bluuebunny/crossref_metadata_2025 huggingface dataset:
A VARIED PATTERN OF CHANGE OF THE SEX DIFFERENTIAL IN SURVIVAL IN THE G7 COUNTRIES
Authors: TROVATO FRANK , HEYEN NILS B.
Published: April 2006

Over the course of the 20th century the sex differential in life expectancy at birth in the industrialized countries has widened considerably in favour of women. Starting in the early 1970s, the beginning of a reversal in the long-term pattern of this differential has been noted in some high-income countries. This study documents a sustained pattern of narrowing of this measure into the later part of the 1990s for six of the populations that comprise the G7 countries: Canada, France, Germany, Italy, England and Wales (as representative of the United Kingdom) and USA. For Japan, a persistence of widening sex differences in survival is noted. The sex differences in life expectancy are decomposed over roughly three decades (early 1970s to late 1990s) from the point of view of four major cause-of-death categories: circulatory diseases, cancers, accidents/violence/suicide, and ‘other’ (residual) causes. In the six countries where the sex gap has narrowed, this has resulted primarily from reduced sex differences in circulatory disease mortality, and secondarily from reduced differences in male and female death rates due to accidents, violence and suicide combined. In some of the countries sex differentials in cancer mortality have been converging lately, and this has also contributed to a narrowing of the difference in life expectancy. In Japan, males have been less successful in reducing their survival disadvantage in relation to Japanese women with regard to circulatory disease and cancer; and in the case of accidents/violence/suicide, male death rates increased during the 1990s. These trends explain the divergent pattern of the sex difference in life expectation in Japan as compared with the other G7 nations.
A note on the motion of a spherical particle in a general quadratic flow of a second-order fluid
Authors: Chan P. C.-H. , Leal L. G.
Published: April 2006

The migration of a rigid sphere in a two-dimensional unidirectional shear flow of a second-order fluid was considered by Ho & Leal (1976). It was found that the sphere would migrate in the direction of decreasing absolute shear rate. The present paper extends the previous results to a general quadratic flow, and also considers the case of a spherical drop.
Steady and transient thermal convection in a fluid layer with uniform volumetric energy sources
Authors: Kulacki F. A. , Emara A. A.
Published: April 2006

Measurements of the overall heat flux in steady convection have been made in a horizontal layer of dilute aqueous electrolyte. The layer is bounded below by a rigid zero-heat-flux surface and above by a rigid isothermal surface. Joule heating by an alternating current passing horizontally through the layer provides a uniformly distributed volumetric energy source. The Nusselt number at the upper surface is found to be proportional to Ra0[sdot ]227 in the range 1[sdot ]4 ≤ Ra/Rac ≤ 1[sdot ]6 × 109, which covers the laminar, transitional and turbulent flow regimes. Eight discrete transitions in the heat flux are found in this Rayleigh number range. Extrapolation of the heat-transfer correlation to the conduction value of the Nusselt number yields a critical Rayleigh number which is within -6[sdot ]7% of the value given by linearized stability theory. Measurements have been made of the time scales of developing convection after a sudden start of volumetric heating and of decaying convection when volumetric heating is suddenly stopped. In both cases, the steady-state temperature difference across the layer appears to be the controlling physical parameter, with both processes exhibiting the same time scale for a given steady-state temperature difference, or [mid ]ΔRa[mid ]. For step changes in Ra such that [mid ]ΔRa[mid ] > 100Rac, the time scales for both processes can be represented by Fo [vprop ] [mid ]ΔRa[mid ]m, where Fo is the Fourier number of the layer. Temperature profiles of developing convection exhibit a temperature excess in the upper 15–20 % of the layer in the early stages of flow development for Rayleigh numbers corresponding to turbulent convection. This excess disappears when the average core temperature becomes large enough to permit eddy transport and mixing processes near the upper surface. The steady-state limits in the transient experiments yield heat-transfer data in agreement with the results of the steady-state experiments.
Chemical amplification at the wave head of a finite amplitude gasdynamic disturbance
Authors: Clarke J. F.
Published: April 2006

Consider a background state which consists of a spatially uniform chemically reactive mixture in a general state of disequilibrium. The analytical method of characteristics is used to show that a plane finite amplitude disturbance propagates through this system at the frozen sound speed and, if the degree of disequilibrium is sufficient, is amplified by the chemical reaction. Some comments are made about the time to shock-wave formation and its relation to the homogeneous explosion ignition time, and also about expansion waves, which are found to have a tendency towards fixed-strength ‘quenching waves’, their strength being proportional to the extent of the ambient disequilibrium.
Lagrangian velocity covariance in helical turbulence
Authors: Kraichnan Robert H.
Published: April 2006

