bluuebunny/crossref_metadata_2025 huggingface dataset:
A time correlation function theory describing static field enhanced third order optical effects at interfaces
Authors: Neipert Christine , Space Brian
Published: December 2006

Sum vibrational frequency spectroscopy, a second order optical process, is interface specific in the dipole approximation. At charged interfaces, there exists a static field, and as a direct consequence, the experimentally detected signal is a combination of enhanced second and static field induced third order contributions. There is significant evidence in the literature of the importance/relative magnitude of this third order contribution, but no previous molecularly detailed approach existed to separately calculate the second and third order contributions. Thus, for the first time, a molecularly detailed time correlation function theory is derived here that allows for the second and third order contributions to sum frequency vibrational spectra to be individually determined. Further, a practical, molecular dynamics based, implementation procedure for the derived correlation functions that describe the third order phenomenon is also presented. This approach includes a novel generalization of point atomic polarizability models to calculate the hyperpolarizability of a molecular system. The full system hyperpolarizability appears in the time correlation functions responsible for third order contributions in the presence of a static field.
Improve molecular beam epitaxy growth of HgCdTe on CdZnTe (211)B substrates using interfacial layers of HgTe∕CdTe superlattices
Authors: Chang Yong , Grein C. H. , Zhao J. , Sivanathan S. , Wang C. Z. , Aoki T. , Smith David J. , Wijewarnasuriya P. S. , Nathan V.
Published: December 2006

Hg Te ∕ Cd Te superlattices (SLs) have been grown on CdZnTe (211)B substrates as interfacial layers to improve the reproducibility and material properties of epitaxial HgCdTe. The interfacial SL layer is found by transmission electron microscopy to be capable of smoothing out the substrate’s surface roughness and to bend or block threading dislocations from propagating from the substrate into the functional HgCdTe epilayers. The best etch pit density values of 4×104cm−2 were achieved in long-wavelength infrared HgCdTe epilayers with such interfacial layers, while typical values were in the low 105cm−2 range. The recombination mechanisms in such layers were dominated by radiative and Auger intrinsic recombination mechanisms, whereas the contributions from the Shockley-Read-Hall mechanism become negligible, which demonstrated that the use of the SL interfacial layers was beneficial for HgCdTe growth using molecular beam epitaxy or MBE.
Changes in surface band bending, surface work function, and sheet resistance of undoped ZnO films due to (NH4)2Sx treatment
Authors: Lin Yow-Jon , Tsai Chia-Lung
Published: December 2006

In this study, the interaction of undoped ZnO films with (NH4)2Sx treatment have been investigated by x-ray photoelectron spectroscopy, photoluminescence, optical transmittance, and four-point probe. According to the experimental results, we find that the formation of Zn–S bonds and the reduction of oxygen vacancies (i.e., the S occupation of oxygen vacancies) near the ZnO surface might lead to an increase in the upward band bending, resulting in an increase in the sheet resistance and work function of ZnO.
Compact high current generator for x-ray radiography
Authors: Kharlov A. V. , Kovalchuk B. M. , Zorin V. B.
Published: December 2006

We report here a design of the portable high current generator, which can be used for a row of experiments and applications, including, but not limited to, X pinch, plasma focus, vacuum spark, etc. The X generator consists of the capacitor bank, multigap spark switch, load chamber, and built-in high voltage triggering generator. The capacitor bank consists of 12 General Atomics 35404 type capacitors (20nF, 25nH, 0.2Ω, 100kV). It stores ∼0.8kJ at 80kV charging voltage. Each three capacitors are commuted to a load by the multigap spark switch, which is able to commute by eight parallel channels. Switches operate in ambient air at atmospheric pressure. At 76kV charging voltage the generator provides ∼260kA with 120ns rise time and 5nH inductive load and ∼220kA with 145ns rise time and 10nH. Delay of output pulse relative to high voltage triggering pulse is ∼65ns with 5ns jitter. The dimensions of the generator are 1240×1240×225mm3 and the weight is ∼250kg, and only one high voltage power supply is required as additional equipment for the generator. The generator with a pumping system is placed on area about 0.5m2. Operation and handling are very simple, because no oil nor purified gases are required for the generator. The X generator has been successfully employed for experiments on the Ni X pinch load. X-ray pulse duration (full width at half maximum above 1keV) was about 5ns. Radiation yield Wr⩾500mJ was observed in the 1.2–1.5KeV range and Wr⩾20mJ in the 3–5keV energy range, which is comparable to results, obtained on the nanosecond accelerators. Clearly resolved images of 6μm wire indicate micron level size of hot spot. These results demonstrate possibility of this generator for application for x-ray backlighting.
Photodissociation dynamics of ClN3 at 193nm
Authors: Goncher Scott J. , Sveum Niels E. , Moore David T. , Bartlett Nate D. , Neumark Daniel M.
Published: December 2006

