bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining the CH3SO2→CH3+SO2 barrier from methylsulfonyl chloride photodissociation at 193 nm using velocity map imaging
Authors: Ratliff Britni J. , Tang Xiaonan , Butler Laurie J. , Szpunar David E. , Lau Kai-Chung
Published: July 2009

These imaging experiments study the formation of the methylsulfonyl radical, CH3SO2, from the photodissociation of CH3SO2Cl at 193 nm and determine the energetic barrier for the radical’s subsequent dissociation to CH3+SO2. We first state-selectively detect the angular and recoil velocity distributions of the Cl(P23/2) and Cl(P21/2) atoms to further refine the distribution of internal energy partitioned to the momentum-matched CH3SO2 radicals. The internal energy distribution of the radicals is bimodal, indicating that CH3SO2 is formed in both the ground state and low-lying excited electronic states. All electronically excited CH3SO2 radicals dissociate, while those formed in the ground electronic state have an internal energy distribution which spans the dissociation barrier to CH3+SO2. We detect the recoil velocities of the energetically stable methylsulfonyl radicals with 118 nm photoionization. Comparison of the total recoil translational energy distribution for all radicals to the distribution obtained from the detection of stable radicals yields an onset for dissociation at a translational energy of 70±2 kcal/mol. This onset allows us to derive a CH3SO2→CH3+SO2 barrier height of 14±2 kcal/mol; this determination relies on the S–Cl bond dissociation energy, taken here as the CCSD(T) predicted energy of 65.6 kcal/mol. With 118 nm photoionization, we also detect the velocity distribution of the CH3 radicals produced in this experiment. Using the velocity distributions of the SO2 products from the dissociation of CH3SO2 to CH3+SO2 presented in the following paper, we show that our fastest detected methyl radicals are not from these radical dissociation channels, but rather from a primary S–CH3 bond photofission channel in CH3SO2Cl. We also present critical points on the ground state potential energy surface of CH3SO2 at the CCSD(T)/aug-cc-pV(Q+d)Z//CCSD(T)/6-311++G(2df,p) level. We include harmonic zero-point vibrational corrections as well as core-valence and scalar-relativistic corrections. The CCSD(T) predicted barrier of 14.6 kcal/mol for CH3SO2→CH3+SO2 agrees well with our experimental measurement. These results allow us to predict the unimolecular dissociation kinetics of CH3SO2 radicals and critique the analysis of prior time-resolved photoionization studies on this system.
Relative abundance and structure of chaotic behavior: The nonpolynomial Belousov–Zhabotinsky reaction kinetics
Authors: Freire Joana G. , Field Richard J. , Gallas Jason A. C.
Published: July 2009

We report a detailed numerical investigation of the relative abundance of periodic and chaotic oscillations in phase diagrams for the Belousov–Zhabotinsky (BZ) reaction as described by a nonpolynomial, autonomous, three-variable model suggested by Györgyi and Field [Nature (London) 355, 808 (1992)]. The model contains 14 parameters that may be tuned to produce rich dynamical scenarios. By computing the Lyapunov spectra, we find the structuring of periodic and chaotic phases of the BZ reaction to display unusual global patterns, very distinct from those recently found for gas and semiconductor lasers, for electric circuits, and for a few other familiar nonlinear oscillators. The unusual patterns found for the BZ reaction are surprisingly robust and independent of the parameter explored.
Effects of activation by proton irradiation on silicon particle detector electric characteristics
Authors: Väyrynen S. , Räisänen J. , Tikkanen P. , Kassamakov I. , Tuominen E.
Published: July 2009

After irradiation with 7 and 9 MeV protons, activation-induced effects were encountered in measurements of current-voltage (IV) and capacitance-voltage (CV) characteristics for Czochralski and float-zone grown silicon particle detectors prepared on printed circuit boards with copper electrodes. With the present detector construction, the S30i(p,n)P30 and C63u(p,n)Z63n reactions induce dominant interference in such measurements. The daughter nuclides are positron emitters with half-lives of 2.5 and 38.5 min, respectively, and the slowing down of the emitted positrons generates a significantly large concentration of electron-hole pairs in the detector volume increasing the leakage current level and decreasing the breakdown voltage. The observed time-dependent characteristics were verified by modeling the activation of the detector structure and the resulting leakage current. As a result, the electrical measurements cannot be performed immediately after irradiation due to silicon activation, and, generally, materials becoming easily activated should be avoided in the detector concept.
The correlation dimension: A robust chaotic feature for classifying acoustic emission signals generated in construction materials
Authors: Kacimi S. , Laurens S.
Published: July 2009

In the field of acoustic emission (AE) source recognition, this paper presents a classification feature based on the paradigm of nonlinear dynamical systems, often referred to as chaos theory. The approach considers signals as time series expressing an underlying dynamical phenomenon and enclosing all the information regarding the dynamics. The scientific knowledge on nonlinear dynamical systems has considerably improved for the past 40 years. The dynamical behavior is analyzed in the phase space, which is the space generated by the state variables of the system. The time evolution of a system is expressed in the phase space by trajectories, and the asymptotic behavior of trajectories defines a space area which is referred to as a system attractor. Dynamical systems may be characterized by the topological properties of attractors, such as the correlation dimension, which is a fractal dimension. According to Takens theorem, even if the system is not clearly defined, it is possible to infer topological information about the attractor from experimental observations. Such a method, which is called phase space reconstruction, was successfully applied for the classification of acoustic emission waveforms propagating in more or less complex materials such as granite and concrete. Laboratory tests were carried out in order to collect numerous AE waveforms from various controlled acoustic sources. Then, each signal was processed to extract a reconstructed attractor from which the correlation dimension was computed. The first results of this research show that the correlation dimension assessed after phase space reconstruction is very relevant and robust for classifying AE signals. These promising results may be explained by the fact that the totality of the signal is used to achieve classifying information. Moreover, due to the self-similar nature of attractors, the correlation dimension, and thus a correlation dimension-based classification approach, is theoretically insensitive to signal absorption.
Downconversion for solar cells in NaYF4:Er,Yb
Authors: Aarts L. , van der Ende B. M. , Meijerink A.
Published: July 2009

