diffusivity), columnar resistance changes more with respect to change in aerosol concentration, and change in eddy diffusivity has negligible effect on it, but for large values of heights (large eddy diffusivity), there is substantial increase in columnar resistance. Furthermore, exceeding a certain critical value of conductivity, columnar resistance becomes independent of conductivity. The estimated values of columnar resistance using this method are very well consistent with the previous studies. Also, calculated percent change in global atmospheric electrical parameters agrees well with the previous results.
Observation of local tidal variability and instability, along with dissipation of diurnal tidal harmonics in the mesopause region over Fort Collins, Colorado (41°N, 105°W)
Authors: Li Tao , She C.‐Y. , Liu Han‐Li , Yue Jia , Nakamura Takuji , Krueger David A. , Wu Qian , Dou Xiankang , Wang Shui
Published: March 2009

During the 9‐day continuous campaign in September 2003, the Colorado State University sodium lidar observed significant short‐term tidal variability in both diurnal and semidiurnal tides above 85 km on days 265–268. Both diurnal and semidiurnal amplitudes dramatically increased on day 267 with a continuous phase advance in diurnal tidal harmonics, causing local atmosphere to become dynamically unstable. Following the dynamical instability associated with tides, we observed an equally dramatic decrease in diurnal amplitude, which was accompanied by rapid and continuous phase retardation at 87 km on day 268; the accompanying diurnal phase profiles changed from propagating mode to evanescent mode. Since the time scale of the observed variability during days 265–268 is less than 1 day, gravity wave/tidal interaction at least is partially responsible for the observed variability. The observed changes in tidal wind amplitudes and phases were observed to correlate with gravity wave (GW) activities and the direction of GW momentum, exhibited and discerned concurrently by an OH all‐sky imager at nearby Yucca Ridge station, consistent with well‐known models of tidal/GW interactions. The stability analysis in the night of 267, when both diurnal and semidiurnal reached the maximum amplitudes, revealed that the running daily tidal waves alone, superimposed with the associated mean state, could force the atmosphere into local dynamical instability near 90–95 km. The eddy diffusion associated with the instability is believed to have caused a strong dissipation of diurnal tide as observed on day 268.
Validation of the coronal mass ejection predictions at the Earth orbit estimated by ENLIL heliosphere cone model
Authors: Taktakishvili A. , Kuznetsova M. , MacNeice P. , Hesse M. , Rastätter L. , Pulkkinen A. , Chulaki A. , Odstrcil D.
Published: March 2009

Modeling is an important tool in understanding physical processes in the space weather. Model performance studies evaluate the quality of model operation by comparing its output to a measurable parameter of interest. In this paper we studied the performance of the combination of the halo coronal mass ejection (CME) analytical cone model and ENLIL three‐dimensional MHD heliosphere model. We examined the CME arrival time and magnitude of impact at 1 AU for different geoeffective events, including the October 2003 Halloween Storm and the 14 December 2006 storm CMEs. The results of the simulation are compared with the ACE satellite observations. The comparison of the simulation results with the observations demonstrates that ENLIL cone model performs better compared to reference mean velocity and empirical models.
ac susceptibility study of a magnetite magnetic fluid
Authors: Ayala-Valenzuela O. E. , Matutes-Aquino J. A. , Galindo J. T. Elizalde , Botez C. E.
Published: March 2009

Magnetite nanometric powder was synthesized from metal salts using a coprecipitation technique. The powders were used to produce magnetic fluid via a peptization method, with hydrocarbon Isopar M as liquid carrier and oleic acid as surfactant. The complex magnetic susceptibility χ=χ′+iχ″ was measured as a function of temperature T in steps of 2.5 K from 3 to 298 K for frequencies ranging from f=10 to 10 000 Hz. The magnetic fluid real and imaginary components of the ac susceptibility show a prominent maximum at temperatures that increase with the measuring frequency, which is attributed to a spin-glass-like behavior. The peak temperature Tp1 of χ″ depends on f following the Vogel–Fulcher law f=f0 exp[E/kB(Tp1−T0)], where f0 and E are positive constants and T0 is a parameter related to particle interactions. There is another kind of peak temperature, Tp2, in the loss factor tan δ=χ″/χ′ which is related to a magnetic aftereffect. The peak temperature Tp2 is far less than Tp1 and shows an Arrhenius-type dependence on f.
Spin-transfer induced switching in nanomagnetoresistive devices composed of Co/Pt multilayers with perpendicular magnetic anisotropy
Authors: Park Jeong-Heon , Moneck Matthew T. , Park Chando , Zhu Jian-Gang
Published: March 2009

