bluuebunny/crossref_metadata_2025 huggingface dataset:
Hafnium oxide gate dielectrics on sulfur-passivated germanium
Authors: Frank Martin M. , Koester Steven J. , Copel Matthew , Ott John A. , Paruchuri Vamsi K. , Shang Huiling , Loesing Rainer
Published: September 2006

Sulfur passivation of Ge(100) is achieved using aqueous ammonium sulfide (NH4)2S(aq). The passivation layer is largely preserved after atomic layer deposition of the high-κ dielectric material HfO2 when sufficiently low growth temperatures (e.g., 220°C) are employed. Oxygen incorporation is moderate and results in an electrically passivating GeOS interface layer. The HfO2∕GeOS∕Ge gate stack exhibits lower fixed charge and interface state density than a more conventional HfO2∕GeON∕Ge gate stack fabricated via an ammonia gas treatment.
Analyticity of the scattering amplitude, causality, and high-energy bounds in quantum field theory on noncommutative space–time
Authors: Tureanu Anca
Published: September 2006

In the framework of quantum field theory on noncommutative space–time with the symmetry group O(1,1)×SO(2), we prove that the Jost-Lehmann-Dyson representation, based on the causality condition taken in connection with this symmetry, leads to the mere impossibility of drawing any conclusion on the analyticity of the 2→2-scattering amplitude in cosΘ, Θ being the scattering angle. Discussions on the possible ways of obtaining high-energy bounds analogous to the Froissart-Martin bound on the total cross section are also presented.
High pressure crystalline phase formation during nanoindentation: Amorphous versus crystalline silicon
Authors: Ruffell S. , Bradby J. E. , Williams J. S.
Published: September 2006

Phase transformations induced by indentation at different unloading rates have been studied in crystalline and amorphous silicon via Raman microspectroscopy and transmission electron microscopy. Unloading was performed at a “slow” rate of ∼0.9mN∕s which is known to create volumes of high pressure phases (Si-III and Si-XII) in crystalline silicon as well as “rapid” unloading (∼1000mN∕s), where amorphous phases are expected. Stark differences between the resulting structures are observed depending on whether the starting material is amorphous or crystalline silicon. Interestingly, amorphous silicon transforms to high pressure phases much more readily than crystalline silicon even after rapid unloading.
Nonlinear electrical properties of three-terminal junctions
Authors: Wallin D. , Shorubalko I. , Xu H. Q. , Cappy A.
Published: September 2006

The authors report on room-temperature electrical measurements of three-terminal junctions made from a semiconductor heterostructure. The correlation between the junction size of the devices and the voltages needed to be applied in order to observe the electrical characteristics of three-terminal ballistic junctions is studied. The authors show that the ballistic behavior of electron transport can be observed in a three-terminal junction with a junction size of a few micrometers, much larger than the mean free path of electrons in the material. The results are explained in terms of a bias-induced enhancement of the electron mean free path in the system.
Non-neutral plasma equilibria with weak axisymmetric magnetic perturbations
Authors: Kotelnikov I. A. , Romé M. , Kabantsev A.
Published: September 2006

The effect of weak axisymmetric magnetic and/or electrostatic perturbations on the equilibrium of a non-neutral plasma in a Malmberg-Penning trap is analyzed. Analytical and semianalytical solutions for the potential variations inside the trap are found in a paraxial limit of the perturbations for various radial density profiles of the plasma, including the case of global thermal equilibrium. It is shown that a magnetic perturbation produces a potential variation with a sign which is changing along the plasma radius. The fraction of magnetically and electrostatically trapped particles thus created is calculated explicitly for the case of a Maxwellian distribution function, and it is shown to be independent from the sign of the magnetic field perturbation. The analysis of the potential perturbation is extended to the case of an anisotropic distribution function, with an arbitrary ratio between the parallel and the perpendicular plasma temperature. Two-dimensional thermal equilibrium simulations for parameters relevant to the CamV device [A. A. Kabantsev, J. H. Yu, R. B. Lynch, and C. F. Driscoll, Phys. Plasmas 10, 1628 (2003)] confirm the predictions of the analytical theory for smooth and weak perturbations of the magnetic field.
Soft x-ray resonant magnetic scattering from an imprinted magnetic domain pattern
Authors: Kinane C. J. , Suszka A. K. , Marrows C. H. , Hickey B. J. , Arena D. A. , Dvorak J. , Charlton T. R. , Langridge Sean
Published: September 2006

The authors report on the use of a Co∕Pt multilayer, which exhibits strong perpendicular magnetic anisotropy, to magnetostatically imprint a domain pattern onto a 50Å thick Permalloy layer. Element specific soft x-ray magnetic scattering experiments were then performed so as to be sensitive to the magnetic structure of the Permalloy only. Off-specular magnetic satellite peaks, corresponding to a periodic domain stripe width of 270nm, were observed, confirmed by magnetic force microscopy and micromagnetic modeling. Thus the authors have exploited the element specificity of soft x-ray scattering to discern the purely magnetic correlations in a structurally flat Permalloy film.
Synthesis of Si nanopyramids at SiOx∕Si interface for enhancing electroluminescence of Si-rich SiOx
Authors: Lin Gong-Ru , Lin Chi-Kuan , Chou Li-Jen , Chueh Yu-Lun
Published: September 2006

