bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonadiabatic coupling vectors for excited states within time-dependent density functional theory in the Tamm–Dancoff approximation and beyond
Authors: Tavernelli Ivano , Curchod Basile F. E. , Laktionov Andrey , Rothlisberger Ursula
Published: November 2010

Recently, we have proposed a scheme for the calculation of nonadiabatic couplings and nonadiabatic coupling vectors within linear response time-dependent density functional theory using a set of auxiliary many-electron wavefunctions [I. Tavernelli, E. Tapavicza, and U. Rothlisberger, J. Chem. Phys. 130, 124107 (2009)]. As demonstrated in a later work [I. Tavernelli, B. F. E. Curchod, and U. Rothlisberger, J. Chem. Phys. 131, 196101 (2009)], this approach is rigorous in the case of the calculation of nonadiabatic couplings between the ground state and any excited state. In this work, we extend this formalism to the case of coupling between pairs of singly excited states with the same spin multiplicity. After proving the correctness of our formalism using the electronic oscillator approach by Mukamel and co-workers [S. Tretiak and S. Mukamel, Chem. Rev. (Washington, D.C.) 102, 3171 (2002)], we tested the method on a model system, namely, protonated formaldimine, for which we computed S1/S2 nonadiabatic coupling vectors and compared them with results from high level (MR-CISD) electronic structure calculations.
Two-point velocity average of turbulence: Statistics and their implications
Authors: Mouri Hideaki , Hori Akihiro
Published: November 2010

For turbulence, although the two-point velocity difference u(x+r)−u(x) at each scale r has been studied in detail, the velocity average [u(x+r)+u(x)]/2 has not thus far. Theoretically or experimentally, we find interesting features of the velocity average. It satisfies an exact scale-by-scale energy budget equation. The flatness factor varies with the scale r in a universal manner. These features are not consistent with the existing assumption that the velocity average is independent of r and represents energy-containing large-scale motions alone. We accordingly propose that it represents motions over scales ≥r as long as the velocity difference represents motions at the scale r.
Cold chemistry with electronically excited Ca+ Coulomb crystals
Authors: Gingell Alexander D. , Bell Martin T. , Oldham James M. , Softley Timothy P. , Harvey Jeremy N.
Published: November 2010

Rate constants for chemical reactions of laser-cooled Ca+ ions and neutral polar molecules (CH3F, CH2F2, or CH3Cl) have been measured at low collision energies (⟨Ecoll⟩/kB=5–243 K). Low kinetic energy ensembles of C40a+ ions are prepared through Doppler laser cooling to form “Coulomb crystals” in which the ions form a latticelike arrangement in the trapping potential. The trapped ions react with translationally cold beams of polar molecules produced by a quadrupole guide velocity selector or with room-temperature gas admitted into the vacuum chamber. Imaging of the Ca+ ion fluorescence allows the progress of the reaction to be monitored. Product ions are sympathetically cooled into the crystal structure and are unambiguously identified through resonance-excitation mass spectrometry using just two trapped ions. Variations of the laser-cooling parameters are shown to result in different steady-state populations of the electronic states of C40a+ involved in the laser-cooling cycle, and these are modeled by solving the optical Bloch equations for the eight-level system. Systematic variation of the steady-state populations over a series of reaction experiments allows the extraction of bimolecular rate constants for reactions of the ground state (S21/2) and the combined excited states (D23/2 and P21/2) of C40a+. These results are analyzed in the context of capture theories and ab initio electronic structure calculations of the reaction profiles. In each case, suppression of the ground state rate constant is explained by the presence of a submerged or real barrier on the ground state potential surface. Rate constants for the excited states are generally found to be in line with capture theories.
Generalized two-fluid equilibria: Understanding RT-1 experiments and beyond
Authors: Yoshida Z. , Mahajan S. M. , Mizushima T. , Yano Y. , Saitoh H. , Morikawa J.
Published: November 2010

Diversity of plasma structures, which degenerates in the ideal magnetohydrodynamic model, can emerge in many ways in a two-fluid plasma endowed with a hierarchy of scales. We study the equilibrium structure of high-beta (high temperature and low-density) electrons in a relatively weak magnetic field. Spontaneous flow generation and strong diamagnetism are clear manifestations of the nonideal two-fluid dynamics scaled, respectively, by the ion and electron-inertia lengths (skin depths). The theory predicts stronger flow and diamagnetism in the nonlinear regime of the two-fluid dynamics.
Stress-induced magnetic and structural anisotropy of nanocrystalline Fe-based alloys
Authors: Ohnuma M. , Yanai T. , Hono K. , Nakano M. , Fukunaga H. , Yoshizawa Y. , Herzer G.
Published: November 2010

The structural anisotropy of Fe–Si–B–Nb–Cu nanocrystalline alloys annealed under tensile stress was studied by x-ray diffraction techniques with transmission geometry. A clear difference was observed in the peak positions of the Fe–Si crystals under two different conditions: with the diffraction vector parallel or perpendicular to the applied stress. The strains calculated from the anisotropy of the peak positions show a linear response to the applied stress, independent of Si content, indicating that the observed structural anisotropy is due to a quenching of the elastic strain, not in the directional ordering of the Fe–Si pair. The induced magnetic anisotropy energy is well explained by the residual strains and their magnetostrictions.
Waves and negative refraction in magnetized plasma with ferrite grains
Authors: Mesfin Belayneh , Mal'nev V. N. , Martysh E. V. , Rapoport Yu. G.
Published: November 2010

