Finding Near-Optimal Independent Sets at Scale

The independent set problem is NP-hard and particularly difficult to solve in large sparse graphs. In this work, we develop an advanced evolutionary algorithm, which incorporates kernelization techniques to compute large independent sets in huge sparse networks. A recent exact algorithm has shown that large networks can be solved exactly by employing a branch-and-reduce technique that recursively kernelizes the graph and performs branching. However, one major drawback of their algorithm is that, for huge graphs, branching still can take exponential time. To avoid this problem, we recursively choose vertices that are likely to be in a large independent set (using an evolutionary approach), then further kernelize the graph. We show that identifying and removing vertices likely to be in large independent sets opens up the reduction space---which not only speeds up the computation of large independent sets drastically, but also enables us to compute high-quality independent sets on much larger instances than previously reported in the literature.Comment: 17 pages, 1 figure, 8 tables. arXiv admin note: text overlap with arXiv:1502.0168

Targeting determinants of dosage compensation in Drosophila

The dosage compensation complex (DCC) in Drosophila melanogaster is responsible for up-regulating transcription from the single male X chromosome to equal the transcription from the two X chromosomes in females. Visualization of the DCC, a large ribonucleoprotein complex, on male larval polytene chromosomes reveals that the complex binds selectively to many interbands on the X chromosome. The targeting of the DCC is thought to be in part determined by DNA sequences that are enriched on the X. So far, lack of knowledge about DCC binding sites has prevented the identification of sequence determinants. Only three binding sites have been identified to date, but analysis of their DNA sequence did not allow the prediction of further binding sites. We have used chromatin immunoprecipitation to identify a number of new DCC binding fragments and characterized them in vivo by visualizing DCC binding to autosomal insertions of these fragments, and we have demonstrated that they possess a wide range of potential to recruit the DCC. By varying the in vivo concentration of the DCC, we provide evidence that this range of recruitment potential is due to differences in affinity of the complex to these sites. We were also able to establish that DCC binding to ectopic high-affinity sites can allow nearby low-affinity sites to recruit the complex. Using the sequences of the newly identified and previously characterized binding fragments, we have uncovered a number of short sequence motifs, which in combination may contribute to DCC recruitment. Our findings suggest that the DCC is recruited to the X via a number of binding sites of decreasing affinities, and that the presence of high-and moderate-affinity sites on the X may ensure that lower-affinity sites are occupied in a context-dependent manner. Our bioinformatics analysis suggests that DCC binding sites may be composed of variable combinations of degenerate motifs

Graphene Field Effect Transistor for Radiation Detection on a Micron to Millimeter Scale

Novel technology in radiation detection is critical to advancing radiation detectors for their many applications. Graphene has shown to be able to change its conductivity in the presence of an electric field; this makes it an excellent candidate to be used as a radiation detector for the detection of the charges generated during radiation interactions. Research has been done on making micron scale graphene field effect transistors (GFET) with graphene on a Si/SiO2 wafer, but it is critical that we try to increase the scale. Unknowns persist in scaling graphene to millimeter sizes. This study plans to elucidate any of the unknowns in graphene conductivity by using 4 different sized GFETs: graphene strip sizes of 10um x 60um, 50um x 300um, 100um x 600um, and 500um x 3000um. These strips of graphene will be etched out of a graphene sheet on Si/SiO2 wafers. Gold pads were connected to these strips of graphene via optical lithography. These devices will have their electrical properties characterized in future experiments to determine if mm scale graphene radiation detection is a worthwhile pursuit

Reconstructing Thermal Quantum Quench Dynamics from Pure States

Simulating the nonequilibrium dynamics of thermal states is a fundamental problem across scales from high energy to condensed matter physics. Quantum computers may provide a way to solve this problem efficiently. Preparing a thermal state on a quantum computer is challenging, but there exist methods to circumvent this by computing a weighted sum of time-dependent matrix elements in a convenient basis. While the number of basis states can be large, in this work we show that it can be reduced by simulating only the largest density matrix elements by weight, capturing the density matrix to a specified precision. Leveraging Hamiltonian symmetries enables further reductions. This approach paves the way to more accurate thermal-state dynamics simulations on near-term quantum hardware.Comment: 8+4 pages, 6+3 figure

Child Labour: What is Happening in New Zealand?

While the rights of New Zealand adult workers have been the primary concern of successive governments and their agencies, the rights of child workers have often been overshadowed. With the recent Government report to the United Nations on New Zealand released, the issues surrounding New Zealand young workers have come to the fore and now require further investigation. The purpose o f this paper is to report on Phase One o f ongoing research into the working lives and experiences of New Zealand children (thoseunder18years). Drawing on existing academic literature as well as government and non-governmental organisations' (NGO) reports and statistics, the paper will present an overview of the status of New Zealand children in terms of the minimum working age; the minimum wage rates; and occupational health and safety standards. Finally, the paper will outline areas of future research

Efficient Parallel Random Sampling : Vectorized, Cache-Efficient, and Online

We consider the problem of sampling $n$ numbers from the range $\{1,\ldots,N\}$ without replacement on modern architectures. The main result is a simple divide-and-conquer scheme that makes sequential algorithms more cache efficient and leads to a parallel algorithm running in expected time $\mathcal{O}(n/p+\log p)$ on $p$ processors, i.e., scales to massively parallel machines even for moderate values of $n$. The amount of communication between the processors is very small (at most $\mathcal{O}(\log p)$) and independent of the sample size. We also discuss modifications needed for load balancing, online sampling, sampling with replacement, Bernoulli sampling, and vectorization on SIMD units or GPUs

The Digital Death Conundrum: How Federal and State Laws Prevent Fiduciaries from Managing Digital Property

This article discusses four types of fiduciaries, each of which is affected by the vast growth in and the need to manage digital property. The article begins by defining digital property and discussing why it must be managed. The article then discusses how digital property affects powers of attorney, conservatorships, probate administration, and trusts. After illustrating the problems that digital property creates for each fiduciary, the article shifts to resolving these problems. It begins by debunking purported solutions by both private and governmental entities. It concludes by offering a holistic approach to resolving the conflicts facing account holders, fiduciaries, and service providers and providing the level of security sought in fiduciary property management, as well as a best-practices approach in the interim to a complete solution