Magnetic properties of microtektites Semiannual status report, 1 Jan. - 31 Jun. 1969

Magnetic susceptibility, magnetization, and Curie constants for normal and bottle-green microtektites found in deep-sea sediment core

NMR Investigation of the Low Temperature Dynamics of solid 4He doped with 3He impurities

The lattice dynamics of solid 4He has been explored using pulsed NMR methods to study the motion of 3He impurities in the temperature range where experiments have revealed anomalies attributed to superflow or unexpected viscoelastic properties of the solid 4He lattice. We report the results of measurements of the nuclear spin-lattice and spin-spin relaxation times that measure the fluctuation spectrum at high and low frequencies, respectively, of the 3He motion that results from quantum tunneling in the 4He matrix. The measurements were made for 3He concentrations 16<x_3<2000 ppm. For 3He concentrations x_3 = 16 ppm and 24 ppm, large changes are observed for both the spin-lattice relaxation time T_1 and the spin-spin relaxation time T_2 at temperatures close to those for which the anomalies are observed in measurements of torsional oscillator responses and the shear modulus. These changes in the NMR relaxation rates were not observed for higher 3He concentrations.Comment: 23 pages, 10 figure

Effect of delayed acquisition times on Gadolinium-enhanced MRI of the presumably normal canine brain

A delay in imaging following intravenous contrast medium administration has been recommended to reduce misdiagnoses. However, the normal variation of contrast enhancement in dogs following a delay has not been characterized. Contrast enhanced MR imaging of 22 dogs was assessed, in terms of identification of normal anatomic structures, to investigate the variation associated with 10 minute delay between contrast medium administration and imaging. All dogs had a normal brain MR imaging study and unremarkable CSF. Specific ROIs were assessed both objectively, using computer software, and subjectively using three observers. Mean contrast enhancement greater than 10% was seen in the pituitary gland, choroid plexus, meninges, temporal muscle, trigeminal nerve and the trigeminal nerve root. Structures with an active blood-brain-barrier had minimal contrast enhancement (&#60;6%). Enhancing structures had significantly more contrast enhancement at t=1min versus t=10min, except in temporal muscle, the trigeminal nerve and the trigeminal nerve root. Inter-observer agreement was moderate to good in favor of the initial post contrast T1w sequence. The observers found either no difference or poor agreement in identification of the non-vascular structures. Intra-observer agreement was very good with all vascular structures and most non-vascular structures. A degree of meningeal enhancement was a consistent finding. The initial acquisition had higher enhancement characteristics and observer agreement for some structures; however, contrast-to-noise was comparable in the delayed phase or not significantly different. We provide baseline references and suggest that the initial T1w post contrast sequence is preferable but not essential should a delayed post contrast T1w sequence be performed

Why HITnet kiosks didn\u27t hit the mark for sexual health education of Western Australian Aboriginal youth

Objective: To assess the use, appropriateness of, and staff feedback on specific sexual health modules, which were installed on Heuristic Interactive Technology (HITnet) kiosks at Aboriginal Community Controlled Health Services (ACCHS). The HITnet kiosks were aimed at Aboriginal youth visiting these sites. Methods: Modules on the HITnet kiosks were assessed for (1) cultural appropriateness using Yunkaporta’s Aboriginal pedagogy framework and (2) compliance with the World Health Organization’s (WHO) advice on key elements for comprehensive sexual health education for young people. Data measuring kiosk use were obtained through HITnet kiosk activity reports. An online survey of ACCHS staff was used to qualitatively assess use of, and staff perceptions of, HITnet kiosks. Results: Kiosk modules were consistent with seven of the eight elements of Yunkaporta’s framework and all of the WHO recommendations. The most popular module generated 3,066 purposeful sessions and the least popular module generated 724 purposeful sessions across nine sites in 2012. While teenagers were the most frequent of the kiosk user groups (39.5% in 2012), the majority of users (56%) were not in the target group (i.e. elders 4%, adults 25%, children 27%). Key issues reported by ACCHS staff (n=11) included: lack of clarity regarding staff responsibility for overseeing kiosk functionality; kiosks attracting “inappropriate ages”; and “lack of privacy” based on kiosk location, screen visibility, and absence of headphones preventing discreet access. Conclusions: The modules were tailored to a young Aboriginal audience through technology thought to be appealing to this group. However, barriers to use of the kiosk included kiosk design features, location, and lack of clarity around responsibility for kiosk operation. Implications: Aboriginal youth need easy access to sexual health messages in a ‘safe’, non-judgmental space. Information and communication that is accessible via personal and mobile devices may be a better vehicle than public kiosks

Impact of disorder on the 5/2 fractional quantum Hall state

We compare the energy gap of the \nu=5/2 fractional quantum Hall effect state obtained in conventional high mobility modulation doped quantum well samples with those obtained in high quality GaAs transistors (heterojunction insulated gate field-effect transistors). We are able to identify the different roles that long range and short range disorders play in the 5/2 state and observe that the long range potential fluctuations are more detrimental to the strength of the 5/2 state than short-range potential disorder.Comment: PRL 106, 206806 (2011

Aerothermal modeling program, phase 2

The main objectives of the Aerothermal Modeling Program, Phase 2 are: to develop an improved numerical scheme for incorporation in a 3-D combustor flow model; to conduct a benchmark quality experiment to study the interaction of a primary jet with a confined swirling crossflow and to assess current and advanced turbulence and scalar transport models; and to conduct experimental evaluation of the air swirler interaction with fuel injectors, assessments of current two-phase models, and verification the improved spray evaporation/dispersion models