bluuebunny/crossref_metadata_2025 huggingface dataset:
Hindsight Bias and Causal Attribution
Authors: Nestler Steffen , Blank Hartmut , von Collani Gernot
Published: August 2008

Hindsight bias describes characteristic changes in the perceptions of events or facts once their outcomes are known. This article focuses on one important facet of this, named creeping determinism, denoting enhanced hindsight perceptions of the inevitability of event outcomes. We suggest a systematic link between the literatures on causal attribution and hindsight bias/creeping determinism and introduce a comprehensive causal model theory (CMT) of creeping determinism. We then distinguish between two alternative versions of CMT, which reflect recent debates in the causal attribution literature. These versions assume, respectively, that individuals make causal attributions by means of covariation analysis or via the discovery of some underlying mechanism. In order to contrast these assumptions, we introduce a new hypothesis concerning the magnitude of creeping determinism, based on the conjunction effect in causal attribution, and we present empirical evidence concerning this hypothesis.
Why the Brewery Ran Out of Beer
Authors: Schyns Birgit , Hansbrough Tiffany
Published: August 2008

According to Heider (1958 ), observers tend to discount situational factors and overemphasize the internal characteristics of the actor when making causal attributions. Specifically, in an organizational setting, leadership perceptions of followers may be influenced by the fundamental attribution error. Accordingly, followers may be more likely to attribute leader mistakes to internal factors. However, we suggest that this tendency may be modified by a variety of factors including the extent to which followers hold romantic leader images, whether leaders match followers’ implicit leadership theories, the characteristics of the mistakes themselves, and the nature of the leader-follower relationship. We develop a model of attribution of mistakes to a direct supervisor, derive propositions for leadership research, and explore implications for practice.
Deep western boundary current and southern frontal systems of the Antarctic Circumpolar Current southeast of the Kerguelen Plateau
Authors: Aoki Shigeru , Fujii Nobuhiro , Ushio Shuki , Yoshikawa Yasushi , Watanabe Shuichi , Mizuta Genta , Fukamachi Yasushi , Wakatsuchi Masaaki
Published: August 2008

The structures of the deep western boundary current and southern frontal systems of the Antarctic Circumpolar Current (ACC) southeast of the Kerguelen Plateau were investigated. Top‐to‐bottom hydrography was conducted around 58°S, and two underway observations were made around 56°S and 61°S. Middepth floats were also used to describe the subsurface flow and temperature fields. Along the 58°S section, a cold dome was located just off the plateau, and northwestward and southeastward flows were found in its western and eastern sides. The observed flow structure was highly barotropic. The maximum volume transport of the bottom water was 22 Sv equatorward, including a possible cyclonic recirculation of 10 Sv. The transport of the deep recirculation can be explained by the potential vorticity homogenization in the closed isopachs formed by the bottom slope off the plateau and the overlying ACC flowing southeastward through the Fawn Trough. The spatial scale of the cold dome, which showed a signature of the southern ACC front, was around 100 km at 58°S, and the similar cold domes were also found around 56°S and 61°S, along with a signature of the southern boundary of ACC around 61°S. The sharp excursion of the southern ACC front was also confirmed by the middepth float trajectories and the distribution of temperature maximum. This indicates the equatorward excursion up to 54°S, with the warmer ACC water just east of the southern frontal systems.
Two‐dimensional array design techniques of millimeter‐wave microstrip comb‐line antenna array
Authors: Sakakibara Kunio , Hayashi Yuki , Kikuma Nobuyoshi , Hirayama Hiroshi
Published: August 2008

Two‐dimensional array design techniques are developed for microstrip comb‐line antenna array. Low sidelobe design is proposed in the plane parallel to the feeding line. Element radiation is controlled by both widths of the radiating element and the feeding line simultaneously. Beam‐tilting design is proposed in the perpendicular plane to the feeding line even though only two feeding lines are arranged. Microstrip slit structure is located around each radiating element in order to cancel reflections from element and slit and to achieve high design accuracy. By using these items, three antennas with different beams are developed for three‐beam switching system. Performance of these antennas is evaluated by experiments in the millimeter‐wave band.
On mapping fracture networks onto continuum
Authors: Botros Farag E. , Hassan Ahmed E. , Reeves Donald M. , Pohll Greg
Published: August 2008