Downconversion is a promising avenue to boost the efficiency of solar cells by absorbing one higher energy visible photon and emitting two lower energy near-infrared (NIR) photons. Here the efficiency of downconversion for the (Er3+,Yb3+) couple is investigated in NaYF4, a well-known host lattice for efficient upconversion with (Er3+,Yb3+). Analysis of the excitation and emission spectra for NaYF4 doped with 1% Er3+ and codoped with 0%, 5%, 10%, or 30% Yb3+ show that visible to NIR downconversion is inefficient. Downconversion by the scheme based on the reverse of the upconversion process is hampered by fast multiphonon relaxation from the F47/2 level (the starting level for downconversion) to the S43/2 level. Energy transfer from the S43/2 level of Er3+ to Yb3+ is shown to be inefficient. Efficient downconversion from the G411/2 of Er3+ level is observed, resulting in emission of two photons (one around 980 nm and one around 650 nm) after absorption of a single 380 nm photon.
Mechanical model and superelastic properties of carbon microcoils with circular cross-section
Authors: Bi H. , Kou K. C. , Ostrikov Kostya (Ken) , Zhang J. Q. , Wang Z. C.
Published: July 2009

Here we report on an unconventional Ni–P alloy-catalyzed, high-throughput, highly reproducible chemical vapor deposition of ultralong carbon microcoils using acetylene precursor in the temperature range 700–750 °C. Scanning electron microscopy analysis reveals that the carbon microcoils have a unique double-helix structure and a uniform circular cross-section. It is shown that double-helix carbon microcoils have outstanding superelastic properties. The microcoils can be extended up to 10–20 times of their original coil length, and quickly recover the original state after releasing the force. A mechanical model of the carbon coils with a large spring index is developed to describe their extension and contraction. Given the initial coil parameters, this mechanical model can successfully account for the geometric nonlinearity of the spring constants for carbon micro- and nanocoils, and is found in a good agreement with the experimental data in the whole stretching process.
On the Kohn–Sham density response in a localized basis set
Authors: Foerster Dietrich , Koval Peter
Published: July 2009

We construct the Kohn–Sham density response function χ0 in a previously described basis of the space of orbital products. The calculational complexity of our construction is O(N2Nω) for a molecule of N atoms and in a spectroscopic window of Nω frequency points. As a first application, we use χ0 to calculate the molecular spectra from the Petersilka–Gossmann–Gross equation. With χ0 as input, we obtain the correct spectra with an extra computational effort that grows also as O(N2Nω) and, therefore, less steeply in N than the O(N3) complexity of solving Casida’s equations. Our construction should be useful for the study of excitons in molecular physics and in related areas where χ0 is a crucial ingredient.
A selection rule for molecular conduction
Authors: Fowler P. W. , Pickup B. T. , Todorova T. Z. , Myrvold W.
Published: July 2009

Conditions for transmission of a π-conjugated molecular conductor are derived within the source and sink potential approach in terms of numbers of nonbonding levels of four graphs: The molecular graph G and the three vertex-deleted subgraphs obtained by removing one or both contact vertices. For all bipartite and most nonbipartite G, counting nonbonding levels gives a simple necessary and sufficient condition for conduction at the Fermi level. The exceptional case is where G is nonbipartite and all four graphs have the same number of nonbonding levels; then, an auxiliary requirement involving tail coefficients of the four characteristic polynomials must also be checked.
Quantum optimal control of isomerization dynamics of a one-dimensional reaction-path model dominated by a competing dissociation channel
Authors: Kurosaki Yuzuru , Artamonov Maxim , Ho Tak-San , Rabitz Herschel
Published: July 2009

Quantum wave packet optimal control simulations with intense laser pulses have been carried out for studying molecular isomerization dynamics of a one-dimensional (1D) reaction-path model involving a dominant competing dissociation channel. The 1D intrinsic reaction coordinate model mimics the ozone open→cyclic ring isomerization along the minimum energy path that successively connects the ozone cyclic ring minimum, the transition state (TS), the open (global) minimum, and the dissociative O2+O asymptote on the O3 ground-state A1′ potential energy surface. Energetically, the cyclic ring isomer, the TS barrier, and the O2+O dissociation channel lie at ∼0.05, ∼0.086, and ∼0.037 hartree above the open isomer, respectively. The molecular orientation of the modeled ozone is held constant with respect to the laser-field polarization and several optimal fields are found that all produce nearly perfect isomerization. The optimal control fields are characterized by distinctive high temporal peaks as well as low frequency components, thereby enabling abrupt transfer of the time-dependent wave packet over the TS from the open minimum to the targeted ring minimum. The quick transition of the ozone wave packet avoids detrimental leakage into the competing O2+O channel. It is possible to obtain weaker optimal laser fields, resulting in slower transfer of the wave packets over the TS, when a reduced level of isomerization is satisfactory.
Using synchronization of chaos to identify the dynamics of unknown systems
Authors: Sorrentino Francesco , Ott Edward
Published: July 2009

