bluuebunny/crossref_metadata_2025 huggingface dataset:
Recovery time scales in a reversed-biased quantum dot absorber
Authors: Viktorov Evgeny A. , Erneux Thomas , Mandel Paul , Piwonski Tomasz , Madden Gillian , Pulka Jaroslaw , Huyet Guillaume , Houlihan John
Published: June 2009

The nonlinear recovery of quantum dot based reverse-biased waveguide absorbers is investigated both experimentally and analytically. We show that the recovery dynamics consists of a fast initial layer followed by a relatively slow decay. The fast recovery stage is completely determined by the intradot properties, while the slow stage depends on the escape from the dot to the wetting layer.
Compressible Hall magnetohydrodynamics in a strong magnetic field
Authors: Bian N. H. , Tsiklauri D.
Published: June 2009

Plasma dynamics becomes anisotropic in the presence of a strong background magnetic field, a feature that may be exploited to yield reduced fluid models. The reduced Hall-magnetohydrodynamics model derived in a recent work by Gomez et al. [Phys. Plasmas 15, 102303 (2008)], reflecting two-fluid effects such as the Hall current and the electron pressure, is extended to account for a crucial aspect of the role of the plasma compressibility, i.e., the compression of the guide field. This reduced model constitutes therefore a description of the two-fluid plasma dynamics in a strong external magnetic field, which can be used also for values of the plasma pressure parameter β of the order of unity or smaller.
Orthogonal surface acoustic wave device based on langasite for simultaneous biosensing and biofouling removal
Authors: Singh Reetu , Sankaranarayanan Subramanian K. R. S. , Bhethanabotla Venkat R.
Published: June 2009

We report a combined three-dimensional structural and fluid structure interaction finite element study of an orthogonal surface acoustic wave (SAW) device based on langasite (LGS). Our simulation results indicate that simultaneous sensing and nonspecifically bound protein removal can be achieved through the use of multidirectional transducers on a single piezoelectric device. We find that the (0, 22, 90) Euler direction on the LGS-based device is suitable for biosensing via propagation of pure shear-horizontal waves, whereas the (0, 22, 0) direction allows for acoustic streaming induced biofouling removal through the propagation of mixed mode waves with prominent surface normal component. This study reveals the possibility of integrating sensing and biofouling removal functions on a single SAW device, thereby enhancing sensor performance.
Bidirectional current-voltage converters based on magnetostrictive/piezoelectric composites
Authors: Jia Yanmin , Or Siu Wing , Chan Helen Lai Wa , Jiao Jie , Luo Haosu , van der Zwaag S.
Published: June 2009

We report a power supply-free, bidirectional electric current-voltage converter based on a coil-wound laminated composite of magnetostrictive alloy and piezoelectric crystal. An electric current applied to the coil induces a magnetic field, resulting in an electric voltage from the composite due to the direct magnetoelectric effect. Conversely, an electric voltage applied to the composite produces a magnetic induction due to the converse magnetoelectric effect, leading to an electric current from the coil. The converter exhibits excellent linear relationships between current and voltage. Compared with traditional current/voltage converters made by operational amplifiers, the advantages of the proposed device include low cost, no power consumption, and bidirectional conversion.
Effects of phase transition on the hardness of shape memory alloys
Authors: Kang Guozheng , Yan Wenyi
Published: June 2009

Based on the dimensional analysis and finite element calculations, the effects of phase transition on the hardness of shape memory alloys were unveiled. It is shown that the hardness of shape memory alloys increases with the increase in the phase transition stress, the increase in the plastic yield stress, and the decrease in the maximum transition strain. However, the ratio of the hardness to the phase transition stress or the ratio of the hardness to the plastic yield stress is not a constant and therefore, the hardness of shape memory alloys cannot be treated as a material property.
Silver halide single mode fibers for broadband middle infrared stellar interferometry
Authors: Lewi T. , Tsun A. , Katzir A. , Kaster J. , Fuchs F.
Published: June 2009

We report the demonstration of silver halide single mode fibers at λ=7.5 μm. The fiber’s modal behavior was tested at λ=10.6 and λ=7.5 μm, using near field measurements. Single mode operation was observed for both wavelengths with propagation losses of ∼16 and ∼40 dB/m at λ=10.6 and λ=7.5 μm, respectively. A rejection ratio of ∼30 dB was achieved at λ=7.5 μm for a 30 cm long fiber segment. These fibers would be particularly useful for modal filtering in the 6–20 μm band. Modal filters are essential technology elements in nulling stellar interferometry.
Plasmon-enhanced magneto-optical activity in ferromagnetic membranes
Authors: González-Díaz J. B. , García-Martín J. M. , García-Martín A. , Navas D. , Asenjo A. , Vázquez M. , Hernández-Vélez M. , Armelles G.
Published: June 2009

Experimental and theoretical evidence of plasmon-enhanced Kerr rotation in purely ferromagnetic membranes with sufficiently small dimensions to be out of extraordinary optical transmission conditions (45 nm pore diameter, 90nm lattice constant), is reported in this work. It is shown that the spectral location of the enhanced Kerr rotation region varies as the refractive index of the material inside the pore is modified. A similar behavior is obtained if the pore radius changes while keeping the pore concentration unchanged. Those are clear signatures indicating that localized surface plasmon resonances propagating along the pores govern the magneto-optical response of the membrane.
Development of enhancement mode AlN/GaN high electron mobility transistors
Authors: Chang C. Y. , Pearton S. J. , Lo C. F. , Ren F. , Kravchenko I. I. , Dabiran A. M. , Wowchak A. M. , Cui B. , Chow P. P.
Published: June 2009