We demonstrate spin-transfer switching of nanomagnetic devices composed of Co/Pt multilayer electrodes with perpendicular magnetic anisotropy. In order to obtain highly spin-polarized current, we have proposed the adoption of thick Co adjacent layers. The film stack has been optimized so that two different Co/Pt multilayer electrodes switch separately, with each having narrow switching field distribution. Detrimental effects of surface roughness have been observed and minimized to achieve well-defined switching behavior. Diverse nanopillar devices fabricated by e-beam lithography and subsequent processes show well-defined single step switching in both perpendicular field and injected current applications. The critical current density obtained is comparable to that of Co/Ni electrode based devices, indicating enhanced spin-transfer efficiency.
Structural analysis of interfacial strained epitaxial BiMnO3 films fabricated by chemical solution deposition
Authors: Naganuma Hiroshi , Kovacs Andras , Harima Tetsuro , Shima Hiromi , Okamura Soichiro , Hirotsu Yoshihiko
Published: March 2009

An interfacial epitaxial BiMnO3 layer was fabricated by chemical solution deposition on SrTiO3 (100) substrate, and the microstructure of the film was analyzed by x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM). The TEM observation revealed the epitaxial growth of BiMnO3 on the SrTiO3 substrate as follows: ([110](001))BiMnO3∥[0-10](001) SrTiO3. XRD and TEM analyses revealed that the mismatch between the epitaxial BiMnO3 and the SrTiO3 substrate causes a distortion in lattice parameters of BiMnO3 and, consequently, a large compressive strain in the BiMnO3 layer.
Expansion and contraction of polymer electrodes under applied voltage
Authors: Kiyohara Kenji , Sugino Takushi , Takeuchi Ichiroh , Mukai Ken , Asaka Kinji
Published: March 2009

The authors developed a scheme for characterizing the expansion and contraction of polymer electrodes when voltage is applied by coupling a symmetry analysis, the elasticity theory, and the experimental measurements. This scheme was applied to the bucky-gel electrodes and the expansion and contraction rates for the cathode and the anode were determined separately. For the case of the bucky-gel electrodes, it was found that the cathode expands and the anode contracts as voltage is applied. The stress exerted inside the electrode layers was also determined and the mechanical efficiency of the actuator composed of the bucky-gel electrodes is discussed.
An efficient direct simulation Monte Carlo method for low Mach number noncontinuum gas flows based on the Bhatnagar–Gross–Krook model
Authors: Ramanathan Shriram , Koch Donald L.
Published: March 2009

The direct simulation Monte Carlo (DSMC) method is the preferred approach for simulating rarefied gas flows in complex geometries. However, the standard DSMC method becomes inefficient in the limit M=U¯/⟨c⟩→0 when the thermal velocity fluctuations which scale with the speed of sound ⟨c⟩ are much larger than characteristic ensemble-averaged flow speed U¯. In this paper, we propose a modified DSMC algorithm which simulates the linearized Bhatnagar–Gross–Krook (BGK) approximation to the Boltzmann equation. The particles in this method are uniformly distributed in space and have a rest-state, equilibrium Maxwellian velocity distribution. The deviations from the equilibrium state are captured by weightings, indicating that each particle represents a noninteger expectation for finding gas molecules with the simulation particle’s velocity in the spatial cell where it is found. The BGK approximation makes the implementation of such a method simple and efficient because the BGK collision rule can be implemented by adjusting particle weightings without the need to create new particles during the simulation. The method can be incorporated into existing DSMC simulation programs with minimal changes. We apply the new algorithm to two test problems—pressure-driven flow through a nanochannel and flow around an isolated sphere. Results obtained with the new method are in excellent agreement with previous theories and simulations.
Changes in the layer roughness and crystallography during the annealing of CoFeB/MgO/CoFeB magnetic tunnel junctions
Authors: Anderson G. I. R. , Wei H.-X. , Porter N. A. , Harnchana V. , Brown A. P. , Brydson R. M. D. , Arena D. A. , Dvorak J. , Han X.-F. , Marrows C. H.
Published: March 2009

