Reactions involving di-trans-[12]annulenes

The low temperature complete dehydrohalogenation of pentabromocyclododecene (C12H17Br5) with potassium tert-butoxide in THF followed by exposure to potassium metal leads to the formation of the anion radical of 1,5-di-trans-[12]annulene, which loses hydrogen and undergoes ring closure to form the anion radical of 11,12-dihydro-[8]annuleno-[6]annulene. This product can, in turn, be isolated as its neutral molecule via reoxidation with iodine. A [12]annulene obtained via the dimerization of 1,5-hexadiyne in the presence of 18-crown-6 and potassium tert-butoxide undergoes ring closure, with concomitant loss of hydrogen, to yield the heptalene anion radical. It follows that the heptalene anion radical precursor was the 1,7-di-trans isomer of [12]annulene.     

Nonchromatographic "stir and filter approach" (SAFA) for isolating Sc3N@C80 metallofullerenes

Separation difficulties have led to a paucity of purified metallic nitride fullerenes (MNFs). Fundamental research and application development has been hampered with limited sample availability. Separation techniques designed to remove contaminant empty-cage fullerenes (e.g., C(60), C(70)...C(2)(n)) and classical metallofullerenes (e.g., non-MNFs) traditionally require expensive and tedious chromatographic methods. Our motivation is an alternative purification approach to minimize dependence on HPLC. Herein we report the use of cyclopentadienyl (CPD) and amino functionalized silica to selectively bind contaminant fullerenes. This "Stir and Filter Approach" (SAFA) provides purified MNF samples at ambient and reflux conditions. Under reflux conditions, purified MNFs (80% recovery, 41 h) are obtained using CPD silica. However, at room temperature, there is an equilibrium established between fullerenes and CPD silica, and no purified MNF samples are obtained using SAFA. In contrast, purified MNF samples (99+%) are readily obtained at room temperature using amino, diamino, and triamino silica at recoveries of 93% (11 h), 76% (9 h), and 50% (6 h), respectively.     

Preclinical radiotherapy at the Australian Synchrotron's Imaging and Medical Beamline: instrumentation,dosimetry and a small‐animal feasibility study

Therapeutic applications of synchrotron X‐rays such as microbeam (MRT) and minibeam (MBRT) radiation therapy promise significant advantages over conventional clinical techniques for some diseases if successfully transferred to clinical practice. Preclinical studies show clear evidence that a number of normal tissues in animal models display a tolerance to much higher doses from MRT compared with conventional radiotherapy. However, a wide spread in the parameters studied makes it difficult to make any conclusions about the associated tumour control or normal tissue complication probabilities. To facilitate more systematic and reproducible preclinical synchrotron radiotherapy studies, a dedicated preclinical station including small‐animal irradiation stage was designed and installed at the Imaging and Medical Beamline (IMBL) at the Australian Synchrotron. The stage was characterized in terms of the accuracy and reliability of the vertical scanning speed, as this is the key variable in dose delivery. The measured speed was found to be within 1% of the nominal speed for the range of speeds measured by an interferometer. Furthermore, dose measurements confirm the expected relationship between speed and dose and show that the measured dose is independent of the scan direction. Important dosimetric parameters such as peak dose, valley dose, the collimator output factor and peak‐to‐valley dose ratio are presented for 5 mm × 5 mm, 10 mm × 10 mm and 20 mm × 20 mm field sizes. Finally, a feasibility study on three glioma‐bearing rats was performed. MRT and MBRT doses were prescribed to achieve an average dose of 65 Gy in the target, and magnetic resonance imaging follow‐up was performed at various time points after irradiation to follow the tumour volume. Although it is impossible to draw conclusions on the different treatments with such a small number of animals, the feasibility of end‐to‐end preclinical synchrotron radiotherapy studies using the IMBL preclinical stage is demonstrated.     