We address the issue of how to identify the equations of a largely unknown chaotic system from knowledge about its state evolution. The technique can be applied to the estimation of parameters that drift slowly with time. To accomplish this, we propose an adaptive strategy that aims at synchronizing the unknown real system with another system whose parameters are adaptively evolved to converge on those of the real one. Our proposed strategy is tested to identify the equations of the Lorenz and the Rössler systems. We also consider the effects of measurement noise and of deviation of our fitting model from consistency with the true dynamics.
Resistance of domain walls created by means of a magnetic force microscope in transversally magnetized epitaxial Fe wires
Authors: Hassel C. , Stienen S. , Römer F. M. , Meckenstock R. , Dumpich G. , Lindner J.
Published: July 2009

Magnetic domain walls are created in a controllable way in transversally magnetized epitaxial Fe wires on GaAs(110) by approaching a magnetic force microscope (MFM) tip. The electrical resistance-change due to the addition of these domain walls is measured. The anisotropic magnetoresistance as well as the intrinsic domain wall resistance contribute to the resistance-change. The efficiency of this procedure is proven by MFM images, which are obtained subsequent to the domain wall creation at a larger sample-to-probe distance. The contribution of the anisotropic magnetoresistance is calculated using micromagnetic calculations, thus making it possible to quantify the intrinsic domain wall resistance.
Maximization of the connectivity repertoire as a statistical principle governing the shapes of dendritic arbors
Authors: Wen Quan , Stepanyants Armen , Elston Guy N. , Grosberg Alexander Y. , Chklovskii Dmitri B.
Published: July 2009

The shapes of dendritic arbors are fascinating and important, yet the principles underlying these complex and diverse structures remain unclear. Here, we analyzed basal dendritic arbors of 2,171 pyramidal neurons sampled from mammalian brains and discovered 3 statistical properties: the dendritic arbor size scales with the total dendritic length, the spatial correlation of dendritic branches within an arbor has a universal functional form, and small parts of an arbor are self-similar. We proposed that these properties result from maximizing the repertoire of possible connectivity patterns between dendrites and surrounding axons while keeping the cost of dendrites low. We solved this optimization problem by drawing an analogy with maximization of the entropy for a given energy in statistical physics. The solution is consistent with the above observations and predicts scaling relations that can be tested experimentally. In addition, our theory explains why dendritic branches of pyramidal cells are distributed more sparsely than those of Purkinje cells. Our results represent a step toward a unifying view of the relationship between neuronal morphology and function.
Mechanical tension contributes to clustering of neurotransmitter vesicles at presynaptic terminals
Authors: Siechen Scott , Yang Shengyuan , Chiba Akira , Saif Taher
Published: July 2009

Memory and learning in animals are mediated by neurotransmitters that are released from vesicles clustered at the synapse. As a synapse is used more frequently, its neurotransmission efficiency increases, partly because of increased vesicle clustering in the presynaptic neuron. Vesicle clustering has been believed to result primarily from biochemical signaling processes that require the connectivity of the presynaptic terminal with the cell body, the central nervous system, and the postsynaptic cell. Our in vivo experiments on the embryonicDrosophilanervous system show that vesicle clustering at the neuromuscular presynaptic terminal depends on mechanical tension within the axons. Vesicle clustering vanishes upon severing the axon from the cell body, but is restored when mechanical tension is applied to the severed end of the axon. Clustering increases when intact axons are stretched mechanically by pulling the postsynaptic muscle. Using micro mechanical force sensors, we find that embryonic axons that have formed neuromuscular junctions maintain a rest tension of ≈1 nanonewton. If the rest tension is perturbed mechanically, axons restore the rest tension either by relaxing or by contracting over a period of ≈15 min. Our results suggest that neuromuscular synapses employ mechanical tension as a signal to modulate vesicle accumulation and synaptic plasticity.
Predicting weakly stable regions, oligomerization state, and protein–protein interfaces in transmembrane domains of outer membrane proteins
Authors: Naveed Hammad , Jackups Ronald , Liang Jie
Published: July 2009

Although the structures of many β-barrel membrane proteins are available, our knowledge of the principles that govern their energetics and oligomerization states is incomplete. Here we describe a computational method to study the transmembrane (TM) domains of β-barrel membrane proteins. Our method is based on a physical interaction model, a simplified conformational space for efficient enumeration, and an empirical potential function from a detailed combinatorial analysis. Using this method, we can identify weakly stable regions in the TM domain, which are found to be important structural determinants for β-barrel membrane proteins. By calculating the melting temperatures of the TM strands, our method can also assess the stability of β-barrel membrane proteins. Predictions on membrane enzyme PagP are consistent with recent experimental NMR and mutant studies. We have also discovered that out-clamps, in-plugs, and oligomerization are 3 general mechanisms for stabilizing weakly stable TM regions. In addition, we have found that extended and contiguous weakly stable regions often signal the existence of an oligomer and that strands located in the interfaces of protein–protein interactions are considerably less stable. Based on these observations, we can predict oligomerization states and can identify the interfaces of protein–protein interactions for β-barrel membrane proteins by using either structure or sequence information. In a set of 25 nonhomologous proteins with known structures, our method successfully predicted whether a protein forms a monomer or an oligomer with 91% accuracy; in addition, our method identified with 82% accuracy the protein–protein interaction interfaces by using sequence information only when correct strands are given.
The JNKs differentially regulate RNA polymerase III transcription by coordinately modulating the expression of all TFIIIB subunits
Authors: Zhong and Shuping , Johnson Deborah L.
Published: July 2009

