bluuebunny/crossref_metadata_2025 huggingface dataset:
Stepwise melting of a model glass former under confinement
Authors: Calvo F. , Wales D. J.
Published: October 2009

The equilibrium thermodynamics of a binary Lennard-Jones model glass former are investigated using exchange Monte Carlo simulations, covering the crystalline and amorphous regions of configuration space in appropriate temperature ranges. We investigate both bulk and film mixtures, the latter being confined between noninteracting flat walls. Both the bulk and film systems exhibit a principal heat capacity peak at the melting point, but confinement leads to a significant depression in the melting temperature by about 25%. Microcanonical caloric curves, as well as analysis of the probability distributions of a bond-orientational order parameter, show that this transition has first-order character. However, the film system shows additional features at lower temperatures, which are interpreted in terms of localized partial melting, perpendicular to the confining walls and near the walls, with some increase in layering. This premelting is associated with local minima on the underlying potential energy surface that are not supported by the bulk system.
Shock wave in a two-dimensional dusty plasma crystal
Authors: Ghosh Samiran
Published: October 2009

Two-dimensional (2D) shock structures of longitudinal dust lattice wave (LDLW) in a hexagonal Yukawa crystal are studied. The nonlinear evolution equation derived for dusty plasma crystal is found to be a 2D Burgers’ equation, where the Burgers’ term, i.e., the dissipation is provided by “hydrodynamic damping” due to irreversible processes that take place within the system. Analytical and numerical solutions of this equation on the basis of crystal experimental parameters show the development of compressional shock structures of LDLW in 2D dusty plasma crystal. The shock strength decreases (increases) with the increase in lattice parameter κ (angle of propagation of the nonlinear wave). The results are discussed in the context of 2D monolayer hexagonal dusty plasma crystal experiments.
Poly(3-hexyl-thiophene) coil-wrapped single wall carbon nanotube investigated by scanning tunneling spectroscopy
Authors: Giulianini Michele , Waclawik Eric R. , Bell John M. , Scarselli Manuela , Castrucci Paola , De Crescenzi Maurizio , Motta Nunzio
Published: October 2009

Scanning tunneling spectroscopy was performed on a (15,0) single wall carbon nanotube partially wrapped by poly(3-hexyl-thiophene). On the bare nanotube section, the local density of states is in good agreement with the theoretical model based on local density approximation and remarkably is not perturbed by the polymer wrapping. On the coiled section, a rectifying current-voltage characteristic has been observed along with the charge transfer from the polymer to the nanotube. The electron transfer from poly(3-hexyl-thiophene) to metallic nanotube was previously theoretically proposed and contributes to the presence of the Schottky barrier at the interface responsible for the rectifying behavior.
Memory characteristics of InAs quantum dots embedded in GaAs quantum well
Authors: Kannan E. S. , Kim Gil-Ho , Ritchie D. A.
Published: October 2009

The memory characteristics of InAs based quantum dot (QD) memory devices has been investigated by carrying out capacitance-voltage and current-voltage measurements. The dots which were embedded in the GaAs quantum well were charged by the electrons from the two dimensional electron gas and a clockwise hysteresis loop is observed on cyclically sweeping the gate bias. The number of trapped electrons is found to be two orders of magnitude lesser than the QD density. Interdot Coulombic interactions and phonon assisted electron tunneling was found to significantly affect the charge trapping ability of the QDs.
Temperature and density dependence of the structural relaxation time in water by inelastic ultraviolet scattering
Authors: Bencivenga F. , Cimatoribus A. , Gessini A. , Izzo M. G. , Masciovecchio C.
Published: October 2009

The density and temperature dependence of the structural relaxation time (τ) in water was determined by inelastic ultraviolet scattering spectroscopy in the thermodynamic range (P=1–4000 bars, T=253–323 K), where several water anomalies take place. We observed an activation (Arrhenius) temperature dependence of τ at constant density and a monotonic density decrease at constant temperature. The latter trend was accounted for by introducing a density-dependent activation entropy associated to water local structure. The combined temperature and density behavior of τ indicates that differently from previous results, in the probed thermodynamic range, the relaxation process is ruled by a density-dependent activation Helmholtz free energy rather than a simple activation energy. Finally, the extrapolation of the observed phenomenology at lower temperature suggests a substantial agreement with the liquid-liquid phase transition hypothesis.
Characterization of optical microring ultrasound detector by using a high frequency focused photoacoustic transmitter
Authors: Won Baac Hyoung , Ling Tao , Huang Sheng-Wen , Ashkenazi Shai , Guo L. Jay
Published: October 2009

We characterize a response of optical microring resonator to high frequency focused ultrasound. To properly evaluate the response over high frequency and broadband spectrum, we use a photoacoustic concave transmitter generating and subsequently focusing the ultrasound. A detected focused profile reveals two types of spatial peaks due to the special ring-shaped detector geometry interacting with the high frequency focused ultrasound. Spectral analysis shows that those peaks are contributed by the main and the side lobes of focused ultrasound, respectively. Experimental focal widths agree with theoretical values within ±2 μm error, which can be attributed to the narrow width of waveguide.
Properties of microturbulence in toroidal plasmas with reversed magnetic shear
Authors: Deng Wenjun , Lin Zhihong
Published: October 2009