The propagation of high frequency electromagnetic waves in the low temperature magnetized plasma with ferrite grains (MPFG) is considered. The dispersion properties of MPFG are simultaneously characterized by the permittivity and permeability tensors. The dispersion of the permeability is caused by the high frequency magnetization of the grain subsystem and is important in the vicinity of the frequency of ferromagnetic resonance, which coincides with the electron cyclotron frequency ωc. The MPFG becomes transparent for the waves that cannot propagate in conventional electron-ion magnetized plasma. It is shown that the refractive index of the extraordinary wave propagating along and transversal to the external magnetic field with frequencies close to ωc can be negative as well as positive. For the typical parameters of MPFG, the group velocity of this wave is much smaller than the speed of light. The refractive index of MPFG matched with the free space is obtained for waves propagating at an arbitrary angle with respect to the applied constant magnetic field. The results obtained clearly shows that the dispersion properties of MPFG have all the known properties of left-handed media in the vicinity of ωc.
Arbitrary amplitude kinetic Alfvén solitary waves and double layers in a non-Maxwellian plasma
Authors: Gogoi Runmoni , Khan Manoranjan
Published: November 2010

To investigate the existence of kinetic Alfvén wave solitons, warm adiabatic ions and kappa distributed electrons are considered in a magnetized plasma. The kappa distribution (having the spectral index κ) is a velocity distribution that has a high energy tail but approaches the Maxwellian when κ→∞. In this work, by using the Sagdeev pseudopotential method, an exact analytical expression for arbitrary amplitude solitary kinetic Alfvén wave is derived. For different sets of plasma parameter values, the Sagdeev potential Ψ (ϕ) has been calculated numerically. It is found that the spectral index κ plays a significant role in determining the shape and size of the solitary waves and double layers. Also, it is observed that both compressive solitary waves and double layers exist depending on the values of different plasma parameters.
Electrohydrodynamics of drops in strong uniform dc electric fields
Authors: Salipante Paul F. , Vlahovska Petia M.
Published: November 2010

Drop deformation in an uniform dc electric field is a classic problem. The pioneering work of Taylor demonstrated that for weakly conducting media, the drop fluid undergoes a toroidal flow and the drop adopts a prolate or oblate spheroidal shape, the flow and shape being axisymmetrically aligned with the applied field. However, recent studies have revealed a nonaxisymmetric rotational flow in strong fields, similar to the rotation of solid dielectric particles observed by Quincke in the 19th century. We present a systematic experimental study of this phenomenon, which highlights the importance of charge convection along the drop surface. The critical electric field, drop inclination angle, and rate of rotation are measured. We find that for small, high viscosity drops, the threshold field strength is well approximated by the Quincke rotation criterion. Reducing the viscosity ratio shifts the onset for rotation to stronger fields. The drop inclination angle increases with field strength. The rotation rate is approximately given by the inverse Maxwell–Wagner polarization time. Novel features are also observed such as a hysteresis in the tilt angle for large low-viscosity drops.
Confinement of electron plasma by levitating dipole magnet
Authors: Saitoh H. , Yoshida Z. , Morikawa J. , Yano Y. , Hayashi H. , Mizushima T. , Kawai Y. , Kobayashi M. , Mikami H.
Published: November 2010

A recent experiment on the Ring Trap 1 device has demonstrated long-term (exceeding 300 s) confinement of non-neutral (pure electron) plasma in a dipole magnetic field; particles diffuse inward, steepening the density gradient and self-organizing into a stable vortex structure [Z. Yoshida et al., Phys. Rev. Lett. 104, 235004 (2010)]. In this study, the internal structures of the plasma are experimentally investigated, and it is shown that the observations are consistent with rigidly rotating charged particle clump. The radial profiles of electrostatic potential and electron density consistently show that the drift velocity has homogeneous angular frequency in the confinement region. The electrostatic fluctuations also rotate rigidly with a phase velocity that agrees with the drift velocity. The magnetospheric system should have a wide application in confining single-species and even multiple-species charged particles.
Comparison of directly and indirectly measured electrocaloric effect in relaxor ferroelectric polymers
Authors: Lu S. G. , Rožič B. , Zhang Q. M. , Kutnjak Z. , Pirc R. , Lin Minren , Li Xinyu , Gorny Lee
Published: November 2010

We report the directly measured electrocaloric effect (ECE) (the adiabatic temperature change ΔT) of relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer and its blend with poly(vinylidene fluoride-chlorotrifluoroethylene). The results show that the directly measured ΔT in the relaxor terpolymer is much larger than that deduced from Maxwell relation and that the relaxor terpolymer possesses a giant ECE at room temperature. The large difference between the directly measured ΔT and that deduced indicates that the Maxwell relation, which is derived for ergodic systems, is not suitable for deducing ECE in the relaxor ferroelectric polymers, which are nonergodic (polar-glass) material systems.
On fluid flows in precessing spheres in the mantle frame of reference
Authors: Zhang Keke , Chan Kit H. , Liao Xinhao
Published: November 2010