RNA polymerase (pol) III-dependent transcription is subject to stringent regulation by tumor suppressors and oncogenic proteins and enhanced RNA pol III transcription is essential for cellular transformation and tumorigenesis. Since the c-Jun N-terminal kinases (JNKs) display both oncogenic and tumor suppressor properties, the roles of these proteins in regulating RNA pol III transcription were examined. In both mouse and human cells, loss or reduction in JNK1 expression represses RNA pol III transcription. In contrast, loss or reduction in JNK2 expression induces transcription. The JNKs coordinately regulate expression of all 3 TFIIIB subunits. While JNK1 positively regulates TBP expression, the RNA pol III-specific factors, Brf1 and Bdp1, JNK2 negatively regulates their expression. Brf1 is coregulated with TBP through the JNK target, Elk-1. Reducing Elk-1 expression decreases Brf1 expression. Decreasing JNK1 expression reduces Elk-1 occupancy at the Brf1 promoter, while decreasing JNK2 expression enhances recruitment of Elk-1 to the Brf1 promoter. In contrast, regulation of Bdp1 occurs through JNK-mediated alterations in TBP expression. Altered TBP expression mimics the effect of reduced JNK1 or JNK2 levels on Bdp1 expression. Decreasing JNK1 expression reduces the occupancy of TBP at the Bdp1 promoter, while decreasing JNK2 expression enhances recruitment of TBP to the Bdp1 promoter. Together, these results provide a molecular mechanism for regulating RNA pol III transcription through the coordinate control of TFIIIB subunit expression and elucidate opposing functions for the JNKs in regulating a large class of genes that dictate the biosynthetic capacity of cells.
Triplex structures in an RNA pseudoknot enhance mechanical stability and increase efficiency of –1 ribosomal frameshifting
Authors: Chen Gang , Chang Kung-Yao , Chou Ming-Yuan , Bustamante Carlos , Tinoco Ignacio
Published: July 2009

Many viruses use programmed –1 ribosomal frameshifting to express defined ratios of structural and enzymatic proteins. Pseudoknot structures in messenger RNAs stimulate frameshifting in upstream slippery sequences. The detailed molecular determinants of pseudoknot mechanical stability and frameshifting efficiency are not well understood. Here we use single-molecule unfolding studies by optical tweezers, and frameshifting assays to elucidate how mechanical stability of a pseudoknot and its frameshifting efficiency are regulated by tertiary stem-loop interactions. Mechanical unfolding of a model pseudoknot and mutants designed to dissect specific interactions reveals that mechanical stability depends strongly on triplex structures formed by stem-loop interactions. Combining single-molecule and mutational studies facilitates the identification of pseudoknot folding intermediates. Average unfolding forces of the pseudoknot and mutants ranging from 50 to 22 picoNewtons correlated with frameshifting efficiencies ranging from 53% to 0%. Formation of major-groove and minor-groove triplex structures enhances pseudoknot stem stability and torsional resistance, and may thereby stimulate frameshifting. Better understanding of the molecular determinants of frameshifting efficiency may facilitate the development of anti-virus therapeutics targeting frameshifting.
Postsynaptic Neuroligin1 regulates presynaptic maturation
Authors: Wittenmayer Nina , Körber Christoph , Liu Huisheng , Kremer Thomas , Varoqueaux Frederique , Chapman Edwin R. , Brose Nils , Kuner Thomas , Dresbach Thomas
Published: July 2009

Presynaptic nerve terminals pass through distinct stages of maturation after their initial assembly. Here we show that the postsynaptic cell adhesion molecule Neuroligin1 regulates key steps of presynaptic maturation. Presynaptic terminals from Neuroligin1-knockout mice remain structurally and functionally immature with respect to active zone stability and synaptic vesicle pool size, as analyzed in cultured hippocampal neurons. Conversely, overexpression of Neuroligin1 in immature neurons, that is within the first 5 days after plating, induced the formation of presynaptic boutons that had hallmarks of mature boutons. In particular, Neuroligin1 enhanced the size of the pool of recycling synaptic vesicles, the rate of synaptic vesicle exocytosis, the fraction of boutons responding to depolarization, as well as the responsiveness of the presynaptic release machinery to phorbol ester stimulation. Moreover, Neuroligin1 induced the formation of active zones that remained stable in the absence of F-actin, another hallmark of advanced maturation. Acquisition of F-actin independence of the active zone marker Bassoon during culture development or induced via overexpression of Neuroligin1 was activity-dependent. The extracellular domain of Neuroligin1 was sufficient to induce assembly of functional presynaptic terminals, while the intracellular domain was required for terminal maturation. These data show that induction of presynaptic terminal assembly and maturation involve mechanistically distinct actions of Neuroligins, and that Neuroligin1 is essential for presynaptic terminal maturation.
Intramitochondrial calcium regulation by the FHIT gene product sensitizes to apoptosis
Authors: Rimessi Alessandro , Marchi Saverio , Fotino Carmen , Romagnoli Anna , Huebner Kay , Croce Carlo M. , Pinton Paolo , Rizzuto Rosario
Published: July 2009

