bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative calcium resistivity based method for accurate and scalable water vapor transmission rate measurement
Authors: Reese Matthew O. , Dameron Arrelaine A. , Kempe Michael D.
Published: August 2011

The development of flexible organic light emitting diode displays and flexible thin film photovoltaic devices is dependent on the use of flexible, low-cost, optically transparent and durable barriers to moisture and/or oxygen. It is estimated that this will require high moisture barriers with water vapor transmission rates (WVTR) between 10−4 and 10−6 g/m2/day. Thus there is a need to develop a relatively fast, low-cost, and quantitative method to evaluate such low permeation rates. Here, we demonstrate a method where the resistance changes of patterned Ca films, upon reaction with moisture, enable one to calculate a WVTR between 10 and 10−6 g/m2/day or better. Samples are configured with variable aperture size such that the sensitivity and/or measurement time of the experiment can be controlled. The samples are connected to a data acquisition system by means of individual signal cables permitting samples to be tested under a variety of conditions in multiple environmental chambers. An edge card connector is used to connect samples to the measurement wires enabling easy switching of samples in and out of test. This measurement method can be conducted with as little as 1 h of labor time per sample. Furthermore, multiple samples can be measured in parallel, making this an inexpensive and high volume method for measuring high moisture barriers.
Influence of electrical fatigue on hole transport in poly(p-phenylenevinylene)-based organic light-emitting diodes
Authors: Stegmaier Katja , Fleissner Arne , Janning Helga , Yampolskii Sergey , Melzer Christian , Seggern Heinz von
Published: August 2011

The hole transport in poly(p-phenylenevinylene) (PPV) was investigated before and after bipolar electrical stress by the time-of-flight (TOF) method. Bipolar structures similar to organic light emitting diodes (OLEDs) were realized, yet with much thicker layers than usually prevailing in OLEDs. During fatigue, the hole mobility is reduced, the field dependence of the mobility is increased, and the hole transport becomes more and more dispersive. These results go along with the fatigue behavior of thin film OLEDs that were investigated by charge extraction via linearly increasing voltage (CELIV). Even though theoretical simulations could show that both thick- and thin-film PPV-based OLED structures are dominated by holes, the presented results indicate that the existence of electrons leads to degradation during hole transport. A possible reason for an enlarged electron density in the otherwise hole dominated device is suggested.
Low effective surface recombination in In(Ga)As/GaAs quantum dot diodes
Authors: Tanriseven Selim , Corbett Brian
Published: August 2011

Size dependent current-voltage measurements were performed on InGaAs quantum dot active region mesa diodes and the surface recombination velocity was extracted from current density versus perimeter/area plots using a diffusion model. An effective surface recombination value of 5.5 × 104 cm/s was obtained that can be reduced by more than an order of magnitude by selective oxidation of Al0.9Ga0.1As cladding layers. The values are three times smaller than those obtained for a single quantum well. The effect of p-type doping in the active region was investigated and found to increase the effective surface recombination.
Heating effects in nanofocusing metal wedges
Authors: Tan Shiaw Juen , Gramotnev Dmitri K.
Published: August 2011

This paper investigates theoretically and numerically local heating effects in plasmon nanofocusing structures with a particular focus on the sharp free-standing metal wedges. The developed model separates plasmon propagation in the wedge from the resultant heating effects. Therefore, this model is only applicable where the temperature increments in a nanofocusing structure are sufficiently small not to result in significant variations of the metal permittivity in the wedge. The problem is reduced to a one-dimensional heating model with a distributed heat source resulting from plasmon dissipation in the metal wedge. A simple heat conduction equation governing the local heating effects in a nanofocusing structure is derived and solved numerically for plasmonic pulses of different lengths and reasonable energies. Both the possibility of achieving substantial local temperature increments in the wedge (with a significant self-influence of the heating plasmonic pulses), and the possibility of relatively weak heating (to ensure the validity of the previously developed nanofocusing theory) are demonstrated and discussed, including the future applications of the obtained results. Applicability conditions for the developed model are also derived and discussed.
Titanium nitride: A new Ohmic contact material for n-type CdS
Authors: Didden Arjen , Battjes Hemme , Machunze Raymond , Dam Bernard , van de Krol Roel
Published: August 2011

In devices based on CdS, indium is often used to make Ohmic contacts. Since indium is scarce and expensive, suitable replacement materials need to be found. In this work, we show that sputtered titanium nitride forms an Ohmic contact with n-type CdS. The CdS films, deposited with chemical bath deposition, have a hexagonal crystal structure and are polycrystalline, mostly with a (002) texture. The thickness of the films is ∼600 nm, and the donor density is 1.9 × 1016 cm−3. The donor density increases to 1.5 × 1017 cm−3 upon annealing. The contact resistivity of sputtered TiN on CdS is found to be 4.7 ± 0.6 Ω cm2. This value is sufficiently small to avoid large resistive losses in most CdS device applications. To demonstrate the use of TiN in a CdS device, a Au/CdS/TiN Schottky diode was constructed. The diode has a potential barrier of 0.69 V and an ideality factor of 2.2.
Anomalous Hall effect in NiPt thin films
Authors: Golod T. , Rydh A. , Krasnov V. M.
Published: August 2011