Photofragment translational spectroscopy was used to identify the primary and secondary reaction pathways in 193nm photodissociation of chlorine azide (ClN3) under collision-free conditions. Both the molecular elimination (NCl+N2) and the radical bond rupture channel (Cl+N3) were investigated and compared with earlier results at 248nm. The radical channel strongly dominates, just as at 248nm. At 193nm, the ClN3 (C̃A″1) state is excited, rather than the B̃A′1 state that is accessed at 248nm, resulting in different photofragment angular distributions. The chlorine translational energy distribution probing the dynamics of the radical bond rupture channel shows three distinct peaks, with the two fastest peaks occurring at the same translational energies as the two peaks seen at 248nm that were previously assigned to linear and “high energy” N3. Hence, nearly all the additional photon energy relative to 248nm appears as N3 internal excitation rather than as translational energy, resulting in considerably more spontaneous dissociation of N3 to N2+N.
Large-scale instabilities in a nonrotating turbulent convection
Authors: Elperin Tov , Golubev Ilia , Kleeorin Nathan , Rogachevskii Igor
Published: December 2006

A theoretical approach proposed by Elperin et al. [Phys. Rev. E 66, 066305 (2002)] is developed further to investigate formation of large-scale coherent structures in a nonrotating turbulent convection via excitation of a large-scale instability. In particular, the convective-wind instability that causes formation of large-scale coherent motions in the form of cells, can be excited in a shear-free regime. It was shown that the redistribution of the turbulent heat flux due to nonuniform large-scale motions plays a crucial role in the formation of the coherent large-scale structures in the turbulent convection. The modification of the turbulent heat flux results in strong reduction of the critical Rayleigh number (based on the eddy viscosity and turbulent temperature diffusivity) required for the excitation of the convective-wind instability. The large-scale convective-shear instability that results in the formation of the large-scale coherent motions in the form of rolls stretched along imposed large-scale velocity, can be excited in the sheared turbulent convection. This instability causes the generation of convective-shear waves propagating perpendicular to the convective rolls. The mean-field equations that describe the convective-wind and convective-shear instabilities, are solved numerically. We determine the key parameters that affect formation of the large-scale coherent structures in the turbulent convection. In particular, the degree of thermal anisotropy and the lateral background heat flux strongly modify the growth rates of the large-scale convective-shear instability, the frequencies of the generated convective-shear waves, and change the thresholds required for the excitation of the large-scale instabilities. This study elucidates the origin of the large-scale circulations and rolls observed in the atmospheric convective boundary layers.
Erosion/redeposition analysis of the ITER first wall with convective and non-convective plasma transport
Authors: Brooks J. N. , Allain J. P. , Rognlien T. D.
Published: December 2006

Sputtering erosion/redeposition is analyzed for IAEA [Report GA10FDR1-01-07-13 (2001)] plasma facing components, with scrape-off layer (SOL) plasma convective radial transport and nonconvective (diffusion-only) transport. The analysis uses the UEDGE code [T .D. Rognlien et al., J. Nucl. Mater. 196, 347 (1992)] and DEGAS code [D. P. Stotler et al., Contrib. Plasma Phys. 40, 221 (2000) ] to compute plasma SOL profiles and ion and neutral fluxes to the wall, TRIM-SP code [J. P. Biersack, W. Eckstein, J. Appl. Phys. A34, 73 (1984)] to compute sputter yields, and the REDEP/WBC code package [J. N. Brooks, Fusion Eng. Des. 60, 515 (2002)] for three-dimensional kinetic modeling of sputtered particle transport. Convective transport is modeled for the background plasma by a radially varying outward-flow component of the fluid velocity, and for the impurity ions by three models designed to bracket existing models/data. Results are reported here for the first wall with the reference beryllium coating and an alternative tungsten coating. The analysis shows: (1) sputtering erosion for convective flow is 20–40 times higher than for diffusion-only but acceptably low (∼0.3nm∕s) for beryllium, and very low (∼0.002nm∕s) for tungsten; (2) plasma contamination by wall sputtering, with convective flow, is of order 1% for beryllium and negligible for tungsten; (3) wall-to-divertor beryllium transport may be significant (∼10%–60% of the sputtered Be current); (4) tritium co-deposition in redeposited beryllium may be high (∼1–6gT∕400s pulse).
Deuteration-induced scission of C58 oligomers
Authors: Löffler Daniel , Jester Stefan-S. , Weis Patrick , Böttcher Artur , Kappes Manfred M.
Published: December 2006

The reaction of solid C58 films with atomic deuterium to yield deuterofullerenes, C58Dx, has been investigated by thermal desorption spectroscopy coupled with mass spectrometric detection, ultraviolet photoionization spectroscopy (21.2eV), and atomic force microscopy (AFM). The average composition of the deuterofullerenes created depends on deuterium dose, beam flux, and surface temperature. Low deuterium exposures at room temperature yield predominantly C58D6–8 cages. Saturation exposures at room temperature yield mass spectra peaked at C58D26. After saturation exposures at elevated surface temperatures (∼500K), the (subsequently) desorbed material reveals a comparatively narrow mass spectral distribution centered at C58D30. Deuteration is associated with cleavage of covalent cage-cage bonds in the starting C58 oligomer material, as evidenced by a considerable lowering of the sublimation energies of C58Dx compared to desorption of C58 desorbed from pure oligomer films. Correspondingly, AFM images reveal a D-induced, thermally activated transition from dendritic C58 oligomer islands into smooth-rimmed islands composed of deuterated cages. Deuterated films exhibit a significantly lower work function than bare C58 films. Progressing deuteration also gradually raises the surface ionization potential.
Time-resolved x-ray-excited optical luminescence characterization of one-dimensional Si–CdSe heterostructures
Authors: Rosenberg R. A. , Shenoy G. K. , Sun X. H. , Sham T. K.
Published: December 2006

