bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of concatamers to study GABAA receptor architecture and function: application to δ-subunit-containing receptors and possible pitfalls
Authors: Sigel Erwin , Kaur Kuldeep H. , Lüscher Benjamin P. , Baur Roland
Published: November 2009

Many membrane proteins, including the GABAA [GABA (γ-aminobutyric acid) type A] receptors, are oligomers often built from different subunits. As an example, the major adult isoform of the GABAA receptor is a pentamer built from three different subunits. Theoretically, co-expression of three subunits may result in many different receptor pentamers. Subunit concatenation allows us to pre-define the relative arrangement of the subunits. This method may thus be used to study receptor architecture, but also the nature of binding sites. Indeed, it made possible the discovery of a novel benzodiazepine site. We use here subunit concatenation to study δ-subunit-containing GABAA receptors. We provide evidence for the formation of different functional subunit arrangements in recombinant α1β3δ and α6β3δ receptors. As with all valuable techniques, subunit concatenation has also some pitfalls. Most of these can be avoided by carefully titrating and minimizing the length of the linker sequences joining the two linked subunits and avoiding inclusion of the signal sequence of all but the N-terminal subunit of a multi-subunit construct. Maybe the most common error found in the literature is that low expression can be overcome by simply overloading the expression system with genetic information. As some concatenated constructs result by themselves in a low level of expression, this erroneous assembly leading to receptor function may be promoted by overloading the expression system and leads to wrong conclusions.
Locating GABA in GABA receptor binding sites
Authors: Lummis Sarah C.R.
Published: November 2009

The Cys-loop family of ligand-gated ion channels contains both vertebrate and invertebrate members that are activated by GABA (γ-aminobutyric acid). Many of the residues that are critical for ligand binding have been identified in vertebrate GABAA and GABAC receptors, and specific interactions between GABA and some of these residues have been determined. In the present paper, I show how a cation–π interaction for one of the binding site residues has allowed the production of models of GABA docked into the binding site, and these orientations are supported by mutagenesis and functional data. Surprisingly, however, the residue that forms the cation–π interaction is not conserved, suggesting that GABA occupies subtly different locations even in such closely related receptors.
Single-channel properties ofN-methyl-D-aspartate receptors containing chimaeric GluN2A/GluN2D subunits
Authors: O'Leary Timothy , Wyllie David J.A.
Published: November 2009

Subtypes of NMDARs (N-methyl-D-aspartate receptors) display differences in their pharmacological and biophysical properties. The differences are, to a large extent, determined by the identities of the GluN2 (glutamate-binding) NMDAR subunits that are co-expressed with GluN1 (glycine-binding) subunits, which form the final tetrameric NMDAR assembly. Of the four GluN2 subunits that exist (termed A–D), NMDARs composed of GluN1/GluN2A and GluN1/GluN2D subunits display the greatest differences in their sensitivities to a variety of agonists, antagonists and channel blockers as well as showing marked differences in their single-channel conductances and deactivation kinetics. Here, we describe a series of experiments where we have generated and studied two chimaeric GluN2A/GluN2D subunits. The first chimaera, referred to as GluN2A(2D-M1M2M3), replaces the membrane-associated regions M1, M2 and M3 of the GluN2A subunit with the corresponding regions found in the GluN2D subunit. The second chimaera, GluN2A(2D-S1M1M2M3S2), replaces the same three membrane-associated regions of the GluN2A subunit plus the LBD (ligand-binding domain) with the corresponding regions of the GluN2D subunit. Our results show that the identity of the GluN2 LBD not only controls glutamate potency, but also influences the potency of the NMDAR co-agonist glycine, whereas the single-channel conductance and the duration of single activations of ion channels can be predicted by the identities of the M1–M3 regions and the LBD.
The role of GABAAR phosphorylation in the construction of inhibitory synapses and the efficacy of neuronal inhibition
Authors: Vithlani Mansi , Moss Stephen J.
Published: November 2009

GABAARs [GABA (γ-aminobutyric acid) type-A receptors] are heteropentameric chloride-selective ligand-gated ion channels that mediate fast inhibition in the brain and are key therapeutic targets for benzodiazepines, barbiturates, neurosteroids and general anaesthetics. In the brain, most of the benzodiazepine-sensitive synaptic receptor subtypes are assembled from α1-3, β1-3 and γ2 subunits. Although it is evident that the pharmacological manipulation of GABAAR function can have profound effects on behaviour, the endogenous mechanisms that neurons use to promote sustained changes in the efficacy of neuronal inhibition remain to be documented. It is increasingly clear that GABAARs undergo significant rates of constitutive endocytosis and regulate recycling processes that can determine the efficacy of synaptic inhibition. Their endocytosis is regulated via the direct binding of specific endocytosis motifs within the intracellular domains of receptor β1-3and γ2 subunits to the clathrin adaptor protein AP2 (adaptor protein 2). These binding motifs contain major sites of both serine and tyrosine phosphorylation within GABAARs. Their phosphorylation can have dramatic effects on binding to AP2. In the present review, we evaluate the role that these phospho-dependent interactions play in regulating the construction of inhibitory synapses, efficacy of neuronal inhibition and neuronal structure.
Neuronal calcium sensors and synaptic plasticity
Authors: Amici Mascia , Doherty Andrew , Jo Jihoon , Jane David , Cho Kwangwook , Collingridge Graham , Dargan Sheila
Published: November 2009

