bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization and application of multiple genetic markers forPlasmodium malariae
Authors: BRUCE M. C. , MACHESO A. , GALINSKI M. R. , BARNWELL J. W.
Published: December 2006

Plasmodium malariae, a protozoan parasite that causes malaria in humans, has a global distribution in tropical and subtropical regions and is commonly found in sympatry with otherPlasmodiumspecies of humans. Little is known about the genetics or population structure ofP. malariae. In the present study, we describe polymorphic genetic markers forP. malariaeand present the first molecular epidemiological data for this parasite. Six microsatellite or minisatellite markers were validated using 76P. malariaesamples from a diverse geographical range. The repeat unit length varied from 2 to17 bp, and up to 10 different alleles per locus were detected. Multiple genotypes ofP. malariaewere detected in 33 of 70 samples from humans with naturally acquired infection. Heterozygosity was calculated to be between 0·236 and 0·811. Allelic diversity was reduced for samples from South America and, at some loci, in samples from Thailand compared with those from Malawi. The number of unique multilocus genotypes defined using the 6 markers was significantly greater in Malawi than in Thailand, even when data from single genotype infections were used. There was a significant reduction in the multiplicity of infection in symptomatic infections compared with asymptomatic ones, suggesting that clinical episodes are usually caused by the expansion of a single genotype.
Can the host immune system promote multiple invasions of erythrocytesin vivo? Differential effects of medication and host sex in a wild malaria-like model
Authors: LA PUENTE J. MARTÍNEZ-DE , MERINO S. , TOMÁS G. , MORENO J. , MORALES J. , LOBATO E. , GARCÍA-FRAILE S.
Published: December 2006

Multiple invasions (MIs) or infections, i.e. those by more than 1 parasite in the same erythrocyte, could be the result of parasite density or, alternatively, to parasite-related factors or host-related factors. According to the last possibility, to our knowledge, only 3 laboratory studies of malaria have found an increase in the occurrence of MIs when antibodies to parasite antigens were present. Therefore, we tested the possibility that MIs were influenced by the host immune status, using as model the malaria-like parasiteHaemoproteusinfecting blue tits (Cyanistes caeruleus). Avian hosts infected withHaemoproteuswere medicated with primaquine or injected with saline solution and the density of infection and the presence of MIs counted. Medication treatment reduced significantly the density of infection byHaemoproteusin females but not in males. For females, the presence of MIs was positively associated with both the density of infection and the immunoglobulin levels on each capture, but no association was found between the treatment and the presence of MIs. For males, the density of infection but not the immunoglobulin levels was positively associated with the presence of MIs. In addition, medicated males supported more MIs than controls. Our results represent the first line of evidence in the wild for a possible role of the host immune system promoting MIs.
Qualitative futures
Authors: PRICE C. J. , TRAVÉ-MASSUYÈS L. , MILNE R. , IRONI L. , FORBUS K. , BREDEWEG B. , LEE M. H. , STRUSS P. , SNOOKE N. , LUCAS P. , CAVAZZA M. , COGHILL G. M.
Published: December 2006

This paper reviews the state of the art in model-based systems and qualitative reasoning, and considers where the field will be in 20 years time. It highlights six areas where developments in model-based systems in general, and in qualitative reasoning in particular, have the potential to provide significant computer-based help. The paper also examines where further technological developments might be needed in order to achieve these qualitative futures.
Crossing the agent technology chasm: Lessons, experiences and challenges in commercial applications of agents
Authors: MUNROE STEVE , MILLER TIM , BELECHEANU ROXANA A. , PĚCHOUČEK MICHAL , MCBURNEY PETER , LUCK MICHAEL
Published: December 2006

Agent software technologies are currently still in an early stage of market development, where, arguably, the majority of users adopting the technology are visionaries who have recognized the long-term potential of agent systems. Some current adopters also see short-term net commercial benefits from the technology, and more potential users will need to perceive such benefits if agent technologies are to become widely used. One way to assist potential adopters to assess the costs and benefits of agent technologies is through the sharing of actual deployment histories of these technologies. Working in collaboration with several companies and organizations in Europe and North America, we have studied deployed applications of agent technologies, and we present these case studies in detail in this paper. We also review the lessons learnt, and the key issues arising from the deployments, to guide decision-making in research, in development and in implementation of agent software technologies.
Introduction
Authors: Heltoft Lars , Rosenkvist Henrik
Published: December 2006

This special issue of the Nordic Journal of Linguistics is devoted to grammaticalization. In our call for papers, we emphasized that the term should be understood in a broad sense, inviting empirically as well as theoretically based papers. Almost all aspects of language may be studied from a grammaticalization perspective, and the concept is generally also understood as including diachronic as well as synchronic linguistic studies. The three selected papers reflect some of the richness of the field of grammaticalization.
From discourse pattern to epistemic marker: Estonian (ei) tea ‘don't know’
Authors: Keevallik Leelo
Published: December 2006

In contemporary informal Estonian, the negative verb form ei tea ‘don't know’ has become a routinized part of generic questions, in which the agent is left unexpressed. This pattern is in accordance with the general impersonal and reference-avoiding style of conversing in Estonia. The study outlines a continuum of synchronic usages from the original expressions sa ei tea ‘you don't know’ and ma ei tea ‘I don't know’ to the epistemic usages of (ei) tea, which are specifically tied to the speech act of questioning. The data is interactional and the analysis relies on the interpretation of (ei) tea-questions by the participants themselves, following the methodology of conversation analysis. It is demonstrated that the development of (ei) tea displays phonological and semantic erosion, pragmatic strengthening, subjectification, and decategorialization. Thus, grammaticalization theory is here combined with interactional linguistics in order to display the emergence of a grammatical structure from a discourse pattern.
From Pages to Clicks – the Questionnaire
Authors: Edwards Janice
Published: December 2006