The effect of helicity on the Lagrangian velocity covarianceUL(t) in isotropic, normally distributed turbulence is examined by computer simulation and by a renormalized perturbation expansion forUL(t). The first term of the latter represents Corrsin's (1959) conjecture (extrapolated to allt), which relatesUL(t) to the Eulerian covariance and the distributionG(x, t) of fluid-element displacement. Truncation of the expansion at the first term yields the direct-interaction approximation forG(x, t). The expansion suggests that with or without helicity Corrsin's conjecture is valid ast→ ∞ and that in either caseUL(t) behaves asymptotically like$t^{-(r+\frac{3}{2})}$if the spectrum of the Eulerian field varies likekr+2at small wavenumbers. Corrsin's conjecture breaks down at small and moderatetif there is strong helicity while remaining accurate at alltin the mirror-symmetric case. Computer simulations for a frozen Eulerian field with spectrum confined to a thin spherical shell inkspace indicate that strong helicity induces an increase in the Lagrangian correlation time by a factor of approximately three. Direct-interaction equations are constructed for the Lagrangian space-time covariance and the resulting prediction forUL(t) is compared with the simulations. The effect of helicity is well represented quantitatively by the direct-interaction equations for small and moderatetbut not for larget. These frozen-field results imply good quantitative accuracy at alltin time-varying turbulence whose Eulerian correlation time is of the order of the eddy-circulation time. In turbulence with weak helicity, the directinteraction equations imply that the Lagrangian correlation of vorticity with initial velocity is more persistent thanUL(t), by a substantial factor.
Hydrodynamic instability of viscous flow between rotating coaxial cylinders with fully developed axial flow
Authors: Chung K. C. , Astill K. N.
Published: April 2006

A linear stability analysis is presented for flow between concentric cylinders when a fully developed axial flow is present. Small perturbations are assumed to be nonaxisymmetric. This leads to an eigenvalue problem with four eigenvalues: the critical Taylor number, an amplification factor and two wavenumbers. The presence of the tangential wavenumber permits prediction of the stability of spiral flow. This made it possible to model the flow more accurately and to extend the range of calculations to higher axial Reynolds numbers than had previously been attainable. Calculations were carried out for radius ratios from 0·95 to 0·1, Reynolds numbers as large as 300 and cases with co-rotation and counter-rotation of the cylinders.
Visual observation of natural convective flow in a narrow vertical cavity
Authors: Seki Nobuhiro , Fukusako Shoichiro , Inaba Hideo
Published: April 2006

Experimental visualization of natural convective flow was carried out by using several kinds of fluid contained in a narrow vertical rectangular cavity with one vertical wall heated, the opposing vertical wall cooled and the upper and lower walls insulated. The effects of the Prandtl number Pr of the working fluid and the width of the cavity W on the flow pattern are discussed qualitatively in the present paper. The occurrence of flow patterns consisting of unicellular flow, steady secondary flow, tertiary flow and transition (from laminar to turbulent) flow is categorically demonstrated by the photographs taken. Moreover, experimental measurements of the net heat transfer through the vertical fluid layer are given for aspect ratios of 6-30 and Prandtl numbers of 4-12 500.
Supersonic flow of a vibrationally relaxing gas past a circular cone
Authors: Kao James , Hodgson J. P.
Published: April 2006

The steady supersonic flow of a vibrationally relaxing gas past a cone is studied using numerical methods. Near the tip of the cone the flow is obtained by means of a coordinate expansion and built on to this is a characteristic network used to obtain the remainder of the flow. Of particular interest is the development of the frozen shock at the tip into a relaxation-dominated wave at distances large compared with the width of the wave. The numerical results are presented in a concise similarity form which will permit accurate extrapolation to very weak waves in atmospheric air.
Wilson Cloud formation by low-altitude nuclear explosions
Authors: Waltz R. E.
Published: April 2006

A model of Wilson Cloud formation following a low-altitude nuclear detonation is developed. It is shown that, for detonation yields between 10−3 kt and 100 kt, simple scaling laws characterize the evolution and physical properties of the Wilson Cloud.
Kinematical studies of the flows around free or surface-mounted obstacles; applying topology to flow visualization
Authors: Hunt J. C. R. , Abell C. J. , Peterka J. A. , Woo H.
Published: April 2006

In flows around three-dimensional surface obstacles in laminar or turbulent streamsthere are a number of points where the shear stress or where two or more component,s of the mean velocity are zero. In the first part of this paper we summarize and extend the kinematical theory for the flow near these points, particularly by emphasizing the topological classification of these points as nodes or saddles. We show that the zero-shear-stress points on the surface and on the obstacle must be such that the sum of the nodes ΣNand the sum of the saddles Σssatisfy\[ \Sigma_N -\Sigma_S = 0. \]If the obstacle has a hole through it, such as a passageway under a building,\[ \Sigma_N -\Sigma_S =-2. \]If the surface is a junction between two pipes,\[ \Sigma_N -\Sigma_S =-1. \]We also consider, in two-dimensional plane sections of the flow, the points where the components of the mean velocity parallel to the planes are zero, both in the flow and near surfaces cutting the sections. The latter points are half-nodes N′ or half-saddles S′. We find that\[ (\Sigma_N +{\textstyle\frac{1}{2}}\Sigma_{N^{\prime}}-(\Sigma_{S^{\prime}}+{\textstyle\frac{1}{2}}\Sigma_{S^{\prime}}) = 1-n, \]where n is the connectivity of the section of the flow considered.

In the second part new flow-visualization studies of laminar and turbulent flows around cuboids and axisymmetric humps (i.e. model hills) are reported. A new method of obtaining a high resolution of the surface shear-stress lines was used. These studies show how enumerating the nodes and saddle points acts as a check on the inferred flow pattern.

