bluuebunny/crossref_metadata_2025 huggingface dataset:
Behavioral manipulation of host caterpillars by the primary parasitoid waspCotesia glomerata(L.) to construct defensive webs against hyperparasitism
Authors: Tanaka Shingo , Ohsaki Naota
Published: February 2006

Many parasitoids control the behavior of their hosts to achieve more preferable conditions. Decreasing predation pressure is a main aim of host manipulation. Some parasitoids control host behavior to escape from their enemies, whereas others manipulate hosts into constructing defensive structures as barriers against hyperparasitism. Larvae of the parasitoid waspCotesia glomerataform cocoon clusters after egression from the parasitized host caterpillar of the butterflyPieris brassicae. After the egression of parasitoids, the perforated host caterpillar lives for a short period and constructs a silk web that covers the cocoon cluster. We examined whether these silk webs protectC. glomeratacocoons against the hyperparasitoid waspTrichomalopsis apanteroctena. In cocoon clusters that were not covered by silk webs (“bare” clusters), only cocoons hidden beneath others avoided hyperparasitism. In covered cocoon clusters, both cocoons hidden beneath others and those with a space between them and the silk web avoided hyperparasitism, whereas cocoons that contacted the silk webs were parasitized. The frequency of cocoons that were hidden beneath others increased with the increasing number of cocoons in a cluster, but the defensive effect of cluster size was thought to be lower than that of silk webs. However, the rate of hyperparasitism did not differ between covered and bare clusters when we allowed the hyperparasitoids to attack the cocoon clusters in an experimental arena. This result was thought to have been caused by low oviposition frequency by these hyperparasitoids. As a result, silk webs did not guard the cocoons from hyperparasitoids in our experiments, but would protect cocoons under high hyperparasitism pressure by forming a space through which the ovipositors could not reach the cocoons.
Measuring nigrescence attitudes in school‐aged adolescents☆
Authors: Gardner‐Kitt Donna L. , Worrell Frank C.
Published: February 2006

In this study, we examined the reliability and validity of Cross Racial Identity Scale (CRIS; Vandiver, B. J., Cross Jr., W. E., Fhagen‐Smith, P. E., Worrell, F. C., Swim, J. K., & Caldwell, L. D. (2000). The Cross Racial Identity Scale. Unpublished scale; Worrell, F. C., Vandiver, B. J., & Cross Jr., W. E., (2004). The Cross Racial Identity Scale: Technical manual (2nd ed.). Berkeley, CA: Author) scores in 143 middle and high school students. Exploratory factor analyses provided support for the six‐factor structure of the CRIS, reliability estimates for the scores were in the moderate to high range, and subscale intercorrelations were low. Multicultural Inclusive scores were significantly correlated with age with high school students reporting significantly higher multicultural attitudes than middle school students. The authors concluded that the CRIS is appropriate for use with adolescent populations.
Accuracy and precision of fish-count data from a “dual-frequency identification sonar” (DIDSON) imaging system
Authors: Holmes John A. , Cronkite George M.W. , Enzenhofer Hermann J. , Mulligan Timothy J.
Published: February 2006

The reliability of sockeye-salmon (Oncorhynchus nerka) count data collected by a dual-frequency, identification sonar (DIDSON) system is evaluated on the basis of comparisons with visual counts of unconstrained migrating salmon and visual counts of salmon constrained to passing through an enumeration fence. Regressions fitted to the DIDSON count data and the visual count data from the enumeration fence were statistically indistinguishable from a line with slope = 1.0 passing through the origin, which we interpret as agreement in both counts. In contrast, the regressions fitted to the DIDSON count data and the unconstrained visual count data had slopes that were significantly <1.0 (p < 0.001) and are consistent with an interpretation of systematic bias in these data. When counts of both unconstrained and constrained fish from the DIDSON system were ≥50 fish event−1, repeated counts of the DIDSON files were observed to produce the same counts 98–99% of the time, respectively, and based on the coefficient of variation, counts of individual passage events varied <3% on average. Therefore, the DIDSON count data exhibit high precision among different observers. As an enumeration fence provides a complete census of all fish passing through it, we conclude that fish-count data produced by the DIDSON imaging system are as accurate as visual counts of fish passing through an enumeration fence when counts range up to 932 fish event−1, the maximum count recorded during our study, regardless of the observer conducting the count. These conclusions should be applicable to typical riverine applications of the DIDSON system in which the bottom and surface boundaries are suitable for acoustic imaging, the migrating fish are adult salmon, and the transducer is carefully aimed so that the beams ensonify the area through which the salmon are migrating.
Evidence of a variable “unsampled” pelagic fish biomass in shallow water (<20 m): the case of the Gulf of Lion
Authors: Brehmer P. , Guillard J. , Guennégan Y. , Bigot J.L. , Liorzou B.
Published: February 2006