Janice Edwards, Librarian at Maclay Murray & Spens, and Chair of the LIM Editorial Board, looks at the responses to the Pages to Clicks questionnaire distributed to members via Lis-Law in the Summer, and its implications for the future provision of legal information.
Leadership in KM and the Role of the CKO
Authors: Webb Jela
Published: December 2006

Paper given by Jela Webb at the 37th BIALL Annual Study Conference in Brighton, June 2006, discussing the meaning of the concept of leadership and outlining the key skills required of a chief knowledge officer.
Responding to Change in the Workplace by Becoming more Business Focussed
Authors: Jannetta Victoria
Published: December 2006

Paper given by Victoria Jannetta at the 37th BIALL Annual Study Conference, Brighton, June 2006, discussing the drivers for change, how to respond to them and how to help staff to adapt to change.
Human Rights and the UK Constitution: Can Parliament Legislate “Irrespective of the Human Rights Act”?
Authors: Smith Roger
Published: December 2006

This article by Roger Smith, Director of Justice, takes its text from the keynote address to the BIALL Joint Study Institute, “Righting the world: freedoms and obligations in a regulated society”, given at St Anne's College, Oxford on 11 August 2006.
The International Bill of Rights and the European Convention on Human Rights
Authors: Ghandi Sandy
Published: December 2006

Paper presented by Sandy Ghandi at the Joint Study Institute held at St Anne's College, Oxford, August 2006.
The New Supreme Court and other Changes in the Justice System
Authors: Walker Robert
Published: December 2006

Paper presented by Robert Walker to the Joint Study Institute, Oxford, August 2006, reviewing the process of constitutional change which started in 2003 and ended with the Constitutional Reform Act 2005.
Ireland – the Name of the State
Authors: Furlong John
Published: December 2006

This article by John Furlong attempts to provide a context and a background for the various names ascribed to the jurisdictional entity of Ireland.
Age Discrimination – the New Regime
Authors: Adamson Louise
Published: December 2006

Louise Adamson, a Professional Support Lawyer in the Employment Team at Maclay Murray & Spens LLP, explores new regulations which tackle discrimination on the grounds of age, highlighting the main provisions and potential legal challenges to the regulations themselves.
Viscoelastic evolution of lunar multiring basins
Authors: Mohit P. Surdas , Phillips Roger J.
Published: December 2006

We investigate the evolution of multiring basins on the Moon. The orbital geophysical and geochemical data collected by Lunar Prospector allow three distinct groups of basins to be identified. Group 1 basins show well‐preserved topography, a bull's‐eye gravity signature, and little mare basalt fill. Group 2 basins contain large amounts of mare basalt and show mare‐dominated gravity and topography signatures. Group 3 basins are characterized by low‐amplitude topographic relief and weak gravity anomalies. While the crustal structures of group 1 and 2 basins appear to date from the collapse of the transient cavity, group 3 basins are highly degraded and show very little crustal thinning. Using a viscoelastic model, we explore the evolution of the lunar multiring basins, with the goal of explaining the degraded condition of group 3 basins. Our results show that while viscous relaxation is a plausible explanation for the state of group 3 farside basins, requiring heat flux > 25–40 mW m−2, the thin nearside crust renders subsolidus ductile flow in the crust unlikely. The existence of many degraded basins on the nearside points to a weakened, and possibly partially molten, lower crust. That South Pole–Aitken appears not to have relaxed suggests that similar conditions did not exist there and that the nearside was hotter than the farside early on. This is likely a consequence of the nearside‐farside crustal thickness dichotomy, which would have caused the farside to reach full crystallization first, leaving the nearside with the remaining liquid and an excess of heat‐producing elements.
Experimental evidence of lateral flow in unsaturated homogeneous isotropic sloping soil due to rainfall
Authors: Sinai G. , Dirksen C.
Published: December 2006

This paper describes laboratory experimental evidence for lateral flow in the top layer of unsaturated sloping soil due to rainfall. Water was applied uniformly on horizontal and V‐shaped surfaces of fine sand, at rates about 100 times smaller than the saturated hydraulic conductivity. Flow regimes near the surface and in the soil bulk were studied by using dyes. Streamlines and streak lines and wetting fronts were visually studied and photographed through a vertical glass wall. Near wetting fronts the flow direction was always perpendicular to the fronts owing to dominant matrix potential gradients. Thus, during early wetting of dry sloping sand, the flow direction is directed upslope. Far above a wetting front the flow was vertical due to the dominance of gravity. Downslope flow was observed during decreasing rainfall and dry periods. The lateral movement was largest near the soil surface and decayed with soil depth. Unstable downslope lateral flow close to the soil surface was attributed to non‐Darcian flow due to variable temporal and spatial raindrop distributions. The experiments verify the theory that predicts unsaturated downslope lateral flow in sloping soil due to rainfall dynamics only, without apparent soil texture difference or anisotropy. This phenomenon could have significant implications for hillside hydrology, desert agriculture, irrigation management, etc., as well as for the basic mechanisms of surface runoff and erosion.
First archaeomagnetic secular variation curve for the Iberian Peninsula: Comparison with other data from western Europe and with global geomagnetic field models
Authors: Gómez‐Paccard M. , Chauvin A. , Lanos P. , McIntosh G. , Osete M. L. , Catanzariti G. , Ruiz‐Martínez V. C. , Núñez J. I.
Published: December 2006

