Nails in Stomach of a Dog

In the annals of canine surgical history, the case of a two and one-half months old collie pup and his stomach full of nails will hold a unique position. The patient, was presented with a history of having swallowed twenty roofing nails after discovering the family tool box in the cellar

Highly sensitive alkane odour sensors based on functionalised gold nanoparticles

We deposit dense, ordered, thin films of Au-dodecanethiol core/shell nanoparticles by the Langmuir-Schafer (LS) printing method, and find that their resistance at ambient temperature responds selectively and sensitively to alkane odours. Response is a rapid resistance increase due to swelling, and is strongest for alkane odours where the alkane chain is similar in length to the dodecane shell. For decane odours, we find a response to concentrations as low as 15 ppm, about 600 times below the lower explosive limit. Response is weaker, but still significant, to aromatic odours (e.g. Toluene, Xylene), while potential interferants such as polar and/or hydrogen-bonding odours (e.g. alcohols, ketones, water vapour) are somewhat rejected. Resistance is weakly dependent on temperature, and recovers rapidly and completely to its original value within the error margin of measurement. (C) 2011 Elsevier B.V. All rights reserved

Transport Properties of Highly Aligned Polymer Light-Emitting-Diodes

We investigate hole transport in polymer light-emitting-diodes in which the emissive layer is made of liquid-crystalline polymer chains aligned perpendicular to the direction of transport. Calculations of the current as a function of time via a random-walk model show excellent qualitative agreement with experiments conducted on electroluminescent polyfluorene demonstrating non-dispersive hole transport. The current exhibits a constant plateau as the charge carriers move with a time-independent drift velocity, followed by a long tail when they reach the collecting electrode. Variation of the parameters within the model allows the investigation of the transition from non-dispersive to dispersive transport in highly aligned polymers. It turns out that large inter-chain hopping is required for non-dispersive hole transport and that structural disorder obstructs the propagation of holes through the polymer film.Comment: 4 pages, 5 figure

A mutant affecting the crystal cells in Drosophila melanogaster

Black cells (Bc, 2-80.6±) mutant larvae of Drosophila melanogaster have pigmented cells in the hemolymph and lymph glands. In this report we present evidence that these melanized cells are a mutant form of the crystal cells, a type of larval hemocyte with characteristic paracrystalline inclusions. Bc larvae lack crystal cells. Furthermore, the distribution pattern of black cells in Bc larvae parallels that of experimentally-blackened crystal cells in normal larvae (phenocopy).In Bc/Bc zygotes black cells appear during mid embryonic development but in Bc + / Bc zygotes pigmented cells are not found until late in the first larval instar.Crystal cells are present in the heterozygous larvae until this time, and paracrystalline inclusions can be seen in some of the cells undergoing melanization in these larvae.The rate of phenol oxidase activity in Bc + / Bc larval cell-free extracts is less than half that of Bc + / Bc + extracts whereas enzyme activity is undetectable in Bc/Bc larvae. We propose that the Bc + gene product is required for maintaining the integrity of the paracrystalline inclusions; in Bc/Bc larvae either the product is absent or nonfunctional so an effective contact between substrate and enzyme results in melanization of the cells.Phenol oxidase itself is either destroyed or consumed in the melanization process accounting for the absence of enzyme activity in Bc/Bc larvae. These studies confirm that the crystal cells store phenolic substrates and are the source of the hemolymph phenol oxidase activity in the larva of D. melanogaster .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47505/1/427_2004_Article_BF00848799.pd

Dominant aerosol processes during high-pollution episodes over Greater Tokyo

This paper studies two high-pollution episodes over Greater Tokyo: 9 and 10 December 1999, and 31 July and 1 August 2001. Results obtained with the chemistry-transport model (CTM) Polair3D are compared to measurements of inorganic PM2.5. To understand to which extent the aerosol processes modeled in Polair3D impact simulated inorganic PM2.5, Polair3D is run with different options in the aerosol module, e.g. with/without heterogeneous reactions. To quantify the impact of processes outside the aerosol module, simulations are also done with another CTM (CMAQ). In the winter episode, sulfate is mostly impacted by condensation, coagulation, long-range transport, and deposition to a lesser extent. In the summer episode, the effect of long-range transport largely dominates. The impact of condensation/evaporation is dominant for ammonium, nitrate and chloride in both episodes. However, the impact of the thermodynamic equilibrium assumption is limited. The impact of heterogeneous reactions is large for nitrate and ammonium, and taking heterogeneous reactions into account appears to be crucial in predicting the peaks of nitrate and ammonium. The impact of deposition is the same for all inorganic PM2.5. It is small compared to the impact of other processes although it is not negligible. The impact of nucleation is negligible in the summer episode, and small in the winter episode. The impact of coagulation is larger in the winter episode than in the summer episode, because the number of small particles is higher in the winter episode as a consequence of nucleation.Comment: Journal of Geophysical Research D: Atmospheres (15/05/2007) in pres

