bluuebunny/crossref_metadata_2025 huggingface dataset:
The heat capacity of nitrogen chain in grooves of single-walled carbon nanotube bundles
Authors: Bagatskii M. I. , Barabashko M. S. , Sumarokov V. V.
Published: May 2013

The heat capacity of bundles of closed-cap single-walled carbon nanotubes with one-dimensional chains of nitrogen molecules adsorbed in the grooves has been first experimentally studied at temperatures from 2 to 40 K using an adiabatic calorimeter. The contribution of nitrogen CN2 to the total heat capacity has been separated. In the region 2–8 K the behavior of the curve CN2(T) is qualitatively similar to the theoretical prediction of the phonon heat capacity of 1D chains of Kr atoms localized in the grooves of SWNT bundles. Below 3 K the dependence CN2(T) is linear. Above 8 K the dependence CN2(T) becomes steeper in comparison with the case of Kr atoms. This behavior of the heat capacity CN2(T) is due to the contribution of the rotational degrees of freedom of the N2 molecules.
A framework for epistemic uncertainty quantification of turbulent scalar flux models for Reynolds-averaged Navier-Stokes simulations
Authors: Gorlé C. , Iaccarino G.
Published: May 2013

Reynolds-averaged Navier-Stokes (RANS) simulations are a practical approach for solving complex multi-physics turbulent flows, but the underlying assumptions of the turbulence models introduce errors and uncertainties in the simulation outcome. The flow in scramjet combustors is an example of such a complex flow and the accurate characterization of safety and operability limits of these engines using RANS simulations requires an assessment of the model uncertainty. The objective of this paper is to present a framework for the epistemic uncertainty quantification of turbulence and mixing models in RANS simulations. The capabilities of the methodology will be demonstrated by performing simulations of the mixing of an underexpanded jet in a supersonic cross flow, which involves many flow features observed in scramjet engines. The fundamental sources of uncertainty in the RANS simulations are the models used for the Reynolds stresses in the momentum equations and the turbulent scalar fluxes in the scalar transport equations. The methodology consists in directly perturbing the modeled quantities in the equations, thereby establishing a method that is completely independent of the initial model form to overcome the limitations of traditional sensitivity studies. The perturbations are defined in terms of the decomposed Reynolds stress tensor, i.e., the tensor magnitude and the eigenvalues and eigenvectors of the normalized anisotropy tensor. The turbulent scalar fluxes are perturbed by using the perturbed Reynolds stresses in a generalized gradient diffusion model formulation and by changing the model constant. The perturbations were parameterized based on a comparison between the Reynolds stresses obtained from a baseline RANS simulation and those obtained from a large-eddy simulation database. Subsequently an optimization problem was solved, varying the parameters in the perturbation functions to maximize a quantity of interest that quantifies the downstream mixing. The result encompasses the value for the quantity of interest obtained from the LES database. It is shown that a traditional sensitivity study, in which the turbulent Schmidt number is varied, cannot capture this uncertainty, which further demonstrates the effectiveness of the proposed approach.
Representations of the twisted affine Nappi-Witten algebras
Authors: Chen Xue , Jiang Cuipo , Jiang Qifen
Published: May 2013

In this paper, we study Verma modules for the twisted affine Nappi-Witten algebras \documentclass[12pt]{minimal}\begin{document}$\widehat{H}_{4}[\tau _{1}]$\end{document}Ĥ4[τ1] and \documentclass[12pt]{minimal}\begin{document}$\widehat{H}_{4}[\tau _{2}]$\end{document}Ĥ4[τ2]. The vertex operator representations of the affine Nappi-Witten algebras \documentclass[12pt]{minimal}\begin{document}$\widehat{H}_{4}[\tau _{1}]$\end{document}Ĥ4[τ1], \documentclass[12pt]{minimal}\begin{document}$\widehat{H}_{4}[\tau _{2}]$\end{document}Ĥ4[τ2], and \documentclass[12pt]{minimal}\begin{document}$\widehat{H}_{4}$\end{document}Ĥ4 are also constructed. Furthermore, the irreducible non-zero level quasifinite modules over the affine Nappi-Witten algebras are classified.
Plasmonic light yield enhancement of a liquid scintillator
Authors: Bignell Lindsey J. , Mume Eskender , Jackson Timothy W. , Lee George P.
Published: May 2013

We demonstrate modifications to the light yield properties of an organic liquid scintillator due to the localization of the tertiary fluorophore component to the surface of Ag-core silica-shell nanoparticles. We attribute this enhancement to the near-field interaction of Ag nanoparticle plasmons with these fluor molecules. The scintillation light yield enhancement is shown to be equal to the fluorescence enhancement within measurement uncertainties. With a suitable choice of plasmon energy and scintillation fluor, this effect may be used to engineer scintillators with enhanced light yields for radiation detection applications.
Low-temperature properties of monoalcohol glasses and crystals
Authors: Ramos M. A. , Hassaine M. , Kabtoul B. , Jiménez-Riobóo R. J. , Shmyt'ko I. M. , Krivchikov A. I. , Sharapova I. V. , Korolyuk O. A.
Published: May 2013