Electrostatic drift wave turbulence in tokamak plasmas with reversed magnetic shear is studied using global gyrokinetic particle simulations. The linear eigenmode of the ion temperature gradient (ITG) instability exhibits a mode gap around the minimum safety factor (qmin) region, particularly when qmin is an integer, due to the rarefaction of rational surfaces. The collisionless trapped electron mode (CTEM) instability is suppressed in the negative-shear region due to the reversal of the toroidal precessional drift of trapped electrons. However, after nonlinear saturation, the ITG gap is filled up by the turbulence spreading and the CTEM fluctuation propagates into the stable negative-shear region. The steady state turbulence occupies the whole volume without any identifiable gap or coherent structures of the heat conductivity, perturbed temperature, or zonal flows in the qmin location or the reversed shear region. Our finding indicates that the electrostatic drift wave turbulence itself does not support either linear or nonlinear mechanism for the formation of internal transport barriers in the reversed magnetic shear when qmin crossing an integer.
Activation of porphyrin photosensitizers by semiconductor quantum dots via two-photon excitation
Authors: Wen Ya-nan , Song Wei-si , An Li-min , Liu Yu-qiang , Wang Ying-hui , Yang Yan-qiang
Published: October 2009

Energy transfer from water-soluble quantum dots (QDs) to porphyrinlike sensitizers is studied by time-resolved spectroscopy of two-photon excitation with femtosecond laser pulses. Evident transfer results are observed. Electron exchange is found to be the dominant transfer mechanism. Relative intensity change between excitonic and trapping emission implies that nonradiative energy transfer occurs through the trapping state of QDs, which presents a way of raising energy transfer efficiency in this type of donor-acceptor pairs. This study underlines the potential of QD-porphyrin model system for applications in two-photon excitation photodynamic therapy.
Surface-enhanced Raman spectroscopy of CdSe quantum dots on nanostructured plasmonic surfaces
Authors: Hugall James T. , Baumberg Jeremy J. , Mahajan Sumeet
Published: October 2009

Although quantum dots (QDs) are widely used as fluorophores they have not so far been used as Raman labels. Here we demonstrate (resonant) surface-enhanced Raman scattering (SERS) of CdSe QDs attached to nanostructured plasmonic surfaces. The 208 cm−1 CdSe longitudinal optical phonon mode is observed for laser excitation at 514, 633, and 785 nm. Tuning the SERS signal into resonance with the localized surface plasmon reveals the effects of optical absorption and emission on QD SERS. Equivalent tuning of the localized plasmons on graded nanovoid samples shows strong resonant SERS enhancements. These results pave the way for exploiting QDs as SERS markers.
Electroluminescence and structural characteristics of InAs/In0.1Ga0.9As quantum dots grown on graded Si1−xGex/Si substrate
Authors: Tanoto H. , Yoon S. F. , Lew K. L. , Loke W. K. , Dohrman C. , Fitzgerald E. A. , Tang L. J.
Published: October 2009

We studied the electroluminescence and structural characteristics of five-layer stacked self-assembled InAs/In0.1Ga0.9As quantum dot (QD) structures grown on graded Si1−xGex/Si substrate. The QD was found to take on a lens shaped structure with aspect ratio of 0.23±0.05. Room-temperature electroluminescence at 1.29 μm was observed from the QD structures. The external quantum efficiency as function of injected current was investigated and the dominant carrier recombination processes were identified from analysis of the current-optical power relationship.
Thermal runaway and optical efficiency in InAs/GaAs quantum dot lasers
Authors: Chia C. K. , Suryana M. , Hopkinson M.
Published: October 2009

In contrast to quantum well lasers, we show thermal runaway effects are prominent for quantum dot (QD) lasers emitting at 1300 nm. In addition to the surface states at the cleaved facet and the effect of strain relaxation, which can couple confined states with surface states, the exposed relaxed QDs at the cleaved facet can themselves contribute to extra nonradiative surface recombination, aggravating the facet heating problem. Notable improvement in optical efficiency after the formation of nonabsorbing mirrors by a laser annealing technique highlights the significance of the thermal runaway problem for 1300 nm QD lasers, and demonstrates an effective postfabrication solution.
Measurement of the lattice plane strain and phase fraction evolution during heating and cooling in shape memory NiTi
Authors: Qiu S. , Krishnan V. B. , Padula S. A. , Noebe R. D. , Brown D. W. , Clausen B. , Vaidyanathan R.
Published: October 2009

We report on in situ neutron diffraction measurements during heating and cooling through the phase transformation in shape memory NiTi. The lattice plane specific strain evolution remains linear with temperature and is not influenced by intergranular stresses, enabling the determination of the thermal expansion tensor of B19′ NiTi. The neutron measurements are consistent with macroscopic dilatometric measurements and a 30 000 grain polycrystalline self-consistent model. The accommodative nature of B19′ NiTi results in macroscopic shape changes being offset (with temperature) from the start and finish of the transformation. The texture does not evolve in the absence of biasing stresses.
Multiple silicon nanowires-embedded Schottky solar cell
Authors: Kim Joondong , Yun Ju-Hyung , Han Chang-Soo , Cho Yong Jae , Park Jeunghee , Park Yun Chang
Published: October 2009