We have studied the Hall effect in sputtered NixPt1−x thin films with different Ni concentrations. Temperature, magnetic field, and angular dependencies are analyzed and the phase diagram of NiPt thin films is obtained. It is found that films with sub-critical Ni concentration exhibit cluster-glass behavior at low temperatures with a perpendicular magnetic anisotropy below the freezing temperature. Films with super-critical Ni concentration are ferromagnetic with parallel anisotropy. At the critical concentration the state of the film is strongly frustrated. Such films demonstrate canted magnetization with the easy axis rotating as a function of temperature. The magnetism appears via consecutive paramagnetic–cluster glass–ferromagnetic transitions, rather than a single second-order phase transition. But most remarkably, the extraordinary Hall effect changes sign at the critical concentration. We suggest that this is associated with a reconstruction of the electronic structure of the alloy at the normal metal–ferromagnet quantum phase transition.
Ferromagnetic resonance and damping properties of CoFeB thin films as free layers in MgO-based magnetic tunnel junctions
Authors: Liu Xiaoyong , Zhang Wenzhe , Carter Matthew J. , Xiao Gang
Published: August 2011

We have investigated the magnetization dynamics of sputtered Co40Fe40B20 thin films in a wide range of thicknesses used as free layers in MgO-based magnetic tunnel junctions, with the technique of broadband ferromagnetic resonance (FMR). We have observed a large interface-induced magnetic perpendicular anisotropy in the thin film limit. The out-of-plane angular dependence of the FMR measurement revealed the contributions of two different damping mechanisms in thick and thin film limits. In thinner films (< 2 nm), two-magnon scattering and inhomogeneous broadening are significant for the FMR linewidth, while the Gilbert damping dominates the linewidth in thicker films (≥ 4 nm). Lastly, we have observed an inverse scaling of Gilbert damping constant with film thickness, and an intrinsic damping constant of 0.004 in the CoFeB alloy film is determined.
Clinical diagnostic of pleural effusions using a high-speed viscosity measurement method
Authors: Hurth Cedric , Klein Katherine , van Nimwegen Lena , Korn Ronald , Vijayaraghavan Krishnaswami , Zenhausern Frederic
Published: August 2011

We present a novel bio-analytical method to discriminate between transudative and exudative pleural effusions based on a high-speed video analysis of a solid glass sphere impacting a liquid. Since the result depends on the solution viscosity, it can ultimately replace the battery of biochemical assays currently used. We present results obtained on a series of 7 pleural effusions obtained from consenting patients by analyzing both the splash observed after the glass impactor hits the liquid surface, and in a configuration reminiscent of the drop ball viscometer with added sensitivity and throughput provided by the high-speed camera. The results demonstrate distinction between the pleural effusions and good correlation with the fluid chemistry analysis to accurately differentiate exudates and transudates for clinical purpose. The exudative effusions display a viscosity around 1.39 ± 0.08 cP whereas the transudative effusion was measured at 0.89 ± 0.09 cP, in good agreement with previous reports.
Enhanced field emission from clustered TiO2 nanotube arrays
Authors: Alivov Yahya , Klopfer Michael , Molloi Sabee
Published: August 2011

Field emission properties of clustered titanium dioxide (TiO2) nanotube arrays have been studied and compared with those of dense, highly aligned TiO2 nanotube arrays. It was found that clustered nanotube arrays showed significant increase of field emission current density (sevenfold) and field enhancement factor (fivefold) compared to regular shape, highly aligned forest-like TiO2 nanotube arrays, which can be explained by the reduction of electric field screening effects. Clustered TiO2 nanotubes arrays were achieved by electrochemical oxidation of titanium sheet in electrolyte consisting of diethylene or ethylene glycol solvents and ammonium fluorine, while the well aligned nanotube arrays were grown using glycerol.
Using a pruned basis, a non-product quadrature grid, and the exact Watson normal-coordinate kinetic energy operator to solve the vibrational Schrödinger equation for C2H4
Authors: Avila Gustavo , Carrington Tucker
Published: August 2011

In this paper we propose and test a method for computing numerically exact vibrational energy levels of a molecule with six atoms. We use a pruned product basis, a non-product quadrature, the Lanczos algorithm, and the exact normal-coordinate kinetic energy operator (KEO) with the πtμπ term. The Lanczos algorithm is applied to a Hamiltonian with a KEO for which μ is evaluated at equilibrium. Eigenvalues and eigenvectors obtained from this calculation are used as a basis to obtain the final energy levels. The quadrature scheme is designed, so that integrals for the most important terms in the potential will be exact. The procedure is tested on C2H4. All 12 coordinates are treated explicitly. We need only ∼1.52 × 108 quadrature points. A product Gauss grid with which one could calculate the same energy levels has at least 5.67 × 1013 points.
Effective Hamiltonian of liquid-vapor curved interfaces in mean field
Authors: Segovia-López José G. , Zamora Adolfo , Santiago J. A.
Published: August 2011

