bluuebunny/crossref_metadata_2025 huggingface dataset:
AO/NAO response to climate change: 2. Relative importance of low‐ and high‐latitude temperature changes
Authors: Rind D. , Perlwitz J. , Lonergan P. , Lerner J.
Published: June 2005

We address the issue of why different models may be getting different responses of the AO/NAO in climate change experiments. The results from part 1 (Rind et al., 2005) suggest that for substantive climate changes, the differences are likely to be found in the patterns of tropospheric climate change, rather than from the stratosphere. We assess the various tropospheric forcings through a variety of experiments. We first use extreme paleoclimate experiments (Ice Age, Paleocene) which feature large variations in the low level latitudinal temperature gradient; the results show that under these circumstances, changes in the eddy transport of sensible heat, and in situ high latitude forcing, dominate the AO response. We next test the effect of more modest SST temperature gradient changes in the current climate, and find a similar result with a model configuration that does not easily transport the low level temperature changes into the upper troposphere. We then reanalyze the results from different 2 × CO2 experiments with the GISS model and find that they can be understood by assessing: (1) the magnitude of tropical SST warming; (2) the translations of that warming into the upper troposphere; (3) the change in the extratropical low altitude temperature gradient; and (4) the change in the high latitude SST/sea ice response. We suggest that these features might explain the varying results among modeling groups, and that forecasts will not converge until these features do.
Speciation and transport of newly deposited mercury in a boreal forest wetland: A stable mercury isotope approach
Authors: Branfireun B. A. , Krabbenhoft D. P. , Hintelmann H. , Hunt R. J. , Hurley J. P. , Rudd J. W. M.
Published: June 2005

As part of the Mercury Experiment to Assess Atmospheric Loadings in Canada and the United States (METAALICUS) the fate and transport of contemporary mercury (Hg) deposition in a boreal wetland was investigated using an experimentally applied stable mercury isotope. We applied high purity (99.2% ± 0.1) 202Hg(II) to a wetland plot to determine if (1) the 202Hg was detectable above the pool of native Hg, (2) the 202Hg migrated vertically and/or horizontally in peat and pore waters, and (3) the 202Hg was converted to methylmercury (MeHg) in situ. The 202Hg was easily detected by ICP/MS in both solid peat and pore waters. Over 3 months, the 202Hg migrated vertically downward in excess of 15 cm below the water table and traveled several meters horizontally beyond the experimental plot to the lake margin along the dominant vector of groundwater flow. Importantly, at one location, 6% of aqueous 202Hg was detected as Me202Hg after only 1 day. These results indicate that new inorganic Hg in atmospheric deposition can be readily methylated and transported lakeward by shallow groundwater flow, confirming the important role of wetlands as contributors of Hg to aquatic ecosystems.
Modulation of voltage‐dependent Ba2+ currents in the guinea‐pig gastric antrum by cyclic nucleotide‐dependent pathways
Authors: Zhu Hai‐Lei , Hirst G David S , Ito Yushi , Teramoto Noriyoshi
Published: June 2005

We have investigated whether the activation of cAMP‐ and cGMP‐dependent pathways modifies the properties of voltage‐dependent Ba2+ currents (IBa) recorded from guinea‐pig gastric myocytes using patch‐clamp techniques. All experiments were carried on single smooth muscle cells, dispersed from the circular layer of the guinea‐pig gastric antrum.

Both dibutyryl cAMP (db‐cAMP, 0.1–1 mM), a membrane‐permeable ester of cAMP, and isoproterenol, a selective β‐stimulant, inhibited IBa in a concentration‐dependent manner.

Forskolin, but not dideoxy‐forskolin, an inactive isomer of forskolin, inhibited the peak amplitude of IBa.

In the presence of either Rp‐cAMP or the PKA (cAMP‐dependent protein kinase) inhibitor peptide 5‐24 (PKA‐IP), neither forskolin nor db‐cAMP inhibited IBa.

After establishing a conventional whole‐cell recording, the peak amplitude of IBa gradually decreased when the catalytic subunit of PKA was included in the pipette. The further application of Rp‐cAMP reversibly enhanced IBa.

Sodium nitroprusside (0.1–1 mM) and 8‐Br‐cGMP (0.1–1 mM) also inhibited IBa in a concentration‐dependent manner.

The inhibitory effects of forskolin or db‐cAMP on IBa were not significantly changed by pretreatment with a cGMP‐dependent protein kinase (PKG) inhibitor. Similarly, the inhibitory actions of 8‐Br‐cGMP on IBa were not modified by PKA‐IP.

The membrane‐permeable cyclic nucleotides db‐cAMP and 8‐Br‐cGMP caused little shift of the voltage dependence of the steady‐state inactivation and reactivation curves.

Neither of the membrane‐permeable cyclic nucleotides db‐cAMP or 8‐Br‐cGMP had additive inhibitory effects on IBa.

These results indicate that two distinct cyclic nucleotide‐dependent pathways are present in the guinea‐pig gastric antrum, and that both inhibited IBa in an independent manner.

