bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of microwave discharges of H2 admixed with CH4 for diamond deposition
Authors: Lombardi G. , Hassouni K. , Stancu G.-D. , Mechold L. , Röpcke J. , Gicquel A.
Published: September 2005

Microwave discharges of H2 admixed with CH4 in a moderate-pressure quartz bell jar reactor used for diamond deposition are studied numerically. Special attention was devoted to high-power densities which provide the most effective way for producing high-quality diamond films. First, a one-dimensional radial model describing the coupled phenomena of chemistry, energy transfer, as well as species and energy transport along the reactor’s radial coordinate was developed. Species densities predicted with the model were compared with measurements with infrared tunable diode laser spectroscopy, resulting in validation of the model. Second, a one-dimensional axial model was used to describe the plasma flow along the reactor axis in a region between the reactor end wall and the substrate surface. This model was particularly useful for studying the plasma behavior in the vicinity of the substrate surface, where thermal and composition gradients are large. Both the radial and axial transport models are based on the same discharge model in which the plasma is described as a thermochemically nonequilibrium flow with different energy distributions for heavy species and electrons. The chemistry was described with a model containing 28 species and 131 reactions. The electron temperature, the gas temperature, and the species concentration were determined by solving a coupled set of equations. A wide range of experimental conditions used for diamond deposition was simulated, from low microwave power density (9Wcm−3, i.e., 600W, 2500Pa, and Tg∼2200K) to high-power density (30Wcm−3, i.e., 2kW, 12000Pa, and Tg∼3200K). The main chemical paths were identified, and the major species, transport effects, and reaction pathways that govern diamond deposition plasmas are discussed.
Electron paramagnetic resonance and luminescent properties of Mn2+:MgGa2O4 phosphor
Authors: Yasoda B. , Sreekanth Chakradhar R. P. , Lakshmana Rao J. , Gopal N. O. , Xu C. N.
Published: September 2005

Electron-paramagnetic-resonance (EPR) and photoluminescence (PL) studies on magnesium gallate (MgGa2O4) phosphor activated with divalent manganese have been carried out. The EPR spectrum exhibits a six-line hyperfine structure centered at g=1.995, which is a characteristic of a Mn2+ ion with a nuclear spin I=5∕2. The spin-Hamiltonian parameters have been evaluated. The concentration and temperature (123–433K) dependences of EPR signals have been studied. The number of spins participating in resonance (N) with temperature obeys the Boltzman law and from the graph of logN versus 1∕T the activation energy has been evaluated. The paramagnetic susceptibilities (χ) have been calculated from the EPR data at different temperatures and it is interesting to note that it obeys the Curie-Weiss behavior. The Curie constant has been evaluated from the 1∕χ versus T graph. A bright green photoluminescence according to the transition T14→A16 whose emission peak is located at 502nm is observed from the phosphor under UV excitation when excited by 267-nm light. Such a stable luminescence performance is promising for use in the field of flat panel light-emitting devices. The mechanism involved in the generation of green emission has been explained in detail.
On the optimization of experimental parameters for x-ray in-line phase-contrast imaging
Authors: Nesterets Ya. I. , Wilkins S. W. , Gureyev T. E. , Pogany A. , Stevenson A. W.
Published: September 2005

General principles and results for the optimization of the performance of x-ray in-line phase-contrast imaging systems for spatially incoherent sources are investigated. In particular, formulas expressing the dependence of image contrast, spatial resolution, and signal-to-noise ratio on instrumental parameters including source size, detector resolution, geometrical factors, x-ray energy as well as sample properties are derived for different models of sample features. The results for some special cases of interest are presented. Optimization procedures are proposed that are expected to be useful in the design of imaging systems seeking to exploit x-ray in-line phase contrast.
Magnetic reconnection during flux conversion in a driven spheromak
Authors: Hooper E. B. , Kopriva T. A. , Cohen B. I. , Hill D. N. , McLean H. S. , Wood R. D. , Woodruff S. , Sovinec C. R.
Published: September 2005

During buildup of a spheromak by helicity injection, magnetic reconnection converts toroidal flux into poloidal flux. This physics is explored in the resistive magnetohydrodynamic code, NIMROD [C. R. Sovinec, A. H. Glasser, T. A. Gianakon, D. C. Barnes, R. A. Nebel, S. E. Kruger, D. D. Schnack, S. J. Plimpton, A. Tarditi, and M. S. Chu, J. Comp. Phys. 195, 355 (2004)], which reveals negative current sheets with λ=μ0j∙B∕B2 reversed relative to the applied current. The simulated event duration is consistent with magnetic diffusion on the sheet thickness and is accompanied by cathode voltage spikes and poloidal field increases similar to those seen in the Sustained Spheromak Physics Experiment, SSPX [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. All magnetic field lines are open during reconnection and their trajectories are very sensitive to their starting points, resulting in chaos. The current sheets are most intense inside the separatrix near the X point of the mean-field spheromak, suggesting that the reconnection occurs near field lines which are closed in the azimuthal average.
Generalized kinetic theory of ensembles with variable charges
Authors: Ivlev A. V. , Zhdanov S. K. , Klumov B. A. , Morfill G. E.
Published: September 2005

A generalized kinetic theory of gaseous ensembles of particles with variable charges is proposed. The evolution of the ensembles due to the mutual particle collisions is investigated. The cases of inhomogeneous and randomly fluctuating charges are studied. It is shown that the particle temperature in such ensembles increases with time, and in some cases can grow by orders of magnitude. The theory is compared with the molecular-dynamics simulations, the relevance to typical experimental conditions is analyzed, and astrophysical implications are discussed.
Avalanche properties in a transport model based on critical-gradient fluctuation dynamics
Authors: Garcia L. , Carreras B. A.
Published: September 2005