A first secular variation (SV) curve for the Iberian Peninsula was computed by hierarchical Bayesian method using a total of 134 archaeomagnetic directions with ages ranging from −775 to 1959 A.D. A general agreement is observed between the Iberian curve and the French and German SV curves, although some interesting differences were found, such as the occurrence of lower inclinations between the 11th and 14th centuries in the Iberian curve. The analysis of these three reference curves indicates that SV in western Europe is characterized by three major directional changes at −125, 200, and 1350 A.D. It is suggested that these cusps are regional features of the geomagnetic field. The Iberian curve has been compared with the predictions of the Jackson, CALSK7K.2, and Hongre global models. Despite large differences recognized between these models, even for the dipolar terms, they predict reasonably well the Iberian archaeomagnetic SV.
Heavy ion acceleration in the divergent solar wind
Authors: Shevchenko Valentin , Galinsky Vitaly , Winske Dan
Published: December 2006

We study the heavy ion acceleration due to cyclotron interaction with both right‐ and left‐hand polarized MHD waves propagating along the magnetic field in the outward direction in the divergent solar wind. It is shown in test‐particle approximation that heavy ions can overcome the gap between the maximum resonant velocity for left‐handed waves and minimum resonant velocity for right‐handed waves and acquire the average parallel velocity on the order of local Alfven speed relative to the protons.
Simultaneous observations of radio wave phase and intensity variations for locating the plasma layers in the ionosphere
Authors: Liou Y. A. , Pavelyev A. G.
Published: December 2006

A new method is introduced to locate the layered structures in the ionosphere based on simultaneous observations of radio wave temporal intensity and phase variations in trans‐ionospheric satellite‐to‐satellite links. The method determines location of the tangent point on the trans‐ionospheric ray trajectory where gradient of refractivity is perpendicular to the ray trajectory and the influence of a layered structure on radio wave parameters is maximal. This new technique was applied to the measurements provided during CHAMP radio occultation (RO) mission. For the considered RO events, the locations of the inclined plasma layers in the lower ionosphere are found and the electron density distributions are retrieved. The method is checked by measuring the location of the tangent point on the ray trajectory in the neutral gas in the atmosphere. The results showed a fairly good agreement.
Regional climate impacts of the Southern Annular Mode
Authors: Gillett N. P. , Kell T. D. , Jones P. D.
Published: December 2006

Previous work on the influence of the Southern Annular Mode (SAM) on surface climate has focused mainly on individual countries. In this study we use station observations of temperature and rainfall to identify the influence of the SAM on land regions over the whole of the Southern Hemisphere. We demonstrate that the positive phase of the SAM is associated with a significant cooling over Antarctica and much of Australia, and a significant warming over the Antarctic Peninsula, Argentina, Tasmania and the south of New Zealand. The positive phase of the SAM is also associated with anomalously dry conditions over southern South America, New Zealand and Tasmania, due to the southward shift of the stormtrack; and to anomalously wet conditions over much of Australia and South Africa. These influences on populated regions of the Southern Hemisphere may have implications for weather and seasonal forecasting, and for future climate change.
Dipole moment of the H2SO4‐H2O complex
Authors: Brauer Carolyn S. , Sedo Galen , Leopold Kenneth R.
Published: December 2006

Stark effect measurements have been performed on three rotational transitions of the H2SO4‐H2O complex using pulsed‐nozzle Fourier transform microwave spectroscopy. The total dipole moment (μT), as well as its projection onto the a‐inertial axis of the complex (μa), have been determined for each of two tunneling states, designated A and B. For the A state, μT is 3.024(94) D and μa is 2.630(20) D. For the B state, these values are 3.052(17) and 2.6402(65) D, respectively. Ab initio calculations at the HF/aug‐cc‐pVTZ, MP2/aug‐cc‐pVDZ, MP2/aug‐cc‐pVTZ, MP2/aug‐cc‐pVQZ, and MP3/aug‐cc‐pVDZ level/basis set have been performed and compared with experimental values for both H2SO4 and H2SO4‐H2O. Models for homogeneous nucleation requiring the dipole moment of the H2SO4‐H2O adduct should use the B‐state value of μT = 3.052(17) D.
Mixing at the head of a canyon: A laboratory investigation of fluid exchanges in a rotating, stratified basin
Authors: Wells Judith R. , Helfrich Karl R.
Published: December 2006

Observations indicate that oceanic mixing is intensified near the head of submarine canyons. How the presence of canyon walls affects the local production and distribution of mixed fluid is an open question. These dynamics are addressed through rotating tank experiments which impose mixing at middepth at the closed end of a channel open to a larger body of water. Turbulence is generated in a linearly stratified fluid with initial buoyancy frequency N by means of a single bar oscillated with frequency ω. The mixed fluid quickly reaches a steady state height h ∼ (ω/N)1/2 independent of the Coriolis frequency f and collapses into the channel interior. A small percentage of the fluid exported from the turbulent zone enters a boundary current. The bulk forms a cyclonic circulation in front of the bar. As the recirculation cell expands to fill the channel, it restricts horizontal entrainment into the turbulent zone. Mixed fluid flux decays with time as t and is dependent on the size of the mixing zone and the balance between turbulence, rotation, and stratification. The recirculation cell is confined within the channel, and export of mixed fluid into the basin is restricted to the weak boundary current. As horizontal entrainment is shut down, long‐term production of mixed fluid relies more on vertical entrainment. However, the scalings indicate that short‐term dynamics are the most applicable to oceanic conditions.
Impact of clouds on radiative heating rates in the tropical lower stratosphere
Authors: Fueglistaler S. , Fu Q.
Published: December 2006