Enhanced electroluminescence (EL) of ITO∕SiOx∕Si-nanopyramid/p-Si∕Al diode is investigated. By using low-power plasma enhanced chemical vapor deposition at high substrate temperature, anomalous (100)-oriented Si nanopyramids with a surface density of 1.6×1010cm−2 are synthesized at SiOx∕Si interface prior to grow Si-rich SiOx film. Si nanopyramids greatly improve Fowler-Nordheim tunneling based carrier transport and benefit from less damaged oxide structure at lower biases. The turn-on voltage and threshold current density of the diode are reduced to 50V and 0.2mA∕cm2, respectively. Defect-related blue-green EL are suppressed to enhance stable near-infrared EL at 30nW with a lifetime >10h.
Intracavity thermal loading measurements and evaluation of the intrinsic fluorescence quantum efficiency in Yb3+:LiNbO3:MgO lasers
Authors: Ramírez M. O. , Jaque D. , Bausá L. E.
Published: September 2006

Direct intracavity thermal loading measurements have been performed on diode pumped Yb3+ doped LiNbO3:MgO laser crystals. The fractional thermal loading has been found to be strongly dependent on the Yb3+ concentration, decreasing more than 40% when the Yb3+ concentration increases from 0.5to2at.%. From the analysis of the concentration dependence of the fractional thermal loading, the intrinsic fluorescence quantum efficiency (free of radiation trapping) of Yb3+ ions in LiNbO3:MgO crystals has been determined and the role of radiation trapping among Yb3+ ions is discussed.
Comparative studies on the stability of polymer versus SiO2 gate dielectrics for pentacene thin-film transistors
Authors: Hwang D. K. , Lee Kimoon , Kim Jae Hoon , Im Seongil , Park Ji Hoon , Kim Eugene
Published: September 2006

The authors report on the electrical reliabilities of poly-4-vinyl phenol (PVP) and SiO2 gate dielectrics for pentacene thin-film transistors (TFTs). SiO2 films were grown by dry oxidation and PVP films were prepared by spin coating and subsequent cross-linking at 175°C for 15min. The pentacene TFTs with the PVP cured for 15min exhibited a large hysteresis and an abnormal drain-current increase under a gate bias stress over time, while the other TFT with SiO2 displayed a small hysteresis but its drain current decreases with time. The hysteresis behaviors induced by PVP and SiO2 were opposite to each other in the gate bias swing direction, due to the difference in hysteresis mechanism between the two types of TFTs. Comparing their hysteresis behavior, the authors fabricated a far more reliable pentacene TFT with PVP by extending the PVP curing time to 1h. Our improved device with PVP exhibited no hysteresis and persistent toughness to the gate bias stress.
Synthesis of YbyCo4Sb12∕Yb2O3 composites and their thermoelectric properties
Authors: Zhao X. Y. , Shi X. , Chen L. D. , Zhang W. Q. , Bai S. Q. , Pei Y. Z. , Li X. Y. , Goto T.
Published: September 2006

Composites containing Yb-filled CoSb3 and well-distributed Yb2O3 particles are synthesized by in situ reaction method. The structural, chemical, and transport properties of the composites are studied. Some Yb2O3 particles with microsize locate at the grain boundaries of matrix and others distribute within YbyCo4Sb12 grains as nanoscale inclusions. The combination of the “rattling” of Yb ions inside the voids of CoSb3 and the phonon scattering of the oxide defects results in a remarkable reduction in the lattice thermal conductivity. The thermoelectric performance of the composites is significantly improved, and the maximum figures of merit reach 1.3 for the Yb0.25Co4Sb12∕Yb2O3 and 1.2 for the Yb0.21Co4Sb12∕Yb2O3 composites at 850K.
Misfit strain relaxation in strained-Si layers on silicon-germanium-on-insulator substrates
Authors: Hirashita Norio , Moriyama Yoshihiko , Sugiyama Naoharu , Toyoda Eiji , Takagi Shin-ichi
Published: September 2006

The critical thickness of tensile-strained-Si layers grown at 600°C on (001) surfaces of silicon-germanium-on-insulator substrates is experimentally studied for a tensile strain range between 0.4% and 1.2% and is found to be rather thinner than Houghton’s critical thickness [J. Appl. Phys. 70, 2136 (1991)] for compressively mismatched SiGe∕Si (001) system. The thinner critical thickness in tensile-strained Si is attributed to the fact that the stress-relieving misfit dislocations are 90° partial dislocations, instead of 60° misfit dislocations for compressive SiGe layers on Si (001) substrates. Although 60° misfit dislocation is found to be increasingly formed with increasing strained-Si layer thickness, the strain relaxation is sluggish and the tensile strain mostly remains for supercritical thickness ten times thicker than the critical thickness.
Evaluation of glass-forming ability for metallic glasses based on order-disorder competition
Authors: Xia Mingxu , Zhang Shuguang , Ma Chaoli , Li Jianguo
Published: September 2006

The authors propose a calculable parameter ε, defined as a negative ratio of mixing entropy to mixing enthalpy, to evaluate the glass-forming ability (GFA) of metallic glasses from the viewpoint of a competition of disordering against ordering. It is found that the GFAs of most typical metallic glasses linearly distribute with ε and the likely formation area of bulk metallic glass could be conservatively restricted within 0.25<ε<0.6K−1. The prediction of Tb–Fe–Al glassy alloys shows promise for rapidly locating glass formers with less cost.
Rollable multicolor display using electrically induced blueshift of a cholesteric reactive mesogen mixture
Authors: Xianyu Haiqing , Lin Tsung-Hsien , Wu Shin-Tson
Published: September 2006

