Eco-friendly location of small hydropower

We address the problem of locating small hydropower dams in an environmentally friendly manner. We propose the use of a multi-objective optimization model to maximize total hydropower production, while limiting negative impacts on river connectivity. Critically, we consider the so called “backwater effects” that dams have on power generation at nearby upstream sites via changes in water surface profiles. We further account for the likelihood that migratory fish and other aquatic species can successfully pass hydropower dams and other artificial/natural barriers and how this is influenced by backwater effects. Although naturally represented in nonlinear form, we manage through a series of linearization steps to formulate a mixed integer linear programing model. We illustrate the utility of our proposed framework using a case study from England and Wales. Interestingly, we show that for England and Wales, a region heavily impacted by a large number of existing river barriers, that installation of small hydropower dams fitted with even moderately effective fish passes can, in fact, create a win-win situation that results in increased hydropower and improved river connectivity.     

Thermodynamics and kinetics of glyoxal dimer formation: a computational study

Density functional theory (B3LYP//6-311+G) calculations including Poisson-Boltzmann implicit solvent were used to study the hydration of glyoxal and subsequent formation of dimeric species in solution. Our calculations show that the dioxolane ring dimer is the thermodynamic sink among all monomers and dimers with varying degrees of hydration. Although fully hydrated species are thermodynamically favored over their less hydrated counterparts, we find that a preliminary dehydration step precedes dimerization and ring closure. Ring closure of the open dimer monohydrate to the dioxolane ring dimer is kinetically favored over both hydration to the open dimer dihydrate and ring closure to form the dioxane ring dimer. The kinetic barriers for different geometric approaches for dimerization suggest an explanation why oligomerization stops after the formation of a dioxolane ring trimer as observed experimentally.     

Discrete element modelling of the quasi-static uniaxial compression of individual infant formula agglomerates

Infant formula is usually produced in an agglomerated powder form. These agglomerates are subjected to many transient forces following their manufacture. These can be difficult to quantify experimentally because of their small magnitudes and short durations. Numerical models have the potential to address this gap in the experimental data. The objective of the research described here was to calibrate a discrete element model for these agglomerates using experimental data obtained for quasi-static loading, and to use this model to study the mechanics of the particle response in detail. The Taguchi method was previously proposed as a viable calibration approach for discrete element models. In this work, the method was assessed for calibration of the model parameters (e.g., bond stiffnesses and strengths) considering three responses: the force at failure, strain at failure and agglomerate stiffness. The Weibull moduli for the simulation results and the experimental data were almost identical following calibration and the 37% characteristic stresses were similar. An analysis of the energy terms in the model provided useful insight into the model response. The bond energy and the normal force exerted on the platens were strongly correlated, and bond breakage events coincided with the highest energy dissipation rates.     

Membrane Cholesterol and the Formation of Cholesterol Domains in the Pathogenesis of Cardiovascular Disease

At least three types of cholesterol-rich membrane domains have been described in biological membranes including cholesterol rafts, membrane caveolae and crystalline cholesterol domains,. While clear biological functions have been ascribed to both rafts and caveolae, little attention has been directed to the biological consequences of cholesterol enrichment of cell membranes and the formation of cholesterol domains. Elevated blood cholesterol levels have been shown to result in the enrichment of the cell plasma membrane with cholesterol in arterial smooth muscle cells (SMC), endothelial cells (EC) and cardiac myocytes. In the early period of cholesterol feeding (within days), the cell membrane enriches with cholesterol and membrane viscosity and membrane bilayer width increase. This latter effect severely alters membrane protein function, and recent data indicates that this induces the modulation of vascular cells (SMC and EC) to the atherosclerotic phenotype. In cardiac myocytes these membrane modifications appear to induce alterations in gene expression patterns that lead to the development of a heart failure phenotype. In addition, as the cholesterol content increases, phase separation of cholesterol occurs resulting in the formation of immiscible cholesterol domains within the membrane. These domains likely initiate nucleation of cholesterol crystals which would explain the origin of “cholesterol clefts” in atherosclerotic lesions. Taken together, these membrane alterations secondary to cholesterol enrichment constitute a “membrane lesion” which contribute to the very early pathogenic events underlying major human diseases including coronary artery disease, stroke and heart failure.     