A simple one-dimensional transport model based on critical-gradient fluctuation dynamics is applied to describe some of the properties of plasma-turbulence-induced transport. This model combines avalanche-like transport with diffusion. The particle flux is self-regulated by the stability properties of the fluctuations. A high-gradient edge region emerges where transport dynamics is close to marginal stability. In steady state, the core remains at the subcritical gradient. The avalanches change from quasiperiodic events triggered mostly near the edge region to intermittent transport events depending on the noise level of the particle source.
Dust acoustic solitary wave with variable dust charge: Role of negative ions
Authors: Ghosh Samiran
Published: September 2005

The role of negative ions on small but finite amplitude dust acoustic solitary wave including the effects of high and low charging rates of dust grains compared to the dust oscillation frequency in electronegative dusty plasma is investigated. In the case of high charging rate, the solitary wave is governed by Korteweg–de Vries (KdV) equation, but in the case of low charging rate, it is governed by KdV equation with a linear damping term. Numerical investigations reveal that in both cases dust acoustic soliton sharpens (flatens) and soliton width decreases (increases) with the increase of negative-ion number density (temperature). Also, the negative ions reduce the damping rate.
Electron energy levels for a finite rectangular quantum wire in a transverse magnetic field
Authors: Gou Bing-Ping , Kong Xiao-Jun
Published: September 2005

Energy levels and oscillator strengths of an electron have been calculated for a finite rectangular quantum wire in a transverse magnetic field. The results show that the decoupled approximation, a numerical method for solving the Schrödinger equation, is not suitable for a quantum wire with a smaller cross section when the quantum wire has a given width in one direction. With a larger cross section, however, this method is suitable for computing energy levels and oscillator strengths of an electron in the low-lying states of a quantum wire. The results also show that the magnetic field has little influence on the suitability of this method.
Morphological instability of elastic thin films–effect of electromechanical interaction
Authors: Yang Fuqian , Song Wei
Published: September 2005

We examine surface evolution of a stressed elastic conducting thin film in an electric field. A dispersion relation describing morphological evolution of the film is derived by using the theory of linear perturbation. The growth behavior of surface perturbations depends on surface energy, elastic energy, electric energy and electromechanical interaction. Under certain conditions, electric field can suppress surface instability. For surface perturbations of large spatial wavelength, the critical frequency is inversely proportional to the square root of the surface energy of the thin film.
Electron-beam-induced growth of silicon multibranched nanostructures
Authors: Fonseca Luis F. , Resto Oscar , Solá Francisco
Published: September 2005

Although successful nanobranching has been demonstrated for some materials using a variety of methods, the controlled fabrication of multibranched nanostructures of silicon is an important challenge faced by nanotechnologist; because it is crucial for the assembly of electronic interconnects at the atomic scale. Here, we report an electron-beam-induced approach that enables to grow silicon nanobranched structures at specific locations and to control the growth process at the nanoscale level. We further present a detailed in situ imaging of the growth dynamics and explain the results by a qualitative model based on local heating and charge concentration processes.
Polymer nanofibers by soft lithography
Authors: Pisignano Dario , Maruccio Giuseppe , Mele Elisa , Persano Luana , Di Benedetto Francesca , Cingolani Roberto
Published: September 2005

The fabrication of polymeric fibers by soft lithography is demonstrated. Polyurethane, patterned by capillarity-induced molding with high-resolution elastomeric templates, forms mm-long fibers with a diameter below 0.3μm. The Young’s modulus of the fabricated structures, evaluated by force-distance scanning probe spectroscopy, has a value of 0.8MPa. This is an excellent example of nanostructures feasible by the combination of soft nanopatterning and high-resolution fabrication approaches for master templates, and particularly electron-beam lithography.
Photovoltaic effect in poly-dioctyl-phenylene-ethynylene-C60 cells upon donor and acceptor excitation
Authors: Umnov A. G. , Korovyanko O. J.
Published: September 2005

We studied photovoltaic effect in poly-dioctyl-phenylene-ethynylene (PPE)-C60 cells using photovoltage and photocurrent spectroscopy. We observe two-step photoexcitation dependence of open circuit voltage Voc. Two values of Voc are due to different Coulomb binding energies for carriers originated from excitons in PPE and C60. Due to built-in potential between PPE and C60 layers, carriers overcome this exciton binding energy and separate at the heterojunction. We describe our results by energy diagram, comparing exciton binding energies in donor and acceptor moieties.
Effect of pore interconnection on Cu-diffusion-induced failures in porous spin-on low-k dielectrics
Authors: Hwang Sang-Soo , Lee Hee-Chan , Ro Hyun Wook , Yoon Do Yeung , Joo Young-Chang
Published: September 2005

The porosity dependence of electric reliability in the spin-on low-k dielectric with the same matrix but with various porosities was examined using time-dependent dielectric breakdown and capacitance voltage measurements. Abrupt changes in the time to dielectric breakdown and a flatband voltage shift were observed when the porosity of low-k dielectrics was between 20% and 30%. Such a characteristic agrees with the positronium annihilation lifetime spectroscopy data, which indicates that the interconnectivity of the pores abruptly increased in those materials with a porosity between 20% and 30%, and it causes an increase in Cu-diffusion-induced failures.
Approach to optimize conversion efficiency of discharge-pumped plasma extreme ultraviolet sources
Authors: Masnavi Majid , Nakajima Mitsuo , Sasaki Akira , Hotta Eiki , Horioka Kazuhiko
Published: September 2005