Electrically controllable blueshift of the reflection band in a planar cholesteric reactive mesogen cell is observed. The responsible mechanism is electric-field-induced Helfrich deformation [J. Chem. Phys. 55, 839 (1971)]. The modified director configuration can be solidified by photopolymerizing the reactive mesogens when a voltage is applied. The correlation between the director configuration and optical properties is validated by the scanning electron microscope photos and the transmission spectra of a planar and an undulated cholesteric film. With masked curing at different voltages, a rollable multicolor display is demonstrated.
Theory and simulations of a gyrotron backward wave oscillator using a helical interaction waveguide
Authors: He W. , Cross A. W. , Phelps A. D. R. , Ronald K. , Whyte C. G. , Samsonov S. V. , Bratman V. L. , Denisov G. G.
Published: September 2006

A gyrotron backward wave oscillator (gyro-BWO) with a helically corrugated interaction waveguide demonstrated its potential as a powerful microwave source with high efficiency and a wide frequency tuning range. This letter presents the theory describing the dispersion properties of such a waveguide and the linear beam-wave interaction. Numerical simulation results using the PIC code MAGIC were found to be in excellent agreement with the output measured from a gyro-BWO experiment.
Microfluidic “jets” for generating steady-state gradients of soluble molecules on open surfaces
Authors: Keenan Thomas M. , Hsu Chia-Hsien , Folch Albert
Published: September 2006

The ability to control the spatiotemporal microenvironment of cultured cells, such as cells in soluble gradients of signaling molecules, is critical for understanding the quantitative relationship between physicochemical signals and the induced biological responses. Existing methods for generating biomolecule gradients either offer little control, result in poor reproducibility, and/or place cells in potentially confounding or adverse conditions. Here the authors report the generation of soluble gradients by a system of microfluidic “jets” that inject picoliter amounts of fluid into an open pool with negligible exposure of the surface to flow. A stable, reproducible gradient can be formed in minutes.
Carrier lifetime and modulation bandwidth of a quantum well AlGaAs∕InGaP∕GaAs∕InGaAs transistor laser
Authors: Feng M. , Holonyak N. , James A. , Cimino K. , Walter G. , Chan R.
Published: September 2006

A quantum well (160Å) transistor laser with a 400μm cavity length that achieves the large 3dB modulation bandwidth of 13.5GHz is described. The fast base recombination (transport determined, τBL<10ps) permits improvement of the carrier-photon damping ratio (>1∕2), resulting in a resonant peak magnitude of unity and consequently a resonance frequency of ∼0GHz (no peak) in the small-signal response. Quantum well band filling and bandwidth saturation are observed on the ground state (λ=1000nm), and increase with operation on the first excited state (λ=980nm).
Achieving fast oxygen response in individual β-Ga2O3 nanowires by ultraviolet illumination
Authors: Feng P. , Xue X. Y. , Liu Y. G. , Wan Q. , Wang T. H.
Published: September 2006

The authors report a route to realize very quick oxygen response and demonstrate it by using individual β-Ga2O3 nanowires. The current across the nanowire is at a low level and varies slightly with changing the oxygen pressure. In contrast, under 254nm ultraviolet illumination, the current increases rapidly to a value that reflects the level of the oxygen pressure around the nanowire. The illumination gives rise to the oxygen sensing. This optically driven oxygen sensing is the origin of the fast response. The results demonstrate a promising approach to realize fast-response gas sensors.
Imaging the electric properties of InAs∕InP(001) quantum dots capped with a thin InP layer by conductive atomic force microscopy: Evidence of memory effect
Authors: Smaali K. , Troyon M. , El Hdiy A. , Molinari M. , Saint-Girons G. , Patriarche G.
Published: September 2006

Conductive atomic force microscopy has been used to study the topography and the electric properties of InAs quantum dots (QDs) grown by metal organic vapor phase epitaxy on a n-type InP(001) substrate and covered with a 5nm thick InP cap layer. Images reveal that the cap layer has not entirely covered the surface, but has formed rounded terracelike structures surrounding the QDs. A high current is detected on the QDs, about ten times less on the terraces, and not detectable on the wetting layer. Charges can be trapped inside the QDs and the surrounding terraces in forward bias conditions with a temporary memory effect and discharged in reverse bias.
Property modulation of zinc oxide hierarchical architectures in photoluminescence and Raman scattering
Authors: Zhang Yugang , Wang Zhenyang , Lu Fang , Zhang Ye , Xiao Yanhe , Zhang Lide
Published: September 2006

By manipulating the driven force (the supersaturation degree), ZnO nanocavities, nanowalls, and nanorods are controllably assembled on the (0001) plane of ZnO microcrystals in sequence via a developed chemical vapor deposition route. Through manipulating the morphologies, the properties of ZnO architectures are facilely modulated. The room-temperature photoluminescence spectra show that the relative intensity of UV emission to the green emission can be tuned by altering their morphologies. The Raman spectra show that there are first redshift and then blueshift of the peak of E2H mode by assembly of the specific building units.
Electron mobility enhancement in AlN∕GaN∕AlN heterostructures with InGaN nanogrooves
Authors: Pokatilov E. P. , Nika D. L. , Balandin A. A.
Published: September 2006

