bluuebunny/crossref_metadata_2025 huggingface dataset:
Single molecule spectroscopy of red- and green-emitting fluorene-based copolymers
Authors: Khalil G. E. , Adawi A. M. , Fox A. M. , Iraqi A. , Lidzey D. G.
Published: January 2009

Single molecule fluorescence spectroscopy is used to study the optical properties of two polymers: a fluorene-based statistical copolymer that contains a low fraction (10%) of a red-emitting thiophene group, and the green-emitting polymer poly(9,9-dioctylfluorene-alt-benzothiadiazole). These polymers were studied when isolated at a low concentration in a polymer matrix (either polynorbornene or polystyrene). For the red-emitting polymer, we compare the relative emission intensity from the green-emitting benzothiadiazole groups with the red-emitting thiophene. We find that red emission from the thiophenes is significantly suppressed in the single molecule regime, suggesting that interchain energy transfer dominates intrachain processes in such polyfluorene copolymers. We then use fluorescence spectroscopy and polarization anisotropy measurements to show that the conformations of both polymers are dependent on their host matrix, adopting a more collapsed, globular conformation in polystyrene and a more extended chain conformation in polynorbornene.
Second-harmonic generation of thermally poled silver doped sodo-borophosphate glasses
Authors: Fargin Evelyne , Soulié Jérémy , Cardinal Thierry , Lahaye Michel , Rodriguez Vincent , Couzi Michel , Adamietz Frédéric
Published: January 2009

Sodium niobium borophosphate glass, with a composition of 0.58(0.95NaPO3+0.05Na2B4O7)+0.42Nb2O5, has been doped with monovalent silver ions. Second harmonic generation (SHG) has been obtained from the poling treatment of this sample. The second order nonlinearity from the anode side was estimated from an analysis of transmitted polarized Maker-fringe patterns. Thanks to the original Maker fringe simulations, a value of 3 pm/V is obtained with the silver doped glass that unambiguously scales an enhancement of ∼35% with respect to the nondoped glass susceptibility. For both glasses, the nonlinear layer is found to be sodium-depleted up to 4 μm inside the anode, in accordance with quantitative energy dispersive x-ray spectroscopy characterizations. This comparative study indicates complex space-charge-migration processes during the poling treatment. The relative enhancement of the SHG signal of the silver doped glass is correlated with the increase in its linear susceptibility.
Ablation dominated implosion dynamics of aluminum and stainless steel nested cylindrical wire arrays
Authors: Williamson K. M. , Kantsyrev V. L. , Esaulov A. A. , Safronova A. S. , Ouart N. D. , Yilmaz F. M. , Shrestha I. K. , Shlyaptseva V. , McBride R. D. , Chalenski D. A. , Douglass J. D. , Greenly J. B. , Hammer D. A. , Kusse B. R.
Published: January 2009

The results of experiments with combined aluminum (Al) and stainless steel (SS) alloy 304, nested wire arrays from the 1 MA COBRA generator at Cornell University are presented. The loads studied consisted of a 6 mm diameter inner array and a 13 mm diameter outer array with a different material in each array: SS or aluminum. Al implodes before SS in all loads studied, even when Al was on the inner array. The new wire ablation dynamic model and spectroscopic modeling are used to interpret these data. The observed implosion dynamics are likely a result of the higher ablation rate of Al. These initial results suggest that combining wire materials with different ablation rates in wire array loads could be developed into a useful technique for x-ray pulse shaping and radiation yield optimization.
Collisional depolarization of OH(A) with Ar: Experiment and theory
Authors: Brouard M. , Bryant A. , Chang Y.-P. , Cireasa R. , Eyles C. J. , Green A. M. , Marinakis S. , Aoiz F. J. , Kłos J.
Published: January 2009

Zeeman quantum beat spectroscopy has been used to measure the 300 K rate constants for the angular momentum depolarization of OH(A 2Σ+) in the presence of Ar. We show that the beat amplitude at short times, in the absence of collisions, is well described by previously developed line strength theory for (1+1) laser induced fluorescence. The subsequent pressure dependent decay of the beat amplitude is used to extract depolarization rate constants and estimates of collisional depolarization cross sections. Depolarization accompanies both inelastic collisions, giving rise to rotational energy transfer, and elastic collisions, which change mj but conserve j. Previous experimental studies, as well as classical theory, suggest that elastic scattering contributes around 20% to the observed total depolarization rate at low j. Simulation of the experimental beat amplitudes, using theoretical calculations presented in the preceding paper, reveals that depolarization of OH(A) by Ar has a rate constant comparable to, if not larger than, that for energy transfer. This is consistent with a significant tilting or realignment of j′ away from j on collision. The experimental data are used to provide a detailed test of quantum mechanical and quasiclassical trajectory scattering calculations performed on a recently developed ab initio potential energy surface of Kłos et al. [J. Chem. Phys. 129, 054301 (2008)]. The calculations and simulations account well for the observed cross sections at high N, but underestimate the experimental results by between 10% and 20% at low N, possibly due to remaining inaccuracies in the potential energy surface or perhaps to limitations in the dynamical approximations made, particularly the freezing of the OH(A) bond.
Evolutionary algorithms to solve complicated NMR spectra
Authors: Meerts W. Leo , de Lange C. A. , Weber A. C. J. , Burnell E. E.
Published: January 2009