We quantify the impact of tropospheric clouds on radiative heating rates in the tropical lower stratosphere using the data collected from the Atmospheric Radiation Measurement (ARM) Tropical Western Pacific (TWP) sites Manus and Nauru. The cloud fields are retrieved from ground‐based millimeter cloud radar observations. We find that the radiative heating rate change due to enhanced upwelling shortwave fluxes only partially compensates that due to reduced upwelling longwave fluxes, resulting in a net change of about −0.2 K/day in the 70–30 hPa layer during the periods of frequent high cloud occurrence. The impact of clouds is particularly large relative to clear sky radiative heating rates around 60 hPa (435–475 K, the base of the “tropical pipe”) where they show a local minimum. The radiative heating rates in this layer with the consideration of cloud effects are close to zero and can be even negative (i.e., diabatic descent). The seasonal and spatial structures of tropical convection, and associated high cloud coverage, suggest that their effect, leading to longitudinal (in addition to the well known latitudinal) gradients in radiative heating rates, may be partially responsible for stratospheric mixing. It is suggested that the effect of high tropospheric clouds on radiative heating rates cannot fully explain the amplitude of diabatic descent in the lower stratosphere over the maritime continent reported in previous studies.
Reduction of proton acceleration in high-intensity laser interaction with solid two-layer targets
Authors: Wei M. S. , Davies J. R. , Clark E. L. , Beg F. N. , Gopal A. , Tatarakis M. , Willingale L. , Nilson P. , Dangor A. E. , Norreys P. A. , Zepf M. , Krushelnick K.
Published: December 2006

Reduction of proton acceleration in the interaction of a high-intensity, picosecond laser with a 50-μm aluminum target was observed when 0.1–6μm of plastic was deposited on the back surface (opposite side of the laser). The maximum energy and number of energetic protons observed at the back of the target were greatly reduced in comparison to pure aluminum and plastic targets of the same thickness. This is attributed to the effect of the interface between the layers. Modeling of the electron propagation in the targets using a hybrid code showed strong magnetic-field generation at the interface and rapid surface heating of the aluminum layer, which may account for the results.
Work function engineering using lanthanum oxide interfacial layers
Authors: Alshareef H. N. , Quevedo-Lopez M. , Wen H. C. , Harris R. , Kirsch P. , Majhi P. , Lee B. H. , Jammy R. , Lichtenwalner D. J. , Jur J. S. , Kingon A. I.
Published: December 2006

A La2O3 capping scheme has been developed to obtain n-type band-edge metal gates on Hf-based gate dielectrics. The viability of the technique is demonstrated using multiple metal gates that normally show midgap work function when deposited directly on HfSiO. The technique involves depositing a thin interfacial of La2O3 on a Hf-based gate dielectric prior to metal gate deposition. This process preserves the excellent device characteristic of Hf-based dielectrics, but also allows the realization of band-edge metal gates. The effectiveness of the technique is demonstrated by fabricating fully functional transistor devices. A model is proposed to explain the effect of La2O3 capping on metal gate work function.
Hydrodynamic instabilities in ablative tamped flows
Authors: Temporal M. , Jaouen S. , Masse L. , Canaud B.
Published: December 2006

Perturbation amplitudes and correlated growth rates of hydrodynamic instabilities in the compressed core of a directly driven inertial confinement fusion capsule are analyzed in planar and spherical geometries, with and without heat conduction. It is found that the maximum Lagrangian perturbation amplitude is always located inside the hot spot and not at the ablation front when heat conduction is switched on. A reduction of the Rayleigh-Taylor growth rate compared to the classical one is also shown. The growth rate is varying in k (against k1∕2 classically), due to the unsteady state regime of the deceleration.
On nonexistence of tokamak equilibria with purely poloidal flow
Authors: Throumoulopoulos G. N. , Weitzner H. , Tasso H.
Published: December 2006

It is proved that irrespective of compressibility, tokamak steady states with purely poloidal mass flow cannot exist in the framework of either magnetohydrodynamics (MHD) or Hall MHD models. Nonexistence persists within single-fluid plasma models with pressure anisotropy and incompressible flows.
Dissociative attachment to ClCN and BrCN
Authors: Royal J. , Orel A. E.
Published: December 2006

We present calculated dissociative attachment cross sections for ClCN and BrCN in the 0–20eV energy range. In this energy region, both Cl−∕Br− and CN− fragments are possible and are produced via dissociation along repulsive resonance curves. Electron scattering calculations, using the complex Kohn variational method and molecular structure calculations, were used to determine the three-dimensional surfaces and resonance parameters. The nuclear dynamics was studied in one, two, and three dimensions using time-dependent wave packet methods, employing the multiconfiguration time-dependent Hartree method for multiple dimensions. The calculated cross sections are reported and compared to the available experiments. Couplings between resonance states will also be examined and discussed.
Intensity-dependent resonance absorption in relativistic laser-plasma interaction
Authors: Xu Hui , Sheng Zheng-Ming , Zhang Jie , Yu M. Y.
Published: December 2006