We investigate, through both asymptotic and numerical analysis, precessionally driven flows of a homogeneous fluid confined in a spherical container that rotates rapidly with angular velocity Ω and precesses slowly with angular velocity Ωp about an axis that is fixed in space. The precessionally driven flows are primarily characterized by two dimensionless parameters: the Ekman number E providing the measure of relative importance between the viscous force and the Coriolis force, and the Poincaré number Po quantifying the strength of the Poincaré forcing. When E is small but fixed and |Po| is sufficiently small, we derive a time-dependent asymptotic solution for the weakly precessing flow that satisfies the nonslip boundary condition in the mantle frame of reference. No prior assumption about the spatial-temporal structure of the precessing flow is made in the asymptotic analysis. A solvability condition is derived to determine the spatial structure of the precessing flow, via a selection from a complete spectrum of spherical inertial modes in the mantle frame. The weakly precessing flow within the bulk of the fluid is characterized by an inertial wave moving retrogradely. Direct numerical simulation of the same problem in the same frame of reference shows a satisfactory agreement between the time-dependent asymptotic solution and the nonlinear numerical simulation for sufficiently small Poincaré numbers.
Magnetic and electronic switching properties of photochromic diarylethene with two nitronyl nitroxides
Authors: Zhu L. , Yao K. L. , Liu Z. L.
Published: November 2010

Magnetic and electronic switching properties of single photochromic diarylethene with two nitronyl nitroxides sandwiched between two gold surfaces for closed and open configurations were investigated theoretically. Apart from the negative magnetoresistance effect in closed configuration, the negative differential resistance behavior in parallel state is also attained, which are potential for electronic applications. In addition, when using Br and H to substitute F atoms in the peripheral of cyclopentene, the on-off ratios are much smaller than that of the F-ligand one.
Propagation of broadband terahertz pulses through a dense-magnetized-collisional-bounded plasma layer
Authors: Yuan Chengxun , Zhou Zhongxiang , Xiang Xiaoli , Sun Hongguo , Pu Shaozhi
Published: November 2010

The terahertz characteristics of a dense-magnetized-collisional-bounded plasma under normal incident are analyzed in this study, which is of practical significance in plasma diagnostics with electromagnetic waves. We theoretically calculate the reflection, absorption, and transmission coefficients for right- and left-handed polarized terahertz waves through a uniform, magnetized, and collisional plasma slab bounded by lossless transparent walls. The power absorption spectra in the frequency range of 0.1–2 THz are given with strong external magnetic fields and different plasma parameters such as plasma density and collisional frequency. Our numerical result is consistent with Jamison’s experimental result. It is found that plasma absorption is mainly caused by the collisional absorption and electron cyclotron resonance. Furthermore, the absorption heavily depends on the polarization mode of the terahertz waves when the external magnetic field B is high enough that the election gyrofrequency is near the incident wave frequency. The relationships between the corresponding parameters of the problem are studied numerically.
Motion of cancer-cell lamellipodia perturbed by laser light of two wavelengths
Authors: Xiao Jian-Long , Hsu Tsi-Hsuan , Hsu Ping-Yu , Yang Wei-Jie , Kuo Po-Ling , Lee Chau-Hwang
Published: November 2010

We employ 405 and 1064 nm laser light to perturb the motions of lung cancer cell lamellipodia. The 405 nm light causes lamellipodial retractions while the 1064 nm light enhances protrusions. With the observation of actin distributions in the lamellipodia, we find that the 1064 nm laser light increases the density of actin near the illuminated site, while the 405 nm light reduces the actin distribution.
FePdB layer for perpendicular magnetic tunnel junctions
Authors: Choi Gyung-Min , Min Byoung-Chul , Shin Kyung-Ho
Published: November 2010

We have investigated the feasibility of using FePdB alloy layers for perpendicular magnetic tunnel junctions (p-MTJs). The perpendicular magnetic anisotropy (PMA) of FePdB films is obtained by depositing amorphous Fe40Pd40B20 layers on proper templates and by postannealing. An FePdB film on a thick Pt (001) underlayer has a PMA energy (Ku) of 4.9×106 erg/cm3, and an FePdB layer sandwiched by two thin MgO (001) layers shows a Ku of 3.7×106 erg/cm3. A double barrier p-MTJ with an FePdB middle layer shows a tunnel magnetoresistance of 6.8%.
An in situ tunable radio-frequency quantum point contact
Authors: Müller T. , Küng B. , Hellmüller S. , Studerus P. , Ensslin K. , Ihn T. , Reinwald M. , Wegscheider W.
Published: November 2010