Discrete fracture network (DFN) and stochastic continuum (SC) are two common modeling approaches used for simulating fluid flow and solute transport in fractured media. Fracture continuum approaches combine the merits of each approach; details of the fracture network are preserved, and a computationally efficient grid is utilized for the solution of fluid flow by assigning a conductivity contrast between the grid cells representing the rock matrix and those representing fractures. In this paper, we propose a fracture continuum approach for mapping individual fractures onto a finite‐difference grid as conductivity fields. We focus on several issues that are associated with this approach, such as enhanced connectivity between fractures that would otherwise not be in connection in a DFN simulation and the influence of grid cell size. To addresses these issues, both DFN and the proposed approach are used to solve for fluid flow through two‐dimensional, randomly generated fracture networks in a steady‐state, single‐phase flow system. The DFN flow solution is used as a metric to evaluate the robustness of the method in translating discrete fractures onto grid cell conductivities on four different regularly spaced grids: 1 × 1 m, 2 × 2 m, 5 × 5 m, and 10 × 10 m. Two correction factors are introduced to ensure equivalence between the total flow of the grid and the original fracture network. The first is dependent on the fracture alignment with the grid and is set to account for the difference between the length of the flow path on the grid and that of the fracture. The other correction is applied for areas in the grid with high fracture density and accounts for the artificial degree of connectivity that exists on the grid but not in the DFN. Fifteen different cases are studied to evaluate the effect of fracture statistics on the results of the proposed approach and by taking average results of 100 realizations in each case in a stochastic Monte Carlo framework. The flow equation is solved for the DFN, and total flow is obtained. The flow is also solved separately for the four‐grid resolution levels, and comparisons between the DFN and the grid total flows are made for the different cases and the different grid resolution levels. The approach performed relatively well in all cases for the fine‐grid resolution, but an overestimation of grid flow is observed in the coarse‐grid resolution, especially for cases wherein the network connectivity is controlled by small fractures. This overestimation shows minor variation from one realization to another within the same case. This allowed us to develop an approach that depends on solving limited number of DFN simulations to obtain this overestimation factor. Results indicate that the proposed approach provides improvements over existing approaches and has a potential to provide a link between DFN and SC models.
Flood frequency hydrology: 2. Combining data evidence
Authors: Merz Ralf , Blöschl Günter
Published: August 2008

In a companion paper (Merz and Blöschl, 2008) we argue that it is very useful to expand the information beyond the flood sample at a site of interest to better represent the diversity of flood processes in estimating flood frequencies. In this paper we present a framework of how to combine different sources of information by hydrological reasoning to obtain more informed estimates of flood frequencies. These sources of information include the local flood peak sample and temporal, spatial, and causal expansion of information. As most of this information is independent, one would expect that the final estimate is more reliable than each of the individual sources, including the flood peak sample alone. To illustrate the proposed framework, four examples from Austria are given. In all four examples the statistical analyses of the flood records do not fully represent the site‐specific flood behavior in the light of the more complete information. The strengths of the proposed framework are its flexibility, in that more weight can be given to sources that are known with better confidence than others, and the ability to account for local particularities of catchments in terms of hydrological processes and data availability.
Parameterization of single scattering properties of mid‐latitude cirrus clouds for fast radiative transfer models using particle mixtures
Authors: Bozzo Alessio , Maestri Tiziano , Rizzi Rolando , Tosi Ennio
Published: August 2008

A new parameterization of single scattering properties has been developed for mid latitude cirrus clouds for application to weather prediction and global circulation models. Ice clouds are treated as a mixture of ice crystals with various habits. The bulk optical properties of ice crystals are parameterized as functions of the effective dimension (De) of measured particle size distributions that are representative of mid latitude cirrus clouds.Deis itself parameterized as a function of temperature and ice water content. The paper describes the results obtained with a stand‐alone version of the radiation routine of the COSMO model and preliminary tests with the full forecast model in various meteorological situations characterized by extended high cirrus clouds over Europe.
PR‐SET7 and SUV4‐20H regulate H4 lysine‐20 methylation at imprinting control regions in the mouse
Authors: Pannetier Maëlle , Julien Eric , Schotta Gunnar , Tardat Mathieu , Sardet Claude , Jenuwein Thomas , Feil Robert
Published: August 2008

Imprinted genes are important in development and their allelic expression is mediated by imprinting control regions (ICRs). On their DNA‐methylated allele, ICRs are marked by trimethylation at H3 Lys 9 (H3K9me3) and H4 Lys 20 (H4K20me3), similar to pericentric heterochromatin. Here, we investigate which histone methyltransferases control this methylation of histone at ICRs. We found that inactivation of SUV4‐20H leads to the loss of H4K20me3 and increased levels of its substrate, H4K20me1. H4K20me1 is controlled by PR‐SET7 and is detected on both parental alleles. The disruption of SUV4‐20H or PR‐SET7 does not affect methylation of DNA at ICRs but influences precipitation of H3K9me3, which is suggestive of a trans‐histone change. Unlike at pericentric heterochromatin, however, H3K9me3 at ICRs does not depend on SUV39H. Our data show not only new similarities but also differences between ICRs and heterochromatin, both of which show constitutive maintenance of methylation of DNA in somatic cells.
Complex Sentence Comprehension and Working Memory in Children With Specific Language Impairment
Authors: Montgomery James W. , Evans Julia L.
Published: August 2008

Purpose

This study investigated the association of 2 mechanisms of working memory (phonological short-term memory [PSTM], attentional resource capacity/allocation) with the sentence comprehension of school-age children with specific language impairment (SLI) and 2 groups of control children.

Method

Twenty-four children with SLI, 18 age-matched (CA) children, and 16 language- and memory-matched (LMM) children completed a nonword repetition task (PSTM), the competing language processing task (CLPT; resource capacity/allocation), and a sentence comprehension task comprising complex and simple sentences.