Studies of small pelagic fish biomass are limited by the fact that research vessels and fishing boats are usually restricted to working areas with a bottom depth >20 m. Consequently, “unsampled” areas can represent a large proportion of the continental shelf, and the biomass in those areas can be important and must be taken into account in assessment methods in order to avoid misleading interpretations in population dynamics. A time-series ten years long has been compiled from acoustic-assessment surveys of small pelagic fish stocks, and the results show an overall increase in the acoustic fish density towards the coast, where values were the highest. Additional experiments on transects covering shallow-water areas (5–20 m) were conducted from 2001 to 2003 with small boats and a research vessel to evaluate the acoustic fish density in those areas. The results confirmed that the fish biomass in shallow water is significant, sometimes very large, and should be evaluated to avoid underestimation. Therefore, surveys should be conducted in shallow water, if at all possible, as well as at greater depths when carrying out surveys destined to support assessment exercises.
Fisheries biology of a short-lived tropical species: Gerres longirostris (Lacépède, 1801) in the Arabian Gulf
Authors: Grandcourt E.M. , Al Abdessalaam T.Z. , Francis F. , Al Shamsi A.T.
Published: February 2006

The population dynamics and reproductive biology of Gerres longirostris were investigated in order to evaluate the impact of fishing on a relatively small, short-lived species with demographic attributes that contrast with other species that have been studied in the region. Well-defined alternating translucent and opaque bands in sagittal otoliths were validated as annuli and used to estimate age. Size-at-age relationships were highly asymptotic, most growth being achieved by the second year. Estimated maximum absolute age was 7.4 years. There were significant differences in the growth trajectories between sexes, females growing faster and to a larger maximum size than males. Spawning was between April and August, and the mean sizes and ages at first sexual maturity were 16.3 cm LF (1.1 years) for males and 20.6 cm LF (1.5 years) for females. The rate of fishing mortality (F = 0.32) approximated the optimum level (Fopt = 0.29), and was within the limit (Flimit = 0.38) biological reference point, indicating that the resource is exploited at an appropriate rate. Nevertheless, given that an independent assessment suggested that annual yields only represented 10% of the total biomass, it appears that even short-lived, fast-growing tropical species should have conservative harvest rates.
Contribution of inflammatory processes to Alzheimer's disease: molecular mechanisms
Authors: Sastre Magdalena , Klockgether Thomas , Heneka Michael T.
Published: February 2006

There is compelling evidence that Alzheimer's disease (AD) amyloid‐β (Aβ) deposition is associated with a local inflammatory response, which is initiated by the activation of microglia and the recruitment of astrocytes. These cells secrete a number of cytokines and neurotoxic products that may contribute to neuronal degeneration and cell death. It has been documented that long‐term intake of non‐steroidal anti‐inflammatory drugs (NSAIDs) decrease the risk for developing AD and delay the onset of the disease. The mechanism behind these NSAIDs is still controversial and several hypotheses have been raised, including changes in the amyloid precursor protein (APP) metabolism, in Aβ aggregation and a decrease in inflammatory mediators. Recently, it was proposed that some NSAIDs might activate the peroxisome proliferator‐activated receptor‐γ (PPAR‐γ). PPAR‐γ belongs to a family of nuclear receptors that are able to regulate the transcription of pro‐inflammatory molecules, such as iNOS. The activation of PPAR‐γ has been recently reported to reduce Aβ levels in cell culture and AD animal models. The implication of PPAR‐γ in the control of Aβ‐induced inflammation suggests a new target for AD therapy and emphasize the contribution of neuroinflammatory mechanisms to the pathogenesis of AD.
Introduction
Authors: Regev Motti
Published: February 2006

How does one tell the history of an art form? Looking at classic examples like Gombrich's The Story of Art (London, Phaidon Press, 1950) or Read's A Concise History of Modern Painting (London, Thames and Hudson, 1959), it seems that, at their core, such projects conventionally consist of annotated lists: extended commentaries on a long line of works and artists, in other words a canon. These works are typically presented as peaks of the aesthetic power of the art form in question, as ultimate manifestations of aesthetic perfection, complexity of form and depth of expression which humans are capable of reaching through this art form. Such presentations hide an implicit promise that, with proper knowledge, encounters with these works will result in extraordinary experiences.
‘On herself and all her property’: women's economic activities in late-medieval Ghent
Authors: HUTTON SHENNAN
Published: February 2006

This article analyses the economic activities of urban Flemish women in actual practice, using contracts and court judgements from the mid-fourteenth-century registers of the aldermen of Ghent. These ‘acts’ show that women routinely invested and managed their own property without male representatives and that distinctions of marital status were often far less significant in medieval Ghent than elsewhere in northern Europe. Another conceptualization of the scope of women's economic activity also existed at the time, in which men acted for women, but it was not the dominant norm in mid-fourteenth-century Ghent.
PDE based determination of piezoelectric material tensors
Authors: KALTENBACHER BARBARA , LAHMER TOM , MOHR MARCUS , KALTENBACHER MANFRED
Published: February 2006