British Journal of Pharmacology (2005) 146, 129–138. doi:10.1038/sj.bjp.0706295
Application of equation-of-motion coupled-cluster methods to low-lying singlet and triplet electronic states of HBO and BOH
Authors: DeYonker Nathan J. , Li Se , Yamaguchi Yukio , Schaefer Henry F. , Crawford T. Daniel , King Rollin A. , Peterson Kirk A.
Published: June 2005

The equilibrium structures and physical properties of the X̃Σ+1 linear electronic states, linear excited singlet and triplet electronic states of hydroboron monoxide (HBO) (ÃΣ−1, B̃Δ1, ãΣ+3, and b̃Δ3) and boron hydroxide (BOH) (ÃΣ+1, B̃Π1, and b̃Π3), and their bent counterparts (HBO ãA′3, b̃A″3, ÃA″1, B̃A′1 and BOH X̃A′1, b̃A′3, c̃A″3, ÃA′1, B̃A′1, C̃A″1) are investigated using excited electronic state ab initio equation-of-motion coupled-cluster (EOM-CC) methods. A new implementation of open-shell EOM-CC including iterative partial triple excitations (EOM-CC3) was tested. Coupled-cluster wave functions with single and double excitations (CCSD), single, double, and iterative partial triple excitations (CC3), and single, double, and full triple excitations (CCSDT) are employed with the correlation-consistent quadruple and quintuple zeta basis sets. The linear HBO X̃Σ+1 state is predicted to lie 48.3kcalmol−1 (2.09eV) lower in energy than the BOH X̃Σ+1 linear stationary point at the CCSDT level of theory. The CCSDT BOH barrier to linearity is predicted to lie 3.7kcalmol−1 (0.16eV). With a harmonic zero-point vibrational energy correction, the HBO X̃Σ+1−BOHX̃A′1 energy difference is 45.2kcalmol−1 (1.96eV). The lowest triplet excited electronic state of HBO, ãA′3, has a predicted excitation energy (Te) of 115kcalmol−1 (4.97eV) from the HBO ground state minimum, while the lowest-bound BOH excited electronic state, b̃A′3, has a Te of 70.2kcalmol−1 (3.04eV) with respect to BOH X̃A′1. The Te values predicted for the lowest singlet excited states are ÃA″1←X̃Σ+1=139kcalmol−1 (6.01eV) for HBO and ÃA′1←X̃A′1=102kcalmol−1 (4.42eV) for BOH. Also for BOH, the triplet vertical transition energies are b̃A′3←X̃A′1=71.4kcalmol−1 (3.10eV) and c̃A″3←X̃A′1=87.2kcalmol−1 (3.78eV).
Compact gate-current model based on transfer-matrix method
Authors: Shangguan W. Z. , Zhou X. , Chiah S. B. , See G. H. , Chandrasekaran K.
Published: June 2005

We present a compact gate-current model based on the scattering matrix method for metal-oxide-semiconductor devices. The analytical integration of the tunneling current over the incident energy is simplified by making use of the single tunneling energy approximation, and the model error is further reduced by introducing different effective conduction band edges for the supply function and for the transmission coefficient function. Results calculated by the proposed model agree with the experimental data with satisfactory accuracy.
Second-order quantized Hamilton dynamics coupled to classical heat bath
Authors: Heatwole Eric M. , Prezhdo Oleg V.
Published: June 2005

Starting with a quantum Langevin equation describing in the Heisenberg representation a quantum system coupled to a quantum bath, the Markov approximation and, further, the closure approximation are applied to derive a semiclassical Langevin equation for the second-order quantized Hamilton dynamics (QHD) coupled to a classical bath. The expectation values of the system operators are decomposed into products of the first and second moments of the position and momentum operators that incorporate zero-point energy and moderate tunneling effects. The random force and friction as well as the system-bath coupling are decomposed to the lowest classical level. The resulting Langevin equation describing QHD-2 coupled to classical bath is analyzed and applied to free particle, harmonic oscillator, and the Morse potential representing the OH stretch of the SPC-flexible water model.
Prediction of pressure-induced redshift of f1→d(t2g)1 excitations in Cs2NaYCl6:Ce3+ and its connection with bond-length shortening
Authors: Ruipérez Fernando , Seijo Luis , Barandiarán Zoila
Published: June 2005

Quantum chemical calculations including embedding, scalar relativistic, and dynamic electron correlation effects on Cs2NaYCl6:(CeCl6)3− embedded clusters predict (i) redshifts of the f1→d(t2g)1 transition with pressure and (ii) bond-length shortening upon f→d(t2g) excitation. Both effects are found to be connected which suggests that new high-pressure spectroscopic experiments could reveal the sign of the bond-length change.
Long-ranged order formation of colloids of implanted ions in a dc biased piezoelectric semiconductor
Authors: Salimullah M. , Rizwan A. M. , Ghosh S. K. , Shukla P. K. , Nambu M. , Nitta H. , Hayashi Y.
Published: June 2005

A dc bias in a piezoelectric semiconductor may drive a beam of electrons which could charge the neutralized colloids of implanted ions and cause a uniform drift of charged colloidal particles. Using a test particle approach and appropriate dielectric-response function for an n-type piezoelectric semiconductor plasma, the potential distribution of uniformly drifting colloidal ions has been investigated. The dynamical oscillatory wake potential, besides the usual static Coulombian Debye–Hückel potential, is found to be contributing more dominantly due to the plasma effect, rather than due to electron–phonon coupling interactions. This periodic wakefield may cause a long-range ordered structure of charged colloidal particles within the semiconductor to exhibit various additional properties.
Room-temperature ferromagnetism in Zn1−xCoxO magnetic semiconductors prepared by sputtering
Authors: Dinia A. , Schmerber G. , Mény C. , Pierron-Bohnes V. , Beaurepaire E.
Published: June 2005

