bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of dielectric and structural relaxations in glass-forming secondary amides
Authors: Wang Li-Min , Richert Ranko
Published: August 2005

Dielectric relaxation dynamics of secondary amides is explored in their supercooled state near the glass transition temperature Tg by investigating N-ethylacetamide and its mixtures with N-methylformamide. All the samples are found to exhibit giant dielectric permittivities, reaching over 500 in N-methylformamide-rich mixtures around Tg. For both the neat and binary systems, the predominant relaxation peak is of the Debye-type throughout the viscous regime, which is an unexpected feature for a glass former with intermediate fragility. The present results combined with the earlier reported high-temperature data reveal that the dielectric strength ΔεD of the Debye relaxation extrapolates to zero at frequencies of 1010–1011Hz, which is about two orders of magnitude lower than the phonon frequency limit typical of the structural relaxation. This Debye process is remarkably similar to the dielectric behavior of many monohydroxy alcohols, which implies a common nature of purely exponential relaxation dynamics in these liquids. Based on the dielectric properties, we conclude that the Debye relaxation in the secondary amides is not a direct signature of the primary or α-relaxation, the latter being obscured at low temperatures due to the relatively low permittivity and close spectral proximity to the Debye peak. As in the case of monohydroxy alcohols, dielectric polarization and structure fluctuate on different time scales in secondary amides. The Kirkwood-Fröhlich correlation factors for Debye-type liquids are also discussed.
Simulations of concentrated suspensions of rigid fibers: Relationship between short-time diffusivities and the long-time rotational diffusion
Authors: Cobb Philip D. , Butler Jason E.
Published: August 2005

Brownian dynamics simulations of the behavior of suspensions of fibers demonstrate that the scaling of the rotational diffusivity with respect to the number density (nL3) is a sensitive function of the thickness and the parameter L2DR0∕DT0, where DR0 is the rotational diffusivity at infinite dilution, DT0 is the average center-of-mass diffusivity at infinite dilution, and L is the fiber length. Existing theories for the long-time rotational diffusivities of rigid fibers in the semidilute and concentrated regimes fail to accurately account for the relationship with the dilute values of the rotational and translational diffusivities of the various physical models used to simulate the fibers. The concentration regime studied in this work ranges from a number density of nL3≈0–150, which is below the transition from an isotropic to nematic state. The effect of the fiber thickness was studied by performing simulations of rods with aspect ratios (fiber length over diameter) of 25, 50, and 500, as well as performing projections for infinitely thin fibers. The excluded volume of the rods was enforced through the use of short-range potentials. For a rod with an aspect ratio of 50 with a parameter of L2DR0∕DT0=9, which corresponds to a slender-body model of the individual fibers, the rotational diffusivity (DR) scales as DR∕DR0∼(nL3)−1.9 in the concentration regime of 70⩽nL3⩽150. Similarly with a parameter of L2DR0∕DT0=4, corresponding to a rigid-dumbbell model, the rotational diffusivity scales as DR∕DR0∼(nL3)−1.1 over the same range of concentrations. For rods with aspect ratios of 25, it is observed that a difference in the scaling is seen for L2DR0∕DT0≲8, with higher values of this ratio exhibiting essentially the same scaling. Additional values of the ratio L2DR0∕DT0 were investigated to determine the overall behavior of the suspension dynamics with respect to this parameter. These findings resolve discrepancies between simulation results for rotational diffusivities reported by previous investigators and provide new insights for the development of an accurate theory for the diffusivity of rigid rods suspended in solution.
Analysis of minor hysteresis loops in plastically deformed low carbon steel
Authors: Takahashi S. , Zhang L. , Kobayashi S. , Kamada Y. , Kikuchi H. , Ara K.
Published: August 2005

We have measured minor hysteresis loops with increasing magnetic-field amplitude Ha step by step and have analyzed them in connection with lattice defects such as dislocations in deformed low carbon steel. We define several magnetic parameters in the minor loops: pseudocoercive force HC*, pseudoremanence MR*, pseudosusceptibility at pseudocoercive force χH*, pseudohysteresis loss WF*, and pseudoremanence work WR*. We find several simple relations between the pseudomagnetic properties, namely, MR*∕Ma*=9∕10 and 3∕5, and WR*∕WF*=1∕6 and 1∕8, before and after plastic deformation, respectively. These relations are due to the similarity of minor loops. Six magnetic coefficients that are sensitive to lattice defects and are independent of Ha, as well as of the magnetic field, are obtained from the pseudomagnetic properties. These coefficients are effective parameters for nondestructive evaluation of degradation before the initiation of cracking. The minor-loop method has several advantages for nondestructive evaluation compared with the traditional method using major loops. The coefficients can give us much information about lattice defects with high accuracy. The measurements can be done at low magnetic fields less than 20Oe and the Ha step does not necessarily have to be fine to obtain detailed information because of the similarity of minor loops.
L
p
estimates on a time-inhomogeneous diffusion process
Authors: Yan Litan , Lu Ligang , Xu Zhiqiang
Published: August 2005