We analyze a one-component simple fluid in a liquid-vapor coexistence state, which forms an arbitrarily curved interface. By using an approach based on density functional theory, we obtain an exact and simple expression for the grand potential at the level of mean field approximation that depends on the density profile and the short-range interaction potential. By introducing the step-function approximation for the density profile, and using general geometric arguments, we expand the grand potential in powers of the principal curvatures of the surface and find consistency with the Helfrich phenomenological model in the second order approximation.
Thermoelectric properties of Ag1−xGaTe2 with chalcopyrite structure
Authors: Yusufu Aikebaier , Kurosaki Ken , Kosuga Atsuko , Sugahara Tohru , Ohishi Yuji , Muta Hiroaki , Yamanaka Shinsuke
Published: August 2011

In the present study, we investigated the high-temperature thermoelectric (TE) properties of AgGaTe2 with chalcopyrite structure. We tried to enhance the TE properties of AgGaTe2 by reducing the Ag content. The reduction of Ag increased the carrier concentration, leading to enhancement of the dimensionless figure of merit (ZT). The maximum ZT value was 0.77 at 850 K obtained in Ag0.95GaTe2, which was approximately two times higher than that of stoichiometric AgGaTe2.
Optoenergy storage, stimulated processes in optical amplification with electro-optic ceramic gain media of Nd3+ doped lanthanum lead zirconate titanate
Authors: Wu Ye , Zhao Hua , Zou Yingyin K. , Chen Xuesheng , Bartolo Baldassare Di , Zhang Jingwen W.
Published: August 2011

Optical amplification was observed in electro-optic (EO) ceramic plates of neodymium doped lanthanum-modified lead zirconate titanate (Nd3+:PLZT), when the pumping and seeding beams are not overlapped temporarily. This striking feature in the gain measurement and the accompanying slowly trailing-off both seen in the optical amplification as well as in the lasing action are satisfactorily explained by electron releasing from the rich vacancy-based carrier traps in the intrinsically disordered ceramics, i.e., the consecutively optical, thermal stimuli are found responsible for the long persistent optoenergy storage, and consequently the slow response of the gain dynamics. These findings in optical amplification, the slowly trailing-off, and the underlying mechanism have opened a new way of developing novel controllable optical devices. The model thus established could serve as a guide in design and refinement of a new generation of products out of this excellent, well commercialized EO PLZT ceramics family and similar others.
The plasmonic resonant absorption in GaN double-channel high electron mobility transistors
Authors: Wang Lin , Chen Xiao-Shuang , Hu Wei-Da , Wang Jun , Wang Jian , Wang Xiao-Dong , Lu Wei
Published: August 2011

We have investigated the plasmonic oscillations in GaN double-channel (DC) high electron mobility transistors (HEMTs). It is shown that the absorption peaks of DC-HEMT can exist in wider frequency regions than that of single channel HEMT. These absorption peaks appear as a result of excitation of elementary plasmon modes supported by separate channels and can be tuned for the entire terahertz domain. Significant resonant enhancement is also observed after varying the two-dimensional electron gas density in DC-HEMTs. These promising properties indicate that DC-HEMTs can have important applications as voltage tunable broadband terahertz detectors, intensity modulators, and filters.
Air stable hybrid inverted tandem solar cell design
Authors: Liu Feng , Nunzi Jean-Michel
Published: August 2011

In order to get an air stable solar cell with high open circuit voltage (Voc), we fabricated an inverted tandem solar cell based on hybrid wet chemistry and vacuum thermal deposition techniques. A thin metallic interfacial layer was applied to improve charge recombination and maximize both the fill factor and Voc of the tandem solar cell. A cationic dye doped electron transport layer was used to minimize space charge induced Voc loss. The tandem cell Voc reached 1.02 V, which equals the sum of the two subcells’ Voc. Increase of the metal nanoparticles’ layer thickness reduces the short circuit current density of the tandem owing to increasing light extinction. Our tandem cell design offers superior air stability due to additional encapsulation effect from top metal oxide layers. It retains about 80% of its original efficiency after storage in air for three months.
Compact device for cleaning scanner-mounted scanning tunneling microscope tips using electron bombardment
Authors: Hellmann D. , Worbes L. , Kittel A.
Published: August 2011

Most scanning probe techniques rely on the assumption that both sample and tip are free from adsorbates, residues, and oxide not deposited intentionally. Getting a clean sample surface can be readily accomplished by applying ion sputtering and subsequent annealing, whereas finding an adequate treatment for tips is much more complicated. The method of choice would effectively desorb undesired compounds without reducing the sharpness or the general geometry of the tip. Several devices which employ accelerated electrons to achieve this are described in the literature. To minimize both the effort to implement this technique in a UHV chamber and the overall duration of the cleaning procedure, we constructed a compact electron source fitted into a sample holder, which can be operated in a standard Omicron variable-temperature (VT)-STM while the tip stays in place. This way a maximum of compatibility with existing systems is achieved and short turnaround times are possible for tip cleaning.
Mismatch relaxation by stacking fault formation of AlN islands in AlGaN/GaN structures on m-plane GaN substrates
Authors: Smalc-Koziorowska Julita , Sawicka Marta , Remmele Thilo , Skierbiszewski Czeslaw , Grzegory Izabella , Albrecht Martin
Published: August 2011