The complexity of H1 NMR spectra of solutes in partially ordered solvents such as liquid crystals increases rapidly with the number of spins. Spectra of simple solutes with sufficient symmetry and containing not too many spins (typically ≤8) are readily analyzed. The analysis of larger spin systems is more difficult, and often impossible. In this paper we present the application of a general automated evolutionary algorithm to solve the highly complex proton NMR spectrum of the 12-spin system pentane, a solute that interconverts rapidly among several symmetry-unrelated conformations. The interpretation of the spectral parameters that are obtained from the analysis requires the use of a model to connect relative orientational orders in symmetry-unrelated conformers.
Formation of heavy-Rydberg ion-pair states in collisions of K(np) Rydberg atoms with attaching targets
Authors: Cannon M. , Dunning F. B.
Published: January 2009

The formation of heavy-Rydberg ion-pair states through electron transfer in collisions between K(np) Rydberg atoms and molecules that attach low-energy electrons is investigated. The measurements show that low-n collisions with a wide variety of target species (SF6, c-C7F14, C6F6, and CCl4) can lead to formation of bound ion-pair states and that, under appropriate conditions, a small fraction of these can subsequently dissociate as free ions through internal-to-translational energy transfer. Analysis of the data suggests that those ion pairs that do dissociate typically have lifetimes of ∼1 μs, although some can have lifetimes of 5 μs or longer.
Discovery of an intermediate phase in bis-thiourea pyridinium chloride inclusion compound
Authors: Pajzderska A. , Wąsicki J. , Czarnecki P. , Toupet L. , Collet E.
Published: January 2009

This paper reports the occurrence of a new phase for bis-thiourea pyridinium chloride inclusion compound, which is intermediate to the high- and low-temperature ones already reported. The structure of the intermediate phase was determined by the x-ray diffraction and the following sequence of space groups was obtained: Cmcm⟶237 KCmc21⟶206 KPbca. The triplication of the lattice a parameter in the intermediate phase was observed. Detailed investigations of its phase transitions were performed by differential scanning calorimetry, x-ray diffraction, and dielectric spectroscopy methods. The phase transition at T1=237 K is continuous while at T2=206 K is discontinuous. Both phase transitions have been classified as of order-disorder type. The high- and low-temperature phases are nonpolar in contrast to the intermediate phase, for which we could not found ferroelectric ordering.
A pn heterojunction diode constructed with a n-type ZnO nanowire and a p-type HgTe nanoparticle thin film
Authors: Seong Hojun , Cho Kyoungah , Kim Sangsig
Published: January 2009

We demonstrate a pn heterojunction diode constructed with a n-type ZnO nanowire (NW) and a p-type HgTe nanoparticle (NP) thin film on a SiO2/p-Si substrate. For the pn heterojunction diode, the rectifying characteristics of both the dark current and the photocurrent excited by 633 nm wavelength light were observed, but the photocurrent excited by 325 nm wavelength light possesses Ohmic characteristics. The optoelectronic characteristics of the pn heterojunction diode were compared with those of the ZnO NW and HgTe NP thin film composing it.
Strong violet and green-yellow electroluminescence from silicon nitride thin films multiply implanted with Si ions
Authors: Cen Z. H. , Chen T. P. , Ding L. , Liu Y. , Wong J. I. , Yang M. , Liu Z. , Goh W. P. , Zhu F. R. , Fung S.
Published: January 2009

Strong visible electroluminescence (EL) has been observed from a 30 nm silicon nitride thin film multiply implanted with Si ions and annealed at 1100 °C. The EL intensity shows a linear relationship with the current transport in the thin film at lower voltages, but a departure from the linear relationship with a quenching in the EL intensity is observed at higher voltages. The EL spectra show two primary EL bands including the predominant violet band at ∼3.0 eV (415 nm) and the strong green-yellow band at ∼2.2 eV (560 nm). Two weak bands including the ultraviolet band at ∼3.8 eV and the near infrared band at ∼1.45 eV emerge at high voltages. The evolution of each EL band with the voltage has been examined. The phenomena observed are explained, and the EL mechanisms are discussed.
Capacitance hysteresis in GaN/AlGaN heterostructures
Authors: Byrum L. E. , Ariyawansa G. , Jayasinghe R. C. , Dietz N. , Perera A. G. U. , Matsik S. G. , Ferguson I. T. , Bezinger A. , Liu H. C.
Published: January 2009

Capacitance characteristics with voltage and frequency of n+-GaN/AlxGa1−xN heterojunction ultraviolet (UV)-infrared (IR) photodetectors are reported. A distinct capacitance step and capacitance hysteresis have been attributed to trap energy states located just above the Fermi level at the GaN/AlGaN interface, most likely due to N-vacancy and/or C-donor impurities. The presence of the hysteresis is due to the accumulation of charge at the heterointerface, which is dependent on the location of the continuum of interface trap states relative to the Fermi level. The Al fraction in the barrier layer has been found to significantly change the positions of the interface trap states relative to the Fermi level.
A second-order ferromagnetic transition in the martensitic state of Ni49.5Mn32.5Cu4Sn14: A critical behavior study
Authors: Wang B. M. , Wang L. , Liu Y. , Zhao B. C.
Published: January 2009