We discuss our work on simple aliphatic glass-forming monoalcohols at low temperatures, including experiments on specific heat, thermal conductivity, Brillouin scattering and x-ray diffraction. The family of simple monoalcohols is an interesting model system for exploring molecular glass-forming liquids, the low-temperature universal properties of glasses, and even the glass transition phenomenon itself. More specifically, we examine the role of the molecular aspect ratio in the kinetics of vitrification/crystallization, the reported appearance of particular cases of polymorphism (in ethanol) and polyamorphism (in butanol), and, especially, the influence of positional isomerism and the location of the hydrogen bond on the lattice dynamics and, therefore, on the universal low-temperature properties of glasses.
Invited Article: Coherent imaging using seeded free-electron laser pulses with variable polarization: First results and research opportunities
Authors: Capotondi F. , Pedersoli E. , Mahne N. , Menk R. H. , Passos G. , Raimondi L. , Svetina C. , Sandrin G. , Zangrando M. , Kiskinova M. , Bajt S. , Barthelmess M. , Fleckenstein H. , Chapman H. N. , Schulz J. , Bach J. , Frömter R. , Schleitzer S. , Müller L. , Gutt C. , Grübel G.
Published: May 2013

FERMI@Elettra, the first vacuum ultraviolet and soft X-ray free-electron laser (FEL) using by default a “seeded” scheme, became operational in 2011 and has been opened to users since December 2012. The parameters of the seeded FERMI FEL pulses and, in particular, the superior control of emitted radiation in terms of spectral purity and stability meet the stringent requirements for single-shot and resonant coherent diffraction imaging (CDI) experiments. The advantages of the intense seeded FERMI pulses with variable polarization have been demonstrated with the first experiments performed using the multipurpose experimental station operated at the diffraction and projection imaging (DiProI) beamline. The results reported here were obtained with fixed non-periodic targets during the commissioning period in 2012 using 20–32 nm wavelength range. They demonstrate that the performance of the FERMI FEL source and the experimental station meets the requirements of CDI, holography, and resonant magnetic scattering in both multi- and single-shot modes. Moreover, we present the first magnetic scattering experiments employing the fully circularly polarized FERMI pulses. The ongoing developments aim at pushing the lateral resolution by using shorter wavelengths provided by double-stage cascaded FERMI FEL-2 and probing ultrafast dynamic processes using different pump-probe schemes, including jitter-free seed laser pump or FEL-pump/FEL-probe with two color FEL pulses generated by the same electron bunch.
Phonon transport analysis of silicon germanium alloys using molecular dynamics simulations
Authors: Hori Takuma , Shiga Takuma , Shiomi Junichiro
Published: May 2013

The phonon transport properties and the lattice thermal conductivity of silicon germanium alloy crystals have been investigated based on phonon gas model by using classical molecular dynamics simulations. The attenuation of the mode-dependent phonon relaxation time due to alloying and its dependence on the alloy fraction were quantified by projecting the molecular dynamics phase space trajectory onto the normal mode of the alloyed crystal. By empirically approximating the group velocities from the extended dispersion relations, the lattice thermal conductivity was calculated based on the phonon gas model under relaxation time approximation. The obtained reduction in the lattice thermal conductivity caused by alloying agrees well with that of the experiment and direct non-equilibrium molecular dynamics calculations. The phonon-mean-free-path dependent contribution to thermal conductivity suggests that the effect of nanostructuring can have non-monotonic dependence on the alloy fraction.
Effect of Cu interfacial layer thickness on spin-injection efficiency in NiFe/Cu/graphene spin valves
Authors: Zhang Chi , Wang Ying , Wu Baolei , Wu Yihong
Published: May 2013

The spin injection efficiency in NiFe/Cu/graphene spin-valves has been investigated systematically with emphasis on the Cu thickness effect. An optimum Cu thickness is found to be around 2.5 nm for which spin injection efficiency up to 8.4% has been measured. With a further increase of Cu thickness, the efficiency decreases to 3.6%−3.8% at 3.5 nm and is hardly measureable at 5 nm and beyond. The decrease is discussed in the context of enhanced spin-flip scattering at the NiFe/Cu interface and grain boundaries in the polycrystalline Cu as well as current shunting induced lengthening of travelling distance of electrons inside Cu. On the other hand, a further reduction of Cu thickness below 2.5 nm results in pinholes which also lowers the spin-injection efficiency. In addition to the Cu thickness, another factor which affects the spin signal is the DC bias voltage. The non-local magnetoresistance is highest when measured under zero-bias condition and becomes smaller when a DC bias is applied. The reduction of efficiency correlates well with the decrease in Cu-graphene contact resistance, which is consistent with the non-ohmic nature of Cu-graphene interface. Hanle spin precession curves were measured at different back gate biases from which the spin relaxation length was determined to be 1.6 μm−2.7 μm.
Helix untwisting and bubble formation in circular DNA
Authors: Zoli Marco
Published: May 2013