Enhancement mode AlN/GaN high electron mobility transistors (HEMTs) were fabricated from originally depletion-mode structures using oxygen plasma treatment on the gate area prior to the gate metallization. Starting with a depletion mode AlN/GaN HEMT, the threshold voltage of the HEMT could be shifted from −3.2 to 1 V depending on the oxygen plasma treatment time to partially convert the AlN barrier layer into Al oxide. The gate current was reduced and the current-voltage curves show metal-oxide semiconductor diodelike characteristics after oxygen plasma treatment.
Holding Property in Trust: Kinship, Law, and Property Enactment on Norwegian Smallholdings
Authors: Flemsæter Frode , Setten Gunhild
Published: June 2009

In this paper we discuss relations between kinship, law, and property enactment. A recent revision of The Norwegian Act Relating to Concession in the Acquisition of Real Property is designed to influence the relation between subjects (property owners) and objects (properties) through ceasing the obligation of residency and cultivation on certain properties, which in turn is intended to increase sales prices of the respective properties. Drawing upon empirical research conducted in four Norwegian local authority districts, we argue that responsibility for past, present, and future generations of family or kin is highly important in property enactment. Although relations between subjects and objects are powerful and inform policy actions, relations between social subjects might be just as influential and powerful. When enacting properties, people may live in more complicated worlds than is often assumed. We assert that further research in legal geography and the emerging field of ‘geographies of relatedness’ might profit from seeing kinship and property as coconstituted.
Intermediaries and the Governance of Choice: The Case of Green Electricity Labelling
Authors: Rohracher Harald
Published: June 2009

This paper is about the reframing of electricity markets as a strategically oriented nonstate governance activity of intermediary organisations. In particular, it is centred on the establishment of ‘green’ electricity labels by environmental and other nongovernmental organisations (NGOs) as an attempt to establish and shape a market for green electricity. Such labels serve as a ‘boundary object’ between electricity generators, suppliers, consumers, and regulators, and are analysed as the creation of new sociotechnical arrangements around green electricity generation and use. The analysis also shows that private governance initiatives of this kind are highly interdependent with state regulatory systems. NGOs have played a vital role in defining and negotiating such standards, enrolling and aligning supply-side and demand-side actors, communicating with a wider public and building trust for the respective products, establishing links with regulators, and shaping policies for renewable electricity at national and European levels. The cases of electricity labelling investigated are an example of new political strategies of civil society intermediary organisations in an increasingly market-driven environment.
Emerging Spatialities of the Screen: Video Games and the Reconfiguration of Spatial Awareness
Authors: Ash James
Published: June 2009

In this paper I develop a nonrepresentational spatiality of screened images, in which space does not refer to the way space is represented in images or the spaces in which images exist. Instead it focuses on the spaces that images themselves produce. Drawing upon the technology of the screen as a contemporary site at which images are experienced, I argue for a dual conception of the ‘space’ of screened images: an existential space constructed through the background context of a user's relation with an image; and an ecological space constructed through the expressive relationship between body and screen. I use video games as an exemplar of these spaces to show how screened images reconfigure the relationship between touch and vision and how this alters users' spatial awareness of the world.
Evaluating ‘Best Practice’ in Integrated Rural Tourism: Case Examples from the England-Wales Border Region
Authors: Ilbery Brian , Saxena Gunjan
Published: June 2009

In this paper we explore and evaluate the concept of integrated rural tourism (IRT) by drawing upon a networks approach and the notion of best practice. By integrating the two an attempt is made to understand the processes that generate the sharing, exchange and transfer of knowledge and skills. The case examples of tourism-focused networks from the England–Wales border region highlight how the innovative practices of individual actors have shaped local resources into tourism products, providing a long-term focus for economic development and local restructuring. It is concluded that the development aspect of best practice, as a pathway to developing IRT, offers a tool to capture the ‘intangibles’ or noneconomic aspects of networking that promote economic growth and development.
Galileo, Measurement of the Velocity of Light, and the Reaction Times
Authors: Foschi Renato , Leone Matteo
Published: June 2009

According to the commonly accepted view, Galileo Galilei devised in 1638 an experiment that seemed able to show that the velocity of light is finite. An analysis of archival material shows that two decades later members of the Florence scientific society Accademia del Cimento followed Galileo guidelines by actually attempting to measure the velocity of light and suggesting improvements. This analysis also reveals a fundamental difference between Galileo's and Florence academy's methodologies and that Galileo's experiment was, in some respects, a pioneering work affecting also the history of the psychology of perception.
Clonality and hybrid origin of the rare Eucalyptus bennettiae (Myrtaceae) in Western Australia
Authors: Walker E. , Byrne M. , Macdonald B. , Nicolle D. , McComb J.
Published: June 2009

