bluuebunny/crossref_metadata_2025 huggingface dataset:
Cross-generational vowel change in American English
Authors: Jacewicz Ewa , Fox Robert Allen , Salmons Joseph
Published: May 2011

This study examines cross-generational changes in the vowel systems in central Ohio, southeastern Wisconsin, and western North Carolina. Speech samples from 239 speakers, males and females, were divided into three age groups: grandparents (66–91 years old), parents (35–51), and children (8–12). Acoustic analysis of vowel dynamics (i.e., formant movement) was undertaken to explore variation in the amount of spectral change for each vowel. A robust set of cross-generational changes in /ɪ, ɛ, æ, ɑ/ was found within each dialect-specific vowel system, involving both their positions and dynamics. With each successive generation, /ɪ, ɛ, æ/ become increasingly monophthongized and /ɑ/ is diphthongized in children. These changes correspond to a general anticlockwise parallel rotation of vowels (with some exceptions in /ɪ/ and /ɛ/). Given the widespread occurrence of these parallel chainlike changes, we term this development the “North American Shift,” which conforms to the general principles of chain shifting formulated by Labov (1994) and others.
Sprinting Research and Spot Jogging Regulation: The State of Bioethics in Cameroon
Authors: TANGWA GODFREY B. , MUNUNG NCHANGWI SYNTIA
Published: May 2011

Cameroon is a Central African country lying at latitude 6°N and longitude 12°E. The country has a surface area of circa 475,442 square kilometers, and is bordered by several other African countries: Nigeria, Chad, the Central African Republic, the Republic of Congo, Equatorial Guinea, and Gabon. With a population of nearly 20 million inhabitants, Cameroon is a very diverse country, geographically, culturally, and linguistically.
Assisting Countries in Establishing National Bioethics Committees: UNESCO’s Assisting Bioethics Committees Project
Authors: TEN HAVE HENK , DIKENOU CHRISTOPHE , FEINHOLZ DAFNA
Published: May 2011

The Universal Declaration on Bioethics and Human Rights adopted by UNESCO in 2005 advocates for the establishment of independent, multidisciplinary, and pluralist ethics committees at national, regional, local, or institutional levels. The purpose of these committees is (a) to evaluate the relevant ethical, legal, scientific, and social issues related to research involving human beings; (b) to provide advice on ethical problems in clinical settings; (c) to assess scientific and technological development, formulate recommendations, and contribute to the preparation of guidelines; and (d) to foster debate, education, and public awareness of and engagement in bioethics (Article 19). Already in the very first draft of the Declaration the need to promote and establish national bioethics committees was mentioned. Although the text was gradually elaborated, the same basic idea has been preserved throughout the process of drafting, negotiating, and adopting the text.
Four Themes in Recent Swedish Bioethics Debates
Authors: HELGESSON GERT , ERIKSSON STEFAN
Published: May 2011

A wide variety of bioethical themes have recently been debated and researched in Sweden, including genetic screening, HPV vaccination strategies, end-of-life care, injustices and priority setting in healthcare, dual-use research, and the never-ending story of scientific fraud. Also, there are some new events related to Swedish biobanking that might be of general interest. Here we will concentrate on four themes: end-of-life care, dual-use research, scientific fraud, and biobanking.
Does a Fish Need a Bicycle? Animals and Evolution in the Age of Biotechnology
Authors: CHAN SARAH , HARRIS JOHN
Published: May 2011

Animals, in the age of biotechnology, are the subjects of a myriad of scientific procedures, interventions, and modifications. They are created, altered, and experimented upon—often with highly beneficial outcomes for humans in terms of knowledge gained and applied, yet not without concern also for the effects upon the experimental subjects themselves: consideration of the use of animals in research remains an intensely debated topic. Concerns for animal welfare in scientific research have, however, been primarily directed at harm to and suffering of animal subjects and their prevention. Little attention has been paid to the benefits research might potentially produce for animals themselves and the interests that some animals may therefore have in the furtherance of particular avenues of science.
Bioethics in the Age of New Media, by Joanna Zylinska. Cambridge, MA: The MIT Press; 2009. 240 pages. $32.00.
Authors: Landa Amy Snow
Published: May 2011

Readers are invited to contact Greg S. Loeben in writing at Midwestern University, Glendale Campus, Bioethics Program, 19555 N. 59th Ave., Glendale, AZ 85308 (gloebe@midwestern.edu) regarding books they would like to see reviewed or books they are interested in reviewing.
Lifetime ruin minimization: should retirees hedge inflation or just worry about it?
Authors: HUANG HUAXIONG , MILEVSKY MOSHE A.
Published: May 2011

Inflation for retirees is different from and mostly higher than the macro-economic (average) inflation rate for the entire population. In the U.S.A, for example, the Consumer Price Index for the Urban population (CPI-U) calculated and reported by the Bureau of Labor Statistics (BLS) has a lesser known cousin called the CPI-E (for the elderly) in which the sub-component weights are based on the consumption patterns of Americans above the age of 62. This suggests that Inflation-Linked Bond Funds (ILBFs) – whose individual component bond adjustments are based on broad population (CPI-U) inflation – might not be the best hedge for individual retirees’ cost of living. But then again, broad shocks to inflation are likely to impact both indices. So, motivated by the question – is it good enough? – the current paper uses lifetime ruin minimization (LRM) techniques to investigate the optimal allocation between an ILBF and a nominal investment fund for a retiree facing an exogenous liability. Our model trades off the benefit of an imperfect hedge against the cost of lower investment growth. However, our numerical results suggest that although ILBFs can be a large part of the optimal retirement portfolio, it should be treated as just another asset class in the broad optimization problem as opposed to a special or unique category.
Bayesian calibration of a flood inundation model using spatial data
Authors: Hall Jim W. , Manning Lucy J. , Hankin Robin K. S.
Published: May 2011