The possibility of enhancing the conversion efficiency of a capillary-discharged xenon plasma via a current step is theoretically demonstrated using a simplified model. The current step is shown to exert a significant effect on the plasma dynamics in capillary discharge extreme ultraviolet sources. In particular, the pinching phase can be maintained at a quasi-steady-state by the current control, which prolongs the emission period of radiating plasma.
High electron mobility W-doped In2O3 thin films by pulsed laser deposition
Authors: Newhouse P. F. , Park C.-H. , Keszler D. A. , Tate J. , Nyholm P. S.
Published: September 2005

High electron mobility thin films of In2−xWxO3+y(0⩽x⩽0.075) were prepared on amorphous SiO2 and single-crystal yttria-stablized zirconia (001) substrates by pulsed laser deposition. Mobilities ranged between 66 and 112cm2∕Vs depending on the substrate type and deposition conditions, and the highest mobility was observed at a W-dopant concentration of x∼0.03. A small band gap shift was detected from films with increasing electron carrier density; the electron effective mass calculated from Burstein-Moss theory was 0.3me. In2−xWxO3+y films have high visible transmittance of ∼80%.
Bias-controlled hole degeneracy and implications for quantifying spin polarization
Authors: Kioseoglou G. , Hanbicki A. T. , Jonker B. T. , Petrou A.
Published: September 2005

We report on a spin injection study from an Fe Schottky tunnel contact into n-AlGaAs∕GaAs∕p-AlGaAs light-emitting diodes with a bulk-like GaAs recombination region. The spectral composition and circular polarization of the electroluminescence allowed us to monitor changes in the band structure induced by the applied bias voltage. At low bias conditions, the holes are confined at the GaAs∕p-AlGaAs interface and have two-dimensional (2D) character with nondegenerate heavy- and light-hole subbands. Increasing the bias voltage moves the structure towards a flatband condition, making the holes three-dimensional (3D)-like. The results are discussed in terms of the quantum selection rules describing radiative recombination in 2D and 3D systems.
Electronic interaction anisotropy between open-shell lanthanide atoms and helium from cold collision experiment
Authors: Krems R. V. , Buchachenko A. A.
Published: September 2005

Based on measurements of the Zeeman relaxation in a cold gas of He3 [C. I. Hancox, S. C. Doret, M. I. Hummon, L. Luo, and J. M. Doyle, Nature (London) 431, 281 (2004)], we show that the electronic interaction anisotropy between rare-earth atoms with nonzero electronic orbital angular momenta and helium is extremely small. The interaction of the rare-earth atoms with He gives rise to several adiabatic potentials with different electronic symmetries. It is demonstrated that the energy splitting between these potentials does not exceed 0.09cm−1 at interatomic distances larger than the turning point for collisions at 0.8K, including the region of the van der Waals interaction minima.
Hard x-ray nanoprobe based on refractive x-ray lenses
Authors: Schroer C. G. , Kurapova O. , Patommel J. , Boye P. , Feldkamp J. , Lengeler B. , Burghammer M. , Riekel C. , Vincze L. , van der Hart A. , Küchler M.
Published: September 2005

Based on nanofocusing refractive x-ray lenses a hard x-ray scanning microscope is currently being developed and is being implemented at beamline ID13 of the European Synchrotron Radiation Facility (Grenoble, France). It can be operated in transmission, fluorescence, and diffraction mode. Tomographic scanning allows one to determine the inner structure of a specimen. In this device, a monochromatic (E=21keV) hard x-ray nanobeam with a lateral extension of 47×55nm2 was generated. Further reduction of the beam size to below 20 nm is targeted.
Shot noise in metallic double dot structures with a negative differential conductance
Authors: Nguyen V. Hung , Nguyen V. Lien , Dollfus Philippe
Published: September 2005

The shot noise of current through a metallic double quantum dot structure exhibiting negative differential conductance is studied. We can exactly solve the master equation and derive an analytical expression of the spectral density of current fluctuations as a function of frequency in the first Coulomb staircase region. For a large range of bias voltage the noise is calculated by Monte Carlo simulation. We show that the noise is always sub-Poissonian though it is considerably enhanced in the negative differential conductance regime.
Water buffalo (Bubalus bubalus)interferon-αgenes: cloning, expression and antiviral activities
Authors: Xi-Ju Shi , Chun Xia , Ming Wang
Published: September 2005

Interferon(IFN)-α genes were cloned from genomic DNA of Fuan and Fuzhong water buffaloes by PCR, and the PCR products were inserted into a pQE30 vector to construct recombinant expression plasmids. Sequence analysis showed that both clones were composed of 498 nucleotides, encoding a mature polypeptide with 166 amino acids (aa). They were defined as two new subtypes, with 91.6–94.2% identity at the amino acid level by comparison with eight previously published bovine IFN-α subtypes. Results of SDS-PAGE and Western blotting showed that each of the recombinant proteins was expressed in inclusion bodies inEscherichia coliwith molecular weight of 20 kDa and the recombinant proteins were 25% of the whole proteins. Inclusion bodies were denatured and renatured with urea and the antiviral activities of the recombinant buffalo IFN-α (rBuIFN-α) were 105U/mg and 106U/mg in CEF/VSV and MDBK/VSV cell lines, respectively. Additionally, rBuIFN-α had good effects against challenge byinfectious bovine rhinotracheitis virus. The rBuIFN-α are potential biological agents for the prevention and treatment of various kinds of bovine viral disease.
Cloning and characterization of the light-inducible Gacab promoter from Gossypium arboreum
Authors: Wei-Min Li , Zhi-Xing Wang , Xin-Wu Pei , Shi-Rong Jia
Published: September 2005

