bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation of gingival T cell lines/clones specific with Porphyromonas gingivalis pulsed dendritic cells from periodontitis patients
Authors: Aroonrerk Nuntana , Pichyangkul Sathit , Yongvanitchit Kosol , Wisetchang Mahisorn , Sa‐Ard‐Iam Noppadol , Sirisinha Stitaya , Mahanonda Rangsini
Published: September 2009

Objectives and background:  It is well documented that in periodontitis lesions, most infiltrated gingival T cells are antigen‐specific memory T cells. These cells play an important role as regulators and effector cells in the pathogenesis of periodontitis. In this study, we used dendritic cells (DCs) as antigen‐presenting cells to generate human gingival T cell lines and clones specific for Porphyromonas gingivalis from periodontitis patients.

Methods:  Autologous DCs were derived from the patients' adherent monocytes using granulocyte‐macrophage colony‐stimulating factor and interleukin (IL)‐4. Lymphocytes were isolated from gingival biopsies using collagenase enzyme digestion and the number was increased by subsequent culturing in IL‐2‐containing medium. T cells were then negatively sorted using flow cytometry, cocultured with P. gingivalis‐pulsed DCs and subsequently expanded in the culture medium containing IL‐2. T cells were kept viable and active by periodic exposure to antigen‐pulsed DCs. The specificity of the T cell lines was tested against four plaque bacteria: P. gingivalis, Actinobacillus actinomycetemcomitans, Prevotella intermedia and Actinomyces viscosus. The established T cell lines were then cloned. Three P. gingivalis‐specific T cell lines and 12 gingival T cell clones were generated. They all showed good specificity against P. gingivalis but not to other plaque bacteria.

Results:  All T cell clones were positive for CD4 and the majority of them produced interferon gamma, but a minimal or negligible amount of IL‐5.

Conclusions:  The data obtained clearly showed that monocyte‐derived DCs could be used as powerful antigen‐presenting cells to generate antigen‐specific T cells from periodontitis tissues.
Comparing and Explaining Public Acceptance Of Ecological Forestry in Tasmania and the U.S. Pacific Northwest
Authors: Ribe Robert , Ford Rebecca , Williams Kath
Published: September 2009

Major controversies have erupted in recent years about extensive and intensive timber harvesting programs in Tasmania and the U.S. Pacific Northwest. These conflicts have centered on ecological impacts and both regions have responded by adopting similar programs of “ecological forestry.” Both programs emphasize the retention of varying amounts of trees in aggregated or dispersed patterns within harvests, and seek to “life boat” mature-forest habitat functions across some harvest prescriptions. Are these programs garnering similar public acceptance? Do people with similar ideologies judge the acceptability of forests similarly in both regions? Do perceptions differ between regions due to differences in ecological, cultural or economic conditions? Similar public perception surveys within each region investigated the acceptance of harvest prescriptions that matched closely between regions. In both surveys, images of the appearance of harvests were presented to respondents with expert-derived information about the magnitude of similar ecological, safety and economic impacts. Respondents rated the acceptability of each prescription. Respondents’ environmental attitudes were classified as forest protectionist, productionist or non-aligned within each region. Statistical and graphical analyses compared the patterns and sources of comparable acceptability judgments between the regions.

Results/Conclusions

Ideologically similar samples of respondents in both regions exhibited comparable patterns of increasing mean acceptability ratings with increasing tree retention levels for all harvest prescriptions, except 30-40% dispersed retention harvests. These comparable respondent samples also exhibited similar correlations between acceptability ratings and levels of harvest impacts by category, exhibiting the same associations between ideologies and preferred impacts across regions. Three exceptions showed that Tasmanians exhibited a greater range of sensitivity for certain impact categories: (1) ground habitat impacts, likely attributable to greater retention of down wood in all Pacific Northwest prescriptions, versus burning most down wood in some Tasmanian prescriptions for regeneration of commercial species; (2) logger safety, likely attributable to greater differences in actual safety levels across the Tasmanian prescriptions; and (3) wildfire risk, likely because the affected Pacific Northwest region has few historical wildfires. Utility functions were estimated for each region’s respondents and applied to the opposite region’s forests. This confirmed that both regions’ respondents would agree about the lower acceptability of Tasmanian 30-40% dispersed retention harvests, likely because Tasmanians retain only a percent of commercial species while felling all other trees, versus Americans’ retention of a percent of all tree types, retaining more trees and more ecosystem components.
Effect of pressure on the magnetic properties of CrB2
Authors: Grechnev G. E. , Panfilov A. S. , Fedorchenko A. V. , Filippov V. B. , Lyashchenko A. B. , Vasiliev A. N.
Published: September 2009

The magnetic susceptibility χ of the itinerant antiferromagnet CrB2 with TN≃87K is studied as a function of the hydrostatic pressure up to 2kbar at fixed temperatures 78 and 300K. The pressure effect on χ is found to be negative in sign and weakly dependent on the magnetic state of the compound. In addition, the measured pressure dependence of the Néel temperature, dTN∕dP=0.1±0.1K∕kbar, is roughly two orders of magnitude smaller than the corresponding value for the pure chromium. The main contributions to χ and their volume dependence are calculated ab initio within the local spin density approximation, and they turn out to be in close agreement with the experimental data.
Grüneisen’s law and particularities of electronic excitations in quasicrystals
Authors: Prekul A. F. , Shchegolikhina N. I. , Podgornykh S. M.
Published: September 2009