Large area applicable silicon nanowire (SiNW)-embedded Schottky solar cell (SC) is fabricated. Multiple semiconducting SiNWs were positioned on two different metals. SiNW forms a Schottky or an Ohmic contact to each metal according to the Fermi level lineup. Electrons or holes have a barrier to transport resulting in a rectifying flow. Under 1 sun illumination, the SiNW Schottky SC provided 0.167 V of photovoltage and 91.91 nA of photocurrent with an ideality factor of 1.2. It discusses the fabrication scheme and mechanism of multiple SiNWs-embedded Schottky SC.
Effects of orientation and composition on the extrinsic contributions to the dielectric response of relaxor-ferroelectric single crystals
Authors: Bernal Ashley , Zhang Shujun , Bassiri-Gharb Nazanin
Published: October 2009

The dielectric response of (1−x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-x%PT,4.5≤x≤12) single crystals is reported for ac field amplitudes up to ∼2 kV/cm at 1 kHz. The Rayleigh law is used to study the dielectric nonlinear response. It is found that the extrinsic contributions are extremely anisotropic. Rhombohedral crystals poled along [001]C showed enhanced extrinsic contributions to their dielectric response with respect to those poled along [111]C, while in tetragonal crystals, the enhancement was observed for poling along [111]C rather than along [001]C. This is attributed to “domain engineering” or higher domain wall concentrations in ferroelectric crystals poled along nonpolar axes.
Azimuth dependent reflection anisotropy of oriented thin films
Authors: Lane P. D. , Isted G. E. , Roseburgh D. S. , Cole R. J.
Published: October 2009

A simplified mathematical description of reflection anisotropy spectroscopy (RAS) measurements is presented. The RAS signals of a nanometer film with arbitrarily aligned dielectric axes are investigated. While RAS spectra are found to be relatively insensitive to tilting of the dielectric axes out of the surface plane, the variation of RAS signals with sample azimuthal orientation angle, θs, reveals a distinct sin θs effect, superimposed on the previously observed sin 2θs and sin 4θs terms, which provides a measure of the tilt angle.
Magnetocaloric effect linked to the martensitic transformation in sputter-deposited Ni–Mn–Ga thin films
Authors: Recarte V. , Pérez-Landazábal J. I. , Sánchez-Alárcos V. , Chernenko V. A. , Ohtsuka M.
Published: October 2009

In this letter, the analysis of the magnetocaloric effect (MCE) in a thin film of Ni–Mn–Ga alloy sputter deposited on alumina substrate is reported. This film has 0.4 μm thickness and exhibits merged martensitic and ferromagnetic transitions. The temperature dependence of the dc magnetization under different constant applied magnetic fields has been measured. The calculated MCE effect under applied magnetic fields up to 60 kOe shows the feasibility of these materials to be implemented in refrigeration system for functional microsystems. In addition, the shift of the martensitic transformation temperature, as a function of the applied magnetic field, has been determined.
Effect of matrix material on the morphology and optical properties of InP-based InAsSb nanostructures
Authors: Lei W. , Tan H. H. , Jagadish C.
Published: October 2009

This paper presents a study on the effect of matrix material on the morphology and optical properties of self-assembled InP-based InAsSb nanostructures. Due to the differences in surface roughness of the growth front, In0.53Ga0.47As matrix layer induces the formation of short quantum dashes (QDashes) and elongated quantum dots, while InP and In0.52Al0.48As matrix layers promote the formation of long QDashes and quantum wires, respectively. The shape anisotropy of InAsSb nanostructures on In0.53Ga0.47As, InP, and In0.52Al0.48As layers is further investigated with polarized photoluminescence measurements. The InAsSb nanostructures show a luminescence polarization degree of 8.5%, 14.3%, and 29% for In0.53Ga0.47As, InP, and In0.52Al0.48As matrixes, which corresponds well with the shape anisotropy observed with atomic force microscope. Furthermore, InAsSb/In0.53Ga0.47As nanostructures also show the longest, thermally stable emission wavelength, which serves as a promising material system for fabricating midinfrared emitters.
A surface-emitting distributed-feedback plasmonic laser
Authors: Li X. F. , Yu S. F. , Kumar Ashwani
Published: October 2009

A surface-plasmon polariton (SPP) waveguide, which is composed of a high-index decoupling layer for the excitation of surface emission, a metal grating layer to achieve coherent optical feedback and guiding of SPP waves as well as a dye polymer medium for the light amplification, is proposed to achieve surface lasing emission. Finite-difference time-domain calculation is performed to design and optimize the lasing performance of the SPP waveguide. It is found that the corresponding laser threshold can be lower than 700 cm−1 and the quality factor can be larger than 700.
Districting Modeling with Exact Contiguity Constraints
Authors: Shirabe Takeshi
Published: October 2009

A classic problem in planning is districting, which aims to partition a given area into a specified number of subareas according to required criteria. Size, compactness, and contiguity are among the most frequently used districting criteria. While size and compactness may be interpreted differently in different contexts, contiguity is an unambiguous topological property. A district is said to be contiguous if all locations in it are ‘connected’—that is, one can travel between any two locations in the district without leaving it. This paper introduces a new integer-programming-based approach to districting modeling, which enforced contiguity constraints independently of any other criteria that might be additionally imposed. Three experimental models are presented, and tested with sample data on the forty-eight conterminous US states. A major implication of this paper is that the exact formulation of a contiguity requirement allows planners to address diverse sets of districting criteria.
Web-Based and Traditional Public Participation in Comprehensive Planning: A Comparative Study
Authors: Stern Eliahu , Gudes Ori , Svoray Tal
Published: October 2009

