bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface gravity wave effects in the oceanic boundary layer: large-eddy simulation with vortex force and stochastic breakers
Authors: SULLIVAN PETER P. , McWILLIAMS JAMES C. , MELVILLE W. KENDALL
Published: November 2007

The wind-driven stably stratified mid-latitude oceanic surface turbulent boundary layer is computationally simulated in the presence of a specified surface gravity-wave field. The gravity waves have broad wavenumber and frequency spectra typical of measured conditions in near-equilibrium with the mean wind speed. The simulation model is based on (i) an asymptotic theory for the conservative dynamical effects of waves on the wave-averaged boundary-layer currents and (ii) a boundary-layer forcing by a stochastic representation of the impulses and energy fluxes in a field of breaking waves. The wave influences are shown to be profound on both the mean current profile and turbulent statistics compared to a simulation without these wave influences and forced by an equivalent mean surface stress. As expected from previous studies with partial combinations of these wave influences, Langmuir circulations due to the wave-averaged vortex force make vertical eddy fluxes of momentum and material concentration much more efficient and non-local (i.e. with negative eddy viscosity near the surface), and they combine with the breakers to increase the turbulent energy and dissipation rate. They also combine in an unexpected positive feedback in which breaker-generated vorticity seeds the creation of a new Langmuir circulation and instigates a deep strong intermittent downwelling jet that penetrates through the boundary layer and increases the material entrainment rate at the base of the layer. These wave effects on the boundary layer are greater for smaller wave ages and higher mean wind speeds.
Pollution abatement cost savings and FDI inflows to polluting sectors in China
Authors: DI WENHUA
Published: November 2007

This paper uses a nested logit model to examine whether potential pollution abatement cost savings adjusted by institutional and socio-economic conditions influence the location choices of Foreign Direct Investment (FDI) among Chinese provinces. It incorporates individual polluting firms’ characteristics instead of looking only at location attributes. The results show that (i) FDI firms in polluting industries tend to locate in provinces with higher potential abatement costs savings adjusted for local environmental regulation; (ii) relatively dirtier firms are more likely to locate in less developed provinces or provinces with fewer similar polluting industries; (iii) firms in pollution-intensive industries are more sensitive to regulation and development status than firms in non-polluting industries; and (iv) firms tend to locate in provinces where they have more bargaining power with local governments. These findings suggest the existence of domestic pollution havens in China.
Shrub encroachment into mesic mountain grasslands in the Iberian peninsula: Effects of plant quality and temperature on soil C and N stocks
Authors: Montané Francesc , Rovira Pere , Casals Pere
Published: November 2007

This paper aims at understanding the effect that shrub encroachment into mesic mountain grasslands has on soil organic carbon (SOC) stocks. Thus we compared organic C and N contents in contiguous soil profiles under a conifer shrub, a legume shrub, and grasses (mesic grasslands) on 21 sites. Soil C and N recalcitrance indexes (RIC and RIN) were estimated as the ratio of unhydrolyzable C and N to total C or N. Contrary to our hypothesis, shrub encroachment did not cause a well‐defined change in soil C stocks. Only a slight increase in C was detected in the top 15 cm soil layer under both shrubs. The C accretion rate in this soil layer was estimated to be approximately 28–42 g m−2 per annum. Legume shrub encroachment also produced a slight decrease in the C/N ratio in the top 15 cm soil layer. No significant changes in the RIC were detected as a result of encroachment; however, slight decreases in the RIN were found at medium depths. Both RIC and RIN showed a negative relationship with site temperature in the upper legume‐shrub soil layers but not in conifer shrubs or under grasses, suggesting a priming effect on the recalcitrant soil stocks produced by the higher‐quality inputs derived from legume encroachment.
A soil‐water retention function that includes the hyper‐dry region through the BET adsorption isotherm
Authors: Silva Orlando , Grifoll Jordi
Published: November 2007

Most existing full‐range soil‐water retention functions extend standard capillary pressure curves into the dry region to zero water content at a finite matric pressure. A description of dryness is commonly taken as oven‐dry conditions given by a matric suction of about 109 Pa at zero liquid saturation. However, no finite pressure can be exerted by a zero amount of water, so a possibly more realistic situation necessarily implies that as water content approaches zero, suction tends to infinity. In this study we propose a full‐range water retention function that takes advantage of the physical consistence of the Brunauer‐Emmett‐Teller (BET) adsorption isotherm to describe the very dry end, and preserves the capillary behavior of the classical Brooks and Corey function in the wet range. The transition from capillary to adsorption mechanisms is accounted for by a generalization of the Bradley's isotherm. Tests on seven widely studied soil data sets show that the experimental water retention curves are well fitted by the proposed retention model. In order to test the present approach, our simulations were compared to experimental data, for water transport under dry conditions, found in the literature. The present model was also compared with a recently proposed extended retention function in a hypothetical experiment designed to test the influence of predicted soil humidity on solute volatilization. These comparisons showed that, under severe dryness, the water dynamics is well described by the proposed model. Moreover, in these conditions the retention function determines the soil humidity, to which solute volatilization calculations can be very sensitive.
Affinity and similarity of local scour holes at bed sills
Authors: Tregnaghi Matteo , Marion Andrea , Gaudio Roberto
Published: November 2007