A 1009 bp promoter sequence of cab gene, which encodes chlorophyll a/b binding protein belonging to a class of light-inducible proteins, was cloned from Gossypium arboreum. Sequence analysis showed that it had no obvious homology with previously published cab promoters. The full-length Gacab promoter and 5′ deletions with length of 197, 504 and 779 bp were fused with gus (uid A) gene, respectively, and plant expression vectors were used for transformation of Nicotiana tabacum cv. NC89. β-Glucuronidase (GUS) histochemical assay of transgenic tobacco plants showed that GUS was expressed specifically in leaves and young green tissues. GUS was not detected in the leaves of transgenic plants grown in the dark for 6 days. However, it was highly expressed in the leaves of these plants after induction with light for another 6 days, demonstrating that the full-length Gacab promoter is a light-inducible promoter. Transient GUS expression in rice calli indicated that the expression level of Gacab504::gus was the highest and stronger than that of the CaMV 35S promoter, while expression was reduced for Gacab197::gus, Gacab779::gus and Gacab1009::gus constructs. This suggests that −197 bp to −1 bp is a basic promoter of Gacab, some positive regulatory elements may exist in −504 bp to −197 bp, and the fragment −1009 bp to −504 bp may contain negative elements.
Are Biomphalaria snails resistant to Schistosoma mansoni?
Authors: Théron A. , Coustau C.
Published: September 2005

Among Biomphalaria glabrata/Schistosoma mansoni snail–trematode combinations, it appears that some parasites succeed whilst others fail to infect snails. Snails that become infected are termed susceptible hosts. Those which are not infected are traditionally determined as ‘resistant’. Here the concept of B. glabrata resistance to S. mansoni is re-examined in the light of additional observations. It is suggested that, in B. glabrata/S. mansoni, compatibility is tested independently for each individual miracidium and host, and that the success or failure of an infection does not depend on the snail susceptibility/resistance status, but on the ‘matched’ or ‘mismatched’ status of the host and parasite phenotypes.
Phenotypic analysis of adults and eggs of Fasciola hepatica by computer image analysis system
Authors: Valero M.A. , Panova M. , Mas-Coma S.
Published: September 2005

Knowledge of the morphological phenotypes of the liver fluke Fasciola hepatica (Trematoda: Digenea) is analysed. The influence of parasite age on its dimensions, the adult fluke growth model, variation in a biometric variable versus time, and variation in a biometric variable versus another biometric variable (allometric model) are revised. The most useful allometric model appears to be (y2m]#x2212;y2)/y2=c [(y1m−y1)/y1]b, where y1=body area or body length, y2=one of the measurements analysed, y1m, y2m=maximum values towards which y1 and y2, respectively, tend, and c, b=constants. A method based on material standardization, the measurement proposal and allometric analysis is detailed. A computer image analysis system (CIAS), which includes a colour video-camera connected to a stereomicroscope (for adult studies) and a microscope (for egg studies), facilitates the processing of digital imaging. Examples of its application for the analysis of the influence of different factors on the liver fluke phenotype are shown using material from the Northern Bolivian Altiplano, where human and domestic animal fascioliasis is caused by F. hepatica only. Comparisons between the development of livestock fluke populations from highlands and lowlands are discussed and the relationships between host species and liver fluke morphometric patterns is analysed.
Mixed infections with Opisthorchis viverrini and intestinal flukes in residents of Vientiane Municipality and Saravane Province in Laos
Authors: Chai J.-Y. , Park J.-H. , Han E.-T. , Guk S.-M. , Shin E.-H. , Lin A. , Kim J.-L. , Sohn W.-M. , Yong T.-S. , Eom K.S. , Min D.-Y. , Hwang E.-H. , Phommmasack B. , Insisiengmay B. , Rim H.-J.
Published: September 2005

Faecal examinations for helminth eggs were performed on 1869 people from two riverside localities, Vientiane Municipality and Saravane Province, along the Mekong River, Laos. To obtain adult flukes, 42 people positive for small trematode eggs (Opisthorchis viverrini, heterophyid, or lecithodendriid eggs) were treated with a 20–30 mg kg−1 single dose of praziquantel and purged. Diarrhoeic stools were then collected from 36 people (18 in each area) and searched for helminth parasites using stereomicroscopes. Faecal examinations revealed positive rates for small trematode eggs of 53.3% and 70.8% (average 65.2%) in Vientiane and Saravane Province, respectively. Infections with O. viverrini and six species of intestinal flukes were found, namely, Haplorchistaichui, H. pumilio, H. yokogawai, Centrocestus caninus,Prosthodendrium molenkampi, and Phaneropsolus bonnei. The total number of flukes collected and the proportion of fluke species recovered were markedly different in the two localities; in Vientiane, 1041 O. viverrini (57.8 per person) and 615 others (34.2 per person), whereas in Saravane, 395 O. viverrini (21.9 per person) and 155207 others (8622.6 per person). Five people from Saravane harboured no O. viverrini but numerous heterophyid and/or lecithodendriid flukes. The results indicate that O. viverrini and several species of heterophyid and lecithodendriid flukes are endemic in these two riverside localities, and suggest that the intensity of infection and the relative proportion of fluke species vary by locality along the Mekong River basin.
Nutritional well-being of young children in Duncan Village, East London, South Africa: accessibility of primary health care clinics
Authors: de Villiers Anniza , Koko-Mhlahlo Kholeka , Senekal Marjanne
Published: September 2005

Objective

The aim was to contribute to the nutritional well-being of young children living in Duncan Village by investigating factors that influence clinic attendance of mothers and to formulate recommendations for optimisation of accessibility of primary health care (PHC) clinics in the area.