The authors have monitored the optical luminescence from one-dimensional Si–CdSe nanoheterostructures as a function of x-ray energy at the Se L3 edge (∼1430eV). The wires consist of a diamond Si core encased in a wurtzite CdSe sheath. The time-resolved luminescence spectrum consists of a short-lifetime band centered at 637nm and a long-lived band at 530nm. By monitoring the intensities of these bands following excitation of a Se 2p3∕2 electron, the authors are able to show that the 637nm band is associated with the CdSe sheath while the 530nm band emanates from the Si core.
Nanostructured magnetic Fe–Ni–Co/Teflon multilayers for high-frequency applications in the gigahertz range
Authors: Greve Henry , Pochstein Christian , Takele Haile , Zaporojtchenko Vladimir , Faupel Franz , Gerber Andreas , Frommberger Michael , Quandt Eckhard
Published: December 2006

Thin multilayer films of sputtered polytetrafluoroethylene (Teflon) and Fe54Ni27Co19 with different layer thicknesses were prepared by vapor-phase tandem deposition. The films show ferromagnetic resonance frequencies from 3.0to4.7GHz and a high-frequency permeability in the range from 100 to 175, while having negligible losses up to 700MHz and a quality factor Q up to 12 at 1GHz. Thus these films could be promising candidates as high-frequency components used, for example, in mobile communication electronics.
Experimental evidence of B clustering in amorphous Si during ultrashallow junction formation
Authors: De Salvador D. , Bisognin G. , Di Marino M. , Napolitani E. , Carnera A. , Graoui H. , Foad M. A. , Boscherini F. , Mirabella S.
Published: December 2006

The authors have investigated ultrashallow p+∕n-junction formation by solid-phase epitaxy, by using x-ray absorption near-edge spectroscopy measurements on the B K edge. A clear fingerprint of B–B clusters is detected in the spectra. The authors demonstrate that B clustering occurs during the very early stages of annealing-induced Si recrystallization, i.e., when B is still in an amorphous matrix. After complete regrowth the local structure around B remains the same as in the amorphous phase, implying that B clusters are transferred to the crystalline structure.
Stress-dependent scaling behavior of dynamic hysteresis in bulk soft ferroelectric ceramic
Authors: Yimnirun Rattikorn , Wongsaenmai Supattra , Ananta Supon , Laosiritaworn Yongyut
Published: December 2006

The effects of frequency f, field amplitude E0, and mechanical stress σ on the hysteresis area ⟨A⟩ and their scaling relations were investigated on soft PZT bulk ceramics. The hysteresis area was found to depend on the frequency and field amplitude with a same set of exponents to the power-law scaling for both with and without stresses, indicating the universality. The inclusion of stresses into the power law was also obtained in the form of ⟨A−Aσ=0⟩∝f−0.25E0σ0.44, which indicates the difference of the energy dissipation between the under stress and stress-free conditions and reveals how the hysteresis area decays with increasing stresses.
Simple-layered high mobility field effect heterostructured two-dimensional electron device
Authors: Willett R. L. , Pfeiffer L. N. , West K. W.
Published: December 2006

The authors present a two-dimensional electron heterostructure field effect device of simplistic design and ease of fabrication that displays high mobility electron transport. This is accomplished using a high efficacy contacting scheme and simple metallic overlapping gate, obviating dopant layers. The resultant devices demonstrate adjustable electron densities and mobilities larger than 8×106cm2∕Vs at the highest densities of 2.4×1011∕cm2. This device type provides an experimental avenue for studying electron correlations and may answer demands for routine fabrication of practical high electron mobility transistors.
All-carbon nanotube-based junction with virtual source and drain of carbon nanotubes by in situ one-step process for practical integrated nanoelectronics
Authors: Lee Yun-Hi , Yoo Je-Min , Lee Jong-Hee , Ju B. K.
Published: December 2006

The authors propose a suspended in situ lateral grown all-carbon nanotube-based junction and report on the dc carrying behaviors of the carbon nanotube junction, especially with and after UV exposure. Also, the release of carriers of the junctions was studied by capacitance (C) measurements with ac excitation. The designed diluted magnetic impurity doped oxide film was adopted as catalyst in the fabrication of the junction. The suspended nanotube channel showed ambipolar function and almost the same low barrier height for the holes and electrons, which was determined by I-T(K) measurements. Subsequent measurements on the channel treated by low intensity UV resulted in a highly conductive channel with high current carrying behavior. Both their junction structure and analogy between dc I-V and capacitance can be applied to develop a practical and accessible system for forming reproducible integrated nanoelectronic junctions as well as to accelerate the realization of all low dimensional molecular devices.
Observation of magnetization waves in negative-index photonic metamaterials
Authors: Dolling G. , Wegener M. , Schädle A. , Burger S. , Linden S.
Published: December 2006

By measuring and calculating oblique-incidence transmittance spectra of a negative-index photonic metamaterial layer, the authors infer the in-plane dispersion relation of the magnetization wave. From the geometry and the dispersion shape, the authors conclude that coupling is predominantly via magnetic dipoles for wave propagation along the magnetic-dipole direction. These magnetization waves are the classical analog of magnon excitations of quantum-mechanical spins.
Optical imaging of thin films with molecular depth resolution
Authors: Köhler R. , Lazar P. , Riegler H.
Published: December 2006