Grüneisen’s law according to which the temperature dependence of the lattice specific heat at constant volume is similar to that of the thermal expansion coefficient is checked experimentally for the icosahedral phase of Al63Cu25Fe12. The specific heat CP(T) and linear thermal expansion coefficient αL(T) are measured in the temperature interval 1.8–400K. It is found that Grüneisen’s law holds quite satisfactorily in the temperature range 200–400K. Significant deviations from this law are found at lower temperatures. These deviations are due to the presence of “excess” specific heat of the Schottky anomaly type. It is shown that this contribution is of electronic origin.
Chemisorption of water and carbon dioxide on nanostructured BaTiO3–SrTiO3(001) surfaces
Authors: Baniecki J. D. , Ishii M. , Kurihara K. , Yamanaka K. , Yano T. , Shinozaki K. , Imada T. , Kobayashi Y.
Published: September 2009

The interaction of water and carbon dioxide with nanostructured epitaxial (Ba,Sr)TiO3(001) thin film and bulk single crystal SrTiO3(001) surfaces was studied using x-ray photoemission spectroscopy (XPS), thermal desorption spectroscopy (TDS), and density functional theory (DFT). On both surfaces, XPS and TDS indicate D2O and CO2 chemisorb at room temperature with broad thermal desorption peaks (423–723 K) and a peak desorption temperature near 573 K. A comparison of thermal desorption Redhead activation energies to adsorption energies calculated using DFT indicates that defect surface sites are important for the observed strong adsorbate-surface reactivity. Numerical calculations of the competetive adsorption/desorption equilibria for H2O and CO2 on SrTiO3(001) surfaces show that for typical atmospheric concentrations of 0.038% carbon dioxide and 0.247% water vapor the surfaces are covered to a large extent with both adsorbates. The high desorption temperature indicates that these adsorbates have the potential to impact measurements of the electronic structure of BaTiO3–SrTiO3(001) surfaces exposed to air, or prepared in high vacuum deposition systems, as well as the electrical properties of thin film ATiO3-based devices.
Hall-effect anomalies near the quantum critical point in CeCu6−xAux
Authors: Sluchanko N. E. , Sluchanko D. N. , Samarin N. A. , Glushkov V. V. , Demishev S. V. , Kuznetsov A. V. , Burkhanov G. S. , Chistyakov O. D.
Published: September 2009

The results of Hall-effect and resistance measurements on the substitutional solid solutions CeCu6−xAux with concentrations 0⩽x⩽0.3, corresponding to a wide neighborhood of the quantum critical point (QCP) at x=0.1, are presented. The measurements are made by rotation of the sample in a constant magnetic field of up to 70kOe in a temperature interval of 1.8–300K. For the classic heavy-fermion compound CeCu6 the temperature dependence of the Hall coefficient RH(T) exhibits a complex activational form with activation energies Ea1∕kB≈110K and Ea2∕kB≈1.5K in the temperature intervals 50–300K and 3–10K, respectively. It is shown that the anomalous behavior of the Hall effect can be explained in a spin-polaron approach, in which the values Ea1,2 can be associated to the binding energy of many-body and one can obtain estimates of the effective mass (meff1,2≈130–150m0) and localization radius (ap1,2*≈1.7 and 14Å) of the charge carriers in CeCu6. For the compound CeCu5.9Au0.1, corresponding to the QCP, one observes correlated power-law behavior of the temperature dependence of the Hall coefficient RH(T)∼T−0.4 and magnetic susceptibility χ(T)∼T−0.4, as is characteristic of the regime of quantum critical behavior. For compounds in the immediate vicinity of the QCP an anomalous, even contribution RH2 to the angular dependence of the Hall voltage appears at temperatures below T*∼24K and becomes stronger with increasing magnetic field. Different scenarios for passage through the QCP and their applicability for describing the Hall-effect anomalies in the substitutional solid solutions CeCu6−xAux are discussed.
Isochoric thermal conductivity of solid n-alkanes: propane C3H8
Authors: Konstantinov V. A. , Revyakin V. P. , Sagan V. V.
Published: September 2009

The isochoric thermal conductivity of solid propane C3H8 is investigated on three samples of different densities in the temperature interval from 50K to the onset of melting. In all cases the isochoric thermal conductivity exhibits dependences that are weaker than Λ∝1∕T. The results obtained are compared with those for other representatives of n-alkanes. The experimental data are discussed within a model in which the heat is transported by low-frequency phonons and by “diffusive” modes above the phonon mobility edge.
Grafted polybutadiene for fast retrieval of optical information
Authors: Mysliwiec J. , Czajkowski M. , Miniewicz A. , Kochalska A. , Sedlakova Z. , Nespurek S.
Published: September 2009

The goal of the investigations was to measure the dynamics of molecular reorientation in polybutadiene backbone based polymer grafted with photochromic thiols. Measurements were performed in a typical degenerate two- and four-wave mixing experiments, in which time constants of dynamic diffraction grating formation were determined. Holographic gratings which were inscribed in polymeric liquid crystalline films show switching times (build-up and decay) within the 20–70 ms range. An excellent reversibility of the recording-erasure process is reported.
Evaluation of B+-implanted n+-n-p HgCdTe structures using transient microwave reflectance
Authors: Manchanda Rachna , Pal R. , Malik A. , Saxena R. S. , Thakur O. P. , Sharma R. K.
Published: September 2009