Design

PHC clinic accessibility was evaluated by assessing the experiences of mothers who attended clinics in the area as well as the experiences of health care workers (HCWs) in these clinics of service delivery and its recipients (mothers/children), using the focus group technique. The ATLAS/ti program was used to analyse the data in the following steps: preparation and importing of the data, getting to know and coding the data, retrieval and examination of codes and quotations, creation of families and creation of networks.

Setting

Duncan Village, a low socio-economic urban settlement in East London, South Africa.

Subjects

Focus group discussions (four to seven participants per group) were conducted with four groups of mothers who do not attend PHC clinics, six with mothers who do attend the clinics (including pregnant women) and four groups of HCWs.

Results

Four networks that provide a summary of all the major trends in the data were created. The results clearly indicate that mothers in Duncan Village perceive and/or experience serious problems that make it difficult for them to attend clinic and even prevent them from doing so. These problems include both the way they are treated at the clinics (especially the problem of verbal abuse) as well as the actual services delivered (no medicines, no help, disorganised, long waiting periods, being turned away). The main problem experienced by the HCWs with service delivery seems to be a heavy workload, as well as the fact that many mothers do not come for follow-up visits.

Conclusion

Efforts to increase the accessibility of PHC clinics in Duncan Village should focus on improving the relationship between mothers and HCWs and the heavy workload experienced by these workers.
Cdc42 and Par6–PKCζ regulate the spatially localized association of Dlg1 and APC to control cell polarization
Authors: Etienne-Manneville Sandrine , Manneville Jean-Baptiste , Nicholls Sarah , Ferenczi Michael A. , Hall Alan
Published: September 2005

Cell polarization is essential in a wide range of biological processes such as morphogenesis, asymmetric division, and directed migration. In this study, we show that two tumor suppressor proteins, adenomatous polyposis coli (APC) and Dlg1-SAP97, are required for the polarization of migrating astrocytes. Activation of the Par6–PKCζ complex by Cdc42 at the leading edge of migrating cells promotes both the localized association of APC with microtubule plus ends and the assembly of Dlg-containing puncta in the plasma membrane. Biochemical analysis and total internal reflection fluorescence microscopy reveal that the subsequent physical interaction between APC and Dlg1 is required for polarization of the microtubule cytoskeleton.
A role for the eIF4E-binding protein 4E-T in P-body formation and mRNA decay
Authors: Ferraiuolo Maria A. , Basak Sanjukta , Dostie Josee , Murray Elizabeth L. , Schoenberg Daniel R. , Sonenberg Nahum
Published: September 2005

4E-transporter (4E-T) is one of several proteins that bind the mRNA 5′cap-binding protein, eukaryotic initiation factor 4E (eIF4E), through a conserved binding motif. We previously showed that 4E-T is a nucleocytoplasmic shuttling protein, which mediates the import of eIF4E into the nucleus. At steady state, 4E-T is predominantly cytoplasmic and is concentrated in bodies that conspicuously resemble the recently described processing bodies (P-bodies), which are believed to be sites of mRNA decay. In this paper, we demonstrate that 4E-T colocalizes with mRNA decapping factors in bona fide P-bodies. Moreover, 4E-T controls mRNA half-life, because its depletion from cells using short interfering RNA increases mRNA stability. The 4E-T binding partner, eIF4E, also is localized in P-bodies. 4E-T interaction with eIF4E represses translation, which is believed to be a prerequisite for targeting of mRNAs to P-bodies. Collectively, these data suggest that 4E-T interaction with eIF4E is a priming event in inducing messenger ribonucleoprotein rearrangement and transition from translation to decay.
LIS-less neurons don't even make it to the starting gate
Authors: Hatten Mary E.
Published: September 2005

The manuscript by Tsai et al. (935–945) is a tour de force analysis of a controversial issue in developmental neurobiology, namely the molecular basis of the devastating human brain malformation, type I lissencephaly (Lis1) (Jellinger, K., and A. Rett. 1976. Neuropadiatrie. 7:66–91). For several decades, defects in neuronal migration have been assumed to underlie all defects in cortical histogenesis. In the paper by Tsai et al., the authors use a variety of elegant approaches, including the first real-time imaging of cortical neurons with reduced levels of LIS1, to demonstrate that LIS1 and dynactin act as regulators of dynein during cortical histogenesis. A loss of LIS1 results in both a failure to exit the cortical germinal zone and abnormal neuronal process formation. Thus, the primary action of the mutation is to disrupt the production of neurons in the developing brain as well as their migration.
Stable interaction between α5β1 integrin and Tie2 tyrosine kinase receptor regulates endothelial cell response to Ang-1
Authors: Cascone Ilaria , Napione Lucia , Maniero Fabrizio , Serini Guido , Bussolino Federico
Published: September 2005

