bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic, environmental, and epigenetic factors in the development of personality disturbance
Authors: Depue Richard A.
Published: October 2009

A dimensional model of personality disturbance is presented that is defined by extreme values on interacting subsets of seven major personality traits. Being at the extreme has marked effects on the threshold for eliciting those traits under stimulus conditions: that is, the extent to which the environment affects the neurobiological functioning underlying the traits. To explore the nature ofdevelopmentof extreme values on these traits, each trait is discussed in terms of three major issues: (a) the neurobiological variables associated with the trait, (b) individual variation in this neurobiology as a function of genetic polymorphisms, and (c) the effects of environmental adversity on these neurobiological variables through the action of epigenetic processes. It is noted that gene–environment interaction appears to be dependent on two main factors: (a) both genetic and environmental variables appear to have the most profound and enduring effects when they exert their effects during early postnatal periods, times when the forebrain is undergoing exuberant experience–expectant dendritic and axonal growth; and (b) environmental effects on neurobiology are strongly modified by individual differences in “traitlike” functioning of neurobiological variables. A model of the nature of the interaction between environmental and neurobiological variables in the development of personality disturbance is presented.
Changing dynamics in problematic personality: A multiwave longitudinal study of the relationship between shyness and aggressiveness from childhood to early adulthood
Authors: Hutteman Roos , Denissen Jaap J. A. , Asendorpf Jens B. , van Aken Marcel A. G.
Published: October 2009

The present longitudinal study investigated cascade effects linking the longitudinal trajectories of shyness and aggressiveness between age 4 and 23 and individual differences in this longitudinal relationship. Results demonstrated that there were cascade effects from shyness to adjacent measures of aggressiveness at three moments in time, and that the dynamics of these relationships changed over time. Children who were shy at age 6 became less aggressive at age 7 and the same effect was found between age 8 and age 10. From adolescence to early adulthood, the direction of the relationship changed and shy adolescents at age 17 became increasingly aggressive 5 years later. Interindividual differences were found in the latter cascade effect in that shyness at age 17 only predicted an increase in aggressiveness at age 23 for adolescents receiving low levels of support from their parents and for adolescents spending little time in part-time work. Together, findings suggest the importance of examining the development of normal variations in personality and personality disorders from a developmental perspective and taking into account person–environment interactions.
Antisocial behavior from a developmental psychopathology perspective
Authors: Frick Paul J. , Viding Essi
Published: October 2009

This paper reviews research on chronic patterns of antisocial behavior and places this research into a developmental psychopathology framework. Specifically, research suggests that there are at least three important pathways through which children and adolescents can develop severe antisocial behaviors. One group of youth shows antisocial behavior that begins in adolescence, and two groups show antisocial behavior that begins in childhood but differ on the presence or absence of callous–unemotional traits. In outlining these distinct pathways to antisocial behavior, we have tried to illustrate some key concepts from developmental psychopathology such as equifinality and multifinality, the importance of understanding the interface between normal and abnormal development, and the importance of using multiple levels of analyses to advance causal theories. Finally, we discuss how this development model can be used to enhance existing interventions for antisocial individuals.
Does change in temperament predict change in schizoid personality disorder? A methodological framework and illustration from the Longitudinal Study of Personality Disorders
Authors: Lenzenweger Mark F. , Willett John B.
Published: October 2009

Personality disorders (PDs) have been thought historically to be enduring, inflexible, and set in psychological stone relatively firmly; however, empirical findings from recent prospective multiwave longitudinal studies establish otherwise. Nearly all modern longitudinal studies of personality disorder have documented considerable change in PDs over time, suggesting considerable flexibility and plasticity in this realm of psychopathology. The factors and mechanisms of change in the PDs remain essentially opaque, and this area of PD research is just beginning to be probed using candidate predictors of change, such as personality systems. In this report, we investigate whether change in temperament dimensions (emotionality, activity, and sociability) predicts change in schizoid personality disorder. We present a latent growth framework for addressing this question and provide an illustration of the approach using data from the Longitudinal Study of Personality Disorders. Schizoid personality disorder was assessed using two different methodologies (structured psychiatric interview and self-report) and temperament was assessed using a well-known psychometric measure of temperament. All constructs were measured at three time points over a 4-year time period. To analyze these panel data, we fitted a covariance structure model that hypothesized simultaneous relationships between initial levels and rates of change in temperament and initial levels and rates of change in schizoid personality disorder. We found that rates of change in the core temperament dimensions studied do not predict rates of change in schizoid personality over time. We discuss the methodological advantages of the latent growth approach and the substantive meaning of the findings for change in schizoid personality disorder.
Reactivity and distortions in the self: Narcissism, types of aggression, and the functioning of the hypothalamic–pituitary–adrenal axis during early adolescence
Authors: Bukowski William M. , Schwartzman Alex , Santo Jonathan , Bagwell Catherine , Adams Ryan
Published: October 2009

