A new algorithm for point spread function subtraction in high-contrast imaging: a demonstration with angular differential imaging

Direct imaging of exoplanets is limited by bright quasi-static speckles in the point spread function (PSF) of the central star. This limitation can be reduced by subtraction of reference PSF images. We have developed an algorithm to construct an optimized reference PSF image from a set of reference images. This image is built as a linear combination of the reference images available and the coefficients of the combination are optimized inside multiple subsections of the image independently to minimize the residual noise within each subsection. The algorithm developed can be used with many high-contrast imaging observing strategies relying on PSF subtraction, such as angular differential imaging (ADI), roll subtraction, spectral differential imaging, reference star observations, etc. The performance of the algorithm is demonstrated for ADI data. It is shown that for this type of data the new algorithm provides a gain in sensitivity by up to a factor 3 at small separation over the algorithm used in Marois et al. (2006).Comment: 7 pages, 11 figures, to appear in May 10, 2007 issue of Ap

Modeling of magnetic field driven simultaneous assembly

The Magnetic Field Driven Simultaneous Assembly (MFDSA) is a method that offers a non-statistical and deterministic solution to the problem of assembly via batch processing; a hybrid of serial and parallel processing. The technique requires the use of electromagnets as well as soft and hard magnetic materials that are applied to devices and recesses respectively. The MFDSA approach offers the ability to check and correct errors in real-time and is capable of scalable, versatile, and high-yield integration. Devices, coated with a layer of soft magnetic material, are moved from initial to final positions along predetermined pathways through the action of an array of electromagnets. Various devices, of arbitrary geometries, with different physical and functional properties, are manipulated simultaneously toward specific desired locations and then dropped onto a template under the influence of gravity by weakening the local applied field. Locations on the template correspond to sites on a substrate that contain recesses. When a number of devices have been dropped onto the template, a substrate is pressed onto it and the soft magnetic layers on the devices adhere to the hard magnetic strips in the recesses, completing integration in a single step. The objectives of this dissertation are the following: to present the MFDSA method; comparing and contrasting it with other extant techniques employed by the semiconductor industry; to discuss key aspects of this solution with respect to the problem of assembly, and to model the calculations involved with determining both device pathways and field interactions that are required to implement the approach. The Fourier Series technique will be used to describe the force of attraction between the device\u27s soft magnetic layer and the recess\u27s hard magnetic strips. Methodology from finite element analysis will be employed to calculate the force exerted on a device by an array of electromagnets. The Swarm Algorithm, which was developed in this work to calculate device pathways, will be presented as a stable, well-defined solution. Other concepts, such as the magnetic retention factor and the collision crosssection area, will be presented and developed. The solution to the problem of assembly, via the Swarm Algorithm, will be compared and contrasted with other analogous problems found in the literature. The results of these models, including software implementation, will be presented

A comparative study of breast surface reconstruction for aesthetic outcome assessment

Breast cancer is the most prevalent cancer type in women, and while its survival rate is generally high the aesthetic outcome is an increasingly important factor when evaluating different treatment alternatives. 3D scanning and reconstruction techniques offer a flexible tool for building detailed and accurate 3D breast models that can be used both pre-operatively for surgical planning and post-operatively for aesthetic evaluation. This paper aims at comparing the accuracy of low-cost 3D scanning technologies with the significantly more expensive state-of-the-art 3D commercial scanners in the context of breast 3D reconstruction. We present results from 28 synthetic and clinical RGBD sequences, including 12 unique patients and an anthropomorphic phantom demonstrating the applicability of low-cost RGBD sensors to real clinical cases. Body deformation and homogeneous skin texture pose challenges to the studied reconstruction systems. Although these should be addressed appropriately if higher model quality is warranted, we observe that low-cost sensors are able to obtain valuable reconstructions comparable to the state-of-the-art within an error margin of 3 mm.Comment: This paper has been accepted to MICCAI201

Historical Development of Research Methods in the Information Systems Discipline

In this article, we report on an investigation that integrated the results from twenty meta-studies on research methods asidentified by a thorough literature review. By conducting this investigation, we seek to reconstruct the historical developmentof research methods in the Information Systems (IS) discipline. Major results of the investigation are: Only the classicalempirical methods (survey, case study, laboratory experiment, and field experiment) have been the subject of intensivediscussion. Survey, case study, and laboratory experiment demonstrate an upward tendency in their historical developmentduring the past forty years (1968-2006), whereas the field experiment does not. The investigation reveals an average adoptionrate of 24 percent for the survey, 13 percent for the case study, 10 percent for the laboratory experiment, and 3 percent for thefield experiment. Finally, we have not observed radical methodological changes in the IS discipline. Key findings and theirimplications for the future development of the IS discipline are discussed