Annealing is necessary to achieve giant tunneling magnetoresistance (TMR) values in sputtered CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs). In this study three complementary techniques were used to study the resulting changes in junction microstructure. The as-deposited TMR was modest, 5%, but rose to 101% after annealing at 325 °C for 1 h, corresponding to the tunneling spin polarization rising from 16% to 58%. Soft x-ray resonant magnetic scattering showed a roughening of the magnetic interfaces of the MTJ free layer, confirmed by transmission electron microscopy, which also showed the changes in the CoFeB and MgO to a lattice-matched polycrystalline form.
Influence of thermal annealing on the electron emission of InAs quantum dots containing a misfit defect state
Authors: Chen J. F. , Yang C. H. , Hsu R. M. , Wang U. S.
Published: March 2009

We have investigated the effect of postgrowth thermal annealing on the electron emission from InAs quantum dots (QDs) containing a misfit-related defect state induced by strain relaxation. Additional carrier depletion in the GaAs bottom layer near the QD, caused by the defect state, can effectively suppress electron tunneling from the QD, leading to the observation of a thermal emission from the QD electron ground state to the GaAs conduction band with a large emission energy of 213 meV, in contrast to defect-free nonrelaxed QDs in which an emission of 58 meV from the QD electron ground state to first excited state is observed. The emission energy is reduced to 193 meV and to 164 meV after annealing at 650 and 700 °C for 1 min, respectively. This emission energy reduction is correlated with the photoluminescence blueshift which is attributed to the interdiffusion of atoms across the QD interface. The electron emission from the QD first excited and ground states is found to be a thermal emission at high temperatures and a tunneling emission at low temperatures. The tunneling energy barrier is found to be comparable to the thermal emission energy, supporting a thermal emission to the GaAs conduction band. This study illustrates a significant effect of a defect state on the electron-emission process in the QDs, suggesting the possibility of modifying the electron emission time of the QDs by purposely introducing a deep defect state.
An investigation of silicon carbide-water nanofluid for heat transfer applications
Authors: Singh D. , Timofeeva E. , Yu W. , Routbort J. , France D. , Smith D. , Lopez-Cepero J. M.
Published: March 2009

Thermal conductivity and mechanical effects of silicon carbide nanoparticles uniformly dispersed in water were investigated. Mean size of SiC particles was 170 nm with a polydispersity of ∼30% as determined from small-angle x-ray scattering and dynamic light scattering techniques. Room temperature viscosity of the nanofluids ranged from 2 to 3 cP for nominal nanoparticle loadings 4–7 vol %. On a normalized basis with water, viscosity of the nanofluids did not significantly change with the test temperature up to 85 °C. Optical microscopy of diluted nanofluid showed no agglomeration of the nanoparticles. Thermal conductivity of the fluid was measured as a function of the nominal nanoparticle loading ranging from 1 to 7 vol %. Enhancement in thermal conductivity was approximately 28% over that of water at 7 vol % particle loadings under ambient conditions. Enhancements in thermal conductivities for the nanofluids with varying nanoparticle loadings were maintained at test temperatures up to 70 °C. Results of thermal conductivity have been rationalized based on the existing theories of heat transfer in fluids. Implications of using this nanofluid for engineering cooling applications are discussed.
Forces on a finite-sized particle located close to a wall in a linear shear flow
Authors: Zeng Lanying , Najjar Fady , Balachandar S. , Fischer Paul
Published: March 2009