Clonality and hybrid origin influence the conservation status of rare and restricted species. Eucalyptus bennettiae Carr & Carr is a rare species known only from a few individuals that may be clonal and may have arisen through hybridisation between other co-occurring species. The hybrid status and clonality of E. bennettiae was investigated with analysis of microsatellite variation in E. bennettiae compared with its putative parents, E. lehmannii subsp. parallela, E. sporadica and E. astringens subsp. redacta, identified through morphological characteristics. Analysis of microsatellite variation revealed clonality with one individual present at each location, and additivity of alleles and no unique alleles in E. bennettiae compared with two of the putative parents, E. lehmannii subsp. parallela and E. sporadica. In addition, E. bennettiae displayed intermediacy in species relationships and measures of relatedness, and assignment tests showed mixed ancestry in relation to these species but not the third putative parent, E. astringens subsp. redacta. These findings confirm that E. bennettiae is a hybrid and evaluation of the taxon for conservation protection shows that it does not satisfy the criteria for listing as a threatened species.
Perfusion culture of Glycyrrhiza inflata suspension cells in a stir-tank bioreactor
Authors: Wang Guirong , Qi Nian Min
Published: June 2009

Cell and tissue browning is a major impediment of plant culture in vitro. Glycyrrhiza inflata Batalin cells died of lethal browning on Day 9 when cultivated in batch mode. Perfusion culture in bioreactors has a high potential for overcoming plant browning in vitro. In the present study, a continuous perfusion-culture system of G. inflata suspension cells was established in a stir-tank bioreactor. The key component of the bioreactor is an annular gravitational settling zone, through which we achieved continuous separation of cells from the medium. We determined the cell-retention efficiency of the reactor by varying rates of agitation, perfusion and aeration. Complete cell retention was obtained under the following conditions: agitation 0–200 rpm, aeration 0–0.6 volume per volume per minute (vvm) and perfusion rate 0–1.0 day−1. These results were also in good agreement with theoretical estimation. An orthogonal test, including three factors and three levels, showed the optimal culture parameters were as follows: agitation rate 150 rpm, aeration rate 0.3 vvm and perfusion rate 1.0 day−1. Under these conditions, the perfusion-culture system in the bioreactor was operated smoothly, and the maximum cell concentration reached 26 ± 1 g L−1 dry weight.
Influence of conservation tillage practices on soil properties and crop yields for maize and wheat cultivation in Beijing, China
Authors: Zhang Xirui , Li Hongwen , He Jin , Wang Qingjie , Golabi Mohammad H.
Published: June 2009

Conservation tillage is becoming increasingly attractive to farmers because it involves lower production costs than does conventional tillage. The long-term effects of sub-soiling tillage (ST), no tillage (NT), and conventional tillage (CT) on soil properties and crop yields were investigated over an 8-year period (2000–07). The study was conducted in a 2-crop-a-year region (Daxing) and a 1-crop-a-year region (Changping) of the Beijing area in China. At 0–0.30 m soil depth, water stability of macro-aggregates (>0.25 mm) was much greater for ST (22.1%) and NT (12.0%) than for CT in Daxing, and the improvements in Changping were 18.9% and 9.5%, respectively. ST and NT significantly (P < 0.05) improved aeration porosity by 14.5% and 10.6%, respectively, at Daxing and by 17.0% and 8.6% at Changping compared with CT treatment. Soil bulk density after 8 years was 0.8–1.5% lower in ST and NT treatments than in CT at both sites. Soil organic matter and available N and P followed the same order ST ≈ NT > CT at both sites. Consequently, crop yields in ST and NT plots were higher than in CT plots due to improved soil physical and chemical properties. Within the conservation tillage treatments, despite similar economic benefit, the effects on crop yields for ST were better than for NT. Mean (2000–07) crop yields for ST were 0.2% and 1.5% higher than for NT at Daxing and Changping, respectively. We therefore conclude that ST is the most suitable conservation tillage practice for annual 2-crop-a-year and 1-crop-a-year regions in the Beijing area.
Long-term effect of pastures on soil quality in acid soil of North-East India
Authors: Ghosh P. K. , Saha R. , Gupta J. J. , Ramesh T. , Das Anup , Lama T. D. , Munda G. C. , Bordoloi Juri Sandhya , Verma Med Ram , Ngachan S. V.
Published: June 2009

North-East India is known for its complex, diverse, risk-prone, and fragile hilly ecosystem. Natural resources in terms of soil, water, vegetation, and soil organic carbon (SOC) are much degraded. Effects of long-term perennial grasses maintained at a permanent fodder block of the ICAR Research Complex, Meghalaya, on soil quality were examined after 15 cropping cycles. The aims were (i) to ascertain whether perennial grass primarily maintained as fodder source for ruminants could conserve resources and improve soil quality in the hilly ecosystem of North-East India, and (ii) to select a suitable perennial grass to minimise land degradation, restore SOC, and improve the soil quality. Soil samples were collected in 2007–08 (dry season) from plots of 8 perennial grasses [Setaria sphacelata (setaria), Brachieria rosenesis (congosignal), Thysanolaena maxima (broom), Penicum maximum var. Makunia and var. Hamil (guinea), Pennisetum purpureum (napier), Paspalum conjugalum (paspalam), Arachis pintoi (wild groundnut)] and analysed for physical, chemical, and biological properties. A control plot had no grass cover.
Hamil and Makunia produced a large amount of green fodder, while Makunia, paspalam, setaria, and congosignal had greatest root biomass. Relative to the control, soil under perennial grasses showed increases of ~30% SOC, 70% mean weight diameter, 20% available soil water, 40% hydraulic conductivity, 63% infiltration rate, and 10% soil microbial biomass carbon. Among grasses, soil under setaria, congosignal, and Makunia had higher values of these attributes than under other species because of better soil binding through an extensive root system. Improvement of soil physical properties and processes under these grasses, coupled with complete ground cover, reduced soil erosion by ~33% and also signified ecological benefits through C-sequestration. Soil quality management in the fragile ecosystem of North-East India should include permanent pastural grasses, particularly, setaria, congosignal, and Makunia.
Mineralogy and geochemical properties of some upland soils from different sedimentary formations in south-eastern Nigeria
Authors: Igwe C. A. , Zarei M. , Stahr K.
Published: June 2009