The effect of light intensity on resonance absorption of p-polarization laser pulses in plasma with steep density gradients is studied by particle-in-cell simulations. For given incident angle and density scale length, the absorption rate decreases with an increase of the laser intensity. This can be attributed to a relativistic reduction of the local plasma frequency and thus detuning of the driving laser field from the excited electron plasma waves near the critical surface. With a further increase of the laser intensity, the absorption rate begins to increase since the laser field can now further penetrate into the plasma up to higher densities and drive density cavities and peaks there. As a result, multiple-resonant absorption is found at different locations.
A novel method to determine electron density by optical emission spectroscopy in low-pressure nitrogen plasmas
Authors: Zhu Xi-Ming , Pu Yu-Dong , Guo Zhi-Gang , Pu Yi-Kang
Published: December 2006

A novel method to determine volume averaged electron density by optical emission spectroscopy is investigated in inductively coupled nitrogen plasma. Using a kinetic model of low-pressure nitrogen discharge, volume averaged electron density can be obtained from experimentally measured vibrational distribution of the excited state C3Πu of the nitrogen molecule. Electron density versus rf power determined by this method and Langmuir probe measurement is compared and found to be in good agreement.
Understanding the nonfouling mechanism of surfaces through molecular simulations of sugar-based self-assembled monolayers
Authors: Hower Jason C. , He Yi , Bernards Matthew T. , Jiang Shaoyi
Published: December 2006

This paper presents a molecular simulation study of the interactions of a protein (lysozyme) with self-assembled monolayers (SAMs) of mannitol and sorbitol terminated alkanethiols in the presence of explicit water molecules and ions. The all-atom simulations were performed to calculate the force generated on the protein as a function of its distance above the SAM surfaces. The structural and dynamic properties of water molecules both above the SAM surfaces and around the SAM head groups were analyzed to provide a better understanding of the nonfouling behavior of the sugar-based SAM surfaces. Results from this work suggest that both mannitol and sorbitol SAMs generate a tightly bound, structured water layer around the SAM chains. This hydration layer creates a repulsive force on the protein when it approaches the surface, resulting in a nonfouling surface despite the presence of hydrogen-bond donor groups. This work demonstrates the importance of strong surface-water interactions for surface resistance to nonspecific protein adsorption.
Ferromagnetic interlayer exchange coupling in semiconductor SbCrTe∕Sb2Te3∕SbCrTe trilayer structures
Authors: Zhou Zhenhua , Chien Yi-Jiunn , Uher Ctirad
Published: December 2006

Semiconductor trilayer structures with ferromagnetic Sb2−xCrxTe3 layers separated by a nonmagnetic Sb2Te3 layer of different thickness have been fabricated by molecular beam epitaxy. Ferromagnetic out-of-plane exchange coupling between the SbCrTe layers was found and the coupling strength, which can be represented by a saturation field HS, depends on both the Sb2Te3 spacer thickness and temperature.
Elastomechanical model of tumor invasion
Authors: Guiot Caterina , Pugno Nicola , Delsanto Pier Paolo
Published: December 2006

Tumor invasion concerns the tumor capability of colonizing the host by means of several complex biochemical processes. Since certain aspects of the problem present a striking resemblance with well known physical mechanisms, the authors propose here an analogy between tumoral invasive branching in a tissue and the mechanical insertion of a solid inclusion in an elastic material specimen. The model, which is an extension of a previous one, based on the universal growth law of West et al. [Nature (London) 413, 628 (2001)], is discussed in the case of multicellular tumor spheroids (and cords), but it may be adapted to understand invasion also in real tumors.
Influence of surface passivation on ultrafast carrier dynamics and terahertz radiation generation in GaAs
Authors: Lloyd-Hughes J. , Merchant S. K. E. , Fu L. , Tan H. H. , Jagadish C. , Castro-Camus E. , Johnston M. B.
Published: December 2006

The carrier dynamics of photoexcited electrons in the vicinity of the surface of (NH4)2S-passivated GaAs were studied via terahertz emission spectroscopy and optical-pump terahertz-probe spectroscopy. Terahertz emission spectroscopy measurements, coupled with Monte Carlo simulations of terahertz emission, revealed that the surface electric field of GaAs reverses after passivation. The conductivity of photoexcited electrons was determined via optical-pump terahertz-probe spectroscopy and was found to double after passivation. These experiments demonstrate that passivation significantly reduces the surface state density and surface recombination velocity of GaAs. Finally, it was demonstrated that passivation leads to an enhancement in the power radiated by photoconductive switch terahertz emitters, thereby showing the important influence of surface chemistry on the performance of ultrafast terahertz photonic devices.
Order enhancement and coarsening of self-organized silicon nanodot patterns induced by ion-beam sputtering
Authors: Gago R. , Vázquez L. , Plantevin O. , Metzger T. H. , Muñoz-García J. , Cuerno R. , Castro M.
Published: December 2006

The temporal evolution of the characteristic wavelength (λ) and ordering range (ξ) of self-organized nanodot patterns induced during Ar+ ion beam sputtering on Si(001) and Si(111) surfaces is studied by atomic force microscopy and grazing incidence x-ray diffraction. The patterns exhibit initial coarsening of λ (up to 54–60nm) and increase in ξ (up to 400–500nm) after which both features stabilize. The pattern formation is only weakly controlled by the crystallographic surface orientation, Si(111) surfaces showing a faster evolution into a proper stationary state. This trend is attributed to a higher sputtering rate at this orientation, as confirmed by theoretical simulations.
Cathodoluminescence investigations of GaInNAs on GaAs(111)B
Authors: Miguel-Sánchez J. , Jahn U. , Guzmán A. , Muñoz E.
Published: December 2006