To understand and better model the hydrodynamic force acting on a finite-sized particle moving in a wall-bounded linear shear flow, here we consider the two limiting cases of (a) a rigid stationary spherical particle in a linear wall-bounded shear flow and (b) a rigid spherical particle in rectilinear motion parallel to a wall in a quiescent ambient flow. In the present computations, the particle Reynolds number ranges from 2 to 250 at separation distances to the wall from nearly sitting on the wall to far away from the wall. First we characterize the structure of the wake for a stationary particle in a linear shear flow and compare with those for a particle moving parallel to a wall in a quiescent ambient [see L. Zeng, S. Balachandar, and P. Fischer, J. Fluid Mech. 536, 1 (2005)]. For both these cases we present drag and lift results and obtain composite drag and lift correlations that are valid for a wide range of Re and distance from the wall. These correlations have been developed to be consistent with all available low Reynolds number theories and approach the appropriate uniform flow results at large distance from the wall. Particular attention is paid to the case of particle in contact with the wall and the computational results are compared with those from experiments.
Langmuir probe-based observables for plasma-turbulence code validation and application to the TORPEX basic plasma physics experiment
Authors: Ricci Paolo , Theiler C. , Fasoli A. , Furno I. , Labit B. , Müller S. H. , Podestà M. , Poli F. M.
Published: March 2009

The methodology for plasma-turbulence code validation is discussed, with focus on the quantities to use for the simulation-experiment comparison, i.e., the validation observables, and application to the TORPEX basic plasma physics experiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)]. The considered validation observables are deduced from Langmuir probe measurements and are ordered into a primacy hierarchy, according to the number of model assumptions and to the combinations of measurements needed to form each of them. The lowest levels of the primacy hierarchy correspond to observables that require the lowest number of model assumptions and measurement combinations, such as the statistical and spectral properties of the ion saturation current time trace, while at the highest levels, quantities such as particle transport are considered. The comparison of the observables at the lowest levels in the hierarchy is more stringent than at the highest levels. Examples of the use of the proposed observables are applied to a specific TORPEX plasma configuration characterized by interchange-driven turbulence.
Photochemical reactions of the low-lying excited states of formaldehyde: T1/S intersystem crossings, characteristics of the S1 and T1 potential energy surfaces, and a global T1 potential energy surface
Authors: Zhang Peng , Maeda Satoshi , Morokuma Keiji , Braams Bastiaan J.
Published: March 2009

Accurate ab initio calculations using the multireference configuration interaction method have been performed to characterize the potential energy surfaces (PESs) of low-lying excited states (S1 and T1) of formaldehyde (H2CO) and hydroxymethylene (HCOH) with emphasis on their isomerization, dissociation, and the possible role of the T1 state in the nonadiabatic photodissociation of H2CO. Two regions on the T1 PES are found to contribute to the nonadiabatic transition to the ground (S0) state. Three minima on the seam of crossing (MSXs), 80–85 kcal/mol (above the S0 global minimum), are located in the HCOH region; they, however, are blocked by a high-energy isomerization transition state at ∼107 kcal/mol. The other MSX discovered in the H2CO region is reachable with energy ≤91 kcal/mol and strong spin-orbit interaction; this may be a more important pathway for the T1 to S0 transition. A full-dimensional PES is generated for the T1 state, fitted by a weighted least-squares method employing a many-body expansion in which each term is a function of the internuclear distances and is invariant under permutations of like atoms. The single global function covers the formaldehyde and the HCOH regions as well as dissociation pathways. The high quality of the fitted PES is demonstrated by the small root-mean-square fitting error of 119 cm−1 and the close agreement between the critical points from ab initio calculations and from the fitted PES.
Marangoni-driven spreading along liquid-liquid interfaces
Authors: Berg S.
Published: March 2009

