Search

Your search keyword '"MacDonald, D"' showing total 6,201 results
Start Over Author "MacDonald, D"
6,201 results on '"MacDonald, D"'

15. Dopant-Free Partial Rear Contacts Enabling 23% Silicon Solar Cells

Author

Bullock, J, Wan, Y, Hettick, M, Zhaoran, X, Phang, SP, Yan, D, Wang, H, Ji, W, Samundsett, C, Hameiri, Z, Macdonald, D, Cuevas, A, and Javey, A

Subjects
selective contacts, silicon photovoltaics, titanium oxide, Macromolecular and Materials Chemistry, Materials Engineering, Interdisciplinary Engineering
Abstract

Over the past five years, there has been a significant increase in both the intensity of research and the performance of crystalline silicon devices which utilize metal compounds to form carrier-selective heterocontacts. Such heterocontacts are less fundamentally limited and have the potential for lower costs compared to the current industry dominating heavily doped, directly metalized contacts. A low temperature (≤230 °C), TiO x /LiF x /Al electron heterocontact is presented here, which achieves mΩcm 2 scale contact resistivities ρ c on lowly doped n-type substrates. As an extreme demonstration of the potential of this heterocontact, it is trialed in a newly developed, high efficiency n-type solar cell architecture as a partial rear contact (PRC). Despite only contacting ≈1% of the rear surface area, an efficiency of greater than 23% is achieved, setting a new benchmark for n-type solar cells featuring undoped PRCs and confirming the unusually low ρ c of the TiO x /LiF x /Al contact. Finally, in contrast to previous versions of the n-type undoped PRC cell, the performance of this cell is maintained after annealing at 350–400 °C, suggesting its compatibility with conventional surface passivation activation and sintering steps.

Published
2019

22. A genetic algorithm approach to fitting interferometric data of post-AGB objects: I. the case of the Ant nebula

Author

Macdonald, D., De Marco, Orsola, Lagadec, Eric, Ma, Jun, and Chesneau, O.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We present GADRAD, a Python module that adopts heuristic search techniques in the form of genetic algorithms, to efficiently model post-asymptotic giant branch (post- AGB) disc environments. GADRAD systematically constructs the multi-dimensional pa- parameter probability density functions that arise from the fitting of radiative transfer and geometric models to optical interferometric data products. The result provides unbiased descriptions of the object's potential morphology, component luminosities and temperatures, dust composition, disc density profiles and mass. Correlation in the estimated parameters as well as potential degeneracies are revealed. Estimated probability distributions of the post-AGB environment parameters provide insight into the shaping processes that may occur in the transition from the post-AGB to the planetary nebula phase. We test parameter recovery on simulated artificial data products of a typical post-AGB environment. We then use GADRAD to model the mid-infrared spectrum and visibilities of the Ant nebula (Mz3), taken with the Very Large Telescope Interferometer's instrument MIDI. Our result is consistent with a large dusty disc with similar parameter values to those previously found by Chesneau et al., except for a larger dust mass of $3.5^{+7.5}_{-2.2}\times10^{-5}$ M$_{\odot}$. The parameter confidence intervals determined by GADRAD, can however be relied upon to impose additional constraints on all disc and system parameters. Based on our analysis and other considerations, we tentatively suggest that Mz3 is a pre-PN ejected during a magnetic (polar) common envelope interaction, where the binary may or may not have survived at the core of the nebula., Comment: Could not address reviewer's comments in timely manner

Published
2017

25. Pan-Canadian consensus recommendations for GIST management in high- and low-throughput centres across Canada.

Author

Beecroft, J. Robert, Brar, Savtaj, Feng, Xiaolan, Hamilton, Trevor, Han-Lee, Cheng, Henning, Jan-Willem, Josephy, P. David, Khalili, Korosh, Ko, Yoo-Joung, Lemieux, Christopher, Liu, David M., MacDonald, D. Blair, Noujaim, Jonathan, Pollett, Aaron, Salawu, Abdulazeez, Saleh, Ramy, Smrke, Alannah, Warren, Blair E., Zbuk, Kevin, and Razak, Albiruni Abdul

