An experimental investigation of flow past a dual step cylinder

Flow development in the wake of a dual step cylinder has been investigated experimentally using Laser Doppler Velocimetry and flow visualization. The dual step cylinder model is comprised of a large diameter cylinder (D) mounted at the mid-span of a small diameter cylinder (d). The experiments have been performed for a Reynolds number (Re _D ) of 1,050, a diameter ratio (D/d) of 2, and a range of large cylinder aspect ratios (L/D). The results show that the flow development is highly dependent on L/D. The following four distinct flow regimes can be identified based on vortex dynamics in the wake of the large cylinder: (1) for L/D ≥ 15, three vortex shedding cells form in the wake of the large cylinder, one central cell bounded by two cells of lower frequency, (2) for 8 < L/D ≤ 14, a single vortex shedding cell forms in the wake of the large cylinder, (3) for 2 < L/D ≤ 6, vortex shedding from the large cylinder is highly three-dimensional. When spanwise vortices are shed, they deform substantially and attain a hairpin shape in the near wake, (4) for 0.2 ≤ L/D ≤ 1, the large cylinder induces vortex dislocations between small cylinder vortices. The results show that for Regimes I to III, on the average, the frequency of vortex shedding in the large cylinder wake decreases with L/D, which is accompanied by a decrease in coherence of the shed vortices. In Regime IV, small cylinder vortices connect across the large cylinder wake, but these connections are interrupted by vortex dislocations. With decreasing L/D, the frequency of dislocations decreases and the dominant frequency in the large cylinder wake increases toward the small cylinder shedding frequency.     

Graphene for energy harvesting/storage devices and printed electronics

Graphene-based materials are intriguing from the perspective of fundamental science and technology because they are non-toxic, chemically and thermally tolerant, and mechanically robust. Graphene exhibits superior electrical conductivity, high surface area and a broad electrochemical window that may be particularly advantageous for their applications in energy storage devices. In addition, graphene can be prepared in the form of a colloidal suspension with adjustable solubility and thus is suitable for printing applications and offers both transparency and good conductivity at the same time. In this review, applications of graphene in solar cells, batteries, supercapacitors and fuel cells are summarized with the latest developments. Furthermore, graphene as a conductive ink for printed electronics is also discussed.     

Multifunctional Poly(N‐vinylcarbazole)‐Based Block Copolymers and their Nanofabrication and Photosensitizing Properties

The synthesis of poly(N‐vinylcarbazole)‐based block copolymers functionalized with rhenium diimine complexes or pendant terpyridine ligands is reported. The copolymers are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and they exhibit interesting morphological properties as a result of the phase separation between different blocks. The rhenium complex polymer block may function as a photosensitizer, while the terpyridine‐containing polymer block can be used as the template for nanofabrication by selective deposition of zinc complexes.

     

Supersymmetry breaking,heterotic strings and fluxes

In this paper we consider compactifications of heterotic strings in the presence of background flux. The background metric is a T² fibration over a K3 base times four-dimensional Minkowski space. Depending on the choice of three-form flux different amounts of supersymmetry are preserved (N=2,1,0$N=2,1,0$). For supersymmetric solutions unbroken space–time supersymmetry determines all background fields except one scalar function which is related to the dilaton. The heterotic Bianchi identity gives rise to a differential equation for the dilaton which we discuss in detail for solutions preserving an N=2$N=2$ supersymmetry. In this case the differential equation is of Laplace type and as a result the solvability is guaranteed.     

Assessing methodologies for calculating road traffic noise levels in Ireland - Converting CRTN indicators to the EU indicators (Lden, Lnight)

To comply with the EU Noise Directive 2002/49/EC, Member States are required to produce strategic noise maps for designated areas, including mapping road traffic noise from major roads. These maps must be presented using the EU indicators L_den and L_night. However, the most common noise indicator used in Ireland at present is the L_A10,18h indicator arising from the use of the Calculation of Road Traffic Noise (CRTN) prediction method. Therefore, a relationship needs to be established between L_A10,18h and L_den and L_night, separately. In addition to noise mapping these indicators are used for noise abatement purposes, so the proposed relationship must be accurate and robust. In 2002, the UK’s Transport Research Laboratory (TRL) published a paper describing mathematical procedures that could be used to convert values of L_A10 to L_den and L_night. These procedures were then adopted for use in Ireland. This paper examines the suitability of the TRL conversion methods 1 and 3 for use under Irish road conditions. Method 2 was not considered in this study, as it was a methodology not applicable in an Irish scenario. Studies concluded that where hourly traffic data are available, the conversion methodology outlined in TRL Method 1 is robust and reproducible. However, in the absence of hourly traffic data where daily traffic counts are used, the relevant conversion procedures produce variable results for both L_den and L_night when applied to Irish road conditions. To reduce the variability, new conversion procedures were developed, specifically for Irish road conditions.     