A multisample, multistudy project aimed at understanding how individual differences in narcissism during early adolescence are related to distortions in the aggression, and the reactivity of the hypothalamic–pituitary–adrenal axis to negative and positive experiences. The findings indicate that individual differences in narcissism are a remarkably stable aspect of personality during early adolescence. It is predictably related to an inflated view of the self that is not warranted by objective indices of social functioning. Further evidence shows that it promotes the continuity of aggressive behavior and is more strongly related to reactive aggression than to proactive aggression and more strongly related to relational aggression than to physical aggression. Finally, there is evidence that distortions in the self may derive from the inadequate functioning of the hypothalamic–pituitary–adrenal axis, one of the body's main response system for dealing with stress. These findings are discussed in terms of the processes by which early adolescents react to threats and arousal in their daily functioning.
A New Model and its Implications for the Origin of Writing: The La Marche Antler Revisited
Authors: d'Errico Francesco
Published: October 2009

Current models for the origin of writing do not pay sufficient attention to the origin and early development of means adopted by modern humans to record, transmit and process information outside the human body. The present article attempts to fill this gap by elaborating a theoretical model able to classify and describe the variability of these systems. The model is applied to the study of the engraved antler from La Marche, one of the better-known Palaeolithic objects to have been interpreted as an early system of notation. Technical analysis of the marks, through application of a range of experimental criteria, suggests that the sets of marks carved on this object should be interpreted as an artificial memory system with a complex code based on the morphology and the spatial distribution of the engraved marks. These results have important implications for current theories on the origin of writing.
Art and an Archaeology of Embodiment: Some Aspects of Archaic Greece
Authors: Shanks Michael
Published: October 2009

This article seeks to gain an understanding of distinctive changes in certain artefacts produced in Corinth in the late eighth and seventh centuries BC. The focus is the development of figurative imagery on miniature ceramic vessels (many of them perfume jars) which travelled from Corinth particularly to sanctuaries and cemeteries in the wider Greek world. Connections, conceptual and material, are traced through the manufacture and iconography of some 2000 pots, through changing lifestyles, with juxtapositions of contemporary poetry from other parts of the Greek world. Aspects of embodiment are foregrounded in a discussion of stylization and drawing, the character of monstrosity (appearing in ceramic decoration), experiences of risk in battle, discipline and control. Techniques of the self (leading through the floral to wider lifestyles) also feature in this context, together with perfume, and the consumption or deposition of the pots in circumstances of contact with death and divinity. The argument is made that the articulation of an ideological field lay at the core of the changes of the early city states such as Corinth. The article is offered as a contribution to a contextual and interpretive archaeology. It attempts to develop concepts for dealing with power relations in an understanding of material culture production which foregrounds human agency and embodied experience.
Process and Agency in Early State Formation
Authors: Flannery Kent V.
Published: October 2009

Most pristine states formed in the context of competing chiefdoms, when one of the latter succeeded in incorporating its rivals into a larger polity. Some of the processes evident during state formation include chiefly cycling, biased transmission, territorial expansion, and the gaining of competitive advantage. In some archaeological circles, however, it has become fashionable to reject ecological, demographic, and technological processes, and seek agent-based or ideological explanations for state formation. This essay, delivered as the tenth McDonald Lecture, examines five agents who modified ideologies and created states from chiefdoms. It concludes that process and agency are complementary, rather than antithetical, perspectives; thus the latter is unlikely to make the former obsolete.
‘Drinking the Feast’: Alcohol and the Legitimation of Power in Celtic Europe
Authors: Arnold Bettina
Published: October 2009

Drinking and feasting were an integral part of life in Iron Age Europe and the British Isles. The distribution of food and especially drink in prescribed fashion played a key role in establishing and maintaining social relationships. Alcoholic beverages were important consumable status items in prehistoric Europe, serving as a social lubricant as well as a social barrier. The metal, ceramic and wooden vessels required for the preparation, distribution and consumption of these beverages were a vehicle for inter- and intragroup competition, and underwent considerable change, both symbolic and material, through time. This article will attempt a cognitive analysis of the material culture of Iron Age drinking and feasting by integrating archaeological and documentary evidence. The impact of contact with the Mediterranean world, gender configurations, and the ideology of power and patronage will be discussed in relation to changing material culture assemblages.
The Dead Must be Fed: Symbolic Meanings of the Shellmounds of the San Francisco Bay Area
Authors: Luby Edward M. , Gruber Mark F.
Published: October 2009

Long viewed as ‘kitchen middens’, the shellmounds of the San Francisco Bay Area have -provided archaeologists of coastal California insight into the subsistence and ecology of precontact native groups. In this article, the authors develop a framework for understanding the cultural significance of these shellmounds which regards them as intentional cultural features, incorporates social context, and builds on earlier subsistence-focused studies of the shellmounds in order to better appreciate the meaning of the numerous human remains interred therein. A structural analysis is then used to show that the concepts of food and ancestors joined together at shellmounds, so much so that ritual attention to the ancestors was very likely regarded as essential to ensuring a continuing supply of food.
Towards the Reconstruction of Magdalenian Artistic Techniques: the Contribution of Microscopic Analysis of Mobiliary Art
Authors: Fritz Carole
Published: October 2009