The authors show that the electron mobility can be strongly enhanced in AlN∕GaN∕AlN heterostructures with the shallow InxGa1−xN channel—nanogroove—in the middle of the potential well. The modified heterostructure has the room-temperature electron mobility, which is five times larger than that in conventional quantum wells. The maximum mobility enhancement is achieved for In content x≈0.05, which is sufficient to weaken the intersubband electron scattering without leading to the substantial electron—interface-phonon scattering. The mobility enhancement is pronounced for a wide range of the carrier densities (1011–1013cm−2), which is important for GaN technology.
Hexagonal ferromagnetic MnAs nanocluster formation on GaInAs∕InP (111)B layers by metal-organic vapor phase epitaxy
Authors: Hara Shinjiroh , Fukui Takashi
Published: September 2006

The authors report the self-assembly of hexagonal MnAs nanoclusters on GaInAs (111)B surfaces by metal-organic vapor phase epitaxy. The ferromagnetic behavior of the nanoclusters dominates the magnetic response of the samples when magnetic fields are applied in a direction parallel to the wafer plane. For the magnetic fields applied in a direction perpendicular to the plane, diamagnetic characteristics are dominant. The results indicate that the c axis of the nanoclusters is perpendicular to the plane, and that their a axis is in plane. They are consistent with the results of crystallographic analysis, where the nanoclusters’ c axis is shown to be along a GaInAs [−1−1−1] direction.
Subpicosecond time-resolved Raman studies of LO phonons in GaN: Dependence on photoexcited carrier density
Authors: Tsen K. T. , Kiang Juliann G. , Ferry D. K. , Morkoç H.
Published: September 2006

Subpicosecond time-resolved Raman spectroscopy has been used to measure the lifetime of the LO phonon mode in GaN for photoexcited electron-hole pair density ranging from 1016to2×1019cm−3. The lifetime has been found to decrease from 2.5ps, at low density, to 0.35ps, at the highest density. The experimental findings should help resolve the recent controversy over the lifetime of LO phonon mode in GaN.
Spatially tunable laser emission in dye-doped cholesteric polymer films
Authors: Huang Yuhua , Chen Liang-Pin , Doyle Charlie , Zhou Ying , Wu Shin-Tson
Published: September 2006

A spatially tunable laser emission of the dye-doped cholesteric polymer film is demonstrated by generating a one-dimensional gradient photonic band gap which is cured by an ultraviolet light. A frequency-doubled pulsed Nd:YAG laser is used to pump the film. The lasing wavelength is tunable from 595to643nm by shifting the position of the film with respect to the pumping beam. Since the spatial distribution of the reflection band is fixed in the cholesteric polymer film, the tuning of the laser wavelength does not require any external field. Therefore, the film is portable and has many applications.
Two-photon absorption of matrix-free Ge nanocrystals
Authors: Gerung Henry , Zhao Yanrui , Wang Li , Jain Ravinder K. , Boyle Timothy J. , Brinker C. Jeffrey , Han Sang M.
Published: September 2006

The authors demonstrate that solution synthesized Ge nanocrystals (NCs) display a highly nonlinear optical absorption. The Ge NCs with an average diameter of 5±2nm are synthesized from germanium(II) bis(trimethylsilyl)amide with hexadecylamine surfactants at 300°C and 1atm in argon atmosphere. The resulting Ge NCs in a powder form are then dispersed on a silica glass substrate. Femtosecond pulses at 820nm wavelength from a mode-locked Ti:sapphire laser are used to measure a two-photon absorption coefficient of the deposited Ge NCs. The calculated coefficient ranges from 1190to1940cm∕GW.
Grain growth behavior at absolute zero during nanocrystalline metal indentation
Authors: Sansoz F. , Dupont V.
Published: September 2006

The authors show using atomistic simulations that stress-driven grain growth can be obtained in the athermal limit during nanocrystalline aluminum indentation. They find that the grain growth results from rotation of nanograins and propagation of shear bands. Together, these mechanisms are shown to lead to the unstable migration of grain boundaries via process of coupled motion. An analytical model is used to explain this behavior based on the atomic-level shear stress acting on the interfaces during the shear band propagation. This study sheds light on the atomic mechanism at play during the abnormal grain coarsening observed at low temperature in nanocrystalline metals.
Absorption coefficient of aluminum near the critical point and the consequences on high-power nanosecond laser ablation
Authors: Wu Benxin , Shin Yung C.
Published: September 2006

During nanosecond laser ablation, the absorption coefficient determines the laser energy deposition in the target, the accurate knowledge of which near the material critical point is crucial for understanding the fundamental physics of high-power nanosecond laser ablation. In this letter, the absorption coefficient of aluminum near the critical point is calculated through the Drude model based on the measured electrical conductivity data, and its effect on laser ablation is investigated numerically using a heat transfer model. The result supports the experimental observations that phase explosion occurs for the ablation of aluminum by sufficiently intense laser pulses, and the model predicted phase explosion threshold is consistent with experimental measurements.
Atomistic study on twinning of Cu2O quantum dots
Authors: Li Luying , Wang Jianbo , Wang Renhui , Liu Huijun , Jia Chunlin , Ma Lili , Yu Ying
Published: September 2006