Oxide layers of suitable thicknesses greatly enhance the reflectivity contrast from molecularly thin films deposited on silicon wafers. This interference enhancement can be used to visualize and to quantify film topologies with a thickness resolution well below 1nm.
Low temperature nitrogen incorporation method for enhanced electrical properties in hafnia based gate dielectrics
Authors: Ramani K. , Essary C. R. , Son S. Y. , Craciun V. , Singh R. K.
Published: December 2006

A low temperature method (∼400°C) for nitrogen incorporation in hafnia based dielectrics has been developed for future gate dielectric applications. Hf metal films were deposited on Si substrates in ammonia ambient and were subsequently oxidized under ultraviolet illumination. Using this method, an interfacial layer comprising Hf–Si–O–N bonding was formed at the hafnia-Si interface, which led to a substantial enhancement in the overall dielectric properties of the film. An equivalent oxide thickness of 11.5Å and leakage current densities lower than 10−4A∕cm2 at a gate bias of −1V were achieved by this approach.
Mixed protonic-electronic conduction and dielectric response in layered vanadyl phosphate nanocomposites
Authors: De Sukanta , Dey Arup , De S. K.
Published: December 2006

The layered vanadyl phosphate, VOPO4∙2H2O, is employed to prepare nanosized conducting polypyrrole by redox intercalation method. Transport and dielectric properties of various compositions have been investigated by impedance technique over a temperature range of 300–120K. Grain boundary conductivity is larger than the bulk conductivity. The conductivity reveals a discontinuity at about 212–235K. The conductivity is predominantly ionic at high temperature and electronic at low temperature. The dielectric spectra reveal a peak in the frequency range up to 2MHz for higher concentration of intercalated polypyrrole. The activation energy of conductivity relaxation is different from that of total conductivity derived from the impedance plot.
Effect of conductive LaNiO3 electrode on the structural and ferroelectric properties of Bi3.25La0.75Ti3O12 films
Authors: Jain M. , Kang B. S. , Jia Q. X.
Published: December 2006

Ferroelectric Bi3.25La0.75Ti3O12 (BLT) films were grown on Pt∕Ti∕SiO2∕Si (Pt∕Si), LaNiO3∕Pt∕Si, and LaNiO3∕Si substrates using chemical solution deposition technique. X-ray diffraction analysis shows that films grown on conductive LaNiO3 electrodes had higher degree of (117) orientation as compared to that grown directly on Pt∕Si substrate. High remanent polarization value (2Pr)∼43.14μC∕cm2 (Ec of 111kV∕cm) under an applied field of 396kV∕cm was obtained for BLT film on LaNiO3∕Pt∕Si as compared to a value of 26μC∕cm2 obtained for BLT film on Pt/Si directly. There was no degradation in the switchable polarization (Psw−Pns) after 1010 switching cycles.
Three-dimensional size determination of particles with photoelectron emission microscopy
Authors: Chelaru Liviu I. , Meyer zu Heringdorf Frank-J.
Published: December 2006

We show that the aspect ratio and the size of particles at surfaces can be estimated with photoelectron emission microscopy when both linear and nonlinear processes are utilized. As the width of the particles is known from regular photoemission microscopy, a complete determination of the particles’ dimensions becomes possible by two-photon photoemission microscopy. Here, the light diffraction pattern of the illuminating light around the particles is emphasized by the nonlinear dependence of the photoemission yield on the electric field components at the surface. This allows the quantitative measurement of the aspect ratio of the particles. The results are in agreement with theory and atomic force microscopy measurements.
Propagation of guided modes in curved nanoribbon waveguides
Authors: Ye Zhuo , Hu Xinhua , Li Ming , Ho Kai-Ming , Yang Peidong
Published: December 2006

The authors develop a plane-wave-based transfer matrix method in curvilinear coordinates to study the guided modes in curved nanoribbon waveguides. The problem of a curved structure is transformed into an equivalent one of a straight structure with spatially dependent tensors of dielectric constant and magnetic permeability. The authors investigate the coupling between the eigenmodes of the straight part and those of the curved part when the waveguide is bent. The authors show that curved sections can result in strong oscillations in the transmission spectrum similar to the recent experimental results of Lawet al. [Science 305, 1269 (2004)].
Ba
Ti
O
3
–
Sr
Ti
O
3
multilayer thin film electro-optic waveguide modulator
Authors: Hiltunen Jussi , Seneviratne Dilan , Sun Rong , Stolfi Michael , Tuller Harry L. , Lappalainen Jyrki , Lantto Vilho
Published: December 2006

Mach-Zehnder electro-optic waveguide modulators were fabricated based on BaTiO3 (BTO)-SrTiO3 (STO) multilayer thin film stacks grown on single crystal MgO substrates by pulsed laser deposition. X-ray diffraction measurements confirmed the formation of a BTO-STO superlattice with periodicity of 11unit cells. Strip-loaded waveguides were formed by patterning a SixNy film deposited onto the BTO-STO stack while Al electrodes of 3mm length and 13μm separation were fabricated in the vicinity of the active waveguide arm of the Mach-Zehnder modulator. An effective electro-optic coefficient of 73pm∕V at 1550nm wavelength was determined for the deposited BTO-STO superlattice by measuring the output intensity as a function of applied electric field.
ac conductivity relaxation processes in CaCu3Ti4O12 ceramics: Grain boundary and domain boundary effects
Authors: Li Wei , Schwartz Robert W.
Published: December 2006