Quantum Confinement and Thickness-Dependent Electron Transport in Solution-Processed In₂O₃ Transistors

The dependence of charge carrier mobility on semiconductor channel thickness in field-effect transistors is a universal phenomenon that has been studied extensively for various families of materials. Surprisingly, analogous studies involving metal oxide semiconductors are relatively scarce. Here, spray-deposited In_{2}O_{3} layers are employed as the model semiconductor system to study the impact of layer thickness on quantum confinement and electron transport along the transistor channel. The results reveal an exponential increase of the in-plane electron mobility (µe) with increasing In2O3 thickness up to ≈10 nm, beyond which it plateaus at a maximum value of ≈35 cm^{2} V^{−1} s^{−1}. Optical spectroscopy measurements performed on In_{2}O_{3} layers reveal the emergence of quantum confinement for thickness <10 nm, which coincides with the thickness that µe starts deteriorating. By combining two- and four-probe field-effect mobility measurements with high-resolution atomic force microscopy, it is shown that the reduction in µe is attributed primarily to surface scattering. The study provides important guidelines for the design of next generation metal oxide thin-film transistors

Structure, Photophysics and the Order-Disorder Transition to the Beta Phase in Poly(9,9-(di -n,n-octyl)fluorene)

X-ray diffraction, UV-vis absorption and photoluminescence (PL) spectroscopy have been used to study the well-known order-disorder transition (ODT) to the beta phase in poly(9,9-(di n,n-octyl)fluorene)) (PF8) thin film samples through combination of time-dependent and temperature-dependent measurements. The ODT is well described by a simple Avrami picture of one-dimensional nucleation and growth but crystallization, on cooling, proceeds only after molecular-level conformational relaxation to the so called beta phase. Rapid thermal quenching is employed for PF8 studies of pure alpha phase samples while extended low-temperature annealing is used for improved beta phase formation. Low temperature PL studies reveal sharp Franck-Condon type emission bands and, in the beta phase, two distinguishable vibronic sub-bands with energies of approximately 199 and 158 meV at 25 K. This improved molecular level structural order leads to a more complete analysis of the higher-order vibronic bands. A net Huang-Rhys coupling parameter of just under 0.7 is typically observed but the relative contributions by the two distinguishable vibronic sub-bands exhibit an anomalous temperature dependence. The PL studies also identify strongly correlated behavior between the relative beta phase 0-0 PL peak position and peak width. This relationship is modeled under the assumption that emission represents excitons in thermodynamic equilibrium from states at the bottom of a quasi-one-dimensional exciton band. The crystalline phase, as observed in annealed thin-film samples, has scattering peaks which are incompatible with a simple hexagonal packing of the PF8 chains.Comment: Submitted to PRB, 12 files; 1 tex, 1 bbl, 10 eps figure

X-ray Raman scattering study of aligned polyfluorene

We present a non-resonant inelastic x-ray scattering study at the carbon K-edge on aligned poly[9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl] and show that the x-ray Raman scattering technique can be used as a practical alternative to x-ray absorption measurements. We demonstrate that this novel method can be applied to studies on aligned $\pi$-conjugated polymers complementing diffraction and optical studies. Combining the experimental data and a very recently proposed theoretical scheme we demonstrate a unique property of x-ray Raman scattering by performing the symmetry decomposition on the density of unoccupied electronic states into $s$- and $p$-type symmetry contributions.Comment: 19 pages, 8 figure

Data assimilation in atmospheric chemistry models: current status and future prospects for coupled chemistry meteorology models

Abstract. Data assimilation is used in atmospheric chemistry models to improve air quality forecasts, construct re-analyses of three-dimensional chemical (including aerosol) concentrations and perform inverse modeling of input variables or model parameters (e.g., emissions). Coupled chemistry meteorology models (CCMM) are atmospheric chemistry models that simulate meteorological processes and chemical transformations jointly. They offer the possibility to assimilate both meteorological and chemical data; however, because CCMM are fairly recent, data assimilation in CCMM has been limited to date. We review here the current status of data assimilation in atmospheric chemistry models with a particular focus on future prospects for data assimilation in CCMM. We first review the methods available for data assimilation in atmospheric models, including variational methods, ensemble Kalman filters, and hybrid methods. Next, we review past applications that have included chemical data assimilation in chemical transport models (CTM) and in CCMM. Observational data sets available for chemical data assimilation are described, including surface data, surface-based remote sensing, airborne data, and satellite data. Several case studies of chemical data assimilation in CCMM are presented to highlight the benefits obtained by assimilating chemical data in CCMM. A case study of data assimilation to constrain emissions is also presented. There are few examples to date of joint meteorological and chemical data assimilation in CCMM and potential difficulties associated with data assimilation in CCMM are discussed. As the number of variables being assimilated increases, it is essential to characterize correctly the errors; in particular, the specification of error cross-correlations may be problematic. In some cases, offline diagnostics are necessary to ensure that data assimilation can truly improve model performance. However, the main challenge is likely to be the paucity of chemical data available for assimilation in CCMM