A second-order ferromagnetic transition is observed in the martensitic state of Ni49.5Mn32.5Cu4Sn14 alloy and the critical behavior around the transition is investigated by dc magnetization measurements. With the help of modified Arrott plots, Kouvel–Fisher method, and Widom scaling relation, the values of TcM (ferromagnetic transition temperature in the martensite), and critical exponents: β (associated with the spontaneous magnetization), γ (relevant to the initial susceptibility), and δ (associated with the critical magnetization isotherm) are obtained. The scaling plots show that the obtained values of the critical exponents are reliable. The values of the critical exponents of Ni49.5Mn32.5Cu4Sn14 are different from those predicted by several theoretical models, i.e., mean-field theory, three-dimensional Heisenberg model, and three-dimensional Ising model. The magnetic interactions exhibit two different behaviors: long-range magnetic interaction below TcM and local magnetic interaction above TcM. The change in Mn moments may be responsible for the change in magnetic interactions around TcM.
Effects of superimposed ultrasound on deformation of gold
Authors: Lum I. , Huang H. , Chang B. H. , Mayer M. , Du D. , Zhou Y.
Published: January 2009

The effects of superimposed ultrasound vibration on plastic deformation of gold are studied both during and after the vibration using an ultrasonic ball bonding machine. It is found that when ultrasonic irradiation is applied along with mechanical force, the metal is softer than when deformed without the vibration. After ultrasound is turned off, the deformed metal remains softer if previously deformed with ultrasound. Possible mechanisms for the acoustic residual softening are discussed as compared to residual hardening. The acoustic residual effect is attributed to the net balance between ultrasound’s dynamic annealing and its potential opposing effect on activating and multiplying dislocations.
Computing the Jones index of quadratic permutation endomorphisms of O2
Authors: Conti Roberto , Szymański Wojciech
Published: January 2009

We compute the index of the inclusions of type III1/2 factors arising from endomorphisms of the Cuntz algebra O2 associated with the rank-2 permutation matrices.
Effects of electron scattering at metal-nonmetal interfaces on electron-phonon equilibration in gold films
Authors: Hopkins Patrick E. , Kassebaum Jared L. , Norris Pamela M.
Published: January 2009

Electron scattering at interfaces between metals and dielectrics is a major concern in thermal boundary conductance studies. This aspect of energy transfer has been extensively studied and modeled on long time scales when the electrons and phonons are in equilibrium in the metal film. However, there are conflicting results concerning electron-interface scattering and energy transfer in the event of an electron-phonon nonequilibrium, specifically, how this mode of energy transfer affects the electron cooling during electron-phonon nonequilibration. Transient thermoreflectance (TTR) experiments utilizing ultrashort pulsed laser systems can resolve this electron-phonon nonequilibrium, and the thermophysical property relating rate of equilibration to electron-phonon scattering events G can be quantified. In this work, G in Au films of varying thicknesses are measured with the TTR technique. At large fluences (which result in high electron temperatures), the measured G is much larger than predicted from traditional models. This increase in G increases as the film thickness decreases and shows a substrate dependency, with larger values of G measured on more conductive substrates. The data suggest that in a highly nonequilibrium system, there could be some thermal energy lost to the underlying substrate, which can affect G.
Synthesis of Sb-additivated SnO2 nanostructures and dependence of photoluminescence properties on Sb additivation concentration
Authors: Jean Sen-Tsun , Her Yung-Chiun
Published: January 2009

Single crystalline Sb-additivated SnO2 nanorods, beaklike nanorods, and nanoribbons were synthesized by an in situ catalyst-assisted thermal evaporation process on single-crystal Si substrates. As the Sb:Sn weight ratios were increased, the morphologies of Sb-additivated SnO2 nanostructures would progressively transform from nanorods to beaklike nanorods and to the mixture of nanowires and nanoribbons. The SnO2 nanorods grow along the [02¯0] direction and with lateral facets defining a square column consisting of {100} and {001} planes. The Sb-additivated SnO2 beaklike nanorods initially grow along the [01¯1¯] direction and then switch to the [031¯] direction to form the beak, while the nanoribbons grow along the [110] direction. The Sb atoms were found to uniformly distribute over the whole Sb-additivated SnO2 nanostructures and that it would not affect the single crystallinity of SnO2 nanostructures. The photoluminescence spectra of the nonadditivated and Sb-additivated SnO2 nanostructures exhibited multipeaks with peak positions centered at 403, 453, 485, 557, and 622 nm. When Sb atoms were additivated into SnO2 nanostructures, the luminescence intensities would significantly decrease and photoluminescence at 557 and 622 nm would almost disappear. These can be explained by the replacements of the six- and fivefold coordinated Sn atoms on low-index facets by five- and fourfold coordinated Sb atoms, respectively, leading to the cancellation of 100° tin coordinated on-plane oxygen bridging vacancies and 130° tin coordinated in-plane oxygen vacancies.
Valley degeneracies in (111) silicon quantum wells
Authors: Kharche Neerav , Kim Seongmin , Boykin Timothy B. , Klimeck Gerhard
Published: January 2009

(111) silicon quantum wells have been studied extensively, yet no convincing explanation exists for the experimentally observed breaking of sixfold valley degeneracy into two- and fourfold degeneracies. Here, systematic sp3d5s∗ tight-binding and effective mass calculations are presented to show that a typical miscut modulates the energy levels, which leads to breaking of sixfold valley degeneracy into two lower and four raised valleys. An effective mass based valley-projection model is used to determine the directions of valley minima in tight-binding calculations of large supercells. Tight-binding calculations are in better agreement with experiments compared to effective mass calculations.
Influence of surface structure on the phonon-assisted emission process in the ZnO nanowires grown on homoepitaxial films
Authors: Hong Woong-Ki , Jo Gunho , Choe Minhyeok , Lee Takhee , Sohn Jung Inn , Welland Mark E.
Published: January 2009