The ac conductivity of CaCu3Ti4O12 ceramics associated with electrical charge carrier motion (ions or vacancies) was investigated as a function of frequency at different temperatures. The long range migration of charge carriers within the ceramic is restricted by two kinds of insulating barriers, namely, grain boundaries and domain boundaries. The potential barriers associated with these boundaries lead to two anomalies in conductivity response and three frequency-dependent contributions to conductivity: long range diffusion of carriers, carrier migration localized within grains, and carrier migration localized within domains.
One-sample measurement in laser nephelometric immunoassay using magnetic nanoparticles
Authors: Yang S. Y. , Wu R. M. , Jian Z. F. , Horng H. E. , Hong Chin-Yih , Yang H. C.
Published: December 2006

In contrast to the type of two-sample measurement used in conventional nephelometric immunoassay, a methodology to achieve a one-sample nephelometric immunoassay is developed in this work. Magnetic nanoparticles instead of latex particles are used as scattering centers. The experimental results show that the sensitivity of assaying avidin or c-reactive protein increased about three times under the action of the magnetic field in nephelometric immunoassay using magnetic nanoparticles.
Thermal stability of lanthanum scandate dielectrics on Si(100)
Authors: Sivasubramani P. , Lee T. H. , Kim M. J. , Kim J. , Gnade B. E. , Wallace R. M. , Edge L. F. , Schlom D. G. , Stevie F. A. , Garcia R. , Zhu Z. , Griffis D. P.
Published: December 2006

The authors have examined the thermal stability of amorphous, molecular beam deposited lanthanum scandate dielectric thin films on top of Si (100) after a 1000°C, 10s rapid thermal anneal. After the anneal, crystallization of LaScO3 is observed. Excellent suppression of lanthanum and scandium diffusion into the substrate silicon is indicated by the back-side secondary ion mass spectrometry (SIMS) analyses. In contrast, front-side SIMS and high-resolution electron energy loss analyses of the amorphous Si∕LaScO3∕Si (100) stack indicated the outdiffusion of lanthanum and scandium into the silicon capping layer during the anneal.
Surface-acoustic-wave-driven luminescence from a lateral p-n junction
Authors: Gell J. R. , Atkinson P. , Bremner S. P. , Sfigakis F. , Kataoka M. , Anderson D. , Jones G. A. C. , Barnes C. H. W. , Ritchie D. A. , Ward M. B. , Norman C. E. , Shields A. J.
Published: December 2006

The authors report surface-acoustic-wave-driven luminescence from a lateral p-n junction formed by molecular beam epitaxy regrowth of a modulation doped GaAs∕AlGaAs quantum well on a patterned GaAs substrate. Surface-acoustic-wave-driven transport is demonstrated by peaks in the electrical current and light emission from the GaAs quantum well at the resonant frequency of the transducer. This type of junction offers high carrier mobility and scalability. The demonstration of surface-acoustic-wave luminescence is a significant step towards single-photon applications in quantum computation and quantum cryptography.
Influence of sputtering pressure on polarity distribution of aluminum nitride thin films
Authors: Kamohara Toshihiro , Akiyama Morito , Ueno Naohiro , Sakamoto Michiru , Kano Kazuhiko , Teshigahara Akihiko , Kawahara Nobuaki , Kuwano Noriyuki
Published: December 2006

The authors have investigated the influence of sputtering pressure on the polarity distribution of aluminum nitride (AlN) films. They have found that sputtering pressure strongly influences the polarity distribution of AlN films prepared on molybdenum electrodes. The polarity distribution of the AlN films was observed by piezoresponse force microscopy. The polarity orientation is decided with respect to each fine grain constituting the AlN films, and polarity conversion from Al polarity to N polarity is observed with increasing sputtering pressure. The piezoelectric response of the films changes from +3.7to−4.4pC∕N with increasing sputtering pressure from 0.36to4.0Pa.
Thermodynamic and Kinetic Aspects on the Biosorption of Cadmium by Low Cost Materials: A Review
Authors: Lodeiro Pablo , Herrero Roberto , Sastre de Vicente Manuel E.
Published: December 2006

Environmental Context. The toxicity of cadmium in waters can be decreased by using a wide variety of low-cost biomaterials. A number of such investigations are reviewed here and the models used to describe the process of biosorption discussed. Fundamental investigations that probe the thermodynamics and kinetics of the biosorption process are essential for a strong understanding of all biosorption processes. Areas that still need addressing are highlighted, in particular with regard to cadmium biosorption, some models for which are ready to be tested in pilot plants.