We have used magnetron cosputtering to grow Zn1−xCoxO magnetic dilute semiconductors. The growth has been performed on SiO2∕Si and Al2O3(0001) substrates. The Co concentration has been varied between 0.1 and 0.25 and the substrate temperature between room temperature and 600°C. X-ray diffraction analysis has shown that for the films grown on Si substrates the structural quality of the film is improved by increasing the growth temperature and/or postgrowth annealing. The films are textured with c axis of the wurtzite structure along the growth direction. However, for the films grown on Al2O3 substrate quasi-epitaxial films have been obtained for 600°C substrate temperature. Magnetization measurements have shown that the ferromagnetism is directly correlated to the structural quality and appears by increasing the growth temperature and/or postgrowth annealing. Moreover, for the highly textured film a clear magnetic perpendicular anisotropy has been evidenced with the easy magnetization axis along the growth direction. To evidence the intrinsic nature of the ferromagnetism in the films, transmission optical measurements have been used. They show three absorption bands that are characteristics of d-d transitions of tetrahedrally coordinated Co2+. This has been supported by nuclear magnetic resonance and magnetic thermal variation.
Coarse-grained rigid blob model for soft matter simulations
Authors: Chao Sheng D. , Kress Joel D. , Redondo Antonio
Published: June 2005

We have developed a coarse-grained multiscale molecular simulation method for soft matter systems that directly incorporates stereochemical information. We divide the material into disjoint groups of atoms or particles that move as separate rigid bodies; we call these groups “rigid blobs,” hence the name coarse-grained rigid blob model. The method is enabled by the construction of transferable interblob potentials that approximate the net intermolecular interactions, as obtained from ab initio electronic structure calculations, other all-atom empirical potentials, experimental data, or any combination of the above. We utilize a multipolar expansion to obtain the interblob potential-energy functions. The series, which contains controllable approximations that allow us to estimate the errors, approaches the original intermolecular potential as the number of terms increases. Using a novel numerical algorithm, we can calculate the interblob potentials very efficiently in terms of a few interaction moment tensors. This reduces the labor well beyond what is required in standard molecular-dynamics calculations and allows large-scale simulations for temporal scales commensurate with characteristic times of nano- and mesoscale systems. A detailed derivation of the formulas is presented, followed by illustrative applications to several systems showing that the method can effectively capture realistic microscopic details and can easily extend to large-scale simulations.
A theoretical analysis of quantum dash structures
Authors: Wei J. H. , Chan K. S.
Published: June 2005

The gain and related characteristics of quantum dash structures are modeled and analyzed using a parabolic effective-mass theory and the density-matrix theory. Size fluctuation is included in the model and its effects are analyzed. Comparison of performance in terms of these characteristics has been made with quantum well (QW) and quantum wire structures. Owing to size fluctuation, quantum dashes have broad gain spectra, which allow wavelength tuning without significant increase in the injected carrier density. Quantum dashes have smaller differential gain than quantum wells, while the linewidth enhancement factors are similar for these two structures. Due to their broad gain profiles, quantum dashes have much smaller large-signal chirp (change of refractive index). These characteristics can be further improved by blueshifting the emission energy without significant change in the injected carrier density. After detuning, the differential gain can be improved only to half of quantum well’s values and the large-signal chirp can be reduced to one-tenth of the QW’s value.
Modification of work function of Ti by self-assembled monolayer molecules on SiO2∕p-Si
Authors: Gu Diefeng , Sistiabudi Rizaldi , Dey Sandwip K.
Published: June 2005

A method was used to change the work function of Ti (ϕTi) using self-assembled monolayer (SAM) molecules of dipolar, aminopropyl triethoxy silane, a change attributed to the change in the electrical potential at the Ti∕SAM interface. The SAM was deposited on SiO2∕Si followed by Ti electrode evaporation to form a Ti∕SAM∕SiO2∕p-Si stack for capacitance-voltage (C–V) analyses. The binding of SAM on the SiO2 surface was confirmed using Fourier-transform infrared spectroscopy, and the surface coverage of SAM was determined by the change in the flat-band voltages VFB with deposition time. After 1h of deposition time, an independence of the total capacitance Ctotal and VFB was indicative of saturated surface coverage of SAM on the SiO2 surface. A relationship between the fraction x (where 0<x<1 and x=1 correspond to a monolayer) of the SiO2 surface covered with SAM, at saturated surface coverage, and the dielectric permittivity of SAM (KSAM) was found to be x=0.15KSAM+0.09; if KSAM is assumed to be 3, x is estimated to be 0.54. The ϕTi on the bare SiO2 surface as well as on the SiO2 surface covered with SAM at saturated surface coverage were determined from VFB versus total equivalent oxide thickness plots. The maximum change in ϕTi from Ti∕SiO2∕p-Si to Ti∕SAM∕SiO2∕p-Si configuration was found to be 0.2V.
High-level injection in n+-p junction silicon devices
Authors: Edmonds Larry D.
Published: June 2005

It is argued that a silicon p-n junction diode operating at high injection in the forward direction can be analyzed by using the regional approximation together with the classical law of the junction. Erroneous predictions made in the past are attributed to incorrect equations describing the quasineutral regions. Corrected equations (exact analytical solutions) are given.
Pressure drop and heat transfer rates in forced convection rotating square duct flows at high rotation rates
Authors: Pallares J. , Grau F. X. , Davidson L.
Published: June 2005

This paper presents and discusses numerical simulations of forced convection heat transfer in a rotating square duct at high rotation rates. The mean pressure gradient has been kept constant in the simulations that were conducted with a second order finite volume code with a dynamical localized subgrid scale model. The rotation number based on the bulk velocity (Ro=2ΩD∕U¯b) was varied from 0.12 to 6.6 and consequently the Reynolds number (Re=U¯bD∕ν) ranged from 3900 to 1810 according to the fact that rotation tends to increase the pressure drop in the duct. A model for estimating the velocities and the corresponding friction coefficient has been developed by analytically solving simplified versions of the momentum budgets within the Ekman layers occurring near the opposite two walls of the duct perpendicular to the rotation axis. The model reproduces accurately the velocity profiles of the numerical simulation at high rotation rates and predicts that the boundary layer quantities scale as Ek1∕2 (Ek=ν∕ΩD2). At Ro>1 the Ekman layers are responsible for most of the pressure drop of the flow while the maximum heat transfer rates are found on the wall where the stratification of the x-momentum is unstable with respect to the Coriolis force. Rotation enhances the differences between the contributions of the local friction coefficients and local Nusselt numbers of the four walls of the duct and considerably increases, in comparison with the non-rotating case, the pressure drop of the flow and the Nusselt number. The overall friction coefficient of the measurements and the simulations existing in the literature, as well as the present numerical predictions, are well correlated with the equation 1.09(Cf∕Ek1∕2)1.25=Ro in the range Ro⩾1 for Re⩽104.
Universal wake structures of Kármán vortex streets in two-dimensional flows
Authors: Roushan Pedram , Wu X. L.
Published: June 2005