Transient microwave reflectance (TMWR) has been used to investigate the n+-n-p HgCdTe structures formed by B+ implantation and moderate annealing. Vacancy-doped p-type bulk HgCdTe (x∼0.285) crystals were used in this work. 130 keV B+ ions were implanted at a dose of 1×1014 cm−2. Samples were successively thinned through etching in 0.5% Br2 in CH3OH solutions with a standardized procedure for differential Hall/resistivity measurements. At every differential etch step, the TMWR signal was also recorded and theoretically analyzed for estimating bulk lifetime and surface recombination velocity. Results for as-implanted as well as moderately annealed samples have been presented. The study indicated the usefulness of TMWR analysis in evaluating implant anneal process for the formation of n+-n-p HgCdTe structures for photodetector fabrication.
Organic thin film photovoltaic cells based on planar and mixed heterojunctions between fullerene and a low bandgap oligothiophene
Authors: Wynands David , Männig Bert , Riede Moritz , Leo Karl , Brier Eduard , Reinold Egon , Bäuerle Peter
Published: September 2009

We present the material α-ω-bis-(dicyanovinylen)-sexithiophen (DCV6T) as donor material in organic solar cells. A systematic study on the potential of DCV6T is given for different active layer concepts. DCV6T is a member of a class of acceptor-substituted oligothiophenes, which showed efficiencies of up to 3.4% and open circuit voltages (Voc) of 1.0V, which were recently reported [K. Schulze et al. Adv. Mater. (Weinheim, Ger.) 18, 2875 (2006)]. To verify the potential of the material (DCV6T), organic solar cells with planar heterojunctions, bulk heterojunctions, and a hybrid-planar-mixed heterojunction are investigated. The planar heterojunction solar cells of DCV6T and C60 show the highest Voc of 0.90V. The mixed heterojunction solar cells have improved currents but a lower Voc of 0.82V. The solar cell using the hybrid-planar-mixed heterojunction achieves the best combination of parameters. It has a Voc of 0.88V, a short circuit current (jsc) of 5.7±0.4mAcm−2, a fill factor of 41.6%, and a power conversion efficiency of 2.1±0.2%.
Perpendicular magnetization of long iron carbide nanowires inside carbon nanotubes due to magnetocrystalline anisotropy
Authors: Weissker Uhland , Löffler Markus , Wolny Franziska , Lutz Matthias Uljas , Scheerbaum Nils , Klingeler Rüdiger , Gemming Thomas , Mühl Thomas , Leonhardt Albrecht , Büchner Bernd
Published: September 2009

Single crystal iron carbide nanowires contained in multiwalled carbon nanotubes have been prepared by aerosol-based thermal chemical vapor deposition. Investigations by transmission electron microscopy reveal the crystallographic [010] axis of the orthorhombic Fe3C nanowires to be predominantly aligned along the nanotube axis. Despite the high aspect ratio of the Fe3C nanowires, magnetic force microscopy measurements imply single domain behavior with the easy magnetic axis of the nanowires perpendicular to the wire axis. In agreement with the structural results, these findings show that the magnetic behavior is dominated by the magnetocrystalline anisotropy contribution, causing the easy axis to be along the [001] direction.
Electrode metal dependence of the rectifying performance for molecular devices: A density functional study
Authors: Deng X. Q. , Zhou J. C. , Zhang Z. H. , Tang G. P. , Qiu M.
Published: September 2009

Carrying out theoretical calculations using the nonequilibrium Green’s function method combined with the density functional theory, the transport properties of the terphenyl molecule connected to the two Y (Y=Li, Al, or Au) metal electrodes are investigated. The results show that the electrode metals have a distinct influence on rectifying performance of such devices. For the Au electrode system, we can observe a best rectifying performance, next for the Al electrode system, and the rectifying effect can be nearly neglected for the Li electrode system. Our findings suggest that the rectifying characteristics are intimately related to electrode materials.
Inverse geometry for grating-based x-ray phase-contrast imaging
Authors: Donath Tilman , Chabior Michael , Pfeiffer Franz , Bunk Oliver , Reznikova Elena , Mohr Juergen , Hempel Eckhard , Popescu Stefan , Hoheisel Martin , Schuster Manfred , Baumann Joachim , David Christian
Published: September 2009

Phase-contrast imaging using conventional polychromatic x-ray sources and grating interferometers has been developed and demonstrated for x-ray energies up to 60 keV. Here, we conduct an analysis of possible grating configurations for this technique and present further geometrical arrangements not considered so far. An inverse interferometer geometry is investigated that offers significant advantages for grating fabrication and for the application of the method in computed tomography (CT) scanners. We derive and measure the interferometer’s angular sensitivity for both the inverse and the conventional configuration as a function of the sample position. Thereby, we show that both arrangements are equally sensitive and that the highest sensitivity is obtained, when the investigated object is close to the interferometer’s phase grating. We also discuss the question whether the sample should be placed in front of or behind the phase grating. For CT applications, we propose an inverse geometry with the sample position behind the phase grating.
A model for static friction in a film-terminated microfibril array
Authors: Liu J. , Hui C. Y. , Jagota A. , Shen L.
Published: September 2009