Abstract. Cadmium is internationally recognized as an important pollutant in the environment, and different methods for its removal from wastewaters (chemical precipitation being the most commonly used) have been reported in the literature. Those methods are in most cases oriented to situations with high concentrations of the pollutant. Thus, alternative removal and recovery methods are being considered for removing very low concentrations of cadmium. These methods are all based on biosorption, the passive adsorption and sequestration of metals by several natural materials of biological origin. In this review we have considered the biosorption of cadmium onto biomaterials from a physicochemical, thermodynamic, and kinetic perspective. The thermodynamic perspective is based on the characterization of the interactions of the binding sites of the biosorbents with cadmium species in aqueous solution. Traditionally, this approach has been quantified using different kinds of isotherms. In addition, the description is completed by taking into account electrostatic effects, and the influence of pH and ionic strength, which are associated with the negative charge developed, in most cases, by the biomaterial. The other point of view in this review is the kinetic one, which is necessary for a full physicochemical description of the sorbate–biosorbent system. Consequently, an updated description of the various approaches commonly employed in kinetic studies in biosorption has been carried out.
Corrigendum to: Valence Bond Formulations of Mechanisms for the Formation and Decomposition of N2O5
Authors: Harcourt Richard D. , Klapötke Thomas M.
Published: December 2006

Environmental Context. N2O5 is an important nitrogen reservoir in polar stratospheric clouds found in Antarctica and involved with the ozone hole. Here we provide valence bond representations for the gas-phase formation and decomposition of this molecule.
Abstract. Qualitative valence bond considerations are used to suggest how electronic reorganization could proceed for (a) the formation of N2O5 via the reactions NO2 + O3 → NO3 + O2, and NO2 + NO3 → N2O5, and (b) the thermal decomposition of N2O5 via the following sets of reactions: (i) N2O5 → NO2 + NO3, 2NO3 → O2NOONO2 → 2NO2 + O2; (ii) NO2 + NO3 → ONOONO2 → NO + O2 + NO2, NO + NO3 → 2NO2. Increased-valence structures, which possess one-electron bonds and fractional electron-pair bonds as well as 'normal' electron-pair bonds, are used to represent the electronic structures of the molecules.
Do Exudates Affect Cadmium Speciation and Bioavailability to the Rhizobacterium Sinorhizobium meliloti?
Authors: Dedieu Karine , Iuranova Tatiana , Slaveykova Vera I.
Published: December 2006

Environmental Context. Heavy metals such as cadmium can affect soil microbes and consequently perturb important nutrient cycles resulting in deterioration of the soil fertility. Conversely, soil bacteria might influence cadmium cycling, bioavailability and ecotoxicity by producing exudates such as proteins, polysaccharides and siderophores. These substances are shown to form complexes with cadmium, decreasing the free concentration of cadmium in soil solutions.
Abstract. To better understand the role of exudates in cadmium (Cd) speciation and biouptake by the bacterium Sinorhizobium meliloti, the content of various exudate components, including siderophores, proteins and polysaccharides, was quantified in the absence and presence of 10 μM Cd at pH 5.0 and pH 7.0. The obtained results demonstrate that the release of exudates by S. meliloti is a constitutive process rather than one induced by the presence of Cd. Nonetheless, exudates complex Cd and significantly reduce its free ion concentration. Cd bioavailability to S. meliloti was characterized by the amount of adsorbed and intracellular Cd. Adsorbed Cd at pH 5.0 was higher than that at pH 7.0, which is consistent with the higher free Cd concentration and lower amounts of exudates released at that pH. The observed reduction in intracellular Cd at pH 5.0 compared with pH 7.0 was attributed to the prevailing competition between protons and Cd ions for transport sites.
Morphological analysis and a resolution of the Ryparosa javanica species complex (Achariaceae) from Malesian and Australian tropical rainforests
Authors: Webber Bruce L. , Woodrow Ian E.
Published: December 2006

A study of morphological variation in Ryparosa javanica (Blume) Kurz ex Koord. & Valeton sensu lato (Achariaceae; Flacourtiaceae pro parte) was undertaken after distinct differences were observed between Australian and Bornean populations. The confusing taxonomic history of R. javanica is first summarised. Phenetic techniques of agglomerative classification and ordination were used to analyse herbarium and field-collected specimens. Distinct groupings based on vegetative characters were supported by reproductive traits, plant architecture, ant–plant associations and geographical discontinuities. This work demonstrates that the current circumscription of R. javanica is a complex of at least nine species: R. javanica sensu stricto now confined to Sumatra, Java and Bali; three species that warrant reinstatement: R. amplifolia (K.Sch.) Mildbr. from New Guinea, R. kurzii King from the Andaman and Nicobar Islands and R. wrayi King from southern Myanmar and Thailand, the Malay Peninsula and northern Sumatra; and five new species described as R. maculata B.L.Webber from eastern New Guinea, R. anterides B.L.Webber from eastern Borneo, R. milleri B.L.Webber from New Guinea, R. maycockii B.L.Webber from western Borneo and R. kurrangii B.L.Webber from northern Australia. A key to the species and commonly mistaken taxa is provided.
Why molecules move along a temperature gradient
Authors: Duhr Stefan , Braun Dieter
Published: December 2006

Molecules drift along temperature gradients, an effect called thermophoresis, the Soret effect, or thermodiffusion. In liquids, its theoretical foundation is the subject of a long-standing debate. By using an all-optical microfluidic fluorescence method, we present experimental results for DNA and polystyrene beads over a large range of particle sizes, salt concentrations, and temperatures. The data support a unifying theory based on solvation entropy. Stated in simple terms, the Soret coefficient is given by the negative solvation entropy, divided by
kT
. The theory predicts the thermodiffusion of polystyrene beads and DNA without any free parameters. We assume a local thermodynamic equilibrium of the solvent molecules around the molecule. This assumption is fulfilled for moderate temperature gradients below a fluctuation criterion. For both DNA and polystyrene beads, thermophoretic motion changes sign at lower temperatures. This thermophilicity toward lower temperatures is attributed to an increasing positive entropy of hydration, whereas the generally dominating thermophobicity is explained by the negative entropy of ionic shielding. The understanding of thermodiffusion sets the stage for detailed probing of solvation properties of colloids and biomolecules. For example, we successfully determine the effective charge of DNA and beads over a size range that is not accessible with electrophoresis.
World Bank & Heavenly Bank in Poverty & Prosperity: The Case of Tanzanian Faith Gospel1
Authors: Hasu Päivi
Published: December 2006