Marangoni-driven spreading at gas-liquid interfaces has been studied extensively over the past years but so far the spreading kinetics along the interface between immiscible liquids has not been investigated systematically. In this study, the spreading kinetics of aqueous solutions of sodium dodecyl sulfate and dodecyl trimethyl ammonium bromide along the interface between thick layers of water and decane has been investigated by means of two different optical visualization techniques (dye tracer and laser shadowgraphy). The spreading kinetics follows a power law where the radius r as function of time t scales as r(t)∝t3/4 indicating large similarities with Marangoni-driven spreading at air-liquid interfaces. The existing scaling law for spreading at air-liquid interfaces is based on the balance between an interfacial tension gradient and the viscous stress in the fluid layers beneath the interface. When the viscous dissipation in the two boundary layers below and above the interface is factored into the scaling law, quantitative agreement with experimental data is obtained. Marangoni-driven spreading along an interface is a fast transport mechanism. The velocity of the leading edge lies within the range of group velocities of capillary waves.
Reversibility and transport properties of dithienylethene photoswitches
Authors: Zhuang Min , Ernzerhof Matthias
Published: March 2009

We consider a particular class of molecular electronic devices (MEDs) built around the photoactive dithienylethene switch. Light of an appropriate frequency can convert the switch from a high to a low conductance form. Various derivatives of the dithienylethene that have recently been investigated experimentally are modeled. The transmission probabilities for the switches are analyzed and we provide an explanation for why certain switches, as a part of a MED, can only be converted from the closed to the open form, while for other switches, this process is reversible.
Enhanced stab resistance of armor composites with functionalized silica nanoparticles
Authors: Mahfuz Hassan , Clements Floria , Rangari Vijaya , Dhanak Vinod , Beamson Graham
Published: March 2009

Traditionally shear thickening fluid (STF) reinforced with Kevlar has been used to develop flexible armor. At the core of the STF-Kevlar composites is a mixture of polyethylene glycol (PEG) and silica particles. This mixture is often known as STF and is consisted of approximately 45 wt % PEG and 55 wt % silica. During rheological tests, STF shows instantaneous spike in viscosity above a critical shear rate. Fabrication of STF-Kevlar composites requires preparation of STF, dilution with ethanol, and then impregnation with Kevlar. In the current approach, nanoscale silica particles were dispersed directly into a mixture of PEG and ethanol through a sonic cavitation process. Two types of silica nanoparticles were used in the investigation: 30 nm crystalline silica and 7 nm amorphous silica. The admixture was then reinforced with Kevlar fabric to produce flexible armor composites. In the next step, silica particles are functionalized with a silane coupling agent to enhance bonding between silica and PEG. The performance of the resulting armor composites improved significantly. As evidenced by National Institute of Justice spike tests, the energy required for zero-layer penetration (i.e., no penetration) jumped twofold: from 12 to 25 J cm2/g. The source of this improvement has been traced to the formation of siloxane (Si-O-Si) bonds between silica and PEG and superior coating of Kevlar filaments with particles. Fourier transform infrared, x-ray photoemission spectroscopy, and scanning electron microscopy studies were performed to examine chemical bonds, elemental composition, and particle dispersion responsible for such improvement. In summary, our experiments have demonstrated that functionalization of silica particles followed by direct dispersion into PEG resulted in superior Kevlar composites having much higher spike resistance.
Deflection of a viscoelastic cantilever under a uniform surface stress: Applications to static-mode microcantilever sensors undergoing adsorption
Authors: Wenzel M. J. , Josse F. , Heinrich S. M.
Published: March 2009

The equation governing the curvature of a viscoelastic microcantilever beam loaded with a uniform surface stress is derived. The present model is applicable to static-mode microcantilever sensors made with a rigid polymer, such as SU-8. An analytical solution to the differential equation governing the curvature is given for a specific surface stress representing adsorption of analyte onto the viscoelastic beam’s surface. The solution for the bending of the microcantilever shows that, in many cases, the use of Stoney’s equation to analyze stress-induced deflection of viscoelastic microcantilevers (in the present case due to surface analyte adsorption) can lead to poor predictions of the beam’s response. It is shown that using a viscoelastic substrate can greatly increase sensitivity (due to a lower modulus), but at the cost of a longer response time due to viscoelastic creep in the microcantilever. In addition, the effects of a coating on the cantilever are considered. By defining effective moduli for the coated-beam case, the analytical solution for the uncoated case can still be used. It is found that, unlike the case of a silicon microcantilever, the stress in the coating due to bending of a polymer cantilever can be significant, especially for metal coatings. The theoretical results presented here can also be used to extract time-domain viscoelastic properties of the polymer material from beam response data.
Nonlinear model for bipolar electric field structures in the magnetosphere with non-Maxwellian electron distribution
Authors: Pajouh H. Hakimi , Abbasi H.
Published: March 2009