Results

(1) The SLI group performed worse than the CA group on each memory task; (2) all 3 groups showed comparable simple sentence comprehension, but for complex sentences, the SLI and LMM groups performed worse than the CA group; (3) for the SLI group, (a) CLPT correlated with complex sentence comprehension, and (b) nonword repetition correlated with simple sentence comprehension; (4) for CA children, neither memory variable correlated with either sentence type; and (5) for LMM children, only CLPT correlated with complex sentences.

Conclusions

Comprehension of both complex and simple grammar by school-age children with SLI is a mentally demanding activity, requiring significant working memory resources.
Phonotactic Probabilities at the Onset of Language Development: Speech Production and Word Position
Authors: Zamuner Tania S.
Published: August 2008

Purpose

To examine the role of phonotactic probabilities at the onset of language development, in a new language (Dutch), while controlling for word position.

Method

Using a nonword imitation task, 64 Dutch-learning children (age 2;2–2;8 [years;months]) were tested on how they imitated segments in low- and high-phonotactic probability environments, in word-initial and word-final position. The relationship between phonological representations and vocabulary development was examined by comparing children’s performance with their receptive and expressive vocabularies.

Results

Segments in high-phonotactic probability environments were at an advantage in production, in both word-initial and word-final position. Significant correlations were found between vocabulary size and children’s mean segment repetition accuracy for word-initial position, but not in word-final position.

Conclusion

The results indicate that phonological representations are mediated not only by children’s developing vocabularies but also by the structure of children’s emerging lexicons.
Age 17 Language and Reading Outcomes in Late-Talking Toddlers: Support for a Dimensional Perspective on Language Delay
Authors: Rescorla Leslie
Published: August 2008

Purpose

This study examined whether late talkers identified at 24–31 months continued to have weaker language and reading skills at 17 years of age than typically developing peers.

Method

Language and reading outcomes at 17 years of age were examined in 26 children identified as late talkers with normal nonverbal ability and normal receptive language at intake and in 23 typically developing children matched at intake on age, socioeconomic status (SES), and nonverbal ability.

Results

Although late talkers performed in the average range on all language and reading tasks at 17 years of age, they obtained significantly lower Vocabulary/Grammar and Verbal Memory factor scores than SES-matched peers. The age 17 Vocabulary/Grammar factor had large correlations with the age 17 Verbal Memory and Reading/Writing factors. The age 17 Vocabulary/Grammar and Reading/Writing factors were strongly predicted by comparable factors at 13 years of age. Age 2 Language Development Survey (L. Rescorla, 1989) vocabulary score explained 17% of the variance in the age 17 Vocabulary/Grammar and Verbal Memory factors.

Conclusions

Results suggest that slow language development at 24–31 months is associated with a weakness in language-related skills into adolescence relative to skills manifested by typically developing peers—findings that are consistent with a dimensional perspective on language delay.
Accuracy Assessment for AG500, Electromagnetic Articulograph
Authors: Yunusova Yana , Green Jordan R. , Mefferd Antje
Published: August 2008

Purpose

The goal of this article was to evaluate the accuracy and reliability of the AG500 (Carstens Medizinelectronik, Lenglern, Germany), an electromagnetic device developed recently to register articulatory movements in three dimensions. This technology seems to have unprecedented capabilities to provide rich information about time-varying positions of articulators. However, strengths and weaknesses of the system need to be better understood before the device is used for speech research.

Method

Evaluations of the sensor positions over time were obtained during (a) movements of the calibration device, (b) manual movements of sensors in a cartridge within the recording field of the cube, and (c) various speech tasks.

Results

Results showed a median error to be under 0.5 mm across different types of recordings. The maximum error often ranged between 1 and 2 mm. The magnitude of error depended somewhat on the task but largely on the location of the sensors within the recording region of the cube.

Conclusion

The performance of the system was judged as adequate for speech movement acquisition, provided that specific steps are taken for minimizing error during recording and for validating the quality of recorded data.
Predictors of Print Knowledge in Children With Specific Language Impairment: Experiential and Developmental Factors
Authors: McGinty Anita S. , Justice Laura M.
Published: August 2008

Purpose

Many children with specific language impairment (SLI) demonstrate delays in print knowledge, yet the reasons for these delays are not well understood. The present study investigates the degree to which developmental risk factors and home literacy experiences predict the print knowledge of children with SLI.

Method

Direct child measures, maternal reports, and observations from 41 mothers and their preschool-aged children with SLI assessed child language and attentional difficulties, family socioeconomic status, the frequency and quality of home literacy, and children’s print knowledge.

Results

Hierarchical multiple regression analyses revealed that individual differences in children’s oral language abilities did not explain individual variability in print knowledge. The quality of home literacy was the only significant predictor of print knowledge, but its influence was moderated by children’s attentional difficulties.