In this work, we present a detailed cathodoluminescence characterization of GaInNAs quantum wells grown on GaAs(111)B. As-grown and annealed InGaAs and GaInNAs quantum wells were maeasured and compared by spatially resolved cathodoluminescence at different photon energies. In the case of GaInNAs quantum wells, an increase of the luminescence intensity, a blueshift, and an increment of the modulation depth of intensity profiles were found after rapid thermal annealing cycles. The latter is caused by the presence of nonradiative areas above the GaInNAs quantum well due to stacking faults formed during the growth.
Facile strategy and mechanism for orthorhombic SnO2 thin films
Authors: Chen Zhiwen , Lai Joseph K. L. , Shek Chan-Hung
Published: December 2006

Orthorhombic phase SnO2 is a material with unknown optical, electrical, and gas-sensing properties. It was found previously only at high pressures and temperatures. A facile strategy for the synthesis of orthorhombic SnO2 is of fundamental importance. Using pulsed-laser deposition, the authors report a kind of experimental realization of a pure orthorhombic SnO2 thin film under low pressure and temperature that are much lower than those of traditional methods. The optical properties of an orthorhombic SnO2 thin film were measured by spectrophotometric transmittance. The oxygen exchange reaction mechanism at the grain interfaces was proposed to explain the formation and optical properties of this orthorhombic phase.
Ordered GaAs quantum dot arrays on GaAs(001): Single photon emission and fine structure splitting
Authors: Kiravittaya S. , Benyoucef M. , Zapf-Gottwick R. , Rastelli A. , Schmidt O. G.
Published: December 2006

Ordered GaAs∕AlGaAs quantum dots (QDs) are fabricated on patterned GaAs(001) substrates and their optical properties are investigated by microphotoluminescence (PL) spectroscopy. QDs exhibit sharp excitonic lines with typical single QD emission features. Photon-correlation spectroscopy shows single photon emission for the neutral exciton transition. Polarization-dependent PL measurements reveal a sharp exciton line and a fine structure exchange splitting of about 70μeV.
Electrical detection of hybridization and threading intercalation of deoxyribonucleic acid using carbon nanotube network field-effect transistors
Authors: Gui Ee-Ling , Li Lain-Jong , Lee P. S. , Lohani Anup , Mhaisalkar S. G. , Cao Qing , Kang Seong Jun , Rogers John A. , Tansil N. C. , Gao Zhiqiang
Published: December 2006

The authors study deoxyribonucleic acid (DNA) sensing characteristics of carbon nanotube network field-effect transistors (CNNFETs) by monitoring their electrical responses upon immobilization with a DNA probe, hybridization with DNA analytes, and intercalation with a N,N′-bis(3-propylimidazole)-1,4,5,8-naphthalene diimide modified with Os(2,2′-bipyridine)2Cl+ pendants. The CNNFETs immobilized by single-stranded DNA molecules demonstrate the selective sensing of its complementary and single-base mismatched DNA (difference of ∼16% in reduction of normalized drain current Id). Subsequent intercalation demonstrates a further sensitivity enhancement (difference of ∼13% in Id reduction) due to specific binding between hybridized DNA and intercalators, corroborated by the x-ray photoelectron spectroscopy study.
Spin-polarized tunneling in metal-insulator-semiconductor Fe∕ZnSe∕Ga1−xMnxAs magnetic tunnel diodes
Authors: Saito H. , Yuasa S. , Ando K. , Hamada Y. , Suzuki Y.
Published: December 2006

The authors fabricated a metal-insulator-semiconductor (M∕I∕SC) structure Fe∕ZnSe∕Ga1−xMnxAs and observed magnetoresistance (MR) ratios up to 40%. The dependence of differential conductivity on bias voltage exhibited pronounced asymmetry characteristic of a M∕I∕p-SC tunnel diode reflecting the characteristic band structure of Ga1−xMnxAs. The bias voltage (Vhalf), where the MR ratio becomes half the zero-bias value, reached 460mV, which is the highest value yet reported in M∕I∕Ga1−xMnxAs magnetic tunnel junctions (Vhalf<100mV). This large Vhalf and the use of a conventional 3d-ferromagnetic metal is an important first step in giving nonvolatile functionality to the established high-current gain tunnel transistors.
Efficient blue electroluminescence from neutral alcohol-soluble polyfluorenes with aluminum cathode
Authors: Zhou Gang , Geng Yanhou , Cheng Yanxiang , Xie Zhiyuan , Wang Lixiang , Jing Xiabin , Wang Fosong
Published: December 2006

Efficient blue polymer light-emitting diodes (PLEDs) have been fabricated with a neutral alcohol-soluble polyfluorene, i.e., poly(9,9-bis(6′-diethoxylphosphorylhexyl)fluorene) (PF-EP), as the emitting layer, high work-function Al as the cathode, and poly(vinyl carbazole) as the hole-transporting layer. The PLEDs display a maximum luminous efficiency of 4.0cd∕A and the luminous efficiency >2.4cd∕A in a wide range of current densities. It is found that the promising performance of the devices is attributed to the fact that the PF-EP is not only an efficient blue light-emitting polymer, but it also can facilitate efficient electron injection at the Al/PF-EP interface.
Enhanced optical field intensity distribution in organic photovoltaic devices using external coatings
Authors: O’Connor Brendan , An Kwang H. , Pipe Kevin P. , Zhao Yiying , Shtein Max
Published: December 2006

