5,812 research outputs found
Cyclic occurrence of gregarine trophozoites (Apicomplexa) in the burrowing echinoid <i>Echinocardium cordatum</i> (Echinodermata, Spatangoidea)
The occurrence of the gregarine Urospora neapolitana in the spatangoid echinoid Echinocardium cordatum was followed monthly over a 1 yr period. Infesting stages (sporozoites) were seen only in the digestive cells of the hosts' gastric caecum while growing stages (trophozoites) only occurred in the hosts' body cavity. Sporozoites showed no variation in abundance over the investigated period. The number of trophozoites, however, clearly varied with a minimum in summer and early autumn. Trophozoite variation appears to be related to the gonadal cycle of the host
The valuation of clean spread options: linking electricity, emissions and fuels
The purpose of the paper is to present a new pricing method for clean spread options, and to illustrate its main features on a set of numerical examples produced by a dedicated computer code. The novelty of the approach is embedded in the use of a structural model as opposed to reduced-form models which fail to capture properly the fundamental dependencies between the economic factors entering the production process
Creation of regular arrays of faceted AlN nanostructures via a combined top-down, bottom-up approach
The realisation of spatially-determined, uniform arrays of faceted aluminium nitride (AlN) nanostructures has had limited exploration, largely due to the fact that selective area growth of AlN via MOVPE (Metal Organic Vapour Phase Epitaxy) has not been realised. Instead, this paper reports the use of a combined top-down, bottom-up approach to realise well-faceted, highly-uniform, periodic nanotextured AlN surfaces. MOVPE regrowth is performed upon dry-etched AlN nanorods and nanoholes, and we present a study into the effect of the growth conditions on the resulting faceting and morphology. Specifically, growth temperature, V/III ratio and growth time are investigated and analysed via scanning-electron and atomic-force microscopy. The V/III ratio was found to influence the nanostructure morphology most whilst the growth temperature was found to have much less of an impact within the temperature range studied. Experiments with a longer growth time are performed to create nanostructures for potential use in applications, such as for AlGaN-based quantum-well or quantum-dot emitters
Influence of the reactor environment on the selective area thermal etching of GaN nanohole arrays
Selective area thermal etching (SATE) of gallium nitride is a simple subtractive process for creating novel device architectures and improving the structural and optical quality of III-nitride-based devices. In contrast to plasma etching, it allows, for example, the creation of enclosed features with extremely high aspect ratios without introducing ion-related etch damage. We report how SATE can create uniform and organized GaN nanohole arrays from c-plane and (11–22) semi-polar GaN in a conventional MOVPE reactor. The morphology, etching anisotropy and etch depth of the nanoholes were investigated by scanning electron microscopy for a broad range of etching parameters, including the temperature, the pressure, the NH3 flow rate and the carrier gas mixture. The supply of NH3 during SATE plays a crucial role in obtaining a highly anisotropic thermal etching process with the formation of hexagonal non-polar-faceted nanoholes. Changing other parameters affects the formation, or not, of non-polar sidewalls, the uniformity of the nanohole diameter, and the etch rate, which reaches 6 µm per hour. Finally, the paper discusses the SATE mechanism within a MOVPE environment, which can be applied to other mask configurations, such as dots, rings or lines, along with other crystallographic orientations
Molecular transport and flow past hard and soft surfaces: Computer simulation of model systems
The properties of polymer liquids on hard and soft substrates are
investigated by molecular dynamics simulation of a coarse-grained bead-spring
model and dynamic single-chain-in-mean-field (SCMF) simulations of a soft,
coarse-grained polymer model. Hard, corrugated substrates are modelled by an
FCC Lennard-Jones solid while polymer brushes are investigated as a
prototypical example of a soft, deformable surface. From the molecular
simulation we extract the coarse-grained parameters that characterise the
equilibrium and flow properties of the liquid in contact with the substrate:
the surface and interface tensions, and the parameters of the hydrodynamic
boundary condition. The so-determined parameters enter a continuum description
like the Stokes equation or the lubrication approximation.Comment: 41 pages, 13 figure
Research Proposal for an Experiment to Search for the Decay {\mu} -> eee
We propose an experiment (Mu3e) to search for the lepton flavour violating
decay mu+ -> e+e-e+. We aim for an ultimate sensitivity of one in 10^16
mu-decays, four orders of magnitude better than previous searches. This
sensitivity is made possible by exploiting modern silicon pixel detectors
providing high spatial resolution and hodoscopes using scintillating fibres and
tiles providing precise timing information at high particle rates.Comment: Research proposal submitted to the Paul Scherrer Institute Research
Committee for Particle Physics at the Ring Cyclotron, 104 page
Superconductivity and Antiferromagnetism in Quasi-one-dimensional Organic Conductors
We review the current understanding of superconductivity in the
quasi-one-dimensional organic conductors of the Bechgaard and Fabre salt
families. We discuss the interplay between superconductivity,
antiferromagnetism, and charge-density-wave fluctuations. The connection to
recent experimental observations supporting unconventional pairing and the
possibility of a triplet-spin order parameter for the superconducting phase is
also presented.Comment: (v1) 30 pages, 13 figures; Review article for the 20th anniversary of
high-Tc superconductivity, to appear in J. Low Temp. Phys. (v2) 1 Ref. adde
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