Two specific conclusions drawn from these studies are that:

for all the flows we observed, there are no closed surfaces of mean streamlines around the separated flows behind three-dimensional surface obstacles, which con-tradicts most of the previous suggestions for such flows (e.g. Halitsky 1968);

the separation streamline on the centre-line of a three-dimensional bluff obstacle does not, in general, reattach to the surface.
Improved dissolution and chemical separation methods for Lu‐Hf garnet chronometry
Authors: Connelly J. N.
Published: April 2006

Garnet‐based Lu‐Hf geochronology using conventional (HF‐HNO3) dissolution methods may be compromised by full or partial digestion of Hf‐rich zircon inclusions. This study integrates two complimentary methods to substantially reduce zircon digestion while assuring complete digestion of garnet and sample‐spike equilibration. Handpicked garnet fractions are heat treated to >1000°C in an evacuated silica glass ampoule to anneal zircon inclusions and then dissolved with 12 M HCl at 210°C and cold 28 M HF. Analyses of heat‐treated garnet (and their high‐temperature breakdown products orthopyroxene‐spinel‐quartz) from Gore Mountain, New York, demonstrate the method is capable of complete dissolution of garnet and routinely achieving sample‐spike equilibration. Independent analyses of annealed and unannealed zircons dissolved by HCl – cold HF demonstrate the benefit of heat treatment prior to dissolution. Analyses of zircon‐rich garnets from peletic paragneisses of Labrador, Canada, show the potential of this method by returning Lu‐Hf ratios commensurate with the degree of heat treatment. Finally, a complementary chemical separation method for Lu and Hf is presented that supports analysis of garnet by MC‐ICP‐MS.
Circulation in the central equatorial Atlantic: Mean and intraseasonal to seasonal variability
Authors: Brandt Peter , Schott Friedrich A. , Provost Christine , Kartavtseff Annie , Hormann Verena , Bourlès Bernard , Fischer Jürgen
Published: April 2006

The zonal equatorial circulation of the upper 700 m in the central tropical Atlantic is studied based on 11 cross‐equatorial ship sections taken at 23–29°W during 1999 to 2005 and on data from a pair of moored Acoustic Doppler current profilers deployed on the equator at 23°W during February 2004 to May 2005. The observations on the equator reveal the existence of two mean westward cores of the Equatorial Intermediate Current below the Equatorial Undercurrent. In contrast to the 2002 moored observations at the same position the intraseasonal variability during the mooring period is dominated by zonal instead of meridional velocity fluctuations.
Temporal invariance of leading EOFs for western United States precipitation over a range of scales
Authors: Small David , Islam Shafiqul
Published: April 2006

We investigate how spatial coherence and temporal variability of precipitation over the western United States changes with temporal aggregation and filtering. We begin by calculating principal components (PC) from finely gridded daily precipitation anomalies across the western United States. The daily data were aggregated to form 5‐day, 10‐day, 20‐day, monthly, and seasonal anomalies and the empirical orthogonal functions (EOFs) were estimated. Our results suggest that the leading EOFs of western United States precipitation do not depend on the temporal aggregation of the data. To examine the sensitivity of the leading empirical orthogonal functions to temporal aggregation and filtering, we then filtered the data with the discrete wavelet transform (DWT) and repeated the EOF analysis for scales of 2 days to 10 years. It appears that western precipitation is strongly persistent with EOFs that do not depend on the temporal aggregation of the data or the timescale of the analysis from 4 days to 7 years. To explore the origin of this time invariance of the EOFs, we simulated synthetic data sets and demonstrated the importance of spatial correlation on the dominant patterns of variability. Precipitation anomalies appear to display a large degree of temporal persistence that is reflected in the similarity of spatial patterns of precipitation ranging from days to seasons. Simulations suggest that the spatial correlation between adjacent grid points is the dominant factor shaping the EOFs.
Aerosol lofting from sea breeze during the Indian Ocean Experiment
Authors: Verma S. , Boucher O. , Venkataraman C. , Reddy M. S. , Müller D. , Chazette P. , Crouzille B.
Published: April 2006

This work was carried out to understand the mechanisms leading to lofting and large‐scale advection of aerosols over the Indian Ocean region due to interaction of the sea breeze with the northeast monsoon winds along the west coast of India. European Centre for Medium‐Range Weather Forecasts (ECMWF) wind fields for the months of February and March 1999 were analyzed at various times of day. Intense sea breeze activity was observed at 1200 UT (1730 local time) along the west coast of India with average intensity larger in March than in February. The sea breeze was seen to extend inland deeper in March than in February. Lofting of air observed as high as 800 hPa (approximately 2 km above sea level) could lead to entrainment of aerosols into the free troposphere and long‐range transport. Upward motion of air was observed everywhere along the west coast of India (from 8° to 20°N), on average higher in March than in February, because of convergence between the sea breeze and the synoptic‐scale flow. A region of intense lofting of air and well‐defined convergence was observed along the coast of the Karnataka region (12°–16°N). A simulation with a general circulation model nudged with ECMWF data indicated that the intrusion of marine air masses with low concentrations of organic matter is seen as deep as 64 km inland in the evening (1500 UT). Intrusion of the sea‐salt plume is seen to a maximum distance of around 200 km from 1500 until 2300 UT. A well‐developed lofted layer of aerosols as high as 3 km was also simulated during sea breeze activity along the west coast of India. The general circulation model simulation shows a clear diurnal evolution of the vertical profile of the aerosol extinction coefficient at Goa but fails to reproduce several features of the lidar observations, for example, the marked diurnal variability of the upper layers between 1 and 3 km. However, the model simulates a diurnal cycle at the surface (0–0.7 km) that is not apparent in lidar measurements. The model simulates long‐range transport and captures the lofted plume downwind of the west coast of India. However, there was a 1–2 day delay in the model transport of lofted aerosols at higher layers to Hulule, 700 km downwind of India, when compared to lidar observations.
Source identification of airborne PM2.5 at the St. Louis‐Midwest Supersite
Authors: Lee Jong Hoon , Hopke Philip K. , Turner Jay R.
Published: April 2006