We carried out temperature-dependent photoluminescence measurements to investigate the influence of surface roughness on the phonon-assisted emission of the surface-tailored ZnO nanowires (NWs). For the rough ZnO NWs, the observation of strong defect emission with vibration peaks by the exciton-phonon coupling reflects the presence of a high density of surface defects, resulting in a rapid shift to lower energy region of free exciton emission and a strong contribution of the first order phonon-assisted free exciton in ultraviolet emission. This investigation indicates that the surface defects associated with roughness have a significant influence on the phonon-assisted exciton emission.
An optical spacer is no panacea for light collection in organic solar cells
Authors: Andersson B. Viktor , Huang David M. , Moulé Adam J. , Inganäs Olle
Published: January 2009

The role of an optical spacer layer has been examined by optical simulations of organic solar cells with various bandgaps. The simulations have been performed with the transfer matrix method and the finite element method. The results show that no beneficial effect can be expected by adding an optical spacer to a solar cell with an already optimized active layer thickness.
Acoustic resonant leaky mode effects
Authors: Hsiao Fu-Li , Chan Chia-Hua , Chen Chii-Chang , Hsu Kuei-Chu
Published: January 2009

An acoustic leaky mode resonator having a structure similar to that of an optical guided-mode resonator is demonstrated experimentally and theoretically. The measured transmission spectra reveal the existence of resonant modes and agree with the predictions of finite-difference time-domain calculations. The resonant modes were investigated by calculating the displacement and the pressure field. The relationship between the resonant frequency and the geometric parameters of the structures was studied. The results can be applied to the design of a narrow pass band acoustic filter.
Reduced nonthermal rollover of wide-well GaInN light-emitting diodes
Authors: Maier Markus , Köhler Klaus , Kunzer Michael , Pletschen Wilfried , Wagner Joachim
Published: January 2009

Nonthermal rollover (or efficiency droop) of the electroluminescence (EL) efficiency has been investigated for near-UV-emitting (AlGaIn)N single-well light-emitting diodes (LED) with varying GaInN well widths grown on substrates with different dislocation densities (DDs). For each DD the well width of the mesa-LEDs has been optimized for maximum EL efficiency at high operating currents. LEDs on freestanding GaN (DD 4×107 cm−2) with an 18 nm thick GaInN wide-well active region show the highest efficiency, and the output power-versus-current characteristic remains linear up to the highest pulsed current density of 750 A/cm2. In contrast, LEDs on sapphire grown with conventional low-temperature nucleation (DD 109 cm−2) exhibit the optimum well width at 3 nm and show significant nonthermal rollover.
Pseudoelastic behavior of Cu–Ni composite nanowires
Authors: Mastorakos Ioannis N. , Zbib Hussein M. , Bahr David F. , Parsons Jessica , Faisal Mased
Published: January 2009

We investigate the pseudoelastic behavior at room temperature of composite nanowires using molecular dynamics simulations. The nanowires are composed of a nickel core surrounded by a copper shell, leading to high coherency stresses. The coherency and surface stresses cause the nanowires to undergo a lattice reorientation, by twinning, from ⟨001⟩ to ⟨110⟩ during relaxation. Nanowires of different cross-sectional areas (varying from 2.17×2.17 up to 2.9×2.9 nm2) were studied. In all cases, under tensile loading, the nanowires reorient to ⟨001⟩ and then under unloading reorient back to ⟨110⟩, thus exhibiting pseudoelastic behavior. This behavior is more pronounced in composite nanowires with a coherent interface than for single crystal nanowires.
Growth of germanium crystals from electrodeposited gold in local crucibles
Authors: Ratchford Joshua B. , Goldthorpe Irene A. , McIntyre Paul C. , Chidsey Christopher E. D.
Published: January 2009

We report a method of using electrodeposited gold catalysts to grow germanium crystals from germane by the vapor-liquid-solid mechanism. Lithographically defined local crucibles in a silicon oxide film on a silicon wafer were used as electrodes for the electrodeposition of gold. At 370 °C in the presence of germane, a germanium crystal grew from the gold-germanium eutectic in each local crucible. X-ray diffraction shows that the germanium crystals grew epitaxially from the silicon wafers. The addition of HCl to the reactive gas mixture during germanium crystal growth prevented germanium deposition on the surface of the silicon oxide film.
Exciton recombination in ZnO nanorods grown on GaN/sapphire template
Authors: Mohanta S. K. , Tripathy S. , Zhang X. H. , Kim D. C. , Soh C. B. , Yong A. M. , Liu W. , Cho H. K.
Published: January 2009

The authors have employed variable temperature photoluminescence (PL) and time-resolved PL spectroscopy to probe the exciton recombination in high density and vertically aligned ZnO nanorods grown on p-type GaN/sapphire template. The low-temperature PL characterizes the dominant near-band-edge excitonic emissions from such nanorod arrays. At 4.3 K, a PL decay time of 432 ps reveals improved crystalline quality. The PL decay time shows irregular behavior due to different types of excitonic transitions dominating the PL spectra at different temperatures and a competitive effect of radiative recombination and nonradiative relaxation processes.
Achieving high free electron mobility in ZnO:Al thin films grown by reactive pulsed magnetron sputtering
Authors: Cornelius S. , Vinnichenko M. , Shevchenko N. , Rogozin A. , Kolitsch A. , Möller W.
Published: January 2009