The present paper examines whether the potential advantages of the expanding practice of web-based public participation only complement the benefits of the traditional techniques, or whether they are empowering enough to replace them. The question is examined in a real-world case of neighborhood revitalization, in which both techniques were practiced simultaneously. Comparisons are made at four major planning junctions, in order to study the contributions of each technique to the qualities of involvement, trust, and empowerment. The results show that web-based participants not only differ from the participation of traditional practices, but they also differ from each other on the basis of their type of web participation. The results indicate that web-based participation is an effective complementary means of public participation, but it cannot replace the traditional unmediated techniques.
An Integrated Activity-Based Modelling Framework to Assess Vehicle Emissions: Approach and Application
Authors: Beckx Carolien , Panis Luc Int , Vankerkom Jean , Janssens Davy , Wets Geert , Arentze Theo
Published: October 2009

Owing to the richer set of concepts which are involved in activity-based transportation models, the potential advantages of an activity-based approach for air quality purposes have been recognized for a long time. However, models that have been developed along these lines are still scarce. In this research the activity-based model ALBATROSS was used in combination with the emission model MIMOSA to assess the travelled distances and the mobile source emissions produced by passenger cars in the Netherlands. The fact that this approach is based on hourly travel and emission values, rather than on aggregated results or peak hour values, a common practice within other traditional models, is an important added value. The predicted values seem to correspond well with the reported values from the Dutch Scientific Statistical Agency. Predictions for travelled distances overestimated the reported values by approximately 8%. Predictions for emissions of nitrogen oxide, carbon dioxide, volatile organic compounds, and particular matter differed by 16%, 11%, 9%, and 3%, respectively, from the officially reported values. This paper is novel in the sense that it both reports on the applied methodology and presents the practical results from a case study of the activity-based emission modelling approach.
An Agent-Based Model of Burglary
Authors: Malleson Nick , Evans Andrew , Jenkins Tony
Published: October 2009

Occurrences of crime are complex phenomena. They are the result of a large number of interrelated elements which can include environmental factors as well as complex human behaviours. Traditionally, crime occurrences have been modelled using statistical techniques, and although such approaches are useful, they face difficulties in providing predictive analyses and with the integration of behavioural information. Also, it is particularly difficult to account for the strongly influential effect of local urban form. Agent-based modelling is a relatively new modelling paradigm that has generated a considerable amount of interest. An agent is an independent component of a system which interacts with other agents and its environment to achieve goals. In this manner, large systems of agents can be created to mimic real scenarios. Most importantly, the agents can incorporate behavioural information to determine how they should achieve their goals, and models can include a highly detailed environment. This paper presents an agent-based model used to predict burglary rates, which, despite its simplicity, yields interesting results. We apply the model to the city of Leeds, UK. The model indicates that the urban configuration in Leeds is a major element in determining the level of crime across the city. It also demonstrates that agent-based modelling is an excellent tool for these types of analyses with much potential.
Effects of Familiarity on Spatial Frequency Thresholds for Face Matching
Authors: Watier Nicholas N , Collin Charles A
Published: October 2009

We examined whether familiarity with a face influences the spatial frequencies (SFs) required for face matching. Using the psychophysical method of constant stimuli and a 3AFC simultaneous matching paradigm, we obtained SF thresholds for familiar- and unfamiliar-face matching from fourteen observers, of which four were personally familiar with a subset of the faces while the remainder served as controls. SF thresholds from the lower extreme of the spectrum were approximately one octave lower for familiar than for unfamiliar faces, while SF thresholds from the upper extreme of the spectrum were approximately a third of an octave higher. These results highlight a quantitative difference between processing familiar and unfamiliar faces.
Mechanisms of NKT cell anergy induction involve Cbl-b-promoted monoubiquitination of CARMA1
Authors: Kojo Satoshi , Elly Chris , Harada Yohsuke , Langdon Wallace Y. , Kronenberg Mitchell , Liu Yun-Cai
Published: October 2009

Repeated injection of α-galactosylceramide, an agonistic ligand for natural killer T (NKT) cells, results in long-term unresponsiveness or anergy, which severely limits its clinical application. However, the molecular mechanisms leading to NKT anergy induction remain unclear. We show here that the decreased IFN-γ production and failed tumor rejection observed in anergized NKT cells are rescued by Cbl-b deficiency. Cbl-b E3 ligase activity is critical for the anergy induction, as revealed by the similarity between Cbl-b
−/−
and its RING finger mutant NKT cells. Cbl-b binds and promotes monoubiquitination to CARMA1, a critical signaling molecule in NFκB activation. Ubiquitin conjugation to CARMA1 disrupts its complex formation with Bcl10 without affecting its protein stability. In addition, CARMA1
−/−
NKT cells are defective in IFN-γ production. The study identifies an important signaling pathway linking Cbl-b-induced monoubiquitination to NFκB activation in NKT cell anergy induction, which may help design approaches for human cancer therapy.
Peroxisome dependency of alkyl-containing GPI-anchor biosynthesis in the endoplasmic reticulum
Authors: Kanzawa Noriyuki , Maeda Yusuke , Ogiso Hideo , Murakami Yoshiko , Taguchi Ryo , Kinoshita Taroh
Published: October 2009