Excessive erosion of gravel bed rivers represents a hazard, which is often controlled by the construction of bed sills. Shape and volume of equilibrium local scour holes at bed sills in high‐gradient streams were investigated by analyzing steady flow experimental data. Scour profiles were normalized by scaling the depths and the longitudinal distance from the upstream sill with the maximum dimensions of the scour hole. Results exhibited a universal geometrical affinity of the scour. Geometrical similarity was also found to occur, but only in a limited range of physical conditions. Evidence on the scaling nature of the scour hole shapes has important implications on the prediction of the eroded volume. In turn, a correct evaluation of the eroded volume is necessary for the optimization of the design of the intersill distance. Prediction formulae are proposed which link the eroded volume to the geometrical, hydraulic, and sediment properties.
Multiple hydrothermal sources along the south Tonga arc and Valu Fa Ridge
Authors: Massoth Gary , Baker Edward , Worthington Tim , Lupton John , de Ronde Cornel , Arculus Richard , Walker Sharon , Nakamura Ko‐ichi , Ishibashi Jun‐ichiro , Stoffers Peter , Resing Joseph , Greene Ronald , Lebon Geoffrey
Published: November 2007

Quantifying hydrothermal venting at the boundaries of tectonic plates is an outstanding geoscience problem. Considerable progress has been made by detailed surveys along mid‐ocean ridges (MORs), but until recently little was known about fluid venting along volcanic arcs. We present the first systematic survey for hydrothermal venting along the 425‐km‐long south Tonga arc and new chemistry data for particle and thermal plumes previously reported along an adjacent 88‐km‐long section of the back‐arc Valu Fa Ridge (VFR). Eleven hydrothermal plumes, recognized by their anomalous light backscattering, Eh, temperature, pH, dissolved 3He, CH4, and total dissolvable Fe and Mn, were identified arising from seven volcanic centers along the arc. Five plumes on the VFR were characterized chemically. Vent field density for the south Tonga arc was 2.6 sites/100 km of arc front, comparable to that found by surveys of the Kermadec arc (1.9 to 3.8 sites/100 km) and to MORs in the eastern Pacific (average value for 2280 km of surveyed ridgecrest: 3.2 sites/100 km). A “vent gap” occurs along a 190 km section of the arc closest to the VFR, and a site density twice the average for MORs on the eastern edge of the Pacific plate was found on this part of the VFR (6.6 sites/100 km). We suggest magmas ascending under the adjacent south Tonga arc have been captured by the VFR. While chemical enrichments of plumes on the south Tonga arc were, in general, slightly less than those on the Kermadec arc, several instances of excessive anomalies in pH suggest a similar presence of fluids enriched in magmatic volatiles (CO2‐SO2‐H2S). Locally, venting on the VFR has contributed to accumulations of 3He, Fe, and Mn within the southern Lau basin. On a broader scale, our results provide considerable support for the notion that venting from intraoceanic arcs on the convergent margin of the Pacific plate adds significantly to the total hydrothermal input into the Pacific Ocean.
On the value of operationally synthesized multiple‐Doppler wind fields
Authors: Bousquet Olivier , Tabary Pierre , Parent du Châtelet Jacques
Published: November 2007

The ability to collect radial velocity measurements at long range resulting from the deployment of innovative Doppler schemes within operational radar networks brings new perspectives in terms of exploitation of operational Doppler data, including the ability to routinely retrieve meso‐β three‐dimensional (3‐D) multiple‐Doppler wind fields over extensive areas. In this paper, we evaluate the potential of this new capability in terms of operational applications using radar data collected by the French radar network ARAMIS. The retrieved 3‐D wind fields are shown to provide reliable and continuous mapping of the kinematic structure of rain events and appear particularly suitable for both short term forecasting and model verification purposes.
Modelling the spread of oil under fast sea ice using three‐dimensional multibeam sonar data
Authors: Wilkinson J. P. , Wadhams P. , Hughes N. E.
Published: November 2007

A substantial portion of the world's remaining oil and gas reserves are found in the Arctic. Exploration pressure will intensify as sea ice thinning and retreat continue, and the subsequent production could involve spills or blowouts under various kinds of sea ice. Existing models for the spread of oil under ice are inadequate because they are unable to replicate the complexity or uniqueness of different ice regimes. Through the novel combination of 3‐D under‐ice imagery from an autonomous under water vehicle (AUV) and oil‐trajectory modelling we demonstrate that it is possible to overcome these deficiencies. Results suggest that we are presently underestimating the spread of oil under sea ice by an order of magnitude. This is an important result with wide ranging ramifications as it suggests that our present ability to contain and recover oil under ice is limited.
Ground‐based microwave ozone radiometer measurements compared with Aura‐MLS v2.2 and other instruments at two Network for Detection of Atmospheric Composition Change sites
Authors: Boyd Ian S. , Parrish Alan D. , Froidevaux Lucien , von Clarmann Thomas , Kyrölä Erkki , Russell James M. , Zawodny Joseph M.
Published: November 2007