Incorporating a variable capacitance diode into a radio-frequency (rf) matching circuit allows us to in situ tune the resonance frequency of a rf quantum point contact, increasing the versatility of the latter as a fast charge sensor of a proximal quantum circuit. The performance of this method is compared in detail to conventional low-frequency charge detection. The approach is also applicable to other rf-detection schemes, such as rf single electron transistor circuits.
Representing ‘Things to Come’: Feeling the Visions of Future Technologies
Authors: Kinsley Samuel
Published: November 2010

Visions of the future pervade the development of computing technologies. This paper addresses the production of embodied anticipation inherent to video representations of technological futures. The focus of inquiry is videos produced by HP Labs and Microsoft to illustrate future worlds of technological experience. The principal concern is that these videos, as visual content and artefacts, are performative in their evocation of bodily attunement to prospective technology use. In the first section I analyse the visually oriented logics that situate the videos. In the second section I investigate the evocation of prospective interaction with technologies by drawing upon and developing conceptualisations of affect and the technological unconscious. I argue there is a politics of anticipation of technical futures, understood as the multiple ways in which technological futurity is encoded and, in particular, the relation this has to embodied understandings of the world.
The Geodemographics of Educational Progression and their Implications for Widening Participation in Higher Education
Authors: Singleton Alex D
Published: November 2010

This paper addresses our ability to analyse progression rates into UK Higher Education (HE) using a range of data available at the individual and neighbourhood levels. The then Department for Children, Schools and Families has recently released data which make it possible to profile national patterns of student educational progression from post-compulsory schooling through to university. However, the linked records lack detailed socioeconomic information, and thus a geodemographic classification is used to analyse the flows of students from different sociospatial backgrounds into the HE system. Rates of progression are shown to vary greatly between these groups, and a disaggregation of HE participants by courses of study demonstrates that the abilities of institutions to attract students from different backgrounds will be constrained by the mix of their course offerings.
Heat Waves and Cold Spells: An Analysis of Policy Response and Perceptions of Vulnerable Populations in the UK
Authors: Wolf Johanna , Adger W Neil , Lorenzoni Irene
Published: November 2010

Heat waves and cold spells pose ongoing seasonal risks to the health and well-being of vulnerable individuals. Current attempts to address these risks in the UK are implemented through fuel-poverty strategies and heat-wave planning. This paper examines evidence from the UK on whether heat waves and cold spells are addressed differently by public policy in the UK given that risks are mediated by similar perceptions that shape behavioural responses by vulnerable individuals. It is based on a review of UK policies and on a qualitative interview study of risk perceptions of elderly people as a primary identified vulnerable group to these weather extremes. The study involved in-depth repeat interviews with fifteen elderly respondents in summer 2007 and winter 2008 in Norwich (UK). Results suggest that neither heat risks nor cold risks are perceived as personal risks and therefore planned preventive measures by individuals are largely elusive. Cold risk policy reduces vulnerability; policy related to heat relies on early warning and public information programmes and does not reduce underlying vulnerability. Both types of policies largely ignore public perceptions of risks and could benefit from a more cohesive approach, supporting similar measures to reduce seasonal vulnerability.
Environmental Justice and Older Age: Consideration of a Qualitative Neighbourhood-based Study
Authors: Day Rosie
Published: November 2010

Environmental justice discourses have engaged far less with age as a significant factor associated with injustice than with other sociodemographic signifiers such as race and class. In this paper I explore material from an empirical study conducted with older people in three neighbourhoods in Scotland, using a framework based on environmental and social justice theory. The analysis highlights various means by which older people can be excluded from and within urban environments and links these with justice narratives of distribution, procedural inclusion, and recognition. Consideration of age enriches environmental justice theory, but also highlights how it needs to connect more fully with wider social justice theory.
Ethnic Segregation and Performance Inequality in the Swedish School System: A Regional Perspective
Authors: Andersson Eva , Östh John , Malmberg Bo
Published: November 2010

Sweden is today an immigrant country with more than 14% foreign born. An increasing share of the immigrants comes from non-European countries. This implies that Sweden has been transformed from an ethnically homogenous country into a country with a large visible minority. In this paper we survey the effect of this change on school segregation. Building on Schelling's model for residential segregation, we argue that establishment of a visible minority has triggered a process of school segregation that in some respects can be compared with the developments in the United States. In order to test the validity of a Schelling-type process in Swedish schools we compare segregation levels in regions with different shares of visible minority students. We use data from the PISA 2003 survey in combination with register data on the ethnic composition of student population in different parts of Sweden. We find that school segregation is higher in regions with a large visible-minority population. We also find that, controlling for student background, there are smaller differences in performance across schools in regions with low shares of minority students.
Knowledge, Space, and Economic Governance: The Implications of Knowledge-Based Commodity Chains for Less-Favoured Regions
Authors: Birch Kean , Cumbers Andrew
Published: November 2010