The exact numerical simulation of piezoelectric transducers requires the knowledge of all material tensors that occur in the piezoelectric constitutive relations. To account for mechanical, dielectric and piezoelectric losses, the material parameters are assumed to be complex. The issue of material tensor identification is formulated as an inverse problem: As input measured impedance values for different frequency points are used, the searched-for output is the complete set of material parameters. Hence, the forward operator F mapping from the set of parameters to the set of measurements, involves solutions of the system of partial differential equations arising from application of Newton's and Gauss' law to the piezoelectric constitutive relations. This, via two or three dimensional finite element discretisation, leads to an indefinite system of equations for solving the forward problem. Well-posedness of the infinite dimensional forward problem is proven and efficient solution strategies for its discretized version are presented. Since unique solvability of the inverse problem may hardly be verified, the system of equations we have to solve for recovering the material tensor entries can be rank deficient and therefore requires application of appropriate regularisation strategies. Consequently, inversion of the (nonlinear) parameter-to-measurement map F is performed using regularised versions of Newton's method. Numerical results for different piezoelectric specimens conclude this paper.
Anxiety in Patients Who Have Had a Myocardial Infarction: The Maintaining Role of Perceived Physical Sensations and Causal Attributions
Authors: Ratcliffe Denise , MacLeod Andrew , Sensky Tom
Published: February 2006

This study investigated whether anxiety in patients who have had a myocardial infarction is maintained through similar processes to those proposed in the cognitive models of panic disorder (Clark, 1986) and health anxiety (Warwick and Salkovskis, 1990). Anxious (n = 22) and non-anxious (n = 29) patients, who all had an MI 3–12 months before testing, participated. The groups were compared on self-report measures of risk perception, bodily vigilance, illness perceptions the type of causal attributions (somatic, normalizing and psychological) generated for congruent and incongruent types of anxiety-related bodily sensations (cardiac, respiratory, gastro-intestinal and cognitive dyscontrol). Anxious, compared to non-anxious, MI participants perceived themselves to be at higher risk of a further MI, had higher levels of bodily vigilance and more negative emotional and cognitive representations of their MI. Anxious participants generated significantly more somatic attributions and fewer normalizing attributions, than non-anxious participants for cardiac sensations. There was also a trend for anxious participants to generate this pattern of attributions for respiratory items. The study provides evidence that the models of health anxiety (Warwick and Salkovskis, 1990) and panic disorder (Clark, 1986) are useful in understanding persistent anxiety following an MI.
GINS, a central nexus in the archaeal DNA replication fork
Authors: Marinsek Nina , Barry Elizabeth R , Makarova Kira S , Dionne Isabelle , Koonin Eugene V , Bell Stephen D
Published: February 2006

In eukaryotes, the GINS complex is essential for DNA replication and has been implicated as having a role at the replication fork. This complex consists of four paralogous GINS subunits, Psf1, Psf2, Psf3 and Sld5. Here, we identify an archaeal GINS homologue as a direct interaction partner of the MCM helicase. The core archaeal GINS complex contains two subunits that are poorly conserved homologues of the eukaryotic GINS subunits, in complex with a protein containing a domain homologous to the DNA‐binding domain of bacterial RecJ. Interaction studies show that archaeal GINS interacts directly with the heterodimeric core primase. Our data suggest that GINS is important in coordinating the architecture of the replication fork and provide a mechanism to couple progression of the MCM helicase on the leading strand with priming events on the lagging strand.
Finite-size effects in dissipative particle dynamics simulations
Authors: Velázquez María Eugenia , Gama-Goicochea Armando , González-Melchor Minerva , Neria Maricela , Alejandre José
Published: February 2006

We have performed dissipative particle dynamics (DPD) simulations to evaluate the effect that finite size of transversal area has on stress anisotropy and interfacial tension. The simulations were carried out in one phase and two phases in parallelepiped cells. In one-phase simulations there is no finite-size effect on stress anisotropy when the simulation is performed using repulsive forces. However, an oscillatory function of stress anisotropy is found for attractive-repulsive interactions. In the case of liquid-liquid interfaces with repulsive interaction between molecules, there is only a small effect of surface area on interfacial tension when the simulations are performed using the Monte Carlo method at constant temperature and normal pressure. An important but artificial finite-size effect of interfacial area on surface tension is found in simulations in the canonical ensemble. Reliable results of interfacial tension from DPD simulations can be obtained using small systems, less than 2000 particles, when they interact exclusively with repulsive forces.
Cluster kinetics of pressure-induced glass formation
Authors: Brenskelle Lisa A. , McCoy Benjamin J.
Published: February 2006

A prior correlation model for glass formation based on cluster-size distribution kinetics is here extended to account for pressure effects as well as temperature effects. The model describes how rapidly cooling or compressing a liquid or colloid leads to structural arrest and a consequent sharp rise in viscosity or dielectric relaxation time. In addition to activation energies, we include activation volumes in the rate coefficients for monomer-cluster addition and dissociation and cluster aggregation and breakage. The approach leads to scaled pressure correlations and plots for viscosity that reveal strong and fragile glass behavior, and agree with experimental data. A simple relationship among viscosity, attractive interparticle energy, and particle volume fraction displays how hard spheres with attractive forces can vitrify at small particle densities.
Calculation of absorption spectra for light-harvesting systems using non-Markovian approaches as well as modified Redfield theory
Authors: Schröder Markus , Kleinekathöfer Ulrich , Schreiber Michael
Published: February 2006