We model the response of a film-terminated microfibril array subjected to shear through contact with a rigid cylindrical indenter. Our model determines the shear force acting on the indenter for a fixed normal indenter force before the onset of uniform sliding. Consistent with experiment, our model shows that (1) the contact area increases only slightly with the applied shear and (2) the fibrils inside the contact zone are subjected to tension at intermediate to large applied shear displacement despite the fact that the applied normal load is compressive. These features can be explained by the fact that in our samples the continuous terminal film supports tension. The model accurately matches the experimentally measured shear force response. With the use of an independently measured critical energy release rate for unstable release of the contact, the model shows how this architecture achieves a strong enhancement in static friction.
Formation of metal nanoparticles by short-distance sputter deposition in a reactive ion etching chamber
Authors: Nie Min , Sun Kai , Meng Dennis Desheng
Published: September 2009

A new method is reported to form metal nanoparticles by sputter deposition inside a reactive ion etching chamber with a very short target-substrate distance. The distribution and morphology of nanoparticles are found to be affected by the distance, the ion concentration, and the sputtering time. Densely distributed nanoparticles of various compositions were fabricated on the substrates that were kept at a distance of 130 μm or smaller from the target. When the distance was increased to 510 μm, island structures were formed, indicating the tendency to form continuous thin film with longer distance. The observed trend for nanoparticle formation is opposite to the previously reported mechanism for the formation of nanoparticles by sputtering. A new mechanism based on the seeding effect of the substrate is proposed to interpret the experimental results.
Effect of the electron energy distribution function in plasma on the Bohm criterion and on the drop voltage through the sheath: Case of microwave expanding plasma
Authors: Jauberteau J. L. , Jauberteau I.
Published: September 2009

This work is devoted to the study of the sheath expansion above a charged species collector immersed into the plasma in the general case of the electron energy distribution function (EEDF) (not necessarily a Boltzmann distributed function). In the first part, considering the general form of the electron kinetic energy distribution function (EEDF) in the plasma and assuming a one dimensional system, we propose an equation describing the limit value of the ion velocity at the sheath edge. Then, we extend this equation to the three dimensional problem. These results are discussed assuming Boltzmann distribution for the one dimensional system and Maxwell–Boltzmann distribution in the case of the three dimensional system. Both one and two temperature distributions are considered. Then, the method is applied to experimental results obtained in expanding microwave discharge sustained in argon. In the second part, we study the drop voltage through the sheath that is produced around a cylindrical collector biased at the floating potential. A theoretical model is given, and results are compared with experimental values measured by means of a cylindrical Langmuir probe immersed in microwave expanding plasma. The model agrees with experiments and points out the role of the EEDF profile on the ion velocity at the sheath edge and, consequently, on the drop voltage through the sheath.
Improved magnetoresistance through spacer thickness optimization in tilted pseudo spin valves based on L1 (111)-oriented FePtCu fixed layers
Authors: Zha C. L. , Fang Y. Y. , Nogués J. , Åkerman Johan
Published: September 2009

Through optimization of the Cu spacer thickness, we demonstrate magnetoresistance (MR) up to 5% in FePtCu/CoFe/Cu/CoFe/NiFe pseudo spin valves based on L10 (111) FePtCu fixed layers with a tilted magnetization. We find an optimum spacer thickness of about 2.4 nm which correlates with a clear onset of strong interlayer exchange coupling below 2.4 nm and spin-independent current shunting in the spacer above 2.4 nm. We argue that yet higher MR should be possible through further reduction in the interlayer exchange coupling.
Evolution of Ni:B2O3 core-shell structure and magnetic properties on devitrification of amorphous NiB particles in air
Authors: Singh Vidyadhar , Srinivas V.
Published: September 2009

The Ni:B2O3 nanoparticles have been synthesized by a novel two-step chemical reduction method, under ambient conditions and subsequent annealing in air. The evolution of this structure has been followed through a sequence of annealing treatments. Structural and magnetic investigations on as-prepared and annealed samples revealed that as-prepared samples are weakly magnetic and develop into spherical ferromagnetic entities with superior magnetic properties. The saturation magnetization (Ms∼42 emu/g) and coercivity (Hc∼482 Oe) at room temperature clearly suggest that the air annealed (500 °C) samples are protected from the oxidation due to formation of B2O3 protective layer. The magnetization results are consistent with the observed microstructural changes and satisfactorily explained on the basis of a core-shell model, where we consider each particle as a magnetically heterogeneous system consisting of a ferromagnetic core of Ni and nonmagnetic shell of B2O3. These results suggest that this kind of nanocomposite systems might have significant potential as a recording media.
Hyperthermal atomic oxygen source for near-space simulation experiments
Authors: Dodd James A. , Baker Paul M. , Hwang Eunsook S. , Sporleder David , Stearns Jaime A. , Chambreau Steven D. , Braunstein Matthew , Conforti Patrick F.
Published: September 2009

