The Bernoulli sieve revisited

We consider an occupancy scheme in which "balls" are identified with $n$ points sampled from the standard exponential distribution, while the role of "boxes" is played by the spacings induced by an independent random walk with positive and nonlattice steps. We discuss the asymptotic behavior of five quantities: the index $K_n^*$ of the last occupied box, the number $K_n$ of occupied boxes, the number $K_{n,0}$ of empty boxes whose index is at most $K_n^*$, the index $W_n$ of the first empty box and the number of balls $Z_n$ in the last occupied box. It is shown that the limiting distribution of properly scaled and centered $K_n^*$ coincides with that of the number of renewals not exceeding $\log n$. A similar result is shown for $K_n$ and $W_n$ under a side condition that prevents occurrence of very small boxes. The condition also ensures that $K_{n,0}$ converges in distribution. Limiting results for $Z_n$ are established under an assumption of regular variation.Comment: Published in at http://dx.doi.org/10.1214/08-AAP592 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Computing the Margin of Victory in Preferential Parliamentary Elections

We show how to use automated computation of election margins to assess the number of votes that would need to change in order to alter a parliamentary outcome for single-member preferential electorates. In the context of increasing automation of Australian electoral processes, and accusations of deliberate interference in elections in Europe and the USA, this work forms the basis of a rigorous statistical audit of the parliamentary election outcome. Our example is the New South Wales Legislative Council election of 2015, but the same process could be used for any similar parliament for which data was available, such as the Australian House of Representatives given the proposed automatic scanning of ballots

Adenovirus infection in pediatric liver transplant recipients

A retrospective review of adenoviral infection in pediatric liver transplant recipients was done at Children’s Hospital of Pittsburgh to define its epidemiology and clinical importance. Medical records of patients with adenovirus were reviewed and data collected regarding clinical course, microbiologic studies, biopsy results, immunosuppression, concurrent infections, and outcome. Of 484 liver transplant recipients, 49 had 53 episodes of adenoviral infection. The most common sites of adenoviral infection were the liver, lung, and gastrointestinal tract. Serotypes 1, 2, and 5 were recovered most often; type 5 was commonly associated with hepatitis. Invasive adenoviral infection occurred in 20 children, leading to death in 9. Median time from transplantation until isolation of adenovirus was 25.5 days. This timing suggests either reactivation or donor-associated transmission. Prospective studies using molecular epidemiologic techniques will be helpful in evaluating transmission patterns of adenovirus in this population. © 1992 Oxford University Press

Aspergillosis of the CNS in a pediatric liver transplant recipient: Case report and review

A 2-month-old infant who had undergone orthotopic liver transplantation at the age of 2 weeks for carbamoyl phosphate synthetase deficiency developed infection of the CNS due to Aspergillus fumigatus. The patient was successfully treated with administration of a combination of antifungal agents (including intraventricular amphotericin B), drainage of the parietal lobe abscess, and cessation of immunosuppression. An intraventricular catheter was used both to obtain ventricular fluid for microbiologic testing and to deliver amphotericin B during nearly 4 months of treatment. We review literature on aspergillosis in solid-organ transplant recipients, especially those in whom the disease involves the CNS, and discuss in particular clinical presentation, diagnosis, treatment, and outcome

Spatial Compressive Sensing for MIMO Radar

We study compressive sensing in the spatial domain to achieve target localization, specifically direction of arrival (DOA), using multiple-input multiple-output (MIMO) radar. A sparse localization framework is proposed for a MIMO array in which transmit and receive elements are placed at random. This allows for a dramatic reduction in the number of elements needed, while still attaining performance comparable to that of a filled (Nyquist) array. By leveraging properties of structured random matrices, we develop a bound on the coherence of the resulting measurement matrix, and obtain conditions under which the measurement matrix satisfies the so-called isotropy property. The coherence and isotropy concepts are used to establish uniform and non-uniform recovery guarantees within the proposed spatial compressive sensing framework. In particular, we show that non-uniform recovery is guaranteed if the product of the number of transmit and receive elements, MN (which is also the number of degrees of freedom), scales with K(log(G))^2, where K is the number of targets and G is proportional to the array aperture and determines the angle resolution. In contrast with a filled virtual MIMO array where the product MN scales linearly with G, the logarithmic dependence on G in the proposed framework supports the high-resolution provided by the virtual array aperture while using a small number of MIMO radar elements. In the numerical results we show that, in the proposed framework, compressive sensing recovery algorithms are capable of better performance than classical methods, such as beamforming and MUSIC.Comment: To appear in IEEE Transactions on Signal Processin

