TRANSPORTATION - WORK GROUP DISCUSSION

Agribusiness,

Composite CDMA - A statistical mechanics analysis

Code Division Multiple Access (CDMA) in which the spreading code assignment to users contains a random element has recently become a cornerstone of CDMA research. The random element in the construction is particular attractive as it provides robustness and flexibility in utilising multi-access channels, whilst not making significant sacrifices in terms of transmission power. Random codes are generated from some ensemble, here we consider the possibility of combining two standard paradigms, sparsely and densely spread codes, in a single composite code ensemble. The composite code analysis includes a replica symmetric calculation of performance in the large system limit, and investigation of finite systems through a composite belief propagation algorithm. A variety of codes are examined with a focus on the high multi-access interference regime. In both the large size limit and finite systems we demonstrate scenarios in which the composite code has typical performance exceeding sparse and dense codes at equivalent signal to noise ratio.Comment: 23 pages, 11 figures, Sigma Phi 2008 conference submission - submitted to J.Stat.Mec

The Witt Ring of a Curve with Good Reduction over a Non-dyadic Local Field

In this work, we present a generalization to varieties and sheaves of the fundamental ideal of the Witt ring of a field by defining a sheaf of fundamental ideals $\tilde{I}$ and a sheaf of Witt rings $\tilde{W}$ in the obvious way. The Milnor conjecture then relates the associated graded of $\tilde{W}$ to Milnor K-theory and so allows the classical invariants of a bilinear space over a field to be extended to our setting using \'etale cohomology. As an application of these results, we calculate the Witt ring of a smooth curve with good reduction over a non-dyadic local field

September 11: Symbolism And Responses To 9/11

Professors Hopkins and Hopkins review the impact of 9/11 as a symbol in American politics. Following the terrorist attacks, 9/11 became a simple reference condensing wide-ranging events and emotions. Various interpretations emerged about what caused 9/11 and enabled the attacks. The authors claim that 9/11 allowed US leaders to pursue certain policy prescriptions that otherwise would have been blocked. Among four possible prescriptions for responding to the attacks, the Bush administration chose a praetorian policy of preventive war, with Iraq as its first example. In the authors’ view, by pursuing an expansive but highly militarized response, the US has overlooked the need to alleviate the conditions that made 9/11 possible. The authors recommend that the US, as part of a multilateral effort, allocate major resources to expanding global public goods, including measures that strengthen barriers to proliferation, enhance fighting of global crime, and reduce incentives for terrorism, especially ones arising in failing states where distorted education and weak protection of human rights encourage organized terrorism

Assessment of recent eastern oyster (Crassostrea virginica) reef restoration projects in the Great Bay Estuary, New Hampshire: Planning for the future

Current oyster populations in New Hampshire total less than 10% of what they were in the 1980s, and the causal factors for the declines include disease, sedimentation, and human harvest. The two major results from a population ecology perspective have been dramatic losses of oyster shell (the major substrate on which oyster larvae typically settle) as well as juvenile annual recruitment to the remaining reefs. Experimental scale oyster restoration projects addressing these two limitations (substrate and natural recruitment) were initiated in the state in the early 2000s by scientists at the University of New Hampshire (UNH). Since the mid-2000s, the focus has been on full restoration-scale projects, and beginning in 2009 most projects have been collaborative efforts by UNH and The Nature Conservancy (TNC). The present study assessed nine recent collaborative efforts, and provided a comprehensive assessment of restoration success with the goal of determining how the restoration process might be improved

Stormwater Management Database for the City of Dover, New Hampshire

The overall goal of the project was to make a significant contribution to the Piscataqua Region Estuaries Partnership goal of increasing oyster (Crassostrea virginica) bottom in New Hampshire, and to do so using methods that positively affect multiple species. The focus was on those organisms (mainly macroalgae, invertebrates, and fish) that spend most of their time on oyster reefs—the resident species. A 0.5 hectare (1.25 acres) area was restored in August 2007 by constructing twelve mini-reefs (each ~6 m in diameter) in an area protected from harvest using spat-on-shell (“spat seeding”) from remotely set larvae. There was a consistent trend over time of higher oyster densities on the mini-reefs and on the natural reef within the protected area compared to the adjacent unprotected natural reef. At the end of the project period (1.8 years post-construction of the mini-reefs), total oyster densities in the overall restoration area were about 26% higher than the adjacent unprotected reef. The constructed mini-reefs also consistently had higher total densities and biomass of resident animals, which consisted mainly of invertebrates (only one fish was captured over the entire study), compared to the other reef areas. A total of 15 species of invertebrates were collected from the mini-reefs compared to 10 and 11 species, respectively, from the natural reef in the restored area and the natural reef in the harvested area. The resident (attached) macroalgae community patterns over time indicated higher biomass on the mini-reefs and the protected natural reefs compared to the unprotected reef area on most sampling dates, though there was typically wide variability among replicates. Macroalgal taxonomic richness was similar in all three areas, and there was a total of fourteen species collected from the three areas. Overall, the project resulted in enhancement of oyster reef habitat within the 0.5 hectare restoration area, and characterized the substantial value of oyster reefs in providing habitat for a variety of plant and animal species