Monolithically integrated InAsSb-based nBnBn heterostructure on GaAs for infrared detection

High operating temperature i nfrared photo detectors with multi -color function that are capable of monolithic integration are of increasing importance in developing the next generation of mid -IR imag e sensors. Applications of these sensors include defense, medical diagnosis, environmental and astronomical observations. We have investigated a novel InAsSb -based nBnBn heterostructure that combines a state -of-art InAsSb nBn detector with an InAsSb/GaSb heterojuncti on detector . At room temperature, r educti on in the dark current density of more than an order of magnitude was achieved compared to previously investigated InAsSb/GaSb heterojunction dete ctors . Electrical characterization from cryogenic temperatures to roo m temperature confirmed that the nBnBn device was diffusion limited for temperature s above 150K. O ptical measurements demonstrated that the nBnBn detector was sensitive in both the SWIR and MWIR wavelength range at room temperature . The specific detectivity (D*) of the competed nBnBn devices was calculated to be 8.6 × 10 8 cm · Hz 1/2 W -1 at 300K and approximately 1.0 × 10 10 cm · Hz 1/2 W -1 when cooled down to 200K (with 0.3V reverse bias and 1550nm illumination ). In addition, all photodetector layers were grown monolithically on GaAs active layers u sing the interfacial misfit array growth mode . Our results therefore pave the way for the development of new active pixel designs for monolithically integrated mid -IR imaging arrays

Low Noise and High Photodetection Probability SPAD in 180 nm Standard CMOS Technology

A square shaped, low noise and high photo-response single photon avalanche diode suitable for circuit integration, implemented in a standard CMOS 180 nm high voltage technology, is presented. In this work, a p+ to shallow n-well junction was engineered with a very smooth electric field profile guard ring to attain a photo detection probability peak higher than 50% with a median dark count rate lower than 2 Hz/μm2 when operated at an excess bias of 4 V. The reported timing jitter full width at half maximum is below 300 ps for 640 nm laser pulses

Formation of Millisecond Pulsars in Globular Clusters

In this contribution we discuss how neutron stars are produced and retained in globular clusters, outlining the most important dynamical channels and evolutionary events that affect thepopulation of mass-transferring binaries with neutron stars and result in the formation of recycled pulsars. We confirm the importance of electron-capture supernovae in globular clusters as the major supplier of retained neutron stars.By comparing the observed millisecond pulsar population and the results obtained from simulations, we discuss several constraints on the evolution of mass-transferring systems.In particular, we find that in our cluster model the following mass-gaining events create populations of MSPs that do not match the observations (with respect to binary periods and companion masses or the number of produced systems) and therefore likely do not lead to NSs spun up to millisecond periods: (i) accretion during a common envelope event with a NS formed through accretion-induced collapse, and (ii) mass transfer from a WD donor. By restricting ourselves to the evolutionary and dynamical paths that most likely lead to neutron star recycling, we obtain good agreement between our models and the numbers and characteristics of observed millisecond pulsars in the clusters Terzan 5 and 47 Tuc.Comment: 6 pages, 3 figures, to appear in the proceedings of the 40 Years of Pulsars conference held at McGill University in August 200

An Evening of Richard Cumming: Susan Carol Kindall in a Faculty Recital

This is the program for the faculty recital, An Evening of Richard Cumming, featuring pianist Susan Carol Kindall. Ms. Kindall was assisted by dramatic reader Jon Secrest, the Cumming Chamber Ensemble, conducted by Craig Hamilton. This recital took place on March 13, 1995, in the Mabee Fine Arts Center Recital Hall

Animated interval scatter-plot views for the exploratory analysis of large scale microarray time-course data.