The base pair fluctuations and helix untwisting are examined for a circular molecule. A realistic mesoscopic model including twisting degrees of freedom and bending of the molecular axis is proposed. The computational method, based on path integral techniques, simulates a distribution of topoisomers with various twist numbers and finds the energetically most favorable molecular conformation as a function of temperature. The method can predict helical repeat, openings loci, and bubble sizes for specific sequences in a broad temperature range. Some results are presented for a short DNA circle recently identified in mammalian cells.
Evolution of strain energy during recrystallization of plated Cu films
Authors: Murray Conal E. , Rosenberg R. , Witt C. , Treger M. , Noyan I. C.
Published: May 2013

The microstructural evolution within plated Cu films has been investigated using high-resolution x-ray diffraction, revealing a change in strain state within the recrystallized grains and the surrounding matrix with time. By approximating the case of an isolated grain in a randomly textured material as an Eshelby inclusion in an elastically isotropic matrix, we can determine the elastic strain energy in addition to the interaction strains that develop within the grain due to the effects of elastic anisotropy. The elastic strain energy density generated by a grain possessing cubic symmetry with arbitrary orientation within an elastically isotropic matrix has been compared to that within a fiber-textured film, revealing that the former case possesses less strain energy. These results suggest that the recrystallization of Cu (111) grains from an electroplated film with a small, initial grain size is less energetically favorable for films exhibiting strong (111) texture than for a randomly textured film. Experimental results indicate a sequence that emerges during the recrystallization process: (111) grains grow first, suggesting that the decrease in surface energy provided by the (111) surfaces is larger than the increase in elastic strain energy created by (111) grains. For sufficiently thick films, (100) grains emerge, lowering the strain energy density in the film, after (111) grain growth has saturated because no further decrease in energy is supplied by (111) surface growth. By examining plated Cu films of different thicknesses, we correlate the appearance of recrystallized (100) grains with a threshold energy density based on the additional energy associated with (100) surfaces relative to (111) surfaces.
Filler geometry and interface resistance of carbon nanofibres: Key parameters in thermally conductive polymer composites
Authors: Gharagozloo-Hubmann Kati , Boden André , Czempiel Gregor J. F. , Firkowska Izabela , Reich Stephanie
Published: May 2013

The thermal conductivity of polymer composites is measured for several tubular carbon nanofillers (nanotubes, fibres, and whiskers). The highest enhancement in the thermal conductivity is observed for functionalized multiwalled carbon nanotubes (90% enhancement for 1 vol. %) and Pyrograf carbon fibres (80%). We model the experimental data using an effective thermal medium theory and determine the thermal interface resistance (RK) at the filler-matrix interface. Our results show that the geometry of the nanofibres and the interface resistance are two key factors in engineering heat transport in a composite.
G-equivariant ϕ-coordinated quasi modules for quantum vertex algebras
Authors: Li Haisheng
Published: May 2013

This is a paper in a series to study quantum vertex algebras and their relations with various quantum algebras. In this paper, we introduce a notion of T-type quantum vertex algebra and a notion of G-equivariant ϕ-coordinated quasi module for a T-type quantum vertex algebra with an automorphism group G. We refine and extend several previous results and we obtain a commutator formula for G-equivariant ϕ-coordinated quasi modules. As an illustrating example, we study a special case of the deformed Virasoro algebra \documentclass[12pt]{minimal}\begin{document}${\mathcal {V}}ir_{p,q}$\end{document}Virp,q with q = −1, to which we associate a Clifford vertex superalgebra and its G-equivariant ϕ-coordinated quasi modules.
Nonlinear dynamics of long-wave Marangoni convection in a binary mixture with the Soret effect
Authors: Morozov M. , Oron A. , Nepomnyashchy A. A.
Published: May 2013

We investigate the nonlinear dynamics of long-wave Marangoni convection in a 2D binary-liquid layer heated from below. Free surface deformations and the Soret effect are taken into account. We employ the set of evolution equations derived in earlier work in the case of small Galileo and Lewis numbers and solve it numerically with periodic boundary conditions. We validate our numerical solution by comparison between the results obtained via two different numerical methods, as well as by comparison with the prior analytical results. We study the transitions between the nonlinear regimes emerging at finite supercriticality values and find a rich variety of patterns. In a sufficiently large computational domain, we observe multistability of waves chaotic in time and spatially replicated periodic and quasiperiodic solutions. For sufficiently high values of the Marangoni number, we also observe a breakdown of model equations.
Damage of multilayer optics with varying capping layers induced by focused extreme ultraviolet beam
Authors: Jody Corso Alain , Zuppella Paola , Barkusky Frank , Mann Klaus , Müller Matthias , Nicolosi Piergiorgio , Nardello Marco , Guglielmina Pelizzo Maria
Published: May 2013

Extreme ultraviolet Mo/Si multilayers protected by capping layers of different materials were exposed to 13.5 nm plasma source radiation generated with a table-top laser to study the irradiation damage mechanism. Morphology of single-shot damaged areas has been analyzed by means of atomic force microscopy. Threshold fluences were evaluated for each type of sample in order to determine the capability of the capping layer to protect the structure underneath.
Note: Neutron shutter for Kolkata superconducting cyclotron
Authors: Pal Gautam , Bandopadhyay Tapas , Nandi Chinmay , Chatterjee Sujoy , Ravishankar R. , Bhattacharya Sumantra , Mitra Mausumi Sengupta , Akhter Javed , Mishra Santosh
Published: May 2013