On the assumption that Magdalenian mobiliary art is the bearer of certain technical traditions which express cognitive and cultural values, research is directed towards the identification and appreciation of these values through the understanding of techniques involved in bone engraving. Examination of a set of 90 objects from sites in southwest France sheds light on repeated artistic activity and graphic ‘recipes’ which do not appear to be characteristic of local or regional groups. In the sequence of actions as well as in their final product, there is no activity specific to the Ariège as opposed to the Gironde. Magdalenian artists have identical shared artistic procedures.
Sally's Rockshelter and the Archaeology of the Vision Quest
Authors: Whitley David S. , Dorn Ronald I. , Simon Joseph M. , Rechtman Robert , Whitley Tamara K.
Published: October 2009

Quartz, the most common mineral on earth, is almost universally associated with shamans. Why this ritual association occurred worldwide has remained unexplained scientifically, at least in part because western scientific thinking assumes that religious beliefs and practices are epiphenomenal and not worthy of study. This association is archaeologi-cally evident at Sally's Rocksheiter, a small rock engraving-vision quest site in the Mojave Desert, where quartz rocks were placed as offerings in cracks around the rock art panel. SEM and electron microprobe foreign materials analyses of Mojave rock engravings show that the association between quartz and rock art was common: almost 65 per cent contained remnants of quartz hammerstones, used to peck the motifs. A combination of ethnohistory and physical sciences explains why quartz, shamans and vision questing were so strongly associated: triboluminescence causes quartz to glow when struck or abraded, which was believed a visible manifestation of supernatural power. Recognition that this belief and behavioural association were based on quartz's physical properties aids our ability to identify the antiquity of the vision quest in the far west, suggesting that Mojave Desert shamanism is the oldest continuously practiced religious tradition so far identified in the world.
Dietary intake of trans fatty acids as a cardiovascular risk factor in a population of Italian teenagers
Authors: Sofi Francesco , Rapini Daniele , Innocenti Giulia , Abbate Rosanna , Gensini Gian Franco , Casini Alessandro
Published: October 2009

Trans fatty acids are unsaturated fatty acids produced by the partial hydrogenation of polyunsaturated oils. Over the last few years, an increasing interest on these fatty acids has been shown because of their role in the pathogenesis of cardiovascular diseases. To date, major scientific associations strongly recommend consuming a low intake of trans fatty acids for the prevention of cardiovascular diseases, but data on the consumption of these fatty acids in the general population are still lacking. We conducted this observational study on a population of Italian teenagers in order to evaluate the consumption of trans fatty acids in the diet. We studied 81 Italian teenagers, 45 males and 36 females, with a median age of 16 years. To assess their consumption of trans fatty acids, we used the “High School Survey”, a questionnaire prepared by the Harvard Medical School. Total calories of the studied population were 2359.2 ± 591.5 kcal/day with a mean intake of trans fatty acids of 3.24 ± 1.48 g/day, corresponding to 1.23% of the total energy. A relevant proportion of subjects, namely 51 (62.9%), exceeded the limit contribution of 1% of energy from trans fatty acids. Their intake of total calories and trans fatty acids significantly increased according to their increasing age (p = 0.0003 for trend). Our data, therefore, obtained in a limited population of Italian adolescents, showed that a consistent proportion of adolescents does not follow the nutritional recommendations for intake of trans fatty acids, likely increasing their risk of cardiovascular diseases.
Distribution of volcanic earthquake recurrence intervals
Authors: Bottiglieri M. , Godano C. , D'Auria L.
Published: October 2009

We analyze the distribution of volcanic earthquake recurrence intervals in the Vesuvio, Campi Flegrei, and Hawaii regions and compare it with tectonic recurrence rates in California. We find that the distribution behavior is similar for volcanic and tectonic seismic events. In both cases, the recurrence interval distributions collapse onto the same master curve if time is rescaled by the average occurrence rate. This implies that both phenomena have the same temporal organization, and it is possible to adopt for volcanic areas that the same occurrence models used for tectonic regions.
Monte Carlo simulation of superdiffusion and subdiffusion in macroscopically heterogeneous media
Authors: Zhang Yong , LaBolle Eric M. , Pohlmann Karl
Published: October 2009

Monte Carlo simulations are developed to approximate one‐dimensional superdiffusion and subdiffusion in macroscopically heterogeneous media with discontinuous or continuous transport parameters. For superdiffusion characterized by a space fractional (α‐order) derivative model, one empirical reflection scheme is built to track particle trajectory across an interface with discontinuous dispersion coefficient D, where the reflection probability depends on both α and the ratio of D. Different from the superdiffusive case, anomalous diffusion described by a time fractional derivative model can be decomposed into a motion component and a hitting time process, where the discontinuity affects only the motion process, implying an efficient Monte Carlo simulation of decoupled continuous time random walks. The discontinuity of effective porosity n is also discussed, and results show the influence of the ratio of n on solute particle dynamics. In addition, for anomalous superdiffusion and subdiffusion in heterogeneous media with spatially continuous D and n, Langevin analysis reveals that the corresponding particle dynamics contain three independent stable Lévy noises scaled by D, the gradient of D, and the gradient of ln(n). A new implicit Eulerian finite difference method is also developed to solve the spatiotemporal fractional derivative models and then extensively cross verify the Lagrangian solutions. Further testing against one field example of mixed superdiffusion and subdiffusion reveals the applicability and flexibility of the novel Monte Carlo approach in simulating realistic plumes in macroscopically heterogeneous media with locally variable transport parameters.
An approach to estimate nonparametric flow duration curves in ungauged basins
Authors: Ganora D. , Claps P. , Laio F. , Viglione A.
Published: October 2009