During angiogenic remodeling, Ang-1, the ligand of Tie2 tyrosine kinase, is involved in vessel sprouting and stabilization through unclear effects on nascent capillaries and mural cells. In our study, we hypothesized that the Ang-1/Tie2 system could cross-talk with integrins, and be influenced by the dynamic interactions between extracellular matrix and endothelial cells (ECs). Here, we show that α5β1 specifically sensitizes and modulates Tie2 receptor activation and signaling, allowing EC survival at low concentrations of Ang-1 and inducing persistent EC motility. Tie2 and α5β1 interact constitutively; α5β1 binding to fibronectin increases this association, whereas Ang-1 stimulation recruits p85 and FAK to this complex. Furthermore, we demonstrate that Ang-1 is able to mediate selectively α5β1 outside-in FAK phosphorylation. Thus, Ang-1 triggers signaling pathways through Tie2 and α5β1 receptors that could cross-talk when Tie2/α5β1 interaction occurs in ECs plated on fibronectin. By using blocking antibodies, we consistently found that α5β1, but not αvβ3 activation, is essential to Ang-1–dependent angiogenesis in vivo.
Computation of dynamical correlation functions of Heisenberg chains: the gapless
anisotropic regime
Authors: Caux Jean-Sébastien , Hagemans Rob , Maillet Jean Michel
Published: September 2005

We compute all dynamical spin–spin correlation functions for the
spin-1/2 XXZ
anisotropic Heisenberg model in the gapless antiferromagnetic regime at zero
temperature, using numerical sums of exact determinant representations for form
factors of spin operators on the lattice. Contributions from intermediate states
containing many particles and string (bound) states are included. We present modified
determinant representations for the form factors valid in the general case with string
solutions to the Bethe equations. Our results are such that the available sum
rules are saturated to high precision. We Fourier transform our results back to
real space, allowing us in particular to make a comparison with known exact
formulae for equal-time correlation functions for small separations in zero field,
and with predictions for the zero-field asymptotics from conformal field theory.
DrosophilaNod Protein Binds Preferentially to the Plus Ends of Microtubules and Promotes Microtubule Polymerization In Vitro
Authors: Cui Wei , Sproul Lisa R. , Gustafson Susan M. , Matthies Heinrich J.G. , Gilbert Susan P. , Hawley R. S.
Published: September 2005

Nod, a nonmotile kinesinlike protein, plays a critical role in segregating achiasmate chromosomes during female meiosis. In addition to localizing to oocyte chromosomes, we show that functional full-length Nod-GFP (NodFL-GFP) localizes to the posterior pole of the oocyte at stages 9–10A, as does kinesin heavy chain (KHC), a plus end-directed motor. This posterior localization is abolished in grk mutants that no longer maintain the microtubule (MT) gradient in the oocyte. To test the hypothesis that Nod binds to the plus ends of MTs, we expressed and purified both full-length Nod (NodFL) and a truncated form of Nod containing only the motorlike domain (Nod318) from Escherichia coli and assessed their interactions with MTs in vitro. Both NodFLand Nod318demonstrate preferential binding to the ends of the MTs, displaying a strong preference for binding to the plus ends. When Nod318-GFP:MT collision complexes were trapped by glutaraldehyde fixation, the preference for binding to plus ends versus minus ends was 17:1. NodFLand Nod318also promote MT polymerization in vitro in a time-dependent manner. The observation that Nod is preferentially localized to the plus ends of MTs and stimulates MT polymerization suggests a mechanism for its function.
The Pseudomonas fluorescens SBW25 wrinkly spreader biofilm requires attachment factor, cellulose fibre and LPS interactions to maintain strength and integrity
Authors: Spiers Andrew J. , Rainey Paul B.
Published: September 2005

The wrinkly spreader (WS) isolate ofPseudomonas fluorescensSBW25 forms a substantial biofilm at the air–liquid interface. The biofilm is composed of an extracellular partially acetylated cellulose-fibre matrix, and previous mutagenesis of WS with mini-Tn5had identified both the regulatory and cellulose-biosynthetic operons. One uncharacterized WS mutant, WS-5, still expressed cellulose but produced very weak biofilms. In this work, the mini-Tn5insertion site in WS-5 has been identified as being immediately upstream of thetol-paloperon. Like Tol-Pal mutants of other Gram-negative bacteria, WS-5 showed a ‘leaky-membrane’ phenotype, including the serendipitous ability to utilize sucrose, increased uptake of the hydrophilic dye propidium iodide, and the loss of lipopolysaccharide (LPS) expression. WS-5 cells were altered in relative hydrophobicity, and showed poorer recruitment and maintenance in the biofilm than WS. The WS-5 biofilm was also less sensitive to chemical interference during development. However, growth rate, cellulose expression and attachment were not significantly different between WS and WS-5. Finally, WS-5 biofilms could be partially complemented with WS-4, a biofilm- and attachment-deficient mutant that expressed LPS, resulting in a mixed biofilm with significantly increased strength. These findings show that a major component of the WS air–liquid biofilm strength results from the interactions between LPS and the cellulose matrix of the biofilm – and that in the WS biofilm, cellulose fibres, attachment factor and LPS are required for biofilm development, strength and integrity.
Enteropathogenic Escherichia coli type III effectors alter cytoskeletal function and signalling in Saccharomyces cerevisiae
Authors: Rodríguez-Escudero Isabel , Hardwidge Philip R. , Nombela César , Cid Víctor J. , Finlay B. Brett , Molina María
Published: September 2005