Conclusions

Findings reveal that language difficulty is not an adequate explanation for the print knowledge delays of children with SLI and suggest that literacy experiences may play an important role in the print knowledge attainment of children with SLI. The quality of home literacy appears to foster print knowledge by compensating for attentional difficulties in children with SLI but is not sufficient to promote print knowledge in children with SLI without attentional difficulties.
Effect of Tongue Exercise on Protrusive Force and Muscle Fiber Area in Aging Rats
Authors: Connor Nadine P. , Russell John A. , Wang Hao , Jackson Michelle A. , Mann Laura , Kluender Keith
Published: August 2008

Purpose

Age-related changes in tongue function may contribute to dysphagia in elderly people. The authors' purpose was to investigate whether aged rats that have undergone tongue exercise would manifest increased protrusive tongue forces and increased genioglossus (GG) muscle fiber cross-sectional areas.

Method

Forty-eight young adult, middle-aged, and old Fischer 344/Brown Norway rats received 8 weeks of tongue exercise. Protrusive tongue forces were measured before and after exercise. GG muscle fiber cross-sectional area was measured in exercised rats and was compared with cross-sectional areas in a no-exercise control group.

Results

A significant increase in maximum tongue force was found following exercise in all age groups. In addition, a trend for increased GG muscle fiber cross-sectional area and a significant increase in variability of GG muscle fiber cross-sectional area was identified postexercise.

Conclusion

The findings of this study have implications for treatment of elderly persons with dysphagia using tongue exercise programs. Specifically, increases in tongue force that occur following 8 weeks of progressive resistance tongue exercise may be accompanied by alterations in tongue muscle fiber morphology. These changes may provide greater strength and endurance for goal-oriented actions associated with the oropharyngeal swallow and should be investigated in future research.
Polymer thin film transistor without surface pretreatment on silicon nitride gate dielectric
Authors: Li Flora M. , Dhagat Parul , Haverinen Hanna M. , McCulloch Iain , Heeney Martin , Jabbour Ghassan E. , Nathan Arokia
Published: August 2008

It is well known that surface modification of the gate dielectric in organic thin film transistors (TFTs) plays an important role in device performance, often giving rise to severalfold improvements in field-effect mobility. This paper reports on solution-processed polymer TFTs with mobilities comparable to high performance counterparts despite the absence of dielectric surface pretreatment. An effective mobility of 0.1cm2∕Vs was obtained with poly(2,5-bis(3-dodecylthiophene-2-yl)thieno[3,2-b]thiophene) transistors on silicon nitride gate dielectric. The results indicate that by judicious preparation of the device layers, one can mitigate the need for dielectric surface pretreatment, thereby reducing fabrication complexity without compromising TFT performance.
Nuclear spin pumping under resonant optical excitation in a quantum dot
Authors: Makhonin M. N. , Tartakovskii A. I. , Ebbens A. , Skolnick M. S. , Russell A. , Fal’ko V. I. , Hopkinson M.
Published: August 2008

We demonstrate nuclear spin pumping in a single InGaAs∕GaAs dot embedded in a p-i-n diode in the regime of resonant optical excitation of spin-polarized electron-hole pairs in the lowest energy states of the dot. A nuclear spin pumping mechanism is proposed relevant to the regime of high electric field where carriers escape from the dot by tunneling. The degree of nuclear spin polarization is shown to increase strongly with the applied electric field, controlling the carrier tunneling from the dot, since at low electric fields the dot is blocked for re-excitation due to the slow hole escape.
Comment on “An optimized potential for carbon dioxide” [J. Chem. Phys. 122, 214507 (2005)]
Authors: Merker Thorsten , Vrabec Jadran , Hasse Hans
Published: August 2008

A molecular model for carbon dioxide is assessed regarding vapor-liquid equilibrium properties. Large deviations, being above 15%, are found for vapor pressure and saturated vapor density in the entire temperature range.
Tunable transport in magnetically coupled MoGe/Permalloy hybrids
Authors: Belkin A. , Novosad V. , Iavarone M. , Fedor J. , Pearson J. E. , Petrean-Troncalli A. , Karapetrov G.
Published: August 2008

We demonstrate controlled magnetotransport anisotropy of magnetically coupled superconductor-ferromagnet MoGe/Permalloy hybrids. The rotatable anisotropy Permalloy ferromagnet with stripe domain structure induces in-plane anisotropy in superconducting order parameter. We show that near the superconductor-normal state phase boundary the superconductivity in MoGe is localized in narrow mesoscopic channels just above the magnetic domain walls. Changing the in-plane direction of magnetic stripe domains it is possible to reconfigure the direction of the superconducting channels and controllably rotate the direction of the in-plane anisotropy axis in the superconductor.
X-ray diffraction imaging of strain fields in a domain-inverted LiTaO3 crystal
Authors: Hassani Kh. , Sutton M. , Holt M. , Zuo Y. , Plant D.
Published: August 2008

We investigate lattice orientation and strain fields across ferroelectric domain walls in a single crystal lithium tantalate using x-ray diffraction imaging (topography). The sample is an actual voltage-operated optical switch consisting of a series of triangular polarization-inverted domains formed in an originally poled single crystal. By applying an electric field only about 2% of the coercive field in the forward and reverse directions, we observed asymmetric lattice rotation of about 10−6 rad, and normal strain variation in the order of 10−5 with reference to the zero-field state. Our results confirm that in congruent LiTaO3 crystals there is unexpectedly large strain field expanding several micrometers across the domain walls, in contrast with the widely accepted theoretical fact that in this material the polarization reversal establishes over only a few lattice constants, resulting in small and localized lattice distortions.
Spatial linear stability of a hypersonic shear layer with nonequilibrium thermochemistry
Authors: Massa L. , Austin J. M.
Published: August 2008