In particle accelerator facilities, experimental areas are isolated from active accelerator area with thick concrete walls. A neutron shutter is used to isolate the experimental areas from the active accelerator area in the beam line. These shutters are provided primarily to reduce the secondary radiations like neutrons in the experimental areas to permissible limit when the primary beam is blocked in the accelerator area. The reduced radiation level in the experimental areas makes the experimental areas accessible. The shutters should allow the primary beam to pass to the experimental caves when they retracted from the beam line. A new neutron shutter has been designed and fabricated. This shutter incorporates compact features with considerable reduction in length, surface area and volume. The attenuation of secondary radiations is evaluated using Monte-Carlo radiation transport code FLUKA. It is found that the features of the shutter are sufficiently good enough to reduce the diffused secondary radiations well within the permissible levels.
Study of site-disorder in epitaxial magneto-electric GaFeO3 thin films
Authors: Sharma Kavita , Raghavendra Reddy V. , Gupta Ajay , Choudhary R. J. , Phase D. M. , Ganesan V.
Published: May 2013

Epitaxial thin films of GaFeO3 (GFO) with different thicknesses (22–170 nm) are prepared on (001) oriented yttria-stabilized zirconia substrate using pulsed laser deposition. The M-H data measured below Curie temperature (TC) mimic two phase composite magnetic system consisting of hard and soft magnetic phases. The results are explained in terms of Fe distribution among the available cation sites of GFO. Thermo-magnetic irreversibility and cusp in zero-field cooled magnetization are observed for all the films and are explained in terms of the magnetic anisotropy of the GFO.
A phonon transistor in an electromechanical resonator array
Authors: Hatanaka D. , Mahboob I. , Onomitsu K. , Yamaguchi H.
Published: May 2013

An electromechanical resonator array is developed that consists of 5 mechanically coupled membranes. Mechanical excitation of the array results in 2 types of oscillations, an extended mechanical oscillation that propagates through all 5 membranes and a localized mechanical oscillation that is confined to just some of the membranes. The dynamic interaction of these 2 types of oscillations is used to implement a transistor in this phononic system.
Atomic-plane-thick reconstruction across the interface during heteroepitaxial bonding of InP-clad quantum wells on silicon
Authors: Talneau A. , Roblin C. , Itawi A. , Mauguin O. , Largeau L. , Beaudouin G. , Sagnes I. , Patriarche G. , Pang C. , Benisty H.
Published: May 2013

An oxide-free heteroepitaxial bonding of InP-clad GaInAs quantum wells on Si showing an atomic-plane-thick reconstruction across the InP-Si interface and no degradation of the quantum wells luminescence is demonstrated. Several InP surface preparation procedures have been investigated to ensure an oxide-free bonding. Such a bonding procedure without oxide or metal mediation allows embedding very-high-index-contrast nanostructuration within optic and optoelectronic integrated devices, thus enabling tailored designs enhancing dedicated optical functions. Heteroepitaxial bonding is also similarly obtained on nanopatterned Si surface.
Fast atom beam-activated n-Si/n-GaAs wafer bonding with high interfacial transparency and electrical conductivity
Authors: Essig S. , Moutanabbir O. , Wekkeli A. , Nahme H. , Oliva E. , Bett A. W. , Dimroth F.
Published: May 2013

Optically transparent, electrically conductive n-Si/n-GaAs direct wafer bonds are achieved by a thorough optimization of surface conditioning using fast atom beams. Bonding at room temperature under high-vacuum conditions is systematically investigated after in situ surface deoxidization using either argon or helium fast atom beams. Using argon, high bond energies of up to 900 mJ/m2 are obtained and further enhanced to achieve bulk strength through rapid annealing at 290 °C, thereby enabling the production of thermally stable and mechanically robust hybrid substrates. Moreover, the interface conductivity is significantly improved by an additional thermal annealing at 400 °C. Although it is anticipated to induce higher quality interfaces, helium treatment yields, however, limited and unstable bonding. This difference is attributed to an important surface nano-texturing that occurs during fast atom beam processing, a phenomenon that is peculiar to helium and absent in argon treatment.
Fabrication of whispering gallery mode cavity using crystal growth
Authors: Kudo Hiroshi , Ogawa Yohei , Kato Takumi , Yokoo Atsushi , Tanabe Takasumi
Published: May 2013

We developed a method for fabricating crystalline whispering gallery mode cavities based on laser-heated pedestal growth. We fabricated sapphire cavities and obtained a Q factor of 1.6 × 104 with a cavity whose radius was about 120 μm. We showed numerically that the cross sectional shape of the cavity is sensitive to the cavity Q, and we controlled it by changing the growth condition in the molten zone, without significantly degrading the crystal structure.
Experimental investigation on thermal barrier coated diesel engine fueled with diesel-biodiesel-ethanol-diethyl ether blends
Authors: Kalil Rahiman M. , Venkatachalam R. , Nedunchezhian N.
Published: May 2013