Cu 2 O nanoparticles are investigated at atomic scale by high-resolution transmission electron microscopy. It is found that growth {111} twinning is the most common type of defects in these nanoparticles. The atomic structure of the twinning boundaries is determined referring to the detailed image simulations based on the structure model refined by first-principles calculation. The twin boundary plane is along a {111} oxygen plane and the twinning shows a crystallographic relation with a symmetry operation of 180° rotation around a ⟨111⟩ axis perpendicular to the plane. The effect of the twinning on the stability of the particles is discussed.
Control of p- and n-type conductivities in Li-doped ZnO thin films
Authors: Lu J. G. , Zhang Y. Z. , Ye Z. Z. , Zeng Y. J. , He H. P. , Zhu L. P. , Huang J. Y. , Wang L. , Yuan J. , Zhao B. H. , Li X. H.
Published: September 2006

Li-doped ZnO films were prepared by pulsed laser deposition. The carrier type could be controlled by adjusting the growth conditions. In an ionized oxygen atmosphere, p-type ZnO was achieved, with the hole concentration of 6.04×1017cm−3 at an optimal Li content of 0.6at.%, whereas ZnO exhibited n-type conductivity in a conventional O2 growth atmosphere. At a Li content of more than 1.2at.% only high-resistivity ZnO was obtained. The amount of Li introduced into ZnO and the relative concentrations of such defects as Li substitutions and interstitials could play an important role in determining the conductivity of films.
Rapid nongenomic actions of thyroid hormone
Authors: Hiroi Yukio , Kim Hyung-Hwan , Ying Hao , Furuya Fumihiko , Huang Zhihong , Simoncini Tommaso , Noma Kensuke , Ueki Kojiro , Nguyen Ngoc-Ha , Scanlan Thomas S. , Moskowitz Michael A. , Cheng Sheue-Yann , Liao James K.
Published: September 2006

The binding of thyroid hormone to the thyroid hormone receptor (TR) mediates important physiological effects. However, the transcriptional effects of TR mediated by the thyroid response element (TRE) cannot explain many actions of thyroid hormone. We postulate that TR can initiate rapid, non-TRE-mediated effects in the cardiovascular system through cross-coupling to the phosphatidylinositol 3-kinase (PI3-kinase)/protein kinase Akt pathway. In vascular endothelial cells, the predominant TR isoform is TRα
1
. Treatment of endothelial cells with
l
-3,5,3′-triiodothyronine (T
3
) increased the association of TRα
1
with the p85α subunit of PI3-kinase, leading to the phosphorylation and activation of Akt and endothelial nitric oxide synthase (eNOS). The activation of Akt and eNOS by T
3
was abolished by the PI3-kinase inhibitors, LY294002 and wortmannin, but not by the transcriptional inhibitor, actinomycin D. To determine the physiological relevance of this PI3-kinase/Akt pathway, we administered T
3
to mice undergoing transient focal cerebral ischemia. Compared with vehicle, a single bolus infusion of T
3
rapidly increased Akt activity in the brain, decreased mean blood pressure, reduced cerebral infarct volume, and improved neurological deficit score. These neuroprotective effects of T
3
were greatly attenuated or absent in eNOS
−/−
and TRα
1
−/−
β
−/−
mice and were completely abolished in WT mice pretreated with LY294002 or a T
3
antagonist, NH-3. These findings indicate that the activation of PI3-kinase/Akt pathways can mediate some of the rapid, non-TRE effects of TR and suggest that the activation of Akt and eNOS contributes to some of the acute vasodilatory and neuroprotective effects of thyroid hormone.
Ancestral reconstruction of the ligand-binding pocket of Family C G protein-coupled receptors
Authors: Kuang Donghui , Yao Yi , MacLean David , Wang Minghua , Hampson David R. , Chang Belinda S. W.
Published: September 2006

The metabotropic glutamate receptors (mGluRs) within the Family C subclass of G protein-coupled receptors are crucial modulators of synaptic transmission. However, their closest relatives include a diverse group of sensory receptors whose biological functions are not associated with neurotransmission, raising the question of the evolutionary origin of amino acid-binding Family C receptors. A common feature of most, if not all, functional Family C receptors is the presence of an amino acid-binding site localized within the large extracellular Venus flytrap domain. Here, we used maximum likelihood methods to infer the ancestral state of key residues in the amino acid-binding pocket of a primordial Family C receptor. These residues were reconstructed in the background of the fish 5.24 chemosensory receptor, a broad-spectrum amino acid-activated receptor. Unlike the WT 5.24 receptor, which was not activated by mGluR agonists and displayed low sensitivity toward
l
-glutamate, the reconstructed ancestral receptor possessed a pharmacological profile characterized by high affinity for both
l
-glutamate and selective Group I mGluR agonists. This pharmacological phenotype could be largely recapitulated by mutating only two residues in the 5.24 receptor-binding pocket. Our results suggest that this primordial Family C receptor may have arisen early in metazoan evolution and that it already was preadapted as a glutamate receptor for its later use at excitatory synapses in glutamate-mediated neurotransmission.
Efficiency of carcinogenesis with and without a mutator mutation
Authors: Beckman Robert A. , Loeb Lawrence A.
Published: September 2006