Despite the growing interest in the Fhit tumor suppressor protein, frequently deleted in human cancers, the mechanism of its powerful proapoptotic activity has remained elusive. We here demonstrate that Fhit sensitizes the low-affinity Ca
2+
transporters of mitochondria, enhancing Ca
2+
uptake into the organelle both in intact and in permabilized cells, and potentiating the effect of apoptotic agents. This effect can be attributed to the fraction of Fhit sorted to mitochondria, as a fully mitochondrial Fhit (a chimeric protein including a mitochondrial targeting sequence) retains the Ca
2+
signaling properties of Fhit and the proapoptotic activity of the native protein (whereas the effects on the cell cycle are lost). Thus, the partial sorting of Fhit to mitochondria allows to finely tune the sensitivity of the organelle to the highly pleiomorphic Ca
2+
signals, synergizing with apoptotic challenges. This concept, and the identification of the molecular machinery, may provide ways to act on apoptotic cell death and its derangement in cancer.
Dendrites of cerebellar granule cells correctly recognize their target axons for synaptogenesis in vitro
Authors: Ito Shoko , Takeichi Masatoshi
Published: July 2009

Neural circuits are generated by precisely ordered synaptic connections among neurons, and this process is thought to rely on the ability of neurons to recognize specific partners. However, it is also known that neurons promiscuously form synapses with nonspecific partners, in particular when cultured in vitro, causing controversies about neural recognition mechanisms. Here we reexamined whether neurons can or cannot select particular partners in vitro. In the cerebellum, granule cell (GC) dendrites form synaptic connections specifically with mossy fibers, but not with climbing fibers. We cocultured GC neurons with pontine or inferior olivary axons, the major sources for mossy and climbing fibers, respectively, as well as with hippocampal axons as a control. The GC neurons formed synapses with pontine axons predominantly at the distal ends of their dendrites, reproducing the characteristic morphology of their synapses observed in vivo, whereas they failed to do so when combined with other axons. In the latter case, synaptic proteins could accumulate between axons and dendrites, but these synapses were randomly distributed throughout the contact sites, and also their synaptic vesicle recycling was anomalous. These observations suggest that GC dendrites can select their authentic partners for synaptogenesis even in vitro, forming the synapses with a GC-specific nature only with them.
Homocysteine Level in Schizophrenia Patients
Authors: Ma Yin Ying , Shek Chi Chung , Wong Max C. K. , Yip Ka Chee , Ng Roger M. K. , Nguyen Desmond G. H. , Poon Ting Keung
Published: July 2009

Objective: Elevated serum levels of homocysteine have been shown to be associated with schizophrenia in some studies, but the evidence is still limited and mixed. The aim of the present study was therefore to evaluate the serum homocysteine level in Chinese in schizophrenia patients and assess its association with clinical phenotypes of the disease.

Method: A total of 250 inpatients and 250 healthy controls were identified at Kowloon Hospital and the Red Cross Blood Donation Centre, respectively. Each subject was evaluated with a structured diagnostic interview. Demographic data were collected and blood was analysed for homocysteine level. The Positive and Negative Syndrome Scale was used to grade clinical symptoms of schizophrenia. Confounding factors affecting homocysteine levels were controlled by strict exclusion criteria or statistical methods.

Results: Serum homocysteine level was elevated in Chinese schizophrenia patients. Both male (mean, 12.26 µmol L−1; control, 11.40 µmol L−1, p = 0.026) and female (mean, 9.61 µmol L−1; control, 8.33 µmol L−1, p < 0.001) patients had a higher serum homocysteine level than the healthy controls, and these differences persisted after controlling for age. There was no significant association between serum homocysteine level and duration of illness, clinical symptoms or age of onset of schizophrenia.

Conclusion: The serum homocysteine levels were elevated in both male and female Chinese schizophrenia patients. The levels were not apparently related to other clinical parameters.
Positive and Negative Symptoms in Schizophrenia: The NMDA Receptor Hypofunction Hypothesis, Neuregulin/ErbB4 and Synapse Regression
Authors: Bennett Maxwell
Published: July 2009

Carlsson has put forward the hypothesis that the positive and negative symptoms of schizophrenia are due to failure of mesolimbic and mesocortical projections consequent on hypofunction of the glutamate N-methyl-d-aspartate (NMDA) receptor. The hypothesis has been recently emphasized in this Journal that the loss of synaptic spines with NMDA receptors, which can be precipitated by stress, can explain the emergence of positive symptoms such as hallucinations and that this synapse regression involves molecules such as neuregulin and its receptor ErbB4 that have been implicated in schizophrenia. In this essay these two hypotheses are brought together in a single scheme in which emphasis is placed on the molecular pathways from neuregulin/ErbB4, to modulation of the NMDA receptors, subsequent changes in the synaptic spine's cytoskeletal apparatus and so regression of the spines. It is suggested that identification of the molecular constituents of this pathway will allow synthesis of suitable substances for removing the hypofunction of NMDA receptors and so the phenotypic consequences that flow from this hypofunction.
Is children's free school meal ‘eligibility’ a good proxy for family income?
Authors: Hobbs Graham , Vignoles Anna
Published: July 2009