A hyperthermal atomic oxygen (AO) beam facility has been developed to investigate the collisions of high-velocity AO atoms with vapor-phase counterflow. Application of 4.5 kW, 2.4 GHz microwave power in the source chamber creates a continuous discharge in flowing O2 gas. The O2 feedstock is introduced into the source chamber in a vortex flow to constrain the plasma to the center region, with the chamber geometry promoting resonant excitation of the TM011 mode to localize the energy deposition in the vicinity of the aluminum nitride (AlN) expansion nozzle. The approximately 3500 K environment serves to dissociate the O2, resulting in an effluent consisting of 40% AO by number density. Downstream of the nozzle, a silicon carbide (SiC) skimmer selects the center portion of the discharge effluent, prior to the expansion reaching the first shock front and rethermalizing, creating a beam with a derived 2.5 km s−1 velocity. Differential pumping of the skimmer chamber, an optional intermediate chamber and reaction chamber maintains a reaction chamber pressure in the mid-10−6 to mid-10−5 Torr range. The beam has been characterized with regard to total AO beam flux, O2 dissociation fraction, and AO spatial profile using time-of-flight mass spectrometric and Kapton-H erosion measurements. A series of reactions AO+CnH2n (n=2–4) has been studied under single-collision conditions using mass spectrometric product detection, and at higher background pressure detecting dispersed IR emissions from primary and secondary products using a step-scan Michelson interferometer. In a more recent AO crossed-beam experiment, number densities and predicted IR emission intensities have been modeled using the direct simulation Monte Carlo technique. The results have been used to guide the experimental conditions. IR emission intensity predictions are compared to detected signal levels to estimate absolute reaction cross sections.
Simulation of formation process of the ordered nanocluster array on Si(111)7×7
Authors: Wang Daimu , Zhu Hui , Wang Liping , Wu Yanning
Published: September 2009

We study the formation process of metal cluster arrays on the Si(111)7×7 reconstructed surface at high temperature using a kinetic Monte Carlo model, in which the formation of clusters is controlled by the two competing processes: the aggregation of adatoms to form clusters in the half cells of the 7×7 surface, and the dissociation of less stable clusters. Both processes are considered to be asymmetric with respect to the two different types of half cells. It leads to ordered self-organized growth of clusters, which occupy only the faulted half cells, forming a cluster array with triangular symmetry. Further, the model introduces a cluster interaction mechanism, which enhances the nucleation and growth in the neighborhood of existing clusters. The simulations show that the cluster interaction suppresses the growth asymmetry so that a low coverage deposition yields a compact aggregation of clusters, which occupy both faulted and unfaulted half cells, forming a local cluster array with a honeycomb symmetry. The simulation results are compared with relevant experimental results, and good qualitative agreements are found.
Efficient sintering of nanocrystalline titanium dioxide films for dye solar cells via raster scanning laser
Authors: Mincuzzi Girolamo , Vesce Luigi , Reale Andrea , Di Carlo Aldo , Brown Thomas M.
Published: September 2009

By identifying the right combination of laser parameters, in particular the integrated laser fluence Φ, we fabricated dye solar cells (DSCs) with UV laser-sintered TiO2 films exhibiting a power conversion efficiency η=5.2%, the highest reported for laser-sintered devices. η is dramatically affected by Φ and a clear trend is reported. Significantly, DSCs fabricated by raster scanning the laser beam to sinter the TiO2 films are made as efficient as those with oven-sintered ones. These results, confirmed on three batches of cells, demonstrate the remarkable potential (noncontact, local, low cost, rapid, selective, and scalable) of scanning laser processing applied to DSC technology.
An integral boundary layer equation for film flow over inclined wavy bottoms
Authors: Häcker T. , Uecker H.
Published: September 2009

We study the flow of an incompressible liquid film down a wavy incline. Applying a Galerkin method with only one ansatz function to the Navier–Stokes equations, we derive a second-order weighted residual integral boundary layer equation, which, in particular, may be used to describe eddies in the troughs of the wavy bottom. We present numerical results which show that our model is qualitatively and quantitatively accurate in wide ranges of parameters, and we use the model to study some new phenomena, for instance, the occurrence of a short wave instability (at least in a phenomenological sense) for laminar flows which does not exist over a flat bottom.
Time-dependent diffusion in tubes with periodic partitions
Authors: Makhnovskii Yu. A. , Berezhkovskii A. M. , Zitserman V. Yu.
Published: September 2009

The presence of obstacles leads to a slowdown of diffusion. We study the slowdown when diffusion occurs in a tube, and obstacles are periodically spaced identical partitions with circular apertures of arbitrary radius in their centers. The mean squared displacement of a particle diffusing in such a system at large times is given by ⟨Δx2(t)⟩=2Defft, t→∞, where Deff is the effective diffusion coefficient, which is smaller than the particle diffusion coefficient in the tube with no partitions, D0. The latter characterizes the short-time behavior of the mean squared displacement, ⟨Δx2(t)⟩=2D0t, t→0. Thus, the particle diffusion coefficient decreases from D0 to Deff as time goes from zero to infinity. We derive analytical solutions for the Laplace transforms of the time-dependent diffusion coefficient and the mean squared displacement that show how these functions depend on the geometric parameters of the tube. To obtain these solutions we replace nonuniform partitions with apertures by effective partitions that are uniformly permeable for diffusing particles. Our choice of the partition permeability is based on the recent result for the corresponding effective trapping rate obtained by means of boundary homogenization. To establish the range of applicability of our approximate theory we compare its predictions with the results found in Brownian dynamics simulations. Comparison shows excellent agreement between the two at arbitrary value of the aperture radius when the tube radius does not exceed the interpartition distance.
Combined optical trapping and microphotoluminescence of single InP nanowires
Authors: Reece Peter J. , Paiman Suriati , Abdul-Nabi Osama , Gao Qiang , Gal Michael , Tan H. Hoe , Jagadish C.
Published: September 2009

