Cruise Report S-221 : scientific data collected aboard SSV Robert C. Seamans, Papeete, French Polynesia – Nuku Hiva, Fench Polynesia – Honolulu, HI, USA, 11 February 2009 – 21 March 2009

Papeete, French Polynesia – Nuku Hiva, Fench Polynesia – Honolulu, HI, USA, 11 February 2009 – 21 March 2009An extensive oceanographic investigation of the tropical Pacific was conducted during Sea Education Association’s cruise S221, Papeete, French Polynesia to Honolulu, HI. As part of SEA’s educational program, undergraduates conduct student-designed oceanographic research during the cruise. Project topics spanned, and integrated, the four “classic” disciplines of oceanography: chemistry, biology, physics and geology

Cruise Report C-210 : Scientific data collected aboard SSV Corwith Cramer, Key West, FL – St. Georges, Bermuda – Falmouth Harbor, Antigua – Christiansted, St. Croix, USVI, 28 March 2007 – 04 May 2007

Key West, FL – St. Georges, Bermuda – Falmouth Harbor, Antigua – Christiansted, St. Croix, USVI, 28 March 2007 – 04 May 2007An extensive oceanographic investigation of the subtropical North Atlantic was conducted during Sea Education Association’s cruise C-210, Key West, FL to St. Croix, USVI (via Bermuda and Antigua, see Figure 1). As part of SEA’s educational program, undergraduates conduct student-designed oceanographic research during the cruise. Project topics spanned, and integrated, the four “classic” disciplines of oceanography: chemistry, biology, physics and geology (Table 7). Student research efforts culminated in a written manuscript and poster presentation to the ship’s company. These papers are available on request from SEA.NS

Cruise Report S-224 : scientific data collected aboard SSV Robert C. Seamans, Honolulu, HI- San Francisco, CA, 22 June 2009 – 19 July 2009

Honolulu, HI- San Francisco, CA, 22 June 2009 – 19 July 2009An extensive oceanographic investigation of the North Pacific Subtropical Gyre was conducted during Sea Education Association’s cruise S224, Honolulu, HI to San Francisco, CA (see Figure 1). As part of SEA’s educational program, undergraduates conduct student-designed oceanographic research during the cruise. Project topics spanned, and integrated, the four “classic” disciplines of oceanography: chemistry, biology, physics and geology

Multi-source spanning trees: algorithms for minimizing source eccentricities

AbstractWe present two efficient algorithms constructing a spanning tree with minimum eccentricity of a source, for a given graph with weighted edges and a set of source vertices. The first algorithm is both simpler to implement and faster of the two. The second approach involves enumerating single-source shortest-path spanning trees for all points on a graph, a technique that may be useful in solving other problems

Linear-time algorithms for scattering number and Hamilton-connectivity of interval graphs.

We prove that for all inline image an interval graph is inline image-Hamilton-connected if and only if its scattering number is at most k. This complements a previously known fact that an interval graph has a nonnegative scattering number if and only if it contains a Hamilton cycle, as well as a characterization of interval graphs with positive scattering numbers in terms of the minimum size of a path cover. We also give an inline image time algorithm for computing the scattering number of an interval graph with n vertices and m edges, which improves the previously best-known inline image time bound for solving this problem. As a consequence of our two results, the maximum k for which an interval graph is k-Hamilton-connected can be computed in inline image time

Minimum-time multidrop broadcast

AbstractThe multidrop communication model assumes that a message originated by a sender is sent along a path in a network and is communicated to each site along that path. In the presence of several concurrent senders, we require that the transmission paths be vertex-disjoint. The time analysis of such communication includes both start-up time and drop-off time terms. We determine the minimum time required to broadcast a message under this communication model in several classes of graphs

Forbidden minors characterization of partial 3-trees

AbstractA k-tree is formed from a k-complete graph by recursively adding a vertex adjacent to all vertices in an existing k-complete subgraph. The many applications of partial k-trees (subgraphs of k-trees) have motivated their study from both the algorithmic and theoretical points of view. In this paper we characterize the class of partial 3-trees by its set of four minimal forbidden minors (H is a minor of G if H can be obtained from G by a finite sequence of edge-extraction and edge-contradiction operations.

Stable isotopic evidence in support of active microbial methane cycling in low-temperature diffuse flow vents at 9°50’N East Pacific Rise

Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 72 (2008): 2005-2023, doi:10.1016/j.gca.2008.01.025.A unique dataset from paired low- and high-temperature vents at 9°50’N East Pacific Rise provides insight into the microbiological activity in low-temperature diffuse fluids. The stable carbon isotopic composition of CH4 and CO2 in 9°50’N hydrothermal fluids indicates microbial methane production, perhaps coupled with microbial methane consumption. Diffuse fluids are depleted in 13C by ~10‰ in values of δ13C of CH4, and by ~0.55‰ in values of δ13C of CO2, relative to the values of the high-temperature source fluid (δ13C of CH4 = -20.1 ± 1.2‰, δ13C of CO2 = -4.08 ± 0.15‰). Mixing of seawater or thermogenic sources cannot account for the depletions in 13C of both CH4 and CO2 at diffuse vents relative to adjacent high-temperature vents. The substrate utilization and 13C fractionation associated with the microbiological processes of methanogenesis and methane oxidation can explain observed steady-state CH4 and CO2 concentrations and carbon isotopic compositions. A mass-isotope numerical box-model of these paired vent systems is consistent with the hypothesis that microbial methane cycling is active at diffuse vents at 9°50’N. The detectable 13C modification of fluid geochemistry by microbial metabolisms may provide a useful tool for detecting active methanogenesis.This work was supported by NSF grants from the division of Ocean Science’s MG&G and RIDGE programs