For an ensemble of B850 rings of the light-harvesting system LH2 of purple bacteria the linear absorption spectrum is calculated. Using different Markovian and non-Markovian, time-dependent and time-independent methods based on second-order perturbation theory in the coupling between the excitonic system and its surrounding environment as well as the modified Redfield theory, the influence of the shape of the spectral density on the linear absorption spectrum is demonstrated for single samples and in the ensemble average. For long bath correlation times non-Markovian effects clearly show up in the static absorption line shapes. Among the different spectral densities studied is one of the purple bacterium Rhodospirillum molischianum obtained by a molecular-dynamics simulation earlier. The effect of static disorder on its line shapes in the ensemble average is analyzed and the results of the present calculations are compared to experimental data.
Ionization in strong electric fields and dynamics of nanosecond-pulse plasmas
Authors: Macheret S. O. , Shneider M. N. , Murray R. C.
Published: February 2006

The paper describes experimental and computational studies of weakly ionized air plasmas sustained by high repetition rate high-voltage nanosecond pulses. The experimentally determined energy cost per newly produced electron in these diffuse volumetric plasmas is on the order of 100eV, two orders of magnitude lower than in diffuse quasineutral dc and rf plasmas, and close to that in the cathode sheaths of glow discharges. Modeling of plasma dynamics in high-voltage nanosecond pulses yielded the energy cost of ionization in good agreement with the experimental values. Both experiments and modeling revealed that the ionization cost per electron in these plasmas is relatively insensitive to the gas density. Detailed investigations of the plasma dynamics revealed a critical role of the thin cathode sheath that was found to take up most of the peak voltage applied to the electrodes. The extremely high values of the ratio of electric field strength to the gas number density (E∕N), much higher than the Stoletov’s field at the Paschen minimum point, result in a very high ionization cost in the sheath. In contrast, the value of E∕N in the quasineutral plasma is closer to that associated with the Stoletov’s point, resulting in a near-optimal electron generation. This behavior (the reversal of ionization efficiencies in the sheath and in the plasma) is opposite to that in conventional glow discharges. The positive space charge in the sheath and its relatively slow relaxation due to the low ion mobility was also found to result in reversal of electric field direction in the plasma at the tail of the high-voltage pulse.
Coupled-cluster theory in a projected atomic orbital basis
Authors: Christiansen Ove , Manninen Pekka , Jørgensen Poul , Olsen Jeppe
Published: February 2006

We present a biorthogonal formulation of coupled-cluster (CC) theory using a redundant projected atomic orbital (PAO) basis. The biorthogonal formulation provides simple equations, where the projectors involved in the definition of the PAO basis are absorbed in the integrals. Explicit expressions for the coupled-cluster singles and doubles equations are derived in the PAO basis. The PAO CC equations can be written in a form identical to the standard molecular orbital CC equations, only with integrals that are related to the atomic orbital integrals through different transformation matrices. The dependence of cluster amplitudes, integrals, and correlation energy contributions on the distance between the participating atomic centers and on the number of involved atomic centers is illustrated in numerical case studies. It is also discussed how the present reformulation of the CC equations opens new possibilities for reducing the number of involved parameters and thereby the computational cost.
Rheological and structural studies of linear polyethylene melts under planar elongational flow using nonequilibrium molecular dynamics simulations
Authors: Baig C. , Edwards B. J. , Keffer D. J. , Cochran H. D. , Harmandaris V. A.
Published: February 2006

We present various rheological and structural properties of three polyethylene liquids, C50H102, C78H158, and C128H258, using nonequilibrium molecular dynamics simulations of planar elongational flow. All three melts display tension-thinning behavior of both elongational viscosities, η1 and η2. This tension thinning appears to follow the power law with respect to the elongation rate, i.e., η∼ε̇b, where the exponent b is shown to be approximately −0.4 for η1 and η2. More specifically, b of η1 is shown to be slightly larger than that of η2 and to increase in magnitude with the chain length, while b of η2 appeared to be independent of the chain length. We also investigated separately the contribution of each mode to the two elongational viscosities. For all three liquids, the intermolecular Lennard-Jones (LJ), intramolecular LJ, and bond-stretching modes make positive contributions to both η1 and η2, while the bond-torsional and bond-bending modes make negative contributions to both η1 and η2. The contribution of each of the five modes decreases in magnitude with increasing elongation rate. The hydrostatic pressure shows a clear minimum at a certain elongation rate for each liquid, and the elongation rate at which the minimum occurs appears to increase with the chain length. The behavior of the hydrostatic pressure with respect to the elongation rate is shown to correlate with the intermolecular LJ energy from a microscopic viewpoint. On the other hand, ⟨Rete2⟩ and ⟨Rg2⟩ appear to be correlated with the intramolecular LJ energy. The study of the effect of the elongational field on the conformation tensor c̃ shows that the degree of increase of tr(c̃)−3 with the elongation rate becomes stronger as the chain length increases. Also, the well-known linear reaction between σ and c̃ does not seem to be satisfactory. It seems that a simple relation between σ and c̃ would not be valid, in general, for arbitrary flows.
Acoustoelectric Y-branch switch
Authors: Talyanskii V. I. , Graham M. R. , Beere H. E.
Published: February 2006

We report an experimental realization of an acoustoelectric Y-branch current switch. A “Y”-shaped mesa configuration with one source and two drain terminals is formed in a GaAs quantum well, which is free of carriers. A surface acoustic wave extracts electrons from the source contact and drives them in the form of packets residing in the wave’s potential minima toward the branching point, where applied voltages on controlling side gates distribute the current between the branches. We discuss the application of the switch as a fast electrometer with sensitivity at the subelectron level.
Effect of SiO2 incorporation on stability and work function of conducting MoO2
Authors: Liang Y. , Tracy C. , Weisbrod E. , Fejes P. , Theodore N. D.
Published: February 2006