Geochemical and mineralogical properties of soil can be used to assess their agricultural productivity potential. Ten soils from 4 geological formations in the south-eastern Nigeria were studied. Soil samples were taken from typical A and B horizons from each soil. The soil properties assessed were the free forms of Fe and Al, particle size distribution, total elements, and clay mineralogy. The soils are deep and highly weathered. Crystalline Fe and Al were more dominant than amorphous or less crystalline forms. The geochemical properties of the soils are dominated by SiO2, Al2O3, and Fe2O3, whereas MgO, TiO2, and ZrO2 occur in moderate to low quantities. Other basic elements such as Na2O, K2O, and CaO are very low in the soils, with an insignificant role in their genesis. The low contents of these elements in the soil may be the cause of their low nutrient release and storage in the soil. Ferritisation, laterisation, and kaolinitisation are the major pedogenic processes in the soil. The dominant clay mineral in all the soils was kaolinite; other minerals present though less common were illite, vermiculite, and smectites. Based on elemental contents and clay mineralogy, the soils can be grouped into 3 distinct groups: those with only kaolinite, illite, and vermiculites; and those that also contain smectite. These groupings can indicate the agricultural fertility potential.
Wildland surface fire spread modelling, 1990 - 2007. 2: Empirical and quasi-empirical models
Authors: Sullivan Andrew L.
Published: June 2009

In recent years, advances in computational power have led to an increase in attempts to model the behaviour of wildland fires and to simulate their spread across landscape. The present series of articles endeavours to comprehensively survey and précis all types of surface fire spread models developed during the period 1990–2007. The current paper surveys models of an empirical or quasi-empirical nature. These models are based on the statistical analysis of experimentally obtained data with or without some physical framework for the basis of the relations. Other papers in the series review models of a physical or quasi-physical nature, and mathematical analogues and simulation models. The main relations of empirical models are those of wind speed and fuel moisture content with rate of forward spread. The focus of the discussion is on the treatment of the wind speed and fuel moisture functions by the models.
Wildland surface fire spread modelling, 1990 - 2007. 3: Simulation and mathematical analogue models
Authors: Sullivan Andrew L.
Published: June 2009

In recent years, advances in computational power have led to an increase in attempts to model the behaviour of wildland fires and to simulate their spread across landscape. The present series of articles endeavours to comprehensively survey and précis all types of surface fire spread models developed during the period 1990–2007. The present paper surveys models of a simulation or mathematical analogue nature. Most simulation models are implementations of existing empirical or quasi-empirical models and their primary function is to convert these generally one-dimensional models to two dimensions and then simulate the propagation of a fire perimeter across a modelled landscape. Mathematical analogue models are those that are based on some mathematical concept (rather than a physical representation of fire spread) that coincidentally represents the spread of fire. Other papers in the series survey models of a physical or quasi-physical nature, and empirical or quasi-empirical nature. Many models are extensions or refinements of models developed before 1990. Where this is the case, these models are also discussed but much less comprehensively.
Integration of AWiFS and MODIS active fire data for burn mapping at regional level using the Burned Area Synergic Algorithm (BASA)
Authors: González-Alonso Federico , Merino-de-Miguel Silvia
Published: June 2009

The present paper presents an algorithm that synergistically combines data from four different parts of the spectrum (near-, shortwave, middle- and thermal infrared) to produce a reliable burned-area map. It is based on the use of a modified version of the BAIM (MODIS – Moderate Resolution Imaging Spectrometer – Burned Area Index) together with active fire information. The following study focusses in particular on an image from the AWiFS (Advanced Wide Field Sensor) sensor dated 21 August 2006 and MODIS active fires detected during the first 20 days of August as well as ancillary maps and information. The methodology was tested in Galicia (north-west Spain) where hundreds of forest fires occurred during the first 20 days of August 2006. Burned area data collected from the present work was compared with official fire statistics from both the Spanish Ministry of the Environment and the Galician Forestry Service. The speed, accuracy and cost-effectiveness of this method suggest that it would be of great interest for use at both regional and national levels.
Short-term impact of post-fire salvage logging on regeneration, hazardous fuel accumulation, and understorey development in ponderosa pine forests of the Black Hills, SD, USA
Authors: Keyser Tara L. , Smith Frederick W. , Shepperd Wayne D.
Published: June 2009