We examine the spatial linear stability of a shear layer in a hypervelocity flow where high temperature effects such as chemical dissociation and vibrational excitation are present. A shock triple point is used to generate a free shear layer in a model problem which also occurs in several aerodynamic applications such as shock-boundary layer interaction. Calculations were performed using a state-resolved, three-dimensional forced harmonic oscillator thermochemical model. An extension of an existing molecular-molecular energy transfer rate model to higher collisional energies is presented and verified. Nonequilibrium model results are compared with calculations assuming equilibrium and frozen flows over a range of (frozen) convective Mach numbers from 0.341 to 1.707. A substantial difference in two- and three-dimensional perturbation growth rates is observed among the three models. Thermochemical nonequilibrium has a destabilizing effect on shear-layer perturbations for all convective Mach numbers considered. The analysis considers the evolution of the molecular vibrational quantum distribution during the instability growth by examining the perturbation eigenfunctions. Oxygen and nitrogen preserve a Boltzmann distribution of vibrational energy, while nitric oxide shows a significant deviation from equilibrium. The difference between translational and vibrational temperature eigenfunctions increases with the convective Mach number. Dissociation and vibration transfer effects on the perturbation evolution remain closely correlated at all convective Mach numbers.
A versatile variable-temperature scanning tunneling microscope for molecular growth
Authors: Kuck Stefan , Wienhausen Jan , Hoffmann Germar , Wiesendanger Roland
Published: August 2008

We describe and discuss the design of a variable-temperature scanning tunneling microscope (STM) system for the study of molecules at temperatures between 18 and 300K in ultrahigh vacuum. The STM head is a refinement of a very rigid design developed and successfully operated in Hamburg. In the current version, the head is connected to a liquid helium flow cryostat, thereby reaching a base temperature of 18K. To minimize the heat load on the STM head, a helium back flow cooled radiation shield is installed. The dimensions and the choice of materials are based on simulations of the heat dissipation. The STM is galvanically isolated from the vacuum chamber to minimize electronic noise and mechanically decoupled by means of springs and an eddy current damping stage. Additionally, the design of the STM head allows the deposition of several molecular materials onto the same cold sample surface. The operation of the STM in imaging mode is demonstrated for TPP/Cu(111) and FePC∕NaCl∕Cu(111). Spectroscopic capabilities of the system are shown for electronic states on NaCl∕Cu(111) and TPP/Cu(111).
Use of zeolites in the capture of charged particles from plasma
Authors: Ahn Sung Il , Lee Seong Eui , Kim Sun Ho , Cho Kwan Hyun , Choi Kyung Cheol
Published: August 2008

The zeolites NaA and 13X were introduced to a coplanar discharge cell to investigate the behavior of charged particles from plasma. The zeolite crystals were attached to the surface without blocking their nanopores. The memory margin related to the accumulated charged particles on the surface indicated that the zeolites absorb charged particles. This phenomenon was also observed at the displacement and discharge current plots. Zeolites with a different window size cause abnormally high displacement and a saturation phenomenon of discharge currents. Note in particular that NaA seems to not only absorb charged particles but also capture gas molecules.
Excitation of dielectric-loaded surface plasmon polariton observed by using near-field optical microscopy
Authors: Fang Zheyu , Zhang Xuejin , Liu Dan , Zhu Xing
Published: August 2008

The excitation of dielectric-loaded surface plasmon polariton (DLSPP) by a CdS nanostripe placed on a Ag layer is observed by using a scanning near-field optical microscopy (SNOM). The spectroscopic redshift of 30 meV of photoluminescence is observed at different positions of the stripe by SNOM and can be explained as the result of Franz–Keldysh effect. Finite difference time domain calculations confirm the observations of the near-field optical images and spectroscopic data. This DLSPP excitation structure is important in the implementation of photonic integrated circuits as well as the optical guiding modes in plasmonic devices.
A conductor/insulator/conductor complex layer at anode for current Enhancement in a Polymer Solar Cell
Authors: Tsai Hsing-Wang , Pei Zingway , Chan Yi-Jen
Published: August 2008

In this letter, a structure in the form of conductor/insulator/conductor was inserted into the anode and photoactive material of a polymer solar cell to enhance the photocurrent by magnifying the internal electrical field. Through this structure, a 15.8% enhancement in photocurrent and a 11.2% enhancement in power conversion efficiency over standard cell were obtained. The mechanism for the internal electrical field enhancement was proposed in terms of modifying the workfunction of the anode material and was proved by the ultraviolet photon spectroscopy.
Negative refraction at the pure Ag/air interface observed in the visible Drude region
Authors: Wu Yun-Hua , Gu Wen , Chen Yue-Rui , Dai Zhong-Hong , Zhou Wei-Xi , Zheng Yu-Xiang , Chen Liang-Yao
Published: August 2008