Ozone measurements made by the Microwave Limb Sounder (MLS) on board the Earth Observing System (EOS) Aura Satellite are compared with measurements made by ground‐based microwave radiometers (MWR) in the Network for Detection of Atmospheric Composition Change (NDACC) stations at Lauder, New Zealand (45°S, 169°E) and Mauna Loa, Hawaii (20°N, 204°E). The latter instruments measure ozone over the pressure range 56 to 0.03 hPa (about 20 to 72 km), allowing validation of ozone to the upper range of the MLS profiles. In addition, because they operate continuously, separate daytime and nighttime comparisons with MLS can be made to account for the large diurnal variations of ozone in the upper stratosphere and mesosphere. MLS‐MWR comparisons show agreement generally within 5% between 24 and 0.04 hPa (about 26 to 70 km) and 5 to 13% elsewhere. To more thoroughly investigate ozone in the stratosphere and mesosphere and establish a consensus between different sets of measurements, comparisons, and analyses with other satellite‐borne instruments, including the Stratospheric Aerosol and Gas Experiment II (SAGE‐II), Halogen Occultation Experiment (HALOE), Global Ozone Monitoring by Occultation of Stars (GOMOS), and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), are also made, using the ground‐based microwave measurements as a reference. The resulting MLS‐consensus difference profiles remove some of the features present in the MLS‐MWR comparisons and indicate that the overall agreement between MLS and the correlative data, between 56 and 0.04 hPa, is mostly within 5% at both sites.
Fredholm factorization of Wiener‐Hopf scalar and matrix kernels
Authors: Daniele V. , Lombardi G.
Published: November 2007

A general theory to factorize the Wiener‐Hopf (W‐H) kernel using Fredholm Integral Equations (FIE) of the second kind is presented. This technique, hereafter called Fredholm factorization, factorizes the W‐H kernel using simple numerical quadrature. W‐H kernels can be either of scalar form or of matrix form with arbitrary dimensions. The kernel spectrum can be continuous (with branch points), discrete (with poles), or mixed (with branch points and poles). In order to validate the proposed method, rational matrix kernels in particular are studied since they admit exact closed form factorization. In the appendix a new analytical method to factorize rational matrix kernels is also described. The Fredholm factorization is discussed in detail, supplying several numerical tests. Physical aspects are also illustrated in the framework of scattering problems: in particular, diffraction problems. Mathematical proofs are reported in the paper.
On the boundary diffraction wave method for the analytical prediction of the radiation from large planar phased array antennas
Authors: Janpugdee P. , Pathak P. H. , Burkholder R. J.
Published: November 2007

A boundary diffraction wave (BDW) formulation is developed for predicting the collective radiation from large finite planar phased array antennas in a relatively efficient manner. This collective radiation is described in terms of a set of Floquet waves (FWs) arising from the array interior, together with the diffraction of these FWs by the finite array element truncation boundary; the latter is represented by a line integral of the incremental diffracted field over this boundary. In general, the BDW line integral must be evaluated numerically. The current distribution over the whole array is first obtained, for a given excitation, by full wave numerical methods. A traveling wave expansion is employed to represent the array distribution so as to facilitate the development of the BDW solution for arrays. Some numerical results based on the BDW are presented to demonstrate the utility and accuracy of the method for analyzing large planar arrays.
Differential in vivo requirements for oligomerization during Groucho‐mediated repression
Authors: Jennings Barbara H , Wainwright S Mark , Ish‐Horowicz David
Published: November 2007

The Groucho (Gro)/transducin‐like enhancer of split family of transcriptional corepressors are implicated in many signalling pathways that are important in development and disease, including those mediated by Notch, Wnt and Hedgehog. Here, we describe a genetic screen in Drosophila that yielded 50 new gro alleles, including the first protein‐null allele, and has two mutations in the conserved Q oligomerization domain that have been proposed to have an essential role in corepressor activity. One of these latter mutations, encoding an amino‐terminal protein truncation that lacks part of the Q domain, abolishes oligomerization in vitro and renders the protein unstable in vivo. Nevertheless, the mutation is not a null: maternal mutant embryos have intermediate segmentation phenotypes and relatively normal terminal patterning suggesting that the mutant protein retains partial corepressor activity. Our results show that homo‐oligomerization of Gro is not obligatory for its action in vivo, and that Gro represses transcription through more than one molecular mechanism.
Managing the Internet Payment Platform project
Authors: Gogan Janis L , Gelinas Ulric J
Published: November 2007

This case examines issues in the assessment and adoption of Internet technologies in a federal US government context, and describes in detail a pilot project to determine the feasibility of adopting an application service provider solution to support procurement by multiple federal agencies using a variety of different legacy transaction systems. The pilot test of the Internet Payment Platform (IPP) by the eMoney group of the United States Treasury's Financial Management Service involved three federal agencies and subsets of their suppliers. Participants saw many benefits from their use of the IPP, but agreed that for full-scale operation it needed to be modified to better fit the government procurement context. The project manager is weighing the pros and cons of conducting another pilot test using the same commercial software as before, or obtaining and customizing a new commercial package, or building a new system from scratch.
Crafting and Executing An Offshore IT Sourcing Strategy: GlobShop's experience
Authors: Ranganathan C , Krishnan Poornima , Glickman Ron
Published: November 2007