Target Localization Accuracy Gain in MIMO Radar Based Systems

This paper presents an analysis of target localization accuracy, attainable by the use of MIMO (Multiple-Input Multiple-Output) radar systems, configured with multiple transmit and receive sensors, widely distributed over a given area. The Cramer-Rao lower bound (CRLB) for target localization accuracy is developed for both coherent and non-coherent processing. Coherent processing requires a common phase reference for all transmit and receive sensors. The CRLB is shown to be inversely proportional to the signal effective bandwidth in the non-coherent case, but is approximately inversely proportional to the carrier frequency in the coherent case. We further prove that optimization over the sensors' positions lowers the CRLB by a factor equal to the product of the number of transmitting and receiving sensors. The best linear unbiased estimator (BLUE) is derived for the MIMO target localization problem. The BLUE's utility is in providing a closed form localization estimate that facilitates the analysis of the relations between sensors locations, target location, and localization accuracy. Geometric dilution of precision (GDOP) contours are used to map the relative performance accuracy for a given layout of radars over a given geographic area.Comment: 36 pages, 5 figures, submitted to IEEE Transaction on Information Theor

The information system of mobile knowledge workers : an activity theory perspective of information sources and interaction

University of Technology, Sydney. Faculty of Engineering and Information Technology.Mobile technology has the potential to connect the mobile knowledge worker (MKW) to information sources which will support their decision making. Many researchers in the fields of innovation adoption and human computer interaction advocate that the development of support technology (such as mobile technology) should be initiated with an understanding of the end user that is based on current work practices, in order to support acceptance and adoption. The object of this research is to describe the existing information system used by mobile knowledge workers (MKWs). The assessment of the existing information system of MKWs under examination in this research goes beyond the identification of data and the technical means of data supply. A holistic view of the information system is applied to take into consideration both the existing sources of information which assist in decision making and the interaction and/or access made by the user (MKW) with such systems. An interpretive philosophical approach was taken via an empirical study of mobile workers in three different contexts. The empirical research resulted in the development of three case studies: Doctors working on ward rounds, Reporters working in the field and construction site workers operating on building sites. The case studies were executed in two rounds, the first round being focussed on the Doctors and Reporters, and the second being a main case study which examined the work practices of construction site workers. Consideration of these MKWs was developed using semi-structured interviews and interpreted through the lens of Activity Theory. The resulting framework adapted from Activity Theory identifies technical, social and environmental factors which influence the way mobile knowledge workers interact with information sources. Of particular note is the identification of a previously overlooked information source which sits outside the organisation: that of the Contributor. Another significant finding is the preference for information provided by Collaborators over information supplied by information tools. The information provided by Collaborators was preferred as it was subject to the application of Collaborators’ knowledge to the situational context

Management of Construction Projects in Vietnam: An Activity Theory Analysis

The analysis of managing construction projects is often reviewed using the iron triangle of time, cost and quality. Researchers in the field of project management have called for new paradigms to be applied to analysing projects. The research in this paper uses Activity Theory as a lens of interpretation to compare the management of construction projects in Vietnam against practices used in developed countries. The research focuses on the work Activity of construction management professionals and the mediating forces that differentiate building in Vietnam. The research found mediating factors such as the physical environment where work was taking place, the low cost of labour and the culture characteristics of loss of face and approach to site safety, played a significant role in the construction Activity in Vietnam. An emergent theme highlighted by using the Activity Theory paradigm is an interconnected relationship between mediating elements in an Activity System