Daily 24‐hour integrated PM2.5 (particulate matter ≤2.5 μm aerodynamic diameter) mass and species concentrations were measured at the St. Louis‐Midwest Supersite in East St. Louis, Illinois, during the sampling period from June 2001 to May 2003. The PM2.5 speciation data were analyzed using a receptor model, positive matrix factorization (PMF), to identify sources contributing to the observed PM2.5 burdens. Species profiles for the identified sources and their contributions to the observed mass concentration at the receptor were derived from the PMF modeling. These source‐specific contributions were then coupled with on‐site wind data to identify the directionality of the identified sources which are compared to known point source locations. Overall, ten source categories were resolved (study average contribution to the PM2.5 mass in parentheses): secondary sulfate (33%), carbon‐rich sulfate (20%), gasoline exhaust (16%), secondary nitrate (15%), steel processing (7%), airborne soil (4%), diesel emissions/railroad traffic (2%), zinc smelting (1.3%), lead smelting (1.3%), and copper production (0.5%). Temperature‐resolved organic and elemental carbon fractions enhanced the source separation between secondary sulfate and carbon‐rich sulfate and between gasoline exhaust and diesel emissions/railroad traffic. A major Saharan dust plume observed throughout the Midwestern U.S. in July 2002 was also observed in this study. Overall, about half (48%) of PM2.5 mass concentration measured at this site was distinctly apportioned to secondary sulfate and secondary nitrate. Contributions from distinct primary emissions included local industrial sources (9%), transportation (gasoline/diesel/railroad, 19%), and airborne dust (4%). The remaining 20% of the PM2.5 mass was apportioned to a carbon‐rich sulfate factor which is likely an admixture of primary emissions and secondary formation. More work is needed to identify the distinct sources contributing to this factor.
Regional distribution and emissions of mercury in east Asia: A modeling analysis of Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) observations
Authors: Pan Li , Woo Jung‐Hun , Carmichael Gregory R. , Tang Youhua , Friedli Hans R. , Radke Lawrence F.
Published: April 2006

Mercury tracer model simulations are performed to support the analysis of the total gas phase mercury (TGM) observations on 15 flights of the NSF/NCAR C‐130 aircraft during the Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) campaign conducted during April 2001. Ninety‐seven percent of the observed mercury concentrations are greater than 1.2 ng/m3. The mean value of the observations is 1.9 ng/m3. No simple relationships between Hg‐CO and Hg‐total sulfur are found; however, strong correlations are observed in individual flight segments. Backward trajectory analysis is used to help characterize regional of Hg/CO ratios, and these are compared with emission‐based ratios from the various sectors. Model predictions using new Hg emission estimates are presented and compared to the observations. Under the condition of a mercury background level of 1.2 ng/m3 the tracer model underestimates the observations when the flights were over the Yellow Sea but is consistent with the observations when the flights were over the Japan Sea. Further analysis suggests that Hg emissions are underestimated in north central China and the eastern coastal areas of China. Model sensitivity studies indicate that the emissions of China may be underestimated by 80–200%.
Seismotectonics of western Turkey from high resolution earthquake relocations and moment tensor determinations
Authors: Zhu Lupei , Akyol Nihal , Mitchell Brian J. , Sozbilir Hasan
Published: April 2006

We have relocated 364 earthquakes in western Turkey between 2002 and 2003 using more than 45,000 accurate P and S differential travel‐times. We also have determined moment tensors for 71 of these earthquakes using their broadband regional waveforms. After relocation the events are highly concentrated in three clusters and delineate two nearly vertical faults. Their strikes agree with the strike of one of the fault planes of the averaged fault‐plane solution of the cluster, which allowed us to pick the true fault plane and the slip direction. We identified a NNW‐striking left‐lateral strike‐slip fault near Buldan that connects the Gediz graben in the north and the eastern end of the Buyuk Menderes graben in the south. The other right‐lateral strike‐slip fault near Izmir strikes ENE–WSW direction. Our results indicate that part of the N–S extension occurring in western Turkey is accommodated by strike‐slip faults and is accompanied by E–W shortening.
Fgf21 is essential for haematopoiesis in zebrafish
Authors: Yamauchi Hajime , Hotta Yuhei , Konishi Morichika , Miyake Ayumi , Kawahara Atsuo , Itoh Nobuyuki
Published: April 2006