Formation of Kármán vortex streets by circular rods is studied in a flowing soap film channel. The two-dimensional fluid flow in the film allows stable vortex streets to be generated and studied over a broad range of Reynolds numbers, 10<Re<2000. There have been many studies of the Kármán vortex streets. The current study focuses on the universal feature of the near-wake structures generated by circular cylinders in a uniform two-dimensional (2D) flow. The new approach in the investigation is to decompose the street into a series of vortex couples, which defines the outer envelope of the wake, and to study the expansion rate of these couples. Our experiment shows that motion of vortex couples are powered by bursts of transverse jets, and the jet intensity determines the asymptotic width and the expansion rate of the wake. A simple model is constructed that not only allows us to extract the kinetic energy encapsulated in the vortices but also explains the universal appearance of the 2D laminar wakes generated by large and small rods. To the best of our knowledge, this is the first time that the efficiency of energy injected into vortices is estimated and this efficiency turns out to be ∼5%.
Multi-echo in phase-separated He3–4He solid solutions under NMR conditions
Authors: Mikhin N. P. , Maidanov V. A.
Published: June 2005

A pulsed NMR method is used to make the first observation and study of the multi-echo in a phase-separated He3–4He solid solution. Analysis of the behavior of the second echo under these conditions in comparison with the results obtained in samples of liquid and solid He3 reveals the presence of a significant amount of liquid He3 in a fine-grained He3 phase and offers a new explanation of the origin of the unusual damping of the first echo observed previously under these conditions.
On the theory of the electron spectrum and superconductivity of copper oxides as antiferromagnetic metals
Authors: Loktev V. M.
Published: June 2005

The electron spectrum of doped copper oxides is considered on the basis of explicitly taking into account the antiferromagnetic structure of their ground state. It is shown that the spin conservation law imposes certain restrictions on the motion of the carriers, making it impossible for a carrier to leave the magnetic sublattice in which it was created. An attempt is made to compare the resulting dispersion of the hole conductivity with the available experimental data.
Short-period oscillations of the resistivity and magnetoresistance in Co/Cu(111) superlattices on mica
Authors: Zorchenko V. V. , Stetsenko A. N. , Anders A. G. , Kutko K. V.
Published: June 2005

In a study of [Co(8 Å)/Cu(dCu)(111)]20 superlattices grown by magnetron sputtering it is found that the resistivity ρs and relative magnetoresistance ΔR/Rs in magnetic fields H=15 kOe oriented parallel or perpendicular to the layers exhibit oscillations as the thickness of the copper spacer layers is varied in the range dCu=6–40 Å. Extrema of ρs and ΔR/Rs are observed at dCu=nd(111), where n is an integer or half-integer and d(111)=2.087 Å is the distance between (111)Cu planes, with a distance between adjacent maxima or minima equal to 1, 1.5, 2, 2.5 and 3d(111). When the magnetic field deviates from the plane of the layers the magnetic-field dependence of the resistivity exhibits an additional maximum due to a feature of the magnetization of the layers in the superlattice in an inclined field. The oscillations of ρs and ΔR/Rs are accompanied by oscillations of the magnetic anisotropy constants in synchrony with them. Analysis of the experimental data and theoretical calculations of the orientation of the magnetic moments of the layers when a magnetic field perpendicular to the layers is turned on allows one to explain the observed effects wherein the roughness of the interfaces between layers varies nonmonotonically with increasing dCu, leading to oscillations of the bilinear and biquadratic exchange interactions of the Co layers.
Interplay between the spin state of manganese and the stability of the crystal structure of MnAs and MnP compounds
Authors: Valkov V. I. , Golovchan A. V.
Published: June 2005

Starting from first principles, a study of the ground states of manganese arsenide and manganese phosphide, which have a hexagonal B81 and a distorted rhombohedral B31 crystal structure, is made by the FP–LMTO method. It is shown that in these compounds a continuous transition from a high-spin to a low-spin state occurs as the volume of the lattice is changed, and it turns out that the magnetic moment of the manganese atoms is the same at equal volumes. Starting from the results of a calculation of the total energy of these systems as a function of the parameters of the structural distortions, it is established that the high-spin state suppresses the structural distortions, while the low-spin state enhances them. It is shown that the difference of the crystal and magnetic structures of manganese arsenide and phosphide is due solely to the different lattice volumes, i.e., the substitution of arsenic by phosphorus is equivalent to the application of external hydrostatic pressure. It is conjectured that a qualitative interpretation of the mechanism of magnetostructural transitions in MnAs should proceed from the idea that the leading role is the degree of occupation of the “antibonding” state of the itinerant carriers of magnetism.
Modulational instability and non-Gaussian statistics in experimental random water-wave trains
Authors: Onorato M. , Osborne A. R. , Serio M. , Cavaleri L.
Published: June 2005