In the present work, diesel-biodiesel-ethanol (DBE) and diesel-biodiesel-diethyl ether (DBD) fuels are tested with normal diesel engine and the diesel engine coated with the layers of aluminum oxide (Al2O3) of 0.3 mm and yttria-stabilized zirconia of 0.2 mm. The various performance and emission parameters are analyzed and determined. The experimental work was carried out in a single cylinder water cooled engine coupled with eddy current dynamometer. The AVL make five gas analyzer and smoke meter were used to measure the different exhaust pollutants. The result shows that the brake thermal efficiency of coated engine is more than that of base diesel at high loads. The thermal barrier coated engine using fuel as diesel, biodiesel, and ethanol (TDBE) produces the lowest carbon monoxide (CO) emissions among all the fuels that are selected. In addition, it produces the lowest carbon dioxide (CO2) at higher loads. Both the thermal barrier coated engine using fuel as diesel, biodiesel, and diethyl ether (TDBD) and TDBE have higher NOx emissions among almost all the fuels used. The TDBE and TDBD have higher smoke emissions at initial loads but eventually show lower smoke emissions at higher loads. The thermal barrier coated diesel engine fueled with DBE and DBD shows an increase in engine power and specific fuel consumption, as well as significant improvements in exhaust gas emissions except NOx.
Terahertz free electron superradiation from mimicking surface plasmons-two electron beams interaction within a 3-mirror quasi-optical cavity
Authors: Zhang Ya-Xin , Zhou Y. , Dong L. , Liu Sheng-Gang
Published: May 2013

Interaction between mimicking surface plasmons and electron beams provides a good opportunity to develop terahertz (THz) radiation sources. In this paper, such an interaction in a special 3-mirror quasi-optical cavity is presented and explored. The 3-mirror quasi-optical cavity acts as a resonant tunable system, the resonance frequency of which can be tuned by adjusting the distance between mirrors. The study demonstrated THz free electron superradiation from the interaction of mimicking surface plasmons and two electron beams that formed a resonance within the structure, with the 3-mirror cavity enhancing the intensity of superradiation. Moreover, this system can work in the high-harmonic superradiation region with relatively high efficiency and low current density. This concept thus shows the application potential for electron-beam-driven terahertz sources.
Circular polarizer via selective excitation of photonic angular momentum states in metamaterials
Authors: Guo Qing-Hua , Yang Mu , Li Teng-Fei , Guo Tian-Jing , Cui Hai-Xu , Kang Ming , Chen Jing
Published: May 2013

We propose a scheme in realizing a compact circular polarizer by using a metamaterial with a properly designed input meta-surface. This scheme is based on the selective excitation of photonic angular momentum states in a coaxial element array by the symmetry-broken input meta-surface. The topological charge m of the excited photonic angular momentum state in the coaxial element determines the handedness of the transmitted light via the orbit-spin conversion of the angular momentum of light. A net circular-polarization generation efficiency of 64.5% for a linearly polarized incidence is demonstrated.
Observation of magnetic anisotropy increment with temperature in composition-graded FeCoZr thin films
Authors: Phuoc Nguyen N. , Ong C. K.
Published: May 2013

Through a systematic investigation, we demonstrate that FeCoZr thin films deposited by gradient composition sputtering technique possess a unique magnetic thermal behavior, namely, the increase in magnetic anisotropy with temperature. Moreover, this gradient composition sputtering technique also offers a viable method to tailor the high-frequency magnetic properties as well as their thermal stability by changing deposition angle and deposition power. The unusual temperature dependence of magnetic anisotropy in such thin films can be interpreted in terms of stress-induced magnetic anisotropy arising from the composition gradient in the films.
Spatial Evaluation of Ecological Qualities to Support Interactive Land-Use Planning
Authors: Janssen Ron , Arciniegas Gustavo A , Verhoeven Jos T A
Published: May 2013

Information on ecological qualities can play an important role in land-use planning. This information is not always in a form that is suitable to support planning and negotiation among stakeholders. In this paper we describe an approach that uses ecological information based on expert knowledge in combination with spatial multicriteria analysis. Important elements of this approach are selection of evaluation criteria, assessment of scores, standardization, weighting, and aggregation. The approach was tested as part of the land-use planning process of the Bodegraven polder, a peat meadow area in the Netherlands. An interactive mapping device (the ‘touch table’) was used to support a series of interactive workshops with the various stakeholders to generate, assess, and discuss land-use plans for the Bodegraven polder. This paper shows the use of ecological information to support decision making and negotiation.
Investigating Travel Thresholds for Sports and Recreation Activities
Authors: Spinney Jamie E L , Millward Hugh
Published: May 2013

Central to the practice of urban planning is the provision of services, which has potential public health and social welfare implications. However, service area analysis, typically, employs arbitrary travel-distance thresholds. Through this study we provide an empirical investigation into the durations and distances that respondents are willing to travel in order to engage in various sports and recreation activities. This research uses time-diary data, augmented with global positioning system information, to investigate individually based and objectively measured travel thresholds (which define travelsheds) for various sports and recreation activities in Halifax, Nova Scotia. Results accord with national time-diary data, and indicate that duration-based and distance-based travelsheds are generally in the order of 15–30 minutes and 4–20 km, respectively. Georeferenced time-diary data provide unique insights into travel thresholds, which may be used to help improve accessibility and thereby increase the frequency and duration of physical activity engagement.
Urban Form and the Environmental Impact of Commuting in a Segregated City, Santiago de Chile
Authors: Gainza Xabier , Livert Felipe
Published: May 2013