Fibroblast growth factors (Fgfs) function as key secreted signalling molecules in many developmental events. The zebrafish is a powerful model system for the investigation of embryonic vertebrate haematopoiesis. Although the effects of Fgf signalling on haematopoiesis in vitro have been reported, the functions of Fgf signalling in haematopoiesis in vivo remain to be explained. We identified Fgf21 in zebrafish embryos. Fgf21‐knockdown zebrafish embryos lacked erythroid and myeloid cells but not blood vessels and lymphoid cells. The knockdown embryos had haemangioblasts and haematopoietic stem cells. However, the knockdown embryos had significantly fewer myeloid and erythroid progenitor cells. In contrast, Fgf21 had no significant effect on cell proliferation and apoptosis in the intermediate cell mass. These results indicate that Fgf21 is a newly identified factor essential for the determination of myelo‐erythroid progenitor cell fate in vivo.
The transient dynamics leading to spin turbulence in high-field solution magnetic resonance: A numerical study
Authors: Datta Sandip , Huang Susie Y. , Lin Yung-Ya
Published: April 2006

The dynamics under the joint action of radiation damping and the distant dipolar field in high-field solution magnetic resonance are investigated. Different dynamical regimes during the evolution are identified and their individual features are discussed. In the steady state, the dynamics can be associated with a strange attractor in phase space on which the motion is chaotic. The possibility of the observed chaotic motion being spatiotemporal is examined.
Gold surface with sub-nm roughness realized by evaporation on a molecular adhesion monolayer
Authors: Mahapatro Ajit K. , Scott Adina , Manning Allene , Janes David B.
Published: April 2006

This letter describes a technique for realizing a gold (Au) surface with roughness at the atomic scale using techniques compatible with integrated device fabrication. The Au layer is electron-beam evaporated on a self-assembled monolayer of (3-Mercaptopropyl) trimethoxysilane on an oxidized silicon substrate and shows a root-mean-square surface roughness of ∼2Å over a 1μm2 area. The physical stability of the Au film toward commonly used chemicals and processes for photolithography and self-assembly, and its suitability for formation of well-ordered organic monolayers indicate that the films are well suited as substrates for future device fabrication in molecular electronics or other devices involving self-assembled monolayers.
Vibronic coupling in benzene cation and anion: Vibronic coupling and frontier electron density in Jahn-Teller molecules
Authors: Tokunaga Ken , Sato Tohru , Tanaka Kazuyoshi
Published: April 2006

Vibronic coupling constants of Jahn-Teller molecules, benzene radical cation and anion, are computed as matrix elements of the electronic part of the vibronic coupling operator using the electronic wave functions calculated by generalized restricted Hartree-Fock and state-averaged complete active space self-consistent-field methods. The calculated vibronic coupling constants for benzene cation agree well with the experimental and theoretical values. Vibronic coupling density analysis, which illustrates the local properties of the coupling, is performed in order to explain the order of magnitude of the coupling constant from view of the electronic and vibrational structures. This analysis reveals that the couplings of the e2g(2) and e2g(3) modes in which the large displacements locate on C–C bonds are strong in the cation. On the other hand, they are greatly weakened in the anion because of the decrease of electron density in the region of the C–C bonds, which originates from the antibonding nature of the singly occupied molecular orbital of the anion. However, the difference of the electronic structure has a little influence on the vibronic coupling of the e2g(4) mode. These results indicate that the vibronic coupling depends not only on the direction of the nuclear displacement but also on the frontier electron density.
Relativistic configuration interaction study of the electronic spectrum of SnTe and SnTe+
Authors: Giri Dipankar , Pati Kashinath , Das Kalyan Kumar
Published: April 2006

Ab initio based relativistic configuration interaction calculations have been performed to study the electronic spectrum of the heaviest tin chalcogenide and its monopositive ion. Potential energy curves and spectroscopic constants of low-lying states of both species within 7eV are reported. The ground-state dissociation energies of SnTe and SnTe+ are computed to be 3.48 and 2.50eV, respectively. The spin-orbit splitting between the two components of the XΠ2 state of SnTe+ is about 3030cm−1. Effects of the strong spin-orbit coupling on the potential curves and spectroscopic properties of both the species are investigated in detail. The electric dipole moments of some of the low-lying states of SnTe and SnTe+ are reported. Transition moments of some important spin-allowed and spin-forbidden transitions are calculated from the configuration interaction wave functions. The radiative lifetime of the excited EΣ0++1 state of SnTe is about 39ns. The X2–X1 transition in SnTe+ is found to be more probable than the similar transition in the lighter ions. The vertical ionization energy of SnTe in the ground state is estimated to be 8.22eV.
Ab initioelectron propagator theory of molecular wires. II. Multiorbital terminal description
Authors: Dahnovsky Yu. , Ortiz J. V.
Published: April 2006

Correlated, ab initio electron propagator methodology may be applied to the calculation of electrical current through a molecular wire. A new theoretical formalism is developed for the calculation of retarded and advanced Green functions in terms of the electron propagator matrix for a bridge molecule. The calculation of the current requires integration in a complex half-plane for a trace that involves terminal and Green function matrices that may have any rank. Because the latter arrays have poles represented by matrices, an alternative expression is developed in terms of ordinary poles which are (n−1)-fold degenerate or nondegenerate. For an arbitrary number of terminal orbitals, the analytical expression for the current is given in terms of pole strengths, poles, and terminal matrix elements of the electron propagator, i.e., the parameters that are found in the output of numerical calculations.
Complex Ohmic conductance of electrolytes in rectangular microchannels
Authors: Campisi Michele , Accoto Dino , Dario Paolo
Published: April 2006