Bayesian theory of model calibration provides a coherent framework for distinguishing and encoding multiple sources of uncertainty in probabilistic predictions of flooding. This paper demonstrates the use of a Bayesian approach to computer model calibration, where the calibration data are in the form of spatial observations of flood extent. The Bayesian procedure involves generating posterior distributions of the flood model calibration parameters and observation error, as well as a Gaussian model inadequacy function, which represents the discrepancy between the best model predictions and reality. The approach is first illustrated with a simple didactic example and is then applied to a flood model of a reach of the river Thames in the UK. A predictive spatial distribution of flooding is generated for a flood of given severity.
Vertically averaged approaches for CO2 migration with solubility trapping
Authors: Gasda S. E. , Nordbotten J. M. , Celia M. A.
Published: May 2011

The long‐term storage security of injected carbon dioxide (CO2) is an essential component of geological carbon sequestration operations. In the postinjection phase, the mobile CO2 plume migrates in large part because of buoyancy forces, following the natural topography of the geological formation. The primary trapping mechanisms are capillary and solubility trapping, which evolve over hundreds to thousands of years and can immobilize a significant portion of the mobile CO2 plume. However, both the migration and trapping processes are inherently complex, spanning multiple spatial and temporal scales. Using an appropriate model that can capture both large‐ and small‐scale effects is essential for understanding the role of these processes on the long‐term storage security of CO2 sequestration operations. Traditional numerical models quickly become prohibitively expensive for the type of large‐scale, long‐term modeling that is necessary for characterizing the migration and immobilization of CO2 during the postinjection period. We present an alternative modeling option that combines vertically integrated governing equations with an upscaled representation of the dissolution‐convection process. With this approach, we demonstrate the effect of different modeling choices for typical large‐scale geological systems and show that practical calculations can be performed at the temporal and spatial scales of interest.
Integrated modelling of cost‐effective siting and operation of flow‐control infrastructure for river ecosystem conservation
Authors: Higgins A. J. , Bryan B. A. , Overton I. C. , Holland K. , Lester R. E. , King D. , Nolan M. , Connor J. D.
Published: May 2011

Wetland and floodplain ecosystems along many regulated rivers are highly stressed, primarily due to a lack of environmental flows of appropriate magnitude, frequency, duration, and timing to support ecological functions. In the absence of increased environmental flows, the ecological health of river ecosystems can be enhanced by the operation of existing and new flow‐control infrastructure (weirs and regulators) to return more natural environmental flow regimes to specific areas. However, determining the optimal investment and operation strategies over time is a complex task due to several factors including the multiple environmental values attached to wetlands, spatial and temporal heterogeneity and dependencies, nonlinearity, and time‐dependent decisions. This makes for a very large number of decision variables over a long planning horizon. The focus of this paper is the development of a nonlinear integer programming model that accommodates these complexities. The mathematical objective aims to return the natural flow regime of key components of river ecosystems in terms of flood timing, flood duration, and interflood period. We applied a 2‐stage recursive heuristic using tabu search to solve the model and tested it on the entire South Australian River Murray floodplain. We conclude that modern meta‐heuristics can be used to solve the very complex nonlinear problems with spatial and temporal dependencies typical of environmental flow allocation in regulated river ecosystems. The model has been used to inform the investment in, and operation of, flow‐control infrastructure in the South Australian River Murray.
Parameter Estimation for Hidden Markov models with Intractable Likelihoods
Authors: Jasra Ajay , Dean Thomas , Simgh Sumeetpal , Peters Gareth
Published: May 2011

In this talk I consider sequential Monte Carlo (SMC) methods for hidden Markov models. In the scenario for which the conditional density of the observations given the latent state is intractable we give a simple ABC approximation of the model along with some basic SMC algorithms for sampling from the associated filtering distribution. Then, we consider the problem of smoothing, given access to a batch data set. We present a simulation technique which combines forward only smoothing (Del Moral et al, 2011) and particle Markov chain Monte Carlo (Andrieu et al 2010), for an algorithm which scales linearly in the number of particles.
Cellular and molecular effects of sirtuins in health and disease
Authors: Horio Yoshiyuki , Hayashi Takashi , Kuno Atsushi , Kunimoto Risa
Published: May 2011

Sirtuins are NAD+-dependent protein deacetylases that are broadly conserved from bacteria to humans. Because sirtuins extend the lifespan of yeast, worms and flies, much attention has been paid to their mammalian homologues. Recent studies have revealed diverse physiological functions of sirtuins that are essentially similar to those of their yeast homologue, Sir2 (silent information regulator 2). Sirtuins are implicated in the pathology of many diseases, for which sirtuin activators such as resveratrol have great promise as potential treatments. In the present review, we describe the functions of sirtuins in cell survival, inflammation, energy metabolism, cancer and differentiation, and their impact on diseases. We also discuss the organ-specific functions of sirtuins, focusing on the brain and blood vessels.
The depolarized Raman 2ν3 overtone of CO2: A line-mixing shape analysis
Authors: Verzhbitskiy I. A. , Kouzov A. P. , Rachet F. , Chrysos M.
Published: May 2011