Carcinogenesis involves the acquisition of multiple genetic changes altering various cellular phenotypes. These changes occur within the fixed time period of a human lifespan, and mechanisms that accelerate this process are more likely to result in clinical cancers. Mutator mutations decrease genome stability and, hence, accelerate the accumulation of random mutations, including those in oncogenes and tumor suppressor genes. However, if the mutator mutation is not in itself oncogenic, acquiring that mutation would add an extra, potentially time-consuming step in carcinogenesis. We present a deterministic mathematical model that allows quantitative prediction of the efficiency of carcinogenesis with and without a mutator mutation occurring at any time point in the process. By focusing on the ratio of probabilities of pathways with and without mutator mutations within cell lineages, we can define the frequency or importance of mutator mutations in populations independently of absolute rates and circumvent the question of whether mutator mutations are “necessary” for cancers to evolve within a human lifetime. We analyze key parameters that predict the relative contribution of mutator mutants in carcinogenesis. Mechanisms of carcinogenesis involving mutator mutations are more likely if they occur early. Involvement of mutator mutations in carcinogenesis is favored by an increased initial mutation rate, by greater fold-increase in mutation rate due to the mutator mutation, by increased required steps in carcinogenesis, and by increased number of cell generations to the development of cancer.
Extreme genetic risk for type 1A diabetes
Authors: Aly Theresa A. , Ide Akane , Jahromi Mohamed M. , Barker Jennifer M. , Fernando Maria S. , Babu Sunanda R. , Yu Liping , Miao Dongmei , Erlich Henry A. , Fain Pamela R. , Barriga Katherine J. , Norris Jill M. , Rewers Marian J. , Eisenbarth George S.
Published: September 2006

Type 1A diabetes (T1D) is an autoimmune disorder the risk of which is increased by specific HLA DR/DQ alleles [e.g., DRB1*03-DQB1*0201 (DR3) or DRB1*04-DQB1*0302 (DR4)]. The genotype associated with the highest risk for T1D is the DR3/4-DQ8 (DQ8 is DQA1*0301, DQB1*0302) heterozygous genotype. We determined HLA-DR and -DQ genotypes at birth and analyzed DR3/4-DQ8 siblings of patients with T1D for identical-by-descent HLA haplotype sharing (the number of haplotypes inherited in common between siblings). The children were clinically followed with prospective measurement of anti-islet autoimmunity and for progression to T1D. Risk for islet autoimmunity dramatically increased in DR3/4-DQ8 siblings who shared both HLA haplotypes with their diabetic proband sibling (63% by age 7, and 85% by age 15) compared with siblings who did not share both HLA haplotypes with their diabetic proband sibling (20% by age 15,P< 0.01). 55% sharing both HLA haplotypes developed diabetes by age 12 versus 5% sharing zero or one haplotype (P= 0.03). Despite sharing both HLA haplotypes with their proband, siblings without the HLA DR3/4-DQ8 genotype had only a 25% risk for T1D by age 12. The risk for T1D in the DR3/4-DQ8 siblings sharing both HLA haplotypes with their proband is remarkable for a complex genetic disorder and provides evidence that T1D is inherited with HLA-DR/DQ alleles and additional MHC-linked genes both determining major risk. A subset of siblings at extremely high risk for T1D can now be identified at birth for trials to prevent islet autoimmunity.
Mg
2+
–RNA interaction free energies and their relationship to the folding of RNA tertiary structures
Authors: Grilley Dan , Soto Ana Maria , Draper David E.
Published: September 2006

Mg
2+
ions are very effective at stabilizing tertiary structures in RNAs. In most cases, folding of an RNA is so strongly coupled to its interactions with Mg
2+
that it is difficult to separate free energies of Mg
2+
– RNA interactions from the intrinsic free energy of RNA folding. To devise quantitative models accounting for this phenomenon of Mg
2+
-induced RNA folding, it is necessary to independently determine Mg
2+
–RNA interaction free energies for folded and unfolded RNA forms. In this work, the energetics of Mg
2+
–RNA interactions are derived from an assay that measures the effective concentration of Mg
2+
in the presence of RNA. These measurements are used with other measures of RNA stability to develop an overall picture of the energetics of Mg
2+
-induced RNA folding. Two different RNAs are discussed, a pseudoknot and an rRNA fragment. Both RNAs interact strongly with Mg
2+
when partially unfolded, but the two folded RNAs differ dramatically in their inherent stability in the absence of Mg
2+
and in the free energy of their interactions with Mg
2+
. From these results, it appears that any comprehensive framework for understanding Mg
2+
-induced stabilization of RNA will have to (
i
) take into account the interactions of ions with the partially unfolded RNAs and (
ii
) identify factors responsible for the widely different strengths with which folded tertiary structures interact with Mg
2+
.
Postnatal adjustment of Chinese parents: A two‐wave panel study in Taiwan
Authors: Lu Luo
Published: September 2006

