Ignorance is Almost Bliss: Near-Optimal Stochastic Matching With Few Queries

The stochastic matching problem deals with finding a maximum matching in a graph whose edges are unknown but can be accessed via queries. This is a special case of stochastic $k$-set packing, where the problem is to find a maximum packing of sets, each of which exists with some probability. In this paper, we provide edge and set query algorithms for these two problems, respectively, that provably achieve some fraction of the omniscient optimal solution. Our main theoretical result for the stochastic matching (i.e., $2$-set packing) problem is the design of an \emph{adaptive} algorithm that queries only a constant number of edges per vertex and achieves a $(1-\epsilon)$ fraction of the omniscient optimal solution, for an arbitrarily small $\epsilon>0$. Moreover, this adaptive algorithm performs the queries in only a constant number of rounds. We complement this result with a \emph{non-adaptive} (i.e., one round of queries) algorithm that achieves a $(0.5 - \epsilon)$ fraction of the omniscient optimum. We also extend both our results to stochastic $k$-set packing by designing an adaptive algorithm that achieves a $(\frac{2}{k} - \epsilon)$ fraction of the omniscient optimal solution, again with only $O(1)$ queries per element. This guarantee is close to the best known polynomial-time approximation ratio of $\frac{3}{k+1} -\epsilon$ for the \emph{deterministic} $k$-set packing problem [Furer and Yu, 2013] We empirically explore the application of (adaptations of) these algorithms to the kidney exchange problem, where patients with end-stage renal failure swap willing but incompatible donors. We show on both generated data and on real data from the first 169 match runs of the UNOS nationwide kidney exchange that even a very small number of non-adaptive edge queries per vertex results in large gains in expected successful matches

Response of linear dynamic systems with random coefficients

Numerous models of physical systems contain parameters whose values are not known exactly. The physical and mathematical complexities arising in the prediction of the statistical behavior of such systems are discussed. Although the discussions are far from providing a satisfactory solution to such problems, they perhaps, by utilization of simple examples, will create a greater awareness of the statistical effect of random parameters

Part time employment and happiness: A cross-country analysis

The relationship between part time employment and job satisfaction is analysed for mothers in Germany, Denmark, the Netherlands, Finland, France, Spain and the UK. The impact of working part time on subjective life satisfaction and mental well-being is additionally analysed for British mothers. Cultural traditions concerning women´s role in society, and institutional differences between the countries are exploited. Results indicate that poor quality jobs can diminish any positive well-being repercussions of part time employment. The results additionally suggest that part time mothers in the UK experience higher levels of job satisfaction but not of overall life satisfaction as compared to their full time counterparts

Actualizing Organizational Core Values: Putting Theory into Practice

The literature on organizational culture and leading by shared values suggests a prescriptive model for use by leaders in actualizing stated organizational core values. Utilizing a qualitative case study approach, this study sought to examine the efficacy of this theoretical model in representing actual efforts by practitioners to embed diversity as a new organizational core value. Leadership actions to embed and actualize diversity as an institutional core value at two private universities were examined and compared. Findings suggest the theoretical model inadequately addresses the critical role of contextual assessment and under represents the dynamic cyclical nature of value embedding and actualization processes, particularly with respect organizations with high stakeholder turnover such as institutions of higher education

Pseudomonas Cytochrome c551 at 2.0 angstrom Resolution: Enlargement of the Cytochrome c Family

The structure of respiratory cytochrome c551 of Pseudomonas aeruginosa, with 82 amino acids, has been solved by x-ray analysis and refined to a crystallographic R factor of 16.2%. It has the same basic folding pattern and hydrophobic heme environment as cytochromes c, c2, and c550, except for a large deletion at the bottom of the heme crevice. This same "cytochrome fold" appears to be present in photosynthetic cytochromes c of green and purple sulfur bacteria, and algal cytochromes f, suggesting a common evolutionary origin for electron transport chains in photosynthesis and respiration