This teaching case discusses the decisions facing GlobShop, a global travel-retail company, in its efforts to offshore a significant portion of its information technology (IT) work. In response to the business challenges that arose due to the September 11, 2001 terrorist attacks, the company decided to outsource many of its IT activities to an Indian vendor. This case traces the key decisions made by the CIO and the challenges that were encountered during the planning and execution of the company's offshore sourcing strategy. These decisions pertain to the choice of tasks to be offshored, decisions about the vendor and the nature of sourcing arrangement, managing the vendor relationship and change management issues induced by offshoring. As GlobShop nears the completion of its 3-year agreement with the offshore vendor, the CIO is faced with decisions regarding continuing offshore outsourcing, extending the contract and related implications for the future of IT organization at GlobShop.
Fixing the Payment System at Alvalade XXI: A Case on IT project Risk Management
Authors: O'Callaghan Ramon
Published: November 2007

This case describes the implementation and subsequent failure of an innovative system installed in the bars of Alvalade XXI, the recently built football stadium in Lisbon, Portugal. Casa XXI, the company running the bars, had entrusted the project to an IT supplier who had limited experience with large systems. During the inauguration, the system failed spectacularly creating a chaotic situation. The fiasco meant not only a financial loss, but also a blow to the reputation of the company. The management blamed the supplier for the failure. The supplier, however, claimed that the problem was not technical but organizational, that is, poor planning of operations. Subsequent tests were inconclusive and failed to restore trust. At the end of the case, the CEO is considering the possibility to switch to an alternative supplier. He also wonders what they could have done to manage the project and the associated risks more effectively. The case highlights risk and project management issues in large systems implementations. The discussion can be structured around cost/benefit analysis, risk assessment, and project management. Relevant dimensions include: company operations, project scope, degree of innovation, technology used, system architecture, supplier selection, and project organization. In addition, the case raises governance questions: Who is responsible for the project? Even if the project is outsourced, how should the roles and responsibilities be apportioned between the company and the IT supplier(s)? What mechanisms should be used to plan and execute IT projects, and control their risks?
Challenges in Delivering Cross-Agency Integrated E-Services: The OBLS Project
Authors: Periasamy K. Pelly , Sia Siew-Kien
Published: November 2007

This case study describes how the Ministry of Trade and Industry, and the Infocomm Development Authority, as lead agencies, jointly initiated and managed the implementation of a one-stop business licensing portal called OBLS (Online Business Licensing Service – https://licenses.business.gov.sg/ ) in the Singapore public sector. While mandate from the top for this strategic cross-agency project was strong, there were many hurdles in the form of people, process and technology that had to be overcome. The case study highlights these issues and challenges, and illustrates how they were successfully overcome for delivering cross-agency integrated e-Service for new business license application.
Time evolution of charged defect states in tritiated amorphous silicon
Authors: Costea Stefan , Kherani Nazir P. , Zukotynski Stefan
Published: November 2007

Tritiated hydrogenated amorphous silicon (a-Si:H:T) thin films were deposited on crystalline silicon and high resistivity glass substrates. The time evolution of the density of defect states in these films was studied using the constant photocurrent method (CPM) and isothermal capacitance transient spectroscopy (ICTS). The density of defect states was found to change with time and to recover upon thermal annealing. The ICTS results revealed that, following thermal annealing, in a sample with approximately 1at.% tritium, the concentration of positively charged dangling bonds (D+) decreased by more than an order of magnitude over a period of 300h. The CPM results showed that, over the same period of time, the concentration of negatively charged dangling bonds (D−) increased by over two orders of magnitude. The D+ and D− concentrations followed exponential functions of time, but the rate was different than that of tritium decay. At the same time, the Urbach energy was found to decrease with time to about 1∕2 of its postanneal value. The change in the D+ and D− concentrations is primarily the result of capture of the beta particle generated electrons in dangling bonds and weak bonds, with steady state achieved through the development of a balance between carrier generation and carrier capture processes. The role of excess carriers was confirmed by CPM experiments under electrical bias.
Theoretical prediction and experimental study of dielectric properties in poly(vinylidene fluoride) matrix composites with micronanosize BaTiO3 filler
Authors: Dang Zhi-Min , Xie Dan , Shi Chang-Yong
Published: November 2007

Composites of micronanosize BaTiO3 (BT) particles embedded into a polyvinylidene fluoride matrix were prepared. They were studied with respect to the effect of nanosize particles on microstructure and dielectric properties. The results show that the dielectric permittivity of composites with nanosize BT is close to the predicted values calculated at high concentration of fillers, if the interactions among BT fillers and between BT fillers and polymer are included. The enhanced dielectric permittivity mainly originates from a noticeably increasing phase interfaces in the composites, which brings out the strong interfacial polarization effect at low frequencies.
Impedance spectroscopy analysis of an electrolytic cell limited by Ohmic electrodes: The case of ions with two different diffusion coefficients dispersed in an aqueous solution
Authors: Batalioto F. , Barbero G. , Figueiredo Neto A. M.
Published: November 2007

We analyze the influence of Ohmic electrodes on the impedance spectroscopy of an electrolytic cell in the shape of a slab. The electrolyte is assumed completely dissociated. The positive and negative ions have different diffusion coefficients. We show that in the very low frequency limit, the electrical impedance of the cell reduces to a pure resistance, whose value depends on the diffusion coefficients and on the conductivity of the electrodes. The ratio between the diffusion coefficients determines the numerical value of the plateaus of the resistance, and the position and amplitude of the local minimum of the reactance of the cell.
Spin dynamics and damping in nanomagnets measured directly by frequency-resolved magneto-optic Kerr effect
Authors: Schneider M. L. , Shaw J. M. , Kos A. B. , Gerrits Th. , Silva T. J. , McMichael R. D.
Published: November 2007