Abstract

Gastrointestinal stromal tumours (GISTs) are mesenchymal tumours that originate from the interstitial cells of Cajal. GISTs are mainly driven by gain-of-function mutations in receptor tyrosine kinase or platelet-derived growth factor receptor alpha. Surgical resection is the only curative treatment for localized tumours and all currently approved medical GIST treatments are based on orally available tyrosine kinase inhibitors. Recent discoveries in the molecular and clinical features of GISTs have greatly impacted GIST management. Due to the provincially rather than nationally administered Canadian healthcare system, there have been inconsistencies in the treatment of GISTs across the country. Therefore, guidance on the latest knowledge, clinical management and treatment of GIST is needed to standardize the approach to GIST management nationwide. To establish pan-Canadian guidance, provide up-to-date data and harmonize the clinical practice of GIST management in high- and low-throughput centres across Canada; a panel of 20 physicians with extensive clinical experience in GIST management reviewed relevant literature. This included radiologists, pathologists, interventional radiologists, surgeons and medical oncologists across Canada. The structured literature focused on seven key domains: molecular profiling, radiological techniques/reporting, targeted localized therapy, intricacies of systemic treatments, emerging tests, multidisciplinary care and patient advocacy. This literature review, along with clinical expertise and opinion, was used to develop this concise and clinically relevant consensus paper to harmonize the knowledge and clinical practice on GIST management across Canada. The content presented here will help guide healthcare providers, especially in Canada, in terms of approaching and managing GIST. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

32. Lentiviral vector vaccines for T-cell-mediated protection against influenza

Author

Macdonald, D., Collins, M. K., Rosenberg, W. M. C., and Maini, M. K.

Subjects
616
Abstract

Vaccines that induce T cells which recognize conserved viral proteins could confer cross-strain protection against pathogens with fast-mutating B cell epitopes. Influenza is an example of such a pathogen for which there is a pressing need for a universal vaccine. Lentiviral vectors are a counterintuitive choice as vaccines since they have low inherent immunogenicity. However, their efficient transduction of non-dividing cells and high capacity permits transduction of antigen presenting cells with not only antigen but also molecular adjuvants that directly or indirectly enhance the T cell response. We therefore investigated the potential of two such adjuvants: viral flice-like inhibitor protein, which activates dendritic cells through nuclear factor kappa-B, and 4-1BB ligand, which activates T cells directly through 4-1BB. By co-encoding these with influenza nucleoprotein, we have shown that the influenza-specific T cell response to lentiviral vector vaccination is significantly enhanced in mice. Furthermore, we have demonstrated that intranasally delivered lentiviral vectors transduce alveolar macrophages with high efficiency, recalling and expanding large and sustained populations of nucleoprotein-specific CD8+ T cells in the lung and airway in mice that have been primed subcutaneously or previously exposed to influenza. These lung-resident T cell populations persist for at least 4 months and are sufficiently abundant to rapidly control a mouse-adapted lethal influenza challenge without invocation of a secondary cytokine response, weight loss or lung injury. Furthermore, dendritic cells expressing 4-1BBL potently trans-activate bystander dendritic cells, both in vitro and in vivo, demonstrating an indirect mechanism by which the 4-1BBL:4-1BB signaling axis can enhance T cell responses.

Published
2014

45. Observation of Cen A by the Rossi X-ray Timing Explorer

Author

Rothschild, R. E., Band, D. L., Blanco, P. R., Gruber, D. E., Heindl, W. A., MacDonald, D. R., Marsden, D. C., Jahoda, K., Pierce, D., Madejski, G., Elvis, M., Schwartz, D. A., Remillard, R., Zdziarski, A. A., Done, C., and Svensson, R.

Subjects
Astrophysics
Abstract

The Rossi X-ray Timing Explorer made a short (10 ks) observation of the radio galaxy Centaurus A on 14 August 1996. Analysis of the combined 2.5-240 keV spectrum has revealed a heavily absorbed(NH=9.42+/-0.24 e22 cm-2) primary power law (index=1.86+/-0.015) and an iron line due to fluorescence of cold matter (EW=162+/-25 eV). Flux from either a jet, primary flux scattered into the line of sight, or primary flux seen through a partial absorber was not required. The iron line width is unresolved at the 95% confidence level (sigma < 0.54 keV). No significant variability in the iron line flux is seen from measurements over the last two decades, while the overall continuum flux varied by more than a factor of four, which implies that the line emission region is distant from that of the primary emission. While radio-quiet Seyfert galaxies exhibit spectral components attributable to Compton reflection from cold matter, Cen A reveals no such component (exposed solid angle ratio < 0.09). This supports unified models of active galaxies that have little difference between Seyfert 2 and low luminosity radio galaxies, Comment: 24 pages, 3 figures, accepted to The Astrophysical Journal

Published
1998
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results