Family income is an important factor associated with children's educational achievement. However, key areas of UK research (for example, on socially segregated schooling) and policy (for example, the allocation of funding to schools) rely on children's free school meal (FSM) ‘eligibility’ to proxy family income. This article examines the relationship between children's FSM ‘eligibility’ and equivalent net household income in a nationally representative survey of England (the Family Resources Survey). It finds that children ‘eligible’ for FSM are much more likely than other children to be in the lowest income households. However, only around one‐quarter to one‐half of them were in the lowest income households in 2004/5. This is principally because the receipt of means‐tested benefits (and tax credits) pushes children eligible for FSM up the household income distribution. The implications for key areas of research and policy are discussed.
Selectivity in Infant Social Referencing
Authors: Stenberg Gunilla
Published: July 2009

In laboratory studies of social referencing, infants as young as 12 months have been reported to prefer looking at the experimenter over the caregiver for clarifying information. From an expertise perspective, such behavior could be interpreted as if the infant seeks information from others and can discriminate between persons who have or do not have relevant information to provide in the laboratory. If this is the case, higher order cognitive capacities might be involved in infant selectivity in looking in social referencing situations. However, it has also been proposed that associative learning processes might account for infant preferences in such studies. To examine whether an expertise perspective or if more basic learning processes best explain infant selectivity in looking, 40 12‐month‐old infants were assigned to 1 of 2 comparable conditions. The experimenter versus the caregiver presented an ambiguous toy and delivered positive information about the toy. The infants preferred to look at the experimenter and they regulated their behavior more in accordance with information coming from the experimenter. Thus, an associative learning account cannot explain infant preferences in looking. The results are discussed in terms of an expertise perspective.
Better Processing of Consonantal Over Vocalic Information in Word Learning at 16 Months of Age
Authors: Havy Mélanie , Nazzi Thierry
Published: July 2009

Previous research using the name‐based categorization task has shown that 20‐month‐old infants can simultaneously learn 2 words that only differ by 1 consonantal feature but fail to do so when the words only differ by 1 vocalic feature. This asymmetry was taken as evidence for the proposal that consonants are more important than vowels at the lexical level. This study explores this consonant‐vowel asymmetry in 16‐month‐old infants, using an interactive word learning task. It shows that the pattern of the 16‐month‐olds is the same as that of the 20‐month‐olds. Infants succeeded with 1‐feature consonantal contrasts (either place or voicing) but were at chance level with 1‐feature vocalic contrasts (either place or height). These results thus contribute to a growing body of evidence establishing, from early infancy to adulthood, that consonants and vowels have different roles in lexical acquisition and processing.
Fault Tolerant Evaluation of Continuous Selection Queries over Sensor Data
Authors: Lazaridis Iosif , Han Qi , Mehrotra Sharad , Venkatasubramanian Nalini
Published: July 2009

We consider the problem of evaluating continuous selection queries over sensor-generated values in the presence of faults. Small sensors are fragile, have finite energy and memory, and communicate over a lossy medium; hence, tuples produced by them may not reach the querying node, resulting in an incomplete and ambiguous answer, as any of the non-reporting sensors may have produced a tuple which was lost. We develop a protocol, FAult Tolerant Evaluation of Continuous Selection Queries (FATE-CSQ), which guarantees a user-requested level of quality in an efficient manner. When many faults occur, this may not be achievable; in that case, we aim for the best possible answer, under the query's time constraints. FATE-CSQ is designed to be resilient to different kinds of failures. Our design decisions are based on an analytical model of different fault tolerance strategies based on feedback and retransmission. Additionally, we evaluate FATE-CSQ and competing protocols with realistic simulation parameters under a variety of conditions, demonstrating its good performance.
Dust studies in DIII-D and TEXTOR
Authors: Rudakov D.L. , Litnovsky A. , West W.P. , Yu J.H. , Boedo J.A. , Bray B.D. , Brezinsek S. , Brooks N.H. , Fenstermacher M.E. , Groth M. , Hollmann E.M. , Huber A. , Hyatt A.W. , Krasheninnikov S.I. , Lasnier C.J. , McLean A.G. , Moyer R.A. , Pigarov A.Yu. , Philipps V. , Pospieszczyk A. , Smirnov R.D. , Sharpe J.P. , Solomon W.M. , Watkins J.G. , Wong C.P.C.
Published: July 2009

Studies of naturally occurring and artificially introduced carbon dust are conducted in DIII-D and TEXTOR. In DIII-D, dust does not present operational concerns except immediately after entry vents. Submicrometre sized dust is routinely observed using Mie scattering from a Nd : Yag laser. The source is strongly correlated with the presence of type I edge localized modes (ELMs). Larger size (0.005–1 mm diameter) dust is observed by optical imaging, showing elevated dust levels after entry vents. Inverse dependence of the dust velocity on the inferred dust size is found from the imaging data. Heating of the dust particles by the neutral beam injection (NBI) and acceleration of dust particles by the plasma flows are observed. Energetic plasma disruptions produce significant amounts of dust; on the other hand, large flakes or debris falling into the plasma may induce a disruption. Migration of pre-characterized carbon dust is studied in DIII-D and TEXTOR by introducing micrometre-size particles into plasma discharges. In DIII-D, a sample holder filled with 30–40 mg of dust is inserted in the lower divertor and exposed, via sweeping of the strike points, to the diverted plasma flux of high-power ELMing H-mode discharges. After a brief dwell (∼0.1 s) of the outer strike point on the sample holder, part of the dust penetrates into the core plasma, raising the core carbon density by a factor of 2–3 and resulting in a twofold increase in the radiated power. In TEXTOR, instrumented dust holders with 1–45 mg of dust are exposed in the scrape-off-layer 0–2 cm radially outside of the last closed flux surface in discharges heated with 1.4 MW of NBI. Launched in this configuration, the dust perturbed the edge plasma, as evidenced by a moderate increase in the edge carbon content, but did not penetrate into the core plasma.
Comparative Analysis of Gelsemine andGelsemium sempervirensActivity on Neurosteroid Allopregnanolone Formation in the Spinal Cord and Limbic System
Authors: Venard Christine , Boujedaini Naoual , Mensah-Nyagan Ayikoe Guy , Patte-Mensah Christine
Published: July 2009