We study random, long-crested surface gravity waves in the laboratory environment. Starting with wave spectra characterized by random phases we consider the development of the modulational instability and the consequent formation of large amplitude waves. We address both dynamical and statistical interpretations of the experimental data. While it is well known that the Stokes wave nonlinearity leads to non-Gaussian statistics, we also find that the presence of the modulational instability is responsible for the departure from a Gaussian behavior, indicating that, for particular parameters in the wave spectrum, coherent unstable modes are quite prevalent, leading to the occurrence of what might be called a “rogue sea.” Statistical results are also compared with ensemble numerical simulations of the Dysthe equation.
Effect of duty cycle on plasma parameters in the pulsed dc magnetron argon discharge
Authors: Seo Sang-Hun , In Jung-Hwan , Chang Hong-Young , Han Jeon-Geon
Published: June 2005

The time-resolved probe measurements of the plasma parameters and the electron energy distribution function are carried out in a unipolar pulsed dc magnetron argon discharge. The cathode target is driven by the 20kHz midfrequency unipolar dc pulses at three operating modes, such as constant voltage, constant power, and constant current with the duty cycles ranging from 10% to 90%. It is observed that as the duty cycle is reduced, the electron temperature averaged during the pulse-on period rapidly increases irrespective of the operating mode although the average electron density strongly depends on the operating mode. The comparison of the measured electron energy distribution functions shows that the electron heating during the pulse-on period becomes efficient in the pulse operation with short duty cycle, which is closely related to the deep penetration of the high-voltage sheath into the bulk during the pulse-on period.
The thermoluminescence activation energy and frequency factor of the main glow of CaSO4:Tm phosphor determined by heating rate method including very slow rates of heating
Authors: Shinsho K. , Suzuki Y. , Yamamoto Y. , Urushiyama A.
Published: June 2005

The typical thermoluminescent phosphor of CaSO4:Tm was investigated using a heating rate method including very slow rates of heating, down to 0.0008°Cs−1. The sufficiently slow rates of heating clearly resolved at least eight narrow components in the main glow. The analysis of the peak temperature values and the half-widths of the resolved components in the glow curves by using various heating rates resulted in the distinctly higher activation energy (E) of 1.67–2.01 eV and a higher frequency factor (s) of 1019s−1 for the resolved components, compared to earlier reported values of E in the range of 0.94–1.42 eV and values of s in the range of 109–1013s−1, respectively.
Studies of the self-ordering process in FePt self-ordered magnetic array media
Authors: Verdes C. , Ahner J. , Jones P. M. , Shukla N. , Chantrell R. W. , Weller D.
Published: June 2005

A model of self-organization in FePt particulate thin films is described. The model is based on Monte Carlo methods and describes the self-organization process from the colloidal state as a result of the evaporation of the solvent and the consequent compression of the film due to surface tension forces. The model predicts the self-ordered state for systems with very narrow particle size distributions (standard deviation of the lognormal distribution σ<0.05). Various forms of interparticle potentials were considered. A comparison of the model with experimental data shows that the interparticle potential must contain an attractive term, in addition to the repulsive term normally expected to arise from the surfactant. Quantum chemistry calculations show that an attractive potential does indeed exist between overlapping oleic acid molecules. Although the ordering predicted by the model is predominantly hexagonal, the conditions for the formation of a square lattice are investigated, and an explanation for the observation of square lattices in some systems is proposed.
Spectrally enhanced light emission from aperiodic photonic structures
Authors: Dal Negro L. , Yi J. H. , Nguyen V. , Yi Y. , Michel J. , Kimerling L. C.
Published: June 2005

Light-emitting silicon-rich, SiNx∕SiO2 Thue-Morse (T-M) multilayer structures have been fabricated in order to investigate the generation and transmission of light in strongly aperiodic deterministic dielectrics. Photoluminescence and optical transmission data experimentally demonstrate the presence of emission enhancement effects occurring at wavelengths corresponding to multiple T-M resonance states. Emission enhancement effects by a factor of almost 6 with respect to homogeneous SiNx dielectrics have been experimentally measured, in good agreement with transfer matrix simulations. The unprecedented degree of structural flexibility of T-M systems can provide alternative routes towards the fabrication of optically active multiwavelength photonic devices.
Laser wavelength and spot diameter dependence of extreme ultraviolet conversion efficiency in ω, 2ω, and 3ω Nd:YAG laser-produced plasmas
Authors: Miyamoto Shuji , Shimoura Atushi , Amano Sho , Fukugaki Keisuke , Kinugasa Hiroaki , Inoue Takahiro , Mochizuki Takayasu
Published: June 2005

Conversion efficiency and spectra of extreme ultraviolet radiations from a cryogenic planar solid xenon target were investigated as a function of laser wavelength (ω, 2ω, and 3ω Nd:YAG) and the laser focus spot size (50–700μm) at the intensity 1010–5×1012W∕cm2. The conversion efficiency increased with laser intensity and reached the maximum value at about 1011W∕cm2 for all colors. It was found that an edge effect appears more strongly at the ω-laser case, indicating more lateral energy loss, while it appears only weakly for higher harmonics. Shorter-wavelength lasers generated significant conversion efficiencies even at lower laser energies; that is, with smaller laser spots. As the wavelength decreased from ω, 2ω, and 3ω, a spectral hump appeared in the extreme ultraviolet band around 13.5nm region, while the spectral intensity at 10.8nm drastically decreased. High-energy photon generation in the tail of 10.8nm peak was found to be strongly suppressed at shorter-wavelength laser (3ω), while the conversion efficiency at 13.5nm was as large as that at ω. This indicates that a Xe[XI] ion-rich plasma have been efficiently produced in the ablation plasma by using 3ω laser without overheating the underdense plasma responsible for extreme ultraviolet emission.
Radiation-induced electron traps in Al0.14Ga0.86N by 1 MeV electron radiation
Authors: Hogsed Michael R. , Yeo Yung Kee , Ahoujja Mo , Ryu Mee-Yi , Petrosky James C. , Hengehold Robert L.
Published: June 2005