A distance‐based regionalization model is developed for the estimation of dimensionless flow duration curves (FDC) in sites with no or limited available data. The curves are dimensionless because they are preliminarily normalized by an index value (e.g., the mean annual runoff). The model aims at representing the FDC as a nonparametric object rather than providing a parametric representation and trying to relate the parameter values to basin descriptors. The regional approach considers the (dis)similarity between all possible pairs of curves and uses distance measures that can be related to basin descriptors, taken among geographic, geomorphologic, and climatic parameters. The (dis)similarity between curves is computed using a predefined metric based on a linear norm and produces a distance matrix. This matrix is then related, by means of linear regression models, to analogous matrices composed of the difference between all possible values of each descriptor within the set of basins. After identification of significant descriptors, a cluster analysis is applied so that the basins can be grouped together. Each region is supposed to be characterized by a single dimensionless flow duration curve. The procedure is applied to 95 basins located in northwestern Italy and Switzerland. The performance in the regional estimation is assessed by means of a cross‐validation procedure through comparison with “standard” parametric regional approaches based on two‐ and three‐parameter models. In most of the cases, the distance‐based model produces better estimates of the flow duration curves using only few catchment descriptors.
Bridging the gap between atmospheric concentrations and local ecosystem measurements
Authors: Lauvaux T. , Gioli B. , Sarrat C. , Rayner P. J. , Ciais P. , Chevallier F. , Noilhan J. , Miglietta F. , Brunet Y. , Ceschia E. , Dolman H. , Elbers J. A. , Gerbig C. , Hutjes R. , Jarosz N. , Legain D. , Uliasz M.
Published: October 2009

This paper demonstrates that atmospheric inversions of CO2 are a reliable tool for estimating regional fluxes. We compare results of an inversion over 18 days and a 300 × 300 km2 domain in southwest France against independent measurements of fluxes from aircraft and towers. The inversion used concentration measurements from 2 towers while the independent data included 27 aircraft transects and 5 flux towers. The inversion reduces the mismatch between prior and independent fluxes, improving both spatial and temporal structures. The present mesoscale atmospheric inversion improves by 30% the CO2 fluxes over distances of few hundreds of km around the atmospheric measurement locations.
Signatures of field‐aligned currents in Saturn's nightside magnetosphere
Authors: Talboys D. L. , Arridge C. S. , Bunce E. J. , Coates A. J. , Cowley S. W. H. , Dougherty M. K. , Khurana K. K.
Published: October 2009

We report first results of a survey of near‐simultaneous and near‐conjugate magnetic field perturbations observed over Saturn's northern and southern nightside auroral regions on ∼40 periapsis passes of the Cassini spacecraft during 2008. Structured azimuthal fields that are generally anti‐symmetric north and south were observed at auroral latitudes on all passes, indicative of the signatures of field‐aligned currents associated with magnetosphere‐ionosphere coupling. Two basic field patterns are discerned. One is associated exclusively with ‘lagging’ fields on high‐latitude field lines in both hemispheres, while the other includes a transition from ‘lagging’ to ‘leading’ fields with decreasing latitude in both hemispheres. The principal field‐aligned currents are found to span the region of the open‐closed field line boundary and the outer magnetosphere/ring current, with the region of upward current, potentially associated with ionospheric auroral emissions, usually being located on closed field lines just equatorward of the boundary.
Transplantation of Human Neural Precursor Cells in Matrigel Scaffolding Improves Outcome from Focal Cerebral Ischemia after Delayed Postischemic Treatment in Rats
Authors: Jin Kunlin , Mao XiaoOu , Xie Lin , Galvan Veronica , Lai Bin , Wang Yaoming , Gorostiza Olivia , Wang Xiaomei , Greenberg David A
Published: October 2009

Transplantation of neural cells is a potential approach for stroke treatment, but disruption of tissue architecture may limit transplant efficacy. One strategy for enhancing the ability of transplants to restore brain structure and function is to administer cells together with biomaterial scaffolding. We electrocoagulated the distal middle cerebral artery in adult rats and, 3 weeks later, injected one of the following into the infarct cavity: artificial cerebrospinal fluid, Matrigel scaffolding, human embryonic stem cell-derived neuronal precursor cells, scaffolding plus cells, or cells cultured in and administered together with scaffolding. Five weeks after transplantation, the latter two groups showed ∼50% and ∼60% reductions, respectively, in infarct cavity volume. Rats given cells cultured in and administered together with scaffolding also showed (1) survival and neuronal differentiation of transplanted cells shown by immunostaining for neuronal marker proteins and cleaved caspase-3, and by patch-clamp recording, 8 weeks after transplantation and (2) improved outcome on tests of sensorimotor and cognitive functions, 4 to 9 weeks after transplantation. These results indicate that transplantation of human neural cells together with biomaterial scaffolding has the potential to improve the outcome from stroke, even when treatment is delayed for several weeks after the ischemic event.
Optical description of solid-state dye-sensitized solar cells. I. Measurement of layer optical properties
Authors: Moulé Adam J. , Snaith Henry J. , Kaiser Markus , Klesper Heike , Huang David M. , Grätzel Michael , Meerholz Klaus
Published: October 2009