In this paper we consider the diffusion process X determined by the one-variable time-dependent Fokker-Planck equation, (∂∕∂t)P(y,t)=−g(t)(∂∕∂y)yP(y,t)+12f(t)2(∂2∕∂y2)P(y,t), where f,g:R+→R+ are two continuous functions, i.e., X satisfies Itô stochastic differential equation, dXt=f(t)dBt−g(t)Xtdt, where B is a standard Brownian motion starting at zero. We obtain Lp estimates on the process, and we show that ∥log(1+Jτ)∥p and ∥sup0⩽t⩽τ∣a(t)Xt∣∥p are equivalent for all stopping times τ of B, where Jt=∫0ta2(s)f2(s)ds and a:R+→R+ the solution to the equation (da∕dt)−g(t)a=−a3f2(t),a(0)=1.
A new molecular-dynamics based approach for molecular crystal structure search
Authors: Buch V. , Martoňák R. , Parrinello M.
Published: August 2005

A new molecular-dynamics based approach is proposed to search for candidate crystal structures of molecular solids. The procedure is based on the observation of spontaneous transitions between ordered and disordered states in molecular-dynamics simulations of an artificial periodic system with a small unit cell. In such a way only the most stable structures are automatically selected. The method can be applied to the solution of crystal structures from low-quality or very complex diffraction data. Tests are presented for H2O-ice polymorphs.
The interplay between space charge and recombination in conjugated polymer/molecule photocells
Authors: Rappaport Noam , Solomesch Olga , Tessler Nir
Published: August 2005

We present an analytic description for the loss of photocurrent efficiency at moderate light intensities and demonstrate a simple technique for extracting the mobility of electrons in semiconducting polymer layers. The underlying theoretical analysis, which is based on a simple drift-recombination scheme, shows good agreement with the measured intensity-dependent photocurrent quantum efficiency over five orders of magnitude in intensity. The electron mobility extraction is demonstrated for pristine MEH-PPV. We use the combination of theoretical and experimental studies to discuss the role of recombination and space-charge effects in reducing photocurrent efficiency. We apply the analytical results to device design criteria and deduce that the minimum, low-field, mobility value of the slow carrier required to achieve close to ideal fill factor is ∼10−2cm2V−1s−1 at AM1.5.
Field emission from quasi-aligned aluminum nitride nanotips
Authors: Shi Shih-Chen , Chen Chia-Fu , Chattopadhyay Surojit , Chen Kuei-Hsien , Chen Li-Chyong
Published: August 2005

We report the field emission properties of the quasi-aligned aluminum nitride (AlN) nanotips grown on differently doped (p+, p, n+, and n type) silicon (Si) substrates by thermal chemical vapor deposition. The AlN nanotips were 10nm at the apex, 100nm at the bottom, and 1200nm in length. The AlN nanotips grown on p+-Si substrate showed the lowest turn-on field of 6V∕μm (highest current density of 0.22A∕cm2 at a field of 10V∕μm), whereas no significant emission could be obtained using n+- and n-Si substrates. Band diagrams of the Si–AlN heterojunction have been used to explain the phenomenon. A 5% variation of the applied field was observed while drawing a current density of 100μA∕cm2 from the nanotips grown on p+-Si substrates.
A protein molecule in an aqueous mixed solvent: Fluctuation theory outlook
Authors: Shulgin Ivan L. , Ruckenstein Eli
Published: August 2005

In the present paper a procedure to calculate the properties of proteins in aqueous mixed solvents, particularly the excesses of the constituents of the mixed solvent near the protein molecule and the preferential binding parameters, is suggested. Expressions for the Kirkwood-Buff integrals in ternary mixtures and for the preferential binding parameter were derived and used to calculate various properties of infinitely dilute proteins in aqueous mixed solvents. The derived expressions and experimental information regarding the partial molar volumes and the preferential binding parameters were used to calculate the excesses (deficits) of water and cosolvent (in comparison with the bulk concentrations of protein-free mixed solvent) in the vicinity of ribonuclease A, ribonuclease T1, and lysozyme molecules. The calculations showed that water was in excess in the vicinity of ribonuclease A for water/glycerol and water/trehalose mixtures, and the cosolvent urea was in excess in the vicinity of ribonuclease T1 and lysozyme. The derivative of the activity coefficient of the protein with respect to the mole fraction of water was also calculated. This derivative was negative for the water/glycerol and water/trehalose mixed solvents and positive for the water/urea mixture. The mixture of lysozyme in the water/urea solvent is of particular interest, because the lysozyme at pH 7.0 is in its native state up to 9.3M urea, while at pH 2.0 it is denaturated between 2.5 and 5M and higher concentrations of urea. Our results demonstrated a striking similarity in the hydration of lysozyme at both pHs. It is worthwhile to note that the excesses of urea were only weakly composition dependent on both cases.
200 mm wafer-scale epitaxial transfer of single crystal Si on glass by anodic bonding of silicon-on-insulator wafers
Authors: Teh W. H. , Trigg Alastair , Tung C. H. , Kumar R. , Balasubramanian N. , Kwong D. L.
Published: August 2005

