Packaging challenges and reliability performance of compound semiconductor focal plane arrays

The development of new high-performance Focal Plane Arrays (FPAs) for imaging systems is driven by advances in photodetector material growth and processing, readout integrated circuits and IR detector chip hybridisation/packaging. The hybridisation of the IR detector chip and the readout integrated circuit (ROIC) through flip-chip bonding is a key packaging challenge for pixel arrays with very small indium bumps and 10-30 m pitch sizes. This paper details the development and use of finite element models that can be used to assess and optimise the compression bonding process, and can enable insights into the impact of chip misalignment on the resulting flip-chip quality and the bonding equipment placement accuracy requirements for a given FPA specification. In addition, the fatigue performance of the indium interconnects of different fine pitch FPAs is evaluated and compared. The modelling results point that high quality interconnects and robust, defects-free assembly require micrometre placement accuracy. It is also possible that indium joints of higher resolution, larger size FPAs accumulate less damage under cryogenic temperature cycling compared to less dense, smaller in size, focal plane arrays

Water-Resources Investigations Report 83-4141

Purpose and scope: This report has been prepared to document these significant floods for future hydraulic and hydrological planning; to provide streamflow information required for orderly development of river basins where the hazard of extreme flooding exists; and to further the general hydrologic knowledge available for Missouri rivers and streams. Streamflow data in the report include peak stages and discharges, flood hydrographs, flood-crest profiles, flood volumes, and flood-frequency information. Descriptions of the storm and of the damages resulting from these floods are given

Issues of the Ends of Life: The Segelberg Series

The Segelberg Series explores the intersection of religious faith and public policy. This book contains the lectures focused on The Ends of Life. Dalhousie University’s School of Public Administration managed the series through a lecture committee under the able leadership of the former Dean of Dalhousie’s Law School, Professor Innis Christie, QC

Effective mobilities in pseudomorphic Si/SiGe/Si p-channel metal-oxide-semiconductor field-effect transistors with thin silicon capping layers

The room-temperature effective mobilities of pseudomorphic Si/Si0.64Ge0.36/Si p-metal-oxidesemiconductor field effect transistors are reported. The peak mobility in the buried SiGe channel increases with silicon cap thickness. It is argued that SiO2/Si interface roughness is a major source of scattering in these devices, which is attenuated for thicker silicon caps. It is also suggested that segregated Ge in the silicon cap interferes with the oxidation process, leading to increased SiO2/Si interface roughness in the case of thin silicon caps

Greater number of group identifications is associated with healthier behaviour: evidence from a Scottish community sample

Objectives: This paper investigates the interplay between group identification (i.e., the extent to which one has a sense of belonging to a social group, coupled with a sense of commonality with in-group members) and four types of health behaviour, namely physical exercise, smoking, drinking, and diet. Specifically, we propose a positive relationship between one's number of group identifications and healthy behaviour. Design: This study is based on the Scottish portion of the data obtained for Wave 1 of the two-wave cross-national Health in Groups project. 1824 patients from 5 Scottish General Practitioner (GP) surgeries completed the Wave 1 questionnaire in their homes. Methods: Participants completed measures of group identification, group contact, health behaviours and demographic variables. Results: Results demonstrate that the greater the number of social groups with which one identifies, the healthier one’s behaviour on any of the four health dimensions considered. Conclusions: We believe our results are due to the fact that group identification will generally i) enhance one's sense of meaning in life, thereby leading one to take more care of oneself, ii) increase one's sense of responsibility toward other in-group members, thereby enhancing one’s motivation to be healthy in order to fulfil those responsibilities, and iii) increase compliance with healthy group behavioural norms. Taken together, these processes amply overcompensate for the fact that some groups with which people may identify can actually prescribe unhealthy behaviours

Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe

The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts (GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for these sources, we investigate the effect of gamma-ray flux attenuation by the EBL. We place upper limits on the gamma-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. (2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A. Reimer, L.C. Reye

Phospholipases A1

Phospholipase A1 (PLA1) is an enzyme that hydrolyzes phospholipids and produces 2-acyl-lysophospholipids and fatty acids. This lipolytic activity is conserved in a wide range of organisms but is carried out by a diverse set of PLA1 enzymes. Where their function is known, PLA1s have been shown to act as digestive enzymes, possess central roles in membrane maintenance and remodeling, or regulate important cellular mechanisms by the production of various lysophospholipid mediators, such as lysophosphatidylserine and lysophosphatidic acid, which in turn have multiple biological functions

Impact of Neuroprotection on Incidence of Alzheimer's Disease

Converging evidence suggests that high levels of education and intellectual activity increase the cognitive reserve and reduce the risk of dementia. However, little is known about the impact that different neuroprotective strategies may have on the incidence of Alzheimer's disease. Using a simple mathematical regression model, it is shown here that age-specific counts of basic cognitive units (surrogate of neurons or synapses) in the normal population can be estimated from Alzheimer's incidence rates. Hence, the model can be used to test the effect of neuroprotection on Alzheimer's incidence. It was found that the number of basic cognitive units decreases with age, but levels off in older people. There were no gender differences after correcting for survival. The model shows that even modest neuroprotective effects on basic cognitive units can lead to dramatic reductions in the number of Alzheimer's cases. Most remarkably, a 5% increase in the cognitive reserve would prevent one third of Alzheimer's cases. These results suggest that public health policies aimed at increasing the cognitive reserve in the general population (e.g., implementing higher levels of education) are likely the most effective strategy for preventing Alzheimer's disease

The Origin of Glucocorticoid Hormone Oscillations

Characterization of a peripheral hormonal system identifies the origin and mechanisms of regulation of glucocorticoid hormone oscillations in rats