The efficiency of a photovoltaic device is limited by the portion of solar energy that can be captured. We discuss how to measure the optical properties of the various layers in solid-state dye-sensitized solar cells (SDSC). We use spectroscopic ellipsometry to determine the complex refractive index of each of the various layers in a SDSC. Each of the ellipsometry fits is used to calculate a transmission spectrum that is compared to a measured transmission spectrum. The complexities of pore filling on the fitting of the ellipsometric data are discussed. Scanning electron microscopy and energy dispersive x-ray spectroscopy is shown to be an effective method for determining pore filling in SDSC layers. Accurate effective medium optical constants for each layer are presented and the material limits under which these optical constants can be used are discussed.
Size-dependent photoconductivity and dark conductivity of m-axial GaN nanowires with small critical diameter
Authors: Chen Hsin-Yi , Chen Reui-San , Chang Fu-Chieh , Chen Li-Chyong , Chen Kuei-Hsien , Yang Ying-Jay
Published: October 2009

The size effects on both the photoconductivity and dark conductivity have been observed in m-axial GaN nanowires grown by chemical vapor deposition (CVD). For these nanowires with diameters at 50–130 nm, the products of carrier lifetime (τ) and mobility (μ) derived from the photocurrent measurements are typically at (2–8)×10−1 cm2/V, which are over two orders of magnitude higher than the maximal reported values [τμ=(1–5)×10−4 cm2/V] for their thin film counterparts. A significant decrease of τμ value at diameter below the critical values (dcrt) at 30–40 nm is observed. Similar size dependence is also found from the dark conductivity study. The temperature-dependent measurements further indicate two different thermal activation mechanisms in GaN nanowires with sizes above and below the dcrt. These results suggest a surface-dominant transport property in GaN nanowires both in dark and under light illumination due to the presence of surface depletion and band bending. Probable reasons leading to the smaller dcrt of the CVD-grown m-axial GaN nanowires, compared to the c-axial ones grown by molecular beam epitaxy are discussed as well.
Stress determination in nickel monosilicide films using x-ray diffraction
Authors: Murray Conal E. , Zhang Zhen , Lavoie Christian
Published: October 2009

Lattice spacing measurements of the (211)/(202), (020)/(013), and (111)/(102) reflections were used to calculate the residual stresses in a Ni monosilicide film after cooling from its formation temperature. The ability to measure stresses in crystalline materials using x-ray diffraction requires the use of appropriate x-ray elastic constants, which link the measured strain to the stress tensor of the grains that satisfy the diffraction condition. X-ray elastic constants were calculated in the Neerfeld–Hill (NH) limit for a polycrystalline aggregate composed of orthorhombic crystals. The anisotropy in grains that possess orthorhombic elasticity introduces significant variation in the stresses determined among the three sets of reflections. However, the in-plane stress calculated due to thermal expansion mismatch between NiSi and the underlying Si substrate shows a close correspondence to the average of x-ray measurements.
Switching current distributions and subgap structures of underdoped (Hg,Re)Ba2Ca2Cu3O8+δ intrinsic Josephson junctions
Authors: Ueda S. , Yamaguchi T. , Kubo Y. , Tsuda S. , Takano Y. , Shimoyama J. , Kishio K.
Published: October 2009

We have investigated the intrinsic Josephson properties in slightly underdoped (Hg,Re)Ba2Ca2Cu3Oy [Hg(Re)1223] intrinsic Josephson junctions (IJJs) with a dimension of 1.0×1.5×0.11 μm3. The current-voltage characteristics of the IJJs exhibit clear multiple branches with subgap structures similar to those of other cuprate superconductors. The switching current distributions P(I) from the zero-voltage to the nonzero-voltage state in the current-biased IJJs agree well with the theoretical curves of the thermally assisted escape model at temperatures above ≈5 K. The plasma frequency fp of the IJJs is estimated to be 1.3 THz from the fluctuation-free critical current density of 2.0×105 A/cm2, which is one of the highest among cuprate superconductors, reflecting the high Tc and a relatively low anisotropy of the Re doped Hg system. The P(I) gradually becomes independent of temperature below ≈5 K, which suggests a crossover of the escape process from thermal activation to quantum tunneling at such a high temperature.
Ferroelectric relaxor behavior and microwave dielectric properties of Ba(Zr0.3Ti0.7)O3 thin films grown by radio frequency magnetron sputtering
Authors: Xu Jin , Zhou Dayu , Menesklou W. , Ivers-Tiffée E.
Published: October 2009