The spin dynamics of sub-100-nm Ni80Fe20 nanomagnets are directly measured using the magneto-optic Kerr effect and a broadband detection scheme. Elliptical dots approximately 68nm in diameter and 10nm thick were fabricated in 20×20μm2 arrays. There is approximately a factor of 2 increase in the effective linewidth when compared to a 20μm diameter continuous disk of the same material. Using micromagnetic simulations, we model the effect of dot-to-dot size variation on the effective linewidth and find that 2nm size variations are more than sufficient to account for the effective increase in linewidth.
Operating a triple stack microchannel plate-phosphor assembly for single particle counting in the 12–300K temperature range
Authors: Rosén Stefan , Schmidt Henning T. , Reinhed Peter , Fischer Daniel , Thomas Richard D. , Cederquist Henrik , Liljeby Leif , Bagge Lars , Leontein Sven , Blom Mikael
Published: November 2007

An assembly consisting of a stack of three microchannel plates (MCPs) and a phosphor screen anode has been operated over the temperature range from 300to12K. We report on measurements at 6.4kHz (using an alpha source) and with dark counts only (15Hz). Without any particle source, the MCP bias current decreased by a factor of 2.1×103 when the temperature was lowered from 300to12K. Using the alpha source, and a photomultiplier tube (PMT) to monitor the phosphor screen anode, we first observed an increase in the decay time of the phosphor from 12to45μs when the temperature was decreased from 300to100K while the decay time then decreased and reached a value of 5μs at 12K. The pulse height distribution from the PMT was measured between 300 and 12K and shows a spectrum typical for a MCP phosphor setup at 300K and 12K but is strongly degraded for intermediate temperatures. We conclude that the present MCP-phosphor detector assembly is well suited for position-sensitive particle counting operation at temperatures down to at least 12K even for count rates beyond 6kHz. This result is crucial and an important part of ongoing developments of new instrumentation for investigations of, e.g., interactions involving complex molecular ions with internal quantum state control.
Development of a two-dimensional dual pendulum thrust stand for Hall thrusters
Authors: Nagao N. , Yokota S. , Komurasaki K. , Arakawa Y.
Published: November 2007

A two-dimensional dual pendulum thrust stand was developed to measure thrust vectors [axial and horizontal (transverse) direction thrusts] of a Hall thruster. A thruster with a steering mechanism is mounted on the inner pendulum, and thrust is measured from the displacement between inner and outer pendulums, by which a thermal drift effect is canceled out. Two crossover knife-edges support each pendulum arm: one is set on the other at a right angle. They enable the pendulums to swing in two directions. Thrust calibration using a pulley and weight system showed that the measurement errors were less than 0.25mN (1.4%) in the main thrust direction and 0.09mN (1.4%) in its transverse direction. The thrust angle of the thrust vector was measured with the stand using the thruster. Consequently, a vector deviation from the main thrust direction of ±2.3° was measured with the error of ±0.2° under the typical operating conditions for the thruster.
Formation mechanism and composition distribution of FePt nanoparticles
Authors: Srivastava Chandan , Balasubramanian Jayendra , Turner C. Heath , Wiest John M. , Bagaria Hitesh G. , Thompson Gregory B.
Published: November 2007

Self-assembled FePt nanoparticle arrays are candidate structures for ultrahigh density magnetic storage media. One of the factors limiting their application to this technology is particle-to-particle compositional variation. This variation will affect the A1 to L10 transformation as well as the magnetic properties of the nanoparticles. In the present study, an analysis is provided for the formation mechanism of these nanoparticles when synthesized by the superhydride reduction method. Additionally, a comparison is provided of the composition distributions of nanoparticles synthesized by the thermal decomposition of Fe(CO)5 and the reduction of FeCl2 by superhydride. The latter process produced a much narrower composition distribution. A thermodynamic analysis of the mechanism is described in terms of free energy perturbation Monte Carlo simulations.
Forces, charges, and light emission during the rupture of adhesive contacts
Authors: Miura Takashi , Chini Michael , Bennewitz Roland
Published: November 2007

Pulling forces and light emission have been recorded simultaneously while rupturing the contact between 1∕16in. balls and adhesive tape. The force curve reveals the formation of glue filaments between the tape and the balls. Multiple light flashes originating in air discharge from the rupturing contact indicate the number of filaments. The charge separation in the moment of rupture has been evaluated by comparison with the light intensity of electric microgap discharges. The charge density is found to be one or two magnitudes larger than previously reported residual contact electrification for adhesive tape.
Microstructured surface design for omnidirectional antireflection coatings on solar cells
Authors: Zhou Weidong , Tao Meng , Chen Li , Yang Hongjun
Published: November 2007