Pure negative refraction was found for a series of prismlike Ag film samples measured in the visible Drude region. Results show that the pseudonegative refraction index nm changes with the photon energy and has a spectral trend to be less negative with the increasing energy. Light refraction will be expected to be positive in the higher energy region where the interband transitions dominate the interaction between the electrons and photons in Ag.
Physical environmental conditions, spawning and early-life stages of an estuarine fish: climate change implications for recruitment in intermittently open estuaries
Authors: Nicholson Geoff , Jenkins Gregory P. , Sherwood John , Longmore Andy
Published: August 2008

Significant variation in the egg and larval survival and juvenile recruitment of estuarine fishes has been linked to fluctuating environmental conditions. This present study compared the distribution and abundance of black bream (Acanthopagrus butcheri) eggs and yolk-sac larvae between two microtidal estuaries of different flow regimes, where the riverine flow into the Glenelg estuary was around eight times the flow volume into the Hopkins estuary. Samples were collected monthly from September to November at sites along each estuary where vertical profiles of temperature, salinity and dissolved oxygen (DO) were measured, and vertically stratified sampling of black bream eggs and yolk-sac larvae was conducted using a Schindler sampler. Salt wedge formation was apparent in both estuaries, with significant de-oxygenation of deeper, saline waters. Eggs occurred in a wide range of DO levels but yolk-sac larvae were less common at the lowest levels. Most eggs and yolk-sac larvae were collected in salinities greater than 10. Results suggested that egg mortality was higher in the Hopkins than the Glenelg estuary, which may be associated with the hypoxic conditions characteristic of low-flow conditions. The results have significant implications in terms of climate change that is predicted to lead to warmer, drier conditions in south-eastern Australia, potentially increasing stratification and subsequent hypoxic zones.
Nitrate uptake rates in freshwater plankton: the effect of food web structure
Authors: Rojo Carmen , Rodrigo María A. , Salazar Guillem , Álvarez-Cobelas Miguel
Published: August 2008

Nitrate incorporation rates by primary producers and the transfer of nitrogen to upper planktonic food web levels in different seasons (spring and summer of different years) were studied using a microcosm experimental approach. The study communities were natural plankton communities from Colgada Lake (central Spain), which is heavily polluted by nitrate. Natural δ15N in phytoplankton and zooplankton was measured and experiments were performed on the 15N supply. Naturally derived δ15N varied from 7.4 to 8.6‰ and from 10.0 to 16.8‰ in phytoplankton and zooplankton respectively. Nitrogen incorporation rates ranged from 0.006 to 0.036 μM h–1 and from 0.0004 to 0.0014 μM h–1 in phytoplankton and zooplankton respectively. The differences in natural δ15N levels and nitrogen incorporation rates between plankton fractions from seasonally different communities reported in the present study suggested that the nitrogen uptake by planktonic communities in Colgada Lake depend on different combinations of dominant zooplankters and phytoplankton size structure. A higher level of nitrogen uptake by phytoplankton occurred when small algae were dominant without competitors (larger algae) or main predators (herbivorous zooplankters). This was because copepods, with the lowest zooplankton nitrogen uptake, were dominant. Phytoplankton nitrogen uptake was lower when big algae were dominant.
Executioner caspase-3 and caspase-7 are functionally distinct proteases
Authors: Walsh John G. , Cullen Sean P. , Sheridan Clare , Lüthi Alexander U. , Gerner Christopher , Martin Seamus J.
Published: August 2008

Members of the caspase family of cysteine proteases play central roles in coordinating the stereotypical events that occur during apoptosis. Because the major executioner caspases, caspase-3 and caspase-7, exhibit almost indistinguishable activity toward certain synthetic peptide substrates, this has led to the widespread view that these proteases occupy functionally redundant roles within the cell death machinery. However, the distinct phenotypes of mice deficient in either of these caspases, as well as mice deficient in both, is at odds with this view. These distinct phenotypes could be related to differences in the relative expression levels of caspase-3 and caspase-7
in vivo
, or due to more fundamental differences between these proteases in terms of their ability to cleave natural substrates. Here we show that caspase-3 and caspase-7 exhibit differential activity toward multiple substrate proteins, including Bid, XIAP, gelsolin, caspase-6, and cochaperone p23. Caspase-3 was found to be generally more promiscuous than caspase-7 and appears to be the major executioner caspase during the demolition phase of apoptosis. Our observations provide a molecular basis for the different phenotypes seen in mice lacking either caspase and indicate that these proteases occupy nonredundant roles within the cell death machinery.
Structural plasticity with preserved topology in the postsynaptic protein network
Authors: Blanpied Thomas A. , Kerr Justin M. , Ehlers Michael D.
Published: August 2008

The size, shape, and molecular arrangement of the postsynaptic density (PSD) determine the function of excitatory synapses in the brain. Here, we directly measured the internal dynamics of scaffold proteins within single living PSDs, focusing on the principal scaffold protein PSD-95. We found that individual PSDs undergo rapid, continuous changes in morphology driven by the actin cytoskeleton and regulated by synaptic activity. This structural plasticity is accompanied by rapid fluctuations in internal scaffold density over submicron distances. Using targeted photobleaching and photoactivation of PSD subregions, we show that PSD-95 is nearly immobile within the PSD, and PSD subdomains can be maintained over long periods. We propose a flexible matrix model of the PSD based on stable molecular positioning of PSD-95 scaffolds.
A critical role for the right fronto-insular cortex in switching between central-executive and default-mode networks
Authors: Sridharan Devarajan , Levitin Daniel J. , Menon Vinod
Published: August 2008