Influence of nitrogen deposition on carbon dynamics in peatlands

The impact of high levels of nitrogen deposition from the atmosphere (primarily from the combustion of fossil fuels and transportation) on soil carbon fluxes and carbon sequestration pathways in peatlands are uncertain and limit our understanding of its consequence on peatlands’ role as global carbon sinks. An alteration in peatlands’ natural carbon accumulation process could result in the increased release of CO2 into the atmosphere, potentially increasing the greenhouse effect and contributing to climate change. Recent studies in forest soils have shown that high concentrations of inorganic nitrogen accelerate the activity of key soil enzymes involved in the degradation of easily decomposable litter (low lignin content) but slow down the decomposition of lignin abundant litter. Peatland soils are adapted to slow rates of nitrogen mineralization; therefore increasing the nitrogen supply in these environments may have an even deeper impact on litter quality, potential litter decomposability, and overall carbon storage capacity. The aim of this study is to use plant wax biomarkers as proxies of vegetational change in litter profiles. An alkane and alcohol profile database of peatland vegetation is currently being characterized for comparison with samples taken from the Whim Moss experimental site (Edinburgh) where different levels of nitrogen has been added to peatland soil since 2002. A temporal study combining the MicroResp technique (community level physiological profiles) and enzyme activity assays is considered to look at the effect of litter compositional changes on soil microbial diversity and biological activity. To better understand how nitrogen deposition in peatland soil affects the mechanisms controlling carbon storage, the incorporation of stable isotope labelling (13C) would allow direct determination of the fate of carbon into the different carbon pools and better pin-point the changes in litter composition

Effects of United States Monetary Policy on the Capital Flows to the Latin America Countries

In the latest time, the US has had an easy Monetary Policy. Because of the increasing link among the countries through interconnections on international trade, financial, and labor markets, such policy has not only had effects in the US economy, but also in the rest of the world. So many countries, especially emerging and developing countries, have suggested that such a policy has been causing an excessive flow of funds out of the US which are disrupting the exchange rate and competitiveness of those countries. An innovation of the analysis is that capital flows are divided in Firm related (direct investment and equity flows) and Debt (debt instruments and private loans obtained from foreign financial institutions). Another innovation is related to the measure of the external factors considering the US alone and a compound of Advanced Countries (AC) that includes: the US, European Union, United Kingdom, and Japan. The performed analysis indicates that the US Monetary Policy has been having a role on the determination of the capital flows to the Latin America Countries (LAC). However, these external push factors have been less important than the pull factors from Latin America. In the model, the push factors reflected to have had influence on the total capital flows, especially through the global liquidity proxies measured by the growth of the monetary stock in the AC. Holding all other things constant, one percent increase in the monetary stock in the US will generate capital flows to the LAC for an amount between 0.47 to 1.71 percentages of GDP. This effect is bigger when using the proxy constructed with the US alone than when using the compound of AC. The long term interest rate registered significance only on the Firm related type of capital flows and only when using the compound of AC. The performed analysis also indicates that there is preeminence of the pull (domestic) over the push (external) factors. This means that the LAC have been pursuing actions such as political stability, sound and consistent economic policies, and more market oriented policies that are attracting capital flows by themselves

CATTLE/BEEF SUBSECTOR'S STRUCTURE AND COMPETITION UNDER FREE TRADE

Industrial Organization, International Relations/Trade,

Nonrigid reconstruction of 3D breast surfaces with a low-cost RGBD camera for surgical planning and aesthetic evaluation

Accounting for 26% of all new cancer cases worldwide, breast cancer remains the most common form of cancer in women. Although early breast cancer has a favourable long-term prognosis, roughly a third of patients suffer from a suboptimal aesthetic outcome despite breast conserving cancer treatment. Clinical-quality 3D modelling of the breast surface therefore assumes an increasingly important role in advancing treatment planning, prediction and evaluation of breast cosmesis. Yet, existing 3D torso scanners are expensive and either infrastructure-heavy or subject to motion artefacts. In this paper we employ a single consumer-grade RGBD camera with an ICP-based registration approach to jointly align all points from a sequence of depth images non-rigidly. Subtle body deformation due to postural sway and respiration is successfully mitigated leading to a higher geometric accuracy through regularised locally affine transformations. We present results from 6 clinical cases where our method compares well with the gold standard and outperforms a previous approach. We show that our method produces better reconstructions qualitatively by visual assessment and quantitatively by consistently obtaining lower landmark error scores and yielding more accurate breast volume estimates