This study focused on examining the relationships between stress, resources, and adjustment of Chinese married mothers and fathers following childbirth. Guided by a generic theoretical model of parenthood transition, the aim of the current study was threefold. First, longitudinal data were collected to clarify the impact of parenthood from 6 weeks postnatal (Time 1) to 6 months postnatal (Time 2). A diachronic design is more advantageous in making causal inferences as baseline levels of mental health and marital satisfaction can be controlled. Second, a gender‐balanced design was adopted to examine the transition processes for both men and women to overcome our shortcomings in understanding men's experiences. Third, this study was conducted in a Chinese society to examine the transition to parenthood as embedded in this particular cultural context. A total of 483 parents (253 females, 230 males) took part in this two‐wave panel study. Hierarchical multiple regression analyses and structural equation modelling techniques were used to test for direct, moderation, and mediation effects of marital congruence and social support as resources. Results showed that (a) parental stress had negative effects on mental health and marital satisfaction, and these relationships were robust across time and gender; (b) marital congruence and social support had direct as well as mediation effects on adjustment; (c) marital congruence also had moderation (stress buffering) effects on the stress/mental health relationship; (d) over the half‐year period, there were no significant changes in stress and adjustment outcomes, yet marital congruence and social support significantly declined, and this trend was the same for both sexes; (e) although males and females did not differ in marital congruence and social support, women reported higher stress, more psychological symptoms, and lower marital satisfaction than men. These gender differences did not change over time. These results were discussed in relation to existing theories and research, as well as the distinct characteristics of the contemporary Chinese society.
Digit Span: Effect of education and culture
Authors: Ostrosky‐Solís Feggy , Lozano Asucena
Published: September 2006

The Digit Span test is one of the most commonly used measures of immediate verbal recall, attentional capacity, and working memory in neuropsychological research and clinical evaluations. This test comprises two modalities, digits forward and digits backward. It has been established that age, education, and culture are important variables that affect performance on this test. The purposes of this study were as follows. First, performance on digit span in a Spanish‐speaking sample was analysed to establish appropriate age and educational ranges in which data from the Digit Span test can be best analysed, and to determine the contribution of age and education to performance on the digit span forward and backward. Second, different studies on digit span were compared and reviewed in order to identify differences in terms of the variables of age, education, and culture. This study evaluated 2574 Spanish‐speaking subjects and three studies were included in the cross‐cultural analysis. Scores from the Spanish‐speaking sample were matched with the data presented by the other studies according to age and level of education. Results showed that the stronger predicting variable in the Spanish‐speaking sample was the level of education, both for digits forward and backward. Regarding culture, differences were found among the studies on digit span for both the forward and backward conditions. It can be argued that learning to read and write affects the development or usage of the abilities measured by the Digit Span task, and that cultural variables such as language and quality of education might also contribute to the differences found between countries.
From morality to moral emotions
Authors: Vélez García Alicia E. , Ostrosky‐Solís Feggy
Published: September 2006

Morals (defined in terms of justice, well‐being, and rights) can be distinguished from social conventionalities, which are standards for particular behaviours that are determined consensually by a certain social group. In all cultures, the notions of psychological damage, injustice, and violation of rights have been determinants for the concept of morals. The study of moral behaviour has been dominated for decades by theories that emphasize the role of reasoning in the moral judgment of adults. Debates about morality have occupied the centre of discussion among theoreticians. Morality‐driven behaviours have traditionally been attributed to logically and verbally mediated processes, commonly referred to as moral reasoning and judgment. However, certain aptitudes, such as social sensitivity and cognition, have been considered to lie at the heart of the evolution of humankind. The assimilation of rules based on punishment or reward, and the attribution of intentions, beliefs, feelings, and desires to other people are some examples of these aptitudes, which are now considered or interpreted as forerunners of human morality. The study of emotions—moral emotions in particular—has increased significantly in the last few decades. Recent proposals have emphasized the role of emotional and intuitive processes in human decision making and thatemotionsare central to the solution of basic problems and to interpersonal relationships. This change in perspective is the result of recent work in the fields of philosophy, cognitive psychology, affective neurosciences, and neurobiology. The field of affective neurosciences has begun to explore different types of moral emotions with different techniques, in particular neuroimaging techniques. In the field of neurobiology, investigators have started to study neural correlates of moral emotions, and have encountered interesting findings, which indicate that the human brain shows a network specialized in moral processing.
Ego‐identity: Can it be reconstituted after a brain injury?
Authors: Biderman D. , Daniels‐Zide E. , Reyes A. , Marks B.
Published: September 2006

Cognitive alterations are frequently observed and studied in persons who present with psychiatric and neurological disorders. Recently an increased number of investigations on the self and attendant processes have interested psychologists, psychiatrists, and neuropsychologists, particularly when a person has suffered brain damage that upsets their daily function in economic, social, personal, behavioural, and emotional ways. At the same time, many theories have been developed to explain the observable changes in ego‐identity of persons with brain injury as well as diverse rehabilitation programs centred on the re‐establishment of the ego‐identity changes. The present article focuses on: (1) the elucidation of the construct of self in current personality theoretical formulations; (2) the major negative effects of brain impairments on the cognitive, neurobehavioural, emotional, and personality functions of persons with brain injuries; (3) the conceptual underpinnings of Kurt Goldstein's views on the neuropsychological rehabilitation endeavour; (4) the illustration, using several clinical examples, that it is possible, following intensive neuropsychological rehabilitative interventions, to restore the shattered self of some brain‐injured persons; and (5) the growing number of holistic programs of rehabilitation for brain‐injured persons all over the world. In conclusion, the sequelae of brain injury not only imply alterations in neurological or cognitive process, but also involve changes in personality aspects. Nevertheless the number of holistic programs has increased, and a particular model of the holistic approach to the neuropsychological rehabilitation of persons with brain injury has been implemented in diverse countries such as Australia, Belgium, Denmark, England, Finland, France, Germany, Holland, Israel, Italy, South Africa, and the United States. Although each one of these programs has been modified to resolve the particular necessities and resources of the different countries, all of them implement Kurt Goldstein's ideas concerning the rehabilitation of persons with brain injuries.
Immunization and facilitation produced by predictable and controllable aversive events alternating with different duration unpredictable and uncontrollable aversive events
Authors: Vicente Francisco , Ferrándiz Pilar , Díaz‐Berciano Cristina
Published: September 2006