Calcium entry plays a major role in the induction of several forms of synaptic plasticity in different areas of the central nervous system. The spatiotemporal aspects of these calcium signals can determine the type of synaptic plasticity induced, e.g. LTP (long-term potentiation) or LTD (long-term depression). A vast amount of research has been conducted to identify the molecular and cellular signalling pathways underlying LTP and LTD, but many components remain to be identified. Calcium sensor proteins are thought to play an essential role in regulating the initial part of synaptic plasticity signalling pathways. However, there is still a significant gap in knowledge, and it is only recently that evidence for the importance of members of the NCS (neuronal calcium sensor) protein family has started to emerge. The present minireview aims to bring together evidence supporting a role for NCS proteins in plasticity, focusing on emerging roles of NCS-1 and hippocalcin.
Activity-dependent gene transcription as a long-term influence on receptor signalling
Authors: McDade Donna M. , Conway Ann-Marie , James Allan B. , Morris Brian J.
Published: November 2009

The regulation of synaptic glutamate receptor and GABAAR (γ-aminobutyric acid subtype A receptor) levels is a key component of synaptic plasticity. Most forms of neuronal plasticity are associated with the induction of the transcription factor zif268 (egr1). Hence, it is predicted that zif268 may regulate transcription of genes associated with glutamate receptors and/or GABAARs. It turns out that receptor regulation by zif268 tends to be indirect. Induction of zif268 in neurons leads to altered expression of proteasome subunit and proteasome-regulatory genes, thereby changing the capacity of the neuron to degrade synaptic proteins, including receptors and receptor subunits. In addition, zif268 alters the transcription of genes associated with GABAAR expression and trafficking, such as ubiquilin and gephyrin. This indirect regulation of receptor turnover is likely to contribute to the delayed, but long-lasting, phases of synaptic plasticity and also to the synaptic dysfunction associated with diseases such as schizophrenia and Alzheimer's disease, where zif268 expression is reduced.
Positive allosteric activation of GABAA receptors bi-directionally modulates hippocampal glutamate plasticity and behaviour
Authors: Shen Guofu , Mohamed Mahmoud S. , Das Paromita , Tietz Elizabeth I.
Published: November 2009

Long-term BZ (benzodiazepine) anxiolytic therapy increases the risk of physical dependence manifested as withdrawal anxiety. BZ-induced potentiation of GABAAR (γ-aminobutyric acid type-A receptor) function by 1-week oral administration of FZP (flurazepam) bi-directionally modulates excitatory glutamatergic synaptic transmission in hippocampal CA1 neurons during drug withdrawal. Previous electrophysiological studies on acutely isolated and intact CA1 neurons, as well as immunofluorescence and post-embedding immunogold electron microscopy studies, suggest increased synaptic insertion of GluR (glutamate receptor) 2-lacking AMPARs (α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors) in 2-day FZP-withdrawn rats. Preliminary studies indicated a similar increase in GluR1, then phospho-Ser831-GluR1, as well as CaMKIIα (Ca2+/calmodulin-dependent protein kinase IIα), but not phospho-Thr286-CaMKII levels at the same time point. In our studies, whole-cell recordings in hippocampal slices revealed that AMPAR mEPSC [miniature EPSC (excitatory postsynaptic current)] amplitude was increased in 1-day FZP-withdrawn rats followed by an increase in estimated single-channel conductance in 2-day-FZP-withdrawn rats. Enhanced conductance was no longer observed in slices pre-incubated for 2 h in the CaMKII inhibitor KN-93, but not the inactive analogue KN-92. To evaluate whether CaMKII-mediated AMPA potentiation could occlude LTP (long-term potentiation), LTP was induced by TBS (theta burst stimulation) and recorded using whole-cell and extracellular techniques. LTP was induced in both groups, but only maintained for <15 min in 2-day FZP-withdrawn rats. LTP was fully restored after 7-day withdrawal. Despite the lack of LTP maintenance, impairment of object recognition, place and context was not observed in 2-day-FZP-withdrawn rats. Since L-VGCC (L-type voltage-gated calcium channel) current density was doubled on drug withdrawal and up to 2 days, Ca2+ entry through L-VGCCs and perhaps subsequently through Ca2+-permeable AMPARs are proposed to be responsible for enhanced CaMKIIα levels and AMPAR potentiation. Mechanisms associated with several different models of activity-dependent plasticity may underlie BZ physical dependence.
RNA editing and its impact on GABAA receptor function
Authors: Daniel Chammiran , Öhman Marie
Published: November 2009

A-to-I (adenosine-to-inosine) RNA editing catalysed by the ADARs (adenosine deaminases that act on RNA) is a post-transcriptional event that contributes to protein diversity in metazoans. In mammalian neuronal ion channels, editing alters functionally important amino acids and creates receptor subtypes important for the development of the nervous system. The excitatory AMPA (α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) and kainate glutamate receptors, as well as the inhibitory GABAA [GABA (γ-aminobutyric acid) type A] receptor, are subject to A-to-I RNA editing. Editing affects several features of the receptors, including kinetics, subunit assembly and cell-surface expression. Here, we discuss the regulation of editing during brain maturation and the impact of RNA editing on the expression of different receptor subtypes.
GABRB2 in schizophrenia and bipolar disorder: disease association, gene expression and clinical correlations
Authors: Chen Jianhuan , Tsang Shui-Ying , Zhao Cun-You , Pun Frank W. , Yu Zhiliang , Mei Lingling , Lo Wing-Sze , Fang Shisong , Liu Hua , Stöber Gerald , Xue Hong
Published: November 2009