In this letter, we demonstrate that microphotoluminescence may be combined with optical trapping for effective optical characterization of single target InP semiconductor nanowires in suspension. Using this technique, we may investigate structural properties of optically trapped nanowires, such as crystalline polytypes and stacking faults. This arrangement may also be used to resolve structural variations along the axis of the trapped nanowire. These results show that photoluminescence measurements may be coupled with optical tweezers without degrading the performance of the optical trap and provide a powerful interrogation tool for preselection of components for nanowire photonic devices.
Radiative lifetimes of NO A Σ2+(v′=,1,2) and the electronic transition moment of the A Σ2+−X Π2 system
Authors: Settersten Thomas B. , Patterson Brian D. , Humphries William H.
Published: September 2009

Improved measurements of the radiative lifetimes of NO A Σ2+(v′=0,1,2) are presented and used to update the absolute electronic transition moment for the NO γ bands. The pressure-dependent fluorescence decay rate was measured in a low-pressure, room-temperature, flow cell containing dilute mixtures of NO in N2 using time-resolved laser-induced fluorescence excited with a picosecond laser and detected with a microchannel-plate photomultiplier tube. Fluorescence decay rates were determined using an analysis procedure that accounted for the electronic response of the detection system and measurement noise. Radiative lifetimes were determined from an extrapolation of the measured decay rates to zero pressure. In comparison with prior measurements of these radiative lifetimes, the improved experimental approach and analysis procedure result in a significant improvement in the measurement precision. The accuracy of the fluorescence decay-rate measurements was confirmed by independent measurements using time-correlated single-photon counting and time-resolved probing of laser-excited population in A Σ2+ using 266 nm photoionization and charge detection. The measured radiative lifetimes are 192.6±0.2 ns for v′=0, 186.2±0.4 ns for v′=1, and 179.4±0.7 ns for v′=2. The measured lifetimes are shown to be in outstanding agreement with those predicted by an electronic transition moment that is identical in form to the function recommended by Luque and Crosley [J. Chem. Phys. 111, 7405 (1999)] after appropriate rescaling. This rescaling does not affect the agreement of the transition moment function with the previously reported vibrational branching ratios and improves agreement with previously reported absolute oscillator strength measurements. Based on the rescaled transition moment, updated values of absolute transition probabilities in the NO A Σ2+−X Π2 system are presented.
Self-pulsing 1050 nm quantum dot edge emitting laser diodes
Authors: Liu Haoling , Smowton Peter , Summers Huw , Edwards Gareth , Drexler Wolfgang
Published: September 2009

We examine self-pulsing, edge emitting, quantum dot laser diodes as continuous broad spectrum light sources emitting at ∼1050 nm. Devices are configured with split contacts. When operated without a saturable absorber, the laser emits a number of discrete narrow modes, which merge to form a broad continuous lasing spectrum on application of the saturable absorber. The broadened spectra are consistent with the modulated carrier density expected under Q-switched operation. This provides a simple technique for generating emission suitable for biomedical applications. The spectral width achieved is ∼10 nm, and the average output power is 7.5 mW.
Thermal decomposition of ammonia borane at high pressures
Authors: Nylén Johanna , Sato Toyoto , Soignard Emmanuel , Yarger Jeffery L. , Stoyanov Emil , Häussermann Ulrich
Published: September 2009

The effects of high pressure (up to 9 GPa) on the thermal decomposition of ammonia borane, BH3NH3, were studied in situ by Raman spectroscopy in a diamond anvil cell. In contrast with the three-step decomposition at ambient pressure, thermolysis under pressure releases almost the entire hydrogen content of the molecule in two distinct steps. The residual of the first decomposition is polymeric aminoborane, (BH2NH2)x, which is also observed at ambient pressure. The residual after the second decomposition is unique to high pressure. Presumably it corresponds to a precursor to hexagonal BN where macromolecular fragments of planar hexagon layers formed by B and N atoms are terminated by H atoms. Increasing pressure increases the temperature of both decomposition steps. Due to the increased first decomposition temperature it becomes possible to observe a new high pressure, high temperature phase of BH3NH3 which may represent melting.
DeltaNp73 regulates neuronal survival in vivo
Authors: Tissir Fadel , Ravni Aurélia , Achouri Younès , Riethmacher Dieter , Meyer Gundela , Goffinet Andre M.
Published: September 2009

Apoptosis occurs widely during brain development, and p73 transcription factors are thought to play essential roles in this process. The p73 transcription factors are present in two forms, the full length TAp73 and the N-terminally truncated DeltaNp73. In cultured sympathetic neurons, overexpression of DeltaNp73 inhibits apoptosis induced by nerve growth factor withdrawal or p53 overexpression. To probe the function of DeltaNp73 in vivo, we generated a null allele and inserted sequences encoding the recombinase Cre and green fluorescent protein (EGFP). We show that
DeltaNp73
is heavily expressed in the thalamic eminence (TE) that contributes neurons to ventral forebrain, in vomeronasal neurons, Cajal-Retzius cells (CRc), and choroid plexuses. In
DeltaNp73
−/−
mice, cells in preoptic areas, vomeronasal neurons, GnRH-positive cells, and CRc were severely reduced in number, and choroid plexuses were atrophic. This phenotype was enhanced when DeltaNp73–positive cells were ablated by diphtheria toxin expression. However, ablation of cells that express DeltaNp73 and Wnt3a did neither remove all CRc, nor did they abolish Reelin secretion or generate a
reeler
-like cortical phenotype. Our data emphasize the role of DeltaNp73 in neuronal survival in vivo and in choroid plexus development, the importance of the TE as a source of neurons in ventral forebrain, and the multiple origins of CRc, with redundant production of Reelin.
Evidence for adaptive radiation from a phylogenetic study of plant defenses
Authors: Agrawal Anurag A. , Fishbein Mark , Halitschke Rayko , Hastings Amy P. , Rabosky Daniel L. , Rasmann Sergio
Published: September 2009