This investigation examined whether immunization to learned helplessness is more effective through predictable and controllable events alternating with inescapable and unpredictable events of different duration, than through experiences with only controllable and predictable events. Prior experience with intermittent success resulted in greater immunization than experience with consistent success. Forty‐two male Wistar rats were distributed at random to one of the six groups (n = 7 each). In groups M‐20, M‐40, and M‐80, uncontrollable and unpredictable episodes of shocks with three levels of duration were intermixed with controllable and predictable events: short mixed immunization, 20 trials; moderate mixed immunization, 40 trials; and long mixed immunization, 80 trials. Group C‐U received immunization treatment with only controllable and predictable events; C‐NT was the control group and received controllability training but with no uncontrollable and unpredictable footshock; and group NT‐U received basic learned helplessness treatment. In the test phase, all the subjects were exposed to escape/avoidance training. The results demonstrated the greater efficacy of immunization in groups M‐20 and M‐40 (short and moderate mixed immunization), in terms of significant differences in latency of response relative to groups M‐80 (long mixed immunization) and C‐U (standard immunization), while the behaviour of groups M‐80 and C‐U was similar. All immunization (mixed and standard) groups presented a shorter latency than group NT‐U (no immunization). These data were discussed according to the “dual‐expectancy hypothesis,” the “interference hypothesis,” the “anxiety hypothesis,” and the “reactance theory.”
Report from the Asian Applied Psychology International‐Regional Conference, Bangkok, Thailand
Authors: Knowles M. C.
Published: September 2006

The Asian Applied Psychology International‐Regional Conference (AAPI‐RC) was held in Bangkok from 14–16th November 2005 under the auspices of the International Association of Applied Psychology (IAAP), the International Union of Psychological Science (IUPsyS), and the International Association for Cross‐Cultural Psychology (IACCP). The Conference was organized by Thammasat University and the Thai Psychological Association under the Conference Presidency of Ubolwanna Pavakanun. The Conference attracted a large number of Thai psychologists and students as well as a wide range of participants from 24 other countries, most from Thailand's near and far neighbours but others also from Europe and North America. Apart from the merits of its Scientific Program, the Conference had two important outcomes. One was to pave the way for the formation of a National Committee that will enable Thailand to become a member of the International Union of Psychological Science. The other was to facilitate the first Convention of the newly formed Asian Psychological Association in August 2006.
Holistic neuropsychological rehabilitation in Finland: The INSURE program—a transcultural outgrowth of perspectives from Israel to Europe via the USA
Authors: Sarajuuri Jaana M. , Koskinen Sanna K.
Published: September 2006

Given the interaction of cognitive, behavioural, psychological, and physical factors resulting from traumatic brain injury (TBI), a comprehensive, multidisciplinary, and neuropsychologically oriented rehabilitation could prove to be particularly promising and efficacious in the neuropsychological rehabilitation of post‐acute brain‐injured individuals. Kurt Goldstein, an eminent pioneer in the development of holistic rehabilitation, stated that brain‐injured patients need environments that help them to avoid catastrophic reactions. In his view, the tasks of rehabilitation are to create, for the brain‐injured individual, an environment that will minimize the chances for the occurrence of catastrophic responses. In this environment, the individual can engage optimally in various remedial activities, which will gradually culminate in the individual finding new meaning in life after rehabilitation. Yehuda Ben‐Yishay incorporated many of Goldstein's ideas and developed a milieu or holistic rehabilitation program in 1978 in New York. The emerging role of psychotherapy for patients and their family members was characteristic of the Neuropsychological Rehabilitation Program that Prigatano established in 1980 in Oklahoma. In Europe, Anne‐Lise Christensen, who was also influenced by the work of A. R. Luria, started a holistic program at Copenhagen University in 1985. Based on these pioneering programs, several similar programs were established in Europe. A Finnish program, INSURE, was established in 1993 in Helsinki. The INSURE program is a post‐acute, interdisciplinary, 6‐week rehabilitation program for selected groups of TBI patients. The core of the program is neuropsychological rehabilitation and psychotherapy with vocational interventions, and follow‐up support. In recent years, a holistic rehabilitation program was also established in Turku for children with acquired brain injury. The European Holistic Working Group was founded in 2001, and the authors will also discuss their personal experiences and future of holistic neurospychological rehabilitation in terms of ongoing research work, computer‐administered cognitive remediation, and quality of life assessment.
Serotonin Transporter Genotype and Acute Subjective Response to Amphetamine
Authors: Lott David C. , Kim Soo‐Jeong , Cook Edwin H. , De Wit Harriet.
Published: September 2006

The authors have previously shown an effect of dopamine transporter genotype on acute subjective responses to d‐amphetamine, which may affect risk of addiction. They now report the results of an evaluation of the role of the serotonin transporter gene (HTT) using a double‐blind, placebo‐controlled, crossover design in which subjects (N = 101) completed self‐report measures of subjective effect. The separate and combined analyses of the gene‐linked polymorphic region (5‐HTTLPR) and the Intron 2 VNTR suggest that these two HTT polymorphisms may contribute to acute subjective responses to d‐amphetamine with a small effect.