We report a low-temperature (350 °C) anodic bonding followed by grind/etch-back method for a 200 mm wafer-scale epitaxial transfer of ultrathin (1.9 kÅ) single crystalline Si on Pyrex glass. Standard back-end-of-line 3 kÅ SiN/3 kÅ undoped silicon glass passivating films were used as the buffer layers between the silicon-on-insulator wafer and the glass wafer. The quality and strain-free state of the transferred transparent Si film to glass was characterized by cross-sectional transmission electron microscopy, x-ray diffraction (XRD), and high-resolution XRD. Complete removal of the bulk Si after bonding was ascertained by Auger electron spectroscopy spectra and depth profiling. Strong adhesion between the transferred film and the glass wafer was verified by standard tape adhesion tests. This process will pave the way for future generations of Si-based microelectronics including bioelectronics.
Existence and atomic arrangement of microtwins in hexagonal MnAs ferromagnetic epilayers grown on GaAs (100) substrates with monolayer InAs Buffers
Authors: Lee H. S. , Yi S. , Kim T. W. , Lee D. U. , Jeon H. C. , Kang T. W. , Lee K. H. , Lee J. Y.
Published: August 2005

Selected-area electron-diffraction pattern (SADP) and high-resolution transmission electron microscopy (HRTEM) measurements were carried out to investigate the existence and the atomic arrangement of microtwins in hexagonal MnAs ferromagnetic epilayers grown on GaAs (100) substrates with monolayer InAs buffer layers by using molecular beam epitaxy. The magnetization curve as a function of the magnetic field at 5 K showed that the MnAs thin films were ferromagnetic, and the magnetization curve as a function of the temperature revealed that the ferromagnetic transition temperature was as high as 325 K. The SADP and HRTEM results showed that an epitaxial relationship was formed among the hexagonal MnAs layer, the InAs layer, and the zincblende GaAs substrate. Microtwins existed between the MnAs grain boundaries on top of the InAs layers. Based on the SADP and HRTEM results, we present a possible atomic arrangement of the microtwins for the MnAs-InAs-GaAs heterostructure.
Effect of damage by 2 MeV He ions and annealing on Hc2 in MgB2 thin films
Authors: Gandikota R. , Singh R. K. , Kim J. , Wilkens B. , Newman N. , Rowell J. M. , Pogrebnyakov A. V. , Xi X. X. , Redwing J. M. , Xu S. Y. , Li Q. , Moeckly B. H.
Published: August 2005

The effect of damage induced by 2 MeV alpha particles, followed by annealing, on the critical temperature (Tc), resistivity (ρ), and upper critical field (Hc2), of three MgB2 films made by different deposition processes has been studied. Damage creates a linear decrease in Tc with residual resistivity (ρ0), and produces maxima in both Hc2⊥(0) and Hc2‖(0). Below Tcs of about 25 K, Hc2(0) depends roughly linearly on Tc, while the anisotropy of Hc2(0) decreases as Tc decreases. Annealing the films reproduces the Tc versus ρ0 dependence but not the Hc2(0) values induced by damage.
Very large electro-optic coefficients from in situ generated side-chain nonlinear optical polymers
Authors: Kang Jae-Wook , Kim Tae-Dong , Luo Jingdong , Haller Marnie , Jen Alex K.-Y.
Published: August 2005

A synthetic/processing method has been developed for achieving highly efficient nonlinear optical polymers. A maleimide-containing chromophore with large molecular nonlinearity was covalently attached onto a anthrathene-containing polymer to generate in situ a side-chain polymer via the Diels-Alder reaction. The poling and covalent side-chain attachment processes can be performed simultaneously in a solid state, resulting in high electro-optic (E-O) coefficients (r33 values up to 50pm∕V at 1310nm) and temporal stability (85% retention of the original dipole alignment after isothermal heating at 85°C for more than 500h). A very high chromophore loading level (39wt%) can be achieved by adding more chromophore into this side-chain polymer without causing any obvious phase separation. Poling of this chromophore-doped side-chain polymer (total dye content: 34wt%) showed a significantly increased E-O coefficient, from 50to110pm∕V.
Rice growth and post-rice mungbean in relation to two puddling intensities under glasshouse conditions
Authors: Kirchhof G. , So H. B.
Published: August 2005

The effect of soil puddling on growth of lowland rice (Oryza sativa) and post-rice mungbean (Vigna radiata) was investigated using mini rice beds under controlled glasshouse conditions. Each mini rice bed was approximately 1 m3in size. Three different soil types were used: a well-drained, permeable loam; a hardsetting, structurally unstable silty loam; and a medium clay. Rice yields were reduced by low puddling compared with high puddling intensity on the loam but not affected on the heavier textured soils (silty loam and clay). Yield of mungbean was reduced on highly puddle, structurally unstable soil, indicating that puddling should be reduced on structurally unstable soils. Under glasshouse condition where crop establishment was not a limiting factor and plant available water in 0.65 m of soil was 100 mm, mungbean yields of >1 t/ha were achieved. However, under conditions where subsoil water reserves were depleted for the production of vegetative biomass during initial optimal growing condition, grain yield remained well below 1 t/ha.
Modelling irrigated Eucalyptus for salinity control on shallow watertables
Authors: Paydar Zahra , Huth Neil , Snow Val
Published: August 2005