We examined the impacts of post-fire salvage logging on regeneration, fuel accumulation, and understorey vegetation and assessed whether the effects of salvage logging differed between stands burned under moderate and high fire severity following the 2000 Jasper Fire in the Black Hills. In unsalvaged sites, fire-related tree mortality created a large standing pool of available fuel, resulting in a rapid increase in surface fuel loads. After 5 years, fine woody debris (FWD) and coarse woody debris (CWD) increased ~1380% and 980% in unsalvaged sites, resulting in FWD and CWD loads of 13 and 25 Mg ha–1, respectively. In contrast, salvage logging limited the rate of accumulation of FWD to ~110% over the same time period and total accumulation of CWD to 16 Mg ha–1. In moderate-severity sites, regeneration was 75% lower in salvaged sites owing to low seed-tree retention, suggesting a re-evaluation of salvage guidelines during future operations in the Black Hills. The likelihood of timely regeneration in high-severity sites, regardless of salvage treatment, is low. We found no discernible effect of salvage logging on understorey development 5 years after fire. Logging caused neither a reduction in total plant cover nor an increase in the abundance of exotic species.
Fuel characterization in the southern Appalachian Mountains: an application of Landscape Ecosystem Classification
Authors: Stottlemyer Aaron D. , Shelburne Victor B. , Waldrop Thomas A. , Rideout-Hanzak Sandra , Bridges William C.
Published: June 2009

Prescribed fire has been widely used in the south-eastern United States to meet forest management objectives, but has only recently been reintroduced to the southern Appalachian Mountains. Fuel information is not available to forest managers in this region and direct measurement is often impractical owing to steep, remote topography. The objective of the present study was to determine whether landscape ecosystem classification (LEC) site units support different types and amounts of fuel in the Chauga Ridges, a subregion of the Blue Ridge Mountain Province. Ecosystem classification identifies vegetation assemblages that are the expressive result of soils, physiography and vegetation, and recur predictably on the landscape. Four fuel complexes were identified using LEC units and field measurements of fuel characteristics. Fuel bed depth, duff (Oe + Oa) thickness, 1000-h fuel loading, and Rhododendron maximum, R. minus, and Vaccinium spp. ground cover were discriminating fuel characteristics of xeric, intermediate, submesic, and mesic site units. Discriminant function analysis provided an overall 64% cross-validation success rate using 138 undisturbed, randomly located plots. This method of characterizing fuel complexes may also be possible in other forested ecosystems where LECs or other ecological vegetation classifications have been developed.
Cholinergic filtering in the recurrent excitatory microcircuit of cortical layer 4
Authors: Eggermann Emmanuel , Feldmeyer Dirk
Published: June 2009

Neocortical acetylcholine (ACH) release is known to enhance signal processing by increasing the amplitude and signal-to-noise ratio (SNR) of sensory responses. It is widely accepted that the larger sensory responses are caused by a persistent increase in the excitability of all cortical excitatory neurons. Here, contrary to this concept, we show that ACH persistently inhibits layer 4 (L4) spiny neurons, the main targets of thalamocortical inputs. Using whole-cell recordings in slices of rat primary somatosensory cortex, we demonstrate that this inhibition is specific to L4 and contrasts with the ACH-induced persistent excitation of pyramidal cells in L2/3 and L5. We find that this inhibition is induced by postsynaptic M4-muscarinic ACH receptors and is mediated by the opening of inwardly rectifying potassium (Kir) channels. Pair recordings of L4 spiny neurons show that ACH reduces synaptic release in the L4 recurrent microcircuit. We conclude that ACH has a differential layer-specific effect that results in a filtering of weak sensory inputs in the L4 recurrent excitatory microcircuit and a subsequent amplification of relevant inputs in L2/3 and L5 excitatory microcircuits. This layer-specific effect may contribute to improve cortical SNR.
DNA polymerase ζ cooperates with polymerases κ and ι in translesion DNA synthesis across pyrimidine photodimers in cells from XPV patients
Authors: Ziv Omer , Geacintov Nicholas , Nakajima Satoshi , Yasui Akira , Livneh Zvi
Published: June 2009

Human cells tolerate UV-induced cyclobutane pyrimidine dimers (CPD) by translesion DNA synthesis (TLS), carried out by DNA polymerase η, the
POLH
gene product. A deficiency in DNA polymerase η due to germ-line mutations in
POLH
causes the hereditary disease xeroderma pigmentosum variant (
XPV
), which is characterized by sunlight sensitivity and extreme predisposition to sunlight-induced skin cancer.
XPV
cells are UV hypermutable due to the activity of mutagenic TLS across CPD, which explains the cancer predisposition of the patients. However, the identity of the backup polymerase that carries out this mutagenic TLS was unclear. Here, we show that DNA polymerase ζ cooperates with DNA polymerases κ and ι to carry out error-prone TLS across a TT CPD. Moreover, DNA polymerases ζ and κ, but not ι, protect
XPV
cells against UV cytotoxicity, independently of nucleotide excision repair. This presents an extreme example of benefit-risk balance in the activity of TLS polymerases, which provide protection against UV cytotoxicity at the cost of increased mutagenic load.
Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding
Authors: Williams Vincent S. , Barrett Paul M. , Purnell Mark A.
Published: June 2009