We recently demonstrated a new process for the formation of partially spherical structures as an omnidirectional antireflection coating (omni-AR). In this paper, we report the simulation results of the angular and spectral dependences of the total reflectivity on various microstructured surfaces based on the rigorous coupled-wave analysis. Close to zero reflection can be achieved in these microstructured surfaces over an extended spectral region for large ranges of light incident angles. The impact of feature size, density, shape, and refractive index has all been investigated. The experimental results agree reasonably well with the theoretical work. Such an omni-AR structure offers an attractive solution to current crystalline silicon solar cells, as well as future thin film, quantum dot, and organic solar cells.
Temporal characteristics of an optical soliton with distributed Raman amplification
Authors: Zheng Hongjun , Liu Shanliang , Li Xin , Tian Zhen
Published: November 2007

The effects of distributed Raman amplification (DRA) on temporal characteristics of an optical soliton that are numerically investigated by using the split-step Fourier method are compared with the experimental data measured by employing the second-harmonic generation frequency-resolved optical gating analyzer. It is found that the numerical results are consistent with the experimental data. DRA that can compensate the fiber loss does not change the temporal wave form of the soliton. The soliton width performs a various oscillation with propagation distance when considering the fiber loss and different Raman gain. Compensation of the fiber loss increases with the increase of the Raman pumping power.
High-pressure phase transition detection in diamond anvil cell using the method of ellipsometry
Authors: Nissim N. , Eliezer S. , Bakshi L. , Perelmutter L. , Moreno D. , Kot E. , Rozenberg G. Kh. , Pasternak M. P.
Published: November 2007

It is suggested to use the ellipsometric technique to measure the electronic properties of static highly compressed matter. The information derived from this technique is important for the theoretical and phenomenological research for the equation of state. This diagnostic was found to be useful and sensitive for measuring pressure induced phase transitions. In particular, high-pressure ellipsometry with a diamond anvil cell was used to detect the α⇄ε phase transition in iron. The polarization of the light reflected from an iron foil was analyzed in the pressure domain of 0–24 GPa and the α⇄ε transition in compression and decompression was detected. These results are in good agreement with Mössbauer spectroscopy, x-ray diffraction, and resistivity measurements.
ZnO nanoparticle size-dependent excitation of surface Raman signal from adsorbed molecules: Observation of a charge-transfer resonance
Authors: Sun Zhihua , Zhao Bing , Lombardi John R.
Published: November 2007

By observing the Raman intensity of several molecules (4-mercaptopyridine and 4-mercaptobenzoic acid) adsorbed on the surface of ZnO nanocrystals as a function of particle size in the range of 18–31nm diameter, we show that a large increase in intensity is observed near 28nm. This is an indication of a size-dependent charge-transfer resonance. We interpret this effect as due to formation of a charge-transfer complex between a surface-bound exciton and the adsorbed molecule.
Solid-phase epitaxy of amorphous Si using single-crystalline Si nanowire seed templates
Authors: Woo Yun Sung , Kang Kibum , Jo Moon-Ho , Jeon Jong-Myeoung , Kim Miyoung
Published: November 2007

We report solid-phase epitaxy of amorphous Si (a-Si) shells using crystalline Si (c-Si) nanowire cores as seed templates. The c-Si core/a-Si shell nanowire heterostructures were in situ synthesized via a two-step chemical vapor deposition: the Au-catalytic decomposition of SiH4 for the core c-Si nanowires and the subsequent homogeneous decomposition of SiH4 at higher temperatures for the a-Si shells. Upon thermal annealing above 600°C, the a-Si shells crystallize into c-Si shells from c-Si core nanowires in an epitaxial fashion. We discuss the crystallization kinetics of a-Si shells within the frame of Gibbs-Thomson effects arising from the finite size of nanowire seeds.
Mechanisms of current formation in resonant tunneling AlN∕GaN heterostructures
Authors: Petrychuk M. V. , Belyaev A. E. , Kurakin A. M. , Danylyuk S. V. , Klein N. , Vitusevich S. A.
Published: November 2007

This paper presents an analysis of transport and noise properties of double-barrier resonant tunneling diodes formed on the basis of AlN∕GaN heterostructures. Two stable states are registered in the I-V characteristics of the diodes. The temperature dependences of current and noise behavior are analyzed to understand the contribution of different mechanisms responsible for current formation in the structures. The evolution of the spectral density of the noise current with temperature reveals several recombination-generation components. The mechanisms responsible for the formation of current in AlN∕GaN∕AlN diodes are discussed taking into account the Poole-Frenkel effect.
Thermodynamic limits of quantum photovoltaic cell efficiency
Authors: Wei Guodan , Shiu Kuen-Ting , Giebink Noel C. , Forrest Stephen R.
Published: November 2007

The intermediate band solar cell has been proposed as an ultrahigh efficiency source of energy due to the possibility of absorption of two sequential sub-band-gap photons to excite charge from a quantum confined (e.g., quantum dot or well) region into the large band gap barrier region [A. Luque and A. Martí, Phys. Rev. Lett. 78, 5014 (1997)]. Unfortunately, high efficiencies using this structure have not yet been realized. Here, we analyze the fundamental limits to power generation in quantum solar cells. When a difference in quasi-Fermi energies between the barrier and the quantum well regions exists due to the presence of photogenerated charge, an upper efficiency limit of 44.5% is achievable due to single photon absorption only. This efficiency is significantly higher than the Shockley-Queisser limit of ∼31% for homojunction cells, but remains below that predicted for two photon excitation (>63%) previously predicted for quantum cells.
Plasmon phenomena as origin of dc induced resistivity oscillations in two-dimensional electron systems
Authors: Iñarrea Jesús
Published: November 2007