We study the mismatch relaxation of 2-5 nm thin elongated AlN islands formed during growth of AlGaN on bulk m-plane GaN by molecular beam epitaxy. The relaxation of these m-plane AlN layers is anisotropic and occurs through the introduction of stacking faults in [0001] planes during island coalescence, while no relaxation is observed along the perpendicular [112¯0] direction. This anisotropy in the mismatch relaxation and the formation of stacking faults in the AlN islands are explained by the growth mode of the AlN platelets and their coalescence along the [0001] direction.
Tolerance study of nanoparticle enhancement for thin-film silicon solar cells
Authors: Akimov Yu. A. , Koh W. S.
Published: August 2011

The improved light trapping caused by incorporation of plasmonic nanoparticles makes it possible to significantly increase the performance of thin-film silicon solar cells. To investigate stability of this enhancement, a systematic study on random distribution of the nanoparticles is performed. Based on predictive numerical modeling, effects such as the influence of random nanoparticle sizes, shapes, and mutual positions are discussed and analyzed with respect to reproducibility of the enhancement by silver nanoparticles for thin-film hydrogenated amorphous silicon solar cells.
Origin of magnetic switching field distribution in bit patterned media based on pre-patterned substrates
Authors: Pfau B. , Günther C. M. , Guehrs E. , Hauet T. , Yang H. , Vinh L. , Xu X. , Yaney D. , Rick R. , Eisebitt S. , Hellwig O.
Published: August 2011

Using a combination of synchrotron radiation based magnetic imaging and high-resolution transmission electron microscopy we reveal systematic correlations between the magnetic switching field and the internal nanoscale structure of individual islands in bit patterned media fabricated by Co/Pd-multilayer deposition onto pre-patterned substrates. We find that misaligned grains at the island periphery are a common feature independent of the island switching field, while irregular island shapes and misaligned grains specifically extending into the center of an island are systematically correlated with a reduced island reversal field.
Magnetism of covalently functionalized carbon nanotubes
Authors: Santos Elton J. G. , Sánchez-Portal D. , Ayuela A.
Published: August 2011

We investigate the electronic structure of carbon nanotubes functionalized by adsorbates anchored with single C-C covalent bonds. We find that despite the particular adsorbate, a spin moment with a universal value of 1.0 μB per molecule is induced at low coverage. Therefore, we propose a mechanism of bonding-induced magnetism at the carbon surface. The adsorption of a single molecule creates a dispersionless defect state at the Fermi energy, which is mainly localized in the carbon wall and presents a small contribution from the adsorbate. This universal spin moment is fairly independent of the coverage as long as all the molecules occupy the same graphenic sublattice. The magnetic coupling between adsorbates is also studied and reveals a key dependence on the graphenic sublattice adsorption site.
Towards a high efficiency amorphous silicon solar cell using molybdenum oxide as a window layer instead of conventional p-type amorphous silicon carbide
Authors: Il Park Sang , Jae Baik Seung , Im Jong-San , Fang Liang , Jeon Jin-Wan , Su Lim Koeng
Published: August 2011

A thermally evaporated molybdenum oxide (MoO3) film was used as a window layer of a hydrogenated amorphous silicon (a-Si:H) solar cell instead of the conventional p-type hydrogenated amorphous silicon carbide (p-a-SiC:H) film. The short circuit current density (JSC) and fill factor were increased due to the wide optical band gap and high conductivity of the MoO3 film. As a result, the conversion efficiency of the fabricated MoO3 solar cell was increased to 6.21% compared to the typical a-Si:H solar cell (5.97%).
Communication: Conformation state diagram of polypeptides: A chain length induced α-β transition
Authors: Ricchiuto Piero , Brukhno Andrey V. , Paci Emanuele , Auer Stefan
Published: August 2011

By using a generic coarse grained polypeptide model, we perform multicanonical molecular dynamics simulations for determining the equilibrium conformation state diagram of a single homopolypeptide chain as a function of the chain length and temperature. The state diagram highlights the thermal regimes of stability for various conformational patterns in polypeptides, including swollen, random and collapsed coils, globular structures, extended and bended α helices, and compact β bundles. Remarkably, at low temperatures we observe a sharp transition from extended α helix to compact β bundles as the chain length increases. This finding indicates that the chain length is one of the intrisic factors that can trigger α-β transformations in a broad class of polypeptides.
Stream/Bounce Event Perception Reveals a Temporal Limit of Motion Correspondence Based on Surface Feature over Space and Time
Authors: Kawachi Yousuke , Kawabe Takahiro , Gyoba Jiro
Published: August 2011

We examined how stream/bounce event perception is affected by motion correspondence based on the surface features of moving objects passing behind an occlusion. In the stream/bounce display two identical objects moving across each other in a two-dimensional display can be perceived as either streaming through or bouncing off each other at coincidence. Here, surface features such as colour (Experiments 1 and 2) or luminance (Experiment 3) were switched between the two objects at coincidence. The moment of coincidence was invisible to observers due to an occluder. Additionally, the presentation of the moving objects was manipulated in duration after the feature switch at coincidence. The results revealed that a postcoincidence duration of approximately 200 ms was required for the visual system to stabilize judgments of stream/bounce events by determining motion correspondence between the objects across the occlusion on the basis of the surface feature. The critical duration was similar across motion speeds of objects and types of surface features. Moreover, controls (Experiments 4a–4c) showed that cognitive bias based on feature (colour/luminance) congruency across the occlusion could not fully account for the effects of surface features on the stream/bounce judgments. We discuss the roles of motion correspondence, visual feature processing, and attentive tracking in the stream/bounce judgments.
Physical modelling of forest fire spreading through heterogeneous fuel beds
Authors: Simeoni Albert , Salinesi Pierre , Morandini Frédéric
Published: August 2011