Understanding the feeding mechanisms and diet of nonavian dinosaurs is fundamental to understanding the paleobiology of these taxa and their role in Mesozoic terrestrial ecosystems. Various methods, including biomechanical analysis and 3D computer modeling, have been used to generate detailed functional hypotheses, but in the absence of either direct observations of dinosaur feeding behavior, or close living functional analogues, testing these hypotheses is problematic. Microscopic scratches that form on teeth in vivo during feeding are known to record the relative motion of the tooth rows to each other during feeding and to capture evidence of tooth–food interactions. Analysis of this dental microwear provides a powerful tool for testing hypotheses of jaw mechanics, diet, and trophic niche; yet, quantitative analysis of microwear in dinosaurs has not been attempted. Here, we show that analysis of tooth microwear orientation provides direct evidence for the relative motions of jaws during feeding in hadrosaurid ornithopods, the dominant terrestrial herbivores of the Late Cretaceous. Statistical testing demonstrates that
Edmontosaurus
teeth preserve 4 distinct sets of scratches in different orientations. In terms of jaw mechanics, these data indicate an isognathic, near-vertical posterodorsal power stroke during feeding; near-vertical jaw opening; and propalinal movements in near anterior and near posterior directions. Our analysis supports the presence of a pleurokinetic hinge, and the straightness and parallelism of scratches indicate a tightly controlled occlusion. The dominance of scratched microwear fabrics suggests that
Edmontosaurus
was a grazer rather than a browser.
Requirement of central ghrelin signaling for alcohol reward
Authors: Jerlhag Elisabet , Egecioglu Emil , Landgren Sara , Salomé Nicolas , Heilig Markus , Moechars Diederik , Datta Rakesh , Perrissoud Daniel , Dickson Suzanne L. , Engel Jörgen A.
Published: June 2009

The stomach-derived hormone ghrelin interacts with key CNS circuits regulating energy balance and body weight. Here we provide evidence that the central ghrelin signaling system is required for alcohol reward. Central ghrelin administration (to brain ventricles or to tegmental areas involved in reward) increased alcohol intake in a 2-bottle (alcohol/water) free choice limited access paradigm in mice. By contrast, central or peripheral administration of ghrelin receptor (GHS-R1A) antagonists suppressed alcohol intake in this model. Alcohol-induced locomotor stimulation, accumbal dopamine release and conditioned place preference were abolished in models of suppressed central ghrelin signaling: GHS-R1A knockout mice and mice treated with 2 different GHS-R1A antagonists. Thus, central ghrelin signaling, via GHS-R1A, not only stimulates the reward system, but is also required for stimulation of that system by alcohol. Our data suggest that central ghrelin signaling constitutes a potential target for treatment of alcohol-related disorders.
Ultrasonication-dependent production and breakdown lead to minimum-sized amyloid fibrils
Authors: Chatani Eri , Lee Young-Ho , Yagi Hisashi , Yoshimura Yuichi , Naiki Hironobu , Goto Yuji
Published: June 2009

Because of the insolubility and polymeric properties of amyloid fibrils, techniques used conventionally to analyze protein structure and dynamics have often been hampered. Ultrasonication can induce the monomeric solution of amyloidogenic proteins to form amyloid fibrils. However, ultrasonication can break down preformed fibrils into shorter fibrils. Here, combining these 2 opposing effects on β
2
-microglobulin (β2-m), a protein responsible for dialysis-related amyloidosis, we present that ultrasonication pulses are useful for preparing monodispersed amyloid fibrils of minimal size with an average molecular weight of ≈1,660,000 (140-mer). The production of minimal and monodispersed fibrils is achieved by the free energy minimum under competition between fibril production and breakdown. The small homogeneous fibrils will be of use for characterizing the structure and dynamics of amyloid fibrils, advancing molecular understanding of amyloidosis.
Syncytin-A knockout mice demonstrate the critical role in placentation of a fusogenic, endogenous retrovirus-derived, envelope gene
Authors: Dupressoir Anne , Vernochet Cécile , Bawa Olivia , Harper Francis , Pierron Gérard , Opolon Paule , Heidmann Thierry
Published: June 2009

In most mammalian species, a key process of placenta development is the fusion of trophoblast cells into a highly specialized, multinucleated syncytiotrophoblast layer, through which most of the maternofetal exchanges take place. Little is known about this process, despite the recent identification of 2 pairs of envelope genes of retroviral origin, independently acquired by the human (
syncytin-1
and
syncytin-2
) and mouse (
syncytin-A
and
syncytin-B
) genomes, specifically expressed in the placenta, and with in vitro cell–cell fusion activity. By generating knockout mice, we show here that homozygous
syncytin-A
null mouse embryos die in utero between 11.5 and 13.5 days of gestation. Refined cellular and subcellular analyses of the
syncytin-A
-deficient placentae disclose specific disruption of the architecture of the syncytiotrophoblast-containing labyrinth, with the trophoblast cells failing to fuse into an interhemal syncytial layer. Lack of
syncytin-A
-mediated trophoblast cell fusion is associated with cell overexpansion at the expense of fetal blood vessel spaces and with apoptosis, adding to the observed maternofetal interface structural defects to provoke decreased vascularization, inhibition of placental transport, and fetal growth retardation, ultimately resulting in death of the embryo. These results demonstrate that
syncytin-A
is essential for trophoblast cell differentiation and syncytiotrophoblast morphogenesis during placenta development, and they provide evidence that genes captured from ancestral retroviruses have been pivotal in the acquisition of new, important functions in mammalian evolution.
A “latent niche” mechanism for tumor initiation
Authors: McGovern Marie , Voutev Roumen , Maciejowski John , Corsi Ann K. , Hubbard E. Jane Albert
Published: June 2009

