Ion trap mass spectrometry on a comet nucleus: the Ptolemy instrument and the Rosetta space mission

In May 2014, the Rosetta spacecraft is scheduled to rendezvous with the comet Churyumov-Gerasimenko ('67P'). One of the instruments on board the 'Lander' which will descend on to the surface of the comet is a miniaturised GC/MS system that incorporates an ion trap mass spectrometer, specially developed for isotope ratio analysis. This article describes the development and optimisation of the ion trap for this unique application, and presents a summary of the range of pre-programmed experiments that will contribute to the characterisation of the solid and volatile cometary materials.     

RPE65 and the Accumulation of Retinyl Esters in Mouse Retinal Pigment Epithelium

The RPE65 protein of the retinal pigment epithelium (RPE) enables the conversion of retinyl esters to the visual pigment chromophore 11‐cis retinal. Fresh 11‐cis retinal is generated from retinyl esters following photoisomerization of the visual pigment chromophore to all‐trans during light detection. Large amounts of esters accumulate in Rpe65^?/? mice, indicating their continuous formation when 11‐cis retinal generation is blocked. We hypothesized that absence of light, by limiting the conversion of esters to 11‐cis retinal, would also result in the build‐up of retinyl esters in the RPE of wild‐type mice. We used HPLC to quantify ester levels in organic extracts of the RPE from wild‐type and Rpe65^?/? mice. Retinyl ester levels in Sv/129 wild‐type mice that were dark adapted for various intervals over a 4‐week period were similar to those in mice raised in cyclic light. In C57BL/6 mice however, which contain less Rpe65 protein, dark adaptation was accompanied by an increase in ester levels compared to cyclic light controls. Retinyl ester levels were much higher in Rpe65^?/? mice compared to wild type and kept increasing with age. The results suggest that the RPE65 role in retinyl ester homeostasis extends beyond enabling the formation of 11‐cis retinal.     

Detection of colorectal metastases in patients being treated with chemotherapy utilising SPIO-MRI: a radiological–pathological study

Objective

Chemotherapy commonly causes liver injury through sinusoidal obstructive syndrome and steatosis. Chemotherapy-induced liver injury may make it more difficult to detect metastases secondary to reduced contrast between the injured liver and metastases. The aim of this study was to determine the sensitivity of superparamagnetic iron oxide (SPIO) contrast-enhanced imaging in patients who have undergone chemotherapy prior to liver surgery.

Methods

Local ethics committee approval was obtained. Thirty-one patients with hepatic metastases completing preoperative chemotherapy were prospectively recruited. Images were reviewed independently by two blinded observers who identified and localized lesions with a four-point confidence scale. The alternative free-response receiver operator characteristic method was used to analyze the results.

Results

The sensitivity in detecting colorectal metastases following chemotherapy was 78% and 76%, respectively, for observers 1 and 2 (95% confidence interval: 71%–85% and 68%–82%). The areas under the alternative free-response receiver operator curves were 0.73 and 0.80 for observers 1 and 2, respectively.

Conclusion

Compared to previously published work on chemotherapy-naïve patients, it is clear that the sensitivity of SPIO-enhanced magnetic resonance imaging (MRI) in detecting colorectal metastases following chemotherapy is reduced. It is therefore critical that all imaging — pre-, during and postchemotherapy — is reviewed when reporting liver MRI prior to surgery.     

Reflection anisotropy spectroscopy: A new probe for the solid-liquid interface

Introducing reflection anisotropy spectroscopy (RAS) as a new probe for solid-liquid interfaces, we present results for the Au(110)/electrolyte interface which serves as a model system. We demonstrate that RAS is sensitive to surface phase transitions, step morphology, and electronic surface states. Using an empirical approach, the RA spectra are reproduced and features are identified which reflect the known character of the bias voltage driven (2x1) to (1x1) phase transition. RAS is established as an experimental technique to probe the electronic structure of solid-liquid interfaces in real time to study a wide range of interface properties.     

A feasibility study of X‐ray phase‐contrast mammographic tomography at the Imaging and Medical beamline of the Australian Synchrotron

Results are presented of a recent experiment at the Imaging and Medical beamline of the Australian Synchrotron intended to contribute to the implementation of low‐dose high‐sensitivity three‐dimensional mammographic phase‐contrast imaging, initially at synchrotrons and subsequently in hospitals and medical imaging clinics. The effect of such imaging parameters as X‐ray energy, source size, detector resolution, sample‐to‐detector distance, scanning and data processing strategies in the case of propagation‐based phase‐contrast computed tomography (CT) have been tested, quantified, evaluated and optimized using a plastic phantom simulating relevant breast‐tissue characteristics. Analysis of the data collected using a Hamamatsu CMOS Flat Panel Sensor, with a pixel size of 100 µm, revealed the presence of propagation‐based phase contrast and demonstrated significant improvement of the quality of phase‐contrast CT imaging compared with conventional (absorption‐based) CT, at medically acceptable radiation doses.     

Alteration of the profile of ink-jet-deposited UV-cured lenses using applied electric fields

Microlens arrays and microoptical components in general are integral components in a wide range of high-tech products. The ability to fabricate such elements cheaply and with a high degree of accuracy is vital for the development of the next generation of optics-based technologies. There are currently a wide range of microoptical element fabrication technologies. These techniques all have advantages and disadvantages and no one technique is yet sufficient to meet all possible application criteria. One method that has been examined recently is the ink-jet deposition method. This method applies well-established ink-jet printer technology and is thus one possible candidate for large-scale fabrication of inexpensive components. The lenses fabricated using this method are normally found to have spherical profiles. In this paper, we examine the possibility of modifying the profile of these spherical lenses using an applied electric field (E-field). We note that the resulting aspheric lenses have a wide number of applications. These include beam shaping and power transfer applications including fiber coupling. In this paper we describe initial experiments involving single lenses. The single lenses produced using applied E-Fields differ significantly from lenses produced with no applied E-field.     

Characterization of a didehydrobenzoxazine intermediate in a novel carbene-to-carbene transformation

Irradiation of N(2) matrix-isolated 3-chloro-3-(2-benzoxazolyl)diazirine gives a mixture of syn- and anti-benzoxazolylchlorocarbenes which could be characterized by IR, UV/vis, and B3LYP modeling. Subsequent irradiation of the carbene caused ring opening to the corresponding quinoimine, which was similarly characterized. In turn, the quinoimine photochemically underwent ring-closure to a novel, highly strained cyclic ketenimine. Unrestricted singlet DFT calculations were required to fit the IR spectrum of the ketenimine, suggesting significant diradical character. Photolysis of the ketenimine led to ring cleavage in yet another fashion, to give an isonitrile-phenoxychlorocarbene, whose spectra were similar to those of the previously characterized phenoxychlorocarbene. Finally, at shorter wavelengths, the phenoxycarbene underwent the expected rearrangement to the corresponding benzoyl chloride.