Cognitively demanding tasks that evoke activation in the brain's central-executive network (CEN) have been consistently shown to evoke decreased activation (deactivation) in the default-mode network (DMN). The neural mechanisms underlying this switch between activation and deactivation of large-scale brain networks remain completely unknown. Here, we use functional magnetic resonance imaging (fMRI) to investigate the mechanisms underlying switching of brain networks in three different experiments. We first examined this switching process in an auditory event segmentation task. We observed significant activation of the CEN and deactivation of the DMN, along with activation of a third network comprising the right fronto-insular cortex (rFIC) and anterior cingulate cortex (ACC), when participants perceived salient auditory event boundaries. Using chronometric techniques and Granger causality analysis, we show that the rFIC-ACC network, and the rFIC, in particular, plays a critical and causal role in switching between the CEN and the DMN. We replicated this causal connectivity pattern in two additional experiments: (
i
) a visual attention “oddball” task and (
ii
) a task-free resting state. These results indicate that the rFIC is likely to play a major role in switching between distinct brain networks across task paradigms and stimulus modalities. Our findings have important implications for a unified view of network mechanisms underlying both exogenous and endogenous cognitive control.
The Rab5 guanylate exchange factor Rin1 regulates endocytosis of the EphA4 receptor in mature excitatory neurons
Authors: Deininger Katrin , Eder Matthias , Kramer Edgar R. , Zieglgänsberger Walter , Dodt Hans-Ulrich , Dornmair Klaus , Colicelli John , Klein Rüdiger
Published: August 2008

Ephrin signaling through Eph receptor tyrosine kinases regulates important morphogenetic events during development and synaptic plasticity in the adult brain. Although Eph-ephrin endocytosis is required for repulsive axon guidance, its role in postnatal brain and synaptic plasticity is unknown. Here, we show that Rin1, a postnatal brain-specific Rab5-GEF, is coexpressed with EphA4 in excitatory neurons and interacts with EphA4 in synaptosomal fractions. The interaction of Rin1 and EphA4 requires Rin1's SH2 domain, consistent with the view that Rin1 targets tyrosine phosphorylated receptors to Rab5 compartments. We find that Rin1 mediates EphA4 endocytosis in postnatal amygdala neurons after engagement of EphA4 with its cognate ligand ephrinB3. Rin1 was shown to suppress synaptic plasticity in the amygdala, a forebrain structure important for fear learning, possibly by internalizing synaptic receptors. We find that the EphA4 receptor is required for synaptic plasticity in the amygdala, raising the possibility that an underlying mechanism of Rin1 function in amygdala is to down-regulate EphA4 signaling by promoting its endocytosis.
Subclonal phylogenetic structures in cancer revealed by ultra-deep sequencing
Authors: Campbell Peter J. , Pleasance Erin D. , Stephens Philip J. , Dicks Ed , Rance Richard , Goodhead Ian , Follows George A. , Green Anthony R. , Futreal P. Andy , Stratton Michael R.
Published: August 2008

During the clonal expansion of cancer from an ancestral cell with an initiating oncogenic mutation to symptomatic neoplasm, the occurrence of somatic mutations (both driver and passenger) can be used to track the on-going evolution of the neoplasm. All subclones within a cancer are phylogenetically related, with the prevalence of each subclone determined by its evolutionary fitness and the timing of its origin relative to other subclones. Recently developed massively parallel sequencing platforms promise the ability to detect rare subclones of genetic variants withouta prioriknowledge of the mutations involved. We used ultra-deep pyrosequencing to investigate intraclonal diversification at the Ig heavy chain locus in 22 patients with B-cell chronic lymphocytic leukemia. Analysis of a non-polymorphic control locus revealed artifactual insertions and deletions resulting from sequencing errors and base substitutions caused by polymerase misincorporation during PCR amplification. We developed an algorithm to differentiate genuine haplotypes of somatic hypermutations from such artifacts. This proved capable of detecting multiple rare subclones with frequencies as low as 1 in 5000 copies and allowed the characterization of phylogenetic interrelationships among subclones within each patient. This study demonstrates the potential for ultra-deep resequencing to recapitulate the dynamics of clonal evolution in cancer cell populations.
Direct observation of reaction intermediates for a well defined heterogeneous alkene metathesis catalyst
Authors: Blanc Frédéric , Berthoud Romain , Copéret Christophe , Lesage Anne , Emsley Lyndon , Singh Rojendra , Kreickmann Thorsten , Schrock Richard R.
Published: August 2008