In a recent article we showed that the 2ν3 transition of CO2 gives rise to a Raman spectrum that is almost entirely depolarized [M. Chrysos, I. A. Verzhbitskiy, F. Rachet, and A. P. Kouzov, J. Chem. Phys. 134, 044318 (2011)]. In the present article, we go further forward in the study of this overtone by reporting a first-principles shape analysis of its depolarized spectrum at room temperature. As a first step in our analysis, a model assuming isolated Lorentzian line shapes was applied, which at low gas densities turns out to be sufficient for qualitative conclusions. As the next step, a sophisticated approach was developed on the basis of the extended strong-collision model in order to properly account for the heavy line mixing between rotational lines. Whereas a marked deviation between model and measured spectra was observed upon application of the simpler model, striking agreement even at the highest CO2 density was found on applying the sophisticated one. Accurate calculated data were used for the rotational line broadening coefficients without resort to arbitrary parameters. Values for the vibrational shift scaling linearly with the density of the gas are given.
Window corrections of z-cut quartz at 1550 nm under elastic, uniaxial compression up to 10 GPa
Authors: Li Xuemei , Yu Yuying , Li Yinghua , Zhang Lin , Weng Jidong
Published: May 2011

Z-cut α-quartz single crystals were shocked up to 10 GPa by symmetric impact to carefully examine their performance as an optical window in new velocity interferometers operating at 1550 nm, such as displacement interferometer system for any reflector (DISAR) [Appl. Phys. Lett. 89, 111101 (2006)]. In situ particle velocity measurements allowed the shock Hugoniot data and velocity corrections to be obtained accurately by a simple probe. The results give the elastic Hugoniot state equation as Ds = 6.270 + 1.651up, and the dependence of velocity correction (Δus) on the true particle velocity (up) at 1550 nm is well described by exponential relation Δus = 0.0948 up1.1876. By combining the velocity correction and shock velocity measurements, the relation of the refractive index (n) versus relative density (ρ/ρ0) for z-cut quartz is also determined to be n = 1.0890 + 0.4393 ρ/ρ0. The wave profile measurements also indicate that the pressure limit where z-cut quartz’s response is simple is 10.04 GPa, and it can be used as an optical window within this limit in shock experiments.
Absolute measurements of x-ray backlighter sources at energies above 10 keV
Authors: Maddox B. R. , Park H. S. , Remington B. A. , Chen C. , Chen S. , Prisbrey S. T. , Comley A. , Back C. A. , Szabo C. , Seely J. F. , Feldman U. , Hudson L. T. , Seltzer S. , Haugh M. J. , Ali Z.
Published: May 2011

Line emission and broadband x-ray sources with x-ray energies above 10 keV have been investigated using a range of calibrated x-ray detectors for use as x-ray backlighters in high energy density (HED) experiments. The conversion efficiency of short- and long-pulse driven Mo and Ag line-emission backlighters at 17 and 22 keV was measured to investigate the crossover region between short- and long-pulse conversion efficiency. It was found that significant 17 and 22 keV line emissions were observed using a 3 ω, 1 ns long-pulse drive for Mo and Ag targets and a comparison between the measured Mo x-ray spectrum and calculations using an atomic physics code suggests that the line emission is due to thermal emission from N-like Mo atoms. Electron temperatures derived from fits to the continuum region of the x-ray spectra agree well with the Thot scaling as 100×(Iλ2)1/3. The continuum emissions from empty and 1 atm Kr-filled imploded CH shell targets were also measured for the use as broadband backlighters.
X-ray attenuation measurements in a cavitating mixing layer for instantaneous two-dimensional void ratio determination
Authors: Aeschlimann Vincent , Barre Stéphane , Legoupil Samuel
Published: May 2011

The purpose of this experimental study was to analyze a two-dimensional cavitating shear layer. The global aim of this work was to obtain a better understanding and modeling of cavitation phenomenon in a 2D turbulent sheared flow which can be considered as quite representative of cavitating rocket engine turbopomp inducers. This 2D mixing layer flow provided us a well documented test case which can be used for the characterization of the cavitation effects in sheared flows. The development of a velocity gradient was observed inside a liquid water flow: Kelvin-Helmholtz instabilities developed at the interface. Vaporizations and implosions of cavitating structures inside the vortices were observed. X-ray attenuation measurements were performed to estimate the amount of vapor present inside the mixing area. Instantaneous two-dimensional void ratio fields were acquired. The real spatial resolutions are 0.5 mm with 2000 fps and 1.5 mm with 20 000 fps. The effective time resolution is equal to the camera frame rate up to a 19% void ratio variation between two consecutive images. This seems to be sufficient in the context of the present flow configuration. The two-phase structures present inside the mixing area were analyzed at three different cavitation levels and their behaviors were compared to non-cavitating flow dynamic. Convection velocities and vortices shedding frequencies were estimated. Results show that vapor was transported by the turbulent velocity field. Statistical analysis of the void ratio signal was carried out up to the fourth order moment. This study provided a global understanding of the cavitating structure evolution and of the cavitation effects on turbulent sheared flows.
Exchange-correlation generalized gradient approximation for gold nanostructures
Authors: Fabiano E. , Constantin Lucian A. , Sala F. Della
Published: May 2011