The SCZ (schizophrenia)-associated GABAA receptor (γ-aminobutyric acid type A receptor) β2 subunit gene GABRB2 was recently associated with BPD (bipolar disorder). Although weaker than its association with SCZ, significant association of GABRB2 with BPD was found in both German and Chinese, especially for the haplotypes rs1816071–rs187269 and rs1816072–rs187269 for which the M–M variants showed higher frequency in disease than the control. Significant genotype-dependent reduction in GABRB2 expression was shown for BPD, but to a lesser extent than that for SCZ. Temporal effects on GABRB2 expression were observed. Moreover, for the homozygous major genotypes of rs1816071, rs1816072 and rs187269, expression increased with time in CON but decreased in SCZ and BPD. The genotypes of these three SNPs (single nucleotide polymorphisms) were further correlated with antipsychotics dosage in SCZ cohorts. The findings highlight the importance of GABRB2 in neuropsychiatric disease aetiology, with respect to haplotype association, as well as reduction of and temporal effects on gene expression in both SCZ and BPD, but to a lesser extent in the latter, supporting the suggestion that functional psychosis can be conceptualized as a continuous spectrum of clinical phenotypes rather than as distinct categories.
Design, construction, and calibration of a three-axis, high-frequency magnetic probe (B-dot probe) as a diagnostic for exploding plasmas
Authors: Everson E. T. , Pribyl P. , Constantin C. G. , Zylstra A. , Schaeffer D. , Kugland N. L. , Niemann C.
Published: November 2009

A three-axis, 2.5 mm overall diameter differential magnetic probe (also known as B-dot probe) is discussed in detail from its design and construction to its calibration and use as diagnostic of fast transient effects in exploding plasmas. A design and construction method is presented as a means to reduce stray pickup, eliminate electrostatic pickup, reduce physical size, and increase magnetic signals while maintaining a high bandwidth. The probe’s frequency response is measured in detail from 10 kHz to 50 MHz using the presented calibration method and compared to theory. The effect of the probe’s self-induction as a first order correction in frequency, O(ω), on experimental signals and magnetic field calculations is discussed. The probe’s viability as a diagnostic is demonstrated by measuring the magnetic field compression and diamagnetism of a sub-Alfvénic (∼500 km/s,MA∼0.36) flow created from the explosion of a high-density energetic laser plasma through a cooler, low-density, magnetized ambient plasma.
Preparation of monodisperse emulsions by hydrodynamic size fractionation
Authors: Mazutis Linas , Griffiths Andrew D.
Published: November 2009

We describe a microfluidic system allowing fast and efficient size-dependent separation of droplets using hydrodynamics. This system allows efficient fractionation of droplets with a difference in volume as small as 2.33-fold (corresponding to a 1.33-fold difference in diameter of spherical droplets) at >4.5 kHz frequencies. To demonstrate the utility of the system we combined the size-fractionation module with a passive droplet fusion module to create an integrated microfluidic platform allowing the preparation of highly monodisperse emulsions composed of >99% pairwise fused droplets. This type of microfluidic platform should be useful for many droplet-based lab-on-a-chip applications.
Dielectric response of tantalum oxide subject to induced ion bombardment during oblique sputter deposition
Authors: Barron S. C. , Noginov M. M. , Werder D. , Schneemeyer L. F. , van Dover R. B.
Published: November 2009

We describe the deposition of insulating tantalum oxide thin films under conditions of controlled ion bombardment, which can be achieved using reactive sputtering on 90° off-axis substrates with an applied substrate bias. Capacitive measurements of Ta2O5 deposited on unbiased off-axis substrates indicate low frequency dielectric constants as high as εr∼300. Low frequency loss tangents are high, tan δ>0.5, and have a pronounced frequency dependence. Deposition of the film off-axis with sufficient applied rf bias to the substrate (negative bias >−70 V) recovers the on-axis properties typical of Ta2O5, e.g., εr∼22 and tan δ∼0.02. The recovery of normal dielectric behavior is attributed to the ion bombardment of the growing film under substrate bias, similar to on-axis depositions but absent from depositions on off-axis substrates with no applied substrate bias. We suggest that insufficiently bombarded films develop a Maxwell–Wagner type polarization along columnar voids. The void structure and the associated dielectric response vary with distance from the sputtering source due to variations in ion density and angle from the sputtering source. A similar dielectric response is observed in depositions on on-axis substrates as a function of angle from the central sputter gun axis. Our results suggest that ion bombardment is necessary for good quality sputtered dielectric films but that a controlled Ar+ flux is essentially equivalent to the uncontrolled O2−/O2− flux of on-axis reactive sputtering.
Schottky’s conjecture on multiplication of field enhancement factors
Authors: Miller Ryan , Lau Y. Y. , Booske John H.
Published: November 2009