Epitaxial Ba(Zr0.3Ti0.7)O3 thin films were grown by radio frequency magnetron sputtering on (100) MgO substrate. Dielectric measurements at low frequencies (10 Hz–1 MHz) indicate that the material is a ferroelectric relaxor in nature. The temperature dependence of relative permittivity (εr) follows the modified Curie–Weiss law and the frequency dispersion of transition temperature can be described using the Vogel–Fulcher relation. Measured at 100 kHz, the tunability (τ) and figure of merit are comparable to (Ba,Sr)TiO3 thin films. In the microwave frequency region (1–50 GHz), the frequency dependence of permittivity and the loss tan δ (12%–21%) make the Ba(Zr0.3Ti0.7)O3 thin films unfeasible for practical tunable devices.
Dielectric function of hydrogenated amorphous silicon near the optical absorption edge
Authors: Malainho E. , Vasilevskiy M. I. , Alpuim P. , Filonovich S. A.
Published: October 2009

We report the results of the optical spectra modeling for hydrogenated amorphous silicon (a-Si:H) thin films produced for photovoltaic cell applications, which allowed us to accurately determine the material’s optical gap (Eg). While for thick films of a-Si:H, as well as for other amorphous semiconductors, Eg is normally estimated from a so called Tauc plot, this is hardly possible for thin films because of the interference effects. We developed a physically founded semianalytical model for the complex dielectric function of a-Si:H, valid below and above the optical gap and containing a small number of adjustable meaningful parameters, including Eg and the characteristic energy scales of the optical transition matrix element distribution and the joint density of states in the absorption tail region. With this model and using the transfer matrix formalism for multilayer optics, we have achieved a good agreement between the calculated and experimental transmittance spectra, which allowed us to self-consistently determine the values of the above parameters. We found that both Eg and the characteristic scale of the subgap absorption tail increase with the hydrogen addition. We have also determined the absorption rate spectra of the films, relevant to any optical spectroscopy of subgap states, such as the photothermal deflection spectroscopy and constant photocurrent measurements.
Discrete microfluidics: Reorganizing droplet arrays at a bend
Authors: Surenjav Enkhtuul , Herminghaus Stephan , Priest Craig , Seemann Ralf
Published: October 2009

Microfluidic manipulation of densely packed droplet arrangements (i.e., gel emulsions) using sharp microchannel bends was studied as a function of bend angle, droplet volume fraction, droplet size, and flow velocity. Emulsion reorganization was found to be specifically dependent on the pathlength that the droplets are forced to travel as they navigate the bend under spatial confinement. We describe how bend-induced droplet displacements might be exploited in complex, droplet-based microfluidics.
Electro-optic properties of BaTeMo2O9 single crystal
Authors: Gao Zeliang , Yin Xin , Zhang Weiguo , Wang Shanpeng , Jiang Minhua , Tao Xutang
Published: October 2009

The electro-optic (EO) properties of monoclinic BaTeMo2O9 (BTM) single crystals are studied using the interference technique by applying the external electric field. The measured room temperature free EO coefficients at 632.8 nm are 10.2 and 9.0 pm/V for γ12 and γ41, respectively. The EO effect (−12ni3γijE) of BTM is about three times as high as that of KH2PO4 (KDP) crystal, which makes it a very promising candidate for the EO applications.
Tuning the insulator to conductor transition in a multiwalled carbon nanotubes/epoxy composite at substatistical percolation threshold
Authors: Faiella Gabriella , Piscitelli Filomena , Lavorgna Marino , Antonucci Vincenza , Giordano Michele
Published: October 2009

A fine tuning of the electrical conductivity from insulator to conductor behavior has been obtained for a multiwalled carbon nanotubes epoxy composite at a fixed substatistical percolation threshold content by varying the organization of the nanotubes network. A multiscale characterization has been carried out by transmission optical microscopy technique and small angle x-ray analysis that revealed a two level structure characterized by different topological arrangements for the micron sized clusters and nanosized isolated bundles, respectively. A picture of the multidimensional organization of the nanotubes network has been proposed to account for the observed transition modulation.
Dressed electrostatic solitary excitations in three component pair-plasmas: Application in isothermal pair-plasma with stationary ions
Authors: Esfandyari-Kalejahi A. , Akbari-Moghanjoughi M. , Haddadpour-Khiaban B.
Published: October 2009

In this work electrostatic solitary waves in a three component pair-plasma consisting of hot isothermal electrons (or negative fullerene ions), positrons (or positive fullerene ions), and stationary positive ions (say, dust particulates) are studied. Using reductive perturbation method, plasma fluid equations are reduced to a Korteweg–de Vries (KdV) equation. Considering the higher-order nonlinearity, a linear inhomogeneous equation is derived, and the stationary solutions of these coupled equations are achieved by applying the renormalization procedure of Kodama–Taniuti. It is observed that in the linear approximation and applying Fourier analysis, two electrostatic modes, namely, upper or optical and lower or acoustic modes, are present. However, the application of reductive perturbation technique confirms that only acoustic-electrostatic mode can propagate in such plasma as KdV soliton, the amplitude and width of which are studied regarding to plasma parameters σ (positron-to-electron temperature ratio) and δ (stationary cold ions-to-electron density ratio). It is also observed that the higher-order nonlinearity leads to deformation of the soliton structure from bell-shaped to W-shaped depending on the variation in values of the plasma parameters σ and δ. It is revealed that KdV-type solitary waves cannot propagate in three component pair-plasma when the pair-species temperature is equal.
Supramolecular assembly in telechelic polymer blends
Authors: Elliott R. , Fredrickson Glenn H.
Published: October 2009