Enteropathogenic Escherichia coli (EPEC) strains cause attaching/effacing lesions in enterocytes through the development of actin-supported pedestals at the site of bacterial adhesion. Pathogenesis requires a type III secretion system (TTSS), which injects into the host cell the intimin receptor, Tir, as well as other effectors called Esps (Escherichia secreted proteins). The genes encoding TTSS structural components and Esps are found within a pathogenicity island called the locus of enterocyte effacement (LEE). This paper describes the application of Saccharomyces cerevisiae as a model to probe the functions of LEE-encoded genes. In a systematic approach, the LEE-encoded translocator and effector proteins were endogenously expressed in yeast and their effects on cell growth, cytoskeletal function and signalling pathways were studied. EspD, EspG and Map inhibited growth by depolarizing the actin cortical cytoskeleton, whereas EspF expression altered the septin cytoskeleton. Specific yeast MAP kinase pathways were activated by EspF, EspG, EspH and Map. The yeast system was used to define functional domains in Map by expressing truncated versions; it was concluded that the C-terminal region of the protein is necessary for actin disruption and toxicity, but not for mitochondrial localization. The utility of the yeast model for functional analyses of EPEC pathogenesis is discussed.
Subinhibitory cerulenin inhibits staphylococcal exoprotein production by blocking transcription rather than by blocking secretion
Authors: Adhikari Rajan P. , Novick Richard P.
Published: September 2005

Cerulenin is an antibiotic that inhibits fatty acid synthesis by covalent modification of the active thiol of the chain-elongation subtypes of β-ketoacyl-acyl carrier protein synthase. It also inhibits other processes that utilize essential thiols. Cerulenin has been widely reported to block protein secretion at sub-MIC levels, an effect that has been postulated to represent interference with membrane function through interference with normal fatty acid synthesis. This study confirms the profound reduction in extracellular proteins caused by low concentrations of the antibiotic, and shows by Northern blot hybridization that this reduction is due to interference with transcription. By exchanging promoters between entB, a gene that is inhibited by cerulenin, and entA, a gene that is not, it was also shown that the antibiotic does not block secretion. Subinhibitory concentrations of cerulenin were also found to block transcriptional activation of at least two regulatory determinants, agr and sae, that function by signal transduction. Interference with the activation of these and other regulatory determinants probably accounts for much of the inhibitory effect on exoprotein production of sub-MIC concentrations of cerulenin.
Characterization of the role of LtgB, a putative lytic transglycosylase in Neisseria gonorrhoeae
Authors: Kohler Petra L. , Cloud Karen A. , Hackett Kathleen T. , Beck Eric T. , Dillard Joseph P.
Published: September 2005

Neisseria gonorrhoeaereleases monomeric peptidoglycan (PG) fragments during growth. These PG fragments affect pathogenesis-related phenotypes including induction of inflammatory cytokines and killing of ciliated fallopian tube cells. Although the biological activities of these molecules have been established in multiple systems, the genes and gene products responsible for their production inN. gonorrhoeaehave not been determined. The authors previously identified genes for three lytic transglycosylase homologues (ltgA,ltgBandltgC) in theN. gonorrhoeaegenome sequence. Mutation ofltgAwas found to affect PG fragment release, and mutation ofltgCaffected cell separation. In this study the effects of complete deletion or point mutations inltgBwere characterized. Point mutations were introduced by a combination of insertion-duplication mutagenesis and positive and negative selection, thereby generating selectable marker-less mutations. TheltgBdeletion mutant had normal growth characteristics and was not affected in PG fragment release. When expressed inEscherichia coli, gonococcal LtgB was able to substitute for lambda endolysin to cause cell lysis. Mutation of the predicted catalytic-site glutamic acid residue did not decrease lysis in this system. However, mutation of a nearby glutamic acid residue eliminated lysis activity.
An unusual Tn21-like transposon containing an ars operon is present in highly arsenic-resistant strains of the biomining bacterium Acidithiobacillus caldus
Authors: Tuffin I. Marla , de Groot Peter , Deane Shelly M. , Rawlings Douglas E.
Published: September 2005

A transposon, TnAtcArs, that carries a set of arsenic-resistance genes was isolated from a strain of the moderately thermophilic, sulfur-oxidizing, biomining bacteriumAcidithiobacillus caldus. This strain originated from a commercial plant used for the bio-oxidation of gold-bearing arsenopyrite concentrates. Continuous selection for arsenic resistance over many years had made the bacterium resistant to high concentrations of arsenic. Sequence analysis indicated that TnAtcArsis 12 444 bp in length and has 40 bp terminal inverted repeat sequences and divergently transcribed resolvase and transposase genes that are related to the Tn21-transposon subfamily. A series of genes consisting ofarsR, two tandem copies ofarsAandarsD, two ORFs (7 and 8) andarsBis situated between the resolvase and transposase genes. Although some commercial strains ofAt. calduscontained thearsDAduplication, when transformed intoEscherichia coli, thearsDAduplication was unstable and was frequently lost during cultivation or if a plasmid containing TnAtcArswas conjugated into a recipient strain. TnAtcArsconferred resistance to arsenite and arsenate uponE. colicells. Deletion of one copy ofarsDAhad no noticeable effect on resistance to arsenite or arsenate inE. coli. ORFs 7 and 8 had clear sequence similarity to an NADH oxidase and a CBS-domain-containing protein, respectively, but their deletion did not affect resistance to arsenite or arsenate inE. coli. TnAtcArswas actively transposed inE. coli, but no increase in transposition frequency in the presence of arsenic was detected. Northern hybridization and reporter gene studies indicated that although ArsR regulated the 10 kb operon containing the arsenic-resistance genes in response to arsenic, ArsR had no effect on the regulation of genes associated with transposition activity.
Regulation of nickel‐induced T‐cell responsiveness by CD4+CD25+cells in contact allergic patients and healthy individuals
Authors: Moed H. , Von Blomberg B. M. E. , Bruynzeel D. P. , Scheper R. J. , Gibbs S. , Rustemeyer T.
Published: September 2005