The study is focused on the improvement of the free electron mobility in Al-doped ZnO films grown by reactive pulsed magnetron sputtering. At optimum growth conditions low-absorbing films are obtained with a Hall mobility of 46 cm2 V−1 s−1, a free electron density of 6.0×1020 cm−3, and an electrical resistivity of 2.26×10−4 Ω cm. The relation between the mobility and free electron density for different growth conditions is discussed in terms of ionized impurity scattering, impurity clustering, and grain boundary limited transport.
Rotation of the magnetic easy axis in La0.67Sr0.33MnO3 thin film on NdGaO3(112)
Authors: Nishikawa Hiroaki , Houwman Evert , Boschker Hans , Mathews Mercy , Blank Dave H. A. , Rijnders Guus
Published: January 2009

The in-plane magnetic anisotropy is studied for pseudocubic {011}pc oriented La0.67Sr0.33MnO3 (LSMO) thin film grown on orthorhombic NdGaO3(NGO)(112)o (the subindices “pc” and “o” indicate the pseudocubic and orthorhombic lattice structure, respectively). The direction of the in-plane remanent magnetization of LSMO thin films with different thicknesses is determined. With increasing film thickness the easy axes rotate and the anisotropy changes from uniaxial to biaxial. This is associated with the increasing symmetry of the LSMO with increasing thickness, starting with a monoclinic LSMO structure at the nonrectangular NGO(112)o surface unit cell of the substrate, developing into an orthorhombic structure at the top part of the thickest films.
Crystal and electronic band structure of Cu2ZnSnX4 (X=S and Se) photovoltaic absorbers: First-principles insights
Authors: Chen Shiyou , Gong X. G. , Walsh Aron , Wei Su-Huai
Published: January 2009

The structural and electronic properties of Cu2ZnSnS4 and Cu2ZnSnSe4 are studied using first-principles calculations. We find that the low energy crystal structure obeys the octet rule and is the kesterite (KS) structure. However, the stannite or partially disordered KS structures can also exist in synthesized samples due to the small energy cost. We find that the dependence of the band structure on the (Cu,Zn) cation ordering is weak and predict that the band gap of Cu2ZnSnSe4 should be on the order of 1.0 eV and not 1.5 eV as was reported in previous absorption measurements.
Evanescent field at nanocorrugated dielectric surface
Authors: Volkov S. N. , Kaplan A. E. , Miyazaki K.
Published: January 2009

We study coupling of laser pulses to an evanescent electric field at a nanocorrugated dielectric surface. We find that the local electric field is increased in the surface grooves, up to a factor of 2, compared to the incident field, thus providing a positive feedback for localized subthreshold ablation, and enabling the corrugation growth.
Invisible slab cloaks via embedded optical transformation
Authors: Yu Guan Xia , Jiang Wei Xiang , Cui Tie Jun
Published: January 2009

We propose a class of invisible slab cloaks based on the embedded optical transformation. The designed slab structures will guide the incident electromagnetic (EM) waves to propagate around the cloaked objects inside the slabs. Such EM waves will return to their original propagation directions without any distortions. We show that there are no singular values in the EM parameters of the slab cloaks and they could be realized using metamaterials. General formulations of the inhomogeneous and anisotropic permittivity and permeability tensors are derived for the slab cloaks using linear and nonlinear optical transformations. Numerical simulations based on the finite element method have been performed to confirm the design and analysis. The potential application of the slab cloak is a new type substrate for integrated circuits, which will protect the devices inside from the interference of EM waves but not disturb their EM properties.
Acoustic mismatch model for thermal contact resistance of van der Waals contacts
Authors: Prasher Ravi
Published: January 2009

Nanoparticles are typically in contact with another surface through weak van der Waals force. Thermal transport in these nanostructured systems is mainly limited by the contact resistance (Rc). Rc of nanoparticles have been typically calculated using the traditional acoustic or diffuse mismatch models, which assume very strong bond at the interface. In this paper, an analytical model of Rc that accounts for the strength of the interfacial bonding is presented. Conductance/area is proportional to the square of the adhesion energy of the interface for weak bonding and is the same as that given by traditional acoustic mismatch model for strong bonding.
Factors Influencing E-Disclosure in Local Public Administrations
Authors: Serrano-Cinca Carlos , Rueda-Tomás Mar , Portillo-Tarragona Pilar
Published: January 2009

We study the determinants of voluntary Internet financial reporting (e-disclosure) by local public administrations. We present hypotheses regarding the relationship between e-disclosure and city size, the issuing of municipal bonds, financial features, Internet visibility, the level of e-government, and diverse political aspects. We also examine the influence of external factors, such as citizens' income level, their educational level, and their sociopolitical commitment. The hypotheses were empirically tested, using a sample of ninety-two Spanish local public administrations. The data support the hypotheses, with different levels of robustness, and show that size, political will, and citizens' income level all affect e-disclosure.
Multilevel Governance at Work: Evidence from Structural Funds Management in Lombardia, Italy
Authors: Percoco Marco , Giove Michele
Published: January 2009