This article discusses the articulation of religious rhetoric with neoliberal principles of the market economy in Tanzania, looking specifically at Pentecostal-charismatic Christianity. Religion is interpreted here as a reflection of and model for a lived reality. On the one hand, a lived reality generates and shapes religious beliefs and ideas. On the other, religious beliefs and ideas inform the ways that economic circumstances are perceived, interpreted and acted upon in specific social and historical contexts. This is a discussion of charismatic Christian perceptions and of the perceived spiritual and economic changes in Tanzania ahead of the general election of 2005. These Biblical allegories, as well as the gospel of prosperity, are brought together through an account of the activities of one particular charismatic ministry. The rhetoric and logic of prosperity through giving are discussed within the anthropological notion of gift exchange as well as with some born-again understandings of the significance of offerings to God as a means to prosperity and accumulation.

This paper draws upon research that was conducted in Tanzania in 2003 and 2004 and funded by the Nordic Africa Institute. An earlier version was presented in a panel organized by Paul Gifford at the AEGIS conference in London 2005.
Materiality and ideology in children's perceptions of past historical writing
Authors: Hoodless Pat
Published: December 2006

This article summarizes a small‐scale investigation into 10‐ and 11‐year‐old children's perceptions of how the attitudes and values of different times in the past are reflected in historical writing for children. The research involved observation, reading and discussion of historical stories written at different times in the past about a particular period and character in the distant past, familiar to the children from their history lessons. The study investigated how children interacted with these texts in order to derive meaning from them. This article analyses the strategies children used and how they began to unpack the complex, multiple layers of meaning in ‘history stories’ by first examining the material properties of their texts. It considers how these material properties influenced the children's understanding of the texts' contents. It also seeks to discover whether young children are capable of comprehending the broader meanings of texts, beyond a literal reading of them, and how they explore texts critically in terms of their ideology. Findings suggest that able readers between the ages of 10 and 11 are indeed able to understand how ideologies are transmitted in such texts written for children, how these ideologies are conveyed to the child reader, and how they differ from the values and attitudes of the present.
The impact of climatic variation on the opportunity for sexual selection
Authors: Twiss Sean D , Thomas Christopher , Poland Veronica , Graves Jeff A , Pomeroy Patrick
Published: December 2006

Many studies have demonstrated influences of climatic variation on a variety of ecological processes, however, its impact on the potent evolutionary force of sexual selection has largely been ignored. The intensity of sexual selection is a fundamental parameter in animal populations, which depends upon the degree of polygamy and will probably be influenced by the impact of local climatic variation upon ‘environmental potential for polygamy’. Here, we provide evidence of a direct effect of local climatic variation on the intensity of sexual selection, by showing a clear correlation between local weather conditions and inter-annual changes in the degree of polygamy in a long-term study of colonially breeding grey seals (Halichoerus grypus). Our results show that changes in local weather conditions alter the annual proportion of males contributing to the effective population size (Ne) by up to 61%. Consequently, over the ‘lifetime’ of a cohort, a broader range of individuals will contribute genetically to the next generation if local weather conditions are variable. In the context of predicted future changes in climatic variation, these findings have broad implications for population genetics of socially structured animal systems through the major influence that the degree of polygamy has uponNe.
Continent-wide variation in feather colour of a migratory songbird in relation to body condition and moulting locality
Authors: Ryan Norris D , Marra Peter P , Kurt Kyser T , Ratcliffe Laurene M , Montgomerie Robert
Published: December 2006

Understanding the causes of variation in feather colour in free-living migratory birds has been challenging owing to our inability to track individuals during the moulting period when colours are acquired. Using stable-hydrogen isotopes to estimate moulting locality, we show that the carotenoid-based yellow–orange colour of American redstart (Setophaga ruticilla) tail feathers sampled on the wintering grounds in Central America and the Caribbean is related to the location where feathers were grown the previous season across North America. Males that moulted at southerly latitudes were more likely to grow yellowish feathers compared with males that moulted more orange–red feathers further north. Independent samples obtained on both the breeding and the wintering grounds showed that red chroma—an index of carotenoid content—was not related to the mean daily feather growth rate, suggesting that condition during moult did not influence feather colour. Thus, our results support the hypothesis that feather colour is influenced by ecological conditions at the locations where the birds moulted. We suggest that these colour signals may be influenced by geographical variation in diet related to the availability of carotenoids.
A model for the spread and control of pandemic influenza in an isolated geographical region
Authors: Roberts M.G , Baker M , Jennings L.C , Sertsou G , Wilson N
Published: December 2006

In the event of an influenza pandemic, the most probable way in which the virus would be introduced to an isolated geographical area is by an infected traveller. We use a mathematical model, structured on the location at which infection occurs and based on published parameters for influenza, to describe an epidemic in a community of one million people. The model is then modified to reflect a variety of control strategies based on social distancing measures, targeted antiviral treatment and antiviral prophylaxis and home quarantine, and the effectiveness of the strategies is compared. The results suggest that the only single strategy that would be successful in preventing an epidemic (with