As an increasing amount of manufacturing employment has relocated to the Global South, the developed economies of the Global North have sought new ways of competing within the global economy. In part they have done so through the promotion of the so-called ‘knowledge-based economy’ (KBE) constituted by innovations and new markets in high-tech industries like telecommunication, information technology, and the life sciences. A KBE discourse has become a central plank of policy at the national and European levels. This raises a series of questions, however, about the ability of less-favoured regions to compete for knowledge-based activities, given existing conditions of uneven development and the unequal distribution of knowledge assets between regions in the developed economies. In this respect, particularly critical to regional outcomes are the forms of economic coordination and governance that emerge in knowledge-based commodity chains. Engaging with recent debates concerned with global commodity chains, this paper builds on the idea that economic governance is increasingly alliance driven, entailing a diverse set of geographies and trust-based relationships between a variety of organisations that include small innovative firms, large multinational corporations, and national (and subnational) policy actors. These forms of governance open up new opportunities for less-favoured regions, although these continue to be constrained by already existing power relations between regions.
On (Not) Forgetting Families: Family Spaces and Spacings in Birzeit, Palestine
Authors: Harker Christopher
Published: November 2010

This paper is a response to Valentine's recent suggestion that the family is an absent presence within geography. Persuaded by her argument, I explore other disciplinary approaches to theorizing families, and, in particular, how discursive appropriations of ‘the family’ and theories of family practices can enlarge our understandings of what families are and how they are done. I then argue that geographers can contribute to such studies by exploring the spaces and spacings that coconstitute family subjectivities. I put these ideas to work in the context of Birzeit, Palestine, where, I argue, particular family spaces and spacings offer more nuanced understandings of this place which challenge limited discursive constructions of the ‘Arab family’ and the ‘Western family’. I situate these theoretical maneuvers within broader geographies of intimacies, while arguing that there is still a great deal of work to be done to further spatialize our understandings of families.
Turban snails as habitat for foliose algae: contrasting geographical patterns in species richness
Authors: Wernberg Thomas , Tuya Fernando , Thomsen Mads S. , Kendrick Gary A.
Published: November 2010

Understanding patterns of species richness is a major goal for ecologists, especially in space-limited habitats where many organisms live on top of others (epibiosis, e.g. by algae growing on gastropods in marine environments). We tested the hypotheses that species richness of epiflora on the gastropod Turbo torquatus would not differ between regions with similarly rich algal floras, and that epifloral richness would increase with increasing gastropod size. Macroalgal floras of Hamelin Bay (HB), Marmion (M), Jurien Bay (JB) and Kalbarri (K), Western Australia, ranged from ∼20 to 40 species reef–1 (JB = HB = M ≥ K). Epiflora on small T. torquatus (shell area <150 cm2) did not differ among regions but epifloral richness increased with increasing basibiont size. Large T. torquatus (>150 cm2) were only found in Hamelin Bay and Marmion, where epifloral richness differed substantially. Epifloral richness was positively related to basibiont size in Marmion but not in Hamelin Bay. However, densities of patellid limpets on large T. torquatus were ∼4× higher in Hamelin Bay than in Marmion, implying that limpet grazing suppresses epifloral richness. Epifloral richness on turbinids is not simply associated with regional species pools or gastropod size; rather, biological interactions at the scale of individual basibionts apparently govern broad scale patterns of epibiosis.
Patterns of demography for rocky-shore, intertidal invertebrates approaching their geographical range limits: tests of the abundant-centre hypothesis in south-eastern Australia
Authors: Hidas Eszter Z. , Ayre David J. , Minchinton Todd E.
Published: November 2010

The abundant-centre hypothesis predicts that species' abundances peak at the centre of their geographical ranges and decline gradually towards their range limits. We tested predictions of this hypothesis for three rocky-shore, intertidal invertebrates with planktonic larvae (the whelk, Morula marginalba, the snail, Afrolittorina pyramidalis, and the barnacle, Tesseropora rosea) by quantifying their patterns of abundance and size, and inferring pulses of recruitment from size-frequency distributions, at multiple spatial scales spanning a 600-km region in south-eastern Australia and encompassing roughly the southern third of their geographical ranges. At the regional scale, abundances for all species were, as predicted, dramatically lower at their range limits. This decline was not gradual, however, because there were large variations in abundance at smaller spatial scales, and abrupt declines at the south-eastern corner of Australia. Size did not change towards the range limit for any species, but size-frequency distributions suggested a decline in the frequency of recruitment events at the range limit for T. rosea. We conclude that the abundant-centre hypothesis is not an appropriate model for abundance distributions of benthic marine invertebrates with planktonic larvae, because of the vagaries of dispersal and recruitment interacting with complex current patterns along non-uniform coastlines.
A cost-effective technique for measuring relative water movement for studies of benthic organisms
Authors: Evans S. N. , Abdo D. A.
Published: November 2010

Because water movement has been shown to affect the structure and community composition of the marine environment, the ability to monitor and record water movement is important in marine research. The present study describes a cost-effective, repeatable method for measuring relative water movement both spatially and temporally with an ‘off the shelf’ accelerometer. The technique involves suspending the accelerometer in the water column near the seafloor; movement of the apparatus by the water column is recorded as changes in acceleration relative to Earth’s gravity. Water movement recorded by this technique was highly correlated (r2 = 0.822, P < 0.01) with measurements from a recognised commercial device (wave-rider buoy). Deployment tests revealed that total wave height showed the most significant relationship (r2 = 0.83) with data from the technique. Use of the technique in a field situation allowed the detection of small-scale water-movement patterns within the Houtman Abrolhos Islands off Western Australia, and the quantification of the relative differences in water movement among coral-monitoring sites. Overall, the technique is a cost-effective way of obtaining basic long-term temporal water-movement data at small spatial scales (less than hundreds of metres).
Historic and current genetic population structure in two pond-dwelling macroinvertebrates in massively altered Australian woodland landscapes
Authors: Lada Hania , Neville Carla , Lacey Briarna , Mac Nally Ralph , Lake P. Sam , Taylor Andrea C.
Published: November 2010

