Stellar Masses of High-Redshift Galaxies

We present constraints on the stellar-mass distribution of distant galaxies. These stellar-mass estimates derive from fitting population-synthesis models to the galaxies' observed multi-band spectrophotometry. We discuss the complex uncertainties (both statistical and systematic) that are inherent to this method, and offer future prospects to improve the constraints. Typical uncertainties for galaxies at z ~ 2.5 are ~ 0.3 dex (statistical), and factors of ~ 3 (systematic). By applying this method to a catalog of NICMOS-selected galaxies in the Hubble Deep Field North, we generally find a lack of high-redshift galaxies (z > 2) with masses comparable to those of present-day ``L*'' galaxies. At z < 1.8, galaxies with L*-sized masses do emerge, but with a number density below that at the present epoch. Thus, it seems massive, present-day galaxies were not fully assembled by z ~ 2.5, and that further star formation and/or merging are required to assemble them from these high-redshift progenitors. Future progress on this subject will greatly benefit from upcoming surveys such as those planned with HST/ACS and SIRTF.Comment: 7 pages, 5 figures. To appear in The Mass of Galaxies at Low and High Redshift, eds. R. Bender & A. Renzini (ESO Astrophysics Symposia, Springer-Verlag), Venice, 24-26 Oct 200

Lyman Break Galaxies in the NGST Era

With SIRTF and NGST in the offing, it is interesting to examine what the stellar populations of z~3 galaxies models imply for the existence and nature of Lyman-break galaxies at higher redshift. To this end, we ``turn back the clock'' on the stellar population models that have been fit to optical and infrared data of Lyman-break galaxies at z~3. The generally young ages (typically 10^8 +- 0.5 yr) of these galaxies imply that their stars were not present much beyond z=4. For smooth star-formation histories SFR(t) and Salpeter IMFs, the ionizing radiation from early star-formation in these galaxies would be insufficient to reionize the intergalactic medium at z~6, and the luminosity density at z~4 would be significantly lower than observed. We examine possible ways to increase the global star-formation rate at higher redshift without violating the stellar-population constraints at z~3.Comment: To appear in "The Mass of Galaxies at Low and High Redshift", ed. R. Bender and A. Renzini, ESO Astrophysics Symposia, Springer-Verlag 7 Pages, 2 figure

To Sell and to Provide? The Economic and Environmental Implications of the Auto Manufacturer's Involvement in the Car Sharing Business

Motivated by the involvement of Daimler and BMW in the car sharing business we consider an OEM who contemplates introducing a car sharing program. The OEM designs its product line by accounting for the trade-off between driving performance and fuel efficiency. Customers have different valuations of driving performance and decide whether to buy, join car sharing, or rely on their outside option. Car sharing can increase the profit from selling. This happens when the OEM prefers to serve the lower-end customers through car sharing and the higher-end through selling. In this case, car sharing increases the efficiency of the vehicles used for the lower-end, and the price charged to the higher-end customers. This is more pronounced for higher-end OEMs, which may help explain Daimler's and BMW's involvement in car sharing. Despite the higher efficiency, car sharing may lower the OEM's Corporate Average Fuel Economy (CAFE) level even when it increases profit and decreases environmental impact. CAFE levels better reflect the environmental benefits of car sharing when they are based on the number of customers served and not the production volume. Finally, if anticipating aggressive CAFE standards, OEMs may include car sharing to better absorb the increase in the production cost

"Hard Racket for a Living" — Making Light-Salted Fish on the East Coast of Newfoundland

This paper describes drying fish, the final phase in the processing of cod in the Newfoundland salt fisheries. Three themes regarding this work emerge: its remarkable labour intensiveness; the complex techniques and knowledge required; and the key roles women played in "making fish." Fishing people's evaluations of this work indicate seemingly contradictory positions: one typifies it and its way of life as sheer thankless toil, the other recalls these with satisfaction, even pleasure. I highlight the latter, neglected view and so begin the project of re-evaluating received academic/bureaucratic interpretations of the salt fisheries and the women and men who worked in them. Résumé Ce document décrit le séchage du poisson, dernière étape du traitement de la morue dans l'industrie de la pêche en eau salée à Terre-Neuve. Trois thèmes ressortent de ce travail : la quantité remarquable de main-d'œuvre qu'il exige, la complexité des techniques et connaissances requises, et le rôle essentiel des femmes dans l'art de « faire du poisson ». L'évaluation de ce travail par les intéressés indique des opinions apparemment contradictoires : certains le caractérisent, avec le mode de vie qu'il entraîne, comme un labeur purement ingrat, alors que d'autres se le rappellent avec satisfaction et même plaisir. L'auteur souligne cette dernière opinion, négligée, et s'attelle ainsi à la tâche de réexaminer les idées reçues d'universitaires ou de bureaucrates sur l'industrie de la pêche et sur les hommes et les femmes qui y ont œuvré