Multilevel governance is widely recognized as one of the striking features of local development policy implementation and management. In Lombardia, Italy, this framework has been applied in the context of European Regional Development Fund actions in order to increase the number and quality of projects. As a consequence the governance of regional development policies now has new meta-actors: the Programmi Integrati per lo Sviluppo Locale (PISL) aimed at promoting and soliciting projects to be submitted for funding by the regional government. In this paper we evaluate the impact of this new governance structure by estimating a discrete choice model over a sample of more than 6000 projects submitted for funding to the Regional Government of Lombardia. We find that projects within the context of the PISL have a slightly greater probability of being funded, although we cannot exclude the existence of adverse selection because we also find that those projects are, on average, of lower quality from a purely formal viewpoint. We finally argue in favour of this new governance structure, even though we identify some critical points to be addressed in the next planning period in order to enhance the effectiveness of development policies.
The effect of the breeding season, cryopreservation and physiological extender on selected sperm and semen parameters of four ferret species: implications for captive breeding in the endangered black-footed ferret
Authors: van der Horst G. , Kitchin R. M. , van der Horst M. , Atherton R. W.
Published: January 2009

In the present investigation, comparative baseline information on selected sperm characteristics of ejaculate spermatozoa of the domestic (Mustela putorius furo), fitch (Mustela sp.) and black-footed ferrets (Mustela nigripes) and the Siberian polecat (Mustela eversmanni) are presented. The main emphasis was to establish differences and similarities among these species in relation to semen and sperm quality during the breeding season, in cryopreservation success and in supporting sperm motility in different extenders or physiological media. The results confirm that most sperm morphology abnormalities were evident during the beginning of the breeding cycle in all four species. No significant interspecies differences were apparent in the sperm attributes examined, for all sampling months during the breeding season. Moreover, all species exhibited comparable patterns of reproductive seasonality. Cryopreservation suppressed sperm characteristics equally in all species studied. Ejaculate spermatozoa of closely related ferret species shared many similar motion characteristics using computer-aided sperm motility analysis. These results suggest that the basic sperm physiology of the ferret species under examination is very similar. Disparate to the interspecies comparisons, there were significant differences for most sperm motion parameters when spermatozoa of any of the ferrets were compared in different extenders. Assisted reproductive technologies developed for use in domestic ferret, fitch ferret or Siberian polecat may be successfully applied to captive breeding of the black-footed ferret using semen during any of the functional breeding months.
In vivo virtual histology of mouse embryogenesis by ultrasound biomicroscopy and magnetic resonance imaging
Authors: Pallares P. , Fernandez-Valle M. E. , Gonzalez-Bulnes A.
Published: January 2009

Feasibility of magnetic resonance imaging (MRI) and ultrasound biomicroscopy (UBM) for sequential in vivo study of mouse embryo development between Days 6.5 and 13.5 of pregnancy was assessed in a first experiment. A second trial, based on the results of the first, determined the accuracy of UBM for imaging morphogenesis from implantation to the late embryo stage (Days 4.5 to 15.5). MRI allowed imaging of the entire uterus and all gestational sacs and embryos inside whilst the small scanning range of UBM precluded accurate counting of fetuses; however, its high resolution identified the decidual reaction at implantation sites from Day 4.5. At later stages, it was possible to assess key morphogenetic processes such as differentiation of the placenta, the cephalic region, the thoracic and abdominal organs, the skeletal system and the limbs, and dynamic structures such as the cardiovascular system. Thus, both techniques are reliable for in utero imaging of mouse embryo development. MRI may be more appropriate for studying embryo lethality and intrauterine growth retardation, because the entire uterus can be viewed. UBM may be more suitable for studies of cellular components of organs and tissues and assessment of haemodynamic changes in the circulatory system.
Interspecies embryo transfer in camelids: the birth of the first Bactrian camel calves (Camelus bactrianus) from dromedary camels (Camelus dromedarius)
Authors: Niasari-Naslaji A. , Nikjou D. , Skidmore J. A. , Moghiseh A. , Mostafaey M. , Razavi K. , Moosavi-Movahedi A. A.
Published: January 2009

Interspecies embryo transfer is a possible approach that can be used to conserve endangered species. It could provide a useful technique to preserve the Iranian and wild Bactrian camels, both of which are threatened with extinction. In the present study, one Bactrian camel was superovulated using decreasing doses of FSH (60, 40, 30, 30, 20, 20 mg, b.i.d.; Folltropin-V; Bioniche, London, ON, Canada) for 6 days, followed by a single injection of FSH (20 mg, i.m.) on Day 7. Daily ovarian ultrasonography was performed until most of the growing follicles had reached a mature size of 13–17 mm, at which time the camel was mated twice, 24 h apart, with a fertile male Bactrian camel. At the time of first mating, female camels were given 20 μg, i.v., buserelin (Receptal; Intervet, Boxmeer, The Netherlands). One day after the donor camel had been mated, the dromedary recipients (n = 8) were injected with 25 mg, i.v., porcine LH (Lutropin-V; Bioniche) to induce ovulation. Embryos were recovered on Day 8.5 after the first mating and transferred non-surgically into recipients on Day 7.5 after LH injection. Pregnancy was diagnosed 25 days after embryo transfer. Healthy Bactrian camel calves (n = 4) were born without any particular complications at the time of parturition (e.g. dystocia and neonatal diseases). The present study is the first report of the birth of Bactrian camel calves from dromedary camels, as well as the first report of interspecies embryo transfer in old world camelids.
Immunoglobulin superfamily member IgSF8 (EWI-2) and CD9 in fertilisation: evidence of distinct functions for CD9 and a CD9-associated protein in mammalian sperm - egg interaction
Authors: Glazar Amanda I. , Evans Janice P.
Published: January 2009