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) play various roles in cell–cell and cell–environment interactions. GPI is synthesized in the endoplasmic reticulum (ER) from phosphatidylinositol (PI) through step-wise reactions including transfers of monosaccharides and preassembled GPI is transferred
en bloc
to proteins. Cellular PI contains mostly diacyl glycerol and unsaturated fatty acid in the sn-2 position, whereas mammalian GPI-APs have mainly 1-alkyl-2-acyl PI and almost exclusively stearic acid, a saturated chain, at the sn-2 position. The latter characteristic is the result of fatty acid remodeling occurring in the Golgi, generating GPI-anchors compatible with raft membrane. The former characteristic is the result of diacyl to alkyl-acyl change occurring in the third GPI intermediate, glucosaminyl-inositolacylated-PI (GlcN-acyl-PI). Here we investigated the origin of the sn-1 alkyl-chain in GPI-APs. Using cell lines defective in the peroxisomal alkyl-phospholipid biosynthetic pathway, we demonstrated that generation of alkyl-containing GPI is dependent upon the peroxisomal pathway. We further demonstrated that in cells defective in the peroxisome pathway, the chain composition of the diacyl glycerol moiety in GlcN-acyl-PI is different from those in the first intermediate N-acetylglucosaminyl-PI and cellular PI, indicating that not only diacyl to alkyl-acyl change but also diacyl to diacyl change occurs in GlcN-acyl-PI. We therefore propose a biosynthetic step within GlcN-acyl-PI in which the diacyl glycerol (or diacyl phosphatidic acid) part is replaced by diradyl glycerol (or diradyl phosphatidic acid). These results highlight cooperation of three organelles, the ER, the Golgi, and the peroxisome, in the generation of the lipid portion of GPI-APs.
Negative regulation of MyD88-dependent signaling by IL-10 in dendritic cells
Authors: Chang JiHoon , Kunkel Steven L. , Chang Cheong-Hee
Published: October 2009

IL-10 produced by dendritic cells (DC) can limit or terminate ongoing inflammatory responses by inhibiting the proinflammatory cytokine production. Currently, the molecular mechanism by which IL-10 suppresses cytokine production is still ill-defined. In this study, we showed that IL-10 produced by DC dampens myeloid differentiation factor (MyD)88-dependent, but not MyD88-independent signaling. At the molecular level, IL-10 induces ubiquitination and subsequent protein degradation of MyD88-dependent signaling molecules, including IL-1 receptor-associated kinase 4 and TNF-receptor associated factor 6. Protein degradation by IL-10 was associated with decreased phosphorylation of p38, JNK, and IKK. All of these events were prevented by either blocking IL-10 receptor signaling or inhibiting proteasome degradation. IL-10 induced LPS hyporesponsiveness using the same mechanisms, i.e., ubiquitination and protein degradation. Thus, a previously undescribed regulatory mechanism by which IL-10-mediated protein degradation contributes to the inhibition of inflammatory cytokine production and endotoxin tolerance in DC.
Miz1 is a signal- and pathway-specific modulator or regulator (SMOR) that suppresses TNF-α-induced JNK1 activation
Authors: Liu Jing , Zhao Yingming , Eilers Martin , Lin Anning
Published: October 2009

The proinflammatory cytokine TNF-α exerts its pleiotropic functions through activation of multiple downstream effectors, including JNK1. Yet, the underlying regulatory mechanism is incompletely understood. Here, we report that the transcription factor Myc-interacting zinc-finger protein 1 (Miz1) selectively suppresses TNF-α-induced JNK1 activation and cell death independently of its transcription activity. Proteomics analysis and yeast two-hybrid screening reveal that Miz1 is a JNK-associated protein. The TNF-α-induced activation of JNK1 is augmented in Miz1-deficient mouse embryonic fibroblasts (Miz1
−/−
MEFs), but the augmentation is abrogated by reintroduction of Miz1 or its transcription-deficient mutant. The regulation by Miz1 is highly specific, because it regulates TNF-α-induced TRAF2 K63-linked polyubiquitination. Neither JNK1 activation by IL-1β or UV nor TNF-α-induced activation of p38, ERK, or IκB kinase complex is affected by the loss of Miz1. The TNF-α-induced cell death also is accelerated in Miz1
−/−
MEFs. Upon TNF-α stimulation, Miz1 is degraded rapidly by the proteasome, relieving its suppression on JNK1 activation. Thus, our results show that in addition to being a transcription factor Miz1 acts as a signal- and pathway-specific modulator or regulator that specifically regulates TNF-α-induced JNK1 activation and cell death.
High-throughput in vivo screening of targeted molecular imaging agents
Authors: Gagnon M. Karen J. , Hausner Sven H. , Marik Jan , Abbey Craig K. , Marshall John F. , Sutcliffe Julie L.
Published: October 2009