With increasing salinity in irrigation areas, the option of tree planting in areas with shallow groundwater is seen as an ‘environmentally friendly’ alternative for controlling salinity. This study uses simulation modelling to investigate the long-term effects of planting Eucalyptus grandis in irrigated areas with shallow and saline watertables in the Riverine Plains where concerns exist about salinity effects on irrigated agriculture. APSIM, a 1-dimensional model of the soil–water–plant system, was modified to describe the interaction between the watertable within the plantation with the, normally shallower, watertable in the surrounding irrigated pasture. The model was tested against measured data and then used to simulate a range of different environmental conditions (depth and salinity of the groundwater, soil) and management options (irrigation with different amounts and salinity). The results of a total of 702 simulation runs helped to identify conditions in which irrigated plantations may be viable and how the irrigation of these plantations may be managed to decrease the impact of salinity on tree growth. The results indicated that if irrigation is to improve productivity, it must be in large amounts (1000 mm or more) and of good quality to have a significant effect on tree production. Irrigation with low salinity water (EC <2 dS/m) can only be used to reliably increase production in conditions where there are deeper watertables (4 m or deeper) on fast-draining soils. In these cases, flexible irrigation practices (scheduled irrigation) need to be employed in order to manage the salt levels within the tree root-zones. The viability of plantations is likely to decrease with increasing irrigation water salinity as salt accumulation in the profile reduces the ability of the trees to act as natural sinks. Depending on the irrigation and groundwater salinity, trees might be effective only up to a few years (as little as 9 years). Optimum response of trees to irrigation is only predicted with fresh water and scheduled irrigation (up to 1700 mm/year). However, if ample fresh water was available, other higher value cropping options are likely to be sought by land managers. Furthermore, the large amounts of water added to the plantation will have negative effects (water and salt export from the plantation) on the surrounding land, which will need further intervention to be sustainable.
Plausible bounds for maximum rate of increase in magpie geese (Anseranas semipalmata): implications for harvest
Authors: Brook Barry W. , Whitehead Peter J.
Published: August 2005

We used improved information on fecundity and credible estimates of survival to define the plausible bounds of maximum intrinsic rate of population increase (r
m) in magpie geese and explored the management and conservation implications, given current estimates of off-take. We considered previous estimates of r
m (0.78, based on time-series analysis of aerial count data) and the corresponding predicted maximum sustainable harvest rates (30–39% per annum) to be excessive, thereby risking poor management decisions. In contrast, our estimate of the maximum plausible range of r
m (0.11–0.28) is substantially lower than the previous estimate, and suggests maximum harvest rates of no more than 5–14% of total population size per annum. We consider that it would be unwise to adopt the prior estimate of r
m for management policy because it would risk over-exploitation. Our results embody a more precautionary approach to assessing maximum sustainable yield for magpie geese in northern Australia, and are not confounded by migration. The move from a simple empirical model to a partially mechanistic one reflects a significant improvement in understanding, but must nevertheless be viewed as part of an ongoing process of model refinement and testing.
Fire heterogeneity in Kakadu National Park, 1980 - 2000
Authors: Price Owen , Edwards Andrew , Connors Greg , Woinarski John , Ryan Greg , Turner Andrew , Russell-Smith Jeremy
Published: August 2005

Although it is generally acknowledged that fire-induced heterogeneity is important for maintaining diverse species assemblages in northern Australian savannas, scant relevant data are currently available to examine this proposition. The study takes advantage of a singular, detailed, bidecadal fire history assembled annually for Kakadu National Park to explore relationships between fire-induced heterogeneity and other terrain features. Three patch-based heterogeneity indices were calculated from assembled fire-history data for the central 1-ha cell of a 5 × 5 cell (25 ha) window; that is, at a spatial scale relevant to the home ranges of many small- to medium-sized native mammals. Two of these indices were first calculated separately for each year, employing different metrics based on the extent of burning occurring in the 5 × 5 cell array, and then averaged for each of four consecutive five-year periods and over all years. The third index was calculated as the sum of the coefficients of variation for four fire-regime variability parameters determined likewise for five- and 20-year periods. Assembled data illustrate that (1) fire-induced heterogeneity in Kakadu increased in each successive five-year period from 1981, and (2) when modelled with independent terrain coverages, significant relationships were obtained for all three heterogeneity indices with terrain roughness, distance to roads, and distance to drainage lines.
Regional patterns of mammal abundance and their relationship to landscape variables in eucalypt woodlands near Darwin, northern Australia
Authors: Price Owen , Rankmore Brooke , Milne Damian , Brock Chris , Tynan Charmaine , Kean Louise , Roeger Lisa
Published: August 2005

Habitat loss and fragmentation are usually construed as having negative consequences for wildlife, and habitat heterogeneity as having a positive effect. We conducted a mammal survey in eucalypt woodlands near Darwin, and found very few mammals in an intact region of the study area. This is consistent with an emerging pattern suggesting that many mammal species are declining across northern Australia, even though habitats remain relatively intact. However, we also found apparently healthy populations of the same species in a fragmented region of the study area. Using a combination of remote sensing, GIS and generalised linear modeling, we found some evidence of relationships between fire regime, fire heterogeneity or vegetation heterogeneity and the distributions of mammal species in this area. However, there was a strong regional component of the distribution that is not explained by these variables. The cause of the lack of mammals in the intact region of the study area has not been revealed by this analysis. One possible reason for this failure is that the landscape variables used in the analysis were too fine to detect variation in mammal abundance occuring at a much courser regional scale.
Biodiversity and invasive grass species: multiple-use or monoculture?
Authors: Ferdinands Keith , Beggs Kerry , Whitehead Peter
Published: August 2005