On the mouse egg, the tetraspanin CD9 is nearly essential for sperm–egg fusion, with another tetraspanin, CD81, playing a complementary role. Based on what is known about these proteins, egg tetraspanins are likely to be involved in regulation of membrane order through associations with other egg membrane proteins. Here, we identify a first-level interaction (stable in 1% Triton X-100) between CD9 and the immunoglobulin superfamily member IgSF8 (also known as EWI-2), the first evidence in eggs of such an interaction of CD9 with another protein. We also compared the effects of antibody-mediated perturbation of IgSF8 and CD9, evaluating the robustness of these perturbations in IVF conditions that heavily favour fertilisation and those in which fertilisation occurs less frequently. These studies demonstrate that IgSF8 participates in mouse gamete interactions and identify discrete effects of antibody-mediated perturbation of CD9 and IgSF8. An anti-IgSF8 antibody had moderate inhibitory effects on sperm–egg binding, whereas an anti-CD9 antibody significantly inhibited sperm–egg fusion and, in certain assays, had an inhibitory effect on binding as well. The present study highlights the critical importance of design of IVF experiments for the detection of different effects of experimental manipulations on gamete interactions.
Relocation of myosin and actin, kinesin and tubulin in the acrosome reaction of bovine spermatozoa
Authors: Oikonomopoulou Ifigenia , Patel Hitesh , Watson Paul F. , Chantler Peter D.
Published: January 2009

The mammalian acrosome reaction is a specialised exocytotic event. Although molecular motors are known to be involved in exocytosis in many cell types, their potential involvement in the acrosome reaction has remained unknown. Here, it has been shown that actin is localised within the equatorial segment and in the marginal acrosomal ridge of the heads of unreacted bull spermatozoa. Myosins IIA and IIB are found within the anterior acrosomal margins of virtually all sperm cells and, less prominently, within the equatorial segment. Tubulin was detected in the equatorial segment and around the periphery of the acrosome while kinesin was prominent in the equatorial segment. After induction of the acrosome reaction by means of the calcium ionophore A23187, the number of cells exhibiting actin fluorescence intensity in the anterior acrosomal margin decreased four-fold and those displaying equatorial segment fluorescence decreased 3.5-fold; myosin IIA immunofluorescence decreased in intensity with most spermatozoa losing equatorial staining, whereas there was little change in the distribution or intensity of myosin IIB immunofluorescence, except for a ~20% decrease in the number of cells exhibiting acrosomal staining. Tubulin became largely undetectable within the head and kinesin staining spread rostrally over the main acrosome region. A possible sequence of events that ties in these observations of molecular motor involvement with the known participation of SNARE proteins is provided.
BRG1 requirement for long-range interaction of a locus control region with a downstream promoter
Authors: Kim Shin-Il , Bultman Scott J. , Kiefer Christine M. , Dean Ann , Bresnick Emery H.
Published: January 2009

The dynamic packaging of DNA into chromatin is a fundamental step in the control of diverse nuclear processes. Whereas certain transcription factors and chromosomal components promote the formation of higher-order chromatin loops, the co-regulator machinery mediating loop assembly and disassembly is unknown. Using mice bearing a hypomorphic allele of the BRG1 chromatin remodeler, we demonstrate that the
Brg1
mutation abrogated a cell type-specific loop between the β-globin locus control region and the downstream β
major
promoter, despite
trans
-acting factor occupancy at both sites. By contrast, distinct loops were insensitive to the
Brg1
mutation. Molecular analysis with a conditional allele of GATA-1, a key regulator of hematopoiesis, in a novel cell-based system provided additional evidence that BRG1 functions early in chromatin domain activation to mediate looping. Although the paradigm in which chromatin remodelers induce nucleosome structural transitions is well established, our results demonstrating an essential role of BRG1 in the genesis of specific chromatin loops expands the repertoire of their functions.
Evolutionary tradeoffs for nitrogen allocation to photosynthesis versus cell walls in an invasive plant
Authors: Feng Yu-Long , Lei Yan-Bao , Wang Rui-Fang , Callaway Ragan M. , Valiente-Banuet Alfonso , Inderjit  , Li Yang-Ping , Zheng Yu-Long
Published: January 2009

Many studies have shown that individuals from invasive populations of many different plant species grow larger than individuals from native populations and that this difference has a genetic basis. This increased vigor in invasive populations is thought to be due to life history tradeoffs, in which selection favors the loss of costly defense traits, thereby freeing resources that can be devoted to increased growth or fecundity. Despite the theoretical importance of such allocation shifts for invasions, there have been no efforts to understand apparent evolutionary shifts in defense-growth allocation mechanistically. Reallocation of nitrogen (N) to photosynthesis is likely to play a crucial role in any growth increase; however, no study has been conducted to explore potential evolutionary changes in N allocation of introduced plants. Here, we show that introduced
Ageratina adenophora
, a noxious invasive plant throughout the subtropics, appears to have evolved increased N allocation to photosynthesis (growth) and reduced allocation to cell walls, resulting in poorer structural defenses. Our results provide a potential mechanism behind the commonly observed and genetically based increase in plant growth and vigor when they are introduced to new ranges.
Dynamic combinatorial synthesis of a catenane based on donor–acceptor interactions in water
Authors: Au-Yeung Ho Yu , Pantoş G. Dan , Sanders Jeremy K. M.
Published: January 2009