Aquatic ecosystems around the world have been massively altered through vegetation clearance and changed flow regimes accompanying agricultural development. Impacts may include disrupted dispersal for aquatic species. We investigated this in lentic (standing) waterbodies in agricultural and predominantly forested landscapes of the box-ironbark region of central Victoria, Australia. We hypothesised that higher representation in forested than agricultural landscapes (i.e. ‘forest-bias’) for a species may reflect an ability to disperse more easily through the former, resulting in lower genetic structure in forested than in agricultural landscapes. Conversely, ‘cosmopolitan’ species would show no difference in genetic structure between landscape types. Molecular genetic analyses of a forest-biased diving beetle, Necterosoma wollastoni, and a cosmopolitan waterboatman, Micronecta gracilis, revealed the following, for both species: (1) no evidence for long-term barriers to gene flow in the region, (2) lack of contemporary genetic differentiation over 30 000 km2 and (3) random distribution of related genotypes in space, implying that neither forest nor farmland inhibits their dispersal in a concerted fashion. Taken together, these results indicate very high gene flow and dispersal in the past and present for both these species. Massive landscape change may have little impact on movement patterns of lentic invertebrates that have evolved high dispersal capabilities.
Opportunities for reducing greenhouse gas emissions in tropical peatlands
Authors: Murdiyarso D. , Hergoualc’h K. , Verchot L. V.
Published: November 2010

The upcoming global mechanism for reducing emissions from deforestation and forest degradation in developing countries should include and prioritize tropical peatlands. Forested tropical peatlands in Southeast Asia are rapidly being converted into production systems by introducing perennial crops for lucrative agribusiness, such as oil-palm and pulpwood plantations, causing large greenhouse gas (GHG) emissions. The Intergovernmental Panel on Climate Change Guidelines for GHG Inventory on Agriculture, Forestry, and Other Land Uses provide an adequate framework for emissions inventories in these ecosystems; however, specific emission factors are needed for more accurate and cost-effective monitoring. The emissions are governed by complex biophysical processes, such as peat decomposition and compaction, nutrient availability, soil water content, and water table level, all of which are affected by management practices. We estimate that total carbon loss from converting peat swamp forests into oil palm is 59.4 ± 10.2 Mg of CO
2
per hectare per year during the first 25 y after land-use cover change, of which 61.6% arise from the peat. Of the total amount (1,486 ± 183 Mg of CO
2
per hectare over 25 y), 25% are released immediately from land-clearing fire. In order to maintain high palm-oil production, nitrogen inputs through fertilizer are needed and the magnitude of the resulting increased N
2
O emissions compared to CO
2
losses remains unclear.
Apparent failure of the Born–Oppenheimer static surface model for vibrational excitation of molecular hydrogen on copper
Authors: Kroes Geert-Jan , Díaz Cristina , Pijper Ernst , Olsen Roar A. , Auerbach Daniel J.
Published: November 2010

The accuracy of dynamical models for reactive scattering of molecular hydrogen, H
2
, from metal surfaces is relevant to the validation of first principles electronic structure methods for molecules interacting with metal surfaces. The ability to validate such methods is important to progress in modeling heterogeneous catalysis. Here, we study vibrational excitation of H
2
on Cu(111) using the Born–Oppenheimer static surface model. The potential energy surface (PES) used was validated previously by calculations that reproduced experimental data on reaction and rotationally inelastic scattering in this system with chemical accuracy to within errors ≤ 1 kcal/mol ≈ 4.2 kJ/mol [Díaz C, et al. (2009)
Science
326:832–834]. Using the same PES and model, our dynamics calculations underestimate the contribution of vibrational excitation to previously measured time-of-flight spectra of H
2
scattered from Cu(111) by a factor 3. Given the accuracy of the PES for the experiments for which the Born–Oppenheimer static surface model is expected to hold, we argue that modeling the effect of the surface degrees of freedom will be necessary to describe vibrational excitation with similar high accuracy.
National housing and impervious surface scenarios for integrated climate impact assessments
Authors: Bierwagen Britta G. , Theobald David M. , Pyke Christopher R. , Choate Anne , Groth Philip , Thomas John V. , Morefield Philip
Published: November 2010