We analyze theoretically the oscillations that the magnetoresistivity of two-dimensional electron systems is present when a high intensity direct current is applied. In the model presented here, we suggest that a plasma wave is excited in the system producing an oscillating motion of the whole two-dimensional electron gas at the plasma frequency. This scenario dramatically affects the way the electrons interact with scatterers giving rise to oscillations in the longitudinal resistivity. With this theoretical model, experimental results are well reproduced and explained.
High permittivity polymer embedded with Co∕ZnO core/shell nanoparticles modified by organophosphorus acid
Authors: Wei T. , Jin C. Q. , Zhong W. , Liu J.-M.
Published: November 2007

The Co∕ZnO core/shell nanoparticles-filled polymer poly(vinylidene fluoride) (PVDF)-based composites (0-3 connectivity) are fabricated, in which the core/shell structure for preventing Co particles from agglomeration is prepared by a simple wet chemistry procedure. At the same time, the N,N-di(phosphonomethyl)iminoacetic acid (DPMIAA) is used to modify the core/shell surface. High dielectric permittivity and low leakage current are achieved for the DPMIAA-modified Co∕ZnO core/shell nanoparticle-PVDF composite, which shows good homogeneity, no cracks, and fine mechanical flexibility.
Cytoskeletal “jellyfish” structure of
Mycoplasma mobile
Authors: Nakane Daisuke , Miyata Makoto
Published: November 2007

Mycoplasma mobile
, a parasitic bacterium lacking a peptidoglycan layer, glides on solid surfaces in the direction of a membrane protrusion at a cell pole by a unique mechanism. Recently, we proposed a working model in which cells are propelled by leg proteins clustering at the protrusion's base. The legs repeatedly catch and release sialic acids on the solid surface, a motion that is driven by the force generated by ATP hydrolysis. Here, to clarify the subcellular structure supporting the gliding force and the cell shape, we stripped the membrane by Triton X-100 and identified a unique structure, designated the “jellyfish” structure. In this structure, an oval solid “bell” ≈235 wide and 155 nm long is filled with a 12-nm hexagonal lattice and connected to this structure are dozens of flexible “tentacles” that are covered with particles of 20-nm diameter at intervals of ≈30 nm. The particles appear to have 180° rotational symmetry and a dimple at the center. The relation of this structure to the gliding mechanism was suggested by its cellular localization and by analyses of mutants lacking proteins essential for gliding. We identified 10 proteins as the components by mass spectrometry and found that these do not show sequence similarities with other proteins of bacterial cytoskeletons or the gliding proteins previously identified. Immunofluorescence and immunoelectron microscopy revealed that two components are localized at the bell and another that has the structure similar to the F
1
-ATPase β subunit is localized at the tentacles.
CERK1, a LysM receptor kinase, is essential for chitin elicitor signaling in
Arabidopsis
Authors: Miya Ayako , Albert Premkumar , Shinya Tomonori , Desaki Yoshitake , Ichimura Kazuya , Shirasu Ken , Narusaka Yoshihiro , Kawakami Naoto , Kaku Hanae , Shibuya Naoto
Published: November 2007

Chitin is a major component of fungal cell walls and serves as a microbe-associated molecular pattern (MAMP) for the detection of various potential pathogens in innate immune systems of both plants and animals. We recently showed that chitin elicitor-binding protein (CEBiP), plasma membrane glycoprotein with LysM motifs, functions as a cell surface receptor for chitin elicitor in rice. The predicted structure of CEBiP does not contain any intracellular domains, suggesting that an additional component(s) is required for signaling through the plasma membrane into the cytoplasm. Here, we identified a receptor-like kinase, designated CERK1, which is essential for chitin elicitor signaling in
Arabidopsis
. The KO mutants for
CERK1
completely lost the ability to respond to the chitin elicitor, including MAPK activation, reactive oxygen species generation, and gene expression. Disease resistance of the KO mutant against an incompatible fungus,
Alternaria brassicicola
, was partly impaired. Complementation with the WT
CERK1
gene showed
cerk1
mutations were responsible for the mutant phenotypes. CERK1 is a plasma membrane protein containing three LysM motifs in the extracellular domain and an intracellular Ser/Thr kinase domain with autophosphorylation/myelin basic protein kinase activity, suggesting that CERK1 plays a critical role in fungal MAMP perception in plants.
Tumor cell-selective regulation of NOXA by c-MYC in response to proteasome inhibition
Authors: Nikiforov Mikhail A. , Riblett MaryBeth , Tang Wen-Hua , Gratchouck Vladimir , Zhuang Dazhong , Fernandez Yolanda , Verhaegen Monique , Varambally Sooryanarayana , Chinnaiyan Arul M. , Jakubowiak Andrzej J. , Soengas Maria S.
Published: November 2007