Of great interest to high power microwave, millimeter wave to terahertz sources, x-ray tubes, electrons guns, etc., is the electric field enhancement obtained from sharp emitting structures fabricated by various microfabrication methods. In this paper, we use conformal mapping to investigate the field enhancement of several rectilinear geometries, including a single rectangular ridge, a trapezoidal ridge, and their superposition, i.e., one ridge on top of another. We show that the composite field enhancement factor of the double ridge with a microprotrusion on top of a macroprotrusion is dominated by the product of the individual protrusions’ field enhancement factors over a very wide range of geometric aspect ratios, as conjectured by Schottky. Simplified scaling laws are proposed. Significant deviation from Schottky’s product rule occurs almost exclusively when the half-width of the macroprotrusion is less than the height of the microprotrusion. Accurate expressions of the divergent electric field near the sharp edges are derived.
Nonvolatile memory with Co–SiO2 core-shell nanocrystals as charge storage nodes in floating gate
Authors: Liu Hai , Ferrer Domingo A. , Ferdousi Fahmida , Banerjee Sanjay K.
Published: November 2009

In this letter, we reported nanocrystal floating gate memory with Co–SiO2 core-shell nanocrystal charge storage nodes. By using a water-in-oil microemulsion scheme, Co–SiO2 core-shell nanocrystals were synthesized and closely packed to achieve high density matrix in the floating gate without aggregation. The insulator shell also can help to increase the thermal stability of the nanocrystal metal core during the fabrication process to improve memory performance.

At the request of the authors, this article is being retracted effective 1 July 2010.
Coupled optoelectronic simulation of organic bulk-heterojunction solar cells: Parameter extraction and sensitivity analysis
Authors: Häusermann R. , Knapp E. , Moos M. , Reinke N. A. , Flatz T. , Ruhstaller B.
Published: November 2009

A comprehensive optoelectronic device model for organic bulk-heterojunction solar cells is presented. First the optical incoupling into a multilayer stack is calculated. From the photon absorption profile a charge transfer exciton profile is derived. In this study we consider the Onsager–Braun mechanism to calculate the dissociation of the CT excitons into free charge carriers. These free charge carriers then migrate toward the electrodes under the influence of drift and diffusion. A general problem arising in computer simulations is the number of material and device parameters, which have to be determined by dedicated experiments and simulation-based parameter extraction. In this study we analyze measurements of the short-circuit current dependence on the active layer thickness and current-voltage curves in poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester based solar cells. We have identified a set of parameter values including dissociation parameters that describe the experimental data. The overall agreement of our model with experiment is good, however, a discrepancy in the thickness dependence of the current-voltage curve questions the influence of the electric field in the dissociation process. In addition transient simulations are analyzed which show that a measurement of the turn-off photocurrent can be useful for estimating charge carrier mobilities.
Strength of lithium fluoride under shockless compression to 114 GPa
Authors: Ao T. , Knudson M. D. , Asay J. R. , Davis J.-P.
Published: November 2009

A magnetic loading technique was used to ramp load single-crystal [100] lithium fluoride specimens to peak stresses of 5–114 GPa. Wave analysis of in situ particle velocity profiles was used to estimate the compressive strength of LiF at peak stress. It was found that the strength increased with peak stress and showed two distinct regions of hardening; the first is believed to be governed by strain hardening and the second by pressure hardening. The quasielastic strain obtained from the initial part of the unloading was shown to saturate at about 1.3% for peak stresses greater than approximately 30 GPa. Over the studied pressure range, the measured strength of LiF varied from its initial value of 0.08 to about 1.1 GPa at the highest compressed state of 114 GPa. Comparison of the measured strength to results from two strength models showed good agreement. It was demonstrated that the strength of LiF introduces systematic error of about 10% when used as an interferometer window for measurements of material strength in isentropic compression experiments.
Energy transfer rates and population inversion of I411/2 excited state of Er3+ investigated by means of numerical solutions of the rate equations system in Er:LiYF4 crystal
Authors: Gomes Laércio , Librantz André Felipe Henriques , Jagosich Fabio Henrique , Alves Wonder Alexandre Luz , Ranieri Izilda Marcia , Baldochi Sonia Lícia
Published: November 2009

In this work, we present the spectroscopic properties of LiYF4 (YLF) single crystals activated by high doping of erbium ions. The most important processes that lead to the up-conversion erbium emissions in the infrared region were identified. A time-resolved luminescence spectroscopy technique was employed to measure the luminescence decays and to determine the most important mechanisms involved in the up-conversion processes that populate the S43/2 excited state. A study of the energy transfer up-conversion (ETU) processes in Er:YLF showed that an ETU rate can be obtained from the I411/2 (ETU1) and S43/2 (ETU2) up-conversion luminescence transient analysis, i.e., from best fittings of the acceptor state luminescence. An analysis of the ETU rate dependence on the wavelength and intensity of pulsed laser excitations allowed us to obtain the ETU rate constants from the lower (I413/2) and upper (I411/2) laser levels to use them in the numerical solutions of the rate equation system for the Er-doped YLF crystal (15 mol %) pumped [continuous wave (cw)] at 972 nm. As a result, we found that the I411/2→I413/2 laser emission (or small signal gain) shows a temporal profile intensity, which passes through a maximum at around 820 μs before getting the steady state regime. It was demonstrated that the ETU2 process (from the I411/2 level) is the mechanism responsible for the laser gain profile observed. The results of the numerical simulation of the rate equation system showed that the highest population inversion density of 8.5×1019 cm−3 for Er3+ (or a small signal gain of 2.54 cm−1) is obtained for 15 mol % of erbium in the YLF crystal when it is pumped by a cw laser at 972 nm using a pump intensity of 5.4 kW cm−2 (or a pumping rate of 300 s−1) for the laser transition near 2.75 μm. It was seen also that a pumping rate of 300 s−1 maximizes the population inversion in the cw pump regime. A simulation using a square wave pump with a pumping time of 1 ms showed a population inversion increasing by a factor of 1.31 with respect to the population inversion obtained in the continuous pump simulation.
Ge–Sb–Te thin films deposited by pulsed laser: An ellipsometry and Raman scattering spectroscopy study
Authors: Němec P. , Moreac A. , Nazabal V. , Pavlišta M. , Přikryl J. , Frumar M.
Published: November 2009