We show the incorporation of different amounts of SiO2 in conducting MoO2 results in materials that have large vacuum work functions tunable by approximately 1eV and improved thermal stability at elevated temperatures. Electrical measurements of MoSixOy∕HfO2∕SiOx∕n-Si capacitors show an approximate 5.1eV work function, suitable for p-channel metal-oxide-semiconductor devices. . Thickening of the interfacial SiOx layer was observed, however, after annealing the stack at higher temperatures in N2.
Optical charge transfer absorption in lithium-intercalated tungsten oxide thin films
Authors: Berggren Lars , Niklasson Gunnar A.
Published: February 2006

Amorphous tungsten oxide exhibits electrochromism when intercalated with protons or lithium ions. Thin films of the material were prepared by dc magnetron sputtering and subsequently electrochemically intercalated with lithium. The optical absorption in the wavelength range 300to2500nm was measured for a number of lithium concentrations. All the spectra can be fitted by a superposition of three Gaussian peaks, representing the three possible electronic transitions between W6+, W5+, and W4+ sites. The variation of the peak strength with lithium concentration is consistent with the predictions of a statistical theory.
Origami fabrication of nanostructured, three-dimensional devices: Electrochemical capacitors with carbon electrodes
Authors: In Hyun Jin , Kumar Sundeep , Shao-Horn Yang , Barbastathis George
Published: February 2006

The Nanostructured Origami™ process consists of patterning a two-dimensional (2-D) membrane with desired micro- and nanoscale features and then folding it into a three-dimensional (3-D) configuration. Electrochemical capacitors, or supercapacitors, are ideal for origami fabrication because their performance can be enhanced through the use of 3-D geometry and nanostructured materials. A supercapacitor with an electrode area of 350×350μm was created using the origami process and characterized using electrochemical analysis methods. The experimentally measured capacitance values of approximately 1μF are consistent with theoretical predictions.
Solvent effect of inkjet printed source/drain electrodes on electrical properties of polymer thin-film transistors
Authors: Lim Jung Ah , Cho Jeong Ho , Park Yeong Don , Kim Do Hwan , Hwang Minkyu , Cho Kilwon
Published: February 2006

We show that the electrical properties of polymer thin-film transistors (PTFTs) can be enhanced by controlling the solvent properties of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT/PSS) solution used as the inkjet-printed source and drain electrodes. Specifically, addition of dimethyl sulfoxide (DMSO) into the PEDOT/PSS solution increased the conductivity of the inkjet-printed PEDOT electrodes and remarkably reduced the contact resistance of the electrodes. The lower contact resistance of the DMSO-treated PEDOT electrode compared to the corresponding electrode without DMSO treatment may be due to enhanced interfacial stability at the contact between the printed PEDOT electrodes and the semiconductor layers.
Optimization of precursor pulse time in improving bulk trapping characteristics of atomic-layer-deposition HfO2 gate oxides
Authors: Akbar Mohammad S. , Lee Jack C. , Moumen Naim , Peterson Jeff
Published: February 2006

We report that precursor HfCl4 plays an important role in optimizing atomic-layer-deposition HfO2 bulk trapping characteristics. By systematic study, it has been observed that, under certain optimized precursor pulse time condition (450ms pulse as compared to standard 150ms), bulk trapping characteristics could be improved significantly without affecting the equivalent oxide thickness and leakage current characteristics of the devices. Slight improvement in mobility of the devices could also be obtained. Secondary-ion-mass-spectroscopy analysis shows that increase in the chlorine composition by increasing precursor pulse time could be attributed to the observed improvement. Drastic increase in pulse time (1500ms) negates the benefit.
Retention loss phenomena in hydrothermally fabricated heteroepitaxial PbTiO3 films studied by scanning probe microscopy
Authors: Ahn W. S. , Jung W. W. , Choi S. K. , Cho Yasuo
Published: February 2006

We observed the retention loss phenomena of the nanodomains with an average diameter of 36nm and that of the square domains with a size of 1 and 25μm2 that were reversed by an applying electric field at an atomic force microscopy conductive tip in a heteroepitaxial PbTiO3 thin film, which was fabricated via hydrothermal epitaxy below Curie temperature, TC. While the nanodomains did not undergo significant retention loss until 5.3×106s, the square domains revealed some retention loss for a fixed period after long latent periods. The observed phenomena were explained in terms of the instability of the curved c∕c domain wall and the compressive strain energy. Analyses showed that the nanodomains composed a cylinder extending to the bottom electrode; however, the square domains had a curved c∕c domain wall, including the compressive strain energy, and these factors caused the retention loss.
Posterior α activity is not phase-reset by visual stimuli
Authors: Mazaheri Ali , Jensen Ole
Published: February 2006