Motivated by the interest that microelectrolytic systems are gaining in the development of the so-called lab-on-a-chip systems, i.e., miniature microfluidic devices for biochemical analysis, we present an analytical study of Ohmic conduction in rectangular charged microchannels filled with electrolytic solution. The study complements a previous one [M. Campisi et al., J. Chem. Phys. 123, 204724 (2005)], concerning ac electro-osmosis. The problem is framed within the theory of nonequilibrium thermodynamics and is based on the solution of the incompressible Navier-Stokes equation with an electrical body force due to the interaction of the applied electric field with the charged electric double layer (EDL) which forms at the solid-liquid interface. We analyze in detail the dependence of the system complex conductance on the ratio linear dimensions over Debye length with an eye on finite EDL effects, and compare its scaling properties with those of electrokinetic and hydraulic complex conductances.
Exact phase boundary of an amphiphile-rich phase in a ternary solution on a Bethe lattice
Authors: Huckaby David A. , Jȩdrzejewski Janusz , Huckaby Dale A.
Published: April 2006

A model ternary solution is considered in which the bonds of a three-coordinate Bethe lattice are covered by rodlike molecules of types AA, BB, and AB, the AB-type molecule representing an amphiphile. The phase boundary in temperature-composition space of an ordered amphiphile-rich phase is calculated exactly.
Electrohydrodynamic “drop-and-place” particle deployment
Authors: Chen C.-H. , Saville D. A. , Aksay I. A.
Published: April 2006

The “drop-and-place” paradigm aims at delivering and positioning liquid drops using a pulsed electrohydrodynamic jet. On-demand drops much smaller than the diameter of the delivery nozzle may also contain particles. We report proof-of-concept experiments on the delivery of single 2μm diameter particles using a 50μm nozzle and identify the control parameters for dosing and positioning accuracies. A positioning accuracy at the micrometer level is achieved by eliminating contact line pinning on a hydrophobic surface and minimizing impingement-induced motion. The dosing statistics follow the random Poisson distribution, indicating that single-particle accuracy can be achieved using a gating mechanism.
p
-type activation of AlGaN by hydrogen desorption using catalytic Ni films
Authors: Naono T. , Fujioka H. , Okabayashi J. , Oshima M. , Miki H.
Published: April 2006

p -type activation of Mg-doped Al0.03Ga0.97N and Al0.08Ga0.92N by annealing process with Ni deposition has been investigated. Hole concentrations in both Al0.03Ga0.97N and Al0.08Ga0.92N by annealing at around 700°C with Ni were almost two times as high as those in samples annealed without Ni. Secondary ion mass spectroscopy has revealed that hydrogen concentrations in AlGaN annealed with Ni are lower than those without Ni. Thermal desorption spectroscopy showed drastic enhancement in hydrogen desorption at around 450°C from AlGaN films with Ni. We conclude that Ni deposition promotes the hydrogen desorption from AlGaN layers, resulting in effective p-type activation.
Modulation of NiGe∕Ge Schottky barrier height by sulfur segregation during Ni germanidation
Authors: Ikeda Keiji , Yamashita Yoshimi , Sugiyama Naoharu , Taoka Noriyuki , Takagi Shin-ichi
Published: April 2006

We have demonstrated wide-range modulation of Schottky barrier height (SBH) of NiGe∕Ge(100) interfaces by using a valence mending adsorbate, sulfur, segregation during Ni germanidation. Implanted sulfur atoms, segregated during Ni germanidation, are expected to act as dangling bond terminator at the NiGe∕Ge interface. The experimental results show that the strong Fermi level pinning feature of NiGe∕Ge interfaces was alleviated, and SBH of NiGe∕n-Ge(100) gradually decreased from 0.61to0.15eV with an increase in the implanted sulfur dose. This method opens a way to realize Ge channel complementary metal-oxide-semiconductor field-effect transistors with metal source/drain.
Synthesis, electrical characterization, and gas sensing properties of molybdenum oxide nanorods
Authors: Taurino Antonella M. , Forleo Angiola , Francioso Luca , Siciliano Pietro , Stalder Michael , Nesper Reinhard
Published: April 2006

Gas sensors have been prepared by using single crystalline MoO3 nanorods. Structures 50–150nm and up to 15μm in length were synthesized by template directed hydrothermal synthesis. Gas sensing tests showed responses to NO2 up to 740% and to NH3 up to 570%. Moreover, preliminary electrical characterizations were performed, as a function of temperature in 20–520°C range temperature, by means of current-voltage measurements. I-V dependence studies show a linear increase in current at low voltage and a quadratic increase at higher voltages. A study of the current-temperature dependence shows that at high temperature current is thermally active and successively decreases that can be explained by taking in account a change of material morphology.
Dielectric and ferroelectric properties of intergrowth Bi7−xLaxTi4NbO21 ceramics
Authors: Yi Z. G. , Li Y. X. , Wang Y. , Yin Q. R.
Published: April 2006