Stem cells, their niches, and their relationship to cancer are under intense investigation. Because tumors and metastases acquire self-renewing capacity, mechanisms for their establishment may involve cell–cell interactions similar to those between stem cells and stem cell niches. On the basis of our studies in
Caenorhabditis elegans
, we introduce the concept of a “latent niche” as a differentiated cell type that does not normally contact stem cells nor act as a niche but that can, under certain conditions, promote the ectopic self-renewal, proliferation, or survival of competent cells that it inappropriately contacts. Here, we show that ectopic germ-line stem cell proliferation in
C. elegans
is driven by a latent niche mechanism and that the molecular basis for this mechanism is inappropriate Notch activation. Furthermore, we show that continuous Notch signaling is required to maintain ectopic germ-line proliferation. We highlight the latent niche concept by distinguishing it from a normal stem cell niche, a premetastatic niche and an ectopic niche. One of the important distinguishing features of this mechanism for tumor initiation is that it could operate in the absence of genetic changes to the tumor cell or the tumor-promoting cell. We propose that a latent niche mechanism may underlie tumorigenesis and metastasis in humans.
Control of retinal isomerization in bacteriorhodopsin in the high-intensity regime
Authors: Florean Andrei C. , Cardoza David , White James L. , Lanyi J. K. , Sension Roseanne J. , Bucksbaum Philip H.
Published: June 2009

A learning algorithm was used to manipulate optical pulse shapes and optimize retinal isomerization in bacteriorhodopsin, for excitation levels up to 1.8 × 10
16
photons per square centimeter. Below 1/3 the maximum excitation level, the yield was not sensitive to pulse shape. Above this level the learning algorithm found that a Fourier-transform-limited (TL) pulse maximized the 13-cis population. For this optimal pulse the yield increases linearly with intensity well beyond the saturation of the first excited state. To understand these results we performed systematic searches varying the chirp and energy of the pump pulses while monitoring the isomerization yield. The results are interpreted including the influence of 1-photon and multiphoton transitions. The population dynamics in each intermediate conformation and the final branching ratio between the all-trans and 13-cis isomers are modified by changes in the pulse energy and duration.
X-ray cross correlation analysis uncovers hidden local symmetries in disordered matter
Authors: Wochner Peter , Gutt Christian , Autenrieth Tina , Demmer Thomas , Bugaev Volodymyr , Ortiz Alejandro Díaz , Duri Agnès , Zontone Federico , Grübel Gerhard , Dosch Helmut
Published: June 2009

We explore the different local symmetries in colloidal glasses beyond the standard pair correlation analysis. Using our newly developed X-ray cross correlation analysis (XCCA) concept together with brilliant coherent X-ray sources, we have been able to access and classify the otherwise hidden local order within disorder. The emerging local symmetries are coupled to distinct momentum transfer (
Q
) values, which do not coincide with the maxima of the amorphous structure factor. Four-, 6-, 10- and, most prevalently, 5-fold symmetries are observed. The observation of dynamical evolution of these symmetries forms a connection to dynamical heterogeneities in glasses, which is far beyond conventional diffraction analysis. The XCCA concept opens up a fascinating view into the world of disorder and will definitely allow, with the advent of free electron X-ray lasers, an accurate and systematic experimental characterization of the structure of the liquid and glass states.
Pharmacokinetics and tumor dynamics of the nanoparticle IT-101 from PET imaging and tumor histological measurements
Authors: Schluep Thomas , Hwang Jungyeon , Hildebrandt Isabel J. , Czernin Johannes , Choi Chung Hang J. , Alabi Christopher A. , Mack Brendan C. , Davis Mark E.
Published: June 2009

IT-101, a cyclodextrin polymer-based nanoparticle containing camptothecin, is in clinical development for the treatment of cancer. Multiorgan pharmacokinetics and accumulation in tumor tissue of IT-101 is investigated by using PET. IT-101 is modified through the attachment of a 1,4,7,10-tetraazacyclododecane-1,4,7-Tris-acetic acid ligand to bind64Cu2+. This modification does not affect the particle size and minimally affects the surface charge of the resulting nanoparticles. PET data from64Cu-labeled IT-101 are used to quantify the in vivo biodistribution in mice bearing Neuro2A s.c. tumors. The64Cu-labeled IT-101 displays a biphasic plasma elimination. Approximately 8% of the injected dose is rapidly cleared as a low-molecular-weight fraction through the kidneys. The remaining material circulates in plasma with a terminal half-life of 13.3 h. Steadily increasing concentrations, up to 11% injected dose per cm3, are observed in the tumor over 24 h, higher than any other tissue at that time. A 3-compartment model is used to determine vascular permeability and nanoparticle retention in tumors, and is able to accurately represent the experimental data. The calculated tumor vascular permeability indicates that the majority of nanoparticles stay intact in circulation and do not disassemble into individual polymer strands. A key assumption to modeling the tumor dynamics is that there is a “sink” for the nanoparticles within the tumor. Histological measurements using confocal microscopy show that IT-101 localizes within tumor cells and provides the sink in the tumor for the nanoparticles.
The Lewis-base behavior of Bunsen’s cacodyl disulfide, Me2As(S)–S–AsMe2, toward molecular halides of group 13
Authors: Ioannou Panayiotis V. , Tsivgoulis Gerasimos M. , Vachliotis Dimitris G.
Published: June 2009