Pulsed laser (532 nm) deposited Ge2Sb2Te5 thin films were investigated by means of spectroscopic ellipsometry and Raman scattering spectroscopy. Tauc–Lorentz and Cody–Lorentz models were employed for the evaluation of optical functions of thin films in as-deposited (amorphous) and crystalline (cubic) phases. The models’ parameters (Lorentz oscillator amplitude, resonance energy, oscillator width, optical band gap, and Urbach energy) calculated for amorphous and crystalline states are discussed. The vibrational modes observed in Raman spectra of amorphous layers are attributed to GeTe4−nGen (n=1, 2, eventually 0) tetrahedra connected by corners (partly by edges) and SbTe3 units. The Raman spectra of crystalline thin films suggest that the local bonding arrangement around Ge atoms changes; GeTe component is thus mainly responsible for the phase transition in Ge2Sb2Te5 alloys.
Interfering pathways in benzene: An analytical treatment
Authors: Hansen Thorsten , Solomon Gemma C. , Andrews David Q. , Ratner Mark A.
Published: November 2009

The mechanism for off-resonant electron transport through small organic molecules in metallic junctions is predominantly coherent tunneling. Thus, new device functionalities based on quantum interference could be developed in the field of molecular electronics. We invoke a partitioning technique to give an analytical treatment of quantum interference in a benzene ring. We interpret the antiresonances in the transmission as either multipath zeroes resulting from interfering spatial pathways or resonance zeroes analogous to zeroes induced by sidechains.
Unimolecular decomposition of tetrazine-N-oxide based high nitrogen content energetic materials from excited electronic states
Authors: Bhattacharya A. , Guo Y. Q. , Bernstein E. R.
Published: November 2009

Unimolecular excited electronic state decomposition of novel high nitrogen content energetic molecules, such as 3,3′-azobis(6-amino-1,2,4,5-tetrazine)-mixed N-oxides (DAATO3.5), 3-amino-6-chloro-1,2,4,5-tetrazine-2,4-dioxide (ACTO), and 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxde (DATO), is investigated. Although these molecules are based on N-oxides of a tetrazine aromatic heterocyclic ring, their decomposition behavior distinctly differs from that of bare tetrazine, in which N2 and HCN are produced as decomposition products through a concerted dissociation mechanism. NO is observed to be an initial decomposition product from all tetrazine-N-oxide based molecules from their low lying excited electronic states. The NO product from DAATO3.5 and ACTO is rotationally cold (20 K) and vibrationally hot (1200 K), while the NO product from DATO is rotationally hot (50 K) and vibrationally cold [only the (0–0) vibronic transition of NO is observed]. DAATO3.5 and ACTO primarily differ from DATO with regard to molecular structure, by the relative position of oxygen atom attachment to the tetrazine ring. Therefore, the relative position of oxygen in tetrazine-N-oxides is proposed to play an important role in their energetic behavior. N2O is ruled out as an intermediate precursor of the NO product observed from all three molecules. Theoretical calculations at CASMP2/CASSCF level of theory predict a ring contraction mechanism for generation of the initial NO product from these molecules. The ring contraction occurs through an (S1/S0)CI conical intersection.
Microwave conductance spectra of single-walled carbon nanotube arrays
Authors: Highstrete Clark , Lee Mark , Talin A. Alec , Vance Andrew L.
Published: November 2009

Complex conductance spectra of single-walled carbon nanotube (SWCNT) arrays have been measured from 0.1 to 50 GHz at temperatures between 4 and 293 K. Using purely capacitive contacts to separate contact effects from the NTs’ response, the intrinsic SWCNT array conductance increased with frequency as fs with exponent s=0.67±0.08 regardless of array size and temperature. The spectra are consistent with the behavior found in many strongly inhomogeneous electronic systems. The origin of disorder in these arrays is likely topological rather than energetic.
Fabrication of a transparent and flexible thin film transistor based on single-walled carbon nanotubes using the direct transfer method
Authors: Tseng S. H. , Tai N. H.
Published: November 2009

The fabrication of transparent and flexible thin film transistors (TFTs), using single-walled carbon nanotube (SWCNT) networks as bottom gates and conducting channels and polymethylmethacrylate (PMMA) as an insulating layer, by the direct transfer method is demonstrated. The fabricated SWCNT-TFTs exhibited a mobility of 23.4 cm2/V s and an ON/OFF current ratio of ∼103. A minor decrease of ∼7% on the performance of the SWCNT-TFTs after bending to a radius of curvature of ∼6 mm was observed. The differences in performance of the devices fabricated with SWCNTs on SiO2/Si and those prepared by transferring SWCNTs onto a polycarbonate substrate are also discussed.
Efficient calculation of the polarization induced by N coherent laser pulses
Authors: Gelin Maxim F. , Egorova Dassia , Domcke Wolfgang
Published: November 2009