Centesimal dilutions (5, 9 and 15 cH) ofGelsemium sempervirensare claimed to be capable of exerting anxiolytic and analgesic effects. However, basic results supporting this assertion are rare, and the mechanism of action ofG. sempervirensis completely unknown. To clarify the point, we performed a comparative analysis of the effects of dilutions 5, 9 and 15 cH ofG. sempervirensor gelsemine (the major active principle ofG. sempervirens) on allopregnanolone (3α,5α‐THP) production in the rat limbic system (hippocampus and amygdala or H‐A) and spinal cord (SC). Indeed, H‐A and SC are two pivotal structures controlling, respectively, anxiety and pain that are also modulated by the neurosteroid 3α,5α‐THP. At the dilution 5 cH, bothG. sempervirensand gelsemine stimulated [3H]progesterone conversion into [3H]3α,5α‐THP by H‐A and SC slices, and the stimulatory effect was fully (100%) reproducible in all assays. The dilution 9 cH ofG. sempervirensor gelsemine also stimulated 3α,5α‐THP formation in H‐A and SC but the reproducibility rate decreased to 75%. At 15 cH ofG. sempervirensor gelsemine, no effect was observed on 3α,5α‐THP neosynthesis in H‐A and SC slices. The stimulatory action ofG. sempervirensand gelsemine (5 cH) on 3α,5α‐THP production was blocked by strychnine, the selective antagonist of glycine receptors. Altogether, these results, which constitute the first basic demonstration of cellular effects ofG. sempervirens, also offer interesting possibilities for the improvement ofG. sempervirens‐based therapeutic strategies.
Selective activation of PI3Kα/Akt/GSK‐3β signalling and cardiac compensatory hypertrophy during recovery from heart failure
Authors: Braz Julian C. , Gill Robert M. , Corbly Angela K. , Jones Bonita D. , Jin Najia , Vlahos Chris J. , Wu Qingyu , Shen Weiqun
Published: July 2009

Aims

Activation of phosphoinositide‐3 kinase (PI3K) is essential for cell growth, relating to adaptive and maladaptive cardiac hypertrophy. This longitudinal canine study was designed to investigate the role of PI3Kα and PI3Kγ in cardiac remodelling during congestive heart failure (CHF) and cardiac recovery (CR).

Methods and results

All dogs were surgically instrumented. Congestive heart failure was induced by cardiac pacing for 3–4 weeks and CR was allowed by terminating pacing for 5–6 weeks after induction of HF. Control dogs had sham surgery, but did not undergo pacing. Left ventricular (LV) contractile function was depressed in CHF and restored to 80–90% of the normal level in CR, with a 25% increase in LV weight. The expression of PI3Kγ was increased four‐fold in CHF, but returned to control levels in CR. In contrast, the expression of PI3Kα in CHF was not different from that in controls, but increased three‐fold in CR and was accompanied by increases in phosphorylation of Akt (five‐fold), GSK‐3β (five‐fold), β‐catenin (three‐fold), mTOR (two‐fold), and P70S6K (two‐fold).

Conclusion

Our results indicate that PI3K isoforms are regulated differently during the course of CHF/CR and that the selective activation of PI3Kα, through Akt, GSK‐3β, and mTOR signalling pathways, may be involved in the development of cardiac compensatory hypertrophy and functional restoration.
Endocytosis and Endosomal Regulation of theS-Receptor Kinase during the Self-Incompatibility Response inBrassica oleracea
Authors: Ivanov Rumen , Gaude Thierry
Published: July 2009

Intracellular trafficking of plant receptor kinases (PRKs) is a key step in regulation of cellular signaling. Our current knowledge in this field is based on systems that address signaling pathways affecting the whole cell. There are, however, signaling phenomena that add a further layer of complexity. In the Brassica self-incompatibility response, a single cell can adequately respond to two opposite stimuli: accepting cross-pollen and rejecting self-pollen simultaneously. To understand how PRK signaling can influence the coexistence of two seemingly exclusive states of the cell, we investigated the subcellular localization and internalization of the S-receptor kinase (SRK) involved in the self-incompatibility response of Brassica oleracea. Here, we describe the unusual subcellular distribution of SRK3, which localizes predominantly to intracellular compartments and to a much lesser extent to the plasma membrane. Using an anti-SRK antibody that fully substitutes for the natural ligand, we demonstrate that the interaction with the receptor takes place at the plasma membrane and is followed by SRK internalization in endosomes that are enriched in the SRK negative regulator Thioredoxin-h-like1.
The Histidine Kinases CYTOKININ-INDEPENDENT1 and ARABIDOPSIS HISTIDINE KINASE2 and 3 Regulate Vascular Tissue Development inArabidopsisShoots
Authors: Hejátko Jan , Ryu Hojin , Kim Gyung-Tae , Dobešová Romana , Choi Sunhwa , Choi Sang Mi , Souček Přemysl , Horák Jakub , Pekárová Blanka , Palme Klaus , Brzobohatý Břetislav , Hwang Ildoo
Published: July 2009