Microarray technologies are a relatively new development that allow biologists to monitor the activity of thousands of genes (normally around 8,000) in parallel across multiple stages of a biological process. While this new perspective on biological functioning is recognised as having the potential to have a significant impact on the diagnosis, treatment, and prevention of diseases, it is only through effective analysis of the data produced that biologists can begin to unlock this potential. A significant obstacle to achieving effective analysis of microarray time-course is the combined scale and complexity of the data. This inevitably makes it difficult to reveal certain significant patterns in the data. In particular, it is less dominant patterns and, specifically, patterns that occur over smaller intervals of an experiment's overall time-frame that are more difficult to find. While existing techniques are capable of finding either unexpected patterns of activity over the majority of an experiment's time-frame or expected patterns of activity over smaller intervals of the time-frame, there are no techniques, or combination of techniques, that are suitable for finding unsuspected patterns of activity over smaller intervals. In order to overcome this limitation we have developed the Time-series Explorer, which specifically supports biologists in their attempts to reveal these types of pattern by allowing them to control an animated interval scatter-plot view of their data. This paper discusses aspects of the technique that make such an animated overview viable and describes the results of a user evaluation assessing the practical utility of the technique within the wider context of microarray time-series analysis as a whole

Time-series Explorer: An Animated Information Visualisation for Microarray Time-course Data

Microarray technologies are a relatively new development that allow biologists to monitor the activity of thousands of genes (normally around 8,000) in parallel across multiple stages of a biological process. While this new perspective on biological functioning is recognised as having the potential to have a significant impact on the diagnosis, treatment, and prevention of diseases, it is only through effective analysis of the data produced that biologists can begin to unlock this potential. A significant obstacle to achieving effective analysis of microarray time-course is the combined scale and complexity of the data. This inevitably makes it difficult to reveal certain significant patterns in the data. In particular it is less dominant patterns and, specifically, patterns that occur over smaller intervals of an experiment's overall time-frame that are more difficult to find. While existing techniques are capable of finding either unexpected patterns of activity over the majority of an experiment's time frame or expected patterns of activity over smaller intervals of the time frame, there are no techniques, or combination of techniques, that are suitable for finding unsuspected patterns of activity over smaller intervals. In order to overcome this limitation we have developed the Time-series Explorer, which specifically supports biologists in their attempts to reveal these types of pattern by allowing them to visualise their data controlling an animated interval scatter-plot linked to two complementary graph views. An evaluation, involving biologists working with real data, tested the extent of the tools desired functionality and assessed the technique's practical utility within the wider context of microarray time-course analysis. This proved the technique not only capable of revealing previously unsuspected temporal patterns but also, in certain cases, more appropriate for finding previously suspected patterns and patterns that occurred over the majority of the time-frame

Size matters: variations in seagrass seed size at local scales affects seed performance

Seed size can have an impact on angiosperm reproductive fitness. Ecological theory predicts plants that will produce larger seeds in stressful environments to increase the chances of seedling survival and numerous small seeds in favourable conditions to increase the number of recruits. We measured seed morphology of the seagrass Heterozostera nigricaulis from four populations under differing environmental conditions in South East Australia. Seed size and mass among sites showed consistent differences over four flowering seasons. Seeds from exposed, ephemeral meadows (Blairgowrie, Edwards Point) were 19%–53% heavier than those from larger, stable meadows at more sheltered sites (Swan Bay, Point Henry). Overall, heavier seeds from exposed sites performed better in germination experiments and persisted (remained viable) longer compared to small seeds from sheltered sites. Seeds from sheltered sites showed contrasting levels of seed performance. Small seeds from Swan Bay had the lowest germination but the proportion of viable seeds after 12 months were much higher (41%) than similar sized seeds from Point Henry (0%). There are clear life history benefits of large seeds that facilitate seed persistence and germination at exposed sites; however, the performance of smaller seeds varied between sites and may be a function of other site-specific advantages