Vegetation cover is a heterogeneous medium composed of different kinds of fuels and non-combustible parts. Some properties of real fires arise from this heterogeneity. Creating heterogeneous fuel areas may be useful both in land management and in firefighting by reducing fire intensity and fire rate of spread. The spreading of a fire through a heterogeneous medium was studied with a two-dimensional reaction–diffusion physical model of fire spread. Randomly distributed combustible and non-combustible square elements constituted the heterogeneous fuel. Two main characteristics of the fire were directly computed by the model: the size of the zone influenced by the heat transferred from the fire front and the ignition condition of vegetation. The model was able to provide rate of fire spread, temperature distribution and energy transfers. The influence on the fire properties of the ratio between the amount of combustible elements and the total amount of elements was studied. The results provided the same critical fire behaviour as described in both percolation theory and laboratory experiments but the results were quantitatively different because the neighbourhood computed by the model varied in time and space with the geometry of the fire front. The simulations also qualitatively reproduced fire behaviour for heterogeneous fuel layers as observed in field experiments. This study shows that physical models can be used to study fire spreading through heterogeneous fuels, and some potential applications are proposed about the use of heterogeneity as a complementary tool for fuel management and firefighting.
Alternative equations to estimate the surface-to-volume ratio of different forest fuel particles
Authors: Hachmi M. , Sesbou A. , Benjelloun H. , Bouanane F.
Published: August 2011

Surface-to-volume ratio is an important fuel descriptor. Surface-to-volume ratio quantification methods currently used are specific and their accuracy varies with fuel types. In this work, we developed a geometric surface-to-volume ratio estimation method based on the perimeter-to-area ratio concept. Dimensions of leaves, twigs and needles of Moroccan tree and shrub species were measured. Our findings are: (i) the thickness of a leaf is variable along its width and length, and its average cross-section is located at its mid-length; (ii) a formula to calculate the ellipse perimeter was established using an elongation coefficient e, determined on the basis of the cross-section thickness and width; and (iii) one general surface-to-volume ratio formula was developed, from which five other equations were derived, according to the specific characteristics of each fuel type, for twigs, leaves, needles with semi-elliptical cross-section, needles with crescent cross-section shape, and needles with cross-section representing half or a sector of a circle respectively. Surface-to-volume ratio values obtained with the developed equations were compared with the currently published data.
Wildland fire spread modelling using cellular automata: evolution in large-scale spatially heterogeneous environments under fire suppression tactics
Authors: Alexandridis A. , Russo L. , Vakalis D. , Bafas G. V. , Siettos C. I.
Published: August 2011

We show how microscopic modelling techniques such as Cellular Automata linked with detailed geographical information systems (GIS) and meteorological data can be used to efficiently predict the evolution of fire fronts on mountainous and heterogeneous wild forest landscapes. In particular, we present a lattice-based dynamic model that includes various factors, ranging from landscape and earth statistics, attributes of vegetation and wind field data to the humidity of the fuel and the spotting transfer mechanism. We also attempt to model specific fire suppression tactics based on air tanker attacks utilising technical specifications as well as operational capabilities of the aircrafts. We use the detailed model to approximate the dynamics of a large-scale fire that broke out in a region on the west flank of the Greek National Park of Parnitha Mountain in June of 2007. The comparison between the simulation and the actual results showed that the proposed model predicts the fire-spread characteristics in an adequate manner. Finally, we discuss how such a detailed model can be exploited in order to design and develop, in a systematic way, fire risk management policies.
Foraging Modes of Predators and Behaviors of Prey Determine the Outcome of Multiple Predator Interactions
Authors: Carey Michael P. , Wahl David H.
Published: August 2011

Interactions with multiple predator species may differ among prey with different antipredator defenses. The interactions between largemouth bass Micropterus salmoides (a cruising predator) and muskellunge Esox masquinongy (an ambush predator) and prey with different antipredator behaviors, bluegill Lepomis macrochirus and fathead minnow Pimephales promelas, was examined in mesocosms. In the combined predator treatment, no differences were found in the foraging sequence for the cruising predator, whereas the ambush predator increased the number of follows and pursuits. Bluegills altered their behavior across predator treatments by changing their activity levels and habitat use. Ultimately, the ambush predator benefited from the combined predators because of a greater encounter frequency with bluegills that led to more captures and a risk‐enhanced effect on bluegills. The high vulnerability of fathead minnow to individual ambush and cruising predators led to a neutral effect from combined predators. Predator foraging modes and prey behavior must be taken into account to understand natural food webs.
AMBIVALENT CITIZENS
Authors: Açikel Fethi , Ateş Kazim
Published: August 2011