One signature of adaptive radiation is a high level of trait change early during the diversification process and a plateau toward the end of the radiation. Although the study of the tempo of evolution has historically been the domain of paleontologists, recently developed phylogenetic tools allow for the rigorous examination of trait evolution in a tremendous diversity of organisms. Enemy-driven adaptive radiation was a key prediction of Ehrlich and Raven's coevolutionary hypothesis [Ehrlich PR, Raven PH (1964)Evolution18:586–608], yet has remained largely untested. Here we examine patterns of trait evolution in 51 North American milkweed species (Asclepias), using maximum likelihood methods. We study 7 traits of the milkweeds, ranging from seed size and foliar physiological traits to defense traits (cardenolides, latex, and trichomes) previously shown to impact herbivores, including the monarch butterfly. We compare the fit of simple random-walk models of trait evolution to models that incorporate stabilizing selection (Ornstein-Ulenbeck process), as well as time-varying rates of trait evolution. Early bursts of trait evolution were implicated for 2 traits, while stabilizing selection was implicated for several others. We further modeled the relationship between trait change and species diversification while allowing rates of trait evolution to vary during the radiation. Species-rich lineages underwent a proportionately greater decline in latex and cardenolides relative to species-poor lineages, and the rate of trait change was most rapid early in the radiation. An interpretation of this result is that reduced investment in defensive traits accelerated diversification, and disproportionately so, early in the adaptive radiation of milkweeds.
A genome-wide view of
Caenorhabditis elegans
base-substitution mutation processes
Authors: Denver Dee R. , Dolan Peter C. , Wilhelm Larry J. , Sung Way , Lucas-Lledó J. Ignacio , Howe Dana K. , Lewis Samantha C. , Okamoto Kazu , Thomas W. Kelley , Lynch Michael , Baer Charles F.
Published: September 2009

Knowledge of mutation processes is central to understanding virtually all evolutionary phenomena and the underlying nature of genetic disorders and cancers. However, the limitations of standard molecular mutation detection methods have historically precluded a genome-wide understanding of mutation rates and spectra in the nuclear genomes of multicellular organisms. We applied two high-throughput DNA sequencing technologies to identify and characterize hundreds of spontaneously arising base-substitution mutations in 10
Caenorhabditis elegans
mutation-accumulation (MA)-line nuclear genomes.
C. elegans
mutation rate estimates were similar to previous calculations based on smaller numbers of mutations. Mutations were distributed uniformly within and among chromosomes and were not associated with recombination rate variation in the MA lines, suggesting that intragenomic variation in genetic hitchhiking and/or background selection are primarily responsible for the chromosomal distribution patterns of polymorphic nucleotides in
C. elegans
natural populations. A strong mutational bias from G/C to A/T nucleotides was detected in the MA lines, implicating oxidative DNA damage as a major endogenous mutagenic force in
C. elegans
. The observed mutational bias also suggests that the
C. elegans
nuclear genome cannot be at equilibrium because of mutation alone. Transversions dominate the spectrum of spontaneous mutations observed here, whereas transitions dominate patterns of allegedly neutral polymorphism in natural populations of
C. elegans
and many other animal species; this observation challenges the assumption that natural patterns of molecular variation in noncoding regions of the nuclear genome accurately reflect underlying mutation processes.
Highly tumorigenic lung cancer CD133
+
cells display stem-like features and are spared by cisplatin treatment
Authors: Bertolini Giulia , Roz Luca , Perego Paola , Tortoreto Monica , Fontanella Enrico , Gatti Laura , Pratesi Graziella , Fabbri Alessandra , Andriani Francesca , Tinelli Stella , Roz Elena , Caserini Roberto , Lo Vullo Salvatore , Camerini Tiziana , Mariani Luigi , Delia Domenico , Calabrò Elisa , Pastorino Ugo , Sozzi Gabriella
Published: September 2009

The identification of lung tumor-initiating cells and associated markers may be useful for optimization of therapeutic approaches and for predictive and prognostic information in lung cancer patients. CD133, a surface glycoprotein linked to organ-specific stem cells, was described as a marker of cancer-initiating cells in different tumor types. Here, we report that a CD133
+
, epithelial-specific antigen-positive (CD133
+
ESA
+
) population is increased in primary nonsmall cell lung cancer (NSCLC) compared with normal lung tissue and has higher tumorigenic potential in SCID mice and expression of genes involved in stemness, adhesion, motility, and drug efflux than the CD133
−
counterpart. Cisplatin treatment of lung cancer cells in vitro resulted in enrichment of CD133
+
fraction both after acute cytotoxic exposure and in cells with stable cisplatin-resistant phenotype. Subpopulations of CD133
+
ABCG2
+
and CD133
+
CXCR4
+
cells were spared by in vivo cisplatin treatment of lung tumor xenografts established from primary tumors. A tendency toward shorter progression-free survival was observed in CD133
+
NSCLC patients treated with platinum-containing regimens. Our results indicate that chemoresistant populations with highly tumorigenic and stem-like features are present in lung tumors. The molecular features of these cells may provide the rationale for more specific therapeutic targeting and the definition of predictive factors in clinical management of this lethal disease.
Diminished dosage of 22q11 genes disrupts neurogenesis and cortical development in a mouse model of 22q11 deletion/DiGeorge syndrome
Authors: Meechan Daniel W. , Tucker Eric S. , Maynard Thomas M. , LaMantia Anthony-Samuel
Published: September 2009