We compare the performance of different exchange-correlation functionals, based on the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation, for the structural and electronic properties of gold nanostructures. In particular we consider PBEsol (constructed to correctly describe solid-state systems) and PBEint [Phys. Rev. B 82, 113104 (2010)10.1103/PhysRevB.82.113104] which was recently introduced for hybrid interfaces and preserves the correct second-order gradient expansion of exchange energy (as in PBEsol) providing as well a significant nonlocality for higher density variation (as in PBE). We find that the PBEint functional gives a well balanced description of atomization energies, structural properties, energy differences between isomers, and bulk properties. Results indicate that PBEint is expected to be the most accurate functional for medium and large size gold clusters of different shapes.
Note: Non-gain microchannel plate gated framing camera
Authors: Cai Houzhi , Liu Jinyuan , Peng Xiang , Niu Lihong , Peng Wenda , Niu Hanben , Long Jinghua
Published: May 2011

An x-ray framing camera using a non-gain microchannel plate (MCP) is reported in this article. The advantage of the non-gain MCP is the less transit time spread. The non-gain MCP gated framing camera has four microstrip line cathodes with 6 mm in width. The time domain reflectometry curves of the four microstrip lines are measured, which show that the characteristic impedance of each microstrip line is about 17 Ω. While the photocathode is driven by the gating electrical pulse with width of 125 ps and amplitude of −1.48 kV with −400 V bias, the measured exposure time of this camera is about 72 ps.
Transport and dynamic properties of O2+(X2Πg) in Kr under the action of an electrostatic field: Single or multiple potential energy surface treatment
Authors: Koutselos Andreas D.
Published: May 2011

Ion transport and dynamic properties are calculated through molecular dynamics simulation of the motion of O2+ in Kr under the action of an electrostatic field. The two lower potential energy surfaces X̃2A″ and Ã2A′ are considered for the interaction of the Π ground state of the ion with a closed shell noble gas. First, we study the reproduction of experimental mobility data through the use of single and multiple potential energy surfaces and establish the contribution of both lower energy states to the interactions. Further, we obtain mean energies and components of the diffusion coefficient parallel and perpendicular to the field, the latter through calculation of the velocity correlation functions. We also calculate components of the angular momentum which provide a measure of the collisional rotational alignment of the ions at high field strength.
Analog of Rabi oscillations in resonant electron-ion systems
Authors: Stella Lorenzo , Miranda Rafael P. , Horsfield Andrew P. , Fisher Andrew J.
Published: May 2011

Quantum coherence between electron and ion dynamics, observed in organic semiconductors by means of ultrafast spectroscopy, is the object of recent theoretical and computational studies. To simulate this kind of quantum coherent dynamics, we have introduced in a previous article [L. Stella, M. Meister, A. J. Fisher, and A. P. Horsfield, J. Chem. Phys. 127, 214104 (2007)]10.1063/1.2801537 an improved computational scheme based on Correlated Electron-Ion Dynamics (CEID). In this article, we provide a generalization of that scheme to model several ionic degrees of freedom and many-body electronic states. To illustrate the capability of this extended CEID, we study a model system which displays the electron-ion analog of the Rabi oscillations. Finally, we discuss convergence and scaling properties of the extended CEID along with its applicability to more realistic problems.
Calculation of inelastic helium atom scattering from H2/NaCl(001)
Authors: Bruch L. W. , Hansen F. Y. , Traeger F.
Published: May 2011

The one-phonon inelastic low energy helium atom scattering theory is adapted to cases where the target monolayer is a p(1 × 1) commensurate square lattice. Experimental data for para-H2/NaCl(001) are re-analyzed and the relative intensities of energy loss peaks in the range 6 to 9 meV are determined. The case of the H2/NaCl(001) monolayer for 26 meV scattering energy is computationally challenging and difficult because it has a much more corrugated surface than those in the previous applications for triangular lattices. This requires a large number of coupled channels for convergence in the wave-packet-scattering calculation and a long series of Fourier amplitudes to represent the helium-target potential energy surface. A modified series is constructed in which a truncated Fourier expansion of the potential is constrained to give the exact value of the potential at some key points and which mimics the potential with fewer Fourier amplitudes. The shear horizontal phonon mode is again accessed by the helium scattering for small misalignment of the scattering plane relative to symmetry axes of the monolayer. For 1° misalignment, the calculated intensity of the longitudinal acoustic phonon mode frequently is higher than that of the shear horizontal phonon mode in contrast to what was found at scattering energies near 10 meV for triangular lattices of Ar, Kr, and Xe on Pt(111).
Errors in particle tracking velocimetry with high-speed cameras
Authors: Feng Yan , Goree J. , Liu Bin
Published: May 2011

Velocity errors in particle tracking velocimetry (PTV) are studied. When using high-speed video cameras, the velocity error may increase at a high camera frame rate. This increase in velocity error is due to particle-position uncertainty, which is one of the two sources of velocity errors studied here. The other source of error is particle acceleration, which has the opposite trend of diminishing at higher frame rates. Both kinds of errors can propagate into quantities calculated from velocity, such as the kinetic temperature of particles or correlation functions. As demonstrated in a dusty plasma experiment, the kinetic temperature of particles has no unique value when measured using PTV, but depends on the sampling time interval or frame rate. It is also shown that an artifact appears in an autocorrelation function computed from particle positions and velocities, and it becomes more severe when a small sampling-time interval is used. Schemes to reduce these errors are demonstrated.
The dissociation of vibrationally excited CH3OSO radicals and their photolytic precursor, methoxysulfinyl chloride
Authors: Alligood Bridget W. , Womack Caroline C. , Straus Daniel B. , Blase Frances R. , Butler Laurie J.
Published: May 2011