Contributions à l’intégration des procédés de fabrication et d'encapsulation d’un commutateur MEMS RF ohmique

Abstract : This dissertation presents studies to resolve process integration problems in the fabrication of packaged radio frequency microelectromechanical system (RF MEMS) ohmic switches with a Au-Ru contact metallurgy and Al-Ge eutectic wafer bonding for wafer-level packaging (WLP). While unpackaged RF MEMS switches have shown promising attributes poor reliability has limited their development into practical products, demanding compatibility with a hermetic sealing solution. The first article, titled ‘Exploring Ru compatibility with Al-Ge eutectic wafer bonding,’ and its supplemental material examine bond impacts associated with the refractory metal ruthenium (Ru). The compatibility of Ru with a wafer bonding process has been virtually unexplored. The main text of this section outlines the results of blanket deposition annealing experiments with Ru, Al and Ge configurations to address concerns of ternary alloy poisoning, melt wettability on Ru, and Ru as a diffusing contaminant in Al and Ge. A brief exploration of the composition process window for Al-Ge alloys contaminated with Ru is made from available phase diagrams, and strong bond outcomes with real product wafers with Ru contacts are presented. The article concludes that Ru has high compatibility within an expected narrow composition process window of marginally reduced melting temperature for Al-Ge alloy. Supplemental material addresses additional process integration problems in the real bond process associated with Ru: alumina thickening, Ru contamination and Al hillock aggravation. These are challenges for the Al surface, which progressively loses bonding ability with Ge through the fabrication process, and can be obviated with unprocessed bonding Al without Ru exposure. The second article, titled ‘Mitigating re-entrant etch profile undercut in Au etch with an aqua regia variant,’ and its supplemental material examine processed Au outcomes and bond-on-contact consequences primarily inflicted on Au. Thermally-stable Au metallization to Si for microswitch contacts in packaged devices is a considerable integration challenge. The main text of this section outlines an etch profile investigation of Au metallization stack variants with adhesion layers to discriminate delamination-based undercutting from galvanic undercutting when using an aqua regia-based solution, showing which mechanism is applicable for this etchant. A brief examination of the electrochemistry of the etchant is made to explain the unusual outcome of mitigated galvanic undercut confirmed by this analysis, with delamination control eliminating or minimizing undercut for thick Au films. In the supplemental material Au surface evolution is tracked across the fabrication process, with the wafer bonding thermal cycle being deemed most significant. Au hillocking and delamination are the primary challenges, and segmentation of Au features is a leading mitigation option that increases the impact of any Au undercut. Together these chapters develop an improved understanding of contact/bond compatibility. Necessary and promising future work for RF MEMS microfabrication and packaging is outlined at the conclusion of this dissertation.Cette thèse présente des études visant à résoudre les problèmes d’intégration de procédés dans la fabrication de commutateurs radiofréquence ohmiques de systèmes microélectromécaniques de (RF MEMS) encapsulés par une métallurgie de contact Au-Ru et un collage eutectique de gaufres Al-Ge pour l'encapsulation au niveau des gaufres (Wafer-Level Packaging, WLP). Bien que les commutateurs MEMS RF non encapsules aient montré des attributs prometteurs, leur faible fiabilité a limité leur développement en produits pratiques, exigeant la compatibilité avec une solution de collage hermétique. Le premier article, intitulé ‹‹Exploring Ru compatibility with Al-Ge eutectic wafer bonding››, et son supplément examinent les effets de liaison associés au ruthénium (Ru), un métal réfractaire. La compatibilité du Ru avec un procédé de collage de gaufres a été très par inexplorée. Le texte principal de cette section présente les résultats d'expériences de recuit des dépôts pleine plaque avec des configurations de Ru, Al et Ge pour répondre aux préoccupations concernant l'empoisonnement des alliages ternaires, la mouillabilité de la masse fondue sur le Ru, et le Ru en tant que contaminant diffusant dans Al et Ge. Une brève exploration de la fenêtre de procédé de composition pour les alliages Al-Ge contaminés par Ru est faite à partir des diagrammes de phase disponibles, et des résultats de collage fort avec des gaufres de produits réels avec des contacts Ru sont présentés. L'article conclut que Ru a une compatibilité élevée dans une fenêtre de procédé de composition étroite attendue de température de fusion marginalement réduite pour l'alliage Al-Ge. Des documents complémentaires traitent de problèmes d'intégration autres dans le procédé de collage réel associés au Ru: épaississement de l'alumine, contamination par le Ru et aggravation de la topographie d'Al. Il s'agit de défis pour la surface de l'aluminium, qui perd progressivement sa capacité de collage avec le Ge au cours du procédé de fabrication, et qui peuvent être évités avec de l'aluminium de collage non traité sans exposition au Ru. Le deuxième article, intitulé ‹‹Mitigating re-entrant etch profile undercut in Au etch with an aqua regia variant››, et son matériel supplémentaire examinent les résultats de la gravure de l'Au et les conséquences de la liaison sur le contact principalement infligées à l'Au. La métallisation thermiquement stable de l'Au sur le Si pour les contacts dans les dispositifs encapsulés est un défi d'intégration considérable. Le texte principal de cette section décrit une étude sur le profil de gravure de variantes d'empilement de métallisation Au avec des couches d'adhérence pour distinguer la sous-coupe basée sur la délamination de la sous-coupe galvanique lors de l'utilisation d'une solution à base d'eau régale, montrant quel mécanisme est applicable pour ce réactif de gravure. Un bref examen de l'électrochimie de l'agent de gravure est effectué pour expliquer le résultat inhabituel de la surgravure galvanique atténuée confirmée par cette analyse, le contrôle de la délamination éliminant ou minimisant la surgravure pour les films d'Au épais. Dans les documents complémentaires, l'évolution de la surface de l'or est suivie tout au long du procédé de fabrication, le cycle thermique de collage des gaufres étant considéré comme le plus important. La formation de bosses et le délaminage de l'or sont les principaux défis à relever, et la segmentation des caractéristiques de l'or est une option d'atténuation importante qui augmente l'impact de toute contre-dépouille de l'or. Ensemble, ces chapitres permettent de mieux comprendre la compatibilité contact/liaison. Les travaux futurs nécessaires et prometteurs pour la microfabrication et le conditionnement des MEMS RF sont présentés en conclusion de cette thèse

