On Computing Maximal Independent Sets of Hypergraphs in Parallel

Whether or not the problem of finding maximal independent sets (MIS) in hypergraphs is in (R)NC is one of the fundamental problems in the theory of parallel computing. Unlike the well-understood case of MIS in graphs, for the hypergraph problem, our knowledge is quite limited despite considerable work. It is known that the problem is in \emph{RNC} when the edges of the hypergraph have constant size. For general hypergraphs with $n$ vertices and $m$ edges, the fastest previously known algorithm works in time $O(\sqrt{n})$ with $\text{poly}(m,n)$ processors. In this paper we give an EREW PRAM algorithm that works in time $n^{o(1)}$ with $\text{poly}(m,n)$ processors on general hypergraphs satisfying $m \leq n^{\frac{\log^{(2)}n}{8(\log^{(3)}n)^2}}$, where $\log^{(2)}n = \log\log n$ and $\log^{(3)}n = \log\log\log n$. Our algorithm is based on a sampling idea that reduces the dimension of the hypergraph and employs the algorithm for constant dimension hypergraphs as a subroutine

A trap-and-haul fishway for multi-species upstream fish passage at a challenging site

Australia’s first trap-and-haul fishway was built on the Nerang River in southeast Queensland during enlargement of the Hinze Dam. In gaining government approval for the project, the constructing alliance (HDA) concluded that providing upstream fish passage would have significant environmental benefits by conserving upstream native fish communities and encouraging recruitment into the reservoir’s recreational fishery. But downstream passage, other than modifications to protect fish emigrating during spill events, could not be justified. Severely constrained outflows from the dam and the impacts of downstream urban development contrast starkly with upstream habitat conditions. North American design approaches were adapted to suit the river’s fishes and streamflows. Challenges for fish passage at the site included the marked restriction of downstream river flows and the location of the flow-release point 300m from the spillway. A barrier weir was built to prevent upstream migrants bypassing the fishway entrance during spillway flows. HDA developed a trap-and-haul system to collect migrating fish at the weir and transport them by tanker to multiple upstream release areas. This system provides flexibility to accommodate varying fish biomass; ability to operate over a range of flows up to 20-year ARI events; facilities for sorting, data collection and removal of pest species; and capacity to limit predation mortalities. Fishway performance studies led to redesign of the entrance vee-trap and other modifications. To 2017, 55,590 fish from 27 large and small-bodied species used the fishway, together with 8 turtles. Fish of three pest species were identified in the sorting facility and removed to prevent their entry to the reservoir. This paper covers the project life cycle for Australia’s first trap-and-haul fishway including the basis for selecting the fishway type, design and construction. Fishway performance studies and results from ongoing operation, including the lessons learned and the improvements made, are also discussed

A Website to help the International Students Experience (WISE)

Our VCU campus has been steadily expanding its international student population and has become an increasingly global university community. We have identified together with GEO, the need to build tangible resources that can support faculty and staff to more effectively educate our international student population. The creation of online content to be added to GEO’s current webpage seems to best fit the existing need. Our project outlines a blueprint for this online content by means of identifying data and resources that should be included as well as determining cost, sustainability and feasibility plans. Ultimately, the goal is to pave the way for centralized online content that can connect faculty and staff with important resources to optimize the academic experience and success of international students at VCU