The literature on the relationship between the built environment and travel has identified population density and the mix of land uses as key characteristics of the urban form that affect travel patterns. However, in cities with strong sociospatial disparities it is not clear if these characteristics apply in the same way. In this paper we use regression analysis to estimate the influence of the spatial growth pattern of Santiago, Chile, on the environmental impact of commuting. Our findings can be summarized in three points: The travel impact increases as the city spreads out because of the monocentric nature of Santiago; the environmental impact of commuting could be reduced by containing commuters within the area where they live; and the use of public transport reduces the impact, but the modal choice depends not only on the effectiveness of the transport system but also on the characteristics of the urban form and other socioeconomic determinants. Consequently, we propose to reorient the growth pattern in three ways: redirecting land-use policy to promote development within the already built area, developing compact areas where residential and economic activities are mixed, and facing sociospatial disparities as a way to encourage the use of public transport. This would reduce the environmental impact of commuting while, at the same time, tackling sociospatial segregation.
Assessment of the Methods and Extents of the Usage of Urban Modeling in Urban Design Practice in US Cities
Authors: Al-Douri Firas A
Published: May 2013

Literature suggests that present urban design plans and methods are inadequate to deal with the scale and complexity of contemporary urban form and multidisciplinary collaborative practice. Although recent developments in urban modeling technologies have brought about a wide range of different techniques and potential implementations that may help address this inadequacy, they have not yet made their desired impact on the design process. Failure to use these capabilities extensively in actual practice may result primarily from a limited understanding of the proper role these tools should play or the impact they may have. There is also hesitation about which are appropriate and effective applications, and little consensus on the methods with which these capabilities should be used in core design activities. More investigation is needed to understand fully their application in urban design practice. This research suggests a methodological framework underlying the methods of using various urban modeling functionalities. A questionnaire survey method was used to document the methods and assess the extents to which designers used urban modeling tools in developing eight urban design plans. The questionnaire survey findings were compared with the theoretical premises. The findings showed that design methodology is the main factor that affects the effectiveness of modeling to support design activities. The findings showed extensive, inconsistent usage and various degrees of support for design activities that resulted in various degrees of impact on urban design aspects. The findings suggest the provision of dynamic visualization supported by efficient networking may advance urban modeling to become a tool of public advocacy and design decision support which can advance urban design practice to informational, communicational, and representational systems.
Using an Agent-Based Crime Simulation to Predict the Effects of Urban Regeneration on Individual Household Burglary Risk
Authors: Malleson Nick , Heppenstall Alison , See Linda , Evans Andrew
Published: May 2013

Making realistic predictions about the occurrence of crime is a challenging research area. City-wide crime patterns depend on the behaviour and interactions of a huge number of people (including victims, offenders, and passers-by) as well as a multitude of environmental factors. Modern criminology theory has highlighted the individual-level nature of crime—whereby overall crime rates emerge from individual crimes that are committed by individual people in individual places—but traditional modelling methodologies struggle to capture the complex dynamics of the system. The decision whether or not to commit a burglary, for example, is based on a person's unique behavioural circumstances and the immediate surrounding environment. To address these problems, individual-level simulation techniques such as agent-based modelling have begun to spread to the field of criminology. These models simulate the behaviour of individual people and objects directly; virtual ‘agents' are placed in an environment that allows them to travel through space and time, behaving as they would do in the real world. We outline an advanced agent-based model that can be used to simulate occurrences of residential burglary at an individual level. The behaviour within the model closely represents criminology theory and uses real-world data from the city of Leeds, UK as an input. We demonstrate the use of the model to predict the effects of a real urban regeneration scheme on local households.
Efficient Synthesis of Novel Porphyrin Dimers with Versatile Linkers via Bis(dipyrromethanes) in an Excellent Mixed-Solvent
Authors: Zhao Hongbin , Liao Junxu , Yang Deliang , Xie Yujia , Xu Yongjun , Wang Hongke , Wang Bangying
Published: May 2013

A general and efficient protocol has been developed to synthesise a series of novel porphyrin dimers with versatile aryl linkers via a simultaneous condensation-cyclisation-oxidation reaction of diverse bis(dipyrromethanes) with dipyrromethane-dicarbinol catalysed by indium(iii) chloride at room temperature in an efficient CH2Cl2 and CH3CN mixed-solvent. The reaction yields increased to 21–26 % based on liquid chromatography-mass spectrometry (LCMS) and isolated yields were 13–19 % due to the use of the proper mixed-solvent. This mild method is applicable to the preparation of linker-tunable porphyrin dimers with targeted functionalities and could potentially be extended to the single-step construction of longer functionalised multiporphyrin arrays.
Circadian clock regulates the host response to
Salmonella
Authors: Bellet Marina M. , Deriu Elisa , Liu Janet Z. , Grimaldi Benedetto , Blaschitz Christoph , Zeller Michael , Edwards Robert A. , Sahar Saurabh , Dandekar Satya , Baldi Pierre , George Michael D. , Raffatellu Manuela , Sassone-Corsi Paolo
Published: May 2013