A Topos for Algebraic Quantum Theory

The aim of this paper is to relate algebraic quantum mechanics to topos theory, so as to construct new foundations for quantum logic and quantum spaces. Motivated by Bohr’s idea that the empirical content of quantum physics is accessible only through classical physics, we show how a noncommutative C*-algebra of observables A induces a topos \({\mathcal{T}(A)}\) in which the amalgamation of all of its commutative subalgebras comprises a single commutative C*-algebra \({\underline{A}}\) . According to the constructive Gelfand duality theorem of Banaschewski and Mulvey, the latter has an internal spectrum \({\underline{\Sigma}(\underline{A})}\) in \({\mathcal{T}(A)}\) , which in our approach plays the role of the quantum phase space of the system. Thus we associate a locale (which is the topos-theoretical notion of a space and which intrinsically carries the intuitionistic logical structure of a Heyting algebra) to a C*-algebra (which is the noncommutative notion of a space). In this setting, states on A become probability measures (more precisely, valuations) on \({\underline{\Sigma}}\) , and self-adjoint elements of A define continuous functions (more precisely, locale maps) from \({\underline{\Sigma}}\) to Scott’s interval domain. Noting that open subsets of \({\underline{\Sigma}(\underline{A})}\) correspond to propositions about the system, the pairing map that assigns a (generalized) truth value to a state and a proposition assumes an extremely simple categorical form. Formulated in this way, the quantum theory defined by A is essentially turned into a classical theory, internal to the topos \({\mathcal{T}(A)}\).These results were inspired by the topos-theoretic approach to quantum physics proposed by Butterfield and Isham, as recently generalized by Döring and Isham.     

The use of calcination in exposing the entrapped Fe particles from multi-walled carbon nanotubes grown by chemical vapour deposition

Multi-walled carbon nanotubes (MWCNTs) were synthesized a by chemical vapour deposition method. The effect of calcination at temperatures ranging from 300 to 550°C in exposing the metal nanoparticles within the nanotube bundles was studied. The degree of degradation of the structural integrity of the MWCNTs during the thermal process was studied by Raman spectroscopy, X-ray diffraction analysis, field-emission scanning electron microscopy, and transmission electron microscopy. The thermal behaviour of the as-prepared and calcined samples was investigated by thermogravimetric analysis. Calcination in air, at 400°C for 1 h, was found to be an efficient and simple method to extract metallic impurities from the amorphous carbon shells with minimal damage to the tube walls and lengths. The nanotubes were observed to be damaged at temperatures higher than 450°C.     

MEKC‐LIF analysis of rhodamine123 delivered by carbon nanotubes in K562 cells

Oxidized single‐walled carbon nanotubes (o‐SWNTs) were employed as the drug carriers to deliver the small molecules of Rhodamine123 (Rho123) into the K562 cells via physical adsorption. However, due to the fluorescence quenching of Rho123 on carbon nanotubes, the quantitative determination of Rho123 in cells is difficult. Based on the MEKC coupled with LIF detection, a quantitative approach was developed for the determination of Rho123 delivered into K562 cells by o‐SWNTs. Where the adsorbed Rho123 on o‐SWNTs could be desorbed by SDS in running buffer and be simultaneously separated with o‐SWNTs due to the differences of their electrophoretic mobility by applying the electric potential at the both ends of capillary. Using this approach, the intracellular uptakes of Rho123 in multidrug‐resistant and multidrug‐sensitive leukemia cells were quantified, and the results showed that o‐SWNTs could be used as the potential drug carriers to deliver small molecules into cells via the physical adsorption along with the circumventing of multidrug resistance of leukemia cells.     

Reliable Synthesis of Various Nucleoside Diphosphate Glycopyranoses

A reliable and high yielding synthetic pathway for the synthesis of the biologically highly important class of nucleoside diphosphate sugars (NDP‐sugars) was developed by using various cycloSal‐nucleotides 1 and 9 as active ester building blocks. The reaction with anomerically pure pyranosyl‐1‐phosphates 2 led to the target NDP‐sugars 20 – 45 in a nucleophilic displacement reaction, which cleaves the cycloSal moiety in anomerically pure forms. As nucleosides cytidine, uridine, thymidine, adenosine, 2′‐deoxy‐guanosine and 2′,3′‐dideoxy‐2′,3′‐didehydrothymidine were used while the phosphates of D ‐glucose, D ‐galactose, D ‐mannose, D ‐NAc‐glucosamine, D ‐NAc‐galactosamine, D ‐fucose, L ‐fucose as well as 6‐deoxy‐D ‐gulose were introduced.     

The Structure of (SCN)x: A Study Using Molecular and Solid‐State Density Functional Theory Calculations

A riddle solved! Despite its simple formula, the structure of the (SCN)_x polymer has remained elusive since its first synthesis in 1929. From energetics as well as NMR chemical shifts, based on DFT calculations, we have strong evidence that it is indeed a tangle of linear chains, made up from N‐linked S₂C₂N five‐membered rings.