The rapid development and translation of targeted molecular imaging agents from bench to bedside is currently a slow process, with a clear bottleneck between the discovery of new compounds and the development of an appropriate molecular imaging agent. The ability to identify promising new molecular imaging agents, as well as failures, much earlier in the development process using high-throughput screening techniques could save significant time and money. This work combines the advantages of combinatorial chemistry, site-specific solid-phase radiolabeling, and in vivo imaging for the rapid screening of molecular imaging agents. A one-bead-one-compound library was prepared and evaluated in vitro, leading to the identification of 42 promising lead peptides. Over 11 consecutive days, these peptides, along with a control peptide, were successfully radiolabeled with 4-[
18
F]fluorobenzoic acid and evaluated in vivo using microPET. Four peptides were radiolabeled per day, followed by simultaneous injection of each individual peptide into 2 animals. As a result, 4 promising new molecular imaging agents were identified that otherwise would not have been selected based solely on in vitro data. This study is the first example of the practical application of a high-throughput screening approach using microPET imaging of [
18
F]-labeled peptides for the rapid in vivo identification of potential new molecular imaging agents.
Olfactory perceptual learning requires adult neurogenesis
Authors: Moreno Mélissa M. , Linster Christiane , Escanilla Olga , Sacquet Joëlle , Didier Anne , Mandairon Nathalie
Published: October 2009

Perceptual learning is required for olfactory function to adapt appropriately to changing odor environments. We here show that newborn neurons in the olfactory bulb are not only involved in, but necessary for, olfactory perceptual learning. First, the discrimination of perceptually similar odorants improves in mice after repeated exposure to the odorants. Second, this improved discrimination is accompanied by an elevated survival rate of newborn inhibitory neurons, preferentially involved in processing of the learned odor, within the olfactory bulb. Finally, blocking neurogenesis before and during the odorant exposure period prevents this learned improvement in discrimination. Olfactory perceptual learning is thus mediated by the reinforcement of functional inhibition in the olfactory bulb by adult neurogenesis.
Macrophages Create an Acidic Extracellular Hydrolytic Compartment to Digest Aggregated Lipoproteins
Authors: Haka Abigail S. , Grosheva Inna , Chiang Ethan , Buxbaum Adina R. , Baird Barbara A. , Pierini Lynda M. , Maxfield Frederick R.
Published: October 2009

A critical event in atherogenesis is the interaction of macrophages with subendothelial lipoproteins. Although most studies model this interaction by incubating macrophages with monomeric lipoproteins, macrophages in vivo encounter lipoproteins that are aggregated. The physical features of the lipoproteins require distinctive mechanisms for their uptake. We show that macrophages create an extracellular, acidic, hydrolytic compartment to carry out digestion of aggregated low-density lipoproteins. We demonstrate delivery of lysosomal contents to these specialized compartments and their acidification by vacuolar ATPase, enabling aggregate catabolism by lysosomal acid hydrolases. We observe transient sealing of portions of the compartments, allowing formation of an “extracellular” proton gradient. An increase in free cholesterol is observed in aggregates contained in these compartments. Thus, cholesteryl ester hydrolysis can occur extracellularly in a specialized compartment, a lysosomal synapse, during the interaction of macrophages with aggregated low-density lipoprotein. A detailed understanding of these processes is essential for developing strategies to prevent atherosclerosis.
Live birth among Iguanian lizards predates Pliocene–Pleistocene glaciations
Authors: Schulte James A. , Moreno-Roark Franck
Published: October 2009

Among tetrapods, viviparity is estimated to have evolved independently within Squamata (lizards and snakes) more than 100 times, most frequently in species occupying cold climate environments. Because of this relationship with cold climates, it is sometimes assumed that many origins of squamate viviparity occurred over the past 2.5–4 Myr during the Pliocene–Pleistocene glaciations; however, this hypothesis is untested. Divergence-dating analysis on a 733-species tree of Iguanian lizards recovers 20 independent lineages that have evolved viviparity, of which 13 multispecies groups derived live birth prior to glacial advances (8–66 Myr ago). These results place the transitions from egg-laying to live birth among squamates in a well-supported historical context to facilitate examination of the underlying phenotypic and genetic changes associated with this complex shift in reproduction.
Relationships between specific surface area and pore size in electrospun polymer fibre networks
Authors: Eichhorn S. J. , Sampson W. W.
Published: October 2009

From consideration of the extent of contact between fibres in electrospun polymer networks, we provide theory relating the specific surface area of the network to the characteristic dimensions of interfibre voids. We show that these properties are strongly influenced by the cross-sectional morphologies of fibres. Whereas porosity has a strong influence on pore dimensions, in the range of porosities typically obtained in real networks, its influence on specific surface area is weak. By considering reference geometries of collapsed ribbons and fibres with circular cross sections, we demonstrate that at a given network porosity, fibre parameters that increase the specific surface area reduce the characteristic dimensions of voids. The implications of the theory, mainly in the context of cell proliferation on electrospun polymer scaffolds, are discussed; the theory has relevance also to future applications of these materials in composites.
Exhaled droplets due to talking and coughing
Authors: Xie Xiaojian , Li Yuguo , Sun Hequan , Liu Li
Published: October 2009

