Showing papers by "British Columbia Institute of Technology published in 2000"

Uncertainty and expectations: taking care of a cardiac surgery patient at home.

Abstract: Family members of postsurgical patients are, by necessity, taking on the caregiving role sooner without any specified resources to help them. The input of these caregivers is essential so nurses can understand their concerns, needs, and struggles and develop strategies to support the caregivers in their caregiving role. This study was designed to increase nursing knowledge regarding the experiences of being a caregiver of a cardiac surgery patient during the immediate postdischarge period. The qualitative research method of Interpretative Description, first described by Thorne, Kirkham, and MacDonald-Emes in 1997 guided the study. In-depth interviews were held with eight spousal caregivers. Findings revealed that the experience was molded by caregivers' past participation as a caregiver, as well as caregivers' and care recipients' outlook on life, their interpersonal relationship, and their expectations. Caregivers engaged in the process of caregiving that involved being vigilant and monitoring the care recipient's recovery, implementing strategies to assist the recovery process, and taking on a role to provide care and seek help as required. The encounter with caregiving affected all realms of caregivers' lives, and they experienced feelings of stress, vulnerability, and having to put their lives on hold; these feelings were often compounded by uncertainty.

Maximum power point tracking for building integrated photovoltaic ventilation systems

Abstract: The objective of this project was to design a device to optimize the interface of a building integrated photovoltaic (BIPV) array with ventilation fans. The developed device tracks the maximum power point of the BIPV array and limits the output voltage to the level required by the fans. The purpose of maximum power point tracking (MPPT) is to automatically match the current and voltage characteristics of the load to the BIPV array's maximum power point at any given illumination. To accomplish this a unique switch mode buck converter was used. The available power from the PV array is a total of approximately 2.5 kW. The two PV sub-arrays supply a voltage up to 220 VDC each and have a maximum power point voltage of 169 VDC. The load consists of two sets of six 133 W, 90 VDC ventilation fans. The device also has a soft-start circuit on board to start the motors slowly to avoid excessive current requirements from the array. This unit achieves efficiencies above 93%.

Enzyme Treatments of the Dissolved and Colloidal Substances Present in Mill White Water and the Effects on the Resulting Paper Properties

Abstract: The composition of the dissolved and colloidal fractions of a “model” white water prepared from a spruce-pine-fir/hemlock thermomechanical pulp was determined. The impact of these fractions on paper properties was assessed and the ability of enzymes to degrade the different components was investigated. The colloidal particles in the white water had an average size of 0.5 μm and a size range from 0.1 μm to 2 μm. Lignins, resin and fatty acids, and esterified extractives, such as sterol esters and triglycerides, were the main constituents of the colloidal particles, while the lignans and neutral polysaccharides were predominantly dissolved in the white water. Reductions in paper strength were mainly caused by the dissolved substances, whereas the colloidal substances were primarily responsible for the reduction in paper porosity and optical properties. Added laccases were able to degrade most of the extractives while lipases specifically hydrolyzed esterified extractives present in the colloidal fr...

A compliance-independent pressure transducer for biomedical device-tissue interfaces.

Abstract: The measurement of the interface pressure between a biomedical device and part of the human body is useful to improve the performance and safety of such devices during design. Testing of a selection of existing interface pressure transducers has demonstrated that many are dependent on device and tissue compliance. Such a transducer is useful only in an application where it has been calibrated for specific device-tissue compliance combinations. To overcome this limitation, the authors developed an interface pressure transducer whose output signal is not affected by changes in interface compliance. This enables the transducer to quantitatively measure pressure in many applications without the need to calibrate it for varying compliance conditions. Surgical retraction and surgical tourniquets were selected as demonstration applications for the developed transducer, because they represent a wide spectrum of device and tissue characteristics and properties, and are in common use.