Invasive plants are recognised as a major threat to biodiversity conservation worldwide. Despite this recognition, our understanding of the mechanisms controlling the invasion process and its impact on flora and fauna is often poor. We examined the impact of an invasive aquatic grass species, para grass (Urochloa mutica), on seasonally inundated wetlands in tropical northern Australia. Flora and avifauna were surveyed at sites invaded by para grass and in native vegetation. Spatial information systems were used to design surveys and determine environmental correlates of para grass distribution and so predict the potential future spread of para grass and infer impacts in the absence of control. Where para grass was present the median number of plant taxa was ~75% lower. Few birds showed preference for habitats invaded by para grass, and most birds were associated with areas of native vegetation or other habitats with little or no para grass. The study identified several wetland habitats that are at greater risk of invasion, based on the apparent habitat preferences of para grass. The degradation or loss of some of these ‘at-risk’ habitats, including Oryza meriodionalis grasslands that play an integral role in the wetland food chain, has important ramifications for the levels of biodiversity supported by the wetlands.
Geographic patterns and correlates of the decline of granivorous birds in northern Australia
Authors: Franklin Donald C. , Whitehead Peter J. , Pardon Guy , Matthews Janet , McMahon Philip , McIntyre Daniel
Published: August 2005

A geographic index of the decline in the distribution and abundance of granivorous birds in tropical northern Australia shows that declines are greatest in Queensland and especially in the south-eastern tropics and in inland areas, and lowest in the north Kimberley and east Arnhem districts. In this paper, we use generalised linear models to investigate interrelationships among an index of decline in 1° by 1° cells and measures of grazing intensity and contemporary patterns of burning, together with the environmental variables of rainfall, vegetation and topographic patterning in the landscape. Grazing intensity was the single strongest human effect but strong correlations between grazing intensity and other human influences suggest that these may have been subsumed within the grazing intensity measure. Impacts of grazing may be worse where pastoral settlement occurred earlier. Topographic variation appeared to be a mitigating effect, suggesting a role for ‘topographic refuges’ from human activities. Relationships among granivore declines, grazing and rainfall are difficult to disentangle using inferential statistics, but a consistent effect is that declines are more severe in areas with greater year-to-year variation in rainfall. We do not suggest that our analyses are conclusive. However, they do support the proposition that better understanding of the causes of decline at finer spatial scales will emerge most strongly in studies that link habitat quality with granivore demography at inland sites of highly variable year-to-year rainfall and with strongly contrasting grazing histories.
Molecular evidence for an activator–inhibitor mechanism in development of embryonic feather branching
Authors: Harris Matthew P. , Williamson Scott , Fallon John F. , Meinhardt Hans , Prum Richard O.
Published: August 2005

The developmental basis of morphological complexity remains a central question in developmental and evolutionary biology. Feathers provide a unique system to analyze the development of complex morphological novelties. Here, we describe the interactions between Sonic hedgehog (Shh) and bone morphogenetic protein 2 (Bmp2) signaling during feather barb ridge morphogenesis. We demonstrate that activator–inhibitor models of Shh and Bmp2 signaling in the tubular feather epithelium are sufficient to explain the initial formation of a meristic pattern of barb ridges and the observed variation in barb morphogenesis in chick natal down feathers. Empirical tests support the assumptions of the model that, within the feather ectoderm, Shh (activator) up-regulates its own transcription and that of Bmp2 (inhibitor), whereas Bmp2 signaling down-regulates Shh expression. More complex models incorporating a second activator and dorsal/ventral polarized modification of activator signaling can produce all of the barb morphogenesis patterns observed during the growth of more complex branched pennaceous feathers: new barb ridge formation, helical growth, and barb ridge fusion. An integrated model of feather morphogenesis and evolution suggests that plumulaceous feather structure evolved by the establishment of activator–inhibitor interactions between Shh and Bmp2 signaling in the basal epithelium of the feather germ. Subsequently, pennaceous feather structure evolved through the integration of barb ridge morphogenesis with a second, local inhibitor and a dorsal/ventral signal gradient within the feather. The model is congruent with paleontological evidence that plumulaceous feathers are primitive to pennaceous feathers.
Precocious metamorphosis in transgenic silkworms overexpressing juvenile hormone esterase
Authors: Tan Anjang , Tanaka Hiromasa , Tamura Toshiki , Shiotsuki Takahiro
Published: August 2005