Recently, we have derived a nonlinear model [H. Abbasi et al., Phys. Plasmas 15, 092902 (2008)] based on general features reported from the polar orbiting (POLAR) and fast auroral snapshot satellite observations of the magnetosphere in the low-frequency ion dynamics. The parametric coupling between large amplitude magnetic field-aligned circularly polarized electromagnetic electron-cyclotron (EMEC) waves and pondermotively driven ion-acoustic perturbations in the magnetosphere has been considered. Accordingly, a nonlinear Schrödinger (NLS) equation for the modulated EMEC wave envelope was derived. In this paper, solitary structures of the NLS equation and their attributes are investigated focusing on the deviation of electron velocity distribution from the Maxwellian equilibrium and the effect of trapped electrons as well. The results are in good agreement with POLAR observations of solitary waves at the Earth’s magnetopause.
Evolution of a relativistic electron beam–plasma return current system
Authors: Kong X. , Park J. , Ren C. , Sheng Z. M. , Tonge J. W.
Published: March 2009

Evolution of a relativistic electron beam-plasma return current system has been studied using particle-in-cell simulations. The mode number-resolved linear growth rates of the oblique instabilities that the system suffers generally agree with the existing theory [A. Bret et al., Phys. Rev. E 72, 016403 (2005)]. The comparison of in- and out-of-plane simulations shows that two-stream type of instabilities dominates the early stage of energy transfer from the beam drift energy to the beam and plasma thermal energy. The end stage of the nonlinear evolution is dominated Weibel/filament type of instabilities, resulting a beam with a moderately increased angular spread, reduced drift energy, and no reduction in the initial cross section.
Permanent-magnet helicon sources and arrays: A new type of rf plasma
Authors: Chen Francis F. , Torreblanca Humberto
Published: March 2009

Helicon discharges are known for their ability to produce high densities of partially ionized plasma, their efficiency arising from an unusual mechanism of rf coupling. However, the requirement of a dc magnetic field has prevented their wide acceptance in industry. The use of permanent magnets greatly simplifies helicon sources, and arrays of small sources extend the use of helicons to the processing of large substrates. An eight-tube array was designed and constructed, and its density uniformity measured in a 53×165 cm2 chamber. Three innovations involved (a) the remote field of ring magnets, (b) a low-field density peak, and (c) rf power distribution. High-density plasmas uniform over large areas requires compatibility in all three areas.
An O(N2) approximation for hydrodynamic interactions in Brownian dynamics simulations
Authors: Geyer Tihamér , Winter Uwe
Published: March 2009

In the Ermak–McCammon algorithm for Brownian dynamics, the hydrodynamic interactions (HIs) between N spherical particles are described by a 3N×3N diffusion tensor. This tensor has to be factorized at each time step with a runtime of O(N3), making the calculation of the correlated random displacements the bottleneck for many-particle simulations. Here we present a faster algorithm for this step, which is based on a truncated expansion of the hydrodynamic multiparticle correlations as two-body contributions. The comparison to the exact algorithm and to the Chebyshev approximation of Fixman verifies that for bead-spring polymers this approximation yields about 95% of the hydrodynamic correlations at an improved runtime scaling of O(N2) and a reduced memory footprint. The approximation is independent of the actual form of the hydrodynamic tensor and can be applied to arbitrary particle configurations. This now allows to include HI into large many-particle Brownian dynamics simulations, where until now the runtime scaling of the correlated random motion was prohibitive.
Plasma restructuring of catalysts for chemical vapor deposition of carbon nanotubes
Authors: Cantoro M. , Hofmann S. , Mattevi C. , Pisana S. , Parvez A. , Fasoli A. , Ducati C. , Scardaci V. , Ferrari A. C. , Robertson J.
Published: March 2009