Electrical properties of defects induced in n-type molecular-beam-epitaxial-grown Al0.14Ga0.86N are studied using deep-level transient spectroscopy (DLTS) to explore the radiation tolerance of AlGaN-based electronic and optoelectronic devices. It has been found that four electron traps labeled R1(0.15±0.02eV), R2(0.21±0.02eV), R3(0.26±0.02eV), and R4(0.33±0.03eV) are created in the electron irradiated Al0.14Ga0.86N. The electron trap R4 is the most prominent radiation-induced defect in the DLTS spectrum and appears to be unique to AlGaN. Although the other radiation-induced traps anneal significantly at or below 400 K, this R4 trap is thermally stable up to 450 K, and could significantly affect the performance of AlGaN-based devices.
Quantitative electron microscopy and fluorescence spectroscopy of the membrane distribution of influenza hemagglutinin
Authors: Hess Samuel T. , Kumar Mukesh , Verma Anil , Farrington Jane , Kenworthy Anne , Zimmerberg Joshua
Published: June 2005

Although lipid-dependent protein clustering in biomembranes mediates numerous functions, there is little consensus among membrane models on cluster organization or size. Here, we use influenza viral envelope protein hemagglutinin (HA0) to test the hypothesis that clustering results from proteins partitioning into preexisting, fluid-ordered “raft” domains, wherein they have a random distribution. Japan HA0 expressed in fibroblasts was visualized by electron microscopy using immunogold labeling and probed by fluorescence resonance energy transfer (FRET). Labeled HA coincided with electron-dense, often noncircular membrane patches. Poisson and K-test (Ripley, B.D. 1977. J. R. Stat. Soc. Ser. B. 39:172–212) analyses reveal clustering on accessible length scales (20–900 nm). Membrane treatments with methyl-β-cyclodextrin and glycosphingolipid synthesis inhibitors did not abolish clusters but did alter their pattern, especially at the shortest lengths, as was corroborated by changes in FRET efficiency. The magnitude and density dependence of the measured FRET efficiency also indicated a nonrandom distribution on molecular length scales (∼6–7 nm). This work rules out the tested hypothesis for HA over the accessible length scales, yet shows clearly how the spatial distribution of HA depends on lipid composition.
Stress granules and processing bodies are dynamically linked sites of mRNP remodeling
Authors: Kedersha Nancy , Stoecklin Georg , Ayodele Maranatha , Yacono Patrick , Lykke-Andersen Jens , Fritzler Marvin J. , Scheuner Donalyn , Kaufman Randal J. , Golan David E. , Anderson Paul
Published: June 2005

Stress granules (SGs) are cytoplasmic aggregates of stalled translational preinitiation complexes that accumulate during stress. GW bodies/processing bodies (PBs) are distinct cytoplasmic sites of mRNA degradation. In this study, we show that SGs and PBs are spatially, compositionally, and functionally linked. SGs and PBs are induced by stress, but SG assembly requires eIF2α phosphorylation, whereas PB assembly does not. They are also dispersed by inhibitors of translational elongation and share several protein components, including Fas-activated serine/threonine phosphoprotein, XRN1, eIF4E, and tristetraprolin (TTP). In contrast, eIF3, G3BP, eIF4G, and PABP-1 are restricted to SGs, whereas DCP1a and 2 are confined to PBs. SGs and PBs also can harbor the same species of mRNA and physically associate with one another in vivo, an interaction that is promoted by the related mRNA decay factors TTP and BRF1. We propose that mRNA released from disassembled polysomes is sorted and remodeled at SGs, from which selected transcripts are delivered to PBs for degradation.
Sequential activation of NKT cells and NK cells provides effective innate immunotherapy of cancer
Authors: Smyth Mark J. , Wallace Morgan E. , Nutt Stephen L. , Yagita Hideo , Godfrey Dale I. , Hayakawa Yoshihiro
Published: June 2005

The CD1d reactive glycolipid, α-galactosylceramide (α-GalCer), potently activates T cell receptor-α type I invariant NKT cells that secondarily stimulate the proliferation and activation of other leukocytes, including NK cells. Here we report a rational approach to improving the antitumor activity of α-GalCer by using delayed interleukin (IL)-21 treatment to mature the α-GalCer–expanded pool of NK cells into highly cytotoxic effector cells. In a series of experimental and spontaneous metastases models in mice, we demonstrate far superior antitumor activity of the α-GalCer/IL-21 combination above either agent alone. Superior antitumor activity was critically dependent upon the increased perforin-mediated cytolytic activity of NK cells. Transfer of α-GalCer–pulsed dendritic cells (DCs) followed by systemic IL-21 caused an even more significant reduction in established (day 8) metastatic burden and prolonged survival. In addition, this combination prevented chemical carcinogenesis more effectively. Combinations of IL-21 with other NK cell–activating cytokines, such as IL-2 and IL-12, were much less effective in the same experimental metastases models, and these cytokines did not substitute effectively for IL-21 in combination with α-GalCer. Overall, the data suggest that NK cell antitumor function can be enhanced greatly by strategies that are designed to expand and differentiate NK cells via DC activation of NKT cells.
A chromosomally integrated bacteriophage in invasive meningococci
Authors: Bille Emmanuelle , Zahar Jean-Ralph , Perrin Agnes , Morelle Sandrine , Kriz Paula , Jolley Keith A. , Maiden Martin C.J. , Dervin Catherine , Nassif Xavier , Tinsley Colin R.
Published: June 2005