Equilibrium, supramolecular assembly in melt blends of two species of telechelic polymers with reversible bonding sites at both ends is theoretically investigated. The bonding between polymers, whether between like or dislike chains, is controlled by affinities of chain bonding set by specified bond energies. Low affinities, or low overall bond strength, results in a monodisperse population of unlinked chains while larger affinities cause longer chains to assemble, forming a polydisperse blend. We investigate sequentially blends with only homobonding (like chain), only heterobonding (dislike chain), and finally a mixed homo- and heterobonding melt. In the first case, the effects of longer chain assembly and polydispersity in a homogeneous melt and its bulk demixing transition are explored. In contrast with the homobonding case, large heterobonding affinities cause alternating blocks to assemble into multiblock copolymers, which can lead to mesophases. The weak bonding region between bulk phase separation and mesophase stability is investigated and a novel Lifshitz point is found indicating a region prone to emulsify. Mixed homo- and heterobonding systems are also examined. Polymeric segments of both species are modeled as flexible Gaussian threads and nonspecific interactions between dissimilar blocks are contactlike Flory–Huggins repulsions. The melts are assumed to be incompressible and all calculations are carried out within mean-field theory. A new integral equation formalism is developed for enumerating all linear species in these complex supramolecular systems, and the random phase approximation and numerical self-consistent field theory are invoked in this context to map out a variety of phase diagrams.
van der Waals forces: Accurate calculation and assessment of approximate methods in dielectric nanocolloids up to 16 nm
Authors: Kim Hye-Young , Kent P. R. C.
Published: October 2009

A microscopic method is used to calculate the van der Waals (VDW) forces between large nanocolloids. We assess the reliability of predictions derived from the most commonly used macroscopic method in practice, the Dzyaloshinskii–Lifshitz–Pitaevskii (DLP) theory combined with the Derjaguin approximation, by calculating the VDW interactions using the “coupled dipole method” (CDM). The CDM, which has demonstrated its ability to calculate VDW interactions for small nanoclusters, accounts for all many-body forces, and it does not assume a continuous, homogeneous dielectric function in each material. It is shown that, out of three explored, one of the routinely assumed properties (“small-separation dominance”) of VDW forces predicted from the macroscopic method is generally applicable for large spherical dielectric nanoclusters of diameter 16 nm allowing much more efficient CDM calculations. The failure of two other routinely assumed properties, “infinite-depth approximation” and “sphere-cube analogy,” demonstrates that the effect of finite-size and shape is important in nanocolloid systems even at the large size of 16 nm.
Monte Carlo simulations for amphiphilic aggregation near a water phase transition
Authors: Heinzelmann G. , Figueiredo W. , Girardi M.
Published: October 2009

In this study we analyze the equilibrium and dynamical properties of a lattice model for amphiphilic aggregation in a waterlike associating solvent. The amphiphiles are described as flexible chains of interconnected sites in a body-centered cubic lattice, with hydrophilic and hydrophobic portions. The solvent molecules occupy a single site and resemble the water tetrahedral molecular structure, with the possibility of hydrogen-bond formation and different densities. Following the phase diagram of the solvent model, we are able to study the effects of a phase transition of the solvent in the micellar dynamics. By carrying out Monte Carlo simulations, we analyze the micelle aggregate size distribution curve, the critical micelle concentration, the surfactant diffusion coefficient, the residence time, and the exit/entering rates of the amphiphiles from/to aggregates of different sizes. We also investigate the dipolar reorientational time correlation function for interfacial water and water molecules in the solvent bulk, as well as the number of hydrogen bonds per molecule in both cases.
Giant lateral photovoltaic effect observed in TiO2 dusted metal-semiconductor structure of Ti/TiO2/Si
Authors: Yu Chong Qi , Wang Hui , Xia Yu Xing
Published: October 2009

A greatly enhanced lateral photovoltaic effect is observed in superthin TiO2 dusted Ti/TiO2/Si structures. The considerably large sensitivity of 113 mV/mm obtained in this structure is nearly twice as much as the highest record of about 60 mV/mm reported in other structures and constitutes a sharp contrast to that of 32 mV/mm in control sample of Ti/Si. This phenomenon betrays the general understanding that the oxide layer at interface between the metal and semiconductor always deteriorates the formation of lateral photovoltage in metal-semiconductor structure. We ascribe it to the enhancement of interference as electrons tunnel through this superthin TiO2 layer.
Nature of the lowest excited states of neutral polyenyl radicals and polyene radical cations
Authors: Starcke Jan Hendrik , Wormit Michael , Dreuw Andreas
Published: October 2009