Shearing apparatus for neutron scattering studies on fluids: Preliminary results for colloidal suspensions

In this paper we study the transient diffusion-limited A+B0, A₀ = B₀ annihilation via deterministic reaction-diffusion equations and via simulation of the stochastic many-particle problem. We show that the two approaches are not equivalent and that the deterministic expressions capture only part of the picture. A lower bound is derived for the density decay which indicates that the overall density follows the power law t^–x with = mm(d/4, 1). Hierarchical oscillations superimposed on the power-law decay are observed for reactions on Sierpinski gaskets.This work is dedicated to Prof. George H. Weiss.     

Synthesis of Aminated Naphthacenetriones: Precursors to Aminated Anthracyclines

An application of aminoacetaldehyde dialkoxy acetal to introduce an amino fuctionality in the 6 and/or 11 position of the naphthacenetrione ring system, resulting in key intermediates to aminated anthracyclines, is described.     

Modeling of a continuous pretreatment reactor using computational fluid dynamics

Computational fluid dynamic simulations are employed to predict flow characteristics in a continuous auger driven reactor designed for the dilure acid pretreatment of biomass. Slurry containing a high concentration of biomass solids exhibits a high viscosity, which poses unique mixing issues within the reactor. The viscosity increases significantly with a small increase in solids concentration and also varies with temperature. A well-mixed slurry is desirable to evenly distribute acid on biomass, prevent buildup on the walls of the reactor, and provides an uniform final product. Simulations provide flow patterns obtained over a wide range of viscosities and pressure distributions, which may affect reaction rates. Results provide a tool for analyzing sources of inconsistencies in product quality and insight into future design and operating parameters.     

Laser desorption postionization for imaging MS of biological material

Vacuum ultraviolet single photon ionization (VUV SPI) is a soft ionization technique that has the potential to address many of the limitations of matrix‐assisted laser desorption/ionization (MALDI) for imaging MS. Laser desorption postionization (LDPI) uses VUV SPI for postionization and is experimentally analogous to a MALDI instrument with the addition of a pulsed VUV light source. This review discusses progress in LDPI‐MS over the last decade, with an emphasis on imaging MS of bacterial biofilms, analytes whose high salt environment make them particularly resistant to imaging by MALDI‐MS. This review first considers fundamental aspects of VUV SPI including ionization mechanisms, cross sections, quantum yields of ionization, dissociation and potential mass limits. The most common sources of pulsed VUV radiation are then described along with a newly constructed LDPI‐MS instrument with imaging capabilities. Next, the detection and imaging of small molecules within intact biofilms is demonstrated by LDPI‐MS using 7.87 eV (157.6 nm) VUV photons from a molecular fluorine excimer laser, followed by the use of aromatic tags for detection of selected species within the biofilm. The final section considers the future prospects for imaging intact biological samples by LDPI‐MS. Copyright © 2010 John Wiley & Sons, Ltd.     

Grazing incidence X-ray studies of ultra-thin Lumogen films

Lumogen^® Yellow S0790 films have been produced on silicon wafer substrates via physical vapour deposition (PVD) and spin-coating (SC) methods. These coatings were characterised with X-ray reflectometry (XRR) and grazing incidence X-ray diffraction (GIXD) techniques. The results show that ultra-thin (less than 12 nm) PVD films coat amorphously, with crystallinity becoming increasingly apparent with increasing film thickness. In contrast, measurements of ultra-thin (less than ∼2 nm) spin-coated films reveal a second, apparently stable crystalline structure.