An external dielectric coating is shown to enhance energy conversion in an organic photovoltaic cell with metal anode and cathode by increasing the optical field intensity in the organic layers. Improved light incoupling in the device is modeled using transfer matrix simulations and is confirmed by in situ measurement of the photocurrent during growth of the coating. The optical field intensity in optimized cell geometries is predicted to exceed that in analogous devices using indium tin oxide, both cell types having equivalent anode sheet resistance, suggesting a broader range of compatible substrates (e.g., metal foils) and device processing techniques.
Giant moment and magnetic anisotropy in Co-doped ZnO films grown by pulse-injection metal organic chemical vapor deposition
Authors: Zukova Anna , Teiserskis Arunas , van Dijken Sebastiaan , Gun’ko Y. K. , Kazlauskiene V.
Published: December 2006

We report on large magnetic moments of up to 18.9μB∕Co in Co-doped ZnO films grown by pulse-injection metal organic chemical vapor deposition. The magnetic moment saturates easily in perpendicular magnetic fields and is considerably reduced when the magnetic field is applied parallel to the film plane. The saturation moment is largest for a small Co doping concentration of 1% and persists up to a temperature well above 900K. These extraordinary magnetic attributes cannot be explained by the spin-only moment of Co2+ ions or Co cluster, but suggest the formation of orbital states in a defect-related impurity band.
Investigation of AlN films grown by molecular beam epitaxy on vicinal Si(111) as templates for GaN quantum dots
Authors: Benaissa M. , Vennéguès P. , Tottereau O. , Nguyen L. , Semond F.
Published: December 2006

The use of AlN epitaxial films deposited on vicinal Si(111) as templates for the growth of GaN quantum dots is investigated by transmission electron microscopy and atomic force microscopy. It is found that the substrate vicinality induces both a slight tilt of the AlN (0001) direction with respect to the [111] direction and a step bunching mechanism. As a consequence, a dislocation dragging behavior is observed giving rise to dislocation-free areas well suited for the nucleation of GaN quantum dots.
Hole capture into self-organized InGaAs quantum dots
Authors: Geller M. , Marent A. , Stock E. , Bimberg D. , Zubkov V. I. , Shulgunova I. S. , Solomonov A. V.
Published: December 2006

Hole capture into and emission from self-organized InGaAs∕GaAs quantum dots (QDs) are studied by means of charge-selective deep level transient spectroscopy. The authors observe hole capture and determine activation energies and apparent capture cross sections for emission and capture. The experimental findings indicate that the capture process into the QDs in the presence of an applied electric field is controlled by phonon-assisted tunneling. An apparent capture cross section (at infinite values of temperature T and electric field F) σF,T=∞≈7×10−12cm2 and an average time tc≈0.3ps (T=300K) for hole capture and relaxation are obtained.
Strong suppression of the yellow luminescence in C-doped GaN in air ambient
Authors: Reshchikov M. A.
Published: December 2006

The authors observed a drastic reduction of the yellow luminescence (YL) intensity in carbon-doped semi-insulating GaN in air or oxygen ambient as compared to the intensity in vacuum. The YL intensity dropped about 300 times while the exciton emission remained almost unchanged. The authors assume that the donor-acceptor-pair transitions involving a gallium vacancy complex in a thin near-surface region cause the strong YL. Oxygen molecules or ions induce the surface states acting as a very efficient channel of nonradiative recombination. The results indicate that carbon may not be involved in the acceptor responsible for the YL band in GaN:C.
Electron dephasing in wurtzite indium nitride thin films
Authors: Jia Z. W. , Shen W. Z. , Ogawa H. , Guo Q. X.
Published: December 2006

The authors present magnetotransport measurements of electron dephasing characteristics in wurtzite indium nitride thin films grown by metal-organic vapor phase epitaxy. Pronounced weak antilocalization effects have been observed at low magnetic fields due to the presence of strong spin-orbit interactions at the top of the valence band. With the aid of the weak localization theory, they are able to demonstrate that the dephasing is connected to three separate processes of the spin-orbit, electron-phonon, and extended structural defect scatterings. The spin-orbit splitting has been determined to be 5.7meV. They have also shown that both the magnetoresistivity and resistivity can be explained using the same temperature-dependent dephasing times.
Improvement of the electrical performance in metal-induced laterally crystallized polycrystalline silicon thin-film transistors by crystal filtering
Authors: Kim Min-Sun , Song Nam-Kyu , Han Shin-Hee , Joo Seung-Ki , Lee Jang-Sik
Published: December 2006

The electrical performance of the polycrystalline silicon (poly-Si) thin-film transistors (TFTs) is greatly affected by the microstructure of the poly-Si. The crystal filtering method is employed to improve the electrical properties of poly-Si TFTs using metal-induced lateral crystallization by the ordering of Si grains. Experimental results indicated that the field-effect mobility of TFTs having crystal filtered poly-Si is more than 2.5 times higher than that of conventional poly-Si TFTs. It is found that the ordered microstructure is one of the key parameters to improve the electrical performance in poly-Si TFTs.
Local environment of a diluted element under high pressure: Zn1−xMnxO probed by fluorescence x-ray absorption spectroscopy
Authors: Pellicer-Porres J. , Segura A. , Sánchez-Royo J. F. , Sans J. A. , Itié J. P. , Flank A. M. , Lagarde P. , Polian A.
Published: December 2006