Cerebrospinal meningitis is a feared disease that can cause the death of a previously healthy individual within hours. Paradoxically, the causative agent, Neisseria meningitidis, is a common inhabitant of the human nasopharynx, and as such, may be considered a normal, commensal organism. Only in a small proportion of colonized people do the bacteria invade the bloodstream, from where they can cross the blood–brain barrier to cause meningitis. Furthermore, most meningococcal disease is caused by bacteria belonging to only a few of the phylogenetic groups among the large number that constitute the population structure of this genetically variable organism. However, the genetic basis for the differences in pathogenic potential remains elusive. By performing whole genome comparisons of a large collection of meningococcal isolates of defined pathogenic potential we brought to light a meningococcal prophage present in disease-causing bacteria. The phage, of the filamentous family, excises from the chromosome and is secreted from the bacteria via the type IV pilin secretin. Therefore, this element, by spreading among the population, may promote the development of new epidemic clones of N. meningitidis that are capable of breaking the normal commensal relationship with humans and causing invasive disease.
C4b-binding protein binds to necrotic cells and DNA, limiting DNA release and inhibiting complement activation
Authors: Trouw Leendert A. , Nilsson Sara C. , Gonçalves Isabel , Landberg Göran , Blom Anna M.
Published: June 2005

After cell death, via apoptosis or necrosis, the uptake of dead cells by neighboring cells or phagocytes prevents the release of intracellular content. An array of molecules, including initiation molecules of the complement system, are involved in marking dead cells for uptake. After binding of these molecules, complement activation takes place, which when uncontrolled might result in a proinflammatory state. In the current study we demonstrate that complement inhibitor, C4b-binding protein (C4BP), binds strongly to necrotic cells, irrespective of the cell type used or the method of induction. After binding of the C4BP–protein S (PS) complex to necrotic cells via PS-phosphatidylserine and C4BP-DNA interactions, C4BP-PS inhibits complement activation on these cells. C4BP binds DNA via a patch of positively charged amino acids, mainly on the second complement control domain of the C4BP α-chain (affinity constant: 190 nM). Furthermore, C4BP limits DNA release from necrotic cells and inhibits DNA-mediated complement activation in solution. The C4BP–necrotic cell interaction also occurs in vivo as necrotic areas of arteriosclerotic plaques and of various cancers stain strongly positive for C4BP. This study describes a novel mechanism in which C4BP limits the inflammatory potential of necrotic cells.
IFN-γ production by alloantigen-reactive regulatory T cells is important for their regulatory function in vivo
Authors: Sawitzki Birgit , Kingsley Cherry I. , Oliveira Vanessa , Karim Mahzuz , Herber Manuela , Wood Kathryn J.
Published: June 2005

The significance of cytokine production by CD4+ regulatory T (T reg) cells after antigen exposure in vivo and its impact on their regulatory activity remains unclear. Pretreatment with donor alloantigen under the cover of anti-CD4 therapy generates alloantigen reactive T reg cells that can prevent rejection of donor-specific skin grafts that are mediated by naive CD45RBhighCD4+ T cells. To examine the kinetics and importance of cytokine gene transcription by such alloantigen-reactive T reg cells, pretreated mice were rechallenged with donor alloantigen in vivo. CD25+CD4+ T cells, but not CD25−CD4+ T cells, showed a fivefold increase in IFN-γ mRNA expression within 24 h of reencountering alloantigen in vivo. This expression kinetic was highly antigen-specific and was of functional significance. Neutralizing IFN-γ at the time of cotransfer of alloantigen reactive T reg cells, together with CD45RBhighCD4+ effector T cells into Rag−/− skin graft recipients, resulted in skin graft necrosis in all recipients; the generation and function of alloantigen-reactive T reg cells was impaired dramatically in IFN-γ–deficient mice. These data support a unique role for IFN-γ in the functional activity of alloantigen-reactive T reg cells during the development of operational tolerance to donor alloantigens in vivo.
Antiviral T cell responses
Authors: Posnett David N. , Engelhorn Manuel E. , Houghton Alan N.
Published: June 2005

Around 700 BCE, a new military formation called the phalanx was established in ancient Greece: a tight column of heavy infantry carrying long spears, or pikes, used in a single prong of attack. Later, in the battle of Marathon described by Herodotus, the Greeks learned the advantages of multipronged attacks, a strategy still used in modern warfare. Is the immune system similar in its approach to combating pathogens or tumors?
Fuglede’s conjecture fails in dimension 4
Authors: Matolcsi Máté
Published: June 2005

In this note we modify a recent example of Tao and give an example of a set

Ω
⊂

R

4

\Omega \subset \mathbb {R}^4

such that

L
2

(
Ω
)

L^2(\Omega )

admits an orthonormal basis of exponentials
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-brace StartFraction 1 Over StartAbsoluteValue normal upper Omega EndAbsoluteValue Superscript 1 slash 2 Baseline EndFraction e Superscript 2 pi i mathematical left-angle x comma xi mathematical right-angle Baseline right-brace Subscript xi element-of normal upper Lamda">

{

1

|

Ω

|

1

/

2

e

2
π
i
⟨
x
,
ξ
⟩

}

ξ
∈
Λ

\{\frac {1}{|\Omega |^{1/2}}e^{2\pi i \langle x, \xi \rangle }\}_{\xi \in \Lambda }

for some set

Λ
⊂

R

4

\Lambda \subset \mathbb {R}^4

, but which does not tile

R

4

\mathbb {R}^4

by translations. This shows that one direction of Fuglede’s conjecture fails already in dimension 4. Some common properties of translational tiles and spectral sets are also proved.
Line arrangements in ℍ³
Authors: Milley Peter
Published: June 2005