Due to the close relation of the polyenyl radicals C2n+1H2n+3• and polyene radical cations C2nH2n+2•+ to the neutral linear polyenes, one may suspect their excited states to possess substantial double excitation character, similar to the famous S1 state of neutral polyenes and thus to be equally problematic for simple excited state theories. Using the recently developed unrestricted algebraic-diagrammatic construction scheme of second order perturbation theory and the equation-of-motion coupled-cluster method, the vertical excitation energies, their corresponding oscillator strengths, and the nature of the wave functions of the lowest excited electronic states of the radicals are calculated and analyzed in detail. For the polyenyl radicals two one-photon allowed states are found as D1 and D4 states, with two symmetry-forbidden D2 and D3 states in between, while in the polyene radical cations D1 and D2 are allowed and D3 is forbidden. The order of the states is conserved with increasing chain length. It is found that all low-lying excited states exhibit a significant but similar amount of doubly excited configuration in their wave functions of 15%–20%. Using extrapolation, predictions for the excitation energies of the five lowest excited states of the polyene radical cations are made for longer chain lengths.
Strong surface Fermi level pinning and surface state density in GaAs0.65Sb0.35 surface intrinsic-n+ structure
Authors: Lin K. I. , Lin H. C. , Tsai J. T. , Cheng C. S. , Lu Y. T. , Hwang J. S. , Chiu P. C. , Chen S. H. , Chyi J. I. , Wang T. S.
Published: October 2009

Room-temperature photoreflectance is employed to investigate the Fermi level pinning and surface state density of a GaAs0.65Sb0.35 surface intrinsic-n+ (SIN+) structure. Based on the thermionic emission theory and current-transport theory, the surface Fermi level VF and surface state density are determined experimentally from the dependence of the surface barrier height on the pump beam intensity. The surface state density Ds is estimated as approximately 1.91×1013 cm−2, and the Fermi level is located 0.63 eV below the conduction band edge at the surface. By sequential etching of the intrinsic layer, the Fermi level pinning in GaAs0.65Sb0.35 SIN+ structure is further demonstrated.
Chemistry at the graphene-SiO2 interface
Authors: Hossain M. Zubaer
Published: October 2009

The structure and energetics and the chemistry of graphene on SiO2 surface are studied from first-principles. It is found that the energetic preference for the graphene layer to bind on specific sites on the O-terminated surface differs substantially from that on the Si-terminated surface. Regardless of the location of binding sites on a particular surface, electrons transfer from the graphene layer to the dielectric surface and its quantity is higher for the O-terminated surface. In addition, the electron transfer strongly depends on the type of surface termination but is independent of the binding site.
Nonvolatile resistive switching in spinel ZnMn2O4 and ilmenite ZnMnO3
Authors: Peng Haiyang , Wu Tom
Published: October 2009

We report that spinel ZnMn2O4 and ilmenite ZnMnO3 show excellent unipolar resistive switching behaviors, with ON/OFF ratios larger than 104. For both oxides, retention of more than 10 h and good endurance are achieved. Conduction of the OFF state is dominated by the space-charge-limited conduction mechanism, while the Ohmic behavior dictates the ON state, which suggests a filamentary conduction mechanism. Our study introduces two promising materials candidates for nonvolatile resistive random access memory devices, and furthermore it suggests that formation and rupture of conducting filaments are universal in certain ternary oxides even though they may possess distinct crystalline structures.
Very low surface recombination velocity on p-type c-Si by high-rate plasma-deposited aluminum oxide
Authors: Saint-Cast Pierre , Kania Daniel , Hofmann Marc , Benick Jan , Rentsch Jochen , Preu Ralf
Published: October 2009

Aluminum oxide layers can provide excellent passivation for lowly and highly doped p-type silicon surfaces. Fixed negative charges induce an accumulation layer at the p-type silicon interface, resulting in very effective field-effect passivation. This paper presents highly negatively charged (Qox=−2.1×1012 cm−2) aluminum oxide layers produced using an inline plasma-enhanced chemical vapor deposition system, leading to very low effective recombination velocities (∼10 cm s−1) on low-resistivity p-type substrates. A minimum static deposition rate (100 nm min−1) at least one order of magnitude higher than atomic layer deposition was achieved on a large carrier surfaces (∼1 m2) without significantly reducing the resultant passivation quality.
Nanowires formation and the origin of ferromagnetism in a diluted magnetic oxide
Authors: Vidal F. , Zheng Y. , Milano J. , Demaille D. , Schio P. , Fonda E. , Vodungbo B.
Published: October 2009

The ferromagnetic response from Co-doped CeO2 epilayers is shown to be linked to the formation of Co metallic nanowires (diameters in the 3–7 nm range) within the oxide matrix. These results (i) illustrate the key role of the shape anisotropy of metallic inclusions in diluted magnetic oxides (DMO), (ii) stress the importance to monitor the out-of-plane response of DMO, and (iii) suggest that some dilute systems previously thought to be intrinsic ferromagnet may be reexamined.