Transient fuel spray impingement at atmospheric and elevated ambient conditions

This study analyses detailed temporally resolved full flow field data for pre- and post-impingement fuel sprays under atmospheric and elevated ambient conditions. A comprehensive suite of diagnostic techniques is utilised comprising of phase-resolved Phase Doppler Interferometry—employing a very fine grid and velocity signature to differentiate between pre- and post-impingement droplets—high-speed imaging (utilising Mie-scattering), high-magnification shadowgraphy and an adapted instantaneous mass-rate tube. Raised ambient conditions are achieved in a high-temperature, high-pressure constant volume rig affording large optical access. Temporal data for the free and impinging sprays is compared and analysed within three phases—early, mid and late injection—defined by the mass-rate tube data. All experimental techniques employed present consistent temporal and spatial trends at atmospheric and elevated ambient conditions, and global trends are consistent with the phenomenological flow structure originally proposed by Ozdemir and Whitelaw. Detailed analysis close to the piston surface reveals approximately a threefold increase in the D₅₀ mean spray diameter for the post-impingement droplet size distribution at the wall spray tip. It is suggested that this is due to droplet coalescence, with some supporting evidence from high-speed imaging. Comparison of transient mass deposited on the surface with model predictions show reasonable agreement with the ‘Wet’ model assumption.     

Misconceptions on Pollution and the Causes of Cancer

The public has numerous misconceptions about the relationship between environmental pollution and human cancer. Underlying these misconceptions is an erroneous belief that nature is benign. In this article we highlight eight of these misconceptions and describe the scientific information that undermines each one.     

Local-field correction of the charged Bose condensate for two and three dimensions

The local-field correction for the dielectric function of the two-dimensional and of the three-dimensional Bose condensate is calculated within a sum-rule version of the Singwi et al. (Phys. Rev.176, 589 (1968)) approach. We derive analytical expressions for small and large wave numbers and give analytical expressions for the density dependence. We compare the results of the groundstate energy for the three-dimensional system with Monte-Carlo computations. In two dimensions a roton structure in the plasmon dispersion is found at low boson density. The plasmon density of states is calculated. A correlation induced charge-density-wave instability in layered structures of two-dimensional Bose gases is discussed.     

Design of triple helix forming C-glycoside molecules

The modeling, synthesis, and characterization of oligomers containing 2-aminoquinazolin-5-yl 2'-deoxynucleotide residues are reported. The 2-aminoquinazoline residues sequence specifically bind via Hoogsteen base pairing as a third strand in the center of the major groove at T:A base pair Watson-Crick duplex sequences. Evidence for the formation of a sequence specific three-stranded structure is based on thermal denaturation UV-vis and fluorescence studies. The novel 2-aminoquinazoline C-nucleotide is a component of a system designed to overcome the homopurine requirement for triple helix structures.     

Elementary excitations in multiple quantum wire structures

We calculate the plasmon dispersion of electrons in multiple quantum wire structures. Wave function overlapping effects between different wires are neglected. The Coulomb interaction potential is calculated for a model with circular wire area. Analytical results for the excitation spectrum of electron multiple quantum wire structures are obtained within an one-subband model. Landau damping of intrasubband plasmons is discussed. Results for an electron superlattice within a two-subband model are presented and the coupling of intersubband plasmons with intrasubband plasmons is calculated. We compare the theoretical results with recent Raman measurements of intrasubband plasmons in Al _x Ga_1–x As/GaAs wire superlattices. The plasmon dispersion for boson multiple quantum wire structures also is calculated.     

Formation constant and stoichiometry of the acetonitrile:18-crown-6 complex by nuclear magnetic resonance, raman and infrared spectroscopy

Crown ethers are increasingly used in a variety of chemical applications. While crown ether complexes with alkali-metal cations have been extensively studied, relatively little is known about their complexes with neutral molecules to form so-called host: guest complexes. The use of NMR is reported for the determination of the formation constant (2.1 +/- 0.1) for the acetonitrile: 18-crown-6 complex. The suitability of Raman spectroscopy for studies of the solid-phase complex is demonstrated and limitations in the use of infrared spectroscopy are discussed.     

Synthesis of uniformly 13C-labeled polycyclic aromatic hydrocarbons

Convergent synthetic pathways were devised for efficient synthesis of a series of uniformly (13)C labeled polycyclic aromatic hydrocarbons de novo from U-(13)C-benzene and other simple commercially-available (13)C-starting compounds. All target products were obtained in excellent yields, including the alternant PAH U-(13)C-naphthalene, U-(13)C-phenanthrene, U-(13)C-anthracene, U-(13)C-benz[a]anthracene, U-(13)C-pyrene and the nonalternant PAH U-(13)C-fluoranthene.