NEMA NU 2-2000 performance measurements on an ADAC MCD camera

Abstract: The clinically oriented NEMA NU-2 2000+ performance standards have been performed on an ADAC molecular coincidence detection dual-head camera. At 1 cm radius, the transverse resolution full-width at half-maximum was measured to be 5.2 (10.0) mm and the axial was 5.0 (10.6) mm. At 10 cm radius, the transverse radial resolution was 4.7 (7.4) mm and the transverse tangential was 8.5 (20.9) mm. The axial resolution was 14.0 (41.1) mm. The peak true count rate was 4370 counts/s at a concentration of 4.3 kBq/ml. The peak noise equivalent count rate (NECR) was 1620 counts/s at 2.9 kBq/ml. The system scatter fraction was 48%, The maximum relative count rate error observed at the NECR peak was -42%. The sensitivity was 1010 counts/sm/rSq in the center and 870 counts/s/MBq at an offset of 10 cm. The contrast for the hot spheres ranged from 18.5 (11.6)% to 11.6 (7.9)% for a contrast ratio of 8:1 (4:1). For the cold spheres, it ranged from 41% to 25% with an overall background variability of 7%. The residual error in scatter and attenuation correction was approximately 50%. All measurements were performed at the maximum allowed crystal-to-crystal distance of 810 mm.

Quantum Computation in Brain Microtubules? Decoherence and Biological Feasibility

Abstract: The Penrose-Hameroff (`Orch OR') model of quantum computation in brain microtubules has been criticized as regards the issue of environmental decoherence. A recent report by Tegmark finds that microtubules can maintain quantum coherence for only $10^{-13}$ s, far too short to be neurophysiologically relevant. Here, we critically examine the assumptions behind Tegmark's calculation and find that: 1) Tegmark's commentary is not aimed at an existing model in the literature but rather at a hybrid that replaces the superposed protein conformations of the `Orch OR' theory with a soliton in superposition along the microtubule, 2) Tegmark predicts decreasing decoherence times at lower temperature, in direct contradiction of the observed behavior of quantum states, 3) recalculation after correcting Tegmark's equation for differences between his model and the `Orch OR' model (superposition separation, charge vs. dipole, dielectric constant) lengthens the decoherence time to $10^{-5} - 10^{-4}$ s and invalidates a critical assumption of Tegmark's derivation, 4) incoherent metabolic energy supplied to the collective dynamics ordering water in the vicinity of microtubules at a rate exceeding that of decoherence can counter decoherence effects (in the same way that lasers avoid decoherence at room temperature), and 5) phases of actin gelation may enhance the ordering of water around microtubule bundles, further increasing the decoherence-free zone by an order of magnitude and the decoherence time to $10^{-2} - 10^{-1}$ s. These revisions bring microtubule decoherence into a regime in which quantum gravity can interact with neurophysiology.

Monte Carlo investigation of scatter in dual head coincidence imaging

Abstract: Scatter is a major problem in dual head coincidence imaging using 3D acquisition. We investigated the scatter response in an ADAC Vertex MCD camera using Monte Carlo simulations. Simulations of different cylindrical phantoms were done to compare with measured values. These show agreement in the relative scatter fraction distribution but underestimate the magnitude of the scatter. The simulation bins by number of scatters to allow the relative contribution from single and multiple scatter to be determined. Results for the NEMA scatter phantom yield global multiple scatter fractions (multiple over total scatter) of 16% in p-p mode and 29% in p-C mode, which do not vary axially. Simulations of a digital anthropomorphic phantom were then done to assess scatter in clinical situations. These showed global scatter fractions 37% to 48% in p-C acquisition for different activity distributions and positioning, significantly higher than from cylindrical phantoms. The global multiple scatter fractions were also higher for the anthropomorphic phantom with values from 31% to 48% in p-C mode. The distributions from the anthropomorphic phantom also showed that the scatter fractions and multiple scatter fractions varied axially and with source distribution and positioning. The characterization of scatter is valuable in guiding scatter correction strategies.