Quansi-optical mode converter for Ka-band application on a gyrotron

A series of electron cyclotron masers (ECMs) has been designed and successfully operated in the frequency range of 6 to 200 GHz over the past 10 years at Strathclyde University. The current Mk. VI ECM operated between 35–200 GHz, the TE _{0 1} ⁰ mode (35.2 GHz) being the lowest order cavity mode excited. Investigation of this ECM and quasi-optical converter combination was made to establish to what extent a Gaussian beam could be produced from the TE _{0 1} ⁰ gyrotron cavity mode.An antenna of the Vlasov (step-cut radiator) configuration was chosen and successfully developed in a series of low-power experiments up to the W-band frequency regime. The low-power experiments demonstrated that such an antenna system could be constructed and operated in the K_a-band frequency region without resorting to high precision quasi-optical components. The final version of the quasi-optical antenna was externally coupled to the output window of the maser and a plane polarized pencil beam was successfully obtained from the combined maser/Vlasov antenna mode converter.A theoretical model involving a single TE _0n ⁰ input mode was chosen to analyse the output beam characteristics from the Vlasov antenna system. Comparison was made between the single mode theoretical model and the experimental results obtained from the maser.     

Optimal Policy for Minimal Repair

The problem of replacement under minimal repair is considered. It is shown that a particular form of control limit policy is optimal in the space of all possible policies. This generalises a previous result.     

Nanomanipulation-Coupled Matrix-Assisted Laser Desorption/ Ionization-Direct Organelle Mass Spectrometry: A Technique for the Detailed Analysis of Single Organelles

We describe a novel technique combining precise organelle microextraction with deposition and matrix-assisted laser desorption/ionization (MALDI) for a rapid, minimally invasive mass spectrometry (MS) analysis of single organelles from living cells. A dual-positioner nanomanipulator workstation was utilized for both extraction of organelle content and precise co-deposition of analyte and matrix solution for MALDI-direct organelle mass spectrometry (DOMS) analysis. Here, the triacylglycerol (TAG) profiles of single lipid droplets from 3T3-L1 adipocytes were acquired and results validated with nanoelectrospray ionization (NSI) MS. The results demonstrate the utility of the MALDI-DOMS technique as it enabled longer mass analysis time, higher ionization efficiency, MS imaging of the co-deposited spot, and subsequent MS/MS capabilities of localized lipid content in comparison to NSI-DOMS. This method provides selective organellar resolution, which complements current biochemical analyses and prompts for subsequent subcellular studies to be performed where limited samples and analyte volume are of concern.

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Synthesis, characterization, and coordination chemistry of several novel electroneutral phosphane ligands

The reaction of fluorocarbon (R_f) reagents C₂F₅Li or C₂F₃Li with diaminochlorophosphanes (R₂N)₂PCl produced four new phosphane ligands of the type (R₂N)₂P(R_f). Addition of (Et₂N)₂PCl to ethereal solutions of C₂F₅Li or C₂F₃Li produced (Et₂N)₂PC₂F₅1 and (Et₂N)₂PC₂F₃2; treatment of (C₄H₄N)₂PCl and (C₄H₈N)₂PCl with C₂F₅Li afforded (C₄H₄N)₂PC₂F₅3 and (C₄H₈N)₂PC₂F₅4. All ligands were isolated as colorless, high-boiling liquids. Substitution reactions of 1-4 with Mo(CO)₆ in a refluxing alkane solvent yielded complexes of the type (L)Mo(CO)₅ (L = (Et₂N)₂PC₂F₅, 5; (Et₂N)₂PC₂F₃6; (C₄H₄N)₂PC₂F₅7 and (C₄H₈N)₂PC₂F₅8) as colorless solids in low to moderate (25-62%) yields. Complexes 5, 7 and 8 were structurally characterized by single crystal X-ray diffraction. A comparison of IR stretching frequencies and X-ray bond length data suggests these ligands approximate the electronic influence of phosphites.     

In situ gelling hexagonal phases for sustained release of an anti-addiction drug

In this study, fluid precursor formulations for subcutaneous injection and in situ formation of hexagonal phase gels upon water absorption were developed as a strategy to sustain the release of naltrexone, a drug used for treatment of drug addiction. Precursor formulations were obtained by combining BRIJ 97 with propylene glycol (PG, 5-70%, w/w). To study the phase behavior of these formulations, water was added at 10-90% (w/w), and the resulting systems were characterized by polarized light microscopy. Two precursor formulations containing BRIJ:PG at 95:5 (w/w, referred to as BRIJ-95) and at 80:20 (w/w, referred to as BRIJ-80) were chosen. Naltrexone was dissolved at 1% or suspended at 5% (w/w). Precursor formulations were transformed into hexagonal phases when water content exceeded 20%. Water uptake followed second-order kinetics, and after 2-4h all precursor formulations were transformed into hexagonal phases. Drug release was prolonged by the precursor formulations (compared to a drug solution in PBS), and followed pseudo-first order kinetics regardless of naltrexone concentration. The release from BRIJ-80 was significantly higher than that from BRIJ-95 after 48 h. The relative safety of the precursor formulations was assessed in cultured fibroblasts. Even though BRIJ-95 was more cytotoxic than BRIJ-80, both precursor formulations were significantly less cytotoxic than sodium lauryl sulfate (considered moderate-to-severe irritant) at the same concentration (up to 50 μg/mL). These results suggest the potential of BRIJ-based precursor formulations for sustained naltrexone release.     

Switching Equivalence Classes of Perfect Codes

The authors present a 1-error correcting perfect code of length 15 and show that it is not switching equivalent to the Hamming code thereby settling a question of Avgustinovich and Solov'evaas96     

Enhancement of Fe(III), Co(III), and Cr(VI) reduction at elevated temperatures and by a thermophilic bacterium

Applied Biochemistry and Biotechnology - An unusual thermophilic bacterium has been isolated from deep subsurface sediments and tested for its ability to enhance Fe(III), Co(III), and Cr(VI)...     

Kernels of nonlinear Hamming codes

Given a binary code,C, of lengthn, thekernel of the code is defined to be the set of all vectors which leave the code invariant under translation. Throughout this paper, various properties of kernels will be considered. However, the main idea of this paper is to show the necessary and sufficient conditions for the existence of kernels of all possible sizes for nonlinear perfect binary codes.