If

M
=

H

3

/

G

M=\mathbb {H}^3/G

is a hyperbolic manifold and

γ
⊂
M

\gamma \subset M

is a simple closed geodesic, then

γ
\gamma

lifts to a collection of lines in

H

3

\mathbb {H}^3

acted upon by

G
G

. In this paper we show that such a collection of lines cannot contain a particular type of subset (called a bad triple) unless

G
G

has orientation-reversing elements. This fact allows us to extend certain lower bounds on hyperbolic volume to the non-orientable case.
A characterization of the projective line
Authors: Requejo B. , Sancho Juan
Published: June 2005

Let

X
X

be a set (with at least three different points) and let

G
G

be a group of bijections of

X
X

. If the action of

G
G

on

X
X

satisfies three natural conditions, then

X
X

admits a canonical structure of a projective line over a commutative field, such that

G
G

is the group of all projective transformations of

X
X

.
Bounds on the number of holomorphic maps of compact Riemann surfaces
Authors: Tanabe Masaharu
Published: June 2005

We give bounds on the number of nonconstant holomorphic maps of compact Riemann surfaces of genera>1>1.
On isomorphisms of algebras of smooth functions
Authors: Mrčun Janez
Published: June 2005

We show that for any smooth Hausdorff manifolds

M
M

and

N
N

, which are not necessarily second-countable, paracompact or connected, any isomorphism from the algebra of smooth (real or complex) functions on

N
N

to the algebra of smooth functions on

M
M

is given by composition with a unique diffeomorphism from

M
M

to

N
N

. An analogous result holds true for isomorphisms of algebras of smooth functions with compact support.
Revisiting two theorems of Curto and Fialkow on moment matrices
Authors: Laurent Monique
Published: June 2005

We revisit two results of Curto and Fialkow on moment matrices. The first result asserts that every sequence

y
∈

R

Z

+
n

y\in \mathbb {R}^{\mathbb {Z}^n_+}

whose moment matrix

M
(
y
)

M(y)

is positive semidefinite and has finite rank

r
r

is the sequence of moments of an

r
r

-atomic nonnegative measure

μ
\mu

on

R

n

\mathbb {R}^n

. We give an alternative proof for this result, using algebraic tools (the Nullstellensatz) in place of the functional analytic tools used in the original proof of Curto and Fialkow. An easy observation is the existence of interpolation polynomials at the atoms of the measure

μ
\mu

having degree at most

t
t

if the principal submatrix

M
t

(
y
)

M_t(y)

of

M
(
y
)

M(y)

(indexed by all monomials of degree

≤
t

\le t

) has full rank

r
r

. This observation enables us to shortcut the proof of the following result. Consider a basic closed semialgebraic set
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper F equals StartSet x element-of double-struck upper R Superscript n Baseline bar h 1 left-parenthesis x right-parenthesis greater-than-or-equal-to 0 comma ellipsis comma h Subscript m Baseline left-parenthesis x right-parenthesis greater-than-or-equal-to 0 EndSet">

F
=
{
x
∈

R

n

∣

h
1

(
x
)
≥
0
,
…
,

h
m

(
x
)
≥
0
}

F=\{x\in \mathbb {R}^n\mid h_1(x)\ge 0, \ldots ,h_m(x)\ge 0\}

, where

h
j

∈

R

[

x
1

,
…
,

x
n

]

h_j\in \mathbb {R}[x_1,\ldots ,x_n]

and

d
:=

max

j
=
1

m

⁡
⌈
deg
⁡
(

h
j

)

/

2
⌉

d:=\operatorname {max}_{j=1}^m \lceil \operatorname {deg}(h_j)/2\rceil

. If

M
t

(
y
)

M_t(y)

is positive semidefinite and has a flat extension

M

t
+
d

(
y
)

M_{t+d}(y)

such that all localizing matrices

M

t

(

h
j

∗
y
)

M_{t}(h_j\ast y)

are positive semidefinite, then

y
y

has an atomic representing measure supported by

F
F

. We also review an application of this result to the problem of minimizing a polynomial over the set

F
F

.
Fixed points of nonexpansive mappings in spaces of continuous functions
Authors: Domínguez Benavides T. , Japón Pineda María
Published: June 2005

Let

K
K

be a compact metrizable space and let

C
(
K
)

C(K)

be the Banach space of all real continuous functions defined on

K
K

with the maximum norm. It is known that

C
(
K
)

C(K)

fails to have the weak fixed point property for nonexpansive mappings (w-FPP) when

K
K

contains a perfect set. However the space

C
(

ω

n

+
1
)

C(\omega ^{n}+1)

, where

n
∈

N

n\in \mathbb {N}

and

ω
\omega

is the first infinite ordinal number, enjoys the w-FPP, and so

C
(
K
)

C(K)

also satisfies this property if

K

(
ω
)

=
∅

K^{(\omega )}=\emptyset

. It is unknown if

C
(
K
)

C(K)

has the w-FPP when

K
K

is a scattered set such that

K

(
ω
)

≠
∅

K^{(\omega )}\not =\emptyset

. In this paper we prove that certain subspaces of

C
(
K
)

C(K)

, with

K

(
ω
)

≠
∅

K^{(\omega )}\not = \emptyset

, satisfy the w-FPP. To prove this result we introduce the notion of

ω
\omega

-almost weak orthogonality and we prove that an

ω
\omega

-almost weakly orthogonal closed subspace of

C
(
K
)

C(K)

enjoys the w-FPP. We show an example of an

ω
\omega

-almost weakly orthogonal subspace of

C
(

ω

ω

+
1
)

C(\omega ^{\omega }+1)

which is not contained in

C
(

ω

n

+
1
)

C(\omega ^{n}+1)

for any

n
∈

N

n\in \mathbb {N}

.