An investigation into the adoption of CDIO in distance learning

The Conceive, Design, Implement and Operate Initiative (CDIO) uses integrated learning to develop deep learning of the disciplinary knowledge base whilst simultaneously developing personal, interpersonal, product, process and system building skills. This is achieved through active and experiential learning methods that expose students to experiences engineers will encounter in their profession. These are incorporated not only in the design-build-test experiences that form a crucial part of a CDIO programme but also in discipline focused studies. Active and experiential learning methods are, of course, more difficult to incorporate into distance education. This paper investigates these difficulties and the implications in providing a programme that best achieves the goals of the CDIO approach through contemporary distance education methods. First, the key issues of adopting the CDIO approach in conventional oncampus courses are considered with reference to the development of the CDIO engineering programmes at the University of Liverpool. The different models of distance based delivery of engineering programmes provided by the Open University in the UK, and Deakin University and the University of Southern Queensland in Australia are then presented and issues that may present obstacles to the future adoption of the CDIO approach in these programmes are discussed. The effectiveness and suitability of various solutions to foreseen difficulties in delivering CDIO programmes through distance education are then considered. These include the further development, increased use and interinstitutional sharing of technology based facilities such as Internet facilitated access to laboratory facilities and computer aided learning (CAL) laboratory simulations, on campus workshops, and the development of a virtual engineering enterprise

Measuring Default Risk Premia from Default Swap Rates and EDFs

This paper estimates the degree of variation over time in the price for bearing exposure to U.S. corporate default risk during 2000-2004, based on the relationship between default probabilities, as estimated by Moody’s KMV EDFs, and default swap (CDS) market rates. The default-swap data, obtained through CIBC from 39 banks and specialty dealers, allow us to establish a strong link between actual and risk-neutral default probabilities in the three sectors that we analyze: broadcasting and entertainment, healthcare, and oil and gas. We find dramatic variation over time in risk premia, from peaks in the third quarter of 2002, dropping by roughly 50% to late 2003.

Collective guilt for harming future ingroup members: The case of American identity and global warming

Three studies address whether people can experience collective guilt for present-day behavior that harms ingroup members in the future. In a correlational study, collective guilt mediated the relationship between perceived harm to future ingroup members on willingness to engage in behaviors that mitigate global warming. An experimental study extended these results by showing similar effects for actual behavior and pro-environmental attitudes. A final experiment extended the other studies by showing similar effects on political conservativism, particularly when global warming was seen as having only a minor impact. These studies suggest that shifting the emphasis from collective for past harm to collective guilt for future harm has important implications for research on collective emotions and pro-environmental behavior