The growth of multiwalled carbon nanotubes and carbon nanofibers by catalytic chemical vapor deposition at lower temperatures is found to be aided by a separate catalyst pretreatment step in which the catalyst thin film is restructured into a series of nanoparticles with a more active surface. The restructuring is particularly effective when carried out by an ammonia plasma. The nature of the restructuring is studied by atomic force microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and Raman. We find that as the growth temperature decreases, there is a limiting maximum catalyst thickness, which gives any nanotube growth. Plasmas are found to restructure the catalyst by a combination of physical etching and chemical modification. Large plasma powers can lead to complete etching of thin catalyst films, and hence loss of activity. Ni is found to be the better catalyst at low temperatures because it easily reduced from any oxide form to the catalytically active metallic state. On the other hand, Fe gives the largest nanotube length and density yield at moderate temperatures because it is less easy to reduce at low temperatures and it is more easily poisoned at high temperatures.
UNIPIC code for simulations of high power microwave devices
Authors: Wang Jianguo , Zhang Dianhui , Liu Chunliang , Li Yongdong , Wang Yue , Wang Hongguang , Qiao Hailiang , Li Xiaoze
Published: March 2009

In this paper, UNIPIC code, a new member in the family of fully electromagnetic particle-in-cell (PIC) codes for simulations of high power microwave (HPM) generation, is introduced. In the UNIPIC code, the electromagnetic fields are updated using the second-order, finite-difference time-domain (FDTD) method, and the particles are moved using the relativistic Newton–Lorentz force equation. The convolutional perfectly matched layer method is used to truncate the open boundaries of HPM devices. To model curved surfaces and avoid the time step reduction in the conformal-path FDTD method, CP weakly conditional-stable FDTD (WCS FDTD) method which combines the WCS FDTD and CP-FDTD methods, is implemented. UNIPIC is two-and-a-half dimensional, is written in the object-oriented C++ language, and can be run on a variety of platforms including WINDOWS, LINUX, and UNIX. Users can use the graphical user’s interface to create the geometric structures of the simulated HPM devices, or input the old structures created before. Numerical experiments on some typical HPM devices by using the UNIPIC code are given. The results are compared to those obtained from some well-known PIC codes, which agree well with each other.
Improved leakage and ferroelectric properties of Mn and Ti codoped BiFeO3 thin films
Authors: Kawae T. , Terauchi Y. , Tsuda H. , Kumeda M. , Morimoto A.
Published: March 2009

Polycrystalline BiFeO3 (BFO), Ti-doped BFO, Mn-doped BFO, and (Mn, Ti)-codoped BFO (BFMT) thin films were fabricated on Pt/SrTiO3 (100) substrate by pulsed laser deposition. Observed leakage current behavior in those ion-doped BFO films indicated the dominance of space-charge-limited current in the high electric field region. The leakage current of the BFMT film was much reduced in relation to the other films due to the formation of deep traps. In the BFMT film, well saturated P-E hysteresis curves were observed. Remanent polarization and coercive field for maximum electric field of 2100 kV/cm were 75 μC/cm2 and 310 kV/cm, respectively.
Ethylene is an endogenous stimulator of cell division in the cambial meristem of
Populus
Authors: Love Jonathan , Björklund Simon , Vahala Jorma , Hertzberg Magnus , Kangasjärvi Jaakko , Sundberg Björn
Published: March 2009

The plant hormone ethylene is an important signal in plant growth responses to environmental cues. In vegetative growth, ethylene is generally considered as a regulator of cell expansion, but a role in the control of meristem growth has also been suggested based on pharmacological experiments and ethylene-overproducing mutants. In this study, we used transgenic ethylene-insensitive and ethylene-overproducing hybrid aspen (
Populus tremula
×
tremuloides
) in combination with experiments using an ethylene perception inhibitor [1-methylcyclopropene (1-MCP)] to demonstrate that endogenous ethylene produced in response to leaning stimulates cell division in the cambial meristem. This ethylene-controlled growth gives rise to the eccentricity of
Populus
stems that is formed in association with tension wood.
Electrophysiological correlates of default-mode processing in macaque posterior cingulate cortex
Authors: Hayden Benjamin Y. , Smith David V. , Platt Michael L.
Published: March 2009