The proteasome controls a plethora of survival factors in all mammalian cells analyzed to date. Therefore, it is puzzling that proteasome inhibitors such as bortezomib can display a preferential toxicity toward malignant cells. In fact, proteasome inhibitors have the salient feature of promoting a dramatic induction of the proapoptotic protein NOXA in a tumor cell-restricted manner. However, the molecular determinants that control this specific regulation of NOXA are unknown. Here, we show that the induction of NOXA by bortezomib is directly dependent on the oncogene c-MYC. This requirement for c-MYC was found in a variety of tumor cell types, in marked contrast with dispensable roles of p53, HIF-1α, and E2F-1 (classical proteasomal targets that can regulate
NOXA
mRNA under stress). Conserved MYC-binding sites identified at the
NOXA
promoter were validated by ChIP and reporter assays. Down-regulation of the endogenous levels of c-MYC abrogated the induction of NOXA in proteasome-defective tumor cells. Conversely, forced expression of c-MYC enabled normal cells to accumulate NOXA and subsequently activate cell death programs in response to proteasome blockage. c-MYC is itself a proteasomal target whose levels or function are invariably up-regulated during tumor progression. Our data provide an unexpected function of c-MYC in the control of the apoptotic machinery, and reveal a long sought-after oncogenic event conferring sensitivity to proteasome inhibition.
How effective is the revised regulatory code for alcohol advertising in Australia?
Authors: JONES SANDRA C. , HALL DANIKA , MUNRO GEOFFREY
Published: November 2007

Introduction and Aims. Australia, like several other countries, has a self‐regulatory approach to advertising. However, in recent years the effectiveness of the regulatory system has been questioned, and there have been increasing public calls for an overhaul of the system. Following a formal review in 2003, the Ministerial Council on Drug Strategy proposed a revised Alcoholic Beverages Advertising Code (ABAC), which came into operation in 2004. Design and Methods. The purpose of the present study was to examine the effectiveness of this revised system. From May 2004 until March 2005 television and magazine advertising campaigns were monitored for alcohol products. Over this period 14 complaints against alcohol advertisements were lodged with the self‐regulatory board, and the authors recruited an independent expert panel to assess the advertisements and complaints. Results. In eight of the 14 cases a majority of the judges perceived the advertisement to be in breach of the code, and in no cases did a majority perceive no breach. Conversely, however, none of the complaints were upheld by the Advertising Standards Board (ASB) and only one by the ABAC Panel. Discussion and Conclusions. The results of this study suggest that the decisions made by the ASB in relation to complaints against alcohol advertisements are not in harmony with the judgement of independent experts, and that the ASB may not be performing an adequate job of representing community standards or protecting the community from offensive or inappropriate advertisements. Further, it appears that the revisions to the ABAC code, and associated processes, have not reduced the problems associated with alcohol advertising in Australia.
What does it mean to want to quit?
Authors: BALMFORD JAMES , BORLAND RON
Published: November 2007

Introduction and Aims. To report on the prevalence of attitudes and beliefs about the importance of wanting to quit and need for use of cessation assistance, that may act as barriers to quitting smoking and adopting cessation assistance. Design and Methods. National telephone survey of 802 randomly selected adults (685 smokers, 117 recent quitters). Results. Seventy per cent of smokers believed that ‘wanting to quit’ was both a necessary and sufficient condition for being able to quit. While only one‐third of smokers believed that they were too addicted to be able to quit, only a quarter believed they could quit any time they want to. Belief that use of cessation assistance is a sign of weakness was endorsed by 35% of participants, and related to stage of change. Discussion and Conclusions. Beliefs about the importance of wanting to quit are commonly held. Many smokers appear to believe that a rational, unambivalent desire to quit is needed before it is worthwhile trying. Short‐term impulses to act are not perceived as sufficient. The role of cessation assistance in helping smokers form a rational desire to quit appears to be poorly understood by the majority of smokers. There is a need to engender greater understanding of the potential value of cessation aids to smokers experiencing ambivalence about wanting to quit.
Barriers and missed opportunities to HIV testing among injection drug users in two Mexico–US border cities
Authors: MOYER LAURA B. , BROUWER KIMBERLEY C. , BRODINE STEPHANIE K. , RAMOS REBECA , LOZADA REMEDIOS , CRUZ MICHELLE FIRESTONE , MAGIS‐RODRIGUEZ CARLOS , STRATHDEE STEFFANIE A.
Published: November 2007

Introduction and Aims. Despite increasing HIV prevalence in cities along the Mexico – US border, HIV testing among high‐risk populations remains low. We sought to identify barriers associated with HIV testing among injection drug users (IDUs) in Tijuana and Ciudad Juarez, the two largest Mexican border cities located across from San Diego, California and El Paso, Texas, respectively. Design and Methods. In 2005, 222 IDUs in Tijuana and 205 IDUs in Ciudad Juarez were recruited by respondent‐driven sampling and administered a questionnaire to collect socio‐demographic, behavioural and HIV testing history data. Blood samples were provided for serological testing of HIV, hepatitis C virus (HCV) and syphilis. Results. Only 38% and 30% of respondents in Tijuana and Ciudad Juarez, respectively, had ever had an HIV test. The factors independently associated with never having been tested for HIV differed between the two sites, except for lack of knowledge on HIV transmission, which was independently associated in both locales. Importantly, 65% of those who had never been tested for HIV in both cities experienced at least one missed opportunity for voluntary testing, including medical visits, drug treatment and spending time in jail. Discussion and Conclusions. Among this high‐risk IDU population we found HIV testing to be low, with voluntary testing in public and private settings utilised inadequately. These findings underscore the need to expand voluntary HIV education and testing and to integrate it into services and locales frequented by IDUs in these Mexico – US border cities.