45°-TFG based in-fiber polarizer at 800nm by UV inscription

We show in-fiber polarizers at 800nm range with polarization extinction ratio (PER) up to 37dB, fabricated by UV-inscribing grating structures tilted at 45° in standard single mode fiber. The results show that the PER of such polarizers increases linearly with the grating length. © OSA 2012.

Practical and cost-effective high-fidelity optical carrier dissemination using coherent communication techniques

We report a unidirectional frequency dissemination scheme for high-fidelity optical carriers deployable over telecommunication networks. For the first time, a 10 Gb/s Binary Phase Shift Keying (BPSK) signal from an ultra-narrow linewidth laser was transmitted through a field-installed optical fibre with round-trip length of 124 km between Cork City and town of Clonakilty, without inline optical amplification. At the receiver, using coherent communication techniques and optical injection-locking the carrier was recovered with noise suppression. The beat signal between the original carrier at the transmitter and recovered carrier at the receiver shows a linewidth of 2.8 kHz. Long term stability measurements revealed fractional instabilities (True Allan deviation) of 3.3 × 10-14 for 1 s averaging time, prior to phase noise cancellation.

Exploration of a simple, low cost, micro gas turbine recuperator solution for a domestic combined heat and power unit

For micro gas turbines (MGT) of around 1 kW or less, a commercially suitable recuperator must be used to produce a thermal efficiency suitable for use in UK Domestic Combined Heat and Power (DCHP). This paper uses computational fluid dynamics (CFD) to investigate a recuperator design based on a helically coiled pipe-in-pipe heat exchanger which utilises industry standard stock materials and manufacturing techniques. A suitable mesh strategy was established by geometrically modelling separate boundary layer volumes to satisfy y + near wall conditions. A higher mesh density was then used to resolve the core flow. A coiled pipe-in-pipe recuperator solution for a 1 kW MGT DCHP unit was established within the volume envelope suitable for a domestic wall-hung boiler. Using a low MGT pressure ratio (necessitated by using a turbocharger oil cooled journal bearing platform) meant unit size was larger than anticipated. Raising MGT pressure ratio from 2.15 to 2.5 could significantly reduce recuperator volume. Dimensional reasoning confirmed the existence of optimum pipe diameter combinations for minimum pressure drop. Maximum heat exchanger effectiveness was achieved using an optimum or minimum pressure drop pipe combination with large pipe length as opposed to a large pressure drop pipe combination with shorter pipe length. © 2011 Elsevier Ltd. All rights reserved.

Comparative physical, mechanical and crystallographic properties of a series of gemfibrozil salts

Objectives Understanding the impact of the counterion on the properties of an acidic or basic drug may influence the choice of salt form, especially for less potent drugs with a high drug load per unit dose. The aim of this work was to determine the influence of the hydrogen bonding potential of the counterion on the crystal structure of salts of the poorly soluble, poorly compressible, acidic drug gemfibrozil and to correlate these with mechanical properties. Methods Compacts of the parent drug and the salts were used to determine Young's modulus of elasticity using beam bending tests. Crystal structures were determined previously from X-ray powder diffraction data. Key findings The free acid, tert-butylamine, 2-amino-2-methylpropan-1-ol and 2-amino-2-methylpropan-1, 3-diol salts had a common crystal packing motif of infinite hydrogen-bonded chains with cross-linking between pairs of adjacent chains. The tromethamine (trsi) salt, with different mechanical properties, had a two-dimensional sheet-like network of hydrogen bonds, with slip planes, forming a stiffer compact. Conclusions The type of counter ion is important in determining mechanical properties and could be selected to afford slip and plastic deformation. © 2010 Royal Pharmaceutical Society of Great Britain.

Octyl co-grafted PrSO3H/SBA-15:tunable hydrophobic solid acid catalysts for acetic acid esterification

Propylsulfonic acid (PrSO3H) derivatised solid acid catalysts have been prepared by post modification of mesoporous SBA-15 silica with mercaptopropyltrimethoxysilane (MPTMS), with the impact of co-derivatisation with octyltrimethoxysilane (OTMS) groups to impart hydrophobicity to the catalyst investigated. Turn over frequencies (TOF) for acetic acid esterification with methanol increase with PrSO3H surface coverage across both families suggesting a cooperative effect of adjacent acid sites at high acid site densities. Esterification activity is further promoted upon co-functionalisation with hydrophobic octyl chains, with inverse gas chromatography (iGC) measurements indicating increased activity correlates with decreased surface polarity or increased hydrophobicity.

Impaired executive functioning in subclinical compulsive checking with ecologically valid stimuli in a working memory task

We previously showed that working memory (WM) performance of subclinical checkers can be affected if they are presented with irrelevant but misleading information during the retention period (Harkin and Kessler, 2009, 2011). The present study differed from our previous research in the three crucial aspects. Firstly, we employed ecologically valid stimuli in form of electrical kitchen appliances on a kitchen countertop in order to address previous criticism of our research with letters in locations as these may not have tapped into the primary concerns of checkers. Secondly, we tested whether these ecological stimuli would allow us to employ a simpler (un-blocked) design while obtaining similarly robust results. Thirdly, in Experiment 2 we improved the measure of confidence as a metacognitive variable by using a quantitative scale (0–100), which indeed revealed more robust effects that were quantitatively related to accuracy of performance. The task in the present study was to memorize four appliances, including their states (on/off), and their locations on the kitchen countertop. Memory accuracy was tested for the states of appliances in Experiment 1, and for their locations in Experiment 2. Intermediate probes were identical in both experiments and were administered during retention on 66.7% of the trials with 50% resolvable and 50% irresolvable/misleading probes. Experiment 1 revealed the efficacy of the employed stimuli by revealing a general impairment of high- compared to low checkers, which confirmed the ecological validity of our stimuli. In Experiment 2 we observed the expected, more differentiated pattern: High checkers were not generally affected in their WM performance (i.e., no general capacity issue); instead they showed a particular impairment in the misleading distractor-probe condition. Also, high checkers’ confidence ratings were indicative of a general impairment in metacognitive functioning. We discuss how specific executive dysfunction and general metacognitive impairment may affect memory traces in the short- and in the long-term.