We have developed a novel method, the equation-of-motion phase-matching approach (EOM-PMA), for the calculation of the response of a quantum system to N coherent laser fields. The N-pulse EOM-PMA is limited to weak fields (its domain of validity is equivalent to the traditional nonlinear response functions approach), but allows for arbitrary pulse durations and automatically accounts for pulse-overlap effects. The N-pulse EOM-PMA allows the evaluation of the time evolution of the N-pulse-induced polarization in any phase-matching direction by performing 2N−1 independent propagations of certain auxiliary density matrices. The N-pulse EOM-PMA can straightforwardly be incorporated into codes which provide the time evolution of the density matrix of material systems of interest and can efficiently be implemented on parallel computers.
Shape-dependent nonlinear absorption and relaxation in CuInS2 nanocrystals
Authors: Venkatram N. , Batabyal Sudip K. , Tian Lu , Vittal Jagadese J. , Ji Wei
Published: November 2009

We report the observation of nonlinear-optical response and relaxation in copper indium sulfide (CuInS2) crystalline nanoparticles and nanorods with femtosecond Z-scans and transient absorption measurements. Dependent on the size and shape, two-photon absorption and saturation in the one-photon absorption manifest themselves in these measurements as laser excitation wavelength of 780 nm is in the proximity of the lowest-lying excitonic energy, particularly for the nanorods. The transient absorption measurements by both one-photon and two-photon excitation reveal that electron-hole recombination is faster in smaller nanoparticles, or in nanorods with smaller aspect ratio. However, the decay to trapping states is independent of the size and aspect-ratio.
Action and Puzzle Video Games Prime Different Speed/Accuracy Tradeoffs
Authors: Nelson Rolf A , Strachan Ian
Published: November 2009

To understand the way in which video-game play affects subsequent perception and cognitive strategy, two experiments were performed in which participants played either a fast-action game or a puzzle-solving game. Before and after video-game play, participants performed a task in which both speed and accuracy were emphasized. In experiment 1 participants engaged in a location task in which they clicked a mouse on the spot where a target had appeared, and in experiment 2 they were asked to judge which of four shapes was most similar to a target shape. In both experiments, participants were much faster but less accurate after playing the action game, while they were slower but more accurate after playing the puzzle game. Results are discussed in terms of a taxonomy of video games by their cognitive and perceptual demands.
Personality in Perspective: Judgmental Consistency across Orientations of the Face
Authors: Rule Nicholas O , Ambady Nalini , Adams Reginald B
Published: November 2009

Though the psychological literature is replete with information about the perception of faces presented at a full-frontal view, we know very little about how faces are perceived–and impressions formed–when viewed from other angles. We tested impressions of faces at full-frontal, three-quarter, and profile views. Judgments of personality (aggressiveness, competence, dominance, likeability, and trustworthiness) and physiognomy (attractiveness and facial maturity) were significantly correlated across full-frontal, three-quarter, and profile views of male faces. When under time pressure, with only a 50 ms exposure to each face, the correlations for profile with full-frontal and three-quarter view judgments of personality (but not physiognomy) dropped considerably. However, judgments of the full-frontal and three-quarter faces were significantly correlated across the self-paced and 50 ms viewing durations. These findings therefore show that perceptions of full faces lead to relatively similar interferences across both viewing angle and time.
The Lee Harvey Oswald Backyard Photos: Real or Fake?
Authors: Farid Hany
Published: November 2009

Ever since the assassination of US President Kennedy, numerous theories have circulated purporting that Lee Harvey Oswald, the accused assassin, acted as part of a larger criminal conspiracy. It has been suggested, for example, that incriminating photographs of Oswald were manipulated, and hence evidence of a broader plot. Specifically, it has been argued that the lighting and shadows in these photos are physically impossible. Because the visual system is often unable to reliably judge 3-D geometry and lighting, a detailed 3-D analysis of the Oswald photos to determine if claims of tampering are warranted.
Transcription factors mediate long-range enhancer–promoter interactions
Authors: Nolis Ilias K. , McKay Daniel J. , Mantouvalou Eva , Lomvardas Stavros , Merika Menie , Thanos Dimitris
Published: November 2009

We examined how remote enhancers establish physical communication with target promoters to activate gene transcription in response to environmental signals. Although the natural IFN-β enhancer is located immediately upstream of the core promoter, it also can function as a classical enhancer element conferring virus infection-dependent activation of heterologous promoters, even when it is placed several kilobases away from these promoters. We demonstrated that the remote IFN-β enhancer “loops out” the intervening DNA to reach the target promoter. These chromatin loops depend on sequence-specific transcription factors bound to the enhancer and the promoter and thus can explain the specificity observed in enhancer–promoter interactions, especially in complex genetic loci. Transcription factor binding sites scattered between an enhancer and a promoter can work as decoys trapping the enhancer in nonproductive loops, thus resembling insulator elements. Finally, replacement of the transcription factor binding sites involved in DNA looping with those of a heterologous prokaryotic protein, the λ repressor, which is capable of loop formation, rescues enhancer function from a distance by re-establishing enhancer–promoter loop formation.
Cerebral and spinal modulation of pain by emotions
Authors: Roy Mathieu , Piché Mathieu , Chen Jen-I. , Peretz Isabelle , Rainville Pierre
Published: November 2009