The dissociation dynamics of methoxysulfinyl radicals generated from the photodissociation of CH3OS(O)Cl at 248 nm is investigated using both a crossed laser – molecular beam scattering apparatus and a velocity map imaging apparatus. There is evidence of only a single photodissociation channel of the precursor: S-Cl fission to produce Cl atoms and CH3OSO radicals. Some of the vibrationally excited CH3OSO radicals undergo subsequent dissociation to CH3 + SO2. The velocities of the detected CH3 and SO2 products show that the dissociation occurs via a transition state having a substantial barrier beyond the endoergicity; appropriately, the distribution of velocities imparted to these momentum-matched products is fit by a broad recoil kinetic energy distribution extending out to 24 kcal/mol in translational energy. Using 200 eV electron bombardment detection, we also detect the CH3OSO radicals that have too little internal energy to dissociate. These radicals are observed both at the parent CH3OSO+ ion as well as at the CH3+ and SO2+ daughter ions; they are distinguished by virtue of the velocity imparted in the original photolytic step. The detected velocities of the stable radicals are roughly consistent with the calculated barriers (both at the CCSD(T) and G3B3 levels of theory) for the dissociation of CH3OSO to CH3 + SO2 when we account for the partitioning of internal energy between rotation and vibration as the CH3OSOCl precursor dissociates.
Two more approaches for generating trajectory-based dynamics which conserves the canonical distribution in the phase space formulation of quantum mechanics
Authors: Liu Jian
Published: May 2011

We show two more approaches for generating trajectory-based dynamics in the phase space formulation of quantum mechanics: “equilibrium continuity dynamics” (ECD) in the spirit of the phase space continuity equation in classical mechanics, and “equilibrium Hamiltonian dynamics” (EHD) in the spirit of the Hamilton equations of motion in classical mechanics. Both ECD and EHD can recover exact thermal correlation functions (of even nonlinear operators, i.e., nonlinear functions of position or momentum operators) in the classical, high temperature, and harmonic limits. Both ECD and EHD conserve the quasi-probability within the infinitesimal volume dxtdpt around the phase point (xt, pt) along the trajectory. Numerical tests of both approaches in the Wigner phase space have been made for two strongly anharmonic model problems and a double well system, for each potential auto-correlation functions of both linear and nonlinear operators have been calculated. The results suggest EHD and ECD are two additional potential useful approaches for describing quantum effects for complex systems in condense phase.
Quantum well thickness dependence of Rashba spin–orbit coupling in the InAs/InGaAs heterostructure
Authors: Lee Tae Young , Chang Joonyeon , Hickey Mark C. , Koo Hyun Cheol , Kim Hyung-jun , Han Suk Hee , Moodera Jagadeesh S.
Published: May 2011

We have investigated the quantum well thickness dependence of spin–orbit coupling in InAs/InGaAs heterostructures. The beat patterns of the oscillatory magnetoresistance were measured to determine the magnitude of the parameter of an inverted type InAs quantum well structures with the thicknesses ranging from 2 to 7 nm. The band energies, electronic charge distribution, and Rashba spin–orbit coupling parameter of the structure were calculated using a self-consistent field method and a k⋅P perturbation scheme. The magnitude of the parameter increases with decreasing the InAs quantum well thickness. Comparison with the calculated data revealed that the increase in the spin–orbit interaction parameter is due to the stronger penetration of the wave function envelope into the barriers where more pronounced band bending and barrier asymmetry occur in both the conduction and valence bands.
System-level simulation of liquid filling in microfluidic chips
Authors: Song Hongjun , Wang Yi , Pant Kapil
Published: May 2011

Liquid filling in microfluidic channels is a complex process that depends on a variety of geometric, operating, and material parameters such as microchannel geometry, flow velocity/pressure, liquid surface tension, and contact angle of channel surface. Accurate analysis of the filling process can provide key insights into the filling time, air bubble trapping, and dead zone formation, and help evaluate trade-offs among the various design parameters and lead to optimal chip design. However, efficient modeling of liquid filling in complex microfluidic networks continues to be a significant challenge. High-fidelity computational methods, such as the volume of fluid method, are prohibitively expensive from a computational standpoint. Analytical models, on the other hand, are primarily applicable to idealized geometries and, hence, are unable to accurately capture chip level behavior of complex microfluidic systems. This paper presents a parametrized dynamic model for the system-level analysis of liquid filling in three-dimensional (3D) microfluidic networks. In our approach, a complex microfluidic network is deconstructed into a set of commonly used components, such as reservoirs, microchannels, and junctions. The components are then assembled according to their spatial layout and operating rationale to achieve a rapid system-level model. A dynamic model based on the transient momentum equation is developed to track the liquid front in the microchannels. The principle of mass conservation at the junction is used to link the fluidic parameters in the microchannels emanating from the junction. Assembly of these component models yields a set of differential and algebraic equations, which upon integration provides temporal information of the liquid filling process, particularly liquid front propagation (i.e., the arrival time). The models are used to simulate the transient liquid filling process in a variety of microfluidic constructs and in a multiplexer, representing a complex microfluidic network. The accuracy (relative error less than 7%) and orders-of-magnitude speedup (30 000X–4 000 000X) of our system-level models are verified by comparison against 3D high-fidelity numerical studies. Our findings clearly establish the utility of our models and simulation methodology for fast, reliable analysis of liquid filling to guide the design optimization of complex microfluidic networks.
Cleaved-facet violet laser diodes with lattice-matched Al0.82In0.18N/GaN multilayers as n-cladding
Authors: Charash R. , Kim-Chauveau H. , Lamy J-M. , Akther M. , Maaskant P. P. , Frayssinet E. , de Mierry P. , Dräger A. D. , Duboz J-Y. , Hangleiter A. , Corbett B.
Published: May 2011