Molecular halides of group 13 in chloroform solutions interact but do not split Bunsen’s cacodyl disulfide, Me2As(S)–S–AsMe2. With BF3·Et2O cacodyl disulfide gives an equilibrated mixture of Me2As(S)–S–AsMe2 and Me2As–SS–AsMe2, whereas AlCl3 causes complete isomerization to Me2As–SS–AsMe2 which is stabilized by complexation to AlCl3. GaCl3 and InCl3 do not isomerize Me2As(S)–S–AsMe2 but only bind to it. Thallium(III) acetate, splits Me2As(S)–S–AsMe2 giving initially the unstable thallium(III) complex, (Me2AsS2)3Tl, which is spontaneously converted to Me2AsS2Tl. The electrons for the reduction Tl(III)→Tl(I) most likely come from two of the –S:− sulfur anions bound to the initially formed (Me2AsS2)3Tl.
Physarum Boats: If Plasmodium Sailed It Would Never Leave a Port
Authors: Adamatzky Andrew
Published: June 2009

Plasmodium of Physarum polycephalum is a single huge (visible by naked eye) cell with a myriad of nuclei. The plasmodium is a promising substrate for non‐classical, nature‐inspired computing devices. It is capable of approximation of the shortest path in a maze, computation of planar proximity graphs and plane tessellations, primitive memory and decision making. The unique properties of the plasmodium make it an ideal candidate for a role of amorphous biological robots with massive parallel information processing and distributed inputs and outputs. We show that when adhered to a lightweight object resting on a water surface the plasmodium can propel the object by oscillating its protoplasmic pseudopodia. In experimental laboratory conditions and computational experiments we study phenomenology of the plasmodium‐floater system, and possible mechanisms of controlling motion of objects propelled by on‐board plasmodium.
An investigation into the online processing of counterfactual and indicative conditionals
Authors: Stewart Andrew J. , Haigh Matthew , Kidd Evan
Published: June 2009

The ability to represent conditional information is central to human cognition. In two self-paced reading experiments we investigated how readers process counterfactual conditionals (e.g., If Darren had been athletic, he could probably have played on the rugby team) and indicative conditionals (e.g., If Darren is athletic, he probably plays on the rugby team). In Experiment 1 we focused on how readers process counterfactual conditional sentences. We found that processing of the antecedent of counterfactual conditionals was rapidly constrained by prior context (i.e., knowing whether Darren was or was not athletic). A reading-time penalty was observed for the critical region of text comprising the last word of the antecedent and the first word of the consequent when the information in the antecedent did not fit with prior context. In Experiment 2 we contrasted counterfactual conditionals with indicative conditionals. For counterfactual conditionals we found the same effect on the critical region as we found in Experiment 1. In contrast, however, we found no evidence that processing of the antecedent of indicative conditionals was constrained by prior context. For indicative conditionals (but not for counterfactual conditionals), the results we report are consistent with the suppositional account of conditionals. We propose that current theories of conditionals need to be able to account for online processing differences between indicative and counterfactual conditionals.
Modulation of spatial Stroop by object-based attention but not by space-based attention
Authors: Luo Chunming , Lupiáñez Juan , Funes María Jesús , Fu Xiaolan
Published: June 2009

Earlier studies have shown that the spatial Stroop effect systematically decreases when a peripheral precue is presented at the same location as the target, compared to an uncued location condition. In this study, two experiments were conducted to explore whether the cueing modulation of spatial Stroop is object based and/or space based. In Experiment 1, we found evidence favouring the view that the cueing modulation of the spatial Stroop effect is entirely object based, as no differences were found in conflict reduction for the same-location and same-object conditions. In Experiment 2, the cue was predictive, and a similar object-based modulation of spatial Stroop was still observed. However, the direction of such modulation was affected by the rectangles’ orientation. Overall, the pattern of results obtained favours the object-integration (Lupiáñez & Milliken, 1999; Lupiáñez, Milliken, Solano, Weaver, & Tipper, 2001) and referential-coding accounts (Danziger, Kingstone, & Ward, 2001) and seems to provide evidence against the attention-shift account (Rubichi, Nicoletti, Iani, & Umilta, 1997; Stoffer, 1991).
Biogenesis of cytochrome b6 in photosynthetic membranes
Authors: Saint-Marcoux Denis , Wollman Francis-André , de Vitry Catherine
Published: June 2009

In chloroplasts, binding of a c′-heme to cytochrome b6 on the stromal side of the thylakoid membranes requires a specific mechanism distinct from the one at work for c-heme binding to cytochromes f and c6 on the lumenal side of membranes. Here, we show that the major protein components of this pathway, the CCBs, are bona fide transmembrane proteins. We demonstrate their association in a series of hetero-oligomeric complexes, some of which interact transiently with cytochrome b6 in the process of heme delivery to the apoprotein. In addition, we provide preliminary evidence for functional assembly of cytochrome b6f complexes even in the absence of c′-heme binding to cytochrome b6. Finally, we present a sequential model for apo- to holo-cytochrome b6 maturation integrated within the assembly pathway of b6f complexes in the thylakoid membranes.