This paper deals with the ambivalent position of Turkish nationalism vis-à-vis the Alevi ethno-religious identity. The Alevi are the largest ethno-religious minority in Turkey. Via a critical pluralist stance, the authors argue that the debates revolving around the origins and nature of the Alevi identity disclose the cultural –and, to a lesser extent, romantic – characteristics of Turkish nationalism and its relative inability to accommodate a fully civic and pluralist notion of national identity. The paper argues that the Alevi question is one of the litmus tests that reveal Turkish nationalism's uneasiness with adopting the idea of an ethno-religiously plural society. Two hegemonic branches of Turkish nationalism conceptualize the Alevi identity through ethno-cultural and religio-cultural lenses. This leads to the Alevi being coded as ‘ambivalent citizens’. This ambivalent status creates a bifurcated yet intertwined process of belonging and non-belonging, authenticity and stigmatization. The paper argues that the unremitting oscillation between the status of ‘genuine self-ness’ and ‘heretical otherness’ discloses the very non-civic and cultural foundations of Turkish nationalism.
Rb and p130 control cell cycle gene silencing to maintain the postmitotic phenotype in cardiac myocytes
Authors: Sdek Patima , Zhao Peng , Wang Yaping , Huang Chang-jiang , Ko Christopher Y. , Butler Peter C. , Weiss James N. , MacLellan W. Robb
Published: August 2011

The mammalian heart loses its regenerative potential soon after birth. Adult cardiac myocytes (ACMs) permanently exit the cell cycle, and E2F-dependent genes are stably silenced, although the underlying mechanism is unclear. Heterochromatin, which silences genes in many biological contexts, accumulates with cardiac differentiation. H3K9me3, a histone methylation characteristic of heterochromatin, also increases in ACMs and at E2F-dependent promoters. We hypothesize that genes relevant for cardiac proliferation are targeted to heterochromatin by retinoblastoma (Rb) family members interacting with E2F transcription factors and recruiting heterochromatin protein 1 (HP1) proteins. To test this hypothesis, we created cardiac-specific Rb and p130 inducible double knockout (IDKO) mice. IDKO ACMs showed a decrease in total heterochromatin, and cell cycle genes were derepressed, leading to proliferation of ACMs. Although Rb/p130 deficiency had no effect on total H3K9me3 levels, recruitment of HP1-γ to promoters was lost. Depleting HP1-γ up-regulated proliferation-promoting genes in ACMs. Thus, Rb and p130 have overlapping roles in maintaining the postmitotic state of ACMs through their interaction with HP1-γ to direct heterochromatin formation and silencing of proliferation-promoting genes.
Formation of the postmitotic nuclear envelope from extended ER cisternae precedes nuclear pore assembly
Authors: Lu Lei , Ladinsky Mark S. , Kirchhausen Tomas
Published: August 2011

During mitosis, the nuclear envelope merges with the endoplasmic reticulum (ER), and nuclear pore complexes are disassembled. In a current model for reassembly after mitosis, the nuclear envelope forms by a reshaping of ER tubules. For the assembly of pores, two major models have been proposed. In the insertion model, nuclear pore complexes are embedded in the nuclear envelope after their formation. In the prepore model, nucleoporins assemble on the chromatin as an intermediate nuclear pore complex before nuclear envelope formation. Using live-cell imaging and electron microscope tomography, we find that the mitotic assembly of the nuclear envelope primarily originates from ER cisternae. Moreover, the nuclear pore complexes assemble only on the already formed nuclear envelope. Indeed, all the chromatin-associated Nup107–160 complexes are in single units instead of assembled prepores. We therefore propose that the postmitotic nuclear envelope assembles directly from ER cisternae followed by membrane-dependent insertion of nuclear pore complexes.
Multispan mitochondrial outer membrane protein Ugo1 follows a unique Mim1-dependent import pathway
Authors: Papić Dražen , Krumpe Katrin , Dukanovic Jovana , Dimmer Kai S. , Rapaport Doron
Published: August 2011

The mitochondrial outer membrane (MOM) harbors several multispan proteins that execute various functions. Despite their importance, the mechanisms by which these proteins are recognized and inserted into the outer membrane remain largely unclear. In this paper, we address this issue using yeast mitochondria and the multispan protein Ugo1. Using a specific insertion assay and analysis by native gel electrophoresis, we show that the import receptor Tom70, but not its partner Tom20, is involved in the initial recognition of the Ugo1 precursor. Surprisingly, the import pore formed by the translocase of the outer membrane complex appears not to be required for the insertion process. Conversely, the multifunctional outer membrane protein mitochondrial import 1 (Mim1) plays a central role in mediating the insertion of Ugo1. Collectively, these results suggest that Ugo1 is inserted into the MOM by a novel pathway in which Tom70 and Mim1 contribute to the efficiency and selectivity of the process.
Regulation of basal resistance by a powdery mildew‐induced cysteine‐rich receptor‐like protein kinase in barley
Authors: RAYAPURAM CBGOWDA , JENSEN MICHAEL K. , MAISER FABIAN , SHANIR JOHANNA VIKGREN , HORNSHØJ HENRIK , RUNG JESPER H. , GREGERSEN PER L. , SCHWEIZER PATRICK , COLLINGE DAVID B. , LYNGKJÆR MICHAEL F.
Published: August 2011