Electrically injected, edge-emitting cleaved-facet violet laser diodes were realized using a 480 nm thick lattice matched Si doped Al0.82In0.18N/GaN multilayer as the cladding on the n-side of the waveguide. Far-field measurements verify strong mode confinement to the waveguide. An extra voltage is measured and investigated using separate mesa structures with a single AlInN insertion. This showed that the electron current has a small thermally activated shunt resistance with a barrier of 0.135 eV and a current which scales according to Vn, where n∼3 at current densities appropriate to laser operation.
Simulation of the two-dimensional electronic spectra of the Fenna-Matthews-Olson complex using the hierarchical equations of motion method
Authors: Chen Liping , Zheng Renhui , Jing Yuanyuan , Shi Qiang
Published: May 2011

We apply the Liouville space hierarchical equations of motion method to calculate the linear and two-dimensional (2D) electronic spectra of the Fenna-Matthews-Olson (FMO) protein complex from Chlorobium tepidum, using a widely used model Hamiltonian. The absorption and linear dichroism spectra of the FMO complex, as well as the main features of the 2D spectra are well reproduced. However, comparison with the recent experimental 2D spectra reveals several limitations of the current model: (1) The homogeneous and inhomogeneous broadening seems to be overestimated for the first exciton peak, but may be underestimated for several other exciton peaks. (2) The calculated oscillations of the diagonal and off-diagonal peaks in the 2D spectra are much weaker than the experimental observations, which indicates that an improved model is needed for the excitonic dynamics of the FMO complex.
Low axial drift stage and temperature controlled liquid cell for z-scan fluorescence correlation spectroscopy in an inverted confocal geometry
Authors: Allgeyer Edward S. , Sterling Sarah M. , Neivandt David J. , Mason Michael D.
Published: May 2011

A recent iteration of fluorescence correlation spectroscopy (FCS), z-scan FCS, has drawn attention for its elegant solution to the problem of quantitative sample positioning when investigating two-dimensional systems while simultaneously providing an excellent method for extracting calibration-free diffusion coefficients. Unfortunately, the measurement of planar systems using (FCS and) z-scan FCS still requires extremely mechanically stable sample positioning, relative to a microscope objective. As axial sample position serves as the inherent length calibration, instabilities in sample position will affect measured diffusion coefficients. Here, we detail the design and function of a highly stable and mechanically simple inverted microscope stage that includes a temperature controlled liquid cell. The stage and sample cell are ideally suited to planar membrane investigations, but generally amenable to any quantitative microscopy that requires low drift and excellent axial and lateral stability. In the present work we evaluate the performance of our custom stage system and compare it with the stock microscope stage and typical sample sealing and holding methods.
Rovibrational eigenenergy structure of the [H,C,N] molecular system
Authors: Mellau Georg Ch.
Published: May 2011

The vibrational-rotational eigenenergy structure of the [H,N,C] molecular system is one of the key features needed for a quantum mechanical understanding of the HCN\documentclass[12pt]{minimal}\begin{document}$\rightleftharpoons$\end{document}⇌HNC model reaction. The rotationless vibrational structure corresponding to the multidimensional double well potential energy surface is well established. The rotational structure of the bending vibrational states up to the isomerisation barrier is still unknown. In this work the structure of the rotational states for low and high vibrational angular momentum is described from the ground state up to the isomerisation barrier using hot gas molecular high resolution spectroscopy and rotationally assigned ab initio rovibronic states. For low vibrational angular momentum the rotational structure of the bending excitations splits in three regions. For J < 40 the structure corresponds to that of a typical linear molecule, for 40 < J < 60 has an approximate double degenerate structure and for J > 60 the splitting of the e and f components begins to decrease and the rotational constant increases. For states with high angular momentum, the rotational structure evolves into a limiting structure for v2 > 7 – the molecule is locked to the molecular axis. For states with v2 > 11 the rotational structure already begins to accommodate to the lower rotational constants of the isomerisation states. The vibrational energy begins to accommodate to the levels above the barrier only at high vibrational excitations of v2 > 22 just above the barrier whereas this work shows that the rotational structure is much more sensitive to the double well structure of the potential energy surface. The rotational structure already experiences the influence of the barrier at much lower energies than the vibrational one.
The calculation of vapor-liquid coexistence curve of Morse fluid: Application to iron
Authors: Apfelbaum E. M.
Published: May 2011