Australia’s first trap-and-haul fishway: Nerang River, Queensland

Australia’s first trap-and-haul fishway was built on the Nerang River in southeast Queensland during enlargement of the Hinze Dam. In gaining government approval for the project, the constructing alliance (HDA) concluded that providing upstream fish passage would have significant environmental benefits by conserving upstream native fish communities and encouraging recruitment into the reservoir’s recreational fishery. But downstream passage, other than modifications to protect fish emigrating during spill events, could not be justified. Severely constrained outflows from the dam and the impacts of downstream urban development contrast starkly with upstream habitat conditions. North American design approaches were adapted to suit the river’s fishes and streamflows. Challenges for fish passage at the site included the marked restriction of downstream river flows and the location of the flow-release point 300m from the spillway. A barrier weir was built to prevent upstream migrants bypassing the fishway entrance during spillway flows. HDA developed a trap-and-haul system to collect migrating fish at the weir and transport them by tanker to multiple upstream release areas. This system provides flexibility to accommodate varying fish biomass; ability to operate over a range of flows up to 20-year ARI events; facilities for sorting, data collection and removal of pest species; and capacity to limit predation mortalities. Fishway performance studies led to redesign of the entrance vee-trap and other modifications. To 2017, 55,590 fish from 27 large and small-bodied species used the fishway, together with 8 turtles. Fish of three pest species were identified in the sorting facility and removed to prevent their entry to the reservoir. This paper covers the project life cycle for Australia’s first trap-and-haul fishway including the basis for selecting the fishway type, design and construction. Fishway performance studies and results from ongoing operation, including the lessons learned and the improvements made, are also discussed

Is there a correlation between infection control performance and other hospital quality measures?

Quality measures are increasingly reported by hospitals to the Centers for Medicare and Medicaid Services (CMS), yet there may be tradeoffs in performance between infection control (IC) and other quality measures. Hospitals that performed best on IC measures did not perform well on most CMS non–IC quality measures

Coupling between Smectic and Twist Modes in Polymer Intercalated Smectics

We analyse the elastic energy of an intercalated smectic where orientationally ordered polymers with an average orientation varying from layer to layer are intercalated between smectic planes. The lowest order terms in the coupling between polymer director and smectic layer curvature are added to the smectic elastic energy. Integration over the smectic degrees of freedom leaves an effective polymer twist energy that has to be included into the total polymer elastic energy leading to a fluctuational renormalization of the intercalated polymer twist modulus. If the polymers are chiral this in its turn leads to a renormalization of the cholesteric pitch.Comment: 8 pages, 1 fig in ps available from [email protected] Replaced version also contains title and abstract in the main tex

Towards deterministic optical quantum computation with coherently driven atomic ensembles

Scalable and efficient quantum computation with photonic qubits requires (i) deterministic sources of single-photons, (ii) giant nonlinearities capable of entangling pairs of photons, and (iii) reliable single-photon detectors. In addition, an optical quantum computer would need a robust reversible photon storage devise. Here we discuss several related techniques, based on the coherent manipulation of atomic ensembles in the regime of electromagnetically induced transparency, that are capable of implementing all of the above prerequisites for deterministic optical quantum computation with single photons.Comment: 11 pages, 7 figure

Critical behavior of 2 and 3 dimensional ferro- and antiferromagnetic spin ice systems in the framework of the Effective Field Renormalization Group technique

In this work we generalize and subsequently apply the Effective Field Renormalization Group technique to the problem of ferro- and antiferromagnetically coupled Ising spins with local anisotropy axes in geometrically frustrated geometries (kagome and pyrochlore lattices). In this framework, we calculate the various ground states of these systems and the corresponding critical points. Excellent agreement is found with exact and Monte Carlo results. The effects of frustration are discussed. As pointed out by other authors, it turns out that the spin ice model can be exactly mapped to the standard Ising model but with effective interactions of the opposite sign to those in the original Hamiltonian. Therefore, the ferromagnetic spin ice is frustrated, and does not order. Antiferromagnetic spin ice (in both 2 and 3 dimensions), is found to undergo a transition to a long range ordered state. The thermal and magnetic critical exponents for this transition are calculated. It is found that the thermal exponent is that of the Ising universality class, whereas the magnetic critical exponent is different, as expected from the fact that the Zeeman term has a different symmetry in these systems. In addition, the recently introduced Generalized Constant Coupling method is also applied to the calculation of the critical points and ground state configurations. Again, a very good agreement is found with both exact, Monte Carlo, and renormalization group calculations for the critical points. Incidentally, we show that the generalized constant coupling approach can be regarded as the lowest order limit of the EFRG technique, in which correlations outside a frustrated unit are neglected, and scaling is substituted by strict equality of the thermodynamic quantities.Comment: 28 pages, 9 figures, RevTeX 4 Some minor changes in the conclussions. One reference adde