For the first time, a measurement of the viscosity of microparticles composed of Newtonian fluids has been made over a range of 12 orders of magnitude (10 À3 to 10 9 Pa s), extending from dilute aqueous solutions to the solid-like behaviour expected on approaching a glass transition. Using holographic optical tweezers to induce coalescence between two aerosol particles (volume <500 femtolitres), we observe the composite particle relax to a sphere over a timescale from 10 À7 to 10 5 s, dependent on viscosity. The damped oscillations in shape illustrate the interplay of surface capillary forces and bulk fluid flow as the relaxation progresses. Viscosity values estimated from the extrapolation of measurements from macroscopic binary aqueous solutions of sucrose are shown to diverge from the microparticle measurements by as much as five orders of magnitude in the limit of ultrahigh solute supersaturation and viscosity. This is shown to be a consequence of the sensitivity of the viscosity to the composition of the particles, specifically the water content, and the often incorrect compositional dependence on water activity that are assumed to characterise aerosols and amorphous phases under dry conditions. For ternary mixtures of sodium chloride, sucrose and water, the measured viscosities similarly diverge from model predictions by up to three orders of magnitude. The Stokes-Einstein treatment for relating the diffusivity of water in sucrose droplets to the particle viscosity is found to depart from the measured viscosities by more than one order of magnitude when the viscosity exceeds 10 Pa s and up to six orders of magnitude at the highest viscosities accessed. Coalescence is shown to proceed with unit efficiency even up to the highest accessible viscosity. These measurements provide the first comprehensive account of the change in a material property accompanying a transition from a dilute solution to an amorphous semi-solid state using aerosol particles to probe the change in rheological properties.

We study the effect of the exciton fine-structure splitting on the polarisation-entanglement of photon pairs produced by the biexciton cascade in a single quantum dot. The entanglement is found to persist despite separations between the intermediate energy levels of up to 4µeV. Measurements demonstrate that entanglement of the photon pair is robust to the dephasing of the intermediate exciton state responsible for the first order coherence time of either single photon. We present a theoretical framework taking into account the effects of spin-scattering, background light and dephasing. We distinguish between the first-order coherence time, and a parameter which we measure for the first time and define as the cross-coherence time.Semiconductor quantum dots are often referred to as 'artificial atoms' due to their threedimensional electronic confinement and discrete energy levels [1]. One application for which they have been proved useful is the generation of polarisation-entangled photon pairs. In this Letter we study how the entanglement responds both to fluctuations in the dot's energetic fine-structure, and also to various dephasing mechanisms within the dot. We report for the first time on the distinction between different types of dephasing within the quantum dot, and investigate whether or not they can affect entanglement. Recently we demonstrated that triggered polarisation-entangled photon pairs may be generated from the radiative decay of a single quantum dot [8,9,10], as proposed by Benson et al [11]. The dot is initially excited to a zero-spin bound complex of two electrons and two heavy-holes (a biexciton.) From here it decays by the sequential emission of two photons, constrained to have total angular momentum zero, and returns to a ground (unexcited) state. If the intermediate states However it is more usually the case that a fine-structure splitting (FSS) exists between the two orthogonal exciton states corresponding to the H and V polarised photons. This means that the decay cascade is forced to take one of two distinguishable paths ( fig. 1b) and the photon polarisations are only classically correlated rather than entangled [12,13,14].How small the FSS must be in order to cross over from polarisation-correlated to polarisation- In order to construct the full density operator for the (mixed state) output it is then necessary to integrate this operator over all values of t. The emission of the exciton photon obeys Poissonian statistics and the probability of emission occurring between time t and t+dt in any given decay cycle is therefore equal to , where τ 1 is the radiative lifetime of the exciton. The density operator for the coherent light emitted from the dot is thereforeOther light which must be included in the complete density matrix for the emission can be divided into background light, spin-scattered light, and dephased light. Background light is uncorrelated in polarisation, originating from areas of the sample other than the dot. Spin-scattered light occurs when the spin of the exc...

We investigate the evolution of quantum correlations over the lifetime of a multiphoton state. Measurements reveal time-dependent oscillations of the entanglement fidelity for photon pairs created by a single semiconductor quantum dot. The oscillations are attributed to the phase acquired in the intermediate, nondegenerate, exciton-photon state and are consistent with simulations. We conclude that emission of photon pairs by a typical quantum dot with finite polarization splitting is in fact entangled in a time-evolving state, and not classically correlated as previously regarded.

The use of adhesive bonding in joining of materials with different characteristics is of major importance in a variety of microelectronic and photonic applications. The curing of such adhesives is also of great consequence, with the use of optical radiation for adhesive curing becoming the method of choice in various applications, especially bonding of components in microelectronics and fiber-optic assembly. This article reviews recent advances in the development of adhesives, their applications, and their curing methods using optical radiation; it also includes a brief overview of the adhesion mechanisms.

Here we demonstrate, for the first time, violation of Bell's inequality using a triggered quantum dot photon-pair source without post-selection. Furthermore, the fidelity to the expected Bell state can be increased above 90% using temporal gating to reject photons emitted at times when collection of uncorrelated light is more probable. A direct measurement of a CHSH Bell inequality is made showing a clear violation, highlighting that a quantum dot entangled photon source is suitable for communication exploiting non-local quantum correlations.

In this work, the coupling of liquid nanochromatography to NanoFlow electrospray mass spectrometry was evaluated for the detection of DNA adducts. The NanoFlow ES LC/MS system was compared with the capillary and conventional ES LC/MS system by analyzing an in vitro reaction mixture resulting from the interaction of 2'-deoxyguanosine 5'-monophosphate with bisphenol A diglycidyl ether and by injecting 2'-deoxyadenosine. By using NanoFlow ES LC/MS, the mass sensitivity could be improved by a factor of 3300. Three different injection methods used in liquid nanochromatography, i.e., split, large-volume, and column-switching injections were compared in terms of sensitivity. Furthermore, NanoFlow ES LC/MS was used to detect 2'-deoxynucleotide adducts isolated from an in vitro mixture of calf thymus DNA and bisphenol A diglycidyl ether. Different 2'-deoxynucleotide adducts could be identified by monitoring typical product ions, diagnostic for the adducts.

Crystal tuning: Organic molecules can be xenophobic, preferring to crystallize with their own kind. Though useful for purification, this precludes the tuning of crystal properties by doping or mixing. Nanoporous steroids provide an exception, as their channels can accept a variety of termini (hexagons and spheres). The steroids can be cocrystallized in any ratio to give a wide range of chiral, potentially porous crystalline materials.

Spliceosomes are assembled in stages. The first stage forms complex E, which is characterized by the presence of U1 snRNPs base-paired to the 5′ splice site, components recognizing the 3′ splice site and proteins thought to connect them. The splice sites are held in close proximity and the pre-mRNA is committed to splicing. Despite this, the sites for splicing appear not to be fixed until the next complex (A) forms. We have investigated the reasons why 5′ splice sites are not fixed in complex E, using single molecule methods to determine the stoichiometry of U1 snRNPs bound to pre-mRNA with one or two strong 5′ splice sites. In complex E most transcripts with two alternative 5′ splice sites were bound by two U1 snRNPs. However, the surplus U1 snRNPs were displaced during complex A formation in an ATP-dependent process requiring an intact 3′ splice site. This process leaves only one U1 snRNP per complex A, regardless of the number of potential sites. We propose a mechanism for selection of the 5′ splice site. Our results show that constitutive splicing components need not be present in a fixed stoichiometry in a splicing complex.