Understanding the impacts of climate change on people and the environment requires an understanding of the dynamics of both climate and land use/land cover changes. A range of future climate scenarios is available for the conterminous United States that have been developed based on widely used international greenhouse gas emissions storylines. Climate scenarios derived from these emissions storylines have not been matched with logically consistent land use/cover maps for the United States. This gap is a critical barrier to conducting effective integrated assessments. This study develops novel national scenarios of housing density and impervious surface cover that are logically consistent with emissions storylines. Analysis of these scenarios suggests that combinations of climate and land use/cover can be important in determining environmental conditions regulated under the Clean Air and Clean Water Acts. We found significant differences in patterns of habitat loss and the distribution of potentially impaired watersheds among scenarios, indicating that compact development patterns can reduce habitat loss and the number of impaired watersheds. These scenarios are also associated with lower global greenhouse gas emissions and, consequently, the potential to reduce both the drivers of anthropogenic climate change and the impacts of changing conditions. The residential housing and impervious surface datasets provide a substantial first step toward comprehensive national land use/land cover scenarios, which have broad applicability for integrated assessments as these data and tools are publicly available.
β-Blocker drugs mediate calcium signaling in native central nervous system neurons by β-arrestin–biased agonism
Authors: Tzingounis Anastassios V. , von Zastrow Mark , Yudowski Guillermo A.
Published: November 2010

G protein-coupled receptors (GPCRs), the largest family of signaling receptors expressed in the CNS, mediate the neuropsychiatric effects of a diverse range of clinically relevant drugs. It is increasingly clear that GPCRs can activate distinct G protein-dependent and -independent transduction pathway(s), and that certain drugs differ in the ability to regulate distinct signaling mechanisms linked to the same receptors. A fundamental question in neuropharmacology is whether such “biased agonism” occurs in physiologically relevant neurons and with endogenous receptors. Here we show that propranolol and carvedilol, two β-blocker drugs that inhibit β-adrenergic signaling via heterotrimeric G proteins, function in hippocampal pyramidal neurons as potent and selective activators of an alternate receptor-linked calcium signaling pathway mediated by β-arrestin-2 and ERK1/2. Our results support the emerging view of β-arrestin–biased agonism as a significant mechanism of drug action and do so in CNS-derived neurons expressing only native receptors.
Silane plus molecular hydrogen as a possible pathway to metallic hydrogen
Authors: Yao Yansun , Klug Dennis D.
Published: November 2010

The high-pressure behavior of silane, SiH
4
, plus molecular hydrogen was investigated using a structural search method and ab initio molecular dynamics to predict the structures and examine the physical origin of the pressure-induced drop in hydrogen intramolecular vibrational (vibron) frequencies. A structural distortion is predicted at 15 GPa from a slightly strained fcc cell to a rhombohedral cell that involves a small volume change. The predicted equation of state and the pressure-induced drop in the hydrogen vibron frequencies reproduces well the experimental data (Strobel TA, Somayazulu M, Hemley RJ (2009)
Phys Rev Lett
103:065701). The bond weakening in H
2
is induced by intermolecular interactions between the H
2
and SiH
4
molecules. A significant feature of the high-pressure structures of SiH
4
(H
2
)
2
is the dynamical behavior of the H
2
molecules. It is found that H
2
molecules are rotating in this pressure range whereas the SiH
4
molecules remain rigid. The detailed nature of the interactions of molecular hydrogen with SiH
4
in SiH
4
(H
2
)
2
is therefore strongly influenced by the dynamical behavior of the H
2
molecules in the high-pressure structure. The phase with the calculated structure is predicted to become metallic near 120 GPa, which is significantly lower than the currently suggested pressure for metallization of bulk molecular hydrogen.
Multiple tail domain interactions stabilize nonmuscle myosin II bipolar filaments
Authors: Ricketson Derek , Johnston Christopher A. , Prehoda Kenneth E.
Published: November 2010

Contractile force transduction by myosin II derives from its assembly into bipolar filaments. The coiled-coil tail domain of the myosin II heavy chain mediates filament assembly, although the mechanism is poorly understood. Tail domains contain an alternating electrostatic repeat, yet only a small region of the tail (termed the “assembly domain”) is typically required for assembly. Using computational analysis, mutagenesis, and electron microscopy we discovered that the assembly domain does not function through self-interaction as previously thought. Rather, the assembly domain acts as a unique, positively charged interaction surface that can stably contact multiple complementary, negatively charged surfaces in the upstream tail domain. The relative affinities of the assembly domain to each complementary interaction surface sets the characteristic molecular staggers observed in myosin II filaments. Together these results explain the relationship between the charge repeat and assembly domain in stabilizing myosin bipolar filaments.
Association mapping of local climate-sensitive quantitative trait loci in
Arabidopsis thaliana
Authors: Li Yan , Huang Yu , Bergelson Joy , Nordborg Magnus , Borevitz Justin O.
Published: November 2010