The vapor-liquid coexistence curve of Morse fluid was calculated within the integral equations approach. The critical point coordinates were estimated. The parameters of Morse potential, fitted for elastic constants in solid phase, were used here to apply the results of present calculations to the determination of iron binodal. The properties of copper and sodium were considered in an analogous way. The calculations of pair correlation functions and isobars at liquid phase have shown that only for sodium these potential parameters allow one to obtain agreement with the measurements data. For iron another parameters are necessary to get this agreement in liquid phase. However, they give rise to very low critical temperature and pressure with respect to the estimates of other authors. Consequently, one can suppose that Morse potential is possibly inapplicable to the calculation of high temperature properties of non-alkali metals in disordered phases.
Discerning passivation mechanisms at a-Si:H/c-Si interfaces by means of photoconductance measurements
Authors: Leendertz C. , Mingirulli N. , Schulze T. F. , Kleider J. P. , Rech B. , Korte L.
Published: May 2011

The photoconductance decay (PCD) measurement is a fast and simple method to characterize amorphous/crystalline (a-Si:H/c-Si) silicon interfaces for high-efficiency solar cells. However, PCD only yields information concerning the overall recombination rate in the structure. To overcome this limitation, we have developed and validated a computer-aided PCD (CA-PCD) analysis method to determine the defect density of recombination-active dangling bonds at the interface and the potential drop in the crystalline absorber adjacent to the interface. As a practical example, we investigate a-Si:H(p)/a-Si:H(i)/c-Si(n) layer stacks and show that the CA-PCD method is capable of discerning the influence of field-effect and defect passivation.
Predicting shape and stability of air–water interface on superhydrophobic surfaces with randomly distributed, dissimilar posts
Authors: Emami B. , Tafreshi H. Vahedi , Gad-el-Hak M. , Tepper G. C.
Published: May 2011

A mathematical framework developed to calculate the shape of the air–water interface and predict the stability of a microfabricated superhydrophobic surface with randomly distributed posts of dissimilar diameters and heights is presented. Using the Young–Laplace equation, a second-order partial differential equation is derived and solved numerically to obtain the shape of the interface, and to predict the critical hydrostatic pressure at which the superhydrophobicity vanishes in a submersed surface. Two examples are given for demonstration of the method’s capabilities and accuracy.
Radially polarized optical vortex converter created by femtosecond laser nanostructuring of glass
Authors: Beresna Martynas , Gecevičius Mindaugas , Kazansky Peter G. , Gertus Titas
Published: May 2011

We demonstrate the generation of optical vortices with radial or azimuthal polarization using a space variant polarization converter, fabricated by femtosecond laser writing of self-assembled nanostructures in silica glass. Manipulation of the induced form birefringence is achieved by controlling writing parameters, in particular, the polarization azimuth of the writing beam. The fabricated converter allows switching from radial to azimuthal polarization by controlling the handedness of incident circular polarization.
High gain 1.55 μm diode lasers based on InAs quantum dot like active regions
Authors: Gilfert C. , Ivanov V. , Oehl N. , Yacob M. , Reithmaier J. P.
Published: May 2011

InP diode lasers with InAs quantum dot (QD) like active regions emitting at 1.55 μm have been fabricated. The QDs were grown in an As2 mode, which reduces the degree of elongation of the nanospecies yielding nearly circular shapes. Lasers with four to six dot layers show low absorption αi<10 cm−1 and high modal gain Γg0 of 10 cm−1 per QD layer (QDL) and above. The high gain values are compatible with an inhomogeneous linewidth that is much narrower than in quantum dash material, which is the common nanoscale gain material in the InP system.
Sub-Poissonian shot noise in CoFeB/MgO/CoFeB-based magnetic tunneling junctions
Authors: Arakawa Tomonori , Sekiguchi Koji , Nakamura Shuji , Chida Kensaku , Nishihara Yoshitaka , Chiba Daichi , Kobayashi Kensuke , Fukushima Akio , Yuasa Shinji , Ono Teruo
Published: May 2011

We measured the shot noise in the CoFeB/MgO/CoFeB-based magnetic tunneling junctions with a high tunneling magnetoresistance ratio (over 200% at 3 K). Although the Fano factor in the antiparallel configuration is close to unity, it is observed to be typically 0.91±0.01 in the parallel configuration. It indicates the sub-Poissonian process of the electron tunneling in the parallel configuration due to the relevance of the spin-dependent coherent transport in the low bias regime.
Laterally proximized aluminum tunnel junctions
Authors: Koski J. V. , Peltonen J. T. , Meschke M. , Pekola J. P.
Published: May 2011

This letter presents experiments on junctions fabricated by a technique that enables the use of high-quality aluminum oxide tunnel barriers with normal metal electrodes at low temperatures. Inverse proximity effect is applied to diminish the superconductivity of an aluminum dot through a clean lateral connection to a normal metal electrode. To demonstrate the effectiveness of this method, fully normal-state single electron transistors (SETs) and normal metal-insulator-superconductor (NIS) junctions applying proximized Al junctions were fabricated. The transport characteristics of the junctions were similar to those obtained from standard theoretical models of regular SETs and NIS junctions.
Crystalline ZrO2-gated Ge metal-oxide-semiconductor capacitors fabricated on Si substrate with Y2O3 as passivation layer
Authors: Wu Yung-Hsien , Wu Min-Lin , Lyu Rong-Jhe , Wu Jia-Rong , Chen Lun-Lun , Lin Chia-Chun
Published: May 2011