A new type of neutral donor–acceptor [2]-catenane, containing both complementary units in the same ring was synthesized from a dynamic combinatorial library in water. The yield of the water soluble [2]-catenane is enhanced by increasing either building-block concentrations or ionic strength, or by the addition of an electron-rich template. NMR spectroscopy demonstrates that the template is intercalated between the 2 electron-deficient naphthalenediimide units of the catenane.
Cross-presenting human γδ T cells induce robust CD8
+
αβ T cell responses
Authors: Brandes Marlène , Willimann Katharina , Bioley Gilles , Lévy Nicole , Eberl Matthias , Luo Ming , Tampé Robert , Lévy Frédéric , Romero Pedro , Moser Bernhard
Published: January 2009

γδ T cells are implicated in host defense against microbes and tumors but their mode of function remains largely unresolved. Here, we have investigated the ability of activated human Vγ9Vδ2
+
T cells (termed γδ T-APCs) to cross-present microbial and tumor antigens to CD8
+
αβ T cells. Although this process is thought to be mediated best by DCs, adoptive transfer of
ex vivo
antigen-loaded, human DCs during immunotherapy of cancer patients has shown limited success. We report that γδ T-APCs take up and process soluble proteins and induce proliferation, target cell killing and cytokine production responses in antigen-experienced and naïve CD8
+
αβ T cells. Induction of APC functions in Vγ9Vδ2
+
T cells was accompanied by the up-regulation of costimulatory and MHC class I molecules. In contrast, the functional predominance of the immunoproteasome was a characteristic of γδ T cells irrespective of their state of activation. γδ T-APCs were more efficient in antigen cross-presentation than monocyte-derived DCs, which is in contrast to the strong induction of CD4
+
αβ T cell responses by both types of APCs. Our study reveals unexpected properties of human γδ T-APCs in the induction of CD8
+
αβ T effector cells, and justifies their further exploration in immunotherapy research.
Reversal of defective lysosomal transport in NPC disease ameliorates liver dysfunction and neurodegeneration in the
npc1
−/−
mouse
Authors: Liu Benny , Turley Stephen D. , Burns Dennis K. , Miller Anna M. , Repa Joyce J. , Dietschy John M.
Published: January 2009

Niemann-Pick type C disease is largely attributable to an inactivating mutation of NPC1 protein, which normally aids movement of unesterified cholesterol (C) from the endosomal/lysosomal (E/L) compartment to the cytosolic compartment of cells throughout the body. This defect results in activation of macrophages in many tissues, progressive liver disease, and neurodegeneration. In the
npc1
−/−
mouse, a model of this disease, the whole-animal C pool expands from 2,082 to 4,925 mg/kg body weight (bw) and the hepatic C pool increases from 132 to 1,485 mg/kg bw between birth and 49 days of age. A single dose of 2-hydroxypropyl-β-cyclodextrin (CYCLO) administered at 7 days of age immediately caused this sequestered C to flow from the lysosomes to the cytosolic pool in many organs, resulting in a marked increase in cholesteryl esters, suppression of C but not fatty acid synthesis, down-regulation of genes controlled by sterol regulatory element 2, and up-regulation of many liver X receptor target genes. There was also decreased expression of proinflammatory proteins in the liver and brain. In the liver, where the rate of C sequestration equaled 79 mg·d
−1
·kg
−1
, treatment with CYCLO within 24 h increased C movement out of the E/L compartment from near 0 to 233 mg·d
−1
·kg
−1
. By 49 days of age, this single injection of CYCLO resulted in a reduction in whole-body C burden of >900 mg/kg, marked improvement in liver function tests, much less neurodegeneration, and, ultimately, significant prolongation of life. These findings suggest that CYCLO acutely reverses the lysosomal transport defect seen in NPC disease.
Arabidopsis
ORC1 is a PHD-containing H3K4me3 effector that regulates transcription
Authors: de la Paz Sanchez María , Gutierrez Crisanto
Published: January 2009

Control of gene expression depends on a complex and delicate balance of various posttranslational modifications of histones. However, the relevance of specific combinations of histone modifications is not fully defined. Downstream effector proteins recognize particular histone modifications and transduce this information into gene expression patterns. Methylation of histone H3 at lysine 4 (H3K4me) is a landmark of gene expression control in eukaryotes. Its recognition depends on the presence in the effector protein of a motif termed plant homeodomain (PHD) that specifically binds to H3K4me3. Here, we establish that
Arabidopsis
ORC1, the large subunit of the origin recognition complex involved in defining origins of DNA replication, functions as a transcriptional activator of a subset of genes, the promoters of which are preferentially bound by ORC1.
Arabidopsis
ORC1 contains a PHD and binds to H3K4me3. In addition to H4 acetylation, ORC1 binding correlates with increased H4K20me3 in the proximal promoter region of ORC1 targets. This suggests that H4K20me3, unlike in animal cells, is associated with transcriptional activation in
Arabidopsis
. Thus, our data provide a molecular basis for the opposite role of ORC1 in transcriptional activation in plants and repression in animals. Since only ORC1 proteins of plant species contain a PHD, we propose that plant ORC1 constitutes a novel class of H3K4me3 effector proteins characteristic of the plant kingdom.
Light-assisted deep-trapping of holes in conjugated polymers
Authors: Bolinger Josh C. , Fradkin Leonid , Lee Kwang-Jik , Palacios Rodrigo E. , Barbara Paul F.
Published: January 2009

The injection of positive charge carriers (holes) into a single conjugated polymer chain was observed to be light-assisted. This effect may underlie critical, poorly understood organic electronic device phenomena such as the build-up of functional deeply trapped charge layers in polymer light emitting diodes. The charging/discharging dynamics were investigated indirectly by a variety of single molecule electro-optical spectroscopic techniques, including an “image-capture” approach.