There is currently a debate as to whether event-related potentials and fields measured by using electroencephalography or magnetoencephalography are generated by ongoing oscillatory activity becoming phase-reset in response to a given stimulus. We performed a magnetoencephalography study measuring brain activity in response to visual stimuli. Using a measure termed the phase-preservation index we investigated the phase of oscillatory α activity (8–13 Hz) before and after the stimulus. We found that in single trials the α oscillations after visual stimuli preserve their phase relationship with respect to the phase before the stimuli. This finding argues against phase-resetting of ongoing oscillations as being responsible for visually evoked responses. The event-related field can be explained primarily by stimulus-locked activity in the θ band that is absent before the stimulus. These findings suggest that different neuronal events are responsible for generating the ongoing oscillations and the visually evoked responses.
A macroporous hydrogel for the coculture of neural progenitor and endothelial cells to form functional vascular networks
in
vivo
Authors: Ford Millicent C. , Bertram James P. , Hynes Sara Royce , Michaud Michael , Li Qi , Young Michael , Segal Steven S. , Madri Joseph A. , Lavik Erin B.
Published: February 2006

A microvascular network is critical for the survival and function of most tissues. We have investigated the potential of neural progenitor cells to augment the formation and stabilization of microvascular networks in a previously uncharacterized three-dimensional macroporous hydrogel and the ability of this engineered system to develop a functional microcirculation
in vivo
. The hydrogel is synthesized by cross-linking polyethylene glycol with polylysine around a salt-leached polylactic-co-glycolic acid scaffold that is degraded in a sodium hydroxide solution. An open macroporous network is formed that supports the efficient formation of tubular structures by brain endothelial cells. After subcutaneous implantation of hydrogel cocultures in mice, blood flow in new microvessels was apparent at 2 weeks with perfused networks established on the surface of implants at 6 weeks. Compared to endothelial cells cultured alone, cocultures of endothelial cells and neural progenitor cells had a significantly greater density of tubular structures positive for platelet endothelial cell adhesion molecule-1 at the 6-week time point. In implant cross sections, the presence of red blood cells in vessel lumens confirmed a functional microcirculation. These findings indicate that neural progenitor cells promote the formation of endothelial cell tubes in coculture and the development of a functional microcirculation
in vivo
. We demonstrate a previously undescribed strategy for creating stable microvascular networks to support engineered tissues of desired parenchymal cell origin.
Maternal mediation, stress inoculation, and the development of neuroendocrine stress resistance in primates
Authors: Parker Karen J. , Buckmaster Christine L. , Sundlass Karan , Schatzberg Alan F. , Lyons David M.
Published: February 2006

The stress inoculation hypothesis presupposes that brief intermittent stress exposure early in life induces the development of subsequent stress resistance in human and nonhuman primates. Rodent studies, however, suggest a role for maternal care rather than stress exposure per se (i.e., the maternal mediation hypothesis). To investigate these two hypotheses, we examined maternal care and the development of stress resistance after exposure to brief intermittent infant stress (IS), mother–infant stress (MIS), or no stress (NS) protocols administered to 30 monkeys between postnatal weeks 17 and 27. Unlike rodents, the IS condition did not permanently increase primate maternal care, nor did measures of total maternal care predict subsequent offspring hypothalamic–pituitary–adrenal-axis responsivity. Although MIS infants received less maternal care than IS and NS infants, both IS and MIS monkeys developed subsequent stress resistance. These findings indicate that rearing differences in the development of stress resistance are more closely related to differences in prior stress exposure than to differences in maternal care. A second experiment confirmed this conclusion in a different cohort of 25 monkeys exposed as infants to high foraging-demand (HFD) or low foraging-demand (LFD) conditions. HFD infants exhibited intermittent elevations in cortisol levels and received less maternal care than LFD infants. In keeping with a key prediction of the stress inoculation hypothesis, HFD males responded to stress in adulthood with diminished hypothalamic–pituitary–adrenal-axis activation compared with LFD males. Results from both experiments demonstrate that stress inoculation, rather than high levels of maternal care, promotes the development of primate stress resistance.
Maternal care effects on the hippocampal transcriptome and anxiety-mediated behaviors in the offspring that are reversible in adulthood
Authors: Weaver Ian C. G. , Meaney Michael J. , Szyf Moshe
Published: February 2006

Early-life experience has long-term consequences on behavior and stress responsivity of the adult. We previously proposed that early-life experience results in stable epigenetic programming of glucocorticoid receptor gene expression in the hippocampus. The aim of this study was to examine the global effect of early-life experience on the hippocampal transcriptome and the development of stress-mediated behaviors in the offspring and whether such effects were reversible in adulthood. Adult offspring were centrally infused with saline vehicle, the histone deacetylase inhibitor trichostatin A (TSA), or the essential amino acid
l
-methionine. The animals were assessed in an unfamiliar open-field arena, and the hippocampal transcriptome of each animal was evaluated by microarray analysis. Here we report that TSA and methionine treatment reversed the effect of maternal care on open-field behavior. We identified >900 genes stably regulated by maternal care. A fraction of these differences in gene expression is reversible by either the histone deacetylase inhibitor TSA or the methyl donor
l
-methionine. These results suggest that early-life experience has a stable and broad effect on the hippocampal transcriptome and anxiety-mediated behavior, which is potentially reversible in adulthood.
Conserved thermodynamic contributions of backbone hydrogen bonds in a protein fold
Authors: Wang Min , Wales Thomas E. , Fitzgerald Michael C.
Published: February 2006