By adopting an amorphous Y2O3 passivation layer, which provides a wide band gap and well passivates Ge surface without the presence of GeOx, a high-permittivity (κ) crystalline ZrO2/Y2O3 stack was explored as the gate dielectric for Ge metal-oxide-semiconductor (MOS) devices on Si substrate. The crystalline ZrO2 is a Ge stabilized tetragonal/cubic dielectric with the κ value of 36.1 and was formed by depositing a ZrO2/Ge/ZrO2 laminate and a subsequent 500 °C annealing. The high-κ crystalline ZrO2/Y2O3 gate stack shows promising electrical characteristics in terms of low interface trap density of 5.8×1011 cm−2 eV−1, negligible hysteresis, and leakage current of 5.6×10−4 A/cm2 at gate bias of flatband voltage (VFB) 1 V for equivalent oxide thickness of 1.13 nm. This gate stack not only demonstrates the eligibility for advanced Ge MOS devices but introduces a more reliable process to form a high-κ crystalline gate dielectric.
Self-organization of core-shell and core-shell-corona structures in small liquid droplets
Authors: Shi R. P. , Wang Y. , Wang C. P. , Liu X. J.
Published: May 2011

It was recently discovered that core-shell and core-shell-corona microstructures in immiscible liquid alloys, which were previously obtained only in outer space, can be fabricated under gravity condition on earth using conventional gas atomization. The origin was attributed solely to Marangoni motion driven by temperature-dependence of interfacial energy. We found in this letter, with the aid of computer simulation, that coupled processes of spinodal decomposition, decomposition-induced fluid flow, collision and collision-induced-collision among second-phase droplets all play critical rules at different stages in the formation of these structures. Their contributions relative to the Marangoni effect are analyzed as function of system size.
Measurement of dwell times of spin polarized rubidium atoms on octadecyltrichlorosilane- and paraffin-coated surfaces
Authors: Ulanski Emily , Wu Zhen
Published: May 2011

We report the measurement of dwell times of spin polarized Rb atoms on octadecyltrichlorosilane (OTS)- and paraffin-coated surfaces. We find that at a cell temperature of 72 °C the dwell times for OTS- and paraffin-coated surfaces are 0.9±0.1 μs and 1.8±0.2 μs, respectively. Since the relaxation probability on paraffin is almost one order of magnitude smaller than that on OTS, the longer dwell time for paraffin indicates that the average strength of the interactions experienced by Rb atoms while they are inside paraffin is much weaker than while they are inside OTS.
Diffusion-limited nonradiative recombination at extended defects in hydride vapor phase epitaxy GaN layers
Authors: Ščajev Patrik , Usikov Alexander , Soukhoveev Vitali , Aleksiejūnas Ramūnas , Jarašiūnas Kęstutis
Published: May 2011

Time-resolved free-carrier absorption and transient grating techniques were applied to determine carrier lifetimes and diffusion coefficients in a set of hydride vapor phase epitaxy GaN layers of various thickness (from 10 to 145 μm). A linear increase in nonradiative carrier lifetime in 80–800 K range found to be in a correlation with decrease of the bipolar carrier diffusion coefficient. This correlation confirmed that recombination rate is governed by carrier diffusive flow to the grain boundaries of columnar defects. A model of diffusion-governed nonradiative lifetime was proposed for fitting the measured lifetime values in the layers of different thickness as well as lifetime dependence on temperature or threading dislocation density.
Communication: Probing the entrance channels of the X + CH4 → HX + CH3 (X = F, Cl, Br, I) reactions via photodetachment of X−–CH4
Authors: Cheng Min , Feng Yuan , Du Yikui , Zhu Qihe , Zheng Weijun , Czakó Gábor , Bowman Joel M.
Published: May 2011

The entrance channel potentials of the prototypical polyatomic reaction family X + CH4 → HX + CH3 (X = F, Cl, Br, I) are investigated using anion photoelectron spectroscopy and high-level ab initio electronic structure computations. The pre-reactive van der Waals (vdW) wells of these reactions are probed for X = Cl, Br, I by photodetachment spectra of the corresponding X−–CH4 anion complex. For F–CH4, a spin-orbit splitting (∼1310 cm−1) much larger than that of the F atom (404 cm−1) was observed, in good agreement with theory. This showed that in the case of the F–CH4 system the vertical transition from the anion ground state to the neutral potentials accesses a region between the vdW valley and transition state of the early-barrier F + CH4 reaction. The doublet splittings observed in the other halogen complexes are close to the isolated atomic spin-orbit splittings, also in agreement with theory.
Electronic excitations of potassium intercalated manganese phthalocyanine investigated by electron energy-loss spectroscopy
Authors: Mahns Benjamin , Roth Friedrich , Grobosch Mandy , Zahn Dietrich R. T. , Knupfer Martin
Published: May 2011

The electronic excitations of manganese phthalocyanine (MnPc) films were studied as a function of potassium doping using electron energy-loss spectroscopy in transmission. Our data reveal doping induced changes in the excitation spectrum, and they provide evidence for the existence of three doped phases: K1MnPc, K2MnPc, and K4MnPc. Furthermore, the addition of electrons first leads to a filling of orbitals with strong Mn 3d character, a situation which also affects the magnetic moment of the molecule.