The dielectric permittivity of Bi7−xLaxTi4NbO21 (x=0–1.75) ceramics at ambient temperature is stable in a wide range of frequencies and can be modulated from 150 to 320 by compositional modification. With increasing La3+ content, both the phase transition temperatures downshift and the phase transition peaks become diffusive when x⩾1.00. The P-E hysteresis loops indicated that the remanent polarization 2Pr of Bi6.5La0.5Ti4NbO21 has a maximum of 24.4μC∕cm2. The Raman scattering experiments revealed that the Bi3+ in [Bi2O2]2+ layers is substituted by La3+ when x⩾1.00 and there is no Bi3+ at the A sites being substituted further when x⩾1.50.
Spectral diffusion of single semiconductor nanocrystals: The influence of the dielectric environment
Authors: Gómez Daniel E. , van Embden Joel , Mulvaney Paul
Published: April 2006

We have explored the influence of different matrices on the emission line shape of individual homogeneously coated CdSe∕CdS∕ZnS nanocrystals. The results obtained corroborate previous observations of a correlation between blinking events and spectral diffusion, but in addition we have found that the extent of spectral diffusion is almost independent of the dielectric environment of the nanocrystal (NC). Additionally, we report the observation of a correlation between the linewidth and emission energy which is not expected to occur in the spherical-symmetric NCs employed in this work. The implications of these results are discussed.
Ion dynamics in compacted clays: Derivation of a two-state diffusion-reaction scheme from the lattice Fokker-Planck equation
Authors: Rotenberg B. , Dufrêche J.-F. , Bagchi B. , Giffaut E. , Hansen J.-P. , Turq P.
Published: April 2006

We show how a two-state diffusion-reaction description of the mobility of ions confined within compacted clays can be constructed from the microscopic dynamics of ions in an external field. The diffusion-reaction picture provides the usual interpretation of the reduced ionic mobility in clays, but the required partitioning coefficient Kd between trapped and mobile ions is generally an empirical parameter. We demonstrate that it is possible to obtain Kd from the microscopic dynamics of ions interacting with the clay surfaces by evaluating the ionic mobility using a novel lattice implementation of the Fokker-Planck equation. The resulting Kd allows a clear-cut characterization of the trapping sites on the clay surfaces and determines the adsorption/desorption rates. The results highlight the limitations of standard approximation schemes and pinpoint the crossover from jump to Brownian diffusion regimes.
Investigation of optical birefringence at ferroelectric domain wall in LiNbO3 by phase-shift polarimetry
Authors: Paturzo Melania , Aiello Lara , Pignatiello Felice , Ferraro Pietro , De Natale Paolo , Angelis Marella de , De Nicola Sergio
Published: April 2006

We investigated the optical birefringence near the wall between two opposite domains in a z-cut congruent LiNbO3 through a full-field polarimetric method. We obtained a measure of domain wall width and determined the direction of the principal axes of stress-induced birefringence. Experimental data show that the principal axes of stress-induced birefringence result to be parallel or perpendicular to the domain wall, according to theoretical predictions. The domain wall width value ranges from 10 to about 50μm, showing a spatial variation that we can appreciate since the used method allows us to obtain two dimensionally resolved measurements.
Biomedical terahertz imaging with a quantum cascade laser
Authors: Kim Seongsin M. , Hatami Fariba , Harris James S. , Kurian Allison W. , Ford James , King Douglas , Scalari Giacomo , Giovannini Marcella , Hoyler Nicolas , Faist Jerome , Harris Geoff
Published: April 2006

We present biomedical imaging using a single frequency terahertz imaging system based on a low threshold quantum cascade laser emitting at 3.7THz (λ=81μm). With a peak output power of 4mW, coherent terahertz radiation and detection provide a relatively large dynamic range and high spatial resolution. We study image contrast based on water/fat content ratios in different tissues. Terahertz transmission imaging demonstrates a distinct anatomy in a rat brain slice. We also demonstrate malignant tissue contrast in an image of a mouse liver with developed tumors, indicating potential use of terahertz imaging for probing cancerous tissues.
Donor and acceptor competitions in phosphorus-doped ZnO
Authors: Xiu F. X. , Yang Z. , Mandalapu L. J. , Liu J. L.
Published: April 2006

Phosphorus-doped ZnO films were grown by molecular-beam epitaxy with a GaP effusion cell as dopant source. Three growth regions were identified to obtain ZnO films with different conduction types. In the oxygen-extremely-rich region, phosphorus-doped ZnO films show n-type conduction with dominant donor-bound excitons (DX0) in the low-temperature photoluminescence (PL) spectra. In the oxygen-rich region, a growth window was found to generate p-type ZnO films. The PL spectra show evident competitions between DX0 and acceptor-bound excitons (AX0). In the stoichiometric and Zn-rich region, ZnO films are n-type with dominant DX0 emissions. Thus, phosphorus doping is amphoteric, having the tendency to form both donors and acceptors in ZnO.
Impact of in situ carbon doping on implant damage and strain relaxation of epitaxial silicon germanium layer on silicon
Authors: Liu J. P. , Domenicucci A. , Madan A. , Li J. , Holt J. , Sudijono John
Published: April 2006

Implant damage and strain relaxation in thin epitaxial silicon germanium (SiGe) layers on silicon (Si) (001) and their dependence on in situ carbon (C) doping in epitaxial SiGe are studied. For a 65nm SiGe layer with ∼25% germanium (Ge), conventional implants used for p-metal-oxide semiconductor source/drain, halo, and extension led to significant implant damage and strain relaxation. Two defect bands were observed, one close to the surface and the other at SiGe∕Si interface. In situ C doping (1019–1020∕cm3) was found to eliminate the implant damage close to SiGe∕Si interface area and prevent significant strain relaxation.
Gender differences in the perceptions of wildlife management objectives and priorities in Australasia
Authors: Miller Kelly K. , Jones Darryl N.
Published: April 2006