The 22q11 deletion (or DiGeorge) syndrome (22q11DS), the result of a 1.5- to 3-megabase hemizygous deletion on human chromosome 22, results in dramatically increased susceptibility for “diseases of cortical connectivity” thought to arise during development, including schizophrenia and autism. We show that diminished dosage of the genes deleted in the 1.5-megabase 22q11 minimal critical deleted region in a mouse model of 22q11DS specifically compromises neurogenesis and subsequent differentiation in the cerebral cortex. Proliferation of basal, but not apical, progenitors is disrupted, and subsequently, the frequency of layer 2/3, but not layer 5/6, projection neurons is altered. This change is paralleled by aberrant distribution of parvalbumin-labeled interneurons in upper and lower cortical layers. Deletion of
Tbx1
or
Prodh
(22q11 genes independently associated with 22q11DS phenotypes) does not similarly disrupt basal progenitors. However, expression analysis implicates additional 22q11 genes that are selectively expressed in cortical precursors. Thus, diminished 22q11 gene dosage disrupts cortical neurogenesis and interneuron migration. Such developmental disruption may alter cortical circuitry and establish vulnerability for developmental disorders, including schizophrenia and autism.
Reduction of phosphoinositide-phospholipase C beta1 methylation predicts the responsiveness to azacitidine in high-risk MDS
Authors: Follo Matilde Y. , Finelli Carlo , Mongiorgi Sara , Clissa Cristina , Bosi Costanza , Testoni Nicoletta , Chiarini Francesca , Ramazzotti Giulia , Baccarani Michele , Martelli Alberto M. , Manzoli Lucia , Martinelli Giovanni , Cocco Lucio
Published: September 2009

Lipid signaling pathways are involved in cell growth, differentiation, and apoptosis, and could have a role in the progression of myelodysplastic syndromes (MDS) into acute myeloid leukemia (AML). Indeed, recent studies showed that phosphoinositide-phospholipase (PI-PL)Cbeta1 mono-allelic deletion correlates with a higher risk of AML evolution. Also, a single patient treated with azacitidine, a DNA methyltransferase inhibitor currently used in MDS, displayed a direct correlation between PI-PLCbeta1 gene expression and drug responsiveness. Consequently, we hypothesized that PI-PLCbeta1 could be a target for demethylating therapy. First, we analyzed the structure of PI-PLCbeta1 gene promoter, then quantified the degree of PI-PLCbeta1 promoter methylation and gene expression in MDS patients at baseline and during azacitidine administration. Indeed, PI-PLCbeta1 mRNA increased in responder patients, along with a reduction of PI-PLCbeta1 promoter methylation. Also, the molecular response correlated to and anticipated the clinical outcome, thus suggesting that PI-PLCbeta1 gene reactivation could predict azacitidine responsiveness. Our results demonstrate not only that PI-PLCbeta1 promoter is hypermethylated in high-risk MDS patients, but also that the amount of PI-PLCbeta1 mRNA could predict the clinical response to azacitidine, therefore indicating a promising new therapeutic approach.
Quantification of rapid environmental redox processes with quick-scanning x-ray absorption spectroscopy (Q-XAS)
Authors: Ginder-Vogel Matthew , Landrot Gautier , Fischel Jason S. , Sparks Donald L.
Published: September 2009

Quantification of the initial rates of environmental reactions at the mineral/water interface is a fundamental prerequisite to determining reaction mechanisms and contaminant transport modeling and predicting environmental risk. Until recently, experimental techniques with adequate time resolution and elemental sensitivity to measure initial rates of the wide variety of environmental reactions were quite limited. Techniques such as electron paramagnetic resonance and Fourier transform infrared spectroscopies suffer from limited elemental specificity and poor sensitivity to inorganic elements, respectively. Ex situ analysis of batch and stirred-flow systems provides high elemental sensitivity; however, their time resolution is inadequate to characterize rapid environmental reactions. Here we apply quick-scanning x-ray absorption spectroscopy (Q-XAS), at sub-second time-scales, to measure the initial oxidation rate of As(III) to As(V) by hydrous manganese(IV) oxide. Using Q-XAS, As(III) and As(V) concentrations were determined every 0.98 s in batch reactions. The initial apparent As(III) depletion rate constants (t < 30 s) measured with Q-XAS are nearly twice as large as rate constants measured with traditional analytical techniques. Our results demonstrate the importance of developing analytical techniques capable of analyzing environmental reactions on the same time scale as they occur. Given the high sensitivity, elemental specificity, and time resolution of Q-XAS, it has many potential applications. They could include measuring not only redox reactions but also dissolution/precipitation reactions, such as the formation and/or reductive dissolution of Fe(III) (hydr)oxides, solid-phase transformations (i.e., formation of layered-double hydroxide minerals), or almost any other reaction occurring in aqueous media that can be measured using x-ray absorption spectroscopy.