Requirements for long-life operation of inert gas hollow cathodes: Preliminary report

An experimental investigation was initiated to establish conditioning procedures for reliable hollow cathode operation via the characterization of critical parameters in a representative cathode test facility. From vacuum pumpdown rates, it was found that approximately 1.5 hours were required to achieve pressure levels within 5 percent of the lowest attainable pressure for this facility, depending on the purge conditions. The facility atmosphere was determined by a residual gas analyzer to be composed of primarily air and water vapor. The effects of vacuum pumping and inert gas purging were evaluated. A maximum effective leakage rate of 2.0 x 10(exp -3)sccm was observed and its probable causes were examined. An extended test of a 0.64 cm diameter Mo-Re hollow cathode was successfully completed. This test ran for 504 hours at an emission current of 23.0 amperes and a xenon flow rate of 6.1 sccm. Discharge voltage rose continuously from 15 to 21 volts over the course of the test. The temperature of the cathode body during the test was relatively stable at 1160 C. Post-test examination revealed ion-bombardment texturing of the orifice plate to be the only detectable sign of wear on the hollow cathode

Structural and thermal response of 30 cm diameter ion thruster optics

Tabular and graphical data are presented which are intended for use in calibrating and validating structural and thermal models of ion thruster optics. A 30 cm diameter, two electrode, mercury ion thruster was operated using two different electrode assembly designs. With no beam extraction, the transient and steady state temperature profiles and center electrode gaps were measured for three discharge powers. The data showed that the electrode mount design had little effect on the temperatures, but significantly impacted the motion of the electrode center. Equilibrium electrode gaps increased with one design and decreased with the other. Equilibrium displacements in excess of 0.5 mm and gap changes of 0.08 mm were measured at 450 W discharge power. Variations in equilibrium gaps were also found among assemblies of the same design. The presented data illustrate the necessity for high fidelity ion optics models and development of experimental techniques to allow their validation

The sensory screen: phenomenology of visual perception in early European avant-garde film

At the beginning of the twentieth century, certain artists, writers, and philosophers became intrigued by the profound ways in which filmic images could pervade aspects of modern thought and experience. For them, film had the potential to reveal radical new dimensions of sensory phenomena. The early development of avant-garde film-making in Europe is culturally crucial not only for its historical and conceptual context of creative transition, but also for its dynamic exploration of processes of visual perception. The central objective of this thesis is to expose and engage these profound perceptual issues within the specific sphere of graphic abstract film. The structural formation of the thesis entails the confluencing of material for analysis into a sequence of key areas comprising the central components of avant-garde cinematic visualisation. The visual implications of each area are analysed in specific depth, whilst acknowledging their respective interactivity. Significantly, the research applies analytic theories of phenomenology in order to focus incisively upon relevant early European avant-garde filmic imagery. The potential vitality of a phenomenological theorisation of early avant-garde film resides not only within their historical contemporaneity, but at the epistemological level of the mind's cognitive engagement with the realms of creative visualisation. It is a system of analysis which aims to establish a nuanced phenomenological theory of visual perception as a matter of prime sustenance to historically crucial cinematic art forms

Evaluating MI512: An information literacy course for PhD students

The purpose of this paper is to provide an overview of a six-week information literacy course for research students that was redesigned following the librarians undertaking the Postgraduate Certificate in Teaching in Higher Education. The paper presents a case study and evaluation of the impact of a teaching programme. Findings — Research students appreciate and value the expertise of library staff and are prepared to devote considerable time to an information literacy programme. The programme received excellent feedback. There is no summative assessment associated with the course and so no quantitative measure of improvement in learning. The paper provides a model programme other librarians can adapt for use at their own institution. Extended doctoral level information literacy courses are relatively uncommon and demonstrates the benefit of this type of course, to research

Tumour-cell susceptibility to cytotoxic or cytostatic effector cells in vitro and the regulation of tumour-cell growth in vivo.

Tumour-cell growth in lung nodules after i.v. transfer to sublethally irradiated mice has been followed after adoptive transfer of different populations of lymphoid cells. Spleen cells deliberately immunized in vitro and in vivo against stimulator cells bearing embryo-associated antigens and which are cytostatic in vitro for targets bearing such antigens, can diminish the number of lung nodules found after i.v. transfer. In contrast, cytotoxic (in vitro) spleen cells, while capable of diminishing local (s.c.) growth of tumour cells, cannot control systemic tumour growth. Within a given solid tumour mass, the subpopulations resistant to cytostatic effector cells in vitro are the ones most likely to produce lung colonies after adoptive transfer in vivo, though they show no more local (s.c.) growth than to cytostatic-sensitive cells in vivo

Making co-enrolment feasible for randomised controlled trials in paediatric intensive care.

Enrolling children into several trials could increase recruitment and lead to quicker delivery of optimal care in paediatric intensive care units (PICU). We evaluated decisions taken by clinicians and parents in PICU on co-enrolment for two large pragmatic trials: the CATCH trial (CATheters in CHildren) comparing impregnated with standard central venous catheters (CVCs) for reducing bloodstream infection in PICU and the CHIP trial comparing tight versus standard control of hyperglycaemia

Differing calcification processes in cultured vascular smooth muscle cells and osteoblasts

© 2019 Published by Elsevier Inc.Arterial medial calcification (AMC) is the deposition of calcium phosphate mineral, often as hydroxyapatite, inthe medial layer of the arteries. AMC shares some similarities to skeletal mineralisation and has been associatedwith the transdifferentiation of vascular smooth muscle cells (VSMCs) towards an osteoblast-like phenotype. Thisstudy used primary mouse VSMCs and calvarial osteoblasts to directly compare the established and widely usedin vitromodels of AMC and bone formation. Significant differences were identified between osteoblasts andcalcifying VSMCs. First, osteoblasts formed large mineralised bone nodules that were associated with widespreaddeposition of an extracellular collagenous matrix. In contrast, VSMCs formed small discrete regions of calcifi-cation that were not associated with collagen deposition and did not resemble bone. Second, calcifying VSMCsdisplayed a progressive reduction in cell viability over time (≤7-fold), with a 50% increase in apoptosis,whereas osteoblast and control VSMCs viability remained unchanged. Third, osteoblasts expressed high levels ofalkaline phosphatase (TNAP) activity and TNAP inhibition reduced bone formation by to 90%. TNAP activity incalcifying VSMCs was∼100-fold lower than that of bone-forming osteoblasts and cultures treated withβ-gly-cerophosphate, a TNAP substrate, did not calcify. Furthermore, TNAP inhibition had no effect on VSMC calci-fication. Although, VSMC calcification was associated with increased mRNA expression of osteoblast-relatedgenes (e.g. Runx2, osterix, osteocalcin, osteopontin), the relative expression of these genes was up to 40-foldlower in calcifying VSMCs versus bone-forming osteoblasts. In summary, calcifying VSMCsin vitrodisplay somelimited osteoblast-like characteristics but also differ in several key respects: 1) their inability to form collagen-containing bone; 2) their lack of reliance on TNAP to promote mineral deposition; and, 3) the deleterious effectof calcification on their viability.Peer reviewedFinal Published versio