The authors report on x-ray absorption measurements performed on Zn1−xMnxO (x=0.05,0.25) at the Mn K edge (6539eV) under high pressure. Mn is found to substitute for Zn both in the low pressure wurtzite phase and in the high pressure rocksalt phase. The Mn–O bond length is determined to be 2.02±0.01Å at ambient conditions, with a compressibility similar to that of Zn–O in pure ZnO, being dictated by the ZnO crystalline environment. The phase transition is reversible in Zn0.95Mn0.05O, but not in Zn0.75Mn0.25O. The authors demonstrate that fluorescence detected x-ray absorption under high pressure can be used to characterize structural changes around minority elements.
Modeling white light-emitting diodes with phosphor layers
Authors: Kang Dun-Yen , Wu Enboa , Wang Da-Ming
Published: December 2006

With a blue light-emitting diode and a phosphor layer to downconvert blue light to a second light, such as yellow, white light can be produced. The authors developed a one-dimensional model to describe the light propagating in the phosphor layer in terms of light absorption, conversion, and reflection. The parameters required for the model were determined from the data obtained by using multiple-layer phosphor films. The model predicts that, with a reflector between the diode and the phosphor layer that is blue-light transparent but reflects other visible light, the normalized white light intensity is above 0.9, higher than that of conventional packages (0.6–0.8).
Area-selective deposition of self-assembled monolayers on SiO2∕Si(100) patterns
Authors: Wang Changshun , Pan Xu , Sun Cunying , Urisu Tsuneo
Published: December 2006

Area-selective deposition of self-assembled monolayers (SAMs) has been demonstrated on patterns of SiO2∕Si(100). The pattern was fabricated by synchrotron radiation stimulated etching of SiO2 thin films on Si substrate. Several kinds of the patterns were obtained with different types of masks. A dodecene SAM was deposited on Si surface and an octadecyltrichlorosilane SAM was deposited on SiO2 surface. The deposited SAMs were densely packed and well ordered characterized by infrared spectroscopy, ellipsometry, and water contact angle measurements.
Liquid-state semiconductor p-n junction at 903K
Authors: Sasaki Yasushi , Hirano Yoshihiko , Iguchi Manabu , Ishii Kuniyoshi
Published: December 2006

A liquid-state semiconductor p-n junction has been fabricated by applying the liquid phase separation of the monotectic Sb-Sb2S3 system at 903K. Electrical conduction types of liquid semiconductor of Sb–S alloy and S2S3-x consisting of the immiscible system are found to be p and n types, respectively, from measured absolute Seebeck coefficients. The p-n junction was formed by the liquid Sb–-S alloy and Sb2S3−x; this is confirmed from the asymmetric current-voltage characteristics or its behavior is rectified. The formation of the liquid-state p-n junction in liquid semiconductors has great prospects in the next-generation direct thermal-to-electrical energy conversion materials.
Assembly and measurement of a hybrid nanowire-bulk thermoelectric device
Authors: Keyani Jennifer , Stacy Angelica M. , Sharp Jeff
Published: December 2006

Bi 1 − x Sb x nanowires are predicted to show an increased thermoelectric efficiency compared to bulk materials. The authors have synthesized dense Bi0.3Sb0.7 nanowire arrays by electrodeposition into porous anodic alumina and fabricated Ni electrical contacts to the wires. The nanowire/alumina composite was assembled into a hybrid nanowire-bulk thermoelectric device, and electrical measurements were used to calculate the device ZT. The nanowire array produced a temperature difference of 7°C and the hybrid couple had a ZT of 0.12, which is on par with an equivalent bulk couple.
High resolution vacuum ultraviolet emission spectrum of D2 from 78to103nm: The DΠu1→XΣg+1 and D′Πu−1→XΣg+1 band systems
Authors: Roudjane Mourad , Launay Françoise , Tchang-Brillet W.-Ü Lydia
Published: December 2006

The emission spectrum of the D2 molecule has been studied at high resolution in the vacuum ultraviolet region 78.5–102.7nm. A detailed analysis of the two DΠu1→XΣg+1 and D′Πu−1→XΣg+1 electronic band systems is reported. New and improved values of the level energies of the two upper states have been derived with the help of the program IDEN [V. I. Azarov, Phys. Scr. 44, 528 (1991); 48, 656 (1993)], originally developed for atomic spectral analysis. A detailed comparison is made between the observed energy levels and solutions of coupled equations using the newest ab initio potentials by Wolniewicz and co-workers [J. Chem. Phys. 103, 1792 (1995); 99, 1851 (1993); J. Mol. Spectros. 212, 208 (2002); 220, 45 (2003)] taking into account the nonadiabatic coupling terms for the DΠu1 state with the lowest electronic states BΣu+1, CΠu1, and B′Σu+1. A satisfactory agreement has been found for most of the level energies belonging to the D and D′ states. The remaining differences between observation and theory are probably due to nonadiabatic couplings with other higher electronic states which were neglected in the calculations.
Add-drop filters in three-dimensional layer-by-layer photonic crystals using waveguides and resonant cavities
Authors: Kohli Preeti , Christensen Caleb , Muehlmeier Jason , Biswas Rana , Tuttle Gary , Ho Kai-Ming
Published: December 2006

A three-dimensional layer-by-layer photonic crystal with a complete photonic band gap is used to experimentally and theoretically demonstrate a sharp tunable bandpass filter. The structure consists of input and output waveguide sections coupled through a nearby cavity. The authors show experimentally and verify with finite difference time domain simulations that this configuration is a bandpass filter where a particular resonant frequency of the cavity is selected from the input guide and transmitted to the output guide leaving out other input frequencies. An excellent coupling efficiency near 100% between the waveguide and the cavity is found for the drop frequencies.