Organisms adapt to day–night cycles through highly specialized circadian machinery, whose molecular components anticipate and drive changes in organism behavior and metabolism. Although many effectors of the immune system are known to follow daily oscillations, the role of the circadian clock in the immune response to acute infections is not understood. Here we show that the circadian clock modulates the inflammatory response during acute infection with the pathogen
Salmonella enterica
serovar Typhimurium (
S.
Typhimurium). Mice infected with
S.
Typhimurium were colonized to higher levels and developed a higher proinflammatory response during the early rest period for mice, compared with other times of the day. We also demonstrate that a functional clock is required for optimal
S.
Typhimurium colonization and maximal induction of several proinflammatory genes. These findings point to a clock-regulated mechanism of activation of the immune response against an enteric pathogen and may suggest potential therapeutic strategies for chronopharmacologic interventions.
Multidecadal to multicentury scale collapses of Northern Hemisphere monsoons over the past millennium
Authors: Asmerom Yemane , Polyak Victor J. , Rasmussen Jessica B. T. , Burns Stephen J. , Lachniet Matthew
Published: May 2013

Late Holocene climate in western North America was punctuated by periods of extended aridity called megadroughts. These droughts have been linked to cool eastern tropical Pacific sea surface temperatures (SSTs). Here, we show both short-term and long-term climate variability over the last 1,500 y from annual band thickness and stable isotope speleothem data. Several megadroughts are evident, including a multicentury one, AD 1350–1650, herein referred to as Super Drought, which corresponds to the coldest period of the Little Ice Age. Synchronicity between southwestern North American, Chinese, and West African monsoon precipitation suggests the megadroughts were hemispheric in scale. Northern Hemisphere monsoon strength over the last millennium is positively correlated with Northern Hemisphere temperature and North Atlantic SST. The megadroughts are associated with cooler than average SST and Northern Hemisphere temperatures. Furthermore, the megadroughts, including the Super Drought, coincide with solar insolation minima, suggesting that solar forcing of sea surface and atmospheric temperatures may generate variations in the strength of Northern Hemisphere monsoons. Our findings seem to suggest stronger (wetter) Northern Hemisphere monsoons with increased warming.
Differential methylation in glucoregulatory genes of offspring born before vs. after maternal gastrointestinal bypass surgery
Authors: Guénard Frédéric , Deshaies Yves , Cianflone Katherine , Kral John G. , Marceau Picard , Vohl Marie-Claude
Published: May 2013

Obesity and overnutrition during pregnancy affect fetal programming of adult disease. Children born after maternal bariatric gastrointestinal bypass surgery (AMS) are less obese and exhibit improved cardiometabolic risk profiles carried into adulthood compared with siblings born before maternal surgery (BMS). This study was designed to analyze the impact of maternal weight loss surgery on methylation levels of genes involved in cardiometabolic pathways in BMS and AMS offspring. Differential methylation analysis between a sibling cohort of 25 BMS and 25 AMS (2–25 y-old) offspring from 20 mothers was conducted to identify biological functions and pathways potentially involved in the improved cardiometabolic profile found in AMS compared with BMS offspring. Links between gene methylation and expression levels were assessed by correlating genomic findings with plasma markers of insulin resistance (fasting insulin and homeostatic model of insulin resistance). A total of 5,698 genes were differentially methylated between BMS and AMS siblings, exhibiting a preponderance of glucoregulatory, inflammatory, and vascular disease genes. Statistically significant correlations between gene methylation levels and gene expression and plasma markers of insulin resistance were consistent with metabolic improvements in AMS offspring, reflected in genes involved in diabetes-related cardiometabolic pathways. This unique clinical study demonstrates that effective treatment of a maternal phenotype is durably detectable in the methylome and transcriptome of subsequent offspring.
Structures of ABCB10, a human ATP-binding cassette transporter in apo- and nucleotide-bound states
Authors: Shintre Chitra A. , Pike Ashley C. W. , Li Qiuhong , Kim Jung-In , Barr Alastair J. , Goubin Solenne , Shrestha Leela , Yang Jing , Berridge Georgina , Ross Jonathan , Stansfeld Phillip J. , Sansom Mark S. P. , Edwards Aled M. , Bountra Chas , Marsden Brian D. , von Delft Frank , Bullock Alex N. , Gileadi Opher , Burgess-Brown Nicola A. , Carpenter Elisabeth P.
Published: May 2013

ABCB10 is one of the three ATP-binding cassette (ABC) transporters found in the inner membrane of mitochondria. In mammals ABCB10 is essential for erythropoiesis, and for protection of mitochondria against oxidative stress. ABCB10 is therefore a potential therapeutic target for diseases in which increased mitochondrial reactive oxygen species production and oxidative stress play a major role. The crystal structure of apo-ABCB10 shows a classic exporter fold ABC transporter structure, in an open-inwards conformation, ready to bind the substrate or nucleotide from the inner mitochondrial matrix or membrane. Unexpectedly, however, ABCB10 adopts an open-inwards conformation when complexed with nonhydrolysable ATP analogs, in contrast to other transporter structures which adopt an open-outwards conformation in complex with ATP. The three complexes of ABCB10/ATP analogs reported here showed varying degrees of opening of the transport substrate binding site, indicating that in this conformation there is some flexibility between the two halves of the protein. These structures suggest that the observed plasticity, together with a portal between two helices in the transmembrane region of ABCB10, assist transport substrate entry into the substrate binding cavity. These structures indicate that ABC transporters may exist in an open-inwards conformation when nucleotide is bound. We discuss ways in which this observation can be aligned with the current views on mechanisms of ABC transporters.
Neuroligin-1 links neuronal activity to sleep-wake regulation
Authors: El Helou Janine , Bélanger-Nelson Erika , Freyburger Marlène , Dorsaz Stéphane , Curie Thomas , La Spada Francesco , Gaudreault Pierre-Olivier , Beaumont Éric , Pouliot Philippe , Lesage Frédéric , Frank Marcos G. , Franken Paul , Mongrain Valérie
Published: May 2013