Respiratory infections can be spread via ‘contact’ with droplets from expiratory activities such as talking, coughing and sneezing, and also from aerosol-generating clinical procedures. Droplet sizes predominately determine the times they can remain airborne, the possibility of spread of infectious diseases and thus the strategies for controlling the infections. While significant inconsistencies exist between the existing measured data on respiratory droplets generated during expiratory activities, a food dye was used in the mouth during measurements of large droplets, which made the expiratory activities ‘unnatural’. We carried out a series of experiments using glass slides and a microscope as well as an aerosol spectrometer to measure the number and size of respiratory droplets produced from the mouth of healthy individuals during talking and coughing with and without a food dye. The total mass of respiratory droplets was measured using a mask, plastic bag with tissue and an electronic balance with a high precision. Considerable subject variability was observed and the average size of droplets captured using glass slides and microscope was about 50–100 µm. Smaller droplets were also detected by the aerosol spectrometer. More droplets seemed to be generated when a food dye was used.
Hyper-Kähler geometry and semi-geostrophic theory
Authors: Delahaies Sylvain , Roulstone Ian
Published: October 2009

We use the formalism of Monge–Ampère operators to study the geometric properties of the Monge–Ampère equations arising in semi-geostrophic (SG) theory and related models of geophysical fluid dynamics. We show how Kähler and hyper-Kähler structures arise, and the Legendre duality arising in SG theory is generalized to other models of nearly geostrophic flows.
Steady electrical and micro-rheological response functions for uncharged colloidal inclusions in polyelectrolyte hydrogels
Authors: Mohammadi Aliasghar , Hill Reghan J.
Published: October 2009

The electric-field-induced response of an uncharged colloidal sphere embedded in a quenched polyelectrolyte hydrogel is calculated from a model where the polymer network is treated as an elastic, porous skeleton saturated with an aqueous electrolyte. We present exact analytical solutions for the steady response to a uniform electric field, as well as the steady susceptibility, defined as the ratio of the particle displacement to the strength of an optical or magnetic force. Even though the particle is uncharged, it attains a finite electric-field-induced displacement owing to hydrodynamic coupling with electroosmotic flow. The steady susceptibility decreases with increasing charge and decreasing electrolyte concentration; in general, charge imparts a small correction to the classical theory for an uncharged linearly elastic continuum.
Mobility of ‘
N
-loops’: bodies cyclically connected by intersecting revolute hinges
Authors: Guest S. D. , Fowler P. W.
Published: October 2009

The mobilities of many objects from toys and molecular models to large-scale deployable structures can be understood in terms of
N
-loops: sets of
N
bodies, cyclically connected by pairs of intersecting revolute hinges. A symmetry-extended version of the Grübler criterion for counting kinematic degrees of freedom is used to explain and rationalize the observed mobilities of
N
-loops with small
N
. Compared with simple counting, the symmetry-based approach gives improved detection and visualization of mechanisms and states of self-stress. It can also give a better account of the differing mobilities of conformers occupying different regions of the phase space, such as the rigid chair and flexible boat forms of cyclohexane.
Long-term changes in metapopulation genetic structure: a quarter-century retrospective study on low-Arctic rock poolDaphnia
Authors: Weider Lawrence J. , Frisch Dagmar , Hebert Paul D. N.
Published: October 2009

Population genetic surveys approximately 25 years apart examined the distribution and abundance of asexual clones of the freshwater zooplankterDaphnia pulexcomplex in rock pools near Churchill, Manitoba, Canada. In 1984–1985, melanic members of this species complex were present in 131 rock pools at this site, but were only detected in 90 of these pools in 2007–2008. Allozymic surveys conducted during these two time periods revealed that 59 per cent of these populations showed unchanged clonal composition. Total clonal replacement occurred in 8 per cent of the populations, while the others (33%) included a mixture of ‘resident’ clones and new ‘colonists’. We discuss these changes in light of shifts in biotic and abiotic factors. We also discuss the use of rock pool habitats as ‘sentinel’ systems for examining long-term environmental changes in the ecological genetics of aquatic organisms in the Arctic.
Evidence that two main bottleneck events shaped modern human genetic diversity
Authors: Amos W. , Hoffman J. I.
Published: October 2009

There is a strong consensus that modern humans originated in Africa and moved out to colonize the world approximately 50 000 years ago. During the process of expansion, variability was lost, creating a linear gradient of decreasing diversity with increasing distance from Africa. However, the exact way in which this loss occurred remains somewhat unclear: did it involve one, a few or a continuous series of population bottlenecks? We addressed this by analysing a large published dataset of 783 microsatellite loci genotyped in 53 worldwide populations, using the program ‘B
ottleneck
’. Immediately following a sharp population decline, rare alleles are lost faster than heterozygosity, creating a transient excess of heterozygosity relative to allele number, a feature that is used by B
ottleneck
to infer historical events. We find evidence of two primary events, one ‘out of Africa’ and one placed around the Bering Strait, where an ancient land bridge allowed passage into the Americas. These findings agree well with the regions of the world where the largest founder events might have been expected, but contrast with the apparently smooth gradient of variability that is revealed when current heterozygosity is plotted against distance from Africa.
Activational effects of odours on avian navigation
Authors: Jorge Paulo E. , Marques Paulo A. M. , Phillips John B.
Published: October 2009