0
=2.0) is targeted antiviral treatment and prophylaxis, and that closing schools combined with either closing work places or home quarantine would only prevent such an epidemic if these strategies were combined with a modest level of antiviral coverage.
Disease induced dynamics in host–parasitoid systems: chaos and coexistence
Authors: Preedy Katharine F , Schofield Pietà G , Chaplain Mark A.J , Hubbard Stephen F
Published: December 2006

All animals and plants are, to some extent, susceptible to disease caused by varying combinations of parasites, viruses and bacteria. In this paper, we present a mathematical model of interactions between a host, two parasitoids and a pathogen which shows that the presence of an infection can preserve and promote diversity in such multi-species systems. Initially, we use a system of ordinary differential equations to investigate interactions between two species of parasitoids, a host and a host infection. We show that the presence of all four species is necessary for the system as a whole to persist, and that in particular, the presence of the pathogen is necessary for the coexistence of the two parasitoid species. The inclusion of infection induces a wide range of dynamics, including chaos, and these dynamics are robust for a wide range of parameter values. We then extend the model to include spatial effects by introducing random motility (diffusion) of all three species and examine the subsequent spatio-temporal dynamics, including travelling waves and other more complicated heterogeneous behaviour. The computational simulation results of the model suggest that infection in the hosts can blunt the effects of competition between parasitoids, allowing the weaker competitor to survive. Regardless of the nature of the stability of the coexistent steady state of the system, there is an initial period of transient dynamics, the length of which can be extended by an appropriate choice of initial conditions. The existence of these transient dynamics suggests that systems subject to regular restoration to a starting state, such as agro-ecosystems, may be kept in a continual state of dynamic transience, and this has implications for the use of natural enemies to control insect pests, the preservation of biodiversity in farmland habitats and the more general dynamics of disease processes.
Effects of age and feeding history on structure-based UV ornaments of a jumping spider (Araneae: Salticidae)
Authors: Lim Matthew L.M , Li Daiqin
Published: December 2006

Recent studies have shown for birds that females sometimes choose mates on the basis of condition-dependent variation in ultraviolet (UV, less than 400 nm) ornamentation, but there have been few comparable studies on invertebrates. Yet many invertebrates have UV structural coloration. Here, we investigateCosmophasis umbratica, a jumping spider (Araneae: Salticidae) that has sexually dimorphic UV-iridescent ornamentation, and we provide evidence that male UV coloration is condition dependent in this species. Spectral-reflection patterns change with male age and prior feeding history. The position of the UV band (i.e. UV hue) of the carapaces of younger (field-collected as subadults and matured as adults in laboratory) males shifted, relative to older (field-collected as adults) males, significantly towards longer wavelengths. Food deprivation significantly decreased the spectral intensity of the abdomen, but not the carapace. Questions concerning the mechanisms by which UV ornaments change are highlighted, as are hypotheses concerning the role of condition-dependent UV variation in male–male competition and as a criterion used by females when making mate-choice decisions.
Does migration of hybrids contribute to post-zygotic isolation in flycatchers?
Authors: Veen Thor , Svedin Nina , Forsman Jukka T , Hjernquist Mårten B , Qvarnström Anna , Hjernquist Katherine A. Thuman , Träff Johan , Klaassen Marcel
Published: December 2006

In the face of hybridization, species integrity can only be maintained through post-zygotic isolating barriers (PIBs). PIBs need not only be intrinsic (i.e. hybrid inviability and sterility caused by developmental incompatibilities), but also can be extrinsic due to the hybrid's intermediate phenotype falling between the parental niches. For example, in migratory species, hybrid fitness might be reduced as a result of intermediate migration pathways and reaching suboptimal wintering grounds. Here, we test this idea by comparing the juvenile to adult survival probabilities as well as the wintering grounds of pied flycatchers (Ficedula hypoleuca), collared flycatchers (Ficedula albicollis) and their hybrids using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in feathers developed at the wintering site. Our result supports earlier observations of largely segregated wintering grounds of the two parental species. The isotope signature of hybrids clustered with that of pied flycatchers. We argue that this pattern can explain the high annual survival of hybrid flycatchers. Hence, dominant expression of the traits of one of the parental species in hybrids may substantially reduce the ecological costs of hybridization.
A pyritized polychaete from the Devonian of Ontario
Authors: Farrell Úna C , Briggs Derek E.G
Published: December 2006

A polychaete from the Middle Devonian Arkona Shale at Hungry Hollow, Arkona, Ontario is preserved in three dimensions in pyrite. The prostomium bears a single median antenna, a pair of lateral antennae and a pair of ventral palps. It is assumed to be fused to a reduced peristomium. The anteriormost three pairs of trunk appendages are modified as tentacular cirri, the third long and biramous. The remainder of the finely annulated trunk bears at least 21 similar biramous parapodia, some of which preserve evidence of chaetae. The postsegmental pygidium is very small and may bear up to two pairs of cirri. The polychaete,Arkonips topororum, falls within the Palpata, Aciculata, among the crown group Phyllodocida. Its remarkable preservation highlights the potential of the Arkona Shale to yield other examples of soft-tissue preservation.