The receptor‐like protein kinases (RLKs) constitute a large and diverse group of proteins controlling numerous plant physiological processes, including development, hormone perception and stress responses. The cysteine‐rich RLKs (CRKs) represent a prominent subfamily of transmembrane‐anchored RLKs. We have identified a putative barley (Hordeum vulgare) CRK gene family member, designated HvCRK1. The mature putative protein comprises 645 amino acids, and includes a putative receptor domain containing two characteristic ‘domain 26 of unknown function’ (duf26) domains in the N‐terminal region, followed by a rather short 17‐amino‐acid transmembrane domain, which includes an AAA motif, two features characteristic of endoplasmic reticulum (ER)‐targeted proteins and, finally, a characteristic putative protein kinase domain in the C‐terminus. The HvCRK1 transcript was isolated from leaves inoculated with the biotrophic fungal pathogen Blumeria graminis f.sp. hordei (Bgh). HvCRK1 transcripts were observed to accumulate transiently following Bgh inoculation of susceptible barley. Transient silencing of HvCRK1 expression in bombarded epidermal cells led to enhanced resistance to Bgh, but did not affect R‐gene‐mediated resistance. Silencing of HvCRK1 phenocopied the effective penetration resistance found in mlo‐resistant barley plants, and the possible link between HvCRK1 and MLO was substantiated by the fact that HvCRK1 induction on Bgh inoculation was dependent on Mlo. Finally, using both experimental and in silico approaches, we demonstrated that HvCRK1 localizes to the ER of barley cells. The negative effect on basal resistance against Bgh and the functional aspects of MLO‐ and ER‐localized HvCRK1 signalling on Bgh inoculation are discussed.
Estimating demographics of the Nile crocodile (Crocodylus niloticus Laurenti) in the panhandle region of the Okavango Delta, Botswana
Authors: Bourquin Sven L. , Leslie Alison J.
Published: August 2011

The population status of the Nile crocodile (Crocodylus niloticus Laurenti) in the panhandle region of the Okavango Delta, Botswana, was assessed using mark–recapture and spotlight survey techniques following a decline because of commercial utilization. A total of 1717 individuals, ranging from 136 to 2780 mm in Snout Vent Length, were captured over a 4‐year period. Eighty‐one per cent of young juveniles encountered were successfully captured, representing 59.3% of total captures and 75% of recaptures. A Bayesian technique was used to estimate the number of young juveniles, and these estimates were then extrapolated for the other size classes. Survival and recapture analyses highlighted individual size‐dependent increases in wariness and survival. The total annual population was estimated to be 2570 ± 151.06 individuals, with an adult population of 649.2 individuals, including 364 females. We suggest that the harvest of breeding animals for commercial purposes should be halted until population recovery in this region is established.
Suppressive role of hepatic dendritic cells in concanavalin A-induced hepatitis
Authors: Tomiyama C , Watanabe H , Izutsu Y , Watanabe M , Abo T
Published: August 2011

Concanavalin A (Con A)-induced hepatitis is a mouse model of acute autoimmune hepatitis. The aim of this study was to investigate the role of hepatic dendritic cells (DC) in the immune modulation of tissue damage. Almost all hepatic DC were plasmacytoid DC (CD11c+ I-Alow B220+); however, conventional DC were CD11c+ I-Ahigh B220–. At an early stage (3–6 h) after Con A administration, the number of DC in both the liver and spleen decreased, increasing thereafter (12–24 h) in parallel with hepatic failure. The hepatic CD11c+ DC population contained many CD11b- cells, while the majority of splenic CD11c+ DC were CD11b+. After Con A administration, the proportion of I-A+ and CD11b+ cells within the CD11c+ DC population tended to increase in the liver, but not in the spleen. Similarly, expression of the activation markers CD80, CD86 and CD40 by CD11c+ DC increased in the liver, but not in the spleen. Next, adoptive transfer of DC isolated from the liver and spleen was performed 3 h after Con A administration to examine the immunomodulatory function of DC. Only hepatic DC had the ability to suppress hepatic failure. Analysis of cytokine production and subsequent identification of the effector cells showed that hepatic DC achieved this by suppressing the production of interleukin (IL)-12 and IL-2, rather than modulating effector cell function.
Dual role of erythrocyte complement receptor type 1 in immune complex-mediated macrophage stimulation: implications for the pathogenesis ofPlasmodium falciparummalaria
Authors: Odera M , Otieno W , Adhiambo C , Stoute J A
Published: August 2011

Given the ability of erythrocytes to bind immune complexes (ICs), we postulated that they can serve a dual role during inflammatory or infectious processes. Erythrocytes could restrict stimulation of macrophages by free ICs by binding C3b-opsonized ICs via their complement receptor 1 (CR1). Conversely, IC-loaded erythrocytes could stimulate macrophages to produce proinflammatory cytokines such as tumour necrosis factor (TNF)-α. To test our hypothesis we selected 72 individuals with low, medium or high red cell CR1 expression and determined their IC binding capacity. We tested the in vitro ability of red cells to inhibit IC-mediated stimulation of TNF-α production by macrophages or to stimulate TNF-α production when loaded with ICs. Plain erythrocytes inhibited IC-induced TNF-α production by macrophages and low CR1 expressors showed the lowest inhibitory capacity. IC-loaded erythrocytes stimulated macrophages to release TNF-α, but the effect was not proportional to the CR1 level. These data support our hypothesis that erythrocytes can serve a dual role in regulation of cytokine responses in a setting of IC formation. Our findings suggest that individuals with low CR1 expression are ill-equipped to clear ICs and prevent IC-mediated stimulation of macrophages. In addition, IC-loaded red cells in areas of sluggish circulation such as in the spleen or in brain capillaries blocked by sequestered malaria-infected red cells may induce inflammation by stimulating monocytes and macrophages, the latter leading to the development of cerebral malaria.
Differential regulation of plant secondary compounds by herbivorous rodents
Authors: Torregrossa Ann‐Marie , Azzara Anthony V. , Dearing M. Denise
Published: August 2011

1. Theory predicts that herbivores will regulate doses of potentially toxic plant secondary compounds (PSCs) by adjusting meal size, the interval between meals and water intake. Furthermore, the PSC concentrations at which these behavioural modifications are employed are predicted to be species dependent because of interspecific variation in biotransformation capacities.