Backbone–backbone hydrogen-bonding interactions are a ubiquitous and highly conserved structural feature of proteins that adopt the same fold (i.e., have the same overall backbone topology). This work addresses the question of whether or not this structural conservation is also reflected as a thermodynamic conservation. Reported here is a comparative thermodynamic analysis of backbone hydrogen bonds in two proteins that adopt the same fold but are unrelated at the primary amino acid sequence level. With amide-to-ester bond mutations introduced by total chemical synthesis methods, the thermodynamic consequences of backbone–backbone hydrogen-bond deletions at five different structurally equivalent positions throughout the β-α-α fold of Arc repressor and CopG were assessed. The ester bond-containing analogues all folded into native-like three-dimensional structures that were destabilized from 2.5 to 6.0 kcal/(mol dimer) compared with wild-type controls. Remarkably, the five paired analogues with amide-to-ester bond mutations at structurally equivalent positions were destabilized to exactly the same degree, regardless of the degree to which the mutation site was buried in the structure. The results are interpreted as evidence that the thermodynamics of backbone–backbone hydrogen-bonding interactions in a protein fold are conserved.
Uncoupling of the base excision and nucleotide incision repair pathways reveals their respective biological roles
Authors: Ishchenko Alexander A. , Deprez Eric , Maksimenko Andrei , Brochon Jean-Claude , Tauc Patrick , Saparbaev Murat K.
Published: February 2006

The multifunctional DNA repair enzymes apurinic/apyrimidinic (AP) endonucleases cleave DNA at AP sites and 3′-blocking moieties generated by DNA glycosylases in the base excision repair pathway. Alternatively, in the nucleotide incision repair (NIR) pathway, the same AP endonucleases incise DNA 5′ of a number of oxidatively damaged bases. At present, the physiological relevance of latter function remains unclear. Here, we report genetic dissection of AP endonuclease functions in base excision repair and NIR pathways. Three mutants of
Escherichia coli
endonuclease IV (Nfo), carrying amino acid substitutions H69A, H109A, and G149D have been isolated. All mutants were proficient in the AP endonuclease and 3′-repair diesterase activities but deficient in the NIR. Analysis of metal content reveals that all three mutant proteins have lost one of their intrinsic zinc atoms. Expression of the
nfo
mutants in a repair-deficient strain of
E. coli
complemented its hypersensitivity to alkylation but not to oxidative DNA damage. The differential drug sensitivity of the mutants suggests that the NIR pathway removes lethal DNA lesions generated by oxidizing agents. To address the physiological relevance of the NIR pathway in human cells, we used the fluorescence quenching mechanism of molecular beacons. We show that in living cells a major human AP endonuclease, Ape1, incises DNA containing α-anomeric 2′-deoxyadenosine, indicating that the intracellular environment supports NIR activity. Our data establish that NIR is a distinct and separable function of AP endonucleases essential for handling lethal oxidative DNA lesions.
Testicular germ cells can colonize sexually undifferentiated embryonic gonad and produce functional eggs in fish
Authors: Okutsu Tomoyuki , Suzuki Kensuke , Takeuchi Yutaka , Takeuchi Toshio , Yoshizaki Goro
Published: February 2006

Understanding the mechanisms that regulate germ-cell development is crucial to reproductive medicine and animal production. Animal gametes originally derive from sexually undifferentiated primordial germ cells (PGCs), which develop into mitotic germ cells (oogonia or spermatogonia) before proceeding to meiosis [Wylie, C. (1999)
Cell
96, 165–174]. Spermatogonia are thought to include a population of cells with stem cell activity, which proliferate throughout the lifespan of male animals and produce spermatozoa [Zhao, G. Q. & Garbers, D. L. (2002)
Dev. Cell
2, 537–547]. However, the functional differences between PGCs and spermatogonial stem cells are poorly understood. Here we show that transplanted adult testicular germ cells can colonize sexually undifferentiated embryonic gonads and resume gametogenesis. Testicular germ cells containing spermatogonial stem cells isolated from adult male rainbow trout (
Oncorhynchus mykiss
) were transplanted into the peritoneal cavity of newly hatched embryos of both sexes, and the behavior of the donor cells was observed. The testicular germ cells differentiated into spermatozoa in male recipients and fully functional eggs in female recipients. Furthermore, the donor-derived spermatozoa and eggs obtained from the recipient fish were able to produce normal offspring. These findings indicate that fish testicular germ cells, probably spermatogonial stem cells, possess a high level of developmental plasticity and sexual bipotency, even after the animal reaches maturity. Furthermore, our results suggest that spermatogonial stem cells are at least partly functionally similar to PGCs.
Regulation of antibacterial defense in the small intestine by the nuclear bile acid receptor
Authors: Inagaki Takeshi , Moschetta Antonio , Lee Youn-Kyoung , Peng Li , Zhao Guixiang , Downes Michael , Yu Ruth T. , Shelton John M. , Richardson James A. , Repa Joyce J. , Mangelsdorf David J. , Kliewer Steven A.
Published: February 2006