Emotions have powerful effects on pain perception. However, the brain mechanisms underlying these effects remain largely unknown. In this study, we combined functional cerebral imaging with psychophysiological methods to explore the neural mechanisms involved in the emotional modulation of spinal nociceptive responses (RIII-reflex) and pain perception in healthy participants. Emotions induced by pleasant or unpleasant pictures modulated the responses to painful electrical stimulations in the right insula, paracentral lobule, parahippocampal gyrus, thalamus, and amygdala. Right insula activation covaried with the modulation of pain perception, consistent with a key role of this structure in the integration of pain signals with the ongoing emotion. In contrast, activity in the thalamus, amygdala, and several prefrontal areas was associated with the modulation of spinal reflex responses. Last, connectivity analyses suggested an involvement of prefrontal, parahippocampal, and brainstem structures in the cerebral and cerebrospinal modulation of pain by emotions. This multiplicity of mechanisms underlying the emotional modulation of pain is reflective of the strong interrelations between pain and emotions, and emphasizes the powerful effects that emotions can have on pain.
Identification of a region of the DNMT1 methyltransferase that regulates the maintenance of genomic imprints
Authors: Borowczyk Ewa , Mohan K. Naga , D'Aiuto Leonardo , Cirio M. Cecilia , Chaillet J. Richard
Published: November 2009

Reprogramming of DNA methylation patterns during mammalian preimplantation development involves the concurrent maintenance of methylation on differentially methylated domains (DMDs) of imprinted genes and a marked reduction of global (non-DMD) genomic methylation. In the developing mammalian embryo, one allele of a DMD is unmethylated, and the opposite parental allele is methylated, having inherited this methylation from the parental gamete. The maintenance of DMDs is important for monoallelic imprinted gene expression and normal development of the embryo. Because the DNMT1 cytosine methyltransferase governs maintenance methylation in mammals, rearrangements of non-DMD, but not DMD methylation in preimplantation embryos suggest that the preimplantation DNMT1-dependent maintenance mechanism specifically targets DMD sequences. We explored this possibility using an engineered mouse ES cell line to screen for mutant DNMT1 proteins that protect against the loss of DMD and/or global (non-DMD) methylation in the absence of the wild-type endogenous DNMT1 methyltransferase. We identified DNMT1 mutants that were defective in maintenance of either DMD and/or non-DMD methylation. Among these, one mutant maintained non-DMD methylation but not imprinted DMD methylation and another mutant maintained just DMD methylation. The mutated amino acids of these mutants reside in a mammal-specific, disordered region near the amino terminus of DNMT1. These findings suggest that DNMT1 participates in epigenetic reprogramming through its ability to distinguish different categories of methylated sequences.
The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography
Authors: Bunce M. , Worthy T. H. , Phillips M. J. , Holdaway R. N. , Willerslev E. , Haile J. , Shapiro B. , Scofield R. P. , Drummond A. , Kamp P. J. J. , Cooper A.
Published: November 2009

The ratite moa (Aves: Dinornithiformes) were a speciose group of massive graviportal avian herbivores that dominated the New Zealand (NZ) ecosystem until their extinction ≈600 years ago. The phylogeny and evolutionary history of this morphologically diverse order has remained controversial since their initial description in 1839. We synthesize mitochondrial phylogenetic information from 263 subfossil moa specimens from across NZ with morphological, ecological, and new geological data to create the first comprehensive phylogeny, taxonomy, and evolutionary timeframe for all of the species of an extinct order. We also present an important new geological/paleogeographical model of late Cenozoic NZ, which suggests that terrestrial biota on the North and South Island landmasses were isolated for most of the past 20–30 Ma. The data reveal that the patterns of genetic diversity within and between different moa clades reflect a complex history following a major marine transgression in the Oligocene, affected by marine barriers, tectonic activity, and glacial cycles. Surprisingly, the remarkable morphological radiation of moa appears to have occurred much more recently than previous early Miocene (
ca.
15 Ma) estimates, and was coincident with the accelerated uplift of the Southern Alps just
ca.
5–8.5 Ma. Together with recent fossil evidence, these data suggest that the recent evolutionary history of nearly all of the iconic NZ terrestrial biota occurred principally on just the South Island.
Arabidopsis
lipins mediate eukaryotic pathway of lipid metabolism and cope critically with phosphate starvation
Authors: Nakamura Yuki , Koizumi Ryota , Shui Guanghou , Shimojima Mie , Wenk Markus R. , Ito Toshiro , Ohta Hiroyuki
Published: November 2009