Insect growth and development are intricately regulated by the titers of juvenile hormones (JHs) and ecdysteroids (and/or their metabolites) in the insect hemolymph. Hydrolysis of the methyl ester of JH by a JH-specific esterase (JHE) is a key pathway for the degradation of JH. Here, we generate transgenic silkworm strains that overexpress JHE by using the binary GAL4/UAS system. Overexpression of JHE from the embryonic stage resulted in larval–pupal metamorphosis after the third stadium, two stadia earlier than that observed in wild-type insects. This precocious metamorphosis suggests that JHs are not critical for normal development of embryo or larva before the second molt in Lepidoptera (moths and butterflies). Our transgenic approach allowed us to dissect the function of key physiological events that occur from embryogenesis. Until now, these types of studies were possible only in later larval stadia by using physical techniques such as allatectomy or the application of JH analogues. We believe that our system will allow further pioneering studies in insect physiology.
Epithelial membrane protein-1 is a biomarker of gefitinib resistance
Authors: Jain Anjali , Tindell Charles A. , Laux Isett , Hunter Jacob B. , Curran John , Galkin Anna , Afar Daniel E. , Aronson Nina , Shak Steven , Natale Ronald B. , Agus David B.
Published: August 2005

We describe a molecular resistance biomarker to gefitinib, epithelial membrane protein-1 (EMP-1). Gefitinib is a small-molecule inhibitor that competes for the ATP-binding site on EGF receptor (EGFR) and has been approved for patients with advanced lung cancers. Treatment with gefitinib has resulted in clinical benefit in patients, and, recently, heterozygous somatic mutations within the EGFR catalytic domain have been identified as a clinical correlate to objective response to gefitinib. However, clinical resistance to gefitinib limits the utility of this therapeutic to a fraction of patients, and objective clinical responses are rare. We aimed to assess the molecular phenotype and mechanism of
in vivo
gefitinib resistance in xenograft models and in patient samples. We generated
in vivo
gefitinib-resistance models in an adenocarcinoma xenograft model by serially passaging tumors in nude mice in presence of gefitinib until resistance was acquired. EMP-1 was identified as a surface biomarker whose expression correlated with acquisition of gefitinib resistance. EMP-1 expression was further correlated with lack of complete or partial response to gefitinib in lung cancer patient samples as well as clinical progression to secondary gefitinib resistance. EMP-1 expression and acquisition of gefitinib clinical resistance was independent of gefitinib-sensitizing EGFR somatic mutations. This report suggests the role of the adhesion molecule, EMP-1, as a biomarker of gefitinib clinical resistance, and further suggests a probable cross-talk between this molecule and the EGFR signaling pathway.
Molecular basis of alanine discrimination in editing site
Authors: Sokabe Masaaki , Okada Ayuko , Yao Min , Nakashima Takashi , Tanaka Isao
Published: August 2005

AlaX is the homologue of the class II alanyl-tRNA synthetase editing domain and has been shown to exhibit autonomous editing activity against mischarged tRNA
Ala
. Here, we present the structures of AlaX from the archaeon
Pyrococcus horikoshii
in apo form, complexed with zinc, and with noncognate amino acid
l
-serine and zinc. Together with mutational analysis, we demonstrated that the conserved Thr-30 hydroxyl group located near the β-methylene of the bound serine is responsible for the discrimination of noncognate serine from cognate alanine, based on their chemical natures. Furthermore, we confirmed that the conserved Gln-584 in alanyl-tRNA synthetase, which corresponds to Thr-30 of AlaX, is also critical for discrimination. These observations strongly suggested conservation of the chemical discrimination among trans- and cis-editing of tRNA
Ala
.
The striatofugal fiber system in primates: A reevaluation of its organization based on single-axon tracing studies
Authors: Lévesque Martin , Parent André
Published: August 2005

The current model of basal ganglia rests on the idea that the striatofugal system is composed of two separate (direct and indirect) pathways originating from distinct cell populations in the striatum. The striatum itself is divided into two major compartments, the striosomes and the matrix, which differ by their neurochemical makeup and input/output connections. Here, neurons located in either striosomes or the extrastriosomal matrix in squirrel monkeys were injected with biotin dextran amine, and their labeled axons were entirely reconstructed with a camera lucida. Twenty-four of 27 reconstructed axons arborized into the three main striatal targets (external pallidum, globus pallidus, and substantia nigra pars reticulata), a finding that is at odds with the concept of a dual striatofugal system. Axons of striosomal neurons formed several columnar terminal fields in the substantia nigra pars reticulata. These data indicate that the substantia nigra pars compacta is neither the only nor the main target of striosomal neurons, a finding that calls for a reevaluation of the organization of the striatonigral projection system.
Crystallization of a mammalian membrane protein overexpressed in
Saccharomyces cerevisiae
Authors: Jidenko Marie , Nielsen Rikke C. , Sørensen Thomas Lykke-Møller , Møller Jesper V. , le Maire Marc , Nissen Poul , Jaxel Christine
Published: August 2005

The Ca
2+
-ATPase SERCA1a (sarcoplasmic–endoplasmic reticulum Ca
2+
-ATPase isoform 1a) from rabbit has been overexpressed in
Saccharomyces cerevisiae
. This membrane protein was purified by avidin agarose affinity chromatography based on natural biotinylation in the expression host, followed by HPLC gel filtration. Both the functional and structural properties of the overexpressed protein validate the method. Thus, calcium-dependent ATPase activity and calcium transport are essentially intact after reconstitution in proteoliposomes. Moreover, the recombinant protein crystallizes in a form that is isomorphous to the native SERCA1a protein from rabbit, and the diffraction properties are similar. This represents a successful crystallization of a mammalian membrane protein derived from a heterologous expression system, and it opens the way for the study of mutant forms of SERCA1a.
Structure and fluctuations of a single floating lipid bilayer
Authors: Daillant J. , Bellet-Amalric E. , Braslau A. , Charitat T. , Fragneto G. , Graner F. , Mora S. , Rieutord F. , Stidder B.
Published: August 2005