Grafting of [W(≡NAr)(=CH
t
Bu)(2,5-Me
2
NC
4
H
2
)
2
] on a silica partially dehydroxylated at 700°C (SiO
2- (700)
) generates the corresponding monosiloxy complex [(≡SiO)W(≡NAr)(=CH
t
Bu)(2,5-Me
2
NC
4
H
2
)] as the major species (≈90%) along with [(≡SiO)W(≡NAr)(CH
2
t
Bu)(2,5-Me
2
NC
4
H
2
)
2
], according to mass balance analysis, IR, and NMR studies. This heterogeneous catalyst displays good activity and stability in the metathesis of propene. Very importantly, solid state NMR spectroscopy allows observation of the propagating alkylidene as well as stable metallacyclobutane intermediates. These species have the same reactivity as the initial surface complex [(≡SiO)W(≡NAr)(=CH
t
Bu)(2,5-Me
2
NC
4
H
2
)], which shows that they are the key intermediates of alkene metathesis.
Synapse formation and clustering of neuroligin-2 in the absence of GABA
A
receptors
Authors: Patrizi Annarita , Scelfo Bibiana , Viltono Laura , Briatore Federica , Fukaya Masahiro , Watanabe Masahiko , Strata Piergiorgio , Varoqueaux Frédérique , Brose Nils , Fritschy Jean-Marc , Sassoè-Pognetto Marco
Published: August 2008

GABAergic synapses are crucial for brain function, but the mechanisms underlying inhibitory synaptogenesis are unclear. Here, we show that postnatal Purkinje cells (PCs) of GABA
A
α1 knockout (KO) mice express transiently the α3 subunit, leading to the assembly of functional GABA
A
receptors and initial normal formation of inhibitory synapses, that are retained until adulthood. Subsequently, down-regulation of the α3 subunit causes a complete loss of GABAergic postsynaptic currents, resulting in a decreased rate of inhibitory synaptogenesis and formation of mismatched synapses between GABAergic axons and PC spines. Notably, the postsynaptic adhesion molecule neuroligin-2 (NL2) is correctly targeted to inhibitory synapses lacking GABA
A
receptors and the scaffold molecule gephyrin, but is absent from mismatched synapses, despite innervation by GABAergic axons. Our data indicate that GABA
A
receptors are dispensable for synapse formation and maintenance and for targeting NL2 to inhibitory synapses. However, GABAergic signaling appears to be crucial for activity-dependent regulation of synapse density during neuronal maturation.
Structure of Vps75 and implications for histone chaperone function
Authors: Tang Yong , Meeth Katrina , Jiang Eva , Luo Cheng , Marmorstein Ronen
Published: August 2008

The vacuolar protein sorting 75 (Vps75) histone chaperone participates in chromatin assembly and disassembly at both active and inactive genes through the preferential binding to histone H3–H4. Vps75 is also one of two histone chaperones, along with antisilencing factor 1, that promotes histone H3-Lys-56 acetylation by the regulation of Ty1 transposition protein 109 (Rtt109) histone acetyltransferase. Here, we report the x-ray crystal structure of Vps75 and carry out biochemical studies to characterize its interaction with Rtt109. We find that the Vps75 structure forms a homodimeric “headphone” architecture that includes an extended helical dimerization domain and earmuff domains at opposite ends and sides of the dimerization domain. Despite the similar overall architecture with the yeast nucleosome assembly protein 1 and human SET/TAF-1β/INHAT histone chaperones, Vps75 shows several unique features including the relative disposition of the earmuff domains to the dimerization domain, characteristics of the earmuff domains, and a pronounced cleft at the center of the Vps75 dimer. These differences appear to correlate with the unique function of Vps75 to interact with Rtt109 for histone acetylation. Our biochemical studies reveal that two surfaces on the earmuff domain of Vps75 participate in Rtt109 interaction with a stoichiometry of 2:1, thus leaving the pronounced central cleft of the Vps75 dimer largely accessible for histone binding. Taken together, our data provide a structural framework for understanding how Vps75 mediates both nucleosome assembly and histone acetylation by Rtt109.
Opposing plant community responses to warming with and without herbivores
Authors: Post Eric , Pedersen Christian
Published: August 2008

If controls over primary productivity and plant community composition are mainly environmental, as opposed to biological, then global change may result in large-scale alterations in ecosystem structure and function. This view appears to be favored among investigations of plant biomass and community responses to experimental and observed warming. In far northern and arctic ecosystems, such studies predict increasing dominance of woody shrubs with future warming and emphasize the carbon (C)-sequestration potential and consequent atmospheric feedback potential of such responses. In contrast to previous studies, we incorporated natural herbivory by muskoxen and caribou into a 5-year experimental investigation of arctic plant community response to warming. In accordance with other studies, warming increased total community biomass by promoting growth of deciduous shrubs (dwarf birch and gray willow). However, muskoxen and caribou reduced total community biomass response, and responses of birch and willow, to warming by 19%, 46%, and 11%, respectively. Furthermore, under warming alone, the plant community shifted after 5 years away from graminoid-dominated toward dwarf birch-dominated. In contrast, where herbivores grazed, plant community composition on warmed plots did not differ from that on ambient plots after 5 years. These results highlight the potentially important and overlooked influences of vertebrate herbivores on plant community response to warming and emphasize that conservation and management of large herbivores may be an important component of mitigating ecosystem response to climate change.