Maintaining wakefulness is associated with a progressive increase in the need for sleep. This phenomenon has been linked to changes in synaptic function. The synaptic adhesion molecule Neuroligin-1 (NLG1) controls the activity and synaptic localization of
N
-methyl-
d
-aspartate receptors, which activity is impaired by prolonged wakefulness. We here highlight that this pathway may underlie both the adverse effects of sleep loss on cognition and the subsequent changes in cortical synchrony. We found that the expression of specific
Nlg1
transcript variants is changed by sleep deprivation in three mouse strains. These observations were associated with strain-specific changes in synaptic NLG1 protein content. Importantly, we showed that
Nlg1
knockout mice are not able to sustain wakefulness and spend more time in nonrapid eye movement sleep than wild-type mice. These changes occurred with modifications in waking quality as exemplified by low theta/alpha activity during wakefulness and poor preference for social novelty, as well as altered delta synchrony during sleep. Finally, we identified a transcriptional pathway that could underlie the sleep/wake-dependent changes in
Nlg1
expression and that involves clock transcription factors. We thus suggest that NLG1 is an element that contributes to the coupling of neuronal activity to sleep/wake regulation.
Insights into foraminiferal influences on microfabrics of microbialites at Highborne Cay, Bahamas
Authors: Bernhard Joan M. , Edgcomb Virginia P. , Visscher Pieter T. , McIntyre-Wressnig Anna , Summons Roger E. , Bouxsein Mary L. , Louis Leeann , Jeglinski Marleen
Published: May 2013

Microbialites, which are organosedimentary structures formed by microbial communities through binding and trapping and/or in situ precipitation, have a wide array of distinctive morphologies and long geologic record. The origin of morphological variability is hotly debated; elucidating the cause or causes of microfabric differences could provide insights into ecosystem functioning and biogeochemistry during much of Earth’s history. Although rare today, morphologically distinct, co-occurring extant microbialites provide the opportunity to examine and compare microbial communities that may be responsible for establishing and modifying microbialite microfabrics. Highborne Cay, Bahamas, has extant laminated (i.e., stromatolites) and clotted (i.e., thrombolites) marine microbialites in close proximity, allowing focused questions about how community composition relates to physical attributes. Considerable knowledge exists about prokaryotic composition of microbialite mats (i.e., stromatolitic and thrombolitic mats), but little is known about their eukaryotic communities, especially regarding heterotrophic taxa. Thus, the heterotrophic eukaryotic communities of Highborne stromatolites and thrombolites were studied. Here, we show that diverse foraminiferal communities inhabit microbialite mat surfaces and subsurfaces; thecate foraminifera are relatively abundant in all microbialite types, especially thrombolitic mats; foraminifera stabilize grains in mats; and thecate reticulopod activities can impact stromatolitic mat lamination. Accordingly, and in light of foraminiferal impacts on modern microbialites, our results indicate that the microbialite fossil record may reflect the impact of the radiation of these protists.
Pirin is an iron-dependent redox regulator of NF-κB
Authors: Liu Fange , Rehmani Imran , Esaki Shingo , Fu Rong , Chen Lirong , de Serrano Vesna , Liu Aimin
Published: May 2013

Pirin is a nuclear nonheme Fe protein of unknown function present in all human tissues. Here we describe that pirin may act as a redox sensor for the nuclear factor κB (NF-κB) transcription factor, a critical mediator of intracellular signaling that has been linked to cellular responses to proinflammatory signals and controls the expression of a vast array of genes involved in immune and stress responses. Pirin’s regulatory effect was tested with several metals and at different oxidations states, and our spectroscopic results show that only the ferric form of pirin substantially facilitates binding of NF-κB proteins to target κB genes, a finding that suggests that pirin performs a redox-sensing role in NF-κB regulation. The molecular mechanism of such a metal identity- and redox state-dependent regulation is revealed by our structural studies of pirin. The ferrous and ferric pirin proteins differ only by one electron, yet they have distinct conformations. The Fe center is shown to play an allosteric role on an
R
-shaped surface area that has two distinct conformations based on the identity and the formal redox state of the metal. We show that the
R
-shaped area composes the interface for pirin-NF-κB binding that is responsible for modulation of NF-κB’s DNA-binding properties. The nonheme Fe protein pirin is proposed to serve as a reversible functional switch that enables NF-κB to respond to changes in the redox levels of the cell nucleus.