The development and activity of the procambium and cambium, which ensure vascular tissue formation, is critical for overall plant architecture and growth. However, little is known about the molecular factors affecting the activity of vascular meristems and vascular tissue formation. Here, we show that the His kinase CYTOKININ-INDEPENDENT1 (CKI1) and the cytokinin receptors ARABIOPSIS HISTIDINE KINASE2 (AHK2) and AHK3 are important regulators of vascular tissue development in Arabidopsis thaliana shoots. Genetic modifications of CKI1 activity in Arabidopsis cause dysfunction of the two-component signaling pathway and defects in procambial cell maintenance. CKI1 overexpression in protoplasts leads to cytokinin-independent activation of the two-component phosphorelay, and intracellular domains are responsible for the cytokinin-independent activity of CKI1. CKI1 expression is observed in vascular tissues of inflorescence stems, and CKI1 forms homodimers both in vitro and in planta. Loss-of-function ahk2 and ahk3 mutants and plants with reduced levels of endogenous cytokinins show defects in procambium proliferation and an absence of secondary growth. CKI1 overexpression partially rescues ahk2 ahk3 phenotypes in vascular tissue, while the negative mutation CKI1H405Q further accentuates mutant phenotypes. These results indicate that the cytokinin-independent activity of CKI1 and cytokinin-induced AHK2 and AHK3 are important for vascular bundle formation in Arabidopsis.
Downy Mildew Resistance in Arabidopsis by Mutation of HOMOSERINE KINASE
Authors: van Damme Mireille , Zeilmaker Tieme , Elberse Joyce , Andel Annemiek , de Sain-van der Velden Monique , van den Ackerveken Guido
Published: July 2009

Plant disease resistance is commonly triggered by early pathogen recognition and activation of immunity. An alternative form of resistance is mediated by recessive downy mildew resistant 1 (dmr1) alleles in Arabidopsis thaliana. Map-based cloning revealed that DMR1 encodes homoserine kinase (HSK). Six independent dmr1 mutants each carry a different amino acid substitution in the HSK protein. Amino acid analysis revealed that dmr1 mutants contain high levels of homoserine that is undetectable in wild-type plants. Surprisingly, the level of amino acids downstream in the aspartate (Asp) pathway was not reduced in dmr1 mutants. Exogenous homoserine does not directly affect pathogen growth but induces resistance when infiltrated in Arabidopsis. We provide evidence that homoserine accumulation in the chloroplast triggers a novel form of downy mildew resistance that is independent of known immune responses.
Resale price maintenance and collusion
Authors: Jullien Bruno , Rey Patrick
Published: July 2009

The article revisits the conventional wisdom according to which vertical restrictions on retail prices help upstream firms to collude. We analyze the scope for collusion with and without resale price maintenance (RPM) when retailers observe local shocks on demand or retail costs. In the absence of RPM, retail prices react to retailers' information, and deviations from collusive behavior are thus difficult to detect. By eliminating retail price flexibility, RPM facilitates the detection of deviations but reduces profits and thus increases the short‐run gains from a deviation. Overall, RPM can facilitate collusion and reduce total welfare when firms adopt it.
Relational delegation
Authors: Alonso Ricardo , Matouschek Niko
Published: July 2009

We analyze a cheap talk game with partial commitment by the principal. We first treat the principal's commitment power as exogenous and then endogenize it in an infinitely repeated game. We characterize optimal decision making for any commitment power and show when it takes the form of threshold delegation—in which case the agent can make any decision below a threshold—and centralization—in which case the agent has no discretion. For small biases, threshold delegation is optimal for any smooth distribution. Outsourcing can only be optimal if the principal's commitment power is sufficiently small.
Dispersal and survival of stocked cyprinids in a small English river: comparison with wild fishes using a multi‐method approach
Authors: Bolland J. D. , Cowx I. G. , Lucas M. C.
Published: July 2009

Mark–recapture and fixed‐station passive integrated transponder (PIT) telemetry were used to compare movements, distribution and survival of stocked juvenile chubLeuciscus cephalusand roachRutilus rutiluswith those of wild conspecifics. Daily activity of wild fish activity was affected by a combination of river flow and temperature, whereas stocked fishes were not influenced by environmental factors. PIT telemetry recorded exploratory movements of stockedL. cephalusimmediately after stocking, a substantial number of stocked fish moved both downstream and upstream during periods of elevated flow, and proportionally more stocked fish moved during the first 6 weeks after release than later on. Proportionally more stocked fish than wild fish moved through PIT antennae, stockedL. cephalusmoved greater distances than wildL. cephalusand were more widely distributed than wild fish. Minimum estimates of survival after 5 months were 50·5% for stockedR. rutilusand 28·0% for stockedL. cephalus. Ultimately, stocked cyprinids appeared to be able to cope with elevated flows and most remained in the river section local to the stocking location.