It is now well established that men and women often differ significantly in their attitudes and responses to workplace situations, challenges and policies. The aim of this study was to examine the effect of gender on perceptions and priorities held by Australasian wildlife managers. Data were collected via a questionnaire distributed during December 2002 – February 2003 to members of the Australasian Wildlife Management Society (AWMS) and registrants of the 2002 AWMS annual conference. The results show that there are now significantly more female AWMS members than there were in the early 1990s, a possible indication of a change in the wider wildlife management profession in Australasia. Consistent with previous research, male respondents held different views from female respondents about wildlife and wildlife management. In particular, male respondents were significantly more likely to express the ‘management/consumptive use of wildlife’ perspective than female respondents. Interestingly, this gap was observed only in the 18–30-year age category. The paper examines what these differences might mean for the future of wildlife management in Australasia.
Linkage of butterfly mate preference and wing color preference cue at the genomic location ofwingless
Authors: Kronforst Marcus R. , Young Laura G. , Kapan Durrell D. , McNeely Camille , O'Neill Rachel J. , Gilbert Lawrence E.
Published: April 2006

Sexual isolation is a critical form of reproductive isolation in the early stages of animal speciation, yet little is known about the genetic basis of divergent mate preferences and preference cues in young species.Heliconiusbutterflies, well known for their diversity of wing color patterns, mate assortatively as a result of divergence in male preference for wing patterns. Here we show that the specific cue used byHeliconius cydnoandHeliconius pachinusmales to recognize conspecific females is the color of patches on the wings. In addition, male mate preference segregates with forewing color in hybrids, indicating a genetic association between the loci responsible for preference and preference cue. Quantitative trait locus mapping places a preference locus coincident with the locus that determines forewing color, which itself is perfectly linked to the wing patterning candidate gene,wingless. Furthermore, yellow-colored males of the polymorphic raceH. cydno alitheaprefer to court yellow females, indicating that wing color and color preference are controlled by loci that are located in an inversion or are pleiotropic effects of a single locus. Tight genetic associations between preference and preference cue, although rare, make divergence and speciation particularly likely because the effects of natural and sexual selection on one trait are transferred to the other, leading to the coordinated evolution of mate recognition. This effect of linkage on divergence is especially important inHeliconiusbecause differentiation of wing color patterns in the genus has been driven and maintained by natural selection for Müllerian mimicry.
Cholesterol modification restricts the spread of Shh gradient in the limb bud
Authors: Li Yina , Zhang Huimin , Litingtung Ying , Chiang Chin
Published: April 2006

Sonic hedgehog (Shh) produced in the zone of polarizing activity is the major determinant of anteroposterior development of the amniote limb. The mature and active Shh protein is cholesterol-modified at its C terminus, and the hydrophobic nature of the modification requires the function of Dispatched (mDispA), a seven-pass transmembrane protein, for Shh release from its source. The current model suggests that the cholesterol moiety promotes the spread of Shh gradient in the limb bud. However, this model is inconsistent with findings in
Drosophila
and not in line with current thoughts on the role of the cholesterol moiety in Shh multimerization. Therefore, it remains unclear how the cholesterol moiety affects the postrelease extracellular behavior of Shh that relates to the shape of its activity gradient in responsive tissues. Here, we report functional analyses in mice showing that Shh lacking cholesterol modification (ShhN) has an increased propensity to spread long-distance, eliciting ectopic Shh pathway activation consistent with target gene expressions and modulating the level of Gli3 processing in the anterior limb mesoderm. These molecular alterations are reflected in the mispatterning of digits in ShhN mutants. Additionally, we provide direct evidence for the long-distance movement of ShhN across the anteroposterior axis of the limb bud. Our findings suggest that the cholesterol moiety regulates the range and shape of the Shh morphogen gradient by restricting rather than promoting the postrelease spread of Shh across the limb bud during early development.
The politics of control in Kenya: Understanding the bureaucratic-executive state, 1952–78
Authors: Branch Daniel , Cheeseman Nicholas
Published: April 2006

Colonial rule in Kenya witnessed the emergence of a profoundly unbalanced institutional landscape. With all capacity resided in a strong prefectural provincial administration, political parties remained underdeveloped. The co-option of sympathetic African elites during the colonial twilight into the bureaucracy, the legislature and the private property-based economy meant that the allies of colonialism and representatives of transnational capital were able to reap the benefits of independence. In the late colonial period these elites not only attained the means of production, they also assumed the political and institutional capacity to reproduce their dominance. The post-colonial state must therefore be seen as a representation of the interests protected and promoted during the latter years of colonial rule. Under Jomo Kenyatta, the post-colonial state represented a ‘pact-of-domination’ between transnational capital, the elite and the executive. The ability of this coalition to reproduce itself over time lay in its capacity to demobilise popular forces, especially those elements of the nationalist movement that questioned both the social and economic cleavages of the post-colonial state. Whilst Kenya may have experienced changes to both the executive and legislature, the structure of the state itself has demonstrated remarkable continuity.