Obstruction of bile flow results in bacterial proliferation and mucosal injury in the small intestine that can lead to the translocation of bacteria across the epithelial barrier and systemic infection. These adverse effects of biliary obstruction can be inhibited by administration of bile acids. Here we show that the farnesoid X receptor (FXR), a nuclear receptor for bile acids, induces genes involved in enteroprotection and inhibits bacterial overgrowth and mucosal injury in ileum caused by bile duct ligation. Mice lacking FXR have increased ileal levels of bacteria and a compromised epithelial barrier. These findings reveal a central role for FXR in protecting the distal small intestine from bacterial invasion and suggest that FXR agonists may prevent epithelial deterioration and bacterial translocation in patients with impaired bile flow.
Geography and macroeconomics: New data and new findings
Authors: Nordhaus William D.
Published: February 2006

The linkage between economic activity and geography is obvious: Populations cluster mainly on coasts and rarely on ice sheets. Past studies of the relationships between economic activity and geography have been hampered by limited spatial data on economic activity. The present study introduces data on global economic activity, the G-Econ database, which measures economic activity for all large countries, measured at a 1° latitude by 1° longitude scale. The methodologies for the study are described. Three applications of the data are investigated. First, the puzzling “climate-output reversal” is detected, whereby the relationship between temperature and output is negative when measured on a per capita basis and strongly positive on a per area basis. Second, the database allows better resolution of the impact of geographic attributes on African poverty, finding geography is an important source of income differences relative to high-income regions. Finally, we use the G-Econ data to provide estimates of the economic impact of greenhouse warming, with larger estimates of warming damages than past studies.
Effective expansion of alloantigen-specific Foxp3+CD25+CD4+regulatory T cells by dendritic cells during the mixed leukocyte reaction
Authors: Yamazaki Sayuri , Patel Munjal , Harper Alice , Bonito Anthony , Fukuyama Hidehiro , Pack Maggi , Tarbell Kristin V. , Talmor Mia , Ravetch Jeffrey V. , Inaba Kayo , Steinman Ralph M.
Published: February 2006

Thymic-derived CD25+CD4+T regulatory cells (Tregs) suppress immune responses, including transplantation. Here we evaluated the ability of dendritic cells (DCs) to expand alloantigen-specific Tregs in the mixed leukocyte reaction (MLR) that develops from polyclonal populations of T cells. The allogeneic DCs, when supplemented with IL-2 in the cultures, were much more effective than bulk spleen cells in expanding the numbers of Tregs. Likewise, DCs and not spleen cells were effective in sustaining expression of the transcription factor Foxp3 in Tregs, but neither IL-2 nor CD80/86 was required for this effect in the cultures. On a per-cell basis, the DC-expanded, but not unexpanded, Tregs were more potent suppressors of a fresh MLR by CD25−CD4+T cells. Suppression was 3- to 10-fold more active for MLRs induced by the original alloantigens than for third-party stimulators. When DC-expanded Tregs were introduced into sublethally irradiated hosts, the T cells suppressed graft-versus-host-disease induced by CD25−CD4+T cells. Again, suppression was more active against the same mouse strain that provided the DCs to expand the Tregs. Therefore, alloantigen-selected Tregs are more effective suppressors of responses to major transplantation antigens, and these Tregs can be expanded from a polyclonal repertoire by DCs.
Cell-type-selective induction of
c-jun
by TAF4b directs ovarian-specific transcription networks
Authors: Geles Kenneth G. , Freiman Richard N. , Liu Wei-Li , Zheng Shuang , Voronina Ekaterina , Tjian Robert
Published: February 2006

Cell-type-selective expression of the TFIID subunit TAF
II
105 (renamed TAF4b) in the ovary is essential for proper follicle development. Although a multitude of signaling pathways required for folliculogenesis have been identified, downstream transcriptional integrators of these signals remain largely unknown. Here, we show that TAF4b controls the granulosa-cell-specific expression of the proto-oncogene
c-jun
, and together they regulate transcription of ovary-selective promoters. Instead of using cell-type-specific activators, our findings suggest that the coactivator TAF4b regulates the expression of tissue-specific genes, at least in part, through the cell-type-specific induction of
c-jun
, a ubiquitous activator. Importantly, the loss of TAF4b in ovarian granulosa cells disrupts cellular morphologies and interactions during follicle growth that likely contribute to the infertility observed in TAF4b-null female mice. These data highlight a mechanism for potentiating tissue-selective functions of the basal transcription machinery and reveal intricate networks of gene expression that orchestrate ovarian-specific functions and cell morphology.
Conformal invariants associated to a measure
Authors: Chang Sun-Yung A. , Gursky Matthew J. , Yang Paul
Published: February 2006

In this note, we study some conformal invariants of a Riemannian manifold (

M
n

,
g
) equipped with a smooth measure
m
. In particular, we show that there is a natural definition of the Ricci and scalar curvatures associated to such a space, both of which are conformally invariant. We also adapt the methods of Fefferman and Graham [Fefferman, C. & Graham, C. R. (1985)
Astérisque
, Numero Hors Serie, 95–116] and Graham, Jenne, Mason, and Sparling [Graham, C. R., Jenne, R., Mason, L. J., & Sparling, G. A. J. (1992)
J. London Math. Soc.
46, 557–565] to construct families of conformally covariant operators defined on these spaces. Certain variational problems in this setting are considered, including a generalization of the Einstein–Hilbert action.