Degradation of an Acetylene Terminated Sulfone (ATS) resin

A study of the rates and mechanisms of degradation of an acetylene terminated sulfone resin, more precisely, bis[4-(3-ethynyl phenoxy) phenyl] sulfone and its higher oligomers, under high vacuum conditions, and under a flowing atmosphere of nitrogen, was made using techniques such as programmed thermogravimetry (TG), Thermal Volatilization Analysis (TVA), and Sub Ambient Thermal Volatilization Analysis (SATVA). Gravimetric product analyses made in conjunction with quantitative Infrared and Nuclear Magnetic Resonance Spectroscopy were used to develop a quantitative product distribution for the process. By so doing, we established the sulfone residue as the thermal weak link in the system, and identified two overlapping processes of backbone polyphenylether thermal decomposition; a low temperature process involving scissions promoted by the sulfone moiety, and a higher temperature process involving more random scissions of residual sulfone free polyphenylethers.

---

Zusammenfassung Mittels TG, TVA und SATVA wurde eine Untersuchung der Reaktionsgeschwindigkeit und des Reaktionsmechanismus des Abbaues von Sulfonharz mit endständigem Acetylen (von bis-[4-(3-ethinylphenoxy)phenyl]sulfon und seiner höheren Oligomere) im Hochvakuum bzw. in einer dynamischen Stickstoffatmosphäre durchgeführt. In Verbindung mit quantitativer IR- und NMR-Spektroskopie wurde eine gravimetrische Analyse der Produkte erstellt, um eine quantitative Produktezusammensetzung des Prozesses zu erhalten. Der Sulfonrest konnte somit als schwaches Kettenglied des Systemes erkannt und zwei überlappende Prozesse der thermischen Zersetzung des hauptkettigen Polyphenylethers identifiziert werden: ein Prozess bei niedrigerer Temperatur beinhaltet durch die Sulfonkomponente geförderte Spaltungen und ein zweiter Prozess verursacht bei höherer Temperatur Random-Spaltungen des verbleibenden sulfonfreien Polyphenylethers.

---

---

W.T.K. Stevenson would like to acknowledge the financial assistance of the National Research Council who funded a Research Associateship at Wright Patterson Air Force Base for the duration of this work. In addition, both authors would like to offer thanks to Mr. J. Heines for his sound technical assistance, and to Mr. R. Grant who fabricated most of the glassware described here.     

Thermodynamic-kinetic correlations in supercooled liquids: a critical survey of experimental data and predictions of the random first-order transition theory of glasses

Thermodynamics and kinetics are thought to be linked in glass transitions. The quantitative predictions of alpha-relaxation activation barriers provided by the theory of glasses based on random first-order transitions are compared with the experimental results for 44 substances. The agreement found between the predicted activation energies near T(g) and experiment is excellent. These predictions depend on the configurational heat capacity change on vitrification and the entropy of melting the crystal which are experimental inputs.     

Higgs Fields,Bundle Gerbes and String Structures

We use bundle gerbes and their connections and curvings to obtain an explicit formula for a de Rham representative of the string class of a loop group bundle. This is related to earlier work on calorons.Both authors acknowledge the support of the Australian Research Council.     

Stationary Headband for Clinical Time-of-Flight Optical Imaging at the Bedside

Conventional brain-imaging modalities may be limited by high cost, difficulty of bedside use, noncontinuous operation, invasiveness or an inability to obtain measurements of tissue function, such as oxygenation during stroke. Our goal was to develop a bedside clinical device able to generate continuous, noninvasive, tomographic images of the brain using low-power nonionizing optical radiation. We modified an existing stage-based time-of-flight optical tomography system to allow imaging of patients under clinical conditions. First, a stationary headband consisting of thin, flexible optical fibers was constructed. The headband was then calibrated and tested, including an assessment of fiber lengths, the existing system software was modified to collect headband data and to perform simultaneous collection of data and image reconstruction, and the existing hardware was modified to scan optically using this headband. The headband was tested on resin models and allowed for the generation of tomographic images in vitro; the headband was tested on critically ill infants and allowed for optical tomographic images of the neonatal brain to be obtained in vivo.     

A new steroid aromatization rearrangement involving inversion of sidechain configuration

The bile acid, cholic acid, has been transformed into 3α-hydroxy-12-methyl-18-nor-5β, 17α-chola-8,11,13-trien-24-oic acid. The constitution of this novel type of steroid (benzenoid C-ring with 17α-sidechain) has been supported by chemical degradation, and confirmed by crystal structure analysis of the methyl ester iodoacetate derivative.