Gambling and the use of credit: an individual and household level analysis

We explore the relationship between gambling and other forms of risk-taking behaviour, i.e. exposure to debt and the use of credit, at the individual and household level using representative pooled cross-section data drawn from the UK Expenditure and Food Surveys (EFS), 2001 to 2007. Gambling and the use of credit are shown to be positively correlated at the household level. While both the incidence and amount of gambling vary according to household income, the positive association between gambling and the use of credit is remarkably stable across household income. In addition to our household level analysis, we also explore the prevalence of intra-household gambling, which has attracted relatively limited attention in the existing literature. It is apparent that there is strong intra-household correlation in both gambling activity and in the use of credit, with somewhat stronger relationships in lower income households

Balancing the Tradeoff between Profit and Fairness in Rideshare Platforms During High-Demand Hours

Rideshare platforms, when assigning requests to drivers, tend to maximize profit for the system and/or minimize waiting time for riders. Such platforms can exacerbate biases that drivers may have over certain types of requests. We consider the case of peak hours when the demand for rides is more than the supply of drivers. Drivers are well aware of their advantage during the peak hours and can choose to be selective about which rides to accept. Moreover, if in such a scenario, the assignment of requests to drivers (by the platform) is made only to maximize profit and/or minimize wait time for riders, requests of a certain type (e.g. from a non-popular pickup location, or to a non-popular drop-off location) might never be assigned to a driver. Such a system can be highly unfair to riders. However, increasing fairness might come at a cost of the overall profit made by the rideshare platform. To balance these conflicting goals, we present a flexible, non-adaptive algorithm, \lpalg, that allows the platform designer to control the profit and fairness of the system via parameters $\alpha$ and $\beta$ respectively. We model the matching problem as an online bipartite matching where the set of drivers is offline and requests arrive online. Upon the arrival of a request, we use \lpalg to assign it to a driver (the driver might then choose to accept or reject it) or reject the request. We formalize the measures of profit and fairness in our setting and show that by using \lpalg, the competitive ratios for profit and fairness measures would be no worse than $\alpha/e$ and $\beta/e$ respectively. Extensive experimental results on both real-world and synthetic datasets confirm the validity of our theoretical lower bounds. Additionally, they show that \lpalg under some choice of $(\alpha, \beta)$ can beat two natural heuristics, Greedy and Uniform, on \emph{both} fairness and profit

American Military Justice and International Criminal Court Complementarity: The Case of UCMJ Article 60

Although the American military is effectively one of the most potent of international institutions, discussions of its regulation have been oddly domestic. The court-martial – the single most important institution for disciplining military forces, preventing atrocities and punishing offenders – has seen its jurisdiction and procedures hotly debated, but most often by those in uniform or individuals interested in domestic military policy. This paper aims to internationalize the discussion, recognizing that the discipline of American military forces is of major concern to both international law and U.S. foreign policy. By exploring the interaction between a major innovation in international law – the International Criminal Court – and the extensive clemency powers exercised by military commanders under the laws governing U.S. courts-martial, I hope to demonstrate that a systematic rethinking of American military justice is now necessary in light of changed international conditions

Design of a 3D integrated circuit for manipulating and sensing biological nanoparticles

We present the design of a mixed-technology microsystem for electronically manipulating and optically detecting nanometer scale particles in a fluid. This lab-on-a-chip is designed using 3D integrated circuit technology. By taking advantage of processing features inherent to 3D chip-stacking technology, we create very dense dielectrophoresis electrode arrays. During the 3D fabrication process, the top-most chip tier is assembled upside down and the substrate material is removed. This puts the polysilicon layer, which is used to create geometries with the process' minimum feature size, in close proximity to a fluid channel etched into the top of the stack. This technique allows us to create electrode arrays that have a gap spacing of 270 nm in a 0.18 ìm SOI technology. Using 3D CMOS technology also provides the additional benefit of being able to densely integrate analog and digital control circuitry for the electrodes by using the additional levels of the chip stack. For sensing particles that are manipulated by dielectrophoresis, we present a method by which randomly distributed nanometer scale particles can be arranged into periodic striped patterns, creating an effective diffraction grating. The efficiency of this grating can be used to perform a label-free optical analysis of the particles. The functionality of the 3D lab-on-a-chip is verified with simulations of Kaposi's sarcoma-associated herpes virus particles, which have a radius of approximately 125 nm, being manipulated by dielectrophoresis and detected optically