Phosphate is an essential nutrient for plant viability. It is well-established that phosphate starvation triggers membrane lipid remodeling, a process that converts significant portion of phospholipids to non-phosphorus-containing galactolipids. This remodeling is mediated by either phospholipase C (PLC) or phospholipase D (PLD) in combination with phosphatidate phosphatase (PAP). Two PLC genes,
NPC4
and
NPC5
, and PLD genes,
PLD
ζ
1
and
PLD
ζ
2
, are shown to be involved in the remodeling. However, gene knockout studies show that none of them plays decisive roles in the remodeling. Thus, although this phenomenon is widely observed among plants, the key enzyme(s) responsible for the lipid remodeling in a whole plant body is unknown; therefore, the physiological significance of this conversion process has remained to be elucidated. We herein focused on PAP as a key enzyme for this adaptation, and identified
Arabidopsis lipin
homologs,
AtPAH1
and
AtPAH2
, that encode the PAPs involved in galactolipid biosynthesis. Double mutant
pah1pah2
plants had decreased phosphatidic acid hydrolysis, thus affecting the eukaryotic pathway of galactolipid synthesis. Upon phosphate starvation,
pah1pah2
plants were severely impaired in growth and membrane lipid remodeling. These results indicate that PAH1 and PAH2 are the PAP responsible for the eukaryotic pathway of galactolipid synthesis, and the membrane lipid remodeling mediated by these two enzymes is an essential adaptation mechanism to cope with phosphate starvation.
Early onset of autoimmune disease by the retroviral integrase inhibitor raltegravir
Authors: Beck-Engeser Gabriele B. , Eilat Dan , Harrer Thomas , Jäck Hans-Martin , Wabl Matthias
Published: November 2009

Raltegravir is a recently, Food and Drug Administration-approved, small-molecule drug that inhibits retroviral integrase, thereby preventing HIV DNA from inserting itself into the human genome. We report here that the activity profile of raltegravir on the replication of murine leukemia virus is similar to that for HIV, and that the drug specifically affects autoimmune disease in mice, in which endogenous retroelements are suspected to play a role. While NZW and BALB/c mice, which do not succumb to autoimmune disease, are not affected by raltegravir, lupus-prone (NZBxNZW) F1mice die of glomerulonephritis more than a month earlier than untreated mice. Raltegravir-treated NZB mice, which share the H-2 haplotype with BALB/c mice, but which are predisposed to autoimmune hemolytic anemia, develop auto-antibodies to their red blood cells >3 months earlier than untreated mice of the same strain. Because nonautoimmune mice are not affected by raltegravir, we consider off-target effects unlikely and attribute the exacerbation of autoimmunity to the inhibition of retroviral integrase.
Role of Relationship Management and Value Co-Creation in Social Marketing
Authors: Desai Darshan
Published: November 2009

This article addresses deep-seated problems in applying traditional relationship marketing and customer relationship management concepts in the context of social marketing. Further, it points out the recent changes in interactive technologies, culture, lifestyle, and the marketing logic and discusses the “makeover” of the concept and practices of the customer relationship management. It describes how the revised logic of marketing is more accommodative of social marketing and how the new avatar of customer relationship management 2.0 is more relevant for social marketers. It explains how the concepts and practices of customer relationship management 2.0, which are rooted in service logic, can be applied in the context of social marketing to co-create value. It explores the role of social marketers and their customers as active relationship partners and describes their interactions as a locus of value co-creations. Through these interactions, customers engage with social marketers to co-create different aspects of the market offerings, and social marketers engage in customers' value-generating processes to co-create better value-in-use. The key building blocks described in the article enable the value co-creations. The article concludes with implications in terms of how social marketers can use these insights to make the world a better place.
Designing and Testing a Shaken Baby Syndrome Prevention Program—The Period of PURPLE Crying: Keeping Babies Safe in North Carolina
Authors: Runyan Desmond K. , Hennink-Kaminski Heidi J. , Zolotor Adam J. , Barr Ronald G. , Murphy Robert A. , Barr Marilyn , Sullivan Kelly , Dougall Elizabeth K. , Nocera Maryalice
Published: November 2009

Each year infants die or are permanently disabled at the hands of their caregivers by abusive head trauma, more commonly known as Shaken Baby Syndrome (SBS). Current medical research confirms the central role of infant crying in triggering shaking by caregivers; anecdotally, inconsolable crying is the most common explanation given by abusers. Although SBS prevention efforts have been initiated, most remain unevaluated. This article provides an overview of a 5-year, evidence-based SBS-prevention program called The Period of PURPLE Crying: Keeping Babies Safe in North Carolina from a social marketing perspective. The project includes three components: (1) in-hospital education for parents of every newborn at all 86 hospitals/birthing centers in North Carolina; (2) reinforcement in community settings such as prenatal visits to health departments or well-child care visits to primary care providers; and (3) a media campaign.
Exploring the Influence of the VERB™ Brand Using a Brand Equity Framework
Authors: Price Simani M. , Potter Lance D. , Das Barnali , Wang Yu-Chung L. , Huhman Marian
Published: November 2009

The Centers for Disease Control and Prevention's Youth Media Campaign designed VERB™ as an aspirational brand to increase physical activity among children aged 9–13 years. In the current study, we explore the influence of the VERB™ brand in the campaign using a brand equity framework. Brand equity responses were collected from 1,007 children from a national cross-sectional telephone survey. Findings indicated that high VERB brand equity was associated with increased positive attitudes toward physical activity and participation in free-time physical activity. The relationship between brand equity and free-time physical activity was partially mediated through attitudes. Brand personality and leadership/popularity constructs were found to be strong predictors in determining physical activity attitudes and behaviors, respectively. As the use of a branding strategy increases in public health, brand equity offers social marketers a framework for evaluating the effectiveness of their efforts.

The findings and conclusions in this article are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.