Quantifying spatial resilience

1. Anthropogenic stressors affect the ecosystems upon which humanity relies. In some cases when resilience is exceeded, relatively small linear changes in stressors can cause relatively abrupt and nonlinear changes in ecosystems. 2. Ecological regime shifts occur when resilience is exceeded and ecosystems enter a new local equilibrium that differs in its structure and function from the previous state. Ecological resilience, the amount of disturbance that a system can withstand before it shifts into an alternative stability domain, is an important framework for understanding and managing ecological systems subject to collapse and reorganization. 3. Recently, interest in the influence of spatial characteristics of landscapes on resilience has increased. Understanding how spatial structure and variation in relevant variables in landscapes affects resilience to disturbance will assist with resilience quantification, and with local and regional management. 4. Synthesis and applications. We review the history and current status of spatial resilience in the research literature, expand upon existing literature to develop a more operational definition of spatial resilience, introduce additional elements of a spatial analytical approach to understanding resilience, present a framework for resilience operationalization and provide an overview of critical knowledge and technology gaps that should be addressed for the advancement of spatial resilience theory and its applications to management and conservation

Combining cross-sectoral, prospective data linkage with other data sources to examine health outcomes for socially excluded populations: A case study from Australia

Introduction Studies of the health of prisoners have proliferated in the past decade. However, relatively few studies have examined health outcomes after release from custody. As such, although >30 million people are released from prison globally each year, the health and health service experiences of this population remain poorly understood. Objectives and Approach Well-powered longitudinal studies are essential for answering these questions but are expensive and difficult to conduct. Internationally, few such studies have been undertaken, and most suffer from either substantial and biased attrition, or recruitment bias. Cross-sectoral linkage of health and justice data circumvents some of these problems but presents its own ethical and methodological challenges. Large longitudinal studies, combining rich survey and clinical data with prospective data linkage, provide unique opportunities to examine and understand health outcomes for these highly marginalised individuals. Results This presentation will describe the process and challenges of establishing the world’s largest (N=2,702) prospective study of adults released from prison: the Health After Release from Prison (HARP) cohort study. The cohort spans two Australian states and includes 538 women and 1,002 Indigenous Australians. An overview of the data collected through face-to-face surveys, medical record review, and prospective linkage with State-based health and correctional records, national Medicare and pharmaceutical records, and the National Death Index, will be provided. Some examples of how these data have been used to answer novel public health questions will be presented. The strengths and limitations of the cohort, and the applicability of this research design for other inclusion health populations, will be discussed. Conclusion/Implications Given their extreme vulnerability, understanding the health of people who cycle through prisons is important to addressing health inequalities at the population level. Novel research designs that combine prospective data linkage with other data sources provide new opportunities to examine the health of socially excluded populations

SN 2003du: Signatures of the Circumstellar Environment in a Normal Type Ia Supernova?

We present observations of the Type Ia supernova 2003du and report the detectionof an unusual, high-velocity component in the Ca II infrared triplet, similar tofeatures previously observed in SN 2000cx and SN 2001el. This feature exhibits a large expansion velocity (~18,000 km/s) which is nearly constant between -7 and +2 days relative to maximum light, and disappears shortly thereafter. Otherthan this feature, the spectral evolution and light curve resemble those of a normal SN Ia. We find that the Ca II feature can plausibly be caused by a dense shell formed when circumstellar material of solar abundance is overrun by the rapidly expanding outermost layers of the SN ejecta. Model calculations show that the optical and infrared spectra are remarkably unaffected by the circumstellar interaction. In particular, no hydrogen lines are detectable in either absorption or emission. The only qualitatively different features are the strong, high-velocity feature in the Ca II IR-triplet, and a somewhat weaker O I feature near 7,300 AA. The morphology and time evolution of these features provide an estimate for the amount of accumulated matter and an indication of the mixing in the dense shell. We apply these diagnostic tools to SN 2003du and infer that about 2 x 10^{-2} M_sun of solar abundance material may have accumulated in a circumstellar shell prior to the observations. Furthermore, the early light curve data imply that the circumstellar material was originally very close to the progenitor system, perhaps from an accretion disk, Roche lobe or common envelope.Comment: 35 Pages, 11 Figures, to appear in ApJ. Resubmission includes expanded discussion & new figures to match with accepted journal versio