In this study, we investigated the capacity of CD4+CD25+ regulatory T cells to suppress nickel‐specific effector T cells, both in nickel‐allergic patients and healthy controls. CD4+ cells isolated from allergic patients showed an increased proliferative response to nickel, whereas CD4+ cells from negative controls did not respond to allergen. When CD4+CD25+ cells were depleted, nickel‐specific responsiveness was strongly increased both in allergic and in non‐allergic individuals, with the most pronounced effect in allergic patients. These regulatory T cells were anergic to nickel but inhibited nickel‐specific CD4+CD25– effector T cells in coculture experiments. CD4+CD25+ cells from nickel‐allergic patients showed only a limited capacity to suppress effector T‐cell responsiveness, because an increased nickel reactivity could still be detected in these cocultures. None of the isolated CD4+CD25+ cells, either isolated from healthy controls or allergic patients, produced IL‐10 in response to nickel. Overall, these results support the view that CD4+CD25+ cells can control the activation of nickel‐specific effector T cells in non‐allergic individuals, whereas this regulatory capacity is impaired in allergic patients. To investigate the presence of allergen‐specific regulatory T cells in truly naïve, non‐sensitized individuals, T‐cell reactivity should also be studied with non‐environmental contact allergens, such as para‐phenylenediamine.
Contact vitiligo following a strong patch test reaction to triglycidyl‐p‐aminophenol in an aircraft industry worker: case report and review of the literature
Authors: Jappe U. , Geier J. , Hausen B. M.
Published: September 2005

Epoxy resin systems (ERSs) are a frequent cause of occupational allergic contact dermatitis. A 50‐year‐old patient developed eczematous skin lesions on the back of his hands, lower arms and eye lids, 2 months after he had started working in aircraft construction. Patch tests showed positive reactions at day 3 to nickel sulfate, epoxy resin based on diglycidyl ether of bisphenol F (DGEBF) and 1,4‐butanediol diglycidyl ether (1,4‐BDDGE). The chemical triglycidyl‐p‐aminophenol (TGPAP) applied at 1% and 0.1% induced the strongest (+++ positive) reaction. About 4 months after the patch test with TGPAP, the patient presented with 2 circular depigmented spots in the former TGPAP‐patch test areas. Dermatohistopathology confirmed the diagnosis of contact vitiligo.
Effect of temperature and moisture on rates of carbon mineralization in a Mediterranean oak forest soil under controlled and field conditions
Authors: Rey A. , Petsikos C. , Jarvis P. G. , Grace J.
Published: September 2005

We examined the relationship between carbon mineralization (Cmin), moisture and temperature in a Mediterranean forest soil under controlled and field conditions. We studied the following.

1 The temperature sensitivity at three soil depths: soil samples were incubated at 4, 10, 20 and 30°C at optimal water content of 60% of water holding capacity (WHC). Values ofCminof the top layer were more than 12 times faster than those measured in deeper layers. We found a temperature sensitivity factor (Q10) of 3.3, 2.7 and 2.2 for the 0–5 cm, 5–10 cm and 10–20 cm layers, respectively.

2 The relationship betweenCmin, moisture and temperature (top layer). The sensitivity ofCminto fluctuating moisture depended on temperature. However, theQ10was not significantly affected by soil moisture. We fitted a multiple polynomial model that predictedCminas a multiplicative function of temperature and moisture (R2 > 0.99).

3 The response ofCminof soil to rewetting after 1 and 24 hours. In all cases, the response was rapid. The soil incubated at 60% WHC or less responded positively to a sudden increase in water content, with the largest increase in the 20% WHC treatment. The model predictedCminin the field well when rewetting effects were taken into account (R2 > 0.81).

These results indicate that sudden changes in soil moisture can lead to increased carbon mineralization during the dry summer. It is necessary to include such responses in models as they may represent a substantial loss of carbon in the overall carbon balance of Mediterranean ecosystems.
13C and 15N natural abundances of urban soils and herbaceous vegetation in Karlsruhe, Germany
Authors: Norra S. , Handley L. L. , Berner Z. , Stüben D.
Published: September 2005

We undertook what we believe to be a unique survey of the natural abundances of 13C and 15N in urban soils and plants in Karlsruhe (Germany), a European city of average size. We found broad patterns of these abundances in both soils and plants, which reflected geology and land use. In contrast with studies on smaller areas (showing the direct effect of human activities), our study first determined the extent to which the abundances correlated with land use or underlying geology and then assessed how we could further test such relationships. The spatial pattern of δ13C in surface soil correlated with that of the underlying parent material; construction activities superimposed a secondary signal. Maize cultivation was a source of less negative soil δ13C, whereas the C3 vegetation is a source of more negative soil δ13C. There was a footprint of less negative plant δ13C in the industrial and port areas; plant δ13C downwind of the city was less negative than upwind, which might relate to atmospheric pollution from the port area or to differences in soil properties. There was no significant effect of wind direction or geology on soil or plant δ15N, which was correlated mainly with land use. The largest soil δ15N was under agriculture and the smallest under woodland. The abundance of 15N in inner‐urban soil and plants was intermediate between those of agriculture and forests. This study represents a major advance in the use of stable isotope geochemistry in understanding urban environments.