Flowering time (FT) is the developmental transition coupling an internal genetic program with external local and seasonal climate cues. The genetic loci sensitive to predictable environmental signals underlie local adaptation. We dissected natural variation in FT across a new global diversity set of 473 unique accessions, with >12,000 plants across two seasonal plantings in each of two simulated local climates, Spain and Sweden. Genome-wide association mapping was carried out with 213,497 SNPs. A total of 12 FT candidate quantitative trait loci (QTL) were fine-mapped in two independent studies, including 4 located within ±10 kb of previously cloned FT alleles and 8 novel loci. All QTL show sensitivity to planting season and/or simulated location in a multi-QTL mixed model. Alleles at four QTL were significantly correlated with latitude of origin, implying past selection for faster flowering in southern locations. Finally, maximum seed yield was observed at an optimal FT unique to each season and location, with four FT QTL directly controlling yield. Our results suggest that these major, environmentally sensitive FT QTL play an important role in spatial and temporal adaptation.
miR-200 family and targets, ZEB1 and ZEB2, modulate uterine quiescence and contractility during pregnancy and labor
Authors: Renthal Nora E. , Chen Chien-Cheng , Williams Koriand’r C. , Gerard Robert D. , Prange-Kiel Janine , Mendelson Carole R.
Published: November 2010

Throughout most of pregnancy, uterine quiescence is maintained by increased progesterone receptor (PR) transcriptional activity, whereas spontaneous labor is initiated/facilitated by a concerted series of biochemical events that activate inflammatory pathways and have a negative impact on PR function. In this study, we uncovered a previously undescribed regulatory pathway whereby micro-RNAs (miRNAs) serve as hormonally modulated and conserved mediators of contraction-associated genes in the pregnant uterus in the mouse and human. Using miRNA and gene expression microarray analyses of uterine tissues, we identified a conserved family of miRNAs, the miR-200 family, that is highly induced at term in both mice and humans as well as two coordinately down-regulated targets, zinc finger E-box binding homeobox proteins ZEB1 and ZEB2, which act as transcriptional repressors. We also observed up-regulation of the miR-200 family and down-regulation of ZEB1 and ZEB2 in two different mouse models of preterm labor. We further demonstrated that ZEB1 is directly up-regulated by the action of progesterone (P
4
)/PR at the
ZEB1
promoter. Excitingly, we observed that ZEB1 and ZEB2 inhibit expression of the contraction-associated genes, oxytocin receptor and connexin-43, and block oxytocin-induced contractility in human myometrial cells. Together, these findings implicate the miR-200 family and their targets, ZEB1 and ZEB2, as unique P
4
/PR-mediated regulators of uterine quiescence and contractility during pregnancy and labor and shed light on the molecular mechanisms involved in preterm birth.
Fluidization of tissues by cell division and apoptosis
Authors: Ranft Jonas , Basan Markus , Elgeti Jens , Joanny Jean-François , Prost Jacques , Jülicher Frank
Published: November 2010

During the formation of tissues, cells organize collectively by cell division and apoptosis. The multicellular dynamics of such systems is influenced by mechanical conditions and can give rise to cell rearrangements and movements. We develop a continuum description of tissue dynamics, which describes the stress distribution and the cell flow field on large scales. In the absence of division and apoptosis, we consider the tissue to behave as an elastic solid. Cell division and apoptosis introduce stress sources that, in general, are anisotropic. By combining cell number balance with dynamic equations for the stress source, we show that the tissue effectively behaves as a viscoelastic fluid with a relaxation time set by the rates of division and apoptosis. If the system is confined in a fixed volume, it reaches a homeostatic state in which division and apoptosis balance. In this state, cells undergo a diffusive random motion driven by the stochasticity of division and apoptosis. We calculate the expression for the effective diffusion coefficient as a function of the tissue parameters and compare our results concerning both diffusion and viscosity to simulations of multicellular systems using dissipative particle dynamics.
M
3
-muscarinic receptor promotes insulin release via receptor phosphorylation/arrestin-dependent activation of protein kinase D1
Authors: Kong Kok Choi , Butcher Adrian J. , McWilliams Phillip , Jones David , Wess Jürgen , Hamdan Fadi F. , Werry Tim , Rosethorne Elizabeth M. , Charlton Steven J. , Munson Sarah E. , Cragg Hannah A. , Smart Alison D. , Tobin Andrew B.
Published: November 2010

The activity of G protein-coupled receptors is regulated via hyper-phosphorylation following agonist stimulation. Despite the universal nature of this regulatory process, the physiological impact of receptor phosphorylation remains poorly studied. To address this question, we have generated a knock-in mouse strain that expresses a phosphorylation-deficient mutant of the M
3
-muscarinic receptor, a prototypical G
q/11
-coupled receptor. This mutant mouse strain was used here to investigate the role of M
3
-muscarinic receptor phosphorylation in the regulation of insulin secretion from pancreatic islets. Importantly, the phosphorylation deficient receptor coupled to G
q/11
-signaling pathways but was uncoupled from phosphorylation-dependent processes, such as receptor internalization and β-arrestin recruitment. The knock-in mice showed impaired glucose tolerance and insulin secretion, indicating that M
3
-muscarinic receptors expressed on pancreatic islets regulate glucose homeostasis via receptor phosphorylation-/arrestin-dependent signaling. The mechanism centers on the activation of protein kinase D1, which operates downstream of the recruitment of β-arrestin to the phosphorylated M
3
-muscarinic receptor. In conclusion, our findings support the unique concept that M
3
-muscarinic receptor-mediated augmentation of sustained insulin release is largely independent of G protein-coupling but involves phosphorylation-/arrestin-dependent coupling of the receptor to protein kinase D1.