2. To investigate these hypotheses, we examined ingestive behaviour of two species of rodents that differ in diet breadth and biotransformation capacity. We compared the spontaneous feeding behaviour of Neotoma stephensi, a juniper specialist, and Neotoma albigula, a generalist, fed a series of diets with increasing concentrations of one‐seeded juniper (Juniperus monosperma). Juniper contains significant quantities of PSCs, particularly alpha‐pinene, a diuretic. We fed each species a series of diets with increasing concentrations of juniper.

3. The specialist, N. stephensi, did not regulate PSC intake at any juniper concentration nor did it alter its drinking behaviour. The generalist, however, showed PSC regulation by decreasing meal size in a dose‐dependent manner, by increasing the interval between meals, and by substantially increasing water intake.

4. Water consumption was the only factor that could significantly predict an individual’s ability to maintain body mass, which suggests that water consumption may be exceptionally important as the PSC content of an individual’s diet varies.

5. These data provide support for the hypotheses that generalist herbivores can and do behaviourally regulate PSC intake and suggest that the differences in foraging behaviour may be correlated with diet content and biotransformation capacity.
Biogeography and the structure of coral reef fish communities on isolated islands
Authors: Hobbs Jean‐Paul A. , Jones Geoffrey P. , Munday Philip L. , Connolly Sean R. , Srinivasan Maya
Published: August 2011

Aim  To determine the applicability of biogeographical and ecological theory to marine species at two remote island locations. This study examines how biogeography, isolation and species geographic range size influence patterns of species richness, endemism, species composition and the abundance of coral reef fishes.

Location  Christmas Island and the Cocos (Keeling) Islands in the tropical eastern Indian Ocean.

Methods  Published species lists and underwater visual surveys were used to determine species richness, endemism, species composition and abundance of reef fishes at the islands. These data were statistically compared with patterns of species composition and abundance from the neighbouring ‘mainland’ Indonesian region.

Results  The two isolated reef fish communities were species‐poor and contained a distinct taxonomic composition with an overrepresentation of species with high dispersal potential. Despite low species richness, we found no evidence of density compensation, with population densities on the islands similar to those of species‐rich mainland assemblages. The mix of Indian and Pacific Ocean species and the proportional representations of the various regional faunas in the assemblages were not influenced by the relative proximity of the islands to different biogeographical provinces. Moreover, species at the edge of their range did not have a lower abundance than species at the centre of their range, and endemic species had substantially higher abundances than widespread species. At both locations, endemism was low (less than 1.2% of the community); this may be because the locations are not sufficiently isolated or old enough to promote the evolution of endemic species.

Main conclusions  The patterns observed generally conform to terrestrial biogeographical theory, suggesting that similar processes may be influencing species richness and community composition in reef fish communities at these remote islands. However, species abundances differed from typical terrestrial patterns, and this may be because of the life history of reef fishes and the processes maintaining isolated populations.
Cluster analysis and food group consumption in a national sample of Australian girls
Authors: Grieger J. A. , Scott J. , Cobiac L.
Published: August 2011

Background:  Food preferences develop early in life and track into later life. There is limited information on food consumption and dietary patterns in Australian girls. The present study aimed to: (i) determine the frequency of food groups consumed over 1 day; (ii) identify dietary clusters based on food group consumption; and (iii) compare dietary intakes and activity variables between clusters.

Methods:  A cross‐sectional analysis of 9–16‐year‐old girls (n = 1114) from the 2007 Australian National Children’s Nutrition and Physical Activity Survey was performed.

Results:  Over the whole day, 30% of all girls consumed carbonated sugar drinks, 46% consumed take‐away food, 56% consumed fruit, 70% consumed at least one vegetable, and 19% and 30% consumed white and/or red meat, respectively. K‐means cluster analysis derived four clusters. Approximately one‐third of girls were identified in a Meat and vegetable cluster; these girls had the highest intakes of red meat and vegetables, and tended to have higher intakes of fruit, whole grain breads, low fat yoghurt, and lower intakes of take‐away foods and soft drinks. They also had the highest intakes of protein, fibre and micronutrients; and tended to perform more physical activity, compared to girls in the remaining clusters.

Conclusions:  Girls identified in the Meat and vegetable cluster, on average, consumed more lean red meat, vegetables, fruits, and low‐fat dairy products, and had a higher intakes of many nutrients. The high percentage of girls not identified in this cluster suggests the need to inform them on how to make healthy, nutrient dense food choices, and why they require increased nutrient intakes at this time.