The sensory basis of the navigational map remains one of the most important and intriguing questions in animal behaviour. In birds, odours have been hypothesized to provide the primary source of map information. Convincing tests have shown that experienced homing pigeons rely on map information obtained at sites where they are exposed to natural odours, even if subsequently released (without additional olfactory information) at a different site. These findings have been interpreted as support for the olfactory map hypothesis. Using this ‘false-release-site’ (FRS) approach, we compared the effects of exposure to natural odours with that of exposure to a series of artificial odours lacking spatial information. Our findings show that olfactory exposure to either natural or artificial odours at an FRS caused pigeons to rely on map information obtained at the FRS, even if subsequently released at the true-release site in the opposite direction from the home loft. Because artificial odours did not provide map information, however, the findings clearly demonstrate that olfactory exposure provides no navigational information to pigeons whatsoever; instead it activates an independent non-olfactory map system. This test decisively contradicts the olfactory map hypothesis, which predicts that olfactory cues are the primary source of navigational information used by birds.
Upgrading Root Physiology for Stress Tolerance by Ectomycorrhizas: Insights from Metabolite and Transcriptional Profiling into Reprogramming for Stress Anticipation
Authors: Luo Zhi-Bin , Janz Dennis , Jiang Xiangning , Göbel Cornelia , Wildhagen Henning , Tan Yupeng , Rennenberg Heinz , Feussner Ivo , Polle Andrea
Published: October 2009

Ectomycorrhizas (EMs) alleviate stress tolerance of host plants, but the underlying molecular mechanisms are unknown. To elucidate the basis of EM-induced physiological changes and their involvement in stress adaptation, we investigated metabolic and transcriptional profiles in EM and non-EM roots of gray poplar (Populus × canescens) in the presence and absence of osmotic stress imposed by excess salinity. Colonization with the ectomycorrhizal fungus Paxillus involutus increased root cell volumes, a response associated with carbohydrate accumulation. The stress-related hormones abscisic acid and salicylic acid were increased, whereas jasmonic acid and auxin were decreased in EM compared with non-EM roots. Auxin-responsive reporter plants showed that auxin decreased in the vascular system. The phytohormone changes in EMs are in contrast to those in arbuscular mycorrhizas, suggesting that EMs and arbuscular mycorrhizas recruit different signaling pathways to influence plant stress responses. Transcriptome analyses on a whole genome poplar microarray revealed activation of genes related to abiotic and biotic stress responses as well as of genes involved in vesicle trafficking and suppression of auxin-related pathways. Comparative transcriptome analysis indicated EM-related genes whose transcript abundances were independent of salt stress and a set of salt stress-related genes that were common to EM non-salt-stressed and non-EM salt-stressed plants. Salt-exposed EM roots showed stronger accumulation of myoinositol, abscisic acid, and salicylic acid and higher K+-to-Na+ ratio than stressed non-EM roots. In conclusion, EMs activated stress-related genes and signaling pathways, apparently leading to priming of pathways conferring abiotic stress tolerance.
Web Content Accessibility Guidelines 2.0
Authors: Ribera Mireia , Porras Merce , Boldu Marc , Termens Miquel , Sule Andreu , Paris Pilar
Published: October 2009

Purpose

The purpose of this paper is to explain the changes in the Web Content Accessibility Guidelines (WCAG) 2.0 compared with WCAG 1.0 within the context of its historical development.

Design/methodology/approach

In order to compare WCAG 2.0 with WCAG 1.0 a diachronic analysis of the evolution of these standards is done. Known authors and publications in the field, the Web Accessibility Initiative (WAI) web pages, WebAIM and the blogosphere were also monitored for comments and third‐party analyses. The analysis of the main changes from WCAG 1.0 to WCAG 2.0 was based on personal experience with WAI guidelines, experimentation with some of the new guidelines, and a selection of best practice online services in the application of the WCAG, including WAI documentation.

Findings

WCAG 2.0 is more educational and is applied to more technologies than WCAG 1.0. The limitations of WCAG 1.0 are mostly due to its origin. In changing from one to the other, new priorities and new elements must be taken into account. The paper concludes that though these guidelines are a useful tool for governments, they are only the first step towards accessibility, which can only be achieved through user‐centred design.

Originality/value

This paper explains the significance and limitations of the WCAG and gives a short guide to adapting web sites to the new regulations.
Transforming organizational identity under institutional change
Authors: He Hongwei , Baruch Yehuda
Published: October 2009

Purpose

The objective of this paper is to report a case study investigating how organizational identity evolves during institutional change within a UK building society.

Design/methodology/approach

The paper employs an inductive case study, which is appropriate for examining such change processes. It builds on grounded theory, considered appropriate for such an explanatory research.

Findings

The paper finds that: institutional change, especially regulation and practice changes, serves as the trigger to increasing salience of identity issues, i.e. identity ambiguity, legitimacy crisis and perceived identity obsolescence; leadership, organizational culture and strategic exercises are salient apparatuses to tackle identity problems caused by external pressure; and a new identity is formed as a result of the managerial interventions, characterised by the rediscovery of historical roots, modernization and dualism.

Research limitations/implications

The paper provides an account of identity change, given a broader business environment change context within which the organization operates. Utilizing qualitative study of one case may be taken as a limitation.

Originality/value

The theoretical contribution reflected in the findings has implications for the interfaces between identity and institutional environment and organizational culture.