During the course of daily activity, our level of engagement with the world varies on a moment-to-moment basis. Although these fluctuations in vigilance have critical consequences for our thoughts and actions, almost nothing is known about the neuronal substrates governing such dynamic variations in task engagement. We investigated the hypothesis that the posterior cingulate cortex (CGp), a region linked to default-mode processing by hemodynamic and metabolic measures, controls such variations. We recorded the activity of single neurons in CGp in 2 macaque monkeys performing simple tasks in which their behavior varied from vigilant to inattentive. We found that firing rates were reliably suppressed during task performance and returned to a higher resting baseline between trials. Importantly, higher firing rates predicted errors and slow behavioral responses, and were also observed during cued rest periods when monkeys were temporarily liberated from exteroceptive vigilance. These patterns of activity were not observed in the lateral intraparietal area, an area linked to the frontoparietal attention network. Our findings provide physiological confirmation that CGp mediates exteroceptive vigilance and are consistent with the idea that CGp is part of the “default network” of brain areas associated with control of task engagement.
Identification of the Signal Directing Tim9 and Tim10 into the Intermembrane Space of Mitochondria
Authors: Milenkovic Dusanka , Ramming Thomas , Müller Judith M. , Wenz Lena-Sophie , Gebert Natalia , Schulze-Specking Agnes , Stojanovski Diana , Rospert Sabine , Chacinska Agnieszka
Published: March 2009

The intermembrane space of mitochondria contains the specific mitochondrial intermembrane space assembly (MIA) machinery that operates in the biogenesis pathway of precursor proteins destined to this compartment. The Mia40 component of the MIA pathway functions as a receptor and binds incoming precursors, forming an essential early intermediate in the biogenesis of intermembrane space proteins. The elements that are crucial for the association of the intermembrane space precursors with Mia40 have not been determined. In this study, we found that a region within the Tim9 and Tim10 precursors, consisting of only nine amino acid residues, functions as a signal for the engagement of substrate proteins with the Mia40 receptor. Furthermore, the signal contains sufficient information to facilitate the transfer of proteins across the outer membrane to the intermembrane space. Thus, here we have identified the mitochondrial intermembrane space sorting signal required for delivery of proteins to the mitochondrial intermembrane space.
5 Why are stative‐active languages rare in Eurasia? A typological perspective on split‐subject marking
Authors: Nichols Johanna
Published: March 2009

This chapter presents a lexical typological study of argument encoding for selected verb glosses across selected languages of Eurasia, the Pacific, and the Americas. Plotting the percentages of A- vs. O-coded Ss for the sample yields a continuum where ergative and accusative languages cluster towards opposite extremes and languages normally classified as semantically aligned fall in between.
6 Losing semantic alignment: from Proto‐Yeniseic to Modern Ket
Authors: Vajda Edward J.
Published: March 2009

Proto-Yeniseic possessed a type of semantic alignment whereby subject and object NPs were zero marked and most undergoer subjects generated verb-internal agreement. Modern Ket exhibits a more complex system of verb-internal subject-object marking involving several different patterns which defy simple semantic classification. This chapter traces this phenomenon diachronically.
9 The semantics of semantic alignment in eastern Indonesia
Authors: Klamer Marian
Published: March 2009

This chapter discusses semantic parameters relevant to the alignment systems of nine lesser-known languages of eastern Indonesia. The alignment is primarily determined by the proto-Agent feature ‘volition’ and the proto-Patient feature ‘undergoer of change of state’. The distinction between dynamic and static predicates plays only a limited role.
15 Voice and transitivity in Guaraní
Authors: Velázquez‐castillo Maura
Published: March 2009

This chapter shows that the closest equivalents to voice alternations in Guarani cut across the transitive divide and respond to spatial relations between events and event participants. The constructions at issue, previously labeled ‘reflexive/passive’ and ‘inverse’, are sensitive to viewpoint and levels of proximity between the predicate and its arguments within inactive situations, and to deviations from the default outward directionality of active events.