A single lipid molecular bilayer of 17 or 18 carbon chain phosphocholines, floating in water near a flat wall, is prepared in the bilayer gel phase and then heated to the fluid phase. Its structure (electron density profile) and height fluctuations are determined by using x-ray reflectivity and nonspecular scattering. By fitting the off-specular signal to that calculated for a two-dimensional membrane using a Helfrich Hamiltonian, we determine the three main physical quantities that govern the bilayer height fluctuations: The wall attraction potential is unexpectedly low; the surface tension, roughly independent on chain length and temperature, is moderate (≈5 × 10
–4
J·m
–2
) but large enough to dominate the intermediate range of the fluctuation spectrum; and the bending modulus abruptly decreases by an order-of-magnitude from 10
–18
J to 10
–19
J at the bilayer gel-to-fluid transition.
Direct measurement of electrical transport through single DNA molecules of complex sequence
Authors: Cohen Hezy , Nogues Claude , Naaman Ron , Porath Danny
Published: August 2005

Seemingly contradicting results raised a debate over the ability of DNA to transport charge and the nature of the conduction mechanisms through it. We developed an experimental approach for measuring current through DNA molecules, chemically connected on both ends to a metal substrate and to a gold nanoparticle, by using a conductive atomic force microscope. Many samples could be made because of the experimental approach adopted here, which enabled us to obtain reproducible results with various samples, conditions, and measurement methods. We present multileveled evidence for charge transport through 26-bp-long dsDNA of a complex sequence, characterized by S-shaped current–voltage curves that show currents >220 nA at 2 V. This significant observation implies that a coherent or band transport mechanism takes over for bias potentials leading to high currents (>1 nA).
Location analysis of estrogen receptor α target promoters reveals that FOXA1 defines a domain of the estrogen response
Authors: Laganière Josée , Deblois Geneviève , Lefebvre Céline , Bataille Alain R. , Robert François , Giguère Vincent
Published: August 2005

Nuclear receptors can activate diverse biological pathways within a target cell in response to their cognate ligands, but how this compartmentalization is achieved at the level of gene regulation is poorly understood. We used a genome-wide analysis of promoter occupancy by the estrogen receptor α (ERα) in MCF-7 cells to investigate the molecular mechanisms underlying the action of 17β-estradiol (E
2
) in controlling the growth of breast cancer cells. We identified 153 promoters bound by ERα in the presence of E
2
. Motif-finding algorithms demonstrated that the estrogen response element (ERE) is the most common motif present in these promoters whereas conventional chromatin immunoprecipitation assays showed E
2
-modulated recruitment of coactivator AIB1 and RNA polymerase II at these loci. The promoters were linked to known ERα targets but also to many genes not directly associated with the estrogenic response, including the transcriptional factor FOXA1, whose expression correlates with the presence of ERα in breast tumors. We found that ablation of FOXA1 expression in MCF-7 cells suppressed ERα binding to the prototypic
TFF1
promoter (which contains a FOXA1 binding site), hindered the induction of
TFF1
expression by E
2
, and prevented hormone-induced reentry into the cell cycle. Taken together, these results define a paradigm for estrogen action in breast cancer cells and suggest that regulation of gene expression by nuclear receptors can be compartmentalized into unique transcriptional domains by means of licensing of their activity to cofactors such as FOXA1.
Subdomains for transport via plasmodesmata corresponding to the apical–basal axis are established during
Arabidopsis
embryogenesis
Authors: Kim Insoon , Kobayashi Ken , Cho Euna , Zambryski Patricia C.
Published: August 2005

The axial body pattern of
Arabidopsis
is determined during embryogenesis by auxin signaling and differential gene expression. Here we demonstrate that another pathway, cell-to-cell communication through plasmodesmata (PD), is regulated during apical–basal pattern formation. The
SHOOT MERISTEMLESS
(
STM
) promoter was used to drive expression in the shoot apical meristem (SAM) and a subset of cells at the base of the hypocotyl of 1×,2×, and 3× soluble green fluorescent proteins (sGFPs), and the P30 movement protein of
Tobacco mosaic virus
(TMV) translationally fused to 1× and 2× sGFP. In the early heart stage, 2× sGFP (54 kDa) moves throughout the whole embryo, whereas 3× sGFP (81 kDa) shows more restricted movement. As the embryo develops, PD apertures are down regulated to form local subdomains allowing transport of different sized tracers. For example, movement of 2× sGFP to the cotyledon, and 3× sGFP to root tips, becomes restricted. Subdomains of cell-to-cell transport align with the apical–basal embryo body axis and correspond to the shoot apex, cotyledons, hypocotyl, and root. Studies with P30–GFP fusions reinforce the distinction between embryonic symplastic subdomains. Although P30 targets embryo cell walls as puncta (diagnostic for functional localization of P30 to PD in adult plants), P30 cannot dilate embryonic PD to overcome the barriers for transport between symplastic subdomains, suggesting that specific boundaries separate symplastic subdomains of the embryo. Thus, cell-to-cell communication via plasmodesmata conveys positional information critical to establish the axial body pattern during embryogenesis in
Arabidopsis
.
Inattentional blindness for negative relationships in human causal learning
Authors: Maldonado Antonio , Jiménez Gracia , Herrera Amparo , Perales José C. , Catena Andrés
Published: August 2005

The present study focuses on the effect of selective attention on causal learning. Three effects of the level of attention to predictive symptoms in positive and negative contingency learning tasks are reported. First, participants accurately detected a positive relationship between an incidental cue and a contingent outcome, although judgements were slightly lower than those for the attended cue. Second, participants were unable to detect negative relationships between incidental cues and outcomes, which suggests a major role of selective attention in this type of learning. Third, participants retrieved the frequency of each trial type more accurately in the attended conditions than in the incidental conditions. These findings show how attention guides and constrains human causal learning and reveal an inattentional blindness effect for negative contingency learning.
Normal Auditory Negative Priming in Schizophrenic Patients
Authors: Zabal Anouk , Buchner Axel
Published: August 2005

Performance of 28 schizophrenic patients and 28 matched controls was compared in an auditory priming task. A large auditory negative priming effect was obtained for the patients as well as for the control group, and the size of the negative priming effect was approximately the same for both groups. Under the same conditions, positive or repetition priming for the patients was enhanced compared to that of the control group. The present findings from an auditory priming task are consistent with a growing body of evidence from the visual domain showing normal rather than reduced or eliminated negative priming in schizophrenic patients.
Automatic–Heuristic and Executive–Analytic Processing during Reasoning: Chronometric and Dual-Task Considerations
Authors: De Neys Wim
Published: August 2005

Human reasoning has been shown to overly rely on intuitive, heuristic processing instead of a more demanding analytic inference process. Four experiments tested the central claim of current dual-process theories that analytic operations involve time-consuming executive processing whereas the heuristic system would operate automatically. Participants solved conjunction fallacy problems and indicative and deontic selection tasks. Experiment 1 established that making correct analytic inferences demanded more processing time than did making heuristic inferences. Experiment 2 showed that burdening the executive resources with an attention-demanding secondary task decreased correct, analytic responding and boosted the rate of conjunction fallacies and indicative matching card selections. Results were replicated in Experiments 3 and 4 with a different secondary-task procedure. Involvement of executive resources for the deontic selection task was less clear. Findings validate basic processing assumptions of the dual-process framework and complete the correlational research programme of K. E. Stanovich and R. F. West (2000).
Classification and recognition in artificial grammar learning: Analysis of receiver operating characteristics
Authors: Lotz Anja , Kinder Annette
Published: August 2005

In two experiments we investigated recognition and classification judgements using an artificial grammar learning paradigm. In Experiment 1, when only new test items had to be judged, analysis of z-transformed receiver operating characteristics ( z-ROCs) revealed no differences between classification and recognition. In Experiment 2, where we included old test items, z-ROCs in the two tasks differed, suggesting that judgements relied on different types of information. The results are interpreted in terms of heuristics that people use when making classification and recognition judgements.
The origin recognition core complex regulates dendrite and spine development in postmitotic neurons
Authors: Huang Zhen , Zang Keling , Reichardt Louis F.
Published: August 2005

The origin recognition complex (ORC) ensures exactly one round of genome replication per cell cycle through acting as a molecular switch that precisely controls the assembly, firing, and inactivation of the replication initiation machinery. Recent data indicate that it may also coordinate the processes of mitosis and cytokinesis and ensure the proper distribution of replicated genome to daughter cells. We have found that the ORC core subunits are highly expressed in the nervous system. They are selectively localized to the neuronal somatodendritic compartment and enriched in the membrane fraction. siRNA knockdown of ORC subunits dramatically reduced dendritic branch formation and severely impeded dendritic spine emergence. Expression of ORC ATPase motif mutants enhanced the branching of dendritic arbors. The ORC core complex thus appears to have a novel role in regulating dendrite and dendritic spine development in postmitotic neurons.
Treatment of the Painful Motion Segment
Authors: Pracyk John B. , Traynelis Vincent C.
Published: August 2005

Study Design.

A retrospective review of the literature.

Objective.

This work serves as a comprehensive update of cervical arthroplasty.

Summary of Background Data.

Cervical arthroplasty has developed as a means to preserve normal spinal motion after an anterior cervical discectomy. Preserving motion may lead to an acute improvement in patient outcome and may decrease the incidence of symptomatic adjacent segment disease in the long-term.

Methods.

The literature concerning the outcomes following anterior cervical decompression and fusion, the indications for cervical arthroplasty, the indications and contraindications for arthroplasty, the surgical technique, and early outcome studies for those devices currently in U.S. FDA IDE trials are reviewed.

Results.

The most data are available for the Prestige, Bryan, and ProDisc-C devices. While these devices all preserve normal segmental motion, the articulations vary (metal on metal, metal on polyurethane, and metal on ultra-high molecular weight polyethylene). Wear testing indicates that these devices will have a long life once implanted. Preliminary outcomes compare very favorably to anterior decompression and arthrodesis.

Conclusions.

Cervical arthroplasty is a promising new technology that may improve patient outcome following anterior cervical decompression.